GIFT OF 
 

A DICTIONARY 
 
 OF 
 
 ELECTRICAL WORDS, 
 
 TERMS AND PHRASES. 
 
 BY 
 
 EDWIN J. HOUSTON, A.M., Ph.D. (Princeton), 
 
 EMERITUS PROFESSOR OF NATURAL PHILOSOPHY AND PHYSICAL GEOGRAPHY IN THE CENTRAL 
 HIGH SCHOOL OF PHILADELPHIA ; PROFESSOR OF PHYSICS IN THE FRANKLIN 
 INSTITUTE OF PENNSYLVANIA J ELECTRICIAN OF THE INTER- 
 NATIONAL ELECTRICAL EXHIBITION, 
 ETC., ETC. 
 
 FOURTH EDITION. WITH APPENDIX. GREATLY ENLARGED, 
 
 NEW YORK: 
 
 McGRAW PUBLISHING COMPANY, 
 
 114 LIBERTY STREET. 
 
vt 
 
 
 Copyright, 1889, 1892, 1894, 1898 
 
 BT 
 
 THB W. J. JOHNSTON COMPANY 
 
 Appendix B. 
 Copyright, 1898 
 
 BT 
 
 EDWIN J. HOUSTON 
 
PREFACE TO THE FIRST EDITION. 
 
 f T > HE rapid growth of electrical science, and the almost daily addition to it of new 
 1 words, terms and phrases, coined, as they too frequently are, in ignorance of 
 ihose already existing, have led to the production of an electrical vocabulary that is 
 already bewildering in its extent. This multiplicity of words is extremely discourag- 
 ing to the student, and acts as a serious obstacle to a general dissemination of elec- 
 trical knowledge, for the following reasons : 
 
 1. Because, in general, these new terms are not to be found ever, in the unabridged 
 editions of dictionaries. 
 
 2. The books or magazines, in which they were first proposed, are either inac- 
 cessible to the ordinary reader, or, if accessible, are often written in phraseology un- 
 intelligible except to the expert. 
 
 3. The same terms are used by different writers in conflicting senses. 
 
 4. The same terms are used with entirely different meanings. 
 
 5. Nearly all the explanations in the technical dictionaries are extremely brief as 
 regards the words, terms and phrases of the rapidly growing and comparatively new 
 science of electricity. 
 
 In this era of extended newspaper and periodical publication, new words are often 
 -coined, although others, already in existence, are far better suited to express the same 
 ideas. The new terms are used for a while and then abandoned ; or, if retained, 
 having been imperfectly denned, their exact meaning is capable of no little ambiguity; 
 and, subsequently, they are often unfortunately adopted by different writers with such 
 varying shades of meaning, that it is difficult to understand their true and exact 
 significance. 
 
 Then again, old terms buried away many decades ago and long since forgotten, are 
 dug up and presented in such new garb that their creators would most certainly fail 
 to recognize them. 
 
 It has been with a hope of removing these difficulties to some extent that the author 
 has ventured to present this Dictionary of Electrical Words, Terms and Phrases to his 
 brother electricians and the public generally. 
 
 He trusts that this dictionary will be of use to electricians, not only by showing the 
 wonderful extent and richness of the vocabulary of the science, but also by giving the 
 general consensus of opinion as to the significance of its different words, terms or 
 phrases. It is, however, to the general public, to whom it is not only a matter of 
 interest but also one of necessity to fully understand the exact meaning of electrical 
 literature,- that the author believes the bo^k will be of the greatest value. 
 
 In order to leave no doubt concerning the precise meaning of the words, terms and 
 phrases thus defined, the following plan has been adopted of giving : 
 
 (i.) A concise definition of the word, term or phrase. 
 
 (2.) A brief statement of the principles of the science involved in the definition. 
 
 i V.JL. I 
 
 2870 
 
(3. ) Where possible and advisable, a cut of the apparatus described or employed 
 in connection with the word, term or phrase defined. 
 
 It will be noticed that the second item of the plan makes the Dictionary ap- 
 proach to some extent the nature of an Encyclopedia. It differs, however, from 
 an Encyclopedia in its scope, as well as in the fact that its definitions in all cases 
 are concise. 
 
 Considerable labor has been expended in the collection of the vocabulary, for 
 which purpose electrical literature generally has been explored. In the alphabetical 
 arrangement of the terms and phrases defined, much perplexity has arisen as to the 
 proper catch-word under which to place them. It is believed that part of the 
 difficulty in this respect has been avoided by the free use of cross references. 
 
 In elucidating the exact meaning of terms by a brief statement of the principles 
 of the science involved therein, the author has freely referred to standard textbooks on 
 electricity, and to periodical literature generally. He is especially indebted to works 
 or treatises by the following authors, viz. : S. P. Thompson, Larden, Gumming, 
 Hering, Prescott, Ayrton, Ayrton and Perry, Pope, Lockwood, Sir William Thom- 
 son, Fleming, Martin and Wetzler, Preece, Preece and Sivewright, Forbes, Max- 
 well, De Watteville, J. T. Sprague, Culley, Mascart and Joubert, Schwendler, 
 Fontaine, Noad, Smee, Depretz, De la Rive, Harris, Franklin, Cavallo, Grove, 
 Hare, Daniell, Faraday and very many others. 
 
 The author offers his Dictionary to his fellow electricians as a starting point only. 
 He does not doubt that his book will be found to contain many inaccuracies, ambig- 
 uous statements, and possibly doubtful definitions. Pioneer work of this character 
 must, almost of necessity, be marked by incompleteness. He, therefore, invites 
 the friendly criticisms of electricians generally, as to errors of omission and commis- 
 sion, hoping in this way to be able finally to crystallize a complete vocabulary of 
 electrical words, terms and phrases. 
 
 The author desires in conclusion to acknowledge his indebtedness to his friends, 
 Mr. Carl Hering, Mr. Joseph Wetzler and Mr. T. C. Martin, for critical exami- 
 nation of the proof sheets ; to Dr. G. G. Faught for examination of the proofs of 
 the parts relating to the medical applications of electricity, and to Mr. C. E. Stump 
 for valuable aid in the illustration of the book ; also to Mr. George D. Fowle, 
 Engineer of Signals of the Pennsylvania Railroad Company, for information concern- 
 ing their System of Block Signaling, and to many others. 
 
 EDWIN J. HOUSTON. 
 CENTRAL HIGH SCHOOL,. PHILADELPHIA, PA., 
 SEPTEMBER, 1889. 
 
PREFACE TO THE SECOND EDITION. 
 
 THE first edition of the "Dictionary of Electrical Words, Terms and Phrases" met 
 with so favorable a reception that the entire issue was soon exhausted. 
 Although but a comparatively short time has elapsed since its publication, electrical 
 progress has been so marked, and so many new words, terms and phrases have been 
 introduced into the electrical nomenclature, that the preparation of a new edition has 
 been determined on rather than a mere reprint from the old plates. 
 
 The wonderful growth of electrical science may be judged from the fact that the 
 present work contains more than double the matter and about twice the number of 
 definitions that appeared in the earlier work. Although some of this increase has 
 been due to words which should have been in the first edition, yet in greater part it 
 has resulted from an actual multiplication of the words used in electrical literature. 
 
 To a certain extent this increase has been warranted either by new applications of 
 electricity or by the discovery of new principles of the science. In some cases, how- 
 ever, new words, terms or phrases have been introduced notwithstanding the fact that 
 other words, terms or phrases were already in general use to express the same ideas. 
 
 The character of the work is necessarily encyclopedic. The definitions are given 
 in the most concise language. In order, however, to render these definitions intel- 
 ligible, considerable explanatory matter has been added. 
 
 The Dictionary has been practically rewritten, and is now, in reality, a new book 
 based on the general lines of the old book, but considerably changed as to order of 
 arrangement and, to some extent, as to method of treatment. 
 
 As expressed in its preface, the author appreciates the fact that the earlier book 
 was tentative and incomplete. Though the wide scope of the second edition, the 
 vast number of details included therein, and the continued growth of the electrical 
 vocabulary must also necessarily make this edition incomplete, yet the author ventures 
 to hope that it is less incomplete than the first edition. He again asks kindly criti- 
 cisms to aid him in making any subsequent edition more nearly what a dictionary of 
 so important a science should be. 
 
 The order of arrangement in the first edition has been considerably changed. The 
 initial letter under which the term or phrase is defined is in all cases that of the noun. 
 
 For example, "Electric Light " is defined under the term " Light, 'Electric " ; 
 
 " Diameter of Commutation " under "Commutation, Diameter of ," "Alter- 
 nating Current Dynamo-Electric Machine" under "Machine, Dynamo- Electric. 
 Alternating Current . " As before, the book has numerous cross references. 
 
 Although the arrangement of the words, terms and phrases under the initial letter 
 of the first word, term or phrase, as, for example, " Electric Light " under the letter E, 
 might possess some advantages, yet, in the opinion of the author, the educational value 
 
VI 
 
 of the work would be thereby considerably decreased, since to a great extent such an 
 arrangement would bring together incongruous portions of the science. 
 
 Frequent cross references render it possible to use the Dictionary as a text-book in 
 connection with lectures in colleges and universities. With such a book the student need 
 make notes only of the words, terms or phrases used, and afterwards, by the use of the 
 definitions and explanatory matter connected therewith, work up the general subject 
 matter of the lecture. The author has successfully used this method in his teaching. 
 
 In order to separate the definitions from the descriptive matter, two sizes of type 
 have been used, the definitions being placed in the larger sized type. 
 
 In the descriptive matter the author has not hesitated to quote freely from standard 
 electrical works, electrical magazines, and periodical literature generally. Among the 
 numerous works consulted, besides those to which reference has already been made 
 in the preface to the first edition, he desires to acknowledge his indebtedness espe- 
 cially to "The Alternating Current Transformer," by J. A. Fleming ; to various works 
 of John W. Urquhart ; to "Modern Views of Electricity," by Prof. O. J. Lodge; to 
 "A Text-book of Human Physiology," by Landois & Sterling; and to "Practical 
 Application of Electricity in Medicine and Surgery, " by Liebig & Rohe. 
 
 The cuts or diagrams used in the book have either been drawn especially for the 
 work or have been taken from standard electrical publications. 
 
 The chart of standard electrical symbols and diagrams has been taken from Prof. 
 F. B. Crocker's paper on that subject. 
 
 The definition of terms used in systems of electric railways have been taken 
 mainly from a paper on " Standards in Electric Railway Practice," by O. T. Crosby. 
 
 The author desires especially to express his obligations to Prof. F. B. Crocker of 
 the Electrical Engineering Department, Columbia College, New York, and to Carl 
 Hering, of Philadelphia, for critical examination of the entire manuscript and for many 
 valuable suggestions ; also to The Electrical World and the Electrical Engineer of New 
 York, and to Prof. Elihu Thomson, Edward Caldwell, T. C. Martin, Dr. Louis Bell, 
 Joseph Wetzler, Nikola Tesla, Wm. H. Wahl, Prof. Wm. D. Marks, Prof. A. . 
 Dolbear, C. W. Pike, John Hoskin, and numerous others, for aid in connection with 
 new words or phrases. So far as they relate to the medical applications of electricity, 
 the proof sheets were revised by Dr. G. G. Faught, of Philadelphia. 
 
 The author desires to thank critics of the first edition and the electrical fraternity in 
 general for valuable suggestions. He presents this second e lition of his Dictionary id the 
 hope that it may to some extent properly represent the vocabulary of electrical science. 
 
 CENTRAL HIGH SCHOOL, EDWIN J. HOUSTON. 
 
 PHILADELPHIA, May, 1892. 
 
PREFACE TO THE THIRD EDITION. 
 
 THE second edition of the "Dictionary of Electrical Words, Terms, and Phrases'* 
 was exhausted in such a comparatively short time that the publishers believed 
 that what new matter might be required for a third edition could best be added in 
 the form of an appendix. 
 
 Although not quite two years have elapsed since the issue of the second edition, 
 yet the growth of electrical science has continued at so rapid a pace, and new words, 
 terms, and phrases have of necessity been introduced so rapidly, that fully twenty per 
 cent., both of new words and new matter, have been found necessary for the third 
 edition. Had this fact been known in time, it might have been better to have 
 developed the additional matter throughout the text, rather than placing it at the end 
 of the book as an appendix. 
 
 Should a demand be made for a fourth edition, the author contemplates re- 
 writing and re-arranging the entire volume. He is thoroughly aware of the inaccuracies 
 and incompleteness of many of the definitions in the second edition, and hopes, in 
 the event of a demand for a fourth edition, to produce a volume more nearly ap- 
 proximating to what an electrical dictionary should be. In the meantime, he again 
 asks the kindly criticisms of his fellow laborers in the electrical field to aid him in the 
 work. 
 
 In order to facilitate the use of the cross-references, all words, terms, and phrases 
 referred to in the appendix are so marked; i. e., (See Appendix Insulation, Kilo- 
 metric, of Cable.} All references not so marked will be found in the main text of the 
 dictionary. 
 
 The author desires to express his obligations to numerous authors and technical 
 journals for information as to new words, terms, and phrases, and to the significance 
 generally given to them in actual use He desires especially to acknowledge his 
 obligations to his colleague, Mr. A. E. Kennelly, and to Professors R. A. Fessenden, 
 C. Wellman Park; to Messrs. C. P. Steinmetz, J. F. Kelly, O. B. Shallenberger, Carl 
 Hering, H. W. Frye, W. D. Weaver, W. F. C. Hasson, Tbwnsend Wolcott, J. B. 
 Cahoon, and many others, for reading of proof sheets and suggestions. 
 
 The author presents this third edition of the Dictionary with the hope that it 
 may prove of value to the electrical fraternity. 
 
 EDWIN J. HOUSTON. 
 
 PHILADELPHIA, May, 1894. 
 
PREFACE TO THE FOURTH EDITION. 
 
 IN preparing the fourth edition of his'" Dictionary of Electrical 
 Words, Terms and Phrases," the author soon found that the 
 recent marvellous growth in the electrical vocabulary was such that 
 it would be impossible to add, in the shape of a separate appendix, 
 the new words, terms and phrases only, that it was necessary to 
 introduce into the book. This will be evident from the fact that 
 the added words exceed in number those already contained in the 
 first, second and third editions. Since it was deemed inadvisable 
 by the publisher to recast the entire book, the only course left open 
 to the author was to alphabetically arrange all the old and new 
 words, and to present them in concise definitions without any ency- 
 clopaedic matter, referring the reader to the matter contained in 
 the earlier editions for illustration and detail. 
 
 It has also been thought advisable to introduce a change in the 
 manner of arrangement, the words, terms and phrases being alpha- 
 betically arranged according, either to the word, or to the first word 
 of the term or phrase. This has permitted the entire suppression 
 of all cross references, which, in view of the author's past expe- 
 rience, he believes will prove an advantage. 
 
 The author desires to acknowledge the very valuable assistance 
 afforded him by his colleague, Dr. A. E. Kennelly, in the prepa- 
 ration of the matter for the fourth edition, both in collecting new 
 terms, as well as in preparing the definitions, and reading the 
 proof. 
 
 The author trusts, that the fourth edition of his electrical Diction- 
 ary will prove of benefit not only to the electrical world but to the 
 reading public generally. 
 
 All criticisms will be gladly received. 
 
 EDWIN J. HOUSTON. 
 
 PHILADELPHIA, December, 1897. 
 
A DICTIONARY 
 
 OF 
 
 ELECTRICAL 
 
 WORDS, TERMS AND PHRASES. 
 
 A. or An. An abbreviation sometimes used 
 in medical electricity for anode. (See Anode?) 
 
 A. C. C. An abbreviation used in medical 
 electricity for Anodic Closure Contraction. 
 (See Contraction, Anodic Closure?) 
 
 A. D. C. An abbreviation used in medical 
 electricity for Anodic Duration Contraction. 
 (See Contraction, Anodic Duration?) 
 
 A. 0. C. An abbreviation used in medical 
 electricity for Anodic Opening Contraction. 
 (See Contraction, Anodic Opening?) 
 
 Abscissa of Rectilinear Co-ordinates. A 
 line or distance cut off along axis of abscissas. 
 
 The abscissa of the point D, Fig. I, on the curve 
 O D R, is the distance D i, or its equal A 2, 
 measured or cut off on the line A C, the axis of 
 abscissas; or, briefly, A 2, is the abscissa of the 
 point D. 
 
 Abscissas, Axis of - One of the 
 
 axes of co-ordinates used for determining the 
 position of points on a curved line. 
 
 Thus the position of 
 the point D, Fig. I, on 
 the curved line O D R, 
 is determined by the per- 
 pendicular distances, D I 
 and D 2, of such point 
 from two straight lines, 
 A B and A C, called the 
 
 axes of co-ordinates. AC, 
 is called the axis of ab- 
 scissas, and AB, the axis of ordinates. The point 
 
 2 
 ***'/ <* 
 
 A, where the lines are considered as starting or 
 originating, is called the point of origin, or, gen- 
 erally, the origin. 
 
 The use of co-ordinates was first introduced by 
 the famous mathematician, Des Cartes. 
 
 Absolute. Complete in itself. 
 
 The terms absolute and relative are used in 
 electricity in the same sense as ordinarily. 
 
 Thus, a galvanometer is said to be calibrated 
 absohittly when the exact current strengths re- 
 quired to produce given deflections ai e known ; 
 or, in other words, when the absolute current 
 strengths are known ; it is said to be calibrated 
 relatively when only the relative current strengths 
 required to produce given deflections are known. 
 
 The word absolute, as applied to the units em- 
 ployed in electrical measurements, was introduced 
 by Gauss to indicate the fact that the values of 
 such units are independent both of the size of the 
 instrument employed and of the value of gravity at 
 the particular place where the instrument is 
 used. 
 
 The word absolute is also used with reference 
 to the fact that the values of the units could 
 readily be redetermined from well known con- 
 stants, in case of the loss of the standards. 
 
 The absolute units of length, mass, and time 
 are more properly called the C. G. S. units, or 
 the centimetre-gramme-second units. (See Units, 
 Absolute. ) 
 
 An absolute system of units based on the milli- 
 gramme, millimetre, and second, was proposed by 
 Weber, and was called the millimetre milli- 
 gramme-second units. It has been replaced by 
 
[Acc, 
 
 the C. G. S. units. (See Units, Centimetre- 
 Gramme-Second. Units, Fundamental.') 
 
 Absolute Block System for Railroads. 
 
 (See Block System for Railroads, Absolute?) 
 
 Absolute Calibration. (See Calibration, 
 Absolute?) 
 
 Absolute Electrometer. (See Electrome- 
 ter, Absolute?) 
 
 Absolute Galvanometer. (See Galva- 
 nometer, Absolute?) 
 
 Absolute Unit of Current. (See Current, 
 Absolute Unit of.) 
 
 Absolute Unit of Electromotive Force. 
 (See Force, Electromotive, Absolute Unit 
 of.) 
 
 Absolute Unit of Inductance. (See -In- 
 ductance, Absolute Unit of.) 
 
 Absolute Unit of Resistance. (See Re- 
 sistance, Absolute Unit of) 
 
 Absolute Unit of Self-Induction. (See 
 Inducti n, Self, Absolute Unit of) 
 
 Absolute Units. (See Units, Absolute) 
 
 Absolute Vacuum. (See Vacuum, Ab- 
 solute) 
 
 Absorption. The taking, or, literally, 
 drinking in, of one form of matter by another, 
 such as a gas, vapor or liquid by a solid ; or 
 of the energy of sound, light, heat, or elec- 
 tricity by ordinary matter. 
 
 Absorption, Acoustic The taking 
 
 in of the energy of sound waves produced by 
 one sounding or vibrating body by another 
 vibrating body. 
 
 Acoustic absorption may result in the dissipa- 
 tion of the absorbed energy, as heat, or in sym- 
 pathetic vibrations. (See Vibrations, Sympathetic.) 
 
 Absorption, Electric The appar- 
 ent soaking of an electric charge into the 
 glass or other solid dielectric of a Leyden jar 
 or condenser. (See Condenser) 
 
 The capacity of a condenser varies with the 
 time the condenser remains charged and with the 
 time taken in charging. Some of the charge 
 acts as if it soaked into the solid dielectric, and 
 this is the cause of the residual charge. (See 
 Charge, Residual.) Therefore, when the con- 
 
 denser is discharged, less electricity appears than 
 was passed in ; hence the term electric absorption. 
 
 Absorption, Luminous -- The ab- 
 
 sorption of the energy of light in its passage 
 through bodies. 
 
 When sunlight falls on an opaque colored body, 
 such for example as a red body, all the colors but 
 the reds are absorbed. The reds are then thrown 
 offand thus cause the color. In the same manne- , 
 when sunlight falls on a transparent colored body, 
 such for example as red, all colors but the reds are 
 absorbed, and the reds are transmitted. 
 
 When sunlight falls on a phosphorescent body, 
 a part of the light is absorbed as heat ; another 
 part is absorbed by the molecules being set into 
 motion sufficiently rapid to cause them to emit 
 light or to become luminous. 
 
 A mass of glowing gas or vapor absorbs waves 
 of light of the same length as those it itself emits. 
 This is the cause of the dark lines of the solar 
 spectrum, called the Fraunhoffer lines. 
 
 The amount of light absorbed by the glass globe 
 of an incandescent lamp, according to Urquhart, 
 is as follows, viz.: 
 
 Clear glass ............. 10 per cent. 
 
 Ground glass ............ 35 " 
 
 Opalescent glass .......... 50 " 
 
 Absorption, Selective -- The absorp- 
 tion of a particular or selected character of 
 waves of sound, light, heat, or electricity. 
 
 Absorption, Thermal -- The ab- 
 
 sorption of heat energy in its passage through 
 a body. 
 
 The phenomena of thermal absorption are 
 similar to those of luminous absorption. A sub- 
 stance that is transparent to heat, or which allows 
 heat waves to pass through without absorption, 
 is called diathermanous, or diathermanic, or 
 is said to be transparent to heat. 
 
 Absorptive Power. (See Power. Absorp- 
 tive) 
 
 Acceleration. The rate of change of 
 velocity. 
 
 Acceleration is thus distinguished from velocity: 
 velocity expresses in time the rate- of- change of 
 position, as a velocity of three metres per second; 
 acceleration expresses in time the rate-of-change 
 of velocity, as an acceleration of one centimetre 
 per second. 
 
 Since all matter is inert, and cannot change its 
 
Ace.] 
 
 
 condition of rest or motion without the applica- 
 tion of some force, acceleration is necessarily due 
 to some force outside the matter itself. A force 
 may therefore be measured by the acceleration it 
 imparts to a given mass of matter. 
 
 Acceleration is positive when the velocity is in- 
 creasing, and negative when it is decreasing. 
 
 Acceleration, Dimensions of The 
 
 ^alue of the acceleration expressed in terms 
 of the length or of distance by the time. (See 
 Acceleration, Unit of.) 
 
 Acceleration, Unit of That ac- 
 celeration which will give to a body unit- 
 velocity in unit-time ; as, for example, one 
 centimetre-per-second in one second. 
 
 Bodies falling freely in a vacuum, and ap- 
 proximately so in air, acquire an acceleration 
 which in Paris or London, at the end of a second, 
 amounts to about 981 centimetres per second, or 
 nearly 32.2 ft. per second. 
 
 V 
 A = , or, in other words, 
 
 The acceleration equals the velocity divided by 
 the time. 
 
 But, since velocity equals the Distance, or the 
 
 Length traversed in a Unit of Time, V = . 
 
 TU r A V T L 
 Therefore, A = -; = -=- = = , or 
 
 The acceleration equals the length, or the dis- 
 tance passed through, divided by the square of the 
 time in seconds. 
 
 These formulae represent the Dimensions of 
 Acceleration. 
 
 Accumulated Electricity. (See Electri- 
 city, Accumulated^) 
 
 Accumulating Electricity. (See Electri- 
 city, Accumulating^) 
 
 Accumulation of Electricity. (See Elec- 
 tricity, Accumulation of.) 
 
 Accumulator. A word sometimes applied 
 to any apparatus in which the strength of a 
 current is increased by the motion past it of a 
 conductor, the currents produced in which 
 tend to strengthen and increase the current 
 which causes the induction. 
 
 [Act. 
 
 The word accumulator is sometimes applied to 
 Sir Wm. Thomson's Electric Current Accumu- 
 lator. 
 
 Current accumulators operate on the reaction 
 principle of dynamo-electric machines. In this 
 sense, therefore, a dynamo -electric machine is an 
 accumulator. (See Machine, Dynamo-Electric, 
 Reaction Principle of.) 
 
 Fig. 2. Barlow's Wheel. 
 
 The copper disc D, Fig. 2, has freedom of 
 rotation, on a horizontal axis at O, in a magnetic 
 field, the lines of force of which, represented by 
 the dotted lines in the drawing, pass downward 
 perpendicularly into the plane of the paper. 
 
 If, now, a current from any source be passed 
 in the direction A, O, B, C, A, through the circuit 
 A, O, B, C, A, which is provided with spring 
 contacts at O, and A, the disc will rotate in the 
 direction of the curved arrow. This motion is 
 due to the current acting on that part of the disc 
 which lies between the two contacts A and O. 
 This apparatus is known as Barlow's Wheel. 
 
 If, when no current is passing through the 
 circuit, the disc be turned in the direction of the 
 arrow, a current is set up in such a direction as 
 would oppose the rotation of the disc. (See 
 Law, Lenz's.) 
 
 If, however, the disc be turned in the opposite 
 direction to that of the arrow, induction currents 
 will as before be produced in the circuit. As 
 this rotation of the disc tends to move the circuit 
 O A, towards the parallel but oppositely directed 
 circuit B C, these two circuits being parallel and 
 in opposite directions tend to repel one another, 
 and there will thus be set up induced currents 
 that tend to oppose the motion of rotation, and 
 the current of the circuit will therefore increase 
 in strength. (See Dynamics, Electro.) Should 
 then a current be started in the circuit, and the 
 original field be removed, the induction will be 
 continued, and a current which, up to a certain 
 extent, increases or accumulates, is maintained in 
 the circuit during rotation of the disc. (Larden.) 
 
 Barlow's Wheel, when used in this manner, is 
 known as Thomson's Electric Current Accumu- 
 lator. 
 
Ace.] 
 
 e 
 
 [Ace. 
 
 Accumulator. A word often applied to 
 a Leyden jar or condenser, which permits the 
 gradual collection from an electric source of 
 a greater charge than it would otherwise be 
 capable of containing. 
 
 A condenser. (See Condenser?) 
 
 The ability of a source to accumulate an in- 
 creased charge when connected to a condenser is 
 due to the increased capacity which a plate or 
 other conductor acquires when placed near 
 another plate or conductor. (See Condenser, 
 jfar, Leyden.) 
 
 Accumulator. Capacity of The 
 
 capacity of a condenser, expressed in micro- 
 farads. (See Condenser, Capacity of.) 
 
 Accumulator or Condenser ; Laws of Ac- 
 cumulation of Electricity. Sir W. Snow 
 Harris, by the use of his Unit-Jar and Elec- 
 tric Thermometer, deduced the following 
 laws for the accumulation of electricity, which 
 we quote from Noad's " Student's Text-Book 
 of Electricity," revised by Preece : 
 
 (I.) "Equal quantities of electricity are given 
 off at each revolution ot the plate of an electrical 
 machine to an uncharged surface, or to a surface 
 charged to any degree of saturation. " 
 
 (2. ) "A coated surface receives equal quantities 
 of electricity in equal times ; and the number of 
 revolutions of the plate is a fair measure of the 
 relative quantities of electricity, all other things 
 remaining the same." 
 
 (3. ) " The free action of an electrical accumula- 
 tion is estimated by the interval it can break 
 through, and is directly proportional to the quan- 
 tity of electricity." 
 
 (4.) " The free action is inversely proportional 
 to the surface/' 
 
 (5.) " When the electricity and the surface are 
 increased in the same ratio, the discharging in- 
 terval remains the same ; but if, as the electricity 
 is increased, the surface is diminished, the dis- 
 charging interval is directly as the square of the 
 quantity of electricity." 
 
 (6.) ' The resistance of air to discharge is as 
 the square of the density directly. " 
 
 According to some later investigations, the 
 quantity a plane surface can receive under a given 
 density depends on the linear b >und<iry of the 
 surface as well &> on the area <>f ; he surface. 
 
 " The amount of electrical charge depends on 
 
 surface and linear extension conjointly. There 
 exists in every plane surface what may be termed 
 an electrical boundary, having an important rela- 
 tion to the grouping or disposition of the electric 
 particles in regard to each other and to surrounding 
 matter. This boundary in circles or globes is 
 represented by their circumferences. In plane 
 rectangular surfaces, it is by their linear extension 
 or perimeter. If this boundary be constant, their 
 electrical charge varies with the square root of 
 the surface. If the surface be constant the charge 
 varies with the square root of the boundary. If 
 the surface and boundary both vary, the charge 
 varies with the square root of the surface multi- 
 plied into the square root of the boundary.'" 
 
 These laws apply especially to continuous sur- 
 faces taken as a whole, and not to surfaces divided 
 into separate parts. 
 
 By electrical charge Harris meant the quantity 
 sustained on a given surface under a given elec- 
 trometer indication ; by electrical intensity, he 
 meant the indication of the electrometer corre- 
 sponding to a given quantity on a given surface. 
 
 (See Condenser, Capacity of. Capacity, Elec- 
 trostatic. Capacity, Specific Inductive. ) 
 
 Accumulators of this character are now 
 generally called Condensers. (For more mcdern 
 principles concerning their construction and 
 capacity see Condenser. Condenser, Capacity of.} 
 
 Accumulator, Secondary or Storage 
 Cell Two inert plates partially sur- 
 rounded by a fluid incapable of acting chem- 
 ically on either of them until after the passage 
 of an electric current, when they become 
 capable of furnishing an independent electric 
 current. 
 
 This use of the term accumulator is the one 
 most commonly employed. A better term for 
 such a cell is a secondary or storage cell. (See 
 Cell, Secondary or Storage.) 
 
 Commercially, an accumulator consists of a 
 single jar and its electrolyte, in which a single 
 set of positive and negative plates is properly 
 placed. 
 
 Accumulator, Water-Dropping - 
 
 An apparatus devised by Sir W. Thomson for 
 increasing the difference of potential between 
 two electric charges. 
 
 The tube X Y, Fig. 3, connects with a reser- 
 voir of water which is maintained at the zero 
 potential of the earth. The water escapes from 
 
Ach.] 
 
 [Act. 
 
 B' 
 
 Water-Drop- 
 
 the openings at C and D, in small drops and falls 
 on funnels provided, as shown, to receive the 
 separate drops and again discharge them. 
 
 The vessels A, A', and B, 
 H', which are electrically _X 
 connected as shown, are 
 maintained at a certain small A ?J|j 
 difference of potential, as 
 indicated by the respective 
 -f- and signs. 
 
 Under these c i r c u m - 
 stances, therefore, C and D, 
 will be charged inductively f'f-3- 
 with charges opposite to &** Ac m " ator - 
 those of A and B, or with and -j- electricities 
 respectively. As the drops of water fall on the 
 funnels, the charges which the funnels thus con- 
 stantly receive are given up to B' and A', before 
 the water escapes. Since, therefore, B, B', and 
 A, A', are receiving constant charges, the differ- 
 ence of potential between them must continually 
 increase. This apparatus operates on the same 
 principle as the replenisher. The drops of water 
 act as the carriers, and A, A', and B, B', as the 
 hollow vessels. (See Replenisher.} 
 
 Achromatic. Free from false coloration. 
 
 Images formed by ordinary lenses do not pos- 
 sess the true colors of the object, unless the edges 
 of the lenses are cut off by the use of a diaphragm ; 
 i e., an opaque 'plate with a central circular 
 opening. The edges of the lenses disperse the 
 light like an ordinary prism, and so produce rain- 
 bow colored (prismatic) fringes in the image. 
 The use of an achromatic lens is to obviate this 
 false coloration. 
 
 Achromatizahle. Capable of being freed 
 from false coloration. 
 
 Achromatize. To free from false color- 
 ation. 
 
 Achromatizing. Freeing from false color- 
 ation. 
 
 Acid, Spent -- A battery acid, or other 
 acid, that has become too weak for efficient 
 action. 
 
 In a voltaic cell the acid of the electrolyte 
 becomes spent by combining with the metal of 
 the positive plate. 
 
 Acidonieter. A special form of hydrom- 
 eter used in determining the specific gravity 
 of the acid liquid in a secondary or storage 
 
 cell. (See Areometer or Hydrometer. Cell. 
 Storage!) 
 
 The scale on the acidometer tube is made to in- 
 dicate the density according to the distance the 
 floating instrument sinks in the liquid. 
 
 Aclinic Line. (See Line, Aclinic?) 
 
 Acoustic Absorption. (See Absorption, 
 Acoustic?) 
 
 Acoustic Engraving. (See Engraving, 
 Acoustic?) 
 
 Acoustic Telegraphy. (See Telegraphy, 
 Acoustic?) 
 
 Acoustic Tetanus. (See Tetanus, Acous- 
 tic'.) 
 
 Acoutemeter, Electric An ap- 
 paratus for electrically testing the delicacy of 
 hearing. 
 
 The Acoutemeter is one of the many applica- 
 tions of Hughes' sonometer. It consists of three 
 flat coils placed parallel to one another on a grad- 
 uated rod, passing through their axes. The 
 central coil, which is used as the primary of an 
 induction coil, is fixed. The other two, which are 
 employed as secondary coils, are movable. (See 
 Sonometer^ Hughes'. Coil, Induction. Micro- 
 ph<me.} A microphone, electrical tuning fork, 
 switches, plugs, and other accessories, are suitably 
 placed and connected. The subject whose hear- 
 ing is to be tested is placed with his back to the 
 apparatus, and with two telephone receivers tightly 
 fixed to his ears. As various sounds are produced , 
 the outer or movable coils are moved gradually 
 away from the central coil, until no sound is 
 heard in the telephone receivers. This distance 
 is in the inverse ratio of the delicacy of hearing of 
 the individual. 
 
 Actinic Photometer. (See Photometer, 
 Actinic?) 
 
 Actinic Ray. (See Ray, Actinic?) 
 
 Actinism. The chemical effects of light, 
 as manifested by the decomposition of various 
 substances. 
 
 Under the influence of the sun's light, the car- 
 bonic acid absorbed by the leaves of plants is de- 
 composed in the living leaves into carbon, which is 
 retained by the plant for the formation of its 
 woody fibre or ligneous tissue, and oxygen, which 
 is thrown off. 
 
Act.] 
 
 [Act. 
 
 The bleaching of curtains, carpets, and other 
 fabrics exposed to sunlight is caused by the actinic 
 power of the light. The photographic picture is 
 impressed by the actinic power of light on a plate 
 covered with some sensitive metallic salt. 
 
 Actinograph. An apparatus for measur- 
 ing and recording the intensity of the chemi- 
 cal effects of light. 
 
 Actinography. The method of measuring 
 and recording the intensity of the chemical 
 effects of light. 
 
 Actinometer. A word sometimes applied 
 to a pyrheliometer. (See Pyrheliometer} 
 
 Actinometer, Electric - An appa- 
 ratus for electrically measuring the intensity 
 of the chemically active rays present in any 
 luminous radiation. 
 
 The rays from the luminous source are per- 
 mitted to fall on a selenium resistance, and their 
 intensity determined by the change observed in 
 the resistance as indicated by the deflections of a 
 galvanometer placed in circuit with the selenium 
 resistance. Or, a thermo-electric pile is employed, 
 and the amount of heat present determined by the 
 indications of a galvanometer placed in its 
 circuit. 
 
 The action 
 
 cataphoresis. (See 
 
 Action, Cataphoric 
 
 of electric osmose or 
 Cataphoresis^) 
 
 Action Currents. (See Currents, Action^) 
 Action, Inductive, Lines of 
 
 Lines within the space, separating a charge 
 and a neighboring body, along which elec- 
 trostatic inductive action takes place. 
 
 Lines of electrostatic force. 
 
 Lines of inductive action pass through the 
 dielectric, separating the two bodies, and termi- 
 nate on the surfaces of the conductor. According 
 to the now generally received notions, the elec- 
 trostatic charge exists in the mass of the dielectric, 
 and not in that of the conductor. The lines of 
 inductive action terminate against the surfaces, 
 one at the positive, and the other at the negative 
 surface. A true E. M. F. exists in the space 
 traversed by lines of inductive action. A con- 
 ductor brought into this space becomes electri- 
 fied, or is strained in such a manner that a 
 momentary current is produced by the rearrange- 
 
 ment of the electrification brought about by 
 electrostatic induction. 
 
 Action, Local, of Dynamo-Electric Ma- 
 chine The loss of energy in a dy- 
 namo-electric machine by the setting up of 
 eddy currents in its pole pieces, cores, or 
 other conducting masses. (See Currents, 
 Eddy.} 
 
 In a dynamo-electric machine local action i 
 obviated by z. lamination of the pole pieces, arma- 
 ture core, etc. (See Core, Lamination of.) 
 
 Action, Local, of Voltaic Cell 
 
 An irregular dissolving or consumption of the 
 zinc or positive element of a voltaic battery, by 
 the fluid or electrolyte, when the circuit is 
 open or broken, as well as when closed, or in 
 regular action. 
 
 Local action is due to small particles of such 
 impurities as carbon, iron, arsenic, or other 
 negative elements, in the positive plate. These 
 impurities form with the positive element minute 
 voltaic couples, and thus direct the corrosive 
 action of the liquid to portions of the plate near 
 them. Local action causes a waste of energy. 
 It may be avoided by the amalgamation of the 
 zinc. (See Zinc, Amalgamation of.) 
 
 Action, Magne-Crystallic , A term 
 
 proposed by Faraday to express differences 
 in the action of magnetism on crystalline 
 bodies in different directions. 
 
 A needle of tourmaline, if hung with its axis 
 horizontal, is no longer paramagnetic, as usual, 
 but diamagnetic. The same is true of a crystal 
 of bismuth. Faraday concluded from these ex- 
 periments that a force existed distinct from either 
 the paramagnetic or the diamagnetic force. He 
 called this the magne -cry stallic force. 
 
 Plucker infers from these phenomena that a 
 definite relation exists between the ultimate form 
 of the particles of matter and their magnetic be- 
 havior. The subject may be regarded as yet 
 somewhat obscure. (See Polarity, Diamagnetic. ) 
 
 Action of a Current on a Magnetic Pole. 
 
 (See Current, Action of, on a Magnetic 
 Pole.) 
 Action, Refreshing, of Current 
 
 The restoration, after fatigue, of muscular and 
 nervous excitability obtained by the action of 
 
Act.] 
 
 9 
 
 [Aer. 
 
 voltaic alternatives. (See Alternatives, Vol- 
 taic?) 
 
 Activity. The work done per second by 
 any agent. (This term is but seldom used.) 
 
 Work-per-second, or, as generally termed 
 in the United States, Power, or Rate of 
 Doing Work. (See Power?) 
 
 Activity, Unit of A rate of work- 
 ing that will perform one unit of work per 
 second. 
 
 In C. G. S. units, the activity of one erg per 
 second. 
 
 The C. G. S. unit of activity is very small. 
 One Watt, the practical unit of activity or power, 
 is equal to ten million ergs per second. (See 
 Waft.) 
 
 The unit of activity generally used for mechan- 
 ical power is the horse-power, or 746 watts. 
 ^See Horse-Power.) 
 
 Actual Cautery. (See Cautery, Actual.) 
 Acute Angle. (See Angle, Acute?) 
 Adapter. A screw nozzle fitted to an elec- 
 tric lamp, provided with a screw thread to en- 
 able it to be readily placed on a gas bracket 
 or chandelier in place of an ordinary gas 
 burner. 
 
 Adherence. The quality or property of 
 adhering. (See Adhesion?) 
 
 Adherence, Magnetic Adhesion be- 
 tween surfaces due to magnetic attraction. 
 
 Magnetic adhesion has been applied, among 
 other things, to a brake action on car wheels, 
 either by causing them to adhere directly to the 
 track or to a brake- block. 
 
 Adhesion. The mutual attraction which 
 exists between unlike molecules. (See At- 
 traction, Molecular?) 
 
 The phenomena of adhesion are due to the 
 mutual attraction of dissimilar molecules. 
 
 Adhesion, Electric Adhesion be- 
 tween surfaces due to the attraction of unlike 
 electrostatic charges. 
 
 Molecular adhesion must be distinguished from 
 the attraction which causes a piece of dry and 
 warmed writing paper, that has been rubbed by a 
 piece of india-rubber, to stick to a papered wall. 
 In this latter case the attraction between the wall 
 
 and the paper is due to the mutual attraction of 
 two dissimilar electrostatic charges. Molecular 
 adhesion must also be distinguished from the at- 
 traction of opposite magnetic poles. 
 
 Adhesion, Galvanoplastic The ad- 
 hesion of a galvanoplastic deposit or coating 
 to surfaces subjected to electroplating. (See 
 Plating, Electro?) 
 
 Adiathermancy. Opacity to heat. 
 
 A substance is said to be diathermanous when 
 it is transparent to heat. Clear, colorless crys- 
 tals of rock salt are very transparent both to light 
 and to heat. Rock salt, covered with a layer or 
 deposit of lampblack or soot, is quite transparent 
 to heat. An adiathermanous body is one which 
 is opaque to h*eat. 
 
 Heat transparency varies not only with differ- 
 ent substances, but also with the nature of the 
 source from which the heat is derived. Thus, a 
 substance may be opaque to heat from a non- 
 luminous source, such as a vessel filled with boil- 
 ing water, while it is comparatively transparent 
 to heat from a luminous source, such as an incan- 
 descent solid or a voltaic arc. 
 
 A similar difference exists as regards transpar- 
 ency to light. A colorless glass will allow light 
 of any color to pass through it. A blue glass will 
 allow blue light to pass freely through it, but will 
 completely prevent the passage of any red light; 
 and so with other colors. 
 
 Adiathermauic. Possessing the quality of 
 adiathermancy. (See Adiathermancy?) 
 
 Adjustable Condenser. (See Condenser, 
 Adjustable?) 
 
 Adjuster, Cord A device for ad- 
 justing the length of a pendant cord. 
 
 Adjustment. Such a regulation of any 
 apparatus as will enable it to properly perform 
 its functions. 
 
 JEpinus' Condenser. (See Condenser, 
 jEpinus'?) 
 
 Aerial Cable. (See Cable, Aerial?) 
 
 Aerial Cable, Suspending Wire of 
 (See Wire, Suspending, of Aerial Cable?) 
 
 Aerial Line. (See Line, Aerial?) 
 
 Aerolites. A name sometimes given to 
 meteorites. 
 
 Meteorites are masses of solids which pass 
 
Aff.] 
 
 10 
 
 [Ago. 
 
 through the upper portions only of the earth's 
 atmosphere on their approach to the orbit of the 
 earth, or which fall through the air on the earth's 
 surface from the sky. They are luminous at 
 night and are followed by a train of fire. The 
 luminosity is due to heat produced by friction 
 through the air. Meteors frequently burst from 
 the sudden expansion of their outer portions. 
 
 Some meteorites are composed of nearly pure 
 iron alloyed with nickel. The majority of them, 
 however, are merely stones or oxidized sub- 
 stances. Their average velocity is about 26 miles 
 a second. 
 
 Affinity, Chemical Atomic attrac- 
 tion. 
 
 The force which causes atoms to unite and 
 form chemical molecules. 
 
 Atomic or chemical attraction generally results 
 in a loss of the characteristic qualities or proper- 
 ties which distinguish one kind of matter from 
 another. In this respect chemical affinity differs 
 from adhesion, or the force which holds unlike 
 molecules together. (See Adhesion. Attraction, 
 Molecular. 1 ) If, for example, sulphur is mixed 
 with lampblack, no matter how intimate the 
 mixture, the separate particles, when examined 
 by a magnifying glass, exhibit their peculiar color, 
 lustre, etc. If, however, the sulphur is chemi- 
 cally united with the carbon, a colorless, transpar- 
 ent, mobile liquid, called carbon bisulphide, re- 
 sults, that possesses a disagreeable, penetrating 
 odor. 
 
 Chemical affinity, or atomic combination, is in 
 fluenced by a variety of causes, viz.: 
 
 (I.) Cohesion. Cohesion, by binding the mole- 
 cules more firmly together, opposes their mutual 
 atomic attraction. 
 
 A solid rod of iron will not readily burn in the 
 flame of an ordinary lamp; but, if the cohesion be 
 overcome by reducing the iron rod to filings, it 
 burns with brilliant scintillations when dropped 
 into the same flame. In this case the increase of 
 surface and the increased temperature of the 
 smaller particles also contribute to the result. 
 
 (2.) Solution. Solution, by giving the molecules 
 greater freedom of motion, favors their chemical 
 combination. 
 
 (3.) Heat. Heat sometimes favors atomic com- 
 bination possibly by decreasing the cohesion, and, 
 possibly, by altering the electrical relations of the 
 atoms. If too great, heat may produce decom- 
 position. There is for most substances a critical 
 
 temperature below which chemical combination 
 will not take place. (See Thermolysis.} 
 
 (4.) Light. Decomposition, or the lessening of 
 chemical affinity, through the agency of light, is 
 called Actinism. Light also causes the direct 
 combination of substances. A mixture of equal 
 volumes of hydrogen and chlorine unites explo- 
 sively when exposed to the action of full sunlight. 
 (See Actinism.) 
 
 (5. ) Electricity. An electric spark will cause 
 an explosive combination of a mixture of oxygen 
 and hydrogen. Electricity also produces chemi- 
 cal decomposition. (See Electrolysis.) 
 
 Helmholtz accounts for the electro-chemical 
 attraction of oxygen for zinc by supposing that all 
 substances possess a definite amount of attraction 
 for electricity, and that the attraction of zinc in 
 this respect exceeds that of copper and the other 
 metals. He thus regards the zinc as attracting 
 its electric charge rather than as attracting the 
 oxygen. Since both zinc and copper are dyad 
 metals, this view, as will be seen, is at variance 
 with later views. 
 
 Chemical affinity may be caused by the opposite 
 attractions of electrical charges naturally possessed 
 by the atoms of matter. This would appear to be 
 rendered probable by the law of electro-chemical 
 equivalence. (See Equivalence, Electro-Chemical, 
 Law of. Electricity, Atom of.) 
 
 After Currents. (See Currents, After ^ 
 
 Aging of Alcohol, Electric (See 
 
 Alcohol, Electric Aging of.) 
 
 Agonal. Pertaining to the agone. (See 
 Agone?) 
 
 Agone. A line connecting places on the 
 earth's surface where the magnetic needle 
 points to the true geographical north. 
 
 The line of no declination or variation of 
 a magnetic needle. (See Needle, Magnetic, 
 Declination of) 
 
 As all the places on the earth where the mag- 
 netic needle points to the true north may be ar- 
 ranged on a few lines, it will be understood that 
 the pointing of the magnetic needle to the true 
 geographical north is the exception and not the 
 rule. In many places, however, the deviation 
 from the true geograpical north is so small that 
 the direction of the needle may be regarded as. 
 approximately due north. 
 
 Agonic. Pertaining to the agone. 
 
Air.J 
 
 11 
 
 [Ala. 
 
 Air-Blast for Commutators. An inven- 
 tion of Prof. Elihu Thomson to prevent the 
 injurious action of destructive flashing at the 
 commutator of a dynamo-electric machine. 
 
 A thin, forcible blast of air is delivered through 
 suitable tubes at points on the three-part commu- 
 tator cylinder of the Thomson -Houston dynamo, 
 where the collecting brushes bear on its surface. 
 The effect is to blow out the arc or prevent its for- 
 mation and thus avoid its destructive action on 
 the commutator segments. The use of the air- 
 blast also permits the free application of oil, thus 
 further avoiding wear. 
 
 Fig. 4. Air -Blast on Commuta 
 
 The blast-nozzles are shown at B 8 , B 8 , Fig. 4, 
 near the collecting brushes. 
 
 The air-supply is obtained from a blower at- 
 tached directly to the shaft of the machine. Its 
 construction and operation will be readily under- 
 stood from an inspection of Fig. 5, in which the 
 
 Fig, 3. The Thomson Blower, 
 
 top is removed for ready examination of the 
 interior parts. 
 
 Air Churning. (See Churning, Air.) 
 
 Air Condenser. (See Condenser, Air) 
 
 Air Field. (See Field, Air) 
 
 Air-Gap. (See Gap, Air) 
 
 Air-Line Wire. (See Wire, Air-Line^) 
 
 Air Magnetic Circuit. (See Circuit, Air 
 Magnetic?) 
 
 Air-Pump. (See Pump, Air.) 
 
 Air-Pump, Geissler's Mercurial 
 
 (See Pump, Air, Geissler's Mercurial) 
 
 Air-Pump, Mechanical (See Pump, 
 
 Air, Mechanical) 
 
 Air-Pump, Mercurial (See Pump, 
 
 Air, Mercurial^ 
 
 Air-Pump, Sprengel's Mercurial 
 
 (See Pump, Air, Sprengefs Mercurial^) 
 
 Air-Space Cut-Out. (See Cut-Out, Air- 
 Spaced) 
 
 Alarm, Burglar A device, generally 
 
 electric, for automatically announcing the 
 opening of a door, window, closet, drawer, or 
 safe, or the passage of a person through a 
 hallway, or on a stairway. 
 
 Electric burglar-alarm devices generally consist 
 of mechanism for the operation of an automatic 
 make and -break bell on the opening or closing of 
 an electric circuit. The bell may either continue 
 ringing only while the contact remains closed, or, 
 may, by the throwing on of a local circuit or 
 battery, continue ringing until stopped by some- 
 non-automatic device, such as a hand-switch. 
 
 The alarm-bell is stationed either in the house 
 when occupied, or on the outside when the house 
 is temporarily vacated, or may connect directly 
 with the nearest police station. 
 
 Burglar-alarm apparatus is of a variety of 
 forms. Generally, devices are provided by means 
 of which, in case of house protection, an annunci- 
 ator shows the exact part where an entrance has 
 been attempted. (See Annunciator, Burglar- 
 Alarm.) Switches are provided for disconnecting 
 all or parts of the house from the alarm when so 
 desired, as well as to per- 
 mit windows to be partly 
 raised for purposes of ven- 
 tilation without sounding 
 the alarm. A clock is fre- 
 quently connected with the 
 alarm for the purpose of 
 automatically disconnect- 
 ing any portion of the 
 house at or for certain in- 
 tervals of time. 
 
 Fig. 6 shows a burglar- Fig. 6. Burglar-Alarm 
 alarm with annunciator, Annunciator. 
 
 switches, switch-key, cut-off, and clock. 
 
 Alarm, Burglar, Central-Station 
 
 A burglar-alarm, the contact points of which .1 
 are placed in the places to be protected, and . 
 
Ala.] 
 
 12 
 
 [Ala. 
 
 connected by suitable circuits with alarms 
 placed in a centrally located station. 
 
 In a system of central-station burglar-alarms, a 
 number of houses, factories, banks, etc., are all 
 connected telegraphically with the nearest police 
 station, or other central station, constantly pro- 
 vided with police officers. A series of contacts are 
 placed on doors, windows, safes and money draw- 
 ers, and connected with alarms and annunciators 
 placed in the central station. An unauthorized 
 entrance, therefore, is automatically telegraphed 
 to the central station and its exact location indi- 
 cated on the annunciator. Systems of central- 
 station fire-alarms are constructed on a similar 
 plan. 
 
 Alarm, Electric 
 
 An automatic de- 
 
 vice by which attention is called to the occur- 
 rence of certain events, such as the opening 
 of a door or window; the stepping of a person 
 on a mat or staircase; the rise or fall of tem- 
 perature beyond a given predetermined point; 
 or, a device intended to call a person to a tel- 
 egraphic or telephonic instrument. 
 
 Electric-alarms are operated by means of the 
 ringing of an electro-magnetic or mechanical bell, 
 
 Fig. ?. Electrically Started Mechanical Alarm, 
 
 which is electrically called into action by either 
 closing or opening an electric circuit, generally 
 the former. 
 
 Electric-alarms may be divided into two classes, 
 Tiz.: 
 
 (I.) Mechanically operated alarms, or those in 
 
 which the alarm is given by clock-work, started 
 by means of an electric current. 
 
 (2.) Those in which the alarm is both set in ac- 
 tion and operated by an electric current. 
 
 In Fig. 7 is shown the general construction of 
 an electrically started mechanical alarm. The 
 attraction of the armature B, by the electro-mag- 
 net A, moves the armature lever pivoted at C, 
 and thus releases the catch e, and permits the 
 spring or weight connected with the clock move- 
 ment to set it in motion and strike the bell. 
 
 Electrically actuated alarm-bells are generally 
 of the automatic make-and -break form. The 
 striking lever is operated by the attraction of the 
 armature of an electro-magnet, and is provided 
 with a contact-point, so placed that when the 
 hammer is drawn away from the bell, by the ac- 
 tion of a spring, on the electro-magnet losing its 
 magnetism, a contact is made, but when the ham- 
 mer is drawn towards the bell the contact is open- 
 ed. When, therefore, the hammer strikes the 
 bell, the circuit is opened, and the electro-magnet 
 releases its armature, permitting a spring to again 
 close the contact by moving the striking lever 
 away from the bell. Once set into action, these 
 movements are repeated while there is battery 
 power sufficient to energize the magnet. 
 
 In Fig. 8, in which is shown an electrically ac- 
 tuated alarm-bell, the battery terminals are con- 
 
 Fig: 8. Automatic Make-and-Break. 
 
 -ected with the right and left hand binding-posts, 
 P and M. The hammer, K, is connected with a 
 striking lever, which forms part of the circuit, 
 and which is attached to the armature of the elec 
 tro-magnet e. A metallic spring, g, bears against 
 the armature when the latter is away from the 
 magnet, but does not touch the armature when 
 it is moved towards the magnet. A small spring 
 draws the lever away from the magnet when no 
 current is passing. The movements of the arma- 
 
Alii. 
 
 13 
 
 [Ale. 
 
 ture thus automatically open and close the circuit 
 of the electro-magnet. 
 
 This form of make-and-break is called an auto- 
 matic make-and-break. 
 
 Alarm, Electrically Operated An 
 
 alarm that is maintained in operation by the 
 electric current. (See Alarm, Electric?) 
 
 Alarm, Electro-Mechanical - A 
 mechanically operated alarm that is started 
 or set in operation by means of an electric 
 current. (See Alarm, Electric?) 
 
 Alarm, Fire, Automatic An in- 
 strument for automatically telegraphing an 
 alarm from any locality on its increase in tem- 
 perature beyond a certain predetermined point. 
 
 Fire-alarms are operated by thermostats, or by 
 means of mercurial contacts; i. e., a contact 
 closed by the expansion of a column of mercury. 
 (See Thermostat. Contact, Mercurial.) 
 
 In systems of fire-alarm telegraphs, the alarm 
 is automatically sounded in a central police sta- 
 tion and in the district fire-engine house. (See 
 Telegraphy, Fire-Alarm. ) 
 
 Alarm, Mercurial Temperature 
 
 An instrument for automatically telegraphing 
 an alarm by means of a mercurial contact on 
 a predetermined change of temperature. 
 
 The action of mercurial contacts is dependent 
 on the fact that, as the mercury expands more 
 than glass by the action of heat, the mercury level 
 reaches a contact-point placed in a glass tube and 
 thus completes the circuit through its own mass, 
 which forms the other or movable contact. 
 Sometimes both contacts are placed on opposite 
 sides of a tube and are closed when the mercury 
 reaches them. 
 
 Mercurial temperature or thermo>tat alarms 
 are employed in hot-houses, incubators, tanks 
 and buildings for the purpose of maintaining a 
 uniform temperature. 
 
 Alarm, Telegraphic - An alarm-bell 
 for calling the attention of an operator to 
 a telegraphic instrument when the latter is of 
 the non-acoustic or needle type. 
 
 In acoustic systems of telegraphy the sounds 
 themselves are generally sufficient. 
 
 Alarm, Telephonic An alarm-bell 
 
 for calling a correspondent to the receiving 
 telephone. 
 
 These alarms generally consist of magneto- 
 electric bells. (See Bell, Magneto- Electric.} 
 
 Alarm, Temperature An electric 
 
 alarm automatically operated on a change of 
 temperature. (See Alarm, Fire, Automatic.} 
 
 Alarm, Thermostat An electric 
 
 alarm that is thrown into action by a thermo- 
 stat. (See Thermostat?) 
 
 Alarm, Water or Liquid Level 
 
 A device for electrically sounding an alarm 
 when a water surface varies materially from 
 a given level. 
 
 An electric bell is placed in a circuit that is au- 
 tomatically closed or broken by the movement of 
 contact-points operated by the change of liquid 
 level. 
 
 A form of electric alarm for a water-level is 
 shown in Fig. 9. The float is provided with 
 contacts for closing an electric circuit, when it 
 either rings a bell, or, by its action on some form 
 of automatic cut-off, stops the water. 
 
 Fig. ?. Water-Level Alarm. Fig. 10. 
 
 When arranged with a double float, as shown 
 in Fig. 10, the alarm may be made to signal 
 either a too high or a too low water level. 
 
 Alarm, Yale-Lock-Switch Burglar - 
 An apparatus whereby the opening of a 
 door by an authorized party provided with the 
 regular key will not sound an alarm, but any 
 other opening will sound such alarm. 
 
 Fig. zi. Yale-Lock-Suritch. 
 
 A Yale-lock burglar-alarm switch is shown in 
 Fig. ii. 
 
 Alcohol, Electric Aging 1 of A pro- 
 cess for the rapid aging of alcohol, by ex- 
 
Ale. 
 
 14 
 
 [All. 
 
 posing it to the action of electrically produced 
 -ozone. 
 
 Instead of the ordinary process of aging alco- 
 hol, by exposing it in partially closed vessels to 
 the action of air, it is exposed to the action of 
 ozone, electrically produced. 
 
 The ozone employed is obtained in substan- 
 tially the usual way by the passage of a rapid 
 succession of electric sparks through air. 
 
 Alcohol, Electric Rectification of 
 
 A process whereby the bad taste and odor of 
 alcohol, due to the presence of aldehydes, 
 are removed by the electrical conversion of 
 the aldehydes into true alcohols through the 
 addition of hydrogen atoms. 
 
 An electric current sent through the liquid 
 between zinc electrodes liberates oxygen and hy- 
 drogen irom the decomposition of the water. 
 "The nascent or atomic hydrogen converts the 
 aldehydes into alcohol and deprives the pro- 
 ducts of their fusel oil, while the oxygen forms 
 insoluble zinc oxide. 
 
 Algebraic Co-efficient. (See Co-efficient, 
 Algebraic?) 
 
 Algebraic Notation. (See Notation, Al- 
 gebraic?) 
 
 All-Night Arc Lamp. (See Lamp, All- 
 Night Arc.} 
 
 All-Night Electric Lamp. (See Lamp, 
 All-Night Arc.} 
 
 Allotropic. Pertaining to allotropy. (See 
 Allotropy.} 
 
 Allotropic State. (See State, Allotropic}. 
 
 Allotropy. A variation of the physical 
 properties of an elementary substance with- 
 out change of composition of its molecules. 
 (See State, Allotropic} 
 
 Alloy. A combination, or mixture, of two 
 or more metallic substances. 
 
 Alloys in most cases appear to be true chemi- 
 cal compounds. In a few instances, however, 
 they may form simple mixtures. 
 
 The composition of a few important alloys is 
 here given: 
 
 Solder, plumber's; Tin 66 parts, Lead 34 parts. 
 
 Pewter, hard; Tin 92 parts, Lead 8 parts. 
 
 Britannia metal; Tin 100 parts, Antimony 8 
 parts, Copper 4 parts, Bismuth, I part. 
 
 Type metal; Lead 80, Antimony 20 parts. 
 Brass, white; Copper 65, Zinc 35 parts. 
 Brass, red; Copper 90, Zinc 10 parts. 
 Speculum metal; Copper 67, Tin 33 parts. 
 Bell metal; Copper 78, Tin 22 parts. 
 Aluminium bronze; Copper 90, Aluminium 10 
 parts. 
 
 Alloy. To form a combination or mixture 
 of two or more metallic substances. 
 
 Alloy, German Silver An alloy 
 
 employed for the wires of resistance coils, 
 consisting of 50 parts of copper, 25 of zinc, 
 and 25 of nickel. 
 
 German silver wire is suitable for resistance 
 coils, because its resistance varies but slightly with 
 changes of temperature. It is cheaper than plati- 
 num-silver alloy, and is therefore employed ex- 
 tensively. Platinum silver alloy, however, has 
 more resistance for a given size of wire, and its re- 
 sistance varies somewhat less than German silver 
 with changes of temperature, and is therefore used 
 where greater accuracy is desired. 
 
 Alloy, Palladium An alloy of pal- 
 ladium with other metals. 
 
 Palladium forms a number of useful alloys with 
 various metals. Some of the palladium alloys are 
 as elastic as steel, are unaffected by moisture or 
 ordinary corrosive agencies, and are entirely de- 
 void of paramagnetic properties; that is to say, 
 they cannot be magnetized after the manner ot' 
 iron. 
 
 These properties have been utilized bv their 
 discoverer, Paillard, in their employment for the 
 hair-springs, escapements and balance wheels of 
 watches, in order to permit the watches to be car- 
 ried into strong magnetic fields without any ap- 
 preciable effects on the rate of the watch. A 
 number of careful tests made by the author, by 
 long continued exposure of watches, thus pro- 
 tected by the Paillard alloys, in extraordinary 
 fields, show that the protection thus given the 
 watches enables them to be carried into the strong- 
 est possible magnetic fields without appreciably 
 affecting their rate. 
 
 The Paillard palladium alloys have the follow- 
 ing composition, viz. : 
 
 Alloy No. i. 
 
 Palladium 60 to 75 parts. 
 
 Copper 15 to 25 " 
 
 Iron I to 5 " 
 
All.] 
 
 15 
 
 [Alp. 
 
 Alloy No. 2. 
 
 Palladium 50 to 75 parts. 
 
 Copper 201030 " 
 
 Iron 5 to 20 " 
 
 Alloy No. j. 
 
 Palladium 651075 " 
 
 Copper 15*025 " 
 
 Nickel I to 5 " 
 
 Gold I to 2j " 
 
 Platinum ^ to 2 " 
 
 Silver 3 to 10 " 
 
 Steel i to 5 " 
 
 Alloy No. 4. 
 
 Palladium 45 to 50 " 
 
 Silver 20 to 25 " 
 
 Copper 15 to 25 " 
 
 Gold 2 to 5 " 
 
 Platinum 2 to 5 " 
 
 Nickel 2 to 5 " 
 
 Steel 2 to 5 " 
 
 The great value of the palladium alloys, when 
 employed for the hair-springs of watches, arises 
 not only from their non-magnetizable properties, 
 and their inoxidizability, but particularly from the 
 fact that their elasticity is approximately the same 
 for comparatively wide ranges of temperature. 
 
 Alloy, Platinum-Silver An alloy 
 
 consisting of one part of platinum, and two 
 parts of silver. 
 
 Platinum silver alloy is now extensively em- 
 ployed for resistance coils from the fact that 
 changes in temperature of the alloy produce but 
 comparatively small changes in its electrical re- 
 sistance. (See Alloy, German Silver.) 
 
 Alphabet, Telegraphic An arbi- 
 trary code consisting of dots and dashes, 
 sounds,deflections of a magnetic needle, flashes 
 of light, or movements of levers, following one 
 another in a given predetermined order, to 
 represent the letters of the alphabet and the 
 numerals. 
 
 Alphabet, Telegraphic : International 
 
 Code The code of signals for letters, 
 
 etc., employed in England and on the Euro- 
 pean continent generally. 
 
 Similar symbols are employed for the numerals 
 and the punctuation marks. 
 
 It will be observed that it is mainly in the 
 
 characters of the American Morse, in which spaces 
 are used, that the Continental characters differ 
 from the American. This is due to the use of the 
 needle instrument, with which a space cannot well 
 be represented. A movement or deflection of the 
 
 Single 
 Needle 
 
 Single 
 
 /Needle 
 
 O 
 
 t _ 
 
 a . 
 b __. 
 c _,_ 
 
 d . 
 
 f .. VN/- 
 
 g '/* 
 
 h .... , NXNX 
 
 ~. ^ 
 
 J* ^/// 
 
 k A/ 
 
 I . S/xx 
 
 m __ // 
 
 International Telegraphic Code. 
 
 needle to the left signifies a dot ; a movement to 
 the right, a dash. 
 
 Alphabet, Telegraphic : Morse's 
 
 Various groupings of dots and dashes, or 
 deflections of a magnetic needle to the right 
 and left, which represent the letters of the 
 alphabet or other signs. 
 
 In the Morse alphabet dots and dashes are em- 
 ployed in recording systems, and sounds, of 
 varying intervals, corresponding to the dots and 
 dashes, in the sounder system. 
 
 A dash is equal in length of time to three dots. 
 The space between the separate characters of a 
 single letter is equal to one dot, except in the 
 American Morse, in which the following letters 
 contain longer spaces: C, O, R, Y, and Z. The 
 lengthened spaces are equal to two dots. L is 
 one and a half times the length of T. 
 
 The sound produced by the down stroke of the 
 sounding lever in the Morse sounder is readily 
 distinguishable from the up stroke. When these 
 differences are taken in connection with the inter- 
 vals between successive sounds there is no diffi- 
 culty in reading by sound. 
 
 (For methods of receiving the alphabet, see 
 Sounder, Morse Telegraphic. Recorder, Morse. 
 Recorder, Bain's Chemical. Recorder, Siphon. 
 Relay. Magnet, Receiving.) In the net die tele- 
 graph, the code is similar to that used in the Morse 
 Alphabet. (See Telegraphy, Single-Needle.) 
 
Alt.] 
 
 16 
 
 [Alt. 
 
 AMERICAN MORSE CODE. 
 ALPHABET. 
 
 a 
 
 b 
 
 c -- - 
 
 d 
 
 e - 
 i 
 
 k 
 
 1 
 
 m 
 
 I 
 
 2 
 
 3 
 
 4 
 
 c 
 
 n 
 
 o - - 
 
 P 
 
 q 
 
 r - -- 
 s 
 
 u 
 
 V 
 
 w 
 
 X 
 
 y .. .. 
 
 & . ... 
 
 NUMERALS. 
 
 6 - 
 
 PUNCTUATION MARKS. 
 
 Period Interrogation . 
 
 Comma Exclamation . 
 
 Printing Single Needle 
 
 t x//// 
 
 2 xx /// 
 
 3 x x v // 
 
 4 
 
 5 
 6 
 7 
 
 8 
 9 
 10 
 
 x x x x 
 x x \ x \ 
 / \ \ x x 
 //x x x 
 ///xx 
 
 _____ ///// 
 
 Period ------ XX xx xx 
 
 Comma ---- .^ \/\/\/ 
 
 Interrogation ______ xx //xx 
 
 Exclamation __ 1 __ _ . //xx// 
 
 Colon ------ ///xxx 
 
 Semicolon ------ /x /x /x 
 
 Alteration Theory of Muscle or Nerve 
 Current (See Theory, Alteration, of 
 Muscle or Nerve Current?) 
 
 Alternating Arc. (See Arc, Alternat- 
 ing.} 
 
 Alternating Current Circuit. (See Cir- 
 cuit, Alternating Current?) 
 
 Alternating Current Condenser. (See 
 
 Condenser, Alternating Current?) 
 
 Alternating Current Dynamo-Electric 
 Machine. (See Machine, Dynamo-Electric, 
 Alternating Current?) 
 
 Alternating Current Electric Motor. 
 
 (See Motor, Electric, Alternating Current?) 
 
 Alternating Currents. (See Currents, 
 Alternating?) 
 
 Alternating Currents, Distribution of 
 Electricity by (See Electricity, Dis- 
 tribution of, by Alternating Currents?) 
 
 Alternating Discharge. (See Dischange, 
 Alternating?) 
 
 Alternating Dynamo-Electric Machine. 
 
 (See Machine, Dynamo-Electric, Alternat- 
 ing Current?) 
 
 Alternating Electrostatic Field. (See 
 
 Field, Alternating Electrostatic.} 
 
 Alternating Electrostatic Potential. 
 (See Potential, Alternating Electrostatic?) 
 
 Alternating Field. (See Field, Alternat- 
 ing?) 
 
 Alternating Influence Machine, Wims- 
 hurst's (See Machine, Wimshurst's 
 Alternating Influence?) 
 
 Alternating Magnetic Field. (See Field, 
 Alternating Magnetic?) 
 
 Alternating Magnetic Potential. (See 
 Potential, Alternating Magnetic.} 
 
 Alternating Potential. (See Potential, 
 Alternating?) 
 
 Alternating Primary Currents. (See 
 Currents, Alternating Primary?) 
 
 .Alternating Secondary Currents. (See 
 Currents, Alternating Secondary?) 
 
 Alternation. A change in direction or 
 phase. 
 
 Alternations. Changes in the direction of 
 a current in a circuit. 
 
 A current that changes its direction 300 times 
 per second is said to possess 300 alternations per 
 second. 
 
 Alternations, Complete A change 
 
 in the direction of a current in a circuit from its 
 
Alt] 
 
 [Amnu 
 
 former direction and back again to that 
 direction. A complete to-and-fro change. 
 
 Complete alternations are sometimes indicated 
 by the symbol ~. 
 
 Alternations, Frequency of A 
 
 phrase employed to denote the number of al- 
 ternations per second. 
 
 Alternative Path. (See Path, Alterna- 
 tive^) 
 
 Alternatives, Voltaic A term used 
 
 in medical electricity to indicate sudden re- 
 versals in the polarity of the electrodes of a 
 voltaic battery. 
 
 An alternating current from a voltaic bat- 
 tery, obtained by the use of a suitable com- 
 mutator. 
 
 Sudden reversals of polarity produce more 
 energetic effects of muscular contraction than do 
 simple closures or completions of the circuit. 
 
 The muscular contraction produced by a voltaic 
 current is much stronger when the direction of the 
 current is rapidly reversed by means of a com- 
 mutator than when the current is more slowly 
 broken and the poles then reversed. 
 
 The effect of voltaic alternatives is to produce 
 quick contractions that are in strong contrast to 
 the prolonged contractions that result from the 
 faradic current. In the faradic machine, the 
 reversals are so rapid that the muscle fails to 
 return to rest before it is again contracted. 
 
 Voltaic alternatives are sometimes indicated by 
 the contraction V. A. 
 
 Alternator. A name commonly given to 
 an alternate current dynamo. (See Machine, 
 Dynamo-Electric, Alternating Current?) 
 
 Alternator, Compensated Excitation of 
 
 An excitation of an alternating current 
 
 dynamo-electric machine, in which the field is 
 but partially excited by separate excitement, 
 the remainder of its exciting current being 
 derived from the commuted currents of a 
 small transformer placed in the main circuit 
 of the machine. 
 
 The object of compensated excitation of an 
 alternator is to render the machine self-governing. 
 
 Amalgam. A combination or mixture 
 of a metal with mercury. 
 
 Amalgam, Electric A substance 
 
 with which the rubbers of the ordinary fric- 
 tional electric machines are covered. 
 
 Electric amalgams are of various compositions. 
 The following formula produces an excellent 
 amalgam : 
 
 Melt together five parts of zinc and three of 
 tin, and gradually pour the molten metal into 
 nine parts of mercury. Shake the mixture until 
 cold, and reduce to a powder in a warm mortar. 
 Apply to the cushion by means of a thin layer of 
 stiff grease. 
 
 Mosaic gold, or bisulphide of tin, and powdered 
 graphite, both act as good electric amalgams. 
 
 An electric amalgam not only acts as a con- 
 ductor to carry off the negative electricity, but, 
 being highly negative to the glass, produces a far 
 higher electrification than would mere leather or 
 chamois. 
 
 Amalgamate. To form into an amalgam. 
 
 Amalgamating. Forming into an amal- 
 gam. 
 
 Amalgamation. The act of forming into 
 an amalgam, or effecting the combination of 
 a metal with mercury. 
 
 Amalgamation of Zinc Plates of Voltaic 
 Cell. (See Plates, Zinc, of Voltaic Cell, 
 Amalgamation of.) 
 
 Amber. A resinous substance, generally 
 of a transparent, yellow color. 
 
 Amber is interesting electrically as being be- 
 lieved to be the substance in which the proper- 
 ties of electric attractions and repulsions, imparted 
 by friction or rubbing, were first noticed. It was 
 called by the Greeks rj\.EM.Tpov, from which the 
 word electricity is -derived. This property was 
 mentioned by the Greek, Thales of Miletus, 600 
 B. c., as well as by Theophrastus. 
 
 American System of Telegraphy. (See 
 
 Telegraphy, American System of.) 
 
 American Twist-Joint. (See Joint, 
 American Twist.) 
 
 American Wire Gange. (See Gauge, 
 Wire, American?) 
 
 Ammeter. A form of galvanometer in 
 which the value of the current is measured 
 directly in amperes. (See Galvanometer!) 
 
 An ampere-meter or ammeter is a commercial 
 form of galvanometer in which the deflection* of 
 
A ill ill. 
 
 18 
 
 [Amp. 
 
 a magnetic needle are calibrated or valued in am- 
 peres. As a rule the coils of wire in an ammeter 
 are of lower resistance than in a voltmeter. The 
 magnetic needle is deflected from its zero position 
 by the field produced by the current whose strength 
 in amperes is to be measured. This needle is held 
 in the zero position by the action of a magnetic 
 field, either of a permanent or an electro-magnet, 
 by the action of a spring, or by a weight under the 
 influence of gravity. There thus exist a variety 
 of ammeters, viz. : permanent -magnet ammeters, 
 electro-magnetic ammeters, spring ammeters and 
 gravity ammeters. 
 
 In the form originally devised by Ayrton and 
 Perry, the needle came to rest almost imme- 
 diately, or was dead-beat in action. (See Damp- 
 ing.') It moved through the field of a permanent 
 magnet. The instrument was furnished with a 
 number of coils of insulated wire, which could 
 be connected either in series or in multiple-arc by 
 means of a commutator, thus permitting the scale 
 reading to be verified or calibrated by the use of a 
 single voltaic cell. (See Circuits, Varieties of. 
 Commutatoi . Calibration, Absolute. Calibra- 
 tion, Relative.) In this case the coils were 
 turned to series, and a plug pulled out, thus intro- 
 ducing a resistance of one ohm. 
 
 c 
 
 Fig. 12. Ayrton and Perry Ammeter. 
 
 Fig. 12 represents an ampere-meter devised by 
 Ayrton and Perry. A device called a commutator 
 for connecting the coils either in series or parallel 
 is shown at C. Binding-posts are provided at 
 P, PS, and S. The dynamo terminals are con- 
 nected at the posts P, PS, and the current will 
 pass only when the coils are in multiple, thus 
 avoiding accidental burning of the coils. In this 
 case the entire current to be measured passes 
 through the coils so coupled. The posts S and 
 PS, are for connecting the single battery cell cur- 
 vent. 
 
 A great variety of ampere-meters, or ammeters, 
 have been devised. They are nearly all, how- 
 
 ever, constructed on essentially the same general 
 principles. 
 
 Commercial ammeters are made in a great va- 
 riety of forms. When the currents to be meas- 
 ured are large, as is generally the case in electric 
 light or power stations, they consist of a coil of 
 insulated wire, often of a single turn, or even of 
 but a part of a turn, having a balanced core of 
 iron or steel capable of moving freely within it. 
 
 Ammeter, Electro-Magnetic A 
 
 form of ammeter in which a magnetic needle is 
 moved against the field of an electro-magnet 
 by the field of the current it is measuring. 
 (See Ammeter.) 
 
 Ammeter, Gravity A form of am- 
 meter in which a magnetic needle is moved 
 against the force of gravity by the field of the 
 current it is measuring. (See Ammeter?) 
 
 Ammeter, Magnetic- Yane An 
 
 ammeter in which the strength of a magnetic 
 field produced by the current that is to be 
 measured is determined by the repulsion ex- 
 erted between a fixed and a movable iron 
 vane, placed in said field and magnetized 
 thereby. (See Voltmeter, Magnetic- Vane.) 
 
 Ammeter, Permanent-Magnet A 
 
 form of ammeter in which a magnetic needle 
 is moved against the field of a permanent mag- 
 net by the field of the current it is measuring. 
 (See Ammeter?) 
 
 Ammeter, Reducteur for (See Re- 
 
 ducteur, or Shunt for Ammeter?) 
 
 Ammeter, Spring A form of am- 
 meter in which a magnetic needle is moved 
 against the action of a spring by the field of 
 the current it is measuring. (See Ammeter) 
 
 Amorphous. Having no definite crys- 
 talline form. 
 
 Mineral substances have certain crystalline 
 forms, that are as characteristic of them as are the 
 forms of animals or plants. Under certain cir- 
 cumstances, however, they occur without definite 
 crystalline form, and are then said to be amor- 
 phous solids. 
 
 Amperage. The number of amperes pass- 
 ing in a given circuit. 
 
 The current strength in any circuit as indi- 
 cated by an ampere-meter placed in the circuit. 
 
Amp.] 
 
 19 
 
 [Amp. 
 
 Ampere. The practical unit of electric 
 current. 
 
 Such a rate-of-flow of electricity as trans- 
 mits one coulomb per second. 
 
 Such a current (or rate-of-flow or trans- 
 mission of electricity) as would pass with an 
 electromotive force of one volt through a cir- 
 cuit whose resistance is equal to one ohm. 
 
 A current of such a strength as would 
 deposit .005084 grain of copper per second. 
 
 A current of one ampere is a current of such 
 definite strength that it would flow through a cir- 
 cuit of a certain resistance and with a certain 
 electromotive force. (See Force, Electromotive, 
 Volt. Resistance. Ohm.) 
 
 Since the ohm is the practical unit of resistance, 
 and the volt the practical unit of electromotive 
 force, the ampere, or the practical unit of current, 
 is the current that would flow through unit resist- 
 ance, under unit pressure or electromotive force. 
 
 To make this clearer, take the analogy of water 
 flowing through a pipe under the pressure of a 
 column of water. That which causes the flow is 
 the pressure or head ; that which resists the flow 
 is the friction of the water against the pipe, which 
 will vary with a number of circumstances. The 
 rate-of-flow may be represented by so many cubic 
 inches of water per second. 
 
 As the pressure or head increases, the flow in- 
 creases proportionally; as the resistance increases, 
 the flow diminishes. 
 
 Electrically, electromotive force corresponds to 
 the pressure or head of the water, and resistance 
 to the friction of the water and the pipe. The 
 ampere, which is the unit rate-of-flow ptr second, 
 may therefore be represented as follows, 
 
 Tp 
 
 viz. : C = , as was announced by Ohm in his 
 R 
 
 law. (See Law of Ohm.) 
 
 This expression signifies that C, the current in 
 amperes, is equal to E, the electromotive force in 
 volts, divided by R, the resistance in ohms. 
 
 We measure the rate-of-flow of liquids as so 
 many cubic inches or cubic feet per second that is, 
 in units of quantity. We measure the rate-of-flow 
 of electricity as so much electricity per second. 
 The electrical unit of quantity is called the Coul- 
 omb. (See Coulomb.'] The coulomb is such a 
 quantity as would pass in one second through a 
 circuit in which the rate-of-flow is one ampere. 
 
 An ampere is therefore equal to one coulomb per 
 second. 
 
 The electro-magnetic unit of current is such a 
 current that, passed through a conducting wire 
 bent into a circle of the radius of one centimetre, 
 would tend to move perpendicular to its plane a 
 unit magnetic pole held at its centre, and 
 sufficiently long to practically remove the other 
 pole from its influence, with unit force, *'. e., the 
 force of one dyne. (See Dyne.) The ampere, or 
 practical electro-magnetic unit, is one-tenth of 
 such a current ; or, in other words, the absolute 
 unit of current is ten amperes. 
 
 An ampere may also be defined by the chemical 
 decomposition the current can effect as measured 
 by the quantity of hydrogen liberated, or metal 
 deposited. 
 
 Defined in this way, an ampere is such a cur- 
 rent as will deposit .00111815 gramme, or 
 .017253 grain, of silver per second on one of the 
 plates of a silver voltameter, from a solution of 
 silver nitrate containing from 15 to 30 per cent, of 
 the salt (See Voltameter), or which will decompose 
 .00009326 gramme, or .001439 grain of dilute 
 sulphuric acid per second, or pure sulphuric acid 
 at 59 degrees F. diluted with about 15 per cent, of 
 water, that is, dilute sulphuric acid of Sp. Gr. of 
 about i.i. The present scientific and commercial 
 practice is to take the ampere to be such a current 
 as will deposit 4 024 grammes of silver in one hour. 
 
 Ampere Arc. (See Arc, Ampere?) 
 Ampere-Feet. (See Feet, Ampere.) 
 Ampere-Hour. (See Hour, Ampere?) 
 
 Ainpdre-Meter. An ammeter. (See Am- 
 meter?) 
 
 Ampere-Meter, Balance or Neutral Wire 
 
 An ampere-meter placed in the cir- 
 cuit of the neutral wire, in the three-wire sys- 
 tem of electric distribution, for the purpose of 
 showing the excess of current passing over 
 one side of the system as compared with the 
 other side, when the central wire is no longer 
 neutral. 
 
 Ampere-Minute. (See Minute, Ampere?) 
 Ampdre Ring. (See Ring, Ampere?) 
 Ampere-Second. (See Second, Ampere?) 
 Ampdre Tap. (See Tap, Ampere?) 
 Ampere-Turn. (See Turn, Ampere?) 
 
 Ampere-Turn, Primary (See Turn, 
 
 Ampere, Primary?) 
 
Amp.] 
 
 20 
 
 [Ane. 
 
 Ampere-Turn, Secondary 
 
 Turn, Ampere, Secondary?) 
 
 (See 
 
 of a 
 
 Ampere- Volt. A watt, or the 
 horse-power. 
 
 This term is generally written volt-ampere. 
 (See Volt-Ampere.} 
 
 Ampere-Winding. (See Winding, Am- 
 pere) 
 
 Ampere's Rule for Effect of Current on 
 Needle. (See Rule, Ampere's, for Effect of 
 Current on Needle.} 
 
 Ampere's Theory of Magnetism. (See 
 Magnetism, Ampere s Theory of.) 
 
 Amperian Currents. (See Currents, Am- 
 perian.) 
 
 Amplitude of Vibration or Ware. (See 
 Vibration or Wave, Amplitude of.) 
 
 Ammunition-Hoist, Electric -- An 
 electrically operated hoist for raising ammu- 
 nition to the deck of a ship. 
 
 In the electric ammunition-hoist the electric 
 motor which moves the hoist is made to follow the 
 motions of the operator's hand, both as regards 
 direction and speed. The motion of a crank, or 
 wheel, causes a switch to start an electric motor in 
 a certain direction, which tends to close the switch, 
 thus necessitating a race between the operator 
 and the motor. Should the operator begin to 
 close the switch more slowly, the m tor will over- 
 take him, will partially close the switch, and thus 
 lower the speed of the motor. 
 
 Analogous Pole. (See Pole, Analogous) 
 
 Analysis. The determination of the com- 
 position of a compound substance by separ- 
 ating it into the simple or elementary sub- 
 stances of which it is composed. 
 
 Analysis, Electric -- The determin- 
 ation of the composition of a substance by 
 electrical means. 
 
 Various processes have been proposed for elec- 
 tric analysis; they consist essentially in decompos- 
 ing the substance by means of electric currents, 
 and are either qualitative or quantitative. (See 
 Electrolysis.) 
 
 Analysis, Electrolytic -- A term 
 sometimes used instead of electric analysis. 
 (See Analysis, Electric) 
 
 Analysis, Qualitative -- A chemical 
 
 analysis which merely ascertains the kinds of 
 elementary substances present. 
 
 Analysis, Quantitative A chemical 
 
 analysis which ascertains the relative propor- 
 tions in which the different components enter 
 into a compound. 
 
 Analyzable. Separable into component 
 parts. 
 
 Analyze. To separate into component 
 parts. 
 
 Analyze, Electrically To separate 
 
 electrically into component parts. 
 
 Analyzer, Electric A gridiron of 
 
 metallic wires which is transparent to electro- 
 magnetic waves, when its length is perpendic- 
 ular to them, but opaque to them /'. e., 
 possessing the ability to reflect them when 
 rotated 90 degrees from its former position. 
 
 The electric analyzer, it will be observed, is 
 analogous to an analyzer for polarized light. A 
 reflecting surface, for example, being able to re- 
 flect polarized light in a given position, and unable 
 to reflect it when rotated 90 degrees from such 
 position, is capable of acting as an analyzer lor 
 polarized light. 
 
 Analyzer, Gray's, Harmonic Telegraphic 
 
 An electro-magnet, the armature of 
 
 which consists of a steel ribbon stretched in 
 a metallic frame and capable through regula- 
 tion, as to tension, by means of a screw, of 
 being tuned to a certain note. 
 
 The steel ribbon is thrown into vibration when- 
 ever pulsations from the transmitting instruments 
 are sent over the line corresponding to the rate t.f 
 motion of the ribbon, but is not set into vibration 
 by any others. If, therefore, a number of different 
 analyzers, tuned to different notes, are placed on 
 the same line, each will be operated only by the 
 pulsations sent into the line corresponding to its 
 rate of motion, and thus multiple transmission in 
 the same direction is possible. In order to- 
 strengthen the tones of the analyzers, each is pro- 
 vided with a resonant air column. (See Reson- 
 ator. Telegraphy, Multiplex.) 
 
 Analyzing. Separating into component 
 parts. 
 
 Anelectric. A word formerly applied to 
 bodies (conductors) which it was believed 
 could not he electrified by friction. 
 
Aue.] 
 
 21 
 
 [Ani. 
 
 This term is now obsolete. Conductors are 
 easily electrified, when insulated. 
 
 Anelectrotonic State. (See State, Anelec- 
 trotonic?) 
 
 Anelectrotonic Zone. (See Zone, Anelec- 
 trotonic^) 
 
 Anelectrotonns. In electro-therapeutics, 
 the decreased functional activity which occurs 
 in a nerve in the neighborhood of the anode, 
 or positive electrode, when applied therapeu- 
 tically. (See Electrotonus) 
 
 Anemometer, Electric An appa- 
 ratus to electrically record or indicate the direc- 
 tion and intensity of the wind. 
 
 In the electric recording anemometer, the force 
 or velocity of the wind, or both, are recorded on 
 a moving sheet of paper, on which the time is 
 marked, so that the exact time of any given 
 change is known. 
 
 Anemoscope. An instrument which indi- 
 cates, but does not measure the intensity or 
 record the direction of the wind. 
 
 The word is often, though improperly, used in- 
 terchangeably for anemometer. 
 
 Angle. The deviation in direction between 
 two lines or planes that meet. 
 
 Angles are measured by arcs of circles. The 
 angle at B A C, Fig. 13, is the deviation of the 
 straight line A B, from A 
 C. In reading the let- 
 tering of an angle the 
 letter placed in the mid- 
 dle indicates the angle 
 referred to. Thus B A 
 C, means the angle be- 
 tweenABandAC; B A 
 
 B 
 
 A C 
 
 Fig. fj. Angles. 
 D, the angle between B A and A D. Angles are 
 valued in degrees, there being 360 degrees in an 
 entire circumference or circle. Degrees are in- 
 dicated thus: 90, or ninety degrees. 
 
 Angle, Acute An angle whose value 
 
 is less than a right angle or 90 degrees. 
 
 B A E, or E A D, in Fig. 13, is an acute angle. 
 
 Angle, Complement of What an 
 
 angle needs to make its value 90 degrees, or a 
 right angle. 
 
 Thus in Fig. 13, B A E, is the complement of 
 the angle E A D. since B AE4-EAD = o/> 
 degrees. 
 
 Angle, Obtnse An angle whose 
 
 value is greater than a right angle or 90 
 degrees. 
 
 E A C, Fig. 13, is an obtuse angle. 
 
 Angle of Declination or Variation. (See 
 Declination, Angle of. Variation, Angle of.) 
 
 Angle of Difference of Phase Between 
 Alternating Currents of Same Period. 
 (See Phase, Angle of Difference of, Between 
 Alternating Currents of Same Period?) 
 
 Angle of Dip. (See Dip. Dip or Incli- 
 nation, Angle of?) 
 
 Angle of Inclination. (See Dip or Incli- 
 nation, Angle of.) 
 
 Angle of Lag of Dynamo-Electric Ma- 
 chine. (See Lag, Angle of, of Dynamo- 
 Electric Machine?) 
 
 Angle of Lead. (See Lead, Angle of) 
 
 Angle of Variation. (See Variation, 
 Angle of.) 
 
 Angle, Plane An angle contained 
 
 between two straight lines. 
 
 Angle, Solid An angle contained 
 
 between two surfaces. 
 
 Angle, Supplement of What an 
 
 angle needs to make its value 180 degrees, or 
 two right angles. 
 
 Thus in Fig. 13, E A C, is the supplement of 
 E A D, because EAD-fEAC = i8o degrees, 
 or two right angles. 
 
 Angle, Unit - An angle of 57.29578 
 or 57 17' 44.8" nearly. (See Velocity, An- 
 gular?) 
 
 Angular Currents. (See Currents, An- 
 gular?) 
 
 Angular Velocity. (See Velocity, Angu- 
 lar?) 
 
 Animal Electricity. (See Electricity, 
 Animal?) 
 
 Animal Magnetism. (See Magnetism, 
 Animal?) 
 
 Anion. The electro-negative radical of a 
 molecule. 
 
 Literally, the term ion signifies a group of 
 wandering atoms. An anion is that group of 
 atoms of an electrically decomposed or electro ly zed 
 
Ani.] 
 
 22 
 
 [Ann. 
 
 molecule which appears at the anode. (See 
 Electrolysis. Anode. ) 
 
 As the anode is connected with the electro- 
 positive terminal of a source, the anion is the 
 electro-negative radical or group of atoms, and 
 therefore appears at the electro-positive terminal. 
 
 A kathion, or electro-positive radical, appears 
 at the kathode, which is connected with the 
 electro-negative terminal of the battery. Oxygen 
 and chlorine are anions. Hydrogen and the 
 metals are kathions. 
 
 Anisotropic Conductor. (See Conductor, 
 Anisotropic?) 
 
 Anisotropic Medium. (See Medium, 
 Anisotropic?) 
 
 Annealing, Electric A process 
 
 for annealing metals in which electric heating 
 is substituted for ordinary heating. 
 
 Annual Inequality of Earth's Magnet- 
 Ism. (See Inequality, Annual, of Earth's 
 Magnetism. 
 
 Annual Variation of Magnetic Needle. 
 
 (See Needle, Magnetic, Annual Variation 
 of.} 
 
 Annunciator, Burglar-Alarm An 
 
 annunciator used in connection with a system 
 of burglar-alarms. (See Alarm, Burglar?) 
 
 Annunciator Clock, Electric 
 
 (See Clock, Electric Annunciator?) 
 
 Annunciator Drop. (See Drop, Annun- 
 ciator?) 
 
 Annunciator Drop, Automatic 
 
 (See Drop, Automatic Annunciator?) 
 Annunciator, Electro-Magnetic 
 
 An electric device for automatically indicating 
 the points or places at which one or more 
 electric contacts have been closed. 
 
 The character of the annunciator depends, of 
 course, on the character of the places at which 
 these points, places or stations are situated. 
 
 Annunciators are employed for a variety of 
 purposes. In hotels they are used for indicating 
 the number of a room the occupant of which 
 desires some service, which he signifies by push- 
 ing a button, thus closing an electric circuit. 
 This is indicated or announced on the annuncia- 
 tor by the falling of a drop, on which is printed a 
 number corresponding with the room, and by the 
 
 ringing of a bell to notify the attendant. The num- 
 ber is released by the movement of the armature 
 of an electro-magnet. The drops are replaced in 
 their former position by some mechanical device 
 operated by the hand. In the place of a drop a 
 
 Fig. 14. Electro- Magnetic Annunciator. 
 
 needle is sometimes u<ed, which, by the attraction 
 of the armature of an electro-magnet, points to 
 the number signaling. 
 
 Annunciators for houses, burglar-alarms, fire- 
 alarms, elevators, etc., are 
 of the same general con- 
 struction. 
 
 Annunciators are general- 
 ly operated by electro-mag, 
 netic attraction or repulsion, 
 and are therefore some- 
 times called electro-magnetic 
 annunciators. 
 
 Fig. 14 shows an annun- 
 ciator suitable for use in 
 hotels. 
 
 The numbers 28 and 85 
 are represented as having 
 been dropped by the closing 
 of the circuit connected 
 with them. 
 
 Annunciator, Eleva- 
 tor An annuncia- 
 tor connected with an 
 Fig. 15. Elevator elevator to indicate the 
 
 Annunciator. n . .. 
 
 floor signaling. 
 
 One form of elevator annunciator is shown in 
 Fig. 15. 
 
Ann.] 
 
 23 
 
 [Ann, 
 
 Annunciator, Fire-Alarm An 
 
 annunciator used in connection with a system 
 of fire-alarms. 
 
 Annunciator, Gravity-Drop An 
 
 annunciator whose signals are operated by 
 the fall of a drop. 
 
 Fig. z6. Gravity-Drop Annunciator. 
 
 A form of gravity-drop annunciator is shown 
 in Fig. 16. The armature mechanism for the 
 release of the drop will be understood by an in- 
 spection of the drawing. 
 
 Annunciator, Hotel An annun- 
 ciator connected with the different rooms of a 
 hotel. 
 
 A hotel-annunciator is generally provided with 
 a return bell and guest-call. 
 
 Annunciator, House An annun- 
 ciator connected with the rooms of a house. 
 
 Annunciator, Needle An annun- 
 ciator, the indications of which are given by 
 the movements of a needle instead of the fall 
 of a drop. 
 
 A form of needle-annunciator is shown in 
 Fig. 17. 
 
 Annunciator, Oral or Speaking Tube 
 
 An annunciator electrically operated 
 
 by means of a puff of breath transmitted 
 through an ordinary speaking tube. 
 
 The oral-annunciator is a contrivance whereby 
 a central office is placed in communication with a 
 number of speaking tubes coming from different 
 points in a hotel or other place. A person 
 in any room, who wishes to communicate 
 with the central office, blows through the 
 speaking tube in his room, and thus, by 
 effecting an electric contact, rings a bell and 
 operates a drop at the annunciator, thus indicat- 
 ing the exact tube at which the attendant is to 
 receive the message. The attendant can thus be 
 placed in easy communication with each of the 
 rooms whose speaking tubes connect with the 
 annunciator. 
 
 Annunciator, Pendulum or Swinging 
 
 An annunciator, the indicating arm of 
 which consists of a pendulous.or swinging arm, 
 
 Fig. 17. Needle-Annunciator. 
 
 which, when at rest, points vertically down- 
 ward, and which is moved to the right or left 
 by the action of the current. 
 
 Pendulous, or swinging-annunciators are gen- 
 erally so arranged as to need no replacement. 
 
Ann.] 
 
 [App. 
 
 On the cessation of the current the indicator arm 
 drops vertically downward. 
 
 A relay is preferably used with pendulum- 
 annunciators, since the rapid makes and breaks 
 of the current by the bell alarm interfere with 
 their satisfactory action. 
 
 Anodal. Pertaining to the anode. (See 
 Anode?) 
 
 Anodal Diffusion. (See Diffusion, Ano- 
 
 Anode. The conductor or plate of a de- 
 composition cell connected with the positive 
 terminal of a battery, or other electric source. 
 
 That terminal of an electric source out of 
 which the current flows into the liquid of a 
 decomposition cell or voltameter is called the 
 anode. 
 
 That terminal of an electric source into 
 which the current flows from a decomposition 
 cell or voltameter is called the kathode. 
 
 The anode is connected with the carbon or 
 positive terminal of a voltaic battery, and the 
 kathode with the zinc, or negative terminal. 
 Theretore the word anode has been used to 
 signify the positive terminal of an electric source, 
 and kathode, the negative terminal, and in this 
 sense is employed generally in electro-thera- 
 peutics. It is preferable, however, to restrict the 
 use of the words anode and kathode to those 
 terminals of a source at which electrolysis is 
 taking place. 
 
 The terms anode and kathode in reality refer 
 to the electro-receptive devices through which 
 the current flows. S.nce it is assumed that the 
 current flows out of a source from its positive 
 pole or terminal, and back through the source at 
 its negative pole or terminal, the pole of any 
 device which is connected with the positive pole 
 of a source is the part or place at which the 
 current enters and flows through it, and that 
 connected with the negative pole, the part at 
 which it leaves. Hence, probably, the change 
 in the use of the words already referred to. 
 
 Since the anion, or the electro negative radical, 
 appears at the anode, it is the anode of an electro- 
 plating bath, or the plate connected with the 
 positive terminal of the source, that is dissolved. 
 
 When the term anode was first proposed by 
 Farauay, voltaic batt ries were the only available 
 electric source, and the term referred only to the 
 
 positive terminal of a voltaic battery when 
 placed in an electrolyte. 
 
 Anodic. Pertaining to the anode. (See 
 Anode?) 
 
 Anodic Electro-Diagnostic Reactions. 
 
 (See Reactions, Kathodic and Anodic Elec- 
 tro-Diagnostic?) 
 
 Anodic Opening Contraction. (See Con- 
 tration, Anodic Opening?) 
 
 Anomalous Magnet. (See Magnet, An- 
 omalous?) 
 
 Anomalous Magnetization. (See Mag- 
 netization, Anomalous?) 
 
 Anti-Induction Cable (See Cable, 
 
 Anti-Induction?) 
 
 Anti-Induction Conductor. (See Con- 
 ductor, Anti-Induction?) 
 
 Antilogous Pole. (See Pole, Antilogous?) 
 
 Anvil. The front contact of a telegraphic 
 key that limits its motion in one direction. 
 (See Key, Telegraphic?) 
 
 Aperiodic Galvanometer. (See Galva- 
 nometer, Aperiodic?) 
 
 Apparatus, Faradic-Induction - 
 
 An induction coil apparatus for producing 
 faradic currents. 
 
 A voltaic battery is connected with the primary 
 of an induction coil, and its current rapidly 
 broken by an automatic break, or by a hand 
 break. The alternating or faradic currents thus 
 produced in the secondary coils are used for 
 electro-therapeutic purposes. (See Coil, Induc- 
 tion.") 
 
 Faradic induction apparatus is made in a great 
 variety of forms. They all operate, however, on 
 essentially the same principles. 
 
 Apparatus, Faradic, Magneto-Electric 
 
 A small magneto-electric machine 
 
 employed in electro-therapeutics for producing 
 faradic currents. 
 
 Magneto-electric faradic machines consist essen- 
 tially of a coil of wire wrapped on an armature 
 core that is rotated before the poles of permanent 
 magnets. No commutator is employed, since it is 
 desired to obtain rapidly alternating currents. 
 
 Apparatus, Interlocking - Devices 
 for mechanically operating from a distant signal 
 
App.] 
 
 [Arc. 
 
 tower, railroad switches and semaphore signals 
 for indicating the position of such switches, 
 by means of a system of interlocking levers, 
 so constructed that the signals and the 
 switches are so interlocked as to render it 
 impossible, after a route has once been set up 
 and a signal given, to clear a signal for a 
 route that would conflict with the one previ- 
 ously set up. (See Block System for Rail- 
 roads^) 
 
 Apparatus, Magneto-Electric Medical 
 A term applied to small magneto- 
 electric machines employed in medical elec- 
 tricity for the production of uncommuted 
 or faradic currents. (See Apparatus, Fara- 
 dic, Magneto- Electric?) 
 
 Apparatus, Registering, Electric 
 
 Devices for obtaining permanent records by 
 electrical means. 
 
 Apparatus, Registering, Telegraphic 
 
 A name sometimes given to a telegraphic 
 recorder. (See Recorder, Chemical, Bain's. 
 Recorder, Morse. Recorder, Siphon?) 
 
 Apparent Co-efficient of Induction. 
 
 (See Induction, Apparent Co-efficient of.) 
 
 Arago's Disc. (See Disc, Arago's?) 
 
 Arc. A voltaic arc. (See Arc, Voltaic:) 
 
 Arc. To form a voltaic arc. 
 
 A dynamo-electric machine is said to arc at the 
 commutator, when the current, passes as visible 
 sparks across the spaces between adjacent seg- 
 ments. 
 
 This action at the commutator is more gener- 
 ally called sparking or burning. 
 
 Arc, Alternating A voltaic arc 
 
 formed by means of an alternating current. 
 
 In order to avoid the extinction of the arc a 
 certain number of alternations per second is nec- 
 essary. The alternating arc produces a loud 
 singing noise. At very high frequencies, how- 
 ever, the noise disappears. 
 
 The alternating arc, not possessing a fixed posi- 
 tive crater, requires to be covered by a good 
 reflector to- throw the light downward. 
 
 Arc, Ampere A single conductor 
 bent in an arc of a circle, and used in electric 
 balances for measuring the electric current. 
 
 Arc Blow-Pipe. (See Blow-Pipe, Elec- 
 tric Arc.} 
 
 Arc, Compound An arc formed 
 
 between more than two .eparate electrodes. 
 
 Arc, Counter Electromotive Force of 
 
 An electromotive force generally be- 
 lieved to be set up on the formation of a 
 voltaic arc, opposed in direction to the electro- 
 motive force maintaining the arc. (See Force, 
 Electromotive, Counter?] 
 
 This counter electromotive force is believed to 
 have its origin partly in the energy absorbed at 
 the crater of the positive carbon, where the car- 
 bon is volatilized, and given out at the nipple on 
 the negative carbon, where it is deposited or 
 solidified. It is to be noted in this connection 
 that the apparent resistance of the carbon voltaic 
 arc is not directly proportional to the length of 
 the arc. 
 
 Arc, Electric A term sometimes 
 
 used for the voltaic arc. (See Arc, Voltaic?) 
 
 Arc, Frying of A frying sound at- 
 tending the formation of a voltaic arc when 
 the carbons are too near together. 
 
 The cause of the frying sound is probably the 
 same as that of hissing. (See Arc, Hissing of .) 
 
 Arc, Hissing of A hissing sound 
 
 attending the formation of voltaic arcs when 
 the carbons are too near together. 
 
 The cause of the hissing is not entirely under- 
 stood. Prof. Elihu Thomson suggests that it is 
 due to a too rapid volatilization of the carbons. 
 
 Arc Lamp. (See Lamp, Arc.} 
 Arc Lamp, Electric (See Lamp, 
 Electric Arc.) 
 
 Arc Lamp, Triple -Carbon Electric 
 
 (See Lamp, Arc, Triple Carbon Electric.) 
 Arc Lighting. (See Lighting, Arc.) 
 
 Arc, Metallic A voltaic arc formed 
 
 between metallic electrodes. 
 
 When the voltaic arc is formed between metallic 
 electrodes instead of carbon electrodes, a flaming 
 arc is obtained, the color of which is characteristic 
 of the burning metal ; thus copper forms a brill- 
 iant green arc. The metallic arc, as a rule is 
 much longer than an arc with the same current 
 taken between carbon electrodes. 
 
 Arc Micrometer. (See Micrometer, Arc.) 
 
Arc.] 
 
 26 
 
 [Arc. 
 
 Arc, Noisy A voltaic arc, the 
 
 maintenance of which is attended by frying, 
 hissing, or spluttering sounds. 
 
 Arc, Quiet A voltaic arc which is 
 
 maintained without sensible sounds. 
 
 Arc, Roaring of A roaring sound 
 attending the formation of a voltaic arc when 
 the carbons are too near together and a very 
 powerful current is used. 
 
 Arc, Simple An arc formed be- 
 tween two electrodes. 
 
 Arc, Spluttering of A spluttering 
 
 sound attending the formation of a voltaic 
 arc. 
 
 Prof. Elihu Thomson suggests that the cause of 
 spluttering is due to the presence of impurities in 
 the carbons, or from the sudden evolution of gas 
 from insufficiently baked carbons. 
 
 Arc, Voltaic The brilliant arc or 
 
 bow of light which appears between the elec- 
 trodes or terminals, generally of carbon, of a 
 sufficiently powerful source of electricity, when 
 separated a short distance from each other. 
 
 The source of light of the electric arc lamp. 
 
 It is tailed the voltaic arc because it was first 
 obtained by the use of the battery invented by 
 Volta. The term arc was given to it from the 
 shape of the luminous bow or arc formed between 
 the carbons. 
 
 To form the voltaic arc the carbon electrodes 
 are first placed in contact and then gradually 
 separated. A brilliant arc of flame is formed be- 
 tween them, which consists mainly of volatilized 
 carbon. The electrodes are consumed, first, by 
 actual combination with the oxygen of the air; 
 and, second, by volatilization under the combined 
 influence of the electric current and the intense 
 heat. 
 
 As a result of the formation of the arc, a crater 
 is formed at the end of the positive carbon, and 
 appears to mark the point out of which the 
 greater part of the current flows. 
 
 The crater is due to the greater volatilization 
 of the electrode at this point than elsewhere. 
 It marks the position of highest temperature of the 
 electrodes, and is the main source of the light of 
 the arc. " When, therefore, the voltaic arc is em- 
 ployed for the purposes of illumination with 
 vertically opposed carbons, the positive carbon 
 should be made the upper carbon, so that the 
 
 focus of greatest intensity of the light may be 
 favorably situated for illumination of the space 
 below the lamp. When, however, it is desired to 
 illumine the side of a building above an arc lamp, 
 the lower carbon should be made positive. 
 
 The positive carbon is consumed about twice as 
 rapidly as the negative, both because the negative 
 oxygen attacks the points of the positive carbon, 
 and because the positive carbon suffers the most 
 rapid volatilization. 
 
 The electric current passes through the space 
 occupied by the voltaic arc because 
 
 (I.) The heated arc is a partial conductor of 
 electricity. 
 
 (2.) Because small charges of electricity are 
 Carried bodily forward from the positive to the 
 negative carbon through the space of the voltaic 
 arc, by means of the minute particles which are 
 volatilized at the positive electrode. 
 
 S. P. Thompson has shown that the tempera- 
 ture of the light-emitting surface of the carbon is 
 the temperature of the volatilization of carbon, 
 and is therefore constant. 
 
 Dr. Fleming found that " A rise of potential 
 along the arc takes 
 place very suddenly, 
 just in the neighbor- 
 hood of the crater." 
 
 The crater in the 
 end of the positive car- 
 bon is seen in Fig. 18. 
 On the opposed end 
 of the negative carbon 
 a projection or nipple 
 is formed by the de- 
 posit of the electrical- 
 ly volatilized carbon. 
 Fig. 18. Voltaic Arc. The rounded masses 
 or globules that appear on the surface of the elec- 
 trodes are due to deposits of molten foreign mat- 
 ters in the carbon. 
 
 The carbon, both of the crater and its opposed 
 nipple, is converted into pure, soft graphite. 
 
 Arc, Voltaic, Resistance of The 
 
 resistance offered by the voltaic arc to the 
 passage of the current. 
 
 As in all other conductors, the ohmic resistance 
 of the arc increases with its length, and decreases 
 with its area of cross-section. The apparent 
 resistance, however, is not directly proportional 
 to the length. An increase of temperature de- 
 creases the resistance of the voltaic arc. 
 
Arc.] 
 
 27 
 
 [Arm. 
 
 The total apparent resistance of the voltaic arc 
 is composed of two parts, viz.: 
 
 (I.) The true ohmic resistance. (See Resist- 
 ance, Ohmic.) 
 
 (2.) The counter electromotive force, or spuri- 
 ous resistance. (See Resistance, Spurious.} 
 
 Arc, Watt 
 
 A voltaic arc, the elec- 
 
 tric power of which is equal to a given number 
 of watts. 
 
 The ordinary long-arc, as employed in arc 
 lighting, has a difference of potential of about 45 
 volts and a current strength of about 10 amperes. 
 It is, therefore, a 45O-watt arc. 
 
 Arch, Auroral The archlike form 
 sometimes assumed by the auroral light. (See 
 Aurora Borealis?) 
 
 Arcing. Discharging by means of voltaic 
 arcs. (See Arc, Voltaic?) 
 
 Arcing at the commutator of a dynamo-electric 
 machine not only prevents the proper operation 
 of the machine, but eventually leads to the de- 
 struction of the brushes and the commutator. 
 
 Areometer, Bead A form of are- 
 ometer suitable for rapidly testing the density 
 of the liquid in a storage cell. 
 
 The bead areometer consists of a glass tube, 
 open at both top" and bottom, containing a few 
 glass beads, so weighted as to float at liquid 
 densities such as 1.105, 1.170, 1.190 
 and 1. 200. To use the instrument, 
 it is immersed in the liquid of the 
 storage cell, and then withdrawn. 
 The finger being kept in the upper 
 opening, the liquid does not escape 
 through the small opening at the 
 bottom. The density is then ascer- 
 tained by noting the beads that 
 float. 
 
 Areometer or Hydrometer. 
 
 An instrument for determin- 
 ing the specific gravity of a liquid. 
 A common form of hydrometer 
 consists, as shown in Fig. 19, of a 
 closed glass tube, provided with a 
 bulb, and filled at the lower end 
 with mercury or shot, so as to in- 
 sure its vertical position when Fig. 19. H v - 
 floating in a liquid. When placed drometer. 
 in different liquids, it floats with part of the tube 
 out of the liquid. The lighter the liquid, the 
 2 Vol. 1 
 
 smaller is the portion that remains out of the 
 liquid when the instrument floats. The specific 
 gravity is determined by observing the depth to 
 which the instrument sinks when placed in different 
 liquids, as compared with the depth it sinks when 
 placed in water. 
 
 Areometry. The measurement of specific 
 gravity by means of an areometer. 
 
 Argaud Burner, Electric Hand-Lighter 
 (See Burner, Argand, Electric Hand- 
 Lighter^) 
 
 Argand Burner, Electric Plain-Pendant 
 (See Burner, Plain Pendant, Argand, 
 Electric?) 
 
 Argand Burner, Electric Ratchet-Pen- 
 dant (See Burner, Ratchet-Pendant, 
 Argand, Electric?) 
 
 Argyroinetry. The art of determining 
 the weight of electrolytically deposited silver. 
 (See Balance, Plating?) 
 
 Arm, Balance One of the resist- 
 ances of an electric balance. (See Arms, 
 Bridge or Balance. Bridge, Electric?) 
 
 Arm, Bridge -. A bridge arm. (See 
 Arms, Bridge or Balance?) 
 
 Arm, Cross A horizontal beam at- 
 tached to a pole for the support of the in- 
 sulators for telegraph, electric light or other 
 electric wires. 
 
 A telegraphic arm. (See Arm, Tele- 
 graphic?) 
 
 Arm, Rocker An arm on which the* 
 
 brushes of a dynamo or motor are mounted 
 for the purpose of shifting their position on 
 the commutator. 
 
 Arm, Semaphore - The movable 
 arm of the signal apparatus employed in block 
 systems for railroads, for the purpose of in- 
 forming engineers of trains of the condition 
 of the road as regards other trains. 
 
 In the absolute block system, as used on some 
 roads, there are two positions for the semaphore 
 arm, viz.: 
 
 (I.) For Danger when in a horizontal position, 
 or at 90 degrees with the vertical supporting pole. 
 
 (2.) Clear when dropped below the horizontal 
 position through an angle of 75 degrees. 
 
 In the Permissive Block System, a third position 
 
Arm.] 
 
 28 
 
 [Arm. 
 
 intermediate between the ist and the 2d, or at an 
 angle of 37 degrees 30 minutes with the horizontal 
 position, is used for caution. (See Block System 
 for Railroads.} 
 
 Arm, Signal A semaphore arm. 
 
 (See Arm, Semaphored) 
 
 Arm, Telegraphic A cross-arm 
 
 placed on a telegraphic pole for the support 
 of the insulators. 
 
 These arms are generally called cross-arms. 
 
 Armature. A mass of iron or other 
 magnetizable material placed on or near the 
 pole or poles of a magnet. 
 
 In the case of a permanent magnet, the arma- 
 ture, when used as a keeper, is of soft iron and is 
 placed directly on the magnet poles. In this case 
 it preserves or keeps the magnetism by closing 
 the lines of magnetic J orce of the magnet through 
 the soft iron of the armature, and is then called a 
 keeper, (See Force, Magnetic, Lines of.) 
 
 In the case of an electro-magnet, the armature 
 is placed near the poles, and is moved toward 
 them whenever the magnet is energized by the 
 passage of the current through the magnetizing 
 coils. This movement is made against the action 
 of a spring or weights, so that on the loss of 
 magnetism by the magnet, the armature moves 
 from the magnet poles. (See Magnet, Permanent. 
 Magnet, Keeper of. ) 
 
 When the armature is of soft iron it moves to- 
 ward the magnet on the completion of the circuit 
 through its coils, no matter in what direction 
 the current flows, and is then called a non-polar- 
 ized armature. (See Armature, Non-Polarized.} 
 
 When made of steel, or of another electro-mag- 
 
 Fig, 20. Bi-polar Armature. 
 
 net, it moves from or toward the poles, accord- 
 ing to whether the poles of the armature are of 
 the same or of a different polarity from those of 
 the magnet. Such an armature is called a 
 polarized armature. (Sec Armature, Polarized.) 
 
 Armature, Bi-polar An armature 
 
 of a dynamo-electric machine the polarity of 
 which is reversed twice in every revolution 
 through the field of the machine. 
 
 A form of bi-polar armature is shown in Fig. 20. 
 The word bi-polar armature is not generally 
 employed. The term applies rather to the field- 
 magnet poles than to the armature. 
 
 Armature Bore. (See Bore, Armature.) 
 
 Armature Bore, Elliptical (See 
 Bore, Elliptical Armature?) 
 
 Armature Chamber. (See Chamber, 
 Armature?) 
 
 Armature Coils, Dynamo 
 
 (See 
 
 Coils, Armature, of Dynamo-Electric Ma- 
 chine?) 
 
 Armature Core, Dynamo - (See 
 
 Core, Armature, of Dynamo-Electric Ma- 
 chine?) 
 
 Armature, Cylindrical - A term 
 sometimes applied to a drum armature. 
 (See Armature, Drum. Armature, Dy- 
 namo-Electric Machine?) 
 
 Armature, Cylindrical Ring. A ring 
 armature with a core in the shape of a com- 
 paratively long cylinder. 
 
 Armature, Disc An armature of a 
 dynamo-electric machine, in which the arma- 
 ture coils consist of flat coils, supported on 
 the surface of a disc. (See Armature, Dy- 
 namo-Electric Machine?) 
 
 Armature, Dissymmetrical Induction of 
 
 Any induction produced in the arma- 
 ture of a dynamo-electric machine that is un- 
 equal in amount on opposite halves, or in sym- 
 metrically disposed portions of the armature. 
 
 Dissymmetrical induction in the armature may 
 cause annoying or injurious sparking at the com- 
 mutator. It may arise 
 
 ( i ) From a lack of symmetry in the amount of 
 the armature windings. 
 
 (2.) From a lack of symmetry in the arrange- 
 ment of the armature windings on the armature 
 core. 
 
 (3. ) From a lack of symmetry of the pole pieces 
 of the machine. 
 
 (4.) From an improper position of the brushes 
 
Arm.] 
 
 Arm. 
 
 as regards the neutral point on the commutator, 
 causing a temporary short-circuiting of one or 
 more of the armature coils. 
 
 Armature, Drum An armature of 
 
 a dynamo-electric machine, in which the 
 armature coils are wound longitudinally over 
 the surface of a cylinder or drum. (See 
 Armature, Dynamo-Electric Machine^ 
 
 A form of drum-armature is shown in Fig. 21. 
 
 Fig. 21. Drum- Armature. 
 
 Armature, Dynamo-Electric Machine 
 
 The coils of insulated wire together 
 
 with the iron armature core, on or around 
 which the coils are wound. 
 
 That part of a dynamo-electric machine in 
 which the differences of potential which 
 cause the useful currents are generated. 
 
 Generally, that portion of a dynamo-elec- 
 tric machine which is revolved between the 
 pole pieces of the field magnets. 
 
 The armature of a dynamo-electric machine 
 usually consists of a series of coils of insulated 
 wire or conductors, wrapped around or grouped 
 on a central core of iron. The movement of 
 these wires or conductors through the magnetic 
 field of the machine produces an electiic cur- 
 rent by means of the electromotive forces so gen- 
 erated. Sometimes the field is rotated ; some- 
 times both armature and field rotate. 
 
 The armatures of dynamo-electric machines 
 are of a great variety of forms. They may for 
 convenience be arranged under the following 
 heads, viz.: 
 
 Cylindrical or drum-armatures, disc-arma- 
 tures, pole-or-radial armatures, ring armatures, 
 (utd spherical-armature*. For further particulars 
 see above terms. Armatures are also Divided 
 
 into classes according to the character of the 
 magnetic field through which they move viz.: 
 unipolar, bipolar, and multipolar armatures. 
 
 The English sometimes use the word cylindrical 
 armature as a synonym of ring-armature. 
 
 A unipolar-armature is one whose polarity is 
 never reversed. A bipolar-armature is one in 
 which the polarity is reversed twice in every 
 rotation; multipolar armatures have their po- 
 larity reversed a number of times in every rota- 
 tion. 
 
 The term armature as applied to a dynamo- 
 electric machine was derived from the fact that 
 the iron core acts to magnetically connect the 
 two poles of the field magnets in the same 
 manner that an ordinary armature connects the 
 poles of a magnet. 
 
 Armature, Flat Ring A ring-arma- 
 ture with a core in the shape of a short cylin- 
 drical ring. 
 
 Armature, Girder - An armature 
 with an H -shaped or girder-like core. ^ 
 
 An H -shaped armature. 
 
 Armature, Intensity An old term 
 for an armature with coils of many turns and 
 of a comparatively high resistance. 
 
 Armature, Lamination of Core of 
 A division of the iron core of the armature 
 of a dynamo-electric machine or motor, so as 
 to avoid the formation of eddy-currents 
 therein. (See Core, Lamination of. Cur- 
 rents, Eddy?) 
 
 Armature, Multipolar A dynamo- 
 electric machine armature whose polarity is 
 reversed more than twice during each rotation 
 in the field of the machine. 
 
 Armature, Neutral A non-polarized 
 armature. (See Armature, Non-Polarized^ 
 
 Armature, Neutral-Relay A relay 
 
 armature, consisting of a piece of soft iron, 
 which closes a local circuit whenever its elec- 
 tro-magnet receives an impulse over the main 
 line. (See Armature, Polarized?) 
 
 This term is applied in contradistinction to a 
 polarized relay armature. 
 
 Armature, Non-Polarized An 
 
 armature of soft iron, which is attracted toward 
 the poles of an electro-magnet on the como 1 " 
 
Arm.] 
 
 30 
 
 [Arm. 
 
 tion of the circuit, no matter in what direc- 
 tion the current passes through the coils. 
 
 The term non-poiarized is ustd in contradistinc- 
 tion to polarized armature. (See Armature, 
 Polarized. ) 
 
 Th non-polanztd armature of a relay magnet 
 is generally called the netitral -relay armature. 
 
 Armature of a Cable, or Cable-Armature. 
 
 A term sometimes employed for the sheath- 
 ing or protecting coat of a cable. 
 
 The term armor sheathing or coating is prefer- 
 able. 
 
 Armature of a Condenser, or Condenser 
 Armature. A term sometimes applied to 
 the metallic plates of a condenser or Leyden 
 jar. 
 
 The use of this term is unnecessary and iU- 
 advised. The term coating or plate would appear 
 to be preferable. 
 
 Armature of Holtz Machine, or Holtz- 
 Machine Armature. The pieces of paper 
 that are placed on the stationary' plate of the 
 Holtz and other similar electrostatic induction 
 machines. 
 
 Armature Pockets. (See-Poc6ets, Arma- 
 ture.) 
 
 Armature, Polarized An armature 
 
 which possesses a polarity independent of 
 that imparted by the magnet pole near which 
 it is placed. 
 
 In permanent magnets the armatures are made 
 of soft iron, and therefore, by induction, become 
 of a polarity opposite to that of the magnet poles 
 that lie nearest them. They have, therefore, only 
 a motion of atiraction toward such poles. (See 
 Induction, Magnetic. ) 
 
 In electro-magnets the armatures may either be 
 made of soft iron, in which case they are attracted 
 only on the passage of the current; or they may 
 be formed of permanent steel magnets, rr may be 
 electro- magnets themselves, in which case the pas- 
 sage of the current through the coils of the elec- 
 tro-magnet, or electro- magnets, may cause either 
 attraction or repulsion, according as the adjacent 
 poles are of opposite polarity or are of the same 
 polarity. 
 
 Armature. Pole An armature the 
 coils of which are wound on separate poles 
 
 that project radially from the periphery of a 
 disc, drum or ring. 
 
 A pole-armature showing the arrangement of 
 
 Fig. 22. Pole-Armature. 
 
 the coils and their connection to the commutator 
 segments is seen in Fig. 22. 
 
 Armature, Quantity An old term 
 
 for an armature wound with but a few coils 
 of comparatively low resistance. 
 
 Armature, Radial - A term some- 
 times used instead of pole-armatune. (See 
 Armature, Pole.) 
 
 Armature, Ring: A dynamo-electric 
 machine armature, the coils of which are 
 wound on a ring-shaped core. 
 c 
 
 Fig. 23. Ring-Armaturt, 
 
 A ring-armature is shown in Fig. 23, together 
 with the disposition of the coils and their connec- 
 tion to the segments of the commutator. 
 
 Armature, Shuttle A variety of 
 
 drum armature in which a single coil of 
 wire is wound in an H-shaped groove formed 
 in a bobbin shaped core. 
 
 The old form of Siemens-armature. 
 
 Armature, Single-Loop A closed 
 
 conducting circuit consisting of a single loop, 
 capable of revolving in a magnetic field so as 
 to cut its lines of force. 
 
 Armature, Spider. (See Spider, Arma- 
 ture) 
 
Arm.] 
 
 31 
 
 [A.rr. 
 
 Armature, Spherical 
 
 A dynamo- 
 
 electric machine armature, the coils of which 
 are wound on a spherical iron core. 
 
 The Thomson-Houston dynamo, which is the 
 only machine employing an armature of this type, 
 has its armature formed by wrapping three coils 
 of insulated wire on a core of iron so shaped as 
 to insure an approximately spherical armature 
 when wrapped. 
 
 Armature, Toothed-Ring An ar- 
 mature, the core of which is in the shape of 
 a ring, provided with a number of teeth in the 
 spaces between which the armature coils are 
 placed. 
 
 Armature, Unipolar A dynamo- 
 electric machine armature whose polarity is 
 not reversed during its rotation in the field 
 of the machine. 
 
 Armature, Ventilation of A pro- 
 cess for insuring the free passage of air 
 through the armature of a dynamo-electric 
 machine in order to prevent overheating. 
 
 Armor of Cable. (See Cable, Armor of.) 
 
 Armored Cable. (See Cable, Armored?) 
 
 Armored Conductor. (See Conductor, 
 Armored.} 
 
 Arms, Bridge or Balance The 
 
 electric resistances, in the electric balance or 
 bridge. (See Bridge, Electric?) 
 
 J'o 
 
 Fig. 24.. Arms of Balance. 
 
 An unknown resistance, such, for example, as 
 D, Fig. 24, is measured by proportioning the 
 known resistances, A, C ana B, so that no current 
 flows through the galvanometer G, across the 
 circuit 9r bridge M G N. 
 
 Arms, Proportionate The two re- 
 sistances or arms of an electric bridge whose 
 relative or proportionate resistances only are 
 required to be known in order to determine, 
 
 in connection with a known resistance, the 
 value of an unknown resistance placed in the 
 remaining arm of the bridge. 
 
 Thus is Fig. 24, A and B, are the proportionate 
 arms. 
 
 Arrangement or Device, Electromotive 
 A term sometimes employed to rep- 
 resent a dynamo-electric machine, voltaic cell 
 or other electric source, by means of which 
 electromotive force can be produced. 
 
 Electric sources do not produce electric cur- 
 rents, but differences of potential or electro- 
 motive force. Electric sources are therefore very 
 properly termed electromotive devices. 
 
 Arrester, Lightning A device by 
 
 means of which the apparatus placed in any 
 electric circuit is protected from the destruc- 
 tive effects of a flash or bolt of lightning. 
 
 In the phenomena of lateral induction and 
 alternative path, we have seen the tendency of a 
 disruptive discharge to take a short-cut across an 
 intervening air space, rather than through a 
 longer though better conducting path. Most 
 lightning arresters are dependent for their opera- 
 tion on this tendency to lateral discharge. (See 
 Induction, Lateral. Path, Alternative.) 
 
 A form of lightning arrester is shown in Fig. 25. 
 
 Fig. 25. Comb Lightning- Arrester. 
 
 The line wires, A and B, are connected by two 
 metallic plates to C and D, respectively. 
 
 These plates are provided with points, as shown, 
 and placed near a third plate, connected to the 
 ground by the wire G. Should a bolt strike the 
 line, it is discharged to the earth through the 
 wire G. 
 
 Various forms are given to lightning arresters 
 of this type. The projections are sometimes placed 
 on the ground connected plate as well as on the 
 plates connected to line wires. This form is 
 sometimes called a comb arrester, or protector. 
 
Arr.J 
 
 32 
 
 [Ast. 
 
 Arrester, Lightning, Comb A 
 
 term sometimes applied to a lightning ar- 
 rester in which both the line and ground 
 plates are furnished with a series of teeth, 
 like those on a comb. (See Arrester, Light- 
 ning) 
 
 Arrester, Lightning, Counter-Electro- 
 motive Force A lightning arrester, 
 in which the passage of the discharge through 
 the instruments to be protected is opposed 
 by a counter-electromotive force, generated 
 by induction on the passage of the discharge 
 of the bolt to earth. 
 
 The counter-electromotive force lightning ar- 
 rester is an invention of Professor Elihu Thomson. 
 
 It assumes a variety of forms. In the shape 
 shown in Fig. 26, the line circuit of the dynamo, 
 
 Fig. 26. Counter-Electromotive Force Lightning 
 Arrester. 
 
 D, has one end connected to ground, and the 
 other end has two conducting paths to ground. 
 One of these paths is through the ordinary comb- 
 protector at P, by the ground plate E; this cir- 
 cuit includes a few turns 
 of wire C'. The other 
 path is through a corres- 
 ponding coil C, either 
 interior or exterior to C', 
 so as to be within its in- 
 ductive field. As will be 
 seen from the figure, C, is 
 ~Fig. 27. Counter-Elec. connected through the 
 tromotive Force Light- machine to the ground. 
 tiing Arrester. The induction coils C 
 
 and C', are thoroughly insulated from each 
 other. 
 
 Should a lightning flash or other static discharge 
 pass through the circuit C', which is of compara- 
 tively low self-induction, a counter-electromotive 
 force is produced in the other coil C, which 
 protects the line circuit. 
 
 In the form of lightning arrester shown in 
 Fig. 27, the coil in the path of the direct light- 
 ning discharge is formed into an exterior mesh or 
 net work surrounding the dynamo to be pro- 
 tected. In this case, the coils of the dynamo act 
 as the secondary coils in which the counter elec- 
 tromotive force is set up. 
 
 Arrester, Lightning, Transformer - 
 
 A form of lightning arrester designed for 
 the protection of transformers. 
 
 The Thomson arrester for transformers oper- 
 ates on the same principle as his arc-line pro- 
 tector. In the latter the arc, when formed, 
 is blown out by the action of the field of an 
 electro-magnet. This arc is formed on curved 
 metallic bows, one of which is connected to line 
 and the other to earth. The arc is formed at the 
 smallest interval between the bows, and is extin- 
 guished by being driven by action of a magnetic 
 field toward greatest interval. 
 
 Arrester Plate of Lightning Protector. 
 
 (See Plate, Arrester, of Lightning Pro- 
 tector^) 
 
 Arrester Plates. (See Plates, Arrester?) 
 
 Articulate Speech. (See Speech, Articu- 
 late^ 
 
 Artificial Carbons. (See Carbons, Arti- 
 ficial) 
 
 Artificial Illumination. (See Illumina- 
 tion, Artificial.) 
 
 Artificial Line. (See Line, Artificial) 
 Artificial Magnet. (See Magnet, Arti- 
 ficial) 
 
 Asphyxia. Suspended respiration, result- 
 ing eventually in death, from non-aeration of 
 the blood. 
 
 In cases of insensibility by an electric shock a 
 species of asphyxia is sometimes brought about. 
 This is due, probably, to the failure of the nerves 
 and muscles that carry on respiration. The exact 
 manner in which death by electrical shock results 
 is not known. (See Death, Electric.) 
 
 Assymrnetrical Resistance. (See Resist- 
 ance, Assymmetrical?) 
 
 Astatic. Possessing no directive power. 
 
 Usually applied to a magnetic or electro-mag, 
 netic-device which is free from any tendency to 
 take a definite position on account of the earth's 
 magnetism. 
 
Ast.] 
 
 33 
 
 [Ato. 
 
 Astatic Circuit. (See Circuit, Astatic?) 
 Astatic Couple. See Couple, Astatic?) 
 Astatic Galvanometer. (See Galvanom- 
 eter, Astatic.) 
 
 Astatic Needle. (See Needle, Astatic?) 
 
 Astatic Pair. (See Pair, Astatic) 
 
 Astatic System. (See System, Astatic) 
 
 Astronomical Meridian. (See Meridian, 
 Astronomical?) 
 
 Asymptote of Curve. (See Curve, Asymp- 
 tote of) 
 
 Atmosphere, An A unit of gas or 
 
 fluid pressure equal to about 1 5 pounds to the 
 square inch. 
 
 At the level of the sea the atmosphere exerts a 
 pressure of about 15 pounds avoirdupois, or, 
 more accurately, 14.73 pounds, on every square 
 inch of the earth's surface. This value has there- 
 fore been taken as a unit of fluid pressure. 
 
 For more accurate measurements pounds to the 
 square inch are employed. 
 
 In the metric system of weights and measures 
 an atmosphere is considered equal to 1,033 
 grammes per square centimetre. 
 
 Atmospheric pressures are measured by instru- 
 ments called Manometers. (See Manometer.) 
 
 Atmosphere, Residual The traces 
 of air or other gas remaining in a space which 
 has been exhausted of its gaseous contents 
 by a pump or other means. 
 
 It is next to impossible to remove all traces of 
 air trom a vessel by any known form of pump or 
 oiher appliance. (See Vacuum, Absolute.) 
 
 Atmosphere, The The ocean of ' 
 
 air which surrounds the earth. 
 
 The atmosphere is, approximately, composed, 
 by weight, of oxygen 23 parts, and nitrogen 77 
 parts. Besides these there are from 4 to 6 parts 
 in 10,000 of carbonic acid gas (or about a cubic 
 inch of carbonic acid to a cubic foot of air), and 
 varying proportions of the vapor of water. 
 
 1 he oxygen, nitrogen and carbonic acid form 
 the constant ingredients of the atmosphere, the 
 vapor of water the variable ingredient. There 
 are in most localities a number of other variable 
 ingredients present as impurities. 
 
 Atmospheric Electricity. (See Electric- 
 ity, Atmospheric) 
 
 Atmospheric Electricity, Origin of 
 
 (See Electricity, Atmospheric, Origin of) 
 
 Atom. The smallest quantity of elemen- 
 tary or simple matter that can exist. 
 An ultimate particle of matter. 
 
 Atom means that which cannot be cut. It is 
 generally believed that material atoms are abso- 
 lutely unalterable in size, shape, weight and den- 
 sity ; that they can neither be cut, scratched, 
 flattened, nor distorted ; and that they are un- 
 affected in size, density, or shape, by heat or 
 cold, or by any known physical force. 
 
 Although almost inconceivably small, atoms 
 nevertheless possess a definite size and mass. 
 According to Sir William Thomson, the smallest 
 visible organic particle, 1-4000 of a millimetre in 
 diameter, will contain about 30,000,000 atoms. 
 
 Atom, Closed-Magnetic Circuit of 
 
 (See Circuit, Closed-Magnetic, of Atom?) 
 
 Atom, Gramme - Such a number 
 of grammes of any elementary substance as is 
 numerically equal to the atomic weight of 
 the substance. 
 
 The gramme-atom of a substance represents 
 the number of calories required to raise the tem- 
 perature of one gramme ot that substance through 
 I degree C. (See Heat, Atomic. Calorie.) Thus, 
 in the case of chlorine, whose atomic weight is 
 35.5, its gramme-atom is 35.5 ; consequently 
 35.5 small calories of heat would be required to 
 raise one gramme-atom of chlorine through I 
 degree C. 
 
 Atom of Electricity. (See Electricity, 
 Atom of.) 
 
 Atom, Yortex A number of particles 
 of the universal ether moving in the manner 
 of a vortex ring. 
 
 The theory of vortex atoms, so formed from 
 vortex rings, was propounded by Sir William 
 Thomson in order to explain how a readily mov- 
 able substance, like the universal ether, could be 
 made to possess the properties of a rigid solid. If 
 it be granted that a vortex motion has once been 
 imparted to the universal ether, Thomson shows 
 that such rings would be indestructible. (See 
 Matter, Thomson's Hypothesis of.) 
 
 Atomic Attraction. (See Attraction, 
 Atomic?) 
 
Ato.] 
 
 34 
 
 [Att. 
 
 Atomic Capacity. (See Capacity, Atom- 
 ic?) 
 
 Atomic Currents. (See Currents, Atom- 
 ic.} 
 
 Atomic Energy. (See Energy, Atomic?) 
 Atomic Heat. (See Heat, Atomic?) 
 
 Atomic or Molecular Induced Currents. 
 
 (See Currents, Induced, Molecular or 
 Atomic?) 
 
 Atomic Weight. (See Weight, Atomic.} 
 
 Atomicity. The combining capacity of 
 the atoms. 
 
 The relative equivalence of the atoms or 
 their atomic capacity. 
 
 The elementary atoms do not always combine 
 atom for atom. Some single atoms of certain 
 elements will combine with two, three, four, or 
 even more atoms of another element. 
 
 The value of the atomic capaciiy of an atom is 
 also called its quantivalence or valency. 
 Elements whose atomic capacity is 
 
 One, are called Monads, or Univalent. 
 Two, " Dyads, " Bivalent. 
 
 Three, " Triads, " Trivalent. 
 
 Four, " Tetrads, " OuaJiivalent. 
 
 Five, " Pentads, " Quinquivalent 
 
 Six, " Hexads, " Sexivalent. 
 
 Seven, " Heptads, " Septivalent. 
 
 Atomization. The act of obtaining liquids 
 in a spray of finely divided particles. 
 
 In most cases the term is not literally correct, 
 as each of the smallest particles so obtained usu- 
 ally consist of many thousands of atoms. 
 
 Atomize. To separate into a fine spray by 
 means of an atomizer., (See Atomizer?) 
 
 Atomizer. An apparatus for readily ob- 
 taining a finely divided jet or spray of liquid. 
 
 A jet of steam, or a blast of air, is driven across 
 the open end of a tube that dips below the surface 
 of the liquid to be atomized. The partial vacuum 
 so formed draws up the liquid, which is then 
 blown by the current into a fine spray. 
 
 Attract. To draw together. 
 Attracted-Disc Electrometer. (See Elec- 
 trometer, Attracted-Disc} 
 
 Attracting 1 . Drawing together. 
 
 Attraction. Literally the act of drawing 
 together. 
 
 In science the name attraction is given to a 
 series of unknown causes which effect, or are as- 
 sumed to effect, the drawing together of atoms, 
 molecules or masses. 
 
 Attraction and repulsion underlie nearly all 
 natural phenomena. While their effects are well 
 known, it is doubtful if anything is definitely 
 known of their true causes. 
 
 Since attraction, pure and simple, necessitates 
 the belief in action at a distance, an action which 
 is now generally discredited, we must, strictly 
 speaking, regard the term attraction as being but 
 a convenient substitution of the effect for the 
 cause. 
 
 It would appear much more reasonable to re- 
 gard the effects of attraction as produced by a 
 true push exerted from the outside of the bodies. 
 According to this notion, two mas-ses of matter 
 undergoing attraction are pushed together rather 
 than drawn or attracted together. 
 
 It has been suggested that gravitation may per- 
 haps be an effect of a longitudinal motion or vibra- 
 tory thrust in the universal ether. If this is the 
 case, and the ether is sensibly incompressible, the 
 velocity of gravitation, it would appear, should be 
 almost infinite. 
 
 Attraction, Atomic The attraction 
 
 which causes the atoms to combine. (See 
 Affinity, Chemical.} 
 
 In the opinion of Lodge, atomic attraction is 
 the result of the attraction of dissimilar charges of 
 electricity possessed by all atoms, which are capa- 
 ble of uniting or entering into chemical combi- 
 nation. (See Electricity, Atom of.} 
 
 Attraction, Capillary - The molec- 
 ular attractions that are concerned in 
 capillary phenomena. (See Capillarity?) 
 
 Attraction, Electro-Dynamic The 
 
 mutual attraction of electric currents, or of 
 conductors through which electric currents 
 are passing. (See Dynamics, Electro.} 
 
 Attraction, Electro-Magnetic The 
 
 mutual attraction of the unlike poles of 
 electro-magnets. (See Magnet, Electro.\ 
 
 Attraction, Electrostatic The 
 
 mutual attraction exerted between unlike 
 electric charges, or bodies possessing unlike 
 ~'ectric charges. 
 
Att.] 
 
 35 
 
 [Aur. 
 
 For example, the pith hall supported on an in- 
 sulated string is attracted, as shown at A, Fig. 28, 
 
 Fig, 28. Electrostatic 
 Attraction. 
 
 Fig. 29. Electrostatic 
 Repulsion. 
 
 by a bit of sulphur which has been briskly rubbed 
 by a piece of silk. As soon, however, as the ball 
 touches the sulphur and receives a charge, it is 
 repelled, as shown at B, Fig. 29. 
 
 These attractions ai d repulsions are due to the 
 effects of electrostatic induction. (See Induction, 
 Elfctrostatic. ) 
 
 Attraction, Magnetic 
 
 The mutual 
 
 attraction exerted between unlike magnet 
 poles. 
 
 Magnetic attractions and repulsions are best 
 shown by means of the magnetic needle N S, 
 Fig. 30. The N. pole of an approached magnet 
 
 Fig. 30. Magnetic Attraction. 
 
 attracts the S. pole of the needle but repels the 
 N. pole. 
 
 The laws of magnetic attraction and repulsion 
 may be stated as follows, viz.: 
 
 (i.) Magnet poles of the same name repel each 
 other; thus, a north pole repels another north 
 pole, a south pole repels another south pole. 
 
 (2.) Magnet poles of unlike names attract each 
 other; thus a north pole 5 
 
 attracts a south pole, or 
 a south pole attracts a N= 
 north pole. 
 
 A small bar magnet, Fig. 31. floating 
 N S, Fig. 31, laid on the Magnet. 
 
 top of a light vessel floating on the surface of a 
 liquid, may be readily employed to illustrate the 
 laws of magnetic attraction and repulsion. 
 
 Attraction, Mass The mutual at- 
 traction exerted between masses of matter. 
 (See Gravitation^) 
 
 Attraction, Molar A term some- 
 times employed for mass attraction. 
 
 Gravitation is an example of mass attraction, 
 where the mass of the earth attracts the mass of 
 some body placed near it. (See Gravitation.) 
 
 Attraction, Molecular The mutual 
 attraction exerted between neighboring 
 molecules. 
 
 The attraction of like molecules, or those of the 
 same kind of matter, is called Cohesion ; that of 
 unlike molecules, Adhesion. 
 
 The tensile strength of iron or steel is due to 
 the cohesion of its molecules. Paint adheres to 
 wood, or ink to paper, by cohesion or the attrac- 
 tion between tne unlike molecules. 
 
 Attraction of Gravitation. A term gen- 
 erally applied to the mutual attraction be- 
 tween masses. (See Gravitation) 
 
 Attractions and Repulsions of Currents. 
 
 (See Currents, Attractions and Repulsions 
 of.} 
 
 Audiphone. A thin plate of hard rubber 
 held in contact with the teeth, and maintained 
 at a certain tension by strings attached to one 
 of its edges, for the purpose of aiding the 
 hearing. 
 
 The plate is so held that the sound-waves from 
 a speaker's voice impinge directly against its flat 
 surface. It operates by means of some of the 
 waves being transmitted to the ear directly 
 through the bones of the head. 
 
 The audiphone is sometimes called a denti- 
 ph<ma. 
 
 Aural Electrode. (See Electrode, Aural.} 
 Aurora Australis. The Southern Light. 
 A name given to an appearance in the south- 
 
Aur.] 
 
 36 
 
 [Aut. 
 
 ern heavens similar to that of the Aurora 
 Borealis. (See Aurora Borealis} 
 
 Aurora Borealis. The Northern Light. 
 
 Luminous sheets, columns, arches, or pillars 
 of pale, flashing light, generally of a red color, 
 seen in the northern heavens. 
 
 The auroral light assumes a great variety of ap- 
 pearances, to which the terms auroral arch, bands, 
 coronas, curtains and streamers are applied. 
 
 The exact cause of the aurora is not as yet 
 known. It would appear, however, beyond any 
 reasonable doubt, that the auroral flashes are due 
 to the passage of electrical discharges through the 
 upper, and therefore rarer, regions of the atmos- 
 phere. The intermittent flashes of light are prob- 
 ably due to the discharges being influenced by the 
 earth's magnetism. 
 
 Auroras are frequently accompanied by mag- 
 netic storms. (See Storm, Magnetic. ) 
 
 The occurrence of auroras is nearly always 
 simultaneous with that of an unusual number of 
 sun spots. Auroras are therefore probably con- 
 nected with outbursts of the solar energy. (See 
 Spots, Sun.) 
 
 The auroral light examined by the spectroscope 
 gives a spectrum characteristic of luminous gaseous 
 matter, i. e., contains a few bright lines; but, ac- 
 cording to S. P. Thompson, this spectrum is pro- 
 duced by matter that is not referable with cer- 
 tainty to that of any known substance. 
 
 Whatever may be the exact cause of auroras, 
 their appearance is almost exactly reproduced by 
 the passage of electric discharges through vacua. 
 
 Aurora Polaris. A general term some- 
 times applied to aurora in the neighborhood 
 of either pole, or in either the northern or 
 the southern hemisphere. 
 
 Auroral Arch. (See Arch, Auroral} 
 Auroral Bauds. (See Bands, Auroral} 
 Auroral Coronae. (See Corona, Au- 
 roral?) 
 
 Auroral Curtain. (See Curtain, Au- 
 roral.} 
 
 Auroral Flashes. (See Flashes, Auroral.} 
 Auroral Light (See Light, Auroral} 
 Auroral Storm. (See Storm, Auroral} 
 Auroral Streamer. (See Streamer, Au- 
 roral} 
 Auroras and Magnetic Storms, Peri- 
 
 odicity of 
 
 Observed coincidences be- 
 
 tween the occurrence of auroras, magnetic 
 storms, and sun-spots. 
 
 The occurrence of auroras, or magnetic storms, 
 at periods of about eleven years apart, corre- 
 sponds to the well-known eleven-year sun-spot 
 period. 
 
 The period also agrees with a variation in the 
 magnetic declination of any place, which, accord- 
 ing to Sabine, occurs once in every eleven years. 
 
 Austral Magnetic Pole. (See Pole, Mag- 
 netic, Austral} 
 
 Autographic Telegraphy. (See Teleg- 
 raphy, Autographic} 
 
 Automatic Annunciator Drop. (See 
 Drop, Annunciator, Automatic} 
 
 Automatic Bell. v See Bell, Automatic 
 Electric} 
 
 Automatic Contact Breaker. (See Con- 
 tact Breaker, Automatic} 
 
 Automatic Cut-Out. (See Cut-Out, Au- 
 tomatic} 
 
 Automatic Cut-Out for Multiple-Connect- 
 ed Electro-Receptive Devices. (See Cut- 
 Out, Automatic, for Multiple-Connected 
 Electro-Receptive Devices.) 
 
 Automatic Cut-Out for Series-Connected 
 Electro-Receptive Devices. (See Cut-Out, 
 Automatic, for Series-Connected Electro-Re- 
 ceptive Devices.) 
 
 Automatic Drop. (See Drop, Auto- 
 matic} 
 
 Automatic Electric Burner. (See Burn- 
 er, Automatic Electric} 
 
 Automatic Electric Safety System for 
 Railroads. (See Railroads, Automatic Elec- 
 tric Safety System for} 
 
 Automatic Fire-Alarm. (See Alarm, 
 Fire, Automatic} 
 
 Automatic Gas Cut-Off. (See Cut-Off, 
 Automatic Gas} 
 
 Automatic Indicator. (See Indicator, 
 Automatic} 
 
 Automatic Make-and-Break. (See Make- 
 and-Break, Automatic} 
 
 Automatic Oiler. (See Oiler, Automatic} 
 
Aut.] 
 
 37 
 
 [B. A, U. 
 
 Automatic Paper-Winder. (See Winder, 
 Telegraphic Paper.} 
 
 Automatic Regulation. (See Regulation, 
 Automatic.) 
 
 Automatic Regulator. (See Regulator, 
 Automatic.} 
 
 Automatic Search-Light. (See Light, 
 Search, Automatic.} 
 
 Automatic Switch for Incandescent Elec- 
 tric Lamp. (See Switch, Automatic, for 
 Incandescent Electric Lamp.} 
 
 Automatic Telegraphy. (See Teleg- 
 raphy, Automatic!) 
 
 Automatic Telephone Switch. (See 
 Switch, Telephone, Automatic?) 
 
 Automatic Time Cut-Outs. (See Cut- 
 Out, Automatic Time.} 
 
 Automatic Yariable Resistance. (See 
 Resistance, Variable, Automatic?) 
 
 Automatically Regulable. (See Regula- 
 ble, Automatically?) 
 
 Automobile Torpedo. (See Torpedo, Au- 
 tomobile?) 
 
 Average or Mean Electromotive Force. 
 (See Force, Electromotive, Average, or 
 Mean?) 
 
 Axes of Co-ordinates. (See Co-ordinates, 
 Axes of?) 
 
 Axial Magnet. (See Magnet, Axial?) 
 
 Axis, Magnetic The line around 
 
 which a magnetic needle, free to move, but 
 which has come to rest in a magnetic field, 
 can be turned without changing the set or 
 direction in which it has come to rest. 
 
 Axis, Magnetic, of a Straight Needle 
 A straight line drawn through the magnet, 
 joining its poles. 
 
 25 30 35 
 
 The magnetic axis of a straight needle may be 
 regarded as a straight line passing through the 
 poles of the needle and its point of support. 
 
 The magnetic axis may not correspond with 
 the geometric axis of the 
 needle. This leads to 
 an error in reading the 
 true direction in which 
 the needle is pointing, 
 which must be cor- 
 rected. Thus, the nee- 
 dle N S, Fig. 32, points 
 to 31 degrees on the 
 scale. In reality, if the 
 magnetic axis of the 
 needle lies in the line 
 N' S', the true deflec- 
 tion of the needle is only 
 28 degrees. 
 
 32. Magnetic 
 Axis. 
 
 Axis of Abscissas. (See Abscissas, Axis 
 of?) 
 
 Axis of Ordinates. (See Ordinates, Axis 
 of?) 
 
 Azimuth. In astronomy, the angular dis- 
 tance between an azimuth circle and the 
 meridian. 
 
 The azimuth of a heavenly body in the North- 
 ern Hemisphere is measured on the arc of the 
 horizon intercepted between the north point of 
 the horizon and the point where the great circle 
 that passes through the heavenly body cuts the 
 horizon. 
 
 Azimuth Circle. (See Circle, Azimuth?) 
 
 Azimuth Compass. (See Compass, Azi- 
 muth?) 
 
 Azimuth, Magnetic The arc inter- 
 cepted on the horizon between the magnetic 
 meridian and a great circle passing through 
 the observed body. 
 
 B. A contraction used in mathematical 
 writings for the internal magnetization, or the 
 magnetic induction, or the number of lines of 
 force per square centimetre in the magnetized 
 material. 
 
 This contraction for internal magnetization is, 
 
 in most mathematical treatises, printed in bold- 
 faced type. 
 
 B. A. Ohm. (See Ohm, B. A?) 
 
 B. A. U. A contraction sometimes em- 
 ployed for the British Association unit or ohm. 
 
B. W. G. 
 
 38 
 
 [Bal. 
 
 B. W. G. A contraction for Birmingham 
 wire gauge. (See Gauge, Birmingham 
 Wire.) 
 
 A contraction sometimes used for the new 
 British wire gauge. 
 
 Back Electromotive Force. (See Force, 
 Electr emotive, Sack.) 
 
 Back-Stroke of Lightning-. (See Light- 
 ning, Back-Stroke of.) 
 
 Bain's Chemical Recorder. (See Re- 
 corder, Chemical, Bain's.) 
 
 Bain's Printing Solution. (See Solution, 
 Bain's Printing) 
 
 Balance Arms. (See Arms, Bridge or 
 Balance?) 
 
 Balance, Bi-fllar Suspension An 
 
 instrument similar in construction to Cou- 
 lomb's torsion balance, but in which the 
 needle is hung by two separate fibres instead 
 of by a single one. (See Balance, Coulomb's 
 Torsion. Suspension, Bi-filar) 
 
 Balance, Centi-Ampdre An am- 
 meter in the form of a balance, whose scale is 
 graduated to give direct readings in centi- 
 amperes. 
 
 Ampere balances giving readings in various 
 decimals or multiples of amperes have been de- 
 vised by Sir William Thomson. The strength of 
 current passing is determined by the action on a 
 movable ring or coil, placed between iwo fixed 
 rings or coils. 
 
 The movable ring is in a horizontal' plane 
 nearly midway between the two fixed rings. 
 The fixed rings are traversed by the current 
 in opposite directions, so that one attracts 
 and the other repels the movable ring. The 
 movable ring is attached to one end of a horizon- 
 tal balance arm, and a similar movable ring, also 
 provided with attracting and repellinlg fixed rings, 
 is attached to the opposite end of the balance arm. 
 In order to avoid disturbance of horizontal com- 
 ponents of terrestrial, or of local magnetic force, 
 the current is sent in the same direction through 
 the two movable rings. The balancing is effected 
 by means of a weight, sliding on a nearly hori- 
 zontal arm attached to the balance. A counter- 
 poise weight is used in connection with the sliding 
 weight. 
 
 A standard Thomson centi-ampere balance 
 is shown in Fig. 33. In measuring a current, 
 
 *%" 33- Centi-Amptre. Balance. 
 
 the weight is moved along the scale until the 
 balance comes to rest. 
 
 Balance, Composite 
 
 A balance 
 
 form of ammeter devised by Sir William Thom- 
 son, which can be used for an ampere-meter, a 
 watt-meter, or a volt-meter, according to the 
 manner in which its sets of fine and coarse 
 wire coils are connected. (See Balance, 
 Centi- Ampere) 
 
 Balance, Coulomb's Torsion An 
 
 apparatus to measure the force of electric or 
 magnetic repulsion between two similarly 
 charged bodies, or between two similar mag- 
 net poles, by opposing to such force the tor- 
 sion of a thin wire. 
 
 The two forces balance each other ; hence the 
 origin of the name. 
 
 F'ff" 34' Coulomb's Torsion Balance. 
 
 Fig. 34 represents a Coulomb torsion bal- 
 ance, adapted to the measurement of .the force 
 
Bal.] 
 
 39 
 
 [Bal. 
 
 of electrostatic repulsion. A delicate needle of 
 shellac, having a small gilded pith ball at one of 
 its ends, is suspended by a fine metallic wire. A 
 proof -plane i B, is touched to the electrified surface 
 whose charge is to be measured, and is then 
 placed as shown in the figure. (See Plane, Proof.) 
 There is a momentary attraction of the needle, 
 anu. .u^"- a repulsion, which causes the needle to 
 be moved a cer+ain distance from the ball on the 
 proof-plane. This distance is measured in degrees 
 on a graduated circle a a, marked on the instru- 
 ment. The force of the repulsion is calculated by 
 determining the amount of torsion required to 
 move the needle a certain distance toward the 
 ball of the electrified proof-plane. 
 
 This torsion is obiained by the movement of the 
 torsion head D, the amount of which motion is 
 measured on a graduated circle at D. The 
 measurement is based on the fact that the force re- 
 quired to twist a wire is proportional to the angle 
 of torsion. 
 
 Balance, Deci-Ampere An ammeter 
 
 in the form of a balance, whose scale is 
 graduated to give direct readings in deci- 
 amperes. (See Balance, Centi- Ampere?) 
 
 Balance, Deka- Ampere An am- 
 meter in the form of a balance, whose scale is 
 graduated to give direct readings in deka- 
 amperes. (See Balance, Centi-Ampere?) 
 
 Balance, Electric A term fre- 
 quently used for Wheatstone's electric bridge. 
 (See Bridge, Electric?) 
 
 The electric bridge is sometimes called a balance 
 because, when in use in measuring resistances, 
 one resistance or set of resistances balances an- 
 other resistance or set of resistances. 
 
 Balance, Hekto-AmpSre An am- 
 meter in the form of a balance, whose scale 
 is graduated to give direct readings in hekto- 
 amperes. (See Balance, Centi- Ampere.} 
 
 Balance Indicator. (See Indicator, Bal- 
 ance.} 
 
 Balance, Induction, Hughes' 
 
 An apparatus for the detection of the presence 
 of a metallic or conducting substance by the 
 aid of induced electric currents. 
 
 Hughes' induction balance is shown in Fig. 35. 
 
 A, B, C and D are bobbins, wound with about 
 300 feet of No. 32 copper wire. The coils ar 
 
 connected as shown, A and B, in the circuit of a 
 battery, and C and D, in the circuit of a telephone. 
 The coils, A and B, and C and D, are placed at 
 
 Fig 33. Hughes' Induction Balance. 
 
 such a distance apart as to prevent any mutual 
 induction occurring between them. The coils 
 are so joined that the direction of the induction 
 of A, on C, is opposite to that of B, on D. 
 
 The coils, A and B, then act as primaries, and C 
 and D, as secondaries. In the battery circuit is an 
 interrupter I, which is caused to continually make 
 and break the circuit. 
 
 The coils are so adjusted that the opposing 
 secondary coils produce but little noise to one 
 listening at the telephone. This can readily be 
 done by the adjusting of a single pair of coils. 
 
 If a angle coin or mass of metal be introduced 
 between either A and C, or B and D, or even 
 above one of the coils, as at d, the balance 
 will be disturbed, since some of the induction is 
 now expended in producing electric currents in 
 the interposed metal, and a sound will therefore 
 be heard in the telephone. But if precisely similar 
 metals are placed in similar positions, between A 
 and C, and B and D, no sound is heard in the 
 telephone, since the inductive effects due to the 
 two metals are the same. 
 
 The slightest difference, however, either in 
 composition, size or position, destroys the balance, 
 and causes a sound to be heard in the telephone. 
 
 A spurious coin is thus readily detected when 
 compared with a genuine coin. 
 
 A somewhat similar instrument has been em- 
 ployed to detect and locate a bullet or other for- 
 eign metallic substance in the human body. 
 
 In order to determine the amount of the dis- 
 turbance, an instrument called a sonometer is 
 used (See Sonometer, Hughes 1 ), in which a single 
 secondary coil, placed in the circuit of a telephone, 
 slides on a graduated bar between two fixed 
 primary coils, so wound as to exert equal and op- 
 posite inductions on the secondary. When, there- 
 f ore, the secondary is exactly in ihe middle of the 
 
Bal.] 
 
 40 
 
 [Bal. 
 
 graduated bar, and consequently exactly midway 
 between the two fixed primary coils, no sounds are 
 heard in the telephone, but when moved to one 
 side or the other the sounds are heard. Switches 
 are so arranged that the telephone can be readily 
 switched from the induction balance to the tele- 
 phone, or vice versa. When, therefore, a metallic 
 disc is placed in one of the coils of the induction 
 balance, and a noise is heard in the telephone, 
 the coil of the sonometer is shifted so that the 
 noise heard in this telephone is judged by the 
 ear to be equal, and the comparison can then be 
 made by means of simple calculations. 
 
 The following table gives, in arbitrary values, 
 the results of various experiments as to the sensi- 
 tiveness in this respect of discs of different 
 metals, of various sizes and shapes : 
 
 Silver, chemically pure 125 
 
 Gold 117 
 
 Silver, commercial 115 
 
 Aluminium 112 
 
 Copper ico 
 
 Zinc 80 
 
 Bronze 75 
 
 Tin 74 
 
 Iron, ordinary . , 53 
 
 German silver 50 
 
 Iron, pure 40 
 
 Copper, alloyed '..-, 40 
 
 Lead 58 
 
 Antimony 35 
 
 Bismuth 10 
 
 Zinc, alloyed 6 
 
 Carbon 2 
 
 {Fleming.} 
 
 An inspection of this table shows that the values 
 found for different metals do not correspond with 
 their electric conducting power, although, roughly 
 speaking, the best conductors stand at the top of 
 the table, and the worst at the bottom. The 
 effects appear to be dependent for their action on 
 the phenomena of magnetic screening, for 
 
 (i.) If slots are cut in the middle of the plate 
 its disturbing action is either removed or very 
 much decreased. 
 
 (2.) If a flat coil of copper wire replaces a disc 
 of metal no effect is produced on the induction 
 balance when its ends are open, but when closed 
 the coil acts just like a disc, or continuous plate 
 of metal. 
 
 (3.) The difference between various metals in- 
 
 serted as discs in the induction balance is less at 
 ' high speeds of reversal than at low speeds. 
 
 Balance, Kilo-Ampere An am- 
 meter in the form of a balance, whose scale is 
 graduated to give direct readings in kilo-am- 
 peres. (See Balance, Centz- Ampere.) 
 
 Balance of Induction in Cable. (See 
 Induction, Balance of, in Cable!, 
 
 Balance, Plating - An automatic 
 device for disconnecting the current from 
 the article to be plated, as soon as a certain 
 increase in weight has been obtained. 
 
 The objects to be plated are suspended at one 
 end of a balance, and when a certain increase in 
 weight has been gained, the balance tips and 
 breaks the circuit. Edison's electric meter is 
 based on this principle. 
 
 Balance, Thermic, or Bolometer. An 
 
 apparatus constructed on the principle of the 
 differential galvanometer, devised by Professor 
 Langley for determining small differences of 
 temperature. (See Galvanometer, Differen- 
 tial^ 
 
 A coil composed of two separately insulated 
 wires, wound together, is suspended in a mag- 
 netic field, and has a current sent through it. 
 Under normal conditions, this current separates 
 into two equal parts, and runs through the wires 
 in opposite directions. It therefore produces no 
 sensible field, and suffers no deflection by the field 
 in which it is suspended. 
 
 Any local application of heat producing a dif- 
 ference in temperature in these coils, causing a 
 difference in resistance, prevents this equality. A 
 field is therefore produced in the suspended coil, 
 which, though extremely small, is rendered meas- 
 urable by means of the powerful field produced 
 in the coil, within which the double coil is sus- 
 pended. 
 
 Differences of temperature as small as one- 
 fourteen thousandth of a degree Fahrenheit are 
 detected by the instrument. 
 
 Balance, Wheatstone's Electric A 
 
 name often given to the electric bridge or 
 balance. (See Bridge, Electric!) 
 
 Balanced-Metallic Circuit. (See Circuit, 
 Balanced-Metallic!) 
 
 Balanced Resistances. (See Resistances, 
 Balanced!) 
 
Bui.] 
 
 41 
 
 [Bar. 
 
 Balata. An insulating material. 
 Balata, when prepared for use as an insulating 
 material, is somewhat like gutta-percha. 
 
 indicate the peculiarities of distribution of the 
 charge thereon. 
 
 Ball, Electric Time 
 
 A ball, sup- 
 
 ported in a prominent position on a tall pole, 
 and caused to fall at the exact hour of noon, 
 or at any other predetermined time, for the 
 purpose of thus giving correct time to an 
 entire neighborhood. 
 
 The release of the ball is effected by the closing 
 of an electric circuit, either automatically, or 
 through the agency of an observer. 
 
 Ball, Fire A term sometimes ap- 
 plied to globular lightning. (See Lightning, 
 Globular?) 
 
 Ball Lightning. (See Lightning, Sail.) 
 Ballistic Curve. (See Curve, Ballistic?) 
 
 Ballistic Galvanometer. (See Galva- 
 nometer, Ballistic.} 
 
 Balloon, Electric 
 
 A balloon, or 
 
 air ship, provided with electric power so as 
 to be able to be steered or moved against the 
 direction of the wind. 
 
 Electric balloons have been moved against the 
 wind and steered with a certain amount of success, 
 by the use of electric motors driven by storage 
 batteries. All thr.t is needed to make aerial navi- 
 gation a commercial success is the ability to ob- 
 tain great power with a small weight. The storage 
 battery does this to a limited extent. 
 
 Bearing in mind the high efficiency of the elec- 
 tric motor, it would appear that the problem of 
 successful aerial navigation will be solved when 
 the discovery is made of means for directly con- 
 verting the chemical potential energy of coal into 
 electrical energy. 
 
 Balloon Signaling for Military Pur- 
 poses. (See Signaling, Balloon, for Mil- 
 itary Purposes?) 
 
 Balls, Pith Two balls of pith, sus- 
 pended by conducting threads of cotton to 
 insulated conductors, employed to show the 
 electrification of the same by their mutual 
 repulsion.' 
 
 The pith balls connected with the insulated 
 cylinder A B, Fig. 36, not only show the electri- 
 fication of the cylinder, but serve also to roughly 
 
 Fig. 36. Pith Ball Cylinder. 
 
 Bands, Auroral Approximately 
 
 parallel streaks of light sometimes seen 
 during the prevalence of the aurora. (See 
 Aurora B area Us.) 
 
 Bank of Lamps. (See Lamps, Bank of.) 
 Banked Battery. (See Battery, Banked.) 
 
 Bar, Detorsion A bar placed in a 
 magnetic instrument called a declinometer for 
 the purpose of removing the torsion of the 
 suspending thread of the magnet. 
 
 The detorsion _>ar of the declinometer is gen- 
 erally made of gun metal of the same weight as 
 that of the suspended magnet. A small magnet 
 is placed in a rectangular aperture in the middle 
 of the bar. 
 
 Bar Electro-Magnet. (See Mag-net, 
 Electro, Bar.) 
 
 Barad. A unit of pressure proposed by 
 the British Association. 
 
 One barad equals one dyne per square cen/<- 
 metre. 
 
 Barometer. An apparatus for measuring 
 the pressure or weight of the atmosphere. 
 
 Barometric Column. (See Column, Baro- 
 metric.) 
 
 Omnibus bars. (See 
 
 Bars, Bus 
 
 Bars, Omnibus?) 
 
 Bars, Krizik's Cores of various 
 
 shapes, provided for solenoids, in which the 
 distribution of the metal in the bar is so pro- 
 portioned as to insure as nearly as possible a 
 uniform attraction or pull while in different 
 positions in the solenoid. 
 
Bar.] 
 
 42 
 
 [Bat. 
 
 Krizik's bars of various shapes are shown in 
 ig- 37- It will be observed that in all cases the 
 
 f'f- 37- Krizik's Bars.' 
 
 mass of metal is greater toward the middle of 
 the core than near the ends. 
 
 When a core of uniform diameter is drawn into 
 a solenoid, the attraction or pull is not uniform in 
 strength for different positions of the bar. When 
 the bar is just entering the solenoid, the pull is 
 strongest ; as soon as the end passes the middle of 
 the core the attraction decreases, until, when the 
 centres of the bar and core coincide, the motion 
 ceases, since both ends of the solenoid attract 
 equally in opposite directions. By proportioning 
 the bars, as shown in the figure, a fairly uniform 
 pull for a considerable length may be obtained. 
 
 Bars, Negative-Omnibus The 
 
 bus-bars that are connected with the negative 
 terminal of the dynamos. (See Bars, Omni- 
 bus.) 
 
 Bars, Neutral-Omnibus The bus- 
 
 bars that are connected with the neutral 
 dynamo terminal in a three-wire system of 
 distribution. 
 
 Bars, Omnibus Heavy bars of con- 
 ducting material connected directly to the 
 poles of dynamo-electric machines, in electric 
 incandescent light or electric railway installa- 
 tions, and therefore receiving the entire current 
 produced by the machine. 
 
 Main conductors common to two or more 
 dynamos in an electrical generating plant. 
 
 The terms bus and omnibus bars refer to the 
 fact that the entire or whole current is carried by 
 them. 
 
 Bars, Positive-Omnibus The bus- 
 bars that are connected with the positive 
 terminal of the dynamos. 
 
 i>ath, Bi-polar An electro-thera- 
 peutic bath, the current applied to which 
 enters at one part of the tub, and leaves at 
 another part. 
 
 The electrodes for the bi-polar bath consist of 
 suitably shaped copper plates, generally called 
 shovel electrodes. 
 
 Bath, Copper An electrolytic bath 
 containing a readily electrolyzable solution 
 of a copper salt, and a copper plate acting as 
 the anode, and placed in the liquid near the 
 object to be electro-plated, which forms the 
 kathode. (See Plating, Electro?) 
 
 The sulphate, the cyanide and the acetate of cop- 
 per are used for copper baths. The use of the sul- 
 phate is objectionable. The cyanide is expensive. 
 The acetate is therefore very generally employed. 
 Wahl gives the following formula for a copper 
 bath, viz. : 
 
 Water i, coo parts. 
 
 Acetate of copper, crystal- 
 lized 20 " 
 
 Carbonate of soda ao " 
 
 Bisulphite of soda 20 " 
 
 Cyanide of potassium (pure) 20 " 
 
 Bath, Electro-Plating- Tanks con- 
 taining metallic solutions in which articles 
 are placed so as to be electro-plated. (See 
 Plating, Electro?) 
 
 Strictly speaking a plating bath includes not 
 only the vessel and its metallic solution, but also 
 the metallic plate acting as the anode and the 
 article to be plated forming the kathode. 
 
 Bath, Electro-Therapeutic A bath 
 
 furnished with suitable electrodes and used 
 in the application of electricity to curative 
 purposes. 
 
 Such baths should be used only under the advice 
 of a regular physician. 
 
 Bath, Gold An electrolytic bath 
 
 containing a readily electrolyzable solution of 
 a gold salt and a gold plate acting as the 
 anode, and placed in the liquid opposite the 
 object to be plated, which forms the kathode. 
 (See Plating, Electro?) 
 
 Electro gilding may be accomplished either with 
 or without the aid of heat. Hot gilding appears 
 to give a smoother and cleaner deposit. 
 
 The following is a fairly good solution for a 
 gold bath: 
 
 Water 1,000 parts. 
 
 Cyanide of potassium, pure. . 20 " 
 
 Gold 10 " 
 
 (Wahl.) 
 
Bat.] 
 
 43 
 
 [Bat. 
 
 The gold is first converted into neutral chloride 
 by dissolving it in 25 parts of pure hydrochloric 
 acid to which 12.5 parts of pure nitric acid has 
 been added. When the gold is completely dis- 
 solved, the liquid is heated until of a dark red 
 color, in order to expel any excess of acid. 
 
 Bath, Head, Electric A variety 
 
 of electric breeze, applied therapeutically to 
 the head of the patient. 
 
 The patient is placed on an insulating stool and 
 connected with one pole of an electrostatic induc- 
 tion machine, the other pole of which is con- 
 nected to a circle of insulated points suspended 
 over the head. 
 
 Bath, Hydro-Electric 
 
 A bath in 
 
 which electro-therapeutic treatment is given 
 by applying one electrode to the metallic lining 
 of the tub, and the other electrode to the body 
 of the bather. 
 
 Bath, Multipolar-Electric An 
 
 electro-therapeutic bath, in .which more than 
 two electrodes are employed. 
 
 It is not clear that the multipolar- electric bath 
 possesses any decided advantages over the bi-polar 
 bath. 
 
 Bath, Nickel An electrolytic bath 
 
 containing a readily electrolyzable salt of 
 nickel, a plate of nickel acting as the anode 
 of a battery and placed in the liquid near the 
 object to be coated, which forms the kathode. 
 (See Plating, Electro^ 
 
 The double sulphate of nickel and ammonium 
 (from 5 to 8 parts dissolved in 100 parts of water) 
 is used for the bath. Some prefer to add 
 sulphate of ammonium and citric acid to the above 
 solution. 
 
 Bath, Shower, Electric A shower 
 
 bath in which the falling drops carry electric 
 charges to the patient subjected thereto. 
 
 The water is rendered slightly alkaline. One 
 pole is immersed in the alkaline water and the 
 other connected to a metallic stool on which the 
 patient is placed. 
 
 Bath, Silver An electrolytic bath 
 
 containing a readily electrolyzable salt of 
 silver and a plate of silver acting as the 
 anode of an electric source and placed in the 
 liquid near the object to be coated, which 
 forms the kathode. v See ^fating. Electro.} 
 
 The double cyanide of silver and potassium 
 is the salt usually employed in the silver bath. 
 
 The following bath is recommended by Rose- 
 leur: 
 
 Water 1,000 parts. 
 
 Cyanide of potassium (pure) 50 " 
 Pure silver 25 " 
 
 The silver (granulated) is treated with pure nitric 
 acid (43 degrees Beaume) and converted into 
 nitrate of silver. The solution is then heated to 
 dryne^s and subsequently fused. The fused nitrate 
 so obtained is dissolved in fifteen times its weight 
 of distilled water and treated with a solution of 
 cyanide of potassium (10 per cent, of the cyanide), 
 by means of which silver cyanide is thrown down 
 as a precipitate. This precipitate is then sepa-- 
 rated and washed. It is added to the i,coo parts 
 of water, dissolved, and the cyanide of potassium 
 afterward added, thus forming the double cyan- 
 ide required for the bath. 
 
 Bath, Stripping 1 A bath for remov- 
 ing an electro-plating of gold, silver, or other 
 metal, either by simple dipping or by electric 
 action. 
 
 Bath, Ungilding 
 
 -A stripping bath 
 
 suitable for the removal of a coating of gold. 
 (See Bath, Stripping^ 
 
 Bath, Unipolar-Electric An electro- 
 therapeutic bath, the water of which forms 
 one of the electrodes of the source, and the 
 other electrode is attached to a metallic rod 
 fixed at a convenient height above the tub. 
 
 The bath tub is formed of non-conducting sub- 
 stances. The terminals of the electrode con- 
 nected with the water terminate in metal plates 
 located at suitable points in the tub. The cur- 
 rent is applied by the patient making and break- 
 ing contact at the vertical metal rod with his 
 hands. 
 
 The unipolar-electric bath is employed instead 
 of local galvanization where it is desired to limit 
 the application to especial organs or particular 
 parts of the body. In general galvanization the 
 patient is placed on an electrode of large sur- 
 face, formed of a large sponge- covered metallic 
 plate, on which he sits or rests. This electrode is 
 connected with the kathode of the battery. The 
 anode is connected with a large sponge electrode, 
 which is moved regularly over the body of the 
 patient; sometimes the moistened hand of 'the 
 operator is used in place of the sponge electrode. 
 
Bat.] 
 
 [Bat. 
 
 Bath, Unsilvering A stripping bath 
 suitable for the removal of a coating of silver. 
 (See Bath, Stripping^ 
 
 Bathometer. An instrument invented by 
 Siemens for obtaining deep-sea soundings 
 without the use of a sounding line. 
 
 The bathometer depends for its operation on 
 the varied attraction of the earth for a suspended 
 weight in parts of the ocean differing in depth. 
 As the vessel passes over deep portions of the 
 ocean, the solid land of the bottom, being further 
 from the ship, exerts a smaller attraction than it 
 would in shallow parts, where it is nearer; for, 
 although in the deep parts of the ocean the water 
 lies between the ship and the bottom, the smaller 
 density of the water as compared with the land 
 causes it to exert a smaller attraction than in the 
 shallower parts, where the bottom is nearer the 
 ship. The varying attraction of the earth is 
 caused to act on a mercury column, the reading 
 of which is effected by means of an electric con- 
 tact. 
 
 Battery, Banked A term some- 
 times applied to a battery from which a num- 
 ber of separate circuits are supplied with cur- 
 rents. 
 
 The term banked -battery is sometimes ap- 
 plied to a multiple arc connected battery. 
 
 Battery, Cautery A term some- 
 times employed in electro-therapeutics, for a 
 multiple connected voltaic battery adapted for 
 producing electric incandescence for cautery 
 effects. 
 
 Battery, Closed-Circuit - A voltaic 
 battery which may be kept constantly on 
 closed-circuit without serious polarization. 
 
 The gravity battery is a closed-circuit battery. 
 As employed for use on most telegraph lines, it is 
 maintained on a closed circuit. When an operator 
 wishes to use the line he opens his switch, thus 
 breaking the circuit and calling his correspondent. 
 Such batteries should not polarize. (See Cell, 
 Voltaic, Polarization of.) 
 
 Battery, Connection of, for Quantity 
 
 A term, now generally in disuse, formerly 
 employed to indicate the grouping of voltaic 
 cells, now known as parallel or multiple. 
 
 The arrangement or coupling of a number of 
 voltaic cells in multiple reduces the internal resist- 
 
 ance of the battery, and thus permits a greater 
 current, or quantity, of electricity to pass ; hence 
 the origin of the term. 
 
 Battery, Dynamo The combina- 
 tion or coupling together of several separate 
 dynamo-electric machines so as to act as a 
 single electric source. 
 
 The dynamos may be connected to the leads 
 either in series, in multiple, in multiple-series or 
 in series-multiple. 
 
 Battery, Dynamo, Electric Machine 
 
 A dynamo battery. (See Battery, Dy- 
 namo.) 
 
 Battery, Electric A general term 
 
 applied to the combination, as a single source, 
 of a number of separate electric sources. 
 
 The separate sources may be coupled either in 
 series, in multiple, in multiple-series, or in series- 
 multiple. ( See Circuits, Varieties of.) 
 
 The term battery is sometimes incorrectly ap- 
 plied to a single voltaic couple or cell. 
 
 Battery, Floating, De la Rive's A 
 
 floating voltaic cell, the terminals of which are 
 connected with a coil of insulated wire, em- 
 ployed to show the attractions and repul- 
 sions between magnets and movable electric 
 circuits. 
 
 The cell, shown in Fig. 38, consists of a vol- 
 
 'f- 3S. Floating Cell. 
 
 taic couple of zinc and copper, the terminals of 
 which are connected to the circular coil of insu- 
 lated wire, as shown, and the whole floated by 
 means of a cork, in a vessel containing dilute sul- 
 phuric acid. 
 
 When the current flows through the coil in the 
 direction shown by the arrows, the approach of 
 the N-seeking pole of a magnet will cause the 
 cell to be attracted or to move towards the mag- 
 net pole, since the south face or end of the coil is 
 nearer the north pole of the magnet. If the other 
 
Bat] 
 
 end were nearer, repulsion would occur, the cell 
 turning round until the south face is nearer the 
 magnet, when attraction occurs. 
 
 This is, strictly speaking, a floating cell, and 
 not a battery. (See Battery, Voltaic.} 
 
 Battery, Galvanic Two or more 
 
 separate voltaic cells so arranged as to form 
 a single source. 
 
 This is more correctly called a Voltaic Battery. 
 (See Battery, Voltaic.) 
 
 Battery, Gas A battery in which 
 
 the voltaic elements are gases as distinguished 
 from solids. 
 
 The electrodes of a gas battery generally con- 
 sist of plates of platinum, or other solid substance 
 which possesses the power of occluding oxygen 
 and hydrogen. The lower parts of these plates 
 dip into dilute sulphuric acid, and the upper parts 
 are respectively surrounded by oxygen and hydro- 
 gen gas derived from the electrolytic decompo- 
 sition of the dilute acid. 
 
 A gas battery consisting of plates of platinum 
 dipping below into acid liquid, and surrounded 
 in the space above the liquid by hydrogen and 
 oxygen H, H' and O, O', etc., respectively is 
 shown in Fig. 39. 
 
 45 [Bat. 
 
 Battery, Leyden Jar The combina- 
 tion of a number of separate Leyden jars so 
 as to act as one single jar. 
 
 A Leyden jar battery is shown in Fig. 40, 
 
 Fig. 39. Gas Battery. 
 
 In charging this battery an electric current is 
 sent through it until a certain quantity of the 
 gases has been produced. If, then, the charging 
 current be discontinued, a current in the oppo- 
 site direction is produced by the battery. The 
 gas battery is in reality a variety of storage bat- 
 tery. (See Electricity, Storage of. Cell, Secon- 
 dary. Cell, Storage.) 
 
 Gas batteries can also be made by feeding con- 
 tinually into the cell a gas capable of acting on 
 the positive elements. 
 
 Battery Gauge. (See Gaug<t, Battery^ 
 
 Fig. 40, Leyden Jar Battery. 
 
 where nine separate Leyden jars are connected 
 as a single jar by joining their outer coatings by 
 placing them in the box F, the bottom of which 
 is lined with tin foil. The inner coatings are 
 connected together by the metal rods B, as 
 shown. 
 
 A discharging rod A, may be employed for 
 connecting the opposite coatings. The handles 
 are made of glass, or any other good insulating 
 material. 
 
 A number of Leyden jars can be coupled in 
 series by connecting the inner coating of the first 
 jar to the outer coating of the second, the inner 
 coating of the second to the outer coating of the 
 third, and so on. The battery so obtained is 
 then discharged by connecting the outer coat 
 ing of the first jar with the inner coating of tbe 
 last. 
 
 Battery, Local A voltaic battery 
 
 used at a station on a telegraph line to 
 operate the Morse sounder, or the register- 
 ing or recording apparatus, at that* point 
 only. (See Telegraphy, American or Morse 
 System of.) 
 
 The local battery is thrown into or out of action 
 by the telegraphic relay. (See Relay.) 
 
 Battery, Magnetic The combina- 
 tion, as a single magnet, of a number of sep- 
 arate magnets. 
 
 A magnetic battery, or compound magnet, is 
 
Bat.] 
 
 4C 
 
 [Bat. 
 
 shown in Fig. 41. It consists of straight bars of 
 steel, p, p, p, with their similar poles placed near 
 together and inserted in 
 masses of soft iron, N and 
 S, as shown. 
 
 Battery, Main 
 
 The battery, in a system 
 of telegraphic communi- 
 cation, that is employed 
 for sending the signals 
 over the main line, as dis- 
 tinguished from any bat- 
 tery employed for any 
 other particular work, 
 such, for example, as that 
 of the local battery. (See 
 
 D .. T ,*. Fig, AT, Magnetic 
 
 Battery, Local.) s *' 
 
 ~ Battery, or Cont- 
 
 Battery, Multiple-Con- pound Magnet. 
 
 nected A battery the single cells of 
 
 vhich are connected to one another and to the 
 mains or conductors in multiple. (See Cir- 
 cuit, Multiple) 
 
 Battery, Open-Circuit A voltaic 
 
 battery which is normally on open-circuit, 
 and which is used continuously only for com- 
 paratively small durations of time on closed- 
 circuit. 
 
 Leclanche'-cells form an excellent open-circuited 
 battery. They have a comparatively high electro- 
 motive force, but rapidly polarize. They cannot 
 therefore be economically used for furnishing 
 currents continuously for long durations of time. 
 When left on open-circuit, however, they readily 
 depolarize. They therefore form an excellent 
 battery for such work as annunciator bells, burg- 
 lar alarms, etc., where the current is only 
 required for short periods of time, separated by 
 comparatively long intervals of rest. (See Cell, 
 Voltaic, Leclanche.) 
 
 Battery Plates of Secondary or Storage 
 
 Cell, Forming of (See Plates of 
 
 Secondary or Storage Cell, Forming of.) 
 
 Battery, Plunge A number of 
 
 separate voltaic cells connected so as to form 
 a single cell or electric source, the plates of 
 which are so supported on a horizontal bar 
 as to be capable of being simultaneously 
 placed in, or removed from, the exciting 
 liquid. 
 
 The plunge battery shown in Fig. 42, consists 
 
 Fig. 42. Plunge Battery, 
 
 of a number of zinc-carbon elements immersed in 
 an electrolyte of dilute sulphuric acid, or in elec- 
 tropoion liquid, contained in separate jars, J, J. 
 (See Liquid, Electropoion.) 
 
 The mode of support to the horizontal bar 
 will be understood from an inspection of the 
 drawing. 
 
 Battery, Primary The combina- 
 tion of a number of separate primary cells so 
 as to form a single source. 
 
 The term primary battery is used in order to 
 distinguish it from secondary or storage battery. 
 (See Cell, Secondary. Cell, Storage.) 
 
 Battery, Secondary The combina- 
 tion of a number of separate secondary or 
 storage cells, so as to form a single electric 
 source. (See Electricity, Storage of.) 
 
 Battery, Selenium The combina- 
 tion of a number of separate selenium cells so 
 as to form an electric source. (See Cell, 
 Selenium.) 
 
 Battery, Series-Connected A bat- 
 tery, the separate cells of which are con- 
 nected to one another and to the line or 
 conductor in series. (See Circuit, Series.) 
 
 Battery Solution. (See Solution, Bat- 
 tery.) 
 
 Battery, Split A voltaic battery 
 
 connected in series, but having one of its 
 middle plates connected with the ground. 
 
 By the employment of the device of a split- 
 battery, the poles of the battery are maintained 
 at potentials differing in opposite directions from 
 the potential of the earth. 
 
 Battery, Storage A number of 
 separate storage cells connected so as to 
 form a single electric source. 
 
Bat.] 
 
 [Bel. 
 
 A cell of a storage battery is shown in Fig. 
 
 43- 
 
 Fig. 43. Storage Battery. 
 
 Battery, Storage, Element of A 
 
 single set of positive and negative plates of a 
 storage cell connected so as to be ready for 
 placing in the acid liquid of the jar or cell. 
 
 A term sometimes applied to one of the 
 storage cells in a storage battery. 
 
 This latter use of the term element is unfortu- 
 nate, since from the analogous case of a primary 
 cell, an element would consist of a single plate, 
 either positive or negative, and not of both. That 
 is, every voltaic couple consists of two elements, 
 the positive and the negative. 
 
 Battery, Thermo A term often 
 
 applied to a thermo-electric battery. (See 
 Battery, Thermo- Electric?) 
 
 Battery, Thermo-Electric The 
 
 combination, as a single thermo-electric cell, 
 of a number of separate thermo-electric cells 
 or couples. (See Couple, Thermo-Electric?} 
 
 Battery, Voltaic The combina- 
 tion, as a single source, of a number of sepa- 
 rate voltaic cells. 
 
 Battery, Water A battery formed 
 
 of zinc and copper couples immersed in an 
 electrolyte of ordinary water. 
 
 Any voltaic couple can be used, the positive 
 element of which is slightly acted on by water. 
 When numerous couples are employed consider- 
 able difference of potential can be obtained. 
 
 Water batteries are employed for charging 
 electrometers. They are not capable of giving 
 any considerable current, owing to their great in- 
 ternal resistance. 
 
 Bead Areometer or Hydrometer. (See 
 Areometer, Bead.} 
 
 Bec-Carcel. The Carcel, or French unit 
 of light. (See CarceZ.) 
 
 Bell, Automatic;Electric An elec- 
 tric bell furnished with an automatic contact- 
 breaker. (See Contact-Breaker, Automatic.) 
 
 A form of automatic-electric bell is shown in 
 Fig. 44. The relation of the electro-magnet, its 
 armature and the bell 
 lever, will be readily 
 understood from an in- 
 spection of the draw- 
 ing. 
 
 Bell, Call 
 
 An electric bell used 
 to call the attention 
 of an operator to the 
 fact that his corre- 
 spondent wishes to 
 communicate with 
 him. 
 
 Bell, Circular 
 
 A bell so construct- 
 ed that all its moving 
 parts are contained in Fig . 44 , Automatic Electric 
 the gong. Bell.* 
 
 Bell, Continuous-Sounding Electric 
 
 An electric bell, which, on the completion 
 of the circuit, continues striking until stopped 
 either by hand or automatically. 
 
 On the completion of the circuit, the attraction 
 of an armature throws a catch off from a lever, 
 and thus permits the lever to fall and complete a 
 contact and allows the current to ring the bell; or 
 the bell is rung by clockwork, which is thrown 
 into action by the passage of a current through an 
 electro-magnet. (See Bell, Electro-Mechanical.) 
 
 Bell, Differential Electric An 
 
 electric bell, the magnetizing coils of which 
 are differentially wound. 
 
 Differential winding is ot advantage where a 
 very strong current is required, as this winding 
 decreases the sparking at the contacts, on the 
 opening of the circuit. 
 
 Bell, Electro-Magnetic, Siemens-Arma- 
 ture Form A form of electro-mag 
 
Bel.] 
 
 48 
 
 [Bel. 
 
 netic bell in which the movements of the bell 
 armature are obtained by the reversal of 
 polarity that takes place when alternating cur- 
 rents are pass- fi^^ 
 
 \_b 
 
 ed through the 
 coils of a sim- 
 ple, single coil, 
 Siemens - arma- 
 
 F*&. 45* Siemens- Armature Form 
 The details of Electro-Magnetic Cell. 
 
 will be readily understood from an examination 
 of Fig. 45. 
 
 Bell, Electro-Mechanical A bell, 
 
 the striking apparatus of which is driven by 
 a weight or spring, called into action by the 
 movement of the armature of an electro- 
 magnet. (See Alarm, Electric?) 
 
 Bell, Extension-Call A device for 
 
 prolonging the sound of a magneto call. 
 
 An alarm bell is automatically connected with 
 
 Fig. 46. Extension-Call Bell. 
 
 the circuit of a local battery by means of the cur- 
 rent generated by the magneto-call, and continues 
 sounding after the current of the magneto call 
 has ceased. 
 
 A form of extension-call bell is shown in Fig. 46. 
 
 Bell, Indicating An electric bell 
 
 in which, in order to distinguish between 
 different bells in the same office, a number 
 is displayed by each bell when it rings. 
 
 Bell, Magneto-Electric An electric 
 
 bell, the curre.it employed to operate or 
 strike which is obtained by the motion of a 
 magneto-electric machine. 
 
 Bell, Night In a telephone ex- 
 change, a bell, switched into connection with 
 the shunted circuit of an annunciator case, and 
 intended, by its constant ringing, to call the 
 attention of the night operator to the falling 
 of a drop. 
 
 Bell, Relay, Electric An electric 
 
 bell m which a relay magnet is employed to 
 switch a local battery into the circuit of the 
 sounding apparatus of the bell. 
 
 The relay bell is suitable for use when the bell 
 to be sounded is situated at a great distance. A? 
 the current from the line, when this is long, is 
 too weak to ring the bell, it throws irito action a 
 local battery by the action of a relay. 
 
 Relay bells were used in the early forms ol 
 acoustic telegraphs as employed in England with 
 relay sounders. 
 
 The dots and dashes of the Morse alphabet were 
 indicated by the sounds of two bells, a tap on 
 one bell indicating a dot, and a tap on the other 
 a dash. This system is now practically aban- 
 doned. 
 
 Bell-Shaped Magnet. (See Magnet, Bell- 
 Shaped?] 
 
 Bell, Shunt, Electric An electric 
 
 bell, the magnetizing coils of which are placed 
 on the line in shunt. 
 
 In the case of shunt-connected electric bells, 
 one of the bells must make and break the circuit 
 for all the rest. The series-connected electric 
 bell is used where the distance between the sepa- 
 rate bells is great, in order to save the expense of 
 multiple connections. 
 
 In most cases, where a number of electric bells 
 are to be simultaneously sounded, connection in 
 multiple is adopted. 
 
 Bell, Single-Stroke Electric An 
 
 electric bell that gives a single stroke only for 
 each make of the circuit. 
 
 -.-. ,- 
 
 47' Single-Stroke Bell. 
 
 Since the bell gives a single stroke for each 
 completion of the circuit, its use permits of ready 
 communication between any two places by any 
 
Bel.] 
 
 49 
 
 [Bla. 
 
 system of prearranged signals. A buzzer may be 
 used for the same purpose. A form of single- 
 stroke bell is shown in Fig. 47. On completing the 
 c rcuit, the current, through its coils, attracts the 
 armature and causes a single stroke of the bell. 
 
 Bell, Telephone-Call - A call bell 
 used to call a correspondent to the telephone. 
 
 The telephone-call bell is generally a magneto- 
 electric bell. 
 
 Bell, Trembling 1 A name some- 
 times given to a vibrating or an automatic 
 make-and-break bell. (See Make-and-Break, 
 Automatic) 
 
 Bell, Vibrating A trembling bell. 
 
 (See Bell, Trembling) 
 
 Bias of Relay Tongue. (See Tongue, 
 Relay, Bias of.) 
 
 Bichromate Yoltaic Cell. (See Cell, Vol- 
 taic, Bichromate^ 
 
 Bi-fllar Suspension. (See Suspension, 
 Bi-filar) 
 
 Bi-fllar Suspension Balance. (See Bal- 
 ance, Bi-filar Suspension) 
 
 Bi-fllar Winding. (See Winding, Bi- 
 filar) 
 
 Binary Compound. (See Compound, Bi- 
 nary^ 
 
 Binding Coils. (See Coils, Binding) 
 
 Binding-Post. (See Post, Binding?) 
 
 Binding-Screw. (See Screw, Binding) 
 
 Binding "Wire for Telegraph Lines. (See 
 Wire, Binding, for Telegraph Lines?) 
 
 Biology, Electro That branch of 
 electric science which treats of the electric 
 conditions of living animals and plants, and 
 the effects of electricity upon them. 
 
 Electro-Biology includes : 
 
 (i.) Electro-Physiology. 
 
 (2.) Electro-Therapy, or Electro-Therapeutics. 
 
 Bioplasm. Any form of living matter pos- 
 sessing the power of reproduction. 
 
 Bioscopy, Electric The determina- 
 tion of the presence of life or death by the 
 passage of electricity through the nerves and 
 muscles. 
 
 Bi-polar. Having two poles. 
 
 Bi-polar Armature. (See Armature* 
 Bi-polar) 
 
 Bi-polar Bath. (See Bath, Bi-polar) 
 
 Birmingham Wire Gauge". (See Gauge, 
 Wire, Birmingham) 
 
 Bi-Telephone. (See Telephone, Bi) 
 
 Bitite. A variety of insulating material. 
 
 Black Electro-Metallurgical Deposit. 
 (See Deposit, Black Electro-Metallurgical) 
 
 Black Lead. A variety of carbon em- 
 ployed in various electrical processes. 
 
 Black lead is also termed plumbago or graphite. 
 (See Plumbago. Graphite.} 
 
 The term black lead is a misnomer, since the 
 substance is carbon and not lead. The term is an 
 old one, and is still very generally used. 
 
 Blasting, Electric The electric 
 
 ignition of powder or other explosive material 
 in a blast. (See Fuse, Electric) 
 
 The current required for the ignition of the 
 fuse is generally obtained by means of a magneto- 
 electric machine. In the form of magneto-blast- 
 ing machine, shown in Fig. 48, the movement 
 
 Fig. 48. Magneto- Blasting Machine. 
 
 of the handle shown at the top of the figure 
 causes the rapid rotation of a cylindrical armature 
 constructed on the Wheatstone and Siemens prin- 
 ciple. The magnets are of iron, and are furnished 
 
Ble.J 
 
 50 
 
 [Boa, 
 
 with coils of insulated wire. On the rotation of 
 the armature the current developed therein in- 
 creases the field of the field magnet, and, when 
 of the proper degree of intensity, is thrown into the 
 outer circuit, and ignites the fuse. 
 
 Bleaching, Electric Bleaching pro- 
 cesses in which the bleaching agents are 
 liberated, as required, by the agency of electro- 
 lytic decomposition. 
 
 In the process of Naudin and Bidet, the cur- 
 rent from a dynamo-electric machine is passed 
 through a solution of common salt between two 
 closely approached electrodes. The chlorine and 
 sodium thus liberated react on each other and 
 form sodium hypochloride, which is drawn off 
 by means of a pump and used for bleaching. 
 (See Electrolysis.} 
 
 Block, Branch 
 
 A device em- 
 
 ployed in electric wiring for taking off a branch 
 from a main circuit. (See Wiring?} 
 
 A form of branch-block, with its fuses attached, 
 is shown in Fig. 49. 
 
 Fig. 49. Branch-Block. 
 
 Block, Cross-Over A device to 
 
 permit the safe crossing of one wire over 
 another in molding or cleat wiring. 
 
 Block, Fuse A block containing 
 
 a safety fuse or fuses for incandescent light 
 circuits. (See Fuse, Safety?) 
 
 Block System for Railroads. (See Rail- 
 roads, Block System for?) 
 
 Block Wire. (See Wire, Block.} 
 
 Blow-Pipe, Electric A blow-pipe 
 in which the air-blast is obtained by a stream 
 of air particles produced at the point of a 
 
 charged conductor by a convection dis- 
 charge. 
 
 The candle flame, Fig. 50, is blown in the di- 
 
 P 
 
 Fig. JO. Convection Blow-Pipe. 
 
 rection of the stream of air particles passing off 
 from the point P. (See Convection, Electric.} 
 
 Blow-Pipe, Electric- Arc A de- 
 vice of Werdermann for cutting rocks, or 
 other refractory substances, in which the heat 
 of the voltaic arc is directed, by means of a 
 magnet, or a blast of air, against the substance 
 to be cut. 
 
 The carbons are placed parallel, so as to readily 
 enter the cavity thus cut or fused. This inven- 
 tion has never been introduced into extensive 
 practice. 
 
 In the welding process of Benardos and 
 Olzewski, the welding temperature is obtained by 
 means of an electric arc taken between two suit- 
 ably shaped electrodes. 
 
 In the electric-arc 
 blow - pipe, shown in 
 Fig. 51, the voltaic arc, 
 taken between two ver- 
 tical carbon electrodes, 
 is deflected into a hori- 
 zontal position under the 
 influence of the inclined 
 poles of a powerful elec- 
 tro-magnet. 
 
 The highly heated car- 
 bon vapor which consti- 
 tutes the voltaic arc is deflected by the magnet in 
 the same direction as would be any other mov- 
 able circuit or current. 
 
 Board, Cross-Connecting In a 
 
 system of telegraphic or telephonic communL 
 cation, a board to which the line terminals are 
 run before entering the switchboard, so as to 
 
 Fig. ^ i. Electric- Arc 
 Blow-Pipe. 
 
Boa.] 
 
 51 
 
 [Boa. 
 
 readily place any subscriber in connection 
 with any desired section of the switchboard. 
 
 Board, Fuse A board of slate or 
 
 other incombustible material on which all 
 the safety fuses in an installation are as- 
 sembled. 
 
 The fuse hoard is used for avoiding accidents 
 from the firing of the fuses. 
 
 Board, Hanger A form of board 
 
 provided for the ready placing or removal of 
 an arc lamp from a circuit. 
 
 . 5S. Hanger-Board. 
 
 A hanger-board contains a switch or cut-out for 
 the ready opening or closing of the circuit. A 
 form of hanger-board is shown in Fig. 52. 
 
 Board, Key Any board to which 
 
 are connected electric keys or switches. 
 
 Board, Legging-Key A key board 
 
 employed for the purpose of legging an 
 operator into a circuit connecting two or more 
 subscribers. (See Leg.) 
 
 Board, Multiple Switch A board 
 
 to which the numerous circuits employed in 
 systems of telegraphy, telephony, annunciator 
 or electric light and power circuits are con- 
 nected. 
 
 Various devices are employed for closing these 
 circuits, or for connecting or cross-connecting 
 them with one another, or with neighboring cir- 
 cuits. 
 
 A multiple switchboard, for example, for a tele- 
 phone exchange, will enable the operator to con- 
 nect any subscriber on the line with any other 
 subscriber on that line, or on another neighbor- 
 
 ing line provided with a multiple switchboard. 
 To this end the following parts are necessary: 
 
 (l.) Devices whereby each lineentering the ex- 
 change can readily have inserted in its circuit a 
 loop connecting it with another line. This is 
 accomplished by placing on the switchboard a 
 separate spring-Jack connection for each sepa- 
 rate line. This connection consists essentially 
 of one or two springs made of any conducting 
 mefal, which are maintained in 
 metallic contact when the plug 
 key is not inserted, but which are 
 readily separated from one another 
 by the introduction of the plug, 
 ke)', Fig. 53, the terminals, a and 
 b, of which are insulated from, 
 each other, and are connected to 
 the ends of a loop coming from 
 another line. As the key is in- Fiff ' S3 ' g P * ug " 
 serted, the metallic spring or 
 springs of the spring-jack are separated and the 
 metallic pieces, a and b, are brought into good 
 sliding contact therewith, thus introducing the 
 loop into the circuit. (See Spring- Jack?) 
 
 (2.) As many separate annunciator-drops as 
 there are separate subscribers. These are pro* 
 vided so as to notify the Central Office of the par- 
 ticular subscriber who desires a connection. 
 Alarm-bells to call the operator's attention to the 
 calling subscriber, or to the falling of a drop, are 
 generally added. (See 'Bell, Call.) 
 
 (3.) Connecting cords and keys for connecting 
 the operator's telephone, and means for ringing 
 subscribers' bells, and clearing out drops. 
 
 Fig. S4- Multiple Switchboard for Electric Light. 
 
 In Multiple Switchboards for the Electric Light 
 or Distributing Switches, spring-jack contacts are 
 connected with the terminals of different circuits. 
 
Boa.] 
 
 [Bod. 
 
 and plug switches with the dynamo terminals. 
 By these means, any dynamo can be connected 
 with any circuit, or a number of circuits can be 
 connected with the same dynamo, or a number 
 of separate dynamos can be placed in the same 
 circuit without interference with the lights. 
 
 Board, Switch A board provided 
 
 with a switch or switches, by means of which 
 electric circuits connected therewith may be 
 opened, closed, or interchanged. 
 
 Board, Switch, Telegraphic ; A 
 
 device employed at a telegraph station by 
 means of which any one of a number of tele- 
 graph instruments, in use at that station, may 
 be placed in or removed from any line con- 
 nected with the station, or by means of which 
 one wire may be connected to another. 
 
 The ability to readily connect one wire with 
 another is of use in case of interruption to tele- 
 graph lines, in which case a through circuit may 
 be made up of sections of 
 different circuits. 
 
 In the switchboard shown 
 hi Fig. 55, the upper left- 
 hand binding post is con- 
 nected to earth; the four 
 remaining binding - posts 
 
 m 
 
 are connected to two sepa- Fig. ss- Telegraphic 
 rate instruments the sec- Switchboard. 
 
 ond and third from the top to one instrument, 
 and the fourth and fifth to another instrument. 
 The four posts at the top of the figure are con- 
 nected to two lines running east and west. 
 
 Various connections are made by the insertion 
 of plug keys in the various openings. 
 
 Board, Switch, Trunking A 
 
 switchboard in which a few subscribers only 
 are connected with the operator, thus enabling 
 him to obtain any other subscriber by means 
 of trunk wires extending to the other sections. 
 (See Wire, Trunk) 
 
 Boat, Electric A boat provided 
 
 with electric motive power. 
 
 Electric power has been applied both to ordi- 
 nary vessels and to submarine torpedo boats. 
 
 Boat, Submarine Electric A boat 
 
 capable of being propelled and steered while 
 entirely under water. 
 
 The motive power of such boats is generally 
 
 electricity. The requisite buoyancy is obtained 
 by means of an air chamber. Artificial ventila- 
 tion is maintained, the fresh air requisite for 
 breathing being derived from a compressed air 
 cylinder. 
 
 Boat, Torpedo A boat used for 
 
 carrying and discharging torpedoes. (See 
 Torpedo) 
 
 Bobbin, Electric An insulated coil 
 
 of wire for an electro-magnet. 
 
 Body, Charged A body containing 
 
 an electric charge. 
 
 Charges are bound or free. (See Charge, 
 Bound. Charge^ free.) 
 
 Body, Electrified A body con- 
 taining an electric charge. 
 
 Body, Human, Resistance of 
 
 The resistance which the human body offers to 
 the passage of an electric current. 
 
 The resistance of the human body to the passage 
 of a current varies with the time. The re- 
 sistance rapidly decreases after a short time. 
 
 "The resistance diminishes because of the con- 
 duction of water in the epidermis under the action 
 of the constant current and the congestion of the 
 cutaneous blood vessels in consequence of the 
 stimulation. " (Landois and Stirling.) 
 
 The resistance also varies markedly with the 
 condition of the surface, the condition of the skin, 
 and with the shape, area, position and material 
 of the electrodes by which the current is led into 
 and carried out of the parts. It very seldom is 
 less than l,ooo ohms under the most favorable 
 conditions, and with ordinary contacts is many 
 times that amount. 
 
 The muscles offer nearly nine times the resist- 
 ance in a direction transverse to the fibres than 
 longitudinally to them. (Hermann.) 
 
 The resistance of the epidermis is greater than 
 that of any other tissue of the body. 
 
 The human body probably possesses a true 
 assymmetrical resistance; that is to say, when 
 taken after the current has been passing for some 
 time, its resistance is different in different direc- 
 tions. This variation in the apparent resistance 
 is believed by some to be due to polarization 
 effects. 
 
 Body, Insulated A body sup- 
 ported on an insulator, or non-conductor of 
 electricity. 
 
Fig. Sb, Electric 
 Body- Protector. 
 
 Bod.] 
 
 Body-Protector, Electric A de- 
 vice for protecting the human body against the 
 accidental passage of an electric discharge. 
 
 To protect the human body from the acciden- 
 tal passage through it of dangerous electric cur- 
 rents, Delany places a light, flexible, conducting 
 wire, A A B L L, in the posi- 
 tion shown in Fig. 56, for 
 the purpose of leading the 
 greater part of the current 
 around instead of through 
 the body. The body-pro- 
 tector thus provides a by- 
 path, or shunt of low resist- 
 ance, around the body, and 
 protects it from the effects 
 of an accidental discharge. 
 The resistance of the con- 
 tacts of the protecting conductor with the skin 
 may interfere somewhat with the efficacy of the 
 device. Inside insulating shoe-soles for lessening 
 the danger from accidental contacts through 
 grounded circuits have also been proposed. 
 
 Boiler-Feed, Electric A device 
 
 for automatically opening a boiler-feed appar- 
 atus electrically when the water in the boiler 
 falls to a certain predetermined point. 
 
 Boiling of Secondary or Storage Cell. 
 (See Cell, Secondary, or Storage, Boiling of.) 
 
 Bole. A unit, seldom or uc/er used, pro- 
 posed by the British Association. 
 
 One bole is equal to one gramme-kine. (See 
 Kine.) 
 
 Bolometer. An apparatus devised by 
 Langley for measuring small differences of 
 temperature. 
 
 A thermal balance. (See Balance, Ther- 
 mic?) 
 
 Bombardment, Molecular The 
 
 forcible rectilinear projection from the nega- 
 tive electrode, of the gaseous molecules of the 
 residual atmospheres of exhausted vessels on 
 the passage of electric discharges. (See 
 Matter, Radiant, or Ultra-Gaseous!) 
 
 BonsaKte. An insulating substance. 
 
 Bore, Armature The space pro- 
 vided between the pole pieces of a dynamo 
 or motor for the rotation of the armature*, 
 
 53 [Box. 
 
 Boreal Magnetic Pole. (See Pole, Mag' 
 netic, Boreal.} 
 
 Bot. A term sometimes used as a con- 
 traction for Board of Trade unit of electric 
 supply, or the energy contained in a current 
 of i ,000 amperes flowing in one hour under a 
 pressure of one volt. 
 
 The term appears inadmissible. If used at all, 
 it should be B. O. T. The usage of giving the 
 names of distinguished dead electricians to new 
 units is a good one, and should be followed here. 
 
 Boucherize. To subject to the boucheriz- 
 ing process. (See Boucherizing!) 
 
 Boucherizing. A process for the preser- 
 vation of wooden telegraph poles, by inject- 
 ing a solution of copper sulphate into the 
 pores of the wood. (See Pole, Telegraphic!) 
 
 Bound Charge. (See Charge, Bound!) 
 
 Box Bridge. (See Bridge, Box!) 
 
 Box, Cable A box placed on a 
 
 large terminal pole and provided to receive the 
 separate conductors where the air-line wires 
 join a cable. 
 
 The wires are distributed in the cable box so 
 as to be readily attached to the air-line wires. 
 
 Box, Cooling, of Hydro-Electric Ma- 
 chine. A box provided in Armstrong's 
 hydro-electric machine for the steam to pass 
 through before leaving the nozzle. 
 
 In passing through the cooling-box some of the 
 steam suffers condensation. The cooling-box, 
 therefore, always contains some water, the pres- 
 ence of which seems to be necessary to the opera- 
 tion of the machine. 
 
 Box, Distributing, of Conduit. A name 
 generally applied to a handhole of a conduit 
 (See Handhole of Conduit!) 
 
 Box, Distribution, for Arc Light Cir- 
 cuits. A de'vice by means of which arc 
 and incandescent lights may be simultane- 
 ously employed on the same line from a con- 
 stant-current dynamo-electric machine or 
 other source of constant currents. 
 
 A portion of the line circuit, whose difference 
 of potential is sufficient to operate the electro- 
 receptive device, as, for example, an incandescent 
 lamp, is divided into such a number of multiple 
 
Box.] 
 
 54 
 
 [Box. 
 
 .circuits as will provide a current of the requisite 
 strength for each of the devices. For example, if 
 the normal current on the line is seven amperes, 
 then each of the seven multiple-connected electro- 
 
 - S7- Series-Multiple Circuit. 
 receptive devices shown in Fig. 57 will have a cur- 
 rent of one ampere passing through it, provided 
 the resistance of each branch is the same,, 
 
 In order to protect the remaining devices from 
 variations in the current on the extinguishment of 
 any of the devices, automatic cut-outs are pro- 
 vided, which divert the current thus cut off 
 through a resistance equivalent to that of the 
 device. 
 
 A variety of distribution boxes are in use. (See 
 Circuits, Varieties of.} 
 
 Box, District-Call A box by 
 
 means of which an electric signal is auto- 
 matically sent over a telegraphic line and 
 received by an electro-magnetic device at the 
 other end of the line. 
 
 Fig. 58. District Cull Box. 
 A system of district calls includes a number of 
 call boxes connected by telegraphic lines with a 
 central station. A wheel, or its equivalent, set in 
 
 motion by the pulling of a lever, makes and 
 breaks an electric circuit and sends over the line 
 a succession of electric impulses of varying length, 
 separated from one another by varying intervals 
 of time. These impulses may be received at the 
 central station as a series of dots and dashes, or 
 may, by means of a Morse sounder, produce suc- 
 cessive sounds. By pulling the lever or handle 
 through different distances, different signals may 
 be sent to the central station and serve as calls for 
 various services, such as messenger boys, fire 
 alarm, police, special, etc. 
 
 The general appearance of a four-call district 
 box is shown in Fig. 58. In order to transmit 
 a call for any particular one of these four services 
 the handle is pulled until it comes opposite to the 
 letters indicating the required service, and is then 
 released. The service required is then indicated 
 at the receiving, or central station, through the 
 varying signals sent over the line by the move- 
 ment of the break-wheel, on the release of the 
 handle. 
 
 Box, Fire-Alarm Signal A signal 
 
 box provided for the purpose of automatically 
 sending an alarm of fire. 
 
 The fire-alarm box shown in Fig. 59, operates 
 
 Fig. JQ. Fire- Alarm Signal-Box. 
 
 on the same principle as the district call box. The 
 movement of the handle in the direction of the 
 arrow drives a wheel that makes and breaks a 
 circuit at certain intervals. 
 
 The fire-alarm signal boxes are connected 
 
Box.] 
 
 55 
 
 [Box. 
 
 either with a central station, or with the engine 
 houses of the district in which the alarm is 
 sounded, or with both. 
 
 Box, Fire- Alarm Telegraph An 
 
 automatic-call signal-box employed for send- 
 ing an alarm of fire to a central station. 
 
 A form of fire-alarm telegraph box is shown in 
 Fig. 60. It consists essentially of a circuit-breaker 
 
 Fig. bO. Fire- Alarm Telegraph Box. 
 that is moved by pulling down a lever. The 
 release of the lever repeats the signal to the fire 
 department at the central station a certain number 
 of times. The box also contains a relay bell, 
 lightning arrester and signal-bell key. 
 
 Box, Fishing 1 A term sometimes 
 
 used instead of junction box. (See Box, 
 Junction.} 
 
 Box, Flush A box or space, flush 
 
 with the surface of a road-bed, provided in a 
 system of underground wires or conduits, 
 to facilitate the introduction of the conduct- 
 ors into the conduit, or for the examination 
 of the conductors. 
 
 Box, Fuse The box in which the 
 
 fuse-wire of a safety-fuse is placed. 
 
 The fuse-box should be formed of moisture- 
 proof^ "ncombustible; insulating materials. 
 
 Box, Junction A moisture-proof 
 
 box provided in a system of underground con- 
 
 the feeders and the mains, and from which 
 the current is distributed to the individual 
 consumer. (See Feeder. Main, Electric?) 
 
 A form of junction box for coupling lengths of 
 conductors is shown in Fig. 6l. 
 
 Box, Patrol Alarm An automatic- 
 signal call-box provided for use on the out- 
 side of buildings. . 
 
 The call-box is placed inside a box, the outer 
 door of which is furnished with a Yale lock. 
 
 Fig. bl. Junction Box. 
 
 ductors to receive the terminals of the feed- 
 ers, in which connection is made between 
 
 Ftg.62. Patrol Box. 
 
 A form of patrol box is shown in Fig. 62. 
 
 Box, Resistance A box containing 
 
 a number of separate coils of known resist- 
 ances employed for determining the value of 
 an unknown resistance, and for other pur- 
 poses. (See Bridge, Electric, Box Form of.) 
 
 Box-Sounding Relay. (See Relay, Box- 
 
 Sounding?) 
 
 Box-Sounding Telegraphic Relay. (See 
 
 Relay, Box-Sounding Telegraphic^) 
 
 Box, Splice A box provided for 
 
 holding splice joints and loops, and so ar- 
 ranged as to be readily accessible for exami- 
 nation, re-arrangmg, cross-connecting, etc. 
 
 Splice-boxes vary in shape and construction 
 according to the purposes for which they are 
 designed. 
 
 Box, Splice, Four-way A splice- 
 box piovided with four ways or tubular con- 
 duits. 
 
 Box, Splice, Two- Way A splice- 
 
Box.J 
 
 56 
 
 [Bra. 
 
 box provided with but two tubular conduits or 
 ways. 
 
 Box, Tumbling A rotating box 
 
 in which metallic articles that are to be 
 electroplated are placed so as to be polished 
 by attrition against one another. 
 
 Boxing the Compass. (See Compass, 
 Boxing the?) 
 
 Bracket, Lamp, Electric A de- 
 vice similar to a bracket for a gas burner for 
 holding or supporting an electric lamp. 
 
 Fig. 63. Lamp Bracket, Fig. 6 4. Lamp Bracket. 
 Lamp brackets are either fixed or movable. 
 
 Fig. 6f. Lamp Bracket, Movable Arms. 
 
 Those shown in Figs. 63 and 64 are fixed. That 
 shown in Fig. 65 is movable. 
 
 Bracket, Telegraphic A support 
 
 or cross piece placed on a telegraph pole 
 for the support of the insulators of tele- 
 graphic lines. 
 
 Telegraphic insulators are supported either on 
 wooden arms, or on iron or metal brackets. 
 
 Fig. 66 shows a form of iron bracket. Fig. 67 
 shows a form of wooden arm. 
 
 Fig. 67. Telegraphic 
 Cross-Ann. 
 
 Fig. 66. Telegraphic 
 Bracket. 
 
 Various well known modifications of these 
 shapes are in common use. (For details, see Pole % 
 Telegraphic.) 
 
 Braid, Tubular A braid of fibrous 
 
 insulating material, woven in the form of a 
 tube, and provided for drawing over a splice 
 after two wires have been connected. 
 
 Braided Wire. (See Wire, Braided^ 
 
 Brake, Electro-Magnetic A brake 
 
 for car wheels, the braking power for which 
 is either derived entirely from electro-magnet- 
 ism, or is thrown into action by electro-mag- 
 netic devices. 
 
 Electro-magnetic car brakes are of a great va- 
 riety of forms. They may, however, be arranged 
 in two classes, viz. : 
 
 (l.) Those in which magnetic adhesion, or the 
 magnetic attraction of the brake to the wheels, is 
 employed. 
 
 (2.) Ordinary brake mechanism in which the 
 force operating the brake is thrown into action by 
 an electro-magnet. 
 
 Brake, Friction A name some- 
 times given to a Prony brake. (See Brake, 
 Prony?) 
 
 Brake, Magneto-Electric : A device 
 
 for checking the swing of a galvanometer, in 
 which a slight inverse current is sent through 
 the coils of the galvanometer. 
 
 The Frey magneto -electric brake, as shown in 
 Fig. 68, consists of a small coil, connected by a 
 
 Fig. 68. Electric Brake. 
 
 contact-key with the galvanometer terminals. A 
 small adjustable magnet coil is provided for 
 regulating the action of the inverse current. To 
 avoid disturbance, the brake is placed at least 
 4 or 5 feet from the galvanometer. Manipulation 
 of the ordinary galvanometer key attains the same 
 end in a much simpler manner. 
 
 Brake, Prony A mechanical de- 
 vice for measuring the power of a driving 
 shaft. 
 
JBra. 
 
 57 
 
 An inflexible beam, Fig. 69, is provided at one 
 end with a clamping device for clamping the 
 driving shaft or pulley, and at the other end A, 
 with a pan for holding weights. 
 
 If the brake be arranged as shown in Fig. 69, 
 and the shaft rotate in the direction of the arrow, 
 the tendency will be to carry the beam around 
 with the shaft, placing it at some given moment 
 
 CD? 
 
 Fig. 69, Prony Brake, 
 
 in the position shown by the dotted line. If a 
 sufficiently heavy weight be placed at x, in a pan 
 hung at A, the beam will assume a position ver- 
 tically downwards. If, however, the torque, or 
 
 Jfr 
 
 Fig. 70. Prony Brake. 
 
 twisting force of the driving shaft, be balanced by 
 the weight, the bar will remain horizontal. The 
 power can then be calculated by multiplying the 
 weight in pounds by the circumference in feet of 
 the circle of which the bar is a radius, and this 
 product by the number of turns of the driving 
 shaft per minute. The product will be the num- 
 
 Fig. 71, Prony Brake. 
 
 ber of foot-pouhds per minute, and, when divided 
 by 33,000, will give the horse-power. 
 
 Some modified forms of the Prony brake are 
 shown in Figs. 70 and 71. 
 
 A simple form of brake consists of a cord passed 
 over the pulley of the machine to be tested. A 
 weight is hung at one end of the cord. The other 
 
 end of the cord is attached to the top of a spring 
 balance, the other end of which is fastened to the 
 floor. A reading of the spring balance is taken 
 while the pulley is at rest and when it is in motion, 
 and the result calculated. 
 
 Branch. A term applied to any principal 
 distributing conductor from which outlets 
 are taken or taps made. 
 
 Branch-Block. (See Block, Branch) 
 
 Branch Conductors. (See Conductor, 
 Branch) 
 
 Branch Fuse. (See Fuse, Branch.) 
 
 Branch, Sub A distributing con- 
 ductor taken from a branch. 
 
 Branding, Electric A process 
 
 whereby the branding tool is heated by elec- 
 trical incandescence instead of by ordinary 
 heat. 
 
 The branding tool consists essentially of a small 
 transformer with devices for regulating the cur- 
 rent strength by switches and choking coils. 
 
 Brassing, Electro Coating a sur- 
 face with a layer of brass by electro-plating. 
 (See Plating, Electro) 
 
 The plating bath contains a solution of copper 
 and zinc ; a brass plate is used as an anode. 
 
 Break. A want of continuity in a circuit. 
 
 Break, Circuit Loop A device for 
 
 introducing a loop in any part of a line 
 circuit. 
 
 A form of circuit loop-break is shown in Fig. 72. 
 
 Fig. J2. Circuit Loop Break. 
 
 It consists essentially of a rigid frame with two 
 porcelain or other suitable insulators for the sup. 
 port of the loop wires. 
 
Bre.] 
 
 58 
 
 [Bri. 
 
 Break-Down Switch. (See Svuitch,Break- 
 Down?) 
 
 Break-Induced Current. (See Current, 
 Break-Induced?) 
 
 Break, Mercury A form of circuit 
 
 breaker operated by the removal of a conduc- 
 tor from a mercury surface. 
 
 Mercury breaks assume a variety of forms. One 
 end of the circuit is connected with the mercury, 
 and the other with the conductor. 
 
 Break Shock. (See Shock, Break\ 
 
 Breaker, Circuit Any device for 
 
 breaking a circuit. 
 
 Breaking the Primary. (See Primary, 
 Breaking the.) 
 
 Breaking Weight of Telegraph Wires. 
 (See Wires, Telegraph, Breaking Weight 
 of.) 
 
 Breath Figures. (See Figures, Breath.) 
 
 Breeze, Electric A term some- 
 times employed in electro-therapeutics for a 
 brush discharge. 
 
 One of the electrodes, consisting of a single 
 point or a number of points, is held near the 
 parts to be treated so that the convective discharge 
 is received thereon. The other electrode is con- 
 nected to the body of the patient. 
 
 Breeze, Electro-Therapeutic An 
 
 electric breeze. (See Breeze, Electric?) 
 Breeze, Head, Electro-Therapeutic - 
 
 A form of electric convective discharge, 
 or electric breeze, applied to the head. (See 
 Breeze, Electric?) 
 
 Breeze, Static An electric breeze 
 obtained by the convective discharge of an 
 electrostatic charge. 
 
 Bridge-Anns. (See Arms, Bridge or 
 Balance?) 
 
 Bridge, Box A box of resistance 
 
 coils so arranged as to be capable of being 
 used directly as a Wheatstone electric balance. 
 (See Bridge, Electric, Box Form of.) 
 
 The commercial form of Wheatstone's 
 balance. 
 
 Bridge, Electric A device for 
 
 measuring the value of electric resistances. 
 
 The electric bridge is also called the Electric 
 Balance. 
 
 This is called a bridge because the wire M, G, 
 N, bridges or joins points of equal potential. 
 
 A, B, C and D, Fig. 73, are four electric re- 
 sistances, any one of which can be determined in 
 ohms, provided the absolute value of one of the 
 others, and the relative values of any two of the 
 remaining three are known in ohms. 
 
 A voltaic battery, Zn C, is connected at Q 
 and P, so as to branch at P, and again unite at 
 
 Fig. 73. Electric Balance. 
 
 Q, after passing through the conductor D C, and 
 B A. 
 
 A sensitive galvanometer, G, is connected at 
 M N, as shown. 
 
 The passage of a current through any resistance 
 is attended by a fall of potential proportional to 
 the resistance. (^e& Potential, Electric.) If, then, 
 the resistances A, C and B, are so proportioned 
 to the value of the unknown resistance D, that no 
 current passes through the galvanometer G, the 
 two points, M and N, in the two circuits, Q M P 
 and Q N P, are at the same potential. That is to 
 say, the fall of potential along Q M P and Q N P, 
 at the points M and N, is equal. Since the fall 
 of potential is proportional to the resistance, it 
 follows that 
 
 A : B : : C : D, 
 
 If then we know the values of A, B and C, the 
 value of D, can be readily calculated. 
 
 T> 
 
 By making the value _, some simple ratio, the 
 
 -A. 
 
 value of D, is easily obtained in terms of C. 
 
 The resistances A, B and C, may consist of 
 coils of wire whose resistance is known. To 
 avoid their magnetism affecting the galvanometer 
 needle during the passage of the current through 
 them, they should be made of wire bent into two 
 
Bri.] 
 
 59 
 
 [Bri. 
 
 parallel wires and wrapped in coils called resist- 
 ance coils; or a resistance box may be used. (See 
 Coil, Resistance. ox, Resistance.) 
 
 There are two general forms of Wheatstone's 
 Bridge, the box form, and the sliding form. 
 
 Bridge, Electric, Armg of The 
 
 resistances of an electric bridge or balance. 
 (See Bridge, Electric^ 
 
 Bridge, Electric, Box Form of 
 
 A commercial form of bridge or balance in 
 which all the known arms or branches'of the 
 bridge, except the unknown arm, consist of 
 standardized resistance coils, whose values are 
 given in ohms. (See Coil, Resistance?) 
 The box form of bridge or balance is shown in 
 
 ig- 74- Box Balance. 
 
 perspective in Fig. 74, and in plan in Fig. 75. 
 The bridge arms, corresponding to the resistances 
 
 Fig: 73. Box Balance. 
 
 A and B, of Fig. 73, consist of resistance coils of 
 10, loo and 1,000 ohms each, inserted in the 
 arms q z, and q x, of Fig. 75. These are 
 called the proportional coils. The arm corre- 
 sponding to resistance C, of Fig. 73, is composed 
 of separate resistances of i, 2, 2, 5, 10, 10, 20, 50, 
 loo, loo, 200, 500, 1,000, 1,000, 2,000 and 5,000 
 ohms. In some forms of box bridges additional 
 decimal resistances are added. 
 
 The resistance coils are wound, as shown in 
 Fig. 76, after the wire has been bent on itself in 
 the middle^ This is done in order to avoid the 
 effects of induction, among which are a disturb- 
 ing action on a galvanometer used near them, 
 and the introduction of a spurious resistance in 
 the coils themselves. (See Resistance^ Spurious.} 
 3 Vol. 1 
 
 To avoid the effects of changes of resistance oc- 
 casioned by changes of temperature, the coils are 
 made of German silver, or, preferably, of alloys 
 called Platinoid or Platinum silver. Even when 
 these alloys are used, care should be taken not to 
 allow the currents to pass continuously through 
 the resistance coils longer than a few moments. 
 
 The coils, C, C', are connected with one another 
 in series by soldering their ends to the short 
 
 Fig. 76. Resistance Coils. 
 
 thick pieces of brass, E, E, E, Fig. 76. On the in- 
 sertion of the plug-keys, at S, S, the coils are cut- 
 out by short-circuiting. Care should be taken to 
 see that the plug-keys are firmly inserted and free 
 from grease or dirt, as otherwise the coil will not be 
 completely cut out. As each plug-key is inserted 
 it should be turned slightly in the opening, so 
 as to insure good contact. 
 
 The following are the connections, viz.: The 
 galvanometer is inserted between q and r, Fig. 77, 
 
 fig. 77- Electric Balance. 
 
 the unknown resistance between z and r; the bat- 
 tery is connected tox and z. A convenient pro- 
 portion being taken for the value of the propor- 
 tional coils, resistances are inserted in the arm C, 
 until no deflection is shown by the galvanometer 
 G. The similarity between these connections and 
 those shown in Fig. 75 will be seen from an 
 inspection of Fig. 77. The arms, A and B, corre- 
 spond to q x and q z, of Fig. 75 ; C, to the arm 
 
Bri.] 
 
 60 
 
 [Bri. 
 
 x r, Fig. 75 ; and D, to the unknown resistance. 
 We then have as before: 
 
 A:B::C:D,orAxD = 
 
 The advantage of the simplicity of the ratios, A 
 and B, or 10, 100 and 1,000 of the bridge box, 
 will therefore be manifest. The battery terminals 
 may also be connected to q and r, and the gal- 
 vanometer terminals to x and z, without disturb- 
 ing the proportions. 
 
 Bridge, Electric, Commercial Form of 
 
 A name sometimes given to the box 
 
 form of Wheatstone's electric balance. (See 
 Bridge, Electric, Box Form of.) 
 
 Bridge, Electric Duplex An ar- 
 rangement of telegraphic circuits in the form 
 of a Wheatstone electric bridge for the pur- 
 poses of duplex telegraphy. (See Teleg- 
 raphy, Duplex, Bridge Method of.) 
 
 Bridge, Electric, Proportionate Arms 
 of (See Arms, Proportionate.) 
 
 Bridge, Electric, Slide-Form of 
 
 A balance in which the proportionate arms of 
 the bridge are formed of a single thin wire, of 
 uniform diameter, generally of German silver, 
 of comparatively high resistance. The length 
 of this wire is usually one metre ; hence this 
 apparatus is often called the metre bridge. 
 
 A Sliding Contact Key slides over the wire; one 
 terminal of the key is connected with the galva-> 
 nometer and the other with the wire when the key 
 is depressed. As the wire is of uniform diameter 
 the resistances of the arms, A and B, Fig. 78, will 
 
 Eia ~: r _,flfc~ 
 
 J """"l 
 
 Fig. 78. Slide Bridge. 
 
 be directly proportional to the lengths. A scale 
 placed near the wire serves to measure these 
 lengths. A thick metal strip connected with the 
 slide wire has four gaps at P, Q, R and S. 
 
 When in ordinary use, the gaps at P and S, are 
 either connected by stout strips of conducting ma- 
 terial or by known resistances, in which latter case 
 they act simply as ungraduated extensions of the 
 slide wire, and, like lengthening the slide wire, 
 increase the sensibility of the instrument. 
 
 The unknown resistance is then inserted in the 
 gap at Q, and a known resistance, generally the 
 resistance box, in that at R. The galvanometer 
 has one of its terminals connected to the metal 
 strip between Q and R, and its other terminal to 
 the sliding key. The battery terminals are con- 
 nected to the metal strips between P and Q, and 
 R and S, respectively. 
 
 These connections are more clearly seen in the 
 form of bridge shown in Fig. 79. The slide wire, 
 w w, consists of three separate wires each a metre 
 
 Fig.JQ. Slide Form of Bridge. 
 
 in length, so arranged that only one wire, or two 
 in series, or all three in series, can be used. Mat- 
 ters being now arranged as shown, the sliding 
 key is moved until no current passes through the 
 galvanometer when the key is depressed. 
 
 The slide form of bridge is not entirely satis- 
 factory, since the uncertainty of the spring-con- 
 tact causes a lack of correspondence between the 
 point of contact and the point of the scale on 
 which the index rests. 
 
 The loss of uniformity in the diameter of the 
 wire, due to constant use, causes a lack of corre- 
 spondence between the resistance of the wire and 
 its length. With care, however, very accurate 
 ' results can be obtained by the slide form. 
 
 Bridge, Inductance An appara- 
 tus for measuring the inductance of a circuit 
 similar to a Wheatstone bridge. (See Induc- 
 tance.) 
 
 Professor Hughes employed an inductance 
 bridge of the following description: 
 
 Four resistances, Q, S, R and P, arranged as 
 shown in Fig. 80, form the bridge. The re- 
 sistances, Q, S and R, consist of sections of Ger- 
 man silver wire, one metre in length, each of 
 the resistance of 4 ohms. P, is a coil of wire pos- 
 sessing sensible inductance. The object of tha 
 
Bri.] 
 
 61 
 
 [Bri, 
 
 bridge is to measure the value of this inductance. 
 I, is an interrupter placed in the circuit of the 
 battery B. 
 
 Suppose the interrupter, I, be placed in the tele- 
 phone circuit between T and c. By shifting the 
 sliding contact so as to alter the value of R, a bal- 
 
 Fig. So. Inductance Bridge. 
 
 ance can be effected and silence obtained in the 
 telephone. 
 
 Now remove the interrupter and place it in the 
 battery circuit between b and a, as shown in Fig. 
 So. If now, the interrupter, I, be made to rapidly 
 interrupt the battery current, this balance is 
 destroyed, and cannot be again obtained by any 
 variation in the value of the resistance, R. 
 
 The reason of this is evident. On the closing 
 or opening of the battery current, the inductance 
 of P, produces a counter electromotive force in 
 P, which produces differences of potential between 
 a and c. If an attempt be made to prevent this, 
 
 Fig. St. Hugkef Inductance Bridge. 
 
 by altering the value of R, the steady balance is 
 destroyed,' and the telephone will be traversed by 
 a current during the time the currents have be- 
 come steady. In order to obtain a balance 
 during rapid alternations of the battery current, 
 Vrofeseor Hughes placed a pair of mutually in- 
 
 ductive coils in the battery and the telephone 
 circuits, as shown in Fig. 81. 
 
 The resistances, Q, S, R and P, are the same 
 as already described. The mutually inductive 
 coils, M x and M s , are placed respectively in the 
 telephone and battery circuits in the manner 
 shown. The coil M 2 , in the battery circuit is 
 fixed, while that in the telephone circuit is so 
 arranged that it can be maintained, with its centre 
 coincident with that of M a , while its axis can be 
 placed at any desired angle with M 8 . When the 
 axes of the coils are at right angles, the inductance 
 is zero. When they are co-linear, the inductance 
 is at its maximum. 
 
 When the coils M 15 and M 8 , are in any inter- 
 mediate position, the inductive electromotive 
 force produced in the telephone circuit can, if 
 the value of R, be changed, be made to balance 
 the impulsive electromotive force due to the in- 
 ductance of P, and the value of this latter can, 
 therefore, be inferred. 
 
 An apparatus in- 
 
 Bridge, Magnetic 
 
 vented by Edison for measuring magnetic 
 resistance, similar in principle to Wheatstone's 
 electric bridge. 
 
 The magnetic bridge is based on the fact that 
 two points at the same magnetic potential, when 
 connected, fail to produce any action on a mag- 
 netic needle. The magnetic bridge consists, as 
 shown in Fig. 82, of four arms or sides made of 
 
 Fig. 82. Magnetic Bridge. 
 
 pure, soft iron. The poles of an electro-magnet 
 are connected to projections at the middle of 
 the short side of the rectangle. By this means 
 a difference of magnetic potential is main- 
 tained at these points. The two long sides are 
 formed of two halves each, which form the four 
 arms of the balance. Two of these only are 
 movable. 
 
 Two curved bars of soft iron, of the same area 
 of cross-section as the arms of the bridge, rest on 
 the middle of the long arms, in the arched shape 
 shown. Their ends approach near the too ot the 
 
Bri.j 
 
 [Bru. 
 
 arch within about a half inch. A space is hol- 
 lowed out between these ends, for the reception of 
 a short needle of well-magnetized hardened steel, 
 suspended by a wire from a torsion head. 
 
 The movements of the needle are measured on 
 a scale by a spot of light reflected from a mirror. 
 
 The electro-magnet maintains a constant dif- 
 ference of magnetic potential at the two shorter 
 ends o. the rectangle. If, therefore, the four 
 bars, or arms of the bridge, are magnetically 
 identical, there will be no deflection, since no 
 difference of potential will exist at the ends of the 
 bars between which the needle is suspended. If, 
 however, one of the bars or arms be moved even 
 a trifle, the needle is at once deflected, the motion 
 becoming a maximum when the bar is entirely 
 removed. If replaced by another bar, differing 
 in cross-section, constitution, or molecular struc- 
 ture, the balance is likewise disturbed. 
 
 The magnetic bridge is very sensitive. It was 
 designed by its inventor for testing the magnetic 
 qualities of the iron used in the construction of 
 dynamo-electric machines. 
 
 Bridge Method of Duplex Telegraphy. 
 
 (See Telegraphy, Duplex, Bridge Method 
 of.} 
 
 Bridge Method of Quadruples Teleg- 
 raphy. (See Telegraphy, Quadruplex, 
 Bridge Method of.} 
 
 Bridge, Metre A slide form of 
 
 Wheatstone's electric bridge, in which the 
 slide wire is one metre in length. (See 
 Bridge, Electric, Slide Form of?) 
 
 Bridge, Resistance A term some- 
 times applied to an electric bridge or balance. 
 (See Bridge, Electric?) 
 
 Bridge, Reversible A bridge or 
 
 balance so arranged that the proportionate 
 coils can be readily interchanged, thus per- 
 mitting the bridge coils to be readily tested by 
 reversing. 
 
 Bridge, Wheatstone's Electric 
 
 A name given to the electric bridge or balance. 
 (See Bridge, Electric?) 
 
 Bridges. Heavy copper wires suitably 
 shaped for connecting the dynamo-electric 
 machines in an incandescent light station to 
 the bus-rods or wires. 
 
 Bright Dipping. (See Dipping, Bright?) 
 Bright Dipping Liquid. (See Liquid, 
 Bright Dipping?) 
 
 Britannia Joint. (See Joint, Britannia?] 
 Broken Circuit. (See Circuit, Broken?) 
 
 Bronzing, Electro Coating a sur- 
 face with a layer of bronze by electro-plating. 
 (See Plating, Electro?) 
 
 The plating bath contains a solution of tin and 
 copper. 
 
 Brush-and-Spray Discharge. (See Dis- 
 charge, Brush-and-Spray?) 
 
 Brush Discharge. (See Discharge, 
 Brush?) 
 
 Brush Electrode. (See Electrode, Brush?) 
 
 Brush, Faradic An electrode in 
 
 the form of a brush employed in the medical 
 application of electricity. 
 
 The bristles are generally made of nickelized 
 copper wire. 
 
 Brush-Holders for Dynamo-Electric Ma- 
 chines. Devices for supporting the collecting 
 brushes of dynamo-electric machines. 
 
 As the brushes require to be set or placed on 
 the commutator in a position which often varies 
 with the speed of the machine, and with changes 
 in the resistance of the external circuit, all brush- 
 holders are provided with some device for moving 
 them concentrically with the commutator cylin- 
 der. 
 
 Brush Rocker. (See Rocker, Brush?) 
 
 Brush, Scratch A brush made 
 
 of wire or stiff bristles, etc., suitable for clean- 
 ing the surfaces of metallic objects before 
 placing them in the plating bath. 
 
 Scratch brushes are made of various shapes and 
 are provided with wires or bristles of varying 
 coarseness. 
 
 Some forms of scratch and finishing brushes 
 are shown in Fig. 83. They are circular in outline 
 
 Fig. 83. Scratch Brushes. 
 
 and are adapted for use in connection with a 
 lathe. 
 
Bru.J 
 
 63 
 
 [Bui. 
 
 Brush, Scratch, Circular 
 
 scratch brush of a circular shape, so fitted as 
 to be capable of being placed in a lathe and 
 set in rapid rotation. 
 
 Brush, Scratch, Hand A scratch 
 
 brush operated by hand, as distinguished 
 from a circular scratch brush operated by a 
 lathe. 
 
 Brushes, Adjustment of Dynamo-Electric 
 
 Machines Shifting the brushes into 
 
 the required position on the commutator 
 cylinder, either non-automatically by hand, or 
 automatically by the current itself. (See 
 Regulation, Automatic, of Dynamo-Electric 
 Machines?) 
 
 Brushes, Carbon, for Electric Motors 
 
 Plates of carbon for leading current 
 
 to electric motors. (See Brushes of Dynamo- 
 Electric Machine?) 
 
 These are generally known simply as brushes. 
 
 Brushes, Collecting, of Dynamo-Electric 
 
 Machine Conducting brushes which 
 
 bear on the commutator cylinder, and take off 
 the current generated by the difference of 
 potential in the armature coils. (See Brushes 
 of Dynamo-Electric Machine?) 
 
 Brushes, Lead of The angle through 
 
 which the brushes of a dynamo-electric ma- 
 chine must be moved forward, or in the 
 direction of rotation, in order to diminish 
 sparking and to get the best output from 
 the dynamo. 
 
 The necessity for the lead arises from the coun- 
 ter magnetism or magnetic reaction of the arma- 
 ture, and the magnetic lag of its iron core. (See 
 Lead, Angle of.) 
 
 The position of the brushes on the commutator 
 to insure the best output is practically the same 
 in a series dynamo for any current strength. 
 In shunt and compound dynamos it varies with 
 the lead. 
 
 Brushes of Dynamo-Electric Machine. 
 
 Strips of metal, bundles of wire, slit plates of 
 metal, or plates of carbon, that bear on the 
 commutator cylinder of a dynamo-electric 
 machine, and carry off the current generated. 
 Rotary brushes consisting of metal discs are 
 sometimes employed. Copper is almost univer- 
 
 Fig, 84. Brushes. 
 
 sally used for the brushes of dynamo-electric 
 machines. Carbon brushes are often used for 
 dynamo-electric motors. 
 
 The brush shown at B, Fig. 84, is formed of 
 copper wires, soldered 
 together at the non- 
 bearing end. A copper 
 plate, slit at the bear- 
 ing end, is shown at C, 
 and bundles of copper 
 plates, soldered together 
 at the non-bearing end, 
 are shown at D. 
 
 The brushes should 
 bear against the com- 
 mutator cylinder with 
 sufficient force to pre- 
 vent jumping, and con- 
 sequent burning, and 
 yet not so hard as to 
 cause excessive wear. 
 
 Brushes, Rotating, of Dynamo-Electric 
 
 Machines Discs of metal, employed 
 
 in place of the ordinary brushes for carry- 
 ing off the current from the armatures of 
 dynamo-electric machines. 
 
 Brushing, Scratch Cleansing the 
 
 surface of an article to be electroplated, by 
 friction with a scratch brush. 
 
 Scratch brushing is generally done with the 
 brushes wet by various solutions. 
 
 Buckling. Irregularities in the shape of 
 the surfaces of the plates of storage cells, fol- 
 lowing a too rapid discharge. 
 
 Bug. A term originally employed in quad- 
 ruplex telegraphy to designate any fault in 
 the operation of the apparatus. 
 
 This term is now employed, to a limited extent, 
 for faults in the operation of any electric appa- 
 ratus. 
 
 Bug-Trap. A device employed to over- 
 come the " bug " in quadruplex telegraphy. 
 
 Bulb, Lamp The chamber or 
 
 globe in which the filament of an incan- 
 descent electric lamp is placed. 
 
 The chamber or globe of a lamp must be of 
 such construction as to enable the high vacuum 
 necessary to the operation of the lamp to be main- 
 tained. 
 
Bun.] 64 
 
 Bunched Cable. (See Cable, Bunched!) 
 Bunched Cable, Straightaway - 
 
 (See Cable, Bunched, Straightaway!) 
 
 Bunched Cable, Twisted (See 
 
 Cable, Bunched, Twisted!) 
 
 Bunsen Voltaic Cell. (See Cell, Voltaic, 
 Bunsens!) 
 
 Buoy, Electric A buoy on which 
 
 luminous electric signals are displayed. 
 
 Burglar Alarm. (See Alarm, Burglar!) 
 
 Burglar Alarm Annunciator. (See An- 
 nunciator, Burglar Alarm!) 
 
 Burglar Alarm Contacts. (See Contacts, 
 Burglar Alarm!) 
 
 Burglar Alarm, Tale Lock Switch for 
 (See Alarm, Yale-Lock-Switch Burglar!) 
 
 Burner, Argand Electric An ar- 
 
 gand gas-burner that is lighted by means of 
 an electric spark. 
 
 The argand electric burner assumes a variety 
 of forms, such as the plain-pendant, the ratchet- 
 pendant and the automatic. They are also used 
 in systems of multiple gas lighting. 
 
 Burner, Argand Electric, Automatic 
 
 An argand burner arranged for automatic 
 electric lighting. (See Burner, Automatic- 
 Electric!) 
 
 Burner, Argand Electric, Hand-Lighter 
 
 A plain-pendant electric burner 
 
 adapted for lighting an argand gas-burner. 
 (See Burner, Plain-Pendant Electric?) 
 
 Burner, Argand-Electric, Plain-Pendant 
 
 A plain-pendant electric burner 
 
 adapted for lighting an argand gas burner. 
 (See Burner, Plain-Pendant Electric!) 
 
 Burner, Argand-Electric, Ratchet-Pend- 
 ant A ratchet-pendant electric burner 
 
 adapted for lighting an argand gas-burner. 
 (See Burner, Ratchet-Pendant Electric!) 
 
 Burner, Automatic-Electric An 
 
 electric device for both turning on the gas 
 and lighting it, and turning it off, by alter- 
 nately touching different buttons. 
 
 The gas-cock is opened or closed by the motion 
 of an armature, the movements of which are con- 
 trolled by two separate electro-magnets. One 
 push-button, usually a white one, turns the gas on 
 
 [Bur. 
 
 by energizing one of the electro-magnets and, 
 at the same time, lights it by means ot a suc- 
 cession of sparks from a spark coil. Another 
 push-button, usually a black one, turns the gas 
 off by energizing the other electro-magiaet. 
 The turning on or off of the gas is accom- 
 plished by positive 
 motions. Automatic 
 burners are also made 
 with a single button. 
 
 An Argand Electric 
 Burner is shown in 
 Kg. 85. 
 
 Burner, Electric 
 Candle - A 
 device for electri- 
 cally lighting a gas 
 jet in a burner sur- 
 rounded by a por- 
 celain tube in imita- 
 tion of a candle. 
 
 Electric candle bur- 
 ners are either simple 
 or ratchet candle bur- 
 ners. 
 
 Burner, Hand- 
 Lighting Electric 
 
 A name sometimes applied to a plain- 
 pendant electric burner. (See Burner, Plain- 
 Pendant Electric!) 
 
 Argand Electric 
 Burner. 
 
 Burner, Jump-Spark 
 
 -A term 
 
 sometimes applied to a gas burner in which 
 the issuing gas is ignited 
 by a spark that jumps be- f . 
 tween the metallic points 
 placed on it. 
 
 Jump-spark burners are 
 used in systems of multiple 
 gas lighting. (See Light- 
 ing, Electric Gas.) 
 
 Burner, Plain-Pen- 
 dant Electric A 
 
 gas-- burner provided 
 
 with a pendant for the 
 
 purpose of lighting the 
 
 gas by means of a spark, F ig. 86. Plain-pliant 
 
 after the gas has been Burner. 
 
 turned on by hand. 
 
 The gas is first turned on by hand at the ordi- 
 
Bur.] 
 
 65 
 
 [But. 
 
 nary key, and is then lighted by pulling the pend- 
 ant C, Fig. 86. A spark irom a spark coil ignites 
 the gas. 
 
 This is sometimes called an electric hund- 
 lighting burner. 
 
 Burner, Ratchet-Pendant Candle Elec- 
 tric A burner for both lighting and 
 
 extinguishing a candle gas jet. 
 
 Burner, Ratchet-Pendant Electric 
 
 A gas-burner in which one pulling of a 
 pendant turns on the gas and ignites it by 
 means of an electric spark from a spark coil, 
 and the next pulling of the pendant turns off 
 the gas. 
 
 A ratchet-wheel and pawl are operated by the 
 motion of the pendant. The first pull of the 
 pendant chain moves the ratchet so as to open a 
 four- way gas cock, and at the same time light 
 the gas at the burner tip by a wipe-spark from a 
 spark coil. On the next pull ot the pendant, the 
 four way cock is turned so as to turn off the g?s. 
 Alternate pulls, therefore, light and extinguish 
 the gas. 
 
 Burner, Simple Candle Electric 
 
 A plain-pendant electric burner. (See Bur- 
 ner, Plain Pendant Electric.) 
 
 Thumb-Cock 
 
 gas- 
 
 Electric 
 
 Burner, 
 
 An electric 
 burner, in which 
 the turning of an 
 ordinary thumb- 
 cock turns on the 
 gas, and ignites it 
 by a spark pro- 
 duced byawiping 
 contact actuated 
 by the motions of 
 the thumb-cock. 
 A form of thumb- 
 cock burner is 
 shown in Fig. 87. 
 
 Burner, Vi- 
 brating -,E 1 e c - 
 
 trie An Fig. 87. Thumb- Cock Burner. 
 
 electric gas-burner in which the gas is lighted 
 after it is turned on by hand, by means of the 
 spark from a spark coil produced on the rapid 
 
 making and breaking of the circuit by a 
 vibrating contact. 
 
 The vibrating-electric burner has a single elec- 
 tro-magnet. It is operated by means of a button 
 or switch, and may be used on single lights or on 
 groups of lights. It bears the same relation to 
 the automatic burner that the plain-pendant 
 burner does to the ratchet burner. 
 
 Burnetize. To subject to the Burnetizing 
 process. (See Burnetizing^) 
 
 Burnetizing. A method adopted for the 
 preservation of wooden telegraph poles by 
 injecting a solution of zinc chloride into the 
 pores of the wood. (See Pole, Telegraphic?) 
 
 Burning at Commutator of Dynamo. 
 
 An arcing at the brushes of a dynamo-elec- 
 tric machine, due to their imperfect contact, 
 or improper position, which results in loss of 
 energy and destruction of the commutator 
 segments. 
 
 Bus. A word generally used instead of 
 omnibus. (See Omnibus?) 
 
 Bus-Bars. (See Bars, Bus?) 
 
 Bus-Rod Wires. (See Wires Bus-Rod^ 
 
 Bus-Wire. (See Wire, Bus.) 
 
 Butt Joint. (See Joint, Butt.) 
 
 Button, Carbon A resistance of 
 
 carbon in the form of a button. 
 
 A button of carbon is used as an electric resist- 
 ance in a variety of apparatus; its principal use, 
 however, is in the transmitting instrument of the 
 electric telephone. In the telephone transmitter, 
 the button is so placed between contact-plates that 
 when the plates are pre.-sed together by the 
 sound-waves, the electrical resistance is dec 'eased 
 by a decrease in the thickness of the carbon button, 
 an increase in its density, and an increase in the 
 number of points where the carbon touches the 
 plates. Rheostats, or resistances, have been 
 made by the use of a number of carbon buttons or 
 discs piled one on another and placed in a glass 
 tube. Discs of carbonized cloth form excellent 
 resistances lor such purposes. 
 
 Button, Press A push button. 
 
 (See Button, Push?) 
 
 Button, Push A device for closing 
 
But.] 
 
 66 
 
 [Cab. 
 
 in electric circuit by the movement of a Buzzer, Electric A call, not as 
 
 Dutton. loud as that of a bell, produced by a rapid 
 
 A button, when pushed by the hand, closes the 
 
 Fig. 8 8. Push Button. Fig. 89. 
 
 
 
 Push Button. 
 
 contact, and thus completes a circuit in which 
 some electro- receptive device is placed. This 
 
 circuit is opened by a spring, p 
 
 on the removal of the pressure. 
 Some forms of push-buttons are 
 shown in Figs. 88, 89 and 90. 
 
 KJloor-push for dining-rooms 
 and offices is shown in Fig. 
 90. 
 
 Fig. 88 shows the general 
 appearance of an ordinary bell- 
 push. The arrangement of the 
 
 Fig. oo. Floor 
 interior spnng contacts will be Push. 
 
 understood by an inspection of Fig. 91. 
 
 Fig. 9 f. Spring Contact of Bell Push. 
 
 automatic make-and-break. (See Make-and- 
 Break, Automatic?} 
 
 The buzzer is generally plrced inside a resonant 
 
 Fig. 92. Buzzer. 
 
 case of wood in order to strengthen the sound by 
 resonance. A form of buzzer is shown in Fig. 92. 
 
 C. An abbreviation for centigrade. 
 
 ^hus, 20 degrees C. means 20 degrees of the 
 centigrade thermometric scale. (See Scale, Cett' 
 tigrade Thermometer.') 
 
 C. A contraction for current. 
 
 Generally a contraction for the current in 
 
 E 
 
 amperes, as C = - 
 
 C. C. A contraction for cubic centimetre. 
 (See Weights and Measures, Metric System 
 of-} 
 
 C. G. S. TJnits.~A contraction for centi- 
 timetre-gramme-second units. (See Units, 
 Centimetre-Gramme-Second.) 
 
 C. P. A contraction for candle power. 
 (See Candle, Standard.) 
 
 Cable. An electric cable. (See Cable, 
 Electric^ 
 
 Cable. To send a telegraphic dispatch, 
 by means of a cable. 
 
 Cable, Aerial A cable suspended 
 
 in the air from suitable poles. 
 
 Cable, Anti-Induction, TTaring 
 
 'A form of anti-induction cable. 
 
 In the Waring an ti- induction cable the separate 
 conductors are covered with a fibrous insulator, 
 from which all air and moisture is expelled, and 
 the fibre then saturated with an insulating ma- 
 
Cab.] 
 
 67 
 
 [Cab. 
 
 terial called ozite. The conductors are then pro- 
 tected from the inductive effects of neighboring 
 conductors by a continuous sheath of lead alloyed 
 with tin. 
 
 Where the cables are bunched, the bunches 
 are sometimes again surrounded by insulating 
 material, and the whole then covered by a con- 
 tinuous lead sheathing ; generally, however, the 
 separately insulated conductors are bunched, 
 and then covered by a single sheathing of lead 
 alloyed with tin. 
 
 Cable, Armature of The armor of 
 a cable. (See Armature of a Cabled) 
 
 Cable, Armor of - - The protecting 
 sheathing or metallic covering on the outside 
 of a submarine or other electric cable. 
 
 Cable, Armored An electric cable 
 provided, in addition to its insulating coat- 
 ing, with a protective coating or sheathing, 
 generally of metal tubing or wire. 
 
 Cable-Box. (See Box, Cable^ 
 
 Cable, Bunched A cable contain- 
 ing more than a single wire or conductor. 
 
 Some forms of bunched, lead-covered cables, 
 are shown in Fig. 93. 
 
 Fig. 93. Bunched Cables. 
 
 Cable, Bunched, Straightaway 
 
 A bunched cable the separate conductors of 
 which extend in the direction of the length of 
 the cable without any twisting, being placed 
 in successive layers. 
 
 In arranging the separate conductors in suc- 
 cessive layers an advantage is gained in testing 
 for a given wire in order to make a loop, splice, 
 or branch with the next adjoining section. This is 
 rendered still easier by giving the conductors 
 of the successive layers some distinctive form of 
 braiding in the fibrous insulating material, or 
 some distinctive color. 
 
 Cable, Bunched, Twisted A 
 
 bunched cable, the separate conductors of 
 which are twisted-pairs placed in successive 
 layers. 
 
 Each twisted-pair of a bunched cable acts as a 
 metallic circuit, and, moreover, possesses the ad- 
 vantage of avoiding the ill effects of induction, so 
 disadvantageous in telephone circuits. 
 
 In laying up the twisted-pairs in successive 
 layers in a bunched cable, the direction of twist- 
 ing is reversed in each successive layer. This 
 form is especially desirable on all long cable lines. 
 
 In the case of twisted cables for telephone lines, 
 the twists are sometimes made as frequent as one 
 in every three or four inches. In such cases the 
 cross-talk of induction is inappreciable. 
 
 Cable, Capacity of The quantity 
 
 of electricity required to raise a given length 
 of a cable to a given potential, divided by the 
 potential. 
 
 The amount of charge for a given potential 
 that any single conductor will take up with 
 the rest of the conductors grounded. (See 
 Capacity, Electrostatic^) 
 
 The ability of a wire or cable to permit a 
 certain quantity of electricity to be passed 
 into it before acquiring a given difference of 
 potential. 
 
 Before a telegraph line or cable can transmit a 
 signal to its further end, its difference of potential 
 must be raised to a definite amount dependent on 
 the character of the instruments and the nature of 
 the system. 
 
 The first effect of electricity being passed into a 
 line is to produce an accumulation of electricity 
 on the line, similar to the charge in a condenser. 
 Cables especially act as condensers, and from the 
 high specific inductive capacity of the insulating 
 materials employed, permit considerable induc- 
 tion to take place between the core and the 
 metallic armor or sheathing, or the ground. 
 
 The capacity of a cable depends on the capacity 
 of the wire ; i. e., on its length and surface, on 
 the specific inductive capacity of its insulation, 
 and its neighborhood to the earth, or to other 
 conducting wires, casings, armors, or metallic 
 coatings. Submarine or underground cables 
 therefore have a greater capacity than air lines. 
 
 This accumulation of electricity produces a re- 
 tardation in the speed of signaling, because the 
 wire must be charged before the signal is received 
 at the distant end, and discharged or neutralized 
 before a current can be sent in the reverse direc- 
 tion. This latter may be done by connecting 
 each end to earth, or by the action of the reverse 
 current itself. 
 
Cab.] 
 
 [Cab. 
 
 The smaller the electrostatic capacity of a cable, 
 therefore, the greater the speed of signaling. (See 
 Retardation. ) 
 
 The capacity of a cable is measured in micro- 
 farads. (See farad, Micro.) 
 
 Cable Clip. (See Clip, Cable?) 
 Cable-Core. (See Core of Cable?) 
 
 Cable, Core-Ratio of The ratio be- 
 tween the diameter of the insulation of a cable 
 and the mean diameter of the strand. 
 
 D 
 The core-ratio is represented by -p; where D, 
 
 is the diameter of the insulation, and d, the mean 
 diameter of the strand. Should the extreme 
 diameter of the strand of a cable be used in cal- 
 culations for insulation resistance, inductive capa- 
 city, etc., erroneous values would be obtained. 
 The measured diameter of the copper conductor 
 is consequently decreased some five per cent., and, 
 in this way, correct values are approximately 
 obtained. (Clark dr 3 Sabitte.) 
 
 Cable, Duplex A conductor con- 
 sisting of two separate cables placed parallel 
 to each other. 
 
 The duplex cable is used especially in the al- 
 ternating current system. 
 
 Cable, Electric The combination 
 
 of an extended length of a single insulated 
 conductor, or two or more separately insu- 
 lated electric conductors, covered externally 
 with a metallic sheathing or armor. 
 
 Strictly speaking, the word cable should be 
 limited to the case of more than a single con- 
 ductor. Usage, however, sanctions the employ- 
 ment of the word to indicate a single insulated 
 conductor. 
 
 The conducting wire may consist of a single 
 wire, of a number of separate wires electrically 
 connected, or of a number of separate wires in- 
 sulated from one another. 
 
 An electric cable consists of the following parts, 
 viz.: 
 
 ( I .) The conducting wire or core. 
 
 (2.) The insulating material for separating the 
 several wires; and 
 
 (3.) The armor or protecting covering, consist- 
 ing of strands of iron wire, or of a metallic coat- 
 Ing or covering of lead. 
 
 As to their position, cables are aerial, sub- 
 marine, or underground. As to their purpose, 
 
 they are telegraphic, telephonic, or electric light 
 and power cables. As to the number of their 
 conductors they are single-wire or bunched 
 cables. Bunched cables are straightaway or 
 twisted. 
 Fig. 94 shows a form of submarine cable the 
 
 Fig. 94. Electric Cablt. 
 
 armor of which is formed of strands of iron 
 wire. 
 
 Cable, Electric Light or Power 
 
 A cable designed to distribute the electric cur- 
 rent employed in electric light or power sys- 
 tems. 
 
 Electric light cables are generally tmderground. 
 They may be submarine. (See Cable, Electric.} 
 
 Cable, Flat A cable, the separate 
 
 conductors of which are laid-up side by side 
 so as to form a flat conductor. 
 
 A flat cable is suitable for house work as being 
 less objectionable in appearance when placed on 
 the outside of ceilings or walls. 
 
 Cable, Flat Duplex A flat, laid-up 
 
 cable containing two wires. 
 
 Cable-Grip. (See Grip, Cable?) 
 Cable-Hanger. (See Hanger, Cable?) 
 
 Cable-Hanger Tongs. (See Tongs, CaKe- 
 Hanger?) 
 
 Cable Laid-Up in Layers. A term applied 
 to a cable, all the conducting wires of which 
 are in layers. 
 
Cab.] 
 
 69 
 
 [Cab. 
 
 Cable Laid-Up in Eeversed Layers. A 
 term applied to a cable in which the conduct- 
 ors, in alternate layers, are twisted in opposite 
 directions. (See Cable, Bunched, Straight- 
 away^) 
 
 Cable Laid-Up in Twisted Pairs. A term 
 applied to a cable in which every pair of wires 
 is twisted together. (See Cable, Bunched, 
 Twisted?) 
 
 Cable Lead. (See Lead, Cable). 
 
 Cable, Multiple-Core A cable con- 
 taining more than a single core. 
 
 Cable-Protector. (See Protector, Cable.) 
 
 Cable-Scrying. (See Serving, Cable.) 
 
 Cable, Single-Wire A cable con- 
 taining a single wire or conductor 
 
 Cable, Sub-Aqueous An electric 
 
 cable designed for use under water. 
 
 The term submarine is more frequently em- 
 ployed. 
 
 Cable, Submarine A cable designed 
 
 for use under water. 
 
 Submarine cables are either shallow-water* or 
 deep-sea cables. Gutta-percha answers admirably 
 for the insulating material of the core. Various 
 other insulators are also used. 
 
 Strands of tarred hemp or jute, known as the 
 cable- serving, are wrapped around the insulated 
 core in order to protect it from the pressure of the 
 galvanized iron wire armor afterwards put on. 
 To prevent corrosion the iron wire is covered 
 with tarred hemp, galvanized, or otherwise 
 coated. 
 
 Submarine cables are generally employed tor 
 telegraphic or telephonic communication. (See 
 Cable, Electric.) 
 
 Cable, Submarine, Deep-Sea A 
 
 submarine cable designed for use in deep 
 water. 
 
 This form of cable is not so heavily armored as 
 the shallow-water submarine cable. 
 
 Cable, Submarine, Shallow- Water 
 
 A submarine cable designed for use in shallow 
 water. 
 
 This cable is provided with a heavier armor or 
 sheathing than a deeo-sea cable to protect it 
 from chafing due to the action of the waves and 
 tides in shaiiow water. (See Cable, Submarine.) 
 
 Cable Support, Underground (See 
 
 Support, Underground Cable.) 
 
 Cable Tank.- (See Tank, Cable) 
 
 Cable, Telegraphic A cable de- 
 signed to establish telegraphic communication 
 between different points. 
 
 Telegraphic cables may be aerial, submarine, 
 or underground. (See Cable, Electric.) 
 
 Cable, Telephonic A cable de- 
 signed to establish telephonic communication 
 between different points. 
 
 Telephonic cables may be aerial, submarine, 
 or underground. (See Cable, Electric.) 
 
 Cable-Terminal. (See Terminal, Cable.} 
 
 Cable, Torpedo A cable, in the 
 
 circuit of which a torpedo is placed. (See 
 Torpedo, Electric?) 
 
 Cable, Twisted-Pair A cable 
 
 containing a single twisted pair, suitable for 
 use as a lead and return, thus affording a 
 metallic circuit. 
 
 Cable, Two, Three, Four, etc., Conductor 
 . A cable containing two, three, four, 
 or more separate conducting wires. 
 
 Cable, Underground An electric 
 
 cable placed underground. 
 
 The conducting wires of an underground cable 
 are surrounded by a good insulating, water-proof 
 substance, and protected by a sheathing or armor. 
 A coating of lead is very generally employed for 
 the sheathing or armor. Underground cables, in 
 order to be readily accessible, should be placed 
 in an underground conduit or subway. (See 
 Cable, Electric. Conduit^ Underground Electric. 
 Suoway, Electric.) 
 
 Cable- Worming. (See Worming, Cable) 
 
 Cablegram. A message received by means 
 of a submarine telegraphic cable. 
 
 Cables, Laying-Up The placing or 
 
 disposing of the separate cables or conduc- 
 tors in a bunched cable. 
 
 The separate conductors in cables may be laid- 
 up " straightaway " or "twisted." (See Cable, 
 Bunched^ Twisted. Cable, Bunched, Straight- 
 away. ) 
 
 Cabling. Sending a telegraphic disp^ch 
 bv means of a cable. 
 
Cal.] 
 
 70 
 
 [Cal. 
 
 Calahan's Stock Printer. (See Printer, 
 Stock, Calahan's) 
 
 Calami ne, Electric -- A crystalline 
 variety of silicate of zinc that possesses pyro- 
 electric properties. (See Electricity, Pyro) 
 
 Cal-Electricity. (See Electricity, Cal) 
 
 Calibrate. To determine the absolute 
 or relative value of the scale divisions, or of 
 the indications of any electrical instrument, 
 such as a galvanometer, electrometer, vol- 
 tameter, wattmeter, etc. 
 
 Calibrating. The act of determining the 
 absolute or relative value of the deflections, 
 or indications of an electric instrument. 
 
 Calibration, Absolute -- The deter- 
 mination of the absolute values of the read- 
 ing of an electrometer, galvanometer, volt- 
 meter, amperemeter, or other similar instru- 
 ment. 
 
 The calibration of a galvanometer, for ex- 
 ample, consists in the determination of the law 
 which governs its different deflections, and by 
 which is obtained in amperes, either the absolute 
 or the relative currents required to produce such 
 deflections. 
 
 For various methods of calibration, see stan- 
 dard works on electrical testing, or on elec- 
 tricity. 
 
 Calibration, Invariable, of Galvanom- 
 eter -- In galvanometers with absolute 
 calibration, a method for preventing the oc- 
 currence of variations in the intensity of the 
 field of the galvanometer, due to the neigh- 
 borhood of masses of iron, etc. 
 
 Calibration, Relative -- The deter- 
 mination of the relative values of the reading 
 of an electrometer, voltmeter, amperemeter, 
 or other similar instrument. 
 
 Caliper, Mi- 
 crometer - 
 A name some- 
 times given to a 
 vernier wire 
 gauge. (See 
 Gauge, Vernier 
 
 Call-Bell, Extension (See Bell, 
 
 Extension Call) 
 Call-Bell, Magneto-Electric An 
 
 electric call-bell operated by currents pro- 
 duced by the motion of a coil of wire before 
 the poles of a permanent magnet. 
 
 A well known form of magneto call-bell is shown 
 
 Fig, 9S- Micrometer Caliper. 
 
 A form of micrometer caliper isshown in Fig. qq. 
 
 Fig. 96. Magneto Call Bell. 
 
 in Fig. 96. The armature is driven by the rota- 
 tion of the handle. 
 
 Call-Bell, Telephone An electric 
 
 bell, the ringing of which is used to call a 
 person to a telephone. 
 
 Call, Electric Bell An electric 
 
 bell sometimes used to call the attention of an 
 operator to the fact that his correspondent 
 wishes to communicate with him, or to notify 
 an attendant that some service is desired. 
 
 Call, Messenger A district call- 
 box. (See Box, District Call) 
 
 Call, Thermo-Electric An instru- 
 ment for sounding an alarm when the tem- 
 perature rises above, or falls below, a fixed 
 point. 
 
 In one form of thermo-electric call a needle is 
 moved over a dial by a simple thermic device and 
 rings a bell when the temperature for which it 
 has been se is attained. The thermo-call is appli- 
 cable to the regulation of the temperature oi 
 
Cal.] 
 
 71 
 
 [Cal. 
 
 dwellings, incubators, hot houses, breweries, dry- 
 ing rooms, etc. 
 
 Callaud Yoltaic Cell. (See Cell, Vol- 
 taic, Callaud's.) 
 
 Calling-Drop. (See Drop, Calling.} 
 
 Calorescence. The transformation of 
 invisible heat-rays into luminous rays, when 
 received by certain solid substances. 
 
 The term was proposed by Tyndall. The light 
 from a voltaic arc is passed through a hollow 
 glass lens filled with a solution of iodine in bisul- 
 phide of carbon. 
 
 This solution is opaque to light but quite trans- 
 parent to heat. 
 
 If a piece of charred paper, or thin platinum 
 foil, is placed in the focus of these invisible rays, 
 it will be heated to brilliant incandescence. (See 
 focus.) 
 
 Caloric. A term formerly applied to the 
 fluid which was believed to be the cause or 
 essence of heat. 
 
 The use of the word caloric at the present time 
 is very unscientific, since heat is now known to 
 be an effect of a wave motion and not a material 
 thing. (SeeJfeat.) 
 
 Calorie. A heat unit. 
 
 There are two calories, the small and the large 
 calorie. 
 
 The amount of heat required to raise the tem- 
 perature of one gramme of water from o degree 
 C. to I degree C. is called the small calorie. 
 
 The amount of heat required to raise 1,000 
 grammes, or a kilogramme, of water from o de- 
 gree C. to I degree C. is called the great calorie. 
 The first usage of the word is the commoner. 
 
 This word is sometimes spelled calory. 
 
 Calorie, Great The amount of 
 
 heat required to raise the temperature of one 
 kilogramme of water from o degree C. to I 
 degree C. 
 
 Calorie, Small The amount of 
 
 heat required to raise the temperature of one 
 gramme of water from o degree C. to i 
 degree C. 
 
 Calorimeter. An instrument for measur- 
 ing the amount of heat or thermal energy 
 contained or developed in a given body. 
 
 Thermometers measure temperature only. A 
 
 thermometer plunged in a cup full of boiling 
 water shows the same temperature that it would 
 in a tub full of boiling water. The quantity of 
 heat energy present in the two cases is of course 
 greatly different, and can be measured by a cal- 
 orimeter only. 
 
 Various forms of calorimeters are employed. 
 
 In order to determine the quantity of heat in 
 a given weight of any body, this weight may be 
 heated to a definite temperature, such as the boil- 
 ing point of water, and placed in a vessel con- 
 taining ice. The quantity of ice melted by the 
 body in cooling to the temperature of the ice, is 
 determined by measuring the amount of water 
 derived from the melting of the ice. Care must 
 be observed to avoid the melting of the ice by ex- 
 ternal heat. 
 
 In this way the amount of heat required to 
 raise the temperature of a given weight of a body 
 a certain number of degrees, or the capacity of 
 the body for heat, may be compared with the 
 capacity of an equal weight of water. This ratio 
 is called the specific heat. (See Heat, Specific.} 
 
 The heat energy, present in a given weight of 
 any substance at a given temperature, can be de- 
 termined by means of a calorimeter; for, since a 
 pound of water heated 1 F. absorbs an amount 
 of energy equal to 772 foot-pounds, the energy can 
 be readily calculated if the number of pounds of 
 water and the number of degrees of temperature 
 are known. (See Heat, Mechanical Equivalent 
 of-) 
 
 Calorimeter, Electric An instru- 
 ment for measuring the heat developed in a 
 conductor or any piece of electrical apparatus, 
 in a given time, by an electric current. 
 
 Fig. 9?. Electric Calorimeter. 
 
 A vessel containing water is provided with ft 
 thermometer T, Fig. 97. The electric current 
 
Cal.] 
 
 72 
 
 [Can, 
 
 passes for a measured time through a wire im- 
 mersed in the liquid. 
 
 The quantity of heat is determined from the 
 increase of temperature, and the weight of the 
 water heated. 
 
 According to Joule, the number of heat units 
 developed in a conductor by an electric current 
 is proportional: 
 
 (i.) To the resistance of the conductor. 
 
 (2.) To the square of the current passing. 
 
 (3.) To the time the current is passing. 
 
 (See Heat Unit, English.) 
 
 The heating power of a current is as the square 
 of the current only when the resistance remains 
 the same. (See //<?#/, Electric.) 
 
 Calorimetric. Pertaining to or by means 
 
 of the calorimeter. 
 
 Calorimetric measurement is the measurement 
 of heat energy made by means of the calorimeter. 
 (See Calorimeter.) 
 
 Calorimetrically. In a Calorimetric man- 
 ner. 
 
 Calorimetric Photometer. (See Photom- 
 eter, Calorimetric.) 
 
 Calorimotor. A name applied to a defla- 
 grator. (See Deflagrator^ 
 
 Calory. A term used for calorie. 
 
 Calorie is the preferable orthography. (See 
 Calorie.) 
 
 Cam, Electro-Magnetic A form 
 
 of magnetic equalizer, which depends for its 
 operation on the lateral approach of a suita- 
 bly shaped polar surface. (See Equalizer, 
 Magnetic?) 
 
 Cam, Listening In a telephone 
 
 exchange system, a metallic cam by means of 
 which an operator is placed in circuit with 
 a subscriber. 
 
 Candle. The unit of photometric intensity. 
 
 Such a light as would be produced by the 
 consumption of two grains of a standard 
 candle per minute. 
 
 An electric lamp of 1 6 candle-power, or one of 
 2,ooo candle-power, is a light that gives respect- 
 ively 1 6 or 2,000 times as much light as one stand- 
 ard candle. 
 
 Candle Burner, Electric (See2?wr- 
 
 ner, Electric Candle?) 
 
 Candle, Electric A term applied 
 
 to the Jablochkoff candle, and other similai 
 devices. (See Candle, Jablochkoff,) 
 
 Candle, Foot A unit of illumina- 
 tion equal to the illumination produced by a 
 standard candle at the distance of I foot. 
 
 According to this unit, the illumination pro- 
 duced by a standard candle at the distance of 
 2 feet would be but the one-fourth of a foot- 
 candle; at 3 feet, the one-ninth of a foot-candle, 
 etc. 
 
 The advantage of the proposed standard lies in 
 the fact that knowing the illumination in foot- 
 candles required for the particular work to be 
 done, it is easy to calculate the position and 
 intensity of the lights required to produce the 
 illumination. 
 
 Candle, Jablochkoff An electric 
 
 arc light in which the two carbon electrodes are 
 placed parallel to each other and maintained 
 a constant distance apart by means of a sheet 
 of insulating material placed between them. 
 
 The Jablochkoff electric candle consists of twa 
 parallel carbons, separated by a layer of kaolin or 
 other heat-resisting insulating material, as shown 
 in Fig. 98. The current is passed into and out of 
 the carbons at one end of the 
 candle, and forms a voltaic arc at 
 the other end. In order to start 
 the arc, a thin strip called the 
 igniter, consisting of a mixture of 
 some readily ignitable substance, 
 connects the upper ends of the 
 carbons. 
 
 An alternating current is em- 
 ployed with these candles, thus 
 avoiding the difficulty which Ft 'f' <> s Ja ~ 
 would otherwise occur from the ****' Candu ' 
 more rapid consumption of the positive than the 
 negative carbon. (See Current^ Alternating.) 
 
 Candle, Metre The illumination pro- 
 duced by a standard candle at the distance of 
 one metre. (See Candle, Foot?) 
 
 Candle-Power. (See Power, Candle.) 
 
 Candle-Power, Bated (See Power, 
 
 Candle, Rated.) 
 
 Candle -Power, Spherical (See 
 
 Power, Candle, Spherical?) 
 
 Candle, Standard A candle of 
 
Cao.] 
 
 definite composition which, with a given con- 
 sumption in a given time, will produce a light 
 of a fixed and definite brightness. 
 
 A candle which burns 120 grains of sperma- 
 ceti wax per hour, or 2 grains per minute, will 
 give an illumination equal to one standard candle. 
 
 Unless considerable care is taken, erroneous re- 
 sults will be obtained from the use of the stand- 
 ard candle. According to Slingo and Brooker 
 the following are among the most important 
 causes of these errors : 
 
 (I.) Defective forms of candle which cause a 
 varying consumption of the material per second, 
 and consequently a varying light for the standard 
 candle. 
 
 (2. ) Variations in the composition of the sper- 
 maceti of which the candle is composed. Sper- 
 maceti is not a definite chemical compound, but 
 consists of a mixture of various substances ; 
 therefore, even if the consumption is maintained 
 constant, the light-giving power is not necessarily 
 Constant. 
 
 (3.) Variations in the composition and charac- 
 ter of the wick, such as the number and size of 
 the threads of which it is formed and the closeness 
 of the strands, all of which circumstances influence 
 the amount of light given off by the candle. 
 
 (4.) The light emitted in certain directions ra- 
 ries in a marked degree with the shape of the 
 wick. The mere bending of a wick may, there- 
 fore, cause the amount of light to vary consider- 
 ably. 
 
 (5.) The light varies with the thickness of the 
 wick. Thick wicks give less light than thin 
 wicks. 
 
 (6.) The light given by the standard candle va- 
 ries with the temperature of the testing-room. 
 As the temperature rises the light given by the 
 standard candle increases. 
 
 (7.) Currents of air, by producing variations 
 in the amount of melting wax in the cup of the 
 candle, vary the amount of light emitted. 
 
 These difficulties in obtaining a fixed amount of 
 light from a standard candle, together with the 
 difficulty of comparing the feeble light of a single 
 candle with the light of a much more powerful 
 source, such as an arc lamp, coupled with the 
 additional difficulty arising from the difference in 
 the colors of the lights, have led to the use of 
 other standards of light than those furnished by 
 the standard candle. 
 
 Caontchonc. or India-Rubber. A resin- 
 
 '3 [Cap. 
 
 ous substance obtained from the milky juices 
 of certain tropical trees. 
 
 Caoutchouc possesses high powers of electric 
 insulation, and is used either pure or combined 
 with sulphur. 
 
 Cap, Insulator A covering or cap 
 
 placed some distance above an insulator, but 
 separated from it by an air space. 
 
 Insulator caps are intended for protection of the 
 insulators from injury by the throwing of stones 
 or other malicious acts. Insulator caps are gen- 
 erally made of iron. They are highly objection- 
 able, owing to the facility they offer for the ac- 
 cumulation of dust and dirt. 
 
 Capacity, Atomic The quantiva- 
 
 lence or valency of an atom. (See Atomi- 
 city) 
 
 Capacity, Dielectric A term em- 
 ployed in the same sense as specific inductive 
 capacity. (See Capacity, Specific Inductive?) 
 
 Capacity, Electro-Dynamic A 
 
 term formerly employed by Sir William 
 Thomson for self-induction. (See Induction, 
 Self.} 
 
 Capacity, Electrostatic The quan- 
 tity of electricity which must be imparted to a 
 given body or conductor as a charge, in order 
 to raise its potential a certain amount. (See 
 Potential, Electric?) 
 
 The electrostatic capacity of a conductor is not 
 unlike the capacity of a vessel filled with a liquid 
 or gas. A certain quantity of liquid will fill a 
 given vessel to a level dependent on the size or 
 capacity of the vessel. In the same manner a 
 given quantity of electricity will produce, in a 
 conductor or condenser, a certain difference of 
 electric level, or difference of potential, dependent 
 on the electrical capacity of the conductor or 
 condenser. 
 
 Or, taking the analogous case of a gas-tight 
 vessel, the quantity of gas that can be forced into 
 such a vesssl depends on the size of the vessel 
 and the pressure with which it is forced in. A 
 tension or pressure is thus produced by the gas 
 on the walls of the vessel, which is greater the 
 smaller the size of the vessel and the greater the 
 quantity of gas forced in. 
 
 In the same manner, the smaller the capacity 
 of a conductor, the smaller is the charge required 
 
Cap.] 
 
 [Cap. 
 
 to raise it to a given potential, or the higher the 
 potential a given charge will raise it. 
 
 The capacity K, of a conductor or condenser, 
 is therefore directly proportional to the charge Q, 
 and inversely proportional to the potential V; or, 
 
 From which we obtain Q = KV; or t 
 
 The quantity ef electricity required to charge a 
 conductor or condenser to a given potential is 
 equal to the capacity of the conductor or condenser 
 multiplied by the potential through which it is 
 raised. 
 
 Capacity, Electrostatic, Unit of -- 
 Such a capacity of a conductor or condenser 
 that an electromotive force of one volt will 
 charge it with a quantity of electricity equal 
 to one coulomb. 
 
 The farad. (See Farad^ 
 
 Capacity of Cable. (See Cable, Capacity 
 
 of-} 
 
 Capacity of Condenser. (See Condenser, 
 Capacity of.) 
 
 Capacity of Ley den Jar. (See Jar, 
 Leyden, Capacity of.) 
 
 Capacity of Line. (See Line, Capacity 
 of.) 
 
 Capacity of Polarization of a Toltaio 
 Cell. (See Cell, Voltaic, Capacity of Polar- 
 ization of.) 
 
 Capacity, Safe Carrying, of a Conductor 
 -- The maximum electric current the 
 conductor will carry without becoming unduly 
 heated. 
 
 Capacity, Specific Inductive -- 
 The ability of a dielectric to permit induction 
 to take place through its mass, as compared 
 with the ability possessed by a mass of air of 
 the same dimensions and thickness, under 
 precisely similar conditions. 
 
 The relative power of bodies for trans- 
 mitting electrostatic stresses and strains 
 analogous to permeability in metals. 
 
 The ratio of the capacity of a condenser 
 whose coatings are separated by a dielectric 
 of a given substance to the capacity of a 
 simflar condenser whose plates are separated 
 by a plate or layer of air. 
 
 The inductive capacity of a dielectric is com- 
 pared with that of air. 
 
 According to Gordon and others, the specific 
 inductive capacities of a few substances, com. 
 pared with air, are as follows: 
 
 Air i.oo 
 
 Glass 3-013 to 3.258 
 
 Shellac 2.740 
 
 Sulphur 2.580 
 
 Gutta-percha 2.462 
 
 Ebonite 2.284 
 
 India-rubber 2.220 to 2.497 
 
 Turpentine 2.160 
 
 Petroleum 2.030 to 2.070 
 
 Paraffin (solid) 1-994 
 
 Carbon bisulphide 1.810 
 
 Carbonic acid 1.00036 
 
 Hydrogen 0.99967 
 
 Vacuum 0.99941 
 
 Faraday, who proposed the term specific in* 
 ductive capacity, employed in his experiments a 
 condenser consisting of a metallic sphere A, Fig. 
 99, placed inside a large 
 hollow sphere B. 
 
 The concentric space 
 between A and B was filled 
 with the substance whose 
 specific inductive capacity 
 was to be determined. 
 
 Capacity, Specific 
 
 Magnetic A term 
 
 sometimes employed in 
 the sense of magnetic 
 permeability. 
 
 Conductibility for lines 
 of magnetic force in the 
 same sense that specific 
 inductive capacity is con- 
 ductibility for lines of 
 electrostatic force. 
 
 This term has received 
 the name of specific mag- " " 
 netic capacity in order to distinguish it from specific 
 inductive capacity. The velocity of propagation 
 of waves in any elastic medium is proportional to 
 the quotient obtained by extracting the square 
 root of the elasticity of the medium divided by 
 the square root of its density; or, 
 
 v = .|f 
 
Cap.] 
 
 [Car. 
 
 Similarly, the speed with which inductive waves 
 travel depends on the relation between the elas- 
 ticity and the density of the medium. Calling =^ ? 
 
 the electric elasticity, then its reciprocal, K, corre- 
 sponds with the dielectric capacity. The elec- 
 trical density, //, corresponds with the magnetic 
 permeability. The velocity of wave transmission 
 is therefore, 
 
 V = 
 
 Capacity, Storage, of Secondary Cell 
 
 (See Cell, Secondary or Storage, Capa- 
 city of.) 
 
 Capillarity. The elevation or depression 
 of liquids in tubes of small internal diameter. 
 
 The liquid is elevated when it wets the walls, 
 and depressed when it does not wet the walls of 
 the tube. 
 
 The phenomena of capillarity are due to the 
 mutual attractions existing between the mole- 
 cules of the liquid for one another, and the 
 mutual attraction between the molecules of the 
 liquid and those of the walls of the tube. 
 
 In capillarity, therefore, the approximately 
 level surface caused by the equal attraction of all 
 the molecules towards the earth's centre is dis- 
 turbed by the unequal attraction exerted on each 
 molecule by the walls of the tube and by the re- 
 maining molecules. 
 
 Capillarity, Effects of, on Toltaic Cell 
 
 Effects caused by capillary action 
 
 which disturb the proper action of a voltaic 
 cell. 
 
 These effects are as follows: 
 
 (i.) Creeping, or efflorescence of salts. (See 
 Creeping, Electric. Efflorescence.') 
 
 (2.) Oxidation of contacts and consequent in- 
 troduction of increased resistance into the battery 
 circuit. The liquid enters the capillary spaces 
 between the contact surfaces and oxidizes them. 
 
 Capillary. Of a small or hair-like diame- 
 ter or size. 
 
 A capillary tube is a tube of small hair-like di- 
 ameter. (See Capillarity.} 
 
 Capillary Attraction. (See Attraction, 
 Capillary) 
 
 Capillary Contact-Key. (See Key, Cap- 
 illary Contact?) 
 
 Capillary Electrometer. (See Electrom- 
 eter, Capillary) 
 
 Carbon. An elementary substance which 
 occurs naturally in three distinct allotropic 
 forms, viz.: charcoal, graphite and the dia- 
 mond. (See Allotropy) 
 
 Carbon-Brushes for Electric Motors. 
 
 (See Brushes, Carbon, for Electric Motors) 
 
 Carbon Button. (See Button, Carbon) 
 
 Carbon-Clutch or Clamp of Arc Lamp. 
 (See Clutch, Carbon, of Arc Lamp.] 
 
 Carbon-Electrodes for Arc Lamps. (See 
 Electrodes, Carbon, for Arc Lamps) 
 
 Carbon-Holders for Arc Lamps. (See 
 Holders, Carbon, for Arc Lamps) 
 
 Carbon Points. (See Points, Carbon) 
 
 Carbon Transmitter for Telephones. 
 (See Transmitter, Carbon, for Telephones) 
 
 Carbonic Acid Gas. (See Gas, Carbonic 
 Acid) 
 
 Carboning Lamps. (See Lamps, Carbon- 
 ing) 
 
 Carbonizable. Capable of being carbon- 
 ized. (See Carbonization, Processes of) 
 
 Carbonization. The act of carbonizing. 
 (See Carbonization, Processes of) 
 
 Carbonization, Processes of 
 
 Means for carbonizing material. 
 
 The carbonizable material is placed in suitably 
 shaped boxes, covered with powdered plumbago 
 or lamp-black, and subjected to the prolonged 
 action of intense heat while out of contact with 
 air. 
 
 The electrical conducting power of the carbon 
 which results from this process is increased by the 
 action ot the heat, and, probably, also, by the de- 
 posit in the mass, ot carbon resulting from the 
 subsequent decomposition of the hydro-carbon 
 gases produced during carbonization. 
 
 When the carbonization is for the purpose of 
 producing conductors for incandescent lamps, in 
 order to obtain the uniformity of conducting 
 power, electrical homogeneity, purity and high 
 refractory power requisite, selected fibrous ma- 
 terial, cut or shaped in at least one dimension 
 
Car.] 
 
 prior to carbonization, must be taken, and sub- 
 jected to as nearly uniform carbonization as pos- 
 sible. 
 
 Carbonize. To reduce a carbonizable ma- 
 terial to carbon. (See Carbonization. Pro- 
 cesses of.) 
 
 Carbonized Cloth Discs for High Resist- 
 ances. (See Cloth Discs Carbonized, for 
 High Resistances^) 
 
 Carbonizer. Any apparatus suitable for 
 reducing carbonizable material to carbon. 
 
 Carbonizing. Subjecting a carbonizable 
 substance to the process of carbonization. 
 (See Carbonization, Processes of,) 
 
 Carbons, Artificial Carbons ob- 
 tained by the carbonization of a mixture of 
 pulverized carbon with different carbonizable 
 liquids. 
 
 Powdered coke, or gas-retort carbon, some- 
 times mixed with lamp-black or charcoal, is made 
 into a stiff dough with molasses, tar, or any other 
 hydro-carbon liquid. The mixture is molded 
 into rods, pencils, plates, bars or other desired 
 shapes by the pressure of a powerful hydraulic 
 press. After drying, the carbons are placed in 
 crucibles and covered with lamp-black or pow- 
 dered plumbago, and raised to an intense heat at 
 which they are maintained for several hours. By 
 the carbonization of the hydro-carbon liquids, the 
 carbon paste becomes strongly coherent, and by 
 the action of the heat its conducting power in- 
 creases. 
 
 To give increased density after baking, the 
 carbons are sometimes soaked in a hydro-carbon 
 liquid, and subjected to a re-baking. This may 
 be repeated a number of times. 
 
 Carbons, Concentric-Cylindrical 
 
 A cylindrical rod of carbon placed inside a hol- 
 low cylinder of carbon but separated from it 
 by an air space, or by some other insulating, 
 refractory material. 
 
 Jablochkoff candles sometimes are made with a 
 solid cylindrical electrode, concentrically placed 
 in a hollow cylindrical carbon. 
 
 Carbons, Cored A cylindrical carbon 
 
 electrode for an arc lamp that is molded 
 around a central core of charcoal, or other 
 softer carbon. 
 
 76 
 
 [Car. 
 
 Much of the unsteadiness of the arc light is due 
 to changes in the position of the arc. Cored car- 
 bons, it is claimed, render the arc light steadier, 
 by maintaining the arc always at the softer carbon 
 and hence at the central point of the electrode. 
 
 A core of harder carbon, or other refractory 
 material, is sometimes provided for the negative 
 carbon. 
 
 Carbons, Flashed Carbons which 
 
 have been subjected to the flashing pro- 
 cess. (See Carbons, Flashing Process for.) 
 
 Carbons, Flashing Process for A 
 
 process for improving the electrical uniformity 
 of the carbon conductors employed in in- 
 candescent lighting, by the deposition of car- 
 bon in their pores, and over their surfaces at 
 those places where the electric resistance is 
 relatively great. 
 
 The carbon conductor or filament is placed in 
 a vessel filled with the vapor of a hydrocarbon 
 liquid called rhigolene, or any other readily de- 
 composable hydrocarbon liquid, and gradually 
 raised to electric incandescence by the passage 
 through it of an electric current A decomposi- 
 tion of the hydrocarbon vapor occurs, the car- 
 bon resulting therefrom being deposited in and on 
 the conductor. 
 
 As the current is gradually increased, the 
 parts of the conductor first rendered incandes- 
 cent are the places where the electric resist- 
 ance is the highest, these parts, therefore, and 
 practically these parts only, receive the deposit 
 of carbon. As the current increases, other 
 portions become successively incandescent and 
 receive a deposit of carbon, until at last the 
 filament glows with a uniform brilliancy, in- 
 dicative of its electric homogeneity. 
 
 A carbon whose resistance varies considerably 
 at different parts could not be successfully em- 
 ployed in an incandescent lamp, since if heated 
 by a current sufficiently great to render the points 
 of comparatively small resistance satisfactorily 
 incandescent, the temperature of the points of 
 high resistance would be such as to lower the life 
 of the lamp, while if only those portions were 
 safely heated, the lamp would not be economical. 
 The flashing process is therefore of very great 
 value in the manufacture of an incandescent 
 lamp. 
 
 The name " flashing " was applied to the pro- 
 cess by reason of the flashing light emitted by the 
 
Car.] 
 
 77 
 
 [Cas. 
 
 carbons when they have been sufficiently treated. 
 The process requires so little time that the dull red 
 which first appears soon flashes to the full lumin- 
 osity required. 
 
 The term "flashing" is sometimes applied to 
 the electrical heating to incandescence, while the 
 carbons are in the lamp chambers, and on the 
 pumps. This flashing is for the purpose of 
 driving off all the gases occluded by the carbon, 
 so that these gases may be carried off by the 
 operation of pumping. This process is more 
 properly called the process for driving off the 
 occluded gases. 
 
 The carbons are sometimes flashed in the liquid 
 itself instead of in its vapor. 
 
 Carbons, Paper Carbons, of textile 
 or fibrous origin, obtained from the carboniza- 
 tion of paper. 
 
 The carbonization of paper is readily effected 
 by submitting the paper to the prolonged action 
 of a high temperature while out of contact with 
 air. 
 
 For this purpose the paper is packed in retorts 
 or crucibles, and covered with lamp-black, or 
 powdered plumbago, in order to exclude the air. 
 
 Since paper consists of a plane of material uni- 
 formly thin in one direction, formed almost en- 
 tirely of fibres of pure cellulose, the greatest 
 length of which extends in a direction nearly par- 
 allel to that in which the paper is uniformly thin, 
 it is clear that sheets of this substance, when car- 
 bonized, should yield flexible carbons of unusual 
 purity and electrical homogeneity, since such 
 carbons are structural in character, and are uni- 
 formly affected by the heat of carbonization to an 
 extent that would be impossible by the carboniza- 
 tion of any material in a mass. 
 
 Carcase of Dynamo-Electric Machine. 
 
 (See Machine, Dynamo-Electric, Carcase of.) 
 Carcel. The French unit of light. The 
 light emitted by a lamp burning 42 grammes 
 of pure colza oil per hour, with a flame 40 
 millimetres in height. 
 
 The bec-carcel. One carcel = 9.5 to 9.6 stand- 
 ard candles. 
 
 Carcel Lamp. (See Lamp, Carcel.) 
 Carcel Standard Gas Jet. (See/<?/, Gas, 
 
 Carcel Standard) 
 Card, Compass A card used in the 
 
 mariner's compass, on which are marked the 
 
 four cardinal points of the compass N, S, E 
 and W, and these again divided into thirty- 
 two points called Rhumbs. (See Compass, 
 Azimuth?) 
 
 Cardew Yoltmeter. (See Voltmeter, 
 Cardew.) 
 
 Carriage, Pen The carriage in an 
 electric chronograph which holds the pen and 
 moves over the sheet of paper on which the 
 record is made. (See Chronograph, Elec- 
 tric.) 
 
 Carriers of Replenisher. (See Replen- 
 isher, Carriers of.) 
 Cascade, Charging Leyden Jars by 
 
 A method of charging jars or condensers 
 by means of the free electricity liberated by 
 induction from one coating, when a charge is 
 passed into the other coating. 
 
 The jars are placed as shown in Fig. 100, with 
 the inside coating of the first jar connected with 
 the outside coating of the one next it. There is in 
 
 Fig. TOO. Cascade Charging of Leyden Jars. 
 
 reality no increase in the entire charge obtained 
 in charging by cascade, since the sum of the 
 charges given to the separate jars is equal to 
 the same charge given to a single jar separately 
 charged. 
 
 The energy of the discharge in cascade can be 
 shown to be less than that of the same charge 
 when confined to a single jar. This i c of course 
 to be expected, since it is energy that <? charged 
 in the jar and not electricity, and, of course, the 
 energy charged in the jar can never exceed the 
 energy employed in charging the jar. There is 
 a small loss for each jar, and this increases ne- 
 cessarily with each jar added. 
 
 Cascade, Connection of Electric Sources 
 
 in A term sometimes used for series- 
 connection of electric sources. 
 
 The term series -connection is the preferable 
 one. (See Connection, Series.) 
 
 Case-Hardening, Electric Super- 
 ficially converting a piece of wire into steef 
 by electrically produced heat. 
 
Cas.] 
 
 78 
 
 [Can. 
 
 In electric case-hardening, the superficial layers 
 of a piece of iron are converted into steel by 
 electrically heating the same, while surrounded 
 by a layer of case-hardening flux and carbonaceous 
 substances such as animal charcoal, shavings of 
 horn, leather cuttings or other similar substances. 
 
 In the case of a readily oxidizable metal like 
 Iron, oxidation is prevented by surrounding the 
 metal by a hydrocarbon gas, which, when suffi- 
 ciently heated, deposits on the surfaces a pro- 
 tective coating of carbon. This layer of carbon 
 gradually carbonizes the iron. 
 
 Case Wiring. (See Wiring, Case.) 
 
 Cataphoresis. A term sometimes em- 
 ployed in place of electric osmose. (See Os- 
 mose, Electric!) 
 
 The word cataphoresis applies to the cases where 
 medicinal substances, such as iodine, cocoaine, 
 quinine, etc., are caused to pass through organic 
 tissues in the direction of flow of an electric cur. 
 rent, or from the anode to the kathode. This 
 action is probably due to an electrolytic action. 
 
 Cataphoric Action. (See Action, Cata- 
 phoric^ 
 
 Catch, Safety A wire, plate, strip, 
 
 or box of readily fusible metal, capable of con- 
 ducting, without fusing, the current ordinarily 
 employed on the circuit, but which fuses and 
 thus breaks the circuit on the passage of an 
 abnormally large current. 
 
 Safety -catches are generally placed on multiple- 
 arc and multiple-series circuits. (See Fusc % 
 Safety.} 
 
 Catelectrotonus. An orthography some- 
 times applied to Kathelectrotonus. (See 
 
 Kathelectrotonus!) 
 
 Cathetometer. An instrument for the ac- 
 curate measurement of vertical height. 
 
 The cathetometer consists essentially of an 
 accurately divided vertical rod which carries a 
 sliding support for a telescope. The telescope is 
 provided with two spider lines at right angles to 
 one another, so placed as to be seen in front of 
 the object whose height is to be measured. From 
 observations taken in different positions, the 
 measurement of the true vertical height is readily 
 obtained. 
 
 Cathion. A term sometimes used instead 
 Ot Kathion. 
 
 More correctly written Kathion. (See 
 Kathion!) 
 
 Cathode. A term sometimes used instead 
 of Kathode. 
 
 Catoptrics. That branch of optics which 
 treats of the reflection of light. 
 
 Causty, Galvano A term some- 
 times used for galvano-cautery. (See Cautery, 
 Galvano!] 
 
 Cauterization. The act of cauterizing, or 
 burning with a heated solid or caustic sub- 
 stance. 
 
 Cauterization, Electric Subject- 
 ing to cauterization by means of a wire elec- 
 trically heated. (See Cautery, Electric?) 
 
 Cauterize. To subject to cauterization, or 
 burning with a heated solid or caustic sub- 
 stance. 
 
 Cauterizer, Electric A term some- 
 times applied to an electric cautery. (See 
 Cautery, Electric!) 
 
 Cautery, Actual A burning or sear- 
 ing with a white-hot metal. 
 
 Cautery Battery. (See Battery, Cautery!) 
 
 Cautery, Electric An instrument 
 
 used for electric cauterization. 
 
 In electro-therapeutics, the application ol 
 variously shaped platinum wires heated to in- 
 candescence by the electric current in place 
 of a knife, for removing diseased growths, or 
 for stopping hemorrhages. 
 
 The operation, though painful during applica- 
 tion, is afterward less painful than that with a 
 knife, since secondary hemorrhage seldom occurs, 
 and the wound rapidly heals. 
 
 Electric cautery is applicable in cases where 
 the knife would be inadmissible owing to the 
 situation of the parts or their surroundings. 
 
 Cautery, Galrano A term fre- 
 quently employed in place of electric cautery. 
 (See Cautery, Electric!) 
 
 Cautery, Galvano Electric An 
 
 electric cautery. (See Cautery, Electric!) 
 
 Cautery, Galvano Thermal A 
 
 term sometimes used for an electric cautery, 
 (See Cautery, Electric!* 
 
Cau. 7 
 
 79 
 
 [Cel. 
 
 Cautery-Knife Electrode. (See Electrode, 
 Cautery-Knife.) 
 
 Cautery, Thermal A cautery 
 
 heated by heat other than that of electric ori- 
 gin, as distinguished from an electric cautery. 
 (See Cautery, Electric?) 
 
 Ceiling Rose. (See Rose, Ceiling!) 
 
 Cell, Depositing An electrolytic 
 
 cell in which an electro-metallurgical deposit is 
 made. (See Metallurgy, Electro?) 
 
 Cell, Electrolytic A cell or vessel 
 
 containing an electrolyte, in which electrolysis 
 is carried on. 
 
 An electrolytic cell is called a voltameter when 
 the value of the current passing is deduced from 
 the weight of the metal deposited. 
 
 Cell, Impulsion A photo-electric 
 
 cell whose sensitiveness to light may be re- 
 stored or destroyed by slight impulses given 
 to the plates, such as by blows or taps, or elec- 
 tro-magnetic impulses. 
 
 An impulsion cell may be prepared by pasting 
 pieces of tin-foil, the opposite faces of which are 
 respectively polished and dull, on the opposite 
 faces of a plate of glass, so as to expose dissimi- 
 lar sides to the light, when the cells are dipped 
 in alcohol. 
 
 Cell, Photo-Electric A cell capa- 
 ble of producing differences of potential 
 when its opposite faces are unequally exposed 
 to radiant energy. 
 
 Photo-voltaic cells are made hi a variety of 
 forms, both with selenium and with different me- 
 tallic substances. (See Cell, Selenittm.) 
 
 Cell, Porous A jar of unglazed 
 
 earthenware, employed in double-fluid voltaic 
 cells, to keep the two liquids separated. 
 
 The use of a porous cell necessarily increases 
 the internal resistance of the cell, from the de- 
 crease it produces in the area of cross section of 
 liquid between the two elements. When the bat- 
 tery is dismantled, the porous cells should be 
 kept under water, otherwise the crystallization of 
 the zinc sulphate or other salt is apt to produce 
 serious exfoliation, or scaling off, or even to 
 crumble the porous cell. 
 
 A porous cell is sometimes called a diaphragm, 
 but only properly so when the cell is reduced to 
 a single separating plate. (See Cell, Voltaic.) 
 
 Cell, Secondary 
 
 A term sometimes 
 
 used instead of storage cell. 
 
 The term secondary cell is used in contradis- 
 tinction to primary or voltaic cell. 
 
 Cell. Secondary or Storage, Boiling of 
 
 A term sometimes applied to the 
 
 gassing of a storage cell. (See Cell, Storage, 
 Gassing 0f.) 
 
 Cell, Secondary or Storage, Capacity of 
 
 The product of the current in am- 
 peres, by the number of hours the battery is 
 capable of furnishing said current, when 
 fully charged, until exhausted. 
 
 The capacity of storage cells is given in ampere- 
 hours. A storage battery with a capacity of 1,000 
 ampere-hours can furnish, say a current of fifty 
 amperes for twenty hours, or a current of one 
 hundred amperes for ten hours ; or a current of 
 twenty-five amperes for forty hours. 
 
 Cell, Secondary or Storage, Gassing of 
 
 An escape of gas due to the decom- 
 position of water on passage of too strong a 
 charging current. 
 
 Cell, Secondary or Storage, Renovation 
 
 of The revivifying or recharging of a 
 
 run-down, or discharged storage cell. 
 
 Cell, Secondary or Storage, Time-Fall 
 
 of Electromotive Force of (See 
 
 Force. Electromotive of Secondary or 
 Storage Cell, Time-Fall, 0f.) 
 
 Cell, Secondary or Storage, Time-Rise 
 
 of Electromotive Force of (See 
 
 Force, Electromotive of, Secondary or 
 Storage Cell, Time-Rise, 0f.) 
 
 Cell, Selenium A cell consisting 
 
 of a mass of selenium fused in between two 
 conducting wires or electrodes of platinized 
 silver or other suitable metal. 
 
 A convenient manner of forming a selenium 
 cell is to wind two separate spirals of platinized 
 silver wire around a cylinder of hard wood, tak- 
 ing care to maintain them a constant distance 
 apart, so as to avoid contact between them. The 
 space between" these wires is filled with fused sele- 
 nium, which is allowed to cool gradually. 
 
 Exposure to sunlight reduces the resistance of 
 a selenium cell to about one-half its resistance in 
 
CeL] 
 
 80 
 
 [Cel. 
 
 the dark, but neither the resistance nor the reduc- 
 tion ratio long remains constant. 
 
 A selenium cell produces a difference of poten- 
 tial, or electromotive force, when one of its elec- 
 trode faces is exposed to light, while the other is 
 kept in darkness. 
 
 According to Von Uljanin, who experimented 
 with selenium melted in between two parallel 
 platinized plates, cooled under pressure, and then 
 reduced from the amorphous to the sensitive crys- 
 talline variety by gradual cooling after two or 
 three heatings in a paraffine bath up to 195 de- 
 grees, the following peculiarities were observed: 
 
 (i.) Exposure of one of the electrodes to sun- 
 light produced an electromotive force which 
 causes a current to flow from the dark to the 
 illumined electrode. 
 
 (2.) The maximum electromotive force was 
 o. 12 volt. 
 
 (3.) The electromotive force disappeared instan- 
 taneously and completely on the darkening of the 
 electrodes. 
 
 (4.) A slight difference in the electromotive 
 force was observed when the positive and nega- 
 tive electrodes were alternately exposed to the 
 light, the maximum electromotive force being 
 attained by the exposure of the negative electrode. 
 
 (5.) If both electrodes are similarly illumined 
 the resulting current strength is decreased and 
 may reach zero. 
 
 (6.) The action of light is instantaneous. 
 
 (7.) Most of the selenium cells experimented 
 with exhibited an electromotive force of polariza- 
 tion. 
 
 (8.) The electromotive force of polarization is 
 diminished by exposure to light. 
 
 (9.) The electrical resistance and sensitive- 
 ness to light as regards the production of an 
 electromotive force decrease with time. This 
 is probably due to a gradual change in the allo- 
 tropic state of the selenium. (See State, Allo- 
 tropic.) 
 
 (10.) The electromotive force produced is pro- 
 portional to the intensity of the illumination only 
 when the obscure rays or heat rays are absent. 
 
 (II.) Of different wave lengths the orange-yel- 
 low rays in the diffraction spectrum, and the 
 greenish-yellow in the prismatic ppectrum pro- 
 duced the greatest effect. 
 
 Among some of the more recent applications 
 of selenium cells are the following: 
 
 (I.) A selenium cell is so placed in a circuit 
 containing an electro-magnet and switch, that on 
 
 one of its electrodes being exposed to the de- 
 creased illumination of coming night it automat- 
 ically turns on an electric lamp, and, conversely, 
 on the approach of daylight, and the consequent 
 illumination of the electrode, turns it off. 
 
 (2.) A device whereby the presence of light, 
 as for example that carried by a burglar, auto- 
 matically rings an alarm and thus calls the atten- 
 tion of the watchman of the building. 
 
 Cell, Standard (See Cell, Voltaic, 
 
 Standard?) 
 
 Cell, Storage ' Two relatively inert 
 
 plates of metal, or of metallic compounds, 
 immersed in an electrolyte incapable of acting 
 considerably on them until after an electric 
 current has been passed through the liquid 
 from one plate to the other and has changed 
 their chemical relations. 
 
 A single one of the cells required to form 
 a secondary battery. 
 
 Sometimes, the jar containing a single cell 
 is called a storage cell. 
 
 This latter use of the word is objectionable. 
 
 A storage cell is also called an accumulator. 
 
 On the passage of an electric current through 
 the electrolyte, its decomposition is effected and 
 the electro-positive and electro-negative radicals 
 are deposited on the plates, or unite with them, 
 so that on the cessation of the charging current, 
 there remains a voltaic cell capable of generating 
 an electric current. 
 
 A storage cell is charged by the passage through 
 the liquid from one plate to the other of an elec- 
 tric current, derived from any external source. 
 The charging current produces an electrolytic de- 
 composition of the inert liquid between the 
 plates, depositing the electro-positive radicals, or 
 kathions, on the plate connected with the negative 
 terminal of the source, and the electro-negative 
 radicals, or onions, on the plate connected with 
 the positive terminal. 
 
 On the cessation of the charging current, and 
 the connection of the charged plates by a con- 
 ductor outside the liquid, a current is produced, 
 which flows through the liquid from the plate 
 covered with the electro-positive radicals, to that 
 covered with the electro-negative radicals, or in 
 the opposite direction to that of the charging cur- 
 rent. 
 
 The simplest storage cell is Plan id's cell, which, 
 as originally constructed, consists of two plates of 
 
Cel.J 
 
 81 
 
 [Cel. 
 
 lead immersed in dilute sulphuric acid, H 2 SO 4 . 
 On the passage of the charging current, the plates 
 A and B, Fig. 101, dipped in H 2 SO 4 , are covered 
 respectively with lead peroxide, PbO 2 , and finely 
 divided, spongy lead. The peroxide is formed on 
 the positive plate, and the metallic lead on the 
 negative plate. The acid and water should have 
 a specific gravity of about 1.170. When the cell 
 is fully charged the acid solution loses its clear- 
 ness and becomes milky in appearance, and the 
 
 Figs. ioi and 102, Storage Cell. 
 
 specific gravity increases to 1. 195. This increase 
 is a good sign of a full charge. 
 
 When the charging current ceases to pass, the 
 cell discharges in the opposite direction, viz., 
 from B' to A', that is, from the spongy lead plate 
 to the peroxide plate through the electrolyte, as 
 shown in Fig. 102. 
 
 As a result of this discharging current the per- 
 oxide, PbO 8 , on A', gives up one of its atoms of 
 oxygen to the spongy lead on B', thus leaving 
 both plates coated with a layer of PbO, lead 
 monoxide, or litharge. When this change is 
 thoroughly effected, the cell becomes inert, and 
 will furnish no further current until again charged 
 by the passage of a current from some external 
 source. 
 
 In order to increase the capacity of the storage 
 cells, and thus prolong the time of their discharge, 
 the coating of lead monoxide thus left on each 
 of the plates, when neutral, is made as great as 
 possible. To effect this, a process called ' 'forming 
 the plates" is employed, which consists in first 
 charging the plates as already described, and 
 then reversing the direction of the charging cur- 
 rent, the currents being sent through the cell in 
 alternately opposite directions, until a consider, 
 able depth of the lead plates has been acted on. 
 
 It will be noticed that during the action of the 
 charging current, the oxygen is transferred from 
 the PbO, on one jjlate, to the PbO, on the other 
 plate, thus leaving one Pb, and the other PbO g ; 
 and that on discharging, one atom of oxygen is 
 
 transferred from the PbO 2 , to the Pb, thus leav- 
 ing both plates covered with PbO. In reality 
 this is but the final result of the action, hydrated 
 sulphate of lead, PbO, H 2 SO 4 , being formed, 
 and subsequently decomposed. Other com- 
 pounds are formed that are but imperfectly un- 
 derstood. 
 
 In order to decrease the time required for form- 
 ing, accumulators, or secondary cells, have been 
 constructed, in which metallic plates covered with 
 red lead Pb 3 O 4 replace the lead plates in the 
 original Plante cell. On charging, the Pb 3 O 4 
 is peroxidized at the anode, i. e., converted into 
 PbO 2 , and deoxidized, and subsequently con- 
 verted into metallic lead at the kathode. Or, in 
 place of the above Pb 3 O 4 , red lead is placed on 
 the anode and PbO, or litharge, on the kathode. 
 
 Plates of compressed litharge have also been 
 recently used for this purpose. Storage cells so 
 formed have a greater storage capacity per unit 
 weight than those in which a grid is employed, 
 but a higher resistance. 
 
 In all cases where a metal plate is employed 
 various irregularities of surface are given to the 
 plates, in order to increase their extent of surface 
 and to afford a means for preventing the separa- 
 tion of the coatings. The metallic form thus 
 provided is known technically as a grid. 
 
 Unless care is exercised, the plates will bucklt 
 from the difference in the expansion of the lead 
 and its filling of oxide. This buckling is attended 
 with lan increase in the resistance of the cell and 
 the gradual separation of the oxides that cover or 
 fill it. 
 
 Cell, Thermo-Electrfe A name 
 
 applied to a thermo-electric couple. (See 
 Couple, Thermo-Electric^ 
 
 Cell, Voltaic The combination of 
 
 two metals, or of a metal and a metalloid, 
 which, when dipped into a liquid or liquids 
 called electrolytes, and connected outside the 
 liquid or liquids by a conductor, will produce 
 a current of electricity. 
 
 Different liquids or gases may take the place of 
 the two metals, or of the metal and metalloid. 
 (See Battery, Gas.) 
 
 Plates of zinc and copper dipped into a solu- 
 tion of sulphuric acid and water, and connected 
 outside the liquid by a conductor, form a simple 
 voltaic cell. 
 
 If the zinc be of ordinary commercial purity : 
 
Cel.] 
 
 [Cel. 
 
 and is not connected outside the liquid by a con- 
 ductor, the following phenomena occur: 
 
 (i.) The sulphuric acid or hydrogen sul- 
 phate, H,,SO 4 , is decomposed, zinc sulphate, 
 ZnSO 4 , being formed, and hydrogen, H 2 , liber- 
 ated. 
 
 (2.) The hydrogen is liberated mainly at the 
 surface of the zinc plate. 
 
 (3.) The entire mass of the liquid becomes 
 heated. 
 
 If, however, the plates are connected outside 
 the liquid by a conductor of electricity, then the 
 phenomena change and are as follows, viz.: 
 
 (i.) The sulphuric acid is decomposed as be- 
 fore; but, 
 
 (2.) The hydrogen is liberated at the surface of 
 the copper plate only. 
 
 (3.) The heat no longer appears in the liquid 
 only, but in all parts of the circuit. 
 
 (4.) An electric current now flows through the 
 entire circuit, and will continue so to flow as long 
 as there is any sulphuric acid to be decomposed, 
 and zinc with which to form zinc sulphate. 
 
 The energy which previously appeared as heat 
 only, now appears in part as electric energy. 
 
 Therefore, although the mere contact of the 
 two metals with the liquid will produce a differ- 
 ence of potential, it is the chemical potential 
 energy which became kinetic during chemical 
 combination that supplies the energy required to 
 maintain the electric current. (See Energy, 
 Kinetic. Energy, Potential.') 
 
 A voltaic cell consists of two plates of different 
 metals, or of a metal and a metalloid (or of two 
 gases, or two liquids, or of a liquid and a gas), 
 each of which is called a 
 voltaic element, and which, 
 taken together, form what is 
 called a voltaic couple. 
 
 The voltaic couple dips in- 
 to a liquid called an electro- 
 lyte, which, as it transmits 
 the electric current, is de- 
 ., composed by it. The ele- 
 ments are connected outside 
 the electrolyte by any con- Fig' 103. 
 ducting material. 
 
 Direction of the Current. In any voltaic cell 
 the current is assumed to flow through the liquid, 
 from the metal most acted on to the metal least 
 acted on, and outside the liquid, through the out- 
 side circuit, from the metal least acted on to the 
 metal most acted on. 
 
 Voltaic 
 Couple. 
 
 In Fig. 103 a zinc-copper voltaic couple is 
 shown, immersed in dilute sulphuric acid. Here, 
 since the zinc is dissolved by the sulphuric acid, 
 the zinc is positive, and the copper negative in 
 the liquid. The zinc and copper are of opposite 
 polarities out of the liquid. 
 
 There is still a considerable difference of opinion 
 as to the exact cause of the potential difference o. 
 the voltaic cell. There can be no doubt that a 
 true contact force exists, but the chemical poten- 
 tial energy of the positive plate is the source 
 of energy which maintains the potential differ- 
 ence. 
 
 The difference in the polarity of the zinc and 
 copper in and out of the liquid is generally de- 
 nied by most of the later writers on electricity, 
 since tests by a sufficiently delicate electrometer 
 show that the entire zinc plate is negative and 
 the entire copper plate positive. Remembering, 
 however, the convention as to the direction of 
 the flow of the current, since the current flows 
 from the zinc to the copper through the liquid, 
 we may still fairly regard the zinc as positive and 
 the copper as negative in the liquid. It will be 
 remembered, that in every source the polarity 
 within the source is necessarily opposite to the 
 polarity outside it. The copper plate is there- 
 fore called the negative plate, and the wire con- 
 nected to its end out of the liquid, the positive 
 electrode. Similarly, the zinc plate is called the 
 positive plate, and the wire connected to it the 
 negative electrode. 
 
 It will of course be understood that in the 
 above sketch the current flows only on the com- 
 pletion of the circuit outside the cell; that is, 
 when the conductors attached to the zinc and 
 copper plates are electrically connected. 
 
 Amalgamation of the Zinc Plate. When zinc 
 is used for the positive element, it will, unless 
 chemically pure, be dissolved by the electrolyte 
 when the circuit is open, or will be irregularly 
 dissolved when the circuit is closed, producing 
 currents in little closed circuits from minute vol- 
 taic couples formed by the zinc and such impuri- 
 ties as carbon, lead, or iron, etc., always found 
 in commercial zinc. (See Action, Local, of Vol- 
 taic Cell.) As it is practically impossible to ob- 
 tain chemically pure zinc, it is necessary b? amal- 
 gamate the zinc plate; that is, to cover it with a 
 thin layer of zinc amalgam. 
 
 Polarization of the Negative Plate. Since the 
 evolved hydrogen appears at the surface of the 
 negative plate, the surface of this plate, unless 
 
Cel.] 
 
 83 
 
 [CeL 
 
 means are adopted to avoid it, will, after a while, 
 become coated with a film of hydrogen gas, or 
 as it is technically called, will become polarized. 
 (See Cell, Voltaic, Polarization of.) 
 
 The effect of this polarization is to cause a fall- 
 ing off or weakening of the current produced by 
 the battery, due to the formation of a counter - 
 electromotive force produced by the hydrogen- 
 covered plate ; that is to say, the negative plate, 
 now being covered with hydrogen, a very highly 
 electro-positive element, tends to produce a 
 current in a direction opposed to that of the 
 cell proper. (See Force, Electromotive, Coun- 
 ter.) 
 
 This decrease in current strength is rendered 
 still greater by the increased resistance in the cell, 
 due to the bubbles of hydrogen, and to the de- 
 creased electromotive force, due to the increase 
 in the density of the zinc sulphate, in the casje of 
 zinc in hydrogen sulphate. 
 
 In the case of storage cells, the counter-elec- 
 tromotive force of polarization is employed as the 
 source of secondary currents. (See Electricity, 
 Storage of. Cell, Secondary. Cell, Storage.) 
 
 In order to avoid the effects of polarization in 
 voltaic cells, and thus insure constancy of cur- 
 rent, the bubbles of gas at the negative plate are 
 mechanically carried off either by roughening its 
 surface, by forcing the electrolyte against the 
 plate as by shaking, or by a stream of air; or else 
 the negative plate is surrounded by some liquid 
 or solid substance which will remove the hydro- 
 gen, by entering into combination with it. (See 
 Cell, Voltaic, Polarization of.) 
 
 Voltaic cells are therefore divided into cells 
 with one or with two fluids, or electrolytes, or 
 into: 
 
 (i.) Single-fluid cells; and 
 
 (2.) Double-fluid cells. 
 
 Very many forms of voltaic cells have been de- 
 vised. The following are among the more im- 
 portant, viz. : Of the Single-Fluid Cells, the 
 Grenet, Poggendorff, or Bichromate, the Zinc- 
 Copper, the Zinc-Carbon and the Smee. Of the 
 Double-Fluid Cells, Grove's, Bunsen's, Callaud 
 or Gravity, DanielPs, Leclancht, Siemens-Halske 
 and the Meidinger. 
 
 Of all the voltaic cells that have been devised 
 two only, viz., the Gravity, a modified Daniell, 
 and the Leclanche, have continued until now in 
 very general use, the gravity cell being used on 
 closed-circuited lines, and the Leclanche on open- 
 circuited lines ; the former being the best suited 
 
 of all cells to furnish the continuous constant cur 
 rents employed in most systems of telegraphy, 
 and the latter for furnishing the intermittent cur- 
 rents required for ringing bells, operating aniiun- 
 ciators, or for similar work. 
 
 Cell, Toltaic, Absorption and Genera- 
 tion of Heat in (See Heat, Absorption 
 
 and Generation of, in Voltaic Cell.) 
 
 Cell, Voltaic, Bichromate A zinc- 
 carbon couple used with an electrolyte 
 known as electropoion, a solution of bichro- 
 mate of potash and sulphuric acid in water. 
 (See Liquid, Electropoion^ 
 
 Bichromate of sodium or chromic acid are 
 sometimes used instead of the bichromate of 
 potassium. 
 
 The zinc, Fig. 104, is amalgamated and placed 
 between two carbon plates. 
 The terminals connected 
 with the zinc and carbon 
 are respectively negative 
 and positive. In the form 
 shown in the figure, the zinc 
 plate can be lifted out of 
 the liquid when the cell is 
 not in action. 
 
 The bichromate cell is 
 excellent for purposes re- 
 quiring strong currents 
 where long action is not 
 necessary. As this cell 
 readily polarizes it cannot 
 be advantageously employ- Fig. 104.. Bichromate 
 ed continuously for any Cell. 
 
 considerable period of time. It becomes depolar- 
 ized, however, when left for some time on open 
 circuit 
 
 The following chemical reaction probably takes 
 place when the cell is furnishing current, viz. : 
 K 2 Cr 2 O 7 + 7H 2 SO 4 + $Zn = 
 
 K 2 S0 4 + 3 ZnS0 4 + Cr s3 (So 4 ) + ;H 2 O. 
 
 This cell gives an electromotive force of about 
 1.9 volts. 
 
 Cell, Voltaic, Bnnsen's A zinc- 
 carbon couple, the elements of which are 
 immersed respectively in electrolytes of dilute 
 sulphuric and strong nitric acids. 
 
 Bunsen's cell is the same as Grove's, except 
 that the platinum is replaced by carbon. The 
 zinc surrounds the porous cell containing the car 
 
Cel.] 
 
 [Cel. 
 
 bon. The polarity is as indicated in Fig. 105. 
 (See Cell, Voltaic, Grove.) 
 
 Fig. 103. Bunsen Cell. 
 
 The Bunsen cell gives an electromotive force 
 of about 1.96 volts. 
 
 Cell, Voltaic, Calland's A name 
 
 sometimes given to the gravity cell. (See 
 Cell, Voltaic, Gravity!) 
 
 Cell, Voltaic, Capacity of Polarization of 
 
 The quantity of electricity required 
 
 to be discharged by a voltaic cell in order to 
 produce a given polarization. (See Cell, Vol- 
 taic, Polarization of.) 
 
 During the discharge of a voltaic cell an electro- 
 motive force is gradually set up that is opposed 
 to that of the cell. The quantity of electricity 
 required to produce a given polarization de- 
 pends, of course, on the condition and size of 
 the plates. Such a quantity is called the capacity 
 of polarization. 
 
 Cell, Voltaic, Closed-Circuit A 
 
 voltaic cell that can be left for a considerable 
 time on a closed circuit of comparatively 
 small resistance without serious polarization. 
 
 The term closed-circuit voltaic cell is used in 
 contradistinction to open-circuit cell, and applies 
 to a cell that can only be kept on closed circuit 
 for a comparatively short time. 
 
 Daniell's cell and the gravity cell are closed-cir- 
 cuit cells. Leclanchd's is an open-circuit cell. 
 
 Cell, Voltaic, Contact Theory of 
 
 A theory which accounts for the production 
 of difference of potential or electromotive 
 force in the voltaic cell by the contact of the 
 elements of the voltaic couple with one an- 
 other by means of the electrolyte. 
 
 The mere contact of two dissimilar substances 
 through the electrolyte will produce a difference 
 of potential, but the cause of the current which a 
 voltaic cell is able to maintain is the chemical 
 potential energy which becomes kinetic during 
 combination. (See Cell, Voltaic. Series, Contact,) 
 
 Most authorities explain the difference of 
 potential produced by the contact of different 
 metals by the fact that the metals are sur- 
 rounded by air. They point out the fact that the 
 order of the metals in the contact-series is 
 almost identical with the order of their electro- 
 chemical power as deduced from their chemical 
 .equivalents, and their heat of combination with 
 oxygen. It would appear, therefore, that the 
 difference of potential between a metal and the 
 air which surrounds it, is a measure of the tend- 
 ency of the metal to become oxidized. 
 
 The origin of the electromotive force of a zinc, 
 copper couple, in an electrolyte of hydrogen sul- 
 phate, is the superior affinity of the zinc for the 
 oxygen, over that of the copper for the oxygen. 
 
 Cell, Voltaic, Creeping in The 
 
 formation, by efflorescence, of salts on the sides 
 of the porous cup of a voltaic cell, or on the 
 walls of the vessel containing the electrolyte. 
 Paraffining the portions of the walls out of the 
 liquid, or covering the surface of the liquid with 
 a neutral oil, obviates much of this difficulty. (See 
 Efflorescence.) 
 
 Cell, Voltaic, Daniell's A zinc- 
 copper couple, the elements of which are im- 
 mersed respectively in electrolytes of dilute 
 sulphuric acid, and a saturated solution of 
 copper sulphate. 
 
 In the form of Daniell's cell, shown in Fig. 106, 
 the copper element is made in the form of a cylin- 
 der c, and is placed in a porous cell. The cop- 
 per cylinder is provided with a wire basket near 
 the top, filled with crystals of blue vitriol, or cop. 
 per sulphate, so as to maintain the strength of the 
 solution while the cell is in use. The zinc is in 
 the shape of a cylinder and is placed so as to sur- 
 round the porous cell. This cell gives a nearly 
 constant electromotive force. 
 
 The constancy of action of Daniell's cell 
 depends on the fact that for every molecule ol 
 sulphuric acid decomposed in the outer cell, an 
 additional molecule of sulphuric acid is supplied 
 by the decomposition of a molecule of copper sul. 
 phate in the inner cell. This will be better ua- 
 
Cel.] 
 
 85 
 
 tCel. 
 
 derstood from the following reactions which take 
 
 place, viz.: 
 
 Zn + H 8 SO 4 = ZnSO 4 -f- H g 
 H, + CuS0 4 = H 8 SO 4 -f Cu. 
 The H 8 SO 4 , thus formed in the inner cell, 
 
 passes through the porous cell, and the copper is 
 
 deposited on the surface of the copper plate. 
 
 Fig io(>. Daniell s Cell. 
 
 The Daniell cell gives an electromotive force 
 of about 1.072 volts. 
 
 A serious objection to this form of cell arises 
 from the fact that the copper is gradually de- 
 posited over the surface and in the pores of the 
 porous cell, thus greatly increasing its resistance. 
 This difficulty is avoided in the gravity cell. (See 
 Cell, Voltaic, Gravity.) 
 
 Cell, Yoltaic, Double-Fluid A 
 
 voltaic cell in which two separate fluids or elec- 
 trolytes are employed. 
 
 One of the elements of the voltaic couple is 
 dipped into one of the fluids and the other ele- 
 ment into the other fluid. In order to Iceep the 
 fluids separate and distinct, they are either sep- 
 arated by means of porous cells, or by the action 
 of gravity. (See Cell, Porous. Cell, Voltaic, 
 Gravity.} 
 
 In the double-fluid cell the negative element is 
 surrounded by a liquid which is capable of pre- 
 venting polarization by combining chemically 
 with the substance that teilds to collect on its 
 surface. In the Daniell cell this substance is the 
 same as that of the negative plate. (See Cell, 
 Voltaic, Polarization of.) 
 
 Cell, Toltaic, Dry A voltaic cell 
 
 in which a moist material is used in place of 
 the ordinary fluid electrolyte. 
 
 The term dry cell is in reality a misnomer, 
 since all such cells are moistened with liquid 
 electrolytes. 
 
 The dry cell, like other cells, is made in a 
 variety of forms. The ab- 
 sence of free liquid permits 
 the cell to be closed. A well 
 known form of dry cell is| 
 shown in Fig. 107. 
 
 Cell, Toltaic, Effects of I 
 
 Capillarity in (See 
 
 Capillarity, Effects of, in 
 Voltaic Cell.} 
 
 Cell, Yoltaic, Exciting 
 Liquid of The elec- 
 trolyte Of a Voltaic Cell. pig, 107. Dry Cell. 
 
 A voltaic cell may have a single electrolyte, in 
 which case it is called a single-fluid cell, or it may 
 have two electrolytes, in which case it is called a 
 double-fluid cell. 
 
 Cell, Yoltaic, Fuller's Mercury Bichro- 
 mate A zinc-carbon couple im- 
 mersed in an electrolyte of electropoion liquid. 
 
 The zinc is attached to a copper rod by being 
 cast thereto, and is placed at the bottom of a 
 porous cell, where it is covered by a layer of 
 mercury. The carbon plate is placed in electro- 
 
 Pig. 108 Fuller's Mercury Bichromate CeU. 
 poion liquid, diluted with water in the proportion 
 of three of the former to two of the latter. The 
 zinc is generally placed in pure water, which 
 rapidly becomes acid. 
 
 The mercury effects the continuous amalgama- 
 tion of the zinc. 
 
 A Fuller mercury bichromate cell is shown 
 in Fig. 1 08. 
 
Cel.] 
 
 86 
 
 [CeL 
 
 Cell, Toltaic, Gravity A zinc- 
 copper couple, the elements of which are em- 
 ployed with electrolytes of dilute sulphuric acid 
 or dilute zinc sulphate, and a concentrated 
 solution of copper sulphate respectively. 
 
 The use of a porous cell is open to the objection 
 of increased internal resistance. Moreover, the 
 porous cell is apt to receive a coating of copper 
 which often deposits on the cell instead of on the 
 copper plate. The gravity cell was devised in 
 order to avoid the use of a porous cell. As its 
 name indicates, the two fluids are separated from 
 each other by gravity. 
 
 The copper plate is the lower plate, and is sur- 
 rounded by crystals of copper sulphate. The 
 tine, generally in the form of an open wheel, or 
 ^row-foot, is sus- 
 pended near the top 
 of the liquid, as 
 shown in Fig. 109. 
 
 When the cell is 
 set up with sul- 
 phuric acid, the re- 
 actions are the same 
 as in the Daniell 
 cell. When copper 
 sulphate and zinc 
 sulphate alone are 
 used, zinc replaces 
 the copper in the 
 
 copper sulphate. 
 
 ., ,. . .v Ftg. fOQ. The Gravity CeU. 
 
 The action is then 
 
 merely a substitution process. (See Cell, Voltaic, 
 Daniels.) 
 
 A dilute solution of zinc sulphate is generally 
 used to replace the dilute sulphuric acid. It 
 gives a somewhat lower electromotive force, but 
 ensures a greater constancy for the cell. 
 
 Cell, Voltaic, Grenet A name 
 
 sometimes given to the bichromate cell. (See 
 Cell, Voltaic, Bichromate^ 
 
 Cell, Voltaic, Grove A zinc-plati- 
 num couple, the elements of which are used 
 with electrolytes of sulphuric and nitric acids 
 respectively. 
 
 The zinc, Z, Fig. no, is amalgamated and 
 placed in dilute sulphuric acid, and the platinum, 
 P, in strong nitric acid (HNO 8 ) in a porous cell 
 to separate it from the sulphuric acid. (See C ell, 
 Porous.) In the Grove cell the current is moder- 
 ately constant, since the polarization of the plati- 
 
 num plate is prevented by the nitric acid, which 
 
 oxidizes and thus removes the hydrogen that 
 
 tends to be liberated at its surface. The con- 
 
 stancy of the current 
 
 is not maintained for 
 
 any considerable time, 
 
 since the two liquids 
 
 are rapidly decom- 
 
 posed, or consumed, 
 
 zinc sulphate forming 
 
 in the sulphuric acid, 
 
 and water in the nitric 
 
 acid. 
 
 The chemical reac- 
 tions are as follows, 
 viz.: 
 Zn 
 
 6H 
 
 2NQ 
 
 I to, Grove's Cell. 
 
 H 2 SO 4 = 
 ZnS0 4 + H 8 ; 
 2HNO 8 = 
 4H 2 O + 2NO; 
 8 = N 8 O 4 . 
 Nitrate of ammo- 
 nium is sometimes formed when the nitric acid 
 becomes dilute by decomposition. The reaction 
 is as follows : 
 
 2HN0 8 -f- 4 H 8 = 3 H 8 O + NH 4 NO. 
 
 The cell gives an electromotive force of 1.93 
 volts. 
 
 When the porous cell is good, the resistance of 
 the Grove cell may be calculated according to 
 the following formula of Ayrton: 
 
 R = 
 
 3-6 Xd 
 
 ohms, 
 
 where d, is the distance in inches between the 
 platinum and zinc plates, and A, the square inches 
 of the immersed portion of the platinum plate. 
 
 Cell, Voltaic, Leclanche* A zinc- 
 carbon couple, the elements of which are used 
 in a solution of sal-ammoniac and a finely 
 divided layer of black oxide of manganese 
 respectively. 
 
 The zinc is in the form of a slender rod and 
 dips into a saturated solution of sal-ammoniac^ 
 NH 4 C1. 
 
 The negative element consists of a plate of car- 
 bon, C, Fig. in, placed in a porous cell, in which 
 is a mixture of black oxide of manganese and 
 broken gas-retort carbon, tightly packed around 
 the. carbon plate. By this means a greatly ex 
 tended surface of carbon surrounded by black 
 
CeL] 
 
 oxide of manganese, MnO 8 , is secured. The entire 
 outer jar, and the spaces inside the porous cell are 
 filled with the solution of sal-ammoniac. 
 
 87 
 
 Fig. TIT. The Leclanchi Cell. 
 
 This cell, though containing but a single fluid, 
 belongs, in reality, to the class or type of double- 
 fluid cells, being one in which the negative ele- 
 ment is surrounded by an oxidizing substance, 
 the black oxide of manganese, which replaces the 
 nitric acid or copper sulphate in the other double- 
 fluid cells. 
 
 This reaction is generally given : 
 
 Zn + 4NH 4 Cl + 2MnO 2 = ZnCl 8 + 2NH 4 C1 
 + 2NH 8 4- Mn 8 8 + H 8 0. 
 
 This reaction is denied by some, who believe 
 the following to take place : 
 
 Zn + 2(NH 4 C1) = ZnCl 8 + 2NH, + H 8 . 
 The ZnCl 2 and NH 8 react as follows : 
 ZnCl 8 + 2(NH 3 ) = 2 (NHj) ZnCl 2 + H 8 . 
 
 2H + 2(Mn z O 2 ) = H 8 O -f Mn 2 O 3 ; 
 or, possibly, 4.H -f- 3MnO 8 = Mn 2 O -}- 2H t O. 
 
 The Leclanche cell gives an electromotive force 
 of about 1.47 volts. It rapidly polarizes, and 
 cannot, therefore, give a steady current for any 
 prolonged time. When left on open circuit, how- 
 ever, it quickly depolarizes. 
 
 Cell, Toltaic, Local Action of 
 
 (See Action, Local, of Voltaic Cell.} 
 
 Cell, Toltaic, Meidinger A zinc- 
 copper couple, the elements of which are em- 
 ployed with dilute sulphuric acid, or solution 
 of sulphate of magnesia, and strong nitric 
 acid, respectively. 
 
 The Meidinger cell is a modification of the 
 Daniell cell. The zinc-copper couple is thus ar- 
 ranged : Z Z, Fig. 112, is an amalgamated zinc 
 ring placed near the walls of the vessel, A A, 
 constricted at b b. The copper element, c, is 
 similarly placed with respect to the walls of the 
 vessel d d. The glass cylinder h, filled with 
 
 [Cel. 
 
 crystals of copper sulphate, has a small hole in 
 its bottom, and keeps the vessel, d d, supplied 
 with saturated so- 
 lution of copper 
 sulphate,, The cell 
 is charged with di- 
 lute sulphuric acid, 
 or a dilute solution 
 of Epsom salts, or 
 magnesium sul- 
 phate. 
 
 Cell, Voltaic, 
 Open-Circuit 
 
 A voltaic 
 
 cell that cannot be 
 kept on closed cir- 
 cuit, with a com- 
 paratively small 
 
 resistance, for any Fig. 112. The Meidinger Cell. 
 
 considerable time without serious polariza- 
 tion. 
 
 A Leclanche' cell is an open-circuit cell. The 
 term open-circuit cell is used in contradistinc- 
 tion to closed-circuit cell, such as the Daniell. 
 (See Cell, Voltaic, Closed-Circuit.) 
 
 Cell, Voltaic, Poggendorff A 
 
 name sometimes given to the Grenet cell. (See 
 Cell, Voltaic, Grenet.} 
 
 Cell, Voltaic, Polarization of The 
 
 collection of a gas, generally hydrogen, on the 
 surface of the negative element of a voltaic 
 cell. 
 
 The collection of a positive substance like hydro- 
 gen on the negative element or plate of r- voltaic 
 cell sets up a counter-electromotive force, which 
 tends to produce a current in the opposite direc- 
 tion to that produced by the cell. (See Force, 
 Electromotive, Counter.) 
 
 Polarization causes a decrease in the normal 
 current of a voltaic cell: 
 
 (I.) On account of the increased resistance of 
 the cell from the bubbles of gas which form part 
 of its circuit. 
 
 (2.) On account of the counter -electromotive 
 force, produced by polarization. 
 
 There are three ways in which the ill effects of 
 the polarization of a voltaic cell can be avoided. 
 These are : 
 
 (i.) Mechanical. The negative plate is fur- 
 nished with a roughened surface which enables th 
 
CeU] 
 
 88 
 
 fCel. 
 
 bubbles of gas to escape from the points on such ur - 
 face ; or, a stream of gas, or air, is blown through 
 the liquid against the plate and thus mechanically 
 brushes the bubbles off. 
 
 (2.) Chemical. The surface of the negative 
 plate is surrounded by some powerful oxidizing 
 substance, such as chromic or nitric acid, which 
 is capable of oxidizing the hydrogen, and thus 
 thoroughly removing it from the plate. 
 
 The oxidizing substance may form th entire 
 electrolyte, as is the case of the bichromate solution 
 employed in the zinc-carbon couple. Generally, 
 however, it has been found preferable to employ 
 a separate liquid, like nitric acid, to completely 
 surround the negative plate, and another liquid for 
 the positive plate, the two liquids being generally 
 kept from mixing by a porous cell, or diaphragm. 
 Such cells are' called double-fluid cells. (See 
 Cell, Voltaic, Double- Fluid.) 
 
 (3.) Electro-Chemical. This also necessitates a 
 double-fluid cell. The negative element is im- 
 mersed in a solution of a salt of the same metal as 
 that forming the negative plate. Thus, a cop. 
 per plate, immersed in a solution of copper sul 
 phate, cannot be polarized, since metallic copper 
 is deposited on its surface by the action of the 
 hydrogen which tends to be liberated there. 
 
 The constancy of action of a Daniell cell depends 
 on a deposition of metallic copper on its copper 
 plate as well as on the formation of hydrogen 
 sulphate, and the solution of additional copper 
 sulphate from the crystallized salt placed in the 
 cell. (See Cell, Voltaic, Daniell's.) 
 
 Cell, Voltaic, Primary, Exhaustion of 
 
 The inability of a primary voltaic 
 
 cell to furnish any further current, unless 
 fresh electrolyte, or fresh positive element, or 
 both, are supplied to it. 
 
 In the case of exhaustion of a primary voltaic 
 cell the stock of fresh energy is supplied to the 
 cell from the chemical potential energy of the 
 positive element, or of the electrolyte or elec- 
 trolytes. (See Energy, Chemical Potential.) 
 
 In most voltaic cells a marked decrease in the 
 current strengtk is observed soon after the cir- 
 cuit is closed, and, therefore, long before the 
 cell is exhausted. This decrease is due 
 
 (i.) To the increased internal resistance due to 
 the bubbles of hydrogen on the negative plate. 
 
 (2.) To the counter-electromotive force of po- 
 larization, where zinc is employed with an elec. 
 trolyte of sulphuric acid. 
 
 (3.) To the decrease in the electromotive force 
 due to an increase in the density of the zinc sul- 
 phate. 
 
 Cell, Voltaic, Secondary, Exhaustion of 
 
 The inability of a secondary cell to 
 
 furnish any further current, unless fresh 
 electro-positive and electro-negative materials 
 are formed in it by the passage of the 
 charging current. 
 
 In the case of the exhaustion of a secondary 
 voltaic cell, the stock of fresh energy supplied 
 to the cell is derived from the electric energy 
 of the charging current. (See Energy, Electric.) 
 
 Cell, Voltaic, Siemens-Halske 
 
 A zinc-copper couple, the elements of which 
 are employed with dilute sulphuric acid and 
 saturated solution of copper sulphate respect- 
 ively. 
 
 The Siemens-Halske cell is a modification of 
 Darnell's. A ring of zinc, Z Z, Fig, 113, sur- 
 
 Fig 113' Siemens- Halskt Cell. 
 
 rounds the glass cylinder, c c. The porous 
 cell is replaced by a diaphragm, f f, of porous 
 paper, formed by the action of sulphuric acid on 
 a mass of paper pulp. Crystals of copper sul- 
 phate are placed in the glass jar, c c, and rest 
 on the copper plate, k, formed of a close copper 
 spiral. Terminals are attached at b and h. The 
 entire cell is charged with dilute sulphuric acid. 
 The resistance of the cell is high, 
 
 Cell, Voltaic, Silver Chloride A 
 
 zinc and silver couple immersed in electro- 
 lytes of sal-ammoniac or common salt and 
 silver chloride. 
 
Cel.] 
 
 89 
 
 [Cel. 
 
 The zinc acts as the positive element, and a 
 silver wire, around which a cylinder of fused 
 silver chloride is cast, as the negative element. 
 The zinc, and the silver wire and silver chloride, 
 are placed in a small glass test-tube and covered 
 with the sal-ammoniac or common salt, and 
 the tube closed by a cork of paraffin, to prevent 
 the evaporation of the electrolyte. When sal- 
 ammoniac is used, the strength of the solution is 
 that obtained by dissolving 23 grammes of pure 
 sal-ammoniac in I litre of water. The silver 
 chloride acts as a depolarizer. 
 
 This cell is used as a standard cell, known as 
 De la Rue's standard cell, from its inventor, 
 Warren De la Rue. Its electromotive force is 
 1.068 volts. 
 
 Cell, Yoltaic, Simple Any voltaic 
 
 cell formed of a single couple immersed in a 
 single exciting liquid. 
 
 Cell, Toltaic, Single-Fluid A vol- 
 taic cell in which but a single fluid or elec- 
 trolyte is used. 
 
 Single-fluid voltaic cells possess the disadvan- 
 tage of polarizing during action. This polariza- 
 tion is due to the electro-positive element of the 
 electrolyte collecting on the surface of the nega- 
 tive plate, or within its mass. For example, 
 where dilute sulphuric acid is the electrolyte, 
 hydrogen gas collects on the negative plate and 
 lowers the electromotive force produced by the 
 cell, by a counter-electromotive force thereby 
 generated. (See Force, Electromotive. Force, 
 Electromotive, Counter.) 
 
 Cell, Toltaic, Since A zinc-silver 
 
 couple used with an electrolyte of dilute sul- 
 phuric acid, H 2 SO 4 . 
 
 A form of Smee cell is shown in Fig. 1 14. Here 
 the plate of silver is placed between two zinc 
 plates. 
 
 The silver plate is roughened and covered with 
 a coating of metallic platinum, in the condition 
 known asplatinum black. (See Platinum Black.) 
 This cell was formerly extensively employed in 
 tlectro-metallurgy but is now replaced by dynamo- 
 tlectric -machines. (See Metallurgy, Electro. 
 Machine, Dynamo-Electric. ) 
 
 A zinc-carbon couple is sometimes used to re- 
 place the zinc-silver couple. A couple of zinc- 
 lead is also used, though not very advanta- 
 geously. 
 
 The Smee cell was one of the earliest forms 
 of voltaic cells. 
 
 In the zinc-silver couple the chemical reaction 
 that takes place when the 
 cell is furnishing current is 
 as follows, viz. : 
 Zn + H 8 SO 4 == ZnSO 4 
 
 + H 2 . 
 
 The Smee cell gives an 
 electromotive force of about 
 .65 volt. 
 
 Cell, Voltaic, Stand- 
 ard A voltaic cell 
 
 the electromotive force of 
 which is constant, and Fig- 114. Smee Cell. 
 which, therefore, may be used in the measure- 
 ment of an unknown electromotive force. 
 
 Absolute constancy of electromotive force is 
 impossible to attain, but if the current of the 
 standard cell is closed but for a short time the 
 electromotive force may be regarded as practically 
 invariable. 
 
 Cell, Toltaic, Standard, Clark's 
 
 The form of standard cell shown in Fig. 115. 
 
 Latimer Clark's standard cell assumes a 
 variety of forms. The H-form is arranged as 
 shown in Fig. 115. The vessel to the left con- 
 tains, at A, an amal- 
 gam of pure zinc. The 
 other vessel contains, 
 at M, mercury covered 
 with pure mercurous 
 sulphate, Hg 8 SO 4 . 
 Both vessels are then 
 filled, above the level 
 of the cross tube, with 
 a saturated solution of 
 zinc sulphate Z, Z, to 
 which a few crystals 
 of the same are added. 
 Tightly fitting corks 
 
 C, C, prevent loss by Fig. sij. Clark's Stand- 
 evaporation. *rd Cell. 
 
 The voltage of this cell in legal volts is 1.438 
 [i 0.00077 (* 15 degrees C.)](Ayrton.) 
 
 The value t, is the temperature in degrees of 
 the centigrade scale. 
 
 Cell, Toltaic, Standard, Rayleigh's Form 
 
 of Clark's A modified form of Clark's 
 
 cell. 
 
 \\ 
 
 w 
 
Cel.] 
 
 90 
 
 [Cel. 
 
 Lord Rayleigh's form of Clark's standard cell 
 is shown in Fig. 116. The electrodes pass respect- 
 ively through the bottom and top of the test tube 
 of glass. On the lower 
 electrode a layer of mer- 
 cury, Hg, is placed. On 
 this rests a layer of mercu- 
 rous sulphate paste made 
 sufficiently semi-fluid with 
 a solution of zinc sulphate 
 to form an approximately 
 level surface. The zinc, 
 Zn, is attached to the up- 
 per electrode and is im- 
 mersed in this semi-fluid 
 paste. 
 
 The mercurous sulphate 
 appears to act to keep the 
 mercury free from impuri- 
 ties. 
 
 The electromotive force j 
 of this cell has been care- 
 fully determined by Ray- Fig Ilt> Ray i eigh < s 
 leigh. Its value in true Form of Clark's 
 
 volts is : Standard Cell. 
 
 E= 1.435 t 1 .00077 (t 15)] when t, is the 
 temperature in degrees Centigrade. 
 
 This cell is often called Clark's normal element. 
 
 Cell, Voltaic, Standard, De la Rue's 
 
 A form of silver-chloride cell. (See Cell, 
 Voltaic, Silver-Chloride?) 
 
 Cell, Voltaic, Stand- 
 ard, Fleming's 
 The form of standard 
 cell shown in Fig. 117. 
 
 The U-tube, Fig. 117, 
 is connected, as shown, 
 by means of taps, with 
 two vessels filled with 
 chemically pure solutions 
 of copper sulphate of sp. 
 gr. i.i at 15 degrees C., 
 and zinc sulphate of sp. 
 gr. 1.4 at 15 degrees C. 
 respectively. To use the 
 cell the zinc rod Zn, con- 
 nected with a wire pass- 
 ing through a rubber 
 stopper, is placed in the 
 left-hand branch. The tap A, is opened and 
 the entire U-tube is filled with the denser 
 zinc sulphate solution. The tap at C, is then 
 
 opened, and the liquid in the right-hand branch 
 above the tap is discharged into the lower vessel, 
 but, from this part only. The tap C, is then 
 closed, and the tap B, opened, and the lighter 
 copper sulphate allowed to fill the right-hand 
 branch above the tap C. The copper rod Cu, fitted 
 to a rubber stopper and connected with a con- 
 ducting wire, is then placed in the copper solution. 
 Tubes are provided at L and M, for the recep- 
 tion of the zinc and copper rods when not in use. 
 The copper rod is prepared for use by freshly 
 electro-plating it with copper. The electro- 
 motive force of this cell is 1.074 volts. If the line 
 of demarkation between the two liquids is not 
 sharp, the arms of the vessels are emptied, and 
 fresh liquid is run in. 
 
 Cell, Voltaic, Standard, Lodge's 
 
 A form of standard Daniell cell. 
 
 Lodge's standard cell is shown in Fig. 118. 
 Through the tube T, in a 
 wide mouthed bottle, is 
 passed the glass tube, in the 
 mouth of which is placed a 
 zinc rod. To the bottom of 
 the tube T, a small test-tube 
 t, containing crystals of cop- 
 per sulphate, is fastened by 
 means of a string or rubber 
 band. The uncovered end 
 of a gutta-percha insulated 
 copper wire projects at the 
 bottom of t, through a tube 
 in a tightly fitting cork, and 
 forms the copper electrode. The bottle is partly 
 filled as shown with a solution of zinc sulphate. 
 
 The internal resistance of this cell is so high 
 that it is only employed in the use of zero methods 
 with a condenser. 
 
 Cell, Voltaic, Standard, Sir William 
 Thomson's - A form of standard 
 Daniell cell. 
 
 Fig. 118. Lodges 
 Form of Daniell' s Cell. 
 
 Fig. 117. Fleming's 
 Standard Cell. 
 
 Fig. 1 19. Thomson's Form of Daniell' s Cell. 
 
 Sir Wm. Thomson's standard cell is shown in 
 Fig.' 119. A zinc disc is placed at the bottom of the 
 
Cel.] 1 
 
 cylindrical vessel and a solution of zinc sulphate 
 01 tp. gr. 1.2 poured over it. By means of the 
 funnel F, a half-saturated solution of copper 
 sulphate is carefully poured over this and floats 
 on it owing to its smaller density. The electro, 
 motive force of this cell is 1.072 true -volts at 
 15 degrees C. 
 
 Cell, Voltaic, Standardizing a De- 
 
 cermining the exact value of the electromotive 
 force of a voltaic cell, in order to enable it to 
 be used as a standard in determining the 
 electromotive force of any other electric 
 source. 
 
 Cell, Toltaic, Two-Fluid A term 
 
 sometimes employed in place of double-fluid 
 cell. (See Cell, Voltaic, Double-Fluid) 
 
 Cell, Toltaic, Water A voltaic 
 
 cell in which the exciting liquid is merely 
 water. 
 
 Any voltaic couple can be used, the positive 
 element of which is acted on by water. (See 
 Battery, Voltaic.) 
 
 Cell, Toltaic, Zinc-Carbon A 
 
 cell in which zinc and carbon form the posi- 
 tive and negative elements respectively. 
 
 A name sometimes given to the bichro- 
 .nate cell. 
 
 Cell, Toltaic, Zinc-Copper A 
 
 cell in which zinc and copper form the posi- 
 tive and negative elements respectively. 
 
 Cell, Toltaic Zinc-Lead A zinc- 
 lead couple sometimes used, though not very 
 advantageously, to replace the zinc-silver 
 couple in a Smee cell. (See Cell, Voltaic, 
 Smee) 
 
 Cells, Coupled A number of sep- 
 arate cells connected in any way so as to 
 (orm a single source. 
 
 Cells, Toltaic, Series-Connected 
 
 A number of separate voltaic cells connected 
 in series so as to form a single source. (See 
 Circuit, Series) 
 
 Cement-Lined Conduit (See Conduit. 
 Cement-Lined) 
 
 Cements, Insulating Various 
 
 mixtures of gums, resins and other substances, 
 possessing the ability to bind two or more 
 4 Vol. 1 
 
 [Chm 
 
 substances together and yet to eleL-traally in- 
 sulate one from the other. 
 
 Centi. (As a prefix) The one-hundredth 
 part of. 
 
 Centi-Ampe're. One-hundredth of an am- 
 pere. 
 
 Centi-AmpSre Balance. (See Balance, 
 Centi-Ampere) 
 
 Centigrade Thermometer Scale. (See 
 Scale, Centigrade Thermometer) i 
 
 Centigramme. The hundredth of a 
 gramme 
 
 One centigramme equals 0.1544 grains avoir- 
 dupoise. (See Weights and Measures, Metric 
 System of.) 
 
 Centilitre. The hundredth of a litre. 
 One centilitre equals 0.6102 of a cubic inch. 
 (See Weights and Measures, Metric System of.) 
 
 Centimetre. The hundredth of a metre. 
 One centimetre equals 0.3937 inch. (See 
 Weights and Measures, Metric System of.) 
 
 Centimetre-Gramme-Second TJnits. (Se 
 
 Units, Centimetre-Gramme-Second) 
 
 Central Galvanization. (See Galvaniza- 
 tion, Central) 
 
 Central Station. (See Station, Central) 
 
 Central Station Burglar Alarm. (See 
 Alarm, Burglar, Central Station) 
 
 Central Station Lighting. (See Light- 
 ing, Electric Central Station) 
 
 Centre of Gravity. (See Gravity, Centre 
 
 Centre of Oscillation. (See Oscillation, 
 Centre of) 
 
 Centre of Percussion. (See Percussion, 
 Centre of) 
 
 Centrifugal Force. (See Force, Centrtfu* 
 gal) 
 
 Centrifugal Governor. (See Governor. 
 Centrifugal) 
 
 Chain Lightning. (See Lightning, 
 Chain) 
 
 Chain, Linked Magnetic and Electric 
 
 A chain of three links, the separate 
 
 links of which consist of the primary circuit, 
 
Cha.j 
 
 /Cha, 
 
 the magnetic circuit, and the secondary cir- 
 cuit respectively, of an induction coil. 
 
 The conception of a linked magnetic and elec- 
 tric chain, in studying the action of an induction 
 cofl, was first developed by Kapp. A linker 1 
 magnetic and electric chain is shown in Fig. 120. 
 
 Fig. 1 20. Linked Magnetic and Electric Chain. 
 
 li, in such a case, the magnetic core or circuit is 
 of varying magnetization, when one of the electric 
 circuits has a periodic current passed through 
 it, the various phenomena of the induction cofl 
 are produced. (See Coil, Induction.) 
 
 Chain, Molecular A polarized chain 
 
 of molecules that is supposed to exist in an 
 electrolyte during its electrolytic decomposi- 
 tion, or in a voltaic cell on closing its circuit. 
 (See Hypothesis, Grotthus.) 
 
 Chain Pull. (See Pull, Cham.) 
 
 Chamber, Armature The armature 
 
 bore. (See Bore. Armature?) 
 
 Chamber of Lamp. (See Lamp, Cham- 
 ber of.) 
 
 Change, Chemical Any change hi 
 
 matter resulting from atomic combination 
 and the consequent formation of new mole- 
 cules. 
 
 Some chemical changes are caused by atomic 
 combinations and the formation of new molecules. 
 They are necessarily attended by ? loss of the spe- 
 cific identity of the substances involved in the 
 change. Thus carbon, a black solid, combined 
 with sulphur, a yellow solid, produces carbon 
 disulphide, a colorless, odorous liquid. (See 
 Atom.) 
 
 Change, Physical Any change hi 
 
 matter resulting from a change in the relative 
 position of its molecules, without the forma- 
 tion of new molecules. 
 
 Ice, when heated, is turned into water; steel, 
 when stroked by a magnet, is rendered perma- 
 nently magnetic; a piece of vulcanite or hard 
 
 rubber stroked by a piece of cat skin becomes 
 electrified. In all these cases, which are'instances 
 of physical changes, the substances retain their 
 specific identity, This is true in all cases of phys- 
 ical changes. (See Molectile.) 
 
 Changing-over Switch. (See Switch, 
 Changing-over^ 
 
 Changing Switch. (See Switch, Chang- 
 ing.) 
 
 Characteristic Curre. (See Curve, 
 Characteristic) 
 
 Characteristic Curve of Parallel Trans- 
 former. (See Curve, Characteristic, of 
 Parallel Transformer?) 
 
 Characteristic Curve of Series Trans- 
 former. (See Curve, Characteristic, of 
 Series Transformer^ 
 
 Characteristics of Sound. (See Sound, 
 Characteristic of.) 
 
 Charge , Bound The condition of 
 
 an electric charge -on a conductor placed near 
 another conductor, but separated from it by 
 a med r um through which electrostatic induc- 
 tion can take place. (See Induction, Elec- 
 trostatic) 
 
 When a charged conductor is placed near an- 
 other conductor, but separated from it by a di- 
 electric or medium through which induction can 
 take place, a charge of the opposite name is in- 
 duced in the neighboring conductor. This charge 
 is so held or bound on the conductor by the mu- 
 tual attraction of the opposite charge that it is 
 not discharged on connection with the earth 
 unless both conductors are simultaneously touched 
 by any good conductor. The bound charge was 
 formerly called dissimulated or latent electricity. 
 (See Electricity, Dissimulated or Latent.) 
 
 Charge, Density of The quantity 
 
 of electricity per unit of area at any point on 
 a charged surface. 
 
 Coulomb used the phrase surface density to 
 mean the quantity of electricity per unit of area 
 at any point on a surface. 
 
 Charge, Dissipation of The gradual 
 
 but final loss of any charge by leakage, which 
 occurs even in a well insulated conductor. 
 
 This loss is more rapid with negatively charged 
 conductors, than with those positively charged. 
 
Crookes, of England, has retained a charge on 
 conductors for years, without appreciable leakage, 
 by placing the conductors in vessels in which a 
 kigh vacuum was maintained. (See Vacuum, 
 High.) 
 
 Charge, Distribution of The vari- 
 ations that exist in the density of an electrical 
 charge at different portions of the surface of 
 all insulated conductors except spheres. 
 
 The density of charge varies at different points 
 of the surface of conductors of various shapes. It 
 is uniform at all points on the surface of a sphere. 
 
 It is greater at the extremities of the longer 
 axis of an egg-shaped body, and greatest at the 
 sharper end. 
 
 It is greater at the corners of a cube than at 
 the middle of a side. 
 
 It is greatest around the edge of a circular disc. 
 
 It is greatest at the apex oi a cone 
 
 Charge, Electric The quantity of 
 
 electricity that exists on the surface of an in- 
 sulated electrified conductor. 
 
 When such a conductor is touched by a good 
 conductor connected with the earth, it is dis- 
 charged. (See Condenser.) 
 
 Charge, Free The condition of an 
 
 electric charge on a conductor isolated from 
 any other conductor. 
 
 It is impossible to obtain a perfectly free charge, 
 since it is impossible to complete^ isclate an 
 insulated conductor. The charge, however, can 
 be comparatively free. 
 
 The charge, on a completely isolatea conductor 
 readily leaves it when it is put in contact with a 
 good conductor connected with the ground. (See 
 Charge, Bound.) 
 
 Charge, Induced Electrostatic 
 
 The charge produced by bringing a body 
 Into an electrostatic fiel 
 
 In order to obtain a permanent charge, /. e., a 
 charge which will be maintained when the body 
 is withdrawn from an electrostatic field, it is nec- 
 essary to connect the body with the earth so that 
 it may lose, or'part with, a charge of the same 
 name as the inducing charge. Then, on the with- 
 drawal of this charge, it will possess a charge op- 
 posite in name to the inducing charge. (See 
 Condenser.) 
 
 Charge, Influence A charge pro- 
 
 [ClUL 
 
 duced by electrostatic induction. (See / 
 duction, Electrostatic) 
 
 Charge, Negative According to the 
 
 double-fluid hypothesis, a charge of negative 
 electricity. 
 
 According to the single-fluid hypothesis, 
 any deficit of an assumed electrical fluid. 
 
 Charge, Positive According to the 
 
 double-fluid hypothesis, a charge of positive 
 electricity. 
 
 According to the single-fluid hypothesis, 
 any excess of an assumed electrical fluid. 
 
 Charge, Residual The charge pos- 
 sessed by a charged Leyden jar for a few 
 moments after it has been disruptively dis- 
 charged by the connection of its opposite 
 coatings. 
 
 The residual charge is probably due to a species 
 of dielectric strain, or a strained position of the 
 molecules of the glass caused by the charge. 
 Such residual charge is not present in air con. 
 densers. In other words, a Leyden jar does not 
 give up all the electric energy charged in r;, on a 
 Single disruptive discharge. 
 
 Charge, Return A charge induced 
 
 in neighboring conductors by a discharge oi 
 lightning. 
 
 Under the influence of induction a lightning 
 stroke produces during its discharge an electric 
 shock in the human body, or a charge in neigh- 
 boring bodies, which is called the back or re- 
 turn stroke of lightning. (See Stroke^ Light- 
 ning, Back or Return.) 
 
 Charged Body. (See Body, Charged) 
 
 Charging Accumulators. Sending an 
 electric current into a storage battery for the 
 purpose of rendering it an electric source. 
 
 There is, strictly speaking, no accumulation of 
 electricity in a storage battery, such, for example, 
 as takes place in a condenser, but a mere storage 
 of chemical energy s which may afterward become 
 electric. (See Cell, Storage.) 
 
 Charging Leyden Jars by Cascade. (See 
 
 Cascade, Charging Leyden Jars by) 
 
 Chart, Inclination A map or chart 
 
 on which the isoclinic lines are marked. (See 
 Map or Chart t Inclination. Lines. 
 
Cluu] 
 
 94 
 
 [Chr. 
 
 Chart, Isodynamic A map or chart 
 
 on which the isodynamic lines are marked. 
 (See Map or Chart, Isodynamic. Lines, 
 Isodynamic?) 
 
 Chart, Isogonal An isogonic chart. 
 
 (See Map or Chart, Isogonal.) 
 
 Chart, Isogonic A map or chart 
 
 on which the isogonic lines are marked. (See 
 Map or Chart, Isogonic. Lines, Isogonic?) 
 
 Chatterton's Compound. (See Com- 
 pound, Chatterton 's.) 
 
 Chemical Change. (See Change, Chem- 
 ical?) 
 
 Chemical Effect. (See Effect, Chemical?) 
 
 Chemical Equivalent. (See Equivalent, 
 Chemical?) 
 
 Chemical Galvano-Cantery. (See Cau- 
 tery, Galvano-Chemical?} 
 
 Chemical Phosphorescence. (See Phos- 
 phorescence, Chemical?) 
 
 Chemical Photometer. (See Photometer, 
 Chemical?) ' 
 
 Chemical Potential Energy. (See En- 
 ergy, Chemical Potential?) 
 
 Chemical Recorder, Bain's (See 
 
 Recorder, Chemical, Bains?) 
 
 Chemistry, Electro That branch 
 
 of electric science which treats of chemical 
 compositions and decompositions effected by 
 the electric current. (See Electrolysis, De- 
 composition, Electrolytic?) 
 
 That branch of chemistry which treats of 
 combinations and decompositions by means 
 of electricity. 
 
 Electro-chemistry treats of the formation of 
 new molecules, by the combination of atoms under 
 the electric force, as well as the decomposition of 
 molecules by electricity. 
 
 The action of a series of sparks passed through 
 air, in forming nitric acid, is an instance of the 
 former, and electrolytic decompositions in gen- 
 eral afford instances of the latter. 
 
 Chimes, Electric Bells rung by 
 
 the attractions and repulsions of electrostatic 
 charges. 
 
 The bells B and B, Fig. 121, are conductively 
 connected to \hefrime or positive conductor -4-, 
 
 of a frictional machine. The bell C, is insulated 
 from this conductor by means of a silk thread, 
 but is connected with the ground by the metallic 
 chain. Under these 
 circumstances the 
 clappers, 1, 1, insu- 
 lated by silk threads, 
 t, t, are attracted to 
 B, B, by an induced 
 charge and repelled 
 to C, where they lose 
 their charge only to 
 be again attracted to 
 B. B. In this way 
 the bells will con- 
 tinue ringing as long 
 
 Fig, lit. Electric Chimes. 
 
 as the electric ma- 
 chine is in operation. 
 
 Choking Coil. (See Coil, Choking?) 
 Chronograph, Electric An elec- 
 tric apparatus for automatically measuring 
 and registering small intervals of time. 
 
 Chronographs, though of a variety of forms, 
 generally register small intervals of time by 
 causing a tuning fork or vibrating bar of steel, 
 whose rate of motion is accurately known, to 
 trace a sinuous line on a smoke-blackened sheet 
 of paper, placed on a cylinder driven at a uni- 
 form rate of motion by clockwork. If the fork 
 is known to produce, say, 256 vibrations per 
 second be used, each sinuous line will represent 
 567 part of a second. 
 
 Fig. 122. Electric Chronograph. 
 
 An electro-magnet is used to make -marks on 
 the line at the beginning and the end of the 
 observation, and thus permit its duration to be 
 measured. 
 
 In the form of electric chronograph shown 
 
Clir.] 
 
 95 
 
 [Cir. 
 
 in Fig. 122, an electro-magnet, the armature of 
 which carries a pen, is supported on a carriage 
 moved by clockwork over a sheet of paper 
 wrapped on a rotating cylinder. A clock is so 
 connected with the circuit of the electro-magnet 
 that it makes or breaks the circuit at the end of 
 every second second, and so moves, or displaces, 
 the armature, as to cause an elevation or depres- 
 sion in the otherwise continuous sinuous line, that 
 would be drawn on the paper by the double 
 motion of its rotation and the movement of the 
 pen-carriage. 
 
 When it is desired to know with great precision 
 the exact time of occurrence of any event, 
 such, for example, as the transit of a star over the 
 meridian, the observer, who carries in his hand a 
 push button, or other form of electric key, closes 
 or opens the circuit at the exact moment and so 
 superposes an additional mark on the sinuous 
 line. Since the exact time of starting the clock 
 is known, and the intervals between the regular 
 successive marks are two seconds each, it is easy to 
 estimate from its position between any two such 
 marks the exact value of the additional mark inter- 
 posed. Fig. 122, taken from Young, shows a form 
 of chronograph by Warner & Swasey. The de- 
 tails of this apparatus will be understood from 
 an inspection of the drawing. 
 
 Chronograph Record. (See Record, 
 Chronograph .) 
 
 Chronoscope, Electric An appa- 
 ratus for electrically indicating, but not 
 necessarily recording, small intervals of time. 
 
 This term is often used for chronograph. 
 
 The interval of time required for a rifle ball 
 to pass between two points may be determined 
 by causing the ball to pierce two wire screens 
 placed a known distance apart. As the screens 
 are successively pierced, an electric circuit is 
 thus made or broken, and marks are registered 
 electrically on any apparatus moving with a 
 known velocity. 
 
 Cigar-Lighter, Electric (See 
 
 Lighter, Cigar, Electric?) 
 
 Cipher Code. (See Code, Cipher!) 
 
 Circle, Azimuth The arc of a 
 
 great circle passing through the point of the 
 heavens directly overhead, called the Zenith, 
 and the point directly beneath, called the 
 
 Nadir. 
 
 Circle, Dipping A term some- 
 times applied to an inclination compass. (See 
 Compass, Inclination?) 
 
 Circle, Galvanic A term some- 
 times used for galvanic circuit. (See Circuit, 
 Galvanic?) 
 
 Circle of Reference. The circle, by refer- 
 ence to which simple harmonic motion may 
 be studied, by comparison with uniform mo- 
 tion around such circuit. (See Motion, 
 Simple Harmonic?) 
 
 Circle, Voltaic A name formerly 
 
 employed for voltaic cell or circuit. (See 
 Cell, Voltaic. Circuit, Voltaic?) 
 
 Circuit, Air-Magnetic That part 
 
 of the path of a line of magnetic induction 
 which takes place wholly through air. 
 
 Circuit, Alternating Current A 
 
 circuit in which an alternating current of 
 electricity is flowing. (See Current, Alter- 
 nating?) 
 
 Circuit, Astatic A circuit consist- 
 ing of two closed curves enclosing equal sur- 
 faces. 
 
 Such a circuit is 
 not deflected by the 
 action of the earth's 
 field. The circuit dis- > 
 posed, as shown in 
 Fig. 123, is astatic and . 
 produces two equal ' 
 and opposite fields at 
 S and S'. (See Mag. 
 
 A 
 
 1 Ci 
 | o 
 
 +j s' 
 
 " I B 
 Fig. 123. Astatic Circuit. 
 
 netism, Ampere's Theory of.) 
 
 Circuit, Balanced-Metallic A me- 
 tallic circuit, the two sides of which have 
 similar electrical properties. 
 
 Circuit Breaker. (See Breaker, Circuit?) 
 
 Circuit, Broken An open circuit. 
 
 A circuit, the electrical continuity of which 
 has been disturbed, and through which the 
 current has therefore ceased to pass. 
 
 Circuit, Closed A circuit is closed, 
 
 completed, or made when its conducting 
 continuity is such that the current can pass. 
 
 Circuit, Closed Iron-Magnetic 
 
 The name applied to the path of any line 
 
dr.] 
 
 96 
 
 [Cir. 
 
 of magnetic force, which takes place entirely 
 through iron, steel, or other paramagnetic sub- 
 stance. 
 Circuit, Closed-Loop Parallel A 
 
 variety of parallel circuit in which the lead 
 and the return circuit are arranged in the 
 form of concentric circuits, with the recep- 
 tive devices placed radially between them, 
 
 Circuit, Closed-Magnetic A mag- 
 netic circuit which lies wholly in iron or other 
 substance of high magnetic permeability. 
 
 All lines of magnetic force form closed circuits. 
 The term closed -magnetic circuit is used in con- 
 tradistinction to a divided circuit, or one in which 
 an air gap exists in the substance of high mag- 
 
 Fig. 124. Closed-Magnetic Circuit. 
 
 netic permeability forming the remainder of the 
 circuit. This introduces so high a resistance that 
 such a circuit is sometimes called an open-mag- 
 netic circuit. An iron ring, such as shown in 
 Fig. 124, forms a closed-magnetic circuit. 
 
 Circuit, Closed-Magnetic, of Atom 
 
 A closed-magnetic circuit, or closed lines 
 of magnetic force supposed to lie entirely in 
 the atom itself. 
 
 The assumption of closed lines of magnetic 
 force in atoms or molecules was made in order to 
 explain the original polarity of the same, and to 
 account for some of the other phenomena of 
 magnetism. 
 
 When the atom is subjected to a magnetizing 
 force, such, for example, as the field of an electric 
 current, these closed lines of force are assumed 
 to open out and produce lines of polarized atoms. 
 According to Lodge, for every single line of force 
 produced by the current passing through a coil 
 of wire surrounding an iron core, some 3,000 
 lines of magnetic force are added to it from the 
 iron. Therefore an iron core greatly increases 
 the magnetic strength of a hollow coil of wire. 
 
 Circuit, Closed-Magnetic, of Molecule 
 
 A closed-magnetic circuit assumed to lie 
 wholly within the molecule. 
 
 As it is not known whether the assumed mag- 
 netic circuit lies within the atom or the molecule, 
 it is called indifferently the closed-atomic or 
 closed-molecular circuit. (See Circuit, Closed- 
 Magnetic^ of Atom.} 
 
 Circuit, Completed A closed 
 circuit. 
 
 A circuit, the conducting continuity of 
 which is unbroken. 
 
 A completed circuit is also called a made or 
 closed circuit. 
 
 Circuit, Compound A circuit con- 
 taining more than a single source, or more 
 than a single electro-receptive device, or both, 
 connected by conducting wires. 
 
 The term compound circuit is sometimes ap- 
 plied to a series circuit. (See Circuit, Series.) 
 The term, however, is a bad one, and is not 
 generally adopted. 
 
 Circuit, Constant-Current A cir- 
 cuit in which the current or number of am- 
 peres is maintained constant notwithstanding 
 changes occurring in its resistance. 
 
 The series-circuit, as maintained for arc-lamps, 
 is a constant-current circuit. (See Regulation, 
 Automatic.') 
 
 Circuit, Constant-Potential A 
 
 circuit, the potential or number of volts of 
 which is maintained approximately constant. 
 The multiple-arc or parallel circuit is an ap- 
 proximately constant-potential circuit. 
 
 Circuit, Derivative A derived or 
 
 shunt circuit. (See Circuit, Shunt.) 
 Circuit, Derived 
 
 A term applied to a shunt 
 circuit. 
 
 If, in addition to the galva- 
 nometer G, the conductor S, 
 Fig. 125, be connected with 
 the circuit of the battery B, a 
 derived circuit will thus be 
 established, and a current will 
 flow through S, diminishing tf ' J2S ' 
 the current in the galvanom- 
 eter. (See Circuit, Shunt.) 
 
 Derived 
 Circuit. 
 
dr.] 
 
 Circuit, Divided-Magnetic A 
 
 magnetic circuit which lies partly in iron, or 
 other substance of high magnetic perme- 
 ability, and partly in air. 
 A divided-magnetic circuit is shown in Fig. 126. 
 
 97 
 
 Fig, 1 2b. Divided Magnetic Circuit. 
 
 Where the iron ring is separated by the air gap, 
 a high magnetic resistance is introduced, owing 
 to the fact that the iron is at these points replaced 
 by air, whose magnetic reluctance is great. 
 
 Circuit, Double-Wire A term 
 
 sometimes used for a simple multiple circuit 
 with two conductors or wires. (See Circuit, 
 Multiple^ 
 
 The term double-wire circuit is used in contra- 
 distinction to single-wire circuit. (See Circuit, 
 Single- Wire.) 
 
 Circuit, Earth A circuit in which 
 
 the ground or earth forms part of the con- 
 ducting path. 
 
 Circuit, Earth, Telegraphic 
 
 That portion of a telegraphic circuit which is 
 completed through the earth or ground. 
 
 Circuit, Electric The path in 
 
 which electricity circulates or passes from a 
 given point, around or through a conducting 
 path, back again to its starting point. 
 
 All simple circuits consist of the following 
 parts, viz.: 
 
 (I.) Of an electric source which may be a 
 voltaic battery, a thermopile, a dynamo-electric 
 machine, or any other means for producing elec- 
 tricity. 
 
 (2.) Of leads or conductors for carrying the 
 electricity out from the source, through whatever 
 apparatuses placed in the line, and back again to 
 the source. 
 
 (3.) Various electro-receptive devices, such as 
 electro-magnets, electrolytic baths, electric 
 motors, electric heaters, etc., through which 
 
 [Cir. 
 
 passes the current by which they are actuated ot 
 operated. 
 
 Circuit, Electrostatic The circuit 
 
 formed by lines of electrostatic force. 
 
 Lines of electrostatic force, like lines of mag- 
 netic force, form closed circuits. Hence the 
 origin of the phrase electrostatic circuit. (See 
 Force, Electrostatic, Lines of.) 
 
 Circuit, External That part of a 
 
 circuit which is external to, or outside the elec 
 trie source. 
 
 The circuit external to the source consists of 
 two distinct parts, viz. : 
 
 (I.) The conductors or leads. 
 
 (2 ) The electro-receptive or translating de- 
 vices. 
 
 It is in the external circuit only that useful 
 work is done by the current. 
 
 Circuit, Forked A term sometimes 
 
 used in telegraphy for a number of circuits 
 that radiate from a given central point. 
 
 Circuit, Galvanic A term some- 
 times employed instead of voltaic circuit. 
 
 The term galvanic in place of voltaic is unwar- 
 ranted by the facts of electric science. (See Cir- 
 cuit, Voltaic.) 
 
 Galvani thought he had discovered the vital 
 fluid or source of animal life. Volta first pointed 
 out the true explanation of the phenomena ob- 
 served in Galvani's frog, and devised means 
 for producing electricity in this manner. The 
 terms voltaic battery, cell, circuit, etc., are there- 
 fore preferable. 
 
 Circuit, Ground A circuit in which 
 
 the ground forms part of the path through 
 which the current passes. 
 
 As the ground is not always a good conductor, 
 the terminals should be connected with the gas or 
 water pipes, or with metallic plates, called ground 
 plates. Such connection, or any similar ground 
 connection, is usually termed the ground or earth. 
 
 Circuit, Ground, Telegraphic 
 
 An earth circuit used in any system of telegra- 
 phy. (See Circuit, Earth, Telegraphic?) 
 
 Circuit, Grounded A ground cir- 
 cuit. 
 
 Circuit, Incomplete An open oi 
 
 broken circuit. 
 
Cir.j 
 
 A circuit whose conducting continuity is 
 incomplete. 
 
 Circuit, Inductive Any circuit in 
 
 which induction takes place, 
 
 Circuit, Internal That part of a 
 
 circuit which is included within the electric 
 source. 
 
 The alectric current passing through the inter- 
 nal circuit does no useful work. 
 
 Circuit, Leg of One part of a 
 
 twisted or metallic circuit. 
 
 Circuit, Line The wire or other 
 
 conductors in the main line of any telegraphic 
 or other electric circuit. 
 
 Circuit, Line, Telegraphic The 
 
 conductor or line connecting different tele- 
 graphic stations. 
 
 Circuit, Local-Battery The cir- 
 cuit, in a telegraphic system, in which is 
 placed a local battery as distinguished from a 
 main battery. (See Telegraphy, American 
 or Morse System of.) 
 
 Circuit, Loop A term sometimes 
 
 applied to a circuit in parallel or multiple-arc. 
 (See Circuit, Multiple?) 
 
 Circuit Loop Break. (See Break, Circuit 
 Loop?) 
 
 Circuit, Made A completed circuit. 
 
 A circuit, whose conducting continuity is 
 unbroken. 
 
 A made circuit is often called a completed or 
 closed circuit. (See Circuit ', Closed.) 
 
 Circuit, Magnetic The path through 
 
 which the lines of magnetic force pass. 
 All lines of magnetic force form closed circuits. 
 
 98 
 
 [Cir. 
 
 Fig. 127. Magnetic Circuit. 
 
 In the bar magnet, shown in Fig. 127, part of 
 this path is through the air. In order to reduce 
 or lower the resistance of a magnetic circuit, iron 
 
 is often placed around the magnet. The magnet 
 is then said to be iron-clad. 
 
 The armature of a magnet lowers the magnetic 
 resistance by affording a better path for the lines 
 of magnetic force than the air between the 
 poles. 
 
 The magnetic circuit always tries to shorten its 
 path, or to render itself as compact as possible. 
 This is seen in the action of an armature drawn 
 towards a magnet pole. 
 
 Circuit, Main-Battery A term 
 
 sometimes used for line circuit. (See Circuit, 
 Line.) 
 
 Circuit, Metallic A circuit in which 
 
 the ground is not employed as any part of the 
 path of the current, metallic conductors being 
 employed throughout the entire circuit. 
 
 Circuit, Multiple A compound cir- 
 cuit, in which a number of separate sources 
 or separate electro-receptive devices, or both, 
 have all their positive poles connected to a 
 single positive lead or conductor, and all their 
 negative poles to a single negative lead or 
 conductor. 
 
 The connection of three Bunsen cells, in mul. 
 tiple, is shown in Fig. 128, where the three car- 
 
 Fig. 128. Batteries connected in a Multiple Circuit. 
 
 bons, C, C, C, are connected together so as to form 
 the positive, or -J- terminal of the battery, and 
 the three zincs, Zn, Zn, Zn, are similarly con- 
 nected together so as to form the negative, or 
 terminal. 
 
 The electromotive force is the same as that of 
 a single cell, or source. The internal resistance 
 of the source is as much less than the resistance ot 
 any single source as the area of the combined 
 negative or positive plates is greater than that of 
 any single negative or positive plate ; or, in othet 
 words, is less in proportion to the number of cells, 
 or other separate sources so coupled. 
 
 The connection of six cells in multiple or 
 parallel circuit, is shown in Fig. 129. 
 
ir.J 
 
 99 
 
 [Cir. 
 
 In the case of the six cells, the current would 
 
 be, 
 
 where E, is the electromotive force, r, the in- 
 ternal, and r', the external resistance. 
 
 Fig. 129. &'* Cells Connected in Multiple. 
 
 In the case of voltaic cells the effect of multiple 
 connection on the internal resistance of the source 
 is to increase the area of cross-section of the 
 liquid in the direct proportion of the number of 
 cells added, and consequently to decrease the re- 
 sistance in the same proportion. 
 
 When strong or large currents of low electro- 
 motive force are required, connections in multi- 
 ple-arc are generally employed. 
 
 The multiple-arc connection was formerly 
 called connection-far -quantity. This term is now 
 abandoned. 
 
 The total -resistance for the parallel circuit is 
 obtained as follows: calling the separate resist- 
 ances of the separate electro-receptive devices, 
 R', R", R"', etc., etc., etc., total resistance, 
 
 p _ R' X R" X R'" 
 
 R' R" -f- R" R'" 4- R' R'" 
 
 or, what is the same thing, the conductivity is the 
 sum of the reciprocal of the separate resistances, 
 '. e. : 
 
 III 
 Conductivity = -pr- + -pir -f- ?><- 
 
 The joint resistance of only two separate resist- 
 ances joined in a multiple-circuit is equal to the 
 product of the separate resistances divided by 
 their sum. 
 
 When the separate resistances joined in multiple 
 arc are all of the same value, the joint resistance is 
 equal to the resistance of one of them divided by 
 their number. 
 
 A term often 
 
 (See Circuit, Mul- 
 
 Circuit, Multiple-Arc 
 
 used for multiple circuit. 
 ttjfr.] 
 
 Circuit, Multiple-Series A com- 
 pound circuit in which a number of separate 
 
 sources, or separate electro-receptive devices, 
 or both, are connected in a number of sepa- 
 rate groups in series, and these separata 
 groups subsequently connected in multiple. 
 In Fig. 130, a multiple-series circuit of six 
 ._ c 
 
 \ 
 
 J 
 
 Fig. 130. Multiple~Series-Connected Cells. 
 
 sources is shown, in which three separate groups 
 of two series-connected cells are coupled in multi. 
 pie. The current takes the paths indicated by the 
 arrows. The electromotive force of the source 
 will be increased in proportion to the number of 
 cells in series, and the internal resistance de- 
 creased in proportion to the number in parallel. 
 
 Fig. 131. Cells Connected in Multiple- Series. 
 
 -J!L+r'. 
 
 2 
 
 In Fig. 131, six cells are arranged in two 
 groups of three series-connected cells, and these 
 three groups connected in parallel. 
 
 Calling r, the resistance of each separate cell, 
 the total resistance for the multiple-series circuit 
 for a circuit containing three cells in parallel and 
 two in series is, 
 
 R 
 
 2r 
 T 
 
 for three in series and two in parallel, 
 
 If, therefore, the circuit of this battery be 
 closed by a resistance equal to r, the current 
 would be in the case of Fig. 130, 
 2E 
 
Cir.] 
 
 100 
 
 [Cir. 
 
 Circuit, Negative Side of The side 
 
 ot a circuit opposite to the positive side. 
 (See Circuit, Positive Side of.) 
 
 That side or half of a circuit connected to or 
 leading from the positive terminal of the source of 
 CNrrent. 
 
 Circuit, Open A broken circuit. 
 
 A circuit, the conducting continuity of 
 which is broken. 
 
 Circuit, Open-Iron Magnetic 
 
 The path of a line of magnetic induction, 
 which passes partly through iron, and partly 
 through an air space. 
 
 The magnetic circuit is always closed, that is 
 the lines of magnetic force always form closed 
 paths. The term "open" is used in contradis- 
 tinction only to "closed " iron magnetic circuit, 
 in which the entire path of a line of force passes 
 through iron. (See Circuit, Magnetic.) 
 
 Circuit, Parallel A name some- 
 times applied to circuits connected in mul- 
 tiple. (See Circuit, Multiple!) 
 
 Circuit, Parallel-Tree A form of 
 
 parallel circuit in which the receptive devices 
 are placed in parallel between the leads and 
 returns, and the branches and sub-branches 
 arranged in a tree-like form. 
 
 Circuit, Positive Side of That side 
 
 of a circuit, bent in the form of a circle, in 
 which, if an observer stood with his head in 
 the positive region, he would see the current 
 pass round him from his right hand towards 
 his left. (Daniell) 
 
 Circuit, Recoil A term sometimes 
 
 applied to the circuit that lies in the alterna- 
 tive path of a discharge. (See Path, Alter- 
 native?) 
 
 Circuit, Return That part of a 
 
 circuit by which the electric current returns to 
 the source. 
 
 In a multiple-circuit the lead that is con- 
 nected to the negative terminals of the 
 separate' sources. 
 
 Circuit, Series A compound cir- 
 cuit in which the separate sources, or the sep- 
 arate electro-receptive devices, or both, are so 
 placed that the current produced in each, or 
 passed through each, passes successively 
 
 through the entire circuit from the first to the 
 last. 
 
 The six cells, shown in Fig. 132, are connected 
 in series by joining the positive pole of each cell 
 with the negative pole of the succeeding cell, the 
 negative and positive poles at the extreme ends 
 
 Fig. 132. Series Circuit. 
 
 being connected by conductors with the external 
 circuit. 
 
 The connection of three Leclanche" cells ut 
 series is clearly shown in Fig. 133. The carbons, 
 
 C +,. C+ 
 
 Fig. 133. Voltaic Cells Connected in Series. 
 
 C, C, of the first and second cells are connected to 
 the zincs, Zn, Zn, of the second and third cells, 
 thus leaving the zinc, Zn, of the first cell, and the 
 carbon, C, of the third cell, as the terminals of 
 the battery. The direction of. the current is 
 shown by the arrows. 
 
 The resistance of such a connection is equal to 
 the sum of the resistances of all of the separate 
 sources. 
 
 The electromotive force is equal to the sum of 
 the separate electromotive forces. 
 
 If the electromotive force of a single cell is 
 equal to E, its internal resistance to r, and the 
 resistance of the leads and electro-receptive d- 
 vices to r', then the current in the circuit, 
 
 C- 
 
 - 
 
 F+7" 
 
 If six of such cells are coupled in series, the cur- 
 rent becomes 
 
 _6E_ 
 ~~6r + r'' 
 
 If, however, the internal resistance of each cell be 
 so small as to be neglected, the formula becomes 
 
 C = 5 
 
Cir.] 
 
 101 
 
 [Cir. 
 
 or the current is six times as great as with one 
 cell. 
 
 The total resistance of the separate sources or 
 electro-receptive devices of the series circuit is 
 as follows, calling R', R", R'", etc., the separate 
 resistance and R, the total resistance, 
 R = R' +R" -f-R'", etc. 
 
 The series connection of battery cells is used 
 on telegraph lines, where a high electromotive 
 force is required in order to overcome a consider. 
 able resistance in the circuit, or in similar cases 
 where the resistance in the external circuit is 
 great, on account of a number of electro-receptive 
 devices being connected to the line in series. 
 
 The series connection was formerly called 
 connection for intensity. The term is now aban- 
 doned. 
 
 Circuit, Series-Multiple -- A com- 
 pound circuit, in which a number of separate 
 sources, or separate electro-receptive devices, 
 or both, are connected in a number of sepa- 
 rate groups in multiple-arc, and these sepa- 
 rate groups subsequently connected in series. 
 
 In the series- multiple circuit the resistance of 
 each multiple group is equal to the resistance of 
 a single branch divided by the number of branches. 
 
 If, for example, r, is the resistance of each sepa- 
 rate branch of say seven parallel circuits in each 
 of the separate groups of multiple circuits, then 
 the resistance, R, of each separate multiple 
 group is 
 
 The total resistance of the series-multiple cir- 
 cuit is equal to the sum of the resistances of the 
 separate multiple groups. The total resistance of 
 the three groups is 
 
 R = - + I + L = J1L. 
 7777 
 
 An example of the series-multiple circuit is 
 shown in Fig. 134, which is the method adopted 
 
 F'g- 134- Series-Multii>le Circuit. 
 
 in the use of distribution boxes. Here a number 
 c multiple -groups or circuits are connected with 
 each other in series, as shown. (See Box, Dis- 
 tribution, for Arc Light Circuits. ) 
 
 Circuit, Short A shunt, or by-path. 
 
 of comparatively small resistance, around the 
 poles of an electric source, or around any 
 portion of a circuit, by which so much of the 
 current passes through the new path, as vir- 
 tually to cut out the part of the circuit around 
 which it is placed, and so prevent it from re- 
 ceiving an appreciable current. 
 
 Circuit, Shunt A branch or add* 
 
 tional circuit provided at any part of a cir- 
 cuit, through which the current branches or 
 divides, part flowing through the original cir- 
 cuit, and part through the new branch. 
 
 A shunt circuit is in multiple circuit with the 
 circuit it shunts. 
 
 In the case of branch circuits each of the cir- 
 cuits acts as a shunt to the others. Any number 
 of additional or shunt circuits may be thus pro- 
 vided. (See Laws, J&rchhojfs.} 
 
 Circuit, Simple A circuit containing 
 
 a single electric source, and a single electro- 
 receptive device, connected by a conductor. 
 
 The term .simple circuit is sometimes applied 
 to a multiple circuit. The term is not, however, 
 a good one, and is not in general use. 
 
 Circuit, Single- Wire A term some- 
 times used for a grounded circuit. (See 
 Circuit, Grounded?) 
 
 The single-wire circuit is sometimes used in the 
 distribution of incandescent lamps in multiple-arc. 
 One pole of the dynamo is put to ground, and the 
 other pole to a single wire or lead. The electro- 
 receptive devices have one of their poles con. 
 nected to this lead and the other pole to earth. 
 The single-wire circuit is a very objectionable 
 circuit so far as safety is concerned. 
 
 It is frequently used,, however, in the wiring of 
 ships. 
 
 Circuit, Through A telephonic or 
 
 telegraphic circuit that has been completed 
 through to a given station by cutting out inter- 
 ruptions or breaks in the line by the connec- 
 tion together of sections of different wires. 
 
 Circuit, Time-Constant of The 
 
 time in which a current due to a constant 
 electromotive force will rise in a conductor 
 to a definite fraction of its maximum value. 
 
 The rauo of the inductance of a circuit to 
 its resistance. 
 
' *** 
 
 Cir.J 
 
 102 
 
 [Cle. 
 
 The time required from the moment of 
 closing the circuit, for a current to rise to 
 
 a value equal to 
 
 e I 
 
 of the full value, or 
 
 .632 of the maximum value. 
 
 In the above, e, equals 2.71828, or the base of 
 the Napierian system of logarithms. 
 
 The time-constant is proportional to the con- 
 ductivity of the circuit and its formal resistance. 
 
 Approximately the time constant of a circuit is 
 the time from closing the circuit, in which the 
 current rises to two-thirds of its maximum value, 
 this maximum value being determined by the 
 
 E 
 formula, C = . 
 
 R 
 
 Thetime-constant of a circuit may be reduced 
 
 (i.) By decreasing the self-induction of the cir- 
 cuit. 
 
 (2.) By increasing the resistance. 
 
 In the case of a magnetic conductor the time- 
 constant is proportional to a quantity (the perme- 
 ability) which is determined by the capacity of 
 the conductor to utilize part of the energy in 
 producing magnetization of its substance. (Flem- 
 ing-) 
 
 Circuit, Yoltaic The path through 
 
 which the current flows out from a voltaic cell 
 or battery, through the translating devices 
 and back again to the cell or b-*tery. 
 
 Circuits, Forked A term employed 
 
 in telegraphy to indicate circuits that radiate 
 from any single point. 
 
 Forked circuits are employed in simultaneously 
 transmitting messages to several stations. 
 
 Circuits, Varieties of Conducting 
 
 paths provided for the passage oT an electric 
 current. 
 
 Electric circuits may be divided, according to 
 their complexity, into 
 
 (i.) Simple. 
 
 (2.) Compound. 
 
 According to the peculiarities of their connec- 
 tions, into 
 
 (i.) Shunt or derived. 
 
 (2.) Series. 
 
 (3.) Multiple, multiple-arc or parallel. 
 
 (4.) Multiple-series. 
 
 (5.) Series-multiple. 
 
 Either the circuits, the sources, or the electro- 
 
 receptive devices may be connected in series, in 
 multiple, in multiple-series or in series-multiple. 
 
 According to their resistance, circuits are 
 divided into 
 
 (i.) High-resistance. 
 
 (2.) Low-resistance. 
 
 According to their relation to the electric 
 source, into 
 
 (I.) Internal circuits. 
 
 (2.) External circuits. 
 
 According to their position, or the work done, 
 circuits are divided into very numerous classes; 
 thus, in telegraphy, we have the following, viz.: 
 
 (i.) The line -circuit. 
 
 (2.) The earth or ground circuit. 
 
 (3.) The local-battery circuit. 
 
 (4.) The main -battery circuit, etc. 
 
 Circular Bell. (See Bell, Circular) 
 Circular Units. (See Units, Circular^ 
 
 Circular Units (Cross-Sections), Table 
 of (See Units, Circular (Cross- Sec- 
 tions), Table of.) 
 
 Clamp, Carbon A carbon clutch. 
 
 (See Clutch, Carbon, of Arc Lamp) 
 
 Clamp for Arc Lamps. A clamp for 
 gripping the lamp-rod, /. e., the rod that sup- 
 ports the carbon electrodes of arc lamps. 
 (See Lamp, Electric, Arc) 
 
 Clamp, Rod A carbon clutch. (See 
 
 Clamp for Arc Lamps) 
 
 Clark's Compound. (See Compound, 
 Clark's) 
 
 Clark's Standard Yoltaic Cell. (See 
 
 Cell, Voltaic, Standard, Clark's) 
 
 Clark's Standard Yoltaic Cell, Ray- 
 
 leigh's Form of (See Cell, Voltaic, 
 
 Standard, Ray leigh's Form of Clark's) 
 
 Clay Electrode. (See Electrode, Clay) 
 
 Cleansing, Fire The removal of 
 grease from metallic articles, that are to be 
 electro-plated, by subjecting them to the action 
 of heat. 
 
 This cleansing is for the purpose of obtaining a 
 uniform, adherent coating. 
 
 Clearance-Space. (See Stiace. Clearance) 
 
Cle.] 
 
 103 
 
 [CIo. 
 
 Clearing-Out Drops. (See Drops, Clear- 
 ing-Out^) 
 
 Cleat, Crossing A cleat so arranged 
 
 as to permit the crossing of one pair of wires 
 under or over another pair without contact 
 with each other. 
 
 Cleat-Wiring. (See Wiring, Cleat.) 
 
 Cleats, Electric Suitably shaped 
 
 pieces of wood, porcelain, hard rubber or 
 other non-conducting material used for fasten- 
 ing and supporting electric conductors to 
 ceilings, walls, etc. 
 
 A simple form of wooden cleat is shown in 
 3S- 
 
 Fig. 135. Wooden Cleat. 
 
 Clepsydra, Electric An instrument 
 
 for measuring time by the escape of water or 
 Other liquid under electrical control. 
 
 Climbers, Pole 
 
 Devices employed by 
 linemen for climbing 
 wooden telegraph poles. 
 
 A climber with straps 
 for attachment to the leg 
 and foot is shown in Fig. 
 136. 
 
 Clip, Cable A 
 
 term sometimes used for 
 cable hanger. (See 
 Hanger, Cabled) 
 
 Clock, Electric 
 
 A clock, the works of 
 
 Which are moved, COn- Fig. 136. Climber and 
 
 trolled, regulated or straps. 
 
 wound, either entirely or partially, by the elec- 
 tric current. 
 
 Electric clocks may be divided into three 
 classes, viz.: 
 
 (i.) Those in which the works are moved en- 
 tirely or partially by the electric current. 
 
 (2.) Those which are controlled or regulated 
 by the electric current. 
 
 Fig. 
 
 Controlling 
 Clock. 
 
 (3.) Those which are merely wound by the 
 
 current. 
 
 ' A clock moving independently of electric power 
 
 is prevented from gain- 
 ing or losing time, by 
 
 means of a slight re- 
 tardation or acceleration 
 
 electrically imparted. 
 
 The entire motion of 
 
 the balance wheel is 
 
 sometimes imparted by 
 
 electricity. 
 
 An example of one oi 
 
 many forms of controll- 
 ing electric clocks is 
 
 shown in Fig. 137, 
 
 where the split battery 
 
 (See Battery, Split), P 
 
 N, is connected, as 
 
 shown, to the spring 
 
 contacts S and S'. In this way currents are sent 
 into the circuit in alternately opposite directions. 
 The pendulum bob, Fig. 138, of the con. 
 trolled clock is formed of a hollow coil of insu- 
 lated wire, which encircles one or both of two 
 permanent magnets, A and A', placed with their 
 opposite poles facing each other. 
 
 When the pendulum of the controlling clock is 
 in the position shown in Fig. 137, the current 
 passes in the direction E P Sn W, etc., and through 
 the coil C, Fig. 138. When the pendulum of the 
 controlling clock is in con- 
 tact with S', the current 
 flows through Wn S' N E, 
 etc., and through the coil 
 C in the opposite direc- 
 tion. In this manner a 
 slight motion forwards or 
 backwards is imparted to 
 the pendulum, which is 
 thus kept in time with the 
 controlling clock. 
 
 Mercury contacts are 
 sometimes employed in 
 place of the springs S and 
 S'. Induction currents may A. 
 also be employed. 
 
 Clocks of non-electric ac- Fig. 138. Controlled 
 tion may be electrically Clock. 
 
 controlled, or correctly set at certain intervals, 
 either automatically by a central clock, or by the 
 depression of a key operated by hand from an 
 astronomical observatory. 
 
Clo.] 
 
 In a system of time-telegraphy, the controlling 
 clock is called the master clock, and the con- 
 trolled clocks, the secondary clocks. 
 
 Secondary clocks are generally mere dials, con- 
 
 104 
 
 [Clo. 
 
 Fig. 139. Mechanism of Secondary Clock. 
 
 taining step-by-step movements, for moving the 
 hour, minute and second hands, as shown in 
 Fig- 139- 
 
 In Spellier's clock, a series of armatures H, 
 Fig. 140, mounted on the circumference of a 
 
 Fig. r 4.0. Spellier's Electric Clock. 
 
 wheel, connected with the escapement wheel, 
 pass successively, with a step-by-step movement, 
 over the poles of electro-magnets. On the com- 
 pletion of the circuit, they are attracted towards 
 the magnet, and on the breaking of the circuit 
 they are drawn away by the fall of the weight F, 
 placed on the lever D, pivoted at E. A pulley at 
 E, runs over the surface of a peculiarly shaped 
 cog on the escapement wheel. 
 
 Clock, Electric Annunciator A 
 
 clock, the hands or works of which, at cer- 
 tain predetermined times, make electric con- 
 tacts and thus ring bells, release drops, trace 
 records, etc. 
 
 Clock, Electrical-Controlling In 
 
 a system of time telegraphy, the master clock, 
 whose impulses move or regulate the second- 
 ary clocks. (See Clock, Electric?) 
 
 Clock, Electrically-Controlled In 
 
 a system of time telegraphy, a secondary 
 clock, that is either driven or controlled by 
 the master clock. (See Clock, Electric!) 
 
 Clock, Electrolytic, Tesla's A time 
 
 piece in which the rotation of the wheel work 
 is obtained by the difference in weight of the 
 two halves of a delicately pivoted and well- 
 balanced wheel placed in an electrolytic 
 bath. 
 
 In the electrolytic clock of Nikola Tesla, a deli- 
 cately formed and balanced disc of copper is sup- 
 ported on a horizontal axis at right angles to the 
 shortest distance between the two electrodes, and 
 placed in a bath of copper sulphate. Its two 
 halves become respectively electro-positive and 
 electro-negative when a current is passed through 
 the bath, and consequently metal is deposited on 
 one half and dissolved from the other half. The 
 rotation of the disc under the influence of gravity 
 is caused to mark time. 
 
 An electrolytic clock could therefore be made 
 to answer roughly as an electric meter. 
 
 Clock, Master The central or con- 
 trolling clock in a system of electric time-dis- 
 tribution, from which the time is transmitted 
 to the secondary clocks in the circuit. (See 
 Clock, Electric!) 
 
 Clock, Secondary Any clock in a 
 
 system of time telegraphy that is controlled 
 by the master clock. (See Clock, Electric!) 
 
 Clock, Self-Winding A clock that 
 
 at regular intervals is automatically wound by 
 the action of a small electro-magnetic motor 
 contained within it. 
 
 This motor is usually run by one or more vol- 
 taic cells, concealed in the case of the clock. 
 
 Closed-Circnit. (See Circuit, Closed!) 
 
 Closed-Circuit Battery. (See Battery, 
 Closed-Circuit!) 
 
 Closed-Circuit, Single-Current/ Signal- 
 ing (See Signaling, Single-Current, 
 
 Closed-Circuit^ 
 
CIo.] 
 
 105 
 
 [Coe. 
 
 Closed-Circuit Thermostat. (See Ther- 
 mostat, Closed-Circuit) 
 
 Closed-Circuit Voltaic Cell. (See Cell, 
 Voltaic, Closed-Circuit) 
 
 Closed-Circuit Voltmeter. (See Volt- 
 meter, Closed-Circuit) 
 
 Closed-Circuited. Placed in a closed or 
 completed circuit. 
 
 A voltaic battery, or other source, is closed-cir- 
 cuited when its poles or terminals are electrically 
 connected with each other. 
 
 Closed-Circuited Conductor. (See Con- 
 ductor, Closed-Circuited) 
 
 Closed-Circular Current. (See Current, 
 Closed- Circular) 
 
 Closed-Coil Disc Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 Closed-Coil Disc) 
 
 Closed-Coil Drum Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 Closed-Coil Drum) 
 
 Closed-Coil Dynamo-Electric Machine. 
 (See Machine, Dynamo-Electric, Closed- 
 Coil) 
 
 Closed-Coil Ring Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 Closed-Coil Ring) 
 
 Closed-Iron-Circuit Transformer. (See 
 Transformer, Closed-Iron-Circuit) 
 
 Closed-Loop Parallel-Circuit. (See Cir- 
 cuit, Closed-Loop Parallel) 
 
 Closed-Magnetic Circuit. (See Circuit, 
 Closed-Magnetic) 
 
 Closed-Magnetic Core. (See Cqre, Closed- 
 Magnetic) 
 
 Closure. The completion of an electric 
 circuit. 
 
 Cloth Discs, Carbonized, for High Re- 
 sistances Discs of cloth carbonized by 
 
 heating to an exceedingly high temperature 
 in a vacuum, or out of contact with air. 
 
 After carbonization the discs retain their flex- 
 ibility and elasticity and serve admirably for high 
 resistances. When piled together and placed in 
 glass tubes, they form excellent variable resist* 
 ances when subjected to varying pressure. 
 
 Cluh-Footed Magnet. (See Magnet, 
 Club-Footed) 
 Clutch, Carbon, of Arc Lamp A 
 
 clutch or clamp attached to the rod or other 
 support of the carbon of an arc lamp, pro- 
 vided for gripping or holding the carbon. 
 (See Lamp, Electric Arc) 
 
 Clutch Rod. (See Rod, Clutch) 
 
 Coating, Metallic A covering or 
 
 coating of metal, usually deposited from 
 solutions of metallic salts by the action of an 
 electric current . (See Plating, Electro) 
 
 Coating of Condenser. A sheet of tin 
 foil on one side of a Leyden jar or condenser, 
 directly opposite a similar sheet on the other 
 side for the purpose of receiving and collecting 
 the opposite charges. (See Jar, Leyden. 
 Condenser) 
 
 Coatings of Leyden Jar. The sheets of 
 tin foil or other conductor on the opposite 
 sides of a Leyden jar or condenser. (See 
 Jar, Leyden. Condenser) 
 
 Code, Cipher A code in which a 
 
 number of words or phrases are represented 
 by single words, or by arbitrary words or syl- 
 lables. 
 
 The message thus received requires the posses- 
 sion of the key to render it intelligible. 
 
 Code,Telegraphic The pre-arranged 
 
 signals of any system of telegraphy. (See 
 Alphabet, Telegraphic. Alphabet, Tele- 
 graphic, Morse's. Alphabet, Telegraphic, 
 International Code) 
 
 Co-efficient, Algebraic A number 
 
 prefixed to any quantity to indicate how 
 many times that quantity is to be taken. 
 
 The number 3, in the expression 3a, is a co- 
 efficient and indicates that the a, is to be taken 
 three times, as a -j- a -f- a = 3a. 
 
 Co-efficient, Economic, of a Dynamo- 
 Electric Machine The ratio between 
 
 the electrical energy, or the electrical horse- 
 power of the current produced by a Hvnamo, 
 and the mechanical horse-power expended in 
 driving the dynamo. 
 
 The economic co-efficient is usually called the 
 efficiency. 
 
Coe.] 
 
 The efficiency may be the commercial effi- 
 ciency, which is the useful or available energy in 
 the external circuit divided by the total mechan- 
 ical energy; or it may be the electrical efficiency, 
 which is the available electrical energy divided 
 by the total electrical energy. 
 
 The efficiency of conversion is the total elec- 
 trical energy developed, divided by the total 
 mechanical energy applied. 
 
 If M, equals the mechanical energy, 
 W, the useful or available electrical energy, 
 
 and 
 w, the electrical energy absorbed by the 
 
 machine, and 
 m, the stray power, or the power lost in 
 
 friction, eddy currents, air friction, etc. 
 Then, since 
 
 106 
 
 [Coi. 
 
 The Commercial Efficiency 
 - W_ W 
 = ~M~~ 
 
 - w-J-m 
 The Electrical Efficiency 
 
 W 
 
 W + w 
 The Efficiency of Conversion 
 
 __ \V_4-_w_. W-f w 
 
 M~~ w + w + m* 
 
 Co-efficient of Electro-Magnetic Inertia. 
 
 (See Inertia, Electro-Magnetic, Co-effi- 
 cient of) 
 
 Co-efficient of Expansion. (See Expan- 
 sion, Co-efficient of) 
 
 Co-efficient of Expansion, Linear 
 
 (See Expansion, Linear, Co-efficient of) 
 
 Co-efficient of Magnetic Induction. (See 
 
 Induction, Magnetic, Co-efficient of) 
 
 Co-efficient of Magnetization. (See 
 Magnetization, Co-efficient of) 
 
 Co-efficient of Mutual- Inductance. (See 
 Inductance, Mutual, Co-efficient of) 
 
 Co-efficient of Mutual-Induction. (See 
 Induction, Mutual, Co-efficient of) 
 
 Co-efficient of Self-Induction. (See In- 
 duction, Self, Co-efficient of) 
 
 Coercitive Force. (See Force, Coerci- 
 tive) 
 
 Coercive Force. (See Force, Coercive) 
 
 Coil, Choking A coil of wire so 
 
 Fig. 14.1. Choking- 
 Coil. 
 
 wound on a core of iron as to possess high 
 self-induction. 
 
 Choking-coils are used to obstruct or cut off an 
 alternating current with a loss of power less than 
 with the use of a mere ohmic resistance. 
 
 Fig. 141 shows a choking-coil. It consists of 
 a circular solenoid of insulated wire, wound 
 on a core of soft iron wire. A thorough divis- 
 ion of the core is obtained by forming it of coils 
 of insulated iron wire. In this way, no eddy 
 currents are produced in the coil. When a simple 
 periodic electromotive force is applied to the 
 terminals of such a coil, if 
 the magnetic permeability 
 of the coil is constant, a 
 simple periodic current is 
 produced, which lags be- 
 hind the phase of the im- 
 pressed electromotive force 
 by a constant angle. If 
 the impressed electromo- 
 tive force is sufficiently great to more than satu- 
 rate the core, the choking coil ceases to choke 
 the current. The higher the periodicity the 
 greater is the choking effect of a given coil, or the 
 smaller the coil may be made to produce a given 
 effect. 
 
 Since an open -magnetic circuit requires a 
 greater current to saturate it than a closed-mag- 
 netic circuit, the complete throttling or choking 
 power of such a coil is increased by forming its 
 core of a closed magnetic circuit, i. e., of a circuit 
 i n which there is no air space or gap . (See Circuit, 
 Divided- Magnetic. Circuit, Closed- Magnetic.) 
 
 Coil, Electric A convolution of in- 
 sulated wire through which an electric current 
 may be passed. (See Magnet, Electro.} 
 
 The term coil is usually applied to a number 
 of turns or to a spool of wire. 
 
 Coil, Impedance A term sometimes 
 
 applied to a choking-coil. (See Coil, Chok- 
 ing.} 
 
 Such a coil has a high self-induction. Its im- 
 pedance is therefore high. (See Induction, Self. 
 Impedance.} 
 
 Coil, Induction An apparatus con* 
 
 sisting of two parallel coils of insulated wire 
 employed for the production of currents by 
 mutual induction. (See Induction, Mutual. 
 Induction, Electro-Dynamic.} 
 
CoL] 
 
 10 ," 
 
 [Coi. 
 
 A rapidly interrupted battery current, sent 
 through a coil of wire called the primary coil, 
 induces alternating currents in a coil of wire called 
 the secondary coil. 
 
 As heretofore made, the primary coil consists of 
 a few turns of a thick wire, and the secondary 
 coil of many turns, often thousands, of fine wire. 
 Such coils are generally called Ruhmkorff coils, 
 from the name of a celebrated manufacturer of 
 them. 
 
 In the form of Ruhmkorff coil, shown in Fig. 
 142, the primary wire, wound on a core formed 
 
 Fig. 142. Ruhmkorff Coil. 
 
 of a bundle of soft iron wires, has its ends brought 
 out as shown at f, f. The fine wire, forming the 
 secondary coil, is wrapped around an insulated 
 cylinder of vulcanite, or glass, surrounding the 
 primary coil. This wire is very thin, and in some 
 coils is over one hundred miles in length. 
 
 If the core of an induction coil were made solid 
 it would heat considerably and therefore cause a 
 loss of energy. The core is therefore laminated, 
 usually by forming it of a bundle of soft iron wire. 
 
 Too great a division of the core, however, is 
 inadvisable, since, although the eddy currents 
 therein are thereby avoided, yet, too great a 
 division of the core acts practically so to 
 decrease the magnetic permeability that the 
 greatest efficiency cannot be obtained. 
 
 The ends of the secondary coil are connected 
 to the insulated pillars A and B. 
 
 The primary current is rapidly broken by 
 means of a mercury break, shown at L and M. 
 
 The commutator, shown to the right and front 
 of the base, is provided for the purpose of cutting 
 off the current through the primary, or for chang- 
 ing its direction. When a battery which produces 
 a comparatively large current of but a few volts 
 electromotive force is connected with the pri- 
 mary, and its current rapidly interrupted, a 
 torrent of sparks will pass between A and B, 
 having an electromotive force of many thousands 
 of times the number of volts of the primary cur- 
 
 rent, but of a correspondingly smaller current 
 strength. 
 
 In such cases, excepting losses during conver. 
 sign, the energy in the primary current, or C E, 
 is equal to the energy in the secondary current, 
 or C' E'. As much therefore as E', the electro- 
 motive force of the secondary current, exceeds E, 
 the electromotive force of the primary current, 
 the current strength C', of the secondary, will b 
 less than the current strength C, of the primary. 
 This is approximately true only, and only in in. 
 duction coils possessing a closed magnetic circuit. 
 (See Transformer.'] 
 
 Fig. 143 shows diagramatically the arrange- 
 
 Fig. 143. Circuit Connections of Induction Coil. 
 
 ment and connection of the different parts of an 
 induction coil. 
 
 The core II', consists of a bundle of soft iron 
 wires, each of which is covered with a thin insu- 
 lating layer of varnish or oxide. A primary wire 
 P P, consisting of a few turns of comparatively 
 thick wire, is wound around the. core, and a 
 greater length of thin wire S S, is wound upon the 
 primary. This is called the secondary. So as 
 not to confuse the details of the figure it is repre- 
 sented as a few turns. 
 
 The terminals of the battery B, are connected 
 to the primary wire, through the automatic inter- 
 rupter, in the manner shown. It will be seen that 
 the attraction of the core TI', for the vibrating 
 armature H, will break contact at the point o, and 
 cause a continued interruption of the battery 
 current. 
 
 The condenser cc', is connected ?s bl.wwn. It 
 acts to diminish the sparking at the contact points 
 on breaking contact, and thus, by making the 
 battery current more sudden, to make its in 
 ductive action greater. 
 
 The reactions which take place when a simple 
 
Coi.] 
 
 108 
 
 [Coi. 
 
 periodic electromotive force is impressed on the 
 primary of an induction coil are substantially 
 thus stated by J. A. Fleming : 
 
 (i.) The application of a simple periodic im- 
 pressed electromotive force produces a simple 
 periodic current, moving under an effective elec- 
 tromotive force of self-induction, and brings into 
 existence a counter- electromotive force of self- 
 induction, which cautes the primary current to 
 kg behind, by an angle called the angle of lag. 
 
 (2.) The field around the primary, and, there- 
 fore, the induction through the secondary, is in 
 consonance with the primary current, and the im- 
 pressed electromotive force in the secondary is 
 in quadrature with the primary current. (See 
 Consonance. Quadrature, In.) 
 
 (3.) The secondary-impressed electromotive 
 force gives rise to a secondary current moving 
 under an effective electromotive force and creat- 
 ing a counter electromotive force of self-induc- 
 tion. 
 
 (4.) This secondary current reacts in its turn 
 on the primary, and creates what is called the 
 back electromotive force, or the reacting-induc- 
 tive-electromotive force of the primary circuit. 
 
 (5.) There is then a phase-difference between 
 the primary and secondary-currents, and also be- 
 tween the' primary-impressed electromotive force 
 and the primary current 
 
 If, as in Fig. 144, two electric circuits are 
 
 Fig. 144. Electr-c and Magnetic Link. 
 
 linked with a magnetic circuit, and a small 
 periodic electromotive force be impressed on the 
 primary, the following phenomena occur: 
 
 (I.) A periodic primary current is set up in 
 the primary circuit, which, though of the same 
 periodic time as the impressed electromotive 
 force, differs from it in phase. 
 
 (2.) A wave of counter electromotive force is 
 produced in the primary circuit by the inductive 
 action, which does not coincide either with the 
 impressed electromotive force, nor with the 
 primary current. 
 
 (3.) A wave of magnetization is produced in 
 the iron core, which lacs behind the primary 
 
 current by somewhat less than 90 degrees oi 
 phase. 
 
 (4.) A wave of impressed electromotive force 
 is produced in the secondary circuit, due to and 
 measured by the rate of change of magnetic in- 
 duction in the core, and lagging 90 degrees, or 
 more, behind the magnetization wave. 
 
 (5.) A wave of secondary current, lagging be 
 hind the secondary electromotive force in phase 
 except where the circuit consists of a few turns o' 
 conductor, or is connected with an external cu - 
 cuit of practically no inductance. [Fleming.} 
 
 Coil, Induction, Inverted An 
 
 induction coil in which the primary coil is 
 made of a long, thin wire, and the secondary 
 coil of a short, thick wire. 
 
 By the use of an inverted coil, a current of high 
 electromotive force and comparatively small cur- 
 rent strength, *'. <., but of few amperes, is con- 
 verted or transformed into a current of compar- 
 atively small electromotive force and large cur- 
 rent strength. For advantages of this conversion 
 see Electricity, Distribution of, by Alternating 
 Currents. 
 
 Inverted induction coils are called converters oe 
 transformers. (See Transformer.} 
 
 Coil, Induction, Medical An 
 
 induction coil used for medical purposes. 
 
 A form of induction coil used for medical pur 
 poses is shown in Fig. 145. 
 
 Fig. t4j. Medical Induction Gat. 
 
 Coil, Induction, Microphone Alt 
 
 induction coil, in which the variations in the 
 circuit of the primary are obtained by means 
 of microphone contacts. (See Microphotie^ 
 
 The carbon -button telephone transmitter is a 
 microphone in its action, its electric resistance 
 varying with the varying pressure caused by the 
 sound waves. The carbon-button is in the prim- 
 ary circuit of an induction coil, variations t 
 
Coi.] 
 
 109 
 
 [Coi. 
 
 primary of which, under the influence of the 
 sound waves, produce corresponding variations 
 in the currents induced in the secondary. 
 
 Coil, Kicking- A term sometimes 
 
 applied to a Choking-Coil. (See Coil, Chok- 
 ing) 
 
 The term kicking-coil has arisen from the fact 
 that the impedance due to self-induction opposes 
 the starting or stopping of the current somewhat 
 in the manner of an opposing kick. 
 
 Coil, Magnet 
 
 A coil of insulated 
 
 wire surrounding the core of an electro-mag- 
 net, and through which the magnetizing cur- 
 rent is passed. (See Magnet, Electro?) 
 
 Coil, Primary - That coil or con- 
 ductor of an induction coil or transformer, 
 through which the rapidly interrupted or alter- 
 nate inducing currents are sent. 
 
 In the Ruhmkorff induction coil the primary 
 coil consists of a comparatively short length of 
 thick wire, the secondary coil being formed of 
 a comparatively great length of fine wire. In 
 the transformer or converter, the primary coil 
 consists of wire that is longer and thinner than 
 that in the secondary coil. In other words, the 
 transformer or converter consists of an inverted 
 induction coil. (See Coil, Induction. Trans- 
 former. ) 
 
 Coil, Reaction A magnetizing coil, 
 
 surrounded by a conducting covering or 
 sheathing, which opposes the passage of 
 rapidly alternating currents less when directly 
 over the magnetizing coil than when a short 
 distance from it. 
 
 A term often used for choking-coil. (See 
 Coil, Choking.) 
 
 Coil, Reaction, Balanced A coil 
 
 employed in a 
 system of distri- 
 bution by means 
 of transformers 
 for maintaining 
 a constant cur- 
 rent in the sec- 
 ondary Circuit, Fi S- I4<> Balanced-Reaction Coil. 
 
 despite changes in the load placed therein. 
 A balanced-reaction coil is shown in Fig. 146. 
 
 A reaction coil is placed in the circuit of lamps in 
 series in a constant potential system. The sheath- 
 ing of this coil is maintained in a balanced position 
 by the counter weight P, and the spring S. If now 
 a lamp is extinguished in the circuit, the increase 
 of current, due to decreased resistance, causes the 
 sheath to be deflected, and, thus increasing the 
 self-induction of the coil, reduces the lamp current 
 to its normal value. 
 
 Coil, Resistance A coil of wire 
 
 of known electrical resistance employed for 
 measuring resistance. 
 
 In order to avoid self-induction and the mag- 
 netizing effects of the coils on the needles of the 
 galvanometer used in electric measurements, as 
 well as the disturbing effects of self-induction, the 
 wire of the resistance coil is doubled on itself 
 before being wound, and its ends connected 
 with the brass bars, E, E, Fig. 147. The inser- 
 
 Fig. 147. Connections of Resistance Coils. 
 
 tion of the plug-key cuts the coil out of the cir- 
 cuit by short-circuiting. (See Box, Resistance. 
 Bridge, Electric. Coil, Resistance, Standard.} 
 
 The coils are made of German silver, or plati- 
 noid, the resistance of which is not much 
 affected by heat. 
 
 Coil, Resistance, Standard A coil 
 
 the resistance of which is that of the stand- 
 ard ohm or some multiple or sub-multiple 
 thereof. 
 
 The standard ohm, as issued by the Electric 
 Standards Committee of England, has the form 
 shown in Fig. 148. The coil of wire is formed of 
 an alloy of platinum and silver, insulated by silk 
 covering and melted paraffine. Its ends are sol- 
 dered to thick copper rods, r, r', for ready con- 
 nection with mercury cups. The coil is at B. 
 The space above it, at A, is filled with paraffine. 
 A hole, at t, runs through the coil for the readv 
 
Coi.l 
 
 no 
 
 [Coi. 
 
 insertion of a thermometer. The lower part of 
 the coil, B, is immersed in water up to the shoul- 
 der of A, and the water stirred from time to 
 
 Fig. 14.8. Standard Ohm. 
 
 time. Since the coil is heated by the current, sue- 
 cessive observations should be at least ten minutes 
 apart. Only mild currents should be passed 
 through the coils. 
 
 Coil, Resistance, Standardized - 
 
 Resistance coils whose resistances have been 
 carefully determined by comparison with a 
 standard ohm or other standard coils. 
 
 Coil, Ruhmkorff A term some- 
 times applied to any induction coil, the 
 secondary of which gives currents of higher 
 electromotive force than the primary. (See 
 Coil, Induction?) 
 
 Coil, Secondary - That coil or con- 
 ductor of an induction coil or transformer, 
 in which alternating currents are induced by 
 the rapidly interrupted or alternating currents 
 in the primary coil. (See Coil, Induction. 
 Transformer^) 
 
 Coil, Shunt - A coil placed in a de- 
 rived or shunt circuit. (See Circuit, Shunt) 
 
 Coil, Spark A coil of insulated wire 
 
 connected with the main circuit in a system 
 of electric gas-lighting, the extra spark pro- 
 
 Fig. I4Q. Spark Coil. 
 
 duced on breaking the circuit of which is em- 
 ployed for electrically igniting gas jets. 
 
 Spark coils are employed where the number of 
 
 gas jets to be simultaneously lighted is not too 
 great. When this number exceeds certain limits, 
 the spark from an induction coil is more ad van- 
 tageously used. 
 A spark coil is shown in Fig. 149. 
 
 Coils, Armature, of Dynamo-Electric 
 
 Machine The coils, strips or bars that 
 
 are wound or placed on the armature core. 
 
 To avoid needless resistance the wire, or othe* 
 conductor, of the armature coils, should be as 
 short and thick as will enable the desired electro- 
 motive force to be obtained without excessive 
 speed of rotation. 
 
 The armature coils should enclose as many 
 lines of force as possible (i. e., they should have 
 as nearly a circular outline as possible). In 
 drum-armatures, the breadth of the armature is 
 frequently made nearly equal to its length, unless 
 other considerations prevent. 
 
 When the armature wire consists of rods or 
 bars, it should be laminated or slit in planes 
 parallel to the lines of force so as to avoid 
 eddy currents. Other things being equal, the 
 
 Fig. Jjo. Series Connection of Armature Coils. 
 
 greater the number of coils, the more uniform 
 the current generated. The separate coils should 
 be symmetrically disposed; otherwise irregular in- 
 duction, and consequent sparking at the commu- 
 tator results. 
 
 The coils of pole-armatures should be wound near 
 the poles rather than on the middle of the cores. 
 In order to avoid undue heating, spaces for 
 air ventilation are not inadvisable. Various con- 
 nections of the armature coils are used. 
 
 In some machines all the coils are connected in 
 a closed circuit. In some, the coils are independ- 
 ent of one another, and, either for the entire 
 revolution, or for part of a revolution, are on an 
 open circuit. 
 
Coi.] 
 
 Ill 
 
 [Col. 
 
 In alternating current dynamos in order to ob- 
 tain the rapid reversals or alternations of current, 
 which in some machines are as high as 12, coo 
 per minute, a number of poles of alternate polar- 
 ity are employed. The separate coils that are 
 used on the armature may be coupled either in 
 series or in multiple-arc. 
 
 Where a comparatively low electromotive force 
 is sufficient, such as for incandescent lamps in 
 multiple-arc, the separate coils are united in 
 parallel; but for purposes where a considerable 
 electromotive force is necessary, as for example, 
 in systems of alternate current distribution, with 
 converters at considerable distances from the 
 generating dynamo, they are often connected in 
 series, as shown in Fig. 150. 
 
 Coils, Binding Coils of wire wound 
 
 on the outside of the armature coils, and at 
 right angles thereto, to prevent the loosening 
 of the armature wires by the action of cen- 
 trifugal force. 
 
 The binding coils are generally made of hard 
 brass wire. 
 
 Coils, Compensating A term some- 
 times applied to the series coils placed on a 
 shunt-wound dynamo. 
 
 Coils, Conjugate Two coils so 
 
 placed, as regards each other, that an interrup- 
 tion of the current in one produces no induced 
 current in the other. 
 
 When two coils are conjugate to each other, the 
 lines of force of one do not pass through the other. 
 Consequently such coils can produce no induc- 
 tion in one another. 
 
 Coils, Henry's A number of sepa- 
 rate induction coils so connected that the 
 currents induced in the secondary wire of 
 the first coil, are caused to induce currents 
 in the secondary wire of the second coil, with 
 whose primary it is connected in series, and 
 so on throughout all the coils. 
 
 A series of three of Henry's coils is shown in 
 Fig. 151. An intermittent battery current is sent 
 
 b 
 
 secondary, d, of the second coil, is connected with 
 the primary, e, of the third coil, and the cur- 
 rents finally induced in f, are employed for any 
 useful purpose, such as the magnetization of a 
 bar of iron at g. 
 
 The current in b, is sometimes called a Secon- 
 dary Current, or a Current of the Second Order; 
 that induced by this secondary current in d, is 
 called a Tertiary Current, or a Current of the 
 Third Order y that in f, a Current of the Fourth 
 Order. Henry carried these successive induc- 
 tions up to currents of the Seventh Order. 
 
 Henry's coils in reality consist of separate in- 
 duction coils, connected, as above explained, in 
 series. 
 
 In Fig. 152, the tertiary current induced in 
 
 A 
 
 n 
 
 Fig. 132. Tertiary Currents of Coils. 
 IV, may be employed to give shocks to a person 
 grasping the handles, e and f. 
 
 Coils, Proportional Pairs of re- 
 sistance coils, generally of 10, 100 and 1,000 
 ohms each, forming the proportional arms of 
 the balance or bridge, and employed in the box, 
 or commercial form of Wheatstone's bridge. 
 (See Bridge, Electric, Commercial Form 
 of.} 
 
 Cold, Production of, by Electricity 
 
 An absorption of energy and consequent 
 reduction of temperature at a thermo-electric 
 junction by the passage of an electric current 
 across such junction in a certain direction. 
 
 When an electric current passes across a thermo- 
 electric junction, the junction is either heated or 
 cooled. In the case of an antimony-bismuth 
 couple, if the current passes from the antimony 
 
 Fig. Jjl- Henry's Coils. 
 
 into a, the secondary, b, of which is connected 
 with the primary, c, of the second coil. The 
 
 Freezing of Water by Electricity. 
 
 to the bismuth the junction is heated; if it passes 
 from the bismuth to the antimony it is cooled. 
 In the apparatus shown in Fig. 153, the antimony- 
 bismuth couple is arranged as shown for the 
 
Col.] 
 
 112 
 
 [Coin. 
 
 freezing of water by means of the electric cur- 
 rent. A and B, represent plates of antimony and 
 bismuth respectively. A small cavity, at E, serves 
 to hold a drop of water. When a current has 
 passed in the direction shown by the arrows, a 
 drop of water, previously cooled to the tempera- 
 ture of melting ice, is solidified by the lowering 
 of the temperature at the junction. 
 
 Collecting Brushes of Dynamo-Electric 
 Machine. (See Brushes, Collecting, of 
 Dynamo-Electric Machine?) 
 
 Collectors, Electric Devices em- 
 ployed for collecting or taking off electricity 
 from a moving electric source. 
 
 Collectors of Electric Frictional Ma- 
 chines. The metallic points that collect the 
 charge from the glass plate or cylinder of a 
 frictional electric machine. 
 
 Collectors of Dynamo Electric Machines. 
 The brushes that rest on the commutator 
 cylinder, and carry off the current generated 
 on the rotation of the armature. 
 
 Collectors are properly called commutators 
 when they are employed to cause an alternate 
 current to become continuous, or to flow in one 
 and the same direction. 
 
 Colloids. One of the two classes into 
 which substances are separated by dialysis. 
 
 By dialysis bodies are separated 'into crystal- 
 loids, or bodies capable of crystallizing, and col- 
 loids or jelly-like bodies, incapable of crystallizing. 
 Colloids possess great cohesion and but slight 
 diffusibility. (See Dialysis.) 
 
 Colombin. An insulating substance, con- 
 sisting of a mixture of sulphate of barium 
 and sulphate of calcium, placed between the 
 parallel carbons of the Jablochkoff candle. 
 
 Column, Barometric A column, 
 
 usually of mercury, approximately 30 inches 
 in vertical height, sustained in a barometer, 
 or other tube, by the pressure of the atmos- 
 phere. 
 
 The space above the barometric column con- 
 tains a vacuum known as the Torricellian vac- 
 uum. (See Vacuum, Torricellian.) 
 
 Column, Electric A term formerly 
 
 applied to a voltaic pile. (See Pile, Voltaic?) 
 Colza Oil. (See Oil, Colza?) 
 
 Combination Gas Fixtures. (See Fx~ 
 tures. Gas, Combination?) 
 
 Combined Tangent and Sine Galvanom- 
 eter. (See Galvanometer, Combined Tan~ 
 gent and Sine?) 
 
 Comb Lightning Arrester. (See Arrester, 
 Lightning, Comb?) 
 
 Comb Protector. (See Protector, Comb?) 
 Commercial Efficiency. (See Efficiency, 
 Commercial?) 
 
 Commercial Efficiency of Dynamo. 
 
 (See Efficiency, Commercial, of Dynamo?} 
 
 Commercial Form of Electric Bridge. 
 (See Bridge, Electric, Commercial Form of.) 
 
 Communicator, Electric A terra 
 
 formerly employed for a telegraphic key. (See 
 Key, Telegraphic?) 
 
 Commntating Transformers, Distribu- 
 tion of Electricity by (See Elec- 
 tricity, Distribution of, by Commutating 
 Transformers?) 
 
 Commutation. The act of commuting, as 
 of currents. 
 
 Commutation, Diameter of In a 
 
 dynamo-electric machine a diameter on the 
 commutator cylinder on one side of which 
 the differences of potential, produced by the 
 movement of the coils through the magnetic 
 field, tend to produce a current in a direction 
 opposite to those on the other side. 
 
 That diameter on the commutator cylinder 
 of an open-circuited armature that joins the 
 points of contact of the collecting brushes. 
 
 Thus in Fig. 154, the directions of the induced 
 electromotive forces are indicated by the arrows. 
 The diameter of commutation is therefore the line 
 n n'. The term neutral line is also sometimes 
 given to this line. It lies at right angles to the 
 line of maximum magnetization m m. 
 
 In a closed-circuited armature, that is, in an arm* 
 ature the coils of which are connected in, a closed 
 circuit, the collecting brushes rest on the commu- 
 tator cylinder at the neutral line, or on the diame* 
 ter of commutation. 
 
 In an open-circuited armature, however, where 
 the coils are independent of each other, the 
 collecting brushes must be set at m m, at right 
 angles to the mutral line n n. The term diame 
 
Com.] 
 
 113 
 
 [Com. 
 
 ter of commutation is, therefore, often applied to 
 this second position. According to this use of the 
 
 Fig. 154* Diameter of Commutation, 
 
 term, the diameter of commutation is that diameter 
 on the commutator which joins the points of con- 
 tact of the collecting brushes. 
 
 The neutral linenn', Fig. 154, it will be noticed 
 does not occupy a vertical position, but is dis- 
 placed somewhat in the direction of rotation, thus 
 necessitating the shifting of the brushes forward 
 in the direction of rotation. This necessary shift- 
 ing of the brushes is known technically as the 
 lead of the brushes. (See Lead, Angle of.) 
 
 It will thus be seen that the term diameter of 
 commutation is used in two different senses. 
 
 In reality, the term refers to the position of cer- 
 tain points on the commutator as distinguished 
 Irom points on the armature coils. On the com- 
 mutator, the diameter of commutation is the line 
 drawn through the two commutator bars at which 
 the currents from the two sides are opposed to 
 each other. 
 
 It is evident that the commutator may be inten- 
 tionally twisted with respect to the armature, so 
 as to bring its diameter of commutation into any 
 desired convenient position. 
 
 Commutation, Dissymmetry of 
 
 A commutation in which the neutral line does 
 not coincide with a diameter of the commu- 
 tator. (See Commutation, Diameter of.) 
 
 Commutator. In general, a device for 
 changing the direction of an electric current. 
 
 Commutator, Burning- at Arcing 
 
 and consequent destructive action on the 
 commutator segments of a dynamo-electric 
 machine. 
 
 When the arcing is pronounced, the intense 
 heat soon 'destroys the commutator. 
 
 Commutator Cylinder, Neutral-Line of 
 
 (See Line, Neutral, of Commutator 
 
 Cylinder^ 
 
 Commutator, Dynamo-Electric Machine 
 
 That part of a dynamo-electric ma- 
 chine which is designed to cause the alter- 
 nating currents produced in the armature to 
 flow in one and the same direction in the ex- 
 ternal circuit. 
 
 One end of an armature coil is connected with 
 A', Fig. 155, and the 
 other with A, The brushes 
 are so set that A, and A', 
 are in contact with B', 
 and B, respectively, as 
 long as the current flows 
 in the same direction in the 
 armature coil connected 
 therewith, but enter into 
 contact with B, and B', Fig. 153. Commutator 
 when the current changes of Dynamo - Electric 
 its direction, and continue Machine. 
 in such contact as long as it flows in this direc- 
 tion. By the t(se of a commutator the (urrent 
 will therefore flow throttgh any circuit connected 
 with the brushes in one and the same constant 
 direction. 
 
 Two-part Commutator 
 
 In action, the commutator is subject to wear 
 from the friction of the brushes, and the burning 
 action of destructive sparks. The rommutator 
 
 A 
 
 Fig. TS7- Two-part 
 Commutator. 
 
 . Two-part 
 Commutator. 
 
 segments are, therefore, made of comparatively 
 thick pieces of metal, insulated from one another 
 
Com.] 
 
 114 
 
 [Com. 
 
 and supported on a commutator cylinder usually 
 placed oruthe shaft of the armature. 
 
 The ends of the armature coils are connected 
 to commutator strips or segments. 
 
 The number of metallic pieces or segments, A. 
 and A', on the commutator cylinder depends on 
 the number, arrangement and connection of the 
 armature coils, and on the 
 disposition of the magnetic 
 field of the machine. 
 
 Figs. 156, 157 and 158 
 show the connections of an 
 armature coil to the plates of 
 a two-part commutator. 
 
 A four-part commutator 
 for a ring-armature, and the **- '5** 
 
 Commutator. 
 connections of the coils 
 
 thereto, are shown in Fig. 159. 
 
 The commutator strips may either connect the 
 separate coils in a closed-circuited armature, in 
 which the coils are all connected with one an- 
 other, or, in an open -circuited armature, in which 
 the separate coils are independent of one another. 
 
 Commutator, RuhmkoriTs A name 
 
 given by Ruhmkorff to a device placed on his 
 induction coil for the purpose of changing or 
 reversing the direction of the battery current 
 through the primary. 
 
 This reverser is shown in Fig. 160. (See 
 Coil, Ruhmkorff.') 
 
 Fig. 160, Ruhmkorff's Commutator 
 
 Two metallic strips, V, V, supported on a 
 cylinder of insulating material, are in contact with 
 the battery terminals A, and D, through iwo 
 vertical springs that b?ar on them. On a half 
 rotation of the cylinder by the thumb screw L, 
 
 the strips V, V, change places as regards the ver- 
 tical springs, and thus reverse the direction o{ 
 the battery current. 
 
 Commuted Currents. (See Currents, 
 Commuted^ 
 
 Commuter, Current Any appa- 
 ratus by means of which electrical currents, 
 flowing alternately in different directions, 
 may be caused to flow in one and the same 
 direction. 
 
 A Commutator. 
 
 Commuting. Causing to flow in one and 
 the same direction. 
 
 Commuting Currents. (See Currents, 
 Commuting^ 
 
 Compartment Manhole of Conduit. (See 
 Manhole, Compartment, of Conduit.) 
 
 Compass, Azimuth A compass 
 
 used by mariners for measuring the horizon- 
 tal distance of the sun or stars from the mag- 
 netic meridian. (See Azimuth, Magnetic!] 
 
 A mariner's Compass. 
 
 A single magnetic needle, or several magnetic 
 needles, are placed parallel to one another on the 
 lower surface of a card, called the compass card. 
 This card is divided into the four cardinal points, 
 N, S, E and W, and these again subdivided into 
 thirty-two points called Rhumbs. 
 
 In the azimuth compass these divisions are sup> 
 plemented by a further division into degrees. 
 
 A form of azimuth compass is shown in Fig. 
 l6l. In order to maintain the compass box in a 
 
 Fig. l6r. Azimuth Compass, 
 
 horizontal position, despite the rolling of the ship, 
 the box, A B, is suspended in the larger box, P 
 Q, on two concentric metallic circles, C D, and 
 
Com.j 
 
 115 
 
 E F, pivoted on two horizontal axes at right angles 
 to each other. This kind of support is technic- 
 ally termed Gimbals. Sights G, H, are provided 
 for measuring the magnetic azimuth of any ob- 
 ject. 
 
 Compass, Boxing the Naming. 
 Consecutively, all the different points or 
 thumbs of the compass from any one of them. 
 (See Compass, Points of.} 
 
 Compass-Card. (See Card, Compass) 
 
 Compass, Inclination A magnetic 
 
 needle moving freely in a single vertical plane; 
 and employed for determining the angle of 
 dip at any place. 
 
 An Inclinometer. (See Inclinometer) 
 A dipping circle. (See Circle, Dipping) 
 The needle M, Fig. 162, is supported on knife 
 
 Fig. ibz Inclination Con: past. 
 
 tdges so as to be free to move only in the verticat 
 plane of the graduated vertical circle C C. This 
 Circle is movable over the horizontal graduated 
 circle H II. In order to determine the true angle 
 of dip, the vertical plane in which the needle is 
 free to move must be placed exactly in the plane 
 of the magnetic meridian. 
 
 To ascertain this plane the vertical circle is 
 moved until the needle points vertically down* 
 wards. It is then in a plane 90 degrees from tha 
 magnetic meridian. The vertical circle is then 
 moved over the horizontal circle 90 degrees, in 
 which position it is in the plane of the magnetic 
 meridian, when the true angle of the dip is read off. 
 
 For an explanation of the reason of this> see 
 
 [Com, 
 
 Component, Horizontal and Vertical^ of thk 
 Earth's Magnetism. 
 
 Compass, Mariner's A name often 
 
 applied to an azimuth compass. (See Com- 
 pass, Azimuth?) 
 
 Compass, Points of The thirty-two 
 
 points into which a compass card is divided. 
 Sixteen of these points are shown in Fig. 163. 
 
 Fig. 163. Points of Compass. 
 
 The position of the remaining points will be 
 readfly seen by an inspection of the figures. 
 These points are as follows: 
 
 I. North. 
 8. N. by E. 
 
 3. N. N. E. 
 
 4. N. E. by N. 
 
 5. N. E. 
 
 6. N. E. by E. 
 
 7. E. N. E. 
 & E. by N. 
 g. East. 
 
 10. E. byS. 
 
 11. E. S. E. 
 
 12. S. E. by E. 
 
 13. S. E. 
 
 14. S. E. by S 
 
 15. S. S. E. 
 
 16. S. by E. 
 
 17. South. 
 
 18. S. by W. 
 
 19. S. S. W. 
 
 20. S. W. by Su 
 
 21. S. W. 
 
 22. S. W. by W. 
 
 23. W. S. W. 
 
 24. W. by S. 
 
 25. West. 
 
 26. W. by N. 
 
 27. W. N. W. 
 
 28. N. W. by W. 
 
 29. N. W. 
 
 30. N. W. by N. 
 
 31. N. N. W. 
 
 32. N. by W. 
 
 Boxing the Compass consists in naming all 
 these points consecutively from any one of them. 
 
 The direction in which the ship is sailing is de. 
 termined by means of a point fixed on the inside of 
 the compass box, directly in the line of the ves- 
 sel's bow. 
 
 Compass, Rhumbs of The points 
 of a mariner's compass. (See Compass^ 
 Points of) 
 
Com.j 
 
 116 
 
 Compensated Alternator. (See Alter- 
 nator, Compensated^ 
 
 Compensated Excitation of Alternator. 
 
 (See Alternator, Compensated Excita- 
 tion of.) 
 
 Compensating Coils. (See Coils. Com- 
 pensating.) 
 
 Compensating Magnet. (See Magnet, 
 Compensating^ 
 
 Complement of Angle* <$&$ Angle, Com- 
 plement of.) 
 
 Completed-Circuit. (See Circuit, Com- 
 pleted.) 
 
 Component. One of the two or more sep- 
 arate forces into which any single force may 
 be resolved ; or, conversely, the separate forces 
 which together produce any single resulting 
 force. 
 
 When two or more forces act simultaneously to 
 produce motion in a body, the body will move 
 
 Ftg. 164. Composition of Forces, 
 
 with a given force in a single direction called the 
 resultant. The separate forces, or directions of 
 motion, are called the components. 
 
 Two forces acting simultaneously on a body at 
 A, Fig. 164, tending to move it in the direction 
 
 Fff.r6f. Rttotution o/Fcne*. 
 
 of the arrows, along A B, and A C, with intend- 
 tiesproportioned to the lengths of the lines A B, 
 and A C, respectively, will move it in the direc- 
 tion A D. obtained by drawing B D, and L> C, 
 
 parallel to A C, and A B, respectively, and then 
 drawing A D, through the po.nt of intersection, 
 D. This is called the Comrosition of Forces. 
 A D, is the resultant force, and A B and A C, 
 are its components. 
 
 Conversely, a single force, acting in the direc- 
 tion of D B, Fig. 165, against a surface, B C, 
 may be regarded as the resultant of the two sep- 
 arate forces, D E, and D C, one parallel to C J, 
 and one perpendicular to it. D E, being parallel 
 to C B, produces no pressure, and the absolute 
 effect of the force will, therefore, be represented 
 by CD. 
 
 This separation of a single force into two or 
 more separate forces is called the resolution of 
 forces, the force, D B, being resolved into the 
 components, D E and D C. 
 
 Component Currents. (See Currents, 
 Component?) 
 
 Component, Horizontal, of Earth's Mag- 
 netism That portion of the earth's 
 
 directive force which acts in a horizontal di- 
 rection. 
 
 That portion of the earth's magnetic force 
 which acts to produce motion in a com- 
 pass needle free to move in a horizontal plane 
 only. 
 
 Let A B, Fig. 166, represent the direction and 
 magnitude of the earth's magnetic field on a mag- 
 netic needle. The magnetic force will lie in the 
 plane of the magnetic merid- 
 ian, which will be assumed to _D A 
 be the plane of the paper C A 
 D. The earth's field, A B, can 
 be resolved into two compo- j 
 nents, AD, the horizontat com- j 
 ponent, and A C, the vertical j 
 component 
 
 In the case of a magnetic ! 
 needle, like the ordinary com- J 
 pass needle, which is free to | 
 move in a horizontal plane only, 
 the horizontal component alone 
 
 directs the needle. A weight . 
 
 ,. , patients of Earth, t 
 
 is applied to balance the vertical Magnetism. 
 component. 
 
 When the needle is free to move in a vertical 
 plane, and this plane corresponds with that of 
 the magnetic meridian, the entire magnetic force, 
 A B, acts to place the needle, supposed to be 
 properly balanced, in the direction of the lines of 
 force of the earth's magnetic field at that point 
 
Com.] 
 
 117 
 
 [Con. 
 
 Component, Yertical, of Earth's Magnet- 
 
 ism - - That portion of the earth's 
 directive force which acts in a vertical direc- 
 tion. 
 
 In the vertical plane at right angles to the plane 
 of the magnetic meridian, the vertical component 
 alone acts, and the needle points vertically down- 
 wards, in no matter what part of the earth it 
 may be. In Fig. 166, A C, is the vertical com- 
 ponent of the earth's directive force. 
 
 Composite Balance. (See Balance, Com" 
 
 Composite-Field Dynamo. (See Dynamo, 
 Composite-Field) 
 
 Composition of Forces. (See Forces, 
 
 Composition of.) 
 
 Compound Arc. (See Arc, Compound?) 
 
 Compound, Binary -- In chemistry, 
 a compound formed by the union of two 
 different elements. 
 
 Water is a binary compound, being formed by 
 the union of two atoms of hydrogen with one 
 atom of oxygen. Its composition is expressed in 
 the mical symbols, H S O, which indicates that two 
 atoms of hydrogen are combined, or chemically 
 united, with one atom of oxygen. Water is 
 therefore a binary compound, because it is formed 
 of two different elementary substances. 
 
 Compound, Chatterton's -- A com- 
 pound for cementing together the alternate 
 coatings of gutta-percha employed on a cable 
 conductor, or for filling up the space between 
 the strand conductors. 
 
 The composition of Chatterton's compound is 
 as follows: 
 
 Stockholm tar ........ I part by weight. 
 
 Resin ............... I ' " 
 
 Gutta-percha ......... 3 " " 
 
 (Clark &> Saline.) 
 
 Compound Circuit. (See Circuit, Com- 
 pound.) 
 
 Compound, Clark's -- A compound 
 for the outer casing of the sheathing of sub- 
 marine cables. 
 
 The composition of Clark's compound is as fol- 
 
 Mineral pitch .65 parts by weight. 
 
 Silica 30 ' " 
 
 Tar 5 " 
 
 (Clark & Sabine.) 
 
 Compound - Horseshoe Magnet. (See 
 Magnet, Compound-Horseshoe) 
 
 Compound Magnet. (See Magnet, Com- 
 pound) 
 
 Compound Radical.^ (See Radical, Com- 
 pound) 
 
 Compound-Winding of Dynamo-Electric 
 Machines. (See Winding, Compound, of 
 Dynamo-Electric Machine.) 
 
 Compound- Wound Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 Compound- Wound) 
 
 Compound-Wound Motor. (See Motor, 
 Compound- Wound) 
 
 Concentration of Lines of Force. (See 
 Force, Lines of, Concentration of) 
 
 Concentric Carbon Electrodes. (See 
 Electrodes, Concentric Carbon) 
 
 Concentric Cylindrical Carbons. (See 
 Carbons, Concentric Cylindrical) 
 
 Condenser. A device for increasing the 
 capacity of an insulated conductor by bring- 
 ing it near another insulated earth-connected 
 conductor, but separated therefrom by any 
 medium that will readily permit induction to 
 take place through its mass. 
 
 A variety of electrostatic accumulator. 
 
 If the conductor A, Fig. 167, standing alone 
 
 f Air Condenser. 
 
 Fig. 167. 
 
 and separated from other conductors, be con. 
 nected with an electric machine, it will receive 
 only a very small charge. 
 
Con.] 
 
 118 
 
 [Con. 
 
 If, however, it be placed near C, but separated 
 from it by a dielectric, such as a plate of glass 
 B, and C, be connected with the ground, A, will 
 receive a much greater charge. (See Dielectric.) 
 
 Suppose, for example, that A, be connected 
 r>th the positive conductor of a frictional electric 
 machine, it will by induction establish a negative 
 Charge on the surface C, nearest it, and repel 
 a positive charge to the earth. The presence of 
 these two opposite charges on the opposed sur- 
 faces of A and C, permits A, to receive a fresh 
 charge from the machine. (See Induction, 
 Electrostatic.) 
 
 The charge in a condenser in reality resides 
 on the opposite surfaces of the glass, or other 
 dielectric separating the metallic coatings, as can 
 be shown by removing the coatings after charg- 
 ing. 
 
 The condenser resulted from the discovery of 
 the Leyden jar. (See Jar, Ley den.) 
 
 The capacity of a condenser is measured in 
 microfarads. (See Farad.) 
 
 In practice condensers are made of sheets of 
 tin foil, connected to A and B, respectively, and 
 separated from one another by sheets of oiled 
 silk, paraffined paper, or thin plates of mica, as 
 shown in Fig. 168. 
 
 Fig. 1 68. Condenser. 
 
 A Leyden jar or condenser does not store elec- 
 tricity any more than a storage battery does. 
 The same quantity of electricity passes out of the 
 opposite coating of the jar that is passed into the 
 other coating. The jar, therefore, possesses no 
 store of electricity. What it really possesses is a 
 store of electrical energy. 
 
 According to Ayrton, if the capacity of a con. 
 denser, in farads, be F, and the difference of po- 
 tential, with which it is charged, be V, volts, the 
 store of electric energy it possesses, or the work it 
 Can do when discharged, is, 
 
 Fx V* 
 Work = ' foot-pounds. 
 
 Condenser, Adjustable A con- 
 denser, the plates of which can be readily 
 adjusted so as to obtain the same capacity 
 as that of the conductor to be measured. 
 
 In order to obtain a comparatively wide range 
 of adjustability, a condenser is composed of say 
 four separate sections: consisting of one of 2 
 microfarads, one of I microfarad and two of $ 
 microfarad, thus making in all 4 microfai ads. 
 
 Condenser, JEpinus A name given 
 
 to an early form of condenser. (See Con- 
 denser!) 
 
 Condenser, Air A condenser in 
 
 which layers of air act as the dielectric. 
 
 A form of air condenser is shown in Fig. 169. 
 
 Fig. tbq. Air Condenser. 
 
 It consists essentially of one set of thin plates of 
 glass partially coated on both sides with sheets oi 
 tin foil, so as to leave uncoated a space of about 
 one inch around the edge of the glass. The glass 
 plates do not act as dielectrics, but merely as sup- 
 ports for the tin foil, hence the foil on both sides 
 of the plates is connected electrically. 
 
 Another set of plates alternating with the above 
 have the tin foil placed over the whole surface of 
 the glass. 
 
 These plates are placed, alternately, over one 
 another on a stand between guide rods of vulcan. 
 ite E, E, E, E, in the manner shown, and are 
 separated from one another by fragments of glass 
 of the same thickness. The plates with the foil 
 over their entire surface are all connected to- 
 gether and to the terminal B, to form the outer 
 coating, and the plates with the foil over nearly 
 all their surfaces are all connected together and 
 to the terminal A, to form the inner coating of 
 the condenser. 
 
 There is thus formed a condenser in which 
 practically two extended conducting surfaces an 
 
Con.J 
 
 119 
 
 [Con. 
 
 separated from each other by a thin layer of air, 
 which acts as the dielectric. 
 
 Condenser, Alternating-Current -- 
 
 A condenser suitable for use in connection with 
 a system for the distribution of electric energy 
 by means of alternating currents. 
 
 Alternating-current condensers must have a very 
 thin dielectric in order to avoid too great bulk. 
 This, of course, introduces a difficulty as regards 
 liability of failure of insulation, which must be 
 carefully avoided. 
 
 Condenser, Armature of -- (See Arm- 
 ature of a Condenser.) 
 
 Condenser, Capacity of -- -The quan- 
 tity of electricity in coulombs a condenser is 
 capable of holding before its potential in volts 
 is raised a given amount. 
 
 The ratio between the quantity of electric- 
 ity in coulombs on one coating and the poten- 
 tial difference in volts between the two coat- 
 ings. (Ayrton!) 
 
 The capacity is directly proportional to the 
 charge Q, and inversely proportional to the po- 
 tential V, or, 
 
 or, since Q = K V, the quantity of electricity re- 
 quired to charge a condenser to a given potential 
 is equal to the capacity of the condenser multi- 
 plied by the potential through which it is carried. 
 
 The capacity of a condenser increases in direct 
 proportion to the increase in the area of its coat- 
 ings. 
 
 When the coatings are plane and parallel to 
 each other, the capacity of the condenser is in the 
 inverse ratio to the distance between the coatings. 
 
 Condenser, Coating of -- (See Coat- 
 ing of Condenser!) 
 
 Con denser, Plate - -A condenser, the 
 metallic coatings of which are placed on 
 suitably supported plates. 
 
 Condenser, Poles of -- (See Poles of 
 
 Condenser.} 
 
 Condenser, Time-Constant of - 
 
 The time in which the charge of a condenser 
 tails to the 1-2.71828 part of its original 
 value. 
 
 Condensers, Distribution of Electricity 
 by Means of -- .(See Electricity, Distri 
 
 btttion of by Alternating Currents, by means 
 of Condensers . Electricity, Distribution of, 
 by Continuous Currents, by means of Con- 
 densers.) 
 
 Conduct. To pass electricity through con- 
 ducting substances. 
 
 To determine the general direction in which 
 electricity shall pass through the ether or 
 dielectric surrounding the so-called conduct- 
 ing substance. (See Conduction, Electric!) 
 
 Conductance. A word sometimes used in 
 place of conducting power. 
 Conductivity. 
 
 Conductance, Magnetic A word 
 
 sometimes used instead of magnetic permea- 
 bility. (See Permeability Magnetic!) 
 
 The magnetic conductance is equal to the total 
 induction through the circuit divided by the 
 magnetizing force. 
 
 Conducting Cord. (See Cord, Conduct- 
 ing.) 
 
 Conducting, Electrical Possessing 
 
 the power of passing electricity through any 
 conducting substance. 
 
 Possessing the power of determining the 
 direction in which electricity shall pass through 
 the ether surrounding a substance, (See 
 Conductor.) 
 
 Conducting Power. (See Power Con- 
 ducting.) 
 
 Conducting Power for Electricity. (Se* 
 
 Power, Conducting, for Electricity.) 
 
 Conducting Power for Lines of Mag 
 netic Force. (See Forte, Magnetic, Lines 
 of, Conducting Power of,) 
 
 Conducting Power, Tables of 
 
 (See Power, Conducting, Tables of.) 
 
 Conduction Current. (See Current, Con- 
 duction!) 
 
 Conduction, Disruptive A species 
 
 of conduction in which the resistance of * u * 
 conductor is suddenly overcome. 
 
 Disruptive conduction is seen in the disruptive 
 discharge of a condenser, or Leyden jar. 
 
 Conduction, Electric The s<x 
 
COIL] 
 
 120 
 
 {Con. 
 
 called flow or passage of electricity through 
 a metallic or other similarly acting substance. 
 
 The ability of a substance to determine the 
 direction in which electric energy shall be 
 transmitted through the ether surrounding it. 
 
 The ability of a substance to determine the 
 direction in which a current of electricity 
 passes from one point to another. 
 
 When a conducting wire has its ends connected 
 with an electric source, a current of electricity is, 
 in common language, said to flow through the wire, 
 and this was formerly believed to be a correct 
 statement. According to modern views, however, 
 the electric energy is believed to pass through the 
 ether or other dielectric surrounding the con- 
 ductor, the so-called conductor forming merely 
 a sink, where the electrical energy dissipates 
 itself. The conductor simply acts to direct the 
 current. 
 
 Since, however, the energy practically passes 
 by means of, and in the general direction of the 
 conductor, there is no objection in speaking of 
 the electricity as flowing through the conductor. 
 
 Conduction, Electric, Disruptive 
 
 A conduction of electric energy which ac- 
 companies a disruptive discharge. (See 
 Discharge, Disruptive.) 
 
 Conduction, Electric, Metallic A 
 
 conducting of electric energy of the same char- 
 acter as that which occurs in metallic sub- 
 stances. 
 
 Conduction, Electrolytic A term 
 
 sometimes employed to indicate the passage 
 of electricity through an electrolyte. 
 
 There is no passage of electricity through an 
 electrolyte in the same sense as through an ordi- 
 nary conductor. 
 
 When, through electrolysis, an electromotive 
 force is brought to bear on a molecule of say 
 HC1, it is assumed by some that the liberated 
 hydrogen atoms travel on the -whole in one di. 
 rection, and the liberated chlorine atoms in the 
 opposite direction. The atoms thus moving 
 through the liquid may by their electric charges 
 be assumed to convey electricity, and this fact 
 has given rise to the term electrolytic conduc- 
 tion. 
 
 In electrolytic conduction the charges are 
 necessarily equal, but the speeds of their motion 
 are unequal. In a given liquid, each atom has 
 
 its own rate of motion, no matter T^ith what it 
 has been combined. Hydrogen travels faster 
 than any other kind of atom. The conductivity 
 of a liquid depends on the sum of the speeds with 
 which the two opposed atoms travel. 
 
 This assumed double stream of oppositely mov 
 ing atoms is denied by most physicists. (Se 
 Hypothesis, Grotthus.} 
 
 Cond uctive-Discharge. (See Discharge, 
 Conductive!) 
 
 Conductivity, Electric The recip- 
 rocal of electric resistance. 
 
 Since the conductivity is greater the less the re- 
 sistance, the conductivity will be equal to the recip- 
 rocal of the resistance, and may be so defined. The 
 
 conductivity is therefore equal to -L. 
 
 R * 
 
 Conductivity, Equivalent A con- 
 ductivity equal to the sum of several conduc- 
 tivities. 
 
 Conductivity per Unit of Mass. The re- 
 ciprocal of the resistance of a substance per 
 unit of mass. 
 
 Conductivity per Unit of Yolume. The 
 
 reciprocal of the resistance of a substance 
 per cubic centimetre or per cubic inch. 
 
 The resistance is measured from one face of 
 the cube to the opposite face. 
 
 Conductivity Resistance. (See Resist- 
 ance, Conductivity!) 
 
 Conductivity, Specific The par- 
 ticular conductivity of a substance for elec- 
 tricity. 
 
 The specific or particular resistance of a 
 given length and unit of cross-section of a 
 substance as compared with the same length 
 and area of cross-section of some standard 
 substance. 
 
 Conductivity, Specific Magnetic 
 
 The specific or particular permeability of a 
 substance to lines of magnetic force. 
 
 The specific magnetic conductivity is measured 
 by the ratio of the magnetization produced to the 
 magnetizing force which produces it. 
 
 The specific magnetic conductivity is the an- 
 alogue of specific inductive capacity, or conduc- 
 tivity for lines of electrostatic force. It is also the 
 analogue for specific conducting power for heat* 
 
Con.] 
 
 121 
 
 [Con. 
 
 Conductor. A substance which will per- 
 mit the so-called passage of an electric current. 
 
 A substance which possesses the ability of 
 determining the direction in which electricity 
 shall pass through the ether or other dielec- 
 tric surrounding it. 
 
 Some electrolytes, such, for example, as vari- 
 ous mixtures of sulphuric acid and water, possess 
 a true power of conducting electricity, and there- 
 fore have a specific resistance. Generally, how- 
 ever, the passage of the electrolyzing current is 
 regarded as different from that of a current which 
 merely heats the conductor. 
 
 The space or region around a conductor 
 through which an electric current is passing has 
 a magnetic field produced in it. 
 
 The term conductor is opposed to non-conductor, 
 or a substance which will not permit the passage 
 of an electric current through it after the manner 
 of a conductor. 
 
 The terms conductors and non-conductors are 
 only relative. There are no such things as 
 either perfect conductors or perfect non con- 
 ductors. 
 
 Conductors in general, are distinguished from 
 electrolytes, in that the latter do not allow the 
 electricity to pass save by undergoing a chemical 
 decomposition. 
 
 Conductor, Anisotropic A con- 
 ductor which, though homogeneous in struc- 
 ture like crystalline bodies, has different 
 physical properties in different directions, just 
 as crystals have different properties in the 
 direction of their different crystalline axes. 
 
 Anisotropic conductors possess different powers 
 of electric conduction in different directions. 
 But in opposite directions along the same axis their 
 conductivity is equal. They differ in this respect 
 from isotropic conductors. (See Conductor, Iso- 
 tropic.) 
 
 Conductor, Anti-Induction 
 
 A con- 
 
 ductor so constructed as to avoid injurious 
 inductive effects from neighboring telegraphic 
 or electric light and power circuits. 
 
 Such anti-induction conductors sometimes con- 
 sist of a conductor for constant currents and a 
 metallic shield surrounding the conductor, and 
 designed to prevent induction from taking place 
 in the wire itself. 
 
 The anti-induction conductor generally con- 
 
 sists of twin conductors surrounded by ordinary 
 insulation and sometimes enclosed by some form 
 of metallic shield, in order to prevent the action 
 of electrostatic induction. 
 
 When a periodic current is to be transmitted 
 through a conductor, the most effective way of 
 annulling its inductive effects on neighboring cir- 
 cuits is to place the lead of the conductor in the 
 axis of another conductor, used as a return. In 
 other words, to employ concentric cylinders, in- 
 sulated from one another and from the earth. 
 Under these conditions, calling the current in one 
 direction positive, and in the other direction 
 negative, the shielding action will be perfect 
 when the algebraic sum of the currents in the 
 core and sheath are zero. 
 
 The same effect is obtained in metallic circuits, 
 by placing the leads parallel to the return, and 
 crossing and recrossing the wires repeatedly. 
 (See Connection, Telephonic Cross.) 
 
 Elihu Thomson renders ordinary telephone 
 conductors, arranged as single lines with earth 
 returns, free from induction by means of the 
 counter-electromotive force produced in a coil of 
 wire by the disturbing cause. 
 
 In applying this system to the case of an elec- 
 tric arc or power line passing alongside a tele- 
 phone line, a wire coil, whose turns are pro- 
 portioned in number to the induction to be bal- 
 anced, is introduced into the electric light line 
 and placed near another coil of finer wire inserted 
 as a loop in the telephone circuit. The second coil 
 is placed parallel to or inclined at an angle to the 
 first coil. In practice, the second coil is inclined 
 until the counter-induction set up in the tele- 
 phone wire is equal to that produced in the main 
 line, and silence is thus produced, so far as in- 
 duction is concerned, in the telephone. 
 
 Conductor, Armored A conduc- 
 tor provided with a covering or sheathing of 
 metal placed over the insulating covering for 
 protection from abrasion or external wear. 
 
 Armored conductors are used in situations 
 where the conductor is exposed to abrasion or 
 other external wear. 
 
 Conductor, Branch 
 
 A conductor 
 
 placed in a shunt circuit. (See Circuit, 
 Shunt.) 
 Conductor, Closed-Circuited A 
 
 conductor connected as a closed or com- 
 pleted circuit. 
 
Con.] 
 
 122 
 
 [Coii. 
 
 Conductor, Conjugate In a system 
 
 of linear conductors, any pair of conductors 
 that are so placed as regards each other that 
 a variation of the resistance or the electro- 
 motive force in the one causes no variation in 
 the current of the other. 
 
 Conductor, Earth- Circuited A 
 
 conductor connected to the ground, or to an 
 earth-connected circuit. 
 
 Conductor, House-Serrice A term 
 
 employed in a system of rrultiple incan- 
 descent lamp distribution for that portion of 
 the circuit which is included between the ser- 
 vice cut-out and the centre or centres of dis- 
 tribution, or between this cut-out and one or 
 more points on house mains. 
 
 Conductor, Isotropic A conduc- 
 tor which possesses the same powers of elec- 
 tric conduction in all directions. 
 
 An electrically homogeneous conducting 
 medium. 
 
 Conductor, Leakage A conductor 
 
 placed on a telegraph circuit for the purpose 
 of preventing the disturbing effects of leakage 
 into a neighboring line by providing a direct 
 path for such leakage to the earth. 
 
 The leakage conductor, as devised by Varley 
 consists of a thick wire attached to the telegraph 
 pole. The lower end of the conductor is grounded, 
 and its upper end projects above the top of the 
 pole. 
 
 There exists some doubt in the minds of expe- 
 rienced telegraph engineers whether it is well to 
 apply leakage conductors to telegraphic or tele- 
 phonic lines of over 12 or 15 miles in length, 
 since such conductors greatly increase the electro- 
 static capacity of the line, and thus cause serious 
 retardation. 
 
 Conductor, Lightning A term 
 
 sometimes used for a lightning rod. (See 
 Rod, Lightning?) 
 
 Conductor, Open-Circuited A con- 
 ductor arranged as an open or broken circuit. 
 
 Conductor, Potential of The rela- 
 tion existing between the quantity of elec- 
 tricity in a conductor and its capacity. 
 
 A given quantity of electricity will raise the 
 
 potential of a conductor higher in proportion as 
 the capacity of the conductor becomes Jess. 
 
 Conductor, Potential of, Methods of 
 
 Yarying The potential of a conductor 
 
 may be varied in the following ways ? 
 
 (I.) By varying its electric charge. 
 
 (2.) By varying its size or shape without alter- 
 ing its charge. 
 
 (3.) By varying its position as regards neigh, 
 boring bodies. 
 
 This resembles the case of a gas whose tension 
 or pressure may be varied as follows, viz. : 
 
 (I.) By varying the quantity of gas. 
 
 (2.) By varying the size of the gas holder in 
 which it is kept, and 
 
 (3.) By varying the temperature. 
 
 Difference of potential, therefore, corresponds 
 
 (i.) With difference of level in liquids. 
 
 (2. ) With difference of pressure in gases. 
 
 (3.) With difference of temperature in heat 
 
 (Ayrton.) 
 
 Conductor, Prime The positive 
 
 conductor of a frictional electric or electro- 
 static machine. (See Machine, Frictional 
 Electric.} 
 
 Conductor, To Short-Circuit a 
 
 To shunt a conductor with a circuit of com- 
 paratively small resistance. 
 
 Conductor, Underground An elec- 
 tric conductor placed underground by actual 
 burial or by passing it through underground 
 conduits or subways. 
 
 Underground conductors, though less unsightly 
 than the ordinary aerial conductors, require to 
 be laid with unusual care to render them equally 
 safe, since, when contacts do occur, all the wires 
 in the same conduit are apt to be simultaneously 
 affected, thus spreading the danger in many dif- 
 ferent directions. They are, however, less liable to 
 dangers arising from occasional accidental crosses 
 or contacts. 
 
 Conductors, Service Conductors 
 
 employed in systems of incandescent lighting 
 connected to the street mains and to the 
 electric apparatus placed in the separate 
 buildings or areas to be lighted. 
 
 Conduit, Cement-Lined A cable 
 
 conduit, the separate ducts of which are sur- 
 rounded by any suitable cement. 
 
Con.] 
 
 123 
 
 [Con. 
 
 (See Man- 
 
 Conduit, Haudhole of 
 
 hole of Conduit} 
 Conduit, Manhole of 
 
 hole of Conduit.} 
 
 Conduit, Multiple A conduit 
 
 formed of concrete or other insulating mate- 
 rial, and furnished with a number of separate 
 ducts. 
 
 Conduit, Open-Box A conduit 
 
 consisting of an open box of wood placed in 
 a trench and closed with a wooden cover 
 after the introduction of the cable. 
 
 Cables or wires may be drawn through such 
 conduits in the usual manner. 
 
 Conduit, Rodding a Introducing a 
 
 wire or rope into the duct of a closed conduit 
 preparatory to drawing the cable through. 
 
 Various methods are in use for rodding a con- 
 duit One much, followed consists in using sec- 
 tions of gas pipe, the ends of which are furnished 
 with screw threads. 
 
 The sections are about four feet in length. One 
 section is pushed into the duct at one manhole 
 and the successive sections are introduced into 
 the duct and screwed onto the section in the duct 
 and pushed through until a sufficient length is 
 obtained to reach the next manhole, a rope or 
 cable is then pulled through from one manhole to 
 the next. 
 
 Conduit, Underground Electric 
 
 An underground passageway or space for 
 the reception of electric wires or cables. (See 
 Subway, Electric} 
 
 Congelation. The act of freezing, or the 
 change of a liquid into a solid on loss of heat, 
 or change of pressure. 
 
 Conjugate Coils. (See Coils, Conjugate) 
 
 Connect. To place or bring into electric 
 contact. 
 
 Connecting. Placing or bringing into elec- 
 tric contact. 
 
 Connection for Intensity. Connection in 
 series. (See Connection, Series?) 
 
 This term is now nearly obsolete. 
 
 Connection for Quantity. Connection in 
 multiple. (See Connection, Multiple?) 
 
 This term is now nearly obsolete. 
 5 Vol. 1 
 
 (See Hand- Connection, Mercurial 
 
 A form 
 
 of readily adjustable connection obtained by 
 providing the poles of one piece of electric 
 apparatus with cups or cavities filled with 
 mercury, into which the terminals of another 
 piece of apparatus are dipped in order to 
 place the two in circuit with each other. 
 
 This form of connection is used particularly 
 when a very perfect contact or one free from 
 friction is desired. 
 
 Connection, Multiple Such a con- 
 nection of a number of separate electric 
 sources, or electro-receptive devices, or circuits, 
 that all the positive terminals are connected 
 to one main or positive conductor, and all the 
 negative terminals are connected to one main 
 or negative conductor. 
 
 In the multiple connection of a number of 
 electro-receptive devices, when the devices are 
 connected as above described to positive and 
 negative leads that are maintained at a constant 
 difference of potential, the current passes through 
 the devices from one lead to the other by branch- 
 ing and flowing through as many separate cir- 
 cuits as there are separate receptive devices, 
 and the opening or closing of one of these cir- 
 cuits does not affect the others. (See Circuits, 
 Varieties of.} 
 
 Connection, Multiple-Series Such 
 
 a connection of a number of separate electric 
 sources, or separate electro-receptive de- 
 vices, or circuits, that the sources or devices 
 are connected in a number of separate groups 
 in series, and each of these groups connected 
 to main positive and negative conductors or 
 leads in multiple arc. (See Circuits, Varie- 
 ties of} 
 
 Connection of Battery for Quantity. 
 (See Battery, Connection of, for Quantity} 
 
 Connection of Electric Sources in Cas- 
 cade. (See Cascade, Connection of Electric 
 Sources in} 
 
 Connection of Voltaic Cells for Inten- 
 sity. (See Intensity, Connection of Voltaic 
 Cells for} 
 
 Connection, Series - The connec- 
 tion of a number of separate electric 
 sources, or electro-receptive devices, or cir- 
 
Con.] 
 
 124 
 
 [Coil. 
 
 cuits, so that the current passes successively 
 from the first to the last in the circuit. (See 
 Circuits, Varieties of.) 
 
 Connection, Series-Multiple Such 
 
 a connection of a number of separate electro- 
 receptive devices, that the devices are placed 
 in multiple groups or circuits, and these 
 separate groups connected with one another 
 in series. 
 
 Connection, Telephonic Cross 
 
 A device employed in systems of telephonic 
 communication for the purpose of lessening 
 the bad effects of induction, in which equal 
 lengths of adjacent parallel wires are alter- 
 nately crossed so as to alternately occupy the 
 opposite sides of the circuit. 
 
 Connector. A device for readily con- 
 necting or joining the ends of two or more 
 wires. (See Post, Binding?) 
 
 Connector, Double 
 A form of bind- 
 ing screw suitable for 
 readily connecting two 
 wires together. 
 
 A form of double con- 
 nector is shown in Fig. 
 170. 
 
 Conning- Tower. 
 (See Tower, Conning) 
 
 Consequent Points. (See Points, Conse- 
 quent?) 
 
 Consequent Poles. (See Poles, Conse- 
 quent?) 
 
 Conservation of Energy. (See Energy, 
 Conservation of.) 
 
 Consonance, "In Consonance." A term 
 employed to express the fact that one simple 
 periodic quantity, /. e., a wave or vibration, 
 agrees in phase with another. 
 
 Constant. That which remains invariable. 
 
 Constant-Current. (See Current, Con- 
 stant?) 
 
 Constant-Current Circuit. (See Circuit, 
 Constant Current?) . 
 
 Constant-Current, Distribution of Elec- 
 tricity by - (See Electricity, Distri- 
 bution of, by Constant Currents?) 
 
 . 170. Double 
 Connector. 
 
 Constant, Dielectric A term some- 
 times employed in place of specific inductive 
 capacity. (See Capacity, Specific Inductive?) 
 
 Constant, Galvanometer The 
 
 numerical factor connecting the current pass- 
 ing through a galvanometer with the deflec- 
 tion produced by such current. 
 
 Sometimes a distinction is made between the 
 galvanometer constant and the reduction factor, 
 the former being used to indicate the relation 
 between the current and the geometrical constant 
 of the galvanometer, while the latter is used in 
 the sense just denned of galvanometer constant. 
 
 Constant Inductance. (See Inductance, 
 Constant?) 
 
 Constant Potential. (See Potential, 
 Constant?) 
 
 Constant-Potential Circuit. (See Cir- 
 cuit, Constant-Potential?) 
 
 Constant, Time, of Electro-Magnet 
 The time required for the magnetizing 
 
 p T 
 
 current to rise to the of its final value. 
 
 e 
 
 Contact-Breaker, Automatic A 
 
 device for causing an electric current to 
 rapidly make and break its own circuit. 
 
 The spring c, Fig. 171, carries an armature of 
 soft iron, B, and is 
 placed in a circuit in 
 such a manner that 
 the circuit is closed 
 when platinum con- 
 tacts placed on the 
 ends of D and B, 
 touch each other. In 
 this case the arma- 
 ture, B, is attracted to 
 the core A, of the 
 electro- magnet, thus 
 breaking the circuit 
 and causing the magnet to lose its magnetism. 
 The elasticity of the spring C, causes it to fly back 
 and again close the contacts, thus again energiz- 
 ing the electro-magnet and again attracting B. 
 and breaking the circuit. The makes and breaks 
 usually follow each other so rapidly as to produc* 
 a musical note. (See Alarm, Electric.) 
 
 B ATTEST 
 
 Fig. r?r. Automatic 
 Contact Breaker. 
 
 Contact, Dotting 
 
 An electric con- 
 
Con.] 
 
 125 
 
 [Con. 
 
 tact obtained by the approach of one con- 
 tact point towards another. 
 
 The term dotting contact is used in contradis- 
 tinction to a rubbing contact. The rubbing 
 contact is generally to be preferred, since it tends 
 automatically to remove dust and keep the con- 
 tact surfaces polished and free from oxides. 
 
 Contact Dynamo. (See Dynamo, Con- 
 tact) 
 
 Contact Electricity. (See Electricity, 
 Contact?) 
 
 Contact, Fire- Alarm A contact so 
 
 arranged that an alarm is given when any 
 predetermined temperature is reached. 
 
 Fire-alarm contacts are generally operated by 
 the expansion of a metal or of a conducting fluid, 
 such as mercury. (See Thermostat.') 
 
 Contact Force. (See Force, Contact?) 
 
 Contact, Full-Metallic A contact. 
 
 which from its small resistance establishes a 
 good or complete connection. (See Contact, 
 Metallic) 
 
 Contact, Intermittent The occa- 
 sional contact of a telegraphic or other line 
 with other wires or conductors by swing- 
 ing, or by alternate contraction or expansion 
 under changes of temperature. 
 
 Contact, Metallic A contact of 
 
 a metallic conductor produced by its coming . 
 into firrr. connection with another metallic 
 conductor. 
 
 Contact, Partial A contact of a 
 
 telegraphic, or other line, arising from defect- 
 ive insulation, bad earths, or connection with 
 an imperfect conductor. 
 
 Contact, Rolling -A contact con- 
 nected with one part of an electric circuit, 
 that completes the circuit by being rolled over 
 a conductor connected with and forming 
 another part of the circuit. 
 
 Rolling contacts are employed on electric rail- 
 roads. (See Railroad, Electric.) 
 
 Contact, Rubbing A contact 
 
 effected -by means of a rubbing motion. 
 Contact Series. (See Series, Contact) 
 Contact, Sliding A contact con- 
 nected with one Dart of a circuit that closes 
 
 or complete?: an electric circuit by being slid 
 over a conductor connected with another 
 part of the circuit. 
 
 Sliding contacts are employed in electric rail- 
 roads, in rheostats, switches, and a variety of other 
 apparatus. (See Railroad, Electric. Rheostat. 
 Key, Discharge.) 
 
 Contact, Spring A spring-sup- 
 ported contact connected with one part of a 
 circuit that completes said circuit by being 
 moved so as to touch another contact con- 
 nected with the other part of the circuit. 
 
 The movement required to bring the two con- 
 tacts together may be non-automatic, as in the case 
 of a push-button, or automatic, as in the case of 
 a thermostat. (See Button, Push. Thermostat) 
 
 Contact Theory of Voltaic Cell. (See 
 Cell, Voltaic, Contact Theory of ) 
 
 Contact, Vibrating A spring con- 
 tact, connected with one part of a circuit and 
 so supported as to be able to vibrate towards 
 and from another contact connected with 
 another part of the circuit, thus automatically 
 closing and opening said circuit. 
 
 A vibrating contact is used in the automatic 
 contact-breaker in which the movement ot an 
 armature towards an electro-magnet is caused to 
 break the circuit of the coi's of the electro-magnet, 
 and, on its movement away trom the magnet, to 
 close another contact which again completes the 
 circuit of the electro-magnet. (See Contact 
 Breaker, Automatic) 
 
 Contact, Wiping A contact ob- 
 tained by a wiping movement of one con- 
 ductor against another. 
 
 The spark for electrically igniting a gas jet is 
 obtained by means of a wiping contact of a spring 
 moved by the motion of the pendant, (See 
 Burner, Plain- Pendant Electric) 
 
 Contacts. A variety of faults occasioned 
 by the accidental contact of a circuit with any 
 conducting body. 
 
 The word contacts as employed above is in the 
 sense of accidental contacts as distinguished from 
 predetermined contacts. 
 
 Contacts of an accidental character are of the 
 following varieties, viz.: 
 
 (I.) Full, or metallic, as when the circuit is 
 
Con.] 
 
 126 
 
 [Con. 
 
 accidentally placed in firm connection with an. 
 other metallic circuit. 
 
 (2.) Partial, as by imperfect conductors being 
 placed across wires, or bad earths, or defective 
 insulation. 
 
 (3.) Intermittent, as by occasional contacts of 
 swinging wires, etc. 
 
 Contacts, Burglar Alarm Con- 
 tacts fitted to windows, doors, tills, steps, 
 floors, etc., so that a movement of the parts 
 from their natural position gives an alarm by 
 sounding a conveniently located bell. 
 
 Contacts, Lamp Metallic plates or 
 
 lings connected with the terminals of an incan- 
 descent lampforready connection with the line. 
 
 Contacts, Mercurial Electric con- 
 tacts that are opened or closed by the ex- 
 pansion or contraction of a mercury column. 
 
 In the commonest forms of mercurial con- 
 tacts, on the expansion of the mercury by heat it 
 reaches a contact point placed in the tube, and 
 thus completes the circuit through it own mass. 
 
 Or, on contraction it breaks a contact, and thus 
 disturbing an electric balance, sounds an alarm. 
 
 Continental Code Telegraphic Alphabet. 
 (See Alphabet, Telegraphic* International 
 Code.) 
 
 Continuity of Current (See Current. 
 Continuous) 
 
 Continuous Current <See Czirrent, Con- 
 tinuous) 
 
 Continuous Current, Distribution of 
 Electricity by (See Electricity, Dis- 
 tribution of, by Constant Currents) 
 
 Continuous Current, Dynamo-Electric 
 
 Machine (See Machine, Dynamo- 
 
 Electric, Continuous Current) 
 
 Continuous-Sounding Electric Bell. 
 (See Bell, Continuous-Sounding Electric) 
 
 Continuous Wires or Conductors. (See 
 Wires or Conductors, Continuous) 
 
 Contraction, Anodic Closure The 
 muscular contraction observed on the closing 
 of a voltaic circuit, the anode of which is placed 
 over a nerve, and the kathode at some other 
 part of the body. 
 
 This term is generally written A. C. C. 
 
 Contraction, Anodic Duration 
 
 The length of time the muscle continues in 
 contraction on the opening or closing of a 
 circuit, the anode of which is placed over the 
 part contracted. 
 
 This terra is generally written A. D. C. 
 
 Contraction, Anodic Opening 
 
 The muscular contraction observed on the 
 opening of a voltaic circuit, the anode of which 
 is placed over a nerve, and the kathode at 
 some other part of the body. 
 
 This term is generally written A. O. C. 
 
 When the anode is placed over a nerve and a 
 weak current is employed, if the circuit be kept 
 closed for a few minutes, it will be noticed that, 
 on opening the circuit the contraction will be 
 much greater than if it had been opened after 
 being closed for only a few seconds. The effect 
 of the A* O. C. therefore depends not only on the 
 current strength, but also on the time during 
 which the current has passed through the nerve. 
 
 Contraction of Lines of Magnetic Force. 
 (See Force, Magnetic, Contraction of 
 Lines of) 
 
 Contractures. In electro-therapeutics, 
 prolonged muscular spasms, or tetanus, caused 
 by the passage of electric currents. 
 
 Contraplex Telegraphy. (See Telegra- 
 phy, Contraplex) 
 
 Controlled Clock. (See Clock. Electric) 
 Controller. A magnet, in the Thomson- 
 Houston system of automatic regulation, 
 whose coils are traversed by the main cur- 
 rent, and by means of which the regulator 
 magnet is automatically thrown into or out of 
 the main circuit on changes in the strength 
 of the current passing. (See Regulation, 
 Automatic) 
 
 Controlling Clock. (See Clock, Electric) 
 
 Controlling Magnet. (See Magnet, Con- 
 trolling) 
 
 Convection Currents. (See Currents.Con- 
 vection) 
 
 Con vect ion, Electric The air par- 
 ticles, or air streams, which are thrown off 
 from the pointed ends of a charged, insulated 
 conductor. 
 
Con.] 
 
 127 
 
 [Cop. 
 
 Convection streams, like currents flowing 
 through conductors, act magnetically, and are 
 themselves acted on by magnets. The same thing 
 is true of the brush discharge, of the voltaic arc, 
 and of convective discharges in vacuum tubes. 
 
 Convection, Electrolytic A term 
 
 proposed by Helmholtz to explain the appa- 
 rent conduction of electricity by an electro- 
 lyte, without consequent decomposition. 
 
 Helmholtz assumes that the atoms of oxygen or 
 hydrogen, adhering to the electrodes during elec- 
 trolysis, are mechanically dislodged and diffused 
 through the liquid, thus carrying off the elec- 
 tricity by the charges received while in contact 
 with the electrodes. 
 
 Convection of Heat, Electric (See 
 
 Heat, Electric Convection of.) 
 
 Convection Streams. (See Streams, Con- 
 vection^) 
 
 Convective Discharge. (See Discharge, 
 Convective?) 
 
 Conversion, Efficiency of, of Dynamo 
 The total electric energy developed by a 
 dynamo, divided by the total mechanical 
 energy required to drive the dynamo. (See 
 Co-efficient, Economic, of a Dynamo-Electric 
 Machine?) 
 
 The efficiency of conversion 
 
 W -j- w _ W + w 
 
 M~~ ~~ W + w -f m, 
 
 where W, equals the useful or available electrical 
 energy, M, the total mechanical energy, w, the 
 electrical energy absorbed by the machine, and 
 m, the stray power, or the power lost in friction, 
 eddy currents, air friction, etc. 
 
 Converted Currents. (See Currents, 
 Converted?) 
 
 Converter. The inverted induction coil 
 employed in systems of distribution by means 
 of alternating currents. 
 
 A term sometimes used instead of trans- 
 former. (See Transformer?) 
 
 Converter, Closed-Iron Circuit 
 
 A closed-iron circuit transformer. (See 
 Transformer, Closed-Iron Circuit?) 
 
 Converter, Constant-Current 
 
 A constant-current transformer. (See Trans- 
 former, Constant-Current.) 
 
 Converter, Efficiency of The effi- 
 
 ciency of a transformer. (See Transformer, 
 Efficiency of.) 
 
 Converter Fuse. (See Fuse, Converter.) 
 
 Converter, Hedgehog - A form of 
 transformer. (See Transformer, Hedgehog.) 
 
 Converter, Multiple - A multiple 
 transformer. (See Transformer, Multiple?) 
 
 Converter, Open-Iron-Circuit An 
 open-iron-circuit transformer. (See Trans- 
 former, Open-Iron-Circuit?) 
 
 Converter, Series - A series trans- 
 former. (See Transformer, Series.) 
 
 Converter, Step-down A step-down 
 transformer. (See Transformer, Step-down.) 
 
 Converter, Step-up - A step-up 
 transformer. (See Transformer, Step-up?) 
 
 Converter, Welding A welding 
 
 transformer. (See Transformer, Welding.) 
 
 Converting Currents. (See Currents, 
 Converting.} 
 
 Cooling Box of Hydro-Electric Machine. 
 (See Box, Cooling, of Hydro-Electric 
 Machine?) 
 
 Co-ordinates, Axes of The axes of 
 
 abscissas and ordinates. 
 
 The two straight lines, usually perpendicular 
 to each other, to which distances representing 
 values are referred for the graphic represen- 
 tation of such values. (See Abscissas, Axes of.) 
 
 Copper Bath. (See Bath, Copper.) 
 Copper Plating. (See Plating, Copper.) 
 Copper Ribbon. A variety of strap cop- 
 per. (See Copper, Strap.) 
 
 Copper, Strap - Copper conductors 
 in the form of straps or flat bars. 
 
 Strap copper is used on the armatures of some 
 dynamos. Heavy copper conductors for such 
 purposes are divided into strap copper so as to 
 avoid eddy currents. The straps are placed 
 alongside one another and insulated by a coating 
 of varnish. 
 
 Copper Wire, Hard-Drawn (See 
 
 Wire, Copper, Hard-Drawn?) 
 
 Copper Wire, Soft-Drawn (See 
 
 Wire, Copper, Soft-Drawn.) 
 
top.] 
 
 128 
 
 [Cor. 
 
 Copper Toltameter. (See Voltameter, 
 Copper.} 
 
 Coppered Plumbago. (See Plumbago, 
 Coppered} 
 
 Coppering, Electro Electro-plating 
 with copper. (See Plating, Electro^) 
 
 Cord-Adjuster. (See Adjuster, Cord.} 
 
 Cord, Conducting A small flexible 
 
 cable, usually containing several conductors 
 separated from one another by insulating ma- 
 terial. 
 
 Cord, Electric A flexible, insulated 
 
 electric conductor, generally containing at least 
 two parallel wires. 
 
 Electric cords are named from the purposes for 
 which they are employed, battery cord*, dental 
 cords, lamp cords, motor cords, switch cords, etc. 
 
 Fig. 1-72. Flexible Cord. 
 
 A two-conductor flexible cord, in which each 
 cord is composed of a number of bare copper wires 
 placed parallel to and in contact with one another, 
 is shown in Fig. i"j2. The several separate wires 
 give flexibility to the cord. 
 
 Cord, Pendant A flexible conductor 
 
 provided for conveying the current to a hang- 
 ing electric lamp supported by it. 
 
 Cords, Telephone Flexible con- 
 ductors for use in connection with a tele- 
 phone. 
 
 Fig. 173. Telephone Cords. 
 
 Telephone cords, attached to an articulating 
 telephone, are shown in Fig. 173. 
 
 Core, Armature, Filamentous 
 
 An armature core, the iron of which consists 
 of wire. 
 
 Core, Armature, H An armature 
 
 core in the shape of the letter H, generally 
 known as the shuttle armature, and some- 
 times as the girder armature. 
 
 This form is also called an I armature. 
 
 The H armature core was the form originally 
 given to the Siemens armature. In this form a 
 single coil of wire was secured on the cross-bar 
 of the H armature core, so as to fill up the entire 
 space inside the letter, and the ends of the wire 
 connected to a two-part commutator. 
 
 Core, Armature, Lamination of 
 
 The subdivision of the core of the armature 
 of a dynamo-electric machine into separate 
 insulated plates or strips for the purpose of 
 avoiding eddy or Foucault currents. 
 
 This lamination must always be perpendicular 
 to the direction of the eddy currents that would 
 otherwise be produced. (See Currents, Eddy.) 
 
 Core, Armature, of Dynamo-Electric 
 Machine The iron core, on, or around 
 which, the armature coils of a dynamo-electric 
 machine are wound or placed. 
 
 The armature core is laminated for the pur- 
 pose of avoiding the formation of eddy or Fou- 
 cault currents. 
 
 In. drum, and in ring-armatures, the laminae 
 should be in the form of thin insulated discs or 
 plates of soft iron ; in pole-armatures they should 
 be in the form of bundles of insulated wires. 
 
 The iron in the cores should be of such an area 
 of cross-section, as not to be readily oversaturated. 
 
 Core, Armature, Radially-Laminated 
 
 An armature core, the iron of which 
 
 consists of thin iron washers. 
 
 Core, Armature, Ribbed A cylin- 
 drical armature core provided with longi- 
 tudinal projections or ribs that serve as 
 spaced channels or grooves for the reception 
 of the armature coils. 
 
 Core, Armature, Tangentially-Laminated 
 
 An armature core, the iron of which 
 
 consists of a coiled ribbon. 
 
 Core, Armature, Ventilation of 
 
 Means for passing air through the armature 
 
Cor.J 
 
 129 
 
 [Cou. 
 
 cores of dynamo-electric machines in order to 
 prevent undue accumulation of heat. 
 
 A properly proportioned dynamo-armature 
 may need no ventilation, since in such' the 
 amount of heat generated is small as compared 
 with the extent of the radiating surface. 
 
 Since, however, in practice all armatures tend 
 to heat at full load, especially in certain installa- 
 tions in heated situations, ventilation of the ar- 
 mature is desirable. 
 
 Core, Closed-Magnetic 
 
 A mag- 
 
 netic core so shaped as to provide a complete 
 iron path or circuit for the lines of magnetic 
 force of its field. 
 
 Core, Laminated 
 
 A core of iron 
 
 which has been divided or laminated, in order 
 to avoid the injurious production of Foucault 
 or eddy currents. 
 
 Core, Lamination of Structural 
 
 subdivisions of the cores of magnets, arma- 
 tures, and pole-pieces of dynamo-electric 
 machines, electric motors, or similar appa- 
 ratus, in order to prevent heating and subse- 
 quent loss of energy from the production of 
 local, eddy or Foucault currents. 
 
 These laminations are obtained by forming the 
 cores of sheets, rods, plates, or wires of iron in- 
 sulated from one another. 
 
 The cores of dynamo-electric machine arma- 
 tures should be subdivided in planes at right 
 angles to the armature coils; or in planes parallel 
 to the direction of the lines of force and to the 
 motion of the armature; or, in general, in planes 
 perpendicular to the currents that would otherwise 
 be generated in them. 
 
 Pole pieces should be divided in planes per- 
 pendicular to the direction of the currents in the 
 armature wires. 
 
 Magnet cores should be divided in planes at 
 right angles to the magnetizing current. 
 
 Core of Cable. The conducting wires of 
 an electric cable. (See Cable, Electric?) 
 
 Core, Open-Magnetic Any mag- 
 netic core so shaped that the lines of magnetic 
 force of- its field complete their circuit partly 
 through iron and partly through air. 
 
 Core Ratio of Cable. (See Cable, Core 
 Ratio of.) 
 
 Core, Ring A hollow, cylindrical 
 
 core of short length. 
 
 Core, Ring, Elongated A hollow, 
 
 cylindrical core of comparatively great length. 
 
 Core, Solenoid A core so arranged 
 
 as to be drawn into a solenoid on the passage 
 of the current through its coils, and to be 
 withdrawn therefrom, on the stopping of the 
 current by the action of a spring or weight. 
 (See Solenoid.) 
 
 Core, Stranded, of Cable The 
 
 conducting wire or core of a cable formed of 
 a number of separate conductors or wires in- 
 stead of a single conductor of the same weight 
 per foot as the combined conductors. 
 
 Core Transformer. (See Transformer, 
 Core. ) 
 
 Cored Carbons. (See Carbons, Cored.) 
 
 Cored Electrodes. (See Electrodes, 
 Cored.) 
 
 Coronae, Auroral A crown-shaped 
 
 appearance, sometimes assumed by the auro- 
 ral light. (See Aurora Borealis) 
 
 Corposant. A name sometimes given by 
 sailors to a St. Elmo's Fire. (See Fire, St. 
 Elmo's?) 
 
 Correlation of Energy. (See Energy, 
 Correlation of) 
 
 Corresponding Points. (See Points, Cor- 
 responding) 
 
 Cosine. One of the trigonometrical func- 
 tions. (See Trigonometry) 
 
 Cotangent. One of the trigonometrical 
 functions. (See Trigonometry) 
 
 Coulomb. The unit of electrical quantity. 
 
 A definite quantity or amount of the thing 
 or effect called electricity. 
 
 Such a quantity of electricity as would pass 
 in one second in a circuit whose resistance is 
 one ohm, under an electromotive force of 
 one volt. 
 
 The quantity of electricity contained in a 
 condenser of one farad capacity, when sub- 
 jected to an electromotive force of one volt. 
 
 The quantity of electricity that flows per 
 second past a cross-section of a conductor 
 
Con.] 
 
 130 
 
 [I'ou. 
 
 conveying an ampere. (Ayrton.) (See Am- 
 pere. Farad. Volt.) 
 
 Coulomb's Torsion Balance. (See Bal- 
 ance, Coulomb's Torsion?) 
 
 Coulomb-Volt. A Joule, or .7373 foot- 
 pound. 
 
 The term is generally written volt-coulomb. 
 (See Volt-Coulomb.) 
 
 Counter, Electric A device for 
 counting and registering such quantities as 
 the number of fares collected, gallons of water 
 pumped, sheets of paper printed, revolutions 
 of an engine per second, votes polled, etc. 
 
 Various electric devices are employed for this 
 purpose. They are generally electro-magnetic 
 in character. 
 
 Counter-Electromou. e Force. (See 
 Force, Electromotive, Counter.} 
 
 Counter Electromotive Force Lightning 
 Arrester. (See Arrester, Lightning, Coun- 
 ter-Electromotive Force!) 
 
 Counter-Electromotive Force of Convec- 
 tive Discharge. (See Force, Electromotive, 
 Counter, of Convective Discharged) 
 
 Counter-Electromotive Force of Mutual 
 Induction. (See Force, Electromotive, 
 Counter, of Mutual Induction?) 
 
 Counter-Electromotive Force of Self-In- 
 duction. (See Force, Electromotive, Coun- 
 ter, of Self -Induction?) 
 
 Counter-Electromotive Force of Self-In- 
 duction of the Primary. (See Force, 
 Electromotive, Counter, of Self-induction of 
 the Primary?) 
 
 Counter-Electromotive Force of Self-in- 
 duction of the Secondary. (See Force, 
 Electromotive, Counter, of Self-induction of 
 the Secondary?) 
 
 Counter-Electromotive Force of the 
 Primary. (See Force, Electromotive ; 
 Counter, of the Primary?) 
 
 Counter Inductive Effect. (See Effect, 
 Counter Inductive?) 
 
 Couple. In mechanics, two equal parallel 
 forces acting in opposite directions but not in 
 the same line, and tending to cause rotation. 
 
 The moment, or effective power of a couple, is 
 
 N; 
 
 equal to the intensity of one of the forces multiplied 
 by the perpendicular distance between the direc- 
 tions of the two forces. 
 
 Couple, Astatic Two magnets of 
 
 exactly equal strength so placed one over the 
 other m the same vertical plane as to com- 
 pletely neutralize each other. 
 
 An astatic couple has no directive tendency. A 
 pair of magnets combined as an astatic couple is 
 called, an astatic needle. (See Needle, Astatic.) 
 
 Couple, Magnetic The couple which 
 tends to turn a magnetic needle, placed in the 
 earth's field, into the plane of the magnetic 
 meridian. 
 
 If a magnetic needle is in any other position 
 than in the magnetic meridian, there will be two 
 parallel and equal forces acting at A and B, Fig. 
 174, in the directions shown by the arrows. 
 Their effect will be to ro- 
 tate the needle until it 
 comes to rest in the mag- 
 netic meridian N S. 
 
 The total force acting 
 on either pole of a needle 
 free to move in any direc- 
 tion, is equal to the 
 strength of that pole mul- 
 tiplied by the total inten- 
 sity of the earth's field at 
 that place ; or, if free to move in a horizontal 
 direction only, is equal to the intensity of the 
 earth's horizontal component of magnetism at 
 that place, multiplied by the strength of that pole. 
 
 The effective power or moment of a magnetic 
 couple is equal to the force exerted on one of the 
 poles multiplied by the perpendicular distance, 
 P Q, between their directions. 
 
 Couple, Moment of The effective 
 
 power or force of a couple. 
 
 The moment of a couple is equal to the inten- 
 sity of one of the forces multiplied by the perpen- 
 dicular distance between the direction of the 
 forces. 
 
 Couple, Thermo-Electric Two dis- 
 similar metals which, when connected at their 
 ends only, so as to form a completed electric 
 circuit, will produce a difference of potential, 
 and hence an electric current, when one of the 
 ends is heated more than the other. 
 
 Thus if a bar of bismuth be soldered to a bar 
 
 is 
 
 174. Magnttic 
 Couple. 
 
Con.] 
 
 131 
 
 [Cre. 
 
 of antimony the combination will form a thermo- 
 elec^ric couple, and the circuit so formed will 
 have a current passing through it when one junc- 
 tion is hotter or colder than the other. 
 
 There is, according to Lodge, a true contact 
 force, at a thermo-electric junction, as is shown by 
 the reversible heat effects produced when an 
 electric current is passed across such junction ; for, 
 in one direction more heat is produced, and in the 
 opposite direction less heat. This, as is well 
 known, differs from the irreversible heat produced 
 by a current through a homogeneous metallic 
 conductor. The reversible heat effects, or as they 
 are called the Peltier effects, may overpower and 
 conceal the heating effects. But, in addition to 
 these effects, since a difference of potential, called 
 a Thomson effect, exists in a substance unequally 
 heated, currents are so produced, and these are 
 also influential in causing the difference of poten- 
 tial of a thermo-electric couple. 
 
 " There are then," says Lodge, "in a simple 
 circuit of two metals with their junctions at differ- 
 ent temperatures, altogether four E. M. Fs., one 
 in each metal, from hot to cold, or vice versa, and 
 one at each junction, and the current which flows 
 around such a circuit is propelled by the resultant 
 of these four." * * * " These four forces, 
 two Thomson forces in the metals, and two Peltier 
 forces at their junctions, may some of them help 
 and some hinder the current." * * * "When- 
 ever they help, the locality is to that extent cooled; 
 whenever they hinder, it is to that extent 
 warmed." 
 
 The action of a thermo-electric couple in pro- 
 ducing a difference of potential is therefore a 
 complicated one, and depends on Peltier and 
 Thomson effects, as well as on the thermo-electric 
 effect. (See Effect, Peltier. Effect, Thomson. 
 Effect, Thermo -Electric.) 
 
 Couple, Yoltaic - Two materials, 
 usually two dissimilar metals, capable of 
 acting as an electric source when dipped in 
 an electrolyte, or capable of producing a 
 difference of electric potential by mere con- 
 tact. 
 
 Liquids and gases are capable of acting as 
 voltaic couples. 
 
 All voltaic cells have two metals, or a metal and 
 a metalloid, or two gaseous or liquid substances 
 which are of such a character that, when dipped 
 into the exciting fluid one only is chemically 
 acted on. 
 
 Each one of these two substances is called an 
 element of the cell, and the two taken collectively 
 form a -voltaic couple. 
 
 The elements of a voltaic couple may consist of 
 two gases or two liquids. (See Battery, Gas.) 
 
 Coupled Cells. (See Cells, Coupled^ 
 
 Coupler, Yoltaic - Any device by 
 means of which voltaic cells may be readily 
 coupled or connected in different forms of 
 circuits. (See Circuits, Varieties of.) 
 
 Coupling of Yoltaic Cells or Other 
 Electric Sources. A term indicating the 
 manner in which a number of separate 
 electric sources may be connected so as to 
 form a single source. (See Circuits, Varie- 
 ties of.) 
 
 Cramp, Telegrapher's - An affec- 
 tion of the hand of a telegrapher due to im- 
 moderate and excessive use of the same 
 muscles, somewhat similar to the disease 
 known as writer's cramp. 
 
 Telegrapher's cramp, like writer's cramp, may 
 be defined as a professional neurosis of co-ordina- 
 tion. It appears not only in certain groups of 
 muscles, but is limited to such groups, only when 
 they are performing certain complicated opera- 
 tions. For example, telegrapher's cramp is 
 practically a paralysis of certain muscles of the 
 hand and wrist of the operator. These muscles, 
 when called on to perform the somewhat delicate 
 movements required in sending a telegraphic dis- 
 patch, are incapable of performing their proper 
 functions, but when called on to perform in part 
 other similar actions, provided all these actions 
 are not required to be used, appear to be un- 
 affected. 
 
 The ability of the operator to send with either 
 hand would lessen the liability to this disease. 
 
 Crater in Positive Carbon. A depression 
 at the end of the positive carbon of an arc 
 lamp which appears when a voltaic arc is 
 formed. (See Arc, Voltaic.) 
 
 Creep, Diffusion The flow of an 
 electric current in portions of a conducting 
 substance, outside the parts that lie in the 
 direct lines between the points where the 
 terminals of the same are applied to the con- 
 ducting substance 
 
t're.J 132 
 
 Creeping, Electric A term some- 
 times applied to the creeping of a current. 
 (See Current, Creeping of.} 
 
 Creeping in Voltaic Cell. (See Cell, Vol- 
 taic, Creeping in.) 
 
 Creeping of Current (See Current, 
 Creeping of, Electric) 
 
 Creeping, Saline The formation 
 
 of salts by efflorescence on the walls of a solid 
 immersed in a solution of a salt. 
 
 Creosoting. A process employed for the 
 preservation of wood, as, for example, tele- 
 graph poles, by injecting creosote into the 
 pores of the wood. (See Pole, Telegraphic) 
 
 Crith. A term proposed by A. W. Hoff- 
 man, as a unit of weight, or the weight of 
 one litre, or cubic decimetre, of hydrogen at 
 O C. and 760 mm. barometric pressure. 
 
 Critical Current. (See Current, Crit- 
 ical) 
 
 Critical Current of a Dynamo. (See 
 Current, Critical, of a Dynamo) 
 
 Critical Distance of Lateral Discharge 
 through Alternative Path. (See Distance, 
 Critical, of Lateral Discharge through 
 an Alternative Path) 
 
 Critical Speed of Compound-Wound Dy- 
 namo. (See Speed, Critical, of Compound- 
 Wound Dynamo) 
 
 Crookes' Dark Space. (See Space, Dark, 
 Crookes') 
 
 Crookes' Electric Radiometer. (See Ra- 
 diometer, Electric, Crookes') 
 Cross Arm. (See Arm, Cross) 
 
 Cross-Connecting Board. (See Board, 
 Cross-Connecting) 
 
 Cross, Electric A connection, gen- 
 erally metallic, accidentally established be- 
 tween two conducting lines. 
 
 A defect in a telegraph, telephone or other 
 circuit caused by two wires coming into 
 contact by crossing each other. 
 
 A swinging or intermittent cross is caused by 
 wires, which are too slack, being occasional^ 
 blown into contact by the wind. 
 
 [Cro. 
 
 A weather cross arises from defective action oi 
 the insulators in wet weather. 
 
 Cross, Swinging or Intermittent 
 
 An accidental contact, generally metallic, 
 caused by wires being brought into occasional 
 contact with one another, or with some other 
 conductor, by the intermittent action of the 
 wind. 
 
 Cross, Weather A contact or leak 
 
 occurring in a telegraphic or other line dur- 
 ing wet weather, from the defective action of 
 the insulators. 
 
 Crossing Cleat (See Cleat, Crossing) 
 
 Crossing, Live-Trolley A device 
 
 whereby a trolley moving over a line that 
 crosses a second line at an angle is enabled 
 to maintain its electrical connection with the 
 line while crossing. 
 
 A live-trolley crossing is necessitated where one 
 line of electric railway crosses another. The 
 upper line must, of course, provide a space or 
 opening for crossing the lower line at the points 
 of intersection. This is effected in the Bagnall 
 live-trolley crossing, shown in Fig. 175, by attach- 
 
 Fig- Z 75- Live-Trolley Crossing. 
 
 ing to the upper trolley wire a bridge piece of 
 light lathe casting, provided at its centre with a 
 gap through which the trolley wire passes. This 
 bridge piece is insulated from the trolley wire by 
 means oi a disc of insulating material at the cen- 
 tre of the bridge, which is provided with a hinged 
 curved lever, that in its normal position rests un- 
 der the influence of gravity in the position shown 
 in the figure. The passage of the trolley wheel 
 along the wire carries the line under it and thus 
 bridges the gap, as shown by the position of the 
 dotted lines. 
 
 Crossing Wires. (See Wires, Crossing) 
 
 Cross-Over Block. (See Block, Cross- 
 Over) 
 
 Cross-Over, Trolley A device by 
 means of which a trolley is enabled to pass 
 over the points where different lines cross one 
 another without serious interrunt ; nn. 
 
Cro.] 
 
 A trolley cross-over, for trolley lines, is shown 
 in Fig. 176. 
 
 [Cur. 
 
 Fig. 176. Trolley Cross -Over. 
 
 Crow-foot Zinc. (See Zinc, Crow-foot?) 
 
 Crucible. Electric A crucible in 
 
 which the heat of the voltaic arc. or of elec 
 trie incandescence, is employed either to per- 
 form difficult fusions, or for the purpose of 
 effecting the reduction of metals from their 
 ores or the formation of alloys. (See Fur- 
 nace, Electric?) 
 
 Crystal. A solid body bounded by sym- 
 metrically disposed plane surfaces, 
 
 A definite form or shape is as characteristic of 
 an inorganic crystalline substance as it is of an 
 animal or plant, Each substance has a form in 
 which it generally occurs. There are, however, 
 certain modifications of the typical forms which 
 cause plane surfaces to appear curved, and the 
 symmetrical arrangement of the faces to disap 
 pear. These modifications often render it ex 
 tremely difficult to recognize the true typical 
 torm 
 
 'For the different fundamental crystalline forms, 
 or systems of crystals, see any standard work on 
 chemistry. 
 
 Crystal. Hemiliedral - A crystal 
 whose shape or form has been modified by 
 the replacement of half its edges or solid 
 angles, 
 
 A hemihedral crystal possesses different forms 
 at the ends or extremities of its axes. Hemi- 
 hedral crystals, when unequally heated, develop 
 electrical charges. 
 
 Electricity produced in this way was formerly 
 C3\\e& pyro-electricity. (See Electricity, J'yro.) 
 
 Crystal, Holohedral A crystal 
 
 whose shape or form has been modified by 
 the replacement of all its edges or solid 
 angles. 
 
 Crystalline Electro-Metallurgical De- 
 posit. (See Deposit. Crystalline. Electro- 
 Metallurgzcal.) 
 
 Crystallization. Solidification from a state 
 of solution or fusion in a definite crystalline 
 iorm. 
 
 The crystallization of a dissolved solid is fa- 
 vored by any cause that gives increased freedom 
 of movement to its molecules, such for example as 
 solution, fusion, sublimation, or precipitation. 
 
 Crystallization by Electrolytical Decom- 
 position. The crystalline deposition of vari- 
 ous metals by the passage of an electric cur- 
 rent through solutions of 'their salts under 
 certain conditions. 
 
 A strip of zinc immersed in a solution of sugar 
 of lead (acetate of lead) soon becomes covered 
 with bright metallic plates of lead, that are elec- 
 trolytically deposited by the weak currents due to 
 minute voltaic couples formed with the zinc by 
 particles of iron, carbon, or other impurities in 
 the zinc. The deposit assumes at times a tree- 
 like growth, and is therefore called a lead tree. 
 (See Couple, Voltaic.) 
 
 Crystallization, Electro Crystalli- 
 zation effected during electrolytic deposition. 
 
 Crystallize. To separate from a liquid 
 or vapor, in the form of a crystalline solid. 
 
 Crystalloid. Those portions of a mixed 
 substance subjected to dialysis, that are capa- 
 ble of crystallization. (See Dialysis.) 
 
 Cube, Faraday's An insulated 
 
 room cubic in shape, covered on the inside 
 with tin foil, which, when charged on the 
 outside gives no indications to an observer on 
 the inside, though furnished with delicate in- 
 struments. 
 
 Faraday's cube illustrates the fact that an elec- 
 trostatic charge resides on the outside of an insu- 
 lated conductor. (See Net, Faraday's.) 
 
 Cup, Mercury A cup or cavity 
 
 filled with mercury and connected with the 
 pole of an electric apparatus for the ready 
 placing of the same in circuit with other elec- 
 tric apparatus. 
 
 To connect apparatus it is only necessary to 
 insert the free terminal of one apparatus in the 
 mercury cup of the other. 
 
 Cup, Porous A porous cell. (See 
 
 Cell, Porous) 
 
 Curb, Double - A device for in- 
 creasing the speed of signaling, by means of 
 which the line is rid of its charge before the 
 next signal is sent, by sending an opposite 
 charge, then another in the same direction, 
 
Cur.] 
 
 134 
 
 LCur. 
 
 then finally another in the same direction 
 before connecting with the ground. 
 
 The effect of the third charge is to reduce the 
 potential of the line more nearly to zero at the 
 end of the signal. 
 
 Curb, Single A device for in- 
 creasing the speed of signaling telegraphic- 
 ally by ridding the line of its previous charge 
 by sending a reversed current through it be- 
 fore connecting with the ground. 
 
 In single-curb signaling the operator in dis- 
 charging the line before sending another signal 
 through it, before putting the line to earth, re- 
 verses the battery, and then connects to earth. 
 
 Current, Absolute Unit of A cur- 
 rent of 10 amperes. (See Ampere. Units, 
 Practical!) 
 
 A current of such a strength that when 
 passed through a circuit of a centimetre in 
 length bent in the form of an arc of a circle 
 one centimetre in radius, will act with the 
 force of a dyne on a magnetic pole of unit 
 strength, placed at the centre of the arc. 
 
 The ampere, the practical unit of current, is 
 but ^5 the value of the absolute unit of current. 
 
 Current, Action of, on a Magnetic Pole 
 
 An attraction or repulsion depend- 
 ent on the name of the pole and the direction 
 of the current. 
 
 Two currents of electricity attract or repel each 
 other according to the direction in which they 
 are flowing, and the mutual positions of their 
 circuits. A current and a magnetic pole exert an 
 action on each other which, strictly speaking, is 
 neither attraction nor repulsion, but which is ro- 
 tation, that may, however, be regarded as being 
 produced by the combined action of attraction 
 and repulsion. 
 
 Current, Alternating A current 
 which flows alternately in opposite directions. 
 
 A current whose direction is rapidly re- 
 versed. 
 
 The non-commuted currents generated by the 
 differences of potential in the armature of a 
 dynamo-electric machine are alternating or 
 simple-periodic-currents. 
 
 In a characteristic curve of the electromotive 
 forces of alternating currents, positive electro- 
 motive forces, or those that would produce cur- 
 
 rents in a certain direction, are indicated by 
 values aboz>e a horizontal line, and negative elec- 
 tromotive forces, by values be-low the line. 
 
 The curves ABC, and C D E, Fig. 177, are 
 
 B 
 
 Fig 177- Curve of Electromotive Forces of Alternating 
 Currents. 
 
 often called phases, and represent the alternate 
 phases of the current. 
 
 Current, Alternative A voltaic 
 
 alternative. (See Alternatives, Voltaic^ 
 Current, Assumed Direction of Flow 
 
 of The direction the current is as- 
 sumed to take, t. e., from the positive pole of 
 the source through the circuit to the negative 
 pole of the source. 
 
 The electricity is assumed to come out of the 
 source at its positive pole, and to return or flow 
 back into the source at its negative pole. This 
 convention as to the direction of the electric cur- 
 rent is in accordance with the assumption of the 
 direction of flow of lines of magnetic forces. 
 
 The old idea'of a dual or double current flowing 
 in opposite directions is still maintained by some, 
 (See Force, Lines of, Direction of.) 
 
 Current, Axial In electro-thera- 
 peutics a current flowing in a nerve in the 
 opposite direction to the normal impulse in 
 the nerve. 
 
 Current. Break-Induced The cur- 
 rent induced by a current in its own, or in 
 another circuit, on breaking or opening the 
 same. 
 
 The current induced in the secondary on 
 the breaking of the primary circuit. 
 
 The break-induced current set up by a current 
 in its own circuit is sometimes called the direct- 
 induced current. 
 
 Lord Rayleigh has shown that within certain 
 limits the break-induced current has a greater 
 effect in magnetizing steel needles, the smaller 
 the number of turns of wire in the secondary. In 
 
Cur.] 
 
 135 
 
 [Cur. 
 
 the case of a galvanometer, it is well known that 
 the opposite is true. The deflection of the gal- 
 vanometer needle depends on the strength of the 
 whole current. The magnetizing power depends, 
 for the greater part, on the strength of the cur- 
 rent at the beginning of its formation 
 
 Current. Closed -Circular - - A cur- 
 rent flowing in a circular circuit. 
 
 A small closed-circular current may be replaced 
 magnetically by a thin disc of steel, magnetized in 
 a direction perpendicular to its iace, and the edge 
 of which corresponds to the edge of the circular 
 conductor. 
 
 Current-Commuter. (See Commuter, 
 Current?) 
 
 Current. Conduction The current 
 
 that passes through a metallic or other con- 
 ducting substance, as contradistinguished 
 from a current produced in a non-conductor 
 or dielectric. (See Current, Displacement) 
 
 Current, Constant A current that 
 
 continues to flow m the same direction for 
 some time without varying m strength, 
 
 This term is sometimes used to mean a con 
 tinuous or direct current in contradistinction to 
 an alternating current, but it ought to be applied 
 only to unvarying currents, such, for example as 
 a constant current of 10 amperes. 
 
 Current, Continuous - An electric 
 current which flows in one and the same 
 direction 
 
 Although the term continuous current is used 
 as synonymous with constant current, it is not 
 entirely so; a continuous current flows constantly 
 in the same direction A constant current not 
 only flows continuously in the same direction, but 
 maintains an approximately constant current 
 strength 
 
 This term continuous current is used in the 
 opposite sense to alternating current, and in the 
 same sense as a direct current. 
 
 Current, Creeping of Electric 
 
 A change in the direction of path of a current 
 from the direct line between the points of 
 connection with the source. 
 
 When the terminals of any electric source are 
 placed in contact with any two points of a metallic 
 sheet of conducting material, the flow of the cur- 
 rent ib not confined to the direct line between the 
 
 Critical 
 Curve of Dynamo 
 Current 
 
 points of contact, but creeps or diffuses into por- 
 tions of the conducting plate surrounding this 
 direct line. (See Current, Diffusion of.) 
 
 In a somewhat similar manner, the current 
 is said to creep, or to establish a partial short- 
 circuit around the poles of a poorly insulated 
 voltaic battery, or other electric source. 
 
 Current, Critical 
 The current at which a 
 certain result is reached, 
 
 Current, Critical, of a 
 Dynamo That value 
 of the current at which the 
 characteristic curve begins 
 to depart from a nearly 
 straight line, (Silvanus Fig 178 
 P Thompson.} 
 
 In Fig. 178 the critical 
 current is shown in three different cases, as oc- 
 curring where the dotted vertical line cuts the 
 characteristic curves. 
 
 The speed at which a series dynamo excites 
 itself is often called the critical speed. 
 
 Current, Demarcation. - A term 
 sometimes applied to an electric current ob- 
 tained from an injured muscle. 
 
 " Every injury of a muscle or nerve causes at 
 the point of injury a dying surface, which behaves 
 negatively to the positive intact substance." 
 (Landois & Stirling.) 
 
 Current Density. The current of elec- 
 tricity which passes in any part of a circuit as 
 compared with the area of cross-section of 
 that part of the circuit. 
 
 In a dynamo- electric machine the current den- 
 sity in the armature wire should not, according to 
 Silvanus P. Thompson, exceed 2.500 amperes 
 per square inch of area of transverse section of 
 conductor. 
 
 The current density in a dynamo wire, of 
 necessity depends on the sectional area of the 
 coils . If, for example, a current of 50 amperes 
 be safe in an armature section of eight turns it 
 may be safely increased to 100 amperes if the 
 conductors are cross- sectioned so as to make but 
 four turns. (Urquhart.) 
 
 In electro- plating, for every definite current 
 strength that passes through the bath, or in other 
 words, for a definite number of coulombs, a 
 definite weight of metal is deposited, the charac- 
 
Cur.] 
 
 136 
 
 [Cur: 
 
 ter of which depends on the current density. The 
 character of an electrolytic deposit will therefore 
 depend on the current density at that part of the 
 circuit where the deposit occurs. 
 
 The following table from Urquhart gives the 
 practical working value for the current density 
 for electro-metallurgical deposits : 
 
 CURRENT DENSITY (OR AMPERES ON 
 CATHODE). 
 
 Amperes 
 Solution of per square foot. 
 
 Copper, acid bath 5.0 to 10.0 
 
 Copper, cyanide bath 3.0 " 5.0 
 
 Silver, double cyanide 2.0 " 5.0 
 
 Gold, chloride in cyanide i.o " 2.0 
 
 Nickel, double sulphate 6.0 " 8.0 
 
 Brass, cyanide 2.0 " 3.0 
 
 Tin 
 
 Current, Diacritical Such a 
 
 strength of the magnetizing current as pro- 
 duces a magnetization of an iron core equal 
 to half-saturation. 
 
 The diacritical current is the current which, 
 flowing through the diacritical number of ampere- 
 turns, will bring up the magnetism produced to 
 half -saturation. 
 
 , The diacritical number of ampere-turns is such 
 a number of ampere-turns as would reduce the 
 magnetic permeability to half its lull value. 
 
 Current, Diffusion of - A term em- 
 ployed to designate the difference in the 
 density of current in different portions of a 
 conductor. (See Current. Creeping of , Elec- 
 tric) 
 
 Current, Diffusion of Electro-Therapeu- 
 tic The difference in the density of 
 
 current in different portions of the human 
 body between the electro-therapeutic elec- 
 trodes. 
 
 When the electrodes are placed at any two 
 given points of the human body, the current 
 branches through various paths, extending in a 
 general direction from one electrode to the other, 
 according to the law of branched or derived cir- 
 cuits, and flowing in greater amount, or with 
 greater density of current, through the relatively 
 better conducting paths. (See Current Density.') 
 
 This is sometimes called the creeping of the 
 Current. (See Current, Creeping of .} 
 
 Current, Direct A current con- 
 
 stant in direction, as distinguished from an 
 alternating current. 
 
 A continuous current. 
 
 Current, Direct-Induced The cur- 
 rent induced in a circuit by induction on it- 
 self, or self-induction, on breaking or opening 
 the circuit. (See Currents, Extra.} 
 
 This is called the direct-induced current because 
 its direction is in the same direction as the induc- 
 ing current. 
 
 Current, Direction of The direc- 
 tion an electric current is assumed to take 
 out from one pole of any source through the 
 circuit and its translating devices back to the 
 source through its other pole. 
 
 Conventionally, the current is assumed to come 
 out from the positive pole of the source and to go 
 back to the source at the negative pole. 
 
 Current, Displacement The rate 
 of change of electric displacement. 
 
 A brief conduction current produced in a 
 dielectric by an electric displacement. (See 
 Displacement, Electric?) 
 
 This is called a displacement current in order 
 to distinguish it from a conduction current in any 
 conductor. 
 
 The displacement current continues while the 
 displacement of electricity is going on. Dis- 
 placement currents have all the properties of con- 
 duction currents, and, like the latter, produce a 
 magnetic field; in fact, they resemble extremely 
 brief conduction currents. 
 
 The difference between conducting substances 
 and dielectrics, lies in the fact that the conducting 
 substances do not possess an elastic force, en- 
 abling them to resist electric displacement. In 
 other words, conducting substances possess no 
 electric elasticity, and can have no true displace- 
 ment current established in them. (See Elasti- 
 city, Electric.} 
 
 A displacement current, like a conduction cur- 
 rent, possesses a magnetic field, or is encircled by 
 lines of magnetic force. (See Field, Magnetic, of 
 an Electric Current. ) 
 
 Current, Electric - The quantity of 
 electricity which passes per second through 
 any conductor or circuit. 
 
 The rate at which a definite quantity of elec- 
 tricity passes or flows through a conductor or 
 circuit. 
 
Cur.] 
 
 137 
 
 [Cur. 
 
 The ratio existing between the electro- 
 motive force, causing the current, and the 
 resistance which may, for convenience, be 
 regarded as opposing it, expressed in terms 
 of quantity of electricity per second. 
 
 The unit of current, or the ampere, is equal to 
 one coulomb per second. (Set Ampere. Coulomb.) 
 
 The word current must not be confounded 
 with the mere act of flowing; electric current 
 signifies rate of flow, and always supposes an 
 electromotive force to produce the current, and a 
 resistance to oppose it. 
 
 The electric current is assumed to flow out 
 from the positive terminal of a source, through 
 the circuit and back into the source at the nega- 
 tive terminal. It is assumed to flow into the 
 positive terminal of an electro-receptive device 
 such as a lamp, motor, or storage battery, and 
 out of its negative terminal; or, in other words, 
 the positive pole of the source is always con- 
 nected to the positive terminal of the electro-re- 
 ceptive device. 
 
 Professor Lodge draws the following com- 
 parison between the motions of ordinary mat- 
 ter, heat and electricity: "Consider the modes 
 in which water may be made to move from place 
 to p'.ace; there are only two. It may be pumped 
 along pipes, or it may be carried about in jugs. 
 In other words, it may travel through matter, or, 
 it may travel with matter. Just so it is with heat, 
 also. Heat can travel in two ways: it can flow 
 through matter, by what is called 'conduction,' 
 or, it can travel with matter, by what is called 
 'convection.' There is no other mode of con- 
 veyance of heat." * * * "For electricity 
 the same is true. Electricity can travel with 
 matter, or it can travel through matter, by con- 
 vection, or by coiMuction, and by no other way." 
 
 In the above, the radiation of heat is apparently 
 lost sight of. 
 
 In the opinion of some, an electric current con- 
 sists of two distinct currents, one of positive and 
 the other of negative electricity, flowing in oppo- 
 site directions. Each of these currents is supposed 
 to be equal in amount to the other. 
 
 The electric current is now regarded as passing 
 through the dielectric surrounding the conductor, 
 rather than through the conductor itself. (See 
 Current, Electric, Method of Propagation of, 
 Through a Circuit.') 
 
 The current that flows or passes in any circuit 
 is, in the case of a constant current, equal to the 
 
 electromotive force, or difference of potential, 
 divided by the resistance, as 
 
 c-t 
 
 K 
 (See Law of Ohm.) 
 
 Current, Electric, Method of Propagation 
 
 of, Through a Circuit When an 
 
 electric current is propagated through a wire 
 or other conductor, it is not sent or pushed 
 through the conductor, like a fluid through 
 a pipe or other conductor, but is, so to speak, 
 rained down on'the surface of the conductor 
 from the medium or dielectric surrounding it. 
 
 Poynting, who has carefully studied this mat- 
 ter, remarks as follows, viz.: "A space contain- 
 ing electrical currents may be regarded as the 
 field where energy is transformed at certain points 
 into the electric or magnetic kind, by means of 
 batteries, dynamos, thermopiles, etc., and in 
 other parts of the field this energy is being again 
 transformed into heat, work done by the electro- 
 magnetic forces, or any other form yielded by 
 currents. 
 
 "Formerly the current was regarded as some- 
 thing traveling in the conductor, and the energy 
 which appeared at any part of the circuit was 
 supposed to be conveyed thither through the 
 conductor by the current. But the existence of in- 
 duced currents and electro-magnetic actions have 
 led us to look on the medium surrounding the 
 conductor as playing a very important part in the 
 development of the phenomena. If we believe in 
 the continuity of the motion of energy, we are 
 forced to conclude that the surrounding _ medium 
 is capable of containing energy, and that it is 
 capable of being transferred from point to point. 
 We are thus led to consider the problem, how 
 does the energy about an electric current pass 
 from point to point; by what paths does it travel, 
 and according to what laws ? Let us take a spe- 
 cific case. Suppose a dynamo at one spot gen- 
 erates an electric current, which is made to operate 
 an electric motor at a distant place. We have 
 here, in the first place, an absorption of energy 
 from the prime motor into the dynamo. We find 
 the whole space bet ween, and around the conduct- 
 ing wires magnetized and the seat of electro- 
 magnetic energy. We have further a retrans- 
 formation of energy in the motor. The question 
 which presents itself for solution is to decide how 
 the energy taken up by the dynamo is trans- 
 mitted to the motor, by what path it travels 
 
Cur.] 
 
 138 
 
 [Cur. 
 
 and according to what laws ? Briefly stated, the 
 tendency of recent views is that this energy is 
 conveyed through the electro-magnetic medium 
 or ether, and that the function of the wire is to 
 localize the direction or to concentrate the flow in 
 a particular path, and thus provide a sink or place 
 in which the energy can be dissipated. * * * " 
 
 Taking again, for instance, the case of the dis- 
 charge of a condenser by a conductor. He says: 
 "Before the discharge we know that the energy 
 resides in the dielectric, between the conducting 
 plates. If these plates are connected by a wire, 
 according to these views, the energy is transferred 
 outwards along the electrostatic, equipotential sur- 
 faces, and moves on to the wire and is there con- 
 verted into heat. According to this view we 
 must suppose the lines of electrostatic induction, 
 running from plate to plate, to move outwards, as 
 the dielectric strain lessens, and while still keep- 
 ing their ends on the plates, to finally converge 
 in on the wire and be there broken up and their 
 energy dissipated as heat." 
 
 In other words, some of the energy of the ex- 
 panding lines of induction is changed into mag- 
 netic energy; this energy is contained in ring- 
 shaped tubes of force, which expand outwards 
 from between the plates and then contract on 
 some other part of the conductor. 
 
 The time of the discharge, then, consists of the 
 following steps, viz. : 
 
 (I.) The time during which the energy of the 
 charge is nearly all electrostatic and is repre- 
 sented by the energy contained in the lines or 
 tubes of electrostatic induction, running from 
 plate to plate of the condenser. 
 
 (2.) The time during which the discharge is at 
 its maximum and the energy consists of two parts, 
 viz.: energy associated with the outward ex- 
 panding lines of electrostatic induction, and energy 
 associated with the closed lines or tubes of mag- 
 netic force, which at first are expanding and after- 
 wards contracting. 
 
 (3.) The time when the energy has been ab- 
 sorbed, or the period in which the energy in the 
 wire or the conductor has either been dissipated 
 in the form of non -luminous radiation or obscure 
 heat. 
 
 (4.) The time during which this non-luminous 
 heat gives up its energy again to the surrounding 
 medium in the shape of heat waves. 
 
 Current, Electro-Therapeutic Polarizing 1 
 
 The current which produces the 
 
 phenomena of electrotonus. (See Electro* 
 tonus.) 
 
 Current, Element of A term 
 
 employed in mathematical discussions to in- 
 dicate a very small part of a current for ease 
 in considering its action on a magnetic needle 
 or other similar body. 
 
 Current, Faradic In electro- 
 therapeutics, the current produced by an in- 
 duction coil, or by a magneto-electric machine. 
 
 A rapidly alternating current, as distin- 
 guished from a uniform voltaic current. 
 
 A voltaic current that 'is rapidly alternated by 
 means of any suitable key or switch is sometimes 
 called a voltaic alternative. The discharge from 
 a Holtz machine is sometimes called a Franklinic 
 Current. (See Alternatives, Voltaic. Current^ 
 Franklinic?) 
 
 Current Filaments. (See Filament, 
 Current.) 
 
 Current, Franklinic A term some- 
 times used in electro-therapeutics for a cur- 
 rent produced by the action of a frictional 
 electric machine. 
 
 The term, Franklinic current, is used in con- 
 tradistinction to Faradic current, or that produced 
 by induction coils, or, in contradistinction to a 
 galvanic or voltaic current, or that produced by 
 a voltaic battery. 
 
 Current, Generation of, by Dynamo-Elec- 
 tric Machine The difference of 
 
 potential developed in the armature coils 
 by the cutting of the lines of magnetic 
 force of the field by the coils, during the rota- 
 tion of the armature. 
 
 
 
 If a loop of wire whose ends are connected to 
 the two-part commutator, shown in Fig. 179, be 
 
 A 
 
 Fig. 779. Induction in Armature Loop. 
 
 rotated in the magnetic field between the magnet 
 poles N and S, in the direction of the large arrow, 
 differences of potential will be generated which 
 
Cur,] 
 
 139 
 
 [Cur. 
 
 will cause currents to 3ow in the direction indi- 
 cated by the small arrows during its motion past 
 the north pole from the top to the bottom, but in the 
 opposite direction during its motion past the south 
 pole from the bottom to the top. If, now, col- 
 lecting brushes rest on the commutator in the 
 positions shown in the Fig. 180. the vertical line 
 180 
 
 Fig. 180. Action of Commutator. 
 
 of the gap between the poles corresponding with 
 the vertical gap between the commutator seg- 
 ments, the currents generated in the loop will be 
 caused to flow in one and the same direction, and 
 B', will become the positive brush, since the end 
 of the loop is connected with it only so long as it 
 is positive. As soon as it becomes negative, from 
 the current in the loop flowing in the opposite 
 direction, the other end, which is then positive, 
 is connected with the positive brush. 
 
 A similar series of changes occur at the nega- 
 tive brush B. 
 
 Theoretically, the neutral points, where the 
 brushes rest, would be in the vertical line coincid- 
 ing with that of the gap between the poles. An 
 inspection of the figure show ; that the neutral 
 line, or the diameter of commutation, is dis- 
 placed in the direction of rotation. (See Commu- 
 tation, Diameter of.) The displacement of the 
 brushes, so necessitated, is called the lead. 
 
 The cause of the lead is the reaction that occurs 
 between the magnetic poles of the field magnets 
 
 Fig i8r Cause of Lead of Brushes, 
 
 and those ( of the armature, the result of which is 
 to displace the field magnet poles, and to cause a 
 change in the density in the field. This is shown 
 in Fig, 181. where the density of the lines of force 
 indicates the position of the diameter of commu- 
 
 tation as being near, or at right angles to the di- 
 ameter of greatest average magnetic density. 
 (See Lead, Angle of. Lag, Angle of.) 
 
 Current-Governor. (See Governor, Cur- 
 rent.) 
 Current, Homogeneous Distribution of 
 
 Such a distribution of a current through 
 
 any conductor in which there is an equal 
 density of current at all portions of any 
 cross-section of the conductor. 
 
 When the flow of a constant current is estab- 
 lished in a solid conducting wire, there is a 
 homogeneous distribution of current in that con- 
 ductor. 
 
 Current, Induced 
 
 The current 
 
 produced in a conductor by cutting lines of 
 force. 
 
 The induced current results from differences of 
 potential produced by electro-dynamic induction. 
 (See Induction, Electro- Dynamic.') 
 
 Current - Induction. (See Induction, 
 Current?) 
 
 Current, Intensity of An old 
 
 term sometimes employed to indicate the 
 current which resulted from a considerable 
 difference of potential, or a great electromotive 
 force. 
 
 This term was also formerly used as synony- 
 mous with strength of current. 
 
 This use of the term is now abandoned. 
 
 Voltaic batteries, connected in series so as to 
 give a considerable difference of potential were 
 spoken of as being connected for intensity. 
 
 This term has also been used for the quantity 
 of electricity conveyed per second across a unit 
 area of cross -section. 
 
 Intensity of current is more properly called 
 density of current. (See Current Density.} 
 
 Current, Intermittent A current 
 
 that does not flow continually, but which flows 
 and ceases to flow at intervals, so that elec- 
 tricity is practically alternately present and 
 absent from the circuit. 
 
 Current, Inverse-Secondary - The 
 make-induced current. (See Current, Make- 
 Induced) 
 
 Current, Jacobi's Unit of Such 
 
 a current that when passed through a volta- 
 meter will liberate a cubic centimetre of 
 
Cr.J 
 
 140 
 
 [Cur. 
 
 oxygen and hydrogen at O degrees C. and 
 760 mm. barometric pressure. 
 
 One Jacobi's unit of current equals * 
 
 10.32 
 ampere. (Obsolete.) 
 
 Current, Make-Induced The 
 
 current induced by a current in its own circuit 
 on making or closing the same. 
 
 The current produced in the secondary of 
 an induction coil on the making or com- 
 pletion of the circuit of the primary. 
 
 The make-induced current is also called the 
 inverse-secondary current, because its direction 
 is opposite to that of the inducing current. 
 
 Current, Make or Break Induced, Dura- 
 tion of The time during which the 
 
 induced inverse or direct -secondary currents 
 continue. 
 
 Blaserna made a number of experiments, which 
 he claims shows : 
 
 (I.) The greater the distance apart of the pri- 
 mary and the secondary, that is, the less their 
 mutual-induction, the less the maximum value of 
 the secondary current, and the greater the delay 
 in establishing that maximum. 
 
 (2.) The delay in establishing the maximum of 
 the break or direct-secondary current is not as 
 great as in the case of the make, or inverse-sec- 
 ondary current. 
 
 (3.) When the coils are near together, the in- 
 duced currents at starting are established by a 
 series of electric oscillations. 
 
 (4 ) The primary current establishes itself by a 
 series of electrical oscillations. 
 
 (5.) That the interposition of dielectric sub- 
 stances, such as glass between '.he coils, Deduces 
 the time between tht making or breaking of the 
 primary current and the beginning of the sec- 
 ondary current. This last conclusion was nega- 
 tived by some experiments of Bernstein. 
 
 Blaserna determined in the case of certain -ex- 
 periments the following value for the durations of 
 the secondary currents : 
 
 Inverse -secondary current lasts 000485 second. 
 
 Direct -secondary current lasts .000275 second. 
 
 Helmholtz contradicts the results of Blaserna, 
 and asserts : 
 
 (i.) That no perceptible difference in the zero 
 points of the currents is produced by varying 
 the distance between the primary and secondary. 
 
 (2 ) That the sparks produced by the breaking 
 
 of the primary last for an appreciable time, some 
 thing like T ^ 5ff to ^VTS of a second. 
 
 (3.) The duration of the break-spark is never 
 constant, but depends in great part on the amount 
 of platinum given off from the contacts at each 
 spark. 
 
 Current-Meter. A form of galvanometer. 
 (See Galvanometer.} 
 
 Current, Momentary A current 
 
 that continues to flow but for a short time. 
 
 Current, Multi-Phase - A rotating 
 current. (.See Current, Rotating.) 
 
 Current, Muscle In electro-thera- 
 peutics, the current flowing through a muscle 
 
 Muscle currents are produced either by stimu 
 lation, or during activity of a muscle. According 
 to L. Hermann, uninjured muscles, or perfectly 
 dead muscles, yield no currents, but such cur- 
 rents result only from an injury, (See Current, 
 Demarcation , ) 
 
 Current, Non-Homogeneous Distribution 
 
 of Such a distribution of current pass- 
 ing through a conductor m which there is an 
 unequal density of current at all portions of 
 any cross-section of the conductor. 
 
 When a rapidly alternating current is passed 
 through any solid conductor, the current density 
 is greater at the surface and less towards the 
 centre. The current distribution in such a con 
 ductor is non -homogeneous, and the want of uni 
 formity of current density is greater as the rapid 
 ity of alternation or periodicity is greater. 
 
 Current, Outgoing The current 
 
 sent out over the line from a station provided 
 with a duple* or quadruplex transmission, as 
 distinguished from the received current. (See 
 Current, Received} 
 
 Current, Periodic A simple 
 
 periodic current. (See Currents, Simple 
 Periodic} 
 
 Current, Periodic, Power of An 
 
 amount of work, per second, equal to the 
 product of the electromotive force taken at 
 successive moments of time during a com- 
 plete cycle, multiplied by the current strength 
 taken at the corresponding moments during 
 the cycle. 
 Since the electromotive force and current in 
 
Car.] 
 
 / 
 
 a periodic circuit may be represented by two 
 simple harmonic functions, the mean value of 
 the two, when of different amplitude and phase, 
 is equal to the product of their maximum value 
 by the cosine of their difference of phase divided 
 by two. 
 
 Current, Polarization In electro- 
 therapeutics, the constant current which when 
 passed through a nerve produces in it the 
 electrotonic st Ue. (See Electrotonus.} 
 
 Current Pulsating A pulsatory 
 
 current. (See Current, Pulsatory?) 
 
 Current, Pulsatory A current, the 
 
 strength of which changes suddenly. 
 
 The pulsatory current usually consists of sudden 
 and distinct impulses, or rushes of current, in 
 contradistinction to an undulatory or harmonically 
 varying current. 
 
 Current, Received The current 
 
 received from the distant end of the line at a 
 station provided with a duplex or quadruplex 
 transmission as distinguished from the out- 
 going, current. 
 
 A term sometimes used in telegraphy to 
 distinguish between currents that come in over 
 the line from a distant station, and those 
 that are sent out to a distant station. 
 
 Current, Rectilinear A current 
 
 flowing through straight or rectilinear por- 
 tions of a circuit. 
 
 In studying the effects of the attractions or repul- 
 sions produced by electric currents the name ex- 
 pressing the peculiarity of shape of any part of 
 the circuit is often applied to the current flowing 
 through that part of the circuit. Thus we speak 
 of a rectilinear current, a sinuous current. 
 
 Current, Reverse-Induced The 
 
 current induced by a current in its own cir- 
 cuit at the moment of making or closing the 
 circuit. 
 
 The current induced in the secondary on 
 closing or making the circuit of the primary. 
 
 This is called the reverse-induced current, be- 
 cause its direction is opposite to that of the current 
 in the inducing circuit. 
 
 Current, Reversed A current whose 
 
 direction is changed at intervals. iSee Cur- 
 rent, Alternating.} 
 
 141 
 
 [Cnr. 
 
 Current Reverser. (See Reverser, Cur- 
 rent?) 
 
 Current, Reversing a Changing the 
 
 direction of an electric current. 
 
 Current, Rotating A term applied 
 
 to the current which results by combin- 
 ing a number of alternating currents, whose 
 phases are displaced with respect to one an- 
 other. 
 
 A rotating current is sometimes called a poly- 
 phase or multiple-phase current, particularly if 
 there are three or more currents combined . 
 
 The rotating current is employed by Tesla, 
 Dobrowolsky and others in a system of distribu- 
 tion by transformers in place of the ordinary 
 alternating current. In practice, three alternating 
 current are combined. The currents and their 
 combination are obtained by means of a specially 
 constructed alternator. When three currents are 
 combined the displacement between each set of 
 phases is 120 degrees. A rotating current, unlike 
 an alternating current, possesses, in a certain 
 sense, a definite direction of flow. Its effect on a 
 magnetic needle is to cause rotation. Hence 
 motors constructed on the principle of rotating 
 currents will start with a load. 
 
 Current, Rotatory - Phase Alternating 
 
 A term sometimes employed for a 
 
 rotating electric current, (See Current, Ro- 
 tating?) 
 
 Current, Secretion . In electro- 
 therapeutics, a current following stimulation 
 of the secretory nerves. 
 
 Current, Simple-Harmonic A term 
 
 sometimes used instead of simple-periodic 
 current. (See Currents, Simple Periodic.} 
 
 Current, Sinuous A term some- 
 times applied to currents flowing through a 
 sinuous conductor. 
 
 Sinuous currents exert the same effects of attrac- 
 tion or repulsion on magnets, or on neighboring 
 circuits, as would a rectilinear current whose 
 length is that of the axis of such sinuous current. 
 
 This can be shown by approaching the circuit 
 A' B', Fig. 182, consisting of the sinuous con- 
 ductor A', and rectilinear conductor B', to the 
 movable conductor A B C, on which it produces 
 110 effect. The current A', therefore, neutral- 
 
Cur.] 
 
 142 
 
 [Cur. 
 
 izes the effects of the current B'; or, it is equal to 
 it in effect. 
 
 Fig. 182. Rectilinear Equivalent of Sinuous Current. 
 
 In calculating the effects of sinuous currents it 
 is convenient to consider them as consisting of a 
 
 Fig. 183. Sinuous Currents. 
 
 succession of short, straight portions at right an- 
 gles to one another, as shown in Fig. 183. 
 
 Current, Steady A current whose 
 
 Strength does not vary from time to time. 
 
 In a steady current the quantity of electricity 
 flowing through each unit of area of the equi- 
 potential surface of the conductor is the same for 
 each succeeding interval of time. Such a current 
 is sometimes called a uniformly distributed cur- 
 rent. 
 
 Current Streamlets. (See Streamlets, 
 Current?} 
 
 Current Strength. The product obtained 
 by dividing the electromotive force by the 
 resistance. 
 
 The current strength for a constant current 
 according to Ohm's law is 
 
 Current strength is proportional to the amount 
 of the magnetic or chemical (electrolytic) effects 
 it is capable of producing. 
 
 For a simple-periodic current, the current 
 strength necessarily varies from time to time. 
 
 The average current strength of a simple, 
 periodic current is equal to the average impressed 
 electromotive force divided by the impedance. 
 (See Impedance. ) 
 
 The maximum current strength is equal to the 
 maximum impressed electromotive force divided 
 by the impedance. 
 
 Current, to Transform a To 
 
 change the electromotive force of a current 
 by its passage through a converter or trans- 
 former. 
 
 To convert a current. 
 
 Current, Transforming a Chang- 
 ing the electromotive force of a current by its 
 passage through a converter or transformer. 
 
 Current, Undulating An undu- 
 
 latory current. (See Currents, Undulatory.} 
 
 Current, Uniformly-Distributed 
 
 A term sometimes employed in the sam: 
 sense as steady current. (See Current. 
 Steady.) 
 
 Current, Unit Strength of Such 
 
 a strength of current that when passed 
 through a circuit one centimetre in length, 
 arranged in an arc one centimetre in radius, 
 will exert a force of one dyne on a unit mag- 
 net pole placed at the centre. 
 
 This absolute unit is equal to ten amperes or 
 practical units of current. (See Ampere.) 
 
 Current, Variable Period of 
 
 The period which exists while an electric 
 current is being increased or decreased in 
 strength, or while it' is being reversed. 
 
 Currents, Action Physiological cur- 
 rents obtained during the activity of a muscle 
 or nerve. 
 
 Currents, After In electro-thera- 
 peutics, currents produced in nervous or 
 muscular tissue when a constant current, 
 which has been flowing through the same, 
 has been stopped. 
 
 After currents are due to internal polarization. 
 
 Currents, Alternating-Primary 
 
 The currents employed in the primary of a 
 
Cur.] 
 
 143 
 
 [Cur. 
 
 transformer to induce alternating currents in 
 the secondary. (See Transformer?) 
 
 Currents, Alternating-Secondary 
 
 The currents induced in the secondary of a 
 transformer by the alternating currents in the 
 primary. (See Transformer) 
 
 Currents, Alternating, Shifting of Phase 
 
 of (See Phase, Shifting of, of Alter- 
 nating Currents?) 
 
 Currents, Amperian The electric 
 
 currents that are assumed in the amperian 
 theory of magnetism to flow around the mole- 
 cules of a magnet. (See Magnetism, Amperes 
 Theory of.) 
 
 The amperian currents are to be distinguished 
 from the eddy, Foucault^ or parasitical currents,. 
 since, unlike them, they are directed so as to pro 
 duce useful effects. (See Currents, Eddy.) 
 
 It is not believed that the amperian currents 
 are produced in magnetizable substances by the 
 act of magnetization. The atoms or molecules 
 were magnetic originally. All the magnetizing 
 force does is to arrange the molecules or atoms, 
 or to set them in one and the same direction. 
 
 Currents, Angular Currents flow- 
 ing through circuits that cross or are inclined 
 to one another at any angle, (See Dynamics, 
 Electro) 
 
 Currents. Atomic A term some- 
 times used instead of molecular or amperian 
 currents. (See Currents, Amperian) 
 
 Currents, Attractions and Repulsions 
 
 Of The mutual attractions or repul- 
 sions exerted by currents on one another 
 through the interaction of their magnetic 
 fields. (See Dynamics, Electro) 
 
 Currents, Commuted Electric cur- 
 rents that have been caused to flow in one 
 and the same direction. (See Commutator) 
 
 Currents, Commuting Causing 
 
 several currents to flow in one and the same 
 direction. 
 
 Currents, Component The two or 
 
 more currents into which it may be conceived 
 that a single current can be divided, so as 
 to produce the same effects of attraction or 
 repulsion that the single current would do. 
 
 The idea of component currents is based on the 
 similar idea ot the components of any single 
 force. 
 
 Currents, Continuity of The 
 
 freedom from variation in current strength or 
 current direction. 
 
 Currents, Convection Currents 
 
 produced by the bodily carrying forward of 
 static charges in convection streams. (See 
 Streams, Convection) 
 
 In a convection current, the static charge is 
 bodily carried forward. 
 
 Rowland has shown experimentally that a 
 moving electric charge is the equivalent of an 
 electric current. He rotated a gilded ebonite 
 disc between two gilt glass discs, near which 
 were placed a number of delicate magnetic 
 needles. When certain rapidity of rotation was 
 obtained, the discs were found to affect the mag- 
 netic needles the same as would a current of elec- 
 tricity flowing in a circular conductor, whose 
 form coincided with the periphery of the disc. 
 
 Currents, Converted Electric cur~ 
 
 rents changed either in their electromotive 
 force or in their strength, by passage through 
 a converter or transformer. (See Trans- 
 former) 
 
 Currents, Converting Changing 
 
 the electromotive force of currents by their 
 passage through a converter or transformer. 
 .(See Transformer) 
 
 Currents, Diaphragm Electric cur- 
 rents produced by forcing a liquid through 
 the capillary pores of a diaphragm. (See 
 Osmose, Electric) 
 
 Currents, Earth 
 
 Electric currents 
 
 flowing through the earth, caused by a differ- 
 ence of potential at different parts. 
 
 The causes of these differences of potential are 
 various and are not well understood. 
 
 Currents, Eddy Useless currents 
 
 produced in the pole pieces, armatures, field- 
 magnet cores of dynamo-electric machines or 
 motors, or other metallic masses, either by 
 their motion through magnetic fields, or by 
 variations in the strength of electric currents 
 flowing near them. 
 
 Sensible eddy currents are producd in the mass 
 
Cur.l 
 
 144 
 
 [Cur. 
 
 of the conducting wire on the armature of a 
 dynamo-electric machine when the wire is com- 
 paratively heavy. 
 
 Such currents are called eddy currents, heal 
 currents, Foucault currents, or parasitical cur- 
 rents. They form closed -circuits of comparatively 
 low resistance, and tend to cause undue heating of 
 armatures or pole pieces. They not only cause a 
 
 Fig, 184. Foucault Currents in Pole Pieces. 
 
 useless expenditure of energy, but interfere with 
 the proper operation of the device. 
 
 To reduce them as far as practicable, the pole 
 pieces, armature cores or armature wires, are 
 laminated. (See Core, Lamination of.) 
 
 These local currents are perhaps preferably 
 called Foucault currents when they take place 
 in magnetic cores, pole pieces or armature 
 cores, and eddy currents when they occur in the 
 armature wire or conductor. When the armature 
 conductor is made up of copper bars, for exam- 
 ple, the eddy currents in the latter are usually 
 considerable. 
 
 Since Foucault currents in dynamo-electric ma- 
 chine cores are due to variations in the magnetic 
 
 Foucault Currents in Pole Pieces. 
 
 strength of the field magnets, or of the arma- 
 ture, they will be of greatest intensity when the 
 changes in the magnetic strength are the greatest 
 and most sudden. 
 
 These changes are most marked, and conse- 
 quently the Foucault currents are strongest at those 
 corners of the pole pieces of a dynamo from which 
 the armature is moved in its rotation, as will be 
 seen from an inspection of Fig. 184. 
 
 Fig. 185, shows Foucault currents generated in 
 pole pieces. 
 
 Currents, Eddy-Conduction A 
 
 term employed for ordinary eddy currents in 
 conductors, in order to distinguish them from 
 eddy-displacement currents. (See Currents, 
 Eddy-Displacement.) 
 
 Currents, Eddy Deep Seated Eddy 
 
 currents set up in the mass of a conductor sub- 
 jected to electro-dynamic induction in con- 
 tradistinction to superficially seated eddy cur- 
 rents. (See Currents, Eddy, Superficial.) 
 
 Currents, Eddy-Displacement 
 
 Eddy currents produced in the mass of a 
 dielectric or insulator, when lines of magnetic 
 or electrostatic force pass through the di- 
 electric or insulator. 
 
 Eddy-displacement currents are produced in 
 a dielectric or non-conductor, when it is moved 
 across a magnetic field, so as to cut the lines of 
 magnetic force. 
 
 Eddy displacement currents would also occur' 
 if a dielectric is subjected to varying electrostatic 
 induction. 
 
 Currents, Eddy, Superficial Eddy 
 
 currents produced in conducting substances 
 that are limited to the outer layers thereof. 
 
 The eddy currents produced by alternating 
 currents are superficial if the alternating currents 
 are sufficiently rapid. The oscillatory currents pro- 
 duced during the discharge of a Leyden jar are 
 more superficial in proportion as the discharge 
 takes place rapidly. When currents are pro- 
 duced in a magnetizable body by the discharge 
 of a Leyden jar, they are more and more super- 
 ficial, as the discharge of the jar is more and more 
 rapid. The reason a slow discharge of a jar or 
 condenser produces a greater magnetizing effect 
 is, because of the checking or screening action 
 the superficial eddy currents exert on the interior 
 of the mass of the magnetizable substance when 
 the discharge is very rapid. 
 
 Currents, Electrotonic - In electro- 
 therapeutics, currents due to internal polariza- 
 tion in the nerve fibre between the conduct- 
 ing core of the nerves and the enclosing 
 sheaths. 
 
 Currents, Extra Currents pro- 
 duced in a circuit by the induction of the 
 current on itself on the opening or closing of 
 
Cur.] 
 
 145 
 
 the circuit. (See Currents, Extra. Induc- 
 tion, Self.) 
 
 The extra current induced on breaking, flows 
 in the same direction as the original current and 
 acts to strengthen and prolong it.. 
 
 The extra current induced on making or com- 
 pleting a circuit flows in the opposite direction 
 to the original current and tends to oppose or re 
 tard the current. 
 
 Both of these currents are called induced or 
 extra, currents. The former is called the direct- 
 induced current, and the latter the reversed-in- 
 duced current. (See Current, Direct-Induced. 
 Current, Reversed-Induced.') 
 
 In order to distinguish this induction from that 
 produced in a neighboring conductor by the pas- 
 sage of the electric current, it is called selj -induc- 
 tion. (See Induction, Self. Induction, Mutual.} 
 
 The effect on a telegraphic line of the self-in- 
 duced or extra currents is to decrease the speed ot 
 signaling by retarding the beginning of a signal, 
 and prolonging its cessation . 
 
 The greater the number of turns of wire in a 
 circuit, or magnet, and the greater the mass ot 
 iron in its core, the greater the strength of the 
 extra currents. 
 
 Currents, Foucault A name some- 
 times applied to eddy currents, especially in 
 armature cores. (See Currents, Eddy?) 
 
 Currents, Heating Effects of The 
 
 heat produced by the passage of an electric 
 current through any circuit. (See Heat, Elec- 
 tric) 
 
 Currents, Imbibition Currents 
 
 produced in tissues by the imbibition or ab- 
 sorption of a fluid. 
 
 Imbibition currents are a species of diaphragm 
 currents. The absorption of a fluid at the 
 demarcation surface of an injured nerve or 
 muscle, or at the contracted portion of muscles, 
 produces imbibition currents. 
 
 Such currents are also produced in plants by 
 the movement of fluids produced by bending the 
 stalk or leaves, or by active movements of certain 
 sensitive plants. 
 
 Currents, Induced-Molecular or Atomic 
 
 Currents induced in the atoms or 
 
 molecules of a magnetizable substance on its 
 being brought into a magnetic field. 
 
 These currents are called induced-molecular 
 or induced-atomic currents in order to distin- 
 
 guish them from the molecular, atomic or amperian 
 currents, or the currents which are assumed to be 
 always- present. It is by the presence of these 
 assumed induced-molecular currents that the 
 phenomena of diamagnetism are explained by 
 Weber. (See Diamagnetism, Weber's Theory 
 of.) 
 
 Currents, Local A name sometimes 
 
 applied to eddy currents. (See Currents, 
 Eddy.) 
 
 Currents, Molecular or Atomic 
 
 A term sometimes employed for amperian 
 currents. (See Currents, Amperian.) 
 
 Currents, Natural A term some- 
 times applied to earth currents. (See Cur' 
 rents. Earth?) 
 
 Currents, Negative A term em- 
 ployed in single-needle telegraphy for cur- 
 rents sent over a line in a negative direction 
 by depressing a key that connects the line 
 with the negative pole of a battery and so 
 deflects the needle to the left, (See Teleg- 
 raphy, Single-Needled) 
 
 Currents, Network of A term 
 
 sometimes applied to a number of shunt or 
 derived circuits. (See Circuit, Sktmt. Cir- 
 cuit, Derived. Laws, Kirchhoff's^) 
 
 Currents of Motion. A term sometimes 
 employed in electro-therapeutics for the cur- 
 rents of electricity that traverse healthy 
 muscle or nerve tissue during the sudden con- 
 traction or relaxation thereof. 
 
 The existence of these currents is denied by 
 some. 
 
 Currents of Rest. A term sometimes em- 
 ployed in electro-therapeutics for the cur- 
 rents of electricity that traverse healthy 
 muscle or nerve tissue while the muscles are 
 passive. 
 
 The existence of these currents is denied by 
 some. 
 
 Currents, Orders of Induced elec- 
 tric currents named from the order in which 
 they are induced, as currents of the first, 
 second, third, fourth, etc., orders. 
 
 An induced current can be caused to induce an- 
 other current in a neighboring circuit, and this a 
 third current, and so on. Such currents are dis- 
 
Cur.] 
 
 146 
 
 [Car. 
 
 tinguished by the term, currents of the second, 
 third, fourth, etc., order. (See Coils, Henry's.) 
 
 Currents, Parasitical A name 
 
 sometimes applied to eddy currents. (See 
 Currents, Eddy?) 
 
 Currents, Positive A term em- 
 ployed in single-needle telegraphy for currents 
 sent over the line in a positive direction by de- 
 pressing a key that connects the line with 
 the positive pole of a battery and so deflects 
 the needle to the right. (See Telegraphy, 
 Single-Needled) 
 
 Currents, Reversed A name some- 
 times applied to alternating currents. (See 
 Current, Alternating?) 
 
 Currents, Secondary The currents 
 
 produced by secondary batteries in contra- 
 distinction to the currents produced by 
 primary batteries. 
 
 The currents produced by the secondary 
 conductor of an induction coil, as distinguished 
 from the currents sent into the primaries. 
 
 This second use of the term secondary current 
 is more usual. 
 
 Currents, Self-Induced A current 
 
 produced by self-induction. 
 
 An extra current. (See Induction, Self. 
 Currents, Extra?) 
 
 Currents, Simple Periodic Cur- 
 rents, the flow of which is variable, both in 
 strength and duration, and in which the flow 
 of electricity, passing any section of the con- 
 ductor, may be represented by a simple peri- 
 odic curve. 
 
 A current of such a nature that the con- 
 tinuous variation of the flow of electricity 
 past any area of cross-section of the con- 
 ductor, or the variations in the electromotive 
 force of which can be expressed by a simple- 
 periodic or harmonic curve. (See Curve, 
 Simple-Harmonic?) 
 
 Alternate currents are simple-periodic currents. 
 
 The average current strength of simple-periodic 
 currents is equal to the average impressed electro- 
 motive force divided by the impedance. 
 
 The transmission of rapidly varying or sim- 
 ple-periodic currents through conductors differs 
 rery greatly from the transmission of steady cur- 
 
 rents. With a steady current, the current density 
 is the same for all areas of cross-section of the 
 conductor. For a rapidly intermittent current, 
 the current density is greater near the surface, 
 and when the rate of intermission is sufficiently 
 great, the current is entirely absent at the centre 
 of the conductor. 
 
 Lord Rayleigh has shown that when the rate ot 
 intermission is 1,050 per second, the effective re- 
 sistance of a wire i6omm. in length, and 30 mm. 
 in diameter, is i . 84 times its resistance to steady 
 currents. He found that the increase of resist- 
 ance is greater in the case of conductors of great 
 diameter than in those of small diameter. 
 
 As regards the character of conductor best 
 suited for transmitting rapidly alternating cur- 
 rents, it can be shown : 
 
 (I.) That for transmitting alternate currents o< 
 moderate frequency, say of about 1,000 per sec- 
 ond, copper conductors should be used in prefer- 
 ence to rods of iron. 
 
 (2.) That the conductor should be in the form 
 of thin strips, or if tubular, of thin walls. 
 
 (3.) That the mere stranding of the conductor, 
 z. e., forming it of separate insulated conductors 
 connected in parallel, will be of no effect in pre 
 venting the current from acting on the outside of 
 the conductor, unless the conductor be arranged 
 in the form of a cable, in which one part forms a 
 lead, and another part the return. 
 
 Stephan draws the following analogy between 
 the flow of alternating currents in a conductor 
 and the flow of heat in a hot wire : 
 
 " Suppose a wire or conductor, uniformly heated 
 from centre to circumference, be suddenly taken 
 into a space where the temperature is high, the 
 outer portions of the wire first rise in temperature, 
 and afterwards the inner portions. In the case of 
 a conductor of circular cross-section, the heat 
 penetrates successive concentric layers. The same 
 phenomena occur when an electromotive force is 
 suddenly set up between the ends of a cylindrical 
 conductor. The current gradually penetrates the 
 conductor from the outside to the centre. 
 
 " Now suppose the heated wire is carried into a 
 cooler space, the heat waves pass out radially 
 from the centre towards the circumference. The 
 cooling wire corresponds to the case of a con- 
 ductor in which the external electromotive force 
 is suddenly removed." 
 
 According to this conception, the heat conduct- 
 ing power of any substance corresponds to its 
 electrical conducting power. 
 
Cur.] 
 
 147 
 
 [Cur. 
 
 According to Stephan, in the case of a con- 
 ductor of iron of 4 mm. in diameter, traversed by 
 an alternating current of 250 alternations per 
 second, the current density on the surface is about 
 twenty-five times as great as that at its axis. 
 
 Where the conductor is of non-magnetic mate- 
 rial, the difference in the current density is not s>o 
 marked. 
 
 Rapidly intermittent currents produce a real 
 increase in the resistance of the conductor, which 
 must not be confused with the fact that the impe- 
 dance is greater than the ohmic resistance, but 
 rather as an actual increase in the rate at which 
 energy is dissipated per unit of current. 
 
 Since current density is greatest at the outside 
 portions of a conductor, and the central portions 
 are nearly, if not entirely, deserted by the cur- 
 rent, we may regard the conductor as having 
 the ohmic resistance of a hollow cylinder of the 
 same diameter as the conductor, with a cor- 
 respondingly smaller area of cross-section, and 
 therefore, of greater ohmic resistance per unit of 
 length. 
 
 The condition of affairs in the case of a con- 
 ductor in which a current of electricity is begin- 
 ning to flow, is now very generally regarded 
 somewhat as follows, viz.: 
 
 The current begins at the surface of the con- 
 ductor, and more or less slowly soaks through 
 towards the centre. If the current is constant, the 
 current soon reaches the deepest layers; but, if it 
 is rapidly intermittent, before it can soak very far 
 into the conductor towards its axis, it is turned 
 back towards the surface, and so becomes con- 
 fined to layers which will be more and more super- 
 ficial, as the rapidity of reversal increases. 
 
 Therefore, for convenience, we may regard a 
 solid conductor, through which a rapidly inter- 
 mittent current of e'ectricity is flowing, as being 
 practically converted into a hollow cylinder of 
 the same diameter as the solid conductor, the 
 area of cross -section of which hollow cylinder 
 becomes smaller and smaller, as the rapidity of 
 alternation is increased. 
 
 Another, and perhaps the more correct concep 
 tion of the condition of affairs in a solid conductor 
 traversed by a rapidly alternating current of elec- 
 tricity, has been pointed out by Maxwell, and after- 
 wards by Heavyside, Rayleigh and Hughes. This 
 conception is to regard the central portions of the 
 conductor as possessing a counter electromotive 
 force greater than the outer portions. The entire 
 current flowing across any section of a conductor 
 
 miy be regarded as made up of little current 
 streamlets, parallel to one another. 
 
 The central streamlets, or filaments, from their 
 mutual induction on one another, experience a 
 greater resistance in reaching their full strength 
 than the surface filaments do. Taken in this 
 sense, we may state generally that the transmis- 
 sion of rapidly alternating currents through con- 
 ductors depends on the inductance, rather than 
 on the resistance; but for steady currents, it de- 
 pends more on the resistance than on the induct- 
 ance. 
 
 In periodic or oscillatory currents, as those 
 produced by the discharge of a Leyden jar, or 
 condenser, the surface streamlets have a current 
 density far greater than the central streamlets. 
 
 The true or ohmic resistance of the circuit is a 
 minimum when the current is uniformly distrib- 
 uted through all parts of the cross-section of the 
 conductor, and the dissipation of energy through 
 the generation of heat is less than for any other 
 distribution. 
 
 The conception of a periodic current flowing 
 through a conductor, starting from the surface 
 and gradually soaking in towards the centre, 
 regards the energy of an electric current not as 
 being pushed through the conductor, as water 
 through a pipe, but as actually being absorbed at 
 its surface, from the surrounding dielectric, or as 
 being, so to speak, rained down on the conductor 
 from the space outside of it. 
 
 Currents, Swelling In electro- 
 therapeutics, currents that begin weak and are 
 gradually made stronger and then weaker. 
 
 Currents, Swelling-Faradic A 
 
 term employed in electro-therapeutics for fara- 
 dic currents that are caused to gradually in- 
 crease in strength and then to gradually de- 
 crease to zero strength. 
 
 Currents, Transient Currents that 
 
 are but of momentary duration. 
 
 Currents, Undnlatory Currents the 
 strength and direction of whose flow gradually 
 change. 
 
 The term undulatory currents is used in con- 
 tradistinction to pulsatory currents, in which the 
 strength changes suddenly. In actual practice, 
 such currents differ from undulatory currents 
 more in degree than in kind, since, when sent 
 into a line, the effects of retardation tend to 
 obliterate, to a greater or less extent, the sudden 
 
Cur.] 
 
 148 
 
 [Cur. 
 
 differences in intensity on which their pulsatory 
 character depends. 
 
 The currents produced in the coils of the Sie- 
 mens magneto-electric key, in which the me- 
 chanical to-and-fro motion of the key sends elec- 
 trical impulses into the line, are, in point of fact, 
 undulatory in character, when they follow one an- 
 other rapidly. 
 
 The currents in most dynamo-electric machines, 
 the number of whose armature coils is compara- 
 tively great, are, so far as the variations in their 
 intensity or strength are concerned, undulatory 
 in character even when non-commuted. 
 
 The currents on all telephone lines that trans- 
 mit articulate speech are undulatory. This is 
 true, whether the transmitter employed merely 
 varies the resistance by variations of pressure, or 
 actually employs makes-and-breaks that rapidly 
 follow one another. (See Current, Pulsatory. 
 Current, Intermittent.') 
 
 The ballistic curve has a smaller vertical height 
 than the parabola. The projectile also has a 
 
 Curtain, Auroral 
 
 A sheet of 
 
 auroral light having the shape of a curtain. 
 (See Aurora Borealis^) 
 
 Curve, Asymptote of A straight 
 
 line which continually approaches a curved 
 line, but meets or becomes tangent to such 
 curved line only at an infinite distance. 
 
 In Fig. 186, the curve C D, continually ap- 
 proaches the asymptote y z, but never meets it. 
 
 It is at first difficult to un- 
 derstand how one line can 
 continually approach an- 
 other and yet never meet it. 
 But it will be readily under- _ 
 stood if it is remembered y '* 
 
 that in all cases of asymp- Fig- z86. Asymptote 
 totic approach each advance "? Curve - 
 
 becomes smaller and smaller. 
 
 This mathematical conception is like a value 
 which, although constantly reduced to one-half 
 of its former value, is nevertheless never reduced 
 to zero or no value. 
 
 Curve, Ballistic The curve ac- 
 tually described by a projectile thrown in 
 any other than a vertical direction through 
 the air. 
 
 The path of a projectile in a vacuum is a para- 
 bola that is, the path A E B, Fig. 187. In air, 
 the effects of fluid resistances cause the projectile 
 to take the path A C D, called a ballistic curve. 
 
 Fig. l8j. Ballistic Curve. 
 
 smaller vertical range. Instead of reaching the 
 point B, it continually approaches the perpen- 
 dicular E F. 
 
 Curve, Characteristic A diagram 
 
 in which a curve is employed to represent 
 the ratio of certain varying values. 
 
 The electromotive force generated in the arma- 
 ture coils of a dynamo-electric machine, when the 
 magnetic field is of a constant intensity, is theo- 
 retically proportional to thft speed of rotation. In 
 practice this is modified by a number of circum- 
 stances. 
 
 The relation existing between the speed 
 and electromotive force may be graphically rep- 
 resented by referring the values to two straight 
 lines, one horizontal and the other vertical, called 
 respectively the axes of abscissas and ordinates. 
 (See Abscissas, Axis of.} If, in a given case, the 
 number of revolutions 
 is marked off along 
 the horizontal line 
 from the point o, Fig. 
 188, in distances from 
 o, proportional to the 
 number of revolu- 
 tions, and the corre- 
 sponding electromo- 
 tive forces are marked 
 off along the vertical line in distances from o, 
 proportional to the electromotive forces, the 
 points where these lines intersect will form the 
 characteristic curve as shown in Fig. 188. 
 
 Curve, Characteristic, of Parallel Trans- 
 former A curve so drawn that its 
 
 ordinate and abscissa at any point represent 
 the secondary electromotive force and the sec- 
 ondary current of a multiple connected trans- 
 former, when the resistance of the secondary 
 circuit has a certain definite value. 
 
 With a constant electromotive force in the pri 
 
 600 
 
 Revolutions. 
 
 Fig. z88. Characteristic 
 Curve. 
 
Car.] 
 
 149 
 
 [Cur. 
 
 mary circuit, i. <?., with the transformers in parallel, 
 the characteristic curve is a straight line parallel 
 to the axis of the current. This curve, as shown 
 in Fig. 189, is practically a straight line. The par- 
 allel transformer will be 
 practically self- regulating 
 under a constant primary 
 electromotive force. 
 
 According to Forbes, if 
 a transformer has its lamp pf gt 7< y 9 . Character- 
 load in parallel with the istic of Parallel Trans- 
 secondary circuit, the ex- former. 
 tinction of its lamps will decrease the efficiency 
 of the transformer. The efficiency is therefore 
 less for light loads than for heavy loads of parallel 
 lamps up to a certain point. 
 
 Curve, Characteristic, of Series Trans- 
 former A curve so drawn that its 
 
 ordinate and abscissa at any point represent 
 the secondary electromotive force and second- 
 ary current of a series-connected transformer, 
 when the resistance of the secondary current 
 has a certain definite value. 
 
 Fig. 190 shows characteristic curve of a series 
 
 Fig. I go. Characteristic of Series Transformer. 
 
 transformer. O a, is drawn perpendicular to the 
 line representing the secondary current, and a b, 
 perpendicular to O a, represents the correspond- 
 ing secondary electromotive force. The various 
 positions of b, as different values are given to O a, 
 produce the elliptic curve which is the character- 
 istic curve of the series transformer. 
 
 " A series transformer, " says Fleming, "with 
 a core sufficiently large to avoid saturation, can 
 never be self-regulating if so used. It can only 
 be made self-regulating with a non saturated core, 
 when working near the extremities of its charac- 
 teristic, either with a small secondary current 
 or a low electromotive force. Both of these con- 
 ditions are uncommercial." 
 
 A curve in which the life of an electric 
 lamp is represented by means of abscissas and 
 ordinates proportional to the life in hours and 
 the candle-power or the volts respectively. 
 
 Curve, Logarithmic 
 
 A curve in 
 
 which the rate of increase or decrease of the 
 
 ordinate is proportional to the ordinate itself. 
 
 On the line O X, Fig. 191, mark off the time 
 
 Curve, Life, of Incandescent Lamp 
 
 M 
 Fig; iqi. Logarithmic Curve. 
 
 in lengths, reckoned from O. Represent the 
 
 current strength by lines drawn vertically to the 
 
 p 
 time-line. Let O Y, equal C = fr 
 
 Applying the electromotive force, the current 
 grows in the wire as represented by the graphic 
 curve. 
 
 According to Fleming, the growth of this cur- 
 rent takes place according to the following law, 
 viz.: "The current strength at any instant, 
 added to the rate of growth of the current strength 
 at that instant multiplied by the time-constant, is 
 equal to the current which would exist if induc- 
 tion were zero. ' ' 
 
 Curve, Permeability A curve repre- 
 senting the magnetic permeability of a mag- 
 netic substance. 
 
 There is a certain temperature for every para- 
 magnetic substance, at which its permeability is 
 no greater than that of air. This temperature 
 for iron is reached at about 750 degrees C.; for 
 nickel, at about 400 degrees C. 
 
 Curve, Simple-Harmonic The 
 
 curve which results when a simple-harmonic 
 motion in one line is compounded with a uni- 
 form motion in a straight line, at right angles 
 thereto. 
 
 A harmonic curve is sometimes called a curve 
 of sines, because the abscissas of the curve are 
 proportional to the times, while the ordinates are 
 proportional to the sines of the angles, which are 
 themselves proportional to the times. 
 
Car.] 
 
 150 
 
 [Cut. 
 
 Carres, Isochasmen Curves drawn 
 
 on the earth's surface between zones having 
 equal frequency of auroral discharges. 
 
 The isochasmen curves are nearly at right 
 angles to the magnetic meridian. 
 
 Curves, Magnetic 
 
 Curved lines 
 
 showing the direction of the lines of mag- 
 netic force in any field, formed by sprinkling 
 iron filings on a sheet of paper or glass held 
 in the field of a magnet, and gently tapping 
 the support so as to permit the filing* to prop- 
 erly arrange themselves. (See Figures, 
 Magnetic?) 
 
 Cut-In, To To introduce an electro- 
 receptive device into the circuit of an electric 
 source by completing or making the circuit 
 through it. 
 
 Cut-Off, Automatic Gas A device 
 
 for automatically cutting out the battery 
 from an electric gas-lighting circuit on the 
 accidental grounding of the circuit. 
 
 Unless the battery is disconnected from the cir- 
 cuit on the establishing of a ground, the battery 
 will polarize and soon become useless. 
 
 Cut-Out, A 
 
 A device by means of 
 
 which an electro-receptive device or loop may 
 be thrown out of the circuit of an electric 
 source. 
 
 In any system of light or power distribution, a 
 cut out is generally placed outside a. building 
 into which a loop or branch of the main cux . '.t 
 runs, so as to permit that loop or branch to be 
 readily disconnected therefrom. In the same way 
 cut-out keys or switches are generally placed in 
 the circuit of the loop and each electro-receptive 
 device. 
 
 Cut-Out, Air-Space A modified 
 
 form of paper cut-out, in which the disc of 
 paper or mica is replaced by the resistance of 
 an air-space. 
 
 Although the resistance of an air-space is so 
 high as to be practically immeasurable, yet it is 
 overcome or broken by a much lower differ- 
 ence of potential than an equal thickness of 
 paper or mica. (See Path, Alternative. Cut- 
 Out, Film.) 
 
 Cut-Out, Automatic Any device 
 
 that will automatically cut-out, or remove, a 
 translating device, or an electric source, from 
 an electric circuit, whenever any predeter- 
 mined effect is produced. 
 
 Cut-Out, Automatic, for Multiple-Con- 
 nected Electro-Receptive Devices 
 
 A device for automatically cutting an electro- 
 receptive device, such as a lamp, out of the 
 circuit of the leads. 
 
 Automatic cut-outs for incandescent lamps, 
 when connected to the leads in multiple-arc, con- 
 sist of strips of readily melted metal called safely 
 fuses, which on the passage of an excessive cur- 
 rent fuse, and thus automatically break the cir- 
 
 Fig. IQ2, Ceiling Cut- Out. 
 
 cuit in that particular branch. (See 
 Safety.) 
 
 A form of ceiling cut-out, made of porcelain, is 
 shown in Fig. 192, with the two halves separated 
 
 Fig. TQ3. Ceiling Cut-Out. 
 
 to show interior details, and in Fig. 193, with the 
 two halves placed together. 
 
Cut] 
 
 151 
 
 [Cyc. 
 
 Cut-Out, Automatic, for Series-Connected 
 
 Electro-Receptive Devices A device 
 
 whereby an electro-receptive device, such 
 as an electric arc lamp, is, to all intents and 
 purposes, automatically cut out, or removed 
 from the circuit, by means of a shunt of low 
 resistance, which permits the greater part of 
 tne current to flow past the lamp. 
 
 It will be observed that the lamp, though still in 
 the circuit, is to all practical intents cut out from 
 the same, since the proportion of the current 
 that now passes through it is too small to oper- 
 ate it. 
 
 In most series arc lamps, cut-outs are oper- 
 ated by means of an electro-magnet placed in a 
 shunt circuit of high resistance around the car- 
 bons. If the carbons fail to properly feed, the 
 arc increases in length and consequently in resist- 
 ance. More current passes through the shunt 
 magnet, until finally, when a certain predeter- 
 mined limit is reached, the armature of the elec- 
 tro-magnet is attracted to the magnet pole and 
 mechanically completes the short circuit past the 
 lamp. 
 
 In some automatic cut-outs the fusion of a 
 readily fused wire, placed in a shunt circuit 
 arrunu the carbons, permits a spring to complete 
 the shor : circuit. 
 
 The automatic cut-out prevents the accidental 
 extinguishing of any single lamp in a series cir- 
 cuit from extinguishing the remaining lamps on 
 that circuit. 
 
 Cut-Out, Automatic Time A 
 
 device arranged so as to automatically cut out 
 a translating device, or an electric source, from 
 a circuit, at the end of a certain predetermined 
 time. 
 
 Cut-Out, Duplex A cut-out so 
 
 arranged that when one bar or strip is fused 
 or melted by an abnormal current another can 
 be immediately substituted for it. 
 
 Cut-Out, Film A cut-out in which 
 
 a film, or sheet of paper or mica, is interposed 
 between a line plate and an earth plate, which, 
 when punctured by a spark, short circuits the 
 instruments on the line. 
 
 Cut-Out, Main-Line An auto- 
 matic cut-out placed on the main line. (See 
 Cut-Out, Automatic?) 
 
 A form of main-line cut-out is shown in Fig. 
 
 Fig. 194. Main-Line Cut-Out, 
 
 194. The fuses are shown as attached to the fuse- 
 block. 
 
 Cut-Out, Paper ' A term sometimes 
 
 employed instead of film cut-out. (See Cut- 
 Out, Film.} 
 
 Cut-Out, Kosette A rosette for an 
 
 electrolier, containing a cut-out. (See Ro- 
 sette} 
 
 Cut-Out, Spring-Jack A device 
 
 similar in general construction to a spring- 
 jack, but employed to cut out a circuit. 
 
 An insulated plug is thrust between spring 
 contacts, thus breaking the circuit by forcing 
 them apart. 
 
 Cut Out, To To remove an elec- 
 tro-receptive device from the circuit of an 
 electric source by disconnecting or diverting 
 the circuit from it. 
 
 Cutting Lines of Force. (See Force, 
 Lines of Cutting.) 
 
 Cycle. A period of time within which a 
 certain series of phenomena regularly recur, 
 in the same order. 
 
 Cycle, Magnetic A single round 
 of magnetic changes to which a magnetizable 
 
Cyc.] 
 
 152 
 
 [Dam. 
 
 substance, such as a piece of iron, is subjected 
 when it is magnetized from zero to a cer- 
 tain maximum magnetization, then decreased 
 to zero, reversed and carried to a negative 
 maximum, and then decreased again to zero. 
 
 Cyclical Magnetic Variation. (See Va- 
 riation, Cyclical Magnetic?) 
 
 Cyclotrope. A name proposed in place 
 of transformer or converter. (See Trans- 
 former^) 
 
 Cylinder, Yortex A number of 
 
 vortex stream-lines grouped parallel to one 
 another about a straight line which forms the 
 axis or core of the vortex. 
 
 Cylindrical Armature. (See Armature, 
 Cylindrical?) 
 
 Cylindrical Carbon Electrodes. (See 
 Electrodes, Cylindrical Carbon?) 
 
 Cylindrical Electro-Magnet. (See Mag- 
 net, Electro, Cylindrical?) 
 
 Cylindrical Magnet. (See Magnet, Cyl- 
 indrical?) 
 
 Cylindrical Ring Armature. (See Arm- 
 ature, Cylindrical Ring?) 
 
 Cymogene. An extremely volatile liquid 
 which is given off from crude coal oil during 
 the early parts of its distillation. 
 
 The two liquids which are obtained from the 
 condensation of the vapors given off during the 
 first parts of the distillation of coal oil are called 
 cymogene, and rhigolene. These liquids are em- 
 ployed on account of their extreme volatility for 
 the artificial production of cold. 
 
 Rhigolene is employed by some for the treat- 
 ment or flashing of the carbons used in incan - 
 descent lamps. (See Carbons, Flashing Process 
 for.) 
 
 Cystoscopy, Electric A name given 
 
 to Hitze's method of ocular examination 
 of the human bladder by electric illumina- 
 tion. 
 
 Damped Magnetic Needle. (See Needle, 
 Magnetic, Damped?) 
 
 Damper. A metallic cylinder provided in 
 an induction coil so as to partially or com- 
 pletely surround the iron core, for the purpose 
 of varying the intensity of the currents induced 
 in the secondary. 
 
 The metallic cylinder acts as a screen or shield 
 for the rapidly alternating currents traversing the 
 field of the primary. (See Screening, Magnetic.") 
 As the damper is pulled out, a greater length of 
 the core is exposed to the induction. 
 
 Damper. A term sometimes applied to a 
 dash-pot or other similar apparatus provided 
 for the purpose of preventing the too sudden 
 movement of a lever or other part of a device. 
 (^tt Dash-Pot. ) 
 
 Some form of damper or dash-pot is used on 
 most electric arc lamps, the upper carbon of 
 which is fed by a direct fall. 
 
 The double use of this word is unfortunate. 
 
 Damping. The act of stopping vibratory 
 motion such as bringing a swinging mag- 
 
 netic needle quickly to rest, so as to deter- 
 mine the amount of its deflection, without 
 waiting until it comes to rest after repeated 
 swingings to and fro. 
 
 Damping devices are such as offer resistance 
 to quick motion, or high velocities. 1 hose gen- 
 erally employed in electrical apparatus are either 
 air or fluid friction, obtained by placing vanes 
 on the axis of rotation, or by checking the move- 
 ments of the needle by means of the currents it 
 sets up, during its motion, in the mass of any con- 
 ducting metal placed near it. These currents, as 
 Lenz has shown, always tend to produce motion 
 in a direction opposed to that of the motion caus- 
 ing them. Bell-shaped magnets are especially 
 suitable for this kind of damping. (See Magnet^ 
 Bell- Shaped.) 
 
 The needle of a galvanometer is dead-beat when 
 its moment of inertia is so small that its oscillations 
 in an intense field are very quick, and the mirror, 
 acting as a vane, causes the movements to die out 
 very rapidly, and the needle therefore moves 
 sharply over the scale from point to point and 
 comes quickly to a dead stop. When the needle 
 or swinging coil is heavy and moves in an intensf 
 
Dam.] 
 
 153 
 
 [Dea, 
 
 field, as in the Deprez-d' Arson val galvanometer, 
 the movements are dead-beat. 
 
 Damping by means of pieces of india rubber is 
 often applied to telephone diaphragms to prevent 
 their excessive or continued vibration. 
 
 Damping, Electric A term some- 
 times employed to express a decrease in 
 the intensity of the electric oscillations pro- 
 duced in a conductor by electric resonance, 
 under circumstances where higher overtones 
 are set up in the conductor. 
 
 Daniell's Toltaic Cell. (See Cell, Vol- 
 taic, Dani ell's.) 
 
 Dark-Space, Crookes' (See Space, 
 
 Dark, Crookes\) 
 
 Dark-Space, Faraday's (See Space, 
 
 Dark, Faraday's.) 
 
 Dash-Pot. A mechanical device to prevent 
 too sudden motion in a movable part of any 
 apparatus. 
 
 The dash-pot of an automatic regulator, or of 
 an arc-lamp, is provided to prevent too sudden 
 movements of the collecting brushes on the com- 
 mutator cylinder, or the too sudden fall of the 
 upper carbon. Such devices consist essentially of 
 a loose fitting piston that moves through air or 
 glycerine. 
 
 Dash-pots are species of damping devices, and, 
 like the damping arrangements on galvanometers 
 or magnet needles, prevent a too free movement 
 of the parts with which they are connected. (See 
 Damper. Damping.) 
 
 Day, Normal Magnetic A day dur- 
 ing which the value of the earth's magnetic 
 elements does not vary greatly from their 
 mean value. (See Elements, Magnetic, of a 
 Place.) 
 
 Day of Disturbance, Magnetic 
 
 A day during which the mean departure of 
 the readings of a declinometer at any place, 
 from the normal monthly value at that place, 
 is once and a half the average. (Lloyd.) 
 
 Dead-Beat. Such a motion of a galvanom- 
 eter needle in which the needle moves sharply 
 over the sqale from point to point and comes 
 quickly to rest. (See Damping.) 
 
 Dead-Beat Discharge. (See Discharge, 
 Dead-JBeat.) 
 
 Dead-Beat Galvanometer. (See Galva- 
 nometer, Dead-Seat.) 
 
 Dead Dipping. (See Dipping, Dead.) 
 Dead Earth. (See Earth, Dead or Total.) 
 
 Dead Turns of Armature Wire, or Dead 
 
 Wire. (See Turns, Dead, of Armature 
 Wire.) 
 
 Death, Electric Death resulting 
 
 from the . passage of an electric current 
 through the human body. 
 
 The exact manner in which an electric current 
 causes death is not known. When the current is 
 sufficiently powerful, as in a lightning flash, or a 
 powerful dynamo current, insensibility is prac- 
 tically instantaneous. 
 
 Death may be occasioned : 
 (i.) As the direct result of physiological shock. 
 (2.) From the action of the current on the res- 
 piratory centres. 
 
 (3.) From the actual inability of the nerves or 
 muscles, or both, to perform their functions. 
 
 (4.) From an actual electrolytic decomposition 
 of the blood or tissues of the body. 
 
 (5.) From the polarization of those parts of the 
 body through which the current passes. 
 
 (6.) From an actual rupture of parts by a dis- 
 ruptive discharge. 
 
 The current required to cause death will de- 
 pend on a variety of circumstances, among 
 which are: 
 
 (i.) The particular path the current takes 
 through the body, with reference to the vital 
 organs that may lie in this path. 
 
 (2.) The freedom or absence of sudden varia- 
 tions of electromotive force. 
 
 (3.) The time the current continues to pass 
 through the body. 
 
 In some fatal cases, it is probably the extra- 
 current, or the induced-direct current on break- 
 ing, that causes death, since, as is well known, 
 its electromotive force may be many times 
 greater than that ot the original current. 
 
 A comparatively low-potential continuous-cur- 
 rent, cannot, therefore, be properly regarded 
 as entirely harmless, simply because its electro- 
 motive force is necessarily small. In the case of 
 alternating currents the danger increases after a 
 certain point with the number of alternations per 
 second. When, however, the number of alter- 
 nations per second reaches a given number, the 
 danger decreases as the frequency of alternations 
 
Dec.] 
 
 154 
 
 [Beg. 
 
 increases. This was conclusively shown by the 
 independent investigations of Tatum and Tesla. 
 
 Decalescence. A term proposed by Prof. 
 Elihu Thomson for an absorption of sensible 
 heat, which occurs at a certain time during 
 the heating of a bar of steel. 
 
 Decalescence will thus be observed to be the 
 reverse of recalescence, which is the phenome- 
 non of the emission of sensible heat at a certain 
 time during the cooling of a heated bar of 
 steel. (See Recalescence) 
 
 Deci (as a prefix). The one-tenth. 
 
 Deci-Ampe're. One-tenth of an ampere. 
 
 Deci-Ampe're Balance. (See Balance, 
 Deci- A mpere) 
 
 Deci-Lux. The one-tenth of a lux. (See 
 Lux) 
 
 Declination. The variation of a mag- 
 netic needle from the true geographical north. 
 The magnetic declination is east or west. (See 
 Needle, Magnetic, Declination of) 
 
 Declination, Angle of - The angle 
 which measures the deviation of the mag- 
 netic needle to the east 
 or west of the true geo- 
 graphical north. 
 
 The angle of variation 
 of a magnetic needle. w hx-i TWi Jr IE 
 
 In Fig. 195, if N S, rep- 
 resents the true north and 
 south line, the angle of de- 
 clination is N O A, and Fig. 195. Declination 
 the sign of the variation is of Needle, 
 
 east, because the deviation of the needle is to- 
 ward the east. (See Needle, Magnetic, Declina- 
 tion of) 
 
 Declinometer. A magnetic needle suit- 
 ably arranged for the measurement of the 
 value of the magnetic declination or varia- 
 tion at any place. 
 
 Decomposition. In chemistry the separa- 
 tion of a molecule into its constituent atoms 
 or groups of atoms. (See Molecule. Atom) 
 
 Decomposition, Electric Chem- 
 ical decomposition by means of an electric dis- 
 charge or current. 
 
 This decomposition may result from an increase 
 
 of temperature produced by the electric discharge, 
 or from the passage of the current. In the latter 
 case it is more properly called electrolytic decom- 
 position. 
 
 Decomposition, Electric, Crystallization 
 
 by (See Crystallization by Electro- 
 
 lytical Decomposition?) 
 
 Decomposition, Electrolytic The 
 
 separation of a molecule into its constituent 
 atoms or groups of atoms by the action of 
 the electric current. 
 
 These atoms or groups of atoms are either 
 electro-positive or electro-negative in character. 
 (See Electrolysis. Anion. Kathion) 
 
 De-energize. To deprive an electro-recep- 
 tive device of its operating current. 
 
 De-energizing. Depriving an electro- 
 receptive device of its operating current. 
 
 Deep-Seated Eddy Currents. (See Cur- 
 rents, Eddy, Deep-Seated?) 
 
 Deep-Water Submarine Cable. (See 
 Cable, Submarine, Deep-Sea.} 
 
 Deflagration, Electrical The fusion 
 and volatilization of metallic substances by the 
 electric current. 
 
 J)eflagrator. The name given to a voltaic 
 battery, of small internal resistance, employed 
 by Hare in the electric deflagration of metal- 
 lic substances. 
 
 Deflection Method. (See Method, Deflec- 
 tion) 
 
 Deflection of Magnetic Needle. (See 
 Needle, Magnetic, Deflection of) 
 
 Degeneration. Such a degeneration of the 
 muscular or cellular structure of any cell or 
 organ that incapacitates it from performing its 
 functions. 
 
 Degeneration of Energy. (See .Energy, 
 Degeneration of) 
 
 Degeneration, Partial, Reaction of 
 
 That form of alteration to electric stimula- 
 tion, in which the nerves show no abnormal 
 reaction to electric stimulation, while the 
 muscles, when directly stimulated by the con- 
 stant current, exhibit the reaction of degen- 
 eration. (See Degeneration, Reaction of!) 
 
Deg.] 
 
 155 
 
 [Dep. 
 
 Degeneration, Reaction of A 
 
 qualitative and quantitative alteration of 
 nerves and muscles to electric stimulation. 
 
 According to Landois and Stirling the following 
 conditions characterize essentially the reaction of 
 degeneration: "The excitability of the muscles 
 is diminished or abolished for the faradic cur- 
 rent, while it is increased for the galvanic current 
 from the third to the fifty -eighth day ; it again 
 diminishes, however, with variations, from the 
 seventy-second to eightieth day ; the anodic clos- 
 ing contraction is stronger than the kathodic 
 closing contraction." * * * "The diminu- 
 tion of the excitability of the nerves is similar for 
 the galvanic and faradic currents. ' ' 
 
 Deka (as a prefix). Ten times. 
 
 Deka-Amp&re. Ten amperes. 
 
 Deka-AmpSre Balance. (See Balance, 
 Deka- A mpere?) 
 
 De la Rue's Standard Yoltaic Cell. (See 
 Cell, Voltaic, Standard, De la Rue's.} 
 
 Deliquescence. The solution of a crystal- 
 line solid arising from its absorption of vapor 
 of water from the atmosphere. 
 
 Demagnetizable. Capable of being de- 
 prived of magnetism. 
 
 Demagnetization. A process, generally di- 
 rectly opposite to that for producing a magnet, 
 by means of which the magnet may be de- 
 prived of its magnetism. 
 
 A magnet may be deprived of its magnetism, 
 or be demagnetized 
 
 (l.) By heating it to redness. 
 
 (2. ) By touching to its poles magnet poles of the 
 same name as its own. 
 
 (3.) By reversing the directions of the motions 
 by which its magnetism was originally imparted, 
 if magnetized by touch, by stroking it with a 
 magnet in the opposite direction from that which 
 would have to be given in order to produce the 
 magnetization which is to be removed from it. 
 
 (4.) By exposing it in a helix to the influence of 
 currents which will impart magnetism opposite to 
 that which it originally possessed. 
 
 Avria claims that a smaller magnetizing force is 
 required to- demagnetize a needle than is required 
 to magnetize it. 
 
 Demagnetization of Watches. (See 
 
 Watches, Demagnetization of.) 
 6 Vol. 1 
 
 Demagnetize. To deprive of magnetism. 
 
 Demagnetizing. Depriving of magnetiza- 
 tion. 
 
 Demarcation Current. (See Current, De- 
 marcation?) 
 
 Demarcation Surface. (See Surf ace, De- 
 marcation?) 
 
 Density, Electric The quantity of 
 
 free electricity on any unit of area of surface. 
 
 The density is said to be positive or negative 
 according as to whether the charge is positive or 
 negative. (See Charge, Density of. Plane, 
 Magnetic Proof.} 
 
 Density, Magnetic The strength 
 
 of magnetism as measured by the number of 
 lines of magnetic force that pass through a 
 unit area of cross-section of the magnet, i. e., 
 a section taken at right angles to the lines of 
 force. (See Field, Magnetic?) 
 
 Density of Charge. (See Charge, Den- 
 sity of.} 
 
 Density of Current. (See Current 
 Density?) 
 
 Density of Field. (See Field, Density of.) 
 
 Density, Surface A phrase used 
 
 by Coulomb to mean the quantity of eiec- 
 tricity per unit of area at any point on a sur- 
 face. (See Charge Density. Density, 
 Electric?) 
 
 Dental-Mallet, Electro-Magnetic 
 
 A mallet for filling tee* 1 " 1 , the blows of which 
 are struck by means of electrically-driven 
 mechanism. 
 
 Electro-magnetism was first employed for this 
 purpose by Bonwill, of Philadelphia. 
 
 Dentiphone. An audiphone. (See Audi- 
 phone?) 
 
 Depolarization. The act of reducing or 
 removing the polarization of a voltaic cell 
 or battery. (See Cell, Voltaic, Polarization 
 
 Depolarize. To deprive of polarization. 
 Depolarizing. Depriving of polarization. 
 
 Depolarizing Fluid. (See Fluid, De- 
 polarizing?) 
 
i)ep.J 
 
 156 
 
 [Dev, 
 
 Deposit, Black, Electro-Metallurgical 
 
 A crystalline variety of electro- 
 metallurgical deposit. (See Deposit, Electro- 
 Metallurgical?) 
 
 Deposit, Crystalline, Electro-Metallurgi- 
 cal A non-adherent, non-coherent 
 
 film of Jectrolytically deposited metal. (See 
 Deposit, Electro-Metallurgical?) 
 
 Deposit, Electro-Metallurgical 
 
 The deposit of metal obtained by any electro- 
 metallurgical process. 
 
 To obtain a good metallic deposit the density 
 of the current must be regulated according to the 
 strength of the metallic solution employed. 
 
 Electro -metallurgical deposits are either 
 
 (l.) Regnline, or flexible, adherent and strongly 
 coherent metallic films, deposited when neither 
 the current nor the solution is too strong; or, 
 
 (2.) Crystalline; or non-adherent and non-co- 
 herent deposits. 
 
 The crystalline deposit may either be of a loose, 
 sandy character, which is thrown down when too 
 feeble a current is used with too strong a metallic 
 solution, or it may consist of a black deposit, which 
 is thrown down when the current is too strong as 
 compared with the strength of the solution. This 
 latter character of deposit is sometimes technically 
 called burning, and takes place most frequently 
 at sharp corners and edges, where the current 
 density is greatest. (See Current Density.) 
 
 Deposit, Electro-Metallurgical Nodular 
 
 A coherent, irregular electro-metal- 
 lurgical deposit which occurs whenever the 
 current density falls below its normal value. 
 Deposit, Electro-Metallurgical, Regnline 
 
 A flexible, adherent and strongly 
 
 coherent film of metal electrolytically de- 
 posited. (See Deposit, Electro-Metallur- 
 gical^) 
 
 Deposit, Electro-Metallurgical, Sandy 
 
 A non-coherent electro-metallurgical 
 
 deposit which occurs whenever the current 
 density exceeds its normal value. 
 Depositing Cell. (See Cell, Depositing?) 
 Depositing Tat (See Vat, Depositing?) 
 Deposition, Electric The deposit- 
 ing of a substance, generally a metal, by 
 the action of electrolysis. (See Electrolysis?) 
 
 The electric deposition of a metal on any con- 
 ducting surface is sometimes called an electro- 
 metallurgical deposition. (See Metallurgy^ 
 Electro.) 
 
 Deprez-d'Arsonval Galvanometer. (See 
 
 Galvanometer, Deprez-d 'Arsonval?) 
 
 Derivative Circuit (See Circuit, De- 
 rivative?) 
 
 Derived Circuit (See Circuit, Derived.) 
 Derived Units. (See Units, Derived?) 
 Destructive Distillation. (See Distilfa* 
 tion, Destructive.) 
 
 Detector Galvanometer. (See Galva- 
 nometer, Detector?) 
 
 Detector, Ground In a system 
 
 of incandescent lamp distribution, a device 
 placed in the central station, for showing by 
 the candle-power of a lamp the approximate 
 location of a ground on the system. 
 
 Fig. 196, shows a form of ground-detector, in 
 
 Ffg. 196. Ground-Detector. 
 
 which a small transformer is placed on a board iu 
 connection with a lamp and a two-way switch. 
 One terminal of the primary of the transformer is 
 put to ground, while the other can be connected 
 by means of the switch to one or the other of the 
 two primary mains of the distribution circuit. 
 Should an earth exist on either main, then when 
 the testing transformer has its pole connected to 
 the other main, the lamp in its secondary circuit 
 will light up, providing the leak is of sufficient 
 magnitude to permit a sufficiently great current 
 to pass through the primary circuit. 
 
 Detorsion Bar. (See Bar, Detorston) 
 Device, Electro-Receptive Various 
 
Dov.J 
 
 157 
 
 [Dev. 
 
 devices placed in an electric circuit, and 
 energized by the passage through them of the 
 electric current. 
 
 A translating device. 
 
 The following are among the more important 
 electro-receptive devices, viz. : 
 
 (I.) Electro- magnets. 
 
 (2.) Electric motors. 
 
 (3.) Electro-magnetic signal apparatus. 
 
 (4.) Telegraphic or telephonic apparatus. 
 
 (5.) An arc or incandescent lamp. 
 
 (6. ) An electric heater. 
 
 (7.) A plating bath or voltameter. 
 
 (8.) An uncharged storage cell. 
 
 (9.) A converter or transformer. 
 
 ELECTRO-RECEPTIVE DEVICES. 
 
 Motion Reproduced. 
 (l.) Electric motor. 
 (2.) Telpherage system. 
 (3.) Telephone receiver. 
 (4.) Telegraphic apparatus. 
 (5.) Telephote receiver. 
 
 Radiant Energy Produced, 
 (6.) Arc or incandescent electric lamp. 
 (7.) Electric heater. 
 (8.) Electric welder. 
 (9.) Leyden jar or battery. 
 
 Chemical Decomposition Effected. 
 (10.) Electrolytic bath. 
 (ll.) Uncharged storage battery. 
 
 Electro-Magnetism Produced. 
 (12.) Electro-magnet. 
 
 Device, Feeding, of an Arc Lamp 
 
 A device for maintaining the carbon electrodes 
 of an arc lamp at a constant distance apart 
 during their consumption. (See Lamp, 
 Electric Arc,} 
 
 Device, Magneto-Receptive Any 
 
 device that is capable of being energized 
 when placed in a magnetic field. 
 
 The term magneto-receptive device is used in 
 contradistinction to electro-receptive device. (See 
 Device, Electro- Receptive.") 
 
 Darice-or Arrangement, Electromotive 
 
 A term sometimes employed instead 
 ->f nn electro source. (See Source, Electric. 
 Arrangement or Device. Electromotive^ 
 
 Derice, Safety, for Arc Lamps, or Series 
 Circuits Any mechanism which auto- 
 matically provides a path for the current 
 around a lamp, or other faulty electro-recep- 
 tive device in a series circuit, and thus pre- 
 vents the opening of the entire circuit on the 
 failure of such device to operate. (See Lamp, 
 Electric Arc?) 
 
 Device, Safety, for Multiple Circuits 
 
 A wire, bar, plate or strip of readily 
 fusible metal, capable of conducting, without 
 fusing, the current ordinarily employed on the 
 circuit, but which fuses and thus breaks the 
 circuit on the passage of an abnormally great 
 current. 
 
 The terms safety-catch, safety-plug, safety* 
 atrip and safety -fuse are also used for this safety 
 device. (See Fuse, Safety.} 
 
 Device, Translating - A term em- 
 bracing electro-receptive and magneto-recep- 
 tive devices. (See Device, Electro-Recefr* 
 jive.) 
 
 Translating devices are placed in an electric 
 circuit, and when traversed by the current effect 
 a change, or translation in the form of the electric 
 energy whereby useful work is accomplished. 
 
 Translating devices depend for their operation 
 on the luminous, heating, magnetic, or chemical 
 effects of the current. 
 
 Devices, Electro-Receptive, Multiple 
 Connected A connection of electro- 
 receptive devices, in which the positive poles 
 of a number of separate devices are all con 
 nected with a single positive lead or conduc- 
 tor, and the negative poles all connected with 
 a single negative lead or conductor. 
 
 The multiple-arc-connection of electro-receptive 
 devices is suitable for constant potential circuits.^ or 
 those in which the electromotive force is main- 
 tained approximately constant. In such circuits 
 the energy absorbed by each device will increase 
 as its resistance decreases, since the energy ab- 
 sorbed is proportional to the current passing. 
 (See Circuits, Varieties of.) 
 
 Multiple-arc-connected electro-receptive devices 
 are employed in incandescent lamp distribution. 
 Each device added reduces the resistance :,f the 
 entire circuit. 
 
Dev.] 
 
 158 
 
 [Dia, 
 
 Deyices,Electro-Receptive,Multiple- Arc- 
 Connected A term used in place of 
 
 multiple-connected electro-receptive devices. 
 (See Devices, Electro-Receptive, Multiple- 
 Connected?) 
 
 Devices, Electro-Receptive, Multiple- 
 Series-Connected A connection of 
 
 electro-receptive devices in which a number of 
 separate' electro-receptive devices are con- 
 nected in groups in series, and each of these 
 separate groups afterwards connected in mul- 
 tiple-arc. 
 
 The multiple r series connection permits electro- 
 receptive devices to be placed on mains whose 
 electromotive force would be too high to permit 
 a single service to be connected directly to them. 
 It is of great value in the distribution of incandes- 
 cent lamps by constant currents, since by per- 
 mitting a higher electromotive force to be em- 
 ployed on the main conductors, it reduces the 
 dimensions of the conductors required for the 
 economical distribution of the current. (See 
 Circuit 's, Varieties of.) 
 
 Devices, Electro-Receptive, Series-Con- 
 
 nectad The connection of electro- 
 receptive devices in which the devices are 
 placed consecutively in the circuit, so that the 
 current passes successively through all of 
 them from the first to the last. 
 
 The series-connection of electro-receptive de- 
 vices is suited to constant -current circuits. The 
 work done in the device is developed by the fall 
 of potential in each device. This kind of con- 
 nection is used in most systems of arc light and 
 telegraphic lines. (See Circuits, Varieties of.) 
 
 Devices, Electro-Receptive, Series-Mill- 
 
 tiple-Connected A connection of 
 
 electro-receptive devices in which a number 
 of separate electro-receptive devices are joined 
 in separate multiple groups, and each of these 
 groups subsequently connected with one an- 
 other in series. 
 
 The effect of series-multiple connections is to 
 split up the current into a number of separate 
 currents of smaller strength, but of the same 
 electromotive force. It is applicable to such cases 
 as the combination of arc and incandescent lamps 
 in the same circuit. (See Circuits, Varieties of .) 
 
 Devices, Translating, Multiple-Con- 
 
 nected 
 
 -A term sometimes used for 
 
 multiple-connected electro-receptive devices. 
 (See Devices, Electro-Receptive, Multiple- 
 Connected^ 
 
 Devices, Translating, Multiple- Arc-Con- 
 nected A term used in place of 
 
 multiple-connected electro-receptive devices. 
 (See Devices, Electro-Receptive, Multiple* 
 Connected?) 
 
 Devices, Translating, Multiple-Series- 
 Connected A term sometimes used 
 
 instead of multiple-series-connected electro- 
 receptive devices. (See Devices, Electro- 
 Receptive, Multiple-Series-Connected?) 
 
 Devices, Translating, Series-Connected 
 ' -A term sometimes used for series- 
 connected electro-receptive devices. (See 
 Devices, Electro - Receptive, Series -Con- 
 nected?) 
 
 Devices, Translating, Series-Multiple- 
 Connected A term sometimes used 
 
 for series-multiple-connected electro-recep- 
 tive devices. (See Devices, Electro-Recep* 
 tive, Series-Multiple-Connected?) 
 
 Dextrorsal Helix. (See Helix, Dex- 
 trorsal?) 
 
 Dextrorsal Solenoid. (See Solenoid, Dex 
 trorsal?) 
 
 Diacritical Current. (See Current, Dia- 
 critical.) 
 
 Diacritical Number. (See Number, Dia- 
 critical?) 
 
 Diacritical Point of Magnetic Satura- 
 tion. (See Saturation, Magnetic, Diacrit- 
 ical Point of.) 
 
 Diagnosis, Electro. Diagnosis by means 
 of the exaggeration or diminution of the re- 
 action of the excitable tissues of the body 
 when subjected to the varying influences of 
 electric currents. 
 
 The electric current has also been applied in 
 order to distinguish between forms of paralysis, 
 and as a final test of death. 
 
 Diagnostic, Electro Pertaining to 
 
 electro-diagnosis. (See Diagnosis, Electro.) 
 
 Diagometer, Rousseau's An ap- 
 paratus in which an attempt is made to 
 
Dia.] 
 
 159 
 
 [IKa. 
 
 determine the chemical composition and con- 
 sequent purity of certain substances by their 
 electrical conducting powers. 
 
 The arrangement of the apparatus is shown in 
 Fig. 197. A dry pile. A, has its negative, or 
 
 Fig. ZQ7- Rousseau's Diagometer. 
 
 terminal, m', grounded. Its positive, or -f- ter- 
 minal is connected to a delicately supported, and 
 slightly magnetized needle, M, terminated by a 
 conducting plate, L. Opposite L, and at the same 
 height, is a fixed plate of slightly larger size. The 
 needle M, when at rest in the plane of the magnetic 
 meridian, is in contact at L, with the fixed plate. 
 If, therefore, the upper plate of the pile is con- 
 nected with the needle M, both plates are similarly 
 charged and repulsion takes place, the needle 
 coming to rest at a certain distance from the fixed 
 plate. 
 
 The substance whose purity is to be determined 
 is placed in the cup G, which is connected, 
 through L, with the fixed plate, A branch wire 
 from the -f- terminal of the pile is then dipped into 
 the substance in G, and its purity determined 
 from the length of time required for the two plates 
 at L, to be discharged through the material in G. 
 
 It is claimed that the instrument will detect the 
 difference between pure coffee and chicory. Its 
 practical application, however, is very doubtful. 
 
 Diagram, Thernio-Electric A 
 
 diagram in which the thermo-electric power 
 between different metals is designated for 
 different temperatures. 
 
 The differences of potential, produced by the 
 mere contact of two metals, varies, not only with 
 the kind of metals, and the physical state of each 
 metal, but also with their temperature. This 
 difference of potential, maintained in conse- 
 quence of the difference of temperature between 
 the junctions of a thermo-electric couple, is ap- 
 proximately proportional to the differences of 
 temperature of these junctions, if these differences 
 are not great, and is equal to the product of such 
 
 differences of temperature and a number depend ent 
 on the metals in the couple. This number is 
 called the thermo-electric power. (See Couple^ 
 Thermo-Electric. Thermo-Electric Power.) 
 ' In Fig. 198 (after Tait), the thermo-electric 
 
 200c 2oO 300<! 350e 400<! 450 
 
 K&5 
 
 Fig. T<)8. Thermo- Electric Diagram. 
 power is shown between lead and iron, and lead 
 and copper. The numbers at the top of the table 
 represent degrees of the centigrade thermometer. 
 Those at the sides represent the differences of 
 potential in micro -volts. 
 
 The thermo-electric power of the copper-iron 
 couple decreases from the freezing point of water, 
 O degrees C., to a temperature of 274.5 degrees 
 C., when it becomes zero. Beyond that temper- 
 ature the thermo-electric power increa ,es, but in 
 the opposite direction. The point at which this 
 occurs is called the neutral point. 
 
 Dial Telegraph. (See Telegraphy, Dial.) 
 
 Dialysis. The act of separating a mixture 
 of crystalloids and colloids by diffusion 
 through a membrane. 
 
 If, for example, the contents of a stomach, in a 
 case of suspected poisoning, be placed in a vessel, 
 the bottom of which is formed of a sheet of 
 parchment paper and floated in water, the 
 crystalloid or substances capable of crystalliz- 
 ing, will pass into the water and the colloid, an 
 uncrystallized ielly-like substance, will remain in 
 the vessel. This process has been used to detect 
 the presence of poison in the stomach in post- 
 mortem cases. 
 
 Diamagnetic. The property possessed by 
 substances like bismuth, phosphorus, anti- 
 mony, zinc and numerous others, of being 
 apparently repelled when placed between the 
 poles of powerful magnets 
 
 When diamagnetic substances in the form of 
 rods or bars are placed, as in Fig. 199, between 
 the poles- of a powerful electro-magnet, they 
 place themselves at right angles to the poles, or 
 are apparently repelled. 
 
 Paramagnetic substances like iron or steel, on 
 the contrary, come to rest under similar circunv 
 
Dia.] 
 
 160 
 
 [Dia. 
 
 Ftg. 799 Effect of Para* 
 magnetism. 
 
 stances in a straight line joining the poles, at 
 right angles to the position shown in Fig. 199. 
 
 Paramagnetic substances are sometimes called 
 ferro-magnetiC) or substances magnetic after the 
 manner of iron. This word is unnecessary and 
 ill-advised. The term sidero-magnetic, which has 
 also been proposed in place of paramagnetic, is 
 also unnecessary. 
 
 Paramagnetic substances appear to concentrate 
 the lines of magnetic force on them; that is, their 
 magnetic resistance is 
 smaller than that of the 
 air or other medium in 
 which the magnet is 
 placed. They, there- 
 fore, come to rest with 
 their greatest dimen 
 sions in the direction of 
 the lines of magnetic 
 force. 
 
 Diamiignetic sub- 
 stances appear to have 
 a greater magnetic re- 
 sistance than that of 
 the air around them. 
 They, therefore, come 
 to rest with their least 
 dimensions in the direction of the lines of mag. 
 netic force. 
 
 The difference between paramagnetic and dia. 
 magnetic substances is generally believed to be 
 due to the varying resistance these substances 
 thus offer to lines of magnetic force as compared 
 with that offered by air or by a vacuum. 
 
 Tyndall comes to the conclusion as the result of 
 extended experimentation: " That the diamag- 
 netic force is a polar force, the polarity of dia- 
 magnetic bodies being opposed to that of para- 
 magnetic ones under the same conditions of 
 excitement." 
 
 This view, however, is not generally accepted 
 by scientists. 
 
 Diamagnetistn is also possessed by certain liquid 
 and gaseous substances. 
 
 Diamagnetic Polarity. (See Polarity, 
 Diamagnettc.} 
 
 Diamagnetically. In a diamagnetic man- 
 ner. 
 
 Diamagnetism. A term applied to the 
 magnetism of diamagnetic bodies. (See Dia- 
 magnettc?) 
 
 Diamagnetism, Weber's Theory of 
 
 A theory to account for the phenomena 
 of diamagnetism. 
 
 Weber's theory of diamagnetism, like Ampere's 
 theory of magnetism, supposes that magnetic 
 substances consist of originally magnetized mole- 
 cules or atoms, and that the act of magnetization 
 consists of polarizing these atoms or molecules, 
 or turning them in one and the same direction. 
 That the original condition of the molecules or 
 atoms is probably due to the passage of electricity, 
 which continually circulates through their mass, 
 the atoms being supposed to possess perfect con- 
 ductivity. 
 
 Suppose the substance through whose mole- 
 cules or atoms these currents are flowing be 
 immersed in a magnetic field. All of the mole- 
 cules or atoms which can turn so as to look along 
 lines of force in the right direction will have the 
 current flowing in them thereby weakened so long 
 as they remain in the field. When drawn out of 
 it, however, these currents will regain their nor- 
 mal strength. 
 
 Suppose now the case of a substance, in which 
 the currents are normal but weak, immersed in a 
 strong magnetic field. There may thereby be 
 effected a complete reversal of the direction of 
 these currents, and others may be produced 
 which flow in the opposite direction, and which 
 will continue so to flow as long as the substance 
 remains in the field. Such currents would then 
 be sufficient to explain the phenomena of diamag- 
 netic action. 
 
 An electric current produced in a circuit near 
 which a momentary current of electricity is sud 
 denly brought has now the opposite direction to 
 that which produces it, and this momentary cur- 
 rent would tend to produce repulsion. When, 
 
 Fig, 200. Weber's Theory of Diamagnetism. 
 too, the circuit is drawn out of the neighborhood 
 in which another current is flowing, another mo 
 
Dia.] 
 
 161 
 
 [Die. 
 
 mentary current is produced in the same direc- 
 tion. This produces attraction. 
 
 Now, regarding the same phenomena from the 
 standpoint of lines of magnetic force, when a 
 conductor through which a current is passing is 
 placed in a magnetic field, any increase in the 
 number of lines of magnetic force passing through 
 it tends to move the conductor out of the magnetic 
 field, while any decrease in the number of lines 
 of force tends to move the conductor into the 
 field. To experimentally show the attractions 
 and repulsions produced by magnetization or 
 demagnetization, the following apparatus may be 
 employed : 
 
 A stout disc of copper, Fig. 200, is supported 
 on a horizontal arm in the position shown in front 
 of the pole of a powerful electro- magnet. When 
 the current is sent through the electro-magnet the 
 disc of copper is repelled from the magnetic pole. 
 When the magnetism is being destroyed by the 
 opening of the circuit and by the weakening of 
 the current, the copper disc is attracted. 
 
 Diamagnetometer. An apparatus de- 
 signed for studying diamagnetism. (See Dza- 
 magnetism.} 
 
 The apparatus for the study of paramagnetism 
 generally receives simply the name of magnet- 
 ometer. 
 
 Diamagnets. Diamagnetic substances 
 subjected to magnetic induction and formerly 
 called diamagnets in contradistinction to or- 
 dinary magnets. 
 
 Diamagnets are supposed by some to possess a 
 polarity the same as that of the inducing pole, 
 instead of the opposite polarity, as in paramagnetic 
 substances. (See Diamagnetism.') 
 
 Diaphragm. A sheet of some solid sub- 
 stance, generally elastic in character and cir- 
 cular in shape, securely fixed at its edges and 
 capable of being set into vibration. 
 
 The receiving diaphragm of a telephone is 
 generally a thin plate or disc of iron, fixed at its 
 edges, placed near a magnet pole and set into 
 vibration by variations in the magnetic strength 
 of the pole, due to variations in the current that 
 is passed over the line. 
 
 The transmitting diaphragm of the telephone 
 or of a phonograph, consists of a plate fixed at its 
 edges and set into vibration by the sound waves 
 striking it. 
 
 Diaphragm. A term sometimes employed 
 for a plate form of porous cell. 
 
 Diaphragm Currents. (See Currents, 
 Diaphragm. Cell, Porous.} 
 
 Diaphragm of Voltaic Cell.- A term 
 sometimes used for the porous cell of a 
 double fluid voltaic cell when in the form of 
 a plate. 
 
 Dice-Box Insulator. (See Insulator, 
 Dice-Box.} 
 
 Dielectric. A substance which permits 
 induction to take place through its mass. 
 
 This word is sometimes, but improperly, writ- 
 ten Di-Electric. 
 
 The substance which separates the opposite 
 coatings of a condenser is called the dielectric. 
 All dielectrics are non-conductors. 
 
 All non-conductors or insulators are dielectrics, 
 but their dielectric power is not exactly propor- 
 tional to their non-conducting power. 
 
 Substances differ greatly in the degree or ex- 
 tent to which they permit induction to take place 
 through or across them. Thus, a certain amount 
 of inductive action takes place between the insu- 
 lated metal plates of a condenser across the layer 
 of air between them. 
 
 A dielectric may be regarded as pervious to 
 rapidly reversed periodic currents, but opaque to 
 continuous currents. There is, however, some, 
 conduction of continuous currents. 
 
 According to Swinburne, there are three species 
 of conduction that may take place in dielectrics, 
 all of which produce a heating of the dielectric, 
 viz.: 
 
 (I.) Metallic Condition, i. e., such a conduc- 
 tion as takes place in a metal. This kind of con- 
 duction arises from the presence of metallic par- 
 ticles embedded in the dielectric. 
 
 (2.) Disruptive Conduction^ or a momentary 
 current accompanying a disruptive discharge. 
 
 (3.) Electrolytic Conduction, or that kind of 
 conduction which accompanies the electrolysis 
 of a conductor. This kind of conduction may 
 take place in some kinds of glass. 
 
 Faraday regarded the dielectric as the true seat 
 of electric phenomena. Conducting substances 
 he considered as mere breaks in the continuity of 
 the dielectric. This is the view now generally 
 held. 
 
 Dielectric Capacity. (See Capacity, Dt- 
 electric?) 
 
Die. 
 
 162 
 
 [Dim. 
 
 Dielectric Constant. (See Constant, 
 Dielectric) 
 Dielectric Density of a Gas. (See Gas, 
 
 Dielectric Density of) 
 
 Dielectric, Polarization of A 
 molecular strain produced in the dielectric of a 
 Leyden jar or other condenser, by the-attrac- 
 tion of the electric charges on its opposite 
 faces, or by the electrostatic stress. (See 
 Strain, Dielectric) 
 
 A term formerly employed in place of 
 electric displacement. 
 
 Faraday, in his study of the action of induction, 
 in denying the possibility of action at a distance, 
 thought that the dielectric through which induc- 
 tion takes place was polarized, and that in this 
 way the induction was transmitted across the 
 intervening space between the inducing and the 
 induced body by the action of the contiguous 
 particles of the dielectric. 
 
 The polarization of the glass of a Leyden jar, 
 and the accompanying strain, are seen by the 
 frequent piercing of the glass, and by the 
 residual charge of the jar. (See Charge, Resid- 
 ual) 
 
 Dielectric Resistance. (See Resistance. 
 Dielectric) 
 
 Dielectric Strain. (See Strain, Dielec- 
 tric) 
 
 Dielectric Strength of a Gas. (See Gas, 
 Dielectric Strength of) 
 
 Dielectric Stress. (See Stress, Dielec- 
 tric) 
 
 Difference of Potential. (See Potential, 
 Difference of) 
 
 Differential Electric Bell. (See Bell, 
 Differential Electric) 
 
 Differential Galvanometer. (See Gal- 
 vanometer, Differential) 
 
 Differential Indnctometer. (See Indue- 
 tometer. Differential) 
 
 Differential Method of Duplex Teleg- 
 raphy. (See Telegraphy, Duplex, Differ- 
 ential Method of) 
 
 Differential Relay. (See Relay, Differ- 
 ential. ) 
 
 Differential Thenno-Pile. (See Pile, 
 Thermo, Differential) 
 
 Differential Voltameter. (See Voltam- 
 eter, Siemens' Differential) 
 Differentially Wound Motor. (See 
 
 Motor. Differentially Wound.} 
 
 Diffusion, Anodal A term applied 
 
 to the introduction of any drug into the human 
 body by electricity. 
 
 The cataphoretic introduction of drugs 
 into the body. (See Cataphoresis) 
 
 A sponge or other similar electrode, saturated 
 with a solution of the drug, is connected with 
 the anode of a source and placed over the part 
 to be treated and its kathode connected to 
 another part of the body in a nearly direct line 
 with the anode and the current passed, 
 
 Diffusion Creep. (See Creep. Diffusion) 
 Diffusion of Electric Current. (See 
 
 Current, Diffusion of) 
 
 Diffusion of Lines of Force. (See Force, 
 Lines of Diffusion of) 
 
 Dimensions of Acceleration. (See Ac- 
 celeration, Dimensions of) 
 
 Dimensions of Units (See Units, Dimen- 
 sions of) 
 
 Diminished Electric Irritability. (See 
 
 Irritability, Electric, Diminished^ 
 
 Dimmer A choking coil, employed 
 
 in a system of distribution by converters or 
 
 transformers, for regulating the potential of 
 
 the feeders. 
 The dimmer consists essentially of a choking 
 
 coil wound around a laminated ring of soft iron, 
 
 Fig. 20 r. Re action Coil Dimmer. 
 
 and provided with an envelope of heavy copper. 
 The copper ring, by its position as regards the 
 choking coil, adjusts or regulates the self-induc- 
 tion of the coil, and consequently regulates the 
 potential of the feeders. The dimmer is used in 
 theatres or similar situations to turn the lights up 
 or down. 
 
Dio.] 
 
 163 
 
 [Dip. 
 
 The reaction coil or dimmer is shown in Fig. 
 201. The choking coil is wound on a ring of 
 iron. The copper sheath is furnished with a 
 handle to permit its position to be readily 
 changed with respect to the coil of insulated wire. 
 A laminated iron drum is supported on bearings 
 inside the ring. When the sheath is over the 
 coil, the coil offers but a small resistance to the 
 passage of the current. When away from it the 
 self-induction of the coil is increased. 
 
 Dioptre. A unit of refracting power. 
 
 A lens of one dioptre has a focal length of 
 one metre. One of two dioptres has a focal 
 length of 50 centimetres; one of four dioptres 
 25 centimetres. This is also spelled dioptry. 
 
 Dioptric. Relating to dioptrics. 
 Dioptrics. The science which treats of 
 the refraction of light. 
 
 Dioptry. A word sometimes used for di- 
 optre. (See Dioptre?) 
 
 Dip, Magnetic The deviation of a 
 magnetic needle from a true horizontal posi- 
 tion. 
 
 The inclination of the magnetic needle to- 
 wards the earth. 
 
 The magnetic needle shown in Fig. 202, though 
 
 Fig. 202. Angle of Dip. 
 
 supported at its centre of gravity, will not retain 
 a horizontal position in all places on the earth's 
 surface. 
 
 In the northern hemisphere its north-seeking 
 end will dip or incline at an angle B O C, called 
 the angle of dip. In the southern hemisphere 
 its south seeking end will dip. 
 
 The cause of the dip is the unequal distance of 
 the magnetic poles of the earth from the poles of 
 the needle. 
 
 The magnetic equator is a circle passing 
 around the earth midway (in intensity) between 
 the earth's magnetic poles. There is no dip at 
 the magnetic equator. At either magnetic pole 
 the angle of dip is 90 degrees. 
 
 Dip, or Inclination, Angle of 
 
 The angle which a magnetic needle, free to 
 move in both a vertical and a horizontal plane, 
 makes with a horizontal line passing through 
 its point of support. 
 
 The angle of dip of a magnetic needle. 
 (See Inclination, Angle of.) 
 
 Diplex Telegraphy. (See Telegraphy, 
 Diplex) 
 
 Dipping. An electro-metallurgical process 
 whereby a deposit or thin coating of metal 
 is obtained on the surface of another metal 
 by dipping it in a readily decomposable 
 metallic salt. 
 
 Cleansing surfaces for electro-plating pro- 
 cesses by immersing them in various acid 
 liquors. 
 
 Dipping, Bright Dipping in acid 
 
 liquors for the purpose of obtaining a bright 
 electro-metallurgical coating. 
 
 Dipping Circle. (See Circle, Dipping?) 
 
 Dipping, Dead Dipping in acid 
 
 liquors for the purpose of obtaining a dead or 
 unpolished surface on an electro-metallurgical 
 coating. 
 
 Dipping, Electro-Metallurgical 
 
 A process for obtaining an electro-metallur- 
 gical deposit on a metallic surface by dipping 
 it in a solution of a readily decomposable 
 metallic salt. 
 
 A bright, polished iron surface, when simply 
 dipped into a solution of copper-sulphate, re- 
 ceives a coating of metallic copper from the elec- 
 trolytic action thus set up. 
 
 This process is known technically as dipping. 
 The term dipping is also used in electro-metal- 
 lurgy to indicate the process of cleaning the 
 
Dir.] 
 
 164 
 
 [Dis. 
 
 articles, that are to be electro-plated, by dipping 
 them in various acid or alkaline baths. 
 
 Direct Current. (See Current, Direct?) 
 
 Direct-Current Electric Motor. (See 
 Motor, Electric, Direct-Current?) 
 
 Direct Electromotive Force. (See Force, 
 Electromotive, Direct) 
 
 Direct Excitation. (See Excitation, 
 Direct.) 
 
 Direct-Induced Current. (See Current, 
 Direct-Induced.) 
 
 Direct, or Break-Induced Current 
 
 (See Current, Direct. Current, Break- 
 Induced) 
 
 Direct Working. (See Working, Direct) 
 
 Direction, Negative, of Electrical Con- 
 vection of Heat A direction in which 
 
 heat is transmitted through an unequally 
 heated conductor by electric convection, 
 during the passage of electricity through the 
 conductor, opposite that of the current. (See 
 Heat, Electric Convection of.) 
 
 Direction of Lines of Force. (See Force, 
 Lines of, Direction of) 
 
 Direction, Positive, of Electrical Con- 
 vection of Heat A direction in 
 
 which heat is transmitted through an un- 
 equally heated conductor by electric convec- 
 tion, during the passage of electricity through 
 the conductor, the same as that of the cur- 
 rent. (See Heat, Electric Convection of.) 
 Direction, Positive, Bound a Circuit 
 
 In a plane circuit looked at from 
 
 one side, a direction opposite to that of the 
 hands of a clock. 
 
 This is a convention which has been made in 
 
 order to conveniently connect the direction of the 
 
 electromotive force produced by induction, with 
 
 the direction of the induction. 
 
 Direction, Positive, Through a Circuit 
 
 In a plane circuit, looked at from 
 
 one side, a direction through the circuit away 
 from the observer. 
 
 Directive Tendency of Magnetic Needle. 
 (See Needle, Magnetic, Directive Ten- 
 dency of.) 
 Disc, Arago's A disc of copper 
 
 or other non-magnetic metallic substance, 
 which, when rapidly rotated under a mag- 
 netic needle, supported independently of the 
 disc, causes the needle to be deflected in the 
 direction of rotation, and, when the velocity 
 of the disc is sufficiently great, to rotate with it. 
 Such disc is shown in Fig. 203 at b. The move- 
 
 Fig. 203. Arago's Disc. 
 
 ment of the needle is due to electric currents, in. 
 duced by the disc moving through the field of the 
 needle so as to cut its lines of magnetic force. To 
 obtain the best results the disc must move very 
 rapidly, and should be ^near the needle. More- 
 over, the needle should be powerful. 
 
 This effect was discovered by Arago, in 1824. 
 Since a magnetic needle moving over a metallic 
 plate produces electric currents in a direction 
 which tends to stop the motioi of the needle, a 
 damping of the motion of a magnetic needle is 
 sometimes effected by causing it to move near a 
 metal plate. The induced currents, which the 
 needle produces in the plate by its motion over it, 
 tend to retard the motion of the needle. (See 
 Damping. Law, Lenz's.) 
 
 Disc Armature. (See Armature, Disc.) 
 
 Disc, Faraday's A metallic disc 
 
 movable in a magnetic field on an axis 
 parallel to the direction of the field. 
 
 Such a disc is shown in Fig. 204, and moves, 
 
 Fig. 204.. Faraday's Disc. 
 
 as will be seen, so as to cut the lines of magnetic 
 force at right angles. 
 
 The difference of potential generated by the 
 motion of such a disc may be caused to produce 
 a current, by providing a circuit which is com- 
 pleted through the portion of the disc that at any 
 
Dis.] 
 
 165 
 
 [Dis. 
 
 moment of its rotation is situated between spring 
 contacts resting on the axis of rotation and the 
 circumference of the disc, respectively. 
 
 In Barlow s or Sturgeon's wheel, Fig. 205, the 
 
 Discharge, Brush-and-Spray 
 
 A 
 
 Fig. 2OJ. Barlow's Wheel. 
 
 wheel itself rotates in the direction shown, when 
 a current is sent through it in a direction indicated 
 by the arrows. 
 
 Discharge. The equalization of the dif- 
 ference of potential between the terminals of 
 a condenser or source, on their connection by 
 a conductor. 
 
 The removal of a charge from the surface 
 of any charged conductor by connecting it 
 with the earth, or another conductor. 
 
 The removal of a charge by means of a 
 stream of electrified air particles. 
 
 The discharge of an insulated conductor, a 
 cloud, a condenser, or a Leyden battery, is oscil- 
 latory. The oscillatory currents continue but for 
 a short time. The discharge is therefore often 
 spoken of as producing momentary currents. 
 
 The discharge of a voltaic battery, or a stor- 
 age battery, is nearly continuous, and furnishes a 
 current which is practically continuous, as dis- 
 tinguished from the momentary currents produced 
 by the discharge of a condenser. 
 
 A discharge may be alternating, brush, brush 
 and spray, conductive, convective, dead-beat, 
 disruptive, flaming, glow, lateral, oscillatory, 
 periodic, stratified, streaming, impulsive and 
 periodic. 
 
 Discharge, Alternating An elec- 
 tric discharge which changes its direction at 
 regular intervals of time. 
 
 A periodic discharge. 
 
 Discharge, Brush A faintly lu- 
 minous discharge that occurs from a pointed 
 positive conductor. 
 
 The brush discharge is a species of convective 
 discharge. In it, the streams of electrified air 
 particles assume the characteristic brush shape. 
 (See Discharge, Convective.) 
 
 form of streaming discharge obtained by in- 
 creasing the frequency of the alternations 
 of a high potential current which assumes 
 the appearance of a spray of silver-white 
 sparks, or a bunch of thin silvery threads 
 around a powerful brush. 
 
 Some idea of the brush-and-spray discharge 
 may be obtained from Fig. 206, taken from 
 
 Fig. 206. Brush-and-Spray Discharge ( Tesla). 
 Tesla, who has carefully studied these phenom- 
 ena. 
 
 The brush-and-spray discharge is best obtained, 
 according to Tesla, by bringing the terminals 
 of a source of rapidly alternating electrostatic 
 currents of high potential somewhat nearer to- 
 gether, when the streaming discharge has been 
 obtained, and preferably increasing the frequency 
 of the alternations. 
 
 The brush-and-spray discharge, when power- 
 ful, closely resembles a gas flame from gas escap- 
 ing under great pressure. Says Tesla : ' ' But 
 they do not only resemble, they are veritable 
 flames, for they are hot. Certainly they are not 
 as hot as a gas-burner, but they would be so if the 
 frequency and the potential would be sufficiently 
 high." 
 
 The brush-and-spray discharge, at higher fre- 
 quencies, passes into a form of discharge for which 
 Tesla has proposed no particular name. He de- 
 scribes this form, in a publication of a lecture 
 before the American Institute of Electrical Engi- 
 neers, as follows, viz. : 
 
 ' ' If the frequency is still more increased, then 
 the coil refuses to give any spark unless at com- 
 paratively small distances, and the fifth typical 
 form of discharge may be observed (Fig. 207). 
 The tendency to stream out and dissipate is then 
 so great that when the brush is produced at one 
 terminal no sparking occurs, even if, as I have re- 
 peatedly tried, the hand, or any conducting ob- 
 ject, is held within the stream ; and, what is more 
 
Dis.] 
 
 166 
 
 [Dis. 
 
 singular, the luminous stream is not at all easily 
 deflected by the approach of a conducting body. 
 
 "At this stage the streams seemingly pass with 
 the greatest freedom through considerable thick- 
 nesses of insulators, and it is particularly interest- 
 ing to study their behavior. For this purpose it 
 is convenient to connect to the terminals of the 
 coil two metallic spheres, which may be placed at 
 any desired distance (Fig. 208) . Spheres are pref- 
 
 Fig. 207. Fifth. Typical Form of Discharge ( Tcsla). 
 
 erable to plates, as the discharge can be better 
 observed. By inserting dielectric bodies between 
 the spheres, beautiful discharge phenomena may 
 be observed. If the spheres be quite close and a 
 spark be playing between them, by interposing a 
 thin plate of ebonite between the spheres the 
 spark instantly ceases and the discharge spreads 
 into an intensely luminous circle several inches in 
 diameter, provided the spheres are sufficiently 
 large. The passage of the stream heats, and, 
 after a while, softens the rubber so much that two 
 
 Fig. 2O8. Luminous Discharge -with Interposed 
 Insulators. 
 
 plates may be made to stick together in this man. 
 ner. If the spheres are so far apart that no spark 
 occurs, even if they are far beyond the striking 
 distance, by inserting a thick plate of glass the 
 discharge is instantly induced to pass from the 
 spheres to the glass in the form of luminous 
 streams. It appears almost as though these 
 
 streams pass through the dielectric. In reality 
 this is not the case, as the streams are due to the 
 molecules of the air which are violently agitated 
 in the space between the oppositely charged sur- 
 faces of the spheres. 
 
 "When no dielectric other than air is present, 
 the bombardment goes on, but is too weak to 
 be visible ; by inserting a dielectric the ind k x> 
 live effect is much increased, and besides, the 
 projected air molecules find an obstacle and the 
 bombardment becomes so intense that the streams 
 become luminous. If by any mechanical means 
 we could effect such a violent agitation of the 
 molecules we could produce the same phenom- 
 enon. A jet of air escaping through a small 
 hole under enormous pressure and striking 
 against an insulating substance, such as glass, 
 may be luminous in the dark, and it might be 
 possible to produce phosphorescence of the glass 
 or other insulators in this manner. 
 
 " The greater the specific inductive capacity of 
 the interposed dielectric, the more powerful the 
 effect pioduced. Owing to this the streams show 
 themselves with excessively high potentials even 
 if the glass be as much as one and one-half to .two 
 inches thick. But besides the heating due to bom- 
 bardment, some heating goes on undoubtedly in 
 the dielectric, being apparently greater in glass 
 than in ebonite. I attribute this to the greater 
 specific inductive capacity of the glass in conse- 
 quence of which, with the same potential differ- 
 ence, a greater amount of energy is taken up in it 
 than in rubber. It is like connecting to a battery 
 a copper and a brass wire of the same dimen- 
 sions. The copper wire, though a more perfect 
 conductor, would heat more by reason of its tak- 
 ing more current. Thus what is otherwise con- 
 sidered a virtue of the glass is here a defect. 
 Glass usually gives way much quicker than ebo 
 nite ; when it is heated to a certain degree thfc 
 discharge suddenly breaks through at one point, 
 assuming then the ordinary form of an arc." 
 
 Discharge, Conductive A dis- 
 charge effected by leading the charge off 
 through a conductor placed in contac* with 
 the charged body. 
 
 Discharge, Convective A dis- 
 charge which occurs from the points on the 
 surface of a highly charged conductor, 
 through the repulsion by the conductor of air 
 particles that in this manner carry off minute 
 charges. 
 
Dis.] 
 
 1C7 
 
 [Dis. 
 
 A convective discharge, though often attended 
 by a feeble sound, is sometimes called a silent 
 discharge, in order to distinguish it from the 
 noisy, disruptive discharge, which is attended by 
 a sharp snap, or when considerable, by a loud 
 report. 
 
 A convective discharge is also called a glow or 
 brush discharge. The latter is best seen at the 
 small button at the end of the prime or positive 
 conductor of a frictional electric machine. 
 
 The positive discharge from a point or small 
 rounded conductor is always brush-shaped; the 
 negative discharge is always star shaped. 
 
 In rarefied gases, the discharge is convective in 
 character and produces various luminous effects 
 of great beauty, the color of which depends on 
 the kind of gas, and the size, shape and material 
 of the electrodes, and on the degree of the vacuum. 
 Thus in the rarefied 
 space of the vessel shown 
 in Fig. 209, the discharge 
 becomes an ovoidal mass 
 of light, sometimes called ] 
 the Philosopher' 1 s Egg. 
 
 When the discharges! 
 in rarefied gases follow 
 one another very rapid- 
 ly, alternations of light 
 and darkness, or stratifi- 
 cations, or stria are pro- ] 
 duced. 
 
 The breadth of the 
 dark bands increases as 
 the vacuum becomes 
 higher. The light por- 
 tions start at the positive 
 electrode, and are hotter | 
 than the dark portions. 
 
 The effects of luminous Fi s-sog. Discharge i 
 convective dischargesare R^efiedAir. 
 
 best seen in exhausted glass tubes, called Geissler 
 lubes, containing residual atmospheres of various 
 gases. (See Tubes, Geissler.) 
 
 Discharge, Dead-Beat A non- 
 oscillatory discharge. (See Discharge, 
 Oscillatory?) 
 
 Discharge, Disruptive A sudden, 
 
 and more or less complete, discharge that 
 takes place across an intervening non-con- 
 ductor or dielectric. 
 
 A mechanical strain of the dielectric occurs, 
 which suddenly breaks down as it were and per- 
 
 mits the discharge to pass as a spark, or rap^ 
 succession of sparks. 
 
 In air, the spark, when long, generally takes 
 the zigzag path, as shown in Fig. 210. 
 
 The sparks produced by disruptive discharges 
 consist of heated gases, 
 together with portions of 
 the conductor that are 
 volatilized by the heat. 
 
 The discharge of a Ley- 
 den jar or condenser may 
 be disruptive, as when 
 the discharging rod is 
 held with one knob con- 
 nected with one coating, 
 and the other near the 
 other coating. It may 
 be gradual, as when the 
 two coatings are alter- 
 nately connected with the 
 ground. The discharge 
 of a Leyden jar as, in- 
 deed, the disruptive dis- 
 charge in general, is os- 
 cillatory. 
 
 The stress is often suf- 
 ficient to pierce the glass. 
 
 Discharge, Dura- 
 tion of The 
 
 Fig. 210. Disruptive 
 Discharge. 
 
 time required to effect a complete disruptive 
 discharge. 
 
 The disruptive discharge is not instantaneous; 
 some time is required to effect it. Estimates of 
 the duration of a flash of lightning based on the 
 duration of a Leyden jar discharge, are mislead- 
 ing from the enormous difference in the quantity 
 and the potential in the two cases. The fact that 
 the disruptive discharge is oscillatory and consists 
 of a number of discharges taking place in alter- 
 nately opposite directions shows that the discharge 
 is not instantaneous. 
 
 Leyden jar discharges, are, however, accom- 
 plished in very small periods of time. 
 
 Discharge, Flaming The white 
 
 and flaming arc-like discharge that occurs 
 between the terminals of the secondary of an 
 induction coil, when, with a great number of 
 alternations per second, the current through 
 the primary is increased beyond that required 
 for the sensitive-thread discharge. (See Dis* 
 charge, Sensitive- Thread!) 
 
Dis.] 
 
 168 
 
 [Dis. 
 
 According to Tesla the flaming discharge is 
 best produced when the number of alternations is 
 not too great and certain relations between ca- 
 pacity, self-induction and frequency are observed. 
 These relations must be such as will permit the 
 flow through the circuit of the maximum current, 
 and thus may be obtained with wide variations in 
 the frequency. The flaming discharge develops 
 considerable heat, and is characterized by the 
 absence of the shrill note accompanying less pow- 
 erful discharges. This is probably due to the 
 enormous frequency. 
 
 Some idea of the flaming discharge may be had 
 
 Fig. 211. Flaming Discharge (Tesla). 
 from an inspection of Fig. 211, taken from Tesla. 
 
 Discharge, Glow A form of con- 
 
 vective discharge. (See Discharge, Con- 
 v&ttve.) 
 
 Discharge, impulsive A dis- 
 charge produced in conductors by suddenly 
 created differences of potential. 
 
 Impulsive discharges are influenced more by the 
 inductance of a conductor than by its true ohmic 
 resistance. (See Inductance. Resistance, Ohmic. ) 
 
 A mass of guncotton simply ignited in the 
 open air, produces but little effect on any resisting 
 object placed below it. If, however, it be rapidly 
 ignited by means of a detonator, and is thus fired 
 with much greater rapidity, it may shatter any- 
 thing placed beneath it. 
 
 In a similar manner, a rapidly discharged cur- 
 rent, or impulsive discharge, produces, through the 
 inductance of the conductor, a series of effects 
 somewhat similar to the above, in which a great 
 impedance is produced by a sudden change of 
 direction. 
 
 Discharge, Induced Currents, Effects 
 
 Produced by Varying classes of 
 
 effects produced by the discharges of induced 
 currents. 
 
 The effects produced by discharges of induced 
 currents are classified by Fleming as follows: 
 
 (l.) Effects depending on the entire quantity of 
 the discharge. 
 
 a. Galvanometric effects. 
 
 If the needle of the galvanometer has a period 
 or time of oscillation that is long, as compared 
 with the time of duration of the discharge, the sine 
 of one-half the angle of deflection is proportional 
 to the whole quantity of the discharge. 
 
 b. Electro-chemical effects. 
 
 The quantity of an electrolyte broken up is 
 proportional to the quantity of electricity which 
 passes through it. 
 
 (2.) Effects depending on the average of the 
 square of the current strength at any instant dur- 
 ing the discharge. 
 
 a. Heating effects. 
 
 The rate of dissipation as heat, according to 
 Joule's law, is proportional to the square of the 
 current strength passing. 
 
 b. Electro-dynamic effects. 
 
 When a discharge passes through a circuit, 
 part of which is fixed and part movable, the forces 
 of attraction and repulsion which take place be- 
 tween them at any instant are proportional to 
 the square of the current strength. 
 
 (3.) Effects depending on rate of change of 
 the current. 
 
 a. Physiological effects. 
 
 The effect of the discharge in producing physi- 
 ological shock increases with the suddenness of 
 the discharge. Of two discharges which reached 
 the same maxima that which reached it first would 
 produce the greatest physiological effect. Recent 
 investigations by Tesla and others would appear to 
 partly disprove the above statement 
 
 b. Telephonic effects. 
 
 The telephone, like the body of an animal, is 
 affected more by the rate of change than by the 
 current strength at any instant. 
 
 c. Magnetic effects. 
 
 Rayleigh has shown that the magnetic effects of 
 the discharge depend upon the maximum current 
 strength during the discharge, or upon the initial 
 current strength, in cases where the current dies 
 away gradually. Since the time required for the 
 permanent magnetizing of a steel wire is small 
 compared with the duration of the induced cur- 
 rent, the amount of magnetism acquired depends 
 essentially on the initial or maximum current 
 strength during the discharge, irrespective of the 
 time during which said discharge lasts. 
 
Dis.J 
 
 169 
 
 [Dis. 
 
 d. Luminous effects. 
 
 These are also dependent in the case of induced 
 discharges on the rate of change of the current. 
 
 Discharge-Key. (See Key, Discharged) 
 
 Discharge, Lateral 
 
 A discharge, 
 
 taking place on the discharge of a Leyden jar, 
 or other disruptive discharge, between parts 
 of the jar or conductors, not in the circuit of 
 the main discharge. 
 
 If a charged Leyden jar is placed on an insulat- 
 ing stool, and is then discharged by the discharg- 
 ing rod, the lateral discharge is seen as a small 
 spark that passes between the outside coating of 
 the jar and a body connected ^vith the earth at 
 the moment of the discharge through the rod. 
 
 A lateral discharge is also seen in the sparks 
 that can be taken from a conductor in good con- 
 nection with the earth, by holding the hand near 
 the conductor, while it is receiving large sparks 
 from a powerful machine in operation. These 
 discharges are due to induction. 
 
 If a Leyden jar be discharged by means of a con- 
 ducting wire bent as shown in Fig. 212, in which 
 
 
 Fig. 212. 
 
 two parts of the circuit are closely approached as at 
 A, whenever a spark occurs at B, another spark 
 produced by a lateral discharge occurs at A. 
 Although the resistance of the metallic circuit is 
 enormously less than the resistance of the air 
 Bpace through which the lateral discharge occurs, 
 yet the counter electromotive force produced in 
 the metallic circuit by the impulsive discharge, 
 renders its resistance far greater than that of 
 the air space. The path of a lateral discharge 
 is called the alternative path. (See Path, Al- 
 ternative, ) 
 
 Discharge, Luminous Effects of 
 
 The luminous phenomena attending and pro- 
 duced by an electric discharge. 
 
 The luminous effects vary as to color, intensity, 
 shape and accompanying acoustic phenomena 
 according to a variety of circumstances, the prin- 
 cipal of which are as follows, viz. : 
 
 (i.) With the kind of gaseous medium through 
 which the discharge passes. Thus, a spark passed 
 through hydrogen has a crimson or reddish color; 
 
 through carbonic acid or chlorine, a greenish 
 color. 
 
 (2.) With the density of the medium. In a 
 partial vacuum, the discharge from an induction 
 coil becomes an ovoidal mass of light. As the 
 vacuum increases, the light at first grows brighter, 
 but as a higher vacuum is reached, striae of al- 
 ternate dark and light bands appear. Finally, 
 with very high vacua the discharge fails to pass. 
 (See Discharge, Convective.') 
 
 (3.) With the nature of the substances forming 
 the points from which the discharge is taken. 
 This is due to the partial volatilization of the ma- 
 terial of the electrodes. 
 
 (4.) With the kind of electricity, i. e., whether 
 positive or negative. A positive charge assumes 
 the shape of a fan; a negative discharge, that of 
 a star. 
 
 (5.) On the density of the discharge. The in- 
 troduction of a Leyden jar or condenser in the 
 circuit of a Holtz machine, for example, causes 
 the spark to change from the faint bluish to the 
 silvery white. 
 
 (6.) The disruptive discharge through air is at- 
 tended by snapping or crackling sound, which, in 
 the case of lightning, reaches the intensity of thun- 
 der. When the disruptive discharge takes place 
 through a vacuum a faint hissing sound is heard, 
 or all sound may entirely disappear. 
 
 (7. ) Luminous effects resulting from molecular 
 bombardment occurring in comparatively high 
 vacua. These luminous effects may result : 
 
 (a.) From actual incandescence of some refrac- 
 tory material produced by the blows of the mole- 
 cules; or, 
 
 (b.) As a result of phosphorescence or fluores- 
 cence due to such blows. 
 
 Canary glass, or glass stained by uranium oxide, 
 fluoresces and emits a yellowish green light; solu- 
 tion of sulphate of quinine emits a bluish light. 
 
 Discharge, Non-Oscillatory A 
 
 dead-beat discharge. (See Discharge, Dead- 
 Beat.} 
 
 Discharge, Oscillating A number 
 
 of successive discharges and recharges which 
 occur on the disruptive discharge of a Leyden 
 jar, or condenser. 
 
 A discharge which periodically decreases 
 by a series of oscillations. 
 
 A discharge which produces a dying-away- 
 backwards and forwards current. 
 
Dis.] 
 
 170 
 
 [Dis 
 
 The disruptive discharge ot a Leyden jar, or 
 condenser, is not effected by a single rush of elec- 
 tricity. When discharged through a compara- 
 tively small resistance, a number of alternate 
 partial discharges and recharges occur, which 
 produce true oscillations or undulatory discharges. 
 
 These oscillations are caused by the induction 
 of the discharge on itself, and are similar to the 
 self-induction of a current. 
 
 The existence of the oscillating discharge in the 
 case of a Leyden jar or condenser, proves, in the 
 opinion of some, that electricity, taken along 
 with matter, possesses i property similar to 
 inertia. 
 
 Discharge, Oscillatory A term 
 
 sometimes used for an oscillating discharge. 
 (See Discharge, Oscillating) 
 
 Discharge, Periodic An electric 
 
 discharge which changes its direction at reg- 
 ular intervals or periods. 
 
 An alternating discharge. 
 
 Discharge, Periodically-Decreasing 
 
 An oscillating discharge whose decrease is 
 periodic. (See Discharge, Oscillating?) 
 
 Discharge, Sensitive-Thread The 
 
 thin, thread-like discharge that occurs be- 
 tween the terminals of the secondary of an in- 
 duction coil of high frequency. 
 
 The sensitive-thread discharge occurs, accord- 
 ing to Tesla, when the number of alternations per 
 
 Fig- 2 1 3- Sensitive- Thread Discharge ( Tesla). 
 
 second is high and the current through the 
 primary small. This discharge has the form of 
 a thin, feebly -colored thread. Though very sensi- 
 tive, being deflected by a mere breath, it is never- 
 theless quite persistent, if the terminals be at 
 one-third of the striking distance apart. Tesla 
 ascribes its extreme sensitiveness, when long, to 
 the motion of suspended dust particles in the air. 
 The general appearance of the sensitive-thread 
 discharge is shown in Fig. 213, taken from Tesla. 
 
 Discharge, Silent A name given 
 
 to a convective discharge in order to distin- 
 guish it from the more noisy disruptive dis- 
 charge. 
 
 The convective discharge in reality is attended 
 by a feeble sound, which, however, is quiet when 
 compared with the more pronounced sound of the 
 disruptive discharge. (See Discharge, Connec- 
 tive.} 
 
 Discharge, Stratified The form 
 
 of alternate light and dark spaces assumed by 
 the discharges of an induction coil through a 
 partially exhausted gas. (See Tube, Strati- 
 fication?) 
 
 The striae are explained by Curtis as follows: 
 'Under the influence of the electric rhythm of 
 the rapidly following discharges the molecules 
 of the residual gas collect in alternately dense 
 and rarefied spaces. The light bands correspond to 
 the spaces where the molecules are comparatively 
 crowded together, and their concomitant friction 
 produces the luminous disturbance. The dark 
 spaces are where the molecules are further apart, 
 and where their collisions are consequently lest 
 frequent." 
 
 Discharge, Streaming A form as- 
 sumed by the flaming discharge between the 
 terminals of the secondary of an induction 
 coil when the frequency of the alternations 
 increases beyond a certain limit, and the 
 potential has consequently increased. 
 
 The streaming discharge partakes of the general 
 characteristics of the flaming discharge. Lumi- 
 nous streams pass in abundance, not only between 
 the terminals of the secondary, but, according to 
 Tesla, who has carefully studied these phe- 
 nomena, between the primary and the secondary, 
 through the insulating dielectric separating 
 
 Fig. 214. Streaming Discharge (Tesla). 
 
 them. The streams not only pass between th 
 terminals, but also issue from all points and pro- 
 
Dis.] 
 
 171 
 
 [Dis. 
 
 jections, as will be seen from Fig. 214, taken from 
 Tesla. 
 
 When the streaming discharge reaches a cer- 
 tain higher limit it becomes a brush-and spray 
 discharge. (See Discharge, Brush-and- Spray.} 
 
 The streaming discharge obtained from an in- 
 duction coil with high frequencies differs from that 
 of an electrostatic machine in that it neither pos- 
 sesses the violet color of the positive static dis- 
 charge nor the brightness of the negative, but is 
 intermediate in color. 
 
 -- A term some- 
 times applied to an oscillatory discharge. (See 
 Discharge, Oscillatory^) 
 
 Discharge, to Electrically - To 
 
 equalize differences of potential by connecting 
 them by means of a conductor. 
 
 Discharge, Undulatory -- A dis- 
 charge, the strength and direction of which 
 gradually change. (See Currents, Undu- 
 
 Discharge, Unidirectional - An 
 
 electric discharge which takes place from the 
 beginning to the end, in one and the same di- 
 rection. 
 
 Discharge, Telocity of -- The time 
 required for the passage of a discharge 
 through a given length of conductor. 
 
 According to modern views it is the ether sur- 
 rounding the wire or conductor which conveys 
 the electric pulses. All the energy which gets into 
 the conductor is dissipated as heat. 
 
 The velocity of propagation of discharge of the 
 pulses produced by the oscillating discharge of a 
 Leyden jar through .the inter-atomic or inter- 
 molecular ether, i.e., through the fixed ether within 
 different substances, varies with the substance. 
 Through free ether the velocity is that of light, or 
 185,000 miles a second. 
 
 The velocity of discharge through long con- 
 ductors or cables is much lessened by incapacity 
 of the cable, and the effects of induction, and will 
 therefore vary in different cases. (See Retard- 
 ation.} 
 
 Discharger, Universal - An appa- 
 ratus for sending the discharge of a powerful 
 Leyden battery or condenser in any desired 
 direction. 
 
 The universal discharger consists es ; ent'al'y of 
 
 metallic rods, supported on insulated pillars and 
 capable of ready motion, both towards and from 
 one another, as well as in vertical and horizon- 
 tal planes. The object which is to receive the 
 discharge is placed on an insulated table between 
 the rods', and the latter connected with the 
 opposite coatings of the battery or condenser, 
 when the discharge passes through it. 
 
 The term universal discharger is sometimes ap- 
 plied to the discharging tongs. 
 
 Discharging, Electrically -- The 
 act of equalizing differences of potential by 
 connection with a conductor. 
 
 Discharging Rod. (See Rod, Discharg- 
 
 Discharging Tongs. (See Tongs, Dis- 
 charging^) 
 
 Disconnect. To break or open an electric 
 circuit. 
 
 Disconnecter. A key or other device for 
 opening or breaking a circuit. 
 
 Disconnecting. The act of opening or 
 breaking an electric circuit. 
 
 Disconnection. A term employed to des- 
 ignate one of the varieties of faults caused 
 by the accidental breaking or disconnection 
 of a circuit. 
 
 Disconnections of this kind may be : 
 
 (I.) Total ; as by a switch inadvertently lefi 
 open; or by the accidental breaking of a part of 
 the circuit. 
 
 (2.) Partial ; as by a dirty contact; a loose, o 
 badly soldered joint; a poorly clamped binding 
 screw; a loose terminal, or a bad earth. 
 
 (3.) Intermittent; as by swinging joints, alter- 
 nate expansions or contractions on changes oi 
 temperature; the collection of dust and dirt in dry 
 weather, and their washing out in wet weather. 
 
 Disconnection, Intermittent - 
 
 Any fault in a line which occurs at intervals 
 or intermittently. 
 
 Disconnection, Partial -- A partial 
 fault in a line caused by any imperfect con- 
 tact. 
 
 Disconnection, Total --- A fault in 
 a line occasioned by a complete break in the 
 circuit. 
 
 Disguised Electricity. (See Electricity,. 
 Disguised.) 
 
Dis.J 
 
 172 
 
 [Dis. 
 
 Disjunctor. A device employed in a sys- 
 tem for tne distribution of electric energy by 
 means of continuous currents by condensers, 
 for the purpose of periodically reversing the 
 constant current sent over the line. (See 
 Electricity, Distribution of, by Continuous 
 Current by Means of Condensers?) 
 
 Dispersion Photometer. (See Photome- 
 ter, Dispersion?) 
 
 Displacement Current. (See Current, 
 Displacement?) 
 
 Displacement, Electric A displace- 
 ment of electricity in a uniform and non- 
 crystalline dielectric when lines of electro- 
 static or magnetic force pass through it. 
 
 The quantity of electricity displaced in any 
 homogeneous, non-crystallizable dielectric, 
 by the action of an electric force through 
 the unit area of cross-section, taken perpen- 
 dicular to the direction of the electric force. 
 
 Electric displacement is produced under an 
 elastic strain, which continues only while the elec- 
 tric force is acting. 
 
 Displacement, Electric, Lines of 
 
 Lines of electric induction along which elec- 
 tric displacement takes place. 
 
 Displacement, Electric, Oscillatory 
 
 A displacement of electricity in a di- 
 electric or non-conductor of an oscillatory 
 character. 
 
 Displacement, Electric, Theory of 
 
 A theory which regards the electricity 
 produced on an insulated conductor, by in- 
 duction through a dielectric, as displaced out 
 of the dielectric on to the conductor, or into 
 the dielectric from the conductor, by the in- 
 fluence of the electric force. 
 
 This conception was introduced into science by 
 Maxwell, after a careful study of Faraday's denial 
 of action at a distance. 
 
 Suppose a small insulated sphere to receive a 
 charge of electricity + Q. It will, by induction, 
 produce an equal and opposite charge Q, on 
 the inner surface, and a similar charge on the 
 outer surface of the small hollow sphere, placed 
 near it, but separated by the dielectric. There 
 has, therefore, been a displacement of electricity 
 throueh the dielectric. The medium of the 
 
 dielectric has connected the two bodies, and the 
 phenomena have appeared by the action of the 
 electric torce on the substance of the dielectric; 
 or, in other words, there has been no action at 
 a distance. 
 
 According to this conception, an electric cur- 
 rent, called a displacement current, exists in the 
 dielectric, while displacement is taking place. 
 
 Displacement Waves. (See Waves, Dis- 
 placement?) 
 
 Disruptive Electric Conduction. (See 
 Conduction, Electric, Disruptive?] 
 
 Dissimulated or Latent Electricity. 
 
 (See Electricity, Dissimulated or Latent?) 
 Dissipation of Charge. (See Charge, 
 
 Dissipation of?) 
 
 Dissipation of Energy. (See Energy, 
 
 Dissipation of.} 
 
 Dissipation of Energy, Hysteresial ' 
 
 (See Energy, Hysteresial, Dissipation of. 
 Hysteresis.} 
 
 Dissipation, Specific Hysteresial - 
 The specific loss of energy by hysteresis in 
 the case of a particular substance. (See 
 Hysteresis.} 
 
 Dissociate. To separate a compound sub- 
 stance into its constituents. 
 
 Dissociation. The separation of a chemi- 
 cal compound into its constituent parts. 
 
 Dissymmetrical Induction of Armature. 
 
 (See Armature, Dissymmetrical Induc- 
 tion of.} 
 
 Dissymmetrical Magnetic Field. (See 
 Field, Magnetic, Dissymmetrical.} 
 
 Dissymmetry of Commutation. (See 
 Commutation, Dissymmetry of.} 
 
 Distance, Critical, of Lateral Discharge 
 
 Through an Alternative Path The 
 
 distance at which a discharge will take place 
 through an air space of given dimensions, ii. 
 preference to passing through a metallic cir- 
 cuit of comparatively small resistance. 
 
 Distance, Explosive A term some- 
 times employed for sparking distance. (See 
 Distance, Sharking?) 
 
 Uist&uce. syarking The distance 
 
Dis.j 
 
 173 
 
 [Dot. 
 
 at which electrical sparks will pass through 
 an intervening air space. (See Spark, Length 
 of.} 
 
 Distant Station. (See Station, Distant.} 
 
 Distillation, Destructive 
 
 The 
 
 action of heat on an organic substance, 
 while out of contact with air, resulting in the 
 decomposition of the substance into simpler 
 and more stable compounds. 
 
 The different products resulting from destruc- 
 tive distillation may be successively collected by 
 the ordinary processes of distillation. 
 
 Distillation, Dry A species of de- 
 structive distillation. (See Distillation, De- 
 structive.} 
 
 Distillation, Electric The dis- 
 tillation of a liquid in which the effects of 
 heat are aided by an electrification of the 
 liquid. 
 
 Beccaria discovered that a liquid evaporates more 
 rapidly when electrified than when unelectrified. 
 Crookes has shown that evaporation is aided 
 by negative electrification, or that evaporation 
 takes place more rapidly at the negative terminal 
 during a discharge than at the positive. (See 
 Evaporation, Electric. ) 
 
 Distributing Box of Conduit. (See Box, 
 Distributing, of Conduit?) 
 
 Distributing Station. (See Station, Dis- 
 tributing.} 
 Distributing Switch for Electric Light. 
 
 (See Switch, Distributing, for Electric 
 Lights.} 
 Bistribution-Box for Arc Light Circuits. 
 
 (See Box, Distribution, for Arc Light 
 Circuits} 
 
 Distribution, Centre of In a sys- 
 tem of multiple-distribution, any place where 
 branch cut-outs and switches are located in 
 order to control communication therewith. 
 
 The electrical centre of a system of distri- 
 bution as regards the conducting network. 
 
 Distribution of Charge. (See Charge, 
 Distribution of} 
 
 Distribution of Electricity. (See Elec- 
 tricity, Distribution of} 
 
 Distribution of Electricity by Alternat- 
 ing Currents (See Electricity, Dis- 
 tribution of, by Alternating Currents.} 
 
 Distribution of Electricity by Alternat- 
 ing Currents by Means of Condensers. 
 (See Electricity, Distribution of, by Alter- 
 nating Currents by Means of Condensers.} 
 
 Distribution of Electricity by Caminu- 
 tating Transformers. (See Electricity, 
 Distribution of, by Commutating Trans- 
 formers?) 
 
 Distribution of Electricity by Constant 
 Potential Circuit. (See Electricity, Multi- 
 ple Distribution of, by Constant Potential 
 Circuit} 
 
 Distribution of Electricity by Contin- 
 uous Current by Means of Transformers. 
 (See Electricity, Distribution of, by Contin- 
 uous Current by Means of Transformers.) 
 
 Distribution of Electricity by Motor- 
 Generators. (See Electricity, Distribution 
 of, by Motor-Generators} 
 
 Distribution, Series, of Electricity by 
 Constant Current Circuit. (See Electricity, 
 Series Distribution of, by Constant Current 
 Circuit} 
 
 District Call-Box. (See Box, District 
 Call} 
 
 Diurnal Inequality of Earth's Magnet- 
 ism. (See Inequality, Diurnal, of Earth's 
 Magnetism?) 
 
 Divided Magnetic Circuit. (See Circuit, 
 Divided Magnetic} 
 
 Door-Opener, Electric A device 
 
 for opening a door from r. distance by elec- 
 tricity. 
 
 Various devices consisting of electro-magnets, 
 acting against, or controlling springs or weights, 
 are employed for this purpose. 
 
 Dosage, Electro-Therapeutical 
 
 The apportioning of the amount of the cur- 
 rent and the duration of its application to the 
 body for the treatment of disease. 
 
 Dosage, Galvanic Electro-thera- 
 peutical dosage. (See Dosage, Electro- 
 Therapeutical) . 
 
 Dotting Contact. (See Contact, Dotting} 
 
DOU.J 
 
 174 
 
 Double-Break Knife Switch. (See 
 
 Switch, Double-Break Knife?) 
 
 Double-Carbon Arc Lamp. (See Lamp, 
 Electric Arc, Double-Carbon) 
 
 Double-Cone Insulator. (See Insulator, 
 Double-Cone) 
 
 Double- Connector. (See Connector, 
 Double) 
 
 Double-Contact Key. (See Key, Double- 
 Contact) 
 
 Double-Cup Insulator. (See Insulator, 
 Double-Cup) 
 
 Double-Curb. (See Curb, Double) 
 
 Double-Curb Signaling. (See Signaling, 
 Curb, Double) 
 
 Double-Current Signaling. (See Signal- 
 ing, Double-Current) 
 
 Double-Current Translator. (See Trans- 
 lator, Double-Current) 
 
 Double-Curr ent Transmitter. (See 
 Transmitter, Double-Current) 
 
 Double-Current Working The 
 
 employment, in systems of telegraphy, by 
 means of suitable keys, of currents from 
 voltaic batteries, in alternately opposite 
 directions, thus increasing the speed of 
 signaling. (See Working, Reverse-Current) 
 
 Double-Fluid Electrical Hypothesis. 
 
 (See Electricity, Double-Fluid Hypothesis 
 of-) 
 
 Double-Fluid Voltaic Cell. (See Cell, 
 Voltaic, Double-Fluid) 
 
 Double-Magnet Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 Double-Magnet) 
 
 Double-Pen Telegraphic Register. (See 
 Register, Double-Pen, Telegraphic.) 
 
 D o n b 1 e-Refraction. (See Refraction, 
 Double) 
 
 Double-Refraction, Electric. (See Re- 
 fraction, Double, Electric) 
 
 Double-Shackle Insulator. (See Insula- 
 tor, Double-Shackle) 
 
 Double-Shed Insulator. (See Insulator, 
 Double-Shed) 
 
 Double-Tapper Key. (See Key, Double- 
 Tapper) 
 Double-Touch, Magnetization by 
 
 A method for producing magnetization by 
 the simultaneous touch of two magnet poles. 
 (See Magnetization, Methods of) 
 
 Double-Transmission. (See Transmis- 
 sion, Double) 
 
 Double-Trolley. (See Trolley, Double) 
 
 Doubler of Electricity. An early form of 
 continuous electrophorus. (See Electro- 
 phorus) 
 
 Drifting Torpedo. (See Torpedo, Drift- 
 ing) 
 
 Drill, Electro-Magnetic A drill 
 
 applied especially to blasting or mining opera- 
 tions, operated by means of electricity. 
 
 Drip Loop. (See Loop, Drip) 
 Driven Pulley. (See Pulley, Driven) 
 Driven Shaft. (See Shaft, Driven) 
 Driving Pulley. (See Pulley, Driving) 
 Driving Shaft. (See Shaft, Driving) 
 Driving Spider. (See Spider, Driving) 
 
 Drop, Annunciator A movable 
 
 signal operated by an electro-magnet, and 
 placed on an annunciator, the dropping of 
 which indicates the closing or opening of the 
 circuit with which the electro-magnet is con- 
 nected. 
 
 The falling of the drop may be attended by the 
 sounding of a bell or other alarm, or, it may give 
 a silent indication. 
 
 Drop, Annunciator, Automatic A 
 
 drop for an annunciator, which on the closing 
 of a circuit, falls and holds the circuit closed 
 until the drop is raised. 
 
 Drop, Annunciator, Gravity A 
 
 drop for an annunciator, acted on by gravity 
 when released by the movement of the arma- 
 ture of an electro-magnet. 
 
 Drop, Automatic A device for au- 
 tomatically closing the circuit of a bell and 
 holding it closed until stopped by resetting a 
 drop. 
 
JDro.J 
 
 .175 
 
 [Dyn. 
 
 The automatic drop is especially applicable to 
 burglar alarms. On the opening of a door or 
 shutter, the closing of the circuit moves the 
 armature of an elec- 
 tro - magnet, and, 
 by the falling of a 
 drop, closes the cir- 
 cuit and holds 
 closed until me- 
 chanically opened 
 by the replacing of 
 the drop. The 
 general appearance 
 of the automatic 
 drop is shown in 
 Fig. 215. 
 
 Drop, Calling 1 
 
 A n an _ Fig. 2 is- Automatic Drop. 
 
 nunciator drop employed to indicate to the 
 operator in a telegraphic or telephonic system 
 that one subscriber wishes to be connected 
 with another. 
 
 Drop of Potential. (See Potential, Drop 
 
 of-} 
 
 Drops, Clearing- Out Restoring 
 
 the drops of annunciators to their normal 
 position after they have been thrown out of 
 the same by the closing of the circuits of their 
 magnets. 
 
 These clearing-out devices as placed on most 
 forms of annunciators are generally mechanical in 
 operation. 
 
 Drum Armatur e. (See Armature, 
 Drum.) 
 
 Drum, Electro-Magnetic A drum, 
 
 used in feats of legerdemain, operated by 
 an automatic electro-magnetic make and 
 break apparatus. 
 
 Dry Distillation. (See Distillation, 
 
 Dry.) 
 
 Dry Electrode. (See Electrode, Dry.) 
 Dry Pile. (See Pile, Dry) 
 
 Dry Voltaic Cell. (See Cell, Voltaic, 
 Dry.) 
 
 Dub's Laws. (See Laws, Dub's.) 
 Duplex Cable. (See Cable, Duplex.) 
 Duplex Cut-Ont. (See Cut-out, Duplex) 
 
 Duplex Flat Cable. (See Cable, Flat 
 Duplex) 
 
 Duplex Telegraphy. (See Telegraphy, 
 Duplex^ 
 
 Duplex Wire. (See Wire, Duplex^ 
 Duration of Electric Discharge. (See 
 Discharge, Duration of.) 
 
 Duration of Make-Induced Current. 
 
 (See Current, Make or Break Induced, Du- 
 ration of.) 
 
 Dust Figures, Lichtenberg's 
 
 (See Figures, Lichtenberg's Dust.) 
 
 Dyad. A chemical element which has two 
 bonds by which it can unite or combine with 
 another element. 
 
 An element whose atomicity is bivalent. 
 
 Dyeing, Electric The application 
 
 of electricity either to the reduction or the 
 oxidation of the salts used in dyeing. 
 
 Goppelsroder, in his processes of electric dyeing^ 
 forms and fixes ani'.ine black on cloth as follows, 
 viz.: the cloth, saturated with an aniline salt, is 
 placed on an insulated metallic plate, inert to the 
 aniline salt, and connected with one pole of a 
 battery or other electric source. The other pole 
 is connected with a metallic plate on which the 
 required design is drawn. On the passage of the 
 current, the design is traced in aniline black on 
 the cloth. A minute or two suffices for the 
 operation. 
 
 A species of electrolytic writing is obtained on 
 cloths arranged as above by substituting a carbon 
 pencil for the metallic plate. On writing with 
 this pencil, as with an ordinary pencil, the pas- 
 sage of the current so directed is followed by the 
 deposition of aniline black. 
 
 By means of a somewhat similar process writ- 
 ing in white on a colored ground is obtained. 
 
 Dynamic Electricity. (See Electricity, 
 Dynamic?) 
 
 Dynamics, Electro That branch 
 
 of electric science which treats of the action 
 of electric currents on one another and on 
 themselves or on magnets. 
 
 The principles of electro-dynamics were dis- 
 covered by Ampere in 1821. 
 
 A convenient form of apparatus, for showing 
 experimentally the action of one current on 
 another, consists of two upright metallic columns 
 
Dyn.J 
 
 176 
 
 [Dyn. 
 
 or pillars, which support horizontal metallic arms 
 containing mercury cups, y, and c, Fig. 216. 
 
 Fig. 2 rb. Deflection of a Circuit by a Current. 
 
 The circuit is bent in the form of a rectangle, 
 circle or solenoid, and terminates in points that 
 dip in the mercury cups. The current is led into 
 and out of the apparatus at the points -}- and 
 at the base of the upright supports. 
 
 When a magnet, or another circuit, is ap- 
 proached to the movable circuit thus provided, 
 attractions or repulsions are produced according 
 to th2 position of the magnet, or the direction of 
 the currents in the two circuits. 
 
 If a magnet A B, Fig. 217, be placed, as shown, 
 
 Fig. 217. Deflection of Circuit by a Magnet. 
 
 below the movable circuit C C, the circuit will 
 tend to place itself at right angles to the axis of 
 the magnet. This movement is the same as 
 would occur if electric currents were circulating 
 around the magnet in the direction.cf the assumed 
 Amperian cur rents. It also illustrates the prin- 
 ciple of the electric motor. (See Magnetism, Am- 
 pere's Theory of.) 
 
 Ampere has given the results of his investigations 
 as to the mutual attractions and repulsions of cur- 
 
 rents in the following statements, which are 
 known as Ampere's Laws : 
 
 (l.) Parallel portions of a circuit attract one 
 another if the currents in them are flowing in the 
 same direction, and 
 repel one another if 
 the currents are flow- 
 ng in opposite direc- 
 tions. 
 
 A current flowing 
 through a spiral tends 
 to shorten the spiral 
 from the attraction of 
 the parallel currents in contiguous turns. 
 
 Similar poles of two solenoids repel each other, 
 as at A, A', Fig. 218, because, when opposed to 
 each other, the currents that produce these poles 
 
 A B 
 
 Fig. 218. Action of Solenoid 
 
 Poles. 
 
 Fig. 2 rq. Antptre's Stand. 
 
 are flowing in opposite directions, as may be 
 seen from an^inspection of the drawing. 
 
 Dissimilar solenoid poles, on the contrary, at- 
 tract each other as at A, B, in Fig. 218, since 
 
 c 
 
 Fig. 2 2O. Electro- Dynamic Attraction. 
 
 the currents which produce them flow in the same 
 direction. 
 
 In Fig. 219, a form of Ampere's stand is shown, 
 in which one of the circuits is in the form of the 
 
177 
 
 [Dyn. 
 
 coil M N ; its action on the movable circuit C B, 
 is to repel it, since the currents, as shown, are 
 flowing in an opposite direction in the adjacent 
 portions of the fixed and movable circuits. 
 
 (2.) Two portions of a circuit intersecting each 
 other mutually attract each other when the cur- 
 rents in both circuits flow 
 either towards or from 
 the point of intersection, 
 but repel each other f 
 they flow in opposite di- 
 rections from this point. 
 
 Thus, in Fig. 220, the , 
 currents in both circuits P 
 P Q and A B C D, flow 
 towards and from the 
 
 Fig. 22T. Continuous 
 Rotation of Current. 
 
 point of intersection Y, and attract one another 
 and cause a motion until the two circuits are 
 parallel. 
 
 If the currents flow in opposite directions they 
 repel each other, and, if free to move, will come 
 to rest when parallel to each other ; therefore, 
 two portions of a circuit crossing each other tend 
 to mjve until they are parallel, and their currents 
 are flowing in the same direction. 
 
 (3.) Successive portions of the circuit of the 
 same rectilinear current, that is, a current flowing 
 in the same straight line, repel one another. 
 
 A circuit O A, Fig. 221, movable on O, as a 
 
 Fig . 222. Mutual Action of Magnetic Fields. 
 
 centre, will be continuously rotated in the direc- 
 tion of the curved arrow by the rectilinear cur- 
 rent, P Q; for, the directions of the currents being 
 as shown by the arrows, there will be attraction 
 in the positions (i) and (2), and repulsion in pe- 
 tition (4). 
 
 The cause of the mutual attractions and repul- 
 sions df electric circuits will readily appear from 
 a consideration of the mutual action of their 
 magnetic fields. 
 
 Thus an inspection of Fig. 222 shows : 
 
 (l.) That parallel currents flowing in the same 
 direction attract, because their lines of force have 
 opposite directions in adjoining parts of the cir- 
 cuit of these lines. 
 
 (2.) That parallel currents flowing in opposite 
 directions repel, because their lines of force have 
 the same directions in adjoining parts of the cir- 
 cuit. 
 
 These laws may therefore be generalized thus, 
 viz. : Lines of magnetic force extending in oppo- 
 site dirtctions attract one another; lines of 
 magnetic force extending in the same direction 
 repel one another. 
 
 Ampere proved that a circuit, doubled on itself 
 so that the current flows in opposite directions in 
 the two parts, exerts no force on external objects. 
 This expedient is adopted in resistance coils to 
 prevent any disturbance of the galvanometer 
 needles. He also showed that a sinuous circuit, 
 or one bent into zigzags, produces the same effects 
 of attraction or repulsion as it would if it were 
 straight. (See Coil, Resistance.} 
 
 The term sinuous current is sometimes applied 
 to the current in a sinuous circuit. (See Current, 
 Sinuous.) This must be distinguished from the 
 term sinusoidal current, which applies to fluctua- 
 tions in the current and not to peculiarities in the 
 shape of the conductor. 
 
 When two inclined magnets, free to move, are 
 left to their mutual attractions and repulsions, they 
 gradually come to rest with their axes parallel to 
 each other. 
 
 Two conductors through which electric cur- 
 rents are flowing act on one another as two 
 magnets would. 
 
 A conductor conveying a current of electricity 
 tends to rotate round a magnetic pole. A mag- 
 netic pole tends t._> rotate continuously round an 
 electric current. 
 
 The motion of a magnet near a conductor 
 produces an electromotive force in that conductor 
 provided the conductor cuts the lines offeree. 
 
 A magnetized substance becomes magnetized 
 when placed in a magnetic field. 
 
 A conductor through which a current of elec- 
 tricity is passing tends to wrap itself around a 
 neighboring magnetic pole. The following ex- 
 periments illustrate this tendency: 
 
 (i.) The experiment suggested by Lodge: A 
 powerful current of electricity is passed through 
 some eight feet in length of gold thread such as 
 is employed for making lace. The thread is 
 hung in a vertical position, near a vertical bar 
 
178 
 
 magnet. As soon as the current passes, the 
 thread will wrap itself around the bar magnet, 
 one half of it twisting itself round the north pole, 
 the other half round the south pole. 
 
 (2.) The experiment suggested by Professor S. 
 P. Thompson: An electric current is sent through 
 a stream of mercury while it is flowing between 
 two poles of a powerful electro-magnet; when 
 the current is sent through the magnet, the 
 stream is twisted in spiral directions which vary, 
 either with the direction of the current, or with 
 the direction of the magnetic polarity. 
 
 (3.) Somewhat similar effects can be shown by 
 the rotation of a stream cf gas round a magnetic 
 pole placed in an exhausted glass receiver. 
 
 Dynamo. The name frequently applied to 
 a dynamo-electric machine used as a gener- 
 ator. (See Machine, Dynamo-Electric?) 
 
 Dynamo Balancing Rheostat. (See 
 Rheostat, Dynamo Balancing?) 
 
 Dynamo-Battery. (See Battery, Dy- 
 namo?) 
 
 Dynamo Brush Trimmer. (See Trim- 
 mer, Dynamo Brush?) 
 
 Dynamo, Composite-Field A 
 
 dynamo whose field coils are series and 
 separately excited. 
 
 Additional separately excited coils placed on 
 the field of a series wound dynamo render it self- 
 regulating. 
 
 A composite dynamo is a form of compounded 
 dynamo. 
 
 Dynamo, Compound-Wound. A com- 
 pound-wound dynamo-electric machine. (See 
 Machine, Dynamo-Electric, Compound- 
 Wound?) 
 
 Dynamo, Contact A form of dyna- 
 mo in which the space between the arma- 
 ture and field magnet poles is so reduced that 
 they actually touch one another. 
 
 In contact dynamos both field and armature 
 revolve. This form of dynamo has not been very 
 successful in practice. 
 
 Dynamo-Electric Machine. (See Ma- 
 chine, Dynamo-Electric?) 
 
 Dynamo-Electric Machine, Alternating 
 Current (See Machine, Dynamo- 
 Electric, Alternating Current?) 
 
 Dynamo-Electric Machine Armature. 
 
 (See Armature, Dynamo-Electric Machine.} 
 Dynamo-Electric Machine Armature 
 Coils. (See Coils, Armature, of Dynamo- 
 Electric Machine?) 
 
 Dynamo-Electric Machine Armature 
 Core. (See Core, Armature, of Dynamo- 
 Electric Machine?) 
 
 Dynamo-Electric Machine Battery. 
 (See Battery, Dynamo-Electric Machine?) 
 
 Dynamo-Electric Machine, Bi-Polar 
 
 (See Machine, Dynamo-Electric, Bi- 
 Polar?) 
 
 Dynamo-Electric Machine, Collecting 
 
 Brushes of (See Brushes, Collecting, 
 
 of Dynamo-Electric Machine?) 
 
 Dynamo-Electric Machine Commutator 
 
 (See Commutator, Dynamo-Electric 
 
 Machine?) 
 
 Dynamo-Electric Machine, Compound- 
 Wound - - (See Machine, Dynamo- 
 Electric, Compound- Wound?) 
 
 Dynamo-Electric Machine, Generation of 
 Current by fSee Current, Genera- 
 tion of, by Dynamo-Electric Machine?) 
 
 Dynamo-Electric Machine, Field Mag- 
 nets (See Magnets, Field, of Dynamo- 
 Electric Machine?) 
 
 Dynamo-Electric Machine, Methods of 
 Increasing the Electromotive Force Gene- 
 rated by (See Force, Electromotive, 
 
 Generated by Dynamo-Electric Machine, 
 Method of Increasing?) 
 
 Dynamo-Electric Machine, Mouse-Mill, 
 Sir William Thomson's - (See Ma- 
 chine, Dynamo-Electric, Mouse-Mill, Sir 
 William Thomson's?) 
 
 Dynamo-Electric Machine, Multipolar 
 (See Machine, Dynamo-Electric, 
 Multipolar?) 
 
 Dynamo-Electric Machine, Pole-Pieces of 
 
 (See Pole-Pieces of Dynamo-Electric 
 
 Machine?) 
 
 Dynamo-Electric Machine, Reversibility 
 
 of (See Machine, Dynamo-Electric, 
 
 Reversibility of?) 
 
179 
 
 Dynamo-Electric Machine, Varieties of 
 
 (See Machine, Dynamo-Electric, 
 
 Varieties of.) 
 
 Dynamo, Inductor A dynamo- 
 electric machine fey alternating currents in 
 which the differences of potential causing the 
 currents are obtained by magnetic changes in 
 the cores of the armature and field coils by 
 the movement past them of laminated masses 
 of iron inductors. 
 
 The coils corresponding to the armature and 
 field magnets of the ordinary dynamo are sta- 
 tionary. The laminated masses of iron, employed 
 to cause magnetic changes in the cores of the field 
 and armature coils, are fixed on an inductor wheel 
 which is rapidly revolved in front of them. The 
 magnets corresponding to the field magnets are 
 called the primary poles, and are magnetized by 
 an exciter. The magnets corresponding to the 
 armature are called the secondary poles and are 
 placed so as to alternate with the primary poles. 
 The inductors are so shaped that they carry the 
 magnetism of one pole of the primary magnet 
 to the secondary poles when the inductor is in 
 one position, and of the opposite pole when in a 
 slightly different position. The inductor wheel 
 therefore acts as a magnetic commutator and 
 changes the position of the secondary magnet as 
 it rotates, thus producing electromotive force. 
 The number of alternations per revolution is 
 equal to twice the number of inductors placed on 
 the inductor wheel. 
 
 Dynamo, Inverted A dynamo-elec- 
 tric machine in which the armature bore or 
 chamber is placed below the field magnet 
 coils. 
 
 The term inverted is used in contradistinction 
 to the overtype dynamo. (See Dynamo, Over- 
 type.} 
 
 Dynamo, Mouse Mill A form of 
 
 dynamo-electric machine designed by Sir 
 William Thomson to act as the replenisher of 
 one of his electrometers. (See Replenisher?) 
 
 Dynamo, Multiphase A polyphase 
 
 dynamo. (See Dynamo, Polyphase. Dyna- 
 mo, Rotating Current?) 
 
 Dynamo, Overtype A dynamo- 
 electric machine, the armature bore or cham- 
 ber of which is placed above the field magnet 
 coils instead of below them as in many forms. 
 
 The overtype form of dynamo possesses tha 
 advantage of better avoiding magnetic leakage. 
 
 Dynamo, Polyphase A name some- 
 times applied to a rotating current dynamo. 
 (See Dynamo, Rotating Current?) 
 
 Dynamo, Pyromagnetic A name 
 
 sometimes applied to a pyromagnetic gen- 
 erator. (See Generator, Pyromagnetic?) 
 
 Dynamo, Kotary-Phase A term 
 
 sometimes employed for a rotating current 
 dynamo. (See Dynamo, Rotating Current?) 
 
 Dynamo, Separately-Excited A 
 
 separately-excited dynamo-electric machine. 
 (See Machine, Dynamo-Electric, Separ- 
 ately-Excited?) 
 
 Dynamo, Series A series-wound 
 
 dynamo- electric 
 machine. (SeeJ/a- 
 chine, Dynamo- 
 Electric, Series- 
 Wound?) 
 
 Dynamo, Shunt 
 
 A shunt- 
 wound dynamo- 
 electric machine. 
 (See Machine, 
 Dynamo - Electric, 
 Shunt- Wound?) 
 
 Dynamograph. 
 
 A term some- 
 times applied to a 
 type-writing tele- 
 graph that records 
 the message in 
 type-written char- 
 acters, both at the 
 sending and the 
 receiving ends. 
 
 Dynamometer. [= 
 A name given to 
 a variety of appar- f,- f . 223 , Parsons' Dyna- 
 atus for measuring mometer. 
 
 the power of an engine or motor. 
 
 In all dynamometers the strain on the belt or 
 other moving part is measured, say in pounds, 
 and the speed of the moving part is also measured 
 in feet per second. The product of the strain in 
 
180 
 
 pounds by the velocity in feet per second, di- 
 vided by 550, will give the horse power. 
 
 One of the many forms of dynamometers is 
 shown in Fig. 223. It is known as Parsons' Dy- 
 namometer. 
 
 The driving pulley is shown at A, and the 
 driven pulley at C. Weights hung at Q 1 , are va- 
 ried so as to maintain the axes of the suspended 
 pulleys, D and B, as nearly as possible at the 
 same height. Then the tension T x and T 2 , on 
 the sides O and O', of the belts, will be repre- 
 sented by the following equation : 
 
 T _ T _ ^ Q 
 1 1 i i -- - , 
 
 Since the same current passes through both tht 
 fixed and movable coils, and they both act on 
 each other, the deflecting force here is evidently 
 proportional to the square of the strength of th 
 
 from which, knowing the belt speed, the horse 
 power may be deduced. 
 
 There are several other forms of dynamometer, 
 such as the cradle dynamometer, in which the 
 machine is supported on knife edges and the 
 torque or pull exerted on or by the machine is 
 balanced by weights sliding on a lever. In these 
 dynamometers the power is transmitted through 
 them and they are therefore called transmission 
 dynamometers. 
 
 Dynamometer, Electro -- A form of 
 galvanometer for the measurement of electric 
 currents. 
 
 In Siemens' Electro-Dynamometer, shown in 
 Fig. 224, there are two coils ; a fixed coil, C, se- 
 cured to an upright support, and a movable coil, 
 L, consisting often of but a single turn of wire. 
 The movable coil is suspended by means of a 
 thread and a delicate spring, S, capable of being 
 twisted by turning a milled screw -head through 
 an angle of torsion measured on a scale by means 
 of an index connected to the screw-head. The 
 two ends of the movable coil dip into mercury 
 cups so connected that the current to be measured 
 passes through the fixed and movable coils in 
 series. 
 
 When ready for use the movable coil is at right 
 angles to the fixed coil. The current to be meas- 
 ured is then sent into the coils, and their mutual 
 action tends to place the movable coil parallel to 
 the fixed coil against the torsion of the spring, S. 
 The amount of this force can be ascertained by 
 determining the amount of torsion required to 
 bring the movable coil back to its zero position. 
 
 Fig, 224.. Siemens' Electro- Dynamometer, 
 
 current to be measured. The deflecting force, 
 and consequently the current strength, is there- 
 fore proportional to the square root of the angle 
 of torsion, and not directly to the angle of tor- 
 sion. 
 
 Dyne. The unit of force. 
 
 The force which in one second can impart 
 a velocity of I centimetre per second to a 
 mass of I gramme. 
 
 The dyne is the unit of force, or a force capa- 
 ble, after acting for one second on a mass of I 
 gramme, of giving it a velocity of I centimetre 
 per second. The weight of a body in dynes, or the 
 force with which it gravitates, is equal tj its 
 mass in grammes, multiplied by the acceleration 
 imparted to it in centimetres per second. For 
 this latitude the acceleration is about 981 centi- 
 metres per second. 
 
E,] 
 
 181 
 
 [Bad. 
 
 E. A contraction sometimes used for 
 earth,, 
 
 A contraction sometimes used for electro- 
 motive force, or E. M. F., as in the well- 
 known formula for Ohm's law, 
 
 E. M. D. P. A contraction for electro- 
 motive difference of potential. (See Poten- 
 tial, Difference of, Electromotive^) 
 
 E. M. F. A contraction generally used for 
 electromotive force. (See Force, Electro- 
 motive?) 
 
 Earth. A fault in a telegraphic or other 
 line, caused by accidental contact of the line 
 with the ground or earth, or with some con- 
 ductor connected with the latter. 
 
 This is more frequently called a ground. 
 
 Earths are of three kinds, viz. : 
 
 (I.) Deader Total Earth. 
 
 (2.) Partial Earth. 
 
 (3.) Intermittent Earth. 
 
 The term earth is also applied to a plate buried 
 in the ground, and intended to make a good con- 
 tact between the earth and a wire circuit, which 
 is connected with the plate. 
 
 Earth Circuit. (See Circuit, Earth?) 
 
 Earth-Circuited Conductor. (See Con- 
 ductor, Earth-Circuited?) 
 
 Earth Currents. Electric currents flow- 
 ing through different parts of the earth caused 
 by a difference of potential at different points. 
 
 The causes of these differences of potential are 
 Tarious and are not well understood. 
 
 Earth, Dead or Total A fault in 
 
 a telegraphic or other line in which the line 
 is thoroughly grounded or connected with 
 the earth. 
 
 Dead earth is sometimes called total earth. 
 
 Earth-Grounded Wire. (See Wire, 
 Earth- Grounded. ) 
 
 Earth, Intermittent A swinging 
 
 earth. (See Earth, Swinging or Jntermit- 
 tent?) 
 
 Earth or Ground. That part of the earth 
 
 or ground which forms part of an electric 
 circuit. 
 
 A circuit is put to earth or ground when the 
 earth is used for a portion of the circuit. 
 
 The resistance of an earth connection may vary 
 in time from the following causes, viz.: 
 
 ( I. ) The corrosion of the ground plate. This is 
 especially apt to occur in the case of a copper 
 plate. 
 
 (2.) From polarization, a counter-electro- 
 motive force being produced, thus introducing a 
 spurious resistance into the circuit. (See Resist- 
 ance, Spurious.) 
 
 Earth, Partial A fault in a tele- 
 graphic or other line in which the line is in 
 partial connection with the earth. 
 
 The term partial earth is used in contradistinc- 
 tion to dead or total earth. 
 
 Earth, Return A circuit in which 
 
 the return current passes back to the source 
 through the earth. 
 
 Earth, Swinging or Intermittent 
 
 A fault in a telegraphic or other line in 
 which the action of the wind, or occasional 
 expansion by heat, brings the line into inter- 
 mittent contact with the earth. 
 
 Earth, Total A term sometimes 
 
 used for dead earth. (See Earth, Dead or 
 Total?) 
 
 Ebonite. A tough, hard, black substance, 
 composed of India rubber and sulphur, which 
 possesses high powers of insulation and of 
 specific inductive capacity. 
 
 Ebonite is often called vulcanite. 
 
 Vulcanite rubbed with cat-skin acts as one of 
 the best known substances for becoming electri- 
 fied by friction. For this purpose both substances 
 should be thoroughly dried. 
 
 Economic Co-efficient of Dynamo-Elec- 
 tric Machine (See Co-efficient, Economic, 
 of a Dynamo-Electric Machine?) 
 
 Eddy Currents. (See Currents, Eddy.) 
 
 Eddy Currents, Deep-Seated (See 
 
 Currents, Eddy, Deep-Seated?) 
 
 Eddy Currents, Superficial (See 
 Currents, Eddy, Superficial?* 
 
Edd.j 
 
 Eddy-Displacement Currents. (See Cur- 
 rents, Eddy-Displacement^ 
 
 Eel, Electric An eel possessing 
 
 file power of giving powerful electric shocks = 
 
 The gymnotus electricus. 
 
 The electricity is produced by an organ ex- 
 tending the entire length of 
 the body. 
 
 According to Faraday, the 
 shock given by a specimen 
 of the animal examined by 
 him was equal to that of 15 
 Leyden jars, having a total 
 surface of 25 square feet. 
 Fig. 225 shows the general 
 appearance of the animal. 
 
 Effect, Acheson 
 
 The increase in the electro- 
 motive force of the sec- 
 ondary of a transformer by 
 the action of the changes 
 in temperature of its core. 
 (See Electricity, Cat.) 
 
 Effect, Chemical Eel, 
 
 The effect occasioned by atomic combina- 
 tion, which results in a loss of those properties 
 or peculiarities by which the substances en- 
 tering into combination are ordinarily recog- 
 nized. 
 
 Atomic combination, resulting in the for- 
 mation of new molecules 
 
 The formation of new molecules necessitates the 
 possession by the new substance of properties dis- 
 tinct and separate from those of its constituents. 
 
 Black carbon, and yellow sulphur, for example, 
 both solids, unite chemically to form a frans- 
 parent colorless liquid. 
 
 Chemical changes differ from physical changes, 
 which latter can occur in a substance without the 
 formation of new molecules, and consequently 
 without the loss by it of the properties it ordi- 
 narily possesses. 
 
 Thus a sheet of vulcanite, electrified by friction, 
 Still retains its characteristic density, shape, color, 
 etc. 
 
 Effect, Counter-Inductive The 
 
 opposal of current or charge oy means of a 
 counter-electromotive force produced by ui- 
 duction. 
 
 Fig. 223. Electric 
 
 [Eft 
 
 In the Thomson counter-electromotive force 
 lightning arrester, a counter-electromotive force, 
 produced by the inductive effects of the passag 
 of the bolt to earth, protects the instrument by 
 opposing the passage of the bolt. (See Arrester % 
 Lightning Counter-Electromotive Force.") 
 
 Effect, Edison An electric dis- 
 charge which occurs between one of the ter- 
 minals of the incandescent filament of an 
 electric lamp, and a metallic plate placed near 
 the filament but disconnected therefrom, as 
 soon as a certain difference of potential is 
 reached between the lamp terminals. 
 
 The effect of the discharge is to produce a cur- 
 rent in a circuit connected to one pole of the lamp 
 terminals and the metallic plate, as may be shown 
 by means of a galvanometer. 
 
 Effect, Electrotonic An altered 
 
 condition of excitability of a nerve produced 
 when in the electrotonic state. (See Elec- 
 trotonus?) 
 
 Effect, Faraday The rotation of 
 
 the plane of polarization of a beam of plane 
 polarized light by its passage through a 
 magnetic field. 
 
 Lodge suggests the following explanation for 
 the Faraday effect : As is well known, a strongly 
 magnetized medium possesses a different magnetic 
 susceptibility to additional magnetizing forces in 
 the same direction than it does in the opposite 
 direction. It therefore follows that the vibra- 
 tions are resolved into two opposed circular com- 
 ponents, which travel through the medium with 
 different rates of velocity, since one tends to mag- 
 netize it and the other to demagnetize it. The 
 plane of rotation will therefore be rotated. 
 
 He also suggests the following explanation for 
 the Faraday effect, viz.: He assumes that the 
 Amperian molecular currents in such substances 
 as exhibit rotation in a magnetic field do not 
 consist of two equal and opposite electrical cur- 
 rents, but that one of the currents is slightly 
 stronger than the other. Suppose, for example, 
 that in iron the positive Amperian current is 
 weaker than the negative, and that the ether as 
 a whole is rotating with the negative current. 
 Any ethereal vibration entering such a medium 
 will begin to screw itself in the direction opposed 
 to that of the magnetizing current. In copper, 
 or other similar substances, the rotation should 
 take place in the opposite direction. 
 
Elf. 
 
 183 
 
 [Eff, 
 
 Effect, Ferranti An increase in the 
 
 electromotive force, or difference of potential, 
 of mains or conductors towards the end of the 
 same farthest from the terminals that are con- 
 nected with a source of constant potential. 
 
 The Ferranti effect refers to the increase of the 
 electromotive force on the mains employed in 
 systems for the transmission of electrical energy 
 \y means of alternating currents. It was found, 
 for example, in the currents used on the 
 mains connected with one of Mr. Ferranti's alter- 
 nating dynamos and leading to the town of Dept- 
 ford, that instead of finding a drop of potential at 
 the ends of the mains farthest from the dynamo, 
 as was expected, a notable increase in the poten- 
 tial occurred. These effects were observed dur- 
 ing the laying of the mains. Testing the poten- 
 tial by placing an incandescent lamp in the circuit 
 across the mains, the increase of the potential 
 with the increase of the length of the main was 
 shown by the increased brilliancy of the light of 
 the incandescent lamp. 
 
 Various explanations have been given as the 
 cause of the Ferranti effect. 
 
 Effect, Hall A transverse elec- 
 tromotive force, produced by a magnetic 
 field in substances undergoing electric dis- 
 placement. 
 
 This transverse electromotive force is probably 
 
 Fig. 2S(>. Hall Effect. 
 
 due to magnetic whirls, in a manner similar to 
 the Faraday effect. 
 
 The Hall effect is produced by placing a very 
 thin metallic strip, conveying an electric current, 
 in a strong magnetic field. 
 
 Tne cross A B C D, Fig. 226, is cut out of a 
 
 gold leaf or other very thin metallic sheet. The 
 ends A and B, are connected with the terminals 
 of a battery S, and the ends C and D, with the 
 galvanometer G. 
 
 None of the battery current can therefore flow 
 through the galvanometer. 
 
 If, now, the metallic cross be placed in a power- 
 ful magnetic field, the lines of force of which are 
 perpendicular to the plane of the cross, the deflec- 
 tion of the galvanometer needle will show the 
 existence of a current, which, if the battery cur- 
 rent flows in the direction of the arrow, or from A, 
 to B, and the lines of magnetic force pass through 
 the paper from the front to the back of the sheet, 
 when the cross is formed of gold, silver, platinum 
 or tin-foil, will flow through C D, from C to D, 
 but in the opposite direction if formed of iron. 
 These effects cease if the conductor is increased 
 in thickness beyond a certain extent. 
 
 As regards the production of the Hall effect by 
 the influence of a magnetic field on conductors, 
 Mr. Shelford Bidwell suggests that since magnet- 
 ism affects the conductivity of metals in a 
 complicated manner, it is possible that metallic 
 substances conveying an electric current in a 
 magnetic field are more or less strained by the 
 mechanical forces, and that, therefore, heat may 
 be unequally developed, and that the resistance 
 thus being modified in places, there may be pro- 
 duced disturbances of the flow which may 
 rapidly produce in part a transverse electromotive 
 force. 
 
 Effect, Hall, Real A transverse elec- 
 tromotive force produced in conductors con- 
 veying electric currents, by magnetic whirls, 
 in a manner similar to that in which the Far- 
 aday effect is produced. (See Effect, Fara- 
 day^ 
 
 Effect, Hall, Spurious An appa- 
 rent transverse electromotive force produced 
 in conductors conveying electric currents in 
 magnetic fields, by changes, produced by mag- 
 netism, in the conductivity of the metals, and 
 the co'nsequent production of local distur- 
 bances in the electrical flow, thus resulting 
 in an apparent transverse electromotive force. 
 
 Effect, Impulsion The restoration 
 
 or loss of sensitiveness of a photo-voltaic eel' 
 to the action of light, produced by means of 
 an impulse such as that of a tap or blow, or 
 electro-magnetic impulse. 
 
Eff.] 
 
 184 
 
 [Eff. 
 
 Effect, Joule The heating effect 
 
 produced by the passage of an electric cur- 
 rent through a conductor, arising merely from 
 the resistance of the conductor. 
 
 The rate at which this occurs is proportional to 
 the resistance of the conductor through which 
 the current is passing multiplied by the square 
 of the current. (See Heat, Electric. ) 
 
 Effect, Kerr A term applied to 
 
 the electrostatic optical effect discovered by 
 Dr. Kerr, viz., that a beam of plane polarized 
 light is elliptically polarized when transmitted 
 across an electrostatic field. 
 
 The Kerr effect does not take place in free space, 
 but occurs in different senses or directions in dif- 
 ferent media. 
 
 Like the Faraday effect, the Kerr effect de- 
 pends on the presence of a dense medium, and the 
 direction of the effect depends on the character of 
 the medium. 
 
 Effect, Mordey A term some- 
 times applied to a decrease in the value of 
 hysteresis in the iron of a dynamo armature at 
 full load. 
 
 Effect, Peltier The heating ef- 
 fect produced by the passage of an electric 
 current across a thermo-electric junction or 
 surface of contact between two different met- 
 als. (See Junction, Ther mo-Electric.) 
 
 The passage of the current across a thermo- 
 electric junction produces either heat or cold. If 
 heat is produced by its passage in one direction, 
 told is produced by its passage in the opposite 
 direction. The Peltier effect may, therefore, 
 mask the Joule effect. 
 
 The Peltier effect is the converse of the thermo- 
 electric effect, where the unequal heating of metal- 
 lic junctions results in an electric current. (See 
 Effect, Joule. Effect, Thomson.) 
 
 The quantity of heat absorbed or emitted by 
 the Peltier effect is proportional to the current 
 strength, and not, as in the Joule effect, to the 
 square of the current. 
 
 Effect, Photo-Yoltaic The change 
 
 in the resistance of selenium or other 
 substances effected by their exposure to 
 light. The photo-voltaic effect is seen in 
 the case of the selenium cell. (See Cell, 
 Selenium?) 
 
 Effect, Seebeck A term sometimes 
 
 used instead of thermo-electric effect. (See 
 Effect, Thermo-Electric?) 
 
 This term has nearly passed out of use. 
 
 Effect, Skin The tendency of alter. 
 
 nating currents to avoid the central portions 
 of solid conductors and to flow or pass mostly 
 through the superficial portions. 
 
 The so-called skin effect is more pronounced 
 the more frequent the alternations. 
 
 Effect, Thermo-Electric The pro- 
 
 duction of an electromotive force at a 
 thermo-electric junction by a difference of 
 temperature between that junction and the 
 other junction of the thermo-electric couple. 
 (See Couple, Thermo-Electric. Junction, 
 Thermo-Electric^) 
 
 Effect, Thomson The production of 
 
 an electromotive force in unequally heated 
 homogeneous conducting substances. 
 
 A term also applied to the increase or de- 
 crease in the differences of temperature in an 
 unequally heated conductor, produced by the 
 passage of an electrical current through the 
 conductor. 
 
 The Thomson effects vary according to whether 
 the current passes from a colder to a 1 otter part 
 of the conductor, or the reverse. 
 
 The Thomson effects differ in direction in differ- 
 ent metals, and are absent in lead. Thomson has 
 pointed out the similarity between this species of 
 thermo-electric phenomena, and convection by 
 heat, or the phenomena of a liquid circulating in 
 a closed rectangular tube, under the influence of 
 differences of temperature, in -which the heated 
 fluid gives out heat in the cooler parts of the cir- 
 cuit, and takes in heat in the warmer parts. 
 This would presuppose that positive electricity 
 carries heat in copper like a real fluid, but that 
 in iron it acts as though its specific luat were a 
 negative quantity, in which respect it is unlike a 
 true fluid. 
 
 " We may express," says Maxwell, " both the 
 Peltier and the Thomson effects by stating that 
 when an electric current is flowing from places of 
 smaller lo places of greater thermo-electric power, 
 heat is absorbed, and when it is flowing in the 
 reverse direction heat is generated, and this 
 whether the difference of thermo-electric power 
 in the two places arises from a difference in the 
 
Eff.] 
 
 185 
 
 [Ele. 
 
 nature of the metals, or from a difference of tem- 
 perature in the same metal." 
 
 Effect, Toltaic A difference of 
 
 potential observed at the point of contact of 
 two dissimilar metals. 
 
 This difference of potential was formerly as- 
 Cribed to the mere contact of dissimilar metals, 
 and is even yet believed by some to be due to 
 such contact. It is, however, perhaps more ac- 
 curately ascribed to the greate-r affinity of oxygen 
 of the air for the positive metal than for the 
 negative metal; that is, to a chemical action on 
 the positive element of a voltaic couple. 
 
 Effective Electromotive Force. (See 
 Force, Electromotive, Effective?) 
 
 Effective Secondary Electromotive 
 Force. (See Force, Electromotive, Second- 
 ary, Effective?) 
 
 Effects of Capillarity on Voltaic Cells. 
 (See Capillarity ; Effects of, on Voltaic Cell?) 
 
 Efficiency, Commercial The useful 
 
 or available energy produced divided by the 
 total energy absorbed by any machine or ap- 
 paratus. 
 
 The Commercial Efficiency = 
 W _ W 
 
 ~M~ W + w -f- m, 
 
 when W = the useful or available energy; M = 
 the total energy; w, the energy absorbed by the 
 machine, and m, the stray power, or power lost 
 in friction of bearings, etc., air friction, eddy cur- 
 rents, etc. 
 
 Efficiency, Commercial, of Dynamo 
 
 The useful or available electrical energy in 
 the external circuit, divided by the total 
 mechanical energy required to drive the 
 dynamo that produced it. (See Co-efficient, 
 Economic, of a Dynamo-Electric Machine?) 
 
 Efficiency, Electric The useful or 
 
 available electrical energy of any source, 
 divided by the total electrical energy. 
 
 W 
 
 The electric efficiency = _, where W, 
 
 W-f-w 
 
 equals the useful or available electrical energy, 
 and w, the electrical energy absorbed by the 
 machine. , 
 
 Efficiency of Conversion. The ratio be- 
 tween the energy present in any result and 
 *he energy expended in producing that result. 
 
 Efficiency of Conversion of Dynamo. 
 
 (See Conversion, Efficiency of, of Dynamo?) 
 Efficiency of Transformer. (See Trans- 
 former, Efficiency of?) 
 
 Efficiency, Quantity, of Storage Battery 
 
 The ratio of the number of ampere- 
 hours taken out of a storage or secondary 
 battery, to the number of ampere-hours put in 
 the battery in charging it. 
 
 Efficiency, Real, of Storage Battery 
 
 The ratio of the number of watt-hours 
 taken out of a storage battery, to the number 
 of watt-hours put into the battery in charg- 
 ing it. 
 
 Efflorescence. The drying of crystals by 
 losing their water of crystallization and be- 
 coming pulverulent or crumbling. 
 
 The term is sometimes loosely applied to 
 the deposition of solid matter by the -crystal- 
 lization of a salt, above the line of the liquid, 
 on the surface of a vessel containing a vaporiz- 
 able saline solution. 
 
 The liquid, by capillarity in a porous vessel, or 
 by adhesion to the walls of an impervious vessel, 
 rises above the level of the main liquid line, and, 
 evaporating, deposits crystals on the vessel. 
 
 This process is technically called creeping, and 
 is often the cause of much annoyance in voltaic 
 cells. 
 
 Egg, Philosopher's A name given 
 
 to the ovoidal, or egg-shaped mass of light 
 that appears when a convective discharge is 
 taken between two electrodes in a partial 
 vacuum. 
 
 The philosopher's egg is but one of the shapes 
 assumed by the convective discharge. (See Dis- 
 charge, Convective.) 
 
 Elasticity, Electric The quotient 
 
 arising from dividing the electric stress by 
 the electric strain. 
 
 It can be shown mathematically that the elec- 
 tric elasticity is equal to 4, or 4 x 3. 1416, divided 
 by the specific inductive capacity. 
 
 Electrepeter. An instrument for chang- 
 ing the direction of an electric current. 
 
 The old term for switch, key, or pole changer. 
 (Obsolete.) 
 
 Electric. Pertaining to electricity. 
 
Ele.] 
 
 186 
 
 [Ele. 
 
 Electric Absorption. (See Absorption, 
 Electric?) 
 
 Electric Acoutemeter. (See Acouteme- 
 ter, Electric?) 
 
 Electric Actinometer. (See Actinomecer ; 
 Electric?) 
 
 Electric Adhesion. (See Adhesion, Elec- 
 tric?) 
 
 Electric Aging of Alcohol. (See Alco- 
 hol, Electric Aging of?) 
 
 Electric Alarm. (See Alarm, Electric?) 
 
 Electric Alarm Speaking-Tube Mouth- 
 Piece. (See Speaking-Tube Mouth-Piece, 
 Electric Alarm?) 
 
 Electric Amalgam. (See Amalgam, 
 Electric?) 
 
 Electric Ammunition Hoist. (See Hoist, 
 Ammunition, Electric?) 
 
 Electric Analysis. (See Analysis, Elec- 
 tric?) 
 
 Electric Analyzer. (See Analyzer, Elec- 
 tric?) 
 
 Electric Anemometer. (See Anemome- 
 ter, Electric?) 
 
 Electric Annealing. (See Annealing, 
 Electric?) 
 
 Electric Annunciator Clock. (See 
 Clock, Electric Annunciator?) 
 
 Electric Arc. (See Arc, Electric?) 
 
 Electric Arc Blow-Pipe. (See Blow- 
 Pipe, Electric Arc?) 
 
 Electric Argand Burner, Hand-Lighter 
 (See Burner, Argand Electric, Hand- 
 Lighter?) 
 
 Electric Argand Burner, Plain-Pendant 
 
 (See Bitrner, Argand Electric, 
 
 Plain-Pendant?) 
 
 Electric Argand Burner, Ratchet-Pend- 
 ant (See Burner, Argand Electric, 
 
 Ratch et-Penda /.) 
 
 Electric Balance. (Gee Balance, Elec- 
 tric?) 
 
 Electric Balloon. (Gee Balloon, Elec- 
 tric?) 
 
 Electric Battery. (Gee Battery, Elec- 
 tric?) 
 
 Electric Bell, Continuous-Sounding 
 
 (See Bell, Continuous-Sounding Electric?) 
 
 Electric Bell, Differential. (See Bell, 
 Differential Electric?) 
 
 Electric Bell, Mechanical. (See Bell, 
 Electro-Mechanical?) 
 
 Electric Bell Pull. (See Pull, Bell, Elec- 
 tric?) 
 
 Electric Bioscopy. (See Bioscopy, Elec- 
 tric?) 
 
 Electric Bi-Polar Bath. (See Bath, Bi- 
 Polar?) 
 
 Electric Blasting. (See Blasting, Elec- 
 tric?) 
 
 Electric Bleaching. (See Bleaching, 
 Electric?) 
 
 Electric Blow-Pipe. (See Blow-Pipe, 
 Electric?) 
 
 Electric Boat. (See Boat, Electric?) 
 Electric Bobbin. (See Bobbin, Electric?) 
 Electric Body-Protector. (See Body-Pro- 
 tector, Electric?) 
 
 Electric Boiler-Feed. (See Boiler-Feed, 
 Electric?) 
 
 Electric Branding. (See Branding, Elec- 
 tric?) 
 
 Electric Breeze. (See Breeze, Electric?) 
 Electric Bridge. (See Bridge, Electric?) 
 Electric Buoy. (See Buoy, Electric?) 
 Electric Burner. (See Burner, Auto- 
 matic Electric?) 
 
 Electric Buzzer. (See Buzzer, Electric?) 
 Electric Cable. (See Cable, Electric?) 
 Electric Calamine. (See Calamine, Elec- 
 tric?) 
 
 Electric Call-Bell. (See Bell, Call.} 
 Electric Calorimeter. (See Calorimeter, 
 Electric?) 
 
 Electric Candle. (See Candle, Electric?) 
 Electric Case-Hardening. (See Case- 
 Hardening, Electric?) 
 
 Electric Cauterization. (See Cauteriza- 
 tion, Electric?) 
 
 Electric Cauterizer. (See Cauterizer, 
 Electric?) 
 
Ele.] 
 
 187 
 
 [Ele. 
 
 Electric Cautery. (See Cautery, Elec- 
 tric^ 
 
 Electric Charge. (See Charge, Electric?) 
 Electric Chimes. (See Chimes, Electric?) 
 
 Electric Chronograph. (See Chrono- 
 graph, Electric?) 
 
 Electric Chronoscope. (See Chronoscope, 
 Electric?) 
 
 Electric Cigar-Lighter. (See Lighter, 
 Cigar, Electric?) 
 
 Electric Circuit. (See Circuit, Electric.) 
 
 Electric Cleats. (See Cleats, Electric?) 
 
 Electric Clepsydra. (See Clepsydra, Elec- 
 tric?) 
 
 Electric Clock. (See Clock, Electric?) 
 
 Electric Coil. (See Coil, Electric?) 
 
 Electric Column. (See Column, Elec- 
 tric?) 
 
 Electric Communicator. (See Commu- 
 nicator, Electric?) 
 
 Electric Conducting. (See Conducting, 
 Electrical?) 
 
 Electric Conduction. (See Conduction, 
 Electric.) 
 
 Electric Convection of Heat. (See Heat, 
 Electric Convection of?) 
 
 Electric Cord. (See Cord, Electric?) 
 Electric Counter. (See Counter, Elec- 
 tric?) 
 
 Electric Creeping. (See Creeping, Elec- 
 tric?) 
 
 Electric Cross. (See Cross, Electric?) 
 Electric Crucible. (See Crucible, Elec- 
 tric?) 
 
 Electric Current. (See Current, Elec- 
 tric?) 
 
 Electric Cystoscopy. (See Cystoscopy t 
 Electric?) 
 
 Electric Damping. (See Damping, Elec- 
 tric?) 
 
 Electric Death. (See Death, Electric?) 
 Electric Decomposition. (See Decom- 
 position, Electric?) 
 7 Vol. ] 
 
 Electric Density. (See Density, Elec- 
 tric?) 
 
 Electric Deposition. (See Deposition, 
 Electric?) 
 
 Electric Determination of Longitude. 
 (See Longitude, Electric Determination 
 of.) 
 
 Electric Displacement. (See Displace- 
 ment, Electric.) 
 
 Electric Distillation. (See Distillation, 
 Electric.) 
 
 Electric Door-Bell Pull. (See Pull, 
 Electric Door-Bell?) 
 
 Electric Double-Refraction. i See 
 
 Double-Refraction, Electric?) 
 
 Electric Dyeing. (See Dyeing, Electric?) 
 
 Electric Dynamometer, Siemens'. (See 
 Dynamometer, Electro?) 
 Electric Eel. (See Eel, Electric?) 
 
 Electric Efficiency. (See Efficiency, Elec- 
 tric?) 
 
 Electric Elasticity. (See Elasticity, Elec- 
 tric?) 
 
 Electric Elevator. (See Elevator, Elec- 
 tric?) 
 
 Electric Endosmose. (See Endosmose, 
 Electric?) 
 
 Electric Energy. (See Energy, Electric?) 
 
 Electric Entropy. (See Entropy, Elec- 
 tric?) 
 
 Electric Escape. (See Escape, Electric?) 
 
 Electric Etching. (See Etching, Elec- 
 tro?) 
 
 Electric Evaporation. (See Evapora- 
 tion, Electric?) 
 
 Electric Excitability of Nerve or Mus- 
 cular Fibre. (See Excitability, Electric, 
 of Nerve or Muscular Fibre?) 
 
 Electric Exhaustion. (See Exhaustion, 
 Electric?) 
 
 Electric Expansion. (See Expansion, 
 Electric?) 
 
 Electric Exploder. (See Exploder, Elec- 
 tric Mine?) 
 
Ele.] 
 
 188 
 
 [Ele. 
 
 Electric Explorer. (See Explorer, Elec- 
 tric?) 
 
 Electric Field. (See Field, Electric) 
 
 Electric Figures, Breath (See 
 
 Figures, Electric, Breath) 
 
 Electric Figures, Lichtenberg's - 
 (See Figures, Electric, Lichtenberg's) 
 Electric Fishes. (See Fishes, Electric) 
 Electric Fly. (See Fly, Electric) 
 Electric Flyer. (See Flyer, Electric) 
 Electric Fog. (See Fog, Electric) 
 Electric Force. (See Force, Electric) 
 Electric Furnace. (See Furnace, Elec- 
 tric) 
 
 Electric Fuse. (See Fuse, Electric) 
 Electric Gas-Lighting. (See Gas-Light- 
 ing, Electric) 
 
 Electric Gas-Lighting, Multiple - 
 (See Gas-Lighting, Multiple Electric) 
 
 Electric Gas-Lighting Torch. (See 
 Torch, Electric Gas-Lighting) 
 
 Electric Gastroscope. (See Gastroscope, 
 Electric) 
 
 Electric Gilding. (See Gilding, Electric) 
 Electric Governor. (See Governor, Elec- 
 tric) 
 
 Electric Hand-Lighter for Argand 
 Burner. (See Burner, Argand Electric 
 Hand-L ighter) 
 
 Electric Head-Bath. (See Bath, Head, 
 Electric) 
 
 Electric Head-Light. (See Head-Light, 
 Locomotive, Electric) 
 
 Electric Heat. (See Heat, Electric) 
 Electric Heater. (See Heater, Electric) 
 Electric Horse Power. (See Power, 
 Horse, Electric) 
 
 Electric Hydrotasimeter. (See Hydro- 
 tasimeter, Electric) 
 
 Electric Ignition. (See Ignition, Elec- 
 tric) 
 
 Electric Images. (See Images, Electric) 
 Electric Incandescence. (See Incandes- 
 cence, Electric) 
 
 Electric Indicator for Steamships. (See 
 Indicator, Electric, for Steamships) 
 
 Electric Indicators. (See Indicators, 
 Electric^ 
 
 Electric Inertia. (See Inertia, Electric) 
 
 Electric Insolation. (See Insolation, 
 Electric) 
 
 Electric Installation. (See Installation, 
 Electric) 
 
 Electric Insulation. (See Insulation, 
 Electric) 
 
 Electric Irritability. (See Irritability, 
 Electric) 
 
 Electric Jar. (See Jar, Electric) 
 
 Electric Jewelry. (See Jewelry, Elec- 
 tric) 
 
 Electric Lamp, Arc (See Lamp, 
 
 Electric, Arc) 
 
 Electric Lamp-Bracket. (See Bracket, 
 Lamp, Electric) 
 
 Electric Lamp, Incandescent (See 
 
 Lamp, Electric, Incandescent) 
 
 Electric Lamp, Semi-Incandescent 
 (See Lamp, Electric, Semi-Incandescent) 
 
 Electric Lamp, Socket for. (See Socket, 
 Electric Lamp) 
 
 Electric Launch. (See Launch, Elec- 
 tric) 
 
 Electric Letter-Box. (See Letter-Box, 
 Electric) 
 
 Electric Light. (See Light, Electric) 
 
 Electric Lighting, Central Station 
 
 (See Station, Central) 
 
 Electric Lighting, Isolated (See 
 
 Lighting, Electric, Isolated) 
 
 Electric Light or Power Cable. (See 
 Cable, Electric Light or Power) 
 
 Electric Lock. (See Lock, Electric) 
 
 Electric Locomotive. (See Locomotive, 
 Electric) 
 
 Electric Log. (See Log, Electric) 
 
 Electric Loom. (See Loom, Electric) 
 
 Electric Loop. (See Loop, Electric) 
 
 Electric Machine, Frictional (See 
 
 Machine, Frictional Electric) 
 
Ele.] 
 
 J89 
 
 [Ele. 
 
 Electric Main. (See Main, Electric?) 
 Electric Masses. (See Masses. Electric) 
 Electric Measurements. (See Measure- 
 ments, Electric.) 
 
 Electric Megaloscope. (See Megalo- 
 scope, Electric?) 
 
 Electric Meter. (See Meter. Electric?) 
 Electric Mine-Exploder. (See Mine-Ex- 
 ploder, Electro-Magnetic. Fuse, Electric?) 
 
 Electric Motor. (See Motor, Electric?) 
 
 Electric Motor, High-Speed (See 
 
 Motor, Electric, High-Speed?) 
 
 Electric Motor, Low-Speed (See 
 
 Motor, Electric, Low-Speed?) 
 
 Electric Mnltipolar Bath - (See 
 Bath, Multipolar, Electric?) 
 
 Electric Musket. (See Musket, Electric?) 
 Electric Organ. (See Organ, Electric?) 
 Electric Oscillations. (See Oscillations, 
 
 Electric?) 
 
 Electric Osmose. (See Osmose, Electric?) 
 Electric Osteotome. (See Osteotome, 
 
 Electric?) 
 
 Electric Overtones. (See Overtones, 
 Electric?) 
 
 Electric Pen. (See Pen, Electric?) 
 Electric Pendant. (See Pendant, Elec- 
 tric?) 
 
 Electric Pendant-Lamps. (See Lamps, 
 Electric Pendant?) 
 
 Electric Pendulum. (See Pendulum, 
 Electric?) 
 
 Electric Permeancy. (See Permeancy, 
 Electric?) 
 
 Electric Phosphorescence. (See Phos- 
 phorescence, Electric?) 
 
 Electric Photometer. (See Photometer?) 
 Electric Piano. (See Piano, Electric?) 
 Electric Plow. (See Plow, Electric?) 
 Electric Position-Finder. (See Finder, 
 Position, Electric?) 
 
 Electric Potential. (See Potential, Elec- 
 tric?) 
 
 Electric Power. (See Power, Electric.) 
 Electric Probe. (See Probe, Electric ) 
 Electric Prostration. (See Prostration, 
 Electric.) 
 
 Electric Protection. (See Protection, 
 Electric, of Houses, Ships and Buildings.) 
 
 Electric Protection of Metals. (See 
 Metals.. Electrical Protection of) 
 
 Electric Pulse. (See Pulse, Electrical?} 
 
 Electric Pyrometer, Siemens'. (See 
 
 Pyrometer, Siemens' . Electric) 
 
 Electric Radiometer, Crookes' 
 
 (See Radiometer, Electric, Crookes ) 
 
 Electric Range-Finder. (See Finder, 
 Range, Electric?) 
 
 Electric Ratchet-Pendant for Argand 
 Burner. (See Burner, Argand Electric, 
 Ratchet-Pendant.) 
 
 Electric Ray. (See Ray, Electric?) 
 
 Electric Reaction Wheel. (See Wheel, 
 Reaction, Electric) 
 
 Electric Rectification of Alcohol. (See 
 
 Alcohol, Electric Rectification of) 
 
 Electric Refining of Metals. (See Metals, 
 Electric Refining of) 
 
 Electric Register, Watchman's 
 
 (See Register, Watchman's Electric.) 
 
 Electric Registering Apparatus. (See 
 Apparatus, Registering, Electric?) 
 
 Electric Relay-Bell. (See Bell. Relay, 
 Electric?) 
 
 Electric Repulsion. (See Repulsion, 
 Electric?) 
 
 Electric Resistance. (See Resistance, 
 Electric?) 
 
 Electric Resonance. (See Resonance, 
 Electric) 
 
 Electric Retardation. (See Retardation, 
 Electric) 
 
 Electric Rings. (See Rings, Electric) 
 
 Electric Safety Lamps. (See Lamp, 
 Electric Safety.) 
 
 Electric Saw. (See Saw, Electric) 
 
Ele.] 
 
 190 
 
 [Ele. 
 
 Electric Seismograph. (See Seismo- 
 graph, Electric.} 
 
 Electric Shadow. (See Shadow, Elec- 
 tric) 
 
 Electric Shock. (See Shock, Electric} 
 
 Electric Shower Bath. (See Bath, 
 Shower Electric.} 
 
 Electric Shunt Bell. (See Bell, Shunt, 
 Electric.} 
 
 Electric Single-Stroke Bell. (See Bell, 
 Single-Stroke Electric} 
 
 Electric Siphon. (See Siphon, Electric.} 
 
 Electric Soldering. (See Soldering, 
 Electric} 
 
 Electric Sphygmograph. (See Sphygmo- 
 graph, Electrical} 
 
 Electric Sterilization. (See Steriliza- 
 tion, Electric} 
 
 Electric Storm. (See Storm, Electric} 
 
 Electric Striae. (See Sir ice, Electric} 
 
 Electric Submarine Boat. (See Boat, 
 Submarine, Electric} 
 
 Electric Sunstroke. (See Sunstroke, 
 Electric} 
 
 Electric Surgings. (See Surgings, Elec- 
 tric} 
 
 Electric Swaging. (See Swaging, Elec- 
 tric} 
 
 Electric Tanning. (See Tanning, Elec- 
 tric.} 
 
 Electric Target. (See Target, Electric} 
 
 Electric Teazer. (See Teaser, Electric 
 Current} 
 
 Electric Telehydrobarometer. (See 7V/- 
 ehydrobarometer, Electric} 
 
 Electric Tell-Tale Signal. (See Signal, 
 Electric Tell-Tale} 
 
 Electric Tempering. (See Tempering, 
 Electric. } 
 
 Electric Tension. (See Tension, Elec- 
 tric} 
 
 Electric Thermo-Call. (See Thermo- 
 Call, Electric} 
 
 Electric Thermometer. (See Thermom- 
 eter, Electric} 
 
 Electric Throwback-Indicator. ( See 
 
 Indicator, Electrical Throwback} 
 
 Electric Time-Ball. (See Ball, Electric 
 Time} 
 
 Electric Time-Meter. (See Meter, Elec- 
 tric Time} 
 
 Electric Torpedo. (See Torpedo, Elec- 
 ' trie} 
 
 Electric Tower. (See Tower, Electric} 
 
 Electric Tramway. (See Tramway, Elec- 
 tric} 
 
 Electric Transmitters. (See Transmit- 
 ter, Electric} 
 
 Electric Trumpet. (See Trumpet, Elec- 
 tric} 
 
 Electric Turn-Table. (See Turn-Table, 
 Electric} 
 
 Electric Typewriter. (See Typewriter, 
 Electric} 
 
 Electric Yalve. (See Valve, Electric} 
 
 Electric Valve Burner, Argand 
 (See Valve Burner, Argand Electric} 
 
 Electric Varnish. (See Varnish, Elec- 
 tric} 
 
 Electric Vibrating Burner. (See Burner 
 Vibrating, Electric} 
 
 Electric Volatilization. (See Volatiliza- 
 tion, Electric} 
 
 Electric Water or Liquid Level Alarm. 
 
 (See Alarm, Water or Liquid Level} 
 
 Electric Welding. (See Welding, Elec- 
 tric} 
 
 Electric Whirl. (See Whirl, Electric} 
 
 Electric Whistle, Automatic Steam 
 (See Whistle, Steam, Automatic Elec- 
 tric} 
 
 Electric Wood Mouldings. (See Mould- 
 ings, Electric Wood} 
 
 Electric Work. (See Work, Electric} 
 
 Electrical Controlling Clock. (See 
 Clock, Electrical Controlling} 
 
 Electrically. In an electrical manner. 
 
 Electrically Controlled Clock. (See 
 Clock, Electrically Controlled} 
 
191 
 
 Electrically Discharge, To (See 
 
 Discharge, To Electrically^) 
 
 Electrically Discharging. (See Dis- 
 charging, Electrically!) 
 
 Electrically Energizing. (See Energiz- 
 ing, Electrically!) 
 
 Electrically Operated Alarm. (See 
 Alarm, Electrically Operated!) 
 
 Electrically Retarding. (See Retard- 
 ing, Electrically') 
 
 Electrician. One versed in the principles 
 and applications of electrical science- 
 
 Electrician, Electro-Therapeutical 
 
 A medical electrician. 
 
 Electrician, Medical One skilled 
 
 in the application of electricity to the human 
 body for diagnosis or curative purposes. 
 
 A medicai electrician should possess a full 
 knowledge, not only of the principles and appli- 
 cations of electric science, but also of physics and 
 chemistry and of the medical sciences. 
 
 Electricity. The name given to the un- 
 known thing, matter or force, or both, which 
 is the cause of electric phenomena. 
 
 Electricity, no matter how produced, is oe- 
 lieved to be one and the same thingc 
 
 The terms frictional-electridty, pyro-electricity, 
 magneto-electricity, voltaic or galvanic electricity, 
 thermo-electricity, contact-electricity, animal or 
 vegetable-electricity, etc., etc., though convenient 
 for distinguishing iLeir origin, have no longer 
 the significance formerly attributed to them as 
 representing different kinds of the electric force. 
 (See Electricity, Single-Fluid Hypothesis of. ) 
 
 Electricity, Accumulated Elec- 
 tricity collected in or by means of accumula- 
 tors. 
 
 Electricity, Accumulating Ob- 
 taining successively increasing electrical 
 charges. (See Electricity, Accumulation of.) 
 
 Electricity, Accumulation of A 
 
 general term applied indifferently to 
 
 (i.) The gradual collecting of electric 
 energy in a Leyden jar or condenser. 
 
 (2.) The increase of an electric charge by 
 the action of various devices called accumu- 
 lators. 
 
 (3.) The production of a charge by the use 
 of machines called influence machines. 
 
 (4.) The collection of electric energy in the 
 so-called storage batteries or accumulators. 
 
 Electricity, Animal - Electricity 
 produced during life in the bodies of animals. 
 
 All animals produce electricity during life. In 
 some, such as the electric eel or torpedo, the 
 amount is comparatively large. In others, it is 
 small. 
 
 Some of these animals, when of full size, are able 
 to give very severe shocks, and use this curious 
 power as a means of defense against their enemies. 
 
 If the spinal cord of a recently killed frog be 
 brought into contact with the muscles of the 
 thigh, a contraction will ensue. (Matteucci.) 
 
 The nerve and muscle of a frog, connected 
 by a water contact with a sufficiently delicate 
 galvanometer, show the presence of a current 
 that may last several hours. Du Bois-Reymond 
 showed that the ends of a section of muscular 
 fibres are negative, and their sides positive, and 
 has obtained a current by suitably connecting 
 them. 
 
 In the opinion of some electro-therapeutists no 
 electric current exists in passive, normal nerve or 
 muscular tissue. In an injured tissue a current, 
 called a demarcation current, is produced. (See 
 Current, Demarcation.) 
 
 All muscular contractions, however, apparently 
 produce electric currents. 
 
 In electro-therapeutics, it is probable that 
 greater success would accrue in practice if the 
 human body were regarded as an electric source 
 as well as an electro-receptive device. 
 
 Electricity, Atmospheric The free 
 electricity almost always present in the atmos- 
 phere. 
 
 The following facts have been discovered con- 
 cerning atmospheric electricity, viz. : 
 
 (i.) The free electricity of the atmosphere is 
 generally positive, but often changes to negative 
 on the approach of fogs and clouds. 
 
 (2.) It exists in greater quantity in the higher 
 regions of the air than near the earth's surface. 
 
 (3.) It is stronger when the air is still than 
 when the wind is blowing. 
 
 (4.) It is subject to yearly and daily changes 
 in its intensity, being stronger in winter than ia 
 summer, and at the -nicul -2 of the day than either 
 at the Beginning or the close. 
 
192 
 
 Ulle 
 
 Electricity, Atmospheric, Origin of - 
 
 The exact cause of the free electricity of 
 the atmosphere is unknown. 
 
 Peltier ascribes the cause of the free electricity 
 of the atmosphere to a negatively excited earth, 
 which charges the atmosphere by induction. (See 
 Induction, Electrostatic.) Free atmospheric elec- 
 tricity has also been ascribed to the evaporation 
 of water; to the condensation of vapor; to the 
 friction of the wind; to the motion of terrestrial 
 objects through the earth's magnetic field; to in- 
 duction from the sun and other heavenly bodies; 
 to differences of temperature; to combustion, and 
 to gradual oxidation of plant and animal life. It 
 is possible that all these causes may have some 
 effect in producing the free electricity of the at- 
 mosphere. 
 
 Whatever is the cause of the free electricity ol the 
 atmosphere, there can be but little doubt that it 
 is to the condensation of aqueous vapor that the 
 high difference of potential of the lightning flash 
 is due. (See Potential, Difference of. ) As the 
 clouds move through the air they collect the free 
 electricity on the surfaces of the minute drops of 
 water of which they are composed, and when 
 many thousands of these subsequently collect in 
 larger drops the difference of potential is tnor- 
 mously increased in consequence of the equally 
 enormous decrease in the surface of any single 
 drop over the sum of the surfaces of the drops 
 that have coalesced to form it. 
 
 Electricity, Atom of A quantity 
 
 of electricity equal in amount to that pos- 
 sessed by any chemical monad atom. 
 
 Professor Lodge points out the fact that the 
 charge of a monad atom of any element is the 
 smallest charge a body can possess, and is pessibly 
 as indivisible as the atom itself. He points out the 
 fact that chemical affinity or atomic attraction may 
 be due to the electrical attraction of atoms contain- 
 ing unlike charges; that although the difference of 
 potential between the atoms is small, probably 
 somewhere between i and 3 volts, the distances 
 separating them are so very small that their 
 mutual attractive force must be almost infinitely 
 great. 
 
 As D'Auria has pointed out, if the centres of at- 
 traction of the atoms be the centres of the 
 atoms themselves, then the atoms, if approached 
 to actual contact, would be separated from one 
 another by a distance equal to half th" sum of 
 their diameters. If, however, the centre ot at- 
 
 traction be situated at any point on the surface of 
 the atoms the distance of separation would be- 
 come equal to zero, calling d, the distance be- 
 tween them, m and m 1 , their respective masses, 
 and S, a co-effecient varying with the substance, 
 and f, the force of mutual attraction, then : 
 
 f = 
 
 from which we see that the value of f x becomes 
 infinite when the atoms are in contact. 
 
 Electricity, Cal Electricity pro- 
 duced by changes of temperature in the core 
 of a transformer. 
 
 The changes of temperature in the transformer 
 core can produce a difference of potential in the 
 secondary circuit which increases the electro- 
 motive force induced in the secondary by the 
 variations in the primary. This is sometimes" 
 called ihe Acheson effect. (See Effect, Ackeson.) 
 
 Electricity, Conservation of A 
 
 term proposed by Lippman to express the 
 fact that when a body receives an electric 
 charge in the open air, the earth and heavenly 
 bodies receive an equal and opposite charge, 
 thus preserving the sum of the total positive 
 and negative electricities in the universe. 
 
 Electricity, Contact Electricity 
 
 produced by the mere contact of dissimilar 
 metals. 
 
 The mere contact of two dissimilar metals re- 
 sults ia the production of opposite electrical 
 charges on their opposed surfaces, or in a differ- 
 ence of electric potential between these surfaces. 
 The cause of this difference of potential is now 
 very generally ascribed to the voltaic couple being 
 surrounded by the atmosphere, the oxygen of 
 which acts more energetically on the positive 
 element than it does on the negative element. 
 
 The mere contact of dissimilar metals cannot 
 produce a constant electric current. An electric 
 current possesses kinetic energy. To produce a 
 constant electric current, therefore, energy must 
 be expended. 
 
 The voltaic pile through the contact of dis- 
 similar metals produces a difference of potential, 
 yet the cause of the current is to be found in 
 chemical action. (See Cell, Voltaic.) 
 
 Electricity, Disguised - Dissimu- 
 lated electricity. (See Electricity, Dissimu- 
 lated or Latent.) 
 
193 
 
 Ele 
 
 Electricity, Dissimulated or latent 
 
 The condition of an electric charge when 
 placed near an opposite charge, as InaLeyden 
 jar or condenser. 
 
 In this case, merely touching one of the 
 charged surfaces will not effect its complete dis- 
 charge. 
 
 Electricity in the condition of a bound charge 
 vvas formerly called latent electricity. This term 
 is now in disuse. Such a charge \z now called a 
 bound charge. (See Charge. Bound. Charge, 
 Free.} 
 
 Electricity, Distribution of Va- 
 rious combinations of electric sources, circuits 
 and electro-receptive devices whereby elec- 
 tricity generated by tha sources is carried or 
 distributed to more or less distant electro- 
 receptive devices by means of the various cir- 
 cuits connected therewith. 
 
 A number of different systems for the distribu- 
 tion of electricity exist. Among the most import- 
 ant are the following, viz. : 
 
 (l.) Direct or continuous-current distribution. 
 
 (2.) Alternating-current distribution. 
 
 (3.) Storage battery or secondary distribution. 
 
 (4.) Distribution by means of condensers. 
 
 (5.) Distribution by means of motor-gener- 
 ators. 
 
 Electricity, Distribution of, by Alterna- 
 ting- Currents A system of electric 
 
 distribution by the use of alternating currents. 
 
 A system of electric distribution in which 
 lamps, motors, or other electro-receptive de- 
 vices are operated by means of alternating 
 currents that are sent over the line, but which, 
 before passing through said devices, are modi- 
 fied by apparatus called transformers or con- 
 verters. 
 
 Such a system embraces : 
 
 (I.) An alternating-current dynamo-electric 
 machine or battery of machines. 
 
 (2.) A conductor or line wire arranged in a 
 metallic circuit. 
 
 (3.) A number of converters or transformers 
 whose primary coils are placed in the circuit of 
 the line wire. 
 
 (4.) A number of electro-receptive devices 
 placed in the circuit of the secondary coil of the 
 converter. (See Transformer.'] 
 
 Electricity, Distribution of, by Alterna- 
 ting Currents by Means of Condensers 
 
 A system of alternate current distribution 
 in which condensers are employed to trans- 
 form current of high potential received from 
 an alternating current dynamo to currents 
 of low potential which are ted to<he -"nps o* 
 other electro-receptive devices, 
 
 In the system of McElroy the conversion from 
 high to low potential is obtained by making the 
 primary plates of the condensers charged by 
 the dynamo smaller than the secondary plates, 
 the ratio of the area of the primary plates to that 
 of the secondary plates being made in accordance 
 with the ratio of conversion desired. 
 
 Electricity, Distribution of, by Commnta- 
 
 ting Transformers A system of elec 
 
 trical distribution in which motor-generators 
 are used, but neither the armature nor the 
 field magnets are revolved, a special commu- 
 tator being employed to change the polarity 
 of the magnetic circuits. 
 
 Electricity, Distribution of, by Constant 
 
 Currents A system for the distribution 
 
 of electricity by means of direct, /. <?., con- 
 tinuous, steady or non-alternating currents, 
 as distinguished from alternating currents. 
 
 Distribution by means of direct currents may 
 be effected in ?. number of ways ; the most im- 
 portant are: 
 
 (i.) Distribution with constant current or 
 series - distribution . 
 
 (2.) Distribution with constant potential or 
 multiple-distribution. 
 
 Strictly speaking, these, as, indeed, all systems, 
 are systems for the distribution of electric energy 
 rather than the distribution of electricity. 
 
 In a system of series-distribution, the electro- 
 receptive devices are placed in the main line in 
 series, so that the electric current passes succes- 
 sively through each of them. In such a system 
 each device added increases the total resistance of 
 the circuit so that the total resistance is equal to 
 the sum of the separate resistances on the line. 
 
 In order, therefore, to maintain the current 
 strength constant, independent of the number of 
 devices added to or removed from the circuit, the 
 electromotive force of the source must increase 
 with each electro-receptive device added, and de- 
 crease with each electro-receptive device taken 
 
Ele.| 
 
 194 
 
 [Ele. 
 
 out- If the number of electro-receptive devices 
 be great, such a circuit is necessarily character- 
 ized by a comparatively high electromotive force. 
 
 Since the current passes successively through 
 all the electro-receptive devices, an automatic 
 safety device is necessary in ore] er to automatically 
 provide a short circuit of comparatively low resist- 
 ance oast a faulty device, and thus prevent a 
 single faulty device from invalidating the action 
 of all other devices in the circuit. 
 
 Arc lamps are usually connected to the line 
 circuit in series. 
 
 In a system of multiple-distribution, the electro- 
 deceptive devices are connected to the main line 
 or leads in multiple-arc, or parallel, so that each 
 device added decreases the resistance of the circuit. 
 In order, therefore, to maintain a proper current 
 through the electro-receptive devices, the mains 
 must be kept at a nearly constant difference of 
 potential. The electro-receptive devices employed 
 in such a system of distribution are generally of 
 high electric resistance, so that the introduction or 
 removal of a few of the electro-receptive devices 
 will not materially alter the resistance of the whole 
 circuit, and will not, therefore, materially affect 
 the remaining lights. 
 
 In this system automatic safety devices, opera- 
 ting by the fusion of a readily melted alloy or 
 metal, are provided for the purpose of preventing 
 too powerful currents from passing through any 
 branch connected with the main conductors or 
 leads. (See Plug, fusible.) 
 
 Incandescent lamps are generally connected 
 with the main conductors or leads in parallel or 
 multiple-arc. 
 
 Distribution of incandescent lamps by series 
 connections is sometimes employed. Such lamps 
 arc usually of comparatively low resistance, and 
 are provided each with an automatic cut-out, 
 which establishes a short circuit past the lamp on 
 its failure to properly operate. 
 
 During the passage of an electric current 
 through any series-distribution circuit, energy is 
 expended in different portions of the circuit, in 
 proportion to the resistance of these parts. In 
 any system, economy of distribution necessitates 
 that the energy expended in the electro-receptive 
 devices must bear as large a proportion as prac- 
 ticable to the energy expended in the source and 
 leads. In series-distribution, this can readily be 
 accomplished even if the resistance of the leads is 
 comparatively high, since the total resistance of 
 the circuit increases with every electro-receptive 
 
 device added. Comparatively thin wires can 
 therefore be employed for a very considerable 
 extent of territory covered, without very great 
 loss. 
 
 In systems of multiple-distribution, however, 
 this is impossible ; for, since every electro-recep. 
 tive device added decreases the total resistance of 
 the circuit, unless the resistance o f the leads is 
 correspondingly decreased the economy becomes 
 smaller, unless the resistance of the leads was orig=> 
 inally so low as to be inappreciable when com- 
 pared with the change of resistance. 
 
 In systems of distribution by alternating cur- 
 rents this is avoided by passing a current of but 
 small strength and considerable difference of 
 potential over a line connecting distant points, 
 and converting this current into a current of largo 
 strength and small difference of potential ai; tKc 
 places where it is required for use. 
 
 Electricity, Distribution of, by Contin- 
 uous Current, by Means of Condensers 
 
 A system of distribution devised by 
 
 Doubrava, in which a continuous current is 
 conducted to certain points in the line where 
 a device called a " disjunctor " is employed, to 
 reverse it periodically, and the reversed cur- 
 rents so obtained directly used to charge con- 
 densers in the circuit of which induction coils 
 are used. 
 
 This method of distribution is a variety of dis- 
 tribution by means of constant currents. 
 
 The condensers are used to feed incandescent 
 lamps or other electro-receptive devices. 
 
 Electricity, Distribution of, by Continu- 
 ous Current, by Means of Transformers 
 
 A system for the transmission of elec- 
 tric energy by means of continuous or direct 
 currents that are sent over the line to suitably 
 located stations where motor-dynamos are 
 used for transformers. 
 
 The dynamo armature is used with two sepa- 
 rate circuits, one of a short and coarse wire, and 
 one of a long fine wire. This construction will 
 permit the conversion of a high to a low potentia. 
 or vice versa; or two separate dynamos can be 
 placed on the same shaft and one used as the 
 motor. 
 
 It is evident that a. motor generator can be con- 
 structed to convert continuous currents into alter- 
 nate, or alternate currents into continuous cur- 
 
195 
 
 [Ele. 
 
 rents. In this last case the armature and fixed 
 circuits must be kept separate. 
 
 Another form of continuous current conversion 
 is effected by means of the motion of a commutator 
 which effects a rotation of magnetic polarity in a 
 double- wound armature of fine and coarse wire. 
 
 Electricity, Distribution of, by Motor 
 Generators A system of electric dis- 
 tribution in which a continuous current of 
 high potential, distributed over a main line, is 
 employed at the points where its electric en- 
 erg)- is to be utilized for driving a motor, 
 which in turn drives a dynamo, the current of 
 which is used to energize the electro-recep- 
 tive devices. 
 
 This method of distribution is a variety of dis- 
 tribution by means of continuous or direct cur- 
 rents. 
 
 In another system of distribution by means of 
 motor generators, the motor and dynamo are 
 combined in one with a double-wound armature, 
 the fine wire coils in which receive the high po- 
 tential driving current and the coarse wire coils 
 lurnish the low potential current used in the dis- 
 tribution circuits. 
 
 Electricity, Double Fluid Hypothesis of 
 A hypothesis which endeavors to ex- 
 plain the causes of electric phenomena by the 
 assumption of the existence of two different 
 electric fluids. 
 
 The double fluid hypothesis assumes: 
 
 (i.) That the phenomena of electricity are due 
 to two tenuous and imponderable fluids, the posi- 
 tive and the negative. 
 
 (2.) That the particles of the positive fluid repel 
 one another, as do also the particles of the nega- 
 tive fluid; but that the particles of positive fluid 
 attract the particles of the negative and vice -versa. 
 
 (3.) That the two fluids are strongly attracted 
 by matter, and when present in it produce elec- 
 trification. 
 
 (4.) That the two fluids attract one another and 
 unite, thus masking the properties of each. 
 
 (5.) That the act of friction separates these 
 fluids, one going to the rubber and the other to 
 the thing rubbed. 
 
 Professor Lodge is disposed to favor the double 
 rather than the single fluid hypothesis. He states 
 in support of this belief the following facts, viz. : 
 
 (I.) An electric wind or breeze is produced 
 both at the positive and negative terminals of an 
 
 electrical machine, and this whether the point be 
 attached directly to these terminals, or whether 
 it be held in the hand of a person near them. 
 
 (2.) The well known peculiarities connected 
 with the spark discharge, seen in Wheatstone's 
 experiments on the velocity of electricity. 
 
 (3.) An electrostatic strain scarcely affects the 
 volume of the dielectric, thus suggesting or show- 
 ing a distorting stress, which alters the shape of 
 the substance of the dielectric, but not its size. 
 
 (4.) The effects of electrolysis in what he as- 
 sumes the double procession of the atoms past 
 each other in opposite directions. 
 
 (5.) The phenomena of self-induction, or the 
 behavior of a thick wire on an alternating current. 
 
 (6.) The apparent absence of momentum in the 
 electric current, or moment of inertia in an elec- 
 tro-magnet so far as tested. 
 
 Electricity, Dynamic A term some- 
 times employed for current electricity in con- 
 tradistinction to static electricity. 
 
 Electricity, Franklinic A term 
 
 sometimes employed in electro-therapeutics, 
 for the electricity produced by a frictional 
 or an electrostatic-induction machine. (See 
 Current, Franklinic^] 
 
 Electricity, Frictional Electricity 
 
 produced by friction. 
 
 This term as formerly employed to indicate 
 static charges as distinguished from currents, is 
 gradually falling into disuse, and the frictional 
 electric machines are being generally replaced by 
 continuous-induction machines, like those of 
 Holtz, Topler-Holtz, or Wimshurst. 
 
 The character of the charge produced by fric- 
 tion depends on .the nature of the rubber as well 
 as on that of the thing rubbed. 
 
 In the following table the substances are so ar- 
 ranged that any one in the list becomes positively 
 electrified when rubbed by any which follows it : 
 
 Positive. 
 Cat's fur. 
 Polished glass. 
 Wool. 
 
 Cork at ordinary temperatures. 
 Coarse brown paper. 
 Cork heated. ' 
 White silk. 
 Black silk. 
 Shellac. 
 Rough glass. (Forbes. 1 ) 
 
Ele.] 
 
 196 
 
 [Ele. 
 
 Negative. 
 
 It will be seen that the character of the charge 
 produced by friction depends on the character of 
 the surfaces rubbed. This is seen from the fore- 
 going table, where 
 
 (i.) The roughness of the surface, as in the 
 case of glass, produces a difference in the nature of 
 the charge; thus, rough glass is at the bottom of 
 the table, and smooth, polished glass near the top. 
 
 (2.) The state of the surface as shown by the 
 color. Black silk rubbed with white silk is nega- 
 tive to it 
 
 (3.) The state of the surface, as varied by the 
 temperature. Hot cork receives a negative charge 
 when rubbed against a piece of cold cork. 
 
 Forbes has pointed out that these differences 
 are probably due to the change produced in the 
 ability of the surface to radiate heat or light. A 
 substance or body which radiates the most light 
 or heat is negative. Thus, a hot body radiates 
 more heat than a cold body, and is negative to it. 
 A rough surface is negative to a smooth surface 
 because it radiates more heat than a smooth sur- 
 face. For the same reason a black surface is neg- 
 ative to a white surface. In this latter case, how- 
 ever, the black surface is the worse radiator of 
 light. 
 
 The contact of dissimilar substances has long 
 been considered by some as one of the requisites 
 for the ready production of electricity by friction. 
 In fact, the production of electricity by friction 
 has been ascribed as an effect due to a true contact 
 force at the points of junction of the rubber and 
 the thing rubbed. Others, however, deny the 
 existence of a true contact force of this nature. 
 (See Force, Contact.) 
 
 Electricity, Galvanic * A term used 
 
 by some in place of voltaic electricity. (See 
 Electricity, Voltaic?) 
 
 The use of the term galvanic electricity would 
 appear to be less logical than the word voltaic, 
 since Volta, and not Galvani, was the first to find 
 out the true origin of the difference of potential 
 produced in the voltaic pile. 
 
 Electricity, Hertz's Theory of Electro- 
 Magnetic Radiations or Waves A 
 
 theory, now generally accepted, which regards 
 light as one of the effects of electro-magnetic 
 pulsations or waves. 
 
 The recent brilliant researches of Dr. Hertz, of 
 Carlsruhe, show that when an impulsive discharge 
 
 is passing through a conductor, ether waves are 
 radiated or propagated in all directions in the 
 space surrounding the conductor, and that these 
 waves are in all respects similar to those of light, 
 except that they are much longer. 
 
 The electro-magnetic waves are set up in the 
 luminiferous ether, and move through it with the 
 same velocity as that of light. Moreover, electro- 
 magnetic waves possess the same powers of reflec- 
 tion, refraction, interference, resonance, etc., etc., 
 as are possessed by waves of light. (See Resona- 
 tor, Electric.) 
 
 When an alternating or simple faradic current 
 or pulse of electricity is transmitted from one end 
 to the other of a long metallic conductor, the 
 pulses are believed to travel through the universal 
 ether surrounding the conductor rather than 
 through the conductor itself. The velocity of this 
 propagation in free ether is the same as that of 
 light, and, indeed, is identical with that of light 
 itself. In the inter-atomic or inter-molecular 
 ether, whether of conductors, or of dielectrics, the 
 velocity of propagation varies with the nature of 
 the medium. 
 
 The waves produced by electric pulses are of 
 much greater length than those of light. 
 
 According to Lodge a condenser of the capacity 
 of a micro-farad, if discharged through a coil hav- 
 ing the self-induction of I ohm, will give rise 
 to waves in the ether 1,200 miles in length, and 
 will possess a rate of oscillation equal to about 157 
 complete wave-lengths per second. 
 
 A common pint Leyden jar discharged through 
 an ordinary discharging rod, will produce a se- 
 ries of waves about 15 to 20 metres in length, 
 and will possess a rate of oscillation equal to about 
 ten million per second. 
 
 Lodge calculates that in order to obtain the short 
 waves requisite to influence the Tetina of the eye, 
 and thus produce light, the circuit in which the 
 electrical oscillations take place must have at least 
 atomic dimensions, and that the phenomena of 
 light may therefore be due to local oscillations or 
 surgings in circuits of atomic dimensions. (See 
 Light, MaxwelFs Electro-Magnetic Theory of.) 
 
 Electricity, Latent A term for- 
 merly applied to bound electricity. 
 
 Electricity, Magneto Electricity 
 
 produced by the motion of magnets past con- 
 ductors, or of conductors past magnets. 
 
 Electricity produced by magneto-electric 
 
Ele.] 
 
 197 
 
 [Ele. 
 
 induction. (See Induction, Electro-Dyna- 
 mic.} 
 
 Electricity, Multiple-Distribution of, by 
 
 Constant Potential Circuit Any 
 
 system for the distribution of continuous cur- 
 rents of electricity in which the electro- 
 receptive devices are connected to the leads 
 in multiple-arc or parallel. (See Electricity, 
 Distribution of, by Constant Currents?) 
 
 Electricity, Natural Unit of A 
 term sometimes used in place of an atom of 
 electricity. 
 
 The natural unit of electricity is an amount 
 equal to the charge possessed by any monad atom 
 of a chemical element. 
 
 The natural unit of electricity is equal to the 
 hundred thousand millionth of the ordinary 
 electrostatic unit, or less than a hundred tril- 
 iionth of a coulomb. (See Electricity, Atom of.) 
 
 Electricity, Negative One of the 
 
 phases of electrical excitement. 
 
 The kind of electric charge produced on 
 resin when rubbed with cotton. 
 
 Electricity, Photo Electrical dif- 
 ferences of potential produced by the action 
 of light. 
 
 Electricity, Plant Electricity pro- 
 duced in plants during their growth. 
 
 Electricity, Positive One of the 
 
 phases of electric excitement. 
 
 The kind of electric charge produced on 
 cotton when rubbed against resin. 
 
 Electricity, Production of, by Light 
 
 The production of electric differences of 
 potential by the action of light. 
 
 Hallwachs nas noticed that a clean metallic 
 plate becomes electrified when light falls upon it. 
 
 Differences of potential are produced in a 
 selenium cell when its electrodes are unequally 
 illumined. A thermo cell is an illustration of a 
 difference of potential produced by non-luminous 
 radiation. 
 
 Electricity, Pyro Electricity de- 
 veloped in certain crystalline bodies by un- 
 equally heating or cooling them. 
 
 Tourmaline, in the crystalline state, poscesses 
 this property in a marked degree. When a 
 crystal of tourmaline is heated or cooled, it 
 
 acquires opposite electrifications at opposite 
 ends or poles. 
 
 In the crystal of tourmaline shown in Fig. 227, 
 the end A, called the analogous pole, acquires a 
 positive electrification, 
 and the end B, called the 
 antilogous pole, a nega- 
 tive electrification, -while 
 the temperature of the 
 cry stalls rising. While 
 cooling, the opposite 
 electrifications are pro- 
 duced. 
 
 A heated crystal of 
 tourmaline, suspended by 
 a fibre, is attracted or 
 repelled by an electrified 
 body or by a second 
 heated tourmaline, in the Fi s- 227. Pyro Electric 
 same manner as an elec- Crystal. 
 
 trified body. 
 
 Many crystalline bodies possess similar prop- 
 erties. Among these are the ore of zinc known 
 as electric calamine or the silicate of zinc, bjra- 
 cite, quartz, tartrate of potash, sulphate of 
 quinine, etc. 
 
 Electricity, Radiation of The 
 
 radiation of electric energy by means of elec- 
 tro-magnetic waves. (See Electricity, Hertz's 
 Theory of Electro-Magnetic Radiations or 
 Waves.) 
 
 Electricity, Resinous A term 
 
 formerly employed in place of negative elec- 
 tricity. 
 
 It was at one time believed that all resinous 
 substances are negatively electrified by friction. 
 This we now know to be untrue, the nature of 
 electrification depending as much on the char- 
 acter of the rubber as on the character of the 
 thing rubbed. Thus resins rubbed with cotton, 
 flannel or silk, become negatively excited, but when 
 rubbed with sulphur or gun cotton, positively 
 excited. The te;ms positive and negative are 
 now exclusively employed. 
 
 Electricity, Series Distribution of, by 
 Constant Current Circuit Any sys- 
 tem for the distribution of constant currents 
 of electricity in which the electro-receptive 
 devices are connected to the line-wire or 
 circuit in series. (See Electricity, Distribu~ 
 tion of, by Constant Currents^ 
 
Jfle.] 
 
 198 
 
 [Ele. 
 
 Electricity, Single-Fluid Hypothesis of 
 
 A hypothesis which endeavors to ex- 
 plain the cause of electrical phenomena by 
 the assumption of the existence of a single 
 electric fluid. 
 
 The single-fluid hypothesis assumes: 
 
 (i.) That the phenomena of electricity are due 
 to the presence of a single, tenuous, imponder- 
 able fluid. 
 
 (2 ) That the particles of this fluid mutually 
 repel one another, but are attracted by all matter. 
 
 (3.) That every substance possesses a definite 
 capacity for holding the assumed electric fluid, 
 and, that when this capacity is just satisfied no 
 effects of electrification are manifest. 
 
 (4.) That when the body has less than this 
 quantity present, it becomes negatively excited, 
 and when it has more, positively excited. 
 
 (5.) That the act of friction causes a redistribu- 
 tion of the fluid, part of it going to one of 
 the bodies, giving it a surplus, thus positively 
 electrifying it, and leaving the other with a 
 deficit, thus negatively electrifying it. 
 
 The single-fluid hypothesis has been provis- 
 ionally accepted by some with this modification, 
 that a negatively excited body is thought to be 
 the one which contains the excess of the assumed 
 fluid, and a positively excited body the one which 
 contains the deficit. 
 
 They make this change on account of the 
 phenomena observed in Crookes' tube, where 
 the molecules of the residual gas are observed to 
 be thrown off from the negative and not from the 
 positive terminal. (See Tube, Crookes'.) 
 
 Another view considers electricity to be due to 
 differences of ether pressure, electricity being the 
 ether itself, and electromotive force, the differences 
 of ether pressures. Positive electrification is as- 
 sumed to result from a surplusage of energy, and 
 negative electrification from a deficit of energy. 
 
 At the present time the views of Hertz are 
 generally accepted. (See Electricity, Hertz's 
 Theory of Electro -Magnetic Radiations or Waves.) 
 
 Electricity, Specific Heat of A 
 
 term proposed by Sir William Thomson to 
 indicate the analogies existing between the 
 absorption and emission of heat in purely 
 thermal phenomena, and the absorption and 
 emission of heat in thermo-electric phe- 
 nomena, (See Heat, Specific^ 
 As we have already seen heat iz either given 
 
 out or absorbed, when an electric current passes 
 from one metal to another across a junction be- 
 tween them. (See Effect, Peltier.') 
 
 So, too, when electricity passes through an un- 
 equally heated wire, the current tends to increase 
 or decrease the differences of temperature, ac- 
 cording to the direction in which it flows, and 
 according to the character of the metal. (See 
 Effect, Thomson.'] 
 
 " If electricity were a fluid," says Maxwell, 
 "running through the conductor as water does 
 through a tube, and always giving out or ab- 
 sorbing heat till its temperature is that of the 
 conductor, then in passing from hot to cold it 
 would give out heat, and in passing from cold to 
 hot it would absorb heat, and the amount of this 
 heat would depend on the specific heat of the 
 fluid." 
 
 Electricity, Static A term applied 
 
 to electricity produced by friction. 
 
 The term static electricity is properly em- 
 ployed in the sense of a static charge but not as 
 static electricity, since that would indicate a par- 
 ticular kind of electricity, and, as is now gen- 
 erally recognized, electricity, from no matter 
 what source it is derived, is one and the same 
 thing. 
 
 Electricity, Storage of - A term 
 improperly employed to indicate such a 
 storage of energy as will enable it to directly 
 reproduce electric energy. 
 
 A so-called storage battery does not store elec- 
 tricity, any more than the spring of a clock can 
 be said to store time or sound. The spring stores 
 muscular energy, i. e., renders the muscular 
 kinetic energy potential, which, again becoming 
 kinetic, causes the works of the clock to move 
 or strike. 
 
 In the same way in a so-called storage battery, 
 the energy of an electric current is caused to 
 produce electrolytic decompositions of such a 
 nature as independently to produce a current on 
 the removal of the electrolyzing current. (See 
 Cell, Secondary. Cell, Storage.) 
 
 Electricity, Thermo - Electricity 
 produced by differences of temperature at the 
 junctions of dissimilar metals. 
 
 If a bar of antimony is soldered to a bar of bis- 
 muth, and the free ends of the two metals are 
 connected by means of a galvanometer, an appli- 
 cation of 'neat to the junction, so as to raise its 
 
Ele.J 
 
 199 
 
 [Ele. 
 
 temperature above the rest of the circuit, will pro- 
 duce a difference of potential, which, if neutral- 
 ized, will cause a current to flow across thejuat- 
 tion from the bismuth to the antimony (against 
 the alphabet, or from B to A). If the junction be 
 cooled below the rest of the circuit, a current is 
 produced across the junction from the antimony 
 to the bismuth (with the alphabet, or from A to B). 
 These currents are called thermo-electric currents, 
 and are proportional to the differences of tem- 
 perature. 
 
 Even the same metal, in different physical 
 states or conditions, such as a wire, part of which 
 is straight and the remainder bent into a spiral as 
 at H C, Fig. 228, if heated at F by the flame of 
 
 F. 
 
 Fig 228. Tfier mo- Electricity. 
 
 a lamp will have a difference of potential devel- 
 oped in it. 
 
 The same thing may also be shown by placing 
 cylinder of bismuth J, Fig. 229, in a gap in a 
 
 A 
 
 Fig, 22(). Thermo- Electric Circuit. 
 
 hollow rectangle of copper A B, inside of which 
 a magnetic needle, M, is supported. 
 
 The rectangle of copper being placed in the 
 magnetic meridian, on heating the junction by the 
 flame of a lamp F, the needle will be deflected 
 by a current produced by the difference of tem- 
 perature. 
 
 Thermo-electricity is generally obtained by 
 means of the combination of a thermo-electric 
 couple, in a thermo-electric cell. (See Couple, 
 Thermo-electric. Cell, Thermo- Electric.'] 
 
 Since the difference of potential produced by 
 a single thermo-electric couple is small, a number 
 of such couples or cells are generally connected in 
 
 series to produce a thermo-electric battery. (See 
 Battery, Thermo-electric. ) 
 
 Electricity, Unit Quantity of 
 
 The quantity of electricity conveyed by unit 
 current per second. 
 
 The practical unit quantity of electricity is the 
 coulomb, which is the quantity conveyed by a 
 current of one ampere in one second. 
 
 Electricity, Unit Quantity of, Natural 
 
 The quantity of electricity pos- 
 sessed as a charge by any elementary monad 
 atom. (See Electricity, Atom of.) 
 
 Electricity, Varieties of A classi- 
 fication of electricity according to its state of 
 rest or motion, or to the peculiarities of its 
 motion. 
 
 Lodge classifies the different varieties of elec- 
 tricity as follows, viz. : 
 
 (i.) Electricity at Rest, or Static Electricity. 
 
 This branch of electric science treats of phenom- 
 ena belonging to stresses and strains in insulated 
 media, when brought into the neighborhood of 
 electric charges, together with the modes of ex- 
 citing such electric charges, and the laws of their 
 interactions. 
 
 (2.) Electricity in Locomotion, or Current Elec- 
 tricity. 
 
 This branch of electric science treats of the phe- 
 nomena produced in metallic conductors, chem- 
 ical compounds and dielectric media, by the pas- 
 sage of electricity through them, and the modes 
 of exciting electricity into motion, together with 
 the laws of its flow. 
 
 (3.) Electricity in Rotation, or Magnetism. 
 
 This branch of electric science treats of the phe- 
 nomena produced in electricity in whirling or 
 vortex motion, the manner in which such whirls 
 may be produced, the strains and stresses which 
 they produce, and the laws of their interactions. 
 
 (4.) Electricity in Vibration, or Radiation. 
 
 This branch of electric science treats of the study 
 of the propagation of periodic or undulatory dis- 
 turbances through various kinds of media, the 
 laws regulating wave velocity, wave length, re- 
 flection, interference, dispersion, polarization and 
 other similar phenomena generally studied under 
 light. 
 
 A misleading classification of electricity is 
 sometimes made according to the sources which 
 produce it. This is misleading, since electricity, 
 no matter how produced, is one and the same. 
 
Ele.] 
 
 200 
 
 [Ele. 
 
 The so-called varieties of electricity may be di- 
 vided int'> different classes according to the nature 
 of the source. The principles of these are as fol- 
 lows : 
 
 (l.) Frictional- Electricity, or that produced by 
 the fricti m of one substance against another. 
 
 (2.) Voltaic-Electricity, or that produced by 
 the contact of dissimilar substances under the in- 
 fluence of chemical action. 
 
 (3.) Thermo-Electricity, or that produced by 
 differences of temperature in a thermo couple. 
 
 (4.) Pyro-Electricity, or that produced by dif- 
 ferences of temperature in certain crystalline 
 solids. 
 
 (5.) Magneto-Electricity, or that produced by 
 the motion of a conductor through the field of 
 permanent magnets. This is a variety of 
 
 (6.) Dynamo-Electricity, or that produced by 
 moving conductors so as to cut lines of magnetic 
 force. 
 
 (7.) Vital-Electricity, or that produced under 
 the influence of life or accompanying life. 
 
 Electricity, Titreous A term for- 
 merly employed to indicate positive elec- 
 tricity. 
 
 It was formerly believed that the friction of 
 glass with other bodies always produces the 
 same kind of electricity. This, however, is now 
 known not to be the case. 
 
 The term is now replaced by positive elec- 
 tricity. (See Electricity, Resinous.} 
 
 Electricity, Yoltaic Differences of 
 
 potential produced by the agency of a vol- 
 taic cell or battery. 
 
 Electricity is the same thing or phase of energy 
 by whatever source it is produced. 
 
 Electrics. Substances capable of becom- 
 ing' electrified by friction. 
 
 Substances like the metals, which, when held 
 in the hand could not be electrified by friction 
 were formerly called non-electrics. 
 
 These terms were used by Gilbert in the early 
 history of the science. 
 
 This distinction is not now generally employed 
 since conducting substances if insulated, may be 
 electrified by friction. 
 
 Electriflable. Capable of being endowed 
 with electric properties. 
 
 Electrification. The act cf becoming 
 electrified. 
 
 The production of an electric charge. 
 
 Electrified Body. (See Body, Electri- 
 fied) 
 
 Electrify. To endow with electrical prop- 
 erties. 
 
 Electrine. Relating to electrum, or am- 
 ber. 
 
 Electrization, Therapeutical Sub- 
 jecting different parts of the human body to 
 the action of electric currents for the cure of 
 diseased conditions. 
 
 Electro-Biology. (See Biology, Electro) 
 
 Electro-Brassing. (See Brassing, Elec- 
 tro) 
 
 Electro-Bronzing. (See Bronzing, Elec- 
 tro) 
 
 Electro - Capillary Phenomena. (See 
 Phenomena, Electro-Capillary) 
 
 Electrocesis. A word proposed for cur- 
 ing by electricity. 
 
 Electro-Chemical Equivalent. (See 
 Eqtiivalent, Electro-Chemical) 
 
 Electro-Chemical Meter. (See Meter, 
 Electro-Chemical) 
 
 Electro-Chemical Telephone. (See Tele- 
 phone, Electro-Chemical) 
 
 Electro-Chemistry. (See Chemistry, 
 Electro) 
 
 Electro-Chromic Rings. (See Rings, 
 Electro-Chromic) 
 
 Electro-Contact Mine. (See Mine, Elec- 
 tro-Contact) 
 
 Electro-Coppering. (See Coppering, 
 Electro) 
 
 Electro-Crystallization. (See Crystalli- 
 zation, Electro) 
 
 Electrocution. Capital punishment by 
 means of electricity. 
 
 Electrode. Either of the terminals of an 
 electric source. 
 
 The term was applied b) Faraday to cither o* 
 the conductors placed in an electrolytic bath and 
 conveying the current into it, and this is its strict 
 meaning. The terms pole or terminal apply to 
 the ends of a break in any electric circuit. 
 
 Electrode, Aural - A therapeutic 
 electrode, shaped for the treatment of the 
 
E!e.] 
 
 201 
 
 [Ele. 
 
 ear. (See Electrode. Electro-Thera- 
 peutic^] 
 
 Electrode, Brush A therapeutic 
 
 electrode fashioned like a wire brush or other 
 conducting brush. (See Electrode, Electro- 
 Therapeutic^ 
 
 Electrode, Cautery-Knife A knife- 
 shaped electrode, that is rendered incan- 
 descent by the passage of the electric cur- 
 rent. 
 
 Electrode, Clay A therapeutic elec- 
 trode of clay shaped to fit the part of the 
 body to be treated. (See Electrode, Electro- 
 Therapeutic^] 
 
 Electrode, Disc A disc-shaped elec- 
 trode employed in electro-therapeutics. (See 
 Electrode, Electro- Therapeutic?) 
 
 Electrode, Dry A therapeutic elec- 
 trode applied in a dry state. (See Electrode, 
 Electro- Therapeutic?) 
 
 Electrode, Electro-Therapeutic 
 
 In electro-therapeutics the electrode mainly 
 concerned in the treatment or diagnosis of the 
 diseased parts. 
 
 Either the positive or the negative electrode 
 may be the therapeutic electrode, and one or the 
 other is employed according to the particular 
 character of the effect it is desired to obtain. 
 The other electrode is placed at any convenient 
 and suitable part of the body, and is called the 
 indifferent electrode, 
 
 The therapeutic electrode is generally placed 
 nearer the organ or part to be treated than the 
 indifferent electrode. 
 
 Electrode-Handle, Pole-Changing and 
 Interrupting A handle provided for 
 the ready insertion of electro-therapeutic 
 electrodes, and provided with means for inter- 
 rupting or changing the direction of the cur- 
 rent. 
 
 Electrode, Illumined That elec- 
 trode of a selenium cell which is exposed to 
 the light. (See Cell, Selenium?) 
 
 Electrode, Indifferent In electro- 
 therapeutics the electrode that is employed 
 merely to complete the circuit through the 
 organ or part subjected to the electric cur- 
 
 rent, and is not directly concerned in the 
 treatment or diagnosis of the diseased parts. 
 Either the positive or the negative electrode 
 may be the indifferent electrode. (See Electrode, 
 Electro- Therapeutic.) 
 
 Electrode, Moist A therapeutic- 
 electrode applied in a moist condition. (See 
 Electrode, Electro- Therapeutic?) 
 
 Electrode, Needle A therapeutic 
 
 electrode in the shape of a needle, and em- 
 ployed for electrolytic treatment. (See Elec- 
 trode, Electro- Therapeutic?) 
 
 Electrode, Negative The electrode 
 
 connected with the negative pole of an elec- 
 tric source. 
 
 Electrode, Non-Illumined That 
 
 electrode of a selenium cell that is protected 
 from the direct action of light. (See Cell, Sel- 
 enium?) 
 
 Electrode, Non- Wasting A term 
 
 sometimes applied to the negative electrode 
 of an arc-lamp when made of iridium or other 
 similar material. 
 
 Electrode, Positive The electrode 
 
 connected with the positive pole of an electric 
 source. 
 
 Electrode, Rectal A therapeutic 
 
 electrode, suitably shaped for the treatment of 
 the rectum. (See Electrode, Electro-Thera- 
 peutic?) 
 
 Electrode, Sponge - A moistened 
 sponge connected to one of the terminals of 
 an electric source and acting as the electro- 
 therapeutic electrode. 
 
 Electrode, TJrethral - An electro- 
 therapeutic electrode suitably shaped for the 
 treatment of the urethra. (See Electrode, 
 Electro- Therapeutic?) 
 
 Electrode, Vaginal An electro- 
 therapeutic electrode suitably shaped for the 
 treatment of the vagina. (See Electrode, 
 Electro- Therapeutic?) 
 
 Electro-Deposi! s. (See Deposits, Elec- 
 tro?) 
 
 Electrodes. T'"se terminals of an electric 
 source. 
 
 The positive electrode is sometimes called the 
 
202 
 
 [Ele. 
 
 Anode, and the negative electrode the Kathode. 
 No matter for what purposes employed, they are 
 generally in electro-therapeutics termed electrodes. 
 In precise use these terms should be restricted 
 to the electrodes when used for electrolytic de- 
 composition. 
 
 The electrodes are made of different shapes and 
 of different materials according to the character of 
 the work the current is to perform. 
 
 Electrodes, Carbon, for Arc-Lamps 
 Rods of artificial carbon employed in arc 
 lamps. 
 
 These are more properly called simply arc- 
 lamp carbons. 
 
 Arc-lamp carbons are moulded into the shape 
 -of rods, from plastic mixtures of carbonaceous 
 materials" and carbonizable liquids. On the sub- 
 sequent carbonization of these rods the ingredients 
 are caused to cohere in one solid mass by the de- 
 posit of carbon derived from the carbonizable 
 materials. (See Carbons* Artificial.') 
 
 Carbons for arc-lamps are generally copper- 
 coated, so as to somewhat decrease their resist- 
 ance, and insure a more uniform consumption. 
 Arc-lamp carbons are sometimes provided with a 
 central core ot softer carbon, which fixes the po- 
 sition of the arc and thus insures a steadier light. 
 (Se' Zarbons, Cored.) 
 
 Electrodes, Cored Carbon elec- 
 trodes of a cylindrical shape provided with a 
 central cylinder of softer carbon. 
 
 The use of cored electrodes for arc lamps is 
 for the purpose of steadying the light by maintain- 
 ing the arc in a central position. This is effected 
 by the greater vaporization of the softer carbon 
 of the core. 
 
 Electrodes, Cylindrical Carbon - 
 Carbon cylinders used for electrodes of arc- 
 lamps, or for battery plates. 
 
 Electrodes, Electro-Therapeutic 
 
 Electrodes of various shapes employed in 
 electro-therapeutics. 
 
 The electro-therapeutic electrode, as distin- 
 guished from the indifferent electrode, is especially 
 shaped for the particular purpose for which it is 
 designed. 
 
 When the electricity is intended to affect the 
 skin or superficial portions of the body only, it is 
 applied dry, and is then generally metallic. To 
 reach the deeper structures, such as the muscle 
 or nerve trunks, moistened sponge electrodes are 
 
 employed. Before their use the skin should be 
 thoroughly moistened. Sponge-electrodes are 
 generally made conducting by a solution of some 
 saline substance, such as common salt. 
 
 Electrodes, Erb's Standard Size of 
 
 Standard sizes of electrodes generally 
 adopted in electro-therapeutics. 
 
 The following standard sizes have been pro- 
 posed by Erb, viz. : 
 (i.) Fine electrode. ... ^ centimetre diameter. 
 
 (2.) Small " 2 " " 
 
 (3.) Medium " 7.5 " " 
 
 (4.) Large " ....6x2 " " 
 
 (5.) Very large do 8 x 16 " " 
 
 Electrodes, Non-Polarizable 
 
 Electrodes employed in electro-therapeutics, 
 that are so constructed as to avoid the effects 
 of polarization. 
 
 Non-polarizable electrodes are obtained by 
 employing two amalgamated zinc wires, dipped 
 into saturated solution of zinc chloride placed in 
 glass tubes, and closing the lower ends of the 
 tubes by a piece of potter's clay. The contact of 
 an electrode so prepared with the tissues of the 
 body does not produce a polarization. 
 
 Electro-Diagnosis. (See Diagnosis, Elec- 
 tro^ 
 
 Electro-Diagnostic. (See Diagnostic, 
 Electro?) 
 
 Electro-Dynamic Attraction. (See At- 
 traction, Electro-Dynamic?) 
 
 Electro-Dynamic Capacity. (See Ca- 
 pacity, Electro-Dynamic?) 
 
 Electro-Dynamic Induction. (See Induc- 
 tion, Electro-Dynamic?) 
 
 Electro-Dynamic Repulsion. (See Re- 
 pulsion, Electro-Dynamic?) 
 
 Electro-Dynamics. (See Dynamics, 
 Electro?) 
 
 Electro-Dynamometer. (See Dynamom- 
 eter, Electro?) 
 
 Electro-Etching. Electric etching. (See 
 Etching, Electro?] 
 
 Electrogenesis. Results following the 
 application of electricity to the spinal cord or 
 nerve after the withdrawal of the electrodes. 
 
 Electro-Gilding. (See Gilding, Electro^ 
 
Ele.] 
 
 203 
 
 [Ele. 
 
 Electro-Kinetics. (See Kinetics, Elec- 
 tro?) 
 
 Electrolier. A chandelier for holding 
 electric lamps, as distinguished from a chan- 
 delier for holding gas-lights. 
 
 Electrology. That branch of science 
 which treats of electricity. (Obsolete.) 
 
 Electrolysis. Chemical decomposition 
 effected by means of an- electric current. 
 
 When an electric current is sent through an 
 electrolyte, i. e., a liquid which permits the cur- 
 rent to pass only by means of the decomposition 
 of the liquid, the decomposition that ensues is 
 called electrolytic decomposition, 
 
 The electrolyte is decomposed or broken up 
 into atoms or groups of atoms or radicals, called 
 ions. 
 
 The ions are of two distinct kinds, viz. : The 
 electro -positive ions, or kathions, and the electro- 
 negative ions, or onions. 
 
 Since the anode of the source is connected with 
 the electro-positive terminal, it is clear that the 
 amons* or the electro-negative ions, must appear 
 at the anode, and the kathions, or electro-positive 
 ions, must appear at the kathode. 
 
 Hydrogen, and the metals generally, are 
 kathions. Oxygen, chlorine, iodine, etc., are 
 anions. 
 
 The vessel containing the electrolyte, in which 
 these decompositions take place, is sometimes 
 called an electrolytic cell. 
 
 An electrolytic cell is called a voltameter when 
 it is arranged for measuring the current passing 
 by means of the amount of decomposition it 
 effects. (See Voltameter.} 
 
 Electrolysis by Means of Alternating 
 Currents. Electrolytic decomposition ef- 
 fected by means of alternating currents. 
 
 When an alternating current is passed through 
 dilute sulphuric acid, in a voltameter provided 
 with large platinum electrodes, no visible decom- 
 position occurs. If, however, the size of the 
 electrodes be decreased below a certain point, 
 then visible decomposition occurs. 
 
 Verdet showed that when no other break ex- 
 ists in the circuit of the alternating current 
 within the voltameter, no indications of elec- 
 trolysis are obtained, unless the alternating 
 current is very powerful. If, however, a break is 
 made in the secondary circuit, so that the dis- 
 
 charge has to pass as a spark, then visible signs 
 of electrolysis are produced by comparatively 
 feeble alternating currents. 
 
 When electrolysis occurs by means of alternat- 
 ing currents 
 
 (i.) The gases collected at both electrodes 
 have the same composition. 
 
 (2.) Where the quantities of electricity that al- 
 ternately pass in opposite directions are unequal, 
 the electrodes show manifest polarization, and, 
 when connected by a conductor, yield a current 
 like a secondary battery. 
 
 (3.) The electrodes manifest no sensible polari- 
 zation where the quantities of electricity that al- 
 ternately pass in opposite directions are equal. 
 
 Electrolysis, Faraday's Laws of 
 
 The principal facts of electrolysis are given 
 in the following laws: 
 
 (i.) The amount of chemical action in any 
 given time is equal in all parts of the circuit. 
 
 (2.) The number of ions liberated in a given 
 time is proportional to the strength of the cur- 
 rent passing. Twice as great a current will 
 liberate twice as many ions. The current may 
 be regarded as being carried through the elec- 
 trolyte by the ions: since an ion is capable of 
 carrying a fixed charge only of -f- or electri- 
 city, any increase in the current strength necessi- 
 tates an increase in the number of ions. 
 
 (3.) When the same current passes successively 
 through several cells containing different elec- 
 trolytes, the weights of the ions liberated at the 
 different electrodes will be equal to the strength 
 of the current multiplied by the electro-chemical 
 equivalent of the ion. (See Equivalence, Elec- 
 tro-Chemical, La-d) of .} 
 
 The chemical equivalent is proportional to the 
 atomic weight divided by the valency. (See 
 Equivalent, Chemical.} 
 
 The electro-chemical equivalent of any element 
 is equal to the weight in grammes of that element 
 set tree by one coulomb of electricity, and is found 
 by multiplying the electro-chemical of hydrogen 
 by the chemical equivalent of that element. (See 
 Equivalent, Electro- Chemical. ) 
 
 Electrolyte, Polarization of The 
 
 formation of molecular groups or chains, in 
 which the poles of all the molecules of any 
 chain are turned in the same direction, viz.: 
 with their positive poles facing the negative 
 plate, and their negative poles facing the 
 
Ele.] 
 
 204 
 
 [Ele, 
 
 positive plate. (See Cell, Voltaic. Hypoth- 
 esis, Grotthus') 
 
 Electrolytic or Electrolytical. Pertain- 
 ing to electrolysis. 
 
 Electrolytic Analysis. (See Analysis, 
 Electrolytic) 
 
 Electrolytic Cell. (See Cell, Electro- 
 lytic, Teslas) 
 
 Electrolytic Clock. (See Clock, Electro- 
 lytic) 
 
 Electrolytic Conduction. (See Conduc- 
 tion, Electrolytic) 
 
 Electrolytic Convection. (See Convec- 
 tion, Electrolytic) 
 
 Electrolytic Decomposition. (See De- 
 composition, Electrolytic) 
 
 Electrolytic Hydrogen. (See Hydrogen, 
 Electrolytic) 
 
 Electrolytic Writing. (See Writing, 
 Electrolytic) 
 
 Electrolytically. In an electrolytic man- 
 ner. 
 
 Electrolyzable. Capable of being elec- 
 trolyzed, or decomposed by means of elec- 
 tricity. 
 
 Electrolyzed. Separated or decomposed 
 by means of electricity. 
 
 Electrolyzing. Causing or producing 
 electrolysis. 
 
 Electro-Magnet. (See Magnet, Electro) 
 
 Electro-Magnetic Ammeter. (See Am- 
 meter, Electro-Magnetic) 
 
 Electro-Magnetic Annunciator. (See 
 Annunciator, Electro-Magnetic) 
 
 Electro-Magnetic Attraction. (See At- 
 traction, Electro-Magnetic) 
 
 Electro-Magnetic Bell-Call. (See Call, 
 Bell, Magneto-Electric) 
 
 Electro-Magnetic Bell, Siemens' Arma- 
 ture (See Bell, Electro-Magnetic, 
 
 Siemens' Armature Form) 
 
 Electro-Magnetic Brake. (See Brake, 
 Electro-Magnetic) 
 
 Electro-Magnetic Cam. (See Cam, 
 Electro-*,* agnetic) 
 
 Electro-Magnetic Dental-Mallet. (See 
 Dental-Mallet, Electro-Magnetic) 
 
 Electro-Magnetic Drill. (See Drill, 
 
 Electro-Magnetic) 
 
 Electro-Magnetic Engine. (See Engine, 
 Electro-Magnetic) 
 
 Electro-Magnetic Exploder. (See Ex- 
 ploder, Electro- Magnetic) 
 
 Electro-Magnetic Eye. (See Eye, Elec- 
 tro-Magnetic) 
 
 Electro-Magnetic Impulse. (See Im- 
 pulse, Electro-Magnetic) 
 
 Electro-Magnetic Induction. (See In- 
 duction, Electro-Magnetic) 
 
 Electro-Magnetic Medium. (See Me- 
 dium, Electro-Magnetic) 
 
 Electro-Magnetic Meter. (See Meter, 
 Electro-Magnetic) 
 
 Electro-Magnetic Momentum of Sec- 
 ondary Circuit. (See Momentum, Elec- 
 tro-Magnetic, of Secondary Circuit) 
 
 Electro-Magnetic Pop-Gun. (See Pop- 
 Gun, Electro-Magnetic) 
 
 Electro-Magnetic Radiation. (See Ra- 
 diation, Electro-Magnetic) 
 
 Electro-Magnetic Repulsion. (See Re- 
 pulsion, Electro-Magnetic) 
 
 Electro-Magnetic Resonator. (See Res- 
 onator, Electro- Magnetic) 
 
 Electro-Magnetic Shunt. (See Shunt, 
 Electro-Magnetic) 
 
 Electro-Magnetic Solenoid. (See Sole- 
 noid, Electro-Magnetic) 
 
 Electro-Magnetic Strain. (See Strain, 
 Electro-Magnetic) 
 
 Electro-Magnetic Stress. (See Stress, 
 Electro-Magnetic) 
 
 Electro-Magnetic Theory of Light, Max- 
 well's (See Light, Maxwell's Elec- 
 tro-Magnetic Theory of) 
 
 Electro-Magnetic Vibrator. (See Vi- 
 brator, Electro-Magnetic) 
 
 Electro-Magnetic Voltmeter. (See T W/- 
 meter, Electro-Magnetic) 
 
Ele.] 
 
 205 
 
 [Ele. 
 
 Electro-Magnetic Units. (See Units, 
 Electro-Magnetic?) 
 
 Electro-Magnetics. (See Magnetics, 
 Electro?) 
 
 Electro-Massage. (See Massage, Elec- 
 tro?) 
 
 Electro-Mechanical Alarm. (See Alarm, 
 Electro-Mechanical?) 
 
 Electro-Mechanical Gong. (See Gong, 
 Electro-Mechanical?) 
 
 Electro-Metallurgical Crystalline De- 
 posit. (See Deposit, Crystalline, Electro- 
 Metallurgical?) 
 
 Electro-Metallurgical Galvanization. 
 
 (See Galvanization, Electro- Metallurgical?) 
 
 Electro-Metallurgical Nodular Deposit. 
 
 (See Deposit, Electro - Metallurgical 
 Nodular?) 
 
 Electro - Metallurgical Regnline De- 
 posit. (See Deposit, Electro-Metallurgical 
 Reguline?) 
 
 Electro-Metallurgical Sandy Deposit. 
 
 (See Deposit, Electro-Metallurgical Sandy?) 
 
 Electro-Metallurgy. (See Metallurgy, 
 Electro?) 
 
 Electrometer. An apparatus for measur- 
 ing differences of potential. 
 
 Electrometers operate, in general, by means 
 of the attraction or repulsion of charged conduc- 
 tors on a suitably suspended needle or disc. As 
 no current is required to flow through the appa- 
 ratus electrometers are especially adapted to many 
 cases where voltmeters could not be so readily 
 used. 
 
 Electrometer, Absolute An elec- 
 trometer the dimensions of which are such 
 that the value of the electromotive force can 
 be directly determined from the amount of 
 the deflection of the needle. 
 
 A form of attracted-disc electrometer. 
 (See Electrometer, At traded- Disc?) 
 
 Electrometer, Attracted-Disc A 
 
 form of electrometer devised by Sir William 
 
 Thomson, in which the force is measured by 
 the attraction between the two discs. 
 
 Thomson's Attracted-Disc Electrometer is 
 shown in Fig. 230. It consists of a plate C, sus- 
 pended from the longer end of a lever 1, within the 
 fixed guard plate, or guard ring B, immediately 
 above a second plate A, supported en an insulated 
 stand, and capable of a measurable approach 
 
 Fig. 230. Attracted-Dise Electrometer. 
 
 towards C, or a movement away from it. The 
 plate, C, is placed in contact with B, by means of 
 a thin wire. By means of this connection the 
 distribution of the charge over the plate, C, is 
 uniform. The electrostatic attraction is meas- 
 ured by the attraction of the fixed disc, A, on the 
 movable disc, C, connected respectively to the two 
 bodies whose difference of potential is to be 
 measured. One of these may be the earth. The 
 fulcrum of the lever 1, is formed of an aluminium 
 wire, the torsion of which is used to measure the 
 force of the attraction; or, it may be measured 
 directly by the counterpoise weight Q. 
 
 This instrument is sometimes called an absolute 
 electrometer, because, knowing the dimensions of 
 the apparatus, the value of the difference of poten- 
 tial can be directly determined from the amount 
 of the motion observed. 
 
 Electrometer, Capillary An elec- 
 trometer in which a difference of potential is 
 
 Fig. 231. Capillary Electrometer 
 
 measured by the movement of a drop of 
 sulphuric acid in a tube filled with mercury. 
 
tie.] 
 
 20G 
 
 [Ele. 
 
 A form of capillary electrometer is shown in 
 yi^. 231, in which a horizontal glass tube with 
 a drop of acid at B, has its ends connected with 
 two vessels M and N, filled with mercury. If 
 a current be passed through the tube, a move- 
 ment of the drop towards the negative pole 
 will be observed. Where the electromotive 
 force does not exceed one volt, the amount of 
 the movement is proportional to the electro- 
 motive force. 
 
 Electrometer, Quadrant An elec- 
 trometer in which an electrostatic charge is 
 measured by the attractive and repulsive 
 force of four plates or quadrants, on a light 
 needle of aluminium suspended within them. 
 
 The sectors or quadrants are of brass, and are 
 so shaped as to form a hollow cylindrical box 
 when placed together. The four sectors, or quad- 
 rants, are insulated from one another, but the 
 opposite ones are connected by a conducting wire, 
 as shown in Fig. 
 232. A light needle 
 of aluminium, u, 
 maintained at some 
 constant potential, 
 by connection with 
 the inner coating 
 of a Ley den jar, is 
 suspended, gener- 
 ally by two par- 
 allel silk threads, 
 so as to freely swing inside the hollow box. This 
 needle, when at rest, is in the position shown by 
 the dotted lines, with its axis of symmetry exactly 
 under one of the slots or spaces between two 
 Apposite sectors. (See Suspension, Bi-Filar.} 
 
 The quadrant electrometer, shown in Fig. 233, 
 .ias one of its quadrants removed so as to show 
 the suspended aluminium needle. 
 
 A similar form of instrument is shown in Fig. 
 234, with all the quadrants in place, and the 
 whole instrument covered by a glass shade. 
 
 To use the quadrant electrometer the pairs of 
 sectors are connected with the two bodies whose 
 difference of potential is to be measured, and the 
 deflection of the needle observed, generally 
 through a telescope, by means of a spot of light 
 reflected from a mirror attached to the upper part 
 of the needle. 
 
 Sometimes the segments are made in the shape 
 of a cylinder, and the needle in the shape of a 
 suspended rectangle. 
 
 Electrometer, Registering 
 
 An elec- 
 
 trometer, the deviations of the needle of 
 which are automatically registered. 
 
 Fig. 232. Quadrant Elec- 
 trometer. 
 
 Fig. 233. Quadrant Electrometer, Showing Suspended 
 Needle. 
 
 The registration of this class of electrometer is 
 obtained by means of photography. The spot of 
 
 Fig. 234. Quadrant Electromettr. 
 
 light, reflected from the mirror ot the electrometer, 
 falls on a fillet' of sensitized paper, moved by 
 clockwork. 
 
Ele. 
 
 207 
 
 [Ele. 
 
 Electromotive Arrangement or Device. 
 
 (See Arrangement or Device, Electromo- 
 tive?} 
 
 Electromotive Difference of Potential. 
 
 (See Potential, Difference of Electromotive?) 
 
 Electromotive Force. (See Force, Elec- 
 tromotive^) 
 
 Electromotive Force, Average (See 
 
 Force, Electromotive, Average or Mean.} 
 
 Electromotive Force, Back or Counter 
 (See Force, Electromotive. Back.) 
 
 Electromotive Force, Direct (See 
 
 Force, Electromotive, Direct?) 
 
 Electromotive Force, Inductive 
 
 (See Force, Electromotive, Inductive?) 
 
 Electromotive Force, Secondary-Im- 
 pressed (See Force. Electromotive \ 
 
 Secondary-Impressed?) 
 
 Electromotive Force, Simple-Periodic 
 (See Force, Electromotive, Simple- 
 Periodic?) 
 
 Electromotive Force, Transverse 
 (See Force, Electromotive. Transverse?) 
 
 Electromotive Impulse. (See Impulse, 
 Electromotive?) 
 
 Electro-Motograph. (See Motograph, 
 Electro?) 
 
 Electro-Muscular. (See Muscular, Elec- 
 tro?) 
 
 Electro-Muscular Excitation. (See Ex- 
 citation, Electro-Muscular?) 
 
 Electronecrosic. Pertaining to capital 
 punishment by means of electricity. 
 
 Electronecrosis. A word proposed for 
 capital punishment by means of electricity. 
 
 Electro-Negative Ions. (See Ions, Elec- 
 tro-Negative?) 
 
 Electronegatives. The atoms or radicals 
 that appear at the anode or positive terminal 
 during electrolysis. 
 
 The anions. (See Electrolysis. Anton?) 
 
 Electro-Nervous Excitability. (See Ex- 
 citability, Electro-Nervous?) 
 
 Electro- Nickeling. (See Nickeling, 
 Electro?) 
 
 Electro-Optics. (See Optics, Electro?) 
 
 Electrophanic. Pertaining to capital pun- 
 ishment by means of electricity. 
 
 Electrophanical. Pertaining to capital 
 punishment by means of electricity. 
 
 Electrophauize. - To inflict capital pun- 
 ishment by means of electricity. 
 
 Electrophany. Capital punishment by 
 means of electricity. 
 
 The word electrophany would appear to be far 
 preferable to the word electrocution, since it is in 
 accordance with etymological usage, while elec- 
 trocution is not. 
 
 Electrophila. A devotee of electricity. 
 
 Electrophobia. A word proposed for fear 
 of electricity. 
 
 Electrophoric. Pertaining to an electro- 
 phorus. (See Electrophorus?) 
 
 Electrophorus. An apparatus for the 
 production of electricity 
 by electrostatic induc- 
 tion. (See Induction, 
 Electrostatic?) 
 
 A disc of vulcanite, or 
 hard rubber B, contained 
 in a metallic form, is rub- 
 bed briskly by a piece of 
 cat's skin and the insu- 
 lated metallic disc, A, is Fig. 233. Electrophortts, 
 placed on the centre of the Charging. 
 
 vulcanite disc, as shown in Fig. 235. 
 
 The negative charge produced in B, by fric- 
 tion, produces by induction a positive charge on 
 the part of A, nearest it, 
 and a negative charge 
 on the part furthest from 
 it. 
 
 In this condition, if 
 the disc be raised from 
 the plate by means of its 
 insulating handle, as 
 shown in Fig. 236, no 
 electrical effects will be 
 noticed, since the two op- 
 posite and equal charges 
 unite and neutralize each Fig. 236. Electrophorus, 
 
 ., Tr i ,, Discharging, 
 
 other. If, however, the 
 
 disc A, be first touched by the finger, and then 
 raised from the disc B, it will be found to 
 itively charged. 
 
 B 
 
Kle.] 
 
 208 
 
 [Ele. 
 
 E 1 e c t r o-Physiology. (See Physiology, 
 Electro) 
 
 Electropic Medium. (See Medium, Elec- 
 tropic) 
 
 Electro-Plating. (See Plating, Electro) 
 
 Electro-Plating Bath. (See Bath, Elec- 
 tro-Plating) 
 
 Electro-Pneumatic Signals. (See Sig- 
 nals, Electro-Pneumatic) 
 
 Electro-Pneumatic Thermostat. (See 
 Thermostat, Electro-Pneumatic) 
 
 Electropoion Liquid. (See Liquid, Elec- 
 tropoion) 
 
 Electro-Positive Ions. (See Ions, Elec- 
 tro-Positive) 
 
 Eleetropositives. The atoms or radicals 
 that appear at the kathode or negative termi- 
 nal of any source during electrolysis. 
 
 Thekathions. (See Electrolysis. Kathion) 
 E 1 e c t r o-Prognosis. (See Prognosis, 
 Electric) , 
 
 Electro-Puncture. (See Puncture, Elec- 
 tro) 
 
 Electro-Receptive Devices. (See Device, 
 Electro-Receptive) 
 
 Electro-Receptive Devices, Multiple-Arc- 
 Connected (See Devices, Electro- 
 Receptive, Multiple- A re- Connected) 
 
 Electro-Receptive Devices, Multiple-Se- 
 ries-Connected (See Devices, Elec- 
 tro-Receptive, Multiple-Series-Connected) 
 
 Electro-Receptive Devices, Series-Con- 
 nected (See Devices, Electro-Recep- 
 tive, Series-Connected) 
 
 Electro-Receptive Devices, Series-Mul- 
 tiple-Connected (See Devices, Elec- 
 tro-Receptive, Series-Multiple-Connected) 
 
 Electroscope. An apparatus for showing 
 the presence of an electric charge, or for de- 
 termining its sign, whether positive or nega- 
 tive, but not for measuring its amount or 
 value. 
 
 In the gold-leaf electroscope, two gold leaves, 
 n, n, Fig. 239, suspended near each other, show 
 by their repulsion the presence of an electric 
 charge. Two pith balls may be used for the same 
 purpose. 
 
 The pith balls B, B, shown in Fig. 237, form 
 a simple electroscope. If repelled by a charge, 
 when approached by a similar charge in S, they 
 will at once be still further repelled, as shown by 
 the dotted lines. 
 
 To use an electroscope for determining the sign of 
 
 Fig- 237' Pi th Bal1 Electroscope. 
 an unknown charge, the gold leaves or pith balls are 
 first slightly repelled by a charge of known name, 
 as, for example, positive, applied to the knob C, 
 Fig. 239. They are then charged by the electrified 
 body whose charge is to be determined. If they 
 are further repelled, its charge is positive. If 
 they are first attracted and afterwards repelled, 
 its charge is negative. 
 
 Two posts B, Fig. 239, connected with the 
 earth, increase the amount of divergence by in- 
 duction. 
 
 Electroscope, Condensing, Volta's 
 
 An electroscope employed for the detection 
 of feeble charges, the leaves of which are 
 charged by means of a condenser. 
 
 The condensing electroscope, Fig. 238, is 
 formed of two metallic 
 plates, placed at the G 
 
 top of the instrument, 
 and separated by a 
 suitable dielectric. 
 The upper plate, P, is 
 removable by means 
 of the insulated han- 
 dle, G. 
 
 To employ the elec 
 trdscope, as for exam- 
 ple, to detect the free 
 charge in an unequal- Fig. ^23 8. ~ Condensing Elec- 
 ly heated crystal of troscope. 
 
 tourmaline, the crystal is touched to the lower 
 plate, while the upper plate is connected to the 
 ground by the finger. On the subsequent re- 
 moval of the upper plate an enormous decrease 
 
Ele.J 
 
 209 
 
 [Ele. 
 
 ensues in the capacity of the condenser, and the 
 charge now raises the potential of the lower 
 plate, and causes a marked divergence of the 
 leaves L, L. (See Electricity, Pyro.) 
 
 Electroscope, Gold-Leaf An elec- 
 troscope in which two leaves of gold are used 
 to detect the presence of an electric charge, 
 or to determine its character whether positive 
 or negative. 
 
 When a charge is imparted to the knob C, Fig. 
 239, the gold leaves n, n, diverge. This will oc- 
 cur whether the charge be 
 positive or negative. 
 
 To determine the char- 
 acter of an unknown 
 charge, the leaves are first 
 caused to diverge by means 
 of a known positive or neg- 
 ative charge. The un- 
 known charge is then given 
 to the leaves. If they di- 
 
 Fig. 23Q. Gold- Leaf 
 Electroscope. 
 
 verge still further, then the charge is of the same 
 name as that originally possessed by the leaves. 
 If, however, they first move to- 
 gether and are afterwards re- 
 pelled, the charge is of the 
 opposite name. 
 
 Electroscope, Pith -Ball 
 
 - An electroscope 
 which shows the presence of 
 a charge by the repulsion of 
 two similarly charged pith 
 balls. (See Electroscope?) 
 
 Any two pith balls, suspend- 
 ed by conducting threads, but 
 insulated from the earth, will 
 serve as an electroscope. 
 
 Electroscope, Quadrant, 
 Henley's An electro- 
 scope sometimes employed 
 to indicate large charges of 
 electricity. 
 
 A pith ball placed on a light 
 arm A, of straw or other simi- 
 lar material, Fig. 240, is pivoted 
 at the centre of a graduated 
 circle B'. The arm, C, is at- Fig. 240. Henley's 
 tached by means of the screw Electroscope. 
 to the prime conductor of an electric machine. 
 The similar charge imparted to A, by contact 
 
 with C, causes a repulsion which may be meas- 
 ured on the graduated arc. 
 
 This instrument approaches the electrometer in 
 the character of its operation, since by its means, 
 approximately correct measurements may be made 
 of the value of the repulsion. It should not, how- 
 ever, be confounded with the quadrant electrom- 
 eter. (See Electrometer, Quadrant.') 
 
 Electroscopically. By means of the elec- 
 troscope. (See Electroscope?) 
 
 Electroscopy. The art of determining the 
 kind of charge a body possesses, by means 
 of an electroscope. 
 
 Electro - Sensibility. (See Sensibility, 
 Electro?) 
 
 Electro-Silvering. (See Silvering, Elec- 
 tro?) 
 
 Electro-Smelting. (See Smelting, Elec- 
 tro?) 
 
 Electrostatic Attraction. (See Attrac- 
 tion, Electrostatic?) 
 
 Electrostatic Capacity. (See Capacity, 
 Electrostatic?) 
 
 Electrostatic Circuit. (See Circuit, 
 Electrostatic?) 
 
 Electrostatic Field. (See Field, Electro- 
 static?) 
 
 Electrostatic Induction. (See Induction, 
 Electrostatic?) 
 
 Electrostatic Induction Machine. (See 
 Machine, Electrostatic Induction?) 
 
 Electrostatic Leakage. (See Leakage, 
 Electrostatic?) 
 
 Electrostatic Lines of Force. (See Force, 
 Electrostatic, Lines of.) 
 
 Electrostatic Repulsion. (See Repulsion, 
 Electrostatic.) 
 
 Electrostatic Screening. (See Screening, 
 Electrostatic?) 
 
 Electrostatic Stress. (See Stress, Elec- 
 trostatic.) 
 
 Electrostatic Units. (See Units, Electro- 
 static?) 
 
 Electrostatics. That branch of electric 
 science which treats of the phenomena and 
 measurement of electric charges. 
 
Ele.] 
 
 210 
 
 [Ele. 
 
 The principles of electrostatics are embraced 
 in the following laws, viz.: 
 
 (i.) Charges of like name, *. e., either positive 
 or negative, repel each other. Charges of unlike 
 name attract each other. 
 
 (2.) The forces of attraction or repulsion be- 
 tween two charged bodies are directly propor- 
 tional to the product of the quantities of elec- 
 tricity possessed by the bodies and inversely 
 proportional to the square of the distance be- 
 tween them. 
 
 These laws can be demonstrated by the use of 
 Coulomb's torsion balance. (See Balance, Tor- 
 sion.') 
 
 Calling q, and q 1 , the quantities of electricity 
 possessed by the two bodies, and r, the distance 
 between them, then, if f, is the force exerted by 
 their mutual action, 
 
 /_5 ( 1 1 
 : r~" 
 
 Electro-Technics. (See Technics, Elec- 
 tro) 
 
 Electrothanasing. Producing death by 
 electricity. 
 
 Electrothanasis. A word proposed for 
 death by electricity. 
 
 The death referred to here is death other than 
 that caused by capital punishment. 
 
 Electrothanasise. To produce death by 
 electricity. 
 
 The death here referred to is other than that 
 caused by capital punishment. 
 
 Electrothanatose. To cause death by 
 electricity. 
 
 Electrothanatosic. Pertaining to capital 
 punishment by means of electricity. 
 
 Eleetrothanatosing. Causing death by 
 electricity. 
 
 Electrothanatosis. A word proposed for 
 death by electricity. 
 
 The death here referred to is death other than 
 that caused by capital punishment. 
 
 Electro-Therapeutic Bath. (See Bath, 
 Electro- Therapeutic) 
 
 Electro-Therapeutic Breeze. (See 
 
 Breeze, Electro- Therapeutic) 
 
 Electro-Therapeutic Diffusion of Cur- 
 rent. (See Current, Diffusion of, Electro- 
 Therapeutic) 
 
 Electro-Therapeutic Dosage. (S e e 
 Dosage, Electro- Therapeutical) 
 
 Electro-Therapeutic Electrode. (See 
 Electrode, Electro- Therapeutic) 
 
 Electro-Therapeutic Electrodes. (See 
 Electrode, Electro- Therapeutic) 
 
 Electro-Therapeutic Galvanization. 
 
 (See Galvanization, Electro- Therapeutical) 
 
 Electro-Therapeutic Head-Breeze. 
 
 (See Breeze, Head, Electro- Therapeidic) 
 
 Electro-Therapeutics. (See Therapeu- 
 tics, Electro) 
 
 Electro-Therapeutist. (See Therapeu- 
 tist, Electro) 
 
 Electro-Therapy. (See Therapy, Elec* 
 tro) 
 
 Electro-Thermal Meter. (See Meter, 
 Electro- Thermal) 
 
 Electro-Tinning. (See Tinning, Elec- 
 tro) 
 
 Electrotisic. Pertaining to capital pun- 
 ishment by means of electricity. 
 
 Electrotisiny. Producing capital punish- 
 ment by means of electricity. 
 
 Electrotisis. A word proposed for capi- 
 tal punishment by means of electricity. 
 
 Electrotonic Current (See Current, 
 Electrotonic) 
 
 Electrotonic Effect. (See Effect, Electro- 
 tonic) 
 
 Electrotonic Excitahility. (See Excita- 
 bility, Electrotonic) 
 
 Electrotonic State. (See State, Electro- 
 tonic) 
 
 Electrotonus. A condition of altered 
 functional activity which occurs in a nerve 
 when subjected to the action of an electric 
 current. 
 
Ele.j 
 
 211 
 
 [Ele. 
 
 The electrotonic state is produced by the 
 passage through a nerve of a constant current 
 called the polarizing current. 
 
 Electrotonus is attended by the modification of 
 the nerve in the following respects, viz. : 
 
 (i.) In its electromotive force. 
 
 (2.) In its excitability. 
 
 The passage of the constant current produces 
 a change in the electromotive force of that part of 
 the nerve traversed by the current. 
 
 This alteration in muscular excitability may 
 consist in either an increased or a decreased func- 
 tional activity. The decreased functional activity 
 ccurs in the neighborhood of the anode, or the 
 positive terminal, and is called the anelectrotonic 
 state. The increased functional activity occurs in 
 the neighborhood of the kathode, or the negative 
 terminal, and is called the kathelectrotonic slate. 
 (See Anelectrotonus. Kathelectrotonus.} 
 
 This altered functional activity affects not only 
 the intra polar parts of the nerve, or that part 
 between the electrodes, but also the extra-polar 
 portions, or, in other words, the remainder of the 
 nerve. 
 
 The electrotonic state is characterized by two 
 varieties, viz.: those in which the electromotive 
 force of the nerve is decreased, and those in which 
 the electromotive force of the nerve is increased. 
 These varieties of electrotonus are called respec- 
 tively the negative and positive phase of electro- 
 tonus. (See Electrotonus, Negative Phase of. 
 Electrotonus, Positive Phase of.) 
 
 Electrotonus, Negative Phase of 
 
 A decrease in the electromotive force of a 
 nerve effected by seeding a current through 
 the nerve in the opposite direction to the 
 nerve current. (See Current, Nerve?) 
 
 Electrotonus, Positive Phase of 
 
 An increase in the electromotive force of a 
 nerve effected by sending a current through 
 the nerve in the same direction as the nerve 
 current. 
 
 The increase in the electromotive force not only 
 affects the portions of the nerve in the intra-polar 
 regions, but in the extra polar regions as well. 
 
 Electrotype. A type, cast, or impression 
 of an o,bject obtained by means of electro- 
 metallurgy. (See Metallurgy, Electro. Elec- 
 trotyping^) 
 
 Electrotyping, or the Electrotype Pro- 
 
 cess Obtaining casts or copies of 
 
 objects by depositing metals in molds by 
 the agency of electric currents. 
 
 The molds are made of wax, or other plastic 
 substance, rendered conducting by coating it with 
 powdered plumbago. 
 
 The mold is connected with the negative 
 battery terminal, and placed in a metallic solu- 
 tion, generally of copper sulphate, opposite a 
 plate of metallic copper, connected with the posi- 
 tive battery terminal. As the current passes, the 
 metal is deposited on the mold at the kathode, 
 and dissolved from the metallic plate at the 
 anode, thus producing an exact copy or cast and 
 at the same time maintaining constant the strength 
 of the bath. 
 
 Electrozemia. A word proposed for capi- 
 tal punishment by means of electricity. 
 
 Elect rum. A name given by the ancienis 
 to various substances that could be readily 
 electrified by friction. 
 
 The term electrum included a number of sub- 
 stances, but was applied mainly either to amber 
 or to an alloy of gold and silver. 
 
 Element. Any kind of matter which can- 
 not be decomposed into simpler matter. 
 
 Matter that is formed or composed of but 
 one kind of atoms. 
 
 Oxygen and hydrogen are elements or varie- 
 ties of elementary matter. They cannot be de- 
 composed into anything but oxygen or hydrogen. 
 Water, on the contrary, is compound matter, 
 since it can be decomposed into its constituent 
 parts, oxygen and hydrogen. 
 
 There are about seventy well-known elements, 
 some of which are very rare, occurring in ex- 
 tremely small quantities. 
 
 The evidence of the true elementary condition 
 of many of the elements is based, to a great ex- 
 tent, on the fact that so far they have resisted all 
 efforts made to decompose them into simpler sub- 
 stances. We should bear in mind, however, that 
 until Davy's use of the voltaic battery, potash, 
 soda, and many other similar compounds were re- 
 garded as true elements. It is not improbable 
 that many of the now so-called elements, may 
 hereafter be decomposed into simpler constitu- 
 ents. 
 
 The following table gives the names, chemical 
 
Ele.] 
 
 212 
 
 [Ele, 
 
 symbols, approximate atomic weights and equiva- 
 lents of the principal elements : 
 
 Names ot 
 Elements. 
 
 i 
 >* 
 
 CA 
 
 Approximate 
 Atomic 
 Weight. 
 
 Chemical Equivalent.* 
 
 
 Al. 
 Sb. 
 As. 
 Ba. 
 Be. 
 Bi. 
 B. 
 Br. 
 Cd. 
 Cs. 
 Ca. 
 C. 
 Ce. 
 Cl. 
 Cr. 
 Co. 
 Cu. 
 D. 
 E. 
 F. 
 Ga. 
 Ge. 
 G. 
 Au. 
 H. 
 In. 
 I. 
 Ir. 
 Fe. 
 La. 
 Pb. 
 Li. 
 Mg. 
 Mn. 
 Hg. 
 Mo. 
 Ni. 
 Nb. 
 N. 
 Os. 
 O. 
 
 Pd. 
 P. 
 Pt. 
 K. 
 R. 
 Rb. 
 Ru. 
 Sm. 
 Sc. 
 Se. 
 bi. 
 Ag. 
 Na. 
 Sr. 
 S. 
 Ta. 
 Te 
 TI. 
 Th. 
 Sn. 
 Ti. 
 W. 
 U. 
 Va. 
 Yb. 
 Y. 
 Zn. 
 Zr. 
 
 27. 
 
 120. 
 
 74-9 
 136.8 
 9.1 
 207.5 
 10.9 
 79.8 
 in. 8 
 132.6 
 40. 
 
 12. 
 140.4 
 
 35-4 
 52- 
 58 9 
 63.2 
 144.6 
 165.9 
 19. 
 68.9 
 72.3 
 
 196.3 
 i. 
 
 113.4 
 126.6 
 192.7 
 55-9 
 *38.5 
 206.5 
 
 7- 
 24. 
 
 53-9 
 199.7 
 95-5 
 57-9 
 93-8 
 14. 
 198.5 
 to. 
 105.7 
 31- 
 194.4 
 
 39- 
 104.1 
 
 85.3 
 104.3 
 150.02 
 
 78!8 
 28.3 
 107.7 
 23. 
 87-4 
 
 a> 
 182.1 
 
 128. 
 203.7 
 233-4. 
 117.7 
 
 i8 3 .' 
 238.5 
 Si-3 
 172.8 
 89.8 
 64.9 
 89.4 
 
 9 > [compounds 
 40 in eus, 24 in ic 
 24.9 iaous, 15 in ic 
 68. A 
 4.6 
 69.2 
 3-6 
 79.8 
 
 55-9 
 66.3 
 20 
 6 
 
 35.4 
 26 mous, 17.3 in ic 
 29-5 
 31.6 
 
 19. 
 
 196. a in out, 65. 4 in ic 
 
 37-8 
 126.6 
 96.4, 64.2, 48.3 
 28 in ous, 18.6 in ic 
 
 103.3 
 7 
 
 12 
 
 2 7 
 
 199.7 in ous, 99.9 in ic 
 28 
 
 '4 
 
 8 
 
 52.9 in <?.?, 26. 4 in if 
 6 . 2 in phosphates 
 97.2 in ous, 48.6111 ic 
 39; 
 52 in ous, 34.7 in ic 
 85-3. 
 52.1 mous, 34. 7 in if 
 
 7- 
 107.7 
 
 23 
 43-7 
 
 203 . 7 in ous, 67 . 9 in ic 
 
 58.9 in ous, 29.4 in ic 
 24 in ous, 12 in ic 
 9 1 . 8 in ous 
 119.2 in ous 
 17.1 mous 
 
 3*-S 
 
 
 
 
 
 
 
 
 
 Caesium 
 
 
 
 
 Chlorine 
 
 
 Cobalt 
 
 
 Didymium 
 
 
 
 Gallium 
 
 Germamun. 
 
 
 Gold 
 
 
 
 Iodine 
 
 
 
 
 Lead 
 
 
 
 Manganese 
 
 Mercury 
 
 Molybdenum 
 Nickel 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Silicon 
 
 
 
 
 
 
 
 Thallium 
 
 
 Tin 
 
 Titanium.......... 
 
 
 
 
 
 Yttrium 
 
 
 
 
 ' Atomic -weight divided by the valency. 
 
 Element, Negative One of the 
 
 substances forming a voltaic couple. (See 
 Couple, Voltaic.!) 
 Element, Negative, of a Toltaic Cell 
 
 That element or plate of a voltaic cell into 
 which the current passes from the exciting 
 fluid of the cell. 
 
 The plate that is not acted on by the elec- 
 trolyte during the generation of current by 
 the cell 
 
 The copper or carbon plate, respectively 
 in a zinc-copper or zinc-carbon couple. 
 
 It must be carefully borne in mind that the 
 conductor attached to the negative element of a 
 voltaic pile is the positive conductor or electrode 
 of the pile, since the current that flows into the 
 plate from the liquid or electrolyte must flow out 
 of the plate where it projects beyond the liquid. 
 
 Element of Current. (See Current, Ele- 
 ment of.) 
 
 Element of Storage Battery. (See Bat- 
 tery, Storage, Element of.) 
 
 Element, Positive That element or 
 
 plate of a voltaic cell from which the current 
 passes into the exciting fluid of the cell. 
 
 The element of a voltaic couple which is 
 acted on by the exciting fluid of the cell. 
 (See Couple, Voltaic.) 
 
 Element, Thermo-Electric One of 
 
 the two metals or substances which form a 
 thermo-electric couple. (See Couple, Ther- 
 mo-Electric.) 
 
 Element, Voltaic One of the two 
 
 metals or substances which form a voltaic 
 couple. (See Couple, Voltaic.) 
 
 Elements, Electrical Classification of 
 
 A classification of the chemical ele- 
 ments into two groups or classes according 
 to whether they appear at the anode or kathode 
 when electrolyzed. 
 
 The chemical elements may be arranged into 
 electro-positive and electro-negative according to 
 whether, during electrolysis, they appear at the 
 negative or positive terminal of the source respec- 
 tively. 
 
 The electro-positive elements or radicals are 
 called kathions, and appear at the kathode or 
 electro-negative terminal. The electro-negative 
 
Ele.J 
 
 213 
 
 [Ene, 
 
 elements are called onions, and appear at the 
 anode, or the electro-positive terminal. (See 
 Ions.) 
 
 The metals generally are electro-positive; oxy. 
 gen, chlorine, iodine, fluorine, etc., are electro- 
 negative. 
 
 Elements, Magnetic, of a Place 
 
 The values of the magnetic intensity, the mag- 
 netic declination or variation, and the mag- 
 netic inclination or dip at any place. 
 
 Elevator Annunciator. (See Annuncia- 
 tor, Elevator?) 
 
 Elevator, Electric An elevator 
 
 operated by electric power. 
 
 Elongated King Core. (See Core, Ring, 
 Elongated?) 
 
 Elongation, Magnetic An increase 
 
 in the length of a bar of iron on its magnetiza- 
 tion. 
 
 This increase in length is thought to greatly 
 strengthen Hughes' theory of magnetism. (See 
 Magnetism, Hughes 1 Theory of.} 
 
 Elongation of Needle. (See Needle, Elon- 
 gation of.) 
 
 Embosser, Telegraphic An appa- 
 ratus for recording a telegraphic message in 
 raised or embossed characters. 
 
 Emptied. A term sometimes applied to a 
 completely discharged secondary or storage 
 cell. 
 
 It is difficult to determine exactly when a stor- 
 age cell is completely emptied or "discharged/' 
 The cell is generally regarded as discharged 
 when its voltage falls below a certain point. 
 
 Endosmose. The unequal mixing of two 
 liquids or gases through an interposed me- 
 dium. 
 
 The presence of an electric current affects the 
 endosmose. (See Currents, Diaphragm.) 
 
 Endosmose, Electric. Differences in the 
 level of liquids capable of mixing through the 
 pores of a diaphragm separating them, pro- 
 duced by the flow of an electric current 
 through the liquid. 
 
 Wiedemann, who investigated these phenom- 
 ena, employed a porous earthenware vessel closed 
 at the bottom and terminated at its upper end by 
 a glass bell provided with a glass tubulure, to 
 
 which was attached a horizontal arm for the es- 
 cape of the liquid raised in the tubulure. The 
 battery terminals were attached to platinum elec- 
 trodes placed respectively inside the porous cell, 
 and in a vessel of water outside of the porous cell, 
 in which the porous cell was placed ; on the passage 
 of the current from the outside of the cell to the 
 inside the liquid rose in the glass tubulure and ran 
 over the horizontal tube into a vessel placed ready 
 to receive it. 
 
 Energizing, Electrically Causing 
 
 electricity to produce any effect in an electro- 
 receptive device. 
 
 An electro-magnet is energized by the passage 
 of a current through its coils. 
 
 Energy. The power of doing work. 
 
 The amount of work done is measured by the 
 product of the farce, by the space through which 
 the force moves. Thus one pound raised verti- 
 cally through ten feet, ten pounds raised through 
 one foot, or five pounds raised through two feet, all 
 represent the same amount of work ; viz., ten foot- 
 pounds. 
 
 If a weight of ten pounds be raised through, a 
 vertical height of one foot, by means of a string 
 passing over a pulley, there will have been ex- 
 pended an amount of energy represented by the 
 work of ten foot-pounds. If the weight be pre- 
 vented in any way from falling, as by securing 
 the string to a fixed support, the weight will have 
 stored in it an amount of energy equal to ten foot- 
 pounds, and if permitted to fall, will be capable 
 of doing an amount of work which, leaving out air 
 resistance and friction, is exactly equal to that 
 originally expended in raising it to the position 
 from which it fell; viz., ten foot-pounds of work. 
 
 Energy, Actual Energy actually 
 
 employed in doing work as distinguished 
 from energy that only possesses the power of 
 doing work, but not actually doing such 
 work. 
 
 This term is also used in the sense of kinetic 
 energy or energy due to motion, but kinetic en- 
 ergy is no more actual than potential energy. 
 
 Energy, Atomic Chemical-potentiai 
 
 energy. (See Energy, Chemical-Potential.} 
 Energy, Chemical-Potential The 
 
 potential energy possessed by the elementary 
 chemical atoms. (See Energy, Potential} 
 If a weight of one pound be raised vertically 
 
Ene.] 
 
 214 
 
 [Eue. 
 
 against the earth's attraction, through a distance 
 of say ten feet, and placed on a suitable support, 
 an amount of energy, equal to the ten foot-pounds 
 of work done on the weight, becomes potential. 
 
 In the same manner if the elementary atoms of 
 carbon and oxygen, when combined so as to form 
 carbonic acid, are raised or separated from one 
 another sufficiently to decompose the carbonic 
 acid and separate the carbon from the oxygen, the 
 amount of potential energy the carbon and oxygen 
 possess, as a result of having been separated, is 
 equal precisely to that originally required to sepa- 
 rate them. In this manner each chemical element 
 possesses a store of chemical -potential energy 
 peculiar to it, and any element with which it may 
 subsequently enter into combination. When ele- 
 ments combine chemically this potential energy is 
 expended in producing heat. 
 
 Energy, Conser?ation of The in- 
 destructibility of energy. 
 
 The total quantity of energy in the universe is 
 unalterable. 
 
 The total energy of the universe is not, how- 
 ever, available for the production of work useful 
 for man. 
 
 When energy disappears in one form it reap- 
 pears in some other form. This is called the con- 
 servation or indestructibility of energy. The com - 
 monest form in which energy reappears is as heat, 
 and in this case some of the heat is lost to the 
 earth by radiation. This degradation or dissipa- 
 tion of energy causes some of the energy of the 
 earth to become non-available to man. 
 
 Energy is therefore available and non-available. 
 (See Entropy.} 
 
 Energy, Correlation of A term 
 
 sometimes applied to the different phases un- 
 der which energy may appear. 
 
 Since energy is indestructible, when it disap- 
 pears in one form or phase, it must reappear in 
 another form or phase. The correlation of the 
 different phases of energy, therefore, necessarily 
 follows from the fact that all energy is indestruc- 
 tible. 
 
 Energy. Degradation of Such a 
 dissipation of energy as to render it non- 
 available to man. (See Energy, Conserva- 
 tion of. Entropy?) 
 
 Energy, Dissipation of The ex- 
 penditure or loss of available energy. 
 
 Energy, Electric 
 
 The powei 
 
 which electricity possesses of doing work. 
 
 In the case of a liquid mass at different levels, 
 the liquid at the higher level possesses a certain 
 amount of potential energy measured by the 
 quantity of the liquid at the higher level, and the 
 excess of its height over that of the lower level; 
 or, by the difference between the two levels. Any 
 difference of level will produce a flow of the liquid 
 from the higher to the lower level, and during 
 the flow of this current of liquid, potential energy 
 will be lost, and a certain amount of work will be 
 done. 
 
 In the case of electricity, the difference of elec- 
 tric level, or potential, between any two points of 
 a conductor, causes an electric current to flo\r 
 between these points toward the lower electric 
 level, during which electric potential energy is 
 lost, and work is accomplished by the electric 
 current. (See Potential, Electric.') 
 
 The amount of this ele^ trie work is measured by 
 the quantity of electricity that flows, multiplied 
 by the difference of potential under which it 
 flows. (See Joule. Volt-Coulomb.) 
 
 Electric energy, however, is generally meas- 
 ured in electric power, or rate of doing electric 
 work. 
 
 Since an ampere is one coulomb-per-second, if 
 we measure the difference of potential in volts, 
 the" product of the amperes by the vo.ts will give 
 the electrical power in volt -amperes, or watts, or 
 units of electric power. C E = Watts. (See 
 Ampere. Volt. Watt.} 
 
 One horse power equals 550 foot-pounds per 
 second. One watt or volt-ampere = 7 J- ff of a 
 horse-power, or one horse-power equals 746 volt 
 amperes or watts, therefore: 
 
 The cttrrent in amperes, multiplied by the dif- 
 ference of potential in volts, divided by 746, 
 equals the rate of doing work in horse-powers. 
 
 Thus, if .7 ampere is required to operate a 
 1 6 candle, no volt, incandescent lamp, it requires 
 4.8 watts per candle. 
 
 One Walt = 44.2394 foot-pounds per minute, i 
 
 One Watt = .737324 foot-pound per second. 
 
 The Heat Activity, or the heat-per- second 
 produced by an electric current, is also propor- 
 tional to -the product C E, or the watts, for the 
 heat is proportional to the square of the current 
 in amperes multiplied by the resistance in ohms, 
 or C 2 R = the watts. (See Calorimeter, Elec- 
 tric.) 
 
Eiie.J 
 
 215 
 
 [Ene. 
 
 By Ohm's Law (See Ohm's Law) 
 
 C = J- (i), or C R = E (2), 
 R 
 
 But the electric power, or the watts, = C E (3). 
 If, now, we substitute the value of E, taken 
 from equation (2) in equation (3) we have 
 CE = C X CR = C 8 R; 
 
 therefore C 8 R = Watts. 
 
 To determine the heating power of a current 
 in small calories, calling H, the amount of heat 
 required to raise I gramme of water through i 
 Cent., and C, the current in amperes 
 
 H = C* R X .24. 
 Or, for any number of seconds, /, 
 
 H = C 2 R/ X .24. 
 (See Calorie.) 
 But from Ohm's Law, 
 
 and the formula for electric power or the watts 
 = C E. (2) By substituting in equation (2) 
 and the value of C, in equation (i), 
 
 C E = EX = = 
 
 That is to say, the electric power in any part of 
 a circuit varies directly as the square of the 
 electromotive force. 
 
 We, therefore, have three expressions for the 
 value of the watt, or the unit of electric power, 
 
 viz. : 
 
 C E = Watts. (i) 
 C*R = Watts. (2) 
 
 = Watts. 
 
 (3) 
 
 (i;) C E = Watts; or the electric power is pro- 
 portional to the product of the quantity of elec- 
 tricity per-second, that passes, in amperes, and 
 the difference of electric potential or /eve/, 
 through which it passes, in volts. 
 
 (2.) C a R = Watts; or the electric power 
 varies directly as the resistance R, when the cur- 
 rent is constant, or as the square of the current, 
 if the resistance is constant. That is to say, if 
 with a given resistance the power of a given 
 current has a certain value, and the current 
 flowing through this same resistance be doubled, 
 the power is four times as great, or is as the 
 square of the current. 
 
 E 
 (3.) =- = Watts, or the electric power is in- 
 
 versely as the resistance R, when the electro- 
 motive force is constant, and is directly propor- 
 tional to the square of the electromotive force if 
 the resistance is constant. , 
 
 A circuit of one ohm resistance will have a 
 power of one watt, when under an electromo- 
 tive force of one volt, since it would then have 
 a current of one ampere flowing through it, and 
 C E = i. If, however, the resistance be halved 
 or becomes .5 ohm, then two amperes pass, or 
 the power equals 2 watts. 
 
 The power varies as the square of the electro- 
 motive force in any part of a circuit, when tht 
 resistance is constant in that part. Thus 2 am- 
 peres, and 2 volts, in a circuit of one ohm 
 resistance, give a power, C E = 2 X 2 =4 watts. 
 If now, R, remaining the same, the electro- 
 motive force be raised to 4 volts, then since E, is 
 doubled, C, or the amperes, is doubled, and C 
 
 E 8 16 
 
 XE = 4X4=i6 watts, or -TT- = = 10. 
 K I 
 
 Energy, Electric, Transmission of 
 
 The transmission of mechanical energy be- 
 tween two distant points connected by an 
 electric conductor, by converting the me- 
 chanical energy into electrical energy at one 
 point, sending the current so produced 
 through the conductor, and reconverting the 
 electrical into mechanical energy at the other 
 point. 
 
 A system for the electric transmission of energy 
 embraces: 
 
 (i.) A conducting circuit between the two 
 stations. 
 
 (2.) An electric source or battery of electric 
 sources or machines at one of the stations, gener- 
 ally in the form f a dynamo-electric machine 
 or machines, for converting mechanical energy 
 into electric energy. 
 
 (3.) Electro-receptive devices, generally electric 
 motors, at the other station for reconverting the 
 electric into mechanical energy. (See Motor, 
 Electric.) 
 
 Energy, Flow of The flow or trans- 
 mission of energy from the medium or die- 
 lectric surrounding a conductor which is 
 directing a current of electricity on to the 
 conductor. (See Law, Poynting's^ 
 
 Energy, Hysteresial, Dissipation of 
 
 The dissipation of energy by means of 
 
Ene.] 
 
 213 
 
 [Ent. 
 
 hysteresis. (See Energy, Dissipation of. 
 Hysteresis?) 
 
 Energy, Kinetic Energy which is 
 
 due to motion as distinguished from potential 
 energy. (See Energy, Potential?) 
 
 Energy-Meter. (See Meter, Energy?) 
 Energy of Position. (See Position, En~ 
 
 er gy f-} 
 
 Energy of Stress. (See Stress, Energy 
 of.) 
 
 Energy, Potential Stored energy. 
 
 Potency, or capability of doing work. 
 
 Energy possessing the power or potency of 
 doing work, but not actually performing such 
 work. 
 
 The capacity for doing work possessed by 
 a body at rest, arising from its position as 
 regards the earth, or from the position of its 
 atoms as regards other atoms, with which it 
 is capable of combining. 
 
 A pound of coal, if raised vertically one foot, 
 possesses, as a mere weight, an amount of energy 
 capable of doing an amount of work equal to oie 
 foot-pound. The atoms of carbon, however, of 
 which it is composed, have been raised or sepa- 
 rated from those of oxygen, or some other elemen- 
 tary substance, and when the coal is burned, or 
 the carbon atoms fall towards the oxygen atoms 
 (*. e., unite with them), the coal gives up the 
 potential energy of its atoms in the form of heat. 
 
 All elementary substances possess in the same 
 way atomic or chemical-potential energy \ or the 
 energy with which they tend to fall together, 
 or enter into combination. This energy varies in 
 amount in different elements and becomes kinetic, 
 as heat, on combination with other elements. (See 
 Energy, Chemical-Potential.) 
 
 Energy, Radiant Energy trans- 
 ferred to or charged on the universal ether. 
 
 Radiant energy is of three forms, viz.: 
 (I.) Obscure radiation, or heat. 
 (2.) Luminous radiation, or light. 
 (3.) Electro-magnetic radiation. 
 
 Energy, Static A term used to ex- 
 press the energy possessed by a body at rest, 
 resulting from its position as regards other 
 bodies, in contradistinction to kinetic energy 
 or the energy possessed by a body whose 
 
 atoms, molecules or masses are in actual 
 motion. 
 
 Potential energy. 
 
 The general term for static energy is potential 
 energy. (See Energy, Potential.) 
 
 Energy, Storage of The change 
 from any form of kinetic energy, to any form 
 of potential energy. (See Energy. Kinetic. 
 Energy, Potential?) 
 
 Engine, Electro-Magnetic A mo- 
 tor whose driving power is electricity. (See 
 Motor. Electric?) 
 
 Engraving, Acoustic Engraving 
 
 by the human voice. 
 
 In the Phonograph, Graphophone and Gramo 
 phone, a diaphragm, set in vibration by th_ 
 speaker's voice, cuts or engraves a record of its 
 to-and-fro movements on a sheet of tin foil, a 
 cylinder of hardened wax, or a specially coated 
 plate of metal or glass. This record is employed 
 in order to reproduce the speech. (See Phonograph.) 
 
 Engraving, Electric - A method 
 for electrically etching or engraving a me- 
 tallic plate by covering it with wax, tracing 
 the design on the wax so as to expose the 
 metal, connecting the metal with the positive 
 terminal of a battery, and placing it in a 
 bath opposite another plate of metal. 
 
 By the action of electrolysis the metal is dis- 
 solved from the exposed portions and deposited 
 on the plate connected with the other terminal 
 of the battery. (See Electrolysis.) 
 
 In this manner the design is obtained in the 
 form of an etching or cutting of the plate. 
 
 By connecting the waxed plate to the negative 
 terminal of the electric source, the metal will be 
 deposited on the exposed portions of the plate, 
 thus producing the design in relief. Unless 
 great care is taken, this latter method is not, 
 however, apt to produce a sufficiently uniform 
 deposit to enable the plate so formed to be used 
 for printing from. 
 
 Electric engraving is sometimes called electro- 
 etching. 
 
 Entropy. In thermo-dynamics the non- 
 available energy in any system. (Clausius 
 and Mayer?) 
 
 In thermo-dynamics, the available energy 
 in any system. (Tait, Thomson and Max 
 well?) 
 
Ent] 
 
 217 
 
 [Eqn. 
 
 As will be noticed, this term is used in entirely 
 different and opposite senses by different scientific 
 men. The latter sense is, perhaps, the one most 
 generally taken. 
 
 Heat energy is available for doing useful exter- 
 nal work only when the source ol heat utilized is 
 hotter than surrounding bodies, that is, when the 
 heat is transferred from a hotter to a colder body. 
 When all bodies have acquired the same temper- 
 ature, they can do no more external work. In 
 the various transformations of energy some of the 
 energy is converted into heat, and this heat is 
 gradually diffused through the universe and thus 
 becomes non-available to man. Therefore, the 
 entropy of our earth is decreasing. 
 
 "Entropy, in thermodynamics," says Max- 
 well, "id a quantity relating to a body such that 
 its increase or diminution implies that heat has 
 entered or left the body. The amount of heat 
 which enters or leaves the body is measured by the 
 product of the increase or diminution of entropy 
 into the temperature at which it takes place." 
 
 Entropy, Electric A term pro- 
 posed by Maxwell for use in thermo-elec- 
 tric phenomena to include the doctrine of 
 entropy in electric science. 
 
 "When an electric current,' 5 says Maxwell, 
 " passes from one metal to another, heat is 
 emitted or absorbed at the junction of the metals. 
 We should, therefore, suppose that the electric 
 entropy has diminished or 'increased when the 
 electricity passes from one metal to the other, the 
 electric entropy being different according to the 
 . nature of the medium in which the electricity is, 
 and being affected by its temperature, stress, 
 strain, etc." 
 
 Equalizer, Feeder An adjustable 
 
 resistance placed in the circuit of a feeder for 
 the purpose of regulating the difference of 
 potential at the junction box. 
 
 Equalizer, Magnetic A device for 
 
 equalizing the otherwise unequal force ex- 
 erted between a magnet pole and its arma- 
 ture at varying distances. 
 
 Since the force of magnetic attraction increases 
 rapidly with the decrease of the distance, it fol- 
 lows that any force sufficiency great to cause the 
 motion of an armature towards a ]>ule, against the 
 force of gravity, will result in t!ie movement of the 
 armature to the pole, and tha-, therefore, no dif- 
 ferentiation as to the final result will be produced 
 
 by a powerful current, and a current just strong 
 enough to start the action. If, however, the 
 armature move against the action of a spring, the 
 latter can be so arranged that the force with 
 which it opposes the motion of the armature in- 
 creases, the nearer the armature is to the pole, 
 and in this way the movement of the armature 
 can be made proportional to the strength of the 
 current energizing the electro-magnet. 
 
 A similar method consists in mechanical devices 
 that cause the armature to work with lessened 
 mechanical advantage as it approaches the po'e. 
 
 Or, thepolar surfaces may be so shaped by cut- 
 ting, or by the addition of suitable projections, 
 as to cause the approach of the armature to be 
 attended by a nearly constant force. 
 
 Equator, Geographical An imag- 
 inary great circle passing around the earth 
 midway between its poles. 
 
 Equator, Magnetic The magnetic 
 
 parallel or circle on the earth's surface v/here 
 a magnetic needle, suspended so as to be free 
 to move in a vertical as well asinahcrizontal 
 plane, remains horizontal. 
 
 An irregular line passing around the earth 
 approximately midway between the earth's 
 magnetic poles. (See Dip or Inclination, 
 Angle of?) 
 
 Equator of Magnet. (See Magnet, Equa- 
 tor of.) 
 
 Equatorial. Pertaining to the equator. 
 
 Equatorially. In the direction of the 
 equator. 
 
 Equipotential Surface of a Conductor 
 through which a Current is Flowing. 
 (See Surface, Equipotential, of a Conductor 
 through which a Current is Flowing?) 
 
 Eqnipotential Surface, or Level Surface 
 Of Escaping Fluid. (See Sttrface, Equipo- 
 tential, or Level Surface of Escaping Fluid.) 
 
 Equipotential Surfaces,Electrostatic 
 
 (See Surfaces, Equipotential, Electro- 
 static?) 
 
 Eqnipotential Surfaces, Magnetic - 
 (See Surfaces, Equipotential, Magnetic?) 
 
 Equivalence, Electro-Chemical, Law of 
 
 The amount of chemical action pro- 
 duced by an electric current, passed through 
 various chemical substances, is proportional 
 to the chemical equivalent of each substance, 
 
Equ.] 
 
 that is, to its atomic weight, divided by its 
 valency. (See Valency.) 
 
 Thus, the atomic weight of oxygen is sixteen 
 times greater than the atomic weight of hydrogen. 
 Oxygen is a diad; that is, has twice the combin- 
 ing power of hydrogen. The passage of a given 
 quantity of electricity will liberate eight times, by 
 weight, as much- oxygen as hydrogen; or, to put 
 it in another way, the passage of a given quan- 
 tity of electricity will liberate two atoms of 
 hydrogen for every atom of oxygen. 
 
 The atomic weight of chlorine is 35.4. The 
 passage of a given amount of electricity will 
 liberate a weight of chlorine 35.4 greater than the 
 weight of hydrogen; or, for every atom of 
 chlorine it will liberate one atom of hydrogen. 
 Here the passage of a given amount of electricity 
 liberates one atom of the monad element hydrogen 
 for every atom of the monad element chlorine. 
 
 The atomic weight of gold is 196.2, and its 
 atomicity or valency is 3. The passage of a 
 
 given amount of electricity will liberate 
 
 10.6.2 _ 
 
 65.4 in ic compounds as great a weight of the 
 triad element gold as of hydrogen; or, will liberate 
 them in the proportion of one atom of gold for 
 every three atoms of hydrogen. 
 
 Generalizing, it appears, therefore, that the 
 passage of the same quantity of electricity through 
 an electrolyte liberates the same number of atoms 
 of a monad element, no matter what their nature 
 may be. It liberates one-half as many of the diad 
 atoms as it does of the monads, and one-third as 
 many of the triad atoms as of the monads. 
 
 Professor Lodge points out, that assuming the 
 truth of the theory that a current of electricity 
 flows in an electrolyte by means of a true electric 
 convection, each atom carrying an electric 
 charge, then it would seem that every monad 
 atom carries an equal charge of electricity, 
 whether it be an atom of hydrogen, chlorine, 
 potassium, silver, or mercury. That each diad 
 element carries twice as much, and that each 
 triad element carries three times as much. 
 
 In general, the number of atoms liberated by a 
 given current of electricity is equal to the num- 
 ber of atoms of hydrogen, divided by the valency 
 of the atom. ' ' The electric charge, ' ' says Lodge, 
 "belonging to each atom of matter, is a simple 
 multiple of a definite quantity of electricity, which 
 quantity is an absolute constant, quite independent 
 of the nature of the particular substance to which 
 the atom belongs." 
 
 218 [Equ- 
 
 The specific charge thus hypothetically given to 
 each atom of matter is believed never to be lost. 
 
 Atoms capable of entering into combination are 
 supposed to be oppositely charged, and chemical 
 affinity is, according to this supposition, believed 
 to be the result of the mutual attractions of opposite 
 electric charges naturally and originally pos- 
 sessed by the atoms of matter. 
 
 Lodge points out the following results which 
 naturally flow from the hypothesis that the atoms 
 of matter possess definite positive and negative 
 charges of electricity, viz.: 
 
 (i.) That the amount of electricity possessed 
 by each monad atom is exceedingly small, being 
 about the hundred thousand millionth part of 
 the ordinary electrostatic unit, or less than the 
 hundred trillionth of a coulomb. 
 
 (2.) The charge being small, the potential is 
 necessarily low. 
 
 Probably something between one and three 
 volts is a high difference of potential between two 
 oppositely charged atoms. 
 
 (3.) The nearness of the attracting atoms, how- 
 ever, can cause a very strong electrostatic attrac- 
 tion between them. 
 
 (4. ) That chemical affinity, or atomic attraction, 
 is caused by the presence of these electric charges. 
 (5.) That the electrical force between two 
 atoms at any distance is ten thousand million 
 billion billion times greater than their gravitation 
 attraction at the same distance, or, the force has 
 an intensity per unit of mass capable of producing 
 an acceleration, nearly one trillion times greater 
 than that of gravity at the earth's surface. 
 
 Equivalent, Chemical The quo- 
 tient obtained by dividing 1 the atomic weight 
 of any elementary substance by its atomicity. 
 (See Weight, Atomic. Atomicity?) 
 
 The ratio between the quantity of an ele- 
 ment and the quantity of hydrogen it is 
 capable of replacing. 
 
 That quantity of an elementary substance 
 that is capable of combining with or replac- 
 ing one atom of hydrogen. 
 
 The chemical equivalent has a different value 
 from the atomic weight whenever the valency 
 is greater than unity. Thus the atomic weight 
 of gold is 196.2, but since in ic compounds one 
 atom of gold is capable of combining with three 
 atoms of hydrogen, the weight of the gold equiva- 
 lent to that of one atom of hydrogen is one-third 
 of 196.2, or 65 4. 
 
Eqn.j 
 
 219 
 
 [Esc. 
 
 Equivalent Conductivity. (See Conduc- 
 tivity, Equivalent?) 
 Equivalent, Electro-Chemical A 
 
 number representing the weight in grammes 
 of an elementary substance liberated during 
 electrolysis by the passage of one coulomb of 
 iiectricity. (See Electrolysis. Coulomb?) 
 
 The chemical equivalent of a substance 
 multiplied by the electro-chemical equivalent 
 of hydrogen. 
 
 The electro- chemical equivalent is, therefore, 
 found by multiplying the electro-chemical equiva- 
 lent of hydrogen by the chemical equivalent of 
 the element. 
 
 It may be determined experimentally that one 
 coulomb of electricity, expended electrolytically, 
 will liberate .0000105 gramme of hydrogen. 
 Therefore a current of one ampere, or one coulomb - 
 fer-second, will liberate .0000105 gramme of hy- 
 drogen per second. The number .0000105 is the 
 electro-chemical equivalent of hydrogen. 
 
 In the same manner the electro-chemical equiva- 
 lents of the other elements are obtained by multi- 
 plying the electro-chemical equivalent of hydrogen 
 by the chemical equivalent of the substance. 
 
 Thus, the chemical equivalent of potassium is 
 39.1, therefore its electro-chemical equivalent is 
 39.1 X .0000105 =.00041055. By multiplying 
 the strength of the current that passes by the 
 electro- chemical equivalent of any substance we 
 obtain the weight of that substance liberated by 
 electrolysis. (See Equivalence, Electro -Chemical, 
 Law of.) 
 
 To determine the electro-chemical equivalent 
 of the other elements see table of chemical equiva- 
 lents on page 212. 
 
 Equivalent, Jonle's The mechan- 
 ical equivalent of heat. (See Heat, Mechan- 
 ical Equivalent of.) 
 
 Equivalent of Heat, Mechanical 
 
 (See Heat, Mechanical Equivalent of.) 
 
 Equivalent Besistance. (See Resistance, 
 Equivalent.) 
 
 Equivolt. A term proposed by J. T. 
 Sprague for the unit of electrical energy, ap- 
 plied especially to chemical decomposition. 
 
 Sprague, defines an equivolt as follows : "The 
 mechanical energy of one volt electromotive force 
 exerted under unit conditions through one equiva- 
 lent of chemical action in grains." 
 8 Vol 1 
 
 This term has not been generally accepted. 
 (See Volt-Coulomb. Joule.) 
 
 Erb's Standard Size of Electrodes. (See 
 
 Electrodes, Erb's Standard Size of.) 
 
 Erg 1 . The unit of work, or the work done 
 when unit force is overcome through unit 
 distance. 
 
 The work accomplished when a body is 
 moved through a distance of one centimetre 
 with the force of one dyne. (See Dyne.) 
 
 A dyne centimetre. 
 
 The work done when a weight of one gramme 
 is raised against gravity through a vertical height 
 of one centimetre is equal to 981 ergs, because 
 the weight of one gramme is i X 981 dynes, or 
 981 ergs. 
 
 The following values for the erg, the unit of 
 work, and the dyne, the unit of force, are taken 
 from Hering: 
 
 I erg = i dyne centimetre. 
 I erg = o.ooooooi joule. 
 981 ergs = i gramme centimetre. 
 1,937.5 ergs = I foot grain. 
 
 13,562,600 ergs .= I foot-pound. 
 
 i dyne = i .0194 milligrammes. 
 I dyne = 0.015731 grain. 
 i dyne = 0.0010194 grammes. 
 I dyne = 0.00003596 ounce avoirdupois. 
 63.568 dynes I grain. 
 981 dynes = i gramme. 
 
 Ergmeter. An apparatus for measuring 
 the work of an electric current in ergs. 
 
 Erg-ten. A term proposed for ten million 
 ergs or i X 10 10 = 10,000,000,000. 
 
 In representing large numbers containing many 
 ciphers the following plan is generally adopted for 
 representing the number of ciphers that are to be 
 added to a given number. Thus, suppose it is 
 desired to represent the number 3,800,000,000. 
 When written 38 X io 8 it indicates that 38 is to 
 be multiplied by lo 8 or 100,000,000, or, in other 
 words, that 38 is to be followed by 8 ciphers, 
 thus 3,800,000,000. 
 
 A negative exponent, as 3 X io~ 8 represents 
 the corresponding decimal thus, .00000003. 
 
 i erg X io 10 , or 10,000,000,000 is called an 
 erg -ten. I X J 6 = an erg -six. These terms 
 are not in general use. Ten meg-ergs is a pref- 
 erable phrase to an erg-ten. (See Meg-erg. ) 
 
 Escape, Electric A term some- 
 
Esc.] 
 
 220 
 
 [Eva. 
 
 times employed to indicate the loss of charge 
 on an insulated conductor. (See Leakage, 
 Electric?) 
 
 Escaping Fluid, Flow-Lines of - 
 (See Flow-Lines of Escaping Fluid?) 
 
 Escaping Fluid, Stream-Lines of - 
 (See Stream-Lines of Escaping Fluid.} 
 
 Essential Resistance. (See Resistance, 
 Essential.} 
 
 Etching, Electro -- A term some- 
 times employed instead of electro-engraving. 
 (See Engraving, Electric?) 
 
 Etching, Galvanic --- Electro-En- 
 graving. (See Engraving, Electric.} 
 
 Ether. The tenuous, highly elastic fluid 
 that is assumed to fill all space, and by vibra- 
 tions or waves in which light and heat are 
 transmitted. 
 
 Although the existence of the ether is assumed 
 in order to explain certain phenomena, its actual 
 existence is very generally credited by scientific 
 men, and, in reality, proofs are not wanting to 
 fairly establish such existence. 
 
 Light and heat are believed to be due to trans- 
 verse vibrations in the ether. Magnetism appears 
 to be due to whirls or whirlpools, and an elec- 
 tric current is believed by some to be due to 
 pulses of waves of ether set in motion by differ- 
 ences in the ether pressures. 
 
 It is not correct to regard the luminiferous 
 ether as possessing no weight, or as being im- 
 ponderable. Maxwell estimates its density as 
 
 1,000,000,000,000,000,000,000 
 
 is very readily moved or set into vibration, its 
 rigidity being estimated at about - 
 
 1,000,000,000 
 
 that of steel. 
 
 According to the speculations of some physi- 
 cists the ether is not discontinuous or granular, 
 but it is similar to what might be regarded as an 
 almost impalpable jelly. 
 
 Ethereal. Pertaining to the universal 
 ether. 
 
 Eudiometer. A voltameter in which sep- 
 arate graduated vessels are provided for the 
 reception and measurement of the gaseous 
 products evolved during electrolysis. (See 
 Voltameter.} 
 
 In all cases electrodes for eudiometers must be 
 used which do not enter into combination with the 
 evolved gaseous products. In the case of oxygen 
 and hydrogen, platinum is generally used. 
 
 A form of eudiometer is shown in Fig. 241. 
 Two separate glass ves- 
 sels, provided at the top 
 with stop cocks, and 
 open at their lower 
 ends, rest in a vessel of 
 water A, over platinum 
 electrodes, connected 
 electrically with binding 
 posts K, K. Both ves- 
 sels are filled with water 
 slightly acidulated with 
 sulphuric acid, and, 
 when connected with 
 a battery of sufficient 
 electromotive force (not 
 less than 1.45 volts), 
 
 electrolysis takes place, Fig. 241. Eudiometer. 
 and hydrogen gas collects in the vessel over 
 the platinum electrode connected with the neg- 
 ative battery terminal, and oxygen in the vessel 
 over the electrode connected with the positive 
 battery terminal. The volume of the hydrogen 
 is approximately twice as great as that of the 
 oxygen. (See Water, Electrolysis of.) 
 
 The proportion is not exactly 2 to i, because, 
 
 (i.) Some of the hydrogen is occluded or ab- 
 sorbed by the platinum electrode. 
 
 (2.) Some of the oxygen is given off as tri- 
 atomic oxygen, or ozone, which is denser and 
 occupies less space than free atomic oxygen. 
 
 Eudiometric. Pertaining to the eudiom- 
 eter. (See Eudiometer?) 
 
 Endiometrically. By means of the eudi- 
 ometer. 
 
 Evaporation. The change from the liquid 
 to the vaporous state. 
 
 Wet clothes exposed to the air are dried by the 
 evaporation of the water. 
 
 Evaporation is greater: 
 
 (I.) The more extended the surfaces exposed. 
 
 (2.) The higher the temperature of the air. 
 
 (3.) The dryer the air, or the smaller the 
 quantity of vapor it contains already. 
 
 (4.) The stronger the wind. 
 
 (5.) The smaller the barometric pressure. 
 
 Evaporation, Electric The forma- 
 
Eva.] 
 
 221 
 
 LExc. 
 
 lion of vapors at the surfaces o f substances 
 by the influence of negative electrification. 
 
 The term electric evaporation was proposed by 
 Crookes for the formation of metallic vapors of 
 such substances as metallic platinum, exposed in 
 high vacua to the effects of negative electrifica- 
 tion. He shows that under these circumstances 
 the surface molecules of the platinum lose their 
 power of cohering and fly off into the space 
 around them, i. e , suffer true evaporation. This 
 action takes place under atmospheric pressures, 
 but, like ordinary evaporation, is greatly facili- 
 tated by the presence of a high vacuum, 
 
 True electric evaporation takes place with 
 liquids as well as with solids. In an experiment 
 with water, the influence of the kind of the elec- 
 trification was clearly shown. A vessel of water 
 
 Fig. 24.2. Electrical Evaporation. 
 
 exposed to the air was first positively electrified, 
 but after an exposure of i| hours only a trifling 
 evaporation was noticeable. The water was 
 then negatively electrified, and at the end of i^ 
 hours had lost y^ 1 ^ part of its weight more than 
 did the positively charged water. 
 
 Professor Crookes experimented with cadmium, 
 and, in order to show that electric evaporation is 
 different from evaporation produced by the agency 
 f heat, tried the following, viz.: A high vacuum 
 U-tube, shaped as shown in Fig 242, was pro- 
 
 Fig 243. Electrical Evaporation. 
 
 vided with platinum poles sealed in the glass at 
 A and B. Two pieces of cadmium, C and D, 
 were placed in the tube in the position shown, 
 and the "hb^ uniformly heated by means of a gas- 
 burner :jid air oath, and maintained at a constant 
 temperacure. i'he current was then passed for 
 ibout an hour, B, being made the negative pole. 
 
 No metal was deposited in the neighborhood oi 
 the positive pole, the portions of the tube sur- 
 rounding the positive pole being quite clean, 
 while the corresponding portions of the other limb 
 of the tube were thickly coated, as shown by the 
 shading in the drawing. 
 
 In another experiment, in which the tempera- 
 ture was kept lower than in the preceding, viz., 
 just below the melting point of the cadmium,, 
 after the current had passed for an hour, the limb 
 of the tube through which the current had passed 
 had received a thick coating, while the other was 
 nearly free from coating, as shown in Fig. 243. 
 Here the increase in the amplitude of the mole- 
 cular oscillation under the influence of the elec- 
 tricity is manifest. 
 
 Evaporation, Electrification by - 
 
 An increase in the difference of potential ex- 
 isting in a mass of vapor attending its sudden 
 condensation. 
 
 The free electricity of the atmosphere is be- 
 lieved by some to be due to the condensation of 
 the vapor of the air that results in rain, hail, 
 clouds, etc. It is probable, however, that the 
 true effect of condensation is mainly limited to 
 the increase of a feeble electrification already 
 possessed by the air or its contained vapor. The 
 small difference of potential of the exceedingly 
 small drops of water in clouds is enormously in- 
 creased by the union or coalescing of many 
 thousands of such drops into a single rain drop. 
 (See Electricity, Atmospheric.] 
 
 Exchange, Telephonic, System of 
 
 A combination of circuits, switches and 
 other devices, by means of which any one of 
 a number of subscribers connected with a 
 telephonic circuit, or a neighboring telephonic 
 circuit or circuits, may be placed in electrical 
 communication with any other subscriber 
 connected with such circuit or circuits. 
 
 A telephone exchange consists essentially of a 
 multiple switchboard, or a number of multiple 
 switchboards, furnished with spring-jacks, an- 
 nunciator drops, and suitable connecting cords. A 
 call bell, or bells, is also provided. The annun- 
 ciator drops are often omitted. (See Board., 
 Multiple Switch.) 
 
 Excitability. Electric, of Nerve or Hi ns- 
 cnlar Fibre The effect produced by an 
 electric current in stimulating the nerve of 
 
Exc.] 
 
 222 
 
 [Exh. 
 
 living animal, or in producing an involuntary 
 contraction of a muscle. 
 
 Du Bois-Reymond has shown that these effects 
 depend : 
 
 (l.) On the strength of the current employed. 
 The excitability occurs only when the current 
 begins to flow, and when it ceases flowing; or, 
 when the electrodes first touch the nerves, and 
 when they are separated from it. Subsequent 
 investigations have shown that this is true only 
 for the frog's nerves, and is true for the human 
 nerves only in the case of moderate currents, 
 strong currents producing tetanus. 
 
 (2.) On the rapidity with which the current 
 used reaches its maximum value, that is, on the 
 rapidity of change of current density. (See 
 Current Density.') 
 
 Excitability, Electro-Nervous 
 
 In electro-therapeutics the electric excitation 
 of a nerve. 
 Excitability, Electrotonic The 
 
 actual excitability of a nerve when in the 
 electrotonic condition. (See Electrotonus. 
 Anelectrotonus. Kathelectrotonus.) 
 
 Excitability, Faradic Muscular or 
 
 nervous excitability following the employment 
 of the rapidly intermittent currents produced 
 by induction coils. (See Coil, Induction.) 
 
 Faradic excitability is different from galvanic 
 excitability, or that produced by means of a con- 
 tinuous voltaic current. (See Excitability, Gal- 
 vanic. ) 
 
 Excitability, Galvanic A term 
 
 sometimes employed for electric excitability 
 of nerve or muscular fibre. (See Excitability, 
 Electric, of Nerve or Muscular Fibre?) 
 
 Excitation, Compensated, of Alternator. 
 (See Alternator, Compensated Excitation 
 
 *f) 
 
 Excitation, Direct The excitement 
 
 of a muscle by placing an electrode on the 
 muscle itself. 
 
 Excitation, Electro-Muscular - 
 In electro-therapeutics the galvanic or faradic 
 excitation of the muscle, or its excitation by 
 the continuous currents of a voltaic battery, or 
 the alternating currents of an induction coil. 
 
 Excitation, Faradic - Excitation of 
 muscle or nerve fibre by means of rapidly 
 
 alternating currents of electricity. (See 
 Excitability, Faradic?) 
 
 Excitation, Indirect The excite- 
 ment of a muscle from its nerve. 
 
 Exciter of Field. (See Field, Exciter of.) 
 
 Exciting Liquid of Voltaic Cell. (See 
 Cell, Voltaic, Pr -imary. Exciting Liquid oj '.) 
 
 Execution, Electric Causing the 
 
 death of a criminal, in cases of capital pun- 
 ishment, by means of the electric current. 
 
 Electric execution has been adopted by the 
 State of New York, in accordance with the 
 following law : 
 
 "The Court shall sentence the prisoner to 
 death within a certain week, naming no day or 
 hour, and not more than eight nor Jess than five 
 weeks from the day of sentence. The execution 
 must take place in the State prison to which con- 
 victed felons are sent by the Court, and the execu- 
 tioner must be the agent and warden of the prison. 
 
 "No newspaper may print any details of the 
 execution, which is to be inflicted by electricity. 
 A current of electricity is to. be caused to pass 
 through the body of the condemned of sufficient 
 intensity to kill him, and the application is to be 
 continued until he is dead." 
 
 Exhaustion, Electric Physiological 
 effects resembling those produced by sun- 
 stroke, resulting from prolonged exposure 
 to the radiation of unsually large voltaic arcs. 
 (See Sun-Stroke, Electric) 
 
 Exhaustion of Primary Voltaic Cell. 
 (See Cell, Voltaic, Primary, Exhaustion of.) 
 
 Exhaustion of Secondary Voltaic Cell. 
 
 (See Cell, Voltaic, Secondary, Exhaustion of.) 
 
 Exhaustion of Voltaic Cell. (See Cell, 
 Voltaic, Exhaustion of.) 
 
 Exhaustion, Reaction of - A con- 
 dition of nervous and muscular irritability to 
 electric excitation when a certain reaction, 
 produced by a given current strength, cannot 
 be reproduced without an increase of current 
 strength. 
 
 The reaction of exhaustion may be regarded as 
 a special variety of the reaction of degeneration. 
 (See Degeneration, Reaction of.) 
 
 The reaction of degeneration embraces the 
 following modifications of irritability, viz. : 
 
Exp.J 
 
 223 
 
 [Eye. 
 
 (i.) Disappearance or diminution of nervous 
 irritability to both galvanic and faradic currents. 
 
 (2.) Disappearance of far:.dic and increase of 
 galvanic irritability of muscles, generally associ- 
 ated with an increase of mechanical irritability. 
 
 (3 ) Disappearance of faradic and increase of 
 galvanic muscular irritability associated generally 
 with increased mechanical irritability. 
 
 (4.) Tardy, delayed contraction of muscles in- 
 stead of quick reaction of normal muscle. 
 
 (5.) Marked modifications of normal sequence 
 i.f contraction. Liebig 6 Rohe. 
 
 Expanding Magnetic Whirl. (See 
 
 Whirl, Expanding Magnetic?) 
 
 Exploder, Electric Mine 
 
 A small 
 
 Expansion, Co-efflcient of 
 
 The 
 
 fractional increase in the dimensions of a bar 
 or rod when heated from 32 degrees to 33 
 degrees F. or from o degree to I degree C. 
 
 The fractional increase in the length of the bar 
 is called the Co-efficient of Linear Expansion. 
 
 The fractional increase in the surface is called 
 the Co-efficient of Surface Expansion. 
 
 The fractional increase in the volume is called 
 the Co-efficient of Cubic Expansion. 
 
 Expansion, Electric - The increase 
 in volume produced in a body on giving such 
 body an electric charge. 
 
 A Leyden jar increases in volume when a 
 charge is imparted to it. This result is due to an 
 expansion of the glass due to the electric charge. 
 According to Quincke, some substances, such as 
 resinous or oily bodies, manifest a contraction of 
 volume on the reception of an electric charge. 
 
 Expansion Joint. (See Joint, Expan- 
 sion?) 
 
 Expansion, Linear, Co-efflcient of 
 
 A number expressing the fractional increase in 
 length of a bar for a given increment of heat. 
 The co-efficients of expansion of a few sub- 
 stances are given in the following table: 
 Temp. 
 
 Aluminium 16 to 100 degrees C. .0.0000235 
 
 loo " ..0.0000188 
 100 
 
 100 
 
 100 
 100 
 
 TOO 
 100 
 
 100 
 
 100 
 
 Brass o 
 
 Copper o 
 
 German silver. . o 
 
 Glass o 
 
 Iron. ". . 13 
 
 T .ea<l . . ' o 
 
 Platinum o 
 
 Silver o 
 
 Zinc. . . , o 
 
 . .0.0000167 
 . .0.0000184 
 . .0.0000071 
 . .0.0000123 
 . .0.0000280 
 . 0.0000089 
 . .0.0000194 
 . .0.0000230 
 
 (Anthony &> Brackett.} 
 
 magneto-electric machine used to produce the 
 currents of high electromotive force employed 
 in the direct firing of blasts. 
 
 Exploder, Electro-Magnetic A 
 
 small magneto-electric machine used to pro- 
 duce the currents of high electromotive force 
 employed in the direct firing of blasts. 
 
 Explorer, Electric An apparatus 
 
 operated by means of induced currents, and 
 employed for the purpose of locating bullets 
 or other foreign metallic substances in the 
 human body. (See Balance, Induction, 
 Hughes'.) 
 
 Explorer, Magnetic - A small, flat 
 coil of insulated wire, used, in connection with 
 the circuit of a telephone, to determine the 
 position and extent of the magnetic leakage 
 of a dynamo-electric machine or other similar 
 apparatus. (See Magnetophone.) 
 
 Explosive Distance. (See Distance, Ex- 
 plosive.) 
 
 Extension Call-Bell (See Bell, Exten- 
 sion Call.) 
 
 External Circuit. (See Circuit, Exter- 
 nal.) 
 
 External Secondary Resistance. (See 
 Resistance, External Secondary ) 
 
 Extra Currents. (See Currents, Extra.} 
 
 Extraordinary Resistance. (See Resist- 
 ance, Extraordinary?) 
 
 Extra-Polar Region. (See Region, Ex- 
 tra-Polar?) 
 
 Eye, Electro-Magnetic A term pro- 
 posed for a certain form of spark-micrometer 
 employed by Hertz in his experiment on elec- 
 tro-magnetic radiation. 
 
 This apparatus has received the above name 
 because it enables the observer to see or localize 
 an electromagnetic disturbance. 
 
 The particular spark-micrometer that has re- 
 ceived the name of the electro-magnetic eye had 
 the form of a circle 35 centimetres in radius, and 
 was formed of a copper wire 2 millimetres in di- 
 ameter. Like all spark-micrometer circuits, it 
 had its terminals separated by a small air-space. 
 
 Eye, Selenium An artificial eye in 
 
Fac.] 
 
 224 
 
 [Far. 
 
 which a selenium resistance takes the place 
 of the retina and two slides the place of the 
 eyelids. 
 
 The selenium resistance is placed in the circuit 
 of a battery and a galvanometer. When the 
 slides L, L, Fig. 244, are shut, the galvanometer 
 deflection is less than when they are open. 
 
 The opening of the aperture between the slides 
 L, L, may be automatically accomplished by the 
 action of the light itself, by moving them by an 
 electro-magnet placed in the circuit of a local bat- 
 tery, and a selenium resistance may be so arranged 
 that when light falls on it the slides L, L, are 
 moved together, and when the amount of such 
 light is small they are moved apart, by the action 
 
 of a spring, In this way there is obtained a 
 device roughly resembling the dilatation or con- 
 
 .B 
 
 Fig. 244.. Selenium Eye, 
 
 traction of the pupil of the eye from the action of 
 light on the iris. (See Photometer, Selenium.) 
 
 Fac-Simile Telegraphy, or Panteleg- 
 raphy. (See Telegraphy, Fac-Simile.} 
 
 Fahrenheit's Thermometer Scale. (See 
 Scale, Thermometer, Fahrenheit's?) 
 
 Fall of Potential. (See Potential, Fall 
 of.) 
 
 False Magnetic Pole (See Pole, 
 
 Magnetic, False.) 
 
 False Resistance. (See Resistance, 
 False.) 
 
 False Zero. (See Zero, False.) 
 
 Fan Guard. (See Guard, Fan.) 
 
 Farad. The practical unit of electric 
 capacity. 
 
 Such a capacity of a conductor or condenser 
 that one coulomb of electricity is required to 
 produce in the conductor or condenser a 
 difference of potential of one volt. 
 
 As in gases, a quart vessel will hold a quart of 
 gas under unit pressure of one atmosphere, so, in 
 electricity, a conductor or condenser, whose capa- 
 city is one farad, will hold a quantity of electricity 
 equal to one coulomb when under an electromotive 
 force of one volt. 
 
 It may cause some perplexity to the student to 
 understand why there should be in electricity one 
 unit of capacity to represent the size of the vessel 
 or conductor, and another to represent the 
 amount or quantity of electricity required to fill 
 
 such vessel. But, like a gas, electricity acts, in 
 effect, as if it were very compressible, so that the 
 quantity required to fill any condenser will de- 
 
 N "' 
 
 Fig 24. J. Elevation of Standardized Condenser. 
 
 pend on the electromotive force under which it is 
 put into the conductor or condenser. 
 
 For purposes of measurement, capacities of 
 conductors are compared with those of condensers 
 
 Fig, 246. Plan of Standardized Condenser. 
 
 whose capacities are known in microfarads, or 
 fractions thereof. The microfarad, or the 
 
 of a farad, is used because of the very 
 
 1,000,000 
 
 great size of a farad. 
 
Far,] 
 
 225 
 
 [Fau. 
 
 Fig. 245 shows an elevation, and Fig. 246 a 
 plan of the form often given to a standardized 
 condenser or microfarad. The condenser is 
 charged by connecting the terminals of the elec- 
 tric source to the binding posts N and N. It is 
 discharged by means of the plug key P', that 
 connects the brass pieces A and B, when pushed 
 firmly into the conical space between them. 
 
 The condenser is made by placing sheets of tin 
 foil between sheets of oiled silk or mica in the 
 box and connecting the alternate sheets to one of 
 (he brass pieces B, and the other set to the brass 
 piece A, as will be better understood from an 
 inspection of Fig. 247. 
 
 Fig. 247 Method of Construction of a Condenser. 
 
 Condensers are generally made of the capacity 
 of the ^ of a microfarad. Sometimes, however, 
 they are made so that either all or part of the 
 condenser may be employed, by the insertion of 
 the different plug keys. 
 
 The form of condenser shown in Fig. 248 is 
 
 Fig. 24.8. Standard Condenser 
 
 capable of ready division into five separate val- 
 ues, viz.: .05, .05, .2, .2 and .5 microfarad. 
 
 Farad, Micro The millionth part 
 
 of a farad. (See Farad.} 
 
 Faraday Effect. (See Effect, Faraday.} 
 Faraday's Cube. 'See Cube, Faraday's) 
 
 Faraday's Dark Space. (See Space, 
 Dark, Faraday's) 
 
 Faraday's Net. (See Net. Faraday's) 
 
 Faradic Apparatus, Magneto-Electric 
 
 (See Apparatus, Faradic . Mag- 
 neto-Electric) 
 
 Faradic Brush. (See Brush, Faradic) 
 
 Faradic Current. (See Current Fara- 
 dic) 
 
 Faradic Excitation. (See Excitation.. 
 Faradic) 
 
 Faradic Induction Apparatus. (See 
 Apparatus, Faradic Induction) 
 
 Faradic Irritability. (See Irritability, 
 Faradic) 
 
 Faradic Machine. (See Machine, Fara- 
 dic) 
 
 Faradization. In electro-therapeutics, the 
 effects produced on the nerves or muscles 
 by the use of a faradic current, in order to 
 distinguish such effects from galvanization 
 or those produced by a voltaic current. (See 
 Galvanization) 
 
 Faradization, General A method 
 
 of applying the faradic current similar to 
 that employed in general galvanization. 
 (See Galvanization, General) 
 
 Faradization, Local A method of 
 
 applying the faradic current in general simi- 
 lar to that employed in local galvanization. 
 (See Galvanization, Local) 
 
 Fault. Any failure in the proper working 
 of a circuit due to ground contacts, cross- 
 contacts or disconnections. (See Contacts. 
 Cross) 
 
 Faults are of three kinds, viz. : 
 
 (i.) Disconnections. (See Disconnection) 
 
 (2) Earths. (See Earth) 
 
 (3.) Contacts. (See Contacts) 
 
 Various methods are employed for detecting 
 and localizing faults, for the explanation of 
 which reference should be had to standard elec- 
 trical works on testing or measurements. 
 
 Fault, Ironwork, of Dynamo A 
 
 ground or connection between the current of 
 a dynamo and any part of its ironwork. 
 
Fau.l 
 
 226 
 
 [Fie. 
 
 If the dynamo is in good connection with the 
 ground, as is frequently the case in marine plants, 
 this fault is the same as a ground. 
 
 Faults, Localization of Determin- 
 ing the position of a fault on a telegraph line 
 or cable by calculations based on the fall in 
 the potential of the line measured at different 
 points, or by loss of charge, etc. 
 
 For details, see standard works on electrical 
 measurements. 
 
 Feed, Clockwork, for Arc Lamps 
 
 An arrangement of clockwork for obtaining 
 a uniform feed motion of one or both elec- 
 trodes of an arc lamp. 
 
 The clockwork is automatically thrown into or 
 out of action by an electro-magnet, usually placed 
 in a shunt circuit around the carbons. 
 
 Feed, To To supply with an electric 
 
 current, as by a dynamo or other source. 
 
 Feeder. One of the conducting wires or 
 channels through which the current is dis- 
 tributed to the main conductors. 
 
 Feeder, Standard or Main The 
 
 main feeder to which the standard pressure 
 indicator is connected, and whose pressure 
 controls the pressure at the ends of all the 
 other feeders. 
 
 The term pressure in the above definition is 
 used in the sense of electromotive force or differ- 
 ence of potential. 
 
 Feeder-Wires. (See Wires, Feeder) 
 Feeders. In a system of distribution by 
 constant potential, as in incandescent elec- 
 tric lighting, the conducting wires extend- 
 ing between the bus-wires or bars, and the 
 junction boxes. 
 
 A feeder differs from a main in that a main 
 consists of a conductor that may be tapped at any 
 point to supply a customer, while a feeder leads 
 direct from the dynamo or other source to a main 
 and is not tapped at any point. 
 
 Feeders, Negative The feeders 
 
 that are connected with the negative terminal 
 of the dynamo. (See Feeders.) 
 
 Feeders, Positive The feeders that 
 
 are connected with the positive terminal of 
 the dynamo. (See Feeders.) 
 
 Feeding Device of Electric Arc Lamp. 
 
 (See Device, Feeding, of an Arc Lamp. 
 Feed, Clockwork, for Arc-Lamps^) 
 Feeding-Wire. (See Wire, Feeding^ 
 
 Feet, Ampe"re The product of the 
 
 current in amperes by the distance in feet 
 through which that current passes. 
 
 It has been suggested that the term ampere- 
 feet should be employed in expressing the strength 
 of electro-magnetism in the field magnets of 
 dynamo-electro machines or other similar ap- 
 paratus. 
 
 Ferranti Effect. (See Effect, Ferranti^ 
 
 Ferro-Magnetic Substance. (See Sub- 
 stance, Ferro-Magnetic?) 
 
 Fibre, Quartz A fibre suitable for 
 
 suspending galvanometer needles, etc., made 
 of quartz. 
 
 The quartz fibre is obtained by fusing quartz and 
 drawing out the fused material as a fine thread, 
 in a manner similar to the production of glass 
 fibres. Quartz fibres possess marked advantage 
 over silk fibres, in that they are 5.4 times stronger 
 for equal diameters, and especially, in that they 
 return to the zero point, after very considerable 
 deflections. 
 
 Quartz fibres are readily obtained by fusing 
 quartz pebbles together in the voltaic arc, and 
 drawing them apart with a rapid, but steady, uni- 
 form motion. 
 
 Fibre Suspension. (See Suspension, 
 Fibre?) 
 
 Fibre, Vulcanized A variety of in- 
 sulating material suitable for purposes not 
 requiring the highest insulation. 
 
 Vulcanized fibre is, however, seriously affected 
 by long exposure to moisture. 
 
 Fibrone. An insulating substance. 
 
 Field, Air That portion of a mag- 
 netic field in which the lines of force pass 
 through air only. 
 
 Field, Alternating An electrostatic 
 
 or magnetic field the positive direction of the 
 lines of force in which is alternately reversed 
 or changed in direction. 
 
 Field, Alternating Electrostatic 
 An electrostatic field, the potential of which 
 is rapidly alternating. 
 
Fie.] 
 
 227 
 
 [Fie. 
 
 An alternating electrostatic field is, according 
 to Tesla's experiments, produced in the neighbor- 
 hood of the terminals of the secondary of an in- 
 duction coil, through whose primary, alternations 
 of high frequency are passing. 
 
 Field, Alternating Magnetic. A mag- 
 netic field the direction of whose lines of 
 force is alternately reversed. 
 
 Field, Density of The number of 
 
 lines of force that pass through any field, per 
 unit of area of cross-section. 
 
 Field, Electric A term sometimes 
 
 used in place of an electrostatic field. (See 
 Field, Electrostatic^) 
 
 Field, Electro-Magnetic The space 
 
 traversed by the lines of magnetic force pro- 
 duced by an electro-magnet. (See Field, 
 Magnetic?) 
 
 Field, Electrostatic The region of 
 
 electrostatic influence surrounding a charged 
 body. 
 
 Electrostatic attractions or repulsions take 
 place along certain lines called lines of electro- 
 static force. These lines of force produce a field 
 called an electrostatic field. Electric level or 
 potential is measured along these lines, just as 
 gravitation levels are measured with a plumb line 
 along the lines of gravitation force. (See Poten- 
 tial, Electric.') 
 
 Work is done when a body is moved along the 
 lines of electrostatic force in a direction from an 
 oppositely charged body, or towards a similarly 
 charged body, just as work is done against 
 gravity when a body is moved along the lines of 
 gravitation force, away from the earth's centre, 
 or vertically upwards. 
 
 Field, Exciter of In a separately 
 
 excited dynamo-electric machine, the dyna- 
 mo-electric machine, voltaic battery, or other 
 electric source employed to produce the field 
 of the field magnets. (See Machine, Dyna- 
 mo-Electric,} 
 
 Field, Intensity of The strength 
 
 of a field as measured by the number of lines 
 of force that pass through it per unit of area 
 of cross-section. (See Field, Electrostatic. 
 Field, Magnetic^ 
 
 Field, Magnetic The region of 
 
 magnetic influence surrounding the poles of a 
 magnet. 
 
 A space or region traversed by lines of 
 magnetic force. 
 
 A place where a magnetic needle, if free 
 to move, will take up a definite position, under 
 the influence of the lines of magnetic force. 
 
 Unit strength of magnetic field is the field 
 which would be produced by a magnetic pole of 
 unit strength at unit distance. 
 
 Magnetic attractions and repulsions are assumed 
 to take place along certain lines called lines of 
 magnetic force. The directions of these lines in 
 any plane of a magnetic field may be shown by 
 sprinkling iron filings over a sheet of paper held 
 in a horizontal position to a magnet pole inclined 
 
 Fig. 249. Magnetic Field. 
 
 to the paper in the desired plane and then gently 
 tapping the paper. 
 
 The groupings of iron filings so obtained are 
 sometimes called magnetic figures . 
 
 The directions of the lines of force thus shown 
 will appear from an inspection of Fig. 249, taken 
 in a plane joining the two poles of a straight bar 
 magnet, and Fig. 250, taken in a plane at right 
 angles to the north pole of a straight bar magnet. 
 
 In Fig. 249, the repulsion of the lines of force 
 at either pole is shown by the radiation of the 
 chains ot magnetized iron particles. The mutual 
 attraction of unlike polarities is shown by the 
 curved lines. 
 
 In Fig. 250, the repulsion of the similarly mag- 
 netized chains is clearly shown. 
 
 Lines of magnetic force are assumed to pass 
 out from the north, pole and back again into the 
 magnet at its south pole. This assumed direction 
 
Fie.] 
 
 228 
 
 [Fie. 
 
 is called the direction of the lines of magnetic 
 force. 
 
 Faraday expressed his conception of lines of 
 magnetic force as follows: 
 
 "Every line offeree must therefore be consid- 
 ered as a closed circuit, passing, in some part of 
 its course, through a magnet and having an equal 
 amount of force in every part of its course. There 
 
 Fig, 230. Magnetic Field. 
 
 exist lines of force within the magnet of the same 
 nature as those without. What is more, they are 
 exactly equal in amount to those without. They 
 have a relation in direction to those without and 
 are, in fact, continuations of them." 
 
 When a conductor, such as a wire through 
 which a powerful current of electricity is flowing, 
 is dipped in a mass of iron filings, a chain of iron 
 filings is formed, the north end of which is urged 
 around the conductor in one direction and the 
 south end in the opposite direction, so that the 
 movable chain of filings surrounis or grips the 
 conductor in concentric rings or circles. 
 
 The density of a magnetic field 'is directly pro- 
 portional to the number of lines of force per unit 
 of area of cross-section. 
 
 A single line of fo*ce, or a unit line of force, is 
 such an intensity of field as exists in each square 
 centimetre of cross-section of a unit magnetic 
 field. 
 
 A magnetic field is uniform, or possesses ttni- 
 form intensity, when it possesses the same num- 
 ber of lines of force per squire centimetre of area 
 of cross-secti >n. 
 
 Field, Magnetic, Alternating - The 
 magnetic field produced by means of an 
 alternating current. 
 
 Field, Magnetic, Dissymmetrical 
 
 A field whose lines of force are not symmet- 
 rically distributed in adjacent halves. 
 
 Field, Magnetic, Expanding of- 
 
 An increase in the length of the lines of mag- 
 netic force in any field, or an increase in the 
 length of their magnetic circuit. 
 
 Field, Magnetic, of an Electric Current 
 The magnetic field surrounding a cir- 
 
 Fig. 231. Field of Current. 
 
 cuit through which an electric current is flow- 
 ing. 
 
 An electric current produces a magnetic field. 
 This was discovered by Oersted -f 
 
 in 1819, and may be shown by 
 sprinkling iron filings on a sheet 
 of paper, placed on the wire 
 conductor conve) ing the cur- 
 rent, at right angles to the direc- 
 tion in which the current is pass- 
 ing. Here the lines of force 
 appear as concentric circles, ex- 
 tending around the conductor, 
 as shown in Fig. 251. Their 
 direction, as regards the length 
 of the conductor, is shown in 
 Fig. 252. The electric current 
 sets up these magnetic whirls 
 around the conductor on its 
 passage through it. 
 
 The direction of the lines of 
 
 ' J Fig. 2 5 2. Direc- 
 
 magnetic. force produced by an tion of Lines of 
 
 electric current, and hence its force, 
 magnetic polarity^ depends on the direction in 
 which the electric current flows. This direction 
 
Fie.] 
 
 229 
 
 [Fie, 
 
 may be remembered as follows: If the current 
 flows towards the observer, the directions of the 
 lines of magnetic force is opposite to that of the 
 hands of a watch, as shown in Fig. 253. 
 
 Fig 233. Direction of Lines of Force. 
 
 It is from the direction of the lines of magnetic 
 force that the polarity of a helix carrying a cur- 
 rent is deduced. (See Solenoid, Magnetic. Mag- 
 net, Electro ) 
 
 A magnetic field possesses the following prop- 
 erties, viz.: 
 
 (i.) All magnetizable bodies are magnetized 
 when brought into a magnetic field. (See Indue, 
 tion, Magnetic.") 
 
 (2.) Conductors moved through a magnetic 
 field so as to cut its lines of force have differences 
 of potential generated in them at different points, 
 and if these points be connected by a conductor, 
 an electric current is produced. (See Induction, 
 Electro-Magnetic. ) 
 
 Field, Magnetic, Pulsatory A field, 
 
 the strength of which pulsates in such manner 
 as to produce oscillatory currents by induc- 
 tion. 
 
 Field, Magnetic, Reversing That 
 
 portion of the field of a dynamo-electric ma- 
 chine, produced by the field-magnet coils, in 
 which the currents flowing in the armature 
 coils are stopped or reversed after the coil has 
 passed its theoretical position of neutrality. 
 
 Sparkless commutation is obtained by placing 
 the brushes on the commutator so as to corre- 
 spond with the reversing field. 
 
 Field, Magnetic, Shifting A term 
 
 proposed by Professor Elihu Thomson to ex- 
 press a field of magnetic lines of changing 
 position with respect to the axis of the pole 
 from which they emanate. 
 
 A shifting magnetic field is especially a phe- 
 nomenon of a rapidly alternating magnetic field 
 
 occurring in a substance like hardened steel in 
 which the coercive force is lairly nigh. It, for 
 example, a single magnet pole of an electro- 
 magnet, whose coils are traversed by a rapidly 
 alternating current of electricity , 15 placed near one 
 end of a steel file, the changing polarity developed 
 thereby moves or shifts Irom the point directly 
 over the pole towards the distant end. The 
 presence of this shifting field can be shown by the 
 rotation of discs of copper suitably inclined to ihe 
 end of the file. In a similar manner a prismatic 
 mass of steel, placed with one of its flat sides 
 on the pole of a rapidly alternating magnetic 
 field, will have a magnetic field developed in it, 
 which will move or shift from the flat base 
 towards the upper edge. Movable masses of good 
 conducting metal, such as copper, will be set in 
 rotation in a direction such as would be caused 
 by an escape of gas therefrom. 
 . The shifting magnetic field travels from the 
 upper portions of the prism just as a stream of 
 escaping gaseous substance would. 
 
 Field, Magnetic, Spreading-Out A 
 
 term sometimes used to represent an expand- 
 ing magnetic field. (See Field, Magnetic, 
 Expanding of.) 
 
 Field, Magnetic, Stray That por- 
 tion of the field of a dynamo-electric machine 
 which is not utilized for the development of 
 differences of potential in the armature, be- 
 cause its lines of force do not pass through 
 the armature. 
 
 Field, Magnetic, Strength of The 
 dynamic force acting on a free magnetic pole, 
 placed in a magnetic field. 
 
 If a free magnetic pole could be placed in a 
 magnetic field, it would begin to move towards 
 the opposite pole of the field, under its magnetic 
 attraction, just as an unsupported body, free to 
 move, would begin to fall towards the earth. 
 The strength of a magnetic field corresponds to 
 the acceleration of the force of gravity in the 
 case of a falling body. The strength of the mag- 
 netic pole corresponds to the mass of the falling 
 body. The force impressed in the case of the 
 magnetic field is equal to the strength of the pole 
 multiplied by the strength of the field. 
 
 Field, Magnetic, Symmetrical A 
 
 field whose lines of force are symmetrically 
 distributed in adjacent halves. 
 
Fie.] 
 
 230 
 
 [Fil. 
 
 Field, Magnetic, Uniform A field 
 
 traversed by the same number of lines of 
 magnetic force in all unit portions of area of 
 cross-section. (See Field, Magnetic?) 
 
 Field, Magnetic, Waste A term 
 
 sometimes employed for stray field. (See 
 Field, Magnetic, Stray.) 
 
 Field, Rotating-Current A mag- 
 netic field produced by means of a rotating 
 current. (See Current, Rotating?) 
 
 Field, Uniform Density of A uni- 
 form density in all equal areas of cross- 
 section of field. 
 
 Field, Yortex-Ring The field of 
 
 influence possessed by a vortex-ring. 
 
 Professor Dolbear points out the fact that the 
 direction of the rotation of a fluid constituting a 
 vortex-ring resembles the magnet flux in a mag. 
 netic field, and shows, from the action of such rings 
 on one another, that they possess a true field, or 
 atmosphere of influence outside their actual 
 bodies. He infers that such rings possess true 
 polarity, since the motions producing them have 
 different directions on opposite sides or ends. 
 
 Figure of Merit of Galvanometer. (See 
 Galvanometer, Figure of Merit of.) 
 
 Figures, Breath Faint figures of 
 
 condensed vapor produced by electrifying a 
 coin, placing it momentarily on the surface of 
 a sheet of clean, dry glass, and then breath- 
 ing gently on the spot where the coin was 
 placed. 
 
 The moisture collects on the electrified portions 
 of the plate and torms a fairly distinct image ol 
 the coin. 
 
 Figures, Electric Figures of various 
 
 shapes produced on electrified surfaces by the 
 arrangement of dust particles or vapor 
 vesicles under the influence of electric charges. 
 
 Electric figures are of two varieties, viz. : 
 
 (i.) Dust figures. 
 
 (2.) Breath figures. 
 
 Figures, Lichtenberg's Dust 
 
 Figures produced by writing on a sheet of shel- 
 lac with the knob of a charged Leyden jar and 
 then sprinkling over the sheet dried and 
 powdered sulphur and red lead, which have 
 
 been previously mixed together, and are so 
 rendered, respectively negative and positive. 
 
 The red lead collects on the negative parts of 
 the shellac surface, and the sulphur on the posi- 
 tive parts, in curious figures, known as Lichten- 
 berg's Dust Figures, one of which is shown in 
 Fig. 254. 
 
 Fig* 2 54- Lichtenberg's Dust Figures. 
 
 These figures show very clearly that an electric 
 charge tends to creep irregularly over the surface 
 of an insulating substance. 
 
 Figures, Magnetic A name some- 
 times applied to the groupings of iron filings 
 on a sheet of paper so held in a magnetic field 
 as to be grouped or arranged under the in- 
 fluence of the lines of force of the same. (See 
 Field, Magnetic?) 
 
 Filament. A slender thread or fibre. 
 The term is applied generally to threads or 
 fibres varying considerably in diameter. 
 
 Filament, Current A term some- 
 times employed in place of current streamlet. 
 (See Streamlets. Current?) 
 
 Filament, Magnetic A polarized 
 
 line or chain of ultimate magnetic particles. 
 
 This is sometimes called a uniform magnetu 
 filament. 
 
 A bar-magnet possesses but two free poles. 
 When broken ai Us neutral point or equator, the 
 bar will develop free poles at the broken ends. 
 This is explained by considering the magnet to 
 be composed of a number of separate particles, 
 separately magnetized. A single chain or fila- 
 ment of such particles is called a magnetic 
 filament. (See Magnet, Neutral Point of. Mag* 
 nettsm, Hughes' Theory of. Magnetism^ 
 E-wing's Theory of.) 
 
 Filament of Incandescent Electric Lamp. 
 
F11.J 
 
 231 
 
 [Fir. 
 
 (See Lamp, Incandescent Electric, Fila- 
 ment of.) 
 Filament, Uniform Magnetic A 
 
 term sometimes applied to a magnetic fila- 
 ment. (See Filament, Magnetic.) 
 
 Filaments, Flashed Filaments for 
 
 an incandescent lamp, that have been sub- 
 jected to the flashing process. (See Carbons, 
 Flashing Process for) 
 
 Filamentous Armature Core. (See Core, 
 Armature, Filamentous.) 
 ; Film Cut-Out (See Cut-Out, Film.) 
 
 Finder, Induction A term some- 
 times employed for a magnetic explorer. 
 
 Finder, Position*, Electric A de- 
 vice by means of which the exact position of 
 an object can be obtained. 
 
 By means of a position -finder a gunner can 
 be telephoned or otherwise ordered to fire at ob- 
 jects he cannot see, and yet obtain a fair degree 
 of accuracy. 
 
 Finder, Range, Electric A de- 
 vice by means of which the exact distance of 
 an enemy's ship or other target can be readily 
 determined. 
 
 The operation of an electric range-finder is based 
 on a method somewhat similar to the solving of a 
 triangle for the purpose of determining distances. 
 If the base line of a triangle and the two angles 
 at the base are known, the other two sides and 
 the included angle can be determined. 
 
 In the range-finder, the resistance of a German 
 silver wire corresponds to the graduated arc of 
 the theodolite used to measure the angles, and a 
 rheostat, as a receiving instrument, measures the 
 values of the angles. The base line is a constant, 
 so that the receiving instrument is marked in 
 yards instead of angles. To use the range-finder, 
 two observers watch the target object continu- 
 ously through a telescope. They do this and 
 nothing else, while a third observer watches a 
 galvanometer and so alters a resistance, by moving 
 a contact or slide key along a resistance wire, as 
 to keep the needle of the galvanometer constantly 
 at zero. The exact distance being thus ascer- 
 tained, the gunner can make the proper allowance 
 in firing.' 
 
 Finder, Wire Any form of galva- 
 nometer used to locate or find the corre- 
 
 sponding ends of different wires in a bunched- 
 cable. 
 
 The different wires in a cable are usually tagged 
 and numbered at the end of the cable and at the 
 joints. The telephone has been successfully em- 
 ployed as a wire finder. 
 
 Fire Alarm Annunciator. (See Annun- 
 ciator, Fire Alarm.) 
 
 Fire Alarm, Automatic (See 
 
 Alarm, Fire Automatic.) 
 
 Fire Alarm Contact (See Contact, Fire 
 Alarm.) 
 
 Fire Alarm Signal Box. (See Box, Fire 
 Alarm Signal.) 
 
 Fire Alarm Telegraph Box. (See Box, 
 Fire Alarm Telegraph.} 
 
 Fire Ball. (See Ball, Fire.) 
 
 Fire Cleansing. (See Cleansing, Fire.) 
 
 Fire Extinguisher, Electric A 
 
 thermostat or mercury contact, which auto- 
 matically completes a circuit and turns on a 
 water supply for extinguishing a fire, on a 
 certain predetermined increase of tempera- 
 ture. 
 
 Fire, Hot, St. Elmo's A term pro- 
 posed by Tesla for a form of powerful brush 
 discharge between the secondary terminals of 
 a high frequency induction coil. (See Dis- 
 charge, Brush-and- Spray?) 
 
 This form of St. Elmo's fire differs from the 
 ordinary form in being hot. Its general appear- 
 ance is shown in Fig. 255, taken from Tesla, 
 
 Fig. 255. St. Elmo's Hot Fire. 
 
 Describing its production he says : '-In many of 
 these experiments, when powerful effects are 
 wanted for a short time, it is advantageous to use 
 
Fir.] 
 
 233 
 
 [Flo. 
 
 iron cores with the primaries. In such case a 
 very large primary coil may be wound and placed 
 side by side with the secondary, and, the nearest 
 terminal of the latter being connected to the 
 primary, a laminated iron core is introduced 
 through the primary into the secondary as far as 
 the streams will permit. Under these conditions 
 an excessively powerful brush, several inches 
 long, which may be appropriately called ' St. 
 Elmo's hot fire, ' may be caused to appear at the 
 other terminal of the secondary, producing strik- 
 ing effects. It is a most powerful ozonizer ; so 
 powerful indeed, that only a few minutes are suf- 
 ficient to fill the whole room with the smell of 
 ozone, and it undoubtedly possesses the quality of 
 exciting chemical affinities." 
 
 Fire, St. Elmo's Tongues of faintly 
 
 luminous fire which sometimes appear on the 
 pointed ends of bodies in connection with the 
 earth, such as the tops of church steeples or 
 the masts of ships. 
 
 The appearance of the St. Elmo's fire is due to 
 brush discharges of electricity. 
 
 Fishes, Electric A term applied to 
 
 various fishes, such as the eel and the ray, 
 which possess the ability of protecting them- 
 selves by giving electric shocks to objects 
 touching them. (See Eel, Electric.} 
 
 Fishing 1 Box. (See Box, Fishing?) 
 
 Fittings or Fixtures, Electric Light 
 
 The sockets, holders, arms, etc., required 
 for holding or supporting incandescent electric 
 lamps. 
 
 Fixed Secondary. (See Secondary, 
 Fixed.) 
 
 Fixtures, Telegraphic A term gen- 
 erally limited to the variously shaped supports 
 provided for the attachment of telegraphic 
 wires. 
 
 Fixtures, Telegraphic House-Top 
 Telegraphic fixtures placed on the roofs of 
 buildings for the support of the lines. 
 
 Flaming Discharge. (See Discharge, 
 Flaming.) 
 
 Flash, Side A sparking or lateral 
 
 discharge taking place from the sides of a 
 conductor, when an impulsive rush of elec- 
 tricity passes through it. 
 
 The phenomenon of siae flashing is due to a 
 lateral discharge which takes the alternative path, 
 instead of a path of much smaller ohmic resist- 
 ance. The tendency to side flash results from 
 the fact that the metallic circuit possesses induct- 
 ance. (See Path, Alternative. Discharge, Lat- 
 eral. Inductance. ) 
 
 Flashed Carbons. (See Carbons, 
 Flashed.) 
 
 Flashed Filaments. ( See Filaments, 
 Flashed.) 
 
 Flashes, Auroral Sudden variations 
 
 in the intensity of the auroral light. 
 
 Intermittent flashes of auroral light that 
 occur during the prevalence of an aurora. 
 (See Aurora Borealis.) 
 
 Flashing of Carbons, Process for the 
 
 (See Carbons, Flashing Process for.) 
 
 Flashing of Dynamo-Electric Machine. 
 
 (See Machine, Dynamo-Electric, Flashing 
 of.) 
 
 Flat Cable. (See Cable, Flat.) 
 
 Flat Duplex Cable. (See Cable, Flat 
 Duplex.) 
 
 Flat Ring Armature. (See Armature, 
 Flat Ring.) 
 
 Flats. A name sometimes applied to those 
 parts of commutator segments the surface of 
 which, through wear, has become lower than 
 the other portions. (See Commutator.) 
 
 Fleming's Gauss. (See Gauss, Flem- 
 ing's.) 
 
 Fleming's Standard Toltaic Cell. (See 
 Cell, Voltaic, Standard, Fleming's.) 
 
 Flexible Electric Light Pendant. (See 
 Pendant, Flexible Electric JLight.) 
 
 Flexible Lead. (See Lead, Flexible.) 
 
 Floating Battery, De la Rive's. (See 
 Battery, Floating, De la Rive's.) 
 
 Flow. In hydraulics, the quantity of 
 water or other fluid which escapes from an 
 orifice in a containing vessel, or through a 
 pipe, in a given time. 
 
 Flow-Lines of Escaping Fluid. Lines 
 \vithin the mass of a fluid in motion, drawn at 
 
Flo.] 2 
 
 a number of points, so that the flow at any 
 instant is tangential at such points to the 
 curved path. 
 
 Flow, Magnetic The magnetic 
 
 flux. (See Flux, Magnetic!) 
 Flow of Current, Assumed Direction of 
 
 (See Current, Assumed Direction 
 of Flow of.) 
 
 Flow of Energy. (See Energy, Flow of) 
 Flow of Lines of Electrostatic Force. 
 
 (See Force, Electrostatic, Lines of, Assumed 
 Flow of.) 
 
 Flow of Magnetic Induction. (See In- 
 duction, Magnetic, Flux or Flow of) 
 
 Fluid, Depolarizing An electro- 
 lytic fluid in a voltaic cell that prevents polari- 
 zation. (See Cell, Voltaic, Polarization of) 
 
 Fluid Insulator. (See Insulator. Fluid) 
 
 Fluoresce. To become self-luminous 
 when exposed to light. 
 
 A body is said to fluoresce when it shines, by 
 means of the light it produces. In this respect it 
 differs from an illumined body, which shines by 
 reflected light. 
 
 Fluorescence. A property possessed by 
 certain solid or liquid substances of becoming 
 self-luminous while exposed to light. 
 
 In fluorescence the refrangibility of rays of 
 light is changed. The invisible rays beyond the 
 violet, the ultra-violet, become visible, so that 
 the light is transformed, the particles absorbing 
 one wave length and emitting another. (See Incan- 
 descence.) 
 
 Canary glass, or glass colored yellow by oxide 
 of uranium, or a solution of sulphate of quinine, 
 possesses fluorescent properties. The path of a 
 pencil of light brought to a focus in either of these 
 substances, or a beam or cone of light passed 
 through them, is rendered visible by the particles 
 lying in this path becoming self-luminous. The 
 path of a beam of light entering the dusty air of 
 a darkened chamber is visible from the light being 
 diffused or scattered in all directions by the float- 
 ing dust particles. 
 
 In a fluorescent substance, the path of the light 
 is also rendered visible by the particles which lie 
 in its path, throwing out light in all directions. 
 There is, however, this difference, that in the 
 
 [Fly. 
 
 case of the dust particles the Kght which comes 
 directly from the beam is reflected ; while in the 
 case of the fluorescent body the light comes from 
 the particles themselves, which are set into vibra- 
 tion by the light that is passing through, and has 
 been absorbed by their mass. 
 
 Fluorescence is, therefore, a variety of phos- 
 phorescence. (See Phosphorescence.) 
 
 Fluorescent Possessing the capability of 
 fluorescing. 
 
 Fluorescing. Exhibiting the property of 
 fluorescence. 
 
 Flush Box. (See Box, Flush.) 
 
 Flimograph. An apparatus for electri- 
 cally registering the varying height of water 
 in a tidal stream or in the ocean ; or, in general, 
 differences of water levels. 
 
 Flux, Magnetic The number of 
 
 lines of magnetic force that pass or flow 
 through a magnetic circuit. 
 
 The total number of lines of magnetic force 
 in any magnetic field. 
 
 The magnetic flux is also called the magnetic 
 flow. 
 
 A Committee of the American Institute of 
 Electrical Engineers on " Units and Standards " 
 proposed the following as the definition of mag- 
 netic flux. 
 
 " The magnetic flux through a surface bounded 
 by a closed curve is the surface integral of mag- 
 netic induction taken over the bounded surface, 
 and when produced by a current is also equal to 
 the line integral of the vector potential of the cur- 
 rent taken round the boundary." 
 
 " The uniform and unit time rate of change in 
 flux through a closed electric circuit establishes 
 unit electromotive force in the circuit." 
 
 Fluxes range in present practical work from 
 loo to 100, 000,000 C. G. S. lines, and the working 
 units would perhaps prefix milli- and micro-. 
 
 Flux of Magnetic Induction. (See In- 
 duction, Magnetic, Flux or Flow of) 
 
 Flux or Flow of Magnetism. (See Mag- 
 netism, Flux or Flow of) 
 
 Fly. Electric A wheel or other de- 
 vice driven by the reaction of a convective 
 discharge. (See Flyer, Electric. Convec- 
 tion, Electric) 
 
Fly.] 
 
 234 
 
 L for. 
 
 Flyer, Electric 
 
 A wheel arranged 
 
 so as to be set into rotation by the escape of 
 convection streams from its points when 
 connected with a charged conductor. 
 
 A wheel formed of 
 light radial armsP, P, P, 
 etc., shaped as shown in 
 Fig. 256, and capable of 
 rotation on the vertical 
 axis A, is set into rapid 
 rotation when connected 
 with the prime conduc- 
 tor of a frictional or in- 
 fluence machine, through 
 the convection streams of 
 air particles, which are Fig. 236. Electric Flyer. 
 shot off from the points or extremities of the 
 radial arms. The wheel is driven by the reac- 
 tion of these streams in a direction opposite to 
 that of their escape. (See Discharge, Convective. ) 
 
 Focus. A point in front or back of a lens 
 or mirror, where all the rays of light meet or 
 seem to meet. (See Lens, Achromatic) 
 
 Fog, Electric A dense fog which 
 
 occurs on rare occasions when there is an 
 unusual quantity of free electricity in the 
 atmosphere. 
 
 During these electric fogs the free electricity of 
 the atmosphere changes its polarity at frequent 
 intervals. 
 
 Following Horn of Pole Pieces of 
 Dynamo-Electric Machine. (See Horns, 
 Following, of Pole Pieces of a Dynamo- 
 Electric Machine?) 
 
 Foot-Candle. (See Candle, Foot.) 
 
 Foot-Pound. A unit of work. (See 
 Work.) 
 
 The amount of work required to raise I 
 pound vertically through a distance of i foot. 
 
 The same amount of work, viz., 3 foot-pounds, 
 is done by raising I pound through a vertical 
 distance of 3 feet, or 3 pounds through a verti- 
 cal distance of I foot. 
 
 Apart from air friction, the amount of work 
 done in raising I pound through I foot, viz., I 
 foot-pound, is the same whether this work be 
 done in one second or in one day. The power, 
 or the rate of doing work, is, however, very dif- 
 ferent in the two cases. (See Power.) 
 
 Force. Any cause which changes or tends 
 
 to change the condition of rest or motion of 
 a body. 
 
 Force, Centrifugal 
 
 The force that 
 
 is supposed to urge a rotating body directly 
 away from the centre of rotation. 
 
 If a stone be tied to a string and whirled around, 
 and the s'ring break, the stone will not fly off di- 
 rectly away from the centre, but will move along 
 the tangent to the point where it was when the 
 string broke. 
 
 The centrifugal force in reality is the force 
 which is represented by the tension to which the 
 string is subjected during this rotation. 
 
 Force, Coercitive A name some- 
 times applied to coercive force. (See Force, 
 Coercive?) 
 
 Force, Coercive The power of re- 
 sisting magnetization or demagnetization. 
 
 Coercive force, in the sense of resisting demag- 
 netization, is sometimes called magnetic reten- 
 tivity. 
 
 Hardened steel possesses great coercive force; 
 that is, it is magnetized or demagnetized with 
 difficulty. 
 
 Soft iron possesses very feeble coercive force. 
 
 It is on account of the feeble coercive force of 
 the soft iron -ore of an electro-magnet that its 
 main value depends, since it is thereby enabled to 
 rapidly acquire its magnetization, on the comple- 
 tion of a circuit through its coils, and to rapidly 
 lose its magnetization on the opening of such 
 circuit. 
 
 Force, Contact A difference of elec- 
 trostatic potential, produced by the contact of 
 dissimilar metals. 
 
 That a difference of potential is produced by 
 the mere contact of dissimilar mitals is now gen- 
 erally recognize!. Such a force is generally 
 called the true contact force. (See Force, True 
 Contact. ) 
 
 According to Lodge, a true contact force has 
 no existence. There is no evidence, he thinks, 
 of a peculiar electromotive force at the point of 
 contact, but that the phenomena are due simply 
 to the fact that the metals are immersed in air or 
 oxygen, which is capable of combining with one 
 of them, and that, therefore, the cause of the 
 phenomena is the greater action, for instance, of 
 the oxygen of the air on the zinc than on the 
 cupper. 
 
For.] 
 
 235 
 
 [For. 
 
 According to this view, the voltaic effect is 
 due not to the difference of potential between 
 the zinc and copper, but to the difference of the 
 action of the air or moisture. 
 
 Force de Cheyal or Cheral Vapeur. 
 
 The French term for horse-power. 
 
 The force de cheval is equal to 75 kilogramme- 
 metres per second, or 32,549 foot-pounds per 
 minute. 
 
 The English horse-power is equal to 33,000 
 foot-pounds per minute. I force de cheval equals 
 .98634 horse-power; I horse-power equals 1.01385 
 force de cheval. (Hering.) 
 
 Force, Electric The force developed 
 
 by electricity. 
 
 This term is generally limited to the force of 
 attraction or repulsion produced by an electro- 
 static charge. 
 
 Force, Electromotive The force 
 
 starting electricity in motion, or tending to 
 start electricity in motion. 
 
 The force which moves or tends to move 
 electricity. 
 
 The term is an unfortunate one. Strictly speak- 
 ing, electromotive force is not a force at all : 
 at least, it is not a force in the Newtonian sense, 
 where force is only that which acts on matter. 
 
 The term electromotive force is generally writ- 
 ten thus : E. M. F. 
 
 The unit of electromotive force is the volt. 
 
 When electric induction takes place, there 
 results a change in the distribution of the thing 
 called electricity, whereby a movement occurs that 
 results in a positive and a negative charge. The 
 cause which produces this movement is called the 
 electromotive force. 
 
 There is an unfortunate want of uniformity at 
 present in the use of the term "electromotive 
 force." By some, the electromotive force is re- 
 garded as something which causes the difference 
 of potential ; by others the electromotive force is 
 regarded as being produced by the difference of 
 potential; and, by still others, electromotive force 
 is regarded as the entire electric moving cause 
 produced i>y any source; while anything less than 
 this is called by them potential difference. 
 
 Those who regard the electromotive force as 
 the cause which produces the potenthl difference 
 look on the electromotive force as acting within 
 
 the source and maintaining a potential difference 
 at its terminals. 
 
 Silvanus P. Thompson uses the term electro- 
 motive force in his "Elementary Lessons in 
 Electricity and Magnetism" as follows: "The 
 term ' electromotive force ' is employed to denote 
 that which moves or tends to move electricity 
 from one place to another. For brevity we some- 
 times write it E. M. F. In this particular case it 
 is obviously the result of difference of potential 
 and proportional to it ; just as in water pipes, a 
 difference in level produces a pressure, and the 
 pressure produces a flow as soon as the tap is 
 turned on, so difference of potential produces 
 electromotive force, and electromotive force sets 
 up a current as soon as a circuit is completed for 
 the electricity to flow through." 
 
 Mascart and Joubert, in their work on ' Elec- 
 tricity and Magnetism," Vol. I., say: "In all 
 cases the difference of potential V 1 V 2 , may be 
 considered as producing the motion of electrical 
 masses ; it is often called the electromotive force." 
 
 Maxwell, in his "Elementary Treatise on Elec- 
 tricity," spe iking of the potential differences 
 which may be shown to exist at the terminals of 
 a Daniell voltaic cell when on opjn circuit, says : 
 "This difference of potential is called the electro- 
 motive force of a Daniell cell." 
 
 Balfour Stewart, in his " Electricity and Mag- 
 netism, ' ' says : ' ' This difference of electric level 
 we shall call E, and, indeed, it is merely a manner 
 of expressing the cause of electromotive force." 
 
 Prof. Fleming, in his "Short Lectures to Elec- 
 trical Artisans," says: "The difference of elec- 
 trical level or potential must be caused by some 
 electromotive force acting in the conductor." 
 
 Prof. Anthony, in "A Review of Modern 
 Electrical Theories," regards the potential dif- 
 ference as due to electromotive force. He says : 
 " Difference of potential results from a changed 
 electrical distribution, an electrical strain, and 
 represents the tendency to return to the state of 
 equilibrium. Electromotive force is the some- 
 thing from without that produced the electric 
 strain." 
 
 Hering, in his "Principles of Dynamo-Electric 
 Machines," says : " Difference of potential is, as 
 the name implies, the difference of electrical po- 
 tential between any two points of a circuit, and 
 may, therefore, be applied to that at the poles of 
 a machine, battery or lamp, or at the ends of 
 leads, or, in general, to any tw > points in a cir- 
 cuit. The term 'electromotive toice,' however, 
 
For.] 
 
 236 
 
 [For. 
 
 applies only to the maximum difference ot potential 
 which exists in the circuit, or, in other words, the 
 total generated difference of potential." 
 
 This last paragraph expresses the distinction 
 between the two terms as ordinarily used in con- 
 nection with dynamos and batteries. 
 
 Force, Electromotive, Absolute Unit of 
 
 A unit of electromotive force ex- 
 pressed in absolute or C. G. S. units. 
 
 The one-hundred- millionth part of a volt, 
 since i volt equals io s C. G. S. units of elec- 
 tromotive force. (See Units, Practical?) 
 
 Force, Electromotive, Average or Mean 
 
 The sum of the values of a number of 
 
 separate electromotive forces divided by their 
 number. 
 
 The square root of the mean square of the 
 electromotive force of an alternating or vari- 
 able current. 
 
 When a wire in the armature of a dynamo- 
 electric machine cuts the lines of magnetic force 
 in the field of the machine, the electromotive 
 force produced depends on the number of lines 
 of force cut per second. This will vary for dif- 
 ferent positions of the coil. The mean value of 
 the varying electromotive forces between the 
 brushes is the average electromotive force. 
 
 Force, Electromotive, Back A 
 
 term sometimes used for counter electro- 
 motive force. 
 
 Counter electromotive force is the preferable 
 term. (See Force, Electromotive, Counter.] 
 
 Force, Electromotive, Counter 
 
 An opposed or reverse electromotive force, 
 which tends to cause a current in the oppo- 
 site direction to that actually produced by 
 the source. 
 
 In an electric motor, an electromotive force 
 contrary to that produced by the current 
 which drives the motor, and which is pro- 
 portional to the velocity attained by the 
 motor. 
 
 Counter electromotive force acts to diminish 
 the current in the same manner as a resistance 
 would, and is therefore sometimes called spurious 
 resistance in order to distinguish it from an ohmic 
 or true resistance. 
 
 Counter electromotive force is sometimes ex- 
 pressed in ohms, though it is not a true ohmic 
 rests ance. (See Resistance, Spurious.) 
 
 The counter electromotive force of a voltaic 
 battery is due to the polarization of the cells. 
 Since this force is due to the current in the cell, it 
 can never exceed such current or reverse its direc- 
 tion. It may, however, equal it and thus stop its 
 flow. (See Cell, Voltaic, Polarization oj.) 
 
 In a storage cell, the charging current produces 
 an electromotive force counter to itself, which, as 
 in a motor, is a true measure of the energy stored 
 in the cell. Economy requires that the electro- 
 motive force of the charging current should be as 
 little as possible greater than that of the counter 
 electromotive force of the cell it is charging. 
 
 In a voltaic arc a counter electromotive force is 
 believed to be set up by polarization. 
 
 Force, Electromotive, Counter, of Can- 
 
 vective Discharge Resistance to the 
 
 passage of an electric discharge through a 
 high vacuum, somewhat of the nature of a 
 counter electromotive force. 
 
 The resistance to the passage of convective dis- 
 charges, therefore, is due to the following causes: 
 
 (i.) True ohmic resistance. 
 
 (2.) Counter electromotive force. 
 
 Force, Electromotive, Counter, of Mutual 
 Induction The counter electromotive 
 force produced by the mutual induction of 
 the primary and secondary circuits on each 
 other. 
 
 Force, Electromotive, Counter, of Self- 
 induction That part of the impressed 
 electromotive force which is producing, or 
 which tends to produce, at any instant a 
 change in the current strength. 
 
 Force, Electromotive, Counter, of Self- 
 induction of the Primary A counter 
 electromotive force produced in the primary 
 circuit of an induction coil by the action 
 thereon of a simple periodic electromotive 
 force. 
 
 The counter electromotive force produced 
 in the primary circuit of an induction coil by 
 the application of a simple periodic impressed 
 electromotive force to the primary circuit. 
 
 Force, Electromotive, Counter, of Self- 
 induction of the Secondary A 
 counter electromotive force produced in the 
 secondary by the periodic variations in the 
 effective electromotive force in the secondary. 
 
For.] 
 
 237 
 
 [For. 
 
 Force, Electromotive, Direct An 
 
 electromotive force acting in the same direc- 
 tion as another electromotive force already 
 existing. 
 
 The term direct electromotive force is em- 
 ployed in contradistinction to counter electromo- 
 tive force. (See Force, Electromotive, Counter. ) 
 
 Force, Electromotive, Effective - 
 
 The difference between the direct and the 
 counter electromotive force. 
 
 Force, Electromotive, Effective, of Sec- 
 ondary The difference between the 
 direct and the counter electromotive force in 
 the secondary of an induction coil. 
 
 Force, Electromotive, Generated by Dy- 
 namo-Electric Machine, Method of Increas- 
 ing The electromotive force of a dy- 
 namo-electric machine may be increased in 
 the following ways, viz : 
 
 (I.) By increasing its speed of rotation. 
 
 (2.) By increasing the strength of the magnetic 
 field in which the armature rotates. 
 
 (3.) By increasing the size of the field through 
 which the armature passes in unit time, the in- 
 tensity remaining the same. 
 
 (4.) By increasing the number of armature 
 windings, i. e., by making successive parts of the 
 same wire pass simultaneously through the field. 
 
 Force, Electromotive, Impressed 
 
 The electromotive force acting on any cir- 
 cuit to produce a current therein. 
 
 The impressed electromotive force may be re- 
 garded as producing two parts, viz. : The effective 
 electromotive force and the counter electromotive 
 force. 
 
 Force, Electromotive, Inductive 
 A term sometimes used in place of counter 
 electromotive force of self-induction. 
 
 Force, Electromotive, Inverse An 
 
 electromotive force which acts in the oppo- 
 site direction to another electromotive force 
 already existing. (See Force, Electromotive, 
 Counter.) 
 
 Force, Electromotive, Motor - A 
 term proposed by F. J. Sprague for the coun- 
 ter electromotive force of an electric motor. 
 (See Force, Electromotive, Counter?) 
 
 This term was propose I by Sprajue as express- 
 
 ing the necessity for the existence of a counter 
 electromotive force in an electric motor, in order 
 to permit it to utilize the energy of the electric 
 current which drives it. 
 
 Force, Electromotive, of Induction 
 
 The electromotive force developed by any 
 inductive action. 
 
 In a coil of wire undergoing induction, the 
 value of the induced electromotive force does not 
 depend in any manner on the nature of the ma- 
 terial of which the coil is composed. 
 
 It has been shown: 
 
 (l.) That the electromotive force of induction is 
 independent of the width, thickness or material of 
 the wire windings. {Faraday.} 
 
 (2.) That it is dependent on the form of the 
 conductor, and the character of the change it ex- 
 periences as regards the magnetic induction which 
 takes place through it. 
 
 Since any increase in the strength of a current 
 flowing through a coiled circuit, produces a coun- 
 ter electromotive force, which opposes the electro- 
 motive force producing the current, it is clear 
 that the impressed electromotive force must do 
 work against this counter electromotive force all 
 the time the current strength is increasing. 
 
 The movement of a circuit of a given length 
 through a given field with a given velocity pro- 
 duces the same electromotive force whether the 
 circuit be formed of conducting material or non- 
 conducting material, or consists of an electrolyte. 
 
 Force, Electromotive, of Secondary or 
 Storage Cell, Time-Jail of A gradual 
 decrease in the potential difference of a stor- 
 age battery observed during the discharge of 
 the same. 
 
 When a secondary or storage battery is first 
 discharged, a slight decrease of its potential dif- 
 ference takes place and a potential difference of a 
 slightly decreased value is maintained nearly con- 
 stant during a protracted period of discharge. 
 
 Force, Electromotive, of Secondary or 
 Storage Cell, Time-Rise of A gradual 
 increase in the potential difference of a 
 secondary or storage cell observed on begin- 
 ning the discharge after a prolonged rest. 
 
 When a secondary or storage cell is discharged 
 and then given a prolonged rest by opening its 
 circuit, a gradual but decided rise in its potential 
 difference is observed on again beginning its dis- 
 charge. 
 
For.) 
 
 23S 
 
 [For. 
 
 Force, Electromotive, Photo An 
 
 electromotive force produced by the action of 
 light on selenium. (See Cell, Selenium?) 
 
 Force, Electromotive, Reacting Induc- 
 tive, of the Primary Circuit The back 
 
 or counter electromotive force produced in the 
 primary circuit by the current set up by in- 
 duction in the secondary. 
 
 Force, Electromotive, Secondary Im- 
 pressed An electromotive force pro- 
 duced in the secondary coil or circuit by a 
 periodic electromotive force impressed on the 
 primary. 
 
 Force, Electromotive, Simple-Periodic 
 
 An electromotive force which varies 
 
 in such manner as to produce a simple 
 periodic current, or an electromotive force the 
 variations of which can be correctly repre- 
 sented by a simple-periodic curve. 
 
 Force, Electromotive, Thermo An 
 
 electromotive force, or difference of potential, 
 produced by differences of temperature 
 acting at thermo-electric junctions. 
 
 Force, Electromotive, Transverse 
 
 An electromotive force excited by a mag- 
 netic field in a substance in which electric 
 displacement is occurring. 
 
 It is to a transverse electromotive force that the 
 Hall effect is due. (See Effect, Hall.) 
 
 Force, Electromotive, Zigzag An 
 
 electromotive force, the curve of which would 
 have the general form of a zigzag. 
 
 Force, Electrostatic The force pro- 
 ducing the attractions or repulsions of charged 
 bodies. 
 
 Force, Electrostatic, Lines of 
 Lines of force produced in the neighborhood 
 of a charged body by the presence of the 
 charge. 
 
 Lines extending in the direction in which 
 the force of electrostatic attraction or repul- 
 sion acts. 
 
 An insulated charged conductor produces 
 around it an electrostatic field, in a manner some- 
 what similar to the magnetic field produced by 
 a macnet or an electric rur-^nt. (See Field, 
 Electrostat'u . > 
 
 Lines of electrostatic force pass through dielec- 
 trics. Whether the force acts to produce electro- 
 static induction, by means of a polarization of the 
 dielectric, or by means of a tension set up in the 
 substance of the dielectric, is not known. 
 
 Force, Electrostatic, Lines of, Assumed 
 
 Flow of A mathematical conception in 
 
 which the phenomena of electricity are com- 
 pared with the similar phenomena of heat. 
 
 In heat no flow of heat occurs over isothermal 
 surfaces, or surfaces at the same temperature. 
 Between different isothermal surfaces, the flow 
 will vary with the power of heat conduction. In 
 electricity, no flow occurs over equipotential sur- 
 faces. Specific inductive capacity corresponds to 
 heat conductivity, and the lines of force to the 
 lines of heat conduction. (See Capacity, Specific 
 Inductive. ) 
 
 Force, Lines of, Contraction of 
 
 A decrease that occurs in the length of the 
 circular lines of force that surround a circuit 
 through which an electric current is passing, 
 while the current is decreasing in intensity or 
 strength. 
 
 The contraction or decrease in the average 
 diameter of the circular lines of force of an elec- 
 tric circuit is similar to the expansion or growth 
 of lines of force, excepting that the movement is 
 one of decrease in diameter, and takes place in 
 the opposite direction, i. e., towards the circuit, 
 instead of away from it. (See Force, Lines of, 
 Growth or Expansion of.} 
 
 Force, Lines of, Cutting Passing a 
 
 conductor through lines of magnetic force, so 
 as to cut or intersect them. 
 
 The cutting of lines of magnetic force produces 
 differences of potential. This is true whether the 
 conductor moves through a stationary field or 
 whether the field itself moves through the 
 stationary conductor, so that the lines of force and 
 the conductor cut one another. This cutting is 
 mutual. Each line of force cuts and is cut by the 
 circuit Since all lines of force form closed-cir- 
 cuits or paths, the cutting of the circuit by the 
 lines of force, or the reverse, forms a link or chain, 
 and the cutting takes place at the moment of 
 linking or unlinking, i. e., of cutting. 
 
 Force, Lines of, Diffusion of The 
 
 deflection of the lines of magnetic force from 
 
For.] 
 
 239 
 
 [For. 
 
 their ordinary position, between the poles 
 that produce them. 
 
 Force, Lines of, Direction of The 
 
 direction in which it is assumed that the lines 
 of magnetic force pass. 
 
 It is generally agreed to consider the lines of 
 magnetic force as coming out of the north pole of 
 a magnet and passing into its south pole, as 
 shown in Fig. 257. 
 
 Fig. 2J7. Direction of Lines of Force. 
 
 This is sometimes called the positive direction 
 of the lines of force and agrees in general with the 
 direction in which the electric current is assumed 
 to flow, which is from the positive to the nega- 
 tive. That is to say, the lines of magnetic force 
 are assumed to flow or pass out of the north pole 
 and into the south pole of a magnet. Of course 
 there is no direct evidence of any flow, or of any 
 particular direction characterizing the lines of 
 force. (See Field, Magnetic.) 
 
 The lines of electrostatic force are assumed to 
 pass out of a positively charged surface and into 
 a negatively charged surface. 
 
 Force, Lines of, Growth or Expansion of 
 
 The increase in the length of path 
 
 through which lines of force pass, consequent 
 on an increase in the strength of the mag- 
 netization of a magnet, or on an increase in 
 the strength of the magnetizing current. 
 
 The circular lines of force which surround a con - 
 ductor through which a current is flowing, may be 
 regarded as starting from the surface c f the con- 
 ductor and growing in bizj as they spread out- 
 wards, at the same time new lines of force being 
 formed in their places. This action continues while 
 the strength of the current is increasing, somewhat 
 like the series of concentric waves which are 
 formed on the surface of water, when a stone is 
 dropped into it. 
 
 In their growth or expansion outwards from 
 the conductor, if the lines of force cut or pass 
 through neighboring conductors, they produce 
 
 therein differences of electric ootential, capable, 
 on being connected by a conductor, of produc 
 ing electric currents. 
 
 Force, Lines of. Radiation of The 
 
 passing of lines of force out of the north 
 pole of a magnet or solenoid. 
 
 In gross matter all lines of magnetic induction 
 either pass through magnetized iron, or other 
 paramagnetic substance which surrounds an 
 electric circuit. Since lines of force pass through 
 a vacuum, the ether which occupies such a space 
 must also be regarded as permitting the passage 
 of lines of force. 
 
 Force, Loops of A term sometimes 
 
 employed in the sense of lines of force. (See 
 Force, Magnetic, Lines of.) 
 
 The term "Lines of Force" is generally 
 adopted in place of Faraday's term "Loops of 
 Force." 
 
 Force, Magnetic The force which 
 
 causes the attractions or repulsions of mag- 
 netic poles. 
 
 Force, Magnetic, Line of Arbitra- 
 rily a single line of magnetic force. 
 
 Practically the lines of magnetic force 
 which pass through a unit area of cross-sec- 
 tion of a magnetic field of unit strength. 
 
 Force, Magnetic, Lines of Lines 
 
 extending in the direction in which the mag- 
 netic force acts. 
 
 Lines extending in the direction in which 
 the force of magnetic attraction or repulsion 
 acts. (See Field, Magnetic?) 
 
 Faraday regarded the lines of magnetic force as 
 possessing tension along one direction. Lines of 
 force act as if they were stretched elastic threads, 
 possessed of the property of lengthening or short- 
 ening, and of repelling one another. 
 
 Force, Magnetic, Lines of, Conducting 
 Power for A term employed by Fara- 
 day for magnetic permeability. (See Perme- 
 ability, Magnetic?) 
 
 Force, Magnetic, Lines of, Positive 
 
 Direction of The direction in which 
 
 a free north-seeking pole would move along 
 the lines of force when placed in a magnetic 
 field. 
 
For.] 
 
 240 
 
 [For. 
 
 Force, Magnetic, Telluric -The 
 
 earth's magnetic force. 
 
 Force, Magneto-Motive The force 
 
 that moves or drives the lines of magnetic 
 force through a magnetic circuit against the 
 magnetic resistance. 
 
 A Committee of the American Institute of Elec- 
 trical Engineers on "Units and Standards" pro- 
 posed the following definition. 
 
 1 he magneto-motive force in a magnetic cir- 
 cuit is 47t multiplied by the flow of the current 
 linked with that circuit. The magneto-motive 
 iorce between two points connected by a line is 
 the line integral of the magnetic force along that 
 line. Difference of magnetic potential constitutes 
 magneto-motive force." 
 
 The same committee gave the electro-magnetic 
 dimensional formula Li M^ T -1 . 
 
 The flow or flux of lines of magnetic force in 
 any magnetic circuit is proportional to the mag- 
 neto-motive force divided by the magnetic resist- 
 ance ; or, expressing the law in the form of Ohm's 
 law for current: 
 
 .. . Magneto -Motive Force 
 
 Magnetic I 1 lux = ^__~T 
 
 Reluctance. 
 
 In this formula the word reluctance is used in 
 place of magnetic resistance. In the case of an 
 electro-magnet, the magneto-motive force is pro- 
 portional to the strength of the current which flows 
 and the number of times it circulates; or, more 
 simply, is proportional to the number of ampere 
 turns. (See Turns, Ampere.) 
 
 Force, Magneto-Motive, Absolute Unit of 
 
 471 multiplied by unit current of one 
 
 turn. 
 
 Force, Magneto-Motive, Practical Unit 
 
 of A value of the magneto-motive force 
 
 equal to 4* multiplied by the amperes of one 
 turn, or to TO of the absolute unit. 
 
 Force, Motor Electromotive - - A 
 
 term proposed by F. J. Sprague for the 
 counter electromotive force of a motor. 
 
 During the rotation of the armature of an 
 electric motor in its field, a counter electromotive 
 force is produced in its coils, which acts as a 
 spurious resistance and opposes the flow or pass- 
 age of the driving current through its coils. As 
 the speed of the motor increases, this counter 
 electromotive force increases and the strength of 
 the driving current decreases until a certain 
 
 maximum speed is reached, when, theoretically, 
 no current passes. 
 
 When a load is placed on the electric motor, 
 the speed, and consequently the counter electro- 
 motive force, is decreased and more driving cur- 
 rent is permitted to pass. It was this considera- 
 tion, viz. : that the load automatically regulates 
 the current required to drive the motor, that kd 
 to the name motor electromotive force. (See 
 Force, Electromotive, Counter.) 
 
 Force, Resolution of The separa- 
 tion of a single force, acting with a given 
 intensity in a given direction, into a number 
 of separate forces -, 
 acting in some other 
 direction. 
 
 Thus the force D B, 
 Fig. 258, acting with 
 the intensity and in the 
 direction shown, may c 
 be resolved into two 
 component forces, D 
 
 Fig. 238. Resolution of 
 Force. 
 
 E and D C, acting in the directions and having 
 the intensities shown. The single force D B, has 
 been resolved into two separate forces D E and 
 CD. 
 
 Force, True Contact A force or 
 
 effect entirely distinct from the voltaic effect, 
 which exists at the points of contact be- 
 tween two dissimilar metals. 
 
 The truth of the existence of a true contact force 
 at the junction of dissimilar metals is seen by the 
 reversible heat effects observed, when a current 
 of electricity is passed across a junction of two 
 dissimilar metals. When the current is passed in 
 one direction, an increase of temperature is pro- 
 duced, but when passed in the opposite direction, 
 a decrease of temperature. (See Effect, Peltier.) 
 
 Hence there would appear to be a force existing 
 at the junction, helping the electricity along in 
 one direction, but opposing it in the opposite di- 
 rection. In one direction the electricity does 
 work and consumes its own energy in so doing. 
 In the other direction it opposes the passage of 
 the current, and there results a generation of 
 heat. 
 
 Force, Tubes of Tubes bounded by 
 
 lines of electrostatic or magnetic force. 
 
 Lines of force never intersect one another. 
 Hence a tube of force may be regarded as con- 
 
For.] 
 
 241 
 
 taining the same number of lines of force at any 
 and every cross-section. 
 
 Tubes of electrostatic force always terminate 
 against equal quantities of positive and negative 
 electricity respectively. They terminate when 
 they meet a conducting surface. 
 
 The term tubes of force is somewhat mislead- 
 ing, since such so-called tubes are in general 
 cones rather than tubes. 
 
 Force, Twisting A term sometimes 
 
 used for torque. (See 'Torque) 
 
 Force, Unit of A force which, act- 
 ing for one second on a mass of one 
 gramme, will give it a velocity of one centi- 
 metre per second. 
 
 Such a unit of force is called a dyne. (See 
 Dyne.) 
 
 Forces, Composition of Finding 
 
 th direction and intensity of a single force 
 which represents the total effect of two or 
 more forces acting simultaneously on a body. 
 (See Component.) 
 
 Forces, Parallelogram of A paral- 
 lelogram constructed about the two lines that 
 represent the direction and intensity with 
 which two forces are simultaneously acting 
 on a body, in order to determine the direction 
 and intensity of the resultant force with 
 which it moves. 
 
 If the two forces A C and A B, Fig. 259, simul- 
 taneously act in the direc- B ID 
 tion of the arrows on a 
 body at A, the direction 
 and intensity of the re- 
 sultant A D, is deter- pig. 239. Farallelo- 
 mined by drawing C D e ram of Forces. 
 and B D, parallel respectively to A B and A C. 
 The diagonal A D, of the parallelogram AC D B, 
 thus produced, gives this resultant. (See Com- 
 ponent. ) 
 
 Fork, Trolley The mechanism 
 
 which mechanically connects the trolley wheel 
 to the trolley pole. (See Trolley.) 
 
 Forked Circuits. (See Circuits, Forked) 
 
 Forked Lightning. (See Lightning, 
 Forked) 
 
 Formal Inductance of Circuit. (See In- 
 ductance, Formal, of Circuit) 
 
 Forming Plates of Secondary or Stor- 
 age Cells. (See Plates of Secondary or Stor- 
 age Cells, Forming of.) 
 
 Formulae. Mathematical expressions for 
 some general rule, law, or principle. 
 
 Formulae are of great assistance in science in 
 expressing the relations which exist between cer- 
 tain forces or values, and the effects that result 
 from their operations, since they enable us to ex 
 press these relations in clear and concise forms. 
 
 Thus in the formulation of Ohm's law: 
 
 C _ E 
 -R 
 
 we see that the continuous current C, in any cir- 
 cuit, is equal to the electromotive force E, divided 
 by the resistance R. Again, we see that the cur- 
 rent is directly proportional to the electromotive 
 force, and inversely proportional to the resistance. 
 
 Formulae are usually written in the form of an 
 equation and therefore contain the sign oiequality 
 or =. 
 
 Formulae, Photometric (See Pho- 
 tometric Formula.) 
 
 Foucault Currents. (See Currents, Fou- 
 cault!) 
 
 Four-Way Splice Box. (See Box, Splice, 
 Four- Way.) 
 
 Frames, Sectional Plating Frames 
 
 employed for so holding the objects to be 
 plated that they shall receive a greater depth 
 of deposit on certain portions of their surface 
 than elsewhere. 
 
 Sectional printing frames depend for their 
 action on the fact that the portions receiving the 
 greater depth of deposit are nearer one of the 
 electrodes than the rest of the surface. 
 
 Franklinic Electricity. (See Elec- 
 tricity, Franklinic.) 
 
 Franklinization. Electrization by means 
 of a frictional or influence machine as distin- 
 guished from faradization or electrization by 
 means of an induction coil. 
 
 This term is used only in medical electricity. 
 
 Free Charge. (See Charge, Free.) 
 
 Free Magnetic Pole. (See Pole, Mag- 
 netic, Free.) 
 
 Frequency of Alternations. (See Alter- 
 nations, Frequency of) 
 
Fri.] 
 
 242 
 
 [Fun. 
 
 Friction Brake. (See Brake, Friction?) 
 Frictional Electrical Machine. (See 
 
 Machine Frictional Electric?) 
 Frictional Electricity. (See Electricity , 
 
 Frictional.} 
 
 Frog 1 , Galvanoscopic The hind legs 
 
 cf a recently killed frog employed as an elec- 
 troscope or galvanoscope, by sending an elec- 
 tric current from the nerves to the muscles. 
 (See Electroscope?) 
 
 In 1786, Luigi Galvani made the observation 
 that when the legs of a recently killed frog were 
 touched by a metallic conductor connecting the 
 nerves with the muscles, the legs were convulsed 
 as though alive. He repeated this experiment 
 and found the move- 
 ments were more pro- 
 nounced when two dis- 
 similar metals, such as 
 iron and copper, were 
 employed in the manner 
 shown in Fig. 260. 
 
 The classic experi- 
 ment created intense 
 excitement in the scien- 
 tific world, and Galvani 
 at first believed that he 
 had discovered the true vital fluid of the animal, 
 but afterwards recognized it as electricity, which 
 he believed to be obtained from the body of the 
 animal. Volta claimed that the movements were 
 due to electricity caused by the contact of dissimi- 
 lar metals, and thus produced his famous voltaic 
 pile. (See /*'/,?, Voltaic.} 
 
 Frog, Trolley The name given to 
 
 the device employed in fastening or holding 
 together the trolley wires at any point where 
 the trolley wire branches, and properly guiding 
 the trolley wheel along the trolley wire on the 
 movement of the car over the track. 
 
 Frog, Trolley, Right-Hand A trol- 
 ley frog used at the point where the branch 
 trolley wire leaves the main line on the right 
 of the direction in which the car is moving. 
 
 Frog Trolley, Standard The trol- 
 ley frog used at the point where two branch 
 lines make equally converging angles to the 
 main line. 
 
 Frog, Trolley, Three-Way A trol- 
 
 Fig: 260. Galvanoscopic 
 Frog 
 
 ley frog used where the line branches in three 
 directions. 
 
 Frying of Arc. (See Arc, Frying of.} 
 Fulgurite. A tube of vitrified sand, be- 
 lieved to be formed by a bolt of lightning. 
 
 The fulgurite consists of an irregular shaped 
 tube of glass formed of sand which has been 
 melted by the electric discharge. 
 
 Fnll Contact. -(See Contact, Metallic.} 
 
 Fuller's Mercury Bichromate Voltaic 
 
 Cell. (See Cell, Voltaic, Fuller's Mercury 
 Bichromate?) 
 
 Fulminate. The name of a class of highly 
 explosive compounds. 
 
 Fulminating gold, silver and mercury are 
 highly explosive substances. Fulminates are 
 employed in percussion caps. 
 
 Function, Trigonometrical Cer- 
 tain quantities, the values of which are de- 
 pendent on the length of the arcs subtended 
 by angles, which are taken for the measures 
 of the arcs or angles instead of the arcs 
 themselves. 
 
 The trigonometrical functions are the sine, the 
 co-sine, the tangent, the co-tangent, the secant 
 and the co-secant. 
 
 These are generally abbreviated thus, viz. : sin., 
 . cos., tan., cot., sec. and co-sec. 
 
 The sine of an angle or arc is the perpendic- 
 ular distance from one L c 
 extremity of the arc to 
 the diameter passing 
 through the other ex- 
 tremily. 
 
 Thus in Fig. 261 B D, G 
 is the sine of the angle 
 B O A, or of the arc, 
 B A. 
 
 The co-sine of an an- 
 gle or arc is that part of Fig. zbr. Trigonometri- 
 the diameter which lies cal Functions. 
 
 between the foot of the sine and the centre. Thus, 
 D O, is the co-sine of the angle B O A, or of the 
 arc B A. 
 
 The co-sine of an arc is equal to the sine of its 
 complement. Thus E O B, or B E, the comple- 
 ment of B A, has for its sine I B. which is equal 
 to O D. (See Ang*e, Complement of.} 
 
 If the arc is greater than a right angle, or 90 
 
 F\ 
 
Fun.] 
 
 243 
 
 [Fus. 
 
 degrees, such, for instance, as the angle TOG, 
 or the arc B E F G, B D, is its sine. This is also 
 the sine of B O A, or B A, which is the supple- 
 ment of T O G, or B E F G. Hence the sine of 
 an arc is equal, to the sine of its supplement. 
 
 The same is true of the co-sine. 
 
 The tangent of an angle or arc is a straight 
 line touching the arc at one extremity, drawn 
 perpendicular to the diameter at that end of the 
 arc, and limited by a straight line connecting the 
 centre of the circle and the other end of the arc. 
 Thus C A, is the tangent of the angle B O A, or 
 the arc B A. 
 
 The co-tangent of an angle or arc is equal to 
 the tangent of its complement. Thus E T, is the 
 co-tangent of the angle B O A, or the arc B A. 
 
 The tangent of an angle or arc is equal to the 
 tangent of its supplement. Thus A C, is the tan- 
 gent of the angle B O A, or the arc B A. It is 
 also equal to the tangent of the angle B O G, or 
 the arc B E F G, the corresponding supplement of 
 the angle B O A, or the arc B A. 
 
 The secant of an angle or arc is the straight 
 line drawn from the centre of the circle through 
 one extremity of the arc and limited by the tan- 
 gent passing through the other extremity. Thus 
 O C, is the secant of the angle B O A, or of the 
 arc B A. 
 
 The secant of an angle or arc is equal to the 
 secant of its supplement. 
 
 The co-secant of an angle or arc is equal to 
 the secant of its complement. 
 
 Thus O T, is the co-secant of the angle BOA, 
 or of the arc B A. 
 
 It will be observed that the co-sine, the co- 
 tangent and the co-secant are respectively the 
 sine, tangent and secant of the complement of 
 the arc, or in other words, the complement-sine, 
 the complement-tangent and tiie comple.nent- 
 secant. 
 
 Fundamental Units. - (See Units, Funda- 
 mental.') 
 
 Furnace, Electric A furnace in 
 
 which heat generated electrically is employed 
 for the purpose of effecting difficult fusions 
 for the extraction of metals from their ores, 
 or for other metallurgical operations. 
 
 In electric furnaces, the heat is derived either 
 from electric incandescence or from the voltaic arc. 
 The latter form is frequently adopted. 
 
 The substance to be treated is. exposed directly 
 
 to the voltaic arc. In some forms of furnace the 
 crushed ore is permitted to fall through the arc, 
 and the melted matter received in a suitable ves- 
 sel in which the separation of the substances so 
 formed is afterwards completed. In other forms 
 of furnace, the ore is placed between two elec- 
 trodes of carbon or other refractory substance, 
 between which a powerful current is passed. In 
 the Cowles furnace, when aluminium is reduced, 
 molten copper forms an alloy with the aluminium 
 as soon as separated. 
 
 Very numerous applications of electricity to 
 furnace operations have been made. 
 
 Fuse Block. (See Block, Fuse.) 
 
 Fuse Board. (See Board, Fuse.) 
 
 Fuse Box. (See Box, Fuse.) 
 
 Fuse, Branch A safety fuse or 
 
 strip placed in a branch circuit. (See Fuse, 
 Safety.) 
 
 Fuse, Converter A safety fuse con- 
 nected with the circuit o( a converter or 
 transformer. 
 
 Fuse, Electric A device for elec- 
 trically igniting a charge of powder. 
 
 Electric fuses are employed both in blasting 
 operations and for firing cannon. 
 
 Electric fuses are operated either by means of 
 the direct spark, or by the incandescence of a 
 thin wire placed in the circuit. They are there- 
 fore either high tension, or low tension fuses. 
 
 The advantages of an electric fuse consist in 
 the fact that its use permits the simultaneous fir- 
 ing of a number of charges in a mining operation, 
 thus obtaining a greater effect from the explosion. 
 A fulminate of mercury is frequently employed 
 in connection with some forms of electric fuses. 
 
 Fuse, Electric, High-Tension A 
 
 fuse that is ignited by the heating power of 
 an electric spark. 
 
 High tension fuses, therefore, require a high 
 electromotive force. This is obtained either by 
 means of induction coils or Ly some form of 
 electrostatic induction machine. 
 
 Fuse, Electric, Low-Tension A 
 
 fuse that is ignited by heating a wire to incan- 
 descence by the passage through it of an 
 electric current. 
 Fuse, Electric, Stratham's A form 
 
Fas.] 
 
 244 
 
 [Gal, 
 
 ot fuse, in which the ignition is effected by the 
 electric spark, is shown in Fig. 262. 
 
 The spark passes through a break A B, in the in- 
 sulated leads D. Since gunpow- 
 der is not readily ignited by an 
 electric spark, a peculiar priming 
 material is employed at A B, in the 
 place of ordinary powder. 
 
 Fuse Links. (See Links, 
 Fuse.) 
 Fuse, Magazine A 
 
 safety fuse so arranged as to 
 readily permit the replacement 
 of the fuse when, burned out. 
 
 A spool contains a coil of fuse ^y~ 2 fr 2 
 wire. In order to release the Stratham's 
 burned-out fuse, a wedge-shaped Fuse. 
 device is provided to open the clamps that hold 
 the fuse strip to release the portions of burned- 
 out fuse left, and connection with the fuse strip 
 is severed while the attachment of the new strip 
 is being made. 
 
 Fuse, Main A safety fuse or strip 
 
 placed in a main circuit. (See Fuse, Safety?) 
 
 Fuse, Platinum A thin platinum 
 
 wire rendered incandescent by the passage of 
 an electric current and employed for the igni- 
 tion of a charge of powder. (See Fuse, 
 Electric?) 
 
 Fuse, Safety A strip, plate or bar 
 
 of lead, or some readily fusible alloy, that au- 
 tomatically breaks the circuit in which it is 
 placed on the passage of a current of suf- 
 
 ficient power to fuse such strip, plate or bar, 
 when such current would endanger the safety 
 of other parts of the circuit. 
 
 Safety fuses are often called safety strips or 
 safety plugs. 
 
 Safety fuses are made of alloys of lead, and 
 are placed in boxes lined with non-combustible 
 material in order to prevent fires from the molten 
 metal. 
 
 Fig. 263 shows a fusible strip F, connected with 
 leads L, L. Safety fuses are placed on all branch 
 circuits, and are made of sizes proportionate to 
 the number of lamps they guard. 
 
 Fig. 263. Safety Fuse. 
 
 Since incandescent lamps are generally placed 
 in the circuit in multiple-arc, or in multiple-series, 
 one or more of the circuits can be opened by the 
 fusion of the plug without interfering with the 
 continuity of the rest of the circuits. In series 
 circuits, however, such as arc-light circuits, when 
 a lamp is cut out, a short circuit or path around 
 it must be provided in order to avoid the extin- 
 guishing of the rest of the lights. 
 
 Fuse Wire. (See Wire, Fuse.) 
 
 Fusible Plug. A term commonly applied 
 to a safety plug. (See Fuse, Safety 
 
 G 
 
 Gains. The spaces cut m the faces of 
 telegraph poles for the support or placing of 
 the cross arms. 
 
 Galvanic Battery. (See Battery, Gal- 
 vanic?) 
 
 Galvanic Cell. (See Cell, Voltaic?) 
 
 Galvanic Circle. (See Circle, Galvanic.) 
 
 Galvanic Circuit. (See Circuit, Gal- 
 vanic?) 
 
 Galvanic Dosage. (See Dosage, Gal- 
 vanic?) 
 
 Galvanic Electricity. (See Electricity, 
 Galvanic?) 
 
 Galvanic Excitability of Nerve or Mus- 
 vjular Fibre. (See Excitability, Electric, 
 of Nerve or Muscular Fibre?) 
 
 Galvanic Irritability. (See Irritability, 
 Galvanic?^ 
 
245 
 
 [Gal. 
 
 Galvanic Multiplier. (See Multiplier, 
 Galvanic?) 
 
 Galvanic Polarization. (See Polariza- 
 tion, Galvanic?) 
 
 Galvanic Taste. (See Taste, Galvanic?) 
 
 Galvanism. A term sometimes employed 
 to express the effects produced by voltaic 
 electricity. 
 
 Galvanization, Central A variety 
 
 of general galvanization in which the kathode 
 is placed on the epigastrium and the anode 
 moved over the body. 
 
 Galvanization, Electro-Metallurgical 
 The process of covering any conduc- 
 tive surface with a metallic coating by elec- 
 trolytic deposition, such, for example, as the 
 thin copper coating deposited on the carbon 
 pencils or electrodes used in systems of arc 
 lighting. 
 
 The term is borrowed from the French, in 
 which it has the above signification. It is prefer- 
 ably replaced by the term electro-plating. (See 
 Plating, Electro.) 
 
 The term galvanization is never correctly ap- 
 plied to the process for covering iron with zinc or 
 other metal by dipping the same in a bath of 
 molten metal. 
 
 Galvanization, Electro-Therapeutical 
 
 In electro-therapeutics, the effects 
 produced on nervous or muscular tissue by 
 the passage of a voltaic current. 
 
 Galvanization, General A method 
 of applying a current therapeutically by the 
 use of electrodes of sufficient size to direct 
 the current through practically the entire 
 body. 
 
 Galvanization, Labile - A term 
 employed in electro-therapeutics, in contradis- 
 tinction to stabile galvanization, to designate 
 the method of applying the current by keep- 
 ing one electrode at rest in firm contact with 
 one part of the body, and connecting the other 
 electrode to a sponge which is moved over 
 the parts of the body that are to be treated. 
 
 Galvanization, Local The applica- 
 tion of galvanization to parts or organs of the 
 body in contradistinction to general galvani- 
 zation. 
 
 Galvanization, Stabile A term 
 
 employed in electro-therapeutics in which the 
 current is caused to pass continuously and 
 steadily through the portions of the body un- 
 dergoing galvanization. 
 
 In stabile galvanization, the current is applied 
 to and removed from the body gradually, in order 
 to avoid shocks at the beginning and end of the 
 application. 
 
 Galvanized Iron. (See Iron, Galvan- 
 ized?) 
 
 Galvano. A word sometimes used in 
 France in place of the word electro, to signify 
 an article reproduced in copper by electro- 
 metallurgy, especially an electrotype or wood- 
 cut. 
 
 Galvano-Causty. (See Causty, Galvano.) 
 
 Galvano-Cautery. (See Cautery, Gal- 
 vano?) 
 Galvano-Cautery, Chemical A 
 
 term sometimes applied to electro puncture 
 or the application of electrolysis to the treat- 
 ment of diseased growths. (See Cautery, 
 Electric. Puncture, Electro?) 
 
 The term chemical galvano-cautery would ap- 
 pear to be poorly chosen, as it would imply the 
 existence of a cautery action, which in point of 
 fact does not exist 
 
 Galvano-Faradization. In electro-thera- 
 peutics, the simultaneous excitation of a nerve 
 or muscle by both a voltaic and a faradic cur- 
 rent. 
 
 Galvano-Magnet. A term sometimes used 
 for electro-magnetic. 
 
 Electro magnetic is by far the preferable term, 
 and is almost universally employed in the United 
 States. 
 
 Galvanometer. An apparatus for meas- 
 uring the strength of an electric current by 
 the deflection of a magnetic needle. 
 
 The galvanometer depends for its operation on 
 the fact that a conductor, through which an elec- 
 tric current is flowing, will deflect a magnetic 
 needle placed near it. This deflection is due to 
 the magnetic field caused by the current. (See 
 Field, Magnetic, of an Electric Current.) 
 
 This action of the current was first discovered 
 by Oersted. A wire conveying a current in the 
 
Gal.] 
 
 246 
 
 [Gal. 
 
 direction shown by the straight arrow, Fig. 264, 
 or from + to , will deflect a magnetic needle in 
 the direction shown by the curved arrows. 
 
 The following rules show the direction of the 
 
 Fig. 264. Oersted's Experiment. 
 
 deflection of a magnetic pole by an electrical cur- 
 rent : 
 
 (I.) Place the right hand on the conductor 
 through which the current is flowing, with the 
 palm facing the north pole, and with the fingers 
 pointing in the direction of the current. The 
 thumb will indicate the direction in which the 
 north pole tends to move. 
 
 (2.) Suppose an ordinary corkscrew so placed 
 along the conductor, through which a current of 
 electricity is passing, that when twisted, it will 
 move in the direction of the current. The han- 
 dle will then turn in the direction in which the 
 north pole of the magnet tends to move. 
 
 (3.) Imagine one swimming along the con- 
 ductor in the direction of the current and facing 
 the magnet. The north pole wiil tend to move 
 towards the left hand of the swimmer. 
 
 Prof. Forbes has shown that the direction of 
 the deflection of a magnet by a current is such 
 A B C 
 
 Fig. 265. Amptre's Apparatus. 
 
 that if the magnet were flexible, it would wrap 
 itself round the current. 
 
 If the wire be bent in the form of a hollow rec- 
 tangle F, D, E, G, Fig. 265, and the needle, M, 
 
 be placed inside the circuit, the upper and lower 
 branches of the current will deflect the needle in 
 the same direction, and the effect of the current 
 will thus be multiplied. Mercury cups are pro- 
 vided at A, B and C, for a ready change in the 
 direction of the current. (See Needle, Astatic.) 
 
 This principle of the multiplication of the de- 
 flecting power of a current was first applied to gal- 
 vanometers by Schweigger, who used a number of 
 turns of insulated wire for the purpose of obtain- 
 ing a greater deflection of the needle. He called 
 such a device a multiplier. In extremely sensi- 
 tive galvanometers, very many turns of wire are 
 employed, in some cases amounting to many 
 thousands. Such galvanometers are of high re- 
 sistance. Others, of low resistance, often con- 
 sist of a single turn of wire and are used in the 
 direct measurement of large currents. 
 
 A Schweigger's multiplier or coil C, C, oi 
 many turns of insulated wire, is shown in Fig. 266. 
 The action of such a coil on the needle M, is com- 
 paratively great, even when the current is small. 
 
 Fig. 266- Schweigger's Multiplier. 
 
 In the case of any galvanometer, when no cur- 
 rent is passing, the needle, when at rest, should in 
 general occupy a position parallel to the plane of 
 the coiL On the passage of the current, the 
 needle tends to place itself in a position at right 
 angles to the direction of the current, or to the 
 length of the conducting wire in the coil. The 
 strength of the current passing is determined by 
 observing the amount of this deflection as meas- 
 ured in degrees on a graduated circle over which 
 the needle moves. 
 
 The needle is deflected by the current from a 
 position of rest, either in the earth's magnetic 
 field or in a field obtained from a permanent or 
 an electro magnet In the first case, when in use 
 to meamre a current, the plane of the galvanom- 
 eter coils must coincide with the planes of the 
 magnetic meridian. In the other case, the instru- 
 
Gal.] 
 
 247 
 
 [Gal. 
 
 ment may be used in any position in which the 
 needle is free to move. 
 
 Galvanometers assume a variety of forms ac- 
 cording either to the purposes for which they are 
 employed, or to the manner in which their deflec- 
 tions are valued. 
 
 Galvanometer, Absolute A galva- 
 nometer whose constant can be calculated 
 with an absolute calibration. (See Calibra- 
 tion, Absolute?) 
 
 Such a galvanometer is called absolute because 
 if the dimensions of its coil and needle are known, 
 the current can be determined directly from the 
 observed deflection of the needle. 
 
 Galvanometer, Aperiodic A gal- 
 vanometer the needle of which comes to its 
 position without any oscillation. 
 
 A dead-beat galvanometer. (See Galva- 
 nometer, Dead-Beat?) 
 
 Galvanometer, Astatic A galva- 
 nometer, the needle of which is astatic. (See 
 Needle, Astatic?] 
 
 Nobili's astatic galvanometer is shown in Fig. 
 267. The astatic needle, suspended by a fibre b, 
 has its lower needle placed inside a coil, a, con- 
 sisting of many turns of insulated wire, its upper 
 needle moving over the graduated dial. The cur- 
 rent to be measured is led into and from the 
 coil at the binding posts, x and y. 
 
 Fig. 267. Astatic Galvanometer. 
 
 In this instrument, if small deflections only are 
 employed, the deflections are sensibly propor- 
 tional to the strength cf the deflecting currents. 
 
 Galvanometer, Ballistic A galva- 
 nometer designed to measure the strength of 
 currents that last but for a moment, such, for 
 example, as the current caused by the dis- 
 charge of a condenser. 
 
 The quantity of electricity passing in any cir- 
 cuit is equal to the current multiplied by the time. 
 Since the current caused by the discharge of a 
 condenser lasts but for a small time, during which 
 it passes from zero to a maximum and back again 
 to zero, the magnetic needle in a ballistic galva- 
 nometer takes the form of a ballistic pendulum, 
 i. e., it is given such a mass, and acquires such a 
 slow motion, that its change of position does not 
 
 Fig. 268. Ballistic Galvanometer. 
 
 practically begin until the impulses have ceased 
 to act. 
 
 In the ballistic galvanometer of Siemens and 
 Halske, the coils R, R, Fig. 268, have a bell- 
 shaped magnet, M, suspended inside them by 
 means cf an aluminium wire. The magnet is pro- 
 vided with a mirror S, for measuring the deflec- 
 tions. The bel'-shap-d magnet is shown in ele- 
 vation at M, and i.i p'ane at n, s. 
 
 In using the ballistic galvanometer, it is neces- 
 sary to see that the needle is absolutely at rest be- 
 fore the charge is sent through the coils. 
 
 A form of ballistic galvanometer by Nalder is 
 shown in Fig. 269. 
 
 The ordinary form of compensating magnet 
 is, in this galvanometer, replaced by the small mag- 
 net A, capable of rotation in a horizontal plane, but 
 incapable of being raised or lowered, as is usual 
 in such magnets. This form of compensating mag- 
 net possesses the advantage of being able to alter 
 the direction of the field on the needle system, 
 
Gal.] 
 
 248 
 
 [Gal. 
 
 without considerably altering its intensity. When 
 the galvanometer is for ready use the magnet A, is 
 turned until the needle is brought to zero. The 
 
 Fig. 2bg. Nalder's Galvanometer. 
 
 combined field of earth and magnet A, are then 
 brought to the degree of sensitiveness required 
 
 Fig. 270. Nalder's Galvanometer. 
 by rotating, magnet B, on its shaft, or altering 
 its distance from the needle. In order to insure 
 ease in replacing the fibre, the front coil is hinged 
 as shown. The fibre D, is supported on E, one 
 end of which it is free to turn, so as to permit of 
 the removal of torsion; D, being twisted can be 
 raised or lowered at E. The needle system with 
 heavy bell-shaped magnet is shown in Fig. 270. 
 
 Galvanometer, Combined Tangent and 
 
 Sine A galvanometer furnished with 
 
 two magnetic needles of different lengths. 
 The small needle is used for tangent measure- 
 ments, and the long needle for sine measure- 
 ments. 
 
 Galvanometer Constant. (See Constant, 
 Galvanometer?) 
 
 Galvanometer, Dead-Beat A gal- 
 vanometer, the needle of which comes quickly 
 to rest, instead of swinging repeatedly to-and- 
 fro. (See Damping?) 
 
 Galvanometer, Deprez-D'Arsonval 
 
 A form of dead-beat galvanometer. 
 
 The movable part of the Deprez-D'Arsonval 
 galvanometer consists of a light rectangular coil 
 
 C, Fig. 271, of many turns of wire, supported 
 
 by two silver wires H J and D E, between the 
 
 poles of a strong permanent horseshoe magnet 
 
 A A. The position of 
 
 the coil may be altered 
 
 as to height by screws 
 
 at H and E. The sup- 
 
 porting wires, prevent 
 
 by their torsion the 
 
 swinging cf the coil, as 
 
 does also the cylinder 
 
 of soft iron B, placed 
 
 inside the coil, and sup- 
 
 ported independently 
 
 of it. The movements if 
 
 of the coil are observed 
 
 by means of a spot of 
 
 light reflected from a 
 
 mirror J, attached to 
 
 the wire H J. 
 
 Galvanometer, Detector -- A form of 
 galvanometer employed for rough testing 
 work. 
 
 A form of detector galvanometer is shown in 
 Fig. 272. 
 
 271. Deprez-D" Arson- 
 val Galvanometer. 
 
 Fig. 2J 2. Detector Galvanometer. 
 
 A gal- 
 vanometer containing two coils so wound as 
 to tend to deflect the needle in opposite 
 directions. 
 
 The needle of a differential galvanometer shows 
 no deflection when two equal currents are sent 
 through the coils in opposite directions, since, 
 under these conditions, each coil neutralizes the 
 other's effects. Such instruments may be used 
 in comparing resistances. The Wheatstone 
 Bridge, however, in most cases, affords a prefer- 
 able method for such purposes. (See Bridge 
 Electric. ) 
 
Gal.] 249 
 
 A form of differential galvanometer is shown in 
 
 Fig- 273- 
 
 Sometimes the current is so sent through the 
 two coils, that each 
 coil deflects the nee- 
 dle in the same di- 
 rection. In this case 
 the instrument is no 
 longer differential in 
 action. 
 
 If the magnetic 
 needle, in such cases, 
 is suspended at the 
 exact centre of the 
 line which joins the 
 centres of the coils, 
 the advantage is 
 gained by obtaining 
 a field of more nearly 
 
 uniform intensity F 'S- 2 73- Differential Galva- 
 around the needle. nomtttr. 
 
 Galvanometer, Figure of Merit of 
 
 The reciprocal of the current required to pro- 
 duce a deflection of the galvanometer needle 
 through one degree of the scale. 
 
 The smaller the current required to produce a 
 deflection of one degree, the greater the figure 
 of merit, or the greater the sensitiveness of the 
 galvanometer. 
 
 Galvanometer, Marine A galva- 
 nometer devised by Sir William Thomson for 
 use on steamships where the motion of mag- 
 netized masses of iron would seriously disturb 
 the needles of ordinary instruments. 
 
 An unscreened needle would be so much af- 
 fected by the motion of the engines, the shaft and 
 the screw, as to be useless for galvanometric 
 measurement. 
 
 The needle of the marine galvanometer is 
 shielded or cut off from the extraneous fields so 
 produced, by the use of a magnetic screen or 
 shield, consisting of an iron box with thick sides, 
 inside of which the instrument is placed. 
 
 The needle is suspended by means of a silk 
 fibre attached both above and below, in line with 
 the centre of gravity of the needle. In this man- 
 ner, the oscillations of the ship do not affect the 
 needle. 
 
 Galvanometer, Mirror A galva- 
 nometer in which, instead of reading the de- 
 flections of the needle directly by its move- 
 
 [Gal, 
 
 ments over a graduated circle, they are read 
 by the movements of a spot of light reflected 
 from a mirror attached to the needle. 
 
 This spot of light moves over a graduated 
 scale, or its movements are observed by means of 
 a telescope. 
 
 Fig. 2-j 4. Mirror Galvanometer. 
 
 A form of mirror galvanometer designed by Sir 
 William Thomson is shown in Fig. 274. Tht 
 needle is attached directly to the back of a light, 
 silvered glass mirror, and consists of several small 
 magnets made of pieces of a watch spring. The 
 needle and mirror are suspended by a single silk 
 fibre and are placed inside the coil. A compen- 
 sating magnet N S, movable on a vertical axis, is 
 used to vary the sensitiveness of the instrument. 
 The lamp L, placed back of a slot in a wide 
 screen, throws a pencil of light on the mirror Q, 
 from which it is reflected to the scale K. 
 
 A form of lamp and scale with slot for light is 
 shown in Fig. 275. 
 
 Fig. 2JS. Galvanometer Lamp and Scale. 
 
 Galvanometer, Potential A term 
 
 sometimes applied to a voltmeter. (See 
 Voltmeter?) 
 
 Galvanometer, Reflecting A term 
 
 sometimes applied to a mirror galvanometer, 
 (See Galvanometer, Mirror) 
 
Gal.] 
 
 250 
 
 [Gal. 
 
 Galvanometer, Sensibility of 
 
 The 
 
 readiness and extent to which the needle of a 
 galvanometer responds to the passage of an 
 electric current through its coils. (See Gal- 
 vanometer^) 
 
 Galvanometer-Shunt. (See Shunt, Gal- 
 vanometer?) 
 
 Galvanometer, Sine A galva- 
 nometer in which a vertical coil is movable 
 around a vertical axis, so that it can be made to 
 follow the magnetic needle in its deflections. 
 
 In the sine galvanometer, the coil is moved so 
 as to follow the needle until it is parallel with the 
 coil. Under these circumstances, the strength 
 of the deflecting currents in any two different 
 cases is proportional to the sines of the angles of 
 deflection. 
 
 A form of sine galvanometer is shown in Fig. 
 276. The vertical wire coil is seen at M. A 
 needle of any length less than the diameter of the 
 coil M, moves over the graduated circle N. The 
 coil M, is movable over the graduated horizontal 
 circle H, by which the amount of the movement 
 
 276. Sine Galvanometer. 
 
 necessary to bring the needle to zero is measured. 
 The current strength is proportional to the sine 
 of the angle measured on this circle, through 
 which it is necessary to move the coil M, from its 
 
 position when the needle is at rest in the plane of 
 the earth's magnetic meridian, until the needle 
 is not further deflected by the current, although 
 parallel to the coil M. 
 
 Galvanometer, Tangent An instru- 
 ment in which the deflecting coil consists of 
 a coil of wire within which is placed a needle 
 very short in proportion to the diameter of 
 the coil, and supported at the centre of the 
 coil. 
 
 Fig. 277. Tangent Galvanometer. 
 
 A galvanometer acts as a tangent galvanometer 
 only when the needle is very small as compared 
 with the diameter of the coil. The length of the 
 needle should be less than one-twelfth the diameter 
 of the coil. 
 
 A form of tangent galvanometer is shown in 
 Fig- 277. The needle is supported at the exact 
 centre of the coil C. 
 
 Under these circumstances, the strengths of 
 two different deflecting currents are proportional 
 to the tangents of the angles of deflection. Tan- 
 gent galvanometers are sometimes made with 
 coils of wire containing many separate turns. 
 
 Galvanometer, Tangent, Obach's 
 
 A form of galvanometer in which the deflect- 
 ing coil, instead of being in a fixed vertical 
 position, is movable about a horizontal axis, 
 so as to decrease the delicacy of the instru- 
 ment, and thus increase its range of work. 
 
 Galvanometer, Torsion A galva- 
 nometer in which the strength of the deflecting 
 current is measured by the torsion exerted on 
 the suspension system. 
 
 A ball-shaped magnet, shown at the right of 
 Fig. 278, is suspended by a thread and spiral 
 
Gal.] 
 
 251 
 
 [Gal. 
 
 spring between two coils of high resistance, 
 placed parallel to each other in the positions 
 shown. On the deflection of the magnet, by the 
 current to be measured, the strength of the current 
 is determined by the amount of the torsion re- 
 quired to bring the magnet back to its zero point. 
 
 Pig. 278. Torsion Galvanometer, 
 
 The angle of torsion is measured on the horizontal 
 scale at the top of the instrument. 
 
 In the torsion galvanometer, unlike the electro- 
 dynamometer, the action between the coils and the 
 movable magnet is as the current strength causing 
 the deflection. In the electro-dynamometer, 
 since an increase of current in the deflecting coils 
 also takes place in the deflected coil, the mutual 
 action of the two is as the square of the current 
 strength causing the deflection. 
 
 Galvanometer, Upright A gal- 
 vanometer, the needle of which moves in a 
 vertical plane. (See Galvanometer, Ver- 
 tical. 
 
 Galvanometer, Tertical A gal- 
 vanometer the needle of which is capable of 
 motion in a vertical plane only. 
 
 In the vertical galvanometer, the north pole of 
 the needle is weighted so that the needle as- 
 sumes a vertical position when no current is pass- 
 ing. In the form shown in Fig. 279, two needles 
 9 Vol. 1 
 
 are sometimes employed, one of which is placed 
 inside the coils C, C. 
 
 The vertical galvanometer is not as sensitive as 
 the ordinary forms. It is employed, however, 
 in various forms for an 
 electric current indica- 
 tor, or even for a 
 rough current meas- 
 
 Galvanometer 
 Voltmeter. An in- 
 strument devised by 
 Sir William Thom- 
 son, for the meas- 
 urement of differ- 
 ences of electric 
 potential. 
 
 Fig, 2TQ. Vertical Galva- 
 nometer. 
 
 This instrument is so arranged that by a single 
 correction for the varying strength of the earth's 
 field in any place, the results are read at once in 
 volts. 
 
 A coil of insulated wire shown at A, Fig. 280, 
 has a resistance of over 5,000 ohms. A magnetic 
 needle, formed of short parallel needles placed 
 above one another, and called a magnetometer 
 needle, is attached to a long but light aluminium 
 index, moving over a graduated scale. A mova- 
 ble, semi-circular magnet B, called the restoring 
 magnet, is placed over the needle, and is used 
 for varying the effect of the earth's field at any 
 point. The sensitiveness of the instrument may 
 be varied either by the restoring magnet or by 
 sliding the magnetometer box nearer to or further 
 away from the coil. 
 
 The voltmeter galvanometer depends for its 
 operation on the fact that when a galvanometer 
 of sufficiently high resistance is introduced be- 
 
 Fig. 280. Galvanometer Voltmeter. 
 
 tween any two points in a circuit, the current that 
 passes through it, and hence the defiection of its 
 needle, is directly proportional to the difference 
 of potential between such two points. 
 
Gal.] 
 
 252 
 
 [Gas. 
 
 Galvanometers for the commercial measure- 
 ments of currents assume a variety of forms. 
 They are generally so constructed as to read off 
 the amperes, volts, ohms, watts, etc., directly. 
 They are called amperemeters or ammeters, volt- 
 meters, ohmmeters, wattmeters, etc. For their 
 tiller description reference should be had to 
 standard works on electrical measurement. 
 
 Galranometric. Of or pertaining to the 
 galvanometer. (See Galvanometer?) 
 
 Galvanometrical. Of or pertaining to the 
 galvanometer. (See Galvanometer.} 
 
 Galvanometrically. In a galvanometric 
 manner. 
 
 Galvano-Plastics. (See Plastics, Gal- 
 vano) 
 
 Galvanoplasty. The art of galvano- 
 plastics. (See Plastics, Galvano) 
 
 GalYano-Puncture. (See Puncture, Gal- 
 vano) 
 
 Galvanoscope. A term sometimes im- 
 properly employed in place of galvanometer. 
 
 A galvanoscope, strictly speaking, is an instru- 
 ment intended rather to show the existence of an 
 electric current than to measure it in degrees. 
 It may, however, be roughly calibrated, and then 
 it differs from a galvanometer only in delicacy 
 and accuracy. 
 
 Galvano-Therapeutics. A term some- 
 times used for electro-therapeutics. 
 
 Electro therapeutics is by far the preferable 
 term and is almost universally employed in the 
 United States. 
 
 Gap, Air A gap, or opening in 
 
 a magnetic circuit containing air only. (See 
 Gap, Air, Magnetic?) 
 
 The air gap between two magnetic poles may 
 be regarded as the space in which an armature 
 acting as a magneto receptive device is placed, 
 which by the action upon it of the lines of mag- 
 netic force passing through the gap has differ- 
 ences of potential generated in its coils of insulated 
 wire. 
 
 Gap, Air, Magnetic A gap filled 
 
 with air which exists in the opening at any 
 part of a core of iron or other medium of high 
 permeability. 
 
 The space between the pole pieces and arma- 
 
 ture core is called the air gap in dynamos or 
 motors even though partly filled with copper con- 
 ductors. It is also called the interference space. 
 
 The gap or air space of an electro-magnet de- 
 creases the strength of its magnetization be- 
 cause 
 
 The increased reluctance of the air gap causes 
 a decrease in the number of lines of magnetic 
 force which pass through the magnetic circuit. 
 
 Gap, Spark A gap forming part of 
 
 a circuit between two opposing conductors, 
 separated by air, or other similar dielectric 
 which is closed by the formation of a spark 
 only when a certain difference of potential 
 is attained. 
 
 Gap, Wire-Gauge (See Gauge, 
 
 Wire, Gap.) 
 
 Gas-Battery. (See Battery, Gas) 
 
 Gas Burner, Argand, Plain-Pendant, 
 
 Electric (See Burner, Argand 
 
 Electric, Plain-Pendant) 
 
 Gas Burner, Argand, Ratchet-Pendant, 
 Electric (See Burner, Argand Elec- 
 tric, Ratchet-Pendant) 
 
 Gas Burner, Automatic Electric 
 
 (See Burner, Automatic Electric) 
 
 Gas Burner, Plain-Pendant, Electric 
 --(See Burner, Plain-Pendant Elec- 
 tric) 
 
 Gas Burner, Ratchet-Pendant, Electric 
 (See Burner, Ratchet-Pendant Elec- 
 tric) 
 
 Gas-, Carbonic Acid A gaseous sub- 
 stance formed by the union of one atom of 
 carbon with two atoms of oxygen. 
 
 Carbonic acid gas is formed during the com- 
 bustion of carbon by a sufficient supply of air. 
 
 Gas, Dielectric Density of A term 
 
 sometimes emploved instead of dielectric 
 strength of gas. (See Gas, Dielectric 
 Strength of) 
 
 Gas, Dielectric Strength of The 
 
 strain a gas is capable of bearing without 
 suffering disruption, or without permitting a 
 disruptive discharge to nass through it. 
 
 The dielectric strength of a gas depends 
 
 (I.) On the nature of the gas. 
 
 (2.) On its pressure. 
 
Gas.] 
 
 253 
 
 [Gau. 
 
 It has been calculated roughly that it requires 
 40,000 volts per centimetre to pass a disruptive 
 discharge through dry air at ordinary pressures. 
 
 Gas-Jet, Carcel Standard (See 
 
 Car eel Standard Gas- Jet.) 
 
 Gas-Jet Photometer. (See Photometer.) 
 
 Gas-Lighting, Electric The electric 
 
 ignition of a gas-jet from a distance. 
 
 Gas-Lighting-, Multiple Electric 
 
 A system of electric gas-lighting in which a 
 number of gas-jets are lighted by means of 
 a discharge of high electromotive force, 
 derived from a Ruhmkorff coil or a static 
 induction machine. 
 
 Such devices are operated by means of minute 
 electric sparks which are 
 caused to pass through 
 the escaping gas-jets. 
 
 The spark for this pur- 
 pose is obtained either by 
 means of the extra current 
 from a spark coil, by means 
 of an induction coil or by 
 static discharges. (See 
 Currents, Extra. Coil, 
 Spark. Coil, Induction.) 
 
 A gas tip for use in multiple gas-lighting ap- 
 paratus is shown in Fig. 281. The spark is 
 formed immediately over the slot in the burner, 
 and therefore ignites the escaping gas. 
 
 Gas, Occlusion of The absorption 
 
 or shutting up of a gas in the pores, or on the 
 surfaces of various substances. 
 
 Carbon possesses in a marked degree the prop- 
 erty of occluding or absorbing gases in its pores. 
 These occluded gases must be driven out from the 
 carbon conductor employed in an incandescent 
 lamp, since otherwise their expulsion, on the in- 
 candesence of the carbon, consequent on the light- 
 ing of the lamp, will destroy the high vacuum of 
 the lamp chamber and thus lead to the ultimate 
 destruction of the filament (See Lamp, Electric, 
 Incandescent. ) 
 
 Gassing. The evolution of gas from the 
 plates of a storage or secondary cell. 
 
 Gastroscope. An electric apparatus for 
 the illumination and inspection of the human 
 stomach. 
 
 Fig. 28 r. Multifile Gas- 
 yet. 
 
 The light is obtained by means of a platinum 
 spiral in a glass tube surrounded by a layer of 
 water to prevent undue heating. The platinum 
 spiral is placed at the extremities of a tube, pro- 
 vided with prisms, and passed into the stomach 
 of the patient. A separate tube for the supply 
 of air for the extension of the stomach is also 
 provided. 
 
 Gastroscopy. The examination of the 
 stomach by the gastroscope. (See Gastro- 
 scope.) 
 
 Gange, Battery. A form of portable gal- 
 vanometer, suitable for ordinary testing work. 
 A form of battery gauge is shown in Fig. 282. 
 
 Fig. 282. Battery Gauge. 
 
 Gauge, Electrometer A device em- 
 ployed in connection with some of Sir Wil- 
 liam Thomson's electrometers to ascertain 
 whether the needle, connected with the layer 
 of acid that acts as the inner coating of the 
 Leyden jar used in connection therewith, is at 
 its normal potential. 
 
 Gauge, Wire, American 
 
 A name 
 
 sometimes applied to the Brown & Sharpe 
 Wire Gauge. (See Gauges, Wire, Varieties 
 of.) 
 
 Gange, Wire, Birmingham A term 
 
 sometimes applied to one of the English wire 
 gauges. 
 
 Gauge, Wire, Gap A wire gauge in 
 
 which gaps are left for the introduction of the 
 wire to be measured, 
 
Gau.] 
 
 254 
 
 [Gau. 
 
 Gauge, Wire, Micrometer A gauge 
 
 employed for accurately measuring the di- 
 ameter of a wire in thousandths of an inch, 
 based on the principle of the vernier or mi- 
 crometer. (See Fig. 283.) 
 
 The wire to be measured is placed between a 
 fixed support B, and the end C, of a long mova- 
 ble screw, which accurately fits a threaded tube a. 
 A thimble D, provided with a milled head, fits 
 over the screw C, and is attached to the upper 
 part. The lower circumference of D, is divided 
 into a scale of twenty equal parts. The tube A,is 
 graduated into divisions equal to the pitch of the 
 screw. Every fifth of these divisions is marked 
 as a larger division. 
 
 The principle of the operation of the gauge is 
 as follows: Suppose the screw has fifty threads to 
 the inch, the pitch of the screw, or the distance 
 between two contiguous threads, is therefore ^ 
 or .02 of an inch. 
 
 One complete turn of the screw will, therefore, 
 advance the sleeve D, over the scale a, the .02 of 
 an inch. If the screw is only moved through 
 one of the twenty parts marked on the end of 
 the thimble or sleeve parts, or the ^ of a com- 
 
 plete turn, the end C, advances towards B, the 
 
 sV of ?V> *' * Tinnr or I mc h- 
 
 Suppose now a wire is placed between B and 
 C, and the screw advanced until it fairly fills the 
 
 Fig. 283. Vernier Wire Gauge. 
 space between them, and the reading shows two 
 of the larger divisions on the scale a, three of the 
 smaller ones and three on the end of the sleeve 
 D, then 
 
 Two large divisions of scale a = .2 inch 
 
 Three smaller divisions of scale a.. = .06 " 
 Three divisions on circular scale 
 
 onD = .003 " 
 
 Diameter of wire .263 
 
 Serious inconvenience has arisen in practice 
 
 NEW LEGAL STANDARD WIRE GAUGE (ENGLISH). 
 Tables of Sizes, Weights, Lengths and Breaking Strains of Iron Wire. 
 
 Size on 
 Wire 
 
 Gauge, 
 
 Diameter. 
 
 Sectional 
 area in 
 sq. inches. 
 
 Weight of 
 
 Length of 
 Cwt. 
 
 Breaking Strains. 
 
 Size on 
 Wire 
 Gauge. 
 
 Inch. 
 
 Millimetres. 
 
 ioo yards. 
 
 Mile. 
 
 Annealed. 
 
 Bright. 
 
 
 500 
 464 
 
 432 
 400 
 
 37' 
 348 
 324 
 300 
 276 
 252 
 232 
 
 212 
 192 
 
 55 
 
 1 60 
 
 144 
 
 128 
 
 116 
 104 
 092 
 080 
 072 
 064 
 056 
 048 
 040 
 036 
 
 12.7 
 
 n. 8 
 n. 
 
 IO.2 
 
 9-4 
 
 8.8 
 
 8.2 
 
 7.6 
 
 e: 4 
 
 5-9 
 5-4 
 4-9 
 4-5 
 4.1 
 3-7 
 3-3 
 
 1.6 
 
 2.3 
 
 2. 
 
 1.8 
 1.6 
 1.4 
 
 1.2 
 I. 
 
 .9 
 
 1963 
 1691 
 1466 
 1257 
 1087 
 0951 
 0824 
 0707 
 0598 
 0499 
 0423 
 
 353 
 0290 
 0243 
 
 0201 
 0163 
 OI29 
 010)6 
 0085 
 0066 
 0050 
 O04I 
 0032 
 OO2, 
 00l8 
 0013 
 
 0010 
 
 Lbs. 
 
 '93 -4 
 166.5 
 144.4 
 123.8 
 107.1 
 93-7 
 
 69.9 
 58.9 
 49.1 
 41.6 
 34-8 
 28.0 
 24. 
 19 8 
 16. 
 12.7 
 10.4 
 
 ' 4 
 6.5 
 
 5- 
 4- 
 3-2 
 2.4 
 1.8 
 
 1.2 
 I. 
 
 Lbs. 
 
 344 
 2930 
 2541 
 2179 
 1885 
 1649 
 1429 
 1225 
 i37 
 864 
 732 
 612 
 502 
 422 
 348 
 282 
 223 
 '83 
 148 
 114 
 88 
 
 7 
 56 
 42 
 3 2 
 
 21 
 
 18 
 
 Yards. 
 
 58 
 67 
 78 
 
 9 1 
 105 
 
 120 
 138 
 101 
 
 190 
 
 228 
 
 269 
 
 322 
 
 393 
 467 
 566 
 700 
 882 
 1077 
 
 1333 
 1723 
 2240 
 2800 
 3soo 
 4067 
 6222 
 9333 
 
 11200 
 
 Lbs. 
 10470 
 9017 
 7814 
 6702 
 5796 
 5072 
 4397 
 377 
 
 3'9 
 2660 
 
 2254 
 1883 
 
 1544 
 1298 
 1072 
 869 
 687 
 564 
 454 
 355 
 268 
 218 
 172 
 131 
 
 97 
 67 
 
 55 
 
 Lbs. 
 15700 
 13525 
 11725 
 10052 
 8694 
 7608 
 6595 
 5655 
 4785 
 399 
 338i 
 2824 
 2316 
 1946 
 1608 
 
 1303 
 1030 
 
 845 
 680 
 532 
 402 
 326 
 257 
 197 
 MS 
 
 IOO 
 
 82 
 
 7/0 
 6/0 
 5/o 
 4/0 
 3/o 
 
 2/0 
 
 1/0 
 
 I 
 
 2 
 
 3 
 4 
 
 I 
 
 8 
 
 9 
 10 
 ii 
 
 12 
 '3 
 
 '4 
 15 
 16 
 17 
 18 
 '9 
 
 20 
 
 6>o 
 
 S/o 
 
 
 **f 
 
 
 
 
 
 3 
 
 
 6 
 
 
 I....... 
 
 
 
 
 
 
 
 
 5 
 
 
 I....... 
 
 
 
 
 (Issued by the Iron and Steel Wire Manufacturers' Association.) 
 
tiau.] 
 
 255 
 
 [Gau. 
 
 from the numerous arbitrary numbers of sizes of 
 wires employed by different manufacturers. 
 These differences are gradually leading to the 
 abandonment of arbitrary sizes for wires and em- 
 ploying in place thereof the diameters directly in 
 inches or thousandths of an inch. 
 
 Gauge, Wire, Bound A device for 
 
 accurately measuring the diameter of a wire. 
 
 The round wire gauge shown in Fig. 284 is 
 very generally used for telegraph lines. Notches 
 
 Fig. 284. Round Wire Gauge. 
 
 for varying widths, cut in the edges of a circular 
 plate of tempered steel, serve to approximately 
 measure the diameter of a wire, the sides of the 
 wire being passed through the slots. Numbers, 
 indicating the different sizes of the wire, are 
 affixed to each of the 
 openings. 
 
 Gauge, Wire, Self- 
 Registering A 
 
 wire gauge arranged 
 to give the exact di- 
 ameter of the wire to 
 be measured directly 
 without calculation. 
 
 A form of self- register- 
 ing wire gauge is shown 
 in Fig. 285. The wire 
 or plate is inserted in the 
 gap between a fixed and Fig-. 283. Wire and 
 a movable plate. The Ptate Gauge. 
 
 numbers corresponding to the diameter of the 
 wire or plate are shown on one side of the gauge 
 and the gauge numbers on the other side. 
 
 Gauge, Wire, Standard A wire 
 
 gauge adopted by the National Telephone 
 Exchange Association at Providence, R. I., 
 and by the National Electric Light As- 
 sociation, at Baltimore, Md., in February, 
 1886. 
 
 The value of the standard as compared with 
 the other gauges will be seen from an inspection 
 of the table in this column: 
 
 Gauges, Wire, Varieties of The 
 
 following table gives a comparison of the 
 principal wire gauges in use. 
 
 COMPARISON OF THE DIFFERENT WIRE 
 GAUGES. 
 
 "3 bo 
 
 !- 
 
 s . 
 
 rt 'f< 
 
 *.**, 
 
 *f 
 
 41 
 
 o y 
 
 ^S 
 
 h tit 
 
 .SO 
 
 C fl> 
 
 Jse- 
 
 t- S rt 
 4) *i3 
 
 JJi 
 
 a-s 
 
 I s 
 
 I s 
 
 jjjf 
 
 1r? 
 
 I** 
 
 <5 
 
 ^ 3 
 
 a " 
 
 So 
 
 o 
 
 
 
 m 
 
 2 Is 
 o, s 
 
 oooooo 
 
 
 
 .46 
 
 
 
 
 00000 
 
 
 
 V 
 
 
 
 
 oooo 
 
 . 4 6 
 
 454 
 
 393 
 
 4 
 
 .400 
 
 
 000 
 
 .40964 
 
 425 
 
 .362 
 
 36 
 
 .372 
 
 
 00 
 
 .3648 
 
 38 
 
 331 
 
 33 
 
 .348 
 
 
 o 
 
 32495 
 
 34 
 
 .307 
 
 305 
 
 324 
 
 
 I 
 
 .2893 
 
 3 
 
 283 
 
 .285 
 
 .300 
 
 
 2 
 
 25763 
 
 284 
 
 .263 
 
 .265 
 
 .276 
 
 
 3 
 
 . 22942 
 
 259 
 
 .244 
 
 .245 
 
 .252 
 
 
 4 
 
 .20431 
 
 238 
 
 225 
 
 225 
 
 .232 
 
 
 5 
 
 -i8i 94 
 
 22 
 
 .207 
 
 .205 
 
 .212 
 
 
 6 
 
 . 16202 
 
 203 
 
 .192 
 
 .19 
 
 .192 
 
 
 7 
 
 .14428 
 
 18 
 
 .177 
 
 '75 
 
 .176 
 
 
 8 
 
 .12849 
 
 165 
 
 .162 
 
 .16 
 
 ,160 
 
 
 9 
 
 IT 443 
 
 148 
 
 .148 
 
 .145 
 
 .144 
 
 
 10 
 
 .10189 
 
 '34 
 
 '35 
 
 .13 
 
 .128 
 
 
 n 
 
 .090742 
 
 12 
 
 .12 
 
 .1175 
 
 .116 
 
 
 12 
 
 .080808 
 
 109 
 
 .105 
 
 .105 
 
 .104 
 
 
 13 
 
 .071961 
 
 095 
 
 .092 
 
 .0925 
 
 
 
 '4 
 
 .064084 
 
 08 3 
 
 .oi 
 
 08 
 
 .080 
 
 .083 
 
 IS 
 
 -057068 
 
 072 
 
 .072 
 
 .07 
 
 .072 
 
 .072 
 
 16 
 
 05082 
 
 06 S 
 
 .063 
 
 .061 
 
 .064 
 
 -065 
 
 17 
 
 .045257 
 
 OSB 
 
 .052 
 
 0525 
 
 .056 
 
 .058 
 
 18 
 
 .040303 
 
 049 
 
 .047 
 
 045 
 
 .048 
 
 049 
 
 '9 
 
 3S390 
 
 042 
 
 .041 
 
 039 
 
 .040 
 
 .04 
 
 20 
 
 .031961 
 
 035 
 
 .035 
 
 .034 
 
 .036 
 
 035 
 
 21 
 
 .028462 
 
 032 
 
 .032 
 
 
 .032 
 
 0315 
 
 22 
 
 .025^47 
 
 028 
 
 .028 
 
 27 
 
 .028 
 
 .0295 
 
 23 
 
 .022571 
 
 025 
 
 .025 
 
 .024 
 
 .024 
 
 .027 
 
 24 
 
 .0201 
 
 022 
 
 .023 
 
 .0215 
 
 .022 
 
 .025 
 
 2=; 
 
 .0179 
 
 02 
 
 .02 
 
 .019 
 
 .020 
 
 .023 
 
 26 
 
 .01594 
 
 018 
 
 .Ol8 
 
 .018 
 
 .018 
 
 .0205 
 
 27 
 
 .014195 
 
 016 
 
 .017 
 
 .017 
 
 .0164 
 
 .01875 
 
 28 
 
 .012641 
 
 014 
 
 .Ol6 
 
 .016 
 
 .0148 
 
 .0165 
 
 29 
 
 .011257 
 
 013 
 
 .015 
 
 015 
 
 .0136 
 
 .0155 
 
 3 
 
 .OIOO25 
 
 012 
 
 .014 
 
 .014 
 
 .OT24 
 
 CI375 
 
 3 1 
 
 .008928 
 
 01 
 
 .0135 
 
 .013 
 
 .OIl6 
 
 .01225 
 
 32 
 
 .00795 
 
 009 
 
 013 
 
 .012 
 
 .OI08 
 
 .01125 
 
 33 
 
 .00708 
 
 008 
 
 .Oil 
 
 .Oil 
 
 .0100 
 
 .01025 
 
 34 
 
 .006304 
 
 007 
 
 .OI 
 
 .OI 
 
 .0092 
 
 .0095 
 
 35 
 
 .005614 
 
 005 
 
 .0095 
 
 .OOg 
 
 .0084 
 
 .009 
 
 36 
 
 .005 
 
 004 
 
 .009 
 
 .COO 
 
 .0076 
 
 0075 
 
 37 
 
 .004453 
 
 
 .0085 
 
 .00725 
 
 .0068 
 
 .0065 
 
 38 
 
 .003965 
 
 
 .008 
 
 .0065 
 
 .006 
 
 .00575 
 
 39 
 
 003531 
 
 
 .0075 
 
 00575 
 
 .005^ 
 
 .005 
 
 40 
 
 .003144 
 
 
 .007 
 
 .005 
 
 .0048 
 
 .0045 
 
 
 
 
 
 1 
 
 
 
256 
 
 [Gau. 
 
 NUMBER, DIAMETER, WEIGHT, LENGTH AND RESISTANCE OF PURE COPPER 
 
 WIRE. 
 
 American Gauge. 
 
 No. 
 
 Diameter. 
 Inches. 
 
 Weight, sp. gr. = 8.889. 
 
 Length. 
 
 Resistance of Pure Copper at 70 Fahrenheit. 
 
 Grs. per !t. 
 
 Lbs. per 1,00-3 
 feet. 
 
 Ft. per Ib. 
 
 Ohms per 1,000 ft. 
 
 Feet per ohm. 
 
 Ohms per Ib. 
 
 DOOO... 
 
 .46000 
 
 4475-33 
 
 640.40 
 
 1-56 
 
 .051 
 
 19605.69 
 
 .0000798 
 
 000. .. 
 
 .40964 
 
 3549- 7 
 
 507.01 
 
 1.97 
 
 .064 
 
 I5547-87 
 
 .000127 
 
 oo... 
 
 .36480 
 
 2814.62 
 
 4^2.09 
 
 2.49 
 
 .o8t 
 
 12330.36 
 
 .000202 
 
 o... 
 
 .32486 
 
 2*33.28 
 
 319.04 
 
 3-'3 
 
 .102 
 
 97 a 3-63 
 
 .000320 
 
 I... 
 
 . 28930 
 
 1770.13 
 
 252.88 
 
 3-95 
 
 .129 
 
 7754-66 
 
 .00051 
 
 2... 
 
 2 5763 
 
 1403.79 
 
 200.54 
 
 4.99 
 
 163 
 
 6149.78 
 
 .000811 
 
 3--- 
 
 .22942 . 
 
 i i i 3 . 20 
 
 159-03 
 
 6.29 
 
 .205 
 
 4876.73 
 
 .001289 
 
 4... 
 
 .20431 
 
 882.85 
 
 1 .'6. 12 
 
 7-93 
 
 .259 
 
 3867.62 
 
 .00205 
 
 5... 
 
 .18194 
 
 700.10 
 
 1OO.OI 
 
 10. OO 
 
 326 
 
 3067.06 
 
 .00326 
 
 6... 
 
 . 16202 
 
 555- o 
 
 79.32 
 
 12. 6l 
 
 .411 
 
 2432.22 
 
 .00518 
 
 I 
 
 M429 
 
 440. 27 
 
 62.90 
 
 15.90 
 
 5i9 
 
 1928.75 
 
 .00824 
 
 8... 
 
 .12849 
 
 349.18 
 
 49.88 
 
 20.05 
 
 654 
 
 1529-69 
 
 .01311 
 
 9... 
 
 "443 
 
 276.94 
 
 39-56 
 
 25.28 
 
 .824 
 
 1213.22 
 
 .02083 
 
 so... 
 
 .10190 
 
 219.57 
 
 31-37 
 
 31.88 
 
 1.040 
 
 961.91 
 
 33H 
 
 ii. .. 
 
 .09074 
 
 I74-15 
 
 24.88 
 
 40.20 
 
 1.311 
 
 762.93 
 
 .05269 
 
 i.*. .. 
 
 .08081 
 
 138.11 
 
 19-73 
 
 50.69 
 
 -653 
 
 605.03 
 
 .08377 
 
 13-.. 
 
 .07196 
 
 109.52 
 
 15-65 
 
 63.91 
 
 2.084 
 
 479.80 
 
 -13321 
 
 14... 
 
 .06408 
 
 86.86 
 
 12.41 
 
 80.59 
 
 2.628 
 
 380.51 
 
 .2118 
 
 15- 
 
 .05707 
 
 68.88 
 
 9.84 
 
 101.63 
 
 3-3M 
 
 301.75 
 
 .3368 
 
 16... 
 
 .05082 
 
 54-63 
 
 7.81 
 
 128.14 
 
 4.179 
 
 239.32 
 
 5355 
 
 17... 
 
 .04525 
 
 43-33 
 
 o. 19 
 
 i6z.59 
 
 5.269 
 
 189.78 
 
 8515 
 
 18 .. 
 
 . 04030 
 
 34-35 
 
 4.91 
 
 203 . 76 
 
 6.645 
 
 150-5 
 
 !-3539 
 
 19... 
 
 .03589 
 
 26.49 
 
 3-78 
 
 264.26 
 
 8.617 
 
 116.05 
 
 2.2772 
 
 20... 
 
 .03196 
 
 91. OI 
 
 3-9 
 
 324.00 
 
 10. 566 
 
 94-65 
 
 3-423 
 
 31... 
 
 .02846 
 
 I7-I3 
 
 2-45 
 
 408.56 
 
 J 3-323 
 
 75.06 
 
 5,443 
 
 22. .. 
 
 025347 
 
 13-59 
 
 1.94 
 
 5i5-i5 
 
 16.799 
 
 59-53 
 
 8.654 
 
 23... 
 
 .022572 
 
 10.77 
 
 1-54 
 
 649.66 
 
 21.185 
 
 47-20 
 
 13-763 
 
 24... 
 
 .0201 
 
 8-54 
 
 1.22 
 
 819.21 
 
 26.713 
 
 37-43 
 
 21.885 
 
 25... 
 
 .0179 
 
 6.78 
 
 97 
 
 1032.96 
 
 33 684 
 
 29.69 
 
 34-795 
 
 26. . 
 
 01594 
 
 S-37 
 
 77 
 
 1302.61 
 
 42.477 
 
 23-54 
 
 55-331 
 
 27. . 
 
 .014195 
 
 4.26 
 
 .61 
 
 1642.55 
 
 53-563 
 
 18.68 
 
 87-979 
 
 28. . 
 
 .012641 
 
 3-38 
 
 .48 
 
 2071.22 
 
 67-542 
 
 14.81 
 
 139.893 
 
 29. . 
 
 .011258 
 
 2.68 
 
 38 
 
 2611.82 
 
 85.170 
 
 11.74 
 
 222.449 
 
 30. . 
 
 .010025 
 
 2.13 
 
 3 
 
 3293.97 
 
 107.391 
 
 9-3i 
 
 353-742 
 
 31. 
 
 .008928 
 
 1.69 
 
 .24 
 
 4152.22 
 
 I35-402 
 
 7-39 
 
 562 . 22 I 
 
 32. . 
 
 .00795 
 
 i-34 
 
 .19 
 
 5236.66 
 
 170.765 
 
 5.86 
 
 894.242 
 
 33- 
 
 .00708 
 
 i. 06 
 
 !5 
 
 660.271 
 
 815.312 
 
 4.64 
 
 1421.646 
 
 34- 
 
 .0063 
 
 .84 
 
 .12 
 
 8328.30 
 
 271-583 
 
 3.68 
 
 226l.82 
 
 35- 
 
 .00561 
 
 .67 
 
 .10 
 
 10501.35 
 
 342.413 
 
 2.92 
 
 3596.104 
 
 36. . 
 
 .005 
 
 -53 
 
 .08 
 
 13238.83 
 
 43 r -7i3 
 
 2.32 
 
 57I5-36 
 
 37- 
 
 .00445 
 
 .42 
 
 .06 
 
 16691.06 
 
 544-287 
 
 1.84 
 
 9084.71 
 
 38. 
 
 .003965 
 
 34 
 
 05 
 
 20854.65 
 
 686.511 
 
 1.46 
 
 14320.26 
 
 39- 
 
 003531 
 
 .27 
 
 .04 
 
 26302 . 23 
 
 865.046 
 
 1.16 
 
 22752.6 
 
 40. . 
 
 .003144 
 
 .21 
 
 .03 
 
 33I75-94 
 
 1091.865 
 
 92 
 
 36223.59 
 
 Gauss. The unit of intensity of magnetic 
 field. 
 
 The term gauss for unit of intensity of mag- 
 netic field was proposed by S. P. Thompson as 
 being that of a field whose intensity is equal to 
 lo 9 C. G. S. units, that is, io 8 lines of force per 
 square centimetre. 
 
 J. A. Fleming proposes, for the value of the 
 gauss, such strength of field as would develop an 
 electromotive force of one volt in a wire one 
 million centimetres in length, moving through 
 such a field with unit velocity. 
 
 Fleming's value for the gauss was assumed on 
 account of the small value of the gauss proposed 
 
 by S. P. Thompson. It is one hundred times 
 greater in value than Thompson's gauss. 
 
 Sir William Thomson proposes, for the value of 
 the gauss, such an intensity of magnetic field as is 
 produced by a current of one weber (ampere) at 
 the distance of one centimetre. 
 
 Oanss, Fleming's Such a strength 
 
 of magnetic field as is able to develop an 
 electromotive force of one volt in a wire one 
 million centimetres in length moved through 
 the field with unit velocity. (See Gauss.) 
 
 Gauss, S. P. Thompson's Such a 
 strength of magnetic field that its intensity 
 is equal to io s C. G. S. units. (See Gauss.) 
 
Gaii.] 
 
 257 
 
 [Gen. 
 
 Gauss, Sir William Thomson's 
 
 Such an intensity of magnetic field as would be 
 produced by a current of one ampere at the 
 distance of one centimetre. (See Gauss.} 
 
 Geissler Mercurial Pump. (See Pump, 
 Air, Geissler, Mercurial.} 
 Geissler Tubes. (See Tubes, Geissler.} 
 
 General Faradization. (See Faradiza- 
 tion, General?) 
 
 General Galvanization. (See Galvaniza- 
 tion, General.} 
 
 Generation of Current by Dynamo-Elec- 
 tric Machine. (See Current, Generation of, 
 by Dynamo-Electric Machine?) 
 
 Generator, Dynamo-Electric An 
 
 apparatus in which electricity is produced by 
 the mechanical movement of conductors 
 through a magnetic field so as to cut the 
 lines of force. 
 
 A dynamo-electric machine. (See Machine, 
 Dynamo-Electric?) 
 
 A dynamo electric machine operates on the 
 general principles of electro-dynamic induction. 
 Strictly speaking, however, in a dynamo-electric 
 generator the conductors are actually moved 
 through the lines of force. In this respect, there 
 fore, a dynamo-electric generator differs from a 
 transformer, in which the lines of force are moved 
 through the conductor. (See Induction, Electro- 
 Dynamic. Transformer. Induction, Mutual.} 
 
 Generator, Motor A dynamo-elec- 
 tric generator in which the power required to 
 drive the dynamo is obtained from an elec- 
 tric current. 
 
 Motor generators are used in systems of elec- 
 trical distribution for the purpose of changing 
 the potential of the current. They consi.-t of 
 dynamos, the armatures of which are furnished 
 with two separate windings, of fine and coarse 
 wire respectively. One of these, generally the 
 fine wire, receives the driving or motor cur- 
 rent, usually of high potential, and the other, 
 the coarse wire, furnishes the current used, usu- 
 ally of low potential. 
 
 The advantage of having the windings, which 
 receive the driving current, of fine wire, is to 
 enable a current of high potential to be dis- 
 tributed over the line from distant stations to 
 
 places where it is desired to use the energy of the 
 current at a much lower potential. 
 
 Motor generators often consist simply of two 
 distinct machines mechanically connected, one 
 acting as a motor and the other as a dynamo. 
 
 Motor generators are sometimes called dynamo- 
 motors or dynamotors. 
 
 Aldrich draws the following distinction between 
 a dynamo-motor and a dynamotor : 
 
 (I.) A dynamo-motor is an energy transformer 
 with the dynamo and motor in the same electric 
 circuit. 
 
 (2.) A dynamotor is an energy transformer with 
 the dynamo and motor iu the same magnetic cir- 
 cuit. 
 
 Fig. 286. Edison's Pyro-Ma^netic Generator. 
 
 Generator, Pyro-Magnetic An ap* 
 
 paratus for producing electricity directly from 
 heat derived from the. burning of fuel. 
 
Gen.] 
 
 258 
 
 [Gil. 
 
 The operation of the pyro-magnetic generator 
 is dependent upon the fa:t that any variation in 
 the number of lines of magnetic force that pass 
 through a conductor will develop differences of 
 electric potential therein. Such variations may 
 be effected either by varying the position of the 
 conductor as regards the magnetic field, or by 
 varying the magnetic field itself. The latter 
 method of generating differences of potential is 
 utilized in the pyro-magnetic generator, and is 
 effected in it by varying the magnetization of rolls 
 of thin iron or nickel by the action of heat. 
 
 A form of pyro-magnetic generator devised by 
 Edison is shown in Figs. 286 and 287. 
 
 Fig. 287. Edison's Pyro- Magnetic Generator. 
 
 This apparatus is sometimes called a pyro- 
 magnetic dynamo. 
 
 Eight electro magnets are provided, each with 
 an armature consisting of a roll of corrugated 
 iron. Each of these armatures is provided with 
 a coil of insulated wire wound on it and pro- 
 tected by asbestos paper. The armatures pass 
 through two iron discs as shown. The armature 
 coils are connected in series in a closed-circuit, 
 the wires from the coils being connected with 
 metallic brushes that rest on a commutator sup- 
 ported on a vertical axis. A pair of metallic 
 rings is provided above the commutator to carry 
 off the current generated. 
 
 The vertical axis is provided below with a semi- 
 circular screen called a guard plate which rotates 
 with the axis and cuts off or screens one-half the 
 iron armatures from the heated air. 
 
 When the axis is rotated, the difference in the 
 
 magnetization of the armatures, when hot and 
 cold, develops electromotive forces which result 
 in the production of an electric current. 
 
 Generator, Secondary A term fre- 
 quently employed for a converter or trans- 
 former. 
 
 The word transformer is now almost univer- 
 sally employed. (See Transformer.) 
 
 Generator, Watt A term sometimes 
 
 employed for stating the power in watts that 
 any electric source is capable of producing. 
 
 Estimating the power of a dynamo-electric 
 machine by the number of watts it is capable of 
 producing is very convenient in practice, and is 
 now very generally adopted. A dynamo capable 
 of furnishing a difference of potential of 1,000 
 volts, and a current of 10 amperes, would be said 
 to be a 10,000 watt-generator. 
 
 The term watt-generator, though applicable to 
 the case of any electric source, is in practice 
 generally limited to the case of dynamo-electric 
 machines or secondary batteries. 
 
 Generators, Motor, Distribution of Elec- 
 tricity by (See Electricity ; Distribu- 
 tion of, by Motor Generators) 
 
 Geographical Distribution of Thunder 
 Storms. (See Storms, Thunder, Geograph- 
 ical Distribution of.) 
 
 Geographical Equator. (See Equator, 
 Geographical.) 
 
 Geographical Meridian. (See Meridian, 
 Geographical.) 
 
 German Silver Alloy. (See Alloy, Ger- 
 man Silver.) 
 
 Gilding, Electric The electrolytic 
 
 deposition of gold on any object. 
 
 Electro-plating with gold. (See Plating, 
 Electro.) 
 
 The surfaces of the object to be gilded are 
 made electrically conducting, if not already so, 
 and are then connected to the negative terminal 
 of a voltaic cell or other source, and immersed in 
 a plating bath containing a solution of a salt of 
 gold, directly opposite a plate of gold, connected 
 with the positive terminal of the source. The 
 objects to be plated thus become the kathode, and 
 the plate of gold the anode of the plating bath. 
 On the passage of a suitable current, the gold is 
 dissolved from the plate at the anode and deposited 
 
Gil.] 
 
 259 
 
 [Gov. 
 
 on the object at the kathode. (See Bath, Gold. 
 Kathode. Anode. ) 
 
 Gilt Plumbago. (See Plumbago, Gilt.) 
 Gimbals. Concentric rings of brass, sus- 
 pended on pivots in a compass box, and on 
 which the compass card is supported so as to 
 enable it to remain horizontal notwithstand- 
 ing the movements of the ship. (See Com- 
 pass, Azimuth.) 
 
 Each ring is suspended on two pivots placed 
 directly opposite each other, that is, at the ends 
 of a diameter, which in one ring is at right angles 
 to that in the other. 
 
 Girder Armature. (See Armature, Gir- 
 der) 
 Globe, Vapor, of Incandescent Lamp 
 
 A glass globe surrounding the cham- 
 ber of an incandescent electric lamp, for the 
 purpose of enabling the lamp to be safely 
 used in an explosive atmosphere, or to permit 
 the lamp to be exposed in places where water 
 is liable to fall on it. 
 
 Such a vapor globe is shown in Fig. 288. In 
 the event of accidental breakage of the outside 
 globe, the lamp chamber 
 proper prevents the igni- 
 tion of the explosive 
 gases. In such cases, 
 however, the outer pro- 
 tecting chamber should 
 be promptly replaced. 
 
 In some forms of vapor 
 globes, a valve is pro- 
 vided, opening outwards, 
 in order to permit the ex- 
 panded air to escape 
 when a given pressure is 
 reached, and yet, at the 
 same time, to prevent the 
 entrance of gas or vapor 
 from without. 
 
 Glow Discharge. 
 
 , T^ - 7 Fl S iS8 l/apor Globe. 
 
 (bee Discharge, Glow.) 
 Glow Lamp. (See Lamp , Electric Glow) 
 Gold Bath. (See Bath, Geld) 
 
 Gold-Leaf Electroscope. (See Electro- 
 scope, Gold-Leaf) 
 
 Gold-Plating.-(See Plating, Gold) 
 Gong, Electro-Mechanical A gong 
 
 struck or operated by mechanical force at 
 times which are dependent on the passage of 
 an electric current. 
 
 The motive power is the mechanical force de- 
 veloped by a bent spring, the fall of a weight, 
 etc. , and, by suitable mechanism, is permitted to 
 act only on the passage of an electric current. 
 
 Gorernor, Centrifugal 
 
 A device for 
 
 maintaining constant the speed of a steam 
 engine or other prime mover, despite sudden 
 changes in the load or work. 
 
 In a ball governor, any increase in speed 
 causes the balls to fly out from the centre of rota- 
 tion by centrifugal force. This motion is utilized 
 to control a valve or other regulating device. If 
 the speed of the engine falls, the balls move 
 towards the centre, shifting the valve or regulat- 
 ing device in the opposite direction. 
 
 Governor, Current A current regu- 
 lator. 
 
 A device for maintaining constant the cur- 
 rent strength in any circuit. 
 
 Current governors are either automatic or non- 
 automatic. (See Regulation, Automatic.) 
 
 Governor, Electric A device for 
 
 electrically controlling the speed of a steam 
 engine, the direction of current in a plating 
 bath, the speed of an electric motor, the re- 
 sistance of an electric circuit, the flow of 
 water or gas into or from a containing vessel, 
 or for other similar purposes. 
 
 The particular form assumed by the apparatus 
 varies with the character of the work it is intended 
 to accomplish. In some cases an ordinary ball 
 or centrifugal governor is employed to open or 
 close a circuit; or, a mass of mercury in a rotat- 
 ing vessel is caused, at a certain speed, to open or 
 close a circuit; or, the resistance of a bundle of 
 carbon discs is caused to vary, either by pressure 
 produced by centrifugal force, or by the move- 
 ment of an armature. 
 
 Governor, Periodic A name ap- 
 plied by Ayrton & Perry to a form of gover- 
 nor for an electric motor, in which the cur- 
 rent is automatically cut out for a certain 
 portion of each revolution. 
 
 Governor, Spasmodic A name 
 
 given by Ayrton & Perry to a form of gover- 
 nor for an electric motor, in which the cur- 
 
Gov.J 
 
 260 
 
 [Gra- 
 
 rent is automatically cut off in proportion as 
 the work is cut off. 
 
 The spasmodic governor consists essentially of a 
 cone dipping into the surface of mercury in a rotat- 
 ing vessel. As the speed of the governor increases 
 on a lightening of the load, the surface of the mer- 
 cury is curved by the increased centrifugal force, 
 until finally the mercury leaves the contact point 
 and thus cuts off the current. 
 
 Governor, Steam, Electric A de- 
 vice used in connection with a valve to so 
 electrically regulate the supply of steam to an 
 engine, that the engine shall be driven at 
 such a speed as will maintain either a con- 
 stant current or a constant potential. 
 
 In the electric governor, the steam valve is 
 operated by an electro-magnet, whose coils, in 
 the case of a constant current machine, are of 
 thick wire placed in the main circuit, and, in 
 that of a constant potential machine, are of thin 
 wire placed in a shunt around the mains. 
 
 Gradnators. Devices, generally electro- 
 magnetic, employed in systems of simultane- 
 ous telegraphic and telephonic transmission 
 over the same wire, so inserted in the line cir- 
 cuit as to obtain the makes and breaks re- 
 quired in a system of telegraphic communi- 
 cation so gradually that they fail to sensibly 
 influence the diaphragm of a telephone placed 
 in the same circuit. 
 
 Gramme. A unit of weight equal to 
 I54323S grains. 
 
 The gramme is equal to the weight of one cubic 
 centimetre of pure water at the temperature of its 
 maximum density. It has various multiples and 
 decimal divisions of the former, the kilogramme 
 or one thousand grammes is the most frequently 
 used ; of the latter, the centigramme or the one- 
 hundredth of a gramme, and the milligramme or 
 the one -thousandth of a gramme. (See Weights 
 and Measures, Metric System of.) 
 
 Gramme Atom. (See Atom, Gramme) 
 
 Gramme Molecule. (See Molecule, 
 Gramme!) 
 
 Gramophone. An apparatus for record- 
 ing and reproducing articulate speech. (See 
 Phonograph.} 
 
 Gramophone Record. (See Record, 
 Gramophone.) 
 
 Graphite. A soft variety of carbon suit- 
 able for writing on paper or similar surfaces. 
 
 Graphite is the material that is employed for 
 the so-called black lead of lead pencils. It is 
 sometimes called plumbago. Strictly speaking, 
 the term graphite is only applicable to the variety 
 of plumbago suitable for use in lead pencils. 
 
 Graphite is used for rendering surfaces to be 
 electro-plated, electrically conducting, and also for 
 the brushes of dynamos and motors. P'or the 
 latter purpose it possesses the additional advantage 
 of decreasing the friction by means of its marked 
 lubricating properties. 
 
 Graphophone, Micro A modifica- 
 tion of the phonograph in which, instead of a 
 single diaphragm, a number of separate non- 
 metallic diaphragms are caused to act on a 
 single diaphragm to record the speech, so that 
 the separate diaphragms can be thrown into 
 strong vibration when reproducing the speech. 
 
 Graphophone, Phonograph A term 
 
 sometimes applied to the graphophone. (See 
 Graphophone, Micro. Phonograph) 
 
 Graphophone Record. (See Record, 
 Graphophone) 
 
 Gray's Harmonic Telegraphic Analyzer. 
 (See Analyzer, Gray's Harmonic Tele- 
 graphic) 
 
 Gray's Harmonic Telegraphy. (See Te- 
 legraphy, Gray's Harmonic Multiple) 
 
 Gravitation. A name applied to the force 
 which causes masses of matter to tend to 
 move towards one another. 
 
 This motion is assumed to be that of attraction, 
 that is, the bodies are assumed to be drawn to- 
 gather. It is not impossible, however, that they 
 may be pushed together. 
 
 Gravitation, like electricity, is well known, so 
 far as its effects are concerned ; but, as to the true 
 cause of either, particularly the former, we are in 
 comparative ignorance. 
 
 The general facts of gravitation may be suc- 
 cinctly stated by the following law, generally 
 known as Newton's law. 
 
 Every particle of matter in the universe is at- 
 tracted by every other particle of matter, and 
 itself attracts every other particle of matter, with 
 a force which is directly proportional to the pro- 
 duct of the masses of the two quantities of matter 
 
Ura.] 
 
 261 
 
 [Gua. 
 
 and inversely proportional to the square of the 
 distance between them. 
 
 Gravity Ammeter. (See Ammeter, Grav- 
 ity.} 
 
 Gravity, Centre of The centre of 
 
 weight of a body. 
 
 Bodies supported at their centres of gravity are 
 in equilibrium, since their weight is then evenly 
 distributed around the point of support. 
 
 Gravity-Drop Annunciator. (See An- 
 nunciator, Gravity-Drop.) 
 
 Gravity, Voltaic Cell (See Cell, 
 
 Voltaic, Gravity.) 
 
 Gravity Voltmeter. (See Voltmeter, 
 Gravity?) 
 
 Great Calorie. (See Calorie, Great.) 
 
 Grenet Voltaic Cell. (See Cell, Voltaic, 
 Grenet?) 
 
 Grid. A lead plate, provided with perfor- 
 ations, or other irregularities of surface, and 
 employed in storage cells for the support of 
 the active material. 
 
 The support provided for the active material 
 on the plate of a secondary or storage cell. 
 
 The grid receives its name from its resemblance 
 to a gridiron. The active material is generally 
 maintained on the grid by means of variously 
 shaped apertures or holes. These are generally 
 larger near the centre, so as to prevent the falling 
 out of the material after it has been hardened by 
 compression. (See Cell, Secondary. Cell, Stor- 
 age.) 
 
 Various forms have been given to the grid. 
 The object of these forms, in general, is to in- 
 sure the retention of the active material by the 
 grid. 
 
 The grids are preferably suspended from suit- 
 able supports fastened to the top of the battery 
 jars, instead of resting on the bottom of the bat- 
 tery jars. 
 
 Grip, Cable A grip provided for 
 
 seizing the end of a cable when it is to be 
 drawn into a duct or conduit. 
 
 Grove's Voltaic Cell. (See Cell, Voltaic, 
 Grove.) 
 
 Grothuss' Hypothesis. (See Hypothesis, 
 Grothuss'.) 
 
 Ground Circuit. (See Circuit, Ground.) 
 
 Ground Detector. ( See Detector, 
 Ground.) 
 
 Ground or Earth. A general term for 
 the earth when employed as a conductor, or 
 as a large reservoir of electricity. 
 
 The term ground is also applied to a fault 
 caused by an accidental and undesired connection 
 between an electric circuit, line or apparatus and 
 the ground. (See Fault.) 
 
 ' Ground Plate of Lightning Protec- 
 tor. (See Plate, Ground, of Lightning 
 Protector?) 
 
 Ground-Return. A general term used 
 to indicate the use of the ground or earth 
 for a part of an electric circuit. 
 
 The earth or ground which forms part of 
 the return path of an electric circuit. 
 
 The ground-return is generally used in the 
 Morse system of telegraphy as practiced in the 
 United States. 
 
 Ground-Wire. The wire or conductor 
 leading to or connecting with the ground or 
 earth in a grounded circuit. 
 
 This is sometimes called an earth -grounded 
 wire. 
 
 A circuit is grounded when it is completed in 
 part by the ground or earth. 
 
 Grounded Circuit. (See Circuit, 
 Grounded?) 
 
 Growth or Expansion of Lines of Force. 
 
 (See Force, Lines of. Growth or Expan- 
 sion of) 
 
 Guard, Fan A wire netting placed 
 
 around the fan of an electric motor for the 
 purpose of preventing its revolving arms 
 from striking external objects. 
 
 Guard, Lightning A term some- 
 times used for lightning rod. (See Rod, 
 Lightning?) 
 
 Guard, Transformer, Lightning 
 
 A transformer lightning arrester. (See Ar* 
 rester, Lightning, Transformer.) 
 
Gua.] 
 
 262 
 
 [Hal. 
 
 Guard, Wire Shade A guard of 
 
 wire netting provided for the protection of a 
 shade. 
 
 A form of wire shade is shown in Fig. 289. 
 
 Fig. 289. Wire Shade Guard. 
 
 Gutta-Percha. A resinous gum obtained 
 from a tropical tree, and valuable electrically 
 for its high insulating powers. 
 
 Gutta-percha readily softens by heat, but on 
 
 cooling becomes hard and tough. Un'ike India- 
 rubber, it possesses bat little elasticity. Its 
 specific inductive capacity is 4.2, that of air being 
 I, and of vulcanized rubber, 2.94. (See Capacity \ 
 Specific Inductive ,) 
 
 Gutta-percha is obtained largely from the East 
 Indies, from a tree which yields a brownish gum. 
 It is a fibrous and tenacious substance with but 
 little flexibility, and is unaffected by acids. Oils 
 produce less effect upon it than on India-rubber. 
 
 Gutta-percha is one of the best insulating mate- 
 rials known for sub-aqueous cables. 
 
 Gymnotus Electricus. The electric eel. 
 (See &l, Electric.} 
 
 Gyrometer. A speed indicator. (See In- 
 dicator, Speed.} 
 
 H. A contraction for the horizontal inten- 
 sity of the earth's magnetism. 
 
 H. A contraction proposed for one unit 
 of self-induction. 
 
 H. A contraction used in mathematical 
 writings for the magnetizing force that exists 
 at any point, or, generally, for the intensity of 
 the magnetic force. 
 
 The letter H, when used in mathematical 
 writings or formulae for the intensity of the 
 magnetic force, is always represented in bold or 
 heavy faced type, thus : H . 
 
 H-Armature Core. (See Core, Arma- 
 ture, H.) 
 Hail, Assumed Electric Origin of 
 
 A hypothesis, now generally rejected, framed 
 to explain the origin of the alternate coatings 
 of ice and snow in a hail stone, by the alter- 
 nate electric attractions and repulsions of 
 the stones between neighboring, oppositely 
 charged, snow and rain clouds. 
 
 It is now generally recognized that the electric 
 manifestations attending hail storms are the 
 effects and not the causes of the hail. (See Para- 
 greles.} 
 
 Hair, Electrolytic Removal of 
 
 The permanent removal of hair from any part 
 
 of the body, by the electrolytic destruction of 
 the hair follicles. 
 
 A platinum negative electrode is inserted in the 
 hair follicle arid the positive electrode, covered with 
 moist sponge or cotton, is held in the hand of the 
 patient. A current of from two to four milli-am- 
 peres from a battery of from eight to ten Le- 
 clanche elements is then passed for from ten to 
 thirty seconds. A few bubbles of gas appear, 
 and the hairs are then removed from the follicles 
 by a pair of forceps. (See Mini-Ampere.) 
 
 When the work is properly done there is no 
 destruction of the skin and therefore no marks or 
 
 In the removal of hair from the face, it is pref- 
 erable that the current should slowly reach its 
 maximum strength. 
 
 Half-Shades for Incandescent Lamps. 
 
 Shr/ies for incandescent electric lamps, in 
 which one-half of the lamp chamber proper 
 is covered with a coating of silver, or other 
 reflecting surface for reflecting the light, or is 
 ground for the purpose of diffusing the light. 
 The half-shade is applicable to cases where it 
 is desired to throw out the light, not in all direc- 
 tions, but on one side only of any plane. Some- 
 times the dividing plane is taken parallel to the 
 length of the incandescing filament and sometimes 
 at right angles to it. When the lamp is placed 
 
Hal.J 
 
 263 
 
 [Hea. 
 
 within a surrounding globe the reflecting surface 
 may be placed on this globe instead of on the 
 lamp chamber. 
 
 Hall Effect. (See Effect, Hall.} 
 Hiilloyau Lines. (See Lines, Halleyan.) 
 Halpine-Savage Torpedo. (See Torpedo, 
 H alpine- Savage?) 
 
 Handhole of Conduit. A box or opening 
 communicating with an underground cable, 
 provided for readily tapping the cable, and 
 of sufficient size to permit of the introduction 
 of the hand. 
 
 Hand-Lighting Argand Electric Burner. 
 (See Burner, Argand Electric, Hand- 
 Lighter^) 
 
 Hand-Lighting Electric Burner. (See 
 Biirner, Hand-Lighting Electric?) 
 
 H a n d R e gulation. ( See Regulation, 
 Hand.) 
 
 Hand-Regulator. (See Regulator, 
 Hand.) 
 
 Hanger-Board. (See Board, Hanger.) 
 
 Hanger, Cable A hanger or hook 
 
 suitably secured to the cable and designed to 
 sustain the weight 
 of the cable by 
 intermediately sup- 
 porting it on iron or 
 steel wires strung 
 above the cable. 
 
 29 ' Cable Ha "S er - 
 
 A cable hanger or 
 cable clip is shown in 
 Fig. 290. The mode 
 of supporting the cable 
 C, by the hanger hook 
 H, will be readily un- 
 derstood from an in- 
 spection of the figure. 
 
 The weight per foot of an aerial cable is gener- 
 ally so great that the poles or supports would re- 
 quire to be very near together, unless the device 
 of intermediate supports, by means of cable clips 
 or hangers, were adopted. 
 
 Hanger, Double-Curve Trolley -- A 
 
 trolley hanger generally employed at the ends 
 of single and double curves, and on inter- 
 mediate points on double track curves, sup- 
 ported by lateral strain in opposite directions. 
 
 Hanger, Single-Curve Trolley A 
 
 trolley hanger supported on a single track 
 curve, except at the ends and on the inside 
 curve of a double track line, by lateral strain 
 in one direction. 
 
 Hanger, Straight-Line Trolley A 
 
 trolley hanger on a straight trolley line suit- 
 ably supported by a span wire so as to have 
 a vertical strain only. 
 
 Hanger, Trolley . A device for sup- 
 porting and properly insulating trolley wires. 
 
 Hard-Drawn Copper Wire. (See Wire, 
 Copper, Hard-Drawn.) 
 
 Harmonic Receiver. (See Receiver, Har- 
 monic.) 
 
 Harmonic Telegraphy. (See Telegraphy, 
 Grays Harmonic Multiple.) 
 
 Head Bath, Electric (See Bath, 
 
 Head, Electric) 
 
 Head Breeze, Electro-Therapeutic 
 
 (See Breeze, Head, Electro- Therapeutic.) 
 
 Head Light, Locomotive, Electric 
 
 An electric light placed in the focus of a par- 
 abolic reflector in front of a locomotive engine. 
 
 The lamp is so placed that its voltaic arc is a 
 little out of the focus of the reflector, so that, by 
 giving a slight divergence to the reflected light, 
 the illumination extends a short distance on either 
 side of the tracks. 
 
 Heat. A form of energy. 
 
 The phenomena of heat are due to a vibratory 
 motion impressed on the molecules of matter by 
 the action of some form of energy. 
 
 Heat in a body is due to the vibrations or 
 oscillations of its molecules. Heat is transmitted 
 through space by means of a wave motion in the 
 universal ether. This wave motion is the same 
 as that causing light. 
 
 A hot body loses its heat by producing a wave 
 motion in the surrounding ether. This process 
 is called radiation. ( See Radiation. ) 
 
 The energy given off by a heated body cooling 
 is called radiant energy 
 
 Radiant energy is transmitted by means of 
 ether waves; it is of two kinds, viz. : 
 
 (I.) Obscure Htat, or heat which does not 
 affect the eye, although it can impress a photo- 
 graphic image on a sufficiently sensitive photo- 
 graphic plate. 
 
Hea.J 
 
 264 
 
 [Hea. 
 
 (2.) Luminous I feat, or heat which accompanies 
 tight. (See Energy, Radiant.] 
 
 Heat is conducted, or transmitted through 
 bodies, with different degrees of readiness. 
 
 Some bodies are good conductors of heat, 
 others are poor conductors. 
 
 Heat is transmitted through liquids by means 
 of currents occasioned by differences in density 
 caused by differences of temperature. These 
 currents are called convection currents. 
 
 Heat is measured as to its relative degree of in- 
 tensity by the thermometer. It is measured as to 
 its amount or quantity by the calorimeter. (See 
 Thermometer, Electric. Calorimeter.) 
 
 The heat unit most commonly employed is, 
 perhaps, the calorie, or the amount of heat re- 
 quired to raise one gramme of water one degree 
 centigrade. 
 
 Another heat unit, very generally employed in 
 the United States and England, is the quantity of 
 heat required to raise one pound of water one de- 
 gree Fahrenheit. This is called the English heat 
 unit. (See Calorie. Units, Heat. Joule. Volt- 
 Coulomb.) 
 
 Heat, Absorption and Generation of, in 
 
 Voltaic Cell The heat effects which 
 
 attend the action of a voltaic cell. 
 
 The chemical action of the exciting liquid or 
 electrolyte on the positive plate or element of a 
 voltaic cell, like all cases of chemical combination, 
 is attended by a development of heat. 
 
 When, however, the circuit of the cell is closed, 
 the energy liberated during the chemical combi- 
 nation appears as electricity, which develops heat 
 in all parts of the circuit. (See Heat, Electric. 
 Cell, Voltaic.) 
 
 Hea*, Atomic 
 
 A constant product 
 
 obtained by multiplying the specific heat of 
 an elementary substance by its atomiciveight. 
 (See Weight, Atomic.} 
 
 Dulong and Petit have discovered the remark- 
 able fact that the product of the specific heat of 
 all elementary substances by their atomic weights 
 '3 nearly the same. The product is called the 
 atomic heat, and is about equal to 6.4. 
 
 Dulong and Petit's law may be stated as fol- 
 ows, viz. : All elementary atoms require the same 
 quantity of heat to heat them to the same number 
 of degrees. 
 
 The atomic heat of any body divided by its 
 specific heat gives its atomic weight. 
 
 The heat imparted to any body performs three 
 kinds of work, viz.: 
 
 (i.) That expended in external work, such, 
 for example, as in overcoming the atmospheric 
 pressure. 
 
 (2.) That expended in internal work, or in 
 overcoming the attractions of the atoms and driv- 
 ing them apart. 
 
 (3.) That expended in overcoming the temper- 
 ature, or the true specific heat, or heat expended 
 in increasing the molecular vis-viva. 
 
 The expenditure ot energy is greatest in the 
 third head. The exact value of the three factors 
 is as yet unknown, and in the opinion of Weber 
 and others the correctness of Dulong and Petit's 
 law cannot be regarded as being satisfactorily 
 established. 
 
 Regnault has proved that Dulong and Petit's law 
 is true for compound bodies, i. e., in all compounds 
 of similar composition the product of the specific 
 heat by the total chemical equivalent is constant. 
 
 The following table from Anthony and Bracket 
 illustrates the law of Dulong and Petit: 
 
 Elements. 
 
 Specific Heat 
 ofEqual Weight. 
 
 Atomic 
 Weight. 
 
 Product of 
 Specific 
 Heat into 
 Atomic 
 Weight. 
 
 
 
 
 
 
 
 f, 
 
 
 Mercury 
 Silver 
 
 o 0314 (Solid) 
 
 199.71 
 
 6.128 
 
 Gold 
 
 
 
 
 Tin 
 
 fi 
 
 
 
 Lead 
 
 5 
 
 
 6 i7 
 
 
 
 
 
 
 
 
 
 "This product the atomic heat of elements, 
 the molecular heat of compounds has the follow- 
 ing physical meaning: Of any substance whose 
 atomic or molecular weight we know, we may 
 take a number of grammes numerically equal to 
 the atomic or molecular weight; for example, 
 35-5 grammes of chlorine, 16 grammes of marsh 
 gas; we may call such quantity the gramme atom 
 or the gramme molecule of the substance. The 
 atomic heat or the molecular heat of a substance 
 is the number of calories of heat necessary to 
 raise the temperature of a gramme atom or a 
 gramme molecule of the substance through i 
 degree C."(Damett.) 
 
 Heat, Electric - The heat developed 
 by the passage of an electric current through 
 a conductor. 
 
Hea.j 
 
 265 
 
 [Hea. 
 
 Heat is developed by the passage of a current 
 through any conductor, no matter what its resist- 
 ance may be. 
 
 If the conductor is of considerable length, and 
 of good conducting power, the heat developed is 
 not very sensible, since it is spread over a consid- 
 erable area, and is rapidly lost by radiation. 
 
 H, the heat generated in any conductor of a 
 resistance R, by the passage through it of an elec 
 trie current C, is equal to 
 
 H = C 2 R, in watts. 
 
 But one watt = .24 small calorie per second. 
 Therefore, the heat which is generated, 
 
 H = C 2 R X -24 calories per second. 
 For the case of a uniform wire of circular cross- 
 section the resistance R, in ohms is directly pro- 
 portional to the length 1, and inversely propor- 
 tional to the area of cross-section ;rr 3 , or 
 
 R =:-.. that is, H = C., 
 
 The temperature to which a wire of a given re- 
 sistance is raised, will of course vary with the 
 mass of the wire, its radiating surface, and its 
 specific heat capacity. If the same number of 
 heat calories are generated in a small weight of a 
 conductor, whose radiating surface is small, the 
 resulting temperature will of course be far higher 
 than if generated in a larger mass provided with 
 a much greater radiating surface. In general, 
 however, its temperature increases as the square 
 of the current strength when the resistance is con- 
 stant, and increases as the resistance of the wire 
 per unit of length is greater. 
 
 The temperature a wire acquires by the passage 
 of a current through it varies inversely as the 
 third power of the radius. If two wires of the 
 same material have the same lengths, but different 
 radii, the temperature, acquired by the pas- 
 sage of an electric current, will depend on the 
 heat developed per second, less that radiated per 
 
 second. Since the former varies as , and the 
 
 r 2 
 
 latter as r, that is, as 1 X 2itr, the temperatures 
 
 attained vary as J-, and not as , as frequently 
 r 8 r 2 
 
 stated. (Larden.) 
 
 The current required to raise the temperature 
 of a bare copper wire a given number of degrees 
 above the temperature of the air is given in the 
 following tab 1 * 
 
 BARE COPPER WIRES. 
 
 Current required to increase the temperature of a copper 
 wire t" Centigrade above the surrounding air, the 
 copper wire being bright polished or blackened. 
 
 Diameter in 
 Centimetres 
 
 CURRENT IN AMPERES. 
 
 and Mils 
 
 
 (thousandths of 
 
 
 
 
 an inch). 
 
 t = i C. 
 
 t = 9 C. 
 
 t = 23 C. 
 
 Cm. 
 
 Mils. 
 
 Bright 
 
 Black 
 
 Bright 
 
 Black 
 
 Bright 
 
 Black 
 
 .1 
 
 40 
 
 I.O 
 
 1.4 
 
 3.0 
 
 4.1 
 
 4.8 
 
 6.6 
 
 .2 
 
 80 
 
 2.8 
 
 3-9 
 
 8-3 
 
 11.5 
 
 '3-5 
 
 18.7 
 
 3 
 4 
 
 1 20 
 
 1 60 
 
 5-2 
 
 8.0 
 
 7.2 
 
 II. 
 
 15-3 
 23.6 
 
 31.2 
 
 32.7 
 
 24.9 
 38-3 
 
 34-4 
 
 53 
 
 
 200 
 
 n. i 
 
 15.4 
 
 33- 
 
 45-7 
 
 53-5 
 
 74-1 
 
 - 
 
 240 
 
 14-6 
 
 20.3 
 
 43-4 
 
 60.0 
 
 70.3 
 
 97-4 
 
 I 
 
 280 
 
 '8.5 
 
 25.6 
 
 54-6 
 
 75.6 
 
 88.7 
 
 123 
 
 .8 
 
 310 
 
 22.6 
 
 3 I- 3 
 
 66.7 
 
 92.4 
 
 1 08 
 
 '50 
 
 9 
 
 350 
 
 26.9 
 
 37-3 
 
 79.6 
 
 no 
 
 129 
 
 179 
 
 I.O 
 
 39 
 
 3'-5 
 
 43-6 
 
 93-3 
 
 129 
 
 
 210 
 
 2.O 
 
 79 
 
 89.2 
 
 123 
 
 264 
 
 365 
 
 428 
 
 593 
 
 3-o 
 
 I ZOO 
 
 164 
 
 227 
 
 485 
 
 671 
 
 787 
 
 1090 
 
 4.0 
 
 1570 
 
 252 
 
 349 
 
 746 
 
 '035 
 
 121 1 
 
 1675 
 
 s- 
 
 6.0 
 7.0 
 
 1970 
 
 2360 
 2760 
 
 353 
 463 
 584 
 
 488 
 642 
 808 
 
 '043 
 '37i 
 1728 
 
 1444 
 1828 
 2392 
 
 1699 
 2225 
 2803 
 
 2343 
 3080 
 3882 
 
 8.0 
 
 3150 
 
 7 J 4 
 
 988 
 
 2110 
 
 2922 
 
 3422 
 
 474' 
 
 9.0 
 
 3540 
 
 851 
 
 1178 
 
 2519 
 
 3486 
 
 4088 
 
 5659 
 
 IO.O 
 
 34-4 
 
 394 
 
 997 
 
 1380 
 
 2950 
 
 4084 
 
 4788 
 
 6626 
 
 
 
 
 
 
 
 
 
 Diameter in 
 Cent metres 
 
 CURRENT IN AMPERES. 
 
 and Mils 
 
 
 (thousandths o 
 
 
 
 an inch). 
 
 t = 49 C. 
 
 t = 81 C. 
 
 Cm. 
 
 Mils. 
 
 Bright. 
 
 Black. 
 
 Bright. 
 
 Black. 
 
 .1 
 
 40 
 
 ^ 5 
 
 8-9 
 
 7-9 
 
 II. 
 
 .2 
 
 80 
 
 18.3 
 
 =5-3 
 
 22.4 
 
 31.0 
 
 3 
 
 170 
 
 33-5 
 
 46.4 
 
 41.2 
 
 57-o 
 
 4 
 
 1 60 
 
 51-7 
 
 71-5 
 
 63.4 
 
 87.8 
 
 5 
 
 aoo 
 
 72.2 
 
 99.9 
 
 88.6 
 
 123 
 
 .6 
 
 240 
 
 94.9 
 
 13* 
 
 116 
 
 161 
 
 7 
 
 380 
 
 119 
 
 165 
 
 M7 
 
 203 
 
 .8 
 
 310 
 
 146 
 
 202 
 
 179 
 
 248 
 
 9 
 
 350 
 
 '74 
 
 2 4 I 
 
 214 
 
 296 
 
 I.O 
 
 390 
 
 204 
 
 283 
 
 251 
 
 347 
 
 2.0 
 
 790 
 
 577 
 
 799 
 
 709 
 
 981 
 
 3-0 
 
 1180 
 
 1061 
 
 1468 
 
 '33 
 
 1805 
 
 4.0 
 
 157 
 
 1633 
 
 2260 
 
 2006 
 
 2776 
 
 S-o 
 
 1970 
 
 2283 
 
 3160 
 
 2802 
 
 3880 
 
 6.0 
 
 2360 
 
 3000 
 
 4'54 
 
 3685 
 
 5100 
 
 7.0 
 
 2760 
 
 378i 
 
 5233 
 
 4642 
 
 6426 
 
 8.0 
 
 3150 
 
 4620 
 
 6396 
 
 5671 
 
 7850 
 
 9.0 
 
 3540 
 
 55" 
 
 7630 
 
 6769 
 
 9370 
 
 IO.O 
 
 34.4 
 
 3940 
 
 6425 
 
 8935 
 
 7926 
 
 10973 
 
 7OOOO 
 
 
 
 
 
 
 
 (Forbes.) 
 
 Heat, Electric Convection of A 
 
 term employed to express the dissymmetrical 
 distribution of temperature that occurs when a 
 
Hea.] 
 
 26t> 
 
 [Hea. 
 
 current of electricity is sent through a 
 metallic wire, the middle of which is main- 
 tained at a constant temperature, and the 
 ends at the temperature of melting ice. 
 
 The distribution of heat during the pas- 
 sage of a current through an unequally 
 heated conductor. 
 
 If the central portions of a metallic bar are 
 heated the curve of heat distribution is sym- 
 metrical. On sending an electric current through 
 the wire it is heated according to Joule's law, 
 and the curve of heat distribution is still sym- 
 metrical. But the current in passing from the 
 colder to the hotter parts of the wire produces 
 an additional heating effect at this point, and in 
 passing from the warmer to the colder parts o f 
 the wire produces a cooling effect. (See Effect, 
 Peltier. Effect, Thomson.) The curve of heat 
 distribution is then no longer symmetrical. The 
 term Electrical Convection of Heat, has been 
 given to the dissymmetrical distribution of heat 
 so effected. 
 
 Sir William Thomson, who studied these 
 effects, found that the electrical convection of 
 heat in copper takes place in the opposite 
 direction to that in iron; that is to say, the elec- 
 trical convection of heat is negative in iron, (*'. <?., 
 the direction is opposite to that of the current), 
 and positive in copper. 
 
 Heat, Irreversible Heat pro- 
 duced in a homogeneous conductor by the 
 passage of electricity through it. 
 
 This heat, according to Joule's law, is propor- 
 tional to the square of the current, and is produced 
 no matter in what direction the current is pass- 
 ing. In this respect it is unlike the heat pro- 
 duced by the passage of electricity through a 
 heterogeneous conductor, in which case heat is 
 developed or liberated only by the passage of the 
 current in a given direction : on the passage of the 
 current in the opposite direction, heat being 
 absorbed and the temperature lowered. (See 
 Heat, Reversible.} 
 
 Heat Lightning. (See Lightning, Heat.) 
 
 Heat, Luminons A variety of radi- 
 ant energy which affects the eye, as light. 
 
 Radiant heat and light are, in reality, different 
 effects produced by one and the same cause, viz., 
 by vibrations or waves in the universal ether. 
 In general the waves producing heat are of 
 
 greater length and smaller frequency than are 
 those producing light. 
 
 Heat, Mechanical Equivalent of 
 
 The amount of mechanical energy, converted 
 into heat, that would be required to raise the 
 temperature of i pound of water i degree 
 Fahr. 
 
 The mechanical equivalence between the 
 amount of energy expended and the amount 
 of heat produced, as measured in heat units. 
 
 Joule's experiments, the results of which are 
 generally accepted, gave 772 foot-pounds as the 
 energy equivalent to that expended in raising the 
 temperature of i pound of water i degree Fahr. 
 
 Heat, Molecular The number of 
 
 calories of heat required to raise the tempera- 
 ture of one gramme-molecule of any sub- 
 stance i degree C. (See Molecule, Gramme. 
 Heat, Atomic.) 
 
 Heat, Obscure A variety of radiant 
 
 energy which does not effect the eye. 
 
 Radiant heat is sometimes divided into lumi- 
 nous heat and obscure heat. (See Heat, Lumi- 
 nous.) 
 
 Heat, Red The temperature at 
 
 which a body, whose temperature is gradually 
 increasing, begins to glow or to emit red rays 
 of light. 
 
 When a refractory solid body is gradually 
 heated to incandescence, the red waves of light 
 are first emitted, then the orange, and successively 
 afterwards the yellow, green, blue, indigo and 
 violet, when the body emits white light or is 
 white hot. 
 
 Heat, Reversible The heat pro- 
 duced in a heterogeneous conductor by the 
 passage through it of an electric current in a 
 certain direction. 
 
 Reversible heat is produced at the junction of 
 two metals, where a difference of potential exists 
 between them, or where their heterogeneity is 
 greatest. It is called reversible because, it de- 
 pends upon the direction in which the :urrent 
 is passing. If the current be passed in a certain 
 direction across the junction, heat is liberated; 
 while, if it be passed in the opposite direction, 
 heat is absorbed, or cold results. 
 
 Reversible heat effects are seen in the Peltier 
 effect. (See Effect, Peltier.) 
 
Hca.J 
 
 267 
 
 [Hel. 
 
 Heat, Specific The capacity of a 
 
 substance for heat as compared with the 
 capacity of an equal quantity of some other 
 substance taken as unity. 
 
 Water is generally taken as the standard for 
 comparison, because its capacity f >r heat is greater 
 than that of any other common substance. 
 
 Different quantities of heat are required to 
 raise the temperature of a given weight of dif- 
 ferent substances through i degree. The spe- 
 cific heats of substances are generally compared 
 with water or with hydrogen, the capacity of 
 these substances for heat being very great. 
 
 According to Dulong and Pettit, the specific 
 heat of all elementary atoms is the same. For 
 example, the heat energy of an atom of hydrogen 
 is equal to that of an atom of oxygen, but since 
 a given mass of hydrogen, under similar condi- 
 tions of temperature and pressure, contains sixteen 
 times as many atoms as an equal mass of oxygen, 
 therefore, when compared weight for weight, 
 hydrogen has a specific heat sixteen times greater 
 than that of oxygen. 
 
 Or, in general, co nparing equal weights, the 
 specific heat of an elementary substance is in- 
 versely proportional t > its atomic weight. (See 
 Heat, Atomic.} 
 
 Heat, Specific, of Electricity 
 
 Electricity, Specific Heat of.) 
 
 (See 
 
 Heat Unit. The quantity of heat required 
 to raise a given weight of water through 
 a single degree. 
 
 There are a number of different heat units. 
 The most important are: 
 
 (I.) The British Heat Unit, or Thermal Unit, or 
 the amount of heat required to raise I pound 
 of water I degree Fahr. This unit represents an 
 amount of work equal to 772 foot pounds. 
 
 (2.) The Greater Calorie, or the amount of heat 
 required to raise the temperature of i.oco 
 grammes of water I degree C. (See Calorie.) 
 
 (3.) The Smaller Calorie, or the amount of heat 
 required to raise the temperature of one gramme 
 of water I degree C. 
 
 (4.) The Joule, or the quantity of heat developed 
 in one second by the passage of a current of one 
 ampere through a resistance of one ohm. 
 
 I joule equals .0002407 large calories. 
 
 I joule equals. 2407 small calories. 
 
 I foot-pound equals 1.356 joules. 
 
 I pound- Centigrade equals 1884.66 joules. 
 
 I " ' 1389.6 foot pounds. 
 
 I " Fahrenheit 1047.03 joules. 
 
 Heat Unit, English - (See Units, 
 Heat.) 
 
 Heat Unit or Calorie. (See Calorie.) 
 Heat Unit or Joule. (See Joule) 
 
 Heat, White - The temperature at 
 which light of all wave lengths from the red 
 to the violet is emitted from a heated body, 
 and the body, therefore, glows with a white 
 light. 
 
 A solid substance heated to white incandescence 
 emits a continuous spectrum, i. e., a spectrum in 
 which all the wave lengths of light from the red 
 to the violet are present. 
 
 Heater, Electric A device for the 
 conversion of electricity into heat for purposes 
 of artificial heating. 
 
 Electric heaters consist essentially of coils or 
 circuits of some refractory metal through which 
 the current is passed. These coils or circuits are 
 surrounded by air or finely divided solids, and are 
 placed inside metallic boxes or radiators, which 
 throw off or radiate the heat produced. 
 
 When employed for the heating of liquids the 
 coils are placed directly in the liquid to be 
 heated, or are surrounded by radiating boxes 
 placed in the liquid. 
 
 Heating Effects of Currents. (See Cur- 
 rents, Heating Effects of.) 
 
 Hedgehog: Transformer. (See Trans r 
 former, Hedgehog) 
 
 Hecto-Ampdre One hundred am- 
 peres. 
 
 Heliograph. An instrument for tele- 
 graphic communication that operates by em- 
 ploying flashes of light to represent the dots 
 and dashes of the Morse alphabet, or the 
 movements of the needles of a needle tele- 
 graph to the right or the left. (See Alphabet, 
 Telegraphic) 
 
 The flishes of light are thrown from the sur- 
 face of a plane mirror. Motions to the right or 
 left may be employed in order to distinguish 
 between the dots and dashes, or the same may be 
 effected by the re ativ: durations of t'le flas.'ic-. of 
 
Ke!.] 
 
 2G8 
 
 [Hoi. 
 
 light, or by the intervals between successive 
 flashes. 
 
 Telegraphic communication has been carried 
 on between steamers during foggy weather by 
 means of their fog horns; or between locomotives 
 by their steam whistles. 
 
 Helix, Dextrorsal A name some- 
 times applied to a dextrorsal solenoid. (See 
 Solenoid, Dextrorsal?) 
 
 The magnetic polarity of a helix or solenoid 
 depends not only on the direction in which the 
 current is passed, but also on the direction in 
 which the wire is coiled or wound . (See Magnet, 
 Electro.} 
 
 Helix, Sinistrorsal A name some- 
 times applied to a sinistrorsal solenoid. (See 
 Solenoid, Sinistrorsal?) 
 
 Hemihedral Crystal. (See Crystal, Hem- 
 ihedral?) 
 
 Henry, A The practical unit of self- 
 induction. 
 
 It has been generally agreed in the United 
 States to ca^ll the practical unit of self-induction 
 a henry, in place of a secohm or quadrant. 
 The name henry should be adopted, not only by 
 American electricians, but also by those of other 
 countries, since the terms secohm or quadrant 
 are contrary to the generally adopted usage of 
 employing for such the names of distinguished 
 electricians, who have passed from their labors. 
 
 The fact that of all discoverers in the field of self- 
 induction, none possesses so great a claim as that of 
 Prof. Henry, must be generally acknowledged. 
 As early as 1832 he published in Silliman's Jour- 
 nal a paper in which he described experiments, 
 showing clearly that the spark obtained by break- 
 ing the current of a battery, in which along wire 
 was interposed, was greater than when a short 
 wire was employed, and that this increased length 
 of spark was further increased by coiling the wire, 
 and that the phenomena were ascribed to the ac- 
 tion of the current on itself. 
 
 A committee of the American Institute of 
 Electrical Engineers, after careful consideration, 
 recommended to the Institute that the value of 
 the practical unit of inductance should be equal to 
 io 9 C. G. S. units of inductance, usually ex- 
 pressed by a length equal to one earth quadrant 
 or 1,000,000,000 centimetres. 
 
 The value of the practical unit of inductance, 
 or the "henry," may in some cases be too high for 
 
 convenience; in such cases it may be expressed 
 by some fractional dimension, such, for example, 
 as milli-henry. 
 
 Hercules Stone. (See Stone, Hercules?) 
 Hermetical Seal. (See Seal, Hermeti- 
 cal.) 
 
 Hertz's Theory of Electricity. (See Elec- 
 tricity, Hertz's Theory of.) 
 
 Heterostatic. A term applied by Sir 
 William Thomson to distinguish a form of 
 electrometer in which the electrification is 
 measured by determining the mutual influ- 
 ence of the attraction exerted by the charge 
 to be measured and the attraction of an oppo- 
 site charge imparted to the instrument by a 
 source independent of the charge to be meas- 
 ured. 
 
 The term heterostatic distinguishes this form of 
 electrometer from an idiostatic instrument, or one 
 in which the measurement is effected by deter- 
 mining the repulsion between the charge to be 
 measured and the repulsion of a charge of the 
 same name, *'. e., positive or negative, imparted 
 to the instrument from an independent source. 
 (See Electrometer.') 
 
 Hick's Automatic Button Repeater. 
 
 (See Repeaters, Telegraphic?) 
 
 High-Bars. A term applied to those com- 
 mutator segments, or parts of commutator 
 segments, which, through less wear, faulty 
 construction or looseness, are higher than ad- 
 joining portions. (See Commutator?) 
 
 High-Frequency Currents, Electric Light- 
 ing by (See Lighting, Electric, by 
 
 High-Frequency Currents?) 
 
 High Resistance Magnet (See Magnet, 
 High Resistance?) 
 
 High Speed Electric Motor. (See Mo- 
 tor, Electric, High Speed?) 
 
 High Tension Electric Fuse. (See Fuse, 
 Electric High Tension?) 
 
 Hissing of Arc. (See Arc, Hissing of?) 
 
 Holder for Safety Fuse. A box or other 
 receptacle of refractory material for holding 
 a safety fuse, and catching the molten metal 
 when fused. 
 
 The holder or fuse box is provided to prevent the 
 
Hoi.] 
 
 269 
 
 molten metal of the fuse from setting fire to any 
 combustible material on which it might other- 
 wise fall. 
 
 Holders, Carbon, for Arc Lamps 
 
 A clutch or clamp attached to the end of the 
 lamp rod or other support, and provided to 
 hold the carbon pencils used on arc lamps. 
 (See Lamp, Arc, Electric?) 
 
 Holders for Brushes of Dynamo-Electric 
 Machine. A device for holding the collect- 
 ing brushes of a dynamo-electric machine. 
 (See Machine, Dynamo-Electric?) 
 
 Hole, Armature A term sometimes 
 
 applied for armature bore or chamber. (See 
 Bore, Armature?} 
 
 Hole, Armature Bore, Elliptical 
 
 An armature bore or chamber ellipsoidal in 
 shape. 
 
 Holohedral Crystal. (See Crystal, Holo- 
 hedral?) 
 
 Holtz Machine. (See Machine, Holtz?) 
 
 Home Station. (See Station, Home?) 
 
 Homogeneous Current Distribution. 
 (See Current, Homogeneous Distribution of.} 
 
 Hood for Electric Lamp. A hood pro- 
 vided for the double purpose of protecting the 
 
 Fig. 2Qi. Arc Lamp Hood. 
 
 body of an electric lamp from rain or sun, 
 and for' throwing its light in a general down- 
 ward direction. 
 
 Hoods for arc lamps are generally conical in 
 shape. 
 
 A form of hood for an exposed arc lamp is 
 shown in Fig. 291. 
 
 Horizontal Component of Earth's Mag- 
 netism. (See Component, Horizontal, of 
 Earth's Magnetism.) 
 
 Horns, Following, of Pole Pieces of 
 a Dynamo - Electric Machine The 
 
 edges or terminals of the pole pieces of a dy- 
 namo-electric machine towards which the 
 armature is carried during its rotation. 
 
 Fig 2Q2. Horns of Dynamo, 
 
 According to S. P. Thompson, the following 
 horns, b, d, Fig. 292, are those towards which 
 the armature is carried ; the leading horns, a, c, 
 those from which it is carried. 
 
 As the change in the magnetic intensity is more 
 sudden when the armature is moved from the 
 pole pieces, and least when moved towards them, 
 it is clear that the leading horns in a dynamo 
 electric machine, and the following horns in an 
 electric motor, become heated during rotation by 
 the production of Foucault currents. (See Cur- 
 rents, Foncault. Machine, Dynamo Electric.) 
 
 Horns, Leading, of Pole Pieces of a Dy- 
 namo-Electric Machine The edges 
 
 or terminals of the pole pieces of a dynamo- 
 electrical machine from which the armature 
 is carried during its rotation. 
 
 Thus, in Fig. 292, a and c, are the leading horns 
 of the pole pieces. 
 
 Horns of Pole Pieces of Dynamo-Electric 
 Machine. The edges of the pole pieces of a 
 dynamo-electric machine towards or from 
 which the armature is carried during its rota- 
 tion. 
 
 These are called the following and the leading 
 horns. 
 
 Horse-Power. A commercial unit 
 power or rate of doing work. 
 
 for 
 
Hor.] 
 
 270 
 
 [Hoa 
 
 A rate of doing work equal to 33,000 pounds 
 raised i foot per minute, or 550 pounds raised 
 I foot per second. 
 
 A rate of doing work equal to 4,562.33 
 kilogrammes raised I metre per minute. 
 
 A careful distinction must be drawn between 
 work and power. The same amount of work 
 is done in raising I pound through 10 feet 
 whether it be done in one minute or in one hour. 
 The power expended or the rate of doing work 
 is, however, quite different, being in the former 
 case sixty times greater than in the latter. 
 I horse-power = 550 foot-pounds per second. 
 " = 33,000 foot-pounds per min- 
 
 ute. 
 " = 4,562.33 kilogramme-metres 
 
 per minute. 
 
 " = 745,941 watts. 
 
 " = 1.01385 metric horse-power. 
 
 Horse-Power, Electric (See Power, 
 
 Horse, Electric?) 
 
 Horse-Power Hour. (See Hour, Horse- 
 Power). 
 
 Horse-Power, Metric A unit of 
 
 power in which rate of doing work is equal 
 to 75 kilogramme-metres. (See Horse- 
 Power.) 
 
 Horseshoe Electro-Magnet. (See Mag- 
 net, Electro, Horseshoed) 
 
 Horseshoe Magnet. (See Magnet, Horse- 
 shoe?) 
 
 Hot, Red Sufficiently heated to 
 
 emit red light only. (See Heat, Red.) 
 
 Hot St. Elmo's Fire. (See Fire, Hot, St. 
 Elmo's.) 
 
 Hot, White Sufficiently heated to 
 
 emit all the colored lights of the spectrum. 
 (SeeJfeat, White.} 
 
 Hotel Annunciator. (See Annunciator, 
 Hotel) 
 
 Hour, Ampdre A unit of electrical 
 
 quantity equal to one ampere flowing for one 
 hour. 
 
 The ampere-hour is in reality a unit of quanti- 
 ty like the coulomb. It is used in the service of 
 electric currents, and is equal to the product of 
 the current delivered by the time in hours. The 
 ampdre hour is not a measure of energy, but when 
 
 combined with the volt, and expressed in watt 
 hours, it is a measure of energy. 
 
 The capacity of any service for maintaining a 
 flow of current is measured in ampere-hours. 
 Thus, if any service, such as a primary or sec- 
 ondary battery, has a capacity of 80 ampere- 
 hours, it will supply 8 amperes for ten hours, 01 
 it may give 10 amperes for eight hours. 
 
 The storing capacity of accumulators is gener 
 ally given in ampere-hours. The same is true ol 
 primary batteries. 
 
 One coulomb equals .0002778 ampSre-hours. 
 
 One ampere-hour equals 3,600 coulombs. 
 
 Hour, Horse-Power A unit of work 
 
 An amount of work equal to one horse- 
 power for an hour. 
 
 One horse power is equal to 1,980,000 foot- 
 pounds, or 745.941 watt hours. 
 
 Hour, Kilo- Watt A unit of electri- 
 cal power equal to a kilo-watt maintained for 
 one hour. 
 
 Hour, Lamp Such a service of elec- 
 tric current as will maintain one electric lamp 
 during one hour. 
 
 The number of lamp-hours is obtained by mul- 
 tiplying the number of lamps by the average 
 number of hours during which the lamps are 
 burning. 
 
 The use of lamp-hours is for the purpose of 
 estimating the current supplied to a consumer by 
 counting the number of hours each lamp is in 
 service. 
 
 To convert lamp-hours to watt-hours, multiply 
 the number of lamp-hours by the number oi 
 watts per lamp. The watt hours, divided by 746, 
 will then give the electrical horse-power hours. 
 (See Hour, Watt.) 
 
 Hour, Watt A unit of electrical 
 
 work. 
 
 An expenditure of an electrical work of 
 one watt for one hour. 
 
 Lamp-hours are converted to watt-hours by 
 multiplying the number of lamp-hours by the 
 number of watts per lamp. (See Hour, Lamp.) 
 
 House Annunciator. (See Annunciator, 
 House.} 
 
 House Main. (See Main, House.} 
 
 House-Service Conductor. (See Conduc- 
 tor, House-Service} 
 
Hon.] 
 
 271 
 
 [Hyp. 
 
 House-Top Fixtures, Telegraphic 
 
 (See Fixtures, Telegraphic House- Top.} 
 House Wire. (See Wire, House?) 
 Hughes' Electro-Magnet. (See Magnet, 
 Electro, Hughes'.) 
 
 Human Body, Electric Resistance of 
 
 (See Body, Human, Resistance of.) 
 
 Hydro-Electric Bath. (See Bath, Hydro- 
 Electric?) 
 
 Hydro-Electric Machine, Armstrong's 
 
 (See Machine, Armstrong's Hydro- 
 Electric?) 
 
 Hydrogen, Electrolytic Hydrogen 
 
 produced by electrolytic decomposition. 
 
 It is the electrolytic hydrogen liberated in a 
 voltaic cell at the surface of the negative plate, 
 which causes polarization and consequent de- 
 crease in the resulting current strength, by rea- 
 son both of the counter-electromotive force it 
 produces and the increased resistance it produces 
 in the cell. 
 
 Electrolytic hydrogen is atomic hydrogen; i. e., 
 hydrogen with its bonds open or free. It there- 
 fore possesses much stronger chemical affinities 
 than does molecular hydrogen. Electrolytic 
 oxygen which is evolved at the same time as the 
 electrolytic hydrogen has been successfully em- 
 ployed in electric bleaching. Hydrogen per- 
 oxide is also formed and acts as a bleaching agent. 
 
 Hydrometer or Areometer. An appa- 
 ratus for determining the specific gravity of 
 liquids. (See Areometer or Hydrometer?) 
 
 Hydro-Plastics. (See Plastics, Hydro?) 
 
 Hydro-Plasty. The art of hydro-plastics. 
 (See Plastics, Hydro?) 
 
 Hydrotasimeter, Electric An elec- 
 trically operated apparatus designed to show 
 at a distance the exact position of any water 
 level. 
 
 In most forms of the electric hydrotasimeter a 
 float placed in the liquid and connected with an 
 electric circuit breaks this circuit, and, at intervals, 
 sends positive impulses into the line when rising 
 and negative impulses when falling. These are 
 registered- by means of an index moved by a step- 
 by-step motion, positive currents moving it in 
 one direction and negative currents moving it in 
 the opposite direction. 
 
 Hygrometer. An apparatus for determin- 
 ing the amount of moisture in the air. 
 
 Hygrometrical. Of or pertaining to the 
 hygrometer. 
 
 Hygrometrically. In the manner of the 
 hygrometer. 
 
 Hypothesis. A provisional assumption of 
 facts or causes the real nature of which is 
 unknown, made for the purpose of studying 
 the effects of such causes. 
 
 When the facts assumed by a hypothesis can 
 be shown to be presumably true the hypothesis 
 becomes a theory. A theory, therefore, gives a 
 more correct expression of the relations between 
 the causes and effects of natural phenomena than 
 does a hypothesis. 
 
 Hypothesis, Double-Fluid Electric 
 
 (See Electricity, Double-Fluid Hypothesis 
 of.) 
 
 Hypothesis, Grothiiss' A hypothe- 
 sis proposed by Grothiiss to account for the 
 electrolytic phenomena that occur on closing 
 the circuit of a voltaic cell. 
 
 Grothtiss' hypothesis assumes: 
 
 (i.) That before the electric circuit is closed 
 the molecules of the electrolyte are arranged in 
 an irregular or unpolarized condition, as repre- 
 
 Fig. 293. GrotkOss' hypothesis of Electrolytic Polari- 
 zation. 
 
 sented at (i), Fig. 293. These molecules are 
 shaded as shown in Fig. 294, to indicate then- com- 
 position and polarity. 
 
 (2.) When the circuit is closed and a current 
 
Hyp.] 
 
 272 
 
 [Hys, 
 
 begins to pass, a polarization of the electrolyte, as 
 shown at (2), ensues, whereby all the negative 
 ends of the molecules of hydrogen sulphate, o 
 sulphuric acid, are turned towards the positive 
 or zinc plate, and all the positive ends towards 
 the negative or copper plate. This, as will be 
 seen, will turn the SO 4 ends towards the zinc, 
 and the H z ends towards the copper. 
 
 (3.) A decomposition of the polarized chain, 
 whereby the SO 4 
 unites with the zinc 
 and the H 2 liberated 
 reunites with the SO 4 
 of the molecule next 
 to it in the chain, and 
 its liberated H s with Fig. 294. Conventionalized 
 the one next to it, and Molecule. 
 
 so on until the last liberated H 2 in the chain is 
 given off at the surface of the copper or negative 
 plate. This leaves the chain of molecules as 
 shown at (3). 
 
 (4.) A semi-rotation of the molecules of the 
 chain, as at (3), until they assume the position 
 shown at (4). This rotation is required, since all 
 the molecules in (3) are turned with their similar 
 poles towards similarly charged battery plates. 
 
 Hypothesis, Single-Fluid Electric 
 
 (See Electricity, Single-Fluid Hypothe- 
 sis of.) 
 
 Hypothetical. Of or pertaining to a hy- 
 pothesis. 
 
 Hypsometer. An apparatus for determin- 
 ing the height of a mountain or other eleva- 
 tion by ascertaining the exact temperature at 
 which water boils at such elevation. 
 
 The use of a thermometer to measure the 
 height of a mountain or other elevation is based 
 on the fact that a given decrease in the tempera- 
 ture of the boiling point of water invariably at- 
 tends a given decrease in the atmospheric press- 
 ure. Therefore, as the observer goes further 
 above the level of the sea, the boiling point of 
 water becomes lower, and from this decrease the 
 height of the mountain or other elevation may be 
 calculated. 
 
 Hypsometrical. Of or pertaining to the 
 hypsometer. 
 
 Hypsometrically. In the manner of the 
 hypsometer. 
 
 Hysteresial Dissipation of Energy. (See 
 Energy, Hysteresial Dissipation of.) 
 
 Hysteresis, Molecular friction to mag- 
 netic change of stress. 
 
 A retardation of the magnetizing or de- 
 magetizing effects as regards the causes 
 which produce them. 
 
 The quality of a paramagnetic substance 
 by virtue of which energy is dissipated on the 
 reversal of its magnetization. 
 
 The ratio of magnetic induction to the mag- 
 netizing force producing it, or, in other words, 
 the magnetic permeability, is greater when the 
 magnetizing force is decreasing, than when it is 
 increasing. This phenomenon is seen in the well 
 known retention of magnetism in iron after the 
 withdrawal of the force causing the magnetization, 
 and was called by Ewing hysteresis, from 
 'vtfrefitao, to lag behind. 
 
 If a curve is constructed in which the hori- 
 zontal abscissas represent the magnetizing force, 
 or the magnetizing current to which they are 
 proportional, and the vertical ordinates the 
 number of lines of induction passing through the 
 body that is being magnetized, both in the case 
 of gradually increasing and gradually decreasing 
 currents, the curve will be found to have greater 
 values for the decreasing than for the increasing 
 current Constructing a curve in this manner for 
 the case of a ring of 
 iron, which has been 
 first suddenly magnet- 
 ized and- then demag- 
 netized, taking the 
 magnetizing force along 
 the line F H, Fig. 
 295, and the result- 
 ing magnetization 
 along the line M N, a 
 loop is formed in the 
 curve, as shown in the 
 figure. The arrows 
 show the direction of Fig. 295. Curves of Hys- 
 the magnetizing force; teresis (Swing). 
 
 the shaded area the work done due to hysteresis. 
 
 The area of this loop represents the amount of 
 energy per unit of volume expended in perform- 
 ing a magnetic cycle, i. e., in carrying the iron 
 ring through a magnetization and subsequent 
 demagnetiz ation. 
 
 The physical meaning of the loop is that a lag- 
 
273 
 
 [Hys. 
 
 ging of magnetization has occurred. This lag- 
 ging of the magnetization is due to hysteresis. 
 Ewing gives the value for the energy in ergs 
 dissipated per cubic centimetre, for a complete 
 magnetic cycle for a number of substances, as 
 follows : 
 
 Energy dissipated 
 in ergs per cubic 
 centimetre, during 
 a complete cy cle of 
 doubly reversed 
 strong magnetiza- 
 Sample of Iron operated upon. tion. 
 
 Very soft annealed iron 9,300 ergs. 
 
 Less soft annealed iron 16,300 " 
 
 Hard drawn steel wire 60.000 " 
 
 Annealed steel wire 70,500 " 
 
 Same steel, glass hard 76,000 " 
 
 Piano-forte steel wire, normal 
 
 temper 116,000 " 
 
 Same, annealed 94,000 ' ' 
 
 Same, glass hard 117,000 " 
 
 Approximately 28 foot-pounds of energy are 
 required to make a double reversal of strong 
 magnetization in a cubic foot of iron. Energy 
 expended in this way takes the form of heat. 
 This heat, however, is to be distinguished from 
 heat produced by Foucault currents. 
 
 According to Ewing, hysteresis is greatly de- 
 creased by keeping the iron in a state of mag- 
 netic vibration. In this way, the energy dis- 
 sipated in a complete magnetic cycle is corre- 
 spondingly decreased. This observation of Ewing 
 agrees with the prior observation of Hughes, who 
 noticed that tapping or twisting a bar of iron 
 greatly accelerates the removal of its residual 
 magnetism. 
 
 The phenomena of hysteresis, according to 
 Fleming, accounts for part of the energy which 
 is dissipated in a dynamo-electric machine: 
 
 (i.) In the field magnets. 
 
 In an ordinarily constructed continuous current 
 dynamo, work is done in magnetizing the field 
 mapnets. not only to give the iron its initial mag- 
 netism, but also to constantly reproduce the mag- 
 netism which the machine loses by reason of the 
 
 continual vibrations to which it ii subjected dur- 
 ing its run. If sufficient residual magnetism 
 were retained, on the withdrawal of the magneti- 
 zing force there would be no necessity for the 
 current in the field magnets ; but, since this is 
 removed by even a small vibration, the energy of 
 the exciting current must needs be expended. 
 
 (2.) In the armature of the dynamo. 
 
 The soft iron of the core is subjected to succes- 
 sive magnetizations and demagnetizations. Ac- 
 cording to Fleming, in the case of a core having 
 a volume of 9,003 cubic centimetres, with fifteen 
 reversals per second, the loss is equal to about i 
 horse-power. 
 
 Hysteresis, Static That quality in 
 
 iron, or other paramagnetic substance, by 
 virtue of which energy is dissipated during 
 every reversal of its magnetization. 
 
 Static hysteresis is so named in order to dis- 
 tinguish it from viscous hysteresis. (See Hystere- 
 sis, Viscous.) 
 
 Hysteresis, Yiscous The time-lag 
 
 observed in magnetizing a bar of iron t 
 which is referable neither to induction in the 
 iron, nor to self-induction in the magnetizing 
 current, but to the magnetic viscosity of the 
 substance. 
 
 A sluggishness exhibited by iron for mag- 
 netization or demagnetization due to magnetic 
 viscosity. 
 
 The difference between static and viscous 
 hysteresis is thus stated by Fleming in consider- 
 ing the analogous mechanical case of lifting a 
 weight in a viscous fluid. "Apart from fluid 
 resistance, the work done in lifting the weight 
 against gravity, say one hundred times, is a hun- 
 dred times the work required to be spent to lift 
 it once ; but if fluid resistance comes into play, 
 and if this varies as the square of the velocity of 
 the moving body, . then the total work done in 
 lifting t'.ie weight through the fluid will be de- 
 pendent also upon the rate at which the cycle is 
 performed." 
 
274 
 
 [111. 
 
 I. H. P. A contraction for indicated horse- 
 power, or the horse-power of an engine as 
 obtained by the means of an indicator card. 
 
 I. W. Cr. A contraction for Indian wire 
 gauge. 
 
 Idio-ElectricSo A name formerly applied 
 to such bodies as amber, resin or glass, which 
 are readily electrified by friction, and which 
 were then supposed to be electric in them- 
 selves. 
 
 This distinction was based on an erroneous 
 conception, and the word is now obsolete. 
 
 Idiostatic. A term employed by Sir Wil- 
 liam Thomson to designate an electrometer 
 in which the measurement is effected by de- 
 termining the repulsion between the charge 
 to be measured and that of a charge of the 
 same sign imparted to the instrument from 
 an independent source. (See Heterostatic) 
 
 Idle Poles. (See Poles, Idle.) 
 
 Igniter, Jablochkoff A small strip 
 
 of carbon, or some carbonaceous material 
 that is readily rendered incandescent by the 
 current, placed between the free ends of the 
 parallel carbons of a Jablochkoff candle, for 
 the establishment of the arc on the passage 
 of the current. 
 
 The igniter is necessary in the Jablochkoff elec- 
 tric candle, since the parallel carbons are rigidly 
 kept at a constant distance apart by the insulat- 
 ing material placed between them, and cannot 
 therefore be moved together as in the case of the 
 ordinary lamp. (See Candle, Jablochkoff.) 
 
 Ignition, Electric The ignition of 
 a combustible material by heat of electric 
 origin. 
 
 The electric ignition of wires is generally ac- 
 complished by electric incandescence. Ignition 
 may be accomplished by the heat of the voltaic 
 arc. (See/fcotf, Electric. Furnace, Electric.') 
 
 The ignition of combustible gases is accom- 
 plished by the heat of the electric spark. (See 
 Burner, Automatic, Electric.} 
 
 Illumination, Artificial The em- 
 ployment of artificial sources of light. 
 
 A good artificial illuminant should possess the 
 following properties, viz.: 
 
 (i.) It should give a general or uniform illumi- 
 nation as distinguished from sharply marked 
 regions of light and shadow. 
 
 To this end a number of small lights well dis- 
 tributed are preferable to a few large lights. 
 
 (2.) It should give a steady light, uniform in 
 brilliancy, as distinguished from a flickering, 
 unsteady light. Sudden changes in the intensity 
 of a light injure the eyes and prevent distinct 
 vision. 
 
 (3.) It should be economical, or not cost too 
 much to produce. 
 
 (4.) It should be safe, or not likely to cause 
 loss of life or property. To this intent it should, 
 if possible, be inclosed in or surrounded by a 
 lantern or chamber of some incombustible mate- 
 rial, and should preferably be lighted at a dis- 
 tance. 
 
 (5 ) It should not give off noxious fumes or 
 vapors when in use, nor should it unduly heat 
 the air of the space it illumines. 
 
 (6. ) It should be reliable, or not apt to be un- 
 expectedly extinguished when once lighted. 
 
 ' The electric incandescent lamp is an excellent 
 artificial illuminant. 
 
 (l.) It is cap able of great subdivision, and can, 
 therefore, produce a uniform illumination. 
 
 (2.) It is steady and free from sudden changes 
 in its intensity. 
 
 (3.) It compares favorably in point of economy 
 with coal oil or gas, provided its extent of use is 
 sufficiently great. 
 
 (4.) It is safer than any known illuminant, 
 since it can be entirely inclosed and can be 
 lighted from a distance or at the burner without 
 the dangerous friction match. 
 
 The leads, however, must be carefully insu- 
 lated and protected by safety fuses. (See Fuse, 
 Safety.) 
 
 (5.) It gives off no gases, and produces far less 
 heat than a gas-burner of the same candle power. 
 
 It perplexes many people to understand why 
 the incandescent electric light should not heat 
 the air of a room as much as a gas light, since it 
 is quite as hot as the gas light. It must be re- 
 membered, however, that a gas-burner, when 
 lighted, not only permits the same quantity of 
 
111.] 
 
 275 
 
 gas to enter the room which would enter it if 
 the gas were simply turned on and not lighted, 
 but that this bulk of gas is still given off, and is, 
 indeed, considerably increased by the combina- 
 tion of the illuminating gas with the oxygen of the 
 atmosphere ; and, moreover, this great bulk of 
 gas escapes as highly heated gases. Such gases 
 are entirely absent in the incandescent electric 
 light, and consequently its power of heating the 
 surrounding air is much less than that of gas 
 lights. 
 
 (6.) It is quite reliable, and will continue to 
 burn as long as the current is supplied to it. 
 
 Illumination, Lighthouse, Electric 
 
 The application of the electric arc light 
 to lighthouses. 
 
 A powerful arc light is placed in the focus of 
 the dioptric lens now commonly employed in 
 lighthouses. Since the consumption of the carbon 
 electrodes would alter the position of the focus of 
 the light, electric lamps for such purposes are 
 constructed to feed both of their carbons, instead 
 of the upper carbon only, as in the case of the 
 ordinary arc lamp. Such lamps are called focus- 
 ing lamps. 
 
 Illumination, Unit of A standard 
 
 of illumination proposed by Preece, equal to 
 the illumination given by a standard candle 
 at the distance of 12.7 inches. 
 
 According to Preece, the illumination of the 
 average streets of London, where gas is employed, 
 is equal to about one-tenth of this standard in the 
 neighborhood of a gas lamp, and about one- 
 fiftieth in the middle space between two lamps. 
 
 The term unit of illumination, in place of in- 
 tensity of light, was proposed by Preece in order 
 to avoid the very great difficulty in determining 
 the intensity of a light in a street or space where 
 there were a number of luminous sources, and 
 where the directions of incidence of the different 
 lights vary so greatly. 
 
 A carcel standard at the distance of a metre 
 will illumine a surlace to the same intensity of 
 illumination as a standard candle at the distance 
 of 12,7 inches. (See Candle, Foot.) 
 
 Illumined Electrode. (See Electrode, 
 Illumined?) 
 
 Imbibition Currents. (See Currents, Im- 
 bibition.] 
 
 Images, Electric A term some- 
 
 times applied to the charge produced on a 
 neighboring surface by induction from a 
 known charge. 
 
 A positive charge produces, by induction, on a 
 flat metallic surface near it, a negative charge 
 which is distributed with varying density over the 
 surface, but acts electrically as would an equal 
 quantity of negative electricity placed back of the 
 plate at the same distance the positive charge is 
 in front of it. The correspondence of this charge 
 with the image of an object seen in a plane mirror, 
 has led to the term electric image. 
 
 Maxwell defines electric image as follows: " An 
 electric image is an electrified point, or system of 
 points, on one side of a surface, which would pro- 
 duce, on the other side of that surface, the same 
 electrical action which the actual electrification of 
 the surface really does produce." 
 
 Impedance. Generally any opposition to 
 current flow. 
 
 The sum of the ohmic resistance and the 
 spurious resistance of a circuit measured in 
 ohms. 
 
 A quantity which is related to the strength 
 of the impressed electromotive force of a sim- 
 ple periodic or alternating current, in the same 
 manner that resistance is related to the steady 
 electromotive force of a continuous current. 
 
 In the case of steady currents, the current 
 strength is equal to the electromotive force dl. 
 vided by the resistance ; or, 
 
 Electromotive force 
 Current strength =; 
 
 Resistance. 
 
 In the case of a simple period ic or alternating cur. 
 rent, the average current strength is equal to the 
 average impressed electromotive force divided by 
 the impedance; or, 
 Average current strength = 
 
 Average impressed electromotive force 
 Impedance. 
 
 Since impedance, like true resistance of the cir- 
 cuit, can be measured in ohms, it is sometimes 
 called the virtual resistance. 
 
 Impedance is a quantity equal to the square 
 root of the sum of the squares of the inductive 
 resistance of the circuit and the ohmic resistance. 
 
 In the case of simple periodic or alternating 
 currents, the average current strength is equal to 
 the average impressed electromotive force, divided 
 by the impedance ; the maximum current strength 
 
lmp.J 
 
 276 
 
 [Inc. 
 
 is equal to the maximum impressed electromotive 
 force, divided by the impedance. 
 
 The impedance of a circuit can be repre- 
 sented geometrically as fol 
 lows: Draw a right angled 
 triangle (Fig. 296), the base 
 of which represents the 
 ohmic resistance of the cir- 
 cuit, and the perpendicular, 
 the inductive resistance 
 
 C RESISTANCE 
 
 Fig. 2<)b. Geometrical 
 ' Representation of Itn- 
 then the hypothenuse will pedance. 
 represent the impedance. 
 
 Since the ohmic resistance equals R, and the in- 
 ductive resistance equals the inductance L, mul- 
 tiplied by 2 it n, in which n, is the frequency, the 
 value of the impedance is equal to 
 /R a + 4 it* n L. 
 
 Impedance Coil. (See Coil, Impedance!) 
 
 Impedance, Impulsive or Oscillatory 
 
 The impedance which a conductor 
 
 offers to an impulsive or oscillatory dis- 
 charge. 
 
 The impulsive impedance varies in simple pro- 
 portion to the frequency of the periodic current. 
 It depends on the form and size of the circuit, but 
 it is independent of its resistance or permeability. 
 
 Imponderable. That which possesses no 
 weight. 
 
 A term formerly applied to the luminiferous 
 or universal ether, but now generally aban- 
 doned. 
 
 It is very questionable whether it is possible for 
 any form of matter to be actually imponderable 
 or to possess no attraction for other matter. 
 
 An imponderable fluid, as, for example, the 
 universal ether, as the term is now generally em- 
 ployed, is a fluid whose weight is comparatively 
 small and insignificant, and not a fluid an infinite 
 quantity of which would be entirely devoid of 
 weight. 
 
 Impressed Electromotive Force. (See 
 Force, Electromotive, Impressed!) 
 
 Impulse, Electro-Magnetic An im- 
 pulse produced in the ether surrounding a 
 conductor by the action of an impulsive dis- 
 charge, or by a pulsating field. 
 
 Impulse, Electromotive An im- 
 pulse producing an impulsive rush of elec- 
 tr'city. 
 
 The term is employed to distinguish between 
 the ordinary electromotive force which produces a 
 steady current of electricity and an electromotive 
 impulse which produces an impulsive rush of elec- 
 tricity or impulsive discharge. 
 
 Impulsion Cell. (See Cell, Impulsion!) 
 
 Impulsion Effect. (See Effect, Impul- 
 sion!) 
 
 Impulsive Impedance. (See Impedance, 
 Impulsive or Oscillatory!) 
 
 Incandesce. To shine or glow by means 
 of heat. 
 
 Incandescence. The shining or glowing of 
 a substance, generally a solid, by reason of a 
 sufficiently high temperature. 
 
 Incandescence, Electric The shin- 
 ing or glowing of a substance, generally a 
 solid, by means of heat of electric origin. 
 
 Electric incandescence of solid substances differs 
 from ordinary incandescence, in the fact that un- 
 less the substance is electrically homogeneous 
 throughout, the temperature is not uniform in all 
 parts, but is highest in those portions where the 
 resistance is highest and the radiation smallest. 
 
 The deposition of carbon in and on a carbon 
 conductor by the flashing process is quite different 
 as performed by electrical incandescence, than it 
 would be if the carbons were heated by ordinary 
 furnace or other heat. (See Carbons, Flashing 
 Process for.} 
 
 Incandescence, Thermal The shin- 
 ing or glowing of a substance, generally a 
 solid, by means of heat other than that of 
 electric origin. 
 
 Incandescent. Shining or glowing with 
 heat. 
 
 Incandescent Ball Electric Lamp. (See 
 Lamp, Electric, Incandescent Ball!) 
 
 Incandescent Electric Lamp, Life Curve 
 
 of (See Curve, Life, of Incandescent 
 
 Lamp!) 
 
 Incandescent Electric Lamp, Life of 
 
 (See Lamp, Electric, Incandescent, Life 
 of!) 
 Incandescent Straight Filament Lamp. 
 
 (See Lamp, Incandescent, Straight Fila- 
 ment.} 
 
Inc.] 
 
 277 
 
 [Ind 
 
 Incandescing. Glowing or shining by 
 means of heat. 
 
 Inclination, Angle of The angle 
 
 which a magnetic needle, free to move in a 
 vertical and horizontal plane, makes with a 
 horizontal line passing through its point of 
 support. 
 
 The angle of magnetic dip. 
 
 A magnetic needle, supported at its centre of 
 gravity, and capable of moving freely in a ver- 
 tical as well as in a horizontal plane, does not 
 retain a horizontal position at all parts of the 
 earth's surface. 
 
 The angle which marks its deviation from the 
 horizontal position is called the angle of dip or 
 inclination. (See Dip, Magnetic.) 
 
 Incandescent Electric Lamp. (See 
 Lamp, Electric, Incandescent.) 
 
 Inclination Chart. (See Chart, Inclina- 
 tion.) 
 
 Inclination Compass. (See Compass, In- 
 clination.) 
 
 Inclination, Magnetic The an- 
 gular deviation from a horizontal position of 
 a freely suspended magnetic needle. (See 
 Dip, Magnetic. Chart, Inclination.) 
 
 Inclination Map. (See Map or Chart, 
 Inclination!) 
 
 Inclination of Magnetic Needle. (See 
 Needle, Magnetic, Inclination of) 
 
 Inclinometer. A name sometimes given 
 to an inclination compass. (See Compass, 
 Inclination.) 
 
 Incomplete Circuit. (See Circuit, In- 
 complete.) 
 
 Increased Electric Irritability. (See 
 Irritability, Electric, Increased.) 
 
 Increment Key. (See Key, Increment.) 
 
 Increment Key of a Quadrnplex Tele- 
 graphic System. (See Key, Increment, of 
 Quadruple* Telegraphic System.) 
 
 India Rubber. A resinous substance ob- 
 tained from the milky juices of several tropi- 
 cal trees. 
 
 India rubber or caoutchouc is obtained from 
 the Siphonia elastica of South America. 
 
 India rubber is quite elastic and possesses high 
 powers of electric insulation. When vulcanized 
 or combined with sulphur, it still retains its 
 powers of electric insulation in a high degree. 
 In this state it is highly electrified by friction. 
 (See Caoutchouc.) 
 
 Indicating Bell. (See Bell, Indicating!) 
 
 Indicator, Automatic Any auto- 
 matic device for electrically indicating the 
 number of times a circuit has been opened or 
 closed, and thus the number of times a given 
 operation has occurred which has caused the 
 opening or closing of such circuit. 
 
 An annunciator with an automatic drop is 
 sometimes called an automatic indicator. (See 
 Annunciator, Electro-Magnetic. Annunciator 
 Drop, Automatic.) 
 
 Indicator, Electric A name ap- 
 plied to various devices, generally operated 
 by the deflection of a magnetic needle, or the 
 ringing of a bell, or both, for indicating, at 
 some distant point, the condition of an electric 
 circuit, the strength of current that is passing 
 through it, the height of water or other liquid, 
 the pressure on a boiler, the temperature, the 
 speed of an engine or line of shafting, the 
 working of a machine or other similar events 
 or occurrences. 
 
 A term sometimes used in place of annun- 
 ciator. (See Annunciator, Electro-Magnetic.) 
 
 Indicators are of various forms. They are 
 generally electro-magnetic in character. They 
 are automatic in action. 
 
 Indicator, Electric Circuit A de- 
 vice, generally in the form of a vertical gal- 
 vanometer, employed to indicate the presence 
 and direction of a current in a circuit, and 
 often to roughly measure its strength. (See 
 Galvanometer, Vertical.) 
 
 Indicator, Electric, for Steamships 
 
 An electric indicator operated by circuits 
 connected with the throttle valve and revers- 
 ing gear of the steam engine. 
 
 The signal "stop, "for example, sent by the 
 navigating officer to the engineer, causes him to 
 close the throttle. This act places the indicator 
 needle at "=top," and thus informs the officer 
 that his signal has been obeyed. In the same 
 
Ind.] 
 
 278 
 
 [Inch 
 
 manner, the opening of the throttle sets the in- 
 dicator needle to "ahead," etc. 
 
 Indicator, Electric Throwback 
 
 An annunciator with a drop that is electrically 
 replaced. (See Annunciator, Electro-Mag- 
 netic^) 
 
 Indicator, Lamp An apparatus 
 
 used in the central station of a system of in- 
 candescent lamp distribution to indicate the 
 presence of the proper voltage or potential 
 difference on the mains. 
 
 Fig. 297. Edison-Htrwell Lamp Indicator. 
 
 The lamp indicator of Edison and Howell is 
 shown in Fig. 297. It consists essentially of a 
 Wheatstone bridge with the resistances arranged 
 as shown. A galvanometer at G, serves, by the 
 movements of its magnetic needle, to act as an 
 indicator. This needle remains at zero, when 
 the potential difference is the exact voltage re- 
 quired on the circuit with which the indicator is 
 connected. The incandescent lamp at L, being 
 one of the resistances, and being constantly 
 traversed by the current, will have a fixed resist- 
 ance for the temperature at which it is designed 
 to run. The other resistances are so proportioned 
 as to insure the needle at G, remaining at zero. 
 If, however, the potential varies, the temperature 
 of the lamp L, varies, and, being carbon, its re- 
 sistance also varies, a rise of temperature cor- 
 responding to a fall of lamp resistance, which 
 destroys the balance of the bridge and deflects 
 the galvanometer needle. The attendant then 
 regulates the potential to bring the needle back to 
 zero. 
 
 Indicator, Mechanical Throwback 
 
 An annunciator with a mechanical drop. 
 (See Annunciator, Electro-Magnetic. An- 
 nunciator, Drop. Annunciator, Gravity?) 
 
 Indicator, Pendnlnm An annun- 
 ciator, the indicating arm of which is operated 
 
 by means of a pendulum. (See Annunciator, 
 Pendulum?) 
 
 Indicator, Potential An apparatus 
 
 for indicating the potential difference between 
 any points of a circuit. 
 
 A voltmeter is a potential indicator. It is, 
 however, more than an indicator, since it gives 
 the value of the potential difference in volts. (See 
 Voltmeter.} A lamp indicator is a potential in- 
 dicator. (See Indicator, Lamp.) 
 
 Indicator, Semaphore An annun- 
 ciator in which a gravity drop or shutter is 
 caused to fall by the action of the electric 
 current, thus exposing a number of other 
 signals back of the drop or shutter. 
 
 Indicator, Speed A name some- 
 times applied to a tachometer. (See Tachom- 
 eter:) 
 
 A form of speed indicator is shown in Fig. 
 298. The endless screw drives the wheel when 
 the triangular point is held firmly against the 
 centre of the revolving shaft or pulley. 
 
 Fig. 298. Speed Indicator. 
 
 Indicator, Voltaic Battery A de- 
 vice for indicating the condition of a voltaic 
 battery. 
 
 Indifferent Point. (See Point, Indif- 
 ferent?) 
 
 Indirect Excitation. (See Excitation, 
 Indirect?) 
 
 Induced Atomic Currents. (See Cur- 
 rents, Induced, Atomic or Molecular?) 
 
 Induced Current. (See Current, In- 
 duced?) 
 
 Induced Direct Current. (See Current, 
 Direct, Induced?) 
 
 Induced Electrostatic Charge. (See 
 Charge, Induced Electrostatic?) 
 
 Induced Molecular Currents. (See Cur* 
 rents. Induced Molecular?} 
 
Ind.] 
 
 Induced Reverse Currents. (See Cur- 
 rent, Reverse, Induced?) 
 
 Inductance --- The induction of a 
 circuit on itself, or on other circuits. 
 
 Self-induction. 
 
 A term now generally employed instead of 
 self-induction. 
 
 That property in virtue of which a finite 
 electromotive force, acting on a circuit, does 
 not immediately generate the full current due 
 to its resistance, and when the electromotive 
 force is withdrawn, time is required for the 
 current strength to fall to zero. (Fleming.) 
 
 A quality by virtue of which the passage of 
 an electric current is necessarily accompanied 
 by the absorption of electric energy in the 
 formation of a magnetic field. 
 
 The inductance of a circuit depends: 
 
 (i. ) On the form or shape of the circuit. 
 
 (2.) On the magnetic permeability of the space 
 surrounding the circuit. 
 
 (3.) On the magnetic permeability of the circuit 
 itself. 
 
 For the variations of current strength in elec- 
 tric circuits, inductance is not unlike mass, or 
 moment of inertia, as regards variations of velo- 
 city. Time is required to produce velocity in a 
 heavy body by the action of any force; so also 
 time is required to produce a current by the 
 action of an electromotive force. 
 
 The electro-magnetic energy present in any 
 given current is equal to the square of the current 
 multiplied by the inductance. Since one of these 
 factors (the current strength) represents the 
 force, the other, the inductance, must have the 
 dimension of a distance or length. Inductance, 
 therefore, is measurable in units of length. If 
 the circuits are formed of magnetizable materials, 
 the inductance of a circuit is the ratio between the 
 total inductance taking place through the circuit 
 to the current producing it. 
 
 If the circuit is formed entirely of non-magnetic 
 material, surrounded entirely by materials of 
 constant magnetic permeability (such as air, in- 
 sulators and diamagnetic materials generally), the 
 inductance is a constant quantity and depends 
 only on the form or shape of the circuit. In this 
 case, the total inductance through the circuit is pro- 
 portional to the magnetizing force, and the mag- 
 netic resistance, or the magnetic conductance of 
 the magnetic circuit, is equal to the total indue- 
 
 279 
 
 [Ind. 
 
 tion through the circuit, divided by the magnetiz- 
 ing force. 
 
 In cases where the magnetic circuit is partly or 
 wholly of paramagnetic substances, where the 
 induction bears no constant ratio to the magnetiz- 
 ing force, and where the induction takes place 
 partly or wholly in media of variable permeability, 
 the co-efficient of self- induction, or the inductance, 
 must be denned in three ways: 
 
 (i.) As the ratio between the counter electro- 
 motive force in any circuit and the time rate or 
 variation of the current producing it. 
 
 (2.) As the ratio between the total induction 
 through the circuit and the current producing it. 
 
 (3.) As the energy associated with the circuit 
 in the form of magnetic field, due to unit current 
 in that circuit, or as the co-efficient by which half 
 the square of the current must be multiplied to 
 obtain the electro-kinetic energy of the circuit at 
 that instant. - (Fleming.) 
 
 A flat sheet or strip of metal possesses less in- 
 ductance than a round conductor of equal cross- 
 section. 
 
 This may be explained by conceiving that a 
 flat conductor presents a greater absorption sur- 
 face to the dielectric. 
 
 Therefore, the perfect form for a conductor 
 transmitting rapidly alternating currents is that 
 of a flat sheet or strip of copper, or preferably a 
 copper tube. 
 
 The experiments of Hughes show that the in- 
 ductance of a conductor may be regarded as an 
 effect due to the time required for the rapidly 
 periodic current to penetrate the conductor, and 
 that the decrease in the inductance, produced by 
 forming the conductor of a strip or bar, is due 
 to the decreased distance the current has to pass 
 to the inner parts. 
 
 Inductance, Absolute Unit of A 
 
 unit of length equal to one centimetre. 
 
 A length equal to an earth quadrant or IO 
 centimetres is called the practical unit of induct- 
 ance. The practical unit of inductance was form- 
 erly called a secohm or quadrant It is now gen- 
 erally called a henry. (See Henry, A.) 
 
 Inductance Bridge. (See Bridge, In- 
 ductance) 
 
 Inductance, Co-efficient of A con- 
 stant quantity, such that when multiplied by 
 the current strength passing in any coil or cir- 
 cuit, will represent numerically the induction 
 through the coil or circuit due to that curren*. 
 
Iiid. 
 
 280 
 
 rind. 
 
 A term sometimes used for co-efficient of 
 self-induction. (See Induction, Co-efficient 
 of-} 
 
 Inductance, Constant The induct- 
 ance which occurs in circuits formed wholly 
 of non-magnetic materials, immersed in or 
 surrounded by media of constant magnetic 
 permeability or magnetic conductance for 
 lines of magnetic force. (See Permeability, 
 Magnetic?) 
 
 When the lines of magnetic force pass through 
 such materials as ordinary insulators, or diamag- 
 netic materials, such as copper, the inductance is 
 constant, provided the geometric form of the cir- 
 cuit remains the same. 
 
 Inductance, Formal, of Circuit 
 
 That part of the counter electromotive force 
 of a circuit which depends on the form of the 
 circuit. 
 
 Inductance, or Self-Induction, Practical 
 
 Unit of A length equal to the earth 
 
 quadrant or 10 centimetres. 
 
 The absolute unit of inductance is equal to i 
 centimetre. 
 
 Inductance, Oscillatory, Electric 
 
 Inductance produced by electric oscillations. 
 
 Inductance, Unit of A term now 
 generally used for unit of self-induction. 
 
 The value of the inductance may be given 
 either in absolute or in practical units of induct- 
 ance. The absolute unit of inductance is equal 
 to a length of one centimetre. The practical unit 
 of inductance is equal to 1,000,000,000 centi- 
 metres or jo 1 centimetres. 
 
 The praciical unit of inductance was formerly 
 called a secohm. The term henry is generally 
 used for this unit. (See Henry, A.) 
 
 Inductance, Variable The induc- 
 tance which occurs in circuits formed partly 
 or wholly of substances like iron or other 
 paramagnetic substances, the magnetic 
 permeability of which varies with the inten- 
 sity of the magnetic induction, and where the 
 lines of force have their circuit partly or 
 wholly in such material of variable magnetic 
 permeability. 
 
 Induction. An influence exerted by a 
 
 charged body or by a magnetic field on. neigh- 
 boring bodies without apparent communica- 
 tion. 
 
 A medium is necessary to connect the body 
 producing the induction and that in which the 
 induction is produced. (See Induction, Electro- 
 static. Induction, Magnetic. Induction, Electro- 
 Dynamic. ) 
 
 Induction, Apparent Co-efficient of 
 
 A term sometimes used for co-efficient of 
 apparent magnetic induction. (See Induc- 
 tion, Magnetic, Apparent Co-efficient of.} 
 
 It is called the apparent co-efficient of induction 
 because its value is different from what it would 
 be if the eddy currents were entirely suppressed. 
 The eddy currents increase the resistance of the 
 primary and decrease its inductance. 
 
 Induction-Balance, Hughes' (See 
 
 Balance, Induction, Hughes'?) 
 
 Induction, Balance of, in Cable 
 
 The removal of induction in a cable by 
 neutralization by the presence of equal and 
 opposite effects. 
 
 A balance is obtained of the inductive effects of 
 the neighboring conductors, whether in the 
 bunched cable or outside of it. 
 
 Induction-Bridge. (See Bridge, Induc- 
 tance?) 
 
 Induction, Co-efficient of A term 
 
 sometimes used for co-efficient of magnetic 
 induction. (See Induction, Magnetic, Co- 
 efficient of} 
 
 Induction Coil. (See Coil, Induction} 
 
 Induction Coil, Inverted (See 
 
 Coil, Induction, Inverted. Transformer} 
 
 Induction, Current A term some- 
 times used for voltaic induction. (See Induc- 
 tion, Voltaic. Induction, Electro-Dynamic} 
 
 Induction, Dissymmetrical, of Armature 
 
 An induction produced by the passage 
 
 of a different number of lines of magnetic 
 force through adjoining halves of the arma- 
 ture. 
 
 Induction, Electro-Dynamic = Elec- 
 tromotive forces set up by induction in con- 
 ductors which are either actually or practically 
 moved so as to cut the lines of magnetic 
 force. 
 
Ind.J 
 
 I 
 
 These electromotive forces, when permitted to 
 act through a circuit, produce an electric current. 
 Electro-dynamic induction may be produced in 
 any circuit in two ways: 
 
 (I.) By causing expanding or contracting lines 
 of magnetic force to pass through that circuit. 
 
 (2.) By causing the circuit or conductor to pass 
 through the lines of magnetic force. 
 
 In all cases the lines of force are made to pass 
 through the conductor or wire. 
 
 There are four cases of electro- magnetic induc- 
 tion: 
 
 (i.) That in which expanding or contracting 
 lines of magnetic force, produced by rapidly vary- 
 ing the current in any circuit, are caused to pass 
 through or cut that circuit and consequently to 
 produce differences of potential therein. 
 
 (2.) That in which expanding or contracting 
 lines of magnetic force produced by any circuit by 
 the rapidly varying strength of the electric 
 current passing through that circuit, are caused 
 to pass through another neighboring circuit and 
 thus produce differences of potential therein. 
 
 (3.) That produced by moving a conductor 
 through a magnetic field so as to cut its lines of 
 magnetic force. In this way the strength of the 
 magnetic field may remain practically constant, 
 but this strength as regards the field of the fixed 
 conductor is varying, as the magnet producing 
 such a field is moved toward or from such cir- 
 cuit, and m this way differences of potential are 
 produced in the circuit. 
 
 (4. ) That produced by moving an inducing field 
 past a fixed conductor. This may le accom- 
 plished by moving an electro-magnet, an electric 
 circuit, or a permanent magnet past the conductor 
 in which the difference of potential is to be in- 
 duced. 
 
 There are therefore four distinct varieties of 
 electro-dynamic induction: 
 
 (i.) Self-induction or inductance. (See Induct- 
 ance.) 
 
 (2.) Mutual induction, or, as it is sometimes 
 called, voltaic current induction. (See Induction, 
 Mutual.} 
 
 (3.) Electro-magnetic induction, or, as it is 
 sometimes calleJ, dynamo-electric induction. 
 (4.) Magneto-electric induction. 
 If the terminals of a voltaic cell be connected 
 with the ends of a comparatively long coil of in- 
 sulated wire, no appreciable spark will be observed 
 on closing the cell, because the current induced 
 by self-induction is in the opposite direction to the 
 
 281 
 
 [Ind. 
 
 current of the cell and weakens it. On breaking 
 contact, however, a spark is readily observed. 
 This is due to the induced current on breaking, 
 which, flowing in the same direction as the cur- 
 rent of the cell, strengthens it. 
 
 Fig. 299. Mutual Induction 
 
 The coil B, Fig. 299, consists of two parallel 
 coils of insulated wire, the terminals of one of 
 which, called the primary coil, are connected 
 with the battery cell P N, and those of the 
 other, called the secondary coil, with the galva- 
 nometer G. 
 
 Under these circumstances it is found : 
 (i.) That at the moment of closing the circuit 
 through the primary coil, a momentary current 
 is produced in the secondary coil in a direction 
 opposite to that of the current through the primary, 
 as is shown by the direction of the deflection of 
 the needle of the galvanometer. 
 
 (2.) At the moment of breaking the circuit 
 through the primary coil, an induced current is 
 produced in the secondary coil in the same direc- 
 tion as that flowing through the primary coil. 
 
 (3.) These induced currents are momentary, 
 and continue in the secondary only while the in- 
 tensity of the current in the primary is varying, 
 *. <?., while variations are occurring in the strength 
 of the magnetic field in which the secondary coil 
 is placed, therefore while the expanding or con- 
 tracting lines of force are passing through the sec- 
 ondary coil. 
 
 If, for instance, when the current is established 
 in the primary coil, and no current exists in the 
 
 Fig. 300. Mutual Induction. 
 
 secondary, the intensity of the current in the 
 primary be varied by establishing a shunt circuit 
 across the battery terminals, as by placing a short 
 wire d, Fig. 300, in the mercury cups g, 2, thus 
 
Ind.] 
 
 282 
 
 [Ind. 
 
 decreasing the intensity of the current in the 
 primary, an induced current will be set up in the 
 secondary circuit in the same direction as the 
 primary current. 
 
 From all of these phenomena, we see that any 
 increase of current in a conductor produces in a 
 neighboring conductor an induced inverse current, 
 or one in the opposite direction to the inducing 
 current, while a decrease of such current produces 
 a direct induced current, or one in the same 
 direction as the inducing current. 
 
 If the induction coil be made, as in Fig. 301, 
 with its primary coil movable into and out of the 
 secondary coil, then the following phenomena will 
 occur: 
 
 (i.) When the primary coil is moved toward 
 the secondary coil an inverse current is induced 
 in the secondary ; and, 
 
 (2 ) When the primary coil is moved away from 
 the secondary coil a direct current is induced in 
 the secondary. 
 
 The movements of permanent magnets towards 
 or from a coil will also produce an induced cur- 
 rent. 
 
 If, for example, the apparatus be arranged as 
 in Fig. 302, then: 
 
 These facts may be expressed by the following 
 laws : 
 (i.) Any increase in thenumber of lines of force 
 
 Fig, 301. Electro- Dynamic Induction. 
 
 (i.) A motion of the magnet towards the coil 
 produces an induced current in the coil in one 
 direction, and 
 
 (2.) Its motion away from the magnet produces 
 an induced current in the coil in the opposite 
 direction. 
 
 The directions of these induced currents are 
 respectively inverse and direct as compared with 
 the direction of the amperian currents which are 
 assumed to produce the magnetic poles of perma- 
 nent magnets, or of the currents that actually 
 produce electro-magnets. (See Magnetism, Am- 
 p$re's Theory of.} 
 
 Fig. 302. Magneto-Electric Induction. 
 
 which pass through a circuit produces an inverse 
 current in that circuit, while any decrease in the 
 number of such lines of force which pass through 
 any circuit produces a direct current in that 
 circuit. 
 
 Fleming's Rule. 
 
 (2.) The intensity of the induced current, or, 
 more correctly, the difference of potential pro- 
 duced, is proportional to the rate of increase or 
 decrease of the lines of force passing through the 
 circuit. 
 
 A conductor, therefore, when moved through 
 
283 
 
 [ind. 
 
 a magnetic field so as to cut the lines of magnetic 
 force, will have a difference of potential generated, 
 and if its circuit is closed so that the difference of 
 potential can neutralize itself, it will have a cur- 
 rent produced in it by induction. 
 
 A simple but effective manner of remembering 
 the direction of such currents is that proposed by 
 Fleming. 
 
 If the hand be held with the fingers extended, 
 as in Fig. 303, and the direction of the forefinger 
 represent the positive direction of the lines of 
 force, i. e., those coming out of the N. pole of a 
 magnet, then, if a wire or other conductor be 
 moved in the direction in which the thumb points, 
 so as to cut these lines of force at right angles, 
 that is, if the conductor have its length moved 
 directly across these lines, it will have an induced 
 current developed in it in the direction in which 
 the middle finger points. (See Force, Lines of, 
 Direction of.) 
 
 Or, the same thing can, perhaps, be even more 
 readily remembered by 
 cutting a piece of paper 
 In the shape shown in v. 
 Fig. 304, marking it as a | 
 shown, and then bending +3 "g 
 the arm P, upward at the Jj $ 
 dotted line, so as to form Q p 
 three axes at right angles 
 to one another. ,_ 
 
 As has been already c -g 
 remarked, a difference of g 
 potential, and not a cur- 8 
 rent, is produced by mov- 
 ing a conductor through 
 a magnetic field so as to 
 cut its lines of force. 
 
 Direction of 
 Motion. 
 
 c 
 304- 
 
 . . 
 
 Fleming's Rule. 
 
 It can be shown that in order to generate a dif- 
 ference of potential of one volt, 100,000,000 C. G. 
 S. lines of force must be cut per second. 
 
 In electro-dynamic induction, the induced cur- 
 rent is produced by the energy absorbed in moving 
 the conductor through the magnetic field. Lenz 
 has shown that in all cases of electro-dynamic 
 induction, produced by the movement either of 
 the circuit or of the magnet, the current induced 
 in the circuit is in such a direction as to produce 
 a magnet pole which would tend to oppose the 
 motion. 
 
 Induction, Electro-Magnetic -- A 
 
 variety of electro-dynamic induction in which 
 electric currents are produced by the motion 
 10 Vol. 1 
 
 of electro-magnets or electro-magnetic sole- 
 noids. (See Induction, Electro-Dynamic^} 
 
 Induction, Electrostatic The pro- 
 duction of an electric charge in a conductor 
 brought into an electrostatic field. 
 
 If the insulated conductor A B, Fig. 305, be 
 brought into the positive electrostatic field of the 
 insulated conductor C, then, 
 
 (I.) A charge will be produced on A and B, as 
 will be indicated by the divergence of the pith 
 balls. 
 
 (2.) This charge is negative at the end A, 
 nearest C, and positive at the end B, furthest 
 from C, as canbesho\\n by sen electroscope. (See. 
 Electroscope. ) 
 
 B 
 
 Fig. 3 OS Electrostatic Induction. 
 
 (3.) The charges at A and B, are equal to each 
 other ; for, if the conductor A B, be removed from 
 the field of C, without touching it, the opposite 
 charges completely neutralize each other. 
 
 (4.) If, however, the conductor A B, be touched 
 at any place by a conductor connected with the 
 earth, it will lose its positive charge, and will 
 remain negatively charged when removed fron? 
 the field of C. It is in this manner that an electro- 
 phorus is charged. (See Electrophonis. ) 
 
 (5.) The amount of the charges produced in the 
 conductor, A B, can never be greater than that 
 in the inducing body C. That is to say, be 
 
 Fig. $06. Induction Precedes Attraction. 
 
 negative electricity at A, may be sufficient in 
 amount to neutralize the positive charge on C, if 
 allowed to do so. la point of fact the charge in- 
 
Ind.] 
 
 284 
 
 [Ind. 
 
 duced is less in amount than the inducing charge, 
 according to the distance between C and A, and 
 the nature and condition of the medium which 
 separates them. 
 
 The attraction? of light bodies by charged sur- 
 faces are due to the opposite charge produced on 
 those parts of th; light bodies that are nearest the 
 charged body 
 
 The pith ball B, Fig. 306, suspended by a silk 
 thread between an insulated positively charged 
 conductor A, and the uninsulated conductor C, 
 will receive by induction a negative charge on 
 the side nearest A, and a positive charge on the 
 side nearest C. It is therefore attracted to A, 
 where, receiving a positive cnarge, it is repelled to 
 C, where it is discharged and again assumes a 
 vertical position. Induction again occurs, and 
 consequent attraction and repulsion. These 
 movements follow one another so long as a suffi- 
 cient charge remains in A. 
 
 Induction, Faradic, Apparatus 
 
 (See Apparatus, Faradic Induction?) 
 
 Induction-Finder. (See Finder, Induc- 
 tion^ 
 
 Induction, Lateral An induction 
 
 observed between closely approached portions 
 of a circuit through which an impulsive dis- 
 charge, such as the disruptive discharge of a 
 Leyden jar, is passed as a long spark, thereby 
 making the resistance of the circuit high. 
 
 A long copper wire, bent in the form of a rec- 
 tangle, has its free ends near their extremities 
 bent so as to approach within half an inch of each 
 other. One of the ends of the wire is provided 
 with a metallic ball and the other end connected 
 with the earth. If, now, a Leyden jar charge is 
 passed through the wire by connecting the outer 
 coating with the end of the earth-connected wire 
 and holding the inside coating near the knob, a 
 spark will pass through the half inch of space be- 
 tween the approached portions of the circuit. 
 
 This discharge is due to what was formerly 
 called lateral induction. The discharge of a 
 Leyden jar is an oscillatory discharge, and it 
 passes through the intervening air space instead 
 of through the conductor because the resistance 
 of the latter to the rapid alternations produces a 
 counter electromotive force which acts as a re- 
 sistance whose value is greater than that of the 
 airspace itself. (See Path, Alternative.) 
 
 Induction, Magnetic The produc- 
 tion of magnetism in a magnetizable substance 
 by bringing it into a magnetic field. 
 
 Suppose a small portion of a magnetizable body 
 is placed in a magnetic field produced in a gap 
 separating two closely approximated poles. To 
 simplify matters, suppose this small portion to be 
 a free unit pole. It will be acted on by two 
 forces: 
 
 (i.) The force due to the magnetic field. 
 
 (2.) The force dae to the free magnetism, 
 which appears at the surface of the gap or cut. 
 
 The force on the unit pole is compounded of 
 these two separate forces, and is called the magnetic 
 induction of the space. Magnetic induction is, 
 therefore, strictly speaking, a quantity. 
 
 The direction of magnetic force and the mag- 
 netic induction are the same in an air space out- 
 side a magnet. Within a bar of iron or other 
 paramagnetic material, under induction in a mag- 
 netic field, the magnetic force at any point is due 
 not only to the external or original field, but also 
 to the field produced by the polarity induced, 
 which acts opposed to the magnetic force at 
 points. Magnetic force and magnetic induction 
 are identical only where there is no magnetism. 
 {Fleming.) 
 
 When a magnetizable body is brought into a 
 magnetic field the following phenomena occur, 
 viz.: 
 
 (i.) The lines of magnetic force pass through 
 the body and are condensed upon it. (See Field, 
 Magnetic. Paramagnetic. ) 
 
 (2.) If the body is free to move around an axis, 
 but is not free to move bodily towards the magnet 
 pole, it will come to rest with its greatest extent 
 or length in the direction ol the lines of force; 
 *'. e., in the direction in which it will offer the 
 least resistance to the lines oJ force that thread 
 through it. 
 
 (3. ) The body will therefore become a magnet, 
 its south pole being situated where the lines of 
 force enter it and its north pole where they pass 
 out from it. Since the lines of magnetic force 
 are assumed to come out of the north pole of a 
 magnet and to enter its south pole, if a magnet- 
 izable substance is brought near a north pole, 
 the lines of force from that north pole will enter 
 it at those parts nearest such north pole, thereby 
 rendering such points south, and will pass out of 
 its further end, which will thereby become north. 
 
 (4.) The Intensity of the induced magnetisrrt 
 
End.] 
 
 / 
 
 jyill depend on the number of lines of force that 
 pass through it. 
 
 (5.) The direction of the axis of magnetization 
 will depend on the directions in which the lines 
 of force thread through the body. (See Axis, 
 Magnetic.] 
 
 285 
 
 [Iiirt. 
 
 N S N' 
 
 Fig. 307, Magnetic Induction. 
 
 If a bar of iron, N' S ,Fij. 307, be brought near 
 the magnetized bar, N S, poles will be produced 
 in it by induction, as may be shown by throwing 
 iron filings on it. 
 
 The nearer the body to Demagnetized is brought 
 to the magnetizing pole the greater will bo the 
 number of lines of torce that thread through it. 
 Consequently, the intensity of the induced mag- 
 netism will be greater ; this will be greatest when 
 the bodies actually touch each other. 
 
 The production of magnetism, therefore, by 
 contact or touch is only a special case of the pro- 
 duction of magnetization by induction. 
 
 The attraction of a magnetizable body by a 
 magnet pole is caused by the mutual attraction 
 which exists between the pole produced by induc- 
 tion and the pole producing the induction. This, 
 it will be seen, is similar to the attraction caused 
 by an electric charge. 
 
 The following terms are given by Fleming as 
 employed in the same sense as magnetic induc- 
 tion of an area: 
 
 (i.) The number of unit tubes of induction 
 passing through the area. 
 
 (2.) The number of lines of force (induction) 
 passing through the area.. (Faraday.) 
 
 (3.) The total magnetic induction through the 
 area. {Maxwell. ) 
 
 (4.) The flux or flow of magnetic induction 
 through an area. (Mascart &* Joubert.} 
 
 (5.) The surface-integral of magnetic induction 
 over an area. {Fleming. ) 
 
 Induction, Magnetic, Apparent Co-effi- 
 cient of The co-efficient of induction 
 
 as influenced by the presence of eddy cur- 
 rents. 
 
 This is- called the co-efficient of apparent in- 
 duction, because its value is not the same as it 
 would be if the eddy currents were entirely sup- 
 Dressed 
 
 The value of the co-efficient of apparent induc- 
 tion depends on the amount of the retardation of 
 the magnetism; or, what is the same thing, on 
 the strength of the eddy currents. 
 
 Induction, Magnetic, Co-efficient of 
 
 A term sometimes used instead of magnetic 
 permeability. (See Permeability, Magnetic.} 
 
 The ratio existing between the number of 
 lines of magnetic induction that pass through 
 any area of cross-section of a magnetic cir- 
 cuit and the magnetizing force producing 
 such induction. 
 
 If B, equals the magnetic induction, or the num- 
 ber of lines of force that pass through any area of 
 cross-section, and H, equals the magnetizing force, 
 and n, equals the permeability, or the co-efficient 
 of magnetic induction ; then, 
 _B 
 ^~H 
 
 Induction, Magnetic, Dynamic 
 
 The induction which takes place in the field 
 of a magnet whose field is moving as regards 
 the body in which induction is occurring. 
 
 This movement of the field may be attained, 
 
 (i.) By the movement of the magnet. 
 
 (2.) By the movement of the body in which 
 induction is taking place. 
 
 (3.) By the expansion or contraction of the lines 
 of magnetic force produced by variations of the 
 strength of the magnetic field; or, in other words, 
 by the movement of the field. (See Induction, 
 Electro-Dynamic. ) 
 
 Induction, Magnetic, Flux or Flow of 
 
 A term employed in the same sense 
 
 as the magnetic induction which takes place 
 through any given area. 
 
 The flux or flow of magnetic induction is equal 
 to the magnitude of the area multiplied by the 
 normal induction which takes place in one unit 
 of that area. 
 
 Induction, Magnetic, Lines of 
 
 Lines which show not only the direction in 
 which magnetic induction takes place, bul 
 also the magnitude of the induction. 
 
 A line of induction may be regarded as a line 
 along which induction takes place, or as the axis 
 of a tube of induction. 
 
 This term is often loosely used for lines of force. 
 
 Induction. Magnetic, Static T>? 
 
Ind.j 
 
 286 
 
 [Ind. 
 
 induction which takes place in the field of a 
 magnet whose field is stationary as regards 
 the body in which induction is occurring. 
 
 The term static magnetic induction is used in 
 contradistinction to dynamic magnetic induction 
 which occurs in a moving field. (See Induction^ 
 Electro-Dynamic. } 
 
 Induction, Magnetic, Surface-Integral 
 
 of A term employed in the same sense 
 
 as the magnetic induction which takes place 
 over a given area. 
 
 Induction, Magneto - Electric A 
 
 variety of electro-dynamic induction in which 
 electric currents are produced by the motion 
 of permanent magnets, or of conductors past 
 permanent magnets. (See Induction, Elec- 
 tro-Dynamic.} 
 
 Induction, Mutual Induction pro- 
 duced by two neighboring circuits on each 
 other by the mutual interaction of their mag- 
 netic fields. (See Induction, Electro-Dy- 
 namic. Currents, Extra) 
 
 Induction produced in neighboring charged 
 conductors by the mutual interaction of their 
 electrostatic fields. (See Field, Electro- 
 static.} 
 
 The mutual induction of two conductors or cir- 
 cuits, is equal to the ratio of the induction which 
 takes place through one of the circuits, to the 
 strength of current in the other circuit, which is 
 producing the induction 
 
 Induction, Mutual, Co-efflcient of 
 
 The quantity which represents the number 
 of lines of force which are common to or 
 linked in with two circuits, which are pro- 
 ducing mutual induction on each other. 
 
 The maximum value the co-efficient of mutual 
 induction can have, is equal to the square root of 
 the product of the inductance of the two circuits, 
 or "1/L X N, in which L and N, are the constant 
 co- efficients of self-induction of the two circuits. 
 
 Induction, Mutual, Loops of Loops 
 
 or lines of induction produced in any circuit 
 by variations in the intensity of the current 
 flowing in a neighboring circuit. 
 
 The lines of induction produced by a circuit, in 
 which a current of electricity is flowing, are 
 closed loops or circles surrounding the circuit 
 once or more. The wire or circuit is formed by 
 
 coiling a conductor a number of times in a cir- 
 cular coil, and this circular coil is placed near 
 another coil in which a varying current is flowing. 
 As the lines of induction grow or increase, 
 ihey cut the circular coil, forming lines of induc- 
 tion in the shape of loops, a number of whfch pass 
 around it. They are called loops of mutual in- 
 duction. 
 
 Induction, Open-Circuit The in 
 
 duction produced in an open circuit by means 
 of electric pulses in neighboring circuits. 
 
 The researches of Hertz have shown that when 
 an impulsive discharge, or an oscillatory dis- 
 charge, occurs, an induction occurs even in open 
 circuited conductors. He shows that these induc- 
 tive- effects are due to electro-magnetic waves or 
 oscillations set up in the surrounding ether, 
 which are propagated through free ether with the 
 velocity of light. When these electro-magnetic 
 waves or radiations impinge on any circuit, if it? 
 dimensions be such that sympathetic vibrations 
 can be excited therein, such vibrations are set up 
 and cause similar phenomena to those of the ex- 
 citing cause, viz., oscillatory discharges or elec- 
 tro-magnetic vibrations. Hertz calls these sym- 
 pathetic circuits, resonators, from their resem- 
 blance to acoustic resonators. (See Resonators, 
 Electric.) 
 
 Induction, Oscillatory A name 
 
 sometimes applied to open-circuit induction. 
 (See Induction, Open-Circuit) 
 
 Induction, Reflection of A term 
 
 proposed by Fleming to express an action 
 which resembles a reflection of inductive 
 power. 
 
 The coils A and B, Fig. 308, are arranged as 
 
 Fig. 308. Reflaction of Induction* 
 
 shown, so as to act as the primary and secondary 
 respectively of an induction coil, and are placed 
 
Ind.] 
 
 287 
 
 [Inu 
 
 conjugate or perpendicular to each other. (See 
 Coils, Conjugate.) Therefore, no sounds are 
 heard in the telephone T, when the current is 
 rapidly reversed. If, however, a plate of copper, 
 C, is placed in the position shown, then sounds 
 are heard in the telephone. The action here 
 resembles a reflection of the inductive action from 
 A to B, by means of the plate C. The explana- 
 tion is, of course, simple. Though A, can exert 
 no action on B, because the two coils are conju- 
 gate to each other, yet A, can produce secondary 
 currents in C ; and these reacting on B, produce 
 tertiary currents in C, and, therefore, sounds in 
 the telephone. 
 
 Induction, Self Induction produced 
 
 in a circuit at the moment of starting or stop- 
 ping the currents therein by the induction of 
 the current on itself. (See Currents, Extra.) 
 
 A coil having unit self-induction, is sometimes 
 said to have one tube of induction, or line of force 
 added to its field for each increase of one unit of 
 current. 
 
 Induction, Self, Absolute Unit of 
 
 A term sometimes employed for absolute unit 
 of inductance. (See Inductance, Absolute 
 Unit of.) 
 
 Induction, Self, Ayrton & Perry's 
 Standard of A standard for the com- 
 parison of values of self-induction. 
 
 The standard of self-induction of Ayrton & 
 Perry consists of three bobbins of wire, two fixed 
 and one movable. The movable bobbin is so ar- 
 ranged as to be capable of motion through 1 80 
 degrees within the fixed bobbins. The coils are 
 wound on the surface of the zone of a sphere. 
 
 This apparatus permits of the ready compari- 
 son of the self-induction in different circuits, or in 
 the same circuit under different conditions. 
 
 Induction, Self, Co-efflcient of 
 
 The number of lines of force the current would 
 induce or enclose in itself when the current 
 flowing through it is equal to one absolute 
 unit. 
 
 A term sometimes employed in the sense 
 of inductance of a circuit. 
 
 The co-efficient of self-induction is defined by 
 Fleming as follows : "In the case of circuits con- 
 veying electric currents, which are wholly made 
 of non-magnetic material, and wholly immersed 
 
 in a medium of constant magnetic permeability, 
 the total induction through the circuit per unit of 
 current flowing in that circuit, when removed 
 from the neighborhood of all other magnets and 
 circuits, is called the co-efficient of self-induction; 
 otherwise the ratio of the numerical values of the 
 electro -magnetic momentum of such circuit, and 
 the current flowing in it, when totally removed 
 from all other currents and magnets, is the nu- 
 merical value of the inductance of the circuit. ' ' 
 
 Since the magnetic lines due to a current in a 
 circuit thread through the convolutions of the cir- 
 cuit itself, any variation in the current induces 
 a difference of potential in the circuit itself, since 
 the lines of force produced by the current in the 
 circuit pass through or cut the circuit. 
 
 The ratio between this self-induced electromo- 
 tive force, and the rate of change in the current 
 which causes it, is called the co-efficient of self- 
 induction.- (S. P. Thompson.) 
 
 For a given coil the co-efficient of self-induction 
 is, according to S. P. Thompson : 
 
 (i.) Proportional to the square of the number 
 of convolutions. 
 
 (2.) Is increased by the use of an iron core. 
 (3.) If the magnetic permeability is assumed as 
 constant, the co-efficient of self-induction is nu- 
 merically equal to the product of the number of 
 lines of magnetic force due to the current, and 
 the number of times they are enclosed by the 
 circuit. 
 
 Induction, Self, Magnetic A re- 
 tardation in the appearance of magnetization, 
 after the application of the magnetizing force, 
 due to the influence of the magnetic lag. 
 
 Magnetic retardation. 
 
 This retardation in the magnetization has re- 
 ceived the name of magnetic self-induction or re- 
 tardation because it corresponds to the retarda- 
 tion in the starting or stopping of a current, in a 
 conducting circuit, due to the self-induction of thfe 
 current. 
 
 Induction, Self, Unit of The unit 
 
 of inductance. (See Inductance, Unit of.) 
 
 The unit of self-induction is now generally 
 called the unit of inductance. 
 
 Induction, Symmetrical, of Armature 
 
 An induction produced by the simul- 
 taneous passage of the same number of lines 
 of magnetic force through adjoining halves of 
 the armature. 
 
Ind.] 
 
 288 
 
 find. 
 
 Induction Telegraphy, Current Induc- 
 tion System of (See Telegraphy, In- 
 duction, Current Induction System of.) 
 
 Induction Telegraphy, Static Induction 
 System of (See Telegraphy, Induc- 
 tion, Static Induction System of.) 
 
 Induction Top. (See Top, Induction.) 
 
 Induction, Total Magnetic The 
 
 total magnetic induction of any space is the 
 number of lines of magnetic induction which 
 pass through that space, where the magnetiz- 
 able material is placed, together with the lines 
 added by the magnetization of the magnetic 
 material. 
 
 Induction, Tubes of A portion of 
 
 a magnetic field containing a number of 
 closely contiguous lines of induction termi- 
 nated by equipotential surfaces^ or surfaces 
 perpendicular to the lines of induction. 
 
 Tubes of induction possess the following char- 
 acteristics : 
 
 (I.) The product of a normal cross-section of a 
 tube and the mean magnetic induction which 
 takes place over that section is the same for all 
 tross-sections of the tube. In other words, the 
 flux or flow of induction is constant throughout 
 the entire length of the tube. 
 
 (2.) The normal cross-section of any equipoten- 
 tial surface at any point of a tube of induction is 
 inversely proportional to the magnetic induction 
 at that point. 
 
 (3.) All tubes of induction form endless tubes. 
 This is necessary, since all lines of induction form 
 closed circuits. 
 
 (4.) All tubes of induction may be expressed 
 by a single line of induction, which, in the case of 
 a uniform field, occupies the centre of the tube. 
 (See Force^ Tubes of.) 
 
 Induction, Toltaic A variety of 
 
 flectro-dynamic induction produced by cir- 
 cuits on themselves or on neighboring circuits. 
 
 Mutual induction. (See Induction, Elec- 
 tro-Dynamic.) 
 
 This kind of induction is usually called current 
 induction. 
 
 Induction, Unipolar A term some- 
 times applied to the induction that occurs 
 when a conductor is so moved through a 
 
 magnetic field as to continuously cut its lines 
 of force. 
 
 If the conducting wire, ABC, Fig. 309, be n> 
 
 39' Unipolar Induction. 
 tated (in a direction toward the observer) around 
 the pole N, of a magnet, it will continuously cut 
 its lines of magnetic force in practically the same 
 direction, and will therefore produce a difference 
 of potential that will result in a continuous cur- 
 rent in the direction of the arrows. The end A, 
 is supported in a recess in N, while the end near 
 C, slides on a projection on the middle of the 
 magnet. 
 
 Unipolar induction occurs in the case of Stur- 
 geon's wheel, in which a metallic disc mounted 
 on an axis is rotated between the poles of a mag- 
 net so as to cut the lines of magnetic force. In 
 this case a difference of potential is generated 
 which will produce a current that flows from the 
 axis to the periphery, provided contact points are 
 placed on the axis of rotation and the periphery 
 of the disc connecting these parts of the disc in a 
 closed circuit. 
 
 Unipolar dynamos operate by the continuous 
 cutting of lines of magnetic force. 
 
 Strictly speaking, there is no such- thing as a 
 unipolar dynamo or unipolar induction, since a 
 single magnetic pole cannot exist by itself. Con- 
 tinuous cutting of lines of magnetic force, how- 
 over, can exist, and produces, unuke the ordinary 
 bipolar induction, a continuous current without 
 the use of a commutator. 
 
 Inductionless Resistance. (See Resist- 
 ance, Inductionless.) 
 
 Inductive Capacity, Specific (See 
 
 Capacity, Specific Inductive!) 
 
 Inductive Circuit. (See Circuit, Indue* 
 five.) 
 
289 
 
 Inducwre Electromotive Force. (See 
 Force, Electromotive. Inductive.) 
 
 Inductive Retardation. (See Retarda- 
 tion, Inductive.} 
 
 Inductive Resistance. (See Resistance, 
 
 Inductive.) 
 
 Inductinty, Specific Magnetic 
 
 A term sometimes employed for specific mag- 
 netic conductivity. (See Conductivity, Spe- 
 cific Magnetic?) 
 
 Inductometer, Differential An 
 
 apparatus for measuring, by means of a gal- 
 vanometer, the momentary currents produced 
 by the discharge of a cable. 
 
 Currents produced by the discharge of a cable 
 are of so short a duration that they do not pro- 
 duce much more than a momentary effect on a 
 galvanometer needle. 
 
 The inductive charge in a cable, or the quan- 
 tity of electricity produced in it by induction, is: 
 
 (i.) Directly as the electromotive force of the 
 charging battery; 
 
 (2.) Inversely as the square root of the thick- 
 ness of the coating of gutta-percha or other insu- 
 lating material between the conducting wires and, 
 the metallic sheathing; 
 
 (3.) Directly as the square root of the diameter 
 of the copper wire of the conductor; and 
 
 (4. ) Dependent on the specific inductive capa- 
 city of the insulating material employed in the 
 cable. 
 
 In order to cause the cable discharge to more 
 thoroughly affect the galvanometer needle, Mr. 
 Latimer Clark employed a differential instrument 
 with a large battery and three reversing keys, by 
 means of which he gave a rapid succession of 
 charges to the cable. He called the instrument a 
 Differential Inductometer. 
 
 Indnctophone A device, suggested by 
 Mr. Willoughby Smith, for obtaining electric 
 communication between moving trains and 
 fixed stations by means of the currents devel- 
 oped by induction in a spiral of wire fixed on 
 the moving engine, by its motion past spirals 
 on the line, into which intermittent currents 
 are passed. 
 
 Tne spiral on the engine is placed in the circuit 
 of a telephone. (See Teletrrat>}' . / ductive.\ 
 
 Inductor Dynamo. (See Dynamo, Indue* 
 tor.) 
 
 Indnctorium. A name sometimes applied 
 trt a Ruhmkorff induction coil. (See Coil, 
 Induction.) 
 
 Inequality, Annual, of Earth's Magnetic 
 
 Variation or Inclination Annual 
 
 variations in the value of the magnetic varia- 
 tion or inclination at any place. (See Varia- 
 tion, Magnetic. Inclination, Magnetic.) 
 
 Inequality, Annual, of Earth's Magnet- 
 ism Variations in the value of the 
 
 earth's magnetism during the earth's revolu- 
 tion depending on the position of the sun. 
 
 Annual variations in the earth's magnetism. 
 (See Variations, Magnetic, Annual.) 
 
 Inequality, Diurnal, of Earth's Magnetic 
 
 Variation or Inclination Diurnal 
 
 variations in the value of the earth's magnetic 
 variation or inclination. (See Variation, 
 Magnetic. Inclination, Magnetic.) 
 
 Inequality, Diurnal, of Earth's Magnet- 
 ism Inequalities or variations in the 
 
 value of the earth's magnetism, dependent on 
 the position of the sun during Jhe earth's 
 rotation. 
 
 Inequality, Lunar, of Earth's Magnetic 
 Variation or Inclination - Small va- 
 riations in the value of the magnetic variation 
 or inclination, dependent on the position of 
 the moon as regards the magnetic meridian. 
 
 Inequality, Lunar, of Earth's Magnet- 
 ism Small variations in the value of 
 
 the earth's magnetism dependent on the po- 
 sition of the moon as regards the magnetic 
 meridian. 
 
 Inertia. The inability of a body to change 
 its condition of rest or motion, unless some 
 force acts on it. 
 
 The inertia of matter is expressed in Newton's 
 first law of motion, as follows 
 
 "Every body tends to preserve its state of rest 
 or of uniform motion in a straight line, except in 
 so far as it is acted on by an impressed force." 
 
 All matter possesses inertia. 
 
 Inertia, Electric A term some- 
 times employed instead of electro-magnetic 
 inertia. (See Inertia, Electro-Magnetic.) 
 
Ine.J 
 
 290 
 
 [Ins. 
 
 A term employed to indrate the tendency 
 of a current to resist its stopping or starting. 
 
 By self-induction an electromotive force is pro- 
 duced in a wire or other conductor at the moment 
 of starting the current in it that tends to oppose 
 the starting of such current, and also an electro- 
 motive force at the moment of stopping the cur- 
 rent, in such a direction as to prolong or continue 
 the current. In other words, self-induction tends 
 to retard the rise or fall of the current. 
 
 Fleming traces the following comparison be- 
 tween the moment of inertia of a rotating wheel 
 and the energy of its rotation on the one side, and 
 the inductance of a circuit and the electro-mag- 
 netic energy of the circuit on the other. 
 
 (i.) The angular momentum of a fly-wheel is 
 equal to the numerical product of its moment of 
 inertia and the angular velocity of the wheel. 
 Similarly the electro-magnetic momentum is equal 
 to the product of the inductance of the circuit by 
 the current flowing through it at any instant. 
 
 (2.) The rate of change of the angular mo- 
 mentum of the wheel, at any instant, is a measure 
 of the rotational force of the couple acting at that 
 instant. 
 
 Similarly the rate of change of the electro-mag- 
 netic momentum of the circuit is the measure of 
 the electromotive force acting on it so far as 
 mere change of current is concerned, and irre- 
 spective of that part of the electromotive force re- 
 quired to overcome the ohmic resistance. 
 
 An electric current does not start or stop in- 
 stantaneously. It requires time to do either, just 
 as a stream of water or other fluid does, and it is 
 this property which is referred to by the term 
 electric inertia. Inertia does not appear to be 
 possessed by electricity apart from matter. ' It 
 is doubtful," says Lodge, "whether electricity 
 of itself, and disconnected from matter, has any 
 inertia." 
 
 Inertia, Electro-Magnetic A term 
 
 sometimes employed instead of inductance, 
 or the self-induction of a current. (See In- 
 ductance. Inertia, Electric?) 
 
 Inertia, Electro-Magnetic, Co-efflcient of 
 
 A term sometimes employed in place 
 
 of the co-efficient of inductance or self-induct- 
 ance of a circuit. 
 
 Inertia, Magnetic The inability of 
 
 a magnetic core to instantly lose or acquire 
 magnetism. 
 
 A magnet core tends to continue in the mag. 
 netic state in which it was placed. 
 
 The magnetic inertia is sometimes called the 
 magnetic lag. 
 
 To decrease the magnetic inertia, the strength 
 of the magnetizing current is increased and the 
 length of the iron core decreased. The iron 
 should also be quite soft. (See Lag, Magnetic. 
 Force, Coercive.') 
 
 Inferred Zero. (See Zero, Inferred) 
 
 Infinity Plug. (See Plug, Infinity.) 
 
 Influence. A term sometimes used instead 
 of electrostatic induction. (See Induction, 
 Electrostatic) 
 
 .The word influence is used by some to apply 
 to the case of electrostatic induction, as distin- 
 guished from electro-magnetic or magnetic induc- 
 tion. 
 
 Influence Charge. (See Charge, Influ- 
 ence) 
 
 Influence Machine. (See Machine, In- 
 fluence) 
 
 Inker, Morse A form of tele- 
 graphic ink-writer. (See Ink- Writer, Tele- 
 graphic) 
 
 Ink- Writer, Telegraphic A device 
 
 employed for recording the dots and dashes 
 of a telegraphic message in ink on a fillet or 
 strip of paper. 
 
 A telegraphic ink-writer is a form of telegraphic 
 recorder. (See Recorder, Morse.) 
 
 Inside Wiring. (See Wiring, Inside) 
 
 Insolation, Electric A term some- 
 times employed for electric sunstroke, or 
 electric prostration. (See Sunstroke, Elec- 
 tric. Prostration, Electric) 
 
 Installation. A term embracing the 
 entire plant and its accessories required to 
 perform any specified work. 
 
 The act of placing, arranging or erecting 
 a plant or apparatus. 
 
 Installation, Electric The estab- 
 lishment of any electric plant. 
 
 An electric light installation, for example, in- 
 cludes the steam engine and boilers, or other 
 prime movers, the dynamo-electric machines, the 
 line wires or leads, and the lamps. 
 
 Insulated Body. (See Body, Insulated^ 
 
ins.] 
 
 291 
 
 fins. 
 
 Insulating- Cements. (See Cements, In- 
 sulating^ 
 
 Insulating Sleere. (See Sleeve, Insula- 
 ting) 
 
 Insulating Stool. (See Stool, Insula- 
 ting) 
 
 Insulating Tape. (See Tape, Insula- 
 ting) 
 
 Insulating Tube. (See Tube, Insula- 
 ting) 
 
 Insulating Varnish. (See Varnish, Elec- 
 tric) 
 
 Insulation, Electric Non-conduct- 
 ing material so placed with respect to a cori- 
 ductor as to prevent the loss of a charge, or 
 the leakage of a current. 
 
 In the case of coils the character of the insula- 
 tion of the coil of wires through which the cur- 
 rent is to pass must be considered from the stand- 
 point of the cooling of the coil by radiation. 
 
 In considering the safest and most economical 
 current density to employ in any dynamo or 
 motor, the depth of the coil, i. e., the thickness of 
 its coils, must be considered, as well as the char- 
 acter of the materials employed for the insulation. 
 Such substances as silk or wool, which are char- 
 acterized by low heat conduction, retain the heat 
 longer than cotton. Hence the depth of a silk 
 covered coil should necessarily bele^s than that of 
 one covered with cotton. 
 
 Insulation Joint. (See Joint, Insula- 
 tion.} 
 
 Insulatian, Porons An insulating 
 material containing air or gas placed between 
 the conductor and the insulating covering. 
 
 A strip of perforated paper is used for cover- 
 ing the bare conductor, and the insulating ma- 
 terial is placed on the outside of this ; or, a cord 
 is wrapped separately around Ae conductor, and 
 the insulating material is placed on the outside of 
 this. By these means, as will be seen, a layer of 
 air exists between the conductor and its insulating 
 covering. 
 
 Insulation Resistance. (See Resistance, 
 Insulation) 
 
 Insulation, Static A term em- 
 ployed in electro-therapeutics for a method 
 of treatment by convection stream or dis- 
 
 charges, in which the patient is seated on an 
 insulated stool connected to one pole or 
 electrode of an influence marline, while the 
 other pole or electrode is connected to the 
 ground. 
 Insulator Cap. (See Cap, Insulator) 
 
 Insulator, Dice-Box A name some- 
 times applied to a double-cone insulator. (See 
 Insulator, Double-Cone) 
 
 Insulator, Double-Cone An insu- 
 lator in which the line wire passes through and 
 is supported by means of a tube consisting of 
 two inverted cones joined at their smaller 
 bases. 
 
 Insulator, Double-Cup An insula- 
 tor consisting of two funnel-shaped cups, 
 placed in an inverted position on the sup- 
 porting pin and insulated from one another 
 by a free air space, except near the ends, 
 which are cemented. 
 
 The wire is wrapped in a groove on the outside 
 of the outer cup. This possesses the advantage 
 of exposing it to the rain, which thus cleanses the 
 insulator and improves its power of insulation. 
 The inner cup is supported on a pin and the outer 
 cup cemented to it. Any leakage must, there- 
 fore, pass over the entire surface of both cups. 
 
 Insulator, Double-Shackle A form 
 
 of insulator used in shackling a wire, consist- 
 ing of two single-shackle insulators. 
 
 Insulator, Double-Shed A double- 
 cup insulator. (See Insulator, Double-Cup) 
 
 Insulator, Fluid An insulator pro- 
 vided with a small, internally placed, annular, 
 cup-shaped space, filled with an insulating 
 oil, thus increasing the insulating power of the 
 support. 
 
 The line wire is wrapped in a groove on the 
 outside of the insulator. Any surface leakage 
 between the wire and ground in wet weather 
 must occur between the outer surface of the insu- 
 lator, which is kept cleansed by the rain, and the 
 inner surface, where it is supported by the pin. 
 But to do this, the current must cross the oil in 
 the cup, which, from its high power of insulation, 
 effectually prevents leakage. 
 
 Insulator, Inrert An insulator 
 
Ins.] 
 
 292 
 
 [Int 
 
 placed on the top of the wire instead of under- 
 neath it, as was formerly done. 
 
 Insulator, Oil A fluid insulator 
 
 filled with oil. (See Insulator, Fluid.) 
 
 Insulator Pins. (See Pins, Insulator.} 
 
 Insulator, Single-Shackle A form 
 of insulator used for shackling a wire. (See 
 Shackling a Wire.) 
 
 Insulator, Single-Shed An insula- 
 tor with a single inverted cup. 
 
 The wire is wrapped around a groove on the 
 outside of the cup, where it is exposed to the 
 cleansing action of the rain. The cup is inverted 
 and supported on a pin, to which it is screwed and 
 cemented. 
 
 Insulator, Telegraphic or Telephonic 
 A non-conducting support of tele- 
 graphic, telephonic, electric light or other 
 wires. 
 
 Insulators are generally made of glass, earthen- 
 
 Fig, 3 to. Glass 
 Insulator. 
 
 Fig. 311 Porcelain 
 
 Insulator. 
 
 ware, porcelain or hard rubber, and assume a 
 variety of forms, some of which are shown in Figs. 
 310, 31 1 and 312. Of whatever material they are 
 made, it is necessary that the 
 surface on which the wire rests, 
 or around which it is wrapped, 
 should be smooth, so as to avoid 
 fbrasion, either of its insulat 
 ing covering or of the wire it- 
 self. 
 
 Two things are to be con 
 sidered in the selection of an 
 insulator, viz.; 
 
 (i.) The insulating power of 
 the material of which the in- 
 sulator is composed, so as to Fig. 3x2. Hard 
 reduce the leakage as much as Rub! >er Insulator. 
 P0sible. (See Leakage ; Electric. \ 
 
 (2.) The tensile strength of the material so 
 
 that in case of heavy wires no breaks may result 
 from the fracture of the insulator. 
 
 Some forms of insulators are shown in Figs. 
 310,311 and 312. They are screwed to the pins 
 by the threads shown. The insulating materials 
 of which they are tormed are of glass, porcelain 
 and hard rubber respectively. 
 
 Insulator, Window-Tube A tube 
 
 of vulcanite or other insulating material pro- 
 vided for the insulation of a wire entering a 
 room. 
 
 The wire conductor passes through the middle 
 of the tube, which is firmly fixed in an opening 
 passing through the window frame. 
 
 Insulator, Z A form of double- cup 
 
 insulator in which the insulating material, 
 earthenware or porcelain, is made in a single 
 piece, instead of in two separate pieces. 
 
 The body of the insulator is conical in form, 
 and the interior air space presents a shape ap- 
 proximately that of the letter Z. 
 
 The double form is used in order to diminish 
 the leakage. 
 
 Intensity Armature. (See Armature, 
 Intensity?) 
 
 Intensity, Connection of Toltaic Cells for 
 
 A term formerly employed for series- 
 connected voltaic battery cells. (Obsolete.) 
 
 Intensity, Magnetic Density of 
 
 magnetic induction. 
 
 Magnetic flux per square centimetre. 
 
 A committee of the American Institute of Elec- 
 trical Engineers on "Units and Standards," pro- 
 poses the following definition for magnetic inten- 
 sity: 
 
 The induction density at a point within an ele- 
 ment of surface is the surface differential at that 
 point. 
 
 The practical unit of magnetic intensity is 
 to 9 or 100,000,000 C. G. S. lines per square cen- 
 timetre. 
 
 In practice, excluding the earth's field, intensi- 
 ties range from 100 to 20,000 C. G. S. lines per 
 square centimetre, and the working unit should, 
 perhaps, have the prefix milli or micro. 
 
 Intensity, Magnetic, Pole of The 
 
 earth's magnetic poles as determined by 
 means of the osculations of a magnetic 
 
 need e. 
 
lot,] 
 
 293 
 
 [loii. 
 
 The points ot the earth's greatest magnetic 
 intensity. 
 
 Intensity of Current (See Current, In- 
 tensity of.} 
 
 Intensity of Field. (See Field, Inten- 
 sity of.) 
 
 Intensity of Light. (See Light, Inten- 
 sity of.} 
 
 Intensity of Magnetization. (Sec Mag- 
 netization, Intensity of.} 
 
 Intensity, Photometric, Unit of - 
 
 The amount of light produced by a candle 
 that consumes two grains of spermaceti wax 
 per minute. (See Candle.) 
 
 Inter Air Space. (See Space. Inter Air.) 
 
 Intercrossing. In a system of telephonic 
 communication, a device for avoiding the dis- 
 turbing effects of induction by alternately 
 crossing equal sections of the line. (See 
 Connection, Telephonic Cross.) 
 
 Interference of Electro-Magnetic 
 Wares. (See Waves, Electro-Magnetic, 
 Interference of.) 
 
 Interlocking Apparatus. (See Appa- 
 ratus Interlocking.) 
 
 Intermittent Contact. (See Contact, In- 
 termittent.) 
 
 Intermittent Cross. A form of electnc 
 cross. (See Cross. Electric.) 
 
 Intermittent Current. (See Currant. In- 
 termittent.) 
 
 Intermittent Disconnection. (S-* Dis- 
 connection, Intermittent ) 
 
 Intermittent Earth. (See Earth, Inter- 
 mittent.) 
 
 Internal Circuit. (See Circuit, In- 
 ternal.) 
 
 internal Polarization of Moist Bodies. 
 
 'See Polarization, Internal, of Moist 
 Bodies.) 
 
 Interrupter. Any device for interrupting 
 or breaking a circuit. 
 
 Interrupter, Automatic An auto- 
 matic contact breaker (See Make~and- 
 Break. Automatic.) 
 
 Interrupter, Reed A term some 
 
 times applied to a tuning-fork interrupter. 
 (See Interrupter, Tuning-Far k.) 
 
 Interrupter, Tuning-Fork An in- 
 terrupter in which the successive makes and 
 breaks are produced by the vibrations of a 
 tuning-fork or reed. 
 
 The tuning-fork or reed is maintained in vibra- 
 tion by any suitable means. Such interrupters 
 are applied to various uses. Synchronous mul- 
 tiplex telegraphy affords an example of such uses. 
 
 Invariable Calibration of Galvanometer 
 
 (See Calibration, Invariable, of Galva- 
 nometer.) 
 
 Inverse Electromotive Force. (See Force. 
 Electromotive, Inverse.) 
 
 Inverse or Make-Induced Current. (See 
 
 Current, Make-Induced) 
 Inverse Secondary Current (See Cur. 
 
 rent, Inverse Secondarv^ 
 
 Inversion, Thermo-Electric An 
 
 inversion of the thermo-electric electromotive 
 force of a couple at certain temperatures. 
 (See Diagram, Thermo-Electric.) 
 
 Invert Insulator. (See insulator, In- 
 vert.) 
 
 Inverted Induction Coil. (See Coil, 
 Induction. Inverted.) 
 
 Inverted Type of Dynamo. (See Dy- 
 namo, Inverted) 
 
 Invisible Electric Floor Matting. (See 
 
 Matting, Invisible Electric Floor.') 
 
 Ions. Groups of atoms or radicals which 
 result frcra the electrolytic decomposition of 
 a molecule. 
 
 The iont are respectively electro-positive and 
 electro-negative. The electro-positive ion ap- 
 pears at the plate connected with the tlectro- 
 negative terminal^ or at the kathode, and is called 
 the kaihion. 
 
 The electro-negative ion appears at the plate 
 connected with the clearo-positive teYminal^ 01 
 at the anode t and is called the anion. (See 
 Electrolysis, Kathion. Anion.) 
 
 Ions, Electro-Negative The neg- 
 
 ative atoms, or groups of atoms, called rad- 
 icals, into which the molecule? of an electro- 
 
lon.J 
 
 [Iso. 
 
 lyte are decomposed by electrolysis. (See 
 Electrolysis) 
 
 The electro-negative ions are called the anions, 
 because they appear at the anode of a decompo- 
 sition cell. (See Anions. Anode.) 
 
 Ions, Electro-Positive 
 
 The pos- 
 
 itive atoms, or groups of atoms, called rad- 
 icals, into which the molecules of an electro- 
 lyte are decomposed by electrolysis. (See 
 Electrolysis.) 
 
 The electro-positive ions are called the kathions, 
 because they appear at the kathode of a decom- 
 position cell. (See Kathion. Kathode.) 
 
 Iron-Clad Electro-Magnet. (See Mag- 
 net, Electro, Iron-Clad?) 
 
 Iron-Clad Magnet. (See Magnet, Iron- 
 Clad) 
 
 Iron Core, Effect of, on the Magnetic 
 Strength of a Hollow Coil of Wire - 
 
 An increase in the number of lines of mag- 
 netic force, beyond those produced by the 
 current itself, due to the opening out of the 
 closed magnetic circuits in the atoms or 
 molecules of the iron. 
 
 The atoms or molecules of the iron possess 
 naturally closed magnetic circuits, or closed lines 
 of magnetic force, lying entirely within the mass 
 of the iron. When the iron is placed in a magnetic 
 field, these minute closed circuits open out and 
 are added to the lines of force produced by the 
 circuit itself. The opening out of these closed 
 atomic or molecular lines of magnetic force is at- 
 tended by the formation of lines of polarized 
 molecules or atoms. 
 
 Roughly speaking, according to Lodge, for 
 each single line of magnetic force produced by the 
 electric current, there are some 3,000 lines of 
 magnetic force added to it from the iron, the ex- 
 act number varying with the kind of iron, the 
 physical condition of the iron and the degree of 
 magnetization. 
 
 Iron, Galvanized Iron covered by 
 
 a layer of zinc by dipping it in a bath of 
 molten zinc. 
 
 The process of galvanizing iron is designed to 
 prevent the corrosion or rusting of the iron on 
 exposure to the air. (See Metals, Electrical Pro- 
 tection of.) 
 
 The word galvanized probably had its origin in 
 
 an assumed galvanic or voltaic action, in causing 
 the zinc to adhere to the iron. The true galvanic 
 or voltaic action, viz., the galvanic protection, 
 comes after the galvanizing process is completed. 
 
 Iron-Work Fault of Dynamo. (See 
 
 Fault, Iron- Work, of Dynamo) 
 
 Irreversible Heat. (See Heat, Irreversi- 
 ble) 
 
 Irritability, Electric Irritability 
 
 of nervous or muscular tissue by an electric 
 discharge. 
 
 Irritability, Electric, Diminished 
 
 A decreased irritability of nervous or muscu- 
 lar tissue, produced by an electric current of 
 given strength. 
 
 Diminished electric irritability is often present 
 in certain diseases of the motor apparatus. 
 
 Irritability, Electric, Increased 
 
 An irritability of nervous or muscular tissue 
 produced by a much weaker electric current 
 than that required to produce it in normal 
 tissue. 
 
 Irritability, Faradic Muscular 
 
 contractions produced by the action of a 
 faradic current on a nerve. 
 
 The action of the faradic current is to cause a 
 prolonged tonic contraction, which continues 
 while the current continues. Though the natural 
 action is to produce a contraction, followed by a 
 relaxation on each make and break, yet the makes 
 and breaks follow one another so rapidly that the 
 relaxation has not time to occur before the next 
 contraction follows. 
 
 Irritability, Galvanic Muscular 
 
 contractions produced by the action of a gal- 
 vanic current. 
 
 The action of a galvanic current is to cause a 
 single, quick, momentary contraction of a muscle 
 on each starting or completion of the circuit. 
 
 The contractions are stronger in the case of 
 galvanic currents when the direction of the cur - 
 rent is reversed with a commutator instead of by 
 an actual break at the poles. Such a break is 
 called a voltaic alternative, and the currents so pro- 
 duced voltaic alternatives. (See Alternative.-, 
 Vo'.taic.) 
 
 Isobaric Lines. (See Lines, Isobaric) 
 
 Isobars. Lines connecting places on the 
 
ISO.] 
 
 295 
 
 [Jar. 
 
 earth's surface which have the same barome- 
 tric pressure. 
 
 The isobaric lines are generally corrected for 
 iiSerences of elevation of the surface. 
 
 Isobars are often called isobaric lines. 
 
 A study of the isobaric lines, or isobars, is of 
 great assistance in making forecasts or predictions 
 of coming changes in the weather. 
 
 Isocuasmen Curves. (See Curves, Iso- 
 ckasmen?) 
 
 ISOChronism. Equality of time of vibra- 
 tion or motion. 
 
 Isochronize. To produce equality of 
 time of vibration or motion. (See Jsochron- 
 zsm?) 
 
 Isochronizing. Producing equality of 
 time of vibration or motion. (See Isochron- 
 tsm.) 
 
 Isochronous Yibrations or Oscillations. 
 (See Vibrations or Oscillations, Isochron- 
 ous^ 
 
 Isoclinic Chart. (See Chart, Inclina- 
 tion^) 
 
 Isoclinic Lines. (See Lines, Isoclinic?) 
 
 Isodynamic Chart. (See Chart, Isody- 
 namic?) 
 
 Isodynamic Lines. (See Lines, Isody- 
 namic?) 
 
 Isodynamic Map. (See Chart, Isody- 
 namic?) 
 
 Iso-Electric Points. (See Points, Iso- 
 Electric?) 
 
 Isogonal. Pertaining to the isogonic lines. 
 Isogonal lanes. (See Lines, Isogonal.) 
 Isogonal Map or Chart (See Map or 
 Chart, Isogonal?) 
 
 Isogonic. Pertaining to the isogonal lines. 
 Isogonic Chart (See Chart, Isogonic?) 
 Isogonic Lines, (See Lines, Isogonic?) 
 Isogonic Map. (See Map, Isogonic?) 
 
 Isolated Electric Lighting. (See Light- 
 ing, Electric, Isolated?) 
 
 Isolatine. A kind of insulating material. 
 Isothermal Surfaces. (See Surfaces, Iso- 
 thermal?) 
 
 Isotropic Conductor. (See Conductor, 
 Isotropic?) 
 
 Isotropic Medium. (See Medium, 
 tropic?) 
 
 J. A contraction proposed for Joule. 
 
 Jablochkoff Candle. (See Candle, Jab- 
 tochkoff.) 
 
 Jacketed Magnet. (See Magnet, Jack- 
 eted?) 
 
 Jacobi's Law. (See Law,Jacobi's?) 
 
 Jar, Electric A name formerly 
 
 given to the Leyden jar. 
 
 Jar, Leyden A condenser in the 
 
 form of a jar, in which the metallic coatings 
 are placed opposite each other on the outside 
 and the inside of the jar respectively. 
 
 The metal coatings should not extend to more 
 than two-thirds of the height of the jar, the rest 
 of the glass being varnished to avoid the creeping 
 of the charges over the glass in damp weather, 
 i'hc inside coating is connected by means of a 
 
 metallic chain to a knob on the top of the jar, as 
 shown in Fig. 313. The conductor supporting 
 the knob passes through a dry cork or plug of 
 some insulating material. 
 
 To charge the jar, the outside coating is con- 
 nected with the earth, as 
 by holding it in the hand, 
 and the outside coating 
 is connected with the 
 conductor of a machine. 
 (See Condenser. Accu- 
 mu/jfor. ) 
 
 The inner coating of 
 the jar is usually con- 
 nected with the knob by 
 means of a chain or wire ***3*3. 
 as shown above. This necessitates a support for 
 the ball and stem, which is generally obtained by 
 a cork or wooden plug inserted in the mouth of 
 
Jar.T 
 
 296 
 
 [Jet. 
 
 the jar. Such a form, however, is extremely ob- 
 jectionable, since, although the top of the jar be 
 Covered with shellac varnish to avoid leakage, it 
 affords but a poor insulation in damp weather, be- 
 sause both the metallic rod supporting the ball and 
 
 'fig, 3 1 4.0 Sir William Thomson's Leyden Jar. 
 
 the damp wood or cork are in connection with the 
 glass and thus facilitate leakage. 
 
 To overcome these objections a form of jar has 
 been devised by Sir William Thomson, in which the 
 knob is supported on three feet, which rest on the 
 inner coating. In this form the uncoated glass 
 can be readily kept dry and clean. This form is 
 shown in Fig. 314. 
 
 A layer of sulphuric acid is sometimes employed 
 for the inner coating of the Leyden jar. This 
 serves the double purpose of acting as a coating 
 and an absorber of moisture during damp 
 weather. 
 
 Jar, Leyden, Capacity of The 
 
 quantity of electricity a Leyden jar will hold 
 at a given difference of potential. 
 
 The capacity of a jar is equal to the quantity 
 of electricity divided by the difference of potential 
 such quantity produces in the jar; or the capacity 
 
 = y, where Q = the quantity, and V, the differ- 
 ence of potential. 
 
 Jar, Leyden, Coatings of (See 
 
 Coatings of Leyden Jar.) 
 
 Jar, Lightning A Leyden jar, the 
 
 coatings of which consist of metallic filings. 
 
 As the discharge passes, an irregular series of 
 sparks appear, which somewhat resemble in their 
 shape a lightning flash. Hence the origin of the 
 term. 
 
 Jar of Secondary Cell. The containing 
 
 vessel in which the plates of a single secondary 
 cell are placed. 
 
 Jar, Porons A porous cell. (See 
 
 Cell, Porous.) 
 
 Jar, Scintillating A Leyden jar, 
 
 the coatings 'of which, instead of being formed 
 of continuous sheets of tin-foil or other con- 
 ducting substances, are formed of small pieces 
 of such substances, placed at regular intervals 
 on the glass or dielectric so as to leave a small 
 space between them. 
 
 Such a jar has received the name of scintillat- 
 ing jar, because when discharged by connecting 
 its two opposite coatings the discharge appears as 
 minute sparks, which jump across the space 
 between the metallic pieces. 
 
 Jar, Unit A small Leyden jar some- 
 times employed to measure approximately the 
 quantity of electricity passed into a Leyden 
 battery or condenser. 
 
 As shown in Fig. 315, the unit jar consists of a 
 small Leyden jar j, whose outer coating is con- 
 nected with a sliding metallic 
 rod b, provided at each end 
 with a rounded knob, and the 
 inner coating of which is con- 
 nected with a metallic knob c, 
 placed as shown, inside a 
 glass jar d, opposite a ball on 
 the lower end of b. 
 
 When, now, the inside of 
 the unit jar, or the end con- 
 nected with c, is connected 
 with the charging source, such 
 as a machine, and the outside 
 at a, is connected with the jar 
 
 or jars to be charged, for 
 
 i ,, . , Fig- 3 ' 5- Unit Jar. 
 
 every spark that passes be- 
 tween d and c, a definite quantity has passed a. 
 
 The value of this unit charge may be varied by 
 varying the distance between d and c. 
 
 The smaller the unit jar is in proportion to the 
 jar to be charged, and the shorter the distance 
 between c and d, the more reliable are the com- 
 parative results obtained. 
 
 Jars, Leyden, Charging, by Cascade 
 
 (See Cascade, Charging Leyden Jars by.) 
 Jet, Gas, Carcel Standard A 
 
 lighted gas jet employed for determining the 
 candle-power of gas by measuring the height 
 
Jet.] 
 
 297 
 
 [Joi. 
 
 of a jet of gas burning under a given press- 
 ure, and used in connection with the light of 
 a larger gas burner, burning under similar 
 conditions, for the photometric measurement 
 of electric lights. 
 
 Fig 316. Seven-Carcel 
 Standard G.^s Jet. 
 
 Fig-. 317. Carcel Candle 
 Burner. 
 
 In Fig. 316 is shown a section of a seven-carcel 
 standard gas jet, and in Fig. 317, a section of a 
 candle burner, connected within the same service 
 pipe. The gas for both burners is received in a 
 chamber, from whence it passes by an opening to 
 the burner, under the constant pressure obtained 
 by the weight of the bell C, ar.d the tube A. The 
 burner shown in Fig. 317, which is used as the 
 standard of comparison, will give a candle->ower 
 determined from the height of the jet of the 
 burning gas. This height is measured in milli- 
 metres by the motion of a circular screen. 
 
 The determination of the candle-power of gas by 
 means of a jet photometer is only approximately 
 correct, unless many precautions are taken. 
 
 Jet Photometer. (See Photometer, Jet^ 
 Jewelry, Electric Minute incan- 
 descent electric lamps substituted for the 
 rarer gems in articles of jewelry. 
 
 The lamps are lighted by means of small pri- 
 mary or storage batteries, carried in the pocket or 
 elsewhere on the person. 
 
 Joint, . American Twist A tele- 
 graphic or telephonic joint in which each of 
 the two wires is twisted around the other. 
 (See /(?//, Telegraphic or Telephonic^ 
 
 The twisted joint is sometimes subsequently 
 soldered. 
 
 Fig 318. American Twist Joint. 
 
 The American twist joint is shown in Fig. 318. 
 This joint is easily made and is very serviceable. 
 
 Joint, Bell-Hanger's 
 
 A joint for 
 
 telegraphic or telephonic wires in which the 
 ends are merely looped together. (See Joint, 
 Telegraphic or Telephonic?) 
 
 Joint, Britannia A telegraphic or 
 
 telephonic joint in which the wires are laid 
 side by side, bound together and subsequently 
 soldered. (See Joint, Telegraphic or Tele- 
 phonic^) 
 
 Fig. 311). Britannia Joint. 
 
 The Britannia joint is shown in Fig. 319. No, 
 16 wire, B. W. G., is used as the binding wire. 
 
 Joint, Butt An end-to-end joint. 
 
 A joint effected in wires by placing the 
 wires end on and subsequently soldering. 
 
 Butt joints are formed by bringing the ends to 
 be joined together and securing them while in 
 such position. 
 
 Joint, Butt and Lap, of Belts The 
 
 joint in a leather belt, employed for transmit- 
 ting power from a line of shafting where the 
 ends are simply brought together and laced, 
 is called a butt joint, in contradistinction to a 
 lap joint, or a joint formed by placing one end 
 of the belt over the other and lacing or rivet- 
 ing the two. 
 
 In using delicate galvanometers, the slightest 
 change in the speed of the engine driving the 
 dynamo-electric machine producing the current, 
 causes an annoying fluctuation of the needle that 
 prevents accurate reading, when lap joints are usect 
 in the belt instead of butt joints, unless the former 
 are very carefully made. Lap joints may also cause 
 a flickering in the lights. When, however, lap 
 joints are made by cutting the belt by an oblique 
 section and properly securing them so that their 
 
Joi.] 
 
 298 
 
 [Joi. 
 
 elevation at the joint is no greater than elsewhere, 
 the lap joint is preferable to the butt joint. 
 
 Joint, Expansion A joint for under- 
 ground conductors, tubes or pipes, exposed 
 to considerable changes of temperature, in 
 which a sliding joint is provided to safely 
 permit a change of length on expansion or 
 contraction. 
 
 Joint, Insulation A joint in an insu- 
 lating material or covering in which a conti- 
 nuity is insured in the conducting as well as 
 the insulating substance. 
 
 Joint, Lap A joint effected by over- 
 lapping short portions near the ends of the 
 things to be joined, and securing them while 
 in such position. 
 
 Joint, Lap, for Wires A joint 
 
 effected between two wires by overlapping 
 their ends and subsequently soldering. 
 
 Joint, Magnetic The line of junc- 
 tion between two separate parts of magnetiza- 
 ble materal. 
 
 Magnetic joints should be of such a nature as 
 to permit the passage of the lines of magnetic 
 force with the least increase in the resistance of 
 the magnetic circuit 
 
 Magnetic joints in the field magnets of a dynamo- 
 electric machine should be as few as possible, since 
 the resistance of the best magnetic joint to the 
 passage of the lines of force is necessarily greater 
 than that of the same material without such 
 joints. 
 
 Joint, Metallic Conducting A joint 
 
 in a conductor in which a continuity of con- 
 ducting power is secured. 
 
 Joint Resistance of Parallel Circuits. 
 
 (See Resistance, Joint, of Parallel Circuits?) 
 
 Joint, Sleeve A junction of the 
 
 ends of conducting wires obtained by passing 
 them through tubes and then twisting and 
 soldering. 
 
 All joints should be soldered, but in so doing 
 care must ba taken that the soldering liquid or 
 solid employed is free from acids or other corro- 
 sive materials, and that all traces of the soldering 
 liquid or solid are removed from the wire before 
 the joint is covered with insulating material. 
 
 Kerite, okonite or other insulating tape, should 
 
 preferably be wrapped around the joint after 
 it is soldered. 
 
 in making a joint in a giitta-percha covered 
 wire, such as a submarine cable, the following 
 method may be employed: The bared and 
 cleansed wires are twisted together and soldered. 
 The soldered joint is then covered with a layer 
 of plastic insulating material made of a mixture 
 of gutta-percha, tar and rosin. (See Chatterton's 
 Compound.'} In order to insure a good junction 
 between this and the gutta-percha covering on the 
 rest of the -wire, the outer surface of the gutta- 
 percha is removed for about two inches from each 
 side of the joint, so as to remove its oxidized sur- 
 face. After the coating is put on, it is warmed 
 gently by a warm joining tool, not by the flame 
 of a lamp. A sheet of -warmed gutta-percha is 
 then wrapped around the joint, and while it and 
 the joint are still hot, another coating of the 
 plastic insulating material is applied. Successive 
 layers of gutta-percha and some other insulating 
 material are generally applied in the case of sub- 
 marine cables. (Culley.) 
 
 Joint, Telegraphic, Mclntire's Parallel 
 
 Sleeve A joint for telegraphic or other 
 
 wires, in which the ends to be joined are 
 slipped into parallel sleeves or tubes, which 
 are afterward twisted around each other. 
 
 A general view of the parallel sleeve joint, both 
 before and after twisting, is shown in Fig. 320. 
 
 Fig. 330. Mclntire's Parallel Sleeve Joint. 
 
 The twisting is done by means of the specially 
 devised twisting clamp shown in Fig. 321. 
 
 Fig. 321. Twisting Clamp for Mclntire's Para 
 
 Joint, Telegraphic or Telephonic 
 
 A juncture of the ends of two electric con- 
 ductors so as to insure a permanent junc- 
 tion whose resistance shall not be appreci- 
 ably greater per unit of length than that of 
 the rest cf the wire. 
 
Joi.] 299 
 
 In making a joint, care should always be taken 
 to scrape the insulating material from the wires 
 and clean their surfaces before twisting them to- 
 gether. 
 
 Telegraph wires were formerly joined by the 
 ordinary bell-hangers' joint; that is, the wires were 
 simply looped together. The constant vibrations 
 to which the wires are subjected caused such a 
 joint to be abandoned and an improvement intro- 
 duced by bolting the ends together, as shown in 
 Fig. 322. 
 
 [Kao. 
 
 Fig. 322. Telegraphic Joint. 
 
 Joint, Testing of Ascertaining the 
 
 resistance of the insulating material around 
 a joint in a cable. 
 
 The resistance of the insulating material of a 
 cable at a joint is necessarily high, since the 
 joint forms but a small part of length of the cable. 
 It should not, however, be large as compared with 
 an equal length of another part of the cable with 
 a perfect core. 
 
 Two methods for testing cable joints are gener- 
 ally employed, viz. : 
 
 (I.) A conductor is charged through the joints 
 for a given time, and the deflection obtained by 
 its discharge compared with the discharge of the 
 same condenser charged for an equal length of 
 time through a few feet of perfect cable. 
 
 (2.) A charged conductor is permitted to dis- 
 charge itself through the joint, and the amount 
 lost in a given time noted. 
 
 For description of different methods, see 
 Kempe's " Handbook of Electrical Testing." 
 
 Joulad. A term proposed for the Joule. 
 
 This term is not generally adopted. (See 
 Joule.} 
 
 Joule. The unit of electric energy or 
 work. 
 
 The volt-coulomb. 
 
 The amount of electric work required to 
 raise the potential of one coulomb of elec- 
 tricity one volt. 
 
 The joule may be regarded as a unit of energy 
 or work in general, apart from electrical work or 
 energy. 
 
 I joule .......... = 10,000,000 ergs. 
 
 I joule .......... = . 73732 foot-pounds. 
 
 I joule .......... = i volt-coulomb. 
 
 I joule .......... = .24 calorie. 
 
 4.2 joules ......... = i small calorie. 
 
 I joule per second = i watt. 
 
 The British Association proposed to call one 
 joule the work done by one watt in one second. 
 
 Joule, as a Heat Unit. The quantity of 
 heat developed by the passage of a current 
 of one ampere through a resistance of one 
 ohm. 
 
 Joule Effect. (See Effect, Joule) 
 
 Joule's Cylindrical Electro-Magnet 
 
 (See Magnet, Electro, Joule's Cylindrical.) 
 
 Joule's Law. (See Laws of Joule?) 
 Junction Box. (See Box, Junction^ 
 .Tump-Spark Burner. (See Burner, 
 fump-Spark^ 
 
 Junction, Thermo-Electric. A junction 
 between any thermo-electric couple. (See 
 Cell, Thermo-Electrzc) 
 
 K. A contraction for electrostatic capa- 
 city. (See Capacity, Electrostatic^ 
 
 K. C. C. In electro-therapeutics, a brief 
 method of writing kathodic closure contrac- 
 tion, or the effects of muscular contraction 
 abserved at the kathode on the closure of a 
 circuit. 
 
 K. I). C. In electro-therapeutics, a brief 
 method of writing kathodic duration con- 
 
 traction, or the effects of muscular contrac- 
 tion observed at the kathode after the current 
 has been passing for some time. 
 
 K. W. A contraction for kilo-watt. (See 
 Watt, Kilo.) 
 
 Kaolin. A variety of white clay some- 
 times employed for insulating purposes. 
 
 Jablochkoff sometimes employed kaolin be- 
 tween the parallel carbons of his electric candle 
 
Kap.] 
 
 300 
 
 [Key. 
 
 for the purpose of insulating them from each 
 other. He also devised an electric lamp in which 
 a spark of considerable difference of potential, 
 obtained from an ordinary induction coil, was 
 caused to raise a surface of kaolin to incan- 
 descence by passage over it. 
 
 Eapp Lines. (See Lines, Kapp) 
 
 Kartarert. A kind of insulating material. 
 
 Katelectrotonus. A word sometimes used 
 instead of kathelectrotonus. (See Kathe- 
 lectrotonus) 
 
 Kathelectrotonic State. (See State, 
 Kathelectrotonic) 
 
 Katheleetrotonic Zone. (See Zone, 
 Kathelectrotonic^ 
 
 Kathelectrotonns. In electro-therapeu- 
 tics, the condition of increased functional ac- 
 tivity that occurs in a nerve in the neighbor- 
 hood of the kathode or negative electrode. 
 (See Electrotonus.) 
 
 Kathion. The electro-positive ion, atom 
 or radical into which the molecule of an 
 electrolyte is decomposed by electrolysis. 
 (See Electrolysis. Ions.) 
 
 Kathion is sometimes written cathion. 
 
 In electrolysis the kathion, or the electro-posi- 
 tive ion or radical, appears at the kathode or 
 electro-negative electrode. Similarly, the anion, 
 or the electro-negative ion or radical, appears at 
 the anode or the electro-positive electrode. 
 
 Kathodal. Pertaining to the kathode. 
 (See Kathode.) 
 
 Kathode. The conductor or plate of an 
 electro-decomposition cell connected with the 
 negative terminal or electrode of a battery or 
 other source. 
 
 The word kathode is sometimes applied to the 
 negative terminal of a battery or source, whether 
 connected with a decomposition cell or not. It 
 is preferable, however, to restrict its use to de- 
 composition cells. (See Anode.) 
 
 The word kathode is sometimes written cathode. 
 
 Kathodic. Pertaining to the kathode. 
 (See Kathode.) 
 
 Kathodic Electro-Diagnostic Reactions. 
 
 (See Reactions, Electro-Diagnostic) 
 Keeper of Magnet. (See Magnet, Keeper 
 
 Kerite. An insulating material. 
 Kerr Effect (Se& Effect, Kerr.) 
 Key Board. (See Board, Key.) 
 
 Key, Capillary Contact A form of 
 
 fluid contact in which the circuit is closed or 
 broken by means of a wire which is dipped 
 into or removed from the surface of a mass 
 of mercury. 
 
 In order to avoid an increase in the resistance 
 of the circuit, due to the formation of oxide ot 
 mercury, the contact surface of the mercury is 
 kept covered with a layer of dilute alcohol. 
 
 Key, Discharge A key employed to 
 
 enable the discharge from a condenser or 
 cable to be readily passed through a galva- 
 nometer for purposes of measurement. 
 
 Key, Discharge, Kempe's A dis- 
 charge key constructed as shown in Fig. 323. 
 
 Fig. 323. Kempe's Discharge Key. 
 
 The solid lever, hinged at one extremity, plays 
 between two contacts connected to two terminals, 
 and has two finger triggers at its free end marked 
 'Discharge" and "Insulate," connected respec- 
 tively to two ebonite hooks. The hook attached 
 to that marked " Discharge " is a little higher than 
 the other, so that when the lever is caught against 
 it, the key rests in an intermediate position be- 
 tween the contacts, and, when caught against the 
 lower trigger, it rests against the bottom contact. 
 When in the last position, a depression of the 
 " Insulate " trigger causes the lever to spring up 
 against the second hook, thus insulating it from 
 either contact, and on the depression of the "Dis- 
 charge " trigger, the lever springs up against the 
 top contact. 
 
 Key, Discharge, Webb's A dis- 
 charge key constructed as shown in Fig. 324. 
 
 A horizontal lever L, Fig. 324, passing between 
 two contacts and hinged at J, is pressed upward 
 by a spring. The free end of this lever termi- 
 nates in two steps, I and 2. A vertical lever, pro- 
 
Key.] 
 
 301 
 
 [Key. 
 
 vided with an insulating handle, is jointed at J', 
 and has at C, a projecting metallic tongue that 
 engages in the upper step when the lever H, is 
 vertical, and on the lower step when it is slightly 
 mored from the free end. 
 
 When the projection C, rests on the lower step 
 2, the lever L, is intermediate between the top 
 and bottom contacts, and is, therefore, discon- 
 
 If 
 
 Fig. 324. Webb's Discharge Key. 
 
 nected from either of them; but, when it rests on 
 the upper step, it is in contact with the lower 
 contact. 
 
 When the lever H, is so moved as to have the 
 projection C, away from both steps, the lever L, 
 is pressed by its spring against the upper contact. 
 
 The battery terminals axe connected with the 
 condenser terminals when the lever L, is touching 
 the lower contact, but when the lever L, touches 
 the top contact, the condenser is connected with 
 the galvanometer terminals. 
 
 Key, Double-Contact Form of Bridge, 
 Sprague's A key designed to succes- 
 sively close two separate circuits. 
 
 K 
 
 123 4 
 
 Fig. 325. Spr ague's Double-Contact Key. 
 
 Sprague's double-contact key is shown in Fig. 
 325. On depressing K, the contacts c, c, are first 
 closed and afterwards contacts at c', c'. Metallic 
 
 pieces, I, 2, 3 and 4, serve to make contacts with 
 apparatus used in connection with the key. 
 
 The battery circuit is connected to I and 2, 
 and the galvanometer to 3 and 4, so that the bat- 
 tery circuit is closed first, and the galvanometer 
 afterwards. This form of key is used in connec- 
 tion with the Wheatstone Bridge. 
 
 Key, Double-Contact, Lambert's 
 
 A key used in cable-work, and constructed 
 as shown in Fig. 326. 
 
 fff 326. Lambert's Double- Contact Key. 
 
 In Thomson's method for the determination of 
 electrostatic capacity, the capacity of the cable 
 is compared with that of a condenser containing 
 a known charge. These two charges are so con- 
 nected electrically as to discharge into and 
 neutralize each other if equal, but if not, t> pro- 
 duce a galvanometer deflection by a charge 
 equal to their difference. 
 
 A Lambert double contact key is shown in Fig. 
 326. The connections are such that the pushing 
 forward of K, depresses keys that permit a bat- 
 tery to simultaneously charge the condenser and 
 the cable. On drawing K, back, the two charges 
 are allowed to mix. Then on depressing K, the 
 difference of the charges, if any, is discharged 
 through the galvanometer. . 
 
 Key, Double-Tapper The key used 
 
 in a system of needle telegraphy to send 
 electric impulses through the lines in alter- 
 nately opposite directions. (See Telegraphy, 
 Single-Needle?) 
 
 Key, Increment A telegraphic key 
 
 so connected that an increase cr increment 
 in the line current occurs whenever the key is 
 depressed. 
 
 The increment key is used in duplex and quad- 
 ruplex systems of telegraphic transmission. 
 
 Key, Increment, of Quadruples Tele- 
 graphic System A key employed to 
 
 increase the strength of the current and so 
 operate one of the distant instruments in a 
 
Key.] 
 
 302 
 
 [Key. 
 
 quadruplex system by an increase in the 
 strength of the current. (See Telegraphy, 
 Quadruplex^) 
 
 Key, Magneto-Electric A tele- 
 graph key for sending an electric impulse 
 into a line, so arranged that a coil of wire on 
 an armature connected with the key lever is, 
 < by the movements of the key, moved toward 
 or from the poles of a permanent magnet, the 
 movements of the key thus producing the 
 currents sent into the line. 
 
 Key, Plug A simple torm of key in 
 
 which a connection is readily made or broken 
 by the insertion of a plug of metal between 
 two metallic plates that are thus introduced 
 into a circuit. 
 
 A form of plug key is shown in Fig. 327. 
 
 Fig. 327. Plug Key. 
 
 Key, Reversing - A key inserted in 
 the circuit of a galvanometer for obtaining 
 deflections of the needle on either side of the 
 galvanometer scale. 
 
 A form of reversing key is shown in Fig. 328. 
 
 The galvanometer terminals are connected-to the 
 
 binding posts 2 and 3, and the circuit terminals 
 
 to the other two posts. On depressing K, the 
 
 3 
 
 Fig. 328. Reversing Key. 
 
 Current flows in one direction and on depressing 
 K', it flows in the opposite direction. Clamps, 
 operated by handles, are provided so as to close 
 either of the keys permanently, if so desired. 
 
 Key, Reversing, of Quadruplex Tele- 
 graphic System A key employed to 
 
 reverse the direction of the current and so 
 operate one of the distant instruments, in a 
 quadruplex system, by a change in the 
 direction of the current. (See Telegraphy, 
 Quadruplex.) 
 
 Key, Short-Circuit A key which 
 
 in its normal condition short circuits the gal- 
 vanometer. 
 
 Fig. 329. Short-Circuit Key. 
 
 Such a short-circuit key is provided for the 
 purpose of protecting the galvanometer from in- 
 jury by large currents being accidentally passed 
 through its coils. In the form shown in Fig. 329, 
 the spring S, rests against a platinum contact ; 
 but when depressed by the insulated head at K, 
 it rests against an ebonite contact, and throws 
 the galvanometer into the desired circuit. 
 
 The key is provided with double binding posts 
 at P and N, for convenience of attachment to re- 
 sistance coils, batteries, etc. 
 
 In the form of a short-circuit key shown in Fig. 
 330, a catch is provided for the purpose of keep- 
 ing the key down when once depressed. Its 
 arrangement will be readily understood from an 
 inspection of the figure. 
 
 JC 
 
 Fig. 330. ShoH-Circuit Key. 
 
 Key, Sliding-Contact The key em- 
 ployed in the slide form of Wheatstone 
 bridge, to make contact with the wire over 
 which the sliding contact passes. (See 
 Bridge, Electric, Slide Form of.) 
 
303 
 
 [Kit. 
 
 Key, Stationary Floor An electric 
 
 key or push button placed on the floor so as 
 to be readily closed by the foot. 
 
 This form of key is especially suitable for use 
 in connection with an electric bell and annuncia- 
 tor for readily calling an attendant. (See Annun- 
 ciator, Electro-Magnetic.} 
 
 Key, Telegraphic The key em- 
 ployed for sending over the line the successive 
 makes and breaks that produce the dots and 
 dashes of the Morse alphabet, or the deflec- 
 tions of the needle of the needle telegraph. 
 (See Telegraphy, American System of.) 
 
 Kick. A recoil. 
 
 Kicking Coil. (See Coil, Kicking.) 
 
 Kilo (as a prefix). One thousand times. 
 
 Kiloampere. One thousand amperes. 
 
 Kiloampere Balance. (See Balance, 
 Kiloampere^) 
 
 Kilodyne. One thousand dynes. (See 
 Dyne.) 
 
 Kilogramme. One thousand grammes, 
 or 2.2046 pounds avoirdupois. (See Weights, 
 French System of) 
 
 Kilojoule. One thousand joules. 
 
 Kilometre. One thousand metres. 
 
 Kilowatt. One thousand watts. 
 
 Kilowatt Hour. (See Hour, Kilowatt!) 
 
 Kine. A unit of velocity proposed by the 
 British Association. 
 
 A kine equals I centimetre per second. 
 
 Kinetic Energy. (See Energy, Kinetic.) 
 
 Kinetic Theory of Matter. (See Matter, 
 Kinetic Theory of.) 
 
 Kinetics, Electro A term some- 
 times applied to the phenomena of electric 
 currents, or electricity in motion, as distin- 
 guished from electrostatics, or the phenom- 
 ena of electric charges, or electricity at rest. 
 
 Kinetograph. A device for the simultane- 
 ous reproduction of a distant stage and its 
 actors under circumstances such that the 
 actors can be heard at any distance from the 
 theatre. 
 
 The sounds heard by the distant audience are 
 actual reproductions of those uttered during the 
 
 performance, though not at the time of their 
 utterance. The appearance of the stage and its 
 actors represents the appearance of a previous 
 reproduction of the play or opera or other per- 
 formance, as taken by means of a Kodak camera 
 with a film cylinder and drop shutter, operated 
 by an electric motor, exposing, say, forty plates 
 a second. By means of a projecting lantern these 
 photographic pictures are thrown on a curtain on 
 a stage at the distant theatre in regular order of 
 sequence, while a loud-speaking phonograph 
 puts song and speech into the mouths of the 
 mimic actors and thus gives the phantom stage 
 the semblance of life and reality. 
 
 Kite, Franklin's A kite raised in 
 
 Philadelphia, Pa., in June, 1752, by means of 
 which Franklin experimentally demonstrated 
 the identity between lightning and electricity, 
 and which, therefore, led to the invention of 
 the lightning rod. 
 
 It is true that Dalibard, on the loth of May, 
 1752, prior to Franklin's experiment, succeeded 
 in drawing sparks from a tall iron pole he had 
 erected in France. This experiment was, how 
 ever, tried at the suggestion of Franklin, to whom 
 it must properly be ascribed. 
 
 A description of this kite is given by Franklin 
 in the following letter: 
 
 Letter XI, from BENJ. FRANKLIN, Esq., of Phil- 
 adelphia, to PETER COLLINSON, Esq., 
 F. R. S., London. 
 
 "OCT. 19, 1752. 
 
 "As frequent mention is made in public papers, 
 from Europe, of the success of the Philadelphia 
 experiment for drawing the electric fire from 
 clouds by means of pointed rods of iron erected 
 on high buildings, etc., it may be agreeable to 
 the curious to be informed that the same experi- 
 ment has succeeded in Philadelphia, though 
 made in a different and more easy manner, which 
 is as follows: 
 
 " Make a small cross of two light strips of cedar, 
 the arms so long as to reach to the four corners of a 
 large thin handkerchief when extended ; tie the 
 corners of the handkerchief to the extremities of 
 the cross, so you have the body of a kite, which, 
 being properly accommodated with a tail, loop 
 and string, will rise in the air like those made of 
 paper, but this, being of silk, is fitter to bear the 
 wet and wind of a thunder gust without tearing. 
 To the top of the upright stick of the cross is to 
 
304 
 
 [Lag. 
 
 foe fixed a very sharp pointed wire rising a foot 
 or more above the wood. To the end of the 
 twine, next the hand, is to be tied a silk ribbon, 
 and where the silk and twine join, a key may be 
 fastened. This kite is to be raised when a thun- 
 der gust appears to be coming on, and the per- 
 son who holds the string must stand within a 
 door or window, or under some cover, so that 
 the silk ribbon may not be wet, and care must be 
 taken that the twine does not touch the frame of 
 the door or window. As soon as any of the 
 thunder clouds come over the kite the pointed 
 wire will draw the electric fire from them, and 
 the kite, with all the twine, will be electrified, 
 and the loose filaments of the twine will stand 
 out every way, and be attracted by an approach- 
 ing finger. And when the rain has wet the kite 
 and twine so that it can conduct the electric fire 
 freely, you will find it stream out plentifully from 
 the key on the approach of your knuckle. At 
 this key the phial may be charged, and from 
 electric fire thus obtained spirits may be kindled, 
 and all the other electric experiments be per- 
 formed, which are usually done by the help of a 
 
 rubbed glass globe or tube, and thereby the 
 sameness of the electric matter with that of light- 
 ning completely demonstrated. 
 
 "B. FRANKLIN." 
 
 Knife Break Switch. (See Switch, Knife 
 Break) 
 
 Knot or Nautical Mile. A length equal 
 to 6,087 feet. 
 
 The English statute mile is equal to 5,280 feet. 
 The value of the nautical mile is therefore in excess 
 of that of the statute mile. 
 
 Kohlrausch's Law. (See Law of Kohl- 
 rausch.) 
 
 Krizik's Bars. (See Bars, KriziPs.) 
 Kyanized. Subjected to the kyanizing 
 process. (See Kyanizing) 
 
 Kyanizing. A process employed for the 
 preservation of wooden telegraphic poles by 
 injecting a solution of corrosive sublimate 
 into the pores of the wood. (See Pole, Tele- 
 graphic?) 
 
 L. A contraction for co-efficient of in- 
 ductance. (See Inductance, Co-efficient of.) 
 
 L. A contraction for length. 
 
 Labile Galvanization. (See Galvaniza- 
 tion, Labile.) 
 
 Lag, Angle of The angle through 
 
 which the axis of magnetism of the armature 
 of a dynamo-electric machine is shifted by 
 reason of the resistance its core offers to sud- 
 den reversals of magnetization. 
 
 An armature of a bi polar dynamo electric ma- 
 chine has its magnetism reversed twice in every 
 rotation. The iron of the core resists these mag- 
 netic reversals. The result of this resistance is to 
 Bhift the axis of magnetism in the direction of ro- 
 tation. The angle through which the axis has 
 thereby been shifted is called the angle of lag. 
 
 The term, angle of lag, is sometimes incorrectly 
 applied so as to include a similar result produced 
 ly the magnetization due to thi armature current 
 itself. It is this latter action which, in armatures 
 With soft iron cores, is the mam cause of the angle 
 
 of lead. (See Brushes, Lead of. Lead^ Angle 
 of.) 
 
 Lag, Angle of, of Cnrrent An 
 
 angle whose tangent is equal to the ratio of 
 the inductive to the ohmic resistance. 
 
 An angle, the tangent of which is equal to 
 the inductive resistance of the circuit, divided 
 by the ohmic resistance of the circuit. 
 
 An angle, the co-sine of which is equal to 
 the ohmic resistance of the circuit, divided 
 by the impedance of the circuit. 
 
 Lag, Magnetic A magnetic viscos- 
 ity as manifested by the sluggishness with 
 which a magnetizing force produces its mag- 
 netizing effects in iron. 
 
 The tendency of the iron core of a magnet, 
 or of the armature of a dynamo-electric ma- 
 chine, to resist, and, therefore, retard mag- 
 netization. 
 
 This retardation, or lag, is called the magnetic 
 lag. 
 
 The lead necessary to give the brushes of a dy- 
 namo-electric machine to insure quiet action has by 
 
Lam.J 
 
 305 
 
 [Lam. 
 
 some been erroneously ascribed to the magnetic 
 lag. The lead, though due to lag in part, in reality 
 is mainly due to the resultant magnetization of 
 the armature both by the field magnets and by its 
 own current. (See Lead, Angle of.) This dis- 
 placement of the brushes is measured by an angle 
 sometimes, though erroneously, called the angle 
 of lag. (See Lag, Angle of.) 
 
 Lamellar Distri- 
 bution of Magnet- 
 ism. (See Magnet- 
 ism, Lamellar Dis- 
 tribution of.) 
 
 Laminated Core. 
 (See Core, Lami- 
 nated) 
 
 Laminating Core. 
 (See Core, Lami- 
 nation of.) 
 
 Lamination of 
 Armature Core. 
 (See Core, Armature, 
 Lamination of) 
 
 Lamination of 
 Cores. (See Core, 
 Lamination of) 
 
 Lamp, All-Night 
 
 A term some- 
 times applied to a 
 double - carbon arc 
 lamp. (See Lamp, 
 Electric Arc, Double* 
 Carbon) 
 
 A form of all-night 
 arc lamp is shown in 
 Fig. 351. When the 
 consumption of the first 
 pair of carbons has Fig. 331. All-Night Arc 
 reached a certain limit Lamp. 
 
 the current is automatically switched over to the 
 other pair. 
 
 Lamp, All-Night Electric A lamp 
 
 provided with carbon electrodes so as to burn 
 all night without recarboning. 
 
 A double-carbon electric lamp. (See 
 Lamp; All-Night) 
 
 Lamp, A~e An electric lamp, the 
 
 source of whose light is a voltaic arc. 
 
 Lamp, Arc, Electric An electric 
 
 lamp in which the light is produced by a vol- 
 taic arc formed between two or more carbon 
 electrodes. 
 
 The carbon electrodes are placed in various 
 positions, either parallel, horizontal, inclined 
 to one another or vertically one above the other. 
 The latter is the form most generally adopted, 
 since it permits the ready feeding of the upper 
 carbon. 
 
 The carbons are maintained during their con- 
 sumption at a constant distance apart, by the aid 
 of various feeding devices. Such devices are op- 
 erated generally by trains of wheel-work, by me- 
 chanical or electrical motors, or by the simple 
 action of a spring, by gravity or by the attraction 
 of a solenoid. 
 
 The carbon pencils or electrodes are held in 
 carbon holders, consisting of chitches or clamps, 
 attached to the end of the lamp rods. 
 
 When the lamp is not in operation the carbons 
 are usually in contact with one another; but, on 
 the passage of the current, they are separated 
 the required distance by the action 
 of an electro-magnet whose coils 
 are traversed by the direct or main 
 current. 
 
 In order to maintain the elec- 
 trodes a constant distance apart, 
 the up per carbon in some lamps is 
 held in position by the operation of 
 a clutch, or, in others, by a detent, 
 that engages in a toothed wheel. 
 The position of this clutch or de- 
 tent is controlled by the action of 
 an electro-magnet whose coils are 
 usually situated in a shunt or de- 
 rived circuit, of high resistance, 
 around the electrodes. When the 
 carbons are at their normal dis- 
 tance apart, the shunt current is 
 not of sufficient strength to move 
 the clutch or detent from the position in which 
 it prevents the downward motion of the upper 
 carbon rod. When, however, by the burning 
 or consumption of the carbons, the resistance 
 of the arc has increased to an extent which can 
 be predetermined, the increased current that is 
 thereby passed through the shunt circuit is now 
 sufficiently strong to release the clutch or de- 
 tent, thus permitting the fall or feed of the upper 
 carbon. In a well designed lamp this occurs 
 
 Fig. 332. 
 Arc Lamp. 
 
Lam.J 
 
 306 
 
 [Lam. 
 
 so gradually as to produce no perceptible effect 
 on the steadiness of the light. 
 
 Arc lamps are generally placed in series circuits, 
 that is, in circuits in which the current passes suc- 
 cessively through all the lamps in the circuit, and 
 returns to the source. In ortler to avoid the break- 
 ing of the entire circuit through the extinguish- 
 -ng of a single arc, on the breaking of its cir- 
 -uit, an automatic safety device is provided for 
 each lamp. This safety device consists essentially 
 of an electro-magnet so placed in a shunt circuit, 
 that, as the resistance of the arc becomes too 
 great, the increased current, which will then flow 
 through the coils of the electro-magnet, at last 
 produces a movement of its armature which closes 
 a short circuit around the lamp, and thus cuts it 
 out of the circuit. 
 
 Arc lamps assume a great variety of forms. A 
 well known form is shown in Fig. 332. 
 
 Lamp, Arc, Triple Carbon -- An arc 
 
 lamp in which three carbon electrodes are 
 used. 
 
 The positive carbons consist of two ordinary 
 cylindrical carbons, placed parallel to each other. 
 The negative carbon is shaped like the figure 8. 
 The arc is established between one of the positive 
 carbons and the corresponding side of the nega- 
 tive carbon. The feeding of the lamp is attended 
 by a shifting back and forth of the arc between 
 the positive carbons and from side to side of the 
 negative carbons. 
 
 The design of the triple carbon arc lamp is to 
 produce a lamp of long life. 
 
 Lamp Bracket, Electric 
 
 - (See Bracket, Lamp, 
 Electric) 
 
 Lamp Bulb. (See Bulb, 
 
 Lamp, Carcel 
 
 An 
 
 oil lamp employed in France 
 as a photometric standard. 
 
 Fig. 333 shows a formofcar- 
 cel lamp. Like the standard 
 candle, the carcel is a standard 
 only when it consumes a given 
 weight of the light-producing 
 substance in a given time. 
 
 Lamp, Chamber of -- 
 
 The glass bulb or chamber of 
 an incandescing electric lamp 
 in which the incandescing 
 
 333- 
 Carcel Lamp. 
 
 conductor is 
 
 placed, and in which is maintained a high 
 vacuum. 
 
 The transparency of the lamp chamber and 
 consequently the efficiency of the lamp may de- 
 crease 
 
 ( I . ) From the settling of dust or dirt on its outer 
 walls. 
 
 (2.) From the deposit of carbon or metal on its 
 inner walls. 
 
 To obviate the first cause of diminished trans- 
 parency the outside of the lamp chamber should 
 be frequently cleansed. The diminished trans- 
 parency, due to the second cause, cannot be 
 removed. When it has reached a certain point, it 
 is more economical to replace the old lamp by a 
 new lamp. 
 
 In a properly made lamp the dimming of tne 
 lamp chamber is not apt to occur unless a stronger 
 current than the normal current is passed through 
 the lamp. 
 
 Lamp Clamp. (See Clamp for Arc 
 Lamps) 
 
 Lamp, Contact A form of semi- 
 incandescent electric lamp in which a carbon 
 pencil is pressed against a slab of carbon or 
 other refractory material. 
 
 The source of light in an electric contact lamp 
 is twofold, viz.: 
 
 (l.) A minute arc formed at the points of im- 
 perfect contact. 
 
 (2.) The incandescence of the carbon pencil, 
 and the points of the slab of carbon against which 
 it is pressed. 
 
 Lamp Contacts. (See Contacts, Lamp) 
 Lamp, Electric, Arc, Carbon Elec- 
 trodes for (See Electrodes, Carbon, 
 
 for Arc Lamps) 
 
 Lamp, Electric, Arc, Differential . 
 
 An arc lamp in which the movements of 
 the carbons are controlled by the differential 
 action of two magnets opposed to each other, 
 one of whose coils is in the direct and the 
 other in a shunt circuit around the carbons. 
 
 Sometimes the differential coils are placed op 
 the same magnet core. 
 
 Lamp, Electric, Arc, Double Carbon 
 
 An electric arc lamp provided with two 
 pairs of carbon electrodes, sa arranged that 
 when one pair is consumed, the circuit is auto- 
 matically completed through the other pair 
 
LUIU.J 
 
 307 
 
 [I.uu. 
 
 Lamp, Electric Glow A *erm em- 
 ployed mainly in Europe for an incandescent 
 electric lamp. (See Lamp, Electric, Incan- 
 descent^) 
 
 Lamp, Electric, Incandescent An 
 
 electric lamp in which the light is produced 
 by the electric incandescence of a strip or 
 filament of some refractory substance, gener- 
 ally carbon. 
 
 The carbon strip or filament is usually bent into 
 the form of a horseshoe or loop, and placed inside 
 a glass vessel called the lamp chamber. The 
 lamp chamber is exhausted by means of a mercury 
 pump, generally to a fairly high vacuum. 
 
 In order to insure the complete removal from 
 the lamp chamber of all the air it originally con- 
 tained, the carbon strips that are placed within it 
 are maintained at a high temperature during the 
 process of exhaustion. This temperature, in 
 practice, is obtained by sending the current 
 through the carbon strip as soon as nearly all 
 the air is removed. Towards the end of the 
 pumping operation the current is increased so 
 as to raise the carbons to their full bril- 
 liancy. 
 
 The lamp chamber is also maintained at a 
 fairly high temperature. 
 
 To insure this heating of the walls of the lamp 
 chamber by the incandescent carbons during 
 pumping, for the purpose of driving off all the 
 air adhering to the walls of the chamber, they are 
 sometimes covered with some readily removable 
 preparation of lamp black. 
 
 The operation of driving off the gases absorbed 
 by the carbons is termed the occluded gas process, 
 and is essential to the successful sealing of an 
 incandescent lamp. By its means, a considerable 
 quantity of air or other gaseous substances shut 
 up or occluded by the carbon is driven out of the 
 far i.on, which it \vould be impossible to get rid of 
 by the mere operation of pumping. In order to 
 insure the success of the operation, it is necessary 
 that tlie heating mut take place while the lamp 
 is being exhausted, since otherwise the expelled 
 gases would b? re-absorbed. (See Gas, Occlu- 
 sion of } 
 
 Both t!ie exhaustion and the incandescence con- 
 thiue. up to the moment the lamp chamber is 
 hermetically sealed; otherwise, some of the air 
 mi'/ht remain in the lamp chamber. 
 
 The lamp chamber is herme L ally sealed, 
 usually by the iusion of the glass ia the manner 
 
 adopted in the sealing of Geissler tubes or 
 Crookes' radiometers. 
 
 For the preparation of the carbon strip, its 
 carbonization and the flashing of the strip, see 
 Carbonization, Processes of. Carbons, Flashing 
 Process for. 
 
 The ends of the carbon strip, 
 or filament, are attached to lead- 
 ing-in wires of platinum that pass 
 through the glass walls of the 
 lamp chamber, and are fused 
 therein by melting the glass 
 around them in the same manner 
 as are the leading-in wires of the 
 Geissler tubes and other similar 
 apparatus. 
 
 Incandescent lamps are gener- 
 ally connected to the leads or cir- fig-. 334. Incan- 
 cuits in multiple-arc or in multi- Ascent Electric 
 pie-series. They are, however, 
 sometimes connected to the line in series. (See 
 Circuits, Varieties of.) 
 
 In the case of multiple-arc or multiple-series 
 connection, the resistance of the filament is com- 
 paratively high. In the case of series-connec- 
 tion the resistance is comparatively low. 
 
 Incandescent electric lamps assume a variety of 
 different forms. In all cases, however, the shape 
 of the filament is such 
 that the leading-in 
 wires that carry the 
 current to and from 
 the filament shall en- 
 ter and leave the lamp 
 chamber at points that 
 are comparatively 
 near together. This 
 is for the purpose of 
 avoiding the unneces 
 sary production of 
 shadows. 
 
 Commercial incan- 
 descent electric lamps 
 are generally marked 
 with the potential dif- 
 ference in volts that 
 must be applie.l at the 
 terminals in order to 
 furnish the current 
 necessary to properly 
 operate teem. If this 
 potential difference is 
 made greater, the can- 
 
 Fig. 33S' Swan fncanJescent 
 
Lam.] 
 
 308 
 
 [Lam. 
 
 Tie-power of the lamp is greatly increased, but its 
 life greatly decreased. 
 
 The lamp chamber is more liable in such cases 
 to become less transparent from the deposit of a 
 '.bin layer of carbon or metal on its inner surfaces. 
 
 In the Swan lamp the filament is made of cot- 
 ton thread. These threads are immersed in a 
 mixture of two parts of sulphuric acid and one of 
 water, which converts the cellulose of the thread 
 into artificial parchment. The filaments are rap- 
 idly washed as soon as they are removed from the 
 sulphuric acid until all traces of the acid are re- 
 moved. They are then passed through discs so 
 as to insure a uniform area of cross-section, and 
 are then wrapped on rods of carbon or earthen- 
 ware of the required outline, packed in a crucible 
 filled with powdered charcoal, and carbonized. 
 
 The form generally given to the Swan filament 
 is that shown in Fig. 335. 
 
 Lamp, Electric, Incandescent Ball 
 
 An incandescent electric lamp in which 
 the light is produced by a sphere or ball of 
 carbon placed in an exhausted receiver of 
 glass. 
 
 When subjected to the effects of electrostatic 
 waves of high frequency of alternation, such a 
 lamp becomes luminous 
 from the incandescence of 
 the carbon ball or sphere. 
 Tesla's incandescent ball 
 electric lamp is a modifica- 
 tion of his straight filament 
 lamp. (See Lamp, Incan- 
 descent, Straight Filament .) 
 
 The construction of Tes- 
 la's ball incandescent elec- 
 tric lamp will be readily 
 understood from an inspec- 
 tion of Fig. 336. 
 
 Lamp, Electric, In- 
 candescent, Half-Shades 
 
 for (See Half- 
 Shades for Incandescent Lamps.) 
 
 Lamp, Electric, Incandescent, Life of 
 
 The number of hours that an incan- 
 descent electric lamp, when traversed by the 
 normal current, will continue to afford a good 
 commercial light. 
 
 The failure of an electric incandescent lamp 
 results either from the volatilization or rupture 
 of the carbon conductor, or from the failure of the 
 
 vacuum of the lamp chamber. Since the em- 
 ployment of the flashing process, and the process 
 for removing the occluded gases, it is not unusual 
 for incandescent lamps to have a life cf several 
 thousand hours. (See Carbons^ Flashing Pro- 
 cess for.') 
 
 The life of an incandescent electric lamp should 
 not be considered as continuing until the filament 
 actually breaks. As soon as the lamp chamber 
 has become covered with such a deposit of car- 
 bon or coating of metal as to considerably de- 
 crease the amount of light which passes through 
 the chamber, the lamp should be considered as 
 useless. 
 
 Lamp, Electric, Incandescent, Three- 
 Filament, for Multi-Phase Circuits 
 
 An incandescent lamp for use on multi- 
 phase circuits, provided with three leading-in 
 wires, connected to the free ends of three 
 filaments, the other ends of which are con- 
 nected in a common joint. 
 
 When properly acting, the current passing 
 through each filament should, at any instant, 
 equal the sum of the currents ia the other two 
 filaments, which, as is well known, is the property 
 of any three-phase circuit. 
 
 Lamp, Electric, Outrigger for 
 
 (See Outrigger for Electric Lamp) 
 
 Lamp, Electric, Pendant An in- 
 candescent electric lamp suspended by flexible 
 twin-wire. 
 
 Lamp, Electric, Safety An in- 
 candescent electric lamp, with thoroughly 
 insulated leads, employed in mines, or other 
 similar places, where the explosive effects of 
 readily igmtable substances are to be feared. 
 
 Such lamps are often directly attached to a 
 portable batter)', in which case they can be read- 
 ily carried about from place to place. 
 
 Lamp, Electric, Semi-Incandescent 
 
 An electric lamp in which the light is due 
 to the combined effects of a voltaic arc and 
 electric incandescence. 
 
 In the Reynier semi-incandescent lamp, shown 
 in Fig. 337, a thin pencil of carbon C, is gentlj 
 pressed against a block of graphite B. A lateral 
 contact is provided at L, through a block o< 
 graphite I, by means of which the curn-nt \ re 
 
Lam.] 
 
 309 
 
 [Lam. 
 
 to the lower part only of the movable rod 
 C, which part alone is rendered incandescent. 
 In this lamp, the light is due both to the incan- 
 
 C 
 
 Fig. 337* Semi- Incandescent Lamp, 
 
 aescence of the rod C, and to the small arc formed 
 at J, between its lower end and the contact block 
 B, though mainly from the latter. The semi- 
 incandescent electric lamp has not as yet been in- 
 produced to any considerable extent. 
 
 Lamp, Electric, Series-Connected Incan- 
 descent An incandescent electric lamp 
 
 adapted for use in series circuits. 
 
 Fig, 338. Serbs Incandescent Electric lamp. 
 
 A form of series incandescent lamp, attached 
 to pendant and shade, is shown hi Fig. 338. 
 
 In thQ series connected incandescent lamp, un- 
 Hlce the multiple-connected incandescent electric 
 lamp, the resistance of the filament is low. This 
 Is done in. order to prevent the total resistance of 
 
 the circuit from requiring too high an electro- 
 motive force for operation. In order to preserve 
 the continuity of the circuit on the failure of any 
 lamp to operate, some form of automatic cut-out 
 is employed. This is generally some form of 
 film cut-out. (See Cut-Out, Film.) 
 
 Lamp Hour. (See Hour, Lamp.) 
 
 Lamp, Incandescent, Electric Filament 
 
 Of A term now generally applied to the 
 
 incandescing conductor of an incandescent 
 electric lamp, whether the same be of very 
 small cross-section or of comparatively large 
 cross-section. 
 
 The term filament is properly applied to a con- 
 ductor containing fibres or filaments extending in 
 the general direction of the length of the incan- 
 descing conductor. Such a conductor is made of 
 carbonizable fibrous material, cut or shaped prior 
 to carbonization so as to have its fibres extend- 
 ing with their greatest length in the direction of 
 length of the filament. 
 
 Lamp, Incandescent, Straight Filament 
 
 An incandescent electric lamp in 
 
 which a straight filament, placed in an ex- 
 hausted glass chamber, is rendered luminous 
 by the effects of electro- 
 static waves or thrusts of 
 high frequency. 
 
 The straight filament in 
 candescent lamp is the in- 
 vention of Tesla. One 
 form of such a lamp is 
 shown in Fig. 339. 
 
 The glass globe b, of the 
 lamp is provided with a 
 cylindrical neck, inside of 
 which is placed a tube m, 
 of conducting material, on 
 the side and over the end 
 of the insulating plug n. 
 
 The light-giving fila- 
 ment e, is a straight car- 
 bon stem, connected to the 
 plate by a conductor cov- 
 ered with a refractory in- 
 sulating material k. An 
 insulated tube-socket p, 
 provided with a metallic lining s, serves to sup 
 port the lamp and connect it with one pole of the 
 source of current. It will be noticed that the coat- 
 
 33Q. Tesla's 
 Straight Filament In- 
 candescent Lamp. 
 
Lam.] 
 
 310 
 
 [Law. 
 
 ings s and m, form the plates of a condenser. 
 The other terminal of the machine may be con- 
 nected to the metal coated walls of the room, 
 or to metallic plates suspended from the ceiling. 
 Lamp Indicator. (See Indicator, Lamp.) 
 
 Lamp, Pilot 
 
 In systems for the 
 
 operation of electric lamps, an incandescent 
 lamp employed in a station to indicate the 
 difference of potential at the dynamo ter- 
 minals, by means of the intensity of its emitted 
 light. 
 
 Lamp Rod. (See Rod, Lamp?) 
 
 Lamp Socket Switch. (See Switch, 
 Lamp Socket?) 
 
 Lamps, Bank of A term applied 
 
 to a number of lamps, equal to about half the 
 load, that were formerly placed in view of the 
 attendant in circuit with a dynamo that is to 
 be placed in a parallel circuit with another 
 dynamo, one of the lamps of which is also 
 in view. 
 
 When the lamps "in bank " were judged to be 
 of the same brilliancy as the one fed by the other 
 dynamo, the attendant switched the dynamo par- 
 allel with the other, and at the same time cut off 
 the bank of lamps from the switched in dynamo. 
 
 The method is, however, wrong. The proper 
 way is to make the voltage of the dynamo equal 
 to that of the circuit. Then connect it and 
 finally raise its electromotive force until it takes 
 its share of the load. 
 
 Lamps, Cartoning Placing carbons 
 
 in electric arc lamps. 
 
 When the carbons are consumed, the lamp 
 requires recarboning. The old carbon ends are 
 replaced by new carbons, and the lamp rods 
 cleansed. 
 
 Large Calorie. (See Calorie, Great.) 
 Latent Electricity. (See Electricity, 
 Latent) 
 
 Lateral Discharge. (See Discharge, 
 Lateral.) 
 
 Lateral Induction. (See Induction, Lat- 
 eral.) 
 
 Lateral Leakage of Lines of Magnetic 
 Force. (See Leakage, Lateral, of Lines of 
 Magnetic Force?) 
 
 Lateral Magnetic Leakage. (See Leak- 
 age, Lateral, of Lines of Magnetic Force?) 
 
 Latitude, Magnetic The distance 
 
 a place is situated north or south of the mag- 
 netic equator 
 
 All places that have the same magnetic latitude 
 have the same value for the magnetic inclination 
 and magnetic intensity, or are on the same isocli- 
 nal and isodynamic lines. The magnetic latitude 
 is the same at all points of a magnetic parallel. 
 
 Launch, Electric A boat, the mo- 
 tive power for which is electricity, suitable for 
 launching from a ship. 
 
 Up to the present time electric launches have 
 been propelled by means of electric motors, driven 
 by means of powerful storage batteries. 
 
 A form of electric launch constructed for the 
 English Government is shown in Fig. 340. It is 
 
 - 340, Electric Launch. 
 
 48^ feet in length over all, by 8 feet 9 inches 
 beam, with an average draft of 2 feet 3 inches. 
 Its speed is 8 knots per hour. It will carry forty 
 fully equipped soldiers. 
 
 Law, Jacobi's -- The maximum work 
 done by a motor is reached when the counter- 
 electromotive force is equal to one-half of the 
 impressed electromotive force, or, 
 
 Law, Joule's ---- The heating power of 
 a current is proportional to the product of 
 the resistance and the square of the current 
 strength. (See Heat, Electric?) 
 
 Law, Natural -- A correct expression 
 of the order in which the causes and effects 
 of natural phenomena follow one another. 
 
 The law of gravitation, for example, correctly 
 expresses the order of sequence of the phenomena 
 which result when unsupported bodies fall to the 
 earth. It should be carefully borne in mind, how- 
 ever, that natural laws cannot be regarded as 
 explaining the ultimate causes of natural phenc- 
 
Law.] 
 
 311 
 
 [Law. 
 
 mena, but merely express their order of occur- 
 rence or sequence. 
 
 We are ignorant, for example, of the true cause 
 of gravitation and are only acquainted with its 
 effects. This is true of all ultimate physical 
 causes, save for our belief in their origin in a 
 Divine will. 
 
 Law of Electro-Chemical Equivalence. 
 (See Equivalence, Electro-Chemical, Law 
 of) 
 
 Law of Kohlrausch. In electrolytic con- 
 duction, each atom has a rate of motion for 
 a given liquid, which is independent of the 
 element with which it may have been com- 
 bined. 
 
 In the following table, the rate of motion of 
 various kinds of atoms through nearly pure water 
 for a difference of potential of one volt per linear 
 centimetre, is given: 
 
 H I.o8 centimetres per hour. 
 
 K 0.205 centimetre " 
 
 Na 0.126 " " 
 
 Li 0.094 " " 
 
 Ag 0.166 " " 
 
 C 0.213 " " 
 
 1 0.216 " " 
 
 NO 8 0.174 " " 
 
 Law of Ohm, or Law of Current 
 Strength. The strength of a continuous 
 current is directly proportional to the differ- 
 ence of potential or electromotive force in the 
 circuit, and inversely proportional to the re- 
 sistance of the circuit, /. e., is equal to the 
 quotient arising from dividing the electromo- 
 tive force by the resistance. 
 
 Fig. 341. Current Strength in Circuit. 
 Ohm's law is expressed algebraically thus: 
 C = 5; or, E = C R. 
 
 If the electromotive force is given in volts, and 
 the resistance in ohms, the formula will give the 
 current strength directly in amperes. 
 
 The resistance of any electric circuit, as, for 
 example, that shown in Fig. 341, consists of three 
 parts, viz.: 
 
 (i.) The internal resistance of the source, r. 
 
 (2.) That of the conducting wires or leads, r'; 
 and 
 
 (3.) That of the electro-receptive, r", energized 
 by the current. Ohm's law applied to this case 
 would be: 
 
 _ 
 
 = 
 
 That is, the resistance of the entire circuit is 
 equal to the sum of the separate resistances of its 
 different parts. 
 
 Since C= H, (i); then E = C R, (2); 
 and R = ?, (3). 
 
 But, since a current of one ampere is equal to 
 one coulomb per second, then, in order to deter- 
 mine in coulombs the quantity of electricity pass- 
 ing in a given number of seconds, it is only neces- 
 sary to multiply the current by the time in seconds, 
 or Q = C T (4). 
 
 Hence, referring to the above equations (i), 
 (2), (3) and (4); according to Ohm's law: 
 
 (i.) The current in amperes is equal to the 
 electromotive force in volts divided by the resist- 
 ance in ohms. 
 
 (2.) The electromotive force in volts is equal to 
 the product of the current in amperes and the 
 resistance in ohms. 
 
 (3.) The resistance in ohms is equal to the elec- 
 tromotive force in volts divided by the current in 
 amperes. 
 
 (4.) The quantity of electricity in coulombs is 
 equal to the current in amperes multiplied by the 
 time in seconds. 
 
 Law of Yolta, or Law for Contact-Series. 
 
 A law for the differences of electric potential 
 produced by the contact of dissimilar metals 
 or other substances. 
 
 " The difference of potential between any two 
 metals is equal to the sum of the differences of 
 potential between the intervening substances in 
 the contact series" (See Electricity, Contact. 
 Series, Contact.) 
 
 Law, Pfluger's 
 
 A given tract of 
 
 nerve is stimulated by the appearance of 
 kathelectrotonus and the disappearance of an- 
 electrotonus ; not, however, by the disap- 
 
Law.J 
 
 312 
 
 Law, 
 
 pearance of kathelectrotonus nor by ihe ap- 
 pearance of anelectrotonus. (Landois and 
 Stirling?} 
 
 Law, Poynting's At any point in 
 
 a magnetic field, or a conductor conveying 
 current, the energy moves perpendicularly to 
 the plane containing the lines of electric force 
 or the lines of magnetic force, and the amount 
 of energy crossing the unit of area of this 
 plane per second is equal to the product of 
 the intensities of the two forces multiplied by 
 the sine of the angle between them, divided 
 by 4?t. 
 
 If E, represents the electric force of a small body 
 charged with positive electricity, and H, the 
 magnetic force or forces of a smaller free unit 
 north pole, and, if these forces at any point in 
 the magnetic field are inclined at an angle, 9, 
 then e, the flow of energy per second at this point, 
 in a direction oerpendicular to the planes of E and 
 His, 
 
 E H sin. 9 
 
 C : 
 
 \it 
 
 There is, therefore, a difference in the direction 
 of the flow of electricity and the flow of electric 
 energy. Electricity may be conceived as passing 
 through the conductor something like water 
 through a pipe, but electrical energy does not 
 travel in this way. Electrical energy travels 
 through the surrounding dielectric, which is 
 thereby strained, and it propagates this strain 
 from point to point until it reaches the conductor 
 and is there dissipated. 
 
 Law, Toltametric The chemical 
 
 action produced by electrolysis in any elec- 
 trolyte is proportional to the amount of elec- 
 tricity which passes through the electrolyte. 
 
 This is called the Voltametric law, because any 
 vessel containing an electrolyte, and furnished 
 with electrodes, so that electrolysis may take place 
 on the passage of the current, and is provided 
 with means for measuring the amount of the 
 electrolysis which occurs, is called a Voltameter. 
 (See Voltameter. Electrolysis.'] 
 
 Laws, Amptfre's, or Laws of Electro- 
 Dynamic Attraction and Repulsion 
 
 Laws expressing the attractions and repul- 
 sions cf electric circuits en one another or 
 on magnets. 
 
 Laws, DuVs " The magnetism ex- 
 cited at any transverse section of a magnet is 
 proportional to the square root of the distance 
 between the given section and the near end 
 of the magnet." 
 
 " The free magnetism at any given trans- 
 verse section of a magnet is proportional to 
 the difference between the square root of half 
 the length of the magnet and the square root 
 of the distance between the given section and 
 the nearest end." 
 
 Laws, KirchhoiTs 
 
 The laws for 
 
 branched or shunted circuits. 
 
 These laws may be expressed as follows: 
 
 (I.) In any number of conductors meeting at a 
 point, if currents flowing to the point be considered 
 as -[-, and those flowing away from it as , the 
 algebraic sum of the meeting currents will be 
 zero. 
 
 This is the same thing as saying as much elec- 
 tricity must flow away from the point as flows to- 
 ward it. 
 
 (2.) In any system of closed circuits the alge- 
 braic sum of the products of the currents into the 
 resistances is equal to the electromotive force in 
 the circuit. 
 
 In this case all currents flowing in a certain 
 direction are taken as positive, and those flowing 
 in the opposite direction as negative. All elec- 
 tromotive forces tending to produce currents in 
 the direction of the positive current are taken as 
 positive, and those tending to produce currents iu 
 the opposite direction, as negative. 
 
 E 
 This follows from Ohm's law; for, since C = , 
 
 R 
 
 the electromotive force E = CR, and this is true, 
 no matter how often the circuit is branched. 
 
 Laws, Lenz's Laws for determining 
 
 the directions of currents produced by electro- 
 dynamic induction. 
 
 The direction of the currents set up by electro- 
 dynamic induction is always such as to oppose 
 the -notions by which such currents were pro- 
 duced. 
 
 Laws of Becquerel, or Laws of Mag- 
 neto-Optic Rotation. Laws for the mag- 
 neto-optic rotation of the plane of polarization 
 of light. (See Rotation, Magneto-Optic^ 
 
 Laws of Con^omfo, o Laws of Electro- 
 
Law. I 3 
 
 static and Magnetic Attractions and Re- 
 pulsions. Laws for the force of attraction 
 and repulsion between charged bodies or be- 
 tween magnet poles. 
 
 The fact that the force of electrostatic attrac- 
 tion or repulsion between two charges, is directly 
 proportional to the product of the quantities of 
 electricity of the two charges and inversely propor- 
 tional to the square of the distance between them, 
 is known as Coulomb'' s Law. Coulomb also as- 
 certained that the attractions and repulsions be- 
 tween magnet poles are directly proportional to the 
 product of the strength of the two poles, and in- 
 Tersely proportional to the square of the distance 
 between them. This is also called Coulomb's 
 Law. 
 
 Coulomb's law, in order to be accurate, must 
 take into account the specific inductive capacity 
 of the intervening medium. The correct expres- 
 sion for the force between two quantities q and q', 
 of electricity would be, therefore, 
 
 where K, is equal to the specific inductive capacity 
 of the medium separating the two charges. 
 
 In a similar manner when the force is exerted 
 between two magnet poles, to be accurate, we must 
 take into account the magnetic permeability of 
 the medium between the two magnets. The cor- 
 rect expression for the force between two magnet 
 poles is, therefore, 
 
 p. _ 
 " 
 
 when ju, is the magnetic permeability. 
 Laws of Faraday, or Laws of Electrolysis 
 
 -- Laws for the effects of electrolytic 
 decomposition. (See Electrolysis!) 
 
 These laws are as follows: 
 
 (i.; The amount of an electrolyte decomposed 
 is directly proportional to the quantity of elec- 
 tricity which passes through it ; or, the rate at 
 which a body is electrolyzed is proportional to 
 the current strength producing such electrolysis. 
 
 (2.) If the same current be passed through dif- 
 ferent electrolytes, the quantity of each ion 
 evolved is proportional to its chemical equivalent. 
 
 Laws of Jonle. Laws expressing the de- 
 velopment of heat produced in a circuit by an 
 electric current. 
 
 These laws may be expressed as follows : 
 
 (l.) The amount of heat developed in any cir- 
 
 [Lea. 
 
 cuit is proportional to its resistance, providing 
 the current strength is constant. 
 
 (2. ) The amount of heat developed in any cir- 
 cuit is proportional to the square of the current 
 passing, providing the resistance is constant. 
 
 (3.) The amount of heat developed in any cir- 
 cuit is proportional to the time the current con- 
 tinues. 
 
 Or, H = C* RtX0.2 4 . 
 
 Where H, equals the heat in small calories, C, 
 equals the current in amperes, R equals the re- 
 sistance in ohms, t, equals the time in seconds, 
 and 0.24, the heat-units per second developed in 
 a resistance of i ohm by the passage of i am- 
 pere. 
 
 Lay Torpedo. (See Torpedo, Lay.) 
 
 Layer, Crookes' 
 
 A layer, or 
 
 stratum, of the residual atmosphere of a 
 vacuous space, in which the molecules, recoil- 
 ing from a heated or electrified surface, do 
 not meet other molecules, but impinge on the 
 walls of the vessel directly opposite such 
 heated or electrified surface. 
 
 A Crookes layer may result as the effect of 
 two different causes, viz. : 
 
 (i.) The rarefaction of the gas is such that the 
 distance between the walls of the vessel and the 
 heated surface is less than the mean-free-path of 
 the molecules. 
 
 (2.) The wall is so near the heated surface that 
 the distance between the two is less than the ac- 
 tual mean-free-path of the molecules. Under 
 these last-named circumstances Crookes' layers 
 may result, whatever be the density of the gas. 
 
 Laying-Up Cables. (See Cables, Lay- 
 ing- Up.) 
 
 Lead, Angle of The angular devia- 
 tion from the normal position, which must be 
 given to the collecting brushes on the com- 
 mutator cylinder of a dynamo-electric ma- 
 chine, in order to avoid destructive burning. 
 (See Commutator, Burning <z/.) 
 
 The necessity for giving the collecting brushes 
 a lead, arises both from the magnetic lag and from 
 the distortion of the field of the machine by the 
 magnetization of the armature current. The 
 angle of lead is, therefore, equal to the sum of the 
 angle of lag, and the angular distortion due to the 
 magnetization produced by the armature current . 
 
Lca.J 
 
 314 
 
 [La. 
 
 Lead, Cable A lead containing a 
 
 conductor formed of several stranded con- 
 ductors, as distinguished from a wire lead or 
 a lead containing a single conductor. 
 
 Lead, Flexible A conductor formed 
 
 of a number of small stranded conductors for 
 the purpose of obtaining flexibility. 
 
 Lead, Flexible Twin A flexible 
 
 conductor in which two parallel and sepa- 
 rately insulated wires are placed. 
 
 Lead of Brushes of Dynamo-Electric 
 Machine. The angular deviation from the 
 normal position, which it is necessary to give 
 the brushes on the commutator of a dynamo- 
 electric machine, in order to obtain efficient 
 action. (See Lead, Angle of.) 
 
 Lead Scoring Tool. (See Tool, Scoring, 
 Lead?) 
 
 Lead Sleeve. (See Sleeve, Lead.) 
 
 Lead, Tee. (See Tee, Lead.) 
 
 Lead, Wire A lead consisting of a 
 
 single conductor, as distinguished from a 
 cable lead, or a lead containing a number of 
 stranded conductors. 
 
 Lead Wire. (See Wire, Lead) 
 
 Leading Horn of Pole Pieces of Dynamo- 
 Electric Machine. (See Horns, Leading, of 
 Pole Pieces of a Dynamo-Electric Machine.) 
 
 Loading-Ill Wires. (See Wires, Lead- 
 ing-In.) 
 
 Leading-Up Wires. (See Wires, Lead- 
 ing- Up.) 
 
 Leads. The conductors in any system of 
 electric distribution. 
 
 In distribution by parallel, the conductors 
 through which the current flows from the source 
 are sometimes called the leads in contradis- 
 tinction to those through which it returns to 
 the source. 
 
 The leads, or main conductors, in a multiple 
 system of electric lighting, must maintain a con- 
 stant potential at the lamp terminals. The dimen- 
 sions of the leads are, therefore, so proportioned as 
 to absorb as small an amount of potential as pos- 
 sible. Since, in incandescent lighting, where the 
 connected to the leads in multiple-arc, 
 
 total resistance of the lamps is comparatively 
 
 small, the resistance of the leads must be quite 
 small in order to avoid a marked drop of poten- 
 tial. Comparatively large conductors must, 
 therefore, be used. 
 
 The main conductor for series circuits, such as 
 for arc-lights, has in all parts the same current 
 strength. Since the sum of the resistances of the 
 lamps in such a circuit is quite high, a compara- 
 tively high resistance in the conductor may be 
 employed without a proportionally large absorp- 
 tion of potential. Comparatively small conduc- 
 tors can therefore be used. (See Electricity, Dis- 
 tribution of, by Constant Currents. Electricity, 
 Distribution of, by Alternating Currents.) 
 
 Leads, Armature, Twist in - A dis- 
 placement of the ends of the wires connected 
 to the commutator segment, with respect to 
 the position of the coils on the armature, for 
 the purpose of obtaining a more convenient 
 position for the diameter of commutation, 
 that is, for the collecting brushes. 
 
 Leak, Oscillatory A leak or grad- 
 ual loss of electricity which takes place in 
 alternately opposite directions. 
 
 Leak, Unidirectional A gradual 
 
 loss or leakage of electricity which takes place 
 in one and the same direction. 
 
 The term has been employed to distinguish 
 such a leak from an oscillatory leak. 
 
 Leakage Conductor. (See Conau<-fo>; 
 Leakage) 
 
 Leakage, Electric The gradual 
 
 dissipation of a current due to insufficient in- 
 sulation. 
 
 Some leakage occurs under nearly all circum- 
 stanres. On telegraphic lines, during wet 
 weather, the leakage is often so great as to inter- 
 fere with the proper working of the lines. 
 
 Leakage, Electrostatic The grad- 
 ual dissipation of a charge due to insufficient 
 insulation. 
 
 The leakage of a well insulated conductor, 
 placed in a high vacuum, is almost inappreciable. 
 Crookes has maintained electric charges in high 
 vacua for years without appreciable loss. 
 
 Leakage, Lateral, of Lines of Magnetic 
 Force The failure of lines of magnetic 
 
Lea.] 
 
 315 
 
 [Len. 
 
 force to pass approximately parallel to one 
 another through a bar of iron or other mag- 
 netizable material, when it has come to rest 
 in a magnetic field in which it is free to 
 move. 
 
 The escape of the lines of magnetic force 
 from the sides of a bar or other similar 
 magnet, instead of from the poles at the 
 end. 
 
 When a bar of magnetizable material, sus- 
 pended so as to be free to move, comes to rest in 
 a magnetic field in which it is undergoing mag- 
 netization, it has its greatest length parallel to 
 the direction of the lines of force. If the bar is a 
 long, thin, straight bar, the lines of force do not 
 all pass in or come out at its ends. On the con- 
 trary, many of these lines of force or induction 
 pass in or come out at other points. The mag- 
 netic induction is, therefore, unequal at different 
 sections of the bar. In other words, the mag- 
 netic flux or intensity is not constant per unit of 
 all cross-sections of such bar. 
 
 Leakage, Magnetic A useless dis- 
 sipation of the lines of magnetic force of a 
 dynamo-electric machine, or other similar 
 device, by their failure to pass through the 
 armature where they are needed. 
 
 Useless dissipation of lines of magnetic 
 force outside that portion of the field of a 
 dynamo-electric machine through which the 
 armature moves. 
 
 Such a leakage can be detected by an instru- 
 ment called a magnetophone. (See Magneto- 
 phone.} 
 
 Magnetic leakage results in lowering the effi- 
 ciency of the dynamo. (See Co-efficient, Econo- 
 mic, of a Dynamo-Electric Machine. ) 
 
 Leclanche~'s Voltaic Cell. (See Cell, 
 Voltaic, Lcdanch^ 
 
 Leg". In a system of telephonic exchange, 
 where a ground return is used, a single wire, 
 or, where a metallic circuit is employed, two 
 wires, for connecting a subscriber with the 
 main switchboard, by means of which any 
 subscriber may be legged or placed directly 
 in circuit with two or more other parties. 
 Leg of Circuit. (See Circuit, Leg of.) 
 Legal Earth Quadrant. (See Quadrant, 
 Legal Earth) 
 11 Vol. 1 
 
 Legal Ohm. (See Ohm, Legal.) 
 
 Legging-Key Board. (See Board, Leg- 
 gtng-Key.) 
 
 Length of Spark. (See Spark, Length 
 of) 
 
 Lens, Achromatic A lens the 
 
 images formed by which are free from the 
 false coloration produced in other lenses by 
 dispersion. 
 
 An ordinary lens can be rendered approxi- 
 mately achromatic by the use of a diaphragm. 
 Achromatic lenses generally consist of the com 
 
 ^%" 34 2 - Equal and Opposite Refracting Angles. 
 
 bination of a double convex lens of flint glass arx? 
 a concave lens of crown glass. 
 
 The ray of light entering the prism A B Cj 
 Fig. 342, suffers dispersion (separation into pris 
 made colors). This dispersion in the sam' 
 
 Principle of Achromatitm. 
 
 medium is proportional to the angle g, between 
 the incident and emergent faces, called the re- 
 fracting angle. 
 
 If, now, another prism B C D, of the same ma- 
 terial, with a refracting angle g', equal to g, is 
 combined with the first prism in the manner 
 shown in Fig. 342, it will produce an equal but 
 opposite dispersion, so that the ray of light will 
 emerge at R', free from rainbow tints, but par- 
 allel to its original direction. 
 
 The variety of glass called crown glass pro- 
 duces only half as great dispersion of light as the 
 variety called flint glass, under the same refract* 
 
t-en.] 
 
 316 
 
 ing angle g. If the prism A B C, of crown glass, 
 Fig- 343, whose angle g, is twice as great as the 
 refracting angle g , of the prism B C D, of flint 
 glass, be placed together in the manner shown, 
 then the ray R, will be transmitted at R' , free from 
 color, but will not eiixrge par ailed to its original 
 direction ; in other words, it suffers refraction or 
 bending. Consequently such a combination can 
 be used to free a pencil of light from false colora- 
 tion and yet permit it to undergo refraction, 
 and thus act as a lens. (See Refraction.') 
 
 The construction ot achromatic lenses is based 
 on this principle. 
 
 The crown glass is generally made with two 
 
 Fig. 344. Piano-Convex Fig. 343. Achromatic 
 Achromatic Lens. Lens. 
 
 convex surfaces ; the flint glass, with one con- 
 cave and one plane surface, as shown in Fig. 
 344- 
 
 Sometimes both surfaces of the flint glass are 
 made curved, as in Fig. 345. 
 
 Lenz's Law. (See Law, Lens's.) 
 
 Letter Box, Electric A device 
 that announces the deposit of a letter in a 
 box by the ringing of a bell, or by the move- 
 ment of a needle or index. 
 
 These devices generally act by the closing or 
 opening of an electric circuit on the fall of the 
 letter into the box. 
 
 Leyden Jar. (See far, Leyden) 
 Leyden Jar Pattery. (See Battery, Ley 
 den Jar.} 
 
 Lichtenberg's Dust Figures. (See Fig- 
 ures, Lichtenberg's Dust) 
 
 Life Curve of Incandescent Electric 
 Lamp. (See Curve, Life, cf Incandescent 
 Electric Lamp?) 
 
 Life of Electric Incandescent Lamp. 
 
 (See Lamp, Incandescent, Life of.) 
 
 Light, Auroral - The light given off 
 during the prevalence of an aurora. (See 
 Aurora Bore alts) 
 
 Light, Electric Light produced by 
 the action of electric energy. 
 
 Electric light is produced by electric energy in 
 various ways, the most important of which are as 
 follows, viz.: 
 
 (I.) By the passage of an electric discharge 
 through a gas or vapor, either in a rarefied condi- 
 tion, at ordinary atmospheric pressure, or at pres- 
 sures higher than that of the ordinary pressure. 
 In any of these cases the gas or vapor is heated to 
 incandescence by the passage of the discharge. 
 
 (2.) By the incandescence of a solid by the 
 heating power of the current, as in the incandes- 
 cent lamp. 
 
 (3.) By the incandescence of a solid by the ac- 
 tion of a rapidly alternating electrostatic field, as 
 in Tesla's incandescent lamp. 
 
 \4. ) By the volatilization of a solid and the form- 
 ation thereby of a voltaic arc. 
 
 (5.) By the combination of the effects of incan- 
 descence and the voltaic arc. 
 
 The amount of light produced in proportion to 
 the amount of energy expended to produce it 
 is probably least in the case of light produced 
 by the sparks of a Wimshurst or Holtz machine, 
 or as in ( I ), than in any other case in which electric 
 energy acts to produce luminous energy. 
 
 Light, Electric, Pumping of (See 
 Pumping of Electric Light) 
 
 Light, Intensity of The brilliancy 
 or illuminating power of a light as measured 
 by a photometer in standard candles or other 
 standard units. (See Photometer. Candle, 
 Standard) 
 
 Light, Maxwell's Electro - Magnetic 
 Theory of A hypothesis for the 
 
317 
 
 cause or light proposed by Maxwell, based 
 on the relations existing between the phe- 
 nomena of light and those of electro-magnet- 
 ism. 
 
 Maxwell's electro-magnetic theory of light as- 
 sumes that the phenomena of light and magnet- 
 ism are each due to certain motions of the ether, 
 electricity and magnetism being due to its rMa- 
 tions, and light to oscillations, or its to-and-fro 
 motions. 
 
 Maxwell proposed this theory to show that the 
 phenomena of light, heat, electricity and magnet- 
 ism could all be explained by one and the same 
 cause, viz., a vibratory or oscillatory motion of 
 the particles of the hypothetical ether. Maxwell 
 died before completing his hypothesis, and it has 
 never since been sufficiently developed to thor- 
 oughly entitle it to the name of a theory. This 
 theory has more recently been elaborated by 
 Hertz. (See Electricity, Hertz's Theory of Elec- 
 tro-Magnetic Radiations or Waves .) 
 
 There are, however, numerous considerations 
 which render it probable that electric and mag- 
 netic phonomena, like those of light and heat, 
 have their origin in a vibratory or oscillatory mo- 
 tion of the luminiferous ether. A few of these, 
 as pointed out by Maxwell, S. P. Thompson, 
 Lodge, Larden and others, are as follows: 
 
 (I.) It is possible that the thing called elec- 
 tricity is the ether itself, negative electrification 
 consisting in an excess of the ether, and positive 
 electrification in a d-ficit. (See Electricity, Sin- 
 gle- Fltdd Hypothesis of.) 
 
 (2.) It is possible that electrostatic phenomena 
 consist in a strain or deformation of the ether. 
 A dielectric may'differ from a conductor in that 
 the former may have such an attraction for the 
 ether as to give it the properties of an elastic 
 solid, while in the latter the ether is so free to 
 move that no strain can possibly be retained by 
 it. (See Dielectric. Conductor.) 
 
 (3.) Dielectrics are transparent and conductors 
 are opaque. 
 
 There are exceptions to this in the case of vul- 
 canite and many other excellent dielectrics. Nor 
 should this similarity be expected to be general in 
 view of the well known differences that exist be- 
 tween diathermancy and transparency. 
 
 (4.) It Is possible that an electric current con- 
 sists of a real motion ot translation of the ether 
 through a conductor. 
 
 (5.) It is possible that electromotive force re- 
 
 sults from differences of ether pressures. This 
 would of course follow from (4). 
 
 (6.) The vibrations of light are propagated in 
 a direction at right angles to the direction in 
 which the light is moving. The magnetic field 
 of a current is propagated in planes at right 
 angles to the direction in which the current is 
 flowing. 
 
 (7.) It is possible that lines of electrostatic and 
 magnetic force consist of chains of polarized ether 
 particles. 
 
 (8.) The velocity of propagation of light agrees 
 very nearly with the velocity of propagaiion of 
 electro-magnetic induction. (See Ratio Velocity.) 
 (9. ) In certain axial crystals the difference of 
 transparency in the direction of certain axes, 
 corresponds with the direction in which such 
 crystals conduct electricity. 
 
 Recent investigations render it almost certain 
 that light and electro-magnetic waves or radia- 
 tions are one and the same, and, therefore, have 
 the same velocity of propagation through free 
 ether. Through fixed ether, that is, through the 
 ether that exists between the molecules of differ- 
 ent kinds of matter, as is well known, the velocity 
 of propagation differs with different substances. 
 (See Electricity, Hertz's Theory of Electro-Mag- 
 netic Radiations or Waves. ) 
 
 Light, Northern (See Aurora 
 
 Borealis^) 
 
 Light, Platinum-Standard The 
 
 light emitted by a surface of platinum one 
 square centimetre in area, at its temperature 
 of fusion. 
 
 This is called the Violle Standard and is ex- 
 tensively used in France. 
 
 Light, Search, Automatic A search 
 
 light in which a parallel or slightly diverging 
 beam of light is automatically caused to 
 sweep the horizon, and thus disclose the ap- 
 proach of a torpedo boat or other similar 
 danger. 
 
 This is called an automatic search light because 
 it may be caused to automatically sweep the hori- 
 zon, instead of being manipulated by hand, as 
 usual. 
 
 Light, Search, Electric An electric 
 
 arc light placed in a focusing lamp before a 
 lens or mirror, so as to obtain either a parallel 
 beam or a slightly divergent pencil of light 
 
318 
 
 for lighting the surrounding space for pur- 
 poses of exploration. 
 
 Light, Southern (See Aurora 
 
 Australis?) 
 
 Light, Tail A light displayed at the 
 
 rear end of trains in order to avoid rear colli- 
 sions. (See Railroads, Block System for.} 
 
 Lighter, Cigar, Electric An ap- 
 paratus for electrically lighting a cigar. 
 A cigar lighter consists essentially of a wire or 
 rod of refractory substance, rendered incandes- 
 cent by the passage of a current obtained from a 
 voltaic battery, secondary generator, or other 
 electric source. 
 
 Lighter, Electric, Argand A name 
 
 sometimes given to an argand electric plain- 
 pendant burner. (See Burner, Argand- 
 Electric, Plain-Pendant?) 
 
 Lighter, Electric, Argand Valve 
 
 A name sometimes given to an argand elec- 
 tric ratchet-pendant burner. (See Burner, 
 Argand- Electric, Ratchet-Pendant?) 
 
 Lighthouse Illumination, Electric 
 
 (See Illumination, Lighthouse, Electric?) 
 
 Lighting, Arc Artificial illumina- 
 tion obtained by means of an arc light. 
 
 The term arc lighting is used in contradistinc- 
 tion to incandescent lighting. In the United 
 States, and, indeed, generally, a number of arc 
 lights are placed in series on the line circuit, con- 
 nected generally with a series dynamo. Each 
 of the lamps is provided with a safety cut-out, 
 which cuts out or removes a defective lamp from 
 the circuit by automatically turning or switching 
 the current through a shunt of low resistance. 
 
 Lighting, Electric, by High Frequency 
 
 Currents A system of electric lighting, 
 
 in which rods, bars or filaments of carbon or 
 other refractory substances are raised to in- 
 candescence when placed in a rapidly alternat- 
 ing electrostatic field. 
 
 This system of electric lighting was invented 
 by Nikola Tesla. Its general principles will be 
 understood from an inspection of Fig. 346. 
 
 G, is a dynamo producing alternating currents 
 of comparatively low potential. A portion of its 
 current P, acting as the primary of an induction 
 coil, induces alternating currents of high 
 
 potential in the secondary circuit S, which, 
 charging the condenser C, is disruptively dis- 
 charged into the circuit A, provided with an air 
 gap at A' through P'. The inductive action 
 of P', on S', products oscillatory currents of 
 
 Fig. 346. 
 
 Tesla.' s High Frequency Currents 
 System of Lighting:. 
 
 enormous frequency and potential in the second- 
 ary circuits connected therewith. In the ap- 
 paratus shown in Fig. 346, two incandescent 
 electric lamps are connected with the secondary 
 circuit, one with a single straight filament, and 
 the other with a ball conductor. The other 
 terminal of S , is connected to the walls of the 
 room to be lighted. (See Lamp, Incandescent, 
 Straight Filament. Lamp, Electric, Incandes- 
 cent Ball.} 
 
 Lighting, Electric, Central Station - 
 
 The lighting of a number of houses or other 
 buildings from a single station, centrally lo- 
 cated. 
 
 Central station lighting is distinguished from iso- 
 lated lighting by the fact that a number of sepa- 
 rate buildings, houses or areas, are lighted by the 
 current produced at a single station, centrally 
 located, instead of from a number of separate 
 electric sources located in each of the houses, etc., 
 to be lighted. (See Electricity, Distribution of. ) 
 
 Lighting, Electric Gas 
 
 Igniting 
 
 gas jets by means of electric discharges. 
 
 Electric sparks are caused to pass through a 
 jet of escaping gas, and thus to light it. These 
 sparks are obtained from a spark-coil, i. e., a 
 coil of insulated wire connected in series with 
 the circuit so as to produce an extra current on 
 the sudden breaking of the circuit, the discharge 
 of which produces a spark capable of igniting the 
 gas. In cases where a number of burners are to 
 be simultaneously lighted the sparks required for 
 
319 
 
 lighting the gas are obtained from the secondary 
 of an induction coil. (See Burner, Automatic 
 Electric.) 
 
 Lighting, Electric, Isolated A 
 
 system of electric lighting where a separate 
 electric source is placed in each house or 
 area to be lighted, as distinguished from the 
 central station lighting, where electric sources 
 are provided for the production of the current 
 required for an entire neighborhood. 
 
 Lighting, Electric, Long-Arc System of 
 
 A system of electric lighting in which 
 
 long arcs are maintained between the carbon 
 electrodes. 
 
 Lighting, Electric, Short-Arc System 
 
 A system of electric lighting in which 
 
 short voltaic arcs are maintained between the 
 carbon electrodes. 
 
 Systems of short arcs require an electromotive 
 force of about 25 volts, which is about one-half 
 that employed in long arcs. To develop an 
 equal amount of heat energy in a short arc as in 
 a long arc, therefore, requires that the current be 
 of double strength. 
 
 The greater part of the light of a voltaic arc 
 is given off from a tiny crater, which is formed in 
 the end of the positive carbon. In the short-arc 
 system the crater lies so near the negative carbon 
 that much of its. light is necessarily obscured, and 
 troublesome shadows are sometimes produced. 
 The long-arc system avoids these difficulties. 
 
 Lightning. The spark or bolt that results 
 from the disruptive discharge of a cloud to 
 the earth, or to a neighboring cloud. (See 
 Electricity, Atmospheric. Kite, Franklin's?) 
 
 Lightning Arrester. (See Arrester, 
 Lightning?) 
 
 Lightning, Back-Stroke of An 
 
 electric discharge, caused by an induced 
 charge, which occurs after the direct dis- 
 charge of a lightning flash. 
 
 The shock is not caused by the lightning flash 
 itself, but most probably by a charge which is in- 
 duced in neighboring conductors by the discharge. 
 A similar effect may be noticed by standing near 
 the conductor of a powerful electric machine, 
 when shocks are felt at every discharge. 
 
 The back-stroke has been ascribed by many to 
 
 the oscillations by which a disruptive discharge 
 is effected. (See Discharge, Oscillating.) 
 
 The effects of the return shock are sometimes 
 quite severe. They are often experienced by 
 sensitive people, on the occurrence ot a lightning 
 discharge, at a considerable distance from the 
 place where the discharge occurred. 
 
 In some instances, the return stroke has been 
 sufficiently intense to cause death. In general, 
 however, its effects are much less severe than 
 those of the direct lightning discharge. 
 
 Lightning, Ball A name some- 
 times given to globular lightning, (See 
 Lightning, Globular?) 
 
 Lightning, Chain A variety of 
 
 lightning flash in which the discharge takes 
 a rippling path, somewhat resembling a 
 chain. 
 
 Lightning Conductor. (See Rod, Light- 
 ning?) 
 
 Lightning, Forked A variety of 
 
 lightning flash, in which the discharge, on 
 nearing the earth or other object, divides into 
 two or more branches. 
 
 Lightning, Globular A rare form 
 
 of lightning, in which a globe of fire appears, 
 which quietly floats for a while in the air and 
 then explodes with great violence. 
 
 The exact cause of globular lightning is un- 
 known. Phenomena allied to it, however, have 
 been observed by Plant6 during the series dis- 
 charge of his rheostatic machine. Similar pheno- 
 mena are sometimes, though rarely, observed 
 during the discharge of a powerful Leyden battery. 
 Sir Wm. Thomson ascribes the effect to an optical 
 illusion due to the persistence of the visual impres- 
 sion of a bright flash. This, however, would not 
 account for the explosion which almost invariably 
 attends globular lightning. 
 
 Lightning Guard. (See Guard, Light- 
 ning?) 
 
 Lightning, Heat 
 
 A variety of 
 lightning flash in which the discharge lights 
 up the surfaces of the neighboring clouds. 
 
 Sheet lightning is unaccompanied by thunder. 
 It may be regarded as a brush discharge from one 
 cloud to another. 
 
 Heat lightning is a variety of sheet lightning. 
 (See Lightning, Sheet.) 
 
L'g.3 
 
 320 
 
 [Liu. 
 
 Lightning Jar. (See Jar, Lightning!) 
 Lightning, Return-Stroke of A 
 
 term sometimes applied to the back-stroke of 
 lightning. (See Lightning, Back-Stroke of.) 
 
 Lightning Rod. (See Rod, Lightning!) 
 
 Lightning Rod for Ships. (See Rod, 
 Lightning, for Ships.) 
 
 Lightning, Sheet A variety of 
 
 lightning flash unaccompanied by any thunder 
 audible to the observer, in which the entire 
 surfaces of the clouds are illumined. 
 
 The cause of sheet lightning has been ascribed 
 to reflection from clouds of lightning flashes 
 that occur too far below the horizon either to 
 permit them to be directly seen, or the thunder 
 to be heard. 
 
 If a Geissler tube, which contains several con- 
 centric tubes, be charged by a Holtz machine, 
 and then touched at different parts by the hands, 
 a succession of luminous discharges will be seen 
 in the dark, that bear a remarkable resemblance 
 to the flashes of heat or sheet lightning. 
 
 Lightning Stroke. (See Stroke, Light- 
 ning.) 
 Lightning Stroke, Back or Return 
 
 (See Stroke, Lightning, Back or Return.) 
 
 Lightning, Summer A name some- 
 times given to heat lightning. (See Light- 
 ning, Heat!) 
 
 Lightning, Volcanic The lightning 
 
 discharges that attend most volcanic erup- 
 tions. 
 
 Volcanic lightning is possibly sometimes due to 
 the friction of volcanic dust particles against one 
 another, or against the air, but is more probably 
 caused by the sudden condensation of the water 
 vapor that is generally disengaged during volcanic 
 eruptions. 
 
 Lightning, Zigzag The common- 
 est variety of lightning flashes, in which the 
 discharge apparently assumes a forked zig- 
 zag, or even a chain-shaped path. 
 
 This form is seen in the discharge of a Holtz 
 machine, or of a Ruhmkorff Induction Coil. 
 
 Photographic pictures of such lightning dis- 
 charges appear to show that these discharges are 
 in reality zigzag curves, rather than sharp angu- 
 lar zigzags. 
 
 Limiting Stop. (See Stop, Limiting!) 
 
 Limb, Rheoscopic A term some- 
 times applied to a sensitive nerve muscle prep- 
 aration, employed to detect the presence of 
 an electric current. (See Frog, Galvano- 
 scope.) 
 
 Line. A wire or other conductor connect- 
 ing any two points or stations. 
 
 Line, Aclinic A line connecting 
 
 places on the earth's surface which have no 
 magnetic inclination. 
 
 The magnetic equator of the earth. (See 
 Equator, Magnetic.) 
 
 Line Adjuster. An instrument invented 
 by Delany for overcoming the effects of leak- 
 age on the adjustment of the relays in a way 
 line. 
 
 When any key is opened, the line circuit is 
 simultaneously broken at both ends so that there 
 is a moment of no current, which causes all the 
 relays to respond. 
 
 Line, Aerial An air line as dis- 
 tinguished from an underground conductor. 
 
 Line, Agonic A line connecting 
 
 places on the earth's surface where the mag- 
 netic needle has no declination, or where it 
 points to the true geographical north. (See 
 Agonic.) 
 
 Line, Artificial A line so made up 
 
 by condensers and resistance coils as to have 
 the same inductive effects on charging or dis- 
 charging as an actual telegraph line. 
 
 In duplex telegraphy by the differential method, 
 the artificial line used must have its capacity 
 balanced against that of the line, so as to avoid 
 the effects of self-induction, and other effects pro- 
 duced by charging and discharging. 
 
 Line, Capacity of The ability of a 
 line or cable to act like a condenser- and 
 therefore like it to possess a capacity. (See 
 Cable, Capacity cf.) 
 
 Line Circuit. (See Circuit, Line!) 
 
 Line Circuit, Telegraphic (See 
 
 Circuit, Line, Telegraphic!) 
 
 Line, Neutral, of a Magnet A line 
 
 joining the neutral points of a magne-t of 
 
Liii.j 
 
 321 
 
 [Liu. 
 
 points approximately midway between the 
 poles. 
 
 This is sometimes called the equator of the 
 magnet. 
 
 The neutral point is the point where the lines 
 of force outside the magnet extend parallel to the 
 surface of the magnet. (Hering.) 
 
 Line, Neutral, of Commutator Cylinder 
 
 A line on the commutator cylinder of 
 
 a dynamo-electric machine connecting the 
 neutral points, or the points of maximum 
 positive and negative difference of potential. 
 (See Machine, Dynamo-Electric,} 
 
 Line of Least Sparking. (See Sparking, 
 Least Line of.) 
 
 Line, Single-Wire . A term some- 
 times used for a solid-wire conductor. (See 
 Line, Solid.) 
 
 Line, Solid A line formed of a 
 
 single conductor, as distinguished from a line 
 formed of several conductors or by a stranded 
 cable. 
 
 Line, Stranded A line formed of 
 
 several strands or separate conductors twisted 
 into one. 
 
 Line, Telegraphic, Telephonic, etc. 
 
 The conducting circuit provided for the 
 transmission of the electric impulses or cur- 
 rents employed in any system of electric 
 transmission. 
 
 Line, Telpher The conducting line 
 
 used in a system of "".elpherage. (See Tel- 
 phe> age.) 
 
 Line, Through A line extending 
 
 between two terminal points, as distinguished 
 from a line containing way stations. 
 
 Line, Trunk In a system of tele- 
 phonic communication any line connecting 
 distant stations and used by a number of 
 subscribers at each end for purposes of inter- 
 communication. 
 
 Line, Way A line communicating 
 
 with way stations. 
 
 Line Wire. (See Wire, Line.) 
 
 Lineman. On? who puts up and repairs 
 line circuits and attends to the devices con- 
 nected therewith. 
 
 In a system of electric lighting the lineman 
 attends to carboning the lamps, cleaning the 
 lamp rods, and, generally, to the minor details of 
 the lines, insulators and the electro-receptive de- 
 vices placed on the line. 
 
 Lines, Halleyan A term sometimes 
 
 applied to the isogonal lines. 
 
 The isogonal lines are sometimes called the 
 Halleyan lines, from Halley, who published the 
 first chart of such lines in the year 1701. 
 
 Lines, Isobaric Lines connecting 
 
 places on the earth's surface which simulta- 
 neously have the same barometric pressure. 
 
 The isobaric lines are sometimes called isobars. 
 
 Lines, Isoclinic Lines connecting 
 
 places that have the same angle of magnetic 
 dip or inclination. (See Dip, Magnetic.) 
 
 Lines, Isodynamic Lines connect- 
 ing places which have the same total mag- 
 netic intensity. 
 
 The magnetic intensity of a place is determined 
 by the number of oscillations that a small mag- 
 netic needle, moved from its position of rest in 
 the magnetic meridian of any place, makes in a 
 given time. This method is similar to that em- 
 ployed for determining the intensity of gravity at 
 any place by observing the number of oscillations 
 that a pendulum of a given length makes in a 
 given time at that place. If, for example, a mag- 
 netic needle at one place makes 21 1 oscillations IP 
 ten minutes, and 245 in the same time at another 
 place, then the relative intensities of magnetism 
 at these places are as the squares of those num- 
 bers, or as 44,521 : 60,025, or as I : 1.348. 
 
 Lines, Isogonal - Lines connecting 
 places that have the same magnetic declina- 
 tion. (See Declination.) 
 
 Lines, Isogonic - A term sometimes 
 used for isogonal lines. (See Lines, Isogcnal.) 
 
 Lines, Isothermal Lines connect- 
 ing points or places which have the same 
 mean temperature. 
 
 Lines, Kapp A term proposed by 
 Mr. Gisbert Kapp for a unit of lines of mag- 
 netic force. 
 
 One Kapp line = 6,000 C. G. S. magnetic lines. 
 
 Since there are 6.4514 square centimetres in -a 
 
 square inch, I Kapp line per square inch 
 
 6,oco 
 
 64514 
 
 930 C. G. S. lines per square cm 
 
Llii.j 
 
 322 
 
 [Loc. 
 
 The totll number of Kapp lines passing through 
 a magnet and air space is equal to the ampere 
 turns divided by the total magnetic reluctance in 
 the magnetic circuit. (Urquharl.) 
 
 Lines of Electric Displacement. (See 
 Displacement, Electric, Lines of.} 
 
 Lines of Electrostatic Force. (See Force, 
 Electrostatic, Lines of.) 
 
 Lines of Force, Cutting (See Force, 
 
 Lines cf, Cutting} 
 
 Lines of Force, Direction of (See 
 
 Force, Lines of, Direction of} 
 
 Lines of Inductive Action. (See Action, 
 Inductive, Lines of} 
 
 Lines of Magnetic Force. (See Force, 
 Magnetic, Lines of} 
 
 Lines of Magnetic Force, Conducting 
 Power for - (See Force, Magnetic, 
 Lines of. Conducting Power for} 
 
 Lines of Magnetic Induction. (See In- 
 duction. Magnetic, Lines of} 
 
 Lines, Overhead A term applied 
 to telegraph, telephone and electric light or 
 power lines that run overhead, in contradis- 
 tinction to similar lines placed underground. 
 
 Lines, Vortex-Stream Lines ex- 
 
 ttnding in the direction in which the particles 
 cf a fluid are moving. 
 
 A vortex stream is supposed to be composed of 
 a number of vortex -stream lines. 
 
 Linked Magnetic and Electric Chain. 
 
 (See Chain, Linked Magnetic and Electric.} 
 
 Links, Fuse - Strips or plates of 
 fusible metal in the form of links, employed 
 for safety fuses for incandescent or other 
 circuits. 
 
 Liquid, Bright Dipping A liquid 
 
 *used in electro-plating for dipping articles 
 preparatory to electro-plating, so as to insure 
 a bright plating deposit on them when after- 
 wards subjected to the plating process. 
 
 A bright dipping liquid is prepared by the ad- 
 dition of I volume of common table salt to a 
 mixture of loo volumes each of sulphuric and 
 nitric acids. For small objects or articles of 
 copper, cr other readily corroded metals, the 
 
 above solution is diluted by the addition of one. 
 eighth its volume of water. 
 
 Liquid, Electropoion A battery 
 
 liquid consisting of i pound of bichromate 
 of potash dissolved in 10 p'ounds of water, to 
 which 2& pounds of commercial sulphuric 
 acid has been gradually added. 
 
 This liquid is employed with the carbon-zinc 
 cell or the bichromate of potash cell. 
 
 Liquid, Exciting, of Voltaic Cell- 
 
 The electrolyte or liquid in a voltaic cell, 
 which acts on the positive plate. 
 
 Liquid Level Alarm. (See Alarm, Watet 
 or Liquid Level} 
 
 Liquid Resistance Load. (See Load 
 Liquid Resistance} 
 
 Liquid, Stripping A liquid em- 
 ployed to remove a coating of one metal 
 from the surface of another, without affecting 
 the other metal. 
 
 The character of the stripping liquid used will 
 depend on the kind of metal to be removed, and 
 whether the stripping is to be accomplished by 
 solution effected by chemical action, or by electro- 
 lytic action. 
 
 Liquid, Specific Resistance of 
 
 (See Resistance, Specific, of Liquid} 
 
 Liquor, Spent 
 
 Any liquor, such as 
 
 that in the acid or other baths used in electro- 
 plating, that has become weakened by use. 
 Listening Cam. (See Cam, Listening} 
 
 Load, Liquid Resistance An arti- 
 ficial load for a dynamo-electric machine, 
 consisting of a mass of liquid interposed be- 
 tween electrodes. 
 
 A liquid is generally rendered better conduct- 
 ing by the addition of a small quantity of soluble 
 salt, such, for example, as sulphate of soda. 
 
 Local Action of Dynamo-Electric Ma- 
 chine. (See Action, Local, of Dynamo- 
 Electric Machine} 
 
 Local Action of Voltaic Cell. (See Ac* 
 tion, Local, of Voltaic Cell.) 
 
 Local Battery. (See Battery, Local.) 
 
 Local Battery Circuit. (See Circuit 
 Local-Battery} 
 
Loc.J 
 
 323 
 
 [Loo. 
 
 Local Currents. (See Currents, Local.} 
 
 Local Faradization. (See Faradization, 
 Local.} 
 
 Local Galvanization. (See Galvaniza- 
 tion, Local) 
 
 Localization of Faults. (See Faults, 
 Localization of.} 
 
 Lock, Electric A lock that is au- 
 tomatically unlocked by the aid of electricity. 
 
 The electric lock is so arranged that the action 
 of a push button at a distance unlocks the door. 
 A speaking tube communicates with the house, 
 and the pressing of a push button on any floor of 
 the house unlocks the door. The mere shutting 
 of the door locks it. 
 
 A form of electric lock is shown in Fig. 347. 
 
 347- Electric Lock. 
 
 Locomotive, Electric -- A railway 
 engine whose motive power is electricity. 
 (See Railroads, Electric) 
 
 Locomotive Head Light, Electric -- 
 
 (See Head Light, Locomotive) 
 
 Lodestone. A name formerly applied to 
 an ore of iron (magnetic iron ore), that natu- 
 rally possesses the power of attracting pieces 
 of iron to it. 
 
 Lodestone, or magnetic iron ore, must be re- 
 garded as a magnetizable substance that has be- 
 come permanently magnetic from its situation in 
 the earth's magnetic field. Such beds of ore 
 concentrate the lines of the earth's magnetic field 
 on them, and thus become magnetic. 
 
 Lodge's Standard Voltaic Cell. (See 
 Cell, Voltaic, Standard, Lodge's) 
 
 Log, Electric An electric device 
 
 for measuring the speed of a vessel. 
 
 A log, operated by the rotation of a wheel, is 
 caused to register the number of its rotations by a 
 step-by-step recording apparatus operated by 
 breaks in the circuit, made during the rotation 
 of the wheel, at any given number of turns, say 
 ico, or some other convenient multiple. Such a 
 log may be kept constantly in the water, and ob- 
 served when required, or it can be caused to 
 make a permanent record ot its actual speed at 
 any time during the entire run. 
 
 Logarithm. The exponent of the power 
 to which it is necessary to raise a fixed num- 
 ber, in order to produce a given number. 
 
 A table of logarithms enables the operations oi 
 multiplication, division, the raising of powers, 
 and the extraction of roots, to be readily per- 
 formed by simple addition, subtraction, multi- 
 plication or division, respectively. When thor- 
 oughly understood, logarithms greatly reduce the 
 labor of mathematical calculations. For the man- 
 ner in which they are used, the student is referred 
 to any standard work on mathematics. 
 
 Logarithmic Curve. (See Curve, Loga- 
 rithmic) 
 
 Long-Coil Magnet. (See Magnet, Lcttg- 
 Coil) 
 
 Long-Core Electro-Magnet. (See Mag- 
 net, Electro, Long-Core) 
 
 Long-Shunt Compound- Wound Dynamo- 
 Electric Machine. (See Machine, Dyna- 
 mo-Electric, Compound- Wound, L o ng- 
 Shunt) 
 
 Longitude, Electric Determination ol 
 
 The determination of the longitude of 
 
 a place, by differences in time between it and 
 a place on the prime meridian, as simultane- 
 ously determined telegraphically. 
 
 In determinations of this character allowance 
 must be made for the retarding effects of long 
 telegraphic lines, or cables. 
 
 Loom, Electric A device by means 
 of which Jacquard cards in the ordinary loo' 
 are replaced by a simple perforated metal 
 plate, the perforations in which correspond 
 to those in the Jaccuard card. 
 
Loo.] 
 
 324 
 
 [Lur. 
 
 The necessary movements are effected by 
 means of electro-magnets. 
 
 Loop Break. A device for introducing a 
 loop in a break made at any part of a circuit. 
 
 The rigidity of the line wire, between the points 
 of attachment of the loop introduced, is main- 
 tained by means of some inflexible non-conducting 
 material inserted in the break. 
 
 Loop Circuit. (See Circuit, Loop.} 
 
 Loop, Drip An inclined loop placed 
 
 where the outside conductors enter a build- 
 ing. 
 
 The inclination is upwards towards the point 
 of entrance to the building. This device of 
 a drip loop is adopted for the purpose of prevent- 
 ing the rain water from flowing along the inclined 
 wire into the building. This is effected by making 
 the wire incline from the building, thus throwing 
 the drainage from the building. 
 
 Loop, Electric A portion of a main 
 
 circuit consisting of a wire going out from 
 one side of a break in the main circuit and 
 returning to the other side of the break. 
 
 Loops are employed for the purpose of con- 
 necting a branch telegraph office with the main 
 line; for placing one or more electric arc lamps 
 on the main line circuit; for connecting a mes- 
 senger call or telephone circuit with a mainline; 
 and for numerous similar purposes. 
 
 Loops of Force. (See Force, Loops of,} 
 
 Loops of Mutual Induction. (See Induc- 
 tion, Mutual, Loops of.} 
 
 Low-Resistance Magnet. (See Magnet, 
 Low-Resistance.} 
 
 Low-Tension Electric Fuse. (See Fuse, 
 Electric, Low- Tension.} 
 
 Loxodrograph. An apparatus for electri- 
 cally recording on paper the actual course o' 
 a ship by the combined action of magnetism 
 and photography. 
 
 Luces. Plural of lux. (See Lux^ 
 
 Luminescence. A limited power of emit- 
 ting light, possessed by certain bodies which 
 have previously acquired potential energy by 
 exposure to light or radiant energy. 
 
 The term luminescence was proposed by E. 
 Wiedemann to cover the case of the emission of 
 
 light under circumstances differing from the emis- 
 sion or radiation of light by incandescence. Lu- 
 minescence applies to the case of a radiation, 
 generally selective in character, that is apparently 
 due to effects allied to, or the same as, those of 
 fluorescence and phosphorescence. For example, 
 magnesium oxide or zinc oxide, when heated 
 above a certain critical temperature, radiates far 
 more light than equally hot carbon. 
 
 The spectrum of such luminescent light is espe- 
 cially rich in certain wave lengths. The ability 
 of the substance to continue to furnish this extra 
 light is, however, limited. After a comparatively 
 short time, the additional light, or selective radia- 
 tion, disappears. The luminescent light is appa- 
 rently due to molecular potential energy stored in 
 the substance during its exposure to light. Lumi- 
 nescence may be developed in bodies in the fol- 
 lowing manner, viz. : 
 
 (I.) By heat. 
 
 (2.) By chemical action. 
 
 (3.) By friction. 
 
 (4.) By exposure to the sun, or by actual impact 
 of light waves. 
 
 (5.) By electricity. 
 
 (6.) By vital forces, as in the fire fly, or the 
 glow worm. 
 
 Luminescence, Rejuvenation of 
 
 Reimparting by exposure to light, or any other 
 suitable means, the power of luminescence to 
 a substance after it has lost this power. 
 
 Luminous Absorption. (See Absorption, 
 Luminous!) 
 
 Lunar Inequality of Earth's Magnetic 
 Variation or Inclination. (See Inequality, 
 Lunar, of Earth's Magnetic Variation or 
 Inclination!) 
 
 Lunar Inequality of Earth's Magnetism. 
 
 (See Inequality, Lunar, of Earth's Mag- 
 netism?) 
 
 Lux. A name proposed by Preece for the 
 unit of intensity of illumination. 
 
 The illumination given by a standard 
 candle at the distance of 12.7 inches. 
 
 The illumination given by I carcel at the 
 distance of i metre. 
 
 The illumination given by a lamp of io,ooc 
 candles at 105.8 feet. (See Illumination 
 Unit of.} 
 
325 
 
 M 
 
 M. A contraction sometimes used to ex- 
 press a gaseous pressure of the .oooooi of 
 an atmosphere. 
 
 1,000,000 M. equals 760 mm. of mercury or I 
 atmosphere of pressure. 
 
 A vessel containing air, which has been ex- 
 hausted to the .oooooi of its pressure at 760 
 mm., or one atmosphere, has a pressure or ten- 
 sion of I M. 
 
 This contraction is used by Crookes in his re- 
 searches on the properties of radiant matter. (See 
 Matter ; Radiant, or Ultra Gaseous. ) 
 
 >u. A contraction used in mathematical 
 writings for magnetic permeability, or the 
 specific conductibility of any substance for 
 lines of magnetic force. 
 
 mm. A contraction for millimetre. (See 
 Weights, French System of.} 
 
 M. P. H. A contraction sometimes used in 
 railroad work to indicate miles per hour. 
 Machine, Armstrong's Hydro-Electric 
 
 A machine for the development of 
 
 electricity by the friction of a jet of steam 
 passing over a water surface. 
 Steam generated in a suitably insulated boiler, 
 
 Fig. 348. Armstrong's Hydro-Electric Machine. 
 
 Fig. 34?, is allowed to escape through a tortuous 
 nozzle, from a series of apertures opposite a 
 pointed comb, attached to an insulated conductor. 
 
 The cooling of the steam during its passage 
 through a flat box, termed the coolino box, con- 
 nected with the nozzles, causes a partial condensa- 
 tion, so that the box always contains a small 
 quantity of water. 
 
 The friction of the drops of water against the 
 orifice, and, possibly, their friction against the 
 water surface itself, are the cause of the electricity 
 produced. 
 
 A conductor connected with the pointed comb 
 furnishes positive electricity. The boiler fur- 
 nishes negative electricity. The hydro-electric 
 machine is not a very economical source of elec- 
 tricity, and is only employed for experimental 
 purposes. It was discovered accidentally through 
 a shock given to an engineer, who placed his 
 hand in a jet of steam escaping from a leaking 
 boiler he was endeavoring to mend. The causes 
 were first studied by Sir Wm. Armstrong, who, 
 in 1840, devised the apparatus just described. 
 
 Machine, Dynamo-Electric A 
 
 machine for the conversion of mechanical 
 energy into electrical energy, by means of 
 magneto-electric induction. 
 
 The term is also applied to a machine by 
 means of which electrical energy is converted 
 into mechanical energy by means of magneto- 
 electric induction. Machines of the latter class are 
 generally called motors, those of the former, 
 generators. 
 
 Prof. S. P. Thompson defines a dynamo-elec- 
 tric machine as follows, viz. : " A machine for 
 converting energy in the form of mechanical 
 power into energy in the form of electric currents, 
 or vice versa, by the operation of setting con- 
 ductors (usually in ihe form of coils of copper 
 wire) to rotate in a magnetic field, or by vary- 
 ing a magnetic field in the presence of conduc- 
 tors." 
 
 The tejm dynamo was first applied to such 
 machines, because in the form in which this 
 machine first appeared, viz.: the series- wound 
 machine, it was self-exciting, or required no ex- 
 citement other than what it received by the rota- 
 tion of its armature in the field of its magnets, 
 or, indeed, in the field of the earth. (See Machine, 
 Dynamo-Electric, Reaction Principle of.) 
 
 A dynamo-electric generator, or a dynamo-elec- 
 
Mac.] 
 
 326 
 
 [Mac. 
 
 f ric machine proper, consists of the following 
 parts, viz.: 
 
 (i.) The revolving portion, usually the arma- 
 ture, in which the electromotive force is developed, 
 which produces the current. 
 
 It must be borne in mind that it is not current, 
 but difference of electric potential, or electromotive 
 force, that is developed by any electric source 
 front which a current is obtained. For ease of 
 reference, however, we will speak of an electric 
 current as being generated by the armature, or by 
 the source. No ambiguity will be introduced if 
 the student bears the above in mind. 
 
 (2.) Thejie/d magnets, which produce the field 
 in which the armature revolves. 
 
 (3. ) hi pole pieces, or free terminals of the field 
 magnets. 
 
 (4. ) The commutator, by which the currents de- 
 veloped in the armature are caused to flow in 
 one and the same direction. In alternating 
 machines, and in some continuous current dynamos 
 Zhis part is called the collector, and does not rec- 
 tify the currents. 
 
 (5.) The collecting brushes, that rest on the 
 commutator cylinder and take off the current 
 generated in the armature. 
 
 Machine, Dynamo-Electric, Alternating- 
 Current A dynamo-electric machine 
 
 ia which alternating currents are produced. 
 
 The field magnets may be either permanent 
 jnagnets or electro-magnets. When electro-mag- 
 aets are used, their coils may be separately ex- 
 cited by another machine whose current is con- 
 tinuous; or, they may be excited by the commuted 
 
 :rrent of a separate coil on the armature; or, they 
 may be partly excited by commuted currents and 
 partly by commuted currents from a transformer, 
 placed in the main circuit of the dynamo. 
 
 Machine, Dynamo-Electric, Armature of 
 
 (See Armature, Dynamo- Electric 
 
 Machine?) 
 
 Machine, Dynamo-Electric, Bed-Piece of 
 
 The frame or base on which a dynamo 
 
 is supported. 
 
 The bed-piece is sometimes called the dynamo 
 frame or base. 
 
 Machine, Dynamo-Electric, Bi-Polar 
 
 A dynamo-electric machine, the armature 
 of which rotates in a field formed by two 
 magnet poles, as distinguished from a ma- 
 
 chine the armature of which rotates in a field 
 formed by more than two magnet poles. 
 
 A dynamo-electric machine whose armature 
 rotates in the field formed by more than two 
 poles is called a multi-polar machine. (See Ma- 
 chine, Dynamo-Electric, Multi-Polar.) 
 
 Machine, Dynamo-Electric, Carca*s of 
 
 ; A term sometimes used in place of 
 
 the field magnet frame of a dynamo-electric 
 machine. (See Machine, Dynamo-Electric, 
 Frame of.) 
 
 The term, field magnet frame, would appear 
 to be the preferable term. The term, however, 
 is used in France, and is derived from the 
 French word for skeleton. 
 
 Machine, Dynamo-Electric, Closed-Coil 
 
 A dynamo-electric machine, the 
 
 armature coils of which are grouped in sec- 
 tions, communicating with successive bars of 
 a collector, so as to be connected continu- 
 ously together in a closed circuit. 
 
 The Gramme dynamo and most continuous- 
 current dynamos are closed-coil dynamos. 
 
 Machine, Dynamo-Electric, Closed-Coil 
 
 Disc A closed-coil dynamo-electric 
 
 machine, ihe armature core of which is disc- 
 shaped. 
 
 Machine, Dynamo-Electric, Closed-Coil 
 
 Drum A closed-coil dynamo-electric 
 
 machine, the armature core of which is 
 drum-shaped. 
 
 Machine, Dynamo-Electric, Closed-Coil 
 
 Ring A closed-coil dynamo-electric 
 
 machine, the armature core of which is ring- 
 shaped. 
 
 Machine, Dynamo-Electric, Collectors 
 
 (See Collectors of Dynamo-Electric 
 
 Machines.} 
 
 Machine, Dynamo-Electric, Compound 
 Winding of (See Winding, Com- 
 pound, of Dynamo-Electric Machine.) * 
 
 Machine, Dynamo-Electric, Compound- 
 Wound Machines whose field mag- 
 nets are excited by more than one circuit of 
 coils, or by more than a single electric 
 source. 
 
 The object of compound winding is to make 
 
Mac.] 
 
 327 
 
 [Mae. 
 
 the dynamo self-regulating under changes in its 
 working load. A shunt- wound dynamo renders 
 both series and multiple circuits approximately 
 constant as regards their working. Multiple cir- 
 cuits, however, require great constancy of poten- 
 tial, and for this purpose the compounding of the 
 dynamos is necessary . 
 
 In the compound dynamo, the shunt coils are 
 superposed on the series coils, or are used in con- 
 nection with them. The shunt coils consist of a 
 much greater number of convolutions of fine wire 
 than the series coils, which are of coarse wire. 
 
 Separate excitation is sometimes compounded 
 either with series or with shunt field magnet 
 coils. 
 
 Compound dynamos are of two classes, viz.: 
 
 (l.) Those designed to produce a constant 
 potential, and 
 
 (2. ) Those designed to produce a constant cur- 
 rent. 
 
 For Constant Potential : 
 
 In the long-shunt compound-wound dynamo, 
 the terminals of the shunt coil are connected with 
 the binding posts of the machine. As the cur- 
 rent leaves the armature it has two paths to take : 
 one, the thick series coils, to the external circuit, 
 and the other the finer and longer shunt coils. 
 The resistance of the shunt coils is greater than 
 that of the armature. Current variations in the 
 armature will, therefore, produce no appreciable 
 effect on the magnetizing power of the shunt, 
 which acts as a nearly uniform exciter of the field. 
 
 In a shunt-wound dynamo connected to a 
 multiple circuit, the introduction of an additional 
 number of receptive devices into the circuit re- 
 quires more current, and this would tend to cause 
 a slight drop in the potential. The object of the 
 series coils is to prevent this drop. The series 
 coils, therefore, act as compensators. If the 
 coils are too powerful the compensation will 
 have the effect of increasing the potential. 
 
 The combination of a series and separately ex- 
 cited machine is shown in Fig. 351. The field is 
 in series with the armature, but has also an ad- 
 ditional and separate excitation. 
 
 The combination of a series and shunt machine 
 insures the excitation of the field both by the 
 main and by the shunted current. Such a com- 
 bination is shown in Fig. 353. 
 
 For Constant Current : 
 
 The combination of shunt and separately ex- 
 cited machines is shown in Fig. 356. In this 
 machine the field is excited by means of a shunt 
 
 to the external circuit, and by a current produced 
 by a separate source. 
 
 The combination of a series and magneto ma- 
 chine is shown in Fig. 352. This, also, is 
 designed to give a constant current. 
 
 Machine, Dynamo-Electric, Compound- 
 Wound, Long-Shunt A compound- 
 wound dynamo- electric machine, in which 
 the shunt-field magnet coils form a shunt to 
 the binding posts of the machine. 
 
 In the short-shunt compound-wound dynamo - 
 electric machine, the ends of the shunt coil are 
 connected to the brushes of the machine. 
 
 Machine, Dynamo-Electric, Compound- 
 Wound, Short-Shunt A compound- 
 wound dynamo-electric machine in which the 
 shunt-field magnet coils form a shunt to the 
 armature only, as distinguished from the 
 armature and series coils combined. 
 
 In the short-shunt dynamo-electric machine, 
 the ends of the shunt coil are connected to the 
 brushes of the machine, and not to the binding 
 posts of the machine, or to the external circuit, as 
 in the long-shunt machine. 
 
 Machine, Dynamo-Electric, Continuous- 
 Current A dynamo-electric machine, 
 
 the current of which is commuted so as to 
 flow in one and the same direction, as dis- 
 tinguished from an alternating dynamo. 
 
 Machine, Dynamo-Electric, Double-Mag- 
 net A term sometimes applied to a 
 
 dynamo-electric machine, the field magnets 
 of which have two consequent poles. 
 
 Machine, Dynamo-Electric, Economic 
 Co-efficient of A name formerly ap- 
 plied to the efficiency of a dynamo-electric 
 machine. (See Machine, Dynamo-Electric, 
 Efficiency of.) 
 
 Machine, Dynamo-Electric, Efficiency 
 
 of The ratio between the electric 
 
 energy or the electrical horse-power produced 
 by a dynamo, and the mechanical energy or 
 horse-power expended in driving the dynamo. 
 
 The Efficiency may be the Commercial Effi- 
 ciency, which is the useful or available energy in 
 the external circuit divided by the total median- 
 ical energy ; or it may be the Electrical Efficiency, 
 which is the available electric energy divided by 
 the total electric energy. 
 
Mac.] 
 
 328 
 
 [M:C. 
 
 The Efficiency of Conversion is the total elec- 
 trical energy developed, divided by the total 
 mechanical energy applied. 
 
 If M, equals the mechanical energy, 
 
 W, the useful or available electrical energy, 
 
 and 
 w, the electrical energy absorbed by the ma- 
 
 chine, and 
 
 m, the Straf Power, or the power lost in 
 friction, eddy currents, air friction, etc. 
 Then, since 
 M = W -f w + m, 
 
 o lira 
 
 Commercial Efficiency . . = - = 
 
 - 
 M 
 
 W 
 
 - . 
 W + w -4-m 
 
 Electrical Efficiency ____ = 
 
 W 
 
 _ . 
 
 W -f- w 
 
 Efficiency of Conversion = + w W + w 
 
 M W-(- w -f- m 
 Machine, Dynamo-Electric, Flashing of 
 
 A name given to long flashing sparks 
 
 at the commutator, due to the short cir- 
 cuiting, of the external circuit at the com- 
 mutator, by arcing over the successive com- 
 mutator insulating strips. 
 
 Machine, Dynamo-Electric, Frame of 
 The bed-piece that supports a dyna- 
 mo-electric machine. 
 
 The frame is sometimes called the dynamo bed- 
 piece. 
 
 The word frame is sometimes applied to the 
 field magnet cores and yokes. 
 
 Machine, Dynamo-Electric, Local Action 
 
 Ot (See Action, Local, of Dynamo- 
 Electric Machine?) 
 
 Machine, Dynamo-Electric, Mouse-Mill, 
 Sir Wm. Thomson's - A dynamo- 
 electric machine designed by Sir Wm. 
 Thomson, named from the resemblance of 
 its armature to a mouse mill. 
 
 The armature conductor of this dynamo con- 
 sists of parallel bars of copper, arranged on a 
 hollow cylinder, like the bars on a mouse mill. 
 
 Machine, Dynamo-Electric, Multipolar 
 
 A dynamo-electric machine, the 
 
 armature of which revolves in a field formed 
 by more than a single pair of poles. 
 
 This form is usually adopted for large machines 
 as being more economical. 
 
 Fig. 349 shows a multipolar dynamo with four 
 poles. 
 
 Machine, Dynamo-Electric, Open-Coil 
 
 A dynamo-electric machine, the 
 
 armature coils of which, though connected to 
 
 Fig. 34Q. Multipolar Dynamo with Four Poles. 
 
 the successive bars of the commutator, are not 
 connected continuously in a closed circuit. 
 
 The Brush and the Thomson-Houston arc dy- 
 namos are open-coil machines. 
 
 Machine, Dynamo-Electric, Open-Coil 
 
 Disc An open-coil dynamo-electric 
 
 machine, the armature of which is disc- 
 shaped. 
 
 Machine, Dynamo-Electric, Open-Coil 
 
 Drum An open-coil dynamo-electric 
 
 machine, the armature core of which is drum- 
 shaped. 
 
 Machine, Dynamo-Electric, Open-Coil 
 
 Ring An open-coil dynamo-electric 
 
 machine, the armature core of which is ring- 
 shaped. 
 
 Machine, Dynamo-Electric, Output of 
 
 The electric power of the current gen- 
 erated by a dynamo-electric machine ex- 
 pressed in volt-amperes, watts or kilo-watts. 
 S. P. Thompson suggests that dynamo- electric 
 machines be rated as to their practical safe ca- 
 pacity in units of output of 1,000 -watts, or one 
 kilo-watt. According to this, an 8-unit machine 
 might give, say, 100 amperes at a difference of 
 potential of 80 volts, or 2,000 amperes at a differ- 
 ence of potential of 4 volts. Such a unit would be 
 far more expressive than the usual method ot rat- 
 ing a machine as having a capacity of such and 
 such a number of lights. 
 
 Machine, Dynamo-Electric, Reaction 
 Principle of The mutual interaction 
 
329 
 
 [Mae. 
 
 between the current generated in the armature 
 coils of a dynamo-electric machine and the 
 field of the machine, each strengthening the 
 other until the full working current, which 
 the machine is capable of developing, is 
 produced. 
 
 When the armature of a series or shunt dynamo 
 commences to rotate, the differences of potential 
 generated in its coils are very small, since the 
 field of the magnet is weak, being merely the 
 residual magnetism. The current so produced 
 in the armature, circulating through the field 
 magnet coils, increases the intensity of the mag- 
 netic field of the machine, and this, reacting on 
 the armature, results in a more powerful current 
 through it. This current again increases the 
 strength of the magnetic field of the machine, 
 which again reacts to increase the current 
 strength in the armature coils, and this continues 
 until the machine is producing its full output. 
 
 A dynamo-electric machine very rapidly 
 "builds /," or reaches its maximum current 
 after starting. The reaction principle was dis- 
 overed by Soren Hjorth, of Copenhagen. 
 
 Machine, Dynamo-Electric, Reversibility 
 
 of The ability of a dynamo to act as 
 
 - 35. Separately Excited Dynamo 
 
 a motor when traversed by an electric cur- 
 rent. (See Motor, Electric.) 
 
 Machine, Dynamo-Electric, Separate 
 Coil - A dynamo- electric machine in 
 which the field magnets are excited by means 
 
 of coils on the armature, separate and dis- 
 tinct from those which furnish current to the 
 external circuit. 
 
 Machine, Dynamo-Electric, Separately 
 
 Excited A dynamo-electric machine 
 
 in which the field magnet coils have no con- 
 nection with the armature coils, but receive 
 their current from a separate machine or 
 source. 
 
 A separately excited dynamo-electric machine 
 is shown in Fig. 350. 
 
 Separate excitation for constant current ma- 
 chines has not come into any extended use in the 
 United States. 
 
 Machine, Dynamo-Electric, Series and 
 Magneto A compound-wound dy- 
 namo-electric machine in which the arma- 
 ture circuit of a magneto-electric machine is 
 connected in series with the armature and 
 field magnet circuits of a series dynamo. 
 
 The circuit connections of a series and magneto 
 dynamo are shown in Fig. 351. 
 
 Fig 3 ST. Series and Magneto Dynamo. 
 
 Machine, Dynamo-Electric, Series and 
 Separately Excited - A compound- 
 wound dynamo-electric machine in which 
 there are two separate circuits on the field 
 magnet cores, one of which is connected in 
 series with the field magnets and the exter- 
 nal circuit, and the other with some source 
 by which it is separately excited. 
 
Mac.] 
 
 330 
 
 [Mac. 
 
 A series and separately excited compound- 
 Wound dynamo-electric machine is shown in 
 Fig- 352. 
 
 Fig. 352. Series and Separately Excited Dynamo. 
 
 This machine is employed for maintaining a 
 constant potential at its terminals. 
 
 Machine, Dynamo-Electric, Series and 
 Shunt Wound A compound-wound 
 
 Fig. 353. Series and Shunt- Wound Dynamo. 
 
 dynamo-electric machine in which the field 
 magnets are wound with two separate coils, 
 one of which is in series with the armature 
 and the external circuit, and the other in 
 shunt with the armature. 
 
 This is usually called a compound-wound ma 
 chine. (See Machine, Dynamo Electric, Com- 
 pound- Wound.) 
 
 A compound-wound series and shunt dynamo- 
 electric machine is shown in Fig. 353. This ma- 
 chine is designed to maintain constant potential 
 at its terminals. 
 
 There are two varieties of series and shunt - 
 wound dynamos, viz. : 
 
 (I.) Long-shunt compound-wound dynamo. 
 
 (2.) Short-shunt compound-wound dynarno. 
 
 (See Machine, Dynamo-Electric, Compound- 
 Wound, Long- Shunt. Machine, Dynamo-Electric, 
 Compound- Wound, Short -Shunt.) 
 
 Machine, Dynamo-Electric, Series- Wound 
 
 A dynamo-electric machine, in which 
 
 the field circuit and the external circuit are 
 
 D D D D 
 
 Fig. 354.. Series Dynamo. 
 
 connected in series with the armature circuit, 
 so that the entire armature current must pass 
 through the field coils. 
 
 A series dynamo -electric machine is shown in 
 Fig. 354. Here the armature circuit, the field 
 circuit and the external circuit are all connected 
 in series. 
 
 Since in a series-wound dynamo the armature 
 coils, the field and the external series circuit are in 
 series, any increase in the resistance of the external 
 circuit will decrease the electromotive force from 
 the decrease in the magnetizing currents. A de- 
 crease in the resistance of the external circuit will, 
 in a like manner, increase the electromotive force 
 from the increase in the magnetizing current 
 
Mac.] 
 
 331 
 
 [Mac. 
 
 The use of a regulator avoids these changes in 
 the electromotive force. 
 
 355- Series Dynamo, 
 
 The dynamo shown in Fig. 355 is series con- 
 nected. The armature is ring shaped. The 
 armature core cons ; sts of a ring made of soft iron 
 wire. The field is bi-polar, and is obtained by 
 the use of four magnet coils and two consequent 
 poles. 
 
 Machine, Dynamo-Electric, Shunt and 
 Separately Excited A compound- 
 wound dynamo-electric machine, in which 
 
 ig- 5f6. Shunt and Separately Excited Dynamo. 
 
 the field is excited both by means of a 
 shunt fo the armature circuit, and by a 
 current produced by a separate source. 
 A bhunt a id separately excited compound- 
 
 wound dynamo electric machine is shown in Fig. 
 356. This machine maintains a constant current 
 in its circuit, notwithstanding changes in its ex- 
 ternal circuit. 
 
 Machine, Dynamo-Elect ic, Shnnt- Wound 
 
 -Adynamo-electricmachinein which 
 
 the field magnet coils are placed in a shunt 
 to the armature circuit, so that on y a 
 portion of the current generated passes 
 through the field magnet coils, but all the 
 difference of potential of the armature acts 
 at the terminals of the field circuit. 
 
 A shunt dynamo-electric machine is shown in 
 Fig- 357- 
 
 O 
 
 D D D D 
 
 Fig. 357. Shunt Dynamo. 
 
 In a shunt dynamo-electric machine, an in- 
 crease in the resistance of the external circuit in- 
 creases the electromotive force, and a decrease in 
 the resistance of the external circuit decreases the 
 electromotive force. This is just the reverse of 
 the series -wound dynamo. 
 
 In a shunt-wound dynamo a continuous balanc 
 ing of the current occurs. The current dividing 
 at the brushes between the field and the e.vtiTiial 
 circuit in the inverse proportion to the resistance 
 of these circuits, if the resistance of the rxfrrml 
 circuit becomes greater, a proportionately yre.itrr 
 current passes through the field magnets, and 5-0 
 causes the electromotive force to become greater. 
 
 If, on the contrary.the resistance of the external 
 circuit decreases, less current passes through the 
 field, and the electromotive force is proportion- 
 ately decreased. 
 
Mac.] 
 
 332 
 
 [Mac. 
 
 In a shunt-wound dynamo the resistance of the 
 shunt should be at least four hundred times that 
 of the armature. It is sometimes as much as one 
 thousand times as great. (Urguhart.) 
 
 To obtain complete regulation of the machine 
 some form of compounding is necessary. (See 
 Machine, Dynamo-Electric, Compound- Wound. ) 
 
 Machine* Dynamo-Electric, Single Mag- 
 net A dynamo-electric machine, in 
 
 which the field magnet poles are obtained 
 by means of a single coil of insulated wire, 
 instead of by more than a single coil. 
 
 Machine, Dynamo- Electric, Sparking of 
 An irregular and injurious oper- 
 ation of a dynamo-electric machine, at- 
 tended with sparks at the collecting 
 brushes. 
 
 Sparking consists in the formation of small 
 arcs under the collecting brushes. One cause-of 
 sparking is to be found in the brushes leaving 
 one commutator strip before making connection 
 with the next strip. 
 
 Sparking from this cause may be avoided by so 
 placing the brushes as to cause them to bridge 
 over the space between two consecutive bars, 
 thus permitting them to touch one bar before 
 leaving the other. Two brushes, electrically con- 
 nected, are sometimes employed for this purpose, 
 or the slots between contiguous bars are slightly 
 inclined to the axis of rotation. 
 
 Sparking causes a burning of the commutator 
 strips, and an irregular consumption of the 
 brushes, both of which produce further irregu 
 larities by the wear of the brushes against the 
 commutator bars. 
 
 At the moment the brush touches two contigu- 
 ous commutator bars, it short circuits the coil 
 terminating at those bars. On the breaking of 
 this closed circuit, a spark appears under the 
 brushes. This spark is often considerable, since 
 from the comparatively small resistance of the 
 coil, it is apt, when short-circuited, to produce a 
 heavy current if not exactly at the neutral point. 
 
 Another cause of sparking is to be found in the 
 self-induction of the armature coils. The extra 
 current on breaking forms an injurious spark 
 under the brushes. This spark may be consid- 
 erable, since the current produced in the coil on 
 momentarily short circuiting it by the brushes 
 simultaneously touching the adjoining commu 
 tator currents may be large. 
 
 Sparking occurs when the brushes are not set 
 
 close to the neutral line. Since the principal 
 cause for the change in the lead of the brushes is 
 the magnetizing effect of the armature coils, it is 
 preferable to make the number of windings of 
 these as few as possible, and to obtain the neces- 
 sary differences of potential by increasing the 
 speed of rotation and the strength of the mag- 
 netic field of the machine. Short armature coils 
 also lessen the sparking due to self-induction. 
 
 Sparking at the brushes is also caused by the 
 jumping of improperly supported or constructed 
 brushes. 
 
 When the brushes are not set close to the neu- 
 tral point, long flashing sparks are apt to occur. 
 
 Alack of symmetry of winding of the arma 
 ture coils will necessarily be attended by injurious 
 flashing, from the impossibility of properly ad- 
 justing the brushes. 
 
 Machine, Dynamo-Electric, Synchroniz- 
 ing Adjusting the phases of two 
 
 alternating current dynamos so as to per- 
 mit their being coupled or joined in par- 
 allel. 
 
 Machine* Dynamo-Electric, to Short Cir- 
 cuit a To put a dynamo-electric ma- 
 chine on a circuit of comparatively small 
 electric resistance. 
 
 Machine, Dynamo-Electric, Unit of Out- 
 put of A unit for the electric power 
 
 furnished by the current of a dynamo- 
 electric machine. 
 
 A unit of output equal to 1,000 watts 
 or i kilowatt. 
 
 A machine furnishing a current of 100 amperes 
 at a difference of potential of So volts, would 
 have an output of S,ooo watts, and would, 
 therefore, be rated as an 8-unit machine. 
 
 Machine, Electric, Rubber of A 
 cushion of leather covered with an electric 
 amalgam, and employed to produce elec- 
 tricity by its friction against the plate or 
 cylinder of a frictional electric machine. 
 (See Machine, Frictional Electric. ) 
 
 Machine, Electrostatic Induction of 
 
 A machine in which a small initial charge 
 produces a greatly increased charge by its 
 inductive action on a rapidly rotated disc 
 of glass or other dielectric. 
 
 An excellent type and example of such a ma- 
 chine is found in the Holtz machine, which con- 
 
Mac.] 
 
 333 
 
 [JLic. 
 
 sists of the following parts, as shown in Fig. 358, 
 viz ; 
 
 (i.) A stationary glass plate A, fixed at its 
 edges to insulated supports- 
 
 (2.) A movable plate B, capable of rapid rota- 
 tation on a horizontal axis, by a driving pulley. 
 
 Fig. 358. Holtz Electric Machine. 
 
 (3.) Armatures of varnished paper f, f', placed 
 on opposite sides of the fixed plate at holes or 
 windows P, P', cut in the plate. The armatures 
 are placed on the side of the fixed plate away from 
 the moving plate, or on the back of the plate, so that 
 the plate, on its rotation, moves towards tongties of 
 paper attached to the middle of the arma ure. 
 
 (4.) Metal combsp'.aced in front of the movable 
 disc opposite the armatures, and connected with 
 the brass balls m, n, one of which is movable 
 towards and from the other by means of a suitably 
 supported insulating handle connected with it. 
 
 A small initial charge is given to one of the 
 armatures by holding a plate of electrified vul- 
 canite against it, and rotating the machine while 
 the balls m, n, are in contact. As soon as the ma- 
 chine is charged the balls zrzgradttally separated, 
 when a torrent of sparks will pass between them 
 so long as the plate is rotated. 
 
 When the balls are separated too far the sparks 
 cease to pass. The balls must then be again 
 brought into contact and gradually separated as 
 before. 
 
 The Holtz machine can be regarded as a re- 
 volving electrophorus provided with means for 
 constantly discharging and recharging the upper 
 metallic plate. (See Electrophorus.} 
 
 The action of the machine is well described by 
 S. P. Thompson in his "Elementary Lessons on 
 Electricity and Magnetism, " as follows: 
 
 "Suppose a small -f- charge to be imparted at 
 the outset to the right armature f ' ; this charge acts 
 
 inductively across the discs upon the metallic 
 comb, repels electricity through it, and leaves the 
 points negatively electrified. They discharge 
 negatively electrified air upon the front surface of 
 the movable disc ; the repelled charge passes 
 through the brass rods and balls, and is dis- 
 charged through the left comb upon the front side 
 of the movable disc. Here it acts inductively 
 upon the paper armature, causing that part of it 
 which is opposite itself to be negatively charged 
 and repelling a -|- charge into its farthest part, 
 viz., into the tongue, which being bluntly pointed, 
 slowly discharges a 4. charge upon the back of the 
 movable disc. If now the disc be turned round, 
 this + charge on the back comes over from the 
 left to the right side, in the direction indicated by 
 the arrow, and, when it gets opposite the comb, 
 increases the inductive effect of the already exist- 
 ing _f- charge on the armature, and therefore 
 repels more electricity through the brass rods and 
 knob into the left comb. Meantime the charge, 
 which we saw had been induced in the left arma- 
 ture, has in turu acted on the left comb, causing 
 a -f- charge to be discharged by the points upon 
 the front of the di:C ; and drawing electricity 
 through the brass rods and knobs, has made the 
 right comb still more highly , increasing the 
 discharge of ly electrified air upon the front 
 of the disc, neutralizing the-f- charge which is be- 
 ing conveyed over from the left. These acti. us re- 
 sult in causing the top half of the moving disc to 
 be ly electrified. The charges on the front 
 serve, as they are carried round, to neutralize the 
 electricities let off by the points of the combs, 
 while the charges on the back, induced respect- 
 ively m the neighborhood of each ot the arma- 
 tures, serve, when the rotation of the disc con- 
 veys them round, to increase the inductive influ- 
 ence of the charge on the other armature." 
 
 The student will be aided in following Prof, 
 Thompson's explanation by the diagrammatic 
 sketch, shown in Fig. 359. Here the rotating plate 
 is shown for convenience in the form of a cylinder. 
 The armatures are shown on the back of the plate 
 at f and f, opposite the brass collecting combs P' 
 and P, with their discharging rods and balls a, a. 
 
 The effect of the positive charge given to the 
 right hand armature f', directly through the 
 comb P', rods a, a, comb P, to left hand arma- 
 ture f, is readily seen. The rotation of the plate 
 being in the direction of the curved arrow; the 
 charging of the front of the plate by convection 
 streams from the combs, and the back of the plate 
 
Mac. ] 
 
 334 
 
 from the points of the paper armatures, as well as 
 the character of the charge, will be understood. 
 There thus results, as is shown, a positive charge 
 on both the front and back of the upper half of 
 
 f'f- 35Q- PM* offfoltz Machine. 
 the rotating plate, and a negative charge on both 
 sides of its lower half. A reversal of polarity of 
 the plate occurs at the line P a a P'. Sometimes 
 the reversal does not occur, and the machine either 
 loses its charge entirely, or in part. A conductor 
 S S, furnished with points, is sometimes provided 
 to lessen the chances of lack of reversal. 
 
 Machine, Faradic A machine for 
 
 producing faradic currents. 
 
 There are two varieties of faradic machines, 
 viz.: magnet o-faradic apparatus and simple in. 
 duction apparatus. 
 
 Machine, Frictional Electric A 
 
 machine for the development of electricity 
 by friction. 
 
 A frictional electric machine consists of a plate 
 or cylinder of glass A, Fig. 360, capable of rota- 
 tion on a horizontal axis. 
 
 A rubber formed of a chamois skin, covered 
 with an amalgam of tin and mercury, is 
 placed at B. By the rotation of the plate the 
 
 Fig, 360. Frictional Electric Machine. 
 rubber becomes negatively and the glass posi- 
 tively excited. An insulated conductor D, called 
 the prime or positive conductor, provided with a 
 comb of points, becomes positively charged by in- 
 duction. The machine will develop electricity 
 
 best if a conductor attached to the rubber is con- 
 nected with the ground, as by a chain. 
 
 Machine, Holtz A particular form 
 
 of electrostatic induction machine. (See 
 Machine, Electrostatic Induction.} 
 
 Machine, Influence An electrical 
 
 machine depending for its action on 
 electrostatic induction. 
 
 The Wimshurst and Holtz machines are influ- 
 ence machines. (See Machine, Electrostatic In- 
 duction. Machine, Wimshurst Electrical. Ma- 
 thine, Holtz.} 
 
 Machine, Influence, Wimshnrst's Alter- 
 nating An electrostatic induction 
 
 machine by means of which a series of 
 rapidly alternating charges are produced. 
 
 Although such a machine furnishes a torrent of 
 sparks between its terminals, yet it is unable to 
 furnish a permanent charge to a Leyden jar 
 or condenser, since its 
 oscillatory discharges, 
 continually undo at any 
 small interval of time 
 what was done at the 
 preceding interval, and 
 thus leave the jar un- 
 charged. 
 
 Machine, Magneto 
 Blasting A 
 
 magneto-e 1 e c t r i c 
 machine employed 
 for generating the 
 
 , . . Fig ibi. Magneto El,'cttic 
 
 current used in elec- MaMftt . 
 
 trie blasting. 
 
 Machine, Magneto-Electric A ma- 
 chine in which there are no field magnet 
 coils, the magnetic field of the machine 
 being due to the action of permanent 
 steel magnets. 
 
 A dynamo in which currents are produced by 
 the motion of armature coils past permanent mag- 
 nets. (See Machine, Dynamo-Electric. ) 
 
 A magneto- electric machine is shown in Fig. 
 361. 
 
 Another form of magneto-electric machine is 
 shown in Fig. 362. 
 
 This latter form of machine is known as a hand 
 generator, in contradistinction to one driven by 
 power and called a power generator. 
 
Mac.] 
 
 335 
 
 [Mac. 
 
 The field is obtained by means of a number of 
 separate permanent magnets so combined as to 
 
 Fig. 362. Magneto- Electric Machine. 
 act as a single magnet. The armature is rotated 
 by hand. 
 
 Machine, Mouse-Mill A form of 
 
 convection induction machine, invented 
 by Sir William Thomson to act as the re- 
 plenisher of his electrometer. (See Ma- 
 chine, Electrostatic Induction.} 
 
 Machine, Rheostatic A machine 
 devised by Plante in which continuous 
 static effects of considerable intensity are 
 obtained by charging a number of con- 
 densers in multiple-arc and discharging 
 them in series. 
 
 The condensers are charged by connecting 
 them with a number of secondary or storage bat- 
 teries. 
 
 Machine Telegraphy. (See Telegraphy, 
 Machine. ) 
 
 Machine, Tiippler Holtz - A modified 
 form of Holtz machine in which the initial 
 charge of the armatures is obtained by the 
 friction of metallic brushes against the 
 armatures. 
 
 Machine, Wimshurst Electrical 
 
 A form of convection electric machine 
 invented by Wimshurst. 
 
 Like the Holtz machine, the Wimshurst ma- 
 chine is a convection induction machine. It is, 
 however, more efficient in action, and will prob- 
 ably soon supersede the former machine. The 
 Wunshurst machine consists of two shellac-var- 
 nished glass plates that are rapidly rotated in op- 
 posite directions. Thin metallic strips are placed 
 on the outside of each of the plates, in the radial 
 positions shown in Fig. 363. These strips act 
 
 both as inductors and carriers ; the carriers of 
 one plate acting as inductors to the other plate. 
 
 Two curved bra<=s rods, terminating in fine wire 
 brushes that touch the plates, are placed as shown, 
 one at the front of the plate, and one at the back, 
 at right angles to each other. Pairs of conduct- 
 
 Fig. 363. The Wimshurst Electrical Machine. 
 
 ors, connected together, provided with collecting 
 points, are placed diametrically opposite each 
 other, as shown. Sliding; conductors, terminated 
 with metallic balls, are provided for discharging 
 the conductors. Leyden jars, the inner coatings 
 of which are connected with two discharging 
 rods, and the outer coatings together, may be em- 
 ployed in this as in the Holtz machine. 
 
 The exact action of this machine is not thor- 
 oughly understood. 
 
 Machines, Dynamo-Electric, Varieties of 
 
 Dynamo-electric machines may be 
 
 divided into classes according to 
 
 (i ) The manner in which the magnetism of 
 the field magnets is obtained. 
 
 (2.) The character of their armatures. 
 
 (3.) The nature of the current obtained, 
 whether continuous or alternating. 
 
 (4.) The form of their field magnets. 
 
 (5.) The nature of their magnetic fields. 
 
 (6.) The manner in which the current of the 
 field magnets, the armature and the external 
 circuits are connected. 
 
 Mack A term proposed by Mr. 
 Oliver Heaviside for a unit of self-induc- 
 tion. 
 
 The term Mack is derived from Maxwell. The 
 unit of self induction has also been a secohm and 
 a quadrant. 
 
Mad.] 
 
 336 
 
 [Mag. 
 
 The term Max would seem to be indicated. 
 In the United States the unit of sell -induction is 
 called a Henry, after Prof. Joseph Henry. (See 
 Henry, A.) 
 
 Made Circuit. (See Circuit, Made ) 
 Magazine Fuse. (See Fuse, Magazine. ) 
 Magne-Crystallic Action. (See Action, 
 Magne-Crystallic. ) 
 
 Magnet. A body possessing the power 
 of attracting the unlike pole of another 
 magnet or of repelling the like pole ; or 
 of attracting readily magnetizable bodies 
 like iron filings to either pole. 
 
 A body possessing a magnetic field. 
 (See Field, Magnetic.} 
 
 The lines of force are assumed in passing 
 through the magnetic field to come out at the north 
 pole of the magnet and to go in at the south pole. 
 All lines of force form closed magnetic circuits. If 
 a magnetizable body is brought into a magnetic 
 field, the lines of magnetic force are concentrated 
 on it and pass through it. The body therefore be- 
 comes magnetic The intensity of the resulting 
 magnetism depends on the number of lines of 
 force that pass through the body, and the polar- 
 ity on the direction in which they pass through it. 
 
 A magnetized bar cannot be regarded as a 
 source of energy in itself. Energy must be ex- 
 pended to magnetize the iron, and must also be 
 expended to demagnetize it. 
 
 Magnet, Anomalous A magnet pos- 
 sessing more than two free poles. 
 
 There is no such thing as a unipolar magnet. 
 
 Fig. 364. Anomalous Magnet. 
 
 All magnets have two poles. Sometimes, how- 
 ever, several magnets are so grouped that there 
 appear to be more than two poles in the same 
 magnet. 
 
 A.. JB> C D 
 
 Fig. 36 J. Anomalous Magnet. 
 
 Thus, in Fig. 364, the magnet ABC appears 
 to possess three poles, two positive poles at A 
 and C, and a central negative pole at B. 
 
 It is clear, however, that the central pole is in 
 reality formed of two juxtaposed negative poles, 
 and that ABC actually consists of two magnets 
 with two poles to each. 
 
 The magnet A B C D Fig. 365, which in like 
 manner appears to possess four separate poles, in 
 reality is formed of three magnets with two poles 
 to each. 
 
 Since unlike magnetic poles neutralize each 
 other, it is clear that only similar poles can thus 
 be placed together in order to produce addition- 
 al magnet poles. 
 
 Fig. 366. Anomalous Magnet. 
 
 The six-pointed star shown in Fig. 366, is an 
 anomalous magnet with apparently seven poles. 
 The formation of the central N-pole, as is evi- 
 dent from an inspection of the drawing, is due to 
 the six separate north poles, n, n, n, n, n, n, of 
 the six separate magnets Sn, Sn, etc. Such a 
 magnet would be formed by touching the star at 
 the point N, with the S-pole of a sufficiently 
 powerful magnet. 
 
 The extra poles are sometimes called con- 
 sequent poles. Their presence may be shown by 
 means of a compass needle, or by rolling the 
 magnet in iron filings, which collect on the poles. 
 
 Magnet, Artificial - -A magnet pro- 
 duced by induction from another magnet, 
 or from an electric current. 
 
 Any magnet not found in nature is called an 
 artificial magnet. 
 
 Magnet, Axial A name sometimes 
 given to a solenoid with an axial or 
 straight core. 
 
 Magnet, Bell-Shaped A modifica- 
 tion of a horseshoe magnet in which the 
 approached poles are semi-annular in 
 shape, and form a split tube. 
 
 Bell -shaped magnets are used in many galra- 
 
Mag.] 337 
 
 nometers, because they can be readily dampened 
 by surrounding them by a mass of copper. The 
 needle in its motion produces currents that tend 
 to oppose, and, therefore, to stop its motion. 
 (See Laws, Lfnz's.) 
 
 Magnet, Club-Footed An electro- 
 magnet whose core is in the Jorm of a 
 horse-shoe and is provided with a mag- 
 netizing coil on one pole only. 
 Magnet Coil. (See Coil, Magnet ) 
 Magnet, Compensating A magnet 
 placed over a magnetic needle, generally 
 over the magnetic needle of a galvanome- 
 ter, for the purpose of varying the direc- 
 tion and intensity of the magnetic force of 
 the earth on such needle. (See Galvanom- 
 eter, Reflecting.} 
 
 A magnet, called a compensating magnet, is 
 sometimes placed on a ship, near the compass 
 needle, for the purpose of neutralizing the local 
 variations produced on the compass needle by 
 the magnetism of the ship. 
 
 Magnet, Compound A number of 
 
 single magnetsplaced par- 
 allel and with their similar 
 poles facing one another, 
 as shown in Fig. 367. 
 
 Compound magnets are 
 stronger in proportion to their 
 weight than single magnets. 
 
 Magnet, Compound 
 Horseshoe A horse- 
 shoe magnet composed 
 of several separate horse- 
 shoe magneto placed with S 
 their similar poles to- 
 gether. Fig. 367. Compound 
 
 Magnet. 
 
 A compound horseshoe magnet is shown in 
 Fig. 368. 
 
 A horseshoe magnet possesses greater portative 
 power than a straight bar magnet of the same 
 weight. (See Power, Portative. ) 
 
 (i.) Because its opposite poles are nearer to- 
 gether; and 
 
 (2 ) Because the magnetic resistance of its 
 circuit is less, the lines of magnetic force closing 
 through the armature, and thus concentrating 
 the magnetic attraction on the armature. 
 
 Electro-magnets are generally made of the 
 horseshoe shap-i. 
 
 [Mag. 
 
 Magnet, Controlling A name 
 
 sometimes applied to the controller in the 
 Thomson-Houston automatic system of 
 current regulation. (See Controller ) 
 
 Generally any mag- 
 net which controls 
 some particular ac- 
 tion. 
 
 Magnet, Cylindri- 
 cal A magnet 
 
 in the shape of a 
 cylinder. 
 
 A helix or solenoid 
 through which a cur- 
 rent of electricity is 
 passing is, so far as ex- 
 ternal space is con- 
 cerned, the exact magr 
 netic equivalent of a 
 cylindrical magnet. 
 
 Magnet, Damping 
 
 Any magnet 
 
 employed for the 
 
 ... . . Fig 368. Compound Horst- 
 
 purpose of checking shot Magnet. 
 
 the velocity of motion of a moving body 
 
 or magnet. 
 
 Dampening magnets generally act by the resist- 
 ance which they offer to the passage of a 
 metallic disc, so moved as to cut the lines offeree 
 of their field. 
 
 Magnet, Electro A magnet pro- 
 duced by the passage of an electric current 
 through a coil of insulated wire surround- 
 ing a core of magnetizable material. 
 
 The magnetizing coil is called a helix or sole- 
 noid. (See Magnetism, Ampere's Theory of.) 
 
 Strictly speaking, the term electro- magnet is 
 limited to the case of a magnet provided with a 
 solt iron core, which enables it to rapidly acquire 
 its magnetism on the passage of the magnetizing 
 current, a-id as rapidly to lose its magnetism on 
 the cessation of such current. 
 
 An elect! ic current passed around a bar of 
 magnetizable material, in the manner and direc- 
 tion shown in Fig. 369, will produce the polarity 
 N and S, at its ends or extremities as marked. 
 
 The directions of the currents required to pro- 
 duce N and S, poles respectively are shown in 
 Fig. 37- 
 
 The cause of this difference of polarity will be 
 readily understood from a study of the direction 
 
Mag.] 
 
 338 
 
 [Mug. 
 
 of lines of magnetic force in the field produced 
 by an electric current. 
 
 Fig, 3tx). Polarity of Current. 
 
 The direction of this polarity may be predicted 
 by the following modification of a rule by Ampere: 
 
 Imagine yourself swimming in the wire in the 
 direction of the current ; if, then, your face is 
 
 Fig. 370. North and South Magnet Poles. 
 
 turned toward the bar that is being magnetized, 
 its North seeking pole will be on your left. 
 
 A 
 
 Fig. 371. Deflection of Fig. 372. Drfl ction of 
 
 Magnetic Needle. Magnetic Needle. 
 
 If, for example, the conductor A B, be traversed 
 by a current in the direction from B, to A, as 
 shown in Fig. 371, the north pole N, of the 
 needle N S, placed under the conductor, is de- 
 flected, as shown, to the left of the observer, who 
 is supposed to be swimming in the current, facing 
 the needle. It the current flow in the opposite 
 
 direction, as from A, to B, as shown in Fig. 372, 
 the N, pole of the needle is deflected as shown, 
 but still to the left of the observer supposed to be 
 swimming as before. 
 
 In any electric circuit, the lines, of magnetic 
 force, produced by the passage of the current, form 
 circles around the circuit in planes at right angles 
 to the direction of the current, as shown in Fig. 
 373. The direction of these lines of force is the 
 same as that of the hands of a watch, if the cur- 
 rent be supposed to flow away from the observer. 
 (See Field, Magnetic, of an Electric Current.} 
 
 Fig. 373. Direction of Lines of Force. 
 
 Remembering now that the lines of force are 
 supposed to come out at the north pole cf a magnet, 
 and to pass in at the south pole, it is evident that 
 if the current flows in the direction shown in Fig. 
 
 Fig. 374. Direction of Lines of Forct, 
 
 374, the lines of force will come out at the north 
 pole and pass in at the south pole. 
 
 Since in a right-handed helix the wire passes 
 around the axis in the opposite direction to that 
 in which it passes in a left-handed helix, it is 
 evident that the helices shown in Fig. 375 at I, 
 and 2, will produce opposite polarities at the 
 points of entrance and exit by a current flowing 
 in the direction of the arrows. 
 
 If the current be sent through the right-handed 
 helix, shown at I, from b, to a, that is, from the 
 left to the right in the figure, a south pole will be 
 produced at b, and a north pole at a. If, how- 
 ever, it be sent from a, to b, the polarity will be 
 reversed. 
 
 If the current be sent through the left-handed 
 
Mag.] 
 
 339 
 
 [Mag. 
 
 helix, shown at 2, from a, to b, that is, trom the left 
 to the right in the figure, a north pole will be pro- 
 duced at a, and a south pole at b. If, however, it 
 be sent in the opposite direction, the polarity will 
 be reversed. 
 
 Therefore, in an electro-magnet, on the core 
 of which several layers or thicknesses of wire are 
 wound, in which the current flows through one 
 layer, in, say a direction from right to left, the cur- 
 rent must return through the next layer in the 
 opposite direction, or from left to right. The 
 polarities of the same extremities of the helices 
 are, however, the same in all cases, since the 
 layers are successively right and left handed 
 to the current. The winding shown at 3, pro- 
 duces consequent poles. 
 
 The following laws express the more important 
 principles concerning electro-magnets : 
 
 (l.) The magnetic intensity (strength) of an 
 electro-magnet is nearly proportional to the 
 strength of the magnetizing current, provided the 
 core is not saturated. 
 
 (2.) The magnetic strength is proportional to 
 the number of turns of wire in the magnetizing 
 coil ; that is, to the number of ampere turns. (See 
 Turns, Ampere.) 
 
 (3 ) The magnetic strength is independent of 
 the thickness or material of the conducting wires. 
 
 These laws may be embraced in the more gen- 
 eral statement that the strength of an electro- 
 
 - 37 f- Right-Handed, Left- Handed and Anomalous 
 Helices. 
 
 magnet, the size of the magnet being the same, 
 is proportional to the number of its ampere turns. 
 (See Turns, Ampere.) 
 
 A short interval of time is required for a cur- 
 rent to thoroughly magnetize a powerful electro- 
 magnet. 
 
 A few moments are also required for a power- 
 ful magnet to thoroughly lose its magnetism. At 
 the same time electro-magnets are capable of 
 acquiring or losing their magnetism with very 
 great rapidity. It is, in fact, on this ability pos- 
 sessed to so remarkable a degree by soft iron, that 
 
 he value of an electro-magnet for many purposes 
 depends. (See Lag, Magnetic.) 
 
 A difference exists between the action of a mag- 
 netized disc and a hollow coil of wire through 
 which a current of electricity is passing. So 
 far as the space outside either is concerned, the 
 action is the same, but the coil is penetrable on 
 the inside and the disc is not, and for the inside of 
 the space, therefore, there is a difference in the ac- 
 tion. 
 
 Magnet, Electro, Bar An electro- 
 magnet, the core of which is in the form of 
 a straight bar or rod. 
 
 Magnet, Electro, Cylindrical An 
 
 electro-magnet, the core of which consists 
 of a hollow cylinder provided with a slot 
 extending parallel to its axis. 
 
 The gap in the cylinder suffices for the placing 
 of the magnetizing coils, and forms the pules. 
 This form of electro-magnet was devised by 
 Joule. Its construction will be understood from 
 an inspection of Fig. 376. 
 
 Fig. yjb. Cylindrical Electro- Magnet. 
 
 Magnet, Electro, Horseshoe An 
 
 electro-magnet, the core of which is in 
 the shape of a horseshoe or U. 
 Magnet, Electro, Hughes' An 
 
 electro-magnet in which a U-shaped per- 
 manent magnet is provided with pole 
 pieces of soft iron, on which only are 
 placed the magnetizing coils. 
 
 A quick acting electro-magnet, in 
 which the magnetizing coils are placed on 
 soft iron pole pieces that are connected 
 with and form the prolongations of the 
 poles of a permanent horseshoe magnet. 
 
 Hughes devised this form of electro magnet in 
 order to obtain the best effects from currents of 
 but short duration. 
 
 He thus obtained a quick acting magnet, neces- 
 sary to insure the success of his system of printing 
 telegraph, where the magnetizing currents at 
 times have a dura. ion cf but the .20 of a second. 
 
Mag.] 
 
 340 
 
 [Mag. 
 
 - 377- Iron- dad 
 Electro- Magnet. 
 
 Magnet, Electro, Joule's Cylindrical 
 
 An electro- magnet provided with 
 
 a hollow cylindrical core. (See Magnet, 
 Electro, Cylindrical. ) 
 
 Magnet, Electro, Iron Clad An 
 
 electro-magnet whose magnetizing coil is 
 almost entirely surrounded by iron. 
 
 The effect of the iron casing is to greatly re- 
 duce the magnetic re- 
 sistance of the circuit. 
 A form of iron-clad elec- 
 tro-magnet is shown in 
 Fig- 377- Here one of 
 the poles is connected 
 with a casing of iron, 
 external to the coils, and 
 is thus brought nearer to 
 the other pole. 
 
 Magnet, Electro, 
 Long-Core An electro-magnet with 
 a long core of iron. 
 
 A long-core electro-magnet magnetizes and 
 demagnetizes much more slowly than a short- 
 core electro-magnet. 
 
 Magnet, Electro, Short-Core An 
 
 electro-magnet with a short core of iron. 
 
 A short-core electro-magnet possesses the 
 power of being magnetized and demagnetized 
 much more rapidly than a long-core magnet. 
 
 Magnet, Electro, Yoked-Horseshoe 
 
 A horseshoe electro-magnet, in which the 
 two straight limbs are formed of two 
 straight rods or bars, yoked together atone 
 pair of ends by a yoke or bar of iron. 
 
 In some cases the magnetizing coils are placed 
 on each of the limbs. Sometimes, however, a 
 single coil is placed at the middle of the yoke 
 and the limbs are left bare. 
 
 Even with the closest possible fitting the re- 
 sistance ot the magnetic circuit is much greater 
 in this form of electro-magnet, owing to the 
 smaller permeability of the air gap at the joints, 
 than it would be if the entire core were made of 
 a single piece of iron. A yoked electro- magnet 
 is, however, more convenient to make and use. 
 
 Magnet, Electro, Zigzag - -A multi- 
 polor electro-magnet, the magnetizing 
 coils of which are separately wound in 
 grooves cut in the face of straight or 
 curved bars. 
 
 A form ot zigzag electro-magnet devised by 
 Joule is shown in Fig. 378. The spiral char- 
 acter of the wind.ng 
 produces the alternate 
 North and South polari- 
 ties shown in the figure. 
 
 Magnet, Equator of 
 A point ap- 
 proximately midway 
 between the poles ofa 
 straight bar magnet, 
 
 i j Fig. 378. Zigzag Electro- 
 
 or nearly midway Magnet: 
 
 from the poles of a horseshoe magnet if 
 measured along the bar from each pole. 
 
 .This term was proposed by Dr. Gilbert. It is 
 now almost entirely displaced by the term neutral 
 point, 
 
 Magnet^ High-Resistance - A term 
 sometimes used in place of long-coil mag- 
 net whose coils have a high electric resist- 
 ance. (See Magnet, Long- Coil. ) 
 
 The term long-coil magnet is, perhaps, the 
 preferable one, because the resistance of a coil, 
 per se, has nothing to do with its magnetizing 
 power, which is determined by its ampere turns. 
 (See Turns, Ampere, Magnet, Long-Coil.} 
 
 Magnet, Horseshoe magnetized 
 
 bar of steel or iron bent in the form ofa 
 horseshoe or letter U. 
 
 Magnet, Iron Clad A magnet whose 
 
 magnetic resistance is lowered by a casing 
 of iron connected with the core and pro- 
 vided for the passage of the lines of mag- 
 netic force. (See Magnet, Tubular.") 
 
 Magnet, Jacketed A term some- 
 times applied to a form of iron-clad mag- 
 net. (See Magnet, Iron-Clad. ) 
 
 Magnet, Keeper of A mass of soft 
 
 iron applied to the poles of a magnet 
 through which its lines of magnetic force 
 pass. (See Field, Magnetic. ) 
 
 The keeper of a magnet differs from its arma- 
 ture in that the keeper while acting as such is 
 always kept on the poles to prevent loss of mag- 
 netization, while the armature, besides acting as 
 a keeper, may be attracted towards, or, if an 
 electro- magnet, be repelled from the magnet 
 poles. While performing its functions the keeper 
 is always fixed, the armatuie generally, though 
 
Mag.l 
 
 341 
 
 [Mag. 
 
 not always, is in motion. A keeper is, of course, 
 only used with permanent magnets. 
 
 Opinion is divided as to the efficacy of the 
 keeper in preventing loss of magnetization in 
 certain cases. 
 
 Magnet, Long Coil -An electro- 
 
 magnet whose magnetizing coil consists 
 of many turns of thin wire. 
 
 Magnet, Low-Resistance A term 
 sometimes used in place of short-coil 
 magnet. (See Magnet, Short-Coil.) 
 
 This term, short-coil magnet, is the preferable 
 one. 
 
 Magnet, Marked Pole of A name 
 
 formerly applied to that pole of a magnet 
 which points approximately to the geo- 
 graphical north. 
 
 If the pole of the magnet that points to the 
 geographical north be in reality the north pole 
 of the magnet, then the earth's magnetic pole in 
 the Northern Hemisphere is of south magnetic 
 polarity. In the United States, and Europe 
 generally, this is regarded as the fact. 
 
 The French, however, formerly called the 
 pole ot the needle that points to the earth's geo- 
 graphical north, the south or austral pole. In 
 America and England it is called the north fole, 
 the marked pole, or the north seeking pole, and 
 the Northern Hemisphere is assumed to possess 
 south magnetic polarity. (See Pole, Magnetic, 
 Austral. Pole, Magnetic, Boreal.) 
 
 Magnet, Moment of - -The effective 
 force of a magnetic couple as obtained by 
 multiplying one of the forces of the couple 
 by the perpendicular distance between 
 the directions of the forces. 
 
 The moment of a magnet is equal to the prod- 
 uct of the volume of the magnet and the in- 
 tensity or magnetization, or simply its magnetiza- 
 tion. 
 
 Magnet. Natural A name some- 
 times given to a lodestone. (See Lode- 
 stone. ) 
 
 Magnet, Neutral Line of (See Line, 
 Neutral, of a Magnet.) 
 
 Magnet, Permanent -A magnet of 
 hardened steel or other paramagnetic sub- 
 stance which retains its magnetism for a 
 long time after being magnetized. 
 
 A permanent magnet is distinguished, in this 
 respect, from a temporary magnet of soft iron, 
 which loses its magnetization very shortly alter 
 being taken from the magnetizing field. 
 
 Magnet, Portatiye Power of The 
 lifting power of a magnet. 
 
 The portative or lifting power of a magnet, 
 depends on the form of the magnet, as well as on 
 its strength. A horseshoe magnet, for example, 
 will lift a much greater weight than the same 
 magnet if in the form of a straight bar. 
 
 This is due not only to the mutual action of the 
 approached poles, but also to the decreased re- 
 sistance of the magnetic circuit, and to the greater 
 number of lines of magnetic force that pass 
 through the armature. The portative power is 
 proportional to the area of contact and the square 
 of the magnetic intensity, the formula being 
 
 p _ A X B 
 
 " 87TX98i, 
 
 in which P, is the lifting power in grammes, A, 
 the area of contact in square centimetres, and B, 
 is the number of lines of force per square centi- 
 metre. 
 
 Magnet Operation (See Operation, 
 
 Magnet. ) 
 
 Magnet, Receiving A name some- 
 
 times given to the relay of a telegraphic 
 system. (See Relay.) 
 
 In general, any magnet, used directly in 
 the receiving apparatus, at the receiving 
 end of a line connecting a system of elec- 
 tric communication between transmitting 
 and receiving instruments. 
 
 Magnet, Regulator A magnet, the 
 
 operation of which is to automatically 
 effect any desired regulation. 
 
 The magnet in the Thomson-Houston 
 system of automatic regulation, by means 
 of which the commutator collecting 
 brushes are automatically shifted to such 
 positions on the commutator as will main- 
 tain the current practically constant, de- 
 spite the changes in the resistance of the 
 circuit external to the machine. (See 
 Regulation, Automatic.} 
 
 Magnet, Relay - -An electro-magnet, 
 whose coils are connected to the main line 
 of a telegraphic circuit, and the movements 
 
Mag.] 
 
 342 
 
 [Mag. 
 
 of whose armature is employed to bring a 
 local battery into action at the receiving 
 station, the current of which operates the 
 register or sounder. 
 
 Magnet, Short-Coil An electro- 
 magnet whose magnetizing coil consists 
 of a few turns of short, thick wire. 
 
 Magnet, Simple A simple mag- 
 netized bar. 
 
 The term simple magnet is used in contradis- 
 tinction to compound magnet. (See Magnet, 
 Compound. ) 
 
 Magnet, Sluggisn A magnet that 
 
 magnetizes or demagnetizes sluggishly. 
 
 An electro-magnet becomes sluggish when sur- 
 rounded by a sheathing of copper, on account of 
 the currents induced in the sheathing in a direc- 
 tion opposite to those passing through the mag- 
 netizing coil. 
 
 Magnet, Solenoidal A thin, uni- 
 formly magnetized straight bar of steel, of 
 such a length that its poles, situated at 
 extremities or ends of its longer axis, act 
 on external objects as if equal and oppo- 
 site quantities of magnetism were con- 
 centrated at such extremities. 
 
 It derives its name solenoidal from the simi- 
 larity between its action and that of a solenoid. 
 Unless very carefully magnetized, a magnet will 
 not act as a solenoid magnet. (See Magnet, 
 Electro. Magnetism, Solenoidal Distribution of.) 
 
 Magnet, Tubular A form of horse- 
 shoe magnet, in which one pole is brought 
 near the opposite pole by a hollow cylin- 
 der or tube of iron, which is placed in con- 
 tact with one of the magnetic poles, so as 
 to completely surround the other, except 
 in the plane of cross-section of that pole. 
 
 A form of iron-clad magnet. (See 
 Magnet, Iron-Clad.} 
 
 There is thus obtained a magnet, with two con- 
 centric poles, one solid and the other annular, 
 the portative power of which is much greater than 
 that of a horseshoe magnet of equal dimensions. 
 
 Magnet, Field, of Dynamo-Electric Ma- 
 chine One of the electro-magnets 
 
 employed to produce the magnetic field 
 of a dynamo-electric machine. 
 
 The field magnets consist of a suitable frame, 
 or core, on which the field magnet coils are 
 wound. 
 
 Thejif/d magnet cores are made of thick and 
 solid iron, as soft as possible. They should con- 
 tain plenty of iron in order to avoid too ready 
 magnetic saturation. 
 
 All edges and corners are to be avoided, since 
 they tend to cause an irregular distribution of the 
 field. 
 
 The field magnets should in general have suffi- 
 cient magnetic strength to prevent the magnet- 
 izing effect of the armature from unduly influ- 
 encing the field, and thus, by causing too great a 
 lead, produce injurious sparking. 
 
 Magnetic or Magnetical. Pertaining to 
 magnetism. 
 
 Magnetic Adherence. (See Adherence, 
 Magnetic. } 
 
 Magnetic Air Circuit. (See Circuit, Air, 
 Magnetic. } 
 
 Magnetic Air (Jap (See Gap, Air, Mag- 
 netic. } 
 
 Magnetic Attraction. (See Attraction, 
 Magnetic. } 
 
 Magnetic Axis. (See Axis, Magnetic. } 
 
 Magnetic Axis of a Straight Needle. 
 
 (See Axis, Magnetic, of a Straight Needle.} 
 
 Magnetic Azimuth. (See Azimuth, Mag- 
 netic } 
 
 Magnetic Battery. (See Battery, Mag- 
 netic.} 
 
 Magnetic Bridge. (See Bridge, Mag- 
 netic.} 
 
 Magnetic Circuit. (See Circuit, Mag- 
 netic.} 
 
 Magnetic Closed-Circuit. (See Circuit, 
 Closed Magnetic. } 
 
 Magnetic Conductance. (See Conduct- 
 ance, Magnetic.} 
 
 Magnetic Core, Closed (See Core, 
 
 Closed- Magnetic. 
 
 Magnetic Core, Open (See Core, 
 
 Open- Magnetic. ) 
 
 Magnetic Couple. (See Coupe, Mag- 
 netic} 
 
Mag.] 
 
 343 
 
 [Mag. 
 
 Magnetic Curves. (See Curves, Mag- 
 netic. } 
 
 Magnetic Day of Disturbance. (See Day 
 of Disturbance, Magnetic. } 
 
 Magnetic Declination. (See Declina- 
 tion } 
 
 Magnetic Density. (See Density, Mag- 
 -efic. ) 
 
 Magnetic Dip. (See Dip, Magnetic.) 
 
 Magnetic Elements of a Place. (See 
 Elements, Magnetic, of a Place. } 
 
 .Magnetic Equalizer. (See Equalizer, 
 Magm tic. } 
 
 Magnetic Explorer. (See Explorer, Mag- 
 netic } 
 
 Magnetic, Ferro Magnetic after 
 
 the manner of iron or other paramagnetic 
 body. (See Paramagnetic. } 
 
 Magnetic Field. (See Field, Magnetic.} 
 
 Magnetic Field, Reversing. (See 
 
 Field, Magnetic, Reversing.} 
 
 Magnetic Field, Shifting. (See 
 
 Field Magnetic, Shifting.} 
 
 Magnetic Figures. See Figures, Mag- 
 netic. Field, Magnetic.} 
 
 MiirnHic Filament. (See Flameni 
 Magnetic} 
 
 Magne'.ic Flow. (See Flow, Magnetic.} 
 Magnetic Flux. (See Flux, Magnetic.} 
 Magnetic Force. (See Force, Magnetic.} 
 Magnetic Inclination. (See Inclination, 
 Magnetic } 
 
 Magm tic Induction. (See Induction, 
 Magnetic } 
 Magnetic Induction, Dynamic. 
 
 (See Induction, Magnetic, Dynamic. } 
 
 Magnetic Induction, Static- (See 
 
 Induction, Magnetic, Static} 
 
 Magnetic Inertia. (See Inertia, Mag- 
 netic } 
 
 Magnetic Intensity. (See Intensity, 
 Magnetic.} 
 
 Magnetic Joint. (See Joint, Magnetic.} 
 
 Magnetic Lag. (See Lag, Magnetic.} 
 
 Magnetic Latitude. (See Latitude, Mag- 
 netic. } 
 
 Magnetic Leakage. (See Leakage, Mag- 
 netic.} 
 
 Magnetic Lines of Force. (See Force* 
 Magnetic, Lines of. } 
 
 Magnetic Mass. (See Mass, Magnetic. } 
 
 Magnetic Memory. (See Memory, Mag- 
 netic. } 
 
 Magnetic Meridian. (See Meridian, 
 Magnetic} 
 
 Magnetic Moment. (See Moment, Mag- 
 netic} 
 
 Magnetic Normal Day. (See Day, Nor- 
 mal, Magnetic.} 
 
 Magnetic Observatory. (See Observa- 
 tory, Magnetic. 
 
 Magnetic Output. (See Output, Mag- 
 netic. } 
 
 Magnetic Parallel. (See Parallels, Mag- 
 netic } 
 
 Magnetic Permeability. (See Permea- 
 bility, Magnetic.} 
 
 Magnetic Permeance. (See Permeance, 
 Magnetic. } 
 
 Magnetic Permeation. (See Permeation, 
 Magnetic. } 
 
 Magnetic Poles. (See Poles, Magnetic. } 
 
 Magnetic Poles, False. (See Pole, 
 
 Magnetic, False.} 
 
 Magnetic Proof Piece. (See Piece, Mag- 
 netic Proof.} 
 
 Magnetic Proof Plane. (See Plane, 
 Proof, Magnetic.} 
 
 Magnetic Reluctance. (See Reluctance, 
 Magnetic.} 
 
 Magnetic Repulsion. (See Repulsion, 
 Magnetic} 
 
 Magnetic Resistance. (See Resistance, 
 Magnetic.} 
 
 Magnetic Retardation. (See Retarda- 
 tion Magnetic} 
 
Mag.] 
 
 344 
 
 [Mag. 
 
 Magnetic Retentiyity. (See Retentivity, 
 Magnetic.') 
 
 Magnetic Saturation. (See Saturation, 
 Magnetic. ) 
 
 Magnetic Screen or Shield. (See Screen 
 or Shield, Magnetic. ) 
 
 ' Magnetic Screening. (See Screening, 
 Magnetic.) 
 
 Magnetic, Self Induction. (See Induc- 
 tion, Self, Magnetic.) 
 
 Magnetic Shells. (See Shells, Magnetic.) 
 Magnetic Shunt. (See Shunt, Magnetic ) 
 
 Magnetic Sidero A term proposed 
 
 by S. P. Thompson to replace the term 
 ferro-magnetic. (See Magnetic, Ferro.) 
 
 Magnetic Solenoid. (See Solenoid, Mag- 
 netic. ) 
 
 Magnetic Sounds. (See Sounds, Mag- 
 netic. ) 
 
 Magnetic Spin. (See Spin, Magnetic.) 
 Magnetic Storm. (See Storm, Mag- 
 netic.) 
 
 M gnetic Strain. (See Strain, Mag- 
 netic.} 
 
 Magnetic Stress. (See Stress, Magnetic. ) 
 Magnetic Susceptibility. (See Suscepti- 
 bility, Magnetic.) 
 
 Magnetic Theodolite. (See Theodolite, 
 Magnetic ) 
 
 Magnetic Unit Pole. (See Pole, Unit, 
 Magnetic. ) 
 
 Magnetic Units. (See Units, Magnetic) 
 
 Magnetic- Vane Ammeter. (See Ammeter, 
 Magnetic- Vane. ) 
 
 Magnetic Vane Voltmeter. (See Volt- 
 ' meter, Magnetic-Vane.) 
 
 Magnetic Variations. (See Variations, 
 Magnetic. ) 
 
 Magnetic Variation Transit. (See Tran- 
 sit, Magnetic Variation.) 
 
 Magnetic Variometer. (See Variometer, 
 Magnetic. ) 
 
 Magnetic Viscosity.- (See Viscosity, Mag- 
 netic) 
 Magnetic Whirl. (See Whirls, Magnetic.) 
 
 Magnetic Whirl, Expanding (See 
 
 Whirl, Magnetic, Expanding.) 
 
 Magnetics, Electro That branch of 
 
 electric science which treats of the rela- 
 tions that exist between electric circuits 
 and magnets. 
 
 Magnetism. That branch of science I 
 which treats of the nature and properties 
 of magnets and the magnetic field. (See 
 Field, Magnetic.) 
 
 A property or condition of matter at- 
 tended by the existence, of a magnetic 
 field. 
 
 Magnetism, Ampere's Theory of A 
 
 theory or hypothesis proposed by Ampere, 
 to account for the cause of magnetism, by 
 the presence of electric currents in the 
 ultimate particles of matter. 
 
 Fig. 37<J. Unmagnetized 
 Bar {after Ampkre}. 
 
 Fig. 380. Magnetized 
 Bar (after Ampere) . 
 
 This theory assumes : 
 
 (I.) That the ultimate particles of all magneti- 
 zable bodies have closed electric circuits in which 
 electric currents are continually flowing. 
 
 (2.) That in an unmagnetized body these cii - 
 cuits neutralize one another because they have 
 different directions. 
 
 (3.) That the act of magnetization consists in 
 such a polarization of the particles as will cause 
 these currents to flow in one and the same direc- 
 tion, magnetic saturation being reached when all 
 the separate circuits are parallel to one another. 
 
 (4.) That coercive force is due to the resistance 
 these circuits offer to a change in the direction 
 of their planes. 
 
 Figs. 379 and 380 show the circular paths of 
 some of these circuits. Fig. 379 shows the as- 
 
Mag.] 
 
 345 
 
 [Mag. 
 
 sumed condition of an unmagnetized bar. Fig. 
 380 the assumed condition of a magnetized 
 bar. 
 
 A careful inspection of the figures will show that 
 in a magnetized bar all the separate currents flow 
 in the same direction. All the circuits except 
 those on the extreme edge of the bar will, there- 
 fore, have the currents flowing in them in opposite 
 directions to that in their neighboring circuits, 
 and, therefore, will neutralize one another . There 
 will remain, however, a current in a circuit on the 
 outside of the bar, which must therefore be re- 
 garded as the magnetizing current. 
 
 Guided by these considerations, Ampere pro- 
 duced a coil of wire, called a solenoid, which is 
 the equivalent of the magnetizing circuit assumed 
 by his theory. 
 
 It therefore follows that an electric current sent 
 through a coil of insulated wire surrounding a 
 rod or bar of soft iron, or other readily magnet- 
 izable material, will make the same a magnet. A 
 magnet so produced is called an electro-magnet. 
 (See Magnet, Electro.} 
 
 The magnetizing coil is called a helix or sole- 
 noid. See Solenoid, Electro -Magnetic.) 
 
 The polarity of the magne' depends on the 
 direction of the current, or on the direction of 
 winding of the helix or solenoid. (See Solenoid, 
 Sinistrorsal. Solenoid, Dextrorsal.) 
 
 The improbability of an electric current con- 
 tinually flowing in a circuit without the expendi- 
 ture of energy, has led, perhaps, the majority of 
 scientific men to reject Ampere's theory of mag- 
 netism. 
 
 Lodge, however, does not agree with the ma- 
 jority of physicists in regarding a constant flow 
 of electricity through the molecules of magnetiza- 
 ble substances as an impossibility. On the sup- 
 position that the atoms or molecules possess 
 no resistance, the current would flow through 
 them lorever. He says: ."To all intents and pur- 
 poses certainly atoms are infinitely elastic, and 
 why should they not also be infinitely conducting ? 
 % Why should the dissipation of energy occur, in 
 respect to an electric current circulating wholly 
 inside an atom? There is no reason why it 
 should. " 
 
 Magnetism, Animal A term some- 
 times applied to hypnotism or artificial 
 somnambulism. 
 
 Magnetism, Earth's, Theories as to Cause 
 
 of The various theories or hypotheses 
 
 respecting the cause of the earth's magnet- 
 ism. 
 
 Any theory or hypothesis which shall satisfac- 
 torily explain the cause of the earth's magnetism 
 must account for the following phenomena, viz. ; 
 
 (i.) Variations in the intensity of the earth's 
 magnetic field. 
 
 (2.) Variations in the earth's magnetic inclina- 
 tion, declination and intensity. 
 
 The following hypotheses have been proposed'. 
 
 1st. That the earth's magnetism is due to the 
 circulation round the earth of electric currents 
 produced by differences of temperature which the 
 earth's surface acquires from exposure to the sun 
 during its rotation. 
 
 As the earth rotates from west to east, the area 
 of greatest heat would move round the earth in 
 the opposite direction, or from east to west. K 
 now those differences of temperature could pro. 
 duce, in a manner not as yet explained, thermo- 
 electric currents circulating round the earth from 
 east to west, such currents would produce, in the 
 Northern Hemisphere of the earth, south mag- 
 netic polarity, and in the Southern Hemisphere 
 north magnetic polarity, which would account for 
 the magnetic polarity of the earth. 
 
 Differences in the intensity of the earth's mag- 
 netic field, and in the inclination and direction of 
 its lines ot magnetic force, would be explained, 
 according to this hypothesis, by the differences in 
 the amount of the solar radiation at different 
 times. 
 
 The objection to this theory is to be found in 
 the fact that by far the larger part of the earth's 
 surface at the Equator is composed of water, so 
 that the differences of potential at such parts, 
 produced by the differences of temperature, are 
 not readily set up in the earth's crust, if, indeed, 
 they are set up at all. 
 
 2d. That the earth's magnetism is due to in- 
 duction from an already magnetized sun. This 
 theory was brought forward by Secci and others. 
 It is not generally credited. 
 
 3d. A theory proposed by Biglow, which ac- 
 counts for the earth's magnetism by rotation in 
 the magnetic field of the sun's light and radia- 
 tion. 
 
 Biglow believes that the earth's magnetism is 
 due to its rotation in the magnetic field of the 
 sun's light. As the sun's light illumines one-half 
 of the earth's surface, the earth's rotation causing 
 different portions of the surface to pass through 
 
346 
 
 this illumim d area, produces, in Prof. Biglow's 
 opinion, th ft differences in the direction and in- 
 tensity of 'Jie magnetic lines of the earth's field 
 that correspond to differences in the earth's mag- 
 netic intensity, declination and inclination. 
 
 It will be observed that in all these theories the 
 sun is the prime factor in the production ot the 
 earth's magnetism. 
 
 The evident connection between the earth's 
 magnetism and the solar radiation is established 
 from the well known connection between the so- 
 called magnetic storms and variations in the in- 
 tensity of the earth's magnetism. 
 
 Magnetic storms are always attended by out- 
 bursts of solar energy, known technically as 
 sun spots. A series of observations on the num- 
 bers and frequency of sun-spots, plotted in the 
 form of a curve, the ordinates of which represent 
 the times of occurrence of the spots and the 
 abscissas, the number of such spots, prove that 
 such curve agrees, in a remarkable manner, with 
 a similar curve representing the variations of the 
 earth's magnetic field. 
 
 An evident connection, too, exists between the 
 earth's magnetism and the pr6valence of the 
 aurora borealis. 
 
 Magnetism, Electro Magnetism 
 
 produced by means of electric currents. 
 
 The discovery by Oersted, in 1820, of the ac- 
 tion of an electric current on a magnetic needle, 
 was almost immediately followed by the simul- 
 taneous and independent discoveries by Arago 
 and Davy, ot the method of magnetizing iron 
 by the passage of an electric current around it. 
 
 These observations were first reduced to a 
 theory by Ampere (See Magnetism^ Ampere's 
 Theory of . Magnet, Electro.) 
 
 Magnetism, Ewing's Theory of - A 
 theory of magnetism proposed by Prof. 
 Ewing, based on the assumption of orig- 
 inally magnetized particles. 
 
 Ewing's theory of magnetism assumes that the 
 ultimate particles ot matter are naturally mag- 
 netic and possess polarity. In this respect Ewing's 
 theory agrees with the theories of Hughes and 
 Weber. Ewing does not believe, however, in the 
 necessity for the assumption of any arbitrary re- 
 straining or constraining force to the movements 
 of these ultimate magnetic particles other than 
 those due to their own mutual magnetic attractions 
 and repulsions. He assumes that in a magnet, 
 
 the centres about which the molecular magnets 
 rotate are maintained at constant distances from 
 one another, save only as they are affected by the 
 action of strain. 
 
 He has experimentally demonstrated the prin- 
 ciples of his theory by means of a model in which 
 a number of small magnetic needles are so sup- 
 ported as to be capable of free motion in a hori- 
 zontal plane, when under varying magnetic 
 forces. 
 
 According to Ewing, "magnetic hysteresis" 
 is not the result of any quasi frictional resistance 
 to molecular rotation, but arises from a molecule 
 moving from one position of stable equilibrium co 
 another position of stable equilibrium through a 
 position of unstable equilibrium. " This pro- 
 cess " says Ewing, "considered mechanically, is 
 not reversible. The forces are different for the 
 same displacement, going and coming, and there 
 is dissipation of energy. In the model, the energy 
 thus expended sets the little bars swinging, and 
 their swings take some time to subside. In the 
 actual solid, the energy which the molecular 
 magnet loses as it swings through unstable posi- 
 tions, generates eddy currents in surrounding 
 matter. Let the magnets of the model be 
 furnished with air vanes to damp their swings 
 and the correspondence is complete." 
 
 In Hughes' modification of Weber's theory of 
 magnetism, it was held, that when magnetized 
 iron was suddenly demagnetized by torsion or 
 flexure, it lost its magnetization because the mo- 
 lecular magnets came to rest in closed chains, which 
 produced no external effects. Experimentation 
 with Ewing's model of a magnet shows that when 
 the separate magnets after having been placed in 
 any particular grouping are permitted to come to 
 rest free from any external magnetic force, they do 
 not arrange themselves in closed chains, but in 
 general the tendency appears to be the formation 
 of lines consisting of two, three or more magnets, 
 each member of a line being strongly controlled 
 by its next member in that line, but influenced 
 by the neighbors which lie off the line on either 
 side. 
 
 The fact that a given force, suddenly applied, 
 produces more magnetic induction than when 
 gradually applied, and leaves less residual mag- 
 netism when suddenly than when gradually re- 
 moved, is presumably due to the inertia of the 
 molecules. 
 
 The influence of mechanical vibration in in- 
 creasing the magnetic susceptibility and decreas. 
 
347 
 
 [Mag. 
 
 ing the magnetic retentiveness, is ascribed by 
 Ewing to the fact that the vibrations cause 
 periodic variations in the distances between the 
 centres of rotation of the magnetic molecules; 
 thus making the molecular magnets respond more 
 readily to changes of magnetic force during the 
 time they are moving away from one another, 
 when their magnetic stability is less, but also in- 
 creasing the ease with which they respond to 
 changes of magnetic force, by causing them to 
 swing. 
 
 Ewing discusses the theoretical effects of tem- 
 perature on magnetism as follows, viz. : Suppose 
 a moderate magnetizing force to be applied so 
 that nothing like saturation is obtained, if now 
 the temperature be raised; then 
 
 (i.) The magnetic permeability increases until 
 the temperature reaches a certain (high) critical 
 value. 
 
 (2.) At this temperature there is suddenly an 
 almost complete disappearance of magnetic 
 quality. 
 
 He explains these facts as follows, viz.: An 
 increase of temperature by increasing the distance 
 between the molecular centres causes a decrease 
 In their stability. 
 
 The loss of magnetic qualities, when a certain 
 temperature is reached, is, he believes, due to the 
 fact that at such temperatures the magnetic 
 molecules are set into actual rotation, when, 
 naturally, all traces of polarity would disappear. 
 
 Ewing's theory of magnetism also accounts to 
 a considerable extent for the effects of stress and 
 consequent elastic strain on the magnetic qualities 
 of iron, nickel and cobalt. 
 
 The following general summary of his theory 
 is taken mainly from Prof. Ewing's original 
 articles as published in the Journal of the Society 
 of Arts: 
 
 (i.) That in considering the magnetization of 
 iron and othtr magnetic metals to be caused by 
 the turning of permanent molecular magnets, we 
 may look simply to the magnetic forces which 
 the molecular magnets exert upon one another as 
 the cause of their directional stability. There is 
 no need to suppose the existence of any quasi- 
 elastic directing force, or any quasi-frictional re- 
 sistance to rotation. 
 
 (2. ) That the intermolecular magnetic forces are 
 sufficient to account for all the general character- 
 istics of the process of magnetization, including 
 the variations of susceptibility which occur as 
 the magnetizing force is increased. 
 
 12_Vol. 1 
 
 (3.) That the intermolecular magnetic forces 
 are equally competent to account for the known 
 facts of retentiveness and coercive force, and the 
 characteristics of cyclic magnetic processes. 
 
 (4.) The magnetic hysteresis and the dissipation 
 of energy which hysteresis involves are due to 
 molecular instability, resulting from intermolec- 
 ular magnetic actions, and are not due to any- 
 thing in the nature of frictional resistance to the 
 rotation of the molecular magnets. 
 
 (5.) That this theory is wide enough to admit an 
 explanation of the differences in magnetic quality 
 which are shown by different substances, or by 
 the same substance in different states. 
 
 (6.) That it accounts in a general way for the 
 known effects of vibration, of temperature, and 
 of stress, upon magnetic quality. 
 
 (7 ) That, in particular, it accounts for the 
 known fact that there is hysteresis in the relation 
 of magnetism to stress. 
 
 (8.) That it further explains why there is in 
 magnetic metals hysteresis in physical quality 
 generally with respect to stress. 
 
 (9.) That, in consequence, any (not very small) 
 cycle of stress occurring in a magnetic metal in- 
 volves dissipation of energy. 
 
 It can be demonstrated by means of experi- 
 ments with a model constructed according to 
 Ewing's hypothesis, that this hypothesis comes 
 nearer than any which had been proposed tefore 
 in explaining the following effects: 
 
 (i.) The behavior of a piece of iron when 
 placed in a magnetic field whose strength is made 
 to pass through a cycle of changes. 
 
 (2.) That nearly all reversals of sign on the 
 change of the magnetizing force are accompanied 
 by small changes in the magnetization. 
 
 (3.) That a piece of iron submitted to vibra- 
 tions or mechanical shocks, is magnetized and 
 demagnetized more readily and with a smaller 
 hysteresial area than if it had remained undis- 
 turbed by vibrations. 
 
 (4.) The phenomenon of "time lag "in mag- 1 
 netization. 
 
 (5.) The phenomena of stress, both those which 
 occur when a body has first been placed in a 
 magnetic field and the stress made to vary, and 
 those which occur when a body is first placed in 
 a constant stress and the magnetizing force is 
 made to vary. 
 
 (6.) The effects of heat on magnetization, both 
 as regards the effect of comparatively low heating 
 on increase of magnetic susceptibility, and ;he 
 
348 
 
 [Mag. 
 
 effect of excessive heating to decrease the sus- 
 ceptibility. 
 
 The author is indebted for the above summary 
 of demonstrable facts to a paper recently read be- 
 fore the Electrical Section of the Franklin Insti- 
 tute, by Prof. Henry Crew. 
 
 Magnetism, Flux or Flow of The 
 
 quantity of magnetism, or the number of 
 lines of force which pass in any magnetic 
 circuit under a given magneto-motive force, 
 against a given magnetic reluctance. 
 
 Magnetism, Galvano 
 
 A term some- 
 
 times used for electro-magnetism. 
 
 Electro-magnetism is by far the preferable 
 term, and is almost universally used in the United 
 States. 
 
 Magnetism, Horizontal Component of 
 Earth's -- (See Component, Horizontal, 
 of Earth's Magnetism.) 
 
 Magnetism, Hughes' Theory of - A 
 
 theory propounded by Hughes to account for 
 the phenomena of magnetism apart from the 
 presence of electric currents. 
 
 Hughes' theory, or, more strictly speaking, 
 hypothesis of magnetism, though very similar to 
 that of Ampere, does not assume the improbable 
 condition of a constantly flowing electric current. 
 
 Hughes' hypothesis assumes: 
 
 (i.) That the molecules of matter, and, per- 
 haps, more probably, the atoms, possess naturally 
 opposite magnetic polarities, which are respect- 
 ively + and , or N and S. 
 
 (2.) That these molecules, when arranged in 
 closed chains or circuits, are capable of neutral- 
 izing one another so far as external action is con- 
 cerned. 
 
 i: 
 
 8 \ 
 
 Fig. 38 z. Closed Molecular Chain. 
 
 Two such arrangements or groupings are 
 shown in Figs. 381 and 382. It will be observed 
 that the magnetic chain or circuit is complete, 
 
 and that, therefore, the substance can possess no 
 magnetic properties so far as external action is 
 concerned. 
 
 4- 
 
 Fig. 382. Closed Groupings. 
 
 (3.) That the act of magnetization consists in 
 such a rotation of the molecules that a polariza- 
 tion of the substance is effected that is, the 
 molecules are rotated on their axes so that one set 
 of poles tend to point in one direction and the 
 other set of poles in the opposite direction. 
 
 Partial magnetization consists in partial polari- 
 zation. Magnetic saturation is reached when the 
 polarization is complete. (See Saturation, Mag- 
 netic.) 
 
 Coercive force is the resistance the body offers 
 to the polarization or rotation of its molecules. 
 (See Force, Coercive.) 
 
 Hughes' hypothesis of magnetism would ap- 
 pear to be strengthened by the following facts: 
 
 (I.) A bar of steel or iron is sensibly elongated 
 on being magnetized. This would naturally re- 
 sult if the molecules be supposed to be longer in 
 one direction than in any other. 
 
 (2.) A tube, furnished at its ends with plates of 
 flat glass and filled with water containing finely 
 divided magnetic oxide of iron, is nearly opaque 
 to light when unmagnetized, but will permit some 
 light to pass through it when magnetized. 
 
 (3.) A magnet, if cut at its neutral point, will 
 possess opposite polarities at the cut ends; and, 
 no matter to what extent this subdivision is car- 
 ried, the particles will still possess opposite polar- 
 ities. 
 
 These facts are, however, also explained by 
 Ampere's hypothesis of magnetism, with, how- 
 ever, the improbable assumption of a constantly 
 flowing current in each molecule. 
 
 The following experiment by Von Betz tends 
 somewhat to confirm Hughes' hypothesis: 
 
 He placed a powerful horseshoe magnet in a 
 solution of iron and deposited a bar or plate of 
 metallic iron between the poles by electrolysis. 
 Here the molecules, at the time of their deposi- 
 tion, were subjected to a polarizing force which 
 tended to place them all in the same direction, 
 and, as the solution from which they were ob- 
 tained permitted great freedom of motion, they 
 were all presumably deposited in lines parallel to 
 one another. When this bar of iron was subse 
 
Mag.] 
 
 [Mag. 
 
 quently magnetized it was found to be much more 
 powerful in comparison to its size than any other 
 magnet. 
 
 Mr. Shelford Bidwell has shown that the act of 
 magnetization produces a shortening rather than 
 a lengthening of the magnetizable material. 
 When the magnetization is moderate there is a 
 true lengthening of the material, but when a 
 more powerful magnetizing force is exerted a 
 true contraction or shortening is observed. 
 
 M 
 
 L 
 
 of 
 
 in 
 
 3$ 3' Bidwell Apparatus. 
 
 The Bidwell apparatus is shown in Fig. 383. 
 The bar of iron to be magnetized is shown at 
 R R. The magnetization is obtained by means of 
 the coil of wire C. The upper end of the bar 
 presses against the rod L, fulcrumed at F. The 
 other end of the bar bears against a pivoted 
 mirror M, from which a pot of light is reflected. 
 
 In the case of the magnetization of nickel, the 
 experiments of Bidwell showed the existence of 
 contraction far both weak and strong currents. 
 This contraction is much greater than in the case 
 of iron. 
 
 Magnetism, Lamellar Distribution 
 
 - The distribution of magnetism 
 magnetic shells. 
 
 A term sometimes applied to such a dis- 
 tribution of magnetism in a plate, that the 
 magnetized particles are arranged with their 
 greatest length in the direction of the thick- 
 ness of the plate, so that the poles are situ- 
 ated at the faces of the plate, and conse- 
 quently the extent of such polar surfaces is 
 great when compared with the thickness of 
 the plate. 
 
 The term lamellar distribution of magnetism is 
 used in contradistinction to solenoidal distribution. 
 (See Magnetism, Solenoidal Distribution of. ) 
 
 A thin sheet or disc of magnetize! material 
 whose opposed extended faces are of opposite 
 
 magnetic polarities, an i the extent of whose sur- 
 fa;e is vc?ry great as co nparei with its thickness, 
 is sometimes called a magnetic shell. 
 
 The field produced by a magnetic shell is ex- 
 actly similar to that produced by a closed voltaic 
 circuit, the edges of the space inclosed by which 
 correspond t ) the edges of the magnetic shell. 
 
 The magnetic intensity, or the number of lines 
 of force per unit arei of cross-section, is equal 
 over all parts of the surface of a si.nple magnetic 
 shell. 
 
 A magnetic shell may be conceived as consist- 
 ing of a very great number of short, straight 
 magnetic needles, placeJ side by side, with their 
 north poles terminating at one of the faces of the 
 sheet and their south poles at the opposite face, 
 the breadth of the sheet being very great as com- 
 pared with its thickness. Such a distribution of 
 magnetism is known as a lamellar distribution. 
 
 Magnetism, Residual The magnet- 
 ism remaining in the core of an electro-mag- 
 net on the opening of the magnetizing cir- 
 cuit. 
 
 The small amount of magnetism retained 
 by soft iron when removed from any mag- 
 netizing field. 
 
 When hard iron or steel is removed from a mag- 
 netizing field it retains nearly all its magnetism. 
 Such magnetism is also, in reality, residual mag- 
 netism, but the term is generally limited to the 
 case of soft iron. 
 
 Magnetism, Solenoidal Distribution of 
 
 - A term sometimes applied to such 
 a distribution of magnetism in P. bar that 
 the magnetized particles are arranged with 
 their poles in the direction of the length of the 
 bar, the ends of which are of opposite mag- 
 netic polarities, and the extent of whose sur- 
 faces is small as compa -ed wt) the length 
 of the bar. 
 
 The term solenoidal distribution - ; used in con- 
 tradistinction to lamellar distribution, (.see Mag- 
 netism, Lamellar Distribution of. ) 
 
 Magnetism, Strength of A term 
 
 sometimes used in the sense of intensity of 
 magnetization. (See Magnetization, Inten- 
 sity of.} 
 
 The term, strength of magnetism, is sometimes 
 u ed for flux or quantity of magnetism. 
 
 Intensity of magnetization, is the preferable 
 term. 
 
350 
 
 [Mag. 
 
 Magnetism, Terrestrial A name 
 
 applied to the magnetism of the earth. 
 
 Terrestrial magnetism has been ascribed to a 
 variety of causes. (See Magnetism, Earth's, 
 Theories as to Cause of. ) 
 
 Magnetism, Vertical Component of 
 
 Earth's (See Component, Vertical^ 
 
 of Earth's Magnetism) 
 
 Magnetite. Magnetic oxide of iron, or 
 Fe 3 O 4 , found in nature, as an ore or mineral. 
 
 Lode-stone consists of .pieces of magnetized 
 magnetite. 
 
 Magnetizable. Capable of being magnet- 
 ized after the manner of a paramagnetic sub- 
 stance like iron. 
 
 The most magnetizable metals are iron, nickel, 
 cobalt and manganese. (See Paramagnetism.) 
 
 Magnetization. The act of calling out or 
 of endowing with magnetic properties. 
 
 Magnetizable substances are magnetized by 
 being placed in magnetic fields. (See Field, Mag- 
 netic. Magnetization, Methods of.) 
 
 The act of initial magnetization is not exactly 
 the same as the act of subsequent magnetization. 
 
 A piece of steel, which has once been magnet- 
 ized and subsequently demagnetized, is a thing en- 
 tirely distinct, as regards its magnetization, from 
 a piece of steel which has never before been mag- 
 netized, and such a piece can never be placed ex- 
 actly in the same position as regards a magnet- 
 izing force, unless it is actually melted and recast, 
 or, perhaps, maintained for a comparatively long 
 time at a white heat. 
 
 Magnetization, Anomalous The 
 
 magnetization obtained from an oscillatory 
 discharge, such as that of a Leyden jar. 
 
 In 1842, Henry described the real character of 
 anomalous magnetization, and showed that there 
 was nothing anomalous in such magnetization, but 
 rather in the fact that the magnetizing currents 
 possessed no simple direction. He remarks on 
 this subject as follows: 
 
 'This anomaly, which has remained so long 
 unexplained, and which, at first sight, appears at 
 variance with all our theoretical ideas of the con- 
 nection of electricity and magnetism, was, after 
 considerable study, satisfactorily referred to an 
 action ot the discharge of a Leyden jar which had 
 never before been recognized. The discharge, 
 
 whatever may be its nature, is not correctly rep- 
 resented (employing the simplicity of Franklin) 
 by the single transfer of an imponderable fluid 
 from one side of the jar to the other ; the phe- 
 nomena require us to admit the existence of a 
 principal discharge in one direction and then 
 several reflex actions backward and forward, each 
 more feeble than the preceding, until the equi- 
 librium is obtained. All the facts are shown to 
 be in accordance with the hypothesis, and a ready 
 explanation is afforded by it of a number of phe- 
 nomena which are to be found in the older works 
 on electricity, but whi h have until this time re- 
 mained unexplained." 
 
 Magnetization by Touch. The produc- 
 tion of magnetism in a magnetizable sub- 
 stance by touching it with a magnet. 
 
 There are three methods of magnetization by 
 touch, viz.: 
 
 (i.) Single touch. 
 
 (2.) Separate touch. 
 
 (3.) Double touch. 
 
 In single touch, the magnetization of a bar of 
 iron or other magnetizable material is effected by 
 the touch of a single magnet. 
 
 In Single Touch, the magnetizing magnet is 
 drawn over the bar to be magnetized from end to 
 end and returned through air, the stroke being 
 repeated a number of times. The end of the 
 bar the magnet leaves is magnetized oppositely 
 to the magnetizing pole. 
 
 By some writers the method of single touch is 
 described as that effected 
 by placing the magnet- 
 izing magnet N S (Fig. 
 384) on the middle of 
 the bar to be magnetized, 
 and drawing it to the 
 end and returning 
 through the air as be- [-J-N s^I| 
 
 fore, and then reversing * 
 
 the pole, placing it on Fi S- 384. Magnetization 
 the middle of the bar * Sin ^ e Touck - 
 and drawing it towards the other end. The 
 
 Fig. 38 5. Magnetization by Separate Touch. 
 
 former would, however, appear to be the better 
 Use of the term single touch. 
 
 In Separate Touch, two magnetizing bars are 
 placed with their opposite poles at the middle 
 
Mag.] 
 
 351 
 
 of the bar to be magnetized and drawn away from 
 each other towards its ends, as shown in Fig. 
 385. This motion is repeated a number of times, 
 the poles being each time returned through the 
 air. 
 
 In the above, as in all cases of magnetization 
 by touch, better effects are produced, if the bar 
 
 ^SyTMSfS^-^"^ 
 
 a 
 
 Fig. 386. Magnetization by Double Touch. 
 
 to be magnetized is rested on the opposite poles 
 of another magnet, or, as shown in Fig. 386, 
 placed near them. 
 
 In Double Touch the two magnets are placed 
 with their opposite poles together on the middle 
 of the bar to be magnetized, as shown in Fig. 
 386. They are then moved to one end of the bar, 
 when, instead of removing them and passing them 
 back through the air to the other end, they are 
 moved over the surface of the bar to be magnet- 
 ized to the other end, and these to and-fro mo- 
 tions are repeated a number of times. The mo- 
 tion is stopped at the middle of the bar, when the 
 magnetizing magnets are moving in the opposite 
 direction to that at which they began to move. 
 This insures an equal number of strokes to the 
 two halves of the bar. The method of double 
 touch produces stronger magnetization than 
 either of the other methods, but does not effect 
 such an even distribution of the magnetism, and 
 therefore is not applicable to the magnetization 
 of needles. 
 
 A variety of double touch is shown in Fig. 387, 
 where four bars, to be magnetized, are placed in 
 the form of a hollow rectangle, with only their 
 ends touching at their edges, the angular spaces 
 
 Fig. 387. Magnetization by Double Touch. 
 
 at the corners being filled with pieces of soft iron. 
 The horseshoe magnet N S, is then moved around 
 the circuit several times in the same direction. 
 This is believed t3 produce a more uniform mag- 
 
 netization than the ordinary method of double 
 touch. 
 
 Magnetization, Co-efficient of A 
 
 number representing the intensity of magnet- 
 ization produced in a magnetizable body, 
 divided by the magnetizing force H. 
 
 Calling k, the co-efficient of magnetization ; I, 
 the intensity of the resulting magnetization, and 
 H, the magnetizing force producing it, then 
 I 
 
 k = 
 
 II 
 
 The co-efficient of magnetization is sometimes 
 called the magnetic susceptibility. 
 
 A paramagnetic body when placed in a mag- 
 netic field concentrates the lines of magnetic force 
 on it, or causes them to pass through it. The 
 intensity of the magnetization so produced de- 
 pend*, therefore, 
 
 (i.) On the intensity of the magnetizing field. 
 
 (2.) On the ability of the metal to concentrate 
 the lines of force on it; that is, on the nature of 
 the metal, or on its magnetic permeability. (See 
 Permeability, Magnetic. Paramagnetism. Dia- 
 magnetism. ) 
 
 The intensity of magnetization will, therefore, 
 be equal to the product of the co- efficient of mag- 
 netization and the intensity of the magnetizing 
 field. It will, also, of course, depend on the area 
 of cross-section of the magnetized body. 
 
 The co-efficient of magnetization of paramag- 
 netic bodies is said to be positive, and that of dia- 
 magnetic bodies to be negative, because paramag- 
 netic bodies concentrate the lines of magnetic 
 force on them, while diamagnetic bodies appear 
 to repel the lines of force. (See Paramagnetic. 
 Diamagnetic. ) 
 
 Magnetization, Critical Current of 
 
 The current at which any certain or definite 
 effect of magnetization is produced. 
 
 Magnetization, Intensity of A 
 
 quantity showing the intensity of the magnet- 
 ization produced in a substance. 
 
 A quantity showing the intensity with 
 which a magnetizable substance is mag- 
 netized. 
 
 The intensity of magnetization depends: 
 
 (i.) On the intensity of the magnetizing field. 
 
 (2.) On the magnetic permeability, or on the 
 conducting power of the substance for lines of 
 magnetic force. 
 
352 
 
 [Hag. 
 
 The greater the strength of the magnetizing 
 field, and the greater the magnetic permeability, 
 the greater is the intensity of the magnetization 
 produced. 
 
 When, therefore, a magnetizable substance is 
 placed in a magnetizing field, the intensity of the 
 magnetization will depend on the magnetic sus- 
 ceptibility of the substance ; that is, on the ratio of 
 the induced magnetization to the magnetizing force 
 producing it. 
 
 Soft iron has a high co-efficient of magnetization, 
 or its magnetic susceptibility is high. (See Sus- 
 ceptibility, Magnetic. Magnetization, Co-ejficient 
 of-} 
 
 The intensity of magnetization through a sub- 
 stance is measured by dividing the magnetic 
 moment by the magnetic volume. 
 
 If a bar of soft iron is placed with its greatest 
 length extending in the direction of the lines of 
 force in a magnetic field, it will have induced in 
 it a certain intensity of magnetization which may 
 be expressed as follows: 
 
 Intensity of Magnetization = ^r-p = k H, 
 
 where m, equals the strength of the magnet ; 1, its 
 length ; k, the co-efficient of magnetization, and 
 H, the intensity of the magnetizing field. (S. P. 
 Thompson.) 
 
 " The moment of a magnet, or of any element 
 of a magnet, may be considered numerically to be 
 made up of two factors, one, its volume, and the 
 other its intensity of magnetization, or simply 
 its magnetization, and hence, for a uniformly mag- 
 netized small linear needle, we may define the 
 intensity of its magnetization by saying that it has 
 magnetic moment of unit volume." (Fleming.) 
 
 Magnetization, Maximum A term 
 
 sometimes used for magnetic saturation. 
 
 Urquhart states, as the result of numerous ex- 
 periments, that the number of lines of magnetic 
 force that usually pass through a bar of soft iron 
 I square centimetre in area of cross- section, when 
 magnetized to a maximum, is equal to 32,000. 
 Ewing gives the number in the particular case of 
 a very extraordinary magnetization as being equal 
 to 45,350 per square centimetre area of cross- 
 section. 
 
 Magnetization, Methods of 
 
 Mag- 
 
 netization effected either by induction from 
 another magnet, or by means of induction by 
 an electric current. 
 
 The substance to be magnetized is brought into 
 a magnetic field, so that the lines of magnetic 
 force pass through it. All methods of magnet- 
 ization may be divided into methods of magnetiza- 
 tion by touch, and magnetization by the electric 
 current. (See Magnetization by Touch.) 
 
 Magnetization, Permanent, Intensity of 
 
 A term employed for the intensity of 
 
 a permanent magnetization produced in hard 
 steel, as distinguished from the magnetization 
 temporarily produced in soft iron. (See Mag- 
 netization, Intensity of) 
 
 Magnetization, Temporary, Intensity of 
 
 The intensity of the magnetization 
 
 temporarily induced in a bar of soft iron, as 
 distinguished from permanent magnetization 
 induced in hard steel. (See Magnetization, 
 Intensity of.) 
 
 Magnetization, Time-Lag of A lag 
 
 which appears to exist between the time of 
 action of the magnetizing force and the ap- 
 pearance of the magnetism. 
 
 The time which must elapse in the case of 
 a given paramagnetic substance before a mag- 
 netizing force can produce magnetization. 
 
 In the opinion of some physicists there is no 
 such thing as a true magnetic time-lag, the ap- 
 parent time-lag being due entirely either to hys- 
 teresis or to eddy currents. According to them, 
 while the magnetizing force is increasing, it pro- 
 duces, in the iron, reversely-directed surface- 
 eddy-currents, which produce a reversed or 
 opposed magnetizing force in the more deeply 
 seated layers of the iron, the time-lag being due 
 to the interval which is required for these eddy 
 currents to die away and thus permit the mag- 
 netizing force to produce its full magnetization. 
 
 According to others, however, a true time- 
 lag does exist entirely apart from the existence of 
 surface-eddy-currents. 
 
 Magnetize. To endow with magnetic 
 properties. 
 
 Magnetized. Endowed or impressed with 
 magnetic properties. 
 
 Magnetizing. Causing or producing mag- 
 netism. 
 
 Magneto-Blasting Machine. (See Ma- 
 chine, Magneto-Blasting?) 
 
Mag/ 353 
 
 Magneto-Electric Bell. (See Bell, Mag- 
 neto-Electric.) 
 
 Magneto-Electric Brake. (See Brake, 
 Magneto-Electric.) 
 
 Magneto-Electric Call-Bell. (See Call- 
 fell, Magneto-Electric.) 
 
 Magneto-Electric Faradic Apparatus. 
 
 (See Apparatus, Faradic, Magneto-Elec- 
 tric.) 
 
 Magneto-Electric Induction. (See In- 
 duction, Magneto-Electric.) 
 
 Magneto-Electric Machine. (See Ma- 
 chine, Magneto-Electric) 
 
 Magneto-Electric Medical Apparatus. 
 (See Apparatus, Magneto-Electric Medi- 
 cal) 
 
 Magneto-Electricity, (See Electricity, 
 Magneto) 
 
 Magnetograph. The permanent record 
 obtained from the action of a self-recording 
 magnetometer. (See. Magnetometer, Self- 
 Jtecording.) 
 
 Magnetometer. An apparatus for the 
 measurement of magnetic force. 
 
 [Mag. 
 
 The magnetometer shown in Fig. 388, consists 
 of a magnetized bar suspended by two wires pass- 
 ing over a pulley, as shown. The magnet is held 
 by the frame S S, provided with a graduated scale 
 K. The mirror S, is supported by a vertical post 
 attached to the frame, and serves to reflect a scale 
 placed below a distant reading telescope. This 
 form of magnetometer, is called the bitilar mag- 
 netometer, and was the one used by Gauss in his 
 study of the earth's magnetism. 
 
 A variety of forms have been given to delicate 
 magnetometers. Some are self-recording. (See 
 Magnetometer, Self-Recording.) 
 
 Magnetometer, Differential A form 
 
 of magnetometer in which the principles of the 
 differential galvanometer, as applied to the 
 electric circuit, are applied to the magnetic 
 circuit. 
 
 The differential magnetometer of Eickemeyer is 
 shown in Figs. 389 and 390. Its principles of 
 operation will be understood from the following 
 considerations. 
 
 Referring to Fig. 389. Suppose Fj and F 2 are 
 two electromotive forces connected in series, and 
 x and y, two resistances to be compared. Each of 
 the resistances x and y, is shunted respectively by 
 two conductors a and b, whose resistance we 
 wish to compare. Since the action of each of 
 them on the galvanometer G, is opposite, its nee- 
 dle remains at zero, when the current in a, is 
 equal to the current in b. 
 
 If, instead of electric circuit, we take the idea 
 of magnetic circuit or the number of lines of 
 magnetic force, and instead of potential difference, 
 
 Fig 388. Magnetometer. 
 
 In some magnetometers the magnetic force is 
 measured by the torsion of a wire, as in the tcr- 
 ion balance. (See Balance, Coulomb' 1 s Torsion.) 
 
 Fig. 389. Eickemeyer' s Differential Magnetometer. 
 
 magneto-motive force, and instead of electric re 
 sistance, magnetic resistance, we have the princi- 
 ples on which the Eickemeyer differential magnet- 
 ometer is founded. 
 
 The magnetic circuit of the differential magnet- 
 ometer consists of two pieces ot soft iron, shaped 
 
Mag.J 
 
 354 
 
 [Mag. 
 
 as shown at Fj and F 8 , Fig. 390. A magnetic 
 coil C, surrounds the middle portion of each cir- 
 cuit as shown. The operation as described by 
 Mr. Chas. Steinmetz, from whom the above de- 
 scription is mainly taken, is as follows, viz. : ' ' The 
 front part Sj of the left iron piece becomes south, 
 and the back part n 1 north polarity; the front 
 part of the right iron piece n g becomes north, and 
 the back part south; and the lines of magnetic 
 force travel in the frant from the right to the left, 
 from n s to B! ; in the back the opposite way, from 
 the left to the right, or from HJ to S;, either 
 through the air, or, when n 2 and s x , or n l and s 2 , 
 are connected by a piece of magnetizable metal, 
 through this and through the air. 
 
 In the middle of the coil C, stands a small soft 
 iron needle with an aluminum indicator, which 
 plays over a scale K, and is held in a vertical 
 position by the lines of magnetic force of the coil 
 C, itself, deflected to the left by the lines of mag- 
 netic force traversing the front part of the instru- 
 ment from n a to Sj, deflected to the right by the 
 lines traversing the back from n a to s 2 . This 
 needle shows by its zero position that the mag- 
 netic flow through the air in front from n 3 to Sj 
 has the same strength as the magnetic flow in the 
 back from n^ to s a through the air. 
 
 Now we put a piece of soft iron x on the front 
 of the instrument. A large number of lines go 
 through x, less through the air from n 3 to Sj ; but 
 all these lines go from n , to s 2 through the air 
 at the back part of the magnetometer, the front 
 part and back part of the instrument being con- 
 nected in series in the magnetic circuit. There- 
 fore the needle is deflected to the right by the 
 magnetic flow in the back of the instrument. 
 
 Now, we put another piece of iron, y, on the 
 back part of the instrument, then equilibrium 
 would be restored as soon as the same number of 
 lines of magnetic force go through x, as through 
 y, because then also the same number of lines go 
 through air in the front as in the back. As will 
 be noted, the air here takes the place of the resist- 
 ances a and b, influencing the galvanometer 
 needle G, as in the diagram Fig. 389. 
 
 The operation of the instrument is exceedingly 
 simple and is as follows : Into the coil C, an elec- 
 tric current is sent which is measured by the am- 
 meter A, and regulated by the resistance-switch 
 R. Then the needle, which before had no fixed 
 position, points to zero. 
 
 Now, we lay the piece of iron, the magnetic 
 properties of which we want to determine, on the 
 
 back part of the instrument. The needle is de- 
 flected to the left. On the front of the instrument 
 we put Norway iron rods of known cross-section 
 and known conductivity, until equilibrium is 
 again restored. Then the iron in the front has 
 the same magnetic resistance as the iron in the 
 back, and the ratio of the cross- sections gives 
 directly the ratio of the conductivities ; so that 
 by a single reading the magnetic conductivity of 
 any piece of iron can be compared with that of 
 the Norway iron standard. 
 
 For absolute determinations, the iron is turned 
 off into pieces of exactly 4 square centimetres 
 cross-section and 20 centimetres in length, both 
 ends fitting into holes in large blocks of Norway 
 iron, which are laid against the pole pieces of the 
 magnetometer, so that the transient resistance 
 from pole face to iron is eliminated. 
 
 Fig. 3 go. Eickemeyer" s Differential Magnetometer, 
 
 Magnetometer, Self-Recording A 
 
 self-recording apparatus, by means of which 
 the daily and hourly variations of magnetic 
 needles in the earth's field, at any locality, are 
 continuously registered. 
 
 The self recording magnetometer employed in 
 the observatory at Kew, consists essentially of 
 means of obtaining a photographic record of a 
 spot of light reflected from a mirror, attached to 
 the needle whose variations are to be recorded. 
 The photographic record is received on a strip of 
 sensitized paper, maintained in uniform and con- 
 tinuous motion by means of suitable clock-work. 
 The record so obtained is called a magneto- 
 graph. 
 
 Magneto-Motive Force. (See Force, 
 Magneto-Motive?) 
 
355 
 
 [M.ak. 
 
 Magneto-Motive Force, Absolute Unit of 
 
 (See Force, Magneto-Motive, Abso- 
 lute Unit oft 
 
 Magneto-Motive Force, Practical Unit of 
 (See Force, Magneto-Motive, Prac- 
 tical Unit of.) 
 
 Magneto-Optic Rotation. (See Rotation, 
 Magneto-Optic) 
 
 Magnetophone. A species of magnetic 
 siren in which sounds are produced in an 
 electro-magnetic telephone by the periodic 
 currents produced in its coils by the rotation 
 ef a perforated metallic disc in a magnetic 
 field. 
 
 As the speed of the disc increases, the pitch of 
 the note increases. The apparatus was invented 
 by Prof. Carhart, in 1883. A similar apparatus 
 is useful in studying the distribution of the mag- 
 netic field of a dynamo-electric machine. In this 
 case, a small, thin coil of insulated wire is held in 
 the different regions around the machine, while 
 the telephone is held to the ear of the observer. 
 Magnetic leakage, or useless dissipation of lines 
 of magnetic force outside the field proper of the 
 machine, is at once rendered manifest by the 
 musical note caused by variations in the intensity 
 of the field. 
 
 Since the intensity of the note heard will vary 
 according to the intensity of the field, and also 
 according to the position in which the coil is held, 
 such a coil becomes a magnetic explorer, and by 
 its use the distribution and varying intensity of an 
 irregular field can be ascertained. Its use is 
 especially advantageous in proportioning dynamo- 
 electric machines and electric motors. (See Ex- 
 plorer, Magnetic. ) 
 
 Magneto-Receptive Device. (See Device, 
 Magneto-Receptive?) 
 
 Magneto-Static Current "Meter. (See 
 Meter, Current, Magneto-Static?) 
 
 Magneto-Static Screening. (See Screen- 
 ing, Magneto-Static?) 
 Magneto-Statics. (See Statics. Magneto?) 
 
 Magneto-Therapy. (See Therapy, Mag- 
 neto?) 
 
 Main Battery. (See Battery, Main.) 
 Main-Battery Circuit. (See Circuit, 
 Ma in-Battery?) 
 
 Main, Electric The principal con- 
 ductor in any system of electric distribution. 
 
 Main Feeder. (See Feeder, Standard or 
 Main?) 
 
 Main Fuse. (See Fuse, Main?) 
 
 Main, House A term employed in 
 
 a system of multiple incandescent lamp dis- 
 tribution for the conductor connecting the 
 house service conductors with a centre of 
 distribution, or with a street main. 
 
 Main-Line Cut-Out. (See Cut-Out, Main- 
 Line?) 
 
 Main, Street In a system of incan- 
 descent lamp distribution the conductors ex- 
 tending in a system of networks through the 
 streets from junction box to junction box, 
 through which the current is distributed 
 from the feeder ends, through cut-outs, to 
 the district to be lighted, and from which 
 service wires are taken. 
 
 Main, Sub A name sometimes 
 
 given to the distributing conductor that is 
 connected directly to a main. 
 
 The branch nearest the main. (See 
 Branch?) 
 
 Main Wire. (See Wire, Main?) 
 
 Mains of Electric Railroads. The wires 
 or conductors used for carrying the current 
 from the feeders through the tap wires to the 
 trolley wires. 
 
 Make. A completion of a circuit. 
 
 Make-and-Break. The periodic alternate 
 completion and opening of a circuit. 
 
 Make-and-Break, Automatic A 
 
 term sometimes employed for such a combi- 
 nation of contact points with the armature of 
 any electro-magnet, that the circuit is auto- 
 matically made and broken with great rapidity. 
 
 An automatic make-and-break is used in most 
 forms of electric alarms in connection with some 
 form of electric bell. (See Alarm, Electric.) 
 
 It is also used in the Ruhmkorff ind action coil 
 in order to produce the variations in the primary 
 circuit. (See Coil, Induction.) 
 
 Make-Induced Current. (See Current, 
 Make-Induced?\ 
 
Mak,] 
 
 356 
 
 [Mar. 
 
 Making- the Primary. (See Primary, 
 Making the.) 
 Mallet, Electro-Magnetic Dental 
 
 (See Dental-Mallet, Electro-Magnetic.) 
 Mangin Projector. (See Projector, Man- 
 
 &*} 
 
 Man-Hole, Compartment, of Conduit 
 
 A man-hole provided with suitably sup- 
 ported shelves or compartments, guarded by 
 locked doors that protect different cable sec- 
 tions. 
 
 Man-Hole of Conduit. An opening of 
 sufficient size to admit a man, communi- 
 cating from the surface of the roadbed with 
 an underground conduit. 
 
 Manipulator, Breguet's The send- 
 ing instrument employed by Breguet in his 
 system of step-by-step or dial telegraphy. 
 (See Telegraphy, Step-by-Step.) 
 
 Manometei. An apparatus for measuring 
 the tension or pressure of gases. 
 
 Manometers are either mercurial or metallic. 
 Mercurial manometers are of two classes, viz., 
 manometers with free air and manometers with 
 compressed air. 
 
 Manometers measure the pressure of gases 
 either in atmospheres, i. e., in multiples or deci- 
 mals of 15 pounds to the square inch, or in inches 
 of mercury. 
 
 Map or Chart, Inclination A chart 
 
 or map on which lines are drawn, showing 
 the lines of equal dip or inclination, or the 
 isoclinic lines. 
 
 An inclination chart is shown in Fig. 391. 
 
 It will be seen that the magnetic equator, or 
 line of no dip, does not correspond with the geo- 
 graphical equator, being generally north of the 
 equator in the Eastern Hemisphere, and south of 
 it in the Western. The figures attached to the 
 lines indicate the value of the angle of dip. 
 
 Map or Chart, Isodynamic A map 
 
 of the earth on a mercator's projection, on 
 which isodynamic lines are drawn. 
 
 An isodynamic chart is shown in Fig. 392. It 
 will be observed that the isodynamic lines do not 
 exactly coincide with the isoclinic lines, since the 
 line of least magnetic intensity does not correspond 
 with the line of the magnetic equator. 
 
 The point of least magnetic intensity is found at 
 
 about lat. 20 degrees S., and Ion. 35 degrees W. 
 The point of greatest magnetic intensity is found 
 at about lat. 52 degrees N. and Ion. 92 degrees 
 VV. 
 
 Another, though weaker point of magnetic in- 
 tensity, is found in Siberia. These are distin- 
 guished from the true magnetic poles by the term 
 Poles of Intensity. 
 
 The Poles of Vertuity, as determined by the 
 dipping needle, and the Poles of Intensity, as de- 
 termined by the needle of oscillation, therefore do 
 not coincide in the Northern Hemisphere. 
 
 Map or Chart, Isogonal A term 
 
 sometimes used for an isogonic map or chart. 
 
 Map or Chart, Isogonic A chart 
 
 on which the isogonal lines are marked. 
 
 An isogonic map or chart is sometimes called 
 a declination map or chart . 
 
 In the declination or variation chart, shown in 
 Fig. 393, the region of western declination is in- 
 dicated by the shading. There is a remarkable 
 oval patch in the northeastern part of Asia, in 
 which the declination is west A similar oval of 
 decreased inclination is seen in the Southern 
 Pacific. 
 
 The entire earth acts like a huge magnet with 
 south magnetic polarity in the Northern Hemi- 
 sphere. 
 
 It is not known whether the earth possesses 
 but a single pair of magnetic poles or more 
 than a single pair. The variations in the dec- 
 lination, and in the intensity of its magnetism, 
 due to the position of the sun, ss well as the 
 marked magnetic disturbances that accompany 
 the occurrence of sun spots, would appear to con- 
 nect the earth's magnetism in some manner with 
 the solar radiation. (See Magnetism, Earth's, 
 Theories as to Cause of.) 
 
 Marine Galvanometer. (See Galvanom- 
 eter, Marine.) 
 
 Mariner's Compass. (See Compass, Azi- 
 muth.) 
 
 Marked Pole of Magnet. (See Magnet, 
 Marked Pole of.) 
 
 Markers. Colored flags, or signal lights, 
 generally green, displayed in systems of 
 block railway signaling at the ends of 
 trains, in order to avoid accidents from trains 
 breaking in two. (See Railroads, Block 
 System for.) 
 
Mar.] 
 
 357 
 
 [Mar. 
 
Mar.] 
 
 358 
 
 [Mar. 
 
Mar.] 
 
 359 
 
 [Mar. 
 
Mas.] 
 
 360 
 
 [Mat. 
 
 Mass. The quantity of matter contained 
 in a body. 
 
 Mass must be carefully distinguished from 
 weight. The weight of a given quantity of 
 matter depends on the attraction which the earth 
 possesses for it, and this, on the earth's surface, 
 varies with the latitude, being greatest at the 
 poles and least at the equator. It also varies 
 with different elevations above the level of the sea. 
 The mass, however, is the same under all circum- 
 stances, whether for different latitudes or alti- 
 tudes, on the earth's surface. 
 
 Mass Attraction. (See Attraction, Mass.] 
 
 Mass, Magnetic A quantity of mag- 
 netism which at unit distance produces an 
 action equal to unit force. 
 
 Mass, Unit of The quantity of mat- 
 ter which under certain conditions will balance 
 the weight of a standard gramme or pound. 
 
 The gramme is equal to the one-thousandth 
 part of a piece of platinum called the kilogramme, 
 deposited as a standard in the archives of the 
 French Government, and intended to be equal to 
 the mass of I cubic centimetre of water at the tem- 
 perature of its maximum density. 
 
 Massage. A treatment for the purpose 
 of effecting changes in general nutrition or 
 action of particular parts of the body, by 
 kneading, rubbing, friction, etc. 
 
 Electro The application 
 
 of electricity to the body during its massage. 
 Connections are established between the patient 
 and a battery by connecting one electrode of a 
 source to the kneading instrument, and the other 
 electrode to the body of the patient. 
 
 Masses, Electric A mathematical 
 conception for such quantities of electricity 
 as at unit distance will produce an attrac- 
 tion or repulsion equal to unit force. 
 
 Electrical masses are assumed to be equal when 
 they produce on two identical bodies of small 
 dimensions charges of the same electric force. 
 
 Master Clock. (See Clock, Master.) 
 Materials, Insulating Non-con- 
 ducting substances which are placed around a 
 conductor, in order that it may either retain 
 an electric charge, or permit the passage of 
 
 an electric current through the conductor 
 without sensible leakage. 
 
 Various gases, liquids or solids may be em- 
 ployed as insulators. A very high vacuum affords 
 the best known insulation. 
 
 Matter. Anything which occupies space in 
 three directions and prevents other matter from 
 simultaneously occupying the same space. 
 
 Matter is composed of atoms, which unite to 
 form molecules. (See Atom. Molecule. ) 
 
 Matter, Elementary Matter which 
 
 cannot be decomposed into simpler matter. 
 
 Varieties of elementary matter are called 
 elements. (See Element. ) 
 
 Matter, Kinetic Theory of -.A 
 
 theory which assumes that the molecules of 
 matter are in a constant state of motion or 
 vibration towards or from one another in 
 paths that lie within the spheres of their 
 mutual attractions or repulsions. 
 
 The molecules of gases have great freedom 
 of motion, and are so far removed from one 
 another as to be but little, if any, influenced by 
 their mutual attractions. They are therefore 
 assumed to move in s-traight lines with very great 
 velocity until they collide against one another, or 
 against the sides of the containing vessel, when 
 they are reflected and again move in straight lines 
 in a new path. 
 
 Matter, Radiant, or Ultra-Gaseous 
 
 A term proposed by Crookes for the 
 peculiar condition of the gaseous matter which 
 constitutes the residual atmospheres of high 
 vacua. 
 
 This is now generally recognized as a fourth 
 state of matter, these four states being: 
 
 (i.) Solid. 
 
 (2.) Liquid. 
 
 (3.) Gaseous. 
 
 (4. ) Ultra-gaseous or radiant. 
 
 The peculiar properties of radiant matter are 
 seen in the mechanical effects of the localized 
 pressures produced when such residual atmos- 
 pheres are locally heated or electrified. 
 
 In Crookes* radiometer, vanes of mica, silvered 
 on one face and covered with lampblack on the 
 opposite face, are supported on a vertical axis so 
 as to be capable of rotation and placed in a glass 
 vessel in which a high vacuum is maintained. On 
 
MatJ 
 
 361 
 
 [Mat. 
 
 exposing the instrument to the radiation from a 
 candle or gas flame, a rapid rotation takes place. 
 (See Radiometer, Crookes' .) 
 
 The explanation is as follows : The lampblack 
 covered surfaces absorb the radiant heat, and be- 
 coming heated, the molecules of gas in the residual 
 atmosphere are shot violently from them, and by 
 their reaction drive the vanes around in the 
 opposite direction to that from which they are 
 thrown off. The molecules are also shot off from 
 the silvered surfaces, but, as these are cooler, the 
 effect is not as great as at the blackened surfaces. 
 
 In a gas, at ordinary pressure, the heated sur- 
 faces are also bombarded by other molecules of 
 the gas, but in high vacua the mean free path of 
 the molecules is so great that there is no interfer- 
 ence, a Crookes 1 layer existing between the vanes 
 and the walls of the glass vessel. (See Layer^ 
 Crookes\) 
 
 When a Crookes' tube is furnished with suit- 
 able electrodes, and electric discharges are sent 
 through it between these electrodes, a stream of 
 molecules is thrown off in straight lines from the 
 surface of the negative electrode, 
 
 Some of the effects of this molecular bombard- 
 ment are seen by the use of the apparatus shown 
 in Fig. 394. When the positive and negative 
 
 Fig. 394* Effects of Molecular Bombardment. 
 
 terminals are arranged as shown, the paths of the 
 molecular streams are seen as luminous streams 
 whose directions are those shown in the figures. 
 
 The figure on the left shows the path taken in 
 a low "vacuum. Streams pass from the negative 
 electrode to each of the positive electrodes. 
 
 The figure on the right shows the discharge in 
 a high vacuum. Here the streams pass off at 
 right angles to the face of the negative electrode, 
 
 and proceed therefrom in straight lines, inde- 
 pendently of the position of the positive electrode. 
 Since, therefore, the negative electrode at a, is in 
 the shape of a concave mirror, the luminous 
 particles converge to a focus near the centre of 
 the glass vessel, and then diverge to the opposite 
 wall. 
 
 Refractory substances placed at such a focus of 
 molecular bombardment, as shown in Fig. 395, are 
 rendered incandescent. 
 
 In a similar manner, phosphorescent substances 
 exposed to such molecular streams emit a beauti- 
 
 Forces cf Molecular Bombardment. 
 
 ful phosphorescent light. (Sea Phosphorescence, 
 Electric.) 
 
 Matter, Thomson's Hypothesis of 
 
 A hypothesis as to the structure of matter 
 suggested by Sir William Thomson, in order 
 to show how the extremely tenuous ether 
 might possess rigidity. 
 
 The fact that the ether, although a fluid sub- 
 stance, possesses the properties of a rigid solid, 
 has given no little trouble to physicists. Thomson 
 explains this rigidity of the ether as being due to 
 a rapid motion in its fluid particles. 
 
 A perfectly flexible rubber tube filled with 
 water or other fluid, possesses, when at rest, a 
 very great degree of flexibility. When in mo- 
 tion, however, the tube becomes more and more 
 rigid, as the flow increases in rapidity. Thorn- 
 
Mat. 
 
 362 
 
 [Ked. 
 
 son imagines the ether to be set in motion in 
 minute vortex rings, and shows that a readily 
 movable fluid body, like ether, once set in such 
 motion should possess the properties of a solid. 
 In a perfect fluid, such as ether, these vortex 
 rings once formed, would be practically imperish- 
 able or indestructible. 
 
 Thomson regards the atoms of matter as con- 
 sisting of such vortex rings. Vortex rings can be 
 formed in the air by cutting a circular aperture 
 in the end of a pasteboard box, and tapping 
 sharply against the end of the box. In order to 
 render the rings visible, the box may be previously 
 filled with smoke. 
 
 Vortex rings formed in smoky air differ from 
 vortex rings in the ether, in the fact that air is 
 not a perfect fluid, while ether is. Air vortex 
 rings increase in size and decrease in energy. 
 Vortex rings of the ether would not vary in size. 
 
 According to Thomson's vortex theory of 
 matter, the atoms of matter are the same as the 
 ether which surrounds them. They cannot be 
 produced in ether by any known way ; therefore, 
 they cannot be manufactured, or, as it were, 
 created. Nor, on the other hand, can they be 
 destroyed; in other words, they are indestruct- 
 ible. They are elastic, capable of definite vibra- 
 tions, possess all the properties of matter save, in 
 the opinion of some, the very important prop- 
 erty of gravitation. As Prof. Lodge points out, 
 the fact that this property is not present should 
 cause Sir William Thomson's theory of matter to 
 be accepted with considerable hesitation. 
 
 Matthiessen's Metre-Gramme Standard. 
 
 (See Metre-Gramme Standard, Matthies- 
 sen's.) 
 
 Matthiessen's Mile Standard. (See Mile 
 Standard, Matthiessen's.) 
 
 Matting, Invisible Electric Floor 
 
 A matting or other floor covering, provided 
 with a series of electric contacts, which are 
 closed by the passage of a person walking 
 over them. 
 
 This matting is provided as an adjunct to a 
 system of burglar alarms. The electric bell or 
 annunciator, connected with the different con- 
 tacts, is disconnected during the day-time, or while 
 the rooms are occupied. (See Alarm, Burglar. ) 
 
 Maximum Magnetization. (See Mag- 
 netization, Maximum^ 
 
 Mclntire's Parallel Sleeve Telegraphic 
 Joint. (See Joint, Telegraphic, Mclntire's 
 Parallel Sleeved) 
 
 Measurements, Electric Deter- 
 minations of the values oi the electromotive 
 force, resistance, current, capacity, energy, 
 etc., in any electric circuit. 
 
 Electric m easurements may be either qualitative 
 or quantitative. 
 
 In qualitative electric measurements the rela- 
 tive values only are obtained; in quantitative 
 measurements the actual values are obtained. 
 
 Mechanical Alarm, Electric (See 
 Alarm, Electro-Mechanical.} 
 
 Mechanical Electric Bell. (See Bell, 
 Electro-Mechanical.) 
 
 Mechanical Equivalent of Heat. (See 
 Heat, Mechanical Equivalent of.) 
 
 Mechanical Mine. (See Mine, Mechani- 
 cal.) 
 
 Mechanical Throwback Indicator. 
 
 (See Indicator, Mechanical Throwback.) 
 
 Medical Induction Coil. (See Coil, In- 
 duction Medical.) 
 
 Medical Magneto-Electric Apparatus. 
 
 (See Apparatus, Magneto-Electric Medi- 
 cal.) 
 
 Medium, Anisotropic A medium 
 
 in which equal stresses do not produce equal 
 strains when applied in different directions. 
 
 A medium, homogeneous in structure like 
 crystalline bodies, but possessing different 
 powers of specific inductive capacity in differ- 
 ent directions. 
 
 An eolotropic medium. (See Medium, 
 Eolotropic.) 
 
 The latter term is used to distinguish it from 
 an isotropic medium. (See Medium, Isotropic.) 
 
 Medium, Eolotropic A medium 
 
 in which equal stresses do not produce the 
 same strains when applied in different direc- 
 tions. (See Medium, Isotropic.) 
 
 Medium, Electro-Magnetic Any 
 
 medium in which electro-magnetic phenom- 
 ena occur. 
 
 The medium through which electro-magnetic 
 waves are propagated is now universally re- 
 
Med.J 
 
 363 
 
 [Viet. 
 
 garded as the luminiferous or universal ether. 
 (See Electricity, Hertz's Theory of Electro-Mag- 
 netic Radiations or Waves,} 
 
 Medium, Iso tropic A medium in 
 
 which equal stresses applied in any direction 
 produce equal strains. 
 
 A transparent medium which possesses the 
 same optical or electric properties in all di- 
 rections. 
 
 An optically homogeneous, transparent 
 medium. 
 
 Such media are called isotropic to distinguish 
 them from anisotropic or eolotropic, or those in 
 which equal stresses produce unequal strains in 
 different directions. (See Medium, Anisotropic. 
 Medium, Eolotropic.) 
 
 Meg or Mega (as a prefix). 1,000,000 
 times ; as, megohm, 1,000,000 ohms ; mega- 
 volt, 1,000,000 volts. 
 
 Megaloscope, Electric An appara- 
 tus for the medical exploration of the cavities 
 of the body. 
 
 The light necessary for exploration is obtained 
 from a small incandescent lamp placed at the 
 extremity of a tube, suitably shaped for introduc- 
 tion into the special organ for which it is devised. 
 The organ so illumined throws its light on a 
 prism, by means of which the light is caused to 
 pass through a series of lenses by which it is 
 viewed . 
 
 Megavolt. 1,000,000 volts. 
 Megohm. 1,000,000 ohms. 
 
 Meidinger Yoltaic Cell. (See Cell, Vol- 
 taic, Meidinger?) 
 
 Memory, Magnetic A term pro- 
 posed by J. A. Fleming for coercive force. 
 
 Soft iron has but a feeble memory of its past 
 magnetization. 
 
 Mercurial Connection. (See Connection, 
 Mercurial?) 
 
 Mercurial Contact. (See Connection, 
 Mercurial?) 
 
 Mercurial Temperature Alarm. (See 
 
 Alarm, Mercurial Temperature?) 
 Mercury Break. (See Break, Mercury?} 
 Mercury Cup. (See Cup, Mercury?) 
 
 Meridian, Astronomical - 
 
 circle passing through any 
 
 A great 
 
 point in the 
 
 heavens, and the North and South poles of 
 the heavens. 
 
 The astronomical meridian corresponds to the 
 geographical meridian. The former is considered 
 as passing around the dome of the heavens; the 
 latter, around the surface of the earth. In order 
 to locate any point in the heavens, a great circle 
 of the heavens is caused to pass through that point 
 and through the astronomical North and South 
 poles. 
 
 Meridian, Geographical The geo- 
 graphical meridian of a place is a great circle 
 passing through that place and the North and 
 South geographical poles of the earth. 
 
 Meridian, Magnetic The magnetic 
 
 meridian of any place is the meridian which 
 passes through the poles of a magnetic needle 
 at that place when in a position of rest under 
 the free influence of the earth's magnetism. 
 
 The plane of the magnetic meridian at any place 
 is a vertical plane pa-sing through the poles of a 
 magnetic needle in a position of rest under the 
 free influence of the earth's magnetism at that 
 place. 
 
 The magnetic meridian may be regarded as the 
 vertical plane in which a freely suspended mag- 
 netic needle comes to rest in the earth's magnetic 
 field. 
 
 Meridional. Pertaining to the meridian. 
 Message Wire. (See Wire, Message?) 
 Messenger Call. (See Call, Messenger.) 
 Metallic Arc. (See Arc, Metallic.) 
 
 Metallic Circuit. (See Circuit, Metal- 
 lic?) 
 
 Metallic Coating. (See Coating, Metal- 
 lic?] 
 
 Metallic Conducting Joint. (See/0//, 
 Metallic Conducting?) 
 
 Metallic Contact. (See Contact, Metal- 
 lic?) 
 
 Metallic Electric Conduction. (See 
 Conduction, Electric, Metallic.) 
 
 Metallization. The rendering of a non~ 
 conducting surface electrically conducting by 
 covering it with a metallic coating, so u.i to 
 
Mol.J 
 
 364 
 
 [Met. 
 
 enable it to readily receive a metallic coating 
 by electro-plating. (See Plating, Electro?) 
 
 Metallochromes. A name sometimes 
 given to Nobili's rings. (See Rings, No- 
 bili's.) 
 
 Metalloid. A name formerly applied to a 
 non-metallic body, or to a body having only 
 some of the properties of a metal, as carbon, 
 boron, oxygen, etc. 
 
 The term is now but little used. 
 
 Metallurgy, Electro That branch 
 
 of applied science which relates to the elec- 
 trical reduction or treatment of metals. 
 
 Metallurgical processes effected by the 
 agency of electricity. 
 
 Electro-Metallurgy embraces : 
 
 (i.) The reduction of metals from their ores, 
 either directly during fusion by the heat of the 
 voltaic arc, or the heat of incandescence, or by 
 the electrolysis of solutions of their ores, or ores 
 in the fused state. (See Electrolysis. Furnace, 
 Electric.) 
 
 (2.) Electroplating. 
 
 (3.) Electrotyping. 
 
 The application of electricity to the reduction 
 of metals is carried on in the electric furnace for 
 the reduction of the aluminium ores, for example. 
 
 Metals, Electric Deflagration of 
 
 The volatilization of metals by electric in- 
 candescence. 
 
 Metals, Electric Refining of - 
 Purifying metals by means of electricity. 
 
 Different methods are employed for the electric 
 refining of metals. They are generally electro- 
 lytic in character. 
 
 Metals, Electrical Protection of 
 
 The protection of a metal from corrosion by 
 placing it in connection with another metal, 
 which, when exposed to the corroding liquid, 
 vapor or gas, will form with the metal to be 
 protected the positive element of a voltaic 
 couple. 
 
 The negative element of a voltaic couple is 
 protected by the presence of the positive element, 
 which is alone corroded. This method has been 
 adopted with considerable success to electrically 
 protect metals from corrosion. 
 
 The following are examples of this protection : 
 
 (I.) Davy proposed to protect the copper 
 
 sheathing of ships from corrosion by attaching 
 pieces of zinc to the copper sheathing. This 
 succeeded too well, since the copper salts which 
 were formerly produced, and acted as a poison 
 to the marine plants and animals, being now 
 absent, permitted these organisms to thrive to 
 such an extent as to seriously foul the ship's 
 bottom. 
 
 (2.) A ring of zinc attached to a lightning rod, 
 near its points, has, it is claimed, the power of 
 protecting the points from corrosion. 
 
 (3.) Iron bars of railings, if sunk or embedded 
 in zinc, are preserved from corrosion near the 
 junction of the two metals, but if sunk in lead are 
 rapidly corroded, because iron is electro-positive 
 to lead, but electro-negative to zinc. 
 
 (4.) Tinned iron rapidly corrodes or rusts 
 when the iron is exposed to the atmosphere by a 
 scratch or abrasion, because the iron is electro- 
 positive to tin. Nickel-plated iron, for the same 
 reason, rusts rapidly on the exposure of an 
 abraded surface. 
 
 (5.) Zinced or galvanized iron, or iron covered 
 with a deposit of zinc, is protected from corro- 
 sion because the zinc, being positive to iron, can 
 alone be corroded, and the zinc is also protected 
 in part by the coating of insoluble oxide that is 
 formed. 
 
 Meteorites. Aerolites. (See Aerolites.) 
 
 Meter, Ampdre - (See Ampere- 
 Meter. Ammeter?) 
 
 Meter, Current A term now ap- 
 plied to an electric meter or galvanometer 
 which measures the current in amperes, as 
 distinguished from one which measures the 
 energy in watts. 
 
 This term is sometimes loosely applied to a 
 galvanometer. 
 
 The term galvanometer is preferable. (See 
 Galvanometer.) 
 
 Meter, Current, Magneto-Static A 
 
 current meter in which a small steel magnet, 
 or system of magnets, is suspended at tht 
 centre of the uniform magnetic field produced 
 by the combined influence of two coils and 
 two systems of powerful permanent magnets. 
 
 Meter, Electric Any apparatus for 
 
 measuring commercially the quantity of elec- 
 tricity that passes in a given time through 
 any consumption circuit. 
 
Mclj 
 
 365 
 
 Electric meters are constructed in a great 
 variety of forms; they may, however, be ar- 
 ranged under the following heads : 
 
 (l.) Electro-Magnetic Meters, or those in which 
 the current passing is measured by the electro- 
 magnetic effects it produces. 
 
 In such meters the entire current may pass 
 through the meter. 
 
 (2.) Electro-Chemical Meters, or those in which 
 the current passing is measured by the electroly- 
 tic decomposition it effects. 
 
 In these meters, a shunted portion only of the 
 current is usually passed through a solution of a 
 metallic salt, and the current strength calculated 
 from the amount of electrolytic decomposition 
 thus effected. 
 
 (3.) Electro- Thermal Meters, or those in which 
 the current passing is measured by a movement 
 effected by the increase in temperature of a resist- 
 ance through which the current is passed, or by 
 the amount of a liquid evaporated by the heat 
 generated by the current. 
 
 (4.) Electric-Time Meters, or those in which 
 no attempt is made to measure the current that 
 passes, but in which a record is kept of the num- 
 ber of hours that an electric lamp, motor or 
 other electro-receptive device is supplied with 
 current. 
 
 Edison's electric meter is of the second class. 
 It consists of two voltameters, or electrolytic cells, 
 containing zinc sulphate, in which two plates of 
 chemically pure zinc are dipped. The current 
 that passes is determined by the amount of the 
 variation in weight of the zinc plates. To deter- 
 mine this, the plates are weighed at stated in- 
 tervals : one plate every month, the other plate, 
 which is intended to act as a check on the first, 
 only once in three months. Some difficulty has 
 been experienced in the employment of meters of 
 this class, from the variations in the value of the 
 shunt resistance, due to variations in the condi- 
 tion and temperature of the electrolytic cell. 
 The use of a compensating resistance, however, 
 has, it is claimed, removed this objection. (See 
 Voltameter. ) 
 
 Meter, Electric-Time An electric 
 
 meter in which the current passing is esti- 
 mated by recording the number of hours that 
 an electric lamp or other electro-receptive 
 device is supplied with a known current. 
 (See Meter, Electric?] 
 
 Meter, Electro-Chemical An elec- 
 tric meter in which the current passing is 
 measured by the electrolytic decomposition it 
 effects. (See Meter, Electric?) 
 
 Meter, Electro-Magnetic An elec- 
 tric meter in which the current passing is 
 measured by the electro-magnetic effects it 
 produces. (See Meter, Electric?) 
 
 Meter, Electro-Thermal An elec- 
 tric meter in which the current passing is 
 measured by means of the heat generated by 
 the passage of the current through a resist- 
 ance. (See Meter, Electric?] 
 
 Meter, Energy A term sometimes 
 
 applied to a watt meter. (See Meter, 
 Watt?] 
 
 Meter, Milli-Ampere An ampere 
 
 meter graduated to read milli-amperes. 
 
 Meter, Watt An instrument gener- 
 ally consisting of a galvanometer constructed 
 so as to measure directly the product of the 
 current, and the difference of potential. 
 
 Since the watt is equal to the product of the 
 
 Fig. 3Q6. Watt Meter. 
 
 current by the electromotive force, if the current 
 and electromotive force are simultaneously meas- 
 ured, their product gives directly the watts. 
 The scale reading of a watt meter may be grad- 
 uated so as to give the watts directly. 
 
 A watt meter consists essentially of a thick wire 
 coil, placed in series in the circuit whose electric 
 power is to be measured, and a thin wire coil 
 
Met.] 
 
 366 
 
 LMic. 
 
 placed in a shunt around the circuit to be meas- 
 ured. These two coils, instead of acting on a 
 needle, act on each other, and the amount of this 
 deflection will, therefore, be proportional to the 
 watts present. 
 A form of watt meter is shown in Fig. 396. 
 
 Method, Deflection A method em- 
 ployed in electrical measurements, as distin- 
 guished from the zero method, in which a 
 deflection, produced on any instrument by a 
 given current, or by a given charge, is utilized 
 for determining the value of that current or 
 charge. 
 
 The conditions remaining the same, the same 
 Current or charge will produce the same deflection 
 at any time. Different deflections produced by 
 currents or charges, the values of which are un- 
 known, are determined by certain ratios existing 
 between the deflections and the currents or 
 charges. These ratios are determined experi- 
 mentally by the calibration of the instrument. 
 (See Calibrate.} 
 
 Deflection methods are opposed to zero or null 
 methods, in which latter a balance of opposite 
 electromotive forces, or a proportionally equal 
 fall of electric potential, is ascertained by the 
 failure of a delicately poised needle to be moved 
 by a current or a charge. 
 
 Method, Null or Zero Any method 
 
 employed in electrical measurements, in which 
 the values of the electromotive force in volts, 
 the resistance in ohms, or the current in am- 
 peres, or other similar units, are determined 
 by balancing them against equal values of the 
 same units, and ascertaining such equality, not 
 by the deflections of the needle of a galvano- 
 meter, or of an electrometer, but by the ab- 
 sence of such deflections. 
 
 The advantage of zero methods is iound in the 
 fact that the galvanometer or electrometer may 
 then be made as sensitive as possible, which is not 
 otherwise the case, since great deflections are 
 generally to be avoided, especially in tangent 
 galvanometers. (See Galvanometer. Electrom- 
 eter.) 
 
 Method of Magnetization by Touch. 
 
 (See Magnetization by Touch.) 
 
 Methven's Screen. (See Screen, Meth- 
 -ven 's.) 
 
 Metre Bridge. (See Bridge, Metre?) 
 Metre Candle. (See Candle, Metre.) 
 Metre-Gramme Standard, Matthiessen's 
 
 A unit of resistance. 
 
 The resistance of a wire one metre in 
 length, and of such a diameter as would cause 
 the wire to weigh one gramme. 
 
 One metre-gramme of pure hard drawn cop per 
 has a resistance of .1469 B. A. units at zero de- 
 grees C. as determined by Matthiessen {Phil. 
 Mag., May, 1865). 
 
 Metre-Millimetre A resistance unit 
 
 of length of a wire or other conductor of the 
 length of one metre and of the area of cross- 
 section of one square millimetre. 
 
 According to the report of the Committee of the 
 American Institute of Electrical Engineers cf 1890, 
 on a Standard Wiring Table, a metre millimetre 
 of pure soft copper wire has a resistance of .02057 
 B. A. units at zero degrees C. From the corre- 
 sponding term, milfoot, millimetre-metre would 
 appear to be the preferable term. 
 
 Metric Horse-Power. (See Horse- Pm. ?*-, 
 Metric?) 
 
 Metric System of Weights and Meas- 
 ures. (See Weights and Measures, Metric 
 System of.) 
 
 Mho. A term proposed by Sir Wm. 
 Thomson for the practical unit of conductiv- 
 ity. 
 
 Such a unit of conductivity as is equal to 
 the reciprocal of I ohm. 
 
 The conducting power is equal to _ or the 
 
 R 
 
 , eciprocal of the resistance. 
 
 The word mho, as is evident, is obtained by in- 
 verting the order of sequence of the letters in the 
 word ohm. 
 
 Mica. A mineral substance employed as 
 an insulator. 
 
 Mica is a silicious mineral. It occurs of vary- 
 ing degrees of transparency, and splits or cleaves 
 readily into transparent laminae. It is a good 
 non conductor, is fairly fire proof, and is not 
 hydroscopic. 
 
 Mica is used extensively in insulating the me- 
 tallic segment of commutators of motors and 
 dynamo-electric machines and in various other 
 electric work. 
 
Mic.] 
 
 36? 
 
 Mica, Moulded An insulating sub- 
 stance consisting of finely divided mica made 
 into a paste, with some fused insulating 
 substance, and moulded into any desired 
 shape. 
 
 Finely divided mica mixed with gum-shellac 
 rendered plastic by means of heat, forms a good 
 insulating substance. 
 
 Micro (as a prefix). The one-millionth; 
 as, a microfarad, the millionth of a farad ; a 
 microvolt, the one-millionth of a volt. 
 
 Micro-Farad. (See Farad, Micro') 
 
 Micro-Gfraphophone. A modified form of 
 phonograph in which several independent 
 non-metallic diaphragms are used instead of 
 the single diaphragm of the phonograph. (See 
 Graphophone, Micro.) 
 
 Micrometer, Arc An apparatus for 
 
 the accurate measurement of the length of a 
 voltaic arc by means of a micrometer. 
 
 The distance between two carbon electrodes 
 one movable and the other fixed placed inside a 
 glass vessel, is accurately determined by means of 
 a micrometer placed on the movable electrode. 
 The operation is similar to that of the vernier 
 wire gauge. 
 
 Micrometer, Spark A term some- 
 times applied to Hertz's electric resonator. 
 (See Resonator, Electric) 
 
 Micron. A measure of length. 
 
 The one-millionth part of a metre. 
 
 The micron is equal to .00004 f an inch, very 
 nearly. 
 
 Microphone. An apparatus invented by 
 Prof. Hughes for rendering faint or distant 
 sounds distinctly audible. 
 
 The microphone depends for its operation on 
 variations produced in the resistance of the circuit 
 of a battery, or other electric source, by means of 
 a loose contact. These variations in the resist- 
 ance are caused to produce corresponding move- 
 ments in the diaphragm of a receiving telephone. 
 
 The loose contact may take a variety of forms. 
 Originally it was made in the form shown in Fig. 
 397, in which a small piece of carbon E, pointed 
 at both ends, is inserted in holes near the ends of 
 cross-pieces of carbon B and C. The thin upright 
 board A, on which these are supported, acts as a 
 
 sounding board or diaphragm, and its movements 
 by sound waves are at once audible to a person 
 listening at the receiving telephone. The walk- 
 ing of a fly over the sounding board is heard as a 
 loud sound. 
 
 The forms of transmitting telephones invented 
 by Reis, Edison, Blake, Berliner and others, are 
 in reality varieties of microphones. 
 
 Fig. 3Q7. Microphone. 
 
 Microphone Relay. (See Relay, Micro- 
 phone) 
 
 Micro-Seismograph. (See Seismograph 
 Micro) 
 
 Microtasimeter. An apparatus invented 
 by Edison to measure minute differences of 
 temperature, or of moisture, by the resulting 
 differences of pressure. 
 
 A change of temperature, or moisture, is caused 
 to produce variations in the resistance of a button 
 of compressed lampblack, placed in the circuit of 
 a delicate galvanometer. The apparatus, though 
 of surprising delicacy, is scarcely capable of prac- 
 tical application, from the fact that the resistance 
 of the carbon does not resume its normal value 011 
 the removal of the pressure. 
 
 Micro- Yolt (See Volt, Micro) 
 
 Mil. A unit of length equal to the -nnnr of 
 an inch, or .001 inch, used in measuring the 
 diameter of wires. 
 
 Mil, Circular A unit of area em- 
 ployed in measuring the areas of cross-sec- 
 tions of wires, equal to .78540 square mil. 
 
 The area of a circle one mil in diameter. 
 
Mil.] 
 
 368 
 
 [Min. 
 
 One circular mil equals .000000785 square inch. 
 
 The area of cross-section of a circular wire in 
 circular mils is equal to the square of its diameter 
 expressed in mils. (See Units, Circular.) 
 
 Mil-Foot A resistance unit of length of 
 one foot of wire or other conductor of one 
 mil diameter. 
 
 The resistance of a mil-foot of soft copper wire 
 or wire I foot long and .001 of an inch in diam- 
 eter is equal to 9.720 B. A. units at O degrees C. 
 
 Mil, Square A unit of area em- 
 ployed in measuring the areas of cross-sec- 
 tions of wires, equal to .00000 1 square inch. 
 
 One square mil equals 1.2732 circular mil. 
 
 Mile, Nautical A knot, or a dis- 
 tance of 6,087 feet, or very nearly 1.15 statute 
 miles. 
 
 The --rTFtnr of the earth's equatorial cir- 
 cumference, or the cV of a degree of longi- 
 tude at the equator, or about 2,029 yards. 
 
 A nautical or geographical mile being the 
 5 T | 5T j of 24,899 miles, has a value somewhat 
 greater than that of the statute mile. 
 
 Mile Standard, Matthiessen's A 
 
 standard of resistance equal to the resistance 
 of one mile of pure copper wire fV inch in 
 diameter at 15.5 degrees C. 
 
 Matthiessen's mile standard has a resistance of 
 13.59 B. A. units at 15.5 degrees C. 
 
 Mile, Statute The ordinary unit of 
 distance on land, equal to 5,280 feet. 
 
 Mill! (as a prefix). The one-thousandth 
 part. 
 
 Milli-Ainpere. The thousandth of an am- 
 pere. 
 
 Milli-Calorie. The smaller calorie. (See 
 Calorie, Small.} 
 
 Milli-Oerstedt. The one-thousandth of 
 an Oerstedt. 
 
 Mimosa Sensitira. A sensitive plant 
 whose leaves fold or shut up when touched. 
 
 The fibres of all the sensitive plants, such, for 
 example, as the above, the Venus' Fly-trap, etc., 
 like all muscular fibre, and indeed all protoplasm, 
 suffer contraction when traversed by electric cur- 
 rents. 
 
 Mine, Electro-Contact - A sub- 
 marine mine that is fired automatically on 
 the completion of the current of a battery 
 
 placed on the shore through the closing of 
 floating contact points by passing vessels. 
 (See Mine, Submarine.} 
 
 Mine Exploder, Electro-Magnetic 
 
 A form of electro-magnetic exploder. (See 
 Exploder, Electro-Magnetic.) 
 
 Mine, Mechanical A submarine 
 
 mine that is fired when struck by a passing 
 ship by the action of some contrivance con- 
 tained within the torpedo itself, and having 
 no connection whatever with the shore. 
 
 Mine, Observation A variety of 
 
 submarine mine that is fired when the 
 enemy's vessels are observed to be within the 
 destructive area of the mine. (See Mine, 
 Submarine.} 
 
 Various means are adopted for obtaining the 
 current required for firing such mines. A suffi- 
 ciently powerful battery is generally used. An 
 electro-magnetic mine exploder may, under cer- 
 tain circumstances, be employed. (See Mine 
 Exploder, Electro -Magnetic.} 
 
 Mine, Submarine A mass of gun- 
 cotton or other explosive contained in a 
 water-tight vessel and placed under water so 
 as to be exploded on the passage over it of 
 an enemy's vessel. 
 
 A submarine mine is a stationary torpedo ar- 
 ranged for the defense of a harbor. A harbor 
 is protected by a number of mines which are so 
 arranged as to be readily exploded by the passage 
 of an enemy's ship, but safely crossed by other 
 vessels. 
 
 Submarine mines consist essentially of gun- 
 cotton or other explosives contained in water-tight 
 vessels anchored in very carefully located posi- 
 tions, and connected with the shore by means of 
 cables. 
 
 An operating-room at the shore end of the 
 cable is furnished with batteries, measuring in- 
 struments, contact keys, etc., etc., by means of 
 which the mines can be exploded by the trans- 
 mission of an electric current through the cables; 
 or, the mines are furnished with automatic cir- 
 cuit closers in which two central points are closed 
 by the passage of the vessel. In ordinary times 
 this current is too weak to ignite the fuse, and 
 merely closes a relay in the operating-room, 
 which in turn directs a current through a bell or 
 indicator, but, ot course, too weak to fire the fuse. 
 
JLin.] 
 
 369 
 
 [Mom. 
 
 In times of war, however, the relay sends a 
 current through the cable sufficiently strong to 
 heat a platinum indium fuse, ignite a fulminate of 
 mercury cap, and thus, by the detonation of the 
 primer of dry gun-cotton, explode the full charge 
 of damp gun-cotton in the torpedo or mine. 
 
 Mine, Subterranean A mass of 
 
 gun powder, gun-cotton or other explosive, 
 placed under ground in vessels suitable for 
 protection against moisture, and fitted with 
 electrically connected electric fuses, which are 
 either exploded automatically by the move- 
 ment of an enemy over them, or by an oper- 
 ator placed at a safe distance within an en- 
 trenchment. 
 
 Molecular Currents. (See Currents, 
 Molecular or Atomic?) 
 Molecular Currents, Induced (See 
 
 One ampere flow- 
 
 (See Hour, Ampere) 
 
 A unit of electrical 
 
 Minute, Ampere 
 
 ing for one minute. 
 
 Minute, Watt 
 
 work. 
 
 The expenditure of an electrical power of 
 one watt for one minute. 
 
 The watt-minute is equal to 60 joules. This 
 unit of electrical work is seldom used. 
 
 Miophone. An apparatus invented by 
 Boudet based on the use of the microphone, 
 and designed for the medical examination of 
 the muscles. 
 
 Mirror Galvanometer. (See Galvanom- 
 eter, Mirror) 
 
 Moist Electrode. (See Electrode, Moist) 
 
 Moisture, Eifect of, on Electrical Phe- 
 nomena The influence of moisture 
 
 on the surfaces of insulators in causing the 
 loss or dissipation of an electric charge. 
 
 This luss is more rapid with negatively charged 
 bodies than with those positively charged. 
 
 Molar Attraction. (See Attraction, 
 Molar.) 
 
 Molecular. Pertaining to the molecule. 
 (See Molecule) 
 
 Molecular Attraction. (See Attraction, 
 
 Molecular.) 
 
 Molecular Bombardment. (See Bom- 
 bardment, Molecular) 
 
 Molecular Chain. (See C'lain, Molecu- 
 lar) 
 
 Currents, Induced Molecular or Atomic) 
 
 Molecular Range. (See Range, Molecu' 
 lar) 
 
 Molecular Repulsion. (See Repulsion 
 Molecular) 
 
 Molecular Rigidity. (See Rigidity, 
 Molecular) 
 
 Molecular Theory of Muscle and Nerve 
 Currents. (See Theory, Alolecular, of Mus- 
 cle and Nerve Currents) 
 
 Molecule. A group of atoms whose 
 chemical bonds or affinities are mutually 
 satisfied. 
 
 The smallest quantity of a compound sub- 
 stance that can exist as such. 
 
 Water is a compound substance formed of two 
 atoms of hydrogen combined with one atom of 
 oxygen. The molecule of water, therefore, or 
 the smallest quantity of water that can exist, must 
 contain two atoms of hydrogen and one of oxygen. 
 
 The molecule of hydrogen consists of two atoms 
 of hydrogen. Since hydrogen is a monad, or an 
 element whose atomicity is one, it can combine 
 with one atom of hydrogen and form a molecule, 
 since then its bonds will be fully satisfied. (See 
 Atomicity.) 
 
 Molecule, Closed-Magnetic Circuit of 
 
 (See Circuit, Closed-Magnetic, of 
 
 Molecule.) 
 
 Molecule, Gramme The weight of 
 
 any substance taken in grammes numerically 
 equal to the molecular weight. 
 
 Moment, Magnetic The sum of the 
 two forces of the directive couple multiplied 
 by half the perpendicular distance between the 
 directions of these forces ; or, in other words, 
 the moment of a magnet is equal to its length 
 multiplied by the intensity of the magnetism 
 of one of its poles. (See Couple, Magnetic) 
 
 Moment of Couples. (See Couple, Mo- 
 ment of) 
 
 Momentary Current. (See Current, Mo- 
 mentary) 
 
 Momentum, Electro-Magnetic, of Sec- 
 ondary Circuit A quantity equal to 
 
Moii.J 
 
 370 
 
 [Mot. 
 
 the co-efficient of mutual induction, multi- 
 plied by the current strength in the primary, 
 when the primary current is fully established. 
 When the primary current is fully established, 
 the number of lines of force which pass through 
 the secondary circuit is equal to the co-efficient of 
 mutual induction, multiplied by the strength of 
 the primary current. 
 
 Monophotal Arc-Light Regulator. (See 
 Regulator, Monophotal Arc-Light?) 
 Mordey Effect. (See Effect, Mordey?) 
 Morse Alphabet. (See Alphabet, Tele- 
 graphic: Morses?) 
 
 Morse Inker. (See Inker, Morsel) 
 Morse Recorder. (See Recorder, Morsel) 
 Morse Register. (See Register, Morse?) 
 Morse System of Telegraphy. (See 
 Telegraphy, Morse System of.) 
 
 Morse's Telegraphic Alphabet. (See Al- 
 phabet, Telegraphic : Morse's.) 
 
 Morse's Telegraphic Sounder. (See 
 Sounder, Morse's Telegraphic?) 
 
 Motion, Energy of A term some- 
 times applied to actual or kinetic energy in 
 contradistinction to potential energy. (See 
 Energy, Actual?) 
 
 Motion, Simple-Harmonic Motion 
 
 which repeats itself at regular intervals, taking 
 place backwards or forwards, and which may- 
 be studied by comparison with uniform mo- 
 tion round a circle of reference. (Dam'ell.) 
 
 Fig. 398. Simple-Harmonic Motion. 
 
 Motion which is a simple periodic function 
 of the time. 
 
 Suppose a pendulum be set swinging in a cer- 
 tain path. If the path of such a pendulum, or, 
 as it is generally called, a conical pendulum, be 
 
 looked at from above or from below, it will appear 
 to be circular; if observed from one side it will 
 appear elliptical, and this elliptical path will ap- 
 pear longer and narrower as the eye of the ob- 
 server approaches the level of the plane in which 
 the bob moves, when the bob will appear to 
 travel backwards and forwards in a straight line. 
 The bob will appear to be moving faster, when it 
 is moving right across the field of view. 
 
 Let the circle Q C R (Fig. 398) be the path in 
 which the bob moves, and let Q A, A B, B C, C o, 
 etc., be equal distances in such path. Let the 
 lines A a, B b, C c, o O, etc., be drawn perpendicu- 
 lar to the line Q R. Then when looked at, with 
 the eye on the level of the plane in which the bob 
 travels, the line Q R, will be the path in which 
 the bob appears to move backwards and for- 
 wards, and the lines, Q a, a b, b c, c O, etc., will 
 represent the spaces apparently traversed in 
 equal intervals of time. 
 
 The circle Q o R, is called the circle of refer- 
 ence. 
 
 Motion, Simple-Harmonic, Amplitude of 
 
 The length of the swing from the 
 
 median position to its extreme position, in 
 either direction. 
 
 The line O Q, or O R, in the circle of reference 
 Q O R (Fig. 398). 
 
 Motion, Simple-Harmonic, Negative Di- 
 rection of The motion which a body, 
 
 with a simple-harmonic motion, has when it 
 appears to move from left to right. 
 
 Motion, Simple-Harmonic, Period of 
 
 The interval of time which elapses between 
 two successive passages of a moving particle, 
 over the same point, in the same direction. 
 
 The period of simple-harmonic motion repre- 
 sents the time of one complete motion around a 
 circle called the circle of reference. (See Motion, 
 Simple -Harmonic. ) 
 
 Motion, Simple-Harmonic, Phase of 
 
 The position of a point executing a simple 
 harmonic motion, expressed in terms of the 
 interval of time which has elapsed since 
 such point last passed through the middle 
 of its path in the positive direction. (An- 
 thony <$- Brackett?) 
 
 The exact position of a particle executing a 
 simple-harmonic motion for any instant of time 
 can be readily expressed in terms of the phase. 
 
Mot. 
 
 371 
 
 [Mot. 
 
 Motion, Simple-Harmonic, Positive 
 
 Direction of The motion which a. 
 
 body moving in simple-harmonic motion has, 
 when it appears to move from right to left. 
 
 Motion, Simple-Periodic A term 
 
 sometimes employed in the sense of simple- 
 harmonic motion. (See Motion, Simple- 
 Harmonic.') 
 
 Motion, Simple-Sine A term some- 
 times employed in the sense of simple-har- 
 monic motion. (See Motion, Simple-Har- 
 monic^) 
 
 Motograph, Electro An apparatus 
 
 invented by Edison whereby the friction of a 
 platinum point against a rotating cylinder of 
 moist chalk, is reduced by the passage of 
 an electric current. 
 
 This result is due to electrolytic action at the 
 points of contact, varying the friction. 
 
 The electro-motograph, though less certain in 
 its action than an electro-magnet, may replace it 
 in certain electric apparatus. 
 
 The detailed construction of the electro-moto- 
 graph will be understood from an inspection of 
 
 Fig- 399- 
 
 The lever A, pivoted with a universal joint at 
 C, has a metallic point at its free extremity F, 
 resting on a strip of moistened paper N, and held 
 against it with some pressure by the action of the 
 spring S. The paper N, rests on the metallic 
 drum G, over which it is moved on the rotation 
 of the drum by clockwork. A spring R, acts to 
 move the lever A, in a direction opposite to that 
 in which it tends to move by the rotation of the 
 drum G. 
 
 The main battery L, is connected at its negative 
 pole to the point F, and at its positive pole, through 
 the key K, to the metallic drum G. The local bat- 
 tery L B, is connected through the sounder X, to 
 the contacts D and X. 
 
 When the key K, is open, the friction of F, on 
 the paper N, is sufficient to move the lever A, to 
 the right so as to close the circuit of the local 
 battery, but when the key K, is depressed, the 
 current of L, passing through the paper, decom- 
 poses the chemicals with which ic is moistened, 
 lessens the friction of the point F, and permits the 
 spring B, to draw the lever A, to the left, thus 
 opening the circuit of the local battery L B. 
 
 The movements of the key are therefore repro 
 duced by the armature of the electro-magnet X. 
 
 An excellent loud speaking telephone has been 
 devised by Edison on the principle of the electro- 
 motograph. 
 
 Fig. 3QQ. Electro-Motograph. 
 
 Motor, Compound-Wound An elec- 
 tric motor whose field magnets are excited by 
 a series and a shunt wire. (See Machine, 
 Dynamo-Electric, Compound- Wound.) 
 
 Motor, Differentially Wound A 
 
 compound-wound motor, in which the cur- 
 rent in the shunt coils opposes in its magnet- 
 izing effects the current in a series coil, so 
 that the efficient magnetizing effect produced 
 is the difference in the magnetizing effect of 
 the two coils. 
 
 Motor, Electric A device for trans- 
 forming electric power mto mechanical 
 power. 
 
 All practical electric motors depend for their 
 operation on the tendency to motion in a mag- 
 netic field of a conductor carrying a current 01 
 on magnetic attraction or repulsion. The entire 
 magnetism may be produced by u, e current, or 
 part may be obtained from permanent magnets, 
 and the rest from electro-magnets. 
 
 A dynamo-electric machine will act as a motor 
 if a current is sent through it. Such a motor is 
 sometimes called an electro-motor. The term 
 electric motor would, however, appear to be the 
 preferable one. 
 
 In all cases the rotation is in such a direction as 
 to induce in the armature an electromotive force 
 opposed to that of the driving current ; this is 
 therefore called the counter electromotive force. 
 
 A magneto-dynamo, or a dynamo the field of 
 which is obtained from permanent magnets, or a 
 separately excited dynamo, will operate as a 
 motor when a current is sent through its arma- 
 ture, and will turn it in the opposite direction to 
 that required to drive it in order to produce a 
 current in the same direction. 
 
 A series dynamo will operate as a motor when 
 
Mot.] 
 
 372 
 
 [Mot. 
 
 a current is sent through it. If the current is 
 sent through it in the opposite direction to that 
 which it produces when in operation as a gener- 
 ator, the polarity of the field is reversed and the 
 dynamo will turn as a motor in the opposite direc- 
 tion to that required to produce the current. If 
 the current is reversed, the polarity of both the 
 field and the armature is again reversed, and the 
 dynamo still rotates as a motor in the opposite 
 direction to that in which it is rotated as a 
 generator. 
 
 A series dynamo, therefore, always rotates as a 
 motor in a direction opposite to that of its rotation 
 as a generator. 
 
 When, however, the polarity of the field only 
 is reversed by changing the connection between 
 the armature and the field, the rotation is in the 
 same direction. 
 
 A shunt dynamo operated as a motor will also 
 turn in but one direction, but this direction is the 
 same as that in which it turns when operating 
 as a generator; for if the direction of the current 
 in the armature is the same as in a generator, 
 that in the shunt is reversed. 
 
 A compound wound dynamo will move in a 
 direction opposite to that of its motion as a gene- 
 rator if the series part is more powerful than the 
 shunt, and in the same direction if the shunt part 
 is more powerful than the series. To use a com- 
 pound-wound dynamo as a differential motor the 
 connections need not be changed. For a cumu- 
 lative motor it is necessary to reverse the connec- 
 tions of the series coils. 
 
 Alternating-Current Dynamo. The current 
 from an alternating-current dynamo, if sent 
 through another similar alternating-current dy- 
 namo running at the same speed, will drive it as a 
 motor. Such a machine possesses the disadvan- 
 tage of requiring to be maintained at a speed de- 
 pending on that of the driving dynamo, and also 
 that it requires to be brought to nearly this speed 
 before the driving current is supplied to it. As a 
 result of this last requirement, variations in the 
 load are apt to stop the motor. Considerable 
 improvements, however, are being introduced 
 into alternate-current motors, by which these 
 difficulties are almost entirely removed. 
 
 An alternating current sent through any self- 
 exciting dynamo -electric machine, such as a 
 shunt or series machine, will drive it continu- 
 ously as a motor. The sudden reversals in the 
 magnetization of its cores will, however, unless 
 Ihe cores are thoroughly laminated, set up power- 
 
 ful eddy currents that will injuriously heat the 
 machine, and there is also excessive sparking at 
 the brushes. 
 
 The reversibility of any dynamo -electric ma- 
 chine, or its ability to operate as a motor if sup- 
 plied with a current, leads to a fact of great 
 importance in the efficiency of electric motors, 
 viz.: that during rotation there is induced in the 
 armature during its passage through the field of 
 the machine, an electromotive force opposed co 
 that produced in the armature by the driving 
 current, or a counter electromotive force. (See 
 Resistance, Spurious. Force, Counter Electro- 
 motive.'] This counter electromotive force acts 
 as a spurious resistance, and opposes the passage 
 of the driving current, so that, as the speed of the 
 electric motor increases, the strength of the dr'v- 
 ing current becomes less, until, when a certain 
 maximum speed is reached, very little current 
 passes. In actual practice, this maximum speed 
 is not attained, or is only momentarily attained, 
 and a small, nearly constant, current is expended 
 in overcoming friction at the bearings, air fac- 
 tion, etc. 
 
 When, however, the load is placed on the 
 motor, that is, when it is caused to do work, the 
 speed is reduced and the counter electromotive 
 force is decreased, thus permitting a greater cur- 
 rent to pass. The fact that the load thus auto- 
 matically regulates the current required t > drive 
 the mo;or, renders electric mo ors very economi- 
 cal in operation. 
 
 The relations between the power required to 
 drive the generating dynamo, and that produced 
 by the electric motor, are such that the maximum 
 work per second is done by the motor when it 
 runs at such a rate that the counter electro- 
 motive force it produces is half that of the current 
 supplied to it. The maximum work or activity of 
 an electric motor is therefore done when its theo- 
 retical efficiency is only 50 per cent. This, 
 however, must be carefully distinguished from 
 the maximum efficiency of an electric motor. A 
 maximum efficiency of 100 per cent, can be at 
 tained theoretically ; and, in actual practice, con- 
 siderably over 90 per cent, is obtained. In such 
 cases, however, the motor is doing work at less 
 than its maximum power. 
 
 This is Jacobi's law of maximum effect, but 
 does not apply to actual motors on account of the 
 Jimitations of current carrying capacity. For 
 example, a motor of 9 horse power and 90 per 
 cent, efficiency loses I horse-power in heat within 
 
Mot.] 
 
 373 
 
 [Mot. 
 
 itself. Hence, if run according to Jacobi's law, 
 it would only produce the same amount, *'. e., I 
 horse-power in useful work instead of 9. More 
 than this would overheat it. 
 
 An efficiency of 100 per cent, is reached when 
 the counter electromotive force of the motor is 
 equal to that of the source supplying the driving 
 current. Supposing now the driving machine to 
 be of the same type as the motor, and the two 
 machines are running at the same speed. If 
 now a load is put on the motor so as to reduce its 
 speed, and thus permit it to produce a counter 
 electromotive force of but 90 per cent., its 
 efficiency will be but 90 per cent. In such a 
 case, therefore, the efficiency is represented by 
 the relative speeds of the generator and the 
 motor. 
 
 Motor, Electric, Alternating-Current 
 
 An electric motor driven or operated 
 
 by means of alternating currents. (See 
 Motor, Electric?) 
 
 Dr. Louis Duncan divides alternating motors 
 into two classes, viz. : 
 
 (i.) Those in which there is but one trans- 
 formation in the machine, viz., that of the electric 
 energy of the armature current into the mechani- 
 cal energy of the armature's rotation. 
 
 (2.) Those in which there are two transforma- 
 tions, viz.: 
 
 (a.) The transformation of electrical energy 
 from the main current to electrical energy in the 
 armature current. 
 
 (b.) The transformation of the electric energy 
 of the armature current into mechanical energy. 
 
 Alternating motors of the first type are iound 
 in the ordinary alternating-current dynamo re- 
 versed. Those of the second type in Tesla's or 
 Thomson's motors. 
 
 Motor, Electric, Direct-Current 
 
 An electric motor driven or operated by 
 means of direct or continuous electric cur- 
 rents, as distinguished from a motor driven 
 or operated by alternating currents. (See 
 Motor, Electric?) 
 
 Motor, Electric, High-Speed The 
 
 ordinary electric motor. 
 
 The term high-speed electric motor is used in 
 contradistinction to low -speed electric motor. 
 (See Motor, Electric, Low-Speed.} 
 
 Motor, Electric, Low-Speed A 
 
 slow-speed motor. (See Motor, Electric, 
 Slow-Speed?) 
 
 Motor, Electric, Overload of A 
 
 load greater than that which an electric motor 
 can carry while at its greatest efficiency of 
 operation, or a load which causes injurious 
 heating of a motor. 
 
 Motor, Electric, Reversing Gear of - 
 
 Apparatus for so reversing the direction of 
 the current through an electric motor as to re- 
 verse the direction of its rotation. (See Rail- 
 road, Electric?) 
 
 Motor, Electric, Slow-Speed - An 
 
 electric motor so constructed as to run with 
 fair efficiency at slow speed. 
 
 The electric motor develops a counter electro- 
 motive for;e when in motion, which, of course, 
 increases with the increase of motion. The elec- 
 tric motor has, as generally constructed, its great- 
 est efficiency at high speed. When used on street 
 railroads, the high speed requires to be decreased 
 by various forms of reduction gear. The loss of 
 power which all such gear involve, together with 
 the noise attending their use, render any decrease 
 in speed that can be obtained on the part of the 
 motor, without serious loss of efficiency, desir- 
 able. 
 
 Motor-Electromotive Force. (See Force, 
 Motor Electromotive.} 
 
 Motor, Pyromagnetic - - A motor 
 driven by the attraction of magnet poles on 
 a movable core of iron or nickel unequally 
 heated. 
 
 The intensity of magnetization of iron decreases 
 with an increase of temperature, iron losing most 
 of its magnetization at a red heat. A disc of iron 
 placed between the poles of a magnet, so as to 
 be capable of rotation, will rotate, if heated at a 
 part nearer one pole than the other, since it be- 
 comes less powerfully magnetized at the heated 
 part. 
 
 In the form of pyromagnetic motor devised by 
 Edison, and shown in Fig. 400, in elevation, and 
 in Fig. 401, in vertical section, the disc of iron is 
 replaced by a series of small iron tubes, or di- 
 vided annular spaces, heated by the products of 
 combustion from a fire placed beneath them. In 
 order to render this heating local, a flat screen is 
 placed dissymmetrically across the top to prevent 
 
Mot.] 
 
 374 
 
 [Mov. 
 
 the passage of air through the portion of the iron 
 tubes so screened. The air is supplied to the 
 furnace by passing down from above through the 
 
 Fig. 400. Pyromagnetic Motor. 
 
 tubes so screened. This is shown in the draw- 
 ings, the direction of the heating and the cooling 
 air currents being indicated by the arrows. The 
 
 Fig. 40 1. Pyromagnetic Motor. 
 
 supply of air from above thus insures the more 
 rapid cooling of the screened portion of the 
 tubes. 
 
 Motor, Rotating-Current 
 
 An 
 
 electric motor designed for use with a rotat- 
 ing electric current. 
 
 Unlike alternating current motors, rotary-cur- 
 rent motors will, like continuous-current motors, 
 readily start with a load. (See Current, Rotating, ) 
 
 Motor, Series-Wound An electric 
 
 motor in which the field and armature are 
 connected in series with the external circuit as 
 in a series dynamo. (See Machine, Dynamo- 
 Electric, Series- Wound?) 
 
 Motor, Shunt-Wound An electric 
 
 motor in which the field magnet coils are 
 placed in a shunt to the armature circuit. 
 (See Machine, Dynamo-Electric, Shunt- 
 Wound?) 
 
 Motor Standards. (See Standards, 
 Motor?) 
 
 Moulded Mica. (See Mica, Moulded?) 
 
 Moulding, Electric Wood Mould- 
 ing of dried, non-conducting wood, provided 
 with longitudinal grooves for the reception 
 and support of electric wires or conductors. 
 
 Wood mouldings are employed for the protec- 
 tion and concealment of electric conductors. 
 
 Moulding Wiring. (See Wiring, 
 Moulding?) 
 
 Mouse-Mill Dynamo. (See Dynamo, 
 Mouse-Mill?) 
 
 Mouse-Mill Machine. (See Machine, 
 Mouse-Mill?) 
 
 Mouth Pieces. (See Pieces, Mouth?) 
 
 Movable Secondary. (See Secondary, 
 Movable?) 
 
 Mover, Prime In a system of dis- 
 tribution of power the motor by which sec- 
 ondary motors or movers are driven. 
 
 In a steam plant, the steam engine is the prime 
 mover; the shafts or machines driven by the main 
 shaft are sometimes called the secondary m vers. 
 The main shaft is called the drivhg shaf . Its 
 motion is carried by means of belts to other 
 shafts, called driven shafts. The pulleys on the 
 driving or driven shafts aie called respectively 
 the driving and driven pulleys. 
 
 Movers, Secondary The shafts or 
 
 machines driven by the main shafts in order 
 to distinguish them from the steam engine or 
 other mover which drives it. (See Mover, 
 Prime?) 
 
Mai.] 
 
 375 
 
 [Mul. 
 
 Multi-Cellular Electrostatic Voltmeter. 
 
 (See Voltmeter, Multi-Cellular Electro- 
 static^) 
 
 Multiphase Current. (See Current, Mul- 
 tiphase.) 
 
 Multiphase Dynamo. (See Dynamo, 
 Multiphase) 
 
 Multiphase System. (See System, Multi- 
 phased) 
 
 Multiple-Arc Circuit. (See Circuit, 
 Multiple-Arc?) 
 
 Multiple- Arc-Connected Electro-Recep- 
 tive Devices. (See Devices, Electro-Recep- 
 tive, Multiple-Arc-Connected?) 
 
 Multiple-Arc-Connected Sources. (See 
 Sources, Multiple-Arc-Connected.) 
 
 Multiple-Arc-Connected Translating De- 
 vices. (See Devices, Translating, Mul- 
 tiple- A re- Connected?) 
 
 Multiple-Brush Rocker. (See Rocker, 
 Multiple-Brush ) 
 
 Multiple-Brush Yoke. (See Yoke, Mul- 
 tiple-Pair Brush?) 
 
 Multiple Cable Core. (See Cable, Mul- 
 tiple-Core?) 
 
 Multiple Circuit (See Circuit, Mul- 
 tiple?) 
 
 Multiple Conduit (See Conduit, Mul- 
 tiple.) 
 
 Multiple-Connected Battery. (See Bat- 
 tery, Multiple-Connected) 
 
 MuMiple-Connected Electro-Receptive 
 Devices. (See Devices, Electro-Receptive, 
 
 Multiple- Connected) 
 
 Multiple-Connected Electro-Receptive 
 
 Devices, Automatic Cut-Out for (See 
 
 Cut-Out, Automatic, for Multiple-Connected 
 Electro-Receptive Devices?) 
 
 Multiple-Connected Translating Devices. 
 (See Devices, Translating, Multiple-Con- 
 nected?) - 
 
 Multiple Connection. - (See Connection, 
 Multiple?) 
 
 Multiple Distribution of Electricity by 
 Constant Potential Circuits. (See Elec- 
 tricity, Multiple Distribution of, by Constant 
 Potential Circuits?) 
 
 Multiple Electric-Gaslighting. (See 
 
 Gaslighting, Multiple Electric?) 
 
 Multiple-Series. A multiple connection 
 of series groups. (See Connection, Series 
 Multiple) 
 
 Usage in regard to this term is divided. By 
 some the term multiple-series is applied to a series 
 connection of parallel groups. This is done on 
 account of the order of the words, multiple-series 
 indicating, it is claimed, a series connection of 
 multiple groups. 
 
 Multiple-Series Circuit. (See Circuit, 
 Multiple- Series.) 
 
 Multiple-Series-Connected Electro-Re- 
 ceptive Devices. (See Devices, Electro- 
 Receptive, Multiple- Series- Connected.) 
 
 Multiple - Series Connected Sources. 
 
 (See Sources, Multiple-Series-Connected.) 
 
 Multiple-Series-Connected Translati ng 
 Devices. (See Devices, Translating, Mul- 
 tiple-Series-Connected) 
 
 Multiple-Series Connection. (See Con- 
 nection, Multiple-Series. ) 
 
 Multiple-Switch Board. (See Board, 
 Multiple-Switc I.) 
 
 Multiple Transformer. (See Trans- 
 former, Multiple?) 
 
 Multiple Transmission. (See Trans- 
 mission, Multiple?) 
 
 Multiple Working of Dynamo-Electric 
 Machines. (See Working, Multiple, of 
 Dynamo-Electric Machines) 
 
 Multiplex Telegraphy. (See Teleg- 
 raphy, Multiplex) 
 
 Mnltiplicafor. A word sometimes used 
 for multiplier. 
 
 Multiplier, Galvanic A term for- 
 merly applied to a galvanometer. (See Gal- 
 vanometer?) 
 
 Multiplier, Schweigger's The 
 
 name first given to a coil consisting of a 
 
Mul.] 
 
 376 
 
 [Nee, 
 
 number of turns of insulated wire, provided 
 for the purpose of increasing the strength of 
 the magnetic field produced by an electric 
 current, and consequently the amount of its 
 deflecting power on a magnetic needle. 
 
 Schweigger's multiplier was in fact an early 
 form of galvanometer. (See Galvanometer.) 
 
 Multiplying 1 Power of Shunt. (See 
 Shunt, Multiplying Power of.) 
 
 Multipolar Armature. (See Armature, 
 Multipolar) 
 
 Multipolar Dynamo-Electric Machine. 
 (See Machine, Dynamo-Electric, Multipo- 
 
 Muscular, Electro 
 
 -Pertaining to 
 
 Multipolar-Electric Bath. (See Bath, 
 
 Multipolar Electric.) 
 
 Muscle Current. (See Current, Muscle) 
 Muscles, Electrical Excitation of -- 
 
 (See Excitation, Electro-Muscular) 
 
 the influence of electricity on the muscles. 
 
 Muscular or Nerve Fibre, Excitability 
 
 of (See Excitability, Electric, oj 
 
 Nerve or Muscular Fibre) 
 
 Muscular Pile, Matteucci's (See 
 
 Pile, Muscular, Matteucci's) 
 
 Musket, Electric A gun in which 
 
 the charge is ignited by a platinum wire ren- 
 dered incandescent by the action of a bat- 
 tery placed in the stock of the gun. 
 
 Mutual Inductance. (See Inductance) 
 
 Mutual Induction. (See Induction, 
 Mutual.) 
 
 Mutual Induction, Co-efficient of 
 
 (See Induction, Mutual, Co-efficient of.) 
 
 Myria (as a prefix). A million times. 
 
 N. A contraction employed in mathe- 
 matical writings for the whole number of 
 lines of magnetic force in any magnetic cir- 
 cuit. 
 
 N. A contraction for North Pole. 
 
 This N, may be distinguished from the N, used 
 for expressing the whole number of lines of mag- 
 netic force, by making the former light and the 
 latter heavy. 
 
 N. H. P. A contraction for Nominal 
 Horse-Power. 
 
 Nominal horse-power is a somewhat indefi- 
 nite term for a quantity dependent on the length 
 of stroke and the dimensions of the cylin- 
 der. This quantity is a dependent one, be- 
 cause it varies necessarily with the type of en- 
 gine. 
 
 Nascent State. (See State, Nascent.) 
 
 Natural Currents. (See Currents, Nat- 
 ural) 
 Natural Law. (See Law, Natural?) 
 
 Natural Magnet. (See Magnet, Nat- 
 ural^ 
 
 Natural Unit of Electricity. (See Elec- 
 tricity, Natural Unit of) 
 Natural Unit of Quantity of Electricity, 
 
 (See Electricity, Unit Quantity of, Natu- 
 ral) 
 
 Nautical Mile. (See Mile, Nautical) 
 
 Needle Annunciator. (See Annunciator, 
 Needle) 
 
 Needle, Astatic A compound mag- 
 netic needle of great sensibility, possessing 
 little or no directive power. 
 
 An astatic needle consisting of two separate 
 magnetic needles, rigidly connected together 
 and placed parallel and directly over each 
 other, with opposite poles opposed. 
 
 An astatic needle is shown in Fig. 402. The 
 two magnets N S, and S' N', are directly opposed 
 in their polarities, and are rigidly connected to- 
 gether by means of the axis a, a. So disposed, 
 the two magnets act as a very weak single needle 
 when placed in a magnetic field. 
 
 Were the two magnets N S, and S' N', of ex- 
 actly equal strength, with their poles placed in 
 exactly the same vertical plane, they would com- 
 pletely neutralize each other, and the needle 
 
flee.] 
 
 377 
 
 [Xee. 
 
 would have no directive tendency. Such a sys- 
 tem would form an Astatic Pair or Couple. 
 
 In practice it is impossible to do this, so that the 
 
 Fig. 402. Astat c Needle. 
 
 needle has a directive tendency, which is often 
 east and west. 
 
 The cause of the east and west directive ten- 
 dency of an unequally bal- 
 anced astatic system will 
 be understood from an in- 
 spection of Fig. 403. Un- 
 less the two needles, N S, 
 and S' N', are exactly op- ; a 
 
 posed, they will form a Fi.'.4<>3- Astatic Pair. 
 single short magnet, N N NN, S S S S, the poles 
 of which are on the sides of the needle. The 
 system pointing with its sides due n-rth and 
 south will appear to have an east and we.-t direc- 
 tion. 
 
 The principal use of the astatic needle is in the 
 astatic galvanometer, in which the needle is de- 
 flected by the passage of an electric current 
 through a conductor placed near the needle. 
 Therefore it is evident that one of the needles 
 must be outside and the other inside the coil. In 
 the most sensitive 
 form of galvanome- 
 ter there is also a 
 coil surrounding the 
 upper needle, the 
 two coils being op- 
 positely connected, 
 so that the deflection 
 on both needles is in 
 the same direction, 
 and the deflecting Fig 404. Astatic System. 
 power is equal to the sum of the two coils, while 
 the direc ive power of the needles is the differ- 
 ence of their magnetic intensities. 
 
 In the astatic system, as shown in Fig. 404, the 
 current, which flows above one needle, flows be- 
 low the other, and therefore deflects both needles 
 
 in the same direction, since their poles point in 
 opposite directions. 
 
 In some galvanometers a varying; degree of 
 sensitiveness is obtained by means of a magnet, 
 called a compensating magnet, placed on an axis 
 ab .ve the magne ic needle. As the compensat 
 ing magnet is moved towards or away from the 
 needle the effect of the earth's field is varied, and 
 with it the sensitiveness of the galvanometer. 
 Such a magnet may form with the needle an 
 astatic system. (See Magnet, Compensating. 
 Galvanometer, Astatic. Galvanometer, Mirror. 
 Multiplier, Schweigger' s). 
 
 Needle Electrode. (See Electrode, Nee- 
 dle) 
 
 Needle, Elongation of A phrase 
 
 sometimes used for the angular deflection of 
 a needle. 
 
 Needle, Magnetic A straight bar- 
 shaped needle of magnetized steel, poised 
 near or above its centre of gravity, and free 
 to move either in a horizontal plane only, or 
 in a vertical plane only, or in both. 
 
 A magnetic needle free to move in a vertical 
 plane only is called a dipping needle. A mag- 
 netic needle free to move in a horizontal plane 
 only, as shown in Fig. 405, is the form employed 
 
 Fi*. 40 j Magnetic Needle. 
 
 in the mariner's compass. This form of magnetic 
 needle is the one most commonly employed. 
 
 For use as a mariner's compass the needle is 
 supported on gimbals and placed in a box pro- 
 vided with a card on which are marked the 
 points of the compass. (See Compass, Azimuth. 
 Compass, Points of.) 
 
 Needle, Magnetic, Annual Variations of 
 
 Variations in the value of the mag- 
 
N-er.J 
 
 378 
 
 [Nee. 
 
 netic declination that take piace at regular 
 penods of the year. 
 
 The annual variations of the magnetic field were 
 discovered by Cassini in 1786. 
 
 Needle, Magnetic, Daily Tariation of 
 
 Variations in the value of the magnetic 
 
 declination that take place at different periods 
 of the day. 
 
 It was noticed, for example, in London that the 
 north pole of the magnetic needle begins to move 
 westward between 7 and 8 A. M. and continues 
 this movement until I P. M., when it begins to 
 move towards the east until near 10 p. M., when 
 it again begins its westward course. 
 
 Needle, Magnetic, Damped A 
 
 magnetic needle so placed as to quickly come 
 to rest after it has been set in motion. (See 
 Damping?) 
 
 Magnetic damping is readily effected by caus- 
 ing the needle to move near a metallic plate. On 
 the motion of the needle the currents set up in the 
 plate by dynamo electric induction tend, accord- 
 ing to Lenz's law, to oppose the motions pro- 
 ducing them. (See Induction, Electro-Dynamic. 
 Laws, Lenz's.) 
 
 Needle, Magnetic, Declination of 
 
 The angular deviation of the magnetic needle 
 from the true geographical north. 
 
 The variation of the magnetic needle. 
 
 The declination of the magnetic needle is either 
 E. or W., (See Declination, Angle of.) 
 
 Declination, or variation, is different at dif- 
 ferent parts of the earth's surface. 
 
 Lines connecting places which have the same 
 value and direction for the declination are called 
 isogonal lines. A chart on which the isogonal 
 lines are marked is called a variation chart. 
 
 The value of the declination varies at dif- 
 ferent times. These variations of the declination 
 are: 
 
 (l.) Secular, or those occurring during great 
 intervals of time. Thus, in London, in 1580 the 
 magnetic needle had a variation of about n 
 degrees east. This eastern declination decreased 
 in 1622 to 6 degrees E., and in 1680 the needle 
 pointed to the true north. In 1692 the declina- 
 tion was 6 degrees W.; in 1730, 13 degrees W. ; 
 in 1765, 20 degrees W. ; and in 1818 the needle 
 reached its greatest western declination and is 
 
 now moving eastwards. The declination, how- 
 ever, is still west. 
 
 (2.) Annual, the needle varying slightly in its 
 declination during different seasons of the year. 
 
 (3.) Diurnal, the needle varying slightly in its 
 declination during different hours of the day. 
 
 (4.) Irregular, or those which occur during 
 the prevalence of a magnetic storm. 
 
 It has been discovered that the occurrence of a 
 magnetic storm is simultaneous with the occur- 
 rence of an unusual number of sun spots. (See 
 Spots, Sun.) 
 
 Needle, Magnetic, Deflection of 
 
 The movement of a needle out of a position of 
 rest in the earth's magnetic field or in the 
 field of another magnet, by the action of an 
 electric current or another magnet. 
 
 The deflection of the needle is sometimes called 
 its elongation. This latter term is, however, but 
 little used, and is unnecessary. 
 
 Needle, Magnetic, Dipping A 
 
 magnetic needle suspended so as to be tree 
 to move in a vertical plane, employed to de- 
 termine the angle of dip or the magnetic in- 
 clination. (See Dip, Magnetic, Inclination, 
 Magnetic. Inclinometer. Chart, Inclina- 
 tion^] 
 
 A dipping needle is shown in Fig. 406. The 
 
 angle B O C, which marks the deviation of the 
 needle from the horizontal position, is called the 
 angle of dip. 
 
Nee.] 
 
 379 
 
 [Neg. 
 
 Needle, Magnetic, Directive Tendency of 
 
 The tendency of a magnetic needle to 
 
 move so as to come to rest in the direction of 
 the lines of the earth's magnetic field. 
 
 The directive power of the magnetic needle is 
 due to the attraction of the earth's magnetic poles 
 for the poles of the needle, or to the action of the 
 earth's magnetic field. Since the force of the 
 earth's magnetism forms a couple, there is no 
 tendency for the needle to move bodily forward 
 towards either of the earth's poles. Its tendency 
 is merely to rotate until it comes to rest within 
 the lines of the earth's magnetic field, entering at 
 its south pole, passing through its mass and 
 coming out at its north pole. 
 
 Of course this would be true in the case of a 
 directing magnet only when it is at a great dis- 
 tance from the needle. Otherwise, there would 
 be motion towards the poles as well as rotation. 
 
 Needle, Magnetic, Inclination or Dip of 
 
 The deviation of a mechanically bal- 
 anced magnetic needle from a horizontal po- 
 sition. 
 
 The direction of a magnetic needle in all parts 
 of the earth, except at the magnetic equator, 
 differs from a level or horizontal position. One 
 of its ends inclines or dips towards the ground. 
 (See Dip, Magnetic. Needle, Magnetic, Dipping.) 
 
 Needle, Magnetic, Orientation of 
 
 The coming to rest of a magnetic needle in 
 the earth's magnetic field. 
 
 Needle, Magnetic, Variation of 
 
 The angular deviation of a magnetic needle 
 from the true geographic north. 
 
 The declination of the magnetic needle. 
 (See Declination.} 
 
 Needle of Oscillation. A small magnetic 
 needle employed for measuring the intensity 
 of a magnetic field by counting the number of 
 oscillations the needle makes in a given time, 
 when disturbed from its position of rest in 
 such field. (See Magnetization, Intensity of. 
 Lines, Isodynamic.) 
 
 This use of a magnetic needle in determining 
 the magnetic intensity of any place is analogous 
 to the use of the pendulum in determining the in- 
 tensity of gravity at any place. 
 
 Suppose, for example, that at a certain place the 
 needle made 245 oscillations in ten minutes, and 
 13 Vol. 1 
 
 that at another place it made 211 in the same 
 time. Then the relative intensities at these two 
 places would be as the square of these two num- 
 bers, or as I : 1.3482. 
 
 Needle, Telegraphic A needle em- 
 ployed in telegraphy to represent by its move- 
 ments to the left or right respectively the dots 
 and dashes of the Morse alphabet. (See 
 Telegraphy, Needle System of.) 
 
 Needle, Throw of A phrase some- 
 times used for the angular deflection of a 
 needle, particularly when the needle is swing- 
 ing. 
 
 The displacement of the magnetic needle is 
 called the deflection, the elongation, or the throw. 
 The first will appear to be the preferable term 
 when the needle conies to rest in a displaced posi- 
 tion. 
 
 Negative Charge. (See Charge, Nega- 
 tive^ 
 
 Negative Direction of Electrical Con- 
 vection of Heat. (See Direction, Negative, 
 of Electrical Convection of Heat.) 
 
 Negative Direction of Simple-Harm on ic 
 Motion. (See Motion, Simple-Harmonic, 
 Negative Direction of.) 
 
 Negative Electricity. (See Electricity, 
 Negative.) 
 
 Negative Electrode. (See Electrode, 
 Negatived) 
 Negative Element of a Voltaic Cell. 
 
 (See Element, Negative, of a Voltaic Cell.) 
 Negative Feeders. (See Feeders, Nega- 
 tive^ 
 
 Negative Omnibus Bars. (See Bars, 
 Negative Omnibus?) 
 
 Negative Phase of Electrotonus. (See 
 Electrotonus, Negative Phase of.} 
 
 Negative Plate of Storage Battery. 
 
 (See Plate, Negative, of Storage Cell.} 
 
 Negative Plate of Voltaic Cell. (See 
 Plate, Negative, of Voltaic Cell.} 
 
 Negative Pole. (See Pole, Negative.} 
 Negative Potential. (See Potential, Neg- 
 ative^ 
 
 Negative Side of Circuit. (See Circuit, 
 Negative Side of.} 
 
380 
 
 [Nig. 
 
 Negative Wire. (See Wire, Negative!) 
 
 Negatively. In a negative manner. 
 
 Negatively Excited. Charged with nega- 
 tive electricity. (See Electricity, Negative?) 
 
 Nerve or Muscular Fibre, - Excitability 
 
 of (See Excitability, Electric, of 
 
 Nerve or Muscular Fibre.} 
 
 Nerves, Action of Electricity on 
 
 Stimulating and other actions produced in 
 nerves by the passage of electricity through 
 them, dependent on the direction and char- 
 acter of the current. (See Electrotonus. 
 Galvanization. Faradization. Galvano- 
 Faradization?) 
 
 Net, Faraday's 
 
 An insulated net 
 
 of cotton gauze, or other similar material, 
 capable of being turned inside out without 
 being thereby discharged, employed for de- 
 monstrating that in a charged, insulated con- 
 ductor the entire charge is accumulated oh 
 the outer surface of the conductor. 
 
 Fig. 407. Faraday's Net. 
 
 Faraday's net, as shown in Fig. 407, consists 
 of a bag N, of cotton gauze, or mosquito netting, 
 supported on an insulating stand I. When tested 
 by a proof plane, no free electric charge is found 
 on the inside, though such a charge is readily 
 v detected by the same means on the outside. By 
 I the aid of the silk strings S, S, the bag can be 
 turned inside out, when the charge will then all 
 be found on the then inside, or the now outside. 
 Faraday was in the habit of protecting his 
 delicate electroscopes against outside electrifica- 
 tion by covering them with gauze. To properly 
 act as an electric screen, the gauze should be con- 
 nected with the earth. 
 
 Faraday constructed a small insulated room, 
 
 twelve feet in height, breadth and depth, covered 
 on the inside with tin-foil, and, on charging this 
 room from the outside, he was unable to detect 
 the presence of any charge on the inside, even by 
 the aid of his most delicate instruments. This 
 room is often referred to as Faraday's Cube. 
 
 Nets, Torpedo 
 
 Steel wire netting 
 suspended from or attached to a ship's side 
 for the purpose of ensuring protection against 
 moving torpedoes. 
 
 Network of Currents. (See Currents, 
 Network of. Laws, Kirchhoff's?) 
 
 Neutral Armature. (See Armature, 
 Neutral?) 
 
 Neutral Feeder. The feeder that is 
 connected with the neutral or intermediate 
 terminal of the dynamos in a three-wire sys- 
 tem of distribution. (See Feeders?) 
 
 Neutral Line of Commutator Cylinder. 
 
 (See Line, Neutral, of Commutator 
 Cylinder?) 
 
 Neutral - Omnibus Bars. (See Bars, 
 Neutral-Omnibus.) 
 
 Neutral Point. (See Point, Neutral.) 
 
 Neutral Points of a Dynamo-Electric 
 Machine. (See Points, Neutral, of Dynamo- 
 Electric Machine?) 
 
 Neutral Points of Magnet. (See Points, 
 Neutral, of Magnet?) 
 
 Neutral Points of Thermo-Electric Dia- 
 gram. (See Points, Neutral, of Thermo- 
 Electric Diagram?) 
 
 Neutral-Relay Armature. - (See Arma- 
 ture, Neutral-Relay?) 
 
 Neutral Section of Magnet. (See Sec- 
 tion, Neutral, of Magnet?) 
 
 Neutral Wire. (See Wire, Neutral.) 
 Neutral Wire Ampere-Meter. (See Am- 
 pere-Meter, Balance or Neutral Wire?) 
 New Ohm. (See Ohm, New.) 
 Nickel Bath. -(See Bath, Nickel?) 
 
 Nickeling, Electro Electroplating 
 
 with nickel. (See Plating, Electro?) 
 
 Nickel-Plating.- (See Plating, Nickel?) 
 Night Bell.- (See Bell, Night* 
 
Nod.] 
 
 381 
 
 [Noi. 
 
 Nodal Point. (See Point, Nodal.} 
 
 Nodes, Electrical Points in an open 
 circuited conductor, through which electrical 
 oscillations are passing, which possess a con- 
 stant mean value of potential, while the poten- 
 tial at its ends alternates between two fixed 
 limits. 
 
 Points on a conductor where the strength 
 of the induced oscillatory current is equal to 
 zero. 
 
 The nodal points on a conductor through which 
 electrical oscillations are passing therefore cor- 
 . respond closely to the nodes on a vibrating wire 
 or cord. 
 
 Dr. Hertz employed the following appara- 
 tus in order to show the position of two nodes 
 in a conductor: An induction coil, A. had its sec- 
 ondary terminals connected as shown in Fig. 408, 
 
 Fig. 408. Nodes in Conductor. 
 
 to two metallic spheres, C and C'. The spark mi- 
 crometer circuit, a c d b, was placed near it, as 
 shown, and the sparking distance of the secondary 
 urcuit of the induction eoil adjusted, ho that the 
 spark micrometer circuit was in unison wiih it. 
 When sparks were passed between the terminals 
 of the induction coil A, sparks pas=e<! between the 
 terminals I and 2, at M, under the influe ce of 
 resonant action. 
 
 If, now, a second micrometer circuit, e g h f, 
 exactly similar to a c d b, was added, as shown in 
 the figure, and the two joined near the term.nals I 
 2 3 4, by conducting wires, as shown, the entire 
 system of the micrometer circuit formed a closed 
 metallic circuit, the fundamental vibration of 
 which would have two nodes, one at the middle 
 point of c d, and the other at g h. The inter- 
 nodes would be at the junctions i 3, and 2 4, and 
 under . these circumstances a true resonant ac- 
 tion existed between the secondary circuit and the 
 micrometer circuit, as was shown by the fact that 
 any alteration in the circuit e g h f , whether by 
 
 increasing or decreasing its length, diminished 
 the sparking distance. Since the conductor con- 
 necting points 2, and 4, was in the position of 
 the node, where the strength of the excited oscil- 
 latory current was zero, its removal from between 
 these points should have no influence on the 
 intensity of the vibration. This was found on 
 trial to be the case. Electrical vibrations may 
 therefore be excited by electrical resonance in 
 conductors corresponding not only to the simple 
 fundamental note or vibration, but also to the 
 higher electrical overtones. 
 
 The apparatus shown in Fi *. 409, from Tesla, 
 illustrates the phenomena of alternative path, as 
 well as electric nodes. The terminals of an in- 
 duction coil are connecter), as shown, to a con- 
 denser and to a thick copper conductor. Though 
 the two incandescent lamps are placed as shown, 
 yet they are raised to luminosity by a species of 
 brush discharge that passes through them, al- 
 though they would be short circuited to any cur- 
 rent but an oscillatory discharge. 
 
 Fig. 4O<). Nodes in a Conductor. 
 
 Nodular Deposit, Electro-Metallurgical 
 
 (See Deposit, Electro-Metallurgical 
 
 Nodular^) 
 Noisy Arc. (See Arc, Noisy.) 
 
Nom.J 
 
 382 
 
 [Num. 
 
 Nominal Candle-Power. (See Power, 
 Candle, Nominal?) 
 Non- Automatic Variable Resistance. 
 
 (See Resistance, Variable, Non- Automatic.} 
 
 Non-Conductors. Substances that offer 
 so great resistance to the passage of an elec- 
 tric current through their mass as to practi- 
 cally exclude a discharge passing through 
 them. 
 
 Njn conductors are called insulators, because 
 they electrically insulate substances placed on or 
 surrounded by them. 
 
 The terms non-conductors or insulators are 
 ordinarily used in a relative sense to mean bodies 
 which allow no practical or appreciable current 
 to pass through them, since there are no sub- 
 stances known, apart, perhaps, from the universal 
 ether, that absolutely prevent the flow of an elec- 
 tric current, the difference of potential of which 
 is sufficiently great 
 
 The entire absence of ordinary matter, as in the 
 case of a high vacuum, appears to render a high 
 vacuum very nearly, if not entirely, an absolute 
 insulator. 
 
 Non-Electrics. A term formerly applied 
 to substances like metals or other conductors 
 which appeared not to become electrified by 
 friction. 
 
 The term non-electric, was used in contradis- 
 tinction to electrics, or substances readily elec- 
 trified by friction. The distinction no longer 
 holds, since non-electrics, ifinsulated, are readily 
 electrified by friction. 
 
 Non-Homogeneous Current-Distribu- 
 tion. (See Current, Non-Homogeneous, 
 Distribution of.) 
 
 Non-Illumined Electrode. (See Elec- 
 trode, Non-Illumined) 
 
 Non-Inductive Resistance. (See Resist- 
 ance, Non-Inductive.) 
 
 Non-Oscillatory Discharge. (See Dis- 
 charge, Non-Oscillatory) 
 
 Non- Polarized Armature. (See Arma- 
 ture, Non-Polarized?] 
 
 Non-Polarizable Electrodes. (See Elec- 
 trodes, Non-Polar izable?) 
 
 Non-Wasting Electrode. (See Electrode, 
 Non- Wasting?) 
 
 Normal Day, Magnetic (See Day, 
 
 Normal Magnetic.) 
 
 Northern Light. The Aurora Borealis. 
 (See Aurora Borealis?) 
 
 Notation, Algebraic A system of 
 
 arbitrary symbols employed in algebra. 
 
 The following brief description of the notation 
 employed in algebra is for the use of the non- 
 mathematical reader. 
 
 Quantities are represented in algebra by let 
 ters, such as a, and b, x, and y, etc. 
 
 Addition is represented thus: a + b. 
 
 Subtraction is represented thus: a b. 
 
 Multiplication is represented thus: a X b, or 
 simply by writing the letters next to each other ab. 
 
 Division is represented thus: a -j- b, or 3 
 
 An Exponent, or figure placed to the right of a 
 letter, above it as a 3 , indicates that the quantity 
 represented by a, is to be multiplied by itself three 
 times, as a X a X a, or a a a. 
 
 A Co-efficient, or figure placed to the left of a 
 quantity, indicates the number of times that quan- 
 tity is to be taken; thus, 3 a, indicates that a is to 
 be added three times, thus: a-f-a-|-a,or3Xa. 
 
 A Radical Sign or Root, thus \/a, or 2 v/a, 
 indicates that the square root of the quantity a t 
 is to be taken. In the same manner s\/~a, indi- 
 cates that the cube root of a is to be taken. 
 
 *. 
 
 These expressions are sometimes written a*, or 
 Equality is indicated thus: a s =a XaXa, or 
 
 A negative exponent a~* indicates _, or is the 
 
 a 2 
 
 exponent of the reciprocal of the quantity indi- 
 cated. 
 
 Null or Zero Method. (See Method, 
 Null or Zero?) 
 
 Null Point. (See Point, Null.) 
 
 Number, Diacritical Such a num- 
 ber of ampere-turns at which a given core 
 would receive a magnetization equal to half 
 saturation. 
 
Obs.] 
 
 383 
 
 [Ohm. 
 
 1. A contraction for megohm. (See 
 Okm, Meg.) 
 
 &. A contraction for ohm. (See Ohm?) 
 Obscure Heat. (See Heat, Obscure?) 
 Observation Mine. (See Mine, Observa- 
 tion?) 
 
 Observatory, Magnetic An obser- 
 vatory in which observations of the variations 
 in the direction and intensity of the earth's 
 magnetic field are made. 
 
 Magnetic observatories are generally furnished 
 with self-registering magnetic apparatus, such as 
 magnetographs, magnetometers, inclinometers. 
 (See Magnetometer. Magnetograph. fnclinome- 
 ter.) 
 
 Magnetic observatories are generally con- 
 structed entirely of non-magnetic materials; that 
 is, of such materials as are destitute of paramag- 
 netic properties. 
 
 Obtuse Angle. (See Angle, Obtuse?) 
 Occlusion of Gas. (See Gas, Occlusion 
 
 Odorscope. An apparatus in which the 
 determination of an odor was attempted by 
 the measurement of the effect the odorous 
 vapor, or effluvia, produced on a variable 
 contact resistance. 
 
 The microtasimeter was used in connection 
 with the odorscope. (See Diagometer, Rous- 
 seau's. Microtasimeter.'] 
 
 Oerstedt, An A proposed term for 
 
 the unit of electric current, in place of an 
 ampere. 
 
 The term has not been adopted. 
 
 Ohm. The unit of electric resistance. 
 
 Such a resistance as would limit the flow 
 of electricity under an electromotive force of 
 one volt to a current of one ampere, or to one 
 coulomb per second. (See Unit, B. A. Ohm, 
 Legal. Ohm, Standard?) 
 
 A value equal to 10 absolute electro-mag- 
 netic units. 
 
 A value which is represented by a velocity 
 of 10, or 1, 000,000,000 centimetres per second. 
 
 It may be difficult at first to see how resistance 
 can be correctly represented by a velocity. The 
 following consideration may render this clear : 
 The formula for calculating the velocity is 
 
 D 
 
 V = -,p or the velocity equals the distance passed 
 
 through in unit time. Now, by examining the 
 formula for the value of the resistance, expressed 
 in terms of the electro-magnetic units (see 
 Units, Electro-Magnetic, Dimensions of), it may 
 be seen to be that resistance = 
 
 Electromotive force 
 Curi ent. 
 
 But this value is of the nature of a velocity, 
 being equal to the length, divided by the time. 
 Resistance, therefore, has the dimensions of a 
 velocity. 
 
 This is clearly expressed by Silvanus P. Thomp- 
 son in his ' ' Elementary Lessons in Electricity 
 and Magnetism," as follows, viz.: " Suppose we 
 have a circuit composed of two horizontal coils, 
 C S, and D T (Fig. 410), i centimetre apart, 
 joined at C D, and completed by means of a 
 sliding piece, A B. Let this variable circuit be 
 placed in a uniform magnetic field of unit inten- 
 sity, the lines of force being directed vertically 
 downwards through the circuit. 
 
 "If, now, the slider be moved along towards 
 S T, with a velocity of n, centimetres per second, 
 the number of additional lines of force embraced 
 by the circuit will increase at the rate of n, per 
 second ; or, in other words, there will be an in- 
 
 g. 410. Resistance as a Velocity. 
 
 duced electromotive force impressed upon the cir- 
 cuit, which will cause a current to flow through 
 the slider from A to B. Let the rails have no 
 resistance, then the strength of the current will 
 depend on the resistance of A B. Now, let A B, 
 move at such a rate that the current shall be of 
 unit strength. If its resistance be one absolute 
 (electro-magnetic) unit, it need only move at the 
 rate of I centimetre per second. If its resistance 
 be greater, it must move with a proportionately 
 
Ohm.J 
 
 384 
 
 [Ohm. 
 
 greater velocity ; the velocity at which it must 
 move to keep up a current of unit strength being 
 numerically equal to its resistance. The resist- 
 ance known as " i ohm " is intended to be so 9 ab- 
 solute electro-magnetic units, and, therefore, is 
 represented by a velocity of io 9 centimetres, or 
 10,000,000 metres (/ earth-quadrant) per 
 second."' 
 
 Ohm, B. A. A contraction for 
 
 British Association ohm. 
 
 Ohm, Board of Trade A unit of re- 
 sistance as determined by a committee of the 
 English Board of Trade. 
 
 A committee consisting of Sir W. Thomson, 
 Lord Rayleigh, Dr. J. Hopkinson and other 
 authorities appointed by the Board of Trade 
 (England) has recently recommended that the 
 ohm be taken as the resistance of a column of 
 mercury 106.3 centimetres in length and one 
 square millimetre area of cross-section at o de- 
 grees C. and since this value agrees with the best 
 experimental results, it will probably be generally 
 and finally adopted. 
 
 Ohm, British Association The 
 
 British Association unit of resistance, 
 adopted prior to 1884. 
 
 The value of the unit of electric resistance, or 
 the ohm, was determined by a Committee of the 
 British Association as being equal to the resistance 
 at o degree C. of a column of mercury I square 
 millimetre in area of cross-section and 104.9 
 centimetres in length. This length was taken as 
 coming nearest the value of the true ohm de- 
 auced experimentally from certain theoretical 
 considerations. Subsequent re-determinations 
 showed the value so obtained to be erroneous. 
 
 The value of the ohm is now taken internation- 
 ally, as adopted by the International Electric 
 Congress in 1884, as the resistance of a column 
 of mercury 106 centimetres in length, and I 
 square millimetre in area of cross-section. This 
 last value is called the legal ohm, to distinguish it 
 from the B. A. ohm, which, as above stated, is 
 equal to a mercury column 104.9 centimetres in 
 length. Usage now sanctions the use of the 
 word ohm to mean the legal ohm. 
 
 This value of the legal ohm is provisional until 
 the exact length of the mercury column can be 
 finally determined. (See Ohm, Board of Trade. ) 
 
 The following are the relative values of these 
 units, viz.: 
 
 i legal ohm = 1.0112 B. A. ohm. 
 
 " " = 1 .0600 Siemens unit. 
 
 I B. A. ohm = .9889 legal ohm. 
 
 i " " = i .0483 Siemens unit. 
 
 i Siemens unit = .9540 B. A. ohm. 
 
 " " = .9434 legal ohm. 
 
 Ohm, Legal The resistance of a 
 
 column of mercury i square millimetre in 
 area of cross-section, and 106 centimetres in 
 length, at the temperature of o degree C. or 
 32 degrees F. (See Unit.B. A.) 
 
 i ohm = 1.00112 B. A. units. This va!ue of 
 the ohm was adopted by the International Elec- 
 tric Congress, in 1884, as a value that should be 
 accepted internationally as the true value of the 
 ohm. This value, however, was provisional, and 
 was never actually legalized. It will probably be 
 replaced by the new (106.3 cm -) hm. (See 
 Ohm, Board of Trade.} 
 
 Ohm, Meg 1 One million ohms. 
 
 Ohm, New A term sometimes used 
 
 for the Board of Trade ohm. (See Ohm, 
 Board of Trade.) 
 
 Ohm, Standard A length of wire 
 
 having a resistance of the value of the true 
 or legal ohm, employed in standardizing re- 
 sistance coils. 
 
 The standard ohm, as issued by the Electric 
 Standards Committee of England, has the form 
 
 J'tf. 411. Standard Ohm. 
 
 shown in Fig. 411. The coil of wire is formed 
 of an alloy of platinum and silver, insulated by 
 silk covering and melted paraffine. Its ends are 
 soldered to thick copper rods r, r', for ready 
 connection with mercury cups. The coil is at 
 B. The space above it at A, is filled with paraffine, 
 except at the opening t, which is provided for 
 the insertion of a thermometer. 
 
Ohm.J 
 
 335 
 
 [Ope. 
 
 Ohm, True An ohm having the 
 
 true theoretical value of the ohm. (See Ohm.} 
 
 Ohmage. The value of the resistance of 
 a circuit expressed in ohms. 
 
 Ohmic Resistance. (See Resistance, 
 Ohmic or True.) 
 
 Ohmmeter. A commercial galvanometer, 
 devised by Ayrton, for directly measuring by 
 the deflection of a magnetic needle, the re- 
 sistance of any part of a circuit through 
 which a strong current of electricity is 
 flowing. 
 
 Ayrton's ohmmeter is represented diagram- 
 matically in Fig. 412. Two coils C C, and c c, 
 
 f. 
 
 Fig. 412, Ayrton's Ohmmeter. 
 
 consisting of a short thick wire, and a long thin 
 wire, respectively, are placed at right angles to 
 each other, and act on a soft iron needle situated 
 as shown. The short, thick wire coil C C, is con- 
 nected in series with the resistance O, to be 
 measured. The long, fine wire coil, of kn<nun 
 high resistance, is placed as a shunt to the un- 
 known resistance. 
 
 Under these circumstances, it can be shown 
 that the action on the needle is that due to the ratio 
 of the difference of potential at the terminals of 
 the unknown resistance and the current strength 
 
 in the thick wire coil, or R = , as may be 
 
 deduced from Ohm's law. 
 
 The coils are so proportioned that the current 
 when flowing through 1he short thick wire moves 
 the needle to the zero of the scale, while the long 
 thin wire produces a deflection directly propor- 
 tional to the resistance. 
 
 Ohm's Law. (See Law of Ohm) 
 
 Oil, Colza An oil obtained from the 
 
 seed of the Brassica oleracea, a species of 
 cabbage. 
 
 Colza oil is extensively used for purposes of il- 
 lumination and in the carcel standard lamp. (See 
 Lamp) Carcel.) 
 
 Oil Cup. A cup containing oil for lubri 
 eating machinery. 
 
 Oil Insulator. (See Insulator, Oil.) 
 
 Oil Transformer. (See Transformer, 
 Oil.) 
 
 Oiler, Automatic An oil cup or res- 
 ervoir that automatically spreads oil over the 
 bearings of r_i. chinery in motion. 
 
 Okonite. A variety of insulating material. 
 
 Omnibus Bars. (See Bars, Omnibus) 
 
 Omnibus Wires. (See Wires, Omnibus^ 
 
 Opacity, Selective Opaque in a cer- 
 tain direction or directions only. 
 
 Certain substances are opaque to polarized lighl 
 in certain planes only. Thus, a plate of tourma- 
 line permits light polarized in a certain plane 
 freely to pass through it, but is entirely opaque 
 in a plane at right angles thereto. 
 
 S. P. Thompson and Lodge have shown that 
 such crystals of tourmaline possess curious prop- 
 erties in regard to the conduction of heat. While 
 warming, the crystal conducts heat better in a cer- 
 tain direction than in the opposite direction. While 
 cooling, exactly the opposite effects are observed. 
 In the same manner, while the crystal is rising in 
 temperature, there is an accumulation of positive 
 electricity at one end, an 1 negative at the other. 
 While the crystal is cooling, the reversa i s true- 
 
 Open-Box Conduit. (See Conduit, Open- 
 Box) 
 
 Open Circuit. (See Circuit, Open) 
 Open-Circuit Electric Oscillations. 
 
 (See Oscillations, Open-Circuit, Electric) 
 Open-Circuit Induction. (See Induction, 
 
 Open-Circuit) 
 Open-Circuit Oscillation, Period of 
 
 The time in which the oscillations set up in 
 a circuit by electrical resonance require to 
 make a complete one to-and-fro motion. 
 
 The period of an open-circuit electric oscillation 
 is determined by the product of the co-efficients 
 of self-induction of the conductor, and does not 
 dt-pend on the composition of the terminals. It is 
 practically independent of their resistances. 
 
 Open-Circuit Single-Current Signaling. 
 
 (See Signaling, Single-Current, Open- 
 Circuit) 
 
Ope.] 
 
 386 
 
 [Ore. 
 
 Open-Circuit Yoltaic Cell (See Cell, 
 Voltaic, Open-Circuit} 
 
 Open-Circuit Voltmeter. (See Volt- 
 meter, Open-Circuit,} 
 
 Open-Circuited. Put on an open circuit. 
 
 Open-Circuited Conductor. (See Con- 
 ductor, Open-Circuited} 
 
 Open-Circuited Thermostat. (See Ther- 
 mostat, Open-Circuit.} 
 
 Open-Coil Drum Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 Open-Coil Drum} 
 
 Open-Coil Dynamo-Electric Machine. 
 
 (See Machine, Dynamo-Electric, Open-Coil} 
 
 Open-Coil Ring Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo- Electric, 
 Open-Coil Ring} 
 
 Open-Iron-Circuit Transformer. (See 
 Transformer, Open-Iron-Circuit} 
 
 Open-Iron Magnetic Circuit. (See Cir- 
 cuit, Open-Iron Magnetic} 
 
 Open Magnetic Core. (See Core, Open- 
 Magnetic} 
 
 Opening Shock. (See Shock, Opening} 
 
 Operation, Magnet - The use of a 
 magnet for the purpose of removing particles 
 of iron from the human eye. 
 
 Optical Strain. (See Strain, Optical} 
 
 Optical Strain, Electro-Magnetic 
 
 (See Strain, Optical Electro-Magnetic} 
 
 Optical Strain, Electrostatic (See 
 Strain, Electrostatic, Optical} 
 
 Optics, Electro That branch of 
 
 electricity which treats of the general relations 
 that exist between light and electricity. 
 
 The phenomena of electro-optics may be ar- 
 ranged under the following heads, viz. : 
 
 (i.) Electrostatic stress, produced by an 
 electrostatic field causing an optical strain in a 
 transparent medium, whereby such medium 
 acquires the property of either rotating the plane 
 of polarization of a beam of plane polarized light, 
 or of doubly refracting light. 
 
 (2.) Electro magnetic stress produced by a 
 
 magnetic field causing an optical strain in a trans- 
 parent medium, whereby such medium acquires 
 the property of either rotating the plane of polar- 
 ization, or of doubly refracting light. (See Re- 
 fraction, Double, Electric} 
 
 (3.) Changes in the electric resistance of bodies 
 caused by the action of light. (See Cell, Sele- 
 nium. ) 
 
 (4.) The relation existing between the values oi 
 the index of refraction of a transparent medium 
 and its specific inductive capacity. (See Refrac- 
 tion. Capacity, Specific Inductive} 
 
 This relation has been shown to be as follows : 
 
 The specific inductive capacity is approxi- 
 mately equal to the square of the index ot re- 
 fraction. 
 
 (5.) The relation existing between the velocity 
 of light and the value of the ratio of electrostatic 
 and the electro-magnetic units, thus giving a 
 basis for an electro-magnetic theory of light. 
 (See Light, Maxwell's Electro-Magnetic Theory 
 of} 
 
 Polarized light reflected from the surface of a 
 magnet, although it penetrates the substance to 
 but a trifling extent, yet has its plane of polariza- 
 tion distinctly rotated by the magnetic whirls in 
 the iron. 
 
 Oral or Speak ing-Tube Annunciator. 
 
 (See Annunciator, Oral or Speaking- Tube} 
 Ordinate. A distance taken on a per- 
 pendicular line called the axis of ordinates, in 
 contradistinction to the axis of abscissas. 
 (See Ordinates, Axis of} 
 
 Thus in Fig. 413, D i, is the ordinate of the 
 point D, in the curve O D R. 
 
 Ordinates, Axis of One of the axes 
 
 of co-ordinates used 
 for determining the 
 position of the points 
 in a curved line. 
 
 Thus in Fig. 413 the 
 line A B, is called the axis 
 of ordinates because it is 
 the line on which the or- 
 
 n 
 
 dinate 2 D, is measured. . 
 
 rig- 
 
 Ores, Electric 
 Treatment of Processes for the ex- 
 traction of metals from their ores. 
 
 These processes are* referable to three dis- 
 tinct classes, viz. : 
 
 AxisofO rdi. 
 
387 
 
 [Osin- 
 
 (I.) Those in which the reduction is effected by 
 means of heat of electric origin. 
 
 (2.) Those in which the reduction is effected by 
 the combined action of heat and electrolysis. 
 
 (3.) Those in which the reduction is effected by 
 means of electrolysis only. 
 
 Organ, Electric A wind organ, in 
 
 which the escape of air into the different 
 pipes is electrically controlled. 
 
 In an electric organ, the keys, instead of oper- 
 ating levers, as usual, to admit the passage of air 
 into the pipes, merely complete the circuit of a 
 battery through a series of controlling electro-mag- 
 nets. With such an arrangement, the keyboard 
 can be placed at any desired distance. 
 
 Electric organs have been constructed, in which 
 a chemical or mechanical record is made of the 
 notes struck by the performer, as well as the 
 musical value of such notes. By such a device 
 the musical creations of a composer are perma- 
 nently recorded in characters that are capable of 
 interpretation by a compositor skilled in musical 
 notation. 
 
 Orientation of Magnetic Needle. (See 
 Needle, Magnetic, Orientation of.) 
 
 Origin, Point of The point where 
 the axes of co-ordinates start or originate. 
 (See Co-ordinates, Axes of.) 
 
 Orthogonal. Rectangular, or right-an- 
 gled. 
 
 Oscillating Discharge. (See Disoharge, 
 Oscillating^) 
 
 Oscillating Needle. (See Needle of 'Oscil- 
 lation.) 
 
 Oscillation, Centre of A point in 
 
 a body swinging like a pendulum, which is 
 neither accelerated nor retarded, during its 
 oscillations, by the portions of the pendulum 
 that are situated respectively above or below it. 
 
 If all the mass were concentrated at the centre 
 of oscillation the time of oscillation would be the 
 same. 
 
 The centre of oscillation is always below the 
 centre of gravity. The vertical distance between 
 the centre of oscillation and the point of support 
 of a pendulum, determines the virtual length of 
 the pendulum, and hence its number of vibra- 
 tions per second. (See Pendulum, Laws oj. ) 
 
 Oscillations, Electric 
 
 The serie s 
 
 of partial, intermittent discharges of which 
 the apparent instantaneous discharge of a 
 Leyden jar through a small resistance actu- 
 ally consists. 
 
 These partial discharges produce a series of 
 electric oscillations of the current in the circuit of 
 the discharge, which consist of true to-and-fro 
 or backward -and-forward motions of the elec- 
 tricity. This phenomenon was discovered by 
 Joseph Henry. 
 
 Oscillations, Open-Circuit, Electric 
 
 Electric oscillations produced in open cir- 
 cuits by the presence of electric pulses in 
 neighboring circuits. 
 
 Oscillatory Discharge. (See Discharge, 
 Oscillatory^) 
 
 Oscillatory Electric Displacement. (See 
 Displacement, Electric, Oscillatory^) 
 
 Oscillatory Electromotive Force. An 
 
 electromotive force which is rapidly periodic. 
 
 Oscillatory Inductance. (See Induc- 
 tance, Oscillatory, Electric?) 
 
 Oscillatory Induction. (See Induction, 
 Oscillatory^ 
 
 Osmose. The unequal mixing of liquids of 
 different densities through the pores of a 
 separating medium. 
 
 If a solution of sugar and water be placed in a 
 bladder, the neck of which is tied to a straight 
 glass tube, and the bladder is then immersed in a 
 vessel of pure water with the tube in a vertical 
 position, the two liquids will begin to mix, the 
 sugar and the water passing through the bladder 
 into the pure water, and the pure water passing 
 into the sugar and water in the bladder. This 
 latter current is the stronger of the two, as will be 
 shown by the water rising in the vertical glass 
 tube. 
 
 The stronger of the two currents, that is, the 
 one directed towards the higher level, or the one 
 which produces the higher level, is called the en- 
 dosmotic current, and the weaker current the 
 exosmotic current. 
 
 Osmose, Electric A difference of 
 
 liquid level between two liquids placed on 
 opposite sides oE a diaphragm produced by 
 the passage of a strong electric current 
 
Osm.J 
 
 388 
 
 [Ozo. 
 
 through the liquids between two electrodes 
 placed therein. 
 
 The higher level is on the side towards which the 
 current flows through the diaphragm, thus appa- 
 rently indicating an onward motion of the liquid 
 with the current, or, in other words, the liquid is 
 higher around the kathode than around the anode. 
 The difference of level is most marked when 
 poorly conducting liquids are employed. 
 
 As a converse of this, Quincke has shown that 
 electric currents are set up when a liquid is forced 
 by pressure through a porous diaphragm. The 
 term diaphragm currents has been proposed for 
 these currents. Their electromotive force depends 
 on the nature of the liquid, on the material of the 
 diaphragm, and on the pressure that forces the 
 liquid through the diaphragm. (See Phenomena, 
 Electro-Capillary. Currents, Diaphragm.} 
 
 Osmotic. Of or pertaining to osmose. 
 (See Osmose.} 
 
 Osteotome, Electric A revolving 
 
 electrically propelled saw, employed in the 
 surgical cutting of bones. 
 
 An electric osteotome consists essentially of a 
 form of revolving engine known as a dental en- 
 gine, furnished with a circular saw, or other ro- 
 tary cutter, driven or propelled by electricity. 
 
 Outgoing Current. (See Current, Out- 
 going) 
 
 Outlet. In a system of incandescent lamp 
 distribution the places in a building where 
 the fixtures or lamps are attached. 
 
 The outlets are left in a building by the wire- 
 man for the electric fixtureman to attach the de- 
 vice intended to be used on the circuits so pro- 
 vided. 
 
 Output, Magnetic The product of 
 
 the magnetic flux by the magneto-motive 
 force. 
 
 Output of Dynamo-Electric Machine. 
 
 (See Machine, Dynamo-Electric, Output of) 
 
 Outrigger for Electric Lamp. A device 
 for suspending an electric arc lamp so as to 
 cause it to stand out from the wall of a 
 building. 
 
 An outrigger and hood with lamp attached are 
 shown in Fig. 414. 
 
 Outrigger Torpedo. - (See Torpedo, Out- 
 rigger) 
 
 Orer-Compounded 1 . The compounding @f 
 a dynamo-electric machine so as to produce 
 
 Fig -414. Outrigger and Hood. 
 
 an increase of voltage under increase of load. 
 Over-compounding is generally employed for 
 compensating for drop or loss of potential in the 
 line or conductor, and is adjusted to a definite 
 percentage of increase from light to full load in 
 accordance with the amount of drop, or loss, for 
 which such compensation was designed. 
 
 Overhead Lines. (See Lines, Overhead.} 
 
 Overhead System, Continuous, of Motive 
 
 Power for Electric Railroads (See 
 
 Railroads, Electric, Continuous Overhead 
 System of Motive Power for.) 
 
 Overload of Electric Motor. (See Motor, 
 Electric, Overload of.} 
 
 Overtones. Additional, faint tones, ac- 
 companying nearly every distinct musical 
 tone, by the presence of which the peculiarity 
 or quality of such tone is produced. (See 
 Sound, Characteristics of.} 
 
 Overtones, Electric Electric vibra- 
 tions produced in open-circuited conductors 
 by electric resonance, of higher rates than the 
 fundamental vibrations. 
 
 The existence of electrical overtones necessitates 
 the existence of electric nodes. (See Nodes, Elec- 
 trical.) 
 
 Overtype Dynamo. (See Dynamo, Over- 
 type) 
 
 Ozite. An insulating substance. 
 
 Ozokerite. An insulating substance. 
 
Ozo.J 
 
 389 
 
 [Par. 
 
 Ozone. A peculiar modification of oxygen 
 which possesses more powerful oxidizing 
 properties than ordinary oxygen. 
 
 Ozone is now generally believed to be tri- 
 atomic oxygen, or oxygen in which the bonds are 
 closed, thus: 
 
 O- 
 
 -O 
 
 The peculiar smell observed when a torrent of 
 electric sparks passes between the terminals of 
 a Holtz machine, or a Ruhmkorff coil, is caused 
 by the ozone thus formed. 
 
 In a similar manner ozone is formed in the at- 
 
 mosphere during the passage through the air of a 
 flash of lightning. 
 
 During the so-called electrolysis of water, a com- 
 pound formed by the union of two volumes of 
 hydrogen with one volume of oxygen, some of the 
 oxygen is given off in the form of ozone. Since 
 ozone has a somewhat smaller volume than that 
 of the oxygen forming it, the volume of the 
 oxygen liberated is somewhat less than half the 
 volume of the hydrogen. 
 
 There are a number of different forms of ap- 
 paratus designed for the production of ozone. 
 They consist essentially either of means for pass- 
 ing a torrent of electric sparks through air or for 
 producing a species of polarization in the air. 
 
 P. D. or p. d. A contraction frequently em- 
 ployed for difference of potential. (See Poten- 
 tial, Difference of.) 
 
 Pacinotti Projections. (See Projections, 
 Pacinotti.) 
 
 Pacinotti Ring. (See Ring, Pacinotti.) 
 
 Pair, Astatic A term sometimes 
 
 applied to an astatic couple. (See Couple, 
 Astatic.') 
 
 Palladium. A metal of the platinum 
 group. 
 
 Metallic palladium has a tin-white color, and, 
 when polished, a high metallic lustre. It is 
 tenacious and ductile, and, like iron, can be 
 welded at a white heat. It is very refractory and 
 possesses in a marked degree the power of ab- 
 sorbing or occluding hydrogen and other gases. 
 It is not affected by oxygen at any temperature, 
 nor readily affected by ordinary corrosive agents. 
 
 Palladium Alloy. (See Ally, Pal- 
 ladium!) 
 
 Pane, Magic A condenser formed 
 
 of a sheet of glass covered on one side with 
 pieces of tin-foil with small spaces between 
 them pasted in some design on the glass. 
 
 On the discharge of a Leyden jar through these 
 metallic pieces, the design is seen as a series of 
 minute sparks, which bridge the spaces between 
 the adjacent pieces of foil. 
 
 Pantelegraphy. A system for the tele- 
 graphic transmission of charts, diagrams, 
 sketches or written characters. 
 
 Pantelegraphy is more frequently called fac- 
 simile telegraphy. (See Telegraphy, Fac- Simile.) 
 
 Paper Carbons. (See Carbons, Paper.) 
 
 Paper Cut-Out (See Cut-Out, Paper) 
 
 Paper Perforator. (See Perforator, 
 Paper.) 
 
 Paper Winder, Automatic A de- 
 vice, driven by clockwork, for automatically 
 delivering the paper fillet on which a tele- 
 graphic message is received. 
 
 Parabolic Reflector. (See Reflector, 
 Parabolic.) 
 
 Paraffin e. A name given to various 
 solid hydrocarbons of the marsh gas series, 
 that are derived from coal oil or petroleum by 
 the action of nitric acid. 
 
 Paraffine possesses excellent powers of insula- 
 tion, and forms a good dielectric medium. Dried 
 wood, boiled in melted paraffine, forms a fair in- 
 sulating material. 
 
 Paraffiue Wire. (See Wire, Paraffined) 
 
 Paraffining. Covering or coating with 
 paraffine. 
 
 The paraffine is applied, while melted by heat, 
 either by means of a brush, or by dipping the 
 article in the fused mas. 
 
Par.] 
 
 390 
 
 [Par. 
 
 Care must be taken in paraffining wooden or 
 other absorbent articles, to dry them before im- 
 mersing in the melted paraffine, since, if water be 
 present, steam is formed explosively, and the 
 melted paraffine scattered in all directions. 
 
 Paragreles. Lightning rods, intended to 
 protect fields against the destructive action of 
 hail. (See Hail, Assumed Electrical Ori- 
 gin of] 
 
 It was formerly believed that hail is caused by 
 electricity. It is now generally believed that the 
 electricity in hail storms is- caused by the hail. 
 It will, therefore, readily be understood that para- 
 greles can afford no real protection. 
 
 Parallax. The apparent angular displace- 
 ment of an object when seen from two dif- 
 ferent points of view. 
 
 In reading the exact division on a scale to which 
 a needle points, care must be taken to look di- 
 rectly down on the needle, and not sideways, so 
 as to avoid the error of displacement due to 
 parallax. 
 
 Parallel Circuit. (See Circuit, Parallel.} 
 Parallel Series. (See Series, Parallel?) 
 
 Parallelogram of Forces. (See Forces, 
 Parallelogram of.} 
 
 Parallels, Magnetic Lines connect- 
 ing places on the earth's surface at right 
 angles to the isogonal lines, or lines of equal 
 declination or variation. 
 
 The magnetic parallels are at right angles to 
 the magnetic meridians. The magnetic parallels 
 lie in planes parallel to the magnetic equator. 
 (SeelVeedte, Magnetic, Declination of . Meridian, 
 Magnetic. ) 
 
 Paramagnetic. Possessing properties or- 
 dinarily recognized as magnetic. 
 
 Possessing the power of concentrating the 
 lines of magnetic force. 
 
 Paramagnetic is a term employed in contra- 
 distinction to diamagnetic. (See Diamagnetic.} 
 A paramagnetic substance, cut in the form of a 
 bar whose length is much greater than its breadth 
 and thickness, will, when suspended in a magnetic 
 field in the manner shown in Fig. 415, take up a 
 position of rest with its greatest length in the direc- 
 tion of the lines of force, i. e., will point axially. 
 
 Fig 413. Diamagnetic 
 Polarity 
 
 In other words, the lines of force will so pass 
 through the paramagnetic substance as to reduce 
 the magnetic resistance of the circuit as much as 
 possible. 
 
 Paramagnetic substances, therefore, concen- 
 trate the lines of force on them. (See Resistance, 
 Magnetic.} 
 
 Diamagnetic substances, on the contrary, when 
 placed as shown in Fig. 415, assume a position of 
 rest with their least dimensions in the direction of 
 the lines of force, i. e. 
 they point equatorially. 
 This is the position in 
 which they are placed 
 by the lines of force, in 
 order to insure the least 
 magnetic resistance in 
 the circuit of these lines. 
 The magnetic resistance 
 of diamagnetic sub- 
 stances is great as com- 
 pared with that of par- 
 amagnetic substances. 
 
 The term ferro -mag. 
 netic has been proposed 
 for paramagnetic. If 
 another term be required, which is doubtful, 
 sidero-magnetic, proposed by S. P. Thompson, 
 would appear to be preferable. (See Magnetic, 
 Ferro. Magnetic, Sidero.} 
 
 Tyndall believes that the magnetic polarity 
 possessed by diamagnetic substances is the result 
 of a distinct polar force, different in its nature 
 from ordinary magnetism. His views, in this re- 
 spect, are not generally accepted. (See Polarity < 
 Diamagnetic.}' 
 
 Paramagneticallr. In a paramagnetic 
 manner. (See Paramagnetism.} 
 
 Paramagnetism. The magnetism of a 
 paramagnetic substance. 
 
 Parasitical Currents. (See Currents, 
 Parasitical.} 
 
 ParatonnSre. A French term for light- 
 ning rod, sometimes employed in English \ 
 technical works. 
 
 Lightning rod would appear to be the prefer- 
 able term. 
 
 Partial Contact (See Contact, Partial.} 
 Parti.il Disconnection. (See Disconnec- 
 tion, Partial?) 
 
Par.] 
 
 391 
 
 [Ten. 
 
 Partial Earth. (See Earth, Partial) 
 
 Partial Reaction of Degeneration. (See 
 Degeneration, Partial Reaction of.) 
 
 Passive State. (See State, Passive) 
 
 Path, Alternative- The path or 
 circuit taken by an impulsive discharge, in 
 preference to another path or circuit, open to 
 the discharge, although of enormously smaller 
 ohmic resistance. 
 
 The alternative path is the path taken by the 
 discharge produced by what was formerly called 
 lateral induction. 
 
 The explanation of the reason the discharge 
 takes the alternative path is that the counter-elec- 
 tromotive force of self-induction of the circuit, 
 produced by the impulsive discharge, is so great 
 as to make the path of the circuit itself, although 
 formed of conducting materials, practically non- 
 conducting. 
 
 If a Leyden jar is provided with discharge wires 
 or conductors, as shown is Fig. 416, a discharge 
 
 would pass across an air space in preference to 
 a metallic circuit, was greater for a thick copper 
 
 Fig. 416. Phenomena of Alternative Path. 
 
 taking place at A, is accompanied simultaneously 
 by an even longer spark at B, between the ends 
 of two long open-circuit leads. 
 
 To explain in a general manner the phenomena 
 of the alternative path, we may say that the dis- 
 charge at A, gives rise to electric oscillations in the 
 leads connected with B, and that there are sent out 
 into the surrounding medium radiations of pre- 
 cisely the same nature as those which produce 
 light, only of a wave length so long as to be un- 
 able to produce on the eye the effects ot light. 
 
 If the space between the balls at B, is too great 
 for the discharge to take place, the wires glow 
 and throw out minute sparks or brushes of light. 
 
 The action of the ordinary lightning arrester 
 depends on the principle of the alternative path. 
 The resistance of the metallic circuit, composed 
 of the line and the instruments, is so great in the 
 case of the impulsive discharge of a lightning 
 flash, that the discharge takes place between a 
 series of points connected with the line plate and 
 another series of points connected with the ground 
 plate. - (See Arrester, Lightning ) 
 
 Dr. Lodge, who has studied the principle of 
 alternative path in the case cf lightning rods, 
 finds that the distance at which the discharge 
 
 Fig. 4 17. Edison Electric Pen. 
 
 rod, 40 feet long, than for an iron rod of No. 27 
 B. W. G. of 33.03 ohmic resistance. 
 
 Patrol Alarm Box. 
 
 (See Box, Patrol 
 Alarm) 
 
 Peltier Effect - 
 
 (See Effect, Peltier) 
 
 Pen Carriage. 
 
 (See Carriage, Pen) 
 
 Pen, Electric 
 
 A device for mani- 
 fold copying, in which 
 a sheet of paper is 
 made into a stencil by 
 minute perforations 
 obtained by a needle 
 driven by a small 
 electric motor and the 
 stencil afterwards em- 
 ployed in connection 
 with an inked roller 
 for the production of 
 any required number 
 of copies. 
 
 Mechanical pens are 
 constructed on the same 
 principle, the perfora- 
 tions being obtained by 
 mecnamcal instead of 
 by electric power. 
 
 In the Edison electric 
 pen, Fig. 417, the yvc-Fig-4z8. Electric Pendant. 
 forations are made by an electric motor driven 
 by a voltaic battery. The manifold press with 
 its inked pad is shown to the left of the figure. 
 
 Pendant Cord. (See Cord, Pendant) 
 Pendant, Electric A hanging fix- 
 
Pen.] 
 
 392 
 
 [Per. 
 
 ture provided with a socket for the support of 
 an incandescent lamp. 
 
 A form of electric pendant is shown in Fig. 
 418. 
 
 Pendant, Flexible Electric Light - 
 A pendant for an incandescent lamp formed 
 by the flexible conductors which support the 
 lamp. 
 
 The ad vantages procured by a flexible pendant 
 are evident in that both the length of the flexible 
 conductor from which the lamp is hanging and 
 position of the lamp can be changed considerably. 
 
 Pendulum Annunciator. (See Annun- 
 ciator, Pendulum or Swinging?) 
 
 Pendulum, Electric A pendulum 
 
 so arranged that its to-and-fro motions send 
 electric impulses over a line, either by making 
 or breaking contacts. 
 
 An electrical tuning fork whose to-and-fro 
 movements are maintained by electric im- 
 pulses. 
 
 Electric pendulums are employed in systems 
 for the electrical disti ibution of time. 
 
 Sometimes instead of using true pendulums for 
 such purposes, coils, mounted on tuning forks, or 
 on the ends of flexible bars of steel, called reeds, 
 are used for the purpose of e^ablishing cur- 
 icnts, or modifying the currents that are already 
 passing in a circuit. The movement of a mag- 
 netic diaphragm, as in the case of a telephone 
 diaphragm, towards and from a coil of wire, is 
 another illustration of an electric pendulum. 
 
 Electric tuning-fork pendulums are employed 
 in Delany's system of synchronous- multiplex teleg- 
 raphy, and in Gray's harm >nic-multiple teleg- 
 raphy. (See Telegraphy, Synchronous-Multi- 
 plex, Delany's System. Telegraphy, Gray's Har- 
 monic-Multiple. ) 
 
 Pendulum, Laws of The laws 
 
 which express the peculiarities of the motion 
 of a simple pendulum. 
 
 A simple pendulum is one in which the entire 
 weight is considered as concentrated at a single 
 point, suspended at the end of a weightless, in- 
 flexible and inextensible line. 
 
 The following are the laws of the simple pen- 
 dulum : 
 
 (I.) Oscillations of small amplitude are approx- 
 imately isochronous; that is, are made in times 
 that are sensibly eqinl. (See Vibration or Wave, 
 Amplitude of. Jsochronism.) 
 
 (2.) In pendulums of different lengths, the 
 duration of the oscillations is proportional to the 
 square root of the length of the pendulum. 
 
 (3.) In the same pendulum, the length being 
 preserved invariable, the duration of the oscilla- 
 tion is inversely proportional to the square root 
 of the intensity of gravity. 
 
 The intensity of gravity, at any latitude, may 
 be determined by the number of oscillations of a 
 pendulum of a given length. In the same man- 
 ner the intensity of a magnetic field, or the in- 
 tensity of magnetization of a magnet, may be de- 
 termined by the needle of oscillation, by observing 
 the number of oscillations a needle makes in a 
 given time when disturbed from its position of 
 rest. (See Needle of Oscillation.) 
 
 Since a simple physical pendulum is a physical 
 impossibility, the virtual length of a pendulum, 
 that is, the vertical distance between its point of 
 support and the centre of oscillation, is taken as 
 the true length of the pendulum. 
 
 If the irregularly shaped body, shown in Fig. 
 419, whose centre of gravity is at G, is made to 
 swing like a pendulum, either on 
 S, or O, its oscillations will be 
 performed in equal times, and 
 the body will act as a simple 
 pendulum, whose virtual length 
 is SO. 
 
 If, while suspended at S, it be 
 struck at O, it will oscillate 
 around S, without producing p !g 4T9 centr- 
 any pressure on the supporting of OscMati . 
 axis at S, on which it turns. If fl mating entirely 
 submerged in a liquid, a blow at O, would c ause 
 it to move in a straight line in the direction of 
 the blow, without rotation. 
 
 The point O, is caUed the centre of percussion, 
 or the centre of oscillation. The centre of oscil- 
 lation is always below the centre of gravity. 
 
 Pentane Standard. (See Standard, Pen- 
 tane.} 
 
 Percussion, Centre of That point in 
 
 a body suspended so as to move as a pendu- 
 lum at which a blow would produce rotation, 
 but no forward motion, or motion of transla- 
 tion. 
 
 Perforator, Paper 
 
 An apparatus 
 
 employed in systems of automatic telegraphy 
 for punching in a fillet of paper the circular or 
 elongated spaces that produce the dots and 
 
Per.] 
 
 393 
 
 [Per. 
 
 dashes of the Morse alphabet, when the fillet is 
 drawn between metal terminals that form the 
 electrodes of a battery. (See Telegraphy, 
 Automatic.) 
 
 Perforator, Pneumatic - A paper 
 perforator operated by means of compressed 
 air. (See Perforator, Paper.) 
 
 Period of Open-Circuit Oscillation. (See 
 Open-Circuit Oscillation, Period of.) 
 
 Period of Simple-Harmonic Motion. 
 (See Motion, Simple-Harmonic, Period of) 
 
 Period of Vibration. (See Vibration, 
 Period of.) 
 
 Period, Vibration The period of a 
 single or a whole vibration in a conductor, in 
 which an oscillatory vibration is being pro- 
 duced by electrical resonance when respond- 
 ing to its fundamental vibration. 
 
 Hertz gives the following value for the vibration 
 period: Calling T, the single or half vibration 
 period; L, the co-efficient of self-induction in abso- 
 lute magnetic measure, and therefore expressed in 
 centimetres; C, the capacity of the terminals, in 
 electrostatic measure, and therefore also expressed 
 in centimetres; v, the velocity of light in centi- 
 metre second?, then, when the resistance of the con- 
 ductor is small, T = it L C . 
 v 
 
 Periodic and Alternate Discharge. (See 
 Discharge, Periodic. Discharge, Alternat- 
 ing^ 
 
 Periodic Current, Power of The 
 
 rate of transformation of the energy of a cir- 
 cuit traversed by a simple periodic current. 
 
 Fig. 420. Power of Periodic Current. (Fleming.) 
 
 If the thin line in the curve, Fig. 420, repre- 
 sents the impressed electromotive force in an in- 
 ductive circuit, and the thick line the correspond- 
 ing current, then, at any instant, say at the point 
 M, the rate at which energy is being expended on 
 the circuit, is equal to the ordinate P M, multi- 
 plied by the ordinate Q M. The mean power is 
 
 the mean of all such products taken at points of 
 time very near together. 
 
 The power of a periodic current, or the work 
 expended per second on such a circuit, is equal 
 to half the product of the maximum values of the 
 current, at any instant, and the maximum value 
 of the impressed electromotive force, multiplied 
 by the cosine of the angle of lag. 
 
 Periodic Governor. (See Governor, 
 Periodic) 
 
 Periodically Decreasing Discharge. 
 
 (See Discharge, Periodically Decreasing) 
 
 Periodicity. The rate of change in the 
 alternations or pulsations of an electric cur- 
 rent. 
 
 Periodicity of Auroras and Magnetic 
 Storms. (See Auroras and Magnetic 
 Storms, Periodicity of.) 
 
 Permanency, Electric The prop- 
 erty possessed by most metallic substances, 
 while in the solid state, of retaining a constant 
 electric conducting power at the same tem- 
 perature. 
 
 The electric permanency of hard drawn wire is 
 small, since such wire becomes gradually an- 
 nealed, and thus changed in its electric resist- 
 ance. 
 
 Matthiessen showed that some specimens of 
 annealed German silver wire increased in their 
 conducting power at the rate of about .02 per 
 cent, yearly. 
 
 Permanent Intensity of Magnetization. 
 
 (See Magnetization, Permanent, Intensity 
 of.) 
 
 Permanent Magnet Voltmeter. (See 
 Voltmeter, Permanent Magnet.) 
 
 Permanent State of Charge on Telegraph 
 Line. (See State, Permanent, of Charge on 
 Telegraph Line) 
 
 Permeability Curve. (See Curve, Per- 
 meability) 
 
 Permeability, Magnetic Conducti- 
 
 bility for lines of magnetic forces. 
 
 The ratio existing between the magnetiza- 
 tion produced, and the magnetizing force pro- 
 ducing such magnetization. 
 
 If jit equals the permeability, B, the magnetiza- 
 
Per. 
 
 394 
 
 [Phe. 
 
 tion produced, or the intensity of magnetic induc- 
 tion, and H, the magnetizing force; then, 
 
 The permeability of non-magnetic materials, 
 such as insulators, or non-magnetic metals, such as 
 copper, etc., is assumed to be practically equal to 
 that of air, or to unity. 
 
 The magnetic permeability decreases as the 
 magnetization increases. When a piece of iron 
 has been magnetized up to a certain intensity, its 
 permeability becomes less for any further magnet- 
 ization; or, the substance shows a tendency to 
 reach magnetic saturation. In good iron, this 
 limit is reached at about 125,000 lines of force to 
 the square inch of rea of cross section. 
 
 The magnetic permeability varies greatly, not 
 only with different specimens of iron, but also with 
 the previous history of the iron, as to whether or 
 not it has before been subjected to magnetization or 
 demagnetization, and also as to whether the value 
 of the permeability is taken while the magnetiza- 
 tion is increasing or decreasing. 
 
 Permeameter. An apparatus devised by 
 S. P. Thompson, for roughly measuring the 
 magnetic permeability. 
 
 Thompson's permeameter consists essentially of 
 a rectangular piece of soft iron, provided with a 
 slot, for the reception of the magnetizing coil. A 
 hole bored in one end of the block serves to receive 
 the bar or rod of iron whose permeability is to be 
 determined. On the magnetization of the bar to 
 be tested, the square root of the force required to 
 detach the rod from the lower surface of the iron 
 block, is a measure of the permeation of the lines 
 of magnetic forces through its end faces. 
 
 Permeance, Magnetic - Magnetic 
 permeability. (See Permeability, Magnetic!) 
 
 Permeating, as of Lines of Force. 
 
 The passing of lines of force through a mag- 
 netic substance. (See Permeability, Mag- 
 netic^ 
 
 Permeation, Magnetic -- The pass- 
 age of lines of magnetic force through any 
 permeable substance. 
 
 Permissive Block System for Railroads. 
 
 (See Railroads, Permissive Block System 
 for.} 
 
 Pfluger's Law. (See Law, PJluger's^] 
 Phantom Wires. (See Wires, Phantom^ 
 
 Phase, Angle of Difference of, between 
 Alternating Currents of Same Period 
 
 The angle which measures the shift- 
 ing of phase of a simple periodic current with 
 respect to another due to lag or other cause. 
 
 Phase, Shifting of, of Alternating Cur- 
 rent A change in phase of current 
 
 due to magnetic lag or other causes. 
 
 Phase of Vibration. (See Vibration, 
 Phase of.) 
 
 Phelps' Stock Printer. (See Printer, 
 Stock, Phelps .} 
 
 Phenomena, Electro-Capillary 
 
 Phenomena observed in capillary tubes at 
 the contact surfaces of two liquids. 
 
 Where acidulated water is in contact with 
 mercury, each liquid possesses a definite sur- 
 face tension, and each a definite shape of sur- 
 face. The two liquids, however, do not actually 
 touch, there being a small interval or space be- 
 tween them. This space acts as a minute accu- 
 mulator. But the liquid and water, being different 
 substances in contact, possess different potentials. 
 Any cause which alters the shape of these con- 
 tact surfaces, and consequently the extent of the 
 spaces between them, necessarily alters the capa- 
 city of the condenser, and consequently the dif- 
 ference of potential. Therefore the mere shaking 
 f the tube, or heating it, will produce electric 
 currents from the resulting differences of po- 
 tential. Conversely, an electric current sent 
 across the contact-surfaces will produce motion as 
 a result of a change in the value of the surface 
 tension. An electro-capillary telephone has been 
 constructed on the former principle, and an 
 electrometer on the latter. (See Electrometer, 
 Capillary.) 
 
 Phenomena, Porret 
 
 -An increase 
 
 in the diameter of a nerve fibre in the neigh- 
 borhood of the positive pole when traversed 
 by a voltaic current. 
 
 When a voltaic current passes through fresh 
 living substance the contents of the muscular fibre 
 exhibit a streaming movement in the direction the 
 current is flowing, viz., from the positive to the 
 
Phe.J 
 
 395 
 
 [Pho. 
 
 negative. This causes the fibre to swell up or 
 increase in diameter at the negative electrode. 
 
 Pherope. A name sometimes applied to 
 a telephote. (See Telephote.) 
 
 Phial, Leyden A name sometimes 
 
 applied to a Leyden jar. (See Jar, Leyden.) 
 
 Philosopher's Egg. (See Egg, Philoso- 
 pher 's.~) 
 
 Phonautograph. An apparatus for the 
 automatic production of a visible tracing of 
 the vibrations produced by any sound. 
 
 Phonautographic apparatus consists essentially 
 of devices by which the sound waves are caused 
 to impart their to-and fro movements to a dia- 
 phragm, at the centre of which a pencil or tracing 
 point is attached. The record, is received on a 
 sheet of paper, or wax, or on a smoked glass or 
 other suitable surface. 
 
 Leon Scott's Phonautograph, which is among 
 the forms best known, consists of a hollow conical 
 
 Fig. 421. Scott's Phonautograph. 
 
 vessel A, Fig. 421, with a diaphragm of parch- 
 ment stretched tightly like a drumhead over its 
 smaller aperture B. A tracing point attached to 
 the centre of the diaphragm, traces a sinuous 
 line on the surface of a soot-covered cylinder C, 
 that is uniformly rotated under the tracing point. 
 As the cylinder is advanced a short distance with 
 every rotation, a sinuous spiral line is .traced on 
 the surtace. 
 
 Phone. A term frequently used for tele- 
 phone. 
 Phonic Wheel. (See Wheel, Phonic.) 
 
 Phonogram. A record produced by the 
 phonograph. (See Phonograph) 
 
 Phonograph. An apparatus for the re- 
 production of articulate speech, or of sounds 
 
 of any character, at any indefinite time after 
 their occurrence, and for any number of times. 
 In Edison's phonograph the voice of the 
 speaker, received by an elastic diaphragm of thin 
 sheet iron or other similai material, is caused to 
 indent a sheet of tin-foil placed on the surface of 
 a cylinder C, Fig. 422, that is maintained at a 
 uniform rate of rotation by the crank at W. In 
 
 Fig. 422. 
 
 the form shown in Fig. 422, the motion is by hand. 
 In a later improved form the cylinder is driven by 
 means of an electric motor or by clockwork. 
 
 In order to reproduce the speech or other 
 sounds the phonogram record is placed on the 
 surface of a cylinder similar to that on which it 
 was received (or is kept on the same surface), 
 and the tracing point, placed at the beginning of 
 the record and being maintained against it by 
 gentle pressure, is caused, by the rotation of 
 cylinder, to follow the indentations of the phono- 
 gram record. As the point is thus moved up and 
 down the hills and hollows of the record surface, 
 
 Fig. 423. Edison's Improved Phonograph. 
 
 the diaphragm, to which it is attached, is given to- 
 and-fro motions that exactly correspond to the 
 to-and fro motions it had when impressed origin- 
 ally by the sounds it recorded on the phono- 
 gram record. A per on listening at this did- 
 
Pho.] 
 
 [Pho. 
 
 phragm will therefore hear an exact reproduction 
 of the sounds originally uttered. 
 
 In this manner the voices of relatives, 'dis- 
 tinguished singers or statesmen can be preserved 
 for future generations. 
 
 In Edison's improved phonograph the record 
 surface consists of a cylindt r of hardened wax. The 
 rotary motion of the cylinder is obtained by means 
 of an electric motor. Two diaphragms are used, 
 one for recording, and one for reproducing the 
 sound waves. As shown in Fig. 423, the record- 
 ing diaphragm is in position against the cylinder. 
 The recording diaphragm is made of malleable 
 glass. The reproducing diaphragm is formed of 
 bolting silk covered with a thin layer of shellac. 
 
 In the Graphophone of Bell and Tainter the 
 point attached to the diaphragm is caused to cut 
 
 Fig. 424.. Bell and Tainter's Graphophoiu. 
 or engrave a cylinder of hardened wax. Two 
 separate diaphragms are employed, one for speak- 
 ing, and the other for hearing. 
 
 The recording surface is made of a mixture of 
 beeswax and paraffine. A uniformity of rotation of 
 the cylinder is obtained by means of a motor pro- 
 vided with a suitable governor. An ordinary con- 
 versation of some five minutes, it is claimed, can 
 be recorded on the surface of a cylinder 6 inches 
 long and I \ inch in diameter. 
 
 In the Gramophone of Berliner, a circular plate 
 of metal, covered with a film of finely divided oil 
 
 or grease, receives the record in a sinuous, spiral 
 line. This record is subsequently etched into the 
 metal by any suitable means, or is photographic- 
 ally reproduced on another sheet of metal. 
 
 Glass covered with a deposit of soot is some- 
 times employed for the latter process. The ap- 
 paratus is shown in Fig. 425, as arranged for the 
 reproduction of speech. 
 
 In Mr. Berliner's apparatus, the record surface 
 is impressed by a point attached to the trans- 
 mitting diaphragm, in a direction parallel to tke 
 record surface, and not, as in the instrument of 
 Mr. Edison, in a direction at right angles to the 
 same. This method would appear to be the best 
 calculated for a more exact reproduction of ar- 
 ticulate speech, since it permits comparatively 
 loud speaking or singing, without interfering 
 
 Fig, 425. Berliner's Gramophone. 
 
 with the quality of the reproduced sounds. Since 
 the resistance to indentation, or vertical cutting, 
 increases more rapidly than the increase in the 
 amplitude of vibration of the cutting point, it 
 follows that the louder the sounds recorded by the 
 phonograph or graphophone, the less complete 
 would be the quality of the reproduced sounds, 
 or the less the probability of the peculiarities of 
 the speaker's voice being recognized. In order 
 to avoid this, the speaker in the phonograph and 
 the graphophone speaks in an ordinary conversa- 
 tional tone only. (S^e Vibration or Wave,, Am- 
 plitude of ) 
 
 For purposes of dictation, and, indeed, most 
 commercial purposes, this is rather an advantage 
 than otherwise. 
 
 Phonograph Record. (See Record 
 Phonograph.} 
 
 Phonoplex. Literally sound folds. 
 
 A system of telegraphy. (See Telegraphy, 
 Phonoplex.} 
 
Pho.] 
 
 397 
 
 [Pho. 
 
 Phonoplex Telegraphy. (See Telegra- 
 phy, Phonoplex^) 
 
 Pkonopore. A modified form of har- 
 monic telegraph. 
 
 Phonozenograph. An instrument devised 
 by De Feltre to indicate the direction of a 
 distant sound. 
 
 A Deprez-D'Arsonval galvanometer, a Wheat- 
 stone's bridge, and a microphone of peculiar con- 
 struction, are placed in the circuit of a voltaic 
 battery and a receiving telephone. The observer 
 determines the direction of the distant sound by 
 means of the sounds heard under different condi- 
 tions in the telephone. 
 
 Phosphoresce. To emit phosphorescent 
 light. 
 
 Phosphorescence. The power of emitting 
 light, or becoming luminous by simple ex- 
 posure to light. 
 
 Bodies that possess the property of phosphor- 
 escence, when exposed to a bright light acquire 
 the power, when subsequently carried into the 
 dark, of continuing to emit light, for periods 
 varying from a few seconds to several hours. 
 The diamond, barium and calcium sulphides, 
 dry paper, silk, sugar, and compounds of ura- 
 nium, are examples of phosphorescent substances. 
 
 The effects of phosphorescence appear to be 
 due, in some cases, to sympathetic vibrations set 
 up in the molecules of the phosphorescent body 
 by the exciting light. (See Vibrations, Sympa- 
 thetic.') 
 
 In other cases, however, that are not exactly 
 understood, the wave length of the emitted light 
 is more rapid than that of the exciting light. 
 
 The fire-fly, the glow-worm, and decaying 
 animal or vegetable matter, exhibit a species of 
 phosphorescence that appears to be due to the ac- 
 tual oxidation or gradual burning of a peculiar, 
 specific, chemical substance. 
 
 Phosphorescence may therefore be divided into 
 two classes, viz. : 
 
 (i.) Physical phosphorescence, or that produced 
 by the actual impact of light, .and, 
 
 (2.) Chemical phosphorescence, or that caused 
 by actual chemical combination or combustion of 
 a specific substance. Tin's is sometimes called 
 spontaneous phosphorescence. 
 
 Physical phosphorescence may be produced in 
 a variety of ways, viz. : 
 
 (I.) By an Elevation of Temperature: 
 A variety of fluorspar, called chlorophane, 
 shines with a beautiful greenish blue light when 
 heated tj less than a red heat. Here the non- 
 luminous rays are apparently transformed into 
 luminous rays. 
 
 A phosphorescent substance like fluorspar 
 eventually loses its ability to phosphoresce. It 
 regains it, however, on exposure to the light, i. t., 
 if such an exhausted body be exposed to sunlight it 
 again phosphoresces on exposure t;> non-luminous 
 heat. The light emitted, during phosphorescence 
 by heat, is, probably, wholly due to potential 
 energy acquired during exposure to the light. 
 (See Luminescence.) The phosphorescence by 
 heat exhibited by fluorspar is sometimes called 
 fluorescence. It is preferable, however, to call 
 the phenomena phosphorescence. (See Fluores- 
 eence. ) 
 
 (2.) By Mechanical Effects: 
 
 The flashes of light emitted during the attri- 
 tion or friction of some bodies, when not traceable 
 directly to electricity, are, most probably, to be 
 ascribed to phosphorescence. 
 
 (3.) By M jlecular Bombardment. 
 
 The molecular bombardment due to the mole- 
 cules of residual gas shot off from the negative 
 electrode of an exhausted receiver through wnch 
 an electric discharge is passing, produces many 
 brilliant effects of phosphorescence. 
 
 (4.) By Electricity. 
 
 An electric spark produces phosphorescence in 
 such substances as canary glass, solution of sul- 
 phate of quinine, etc., etc. 
 
 (5.) Exposure to Sunlight, or, in fact, to any 
 light. 
 
 The different rays of the sun are not equally 
 able to excite phosphorescence. As a rule the 
 violet or ultra violet rays excite the greatest phos- 
 phorescence. The light excited is often, though 
 not always, of a greater wave length than the 
 exciting light. 
 
 Phosphorescent paints for rendeiing the posi- 
 tion of a push button, electric call, match safe, 
 gas pendant or some other similar object visible 
 at night, consist essentially of sulphides of cal- 
 cium or barium, or of mixtures of the same. 
 
 Phosphorescence, Chemical A 
 
 variety of phosphorescence, in which the errit- 
 ted light is produced by the actual combustion 
 
398 
 
 [i'ho. 
 
 of a specific chemical substance by the oxygen 
 of the air. 
 
 Chemical phosphorescence is seen in the fire 
 fly and the glow-worm. (See Phosphorescence.} 
 
 Phosphorescence, Electric Phos- 
 phorescence caused in a substance by the 
 passage of an electric discharge. 
 " The phosphorescent material is placed in an 
 exhausted glass tube, as shown in Fig. 426, and 
 submitted to the action of a series of discharges, 
 as from a Ruhmkorff coil, or Holtz machine. 
 The violet-blue light of such discharge is very 
 efficient in producing phosphorescence. Phosphor- 
 escence is thus effected by subjecting the phos- 
 phorescent material to the molecular bombard- 
 ment which is produced by such discharges in a 
 high vacuum. (See Bombardment, Molecular.) 
 
 Phosphorus. Electric Smelting of 
 
 Fig. 426. Electric Phosphorescence. 
 
 Phosphorescence, Physical Phos- 
 
 phorescence produced in matter by the actual 
 impact of light waves resulting in a vibratory 
 motion of the molecules of sufficient rapidity 
 to cause them to emit light. 
 
 Physical phosphorescence is distinguished from 
 chemical phosphorescence in that in the former 
 the energy required to produce molecular vibra- 
 tions is imparted by the light to which the phos- 
 phorescent body is exposed, while in chemical 
 phosphorescence the energy producing the light 
 is derived from the chemical potential energy 
 of the specific substance burned. (See Phosphor, 
 escence. ) 
 
 Phosphorescent, Possessing the proper- 
 ties or qualities of phosphorescence. 
 
 Phosphorescing 1 . Emitting phosphores- 
 cent light. (See Phosphorescence?) 
 
 Phosphorescope. An apparatus for meas- 
 uring the phosphorescent power of any sub- 
 stance. (See Phosphorescence?) 
 
 - An electric process for the direct production 
 of phosphorus. 
 
 In the electric smelting of phosphorus, the 
 crude material, consisting of a mixture of bones or 
 animal phosphates and carbon, is fed into a space 
 between two electrodes connected to the poles of 
 a source of powerful alternating currents. The 
 apparatus is similar in general to the Cowles fur- 
 nace for the reduction of aluminium. The heat 
 produced by the alternating currents decomposes 
 the phosphates, and the volatilized phosphorus 
 is condensed in suitable chambers. 
 
 Photochronograph. An electric instru- 
 ment for automatically recording the transit 
 of a star across the meridian. 
 
 In a small camera connected with the eye -piece 
 of the transit instrument is placed a sensitized 
 plate. 
 
 A sidereal clock has an electric attachment to 
 its pendulum, so made that a shutter alternately 
 exposes and conceals the photographic plate, and 
 thus permits the image of a star to be formed on 
 the plate at intervals during its passage across 
 the field of the telescope. An image of the spider 
 lines is afterwards fixed on the plate by the light 
 of a lamp, held for a few moments before the ob- 
 ject glass of a telescope. A shutter is provided, 
 by means of which this light is prevented from 
 falling on the trail of the star across the field of 
 the glass. In this manner the time of passage of 
 the star across the meridian is automatically re- 
 corded on the photographic plate. 
 
 The photochronograph is also adapted for 
 similarly automatically recording the transit or 
 passage of any heavenly body across any imagin- 
 ary line in the heavens. 
 
 Photo-Electric Cell. (See Cell, Photo- 
 Electric?) 
 
 Phot o-Electricity. ( See Electricity, 
 Photo?) 
 
 Photo-Electromotive Force. (See Force, 
 Electromotive, Photo?) 
 
 Photometer. An apparatus for measuring 
 the intensity of the light emitted by any 
 luminous source. 
 
 There are various methods for measuring the 
 intensity of a beam of light passing through any 
 given space, or emitted from any luminous 
 
Pho. 
 
 399 
 
 [Pho. 
 
 source; these methods are embraced in the use 
 of the following apparatus: 
 
 (l.) Calorimetric Photometer, in which the light 
 to be measured is absorbed by the face of a 
 thermo-electric pile, and the electric current 
 thereby produced is carefully measured. Since 
 obscure radiation or heat will also thus produce 
 an electric current, it is necessary first to absorb 
 all the heat by passing the beam of light through 
 an alum cell. 
 
 (2.) Actinic, or Chemical Photometers, in which 
 the intensity of the light is estimated by a com- 
 parison of the depth of coloration produced on a 
 fillet of photographic paper under similar con- 
 ditions of exposure to a standard light, and the 
 light to be measured. 
 
 The combination of pure hydrogen and chlorine, 
 or the decomposition of pure mercurous chloride, 
 have been employed for the purpose of determin- 
 ing the intensities of two lights by measuring the 
 amount of chemical action effected. 
 
 (3.) Shadow Photometers, in which a shadow 
 produced by the light to be measured is compared 
 with a shadow produced by a standard candle. 
 (See Candle, Standard.) 
 
 Fig. 427. The Shadow Photometer. 
 
 Rumford's photometer, shown in Fig. 427, is 
 an example of this form of instrument. The 
 standard candle, shown at L, casts a shadow C", 
 of an opaque rod C, on the screen at B. 
 
 The light to be measured L', is moved away 
 from the screen until its shadow C', on the screen 
 at A, is judged by the eye to be of the same 
 depth. The distance between the screen and the 
 lights is then measured in straight lines. The 
 relative intensities of the two lights are then pro- 
 portional to the squares of their distances. If, for 
 example, the candle be at 10 inches from the 
 screen, and the lamp at 40 inches, then the 
 intensities are as io s : 40' or as 100 : 1,600, or the 
 lamp is a 16 candle-power lamp. 
 
 This photometer is based on the fact that the 
 shadow of each source is illumined by the light 
 of the other source. 
 
 These results are more accurate if the two 
 shadows are adjoining or nearly adjoining. 
 
 (4. ) Translucent-Disc Photometers. The light 
 to be measured and a standard candle are placed 
 on opposite sides of a sheet of paper the centre of 
 which contains a grease spot. The standard 
 candle is kept at a fixed distance from the paper 
 and both it and the paper are moved towards or 
 from the light to be measured until both sides of 
 the paper are adjudged to be equally illumined. 
 
 In Bunsen's photometer a vertical sheet of 
 paper' with a grease spot at its centre, is exposed 
 to the illumination of a standard candle on one 
 side, and the light to be measured on the other. 
 
 The sheet of paper is placed inside a dark box 
 provided with two plane mirrors placed at such 
 an angle to the paper that an observer can readily 
 see both sides of the paper at the same time. 
 
 This box can be slid along a graduated, hori- 
 zontal scale towards, or from, the light to be 
 measured, and carries with it the standard candle 
 mounted on it at a constant distance of 10 inches. 
 If the box is too near the light to be measured, 
 the grease spot appears brighter on the side of the 
 sheet of paper nearest the candle. If too near 
 the candle, it appears brighter on the side of the 
 sheet of paper nearest the light to be measured. 
 The position in which the spot appears equally 
 bright on both sides, is the position in which both 
 sides of the paper are equally illumined, and the 
 relative intensities of the two lights are then 
 directly as the squares of their distances from the 
 sheet of paper. 
 
 Shadow, and translucent-disc photometers 
 being dependent on equal illumination, are re- 
 liable only when the color of the lights compared 
 is the same. For the determination of the photo- 
 metric intensity of very bright lights, the standard 
 candle is replaced by a carcel lamp, a standard 
 gas jet, or by the light emitted by a given mass 
 of platinum, heated to incandescence by a given 
 current of electricity. (See Lamp, Carcel. Gas- 
 jet, Carcel Standard. Light, Platinum Stand- 
 ard.} 
 
 Preece's photometer belongs to the class of 
 translucent disc photometers. A tiny incandes- 
 cent lamp is placed in a box, the top of which has 
 a white paper screen on which is a grease spot. 
 The box is placed in the street where the intensity 
 of illumination is to be measured, and the inten- 
 
Pho.] 
 
 400 
 
 [rko. 
 
 sity of the light of the incandescent lamp is 
 varied until the grease spot disappears. The 
 current of electricity then passing through the 
 incandescent lamp acts as the measure of the 
 iliumination. 
 
 In the case of the shadow photometer, or of 
 Bunsen's photometer, if the intensity of illumina- 
 tion is the same, the relative intensities of the two 
 lights may be determined as follows: 
 
 Calling I, and i, respectively the relative inten- 
 sities of the standard light, and the light to be 
 measured, and D, and d, their respective dis- 
 tances from the screen, then 
 
 I : i : : D 8 : d 2 , or I X d 2 = i X D 2 ; 
 
 / d 2 
 that is, i = I ^ 
 
 Or, the intensity of the light to be measured is 
 
 (d 8 \ 
 = j times the intensity of the standard light. 
 
 If, for example, D and d, represent 10 and 100 
 inches, respectively, the intensity of i, is 100 times 
 the intensity I, the standard 1'ght. 
 
 (5.) Dispersion Photometers. A class of pho- 
 tometers in which, in order to more readily com- 
 pare or measure a very bright or intense light, 
 like that of an arc lamp, the intensity of the light 
 is decreased by dispersion a readily measurable 
 amount. 
 
 Ayr ton &* Perry's Dispersion Photometer. A 
 photometer in which, in order to bring an in- 
 tensely bright light, like an electric arc light, to 
 
 Fig. 428. Ayrton &* Perry's Dispersion Photometer. 
 
 such an intensity as will permit it to be readily 
 compared with a standard candle, its intensity is 
 weakened by its passage through a diverging 
 (concave) lens. 
 
 Ayrton & Perry's dispersion photometer is 
 shown in two different positions, Figs. 428 and 
 429. The apparatus is supported on a tripod 
 stand E, arranged so as to obtain exact leveling. 
 
 A plane mirror H, movable around a pin placed 
 directly under its centre, can be rotated and thus 
 reflect the light after its passage through the 
 diverging lens, while still maintaining its distance 
 from the electric light. 
 
 The horizontal axis of this mirror is inclined 
 45 degrees to its reflecting surface in order to 
 avoid errors arising from varying absorption at 
 different angles of reflection. 
 
 The inclination of the beam to the horizontal 
 is indicated by means of an index attached to the 
 mirror and moving over the graduated circle G. 
 
 A black rod A, casts its shadow on a screen of 
 white blotting paper B. A standard candle, 
 placed in the holder D, casts its shadow alongside 
 the shadow cast by the electric light. The lens 
 is now displaced until the shadow of the electric 
 light is of the same intensity as that of the candle, 
 when viewed successively through sheets of red 
 and green glass. 
 
 A graduated scale serves to mark the distances 
 of the candle and the lens, respectively, from the 
 screen, from which data the intensity ot the 
 electric light may be calculated. 
 
 Fig. 429. Ayrton and Perry's Dispersion Photometer. 
 
 (6.) Selenium Photometers. Instruments in 
 which the relative intensities of two lights are de- 
 termined by the variations produced in a selenium 
 resistance. 
 
 In Siemens' Selenium photometer a selenium 
 cell is employed in connection with an electric 
 circuit for determining the intensity of light. 
 
 The tube A B, Fig. 430, is furnished at A, with 
 a diaphragm, and at B, with a selenium plate, 
 connected by wires G G, with the circuit of a 
 battery and a galvanometer. 
 
 A graduated scale L M, bears the standard 
 candle N. The tube A B, is capable of rotation 
 on the vertical axis F. A reflecting mirror gal- 
 vanometer is used in connection with the selenium 
 photometer. The light to be measured is placed 
 
PaO.] 
 
 401 
 
 [Pho. 
 
 at right angles to the scale L M, and the tube A 
 B, directed towards it, and the ga.vanometer de 
 flection compared with the deflection obtained 
 when turned towards the standard candle. 
 
 (7.) Gas-jet Photometers. Instruments in 
 which the candle-power of a gas-jet is determined 
 by measuring the height at which the jet burns 
 when under unit conditions of volume and press- 
 ure of gas consumed . 
 
 Fig. 430. Siemens' Selenium Photometer. 
 
 In determining the candle-power of an intense 
 light like the electric arc light, a large gaslight 
 is used instead of a standard candle, and the 
 photometric power of this gaslight is carefully 
 determined by comparison with a gas- jet photom- 
 eter. (See Jet, Gas, Car eel Standard.} 
 
 Photometer, Actinic 
 
 A photom- 
 
 eter in which the intensity of any light is meas- 
 ured by the amount of chemical decomposi- 
 tion it effects. (See Photometer.) 
 
 In some actinic photometers the intensity of the 
 light to be measured is determined by the com- 
 parison of the depth of coloration of a sensi- 
 tized film under similar conditions of exposure 
 to a standard light and the light to be measured. 
 
 Photometer, Calorimetric A pho- 
 tometer in which, the light to be measured is 
 absorbed by the face of a thermo-electric pile, 
 and the intensity of the light estimated from 
 the strength of the electric current thereby 
 produced. 
 
 In order to avoid the error arising from the 
 current produced from the absorption of the ob- 
 scure radiation from the light, all tlie hear, is first 
 absorbed by passing the light through an alum 
 cell. (See Photometer. ) 
 
 Photometer, Chemical A photom- 
 eter in which the intensity of the light to be 
 
 measured is determined from the amount of 
 chemical action effected m a given time. 
 
 Photometer, Dispersion A photom- 
 eter in which the light to be measured is de- 
 creased in intensity a known amount so as to 
 more readily permit it to be compared with a 
 standard light of much smaller intensity. 
 (See Photometer?) ~~ 
 
 Photometer, Electric An electrical 
 
 instrument for measuring the intensity of 
 illumination. 
 
 A form of electric photometer invented by C. 
 R. Richards depends for its indications on the 
 variations that occur in the resistance of a wire on 
 change of temperature. An iron wire, whose 
 change of temperature is utilized for measuring 
 the intensity of any light to whose radiations it is 
 opposed, is covered by a deposit of lampblack. 
 On exposure to the light whose intensity is to 
 be measured, the light is absorbed l<y the lamp- 
 black and an increase in temperature occurs. 
 
 In order to get rid of the heat rays that are 
 associated with the light rays, the rays before 
 falling on the soot-covered wire are caused to pass 
 through a solution of alum ; the intensity of the 
 light is then calculated by reference to the change 
 in the resistance of the soot-covered wire, which 
 is made one of the arms of a Wheatstone bridge. 
 
 Photometer, Gas-Jet A photom- 
 eter in which the candle-power of a gas-jet is 
 estimated from a measurement of the height 
 at which the jet burns under unit conditions 
 of volume and pressure. (See Photometer?) 
 
 Photometer, Jet An apparatus for 
 
 determining the candle power of a luminous 
 source by means of the height of a jet of the 
 gas, whose candle-power is being determined, 
 when burning under constant conditions as 
 to pressure, etc. (See Jet, Gas, Carcel 
 Standard?) 
 
 Photometer, Selenium A photom- 
 eter in which the intensity of a light is esti- 
 mated by the comparison of the changes in 
 the resistance of a selenium resistance suc- 
 cessively exposed under similar conditions to 
 this light and to a standard light. (See 
 Photometer?) 
 
 Photometer, Shadow A photom- 
 eter in which the intensity of the light to be 
 
Pho.] 
 
 402 
 
 [Pho. 
 
 measured is estimated by a comparison of 
 the distances at which it and a standard light 
 produce a shadow of the same intensity. 
 (See Photometer?) 
 
 Photometer, Translucent Disc A 
 
 photometer in which the light to be measured 
 is placed on one side of a partly translucent 
 and partly opaque disc, and a standard can- 
 dle is placed on the opposite side, and the in- 
 tensity of the light estimated by the distances 
 of the light from the disc when an equal illu- 
 mination of all parts of the disc is obtained. 
 (See Photometer?) 
 
 When the illumination of the opposite sides of 
 such a disc is equal, the relative positions of the 
 transparent and opaque portions of the disc are 
 indistinguishable. 
 
 Photometer, Yarley's A form of 
 
 photometer in which the intensity of the light 
 to be measured is determined from the rel- 
 ative openings of two concentric circular 
 diaphragms placed in two rotating discs, and 
 through which the standard light and the 
 light to be measured respectively pass. 
 
 The general arrangement of Varley's photo- 
 meter is shown in Fig. 431. The concentric cir- 
 
 ring is fully open, the other is completely closed , 
 or, if one ring, say the outer, is opened 160 de- 
 grees, the inner is opened 20 degrees. The 
 quantity of light then which passes through the 
 outer ring from the light to be measured is eight 
 times that passed through the inner ring. The 
 circle is divided into 2,000 parts, instead of int9 
 360 degrees, and, by means of a vernier, these 
 parts are further divided into 10 parts, permitting 
 a reading of the 20,000 divisions. 
 
 Two collimeters placed in front of the disc, 
 project a disc with a black centre, and a luminous 
 spot respectively. The discs are regulated until 
 the light projected on the screen produces a uni- 
 form disc. This is readily ascertained, since if 
 one or the other predominate, a disc with gray 
 spot, or a gray marginal ring with a bright spot, 
 will appear. 
 
 The general appearance of the circular dia- 
 phragm, corresponding to different relative posi- 
 tions of the two discs, is shown in Fig. 432. 
 
 43 1. Varlev's Photometer. 
 
 cular apertures extend circumferentially 180 de- 
 grees, and are reversed so that when one half 
 
 Fig. 4.32. Circular Diaphragm of Varley's Photometer. 
 
 Photometric. Of or pertaining to the 
 photometer. (See Photometer?) 
 
 Photometrically. In a photometric man- 
 ner. 
 
 Photophone. An instrument invented by 
 Bell for the telephonic transmission of artic- 
 ulate speech along a ray of light instead of 
 along a conducting wire. 
 
 A beam of light, reflected from a diaphragm 
 against which the speaker's voice is directed, is 
 caused to fall on a selenium resistance inserted in 
 the circuit of a voltaic battery, and a telephone. 
 The changes thus effected in the resistance of the 
 circuit by the varying amounts of light reflected on 
 the selenium resistance from the diaphragm, while 
 moving to-and-fro under the influence of the speak- 
 er's voice, produce in the receiving telephone a 
 series of to-and fro movements similar to those im- 
 pressed on the transmitting diaphragm. One lis- 
 tening at the telephone can hear whatever has been 
 spoken in the neighborhood of the transmitting 
 diaphragm. Telephonic communication can, 
 therefore, by such means be carried on afong ? 
 
Pho.] 
 
 403 
 
 [fie. 
 
 ray or beam of light, theoretically through any 
 distance. (See Resistance, Selenium.') 
 
 A block of vulcanite or of certain other sub- 
 stances may be used as the receiver, since it has 
 been discovered that a rapid succession of flashes 
 of light produces an audible sound in small masses 
 of these substances. 
 
 The term sonorescence has been proposed for 
 the property possessed by such substances of 
 emitting sounds when subjected to such inter- 
 mittent, flashes of light. (See Sonorescence. .) 
 
 Photophore, Troure's 
 
 An appa- 
 
 ratus in which the light of a small incandescent 
 electric lamp is employed for purposes of 
 medical exploration. 
 
 A small incandescent lamp is placed in a tube 
 containing a concave mirror and a converging 
 lens. 
 
 Photo-Telegraphy. The electric produc- 
 tion of pictures, writing, charts or diagrams 
 at a distance. 
 
 Photo-Telegraphy is sometimes called telepho- 
 tography; it is a species of fac-simiie telegraphy. 
 (See Telegraphy, Fac-Simile. Telepho(ographv-) 
 
 Photo- Voltaic Effect. (See Effect, Photo- 
 Voltaic) 
 
 Physical Change. (See Change, Phy- 
 sical?) 
 
 Physical Phosphorescence. (See Phos- 
 phorescence, Physical?) 
 
 Physiological. Pertaining to physiology. 
 
 Physiological Rheoscope. (See Rheo- 
 scope, Physiological.} 
 
 Physiologically. In a physiological man- 
 ner. 
 
 Physiology, Electro The study of 
 
 electric phenomena of living animals and 
 plants. 
 
 Living animals and plants present electric 
 phenomena, due to the electricity naturally pro- 
 duced by them. It is the province of electro- 
 physiology to ascertain the causes and effects of 
 these phenomena. 
 
 Piano, Electric 
 
 A piano in which 
 
 the strings are strucK by hammers actuated 
 by means of electro-magnets, instead of by 
 the usual mechanical action of levers. 
 
 An electric piano-action is mainly useful in per- 
 mitting the instrument to be played at any dis- 
 tance from the key-board, it is also of value 
 from the ease it affords in recording the pieces 
 played. 
 
 It fails, however, to properly preserve the vari- 
 ous modulations of force so requisite for brilliant 
 instrumentation. 
 
 Pickle. An acid solution in which me- 
 tallic objects are dipped before being gal- 
 vanized, or electroplated, in order to 
 thoroughly cleanse their surfaces. 
 
 The pickle used for the preparation of iron for 
 galvanization is a weak solution of sulphuric acid 
 in water. Various acids, or acid liquids, are em 
 ployed for insuring the thorough cleansing of 
 metallic surfaces so necessary in order to ensure 
 an even, uniform, adherent coating of metal by 
 the process ot electroplating. (See Plating, 
 Electro. ) 
 
 Piece, Magnetic Proof A para- 
 magnetic rod, ellipsoid or sphere employed 
 for ascertaining the distribution of magnetism 
 over a magnet by the force required to de- 
 tach the same. (See Paramagnetic?) 
 
 Prof. S. P. Thompson points out the fact 
 that the presence of the proof-piece so alters the 
 distribution of magnetism on the magnet to be 
 measured as to render this method unreliable. 
 He also shows that the force required for detach- 
 ment depends on the magnetic permeability of 
 the proof-piece, as well as on its shape and its 
 position in the magnetic circuit. 
 
 Pieces, Month Openings into air 
 
 chambers, generally circular in shape, placed 
 over the diaphragms of telephones, phono- 
 graphs, gramophones or graphophones to 
 permit the ready application of the mouth in 
 speaking, so as to set the diaphragm into 
 vibration. 
 
 The mouth piece miy be also utilized by the 
 ear of an observer listening so as to be affected 
 by its vibrations. 
 
 Pieces, Pole, of Dynamo-Electric Ma- 
 chine Masses of iron connected with 
 
 the poles of the field magnet frames of 
 dynamo-electric machines, and shaped to 
 conform to the outline or contour of the 
 armature. 
 
Pi I.'] 
 
 The pole pieces are made in a variety of forms, 
 but in all cases are so shaped as to conform to the 
 outline of the space in which the armature rotates. 
 
 The pole pieces are brought as near as possible 
 to the armature, so as to increase the intensity of 
 the magnetic induction. The intervening air 
 space should be as thin as possible, but of as large 
 an area as convenient. 
 
 The opposite pole pieces should not have their 
 ext. nsions brought too near together, as this will 
 pjrmit o'f serious loss through magnetic leakage. 
 The distance between them should be as many 
 times the depth of the armature windings as 
 possible. (See Leakage, Magnetic. ) 
 
 Rounded edges are preferable to sharp edges 
 for the same reason. 
 
 Pile, Dry A voltaic pile or battery 
 
 consisting of numerous cells, the voltaic 
 couple in each of which consists of sheets of 
 paper covered with zinc-foil on one side and 
 black oxide of manganese on the other. 
 
 Various modifications of the above form have 
 been made. 
 
 The term dry-pile is a misnomer, since all such 
 piles contain substances moistened by liquid 
 electrolytes. 
 
 Pile, Muscular, Matteucci's A vol- 
 taic battery or pile, the elements of which are 
 formed of longitudinal and transverse sections 
 of muscle alternately connected. 
 
 Matteucci's experiments appear to show that 
 the lower the animal is in tne scale of creation, 
 the stronger is the current produced, and the 
 longer its duration. Du Bois-Reymond has 
 shown that the muscular current is not due to 
 contact, but to the differences of electric poten- 
 tial naturally possessed by the muscles the.ii- 
 selves. 
 
 The nerves also possess the power of producing 
 differences of electromotive force, and hence cur- 
 rents. (See. Electrotonus. ) 
 
 Pile, Thermo, Differential A ther- 
 mopile in which the two opposite faces are 
 exposed to the action of two nearly equal 
 sources of heat in order to determine accu- 
 rately the differences in the thermal intensities 
 of such sources of heat. 
 
 fPil. 
 
 series, so as to form a single thermo-electric 
 source. (See Couple, Ther mo-Electric?) 
 
 A thermo electric pile is sometimes called a 
 thermo-electric battery. 
 
 Fig 433 shows Nobili's thermopile, in which 
 a number of bismuth- 
 antimony thermo-elec- 
 tric couples connected 
 in a continuous se- 
 ries, as shown panly 
 in Fig. 434, are insu- 
 lated from one another, 
 except at their June 
 tions, and packed in a 
 metallic box, supported 
 as shown in Fig 433. 
 The free terminals of Fig. 433. Thf? 'mo- Electric 
 the series are con- Pile. 
 
 nected to binding posts. Differences of tem- 
 perature between ihe two faces of the pile, where 
 the junctions are exposed, result in a difference 
 of potential equal to the sum of the differences of 
 potential of all the thermo-electric couples. 
 
 A careful inspec- ^> i 
 
 tion will show that (' ==~===^ 
 
 the junctions are 
 formed successively 
 at opposite faces of 
 the pile, so that if 
 the junctions be 
 numbered succes- 
 sively, the even junc- 
 tions will come at 
 one face, and the 
 
 Ft'f. 434. Series-Connected 
 Thermo- Electric Couples. 
 
 odd junctions at the other. This is necessary 
 in order to permit all the thermo-electric couples 
 to add their differences of potential ; for, if, as 
 in fig. 43S> a thermo-electric chain be formed, 
 
 Pile, Tjenno-Electric 
 
 -A number 
 
 of separate thermo-electric couples, united in 
 
 Fig. 435. Thermo-Llectnc Circuit. 
 
 no currents will result from equally heating any 
 two consecutive junctions ], J, of the metals A 
 and B, since the electromotive forces so produced 
 oppose each other. 
 
 Thermopiles have been constructed by 
 Clamond, of couples of iron and an atioy of zinc 
 and antimony, of sufficient power to produce a 
 voltaic arc whose illuminating power equaled 40 
 
pr.i 
 
 405 
 
 ffcla. 
 
 carcel b - irr?e r ^. Many practical difficulties exist 
 which will have to be surmounted, however, before 
 such piles can be employed as commercial electric 
 sources. 
 
 Pile, Voltaic A battery consisting 
 
 of a number of voltaic couples connected so 
 as to form a single electric source. 
 
 A form simi ar to Volta's original pile, consist- 
 ing ot alternate discs of copper and zinc, separated 
 from each other by discs of wet cloth, and piled 
 on one another, so as to form a numher of separate 
 voltaic couj-les connected in series, is shown in 
 Fig. 436. The thick plates marked Zn, are of 
 zinc ; the opper plates, marked Cu, are much 
 
 Pin, Insulator 
 
 A bolt by means 
 
 Fig- 43(>. Voltaic Pile. 
 
 thinner. The discs of moistened cloth are shown 
 at d d. One end of such a pile would then be 
 terminated by a plate of copper, and the other 
 by a plate of zinc. The copper end forms the 
 positive electrode, and the zinc end the negative 
 electrode. (See Cell, Voltaic ) 
 
 Pilot Lamp. (See Lamp, Pilot.) 
 
 Pilot Transformer. (See Transformer, 
 Pilot.) 
 
 Pilot Wires. (See Wires, Pilot.) 
 
 of which an insulator is attached to the tele- 
 graphic support or arm. 
 
 The insulator pins or bolts are generally fixed to 
 the insulator by means of 
 screw threads turned on 
 their ends. They are then 
 cemented to the insulators by 
 any suitable moisture-proof 
 cement. 
 
 The pin and insulator con- 
 nected to one another by 
 means of a screw thread are 
 shown in Fig. 437. 
 
 Pin, Switch - A 
 
 metallic pin or plug pro- 
 vided for insertion in a 
 telegraphic switch board. 
 A form of switch pin is 
 shown in Fig. 438. The 
 metallic end is conical in 
 form, and is provided with 
 two longitudinal slots at Fig. 437. Insulator 
 right angles to each other in 1'in. 
 
 order to insure a light spring connection with 
 the metallic contact plate in which the pin is in- 
 serted. 
 
 Pith. A light, cellular material, forming the 
 central portions of most exogenous plants. 
 
 An excel'ent pith, suitable for 
 electrical purposes, is furnished by 
 the dried interior of the elder- berry 
 stick. 
 
 Pith Ball. (See Balls, Pith.) 
 
 Pith - Ball Electroscope. 
 
 (See Electroscope, Pith-Ball.) 
 
 Pivot Suspension. (See Sus- 
 pension, Pivot) 
 
 Plain-Pendant Argand Elec- 
 tric Burner. (See Burner, 
 Plain-Pendant Electric) 
 
 Plain-Pendant Electric Burner. (See 
 Burner, Plain-Pendant Electric.) 
 
 Plane Angle. (See Angle, Plane) 
 
 Plane, Proof A small insulated 
 
 conductor employed to take test charges from 
 the surfaces of insulated, charged conductors. 
 
40G 
 
 [Pla. 
 
 The proof-plane is used in connection with 
 some form of electrometer. (See Balance, Cou- 
 lomb''! Torsion.') 
 
 Plane, Proof, Magnetic A small 
 coil of wire placed in the circuit of a delicate 
 galvanometer, and used for the purpose of 
 exploring a magnetic field. 
 
 When the coil is suddenly inverted in a mag- 
 netic field, if a long-coil galvanometer provided 
 with a heavy needle is used, the number of lines 
 of force which pass through the area of cross-sec- 
 tion of the coil will be proportional to the sine of 
 half the angle of the first swing of the needle. 
 
 Plant. A word sometimes used for in- 
 stallation, or for the apparatus required to 
 carry on any manufacturing operation. 
 
 An electric plant includes the steam engines 
 or other prime motors, the generating dynamo or 
 dvnamos, the lamps and other electro-receptive 
 devices, and the circuits connected therewith. 
 
 Plant Electricity. (See Electricity, 
 Plant. Plants, Electricity of.) 
 
 Plants, Electricity of Electricity 
 
 produced naturally by plants during their vig- 
 orous growth. 
 
 DuBois-Reymond and others have shown that 
 plants while in a vigorous vital state are active 
 sources of electricity. 
 
 If one of the terminals of a galvanometer be 
 inserted into a fruit near its stem, and the other 
 terminal into the opposite part of the fruit, the 
 galvanometer at once shows the presence of an 
 electric current. 
 
 Buff has shown that the roots and interior por- 
 tions of plants are always negatively charged, 
 while the flowers, fruits and green twigs are posi- 
 tively charged. 
 
 Plant tissue or fibre, like the muscular fibre of 
 animals, exhibits in many cases a true contraction 
 on the passage through it of an electric current. 
 This is seen in the Mimosa sensitiva, or Sensitive 
 Fern, in the Venus' Fly-Trap, and in several other 
 species of plants. 
 
 Fouillet concludes from numerous observations 
 that the free positive electricity of the atmosphere 
 is partly due to the vapors disengaged by grow- 
 ing plants. 
 
 The peculiar geographical distribution of thun- 
 der storms, however, does not favor this assump- 
 
 tion. (See Storm, Thunder, Geographical Dis- 
 tribution of.) 
 
 Plastics, Galvano A term some- 
 times employed for electrotyping, that is 
 where the deposits are sufficiently thick to 
 permit of ready separation from the object 
 which forms the mould. 
 
 Literally, the cold moulding or shaping of 
 metals by electrotyping. (See Plating, Elec- 
 tro. Metallurgy, Electro?) 
 
 The word galvano-plastics is sometimes used 
 as synonymous with electrotyping, electro-plat- 
 ing, or electro-metallurgy generally. 
 
 Plastics, Hydro The art of elec- 
 trically shaping or depositing metals in the 
 wet by electrotyping. (See Plastics, Gal- 
 vano.) 
 
 Plate, Arrester, of Lightning Protector 
 
 That plate of a lightning protector 
 
 which is- directly connected with the circuit 
 to be protected, as distinguished from the plate 
 that is connected with the ground. (See 
 Arrester, Lightning?) 
 
 Plate Condenser. (See Condenser, Plate?) 
 Plate, Ground, of Lightning Arrester 
 
 That plate of a comb lightning arrester 
 which is connected to the earth or ground. 
 (See Arrester, Lightning, Comb?) 
 
 Plate, Negative, of Storage Cell 
 
 That plate of a storage cell which, by the 
 action of the charging current, is converted 
 into or partly covered with a coating of spongy 
 lead. 
 
 That plate of a storage battery which is 
 connected with the negative terminal of the 
 charging source, and which is therefore the 
 negative pole of the battery on discharging. 
 
 The usage is the reverse of that in the case of 
 the primary battery. 
 
 Plate, Negative, of Yoltaic Cell - 
 
 The electro-negative element of a voltaic 
 couple. (See Couple, Voltaic?) 
 
 That element of a voltaic couple which is 
 negative in the electrolyte of the cell. (See 
 Electrolyte?) 
 
 The negative plate of a voltaic rell is the plate 
 not acted on by the electrolyte. In a zinc carbon 
 
Pla.] 
 
 407 
 
 [Pla. 
 
 couple in dilute sulphuric acid, the carbon plate 
 is the negative plate. (See Cell, Voltaic.) 
 
 The negative plate is to be carefully distin- 
 guished from the negative pole, which is the ter- 
 minal connected to the positive plate. The 
 terminal connected to the negative plate is the 
 positive pole. (See Cell, Voltaic.) 
 
 Plate, Positive, of Storage Battery - 
 
 That plate of a storage battery which is 
 converted into, or covered by, a layer of lead 
 peroxide, by the action of the charging current. 
 That plate of a storage battery which is 
 connected with the positive terminal of the 
 charging source and which is, therefore, the 
 positive pole of the battery on discharging. 
 
 'It will be noticed that the usage in this respect 
 is the reverse of that in the case of primary bat- 
 teries, in which the positive plate is positive in 
 the liquid only; the end which projects from the 
 liquid, or the terminal connected with it being 
 negative. 
 
 In storage batteries, the positive plate is con- 
 nected with the positive pole. (See Battery, 
 Storage. Cell, Voltaic.) 
 
 Plate, Positive, of Voltaic Cell - 
 
 The electro-positive element of a voltaic 
 couple. (See Couple, Voltaic.} 
 
 That element of a voltaic couple which is 
 positive in the electrolyte of the cell. (See 
 Electrolysis.) 
 
 The positive plate of a voltaic cell is the plate 
 out from which the current flows through the 
 electrolyte. 
 
 The zinc plate of a zinc-carbon couple is the 
 positive plate. (See Cell, Voltaic. ) 
 
 The current leaves the cell, however, to flow or 
 pass through the external circuit at the wire or 
 terminal connected with the negative plate. (See 
 Cell, Voltaic.) 
 
 Plate, Primary, of Condenser 
 
 That plate of a condensing transformer in 
 which the inducing charge is placed in order 
 to induce a charge of different potential in the 
 secondary plate. 
 
 Plate, Secondary, of Condenser 
 
 That plate of a condensing transformer in 
 which 'the induced charge is produced by the 
 induction of a charge on the primary plate. 
 
 Plate, Zinc, of Voltaic Cell, Amalgama- 
 
 tion of Covering the surface of the 
 
 zinc plate of a voltaic cell with a thin layer of 
 amalgam in order to avoid local action. (See 
 Action, Local, of Voltaic Cell. Zinc, Amal- 
 gamation of.) 
 
 Plates, Arrester A term sometimes 
 
 applied to the two plates of an ordinary cflmb 
 lightning arrester. (See Arrester, Lightning, 
 Comb.) 
 
 The plate that is connected to the line to be 
 protected, is more correctly called the arrester 
 plate, and that connected to the ground the ground 
 plate. 
 
 Plates of Secondary or Storage Cell, 
 
 Forming of Obtaining a thick coating 
 
 of lead peroxide on the lead plates of a storage 
 battery, by repeatedly sending the charging 
 current through the cell alternately in opposite 
 directions. 
 
 The effect of sending a current between two 
 lead plates immersed in dilute sulphuric acid, is to 
 coat one of the plates with lead peroxide. On the 
 sending of the current in the opposite direction, 
 the other plate is coated with lead peroxide. If 
 now the current is sent in the opposite direction, 
 more peroxide is deposited on one of the plates, 
 and the peroxide at the other plate is converted 
 into spongy lead. 
 
 At the end of charging, the battery will form 
 an independent source of current. (See Cell, 
 Storage. ) 
 
 Platform, Pole A platform, capable 
 
 of supporting several men, placed on a termi- 
 nal pole provided with a cable box, for the 
 purpose of affording a ready means of inspect- 
 ing and arranging the conductors in the box. 
 
 Plating Balance. (Se&Balance, Plating.) 
 
 Plating Bath, Electro - - (See Bath, 
 Electro-Plating?) 
 
 Plating, Copper Electro-plating 
 
 with copper. (See Plating, Electro. Bath, 
 Copper^ 
 
 Plating, Electro The process of 
 
 covering any electrically conducting surface 
 with a metal by the aid of the electric 
 current. 
 
 By the aid of electro-plating, the baser metals 
 are covered w th silver, gold or platinum, or with 
 any other metal, such as nickel or copper. 
 
Pla.J 
 
 408 
 
 [Pla. 
 
 The process of electro-plating is carried on as 
 follows: 
 
 The object to be plated is connected with the 
 negative terminal of a battery and placed in a so- 
 lution of the metal with which it is to be plated, 
 opposite a plate of that metal connected to the 
 positive terminal of the bat ery. If, for example, 
 the object is to be plated with copper, it is pi ced 
 in a solution of copper sulphate or blue vitriol, 
 opposite a plate of copper. By this arrangement 
 the object to be plated forms the kathode of the 
 plating bath, and the plate of copper forms the 
 anode. 
 
 On the passage of the current the copper sul- 
 phate (Cu SO 4 ) is decomposed, metallic copper 
 being deposited in an adherent layer on the arti- 
 cles attached to the kathode, and the acid radical 
 (SO 4 ) appearing at the anode, where it combines 
 with one of the atoms of the copper plate. Since 
 for every molecule of copper sulphate decomposed 
 in theelecirolyte,anewmoleculeol copper sulphate 
 is thus formed, by the gradual solution of the copper 
 anode, the strength of the solution in the bath is 
 maintained as long as any of the copper plate re- 
 mains at the anode, and the ordinary activity of 
 the cell is not otherwise interfered with. 
 
 When any other metals, such as gold, silver or 
 nickel, for example, are to be deposited, suitable 
 solutions of their salts are placed in the bath, and 
 plates of the same metal hung at the anode. 
 
 The character and coherence of the metallic 
 coatings thus obtained depend on the nature and 
 strength of the plating bath, and on the density 
 of the current employed. The size and position 
 of the anode, as compared with the size and posi- 
 tion of the objects to be plated, must therefore be 
 carefully attended to, as well as the strength of 
 
 Fig. 43Q. Electro- Plating 
 
 the metallic solution and the current strength 
 passing. (See Current Density.} 
 
 Fig. 439, shows a bath arranged for silver- 
 plating. 
 
 The anode consists of a plate of i-ilver. The 
 
 spoons, forks, etc., to be plated are immersed in 
 a suitable silver solution and connected with the 
 kathode. 
 
 The electro-plating process when employed for 
 the production of electrotype plates is called 
 electrotyping. Here the object is to obtain a re- 
 production in metal of any particular form, such 
 as of type or of some natural object. It was 
 called by Jacobi the galvanofilastic process. The 
 term electrotyping is, however, more generally 
 adopted. (See Electrotyping, or the Electrotype 
 Process.') 
 
 Plating, Gold Electro-plating with 
 
 gold. (See Plating, Electro. Bath, Gold.} 
 
 Plating, Nickel Electro - plating 
 
 with nickel. (See Plating, Electro. Bath, 
 Nickel} 
 
 Plating, Sectional Plating an article 
 
 with a greater thickness of metal at certain 
 points than at the rest of the surface. 
 
 Sectional plating is employed for such objects 
 as spoons, etc., which are, by this method, given 
 a greater thickness of deposit at the under portions 
 of the bowl and handle, where the spoon usually 
 rests, and is, therefore, exposed to the greatest 
 wear. 
 
 Sectional plating is effected by means of sec- 
 tional plating frames. (See Plating, Electro. 
 Frames, Sectional Plating. ) 
 
 Plating, Silver Electro-plating 
 
 with silver. (See Plating, Electro. Bath, 
 Silver?) 
 
 Platinoid. An alloy consisting of German 
 silver containing I or 2 per cent, of metallic 
 tungsten. 
 
 Platinoid is suitable for use in resistance coils on 
 account of the comparatively small influence pro- 
 duced on its electric resistance by changes t f 
 temperature. 
 
 Its resistance is 60 per cent, higher than that 
 of German silver. 
 
 Platinum. A refractory and not readily 
 oxidizable metal, of a tin-white color. 
 
 The co-efficient of expansion of platinum by 
 heat is very nearly that of ordinary giass. Pla- 
 tinum is, therefore, generally employed ior the 
 leading-in conductors of an incandescent lamp. 
 These conductors are fused into the glass of t>e 
 lamp chamber. On the heating of the wires by 
 
Pla.] 
 
 409 
 
 [Plu. 
 
 the current, the glass expands t qually with the 
 wires, and the vacuum in the lamp chamber is 
 not, therefore, injured. 
 
 Platinum Alloy. (See Alloy, Platinum- 
 Silver^) 
 
 Platinum Black. Finely divided platinum 
 that possesses, in a marked degree, the power 
 of absorbing or occluding gases. 
 
 Platinum black is obtained by the action of 
 potassium hydrate on platinum chloride. Unlike 
 metallic platinum it is of a black color. 
 
 Platinum Fuse. (See Fuse, Platinum?) 
 
 Platinum-Silver Alloy. (See Alloy, Plat- 
 inum-Silver^ 
 
 Platinum Standard Light. (See Light, 
 Platinum Standard^) 
 
 Platymeter. An instrument invented by 
 Sir William Thomson for comparing the 
 capacities of two condensers. 
 
 Plow. The sliding contacts connected to 
 the motor of an electric street car, and placed 
 within the slotted underground conduit, and 
 provided for the purpose of taking off the 
 current from the electric mains placed therein, 
 as the contacts are pushed forward over them 
 by the motion of the car. 
 
 Similar contacts, placed in the rear of the motor 
 car and drawn after the train, form what is techni- 
 cally known as the sled, or when rolling on over- 
 head wires as trolleys. (See Railroad, Electric.) 
 
 Plow, Electric A plow driven by 
 
 an electric motor placed either on a wagon to 
 which the plow is attached, or by a stationary 
 electro-motor, by the aid of cords or other 
 flexible belts. 
 
 One of the first practical applications of the elec- 
 tric transmission of energy was for the operation 
 of a plow, driven electrically, by an electric current 
 generated at some distance, and transmitted to 
 the electric motor by suitable conductors. 
 
 Pliicker Tube. (See Tube, Pliicker.) 
 
 Plug. A piece of metal in the shape of a 
 plug, provided for making or breaking a cir- 
 cuit by placing in, or removing from, a con- 
 ical opening formed in the ends of two 
 closely approached pieces of metal which are 
 
 connected with the circuits to be made or 
 broken. 
 
 As the plug is inserted in the opening it bridges 
 over the opening and thus closes the circuit con- 
 nected with the separate pieces of metals. On 
 removing the plug the circuit is opened or broken. 
 
 Plug. In telegraphy, an inexpert operator. 
 
 Plug, Double A plug so constructed 
 
 that when inserted in a spring-jack it makes 
 two connections, one at its point and one at 
 its shank. (See Spring-Jack.) 
 
 Plug, Fusible A term sometimes 
 
 applied to a safety fuse. (See Plug, Safety.) 
 
 Plug, Infinity A plug hole in a box 
 
 of resistance coils, in which the two pieces of 
 brass it connects are not connected by any 
 resistance coil, and which, therefore, leaves, 
 when withdrawn, an open circuit of an in- 
 finite resistance. 
 
 Plug, Safety A wire, bar, plate or 
 
 strip of readily fusible metal, capable of con- 
 ducting, without fusing, the current ordinarily 
 employed on the circuit, but which fuses, and 
 thus breaks the circuit, on the passage of an 
 abnormal current. (See Fuse, Safety.) 
 
 A safety plug is only used on circuits in which 
 the electro-receptive devices are connected with 
 the leads in multiple. In this case the fusing of 
 the safety plug, and the consequent opening of the 
 circuit with which it is connected, does not affect 
 the rest of the circuit. On series-connected circuits 
 a different form of safety device is used. (See 
 Cut -Out, Automatic, for Series-Connected Elec- 
 tro-Receptive Devices. ) 
 
 Plug, Short-Circuiting A plug by 
 
 means of which one part of a circuit is cut 
 out by being short-circuited. 
 
 Plug Switch. (See Switch, Plug.) 
 
 Plug, Wall A plug provided for 
 
 the insertion of a lamp or other electro-re- 
 ceptive device in a wall socket, and thus con- 
 necting it with a lead. 
 
 Plugging. Completing a circuit by means 
 of plugs. 
 
 Plugs, Grid Plugs of active ma- 
 terial that fill the spaces or apertures in the 
 lead grid or plate of a storage battery. 
 
Plu.] 
 
 410 
 
 [Poi. 
 
 The active material forming the plugs is placed 
 in the spaces in the grid while in the plastic con- 
 dition. On the subsequent hardening of this ma- 
 terial, these grid plugs cannot readily fall out, 
 since the spaces are so shaped that their interior 
 portions are 01 greater diameter than at the sur- 
 face of the plates. 
 
 Plumbago. An allotropic modification of 
 carbon. 
 
 Plumbago, the material commonly known as 
 black lead, is the same as graphite. Powdered 
 plumbago is employed in electrotyping processes 
 for rendering non-conducting surfaces electrically 
 conducting. For this purpose powdered plum- 
 bago is dusted on the surfaces, which thus acquire 
 the power of receiving a metallic lustre by fric- 
 tion. Stove polishes are formed of mixtures of 
 plumbago and other cheap materials. (See 
 Graphite.} 
 
 Strictly speaking, the term graphite is properly 
 applied to such varieties of plumbago as are suit- 
 able for direct use for writing purposes, as in lead 
 pencils. 
 
 Plumbago, Coppered - - Powdered 
 plumbago coated with copper, for use in the 
 metallization of objects to be electro-plated. 
 (See Metallization?) 
 
 Plumbago, Gilt Powdered plum- 
 bago whose conducting power for electricity 
 has been increased by coating it with metallic 
 gold. 
 
 Gilt plumbago is used for rendering non-con- 
 ducting surfaces electrically conducting and thus 
 preparing them for electro-plating. 
 
 To prepare gilt plumbago, dissolve in ico parts 
 of sulphuric ether I part of chloride of gold, mix 
 in this 60 parts of powdered plumbago, and ex- 
 pose to air and light until all ether has volatilized. 
 Then dry in an oven. 
 
 Plumbago, Silvered Powdered 
 plumbago coated with metallic silver for use 
 in the metallization of objects to be electro- 
 plated. 
 
 Plunge Battery. (See Battery, Plunged) 
 
 Pneumatic Perforator. (See Perforator, 
 Pneumatic?) 
 
 Pneumatic Signals, Electro - (See 
 Signals, Electro-Pneumatic?) 
 
 Pockets, Armature - Spaces pro- 
 vided in an armature for the reception of the 
 
 armature coils. (See Coils, Armature, of 
 Dynamo-Electric Machine?) 
 
 Poggendorff's Voltaic Cell. (See Cell, 
 Voltaic, Poggendorff's.} 
 
 Point, Carbon : A term formerly 
 
 applied to the carbon electrodes used in the 
 production of the voltaic arc. 
 
 Point, Indifferent A point in the 
 
 intra-polar regions of a nerve where the ane- 
 lectrotonic and kathelectrotonic regions meet, 
 and where the excitability is therefore un- 
 changed. 
 
 This is sometimes called the neutral point. 
 
 Point of Lightning Rod. (See Rod, 
 Lightning, Points on.) 
 
 Point of Origin. (See Origin, Point of.) 
 
 Point, Neutral In electro-thera- 
 peutics, a term sometimes used instead of in- 
 different point. (See Point, Indifferent.) 
 
 Point, Nodal The null point in a 
 
 circuit traversed by electric oscillations. (See 
 Point, Null.) 
 
 Point, Null Such a point on a 
 
 micrometer circuit, that when joined or con-, 
 nected with the second- 
 ary circuit of an in- 
 duction coil, the sparks 
 in the micrometer cir- 
 cuit are either very 
 greatly decreased or 
 are entirely absent. 
 
 The null point on the 
 micrometer circuit is situ- 
 ated symmetrically with 
 respect to the micrometer 
 knobs. 
 
 If the induction coil A, 
 Fig. 440, has its second- 
 ary circuit connected as 
 shown with the microm- Fig. 440. Null Point. 
 eter circuit at the point e, situated at the centre 
 of the micrometer circuit, the point will be a null 
 point, and the effects of sparks at the micrometer 
 knobs, at M, will be greatly decreased. Under 
 the conditions shown in the figure, the electrical 
 oscillations in the micrometer circuit must be re- 
 garded as in the condition of stationary waves or 
 vibrations. It would seem, therefore, that defi- 
 nite waves or vibrations are setup in the microm- 
 
Poi.] 
 
 411 
 
 [Pol. 
 
 eter circuit, in the same way as are the vibra- 
 tions produced in an elastic bar set in vibration 
 by a violin bow, or by a blow from a hammer. 
 
 Points, Consequent The points or 
 places in an anomalous magnet where the 
 consequent poles are situated. (See Magnet, 
 Anomalous. Pole, Anomalous?) 
 
 Points, Corresponding - Points 
 where the lines of electrostatic force sur- 
 rounding an insulated charged conductor 
 enter the surfaces of neighboring conductors. 
 
 Points on the surface of a body placed in 
 an electrostatic field where the lines of elec- 
 trostatic force enter its surface, and thus pro- 
 duce a charge equal and opposite to that 
 of the surface of the body at the points from 
 which they came. 
 
 Corresponding points receive, in accordance 
 with the laws of electrostatic induction, charges 
 equal and opposite to those of the surfaces from 
 which the lines of electrostatic force originate. 
 
 Points, Electric Action of The 
 
 effect of points placed on an insulated, 
 charged conductor, in slowly discharging the 
 conductor by electric convection. (See Con- 
 fection, Electric.} 
 
 The cause of this action of points is to be at- 
 tributed to the increased density of a charge on 
 the surface of a conductor at the points and the 
 consequent production of convection streams of 
 air, which thus gradually carry off the charge. 
 (See Charge, Distribution of.) 
 
 Points, Iso-Electric A term some- 
 times used in electro-therapeutics for points 
 of equal potential. 
 
 Points, Neutral, of Dynamo-Electric Ma- 
 chine Two points of greatest differ- 
 ence of potential, situated on the commutator 
 cylinder, at the opposite ends of a diameter 
 thereof, at which the collecting- brushes must 
 rest in order to catry off the current quietly. 
 
 These are called the neutral points because the 
 coils that are short-circuited by the brushes lie in 
 the magnetically neutral points of the armature. 
 (See Line, Neutral, of Commutator Cylinder.) 
 
 Points, Neutral, of Magnet Points 
 approximately midway between the poles of 
 14 Vol. 1 
 
 a magnet. (See Line, Neutral, of a Magnet. 
 Magnet, Equator of.) 
 
 Points, Neutral, of Therino-Electric Dia- 
 gram The points on alhermo-electric 
 
 diagram where the lines representing the 
 thermo-electric powers of any two metals 
 cross one another. 
 
 A mean temperature for any two metals irr 
 a thermo-electric series, at which, if their two 
 junctions are slightly over and slightly undep 
 the mean temperature (the one as much 
 above as the other is below), no effective 
 electromotive force is developed. (See Dia- 
 gram, Ther mo-Electric. Couple, Thermo- 
 Electric^) 
 
 Points or Rhumbs of Compass. (See 
 Compass, Points of.) 
 
 Polar Region. (See Region, Polar.) 
 
 Polar Tips. (See Tips, Polar.) 
 
 Polarity, Diamagnetic A polar- 
 ity the reverse of ordinary magnetic polarity, 
 the existence of which was assumed by Fara- 
 day to explain the phenomena of diamag- 
 netism. (See Diamagnetism.) 
 
 Faraday assumed that diamagnetic substances, 
 when brought into a magnetic field, acquired 
 north magnetism in those parts that were nearest 
 the north pole, instead of south magnetism, as 
 with ordinary magnetic substances. The north 
 pole thus obtained would, he thought, explain 
 the apparent repulsion of a slender rod of a-iy di- 
 amagnetic material delicately suspended lu a 
 strong magnetic field, and cause it to point equa- 
 torially, or with the lines of force passing through 
 its least dimensions. This supposition was sub^e- 
 quently abandoned by Faraday. It has recently 
 been r.vived by Tyndall. (S_-e Diamagnetism.) 
 
 The action of a diamagnetic body, when placed 
 in a magnetic field, is now generally ascribed to 
 the fact that the atmosphere, by which such body 
 is surrounded, is more powerfully paramagnetic 
 than the diamagnetic substance. The diamag 
 netic substance comes to rest in an equatorial posi- 
 tion, because in that position there is the greatest 
 length of air in the path of the magnetic lines, 
 which has a smaller magnetic resistance than the 
 diamagnetic substance. 
 
 Polarity, Magnetic The polarity 
 
 acquired by a magnetizable substance when 
 brought into a magnetic field. 
 
Pol.] 
 
 412 
 
 [Pol. 
 
 The direction of magnetic polarity, acquired by 
 a substance when brought into a magnetic field, 
 depends on the direction in which the lines of 
 magnetic force pass through it. Where these 
 lines enter the substance a sou:h pole is pro- 
 duced, and where they pass out, a north pole is 
 produced. The axis of magnetization lies in the 
 direction of the lines of force as they pass 
 through the body, and the intensity of magnetiza- 
 tion depends on the number of these lines of 
 force which pass through the body. 
 
 The cause of magnetic polarity is not definitely 
 known. Hughes' hypothesis attributes it to a 
 property inherent in all matter. Ampere at- 
 tributes it to closed electric circuits in the ultimate 
 particles. Whatever its cause, it is invariably 
 manifested by a magnetic field, the lines of force of 
 which are assumed to have the direction already 
 mentioned. (See Magnetism, Hughes'" Theory 
 of. Magnetism, Ampere's Theory of. Magnet- 
 ism, Swing's Theory of.) 
 
 Polarization, Galvanic A term 
 
 sometimes applied to the polarization of a 
 voltaic cell. (See Cell, Voltaic, Polariza- 
 tion of.) 
 
 Polarization, Internal, of Moist Bodies 
 
 A polarization exhibited by such 
 
 moist bodies as the nerves, muscular fibres, 
 the juicy parts of vegetables and animals, or 
 in general by all bodies possessing a firm struc- 
 ture filled with a liquid, on the passage 
 through them of a strong electric current. 
 
 Polarization, Magnetic Rotary 
 
 The rotation of the plane of polarization of a 
 beam of plane-polarized light consequent on 
 its passage through a plate of glass subjected 
 to the stress of a magnetic field. (See Rota- 
 tion, Magneto-Optic?) 
 
 Polarization of Dielectric. (See Dielec- 
 tric, Polarization of.) 
 
 Polarization of Electrolyte. (See Elec- 
 ^ trolyte, Polarization of.) 
 
 Polarization of Yoltaic Cell. (See Cell, 
 Voltaic, Polarization of.) 
 
 Polarized Armature. (See Armature, 
 
 Polarized.) 
 
 Polarized Relay. (See Relay, Polarized.) 
 Polarizing Current. (See Curr f ,it , 
 
 Polarization.) 
 
 Polarizing Electro-Therapeutic Current. 
 
 (See Current, Electro- Therapeutic Polar- 
 izing?) 
 
 Pole, Analogous 
 
 That pole of a 
 
 pyro-electric substance, like tourmaline, which 
 acquires a positive electrification while the 
 temperature of the crystal is rising. (See 
 Electricity, Pyro?) 
 
 Pole, Anomalous A name some- 
 times given to those parts or poles in an 
 anomalous magnet which consist of two simi- 
 lar free poles placed together. (See Magnet, 
 Anomalous.) 
 
 Pole, Antilogous That pole of a 
 
 pyro-electric substance, like tourmaline, which 
 acquires a negative electrification when the 
 temperature of the crystal is rising, and a 
 positive electrification when it is falling. (See 
 Electricity, Pyro.) 
 
 Pole, Armature (See Armature, 
 
 Pole?) 
 
 Pole Changer. A switch or key for chang- 
 ing or reversing the direction of current pro- 
 duced by any electric source, such as a bat- 
 tery 
 
 The commutator of a Ruhmkorff coil is a sim- 
 ple form of pole changer. It is, however, usu- 
 ally called a commutator. (See Coil, Induction. ) 
 
 Pole-Changing and Interrupting Elec- 
 trode Handle. (See Electrode-Handle, 
 Pole-Changing and Interrupting?) 
 
 Pole-Changing Switch. (See Switch, 
 Pole-Changing?) 
 
 Pole Climbers. (See Climbers, Pole?) 
 
 Pole, Consequent A magnet pole 
 
 formed by two free north or two free south 
 poles placed together. (See Magnet, Anom- 
 alous?) 
 
 Pole, Magnetic, Austral 
 
 A name 
 
 formerly employed in France for the north- 
 seeking pole of a magnet. 
 
 That pole of a magnet which points to the 
 earth's geographical north. 
 
 It will be observed that the French regarded the 
 magnetism of the earth's Northern Hemisphere 
 
Pol.] 
 
 413 
 
 [Pol. 
 
 as north, and so named the north-seeking pole of 
 the needle the austral or south pole. 
 
 The north-seeking pole of the magnet is some- 
 times called the boreal or north pole. (See Pole, 
 Magnetic, Boreal,) 
 
 Pole, Magnetic, Boreal A name 
 
 formerly employed in France for the south- 
 seeking pole of a magnet, as distinguished 
 from the austral or north-seeking pole. 
 
 That pole of a magnet which points to- 
 ward the geographical south. 
 
 If the earth's magnetic pole in the Northern 
 Hemisphere be of north magnetism, then the pole 
 of a needle that points to it must be of the oppo- 
 site polarity, or of south magnetism. In this 
 country we call the end which points to the nonh. 
 the north-seeking pole or marked pole. In 
 France the end which points to the north was 
 formerly called the austral pole. Austral means 
 sjuth pole. (See Pole, Magnetic, Austral.) 
 
 Pole, Magnetic, False A term pro- 
 posed by Mascart and Joubert to designate 
 the place or places on the earth which appar- 
 ently act as magnetic poles, in addition to 
 the two true magnetic poles, near the earth's 
 geographical poles. 
 
 According to these authorities, the earth pos- 
 sesses two magnetic poles only, viz., a negative 
 pole in the Northern Hemisphere and a positive 
 pole in the Southern Hemisphere. The addi- 
 tional poles are called by them the false magnetic 
 poles. 
 
 Pole, Magnetic, Free A pole in a 
 
 piece of iron, or other paramagnetic sub- 
 stance, which acts as if it existed as one mag- 
 netic pole only. 
 
 A free magnetic pole has in reality no physical 
 existence. The conception, however, is of use in 
 describing certain magnetic phenomena. If the 
 bar of iron be so long as to practically place one 
 pole beyond the sensible action of the other, either 
 pole may be regarded as a free pole. 
 
 Pole, Magnetic, Marked That pole 
 
 of a magnetic needle which points approxi- 
 mately to the earth's geographical north. 
 (Obsolete.) 
 
 The north-seeking pole of a magnetic needle. 
 
 Pole, Magnetic, North - That pole 
 of a magnetic needle which points approxi- 
 mately to the earth's geographical north. 
 
 The north-seeking pole of a magnetic 
 needle. 
 Pole, Magnetic, North-Seeking 
 
 That pole of a magnetic needle which points 
 approximately towards the earth's geographi- 
 cal north. 
 
 Pole, Magnetic, Salient - A term 
 sometimes applied to the single poles at the ex- 
 tremities of an anomalous magnet, in order to 
 distinguish them from the double or consequent 
 pole formed by the juxtaposition of two simi- 
 lar magnetic poles. (See Magnet, Anoma- 
 lous^) 
 
 Pole, Magnetic, South - That pole 
 of a magnetic needle which points approxi- 
 mately towards the earth's geographical south. 
 
 The south-seeking pole of a magnetic 
 needle. 
 
 Pole, Magnetic, South-Seeking 
 
 That pole of a magnetic needle which points 
 approximately toward the geographical south. 
 
 Pole, Negative That pole of an 
 
 electric source through which the current is 
 assumed to enter or flow back into the source 
 after having passed through the circuit ex- 
 ternal to the source. 
 
 Pole-Pieces of Dynamo-Electric Machine. 
 
 (See Pieces, Pole, of Dynamo-Electric 
 Machined) 
 
 Pole Platform. (See Platform, Pole) 
 
 Pole, Positive That pole of an 
 
 electric source out of which the electric cur- 
 rent is assumed to flow. 
 
 Pole Steps. Short rods or bars shaped so 
 as to be readily inserted in holes near the 
 base of telegraph or electric light 'poles, so as 
 to serve as steps to enable a lineman to reach 
 the permanently placed steps. 
 
 Permanent steps are placed only at some dis- 
 tance from the ground, in order to prevent the 
 ready climbing of the poles by unauthorized 
 persons. 
 
 Pole, Telegraphic A wooden or iron 
 
 upright on which telegraphic or other wires 
 are hung. 
 
 Wooden poles are generally round. 
 
Pol.J 
 
 414 
 
 [Pol. 
 
 The terminal pole, or the last pole at each end 
 of the line, or where the wires bend at an angle 
 of nearly 90 degrees, is made larger than usual 
 and is often cut square. 
 
 The holes for the poles must be dug in the true 
 line of the wires, and not at an angle to such line. 
 As little ground should be disturbed in the dig- 
 ging as possible. Earth borers, or modifications 
 of the ordinary ship auger, are generally em- 
 ployed for this purpose. When the pole is placed 
 in position the ground should be rammed or 
 punned around the pole. 
 
 In setting the pole, it is generally buried at least 
 5 feet in the ground. In England the poles are 
 planted to a depth of about one-fifth of their 
 length. In embankments and loose ground, they 
 are planted deeper than in more solid earth. On 
 curves, the poles should be inclined a little so as 
 to lean back against the lateral strain of the wire, 
 since by the time the ground has completely set, 
 the strain of the wire will have pulled them into 
 an erect position. 
 
 Care must be taken to so plant the poles on 
 that side of a road or railway that the prevailing 
 winds will blow them off the roadbed, should it 
 overturn them. As to location, the top of steep 
 cuttings is preferable to the slope. In all exposed 
 positions, it is preferable to strengthen the poles 
 by stays attached to both sides. 
 
 Where the number of wires is unusually large, 
 heavy timber, or in case of its absence, double 
 
 Fig. 441. Telegraphic 
 Brackets. 
 
 Fig. 442. Telegraphic 
 Anns. 
 
 poles suitably braced together, must be employed. 
 In long lines the poles should all be numbered in 
 order to afford ease of reference in case of repair. 
 
 When, even with the best punning, and other 
 precautions, the pole is judged to be unable to 
 resist the strain on it, stays and struts are em- 
 ployed. A stay is used when it is desired to re- 
 move the/w//or tension from the pole ; a strut, 
 when it is desired to remove the thrust or pressure. 
 
 The arms or brackets, or the cross-pieces that 
 
 support the insulators, should all be placed on 
 the same side of the poles. Some common forms 
 of brackets are shown in Fig. 441, and of tele- 
 graphic arms in Fig. 442. 
 
 Saddle brackets should be placed on alternate 
 sides of the poles. When the strain on an insula- 
 tor is too great, on account of the wire going off 
 at a sharp angle, a shackle is used. This is a 
 special form of insulator which confines the strain 
 to one spot. 
 
 Fig. 443. Double Shackles. 
 
 A form of double shackle is shown in Fig. 
 443. The wire passes around the recess at B, 
 between the two insulators. 
 
 On curves, or in any situation where there is a 
 probability, in case of the breaking of an insula- 
 
 Fig. 444. Hook Guard, 
 
 tor, of a wire getting into a dangerous position, 
 guards should be employed. 
 
 Guards are of two kinds, viz.: hoop guards 
 and hook guards. A form of hook guard is 
 shown in Fig. -*|/|/|- 
 
 When wooden poles are employed various pre- 
 servative methods are adopted to protect the 
 wood from decay, which is very apt to occur, 
 especially where the pole enters the ground. 
 Some of these forms are as follows, viz. : 
 
 ( I . ) Charring and tarring the butt end of the 
 pole where it enters the ground, so as to expel 
 the sap and destroy injurious plant or animal 
 germs. 
 
Pol.] 
 
 415 
 
 [For. 
 
 The charred end is then cleansed and dipped 
 in a mixture of tar and slaked lime. 
 
 (2.) Bumetizing, or the introduction of 
 chloride of zinc into the pores of the wood, by 
 placing the poles in an open tank tilled with a 
 solution of this salt. 
 
 (3 ) Ayanizing, or the similar introduction of 
 corrosive sublimate, or mercuric chloride. 
 
 (4.) Boucherizing, or the injection of a solution 
 of copper sulphate into the pores of the wood. 
 
 (5.) Creosoting, or the application of creosote 
 to well seasoned poles. 
 
 Pole, Telegraphic, Punning of 
 
 Ramming or packing the earth around the 
 base of a telegraph pole for the purpose of 
 more securely fixing it in the ground. 
 
 Pole, Telegraphic, Terminal The 
 pole at either end of a telegraphic line. 
 
 As the first or last pole in a telegraphic line is 
 not supported on opposite sides by the line wires, 
 it is generally made stouter than the intermediate 
 poles, and greater care is taken to fix it securely 
 in the ground. 
 
 Pole, Testing A term sometimes 
 
 employed in electro-therapeutics for the in- 
 different pole or electrode. (See Electrode, 
 Indifferent?) 
 
 Pole, Trolley The pole which sup- 
 ports the trolley bearing and rests on the 
 socket in the trolley base frame in an over- 
 head wire electric railway system. 
 
 Pole, Unit, Magnetic A magnetic 
 pole of such a strength that it would act with 
 a unit or dyne of force on another unit pole at 
 a distance of one centimetre. 
 
 Poles, Consequent The name given 
 to single magnetic poles formed by two free 
 N. poles or two free S. poles placed together. 
 (See Magnet, Anomalous?) 
 
 Poles, Idle Poles or electrodes in 
 Crookes' tubes, between which discharges are 
 not taking place. 
 
 The idle poles have no connection with the in- 
 duction coils or other sources from which the elec- 
 tric discharges are obtain* d. These poles are pro- 
 vided for attaching galva.nometer wires, etc., in the 
 study of the Edison effect, or for the study of the 
 
 electrical condition of the dark space and other 
 regions of the atmosphere of the tube. 
 
 Poles, Magnetic The two points 
 
 where the lines of magnetic force pass from 
 the iron into the air, and from the air into 
 the iron. 
 
 The two points in a magnet where the 
 magnetic force appears to be concentrated. 
 
 In reality the magnetic force is most concen- 
 trated at the neutral points of a magnet, through 
 which all the lines of force pass. 
 
 All magnets possess at least two poles, one 
 positive or north, and the other negative or south. 
 
 The lines of magnetic force are assumed to 
 come out of a magnet at its north pole, and to 
 enter it at its south pole. 
 
 Poles, Magnetic, of Verticity (See 
 Verticity, Poles of, Magnetic?) 
 
 Poles of Condenser. The terminals of a 
 condenser. (See Condenser.} 
 
 Poles of Magnetic Intensity. (See In- 
 tensity, Magnetic, Pole of.) 
 
 Polyphase Current. (See Current, 
 Multi-Phase:) 
 
 Polyphotal Arc Light Regulators. (See 
 Regulator, Polyphotal Arc-Light?) 
 
 Popgun, Electro-Magnetic A mag- 
 netizing coil, provided with a tubular space 
 for the insertion of a core, much shorter than 
 the length of the coil, which, when the ener- 
 gizing current is passed through the coil, 
 is thrown violently out from the coil. 
 
 The movement and consequent expuUion of the 
 core is due to the action of the lines of magnetic 
 force which complete their circuit through the 
 core. 
 
 Porcelain. A variety of insulating ma- 
 terial. 
 
 A translucent variety of earthenware. 
 Porous Cell. (See Cell, Porous?) 
 Porous Cup. (See Cup, Porous?) 
 Porous Insulation. (See Insulation, 
 Porous?) 
 
 Porous Jar. (See far, Porous.) 
 Porret's Phenomena. (See Phenomena, 
 Porret?) 
 
Por.J 
 
 416 
 
 TPos. 
 
 Portative Power. (See Power, Porta- 
 
 placed on the top of the carrier and connected the 
 several helices successively with the electric 
 
 Portelectric. An electric carrier. 
 
 A system of electric transportation by 
 means of the successive attractions of a num- 
 ber of hollow helices of insulated wire on a 
 hollow solenoidal iron car. 
 
 The solenoidal car forms the movable core of the 
 helical coils. As it moves through these coils it 
 automatically closes the circuit of an electric cur- 
 rent through the coils in advance of it and opens 
 the circuit of the coils in its rear. In this way the 
 solenoidal car advances in a line coincident with 
 the axis of the helical coils, being virtually sucked 
 through them by their magnetic attractions. This 
 system of electric propulsion is unique in systems 
 of electric traction. The motor becomes a mere 
 mass of iron or other paramagnetic material. 
 The system is suitable for the carriage of mail or 
 other comparatively light articles at a high speed. 
 
 In an experimental plant at Dorchester, Mass., 
 a track of 2,784 feet in length was laid in the ap- 
 proximate form of an oval. The track was 
 formed by an upper and lower rail of steel, suit- 
 ably supported by stringers. 
 
 The car, which forms the movable core of the 
 solenoidal coils, was of wrought iron, and was 
 cylindrical in shape, with conical ends. It was 
 
 Fig. 4^5. Portelectric Track. 
 
 12 feet in length and 10 inches in diametei, and 
 weighed about 500 pounds. It would carry about 
 10,000 letters. It had two flanged wheels above 
 and two below. 
 
 The solenoidal coils, by the attractive power of 
 which the core was moved, embraced the track 
 and the movable core or carrier. They were 
 fixed along the track at intervals of 6 feet from 
 centre to centre. Each coil was formed of 630 
 turns of No. 14 copper wire. The upper track 
 rail is divided into sections which form conductors 
 for the driving current. A central wheel was 
 
 Fig. 446. Portelectric Car. 
 
 source as the carrier was drawn forward. A 
 speed of about 34 miles an hour was reached. 
 
 A section of the track is shown in Fig. 445, and 
 the shape and general structure of the carrier in 
 Fig. 446. 
 
 Portrait, Electric A portrait 
 
 formed on paper by the electric volatilizatio? 
 of gold or other metal. 
 
 An electric portrait is obtained by cutting OH 
 a thin card a portrait in the form of a stencil. A 
 sheet of gold leaf is then placed on one side of the 
 
 Fig. 447, Electric Portrait. 
 
 paper stencil, and a sheet of paper on the othei 
 side ; sheets of tin-foil are then placed on the out. 
 side, as shown in Fig. 447, and the whole firmly 
 pressed together. If, now, a disruptive discharge 
 is passed through from one sheet of tin-foil to the 
 other, the gold leaf is volatilized, and a purplish 
 stain is left on the paper of the outlines of the 
 stenciled card, thus forming an electric portrait. 
 
 Position, Energy of A term used 
 
 for stored energy, or potential energy. (See 
 Energy, Potential.) 
 
 Positive Direction of a Simple-Harmonic 
 Motion. (See Motion, Simple-Harmonic, 
 Positive Direction of.) 
 
Pos.] 
 
 417 
 
 [Pot. 
 
 Positive Direction of Lines of Magnetic 
 Force. (See Force, Magnetic, Lines of, 
 Positive Direction of.) 
 
 Positive Direction of the Electrical Con- 
 Tection of Heat. (See Direction, Positive, 
 ef Electrical Convection of Heat?) 
 
 Positive Direction Round a Circuit. 
 (See Direction, Positive, Round a Cir- 
 cuit^ 
 
 Positive Direction Through a Circuit. 
 (See Direction, Positive, Through a Cir- 
 cuit?) 
 
 Positive Electricity. (See Electricity, 
 Positive?] 
 
 Positive Electrode. (See Electrode, 
 Positive?) 
 
 Positive Feeders. (See Feeders, Posi- 
 tive?) 
 
 Positive-Omnibus Bars. (See Bars, Posi- 
 tive Omnibus?) 
 
 Positive Phase of Electrotonus. (See 
 Electrotonus, Positive Phase of?) 
 
 Positive Plate of Storage Battery. (See 
 Plate, Positive, of Storage Battery?) 
 
 Positive Plate of Yoltaic Cell. (See 
 Plate, Positive, of Voltaic Cell?) 
 
 Positive Pole. (See Pole, Positive?) 
 
 Positive Potential. (See Potential, Posi- 
 tive?) 
 
 Positive Side of Circuit (See Circuit, 
 Positive Side of?) 
 
 Positively. In a positive manner. 
 
 Positively Excited. Excited or charged 
 with positive electricity. (See Electricity, 
 Positive?) 
 
 Post, Binding A device for con- 
 necting the terminal of an electric source 
 with the terminal of an electro-receptive de- 
 vice, or for connecting different parts of an 
 electric apparatus with one another. 
 
 The conducting or circuit wire is either intro- 
 duced in the opening a, or c', Fig. 448, and 
 clamped by the screw b, or b', or is placed in 
 the space d, d, and kept in place by means of a 
 thumbscrew. Sometimes two openings are 
 provided at c, and c', for the purpose of connect- 
 ing two wires together. 
 
 A device for coupling or connecting the ends 
 of two wires to each other. It is then called a 
 coupler. (See Couple, Voltaic.') 
 
 I' 
 
 Fig. 448. Binding Posts. 
 
 Pot, Porous The porous jar or cell 
 
 of a voltaic cell. (See Cell, Porous?) 
 
 Potential, Alternating A poten- 
 tial, the sign or direction of which is alter- 
 nately changing from positive to negative. 
 
 An alternating potential may be obtained either 
 in the case of an electrostatic field, or in that 
 of a magnetic field. 
 
 Potential, Alternating Electrostatic 
 
 The potential of a charge that is under- 
 going rapid alternations. 
 Potential, Alternating, Magnetic 
 
 The difference of magnetic potential pro- 
 duced by alternating electric currents. 
 
 Potential, Constant A potential 
 which remains constant under all conditions. 
 
 A machine or other electric source is said to 
 have a constant potential when it is capable, 
 while in operation, of maintaining a constant 
 difference of electric pressure between its two 
 terminals on changes of load. (See Circuit, 
 Constant -Potential. ) 
 
 Potential, Difference of A term 
 employed to denote that portion of the 
 electromotive force which exists between 
 any two points in a circuit. 
 
 The difference of potential at the poles of any 
 electric source, such as a battery or, dynamo, is 
 that portion of the total electromotive force 
 which is available, and is equal to the total 
 electromotive force, less what is lost in the 
 source. 
 
 Some difference of opinion exists as to the exact 
 meaning that is attached to the phrase difference 
 of potential. 
 
 A positively electrified body is said to have a 
 higher electric potential than the earth, whose 
 potential is taken as zero. 
 
Pot.] 
 
 418 
 
 [Pot 
 
 Potential, Difference of, Methods of 
 
 Measuring Methods employed for de- 
 termining differences of potential. 
 
 These methods are as follows: 
 
 (i.) By the Method of Weighing, that is, by 
 obtaining the -weight required to overcome the 
 attraction between two oppositely charged plates, 
 or oppositely energized coils; or by measuring 
 the repulsion between similarly charged surfaces, 
 or similarly energized coils. 
 
 (2.) By the Use of Electrometers, or apparatus 
 designed for measuring differences of potential. 
 (See Electrometers. ) 
 
 (3-) -By the Use of Galvanometers. 
 
 Differences of potential, in the case of currents, 
 may be determined from the quantity of electri- 
 city which flows per second through a given 
 circuit, that is, by the number of amperes, just 
 as the pressure of water at any point in the side 
 of a containing vessel can be determined by the 
 quantity of water that flows per second. Differ- 
 ence of potential in the case of currents, there- 
 fore, may be measured by any galvanometer 
 which measures the current directly in amperes, 
 provided the resistance of the circuit is known. 
 
 Potential, Drop of A term some- 
 times used instead of fall of potential. (See 
 Potential, Fall of.) 
 
 Potential, Electric The power of 
 doing electric work. 
 
 Electric level. 
 
 Electric potential can be best understood by 
 comparison with the case of a liquid such as 
 water. 
 
 The ability of a water supply or source to do 
 work depends: 
 
 (I.) On the quantity of water. 
 
 (2. ) On the level of the water, as compared with 
 some other level; or, in other words, on the dif- 
 ference between the two levels. 
 
 In i like manner the ability of electricity to do 
 work depends: 
 
 (i.) On the quantity of electricity. 
 
 (2.) On the electric potential at the place where 
 the electricity is produced, as compared with that 
 at some other place; or, in other words, on the 
 difference of potential. 
 
 In the case of water flowing through a pipe, 
 when its flow has been fully established, the quan- 
 tity which passes in a given time is the same at 
 any cross-section of the pipe. 
 
 In the case of electricity, the quantity of elec- 
 tricity flowing through any conductor, or part of 
 a circuit, is the same at any cross-section. A gal- 
 vanometer introduced into a break in any part of 
 the conductor would show the same strength of 
 current. 
 
 But, though the quantity of water which passes 
 is the same at any cross-section of a pipe, the 
 pressure per square inch is not the same, even in 
 the case of a horizontal pipe of the same diameter 
 throughout, but becomes less, or suffers a loss of 
 head, or difference of pressure, at any two points 
 along the pipe. This difference of pressure causes 
 the flow of water between these two points against 
 the resistance of the pipe. 
 
 So, too, in the case of a conductor carrying an 
 electric current, when the full current strength 
 has been established, the quantity of electricity 
 that passes is the same at all cross-sections. 
 
 Fig. 449. Hydraulic Gradient. 
 
 The electric pressure or potential, however, 
 is by no means the same at all points in the 
 conductor, but suffers a loss of electric head or 
 level, in the direction in which the electricity is 
 flowing. It is this electric head or level, or dif- 
 ference of electric potential, that causes the elec- 
 tricity to flow against the resistance of the con- 
 ductor. 
 
 These analogies can be best shown by the fol- 
 lowing illustration: 
 
 In Fig. 449, a reservoir, or source of water, at 
 C, communicates with the horizontal pipe A B, 
 furnished with open vertical tubes at a, b, c, d, e, 
 f, g, and B. If the outlet at B, is closed, the level 
 of the water in the communicating vessels is the 
 same as at the source; but if the liquid escape 
 freely from B, the level of the water in the branch 
 pipes will be found on the inclined dotted line, or 
 at a', b', c', d', e', f, g', which may be called 
 the hydraulic gradient. 
 
 The pressure per square inch, at any cross sec 
 tion of the horizontal pipe, which is measured by 
 the height of the liquid in the vertical pipe at that 
 point, decreases in the direction in which the liquid 
 is flowing. The force that urges the liquid 
 
Pot.] 
 
 419 
 
 Pot 
 
 through the pipe between any two points, may 
 be called the liquid-motive force (Fleming) and is 
 measured by the difference of pressure between 
 these points. 
 
 In Fig. 450, the dynamo-electric machine at D, 
 has its negative pole grounded, and its positive 
 pole connected to a long lead, A B, the positive 
 pole of which is also grounded. A fall of poten- 
 tial, represented by the inclined dotted line, 
 occurs between A and B, in the direction in -which 
 the electricity is flowing. 
 
 Fig. 450. Fall of Electric Potential 
 
 The dynamo-electric machine may be regarded 
 as a pump that is raising the electricity from a 
 lower to a higher level, and passing it through 
 the lead A B. The electric pressure or potential 
 producing the flow is greatest near the dynamo and 
 least at the further end, the differences at the 
 points a, b, c, d, e, f, and g, being represented by 
 the vertical lines aa', bb', c c', d d', e e', f f, and 
 
 gg' 
 
 The electricity flows between any two points as 
 a and b, in the conductor A B, in virtue of the 
 difference of electric pressure or potential be- 
 tween these two parts, or the difference between 
 a a' and b b' . 
 
 Differences of potential must be distinguished 
 from differences in electric charge, or electrostatic 
 density. If two conductors at different potentials 
 are connected by a conductor, a current will flow 
 through this conductor. When their potential is 
 the same, no current flows. The density of a 
 charge is the quantity of electricity per unit of 
 area. 
 
 The electric potential is the same at all points 
 of an insulated charged conductor; the density is 
 different at different points, except in the case of 
 a sphere. The potential, however, is the same, 
 since no current flows, or the charge does not re- 
 distribute itself. The density on an insulated, 
 isolated sphere, is uniform over all parts of the 
 surface, and its potential is the same at all points. 
 If now the sphere be approached to another body, 
 its density will vary at different parts of its sur- 
 
 face, and while the charge ic redistributing itself 
 so as to produce these differences in density the 
 potential will vary. As soon, however, as this 
 redistribution is effected and no further current 
 exists, the potential is the same over all' points, 
 though the density differs at different points. 
 
 An electric source not only produces but also 
 maintains a difference of potential. In the case 
 of the flow of liquid in a pipe, ii a continuous 
 current of the liquid be maintained from the 
 higher level in the reservoir to a lower level, as, 
 for example, by means of a pump, it must flow 
 through the pump to the reservoir, from the lower 
 level towards the higher level. In case of an 
 electric source, since the thing called electricity 
 flows through a closed circuit, if its direction of 
 flow in that part of the circuit external to the 
 source i. e. t in the external or useful current - 
 be from a higher to a lower level, then its flow 
 through the remainder of the circuit i. e., 
 through the source must be from the lower to the 
 higher level. Since, however, the electrical po- 
 tential of a body represents the work the elec- 
 tricity is capable of doing, the work done by the 
 electricity may be regarded as being that done 
 when it passes from the higher to the lower level. 
 
 Potential, Electrostatic The 
 
 power of doing work possessed by a unit 
 quantity of positive electricity charged or re- 
 siding on an insulated body. 
 
 Potential, Electrostatic, Difference of 
 
 Difference of potential of an electric 
 
 charge. (See Potential, Difference of. 
 Electrostatics?) 
 
 Potential Energy. (See Energy, Poten- 
 tial) 
 
 Potential, Fall of A decrease of 
 
 potential in the direction in which an elec- 
 tric current is flowing, proportional to the re- 
 sistance when the current is constant. (See 
 Potential, Electric) 
 
 Potential Galvanometer. (See Galva- 
 nometer, Potential) 
 
 Potential Indicator. (See Indicator, 
 Potential) 
 
 Potential, Magnetic The amount 
 
 of work required to bring up a unit north- 
 seeking magnetic pole from an infinite dis- 
 tance to a given point in a magnetic field. 
 
Pot.] 
 
 420 
 
 [Pun. 
 
 Potential of Conductor, Methods of 
 
 Varying (See Conductor, Potential 
 
 of, Methods of Varying?) 
 
 Potential of Conductors. (See Conduc- 
 tor, Potential of.) 
 
 Potential, Negative That potential 
 
 in the circuit external to the source towards 
 which the electric current flows. 
 
 Generally the lower potential, or lower 
 level. 
 
 Potential, Positive That potential 
 
 in the circuit external to the source, from 
 which the electric current flows. 
 
 The higher potential or higher level. 
 
 Potential, Uniform A potential 
 
 that does not vary. 
 
 A constant potential. (See Potential, Con- 
 stant.) 
 
 An electric source is said to generate a uniform 
 potential when it maintains a constant difference 
 of potential at its terminals. 
 
 Potential, Unit Difference of 
 
 Such a difference of potential between two 
 points that requires the expenditure of one 
 erg of work to bring a unit of positive elec- 
 tricity from one of these points to the other, 
 against the electric force. (See Erg) 
 
 The practical unit of difference of potential is 
 the volt. (See Volt.) 
 
 Potential, Zero An arbitrary level 
 
 from which electric potentials are measured. 
 
 As we measure the heights of mountains from 
 the arbitrary mean level of the sea, so we measure 
 electric levels from the arbitrary level of the po- 
 tential of the earth. 
 
 Potentiometer. An apparatus for the 
 galvanometric measurement of electromotive 
 forces, or differences of potential, by a zero 
 method. (See Method, Null or Zero) 
 
 In the potentiometer the difference of potential 
 to be measured is balanced or opposed by a 
 known difference of potential, and the equality 
 of the balance is determined by the failure of one 
 or more galvanometers, placed in shunt circuits, 
 to show any movement of their needles. 
 
 The principle of operation of the potentiometer 
 will be understood from an inspection of Fig. 451. 
 A secondary battery S, has its terminals con- 
 
 nected to the ends of a uniform wire A B, of high 
 resistance called the potentiometer wire. There 
 will, therefore, occur a regular drop or fall of po- 
 tential along this wire, which, since the wire is 
 uniform, will be equal per unit of length. This 
 drop of potential can be shown by connecting the 
 terminals of a delicate galvanometer, generally of 
 high resistance, to different parts of the wire, 
 when the deflection of the needle will be propor- 
 
 S 
 
 Fig. 451. Potentiometer. 
 
 tional to the drop of potential between the two 
 points of the wire touched. If, now, the terminals 
 of a standard cell be inserted in tne circuit of 
 the galvanometer, so as to oppose the current 
 taken from the potentiometer wire, and the con- 
 tacts of the potentiometer wire be slid along the 
 wire until no deflection of the galvanometer needle 
 is produced, the drop of potential between these 
 two points on the wire will be equal to the differ- 
 ence of potential of the standard cell. (See Cell, 
 Voltaic, Standard.) 
 
 Suppose, now, it be desired to measure the dif- 
 ference of potential between two points a and b, 
 on the wire C, through which a current is flow- 
 ing. Connect the points b and d, and a and c, 
 as shown, with the delicate high resistance gal- 
 vanometer G, in either of them. Now slide c, 
 towards d, until the needle of G, shows no deflec- 
 tion. The potential between a and b, is then 
 equal to that between c and d. 
 
 Potentiometer Wire. (See Wire, Po- 
 tentiometer) 
 
 Power. Rate of doing work. 
 
 Mechanical power is generally measured in 
 horse power, which is equal to work done at the 
 rate of 550 foot-pounds per second. 
 
 The C. G. S. unit of power is one erg per 
 second. 
 
 The practical unit of power is the watt, or 
 10,000.000 ergs per second. The kilowatt is 
 even more frequently used as the unit of power 
 than the watt. (See Power, Unit of.) 
 
 Power, Absorptive The property 
 
Pow.] 
 
 42 L 
 
 [Po>v. 
 
 possessed by many solid bodies of taking in 
 and condensing gases within their pores. 
 
 Carbon possesses marked absorptive powers. 
 The absorption of gases in this manner by solid 
 bodies is known technically as the occltision of 
 gasts. '(See Gas, Occlusion of.) 
 
 One volume of charcoal, at ordinary tempera- 
 tures and pressures, absorbs of 
 
 Ammonia 90 volumes 
 
 Hydrochloric acid 85 
 
 Sulphur dioxide 65 
 
 Hydrogen sulphide 55 
 
 Nitrogen monoxide 40 " 
 
 Carbonic acid gas 35 " 
 
 Ethylene 35 " 
 
 Carbon monoxide 9.42 " 
 
 Oxygen 9.25 " 
 
 Nitrogen 6.50 " 
 
 Hydrogen 1.25 " 
 
 (Saussure.) 
 
 Power, Candle An intensity of 
 
 light emitted from a luminous body equal to 
 the light produced by a standard candle. 
 (See Candle, Standard.) 
 
 The light-giving power of one standard 
 candle. 
 
 Power, Candle, Nominal A term 
 
 sometimes applied to the candle-power taken 
 in a certain favorable direction. 
 
 This term is generally used in arc lighting. 
 In the ordinary arc lamp the greatest amount of 
 light is emitted at a particular point, viz., from 
 the crater in the upper or positive carbon. (See 
 Arc, Voltaic.) 
 
 Power, Candle, Bated A term 
 
 sometimes used for nominal candle-power. 
 
 Power, Candle, Spherical The 
 
 average or mean value of candle power 
 taken at a number of points around the source 
 of light. 
 
 Power, Conducting The ability of 
 
 a given length and area of cross-section of a 
 substance for conducting light, heat, elec- 
 tricity or magnetism, as compared with an 
 equal length and area of cross-section of 
 some other substance taken as a standard. 
 
 Power, Conducting, for Electricity 
 
 The ability of a given length and area of 
 
 cross-section of a substance to conduct elec- 
 tricity, as compared with an equal length and 
 area of cross-section of some other substance, 
 such as pure silver or copper. 
 
 No substance is known that does not offer some 
 resistance to the passage of an electric current. 
 
 The following table is taken from Sylvanus P. 
 Thompson's ' ' Elementary Lessons in Electricity 
 and Magnetism' ' : 
 
 GOOD CONDUCTORS. 
 
 Silver, 
 Copper, 
 
 Other metals, 
 Charcoal. 
 
 PARTIAL CONDUCTORS. 
 
 Water, 
 
 The human body, 
 
 Cotton, 
 
 Wood, 
 
 Marble, 
 
 Paper. 
 
 NON-CONDUCTORS. 
 
 Oils, 
 
 Porcelain, 
 Dry wood, 
 Silk, 
 Resins, 
 
 Gutta-percha, 
 
 Shellac, 
 
 Ebonite, 
 
 Paraffine, 
 
 Glass, 
 
 Dry air. 
 
 Heat decreases the conducting power of ele- 
 mentary substances. This decrease in the con- 
 ducting power is approximately proportional to 
 the increase of temperature. Carbon is an ex - 
 ception to the law, being a better conductor at a 
 red or white heat than when cold. 
 
 The resistance of some alloys, such as German 
 silver and platinoid, is but little affected by mod- 
 erate changes of temperature. These alloys are, 
 therefore, employed in the construction of resist- 
 ance coils. 
 
 At a red heat insulators become fairly good 
 conductors of electricity. 
 
 At very low temperatures the conducting 
 powers of the metals increase. 
 
 Wroblewski has shown that at extremely low 
 temperatures copper increases in its conducting 
 power for electricity. He cooled copper to 200 
 degrees C., the temperature of the solidification 
 of nitrogen, and found that at this temperature 
 its conducting power increased to about nine times 
 its conducting power at O degrees C. 
 
 It may be remarked here that at exceedingly 
 low temperatures a metal would take in or absorb 
 heat from the surrounding medium with very 
 great rapidity. In this sense it might be said that 
 
Pow.J 
 
 422 
 
 [Pow. 
 
 its conducting power for heat was greatly in- 
 creased. 
 
 Kohlrausch estimates the conducting power of 
 distilled water at .000000000025, that of mer- 
 cury being taken as unity. 
 
 The best conductors of electricity are the best 
 conductors of heat. 
 
 This fact is well illustrated by the following 
 table from Ayrton : 
 
 RELATIVE CONDUCTIVITIES PER CUBIC UNIT. 
 
 Name of Metal. Electricity. Heat. 
 
 Silver, annealed ico 100 
 
 Copper, " 94.1 74.8 
 
 Gold, " 73 54.8 
 
 Platinum 16.6 9.4 
 
 Iron 15.5 IO.I 
 
 Tin 11.4 15.4 
 
 Lead 7.6 7.9 
 
 Bismuth i.i 1.8 
 
 The electric conductivity of porous conductors 
 decreases much more rapidly than the heat con- 
 ductivity. 
 
 Practically perfect insulators for electricity can 
 be obtained, but are unknown for heat. 
 
 Edlund believes the universal ether to be al- 
 most a perfect conductor. He bases this belief 
 on the phenomena of sun spots, the occurrence of 
 which is almost immediately followed by the 
 occurrence of magnetic disturbances on the 
 earth. 
 
 Lodge regards the luminiferous ether as being 
 almost a perfect non-conductor, because he thinks 
 that conductors must be opaque. It may be sug- 
 gested in this connection that Edlund's hypothesis 
 as to the conductibility of magnetic effects through 
 the ether is also capable of an explanation by the 
 effects of magnetic induction. 
 
 The conducting power for alternating currents 
 is not the same as for steady currents. When 
 the alternations become very high, the difference 
 between these conducting powers of the metals 
 becomes almost inappreciable. 
 
 Iron is an enormously worse conductor of 
 electricity than copper for rapidly alternating 
 currents, at least when the alternations are not 
 too great. When, however, the alternations are 
 extremely high, such as those which are produced 
 by the discharge of a Leyden jar or lightning 
 flash, the iron is as good a conductor as the cop- 
 per. The reason for this is evident. The dis- 
 charge in such cases keeps to the extreme outer 
 
 layer of the conductor, so that the composition of 
 the substance is practically of no effect. 
 
 Hughes has shown that the resistance of an iron 
 telephone line of the usual diameter, to periodic 
 currents of about loo per second, is somewhat 
 more than three times its resistance for steady 
 currents. 
 
 There is no such thing as conduction of elec- 
 tricity in gases. Electricity makes its way through 
 a gas by a sudden piercing of the dielectric, or, in 
 other words, by a disruptive discharge. (See 
 Discharge, Disruptive.') In such a disruptive 
 discharge it may be assumed that the gas be- 
 comes a conductor of electricity while the dis- 
 charge is passing. It would then partake of the 
 nature of an electrolytic conductor, since the dis- 
 charge takes place by means of a true locomotion 
 of atoms. (See Conduction, Electrolytic.) 
 
 Power, Conducting, for Heat The 
 
 ability of a substance to transmit heat through 
 its mass. 
 
 The metals are good conductors of heat. They 
 are also good conductors of electricity. The 
 conducting powers for heat and electricity are 
 nearly identical. As the temperature of a body 
 increases, its conducting power for heat is de- 
 creased. Carbon forms an exception to this 
 statement. 
 
 The flow of heat across a wall formed of a 
 homogeneous material, the exposed faces of which 
 are of equal extent and are maintained at a con- 
 stant difference of temperature, takes place in 
 accordance with the following laws: 
 
 (l.) The rate of flow across all perpendicular 
 sections is the same. 
 
 (2.) A uniform drop of temperature occurs 
 from one side of the wall to the other in the direc- 
 tion in which the flow is taking place. 
 
 (3. ) The rate of flow is proportional to the dif- 
 ference in temperature. 
 
 The similarity between the laws of the flow of 
 heat under the circumstances just named and the 
 flow of electricity through a conductor is evident; 
 the electrical current being the same in all parts 
 of the circuit, a drop of potential occurring in 
 the direction in which the current is moving, 
 and the flow being proportional to the difference 
 of potential. 
 
 Power, Conducting, Tables of 
 
 Tables in which the relative conducting 
 
Pow.] 
 
 423 
 
 [Povv. 
 
 powers of different substances are given. (See 
 Resistance, Tables of.) 
 
 Power, Electric Power developed 
 
 by means of electricity. 
 
 Power, Electric, Distribution of 
 
 The distribution of electric power by means 
 of any suitable system of generators, connect- 
 ing circuits and electric motors. 
 
 Power, Electric Transmission of 
 
 The transmission of mechanical energy by 
 converting it into electric energy at one point 
 or end of a line, and reconverting it into 
 mechanical energy at some other point on the 
 line. (See Energy, Electric, Transmission 
 of.) 
 
 Power, Horse A rate ot doing work 
 
 equal to 550 foot-pounds per second, or 33,- 
 ooo foot-pounds per minute. 
 
 I horse- power=745- 94 X io 7 ergs per second. 
 
 " =745.941 watts. (See Watt.) 
 
 " =42.746 Ib. Fahr. heat units 
 
 per min. (See Units, 
 
 Heat.} 
 " =23.748 Ib. Cent, heat units per 
 
 min. (See Units, Heat.) 
 
 Power, Horse, Electric Such a 
 
 rate of doing electric work as is equal to 
 746 watts or 746 volt-coulombs per second. 
 
 This rate is equivalent to 33,000 foot-pounds 
 per minute, or 550 foot-pounds per second. 
 
 Just as I pound of water raised through the 
 vertical distance of I foot requires the expendi- 
 ture of a foot-pound of energy, so I coulomb of 
 electricity acting through the difference of poten- 
 tial of I volt requires a certain amount of work 
 to be done on it. (See Coulomb. Volt. Po- 
 tential, Electric.) 
 
 This amount is called a volt-coulomb or joule, 
 and measured in foot-pounds is equal to .737324 
 foot-pounds. The volt -coulomb, or joule, isthere- 
 fore the unit of electric work, just as the foot- 
 pound is the unit of mechanical work. 
 
 The electric work of any circuit in joules is 
 equal to the product of the volts by the coulombs. 
 
 If we determine the rate per second at which 
 the coulombs pass, and multiply this product by 
 the volts, we have a quantity which represents the 
 electrical power, or rate of doing electrical work. 
 
 But I ampdre is equal to I coulomb per second; 
 therefore, if we multiply the current in am- 
 peres by the difference of potential in volts, the 
 product is equal to the electrical power or rate of 
 doing electrical work. 
 
 The product of an ampere by a volt is called 
 a volt-amp&re, or a watt. 
 
 One watt = .0013406 horse-power, or 
 
 Ons horse-power = 745.941 watts. 
 
 C E 
 
 Therefore the electrical horse-power = z 1 
 
 746 
 
 where C = the current in amperes and E = the 
 difference of potential in volts. 
 
 Power, Multiplying, of Shunt 
 
 (See Shunt, Multiplying Power of.) 
 
 Power of Periodic Current. (See Cur- 
 rent, Periodic, Power of.) 
 
 Power, Portative 
 
 -The carrying 
 
 power of a magnet. (See Magnet, Porta- 
 tive Power of.) 
 
 Power, Projecting, of Magnet The 
 
 power a magnet possesses of throwing or pro- 
 jecting its lines of magnetic force across an 
 intervening air space or gap. 
 
 The greater the air space the greater the mag- 
 netic reluctance, and consequently the greater the 
 magnetizing force required to overcome it. Mag- 
 nets of great projecting power are generally of 
 great length, to accommodate the long coils of 
 wire required. 
 
 Power, Resuscitating, of Secondary Bat- 
 tery Cell The power possessed by an 
 
 apparently completely discharged secondary 
 or storage cell of furnishing additional current 
 after a protracted rest. 
 
 This resuscitating power is probably due to 
 depolarization. It is therefore present in primary 
 as well as in secondary batteries. 
 
 Power, Stray That part of the 
 power employed in driving a dynamo, which 
 is lost through friction, air churning or air 
 currents, eddy currents, hysteresis, etc. 
 
 Power, Tliermo-Electric A num- 
 ber which, when multiplied by the difference 
 of temperature of a thermo-electric couple, 
 will give the difference of potential thereby 
 generated in micro-volts. (See Diagram, 
 Thermo-Electric) 
 
Pow.] 
 
 424 
 
 LPri. 
 
 Power, Units of Various units em- 
 ployed in the measurement of power. 
 
 The following table of units of power is taken 
 from Hering's work on dynamo-electric machines. 
 
 Unit of Power. 
 
 i erg per second. . = .0000001 watt. 
 I watt, or I volt- 
 ampere, or i 
 joule per second, 
 or I volt-coulomb 
 
 per second = looooooo ergs per second. 
 
 " = 44.2394 foot-pounds per 
 
 min. 
 " = 6. 1 1622 kilogram - metres 
 
 per min. 
 =. 0573048 Ib.-Fah., heat unit 
 
 per min. 
 " = .318360 Ib.-Cent., heatunit 
 
 per min. 
 " = .0144402 klgr.-Cent. heat 
 
 unit per min. 
 
 " = .0013592 metric horse- 
 
 power. 
 
 ' = .0013406 horse power. 
 
 I foot-pound per 
 
 Klin = 226043 ergs per second. 
 
 " = .0226043 watt. 
 
 " = .13825 kilogram-metre per 
 
 min. 
 
 " = .00003072 metric horse- 
 
 power. 
 
 " = .000030303 horse-power. 
 
 I kilogram - metre 
 
 per min = 1635000 ergs per second. 
 
 " = .163500 watt. 
 
 " =7.23314 foot-pounds per 
 
 min. 
 
 = .0002222 metric horse- 
 
 power. 
 
 " = .0002192 horse-power. 
 
 I metric horse- 
 power, or i 
 French horse- 
 power, or I che- 
 val-vapeur, or I 
 force de cheval, 
 or i Pferdekraft. = 735.75 X io 7 ergs per 
 
 second. 
 
 " = 735.750 watts. 
 
 " = 32549.0 foot-pounds per 
 
 min. 
 
 " = 4500 kilogram-metres per 
 
 min. 
 
 I metric h.-p., etc. =42.162 Ib.-Fah., heat units 
 
 per min. 
 " = 23.423 Ib.-Cent., heat units 
 
 per min* 
 " = 10.625 klg.-Cent., heat 
 
 units per min. 
 
 " = .98634 horse-power heat 
 
 units per min. 
 
 I horse-power =745.94 x io 7 ergs per 
 
 second. 
 
 " = 745-941 watts. 
 
 " . . . . = 33000 foot pounds per min. 
 
 " = 4562.33 kilogram - metres 
 
 per min. 
 
 " =42.746 Ib. -Fah., heat units 
 
 per min. 
 
 " = 23.748 Ib.-Cent., heat units 
 
 per min. 
 
 " = 10.772 klg.-Cent., heat 
 
 units per min. 
 
 " = 1.01385 metric horse- 
 power. 
 
 I Ib.-Fah., heat 
 
 unit per min. . . . = 17.45 X io 7 ergs per sec. 
 " = 17.4505 watts. 
 
 " = .23718 metric horse-power. 
 
 " = .023394 horse-power. 
 
 I Ib. Cent., heat 
 
 unit per min = 31.41 x io 7 ergs per sec. 
 
 " =31.4109 watts. 
 
 " = .04269 metric horse-power. 
 
 " = .042109 horse-power, 
 
 i klgr.-Cent., heat 
 
 unit per min = 69.25 x io 7 ergs per sec. 
 
 " = 69.249 watts. 
 
 " = .0941 2 metric horse-power. 
 
 = .092835 horse-power. 
 
 Poynting's Law. (See Law, Poyntmg's.) 
 
 Practical Unit of Inductance, or Self- 
 induction. (See Inductance, or Self-Induc- 
 tion^ Practical Un it of.) 
 
 Practical Unit of Magneto-Motive Force. 
 
 (See Force, Magneto-Motive, Practical 
 Unit of.) 
 
 Practical Units. (See Units, Practical?) 
 
 Pressel. A press switch or push connected 
 to the end of a flexible, pendant conductor. 
 Pressure Wires. (See Wires, Pressure!) 
 
 Primary Battery. (See Battery, Print' 
 
 ary.) 
 
Pri.] 
 
 425 
 
 [Pro. 
 
 Primary, Breaking the Breaking 
 
 or opening the circuit of the primary of an 
 induction coil. (See Primary, The.) 
 
 Primary Coil. (See Coil, Primary.} 
 
 Primary, Making the Closing or 
 
 completing the circuit of the primary of an 
 induction coil. (See Primary, The.} 
 
 Primary Plate Condenser. (See Plate, 
 Primary, of Condenser?) 
 
 Primary Spiral. (See Spiral, Primary) 
 
 Primary, The That conductor in 
 
 an induction coil, or transformer, which re- 
 ceives the impressed electromotive force, or 
 which carries the inducing current. 
 
 On changes in the jurrent intensity in the 
 primary, currents are induced in the secondary. 
 (See Induction, Electro-Dynamic. Coil, Induc- 
 tion. Transformer.') 
 
 Prime Conductor. (See Conductor, 
 Prime) 
 
 Prime Motor. (See Mover, Prime) 
 Prime Mover. (See Mover, Prime) 
 
 Printer, Stock, Callahan's A form 
 
 of printing telegraph used in sending stock 
 quotations telegraphically. (See Telegraphy, 
 Printing. Ticker, Stock) 
 
 Printer, Stock, Phelps' A form of 
 
 printing telegraph used in sending stock quo- 
 tations telegraphically. (See Ticker, Stock. 
 Telegraphy, Printing) 
 
 Probe, Electric A metallic con- 
 ductor inserted in the body of a patient in 
 order to ascertain the exact position of a 
 bullet, or other foreign metallic substance. 
 
 Two conductors are placed parallel to each 
 other, and are separated at the extremity of the 
 probe by any suitable insulating material. On 
 contact with the metallic substance, an electric 
 bell is rung by the closing of the circuit, or the 
 same thing is more readily detected by the de- 
 flection of the needle of a galvanometer, or by a 
 telephone placed in the circuit. 
 
 Process, Electrotyping (See Elec- 
 
 trotyping, or the Electrotype Process) 
 
 Processes of Carbonization. (See Car- 
 bonization, Processes of) 
 
 Production of Electricity by Light.' 
 
 (See Electricity, Production of, by Light) 
 
 Prognosis, Electric In electro- 
 therapeutics, a prognosis, or prediction of the 
 fatal or non-fatal termination of a disease, 
 from an electro-diagnosis based on the exag- 
 gerated or diminished reactions of the excit- 
 able tissues of the body when subjected to 
 the varying influences of electric currents. 
 (See Diagnosis, Electro) 
 
 Projections, Pacinotti Radial 
 
 projections or teeth in an armature core ex- 
 tending from the central shaft, so as to form 
 slots, pockets, or armature chambers, for the 
 reception of the armature coils. 
 
 The term Pacinotti projections was given to 
 these teeth because they were first introduced by 
 Pacinotti in his dynamo-electric machine. 
 
 Projector, Mangin A special form 
 
 of search light. 
 
 The Mangin reflector consists of a concavo- 
 convex mirror, the convex surface of which is 
 silvered and acts as a reflector. The radii ot 
 curvature of the two surfaces are such that the 
 light undergoes the two refractions, i. e., on en- 
 tering and on passing out of the mirror, in such a 
 manner as to pass out of the mirror in absolute 
 parallelism, and thus destroy all aberration. 
 
 Fig. 452. Mangin Projector. 
 
 The Mangin projector is shown in longitudinal 
 and in cross-section in Fig. 452, and the projector 
 B, is placed in one end of the cylinder A, furnished 
 with the openings for the ventilation of the cham- 
 ber. 
 
 The cylinder is supported on trunnions, and by 
 means of screws can be given any desired inclina- 
 tion, in a manner which will be readily under- 
 stood from an inspection of the drawing. 
 
 The source of light is an arc lamp of the focus- 
 ing type. A smill disc is placed in front of the 
 
Pro.] 
 
 426 
 
 [Pul. 
 
 arc in order to stop the direct light from the arc 
 which would have divergent rays. The door C, 
 is formed of a number of cylindrical lenses, placed 
 parallel to one another, which cause the rays to 
 diverge horizontally, when so desired. 
 
 Prony Brake. (See Brake, Prony) 
 
 Proportional Coils. (See Coils, Propor- 
 tional^) 
 
 Proportionate Arms. (See Arms, Pro- 
 portionate^ 
 
 Proportionate Arms of Electric Bridge. 
 
 (See Arms, Proportionated) 
 
 Prostration, Electric Physiological 
 exhaustion or prostration, resembling that 
 produced by sunstroke, resulting from pro- 
 longed exposure to the radiation of an unusu- 
 ally large voltaic arc. (See Sunstroke, 
 Electric?) 
 
 Protection, Electric, of Houses, Ships 
 and Buildings Generally Means for 
 protection against the destructive effects of a 
 lightning discharge, consisting essentially in 
 the use of lightning rods. (See Rod, Light- 
 ning^ 
 
 Protection, Electric, of Metals 
 
 (See Metals, Electrical Protection of.) 
 
 Protectiye Sheath. (See Sheath, Pro- 
 tective) 
 
 Protector, Cable A device for the 
 
 safe discharge of the static charge produced 
 on the metallic sheathing of a cable, or on 
 conductors surrounding or adjacent to the 
 cable, consequent on changes in the electro- 
 motive force applied to the conducting core of 
 such cable. 
 
 The cable protector is provided for the purpose 
 of preventing the discharge of the charge from 
 piercing and thus injuring the insulation of the 
 cable itself. 
 
 Protector, Comb A term some- 
 times applied to a lightning protector or ar- 
 rester, in which both the line and ground 
 plates are furnished with a series of teeth, 
 like those on a comb. (See Arrester, Light- 
 ning) 
 
 Protector, Toltaic Battery A de- 
 vice for automatically disconnecting a voltaic 
 battery, whenever the circuit in which it is 
 placed becomes grounded. 
 
 The battery protector is used in systems of elec- 
 tric gaslighting, where, unless great care is exer- 
 cised in insulating the circuits, considerable annoy- 
 ance is often experienced from the readiness with 
 which grounds are established. This arises from 
 the high electromotive force of the spark ob- 
 tained from the spark coil, piercing the insula- 
 tion and establishing a ground through the gas 
 pipes. 
 
 Protoplasm, Effects of Electric Currents 
 
 on Contractions observed in all pro- 
 toplasm on the passage of an electric current 
 through it. 
 
 Protoplasm, the basis of plant and animal life, 
 or the jelly-like matter that fills all organic cells, 
 whatever may be the origin of such cells, suffers 
 contraction when traversed by an electric cur- 
 rent. 
 
 An increased activity in the movements of a 
 form of microscopic life called the anuzba is occa- 
 sioned by slight shocks from an induction coil ; 
 stronger discharges produce tetanic contractions, 
 with, in some cases, expulsion of food or even of 
 the nucleus. A uniform strength of current pro- 
 duces contraction and imperfect tetanus. 
 
 Pull. A contact maker, similar in general 
 construction to a push button, but operated 
 by means of a pulling rather than a pushing 
 force. 
 
 The pull is preferable to the push in exposed 
 positions, such as outer doors, where moisture is 
 apt to injure pushes. 
 
 Pull, Chain A chain pendant at- 
 tached to a pendant burner for the move- 
 ment of the wipe-spark spring and the 
 ratchet in an electrically lighted gas burner. 
 
 Pull, Door Bell, Electric A cir- 
 cuit-closing device attached to a bell pull and 
 operated by the ordinary motion of the pull 
 
 Pull, Electric Bell A circuit-clos- 
 ing device operated by a pull. 
 
 Fig. 453 shows a form of electric bell pull. On 
 pulling the bell handle, contact springs, that 
 rest on a ring of insulating material when the 
 
Pul.] 
 
 427 
 
 IPum, 
 
 pull is in its normal position, are brought into con- 
 tact with a metal ring, thus completing the cir- 
 
 '? 453 Electric Bell Pull. 
 
 euit. The bell pull is often used to replace the 
 ordinary push button. 
 
 Pulley, Driven -- A pulley attached 
 to the driven shaft. (See Mover, Prime?) 
 
 Pulley, Driving --- A pulley attached 
 to the driving shaft. (See Mover, Primed) 
 
 Pulsating Current. (See Current, Pul- 
 sating?) 
 
 Pulsation. A quantity of the nature of 
 an angular velocity, equal to i it multiplied 
 by the frequency of the oscillation, or, equal 
 to 2 it divided by the duration of a single 
 period. 
 
 Pulsatory Current. (See Current, Pul- 
 satory?) 
 
 Pulsatory Magnetic Field. (See Field, 
 Magnetic, Pulsatory?) 
 
 Pulse, Electrical -- An electric oscil- 
 lation. 
 
 A momentary flow of electricity from a 
 conductor, which gradually varies from the 
 zero value to the maximum, and then to the 
 zero value again, like a pulse or vibration in 
 an elastic medium. 
 
 Electric pulses are set up in conductors con- 
 rected with the coatings of a Leyden jar, on the 
 discharge of the same. Such pulses produce a 
 series of electrical oscillations, which move alter- 
 nately backwards and forwards, until the dis- 
 charge is gradually dissipated. (See Oscillations, 
 Electric.) ' 
 
 The circumstances influencing the rate of 
 propagation of an electric pulse through different 
 parts of a closed circuit, according to Lodge, are 
 
 (i.) The extra inertia, or the so-called magnetic 
 susceptibility in the conducting substance, es- 
 pecially at its outer parts. 
 
 (2. ) An undue constriction or throttling of the 
 medium through which the disturbance is pass- 
 ing. 
 
 (3.) The nature of the insulating medium. 
 
 Pump, Air, Geissler Mercurial - 
 A mercurial air pump, in which the vacuum 
 is attained by the aid of a Torricellian vacuum. 
 
 In the Geissler Mercury Pump, Fig. 454, a 
 vacuum is obtained by means of the Torricellian 
 vacuum produced in 
 a large glass bulb that 
 forms the upper ex- 
 tremity of a barome- 
 tric column. The 
 lower end of this tube 
 or column is con- 
 nected with a reser- 
 voir of mercury by 
 means of a flexible 
 rubber tube. To fill 
 the bulb with mer- 
 cury the reservoir is 
 raised above its level, 
 *. <?., above thirty 
 inches, the air it con- 
 tains being allowed to 
 escape through an 
 opening governed by 
 a stopcock. The ves- 
 sel to be exhausted is 
 connected with the 
 bulb, and by means 
 of a two-way exhaus- 
 tion cock, communi- Fig. 434. Geissler"* Mer- 
 cation can be made curial Air Pump, 
 
 with the bulb, when it contains a Torricellian 
 vacuum, and shut off from it while its air is being 
 expelled. 
 
 In actual practice the mercury is mechanically 
 pumped into the barometric column, and the 
 valves are opened either by hand, or automati- 
 cally by electrical means. 
 
 Pump, Air, Mechanical A mechan- 
 ical device for exhausting or removing the air 
 from any vessel. 
 
 An excellent form of air pump is shown in Fig. 
 455' which is a drawing of Bianchi's pump. 
 
 Three valves, all opening upwards, are placed 
 
Pum.] 
 
 428 
 
 IP.VT. 
 
 455> Barrel of 
 Bianchi's Air Pump. 
 
 at the top and bottom of the cylinder, and in the 
 piston, respctively. These valves are mechan- 
 ically opened and closed at the proper moment 
 by the movements of the piston, i. e., their action 
 is automatic. This enables a much higher vacuum 
 to be obtained than when the valves open and 
 close by the tension of the air. 
 
 Mechanical pumps are unable to readily pro- 
 duce the high vacua employed in most electric 
 lamps. Mercury pumps 
 are employed for this 
 purpose. (See Pump, 
 Air, Mercurial.) 
 
 Pump, Air, Mer- 
 curial A de- 
 vice for obtaining a 
 high vacuum by the 
 use of mercury. 
 
 Mercury pumps are 
 in general of two types 
 of construction, viz. : 
 
 (i.) The Geissler 
 pump. 
 
 (z.) The Sprengel pump. (See Pump, Air, 
 Geissler Mercurial. Pump, Air, SprengeFs 
 Mercurial.) 
 
 Punip, Air, Sprengel's Mercurial 
 
 A mercurial air pump in which the vacuum 
 is obtained by 
 means of the fall 
 of a stream of mer- 
 cury. 
 
 In the Sprengel 
 mercury pump, Fig. 
 456, the fall of a mer- 
 cury stream causes 
 the exhaustion of a 
 reservoir connected 
 with the vertical 
 tube, by the mechan- 
 ical action of the 
 mercury in entang- 
 ling bubbles of air. 
 These bubbles are 
 largest at the begin- 
 ning of the txhaus- 
 tion, but become 
 smaller and smaller Fig. 456. SprengeFs Mer- 
 near the end, until, curial Air Pump. 
 
 at last, the characteristic metallic click of mer- 
 cury or other liquid falling in a good vacuum 
 
 is heard. The exhaustion may be considered as 
 completed when the bubbles entirely disappear 
 from the column. 
 
 The Sprengel pump produces a better vacuum 
 than the Geissler pump, but is slower in its 
 action. 
 
 In actual practice, the mercury that has fallen 
 through the tube is again raised to the reservoir 
 connected to the drop tube by the action of a 
 mechanical pump. 
 
 Pumping of Electric Lights. A term 
 sometimes applied to a pulsating or period- 
 ical increase and decrease in the brilliancy of 
 the light. 
 
 This action is generally due to the periodic slip- 
 ping of the belt or other driving mechanism. In 
 the case of arc lamps it may also be caused by the 
 improper action of the feeding device of the 
 lamp. 
 
 Puncture, Electro The application 
 
 of electrolysis to the treatment of aneurisms 
 or diseased growths. 
 
 The blood is decomposed by the introduction 
 of a fine platinum needle connected with the 
 anode of a battery, and insulated, except near its 
 point, by a covering of vulcanite. 
 
 The kathode is a sponge-covered metallic plate. 
 
 Puncture, Galrano A term some- 
 times applied to electro-puncture. (See 
 Puncture, Electro?) 
 
 Punning of Telegraph Pole. (See Pole, 
 Telegraphic, Punning of.) 
 
 Push, A name sometimes applied to a 
 push button, or to a floor push. (See Push, 
 Floor. Button, Push.) 
 
 Push Button. (See Button, Push.) 
 
 Push-Button Rattler. (See Rattler, 
 Push-Button.} 
 
 Push, Floor A push button placed 
 
 on the floor of a room so as to be readily 
 operated by means of the foot. (See But- 
 ton, Push.) 
 
 Pyknometer, A term sometimes used 
 for the specific gravity bottle employed in 
 determining the specific gravity of a liquid. 
 
 Pyrheliometer. An apparatus for mea- 
 suring the energy of the solar radiation. 
 
429 
 
 [Qua, 
 
 The pyrheliometer consists essentially of a 
 short cylinder, the area of whose base is accu- 
 rately determined. The cylinder being filled with 
 a known weight of water, the water surface is ex- 
 posed for a definite time to the sun's radiation, 
 and the increase in temperature carefully deter- 
 mined. The product of the weight of the water 
 thus heated by the increase in degrees, gives 
 the number of heat units, from which the total 
 energy absorbed is readily calculable. In order 
 to avoid loss by reflection or diffusion from the 
 water surface, it is covered by a layer of lamp- 
 black. (See Units, Heat. Calorimeter.) 
 
 Pyro - Electricity. (See Electricity, 
 Pyro) 
 Pyro-Magnetic Generator or Dynamo. 
 
 (See Generator, Pyro-Magnetic^) 
 
 Pyro-Magnetic Motor. (See Motor, Pyro- 
 Magnetic^ 
 
 Pyrometer. An instrument for deter- 
 mining temperatures higher than those that 
 can be readily measured by thermometers. 
 
 Pyrometers are operated in a variety of ways. 
 A common method is by the expansion of a metal 
 rod. 
 
 Pyrometer, Siemens' Electric An 
 
 apparatus for the determination of tempera- 
 
 ture by the measurement of the electric resist- 
 ance of a platinum wire exposed to the heat 
 whose temperature is to be measured. 
 
 The platinum wire is coiled on a cylinder of 
 fire-clay, so that its separate convolutions do not 
 touch one another. It is protected by a platinum 
 shield, and is exposed to the temperature to be 
 measured while inside a platinum tube. 
 
 The resistance of the platinum coil at O degree 
 C. having been accurately ascertained, the temper- 
 ature to which it has been exposed can be calcu- 
 lated from the change in its resistance when ex- 
 posed to the unknown temperature. 
 
 Pyrometer, Siemens' Water A 
 
 pyrometer employed for determining the tem- 
 perature of a furnace, or other intense source 
 of heat, by calorimetric methods, /. e., by the 
 increase in the temperature of a known 
 weight of water, into which a metal cylinder 
 of a given weight has been put, after being 
 exposed for a given time to the source of 
 heat to be measured. 
 
 When copper cylinders are employed, the in- 
 strument possesses a range of temperatu e of 
 1, 800 degrees F. ; when a platinum cylinder is 
 used, it has a range of 2,700 degrees F. 
 
 Q 
 
 Q. A contraction for electric quantity. 
 
 Quad. A contraction sometimes em- 
 ployed in place of quadruplex telegraphy. 
 (See Telegraphy, Quadruplex^ 
 
 Quadrant. A term proposed for the unit 
 of self-induction. 
 
 An earth quadrant is equal to io 9 centi- 
 metres. 
 
 In the United States the word henry is used 
 for the unit of self-induction. (See Henry, A.} 
 
 Quadrant Electrometer. (See Electro- 
 meter, Quadrant.) 
 
 Quadrant Electroscope, Henley's. (See 
 Electroscope, Quadrant, Henley's.) 
 
 Quadrant, Legal A length equal to 
 
 9,978 kilometres, instead of the assumed 
 10,000 kilometres. 
 
 Quadrant, Standard A length equal 
 
 to 10,000 kilometres. 
 
 Quadrature, In A term employed 
 
 to express the fact that one simple periodic 
 quantity lags 90 degrees behind another. 
 
 The electromotive force of s-elf-induction is said 
 to be in quadrature with the effective electro- 
 motive force or current. 
 
 Quadrnplex Telegraphy, Bridge Method 
 
 of (See Telegraphy, Quadruplex, 
 
 Bridge Method of.) 
 
 Qualitative Analysis. (See Analysis, 
 Qualitative.) 
 
 Quality or Timbre of Sound. (See Sound,. 
 Quality or Timbre of.) 
 
 Quantitative Analysis. (See Analysis,, 
 Quantitative.) 
 
Qua.] 
 
 430 
 
 [Rad. 
 
 Quantity Armature. (See Armature, 
 Quantity?) 
 Quantity, Connection of Battery for 
 
 (See Battery, Connection of, for 
 
 Quantity.} 
 Quantity Efficiency of Storage Battery. 
 
 (See Efficiency, Quantity, of Storage Bat- 
 tery) 
 
 Quantity, Unit of Electric A 
 
 definite amount or quantity of electricity 
 called the coulomb. (See Coulomb?) 
 
 Although the exact nature of electricity is un- 
 known, yet, like a fluid (a liquid or gas), electricity 
 can be accurately measured as to quantity. 
 
 A current of I ampdre, for example, is a 
 current in which one coulomb of electricity passes 
 in every second. 
 
 A condenser of the capacity of I farad, is 
 large enough to hold I coulomb of electricity 
 if forced into the condenser under an electro- 
 motive force of i volt. (See Capacity, Electro- 
 static. Farad. Volt. Ampere.} 
 
 Quiet Arc. (See Arc, Quiet?) 
 
 Quiet Discharge. (See Discharge, Si- 
 lent?) 
 
 Qnicking Solution. (See Solution, 
 Quicking?) 
 
 R. A contraction used for ohmic resist- 
 ance. 
 
 p. A contraction used for specific resist- 
 ance. 
 
 Radial Armature. (See Armature, 
 Radial?) 
 
 Radially Laminated Armature Core. 
 (See Core, Armature, Radially-Laminated?) 
 
 Radiant Energy. (See Energy, Radiant) 
 
 Radiant Matter. (See Matter, Radiant, 
 or Ultra-Gaseous?) 
 
 Radiate. To transfer energy by means of 
 waves. 
 
 Radiating. Transferring energy by means 
 of waves. 
 
 Radiation. Transference of energy by 
 means of waves. 
 
 When an elastic body is set into vibration, 
 whether it be the vibrations that produce light, 
 heat or electricity, energy is charged on the 
 body, and the body will then continue to vibrate 
 until it imparts to some medium surrounding it 
 an amount of energy exactly equal to that orig- 
 inally imparted to itself. 
 
 In the case of a sonorous body the energy is 
 transferred from the vibrating body to the air 
 around it. For example, in the case of an elastic 
 metallic wire set into vibration, the wire will con- 
 tinue to vibrate until it does as much work on 
 the surrounding air as was originally done on it, 
 in order to set it into vibration. 
 
 In the case of a heated body the energy is 
 transferred from the body to the luminiferous 
 ether around it. For example, in the case of the 
 same wire heated above the temperature of the 
 air, the energy imparted to the molecules of the 
 metal by the source of heat causes them to 
 move towards and from one another. These 
 to and -fro motions of the molecules cause the 
 surrounding ether to be set into waves, and as 
 much energy is imparted to the ether, as was 
 originally imparted to the wire in order to heat it. 
 
 In the case of a luminous body the energy is 
 transferred from the body to the luminiferous 
 ether. For example, if the wire is heated to 
 luminosity by a certain amount of energy im- 
 parted to it, the surrounding ether is now set 
 into waves of both light and heat, which differ 
 from one another only in their wave length, and 
 the luminous body will continue to radiate light 
 and heat until it imparts to the surrounding 
 ether an amount of energy exactly equal to that 
 originally imparted to it. 
 
 So, too, in the case of a body charged with 
 electricity. If disruptively discharged, the im- 
 pulsive rush of electricity, so produced, causes the 
 energy charged on it to be radiated as electro- 
 magnetic waves into the surrounding ether. The 
 discharging body is, to all intents and purposes, in 
 the same condition as the vibrating elastic wire, 
 and dissipates or radiates its energy in much the 
 same manner. 
 
 Radiation, Electro-Magnetic 
 The sending out in all directions from a con- 
 
Had.] 
 
 431 
 
 [Rad. 
 
 ductor, through which an oscillating discharge 
 is passing, of electro-magnetic waves in all 
 respects similar to those of light except that 
 they are of much greater length. (See Elec- 
 tricity, Hertz's Theory of Electro-Magnetic 
 Radiations or Waves.) 
 
 Radiation of Electricity. (See Electri- 
 city, Radiation of.) 
 
 Radiation of Lines of Force. (See Force, 
 Lines of, Radiation of.) 
 
 Radical, Compound A group of 
 
 unsaturated atoms. 
 
 A group of elementary atoms, some of the 
 bonds of which are open, or not connected 
 or joined with the bonds of other atoms. 
 (See Atomicity?) 
 
 For example, hydroxyl, HO, is a compound 
 radical, with one of the two bonds of the diad 
 oxygen atom, open or unsaturated. 
 
 Radical, Simple An unsaturated 
 
 atom with its bond or bonds free. 
 
 A single unsaturated atom as distinguished 
 from an unsaturated group of atoms. 
 
 Radicals. Unsaturated atoms or groups of 
 atoms, in which one or more of the bonds are 
 left open or free. 
 
 Radicals are either Simple or Compound. 
 
 The radical may be regarded as the basis to 
 which other elements may be added, or as the 
 nucleus around which they may be grouped. 
 
 Thus H a O, forms a complete chemical molecule, 
 because the bonds of all its constituent atoms are 
 saturated, thus H O H. But H O , or 
 hydroxyl, is a radical, because its oxygen atom 
 possesses one unsaturated or free bond. By 
 combining with the radical (NO 8 ), it forms nitric 
 acid, thus H O (NO 2 ) or H NO 8 . 
 
 During electrolysis, the molecules of the elec- 
 trolyte are decomposed into two groups of simple 
 or compound radicals, called ions. These ions are 
 respectively electro-positive and electro-negative, 
 and are called kathions and onions. (See Ions. 
 Electrolysis.) 
 
 Radiometer, Crookes' An appara- 
 tus for showing the action of radiant matter 
 in producing motion from the effects of the 
 reaction of a stream of molecules escaping 
 from a number of easily moved heated sur- 
 faces. (See Matter, Radiant, or Ultra- 
 Gaseous^) 
 
 Radiometer, Electric, Crookes 
 
 A radiometer in which the repulsion of the 
 molecules of the residual atmosphere takes 
 place from electrified instead of from heated 
 surfaces. (See Radiometer, Crookes'!) 
 
 Radio-Micrometer, Boys' An elec- 
 trical apparatus for measuring the intensity 
 of radiant heat. 
 
 The action of the radio-micrometer depends on 
 the deflection, by a magnetic field, of a suspended 
 thermo-electric circuit composed of three metals, 
 viz.: two bars of antimony and bismuth, or of 
 their alloys, which are soldered side by side to 
 the end of a minute disc or strip of copper foil, as 
 shown in Fig. 457. This disc or foil of copper is 
 
 Fig. 457. Boys' Radio-Micrometer. 
 
 provided for the purpose of receiving the radia- 
 tion that is to be measured. The upper ends of 
 the thermo-couple are soldered to the ends of a 
 long, narrow, inverted U-shaped piece of copper 
 wire, which completes the thermo-electric circuit. 
 
 The absorption of radiant energy by the cop- 
 per disc connected to the thermo-electric couple 
 produces an electric current, and the circuit, 
 being suspended in a magnetic field, is at once 
 deflected to a degree dependent on the intensity 
 of the radiation, or of the current generated at 
 the thermo-electric junction. 
 
 The means adopted for the suspension of the 
 system are shown in Figs. 457 and 458. A 
 small piece of straight wire is soldered to the up- 
 
Had.j 
 
 432 
 
 [Rai. 
 
 QUARTZ 
 FIBRE 
 
 GLASS 
 TUBE 
 
 per end of the copper stirrup, which completes 
 the thermo-electric circuit. This wire is cemented 
 to the lower end of a glass tube, the upper end 
 of which is provided with a mirror, and the whole 
 suspended, as shown, by a 
 quartz fibre in the field of a 
 powerful magnet. 
 
 In a radio-micrometer made 
 by Prof. Boys, the minuteness of 
 the suspended circuit may be 
 judged from the following ac- 
 tual dimensions, viz. : Thermo- 
 electric bars, x ^ x ^fa inch ; 
 copper circuit of number 36 
 copper wire, I inch long and 
 about ^j inch wide ; copper 
 heat-receiving surface, black- 
 ened on the face exposed to the 
 radiation, -fa inch in diameter, 
 or i x & inch; receiver, ^ inch 
 square, yfa inch thick ; quartz 
 fibre 4 inches long, ^fo^ inch in 
 diameter. 
 
 This instrument, when pro- 
 perly adjusted for extreme sen- 
 sitiveness, should give clear in- 
 dications when the blackened 
 surface is warmed but the Fig. 458. Boys' 
 Tillf&ffffiT degree Centigrade. It Radio-Micrometer. 
 will respond to the heat radiated on the surface 
 of a half penny from a candle flame at a dis- 
 tance of 1,530 feet. 
 
 In order to avoid the disturbance due to the 
 magnetic qualities of the antimony and bismuth 
 bars, the central portions of the metallic block, 
 inside which the system is suspended, is made 
 of iron, as shown by the heavier shading in 
 Fig- 457- 
 
 This mass of iron serves as a magnetic screen 
 to the thermo-electric bars, but permits the action 
 of the field on the circuit. 
 
 Radiophone. A name sometimes given to 
 the photophone. (See Photophone^ 
 
 Radiophony. The production of sound by 
 a body capable of absorbing radiant energy 
 when an intermittent beam of light or heat 
 falls on it. 
 
 The action of radiant energy, when absorbed 
 by matter, is to cause its expansion by the conse- 
 quent increase of temperature. This occurs even 
 when the body is but momentarily exposed to a 
 
 COPPER 
 WIRE 
 
 Bt. 
 
 flash of light, but the instantaneous expansion 
 thus produced immediately dies away, and by 
 itself is indistinguishable. If, however, a suffi- 
 ciently rapid succession of such flashes fall on the 
 body, the instantaneous expansions and contrac- 
 tions produce an appreciable musical note. 
 
 The sounds so produced have been utilized by 
 Bell and Tainter in the construction of the Phtto- 
 phone. (See Photophone.'] 
 
 Railroad, Electric A railroad, or 
 
 railway, the cars on which are driven or pro- 
 pelled by means of electric motors connected 
 with the cars. 
 
 The electric current that drives the motor is 
 derived either from storage batteries placed on 
 the cars, or from a dynamo-electric machine, or 
 battery of dynamo-electric machines, conveniently 
 situated at some point on the road. The current 
 from the dynamo is led along the line by suitable 
 electric conductors and is passed into the electric 
 motor as the car runs along the tracks in various 
 ways, viz. : 
 
 Systems for the electric propulsion of cars may, 
 therefore, be divided into the dependent system, in 
 which the driving current is obtained from conduc- 
 tors placed somewhere outside the cars, and the 
 independent system, where the current is derived 
 from primary or secondary batteries placed on 
 the cars. (See Railroads, Electric, Dependent 
 System of Motive Power for. Railroads, Electric, 
 Independent System of Motive Power for.} 
 
 In the dependent system, the conductors which 
 supply the car with current are placed either 
 overhead, on the surface of the road-bed or un- 
 derground. Thus arise three divisions of the 
 dependent system: 
 
 (I.) The Surface System. 
 
 (2. ) The Underground System. 
 
 (3.) The Overhead System. 
 
 (I.) The Surface System. By placing one or 
 both rails in the circuit of the dynamo and taking 
 the current from the tracks by means of sliding 
 or rolling contacts connected with the motor. 
 
 (2.) The Underground System. By placing the 
 conducting wires parallel to each other in a longi- 
 tudinally slotted underground conduit in the road- 
 bed, and provided with two central plates, insu- 
 lated from one another and connected respectively 
 to the motor terminals, and taking the current 
 by means of a traveling brush or roller, called a 
 plow, sled or shoe. On the movement ot the car 
 over the track, these traveling contacts touch the 
 
ilai.j 
 
 433 
 
 [Rai. 
 
 two parallel line conductors in the conduit and 
 <ake the electric current therefrom. (See Plow. 
 Sled.) 
 
 (3.) The Overhead System. By placing the 
 (ine conductors on poles along the road, and 
 taking the current therefrom by means of suitable 
 traveling contacts called trolleys, or by sliders. 
 
 Where a single conductor is employed, the re- 
 turn conductor generally consists of the track 
 itself, or of the track and ground. (See Trolley.} 
 
 The first method, viz., that of using the tracks 
 alone as conductors, is not much employed. 
 
 The use of the track and ground as a return for 
 the current is now very generally employed. 
 
 In some systems the track is divided into sec- 
 tions which are successively brought into connec- 
 tion with the main conductors by contacts effected 
 by the attraction between magnets carried on the 
 car and contact pieces of magnetic material placed 
 below the surface. The rail section thus tempo- 
 rarily energized is placed in connection with the 
 motor. 
 
 In order to regulate the speed, various devices 
 are employed to vary the current strength in the 
 motor circuit. These devices consist essentially 
 of rheostats or resistances introduced into, or re- 
 moved from, the motor circuit on the movement 
 by hand of a lever that forms part of the circuit, 
 over contact plates connected to the resistance 
 coils. 
 
 In order to change the direction of the car, the 
 direction of rotation of the electric motor is 
 changed. This is effected by some form of re- 
 versing gear or mechanism that changes the di- 
 rection of rotation of the motor, either by shifting 
 the brushes, by changing the field, or by any 
 other means. (See Telpherage. Motor, Elec- 
 tric. Rheostat.) 
 
 Railroads, Absolute Block System for 
 
 A block system in which one train 
 
 only is permitted to occupy a given block at 
 any time. (See Railroads, Block System for.*) 
 
 Railroads, Automatic Electric Safety Sys- 
 tem for A system for automatically 
 
 preventing the approach of two trains at any 
 speed beyond a predetermined distance of 
 each other. 
 
 The system consists essentially in the automatic 
 closing of the circuit of an electric motor placed 
 on the locomotive between the steam dome and 
 the sand box. This motor is in circuit with a 
 local battery placed on the cow-catcher, and in- 
 
 troduced in the circuit of the motor by a magaet 
 placed on the cow-catcher, as shown in Fig. 459, 
 
 Fig. 459. Locomotive tuith Safety System. 
 which represents a locomotive provided with tkis 
 system. 
 
 The magnet is on open circuit with generators 
 placed on the rear car of a second train, or with 
 generators at a bridge or crossing. 
 
 By means of double sectional-conductors placed 
 along the track, the generators are automatically 
 closed through the magnet, one conductor being 
 in permanent connection with the magnet, while 
 the other is connected to the generator in the rear 
 car of a second train, at a switch or crossing. The 
 other terminals of the magnet and generators are in 
 permanent electricial connection with the rails, 
 which are employed as return ground conductors. 
 
 Fig. 460 shows the application of the safety 
 electric system to a bridge. 
 
 Fig. 460. Safety System for Bridge. 
 
 Fig. 461 shows the application of the safety 
 system at grade crossing. 
 
 Fig. 461. Safety System for Grade Crossing. 
 
 The author is indebted to Mr. E. P. Thompson 
 for cuts and general description. 
 
 Railroads, Block System for A sys- 
 tem for securing safety from collisions of mov- 
 ing railroad trains by dividing the road into a 
 number of blocks or sections of a given 
 length, and so maintaining telegraphic com- 
 munication between towers located at the 
 ends of each of such blocks as to prevent, 
 
Rai.J 
 
 434 
 
 [Rai. 
 
 by the display of suitable signals, more than 
 one train or engine from being on the same 
 block at the same time. 
 
 There are two kinds of railway block systems 
 in common use, viz.: 
 
 (I.) 1\\& Absolute Block System. 
 
 (2.) The Permissive Block System. 
 
 In the absolute system, which is the safer, one 
 train only is permitted on any particular block at 
 a given time. 
 
 In the permissive block system more than one 
 train is permitted, under certain circumstances 
 and conditions, to occupy the same block simul- 
 taneously, each train then being notified of the 
 fact that it is not alone on the block. 
 
 The absolute block system, though expensive 
 to construct and maintain, is the only one that 
 should be permitted by law to exist on roads whose 
 traffic exceeds a certain amount. 
 
 An absolute block system is employed on the 
 London Underground Railroad, and on the Penn- 
 sylvania Railroad Systems. 
 
 The system in use on the New York Division 
 of the Pennsylvania Railroad is as follows : 
 
 The road between Philadelphia and Jersey City 
 is divided into some seventy sections, the length 
 of each section being dependent on the amount of 
 
 Fig. 462. Slock Tower. 
 
 daily traffic , thus, between Jersey City and New- 
 ark, where the traffic is great, there are some 
 fifteen sections, although the distance is only 7.9 
 miles. 
 
 In each block-tower there are connections with 
 three separate and distinct telegraph lines or cir- 
 cuits, viz. : 
 
 (i.) A line or wire called the train wire, con- 
 necting the block-tower with the General Dis- 
 patcher's office at Jersey City. This line is used 
 for sending train orders only. 
 
 (2.) A line or wire called the block wirt, con- 
 
 necting each block-tower with the next tower on 
 each side of it. 
 
 (3.) A line or wire called the message wire, and 
 used for local traffic or business. 
 
 The general arrangement of the block-tower is 
 shown in Fig. 462. 
 
 Each of the block-towers is sufficiently elevated 
 above the road-bed to afford the operator an un- 
 obstructed view of the tracks. 
 
 The operator, having ascertained the actual 
 condition <}f the track, either by observation or by 
 telegraphic communication with the stations on 
 either side of him, gives notice of this condition to 
 all trains passing his station by the display of 
 certain semaphore signals. 
 
 The semaphore signals as used on the Penn- 
 sylvania Railroad are shown in Figs. 463 and 464. 
 
 The form shown in Fig. 463 is used in the abso- 
 
 *g- 4(>3- Semaphore Signal Absolute System. 
 lute system, and that shown in Fig. 464 in the per- 
 missive system. These signals consist essentially 
 of an upright support provided with a movable 
 arm A B, called the semaphore arm, capable of 
 being set in any of two or three positions. The 
 semaphore signal is placed outside the signal 
 tower, often several hundred feet away, but is 
 readily set from the tower in any of the desired 
 positions by the operator, by the movement of 
 rods connected with levers. 
 
 In the permissive system, the semaphore arm 
 can be set in three positions, viz. : 
 
 (i.) In a horizontal position, or where the 
 semaphore arm makes an angle of 90 degrees with 
 the upright. 
 
 (2.) Or it may be dropped down from the 
 horizontal position through an angle of 75 
 degrees, as shown in Fig. 463. 
 
 (3.) Or it may occupy a position exactly inter < 
 
Rai.] 
 
 435 
 
 [Rid. 
 
 mediate between the first and second, or 37 30' 
 below the horizontal, as shown in Fig. 464. 
 
 Position No. I is the danger signal, and when 
 it is displayed the train may not enter the block 
 it governs. 
 
 Position No. 2 shows that the track is clear, 
 and that the train may safely enter the block it 
 governs. 
 
 Position No. 3, which is used in the permissive 
 block system, only signifies caution, and permits 
 the train to cautiously enter the block and look 
 out for further signals. 
 
 The semaphore arm consists of a light wooden 
 arm, 1 1 inches wide by 5^ feet in length, painted 
 red or other suitable color that can be easily dis- 
 tinguished by daylight. 
 
 By night the positions of the semaphore arm 
 are indicated by colored lights. These lights are 
 
 Fig. 464. Semaphore Signal Permissive System. 
 
 operated as follows, viz. : in the absolute system, 
 the semaphore arm A B, pivoted at A, bears at 
 its shorter end a disc or lens of red glass R, and, 
 in the permissive system, below this another disc 
 or lens of green glass G. An oil lantern, pro- 
 vided with an uncolored glass lens, is so sup- 
 ported on a bracket fastened to the upright that 
 when the semaphore arm points to danger the 
 red glass is immediately in front of the lantern ; 
 when it points to caution, the green glass is in 
 front of the lantern; but when it points to safety, 
 the lantern is left uncovered save by its uncolored 
 glass. 
 
 At night, therefore, when the semaphore arm 
 is set to danger, a red light is displayed; when it 
 points to caution, a green light is displayed ; and 
 when it points to safety, a white light is displayed. 
 
 In some systems the position of the semaphore 
 
 arm is shown at night by means of light reflected 
 from a parabolic mirror ; at the focus of which the 
 signal lantern is placed. This method possesses 
 the advantage over other systems of rendering it 
 very improbable that the engineer would mistake 
 an ordinary light for a signal light. 
 
 The green light is only used in the permissive 
 block system. In the absolute block system, the 
 semaphore arm has two positions only ; viz., dan- 
 ger, or horizontal, and safety, or 75 degrees below 
 the horizontal. 
 
 A single arm is used when it is intended to 
 govern a single track only. Where the condition 
 of a number of tracks is to be indicated, several 
 arms are employed, one above the other. 
 
 When seman r.ore signals are placed on each side 
 of a double-track road, the semaphore arm point- 
 ing to the right of the vertical support governs 
 the line running to the right. 
 
 When the semaphore signals are placed at 
 junctions or switch-crossings, the operator in the 
 signal-tower opens or. closes the switches from 
 the tower by the movements of levers that set the 
 switches, and then displays the proper semaphore 
 signal for that crossing or route ; red, or danger, 
 if the route is blocked, and white, or safety, if it 
 is clear. Here the interlocking apparatus is em- 
 ployed, which consists in devices by means of 
 which, when a route has once been set up and a 
 signal given for that route, the switches and sig- 
 nals are so interlocked that no signal can pos- 
 sibly be given for a conflicting route. 
 
 The signals or switches are operated by means 
 of iron rods passing over rollers or pulleys. 
 These rods are attached by suitable connections 
 to the switch or semaphore signals, and are 
 operated by means of levers from the signal- 
 tower. Switches can be operated as far as 1,000 
 feet from the tower; signals as far as 2,500 feet. 
 
 Colored switch-signals are placed opposite the 
 end of the switches to indicate the positions of 
 the switch. These signals consist of red and 
 white discs for day, and a lantern provided with 
 red and white glasses for night. When the 
 switch on any line is open, the switch-signal shows 
 red; when shut, it shows white. These switch- 
 signals are only used in the yards. 
 
 No passenger train is permitted on a block, 
 after another train has passed the signal station, 
 until a dispatch has been received from the 
 station ahead that the train has passed and the 
 block is thus cleared. 
 
 As an additional precaution against rear col- 
 
Rai.] 
 
 436 
 
 [Rai. 
 
 lisions, tail-lights are displayed at the ends of the 
 trains. These consist of lanterns placed on each 
 side of the rear end of the last car. These 
 lanterns are furnished with three glass slides. 
 The side of the lantern towards the rear of the 
 car shows a red light; that to the front and side 
 of the car shows a green light. The engineer, 
 looking out of the cab, can thus see a green light, 
 which serves as a "marker** and indicates to 
 him that his train is intact By day a green flag, 
 placed in the same position as the lantern, serves 
 the same purpose as a marker. An observer on 
 the track, or in the tower, sees the red lights on 
 the rear of the train when it has passed. 
 
 Freight trains are now run on separate tracks, 
 except in places where the extra tracks are not 
 yet completed. Here they do not run on schedule 
 time, but are permitted to follow one another at 
 intervals that depend on the condition of the 
 tracks as shown by the signals displayed. 
 
 Railroads, Electric, Continuous Over- 
 head System of Motive Power for 
 
 A variety of the dependent system of motive 
 power for electric railroads in which a con- 
 tinuous bare conductor is connected with the 
 terminals of a generating dynamo, and sup- 
 ported overhead by suitable means, and a 
 traveling wheel or trolley is moved over the 
 same by the motion of the car, in order to 
 carry off the current from the line to the car 
 motor. (See Railroads, Electric, Depend- 
 ent System of Motive Power for .) 
 Railroads, Electric, Continuous Surface 
 
 System of Motive Power for A 
 
 variety of the dependent system of motive 
 power for electric railroads, in which the ter- 
 minals of the generating dynamo are con- 
 nected to the continuous bare metallic con- 
 ductor that extends along the entire track on 
 the surface of the roadway or street, and from 
 which the current is taken off by means of a 
 traveling conductor connected with the mov- 
 ing car. (See Railroads, Electric, Continu- 
 ous Underground System of Motive Power 
 for.) 
 
 Railroads, Electric, Continuous Under- 
 ground System of Motive Power for 
 
 A variety of the dependent system of motive 
 power for electric railways, in which a con- 
 tinuous bare conductor is placed under- 
 
 ground in an open slotted conduit, and the 
 current taken off from the same by means of 
 sliding or rolling contacts carried on the mov- 
 ing car. (See Railroads, Electric, Depend- 
 ent System of Motive Power for) 
 
 Railroads, Electric, Dependent System 
 of Motive Power for A term now 
 generally used for a system of motive power 
 for the propulsion of electric railway cars, in 
 which the electric current is taken from wires 
 or conductors connected with electric sources 
 external to the cars. 
 
 A dependent system of motive power for elec- 
 tric railways includes three distinct varieties, 
 namely : 
 
 (i.) The Underground System. 
 
 (2.) The Surface System. 
 
 (3.) The Overhead System. 
 
 In all of these systems the bare conductor con- 
 nected with the terminals of a generating dynamo 
 may form either one continuous wire or it can 
 be divided into separate portions or sections. 
 
 The underground system embraces two distinct 
 varieties : 
 
 ist. A continuous bare conductor placed in an 
 open slotted conduit. 
 
 2d. A sectional bare conductor placed in an 
 open slotted conduit. 
 
 In the first variety of the underground system, 
 bare conductors are placed in an open slotted 
 conduit, and connected with the terminals of a 
 dynamo-electric machine which generates the 
 current that is to be employed for the propulsion 
 of the cars. Traveling contacts placed on the 
 car and connected with an electric motor, carry 
 off the current from the bare conductor by rolling 
 or sliding over it. 
 
 In the second variety of the underground sys- 
 tem, a section of a bare conductor, or bare metal- 
 lic points that, on the passage of the car over 
 them are automatically connected with the gen- 
 erating dynamo, replace the continuous metallic 
 conductors of the first system. 
 
 In the surface system, the wires or conductors 
 that are connected with the generating dynamo, 
 instead of being placed in the underground open 
 slotted conduit, are placed directly on the surface 
 of the street or roadbed and the current carried 
 off from the same by suitable contacts placed on 
 the car. 
 
 In most cases, however, in which the surface 
 system is adopted, the conductors that are con- 
 
Eai.] 
 
 437 
 
 [Rai. 
 
 nected with the generating dynamo do not ex- 
 tend throughout the entire length of the track, 
 but are limited to sections of the track that are 
 suitably connected with the generating dynamo. 
 In some of these systems arrangements are 
 devised, by which the car, as it passes over the 
 track, automatically connects these sections with 
 the generating dynamo while passing over the 
 same, and disconnects them after such sections 
 have been passed. 
 
 The overhead system embraces two varieties: 
 
 (i.) A continuous trolley wire. 
 
 (2.) A divided or sectional trolley wire. 
 
 In the continuous trolley wire system, the cur- 
 rent is taken off from the continuous wire by 
 means of a trolley wheel that moves over the 
 trolley wire. 
 
 Such a system is especially suitable for suburban 
 Districts or small towns. In such a system the 
 trolley wire is connected with a number of feeder 
 wires that either extend from the generating sta- 
 tion the entire length of the line, and are con- 
 nected with such line at suitable points; or, sepa- 
 rate feeders extend from the station to points on 
 the line where they are tapped into the trolley 
 wire. 
 
 In the divided or sectional trolley wire system 
 the wire is divided into suitable sections, and 
 feeders extend the entire length of the line and 
 are connected to the central points of each section; 
 or, the feeders extend the entire length of the 
 line and tap into both ends of the section. 
 
 The author is indebted to G. W. Mansfield for 
 the principal facts contained in the above descrip- 
 tive matter. 
 
 Rail roads. Electric, Diyided Overhead 
 System of Motive Power for A sec- 
 tional overhead system of motive power for 
 electric railroads. (See Railroads, Electric, 
 Sectional Overhead System of Motive Power 
 for,} 
 
 Railroads, Electric, Divided Surface 
 System of Motive Power for A sec- 
 tional system of motive power for electric 
 railroads. (See Railroads, Electric, Sec- 
 tional Surface System of Motive Power 
 for.) 
 
 Railroads, Electric, Divided Under- 
 ground System of Motive Power for 
 
 A sectional system of motive power for 
 electric railroads. (See Railroads, Electric, 
 
 Sectional Underground System of Motive 
 Power for.} 
 
 Railroads, Electric, Double-Trolley Sys- 
 tem for A system of electric railroad 
 
 propulsion, in which a double trolley is em- 
 ployed to take the driving current from two 
 overhead trolley wires. 
 
 The double-trolley system differs from the 
 single-trolley system in that it employs no earth 
 return. The parallel wires also avoid the effects 
 of injurious induction in neighboring telegraph 
 or telephone wires. (See Railroads, Electric, 
 Dependent System of Motive Power for.") 
 
 Railroads, Electric, Independent System 
 
 of Motive Power for A term for the 
 
 electric propulsion of railway cars by means 
 of primary or storage batteries placed on the 
 car and directly connected with the motor. 
 
 This is called the independent system, because, 
 unlike the dependent system, the energy required 
 for the propulsion of the car is obtained directly 
 from the energy of the electric source placed on 
 the car, instead of, as in the dependent system, 
 outside of the car. 
 
 Railroads, Electric, Sectional Overhead 
 
 System of Motive Power for A variety 
 
 of the dependent system of motive power for 
 electric railroads, in which sections of bare 
 conductors are supported overhead on poles 
 placed along the railroad track, and the cur- 
 rent taken off from the same by means of 
 traveling conductors such as the trolley 
 wheel, which is moved over the trolley wire 
 by the motion of the car. 
 
 Various systems are employed for connecting 
 the different sections of the trolley wire by means 
 of feeder wires with the generating dynamo. 
 (See Railroads, Electric, Dependent System of 
 Motive Power for.} 
 
 Railroads, Electric, Sectional Surface 
 System of Motive Power for A 
 
 variety of the dependent system of motive 
 power for electric railroads in which conduc- 
 tors are placed on the roadbed or along the 
 track, and the current taken off from the same 
 by means of contacts connected with the mov- 
 ing car, and so arranged as to automatically 
 switch in such bare sections on the passage 
 
Rai.] 
 
 438 
 
 [Ray. 
 
 of the car over them, and to switch them out 
 as the car leaves them. (See Railroads, 
 Electric, Dependent System of Motive Power 
 for) 
 
 Railroads, Electric, Sectional Under- 
 ground System of Motive Power for 
 
 A variety of the dependent system of 
 motive power for electric railroads in which a 
 sectional conductor is placed underground in 
 a slotted conduit, and the current taken from 
 the same by means of sliding or rolling con- 
 tacts connected with the moving car. (See 
 Railroads, Electric, Dependent System of 
 Mot i-ve Power for.) 
 
 Railroads, Electric, Section Line of 
 
 Any part of the overhead electric conduc- 
 tors insulated from other parts so as to permit 
 its supply of electric power to be separately 
 controlled. 
 
 Railroads, Electric, Signal Service Sys- 
 tem for The system of electric signals 
 
 used on railways for ascertaining the condition 
 of the roads, sending instructions to engineers, 
 and conveying intelligence generally from 
 stations along the road to the running trains. 
 
 Railroads, Electric, Single-Trolley Sys- 
 tem A system of electric railroad 
 
 propulsion in which a single trolley is em- 
 ployed to take the driving current from a 
 single overhead trolley wire. 
 
 The earth, or a conductor placed along the 
 track on the roadbed, acts as the return. (See 
 Railroads, Electric, Dependent System of Mo- 
 tive Power for.) 
 
 Railroads, Permissive Block System for 
 
 A block system in which more than 
 
 one train is permitted under given conditions 
 to occupy the same block simultaneously. 
 (See Railroads, Block System for.) 
 
 Railway, Electric An electric rail- 
 road. (See Railroad, Electric) 
 
 Range, Molecular The distance at 
 
 which the molecules of matter exert a sensi- 
 ble attraction for one another. 
 
 This distance has been estimated in the case of 
 zinc and oxygen as equal to about the ten-mil- 
 lionth of a millimetre. 
 
 Ratchet-Pendant Argand-Electric Burner. 
 
 (See Burner, Argand-Electric, Ratchet- 
 Pendant^ 
 
 Ratchet-Pendant Electric Burner. (See 
 Burner, Ratchet-Pendant, Electric) 
 
 Ratchet-Pendant Electric Candle Burner. 
 
 (See Burner, Ratchet-Pendant Candle 
 Electric) 
 
 Ratio, Velocity A ratio, in the 
 
 nature of a velocity, that exists between the 
 dimensions of the electrostatic and the elec- 
 tro-magnetic units. 
 
 This ratio will be understood from the com- 
 parison of the following units. In each case the 
 numerator gives the dimensions in the electro- 
 static and the denominator the dimensions in the 
 electro-magnetic system : 
 
 Quantity, 
 
 Here the value of the ratio, viz., the length 
 divided by the time, is clearly in the nature of a 
 
 velocity, for V = . 
 
 Potential, 
 
 Capacity, 
 
 L-i T* 
 
 L-i T 
 Resistance, j ^zj 
 
 _ 
 
 V 3 
 
 A remarkable similarity exists between the 
 value of the -velocity expressed in C. G. S. units, 
 and the velocity of light, which is of great signifi- 
 cance in the electro-magnetic theory of light. (See 
 Light, Maxwell's Electro-Magnetic Theory of.) 
 
 The velocity of light is 2.9992 X io 10 cen- 
 timetres per second. 
 
 The velocity ratio, v, is 2.9800 X io 10 centi- 
 metres per second. 
 
 Rattler, Push-Button A device 
 
 connected with a push button to show that 
 the bell connected at a distant point, in the 
 circuit of a push button, rings when the button 
 is pressed. 
 
 Ray, Actinic A ray of light or other 
 form of radiant energy that possesses the 
 
Ray.] 
 
 439 
 
 [Rec. 
 
 power of effecting chemical action. (See 
 Decomposition ) 
 
 All rays of light, and even some of those in- 
 visible to the human eye, are actinic to some 
 particular chemical substance or another. 
 Whether the ether waves produce the effects of 
 heat, of light or of chemical decomposition de- 
 pends on the nature of the material on which 
 they fall, as well as on the character of the waves 
 themselves. 
 
 Ray, Electric (Raia torpedo) A 
 
 species of fish named the ray, which, like the 
 electric eel, pos- 
 sesses the power 
 of producing elec- 
 tricity. 
 
 The electric or- 
 gan is situated at 
 the back of the 
 head, and consists 
 of hundreds of poly- 
 gonal, cellular 
 laminae, supplied 
 with numerous 
 nerve fibres, as 
 shown in Fig. 465. 
 (See Fishes. Elec- 
 tric.') 
 
 Rayleigh's 
 Form of Clark's 
 Standard Yoltaic 
 Cell. (See Cell, 
 
 Voltaic, Stand- 
 ard, Rayleigh's 
 
 Form of Clark's) Fig. 463. The Raia Torpedo. 
 
 Reaction. In electro -therapeutics mus- 
 cular contractions following the closing or 
 opening of an electric circuit. 
 
 Reaction Coil. (See Coil, Reaction!) 
 
 Reaction of Degeneration. (See Degen- 
 eration, Reaction of.) 
 
 Reaction of Exhaustion. (See Exhaus- 
 tion, Reaction of.) 
 
 Reaction Principle of Dynamo-Electric 
 Machines. (See Machine, Dynamo-Elec- 
 tric, Reaction Principle of) 
 
 Reaction Telephone. (See Telephone, 
 Reaction) 
 
 Reaction Time. (See Time, Reaction) 
 
 Reaction Wheel, Electric (See 
 
 Wheel, Reaction, Electric) 
 
 Reactions, Kathodic and Anodic Electro- 
 Diagnostic The reactions which oc- 
 cur at the kathode or anode of an electric 
 source placed on or over any part of a living 
 body. 
 
 Fig. 466. Kathodic and Anodic Reactions. 
 
 Fig. 466, from De Watteville's " Medical Elec- 
 tricity" represents what he assumes takes place at 
 the points of entrance and exit of the current in a 
 nerve submitted to the action of the anode of an 
 electric source. Two zones are formed, an anodic 
 and a kathodic zone; the virtual anode is formed 
 by the portion of the skin nearer the nerve, and 
 the virtual kathode by the adjoining muscles. 
 There are thus formed two zones of influence 
 one immediately around the anode, called the 
 polar or anodic electrotonic zone, and one sur- 
 rounding this and including the virtual kathode, 
 and called the peripolar, or kathelectrotonic zone. 
 
 Reading* Telescope. (See Telescope, 
 Reading) 
 Real Efficiency of Storage Battery. 
 
 (See Efficiency, Real, of Storage Battery) 
 
 Real Hall Effect (See Effect, Hall, 
 Real) 
 
 Recalescence. The property, possessed 
 by incandescent steel when cooling, of 
 again becoming incandescent after a certain 
 degree of cooling has been reached. 
 
 The property of recalescence was first pointed 
 out by Barrett. 
 
 A steel wire heated at the middle or near one 
 end to a bright red, and allowed to cool in 
 a dim light, will cool until a low red heat is 
 reached, when it will be observed to reheat at 
 some point in the originally heated portion. This 
 reheating is manifested by a brighter red spot 
 
Roc. 
 
 440 
 
 [Rec. 
 
 which moves along the portion originally heated. 
 This reheating is called recalescence, and is due 
 to latent heat (potential energy), which, disap- 
 pearing when the bar was heated, again becomes 
 sensible (kinetic energy) on cooling. 
 
 The temperature at which recalescence takes 
 place is sensibly the temperature at which heated 
 steel regains its magnetizability. 
 
 Received Current. (See Current, Re- 
 ceived.} 
 
 Receiver, Gramophone The re- 
 ceiver employed in the gramophone. (See 
 Gramophone.} 
 
 Receiver, Graphophone The re- 
 ceiver employed in the graphophone. (See 
 Phonograph.} 
 
 Receiver, Harmonic A receiver, 
 
 employed in systems of harmonic telegraphy, 
 consisting of an electro-magnetic reed, tuned 
 to vibrate to one note or rate only. (See Te- 
 legraphy, Grays Harmonic Multiple?) 
 
 Receiver Magnet. (See Magnet, Receiv- 
 ing) 
 
 Receiver, Phonographic The ap- 
 paratus employed in a telephone, phono- 
 graph, graphophone or gramophone for the 
 reproduction of articulate speech. (See 
 Phonograph?] 
 
 Receiver, Telephonic The receiver 
 
 employed in the telephone. (See Tele- 
 phone^ 
 
 Receptive Device, Electro (See 
 
 Device, Electro-Receptive?) 
 
 Receptive Device, Magneto - (See 
 Device, Magneto-Receptive?) 
 
 Reciprocal The reciprocal of any 
 
 number is the quotient arising from dividing 
 unity by that number. 
 
 Thus, for example, the reciprocal of 4, is \ or 
 .250. 
 
 The conducting power of any circuit is equal 
 to the reciprocal of its resistance ; or, in other 
 words, the conducting power is inversely propor- 
 tional to the resistance. 
 
 The following table contains the reciprocals 
 of the numerals up to 100 : 
 
 TABLE OF RECIPROCALS. 
 
 Re- 
 
 
 Re- 
 
 
 Re- 
 
 
 Re- 
 
 
 Re- 
 
 cipro- 
 
 No. 
 
 cipro- 
 
 No. 
 
 cipro^ 
 
 No. 
 
 cipro- 
 
 No. 
 
 cipro- 
 
 cal. 
 
 
 cal. 
 
 
 cal. 
 
 
 cal. 
 
 
 cal. 
 
 0.5000 
 
 22 
 
 o 0455 
 
 42 
 
 o 0338 
 
 62 
 
 o 0:61 
 
 82 
 
 O O 22 
 
 -3333 
 
 23 
 
 o 435 
 
 43 
 
 o 0233 
 
 63 
 
 o 0159 
 
 83 
 
 O O 2O 
 
 o 2500 
 
 24 
 
 o 0417 
 
 44 
 
 o 0227 
 
 64 
 
 o 0156 
 
 84 
 
 009 
 
 O 2OOO 
 
 25 
 
 o 0400 
 
 45 
 
 O O222 
 
 65 
 
 o 0154 
 
 85 
 
 008 
 
 o 1667 
 
 26 
 
 o 0385 
 
 46 
 
 o 0217 
 
 66 
 
 o 0152 
 
 86 
 
 006 
 
 o 1429 
 
 2 7 
 
 o 0370 
 
 47 
 
 o 0213 
 
 67 
 
 o 0149 
 
 87 
 
 005 
 
 o 1250 
 
 28 
 
 o 0357 
 
 48 
 
 o 0208 
 
 68 
 
 o 0147 
 
 88 
 
 O04 
 
 IIII 
 
 29 
 
 o 0345 
 
 49 
 
 o 0204 
 
 69 
 
 o 0145 
 
 89 
 
 O O 2 
 
 o 1000 
 
 3 
 
 o 0333 
 
 5 
 
 O O2OO 
 
 70 
 
 o 0143 
 
 90 
 
 O O I 
 
 o 0909 
 
 3i 
 
 o 0323 
 
 5i 
 
 o 0106 
 
 7' 
 
 o 0141 
 
 9 1 
 
 O O O 
 
 o 0833 
 
 32 
 
 o 0313 
 
 52 
 
 o 0192 
 
 72 
 
 o 0139 
 
 92 
 
 o o 09 
 
 o 0769 
 
 33 
 
 o 0303 
 
 53 
 
 o 0189 
 
 73 
 
 o 0137 
 
 93 
 
 o o c8 
 
 o 0714 
 
 34 
 
 o 0294 
 
 54 
 
 o 0185 
 
 74 
 
 o 0135 
 
 94 
 
 06 
 
 o 0667 
 
 35 
 
 o 0286 
 
 55 
 
 o 0182 
 
 75 
 
 o 0133 
 
 95 
 
 o o 05 
 
 o o6as 
 
 36 
 
 o 0278 
 
 56 
 
 o 0179 
 
 76 
 
 o 0132 
 
 96 
 
 o o 04 
 
 o 0588 
 
 37 
 
 o 0270 
 
 57 
 
 o 0175 
 
 77 
 
 o 0130 
 
 97 
 
 o o 03 
 
 o 0556 
 
 38 
 
 o 0263 
 
 58 
 
 o 0172 
 
 78 
 
 o 0128 
 
 98 
 
 o o 02 
 
 o 0526 
 
 39 
 
 o 0256 
 
 59 
 
 o 0169 
 
 79 
 
 o 0127 
 
 )<) 
 
 O O OI 
 
 o 0500 
 
 4 
 
 o 0250 
 
 60 
 
 o 0167 
 
 80 
 
 o 0125 
 
 IOO 
 
 o o oo 
 
 o 0476 
 
 4 
 
 o 0244 
 
 61 
 
 o 0164 
 
 81 
 
 o 0123 
 
 
 
 ( Clark or* Sabine. ) 
 
 Recoil Circuit. (See Circuit, Recoil.} 
 
 Record, Chronograph A record 
 
 made by means of a chronograph for the pur- 
 pose of measuring and recording small inter- 
 vals of time. (See Chronograph, Electric?) 
 
 Record, Gramophone The irregular 
 indentations, cuttings or tracings made by a 
 point attached to the diaphragm spoken 
 against, and employed in connection with the 
 receiving diaphragm for the reproduction of 
 articulate speech. 
 
 Record, Graphophone The record 
 
 made by the movement of the diaphragm of 
 the graphophone. (See Phonograph.} 
 
 Record, Phonographic The record 
 
 produced in a phonograph, for the subse- 
 quent reproduction of audible articulate 
 speech. 
 
 Record, Telephonic The record 
 
 produced by the diaphragm of a receiving 
 telephone. 
 
 Various methods have been proposed for ob- 
 taining telephonic records, but none of them 
 have yet been introduced into actual commercial 
 use. 
 
 Recorder, Chemical, Bain's A n ap- 
 paratus for recording the dots and dashes of 
 
Rec.] 
 
 441 
 
 [Rcc. 
 
 a Morse telegraphic dispatch, on a sheet of 
 chemically prepared paper. 
 
 A fillet of paper soaked in some chemical sub- 
 stance, such as ferro-cyanide of potassium, is 
 moved at a uniform rate between the two ter- 
 minals of the line, one of which is iron tipped, so 
 that on the passage of the current, a blue dot, or a 
 dash, will be made on the paper according to the 
 length of time the current is passing. 
 
 In order to insure a moist condition of the paper 
 fillet, some deliquescent salt, like ammonium 
 nitrate, is generally mixed with the ferro-cyanide 
 of potassium. 
 
 Fig. 467. Bain Recorder. 
 
 A Bain recorder is shown in Fig. 467. A, is 
 a drum of brass, tinned on the outside. The 
 paper fillet is drawn from the roll and kept 
 pressed against the cylinder A, by a small wooden 
 roller B. The needle, which is a metallic point, 
 is placed in connection with one end of the line 
 wire, and the brass drum is connected with the 
 other end through the earths Care must be ob- 
 served to connect the needle point with the posi- 
 tive electrode, as otherwise the paper will not be 
 marked. (See Electrolysis.') 
 
 The Bain recorder is now almost entirely re- 
 placed by the Morse sounder. (See Sounder, 
 Morse Telegraphic.} 
 
 Recorder, Morse An apparatus for 
 automatically recording the dots and dashes 
 of a Morse telegraphic dispatch, on a fillet of 
 paper drawn under an indenting or marking 
 point on a striking lever, connected with the 
 armature of an electro-magnet. 
 
 This apparatus is sometimes called a Morse 
 register. 
 
 The Morse recording or registering apparatus 
 is shown in Fig. 468. 
 
 The paper fillet passes between a pair of rollers 
 r, driven by the clockwork W. The upper roller 
 is provided with a groove, so that the movement 
 of the stylus at the bent end of the lever L, by the 
 
 electro-magnet M, moving its armature attached 
 to the lever L, may indent or emboss the paper 
 fillet. When no current is passing, the armature 
 of the magnet and the lever L, are drawn back by 
 the action of an adjustable spring at n. 
 
 Fig. 468. Morse Recorder. 
 
 In the drawing, the ordinary Morse sounder is 
 shown on the right. The sounder has almost 
 entirely replaced the recording apparatus. 
 
 Recorder, Siphon An apparatus 
 
 for recording in ink on a sheet of paper, by 
 means of a fine glass siphon supported on a 
 fine wire, the message received over a cable. 
 
 One end of the siphon dips in a vessel of ink. 
 The record is received on a fillet of paper moved 
 mechanically under the siphon. The ink is dis- 
 charged from the siphon by electric charges im- 
 parted to the ink by a static electric machine. 
 
 Fig. 46 >p. The Siphon Recorder. 
 
 In the annexed sketch of the siphon recorder, 
 Fig. 469, a light rectangular coil b b, of very fine 
 wire, is suspended by a thin wire f f, between the 
 poles N, S, of a powerful compound permanent 
 magnet, and moving on the vertical axis of the 
 supporting wire f f, and adjustable as to tension, 
 at h. A stationary soft iron core a, is magnetized 
 
 SIPHON RECORDER 
 
 Fig. 470. Record of Siphon Recorder. 
 
 by induction and strengthens the magnetic field 
 of N, S. The cable current is received by the 
 
Rec.] 
 
 442 
 
 coil b b, through the suspending wire f f , and is 
 moved by it to the right or the left, according to 
 its direction, to an extent that depends on the 
 current strength. 
 
 The fine glass siphon n, which dips into a 
 reservoir of ink at m, is capable of movement on 
 a vertical axis 1, and is moved backwards or for- 
 wards, in one direction by a thread k, attached 
 
 S E T T L ED 
 Fig. 471. Record of Siphon Recorder. 
 to b, and in the opposite direction by a retractile 
 spring attached to an arm of the axis 1. 
 
 As the paper is moved under the point of the 
 siphon, an irregular curved line is marked thereon. 
 
 Two records as actually received by a siphon 
 recorder are shown in the Figs. 470 and 471. 
 Movements upwards correspond to the dots, and 
 downwards to dashes. 
 
 Rectification of Alcohol, Electric - 
 (See Alcohol, Electric Rectification of.} 
 
 Rectified. Turned in one and the same 
 direction. 
 
 The alternate currents in a dynamo-electric 
 machine are rectified or caused to flow in one ajid 
 the same direction by means of a commutator. 
 
 The word commuted, generally used in this 
 connection, would appear to be preferable to the 
 word rectified. (See Commutator.) 
 
 Rectilinear Co-ordinates, Abscissa of 
 
 (Set Abscissa of Rectilinear Co-ordinates) 
 
 Rectilinear Current (See Current, Rec- 
 tilinear^) 
 
 Red Heat (See Heat, Red) 
 
 Red Hot (See Hot, Red) 
 
 Reducteur or Resistance for Yoltmeter. 
 A coil of known resistance as compared 
 with the resistance of the coils of a voltmeter, 
 and connected with them in series for the 
 purpose of increasing the range of the instru- 
 ment. (See Voltmeter) 
 
 Reducteur or Shunt for Ammeter. A 
 shunt coil connected in multiple with the coils 
 of an ammeter for the purpose of changing 
 the value of the readings. 
 
 The ratio of the resistance of the reducteur and 
 the ammeter coils is known. A reducteur in- 
 creases the range of current measured by the am- 
 meter 
 
 Refining of Metals, Electric 
 
 the 
 
 refining of metals by the application of elec- 
 trolysis. 
 
 When certain precautions are taken, metals 
 thrown down from their solutions, are obtained in 
 a chemically pure condition. This fact is utilized 
 in the electrical refining of metals. If, for exam- 
 ple, a plate of impure copper is to be refined 
 electroly tically, it is used as the anode of a copper 
 bath, and placed opposite a thin plate of pure cop- 
 per forming the kathode. The passage of the 
 current gradually dissolves the copper from the 
 plate at the anode, and deposits it in a chemically 
 pure condition on the plate at the kathode. 
 
 Somewhat similar principle* are employed for 
 electrically refining other metals. 
 
 Reflect. To throw off from a surface, ac- 
 cording to the laws of reflection, as of waves 
 in an elastic medium. (See Reflection, Laws 
 of) 
 
 Reflecting. Throwing off from a surface, 
 according to the laws of reflection. (See 
 Reflection, Laws of) 
 
 Reflecting Galvanometer. (See Gal- 
 vanometer, Reflecting) 
 
 Reflection. The throwing back of a body 
 or wave from a surface at an angle equal to 
 that at which it strikes such surface. (See 
 Reflection, Laws of) 
 
 Reflection, Laws of The laws gov-r 
 
 erning the reflection of light 
 
 (I.) The angle of reflection, or the angle in- 
 cluded between the reflected ray and the perpen- 
 dicular to the reflecting surface at the point of 
 incidence, is equal to the angle of incidence, or 
 the angle included between the striking ray and 
 the perpendicular to the reflecting surface at the 
 point of incidence. 
 
 (2.) The plane of the angle of incidence co- 
 incides with the plane of the angle of reflection. 
 
 Reflection of Electro-Magnetic Wares. 
 
 (See Waves, Electro-Magnetic, Reflection 
 of) 
 
 Reflection of Induction. (See Induc- 
 tion, Reflection of) 
 
 Reflector. A plane or curved surface, 
 capable of regularly reflecting light. 
 
 Reflector, Parabolic A reflector, 
 
Ref.j 
 
 413 
 
 [Keg. 
 
 or mirror, the reflecting surface of which is 
 a paraboloid, or such a surface as would be 
 obtained by the revolution of a parabola 
 about its axis. 
 
 A parabolic curve, which may be regarded as 
 a section of a parabola, is shown in Fig. 472. 
 A parabola has the following properties: If lines 
 F P, F P, etc., be drawn from the point F, 
 called the focus, to any point, P, P, etc., in the 
 curve, and the lines Pp, Pp, Pp, etc., be then 
 drawn severally parallel to the axis, V M, then 
 all such angles, F P p, F P p, will be bisected by 
 verticals to tangents at the point P, P, and P. 
 
 Therefore, if a light be placed at the focus of a 
 parabolic reflector, all the light reflected from the 
 surface of the parabola will pass off sensibly par- 
 allel to the axis V M. 
 
 In Locomotive Head 'lights ; a 
 lamp is placed at the focus of 
 a parabolic reflector, and the 
 parallel beam so obtained is 
 utilized for the illumination of 
 the track. In a search light an v ! 
 electric arc lamp is placed at p \ 
 the focus of a parabolic reflec- 
 tor, or at the focus of a lens. 
 
 A parabolic reflector is 
 used for search lights, some- Fig. 472. Parabolic 
 times in connection with an Reflector. 
 
 arc lamp. A focusing arc lamp must be used for 
 this purpose, so as to maintain the voltaic arc at 
 the focus of the parabolic reflector, notwithstand- 
 ing the unequal consumption of the positive and 
 negative carbons. (See Arc, Voltaic.') 
 
 Refract. To change the direction of waves 
 in any elastic medium in accordance with 
 the laws of refraction. (See Refraction) 
 
 Refracting. Changing the direction of 
 waves in an elastic medium in accordance 
 with the laws of refraction. 
 
 Refraction. The bending of a ray of 
 sound, light, heat, or electro-magnetism at 
 the surface of any medium whose density 
 differs from that through which such ray 
 was previously passing. 
 
 Rays of sound, light, heat or electro-mag- 
 netism are transmitted or propagated in straight 
 lines as long as the density of the homogeneous 
 medium through which they are pissing under- 
 goes no change. That is, as long as the medium 
 15 Vol. 1 
 
 is homogeneous or isotropic. (See Medium, Iso- 
 tropic.) As the rays enter the surface of a 
 medium which differs in density from that through 
 which they have been passing, they are bent or 
 refracted at the surface of such a medium. 
 
 This bending takes place towards a perpen- 
 dicular to the refracting surface at the point of in- 
 cidence, when the medium in to which the rays are 
 entering is of greater density than that they are 
 leaving, and from the perpendicular when the 
 medium they are entering is of less density than 
 that they are leaving. 
 
 The refraction or bending of the ray is caused 
 by the difference in the velocity with which the 
 waves are propagated through the two media. 
 
 There is no refraction or deviation when the 
 two rays enter the new medium at right angle, 
 to its surface, or when there is no angle of inci- 
 dence. 
 
 Refraction, Double The property 
 
 possessed by certain substances of splitting 
 up a ray of light passed through them into 
 two separate rays, and thus doubly refracting 
 the ray. 
 
 Certain specimens of calc spar possess the prop- 
 erty of double retraction. Each of the two rays 
 into which the original ray is separated is polar- 
 ized. Such calc spar is called doubly refracting 
 calc spar. 
 
 Refraction, Double, Electric The 
 
 property of doubly refracting light acquired 
 by some transparent substances while in an 
 electrostatic or electro-magnetic field. 
 
 Transient or momentary powers of double 
 refraction, acquired by a transparent sub- 
 stance while placed in an electric field. 
 
 The intensity of double refraction is propor- 
 tioned to the square of the electric force. 
 
 The action of an electric field in endowing a 
 substance with the power of double refraction 
 while kept in such field, is due to the strain pro- 
 duced by the electrostatic stress of the field. 
 
 A similar transient power of double refraction 
 is acquired by many bodies when subjected to 
 the strain produced by a simple mechanical 
 stress. 
 
 Refreshing Action of Current (See Ac- 
 tion, Refreshing, of Current?) 
 
 Region, Extra-Polar A term ap- 
 plied in electro-therapeutics to the region. 
 
Reg.] 
 
 which lies outside or beyond the therapeutic 
 electrode. 
 
 The term extra-polar region is used in contra- 
 distinction to polar region. (See Region, Polar.) 
 
 Region, Polar A term applied in 
 
 electro-therapeutics to that region or part of 
 the body which lies directly below the thera- 
 peutic electrode. 
 
 Register, Double-Pen Telegraphic 
 
 A telegraphic register provided with two 
 separate styluses or pens for recording the 
 telegraphic message on a fillet of paper. (See 
 Register, Telegraphic!) 
 
 Register, Morse A name sometimes 
 
 given to a Morse recorder. (See Recorder, 
 Morse?) 
 
 Register, Telegraphic An appa- 
 ratus employed at the receiving end of a tele- 
 graphic line for the purpose of obtaining a 
 permanent record of the telegraphic dispatch. 
 
 The telegraphic register consists essentially of 
 means whereby a fillet or tape of paper is drawn 
 mechanically under a pen or stylus attached to 
 the armature of an electro-magnet and moving 
 therewith. 
 
 The pen or stylus presses against the paper 
 whenever the armature is attracted to the elec- 
 tro-magnet, and is held there while the cur- 
 
 444 
 
 [Reg. 
 
 Fig. t73 t*k- Writing Register. 
 cent is passing through the coils of the electro- 
 magnet. By these means the dots and dashes of 
 the telegraphic alphabet are recorded on the 
 paper fillet as embossed or printed dots and 
 dashes. The Morse register is an apparatus of 
 this description. (See Recorder, Morse.) 
 
 A form of ink-writing telegraphic register is 
 shown in Fig. 473. It is self-starting. 
 
 Register, Time, for Railroads A 
 
 telegraphic recording apparatus or register 
 designed to record all telegraphic messages 
 transmitted over a line. 
 
 The record is received on an endless band or 
 fillet of paper. It is useful in case of disputes as 
 to the time certain messages were sent over the 
 line. 
 
 Register, Watchman's Electric 
 
 A device for permanently recording the time 
 of a watchman's visit to each of the dif- 
 ferent localities he is required to visit at stated 
 intervals. 
 
 These registers are of a variety of forms. They 
 consist, however, in general, of a drum or disc of 
 paper driven by clockwork, on which a maik is 
 made by a stylus or pencil, operated on the clos- 
 ing of a circuit by the pressing of a push button 
 or the pressing of a key by the watchman at each 
 station. 
 
 Registering Apparatus, Electric 
 
 (See Apparatus, Registering, Electric!) 
 
 Registering Electrometer. (See Elec- 
 trometer, Registering!) 
 
 Regulable, Automatically Capa- 
 ble of being automatically regulated. (See 
 Regulation, Automatic!) 
 
 Regulate, Automatically To regu- 
 late in an automatic manner. (See Regula- 
 tion, Automatic!) 
 
 Regulation, Automatic Regulation 
 
 automatically effected. 
 
 Regulation, Automatic, of Dynamo-Elec- 
 tric Machine Such a regulation of a 
 
 dynamo-electric machine as will automati- 
 cally preserve constant either the current or 
 the potential difference. 
 
 The automatic regulation of dynamo-electric 
 machines may be accomplished in the following 
 ways, viz.: 
 
 (I.) By a Compound Winding of the Machine. 
 
 This method is particularly applicable to con- 
 stant-potential machines. By this winding, the 
 magnetizing effect of the shunt coils is maintained 
 approximately constant, while that of the series 
 coils varies proportionally to the load on the ma- 
 chine. 
 
 The series coils are sometimes wound close to 
 
-Keg.] 
 
 445 
 
 [Beg. 
 
 the poles of the machine, and the shunt coils 
 nearer the yoke of the magnets. Custom, how- 
 ever, varies in this respect, and very generally 
 the shunt coils are placed nearer the poles than 
 the series coils. (See Machine, Dynamo -Electric, 
 Compound- Wound.") 
 
 (2.) By Shifting the Position of the Collecting 
 Brushes. 
 
 In the Thomson-Houston system of current 
 regulation, the current is kept practically con- 
 stant by the following devices: The collecting 
 brushes are fixed to levers moved by the regula- 
 tor magnet R, as shown in Fig. 474, the arma- 
 ture of which is provided with an opening for the 
 entrance of the paraboloidal pole piece A. A 
 dash-pot is provided to prevent too sudden move- 
 ment. 
 
 When the current is normal, the coil of the 
 regulator magnet is short-circuited by contact 
 points at S T, which act as a shunt of very low re- 
 sistance. These contact points are operated by 
 the solenoid coils of the controller, traversed by 
 the main current. The cores of this solenoid are 
 suspended by a spring. When the current be- 
 comes too strong, the contact point is opened, 
 and the current, traversing the coil of the regu- 
 lar magnet A, attracts its armature, which shifts 
 the collecting brushes into a position in which a 
 smaller current is taken off. 
 
 A carbon shunt, r, of high resistance, is pro- 
 vided to lessen the spark at the contact points S 
 T, which occurs on opening the circuit. 
 
 Fig. 474- Thomson- Houston Regulator* 
 
 In operation the contact points are continually 
 opening and closing, thus maintaining a practi- 
 cally constant current in the external circuit. 
 
 (3.) By the Automatic Variation of a Resist, 
 ance shun ting the field magnets of the machine, 
 as in the Brush system. 
 
 In Fig. 475 the variable resistance C, forms a 
 part of the shunt circuit around the field mag- 
 nets F M.. This resistance is formed of a pile of 
 carbon plates. On an increase of the current, 
 such, for example, as would result from turning 
 out some of the lames, the electro magnet B, 
 
 placed in the main circuit, attracts its armature 
 A, and, compressing the pile of carbon plates C, 
 lowers their resistance, thus diverting a propor- 
 tionally larger portion of the current from the 
 field magnet coils F M, and maintaining the cur- 
 rent practically constant. 
 
 In some machines the same thing is done by 
 hand, but this is objectionable, since it requires 
 the presence of an attendant. 
 
 (4.) By the Introduction of a Variable Resist- 
 ance into the shunt circuit of the machine, as in 
 the Edison and other systems. 
 
 Fig. 47 S- The Brush Regulator. 
 
 This resistance may be adjusted either auto- 
 matically by an electro-magnet whose coils are 
 in an independent shunt across the mains, or may 
 be operated by hand. 
 
 In Fig. 476, the variable resistance is shown 
 at R, the lever switch being in this case operated 
 by hand whenever the potential rises or falls be- 
 low the proper value. 
 
 Fig. 476. The Edison Regulator. 
 
 The machine shown is thus enabled to main- 
 tain a constant potential on the leads to which the 
 lamps L, L, L, etc., are connected in multiple arc. 
 
 (5.) Dynamometric Governing, in which a 
 series dynamo is made to yield a constant cur- 
 rent by governing the steam engine that drives 
 it, by means of a dynamometric governor. This 
 governor operates by maintaining a constant 
 torque or turning moment, instead of by means of 
 
Beg.] 
 
 446 
 
 [Rel. 
 
 the usual centrifugal governor which maintains a 
 constant speed. 
 
 (6.) Electric Governing of the Driving Engine, 
 in which the governor is regulated by the cur- 
 rent itself instead of by the speed of rotation, as 
 usual. 
 
 Regulation, Hand Such a regula- 
 tion of a dynamo-electric machine as will pre- 
 serve constant, either the current or the 
 potential, said regulation being effected by 
 hand as distinguished from automatic regu- 
 lation. 
 
 Regulator, Automatic 
 
 A device 
 
 for securing automatic regulation as dis- 
 tinguished from hand regulation. (See 
 Regulation, Hand. Regulation, Automatic?) 
 
 Regulator, Hand - A resistance 
 box, the separate coils or resistances of which 
 can be readily placed in or removed from a 
 circuit by means of a hand-moved switch. 
 
 The term hand regulator is used as distin- 
 guished from automatic regulator. (See Regu- 
 lator, Automatic. Regulation, Automatic.} 
 
 Regulator Magnet. (See Magnet, Regu- 
 lator^ 
 
 Regulator, Monophotal Arc-Light - 
 
 A term sometimes employed for an electric 
 arc lamp in which the whole current passes 
 through the arc-regulating mechanism, and 
 which is usually operated singly in circuit 
 with a dynamo. 
 
 Regulator, Polyphotal Arc-Lamp 
 A regulator for an arc lamp suitable for 
 maintaining a number of lamps m series cir- 
 cuit with the dynamo. 
 
 Polyphotal regulators differ from monophotal 
 regulators in that their regulating electro mag- 
 nets are energized by a shunt circuit around the 
 electrodes of the lamp, while in monophotal regu- 
 lators such electro-magnets are placed in the di- 
 rect circuit The terms monophotal and poly- 
 photal are not generally used in America. 
 
 Reguline Electro-Metallurgical Deposit. 
 
 (See Deposit, Electro-Metallurgical, Reg- 
 
 Relative Calibration. (See Calibration^ 
 Relative?) 
 
 Relay. An electro-magnet, employed in 
 systems of telegraphy, provided with contact 
 points placed on a delicately supported arma- 
 ture, the movements of which throw a battery, 
 called the local battery, into or out of the 
 circuit of the receiving apparatus. 
 
 A relay is sometimes called a receiving magnet. 
 
 Rejuvenation of Luminescence. (See 
 Luminescence, Rejuvenation of.) 
 
 Fig. 477 Telegraphic Relay. 
 
 The use of a relay permits much smaller cur- 
 rents to be used than could otherwise be done, 
 since the electric impulses, on reaching a distant 
 station, are required to do no other work than 
 attracting a delicately poised movable contact, 
 and thus, by throwing a local battery into the 
 circuit of the receiving apparatus, to cause such 
 local battery to perform the work of register- 
 ing. Its use is especially required in the Morse 
 system of telegraphy in order to cause the sounder 
 to be distinctly heard. 
 
 A form of relay that is much used is shown in 
 
 Fig- 477- 
 
 The electro- magnet M, is wound with many 
 turns of very fine wire. In the form used by the 
 Western Union Telegraph Company, there are 
 about 8, 500 turns, having resistance of 150 ohms. 
 A screw m, is provided for moving the electro- 
 magnet M, a slight distance in or out, for the pur- 
 poses of adjustment. A semi-cylindrical arma- 
 ture A, of soft iron, is attached to the insulated 
 armature lever a, the lower end of which is sup- 
 ported by a steel arbor, which is pivoted between 
 two set screws. 
 
 A retractile spring S', regulable at S, is pro- 
 vided for moving the armature away from the 
 electro-magnet. There are four binding posts, 
 two of which are placed in the circuit of the 
 electro-magnet, and two in that of the local bat- 
 tery. The ends of the line wire are connected 
 with the former, and the receiving instrument 
 placed ii. the circuit of the latter. A platinum 
 
Rel.] 
 
 447 
 
 [Rel. 
 
 contact is placed on the end of a screw supported 
 at F, opposite a similar contact, near the end a, 
 of the armature iever. The contact is regulable 
 by means of a screw c. 
 
 On the energizing of the electro -magnet, the 
 attraction of its armature closes the platinum 
 contact, and, by thus completing the circuit of the 
 local battery, causes an attraction of the armature 
 of the receiving apparatus. On the cessation of 
 the current in the main line, the spring S , pulls 
 the armature away from the magnet, breaks the 
 circuit of the local battery, and thus permits a 
 similar spring on the receiving instrument to pull 
 its armature away. Thus all the movements of 
 the armature of the relay are reproduced with in- 
 creased intensity by the armature of the receiving 
 instrument. 
 
 The connections of the relay to the local bat- 
 tery and the registering apparatus, will be better 
 understood from an inspection of Fig. 478, which 
 represents a form of relay much used in Germany. 
 
 Relay, Differential A telegraphic 
 
 Fig. 478. Telegraphic Relay, German Pattern. 
 
 The retractile spring f, is regulated by the up- 
 and-down movements of its lower support, which 
 slides in the vertical pillar S. The line wire is 
 shown at m m, connected at one end to earth by 
 a ground wire. 
 
 The registering apparatus R, is connected in 
 the circuit of the local battery L, as shown. 
 The contacts are made by the end B, of the lever 
 B B', attached to the armature A, of the electro- 
 magnet M M. 
 
 Relay Bell. (See Bell, Relay, Electric) 
 
 Relay, Box-Sounding Telegraphic 
 
 A relay the magnet of which is surrounded 
 by a resonant case of wood for the purpose 
 of increasing the intensity of the sound made 
 by the armature of the magnet. 
 
 A form of box-sounding relay is shown m Fig. 
 479- 
 
 Fig. 479 Box- Sounding Relay 
 
 relay containing two differentially wound coils 
 of wire on its magnet cores. 
 
 When the currents which pass through these 
 two coils are of the same strength, there is no 
 movement of the armature, since the fields of the 
 two coils neutralize each other. 
 
 The differential relay is used in the differential 
 method of duplex and quadruplex telegraphy. 
 (See Telegraphy, Duplex Differential Method of. 
 Telegraphy, Quadruplex Differential Method of .} 
 
 Relay Magnet A name sometimes given 
 to a relay. (See Relay) 
 
 Relay, Microphone A device for 
 
 automatically repeating a telephonic message 
 over another wire. 
 
 Fig. 480. Microphone Relay. 
 A form of microphone relay is shown in Figs. 
 480 a'nd 481. 
 
 Several minute microphones mounted on the 
 
 Fig. 481. Microphone Relay. 
 
 diaphragm of the telephone whose message is to 
 be repeated, so vary the resistance of a local bat- 
 tery included in their circuit as to automatically 
 repeat the articulate speech received. 
 
 The microphones may oe connected either in 
 
Rel.] 
 
 448 
 
 [Bel. 
 
 multiple arc or in series, as shown respectively to 
 the left and right in Fig. 480. 
 
 Relay, Pocket Telegraphic A form 
 
 of telegraphic relay of such small dimensions 
 as to permit it to be readily carried in the 
 pocket. 
 
 Relay, Polarized A telegraphic re- 
 lay provided with a permanently magnetized 
 armature in place of the soft iron armature of 
 the ordinary instrument. 
 
 In the form of polarized relay shown in Fig. 
 482, N S, is a steel magnet, whose magnetism is 
 consequently permanent, with its north and south 
 poles at N, and S, respectively. The cores of 
 the electro-magnet m, m', are of soft iron, and, 
 since they rest on the north pole of the permanent 
 steel magnet, the poles, brought very near to- 
 gether by the armatures at n, n', will be of the 
 same polarity as N, when no current is passing 
 through the coils m, m' ; but when such current 
 does pass, one of these poles becomes of stronger 
 north polarity, while the other changes its polar- 
 ity to south. 
 
 By these means to-and fro movements of the 
 armature lever, with its contact point, are effected 
 without the use of a retractile spring ; movement 
 in one direction occurring on the closing of the 
 circuit due to the electro-magnetism developed 
 
 Fig. 482. Polarized Relay. 
 
 by the coils m, m', and movement in the opposite 
 direction, on the losing of this magnetism on 
 breaking the circuit, by the permanent magnet- 
 ism of the steel magnet N S. 
 
 These movements are imparted to the soft iron 
 lever c, c', pivoted at B, and passing between the 
 closely approached soft iron poles at n, n'. This 
 lever rests at the end c', against a contact point 
 
 when moved in one direction, and against an in- 
 sulated point when moved in the opposite direc- 
 tion. It rests against the insulated point when 
 no current is passing through the coils m, m'. 
 
 If the armature lever were placed in a position 
 exactly midway between the poles n, and n', it 
 would not move at all, being equally attracted by 
 each; but if moved a little nearer one pole than 
 the other, it would be attracted to, and rest 
 against, the nearer pole. 
 
 When alternating currents are employed on 
 the line, the lever c, c', must be adjusted as nearly 
 as possible in the middle of the space between n 
 and n', in which case it will remain on the side to 
 which it was last attracted, until a current in the 
 opposite direction moves it to the other side. 
 
 LB 
 
 SOB 
 
 Fig. 483. A Detail of the Polarized Relay. 
 
 The space between the magnet poles n, n', 
 and the contacts of the armature lever at D, and 
 D', are shown in detail in Fig. 483, which is a 
 plan of Fig. 482. The binding posts for the line 
 battery are shown at L B, i, and 2, and those 
 for the local battery at A and B. The dotted 
 lines show the connections. 
 
 Since the polarized relay dispenses with the re- 
 tractile spring, it is far more sensitive than the 
 ordinary instrument. Once adjusted, no further 
 regulation is required, in which respect it differs 
 very decidedly from non-polarized relays. 
 
 There are other forms of polarized relays, but 
 the above will suffice to illustrate the general 
 principle of their operation. 
 
 Relay Shunt, Steam's (See Shunt, 
 
 Relay, Steam's.) 
 
 Reluctance, Magnetic A term re- 
 cently proposed in place of magnetic resist- 
 ance to express the resistance offered by a 
 
Rel.] 
 
 449 
 
 [Rep. 
 
 medium to the passage through its mass of 
 lines of magnetic force. 
 
 The term reluctance, in the sense of resistance 
 to passage of lines of magnetic force, has been 
 proposed in place of resistance, for the purpose 
 of carrying out the conception of regarding the 
 flow of lines of force in a magnetic circuit as 
 being due to a magneto-motive force, and being 
 opposed by a reluctance of the substances form- 
 ing such circuit to the passage of such lines. 
 
 According to this conception, 
 
 The magnetic flux = 
 
 The magneto-motive force 
 The reluctance. 
 
 Reluctance, Magnetic, Unit of 
 
 Such a magnetic reluctance in a closed cir- 
 cuit that permits unit magnetic flux to 
 traverse it under the action of unit magneto- 
 motive force. 
 
 In present practical work reluctances vary 
 from 100,000 to 100,000,000 of the practical 
 units. 
 
 Reluctivity. A term proposed for mag- 
 netic reluctance. (See Reluctance, Mag- 
 netic^) 
 
 This term is not generally adopted. 
 
 Removable Key Switch. (See Switch, 
 Removable Key?) 
 
 Renovation of Secondary Cell. (See 
 Cell, Secondary or Storage, Renovation of.) 
 
 Renovation of Secondary or Storage 
 Cell. (See Cell, Secondary or Storage, 
 Renovation of.) 
 
 Reofore. A rheophore. (See Rheophore.) 
 
 Repeaters, Telegraphic Tele- 
 graphic devices, whereby the relay, sounder 
 or registering apparatus, on the opening and 
 closing of another circuit, with which it is 
 suitably connected, is caused to repeat the 
 signals received. 
 
 Repeaters are employed to establish direct 
 communication between very distant stations, or 
 to connect branch lines to the main line. 
 
 Fig. 484, shows Wood's Button Repeater. This 
 repeater 'consists simply of a three-point switch 
 L, capable of being placed on the points i, 2 and 
 3 ; and a ground switch at 4. The circuits are 
 arranged between the sounders S, S', relays 
 
 M, M', main batteries B, B', and the two main 
 lines E, and W, in the manner shown. 
 
 Fig. 484. Woofs Button Repeater. 
 
 If the lever L, is in the position shown in the 
 drawing, the lines E and W, form independent 
 circuits. 
 
 If the ground switch 4 is closed, and the lever 
 L, is placed on 2, 2, the eastern line repeats into 
 the western. If the lever L, is placed on the 
 plates 3, 3, the western line repeats into the 
 eastern. 
 
 This repeater is non- automatic and can be 
 worked in but one direction at a time ; moreover, 
 it requires the services of an attendant. 
 
 The automatic repeater can be operated in both 
 directions, and dispenses with the constant ser- 
 vices of an attendant at the repeating station. 
 
 In sending a dispatch through a repeater, the 
 dots and dashes are prolonged so as to give the 
 lever of the repeating instrument time in which 
 to move backwards and forwards. 
 
 Fig. 483- HicVs Automatic Button Repeater. 
 
 In Hick's Automatic Repeater, shown in Fig. 
 485, the switch or circuit-changer is automatic in 
 its action. 
 
 The relay magnets are shown at M, M', the 
 sounders at R and R' ; f, f, are platinum con- 
 tacts operated by levers 1 and 1', and L and L', 
 are extra local magnets, that act on armatures 
 
Rep.] 
 
 450 
 
 [Rep. 
 
 placed directly opposite the armatures of the relay 
 magnets. 
 
 The extra local magnet L, is cut out of the 
 circuit of B', the extra local battery, when the 
 main circuit is broken, and the armature is in 
 contact with c. As soon as this happens, how- 
 ever, the spring s, drawing away the armature, 
 and thus opening the short-circuit of no rcsist- 
 ance between c and a, establishes a circuit 
 through L. On a, coming in contact with c, the 
 circuit is again broken. 
 
 The tension of the spring s, is so regulated that 
 a very rapid vibration of a, is maintained so con- 
 stantly, that it is impossible to close the main cir- 
 cuit when L, is not cut out. The armature a, 
 will therefore respond to very weak impulses of 
 the relay magnet 
 
 On breaking the western main circuit N, the 
 lever a, vibrates very rapidly. The lever 1, of the 
 sounder R, first breaks the circuit of L, and after- 
 wards that of the eastern main circuit E, which 
 passes through M. Both L' and M', being 
 broken, a slight tension of s', will hold a, in 
 place, thus avoiding the breaking of the western 
 main circuit through the closing of the local cir- 
 cuit through R. On the closing of the western 
 circuit, the reverse of these operations occurs. 
 
 The author has taken the above explanation 
 mainly from Pope's work on " Modern Practice 
 of the Electric Telegraph." 
 
 Repeating Sounder. (See Sounder, Re- 
 peating.} 
 
 Replenisher. A static influence machine 
 devised by Sir William 
 Thomson for charging 
 the quadrants of his 
 quadrant electrometer. 
 
 Two brass carriers C 
 and D, shown in Fig. 486, 
 are electrically fixed to the 
 end of the vulcanite rod 
 E, which is capable of ro- 
 ., tation by the thumb screw 
 at M, in the direction 
 shown by the arrow. Hol- 
 low metal half-cylinders, 
 A and B, act as inductors, 
 a strip of brass fixed around Fig. 486. The Reflen- 
 the edges of a piece of vul- 
 canite P, connecting the metallic springs S, and 
 S', as shown. 
 
 The action of the replenisher is readily under- 
 
 stood from the following considerations, as sug- 
 gested by Ayrton in his "Practical Electricity " : 
 
 A and B, Fig. 487, are two insulated hollow 
 metallic vessels having a small difference of po- 
 tential between them, A, being the higher. C, 
 and D, are two small uncharged conductors held 
 by insulating strings. If C and D, be held near 
 A and B, as shown, the potential of C, will, by 
 induction, be raised somewhat above that of D, 
 so that when connected by a conductor, such as 
 the metallic wire W, a small quantity of positive 
 electricity will flow from C, to D, thus leaving D, 
 positively, and C, negatively charged. 
 
 If, now, C and D, are removed from W, and 
 placed in the bottom of B and A, as shown in 
 Fig. 488, the difference of potential between A, 
 and B, will be thereby increased, and if they are 
 then withdrawn, and totally discharged, and 
 
 Fig. 487. Action of Replenisher. 
 
 again placed in the first position shown, an ad- 
 ditional charge can be given to A and B, and this 
 can be repeated as often as desired. 
 
 In the replenisher, A and B, correspond to the 
 vessels A and B ; the brass carriers C and D, 
 to the balls C and D, and the spring S S, and M, 
 
 Fig. 488. Action of Replenisher. 
 
 to the wire W. No initial charge need be given 
 to A and B, since they are invariably found to 
 
Rep.] 
 
 451 
 
 [Res. 
 
 be at a sufficient difference of potential to build 
 up the charge. 
 
 Replenisher, Carriers of The 
 
 moving conductors of a replenisher which 
 carry the charges and thus permit of an ac- 
 cumulation of such charges. (See Re- 
 plenisher.) 
 
 Repulsion, Electric - The mutual 
 driving apart or tendency to mutually drive 
 apart existing between two similarly charged 
 bodies, or the mutual driving apart of similar 
 electric charges. 
 
 Repulsion, Electro-Dynamic The 
 
 mutual repulsion between two electric circuits 
 whose currents are flowing in opposite direc- 
 tions. 
 
 Parallel currents flowing in opposite directions 
 repel one another, because their lines of magnetic 
 force have the same direction in adjoining parts of 
 the circuit. (See Dynamics, Electro.) 
 
 Repulsion, Electro-Magnetic The 
 mutual repulsion produced by two similar 
 electro-magnetic poles. 
 
 Repulsion, Electrostatic The 
 
 mutual repulsion produced by two similar 
 electric charges. 
 
 Repulsion, Magnetic The mutual 
 repulsion exerted between two similar mag- 
 netic poles. 
 
 Repulsion, Molecular The mutual 
 
 repulsion existing between molecules arising 
 from their kinetic energy. (See Matter, Ki- 
 netic Theory of.) 
 
 Residual Atmosphere (See Atmosphere, 
 Residual.) 
 
 Residual Charge. (See Charge, Resid- 
 ual.) 
 
 Residual Magnetism. (See Magnetism, 
 Residual.) 
 
 Resin. A general term applied to a variety 
 of dried juices of vegetable origin. 
 
 Resins are, in general, transparent, inflamma- 
 ble solids, soluble in alcohol, and, in general, 
 excellent non-conductors of electricity. Rosin is 
 one of the varieties of resin. 
 
 Resinous Electricity. (See Electricity, 
 Resinous.) 
 
 Resistance. Something placed in a circuit 
 for the purpose of opposing the passage or 
 
 * 
 
 flow of the current in the circuit or branches 
 of the circuit in which it is placed. 
 
 The electrical resistance of a conductor is 
 that quality of the conductor in virtue of 
 which there is a fixed numerical ratio be- 
 tween the potential difference of the two 
 opposing faces of a cubic unit of such con- 
 ductor, and the quantity of electricity which 
 traverses either face per second, assuming a 
 steady flow to take place normal to these 
 faces, and to be uniformly distributed over 
 them, such flow taking place solely by an elec- 
 tromotive force outside the volume considered. 
 
 The term is used in the first definition in the 
 concrete sense of something intended for or used 
 as a resistance. For the physical definitions and 
 facts see Resistance, Electric. 
 
 Gases offer very high resistance to the flow of 
 an electric current. Their non-conducting power 
 causes the increase of resistance which attends 
 the polarization of a voltaic cell. (See Cell, 
 Voltaic, Polarization of.) 
 
 Resistances consist of coils, strips, bars or 
 spirals of metal, or plates of carbon, or metallic 
 powders, powdered or granulated carbon, or 
 liquids. 
 
 Resistance, Absolute Unit of The 
 one thousand millionth of an ohm. (See 
 Ohm. Units, Practical.) 
 
 Resistance, Assymmetrical - Con- 
 ductors or parts of conductors, which offer a 
 greater resistance to the flow of an electric 
 current in one direction than in another. 
 
 Assymmetrical conductors are unknown, so far 
 as structural peculiarities are concerned, but can 
 be obtained by the use of counter electromotive 
 forces, acting as resistance. This term was pro- 
 posed by Wilke in discussing the obtaining of 
 continuous currents by commutatorless dynamo- 
 electric machines. 
 
 The resistance of the human body is possibly an 
 assymmetrical resistance. 
 
 An evident application of an assymmetrical re- 
 sistance is to direct alternating currents so as to 
 cause the current that passes to flow in and to the 
 same direction. 
 
 Resistance, Balanced A resistance 
 
 so placed in a circuit as to be balanced or 
 made equal to another resistance connected 
 therewith. 
 
Kes.] 
 
 452 
 
 [Res. 
 
 Resistance, Balanced, for Dynamos 
 
 A resistance that possesses a range suf- 
 ficient to balance one dynamo against another 
 with which it is desired to run in parallel. 
 ( Urquhart) 
 
 Resistance Box. (See Box. Resistance^ 
 
 Resistance Bridge. (See Bridge, Resist- 
 ance) 
 
 Resistance Coil. (See Coi2. Resistance^ 
 
 Resistance Coil, Standard (See 
 
 Coil, Resistance, Standard) 
 
 Resistance, Conductivity The re- 
 sistance offered by a substance to electric 
 conduction, or to the passage of electricity 
 through its mass. 
 
 Resistance, Dielectric A term 
 
 sometimes employed for the resistance of a 
 dielectric to mechanical strains produced by 
 electrification. 
 
 The dielectric resistance of the glass, or other 
 dielectric of a Leyden jar or condenser, is fre- 
 quently overcome by the passage of the charges 
 on the conducting surfaces, and the glass is thus 
 pierced. 
 
 The term dielectric resistance would appear 
 to be badly chosen; for. like all substances, dielec- 
 trics possess a true ohmic resistance, which in 
 creases with the increase of length, and decreases 
 with the increase of area of cross-section. 
 
 The resistance of the dielectric, however, differs 
 from the ordinary ohmic resistance of conductors, 
 in that the resistance of the dielectric is suddenly 
 overcome, and the discharge passes disruptively 
 as a spark. 
 
 Resistance, Effect of Heat on Electric 
 
 Nearly all metallic conductors have 
 
 their electric resistance increased by an in- 
 crease of temperature. 
 
 The carbon conductor of an incandescent elec- 
 tric lamp, on the contrary, has its resistance 
 decreased when raised to electric incandescence. 
 The decrease amounts to about three-eighths of its 
 resistance when cold. 
 
 The effects of heat on electric resistance may be 
 summarized as follows: 
 
 (i.) The electric resistance of metallic conduc- 
 tors increases as the temperature rises. In some 
 alloys this increase is small. 
 
 (2.) The electric resistance of electrolytes de- 
 creases as the temperature nses. 
 
 (3.) The electric resistance of dielectrics and 
 non-conductors decreases as the temperature rises. 
 
 RESISTANCE AND CONDUCTIVITY OF PURE 
 COPPER AT DIFFERENT TEMPERATURES. 
 
 v 
 
 
 to 
 
 w JJ 
 
 
 
 
 
 V 
 
 o 
 
 5 
 
 " 2 
 
 V 
 
 o 
 
 B 
 
 t* ^ 
 
 
 a 
 
 S rt 
 
 
 
 11 
 
 I 
 
 1 
 
 B ^ 
 
 I 
 
 o 
 
 3 
 "O 
 
 
 
 
 
 V B 
 
 gj 
 
 8 
 M 
 
 
 o 
 
 
 
 00000 
 
 I.OOOOO 
 
 16 
 
 .06168 
 
 .94190 
 
 I 
 
 00381 
 
 .99624 
 
 17 
 
 .06563 
 
 .93841 
 
 a 
 
 00756 
 
 .99250 
 
 18 
 
 .06959 
 
 93494 
 
 3 
 
 01135 
 
 .98878 
 
 '9 
 
 07356 
 
 .93148 
 
 4 
 
 S 
 
 01515 
 01896 
 
 .98508 
 .98139 
 
 20 
 21 
 
 .07742 
 .08164 
 
 .928x4 
 .62452 
 
 6 
 
 02280 
 
 97771 
 
 22 
 
 08553 
 
 .92121 
 
 I 
 
 02663 
 
 03048 
 
 97406 
 .97042 
 
 2 3 
 24 
 
 .08954 
 09365 
 
 .91782 
 9'445 
 
 9 
 
 03435 
 
 .96679 
 
 25 
 
 .09763 
 
 .91110 
 
 10 
 
 03822 
 
 .96319 
 
 26 
 
 0161 
 
 .90776 
 
 ii 
 
 04199 
 
 9597 
 
 27 
 
 0567 
 
 .90443 
 
 12 
 
 04599 
 
 95603 
 
 28 
 
 1972 
 
 .90113 
 
 >3 
 
 04990 
 
 95247 
 
 29 
 
 1382 
 
 .89784 
 
 4 
 
 05406 
 
 .94893 
 
 30 
 
 . 1782 
 
 .89457 
 
 15 
 
 05774 
 
 94541 
 
 
 
 
 (Latimer Clark.) 
 
 Resistance, Electric The ratio be- 
 tween the electromotive force of a circuit 
 and the current that passes therein. 
 
 The reciprocal of electrical conductivity. 
 Resistance can be defined as the reciprocal of 
 electrical conductivity because even the best 
 electrical conductors possess appreciable resist- 
 ance. 
 
 Ordinarily the resistance of a circuit may be 
 conveniently regarded as that which opposes or 
 resists the passage of the current. Strictly speak- 
 ing, however, this is not true, since from O&m's 
 law (See Law of Ohm, or Law of Current 
 Strength} 
 
 E 
 
 C = , from which we obtain 
 R 
 E 
 R = , which shows that resistance is a 
 
 C 
 
 ratio between the electromotive force that causes 
 the current and the current so produced. 
 
 Resistance may be expressed as a velocity. 
 The dimensions of resistance in terms of the 
 electro-magnetic units are 
 L 
 
 (See Units, Electro- Magnetic.) But these are the 
 dimensions of a velocity, which is the ratio of the 
 distance passed over in unit time. Resistance may 
 therefore be expressed as a velocity. 
 
Res.] 
 
 453 
 
 [Res. 
 
 "The resistance known as 'one ohm' is in. 
 tended to be io9 absolute electro-magnetic units, 
 and, therefore, is represented by a velocity of icP 
 centimetres or 10,000,000 metres (one earth quad- 
 rant) per second." (Sylvanus Thompson.) 
 
 Resistance may be represented by a velocity, 
 one ohm being the resistance of a wire, which, 
 if moved through a unit field of force at the rate 
 of 1,000,000,000 (lo 9 ) centimetres per second will 
 have a current of one ampere generated in it. 
 (See Resistance, Ohmic. Resistance, Spurious.) 
 
 The true value of the ohm is exactly to 9 centi- 
 metres. The material standards employed, *. e., 
 the B. A. and "legal " ohms, are not absolutely 
 of this value. 
 
 One mil-foot of soft copper at 10.22 degrees C. 
 or 50.4 degrees F. has the standard resistance of 
 exactly 10 legal ohms ; at 15.56 or 59.9 degrees 
 F., it has a resistance of 10.20 legal ohms, and 
 at 23.9 degrees C. or 75 degrees F., 10.53 legal 
 ohms. 
 
 RESISTANCE. 
 
 Resistance of Wires of Pure Annealed Copper at o" C. 
 (Density = <?.?.) 
 
 C ; 
 
 
 
 Resistance of Wire of Pure An- 
 
 t t 
 
 &> QJ 
 
 v a 
 a P 
 
 s Mi 
 
 nealed Copper at O degree C. 
 
 |j ! 
 
 c? bboj 
 
 01 qj O Jz 
 
 Ohms 
 
 Metres 
 
 Ohms 
 
 .2 M 
 
 b*. CD 
 
 3 5 *** fi 
 
 per 
 
 per 
 
 per 
 
 
 
 
 *~ 
 
 Kilometre. 
 
 Ohm. 
 
 Kilogramme. 
 
 5 
 
 '75 
 
 5-7 
 
 .8 
 
 1230.5 
 
 .00456 
 
 4-4 
 
 135.28 
 
 7-4 
 
 i. 06 
 
 944.38 
 
 .00784 
 
 3-9 
 
 106.35 
 
 9-5 
 
 1.35 
 
 722 
 
 .0128 
 
 3-4 
 
 80.8 
 
 12.5 
 
 i. 80 
 
 563-92 
 
 .0222 
 
 3 
 
 62.93 
 
 16 
 
 2-3 
 
 439-0? 
 
 .0365 
 
 7 
 
 51 
 
 19.8 
 
 2.8 
 
 355.65 
 
 557 
 
 4 
 
 40.23 
 
 25 
 
 3-6 
 
 281 
 
 .088 
 
 .2 
 
 33.82 
 
 29 
 
 4.2 
 
 236.08 
 
 a 3 
 
 
 27-95 
 
 36 
 
 
 I95-I5 
 
 .185 
 
 .8 
 
 22.7 
 
 44 
 
 6-3 
 
 158.08 
 
 .278 
 
 .6 
 
 17.89 
 
 56 
 
 8 
 
 124.9 
 
 448 
 
 5 
 
 15.75 
 
 63 
 
 9.1 
 
 109.75 
 
 574 
 
 4 
 
 13-7 
 
 73 
 
 10.5 
 
 95-651 
 
 -763 
 
 3 
 
 11.84 
 
 85 
 
 12 
 
 82.42 
 
 1-03 
 
 .2 
 
 10.06 
 
 100 
 
 '4 
 
 70.247 
 
 1.42 
 
 .1 
 
 8-47 
 
 119 
 
 17 
 
 59.024 
 
 2.02 
 
 
 6-99 
 
 144 
 
 20 
 
 48.782 
 
 *-95 
 
 .O 
 
 5.66 
 
 178 
 
 25 
 
 39-5I5 
 
 4.19 
 
 .8 
 
 4-47 
 
 225 
 
 S 2 
 
 31.225 
 
 7.21 
 
 7 
 
 2.83 
 
 ' 294 
 
 42 
 
 23.9 
 
 12.3 
 
 .6 
 
 2.52 
 
 400 
 
 57 
 
 17-56 
 
 ' 22.78 
 
 5 
 
 1.74 
 
 576 
 
 81 
 
 12.305 
 
 46. 8 1 
 
 4 
 
 I-I75 
 
 902 
 
 122.4 
 
 8.173 
 
 110.41 
 
 34 
 
 .808 
 
 1251 
 
 177.9 
 
 5.622 
 
 222.55 
 
 3 
 
 .7181 
 
 1607 
 
 228.5 
 
 4-377 
 
 367-2 
 
 .24 
 
 .4026 
 
 2508 
 
 357 
 
 2.801 
 
 895.36 
 
 .a 
 
 .2797 
 
 3614 
 
 
 -945 
 
 1.857.6 
 
 .16 
 
 .179 
 
 559 
 
 803.1 
 
 1-245 
 
 4,489 
 
 .12 
 
 .1007 
 
 9929 
 
 1428 
 
 7 
 
 I4.I79 
 
 .1 
 
 .0699 
 
 14369 
 
 2056 
 
 .486 
 
 29.549 
 
 .08 
 
 .0447 
 
 24570 
 
 3213 
 
 3" 
 
 78,943 
 
 .06 
 
 0252 
 
 
 5713 
 
 >73 
 
 227,515 
 
 .04 
 
 OII2 
 
 88878 
 
 12848 
 
 .078 
 
 1142,405 
 
 The following table, based on Matthiessen's 
 measurements, gives the relative resistances of 
 equal lengths and cross-sections of a number of 
 different substances used in electricity as com. 
 pared with silver. 
 
 LEGAL MICROHMS. 
 
 
 Resistance in Microhms 
 
 
 
 at o degree C. 
 
 
 NAMES OF METAL. 
 
 
 Relative 
 Resistance. 
 
 
 
 
 Cubic 
 Centimetre. 
 
 Cubic Inch. 
 
 
 Silver, annealed... 
 
 1.504 
 
 0.5921 
 
 
 Copper, annealed. 
 Silver, hard drawn 
 
 1.598 
 1.634 
 
 0.6292 
 0.6433 
 
 '063 
 
 Copper, h'rd dr"wn 
 
 * 
 1.634 
 
 0.6433 
 
 !o86 
 
 Gold, annealed. . . . 
 
 2.058 
 
 0.8102 
 
 369 
 
 Gold, hard drawn. 
 Aluminium, ann'ld 
 
 2.094 
 2.912 
 
 0.8247 
 1.147 
 
 393 
 935 
 
 Zinc, pressed 
 
 5.626 
 
 2.215 
 
 3-741 
 
 Platinum, annealed 
 
 9.057 
 
 3-565 
 
 6. 022 
 
 Iron, annealed.. . 
 
 9.716 
 
 3-825 
 
 6.460 
 
 Nickel, annealed . 
 
 12.47 
 
 4.907 
 
 8.285 
 
 Tin, pressed 
 
 13.21 
 
 5-202 
 
 8.784 
 
 Lead, pressed... . 
 German silver... . 
 
 19.63 
 20.93 
 
 7 .728 
 8.240 
 
 13-05 
 13.92 
 
 Antimony, pressed 
 
 35-5 
 
 13.98 
 
 23.60 
 
 
 
 77 1C 
 
 
 Bismuth, pressed. . 
 
 94-32 
 
 67 *5 
 
 87-23 
 
 (Ayrton.) 
 
 The above resistances are for chemically pure 
 substances only. Slight impurities produce a very 
 considerable increase in the resistance. 
 
 Resistance, Electric, of Liquids -- 
 
 The resistance offered by a liquid mass to 
 the passage of an elec- 
 trie current 
 
 As a rule the electric re- 
 sistances of liquids, with 
 the single exception of mer- 
 cury, are enormously high- 
 er than those of metallic 
 bodies. 
 
 To roughly determine 
 the resistance of a liquid, 
 a section is taken between 
 two parallel metallic plates 
 A and B, Fig. 489, placed 
 as shown in the figure, and 
 an electric current is pass- 
 ed between them. 
 
 In order to accurately 
 vary the size of the plates 
 immersed in the liquid, and 
 
 4$<). Resistance oj 
 Liquid. 
 
 (Hospitalier. ) 
 
 hence the area of cross-section of the liquid con- 
 ductor, as well as the distance between the plates, 
 the apparatus shown in Fig. 490 may be used, in 
 
K*S.J 454 [Res. 
 
 TABLE OF CONDUCTING POWERS AND RESISTANCES IN OHMS B. A. UNITS. 
 
 NAMES OF METALS. 
 
 Conducting 
 power at o de- 
 gree C. 
 
 Resistance of a 
 wire one foot 
 long weighing 
 one grain. 
 
 Resistance of a 
 wire one metr- 
 long weighing 
 one gramme. 
 
 Resistance of a 
 wire one foot 
 !ng nftro '"eh 
 in diameter. 
 
 Resistance of a 
 wire one metre 
 long, one milli- 
 metre in diam- 
 eter. 
 
 Approximate 
 percentage of 
 variation in re- 
 sistance for i de- 
 gree of tempera- 
 ture at 2odeg. 
 
 
 
 0.2214 
 0.2421 
 0.2064 
 0.2106 
 0.5849 
 0-5950 
 0.06822 
 0.5710 
 3-536 
 1.2425 
 1.0785 
 1.317 
 3- a 36 
 3-324 
 5-54 
 18.740 
 
 4.243 
 
 3.652 
 8.391 
 
 0.1544 
 o. 1689 
 o. 1440 
 0.1469 
 0.4080 
 0.4150 
 0.05759 
 0.3983 
 2.464 
 0.7522 
 0.8666 
 0.9184 
 2.257 
 2.3295 
 
 3-525 
 13.071 
 
 2.959 
 1.850 
 1.668 
 
 9.936 
 9- J 5i 
 9.718 
 9.940 
 12.52 
 12.74 
 17.72 
 32.22 
 55-9 
 59-4 
 75-78 
 80.36 
 
 U9-39 
 2:6.0 
 798.0 
 600.0 
 
 43-35 
 127.32 
 66.10 
 
 o 01957 
 o 02103 
 o 02057 
 o 02104 
 o 02650 
 o 02697 
 o 03751 
 o 07244 
 o 1166 
 o 1251 
 o 1604 
 o 1701 
 o 2527 
 o 457' 
 
 1 689 
 
 I 270 
 
 0.3140 
 
 0.2695 
 
 0.1399 
 
 o-377 
 
 
 100.00 
 
 
 0.388 
 
 Copper, hard drawn ..... 
 
 99-55 
 
 o-355 
 
 
 77.96 
 
 
 
 Zinc, pressed ............ 
 
 29.02 
 
 0.365 
 
 
 
 16.81 
 13.11 
 12.36 
 8.32 
 4.62 
 1.24 
 
 
 
 
 
 0.365 
 0.387 
 0.389 
 o-354 
 
 O.O72 
 O.O3I 
 0.044 
 
 0.065 
 
 
 Antimony, pressed ...... 
 Bismuth, pressed.. . ...... 
 
 
 Platinum - silver, alloy, 
 
 
 German silver, hard or 
 
 
 Gold, silver, alloy, hard 
 
 
 
 
 which these distances are readily adjustable, as 
 shown. 
 
 Resistance, Equivalent A single 
 
 resistance which may replace a number of 
 separate resistances in a circuit without alter- 
 ing the value of the current traversing it. 
 
 Resistance, Essential A term 
 
 sometimes used instead of internal resist- 
 ance. 
 
 f*f- 49O. Apparatus for Measuring Resistance <tf 
 Liquid. 
 
 Resistance, External Secondary A 
 
 term proposed by Du Bois Reymond for the 
 change in the resistance of a circuit external to 
 the electric source when cataphoric action 
 takes place. (See Action, Cataphoric^) 
 
 " If the copper electrodes of a constant battery 
 be placed in a vessel filled with a solution of 
 cupric sulphate and from each electrode there 
 projects a cushion saturated with this fluid, then, 
 
 (Jenkin.) 
 
 on placing a piece of muscle, cartilage, vegetable 
 tissue, or even a prismatic strip of coagulated 
 albumen across these cushions, we observe, that 
 very soon after the circuit is closed, there is a 
 considerable variation of the current. * * * 
 This phenomenon is called ' external secondary 
 resistance.' " (Landois and Sterling.) 
 
 Resistance, Extraordinary A term 
 
 sometimes employed instead of external re- 
 sistance. (See Resistance, External Secon- 
 dary^) 
 
 Resistance, False A resistance aris- 
 ing from a counter electromotive force and 
 not directly from the dimensions of the circuit, 
 or from its specific resistance. 
 
 The false resistance of any circuit is sometimes 
 called its spurious resistance. (See Force, Electro- 
 motive, Counter. Resistance \ Spurious.) 
 
 Resistance, Inductionless A term 
 
 sometimes used instead of non-inductive re- 
 sistance. (See Resistance, Non-Inductive.) 
 
 Resistance, Inductive A resistance 
 
 which possesses self-induction. 
 
 Resistance, Insulation The re- 
 sistance of a line or conductor existing be- 
 tween the line or conductor and the earth 
 through the insulators, or between the two 
 
Bes.j 
 
 wires of a cable through the insulating 
 material separating them. 
 
 The insulation resistance of a telegraph line is 
 the resistance that exists between the line and the 
 earth, through its insulators. The insulation re- 
 sistance will decrease as the length of line in- 
 creases, since for any increase in the number of 
 poles and insulators there is a proportional in- 
 crease in the area of cross-section of the insula- 
 ting supports. 
 
 If the insulation resistance is 1,000,000 ohms 
 per mile, in a line 200 miles m length, the insula- 
 tion resistance is only 5,000 ohms, that is, 
 
 1,000,000 
 
 = 5,000 ohms. 
 200 
 
 Resistance, Joint, of Parallel Circuits 
 
 The joint resistance of two parallel 
 
 circuits is determined by means of the follow- 
 ing formula ; 
 
 R =FTT- 
 
 Where R = the joint resistance of any two cir- 
 cuits whose separate resistances are respectively 
 r and r . 
 
 When there are three resistances r, r' and r*, 
 in parallel, the joint resistance, 
 
 . , .. 
 
 rr -|-rr -j-rr 
 
 (See Circuits, Varieties of. ) 
 
 Resistance, Magnetic The recipro- 
 cal of magnetic permeability or conducti- 
 bility for lines of magnetic force. 
 
 Resistance offered by a medium to the 
 passage of the lines of magnetic force through 
 it. 
 
 The magnetic resistance of the circuit of the 
 lines of force is reduced by forming the circuit of 
 a medium having a high magnetic permeability, 
 such as soft iron. This is accomplished by the 
 armature or keeper of a magnet, or by the iron in 
 an iron-clad magnet. (See Magnet, Iron- Clad.) 
 
 Resistance, Measurement of 
 
 Methods employed for determining the re- 
 sistance of any circuit or part of a circuit. 
 
 Numerous methods are employed for this pur- 
 pose. Amon^ these are : 
 
 (l .) TJie use of a resistance box with a Wheat- 
 stone bridge, by opposing or balancing the un- 
 known resistance against a known resistance. 
 (See Balance, Wheatstone' 1 s Electric.) 
 
 [Res. 
 
 (2.) The differential galvanometer. (See Gal- 
 vanometer, Differential^) 
 
 (3 . ) The method of substitution. 
 
 (4.) Comparison of the deflections of a gal- 
 vanometer. 
 
 Method of Substitution. A resistance-box R, 
 Fig. 491, galvanometer G, and the resistance x, 
 that is to be measured, are placed in the direct 
 circuit of the battery B, by means of conductors 
 of such thick wire that their resistance can be 
 neglected. 
 
 The deflection of the ga'vanometer is first 
 measured with x, in circuit, and no resistance in 
 tne box R. The resistance x, is then cut out of 
 the circuit by placing a thick copper wire across 
 the terminals of the mercury cups at mm', and 
 resistances unplugged in R, until the same deflec- 
 tion is obtained. Then, if the electromotive force 
 of the battery has remained constant, the resist- 
 ances unplugged equal the unknown resistance. 
 
 For full description of the various methods of 
 determining resistance the reader is referred to 
 ''Ayrton's Practical Electricity,'' ''Kempe's 
 Handbook of Testing," or other standard books 
 on electrical measurements. 
 
 in' 
 
 Fig. 49 z S^stitution Method. 
 
 When several resistances are placed in series ill 
 any circuit, by measuring the difference of poten- 
 tial at their terminals, their values can be deter, 
 mined by simple calculation, being directly pro- 
 portional to these differences of potential. 
 
 This method is especially applicable to the 
 measurement of such low resistances as the arma- 
 tures of dynamo-electric machines. 
 
 Resistance, Non-inductive A re- 
 sistance m which self-induction is practically 
 absent. 
 
 An incandescent lamp filament is practically a 
 non-inductive resistance when compared with a 
 coil on the helix of an electro-magnet. 
 
 Resistance of Human Body. (See Body, 
 Human, Resistance of.) 
 
Res.] 
 
 456 
 
 [Res. 
 
 Resistance of Toltaic Arc. (See Arc, 
 Voltaic, Resistance of.) 
 
 Resistance, Ohmic The true resist- 
 ance of a conductor due to its dimensions 
 and specific conducting power, as distin- 
 guished from the spurious resistance produced 
 by a counter electromotive force. (See Force, 
 Electromotive, Counter. Resistance, Spuri- 
 ous.) 
 
 The term ohmic resistance must be regarded as 
 a pleonasm. Its use can only be permitted in 
 contradistinction to counter electromotive force 
 resistance. True and spurious resistance would 
 seem preferable. 
 
 Resistance or Cell, Selenium A 
 
 mass of crystalline selenium, the resistance of 
 which is reduced by placing it in the form of 
 narrow strips between the edges of broad 
 conducting plates of brass. 
 
 The selenium employed for this purpose is the 
 vitreous variety which has been fused and main* 
 tained for several hours at about 220 degrees C., 
 by means of which its resistance is reduced. 
 
 By exposure to sunlight, the resistance of a 
 selenium cell is decreased fully one-half its re- 
 sistance in the dark. The selenium cell is used 
 in the photophone. (See Photophone.) 
 
 Resistance or Reducteur for Voltmeter. 
 
 (See Reducteur or Resistance for Volt- 
 meter.) 
 
 Resistance, Secondary A term 
 
 sometimes used in place of external secon- 
 dary resistance. (See Resistance, External 
 Secondary) 
 
 Resistance Slide. (See Slide, Resist- 
 ance^ 
 
 Resistance, Specific The particular 
 
 resistance which a substance offers to the 
 passage of electricity through it. 
 
 In absolute measure, the resistance in ab- 
 solute units between the opposite faces of a 
 centimetre cube of the given substance. 
 
 In the practical system the resistance given 
 in ohms. 
 
 Resistance, Specific Conduction 
 
 A term sometimes used instead of specific 
 resistance. (See Resistance, Specific!) 
 
 Resistance, Specific, of Liquids - 
 
 The resistance of a given length (one centi- 
 metre) and area of cross-section (one square 
 centimetre) of any liquid as compared with 
 the resistance of an equal length and cross- 
 section of pure silver. 
 
 The resistance of a few common liquids and so. 
 lutions is here given from Lupton: 
 
 Water, pure, at 75 degrees C. . I.l88 X IO ohms, 
 i. e., 118,800,000. 
 
 Water at 4 degrees C 9-IQo X IO* 
 
 Water at n degrees C 3-4OO X IO* * 
 
 Dilute hydrogen sulphate (sul- 
 phuric acid) at 18 degrees 
 C., 5 per cent, acid 4.88 
 
 Dilute hydrogen sulphate at 
 1 8 degrees C., 3 per cent, 
 acid 1.38 ohms. 
 
 Nitric acid at 18 degrees C., 
 
 density 1.32 i.6l 
 
 Saturated solution of copper 
 sulphate (blue vitriol) at 10 
 degrees C 29.30 
 
 Saturated solution of zinc sul- 
 phate at 14 degrees C 21.50 ' 
 
 Hydrochloric acid, 20 per cent, 
 acid, at 18 degrees C 1.34 " 
 
 Sal ammoniac, 25 percent, salt 2.53 * 
 
 Common salt, saturated, at 13 
 degreesC ...5.30 
 
 It will be observed that the resistance varies 
 considerably with differences of temperature. 
 
 Resistance, Spurious A false re- 
 sistance arising from the development of a 
 counter electromotive force. (See Resist- 
 ance, False. Force, Electromotive, Coun- 
 ter.) 
 
 The spurious resistance is also called the false 
 resistance, in order to distinguish it from the true 
 or ohmic resistance. (See Resistance, Electric.) 
 
 Resistance, Standard A resistance 
 
 used for comparison with or the determina^ 
 tion of unknown resistances. 
 
 A committee appointed by the American Insti- 
 tute of Electrical Engineers in 1890 reported the 
 following values for the standard resistance of 
 copper wire; at O degree C. in B. A. U. and legal 
 ohms, viz.: 
 
Res.] 
 
 457 
 
 [Res. 
 
 STANDARD RESISTANCE AT o* C. 
 
 B. A. U. Legal Ohms. 
 Meter-mfllimetre," 
 
 " soft copper "... .02057 .02034 
 
 Cubic centimetre... .000001616 .000001598 
 
 Mil-foot" 9.720 9.612 
 
 Resistance, Tables of Tables in 
 
 which the resistance of equal lengths and 
 cross-sections of different substances is 
 given in ohms, or other units of resistance. 
 
 Resistance Thermometer. (See Ther- 
 mometer, Electric Resistance?) 
 
 Resistance, Transition A term 
 
 sometimes used in electro-therapeutics for a 
 change in the value of the resistance caused 
 by polarization. 
 
 Whenever an electric current passes through 
 a fluid substance and decomposes the fluid, the 
 decomposition products collect on the electrodes 
 and produce an increase in the resistance of the 
 circuit. 
 
 Resistance, True The resistance 
 
 which a conductor offers to the passage of a 
 current by reason of its dimensions and spe- 
 cific conducting power, as distinguished from 
 a spurious resistance produced by a counter 
 electromotive force. 
 
 The true resistance is sometimes called the 
 ohmic resistance. (See Resistance, Spurious. 
 Resistance, Ohmic.} 
 
 Resistance, Unit of Such a resist- 
 ance that unit difference of potential is re- 
 quired to cause a current of unit strength 
 to pass. (See Ohm. Potential, Electric. 
 Potential, Difference of.) 
 
 Resistance, Unit of, Absolute The 
 
 one thousand millionth of an ohm. (See 
 Ohm. Units, Practical?} 
 
 Resistance, Unit of, Jacobi's The 
 
 electric resistance of 25 feet of a certain 
 copper wire weighing 345 grains. 
 
 Another unit of electric resistance proposed 
 by Jacobi was the resistance of a copper wire 
 one metre in length and one millimetre in diame- 
 ter. 
 
 Resistance, Unit of, Matthiessen's 
 
 . The resistance of one statute mile of pure 
 annealed copper wire -iV inch in diameter at 
 
 15.5 degrees C, and determined by him to be 
 13.59 B. A. ohms. 
 Resistance, Unit of, Varley's The 
 
 resistance of one statute mile of a special 
 copper wire ^ inch in diameter. 
 
 Varley's unit was afterwards adjusted by him 
 to equal 25 Siemens Mercury Units. 
 
 Resistance, Variable A resistance 
 
 the value of which can be readily varied. 
 Variable resistances are either : 
 (I.) Automatically variable resistances; or 
 (2.) Non- automatically variable resistances. 
 
 Resistance, Variable, Automatic 
 
 A resistance the value of which can be auto- 
 matically varied. 
 
 A pile of carbon plates resting on one another, 
 in loose contact, offers a high resistance, but when 
 compressed as by an electro-magnet their resist- 
 ance is lowered. Brush employs such an auto- 
 matic resistance in the regulation of his dynamo- 
 electric machine. (See Regulation, Automatic.) 
 
 Resistance, Variable Non-Antomatic 
 
 A resistance the value of which is regulated 
 by hand. (See Rheostat?) 
 
 Resistance, Virtual A term some- 
 times employed instead of impedance. (See 
 Impedance?) 
 
 Resonance, Electric The setting 
 
 up of electric pulses in open-circuited con- 
 ductors, by the action of pulses in neighboring 
 conductors. 
 
 Electric resonance, like acoustic resonance, 
 takes place when a correspondence exists between 
 the time-rate of vibration of the body producing 
 the resonance, and the body in which the reso- 
 nance is produced. In other words, when the 
 wave lengths are the same in the two bodies, or 
 when the wave length in one is equal to a half 
 wave length, or some definite multiple of a half 
 wave length of the other. 
 
 Partial resonance may occur, when there is a 
 small difference between the wave lengths of the 
 two bodies. Beyond certain limits, however, this 
 is so small as to be practically absent. 
 
 When an electrical pulse is started in a con- 
 ductor by the discharge of a Leyden jar, a side flash 
 spark is obtained in the alternative path, between 
 the discharge points. The length of this spark has 
 its greatest value, when the time required for the 
 
Res.] 
 
 458 
 
 O 
 
 pulse to travel backwards and forwards along the 
 conducting wires, is exactly equal to the time of 
 a complete oscillation in the circuit, or when the 
 length of the open-circuit wires is equal to half a 
 wave length, or some multiple oi half a wave 
 length. 
 
 The fact that the length of the spark is greatest 
 when certain relations exist between the dimen- 
 sions of the two circuits, shows that the time-rate 
 of an electrical pulse in any circuit depends on 
 the dimensions of that circuit. 
 
 In the case of acoustic resonance, in order that 
 one tuning fork may be able to excite vibrations in 
 another, the fork producing or exciting the vibra- 
 tion must be strictly in unison with the fork in 
 which the vibrations are excited, and any varia- 
 tions produced in the rate of vibration of the 
 sounding fork, by overloading it, or, in other 
 words, by altering its dimensions, checks the 
 effects of its resonance. 
 
 In a similar manner, any alterations in the di- 
 mensions of the circuit, checks or diminishes the 
 effects of electric reson- 
 ance in a neighboring cir- 
 cuit, which was previously 
 in unison with it. This 
 has been experimentally 
 shown by Hertz as fol- 
 lows: 
 
 An induction coil A, 
 Fig. 492, has the terminals 
 of its secondary connected 
 to an open rectangular cir- 
 cuit provided with spark- 
 ing terminals, I, and 2, 
 called a spark micrometer. 
 Under certain conditions, 
 when the discharge oc- 
 curs at the terminals B, 
 of the ordinary discharger, sparks are produced 
 by electric resonance in the electric resonator 
 formed by the spark micrometer at M. 
 
 Supposing, now, that a certain character of spark 
 is obtained at the terminals B, that is, a cei, 
 tain velocity of electrical pulsations is obtained 
 which depends on the nature of the spark; sup- 
 pose, moreover, that the dimensions of the spark 
 micrometer or electric resonator are such that the 
 greatest length of spark is obtained. Then, any 
 alteration in the character of these sparks, be- 
 tween the terminals at B, varies the intensity of 
 C'he sparks in the spark micrometer. 
 
 3 for example, the apparatus be arranged 
 
 B 
 
 O 
 
 1 t 
 
 
 Fig. 49 a. Electrical 
 Resonance. 
 
 as shown in Fig. 493, in which one of the sec- 
 ondary terminals of the induction coil has con- 
 nected with it a copper wire i g h. The sparks at 
 M, decrease considerably. When, however, the 
 conductor C, is connected with the free end H, 
 of this additional conductor, then this effect is 
 not observed, as is shown by the fact that when 
 the conductor C, is attached at the point G, it 
 produces no effect on it. 
 
 Fig. 493. Electric Resonance. 
 
 In another experiment with the same apparatus, 
 matters may be arranged that the sparks in the 
 micrometer circuit pass singly. When, now, an- 
 other conductor C', is attached to K, a stream of 
 sparks immediately passes. 
 
 It would appear, therefore, from the above ex- 
 periments, that when two circuits are taken, 
 having as nearly as possible the same vibration 
 periods, any alteration in the dimensions of either 
 will prevent one from producing electrical reso- 
 nance in the other. 
 
 In the above experiments Hertz demonstrated 
 the following facts, viz., 
 
 (I.) The sparks in the micrometer circuit are 
 smaller when the discharges take place between 
 points, or a point and a plate, instead of between 
 knobs. 
 
 (2.) The micrometer sparks are feebler in rare- 
 fied gas than in air at ordinary pressures. 
 
 (3.) Extremely slight differences in the nature 
 of secondary sparks produce considerable differ- 
 ence in the length of the micrometer sparks. 
 
 Hertz found the above results were obtained 
 when the secondary sparks were of a brilliant 
 color, and were attended by a sharp crack. 
 
 (4.) The length of the spark in the micrometer 
 
Res.] 
 
 459 
 
 circuit varies with the length of the micrometer 
 circuit. 
 
 This, of course, follows from the fact that any 
 alteration of the length in the micrometer circuit, 
 produces, by electrical retardation, a correspond- 
 ing alteration in the time of the electrical pulses. 
 
 (5.) No effect is produced in the length ot the 
 micrometer spark by variations in the material, 
 the resistance, or the diameter of the wire forming 
 the micrometer circuit. 
 
 This is probably because the rate of propaga- 
 tion of electrical pulses along a conductor, de- 
 pends mainly on the capacity of the conductor, 
 and on its co-efficient of self-induction, and only 
 to a slight extent on its resistance. 
 
 (6.) The length of wire connecting the microm- 
 eter circuit with the secondary circuit has but 
 little effect, provided such length does not exceed 
 a few metres. 
 
 Local disturbances, therefore, must traverse 
 conductors without undergoing any appreciable 
 change. 
 
 (7. ) The position of the point on the micrometer 
 circuit connected with the secondary circuit, is of 
 the greatest importance. 
 
 When the point on the micrometer circuit is 
 situated symmetrically with respect to the two mi- 
 crometer knobs, variations of potential will reach 
 the terminals in the same phase, and there will be 
 but little effect, as seen by the sparks between the 
 micrometer knobs. Such a point on the microm j 
 eter knobs is called the null point, or it is called as 
 in a corresponding case in acoustics, a nodal point. 
 (See Point, Null. Point, Nodal.} 
 
 (8.) When the conductors are of sufficient 
 length, their approach produces disturbances in 
 a previously adjusted and quiet spark microm- 
 eter, just as the approach of a conductor would. 
 
 Probably one of the most curious effects con- 
 nected with the phenomena of electrical resonance 
 is that pointed out by Lodge, viz. : that when the 
 spark from a secondary circuit is so placed that 
 the light is visible from a micrometer circuit, the 
 effects of the discharge are greatly increased. 
 Lodge also found that the light from burning 
 magnesium wire, or, in general, light rich in the 
 ultra-violet rays, produces the same effect. 
 
 Resonator, Electric An apparatus 
 
 employed by Hertz in his investigations on 
 electric resonance. (See Resonance, Elec- 
 tric^ 
 
 An Jrfric resonator consists essentially of an 
 
 open-circuited conductor, or circuit of such dimen- 
 sions that electro-magnetic waves or pulses are 
 propagated through it at the same rate as those 
 which are occurring in a neighboring circuit 
 from which electro-magnetic radiation is tak- 
 ing place. Under these circumstances electro- 
 magnetic pulses are set up sympathet cally by 
 resonance in the open circuit of the resonator, like 
 the sympathetic vibrations in a tuning fork, when 
 placed near another vibrating tuning fork, which 
 is giving off sound waves of exactly the same 
 period of vibration as its own. 
 
 Resonator, Electro-Magnetic A 
 
 term applied to the Hertz spark micrometer, 
 in which electro-magnetic waves are produced 
 by electric resonance. (See Resonance, Elec- 
 tric.) 
 
 Resultant. In mechanics, a single force 
 that represents in direction and intensity the 
 effects of two or more separate forces. 
 
 The separate forces are called the components. 
 (See Components.) 
 
 Retardation. A decrease in the speed of 
 telegraphic signaling caused either by the 
 induction of the line conductor on itself, or 
 by mutual induction between it and neighbor- 
 ing conductors, or by condenser action, or by 
 all. 
 
 The line must receive a certain charge before 
 a current sent into it at one end can produce a 
 signal at the other end. This charge will de- 
 pend on the length and surface of the wire, on the 
 neighborhood of the wire to the earth or other 
 wires, and on the nature of the insulating mate 
 rial between the wire and neighboring conductors. 
 This results in a charge given to the wire which 
 is lost as a current for signaling. The greater the 
 electrostatic capacity of the line wire, the greater 
 will be the retardation in signaling. (See Capa- 
 city, Specific Inductive. Dielectric. Capacity, 
 Electrostatic. Induction, Electro-Dynamic.) 
 
 Retardation in signaling is produced by the 
 following causes : 
 
 (i.) Self-Induction which produces extra cur- 
 rents. (See Induction, Self. Currents, Extra.) 
 
 The extra current on making, retards the be- 
 ginning of the signal ; the extra current on break- 
 ing, retards its stopping. 
 
 (2.) Mutual Induction between the line con 
 ductor and neighboring conductors. 
 
Ret.] 
 
 460 
 
 [Rhe. 
 
 (3.) The Magnetic Inertia or Lag, or the time 
 required to magnetize or demagnetize the core of 
 the electro -magnetic receptive devices used on 
 the line. 
 
 (4.) By Condenser Action, the cable acting as a 
 condenser. 
 
 Retardation, Electric A retarda- 
 tion in the starting or stopping of an electric 
 current, arising from self-induction. (See In- 
 duction, Self. Retardation?) 
 
 Retardation, Inductive A retarda- 
 tion in the appearance of a signal at the dis- 
 tant end of a cable, produced by the action of 
 induction. (See Retardation?) 
 
 Retardation, Magnetic - A retarda- 
 tion in the magnetization or demagnetization 
 of a substance due to magnetic lag. (See 
 Retardation. Lag, Magnetic?) 
 
 Retarding, Electrically 
 
 Decreas- 
 
 ing the speed of telegraphic signaling, by 
 means of induction. (See Retardation?) 
 
 Retentivity, Magnetic A term pro- 
 posed by Lament in place of coercive force, 
 or the power possessed by a magnetizable 
 substance of resisting magnetization or de- 
 magnetization. (See Force, Coercive?) 
 
 Return Circuit. (See Circuit, Return?) 
 
 Return, Earth (See Earth Re- 
 
 tiirn?) 
 Return Ground. (See Ground-Return?) 
 
 Return Wire or Conductor. (See Wire, 
 Return?) 
 
 Returns. In a system of distribution, those 
 conductors through which the current flows 
 back from the electro-receptive devices to 
 the source. (See Leads?) 
 
 The word returns is sometimes used in a sys- 
 tem of distribution by parallel circuits, to distin 
 guish between the conductor by which the cur- 
 rent goes back or returns from the receptive de- 
 vices to the dynamo, and the conductor that leads 
 it to the receptive devices. The term leads is, 
 however, often applied to both conductors. 
 
 Reverse-Induced Current (See Current, 
 Reverse-Induced?) 
 
 Reversed Currents. (See Currents. Re- 
 versed?) 
 
 Reverser, Current A switch, or 
 
 other apparatus, designed to reverse the di- 
 rection of a current. 
 
 Reversible Bridge. (See Bridge, Rever- 
 sible?) 
 
 Reversible Heat. (See Heat, Reversible?) 
 
 Reversibility of Dynamo. The ability 
 of a dynamo to operate as a motor when tra- 
 versed by an electric current. (See Motor, 
 Electric?) 
 
 Reversing Gear of Electric Motor. (See 
 Motor, Electric, Reversing Gear of?) 
 
 Reversing Key. (See Key, Reversing?) 
 
 Reversing Key of Quadruplex Tele- 
 graphic System. (See Key, Reversing, of 
 Quadruple x Telegraphic System?) 
 
 Reversing Magnetic Field. (See Field, 
 Magnetic, Reversing?) 
 
 Rheochord. A word formerly employed 
 instead of rheostat. (See Rheostat?) 
 
 Rheometer. A word formerly employed 
 for any device for measuring the strength of 
 a current. 
 
 This word is now obsolete and is replaced by 
 the word galvanometer. (See Galvanometer.'] 
 
 Rheomotor. A word formerly employed 
 to designate any electric source. 
 
 This word is now obsolete, and replaced by 
 the various names of the different electric sources. 
 (See Source, Electric.") 
 
 Rheophore. A word formerly employed to 
 indicate a portion of a circuit conveying a cur- 
 rent and capable of deflecting a magnetic 
 needle placed near it. (Obsolete.) 
 
 Rheoscope. A word formerly employed in 
 place of the present word galvanoscope, foi 
 an instrument intended to show the presence 
 of a current, or its direction, but not to 
 measure its strength. (Obsolete.) 
 
 Rheoscope, Physiological A sensi- 
 tive nerve-muscle preparation employed to 
 determine the presence of an electric current. 
 (See Frog, Galvanoscope?] 
 
Rhe.] 
 
 461 
 
 [Kin. 
 
 A term sometimes applied in electro-thera- 
 peutics to the frog's legs preparation adapted 
 to show the presence of any electric current. 
 
 The physiological rheoscope is adapted to 
 show the presence of an electric current without 
 the use of a galvanometer. On the passage of 
 the electric current the frog's legs twitch con- 
 vulsively. 
 
 Rheostat. An adjustable resistance. 
 
 A rheostat enables the current to be brought 
 to a standard, i. e., to a fixed value, by adjusting 
 the resistance; hence the name. 
 
 The term rheostat is applied generally to a 
 readily variable resistance, the varying values of 
 which are known. 
 
 Rheostat, Dynamo-Balancing An 
 
 adjustable resistance whose range is sufficient 
 to balance the current of one dynamo against 
 another with which it is required to run in 
 parallel. 
 
 Rheostat, Water A rheostat the 
 
 resistance of which is obtained by means of a 
 mass of water of fixed dimensions. (See 
 Rheostat?) 
 
 Rheostat, Wheatstone's A form of 
 
 apparatus sometimes employed for an adjust- 
 able resistance. 
 
 This apparatus is very seldom employed in 
 accurate work. 
 
 The parallel cylinders A and B, Fig. 494, are 
 formed respectively of conducting and non-con- 
 ducting materials, the bare wire on which can be 
 wound from either 
 cylinder to the other. 
 When introduced into 
 a circuit, only the re- 
 sistance of that part 
 of the wire that is on 
 B, is introduced into 
 the circuit, since the 
 bare wire on A, is 
 short-circuited by the 
 metallic cylinder. 
 This rheostat is not 
 
 Fig. 494. 
 
 Rheostat. 
 
 very suitable for accurate measurements, owing 
 to the difficulty of invariably obtaining reliable 
 contacts. 
 
 Rheostatic Machine. (See Machine, 
 Rheostatic.) 
 
 Rheotorae. A word formerly employed 
 for any device by means of which a circuit 
 could be periodically interrupted. 
 
 This word is now obsolete, and is replaced by 
 interrupter. (See Interrupter.) 
 
 Rheotrope. A word formerly employed 
 for any device by which the current could 
 be reversed. 
 
 This word is now obsolete and replaced by 
 commutator or current reverser. (See Reverser^ 
 Current.) 
 
 Rhigolene. A highly volatile hydro-car- 
 bon obtained during the distillation of coal 
 oil, and employed in the flashing treatment of 
 carbons for incandescent lamps. (See Car- 
 bons, Flashing Process for.) 
 
 Rhumbs of Compass. (See Compass, 
 Rhumbs of.) 
 
 Ribbed Armature Core. (See Core, 
 Armature, Ribbed.) 
 
 Ribbon Copper. (See Copper, Ribbon) 
 
 Right Handed Solenoid. (See Solenoid, 
 Right-Handed.) 
 
 Right-Hand Trolley Frog. (See Frog, 
 Trolley, Right-Hand.) 
 
 Rigidity, Molecular Resistance 
 
 offered by the molecules of a substance to 
 rotation or displacement. 
 
 The molecular rigidity of a magnetizable sub- 
 stance was until recently considered to be the 
 cause of fhe'tlifferences of coercive force or mag- 
 netic retentivity possessed by different substances. 
 The general acceptance of Ewing's theory of 
 magnetism has, of course, caused the above view 
 to be considerably modified. (See Magnetism, 
 Ewings Theory of. Force, Coercive. Retentiv- 
 ity, Magnetic.} 
 
 Ring, Ampdre The turn or turns 
 
 of wire used in electric balances for the meas- 
 urement of electric current. 
 
 Ring Armature. (See Armature, Ring.) 
 
 Ring Armature Core.- (See Core, Arma- 
 ture, of Dynamo-Electric Machine?) 
 
 Rings, Electric A term sometimes 
 
 used instead of Nobili's rings. (See Metal- 
 lochromes.) 
 
Bin.] 
 
 462 
 
 [Rod. 
 
 Rings, Electro-Chromic A term 
 
 sometimes applied to metallochromes. (See 
 Metallochromes^ 
 
 Rings, Nobili's A term sometimes 
 
 used for metallochromes. (See Metallo- 
 thromes.} 
 
 Roaring of Arc. (See Arc,' Roaring of.} 
 
 Rocker Arm. (See Arm, Rocker.} 
 
 Rocker, Brush In a dynamo-elec- 
 tric machine or electric motor, any device for 
 shifting the position of the brushes on the 
 cummutator cylinder. 
 
 Rocker, Multiple-Pair Brush A 
 term sometimes used for multiple-pair brush 
 yoke. (See Yoke, Multiple-Pair Brttsh.} 
 
 Rocker, Single-Brush - A device 
 by means of which a single pair of brushes 
 are so supported on a dynamo-electric ma- 
 chine or electric motor, as to be capable 
 of being readily shifted into the desired 
 position on the commutator cylinder. 
 
 Rocker, Single-Pair Brush A 
 
 term sometimes used for single-pair brush 
 yoke. (See Yoke, Single-Pair Brush.) 
 
 Rod Clamp. (See Clamp, Rod^ 
 
 Rod, Clutch A clutch or clamp pro- 
 vided in an arc lamp to seize the lamp rod and 
 thus arrest its fall, during feeding, beyond a 
 certain predetermined point. 
 
 The clutch or clamp is caused to release or hold 
 the lamp rod by the action of an electro-magnet 
 placed in a shunt circuit around the electrodes. 
 (See Lamp, Arc, Electric.') 
 
 Rod, Discharging A jointed rod 
 provided at both ends 
 with balls and con- 
 nected at the middle by 
 a swinging joint which 
 permits the balls to 
 move towards or from 
 one another, employed 
 for the disruptive dis- 
 charge of Leyden bat- 
 teries or condensers. 
 (See Discharge, Dis- 
 ruptive. Jar, Leyden.) 
 
 The insulated handles H, H, Fig. 495, permit 
 
 the balls at M, M, to be readily applied to the 
 opposite coatings of the jar or condenser. 
 
 The name discharging tongs is sometimes ap- 
 plied to this apparatus. 
 
 Rod, Lanip 
 
 A metallic rod pro- 
 
 Fig. 4Q5- Discharging 
 Rod. 
 
 vided in electric arc lamps for holding the 
 carbon electrodes. 
 
 When the upper carbon only is fed, as is the 
 case in most arc lamps, there is usually but one 
 lamp rod provided. The clutch or clamp of the 
 feeding device acts against this rod, which must 
 of necessity be at least as long as the upper carbon. 
 (See Lamp, Arc, lee trie.) 
 
 Rod, Lightning - A rod, or wire 
 cable of good conducting material, placed on 
 the outside of a house or other structure, in 
 order to protect it from the effects of a light- 
 ning discharge. 
 
 Lightning rods were invented by Franklin. 
 The results of a very extended inquiry on the 
 subject, leave no room for doubt that a lightning 
 rod, properly placed and constructed, affords an 
 efficient protection to the buildings on which 
 it is placed. 
 
 To insure this protection, however, the fol- 
 lowing conditions were, until very recently, gen- 
 erally insisted on in order to permit the rod tj 
 properly act, viz. : 
 
 (i.) The rod, generally of iron or copper, 
 should have such an area of cross- section as to 
 enable it to carry without fusion the heaviest bolt 
 it is liable to receive in the latitude in which it is 
 located. 
 
 When of iron, the area of cross-section should 
 be about seven times greater than when of 
 copper. 
 
 (2. ) The rod should be continuous throughout, 
 all joints being carefully avoided. 
 
 When joints are used, they should be made of as 
 low resistance as possible, and should be pro- 
 tected against corrosion. 
 
 (3.) The upper extremity of the rod should 
 terminate in one or more points formed of some 
 metal that is not readily corroded, such as pla- 
 tinum or nickel. 
 
 (4.) The lower end of the rod should be car- 
 ried down into the earth until it meets perma- 
 nently damp or moist ground, where it should 
 be attached to a fairly extended metallic surface 
 buried in the ground. 
 
 Metallic plates will answer for grounding the 
 
Rod.] 
 
 463 
 
 [Rod. 
 
 rod, but, if gas or water pipes are available, the 
 rod should be placed in good electrical connec- 
 tion therewith, by wrapping it around and 
 solder ing it to such pipes. 
 
 This fourth requirement is of great importance 
 to the proper action of a lightning rod, and un- 
 less thoroughly fulfilled, may render the rod 
 worthless, no matter how carefully the other re- 
 quirements are attended to. When a bolt strikes 
 a lightning rod which is not properly grounded, 
 the discharge is almost certain to destroy the 
 building to which the rod is connected. 
 
 (5. ) The rod should not be insulated from the 
 building, unless to prevent stains from the oxi- 
 dation of the metal. On the contrary, the rod 
 should be directly connected with all masses of 
 metal in its path, such as tin roofs, gutter spouts, 
 metallic cornices, etc. In this way only can dan- 
 gerous disruptive lateral discharges from the rod 
 to such masses of metal be avoided. 
 
 (6.) The rod should project above the roof or 
 highest part of the building, or, in other words, 
 the height of the rod should bear a certain pro- 
 portion to the size of the building to be pro- 
 tected. 
 
 A rod will protect a conical space around it, 
 the radius of whose base is equal to the vertical 
 height of the rod above the ground, but whose 
 sides are curved inwards instead of being straight. 
 Where the building is very high, a number of 
 separate rods all connected to one another should 
 be employed. 
 
 A lightning rod sometimes fails to protect a 
 house or barn, from the fact that a heated, ascend- 
 ing current of air from a fire in the house, or 
 from the gradual heating of green hay or grain in 
 the barn, acting as a conductor, increases the vir- 
 tual height of the house beyond the ability of its 
 rods to protect it. 
 
 (7.) A stranded conductor is much better than 
 an equal cross-section of a solid rod of the same 
 metal. 
 
 A copper tape is better than a copper rod for 
 lightning rods, because a rapidly periodic current, 
 whose periodicity is sufficiently great, passes 
 practically over the surface of the conductor only. 
 Considering an electric current as taking its 
 energy from the surrounding dielectric, a tape is 
 better, because the surface which absorbs the 
 energy is greater in the case of a tape than of a 
 solid rod. (See Law, Poynting's.) 
 
 A lightning rod more frequently acts to quietly 
 discharge an impending cloud by connective dis- 
 
 charge than by an actual disruptive discharge of 
 the same. (See Discharge, Convective, Dis- 
 charge, Disruptive.') 
 
 Lightning rods should be frequently tested to 
 see that no breaks or oxidation of their joints 
 have occurred. 
 
 Professor Lodge takes exception to some of the 
 heretofore generally received notions concerning 
 the action of lightning rods. He distinguishes 
 between two distinct kinds of discharge that may 
 occur between a charged cloud and the earth, 
 viz.: 
 
 (I.)- A steady strain or current. 
 
 (2.) An impulsive rush or oscillatory discharge. 
 
 A discharge by a steady strain or current oc- 
 curs when the cloud gradually approaches a point 
 on the earth; or, in the case of the cloud being 
 stationary, when it receives its charge gradually 
 by the approach of another cloud. 
 
 In steady discharge, the lightning rod, with its 
 pointed end, either quietly discharges the cloud 
 by a convective discharge, or by a harmless con- 
 ductive discharge through the rod, after a spark 
 has passed disruptively between the cloud and 
 the rod. (See Discharge, Convective. Dis- 
 charge, Conductive. Discharge, Disruptive.') 
 
 The impulsive discharge or rush occurs when- 
 ever the cloud that discharges to the earth re- 
 ceives its charge suddenly, as by the discharge 
 into it of a neighboring cloud, or when a bound 
 charge, produced by the presence of a neighbor- 
 ing charged cloud, is suddenly liberated by dis- 
 harge, and, thus becoming free, impulsively dis- 
 charges to the earth. 
 
 In all cases of an impulsive discharge or rush, a 
 counter electromotive force is set up in the rod, 
 which resists the discharge through the rod and 
 causes the electricity to rush back and spit off in 
 lateral discharges. In this case the conducting 
 power of the rod has no effect in facilitating the 
 discharge. Indeed, the smaller its resistance, and 
 the longer the oscillations last, the greater the 
 danger from lateral discharges. (See Discharge, 
 Lateral. Path, Alternative.) 
 
 The following principles advanced by Lodge 
 differ from the views heretofore generally re- 
 ceived, viz.: 
 
 (l.) Iron is a better substance for a lightning 
 rod than copper, because it is equally as good a 
 conductor as copper for very rapidly alternating 
 currents, and is more difficult to fuse. 
 
 (2.) All neighboring metallic conductoisaiUould 
 be connected to earth. These connections should 
 
Rod ' 
 
 464 
 
 [Rot. 
 
 preferably be by separate conductors rather than 
 by the rod itself. 
 
 (3.) The lightning conductors should have a 
 good separate earth, but should be connected to 
 water pipes, gas pipes, etc., if near them, by an 
 underground connection. 
 
 (4.) The lightning conductor should be de- 
 tached from the building and not close against it. 
 
 (5.) The rod should be of flat section, or a 
 stranded conductor. 
 
 Rod, Lightning, for Ships A 
 
 system of rods designed to afford electric 
 protection for vessels at sea. 
 
 Since the lightning discharge takes place be- 
 tween the points of greatest difference of poten- 
 tial, and these points are generally the cloud 
 and the nearest point of the earth, tall objects are 
 especially liable to be struck. 
 
 Ships at sea should, therefore, be thoroughly 
 protected from lightning. 
 
 In Harris' system of lightning protection for 
 ships, the rods are connected with a series of 
 copper plates and rods so placed on the masts as 
 to readily yield to strains. These plates or rods 
 are electrically connected with the copper sheath- 
 ing of the vessel and -with all large masses of 
 metal in the vessel. This latter precaution is 
 especially necessary in the case of men-of-war, 
 in order to protect the powder magazine. 
 
 Harris' method for the lightning protection of 
 ships was adopted only after very considerable 
 opposition. It proved, however, so efficacious in 
 practice that serious effects of lightning on vessels 
 so protected are now almost unknown. In 1845, 
 Harris received the honor of knighthood from 
 the English Government for his services in this 
 respect 
 
 Hod, Lightning, Points on Points 
 
 of inoxidizable material, placed on lightning 
 rods, to effect the quiet discharge of a cloud by 
 convection streams. (See Rod, Lightning. 
 Convection, Electric?) 
 
 Rod, Thnnder A term formerly 
 
 used for lightning rod. (See Rod, Light- 
 ning^ 
 
 Rods, Bus Heavy copper rods em- 
 ployed in a central or distributing station, to 
 which all the terminals of the generating dy- 
 namos are connected, and from which the cur- 
 rent passes to the different points of the dis- 
 tribution system over the feeders. 
 
 Bus rods are often called bus bars or bus wires. 
 (See Wires, Bus.) 
 
 Rodding a Conduit. (See Conduit, Rod- 
 ding a.} 
 
 Rolling Contact. (See Contact, Rolling.} 
 
 Rose, Ceiling An ornamental ceil- 
 ing plate through which an electric conductor 
 passes. 
 
 Rosette. An ornamental plate provided 
 with contacts connected to the terminals of 
 the service wires, and placed in a wall for the 
 ready attachment of the incandescent lamp. 
 
 A word sometimes used in place of rose. 
 
 Rosette Cut-Out. (See Cut-Out, Rosette.) 
 
 Rotary Magnetic Polarization. (See 
 Polarization, Magnetic Rotary?) 
 
 Rotary-Phase Current. (See Current, 
 Rotating?) 
 
 Rotary-Phase Dynamo. (See Dynamo, 
 Rotary-Phase?) 
 
 Rotary-Phase Motor. (See Motor, Ro- 
 tating Current?) 
 
 Rotary-Phase Transformer. (See Trans- 
 former, Rotary-Phase?) 
 
 Rotating Brushes of Dynamo-Electric 
 Machine. (See Brushes, Rotating, of 
 Dynamo-Electric Machines?) 
 
 Rotating Current. (See Current, Rota- 
 ting?) 
 
 Rotating Current Field. (See Field, 
 Rotating Current?) 
 
 Rotating Current Motor. (See Motor, 
 Rotating Current?) 
 
 Rotating Current Transformer. (See 
 Transformer, Rotatory Current?) 
 
 Rotation, Electro-Magnetic A 
 
 rotation obtained by electro-magnetic attrac- 
 tions and repulsions. (See Disc, Arago's. 
 Disc, Faraday's. Motor, Electric?) 
 
 Rotation, Magneto-Optic A rota- 
 tion of the plane of polarization of a beam 
 of polarized light on its passage through a 
 transparent medium when placed in a strong 
 magnetic field. 
 
 The medium only possesses such properties 
 while in the field. 
 
Rub.] 
 
 465 
 
 [Sai. 
 
 In a ray of ordinary light the vibrations of the 
 ether particles are at right angles to the direction 
 of the ray, or to the direction in which the light 
 is moving. But the vibrations occur indiscrimi- 
 nately in all planes passing through the line of 
 direction. Under certain circumstances, all the 
 ether particles may be caused to move in planes 
 that are parallel to one another. Such a beam of 
 jight is called a plane polarized beam. 
 
 A plane polarized beam of light, when passed 
 through many transparent substances, will have 
 its ether particles vibrating in the same plane 
 when it emerges from the medium, as it had before 
 it entered. Some transparent substances, how- 
 ever, possess the property of rotating or turning 
 the plane of polarization of the light to the right 
 
 Fig. 496. Magneto- Optic Rotation. 
 
 or to the left. This property is called respec- 
 tively right-handed rotary polarization, and left' 
 handed rotary polarization. 
 
 Many substances that ordinarily possess no 
 power of rotary polarization acquire this power 
 when placed in a magnetic field. This property 
 of a magnetic field was discovered by Faraday. 
 
 The effect is to be ascribed to the strain produced 
 in the transparent medium by the stress of the 
 magnetic field. It may be caused in solid bodies 
 by mechanical force. 
 
 The apparatus for demonstrating the rotation 
 of the plane of polarization by a magnetic field is 
 shown in Fig. 496. 
 
 A powerful electro-magnet, M, M, is provided 
 with a hollow core. The substance c, is placed 
 in the field produced by the approached poles, 
 and its action on the light of a lamp, placed at 
 the end 1, is observed by suitable apparatus at a. 
 
 Rubber of Electrical Machine. A 
 
 cushion of leather, covered with an electric 
 amalgam, and employed to produce electricity 
 by its friction against the plate or cylinder of 
 a frictional electric machine. (See Machine, 
 Frictional Electric?) 
 
 Rubbing Contact. (See Contact, Rub- 
 bing.) 
 
 Ruhmkorff Coil. (See Coil, Ruhmkorff) 
 
 RuhmkorlTs Commutator. (See Com- 
 mutator, Ruhmkorjf ~'s.) 
 
 Rule, Ampere's, for Effect of Current on 
 
 Needle A magnetic needle, when 
 
 placed near a conductor through which a 
 current is flowing, has its north pole deflected 
 to the left of the observer, who is supposed 
 to be swimming with the current and facing 
 the needle. 
 
 s 
 
 S. A contraction employed for second. 
 
 S. H. M. A contraction employed for 
 simple harmonic motion. 
 
 S. N. Code. A contraction for single needle 
 code. 
 
 S. W. G. A contraction for Standard Wire 
 Gauge. 
 
 Saddles, Telegraphic B rackets 
 
 placed on the top of telegraphic poles for 
 the support of the insulators. 
 
 Saddle brackets are usually employed for the 
 wire attached to the top of a telegraph pole. (See 
 Pole, Telegraphic.) 
 
 Safe Carrying Capacity of a Conductor. 
 
 - (See Capacity, Safe Carrying, of a Con- 
 ductor.) 
 
 Safety Catch. (See Catch, Safety) 
 Safety Device for Multiple Circuits. (See 
 Device, Safety, for Multiple Circuits.) 
 Safety Fuse. (See Fuse, Safety.) 
 
 Safety Lamp, Electric (See Lamp, 
 
 Electric Safety?) 
 
 Safety Plug. (See Plug, Safety.) 
 Safety Strip. (See Strip, Safety) 
 Saint Elmo's Fire. (See Fire, St. El- 
 mo's?) 
 
1.J 
 
 4G6 
 
 [Scli. 
 
 Salient Magnetic Pole. (See Pole, Mag- 
 netic, Salient?) 
 Saline Creeping. (See Creeping, Saline.} 
 
 Salts, Electrolysis of The decom- 
 position of a salt into its electro-positive and 
 negative radicals or ions. (See Electrolysis.) 
 
 Sandy Deposit, Electro-Metallurgical 
 
 (See Deposit, Electro-Metallurgical, 
 
 Sandy.) 
 
 Saturated Solution. (See Solution, Sat- 
 urated.) 
 
 Saturation, Magnetic The max- 
 imum magnetization which can be imparted 
 to a magnetic substance. 
 
 The condition of iron, or other paramag- 
 netic substance, when its intensity of mag- 
 netization is so great that it fails to be further 
 sensibly magnetized by any magnetic force, 
 however great. 
 
 When the core of an electro-magnet is saturated 
 by the passage of an electric current, the only 
 further increase of its magnetization that is possi- 
 ble, is that due to the magnetic field of the in- 
 creased current which may be sent through its 
 coils. This is comparatively insignificant. 
 
 A permanent magnet is sometimes said to be 
 super-saturated, that is, to have received more 
 magnetism than it can retain for any considerable 
 time after its magnetization. 
 
 In the saturated field magnets of a dynamo-elec- 
 tric machine the magnetic density is seldom taken 
 at a larger value than 16,000 lines per square cen- 
 timetre of area of cross- sect ion. But this is only 
 practical saturation, since Ewing has forced 
 45,300 lines per square centimetre by using an 
 enormously high magnetizing force (H = 24,500). 
 
 Saturation, Magnetic, Diacritical Point 
 
 of A term proposed by S. P. Thomp- 
 son for such a value of the co-efficient of 
 magnetic saturation, that the core is mag- 
 netized to exactly one-half its possible max- 
 imum of magnetization. 
 
 Saw, Electric A platinized steel 
 
 wire, employed while incandescent for cut- 
 ting hard substance. 
 
 Scale, Tangent A scale designed 
 for use with a galvanometer, on which the 
 values of the tangents are marked, instead of 
 
 equal degrees as ordinarily, thus avoiding the 
 necessity of finding from tables the tangents 
 corresponding to the degrees. 
 
 Such a scale may be constructed as follows: 
 Draw the tangent B T, to the circle, Fig. 497, 
 and lay off on it any number of equal divisions 
 or parts, as, for example, the thirty shown in the 
 annexed figure. Connect these parts with the 
 centre C, of the circle. The arc of the circle will 
 
 Pig- 4Q7- Tangent Scale. 
 
 thus be divided into parts proportional to the 
 value of the tangents of the angles. 
 
 These parts are more nearly equal the nearer 
 they are to B, and grow smaller and smaller the 
 further they are from B. In tangent galva- 
 nometers it is therefore very difficult to accurately 
 determine the current strength when the deflec- 
 tions of the needle are very large. 
 
 Scale, Thermometer, Centigrade A 
 thermometer scale, in which the length of the 
 thermometric tube between the melting point 
 of ice and the boiling point of water is divided 
 into one hundred equal parts or degrees. 
 
 Centigrade degrees are indicated by a C., thus 
 O degree C. or 100 degrees C., to distinguish them 
 from Fahrenheit degrees that are marked F. 
 In the Fahrenheit scale the freezing point of 
 water is taken at 32 degrees, and the boiling point 
 at 212 degrees. 
 
 Scale, Thermometer, Fahrenheit's 
 
 A thermometer scale in which the length 
 of the thermometer tube between the melting 
 point of ice and the boiling point of water is 
 divided into 180 equal parts called degrees. 
 
 Fahrenheit degrees are indicated by an F., 
 thus, 32 degrees F. 
 
 The freezing point of water in Fahrenheit's 
 scale is marked 32 degrees F., and the boiling 
 point of water is marked 212 degrees F. 
 
 Schiseophone. An electro-mechanical ap- 
 pliance for detecting flaws and internal de- 
 fects in rails or other metallic masses. 
 
 The schi>eophone consists essentially in the 
 combination of a microphone and telephone with 
 a mechanical hammer and induction balance. 
 
Sch. 
 
 467 
 
 [Scr. 
 
 Schweigger's Multiplier. (See Multi- 
 plier, Schweigger 's.) 
 
 Scintillating Jar. (See Jar, Scintillat- 
 ing^ 
 
 Scratch Brush. (See Brush, Scratch?) 
 
 Scratch Brush, Circular (See 
 
 Brush, Scratch, Circular?) 
 
 Scratch Brush, Hand (See Brush, 
 
 Scratch, Hand?) 
 
 Scratch Brushing. (See Brushing, 
 Scratch?) 
 
 Screen, Electric A closed conduc- 
 tor placed over a body to screen or protect it 
 from the effects of external electrostatic fields. 
 
 An electric screen is sometimes called an elec- 
 tric shield. 
 
 The ability of a closed, hollow conductor to act 
 as a screen, arises from the fact that all points on 
 its inner surface are at the same potential, and 
 therefore are not affected by an increase or de- 
 crease in the potential of the outside of the con- 
 ductor as compared with that of the earth. (See 
 Net, Faraday 1 s.) 
 
 No considerable thickness is required for the 
 efficient operation of an electric screen. 
 
 Screen, Magnetic A hollow box 
 
 whose sides are made of thick iron, placed 
 around a magnet or other body so as to cut 
 it off or screen it from any magnetic field ex- 
 ternal to the box. 
 
 Magnetic screens are placed around delicate 
 galvanometers to avoid any variations in their 
 field due to extraneous masses of iron or neigh- 
 boring magnets. They are also sometimes placed 
 around watches to shield or screen the works 
 from the effects of magnetism. 
 
 To act effectively, when the external fields are 
 at all powerful, magnetic screens must be made 
 of thick iron. They differ in this respect from 
 electrostatic shields, which will afford protection 
 against electrostatic charges although they may 
 be but mere films. 
 
 Screen, Methven's A vertical rec- 
 tangular metallic screen used in connection 
 with a standard argand burner, for furnish- 
 ing a standard amount of light for photo- 
 metric purposes. 
 
 In a rectangular screen a small vertical slot is 
 made of such dimensions as to permit an amount 
 
 of light to pass just equal to two standard candles. 
 The proper burning of the argand lamp is de- 
 termined by supplying sufficient gas to produce 
 a flame exactly 3 inches high. The glass 
 chimney used in the burner is 6 inches high, 
 and is provided with two horizontal wires placed 
 on each side of the burner at the required height. 
 
 Methven's screen possesses the advantage of 
 being easily used and of furnishing a reliable 
 standard of light. Extended experiments made 
 with it appear to show that the amount of light 
 produced depends rather on the height of the 
 gas flame than on the quality of the gas itself. 
 In using Methven's screen care should be taken 
 
 ( i . ) To see that the gas flame is of exactly the 
 required height. 
 
 (2.) That the chimney on the lamp is quite 
 clean. 
 
 (3.) That the top of the flame is as regular as 
 possible. 
 
 As this last point is almost impossible to obtain in 
 actual practice, the flame is 
 ad justed so that the highest 
 point extends about one- 
 eighth of an inch above the 
 height of the horizontal 
 wires. 
 
 (4.) That the lamp and 
 apparatus be permitted to 
 acquire its normal temper- 
 ature before the readings 
 are taken. 
 
 Fig. 498 shows the con- 
 struction of the ordinary 
 Methven standard screen. 
 The vertical slot in the 
 screen is placed as shown 
 before the standard argand Ft '&- 49&- 
 burner. Horizontal wires Standar 
 for the adjustment of the height of the flame are 
 placed one on each side of the gas chimney. 
 
 Screening, Electrostatic Screening 
 or shielding from the inductive effects of a 
 charge. 
 
 A continuous metallic surface surrounding an 
 air space to be shielded, completely protects any 
 body placed within such air space from electro- 
 static influence. (See Cube, Faraday's.) 
 
 Screening, Magnetic Preventing 
 
 magnetic induction from taking place by in- 
 terposing a metallic plate, or a closed circuit 
 of insulated wire, between the body producing 
 
Scr.] 
 
 468 
 
 [Scr. 
 
 the magnetic field and the body to be mag- 
 netically screened. 
 
 A magnetic needle is screened from the action 
 of the earth's field by placing it inside a hollow 
 iron box, which prevents the lines of force of the 
 earth's field from passing through it by concen- 
 trating them on itself. This action is dependent 
 on the fact that iron is paramagnetic and there- 
 fore offers the lines of force less resistance 
 through its mass than elsewhere. A plate of 
 copper would not effect any such magnetic 
 shielding or screening. 
 
 In any magnetic field, however, in which the 
 strength of the field is undergoing rapid, periodic 
 variations, a plate of copper or other electric 
 conductor may act as a screen to protect neigh- 
 boring conductors from the effects of magnetic 
 induction, and its ability to thoroughly effect 
 such a screening will depend directly on its 
 conducting power. 
 
 If, for example, the copper plate c (Fig. 499), 
 be interposed between a coil of copper ribbon a, 
 and the fine wire coil b, it will greatly reduce the 
 intensity of the induced currents, produced when 
 rapidly alternating currents are sent through a. 
 If, however, the copper plate be slit, as shown to 
 the right at a, the screening effect is lost, but is 
 regained if the slit be connected by a conductor. 
 Similarly a flat coil of insulated wire effects no 
 screening action when open, but when closed acts 
 as the uncut copper plate. 
 
 Here the screening action is due to thp fact 
 that the energy of the field is spent in producing 
 eddy currents in the interposed metal screen or 
 coils. If the metal screen is discontinuous in the 
 direction in which the eddy currents tend to flow, 
 the inability of the screen to absorb the energy as 
 eddy currents prevents its action as a screen. 
 
 Fig. 
 The word magnetic screening is generally em- 
 
 induction from occurring in a neighboring con- 
 ductor, by interposing some conducting substance 
 in which eddy currents can be freely established. 
 
 As to the efficiency of the screening action, if the 
 makes-and -breaks do not follow one another very 
 rapidly, the following principles can be proved : 
 
 (i.) If the screening material have absolutely 
 no electrical resistance it will effect a perfect mag- 
 netic screening when placed between the primary 
 and secondary, no matter what its thickness 
 may be. 
 
 (2.) If the screen have a finite conductivity, 
 the screening will be imperfect, unless the thick- 
 ness of the material employed is considerable. 
 
 If, however, the makes-and-breaks follow one 
 another very rapidly, then 
 
 The screening effect of even imperfect conduc- 
 tors will become manifest with comparatively 
 thin screens of metal. 
 
 As to magnetic screening, therefore, it follows 
 that the less the conductivity, the greater must 
 be the speed of reversal, in order that the screen- 
 ing action may be effective. 
 
 Where a screen of iron is employed, an ad- 
 ditional effect is produced by the fact that the 
 small magnetic resistance of the metal, or its con- 
 ductivity for lines of magnetic force, causes the 
 lines of induction to pass through its mass, and 
 thus effect a screening action for the space on the 
 other side. This action is, by some, called mag- 
 netic screening. 
 
 In the case of iron screens, considerable thick- 
 ness is required in the metal plate, in order to 
 obtain efficient screening action of this latter 
 character. On account of this action of iron, in 
 conducting away lines of force, a much smaller 
 speed of reversal is required, in order to obtain 
 effective screening action, where plates of iron 
 are used, than in the case of plates of other 
 metal. 
 
 The apparatus shown in Fig. 500 was employed 
 
 SOO. Willoughby Smith's Apparatus. 
 
 by Mr. Willoughby Smith, in studying the effects 
 of magnetic screening. 
 
 The flat coils A, and B, were employed for the 
 primary and secondary coils respectively, and 
 
 ployed in the latter sense of preventing magnetic were connected to the battery C, and the galva- 
 
Sen] 
 
 469 
 
 [Sec. 
 
 nometer F, as shown. Current reversers, D and 
 E, were so arranged as to reverse galvanometer 
 and battery alternately, and so cause the oppo- 
 site induced currents to affect the galvanometer in 
 the same direction. If the commutators were 
 caused to reverse the current slowly, a plate of 
 copper interposed between A and B, produced 
 but little effect on the galvanometer, but if the re- 
 versers were driven at a very rapid rate, a marked 
 decrease of deflection occurred. 
 
 The screening action of the metals, or their 
 ability to diminish the galvanometer deflection, 
 is in the order of their electrical conductivity, ex- 
 cept in the case of iron, which, as we have seen 
 already, has an additional screening power, due 
 to its conducting away the lines of magnetic force. 
 
 It follows from the preceding principles that 
 the use of lead covered cables, for the conveyance 
 of periodic currents, of the frequency of, say, sixty 
 to one hundred alternations per second, is of but 
 little or no advantage for protecting neighboring 
 telephones from inductive action, because 
 
 (i.) Lead is a poor conductor. 
 
 (2.) The rapidity of alternation is too slow. 
 
 J. J. Thomson made some experiments with 
 electrical oscillations produced by resonance, of 
 about io s in frequency. He obtained this fre- 
 quency of oscillation from oscillations set up in 
 the primary of an induction coil, in a secondary 
 circuit of suitable dimensions. The presence of 
 these secondary vibrations or waves was shown 
 by means of the sparks seen at the terminals of a 
 spark-micrometer circuit. Under these circum- 
 stances he found that the interposition of a thin 
 sheet of tin foil or gold leaf at once completely 
 stopped the secondary sparks by the shielding 
 action it exerted. 
 
 Screening, Magnetostatic Screen- 
 ing from the inductive effect of a stationary 
 magnetic field. 
 
 Magnetostatic screening differs from electrostatic 
 screening in that the plate of iron or other para- 
 magnetic material surrounding the space to be 
 screened must have a fairly considerable thick- 
 ness. This arises from the fact that the magnetic 
 susceptibility of the substance is not infinitely 
 great. 
 
 Screw, Binding A name some- 
 times applied to a binding post. (See Post, 
 Binding.} 
 
 Seal, Hennetical Such a sealing of 
 
 a vessel, designed to hold a vacuum, or gas- 
 eous atmosphere under pressures greater or 
 less than that of the atmosphere, as will pre- 
 vent either the entrance of the external at- 
 mosphere into the vessel, or the escape of the 
 contained gas into the atmosphere. 
 
 Hermetical sealing may be accomplished either 
 by the use of suitable cements, or by the direct 
 fusion of the walls of the containing vessel. The 
 latter method is generally employed. 
 
 Search Light, Automatic (See 
 
 Light, Search, Automatic?) 
 
 Search Light, Electric (See Light, 
 
 Search, Electric?) 
 
 Secohm. The practical unit of self-induc- 
 tion, or the practical unit of inductance. 
 
 The secohm is equivalent to a length equal to 
 that of an earth quadrant, or 10'' centimetres. 
 
 The word secohm is a contraction for second, 
 ohm, and implies the fact that the product of the 
 ohm and the second are taken. 
 
 The word henry is now generally used in the 
 United States for secohm. (See Henry.} 
 
 Secohmmeter. An apparatus for measur- 
 ing the co-efficient of self-induction, mutual 
 induction and capacity of conductors. (See 
 Secohm. Induction, Mutual. Induction, 
 Self.) 
 
 The principle of the secohmmeter depends 
 upon successively performing the cycle of magnetic 
 operations, by making and breaking the circuit 
 of a galvanometer by means of a commutator 
 capable of working at a definite speed. 
 
 Second, Ampere One ampere flow- 
 ing for one second. (See Hour, Ampere.} 
 
 Second, Watt A unit of electrical 
 
 work. 
 
 A watt -second equals the work due to the ex- 
 penditu re of an electrical power of one watt for 
 one second. It is the same as a volt-coulomb. 
 
 The watt-second and the H. P. hour, etc., 
 
 are units of work, since Power = ?E_, 
 
 Time 
 therefore, power X time = work. 
 
 Secondary Battery. (See Battery, Sec- 
 ondary.} 
 
 Secondary Battery, Cell of (See 
 
 Cell, Secondary.) 
 
Sec.] 
 
 [Sec. 
 
 Secondary Cell. (See Cell, Secondary?) 
 
 Secondary Cell, Jar of (See Jar of 
 
 Secondary Cell.) 
 
 Secondary Clock. (See Clock. Second- 
 ary.) 
 Secondary Coil. (See Coil, Secondary) 
 
 Secondary Currents. (See Currents, 
 Secondary) 
 
 Secondary, Fixed - The secondary 
 of an induction coil, that, as is common in 
 such coils, is fixed, as contradistinguished 
 from a movable secondary. (See Secondary, 
 Movable.) 
 
 Secondary Generator. (See Generator, 
 Secondary.) 
 
 Secondary Impressed Electromotive 
 Force. (See Force, Electromotive, Second- 
 ary Impressed) 
 
 Secondary, Movable The second- 
 ary conductor of an induction coil, which, in- 
 stead of being fixed as in most coils, is mova- 
 ble. 
 
 The peculiar movements observed in the 
 secondary of an induction coil when the second- 
 ary is free to move, have been carefully studied 
 by Prof. Elihu Thomson. The secondaries 
 employed for this purpose are in the shape of 
 rings, discs, spheres, wedges, bars, wheels, etc., 
 etc. 
 
 The primary is in the form of a straight cylin- 
 drical coil surrounding a straight core. The coils 
 are traversed by rapidly alternating currents and 
 possess considerable impedance. 
 
 Among the many phenomena concerning the 
 behavior of movable secondaries in such a rapidly 
 alternating field are the following, viz.: 
 
 (A.) A metallic ring, resting on lugs attached 
 to the coils of the primary, is thrown violently off 
 the magnet on the passage of alternating currents 
 through the primary. 
 
 (2.) Two metallic rings of the same diamete, 
 brought into the field are mutually attracted to 
 each other, with sufficient force to sustain the 
 weight of one of the rings when the other ring is 
 held in the field. 
 
 (3.) Metallic spheres are set into rotation when 
 so held near the primary pole as to be shielded 
 
 from the action of part of the rapidly alternating 
 field. Wken held on one side of the pole, this 
 rotation occurs in the opposite direction to that 
 when held on the opposite side. 
 
 (4.) Metallic discs similarly placed are simi- 
 larly set into rotation. 
 
 (5.) The speed ot rotation of spheres or discs 
 varies in different positions. 
 
 (6.) Spheres or discs of diamagnetic substances 
 attain their maximum rotation when held in posi- 
 tion at right angles to those of paramagnetic sub- 
 stances. 
 
 (7.) Bars of steel or substances possessing high 
 coercive power, placed dissymmetrically on the 
 primary as regards their centres of gravity, ex- 
 hibit the phenomena of a shifting magnetic field. 
 (See field, Magnetic, Shifting.) 
 
 (8.) A wedge-shaped piece of steel placed with 
 a flat face on the primary, exhibits a shifting 
 magnetic field, and acts on movable metallic 
 masses near it, just as though a fluid substance 
 was escaping with great velocity from its edges. 
 
 Secondary Movers. (See Movers, Second- 
 ary.) 
 
 Secondary Plate of Condenser. (See 
 Plate, Secondary, of Condenser) 
 
 Secondary Spiral. (See Spiral, Second- 
 ary.) 
 
 Secretion Current. (See Current, Secre- 
 tion.) 
 
 Section Line of Electric Railway. (See 
 Railroads, Electric, Section Line of) 
 
 Section, Neutral, of Magnet A 
 
 section passing through the neutral line or 
 equator of a magnet. (See Line, Neutral, 
 of a Magnet. Magnet, Equator of) 
 
 Section, Trolley - A single contin- 
 uous length of trolley wire, with or without 
 its branches. 
 
 Sectional or Divided Overhead System 
 of Motive Power for Electric Railroads. 
 
 (See Railroads, Electric, Sectional Over- 
 head System of Motive Power for.) 
 
 Sectional or Divided Surface System of 
 Motive Power for Electric Railroads. 
 
 (See Railroads, Electric, Sectional Surf ace 
 System of Motive Power for) 
 
Sec.] 
 
 471 
 
 [Sep. 
 
 Sectional or Divided Underground 
 System of Motive Power for Electric Bail- 
 roads. (See Railroads, Electric, Sectional 
 Underground System of Motive Power for.} 
 
 Sectional Plating. (See Plating, Sec- 
 tional.) 
 
 Sectional Plating Frame. (See Frames, 
 fictional Plating.) 
 
 Seebeck Effect. (See Effect, Seebeck?) 
 
 Seismograph, Electric An appa- 
 ratus for electrically recording the direction 
 and intensity of earthquake shocks. 
 
 Seismograph, Micro An electric 
 
 apparatus for photographically registering 
 the vibrations of the earth produced by earth- 
 quakes or other causes. 
 
 The micro-seismograph consists essentially of a 
 microphone placed on the ground and connected 
 with a telephone. A small concave mirror mova- 
 ble about a horizontal axis is supported on a 
 plate of aluminium supported on a platinum wire 
 connected with the diaphragm of the telephone. 
 The movements of the diaphragm of the telephone 
 are permanently recorded on a strip of sensitized 
 paper that is moved before the mirror. 
 
 Selective Absorption. (See Absorption, 
 Selective?) 
 
 Selenium. A comparatively rare element 
 generally found associated with sulphur. 
 
 Selenium Battery. (See Battery, Selen- 
 ium?) 
 
 Selenium Cell. (See Cell, Selenium?) 
 
 Selenium Eye. (See Eye, Selenium?) 
 
 Selenium Photometer. (See Photometer, 
 Selenium?) 
 
 Self-Induced Current. (See Currents, 
 Self-Induced?) 
 
 Self-Induction. (See Induction, Self.} 
 
 Self-Induction, Co-efficient of (See 
 
 Induction, Self Co-efficient of.) 
 
 Self-Becording Magnetometer. (S e e 
 Magnetometer, Self -Recording?) 
 
 Self-Begistering Wire Gauge. (See 
 Gauge, Wire, Self -Registering?) 
 
 Self-Winding Clock. (See Clock, Self- 
 Winding?) 
 
 Semaphore. A variety of signal apparatus 
 employed in railroad block systems. 
 
 The semaphore used on the Pennsylvania Rail- 
 road consists of a wooden post, in the neighbor- 
 hood of twenty feet in height, on which a wooden 
 arm or blade six feet in length and a foot in 
 width, is displayed. 
 
 When the block is clear, during the day the 
 arm is placed pointing downwards at an angle of 
 75 degrees with the horizontal ; during night 
 semaphore displays a white light. When the 
 block is not clear, the arm or blade is placed in a 
 horizontal position by day, or displays a red light 
 at night. (See Railroads, Block System for.) 
 
 Semaphore Arm. (See Arm, Semaphore?) 
 
 Semaphore Indicator. (See Indicator, 
 Semaphore?) 
 
 Sender, Zinc A device employed 
 
 in telegraphic circuits, by means of which, in 
 order to counteract the retardation produced 
 by the charge given to the line, a momen- 
 tary reverse current is sent into the line after 
 each signal. 
 
 A zinc sender generally consists of a low resist- 
 ance Siemens relay introduced between the line 
 and the front contact of the signaling key. 
 
 Sensibility, Electro An effect pro- 
 duced on a sensory nerve by its electrization. 
 
 Sensibility of Galvanometer. (See Gal- 
 vanometer, Sensibility of.) 
 
 Sensitive Thread Discharge. (See Dis- 
 charge, Sensitive Thread?) 
 
 Separate Coil Dynamo-Electro Machine. 
 (See Machine, Dynamo-Electric, Separate 
 Coil.) 
 
 Separate Touch, Magnetization by 
 
 (See Touch, Separate?) 
 
 Separately Excited Dynamo. (See Dy- 
 namo, Separately Excited) 
 
 Separately Excited Dynamo-Electric 
 Machine. (See Machine, Dynamo-Electric, 
 Separately Excited.) 
 
 Separator. An insulating sheet of ebonite, 
 or other similar substance, corrugated and 
 perforated so as to conform to the outline of 
 the plates of a storage battery, and placed 
 between them at suitable intervals, in such a 
 
Sen] 
 
 472 
 
 [Ser. 
 
 manner as to avoid short-circuiting, without 
 impeding the free circulation of the liquid. 
 
 Series and Magneto Dynamo-Electric 
 Machine. (See Machine, Dynamo- Electric, 
 Series and Magneto?) 
 
 Series and Separately Excited Dynamo- 
 Electric Machine. (See Machine, Dynamo- 
 Electric, Series and Separately Excited?) 
 
 Series and Shunt-Wound Dynamo-Elec- 
 tric Machine. (See Machine, Dynamo- 
 Electric, Series and Shunt- Wound?) 
 
 Series Circuit. (See Circuit, Series?) 
 
 Series-Connected Battery. (See Battery, 
 Series- Connected?) 
 
 Series-Connected Electro-Receptive De- 
 vices. (See Devices, Electro-Receptive, Se- 
 ries-Connected. ) 
 
 Series-Connected Electro-Receptive De- 
 vices, Automatic Cut-out for (See 
 Cut-out, Atttomatic, for Series-Connected 
 Electro-Receptive Devices?) 
 
 Series-Connected Sources. (See Sources, 
 Series-Connected?) 
 
 Series-Connected Translating Devices. 
 (See Devices, Translating, Series-Con- 
 nected?) 
 
 Series-Connected Yoltaic Cells. (See 
 Cells, Voltaic, Series-Connected?) 
 
 Series Connection. (See Connection, 
 Series?) 
 
 Series, Contact A series of metals 
 
 arranged in such an order that each becomes 
 positively electrified by contact with the one 
 that follows it. 
 
 The contact values of some metals, according 
 to Ayrton and Perry, are as follows: 
 
 CONTACT SERIES. 
 
 Difference of Potential in Volts. 
 
 Zinc 
 
 Lead 
 
 Lead 
 
 Tin 
 
 Tin 
 
 Iron 
 
 Iron 
 
 Copper 
 
 Copper 
 
 Platinum 
 
 Platinum | 
 
 Carbon f "3 
 
 .210 
 .069 
 
 .146 
 .238 
 
 The difference in potential between zinc and 
 carbon is equal to 1.089, and is obtained by add- 
 ing the successive differences of potential between 
 the intermediate couples, thus: 
 . 210 -f .069 +.313 + .14 6-|- .238 +.113 =1.089. 
 
 This fact is known technically as Volta' 's Law, 
 which may be formulated as follows: 
 
 The difference of potential, produced by the con- 
 tact of any two metals, is equal to the sum of the 
 differences of potentials between the intervening 
 metals in the contact series. 
 
 Series Distribution of Electricity by 
 Constant Currents. (See Electricity, Se- 
 ries Distribution of, by Constant Current 
 Circuit?) 
 
 Series-Multiple. A series of multiple 
 connections. (See Circuit, Series-Multiple?) 
 
 Series-Multiple Circuit. (See Circuit, 
 Series-Multiple?) 
 
 Series - Multiple-Connected Electro-Re- 
 ceptive Devices. (See Devices, Electro-Re- 
 ceptive, Series-Multiple-Connected?) 
 
 Series-Multiple-Connected Sources. 
 (See Sources, Series-Multiple-Connected?) 
 
 Series-Multiple-Connected Translating 
 Devices. (See Devices, Translating, Series- 
 Multiple-Connected?) 
 
 Series-Multiple Connection. (See Con- 
 nection, Series-Multiple?) 
 
 Series, Parallel A term some- 
 times applied to a multiple-series connection. 
 (See Connection, Multiple-Series?) 
 
 Series, Thermo-Electric A list of 
 
 metals so arranged according to their ther- 
 mo-electric powers, that each metal in tke 
 series is electro-positive to any metal lower in 
 the list. 
 
 Series-Transformer. (See Transformer, 
 Series?) 
 
 Series Turns of Dynamo-Electric Ma- 
 chine. (See Turn-s, Series, of Dynamo- 
 Electric Machine?) 
 
 Series Winding. (See Winding, Series,} 
 
 Series-Wound Dynamo. (See Dynamo, 
 Series?) 
 
 Series-Wound Dynamo-Electric Machine. 
 (See Machine, Dynamo-Electric, Series^ 
 Wound?) 
 
Ser.J 
 
 473 
 
 [She. 
 
 Series-Wound Motor. (See Motor, Se- 
 ries- Wound.} 
 
 Service Conductors. (See Conductors, 
 Service.) 
 
 Service, Street In a system of in- 
 candescent lamp distribution that portion of 
 the circuit which is included between the 
 main and the service cut-out. 
 
 Serving, Cable The covering of 
 
 hemp or jute spun around the insulated core 
 of a cable to act as a protection against the 
 pressure of the iron wire which forms the 
 armor of the cable. 
 
 Shackling a Wire. Inserting an insula- 
 tion between the two ends of a cut wire. 
 
 Shaded or Screened. Cut off or screened 
 from the effects of an electrostatic or mag- 
 netic field. (See Screening, Magnetic. Screen, 
 Magnetic. Screen, Electric.) 
 
 Shadow, Electric - A term some- 
 times used for molecular shadow. (See 
 Shadow, Molecular.) 
 
 Shadow, Molecular The compara- 
 tively dark space on those parts of the walls 
 of Crookes' tubes, which have been protected 
 from molecular bombardment by suitably 
 placed screens. 
 
 Fig jo i. Molecular Shadow. 
 
 If a, in the Crookes tube, shown in Fig. 501, 
 be connected with the negative pole of an elec- 
 tric source, and the cross-shaped mass of alu- 
 minium at b, be connected with the positive elec- 
 trode, on the passage of a series of rapid 
 discharges, phosphorescence is produced by the 
 molecular bombardment from a, in all parts of 
 the vessel opposite a, except those lying in the 
 
 projection of its geometrical shadow. (See Phos- 
 phorescence, Electric. ) 
 
 Shadow Photometer. (See Photometer, 
 Shadow?) 
 
 Shaft, Driven A shaft which re- 
 ceives its power from the driving shaft. (See 
 Mover, Prime?) 
 
 Shaft, Driving- The main line of 
 
 shafting which takes its power directly from 
 the prime mover. 
 
 Shallow-Water Submarine Cable. (See 
 
 Cable, Submarine, Shallow- Water.) 
 
 Sheath, Protective A device at- 
 tached to a transformer or converter, to pre- 
 vent any connection from taking place between 
 the high-potential primary circuit and the 
 low-potential secondary circuit. 
 
 The protective sheath devised by Prof. Elihu 
 Thomson consists essentially in an earth -con- 
 nected copper strip or divided plate interposed 
 between the windings for the secondary and pri- 
 mary circuit. Should the primary circuit lose its 
 high insulation it becomes grounded. 
 
 Sheet, Current The sheet into 
 
 which a current spreads when the wires of 
 any source are connected at any two points 
 near the middle of a very large and thin con- 
 ductor. 
 
 A continuous electric current does not flow 
 through the entire mass of a conductor in any 
 single line of direction. If the terminals of any 
 source are connected to neighboring parts of a, 
 greatly extended thin conductor, the current 
 spreads out in a thin sheet known as a cur- 
 rent sheet, and instead of flowing in a straight 
 line between the points, spreads over the plate 
 in curved lines of flow, which, so far as shape is 
 concerned, are not unlike the lines of magnetic 
 force. 
 
 Sheet Lightning. (See Lightning, 
 Sheet) 
 
 Shellac. A resinous substance possessing 
 valuable insulating properties, which is ex- 
 uded from the roots and branches of certain 
 tropical plants. 
 
 The specific inductive capacity of shellac as 
 compared with air is 2.74. 
 
She.] 
 
 474 
 
 [Shn. 
 
 Shell, Magnetic A sheet or layer 
 
 consisting of magnetic particles, all of whose 
 north poles are situated in one of the flat 
 surfaces of the layer, and the south poles in 
 the opposite surface. (See Magnetism, La- 
 mellar Distribution of.) 
 
 Shell Transformer. (See Transformer, 
 Shell) 
 
 Shield, Magnetic, for Watches A 
 
 hollow case of iron, in which a watch is per- 
 manently kept, in order to shield it from the 
 influence of external magnetic fields. (See 
 Screen, Magnetic.) 
 
 Shifting Magnetic Field. (See Field, 
 Magnetic, Shifting.) 
 
 Shifting Zero. (See Zero, Shifting) 
 
 Ships, Lightning Rods for (See 
 
 Rod, Lightning, for Ships.) 
 
 Ship's Sheathing, Electric Protection of 
 
 Attaching pieces of zinc to the copper 
 
 sheathing of a ship for the purpose of prevent- 
 ing the corrosion of the copper by the water. 
 (See Metals, Electrical Protection of.) 
 
 Shock, Break A term sometimes 
 
 employed in electro-therapeutics for the 
 physiological shock produced on the opening 
 or breaking of an electric circuit. 
 
 Shock, Electric The physiological 
 
 shock produced in an animal by an electric 
 discharge. 
 
 Shock, Opening The physiological 
 
 shock produced on the opening or breaking 
 of an electric circuit. 
 
 Shock, Static A term employed in 
 
 electro-therapeutics for a mode of applying 
 Franklinic currents or discharges, by placing 
 the patient on an insulating stool and apply- 
 ing one pole of a static machine provided 
 with small condensers or Leyden jars, to an 
 insulated platform on which the patient is 
 placed, while the other pole is applied to the 
 body of the patient by the operator. 
 
 * 
 
 The electrode applied to the body of the pa- 
 tient is provided with a ball electrode. Shocks 
 are given to the patient on the approach of 
 this electrode by the discharge of the Leyden 
 jars. 
 
 Short-Arc System of Electric Lighting. 
 
 (See Lighting, Electric, Short-Arc Sys- 
 tem^) 
 
 Short-Circuit. To establish a short cir- 
 cuit. (See Circuit, Short.) 
 
 Short-Circuit Key. (See Key, Short- 
 Circuit.) 
 
 Short-Circuiting. Establishing a short 
 circuit. (See Circuit, Short.) 
 
 Short-Circuiting Plug. (See Plug, 
 Short-Circuiting ) 
 
 Short-Coil Magnet. (See Magnet, Short- 
 Coil) 
 
 Short-Core Electro-Magnet. (See Mag- 
 net, Electro, Short-Core) 
 
 Short-Shunt Compound-Wound Dyna- 
 mo-Electric Machine. (See Machine, Dy- 
 namo-Electric, Compound- Wound, Short- 
 Shunt) 
 
 Shunt. An additional path established 
 for the passage of an electric current or dis- 
 charge. 
 
 Shunt. To establish an additional path 
 for the passage of an electric current or dis- 
 charge. 
 
 Shunt and Separately Excited Dynamo- 
 Electric Machine. (See Machine, Dynamo- 
 Electric, Shunt and Separately Excited) 
 
 Shunt Circuit. (See Circuit, Shunt.) 
 
 Shunt Dynamo-Electric Machine. (See 
 Machine. Dynamo-Electric, Shunt- Wound) 
 
 Shunt, Electric 
 
 Shunt, Electric) 
 
 Bell 
 
 (See Bell. 
 
 Shunt, Electro-Magnetic In a sys- 
 tem of telegraphic communication an electro- 
 magnet whose coils are placed in a shunt 
 circuit around the terminals of the receiving 
 relay. 
 
 The electro-magnetic shunt operates by its 
 self-induction. Its poles are permanently closed 
 by a soft iron armature so as to reduce the resist- 
 ance of the magnetic circuit. (See Induction, 
 Self.) 
 
Shu.] 
 
 475 
 
 [Shu. 
 
 On making the circuit in the coils of a receiv- 
 ing relay, a current is produced in the coils of the 
 electro magnetic shunt in the opposite direction 
 to the relay current; and, on breaking the circuit 
 in the relay, a current is produced in the coils of 
 the electro-magnetic shunt in the same direction 
 as the current in the relay. 
 
 The connection of the coils of the electro-mag- 
 netic shunt with those of the receiving relay, how- 
 ever, is such that on making the circuit in the 
 relay the current in the shunt coils flows through 
 the relay in the same direction, and on breaking 
 the circuit it flows in the opposite direction. 
 Therefore this shunt produces the following effects: 
 
 (i.) At the commencement of each signal in 
 the receiving relay, it produces an induced cur- 
 rent in the same direction which strengthens the 
 current in the relay. 
 
 (2.) At the ending of each signal in the receiv- 
 ing relay, it produces a current in the opposite 
 direction, which hastens the motion of the tongue 
 of the polarized relay. (See Relay, Polarized.) 
 
 Shnnt, Galvanometer A shunt 
 
 placed around a sensitive galvanometer for 
 the purpose of protecting it from the effects 
 of a strong current, or for altering its sensi- 
 bility. (See Ihunt} 
 
 The current which will flow through the shunt 
 wire depends on the relative resistance of the gal- 
 vanometer and of the shunt. In order that only 
 
 total curtent shall pass 
 through the galvanome- 
 ter, it is necessary that 
 the resistances of the 
 shunt shall be the \, fa 
 or 5^, of the galvanom- 
 eter resistance. 
 
 Fig. 302 shows a 
 shunt, in which the re- 
 sistances, as compared 
 with that of the galva- 
 nometer, are those above 
 referred to. The galva- 
 nometer terminals are 
 
 connected at N, N. Plug 
 
 Fig. JO2. Galvanometer 
 
 Shunt. 
 
 keys are used to connect one or another of the 
 shunts with the circuit. (See Shunt, Multiplying 
 Power of.) 
 
 Shunt, Magnetic An additional 
 
 path of magnetic material provided in a mag- 
 16 Vol. 1 
 
 netic circuit for the passage of the lines of 
 force. 
 Shunt, Multiplying Power of - _ A 
 
 quantity, by which the current flowing through 
 a galvanometer provided with a shunt, must 
 be multiplied, in order to give the total cur- 
 rent. 
 
 The multiplying power of a shunt may be de- 
 termined from the following formula, viz.: 
 
 / 
 
 X C, in which 
 
 = the mul- 
 
 tiplying power of a shunt whose resistance is s; 
 g, is the galvanometer resistance; C, the current 
 through the galvanometer, and A, the total cur- 
 rent passing; s and g, are taken in ohms, and C 
 and A, in amperes. 
 
 Suppose, for example, that but ^ the entire 
 current is to flow through the galvanometer; then 
 the resistance of the shunt must evidently be g, 
 for, 
 
 s i i 
 
 or, ios = 
 
 10 s s = 
 
 9 s=g; or, 
 
 Shunt or Reducteur for Ammeter. (See 
 Reducteur or Shunt for Ammeter) 
 
 Shunt Ratio. The ratio existing between 
 the shunt and the circuit which it shunts 
 (See Shunt, Multiplying Power of.} 
 
 Shunt, Relay, Stearns' ---- A shunt 
 employed in the differential method of duplex 
 telegraphy to short-circuit the relay and then 
 permit the line current to be cut off directly 
 after it has completed its work in closing the 
 local circuit. 
 
 The use of the relay shunt permits the slacken- 
 ing of the armature spring of the relay, because 
 the decreased duration of the line current does 
 not produce so strong a magnetization of the 
 iron. 
 
 Shunt-Turns of Dynamo-Electric Ma- 
 chine. (See Turns, Shunt, of Dynamo- 
 Electric Machine?) 
 
 Shunt->Vouu<l Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 Shunt- Wound?) 
 
 Shunt- Wound Motor. (See Motor, 
 Shunt- Wound} 
 
Shu.] 
 
 476 
 
 [Sig. 
 
 Shunting. Establishing a shunt circuit. 
 
 Shuttle Armature. (See Armature, 
 Shuttle?) 
 
 Side A, of Quadruples Table. (See Table, 
 
 Quadruple*, A, Side of.) 
 
 Side B, of Quadruples Table. (See Table, 
 Quadruplex, B, Side of.) 
 
 Side Flash. (See Flash, Side.) 
 
 Sidero-Magnetic. (See Magnetic, Side- 
 ro.) 
 
 Siemens' - Armature Electro-Magnetic 
 Bell. (See Bell, Electro-Magnetic, Siemens' 
 Armature Form.) 
 
 Siemens' Differeutial Voltameter. (See 
 Voltameter Siemens' Differential.) 
 
 Siemens' Electric Pyrometer. (See Py- 
 rometer, Siemens Electric?) 
 
 Siemens-Halske Voltaic Cell. -(See Cell, 
 Voltaic, Siemens-Halske?} 
 
 Siemens' Water Pyrometer. (See Py- 
 rometer, Siemens' Water.) 
 
 Signal Arm. (See Arm, Signal.} 
 
 Signal, Electric Tell-Tale - An 
 electrically operated signal, generally silent, 
 whereby the appearance of a white or colored 
 disc, on a black or otherwise uniformly 
 colored surface, indicates the occurrence of 
 a certain predetermined event 
 
 Signal Service for Electric Railways. 
 (See Railroads, Electric, Signal Service 
 System for.} 
 
 Signals, Electro-Pneumatic - Sig- 
 nals operated by the movements of dia- 
 phragms or pistons moved by compressed 
 air, the escape of which is controlled electri- 
 cally. 
 
 Signaling, Balloon, for Military Pur- 
 poses Transmitting intelligence of the 
 movements of an enemy's army obtained from 
 observations made in balloons by means of tel- 
 ephone circuits connected with the balloon. 
 
 Signaling, Curb In cable teleg- 
 raphy a system for avoiding the effects of 
 retardation by rapidly discharging the cable 
 before another electric impulse, is sent into 
 
 it, by reversing the battery, before connecting 
 it to earth, and then connecting to earth be- 
 fore beginning the next signal. 
 
 Signaling, Double-Curb In curb 
 
 signaling, a method by which the cable, after 
 being connected with the battery for sending 
 a signal, is subjected to a reverse battery, bat 
 instead of being put to earth after this con- 
 nection, as in single-curb signaling, the bat- 
 tery is again reversed and connected to earth. 
 
 The time during which the cable is connected 
 to the reversed battery before being put to earth, 
 that is, the time during wh'ch it receives the 
 positive and negative currents, may be made of 
 any suitable duration. 
 
 Signaling, Double-Current Signal- 
 ing by means of currents that alternately 
 change their direction. 
 
 Double-current signaling was devised by Var- 
 ley in order to avoid the effects of the induction 
 of underground conductors on Morse tele- 
 graphic apparatus. The idea of reversing the 
 direction of the current was to hasten the dis- 
 charge of the wire, which was prolonged by in- 
 duction. Double current working, however, 
 possesses other advantage.-, and is ued in duplex 
 and quadruplex transmission. 
 
 Signaling, Single-Curb - In curb 
 signaling, a method by which the cable, after 
 connection with the battery for sending a 
 signal, is subjected to a reverse battery cur- 
 rent, and then put to earth before again being 
 connected to the battery for sending the next 
 signal. 
 
 Signaling, Single-Current Signal- 
 ing by making or breaking the circuit of a 
 single current. 
 
 Single-current signaling is of two kinds, viz. : 
 
 (l.) Open-Circuit Signaling, in which the bat- 
 teries are fixed at each station, and are in circuit 
 only when signaling. 
 
 (2.) Closed -Circuit Signaling, where the bat- 
 teries are divided, one half generally being at each 
 end of the line, and so connected that both sets 
 flow in the same direction. 
 
 Signaling, Single-Current, Closed-Circuit 
 
 A system of single-circuit signaling in 
 
 which the sending batteries are placed at 
 each end of the line and are so connected as 
 
477 
 
 [Sin. 
 
 to remain always in circuit. (See Signaling, 
 Single- Current?) 
 Signaling, Single-Current, Open-Circuit 
 
 A system of single-current signaling 
 
 in which the sending batteries, fixed at each 
 station, are in circuit during signaling only. 
 (See Signaling, Single-Current.) 
 
 Signaling, Velocity of Transmission of 
 
 The speed or rate at which successive 
 
 signals can be sent on any line without the 
 retardation producing serious interference. 
 (See Retardation?) 
 
 Silent Discharge. (See Discharge, Si- 
 lent?, 
 
 Silver Bath. (See Bath, Silver.) 
 
 Silver Chloride Voltaic Cell. (See Cell, 
 
 Voltaic, Silver Chloride?) 
 
 Silver Plating. (See Plating, Silver?) 
 
 Silver Voltameter. (See Voltameter, 
 Silver?) 
 
 Silvered Plumbago. (See Plumbago, Sil- 
 vered?) 
 
 Silvering, Electro Covering a sur- 
 face with a coating of silver by electro-plat- 
 ing. (See Plating, Electro?) 
 
 Electro-plating with silver. 
 
 Silurus Electricus. The electric eel. 
 (See Eel, Electric?) 
 
 Simple Arc. (See Arc, Simple?) 
 Simple Circuit. (See Circuit, Simple?) 
 
 Simple Electric Candle-Burner. (See 
 Burner, Simple Candle Electric?) 
 
 Simple-Harmonic Current. (See Cur- 
 rent, Simple-Harmonic?) 
 
 Simple-Harmonic Curve. (See Curve, 
 Simple-Harmonic?) 
 
 Simple-Harmonic Motion. (See Motion, 
 Simple-Harmonic?) 
 
 Simple Magnet. (See Magnet, Simple?) 
 
 Simple-Periodic Current. (See Cur- 
 rents, Simple-Periodic?) 
 
 Simple-Periodic Electromotive Force. 
 (See Force, Electromotive, Simple- 
 Periodic?) 
 
 Simple-Periodic Motion. (See Motion, 
 Simple-Periodic?) 
 
 Simple Radical. (See Radical, Simple.) 
 
 Simple-Sine Motion. (See Motion, 
 Simple- Sine?) 
 
 Simple Voltaic Cell. (See Cell, Voltaic, 
 Simple?) 
 
 Simplex Telegraphy. (See Telegraphy, 
 Simplex?) 
 
 Sims-Edison Torpedo. (See Torpedo, 
 Sims-Edison-) 
 
 Sine Galvanometer. (See Galvanometer, 
 
 Sine.) 
 
 Single-Brush Rocker. (See Rocker, 
 Single-Brush .) 
 
 Single-Cup Insulator. (See Insulator, 
 Single-Shed) 
 Single Curb. (See Curb, Single.) 
 
 Single-Current Signaling. (See Signal 
 ing, Single-Current.) 
 
 Single-Curve Trolley Hanger. (See 
 Hanger, Single-Curve Trolley.) 
 
 Single-Fluid Hypothesis of Electricity. 
 
 (See Electricity, Single-Fluid Hypothesis 
 of.} 
 
 Single-Fluid Voltaic Cell. (See Cell, 
 Voltaic, Single-Fluid.) 
 
 Single-Loop Armature. (See Armature, 
 Single-Loop.) 
 
 Single-Magnet Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 . Single-Magnet.) 
 
 Single-Pair Yoke. (See Yoke, Single- 
 Pair.} 
 
 Single-Shackle Insulator. (See Insula- 
 tor, Single- Shackle} 
 
 Single-Shed Insulator. (See Insulator, 
 Single-Shed?) 
 
 Single-Stroke Electric Bell. (See Bell, 
 Single-Stroke Electric} 
 
 Single Touch. (See Touch, Single.) 
 
 Single-Wire Cable. (See Cable. Single- 
 
 \Vire.) 
 
Sin.] 
 
 478 
 
 [Sine. 
 
 Single-Wire Circuit. (See Circuit, 
 Single- Wire?) 
 
 Sinistrorsal Solenoid or Helix. (See So- 
 lenoid, Sinistrorsal?) 
 
 Sinuous Currents. (See Current, Sinu- 
 ous?) 
 
 Siphon, Electric A siphon in 
 
 which the stoppage of flow, due to the 
 gradual accumulation of air, is prevented by 
 electrical means. 
 
 In the electric siphon, an opening is provided 
 at the highest part of the bend of the siphon tube, 
 and a chamber is attached thereto, provided with 
 a float. Contact points are so connected with the 
 float that when it falls, contact is made, and when 
 it rises, contact is broken. 
 
 The closing of the circuit, on the fall of the 
 float, operates an electric motor which drives an 
 air pump which exhausts the air from the siphon. 
 Or the float being raised in the siphon, the con- 
 tact is broken and the operation of the pump is 
 stopped. 
 
 Siphon Recorder. (See Recorder, Si- 
 phon?) 
 
 Sir William Thomson's Standard Cell. 
 (See Cell, Voltaic, Standard, Sir William 
 Thomson's?) 
 
 Skin Effect. (See Effect, Skin.} 
 
 Skin, Faradization of The thera- 
 peutic treatment of the skin by a faradic cur- 
 rent. 
 
 For efficient faradization the skin should be 
 thoroughly dried and a metallic brush or elec- 
 trode employed. For very sensitive parts, as, 
 for example, the face, the hand of the operator, 
 first thoroughly dried, is to be preferred as an 
 electrode. 
 
 Skin, Human, Electric Resistance of 
 
 The electric resistance offered by the 
 skin of the human body. 
 
 The electric resistance of the skin is subject to 
 marked differences in different parts of the body, 
 where its thickness or continuity varies. It 
 varies still more with variations in its condition of 
 moisture. Even in the same individual the re- 
 sistance varies materially under apparently 
 similar conditions. 
 
 Sleeve, Insulating A tube of treated 
 
 paper or other insulating material, provided 
 
 for covering a splice in an insulated con- 
 ductor. 
 
 Sleeve Joint (See/0/#/, Sleeve.) 
 
 Sleeve, Lead A lead tube provided 
 
 for making a joint in a lead-covered cable. 
 
 Sled. The sliding contacts drawn after a 
 moving electric railway car through the slotted 
 underground conduit containing the wires or 
 conductors from which the driving current is 
 taken. 
 
 Slide Bridge. (See Bridge, Electric, 
 Slide Form of.) 
 
 Slide, Resistance A rheostat, in 
 
 which the separate resistances or coils are 
 placed in or removed from a circuit by means 
 of a sliding contact or key. 
 
 Apparatus employed in telegraphy for 
 charging a conductor to a given fraction of 
 the maximum potential of the battery so as 
 to adjust its charge in order to balance the 
 varying charge of a cable. 
 
 The resistance slide consists essentially of a set 
 of resistance coils of high insulation and of equal 
 resistance. Suppose, for example, ten such equal 
 coils to be connected in series, then if connected 
 to the charging battery the potential will vary by 
 one-tenth at the junction between each pair. A 
 condenser, therefore, will be charged to any 
 number of tenths of the potential of the charging 
 battery by connecting it at suitable points. 
 
 A second set of coils of equal resistance is ar- 
 ranged so as to subdivide any of the lower coils, 
 thus permitting an adjustment to within a hun- 
 dredth of the potential of the battery. 
 
 Slide Wire. (See Wire, Slide) 
 Sliding Contact. (See Contact, Sliding.) 
 
 Slow-Speed Electric Motor. (See Motor, 
 Electric, Slow-Speed!) 
 
 Sluggish Magnet. (See Magnet, Slug- 
 gish^ 
 
 Small Calorie. (See Calorie, Small?) 
 
 Smee Yoltaic Cell. (See Cell, Voltaic, 
 Smee?) 
 
 Smelting, Electro The separation 
 
 or reduction of metallic substances from their 
 ores by means of electric currents. 
 
Sna.] 
 
 479 
 
 [Sol. 
 
 Snap Switch. (See Switch, Snap.) 
 Soaking-In. A term sometimes employed 
 by telegraphers to represent the gradual 
 penetration of an electric charge by a neigh- 
 boring dielectric. 
 
 An electric displacement occurs in the neigh- 
 boring dielectric, and produces thereby what is 
 generally called the residual charge. 
 
 Soakiug-Ont. A term sometimes em- 
 ployed by telegraphers to represent a gradual 
 discharge which occurs in the case of a 
 charged conductor in a neighboring dielec- 
 tric. 
 
 When a condenser, or other similar conductor, 
 is discharged, the discharge is not instantaneous. 
 The charge which soaked in, gradually recovers, 
 or soaks- out. 
 
 Socket, Electric Lamp A support 
 
 - S3- Lamp Socket. 
 
 for the reception of an incandescent electric 
 lamp. 
 
 Incandescent lamp sockets are generally made 
 so that the mere insertion of the base of the lamp 
 
 . 304. Lamf Socket. 
 
 in the socket completes the connection of the lamp 
 terminals with the terminals of the socket. The 
 
 socket terminals are connected with the leads that 
 supply current to the lamp; the removal of the 
 lamp from the socket automatically breaks its cir- 
 cuit. The socket is generally provided with a key 
 for turning the lamp on or off without removing 
 it from the socket. 
 
 Figs. 503 and 504 show forms of lamp sockets 
 for incandescent lamps and the details of the key 
 for connecting or disconnecting the lamp with the 
 leads. 
 
 Socket, Wall A socket placed in a 
 wall and provided with openings for the inser- 
 tion of a wall plug with which the ends of a 
 flexible twin-lead are connected. 
 
 A wall-socket permits the temporary connec- 
 tion of a portable electric lamp, a push button or 
 other device with the conductor or lead. 
 
 Soft-Drawn Copper Wire. (See Wire, 
 Copper, Soft-Drawn?) 
 
 Soldering, Electric A process for 
 
 obtaining metallic joints, in which heat gen- 
 erated by the electric current is used to melt 
 the solder in the place of ordinary heat. 
 
 Solenoid. A cylindrical coil of wire the 
 convolutions of which are circular. 
 
 An electro-magnetic helix. (See Solenoid, 
 Electro-Magnetic, or Electro-Magnetic 
 Helix.) 
 
 A solenoid is termed dextrorsal or sinistrorsal 
 according to the direction in which its wire is 
 wound. (See Solenoid, Dextrorsal. Solenoid, 
 Sinistrorsal.) 
 
 Solenoid Core. The core, usually of soft 
 iron, placed within a solenoid and magnetized 
 by the magnetic field of the current passing 
 through the solenoid. 
 
 The soft iron core of a solenoid differs from 
 that of an electro-magnet in the fact that the core 
 of the solenoid is movable, while that of the elec- 
 tro-magnet is fixed. (See Magnet, Electro.) 
 
 In order to obtain a nearly uniform pull in its 
 various positions in the solenoid, the soft iron cores 
 are made of a shape which insures a greater mass 
 of metal towards the middle of the core. (See 
 Bars, KriziVs.) 
 
 Solenoid, Dextrorsal A solenoid 
 
 in which the winding is right-handed. (See 
 Solenoid, Practical.) 
 
 Solenoid, Electro-Magnetic, or Electro- 
 Magnetic Helix The name given to 
 
Sol.] 
 
 480 
 
 [Sol. 
 
 a cylindrical coil of wire, each of the convo- 
 lutions of which is circular. 
 
 A circuit bent in the form of a helix, supported 
 at its two extremities, as shown in Fig. 505, and 
 traversed by an electric current, will move into 
 the magnetic meridian of the place, and, if free to 
 move in a vertical plane, will come to rest in the 
 line of the magnetic inclination or dip of the place. 
 
 A solenoid traversed by an electric current ac- 
 quires thereby all the properties of a magnet, and 
 is attracted and repelled by other magnets. Its 
 poles are situated at the ends of the cylinder on 
 which the solenoid may be supposed to be wound. 
 
 Solenoid, Ideal A solenoid con- 
 sisting of a cylinder built up of a number of 
 true circular currents, with all faces of like 
 polarity turned in the same direction and 
 entirely independent of one another. 
 
 The practical solenoid differs from the ideal 
 solenoid in that the successive circular circuits or 
 currents are all connected with one another in 
 series. 
 
 The polarity of a solenoid depends on the direc- 
 tion of the current as regards the direction in 
 which the solenoid is wound. 
 
 This solenoid is sometimes called an electro- 
 magnetic solenoid or helix, in order to distinguish 
 
 Fig. SS- Practical Solenoid. 
 it from a solenoidal magnet. (See Magnet, Sole- 
 noidal.) 
 A solenoid, if suspended so as to be free to 
 
 move, will come to rest in the plane of the mag- 
 netic meridian when traversed by an electric 
 current. 
 
 It will also be attracted or repelled by the ap- 
 proach of a dissimilar or similar magnet pole 
 respectively, as shown in Fig. 505. 
 
 Solenoid, Left-Handed A sinistror- 
 sal solenoid or one in which the winding is 
 left-handed. (See Solenoid, Practical.} 
 
 Solenoid, Magnetic A spiral coil 
 
 of wire which acts like a magnet when an 
 electric current passes through it. 
 
 The magnetic solenoid must be distinguished 
 from a solenoidal magnet. (See Magnet, Sole- 
 noidal. Solenoid, Electro-Magnetic, or Electro- 
 Magnetic Helix.} 
 
 Solenoid, Practical The name ap- 
 plied to the ordinary solenoid in order to dis- 
 tinguish it from the ideal solenoid. (See 
 Solenoid, Ideal.} 
 
 A Practical Solenoid consists, as shown in Figs. 
 
 Fig. job. Practical Solenoid. 
 
 505 and 506, of a spiral coil of wire in which the 
 successive circular circuits are connected to one 
 another in series. 
 
 F *g> SO?. Right-Handed Helix. Fig. 508. Left-Handed 
 Helix. Fig. S9- Helix, -with Consequent Poles. 
 
 The polarity of the solenoid depends on the 
 direction of the current, and therefore on the 
 direction of winding. In any solenoid, however, 
 the polarity may be reversed by reversing the 
 direction of the current. (See Magnet, Electro. } 
 
 A Right. Handed, or Dextrorsal Solenoid, is one 
 wound in the direction shown in Fig. 507 at I. 
 
Sol.] 
 
 481 
 
 [Sou. 
 
 A Left-Handed, or Sinistrorsal Solenoid, is one 
 wound in the direction shown in Fig. 508 at 2. 
 
 The solenoid shown in Fig. 509 at 3, is wound 
 so as to produce consequent poles. (See Poles , 
 Consequent. ) 
 
 Solenoid, Right- if anded A dex- 
 
 trorsal solenoid, the winding in which is right- 
 handed. (See Solenoid, Practical?) 
 
 Solenoid, Sinistrorsal A solenoid 
 in which the winding is left-handed. (See 
 Solenoid, Practical?) 
 
 Solenoidal. Pertaining to a solenoid. 
 
 Solid Angle. (See Angle, Solid.) 
 
 Solid Line. (See Line, Solid.) 
 
 Solution. A liquid in which another sub- 
 stance, generally a solid, is dissolved. 
 
 The liquid may contain either a solid, another 
 liquid, or a gas. 
 
 Solution, Bain's Printing The 
 
 solution used in Bain's chemical telegraph. 
 
 Bain's solution is made by mixing together one 
 part of a saturated solution of potassium ferro- 
 cyanide, with two parts of water. 
 
 Solution, Battery The exciting 
 
 liquid for voltaic cells. (See Cell, Voltaic.) 
 
 Solution, Chemical, Bain's A solu- 
 tion employed in connection with Bain's re- 
 cording telegraph. (See Recorder, Chemical, 
 Bain's) 
 
 Solution, Quicking A solution of 
 
 a salt of mercury, in which objects to be elec- 
 tro-plated are dipped after cleansing, just 
 before being placed in the plating bath. 
 
 If the articles have been properly cleansed, im- 
 mersion in the quicking solution will cover them 
 with a uniform, silver-like coating, which will in- 
 sure an adherent, uniform coating in the plating 
 bath. 
 
 Solution, Saturated A solution in 
 
 which as much of the solid or other substance 
 has been dissolved in the liquid as it will take 
 at a given temperature. 
 
 Solution, Super-Saturation of 
 
 The condition assumed by a warmed satu- 
 rated solution of a. salt, when placed in a 
 closed vessel out of contact with the air, and 
 allowed to cool without being shaken. 
 
 Under the above circumstances the solution 
 may be cooled without depositing any crystals. 
 
 Such a solution is said to be super-saturated. It 
 will immediately deposit crystals if a crystal of the 
 salt dissolved or a crystal of an. isomorphous salt 
 be dropped in the solution, or often if merely 
 shaken. 
 
 It is important in standard voltaic cells in 
 which zinc sulphate is used, that the solution be 
 saturated but not super saturated. 
 
 Sonometer, Hughes' An apparatus 
 for determining Lhe amount of inductive dis- 
 turbance in an induction balance, by compar- 
 ing the sounds heard in a telephone, as 
 a result of such induction, with the sounds 
 heard in the same telephone under circum- 
 stances in which the amount of disturbance 
 is directly measurable. 
 
 An apparatus devised by Professor Hughes to 
 be used in connection with the induction balance, 
 in order to measure the amount of disturbance of 
 balance produced therein in any particular case. 
 
 Sonorescence. A term proposed for the 
 sounds produced when a piece of vulcanite or 
 any other solid substance is exposed to a 
 rapid succession of flashes of light. (See 
 Photopkone.) 
 
 Sound. The sensation produced on the 
 brain, through the ear, by the vibrations of a 
 sonorous body. 
 
 The sound waves that are capable of pro- 
 ducing the sensation of sound on the brain 
 through the ear. 
 
 The word sound is therefore used in science in 
 two distinct senses, viz.: 
 
 (i.) Subjectively, as the sensation produced by 
 the vibrations of a sonorous body. 
 
 (2.) Objectively, as the waves or vibrations that 
 are capable of producing the sensation of sound. 
 
 Sound is transmitted from the vibrating body 
 to the ear of the hearer by means of alternate to- 
 and-fro motions in the air, occurring in every 
 direction around the vibrating body and firming 
 spherical waves called waves of condensation and 
 rarefaction. Unlike light and heat, these waves 
 require a tangible medium such as air to trans- 
 mit them. 
 
 Sound, therefore, is not propagated in a 
 vacuum. The vibrations of sound are longi- 
 tudinal, that is, the to-and-fro motions occur in 
 i he same direction as that in which the sound is 
 traveling. The vibrations of light are iransversf, 
 
SOU.] 482 
 
 that is, the to-and-fro motions are at right angles 
 to the direction in which the light is traveling. 
 
 Sound. (Objectively.) The waves in the 
 air or other medium which produce the sen- 
 sation of sound. 
 
 Sound. (Subjectively.) The effect pro- 
 duced on the ear by a vibrating body. 
 
 Sound, Absorption of Acoustic ab- 
 sorption. (See Absorption, Acoustic?) 
 Sound, Characteristics of The 
 
 peculiarities that enable different musical 
 sounds to be distinguished from one another. 
 
 The characteristics of musical sounds are: 
 
 (i.) The Tone or Pitch, according to which a 
 sound is either grave or shrill. 
 
 (2.) The Intensity or Loudness, according to 
 which a sound is either loud or feeble. 
 
 (3.) The Quality or Timbre, the peculiarity 
 which enables us to distinguish between two 
 sounds of the same pitch and intensity, but 
 sounded on different instruments, as for example, 
 on a flute and on a piano. 
 
 Sound, Quality or Timbre of That 
 
 peculiarity of a musical note which enables 
 us to distinguish it from another musical note 
 of the same tone or pitch, and of the same 
 intensity or loudness, but sounded on another 
 instrument. 
 
 The middle C, for example, of a pianoforte, is 
 readily distinguishable from the same note on a 
 flute, or on a violin ; that is to say, its quality is 
 different. The differences in the quality of musi- 
 cal sounds are caused by the admixture of addi- 
 tional sounds called overtones which are always 
 associated with any musical sound. 
 
 Briefly, nearly all so-called simple musical 
 sounds are in reality chords or assemblages of a 
 number of different musical sounds. 
 
 In the case of the many different notes that are 
 present in an apparently simple note or tone, one 
 of the notes is far louder than all the others and is 
 called the fundamental tone or note, and is what 
 is recognized by the ear as the note proper. The 
 others are called the overtones. The overtones 
 are too feeble to be heard very distinctly, but 
 their presence gives to the fundamental note its 
 own peculiar quality. In the case of a note 
 sounded on the flute, these overtones are dif- 
 ferent either in number or in their relative intensi- 
 ties from the same note sounded on another instru- 
 
 [Son. 
 
 ment Their fundamental tones, however, are 
 the same. 
 
 The peculiarities which enable us to distinguish 
 the voice of one speaker or singer from another 
 are due to the presence of these overtones. The 
 overtones must be correctly reproduced by the 
 diaphragm of the telephone, or phonograph, 
 graphophone, or gramophone, if the articulate 
 speech is to be correctly reproduced wit'n all its 
 characteristic peculiarities. 
 
 Sounder, Morse Telegraphic An 
 
 electro-magnet which produces audible 
 sounds by the movements of a lever attached 
 to the armature of the magnet. 
 
 The Morse sounder has nrw almost entirely 
 supplanted the paper recorder or register. On 
 short lines it is placed directly in the telegraphic 
 circuit. On long lines it is operated by a local 
 battery, thrown into or out of the action by the 
 relay. (See Relay.) 
 
 Fig. 310. Morse Sounder. 
 
 The Morse sounder, shown in Fig. 510, con- 
 sists of an upright electro-magnet M, whose soft 
 iron armature A, is rigidly attached to the striking 
 lever B, working in adjustable screw pivots as 
 shown. The free end of the lever is limited in its 
 strokes by two set screws N, N. The lower of 
 these screws is set so as to limit the approach of 
 the armature A, to the poles of the electro-magnet; 
 the upper screw is set so as to give the end B, 
 sufficient play to produce a loud sound. A re- 
 tractile spring, attached to the striking lever near 
 its pivoted end, and provided with regulating 
 screw S S, pulls the lever back when the current 
 ceases to flow through M. 
 
 The dots and dashes of the Morse alphabet are 
 reproduced by the sounder, as audible signals, 
 that are distinguished by the operator by means 
 of the different sounds produced by the up and 
 down stroke of the lever as well as by the differ 
 
Sou.] 
 
 483 
 
 [Son. 
 
 ence in the intervals of time between the succes- 
 sive signals. 
 
 Another form of telegraphic sounder, similar 
 in its general construction to that already de- 
 scribed, is shown in Fig. 511. 
 
 Fig. 511. Telegraphic Sounder. 
 
 Sounder, Repeating -- A telegraphic 
 sounder which repeats the telegraphic dis- 
 patch into another circuit. 
 
 Sounds, Magnetic -- Faint clicks 
 heard on the magnetization of a readily mag- 
 netizable substance. 
 
 One of the earlier forms of Reis' telephone, 
 operated by means of a rapid succession of these 
 faint magnetic sounds. 
 
 Source, Electric -- Any arrangement 
 capable of maintaining a difference of poten- 
 tial or an electromotive force. 
 
 The following are the more important electric 
 sources, arranged according to the character of 
 the energy which is converted into electric 
 energy. 
 
 ELECTRIC SOURCES. 
 
 1. Voltaic Cell or Primary 
 
 Battery. 
 
 2. Charged Storage Cell or 
 
 Secondary Battery. 
 
 3. Thermo Cell or Thermo 
 
 Battery. 
 
 4. Selenium Cell or Sele- 
 
 nium Battery. 
 
 5. Magneto - Electric Ma- ~| 
 
 chine. 
 
 6. Dynamo-Electric Ma- 
 
 chine. 
 
 7. Frictional Electric Ma- 
 
 chine. 
 
 8. Electrostatic Induction 
 
 Machine. 
 
 9. Magneto-Electric Tele- 
 
 phone Transmitter. 
 
 Chemical Poten- 
 tial Energy. 
 
 Radiant Energy. 
 
 Mechanical 
 Energy. 
 
 10. Pyromagnetic Generator. 
 
 11. Animal or Plant .......... Vital Energy. 
 
 Sources, Multiple-Arc-Connected 
 
 A term sometimes applied to sources connect- 
 ed in multiple. (See Sources, Multiple-Con- 
 nected?) 
 
 Sources, Multiple-Connected The 
 
 connection of a number of separate sources 
 so as to form a single source by joining the 
 positive poles of all the separate sources to a 
 single positive lead or conductor, and all the 
 negative poles to a single negative lead or 
 conductor. 
 
 The multiple connection of sources results in 
 each of the sources discharging its current into 
 the main conductor in a direction parallel to 
 that of the other sources. 
 
 The electromotive force in the same is that of 
 any single source, but the resistance of the com- 
 bined source decreases with each source added. 
 Supposing the resistance of each source be the 
 same, then if ten such sources are connected in 
 multiple -arc, the resistance of the combined source 
 is but one-tenth the resistance of a single source. 
 (See Circuit, Multiple.') 
 
 Sources are combined in multiple-arc whenever 
 the current furnished by the separate sources is 
 insufficient to properly operate the electro-recep- 
 tive or translating device with which it is con- 
 nected. 
 
 Sources, Multiple-Series-Connected 
 
 The conection of a number of separate 
 sources so as to form a single source by con- 
 necting a number of the sources in groups 
 in series, and joining these groups together 
 in multiple-arc. 
 
 The battery of sources obtained by connecting 
 a number of separate sources in multiple-series 
 will have an electromotive force equal to the 
 sum of the separate electromotive forces of the 
 sources connected in any of the separate series- 
 connected groups. 
 
 The current produced will be greater in propor- 
 tion to the number of separate groups in parallel. 
 The internal resistance will be increased in pro- 
 portion to the number of coils in series, and de- 
 creased in proportion to the number of groups in 
 multiple-arc or parallel. 
 
 Sources are connected in multiple-series when 
 both the electromotive force and the current of 
 any single source are insufficient to operate the 
 electro-receptive or translating device. (See 
 Circuit^ Multiple- Series.} 
 
Sou.] 
 
 484 
 
 [Spa. 
 
 Sources, Parallel Connected A 
 
 term sometimes applied to multiple-connected 
 sources. (See Sources, Multiple-Connected^) 
 
 Sources, Series-Connected The 
 
 connection of a number of separate electric 
 sources so as to form a single source, in 
 which the separate sources are placed in a 
 single line or circuit by so connecting their op- 
 posite poles that the current produced in each 
 passes successively through each of the 
 sources. 
 
 The series-connection of sources results in an 
 electromotive force equal to the sum of the sepa- 
 rate electromotive forces produced by each 
 source that is, a rise of potential occurs with each 
 source added. This connection increases the re- 
 sistance of the circuit by the amount of the resist- 
 ance of each source introduced into the circuit. 
 The value of the resulting current depends on the 
 total electromotive force and resistance of the 
 series-connected sources. 
 
 Sources are connected in series when the 
 electromotive force furnished by a single source 
 is insufficient for the character of work required 
 to be done. (See Circuit ', Series.) 
 
 Sources, Series-Multiple-Connected 
 
 The connection of a number of separate 
 electric sources, so as to form a single source, 
 in which the separate sources are connected 
 in a number of separate multiple groups or 
 circuits, and these groups or circuits separ- 
 ately connected together in series. (See Cir- 
 cuit, Series-Multiple.) 
 
 Southern Light. A name sometimes given 
 to the Aurora Australis. (See Aurora Aus- 
 tralis.) 
 
 Space, Clearance The space be- 
 tween the revolving armature of a dynamo- 
 electric machine, or electric motor, and the 
 polar faces of the pole pieces, 
 
 Space, Dark, Crookes' A dark 
 
 space surrounding the negative electrode in a 
 rarefied space through which electric dis- 
 charges are passing. 
 
 Crookes' dark space lies immediately between 
 the negative electrode and its glow or luminous 
 discharge. It differs, therefore, from Faraday's 
 dark space, which lies between the luminous dis- 
 charges of the negative and positive electrodes. 
 
 The radius of Crookes' dark space increases 
 with the degree of exhaustion. It varies also 
 with the character of the residual gas, with the 
 temperature of the negative electrode, and some- 
 what with the intensity of the spark. When the 
 vacuum becomes sufficiently high, the dark space 
 fills the entire tube through which the discharges 
 are passing. 
 
 Crookes has found that in the case of substances 
 that become phosphorescent under the electric 
 discharge, phosphorescence best takes place when 
 the body is placed on the boundary of the dark 
 space. 
 
 Space, Dark, Faraday's The gap 
 
 in the continuity of the luminous discharges 
 that occurs between the glow of the positive 
 and negative electrodes. 
 
 Faraday's dark space is seen in a partially ex- 
 hausted tube through which the discharges of 
 an induction coil are passing. It occurs in as 
 low a vacuum as 6 millimetres of mercury. 
 As the vacuum becomes higher, the length of the 
 dark space increases. 
 
 Space, Inter-Air A term some- 
 times employed for the air space between the 
 outer surface of the revolving armature of a 
 dynamo-electric machine and the adjacent 
 faces of the pole pieces. (See Space, Clear- 
 ance.) 
 
 Space, Interferric A term some- 
 times used for air gap. (See Gap. Air.) 
 
 Span Wire. (See Wire Span.) 
 
 Spark Coil. (See Coil. Spark) 
 
 Spark Gap. (See Gap, Spark.) 
 
 Spark, Length of The length of 
 
 spark that passes between two charged con- 
 ductors depends : 
 
 (I.) On the difference of potential between 
 them. 
 
 (2.) On the character of the gaseous medium 
 that separates the two conductors. 
 
 (3.) On the density or pressure of the gaseous 
 medium between the conductors. 
 
 Up to a certain pressure, a decrease in the 
 density causes an increase in the length of the 
 distance the spark will pass. When this limit is 
 reached, a further decrease of density decreases 
 the length of spark. A high vacuum prevents 
 the passage of a spark even under great differ- 
 ences of potential. 
 
Spa.] 
 
 485 
 
 [Spa. 
 
 (4.) On the kind of material that forms the 
 electrodes between which the charges pass. 
 
 (5.) On the shape of the charged conductor. 
 
 (6.) On the direction of the current. 
 
 Sparks from the prime conductor are denser 
 and more powerful than those from the negative 
 conductor. 
 
 It will be observed that the length of the spark 
 practically depends mainly on two circumstances, 
 Ariz., on the differences of potential of the oppo- 
 site charges, and the conducting power of the 
 medium that separates the two bodies. 
 
 Spark, f -Shaped A variety of 
 
 three-branched spark obtained by the dis- 
 charge of a Leyden jar through a peculiar 
 form of induction coil. (See Spark, Three- 
 Branched.} 
 
 Spark, Three-Branched A pecu- 
 liar form of branched spark obtained by the 
 discharge of a Leyden jar through a peculiar 
 form of induction coil. 
 
 The three- branched spark was obtained by 
 Elihu Thomson by the use of the following appa- 
 ratus: The discharges of a Leyden jar, charged by 
 a Topler-Holtz machine, were sent through an in- 
 duction coil, the primary and secondary of which 
 L 
 
 charged from a Topler-Holtz machine. The 
 discharge, in passing from the knob of the jar to 
 the wire L, representing the line, passed by the 
 
 Fig. 312. Apparatus for Three-Branched Sparks. 
 were of few turns. The circuit connections were 
 as shown in Figs. 512 and 513, and the apparatus- 
 is described by Thomson as follows: 
 
 "A double coil was made, Fig. 512, in which 
 the inner turns were about twelve and the outer 
 turns twenty. These were kept separate from each 
 other and a branch wire taken from the line and 
 slid from point to point on the outer wire enabled 
 the effective length of the same to be adjusted. 
 The inner coil was connected through a small 
 spark gap, as at A, to the outer coating of a Ley- 
 den jar, while the wire L, was brought near the 
 pole of the jar, which was continually being 
 
 Fig. 313. Apparatus/or Tand Y Shaped Sparks. 
 
 inner coil. When a certain length of the outer 
 coil was employed, only a very short, almost im- 
 perceptible spark was obtainable at a. If the 
 balance of the turns were disturbed by including 
 more or less than the proper number of the outer 
 turns, not only did a vigorous spark occur, but 
 the gap at a, could be quite considerably extended, 
 in accordance with the amount of departure taken 
 from the proper number of turns required to pro- 
 duce the balance. This ex- 
 periment indicates that it is 
 possible to make a selective 
 path for the Leyden jar dis- 
 charge, and to have a struc- 
 ture so proportioned that 
 the discharges reaching line 
 will pass to earth without F *- 
 tending to go through the cir- 
 cuit of the dynamo. The action is apparently 
 due to a balance of electromotive forces such 
 that the discharge which tends to pass from the 
 line in going to earth induces in the coil con- 
 nected to the dynamo a counter electromotive 
 force which nearly wipes out the potential of the 
 discharge before it reaches the dynamo. This 
 balance of inductive effects is certainly very strik- 
 ing, and once obtained, it is disturbed, as, in the 
 experiments, by changing the relative lengths of 
 the coils in inductive relation through so small 
 an amount as an inch or two. 
 
 " It may be mentioned here that some curious 
 
 Three- 
 Branched Sparks. 
 
Spa.] 
 
 486 
 
 [Spe. 
 
 effects of spark were obtained in these experi- 
 ments. When a disturbance of the balance ex- 
 ists and a spark is obtained at a, the character of 
 the spark is different from that of the Leyden jar 
 discharge. It appears to be less luminous, the 
 noise less sharp, and its color would indicate a 
 greater power of volatilizing metal and perhaps a 
 greater duration. It is in part, no doubt, due to 
 a current local to the coils in series with one an- 
 other. 
 
 'Another curious effect was the production of 
 T-shaped and Y- s ^ a P e< ^ sparks, or three- 
 branched sparks (such as are shown in Figs. 513 
 and 5 14.)" 
 
 "These were obtained by separating the elec- 
 trodes at A, an inch and a half or thereabouts, 
 and bringing the third eJectrode from the outer 
 coil to the position shown in Fig. 513. The dis- 
 charges were now obtained as before from the 
 charged jar. In this case the discharge appears 
 to split and unite in air, producing the curious 
 shaped sparks shown. It would seem that to ob- 
 tain these effects particularly the sparks which 
 were three- branched from a common point in the 
 centre between the discharge electrodes the 
 dielectric air must break down simultaneously be- 
 tween the three electrodes. It would easily ex- 
 plain the T-shapes to assume the straight part 
 above to form first, and the cross or transverse 
 spark to strike from the side of this spark to the 
 third electrode." 
 
 Spark Tube. (See Tube, Spark,} 
 
 Spark, Wipe In an electric gas- 
 lighting pendant burner, a spark obtained 
 from a spark coil by the wiping contact of a 
 spring, moved by the pulling of the pendant. 
 (See Burner, Ratchet-Pendant, Electric?) 
 
 Spark, Y-Shaped A variety of three- 
 branched spark obtained by the discharge of 
 a Leyden jar through a peculiar form of induc- 
 tion coil. (See Spark, Three-Branched!) 
 
 Sparking Discharge. (See Discharge, 
 Disruptive) 
 
 Sparking Distance. (See Distance, 
 Sparking!) 
 
 Sparking, Line of Least The line 
 
 on a commutator cylinder of a dynamo con- 
 necting the points of contact of the collecting 
 brushes where the sparking is a minimum. 
 
 In some forms of dynamos the line of least 
 
 sparking lies parallel to the lines of magnetic 
 force of the field. 
 
 In most forms, however, it is at right angles to 
 such lines. The exact position of all these lines 
 is changed by the angular lead of the brushes. 
 (See Lead, Angle of.) 
 
 Sparking of Dynamo-Electric Machine. 
 
 (See Machine, Dynamo-Electric, Sparking 
 of.) 
 
 Spar Torpedo. (See Torpedo, Spar.) 
 
 Spasmodic Governor. (See Governor, 
 Spasmodic) 
 
 Speaking-Tube Annunciator. (See An- 
 nunciator, Oral or Speaking- Tube) 
 
 Speaking-Tube Mouth Piece, Electric 
 
 Alarm A mouth piece for a speaking 
 
 tube, so arranged, that the movement of a 
 pivoted plate covering the mouth piece au- 
 tomatically rings a bell at the other end of 
 the tube. 
 
 Specific Conduction Resistance. (See 
 Resistance, Specific Conduction) 
 
 Specific Conductivity. (See Conduc- 
 tivity, Specific) 
 
 Specific Heat (See Heat, Specific) 
 
 Specific Heat of Electricity. (See Elec- 
 tricity, Specific Heat of) 
 
 Specific Hysteresial Dissipation. (See 
 Dissipation, Specific Hysteresial.) 
 
 Specific Inductive Capacity. (See Ca- 
 pacity, Specific Inductive) 
 
 Specific Magnetic Capacity. (See Ca- 
 pacity, Specific Magnetic) 
 
 Specific Magnetic Conductivity. (See 
 Conductivity, Specific Magnetic) 
 
 Specific Magnetic Inductivitv. (See In- 
 ductivity, Specific Magnetic) 
 
 Specific Resistance. (See Resistance, 
 Specific) 
 
 Specific Resistance of Liquids. (See 
 Resistance, Specific, of Liquids) 
 
 Speech, Articulate The successive 
 
 tones of the human voice that are necessary 
 to produce intelligible words. 
 
 The phrase articulate speech refers to the join- 
 ing or articulation of the successive sounds in- 
 volved in speech. The receiving diaphragm of a 
 
Spe.J 
 
 487 
 
 [Spo. 
 
 telephone is caused to reproduce the articulate 
 speech uttered near the transmitting diaphragm. 
 
 Speed, Critical, of Compound- Wound 
 
 Dynamo The speed at which bath the 
 
 series and shunt coils of the machine give the 
 same difference of potential when the full load 
 is on the machine, as the shunt coil would if 
 used alone on open-circuit. 
 
 Speed Indicator. (See Indicator, Speedy 
 
 Speeding. Varying the number of revolu- 
 tions per minute. 
 
 The speeding of a dynamo is for the purpose 
 of obtaining the current requisite to properly 
 operate the electro receptive device placed in its 
 circuit. 
 
 Spent Acid. (See Acid, Spent '.) 
 
 Spent Liquor. (See Liquor, Spent.) 
 
 Spherical Armature. (See Armature, 
 Spherical!) 
 
 Sphygmogram. A record made by a 
 sphygmograph. (See Sphygmograph!) 
 
 Sphygmograph. An instrument for re- 
 cording the peculiarities of the normal or 
 abnormal pulse. 
 
 Sphygmograph, Electrical An in- 
 strument for electrically recording the peculi- 
 arities of the pulse. 
 
 Sphygmophone. An apparatus in which 
 a microphone is employed for the medical 
 examination of the pulse. (See Microphone.) 
 
 Spider, Armature A light frame- 
 work or skeleton consisting of a central sleeve 
 or hub keyed to the armature shaft, and pro- 
 vided with a number of radial spokes or arms 
 for fixing or holding the armature core to 
 the dynamo-electric machine. 
 
 Spider, Driving Radial arms or 
 
 spokes connected to the armature of a dynamo- 
 electric machine and keyed to the shaft ,so as 
 to act as a driving wheel for the armature. 
 
 Spin, Magnetic A term sometimes 
 
 employed instead of magnetic field. 
 
 The term magnetic spin is sometimes used in- 
 stead of magnetic field because the magnetism is 
 now generally believed to be due to the effects of 
 a rotary motion or spin in the surrounding uni- 
 versal ether. 
 
 Spiral, Primary The primary of an 
 
 induction coil or transformer. (See Trans- 
 former. Coil, Induction!) 
 
 Spiral, Boget's A suspended wire 
 
 spiral conveying a strong electric current and 
 devised to show the attractions produced by 
 parallel currents flowing in the same direc- 
 tion. 
 
 The lower end of the wire spiral dips into a 
 mercury cup. On the passage of the current, the 
 attraction of the neighboring turns of the spiral 
 for each other shortens the length of the spiral 
 sufficiently to draw it out of the mercury and thus 
 break the circuit. When this occurs the weight 
 of the spiral causes it to fall and again re-estab- 
 lish the circuit. A rapid automatic-make-and- 
 break is thus established, accompanied by a brill- 
 iant spark at the mercury surface due to the ex. 
 tra spark on breaking. 
 
 Spiral, Secondary The secondary 
 
 coil of an induction coil or transformer. (See 
 Transformer. Coil, Induction.) 
 
 Splice Box. (See Box, Splice?) 
 Split Battery. (See Battery, Split.) 
 Split Lead Tee. (See Tee, Split Lead.) 
 Spluttering of Arc. (See Arc , Splutter- 
 ing of.) 
 
 Spots, Sun Dark spots, varying in 
 
 number and position, which appear on the 
 face of the sun and are believed by some to be 
 caused by huge vortex motions in the masses 
 of glowing gas that surround the sun's body. 
 
 Sun spots occur in greater number at intervals 
 of about every eleven years. 
 
 Their occurrence is generally attended with 
 unusual terrestrial magnetic variations. (See 
 Storm, Magnetic.) 
 
 In the opinion of most astronomers the sun 
 spots mark depressions in the atmosphere of the 
 sun. Their exact causes are unknown, though 
 they appear to be dependent on a local cooling 
 or condensation of the sun's atmosphere. 
 
 When observed through a telescope the sun 
 spot appears as a dark region surrounded by a 
 less dark region. Though darker by contrast 
 with thi rest of the sun's face, yet such spots are 
 in reality much brighter than the most brilliant 
 arc light. The outline of the sun spot is quite 
 irregular. 
 
Spr.J 
 
 488 
 
 [Sla. 
 
 Spreading-Out Magnetic Field. (See 
 Field, Magnetic, Spreading-Out?) 
 
 Sprengel Mercury Pump. (See Pump, 
 Air, SprengeFs Mercurial?) 
 
 Spring Ammeter. (See Ammeter, 
 Spring?) 
 
 Spring Contact. (See Contact, Spring?) 
 
 Spring, Hold-Off A spring which 
 
 acts to keep one thing away from another in 
 opposition to some force tending to keep it in 
 contact with such a thing. 
 
 Spring, Hold-On A spring which 
 
 acts to keep one thing against another in op- 
 position to some force tending to pull it 
 away. 
 
 A hold on spring is sometimes employed in a 
 dynamo-electric machine for the purpose of keep- 
 ing the collecting brushes in proper pressure 
 against the segments of the commutator. 
 
 Spring-Jack. A device for readily insert- 
 ing a loop in a main electric circuit. The 
 spring-jack is generally used in connection 
 with a multiple switch board. (See Board, 
 Multiple Switch.) 
 
 Spring-Jack Cut-Out (See Cut-Out, 
 Spring-Jack.) 
 
 Spurious Hall Effect. (See Effect, Hall, 
 
 Spurious?) 
 
 Spurious Resistance. (See Resistance, 
 Spurious?) 
 
 Stabile Galvanization. (See Galvaniza- 
 tion, Stabile?) 
 
 Staggering. A term sometimes applied to 
 the position of the brushes on a commutator 
 cylinder, in which one brush is placed slightly 
 in advance of the other brush so as to bridge 
 over a break. 
 
 When a break occurs in the circuit ot the arma- 
 ture wires, the device of staggering the brushes is 
 adopted for temporarily bridging over the break. 
 When a break occurs, the rewinding of the arma- 
 ture is the only radical cure. 
 
 Standard Candle. (See Candle, Stand- 
 ard?) 
 
 Standard Carcel Gas Jet (See Jet, Gas, 
 Carcel Standard?) 
 
 Standard, Dynamo The supports 
 
 for tha bearings of a dynamo-electric ma- 
 chine. . . 
 
 Standard Earth Quadrant (See Quad- 
 rant, Standard?) 
 
 Standard of Self-Induction, Ayrton & 
 
 Perry's (See Induction, Self, Ayrton 
 
 &*> Perry's Standard of.) 
 
 Standard Ohm. (See Okm, Standard?) 
 
 Standard, Pentane A standard 
 
 source of light used in photometric measure- 
 ments, in place of a Methven screen. 
 
 The pentane standard is constructed in general 
 in the same manner as the Methven standard. 
 In place, however, of ordinary coal gas, a mixture 
 of pentane and air is used. Pentane is a variety 
 of coal oil left after several distillations of ordinary 
 crude oil. It distills at a temperature not greater 
 than 50 degrees centigrade. 
 
 The mixture for burning consists of about 
 twenty volumes of air to seven volumes of pen- 
 tane. A burner of the pentane standard is some- 
 what similar to the Methven standard, but differs 
 in a number of minor details. 
 
 Standard Resistance Coil. (See Coil, 
 Resistance, Standard?) 
 Standard Size of Electrodes, Erb's 
 
 (See Electrodes, ErVs Standard Size of.) 
 
 Standard Voltaic Cell. (See Cell, Voltaic, 
 Standard.} 
 Standard Voltaic Cell, Clark's 
 
 (See Cell, Voltaic, Standard, Clark's.) 
 
 Standard Voltaic Cell, Clark's, Raj leigh's 
 Form of (See Cell, Voltaic. Stand- 
 ard, Ray leigh's Form of Clark's?) 
 
 Standard Voltaic Cell, Fleming's 
 (See Cell, Voltaic, Standard, Fleming's.) 
 
 Standard Voltaic Cell, Lodge's 
 
 (See Cell, Voltaic, Standard, Lodges.) 
 
 Standard Voltaic Cell, Sir William 
 Thomson's (See Cell, Voltaic, Stand- 
 ard, Sir William Thomson's.) 
 
 Standard Wire Gauge. (See Gauge, 
 Wire, Standard.) 
 
Sta.] 
 
 489 
 
 [Sta. 
 
 Standardizing a Yoltaic Cell. (See Cell, 
 Voltaic, Standardizing a.) 
 
 Standards, Motor A name applied 
 to the supports for the bearings of an electric 
 motor. 
 
 State, Allotropic A modification 
 
 of a substance, in which, without changing 
 its chemical composition, it assumes a condi- 
 tion in which many of its physical and chem- 
 ical properties are different from those it or- 
 dinarily possesses. 
 
 Thus the element carbon occurs in three widely 
 different allotropic states, viz. : 
 
 (i.) As charcoal, or ordinary carbon; 
 
 (2.) As graphite, or plumbago; and 
 
 (3.) As the diamond. 
 
 State, Anelectrotonic The condi- 
 tion of decreased functional activity which 
 occurs in a nerve in the neighborhood of the 
 anode or positive terminal of a source to 
 whose influence it is subjected. (See Anelec- 
 trotonus^} 
 
 State, Electrotonic A peculiar 
 
 state supposed by Faraday to exist in a wire or 
 other conductor, whereby differences of po- 
 tential are produced by means of its move- 
 ment through a magnetic field. 
 
 In his early researches Faraday regarded this 
 state as a necessary condition in which a wire or 
 conductor must exist, prior to its movement 
 through a magnetic field, in orde to have a dif- 
 ference of potential produced; but at a later day 
 he abandoned this idea, and explained the true 
 causes of electrodynamic induction. (See In- 
 duction, Electro- Dynamic.) 
 
 The term electrotonic state is to be carefully dis- 
 tinguished from electrotonus, or the change pro- 
 duced in the functional activity of a nerve by an 
 electric current. (See Electrotonus. ) 
 
 State, Kathelectrotonic The con- 
 dition of increased functional activity of a 
 nerve in the neighborhood of the kathode or 
 negative terminal of a source to whose in- 
 fluence it is subjected. (See Kathelectro- 
 tonus.} 
 
 The kathelectrotonic state is one of the states 
 or conditions of electrotonus or altered functional 
 activity produced in a nerve by an electric cur- 
 rent. (See Electrotonus, } 
 
 State, Nascent A term used in 
 
 chemistry to express the state or condition of 
 an elementary atom or radical just liberated 
 from chemical combination, when it possesses 
 chemical affinities or attractions more ener- 
 getic than afterwards. 
 
 According to Grothiiss' hypothesis, during the 
 decomposition of a chain of polarized molecules, 
 such for example as in the case of hydrogen sul- 
 phate, H s SO 4 , in a zinc-copper voltaic cell, the 
 two atoms of hydrogen H g , liberated by the com- 
 bination of the SO 4 , with an atom of zinc, Zn, pos- 
 sess a stronger affinity for the SO 4 of the molecule 
 next to it, than does its own H 2 , and thus liber- 
 ates its two atoms of hydrogen, which in turn 
 unite with the SO 4 , of the next molecule in the 
 polarized chain, and this continues until the two 
 atoms of hydrogen liberated from the last mole- 
 cule in the chain are given off at the copper plate. 
 (See Hypothesis, Grothitss'.) 
 
 The peculiar properties characteristic of the 
 nascent state of elements is doubtless due to 
 the fact that the elements are then in a. free 
 state, with their bonds open or unsatisfied, and 
 therefore possess greater affinities than when they 
 are united in molecules. Thus H , H , or 
 atomic hydrogen, should possess different affinities 
 than H H, or molecular hydrogen. 
 
 State, Passive 
 
 The condition of a 
 
 metallic substance in which it may be placed 
 in liquids that would ordinarily chemically 
 combine with it, without being attacked or 
 corroded. 
 
 It is very doubtful whether metallic bodies can 
 be properly regarded as possessing an actual 
 passive state. Iron, for example, which is one of 
 the metals that is said to be capable of assuming 
 this so-called passive state, can be placed in this 
 condition by immersing it for a few moments in 
 concentrated nitric acid, and subsequently wash- 
 ing it. It will then, unlike ordinary iron, neither 
 be attacked by concentrated nitric acid, nor will 
 it precipitate copper from its solutions. This 
 condition is now generally believed to be due to 
 the formation of a thin coating of magnetic oxide 
 on its surface. 
 
 Many of the instances of the so-called passive 
 state are simply cases of the well known electrical 
 preservation of metals that form the negative 
 element of a voltaic combination, under which 
 circumstances the positive element only of the 
 
Sta.J 
 
 490 
 
 [Ste 
 
 voltaic couple is chemically attacked by the elec- 
 trolyte. (See Cell, Voltaic. Metals, Electrical 
 Protection of. ) 
 
 State, Permanent, of Charge on Tele- 
 graph Line The condition of the 
 
 charge on a telegraph wire when the current 
 reaching the distant end has the same 
 strength as at the sending end. 
 
 State, Variable, of Charge of Telegraph 
 
 Line The condition of the charge on 
 
 a telegraph wire while the strength of the 
 current is increasing up to the full strength 
 in all parts. 
 
 The duration of the variable state is directly as 
 the length of the line, the electrostatic capacity 
 and the total resistance. It is increased by leak- 
 age, by static capacity and by the effects of the 
 extra current. (See Currents, Extra.} 
 
 Static Breeze. (See Breeze, Static.) 
 
 Static Electricity. (See Electricity, 
 Static) 
 
 Static Energy. (See Energy, Static) 
 
 Static Hysteresis. (See Hysteresis, 
 Static) 
 
 Static Insulation. (See Insulation, 
 Static) 
 
 Static Magnetic Induction. (See Induc- 
 tion, Magnetic, Static) 
 
 Static Shock. (See Shock, Static) 
 
 Statics. The science which treats of the 
 relations that must exist between the points 
 of application of forces and their direction 
 and intensity, in order that equilibrium may 
 result. 
 
 Statics, Electro That branch of 
 
 electric science which treats of the phenome- 
 na and measurement of electric charges. 
 
 Some of the more important principles ot elec- 
 trostatics are embraced in the following laws: 
 
 (l.) Charges of like name, i. e., either positive 
 T negative, repel each other. Charges ot unlike 
 aame attract each other. 
 
 (2.) The forces of attraction or repulsion be 
 tween two charged bodies are directly propor- 
 tional to the product of the quantities of electricity 
 possessed by the bodies and inversely proportional 
 to the square of the distance between them. 
 
 These laws can be demonstrated by the use of 
 Coulomb's torsion balance. (See Balance, Cou- 
 lomb' 1 s Torsion.) 
 
 Statics, Magneto That branch of 
 
 magnetism which treats of magnetic attrac- 
 tions and repulsions, the distribution of lines 
 of magnetic force and other facts regarding 
 fixed magnets. 
 
 Station, Central A station, cen- 
 trally located, from which electricity for light 
 or power is distributed by a series of con- 
 ductors radiating therefrom. 
 
 Station, Distant A term applied by 
 
 an operator to the distant end ot the line in 
 order to distinguish it from his own end. 
 
 Station, Distributing A station 
 
 from which electricity is distributed. 
 A central station. 
 
 Station, Home A term applied by 
 
 an operator to his end of the line, in order to 
 distinguish it from the other or distant sta- 
 tion. 
 
 Station, Transforming In a system 
 
 of distribution by transformers or converters 
 a station where a number of transformers are 
 placed, in order to supply a group of houses 
 in the neighborhood. (See Transformer. 
 Electricity, Distribution of, by Alternating 
 Currents.) 
 
 Stationary Floor Key. (See Key, Sta- 
 tionary Floor) 
 
 Stationary Torpedo. (See Torpedo, Sta- 
 tionary) 
 
 Stay Rods, Telegraphic Metal rods 
 
 attached to a telegraph pole, and securely 
 fastened in the ground in order to counteract 
 the effects of a pull or tension on the poles. 
 (See Pole, Telegraphic.} 
 
 Stay rods should be used in all exposed situa 
 tions, or where the poles are exposed to severe 
 strains. 
 
 Steady Current. -^-(See Current, Steady.) 
 
 Stearns' Relay Shunt. (See Shunt, Re- 
 lay, Stearns ) 
 
 Steel, Qualities of. Requisite for Mag- 
 netization Qualities which must be 
 
SteJ 
 
 491 
 
 [Sto. 
 
 possessed by steel in order to permit it to per- 
 manently retain a considerable magnetization. 
 
 For the purposes of permanent magnetization 
 steel should possess the following qualities: 
 
 It should be hard and fine grained. Hard cast 
 steel answers the purpose very well. Scoresby 
 showed that an intimate relation exists between 
 the quality of the iron from which the steel is 
 made, and the ability of the steel to take and re- 
 tain considerable magnetism. 
 
 The steel should be hardened as high as possi- 
 ble and the temper afterwards drawn by heat to 
 a violet-straw color. Practice is not uniform in 
 this respect, the exact color varying with the 
 quality of the steel. 
 
 An admixture with the steel of about y^ of one 
 per cent of tungsten is said to increase its mag- 
 netic powers. 
 
 Cast steel is not generally employed for mag- 
 nets, wrought steel being generally preferred. 
 
 Step-by-Step, or Dial Telegraphy. (See 
 
 Telegraphy, Step-by- Step?) 
 
 Step-Down Transformer. (See Trans- 
 former, Step-Down?) 
 
 Step-Up Transformer. (See Transform- 
 er, Step-Up) 
 
 Sterilization, Electric Sterilizing 
 
 a solution by depriving it of whatever germs 
 it may contain by means of electrical cur- 
 rents. 
 
 The following experiments were recently made 
 on sterilization by means of electric currents: 
 The fluid, with the culture, was placed in a glass 
 test tube, wound about with a wire coil connected 
 either with a dynamo or accumulator or other 
 electric source. Some increase in temperature 
 ras made, but never over 98 Fahr. When a 
 Current 1.25 volts, 2.5 amperes passed, a com- 
 plete sterilization of Micrococus Prodigiosus oc- 
 curred at the end of twenty-four hours. 
 
 Blood and water containing pathogenic germs 
 was sterilized in five to thirty minutes. The 
 above described effects would appear to be mag- 
 netic rather than electric. 
 
 Sticking. A word applied by telegraphers 
 to the failure of the positive pole relay arma- 
 ture to leave the magnet pole on the cessation 
 of the current. 
 
 In telegraphy, when from any cause a circuit 
 is imperfectly broken by an operator's key, or at 
 
 the points of contact of a relay or other instru- 
 ment, such failure is called sticking. When an arc 
 is formed at the points of a relay where the local 
 circuit is made and broken, the relay "sticks." 
 The arc is caused by burning of the platinum 
 points. Sticking may be a result of a too weak 
 retractile spring. 
 
 Stone, Hercnles A name given by 
 
 the ancients to the lodestone. (See Lode- 
 stone?) 
 
 Stool, Insulating A stool provided 
 
 with insulating supports of vulcanite or other 
 insulator, employed to afford a ready insulat- 
 ing stand or support. 
 
 Stop, Limiting A stop set so as to 
 
 limit the motion of an electrically vibrating or 
 oscillating bar to any predetermined extent. 
 
 Such limiting stops are common on telegraphic 
 and various other electrical apparatus. 
 
 Stopping-Off. A process employed in 
 electro-plating, in which a metallic article, al- 
 ready electro-plated over its entire surface, is 
 electro-plated with another metal over certain 
 parts only. 
 
 The process of stopping-off consists of covering 
 the parts which are to receive the metallic coat- 
 ing, with various stopping-off varnishes. By this 
 means articles can be electro-plated on \ arts of 
 their surfaces with gold and on the remainder 
 with silver. The whole surface is first silvered 
 and the portions intended to be afterwards gilded 
 are then stopped off and the object placed in the 
 gilding bath. 
 
 Stopping-Off Varnish. (See Varnish, 
 
 Stopping-Off.} 
 
 Storage Battery. (See Battery, Storage?) 
 Storage Capacity of Secondary Cell. 
 
 (See Cell, Secondary or Storage, Capacity 
 
 of?) 
 
 Storage Cell. (See Cell, Storage?) 
 Storage of Electricity. (See Electricity, 
 
 Storage of?) 
 
 Storm, Auroral A term sometimes 
 
 employed to express an unusual prevalence 
 of auroras. 
 
 Storm, Electric An unusual con- 
 dition of the atmosphere as regards the quan- 
 tity of its free electricity. 
 
Sto.j 
 
 492 
 
 [Str. 
 
 A thunder storm is a variety of electric storm. 
 (See Storm. Thunder.} 
 
 Storm, Magnetic Irregularities oc- 
 curring in the distribution of the earth's 
 magnetism, affecting the magnetic declina- 
 tion, dip, and intensity. 
 
 Magnetic storms have been observed to accom- 
 pany auroral displays, and to be coincident with 
 the occurrence of sun spots, or unusual outbursts 
 of solar activity. 
 
 The coincidence of magnetic storms and out- 
 bursts of solar activity is unquestioned. Wolf, 
 of Zurich, has shown by a comparison of nu- 
 merous observations of sun spots, the unques- 
 tioned correspondence, in the times of their 
 greatest activity, which occur every n.i years, 
 with the time of occurrence of an unusual number 
 of sun spots. He has placed these results in the 
 form of curves. Those shown in Fig. 515 are 
 taken from observations at Paris and Prague. 
 The full lines represent the periods of sun spots. 
 The dotted lines the periods of magnetic storms. 
 
 Fig. SfS- Wolfs Sun Spot Numbers. 
 
 Storm, Thunder A storm during 
 
 which electrical discharges accompanied by 
 thunder take place between two clouds or be- 
 tween a cloud and the earth. (See Elec- 
 tricity. Atmospheric. Storms, Thunder, 
 Geographical Distribution of.) 
 
 Storms, Thunder, Geographical Dis- 
 tribution of The following general 
 
 facts as to the geographical distribution of 
 thunder storms, show the intimate relation 
 between the trequency of thunder storms and 
 the time and place of the condensation of 
 vapor. 
 
 (i.) Thunder storms seldom, if ever, occur in 
 the polar regions. 
 
 This is probably because the rainfall in the 
 
 polar regions results from the condensation of the 
 vapor that was formed in the equatorial or tem- 
 perate regions, so that a considerable time 
 elapses between the evaporation and condensa- 
 tion. 
 
 (2.) Thunder storms seldom, if ever, occur in 
 rainless districts, owing probably to the absence 
 of the condensation of vapor. 
 
 (3.) Thunder storms are most frequent and 
 violent in the equatorial regions, where the rain- 
 fall results from the condensation of the vapor by 
 the action of ascending currents, conveying the 
 vapor almost immediately after its formation into 
 the upper and colder regions of the atmosphere. 
 
 (4.) Thunder storms occur in regions beyond 
 the tropics, at those seasons of the year when the 
 rainfall results from the condensation of the vapor 
 shortly after the time of its formation, viz., in the 
 temperate zones in the hotter parts of the year. 
 
 Straight-Line Trolley Hanger. (See 
 Hanger, Straight-Line Trolley?) 
 
 Straightaway Bunched Cable. (See 
 Cable, Bunched, Straightaway?) 
 
 Strain, Dielectric The strained 
 
 condition in which the glass, or other dielec- 
 tric of a condenser, is placed by the charging 
 of the condenser. 
 
 The deformation of a body under the in- 
 fluence of a stress. (See Stress.) 
 
 The stress in this case, *'. e., the force produc- 
 ing the deformation or strain, is the attraction of 
 the opposite charges. This stress, in the case of 
 a Ley den jar, is often sufficiently great to cause 
 a rupture of the glass. 
 
 Strain, Electro-Magnetic The de- 
 formation produced by an electro-magnetic 
 stress. (See Stress^ Electro-Magnetic.) 
 
 Strain, Electrostatic, Optical A 
 
 strain or deformation produced in a plate of 
 glass, or other transparent solid, by subject- 
 ing it to the stress of an electrostatic field. 
 (See Stress, Electrostatic.) 
 
 To obtain the electrostatic stress, holes are 
 drilled in the plate of glass, and wires from a 
 Holtz machine or induction coil placed therein, 
 the wires being separated by a thin layer of glass. 
 
 The glass, on being traversed by a beam of 
 plane polarized light, rotates the plane of polar- 
 ization of the light in the same direction as the 
 glass would if subjected to a strain in the direc 
 
Str.] 
 
 493 
 
 [Str. 
 
 tion of the lines of electric force. (See Rotation, 
 Magneto- Optic. ) 
 
 Strain, Magnetic The deformation 
 
 produced in the air-gap between two dissimi- 
 lar magnetic poles, or in any substance placed 
 therein, by the stress of the lines of magnetic 
 force bridging such gap. 
 
 Strain, Optical A deformation or 
 
 alteration of volume produced in a plate of 
 glass, or other transparent medium, by the 
 action of any stress. (See Strain, Electro- 
 Magnetic. Strain, Electrostatic, Optical?) 
 
 Strain, Optical Electro-Magnetic 
 
 A strain produced in a plate of glass or other 
 transparent medium by placing it in a mag- 
 netic field. (See Stress, Electro-Magnetic. 
 Rotation, Magneto-Optic?] 
 
 Optical strain, whether electrostatic or mag- 
 netic, or even mechanical, often causes a medium 
 to acquire the power of double refraction or ro- 
 tary polarization. (See Refraction, Double, 
 Electric. Rotation, Magneto-Optic.) 
 
 Stranded Core of Cable. (See Core, 
 
 Stranded, of Cable?) 
 
 Stranded Line. (See Line, Stranded?) 
 Strap Copper. (See Copper, Strap?) 
 Straps and Climbers. Devices employed 
 
 by linemen for climbing wooden telegraph 
 
 poles. 
 
 Stratham's Electric Fuse. (See Fuse, 
 Electric, Stratham's?) 
 
 Stratification Tube. (See Tube, Stratifi- 
 cation?) 
 
 Stratified Discharge. (See Discharge, 
 Stratified.) 
 
 Stray Field. (See Field, Magnetic, 
 Stray.) 
 
 Stray Power. (See Power, Stray?) 
 Stream-Lines of au Escaping Fluid. 
 
 Lines which show the actual path of the 
 particles of an escaping fluid. 
 
 When the escape has reached a steady condi- 
 tion, the stream-lines correspond to the flow lines. 
 
 Streamers. Pillars or parallel flashing 
 columns of light frequently seen during the 
 prevalence of an aurora. (See Aurora Bo- 
 realis.) 
 
 Streamers, Auroral A term some- 
 times applied to the flashing columns or pillars 
 of light that are thrown out in the shape of 
 streams, from portions of the sky during the 
 prevalence of an aurora. (See Aurora Bo- 
 realis.) 
 
 Streaming Discharge. (See Discharge, 
 Streaming?) 
 
 Streamlets, Current A theoretical 
 
 conception of a series of parallel current 
 streams or current filaments, flowing through 
 a solid conductor. 
 
 In the case of uniform distribution of an elec- 
 tric current where the current density is the same 
 for all areas of cross- section, these current stream- 
 lets are all of the same strength. 
 
 In the case of rapidly alternating currents, 
 however, the current streamlets are of greater 
 strength near the surface. When the rate of al- 
 ternation is sufficiently great, they are almost 
 entirely absent at the central parts. 
 
 The conception of current streamlets is made 
 in order to account for the increase in the resist- 
 ance of a solid conductor through which rapidly 
 alternating currents of electricity are passing. 
 (See Currents, Simple-Periodic.) 
 
 Streams, Convection Streams of 
 electrified air or other gaseous or vaporous 
 particles given off from the pointed ends of 
 charged, insulated conductors. (See Con- 
 vection, Electric?) 
 
 Street Mains. (See Main, Street.) 
 Street Service. (See Service, Street?) 
 
 Strength, Field The intensity or 
 
 total flux of magnetism of a dynamo. 
 
 This term is also sometimes roughly used for 
 the current strength in the field magnet circuit of 
 a dynamo-electric machine. 
 
 Strength of Current. (See Current 
 Strength?) 
 
 Strength of Magnetic Field. (See Field, 
 Magnetic, Strength of.) 
 
 Strength of Magnetism. (See Magnetism, 
 Strength of.) 
 
 Stress. The pressure, pull, or other force 
 producing a deformation or strain. 
 
Str. 
 
 494 
 
 [Sub. 
 
 Stress, Dielectric The force pro- 
 ducing the deformation or strain in a dielec- 
 tric. 
 
 A dielectric strain, in the case of a Leyden jar 
 or condenser, is sometimes sufficiently great to 
 pierce the dielectric. 
 
 Stress, Electro-Magnetic The force 
 
 or pressure in a magnetic field, which produces 
 a strain or deformation in a piece of glass . or 
 other similar substance placed therein. (See 
 Strain, Optical Electro-Magnetic) 
 
 Stress, Electrostatic The force or 
 
 pressure in an electrostatic field, which pro- 
 duces strain or deformation in a piece of glass 
 or other substance placed therein. (See 
 Strain, Electrostatic, Optical.) 
 
 Stress, Energy of A term some- 
 times used in place of potential energy. (See 
 Energy, Potential.) 
 
 Stress, Magnetic The force acting 
 
 to produce a strain in the air-gap between 
 two dissimilar magnet poles by the action of 
 the lines of magnetic force, bridging such air 
 
 gap- 
 
 Striae, Electric Parallel streaked 
 
 bands, consisting of alternate light and dark 
 spaces, produced in tubes containing low 
 vacua, by the passage of rapidly alternating 
 currents through them. (See Tube, Strati- 
 fication.) 
 
 Strip, Safety A strip or bar used as 
 
 a safety fuse. (See Fuse, Safety.) 
 
 Stripping. Dissolving the metal coating 
 from a silver-plated or othe'r metal-plated ar- 
 ticle. 
 
 The object of the "stripping " process is tore- 
 cover silver from imperfectly plated ware, or 
 from old ware which is to be replated. 
 
 Stripping of silver is accomplished either in the 
 cold or by aid of heat, by the use of the following 
 solutions, viz.: 
 Concentrated sulphuric acid, 
 
 (Baume', 66 degrees) ico parts. 
 
 Concentrated nitric acid, 
 
 (Baume, 40 degrees). IO " 
 
 The objects are suspended in this liquid, which, 
 provided it be not diluted with water, possesses 
 the property of dissolving the silver without 
 touching the metal underneath. 
 
 Stripping Baths. (See Bath, Strip- 
 ping^ 
 
 Stripping Liquid. (See Liquid, Strip- 
 ping^ 
 
 Stroke, Lightning A disruptive 
 
 discharge between two oppositely charged 
 clouds, or between a cloud and the earth. 
 (See Discharge, Disruptive!) 
 
 Stroke, Lightning, Back or Return 
 
 An electric shock, caused by an induced 
 charge, produced by the discharge of a light- 
 ning flash. 
 
 The shock is not caused by the lightning flash 
 itself, but by a charge which is induced in neigh- 
 boring conductors by the discharge. These in- 
 duced effects are, in fact, effects of electro-dy- 
 namic induction. (See Induction, Electro-Dy- 
 namic.) A similar effect may be noticed by 
 standing near the conductor of a powerful electric 
 machine, when shocks are felt at every discharge. 
 
 The effects of the return shock are sometimes 
 quite severe. These effects are often experienced 
 by sensitive people on the occurrence of a light- 
 ning discharge at a considerable distance. 
 
 In some instances the return stroke has been 
 sufficiently intense to cause death. In general, 
 however, the effects are much less severe than 
 those of the direct lightning discharge. 
 
 Struts for Telegraphic Poles. Inclined 
 wooden or iron poles, applied to telegraph 
 poles in order to support the thrust or press- 
 ure acting on them. (See Pole, Tele- 
 graphic) 
 
 Sturgeon's or Barlow's Wheel. A wheel 
 capable of rotation on a horizontal axis, which, 
 when placed between the poles of a magnet, 
 rotates when a current is passed through it 
 between the axis and the circumference. 
 
 Sub-Aqueous Cable. (See Cable, Sub- 
 Ayueous.) 
 
 Sub-Branch. (See Branch, Sub.) 
 
 Sub-Main. (See Main, Sub) 
 
 Submarine Boat. (See Boat, Sub- 
 marine, Electric) 
 
 Submarine Cable. (See Cable, Sub- 
 marine.) 
 
 Submarine Mine. (See Mine, Sub- 
 marine.) 
 
Sab.] 
 
 [Sur. 
 
 Submarine Telegraphy. (See Teleg- 
 raphy, Submarined) 
 
 Substance, Ferro-Magnetic A 
 
 term proposed in place of paramagnetic, for 
 substances that are magnetic after the man- 
 ner of iron. (See Paramagnetic?) 
 
 Subterranean Mine. (See Mine, Sub- 
 terranean.} 
 
 Subway, Electric 
 
 An accessible 
 
 underground way or passage provided for the 
 reception of electric wires or cables. 
 
 Underground electric conductors, like all elec- 
 tric conductors, are liable to faults, crosses, etc. 
 Unless they are readily accessible, very serious 
 loss and damage may occur before the fault is 
 located and corrected. 
 
 Sulphating. A name applied to one of the 
 sources of loss in the operation of a storage 
 battery, by means of the formation of a coating 
 of inert sulphate of lead on the battery plates. 
 
 The addition of a solution of sulphate of soda 
 to the sulphuric acid liquid is claimed to have the 
 effect of decreasing the extent of the sulphating. 
 
 Summer Lightning. (See Lightning, 
 Summer?) 
 
 Sun Spots. (See Spots, Sun.} 
 
 Sunstroke, Electric, or Electric Prostra- 
 tion or Insolation Physiological 
 
 effects, similar to those produced by exposure 
 to the sun, experienced by those exposed for 
 a long while to the intense light and heat of 
 the voltaic arc. 
 
 Electric sunstroke is sometimes called electric 
 insolation, or electric prostration. 
 
 The effects of electric sunstroke were first 
 noticed by Desprez in his classic experiments on 
 the fusion or volatilization of carbon. 
 
 On undue exposure to an intense electric light 
 the eyes are irritated and the skin burned as 
 by the sun. In some cases it is claimed that the 
 effects of sunstroke, or excessive production of 
 heat, as in true insolation, are produced. In the 
 applications of electricity to electric furnaces, 
 these same effects have been noticed in an inten- 
 sified degree. 
 
 From some recent investigations it would ap- 
 pear that these effects are to be ascribed to the 
 light rather than to the heat. 
 
 The symptoms are as follows: Pain in the 
 throat, face and temples, followed by a coppery 
 red color of the skin, irritation and watering of 
 the eyes, when the symptoms disappear. The 
 skin peels off in about five days. 
 
 Superficial Eddy Currents. (See Cur- 
 rents, Eddy, Superficial.} 
 
 Super-Saturation of Solution. (See 
 Solution, Super-Saturation of.} 
 
 Supplement of Angle. (See Angle, Sup- 
 plement of.} 
 
 Supply, Unit of, Electrical A unit, 
 
 provisionally adopted in England by the 
 Board of Trade, equal to 1,000 amperes flow- 
 ing for one hour under an electromotive force 
 of one volt. 
 
 This would, of course, equal 1,000 watt-hours, 
 and would be the same as 100 amperes flowing 
 for ten hours under one volt. 
 
 One unit of electrical supply is equal to 1.34 
 actual horse-power expended for one hour, and 
 will feed 13. 4 Swan lamps of 21 candle-power for 
 one hour. It is equal in illuminating power in 
 Swan lamps to the light produced by loo cubic 
 feet of gas consumed in twenty 14-candle burners 
 in one hour. 
 
 The unit of electrical supply is called a "Board 
 of Trade unit," a B. O. T. unit, or simply a bot. 
 It is equal to one kilo-watt hour. 
 
 Support, Tripod Roof A support 
 for a housetop telegraphic line. 
 
 The tripod roof support, as its name indicates, 
 consists of a three-legged support for any suitable 
 insulator. 
 
 A common form is shown in Fig. 516. 
 
 Support, Underground Cable A 
 
 support provided for holding a cable where 
 it passes around the side of a man-hole, un- 
 derground conduit, or other similar location. 
 
 Surface, Demarcation 
 
 The surface 
 
 at which a demarcation current is generated. 
 
 The surface which marks the point of in- 
 jury in a muscle or nerve. 
 
 Demarcation currents in electro-therapeutics, 
 are currents produced in injured nerves or 
 muscles. They are probably due to the chemical 
 changes that take place between the injured and 
 the uninjured tissues. The demarcation surface is 
 
Sur.] 
 
 496 
 
 [Sur. 
 
 the surface separating parts in a normal condi- 
 tion from those in an abnormal condition. 
 
 An injury to a muscle or nerve causes or pro- 
 duces at such surface a dying substance which is 
 
 Fig. Jf6. Tripod Roof Support. 
 
 negative to the uninjured, normal or positive sub- 
 stance. Such a surface results in a demarcation 
 current. 
 
 Surface Density. (See Density, Surfaced) 
 
 Surface, Equipotential, of a Conductor 
 Through Which a Current is Flowing 
 
 A surface described within the mass of a 
 conductor, conveying an electric current, at 
 points perpendicular to the direction of the 
 flow, all possessing the same potential. 
 
 Surface, Equipotential, or Level Surface 
 of Escaping Fluid A surface de- 
 scribed within the mass of a fluid in motion 
 at all places perpendicular to the stream lines 
 passing such surface. 
 
 Surface Integral of Magnetic Induction. 
 (See Induction, Magnetic, Surface-Inte- 
 gral of.) 
 
 Surfaces, Eqnipotential, Electrostatic 
 
 Surfaces, all the points of which are 
 
 at the same electric potential. (See Poten- 
 tial, Electric?) 
 
 Electric surfaces perpendicular to the lines 
 of electric force over which a quantity of 
 electricity, considered as being concentrated 
 at a point, may be moved without doing 
 work. (See Field, Electrostatic.} 
 
 Equipotential surfaces correspond with a water 
 level, over which a body may be moved horizon- 
 tally without doing any work against the force of 
 gravity. 
 
 In the case of the charged insulated sphere, 
 shown in Fig. 517, the equipotential surfaces, 
 represented by the circles, are concentric. 
 
 Fig. 317. Equipotential Surfaces. 
 
 Surfaces, Equipotential, Magnetic 
 
 Surfaces surrounding the poles of a mag- 
 net, or system of magnets, where the mag- 
 netic potential is the same. (See Potential, 
 Magnetic?) 
 
 Magnetic equipotential surfaces extend in a 
 direction perpendicular to the lines of magnetic 
 force. (See Field, Magnetic.) 
 
 No work is required in order to move a unit 
 pole over equipotential magnetic surfaces, be- 
 cause in so doing it cuts no lines of magnetic 
 force. Work, however, is done when the motion 
 is from one equal potential surface to another. 
 
 Equipotential surfaces, whether electric or mag- 
 netic, cannot intersect one another, since their 
 potential is the same at all points. 
 
 Surfaces, Isothermal Surfaces con- 
 necting points in a body which have the same 
 temperature. 
 
 Surging Discharge. (See Discharge, 
 Surging.) 
 
 Snrgings, Electric Electric oscilla- 
 tions set up in a charged conductor that is 
 undergoing rapid discharge. 
 
 These surgings produce waves in the surround- 
 ing ether that travel outwards with the velocity of 
 
Sns.] 
 
 497 
 
 [Sus. 
 
 light. (See Electricity, Hertz's Theory of Elec- 
 tro-Magnetic Radiations or Waves.} 
 
 Susceptibility, Magnetic --- The ratio 
 existing between the induced magnetization 
 and the magnetic force producing such mag- 
 netism, or the intensity of magnetism divided 
 by the magnetic force. 
 
 Susceptibility relates to the poles produced in a 
 body by a magnetizing force, whereas permea- 
 bility refers its power to conduct lines of force. 
 When the inducing field has unit strength oi 
 magnetization, the magnetic susceptibility will 
 measure directly the strength of the magnetiza- 
 tion. 
 
 When a bar of iron is placed in a magnetic 
 field, it is threaded by the lines of magnetic force, 
 and thus becomes magnetized by induction. This 
 induction will necessarily depend both on the 
 number of lines of force in the magnetizing field 
 and on the magnetic permeability of the magnet- 
 ized body; or, in other words, the induction is 
 equal to the product of the intensity of the mag- 
 netizing field and the magnetic permeability of 
 the body in which the induction occurs. 
 
 The magnetic susceptibility is sometimes called 
 the Co-efficient of Magnetization; calling K, the 
 susceptibility, H, the magnetizing force, and I, the 
 intensity of the resulting magnetization; then 
 
 K=I. 
 H 
 
 The magnetic permeability is sometimes called 
 the Co-efficient of Magnetic Induction, calling #, 
 the permeability, B, the magnetic induction and 
 H, the magnetic force producing the induction ; 
 then 
 
 Suspending Wire of Aerial Cable. (See 
 
 Wire, Suspending, of Atrz'al Cable.) 
 
 Suspension, Bifllar -- The suspen- 
 sion of a needle by two 
 parallel wires or fibres, 
 as distinguished from 
 a suspension by a sin- 
 gle wire or fibre. 
 
 A bifilar suspension is 
 shown in Fig .518. The 
 two threads, a b and a' 
 b', are connected to the Fif.jiS. Bifilar 
 needle M N, so as to per- sitm - 
 
 mit it to hang in a true horizontal position. Any 
 
 M b 
 
 \ 
 
 j 
 
 . ffe 
 
 &' N 
 
 twisting, around the imaginary axis c c', causes 
 the lines of suspension, ab and a' b', to tend to 
 cross one another and so shorten the axis c c' . 
 
 Harris, who was the first to employ the bifilar 
 suspension, showed that the reactive force im- 
 parted to the suspension threads by turning the 
 needle, was: 
 
 (i.) Directly proportional to the distance be- 
 tween the threads. 
 
 (2.) Inversely as their lengths. 
 
 (3.) -Directly proportional to the weight of the 
 suspended body. 
 
 (4.) Proportional to the angle of twist or torsion 
 of the threads on each other. 
 
 Any deflection of the needle shortens the verti- 
 cal distance between the points of support and 
 the needle, and so tends to lift the needle. The 
 motions are therefore balanced against the force 
 of gravity instead of against the torsion of the 
 fibre. 
 
 Suspension, Combined Fibre and Spring 
 
 The suspension of a needle by the 
 
 combined use of a spiral spring and a single 
 fibre. 
 
 In this form of suspension the spring is intro- 
 duced between the fibre and the needle. It is 
 valuable for marine galvanometers and other ap- 
 paratus exposed to tilting or rolling motions, be- 
 cause it permits the instrument to be tilted 
 through several degrees without causing any con- 
 siderable variation in the deflections produced by 
 the current or the charge. 
 
 Suspension, Fibre Suspension of a 
 
 needle by means of a fibre of unspun silk or 
 other material. 
 
 A fibre suspension generally means a single 
 fibre or thread. It may, however, be applied to 
 a bifilar suspension. (See Suspension, Bifilar.} 
 
 A fibre suspension is to be preferred to a pivot 
 suspension, since it eliminates all friction . It has, 
 however, the disadvantage of necessitating level- 
 ing screws. 
 
 Suspension, Knife-Edge The sus- 
 pension of a needle on knife edges that are 
 supported on steel or agate planes. 
 
 A suspension of this kind is used in the dip- 
 ping needle, since it permits of freedom of mo- 
 tion in a single vertical plane only. 
 
 Suspension, Pivot Suspension of a 
 
 needle by means of a jeweled cup and a me- 
 tallic pivot. 
 
Swa.J 
 
 498 
 
 [Swi. 
 
 The jeweled cup is placed above the centre of 
 gravity of the needle, and is supported on a steel 
 point. As a rule, compass needles have this 
 variety of support. 
 
 Swage. A particular form of anvil on 
 which highly heated metallic plates are shaped 
 by hammering them into forms the same as 
 that of the anvil on which they are placed. 
 
 Swage. To fashion heated metallic plates 
 by hammering them into the form of an, anvil 
 on which they are supported. 
 
 Swaging. Fashioning highly heated me- 
 tallic plates into any desired form by ham- 
 mering while on suitable dies. 
 
 Swaging, Electric The forming or 
 
 shaping of metallic plates by hammering 
 them against suitable anvils or dies while 
 softened by electrical heating. 
 
 The electro-swaging apparatus consists of a 
 welding transformer provided with a movable 
 clamp. The pressure required for the swaging 
 is attained by the use of steam admitted into a 
 cylinder by a lever which operates a four-way 
 valve. 
 
 The rod, bar, or plate of metal to be shaped or 
 swaged, is first heated by the passage of a pow- 
 erful heating current, obtained preferably from a 
 welding transformer, one of the clamps of which 
 is movable. When the metal is.suitably softened 
 by the passage of the current, it is then subjected 
 to swaging. 
 
 Swelling Current. (See Currents, Swell- 
 ing^ 
 
 Swelling Faradic Current. (See Cur- 
 rents, Swelling JFaradtc.) 
 
 Swinging Annunciator. (See Annuncia- 
 tor, Pendulum or Swinging.) 
 
 Swinging Cross. (See Cross, Swinging 
 or Intermittent!) 
 
 Switch, Automatic, for Incandescent 
 
 Electric Lamps A device by which 
 
 incandescent electric lamps can be lighted or 
 extinguished at a distance by means of push 
 buttons. 
 
 The automatic switch for incandescent lamps 
 corresponds in electric lighting to the automatic 
 gaslighting device in systems ot' electric gaslight- 
 ing. It consists essentially of two electro- 
 magnets, one for turning the switch which lights 
 
 the lamp by cutting them into the circuit of the 
 lighting mains or conductors, and the other for 
 extinguishing them, by cutting them out. These 
 electro-magnets are operated by two push buttons, 
 a black one to extinguish the lamp and a white 
 button to light it. 
 
 The details of the automatic switch are shown in 
 Fig. 520. The mains M 1 andM 2 , areconnected to 
 one set of contacts, and the branches containing 
 
 Fig, 519. Automatic Switch. 
 
 the lamps to be lighted, to the contacts between 
 them. The push buttons, P 1 and P 2 , are con- 
 nected by their wires to the main M 1 and the 
 branch B*. 
 
 These buttons are made respectively positive 
 and negative, and are marked -f- and . The 
 third wire of the push button is connected as 
 shown to the lamp L, and the switch magnet, 
 SM. 
 
 When the contact is closed atP 1 , the arma- 
 ture of S M, closes the contact through C. 
 When the button is released, connection is estab- 
 
 Fig. J2O. Automatic Switch. 
 
 lished between the magnet and the lamp L, in 
 series. This is for the purpose of cutting down 
 the circuit to the ^ of an ampere, and thus per- 
 mitting a thin wire to serve between the button 
 and the switch magnet. 
 
 When the button, P 2 , is closed the lamps are 
 turned out. 
 
 Switch Board. (See Board, Switch?) 
 
 Switch Board, Multiple (See 
 
 Board, Multiple Switch?) 
 
Swi.] 
 
 499 
 
 [Swi. 
 
 Switch Board, Telegraphic (See 
 
 Board, Switch, Telegraphic!) 
 
 Switch Board, Trunking (See 
 
 Board, Switch, Trunking?) 
 
 Switch, Break-Down A special 
 
 switch, employed in small three-wire systems, 
 for connecting the positive and negative bus- 
 wires in such a manner as to practically 
 convert it into a two-wire system and permit 
 the system to be supplied with current from 
 a single dynamo. (See Wires, Bus.} 
 
 Switch, Changing A switch de- 
 signed to throw a circuit from one electric 
 source to another. 
 
 A changing switch, for example, is of use in 
 disconnecting a circuit from one dynamo and 
 connecting it to another; or, in other words, to 
 suddenly transfer the load from one dynamo to 
 another. 
 
 Switch, Changing-Over A term 
 
 sometimes applied to a changing switch. 
 (See Switch, Changing!) 
 
 Switch, Distributing A multiple 
 
 switch board. (See Board, Multiple Switch!) 
 
 Switch, Distributing, for Electric 
 
 Lights A switch employed in a 
 
 system of arc lighting by series-distribu- 
 tion, by means of which any particular 
 dynamo-electric machine or a number of 
 
 Fig. J2T. Double- Break Knife Switch. 
 
 separate dynamo-electric machines can 
 be connected with the same circuit without 
 interfering with the lights. (See Board, Mul- 
 tiple Switch!) 
 
 Switch, Double-Break A term 
 
 sometimes used for double-pole switch. (See 
 Switch, Double-Pole.) 
 
 Switch, Double-Break Knife A 
 
 knife switch provided with double-break con- 
 tacts. 
 
 A double-break knife switch is shown in Fig. 
 521- 
 
 Switch, Double-Pole A switch 
 
 that makes or breaks contact with both poles 
 of the circuit in which it is placed. 
 
 A switch consisting of a combination of 
 two separate switches, one connected to the 
 positive lead and the other to the negative 
 lead. 
 
 Double-pole switches are used in most systems 
 of incandescent lighting in order to insure the 
 thorough separation of the circuit from the main 
 conductor or leads when cut out and to diminish 
 the spark. 
 
 Switch, Feeder The switch em- 
 ployed for connecting or disconnecting each 
 conductor of a feeder from the bus-bars in a 
 central station. 
 
 Switch, Four-Point A switch by 
 
 which a circuit can be completed through 
 four central points. 
 
 Switch, Knife A switch which is 
 
 opened or closed by the motion of a knife 
 
 - 532. Lamp-Socket Switch. 
 
 contact which moves between parallel contact 
 plates. 
 
 A knife-edge switch. (See Switch, Knife- 
 Edge} 
 
 Switch, Knife-Break - A knife 
 switch. (See Switch, Knife.} 
 
 Switch, Knife-Edge -- A term some- 
 times used in place of knife switch. (See 
 Switch, Knife.) 
 
Swi.] 
 
 500 
 
 [Swi. 
 
 Switch, Lamp-Socket A switch 
 
 placed in the socket of an incandescent lamp 
 and provided for throwing the lamp in and 
 out of the circuit. 
 
 A form of lamp socket switch is shown in Fig. 
 522. Its operation will be understood from an 
 inspection of the drawing. 
 
 Switch Pin. (See Pin, Switch^ 
 
 Switch, Plug A switch in which a 
 metal plug is withdrawn to throw into a cir- 
 cuit a coil or other device, the ends of which 
 are connected to metallic blocks that are suf- 
 ficiently near together to be joined and short- 
 circuited by the insertion of the plug. 
 
 Switch, Pole-Changing A switch 
 
 employed for changing the direction of the 
 current in any circuit. 
 
 A form of pole-changing switch is shown in Fig. 
 S23- 
 
 Fig. 323. Pole-Changing Switch. 
 
 If the two outer contacts are connected to the 
 same pole as the source, as, for example, the 
 positive, and the two intermediate contacts are 
 connected to the other pole, or to the negative, 
 then in the position shown in the cut, the current 
 will flow through any receptive device connected 
 with the switch, in one direction, but if the 
 switch is moved to the left, it will flow in the op- 
 posite direction. 
 
 Switch, Removable Key A plug 
 
 switch. (See Switch, Plug.) 
 
 Switch, Reversing A switch for 
 
 reversing the direction of the battery current 
 through a galvanometer. 
 
 A simple reversing switch consists of four in- 
 sulated brass segments mounted on a plate of 
 ebonite and furnished with openings between 
 them for plug connections. 
 
 The battery terminals are connected to two di- 
 agonally opposite segments, as B, and D, Fig. 
 524, and the leading wires of the galvanometer, 
 
 or other instrument, to the other segments, as C 
 and A, If, now, the plugs are placed between B 
 and C*, and A and D, the battery current flows 
 in one direction. If, however, the plugs are 
 
 Fig. 5 2 4" Reversing Switch. 
 
 placed between A and B, and C and D, the bat- 
 tery current will flow in the opposite direction. 
 
 The battery current is cut off if one plug is re- 
 moved. In practice, however, it is preferable to 
 remove both plugs, so as to avoid any current 
 from want of sufficient insulation. 
 
 Switch, Snap A switch in which 
 
 the transfer of the contact points from one 
 position to another is accomplished by means 
 of a quick motion obtained by the operation 
 of a spring. 
 
 The object of the snap switch is to prevent the 
 switch resting in any half way position, and thus 
 preventing the establishing of an arc. 
 
 Switch, Telephone, Automatic A 
 
 device' for automatically transferring the con- 
 nection of the main line from the call bell to 
 the telephone circuit. 
 
 In most telephone circuits, as now arranged, 
 the automatic switch, besides transferring the main 
 line from the call bell to the telephone circuit, 
 
 Fig: 323. Automatic Telephone Switch. 
 
 closes the local battery circuit of the transmitter 
 on the removal of the telephone from its support- 
 ing hook. 
 
Swi.] 
 
 501 
 
 [Sym. 
 
 The means whereby this is accomplished are 
 shown in Fig. 525. On the removal of the tele- 
 phone from the hook L, the lever is pulled up- 
 wards by the spring Z, thus closing the contacts I, 
 2 and 3, by which the local battery S, is closed 
 through the circuit of the transmitter, the tele- 
 phone disconnected from the circuit of the call bell 
 M, B, and connected with the circuit of the trans- 
 mitter. On replacing the telephone on the hook 
 L, its weight depresses the lever, breaking con- 
 nection with I, 2 and 3, and establishing connec- 
 tion with the call circuit. 
 
 Switch, Three-Point A switch by 
 
 means of which a circuit can be completed 
 through three different contact points. 
 
 Switch, Time An automatic switch 
 
 hi which a predetermined time is required 
 
 either to insert a resistance in or remove it 
 from a circuit. 
 Switch, Two-Point A switch by 
 
 SYMBOLS COMMONLY USED IN ELECTRICAL WORK. 
 
 means of which a circuit can be completed 
 through two different contact points. 
 
 Switch, Two- Way A switch pro- 
 vided with two contacts connected with two 
 separate and distinct circuits. 
 
 Switch, Yale-Lock, for Burglar Alarm 
 
 (See Alarm, Yale-Lock Switch 
 
 Burglar?) 
 
 Switched-In. Placed in a circuit by means 
 of a switch. (See Closed-Circuited^) 
 
 Switched-Out. Cut out of a circuit by 
 means of a switch. (See Open-Circuited^) 
 
 Symbols and Diagrams, Standard Elec- 
 tric Standard symbols and diagrams 
 
 used in electro-technics. 
 
 The standard electric diagrams and symbols 
 shown on pages 501, and 502, were arranged by 
 Prof. F. B. Crocker, and are reproduced from 
 the Electrical Engineer. 
 
 MECHANICAL. 
 
 ELECTRICAL. 
 
 MAGNETIC. 
 
 Lori. Length 
 
 D. Diameter 
 
 E.orE.jf.F. Electromotive 
 
 T. Volt 
 
 N. North pole 
 
 Morni. Mass 
 
 r. Radius 
 
 force 
 
 amp. Ampere 
 
 S. 
 
 South pole 
 
 fort. Time 
 
 H.P. Horsepower 
 
 P.D. Potential difference 
 
 co. Ohm 
 
 m 
 
 . Strength of pole 
 
 T. Velocity 
 
 I.H.P. Indicated " 
 
 C. Current 
 
 O. Megohm. 
 
 H. Magnetizing force 
 
 fort. Force 
 
 B.H.P. Brake " 
 
 B. Resistance 
 
 B.A.U. Brit. Ass'n Unit 
 
 
 (C.G.S.) 
 
 g. Acceleration 
 due to gravity. 
 
 W<TTW. Work. 
 
 r.p.m. Revolutions 
 per min. 
 C.Q.S. Centimetre 
 
 p. Specific resistance 
 Q. Quantity 
 K. Electrostatic capacity. 
 
 mfd. Microfarad 
 h. or hy. Henry 
 z. Electrochemical 
 
 B. Magnetic induction 
 (C.G.S. lines) 
 \. Intensity of mag- 
 
 P. Power. 
 rt.lb. Footpound. 
 
 gramme second 
 (System) 
 A.YF.G. American 
 
 L. Inductance ( Coeffic. of) 
 A.M. Amperemeter. 
 
 equivalent 
 i. Joule 
 
 fj.. 
 
 Magnetic per- 
 meability 
 
 
 Wire Gauge 
 
 Y.M. Voltmeter 
 
 K.W. Kilowatt 
 
 K. 
 
 Magnetic sus- 
 
 
 B.W. Q.Birmingham 
 Wire Gauge 
 
 F.M. Field Magnet 
 -\- Positive pole or terminal 
 Negative ' ' ' 
 
 ...Complete period 
 
 (Alt. cur.) 
 ~CL Dynamo 
 
 H 
 
 ceptibility 
 . Horizontal 
 intensity of Earth's 
 
 
 
 
 -llll- Battery 
 
 
 magnetism 
 
 Siemens I Jlrmatitrt 
 
 Jlmmetef ortbUmettr 
 
 Alternating Current 
 Transformer Diagram 
 | mmary SM.f 
 Pnmttry Current 
 B Secondary E JHf 
 
 Incandescent Lighting 
 
Sym.J 
 
 502 
 
 [Sym. 
 
 Morse Telerrrafili System 
 
 RJutatol RetutnnetCM ? -print SwUf* 
 
 ,=, \Q>ndNlitr 
 
 Alternating Current Transformer System 
 
 Crocker's Chart of Standard Electric Symbols and Diagrams. 
 
Sym.J 
 
 503 
 
 [Sys. 
 
 Symmetrical Induction of Armature. 
 
 (See Induction, Symmetrical, of Armature, ,) 
 Symmetrical Magnetic Field. (See 
 Field, Magnetic, Symmetrical!) 
 
 Sympathetic Electrical Vibrations. 
 (See Vibrations, Sympathetic Electrical!) 
 
 Sympathetic Vibrations. (See Vibra- 
 tions, Sympathetic!) 
 
 Synchronism. The simultaneous occur- 
 rence of any two events. 
 
 A rotating cylinder, or the movement of an 
 index or trailing arm, is brought into synchronism 
 with another rotating cylinder or another index 
 or trailing arm, not only when the two are mov- 
 ing with exactly the same speed, but when in ad- 
 dition they are simultaneously moving over simi- 
 lar portions of their respective paths. 
 
 In the Breguet Step-by-Step or Dial Telegraph 
 (See Telegraphy, Step-by-Step), the movements of 
 the needle on the indicator are synchronized with 
 the movements of the needle on the manipulator. 
 In systems of Fac- Simile Telegraphy the move- 
 ments of the transmitting apparatus are syn- 
 chronized with those of the receiving apparatus. 
 
 In Delany's Synchronous Multiplex Telegraph 
 System, the trailing arm that moves over a cir- 
 cular table of contacts at the transmitting end, 
 is accurately synchronized with a similar trailing 
 arm moving over a similar table at the receiving 
 end. 
 
 Delany, who was the first to obtain rigorous 
 synchronism at the two ends of a telegraphic 
 line hundreds of miles in length, accomplishes 
 this by the use of La Cour's phonic wheel, 
 through the agency of correcting electric im- 
 pulses, automatically sent in either direction over 
 the main line, when one trailing arm get: a short 
 distance in advance or back of the other. 
 
 With alternating current dynamos, where one 
 dynamo is feeding incandescent lamps connected 
 to the leads in multiple, and it is desired to 
 couple another alternating current dynamo in 
 parallel with the first, it is necessary to obtain a 
 complete synchronism of the two dynamos before 
 coupling them, since otherwise the lamps will 
 show variations in their light, and the machine 
 may suffer. 
 
 Synchronizable. Capable of being syn- 
 chronized. (See Synchronism!) 
 
 Synchronize. To cause to occur or act 
 simultaneously. (See Synchronism.) 
 
 Synchronized. Caused to occur or act 
 simultaneously. (See Synchronism!) 
 
 Synchronizing Dynamo-Electric Ma- 
 chine. (See Machine, Dynamo-Electric, 
 Synchronizing!) 
 
 Synchronous Multiplex Telegraphy. 
 
 (See Telegraphy, Synchronous Multiplex, 
 Delany's System!) 
 
 System, Astatic An astatic com- 
 bination of magnets. 
 
 An astatic needle consists of an astatic system 
 of two magnetic needles. The needles are 
 rigidly fixed together with their opposite poles 
 facing each other. The two needles form an as- 
 tatic pair or couple. (See Needle, Astatic.) 
 
 System, Block, for Railways (See 
 
 Railroads, Block System for!) 
 
 System, Centimetre - Gramme - Second 
 
 (See Units, Centimetre - Gramme - 
 
 Second!) 
 
 System, Continuous Underground, of 
 
 Motive Power for Electric Railroads 
 
 (See Railroads, Electric, Continuous Un- 
 derground System of Motive Power for!) 
 
 System, Dependent, of Motive Power for 
 
 Electric Railroads (See Railroads, 
 
 Electric, Dependent System of Motive 
 Power for.) 
 
 System, Independent, of Motive Powei 
 for Railroads (See Railroads, Elec- 
 tric, Independent System of Motive Power 
 for.) 
 
 System, Multiphase A term fre- 
 quently applied to a system of rotating elec- 
 tric currents. (See Current, Rotating!) 
 
 System of Distribution of Electricity by 
 Commntating Transformers. (See Elec- 
 tricity, Distribution of, by Commutating 
 Transformers!) 
 
 System of Distribution of Electricity by 
 Condensers. (See Electricity, Distribution 
 of, by Alternating Currents by Means of 
 Condensers. Electricity, Distribution of, by 
 Continuous Current by Means of Condens- 
 ers!) 
 
 System of Distribution of Electricity bf 
 Means of Alternating Currents. (See Elec* 
 
504 
 
 [Tai. 
 
 tricity, Distribution of, by Alternating Cur- 
 rents.} 
 
 System of Distribution of Electricity by 
 Motor Generators. (See Electricity, Dis- 
 tribution of, by Motor Generators^) 
 
 System, Three-Wire A system of 
 
 electric distribution for lamps or other trans- 
 lating devices connected in multiple, in which 
 three wires are used instead of the two usually 
 employed. 
 
 In the three-wire system two dynamos are gen- 
 erally employed, which are connected with one 
 another in series. 
 
 The three conductors are connected as shown 
 in Fig. 527, the central conductor to the junction 
 of the two dynamos and the two others to their 
 free terminals, and the difference of potential be- 
 tween the central and the two outer conductors 
 is maintained the same. The lamps, or other 
 electro-receptive devices, are placed in multiple- 
 arc between either branch, and so distributed 
 that the current in each branch is the same. 
 When such balance is established no current 
 flows through the central or neutral conductor. 
 But when that balance is disturbed, the surplus 
 current in one branch is taken up by the central 
 conductor. 
 
 The three-wire system effects considerable 
 
 economy in the weight of wire required. Since in 
 the multiple- series-connection of electro -receptive 
 devices whatever difference of potential is im- 
 pressed on the mains is fed to each device, no 
 higher difference of potential can be employed on 
 the mains than that which the devices are capa- 
 ble of taking. In the case of an incandescent 
 lamp, if such difference be exceeded, too strong 
 a current is passed through the lamps with a 
 consequent decrease in their life. 
 
 In the three- wire system of distribution a higher 
 difference of potential can be maintained on the 
 mains than is required for any lamp placed in 
 
 Fig. 327- Three-Wire System. 
 
 connection therewith, and in this manner a con- 
 siderable saying is effected in the cot of the leads. 
 
A DICTIONARY 
 
 OF 
 
 ELECTRICAL WORDS 
 
 VOLUME TWO 
 
 T. A symbol used for time. 
 
 T-shaped Spark. (See Spark, T-Shaped) 
 
 Table, Quadruplex, A-Side of 
 
 That side of a quadruplex system which is 
 worked by means of reverse currents. (See 
 Telegraphy, Quadruple*) 
 
 Table, Quadruplex, B-Side of - 
 
 That side of a quadruplex system which is 
 worked by means of strengthened currents. 
 (See Telegraphy, Quadruplex.) 
 
 Tables of Conducting Powers. (See 
 Powers, Conducting, for Electricity. Re- 
 sistance, Electric) 
 
 Tachograph. An apparatus for recording 
 the number of revolutions per minute of a 
 shaft or machine. 
 
 Tachometer. An apparatus for indicating 
 at any moment on a revolving dial the exact 
 number of revolutions per minute of a shaft 
 or machine. 
 
 A tachometer is sometimes called a speed in- 
 dicator. 
 
 Tachyphore. A term proposed by Wurtz 
 for a system of electric transportation, in 
 which a carriage, formed of magnetic ma- 
 terial, is propelled by the sucking action of 
 solenoids placed along the track and ener- 
 gized in succession during the passage of the 
 car. 
 
 This is generally called the portelectric sys- 
 tem. (See Portelectric.) 
 
 Tail Light. (See Light, Tail) 
 1 Vol. 2 
 
Tai.J 
 
 505 
 
 [Tag. 
 
 Tailings. False markings received in sys- 
 tems of automatic telegraphy, due to retard- 
 ation. (See Retardation?) 
 
 Tailings. A term applied to the current 
 that runs out of a line at the receiving end. 
 
 The current that continues to run out at 
 the receiving end of the circuit after the send- 
 ing current is broken. 
 
 The tailings in a telegraphic line are due to the 
 effects of self-induction and static capacity follow- 
 ing the breaking of the circuit which produce a 
 current in the same direction as that sent into the 
 line. Consequently, on the breaking of the cir- 
 cuit, the current continues to flow out of the line at 
 the distant or receiving end. This prolongation 
 of the original current is known technically as 
 the tailing or the tailing current. 
 
 Talk, Cross In telephony an indis- 
 tinctness in the speech transmitted over any 
 circuit, due to this circuit receiving, either by 
 accidental contacts or by induction, the speech 
 transmitted over neighboring circuits. 
 
 Tangent. One of the trigonometrical 
 functions. (See Function, Trigonometrical?) 
 
 Tangent and Sine Galvanometer, Com- 
 bined (See Galvanometer, Combined 
 
 Tangent and Sine.) 
 
 Tangent Galvanometer. (See Galva- 
 nometer, Tangent?) 
 
 Tangent Scale. (See Scale, Tangent?) 
 
 Tangentially Laminated Armature Core. 
 
 (See Core, Armature, Tangentially Lam- 
 inated^) 
 
 Tank, Cable A water-tight tank in 
 
 which a section of a cable is placed for pur- 
 poses of testing. 
 
 The cable is tested either when merely covered 
 by water, or when subjected to a pressure ap- 
 proximately equal to or in excess of that to which 
 it will be subjected when laid in the water. 
 
 Reid has constructed cable tanks for testing 
 under pressures as great as 4,500 pounds per 
 square inch. The pressure is obtained by means 
 of force pumps. 
 
 When a cable section is subjected to these 
 pressures any flaws or defects would be at once 
 detected by the entrance of the water. 
 
 Tanning, Electric An application 
 
 of electric currents to tanning leather. 
 
 The dressed hides are steeped in a solution of 
 tannin through which an electric current is 
 passed. 
 
 It is claimed, that by this process, the hides 
 are thoroughly tanned in from one to four days, 
 in place of from four to twelve months, as re- 
 quired by the ordinary process. 
 
 The tanning solution is placed in a vat fur- 
 nished with suitable electrodes and filled with the 
 tanning liquid, and the articles to be tanned are 
 placed between the electrodes and a motion erf 
 revolution given to the vat. By these means 
 the time required for the completion of the pro- 
 cess is considerably shorter than that required by 
 the ordinary process. 
 
 Tap. A conductor attached to a larger 
 conductor in a shunted circuit. 
 
 Tap, AmpSre A tap provided for 
 
 carrying off a current of one ampere. 
 
 Tap Wires. (See Wires, Tap) 
 
 Tape, Insulating 
 
 -A ribbon of 
 
 flexible material impregnated with kerite, 
 okonite, rubber or other suitable insulating 
 material, employed for insulating wires or 
 electric conductors at joints, or other exposed 
 places. 
 
 Sometimes the tape is formed entirely of some 
 or another the above named insulating materials. 
 
 Taped Wire. (See Wire, Taped.} 
 
 Tapper, Double-Key (See Key, 
 
 Double Tapper.) 
 
 Target, Electric A target in which 
 
 the point struck by the ball is automatically 
 registered by means of electric devices. 
 
 A variety of targets have been devised. Gen- 
 erally, however, the target is divided into a num- 
 ber of separate sections provided with circuits of 
 wires, on the making or breaking of any of which, 
 by the impact of the ball, the section struck is au- 
 tomatically indicated on an electric annunciator. 
 (See Annunciator, Electro-Magnetic.) 
 
 Taste, Galvanic A sensation of taste 
 
 produced when a voltaic current is passed 
 through the tongue or in the neighborhood o 
 the gustatory nerves, or nerves of taste. 
 
TeaJ 506 
 
 [Tel. 
 
 Teaser. An electric current teaser. (See 
 Teaser, Electric Current.} 
 
 Teaser, Electric Current A coil 
 
 of fine wire placed on the field magnets of a 
 dynamo-electric machine, underneath the se- 
 ries coil wound thereon, and connected as a 
 shunt across the main circuit. 
 
 The name' teaser was applied by Brush to the 
 coil of fine wire used as above described to main- 
 lain constant electromotive force under variations 
 of load. 
 
 Technics, Electro - The science 
 which treats of the physical applications of 
 electricity and the general principles applying 
 thereto. 
 
 Tee, Lead A tee-shaped lead tube 
 
 provided for the purpose of taking a branch 
 joint from a main cable to a service line. 
 
 Tee, Split-Lead - A tee-shaped lead 
 tube that is split for readily covering a joint 
 at a loop in a cable. 
 
 Tel-Autogrram. The recorded message 
 obtained by means of a tel-autograph. (See 
 Tel-Autograph^ 
 
 Tel-Autograph. A telegraphic system for 
 the fac-simile reproduction of handwriting. 
 
 Teleautograph. An orthography some- 
 times employed for tel-autograph. (See Tel- 
 Autograph!) 
 
 Tele- Barometer, Electric An elec- 
 tric recording barometer for indicating and 
 recording barometric or other pressures at a 
 distance. 
 
 Telegrapher's Cramp. (See Cramp, 
 Telegrapher's?) 
 
 Telegraphic. Pertaining to telegraphy. 
 
 Telegraphic Alarm. (See Alarm, Tele- 
 graphic) 
 
 Telegraphic Alphabet. (See Alphabet, 
 Telegraphic) 
 
 Telegraphic Alphabet, Continental Code 
 (See Alphabet, Telegraphic : Inter- 
 national Code.} 
 
 Telegraphic Alphabet, Morse's 
 
 (See Alphabet, Telegraphic :' Morse's) 
 
 Telegraphic Arm. (See Arm, Tele* 
 graphic) 
 
 Telegraphic Bracket. (See Bracket. 
 Telegraphic) 
 
 Telegraphic Cable. (See Cable, Tele- 
 graphic) 
 
 Telegraphic Code. (See Code, Tele- 
 graphic) 
 
 Telegraphic Earth-Circuit. (See Cir- 
 cuit, Earth, Telegraphic) 
 
 Telegraphic Embosser. (See Embosser, 
 Telegraphic) 
 
 Telegraphic Fixtures. (See Fixtures, 
 Telegraphic) 
 
 Telegraphic Fixtures, House-Top 
 
 (See Fixtures, Telegraphic House- Top) 
 
 Telegraphic Ground Circuit. (See Cir- 
 cuit, Ground, Telegraphic) 
 
 Telegraphic Joints. (See Joint, Tele- 
 graphic or Telephonic) 
 
 Telegraphic Key. (See Key, Telegraph- 
 ic) 
 
 Telegraphic Line Circuit. (See Circuit, 
 Line, Telegraphic) 
 
 Telegraphic Needle. (See Needle, Tele- 
 graphic) 
 
 Telegraphic Paper Winder. (See Wind- 
 ers, Telegraphic Paper) 
 
 Telegraphic Pocket Belay. (See Relay, 
 Pocket Telegraphic) 
 
 Telegraphic Register. (See Register, 
 Telegraphic) 
 
 Telegraphic Switch Board. (See Board, 
 Switch, Telegraphic) 
 
 Telegraphic Translator. (See Trans- 
 later, Telegraphic) 
 
 Telegraphically. In a telegraphic 
 manner. 
 
 Telegraphing. Sending a communication 
 by i.ieans of telegraphy. 
 
 Telegraphy, Acoustic A non-re- 
 cording system of telegraphic communica- 
 tion, in which the dots and dashes of the 
 Morse system, or the deflections of the needle 
 in the needle system, ate replaced by sounds 
 
Tel.] 
 
 507 
 
 [TeL 
 
 that follow one another at intervals, that 
 represent the dots and . dashes, or the de- 
 flections of the needle, and thereby the letters 
 of the alphabet. 
 
 Morse invented a sounder, for this purpose, 
 which is used very generally. (See Sounder, 
 Morse Telegraphic.} 
 
 Steinheil and Bright each invented acoustic 
 systems of telegraphy in which electro-magnetic 
 btlls are used. 
 
 For details of the apparatus and system see 
 Telegraphy, Morse System of. 
 
 Telegraphy, American System of 
 
 A term sometimes applied to the Morse sys- 
 tem of telegraphy. (See Telegraphy, Morse 
 System of.) 
 
 Telegraphy and Telephony, Simultane- 
 ous, Over a Single Wire Any system 
 
 for simultaneous transmission of telegraphic 
 and telephonic messages over a single wire. 
 
 These systems are based, in general, on the 
 fact that a gradual make-and-break in a tele- 
 phone circuit fails to appreciably affect a tele- 
 phone diaphragm. By the use of graduators the 
 makes and breaks required for the transmission 
 of the telegraphic dispatch are effected so grad- 
 ually that they fail to appreciably influence the 
 telephone diaphragm, and thus permit simultane- 
 ous telegraphic and telephonic transmission over 
 a single wire. (See Graduators.) 
 
 Telegraphy, Autographic A name 
 
 sometimes applied to fac-simile telegraphy. 
 (See Telegraphy, Fac-Szmzle.) 
 
 Telegraphy, Automatic A system 
 
 by means of which a telegraphic message is 
 automatically transmitted by the motion of a 
 previously perforated fillet of paper contain- 
 ing perforations of the shape and order re- 
 quired to form the message to be transmitted. 
 
 The paper passes between two terminals of the 
 main line, the circuit of which is completed when 
 the terminals come into contact at the perforated 
 parts, and is broken when separated by the 
 un perforated parts of the paper. 
 
 In the automatic telegraph some form of regis- 
 tering apparatus is employed. 
 
 In the Wheatstone system, the perforations 
 me hanically control the movements ot the levers 
 which make contacts between the line and the 
 battery. 
 
 The advantage of automatic telegraphy arises 
 from the fact that the rate of transmission or re- 
 ception of signals does not depend on the expert- 
 ness of the operators, and the messages may be 
 perforated on the slips preparatory to transmis- 
 sion. 
 
 Type printing telegraphs are often used for 
 registering apparatus, in which case the im- 
 pulses required for the transmission of the dif- 
 ferent letters are automatically sent into the line 
 by the depression of corresponding keys on a 
 suitably arranged key -board. 
 
 Telegraphy, Chemical A system 
 
 by means of which the closings of the main- 
 line-circuit, corresponding to the dots and 
 dashes of the Morse alphabet, are recorded 
 on a fillet of paper by the electrolytic action 
 of the current on a chemical substance with 
 which the paper fillet is impregnated. (See 
 Recorder, Chemical, Bain's?) 
 
 Telegraphy, Contraplex 
 
 Duplex 
 
 telegraphy in which transmissions are simul- 
 taneously made from opposite ends of the 
 line. 
 
 When the transmissions are simultaneously 
 made from the same end of the line, the system is 
 called diplex telegraphy. (See Telegraphy, Di- 
 
 Telegraphy, Dial 
 
 A system of 
 
 telegraphy in which the messages are received 
 by the motions of a needle over a dial plate. 
 (See Telegraphy, Step-by-Step^) 
 
 Telegraphy, Diplex A method of 
 simultaneously sending two messages in the 
 same direction over a single wire. 
 
 Diplex telegraphy is to be distinguished from 
 duplex telegraphy, where two messages are simul- 
 taneously transmitted over a single wire in oppo- 
 site directions. 
 
 Telegraphy, Double-Needle A sys- 
 tem of needle telegraphy in which two sepa- 
 rate and independently operated needles are 
 employed. 
 
 This system differs from the single-needle sys- 
 tem only in the (act that two needles, entirely in- 
 dependent of each oi hi r, are mounted side by side, 
 on the same dial, so as to permit their simultane- 
 ous operation by the right and left hand of th^ 
 
Tel.] 
 
 508 
 
 I'el. 
 
 operator. Each needle has then-fore a separate 
 wire. 
 
 The increase in speed of signaling thus obtained 
 is not, however, sufficiently great to balance the 
 increased expense of construction. Single -needle 
 instruments, therefore, are preferred to those 
 with two needles. 
 
 / Telegraphy, Duplex, Bridge Method of 
 
 A system whereby two telegraphic 
 messages can be simultaneously transmitted 
 over a single wire in opposite directions. 
 
 Various duplex telegraphs have been devised. 
 
 The Bridge Duplex is shown in Fig. 528. The 
 receiving relay is placed in the cross wire of a 
 Wheatslone bridge. (See Bridge, Electric.} 
 
 F ; g. 328. Duplex Telegraphy, Bridge, Method. 
 
 When the ends of this cross wire are at the 
 same potential, whicn will occur when the resist- 
 ances in the four arms are proportionately equal, 
 no current passes. 
 
 The battery is connected through the trans- 
 mitter K, which is arranged so that the battery 
 contact is made before the connection of the line 
 to earth is broken, to H, where the circuits 
 branch to form the arms of the bridge. Adjust- 
 able resistances A, B, are placed in the two arms 
 of the bridge. 
 
 The line wire L, connected as shown, forms 
 the third arm, and a rheostat or other adjustable 
 resistance R, connected to a condenser C, as 
 shown, forms the fourth arm. (See Rheostat.) 
 The relay M, is placed in the cross wire of the 
 bridge thus formed. Small resistances V, and 
 W, are placed in the circuit of the battery to pre- 
 vent injurious short circuiting. 
 
 A similar disposition of apparatus is provided 
 at the other end of the line. If, now, the four re- 
 sistances at one end are sui'ably adjus eH, the 
 relay will not respond to the outgoing cu;rent; 
 but, since an earth circuit ii emp'oyed, it \\ill 
 
 respond tc the incoming current. The relay at 
 either end, therefore, will only respond to signals 
 from the other end. The operator may thus 
 signal the distant station w hile, at the same time, 
 his relay, not being affected by his sending, is in 
 readiness to receive signals from the other end. 
 
 Telegraphy, Duplex, Differential Method 
 
 of A system of duplex telegraphy in 
 
 which the coils of the receiving and transmit- 
 ting instruments are differentially wound. 
 
 A differential system of duplex telegraphy is 
 shown in Fig. 529. The coils of the receiving 
 and transmitting galvanometers at A and B, are 
 differentially wound. One of the coils of A, is 
 connected to that of B, through the line, as 
 shown; and the other, in each to the rheostat; 
 at R, and R'. As thrse coils are differentially 
 wound, when equal currents flow in opposite 
 directions through either of the instruments at A 
 B, no deflection of the galvanometer occurs. 
 
 The battery at A, has its copper terminal, and 
 that at B, its zinc terminal, connected to earth. 
 When the keys at A and B, are depressed simul- 
 taneously, the currents sent into the li;ie flow in 
 the same direction and strengthen each other. 
 
 Suppose now that only the key at A, be de- 
 pressed. The current divides equally between 
 rheostat and line, the resistance e a b b a' e', r', 
 being made equal to th^ resistance e c d R. 
 
 This current passes through both coils of the 
 instrument at A, and produces no deflection of 
 the needle; but since it only passes through one 
 coil at B, it deflects the galvanometer needle, and 
 produces a s-ijnal. 
 
 b b' 
 
 Earth 
 
 Fig.szq. Duplex Telegraphy, Differential Method. 
 
 If the keys at A, and B, are simultaneously 
 closed, the effect on the line is to add the current 
 of the two batteries, but each rheostat circuit is 
 traversed by its own battery current only. 
 
 The line-connec:ed coils of the ga vanometer 
 have, the -el re, the stronger currents flowing 
 through them, and the needles of both are moved, 
 just as if, with a single battery discharging into 
 the line, its resistance had been decreased. Each 
 
Tel.J 
 
 509 
 
 [Tel. 
 
 sender's instrument is unaffected by the currents 
 he sends into the line, and is, therefore, ready to 
 be operated by the currents sent into the line by 
 the sender at the other end of the line. 
 
 The two currents in duplex telegraphy, there- 
 fore, do not pass each other on the line; on the 
 contrary, they are sent into the line in the same 
 direction. 
 
 Since, when either key is moving there is a 
 small interval of time when the circuit is broken 
 for incoming currents, the keys are generally 
 made so as to close the second contact before 
 breaking the first. 
 
 In order to avoid disturbing the balance on the 
 introduction of the resistance of the batteries at A 
 or B, on closing the circuits, an equal resistance 
 is added at r and r', between the back stop and 
 the earth. 
 
 Since the proper operation of duplex telegraphy 
 requires a balance in the resistance of the circuits 
 of the differentially wound coils, a rheostat at R, 
 and R', is necessary. 
 
 Besides balancing the line for resistance, it is 
 necessary to balance it for capacity. A condenser 
 is, therefore, necessary when the circuit exceeds 
 in length about 100 miles, or has much cable or 
 underground wire. 
 
 Telegraphy, Fac-Simile - A system 
 whereby a fac-simile or copy of a chart, 
 diagram, picture or signature is telegraphically 
 transmitted from one station to another. 
 
 Fac-simile telegraphy is sometimes called auto- 
 graphic telegraphy, or pantelegraphy. 
 
 Bakewell's fac-simile telegraph, which was one 
 of the first devised, consists of two similar metal 
 cylinders c, c', arranged at the two ends of a 
 telegraph line L, at M and M', as shown in Fig. 
 53- These cylinders are synchronously rotated 
 
 530. Bakewell's Fac-Simile Telegraphy. 
 
 and provided with metallic arms or tracers r, r', 
 placed on a horizontal screw in the line circuit 
 and moved laterally over the surface of the 
 cylinder on its rotation. 
 
 At the transmitting station the chart, writing, 
 
 or other design is traced with varnish, or other 
 non-conducting liquid, on the surface of the 
 metallic cylinder, as at M, and a sheet of chemi- 
 cally prepared paper, similar to that employed in 
 the Bain chemical system is placed on the surface 
 of the receiving cylinder at M'. (See Recorder, 
 Chemical, Bain's.) 
 
 The two cylinders being synchronously rotated, 
 the metallic tracer breaks the circuit in whick it 
 is placed when it moves over the non-conducting 
 lines on the cylinder, and thus causes correspond- 
 ing breaks in the otherwise continuous blue spiral 
 line traced on the paper-covered surface of M'. 
 
 The telegraph keys at R, R', are used for the 
 purposes of ordinary telegraphic communication 
 before or after the record is transmitted. 
 
 Caselli's Pan-Telegraph is an improvement on 
 Bakewell's Copying Telegraph. Better methods 
 are employed for maintaining the synchronism 
 between the transmitting and receiving instru- 
 ments, for which purpose a pendulum, vibrating 
 between two electro-magnets, is employed. 
 
 Telegraphy, Fire Alarm A systeu. 
 of telegraphy by means of which alarms can 
 be sent to a central station, or to the fire 
 engine houses in the district, from call boxes 
 placed on the line. 
 
 The alarms are generally sounded by an ap- 
 paratus similar to a district call, so that the pall- 
 ing back of a lever rotates a wheel, by means et 
 which successive makes and breaks are produced, 
 the number and sequence of which enable the 
 receiving stations to locate the particular box 
 from which the signal is sent. 
 
 In the case of some buildings, the alarms are 
 automatic, and either call for help from tke 
 central office, or for the watchman in the build- 
 ing, or else turn on a series of water faucets er 
 jets, in order to extinguish the fire. In tbese 
 cases thermostats are used. (See Thermostat. ) 
 
 Telegraphy, Gray's Harmonic Multiple 
 
 A system for the simultaneous trans- 
 mission of a number of separate and distinct 
 musical notes over a single wire, which 
 separate tones are utilized for the simultane- 
 ous transmission of an equal number of tele- 
 graphic messages. 
 
 The separate to ies are thrown into the lines 
 by means of tuning forks automatically vibrated 
 by electro-magnets. Th.se forks inierrupt the 
 
Tel.] 
 
 510 
 
 circuit of batteries connected with the main line 
 at the sending end of the line. 
 
 The composite tone thus formed, is separated 
 into its component tones by receiving electro- 
 magnets called harmonic receivers, the armature 
 of each of which consists of a steel ribbon or 
 plate tuned to one of the separate notes sent into 
 the line. As the complex or undulatory current 
 passes through the coils of each harmonic re- 
 ceiver, that note only affects the particular arma- 
 ture that vibrates in unison with its ribbon or 
 rued. The operator, therefore, at this receiver 
 is in communication only with the operator at 
 i he key of the circuit that is sending this par- 
 ticular note into the line. The same is true of the 
 other receivers. 
 
 The Morse alphabet is used in this system, the 
 dots and dashes being received as musical tones. 
 In practice it was found that there was no diffi- 
 culty in each operator recognizing the particular 
 sound of his own instrument in receiving, although 
 many instruments were in the same room. 
 
 By a subsequent invention the signals received 
 are converted into the regular Morse characters 
 by means of an ingenious device. 
 
 Telegraphy, Induction - A system 
 for telegraphing by induction between moving 
 trains and fixed stations on a railroad, by 
 means of impulses transmitted by induction 
 between the car and a wire parallel with the 
 track. 
 
 Two systems of inductive telegraphy are in 
 actual use, viz., 
 
 (i.) The Static Induction system of W. W. 
 Smith and Edison, and 
 
 (2. ) The Current or Dynamic Induction system 
 of Willoughby Smith and Lucius J. Phelps. 
 
 In the System of Static Induction, one of the 
 condensing surfaces which receives or produces 
 the charge, consists of a wire placed on the road 
 so as to come as near the top of the cars of the 
 moving train as possible. The other condensing 
 surface is composed of the metal roofs of the mov- 
 ing cars. 
 
 Each condensing surface is connected to suit- 
 able instruments and batteries, and to the earth ; 
 the line wire at the fixed station being connected 
 to earth through a ground plate, and the metal 
 roof of the cars to earth through the wheels and 
 track. 
 
 Under these circumstances variations in the 
 charge of either of the condensing surfaces pro- 
 
 duce inductive impulses that are received by the- 
 other surface as telegraphic signals. 
 
 The Morse alphabet is employed, but in place 
 of the ordinary receiver or sounder, a telephone 
 is used. 
 
 In the System of Current Induction, the line 
 wire is placed near the track, so as to be parallel 
 with a coil of insulated wire placed on the side of 
 the car, and which receives the inductive impulses. 
 The coil of wire on the train is connected with 
 instruments and batteries, and forms a metallic 
 circuit. The line wire is also connected with 
 suitable batteries and receiving and transmitting 
 instruments. 
 
 An induction coil is generally employed, since 
 the greater and more rapidly varying difference 
 of potential of its secondary wire renders it better 
 suited for producing effects of induction. A tele- 
 phone is employed as a receiver, as in the system 
 of static induction. The metallic car roof and 
 the lower truss rods have been successfully used as 
 the secondary conductor of the induction coil. 
 
 The automatic make-and-break used for operat- 
 ing the induction coil, causes the Morse characters 
 employed in this system to be received in the 
 receiving telephone as shrill buzzing sounds. 
 
 The receiving telephones used on the trains 
 have a resistance of about 1,000 ohms. 
 
 Telegraphy, Induction, Current System 
 
 of A system of induction telegraphy 
 
 depending on current induction between a 
 fixed circuit along the road, and a parallel 
 circuit on the moving train. 
 
 The circuit on the train generally consists of a 
 coil of wire. (See Telegraphy, Induction. ) 
 
 Telegraphy, Induction, Dynamic System 
 
 of A term sometimes used in place of 
 
 a system of telegraphic current induction. 
 (See Telegraphy, Induction?) 
 
 Telegraphy, Induction, Static System of 
 
 A system of inductive telegraphy de- 
 pending on the static induction between the 
 sending and receiving instrument. 
 
 A fixed wire placed along the road so as to come 
 near another wire or metallic surface on the mov- 
 ing train, imparts to the latter a static charge, 
 which is utilized for the transmission of dispatches. 
 The metal roof of the car is generally used for the 
 condensing surface receiving the charge. (See 
 Telegraphy, Induction.) 
 
Tel.] 
 
 oil 
 
 [Tel. 
 
 Telegraphy, Machine A term some- 
 times applied instead of automatic telegraphy. 
 (See Telegraphy, Automatic?) 
 
 A system of telegraphy is properly called ma- 
 chine telegraphy when both the transmission and 
 the receiving of the telegraphic messages are ac- 
 complished by machine, instead of by the hand, as 
 usual. 
 
 Telegraphy, Morse System of A 
 
 system of telegraphy in which makes and 
 breaks occurring at intervals corresponding 
 to the dots and dashes of the Morse alphabet 
 ace received by an electro-magnetic sounder 
 or receiver. 
 
 A metallic lever A, Fig. 531, is supported on a 
 pivot at G, between two set screws D, D, so as to 
 have a slight movement in a vertical plane. This 
 motion is limited in one direction by a stop at C, 
 called the anvil or front contact, and in the other 
 direction by a set screw F, which constitutes its 
 back stop. 
 
 The front stop C, is provided with a platinum 
 contact or stud, which may be brought into 
 contact with, or separated from, a similar stud 
 placed directly opposite it. These contacts are 
 connected to the ends of the circuit so that on 
 
 ig- 531- Telegraphic Key. 
 
 the movements of the key, by the hand of the 
 operator placed on the insulated head B, the line 
 is closed and broken in accordance with the dots 
 and dashes of the Morse alphabet. A spring, the 
 pressure of which is regulated by the screw F', is 
 provided for the upward movement of the key. 
 A switch H, is provided for closing the line when 
 the key is not in use. 
 
 The system generally used in the United States 
 is known as the " Closed- Circuit System," the bat- 
 tery being connected to line whether the line is in 
 use or not. This battery is generally placed at 
 both ends of the line. 
 
 In Europe, the " Open-Circuit System " is gen- 
 
 erally used. Alternating currents and polarized 
 relays are employed. One pole is connected to 
 the line at the front of the key, and the other 
 pole to the back of the key. When the line is 
 not in use, it is connected to earth at both ends 
 by switches conveniently placed for the operators. 
 With this system, intermediate stations must each 
 have a main battery, while in the closed-circuit 
 system, the terminal batteries answer for all inter- 
 mediate offices, which in some cases amount to as 
 many as fifty. 
 
 In the Morse system, eacji station is provided 
 with a key, relay, sounder or register, and local 
 battery. The closed-circuit, connecting one 
 station with another, being broken by the open- 
 ing of the switch H, or the working of the key, 
 so as to open and close its contacts, the armature 
 of the relay opens or closes the circuit of the 
 local battery and operates the sounder or register- 
 ing apparatus connected therewith. (See Sounder, 
 Morse Telegraphic. Apparatus, Registering, 
 Telegraphic. ) 
 
 Telegraphy, Multiplex A system 
 
 of telegraphy for the simultaneous transmis- 
 sion of more than four separate messages 
 over a single wire. (See Telegraphy, Syn- 
 chronous-Multiplex, Delany's System.} 
 
 Telegraphy, Needle System of - A 
 
 system of telegraphy in which signals are 
 transmitted by means of the movements of 
 needles under the influence of the electric 
 current. (See Telegraphy, Single-Needle?) 
 
 Telegraphy, Phonoplex 
 
 A system 
 
 of telegraphic transmission in which pulsatory 
 currents, superposed on the ordinary Morse 
 currents, actuate a modified telephonic re- 
 ceiver, and thus permit the simultaneous 
 transmission of several separate messages 
 over a single wire without interference. 
 
 Telegraphy, Printing A system of 
 telegraphy in which the messages received 
 are printed on a paper fillet. 
 
 In Callahan's Printing Telegraph, two type 
 wheels are employed, one of which carries letter 
 type and the other numerals on its circumference. 
 These printing wheels are placed alongside of 
 each other, as shown in Fig. 532, but on separ- 
 ate and independent axes. 
 
 The type wheels are moved by a step -by -step 
 device. The impulses necessary to bring the 
 
T.I.] 
 
 512 
 
 |TeL 
 
 desired letters in positi -n for printing are auto- 
 matically sent by a circuit maker and breaker. 
 These impulses are sent into the line by the de- 
 pression of keys on a suitably arranged key- 
 board. 
 
 When the proper letter or numeral is reached 
 at the receiving end, the printing wheel is 
 stopped, and a paper fillet is pressed against its 
 surface. The printing wheel is kept covered 
 with ink by means of an inked roller. 
 
 The transmitting instrument is similar in its 
 operation to the Breguet manipulator. Separate 
 transmitters are used for each of the wires. (See 
 Telegraphy, Step- by - Step . ) 
 
 Fig. S3 2 - Callahan's Printing Telegraph. 
 
 Telegraphy, Quadruplex A system 
 for the simultaneous transmission of four mes- 
 sages over a single wire, two in one direction 
 and the remaining two in the opposite direc- 
 tion. 
 
 Quadruplex telegraphy consists in fact of du- 
 plex telegraphy duplexed. 
 
 There are various systems of quadruplex teleg- 
 raphy. The most important are the bridge 
 method and the differential method. (See Teleg- 
 raphy, Quadruplex, Bridge Method of. Telegra- 
 phy, Quadruplex, Differential Method of.} 
 
 Telegraphy, Quadruplex, Bridge Method 
 
 of A system of quadruplex telegraphy 
 by means of a double bridge duplex system. 
 (See Telegraphy, Quadruplex.) 
 
 In the bridge method of quaHruplex telegraphy, 
 as in the differential metho-l, changes in the po'ar- 
 ity and strength of the current are utilized to 
 e-tablish a double duplex -ystcm of transmission. 
 Fig. 533 from Prescott's " EU-ctncity an I Electric 
 Telegraphy, "from which the following desciiption 
 
 is taken, shows the method first employed by the 
 Western Union Telegraph Company in 1874. 
 
 A double current transmitter, or pole changer, 
 is shown at T', with its operating key K' and 
 local battery e'. This instrument interchanges 
 the poles of the main battery E', wnen K, is de- 
 pressed, and thus reverses the polarity of current 
 on the line. 
 
 The increment transmitter T 2 , is connected to 
 the battery wire 12 of T', in such a way that 
 when K', is depressed, the main battery E', is 
 placed in series with battery E, of say twice the 
 strength of E', thus permitting a current of three- 
 fold the original strength to be sent into the line. 
 
 Fig. 533. Quadruplex Telegraphy, Bridge Method. 
 
 Two receiving instruments R' and R 2 , a e 
 placed at the distant end of the line. R', is a 
 polarized relay whose armature is deflected in 
 one direction by positive currents, and in the 
 opposite direction by negative currents, independ- 
 ently of their strength. That is to say, R', re- 
 sponds to changes in the direction of the currents 
 that pass through its coils, but not to changes in 
 their strength. (See Relay, Polarized.} 
 
 Relay R 2 , is non-polarized and the movements 
 of its soft iron armature depend on a change in 
 the strength of the current only. That is to say, 
 R a , responds to changes in the strength of the 
 current passing through its coils, but not to 
 changes in their direction. 
 
 These two relays R and R 8 , are placed in the 
 bridge wire of a \Vheatstone bridge. Ti.e entire 
 apparatus of transmitting keys and relays is 
 duplicated at each end of the line. Under these 
 conditions, signals transmitted from either end of 
 the line affect the instruments at the other end of 
 the line, but not th.ir own instruments, in the 
 sime manner as in the case of the bridge du 
 plex. (See Telegraphy, Duplex, Bridge Method 
 of.} 
 
 Telegraphy, Quadruplex, Differential 
 
Tel.] 
 
 513 
 
 [Tel, 
 
 Method of A system of quadruplex 
 
 telegraphy by means of a double differential 
 duplex system. 
 
 Quadruplex telegraphy depends for its opera- 
 tio.i on the use of two differentially wound relays 
 it each sta'ion. One of these relays A, as shown 
 in Fi^. 534, which shows the general arrangement 
 of the system, gives signals on a change in the 
 i.irection < I the current, but none on a change in 
 the current strength. The other B, gives signals 
 on changes in current strength, but none on 
 changes in direction. They are, therefore, in- 
 dependent of each other, and operate sounders 
 that are under the independent control of two 
 distinct receiving operators. 
 
 A table, divided into four sections, is provided 
 with places for two sending and two receiving 
 clerks. The name " A side " is given to the side 
 worked by the reversed currents, and the "B_ 
 side "to that worked by the strengthened cur- 
 nnts. 
 
 CORRECTING 
 
 BATTERY 1. BATTERY 2. 
 
 Fig. 3 3 4. Quadruple* Telegraphy, Differential Method. 
 
 Referring to Fig. 534 the reversing key on the 
 " A side " is merely indicated so as to avoid con- 
 fusion by too great detail ; as is also the case with 
 the increment key or the strengthening key at B. 
 From the connections it will be seen that when 
 the increment key is at rest, the reversing key 
 sends currents from battery I. When the incre- 
 ment key is depressed, the reversing key is shifted 
 from battery I, and connected by its copper con- 
 necti n C, with the battery 2, of double the 
 strength of I. Since, however, I, is thus connect- 
 ed in series with C, the current strength is in- 
 creased threefold. 
 
 From the reversing key the current passes 
 to the junction of the two coils with which the 
 relay B, is differentially wund. It divides here 
 between these coils, which are connected to simi- 
 
 lar coils on relay A, as shown. The current 
 from one coil on A, is sent to line, while that trom 
 the other coil goes to earth through the compen- 
 sating rheostat. This arrangement forms a du- 
 plex system, the outgoing currents of which have 
 no effect on the home relays. 
 
 Resistances R 2 and R ;i , are connected to the 
 batteries I and 2, and the stops in the increment 
 key in the manner shown, to the resistance of R 3 
 and R 3 . The former is used in order to main- 
 tain the resistance of the circuit, whether the bat- 
 tery is in or out of circuit. The latter is called 
 the spark coil, and is intended to decrease the 
 sparking on closing circuit. 
 
 When both are at rest, battery I, has its zinc 
 connected to line through A, and its copper to 
 earth through R 2 , C I, the lever of key B and 
 key A, which last two are permanently connect- 
 ed. A reversed or spacing current goes to line, 
 without affecting the home relays, since it passes 
 in opposite directions and with equal strength 
 through differentially wound coils. 
 
 When, however,, the key A, is worked alone, 
 it reverses the current and the signal is recorded 
 by tlje distant relay A. 
 
 If key B, is worked alone, it breaks connection 
 with copper at the junction of the two batteries, 
 and makes contact with terminal copper of battery 
 2, so as to send a zinc current of threefold strength. 
 The distant relay B, records a signal because the 
 current is now strong enough to move it. Relay 
 A, however, is not affected, since the current has 
 not been reversed. 
 
 When both keys are simultaneously in action, 
 then whenever B, is pressed, although the strength 
 of A, may be increased, since its direction is not 
 changed, the polarized tongue of its relay is un- 
 affected by the movement of B, but any increase 
 of current causes the armature of the distant re- 
 lay of B, to move. 
 
 This armature is held in position by springs of 
 such a strength as to prevent its motion by a 
 weak current, and being unpolarized, responds to 
 either positive or negative currents. It, there- 
 fore, re-ponds to B, and records a signal. When 
 A, is pressed, it reverses the current, and conse- 
 quently moves the distant relay A, but has no 
 effect on B, since it causes no alternation in the 
 strength of the current. 
 
 The author has taken the above almost liter- 
 ally fromCulley's " Handbook ot Practical Teleg- 
 raphy, " to which the reader is referred for a fuller 
 description and details of apparatus. 
 
Tel.] 
 
 514 
 
 [Tel. 
 
 Telegraphy, Simplex A system of 
 
 telegraphy in which a single message only 
 can be sent over the line. 
 
 Telegraphy, Single-Needle A sys- 
 tem of telegraphy by means of which the 
 
 F'- S3S- Single-Needle Telegraphic Apparatus. 
 
 signals transmitted are received by observing 
 the movements of a vertical needle over a 
 dial. 
 
 Fif. S3 6. Wheat stone and Cooke's Single- Needle Appa- 
 ratus, Internal Arrangement. 
 
 Movements of the top of the needle to the right 
 
 of the observer represent the dashes, and move- 
 ments to the left, the 'dots of the Morse alpha- 
 bet. 
 
 The single-needle apparatus of Wheatstone and 
 Cooke's system is shown in Figs. 535, and 536. 
 Fig. 535, shows the external appearance, and Fig. 
 
 Fig. S3 ? Wheatstone and Cooke's Single-Needle Ap- 
 paratus. External View. 
 
 536, the internal arrangements as seen from the 
 back. An astatic needle is placed inside two coi) 
 of insulated wire C C. Only 
 one of these needles N, is vis- 
 ible on the face of the receiving 
 instrument. The current from 
 the line enters at L, passes 
 through the coil C C, and 
 leaves at N. 
 
 The movements of the needle 
 to the right or the left are ob- 
 tained by changing the direc- 
 tion of the current in the coils 
 C C. This is effected by work- 
 ing the handle when sending, 
 and thus moving the commuta- 
 tor at S, S, and bringing the 
 contact springs resting thereon 
 into different contacts. 
 
 In the more modern form of single-needle in- 
 strument, shown in Fig. 537, a single magnetic 
 needle N S, Fig. 538, only is placed in the 
 coil. 
 
 This needle is rigidly attached to a light needle 
 a, b, used only as a pointer, and is alone visible 
 in the front of the instrument. The relative dis- 
 position of these needles is shown in Fig. 538. 
 
 The reversals of the current, required to deflect 
 the needle to the right or left, are obtained by 
 
 Fig. 338. Needle 
 and Pointer. 
 
Tel.] 
 
 515 
 
 [Tel. 
 
 means of a double key or tapper, shown in Fig. 
 
 539- 
 
 The levfrs L and E, are connected respectively 
 to line and earth, and, when not in use, rest against 
 C, connected with the po.-iiive 
 side of the battery; but when de- 
 pre<?ed connect with Z, attached 
 to the negative side of the bat- 
 tery. 
 
 The depression of L, therefore, 
 sends a negative current into the 
 line and deflects the needle, say, 
 to the left, while the depression 
 of E, sends a positive current into 
 the line and deflects the needle Fig. SS9- Double 
 to the right. The terms positive Key or Tapper. 
 and negative currents are usL'd in telegraphy to 
 indicate currents whose direction is positive or 
 negative. 
 
 Telegraphy, Speaking A system 
 
 for the telegraphic transmission of articulate 
 speech. (See Telephone.] 
 
 Telegraphy, Step-by-Step A sys- 
 tem of telegraphy in which the signals are 
 registered by the movements of a needle over 
 a dial on which the letters of the alphabet, 
 etc., are marked. 
 
 Dial telegraphs are especially employed for 
 communication by those who are unable to readily 
 read the Morse characters. 
 
 The annexed instrument, devised by Breguet, 
 "was formerly used on some of the railway sys- 
 tems of France. 
 
 A needle advances over a dial by a step-by-step 
 
 Fig. 340. Step-by-Step Wheel. 
 
 movement in one direction only. The alternate 
 to-and-fro motions of the armature of an electro- 
 magnet are employed to i npart a step-by-step 
 mot on to a peculiarly shaped toothed wheel 
 
 T, T, Fig. 540, through the action of a horizontal 
 arm c, attached thereto and moving between the 
 two prongs of a fork d. vibrating on a horizontal 
 axis to which is attached a vertical pallet i. 
 
 The receiving instrument is called the indicator, 
 and consists of a needle attached to the axis of 
 this wheel. The needle moves over the fiace of 
 
 Fig. 341. Breguet' s Indicator. 
 
 the dial, shown in Fig. 541, on which are marked 
 the letters of the alphabet and the numerals. 
 
 The sending instrument is called the manipu- 
 lator. It consists of a device for readily sending 
 over the line the number of successive impulses 
 required to move the needle step-by-step from 
 any letter on the indicator to which it may be 
 pointing, to the next it is desired to send. 
 
 The dial, shown in Fig. 542, is marked on its 
 face with the same characters as the indicator. 
 The edge of the wheel is provided with twenty-six 
 notches in which a pin attached to a movable arm 
 engages. The arm is jointed so that it can be 
 placed in any of the notches on the face of the 
 wheel. 
 
 Fig. 542. Breguet' s Manipulator. 
 
 Below the dial face, and attached to the same 
 axis as the movab'e aim, is a wheel provided 
 with undulations consisting of thirteen eleva'ions 
 and thirteen depressions. 
 
Tel.] 
 
 516 
 
 [Tel. 
 
 A lever T, pivoted at a, rests in these undu- 
 lations at its upper end, and plays between two 
 contact points at P and Q. 
 
 If, now, the dials of the indicator and the man- 
 ipulator both being at O, a movement is given to 
 the arm by the handle M, to any point on the 
 manipulator, there are thus produced the required 
 number of makes and breaks to move the needle 
 of the indicator to the corresponding letter or 
 character. 
 
 Telegraphy, Submarine A system 
 
 of telegraphy in which the line wire consists 
 of a submarine cable. 
 
 In long submarine cables, in order to avoid 
 retardation from the self-induction of the cur- 
 rent, and the static charge arising from the cable 
 acting as a condenser, very small currents are 
 used. To detect these a very sensitive receiving 
 instrument, such as the mirror galvanometer, or 
 the siphon recorder, is employed. (See Galva- 
 nometer, Mirror. Recorder, Siphon.} 
 
 According to Culley, the retardation in the 
 case of one of the submarine cables between 
 Newfoundland and Ireland, amounts to two- 
 tenths of a second before a signal sent from one end 
 produces any appreciable effect at the other end, 
 while three-tenths of a second are required for the 
 current through the cable to gain its full strength. 
 
 Telegraphy, Synchronous- M u 1 1 i p 1 e x, 
 
 Delany's System A system devised 
 
 by Delany for the simultaneous telegraphic 
 transmission of a number of messages either 
 all in the same direction, or part in one direc- 
 tion and the remainder in the opposite direc- 
 tion. 
 
 The Delany system embraces the following 
 parts : 
 
 (i.) A circular table of alternate 1 y insulated 
 and grounded contacts at either end of a tele- 
 graphic line. 
 
 (2.) A synchronized rotating arm or trailing 
 contact, at each end ot the line, driven by a 
 phonic -wheel, and maintained in synchronous 
 rotation by means of electric impulses automatic- 
 ally sent out over the main line in either direc- 
 tion, on the failure of the wheel at either end to 
 rotate synchronously with that at the other end. 
 
 (3.) Transmitting and receiving instruments 
 connecting similar conta ts at each end of the 
 main line, and forming practically separate aid 
 independent lines for the simultaneous transmis- 
 
 sion of dispatches over the main line in either 
 direction. 
 
 The main line is simultaneously connected at 
 both of its ends to corresponding operating in- 
 struments, and transferred from one set of instru- 
 ments to another so rapidly that the operators, 
 either sending or receiving, cannot realize that 
 the line has been disconnected from their instru- 
 ments and given to others, because each of them 
 will always have the line ready for use, even at 
 the highest rate of manipulation, and will, there- 
 fore, to all practical intents and purposes, have 
 at his disposal a private wire between himself 
 and the operator with whom he is in communica- 
 tion. 
 
 Therefore, although more than one operator 
 may be spoken of as simultaneously using the 
 line at any given time, yet in reality no two ope- 
 rators are absolutely using it at the same time;, 
 but they follow one another at such short in- 
 tervals, and the line is taken from one operator 
 and transferred to another so rapidly, that none 
 of them can at any time tell but that he has the 
 line alone, and that therefore it is practically 
 open for the use of every operator just as if he 
 alone had control of it. 
 
 There will, therefore, be established, by the 
 use of a single line, as many private and separate 
 lines as there are transferences of the line from 
 the time it is taken from the first operator, and 
 again given back to him. 
 
 This system has been extended to as many as 
 seventy-two distinct and separate priming cir- 
 cuits, maintained and operated on a single con- 
 necting line wire. 
 
 The speed at which the circuits may be operated 
 is in the inverse order of the number of circuits 
 organized. The best results, practically, are 
 obtained from six divisions of the contacts in the 
 circle, which gives each operator about 36 con- 
 tacts with the line per second, a speed which ad- 
 mits of the highest rate of transmission on each of 
 the six circuits. 
 
 Fig. 543 shows the apparatus at each end of 
 the line, at the stations X and Y. The apparatus 
 at each end is substantially identical. A steel 
 fork a, at each station, is automatically and con- 
 tinuously vibrated by the action of the local bat- 
 tery L B, and the electro-magnet A, called the 
 vibrator magnet. 
 
 Platinum contacts x, x 1 , placed on the inm-r 
 face> of the tines of the fork, make and bnak 
 contact with delicate contact springs y, y 1 . 
 
Tel.] 
 
 51? 
 
 |Te<, 
 
 The fork being mechanically started into a 
 vibratory motion, will automatically make and 
 break its local circuit, and thus send impulses 
 into the fork magnet A, that will continuously 
 maintain the vibrations of the fork, in a well 
 known manner. 
 
 The making and breaking of the contacts x 
 and y, consequent on the fork's vibration, open 
 and close another local battery placed in a circuit 
 called the motor circuit, in which is also placed an 
 electro-magnet D, the function of which is to 
 maintain the continuous rotation of the trans- 
 mission apparatus C. 
 
 disc C, is rotated by the electro-magnet D, the 
 trailing contact f, sweeps around the circular 
 
 Fig. 343. Delany's Synchronous Mutiplex Telegraph. 
 
 The continuous vibration of the fork makes and 
 breaks the contacts at x and y, and thereby 
 makes and breaks the motor circuit. The alter- 
 nate magnetizations and demagnetizations of the 
 cores of the motor-magnet D, cause the rotation 
 of the transmission apparatus C. 
 
 The motor magnet and transmission wheel or 
 disc C, provided with projections c, c, is the in- 
 vention of Paul La Cour, and is styled by him a 
 "phonic wheel." 
 
 The transmission apparatus is illustrated in de- 
 tail in Figs. 544 and 545, and is an exact coun- 
 terpart of the receiving apparatus at the other 
 end of the line. A base plate E, provided with 
 
 f'f- 544- 'I he I'honic II heel. 
 
 binding posts, carries a vertical rotary shaft F. 
 A circular table F 1 , is provided with a series of 
 insulated contacts arranged symmetrically around 
 the axis of rotation of the shaft. A radial arm F z , 
 connected with the shaft F, carries at its outer 
 extremity a trailing contact finger f. As the 
 
 Fig* 545- Th* Phonic Wheel. 
 
 table F 1 , and is brought successively into contact 
 with the insulated contact pieces placed on the 
 upper face of the table F 1 . 
 
 The main line Q, Q, has one of its ends con- 
 nected with the trailing finger f. As the shaft 
 F, rotates, the line is therefore brought into suc- 
 cessive electrical connection with the series of in- 
 sulated contacts in the upper face of the table 
 FI. 
 
 Any suitable number of insulated contacts may 
 be placed on the circular table F 1 ; sixty are 
 shown in Fig. 546. In practice these contacts 
 are connected in accordance with the number of 
 circuits which it is desired to simultaneously 
 maintain on the same wire. In the special case 
 shown in the figure above referred to, it is ar- 
 ranged so that four separate circuits shill be 
 established on the same line wire. 
 
 The sixty contacts are placed in six indepen- 
 dent series, numbered from I to 10, consecu- 
 tively. In the arrangement here shown two of 
 the contact pieces in each series of ten are con- 
 nected in the same circuit, and, as there are six 
 series, each of the circuits so connected will have 
 twelve contacts for each rotation of the disc, and 
 twelve electrical impulses, as will be afterwards 
 described. 
 
 The detailed mechanism, by means of which 
 the separate and independent circuits so obtained 
 are utilized for the transmission and reception of 
 messages, is shown in Fig. 546. R, R 1 , R s and 
 R 3 , are polarized relays; S, S 1 , S* and S ;J are 
 ordinary Morse sounders, although in the practice 
 of this invention some improvement has been in- 
 troduced in connection with the receiving instru- 
 ments. The connections with the main and the 
 local batteries M B and L B, are clearly shown 
 in the figure. 
 
 It will be noticed that the relay R, is connected 
 
Tel.] 
 
 518 
 
 [Tel. 
 
 -with the wire r, and with the contacts I and 5 ; 
 R 1 is connected by r 1 , with the contacts 2 and 6, 
 R e , by the wire r', with the contacts 3 and 7, 
 and R 8 , by the wire r 3 , with the contacts 4 and 
 8. Similar instruments and circuits are placed 
 at each end of the line. 
 
 Without further describing the operation of the 
 instruments shown in the figure, it need only now 
 be borne in mind that the corresponding relays at 
 the distant stations are connected with the corre- 
 spondingly numbered contacts. When, therefore, 
 the trailing contact finger at each station simul- 
 taneously touches the contacts bearing the same 
 number, the corresponding instruments connected 
 
 Pig, 34.6, Working and Receiving Currents. 
 
 with these contacts at each station will be placed 
 in communication over the main line, the trailing 
 contact finger f, completing the connection of 
 the main line with the contact arm in the man- 
 ner already described. 
 
 Telegraphy, Time A system for 
 
 the telegraphic transmission of time. 
 
 A system of time telegraphy includes a master 
 clock, the movements of whose pendulum automati- 
 cally transmit a number of electric impulses to a 
 number of secondary docks and thus moves them ; 
 or self-winding clocks are employed, which are 
 corrected daily by an impulse sent over the line 
 from a master clock. (See Clock, Electric.') 
 
 Telegraphy, Writing A species of 
 
 :ac-simile telegraphy, by means of which 
 the motions of a pen attached to a transmit- 
 ting instrument so vary the resistance on 
 two lines connected with a receiving instru- 
 ment as to cause the current received thereby 
 to reproduce the motions, on a pen or stylus, 
 which transfers them to a sheet of paper. 
 
 A system of writing telegraphy consists 
 essentially of transmitting and receiving in- 
 struments connected by a double line wire. 
 
 The transmitting instrument is shown in Fig. 
 547- 
 
 Fig. 547. Transmitter of Writing Telegraphy. 
 
 A stylus or pen resting on a top plate, is con- 
 nected by the rod C, with a series of steel contact 
 springs S, S, secured to the base and placed at 
 right angles to one another. A series of resist- 
 ances R, R, are connected with the lower ends 
 of these contact springs. Two contact bars, 
 B, B, are provided on the side facing the springs 
 with platinum contacts opposite the contacts on 
 the springs. The stylus rod C, is securely fixed 
 to the base, but a spring at the lower end per- 
 mits of its free movement. A pressure block at 
 P, is fastened to the stylus rod, as shown, and in 
 its normal position the pressures are adjusted so 
 that contact is secured with the first spring. 
 
 A movement of the stylus, as in writing, 
 presses the contact bar against the spring, vary- 
 ing the position and number of contacts, and 
 thereby cutting in or out the resistance necessary 
 to effect the proper movement of the receiving 
 pen. 
 
 The receiving instrument is shown in Fig. 548. 
 It consists of two electro-magnets placed at right 
 angles to each other. A double armature sup- 
 
Tel. 
 
 519 
 
 [Tel. 
 
 ports the receiving stylus or pen in the manner 
 shown. The variations in the current sent over 
 the line by the varying resistances introduced 
 into the circuit, or cut out or in by the action of 
 the transmitting stylus, causes variations in the 
 position of the double armature, under the vary- 
 ing magnetic attraction of the receiving electro- 
 magnet, and thus causes the receiving pen to 
 correctly reproduce the motions of the trans- 
 mitting pen. 
 
 Fig. 548, Receiver of Writing Telegraph. 
 
 This system has been operated over a line 
 nearly 500 miles in length, when it successfully 
 reproduced written characters. 
 
 The author is indebted for the drawings and 
 the general facts to the Electrical Engineer of 
 New York. 
 
 Tele-Hydro-Barometer, Electric 
 
 An apparatus for electrically transmitting to, 
 and recording at a distant station the height 
 of water or other liquid. 
 
 Tele-Manometer, Electric A 
 
 gauge for electrically indicating and record- 
 ing pressure at a distance. 
 
 The tele-manometer includes a pressure gauge 
 furnished with electric contacts operated by the 
 movements of the needle of the steam gauge, for 
 instance, and indicating and recording apparatus. 
 An alarm bell is provided to call attention to any 
 
 rise of the pressure above or its fall below the 
 given or predetermined limits for which the 
 hands have been set. 
 
 Telemeter. An apparatus for electrically 
 indicating and recording at a distance the 
 pressure on a gauge, the reading of a ther- 
 mometer, or the indications of similar in- 
 struments. (See Tele-Hydro-Barometer, 
 Electric. Tele-Manometer, Electric. Tele- 
 Thermometer, Electric?) 
 
 Telephone. To communicate by means 
 of a telephone. 
 
 Telephone. An apparatus for the electric 
 transmission of articulate speech. 
 
 The articulating telephone, though first 
 brought into public use by Bell, was invented by 
 Reis, in Germany, in 1861. In America, after 
 very protracted litigation, Bell has been decided 
 legally to be the first inventor, but scientific men 
 very generally recognize the principles of the in- 
 vention to be fully anticipated by the earlier in- 
 struments of Reis. Bell, however, is ittstly en- 
 titled to the credit of inventing the first really 
 successful telephone. 
 
 In Bell's magneto-electric telephone, the 
 transmitting and receiving instruments are iden- 
 tical. A coil C, of insulated wire connected with 
 the line, is placed on a core of magnetized steel, 
 mounted opposite the centre of a circular dia- 
 phragm of thin sheet iron, rigidly supported at 
 its edges. 
 
 In transmitting, the message is spoken into the 
 mouth-piece at one end, as at D, in Fig. 549, and 
 the to-and-fro motions thus 
 imparted to the metallic 
 diaphragm attached to the 
 mouth-piece P, produce in- 
 duction currents in the coil 
 C, on the magnet M. (See In- 
 duction, Electro-Dynamic.} 
 These impulses, passing over 
 the main line E L, Fig. 550, 
 produce similar movements 
 in the diaphragm P', of the 
 receiving instrument, at D', 
 and thus cause it to repro- 
 duce the message, in articu- 
 late sounds, to one listening at the receiving in- 
 strument. A ground circuit is shown in the 
 figure, as usually employed in practice, except 
 for long distance and in large cities. 
 
Tel.] 
 
 520 
 
 [Tel. 
 
 A magneto-telephone constitutes in reality a 
 magneto-electric machine, driven or propelled by 
 the voice of the speaker, in which the currents 
 so produced instead of being commuted are em- 
 ployed uncommuted to reproduce the uttered 
 speech. 
 
 In actual practice the instrument above de- 
 scribed is replaced by the electro-magnetic tele- 
 
 E a L 
 
 D' 
 
 B 
 
 Fig. SS- Telephone Circuit. 
 
 phone, in which the to-and-fro motions of the 
 transmitting diaphragm are caused to vary the 
 resistance of a button of carbon, or a variable con- 
 tact transmitter similar to 
 that employed by Reis in 
 some of his instruments. 
 The variable resistance 
 is placed in the circuit of 
 a battery, so that on 
 speaking into the trans- 
 mitter, electric impulses 
 are sent over the line and 
 are received by a tele- 
 phone with a magnet core 
 provided with a coil in the 
 main-line circuit. 
 
 The telephone is ar- 
 ranged for actual com- 
 mercial use in the United 
 States in the manner/ 7 /^. 55 ' Telephone Ap- 
 shown in Fig. 551. paratus. 
 
 Telephone. Bi A term sometimes 
 
 applied to a double telephone receiver so ar- 
 ranged as to permit of easy application to 
 both ears of the listener at the receiving in- 
 strument. 
 
 Telephone Cords. (See Cords, Tele- 
 phoned) 
 
 Telephone, Electro-Capillary - A 
 telephone in which the movements of the 
 transmitting diaphragm produce currents by 
 means of variations in the electromotive 
 forces of the contact surfaces of liquids in 
 capillary tubes. (See Phenomena, Electro- 
 Capillary^) 
 
 In Breguet's telephone both the transmitting 
 and the receiving instruments are similar in con- 
 
 struction and operate by means of electro-capil- 
 lary phenomena. A vertical capillary tube com- 
 municates at its upper end with an air space 
 below a diaphragm, and at its lower end with a 
 mercury surface on which rests a layer of acidu- 
 lated water. 
 
 A line wire connects the mercury reservoirs of 
 the transmitting and receiving instruments, the 
 remainder of the circuit being formed by another 
 wire connecting the mercury near the upper parts 
 of the two vertical tubes. 
 
 The alterations in the contact surfaces at the 
 transmitting end produced by the movements of 
 the diaphragm, cause electric impulses that pro- 
 duce similar movements of the diaphragm at the 
 receiving end. 
 
 Telephone, Electro-Chemical A 
 
 name sometimes given to the Edison electro- 
 motographic telephone. (See Telephone, 
 Electro-Motographic?) 
 
 Telephone, Electro-Motographic 
 
 A telephone in which the receiver consists of 
 a diaphragm of mica or other elastic material 
 operated on the principle of the electro- 
 motograph. 
 
 A straight lever, which forms part of the line 
 circuit, is rigidly attached at one end to the centre 
 of the receiving diaphragm, and rests near its 
 other end on the surface of a chalk cylinder 
 moistened with a solution of caustic potash or 
 potassium iodide, maintained in rotation by suit- 
 able mechanical means. 
 
 Electric impulses being sent into the line by the 
 voice of a speaker talking at a transmitter of ordi- 
 nary construction reduce the friction between the 
 lever and the cylinder, and produce slipping 
 movements of the lever that reproduce articulate 
 speech in the receiving diaphragm. 
 
 Telephone, Reaction An electro- 
 magnetic telephone in which the currents in- 
 duced in a coil of wire attached to the dia- 
 phragm are passed through the coils of the 
 electro-magnet, and thus react on and 
 strengthen it. 
 
 Telephone Switch, Automatic (See 
 Switch, Telephone, Automatic?) 
 
 Telephonic. Pertaining to the telephone. 
 
 Telephonic Alarm. (See Alarm, Tele" 
 phonic?) 
 
Tel.] 
 
 521 
 
 [Tel, 
 
 Telephonic Cable. (See Cable, Tele- 
 phonic^) 
 
 Telephonic Exchange. (See Exchange, 
 Telephonic, System of.) 
 
 Telephonic Exchange, System of 
 (See Exchange, Telephonic, System of.) 
 
 Telephonic Joints. (See Joint, Tele- 
 graphic or Telephonic?) 
 
 Telephonically. In the manner of the 
 telephone. (See Telephoned) 
 
 Telephoning. Communicating by means 
 of the telephone. 
 
 Telephote. An apparatus for the tele- 
 graphic transmission of pictures by means of 
 the action of light on selenium 1 . (See Tele- 
 photography^) 
 
 The telephote is sometimes called the pherope. 
 
 Telephotography. A system for fac- 
 simile transmission by means of dots and 
 lines transmitted by means of a continuous 
 current whose intensity is varied by a trans- 
 mitting instrument containing a selenium re- 
 sistance. (See Telegraphy, Fac-Simile. 
 Resistance or Cell, Selenium?) 
 
 The transmitter consists of a dark box mounted 
 on an axis, so as to be capable of a sidewise 
 motion. The picture to be transmitted is 
 thrown continuously on the face of the box by 
 any lantern projection apparatus, and a small 
 opening containing a selenium resistance receives 
 
 wise continuous current in the circuit of which the 
 selenium resistance is placed. 
 
 The picture is received at the other end on a 
 sheet of chemically prepared paper moved syn- 
 chronously with the transmitting box. 
 
 Telescope, Reading A telescope 
 
 employed in electric measurements for read- 
 ing the deflections of the galvanometer. 
 
 The image of numbers on an illumined scale is 
 seen in the mirror through the telescope, shown 
 in Fig. 552. 
 
 Teleseme. A self-registering hotel an- 
 nunciator, by means of which a dial operated 
 in a room indicates on the annunciator the 
 article or service required. 
 
 Tele-Thermometer, Electric - An 
 electric recording thermometer for indicating 
 and recording temperature at a distance. 
 
 The tele- thermometer consists essentially of a 
 transmitter and a receiver. The transmitter 
 consists of a delicate thermometer provided with 
 suitable contacts. The receiver, which is in 
 circuit with the transmitter, has, in some forms, 
 a recording dial on which a continuous record, 
 for a day or week, is made. In cases where it is 
 desired that a given maximum temperature shall 
 not be exceeded, an alarm bell, connected with 
 contacts on the dial face, is rung. 
 
 Telluric Magnetic Force. (See Forct, 
 Magnetic, Telluric?) 
 Telpher Line. (See Line, Telpher^ 
 Telpherage. A system for the convey- 
 ance of carriages suspended from electric 
 
 ffg. 352. Reading Telescope. 
 
 the alternations of light and shade, and transmits 
 the same a-; variatio .sin the strength of the other- 
 
 fif-SSS- C.rcuitfor Telphtrage System 
 
 conductors, and driven by means of electric 
 motors, that take directly from the conductors 
 the current required to energize them. 
 
Tern.] 
 
 522 
 
 [The. 
 
 Two lines are provided, an up and a down line, 
 that cross each other at regular intervals. Each 
 line is in segments, and the alternate segments 
 are insulated from each other, but are connected 
 electrically by cross-pieces on the supporting 
 posts. In this way the line shown in Fig. 553 is 
 obtained. 
 
 The two lines are maintained at a difference of 
 potential by a dynamo-electric machine at D, 
 Fig. 554. As the train at L T, or L' T', is of 
 such a length as to come into contact with two 
 different segments at the same time, it receives a 
 current sufficient to run the motor connected with 
 it, the current being received through a conduc- 
 tor joining a pair of wheels that are insulated 
 from the truck. 
 
 The general arrangement of the line is shown 
 in the annexed Fig. 554 
 
 Fig. SS4- Circuit for Telpherage System. 
 
 Temperature Alarm. (See Alarm, Tem- 
 perature.} 
 
 Temperature, Effects of, on Electric Re- 
 sistance (See Resistance, Effect of 
 
 Heat on Electric?) 
 
 Tempering, Electric A process 
 
 for temperaing metals in which heat of elec- 
 tric origin is employed instead of ordinary 
 furnace heat. 
 
 Temporary Intensity of Magnetization. 
 
 (See Magnetization, Temporary Intensity 
 of.) 
 
 Tension, Electric A term often 
 
 loosely applied to signify indifferently surface 
 density, electromotive force, dielectric stress, 
 or difference of potential. 
 
 This term is now very generally abandoned. 
 
 Terminal, Cable A water-tight 
 covering provided at the end of a cable to 
 prevent injury to the cable insulation by the 
 moisture of the air. 
 
 Terminal, Negative The negative 
 
 pole of a battery or other electric source, or 
 the end of the conductor or wire connected 
 with the positive plate. 
 
 Terminal, Positive The positive 
 
 pole of a battery or other electric source, or 
 the end of the conductor or wire connected 
 to the negative plate. 
 
 Terminals. A name sometimes applied 
 to the poles of a battery or other electric 
 source, or to the ends of the conductors or. 
 wires connected thereto. 
 
 The two terminals are distinguished as the 
 positive and the negative. Their names are un- 
 like those of the battery plates to which they 
 are connected, the positive terminal being con- 
 nected with the negative plate and the negative 
 terminal with the positive plate. 
 
 Terrestrial Magnetism. (See Magnet- 
 ism, Terrestrial) 
 
 Testing, Methods of Various 
 
 methods for determining the values of the 
 current strength in any circuit, the difference 
 of potential, the resistance, the coulombs, 
 the farads, the joules, the watts, etc. (See 
 Measurements, Electric) 
 
 The investigation of an apparatus or cir 
 cuit for the purpose of determining whether 
 it is in standard or working condition. 
 
 Testing of Joints. (See Joint, Test- 
 ing of.) 
 
 Testing Pole. (See Pole, Testing) 
 
 Testing Transformer. (See Trans- 
 former, Testing.) 
 
 Tetanus. Continuous, spasmodic contrac- 
 tion of the muscles. 
 
 Tetanus, Acoustic Tetanus pro- 
 duced in a muscle by means of alternate 
 currents induced in a coil of wire by a mag- 
 netized steel spring vibrating near the coil 
 with sufficient rapidity to give a musical note. 
 
 The rapidity of the inductive shock can be de- 
 termined from the pitch of the musical note; hence 
 the use of the term acoustic. 
 
 Theatrophone. A system of telephonic 
 communication between theatres or operas 
 and subscribers, by means of slot machines. 
 
 Any person at a cafe, club, restaurant or other 
 public place, by the theatrophone, is automati- 
 cally placed in communication with the theatre 
 by means of a Deceiving telephone so as to hear 
 
The.] 
 
 523 
 
 [The. 
 
 the performance by dropping a given piece of 
 money in the slot of the machine. 
 
 Theodolite, Magnetic 
 
 An appa- 
 
 ratus for measuring the declination or varia- 
 tion of the magnetic needle at any place. 
 
 A divided circle, like that on a theodolite, is 
 supported horizontally. The needle is formed of 
 a tubular magnet, having an achromatic lens at 
 one end and a scale at the focus of the lens at the 
 other end. 
 
 Theory, Alternation, of Muscular Nerve 
 
 Current A theory proposed by L. 
 
 Hermann, in which the currents of nerves or 
 muscular fibres are regarded as a result of 
 their alteration from an original condition. 
 
 Hermann states: 
 
 (i.) That protoplasm undergoing partial death 
 at any part, either while dying or by metamor- 
 phosis, becomes negative to the uninjured part 
 
 (2.) Protoplasm, when excited at any part, be- 
 comes negative to the unexcited part. 
 
 (3.) Protoplasm, when partially heated at any 
 part, becomes positive, and, on cooling, negative 
 to the unchanged part. 
 
 (4. ) Protoplasm is strongly polarizable on its 
 surface, the polarization constantly diminishing 
 with excitement and while dying. 
 
 According to this theory, passive, uninjured 
 and absolutely fresh tissues are devoid of elec- 
 tric currents. This matter must still be regarded 
 as unsettled. (See Theory, Molecular, of Mus- 
 cles or Nerve Current. ) 
 
 Theory, Contact, of Toltaic Cell 
 
 (See Cell, Voltaic, Contact Theory of.) 
 
 Theory, Difference A theory as to 
 
 the cause of the electric currents excited be- 
 tween injured and uninjured protoplasm. 
 
 Theory, Molecular, of Muscles or Nerve 
 
 Current A theory proposed by Du 
 
 Bois Reymond, in which every nerve or mus- 
 cular fibre is regarded as composed of a 
 series of electromotive molecules arranged 
 in series and surrounded by a neutral con- 
 ducting fluid. 
 
 " The molecules are supposed to have a posi- 
 tive equatorial zone directed towards the surface 
 and two negative polar surfaces directed toward 
 the transverse section. Every fresh transverse 
 section exposes new negative surfaces, and every 
 
 artificial longitudinal section new positive area." 
 (Landois and Sterling.) 
 
 Theory of Electric Displacement. (See 
 Displacement, Electric, Theory of.) 
 
 Therapeutical Electrization. (See Elec- 
 trization, Therapeutical?) 
 Therapeutic Bath, Electro (See 
 
 Bath, Electro- Therapeutic?) 
 
 Therapeutics, Electro, or Electro- 
 Therapy The application of electricity 
 
 to the curing of disease. (See Biology, Elec- 
 tro^ 
 
 Therapeutist, Electric One skilled 
 
 in electro-therapy. 
 
 An electro-medical practitioner. 
 
 Therapy, Electro A term some- 
 times used instead of electro-therapeutics. 
 (See Therapeutics, Electro, or Electro- 
 Therapy^) 
 
 Therapy, Magneto Alleged electro- 
 therapeutic effects produced by the move- 
 ments of magnets over the body of the 
 patient. 
 
 It is asserted by eminent authorities that such 
 effects have an actual existence. They should, 
 however, until more carefully investigated, be 
 accepted with extreme caution. 
 
 Therm. A heat unit propose 1 by the 
 British Association. 
 
 A therm is the amount of heat required to 
 raise the temperature of one gramme of pure 
 water at the temperature of its maximum density 
 one degree centigrade. (See Calorie.} 
 
 Thermaesthesiometer. An instrument 
 employed in electro-therapeutics for testing 
 the temperature sense in nervous diseases. 
 
 The thermaesthesiometer consists of two ther- 
 mometers movable on a standard, with flat ves- 
 sels of mercury in order to readily apply them to 
 the skin. The mercury vessel of one of the two 
 thermometers is surrounded by an insulated 
 platinum wire and may be warmed at pleasure by 
 passing a galvanic current through the wire. 
 
 The two vessels, brought to different tempera- 
 tures, are set on the same part of the skin, one 
 after the other, so as to test the sensibility of the 
 skin for the differences in temperature. 
 
 Thermal Absorption. (See Absorption, 
 Thermal?) 
 
The.] 
 
 524 
 
 [The. 
 
 Thermal Cautery. (See Cautery, Ther- 
 mal^ 
 
 Thermal Incandescence. (See Incan- 
 descence, Thermal?) 
 
 Thermic Balance. (See Balance, Ther- 
 mic, or Bolometer?) 
 
 Thermo-Battery. (See Battery, Thermo?) 
 
 Thermo Call. A call operated by means 
 of thermo currents. 
 
 Thermo-Cell. (See Cell, Thermo-Elec- 
 tric?) 
 
 Thermo-Electric Battery. (See Battery t 
 Ther mo-Electric?) 
 
 Thermo-Electric Cell. (See Celt, 
 Thermo-Electric?) 
 
 Thermo-Electric Couple. (See Couple, 
 Thermo-Electric?) 
 
 Thermo-Electric Diagram. (See Dia- 
 gram, Thermo-Electric?) 
 
 Thermo-Electric Effect. (See Effect, 
 Thermo-Electric?) 
 
 Thermo-Electric Inversion. (See In- 
 version, Thermo-Electric?) 
 
 Thermo-Electric Pile, Differential 
 
 (See Pile, Thermo, Differential?) 
 
 Thermo-Electric Pile or Battery. (See 
 
 Pile, Thermo-Electric?) 
 
 Thermo-Electric Power. (See Power, 
 Thermo-Electric?) 
 
 Thermo-Electric Series. (See Series, 
 Thermo-Electric?) 
 
 Thermo-Electricity. (See Electricity, 
 Thermo^ 
 
 Thermo-Electrometer. A name some- 
 times, but not happily, applied to an electric 
 thermometer. (See Thermometer, Electric?) 
 
 Thermo-Electromotive Force. (See 
 Force, Electromotive, Thermo?) 
 
 Thermolysis. A term applied to the 
 chemical decomposition of a substance by 
 
 heat. 
 
 Thermolysis, or dissociation, is an effect pro- 
 duced by an action of heat somewhat similar to 
 the effect of electrolysis, or chemical decomposi- 
 tion produced by the passage of an electric cur- 
 rent. When a chemical substance is heated, the 
 
 vibration of its molecules is attended by an inter- 
 atomic vibration of its constituent atoms so that a 
 decomposition ensues. If the temperature is not 
 excessive, these liberated atoms recombine with 
 others which they meet. At higher temperatures, 
 however, such recombination is impossible, and a 
 permanent decomposition ensues, called ther- 
 molysis or dissociation. 
 
 Thermometer, Electric A device 
 for determining the effects of an electric dis- 
 charge by the movements of a liquid column 
 on the expansion of a confined mass of air 
 through which the discharge is passed. 
 
 Thermometer, Electric Resistance 
 
 A thermometer the action of which is 
 based on the change in the electric resistance 
 of metallic substances with changes in tem- 
 perature. 
 
 The electric resistance thermometer is used, 
 among other purposes, for determining the temper- 
 ature of the sea at different depths. Its operation 
 is based on the electric resistance of two perfectly 
 similar coils of insulated wire, enclosed in separate 
 water- tight copper cases. One coil is placed where 
 the temperature is to be determined, and the other 
 in a vessel of water, the temperature of which is 
 altered until the two coils show the same resist- 
 ance, when, of course, the temperature of the 
 distant coil is the same as that of the water sur- 
 rounding the other coil. 
 
 Thermometer Scale, Centigrade 
 
 (See Scale, Thermometer, Centigrade?) 
 
 Thermometer Scale, Fahrenheit 
 
 (See Scale, Thermometer, Fahrenheit?) 
 
 Thermophone. Any instrument by means 
 of which sounds are produced by the absorp- 
 tion of radiant energy. (See Photophone?) 
 
 A telephone has been constructed in which the 
 motions of the receiving diaphragm are effected 
 by the expansions and contractions of a thin me- 
 tallic wire connected to the diaphragm and placed 
 in the circuit of the main line. 
 
 Thermostat. An instrument for automati- 
 cally maintaining a given temperature by the 
 closing of an electric circuit through the ex- 
 pansion of a solid or liquid. 
 
 Thermostats are often used in systems of auto- 
 matic fire telegraphy and in systems of automatic 
 temperature regulation in connection with indi- 
 
The.] 
 
 525 
 
 [Tic. 
 
 eating instruments for sounding an alarm or giv- 
 ing notice when the temperature changes. 
 
 They are operated either on open or closed cir- 
 cuits. 
 
 Thermostat Alarm. (See Alarm, Ther- 
 mostat?) 
 
 Thermostat, Closed-Circuit A 
 
 thermostat maintained normally on a closed 
 circuit. 
 
 In closed-circuit thermostats, the adjustment 
 for any degree of temperature within a given 
 range is effected by means of a screw. 
 
 Thermostat, Electro-Pneumatic 
 
 An instrument for automatically indicating 
 the existence of a given temperature by the 
 closing of an electric circuit on the expansion 
 of a gas. 
 
 Thermostat, Mercurial A thermo- 
 stat operating by the ex- 
 pansion of a mercury 
 column. 
 
 A mercurial thermostat 
 is shown in Fig. 555. One 
 terminal is connected di- 
 rectly with the mercury; 
 the other is placed in the 
 arm to the left. On a cer- 
 tain predetermined tem- 
 perature being reached, the 
 rise of the mercury column 
 completes the circuit and 
 rings an alarm bell. By 
 connecting the thermostat 
 with an annunciator, the 
 particular locality where an 
 excessive temperature has 
 been reached is indicated. 
 Such a system is in use in a well known system of 
 fire alarm. 
 
 . 5SS- Mercurial 
 Thermostat. 
 
 Thermostat, Open-Circuit 
 
 A ther- 
 
 mostat maintained normally on an open cir- 
 cuit. 
 
 In open -circuit thermostats the adjustment for 
 temperature within a given range is effected by 
 varying the distance of the fixed and movable 
 contact points. 
 
 Thermostatic. Of or pertaining to a ther- 
 mostat. (See Thermostat!) 
 
 Thompson's Gauss. (See Gauss, S. P. 
 Thompson's!) 
 
 Thomson's Gauss. (See Gauss, Sir Wil- 
 liam Thomson's!) 
 
 Three-Branched Sparks. (See Spark, 
 Three-Branched!) 
 
 Three-Filament Incandescent Electric 
 Lamp for Multiphase Circuits. (See Lamp, 
 Electric, Incandescent, Three-Filament, 
 for Multiphase Circuits?) 
 
 Three-Way Trolley Frog. (See Frog, 
 Trolley, Three- Way?) 
 
 Three- Wire System. (See System, Three- 
 Wire.} 
 
 Throttling 1 . Choking, or stopping off. 
 
 Through Circuit. (See Circuit, 
 Through!) 
 
 Through Line. (See Line, Through!) 
 
 Throwback Indicator, Electrical . 
 
 (See Indicator, Electric Throwback!) 
 
 Throwback Indicator, Mechanical 
 
 (See Indicator, Mechanical Throwback!) 
 
 Throw of Needle. (See Needle, Throw 
 of!) 
 
 Thumb-Cock Electric Burner. (See 
 
 Burner, Thumb-Cock Electric!) 
 
 Thunder. A loud noise accompanying a 
 lightning discharge. 
 
 Thunder is due to the sudden rush of the sur- 
 rounding air to fill the partially vacuous space 
 accompanying the disruptive discharge of a cloud. 
 This space is caused mainly by the condensation of 
 the vapor formed on the passage of the discharge 
 through drops of rain or moisture in the air, as 
 well as by the expansion of the air itself. 
 
 Thunder Rod. (See Rod, Thunder?) 
 Thunder Storms, Geographical Distribu. 
 tion of (See Storms, Thunder, Geo- 
 graphical Distribution of!) 
 
 Tick, Magnetic A faint metallic 
 
 click heard on the magnetization and demag- 
 netization of a magnetizable substance. 
 
 Ticker Service, Stock The simul- 
 taneous transmission of stock quotations or 
 other desired information to a number of 
 subscribers. 
 
 The stock ticker-service includes a central 
 transmitting station connected with a given num- 
 
Tic.] 
 
 526 
 
 [Tis. 
 
 her of subscribers, each of whom is furnished 
 with a stock ticker. The transmitter at the cen- 
 tral station consists of a keyboard and a cylinder 
 furnished with spiral pins. The spiral pins are 
 connected through a series of pole-changers to 
 separate line wires radiating in all directions from 
 the central office. 
 
 The connections are such that, a rapid rota- 
 tion being given by means of an electric mo- 
 tor to the cylinder, the impulses sent out by the 
 keyboard are transmitted to each of the separate 
 circuits. Since each of these circuits has a num- 
 ber of ticker printers connected with it, reports of 
 fluctuations in prices are simultaneously printed 
 in hundreds of different offices. 
 
 Ticker, Stock A form of step-by- 
 step telegraphic instrument employed for au- 
 tomatically sending and recording stock quo- 
 tations to any desired number of subscribers. 
 (See Telegraphy, Step-by-Step.) 
 
 A form of printing telegraph. 
 
 Callahan's Printing Telegraph is used as a 
 stock ticker. (See Telegraphy, Printing.) 
 
 Phelps' Stock Printer is employed extensively 
 as a stock ticker. This form of printing telegraph 
 requires but a single wire, and has a working 
 speed of almost thirty words a minute, 
 
 A. double type-wheel, maintained in motion by 
 clockwork, is stopped at the desired characters 
 by the motion of a polarized relay, working be- 
 tween the poles of two electro magnets, furnished 
 with a soft iron or non-polarized armature. The 
 release of the armature of the printing mag- 
 net releases a train, and thus insures the impres- 
 sion of the character it is desired to print. 
 
 The type-wheel is driven by a step-by-step 
 movement obtained by means of rapidly alter- 
 nating pulsations. Although these pass through 
 the coils of the printing magnet, they follow one 
 another too rapidly to charge its coils, so that the 
 armature is unaffected until a pause is made, 
 when, its armature being attracted, it releases 
 the printing mechanism. The message is received 
 on a fillet of paper, fed by a suitable mechanism. 
 
 Time-Ball, Electric (See Ball, 
 
 Electric Tinted) 
 
 Time-Constant of Circuit (See Circuit, 
 Time-Constant of.) 
 
 Time-Constant of Condenser. (See Con- 
 dtnser, Time-Constant of.) 
 
 Time-Constant of Electro-Magnet. (See 
 
 Constant, Time, of Electro-Magnet?) 
 
 Time Cut-Out, Automatic An au- 
 
 omatic cut-out arranged on a storage bat- 
 tery so as to cut it in or out of the circuit of 
 the charging source at predetermined times. 
 
 Time-Fall of Electromotive Force of 
 Secondary or Storage Cell During Dis- 
 charge. (See Force, Electromotive, of Sec- 
 ondary or Storage Cell, Time-Fall of.) 
 
 Time-Lag of Magnetization. (See Mag- 
 netization, Time-Lag of.) 
 
 Time, Reaction The time required 
 
 for the effects of an electric current to pass 
 from a nerve to a muscle. 
 
 Time-Rise of Electromotive Force of 
 Secondary or Storage Cells During Dis- 
 charge. (See Force, Electromotive, of Sec- 
 ondary or Storage Cell, Time-Rise of.) 
 
 Time-Switch. (See Switch, Time.) 
 
 Time, Telegraphic, Register for Rail- 
 roads (See Register, Time, for Rail- 
 roads?) 
 
 Time Telegraphy. (See Telegraphy, 
 Time?) 
 
 Tinned Wire. (See Wire, Tinned?) 
 
 Tinning, Electro Covering a sur- 
 face with a coating of tin by electro-plating. 
 (See Plating, Electro?) 
 
 Stannic chloride, or the perchloride of tin, dis. 
 solved in water in the proportion of 30 parts of the 
 salt to 1,250 of water, makes a good tinning 
 bath. 
 
 Tinnitus, Telephone A professional 
 
 neurosis, or abnormal nervous condition of the 
 auditory apparatus, believed to be caused by 
 the continual use of the telephone. 
 
 Tips, Polar The free ends of the 
 
 field magnet pole pieces of a dynamo-electric 
 machine. 
 
 Tissue, Nerve or Muscular Excitability 
 of- Electric stimulation of nervous or 
 muscular tissue. 
 
Ton.] 
 
 527 
 
 [Tor. 
 
 The general effects of electric stimulation of 
 nervous or muscular tissue may be summarized 
 as follows: 
 
 (l.) Electric stimulation of a motor nerve, pro- 
 duces a contraction of the muscles to which such 
 nerve is distributed. 
 
 (2.) Electric stimulation of a sensory nerve, 
 produces pain in the parts to which the nerve is 
 distributed. 
 
 (3.) Electric stimulation of mixed motor and 
 sensory nerves produces both of the effects men- 
 tioned under (i) and (2.) 
 
 Tongs, Cable Hanger Tongs pro- 
 vided with long handles for the purpose of 
 attaching the hangers of an aerial cable to 
 the suspending wire or rope. 
 
 Tongs, Discharging A term some- 
 times used for a discharging rod. (See Rod, 
 Discharging?) 
 
 Tongue, Relay, Bias of A term 
 
 employed to signify such an adjustment of a 
 polarized relay, that on the cessation of the 
 working current, the relay tongue shall 
 always rest against the insulated contact, and 
 not against the other contact, or vice versa. 
 
 Sometimes, as in the split-battery duplex, the 
 bias is toward the uninsulated contact. (See 
 Relay ; Polarized,} 
 
 Tool, Lead Scoring A tool for 
 
 readily scoring the surface of the lead of a 
 lead-covered cable, when the same is to be 
 removed preparatory to making joints. 
 
 Toothed-Ring Armature. (See Arma- 
 ture, Toothed-Ring?) 
 
 Top, Induction A top consisting 
 
 of an iron disc supported on a vertical axis, 
 which, when spun before the poles of a steel 
 magnet, assumes an inclined position, through 
 the influence of the currents induced in the 
 disc. 
 
 The top maintains the inclined position so long 
 only as the strength of the induced currents is 
 sufficiently great ; that is, while speed of rotation 
 is sufficiently great. 
 
 Toppler-Holtz Machine. (See Machine, 
 Toppler-Holtz?) 
 Torch, Electric Gaslighting A 
 
 gaslighting appliance consisting of the com- 
 
 bination of a portable voltaic battery and a 
 spark or induction coil. 
 
 The torch is mounted on the end of a rod pro- 
 vided with means for turning on the gas. A key 
 is then touched and the gas lighted by the spark 
 produced by an induction coil or a small electro- 
 static induction machine. 
 
 Torpedo, Automobile A torpedo 
 
 which contains in itself the power for its own 
 motion. 
 
 The moving power may be that derived from 
 compressed air or gas, or from a storage bat- 
 tery contained within the torpedo. An auto- 
 mobile torpedo provided with a storage battery 
 and electric motor would then be distinguished 
 from an electrically propelled torpedo, connected 
 by means of cables with a driving dynamo 
 located outside the torpedo on a ship, or on the 
 shore. 
 
 Torpedo Boat. (See Boat, Torpedo?) 
 
 Torpedo Cable. (See Cable, Torpedo?) 
 
 Torpedo, Drifting A torpedo sus- 
 pended from a float, and connected by means 
 of rope with similar torpedoes, allowed to 
 drift with the current, so as to catch against 
 a vessel. 
 
 Torpedo, Electric A name some- 
 times given to the electric ray. (See Ray, 
 Electric?) 
 
 Torpedo, Electric An electrically 
 
 operated torpedo. 
 
 This latter usage of the term is the commoner. 
 
 Torpedo, Halpine-Savage A special 
 
 form of torpedo, in which electricity is both 
 the propelling and directing power, and in 
 which the electric source furnishing the pro- 
 pelling current is contained within the 
 torpedo. 
 
 In the Halpine Savage torpedo, the propelling 
 power is obtained from a storage battery placed 
 within the torpedo. 
 
 Torpedo, Lay A moving torpedo, 
 
 in which the moving power is carbonic acid 
 gas, or compressed air, or other similar power 
 not electric, and the guiding power is electric. 
 
 The Lay torpedo has the form of a cylindrical 
 boat furnished with conical ends. The explosive is 
 placed in the fore part of the torpedo. Flags are 
 
Tor.] 
 
 528 
 
 [Ton. 
 
 attached to the torpedo, showing the operator the 
 exact course taken by it. 
 
 The torpedo is started, stopped and steered by 
 means of electric currents sent to the torpedo 
 through an insulated cable connected with the 
 torpedo. 
 
 Torpedo Nets. (See Nets, Torpedo^ 
 
 Torpedo, Outrigger A pole or 
 
 spar torpedo. 
 
 The torpedo is placed in a metallic case and 
 supported on the end of a spar or outrigger. The 
 spar is depressed until the torpedo is sunk below 
 the water line. The torpedo is fired when its end 
 conies in contact with the side of the enemy's 
 vessel. 
 
 Torpedo, Sims-Edison A special 
 
 form of torpedo in which electricity is both 
 the propelling and the directing power, but the 
 electric source is situated outside of the 
 torpedo. 
 
 The torpedo is propelled by means of an electric 
 motor placed in the torpedo, and driven by means 
 of an electric current transmitted through a cable 
 connected with the sending station. 
 
 Torpedo, Spar A torpedo, attached 
 
 io the end of a spar, and designed to be 
 exploded by percussion against the side of an 
 enemy's vessel, when thrust against the side 
 below the water-line. 
 
 The spar torpedo is but little used, having 
 been replaced by more efficient forms. 
 
 Torpedo, Stationary A term some- 
 times employed instead of a submarine 
 mine. (See Mine, Submarined) 
 
 A stationary torpedo is so named in order to 
 distinguish it from a torpedo which is moved 
 through the water by any means. (See Torpedo, 
 Towing.) 
 
 Torpedo, Towing A torpedo ar- 
 ranged to be towed on the surface after a ves- 
 sel and explode when it strikes the side of 
 an enemy's vessel. 
 
 The torpedo is shaped so that it maintains dur- 
 ing its motion a certain distance from the sides of 
 the towing boat or vessel. 
 
 Torque. That moment of the force ap- 
 plied to a dynamo or other machine which 
 turns it or causes its rotation. 
 
 The mechanical rotary or turning force 
 which acts on the armature of a dynamo^ 
 electric machine or motor and causes it to 
 rotate. 
 
 In the case of the armature of a dynamo- 
 electric machine the torque is equal to the radius 
 of the armature, multiplied by the pull at the 
 circumference, or the radius of its pulley multiplied 
 by the pull at the circumference of the pulley. 
 
 A torque is exerted on the shaft of a motor from 
 the electro-magnetic action, or pull at the 
 periphery of the armature. 
 
 The torque is usually measured in pounds of 
 pull at the end of a radius or arm I foot in 
 length. 
 
 Torricellian Yacuum. (See Vacuum, 
 Torricellian?) 
 
 Torsion Balance, Coulomb's (See 
 
 Balance, Coulomb's Torsion?) 
 
 Torsion Galvanometer. (See Galvanom- 
 eter, Torsion?) 
 
 Total Disconnection. (See Disconnec- 
 tion, Total?) 
 
 Total Earth. (See Earth, Total?) 
 
 Total Magnetic Induction. (See Induc- 
 tion, Total Magnetic?) 
 
 Touch, Double A method of mag- 
 netization in which two closely approximated 
 magnet poles are simultaneously drawn from 
 one end of the bar to be magnetized to the 
 other and back again, and this repeated a 
 number of times. 
 
 Touch, Separate A method of 
 
 magnetization in which two magnetizing poles 
 are simultaneously applied to the bar to be 
 magnetized and drawn over it in opposite di 
 rections. (See Magnetization by Touch?) 
 
 Touch, Single A method of mag- 
 netization in which a single magnetizing bar 
 is drawn from one end to the other of the bzr 
 to be magnetized, and returned through the 
 air for the next stroke. (See Magnetization, 
 Methods of?) 
 
 Tourmaline. A mineral consisting of 
 natural silicates and borates of alumina, lime, 
 iron, etc., possessing pyro-electric properties, 
 (See Electricity, Pyro.) 
 
Tow.] 
 
 529 
 
 [Tra. 
 
 Tower, Conning A shot-proof 
 
 tower from which the commander of a turret 
 ship directs the movements of a vessel during 
 action. 
 
 Tower, Electric A high tower pro- 
 vided for the support of a number of electric 
 arc lamps, employed in systems of general 
 illumination. 
 
 Tower System of Electric Lighting. 
 The lighting of extended areas by means of 
 arc lights placed on the tops of tall towers. 
 
 The tower system of electric illumination is only 
 applicable to wide open spaces, since otherwise 
 objectionable shadows are apt to be formed. 
 
 Towing Torpedo. (See Torpedo, Taw- 
 ing) 
 
 Traction, Magnetic The force with 
 
 which a magnet holds on to or retains its 
 armature, when once attached thereto. 
 
 Magnetic traction is to be distinguished from 
 magnetic attraction, or the ability of a magnet 
 pole to draw an armature or other magnets to- 
 wards it from a distance. 
 
 Train Wire. (See Wire, Train) 
 
 Tramway, Electric A railway over 
 
 which cars are driven by means of elec- 
 tricity. 
 
 An electric railroad. 
 
 The term tramway is sometimes applied to 
 roads in cities, as distinguished from inter-urban 
 roads. 
 
 Transformer. An inverted Ruhmkorff 
 induction coil employed in systems of dis- 
 tribution by means of alternating currents. 
 
 A transformer is sometimes called a converter. 
 The word transformer is, however, the one most 
 employed. 
 
 A transformer consists essentially of an induc- 
 tion coil, Fig. 556, in which the primary wire is 
 long and thin, and consequently has many turns, 
 as compared with the secondary wire, S, S, which 
 is short, thick, and has few turns. 
 
 To prevent heating and loss of energy in con- 
 version, the core of the transformer is thoroughly 
 laminated; to lower the resistance of its mag- 
 netic circuit, the transformer is usually iron-clad. 
 
 In a system of electrical distribution by means 
 of transformers, alternating currents, of small 
 Current strength and comparatively considerable 
 
 difference of potential, are sent over a line from a 
 distant station, and passing into the primary wire 
 of a number of converters, generally connected 
 to the line in multiple arc, produce, by induction 
 
 Fig. 556. Transformer. 
 
 currents of comparatively great strength and 
 small difference of potential in the secondary 
 wires. 
 
 Various electro -receptive devices are connected 
 in multiple arc to circuits connected with the sec- 
 ondary wires. 
 
 This method of distribution greatly reduces the 
 cost of the main conducting wires or leads in all 
 cases where the distance is considerable, since 
 considerable energy may be conveniently sent 
 over a comparatively thin wire, with but a trifling 
 loss, if the difference of potential is sufficiently 
 great. 
 
 The general arrangement of the converters on 
 the main line, and the connection of the second- 
 ary circuits with the electro-receptive devices in 
 
 _L_L 
 
 Fig. SS7- Transformer Circuits. 
 
 such a system, are shown in Fig. 557. The trans- 
 formers are supported on the line poles, as more 
 
Tra.] 
 
 530 
 
 [Tra. 
 
 dearly shown In Fig. 558, in which the terminals 
 of the primary and secondary of the converter 
 are readily seen. 
 
 When the converter is properly constructed, 
 the loss of conversion at full load is but small ; 
 that is to say, the number of watts in the secon- 
 dary is very nearly equal to the number in the 
 primary. A current of IO amperes, at 2,000 
 volts, when passed into a converter the number 
 of whose turns in the primary is twenty times the 
 number in its secondary, will produce in its sec- 
 ondary a current whose strength is about twenty 
 times as great, that is, nearly 200 amperes, but 
 whose voltage is only about one-twentieth, or, 
 loo; the watts in the two cases are nearly the 
 same, or theoretically 20,000 watts. 
 
 The ratio between the windings of the primary 
 and the secondary circuits is called the co-effi- 
 cient of transformation. 
 
 In general, the shorter the wire on the second- 
 ary, and the smaller its number of turns, the 
 greater is the reduction in the difference of po- 
 tential, and the greater the current produced. 
 The reduction is nearly proportionate to the ratio 
 of the number of windings of the two coils. 
 
 Transformer, Constant-Current 
 
 Fig. 338. Transformer Attached to Poles. 
 
 Transformer, Closed Iron Circuit 
 
 A transformer the core of which forms a 
 complete magnetic circuit. 
 
 These transformers are sometimes called iron- 
 clad transformers. 
 
 Transformer, Commuting A term 
 
 sometimes applied to a variety of motor gen- 
 erator in which neither the armature nor the 
 field magnets revolve, the variations in the 
 polarity of the magnetic circuit being obtained 
 by means of special comrrutators. 
 
 transformer in which a current of a constant 
 potential in the primary is converted into a 
 current of constant strength in the secondary, 
 despite changes in the load on the secondary. 
 
 Transformer, Core A transformer 
 
 in which the primary and secondary wires 
 are wrapped around the outside of a core 
 consisting of a bundle of soft iron wires or 
 plates. 
 
 A Ruhmkorff coil is a core transformer. 
 
 Transformer, Efficiency of" The 
 
 ratio between the whole energy supplied in 
 any given time to the primary circuit of a 
 transformer and that which appears in the 
 form of electric current in the secondary 
 circuit. 
 
 The energy applied to the primary circuit of a 
 transformer is dissipated: 
 
 (i.) By eddy currents in the core of the trans- 
 former. (See Currents, Eddy.) 
 
 (2.) By hysteresis, or magnetic friction. (See 
 Hysteresis. ) 
 
 (3.) By heating of the primary circuit. 
 
 (4.) By heating of the secondary circuit. 
 
 When a transformer is overloaded, its efficiency 
 decreases. There is a certain range of second- 
 ary resistance and current, within which a trans- 
 former is most advantageously operated. 
 
 Transformer Guard. (See Guard, Trans- 
 former, Lightning?) 
 
 Transformer, Hedgehog A name 
 
 applied to a particular form of open-iron cir- 
 cuit transformer. (See Transformer^) 
 
 The advantages claimed for the hedgehog trans- 
 former are that it can be made to give a higher 
 all-day efficiency, since it insures a smaller loss 
 from hysteresis in the iron. The efficiency for 
 very small loads, or for no loads is greater than in 
 the closed-circuit transformer. 
 
 Transformer, Leakage Current of 
 
 A term sometimes used for the current which 
 escapes from the primary through the dielec- 
 tric of a transformer to the secondary circuit. 
 
 The term is a bad one, since the true leakage 
 current would be the current which represents 
 the leakage between the primary or secondary 
 circuit and the ground. 
 
Tra.] 
 
 531 
 
 [Tra. 
 
 Transformer Lightning Arrester. (See 
 Arrester, Lightning, Transformer?) 
 
 Transformer, Multiple Any form 
 
 of transformer which is connected in multiple 
 to the primary circuit. 
 
 A multiple or parallel transformer is self-regu- 
 lating under variable loads, provided the electro- 
 motive force in the primary is maintained con- 
 stant. 
 
 Transformer, Oil A transformer 
 
 which is immersed in oil in order to insure a 
 high insulation. 
 
 Transformer, Open-Iron Circuit 
 
 A transformer the iron of which does not form 
 a complete magnetic circuit, but is formed 
 instead partly of iron and partly of air. 
 
 Transformer, Pilot A small trans- 
 former, placed at any desired portions of a 
 line in order to determine the drop of poten- 
 tial. 
 
 The pilot transformer is used in connection with 
 a lamp or other suitable indicating device. Its use 
 is similar to the use of the pilot incandescent lamp. 
 
 Transformer, Rotary-Current A 
 
 transformer operated by means of a rotary 
 current. (See Current, Rotating?) 
 
 The rotary current transformer for a rotary 
 current of three separate alternating currents com- 
 bined, transforms all three currents together. 
 There are three cores, connected at one set of 
 ends and at the other to the circumference of an 
 iron ring. Each core contains a primary and 
 secondary wire. 
 
 Transformer, Rotary-Phase A ro- 
 tary current transformer. (See Transfor- 
 mer, Rotary-Current?) 
 
 Transformer, Series Transformers 
 
 which are connected in series with the pri- 
 mary circuit. 
 
 A series transformer is not as readily made self- 
 regulating under variations in the load as a mul- 
 tiple transformer. If, however, its core is not 
 saturated, and the electromotive force of its 
 secondary is small, it can be made fairly self-regu- 
 lating. Series transformers are used in the 
 Jablochkoff system for feeding arc lamps in the 
 shape of Jablochkoff candles. 
 
 Transformer, Shell A transformer 
 
 in which the primary and secondary coils are 
 laid on each other, and the iron core is then 
 wound through and over them so as to en- 
 close all the copper of the primary and 
 secondary circuits within the iron. 
 
 The iron shell surrounding the copper may 
 consist of the thin plates of iron, built up so as to 
 leave a rectangular space for the introduction of 
 the primary and secondary. 
 
 Transformer, Step-Down A trans- 
 former in which a small current of compara- 
 tively great difference of potential is con- 
 t verted into a large current of comparatively 
 small difference of potential. 
 
 An in verted Ruhmkorff induction coil. 
 
 Transformer, Step-Up A trans- 
 former in which a large current of compara- 
 tively small difference of potential is con- 
 verted into a small current of comparatively 
 great difference of potential. 
 
 The term step-up transformer is used in contra- 
 distinction to the step -down transformer. 
 
 The old form of Ruhmkorff coil is an example 
 of a step-up transformer. 
 
 Transformer, Testing A trans- 
 former employed in any system of distribu- 
 tion for the purposes of testing for grounds, 
 condition of line, drop of potential, etc. 
 
 Transformer, Welding A trans- 
 former suitable for changing a small electric 
 current of comparatively high difference of 
 potential, into the heavy currents of low 
 difference of potential required for welding 
 purposes. 
 
 Welding transformers have in general a very 
 low resistance in their secondary coils, and almost 
 invariably consist of a single turn or at the most 
 of a few turns of very stout wire. 
 
 Transforming Currents. (See Current, 
 Transforming a.) 
 
 Transforming Down. Transforming by 
 means of a step-down transformer. (See 
 Transformer, Step-Down?) 
 
 Transforming Station. (See Station, 
 Transforming.) 
 
 Transforming Up. Transforming by 
 means of a step-up transformer. (See 
 Transformer, Step-Up?) 
 
Tra.] 
 
 532 
 
 [Tra. 
 
 Transient Currents. (See Currents, Transmission, Multiple The simul- 
 
 Transient.) 
 
 Transit, Magnetic Variation An 
 
 apparatus for measuring the declination or 
 variation of the magnetic needle at any place. 
 The variation transit generally consists of an 
 altitude and azimuth instrument, the telescope of 
 which is so arranged as to be readily converted 
 into a microscope. 
 
 Transition Resistance. (See Resistance, 
 Transition.) 
 
 Translator, Double-Current A 
 
 telegraphic translater or repeater designed to 
 operate on double current transmission. 
 
 A tele- 
 
 Translater, Single-Current 
 
 graphic translater or repeater designed to 
 operate a single-current transmission. 
 
 Translater, Telegraphic A term 
 
 sometimes applied to a telegraphic repeater. 
 (See Repeaters, Telegraphic?) 
 
 Translating Device. (See Device, Trans- 
 lating?) 
 
 Translating Devices, Multiple-Arc-Con- 
 nected (See Devices, Translating, 
 
 Multiple-Arc-Connected.) 
 
 Translating Devices, Multiple-Con- 
 nected (See Devices, Translating, 
 
 Multiple- Connected.) 
 
 Translating Devices, Multiple-Series- 
 Connected (See Devices, Translat- 
 ing, Multiple-Series-Connected?) 
 
 Translating Devices, Series-Connected 
 
 (See Devices, Translating, Series- 
 Connected.) 
 
 Translating Devices, Series-Multiple- 
 Connected (See Devices, Translat- 
 ing, Series-Multiple-Connected.) 
 
 Translucent- Disc Photometer. (See 
 Photometer, Translucent-Disc.) 
 
 Transmission, Double The simul- 
 taneous sending of two messages over a sin- 
 gle wire in opposite directions. (See Teleg- 
 raphy, Duplex, Bridge Method of.) 
 
 taneous sending of more than two messages 
 over a single line or conductor. 
 
 Transmission of Energy. (See Energy, 
 Electric, Transmission of.) 
 
 Transmitter, Carbon, for Telephones 
 
 A telephone transmitter consisting of 
 
 a button of compressible carbon. 
 
 The sound waves impart to-and-fro movements 
 to the transmitting diaphragm, and this to the 
 carbon button, thus varying its resistance by pres- 
 sure. This button is placed in circuit with the 
 battery and induction coil. (See Telephone.') 
 
 Transmitter, Double-Current The 
 
 transmitting instrument employed in systems 
 of telegraphy, by means of which the direc- 
 tion of the currents on the line is alternately 
 changed, according to whether the key rests 
 on its front or on its back stop. 
 
 Double-current transmitters are used in con- 
 nection with instruments, such as polarized re- 
 lays, which respond to change in the direction of 
 the current, rather than to changes in its in- 
 tensity. 
 
 Transmitter, Electric A name 
 
 applied to various electric apparatus employed 
 in telegraphy or telephony to transmit or send 
 the electric impulses over a line wire or con- 
 ductor. 
 
 The sending instrument as distinguished 
 from the receiving instrument. 
 
 In most telegraphic systems, the transmitting 
 instrument consists of various forms of keys for in- 
 terrupting or varying the current. In the tele- 
 phone the transmitter consists of a diaphragm 
 operated by the voice of the speaker. (See Tele- 
 phone.) 
 
 Transmitter, Water-Jet Telephone - 
 
 A telephone transmitter consisting of a jet 
 of water issuing vertically downwards from a 
 small orifice. 
 
 The jet forms a part of the circuit of the re- 
 ceiving telephone. In order to reduce its resist- 
 ance, the water is rendered acid by the addition 
 of sulphuric acid, and a battery of high electro- 
 motive force is employed. Since the jet has a 
 high resistance, a battery of high resistance can 
 be used without inconvenience. 
 
Tra.] 
 
 533 
 
 [Tre. 
 
 Transposing. In a system of telephonic 
 communication a device for avoiding the bad 
 effects of induction by alternately crossing 
 equal lengths of consecutive sections of the 
 line. (See Connection, Telephonic Cross.) 
 
 Transverse Electromotive Force. (See 
 Force, Electromotive, Transverse.} 
 
 Treatment, Hydro-Carbon, of Carbons 
 
 Exposing carbons, while electrically 
 
 heated to incandescence, to the action of a 
 carbonizing gas, vapor or liquid, for the pur- 
 pose of rendering them more uniformly elec- 
 trically conducting throughout. (See Car- 
 bons, Plashing Process for?) 
 
 Tree, Parallel, Circuit (See Cir- 
 cuit, Parallel- Tree.) 
 
 Trembling Bell. (See Bell, Trembling.) 
 
 Trigonometrical. Of or pertaining to 
 trigonometry. (See Trigonometry.) 
 
 Trigonometrical Function. (See Func- 
 tion, Trigonometrical^) 
 
 Trigonometrically. In a trigonometrical 
 manner. 
 
 Trigonometry. That branch of mathe- 
 matical science which treats of the methods 
 of determining the values of the angles and 
 sides of a triangle. 
 
 There are in every triangle three sides and 
 three angles. If any three of these parts are 
 given, except the three angles, the values of the 
 remaining parts can be determined by means of 
 
 Fig. SS9- Dynamo Brush Trimmer. 
 trigonometry, by what is called the solution of 
 ihe triangle. (See Function, Trigonometrical.) 
 
 Trimmer. An employee of an electric 
 light company who renews the carbons in 
 arc lamps. 
 
 Trimmer, Dynamo Brush A de- 
 vice for insuring rapid and accurate trimming 
 of dynamo brushes. 
 
 The brush trimmer consists of a knife, placed 
 as shown in Fig. 559 on a rigid support. The 
 brushes are placed under a clamp, and against a 
 straight edge, so that a single cut with the knife 
 blade insures a clean and true cut. 
 
 Trimming. A term sometimes applied to 
 the act of placing the carbons in an electric 
 arc lamp. 
 
 The phrase, carboning a lamp, would appear 
 to be preferable to trimming a lamp. 
 
 Triple-Carbon Arc Lamp. (See Lamp, 
 Arc, Triple-Carbon^ 
 
 Tripod Roof Support. (See Support, 
 Tripod Roof) 
 
 Trolley. A rolling contact wheel that 
 moves over the overhead lines provided for a 
 line of electric railway cars, and carries ofl 
 the current required to drive the motor car. 
 
 Trolley Crossing. A device placed at tha 
 crossing of two trolley wires, by which tha 
 trolley wheel running on one wire may cross 
 the other. 
 
 Such a device can also be made to hold the two 
 wires together. 
 
 Trolley Crossing, Insulated A de^ 
 
 vice used at the crossing of two trolley wires, 
 which insulates the wires from each other, 
 but which permits the trolley wheel of one 
 line to cross the other trolley line. 
 
 Trolley Cross-Over. (See Cross-Over, 
 Trolley) 
 
 Trolley, Double The traveling con- 
 ductors, which move over the lines of wire in 
 any system of electric railways that employs 
 two overhead conductors. 
 
 In one form of double trolley a bar of wood 
 carries two hangers, separated from each other, 
 and furnished with diverging feet, with clips that 
 embrace the two conducting wires. These wires 
 serve also as the track for the two-wheeled trolley. 
 The trolley consists of two plates connected to and 
 insulated from each other under the conductors, 
 
Tro.J 
 
 534 
 
 [Tub. 
 
 and carrying flanged wheels, extending in over 
 the conductors. 
 
 Swinging from the axles of the poles are arms, 
 which form a bail-like draft loop, with insulated 
 material between their lower ends, and furnish 
 means for connection with the car motor. In 
 order to remove this trolley from the conducting 
 wires, these arms are pressed together at points 
 between two points of hangers, which allows 
 them to pass between the inner ends of the wheel 
 axles. 
 
 The trolley cannot be removed from the wires 
 except at the end of the track, and it is therefore 
 found in practice to be particularly useful in 
 mines, where, from the nature of the galleries, the 
 trolley wheel is very apt to become detached from 
 the trolley wires. 
 
 Trolley, Drop The trolley wheel 
 
 and rod for an electric car which drops away 
 from the wire on slipping from the wire, and 
 is reset upwards through proper elastic press- 
 ure. 
 
 Trolley Fork. (See Fork, Trolley) 
 Trolley Frog. (See Frog, Trolley) 
 
 Trolley Frog, Standard (See Frog, 
 
 Trolley, Standard) 
 
 Trolley Hanger. (See Hanger, Trolley) 
 ' Trolley Pole. (See Pole, Trolley) 
 Trolley Section. (See Section, Trolley) 
 
 Trolley, Single A traveling con- 
 ductor or wheel which moves over a single 
 conductor in a system of electric railways, 
 and takes off the current for driving the elec- 
 tric motor, in connection with an earth or 
 grounded return conductor. 
 
 Trolley Wheel. (See Wheel, Trolley) 
 Trolley, Wire (See Wire, Trolley) 
 
 True Contact Force. (See Force, True 
 Contact) 
 
 True Resistance. (See Resistance, 
 True) 
 
 Trumpet, Electric An electro- 
 magnetic buzzer, the sound of which is 
 strengthened by means of a resonator in the 
 shape of a trumpet. (See Buzzer, Electric. 
 Resonator, Electric) 
 
 The electric trumpet is used to replace electric 
 bells. It gives a louder and more penetrating 
 sound than the electric bell. 
 
 Trunking Switch Board. (See Board, 
 Switch, Trunking) 
 
 Tube, Crookes' A tube containing 
 
 a high vacuum and adapted for showing any 
 of the phenomena of the ultra-gaseous state 
 of matter. (See Matter, Radiant, or Ultra- 
 Gaseous) 
 
 Tube, Insulating A tube of insu- 
 lating material provided for covering a splice 
 in an insulated conductor. 
 
 Tube, Mercury Vacuous glass tubes 
 
 in which a flash of light is produced by the 
 fall of a small quantity of mercury placed in- 
 side it. 
 
 The light is caused by the electricity produced 
 by the friction of the mercury in falling against 
 the sides of a spiral glass tube placed inside the 
 vacuous tube. 
 
 Tube, Pliicker : A modification of a 
 
 Geissler tube adapted for the study of the 
 stratification of the light, and the peculiar- 
 ities of the space adjoining the negative elec- 
 trode. (See Tubes, Geissler) 
 
 Tube, Spark 
 
 A high vacuum tube, 
 
 across which, when the vacuum is sufficiently 
 high, the spark from an induction coil will not 
 pass. 
 
 A spark tube, connected with incandescent 
 lamps while undergoing exhaustion, acts as a 
 simple gauge to determine the degree of ex- 
 haustion. When an induction coil discharge 
 ceases either to pass, or to pass freely, the vacuum 
 is considered as sufficient, according to circum- 
 stances. 
 
 Tube, Stratification An exhausted 
 
 glass tube, the residual atmosphere of which 
 displays alternate dark and light stria', or 
 stratifications, on the passage through it of 
 an induction coil discharge. (See Discharge, 
 Luminous Effects of) 
 
 Tubes, Geissler Vacuum tubes of 
 
 glass containing various gases, liquids or 
 solids, provided with platinum electrodes, 
 passed through and fused into the glass, de- 
 signed to show the various luminous effects 
 
Tub.] 
 
 535 
 
 [Twi. 
 
 of electric discharges through gases at com- 
 paratively low pressures. 
 
 Geissler tubes are made of a great variety of 
 shapes, and often include tubes, spirals, spheres, 
 etc., within other tubes. These enclosed tubes 
 are made either of ordinary glass, or of uranium 
 glass in order to obtain the effects of fluorescence. 
 
 The vacuum in Geissler tubes is by no means 
 what might be called a high vacuum. Indeed, if 
 the exhaustion of the tube be pushed too far, 
 much of the brilliancy of the luminous effects is 
 lost. 
 
 Some of the many forms of Geissler tubes are 
 shown in Fig. 560. 
 
 Fig. 360. Geisder Tubes. 
 
 Tubes of Force. (See Force, Tubes of.) 
 
 Tubes of Induction. (See Induction, 
 Tubes of.) 
 
 Tubes, Yacuum Glass tubes, from 
 
 which the air has been partially exhausted and 
 through which electric discharges are passed 
 fcr the production of luminous effects. (See 
 Tubes, Geissler) 
 
 Tubular Braid. (See Braid, Tubular.} 
 Tumbling Box. (See Box, Tumbling) 
 Tuning-Fork or Reed Interrupter. (See 
 Interrupter, Tuning-Fork. Interrupter, 
 Reed) 
 
 Turn, Ampere A single turn or 
 
 winding in a coil of \vire through which one 
 l/npere passes. 
 
 ..Vn ampere-turn is soinetiiues called an ampere- 
 winding. Magneto-motive force in a magnetic 
 circuit is proportioned to the number of ampere- 
 tarns linked with it. The practical unit of mag- 
 neto-motive foice is _L_ x ampere turn = .0796 
 
 4 "t 
 ampere turn. Therefore the magneto-motive 
 
 force, m. m. f., is found by multiplying the am- 
 pere turns by 4 it or 12.57. 
 
 The number of amperes multiplied by the 
 number of windings or turns of wire in a coil give 
 the total number of ampere-turns in the coil. 
 
 In a coil of fixed dimensions the magnetizing 
 force developed by a given number of ampere-turns 
 remains the same as long as the product of the 
 amperes and the current remains the same. That 
 is to say, the same amount of magnetizing force 
 can be obtained by the use of many windings and 
 a small current, as in shunt dynamos, or by a few 
 turns and a proportionally large current, as in 
 series dynamos. (See Machine, Dynamo-Elec- 
 tric.} 
 
 Turns, Ampere, Primary The 
 
 ampere-turns of the primary of an induction 
 coil. 
 
 Turns, AmpSre, Secondary The 
 
 ampere-turns of the secondary of an induc- 
 tion coi j . 
 
 Turns, Dead 
 
 The number of revo- 
 
 lutions a self-exciting dynamo makes before 
 it excites itself. 
 
 Turns, Dead, of Armature Wire 
 
 Those turns of the wire on the armature of a 
 dynamo-electric machine which produce no 
 useful electromotive force or resultant current, 
 on the movement of the armature through the 
 magnetic field of the machine. 
 
 The wire on the inside of a Gramme or ring 
 armature is dead wire, but not dead turns. 
 
 Turns, Series, of Dynamo-Electric Ma- 
 chines The ampere-turns in the 
 
 series circuit of a compound-wound dynamo- 
 electric machine. (See Machine, Dynamo- 
 Electric, Compound- Wound.) 
 
 Turns, Shunt, of Dynamo-Electric Ma- 
 chine The ampere-turns in the shunt 
 
 circuit of a compound-wound dynamo-elec- 
 tric machine. (See Machine, Dynamo-Elec- 
 tric, Compound- Wound.) 
 
 Tnrn-Table, Electric A table, suit- 
 able for show windows, revolved around a 
 vertical axis by means of an electric motor. 
 
 Twig. A sub-branch. (See Branch, 
 Sub.) 
 
 Twin Wire. (See Wire, Twin.) 
 
Twi. 
 
 536 
 
 [Unl* 
 
 Twist in Leads. (See Leads, Armature, 
 Twist in.) 
 
 Twisted Bunched Cable. (See Cable, 
 Bunched, Twisted.) 
 
 Twisted-Pair Cable. (See Cable, Twisted- 
 Pair.) 
 
 Twisting Force. (See Force, Twisting.) 
 
 Two-Fluid Voltaic Cell. (See Cell, Vol- 
 taic, Two-Fluid.) 
 
 Two-Point Switch. (See Switch, Two- 
 Point) 
 
 Two, Three, Four, etc., Conductor Cable 
 
 (See Cable, Two, Three, Four, etc., 
 
 Conductor.) 
 
 Two-Way Splice Box. (See Box, Splice, 
 Two- Way!) 
 
 Two-Way Switch. (See Switch, TW+. 
 Way.) 
 
 Type-Printing Telegraph. (See Teleg- 
 raphy ', Printing!) 
 
 Typewriter, Electric A typewrit- 
 ing machine, in which the keys are intended 
 to make the contacts only of circuits of 
 electro-magnets, by the attraction of the arzna* 
 tures of which the movements of the type 
 levers required for the work of printing ar* 
 effected. 
 
 Electric typewriters secure a uniformity of im- 
 pression that is impossible to obtain with hand 
 worked machines. They also greatly lessen the 
 mechanical labor of writing . (See Dynamograph . ) 
 
 U. A contraction sometimes used for unit. 
 
 Ultra-Gaseous Matter. (See Matter, 
 Radiant, or Ultra-Gaseous!) 
 
 Underground Cable. (See Cable, Under- 
 ground!) 
 
 Underground Conductor. (See Con- 
 ductor, Underground!) 
 
 Undulating Currents. (See Currmf, 
 Undulating!) 
 
 Undulatory Currents. (See Currents, 
 Undulatory.) 
 
 Undulatory Discharge. (See Discharge, 
 Undulatory.) 
 
 Ungilding Bath. (See Bath, Ungild- 
 
 Unidirectional Discharge. (See Dis- 
 charge, Unidirectional.) 
 
 Unidirectional Leak. (See Leak, Uni- 
 directional!) 
 
 Uniform Density of Field. (See Field, 
 Uniform Density of.) 
 
 Uniform Magnetic Field. (See Field, 
 Magnetic, Uniform!) 
 
 Uniform Magnetic Filament. (See Fila- 
 ment, Uniform Magnetic!) 
 
 Uniform Potential. (See Potential. 
 Uniform.) 
 
 Uniformly Distributed Current (See 
 Current, Uniformly Distributed.) 
 
 Unipolar Armature. (See Armature, 
 Unipolar!) 
 
 Unipolar-Electric Bath. (See Bath, Un-:* 
 polar-Electric!) 
 
 Unipolar Induction. .'See TrtJvct&n, 
 Unipolar!) 
 
 Unit Angle. (See Angle, Unit. Velocity, 
 Angular.) 
 
 Unit Angular Velocity. (See Velocity^ 
 Angular.) 
 
 Unit, B. A. A term formerly ap- 
 plied to the British Association unit of re- 
 sistance, or ohm. (See Ofi*n.) 
 
 Unit-Difference of Potential or Electro- 
 motive Force (See Potential, Unit. 
 
 Difference of.) 
 
 Unit, Magnetic, A A term some- 
 times used for a line of magnetic force, or 
 the amount of magnetism irduccd in an area 
 of one square centimetre at the centre of a 
 coil having a diame t er of 10 centimetres and 
 carrying a current of 7.9578 amperes. 
 
 Unit, Natural, of Electricity (See 
 
 Electricity, Natural Unit of.) 
 
 2 Vol. 2 
 
Uni.] 
 
 537 
 
 [Uni. 
 
 Unit of Acceleration. (See Acceleration, 
 Unit of.} 
 
 Unit of Activity. (See Activity, Unit of.) 
 
 Unit of Current, Absolute (See 
 
 Current, Absolute Unit of.) 
 
 Unit of Current, Jacobi's (See 
 
 Current, Jacobi's Unit of.) 
 
 These units are more frequently called the 
 centimetre-gramme-second units. 
 
 Units, Centimetre-Gramme-Second 
 
 A system of units in which the centimetre 
 is adopted for the unit of length, the gramme 
 for the unit of mass, and the second for unit 
 of time. 
 
 This is the same as the absolute system of 
 units. 
 
 Units, C. G. S. The centimetre- 
 
 gramme-second units. (See Units, Funda- 
 mental.) 
 
 Units, Circular Units based upon 
 
 the value of the area of a circle whose diame- 
 ter is unity. 
 
 The advantages possessed by the circular units 
 of cross- section arise from the fact that in these 
 units the areas are equal to the squares of the 
 diameter. No necessity exists, therefore, for mul- 
 tiplying by .7854. 
 
 Unit of Electrical Supply. (See Supply, 
 Unit of, Electrical.) 
 
 Unit of Electromotive Force, Absolute 
 
 (See Force, Electromotive, Absolute 
 
 Unit of.) 
 
 Unit of Electrostatic Capacity. (See 
 Capacity, Electrostatic, Unit of.) 
 
 Unit of Heat (See Heat Unit.) 
 
 Unit of Inductance. (See Inductance, 
 Unit of.) 
 
 UnitofMass. (See J/<m, Unit of .) 
 
 Unit of Photometric Intensity. (See 
 
 Intensity, Photometric, Unit of.) 
 
 Units, Circular (Cross-Sections), Table 
 Unit of Power. (See Power, Unit of.) of 
 
 Unit of Pressure, New TheBarad: i circular mil = .78540 square mil. 
 
 (SeeBarad.) " " = .00064514 circular 
 
 Unit of Resistance.-(See Resistance, millimetre. 
 
 Unit of.) = 000 5o66 9 square 
 
 millimetre. 
 
 Unit of Resistance, Absolute (See i square mil = 1.2732 circular mils. 
 
 Resistance, Absolute Unit of.) " = .00082141 circular 
 
 Unit of Resistance, Jacobi's (See millimetre. 
 
 Resistance, Unit of, facobi's.) ' circular millimetre = 1550. i circular mils. 
 
 TT . , " " = 1217.4 square mils. 
 
 Unit of Resistance, Matthiessen's = ' s ^ uare mim 
 
 (See Resistance, Unit of, Afatthiessen's.) metre. 
 
 Unit of Resistance. Varley's (See I square millimetre =1973. 6 circular mils. 
 
 Resistance, Unit of , Var ley's.) " " =1.2732 circular mU- 
 
 *T . * IT -i j. -HT limetres. 
 
 Unit cf Velocity, New (See Ve- -,,. , . ,. ,. r i 
 
 , ._ If d, is the diameter of a circle, the area in. 
 
 loctty, New Unit of.) ., ., . 
 
 J ' other units is: 
 
 Unit Quantity of fllfcctricity. (See Elec- If d, is in mils, the area in 
 
 tricity. Unit Quantity of.) square millimetres. ...=dX .00050669. 
 
 Unit-Strength of Current (See Cur- d ' in millimetres area in 
 
 rmt, Unit Strength of.) S 5 uare mUs = d * x I2I 7-4- 
 
 T . d, in centimetres, area in 
 
 Units, Absolute A system of units square inches = d , x I2I74< 
 
 bas^d on the centimetre for the unit of length, a, in inches, area in square 
 
 th^ gramme for the unit of mass, and the centimetres =d a x 5.0669. 
 
 second for the unit of time. (ffering.), 
 
Uni.] 
 
 538 
 
 [Uni. 
 
 Units, Derived --- Various units ob- 
 tained or derived from the fundamental units 
 of Length, L., Mass, M., and Time, T. 
 
 The derived units and their dimensions are as 
 follows: 
 
 Area, L 2 . The square centimetre. 
 
 Volume, L 3 . The cubic centimetre. 
 
 Velocity, V. Unit distance traversed in unit 
 time, or 
 
 v = t. (i) 
 
 Acceleration, A. The rate of change which 
 will produce a change of velocity of one centi- 
 metre per second. 
 
 A = ^. (2) 
 
 Substituting in equation (2) the value of V, in 
 equation (i), we have 
 L 
 
 A T_L 
 ~~ 
 
 Force, F. The dyne, or the force required to 
 act on unit mass in order to impart to it unit 
 velocity. 
 
 F=MXA. (4) 
 
 Substituting the value of A, derived from equa- 
 tion (2), we have 
 
 Substituting the value of V, derived from equa- 
 tion (i), we have 
 
 M L _ ML 
 
 r rp X Tj. - -p2 (5) 
 
 Work or Energy, \V. The erg, or the work 
 done in overcoming unit force through unit dis- 
 tance. 
 
 Prwer, P. The unit rate of doing work. 
 
 p _W_ 
 
 - T ~ 
 
 Units, Dimensions of 
 
 ML* 
 : ~T^~ 
 
 (6) 
 
 The values 
 
 given to the units of length, L ; mass, M, and 
 time, T. (See Units, Derived^ 
 
 Units, Electro-Magnetic A system 
 of units derived from the C. G. S. units, em- 
 
 ployed in electro-magnetic measurements. 
 (See Units, Centimetre-Gramme-Second. \ 
 
 Units based on the attractions or repul- 
 sions between two unit magnetic poles at 
 unit distance apart. (See Units, Electro- 
 static. ) 
 
 Units, Electro-Magnetic, Dimensions of 
 
 Current Strength = Intensity of FieldxLength = 
 v/ML 
 T" 
 
 Quantity = Current X Time= ,/M X L . 
 Potential, Difference of Potential, Electromo- 
 
 tive Force =; 
 
 W rk . 
 Quantity 
 
 Resistance = 
 
 Electromotive Force L 
 Current ~ T 
 
 Capacity = Quantity _ T^ 
 Potential"" L 
 
 Units, Electrostatic Units based 
 
 on the attractions or repulsions of two unit 
 charges of electricity at unit distance apart. 
 
 'Two systems of electric units are derived from 
 the C. G. S. system, viz., the electrostatic and 
 electro -magnetic. These units are based re=pec- 
 tively on the force exerted between two quanti- 
 ties of electricity and between two magnet poles. 
 The electrostatic units embrace the units of 
 quantity, potential and rapacity. No particular 
 names have as yet been adopted for these units. 
 
 Unit of Quantity. That quantity of electricity 
 which will repel an equal quantity of the san.e 
 kind of electricity placed at a distance of or.e i % cr.- 
 timetre from it with the force of one dyne. 
 
 Electrostatic potential, or power of doing elec- 
 trostatic work, is measured in units of WO-K, or 
 
 difference of Poi'ntinl. Such a differ- 
 ence of potential between two points as requires 
 the expenditure cf one^rfof work to bring up 
 a unit of positive electricity from one point to the 
 other against the ele< . ; c force. 
 
 Unit of Cavd-My. Such a capacity of conduc- 
 tor as will take a charge of one unit of electricity 
 when the potential is unity. 
 
 The ratio between the inducfive cap^vityofa 
 substance and that of air, measured under pre 
 
Uiii.] 
 
 539 
 
 [Uni. 
 
 cisely similar conditions, is called the specific in- 
 ductive capacity. 
 
 The specific inductive capacity is obtained by 
 comparing the capacity of a condenser filled with 
 the particular substance and the capacity of the 
 same condenser when filled with air. The spe- 
 cific inductive capacity of air is taken as unity. 
 
 Units, Electrostatic, Dimensions of 
 
 Quantity = v/Force X (Distance) = \/F X L = 
 
 Current = 
 
 Time 
 
 Potential 
 
 Work 
 
 Resistance = 
 
 Quantity T 
 
 Potential 
 Current 
 
 
 Capacity = Qtity L 
 Potential ~ *" 
 
 Specific Inductive Capacity = 
 
 One Quantity 
 
 Another Quantity = A Sim ple Ratio or Number. 
 
 Electromotive Intensity = 
 
 Force 
 Quantity 
 
 The fractional and negative exponents used 
 above are merely convenient methods of express- 
 ing the extraction of roots and division respec- 
 tively by the quantity represented by these expo- 
 nents. 
 
 Units, Fundamental The units of 
 
 length, time and mass, to which all other 
 quantities can be referred. 
 
 The unit of length is now generally taken as 
 the centimetre, the unit of time as the second, and 
 the unit of mass as the gramme. These form a 
 system of measurement known as the centimetre- 
 gramme-second system, or the C. G. S. system, or 
 absolute system. (See Units, Derived.) 
 
 The dimensions of the fundamental units are 
 designated thus: 
 
 Length = L. 
 Mass = M. 
 Time T. 
 
 Units, Heat Units based on the 
 
 quantity of heat required to raise a given 
 weight or quantity of a substance, generally 
 water, one degree. 
 
 The principal heat units are the English heat 
 unit, the greater and smaller calorie and the 
 joule. (See Calorie. Joule.') 
 
 The following table gives the values of some of the prin- 
 cipal heat units : 
 
 i gram, centigrade, .001 kilogram centigrade, 
 
 i pound Fahrenheit, 1,047.03 joules. 
 
 772. foot-pounds. 
 
 106.731 kilogram metres. 
 .55556 pound centigrade. 
 .25200 kilogram centigrade. 
 .29084 watt- hours. 
 .0003953 metric horse-power. 
 .0003899 horse-power hours, 
 i pound centigrade, 1,884.66 joules. 
 
 1,389.6 foot-pounds. 
 
 192.116 kilogram metres. 
 1.800 pound Fahrenheit. 
 .4536 kilogram centigrade. 
 .52352 watt -hour. 
 .0007115 metric horse-powet 
 
 hour. 
 
 .0007018 horse power hour, 
 i kilogram centigrade, 4, 1 54.95 j oules. 
 
 3,063.5 foot-pounds. 
 
 423.54 kilogram metres. 
 
 3.9683 pound Fahrenheit. 
 2.2046 pound centigrade. 
 1.1542 watt-hour. 
 .001569 metric horse-powef 
 
 hour. 
 
 .0015472 horse-power hour. 
 Her ing. 
 
 Units, Magnetic Units based on 
 
 the force exerted between two magnet poles. 
 
 Unit strength of a magnetic pole is such a 
 magnetic strength of pole that repels another 
 magnetic pole of equal strength placed at 
 unit distance with unit force, or with the 
 force of one dyne. 
 
 Magnetic Potential. Is the power of doing 
 work possessed by a magnetic pole. 
 
 Magnetic potential is measured like electro- 
 static potential in units of work or in ergs. 
 
 Magnetic Potential, Unit Difference of. Such 
 a difference of magnetic potential between two 
 points that requires the expenditure of one erg of 
 work to bring a magnetic pole of unit strength 
 from one to the other. 
 
 Unit Intensity of Magnetic Field. Such an 
 intensity of magnetic field as acts on a north or 
 south seeking pole of unit strength with the force 
 of one dyne. 
 
Uni,] 
 
 540 
 
 Units, Magnetic, Dimensions of 
 
 Strength of Pole, or i 
 Quantity of Magnetism j 
 
 = V Force X (Distance) 8 = v/ML 
 
 Magnetic Potential 
 
 Work 
 
 Strength of Pole T 
 
 Force __ ^~M~. 
 
 Intensity of Field = Strengt h of Pole T X v/ L 
 
 Units, Practical - Multiples or frac- 
 tions of the absolute or centimetre-gramme- 
 second units. 
 
 The practical units have been introduced be- 
 cause the absolute units are either too small or 
 too large for actual use. 
 
 Electromotive Force. The Volt = 100,000, - 
 ooo C. G. S. or absolute units, thaj: is, io 8 abso- 
 lute units of resistance. (See Volt.) 
 
 Resistance. The Ohm = 1,000,000,000 abso- 
 lute units of electromotive force, or io 9 absolute 
 units. (See Ohm.) 
 
 Current. The Ampere = fa absolute unit of 
 current. (See Ampere.) 
 
 Quantity. The Coulomb = fa absolute unit of 
 quantity, of the electro-magnetic system. (See 
 Coulomb.) 
 
 Capacity. The Farad = - abso- 
 
 * * I,OOO,OOO,OOO 
 
 lute unit of capacity, or io 9 units of capacity. 
 (See Farad. Henry. Watt. Joule.) 
 
 Units, Proposed New The follow- 
 ing units and terms have recently been pro- 
 posed by Oliver Heaviside. 
 
 Some of these have been generally adopted. 
 
 Conductance. Capacity for conducting elec- 
 tricity. 
 
 Numerically, the ratio, in absolute measure, ot 
 the current strength to the total electromotive 
 force in a circuit of uniform flow. A quantity 
 with the nature of a slowness or reciprocal to a 
 Telocity. The practical unit is called the mho. 
 
 Conductivity. Conductance per unit volume. 
 
 Elastance. Capacity of a dielectric for oppos- 
 ing electric charge or displacement. 
 
 "Numerically, the ratio, in absolute measure, 
 of the difference of potential in an electrostatic cir- 
 cuit to the total charge or displacement therein 
 produced. The reciprocal of permittance and a 
 quantity of the inverse nature of a length." 
 
 " Elastivity. Elastance per unit volume of di- 
 electric." 
 
 Impedance. Capacity for opposing the variable 
 flow of electricity. 
 
 "Numerically, in the absolute measure, the 
 ratio of the total electromotive force to the cur- 
 rent strength at any instant in a circuit of a vari- 
 able flow. A quantity with the nature of a 
 velocity and in any circuit always greater than 
 the resistance." 
 
 "Inductance. Capacity for magnetic induc- 
 tion." 
 
 "Numerically, in absolute measure, the num- 
 ber of unit lines of magnetic force linked with a 
 circuit traversed by the unit current strength. 
 Sometimes alluded to as the co-efficient of self in- 
 duction. A quantity of the nature of a length.'* 
 
 " Inductivity '. Specific capacity for magnetic 
 induction. 
 
 "The numerical ratio of the induction in a 
 medium to the induction producing it." 
 
 Permittance. Electrostatic capacity. Capa- 
 city of a dielectric for assisting charge or displace- 
 ment. 
 
 "Numerically, the ratio, in absolute measure, 
 of the total charge or displacement in the electro- 
 static circuit, to the difference of potential pro- 
 ducing it. A quantity with the nature of a 
 length." 
 
 " Permittivity. The numerical ratio of the 
 permittance of a dielectric to that of air. 
 
 " Also known as specific inductive capacity." 
 
 "Reluctance. Capacity for opposing mag- 
 netic induction. 
 
 "Numerically, the ratio, in absolute measure, 
 of the magneto-motive force in a magnetic cir- 
 cuit to the total induction therein produced. A 
 quantity with the nature of the reciprocal of a 
 length. Sometimes described as magnetic resist- 
 ance." 
 
 Reluctancy or Reluctivity. Reluctance per unit 
 volume. 
 
 "Sometimes described as specific magnetic re- 
 sistance. A numeric, the reciprocal of induc- 
 tivity." 
 
 " Resistance. Capacity for opposing the 
 steady flow of electricity. 
 
 "Numerically, in absolute measure, the -itio 
 of the total electromotive force to the current 
 strength in a circuit of uniform flow. A quantity 
 with the nature of a velocity. The practical unit 
 is called the ohm." 
 
 " Resistivity. Resistance per unit volume; 
 sometimes alluded to as specific resistance. ' ' 
 
 Universal Discharger. (See Discharger. 
 Universal.} 
 
 Upright Galvanometer. -(See Galva- 
 
Tac.] 
 
 541 
 
 [Var. 
 
 V. A contraction sometimes used for volt. 
 
 V. A contraction sometimes used for ve- 
 locity. 
 
 V. A contraction sometimes used for vol- 
 ume. 
 
 V. A. A contraction sometimes used for 
 voltaic alternative. (See Alternatives, Vol- 
 taic.} 
 
 Vacuum, Absolute A space from 
 
 which all traces of residual gas have been 
 removed. 
 
 A term sometimes loosely applied to a par- 
 tial vacuum. 
 
 It is doubtful whether an absolute vacuum is 
 attainable by any physical means. 
 
 Vacuum, High A space from which 
 
 nearly all traces of air or residual gas have 
 been removed. 
 
 Such a vacuum that the length of the 
 mean free path of the molecules of the residual 
 atmosphere is equal to or exceeds the di- 
 mensions of the containing vessel. (See 
 Layer, Cr cokes'.} 
 
 Vacuum, Low Such a vacuum that 
 
 the mean free path of the molecules of the 
 residual gas is small as compared with the 
 dimensions of the containing vessel. (See 
 Tubes, Geissler.} 
 
 In a high vacuum groups of molecules can 
 move across the containing vessel without meet- 
 ing other groups of molecules. In a low vacuum 
 such a group of molecules would be broken up by 
 collision against other groups before reaching 
 the other side of the vessel. 
 
 Vacuum, Partial A name some- 
 times applied to a low vacuum. (See Vac- 
 uum, Low.} 
 
 Vacuum, Torricellian The vacuum 
 
 which exists above the surface of the mercury 
 in a barometer tube or other vessel over thirty 
 inches in vertical height. 
 
 The Torricellian vacuum is high only when the 
 mercury has been carefully boiled and the tube 
 or other vessel vigorously heated, so as to thor- 
 
 oughly drive out the moisture and adherent film 
 of air. 
 
 Vacuum Tubes. (See Tubes, Vacuum} 
 Valency. The worth or value of a chem- 
 ical atom as regards its power of displacing 
 other atoms in chemical compounds. (See 
 Atomicity} 
 
 The worth or valency of an atom of oxygen is 
 twice as great as that of hydrogen, since one 
 atom of oxygen is able to replace two hydrogen 
 atoms in chemical combinations. 
 
 Valve, Electric 
 
 An electrically 
 
 controlled or operated valve. 
 
 In systems of electro-pneumatic signals, gaseous 
 or liquid pressure controlled by electrically oper- 
 ated valves is employed to move signals, ring 
 bells, control water and air valves, or to perform 
 other similar work. 
 
 Vapor Globe of Incandescent Lamp. 
 
 (See Globe, Vapor, of Incandescent Lamp} 
 
 Variable Inductance. (See Inductance, 
 Variable} 
 
 Variable Period of Electric Current 
 
 (See Current, Variable Period of} 
 
 Variable Resistance. (See Resistance, 
 Variable} 
 
 Variable Resistance, Automatic 
 
 (See Resistance, Variable, Automatic} 
 
 Variable Resistance, Non- Automatic 
 
 (See Resistance, Variable, Non-Auto- 
 matic} 
 
 Variable State of Charge of Telegraph 
 Line. (See State, Variable, of Charge of 
 Telegraph Line} 
 
 Variation, Angle of The angle 
 
 which measures the deviation of the magnetic 
 needle to the east or west of the true geo- 
 graphic north. 
 
 The angle of declination of the magnetic 
 needle. (See Declination, Angle of} 
 
 Variation, Annual An approxi- 
 mately regular variation in the magnetic 
 
Var.] 
 
 542 
 
 [Vel. 
 
 needle which occurs at different seasons of 
 the year. 
 
 Variation Chart or Map. (See Map or 
 Chart, Isogonic.) 
 
 Variation, Cyclical Magnetic Secu- 
 lar magnetic variations occurring during 
 great cycles of time. (See Variation, 
 Secular. Variation, Magnetic.) 
 
 Variation, Diurnal 
 
 An approxi- 
 
 mately regular variation of the magnetic 
 needle, which occurs at different hours of the 
 day. (See Declination.) 
 
 Variation, Irregular A variation 
 
 of the magnetic needle which occurs at ir- 
 regular intervals. (See Declination.} 
 
 Variation, Magnetic Variations in 
 
 the value of the magnetic declination, or 
 inclination, that occur simultaneously over 
 all parts of the earth. 
 
 The term is also applied to the magnetic decli- 
 nation itself. 
 
 These variations are: 
 
 (I.) Secular, or those occurring at great cycles 
 of time. 
 
 (2.) Annual, or those occurring at different 
 seasons of the year. 
 
 (3.) Diurnal, or those occurring at different 
 hours of the day. 
 
 (4.) Irregular, or those accompanying mag- 
 netic storms. The first three are periodical ; the 
 last is irregular. (See Declination, Angle of. 
 Chart, Inclination.) 
 
 Variation, Secular A variation in 
 
 the magnetic declination which occurs at 
 great cycles or intervals of time. (See Dec- 
 lination.) 
 
 Varieties of Circuits. (See Circuits, 
 Varieties of) 
 
 Variometer, Magnetic An instru- 
 ment for comparing the horizontal compo- 
 nent of the earth's magnetism in different 
 localities. 
 
 Varnish, Electric A varnish formed 
 
 of any good insulating material. 
 Shellac dissolved in alcohol, applied to a 
 
 thoroughly dried surface and afterwards hard- 
 ened by baking, forms an excellent varnish. 
 
 Varnish, Stopping-OfF A varnish 
 
 used in electro-plating to cover portions 
 which are not to receive the metallic coaN 
 ing. 
 
 A good stopping-off varnish is made by mixing 
 together 10 parts of resin, 6 parts of beeswax, 
 4 parts of sealing-wax and 3 parts of rouge, dis. 
 solved in turpentine. (See Stopping- Off.) 
 
 Vat, Depositing The vat in which 
 
 the process of electro-plating is carried on. 
 (See Plating. Electro.) 
 
 The depositing vat contains the plating liquid, 
 the metallic anode and the object to be plated. 
 
 Vegetation, Effects of Electricity on 
 
 Most vegetable fibres contract when 
 
 an electric current is passed through them 
 while on the living plant. 
 
 Some experiments appear to show that electric 
 charges and currents hasten the germination and 
 growth of certain plants. Other experiments 
 seem to show that under certain circumstances 
 electric currents retard plant growth. The di- 
 rection of the currents is probably of main im- 
 portance. 
 
 Velocimeter. Any apparatus for measur- 
 ing the speed of a machine. 
 
 Velocity, Angular The velocity of 
 
 a body moving in a circular path, measured, 
 not as usual, by the length of its path divided 
 by the time, but with reference to the angle 
 it subtends and to the length of the radius. 
 
 Unit angle is that angle subtended by a part 
 of the circumference equal to the length of the 
 radius, or 57 degrees 17 minutes 44 seconds .8 
 nearly. (Daniell.) 
 
 Unit angular velocity is the velocity under 
 which a particle moving in a circular path, whose 
 radius equals unity, would traverse unit angle in 
 unit time. 
 
 Velocity, New Unit of The kine. 
 
 (See Kine) 
 
 Velocity of Discharge. (See Discharge, 
 Velocity of) 
 
 Velocity Ratio. (See Ratio, Velocity) 
 
Ven.J 
 
 543 
 
 [Vib. 
 
 Ventilation of Armature. (See Arma- 
 ture, Ventilation of.} 
 
 Vernier. A device for the more accurate 
 measurement of small differences of length 
 than can be detected by the eye alone, by 
 means of the direct reading of the position 
 of a mark on a sliding scale. 
 
 The sliding scale is called the vernier. There 
 are a variety of vernier scales in use. 
 
 Vertical Component of Earth's Magnet- 
 ism. (See Component, Vertical, of Earth's 
 Magnetism.) 
 
 Vertical Electrostatic Voltmeter. (See 
 Voltmeter, Vertical, Electrostatic.} 
 
 Verticity, Poles of, Magnetic The 
 
 earth's magnetic poles, as determined by 
 means of the dipping needle. 
 
 The point of the north where the angle of dip 
 is 90 degrees. (See Map or Chart, Inclination. ) 
 
 Vibrating. Moving to-and-fro. 
 Vibrating Bell. (See Bell, Vibrating} 
 
 Vibrating Contact. (See Contact, Vibrat- 
 ing.) 
 
 Vibration. A to-and-fro motion of the 
 particles of an elastic medium. (See Wave} 
 
 Vibration or Wave, Amplitude of 
 
 The ratio that exists in a wave between 
 the degree of condensation and rarefaction 
 of the medium in which the wave is propa- 
 gated. 
 
 The amplitude of a wave is dependent on the 
 amount of energy charged on the medium in 
 which the vibration or wave is produced. 
 
 A vibration or wave is a to-and-fro motion pro- 
 duced in an elastic material or medium by the 
 action of energy thereon. S-jund, light and heat 
 are subjectively effects produced by the action of 
 vibrations or waves, which in the case of sound 
 are set up in the air, and, in that of light and 
 heat, in a highly tenuous medium called the lumi- 
 niferous ether. Objectively they are the waves 
 themselves. 
 
 As the amplitude of a sound wave increases, the 
 loudness or intensity of the sound increases. As 
 the amplitude of the ether wave increases, the 
 brilliancy of the light or the intensity of the light 
 or heat increases. 
 
 Let A C, Fig. 561 represent an elastic cord or 
 string tightly stretched between A and C. If 
 the string be plucked by the finger, it will move 
 to-and fro, as shown by the dotted lines. Each 
 to-and-fro motion is called a vibration. The 
 
 Fig. 56 z. Amplitude of Wave. 
 vertical distance B D, or B E, represents the 
 amplitude of the vibration, and the sound pro- 
 duced is louder, the greater the amount of energy 
 with which the string has been plucked, or, in 
 other words, the greater the value of B D, or 
 BE. 
 
 Vibrations assume various forms in solid or 
 fluid media, but in all cases the amplitude' will 
 increase with the increase in the energy that 
 causes the vibration. 
 
 Vibration Period. (See Period, Vibra- 
 tion} 
 
 Vibration, Period of The time 
 
 occupied in executing one complete vibration 
 or motion to-and-fro. 
 
 Vibration, Phase of The position 
 
 of the particles in motion in a wave or vibra- 
 tion at any instant of time during the wave 
 period, as compared with a zero line, or a line 
 passing through their mean or middle position. 
 
 Vibrations, Isochronous 
 
 Vibra- 
 
 tions which perform their to-and-fro motions 
 on either side of the position of rest in equal 
 times. 
 
 The vibrations of a pendulum are practically 
 isochronous, no matter what the amplitude of the 
 swing may be, that is, whether the pendulum 
 swings through a large arc or a small arc, pro- 
 vided this arc be not very great. 
 
 All vibrations that produce musical sounds may 
 be regarded as isochronous; that is, in any case, 
 the time required to complete a to-and-fro motion 
 is the same at the beginning when the sound is 
 loud, as at the end, when it is faint. 
 
 Vibrations, Sympathetic Vibra- 
 tions set up in bodies by waves of exactly the 
 same wave rate as those produced by the 
 vibrating body. 
 
 The pitch or tone of the note produced by the 
 body set into sympathetic vibration, is exactly the 
 
Tib.] 
 
 544 
 
 [Vol. 
 
 same as the pitch or tone of the exciting waves or 
 vibrations. 
 
 Hertz's experiments show that sympathetic vi- 
 brations are excited by electro-magnetic waves. 
 (See Electricity ', Hertz's Theory of Electro-Mag- 
 netic Radiations or Waves.') 
 
 Vibrations, Sympathetic, Electrical 
 
 Vibrations set up in circuits, by the effect 
 of pulses in neighboring circuits, that are of 
 exactly the same mean length. 
 
 Vibrations, Synchronous Vibra- 
 tions that are performed not only in the same 
 time as one another, but which pass through 
 the same portions of their to-and-fro move- 
 ment at the same time. 
 
 Vibrator, Electro-Magnetic A 
 
 lever, or arm, automatically moved to-and- 
 fro by the alternate attractions of an electro- 
 magnet and an opposing spring, or by the 
 successive action of two electro-magnets. 
 
 In either case the movement of the lever is 
 utilized to permit the action of first one and then 
 the other device. Automatic or trembling bells 
 are operated by means of an electro-magnetic 
 vibrator. 
 
 Villari Critical Point. A term proposed 
 by Sir William Thomson for that strength of 
 magnetic field at which the reversal of the 
 effects of tension occurs. 
 
 Both magnetic susceptibility and permeability 
 are affected by mechanical stress, vibration and 
 changes of temperature. In a weak magnetic 
 field the susceptibility of iron wire is increased by 
 longitudinal tension, while in a strong field it 
 may be decreased. The particular strength of 
 field at which the reversal occurs is called the 
 Villari critical point. 
 
 Viscosity, Magnetic 
 
 That prop- 
 
 erty of iron or other paramagnetic substance 
 in virtue of which a certain time is required 
 before a given magnetizing force can pro- 
 duce its effects. (See Hysteresis, Viscous.) 
 
 Viscous Hysteresis. (See Hysteresis, 
 Viscous.) 
 
 Vis- Viva. The energy stored in a moving 
 body, and therefore the measure of the amount 
 of work that must be performed in order to 
 bring a moving body to rest. 
 
 If M, is the mass and V, the velocity 
 
 MV* 
 The Vis-Viva = 
 
 2 
 
 Vitreous Electricity. (See Electricity, 
 Vitreous.) 
 Vitrite. An insulating substance. 
 
 Volatilization, Electric A term 
 
 sometimes used instead of electric evapora-. 
 tion. (See Evaporation, Electric.) 
 
 Volcanic Lightning. (See Lightning, 
 Volcanic.) 
 
 Volt. The practical unit of electro- 
 motive force. 
 
 Such an electromotive force as is induced 
 in a conductor which cuts lines of magnetic 
 force at the rate of 100,000,000 per sec. 
 
 Such an electromotive force as would 
 cause a current of one ampere to flow against 
 the resistance of one ohm. 
 
 Such an electromotive force as would 
 charge a condenser of the capacity of one 
 farad with a quantity of electricity equal to 
 one coulomb. 
 
 io 8 absolute electro-magnetic units of elec- 
 tromotive force. 
 
 Volt-Ammeter. A wattmeter. 
 
 A variety of galvanometer capable of di- 
 rectly measuring the product of the difference 
 of potential and the amperes. (See Watt- 
 meter.) 
 
 Volt ArnpSre. A watt. (See Watt.) 
 
 Volt-Coulomb. The unit of electric work. 
 
 The joule. (See/0#&.) 
 
 Volt, Mega One million volts. 
 
 Volt, Micro The one-millionth of a 
 
 volt. 
 
 Voltage. This term is now very com- 
 monly used for either the electromotive force 
 or difference of potential of any part of a 
 circuit as determined by the reading of a 
 voltmeter placed in that part of the circuit. 
 
 Voltage, Terminal The electro- 
 motive force expressed in volts of a dynamo 
 or other electric source, as indicated by a 
 voltmeter placed across its terminals. 
 
 The terminal voltage is greater than that on 
 the leads or conductors at some distance from 
 
Vol.] 
 
 545 
 
 [Yol 
 
 the source and less than that generated by the 
 source. 
 
 There is an exception to this general statement 
 in the case of ceitain leads connected with an 
 alternating dynamo-electric machine. (See Ef- 
 fect ', Ferranti) 
 
 Voltaic Arc. (See Arc, Voltaic) 
 Voltaic Battery. (See Battery, Voltaic) 
 
 Voltaic Battery Indicator. (See Indica- 
 tor, Voltaic Battery?) 
 
 Voltaic Battery Protector. (See Pro- 
 tector, Voltaic Battery) 
 
 Voltaic Cell. (See Cell, Voltaic) 
 
 Voltaic Cell, Bichromate (See 
 
 Cell, Voltaic, Bichromate.) 
 
 Voltaic Cell, Bunsen's (See Cell, 
 
 Voltaic, Bunsen's.) 
 
 Voltaic Cell, Calland's (See Cell, 
 
 Voltaic, Callaud's.) 
 
 Voltaic Cell, Capacity of Polarization of 
 
 (See Cell, Voltaic, Capacity of Polar- 
 
 ization of.) 
 
 Voltaic Cell, Closed-Circuit (See 
 
 Cell, Voltaic, Closed-Circuit.) 
 
 Voltaic Cell, Contact Theory of 
 
 (See Cell, Voltaic, Contact Theory of) 
 
 Voltaic Cell, Creeping of (See 
 
 Cell, Voltaic, Creeping in) 
 
 Voltaic Cell, Daniell's (See Cell, 
 
 Voltaic, DanielFs) 
 
 Voltaic Cell, Double-Fluid - (See 
 Cell, Voltaic, Double-Fluid) 
 
 Voltaic Cell, Dry - (See Cell, Vol- 
 taic, Dry) 
 
 Voltaic Cell, Gravity (See Cell, 
 
 Voltaic, Gravity) 
 
 Voltaic Cell, GrenSt (See Cell, 
 
 Voltaic, Grenet.) 
 
 Voltaic Cell, Grove (See Cell, Vol- 
 taic, Grove) 
 
 Voltaic Cell, Leclanchg (See Cell, 
 
 Voltaic', Leclanche) 
 
 Voltaic Cell, Local Action of (See 
 
 Action, Local, of Voltaic Cell) 
 
 Voltaic Cell, Meidinger (See Cell, 
 
 Voltaic, Meidinger) 
 
 Voltaic Cell, Negative Plate of 
 
 (See Plate, Negative, of Voltaic Cell) 
 
 Voltaic Cell, Open-Circuit (See 
 
 Cell, Voltaic, Open-Circuit) 
 
 Voltaic Cell, Poggendorff (See 
 
 Cell, Voltaic, Poggendorff) 
 
 Voltaic Cell, Polarization of (See 
 
 Cell, Voltaic, Polarization of) 
 
 Voltaic Cell, Positive Plate of - 
 (See Plate, Positive, of Voltaic Cell) 
 
 Voltaic Cell, Siemens-Halske - 
 (See Cell, Voltaic, Siemens-Halske.) 
 
 Voltaic Cell, Simple - (See Cell, 
 Voltaic, Simple) 
 
 Voltaic Cell, Single-Fluid - (See 
 Cell, Voltaic, Single-Fluid) 
 
 Voltaic Cell, Smee (See Cell, Vol- 
 taic, Smee) 
 
 Voltaic Cell, Standard (See Cell, 
 
 Voltaic, Standard) 
 
 Voltaic Cell, Standard, Clark's - 
 (See Cell, Voltaic, Standard, Clark's) 
 
 Voltaic Cell, Standard, Clark's, Ray- 
 
 leigh's Form of (See Cell, Voltaic, 
 
 Standard, Rayleigh's Form of Clark's) 
 
 Voltaic Cell, Standard, Fleming's 
 
 (See Cell, Voltaic, Standard, Fleming's) 
 
 Voltaic Cell, Standard, Lodge's 
 (See Cell, Voltaic, Standard, Lodge's) 
 
 Voltaic Cell, Standard, Sir Win. Thom- 
 son's (See Cell, Voltaic, Standard 
 
 Sir William Thomson's) 
 
 Voltaic Cell, Standardizing (See 
 
 Cell, Voltaic, Standardizing a) 
 
 Voltaic Cell, Two-Fluid (See Cell, 
 
 Voltaic, Two-Fluid.) 
 
 Voltaic Cell, Water (See Cell, 
 
 Voltaic, Water) 
 
 Voltaic Cell, Zinc-Carbon (See 
 
 Cell, Voltaic, Zinc-Carbon) 
 
 Voltaic Cell, Zinc-Copper - (See 
 
 Cell, Voltaic, Zinc-Copper) 
 
 Voltaic Circle. (See Circle, Voltaic.) 
 
Vol.] 
 
 546 
 
 [Vol. 
 
 Yoltaic Circuit. (See Circuit, Voltaic} 
 Voltaic Couple. (See Couple, Voltaic.} 
 Yoltaic Effect (See Effect, Voltaic} 
 Voltaic Electricity. (See Electricity, 
 Voltaic.} 
 
 Voltaic Element. (See Element, Vol- 
 taic} 
 
 Voltaic or Current Induction. (See In- 
 duction, Voltaic} 
 
 Voltameter. An electrolytic cell em- 
 ployed for measuring the quantity of the 
 electric current passing through it by the 
 amount of chemical decomposition effected 
 in a given time. 
 
 Various electrolytes are employed in voltam- 
 eters, such as aqueous solutions of sulphuric 
 acid, copper sulphate, or other metallic salts. 
 
 In the sulphuric acid voltameter shown in Fig. 
 562, the battery terminals are connected with pla- 
 tinum electrodes, immersed in water slightly acidu- 
 lated with sulphuric acid, and placed inside glass 
 tubes, also filled with acidulated water. On the 
 passage of the current hydrogen appears at the 
 kathode, and oxygen at the anode, in nearly the 
 proportion of two volumes to one. (See Ozone.} 
 
 Fig. 562. A Sulphuric Acid Voltameter. 
 
 In the case of water containing sulphuric acid 
 (hydrogen sulphate) the decomposition would ap- 
 pear to be that of the sulphuric acid rather than 
 that of the water. The reaction is as follows: 
 H 2 SO 4 =H, + SO 4 . 
 
 The hydrogen appears at the electro negative 
 terminal or kathode. The SO 4 appears at the 
 electro positive terminal or anode, but combines 
 with one molecule of water, thus, SO 4 -4- H 2 O = 
 H 2 SO 4 -|- O, gaseous oxygen being driven off at 
 the anode. 
 
 Voltameters are not as well suited as galva- 
 nometers for the measurement of electric currents, 
 because a certain electromotive force must be 
 reached before electrolysis is effected. 
 
 The voltameter in reality measures the cou- 
 lombs, and, therefore, is valuable as a current 
 measurer only when the current is constant. 
 
 Coulomb-meter would, therefore, be the pref- 
 erable term. 
 
 Then, again, time is required to produce the 
 results, and considerable difficulty is experienced 
 in maintaining the current strength constant, 
 either on account of variations in the electro- 
 motive force of the source, or of variations in the 
 resistance of the voltameter. 
 
 Voltameter, Copper A voltameter 
 
 in which the quantity of the current passing 
 te determined by the weight of copper de- 
 posited. 
 
 A current, the strength of which is constant, is 
 passed through the voltameter for a given time. 
 The kathode, preferably of platinum, is thor- 
 oughly cleaned and dried with a current of heated 
 air and accurately weighed before and after. 
 The current strength is then deduced from the 
 increase in weight and the time. 
 
 A galvanometer is kept in the circuit of the 
 battery and voltameter. If a Daniell battery is 
 used, it should be kept on closed-circuit through 
 a resistance for some time before use, in order to 
 insure normal current. 
 
 It will be noticed that the indications of this 
 voltameter are based on the gain in weight of the 
 kathode. The loss in weight of the anode is mis- 
 leading, owing to secondary chemical action and 
 disintegration. 
 
 Voltameter, Gas A term sometimes 
 
 used for volume voltameter. (See Voltam- 
 eter, Volume} 
 
 Voltameter, Siemens' Differential 
 A form of voltameter employed by Sir Wil- 
 liam Siemens for determining the resistance of 
 the platinum spiral used in his electric pyrom- 
 eter. (See Pyrometer, Siemens' Electric} 
 
 Two separate voltameter tubes, provide! with 
 platinum electrodes and filled with dilute sulphu- 
 ric acid, are provided with carefully graduated 
 tubes to determine the volume of the decomposed 
 gases. (See Voltameter, Volume.} 
 
 A current from a battery is divided by a suit- 
 able commutator into two circuits connected re- 
 spectively with the two voltameter tubes. In one 
 of these circuits a known resistance is placed, in 
 the other the resistance to be measured, i. t., the 
 platinum coil used in the electric pyrometer. 
 
Tol. 
 
 547 
 
 [Vol. 
 
 Voltameter, Silver 
 
 A voltameter 
 
 in which the quantity of the current passing 
 is determined by the weight of silver de- 
 posited. 
 
 A solution of silver nitrate is used as the elec- 
 trolytic liquid. When the current to be measured 
 is strong the strength of the silver nitrate solution 
 is made stronger. 
 
 Voltameter, Volume A voltameter 
 
 \n which the quantity of the current passing 
 > determined by the volume of the gases 
 r olved. 
 
 a some forms of volume voltameter in which 
 ailute sulphuric acid is electrolyzed, both the 
 hydrogen and the oxygen are measured, either 
 separately or together. 
 
 In one form of volume voltameter the hydrogen 
 only is collected, and thus the error in volum- 
 etric determinations arising from the decrease in 
 volume from the formation of ozone is avoided. 
 The evolved oxygen is isolated from the hydrogen 
 by placing a porous jar between the electrodes. 
 The negative electrode, is formed of platinum 
 fused in the tube, which, for ease of connec- 
 tion, is partially filled with mercury. 
 
 The graduated glass tube, in which the hy- 
 drogen is collected, is maintained at a nearly con- 
 stant temperature by means of a water column. 
 A thermometer is provided for corrections of 
 volume as affected by temperature. 
 
 The voltameter contains dilute sulphuric acid, 
 about 30 per cent, of acid. 
 
 Voltameter, Weight - A voltameter 
 in which the quantity of the current passing 
 is determined by the difference in the weight 
 of the instrument after the circuit has passed 
 for a given time. 
 
 A weight voltameter consists essentially of 
 platinum electrodes and some means for thor- 
 oughly drying the evolved gases. A vessel filled 
 with pumice stone moistened with sulphuric acid, 
 or a chloride of calcium tube, may be used for this 
 purpose. The voltameter is carefully weighed 
 before and after the decomposition. The differ- 
 ence in weight gives the weight of the sulphuric 
 acid decomposed. 
 
 Voltametric Law. (See Law, Voltamet- 
 
 rzc.) 
 
 Voltmeter. An instrument used for meas- 
 
 uring difference of potential. (See Galva- 
 nometer. Potential, Difference of. Volt) 
 
 A voltmeter may be constructed on the principle 
 of a galvanometer, in which case it differs from 
 an ammeter, or ampere meter, which measures 
 the current, principally in that the resistance 
 of its coils is greater, and that in an ampere meter 
 the coils are placed in the circuit, while in a volt- 
 meter they are placed as a shunt to the circuit. 
 
 The difference of potential is determined from 
 the reading of a voltmeter, by the fact that accord- 
 ing to Ohm's law, the product of the current and 
 the resistance is equal to the electromotive force, 
 
 E 
 
 as C = from which we obtain C X R = E. 
 R 
 
 In the ordinary operation of a voltmeter, the 
 action of the current in passing through a coil of 
 insulated wire is to produce a magnetic field, 
 which causes the deflection of a magnetic needle. 
 Since the resistance of the voltmeter is constant 
 the current passing, and hence the deflection of 
 the needle, will vary with the value of E. The 
 magnetic field produced by the current deflects 
 the magnetic needle against the action of another 
 field, which may be either the earth's field, or an 
 artificial field produced by a permanent or an 
 electro-magnet. Or, it may deflect it against the 
 action of a spring, or against the force of gravity 
 acting on a weight. There thus arise varieties of 
 voltmeters, such as permanent-magnet voltmeters, 
 spring voltmeters, and gravity voltmeters. 
 
 Or, the current produced by a given difference 
 of potential may be used to heat a wire, and the 
 value of the potential difference determined by 
 the movement of a needle by the consequent 
 expansion of a wire. Cardew's voltmeter operates 
 on this principle. (See Voltmeter, Cardew's.) 
 
 Or, the potential difference to be measured 
 may be utilized to charge a readily movable 
 needle, and thus produce electrostatic attractions 
 and repulsions. 
 
 This form of instrument is in reality a form of 
 electrometer. (See Electrometer, Quadrant. 
 Attraction, Electrostatic.) 
 
 Voltmeter, Cardew's 
 
 A form of 
 
 voltmeter in which the potential difference is 
 measured by the amount of expansion caused 
 by the heat of a current passing through a 
 fixed resistance. 
 
 The current produced by the difference < f 
 potential to be measured is passed through a high 
 
Vol.] 
 
 548 
 
 resistance wire of platinum silver, the expansion of 
 which is caused to move a needle across a 
 graduated arc. The wire is thin and therefore 
 quickly acquires the temperature due to the 
 current. 
 
 The Cardew voltmeter possesses an advantage 
 of being independent of changes of temperature. 
 It is also capable of being used to measure the 
 potential difference of alternating currents. 
 
 Toltmeter, Closed-Circuit A volt- 
 meter in which the points of the circuit, be- 
 tween which the potential difference is to be 
 measured, are connected with a closed coil 
 or circuit, and which gives indications by 
 means of the current so produced in said 
 circuit. 
 
 All galvanometer- volt meters are of the closed- 
 circuited type. 
 
 The Weston standard voltmeter shown in Fig. 
 563 is a closed-circuit voltmeter. 
 
 Fig. 563- Weston Standard Voltmeter. 
 
 Voltmeter, Electro-Magnetic 
 
 form of voltmeter in which the 
 
 A 
 
 difference 
 
 of potential is measured by the movement of 
 a magnetic needle in the field of an electro- 
 magnet. (See Voltmeter?) 
 
 Yoltmeter, Gravity A form of volt- 
 meter in which the potential difference is 
 measured by the movement of a magnetic 
 needle against the pull of a weight. 
 
 Sir William Thomson's balance instruments are 
 used as gravity voltmeters. (See Voltmeter ) 
 
 Voltmeter, Magnetic-Vane A volt- 
 meter in which the potential difference is 
 measured by the repulsion exerted between a 
 
 fixed and a movable vane of soft iron placed 
 within the field of the magnetizing coil. 
 
 A pointer, fixed to the moving vane, serves to 
 measure the amount of the repulsion, and conse- 
 quently the potential difference producing 'the 
 magnetizing current. The moving vane moves 
 under the magnetic repulsion against the action 
 of a spring. Discs of copper for damping the 
 movements f the movable vane, are placed be- 
 fore and behind it. 
 
 Voltmeter, Multi-Cellular Electrostatic 
 
 An electrostatic voltmeter in which a 
 
 series of fixed and movable plates are used 
 instead of the single pair employed in- the 
 quadrant electrometer. 
 
 The movable pairs of plates are connected to a 
 movable axis and placed vertically above one 
 another. To the top of the axis is fixed a light 
 aluminium needle or pointer, which moves over a 
 graduated scale. A series of fixed plates, suita- 
 bly supported and insulated from the ground, 
 alternate with the needle plates. 
 
 Voltmeter, Open-Circuit A volt- 
 meter in which the points of the circuit where 
 potential difference is to be measured are 
 connected with an open circuit and give in- 
 dications by means of the charges so pro- 
 duced. 
 
 Electrometer-voltmeters are of the open-cir- 
 cuited type. 
 
 Voltmeter, Permanent Magnet A 
 
 form of voltmeter in which the difference of 
 potential is measured by the movement of a 
 magnetic needle under the combined action 
 of a coil and a permanent magnet, against the 
 pull of a spring. (See Voltmeter^) 
 
 Voltmeter, Beducteur or Resistance for 
 
 (See Reducteur or Resistance for 
 
 Voltmeter?) 
 
 Voltmeter, Vertical Electrostatic - 
 
 A form of voltmeter the needle of which 
 moves in a vertical instead of in a horizontal 
 plane. 
 
 The construction of the vertical electrostatic 
 voltmeter is, in general, similar to that of the- 
 quadrant electrometer. (See Electrometer, Quad- 
 rant.) 
 
Vol.] 
 
 549 
 
 [Wat. 
 
 The fixed and movable sectors, the pointer and 
 the graduated scale, however, are in vertical in- 
 stead of horizontal planes. 
 
 Fig. 364. I'erticai t.lrctrostatic loltmeter. 
 
 The general arrangement of the vertical elec- 
 trostatic voltmeter will be readily understood by 
 an inspection of Fig. 564. 
 
 Volume Voltameter. (See Voltameter, 
 Volume?) 
 Vortex Atom. (See Atom, Vortex!) 
 
 Vortex Cylinder. (See Cylinder, Vor- 
 tex?) 
 
 Vortex-Ring Field. (See Field, Vortex- 
 Ring^ 
 
 Vulcabeston. An insulating substance 
 composed of asbestos and rubber. 
 
 Vulcanite. A variety of vulcanized rub- 
 ber extensively used in the construction of 
 electric apparatus. 
 
 Vulcanite is sometimes called ebonite from its 
 black color. It is also sometimes called hard 
 rubber. 
 
 Though an excellent insulator, vulcanite will 
 lose its insulating properties by condensing a film 
 of moisture on its surface. This can be best re- 
 moved by the careful application of heat. 
 
 The surface is very liable to become covered by 
 a film of sulphuric acid, due to the gradual oxi- 
 dation of the sulphur. Mere friction will not re- 
 move this film, but it may be removed by wash- 
 ing with distilled water. A thick coating of var- 
 nish will obviate this last defect. 
 
 Vulcanized Fibre. (See Fibre, Vulcan- 
 z'zed.) 
 
 W. A contraction sometimes used for 
 watt. 
 
 W. A contraction sometimes used for 
 work. 
 
 W. A contraction sometimes used for 
 weight. 
 
 Wall Plug. (See Plug, Wall.} 
 Wall Socket. (See Socket, Wall.) 
 Ward. A term proposed by James Thom- 
 son for a line and direction in a line. 
 
 Sir William Thomson thus defines the ward of 
 magnetization:' " The ward in which the magnet, 
 izing force urges a portion of the ideal northern 
 magnetic matter or northern polarity." 
 
 Waring Anti-Induction Cable. (See 
 Cable, Anti-Induction, Waring!) 
 
 Waste Field. (See Field, Magnetic, 
 Wasted 
 Watches, Demagnetization of Pro- 
 
 cesses for removing magnetism from 
 watches. 
 
 C 
 
 fO OOOOO O 
 
 AJOOOOOOO 
 I OOOOO OO 
 I O O O O OOOOO 
 
 Source of Alternating 
 Current. 
 
 Fig, 565. Wright's Demagnetization Apparatus. 
 
 The demagnetization of watches can be readily 
 effected by a method proposed by J. J. Wright. 
 
Wat.] 
 
 550 
 
 [ Wat. 
 
 The watch is held by its chain and slowly lowered 
 to the bottom of a hollow conical coil of wire, and 
 then slowly withdrawn from the coil. 
 
 The wire is wound on the coil, as shown in 
 Fig. 565, in the shape of a cone, viz.: with a 
 single turn at the top, and gradually increasing 
 in number of turns towards the bottom. The 
 conical coil is connected with a source of rapidly 
 alternating currents. 
 
 As the watch is lowered into the coil, it gradu- 
 ally becomes more and more powerfully magnet 
 ized with alternately opposite polarities, thus 
 completely removing any polarity it previously 
 possessed. As it is now slowly raised from out 
 the hollow cone, this magnetization becomes less 
 and less, until, if removed from the conical coil 
 while high above its apex, all sensible traces of 
 magnetism will have disappeared. 
 
 Watchman's Electric Register. (See 
 Register, Watchman's Electric?) 
 
 Water Battery. (See Battery, Water.') 
 
 Water-Dropping Accumulator. (See Ac- 
 cumulator, Water-Dropping.} 
 
 Water, Electrolysis of The de- 
 composition of water by the passage through 
 it of an electric current. 
 
 Water does not appear to conduct electricity 
 when pure; it is therefore not quite certain that 
 pure water can be electrolytically decomposed. 
 The addition of a small quantity of sulphuric 
 acid, or of a metallic salt, however, renders its 
 electrolysis readily accomplished. (See Vol- 
 tameter. ) 
 
 In the opinion of most, it is the sulphuric acid 
 that is decomposed rather than the water. 
 
 Water Horse-Power. The Indian Gov- 
 ernment's term for horse-power developed 
 by falling water. 
 
 The estimate is made by the following simple 
 rule : 15 cubic feet of water falling per second 
 through I foot equals I horse power. 
 
 Water- Jet TelepSione Transmitter. (See 
 
 Transmitter, Water-Jet Telephone?) 
 
 Water -Level Alarm. (See Alarm, 
 Water or Liquid Level.} 
 
 Water-Proof Wire. (See Wire, Water- 
 Proof.) 
 
 Water Pyrometer. (See Pyrometer, 
 Siemens' Water.} 
 
 Water Rheostat. (See Rheostat, Water} 
 
 Water Voltaic Cell. (See Cell, Voltaic, 
 Water.} 
 
 Watt. The unit of electric power. The 
 volt-ampere. 
 
 The power developed when 44.25 foot- 
 pounds of work are done per minute, or 
 0.7375 foot-pounds per second. 
 
 The T ff of a horse-power. 
 
 There are three equations which give the 
 value of the watts, viz. : 
 
 (i.) C E = The watts. 
 
 (2.) C 8 R = The watts. 
 
 (3.) E* = The watts. 
 R 
 
 Where C = the current in amperes ; E = th*> 
 electromotive force in volts, and R = the resist 
 ance in ohms. (See Energy, Electric.} 
 
 Watt Arc. (See Arc, Watt} 
 
 Watt Generator. (See Generator, Watt} 
 
 Watt-Hour. A unit of electric work. 
 
 A term employed to indicate the expendi- 
 ture of an electrical power of one watt, for an 
 hour. 
 
 Watt-Hour, Kilo - - The Board of 
 
 Trade unit of work equal to an output of one 
 kilo-watt for one hour. 
 
 Watt, Kilo One thousand watts. 
 
 A unit of power sometimes used in stating 
 the output of a dynamo. 
 
 A dynamo of 20 units, or a 2O-unit machine, is 
 one capable of giving an output of 20 kilo-watts. 
 
 Watt-Meter. A galvanometer by means 
 of which the simultaneous measurement of 
 the difference of potential and the current 
 passing is rendered possible. 
 
 The watt-meter consists of two coils of insu- 
 lated wire, one coarse and the other fine, placet 
 at right angles to each other as in the ohm-metet, 
 only, instead of the currents acting on a sus- 
 pended magnetic needle, they act o:\ each other 
 as in the electro-dynamometer. 
 
 Watt-Minute. A unit of electric work. 
 
 An expenditure of electric power of one 
 watt for one minute. 
 
 Watt-Second. A unit of electric work. 
 
 An expenditure of electric power of one 
 watt for one second. 
 
Web.] 
 
 551 
 
 [Wav. 
 
 Wave. A disturbance in an elastic me- 
 dium that is periodic both in space and 
 time. 
 
 Wave, Electric An electric disturb- 
 ance in an elastic medium that is periodic 
 both in space and time. (See Oscillations, 
 Electric?) 
 
 Waves, Amplitude of The ampli- 
 tude of a vibration. (See Vibration or 
 Wave, Amplitude of.} 
 
 Waves, Displacement Waves pro- 
 
 duced in the ether of dielectrics by means of 
 electric displacement. 
 
 The electric stress applied to a dielectric to pro- 
 duce electric displacement soon strains it to its 
 utmost and no further displacement can occur 
 until the direction of the electric power is re- 
 versed. A rapidly intermittent current therefore 
 can pass through a dielectric and thus produce a 
 series of displacement waves. 
 
 Dielectrics, therefore, may be considered as 
 pervious or transparent to rapidly intermittent or 
 reversed periodic currents, but opaque or imper- 
 vious to continuous currents. A condenser inter- 
 polated in a telephone circuit does not prevent tele- 
 phonic communication, though it does effectually 
 stop all continuous currents. 
 
 Waves, Electro-Magnetic Waves 
 
 in the ether that are given off from a circuit 
 through which an oscillating discharge is 
 passing, or from a magnetic circuit under- 
 going variations in magnetic intensity. 
 
 Waves, Electro-Magnetic, Interference 
 of Interference effects similar to those 
 produced in the case of waves of light, ob- 
 served in the case of electro-magnetic radi- 
 ations, or waves, in which one system of 
 waves, retarded a half wave length behind 
 another system of equal wave length and am- 
 plitude, results in a complete loss of motion 
 of the particles of the ether they tend to 
 simultaneously affect. 
 
 In order that complete interference may take 
 place, it is necessary 
 
 (l.) That the two waves, or system of waves, 
 must meet in opposite phases. That is, that one 
 be retarded -back of the other one-half a wave 
 length, or some odd number of half wave lengths. 
 
 (2.) That the waves simultaneously affect the 
 
 same particles of ether in which they are mov- 
 ing. 
 
 (3.) That the energy charged on the ether in 
 the shape of waves of electro-magnetic radiation, 
 must be equal in the case of each system of waves. 
 
 (4.) That the two systems of waves must have 
 the same wave length. 
 
 These conditions, it will be seen, are exactly 
 the same as in the case of the interference of 
 light. 
 
 It will, of course, be readily understood that if 
 electro-magnetic radiations can produce the 
 effect of resonance, they must also necessarily 
 produce interference effects. 
 
 Waves, Electro-Magnetic, Reflection of 
 
 Reflection of electro-magnetic waves 
 
 similar to the reflection of waves of light. 
 
 In his experiments on electro-magnetic radia- 
 tions, Dr. Hertz shows that true reflection of 
 electro- magnetic waves occurs from the surfaces 
 of certain substances placed in the path of the 
 waves. 
 
 In some experiments made in a large room, 
 Dr. Hertz obtained undoubted indications of re- 
 flection of electro-magnetic waves from the walls 
 of the room. 
 
 Waves of Condensation and Rarefaction. 
 
 The alternate spheres of condensed and 
 rarefied air by means of which sound is 
 transmitted. (See Waves, Sound.} 
 
 Waves, Sound Waves produced in 
 
 air or other elastic media by the vibrations 
 of a sonorous body. (See Sound.) 
 Way Line. (See Line, Way.) 
 Weather Cross. (See Cross, Weather.} 
 Weber. A term formerly employed for 
 the unit of electric current, and replaced by 
 ampere. (See Ampere.} 
 
 The term weber was originally used to express 
 a quantity of electricity equal to what is now 
 called one coulomb, and a current designated by 
 one weber per second. It was, however, used 
 finally as a unit of current. 
 
 Weber. A term proposed by Clausius and 
 Siemens for a magnetic pole of unit strength, 
 but not adopted. 
 
 This same term was also employed to derig. 
 nate the unit strength of current, now replaced 
 by the term ampdre. 
 
Web.] 
 
 552 
 
 [Wei. 
 
 Weber's Theory of Diamaguetism. 
 
 (See Diamagnetism, Weber's Theoiy of.) 
 
 Weight, Atomic The relative 
 
 weights of the atoms of elementary sub- 
 stances. 
 
 Since the atoms are assumed to be indivisible, 
 they must unite or combine as wholes and not 
 as parts. Although we cannot determine exactly 
 the actual weights of the different elementary 
 atoms, yet we can determine their relative weights 
 by ascertaining the smallest proportions in which 
 any two elements that combine atom for atom 
 will unite with each other. Such numbers 
 will represent the relative weights of the atoms 
 as compared with hydrogen. 
 
 Weight Voltameter. (See Voltameter, 
 Weight?) 
 
 Weights and Measures, Metric System 
 
 of A system of weights and measures 
 
 adopted by almost all civilized nations except 
 English-speaking, and by the scientific world 
 generally. 
 
 For measures of length, the one ten -millionth 
 part of the quadrant of a meridian of the earth is 
 taken as the unit of length. This unit of length 
 is called a metre, and various subdivisions and 
 multiples of its length are made on the decimal 
 system. 
 
 For a system of weights, the weight of one 
 cubic centimetre of pure water at 39.2 degrees 
 Fahr., the temperature of the maximum density of 
 water, is taken as the unit of weight. This is 
 called a gramme, and various multiples and sub- 
 divisions of this unit are made on the decimal 
 system. 
 
 The following table of French measures and 
 their corresponding English values are taken 
 irom Deschanel's " Elementary Treatise on 
 Natural Philosophy ": 
 
 Length. 
 
 \ millimetre = .03937 inch, or about ^ inch. 
 
 i centimetre = .3937 inch. 
 
 I decimetre 3.937 inches. 
 
 I metre = 39.37 inches = 3.281 feet = 
 1.0936 yard. 
 
 I kilometre = 1093.6 yards, or about mile. 
 
 Deschanel gives the length of the meter as 
 equal to 39.370432 inches. 
 
 U. S. Coast Survey Bull. No. 9 of 1889, gives 
 value of meter = 39.36980 inches. Therefore, 
 39.37 is probably as accurate as any other figure. 
 
 Area. 
 
 I square millimetre = .00155 square inch. 
 I square centimetre = .155 square inch. 
 I square decimetre =15.5 square inches. 
 I square metre =1550 square inches = 10.764 
 square feet = 1.196 square yards. 
 
 Volume. 
 
 I cubic millimetre = .000061 cubic inch. 
 
 I cubic centimetre = .061025 cubic inch. 
 
 I decimetre = 61.0254 cubic inches. 
 
 Cubic metre = 61025 cubic inches = 35.3156 
 cubic feet = 1.308 cubic yards. 
 
 The litre (used for liquids) is the same as the 
 cubic decimetre, and is equal .to 1.7617 pint, or 
 .22021 gallon. 
 
 Mass and Weight. 
 
 i milligramme = .01543 grain. 
 
 I gramme = 15.432 grains. 
 
 I kilogramme = 15432.3 grains = 2.205 pounds 
 avoirdupois. 
 
 More accurately, the kilogramme is 2.20462125 
 pounds. 
 
 Miscellaneous. 
 
 I gramme per square centimetre = 2.0481 
 pounds per square foot. 
 
 I kilogramme per square centimetre = 14.223 
 pounds per square inch. 
 
 I kilogram metre = 7.2331 foot-pounds. 
 
 I force de cheval 75 kilogrammetres per 
 second, or 542^ foot pounds per second, nearly, 
 whereas i horse-power (English) = 550 foot- 
 pounds per second. 
 
 Conversion of English into French measures; 
 Length. 
 
 i inch = 2.54 centimetres, nearly. 
 
 I foot = 30.48 centimetres, nearly. 
 
 i yard = 91.44 centimetres, nearly. 
 
 i statute mile = 160933 centimetres, nearly. 
 
 More accurately, I inch = 2.5399772 centi 
 metres. 
 
 Area. 
 
 I square inch = 6.45 square centimetres, nearly. 
 
 I square foot = 929 square centimetres, nearly. 
 
 i square yard = 8361 square centimetres, 
 nearly. 
 
 I square mile = 2.59 X lo 1 square centimetres, 
 nearly. 
 
 Volume. 
 
 I cubic inch = 16.39 cubic centimetres, nearly. 
 
 I cubic foot = 283 1 6 cubic centimetres, nearly. 
 
Wei.] 
 
 553 
 
 I cubic yard = 764535 cubic centimetres, 
 nearly. 
 
 I gallon = 4541 cubic centimetres, nearly. 
 
 Mass. 
 
 l gr\in = .0648 gramme, nearly. 
 I ounce avoirdupois = 28.35 grammes, nearly. 
 I pound avoirdupois = 453. 6 grammes, nearly. 
 I ton = 1.016 X io 6 grammes, nearly. 
 More accurately, I pound avoirdupois = 
 453.59265 grammes. 
 
 Velocity. 
 
 i mile per hour = 44.704 centimetres per 
 second. 
 
 I kilometre per hour = 27.7 centimetres per 
 second. 
 
 Density, 
 
 l pound per cubic foot = .016019 gramme per 
 cubic centimetre. 
 
 62.4 pounds per cubic foot = I gramme per 
 cubic centimetre. 
 
 Force (assuming g = 981). 
 Weight of I grain = 63.57 dynes, nearly. 
 
 " I ounce avoirdupois = 2.78 X io 4 
 
 dynes, nearly. 
 " I pound avoirdupois = 4.45 X io 8 
 
 dynes, nearly. 
 
 11 I ton = 9.97 X io a dynes, nearly. 
 
 " I gramme = 981 dynes, nearly. 
 
 41 I kilogramme 9.81 X io 5 dynes, 
 
 nearly. 
 
 Work (assuming g = 981). 
 I foot-pound = 1.356 X io 7 ergs, nearly. 
 I kilogrammetre = 9.81 x io 7 ergs, nearly. 
 Work in a second by one theoretical "horse- 
 power" = 7.46 X io 9 ergs, nearly. 
 
 Stress (assuming g = 981). 
 
 I pound per square foot = 479 dynes per 
 square centimetre, nearly. 
 
 I pound per square inch = 6.9 X io 4 dynes per 
 centimetre, nearly. 
 
 I kilogramme per square centimetre = 9.81 
 X io 5 dynes per square centimetre, nearly. 
 
 760 millimetres of mercury at o degree C. 
 1.014 X lo 15 dynes per square centimetre, nearly. 
 
 30 inches of mercury at o degree C. = 1.163 
 X io" dynes per square centimetre, nearly. 
 
 Welding, Electric Effecting the 
 
 welding union of metals by means of heat of 
 electric origin. 
 
 In the process of Elihu Thomson, the metals 
 
 are heated to electric incandescence by currents 
 obtained from transformers, and are subsequently 
 pressed or hammered together. 
 
 Fig. 566, shows the Thomson apparatus for the 
 direct system of electric welding. The dynamo 
 is combined with the welding apparatus. The 
 armature contains two separate windings; one of 
 fine wire, in series with the field magnet coils, 
 and another of very low resistance, being fcrmeci 
 of a U-shaped bar of -copper. No commutation 
 is used, the alternating currents being welt 
 adapted for heating purposes. The terminals of 
 the dynamo are, therefore directly co mected to- 
 the clamps that hold the bar to the welder. 
 
 Fig. 567, shows the apparatus for the Thomson 
 Indirect System of Electric Welding. This sys- 
 tem is applicable to heavy work, and to cases 
 where more than one welding machine is operated 
 by the current from a single dynamo. 
 
 In this case a high tension current is converted 
 
 Fig. J66. The Thomson Direct Welder. 
 
 into the large welding current employed, by means 
 of a suitably proportioned transformer. 
 
 The welding process is the same in either sys- 
 tem, and consists essentially in leading the weld- 
 ing current into the pieces to be united through 
 their points of junction when brought into firm 
 end contact. As the current is led across the 
 junction the temperature rises sufficiently to soften, 
 the metal, when the pieces are firmly pressed to- 
 gether by the motion of the clamps or holders. 
 
 In the process of Benardos and Olzewski, the 
 heat of the voltaic arc is employed for a some- 
 what similar purpose, but by a different process. 
 
 In the Thomson system of electric welding 
 alternating currents are employed. They are 
 either supplied by an alternating current dynamo 
 or by a transformer. 
 
 The process of welding is substantially as fol- 
 
Wei.] 
 
 554 
 
 [Win. 
 
 lows, viz.: the welding junctions are made slightly 
 convex, so as to touch in but one part of their 
 opposing faces. They are made to touch near 
 their centres and the welding heat is first reached 
 near their points of junction. Pressure is then 
 applied by means of a screw, lever or hydraulic 
 pre-sure until all the surfaces are at the welding 
 temperature. 
 
 This operation requires in practice but a few 
 seconds for small work, and at the most but a 
 
 Fig. 367. The Thomson Indirect Welder. 
 
 few minutes for larger work. The heating is 
 practically local, extending in most cases a dis- 
 tance equal to about the diameter of the weld. 
 
 For the purpose of controlling the electro- 
 motive force, and thus adapting the same welder to 
 different classes of work, when a transformor is 
 used, a second transformer provided with a mov- 
 able core is placed in series with the first. A 
 number of coils of insulated wire are placed in a 
 segment of a split-ring laminated-core. These 
 may be connected in series or in multiple by a 
 switch. An iron armature placed within, the 
 split ring encloses the annular core and acts as 
 the low-resistance secondary. When this is placed 
 so as to embrace the primary coils, the difference 
 of potential will be different than if moved to one 
 side or the other of the ring. 
 
 Welding Transformer. (See Trans- 
 former, Welding.} 
 
 I Wheatstone's Electric Balance. (See 
 Balance, Wheatstone's Electric.) 
 
 Wheatstone's Electric Bridge. (See 
 Bridge, Wheatstone's Electric.} 
 Wheel. Barlow's or Sturgeon's A 
 
 wheel or disc of metal capable of rotation on 
 a horizontal axis, that is set into rotation when 
 placed between the poles of magnets and 
 
 traversed by a current of electricity from the 
 centre to the circumference. 
 
 Wheel, Phonic A wheel maintained 
 in synchronous rotation by means of timed 
 electric impulses sent over a line, and em- 
 ployed in Delany's synchronous multiplex 
 telegraphic system. 
 
 The phonic wheel was invented by La Cour, but 
 was first put into successful operation in multiplex 
 telegraphy by Delany in his system of synchronous 
 multiplex telegraphy. (See Telegraphy, Synchron- 
 ous Multiplex, Delany's System.) Delany ob- 
 tains the exact synchronism of the phonic wheel 
 by means of a series of correcting electric impulses, 
 automatically sent over the line on the failure of 
 the phonic wheel at either end of the line to ex- 
 actly synchronize with that at the other end. 
 
 Wheel, Reaction, Electric A wheel 
 driven by the reaction of a convective dis- 
 charge. (See Flyer, Electric.) 
 
 Wheel, Trolley A metallic wheel 
 
 connected with the trolley pole and moved 
 over the trolley wire on the motion of the car 
 over the tracks, for the purpose of taking the 
 current from the trolley wire by means of 
 rolling contact therewith. 
 
 Whirl, Electric A term employed 
 
 to indicate the circular direction of the lines 
 of magnetic force surrounding a conductor 
 conveying an electric current. (See Field, 
 Electro-Magnetic^ 
 
 This is more correctly called a magnetic whirl. 
 (See Whirl, Magnetic.) 
 
 Whirl, Expanding Magnetic One 
 
 of the magnetic whirls which are sent out 
 from a conductor through which a current of 
 gradually increasing strength is passing, or 
 from a magnet whose magnetism is increas- 
 ing. 
 
 These magnetic whirls, according to Hertz, 
 move outward through free ether with the velo- 
 city of light. 
 
 Whirl, Magnetic The lines of mag- 
 netic force which surround the circuit of the 
 conductor conveying an electric current. 
 
 Whistle, Steam, Automatic Electric 
 
 A steam whistle, employed on foggy days 
 in some systems of railway signals, when the 
 
Whi.] 
 
 555 
 
 [Wir 
 
 visual signals cannot be seen, in which the 
 passage of the steam through the whistle is 
 automatically obtained by the closing of an 
 electric contact, or the passage of the loco- 
 motive over a certain part of the track. 
 
 White Heat (See Heat, White.) 
 
 White Hot. (See Hot, White.} 
 
 Wimshurst Electrical Machine. (See 
 Machine, Wimshurst Electrical.) 
 
 Wind, Electric - The convection 
 stream of air particles produced at the ex- 
 tremities of points attached to the surface of 
 charged, insulated conductors. (See Con- 
 vection, Electric. Flyer, Electric.) 
 
 Windage of Dynamo. A term proposed 
 for the air gap between the armature and the 
 pole pieces of a dynamo. 
 
 This term is not much used. 
 
 Winders, Telegraphic Paper Ap- 
 paratus for winding or coiling the paper fillets 
 used on telegraphic registers. 
 
 \Vhen moved by means of a spring they are 
 genera.ly styled automatic winders. 
 
 Winding 1 , Ampdre A single wind- 
 ing or turn through which one ampere passes. 
 
 Ampere-winding is used in the same significa- 
 tion as ampere-turn. (See Turn, Ampere.) 
 
 Winding, Bifllar A winding of a 
 
 coil of wire in which, instead of winding the 
 wire in one continuous length, it is doubled 
 on itself and then wound. 
 
 This method is employed in resistance coils, so 
 as to avoid the induction effects. (See Coil, 
 Resistance.) 
 
 Winding, Compound, of Dynamo-Electric 
 
 Machine A method of winding in 
 
 which shunt and series coils are placed on 
 the field magnets. (See Machine, Dynamo- 
 Electric, Compound- Wound.) 
 
 Winding, Series - A winding of a 
 dynamo-electric machine in which a sin- 
 gle set of magnetizing coils are placed on the 
 field magnets, and connected in series with 
 the armature and the external circuit. (See 
 Machine, Dynamo-Electric, Series- Wound.) 
 
 Window-Tube Insulation. (See Insula- 
 tor, Window-Tube.) 
 
 Wipe Spark. (See Spark, Wipe.} 
 Wiping Contact. (See Contact, Wiping^ 
 
 Wire, Air-Line That portion of c 
 
 circuit which is formed by air-strung wires, in 
 contradistinction to the portion which passes 
 through underground or submarine cables. 
 
 Wire, Binding, for Telegraph Lines 
 
 The wire used for securing lines of ^vvire 
 conductors to the insulators. 
 
 The line wire rests against the insulators at as 
 small an area of contact as possible, generally 
 only a mere edge. In order to attach the wire 
 to the insulator, and protect the wire from chaf- 
 ing, it is secured to the insulator by binding with 
 wire. 
 
 Wire, Block A line or wire em- 
 ployed in a block system for railroads, con- 
 necting a block tower with the next tower 
 on each side of it. (See Railroads, Block 
 System for.) 
 
 Wire, Braided A conducting wire 
 covered with a braiding, as distinguished from 
 a wire that is merely wrapped with insulating 
 material. 
 
 Cotton or silk is used for braiding. The cov- 
 ering is often coated by a layer of some insu- 
 lating gum or varnish dissolved in a rapidly 
 drying liquid. It is sometimes covered with melted 
 paraffine. 
 
 Fig. 568. Braided Wire. 
 
 A copper wire covered with insulating material 
 and then braided is shown in Fig. 568. 
 
 Wire, Calling A wire employed in 
 
 a telegraphic or telephonic system, by means 
 of which a subscriber communicates with the 
 central office, or one central office communi- 
 cates with another. 
 
 This wire is termed the calling wire in order to 
 distinguish from the wire actually used ior talking 
 or telegraphing. 
 
 Wire, Conductibility and Sizes of 
 
 For tables giving the resistance, size, weight 
 per foot, etc., of wire according to some of 
 the principal wire gauges see pages 254 and 
 256. 
 
Wir.] 
 
 556 
 
 [Wir. 
 
 Wire, Copper, Hard-Drawn Copper 
 
 wire that is drawn three or four times after 
 annealing. 
 
 The drawing subsequent to annealing renders 
 the wire hard and elastic, with but a trifling de- 
 crease in its conductivity. A hard-drawn wire, 
 of course, possesses greater limits of elasticity 
 than soft-drawn wire, and, therelore, m the case 
 of air lines, permits of the use of a longer distance 
 between adjacent poles. 
 
 Wire, Copper, Soft-Drawn Copper 
 wire that is softened by annealing after 
 drawing. (See Wire, Copper, Hard- 
 Drawn,) 
 
 Wire, Dead, of Armature - That 
 part of the wire on the armature of a dynamo 
 which produces no electromotive force or 
 resultant current. 
 
 It is called dead because it does not move 
 through the field of the machine. 
 
 Wire, Duplex An insulated con- 
 ductor containing two separate parallel wires. 
 
 Wire, Earth-Grounded A wire 
 
 one terminal of which is grounded or put to 
 earth, so that the earth forms a part of the 
 circuit in which the wire is placed. 
 
 Wire, Feeding 1 A term sometimes 
 applied to the wire or lead of a multiple cir- 
 cuit which feeds the main. 
 
 In a system of electric railroads the feeding 
 !rires feed the trolley wires. 
 
 Wire Finder. (See Finder, Wire.) 
 
 Wire, Fuse A readily fusible wire 
 
 employed in a safety catch to open the cir- 
 cuit when the current is excessive. (See 
 Catch, Safety.) 
 
 Wire Gauge, Vernier (See Gauge, 
 
 Wire, Micrometer) 
 
 Wire, Grounded (See Ground or 
 
 Earth.) 
 
 Wire, House In a system of in- 
 
 :andescent electric lighting any conductor 
 that is connected with a service conductor 
 and leads to the meter in the house. 
 
 Wire, Insulated Wire covered 
 
 with any insulating material. 
 
 Cotton and silk are generally employed for in- 
 snlating purposes, either alone, or in connection 
 with various gums, resins, or other materials, 
 which are rendered plastic by heat, but which 
 solidify on cooling. India rubber, caoutchouc, 
 and various mixtures and compounds are also em- 
 ployed for the same purpose. 
 
 For most of the purposes of line wires, high in- 
 sulating powers, combined with a low specific 
 inductive capacity, are required in the insulating 
 materials. 
 
 For overhead wires a waterproof covering is 
 necessary. In the neighborhood of combustible 
 materials, some fireproof covering is desirable. 
 
 Wire, Lead A lead fuse wire. 
 
 Wire, Line In telegraphy the wire 
 that connects the different stations with om 
 another. 
 
 In bell and annunciator circuits, the term lin. 
 wire is sometimes applied to all circuits other 
 than the main line. 
 
 In arc light circuits the term line wire is applied 
 to the entire metallic circuit, to which the lamps 
 are connected in series. 
 
 Wire, Main The principal wire. 
 
 In any system of bell circuits, the mam wire is 
 the wire which runs from one pole of the battery 
 to one of the springs of all the pushes, in distinc- 
 tion from the line wires, or the rest of the wires 
 in the battery circuit. 
 
 Wire, Message - A line or wire em- 
 ployed in a block system for railroads, ex- 
 tending along the road and used for local 
 traffic or business. (See Railroads, Block 
 System for) 
 
 Wire, Negative A term sometimes 
 applied to that wire of a parallel circuit which 
 is connected to the negative pole of a source. 
 
 Wire, Neutral The middle wire of 
 
 a three-wire system of electric distribution 
 
 Wire, Omnibus An onmibus. bar. 
 
 (See Bars, Omnibus) 
 
 A bus bar or wire. (See Wires, Bus) 
 
 Wire, Paraffined Wire wrapped or 
 
 braided with some textile material and after- 
 wards coated with paraffine. 
 
 The term paraffined wire is sometimes limited 
 to a wrapped wire that is afterwards paraffine 
 coated. 
 
Wir.] 
 
 557 
 
 fWir. 
 
 Wire, Positive 
 
 The wire or con- 
 
 ductor connected to the positive pole or ter- 
 minal of any electric source. 
 
 Wire, Potentiometer The wire of 
 a potentiometer which has been calibrated in 
 order to measure the drop of potential in any 
 circuit. (See Potentiometer} 
 
 Wire, Return The wire or con- 
 ductor by means of which the current returns 
 to the electric source after having passed 
 through the electro-receptive devices. (See 
 Sources, Electric. Device, Electro-Recep- 
 tive.} 
 
 Wire, Shade Guard (See Guard, 
 
 Wire Shade.} 
 
 Wire, Slide - A wire of uniform 
 oiameter employed in Wheatstone's electric 
 bridge for the proportionate arms of the 
 bridge. 
 
 A sliding contact key moves over the slide 
 wire and determines the length of the arms. 
 Some forms of bridges have a double or a triple 
 slide wire. (See Bridge, Electric, Slide-Form of.) 
 
 Wire, Span The wire employed in 
 
 systems of electric railways for holding the 
 trolley wire in place. 
 
 The span-wire is used when the poles are 
 erected on both sides of the street or road-bed, 
 and the trolley wire, suitably insulated from the 
 span wire, is suspended therefrom. 
 
 Wire, Suspending, of Aerial Cable 
 
 The wire from which an aerial cable is strung 
 or suspended. 
 
 In case the aerial cable is unusually heavy the 
 suspending wire is replaced by a wire rope. (See 
 Cable, A?rial.) 
 
 Wire, Taped - A conducting wire 
 covered with an insulating material in the 
 shape of tape. 
 
 A wire covered with an insulating material and 
 subsequently taped is shown in Fig. 569. 
 
 Taped Wire. 
 
 Copper wire covered 
 with a coating of tin prior to its being insu- 
 lated. 
 
 Wire, Tinned 
 
 The coating of tin is for the purpose of insur- 
 ing greater ease in soldering. It is also useful 
 in case vulcanized rubber is used for the insulator, 
 to prevent the sulphur from attacking the copper. 
 
 Wire, To To fix or place the con- 
 ductors or mains for any electric circuit. 
 
 Wire, Train A line of wire em- 
 ployed in a block system for railroads, con- 
 nected with the general dispatcher's office, 
 and used for sending train orders only. (See 
 Railroads, Block System for} 
 
 Wire, Trolley The wire over which 
 
 the trolley passes in a system of electric rail- 
 ways, and from which the current is taken to 
 drive the motors on the cars. 
 
 A bare conductor or wire, supported over- 
 head on suitable hangers and provided for 
 transmitting current by the trolley to the 
 motor connected with the car on the passage 
 of the trolley wheel over its surface. (See 
 Wheel, Trolley} 
 
 Trolley wires, being necessarily bare, are 
 carefully insulated at their points of attachment 
 to all supports. 
 
 Wire, Trolley, Continuous A trol- 
 ley wire or conductor employed in overhead 
 dependent systems of electric railways. (See 
 Railroads, Electric, Dependent System of 
 Motive Power for.) 
 
 Wire, Trolley, Sectional or Divided 
 
 A trolley wire or conductor for systems of 
 electric railroads in which the wire is divided 
 into a number of separate sections that are 
 suitably connected with the generating dyna- 
 mo by means of feeder wires. (See Rail- 
 roads, Electric, Dependent System of Motive 
 Power for.} 
 
 Wire, Trunk A main line or wire, 
 
 extending between two distant stations, such 
 as between two large cities, and provided 
 solely for communication between them, not 
 being tapped at intermediate points. 
 
 Wire, Twin - A conductor, consist- 
 ing of two separately insulated wires, bound 
 together by an additional insulating covering. 
 
 Wire, Water-Proof A wire pro- 
 tected from the weather by a coating of any 
 waterproof material. 
 
Wir.J 
 
 558 
 
 [Wir. 
 
 Wire, Wrapped Wire that is insu- 
 lated by placing strands of some insulating 
 material, like cotton, parallel to its length, 
 and then wrapping a number of strands 
 around the wire. 
 
 The wrapped wire is afterwards either coated 
 with paraffine or other insulator, or is used with- 
 out such coating. 
 
 Wires, Bus A term sometimes used 
 
 for omnibus bars or wires. 
 
 The wires which receive the full current 
 generated by the electric source, and carry 
 it to the feeders. 
 
 The bus-wires collect the current from all the 
 sources, hence the name. 
 
 Wires, Breaking- Weight of The 
 
 weight required to be hung at the end of a 
 wire in order to break it. 
 
 Ordinary copper wire will break at about 17 
 tons to the square inch of area of cross section. 
 Common wrought iron breaks at 25 tons to the 
 square inch. These figures are to be regarded as 
 approximate only, since almost inappreciable 
 differences in the physical condition of metals, as 
 well as slight variations in their chemical com- 
 position, often produce marked differences in 
 their breaking weights. 
 
 Wires, Cross (See Cross, Electric) 
 
 Wires, Crossing A device employed 
 
 in telegraphic circuits whereby a faulty con- 
 ductor is cut out of the circuit of a telegraph 
 line by crossing over to a neighboring, less 
 used, line. 
 
 To cut out a faulty section of wire in any cir- 
 cuit, such as C D, in the circuit A B C D E, Fig. 
 570, a cross-connection is made to a line X Y, 
 running near it, and which may be temporarily 
 thrown out of use. By this means the interrup- 
 tion of an important circuit may be repaired. 
 
 ABODE 
 
 Fig. 570. Crossing Wires. 
 
 Wires, Dead Disused and aban- 
 doned electric wires. 
 
 The term dead is often applied to a wire 
 through which no current is passing. The term, 
 however, is more properly applied to a wire 
 formerly employed, hut subsequently abandoned. 
 
 Dead wires in the neighborhood of active wires 
 are a constant menace to life and property, and 
 should invariably be carefully reimved. 
 
 It is often a matter of considerable importance 
 to be able to determine whether or not a current 
 is passing through a wire. When the wire is not 
 enclosed in a moulding, or fastened against a 
 wall, this can readily be ascertained by bringing 
 a small compass needle near the wire, when it 
 will tend to set itself across the wire. 
 
 The term dead wire, as will be seen, is used in 
 two distinct senses. 
 
 Wires, Leading-In The wires OT 
 
 conductors which lead the current through 
 (into and out of) an electric lamp. 
 
 The term leading-in wires is generally applied 
 to incandescent electric lamps, Geissler or 
 Crookes tubes, and to various other apparatus. 
 
 Wires, Leading-Tip Wires em- 
 ployed for raising an aerial cable to the cable 
 hangers. 
 
 Wires, Omnibus A term sometimes 
 
 used for bus wires. (See Wires, Bus.) 
 
 Wires or Conductors, Continuous 
 
 Wires or conductors free from joints. 
 
 Wires or conductors without soldered or 
 twisted joints or without any joints whatso- 
 ever. 
 
 Wires, the entire lengths of which have 
 been taken from the hitherto uncut coil of 
 wire from the draw plate. 
 
 Strictly speaking, any metallic circuit consists 
 of a continuous wire, whether in one piece or in 
 several sections or pieces. The preferable term 
 would appear to be un jointed wires or conductors. 
 
 Wires, Phantom A term applied 
 to the additional circuits or wires obtained in 
 any single wire or conductor by the use of 
 some multiplex telegraphic system. (See 
 Telegraphy, Multiplex. Telegraphy, Syn- 
 chronous-Multiplex, Delany's System?) 
 
 Wires, Pilot 
 
 In a system of incan- 
 
 descent lighting, where a comparatively low 
 potential is employed on the mains, thin wires 
 leading directly from the generating station 
 to different parts of the mains, in order to 
 determine the differences of potential at such 
 points. 
 
Wir.] 
 
 539 
 
 [Wor. 
 
 Pilot wires indicate on a voltmeter the differ- 
 ence of potenti il at the various points. The pilot 
 wires extend to the various seats of supply, and 
 so give instant warning of any change in the 
 value of the potential. 
 
 Wires. Pressure -- In a system of 
 incandescent electric lighting, wires or con- 
 ductors, series-connected with the junction 
 boxes, and employed in connection with suit- 
 ible voltmeters, to indicate the pressure at 
 the junction boxes. 
 
 The pressure wires are sometimes called the 
 wires. 
 
 The joule. (See 
 
 Wires, Tap -- The wires or conduc- 
 tors used to carry the current from the feed- 
 ers or mains at the pole to a near point on 
 the trolley wire. 
 
 Wiring 1 . Collectively the wires or con- 
 ducting circuits used in any system of electric 
 distribution. 
 
 Wiring 1 . Placing or establishing the wires 
 or conductors for any electric circuit. 
 
 Wiring, Case -- Placing or establish- 
 ing electric conductors or wires that are held 
 in place on the walls or ceiling of a room, by 
 means of continuous cleats. 
 
 Wiring, Cleat ---- Placing or estab- 
 lishing electric conductors or wires that are 
 held in place on the walls or ceiling of a 
 room by means of suitably shaped insulating 
 cleats. 
 
 Wiring, Inside 
 
 The conductors 
 
 that, in a system of incandescent electric 
 lighting, lead to the interior of the house or 
 area to be lighted. 
 
 Wirin-r, Moulding 
 
 Electric con- 
 
 ductors or wires that are held in place on the 
 walls or ceiling of a room by means of suit- 
 ably shaped mouldings. 
 
 Work. The product of the force by the 
 distance through which the force acts. 
 
 A force whose intensity is equal to one pound 
 acting through the distance of one foot, does an 
 amount of work equal to one foot-pound. 
 
 Work is to be distinguished from the more gen- 
 eral term energy . 
 
 Work, Electric 
 
 Joule.} 
 
 The product of the volts by the coulombs. 
 I joule = 10,000,000 ergs, or .73732 foot-pounds. 
 
 " = i volt-coulomb. 
 
 " =1 watt for I second. 
 
 Work, Electric, Unit of The volt- 
 coulomb or joule. (See Volt-Coulomb. Joule?) 
 
 Work, Unit of - The erg. 
 
 The amount of work done when a force of 
 one dyne acts through the distance of one 
 centimetre. (See Erg.} 
 
 Raising one gramme against gravity, through 
 the distance of one centimetre, requires an 
 amount of work equal to 980 ergs. 
 
 Work, Units of Various units em- 
 ployed for the measurement of work. 
 
 The following table of Units of Work is taken 
 from Hering's work on Dynamo-Electric Ma- 
 chines : 
 
 WORK. 
 
 I erg = i dyne-centimetre. 
 
 I " = .0000001 joule. 
 
 I gramme-centimetre . . =981.00 ergs. 
 
 I " . . = .ooooi kilogr. -metre. 
 
 I foot-grain = 1937 5 ergs. 
 
 f 10,000,000 
 
 7373 2 4 
 
 pound, .101937 
 = \ kilogram - metre, 
 .0013592 metric 
 horse power for 
 i one second. 
 .0013406 horse-power 
 
 for one second. 
 " =.0009551 pound- 
 
 " Fah., heat unit. 
 
 " = .0005306 pound- 
 
 Centig. , heat unit. 
 
 " = .OCO24O7 kilogr.- 
 
 Centig.. heat unit. 
 ' = .0002778 wan -hour. 
 
 I foot-pound = 13562600 ergs. 
 
 " = 1.35626 joules. 
 
 " = . 13825 kilogr. metre. 
 
 " =.0018434 metric 
 
 horse-power for 
 
 e second. 
 
 " ..i, =.00181818 horse- 
 
 power for one 
 rrcond. 
 
 i joule, or i volt-cou- ") 
 lomb, or I watt 
 during every second 
 or i volt-ampere 
 during every 
 second . . 
 
 ergs, 
 foot - 
 
 i volt ampere during 
 every second 
 
 i _. 
 
Wor. 
 
 56U 
 
 [Wor. 
 
 I foot-pound = .0012953 pound- 
 
 Fah., heat unit. 
 
 " ,.... = .0007196 pound- 
 
 Centig., heat unit. 
 
 " = .0003264 k i 1 o g r . - 
 
 Centig., heat unit. 
 
 " = .0003767 watt-hour. 
 
 I kilogram-metre =98 100000 ergs. 
 
 " = 9.81000 joules. 
 
 " = 7.23314 foot-pounds. 
 
 " = .01333 metric horse- 
 
 power for one 
 second. 
 
 11 =.013151 horsepower 
 
 for one second. 
 
 " = .009369 pound-Fah., 
 
 heat unit. 
 
 " =.005205 pound- 
 
 Centig., heat unit. 
 
 " = .002361 kilogr.- 
 
 Centig., heat unit. 
 
 " = .002725 watt-hour. 
 
 I watt-hour = 3600 joules. 
 
 " = 2654.4 foot-pounds. 
 
 " =366.97 kilogram. 
 
 metres. 
 
 " =3-4383 pound-Fah., 
 
 heat units. 
 
 44 = 1.9102 pound- 
 
 Centig., heat units. 
 
 " =.8664 kilogr.- 
 
 Centig., heat units. 
 
 " =.0013592 metric 
 
 horse- power-hour. 
 
 " =.0013406 horse. 
 
 power-hour. 
 I metric h.-p.-hour . . . . = 2648700 joules. 
 
 " . . . . = 1952940 foot-pounds. 
 
 " ....=270000 kilogram- 
 
 metres. 
 " . . . . = 2529.7 pound-Fah., 
 
 heat units. 
 
 41 .... = 1405.4 pound- 
 
 Centig. , heat units. 
 
 44 . . . . = 637.5 kilogr. -Centig., 
 
 heat units. 
 
 . . . . = 735-75 watt-hours. 
 * . . . . = .98634 horse-power* 
 
 hour. 
 
 I norse-power-hour = 2685400 joules. 
 
 kt .... = 1980000 foot- 
 
 pounds. 
 
 " ....=273740 kilogram- 
 
 metres. 
 
 I horse-power-hour = 2564.8 pound-Fah., 
 
 heat units. 
 
 " .... = 1424.9 pound- 
 
 Centig. , heat units. 
 
 " =646.31 kilogr.- 
 
 Centig., heat units. 
 
 " = 745.941 watt-hours. 
 
 " = 1.01385 metric horse- 
 
 power-hour. 
 HEAT. 
 
 I gram-Centig = .001 kilogram -Centi- 
 grade. 
 
 I pound-Fahr = 1047.03 joules. 
 
 " = 772 foot-pounds. 
 
 " = 106.731 kilogram- 
 
 metres. 
 
 " =.55556 pound-Centi- 
 
 grade. 
 
 " =.25200 kilogram- 
 
 Centigrade 
 
 " = .29084 watt-hour. 
 
 * = .0003953 metric 
 
 horse - power-hour. 
 
 " = .0003899 horse- 
 
 power hour. 
 
 i pound-Centig = 18.84.66 joules. 
 
 " = 1389.6 foot-pounds. 
 
 " = 192. 1 16 kilogram- 
 
 metres. 
 
 " = 1.8000 pound- 
 
 Fahrenheit. 
 
 " = .4536 kilogram-Centi- 
 
 grade. 
 
 44 = .52352 watt-hours. 
 
 " ... =.0007115 metric 
 
 horse - power-hour. 
 
 " =.0007018 horse- 
 
 power-hour. 
 
 i kilogram-Centig = 4154.95 joules. 
 
 " = 3063.5 foot-pounds. 
 
 " =423.54 kilogram- 
 
 metres. 
 
 ' =3.9683 pound- 
 
 Fahrenheit. 
 
 =2.2046 pound-Centi- 
 
 grade. 
 
 " = 1.1542 watt hours. 
 
 * = .001569 metric horse- 
 
 power-hour. 
 
 " .....= .0015472 horse- 
 
 power-hour. 
 
 Working, Direct 
 
 The transmis- 
 
Wor.] 
 
 561 
 
 [Yok. 
 
 sion of signals over a telegraph line with- 
 out the use of relays or repeaters. 
 
 Working, Multiple, of a Dynamo-Elec- 
 tric Machine A term sometimes used 
 
 for the parallel working of dynamo-electric 
 machines. (See Working, Parallel, of Dy- 
 namo-Electric Machines.) 
 
 Working:, Parallel, of Dynamo-Electric 
 
 Machines The operation of working 
 
 several dynamo-electric machines as a single 
 source, by connecting them with one another 
 in parallel or multiple arc. 
 
 The effect of parallel working is to reduce the 
 internal resistance of the dynamo. 
 
 If a current be required in a circuit at an electro- 
 motive force equal only to that of a single machine, 
 and the requirements of the circuit are equal to 
 the output of more than a single dynamo, a num- 
 ber of dynamos must then be coupled in mul- 
 tiple. 
 
 Working, Reverse-Current A 
 
 term sometimes used in telegraphy for a 
 method of working by means of a double 
 current in place of a single current. 
 
 The double-current system of working was de- 
 vised by Varley to permit Morse characters to be 
 sent rapidly through underground conductors. 
 In order to avoid the retardation due to induction, 
 the current was reversed between each signal. 
 This reversion in the conductor hastened the dis- 
 charge of the conductor. 
 
 Working, Series, of Dynamo-Electric 
 
 Machines Such a coupling of several 
 
 dynamo-electric machines as will deliver the 
 current supplied by them in series. . 
 
 As in all series connections of sources, there re- 
 sults an electromotive force equal to the sum of 
 the electromotive forces of the different dynamos. 
 
 Worming, Cable A central core of 
 
 hemp or jute around which are wrapped the 
 several separate conductors of a cable con- 
 taining more than a single separate conduc- 
 tor. 
 
 Wood's Button Repeater. (See Repeat- 
 ers, Telegraphic.) 
 
 Wrapped Wire. (See Wire, Wrapped.) 
 
 Writing, Electrolytic Imprinting 
 
 written characters on cloths, or other textile 
 fabrics, by the electrolytic decomposition of a 
 dyeing substance with which they are im- 
 pregnated. 
 
 The cloths, etc., to be written on, are impreg- 
 nated with an aniline salt, and placed on an insu- 
 lated metallic plate next to the salt, which is con- 
 nected to one pole of an electric source. The 
 other pole is connected to a carbon electrode, 
 which is used as the writing stylus or pencil. By 
 suitably connecting the terminals the writing is 
 obtained in color on a white ground, or in white 
 on a colored ground. (See Dyeing, Electric.) 
 
 Writing Telegraphy. (See Telegraphy, 
 Writing.) 
 
 T-Shaped Sparks. (See Spark, 
 Y-Shaped) 
 
 Yale-Lock-Switch Burglar Alarm. (See 
 Alarm, Yale-Lock-Switch Burglar) 
 
 Yoke, Multiple-Brush - A term 
 sometimes applied to multiple brush rocker 
 of a dynamo or motor. (See Rocker, Mul- 
 tiple-Pair Brush.) 
 
 Yoke,' Multiple-Pair Brush A 
 
 device for holding a number of pairs of 
 brushes of a dynamo-electric machine in such 
 
 a manner that they can be readily moved or 
 rotated on the commutator cylinder. 
 
 The brushes are placed side by side on the com- 
 mutator cylinder. In such cases the several pairs 
 of brushes are so arranged that they can be 
 thrown off or out of contact with the commutator 
 cylinder while cleaning the cylinder, without stop- 
 ping the machine. 
 
 Yoke, Single-Brush A term some- 
 times used for single-brush rocker. (See 
 Rocker, Single-Brush.) 
 
Yok.] 
 
 562 
 
 [Zon. 
 
 Yoke, Single-Pair A single-brush 
 
 rocker. (See Rocker, Single-Brush?) 
 
 Yoke, Single-Pair Brush A device 
 for holding a single pair of collecting brushes 
 of a dynamo-electric machine in such a way 
 
 that they can be readily moved or rotated on 
 the commutator cylinder. 
 
 Yoked-Horseshoe Electro-Magnet. (See 
 Magnet, Electro, Yoked-Horseshoe.} 
 
 Z. A symbol sometimes used in electro- 
 therapeutics for contraction. 
 
 The use of Z, is for the purpose of avoiding 
 the letter C, which has already been used for cur- 
 rent or ampere in Ohm's law. Increasing 
 strengths of contraction are represented by Z', 
 Z", Z'". 
 
 Z. A symbol for electro-chemical equiva- 
 lent. 
 
 Zero, False A zero taken midway 
 
 between any two equal and opposite deflec- 
 tions of a measuring instrument. 
 
 Zero, Inferred A zero deduced or 
 
 inferred from the deflection produced by a 
 charge that is to be measured by comparison 
 with the value of the deflection by means of 
 a known charge in an electrical measuring 
 instrument. 
 
 An inferred zero is usually completely off the 
 scale, hence its name. It does not actually exist. 
 
 Zero Methods. (See Method, Null or 
 Zero.} 
 
 Zero Potential. (See Potential, Zero.} 
 
 Zero, Shifting A zero that changes 
 or shifts in position ; a polar zero in a measur- 
 ing instrument. 
 
 Zigzag Electro-Magnet. (See Magnet, 
 Electro, Zigzag} 
 
 Zigzag Electromotive Force. (See 
 Force, Electromotive, Zigzag} 
 
 Zigzag Lightning. (See Lightning, Zig- 
 zag} 
 
 Zinc, Amalgamation of - The cov- 
 ering or amalgamation of zinc with a layer 
 of mercury. 
 
 To amalgamate a plate of zinc, its surface is 
 first thoroughly cleaned by immersing the plate in 
 dilute sulphuric acid of about I part of acid to 
 
 10 or 12 parts of water. A few drops of 
 mercury are then rubbed over its surface, thus 
 coating it with a bright metallic film of zinc 
 amalgam. Care must be taken not to use too 
 much mercury, since the zinc plate would thus be 
 rendered brittle. 
 
 Zinc-Carbon Voltaic Cell. (See Cell, 
 Voltaic, Zinc-Carbon} 
 
 Zinc-Copper Voltaic Cell. (See Cell, 
 Voltaic, Zinc-Copper} 
 
 Zinc, Crow-Foot A crow-foot- 
 shaped zinc used in the gravity voltaic cell. 
 (See Cell, Voltaic, Gravity} 
 
 The term "crow-foot " refers to the shape of 
 the claws. It is hardly a happy term. 
 
 Zinc-Lead Voltaic Cell. (See Cell, Vol- 
 taic, Zinc-Lead} 
 
 Zinc Sender. (See Sender, Zinc} 
 
 Zincode of Voltaic Cell. A term for- 
 merly employed to indicate the zinc terminal 
 or electrode of a voltaic cell. 
 
 The negative electrode or kathode are prefer- 
 able terms. 
 
 Zone, Anelectrotonic A name 
 
 sometimes given to the polar zone. (See 
 Zone, Polar} 
 
 Zone, Kathelectrotonic A name 
 
 sometimes given to the peripolar zone. (See 
 Zone, Peripolar} 
 
 Zone, Peripolar A term proposed 
 by De Watteville for the zone or region sur- 
 rounding the polar zone on the body of 
 a patient undergoing electro-therapeutic 
 treatment. 
 
 Zone, Polar A term proposed by 
 
 De Watteville for the zone or region surround- 
 ing the therapeutic electrode applied to the 
 human body for electric treatment. 
 
APPENDIX 
 
 References to Words, Terms and Phrases which appear in the Appendix are preceded by the 
 words "See Appendix"; all other references apply to the main portion of the Dictionary. 
 
 A. A symbol proposed for ampere, the 
 practical unit of electric current. 
 
 a. A symbol proposed but not adopted 
 for acceleration. 
 
 The defining equation is a = 
 
 This letter is sometimes, though rarely, 
 employed as the symbol for ampere. 
 
 a. A symbol proposed for angle ex- 
 pressed in circular measure. 
 
 SLTC 
 
 The defining equation is a= : 
 
 radius 
 
 A. li. An abbreviation used for ampere 
 hour, a commercial unit of electric quan- 
 tity. 
 
 A. t. An abbreviation lor ampere-turn, 
 a practical unit of magneto-motive force. 
 
 Abscissas. Plural of abscissa. 
 
 Absorptive. Possessing the power of ab- 
 sorption. (See Absorption.} 
 
 Acceleration, Angular The time 
 
 rate of change of angular velocity. 
 
 Accumulation Method for Testing Joints 
 in Electric Cables. (See Appendix 
 Method, Accumulation, for Testing Joints 
 in Electric Cables.} 
 
 Accumulator, Bi-Metallic A term 
 
 applied to a secondary or storage cell in 
 which two different metallic substances are 
 employed in connection with a single elec- 
 
 trolytic fluid composed of a solution of a 
 salt of one of the metals of the plates. 
 
 Many different bi-metallic accumulators 
 have been designed; for example, the cop- 
 per-lead accumulator, in which plates of 
 copper and lead are immersed in an electro- 
 lyte of copper sulphate; or the copper-zinc ac- 
 cumulator, in which plates of zinc and copper 
 are immersed in an electrolyte of zinc sul- 
 phate; or the zinc-lead accumulator, in which 
 plates of zinc and lead are immersed in an 
 electrolyte of zinc sulphate. 
 
 Accumulator, Charge A term 
 
 sometimes employed for a Leyden jar or 
 condenser. (See Jar, Leyden. Condenser.") 
 
 Accumulator, Copper-Lead An 
 
 electro-chemical or electrolytic accumula- 
 tor consisting of plates of copper and lead 
 immersed in a solution of copper sulphate. 
 
 Accumulator, Copper-Zinc An 
 
 electro-chemical or electrolytic accumu- 
 lator consisting of plates of copper and 
 zinc immersed in a solution of zinc sul- 
 phate. 
 
 Accumulator, Current A term 
 
 sometimes employed for a Barlow wheel 
 when used as an electrical accumulator. 
 (See Accumulator.} 
 
 A series-wound dynamo-electric machine 
 
 constitutes in reality a current accumulator. 
 
 Accumulator, Electro-Chemical 
 
 563 
 
Ace. j 564 
 
 The name generally given to the ordinary 
 secondary or storage battery, in which the 
 difference of potential is produced by 
 chemical action. (See Cell, Storage.} 
 
 Accumulator, Electrolytic An 
 
 electro-chemical accumulator. (See Appen- 
 dix Accumulator, Electro- Chemical.} 
 
 Accumulator, Storage A term 
 
 sometimes employed for storage cell. (See 
 Cell, Storage.} 
 
 Accumulator, Zinc-Lead An elec- 
 trolytic accumulator consisting of plates of 
 zinc and lead immersed in a solution oi 
 line sulphate. 
 
 Acoustic Interference. (See Appendix 
 Interference, Acoustic.} 
 
 Acoustic Resonance. (See Appendix 
 Resonance, Acoustic?) 
 
 Acoustic Telegraph. (See Appendix 
 Telegraph, Acoustic.} 
 
 Actinometer. An instrument devised to 
 Measure the relative intensity of the sun's 
 rays, or of such artificial light as the elec- 
 tric light, etc., etc, 
 
 The actinic power of the sun's rays to 
 cause chemical decomposition varies with 
 the condition of the atmosphere and the 
 position of the sun above the horizon. 
 
 Action, Gyrostatic, of Dynamos on Ship- 
 board The action which occurs at 
 
 the bearings of a dynamo running on board 
 a tossing ship, whereby gyrostatic stresses 
 are set up. 
 
 Action, Protective A term pro- 
 posed for the protective action afforded by 
 a magnetic field to paramagnetic metals 
 when exposed to chemical action. 
 
 The proposed term is not good in view of 
 the fact that it is used to cover a number of 
 other kinds of protective actions. 
 
 Experiments as to the protective action of 
 a magnetic field on iron, nickel and cobalt 
 were undertaken by Prof. Rowland and Dr. 
 Bell. The results of these experiments, as 
 stated by the experimenters, are as follows : 
 
 [Ala. 
 
 "When the magnetic metals are exposed 
 to action in a magnetic field, such action is 
 decreased or arrested at any points where 
 the ratio of the variation of the square of the 
 magnetic force tends towards a maximum." 
 
 The results obtained by Rowland and Bell 
 were apparently at variance with some more 
 recent experiments of Squier, and showed 
 that the currents produced by couples of 
 similar metals when exposed to chemical 
 action in a magnetic field had a direction of 
 flow through the liquid from the magnetized 
 to the non-magnetized electrode i. e., in the 
 opposite direction to that pointed out by 
 Squier in the phenomena of the protective 
 throw. (See Appendix Throw, Protective.) 
 
 Adielectric. A term proposed for sub- 
 stances that are not dielectrics, that is, 
 substances whose electric conductivity at 
 ordinary temperatures decreases as the tem- 
 perature increases. 
 
 Adjustable Rheostat. (See Appendix 
 Rheostat, Adjustable.} 
 
 Aelotropic. Heterogeneous with respect 
 to direction. 
 
 Aelotropic Medium. (See Appendix 
 Medium, Aelotropic.) 
 
 After-Working of Dielectric. (See Ap- 
 pendix Dielectric, After-Working of.} 
 
 Age-Coating of Chamber of Incandescent 
 Electric Lamp. (See Appendix Chamber 
 of Incanaescent Electric Lamp, Age- Coat- 
 ing of.} 
 
 Ageing of Incandescent Electric Lamp. 
 (See Appendix Lamp, Incandescent 
 Electric, Ageing of.} 
 
 Agglomerate Leclanche' Voltaic Cell. 
 (See Appendix Cell, Voltaic, Agglomerate 
 Leclanche.} 
 
 Air Telegraphy. (See Appendix Teleg- 
 raphy, Air.} 
 
 Alarm, Frost An alarm sounded 
 
 or set in operation by means of mechan- 
 ism operated by a fall of temperature to or 
 below 32 F. 
 
 Alarm, Photo-Electric A selenium 
 
All.] 
 
 505 
 
 [AH. 
 
 cell proposed for use in connection with the 
 circuit of an electric source and suitable 
 electro-receptive devices, so as to, permit 
 the passage of a stronger current through 
 the circuit and the consequent sounding of 
 an alarm on the exposure of one of its faces 
 to the light. 
 
 By means of this device a burglar, carry- 
 ing a light, can be made automatically to ring 
 an alarm bell, and thus call the attention of 
 a watchman or policeman to his presence. 
 
 Allotropism. Allotropy. (See Allo- 
 tropy.} 
 
 Alternating Current Arc. (See Appendix 
 Arc, Alternating Current.} 
 
 Alternating Current Potentiometer. 
 
 (See Appendix Potentiometer, Alternat- 
 ing Current.} 
 
 Alternating Current Rotary Transformer. 
 
 (See Appendix Transformer, Alternat- 
 ing Current Rotary.} 
 
 Alternating Electromotive Force. (See 
 Appendix Force, Electromotive, Alternat- 
 ing.} 
 
 Alternation, Periodicity of The 
 
 number of alternations per second pro- 
 duced by a generator. 
 
 The term periodicity of alternation is 
 synonymous with frequency, a briefer and 
 more commonly employed word. 
 
 When any particular periodicity or fre- 
 quency is spoken of, as, for example, 250 
 alternations per second, 125 complete periods 
 or cycles per second are meant. 
 
 Commercially, the word alternations is 
 used for half-periods or double-frequencies. 
 A dynamo with 250 alternations per second 
 has 125 periods per second. 
 
 Alternations, Co-phasal Alterna- 
 tions whose electromotive forces similarly 
 and simultaneously vary. 
 
 The maximum and minimum electromo- 
 tive forces of co-phasal alternations are both 
 simultaneously and similarly directed. 
 
 Any number of periodic functions are said 
 
 to be co-phasal when the ratio between their 
 instantaneous values is constant ; when one 
 is a maximum all the remainder will be 
 maxima, and when one is a minimum all the 
 remainder will be minima. 
 
 Alternator, Compensated An al- 
 ternating current dynamo-electric machine 
 for sustaining a uniform voltage at some 
 point of its circuit under varying loads, 
 in which the field magnets are excited 
 partly by rectified or commuted currents 
 taken from separate armature coils, and 
 partly by currents furnished by the com- 
 muted current from a small transformer, 
 whose primary coil is placed in the main 
 circuit. 
 
 Alternator, Compound An alter- 
 nating current dynamo-electric machine 
 whose field magnets are compound-wound. 
 
 The current from the machine is commonly 
 run through a series transformer whose sec- 
 ondary winding is connected with the field 
 magnets through a commutator. 
 
 Alternator, Magnetic An alter- 
 nating dynamo-electric machine in which 
 permanent field magnets are employed. 
 
 Alternator, Magneto A term 
 
 sometimes employed for magnetic alter- 
 nator. (See Appendix Alternator, Mag- 
 netic.} 
 
 Alternator, Multiphase An alter- 
 nating current dynamo capable of produc- 
 ing multiphase currents. 
 
 Alternator, Separate-Coil An al- 
 ternating current dynamo-electric machine 
 in which the field magnets are excited by 
 means of current taken from the coils on 
 the armature, which current is first recti- 
 fied, or caused to flow in one and the same 
 direction, by means of a commutator. 
 
 Alternator, Separately-Excited An 
 
 alternating current dynamo-electric ma- 
 chine in which the field magnets are ex- 
 cited by means of current furnished from a 
 separate source. 
 
JLU.] 
 
 566 
 
 [Amp. 
 
 Alternator, Two-Phase An alter- 
 nating current dynamo capable of produc- 
 ing two-phase currents. 
 
 The term di-phase alternator would appear 
 to be preferable. 
 
 Alternators, Parallel Connection of 
 
 The connection of two or more alternat- 
 ing current dynamo-electric machines in 
 parallel, so as to form a single electric 
 source. 
 
 When two alternating current dynamo- 
 electric machines are connected in parallel, 
 if the armature self-induction and resistance 
 are not too high, and the engines driving the 
 dynamos are under control, or in other words 
 governed, then such machines, even if out of 
 synchronism, when connected, will almost 
 immediately pull each other into synchron- 
 ism, each promptly exercising an automatic 
 control over the other. 
 
 When alternators possess marked synchro- 
 nizing power, care must be exercised to 
 adjust them fairly to equality of E. M. F. 
 and phase, in order that they may not be in- 
 jured by mechanical shock due to excessive 
 cross currents, when first connected in 
 parallel. A certain amount of armature self- 
 induction is therefore desirable to render 
 parallel working safe. 
 
 It is a matter of prime importance in the 
 parallel running of alternators that the 
 shape of the wave of E. M. F. is the same in 
 all machines. Otherwise cross currents will 
 flow between the machines under all adjust- 
 ments. A difficulty is occasionally experi- 
 enced in the parallel connection of alternators 
 of different size, due to differing wave form. 
 
 Alternators, Parallel, Hunting of 
 
 A periodical increase and decrease in the 
 speed of alternators when running in 
 parallel connection as motors or as 
 dynamos under certain conditions. 
 
 Alternators, Series Connection of 
 
 The connection of two or more alternating 
 current dynamo-electric machines in series, 
 so as to form a single electric source. 
 
 The series connection of alternating dyna- 
 mo-electric machines is impracticable in or- 
 
 dinary work; for, should such connection be 
 made when the two machines are furnishing 
 currents in the same phase, as soon as either 
 machine' differs in the slightest degree in 
 phase from the other such difference would 
 tend to rapidly increase, until the two ma- 
 chines were in opposite phases, when, of 
 course, no current would be produced. Hence, 
 alternators can be run in series only when 
 their armatures are mechanically and rigidly 
 connected with each other. 
 
 Amalgamating Solution. (See Appendix 
 Solution, Amalgamating.) 
 
 Amalgamator, Electric Any ap- 
 paratus for the electrical treatment of gold 
 or silver ores with mercury. 
 
 An electric amalgamator consists essen- 
 tially of an amalgamator driven by elec- 
 tric instead of by ordinary mechanical power. 
 
 American Morse Code. (See Appendix 
 Code, American Morse.} 
 
 Ammeter, Steel-Yard A form of 
 
 ammeter in which the strength of the cur- 
 rent is measured by means of the electro- 
 magnetic forces applied to one extremity 
 of a steel-yard lever provided with sliding 
 weights for balancing these forces. 
 
 Ampere, B. A. Such a current as 
 
 would deposit 0.001118 gramme of silver 
 per second from a neutral solution of 
 nitrate of silver in distilled water. 
 
 This value of the ampere was adopted by 
 the British Association at its meeting held in 
 Edinburgh in August, 1892, the English 
 Board of Trade, and by the Chicago Congress 
 of 1893. 
 
 Equal to the international ampere. 
 
 Ampere-Centimetre. A term proposed 
 as a unit of magnetism. 
 
 The ampere-centimetre as a unit of mag- 
 netism is based on an assumption denied by 
 some that any unit length of circuit, say one 
 centimetre, conveying a unit current of one 
 ampere, will generate a constant number of 
 lines of magnetic force. 
 
 The proposed unit has not been accepted. 
 
 Ampere, International r The value 
 
Amp.] 
 
 567 
 
 [App. 
 
 of the international ampere adopted by the 
 Chicago Congress ot 1893 as equal to one- 
 tenth of the unit of current of the C. G. S. 
 system of electro-magnetic units, and 
 which is represented sufficiently well for 
 practical use by the unvarying current 
 which when passed through a solution of 
 nitrate of silver in water, and in accord- 
 ance with certain specifications, deposits 
 silver at the rate of o.oomS of a gramme 
 per second. 
 
 Ampere Meter, Milli An ampere 
 
 meter, which measures in milli-amperes 
 the current passing through it. 
 
 Ampere Yards. (See Appendix Yards, 
 Ampere.] 
 
 Anaesthesia. Insensibility, especially to 
 pain. 
 
 Anaesthesia, Electric Nervous in- 
 sensibility produced by means of electricity. 
 
 Local anaesthesia is obtained by means of 
 induction apparatus in which the number of 
 makes and breaks can be readily varied. It 
 has been found in certain cases, when the 
 makes and breaks follow one another with a 
 given rapidity, which can be determined by 
 means of the musical note produced, that such 
 slight operations as the lancing of a felon can 
 readily be performed without pain, after the 
 part has been subjected to the action of the 
 current for but a few minutes. 
 
 Anemograph, Electric An ap- 
 paratus for electrically registering the direc- 
 tion and velocity of the wind. 
 
 Angle of Maximum Sensitiveness of Gal- 
 vanometer. (See Appendix Galvanom- 
 eter, Angle of Maximum Sensitive- 
 ness of.) 
 
 Angle, Phase The angle com- 
 prised between two different current 
 maxima. 
 
 Angular Acceleration. (See Appendix 
 Acceleration, Angular.) 
 
 Annunciator, Speaking-Tube An 
 
 oral annunciator. (See Annunciator, Oral.) 
 
 Annunciator, Swinging 
 
 A pendu- 
 
 lum annunciator. (See Annunciator, Pen- 
 dulum.) 
 
 Annunciator Wire. (See Appendix 
 Wire, Annunciator.} 
 
 Anodic Kays of Vacuum Tube. (See Ap- 
 pendix Rays, Anodic, of Vacuum Tube.) 
 
 Anomalous Helix. (See Appendix 
 Helix, Anomalous.} 
 
 Anomalous Solenoid. (See Appendix 
 Solenoid, Anomalous.} 
 
 Anomalous Spiral. (See Appendix 
 Spiral, Anomalous.} 
 
 Anti-Node. The point on a vibrating 
 body midway between two successive nodes. 
 (See Appendix Node.} 
 
 The point of maximum motion in a vibrat- 
 ing body. 
 
 Apparatus, Individual Signalling 
 
 Any apparatus by means of which individ- 
 ual signals are operated. (See Appendix 
 Signal, Individual.} 
 
 Lockwood arranges the different methods 
 according to which individual signals can be 
 operated underthe following heads, namely: 
 
 (i.) Signals operated at each sub-station or 
 circuit with different strengths of current. 
 
 (2.) Signals operated by currents of op- 
 posed direction. 
 
 (3-) Signals operated both by changes in 
 the strength and direction of the current. 
 
 (4.) Electro-magnetic step-by-step devices, 
 acting to bring the sub-station signals to a 
 ringing point differing for each sub-station, 
 and then to close a local branch or shunt cir- 
 cuit, including a local bell, to operate alter, 
 nating mechanism, or in some way to 
 introduce a bell magnet into the circuit. 
 
 (5.) Signals operated by means of various 
 arrangements of clockwork bells. 
 
 (6.) Signals operated by means of galva- 
 nometers, the movements of whose needles 
 cause bells to ring. 
 
 To which may be added, signals operated 
 by currents of different periodicity. 
 
 Apparatus, Polyphase Apparatus 
 
App.J 
 
 568 
 
 [Arm. 
 
 operated by polyphase currents. (See Ap- 
 pendix Currents, Polyphase.} 
 
 Apparatus, Selective Signalling A 
 term sometimes used in place of indi- 
 vidual signalling apparatus. (See Appendix 
 Apparatus, Individual Signalling.} 
 
 Apparent Resistance. (See Appendix 
 Resistance, Apparent.} 
 
 Arc, Alternating Current - An arc 
 formed by means of an alternating current. 
 
 Since in the alternating current the elec- 
 trodes become alternately positive and nega- 
 tive, neither carbon in the case of a carbon 
 arc is markedly brighter than the other, and 
 the rate of consumption of both carbons is 
 the same. 
 
 Arc, Carbon A voltaic arc formed 
 
 between two carbon electrodes. 
 
 The carbon voltaic arc is the one ordina- 
 rily employed, and is formed through a cloud 
 of volatilized carbon. (See A re, Voltaic.} 
 
 Arc, Common, of Aurora Glory 
 
 The inner or common arc of an aurora 
 glory. (See Appendix Glory, Aurora.} 
 
 Arc, Continuous Current A vol- 
 taic arc produced by means of a continu- 
 ous electric current. 
 
 In a continuous current arc the light is 
 principally emitted from a crater in the posi- 
 tive carbon. 
 
 Arc, Copper A voltaic arc formed 
 
 between two copper electrodes. 
 
 A copper arc is formed through a cloud of 
 volatilized copper. Most metallic arcs are 
 longer than carbon arcs. They possess the 
 characteristic color of the volatilized metal; 
 for example, the copper arc is green. (See 
 Arc, Voltaic.} 
 
 A copper or other metallic arc would be 
 formed from copper or other metallic rod if it 
 formed the. positive electrode, and a block of 
 carbon or other non-metallic substance 
 formed the negative electrode, since it is the 
 material of the positive electrode that is vola- 
 tilized. 
 
 Arc Lighting Dynamo-Electric Machine. 
 
 3 Vol. 2 
 
 (See Appendix Machine, Dynamo- 
 Electric, Arc Lighting} 
 
 Arc, Two Thousand Candle Power, Pro- 
 posed Definition for The light of an 
 arc produced by 10 amperes of current 
 and 45 volts potential difference between the 
 carbons. 
 
 A 45O-watt arc restricted as above. 
 
 Such an arc is sometimes called a full arc. 
 
 The difficulty in measuring the photometric 
 intensity of a continuous current carbon arc 
 is so great that considerable controversy has 
 arisen as to whether or not a given candle 
 power is present in certain cases. This dif- 
 ficulty arises not only from the fact that the 
 light is of much greater intensity in certain 
 directions than in others, but also from the 
 fact that the candle power of an arc having 
 a certain watt value may differ greatly with 
 the quality of the carbons employed. 
 
 The adoption of the above definition would, 
 therefore, seem to be extremely advisable. , 
 
 Armature, Balanced An armature 
 
 of an electro-magnet whose motion to- 
 ward or from the magnetic poles is op- 
 posed by the pull of a spring, or the action 
 of a weight, so that on the cessation of the 
 magnetic attraction the armature will be 
 caused to assume the position it had before 
 the magnetic action began. 
 
 Strictly speaking, such an armature is not 
 balanced; the term, however, is a convenient 
 one. 
 
 Armature, Balanced An armature 
 
 of a dynamo-electric machine so constructed 
 or adjusted that the line joining the centres 
 of inertia of all its cross sections practically 
 coincides with the axis of rotation. 
 
 A balanced dynamo armature runs 
 smoothly and without mechanical jars or 
 vibrations. 
 
 Armature, Balanced An armature 
 
 of a dynamo or motor in which the winding 
 is such as to insure electrical symmetry. 
 
 Armature, Coreless, of Dynamo or Motor 
 
 An armature of a dynamo or motor 
 
Arm,] 
 
 569 
 
 [Ato. 
 
 not provided with a core of iron or other 
 magnetizable material. 
 
 Armature, Di-Phase An armature 
 
 of a motor wound so as to be operated by 
 di-phase currents. 
 
 Armature, Magnetic Sticking of 
 The adherence of the armature of an elec- 
 tro-magnet to the poles, after the current 
 has ceased to pass through the magnetizing 
 coils. 
 
 The cause of sticking is to be ascribed to 
 the residual magnetism. 
 
 Sticking is sometimes avoided by means 
 of core pins, or by a non-magnetizable coat- 
 ing of armature or core. (See Appendix 
 Pins, Core.) 
 
 Armature, Polyphase An arma- 
 ture of a motor wound so as to be operated 
 by polyphase currents. 
 
 Armature Reaction. (See Appendix 
 Reaction, Armature,) 
 
 Armature, Three-Phase A tri- 
 
 phase armature. (See Appendix Arma- 
 ture, Tri-Phase.} 
 
 The term tri-phase armature would appear 
 to be preferable. 
 
 Armature, Tri-Phase An arma- 
 ture of a motor wound so as to be operated 
 by tri-phase currents. 
 
 Armature, Two-Phase A di-phase 
 
 armature. (See Appendix Armature, Di- 
 Phase.) 
 
 The term di-phase armature would appear 
 to be preferable. 
 
 Arms, Side A term applied to the 
 
 supports for the bearings of railway mo- 
 tors. 
 
 Arrival Curve of Telegraphic Circuit. 
 
 (See Appendix Curve, Arrival, of Tele- 
 graphic Circuit.) 
 
 Arriving Current of Telegraphic Circuit. 
 
 (See Appendix Current, Arriving, of 
 Telegraphic Circuit.) 
 
 Asbestos-Porcelain. A porous substance 
 somewhat resembling ordinary porcelain. 
 
 Asbestos-porcelain is made by obtaining 
 asbestos fibres in an exceedingly fine powder 
 and forming this powder into a paste with 
 water, consolidating it under heavy press- 
 ure, and subsequently exposing the dried 
 particles to the effects of a high temperature. 
 
 Asbestos-porcelain, it is claimed, forms a 
 material which, though resembling ordinary 
 porcelain, is highly porous. It has been suc- 
 cessfully used for the porous cells of voltaic 
 batteries, for which purposes it is claimed to 
 offer a better conducting path for the current 
 than the ordinary unglazed earthenware gen- 
 erally employed for such purposes. (See Cell* 
 Porous.} 
 
 Astatic Multiplier. (See Appendix 
 Multiplier, Astatic.} 
 
 Atmosphere, Electric A term for- 
 merly employed for a space filled with 
 electric effluvia. (See Appendix Effluvia, 
 Electric.} 
 
 A term sometimes employed for an elec- 
 tro-static field. 
 
 A space occupied by or permeated with 
 electric sparks or glow. 
 
 Atmosphere, Magnetic A term 
 
 formerly employed for a space filled with 
 magnetic effluvia. (See Appendix 
 Effluvia, Magnetic.} 
 
 A term sometimes employed for a mag- 
 netic field. 
 
 Atom, Dyad An atom whose val- 
 ency, atomicity or combining power is two. 
 (See Atomicity. Element.} 
 
 Atom, Heptad An atom whose 
 
 valency or atomicity is seven. (See Atom- 
 icity. Element.} 
 
 Atom, Hexad An atom whose 
 
 valency or atomicity is six. (See Atomicity. 
 Element} 
 
 Atom, Monad An atom whose 
 
 valency or atomicity is one. (See Atomicity. 
 Element.) 
 
 Atom, Pentad An atom whose 
 
 valency or atomicity is five. (See Atom- 
 icity. Element.) 
 
Ato.] 
 
 570 
 
 [Bac. 
 
 Atom, Tetrad 
 
 An atom whose 
 
 valency or atomicity is four. (See Atom- 
 icity. Element?) 
 
 Atom, Triad An atom whose 
 
 valency or atomicity is three. (See Atom- 
 icity. Element.} 
 
 Atomic. Of or pertaining to the atom. 
 (See Atom.) 
 
 Attachment, Electric Clamp A 
 
 device employed in connection with a floor 
 push, adapted for ready clamping to a 
 table or other support for the purpose of 
 holding a push button electrically con- 
 nected with the floor push. 
 
 Attachment Plug. (See Appendix Plug, 
 Attachment.') 
 
 Audible Telegraphic Signal. (See Ap- 
 pendix Signal, Telegraphic, Audible.} 
 
 Audiometer. A word sometimes used in 
 place of Sonometer. (See Appendix Sonom- 
 eter.} 
 
 Aura, Electric A term formerly 
 
 employed for the breeze produced by elec- 
 tric convection. (See Convection, Electric.} 
 
 Aurora, Electrostatic A luminous 
 
 phenomenon attending the production of an 
 electrostatic corona. (See Appendix 
 Corona, Electrostatic.} 
 
 Aurora Glory. (See Appendix Glory, 
 Aurora.} 
 
 Aurora, Polar A term sometimes 
 
 used indifferently for the aurora borealis, 
 or the aurora australis. 
 
 Austral Fluid. (See Appendix Fluid, 
 Austral.} 
 
 Auto-Exciting. Self-exciting. 
 
 Auto-Induction. (See Appendix Induc- 
 tion, Auto.} 
 
 Automatic Guard for Series-Connected 
 Incandescent Lamps. (See Appendix 
 Guard, Automatic, for Series-Connected 
 Incandescent Lamps.} 
 
 Automatic Photo-Electric Switch. (See 
 Appendix Switch, Automatic Photo-Elec- 
 tric.} 
 
 Automatic Repeater. (See Appendix 
 Repeater, Automatic?) 
 
 Automatic Telegraph. (See Telegraph, 
 Automatic} 
 
 Automatic Telegraphic Transmitter. 
 
 (See Appendix Transmitter, Automatic 
 Telegraphic.) . 
 
 Auto-Reyersible or Multiple Tele-Radio- 
 phone. (See Appendix Tele-Radiophone, 
 Auto-Reversible or Multiple.) 
 
 Axial Current. (See Appendix Cur- 
 rent, Axial} 
 
 gg. A symbol employed for magnetic 
 induction. 
 
 The defining equation is $:=/* 3C 
 
 B. A. Ampere. (See Appendix Ampere, 
 B. A} 
 
 B. A. Ohm. (See Ohm, B. A.) (See Ap- 
 pendix Ohm, B. A.} 
 
 B. T. U. A contraction for Board of 
 Trade unit, the commercial unit of elec- 
 trical work adopted by the British Board of 
 
 Trade, viz., the kilowatt-hour, or the amount 
 of work which would be accomplished in 
 one hour at the rate of one kilowatt. 
 
 This contraction is a bad one, since it is 
 already employed for British thermal unit. 
 
 B. T. U. A contraction for British 
 thermal unit. 
 
 Back Magnetization. (See Appendix 
 Magnetization, Back.) 
 
 Backing Pan. (See Appendix Pan, 
 Backing.) 
 
Bac. 
 
 571 
 
 [Bat. 
 
 Backward Induction of Dynamo Arma- 
 ture. (See Appendix Induction, Back- 
 ward, of Dynamo Armature.} 
 
 Bad Earth. (See Appendix Earth, 
 Bad.} 
 
 Balance, Coulomb's Electric --- A 
 term sometimes employed for Coulomb's 
 torsion balance when used for measuring 
 the force of electric repulsion. (See Bal- 
 ance, Coulomb's Torsion.} 
 
 Balance, Coulomb's Magnetic Torsion 
 
 -- A nam. sometimes given to Cou- 
 
 lomb's torsion balance when employed to 
 
 measure the force, of magnetic repulsion. 
 
 (See Balance, Coulomb's Torsion.} 
 
 Balance, Duplex --- The condition 
 of a line in duplex telegraphy, when send- 
 ing signals leave the home instruments un- 
 affected and ready for response to received 
 signals, 
 
 Balance, Electro-Dynamic -- A bal- 
 ance form of electro-dynamometer. (See 
 Dynamometer, Electro. Balance, Centi- 
 Ampere.} 
 
 Balanced Armature. (See Appendix 
 Armature, Balanced.} 
 
 Balancing Wire or Conductor. (See 
 Appendix Wire or Conductor, Balanc- 
 
 Barker's Revolving Contact Breaker. 
 
 (See Appendix Breaker, Contact, Barker's 
 Revolving.} 
 
 Barker's Wheel. (See Appendix 
 Wheel, Barkers.} 
 
 Base, Socket -- A base for holding 
 a lamp socket in position. 
 
 Basket, Dipping -- A perforated 
 basket of non-corrosive material, em- 
 ployed for the reception ot articles that are 
 to be prepared for the process of electro- 
 plating by dipping them in the cleansing 
 bath. (See Dipping.} 
 
 Basket, Stoneware Dipping -- A 
 stoneware basket in which the articles are 
 
 placed that are to be subjected to the dip- 
 ping process in electro-metallurgy. (See 
 Appendix Basket, Dipping.} 
 
 Bath, Electric Light A variety of 
 electro-therapeutic bath, in which all the 
 patient's body, except the head, is exposed 
 to the radiant light and heat of a number 
 of incandescent electric lamps placed in- 
 side a closed chamber or box. 
 
 By the use of the electric light bath it is 
 claimed that the temperature of the body is 
 rapidly increased, and that the effect on the 
 skin is the same as that of sunshine. The 
 therapeutic value of such a bath is, perhaps, 
 to be questioned. 
 
 Battery, Compound A term pro- 
 posed by Henry for a number of separate 
 voltaic cells, coupled so as to iorm a 
 single cell, in contradistinction to a single 
 cell. 
 
 The term battery wasoriginally sometimes 
 loosely applied either to indicate a single 
 voltaic cell, or a numberof cells so joined to- 
 gether as to form a single electric source. 
 
 Indeed, the term is still loosely employed 
 even at the present day by some writers. In 
 the time of Henry the word battery was ap- 
 parently indifferently applied to a single 
 cell or a number of cells, and Henry pro- 
 posed the term compound battery to distin- 
 guish between a single cell, or, as he called it, 
 a battery, and a number of cells joined so as 
 to form a single source, which he terms a 
 compound battery, but which is to-day, by all 
 careful writers, termed a battery. 
 
 Battery, Distant A battery em- 
 ployed in a telegraphic system at the re- 
 ceiving end of the line. 
 
 Battery, Dry A number of sepa- 
 rate dry voltaic cells combined so as to act 
 as a single source. 
 
 A dry pile. (See Pile, Dry.} 
 
 Battery, Element of (See Ap- 
 pendix Element of Battery} 
 
 Battery, Home The battery em- 
 ployed in a telegraphic system at the send- 
 ing end of the line. 
 
Bat.] 
 
 572 
 
 [Bic. 
 
 Battery, Polarization A term 
 
 sometimes employed for a secondary or 
 storage battery. 
 
 The term secondary or storage battery 
 would appear to be preferable. 
 
 Battery, Secondary, Current Efficiency of 
 The ratio between the ampere- 
 hours of the discharge and the ampere- 
 hours of the charge. 
 
 Battery, Secondary, Efficiency of 
 
 The ratio between the amount of electrical 
 work given out by a battery during its dis- 
 charge, and the amount of work expended 
 in charging it. 
 
 The efficiency of a secondary battery varies 
 with the rates of charge and discharge ; the 
 higher these rates the lower the efficiency. 
 
 The efficiency of a secondary battery is ob- 
 tained by dividing the amount of electrical 
 work in joules or watt-hours, which a battery 
 will produce after being charged, by the 
 amount of similarly estimated electrical work 
 expended in charging it. This is generally 
 known as the watt-efficiency. 
 
 The current-efficiency is obtained by divid- 
 ing the ampere-hours of the discharge by the 
 ampere-hours of the charge. 
 
 Battery, Secondary, Watt-Efficiency of 
 
 The ratio between the amount of 
 
 electrical work in watt-hours a battery will 
 yield after being charged, and the amount 
 of work in watt-hours expended in charg- 
 ing it. 
 
 Battery Syringe. (See Appendix 
 Syringe, Battery.} 
 
 Battery System for Electric Railway. 
 (See Appendix Railway, Electric, Bat- 
 tery System for.} 
 
 Bead, Chain. (See Appendix Chain, 
 Bead} 
 
 Bead Lightning. (See Appendix Light- 
 ning, Bead.} 
 
 Bearing, Magnetic The angle in- 
 cluded between the horizontal line from an 
 observer to an object and the observer's 
 magnetic meridian. 
 
 Bega. A prefix proposed by Houston 
 and Kennelly for a thousand million, or io 9 
 
 Begadyne. A term proposed by Houston 
 and Kennelly for one thousand million 
 dynes, or io 9 dynes. 
 
 Begerg. A term proposed by Houston 
 and Kennelly for one thousand million ergs, 
 or io 9 ergs. 
 
 Beginning of Current. (See Appendix 
 Current, Beginning of.} 
 
 Begohm. A term proposed by Houston 
 and Kennelly for one thousand million 
 ohms ; i.e., io 9 ohms. 
 
 Bell, Electric, Continuous Action 
 
 An electric bell which continues to ring 
 when once started until stopped either by 
 hand or automatically. 
 
 Bell, Extension A term some- 
 
 times employed for extension call bell. 
 (See Bell, Extension Call.} 
 
 Belt, Creeping of An action of a 
 
 belt due to its retractility, whereby the driv- 
 ing pulley travels somewhat faster than the 
 driven pulley. 
 
 Suppose the belt possesses true elasticity 
 or retractile power, then it will be stretched 
 on the work side and come back to its 
 original length on the idle side. It therefore 
 reaches the driving pulley in a stretched con- 
 dition and leaves it in a contracted condition. 
 It also reaches the driven pulley in a con- 
 tracted condition and leaves it in an elongated 
 condition. Suppose this stretch or elonga- 
 tion is one per cent, in a given case, the driv- 
 ing pulley must move 101 feet for every 100 
 feet of the driven pulley, then there is no 
 slip of the belt, only a creep. 
 
 The slip of a belt may cause a consider- 
 able loss of peripheral velocity in the pulley. 
 
 Belt, Slipping of The slipping of 
 
 a belt on the revolving pulley it covers, 
 causing a loss of speed. 
 
 Bicro. A prefix proposed by Houston 
 and Kennelly denoting the thousand- 
 millionth part, or io~ 9 - 
 
Bic.] 
 
 573 
 
 [Bon. 
 
 Bicrofarad. A term proposed by Hous- 
 ton and Kennelly for the thousandth part 
 of a microfarad, or io- 9 farad. 
 
 Bierohenry. A term proposed by Hous- 
 ton and Kennelly for the thousand"- millionth 
 part ol a henry, or one centimetre. 
 
 Bi-Metallic Accumulator. (See Appendix 
 Accumulator, Si-Metallic.} 
 
 Biologist, Electro One skilled in 
 the art of electro-biology. 
 
 Bioscopist, Electro One skilled in 
 
 the science of electro-bioscopy. 
 
 Blavier's Formulae. (See Appendix 
 Fortuities, Blavier's.} 
 
 Blavier's Test. (See Appendix Test, 
 Blavier's.') 
 
 Block, Ceiling - - An attachment 
 
 fastened to ceilings for suspending flexi- 
 ble cords and connecting them with the 
 supply wires of an incandescent system. 
 
 Block, Double, Duplex - In teleg- 
 raphy, especially in submarine telegraphy, 
 duplex transmission obtained by the aid of a 
 condenser inserted in each arm of the Wheat- 
 stone balance. (See Telegraphy, Duplex, 
 Bridge Method of.} 
 
 Block, Service The set of termi- 
 nals from which service wires are taken 
 to the interior of a building, usually secured 
 to a pole or to the exterior of a building. 
 
 Blow, To A phrase frequently 
 
 employed to indicate the fusion of a safety 
 fuse. (See Fuse, Safety.} 
 
 Blowing of Fuse. (See Appendix Fuse, 
 Blowing of.} 
 
 Blowing Point of Fuse. (See Appendix 
 Fuse, Blowing Point of.} 
 
 Blue Magnetic Pole. (See Appendix 
 Pole, Magnetic, Blue.} 
 
 Board, Distributing A term 
 
 sometimes employed in a system of tele- 
 graphic or telephonic communication for a 
 cross connecting board. (See Board, Cross- 
 Connecting.} 
 
 Board, Distributing Switch A 
 
 switch board employed for distributing 
 electric current to different circuits. 
 
 A distributing switch board is usually pro- 
 vided with wedge-plugs and spring-jacks. 
 
 Board, Lightning Arrester In a 
 
 system of telephonic or telegraphic com- 
 munication the board to which the light- 
 ning arrester is connected. 
 
 The lightning arrester board often forms 
 part of the test-board. 
 
 Board, Test In a system of tele- 
 phonic or telegraphic communication the 
 board, provided with devices for readily 
 connecting testing instruments to any par- 
 ticular line, to which all the separate lines 
 are connected. 
 
 Bob, Polishing A disc of hard, 
 tough wood, provided on its edge with a 
 ring or rim of tough leather or hide, and 
 employed, when mounted on a shaft and 
 put into rapid rotation, for polishing ar- 
 ticles so as to prepare them for electro- 
 plating. (See Plating, Electro.} 
 
 The polishing bobs are charged for use with 
 any suitable abrasive material, such as 
 emery, etc. 
 
 Bobbed. A word sometimes employed 
 to characterize a surface that has been 
 polished by the action of a bob. (See Ap- 
 pendix Bob, Polishing.} 
 
 Body, Induct eons A term proposed 
 
 by Faraday for a body in which a charge 
 is induced by the action of a neighboring 
 charged body. 
 
 Body, Inductric A term proposed 
 
 by Faraday for the body containing the in- 
 ducing electric charge. 
 
 Bolognian Stone. (See Appendix Stone, 
 Bolognian.} 
 
 Bond, Electric Rail An electric 
 
 bond or connection between contiguous 
 rails of a road using a grounded return. 
 
 In a system of electric roads, where the 
 return circuit is grounded, the track offers an 
 
Bon.] 
 
 574 
 
 [Bro. 
 
 excellent return provided the return joints 
 between contiguous rails are electrically con- 
 nected. To do this thoroughly, requires, of 
 course, such an electric connection as will 
 render the bonds of no higher linear resist- 
 ance than the main body of the rails. 
 
 Bony Current. (See Appendix Cur- 
 rent, Bony.') 
 
 Booster. A scarcely euphonious word 
 employed to designate a dynamo inserted 
 in a special feeder or group of feeders ot 
 an Edison incandescent system in order to 
 raise the pressure above the rest of the 
 system. 
 
 Boreal Fluid. (See Appendix Fluid, 
 Boreal.') 
 
 Bougie-Metre. A name proposed for the 
 practical unit of illumination. 
 
 A unit of illumination equal to the normal 
 illumination from the bougie-decimale at 
 a distance of one metre. 
 
 This unit was proposed by a Sub-Commit- 
 tee of the American Institute of Electrical 
 Engineers on the provisional programme of 
 the Chicago International Electrical Con- 
 gress of 1893, on the occasion of the World's 
 Columbian Exposition. 
 
 The bougie-decimale is practically equal to 
 one English standard candle. By making 
 the distance equal to one metre, the practical 
 unit of illumination will be approximately 
 equal to y^ carcel-metre, or one metre-candle, 
 or to one metre-kerze. 
 
 Bow, Yoltaic A voltaic arc. (See 
 
 Arc, Voltaic.'] 
 
 Bowl, Stoneware Dipping A per- 
 forated bowl made of stone or earthen ware 
 in which articles are placed that are to be 
 subjected to the dipping process in electro- 
 metallurgy. (See Dipping.} 
 
 Box, Section In a system of elec- 
 tric street railways the box containing the 
 section switches and fuses used for the 
 control of a section or a line section. 
 
 Box, Starting, of Shunt-Wound Motor 
 
 A box provided with a rheostat or 
 
 variable resistance. 
 
 The armature resistance of a shunt-wound 
 motor is generally made very low, in order 
 to insure high efficiency and constancy of 
 speed. In starting the motor, if it is con- 
 nected to the constant potential circuit and 
 the driving current be permitted to pass 
 directly through its armature, the rush of 
 current would be sufficient to injure the 
 machine. To avoid this the current is first 
 sent through a rheostat, or starting box, 
 and, when the speed of the motor is suffi- 
 ciently high, and a suitable counter-electro- 
 motive force is generated in the armature, 
 the resistance coils are gradually cut out 
 until the motor is connected directly to the 
 constant potential mains. 
 
 Branched Series. (See Appendix 
 Series, Branched.} 
 
 Break Key. (See Appendix Key, 
 Break.} 
 
 Break, Quick A break of a cir- 
 cuit obtained by means of a quick-break 
 switch. (See Appendix Switch, Quick- 
 Break.} 
 
 Breaker, Contact Any device for 
 
 opening or breaking an electric circuit. 
 
 Breaker, Contact, Barker's Revolving 
 
 A form of contact breaker in which 
 
 a toothed wheel is rapidly revolved so that 
 its teeth pass successively into and out of a 
 mercury surface, and a rapid making and 
 breaking of an electric circuit connected 
 therewith is thus obtained. 
 
 Breaking Down of Dielectric. (See Ap- 
 pendix Dielectric, Breaking Down of.} 
 
 Bridge, Thomson's A modified 
 
 form of Wheatstone's bridge proposed by 
 Kelvin for the measurement of very small 
 resistances. 
 
 Broiler, Electric A device for 
 
 broiling b'y means of electrically generated 
 heat. 
 
 Rods of insulated metal are suitably con- 
 nected in parallel, and raised to incandescence 
 
Biu. 
 
 575 
 
 [Bur. 
 
 by means of electrically generated heat. (See 
 Heat, Electric.} 
 
 In one form of apparatus made, when a 
 potential difference of no volts is applied to 
 the terminals, a current of seven amperes 
 passes and heats the broiler sufficiently for 
 use in about three or four minutes. 
 
 Brush, Cup A brush employed in 
 
 cleansing surfaces that are to be prepared 
 for electro-plating, and suitably shaped lor 
 polishing the inside of a cup or other simi- 
 lar hollow surface. 
 
 Brush, Inside Box 
 
 A brush em- 
 
 ployed in cleansing surfaces so as to 
 prepare them for electro-plating, suitably 
 shaped for polishing the inside of tubular 
 surfaces. 
 
 Brush, Potash 
 
 A brush employed 
 
 in cleansing, by the use of a caustic, sur- 
 faces that are to be electro plated. 
 
 Brush, Thimble A brush employed 
 in cleansing articles that are to be pre- 
 pared for electro-plating, and suitably 
 shaped for such surfaces as the inside of a 
 thimble. 
 
 Brushes, Distributing, of Electric Motor 
 
 The brushes of an electric motor 
 
 corresponding in position to the collecting 
 brushes of a dynamo-electric machine. 
 
 It is evident that the brushes of an electric 
 motor differ somewhat in their function from 
 the collecting brushes of a dynamo-electric 
 machine, since in the former case the brushes 
 act to distribute a current generated outside 
 the motor to certain coils on the armature of 
 the motor, while in the laiter case they com- 
 mute the direction of the current generated 
 in the armature. 
 
 Brushes, Finishing A term em- 
 ployed in electro-plating for finer brushes 
 than scratch brushes. 
 
 Bucking'. A word employed in the 
 operation of street railway passenger cars 
 for the sudden stopping of a car, as if by a 
 collision. 
 
 The car sometimes refuses to go further ; 
 it often, however, stops and then goes ahead 
 again almost immediately as if nothing had 
 occurred. The cause of bucking is to be as- 
 cribed to the fact that the armature being 
 grounded, if a second ground occurs in any 
 part of the machine, between the armature 
 and the trolley, with the ordinary method of 
 connecting up, a heavy current flows, produc- 
 ing an intensely strong magnetic field and 
 at the same time the armature is short cir- 
 cuited by means of the two ground connec- 
 tions. Under these circumstances the 
 dynamo, being short circuited, operates as a 
 powerful electro-magnetic brake. This effect 
 also occurs when the armature is short-cir- 
 cuiied by heavy sparking at the brushes, or 
 bad insulation (not to ground) in the com- 
 mutator. 
 
 The term bucking is sometimes used 
 loosely for any cause which prevents an 
 electric motor from properly operating. 
 
 Buffing. Preparing surfaces for the re- 
 ception of an electro-plating by subjecting 
 them to the polishing action of a revolving 
 wheel covered with a buff on the surface of 
 which rouge has been spread. 
 
 Building Iron. (See Appendix Iron, 
 Building.} 
 
 Building Process for Moulds of Electro- 
 types. (See Append x Process, Build- 
 ing, for Moulds of hlectrotypcs.} 
 
 Buoy, Electrically Illumined A 
 
 buoy illumined by means of an electric in- 
 candescent lamp. 
 
 The electric buoys are connected with the 
 generating station on the shdre by means of 
 heavily armored cables. Spar buoys have 
 been successfully lighted by such means. 
 
 Burglar Alarm Contacts. (See Appendix 
 Contacts, Burglar Alarm.} 
 
 Burglar Alarm Matting. (See Appendix 
 Matting, Burglar Alarm.} 
 
 Burglar Alarm Trap. (See Appendix 
 Trap, Burglar Alarm.} 
 
 Burned-Out Incandescent Lamp. (See 
 
Bar.] 
 
 576 
 
 [Cal. 
 
 Appendix Lamp, Burned-Out Incan- 
 descent.") 
 
 Burnishing. A word employed in 
 electro-plating for a process by means of 
 which surfaces are prepared for electro- 
 plating by subjecting them to the action of 
 burnishing tools. 
 
 The burnishing action consists essentially 
 in smoothing and brightening a surface by 
 crushing down the small inequalities of the 
 surface. The burnishing action is not unlike 
 the smoothing action of a hot iron in ironing. 
 
 Button, Commutator-Press A 
 
 form of press button in which the current 
 from a Hittery or other source is reversed 
 
 in direction to the current previously flow- 
 ing from the ordinary signalling button. 
 
 Button, Push, Double-Contact A 
 
 push button provided with two contacts. 
 
 Button Repeater. (See Appendix Re- 
 peater, Button.} 
 
 Buzz. A verb expressive of the action 
 of an electric bell when it fails to strike dis- 
 tinctly and only gives a sound something 
 like that of a buzzer. 
 
 An electric bell will "buzz" if the con- 
 tacts are out of proper adjustment, or if the 
 current passing is too strong. 
 
 By-Pass of Discharge. A term some- 
 times employed for alternative path. (See 
 Path, Alternative.} 
 
 C. A symbol used for capacity. 
 The defining equation is C= ^ 
 
 E! 
 
 The same symbol is also used for current. 
 
 C. A symbol used for coulomb, the 
 practical unit ot electric quantity. 
 
 The same symbol is also used for current 
 and proposed for capacity. 
 
 cm. An abbreviation frequently em- 
 ployed for the centimetre, the C. G. S. unit 
 of length. 
 
 cm 12 . An abbreviation frequently em- 
 ployed for square centimetre, the C. G. S. 
 unit of surface. 
 
 cm 3 . An abbreviation frequently em- 
 ployed for cubic centimetre, the C. G. S. unit 
 of volume. 
 
 cm : s. An abbreviation frequently em- 
 ployed for centimetre per second, the C. G. 
 S. unit of velocity. 
 
 cm : s 2 . An abbreviation frequently em- 
 ployed for centimetre per second per sec- 
 ond, the C. G. S. unit of acceleration. 
 
 C^ R Loss. (See Appendix Loss, 
 
 Cable, Concentric A cable pro- 
 vided with both a leading out and a return 
 conductor, one forming a central core or 
 conductor and the other an enclosing 
 tubular conductor, suitably insulated from 
 each other. 
 
 In a concentric cable the central conductor 
 is heavily insulated and enclosed in a metallic 
 tube which latter acts as a return conductor. 
 
 Cable, Linear Capacity of The quo- 
 tient of the capacity of a cable by its 
 length. 
 
 Cable, Linear Insulation of The 
 
 product of the insulation resistance of a 
 cable and its length. 
 
 The linear insulation is preferably meas- 
 ured in kilometre megohms, or mile 
 megohms. 
 
 Cage Protector for Lightning Discharges. 
 (See Appendix Protector, Cage, for 
 Lightning Discharges.} 
 
 ( ;illan Voltaic Cell. (See Appendix 
 Cell, Voltaic, Callan,} 
 
 Callan's Electro-Magnetic Repeater. 
 (See Appendix Repeater, Electro-Mag' 
 netic, Callan's} 
 
Cal.] 
 
 577 
 
 LCel. 
 
 Calorimetry. The science of measuring 
 quantities of heat. (See Calorimeter.} 
 
 Capacitance. A term analogous to 
 resistance, proposed by Hospitalier for the 
 true or specific capacity of a medium. 
 
 Capacity for Heat, Mean Thermal 
 
 The mean thermal capacity for heat of a 
 body between two stated temperatures is the 
 quantity of heat required to raise it from 
 the lower of these temperatures to the 
 higher, divided by the difference of tem- 
 peratures. (See Heat, Specific.} 
 
 Capacity, Kilometric, of Cable The 
 
 capacity of a cable in microfarads per kilo- 
 metre. (See Cable, Electric.} 
 
 Capacity, Magneto-Inductive A 
 
 term sometimes employed for magnetic per- 
 meability. (See Permeability, Magnetic.} 
 
 The word permeability is preferable. 
 
 Capacity, Specific Dielectric A 
 
 term sometimes employed in place of 
 specific inductive capacity. (See Capacity, 
 Specific Inductive.} 
 
 Carbon Arc. (See Appendix Arc, Car- 
 bon.} 
 
 Carbon Pencil. (See Appendix Pencil, 
 Carbon} 
 
 Carbons, Skew Adjustment of, in Arc 
 Lamp The adjustment of the car- 
 bons of an arc lamp by means of which the 
 positive carbon is placed a short distance 
 in front of, back and out of a vertical line 
 with, the negative carbon. 
 
 The skew adjustment is employed in a 
 projector or search light for the purpose of 
 insuring the formation of the crater on the 
 edge of the positive carbon so that the prin- 
 cipal part of the light is thrown out hori- 
 zontally. 
 
 Cardan's Suspension of Compass Needle. 
 
 (See Appendix Suspension of Compass 
 Needle, Cardan's} 
 
 Carrying- Capacity of Safety Fuse. (See 
 Appendix Fuse, Safety, Carrying 
 Capacity of} 
 
 A process for 
 the casting of metals that have been fused 
 by means of heat of electric origin. 
 
 The metals are fused by heat in a specially 
 provided furnace from which all the air has 
 been exhausted. The fused metal is then 
 run into moulds from which the air has also 
 bedn exhausted. 
 
 The vacuum and the electric melting, it is 
 claimed, produce a greater liquidity of the 
 metal than do the ordinary methods, and 
 hence insure a readier flow and more sharply 
 marked castings. The metal of the casting 
 is also for the same reason extremely close 
 and fine grained, and is free from blow-holes. 
 
 Castor and Pollux Light. (See Appen- 
 dix Light, Castor and Pollux} 
 
 Cataphoric Electrode. (See Appendix 
 Electrode, Cataphoric} 
 
 Cataphoric Medication. (See Appendix 
 Medication, Cataphoric^ 
 
 Ceiling Block. (See Appendix Block, 
 Ceiling.} 
 
 Ceiling Rosette. (See Appendix 
 Rosette, Ceiling.} 
 
 Cell, Double-Liquid A term some- 
 times employed in place of double-fluid 
 cell. (See Cell, Voltaic, Double-Fluid.} 
 
 Cell, Dry Gelatine A term applied 
 
 to a type of dry voltaic cell in which the 
 exciting liquid is absorbed by, or com- 
 bined with, a variety of gelatinous sub- 
 stances. 
 
 The term gelatine dry cell is by no means 
 limited to cases in which gelatine, either in 
 whole or in part, forms the material for the 
 retention of the exciting liquid. On the con- 
 trary, such cells most frequently contain a 
 mixture of various mineral substances which 
 on standing assume a gelatinous or semi- 
 gelatinous condition from the water com- 
 bining with the substances. 
 
 Cell, Earth A term frequently 
 
 applied to a variety of cell consisting of 
 any voltaic couple buried in a compara- 
 tively moist stratum of earth. 
 
Cel.] 
 
 578 
 
 [Cel. 
 
 In such cases the moisture of the earth 
 acts as the electrolyte and the electromotive 
 forces developed depend on the character of 
 the voltaic couples employed. 
 
 The term earth cell is sometimes improp- 
 erly applied to the case of two similar metal- 
 lic plates buried in the earth at considerable 
 distances from one another. In such cases 
 the current produced is obtain2d in part at 
 least by means of the difference of potential 
 caused between the two points of the earth 
 at which the separate plates are located. 
 
 It is evident, however, that the current 
 produced by such earth cells, improperly so- 
 called, is in reality obtained from the earth 
 as an electric source, the plates with their 
 metallic terminals simply forming conduct- 
 ors for carrying off the current generated by 
 the difference of potential already existing 
 in the earth. (See Currents, Earth.) 
 
 Cell, Galvanic A term sometimes 
 
 employed instead of voltaic cell. (See 
 Cell, Voltaic.) 
 
 Cell, Gas A term sometimes ap- 
 plied to one of the cells of a gas battery. 
 (See Battery, Gas.) 
 
 Cell, Lead Sulphate of Copper A 
 
 form of storage cell in which two plates of 
 lead are immersed in a solution of copper 
 sulphate. 
 
 On the passage of the charging current 
 one lead plate becomes coated with lead 
 peroxide and the other with metallic copper. 
 (See Cell, Storage.) 
 
 Cell, Lead Sulphate of Zinc A 
 
 form of storage cell in which two plates ot 
 lead are immersed in a solution of zinc 
 sulphate. 
 
 On the passage of the charging current 
 one plate becomes coated with lead peroxide 
 and the other with metallic zinc. 
 
 This cell, according to Reynier, has an 
 electromotive force of as high as from 2.8 
 to 2.6 volts, but soon falls to from 2.3 to 2 
 volts. (See Cell, Storage.) 
 
 Cell, Light A term sometimes 
 
 employed for a photo-electric cell. (See 
 Cell, Photo- Electric.) 
 
 Radiant energy, whether of the luminous 
 type, as in the case of light, or of the non- 
 luminous type, as in the case of heat, pro- 
 duces a difference of potential under a variety 
 of circumstances. 
 
 In some cases violet-colored light seems to 
 produce the most marked effects. 
 
 Roughly speaking, photo-electric, or light 
 cells, can be grouped into two fairly sharply 
 marked classes, namely: 
 
 (i.) Those in which the electricity accom- 
 panies some chemical decomposition which 
 acts to produce a current. 
 
 (2.) Those in which slight molecular 
 changes occur which result in the production 
 of an electric current. 
 
 The production of electricity in cells of the 
 latter type, by the action of light alone, is 
 probably analogous to the production of 
 pyro-electricity in the case of certain crys- 
 talline bodies. (See Electricity, Pyro.) 
 
 Cell, Magneto-Chemical A cell in- 
 vented by Balsamo, in which two similarly 
 magnetized bars are immersed with the 
 north pole of one and the south pole of the 
 other in a solution of oxalic acid. 
 
 Under these circumstances the magnet 
 having its north pole immersed in the ex- 
 citing liquid acts like the zinc plate, and the 
 one having its south pole like the copper of 
 an ordinary zinc-copper couple immersed in 
 dilute sulphuric acid. 
 
 The influence a magnetic fluid exerts on 
 chemical action has been investigated by 
 Rowland and Bell, and by Squier. (See 
 Appendix Action, Protective. Throw, Pro- 
 tective. Throw, Concentration.) 
 
 Cell, Photo-Electric Impulsion A 
 
 term sometimes applied to an impulsion 
 cell. (See Cell, Impulsion.) 
 
 Cell, Primary A term sometimes 
 
 employed for a voltaic cell. (See Cell, Vol- 
 taic.) 
 
 The term primary cell is employed in con- 
 tradistinction to secondary or storage cell. 
 (See Cell, Storage.) 
 
 Cell, Regenerative A term pro- 
 posed for an early form of storage or sec- 
 
Cel.J 
 
 [Cha. 
 
 ondary cell, invented by Thomson and 
 Houston, consisting of two plates of cop- 
 per immersed in a solution of zinc sul- 
 phate. 
 
 Two plates were placed, one at the bottom 
 of the solution, and the other near the top. 
 On the passage of the charging current, 
 one of the plates through the decomposition 
 of the zinc sulphate was partially con- 
 verted into copper sulphate and the other 
 plate was coated with metallic zinc. The con- 
 nections were such that the plate partially 
 converted into zinc sulphate was placed at 
 the bottom of the cell, and the one partially 
 converted into and covered by metallic zinc, 
 at the top. 
 
 The passage of the charging current thus 
 produced a variety of gravity cell. On the 
 exhaustion of the cell there remained two in- 
 ert plates of copper immersed in a solution 
 of zinc sulphate. 
 
 Cell, Thermo-Cheinical A variety 
 
 of heat cell in which a difference of po- 
 tential is produced and maintained between 
 two plates immersed in a suitable liquid 
 when one plate is kept at a higher tem- 
 perature than the other. 
 
 A heat cell forms in reality a species of 
 storage battery in which the charging of the 
 cell is obtained by the expenditure of heat 
 energy. 
 
 In true heat cells a chemical action occurs 
 which is readily and completely reversible 
 by heat. 
 
 Cell, Voltaic, Agglomerate Leclanche 
 
 A variety of Leclanche' cell in 
 
 which the mixture of carbon and dioxide of 
 manganese is made into a solid mass by 
 pressure. 
 
 The advantage claimed for the agglomer- 
 ate Leclanchfe cell is that the porous cup em- 
 ployed in the other forms of this cell is dis- 
 pensed with. 
 
 Cell, Voltaic, Callan A zinc-iron 
 
 couple, the elements of which are immersed 
 respectively in an electrolyte of dilute sul- 
 phuric acid, and an electrolyte consisting 
 
 of a mixture of strong nitric and sulphuric 
 acids. 
 
 In the Callan cell the iron plays the part of 
 the negative element. It is not attacked by 
 the nitric acid provided the acid be suffi- 
 ciently strong. The reasons generally as- 
 signed for the non-action of the acid on the 
 iron are either the so-called passive state 
 of the iron or the formation on the surface 
 of an insoluble oxide. (See Slate, Passive.) 
 
 This cell is sometimes called the iron cell, 
 or the Maynooth. It is difficult to maintain 
 this cell in good action, owing to the liability 
 of the nitric acid to act on the iron when- 
 ever its strength falls below a certain point. 
 
 Cell, Toltaic, Heat A cell in which 
 
 heat energy is changed or converted into 
 electric energy. 
 
 Park Benjamin divides heat cells into three 
 classes, namely: 
 
 (i.) Those in which heat acts upon the 
 materials of the cell by causing fusion or de- 
 composition. 
 
 (2.) Those in which heat acts to set free 
 chemical affinities whereby the cell is caused 
 to operate, regeneration after exhaustion 
 taking place at a lower temperature. 
 
 (3) Thermo-chemical cells, or those in 
 which the difference of potential is maintained 
 between two plates immersed in a liquid by 
 heating one plate to a higher temperature 
 than the other. 
 
 Cell, Voltaic, Maynooth 
 
 A name 
 sometimes given to the Callan voltaic cell. 
 (See Appendix Cell, Voltaic, Callan.) 
 
 Cell, Voltaic, Single-Liquid A term 
 
 sometimes employed in place of a single- 
 fluid cell. (See Cell, Voltaic, Single- 
 Fluid.) 
 
 Cessation of Current. (See Appendix 
 Current, Cessation of.) 
 
 Chain, Bead A chain employed in 
 
 connection with a pendant electric burner. 
 (See Burner, Plain Pendant Electric.) 
 
 Chain, Galvanic A term tormerly 
 
 applied to a galvanic, or more properly 
 
Cha.] 
 
 580 
 
 LChr. 
 
 speaking, voltaic circuit. (See Circuit, 
 Voltaic.} 
 
 Chamber of Incandescent Electric Lamp. 
 Age-Coating of The gradual darken- 
 ing of the enclosing glass chamber of an 
 incandescent electric lamp. 
 
 This coating may be due to a deposit of 
 carbon or a hydrocarbon, or a deposit of metal 
 deflagrated or volatilized by the heat of the 
 filament. 
 
 Charge Accumulator. (See Appendix 
 Accumulator, Charge.") 
 
 Charge Current on Telegraphic Line. 
 (See Appendix Line, Telegraphic, Charge 
 Current on.) 
 
 Charge, Linear Density of The 
 
 amount of electricity per unit of length of 
 conductor. (See Charge, Electric.) 
 
 Charge, Minus A negative charge. 
 
 (See Charge, Negative.) 
 
 Charge, Plus A positive charge. 
 
 (See Charge, Positive.) 
 
 Charge, Sweeping-Out A phrase 
 
 employed in double-current signalling for 
 the freeing of the line from a charge pro- 
 duced by the sending of one signal, by re- 
 versing the direction of the current through 
 the line. 
 
 The "sweeping-out" of the charge on a 
 telegraphic line decreases the amount of re- 
 tardation. (See Retardation.) 
 
 Charge, Volume Density of The 
 
 amount of electricity per unit of volume. 
 (See Charge, Electric.) 
 
 Check, Telephone Time A device 
 
 by means of which, in a telephone ex- 
 change system, a drop shutter is automati- 
 cally released at a particular trunk wire 
 indicator, at the beginning of the time that 
 a subscriber is given the use of the trunk 
 line, and automatically disconnected, and 
 the central station operator's attention is 
 called to the fact of such disconnection. 
 
 By the use of the time-check, disputes as 
 
 to the length of time a subscriber is given 
 the use of a trunk line is avoided. 
 
 A telephone time-check is sometimes 
 called a telephone meter. (See Appendix 
 Meter, Telephonic} 
 
 Chemical Generator of Electricity. (See 
 Appendix Generator, Chemical, of Elec- 
 tricity.} 
 
 Chemical Telegraph. (See Appendix-^ 
 Telegraph, Chemical.} 
 
 Chemism. A word sometimes em- 
 ployed for chemical affinity. (See Affinity, 
 Chemical.} 
 
 Chemistry, Thermo That branch 
 
 of chemistry which treats of the measure- 
 ment of chemical energy in thermal units. 
 
 According to Berthelot : 
 
 (i.) The amount of heat set free in any 
 chemical reaction is a measure of the total 
 work done during that reaction. 
 
 (2.) Changes produced in any system not 
 attended by external effects produce an evolu- 
 tion of heat dependent only on the initial and 
 final states of the system. 
 
 (3.) Every chemical change effected in a 
 system independent of external energy tends 
 to produce that body or system of bodies, 
 the formation of which evolves a maximum 
 heat. 
 
 Choke Magnet. (See Appendix Mag- 
 net, Choke} 
 
 Chronograph, Spark A form of 
 
 electric chronograph in which the time of a 
 certain event is indicated by means of the 
 spark of a Ruhmkorff or spark coil. 
 
 In a form of spark chronograph for meas- 
 uring the time in which a falling body moves 
 through different parts of its path, the path 
 of the body is marked on a moving sheet of 
 paper by means of a series of sparks frcm a 
 Ruhmkorff coil. 
 
 Chronometer, Electric An elec- 
 trically controlled or operated mechanism 
 for indicating or recording time. (See 
 Clock, Electric.) 
 
Cir.] 
 
 581 
 
 [CIo. 
 
 Circuit Closer. (See Appendix Closer, 
 Circuit.} 
 
 Circuit Closer for Pull Bell. (See Ap- 
 pendix Pull Bell, Circuit Closer for.} 
 
 Circuit, Consumption A circuit in 
 
 which the energy of the electric current is 
 consumed or utilized for energizing electro- 
 receptive devices. 
 
 Electric energy is consumed in all parts of 
 an electric circuit. The term consumption 
 circuit, however, is limited to that part of an 
 electric circuit in which the electro-receptive 
 devices are placed which are energized by 
 the passage of the electric current through 
 them. 
 
 Circuit, Electrical Tuning of (See 
 
 Appendix Tuning of Electrical Circuit.} 
 
 Circuit, Magnetic, External A 
 
 term sometimes employed for that part of 
 a magnetic circuit which lies outside of a 
 magnet. (See Circuit, Magnetic.} 
 
 Circuit, Magnetic, Internal A 
 
 term sometimes employed for that part of a 
 magnetic circuit which lies within the mag- 
 net. (See Circuit, Magnetic.} 
 
 Circuit, Multiple-Parallel A term 
 
 sometimes employed for a multiple of 
 parallel circuits. (See Circuit, Multiple.} 
 
 Circuit, Parallel-Arc A term 
 sometimes employed in place of parallel or 
 multiple circuit. (See Circuit, Multiple.} 
 
 Circuit, Resonant A circuit whose 
 dimensions are such as to bring it into res- 
 onance with, or to tune it to, the period ot 
 another circuit. 
 
 Circuit, Surging-^ An electrical 
 
 circuit through which electrical surgings 
 are passing. 
 
 Lodge employs this term, surging circuit, 
 in the following restricted sense. 
 
 ' I have been accustomed especially to 
 apply the name ' surging circuit ' to the case 
 where sparks are obtained not between two 
 distinct parts of a circuit, but between two 
 points on one and the same good conductor. 
 
 under circumstances when it does not form 
 the alternative path to anywhere, and when 
 it would ordinarily be supposed that there 
 was no possible reason for a spark at all." 
 
 The term surging circuit is applied gen- 
 erally to circuits through which surging dis- 
 charges are passing; as, for example, the 
 condenser-motor circuit in the Stanley-Kelley 
 system. 
 
 Circuit, Telegraphic, Working Efficiency 
 
 of The variation or margin between 
 
 the joint resistance of the conductor and the 
 resistance of the insulator by which the con- 
 ductor is supported. 
 
 According to F. L. Pope the working effi- 
 ciency may be increased in two ways, viz.: 
 
 (i.) By increasing the insulation resist- 
 ance. 
 
 (2.) By decreasing the resistance of the 
 conductor. 
 
 Circular Magnetization. (See Appendix 
 Magnetization, Circular.} 
 
 Clamp, Feeder Any clamping de- 
 vice for connecting or fastening a feeder 
 wire to a trolley wire. 
 
 Clip. A slight break in the signal re- 
 ceived in a system of duplex telegraphy 
 under certain circumstances. 
 
 Clip, Feeder In a system of elec- 
 tric street railways a clamp furnished with 
 a device whereby a feeder wire may be 
 readily connected to a trolley wire. 
 
 Clips, Stay-Eye Iron bands 
 
 clamped to the string beams of the roof 
 with an iron ring projecting from the sur- 
 face of the roof, to which the stay rods of 
 telegraphic or telephonic standards are 
 screwed. 
 
 Clock, Directing A term some- 
 times employed instead of controlling or 
 master clock. (See Clock, Electrical- 
 Controlling^ 
 
 Clock, Electric, Watchman's A 
 
 watchman's electric register. (See Regis- 
 ter, Watchman's, Electric.} 
 
Clp.j 
 
 582 
 
 [Com. 
 
 Clock, Primary Electric A term 
 
 sometimes employed in place of the con- 
 trolling or master clock. (See Clock, 
 Master?) 
 
 Clock, Standard In a system of 
 
 time telegraphy the master clock. (See 
 Clock, Master."] 
 
 Closed-Circuit Transformer. (See Ap- 
 pendix Transformer, Closed- Circuit?) 
 
 Closed-Conducting Sheath for Lightning 
 Protection. (See Appendix Sheath, 
 Closed-Conducting, for Lightning Protec- 
 tion.} 
 
 Closer, Circuit Any device for 
 
 completing or closing a circuit. 
 
 Clown's-Hat Curve. (See Appendix 
 Curve, Clown' s-Hat} 
 
 Code, American Morse A term 
 
 sometimes employed for the Morse tele- 
 graphic alphabet. (See Alphabet: Tele- 
 graphic, Morse's.} 
 
 Code, Dot-and-Dash A term some- 
 times employed for the Morse telegraphic 
 code. (See Code, Telegraphic.} 
 
 Code, International Morse A 
 
 term sometimes employed for the interna- 
 tional telegraphic alphabet. (See Alpha- 
 bet, Telegraphic: International Code} 
 
 Coil, Faradic A term sometimes 
 
 employed in place of a Fradic machine or 
 medical induction coil. (See Machine, 
 Faradic.} 
 
 Coil, Ground A small rheostat 
 
 employed in duplex telegraphy at the home 
 station for the purpose of giving the appara- 
 tus in such station an equal resistance to 
 the currents coming from the distant sta- 
 tion. (Pope.) 
 
 The resistance of the ground coil should 
 be equal to the resistance of the spark coil, 
 plus the internal resistance of the battery. 
 
 Coil, Induction Ribbon An induc- 
 tion coil, the primary and secondary cir- 
 
 cuits of which are made of metallic ribbons 
 
 instead of wires. 
 
 Coil, Induction, Self A coil of wire 
 
 possessing a self induction. 
 
 A choking coil. (See Coil, Choking} 
 Coil, Spark, Telegraphic A small 
 
 rheostat employed in duplex telegraphy at 
 
 the home station in connection with the 
 
 ground coil. (See Appendix Coil, 
 
 Ground.} 
 
 The resistance of the spark coil should 
 be made sufficiently great to prevent the po- 
 larization of the battery when it is momenta- 
 rily short-circuited. 
 
 Coils, Differential Coils that are 
 
 differentially wound. (See Appendix 
 Winding, Differential.} 
 
 Coils, Field, of Dynamo The coils 
 
 of wire wound on the field magnet cores 
 for the production of the magnetic field. 
 
 Coked Core of Incandescent Filament. 
 
 (See Appendix Core, Coked, of Incandes- 
 cent Filament} 
 
 Coked Filament. (See Appendix Fila- 
 ment, Coked.} 
 
 Coking, Electrical Subjecting a 
 
 carbon to the coking process. (See Ap- 
 pendix Process, Coking, for Filament of 
 Incandescent Electric Lamp} 
 
 Coking of Filament. (See Appendix 
 Filament, Coking of} 
 
 Coking Process for Filament of Incandes- 
 centElectric Lamp. (See Appendix Proc- 
 ess, Coking, for Filament of Incandescent 
 Electric Lamp} 
 
 Collecting Combs. (See Appendix 
 Combs, Collecting} 
 
 Comazant. A term formerly applied to 
 St. Elmo's fire. 
 
 A corposant. (See Corposant. Fire, 
 St. Elmo's.} 
 
 Combination Fittings for Chandeliers, 
 Brackets, etc. (See Appendix Fittings, 
 
Com.] 
 
 583 
 
 [Con. 
 
 Combination, for Chandeliers, Brackets, 
 etc.} 
 
 Combs, Collecting A term some- 
 times employed for the collecting points of 
 a frictional electrical machine, or of an 
 electrostatic induction machine. (See Ma- 
 chine, Frictional Electric. Machine, 
 Electrostatic Induction.} 
 
 Common Arc of Aurora Glory. (See Ap- 
 pendix Arc, Common, of Aurora Glory.} 
 
 Commutator P^ress-Button. (See Ap- 
 pendix Button, Commutator-Press^ 
 
 Commutatorless. Not provided with a 
 commutator. (See Commutator, Dynamo- 
 Electric Machine.} 
 
 Compass, Declination A decli- 
 nometer. (See Declinometer.} 
 
 Compensated Alternator. (See Appen- 
 dix Alternator, Compensated.} 
 
 Compensating- Alternating Dynamo-Elec- 
 tric Machine. (See Appendix Machine, 
 Dynamo- Electric, Compensating- Alter- 
 nating.} 
 
 Compensator, Magnetic A device 
 
 for neutralizing the effects produced on a 
 magnetic needle by the local magnetism of 
 a ship. 
 
 Complex-Harmonic Alternating Electro- 
 motive Forces. (See Appendix Forces, 
 Electromotive, Complex-Harmonic Alter- 
 nating.} 
 
 Complex-Harmonic Curients. (See Ap- 
 pendix Currents, Complex-Harmonic.} 
 
 Complex-Magnetic Shell. (See Appen- 
 dix Shell, Complex-Magnetic.} 
 
 Compound Alternator. (See Appendix 
 Alternator, Compound.} 
 
 Compound Battery. (See Appendix 
 Battery, Compound.} 
 
 Compound Electro-Magnet. A term 
 sometimes applied to an induction coil. 
 (See Appendix Magnet, Electro-Com- 
 pound} 
 
 Compound Magnet. (See Appendix 
 Magnet, Compound.} 
 
 Concentration Throw. (See Appendix 
 Throw, Concentration} 
 
 Concentric Cable. (See Appendix 
 Cable, Concentric} 
 
 Concentric Wiring. (See Appendix 
 Wiring, Concentric} 
 
 Conductance, Specific Specific 
 
 conductivity. (See Conductivity, Specific.) 
 
 Conductibility. Possessing the power of 
 conducting electricity. 
 
 Conductivity. 
 
 Conducting Cord and Tip. (See Appen- 
 dix Cord and Tip, Conducting.) 
 
 Conducting Cord Tip. (See Appendix 
 Tip, Conducting Cord.) 
 
 Conduction Lightning Protection. (See 
 Appendix Protection, Conduction Light- 
 ning} 
 
 Conduction Lightning Protector. (See 
 Appendix Protector, Conduction Light- 
 ning.) 
 
 Conduction, Metallic A term 
 
 sometimes employed for the conduction of 
 electricity through a solid conductor in con- 
 tradistinction to its conduction through an 
 electrolyte. (See Conduction, Electrolytic.) 
 
 Conduction Resistance. (See Appendix 
 Resistance, Conduction.) 
 
 Conductivity, Percentage, of Wire 
 
 The conductivity of a particular copper 
 wire compared with the conductivity of 
 another wire of the same dimensions of pure 
 material at a standard temperature. 
 
 The percentage conductivity is readily ob- 
 tained by multiplying the calculated resist- 
 ance of the pure material by 100 and dividing 
 the result by the measured resistance of the 
 particular wire. 
 
 Conductor, Electric, Glowing of 
 
 Emitting light from any conductor heated 
 to electrical incandescence. 
 
Con.] 
 
 584 
 
 [Con. 
 
 The current strength required to produce 
 a glow in a conductor varies in a marked 
 manner with the character and density of 
 the gas surrounding the conductor. 
 
 Conductor, Electric, Melting of 
 
 Fusion of a conductor by means of the heat 
 of electric currents. 
 
 The strength of current required to fuse 
 or melt a conductor varies with a number of 
 circumstances, so that a wire which will not 
 fuse under the influence of a certain current 
 strength may fuse at another time under a 
 much smaller current strength if the con- 
 ditions are different. Among these influences 
 may be mentioned the nature of the medium 
 surrounding the conductor, as well as the 
 temperature of said medium. Sometimes, 
 too, a coating of oxide forms on the surface 
 of the conductor, which modifies its ability 
 to throw off or radiate its heat. 
 
 When subjected to alternating currents a 
 fuse wire has its fusing point gradually 
 lowered. 
 
 Conductor, Electric, Volatilization of 
 
 The volatilization of a conductor pro- 
 duced by the passage of an electric current 
 through it. 
 
 The current required to volatilize a con- 
 ductor will necessarily vary with the same 
 circumstances that modify its electric glow- 
 ing or melting. (See Appendix Conductor, 
 Electric, Glowing of. Conductor, Electric, 
 Melting of.) 
 
 Conduct or or Line Wire, Dip of 
 
 The sag of a telegraphic or telephonic wire 
 or conductor between two supports due to 
 its weight. 
 
 Conductor Resistance. (See Appendix 
 Resistance, Conductor.) 
 
 Conductor, Semi A term some- 
 times applied to substances, such as acids, 
 saline salts, water, etc., whose power of 
 conduction for electricity is neither very 
 high nor very low. 
 
 Substances that occupy an intermediate 
 position between conductors and so-called 
 non-conductors for electricity. 
 
 Conductor, Stranding of Forming 
 
 a conductor of several smaller conductors 
 for the purpose of reducing the self-induc- 
 tion or eddy currents, or of increasing its 
 flexibility. (See Induction, Self.) 
 
 Conductor System for Railroad. (See 
 Appendix Railroad, Conductor System 
 for.) 
 
 Conflict, Electric -A term proposed 
 
 by Oersted for a magnetic field surround- 
 ing a conductor through which a current 
 of electricity is flowing. 
 
 Oersted speaks as follows of his discovery 
 of the magnetic qualities of the region around 
 a conductor through which an electrical cur- 
 rent is flowing : " That this conflict performs 
 circles around the wire, for without this con- 
 dition it seems impossible that one part of 
 the wire when placed below the magnetic 
 needle shall drive its pole to the east, and 
 when placed above it to the west." 
 
 Connector, Copper A particular 
 
 form of connector employed in the gravity 
 voltaic cell for connecting the copper ele- 
 ment to the circuit wire or conductor. 
 
 A name applied technically to a form of 
 electric light fitting or coupler for connect- 
 ing large wires or conductors. 
 
 Consonance. Literally, sounding at the 
 same time. 
 
 Strictly speaking, two sounds are said to 
 be in consonance when they are sounded to- 
 gether. In this sense we speak of pleasing 
 consonances or harmonious chords. Often, 
 however, the word consonance is used in 
 contradistinction to dissonance as indicating 
 two sounds that are in unison with each 
 other. 
 
 The word consonance is also frequently 
 employed in the sense of increasing or re- 
 enforcing a sound; such, for example, as the 
 method of increasing the sound produced by 
 a vibrating string or cord by stretching the 
 cord over an elastic body like a table. In 
 such cases the table takes up the motions or 
 vibrations of the cord, and, by thus setting in 
 motion a greater mass of air, increases the 
 
Con.] 
 
 535 
 
 [Con. 
 
 amplitude of the waves and consequently 
 the intensity of the sound. This use of the 
 word consonance is to be distinguished from 
 resonance, in which an increase in the inten- 
 sity of the sound is also produced by waves 
 or vibrations set up in another body with, 
 however, this difference : in the case of reso- 
 nance the re-enforcement is effected by vibra- 
 tions set up in a body that is tuned to vibrate 
 in exact unison with a vibrating body; while 
 in the case of consonance no such tuning is 
 necessary ; or, briefly, consonant vibration is 
 forced vibration, while resonant vibration is 
 natural or free vibration excited by the 
 vibrating body. 
 
 Consonator. Any body possessing the 
 power of increasing the strength of sound 
 by consonance. (See Appendix Con- 
 sonance.') 
 
 This use of the word consonator is analo 
 gous to the use of the word resonator; viz., 
 a body having the power of increasing the 
 strength of sound by resonance. (See Reso- 
 nator?) A consonator, however, differs from 
 a resonator in the manner in which it 
 strengthens the sound. 
 
 Constant-Potential Motor. (See Appen- 
 dix Motor, Constant-Potential.} 
 
 Constant, Yerdet's The mag- 
 neto-optic constant of a transparent sub- 
 stance, usually expressed in minutes of arc 
 rotation of the plane of polarization, for a 
 luminous ray of definite wave length through 
 the magnetized substance at a definite 
 temperature between points on the ray 
 path whose magnetic potential differs by 
 unity. 
 
 Verdet's constant is usually taken for the 
 D line at the temperature of I5C. Its value 
 for monohydrated sulphuric acid according 
 to Bichat, and Mascart and Joubert equals 
 0.0104 ' 
 
 Consumption Circuit. (See Appendix 
 Circuit, Consumption.} 
 
 Contact Breaker. (See Appendix 
 Breaker, Contact.} 
 Contact, Drop Relay A form of 
 
 relay contact in which the attraction of 
 an armature on the passage of a current 
 releases a drop and thus completes a local 
 circuit which remains closed until the drop 
 is replaced or reset. 
 
 By the suitable combination of a drop re- 
 lay and a bell, the bell may become a con- 
 tinuous ringing bell. 
 
 Contact, Floor A term sometimes 
 
 employed in place of floor push. (See 
 Push, Floor.} 
 
 Contact, Full A variety of fault 
 
 produced by a part of the circuit being 
 accidentally placed in contact with a good 
 metallic circuit. (See Contacts.} 
 
 Contact, Relay A term frequently 
 
 applied to a form of electro-magnetic in- 
 strument by means of which a local circuit 
 is co'mpleted by the passage of a current. 
 
 A relay contact is in reality a form of key 
 or push, which, instead of being opened or 
 closed by means of the hand, is closed by 
 means of an electro-magnet. Relay contacts 
 are of two kinds, namely, spring relay con- 
 tacts and drop relav contacts. 
 
 Contact Resistance. (See Appendix 
 Resistance, Contact.} 
 
 Contact, Spring Relay A form of 
 
 relay contact which is interrupted by the 
 action of a spring, as soon as the current 
 is broken. 
 
 Contact Theory of Electricity. (See 
 Appendix Theory, Contact, of Elec- 
 tricity} 
 
 Contact, Total A term sometimes 
 
 employed for full metallic contact. (See 
 Contact, Full-Metallic.} 
 
 Contact, Window or Blind A 
 
 variety of burglar-alarm contact by means 
 of which an alarm bell is rung by a slight 
 pressure against a blind caused by any at- 
 tempt to enter from without after having 
 broken 'the glass in the window. (See 
 Alarm, Burglar.} 
 
Con.] 
 
 586 
 
 [Cor. 
 
 Contacts, Burglar Alarm Con- 
 tacts by means of which the opening or 
 closing of a door or window, or the passage 
 of a person across a given space, is caused 
 to ring an alarm bell. (See Alarm, Burglar.} 
 
 Continuous Action of Electric Bell. (See 
 Appendix Bell, Electric, Continuous Ac- 
 tion of.) 
 
 Continuous Current Arc. (See Appendix 
 Arc, Continuous Current.) 
 
 Continuous Current Transformer. (See 
 Appendix Transformer, Continuous Cur- 
 rent.) 
 
 Contracting Magnetic Whirl. (See Ap- 
 pendix Whirl, Contracting Magnetic.) 
 
 Contraction, Over-Maximal An in- 
 crease in the electrical stimulation of a 
 motor nerve beyond the point where an 
 apparent maximum stimulus has been 
 reached. 
 
 Between the condition of the first maxi- 
 mum and the second maximum an increase 
 in the strength of the current is followed by 
 a decrease in the stimulation. On, how- 
 ever, a further increase in the current 
 strength a second increase in the contrac- 
 tion, termed the over-maximal contraction, 
 occurs. 
 
 Contraplex Telegraph. (See Appendix 
 Telegraph, Contraplex.) 
 
 Convection Transference. (See Appen- 
 dix Transference, Convection.) 
 
 Conversion of Electromotive Force. 
 (See Appendix Force, Electromotive, 
 Conversion of.) 
 
 Conversion, Ratio of A term some- 
 times employed instead of ratio of trans- 
 " formation. (See Appendix Transforma- 
 \ tion, Ratio of.) 
 
 Convert. To transform or change. 
 
 Converter, Rotary A rotary trans- 
 former. (See Appendix Transformer, 
 Rotary.) 
 
 Converting. Transforming or changing. 
 
 Co-phasal. Two or more quantities 
 which vary harmonically, and whose rates 
 of increase or decrease at any given time 
 maintain a constant ratio. 
 
 Co-phasal Alternations. (See Appendix 
 Alternations, Co-phasal.) 
 
 Copper Arc. (See Appendix Arc, Cop' 
 per.) 
 
 Copper Connector. (See Appendix 
 Connector, Copper.) 
 
 Copper-Lead Accumulator. (See Appen- 
 dix Accumulator, Copper-Lead.) 
 
 Copper Resistance. (See Appendix 
 Resistance, Copper.) 
 
 Copper Shell of Electrotype. (See Ap- 
 pendix Shell, Copper, of Electrotype.) 
 
 Copper-Zinc Accumulator. (See Appen- 
 dix Accumulator, Copper-Zinc.) 
 
 Cord and Tip, Conducting A con- 
 ducting cord provided at one of its ends 
 with a tip for the purpose of ready inser- 
 tion in a wall socket. 
 
 Cord, Incandescent Lamp A flex- 
 ible lamp cord of two strands suitable for 
 use with a pendent incandescent lamp. 
 
 Core, Coked, of Incandescent Filament 
 A filament for an incandescent elec- 
 tric lamp, formed of a core of electrically 
 coked carbon, whose surface is covered 
 with a deposit of carbon derived from the 
 electrical decomposition of a hydrocarbon 
 gas or vapor. 
 
 Core Loss of Transformer. (See Appen- 
 dix Loss, Core, of Transformer.) 
 
 Core Pins of Magnet. (See Appendix 
 Pins, Core, of Magnet.) 
 
 Cores, Krizik's Cores for magnetic 
 
 solenoids shaped so as to insure an ap- 
 proximately uniform pull in different posi- 
 tions in the solenoid. (See Bars, Krizik's.) 
 
 Coreless Armature of Dynamo or Motor. 
 (See Appendix Armature, Coreless, of 
 Dynamo or Motor.} 
 
Cor.] 
 
 587 
 
 [Cor. 
 
 Corona, Electrostatic A luminous 
 
 effect produced on the surface of a thin 
 sheet of mica, or other similar insulating 
 material, when placed between two elec- 
 trodes between which discharges of com- 
 paratively high difference of potential are 
 passing. 
 
 Steinmetz describes the phenomena of the 
 electrostatic aurora and corona in the Elec- 
 trical Engineer for April 5, 1893, as follows : 
 
 "Very interesting luminous effects take 
 place when a thin sheet of good insulating 
 material, as mica, is placed between the elec- 
 trodes. At a difference of potential of 830 
 volts and a thickness of mica of 1.8 milli- 
 centimetres, in darkness a faint bluish 
 glow becomes visible between the mica 
 and the electrodes. This glow is very 
 perceptible at 970 volts, and faintly visi- 
 ble in broad daylight at 1,560 volts. With 
 increasing difference of potential, this bluish 
 glow increases in intensity, forming a sharply 
 defined, smooth blue line around the elec- 
 trodes at their point of contact with the 
 mica. 
 
 " At a difference of potential of 4.5 kilo- 
 volts thickness of mica of 2.3 milli-centi- 
 metres violet creepers of about two mm. 
 length break here and there out of the line 
 of bluish glow. These creepers are distinctly 
 different from the blue glow surrounding the 
 electrodes and increasein number and length 
 with increasing potential, until they form a 
 broad electrostatic aurora surrounding the 
 electrodes on either surface of the mica 
 sheet, consisting of an infinite number of 
 small violet streamers, rushing with a hiss- 
 ing noise over the mica. This corona in- 
 creases rapidly in width until it reaches the 
 edges of the mica sheet. Then white sparks 
 of intense brightness pass from electrode to 
 electrode over the surface of the mica, first 
 few in number, then with increasing poten- 
 tial, covering the whole sheet with an in- 
 finite number of streaks of lightning with a 
 roaring noise. The amount of current pass- 
 ing through these sparks is exceedingly 
 small, for no perceptible reaction upon the 
 primary circuit was noticed. The length of 
 these sparks is many times larger than the 
 
 sparking distance in air, being tenfold at 17 
 kilovolts. They are intensely hot, and leave 
 whitish marks, due to calcination, on the 
 mica when passing over it. The sheet of 
 mica, and especially the electrodes, become 
 heated very rapidly, the mica twists and be- 
 gins to splinter, to separate into sheets, until 
 finally it breaks down. 
 
 " The width of the electrostatic corona is 
 half the length of these sparks. The length of 
 these sparks depends somewhat upon fre- 
 quency and the thickness of the mica sheet, 
 being greater for higher frequency and thin- 
 ner mica disc, but apparently only in so far 
 as the capacity, or rather the charging cur- 
 rent of the condenser, represented by the 
 mica disc as dielectric, is increased there- 
 by." 
 
 Corrosion, Electrolytic A term 
 
 frequently employed for the corrosion ot 
 water or gas pipes or other masses o.t 
 metal buried in the earth by electrolytic 
 action. 
 
 In the case of such large currents as those 
 employed in the electric railway car systems, 
 or other similar earth-connected circuits, the 
 corrosion may become marked. In such cases 
 electrolytic corrosion is due to the return 
 current. 
 
 The amount of corrosion varies according 
 to whether the railroad tracks are made the 
 positive or negative terminal of the driving 
 source. 
 
 It is claimed by some that electrolytic cor- 
 rosion is lessened by connecting the trolley 
 line to the negative terminal of the battery 
 and the tracks to the positive terminal. 
 
 Perrine describes this matter as follows : 
 
 "A more complete system of ground- 
 ing seems, however, to offer at least a par- 
 tial solution of this difficulty, which may 
 only be completely worked out in a careful 
 study of the special conditions in some par- 
 ticular case. 
 
 " For such a complete system of ground- 
 ing, in order to reduce to a minimum elec- 
 trolytic corrosion, the negative pole of the 
 dynamo should be connected to the trolley 
 and feeder line ; then at the station connec- 
 tions should be made not only with the rails 
 
Cos. 
 
 588 
 
 [Con. 
 
 and wells, but also with all water and gas 
 pipes, which piping system should also be 
 frequently connected to the track and track 
 feeder, so that whatever current passes by 
 the medium of these pipes should flow out of 
 the earth into them, and thence to the rails 
 by means of metallic and not electrolytic 
 conduction. If 'this be completely accom- 
 plished there can be no corrosion of the pipes 
 caused by the current flowing out of the 
 pipes to the rails, and the only corrosion 
 possible will be that due to the local action 
 caused by the difference of potential along 
 the pipes themselves." 
 
 It would appear that the total corrosion of 
 pipes that are not in metallic connection with 
 the circuit is independent of the polarity of 
 the terminal, since the same amount of cur- 
 rent which enters the pipe from the ground 
 must leave it by again passing to ground. 
 In this manner the area of entrance into the 
 pipe is protected and its area of exit cor- 
 roded electrolytically. By changing the 
 terminals the protected and corroded parts 
 are merely interchanged. 
 
 By making the shunt current passing 
 through the pipes leave the pipes by means 
 of a metallic conductor instead of by the 
 ground, the entire system of pipes is brought 
 below the potential of the ground and a pro- 
 tection or partial protection is thus effected. 
 
 Experiments made on the West End Rail- 
 road of Boston and elsewhere, appear to 
 show that it makes but little difference which 
 terminal is connected to earth. It is by 
 many considered best to alternately connect 
 the positive and negative terminals to earth 
 for a period of a week at a time and not to 
 depend on the earth for a return, or make 
 use of a supplemental wire, but to double- 
 bond the rails with heavy copper wire, plac- 
 ing the connections back z\ to 3 feet respect- 
 ively from the end of the rails to avoid the 
 motion of the joint. With a rail 70 pounds 
 to the yard, on a four track road, this is 
 equivalent to about 28 inches cross-section of 
 steel, the carrying capacity of which is 4^ 
 square inches of copper. If, therefore, an 
 equally good connection is made from the rails 
 to the generator at the power station, there is 
 thus provided a path capable of carrying 
 
 10,000 amperes without undue heating. Rails 
 bonded in this manner and used as returns, 
 will avoid the variable resistance of the earth 
 arising from dry weather, poor contact with 
 earth, frost, etc., and will consequently avoid 
 electrolytic corrosion in neighboring pipes. 
 
 Cosine Law of Illumination. (See Ap- 
 pendix Illumination, Cosine Law of.} 
 
 Coulomb, International The value 
 
 of the international coulomb adopted by the 
 Chicago Congress of 1893, as equal to the 
 quantity of electricity transferred by a cur- 
 rent of one international ampere in one 
 second. 
 
 Coulomb Meter. (See Appendix Meter, 
 Coulomb.} 
 
 Coulomb's Electric Balance. (See Ap- 
 pendix Balance, Coulomb's Electric.} 
 Coulomb's Magnetic Torsion Balance. 
 
 (See Appendix Balance, Coulomb's Mag- 
 netic Torsion.} 
 
 Counter, Electro-Chronometric 
 
 An apparatus employed in a system of elec- 
 trical clocks to so transmit the motion 
 of an ordinary clock to a number of sepa- 
 rate clocks as to control or operate them. 
 
 Electro-chronometric counters consist es- 
 sentially of two parts, namely, 
 
 (l.) The indicator or apparatus connected 
 with the regulating clock and operating to 
 periodically make and break the current of a 
 battery. 
 
 (2.) The mechanism that moves the clock 
 hands when actuated by the current sent into 
 the line by the indicator. 
 
 Counter-Electromotive Force of Elec- 
 trolysis. (See Appendix Electrolysis, 
 Counter-Electromotive Force of.} 
 
 Couple, Molecular Voltaic A vol- 
 taic couple formed of the atoms or radicals 
 of a molecule. 
 
 Lermantoff has shown that during the 
 development of the photographic image in 
 moist collodion a true electrolysis occurs, 
 each silver molecule produced by the action 
 of the light on the sensitized plate forming a 
 
Cra.] 
 
 589 
 
 [Cur. 
 
 voltaic couple with a molecule of silver 
 nitrate and a molecule of iron sulphate of a 
 developer. 
 
 Crater of Arc. A crater formed in 
 the end of the positive carbon electrode in 
 a carbon voltaic arc. (See Arc, Voltaic.') 
 
 Creeping of Belt. (See Appendix Belt, 
 Creeping of.") 
 
 Cross-Fire. A term employed in teleg- 
 raphy for an escape or leakage of current 
 from one telegraphic line to another, due to 
 defective insulation. 
 
 A cross-fire is sometimes called a weather 
 cross. (See Cross, Weather.) 
 
 Cross-Induction of Dynamo Armature. 
 
 (See Appendix Induction, Cross, of 
 Dynamo Armature.) 
 
 Cross, Metallic A form of fault 
 
 attended by a leakage or escape of current 
 from a telegraphic line due to the absolute 
 contact between two or more wires or con- 
 ductors, so that part of the current from 
 one line passes to the other. 
 
 Cross-Over, Trolley In a system 
 
 of electric street railways a device permit- 
 ting the ready passage of a trolley wheel in 
 a continuous direction from one to another 
 of two adjacent wires. 
 
 Cross, Peltier's A cross made by 
 
 placing two plates of dissimilar metals in 
 contact at right angles to each other, and 
 employed for the study of the Peltier effect. 
 (See Effect, Peltier.) 
 
 Crossing Frog. A term sometimes em- 
 ployed in place of trolley cross-over. 
 
 Crystal, Pyro-Electric Any crys- 
 talline substance capable of producing 
 pyro-electric phenomena on being unequally 
 heated. 
 
 Tourmaline, electric calamine, boracite, 
 quartz, tartrate of potash, and sulphate of 
 quinine are examples of pyro-electric crys- 
 tals. 
 
 Cubic Energy. (See Appendix Energy, 
 Cubic.) 
 
 Cup Brush. (See Appendix Brush, 
 Cup.) 
 
 Current Accumulator. (See Appendix 
 Accumulator, Current.) 
 
 Current, Arriving, of Telegraphic Circuit 
 
 A term employed to designate the 
 
 current on a telegraphic line or conductor 
 near the distant end of the wire close to 
 where it enters the ground or earth. 
 
 Current, Axial A term proposed 
 
 for a current whose direction coincides 
 with the direction of the lines of magnetic 
 force. 
 
 This use of the term axial current is in 
 contradistinction to a radial current, or one 
 whose direction is at right angles to the 
 direction of the lines of magnetic force. 
 
 The term axial current is employed in elec- 
 tro-therapeutics in a different sense to the 
 above. (See Current, Axial.) 
 
 Current, Beginning of A term 
 
 sometimes employed for the making or 
 closing of the current in any circuit. 
 
 Current, Bony A term proposed 
 
 by Becquerel for the electric current re- 
 sulting ffom the difference of potential ex- 
 isting between two different parts of a bone 
 of a recently killed animal. 
 
 If a bone be taken from a recently killed 
 animal and the marrow connected by means 
 of metallic terminals with the surface of the 
 bone, an electric current will flow through 
 the circuit, for which Becquerel proposed the 
 'name bony current. 
 
 This term is not generally adopted. 
 
 Current, Cessation of A term 
 
 sometimes employed for the breaking oi 
 the current in any circuit. 
 
 Current, Demagnetizing A cur- 
 rent whose magnetic field is employed to 
 decrease the strength of an already existing 
 magnetic field by directing its lines of 
 force oppositely to that of the existing field. 
 
Cnr.] 
 
 590 
 
 [Cur. 
 
 Current, Effective 
 
 A term pro- 
 
 posed by Ayrton, but not accepted, for the 
 current producing a given effect. 
 
 This term, Ayrton thinks, is an unfortunate 
 one, since the effective current will of course 
 depend on the character of the effect the cur- 
 rent is desired to produce. 
 
 If, however, the word "effect" be under- 
 stood to mean " power," then the vagueness 
 ceases, and, since the power is proportional 
 to the square of the current, the effective 
 current is the square root of the mean 
 squares, but all the effects produced by an 
 alternating current are proportional to the 
 square root of the mean squares. 
 
 The ordinary meaning of effective current 
 is that given it by the definition of the Elec- 
 trical Congress of Paris, in 1889, viz., the 
 square root of the time average of the square 
 of the current. 
 
 An alternating or periodically varying 
 current has an "effective" strength such 
 that if this effective strength were steadily 
 maintained in the same direction through a 
 given resistance it would generate as much 
 heat in a given length of time as the periodi- 
 cal current. 
 
 When electrolysis or the magnetization of 
 iron is the effect produced, the effective cur- 
 rent is identical with the mean current. 
 Where a heating or dynamometric effect is to 
 be produced, the effective current is equal to 
 the square root of the mean square of the 
 current. 
 
 Current, Effective Starting, of Motor 
 
 The indicated value of the starting 
 
 current of a motor as observed on an 
 ammeter. 
 
 Current Efficiency of Secondary Battery. 
 
 (See Appendix Battery, Secondary, 
 Current Efficiency of.) 
 
 Current, Entering, of Telegraphic Cir- 
 cuit A term employed to designate 
 
 the current on a telegraphic line or con- 
 ductor near the battery. 
 
 Current, Harmonics of A term 
 
 sometimes used for the upper harmonics of 
 
 a current. (See Appendix Current, 
 Upper Harmonics of.) 
 
 Current, M. A term proposed by 
 
 Ayrton for mean current. 
 
 This term, M. current, is employed to sig- 
 nify the average value with respect to time, 
 and is obtained by dividing the total quantity 
 of electricity which passes through a given 
 circuit in a given number of seconds by the 
 number of seconds. It has not been gen- 
 erally accepted. 
 
 Current, M. S. A term proposed 
 
 by Ayrton for mean square current. 
 
 This term was proposed in order to avoid 
 the use of the alleged vague term, effective 
 current. It applies to cases where the effec- 
 tive current has a value equal to the mean 
 square of the current. It has not been gen- 
 erally accepted. 
 
 Current, Maximum Starting, of Motor 
 
 The highest value that the starting 
 
 current of a motor attains. 
 
 Current of Charge on Telegraphic Line. 
 
 (See Appendix Line, Telegraphic, 
 Charge Current on.) 
 
 Current, Polyphase A term now 
 
 generally employed in place of multiphase 
 current. (See Current, Multiphase.} 
 
 Current, Polyphase Alternating, Pro- 
 posed A. I. E. E. Definition for A 
 
 combination of more than two alternating 
 currents differing in phase. 
 
 Current, B. M. S. A term pro- 
 posed by Ayrton tor the square root of the 
 mean square of the current. 
 
 This term was proposed in order to avoid 
 the use of the alleged vague term, effective 
 current. It applies to cases where the effec- 
 tive current has a value equal to the square 
 root of the mean square of the current. It 
 has not been generally accepted. 
 
 Current, Radial A term proposed 
 
 for a current whose direction is at right 
 angles to the direction of the lines of mag- 
 netic force. 
 
Car.] 
 
 591 
 
 [Cur. 
 
 This use of the word radial current is in 
 contradistinction to the word axial current, 
 whose direction coincides with that of the 
 lines of magnetic force. (See Appendix 
 Current, Axial.) 
 
 Current, Simple or Two-Phase Alternat- 
 ing 1 Two alternating currents whose 
 
 phases differ by 90 or by 270. 
 
 Current, Sinusoidal A term some- 
 times employed for sinuous current. (See 
 Current, Sinuous.) 
 
 A simple-harmonic current in respect to 
 time. 
 
 A current whose strengths graphically 
 set forth as ordinates as time to abscissas 
 follow a sinusoidal curve. 
 
 Current, Starting, of Motor The 
 
 current which a motor requires in order to 
 start from a state of rest. 
 
 Current Transformation. (See Appen- 
 dix Transformation, Current.) 
 
 Current, Triphase A term some- 
 times employed in place of three-phase 
 current. (See Appendix Currents, Three- 
 Phase.) 
 
 Current, Triphase Alternating, Proposed 
 A. I. E. E. Definition for Three al- 
 ternating currents whose phases differ by 
 60 or 120. 
 
 Current, Tubular A term some- 
 times applied to a current that traverses 
 the superficial portions only of a conductor. 
 
 When a rapidly intermittent current is sent 
 through a solid conductor, the current den- 
 sity is greater at the surface of the conductor 
 than in the central portions, and, when the 
 rapidity of alternation becomes very great, 
 is confined to an exceedingly thin outer layer. 
 
 A tubular current possesses no magnet- 
 izing power on anything placed inside the 
 tube. 
 
 Current, Upper Harmonics of A 
 
 series of higher harmonic currents of 
 greater- frequency than the fundamental 
 current impressed on a simple-harmonic 
 
 current by any means. (See Appendix-^ 
 Currents, Complex-Harmonic.) 
 
 Current, Yirtual A somewhat 
 
 vague term sometimes employed for a cur- 
 rent virtually equivalent to something else. 
 
 A term employed for the square root of 
 the mean square of the current strength,, 
 
 Current, Working, of Motor The 
 
 current required to maintain a motor when 
 its load is on. 
 
 Currents, Complex-Harmonic 
 
 Currents which result from the superposi- 
 tion of several simple-harmonic currents. 
 (See Current, Simple-Harmonic.) 
 
 Currents resulting from the co-existence 
 of the higher harmonic currents with the 
 fundamental harmonic current. 
 
 Unless certain precautions are taken the 
 currents produced in the secondary circuit of 
 a transformer or induction coil are by no 
 means simple-harmonic currents. It is true, 
 of course, that the fundamental frequency 
 has the same frequency as that of the cur- 
 rents sent through the primary circuit, but 
 the currents so induced in the secondary, 
 however, are complex-harmonic currents, 
 their frequency depending, according to Pu- 
 pin: " On the fundamental frequency of the 
 ohmic resistance, and especially on the self- 
 induction and electrostatic capacity of the 
 primary or secondary circuits." 
 
 Complex-harmonic currents of the second- 
 ary of induction coils possess a fundamental 
 frequency the same as the frequency of the 
 currents impressed on the primary, but they 
 hav*e associated with them a number of 
 higher harmonic currents, which correspond 
 to the overtones of a musical note. 
 
 These overtones are due to rapid elec- 
 trical oscillations accompanying the spark 
 discharges. The association of these higher 
 harmonic currents with the fundamental 
 harmonic current produces what are called 
 complex-harmonic currents. 
 
 Complex-harmonic currents always exist 
 when there is iron in a circuit, especially if 
 the iron is highly magnetized, when they are 
 due to the fact that the magnetization pro- 
 
Cur.J 
 
 592 
 
 [Cur. 
 
 duced is not proportional to the magnetizing 
 iorcc. 
 
 It is only In circuits of constant resistance, 
 containing no iron, that the current produced 
 by a simple harmonic or sine wave of E. M. 
 F. is a sine wave. Magnetic hysteresis, or 
 a periodically varying resistance as by an 
 electric arc, causes a distortion of the cur- 
 rent and a consequent superposition of 
 higher harmonics on the fundamental wave. 
 Consequently the primary currents of trans- 
 formers at open secondary circuit or very 
 light load are complex harmonics, and 
 approach more nearly to true sine shapes at 
 increasing loads. When, however, the second- 
 ary . M. Fs. of a transformer are simply 
 harmonics, the secondary currents are also 
 simply harmonics, in circuits without iron cored 
 coils. 
 
 Currents produced by complex-harmonic 
 E. M. F. are also complex harmonic ; gen. 
 erally, however, the higher complex harmonics 
 of the E. M. F. wave are larger than the com- 
 plex harmonics of the current wave. 
 
 Currents, Mutually-Induced -- Cur- 
 rents set up or produced by means of 
 mutual induction. (See Induction, Mu- 
 
 Currents, Polyphase - Currents 
 4itfering in phase from one another and, 
 therefore, requiring separate circuits for 
 Hse. 
 
 The currents may differ from one another 
 by one-half phase, by one-third of a phase, 
 a quarter phase and so on, when they are 
 respectively called di phase or two -phase 
 currents, triphase or three-phase currents, 
 and four -phase currents. An ordinary alter- 
 nating current is called a single phase or uni- 
 phase current. The latter term is the. prefer- 
 able one. 
 
 The term polyphase currents is applied to 
 all currents over three-phase, though some- 
 times also to all currents over two-phase. 
 
 Currents, Polyphased, Alternating - 
 
 Two or more alternating currents dif- 
 fering in phases from each other. 
 
 Currents, Skin -- A term some- 
 
 times applied to the currents that are lim- 
 ited to the surface of a solid conductor. 
 
 Rapidly alternating currents are limited to 
 the surface of solid conductors since before 
 any such currents have time to penetrate 
 toward the centre of a solid conductor their 
 direction is reversed, thus limiting them to 
 the surface portions. 
 
 Currents, Three Phase Triphased 
 
 currents. (See Appendix Currents, Tri- 
 phased, Alternating.) 
 
 Currents, Triphased, Alternating 
 
 Three alternating currents differing 
 1 20 in phase from each other. 
 
 In the two-phase system two currents differ- 
 ing in phase 90 have a common return wire 
 whose area should be V 2 greater than either 
 leading wire. 
 
 In the three-phase system each of three 
 currents differing in phase 120 uses alter- 
 nately one or two of the three wires for a 
 return. 
 
 Curve, Arrival of Telegraph Circuit 
 
 A curve of ordinates and abscissas 
 
 which represent respectively the times and 
 the gradual increase of current at the re- 
 ceiving end of a telegraph circuit from the 
 time the circuit is closed until the time 
 the current has reached its full strength. 
 
 Curve, Clown's Hat A term pro- 
 posed for the curve of a current or 
 electromotive force in which the pressure 
 generated increases or decreases at a 
 maximum rate of change, 
 
 The name is taken from the shape of the 
 curve being somewhat similar to the shape of a 
 peaked or clown's hat. 
 
 Curve, Top-Hat A term proposed 
 
 for the current or E. M. F. in which the 
 pressure generated is fairly constant for a 
 considerable time at its maximum rise 
 and fall. 
 
 The name is taken from the shape of the 
 curve being somewhat similar to that of a 
 top-hat, or flat crowned hat. A current for 
 the primary of a transformer r induction 
 
Cut.] 
 
 593 
 
 [Dec. 
 
 coil, however, of the top-hat type, makes a 
 bad form of secondary current curve, for in 
 such a curve the rate of change, whether 
 increasing or decreasing, would be small. 
 The current whose curve of electromotive 
 force is sharp and peaked like a clown's hat 
 would, of course, be preferable. 
 
 Cut-In, A A term sometimes 
 
 employed in place of film cut-out. 
 
 An automatic-guard cut-out. (See Cut- 
 Out, Film.") (See Appendix Guard, Auto- 
 matic, for Series- Connected Incandescent 
 Lamps.} 
 
 Cut-Out, D. P. A contraction 
 
 for double-pole cut-out. (See Appendix 
 Cut- Out, Double-Pole,} 
 
 Cut-Out, Double-Pole A cut-out 
 
 which provides in one operation the cut- 
 ting out of both the positive and the nega- 
 tive leads. 
 
 Cut-Out, Electro-Magnetic 
 
 A term 
 
 sometimes employed for a cut-out operated 
 by means of an electro-magnet. (See Cut- 
 Out, Automatic, for Series-Connected 
 Electro-Receptive Devices.) 
 A form of electro-magnetic cut-out is used 
 
 in charging accumulators and sometimes in 
 street railway circuits. 
 
 Cut-Out, S. P. A contraction for 
 
 single-pole cut-out. (See Appendix Cut- 
 Out, Single-Pole.) 
 
 Cut-Out, Single-Pole A cut-out by 
 
 means of which the circuit is broken or 
 cut in one of the two leads only. 
 
 Cut-Out, Wedge A form of cut- 
 out employed on telegraphic circuits. 
 
 The ends of the instrument wire are con- 
 nected to the opposite sides of a wedge 
 formed of two brass plates suitably insulated 
 from one another. The ends of the line wire 
 or conductor are suitably connected to two 
 metallic pieces that are maintained in elec- 
 trical contact by means of a spring electri- 
 cally connected to one of the pieces and 
 caused to bear with elastic pressure against 
 the other piece. In order to introduce an 
 instrument into the line circuit, a switch- 
 wedge, or plug, is inserted between the two 
 pieces, and, thus separating them, opens 
 the circuit of the line wire or conductor, and 
 at the same time connects it with the instru- 
 ment thus introduced. 
 
 Cyclic. Of or pertaining to a cycle. 
 (See Cycle.) 
 
 D. B. Switch. (See Appendix Switch, 
 D.B.) 
 
 D. P. Cut-Out. (See Appendix Cut- 
 Out, D. P.) 
 
 D. P. Switch. (See Appendix Switch, 
 D. P.) 
 
 Damping Magnet. (See Magnet, Damp- 
 ing.) 
 
 Dark Discharge. (See Appendix Dis- 
 charge, Dark.) 
 
 Dark Segment of Aurora. (See Appen- 
 dix Segment, Dark, of Aurora.) 
 
 Dead Ground. (See Appendix Ground, 
 Dead.) 
 
 Declination Compass. (See Appendix 
 Compass, Declination.) 
 
 Decomposition, Electro-Chemical 
 
 A term often employed for electrolytic 
 decomposition. (See Electrolysis.) 
 
 Decomposition, Molecular 
 
 The 
 
 separation or breaking up of a molecule 
 into its constituent atoms or radicals. 
 
 Molecular decomposition may be effected 
 in the following ways, namely: 
 
 (1) By electrolysis, or the action of an 
 electric current. 
 
 (2) By thermolysis, or the action of heat. 
 
 (3) By actinism, or the action of light. 
 
Def.] 
 
 594 
 
 [Die. 
 
 (4) By chemism, or the action of superior 
 chemical affinity. 
 
 (5) By pressure. 
 
 Deflecting Magnet. (See Appendix 
 Magnet, Deflecting.} 
 
 Degree, Water-Gramme The 
 
 amount of heat required to raise the tem- 
 perature of one gramme of water at 4 C., 
 the temperature of its maximum density, 
 one degree centigrade. 
 
 A small calorie. (See Calorie, Small.} 
 
 Delta Triphase System. (See Appendix 
 System, Delta Triphase.} 
 
 Demagnetizing Current. (See Appen- 
 dix Current, Demagnetizing.} 
 
 Depolarizer. The material employed in 
 a voltaic cell for the purpose of depolarizing 
 it. (See Cell, Voltaic, Polarization of.} 
 
 In most cases the depolarizer is a different 
 liquid and is kept separate from the exciting 
 liquid or electrolyte. In some cases, how- 
 ever, the depolarizer is mixed with the excit- 
 ing liquid. 
 
 Deposit, Electro Metallurgical Burnt 
 
 A term sometimes applied to a black 
 
 deposit of metal which is thrown down 
 when the intensity of the depositing cur- 
 rent is too strong. (See Deposit, Electro- 
 Met a llurgica I. } 
 
 Deviation, Quadrantal, of Mariner's Com- 
 pass The deviation of the magnetic 
 
 needle due to the induced magnetism in 
 the iron of a ship acting as a mass of soft 
 iron, and not as a permanent magnet. 
 
 Quadrantal deviation changes sign and 
 passes through successive opposite maxima 
 four times in one complete revolution of the 
 ship. 
 
 Quadrantal deviation is corrected by plac- 
 ing masses of soft iron, usually spherical in 
 shape, in suitable positions on each side of 
 the compass. 
 
 Deviation, Semi-Circular, of Mariner's 
 Compass The deviation of a mag- 
 netic needle due to the permanent mag- 
 
 netism in the iron of a ship having its 
 resultant in the horizontal plane. 
 
 Semi-circular deviation passes through 
 two opposite maxima and two zero points as 
 the ship completes a revolution, and these 
 zero points of deviation occur when the 
 resultant magnetic axis of the ship coincides 
 with the magnetic meridian. 
 
 Semi-circular deviation is corrected by 
 fastening a permanent magnet in the proper 
 position near the compass to neutralize the 
 influence of the ship's iron. 
 
 Diagram, Load A diagram or 
 
 curve representing to scale the load or ac- 
 tivity of a plant at different times. 
 
 Dial, Induced Single-Needle A 
 
 dial employed in single-needle telegraphy 
 in which both the needle and its axle are 
 formed of soft iron and have magnetism 
 induced in them by means of permanent 
 horseshoe magnets placed so as to act 
 magnetically on the needle. 
 
 The object of the induced single-needle 
 telegraphic dial is for the purpose of avoid- 
 ing the weakening of the magnetism of the 
 needle, or its total loss or reversal, by vari- 
 ous means, such, for example, as a discharge 
 of lightning, the effect of earth currents, etc. 
 
 Dial Telegraph. (See Appendix Tele- 
 graph, Dial.} 
 
 Dialyzing. Subjecting to the process of 
 dialysis. (See Dialysis.} 
 
 Diamagnetized. Endowed with dia- 
 magnetic properties. (See Diamagnetism.} 
 
 Diamond Drill. (See Appendix Drill, 
 Electric, Diamond} 
 
 Dielectric, After- Working of A 
 
 term sometimes employed for a residual 
 charge. (See Charge, Residual.} 
 
 The term after-working of a dielectric was 
 proposed by Boltzmann. It is not much 
 used in the United States. 
 
 Dielectric, Breaking-Down of - 
 Such a weakening of a dielectric that per- 
 mits a disruptive discharge to pass through 
 
Die.] 
 
 595 
 
 [Dis. 
 
 its substance. (See Appendix Dielectric, 
 Disruptive Strength of.} 
 
 Dielectric, Disruptive Strength of 
 
 The resistance which an insulating 
 medium or dielectric offers to the disrupt- 
 ive passage of an electric discharge 
 through it. 
 
 According to Steinmetz the disruptive 
 strength of different materials shows no re- 
 lation to their electric resistance. 
 
 Dielectric Hysteresis. (See Appendix 
 Hysteresis, Dielectric.) 
 
 Difference of Tension. (See Appendix 
 Tension, Difference of.) 
 
 Differential Coils. (See Appendix 
 Coils, Differential.) 
 
 Differential Electro-Dynamometer.- (See 
 Appendix Dynamometer, Electro, Differ- 
 ential.) 
 
 Differential Electro-Magnet. (See Ap- 
 pendix Magnet, Differential, Electro.) 
 
 Differential Winding. (See Appendix 
 Winding, Differential.) 
 
 Diffusing Globes for Electric Lights. 
 
 (See Appendix Globes, Diffusing, for 
 Electric Lights) 
 
 Di-Phase Armature. (See Appendix 
 Armature, Di-Phase.) 
 
 Di-Phase Generator. (See Appendix 
 Generator, Di Phase.) 
 
 Di-Phase Motor, (See Appendix 
 Motor, Di-Phase.) 
 
 Diplex Telegraph. (See Appendix 
 Telegraph, Diplex.) 
 
 Dip of Line Wire or Conductor. (See 
 Appendix Conductor or Line Wire, Dip 
 of-} 
 
 Dipping Basket. (See Appendix Bas- 
 ket, Dipping) 
 
 Dipping Hook. (See Appendix Hook, 
 Dipping.) 
 
 Dips. Acid solutions employed in elec- 
 tro-plating in which articles that are to be 
 plated are cleansed by dipping. 
 
 Direct-Current Dynamo-Electric Ma- 
 chine. (See Appendix Machine, Dyna- 
 mo-Electric, Direct- Current.) 
 
 Direct-Current Exciter. (See Appendix 
 Exciter, Direct- Current) 
 
 Direct-Current Rotary Transformer. 
 
 (See Appendix Transformer, Direct-Cur- 
 rent Rotary.) 
 
 Direct Reading Galvanometer. (See 
 Appendix Galvanometer, Direct Read- 
 ing.) 
 
 Direct Working of Telegraphic Sounder. 
 
 (See Appendix Working, Direct, of 
 Telegraphic Sounder.) 
 
 Directed Streaming Discharge. (See 
 Appendix Discharge, Directed-Stream- 
 ing.) 
 
 Directing Clock. (See Appendix Clock, 
 Directing.) 
 
 Disc, Retarding A copper disc 
 
 supported on a rotating shaft, and so 
 placed as to cut the lines of force from a 
 magnet for the purpose of retarding the 
 speed of rotation. 
 
 In Elihu Thomson's recording electric 
 meter a copper disc, moving in the field of a 
 permanent magnet, is so retarded that the 
 resulting number of revolutions is directly 
 proportional to the energy to be measured. 
 
 . Discharge, Dark A term applied 
 
 by Faraday to that portion of a convective 
 discharge, separating the positive from the 
 negative electrode, that occurs under 
 certain circumstances through a rarefied 
 gas. 
 
 Discharge, Directed-Streaming 
 
 A Tesla discharge which assumes the 
 shape of a hollow luminous cone. 
 The discharge takes place between a sphere or 
 ball S (Fig. 570), and a ring-shaped electrode. 
 
Dis.] 
 
 596 
 
 [Dis. 
 
 W, thereby producing a hollow luminous cone 
 such as is shown in the figure. 
 
 57O. Directed-Streaming Discharge. 
 
 Discharge, Luminous Disc-Shaped 
 
 A name given to a variety of Tesla dis- 
 charge that occurs between ring-shaped ter- 
 minals. 
 
 The terminals are arranged as shown in Fig. 
 571. On the passage of the current a luminous 
 
 Irfc 
 
 shaped terminals C, C, which presents the ap- 
 pearance shown in the figure. 
 
 Discharge, Slow, Method of An 
 
 insulation test for a well-insulated telegraphic 
 line, by the observation of the rate at which 
 a charge leaks out when the conductor is left 
 insulated. 
 
 A well-insulated cable will take, say, half an 
 hour to fall to half charge, and, with uniform 
 cables, this time is independent of their length. 
 
 Discharge, Spark An electric dis- 
 charge effected by means of a spark. 
 
 A disruptive discharge. (See Discharge, Dis- 
 ruptive.) 
 
 Discharge, Tesla An exceedingly 
 
 high frequency discharge. 
 
 The Tesla discharge is so named after its dis- 
 coverer, Nikola Tesla. 
 
 Dish, Chafing, Electric An elec- 
 trically heated chafing dish. 
 
 An electric heater is applied to an ordinary 
 chafing dish, so as to permit the electrical heat- 
 ing to take the place of ordinary heating. 
 
 A form of electrically heated chafing dish is 
 shown in Fig. 572, and will be readily understood 
 from inspection. (See Heater, Electric.) 
 
 Fig. 5f I. Luminous Disc-Shaped Discharge. 
 
 disc-shaped discharge occurs between the ring- 
 
 Fig. 572. Electric Chafing Dish. 
 
 Disruptive Strength of Dielectric. (See 
 Appendix Dielectric, Disruptive Strength 
 of.) 
 
 Dissonance, Electric Electric dis- 
 agreement. 
 
 Two alternating currents are in electric dis- 
 sonanee when their periods are different. The 
 term electric dissonance is employed in contra- 
 distinction to electric consonance. 
 
 Distance, Striking The distance 
 
 through which a disruptive discharge will 
 pass. (See Discharge, Disruptive.) 
 
 Distance, Striking, for Various Sub- 
 stances Tables of Steinmetz give the 
 
 following values for the striking distances of 
 various mediums under certain circumstances. 
 
Dis.] 
 
 597 
 
 [Dis. 
 
 8 IN MILLI-CENTIMETRES, V IN KILO-VOLTS. 
 
 Air S = 36 (, i-3 V _ I )+54V + i. 2 V 18 < V < 24.. 
 
 Mica S= .2 4 V+.oi4 5 V 8 < V < 20.3 
 
 Vulcanized Fibre 8 = 7.66 V + 2. 3 V* 2.2 < V < 22.5 
 
 Dry Wood Fibre S = 7.66 V 2.8 < V < 21.6 
 
 Paraffined Paper ; S = 3 V 6.9 "5: V < 24.8 
 
 Melted Paraffin, 65 C S = 12.4 V 3.9 < V < 27.1 
 
 Boiled Linseed Oil. 21 C 8 = 12.5 V 7.6 < V < 21.3 
 
 Turpentine Oil 8 = 15.7 V 7.1 < V < 15.6 
 
 Copal Varnish S = 30 V 9.7 "^ V "^ 20.4 
 
 Crude Lubricating Oil S = 60 V 4.4 "^ V "f~ 15.9 
 
 Vulcabeston S = 28 V 4.0 < V < 12.6 
 
 Asbestos Paper S = 23 V 2.7 "^ V "5: 5.0 
 
 Creeping discharge over surface of Mica S = 55 (V 2)" 4.5 _V_ 17.1 
 
 In the above table d equals the thickness 
 of the dielectric in milli-centimetres, or 
 thousandths of a cm.; e equals the Napierian 
 base, and V equals the potential difference in 
 kilo-volts. 
 
 The last column gives the lowest and highest 
 values of V m the experiments on the different 
 materials. 
 
 The following table gives the data concerning 
 a disruptive discharge through air: 
 
 TABLE I. DISRUPTIVE DISCHARGE THROUGH AIR. 
 
 S = 36 
 
 _ t 1+54 V + 1.2 V. 
 
 Maximum Differ- 
 
 Sparking Distance 
 
 Electrostatic Gra- 
 
 Sparking Distance 
 
 Difference. 
 
 Difference in 
 
 ence of Potential 
 in Kilo- Volts. 
 
 observed in Milli- 
 centimetres. 
 
 dient, in Kilo- 
 Volts per cm. 
 
 calculated in Milli- 
 centimetres. 
 
 8 8 
 
 per cent, of 
 8 
 
 
 
 
 
 calc. obs. 
 
 calc. 
 
 V 
 
 8 
 
 g 
 
 8 
 
 A 
 
 % 
 
 
 obs. 
 
 
 calc. 
 
 
 
 .18 
 
 3-0 
 
 60 
 
 2.2 
 
 .8 
 
 (-36) 
 
 .26 
 
 4.6 
 
 57 
 
 3.8 
 
 .8 
 
 (-21) 
 
 .29 
 
 5.1 
 
 57 
 
 4.5 
 
 .8 
 
 13-3 
 
 .46 
 
 8.1 
 
 57 
 
 8.9 
 
 + -8 
 
 + 9- 
 
 .48 
 
 9.1 
 
 53 
 
 9-5 
 
 + -4 
 
 + 4-2 
 
 53 
 
 ii 
 
 48 
 
 II. O 
 
 
 
 
 
 '43 
 
 16 
 48 
 
 44 
 30 
 
 17.1 
 
 + i.l 
 + 1-3 
 
 + 6,4 
 
 + 2.6 
 
 1.76 
 
 68 
 
 26 
 
 66.4 
 
 1.6 
 
 2.4 
 
 2.46 
 
 100 
 
 25 
 
 105.7 
 
 + 5-7 
 
 + 5-4 
 
 3.96 
 
 190 
 
 21 
 
 197 
 
 + 7 
 
 + 3-5 
 
 5-5 
 
 287 
 
 ig 
 
 297 
 
 +10 
 
 + 3-4 
 
 9-5 
 
 575 
 
 17 
 
 584 
 
 + 9 
 
 + 1.6 
 
 12.7 
 
 860 
 
 15 
 
 
 16 
 
 
 iS-7 
 
 1150 
 
 
 IIIO 
 
 40 
 
 -3% 
 
 19 6 
 
 1440 
 
 14 
 
 1480 
 
 +40 
 
 + 2.7 
 
 21.6 
 
 173 
 
 13 
 
 1800 
 
 +70 
 
 + 3-9 
 
 24.0 
 
 20IO 
 
 12 
 
 1950 
 
 60 
 
 
 Average 
 
 
 14.7 
 
 4-2 
 
 
 Distant Battery. (See Appendix Bat- 
 tery, Distant?) 
 
 Distortion of Magnetic Field. (See 
 
 Appendix Field, Magnetic, Distortion of) 
 
Dis.] 
 
 598 
 
 Distributing Board. (See Appendix 
 Board, Distributing) 
 
 Distributing Brushes of Electric Motor. 
 
 (See Appendix Brushes, Distributing, of 
 Electric Motor.) 
 
 Distributing Switch Board. (See Appen- 
 dix Board, Distributing- Switch.) 
 
 Distribution of Complex Lamellar Mag- 
 netism. (See Appendix Magnetism, Com- 
 plex Lamellar, Distribution of.) 
 
 Disturbance, Magnetic A term 
 
 sometimes employed for the temporary varia- 
 tions in the intensity of the earth's magnet- 
 ism caused by a magnetic storm. 
 
 Divided Touch. (See Appendix Touch, 
 Divided?} 
 
 Door Trigger. (See Appendix Trigger, 
 Door.) 
 
 Dot-and-Dash Code. (See Appendix 
 Code, Dot-and-Dash.) 
 
 Double Block, Duplex. (See Appendix 
 Block, Double Duplex.) 
 
 Double-Bronze Wire. (See Appendix 
 Wire, Double-Bronze.) 
 
 Double-Contact Push. (See Appendix 
 Push, Double-Contact.) 
 
 Double-Contact Push Button. (See Ap- 
 pendix Button, Push, Double-Contact) 
 
 Double-Current Telegraphic Working. 
 
 (See Appendix Working, Double-Current 
 Telegraphic) 
 
 Double-Curve Pull-Off. (See Appendix 
 Pull-Off, Double-Curve) 
 
 Double-Curve Trolley Hanger. (See 
 
 Hanger, Double-Curve Trolley.) 
 
 Double Liquid Voltaic Cell. (See Cell, 
 Voltaic, Double Liquid) 
 
 Double-Pole Cut-Out. (See Appendix 
 Cut-Out, Double-Pole) 
 
 Double-Wire System for Electric Light 
 
 Leads. (See Appendix Leads, Doubt?- 
 Wire System for Electric Light) 
 
 Drifting of Zero Point. A term fre- 
 quently employed in place of shifting of zero 
 point. (See Appendix Shifting of Spot of 
 Light) 
 
 Drift of Needle. (See Appendix Needle, 
 Drift of) 
 
 Drill, Electric Diamond A dia- 
 mond drill driven by electric power. 
 
 Drill, Electro-Percussion A drill 
 
 for quarrying or mining purposes, in which 
 the reciprocating motion is obtained by send- 
 ing alternately a current through a pair of sole- 
 noids of which the drill stock forms the core. 
 
 Drill, Electro-Keciprocating An 
 
 electro-percussion drill. (See Appendix 
 Drill, Electro-Percussion) 
 
 Drop Relay-Contact (See Appendix 
 Contact, Drop-Relay) 
 
 Drop Trolley. (See Trolley, Drop) 
 
 Dry Battery. (See Appendix Battery, 
 Dry) 
 
 Dry Gelatine Cell. (See Appendix Cell, 
 Dry Gelatine) 
 
 Duplex Balance. (See Appendix Bal- 
 ance, Duplex) 
 
 Duplex Telegraph. (See Appendix 
 Telegraph, Duplex) 
 
 Duplex Telephony. (See Appendix 
 Telephony, Duplex?) 
 
 Dust, Electrical Aggregation of, in Dust- 
 Laden Air A coalescence of a great 
 
 number of separate particles of dust, in dust- 
 laden air, by means of the action of an elec- 
 trical brush discharge. 
 
 If a brush or convection discharge be passed 
 through dust or smoke-laden air, contained for 
 purposes of observation in a glass globe, the 
 electrical aggregation of the particles of dust or 
 smoke rapidly clears the air. This method is 
 practically employed in the manufacture of lamp- 
 black. 
 
 Dyad Atom. (See Appendix Atom, 
 Dyad) 
 
 Dynamic Multiplier. (See Appendix 
 Multiplier, Dynamic) 
 
 Dynamics. That branch of mechanics 
 
Dyn.J 
 
 which treats of the action of a force in pro- 
 ducing motions or pressures. 
 
 Dynamo-Electric Machine for Electro- 
 Plating. (See Appendix Machine, Dy- 
 namo-Electric, for Electro-Plating!) 
 
 Dynamo, Idle Wire of (See Appen- 
 dix Wire, Idle, of Armature of Dynamo!) 
 
 Dynamometer, Electro, Differential 
 
 A double dynamometer with the moving 
 coils rigidly connected and oppositely influ- 
 enced, so that the movement of the suspen- 
 sion system can be reduced to zero by elec- 
 trical adjustments when the instrument is 
 under operation. 
 
 Dynamo, Motor (See Appendix 
 
 Motor, Dynamo?) 
 
 Dynamo or Motor Frame. (See Appen- 
 dix Frame, Dynamo or Motor!) 
 
 Dynamo Standards. (See Appendix 
 Standards, Dynamo!) 
 
 Dynamos Coupled in Potential Series. 
 
 (See Appendix Series, Potential, Dynamos 
 Coupled z'n.) 
 
 Dynamotor. A continuous current trans- 
 former. 
 
 599 
 
 [Eff. 
 
 A term now generally employed for motor- 
 generator. (See Generator, Motor!) 
 
 A motor-dynamo, or motor-generator, is prac- 
 tically a dynamo driven by means of an electric 
 current. The motor-dynamo consists of two dis- 
 tinct or separate armatures placed on the same 
 shaft, or two separate armature windings placed 
 on the same core. On sending the current 
 through one armature or winding it acts as a 
 motor and turns the shaft, thus producing current 
 in the other armature or winding. Such a ma- 
 chine is sometimes called a rotary transformer, 
 though this name is preferably limited to a ma- 
 chine containing only a single armature, which 
 acts as a generator and motor armature. (See 
 Transformer, Constant Current.') 
 
 Such a machine is employed for transforming 
 continuous currents into continuous currents of 
 different potential, or for transforming alternating 
 or polyphase currents into continuous currents, or 
 vice versa. 
 
 Dyne : cm. An abbreviation proposed for 
 dyne-centimetre, the C. G. S. unit of moment 
 of couple. 
 
 Dyne : cm 2 . An abbreviation proposed for 
 dyne per square centimetre, the C. G. S. unit 
 of pressure. 
 
 E. A symbol proposed for electromotive 
 force. 
 The defining equation is E = RC. 
 
 e. A symbol proposed for difference of 
 potential. 
 
 The defining equation is e = rC. 
 
 E. H. P. A contraction for electrical horse- 
 power. 
 
 Earth, Bad A term sometimes em- 
 ployed for a ground or connection to earth, 
 the electric resistance of which is compara- 
 tively high. (See Earth or Ground. ) 
 
 Earth Cell. (See Appendix Cell, Earth.) 
 
 Earth, Good A term sometimes em- 
 ployed for a ground or connection to earth, 
 
 the electric resistance of which is compara- 
 tively low. (See Earth or Ground!) 
 
 Earthed. Connected to ground or earth. 
 
 Easement. A permit, obtained from the 
 owner of a property, for the erection of poles 
 or attachments for telephonic, telegraphic or 
 other electric lines. 
 
 Effect, Page The faint sounds pro- 
 duced when a piece of iron is rapidly magnet- 
 ized and demagnetized. 
 
 A faint click is produced when a bar of iron is 
 magnetized or demagnetized. When, therefore, 
 such a bar undergoes rapid magnetization and de- 
 magnetization these separate sounds link them- 
 selves into a continuous musical note, thus pro- 
 ducing what is known as the Page effect. In the 
 
Eff, 
 
 600 
 
 [Elo. 
 
 larger masses of iron employed in transformer 
 cores and alternator armatures, the Page effect 
 sometimes rises to a loud humming noise. 
 
 Effects of Temperature on the Electric 
 Resistance of Metals. (See Appendix 
 Resistance, Electric, of Metals, Effect of 
 Temperature on.) 
 
 Effective Current. (See Appendix Cur- 
 rent, Effective?) 
 
 Effective Starting Current of Motor. 
 (See Appendix Cur rent, Effective Starting, 
 of Motor?) 
 
 Efficiency of Electric Lamp. (See Appen- 
 dix Lamp, Electric, Efficiency of.) 
 
 Efficiency of Electric Motor. (See 
 Appendix Motor, Efficiency of Electric?) 
 
 Efficiency of Radiation. (See Appendix 
 Radiation, Efficiency of.) 
 
 Efficiency of Secondary Battery. (See 
 Appendix Battery, Secondary, Efficiency 
 of.) 
 
 Effluvia, Electric A term em- 
 ployed in the early history of electricity for 
 supposed effluvia proceeding from an electri- 
 fied body and causing electrical phenomena. 
 
 Effluvia, Magnetic A term em- 
 ployed in the early history of magnetism for 
 assumed, imponderable effluvia which were 
 supposed to be given off by magnets. 
 
 The doctrine of magnetic effluvia may be re- 
 garded as a forerunner of the doctrine of lines of 
 magnetic force introduced into science by Fara- 
 day. 
 
 In some of his earlier writings Boyle framed 
 the hypothesis of a magnetic atmosphere, or 
 region surrounding a magnet He conceived 
 the idea that magnetic effluvia, emitted from 
 one of the poles of the magnet, passed through 
 the space surrounding the magnet and re-entered 
 it at its other pole. As will be seen, this concep- 
 tion closely resembles the modern conception con- 
 cerning the flow of lines of magnetic force, or of 
 magnetic flux. 
 
 Egg, Electric A term formerly em- 
 ployed for an egg-shaped vessel containing 
 a partial vacuum through which an electric 
 discharge is passed for the purpose of obtain- 
 ing luminous effects. 
 
 Elastance. A word proposed for the re- 
 ciprocal of permittance. (See Appendix 
 Permittance.) 
 
 Elastivity. The elastance of a dielectric 
 referred to unit volume. 
 
 If the dielectric possesses great permittance it 
 has of course but little elastance. 
 
 Electric Amalgamator. (See Appendix 
 Amalgamator, Electric?) 
 
 Electric Anaesthesia. (See Appendix 
 Ancesthesia, Electric?) 
 
 Electric Anemograph. (See Appendix 
 Anemograph, Electric?) 
 
 Electric Atmosphere. (See Appendix 
 Atmosphere, Electric?) 
 
 Electric Aura. (See Appendix Aura, 
 Electric?) 
 
 Electric Broiler. (See Appendix 
 Broiler, Electric?) 
 
 Electric Casting. (See Appendix Cast- 
 ing, Electric^] 
 
 Electric Chaflng-Dish. (See Appendix 
 Dish, Chafing, Electric?) 
 
 Electric Chronometer. (See Appendix 
 Chronometer, Electric?) 
 
 Electric Clamp Attachment. (See Ap- 
 pendix Attachment, Electric Clamp?) 
 
 Electric Coil Heater. (See Appendix 
 Heater, Coil, Electric?) 
 
 Electric Conflict. (See Appendix Con- 
 flict, Electric?) 
 
 Electric Deck-Planer. (See Appendix 
 Planer, Electric Deck?) 
 
 Electric Dissonance. (See Appendix 
 Dissonance, Electric?) 
 
 Electric Door-Trip. (See Appendix 
 Trip, Door, Electric?) 
 
 Electric Effluvia. (See Appendix Efflu- 
 via, Electric?) 
 
 Electric Egg. (See Appendix Egg .Elec- 
 tric?) 
 
 Electric Escapement (See Appendix 
 Escapement, Electric.) 
 
 4 Vol. 2 
 
Ele.] 
 
 G01 
 
 [Ele. 
 
 Electric Excitation. (See Appendix 
 Excitation, Electric?) 
 
 Electric Flat-Iron. (See Appendix 
 Flat-iron, Electric?) 
 
 Electric Fluid. (See Appendix Fluid, 
 Electric?) 
 
 Electric Forge. (See Appendix Forge, 
 Electric?) 
 
 Electric Glue-Pot. (See Appendix 
 Glue-Pot, Electric?) 
 
 Electric Gnomon. (See Appendix Gno- 
 mon, Electric?) 
 
 Electric Harpoon. (See Appendix Har- 
 poon, Electric?) 
 
 Electric Horology. (See Appendix 
 Horology, Electric?) 
 
 Electric Hummer. (See Appendix 
 Hummer, Electric?) 
 
 Electric-Light Bath. (See Appendix 
 Bath, Electric-Light?) 
 
 Electric Machine Tool. (See Appendix 
 Tool, Electric Machine?) 
 
 Electric Matter. (See Appendix Mat- 
 ter, Electric?) 
 
 Electric Meteorograph. (See Appendix 
 Meteorograph, Electric?) 
 
 Electric Meteorology. (See Appendix 
 Meteorology, Electric?) 
 
 Electric Mining. (See Appendix Min- 
 ing, Electric?) 
 
 Electric Pendulum. (See Appendix 
 Pendulum, Electric?) 
 
 Electric Photo-Micography. (See Ap- 
 pendix Photo-Micography, Electric?) 
 
 Electric Pocket Gauge. (See Appendix 
 Gauge, Electric Pocket?) 
 
 Electric Pressure. (See Appendix 
 Pressure, Electric?) 
 
 Electric Radiation. (See Appendix 
 Radiation, Electric?) 
 
 Electric Radiator. (See Appendix Ra- 
 diator, Electric?) ^ 
 
 Electric Rail Bond. (See Appendix 
 Bond, Electric Rail.} 
 
 Electric Residue. (See Appendix Rest- 
 due, Electric?) 
 
 Electric Spark. (See Appendix Spark> 
 Electric.) \ 
 
 Electric Stopper Lamp. (See Appendix 
 Lamp, Electric Stopper.) 
 
 Electric Stove-Plate. (See Appendix 
 Stove-Plate, Electric?) 
 
 Electric Telegraph. (See Appendix 
 Telegraph, Electric?) 
 
 Electric Tourniquet. (See Appendix 
 Tourniquet, Electric?) 
 
 Electric Wand. (See Appendix Wand, 
 Electric?) 
 
 Electric Windmill. (See Appendix 
 IVindmill, Electric. ) 
 
 Electrical Aggregation of Dust in Dust- 
 Laden Air. (See Appendix Dust, Electri- 
 cal Aggregation of, in Dust-Laden Air.) 
 
 . Electrical Aggregation of Raindrops. 
 
 (See Appendix Raindrops, Electrical Ag- 
 gregation of.) 
 
 Electrical Baking Oven. (See Appendix 
 Oven, Baking, Electrical.) 
 
 Electrical Bombardment Lamp. (See 
 Appendix Lamp, Bombardment, Electri- 
 cal?) 
 
 Electrical Coking. (See Appendix Cok- 
 ing, Electrical?) 
 
 Electrical Equivalent of Heat. (See 
 Appendix Heat, Electrical Equivalent of?) 
 
 Electrical Harmonics. (See Appendix 
 Harmonics, Electrical?) 
 
 Electrical Stimulus of Nerve. (See 
 Appendix Stimulus, Electrical, of Nerve?) 
 
 Electrically Illumined Buoy. (See 
 
 Appendix Buoy, Electrically Illumined.) 
 
 Electrically Tuned System. (See Appen- 
 dix System, Electrically Tuned.) 
 
 Electricity, Reversible Heating Effect of 
 
 A term sometimes employed in place 
 
 of the Peltier effect. (See Effect, Peltier?) 
 
Ele.] 
 
 602 
 
 [Ele. 
 
 An effect of this character is called reversible, 
 because when the current is passed across an 
 electro-thermal junction in one direction, heat is 
 produced, while if it is passed in the opposite di- 
 rection, cold is produced. 
 
 Electricity, Spontaneous A term 
 
 formerly employed for the electricity pro- 
 duced by the melting of sulphur. 
 
 This term is, of course, not employed at present, 
 since electricity can never, properly speaking, be 
 produced spontaneously. 
 
 Electrification, Negative The 
 
 charging of a body with negative electricity. 
 
 The negative charge. 
 
 Electrification, Positive The 
 charging of a body with positive electricity. 
 
 The positive charge. 
 
 Electripherous. A word proposed for 
 anything capable of bearing or transmitting 
 electricity. 
 
 This word is unnecessary and its use should 
 not be encouraged. 
 
 Electrize, To To charge or electrify 
 
 a body. 
 
 The word corresponds to magnetize, to render 
 a body magnetic or endow it with magnetic prop- 
 erties. 
 
 The word is sometimes spelled electrise. 
 
 Electrizer. That which electrizes or 
 charges with electricity. 
 
 Electro-Biologist. (See Appendix Biol- 
 ogist, Electro?) 
 
 Electro-Bioscopist. (See Appendix 
 Bioscopist, Electro) 
 
 Electro-Chemical Accumulator. (See 
 Appendix Accumulator, Electro-Chemicaf.) 
 
 Electro-Chemical Decomposition. (See 
 Appendix Decomposition, Electro-Chemi- 
 cal) 
 
 Electro-Chemical Filtration. (See Ap- 
 pendix Filtration, Electro-Chemical.) 
 
 Electro-Chronometric Counter. (See 
 Appendix Counter, Electro-Chronometric.) 
 
 Electro-Compound Magnet. (See Appen- 
 dix Magnet, Electro-Compound.) 
 
 Electro-Culture. Stimulating the growth 
 of vegetation by means of electricity. 
 
 The term is a bad one, since it should equally 
 apply to a similar stimulation of animal growth. 
 
 The term electro-culture has been proposed to 
 characterize the electric stimulation of vegetation, 
 which consists essentially in sending an electric 
 current either through the plant whose growth is 
 to be stimulated, or through the earth near the 
 plant. 
 
 In an experiment recently tried in France, a 
 kilogramme of potatoes placed in the path of a 
 weak current, under conditions exactly similar to 
 those of an equal weight of potatoes uninfluenced 
 by the electric current, produced 21 kilogrammes 
 of healthy tubers as compared to 12 J kilogrammes 
 of non -electrically stimulated tubers. 
 
 These experiments developed the fact that if a 
 quantity of manure be planted near the positive 
 pole of an electric source, the assimilable parts of 
 the manure are transported or carried towards 
 the negative pole. 
 
 The phenomena would, therefore, appear to be 
 connected with those of electric osmose or cata- 
 phoresis. (See Osmose, Electric. C diaphoresis.) 
 
 Electrode, Cataphoric In electro- 
 therapeutics an electrode impregnated with 
 the medicament it is desired to introduce into 
 the part to be treated by cataphoric medica- 
 tion. (See Appendix Medication, Cata- 
 phoric.) 
 
 Electro-Deposition. A term sometimes 
 employed for electric deposition. (See Metal- 
 lurgy, Electro.) 
 
 Electro-Dynamic Balance. (See Appen- 
 dix Balance, Electro-Dynamic) 
 
 Electro-Dynamic Interrupter. (See Ap- 
 pendix Interrupter, Electro-Dynamic) 
 
 Electro-Dynamic Rotation. (See Appen- 
 dix Rotation, Electro-Dynamic) 
 
 Electro-Dynamic Whirls. (See Appen- 
 dix Whirls, Electro-Dynamic) 
 
 Electro-Genesis. A word proposed for 
 the production of electricity. 
 
 Electro-Genie. Producing electricity. 
 
 Electro-Gilding. (See Appendix Gild- 
 ing, Electro) 
 
 Electrograph. A curve produced by a 
 recording electrometer. 
 
 Electrography. A word proposed for that 
 branch of science which treats of electricity. 
 
Ele.] 
 
 603 
 
 [Ele. 
 
 A word proposed for the copying of fine en- 
 graving on copper or steel by means of elec- 
 tro-deposition. 
 
 It will be seen that the word electrography has 
 been proposed for two entirely distinct senses. 
 The first use of the word would appear to be 
 entirely unjustifiable. 
 
 Electro-Kinetic Energy. (See Appendix 
 Energy, Electro- Kinetic?) 
 
 Electro-Lithotrity. (See Appendix 
 Lithotrity, Electro?) 
 
 KIcrtrolizatioii. The act of being elec- 
 trolyzed. 
 The word is sometimes spelled electrolisation. 
 
 Electrologist. An electrician. 
 
 The use of this word is entirely unnecessary. 
 
 Electrolysis, Counter - Electromotive 
 
 Force of The counter-electromotive 
 
 force produced in a plating bath or a second- 
 ary cell by electrolysis. 
 
 Electrolyte. The exciting liquid in a 
 voltaic cell. 
 
 A compound liquid which is separable into 
 its constituent ions by the passage of elec- 
 tricity through it. 
 
 Electrolytic Accumulator. (See Appen- 
 dix Accumulator, Electrolytic?) 
 
 Electrolytic Corrosion. (See Appendix 
 Corrosion, Electrolytic?) 
 
 Electrolytic Meter. (See Appendix 
 Meter, Electrolytic?) 
 
 Electro-Magnetic Cut-Ont. (See Appen- 
 dix Cut-Out, Electro-Magnetic?) 
 
 Electro-Magnetic Gyroscope. (See Ap- 
 pendix Gyroscope, Electro-Magnetic?) 
 
 Electro-Magnetic Interference. (See 
 Appendix Interference, Electro-Magnetic?) 
 
 Electro-Magnetic Multiplier. (See Ap- 
 pendix Multiplier, Electro-Magnetic?) 
 
 Electro-Magnetic Separator. (See Ap- 
 pendix Separator, Electro- Magnetic?) 
 
 Electro-Magnetic Sorter.- (See Appen- 
 dix Sorter, Electro-Magnetic?) 
 
 Electro-Magnetic Telegraph. (See Ap- 
 pendix Telegraph, Electro-Magnetic.) 
 
 Electro-Metallurgical Burnt Deposit 
 
 (See Appendix Deposit, Electro-Metal- 
 lurgical Burnt?) 
 Electrometer, Heterostatic - An 
 
 electrometer in which the electrification to 
 be tested is not the only electrification em- 
 ployed. (See Heterostatic?) 
 
 Electrometer, Idiostatic An elec- 
 trometer in which the electrification to be 
 tested is the only electrification employed. 
 (See Idiostatic?) 
 
 Electrometer, Long-Range A form 
 
 of attracted-disc electrometer in which the 
 range of the scale is comparatively long. 
 
 Electrometer, Repulsion An elec- 
 trometer in which the differences of potential 
 are measured by means of the repulsion 
 existing between two similarly charged 
 bodies. 
 
 Coulomb's torsion balance is an instrument of 
 this class. A gold-leaf electrometer, when ar- 
 ranged so that the amount of deviation can be 
 readily measured, is also a repulsion electrometer. 
 
 form of electrometer in which the needle is 
 unaffected when it is placed symmetrically as 
 regards the deflecting segments. 
 
 A quadrant electrometer is a form of sym- 
 metrical electrometer. 
 
 Electrometer, Thermo A term 
 
 sometimes employed for an electric ther- 
 mometer. 
 
 This use of the term probably arose from the 
 fact that such an instrument may be employed to 
 measure roughly the difference of potential be- 
 tween points between which a spark passes. 
 
 Electrometer Voltmeter. (See Appen- 
 dix Voltmeter, Electrometer?) 
 
 Electrometric. Of or pertaining to an 
 electrometer. 
 
 Electromotive Force, Transformation of 
 
 (See Appendix Transformation, as 
 
 of Electromotive Force?) 
 
 Electronome. A term proposed for a 
 measurer of electricity. 
 
 This term is not only unnecessary, but is devoid 
 of any precise meaning and may serve as an 
 
Ele.] 
 
 604 
 
 [End. 
 
 illustration of the thoughtless manner in which 
 electric words are proposed. 
 
 Electropath. One skilled in the art of 
 electro-therapy. 
 
 Electropathy. A word proposed for the 
 treatment of disease by means of electricity. 
 
 The word electro-therapy or electro-thera- 
 peutics is generally used. 
 
 Electro-Percussion Drill. (See Appen- 
 dix Drill, Electro-Percussion.) 
 
 Electrophone. A word proposed by Ader 
 for a form of telephone employing carbon 
 contacts. 
 
 Electro-Physiologist. (See Appendix 
 Physiologist, Electro?) 
 
 Electro-Potential Energy. (See Appen- 
 dix Energy, Electro-Potential?) 
 
 Electro-Puncturation. (See Appendix 
 Puncturation, Electro?) 
 
 Electro-Reciprocating Drill. (See Ap- 
 pendix Drill, Electro-Reciprocating.) 
 
 Electroscope, Semaphoric A name 
 sometimes given to Henley's quadrant elec- 
 troscope. (See Electroscope, Quadrant, 
 Henley's?) 
 
 Electroscopic Gauge. (See Appendix 
 Gauge, Electroscopic?) 
 
 Electrostatic Aurora. (See Appendix 
 Aurora, Electrostatic?) 
 
 Electrostatic Corona. (See Appendix 
 Corona, Electrostatic?) 
 
 Electrostatic Influence. (See Appendix 
 Influence, Electrostatic?) 
 
 Electrostatic Motion. (See Appendix 
 Motion, Electrostatic?) 
 
 Electrostatic Motor. (See Appendix 
 Motor, Electrostatic?) 
 
 Electrostatic Strain. (See Appendix 
 Strain, Electrostatic?) 
 
 Electro-Steeling. (See Appendix Steel- 
 ing, Electro?) 
 
 Electro-Stereotype. (See Appendix 
 Stereotype, Electro?) 
 
 Electro-Synthesis. (See Appendix Syn- 
 thesis, Electro?) 
 
 Electro-Thermancy. (See Appendix 
 Thermancy, Electro?) 
 
 Electro-Thermotic. (See Appendix 
 Thermotic, Electro?) 
 
 Electro-Tint. (See Appendix Tint- 
 Electro?) 
 
 Electrotome. A term formerly applied to 
 an automatic contact breaker which vibrated 
 with sufficient rapidity to produce a musical 
 note. (See Contact Breaker, Automatic?) 
 
 Electro-Tonicity. (See Appendix Toni- 
 city, Electro?) 
 
 Electro, Turtle-Back An electro- 
 type curved so as to be capable of being em- 
 ployed in the cylinder of a rotary newspaper 
 press. 
 
 Element of Battery. A term sometimes 
 applied to a single electric source or a battery 
 of sources. 
 
 Element of Voltaic Battery. A term 
 sometimes applied to a single cell of a voltaic 
 battery. 
 
 The term element is properly applied to a 
 single complete voltaic cell only when such a 
 cell forms one of a number of cells so connected 
 in a battery as to form a single electric source. 
 
 It would appear that the use of the word ele- 
 ment in the case of a single voltaic cell, whether 
 connected with the battery or not, is inadvisable. 
 
 Elliptical Rotary Magnetization. (See 
 Appendix Magnetization, Elliptical Ro- 
 tary?) 
 
 Elongation, Maximum Negative 
 
 The position of a vibrating body when it is 
 at the extremity of its path on the negative 
 side. 
 
 Elongation, Maximum Positive 
 
 The position of a vibrating body when it is 
 at the extremity of its path on the positive 
 side. 
 
 Emission, Selective A selective 
 
 radiation. (See Appendix Radiation, Se- 
 lective?) 
 
 End-to-End Joint. (See Appendix Joint, 
 End-to-End?) 
 
End.] 
 
 605 
 
 [Fac. 
 
 Endosmose, Voltaic A term some- 
 times employed in place of electric osmose. 
 (See Osmose, Electric.) 
 
 Energetics. That branch of mechanics 
 which treats of the transfer, transformation 
 or modification of energy. 
 
 Energy, Cubic A term sometimes 
 employed for volumetric energy. (See 
 Appendix Energy, Volumetric?) 
 
 Energy, Electro-Kinetic Electric 
 
 energy that is actually engaged in doing 
 work. (See Energy, Kinetic?) 
 
 Energy, Electro-Potential Elec- 
 tric energy possessing the power of, but not 
 actually doing, work. (See Energy, Poten- 
 tial?) 
 
 Energy, Specific Volumetric en- 
 ergy. 
 
 Energy, Tolumetric A term pro- 
 posed by Hospitalier for a quantity equal to 
 the work divided by the volume. 
 
 Energy, Volumetric, C. G. S. Unit of 
 An erg per cubic centimetre. 
 
 Entering Current of Telegraphic Cir- 
 cuit. (See Appendix Current, Entering, 
 of Telegraphic Circuit?) 
 
 Epoch. The time reckoned in the case of 
 a vibrating body from the point of reckoning 
 to the point of maximum positive elongation. 
 
 Equalizing Wires. (See Appendix 
 Wires, Equalizing?] 
 
 Equatorial Region of Magnet. (See 
 Appendix Region, Equatorial, of Magnet?) 
 
 Ergometer. A term proposed for an in- 
 strument for measuring the amount of work 
 done by a machine. 
 
 This would more properly be called an erg- 
 meter. The word, however, is seldom used. 
 
 Erg : s. An abbreviation proposed for erg 
 per second, the C. G. S. unit of power. 
 Error, Heeling, of Mariner's Compass 
 
 The error in deviation of the mag- 
 netic needle produced by that portion of the 
 induced and permanent magnetism of the 
 iron in a ship brought into action by the roll- 
 ing or heeling of the vessel. 
 
 Escape. A term employed in telegraphy 
 for leakage of the current from the line wire 
 or conductor, from the effect of insufficient 
 or faulty insulation, or from contact of the 
 line with wet buildings or other uninsulated 
 bodies. 
 
 Escapement, Electric . An electri- 
 cally actuated clock escapement. 
 
 Evanescent Telegraphic Signal. (See 
 Appendix Signal, Telegraphic, Evanes- 
 cent.) 
 
 Exciter, Direct Current A source 
 
 of direct current, generally a direct current 
 dynamo, employed for exciting the field mag- 
 nets of an alternating current dynamo. 
 
 Excitation, Electric The produc- 
 tion of electrification by any means. 
 
 Exhausted Plates of Storage Cell. (See 
 Appendix Plates, Exhausted, of Storage 
 Cell?) 
 
 Extension Bell. (See Appendix^//, 
 Extension?) 
 
 External Magnetic Circuit. (See Ap- 
 pendix Circuit, Magnetic, External?) 
 
 External Magnetic Field. (See Appea- 
 dix Field, Magnetic, External?) 
 
 F. A symbol proposed for farad, the 
 practical unit of capacity. 
 
 F. A symbol proposed for force. 
 The defining equation is F = M X A. The 
 same symbol is also proposed for farad. 
 
 eF. A symbol proposed for magneto- 
 motive force. 
 
 The defining equation is eF = qit N I. 
 
 F. M. A contraction sometimes employed 
 for field magnets. 
 
 Fac-Simile Telegraph. (See Appendix 
 Telegraph, Fac-Simile?) 
 
 Factor, Power - The factor, less 
 than unity, which must be applied to the ap- 
 
Fal.] 
 
 606 
 
 [Fil. 
 
 parent activity in an alternating current cir- 
 cuit as obtained by the product of the volts 
 and the amperes, in order to obtain the true 
 activity. * 
 
 With sinusoidal currents and electromotive 
 forces, the power factor is also equal to the cosine 
 of the angle of lag in the current before or behind 
 the pressure. 
 
 Fallback Indicator. (See Appendix 
 Indicator, Fallback?) 
 
 Farad, International The value of 
 
 the international farad adopted by the Chi- 
 cago Congress of 1 893 as equal to the capac- 
 ity of a conductor charged to a potential of 
 one international volt by one international 
 coulomb of electricity. 
 
 Faradic Coil. (See Appendix Coil, Far- 
 adic?) 
 
 Faradism. A word sometimes employed 
 for faradization. 
 
 Faradization would appear to be the preferable 
 word. (See Faradization. ) 
 
 Fault, Low Test A term sometimes 
 
 applied to a fault in an underground cable 
 when the insulation resistance falls below a 
 certain minimum value, say, for example, 5 
 megohms per 100 volts per mile. 
 
 Fault, Resultant The apparent 
 
 position and magnitude of a fault in a cable 
 due to the resultant of all its leakage upon 
 the electrical measurements made. 
 
 Feeder Clamp. (See Appendix Clamp, 
 Feeder.) 
 
 Feeder Clip. (See Appendix Clip, 
 Feeder?) 
 
 Feeder for Trolley Conductor. A wire 
 or conductor of low resistance, employed for 
 transmitting electric current directly from the 
 power station to the trolley wire, and serving 
 to maintain the potential at the point of junc- 
 tion. 
 
 Ferro-Magnetic. A word sometimes em- 
 ployed in place of paramagnetic. 
 
 Ferro-Magnetism. A word sometimes 
 applied to the magnetism possessed by iron, 
 or, in general, by paramagnetic substances. 
 (See Paramagnetic?) 
 
 Field Coils of Dynamo. (See Appendix, 
 Coils, Field, of Dynamo?) 
 
 Field, Magnetic, Distortion of A 
 
 change in the direction or grouping of lines 
 of magnetic force, in the field of a dynamo- 
 electric machine or electric motor, produced 
 by the reaction of the armature, or the mag- 
 neto-motive force of the armature current. 
 
 This distortion of the field renders it necessary 
 to give a lead to the collecting or distributing 
 brushes. (See Lead, Angle of. Lead of 
 Brushes of Dynamo-Electric Machine. ) 
 
 Field, Magnetic, External That 
 
 portion of a magnetic field which lies outside 
 the magnet or external to it. (See Field, 
 Magnetic?) 
 
 Field, Magnetic, Internal That 
 
 portion of a magnetic field which lies within 
 the magnet. 
 
 Field of Force. (See Appendix Force, 
 Field of?) 
 
 Field Plates. (See Appendix Plates, 
 Field?) 
 
 Field Spools of Dynamo-Electric Ma- 
 chine. (See Appendix, Spools, Field, of 
 Dynamo-Electric Machine?) 
 
 Figures, Karsten's A name some- 
 times given to electric breath figures. (See 
 Figures, Breath?) 
 
 Filament, Coked A carbon fila- 
 ment for an incandescent electric lamp that 
 has been subjected to electrical heating in a 
 vacuum, not only until thoroughly freed from 
 its occluded gases, but also until its carbon is 
 changed into a variety of coke. 
 
 The coked carbon filament is the invention of 
 Lodyguine. The coking is carried on in a 
 vacuum, the process being continued for about 
 eight seconds after the occluded gases have been 
 driven off. 
 
 The carrying off of the occluded gas is effected 
 in the usual manner, and the strength of the cur- 
 rent is then increased considerably. Under 
 these circumstances the carbon of the filament 
 becomes changed into a variety of coke. 
 
 It is claimed that under the coking process the 
 filament has its permanent or cold resistance 
 greatly decreased until it becomes approximately 
 
Fil.] 
 
 607 
 
 [Flu. 
 
 of the same value as that of the hot resistance of 
 the filament before it was coked. The process is 
 sometimes carried further than this, depending 
 on the character cf the original carbonization. 
 
 It is necessary, however, to stop the coking 
 treatment when this point of resistance has been 
 reached, since, if the heating be continued beyond 
 this, the resistance of the filament again rises. 
 
 Filament, Coking of Subjecting a 
 
 filament to the coking process. (See Fila- 
 ment, Coked.) 
 
 Filament, Incandescent A fila- 
 ment that is rendered incandescent by the 
 passage of an electric current. (See Lamp, 
 Incandescent, Electric Filament of.) 
 
 In other words, a filament is incandescent only 
 while it is actually emitting its own light 
 
 Filament, Incandescing A fila- 
 ment that can be rendered incandescent by 
 the passage of an electric current. (See 
 Lamp, Incandescent, Electric Filament of.) 
 
 Filament, Mounting of A suitable 
 
 connection for the filament to the leading- 
 in wires inside the chamber of an incan- 
 descent electric lamp. 
 
 Filament, Treated Coked A car- 
 bon filament the core of which has been elec- 
 trically coked and whose surface is covered 
 with electrically deposited carbon derived 
 from the decomposition of a hydrocarbon gas 
 or vapor. 
 
 Filtration, Electro-Chemical A 
 
 term formerly employed in place of electric 
 endosmose. (See Osmose, Electric. Phe- 
 nomena, Par ret.) 
 
 Finishing Brushes. (See Appendix 
 Brushes, Finishing) 
 
 Fire Alarm Telegraph. (See Appendix 
 Telegraph, Fire Alarm) 
 
 Fire Glow. (See Appendix Glow, Fire) 
 
 Fittings, Combination, for Chandeliers, 
 
 Brackets, Etc. Fittings that provide 
 
 for the use of both gas and electricity 
 
 Five- Wire System. (See Appendix Sys- 
 tem, Fi've- Wire) 
 
 Flash, Multiple Lightning Several 
 
 lightning flashes that apparently come from 
 the same cloud. 
 
 Lodge traces the cause of multiple lightning 
 flashes to the same circumstances that produce 
 in a Leyden jar the tendency of the jar to neu- 
 tralize its charges by overflowing. (See Appen- 
 dix Jar, Leyden, Overflow of .) 
 
 Flashing. A process to which carbons 
 are subjected, in order to give them a uniform 
 electrical resistance throughout their entire 
 length. (See Carbons, Flashing Process 
 for.) 
 
 Flat-Iron, Electric An electrically 
 
 heated flat-iron. 
 
 A hollow flat-iron provided with a suitably 
 placed electric heater. (See Heater, Electric.) 
 
 Floor Contact. (See Appendix Contact, 
 Floor) 
 
 Fluid, Austral A term formerly 
 
 employed for the magnetic fluid that was 
 supposed to exist around or emanate from 
 the austral pole of a magnet. (See Pole, 
 Magnetic Austral.) 
 
 Fluid, Boreal A term formerly 
 
 employed for the magnetic fluid that was 
 supposed to exist around or emanate from 
 the boreal pole of a magnet. (See Pole, 
 Magnetic, Boreal.) 
 
 Fluid, Electric An assumed fluid 
 
 which was formerly believed to be the cause 
 of electric excitement. 
 
 A belief in electric fluids no longer exists among 
 intelligent electricians. 
 
 Fluid, Magnetic A term formerly 
 
 employed for an assumed fluid which was be- 
 lieved to cause magnetic phenomena. 
 
 The belief in magnetic fluids no longer exists. 
 
 Fluid, Negative A specific fluid 
 
 which was formerly believed by the advo- 
 cates of the double-fluid electric hypothesis 
 to be the cause of negative electric excite- 
 ment. (See Appendix Fluid, Positive.) 
 
 A deficit of an assumed single electric fluid. 
 (See Electricity, Single-Fluid Hypothesis 
 of.) 
 
 Fluid, Positive A specific fluid 
 
 which was formerly believed by the adherents 
 
Flu.] 
 
 608 
 
 [Fra. 
 
 of the double-fluid electric hypothesis to be 
 the cause of positive electric excitement. 
 
 A surplusage of an assumed single electric 
 fluid. 
 
 According to the views of the single-fluid elec- 
 tric hypothesis, positive excitement was supposed 
 to be due to the surplusage of an assumed single 
 electric fluid, the negative excitement being as- 
 sumed to be due to its deficit. (See Electricity, 
 Single- Fluid Hypothesis of.) 
 
 Flush-Key Switch. (See Appendix 
 Switch, Flush-Key.) 
 
 Force, Electric, Transformation of 
 
 Producing or effecting a change in the 
 value of the electromotive force by means of 
 an induction coil, transformer or condenser, 
 or by electric resonance. (See Transformer?) 
 
 Force, Electromotive, Alternating 
 
 An electromotive force periodically passing 
 through zero between positive and negative 
 values. (See Current, Alternating?) 
 
 Force, Electromotive, Conversion of 
 
 A change in the value of the electromo- 
 tive force produced by means of an induction 
 coil,- transformer or condenser, or by electric 
 resonance. (See Transformer?) 
 
 Force, Electromotive, Impressed, Pro- 
 posed A. I. E. E. Definition for The 
 
 ratio of the total activity in an electrically 
 conducting circuit to its instantaneous cur- 
 rent strength. 
 
 Force, Electromotive, Opposing . 
 
 A term sometimes employed for counter- 
 electromotive force. (See Force, Electro- 
 motive, Counter?) 
 
 Force, Electromotive, Voltaic A 
 
 term sometimes employed for the electromo- 
 tive force generated at the electrodes of an 
 electrolytic cell, in contradistinction to the 
 counter-electromotive force produced at such 
 electrodes by their polarization. 
 
 Force, Field of - The space trav- 
 ersed or crossed by the lines of electrostatic 
 or magnetic force. 
 
 An electrostatic field. (See Field, Elec- 
 trostatic^) 
 
 A magnetic field. (See Field, Magnetic?) 
 
 Force, Magne-Crystallic A name 
 
 proposed by Faraday for the force assumed as 
 the cause producing the change in the nature 
 of the magnetism of certain crystalline bodies 
 in different directions. (See Action, Magne- 
 Crystallic?) 
 
 Force, Volta Electromotive An 
 
 electromotive force produced by means of 
 the voltaic cell. (See Cell, Voltaic.) 
 
 Forces, Electromotive, Complex-Har- 
 monic Alternating The electromo- 
 tive forces producing complex harmonic alter- 
 nating currents. (See Appendix Currents, 
 Complex-Harmonic.) 
 
 Forge, Electric A forge so ar- 
 ranged that the metals to be subjected to 
 forging can be electrically heated while in 
 place on the forge. 
 
 Formulae, Blavier's The formulas 
 
 employed for computing the Blavier test 
 (See Appendix Test, Blavier's?) 
 
 Formulas. Plural of formula. 
 
 Four-Pole Dynamo-Electric Machine. 
 
 (See Appendix Machine, Dynamo-Electric, 
 Four-Pole?) 
 
 Fourth State or Condition of Matter. 
 
 (See Appendix Matter, Fourth State or 
 Condition of.) 
 
 Four- Way Switch. (See Appendix 
 Switch, Four- Way.) 
 
 Four-Wire System. (See Appendix 
 System, Four- Wire?) 
 
 Frame, Dynamo or Motor A term 
 
 applied to the iron body of a dynamo or 
 motor, including the pole pieces and stand- 
 ards of the machine, but exclusive of the 
 base plates and bearings. (See Machine, 
 Dynamo-Electric. Motor, Electric?) 
 
 Frame, Trolley Base A frame for 
 
 receiving the standard which supports the 
 trolley pole. 
 
 Franklinism. A word sometimes em- 
 ployed for franklinization. 
 
 Franklinization would appear to be the prefer- 
 able word. (See Franklinization.) 
 
Fre.] 
 
 609 
 
 [Gal. 
 
 Free or Insulated. (See Appendix Insu- 
 lated or Free.) 
 
 Frequencies, Harmonic Frequen- 
 cies higher than the fundamental, present in 
 complex-harmonic currents. (See Appen- 
 dix Currents, Complex-Harmonic.) 
 
 Frequencies, Tesla A term em- 
 ployed for exceedingly high frequencies. 
 
 The frequencies employed by Tesla amounted 
 to many hundreds of thousands per second. 
 
 Frequency, Fundamental The 
 
 nominal or lowest frequency of a current 
 which has harmonics. 
 
 Frequency, Yibration A term 
 
 expressing the number of vibrations per 
 second. 
 
 In the case of a musical note the vibration fre- 
 quency corresponds to the pitch of the note. 
 
 Frog Crossing. (See Appendix Cross- 
 ing Frog.) 
 
 Frost Alarm. (See Appendix Alarm, 
 Frost) 
 
 Full Contact. (See Appendix Contact, 
 Full) 
 
 Full Load. (See Appendix Load, Full.) 
 
 Fundamental Frequency. (See Appen- 
 dix Frequency, Fundamental.) 
 
 Fuse, Blowing of A term some- 
 times employed for the fusing or volatiliza- 
 
 tion of a fuse wire or safety plug. (See 
 Fuse, Safety.) 
 
 Fuse, Blowing Point of The tem- 
 perature or the current strength at which a 
 fuse blows out or melts. 
 
 The exact current strength at which a fuse 
 blows out or melts varies, not only with the tem- 
 perature of the wire, but also with the position 
 in which the fuse wire is placed in the fuse block, 
 and the nature of the block, its size, whether the 
 current is direct or alternating, etc. 
 
 The ratio, which should exist between the carry- 
 ing capacity of a fuse, and the condition of its 
 ultimate fusing, will of course depend on the 
 character of the circuit the fuse is intended t 
 guard. With small currents, such for example as 
 are employed in electric lighting, a narrow margin 
 may be employed without detriment, but in the 
 case of railway systems, however, a wider range 
 is necessarily given to the blowing point of the 
 fuse, for the amount of current required in such 
 systems, near heavy grades, is so much in com- 
 parison to what is ordinarily employed that if 
 too narrow a limit were given to the fusing point 
 considerable annoyance would be experienced 
 from the fuse blowing out too frequently. 
 
 Fuse, Safety, Carrying Capacity of - 
 
 The current strength a fuse wire or plug 
 can carry without the line it protects becom- 
 ing dangerously heated. 
 
 g. An abbreviation proposed for one 
 gramme, the C. G. S. unit of mass. 
 
 g. cm 2 . An abbreviation proposed for 
 gramme centimetre squared, the C. G. S. unit 
 of moment of inertia. 
 
 Galvanic Cell. (See Appendix Cell, 
 Galvanic) 
 
 Galvanic Chain. (See Appendix Chain, 
 Galvanic.) 
 
 Galvanic Ring. (See Appendix Ring, 
 Galvanic.) 
 
 Galvanist One skilled in the "art of 
 galvanism." (Obsolete.) 
 
 The word has no precise meaning, since the 
 word galvanism is employed in two entirely dif- 
 ferent senses ; namely, as current electricity and 
 as a particular method of applying electricity to 
 the curing of diseases. 
 
 Galvanoglyphy. The process of produc- 
 ing an electrotype. 
 
 This word, though good etymologically, is un- 
 necessary ; moreover, the word electrotype is 
 almost universally employed. 
 
 Galvanography. A term proposed for 
 the copying of fine engravings on copper or 
 steel plates by means of electro-deposition. 
 
 Galvano-Magnetic. A word proposed for 
 electro-magnetic. 
 
Gal.] 
 
 610 
 
 [Gen. 
 
 The use of this word is unwarranted and should 
 not be encouraged. 
 
 Galvanometer, Angle of Maximum Sensi- 
 tiveness of The angle of deflection at 
 which a given small alteration in the strength 
 of the current produces the greatest change 
 in the deflection of the needle. 
 
 Galvanometer, Direct Beading 
 A galvanometer in which the absolute value 
 of the deflection in current strength is ob- 
 tained directly without the use of tables or 
 curves. 
 
 Galvanometer, Helmholtz - A 
 
 double-ring tangent galvanometer, the two 
 ring coils of which are parallel to each other 
 and are placed on opposite sides of the mag- 
 netic needle at such positions that their mag- 
 netic field at the needle may be as nearly 
 uniform as possible, and much more nearly 
 uniform than a single coil could produce. 
 
 Galvanometer, Optical A form of 
 
 galvanometer proposed by Potier based on 
 the magnetic rotary power of liquids. (See 
 Refraction, Double, Electric?) 
 
 Galvanometer, Pocket A galvan- 
 ometer small enough to be readily carried in 
 the pocket. 
 
 Galvanometer Voltmeter. (See Appen- 
 dix Voltmeter, Galvanometer?) 
 
 Galvanotonus. A term proposed by 
 Pfliiger for the state of tetanus produced in a 
 muscle that has been overstimulated electri- 
 cally. 
 
 Galvanotropism. Movements produced 
 in living organisms by the passage of elec- 
 tricity through them. 
 
 The word galvanotropism has been proposed 
 to describe such phenomena as the movements 
 observed in the roots of plants, when placed be- 
 tween two opposite electrodes. The direction of 
 these movements seems to be such as would place 
 the longer axis of the root in the direction of the 
 plane of the current. 
 
 Gap, Air, Shunting An air gap in 
 
 a circuit placed around a galvanometer or 
 other instrument for the purpose of affording 
 protection to the galvanometer or other instru- 
 ment from the effects of powerful disruptive 
 discharges. 
 
 The inductive resistance of the coil to the 
 rapidly varying oscillatory discharges is so great 
 that the discharges take instead a path through 
 an air gap. Since such an air gap thus shunts the 
 discharge from the galvanometer or other coils, it 
 is called a shunting air gap. 
 
 Gas Cell. (See Appendix Cell, Gas.) 
 
 Gas Polarization. (See Appendix Po- 
 larization, Gas.) 
 
 Gauge, Electric Pocket A gauge 
 
 for an electric battery or other similar source 
 small enough to be readily carried in the 
 pocket. 
 
 Gauge, Electroscopic A term ap- 
 plied by Gaugain to a form of discharging 
 gold-leaf electroscope. (See Electroscope, 
 Gold-Leaf.) 
 
 Gauss, Proposed A. I. E. E. Definition for 
 
 A practical unit of magnetic intensity* 
 
 the value of which is equal to one C. G. S. 
 unit ; that is, one C. G. S. line per square 
 centimetre. 
 
 This unit is a modification of that proposed by 
 a Sub-Committee of the American Institute of 
 Electrical Engineers on the Provisional Pro- 
 gramme for the International Electrical Con- 
 gress, held in Chicago, 1893, on the occasion of 
 the World's Columbian Exposition. 
 
 Generator, Chemical, of Electricity 
 
 A term sometimes employed in place of a 
 voltaic pile or battery. 
 
 This use of the term generator is sanctioned by 
 the similar use of the word in other connections. 
 Of course it will be understood that it is difference 
 of potential and not electricity that is generated. 
 
 Generator, Di phase A generator 
 
 which delivers two-phase or diphase currents. 
 
 Generator, High-Voltage Electro-Mag- 
 netic An electro-magnetic generator 
 
 arranged so as to give a high electromotive 
 force. 
 
 Generator, Polyphase - A gener- 
 ator which delivers more than single-phase 
 currents. 
 
 The term polyphase is frequently employed 
 only in the sense of greater than diphase. 
 
 Generator, Railway A dynamo- 
 
Gen.] 
 
 611 
 
 [Gro. 
 
 electric machine which develops the current 
 employed in systems of electric railways. 
 
 Generator, Self-Compounding Polyphase 
 
 A polyphase generator whose field 
 
 magnets are compound-wound. 
 
 Generator, Thermo-Electric A 
 
 term sometimes employed for a thermo-elec- 
 tric pile. (See Pile, Thermo-Electric^) 
 
 The term is equally applicable to the pyro- 
 magnetic generator. 
 
 Generator, Three-Phase A tri- 
 
 phase generator. (See Appendix Gener- 
 ator, Tri-Phase^ 
 
 The term tri-phase generator would appear to 
 be preferable. 
 
 Generator, Tri-Phase A generator 
 
 which delivers three-phase or tri-phase cur- 
 rents. 
 
 Generator, Two-Phase A di-phase 
 
 generator. (See Appendix Generator, Di- 
 Phase.} 
 
 The term di-phase generator would appear to 
 be preferable. 
 
 Gilbert. A term proposed for the prac- 
 tical unit of magneto-motive force. 
 
 A unit of magneto-motive force having 
 the value of the absolute unit or equal to 
 
 ampere-turn. 
 4* 
 
 This unit is a modification of that proposed by 
 a Sub-Committee of the American Institute of 
 Electrical Engineers on Provisional Programme 
 for the International Electrical Congress, held 
 in Chicago, in 1893. 
 
 Gilding, Electro Electric gilding. 
 
 Electro-plating with gold. (See Gilding, 
 Electric^ 
 
 Glass Screw Insulator. (See Appendix 
 Insulator, Glass-Screw.) 
 
 Globes, Diffusing, for Electric Lights. 
 
 Globes so constructed as to insure 
 
 a diffusion of the light. 
 
 The diffusion is generally obtained by means 
 of ground glass. In order to avoid the loss of 
 light that attends the use of ground glass, diffusion 
 globes have been made of clear glass furnished 
 with a number of refraction or total internal re- 
 
 flecting lenses, in the manner of the well-known 
 Fresnel lens. 
 
 Glory, Aurora A term proposed 
 
 by Nordenskjb'ld for an almost constant 
 crown of light, single, double or multiple, 
 which occupies a nearly fixed position in the 
 heavens. 
 
 Nordenskjold describes the aurora glory as fol- 
 lows: 
 
 " Our globe, even during a minimum aurora 
 year, is adorned with an almost constant crown 
 of light, single, double, or multiple, whose inner 
 edge was usually, during the winter of 1878-79, 
 at a height of about 0.03 of the radius of the 
 earth (120 miles) above its surface, whose surface 
 was somewhat under the earth's surface, having 
 its centre a little north of the magnetic pole, and 
 which, with a diameter of about 0.32 radius of 
 the earth (about 1,280 miles), extends in a plane 
 perpendicular to the earth's radius which passes 
 through the centre of this luminous ring. " 
 
 Glow, Fire A term employed by 
 
 the ancients for an aurora. (See Aurora 
 Borealis. Aurora Australis.) 
 
 Glow Illumination. (See Appendix 
 Illumination, Glow?) 
 
 Glow Lamp. (See Appendix Lamp, 
 
 Glow.) 
 
 Glowing of Electric Conductor. (See 
 Appendix Conductor, Electric, Glowing of.) 
 
 Glue-Pot, Electric An electrically 
 
 heated glue-pot. 
 
 An electric heater is applied to a glue-pot of 
 ordinary construction. (See Heater, Electric,} 
 
 Gnomon, Electric A term formerly 
 
 applied to a variety of pith ball electrometer. 
 
 Good Earth. (See Appendix Earth, 
 Good.) 
 
 Ground Coil. (See Appendix Coil, 
 Ground?) 
 
 Ground, Dead A term sometimes 
 
 applied to a fault or interruption in a tele- 
 graphic line in which the escape to earth or 
 ground is so great that it is impossible to 
 operate the line. 
 
 Dead earth. (See Earth, Dead or Total.) 
 
 Grounding. A word sometimes employed 
 
Gro.] 
 
 612 
 
 [Ear. 
 
 n electro-metallurgy for a preparatory pro- 
 cess in burnishing. (See Appendix Bur- 
 nishing^) 
 
 Grouping System for Electric Light 
 Leads. (See Appendix Leads, Grouping 
 System for Electric Light?) 
 
 Guard, Automatic, for Series-Connected 
 
 Incandescent Lamps A device placed 
 
 on each series-connected incandescent elec- 
 tric lamp for the purpose of short circuiting 
 
 the holder should the lamp filament break, 
 A film cut-out. (See Cut-Out, Film?) 
 An automatic guard may consist of a sheet of 
 
 paraffine paper placed between two metallic 
 
 knobs. 
 
 Gyroscope, Electro-Magnetic A 
 
 gyroscope driven by an electro-magnet. 
 
 Gyrostatic Action of Dynamos on Ship- 
 board. (See Appendix Action, Gyrostatr'c, 
 of Dynamos on Shipboard?) 
 
 H. A symbol used for field intensity. 
 
 F 
 The defining equation is H = 
 
 Here F = the force and m the strength of the 
 pole. 
 
 H. An abbreviation proposed for henry, 
 the practical unit of mutual induction, self- 
 induction, or inductance. 
 
 This abbreviation is seldom used. 
 
 h. An abbreviation for hour, one of the 
 practical units of time. 
 
 3C. A symbol proposed for magnetizing 
 force. 
 
 The defining equation is 3C = 4 * N \ 
 
 \j 
 
 Where N, is the number of windings, and L, 
 the length of the solenoid generating the mag- 
 netizing force. 
 
 HP or H* A contraction for horse-power. 
 This contraction is universally employed in all 
 English-speaking countries. 
 
 Harmonic Frequencies. (See Appendix 
 Frequencies, Harmonic?) 
 
 Harmonic Motion. (See Appendix Mo- 
 tion, Harmonic?) 
 
 Harmonic Telegraph. (See Appendix 
 Telegraph, Harmonic?) 
 
 Harmonics, Electrical A term 
 
 sometimes employed in place of the upper 
 harmonic currents generally. (See Appen- 
 dix Currents, Complex-Harmonic?) 
 
 Harmonics of Current. (See Appendix 
 Current, Harmonics of?) 
 
 Harmonics, Weeding-Out of Get- 
 ting rid of, or removing some or all of the 
 upper harmonic currents from a funda- 
 mental harmonic current. 
 
 The weeding-out process is generally effected 
 by means of electric resonance. The presence of 
 self-induction or capacity in the circuit has the 
 same effect. It is partly on this account that we 
 cannot yet speak across the Atlantic cable, the 
 upper harmonics of the voice being weeded out 
 more than the lower and made to lag more. 
 (See Appendix Harmonics, Weeding. Out oj ', by 
 Electrical Resonance.) 
 
 Harmonics, Weeding-Ont of, by Electri- 
 cal Resonance The weeding-out of 
 
 the upper harmonics of a complex-harmonic 
 current by altering the natural period of the 
 system until it is in unison or in resonance 
 with the fundamental harmonic. 
 
 "A resonant circuit," says Pupin, "behaves 
 towards a complex-harmonic electromotive force 
 just the same as an acoustic resonator toward a 
 source of complex sound. It brings out prom- 
 inently that harmonic with which it is in reso- 
 nance. To express this numerically, say that 
 the ratio of the amplitude of the fundamental har- 
 monic electromotive force to that of the next 
 higher harmonic (supposing it to be even no 
 higher than an octave) is 2 to I. Then the cir- 
 cuit can be easily brought into resonance with 
 the fundamental harmonic in such a way as to 
 increase the ratio of the amplitudes of the cor- 
 responding simple harmonic currents 60 : i . The- 
 oretically (and to a great extent practically also) 
 that ratio can be made anything we please by in- 
 creasing continually the coefficient of self-indue- 
 
Har.J 
 
 613 
 
 [Her. 
 
 tion and diminishing the capacity without de- 
 stroying the resonance. In other words, we can, 
 by the proper single tuning, weed out the upper 
 harmonics as much as we please. But, as will be 
 indicated later on, it is flot always advisable to 
 avail ourselves too much of a means of weeding 
 out the upper harmonics by using very large self- 
 induction. The best method of tuning depends 
 on the nature of the problem before us." 
 
 Harpoon, Electric A harpoon con- 
 taining a bomb, that is electrically fired or 
 exploded by the harpooner after imbedding 
 the harpoon. 
 
 Heat, Electrical Equivalent of A 
 
 quantity representing the electrical energy 
 produced by the action of a given amount or 
 quantity of heat energy. 
 
 Heater, Coil, Electric An electric 
 
 heater in which 
 the heat is pro- 
 duced by the pas- 
 sage of an electric 
 current through a 
 coiled metallic rib- 
 bon. 
 
 A form of coil 
 heater is shown in 
 Fig- 573- 
 
 Heater, Pri- 
 mary Electric 
 
 A term 
 
 proposed for the 
 main electric heat- 
 er in a building. 
 (See Heater, Elec- 
 tric) 
 
 Heeling Error 
 
 573- G>M Heater. 
 
 of Mariner's Compass. (See Appendix 
 Error, Heeling, of Mariner's Compass. 
 
 Helix. A word sometimes used in elec- 
 tricity and magnetism in place of coil or sole- 
 noid. (See Coil, Electric?) 
 
 Helix, Anomalous A helix so 
 
 wound as to produce an anomalous magnet. 
 (See Magnet, Anomalous) 
 
 Helix, Left-Handed A term some- 
 times employed in place of a left-handed 
 
 solenoid. (See Solenoid, Left-Handed. 
 Solenoid, Practical) 
 
 Helix, Magnetic A coil that is 
 
 rendered magnetic by the passage through it 
 of an electric current. (See Coil, Electric) 
 
 Helix, Magnetizing A magnetiz- 
 ing coil. (See Coil, Electric) 
 
 Helix, Right-Handed A term 
 
 sometimes employed in place of right-handed 
 solenoid. (See Solenoid, Right-Handed. 
 Solenoid, Practical) 
 
 Helmholtz Galvanometer. (See Appen- 
 dix Galvanometer, Helmholtz) 
 
 Henry, International The value 
 
 of the international henry adopted by the 
 Chicago Congress of 1893, as equal to the 
 induction in a circuit when the electromotive 
 force induced in this circuit is one interna- 
 tional volt, while the inducing current varies 
 at the rate of one ampere per second. 
 
 Henry, Proposed A. I. E. E. Definition 
 
 for The name adopted by the Elec- 
 trical Congress of 1 893 for the practical unit 
 of inductance. 
 
 A unit of inductance having the value of 
 io 9 absolute units, or nearly the length of an 
 earth's quadrant. 
 
 This name was proposed by a Sub-Committee 
 of the American Institute of Electrical Engineers 
 on Provisional Programme of the International 
 Electrical Congress, in Chicago, 1893, on the occa- 
 sion of the World's Columbian Exposition. 
 
 This name was adopted by the said Inter- 
 national Electrical Congress in August, 1893, with 
 the. following definition : 
 
 A henry is the induction in a circuit when the 
 electromotive force induced in this circuit is one 
 international volt, while the inducing current 
 varies at the rate of one international ampere per 
 second. 
 
 Heptad Atom. (See Appendix Atom, 
 Heptad) 
 
 Hertz's Axial Oscillator. (See Appen- 
 dix Oscillator, Hertz s Axial) 
 
 Hertz's Linear Oscillator. (See Appen- 
 dix Oscillator, Hertz's Linear) 
 
 Hertz's Oscillator. (See Appendix < 
 Oscillator, Hertz's) 
 
Her,] 
 
 614 
 
 [Idl. 
 
 Hertzian Waves. (See Appendix 
 Waves, Hertzian.} 
 
 Heterostatic Electrometer. (See Appen- 
 dix Electrometer, Heterostatic!) 
 
 Hexad Atom. (See Appendix Atom, 
 Hexad!) 
 
 High-Frequency Transformer. (See Ap- 
 pendix Transformer, High-Frequency!) 
 
 High- foliage Electro-Magnetic Gener- 
 ator. (See Appendix Generator, High- 
 Voltage Electro-Magnetic!) 
 
 Home Battery. (See Appendix Battery, 
 Home!) 
 
 Hook, Dipping A metallic hook 
 
 provided for holding articles that are to be 
 cleansed, in order to prepare them for electro- 
 plating by subjecting them to the dipping 
 process. (See Dipping!) 
 
 The dipping hook should be made of metal as 
 nearly resembling the article to be plated as pos- 
 sible, so as thereby to prevent voltaic action tak- 
 ing place between the two metals with a conse- 
 quent marking at the points of contact. 
 
 Horizontal Intensity of Earth's Magnet- 
 ism. (See Appendix Magnetism, Hori- 
 zontal Intensity of Earth's!) 
 
 Horology, Electric That branch of 
 
 electric science which treats of the applica- 
 tions of electricity to the regulation or opera- 
 tion of clocks. (See Clock, Electric!) 
 
 Hummer. A word sometimes employed 
 in place of buzzer. (See Buzzer, Electric!) 
 
 If inn in cr, Electric A term some- 
 times used for electric buzzer. 
 
 Hunting of Parallel Alternators. (See 
 
 Appendix Alternators, Parallel, Hunting 
 of-) 
 
 Hysteresis, Dielectric A term pro- 
 posed by Steinmetz for a variety of molecular 
 friction, analogous to magnetic hysteresis, pro- 
 duced in a dielectric under changes of electro- 
 static stress. 
 
 The losses caused by dielectric hysteresis are 
 probably proportional to the frequency and to the 
 square of the E. M. F., i. e,, to the electrostatic 
 field intensity. 
 
 Losses ascribed to defective insulation are often, 
 in the opinion of Steinmetz, caused, at least in part, 
 by dielectric hysteresis. 
 
 Hysteresis, Magnetic A variety of 
 
 molecular friction produced in the molecules 
 of a magnetizable substance during changes 
 of magnetic stress. 
 
 According to Steinmetz, the loss occasioned by 
 magnetic hysteresis is proportional to the fre- 
 quency and to the 1. 6th power of the magnetic 
 variation. 
 
 According to Steinmetz, for a magnetic cycle 
 performed between the limits of magnetic induc- 
 tion B x and B, the loss in ergs per cubic cm. is 
 
 ,1.6 
 
 ( B *7 Bf ) 1 
 
 where n, the coefficient of hysteresis, averages 
 .0033 in average good sheet iron, .013 in cast 
 iron, .003 to .03 in cast steel, and reaches as high 
 as .08 in hardened steel. 
 
 With alternating magnetism the formula can 
 be written 
 
 L=nB 1 ' 6 
 
 The actual existence of magnetic hysteresis is 
 denied by some able electricians. 
 
 7. A symbol 
 current. 
 
 proposed for intensity of 
 
 E 
 
 The defining equation is I = =r- 
 
 3 A symbol used in France and 
 
 Germany for intensity of magnetization. 
 
 _m 
 
 The defining equation is c) y 
 
 Idiostatic Electrometer. (See Appendix 
 Electrometer, Idiostatic!) 
 
 Idle Wire of Armature. (See Appendix 
 Wire, Idle, of Armature!) 
 
 Idle Wire of Armature of Motor. (See 
 Wire, Idle, of Armature of Motor!) 
 
 Idle Wire of Dynamo. (See Appendix 
 Wire, Idle, of Armature of Dynamo!) 
 
IdL] 
 
 615 
 
 [Ind. 
 
 Idle Wire of Motor. (See Appendix 
 Wire, Idle, of Armature of Motor.) 
 
 Illumination, Cosine Law of The 
 
 intensity of the illumination emitted from or 
 received by any element of surface is propor- 
 tional to the cosine of the angle between its 
 normal, and the direction of the radiation. 
 
 Illumination, Glow A term pro- 
 posed for an illumination similar to that of 
 the glow-worm ; that is, illumination without 
 sensible heat. 
 
 All artificial sources of light, such, for example, 
 as a coal-oil lamp, a gas jet, an incandescent elec- 
 tric lamp, or an arc lamp, contain a much greater 
 percentage of non-luminous than of luminous 
 radiation, that is, of heat than light, being at the 
 most a few per cent, of light, and considerably 
 over 95 per cent, of heat. 
 
 The most economical artificial lighting is, of 
 course, impossible under these circumstances. 
 
 In the light emitted by a firefly or a glow 
 worm, practically all the radiation consists of. 
 light or radiation within the limits of visibility. 
 
 The term glow illumination has been proposed 
 for illumination by light such as is furnished by a 
 firefly or glow-worm; viz., for the light emitted 
 by any source which is capable of producing 
 luminous radiation only. In some forms of Tesla 
 lamps the illumination closely approaches glow 
 illumination. 
 
 Immediate False Zero. (See Appendix 
 Zero, Immediate False.) 
 Incandescent Bombardment Lamp. 
 
 (See Appendix Lamp, Incandescent Bom- 
 bardment.) 
 
 Incandescent Filament. (See Appendix 
 Filament, Incandescent^) 
 
 Incandescent Lamp Cord. (See Appen- 
 dix Cord, Incandescent Lamp.) 
 
 Incandescent Lighting Dynamo-Electric 
 Machine. (See Appendix Machine, Dy- 
 namo-Electric, Incandescent Lighting.) 
 
 Incandescing Filament. (See Appendix 
 Filament, Incandescing.) 
 
 Inclination Magnetometer. (See Appen- 
 dix Magnetometer, Inclination) 
 
 Indicator, Disc, Mechanical Replacement 
 
 Of Such a replacement or resetting of 
 
 a disc, arm, shutter or semaphore of an indi- 
 cator as must be done by hand. 
 
 A non-automatic replacement of an indi- 
 cator disc. 
 
 Indicator, Fall-Back A term some- 
 times employed in place of drop indicator. 
 
 Indicator, Light, of Railroad Signal 
 
 A device by means of which an indi- 
 cation is given as to whether a signal lamp is 
 lighted or not. 
 
 The light indicator is operated by means of a 
 metallic bar, which increases in length by means 
 of the heat of the lamp when lighted. 
 
 Indicator, Polarized A term some- 
 times employed for an indicator provided 
 with a polarized armature. 
 
 Indicator, Pole An apparatus em- 
 ployed for readily determining whether the 
 poles of a dynamo battery or other source 
 are positive or negative. 
 
 A convenient form of pole indicator consists of 
 a small electrolytic cell filled with a solution of a 
 metallic salt. On the passage of the current 
 through the electrolyte the character of the poles 
 is readily determined by the change in color of 
 the liquid adjacent to one pole of the indicator. 
 
 There are other well-known forms of pole in- 
 dicators. 
 
 Indicator, Tele A term sometimes 
 
 employed in place of telemeter. (See Telem- 
 eter) 
 
 Indicator, Telephone An indi- 
 cator employed on a telephone circuit to indi- 
 cate the number of the correspondent calling. 
 (See Indicator, Electric) 
 
 A telephone indicator, as generally constructed, 
 consists of some form of mechanical drop oper- 
 ated by the attraction of the armature of an 
 electro-magnet which, permitting the fall of a 
 drop or shutter, exposes the particular number of 
 the correspondent calling. 
 
 Indicator, Tri-Polar An electro- 
 magnetic indicator, with three poles. 
 
 A straight- bar magnet is employed, one end of 
 which forms one pole and the other end is con- 
 nected with a U-shaped piece of soft iron, so as 
 to bring the two free ends of the latter up to the 
 
Ind.] 
 
 616 
 
 [Ind. 
 
 line on the other pole. There are thus produced 
 three poles; hence, the name, tri-polar. 
 
 Indifferent Point (See Appendix 
 Point, Indifferent?) 
 
 Individual Signal. (See Appendix 
 Signal, Individual!) 
 
 Individual Signaling Apparatus. (See 
 Appendix Apparatus, Individual Signal- 
 ing. 
 
 Induced Electric Surgings. (See Appen- 
 dix Surgings, Induced Electric!) 
 
 Induced Single-Needle Dial. (See Ap- 
 pendix Dial, Induced Single-Needle!) 
 
 Inductance, Mutual, Proposed A. I. E. E. 
 Definition for The mutual induc- 
 tance of one electric circuit upon another is 
 the ratio of the total magnetic induction 
 linked with the second, due to a uniform cur- 
 rent in the first, to the strength of that 
 current. 
 
 The mutual inductance between two electric 
 circuits is reciprocally equal when the environ- 
 ing medium has constant inductivity. 
 
 The C. G. S. unit of mutual inductance is one 
 centimetre; the practical unit of self-inductance 
 is one henry. 
 
 The following modification of the definition 
 would appear to be preferable, viz. : the mutual 
 inductance of one circuit on another is the ratio 
 of the sum of the linkages of lines of magnetic 
 induction with the second, due to a uniform cur- 
 rent in the first, to the strength of that current. 
 
 Inductance, Non-Ferric A term 
 
 proposed to distinguish an inductance in 
 which no iron or magnetic metal enters. 
 
 A coil of copper forms a non-ferric inductance ; 
 the insertion of an iron core into the coil makes 
 it become a ferric inductance. 
 
 Inductance, Self, Proposed A. I. E. E. 
 
 Definition for The ratio of the total 
 
 magnetic induction, linked with and estab- 
 lished by an electric current, to the uniform 
 strength of the same. 
 
 The inductance of a conducting circuit is con- 
 stant when its environing medium has constant 
 inductivity. A modification has been proposed 
 for this definition similar to that proposed for 
 mutual inductance. 
 
 Inductance, Specific A term pro- 
 posed for the comparative value of induc- 
 tance. (See Inductance,') 
 
 Inductance Speed. (See Appendix 
 Speed, Inductance!) 
 
 Inducteous Body. (See Appendix Body, 
 Inducteous!) 
 
 Induction, Auto A term sometimes 
 
 employed instead of self-induction. (See In- 
 duction, Self.) 
 
 Induction, Backward, of Dynamo Arma- 
 ture The component of the armature 
 
 magnetization opposing the magnetization of 
 the field magnets. (See Appendix Induc- 
 tion, Cross, of Dynamo Armature.) 
 
 Were there no forward lead given to the 
 brushes, there would be no back induction ; there 
 would, however, be cross induction. 
 
 Induction, Cross, of Dynamo Armature 
 
 A term sometimes employed in place 
 
 of the induction produced in the armature of 
 a dynamo-electric machine from the ampere 
 turns acting across the main magnetic cir- 
 cuit, /'. e., those due to the ^current in the 
 armature, and is the lead of the brushes 
 tending to produce magnetic poles crosswise 
 to the regular poles of the machine. 
 
 Induction, Magne-Electric A term 
 
 formerly employed for magneto-electric in- 
 duction. (See Induction, Magneto-Electric!) 
 
 Induction, Magnetic, Terrestrial 
 
 The production of magnetism by the action 
 of the earth's magnetic field. 
 
 Induction Motor. (See Appendix Mo- 
 tor, Induction!) 
 
 Induction Telegraph. (See Appendix 
 Telegraph, Induction!) 
 
 Indnctivity. A word proposed for spe- 
 cific inductance. (See Appendix Induct- 
 ance, Specific!) 
 
 Inductivity, Proposed A. I. E. E. for 
 
 The inductivity at any point in an 
 
 isotropic medium is the ratio added to unity 
 of 4 n times the intensity of the magnetiza- 
 tion there existing to the magnetizing flux 
 density. 
 
Ind.J 
 
 617 
 
 [Int. 
 
 The ratio of the flux density to the mag- 
 netizing force. 
 
 The conventional symbol is fi and it is synony- 
 mous with permeability. 
 
 Inductric Body. (See Appendix Body, 
 Inductric.) 
 
 influence, Electrostatic A word 
 
 sometimes employed in place of electro- 
 static induction. (See Induction, Electro- 
 static.) 
 
 There would appear to be no real necessity 
 for the abandonment of the term induction for 
 the effects produced by an electrostatic field. 
 The general similarity of the phenomena would, 
 indeed, appear to render it advisable to retain 
 the word electrostatic induction, to show its close 
 relation to electro-magnetic induction. 
 
 In-Put. The energy absorbed by a ma- 
 chine in driving it or causing it to perform a 
 certain amount of work. 
 
 This word is used in contradistinction to out- 
 put. 
 
 Inside Box Brush. (See Appendix 
 Brush, Inside Box.) 
 
 Instrument, S. N., Telegraphic A 
 
 contraction employed for single-needle tele- 
 graphic instrument. 
 
 Insulated or Free A term em- 
 ployed in telegraphy. 
 
 A wire is said to be free insulated when it is 
 disconnected from its apparatus and left insu- 
 lated. 
 
 Insulation, Kilometric, of Cable 
 
 The insulation of a cable measured in kilo- 
 metre-megohms or the average insulation of 
 one kilometre in megohms. 
 
 Insulation Lightning Protection. (See 
 Appendix Protection, Insulation Light" 
 ning.) 
 
 Insulation Lightning Protector. (See 
 Appendix Protector, Insulation Light- 
 ning.) 
 
 Insulator, Glass-Screw A glass in- 
 sulator provided with a screw thread inside 
 the glass for the purpose of ready attach- 
 ment to the insulator pin. 
 
 Insulator, Shackle A term some- 
 
 tfmes employed for any form of shackle in- 
 
 sulator. (See Insulator, Single- Shackle. 
 Insulator, Double-Shackle.) 
 
 Insulator, Tree A variety of insu- 
 lator suitable for attachment to trees, and 
 designed so as to keep the conductor from 
 being brought into contact with the branches. 
 
 The insulator -proper is mounted on a shaft 
 which plays in a ball and socket joint, the cup 
 of which is fastened to the tree ; the line is there- 
 fore kept in its normal position despite the move- 
 ments of the tree. 
 
 In-Take. A word sometimes used in place 
 of In-Put. 
 
 Intensity of Radiation. (See Appendix 
 Radiation, Intensity of.) 
 
 Interference, Acoustic Interfer- 
 ence of sound waves. 
 
 The term acoustic interference is employed in 
 contradistinction to luminous interference. 
 
 Interference, Electro-Magnetic 
 
 A 
 
 term sometimes employed for the interference 
 of electro-magnetic waves. 
 
 The term electro-magnetic interference is em- 
 ployed in contradistinction to acoustic or lumi- 
 nous interference, even though it be granted that 
 luminous waves are electro -magnetic waves. 
 
 Interference, Luminous A term 
 
 sometimes employed for the interference of 
 light waves. 
 
 The term luminous interference is used in 
 contradistinction to acoustic or electric inter- 
 ference. 
 
 Internal Magnetic Circuit. (See Ap- 
 pendix Circuit, Magnetic, Internal.) 
 
 Internal Magnetic Field. (See Appen- 
 dix Field, Magnetic, Internal.) 
 
 International Ampdre. (See Appendix 
 Ampere, International?) 
 
 International Coulomb. (See Appendix 
 Coulomb, International?) 
 
 International Farad. (See Appendix 
 Farad, International?) 
 
 International Henry. (See Appendix 
 Ifenry, International.) 
 
 International Joule. (See Appendix 
 Joule, International?) 
 
Int.] 
 
 618 
 
 [Int. 
 
 International Morse Code. (See Appen- 
 dix Code, International Morse?) 
 
 International Ohm. (See Appendix 
 Ohm, International?) 
 
 International Volt (See Appendix 
 Volt, International?) 
 
 International Watt (See Appendix 
 Watt, International?) 
 
 Interrupter, Electro-Dynamic A 
 
 name proposed by Pupin for an interrupter for 
 the primary circuit of an induction coil con- 
 sisting of an elastic wire stretched like the 
 wire of a sonometer or monochord between 
 the poles of a permanent horseshoe magnet. 
 
 The term sonometer interrupter might, per- 
 haps, be more descriptive of the apparatus em- 
 ployed. 
 
 The circuit connections are such that when the 
 wire is set into vibration these vibrations are con- 
 tinued under the action of the field produced by 
 the magnet. The construction and operation of 
 an electro-dynamic interrupter are given by its 
 inventor, Pupin, as follows : 
 
 "In the meantime experience suggested the 
 form given in Fig. 574 as best suited to the pur- 
 pose for which the interrupter was first de- 
 signed. The diagram of Fig. 575 explains the 
 
 Fig. 574- 
 
 A / h 
 
 Fig. ^re- 
 
 construction of the apparatus more clearly. A 
 stout aluminium, or phosphor-bronze wire, the 
 vibrator, is stretched between the pole pieces d 
 and e, of two permanent Weston magnets, such 
 as this distinguished electrician uses in his 
 voltmeters. 
 
 " Fig- 576 * ves th e fr nt ^ ew * one of the 
 magnets. The cross-section of the vibrator is 
 seen therebetween the pole pieces N, S, as a black 
 dot. The short line a b extending from the vi- 
 brator to the mercury cup below is the dipper, a 
 short, thin, amalgamated copper wire, which is 
 soldered to the vibrator. The vibrator rests on 
 
 two hard-rubber bridges f g. One of its ends is 
 rigidly attached to the wooden frame of the 
 apparatus, the other end is attached to a lever h, 
 which, worked by a micrometer screw, varies 
 the tension of the vibrator. 
 There are three mercury 
 cups, a, b, c, and three 
 dippers (which unfortun- 
 ately do not appear in Fig. 
 574). The middle cup b, is I 
 fixed in position, and the 
 middle dipper, being at the 
 nodal point of the vibrator, 
 makes a permanent contact 
 there. The other two dippers make contact with 
 mercury cups which can be raised or lowered by 
 means of a nut and screw as represented in Fig. 
 574, and indicated in diagram 575. The con- 
 struction of the adjustable mercury cups and the 
 stretching lever were copied from Dr. Max Wien's 
 magnetic interrupter (Wiedem. Ann. 1891 and 
 1892). The middle cup (see Fig. 577) is connected 
 to one pole, F, of the gravity or storage cell, the 
 other two cups are connected one to one end and 
 the other to the other end of the primary of the 
 
 Fig. S7(>- 
 
 Fig. S77> 
 
 small coil A B. From the middle point, C, of the 
 primary a wire leads to the other pole of the cell. 
 Auxiliary small coils, E and D, and condensers, 
 H and G, are inserted in the circuits as indicated. 
 Their functions will be explained further below. 
 
 "The vibrator vibrates with a node at the 
 middle dipper as soon as the tension has reached a 
 certain, by no means high, limit. A permanent 
 contact is therefore maintained at this point, and 
 the contact is made at one of the cups just at 
 about the same moment as it is broken at the 
 other cup. Leaving the condensers out of con- 
 sideration for the present, it is evident that this 
 form of the current make-and-break produces 
 the same effect upon the iron core of the coil as 
 an alternating current would. The advantage of 
 this needs no comment ; but although the iron 
 core consists of the finest iron wire that can be 
 obtained in the market, yet it must be remem- 
 
Int.] 
 
 619 
 
 [Iso. 
 
 bered that the vibrator is expected to work some- 
 times at the rate of 512, or more, complete periods 
 per second. Another immediate advantage 
 which this interrupter offers is a considerable 
 diminution of sparking. The addition of con- 
 densers, besides performing other functions 
 which will be discussed presently, reduces the 
 break sparks almost to invisibility, even when 
 currents as large as half of an ampere are used. 
 Each half of the primary coil consists of 532 turns 
 of No. 22 silk-covered wire wound over an iron 
 core of 30 centimetres in length, 4 square centi- 
 metres in cross-section, and consisting of very 
 fine, soft iron wire." 
 
 Interrupter, Sonometer A term 
 
 sometimes employed in place of electro- 
 dynamic interrupter. (See Appendix In- 
 terrupter, Electro-Dynamic^) 
 
 Interrupter, Telegraphic A de- 
 vice for making and breaking a circuit at a 
 definite rate. 
 
 A telegraphic key or other analogous de- 
 vice. 
 
 Interrupter, Telegraphic, Mechanical 
 
 A form of mechanical telegraphic 
 
 sounder for learners in which no battery is 
 required. 
 
 A mechanical telegraphic interrupter is pro- 
 vided with a full-size key with a full set of adjust- 
 ments. In fact, it resembles an ordinary key, 
 except in that it requires no battery to operate it. 
 It differs, therefore, from the snappei sounder, 
 which is not intended to resemble a sounder, but 
 merely to give the sounds of the Morse characters 
 with the simplest mechanism. 
 
 Interruption, Telegraphic A term 
 
 sometimes employed in telegraphy for faults 
 in general. 
 
 According to Pope, telegraphic faults or inter- 
 ruptions arise from the following causes, viz. : 
 
 (l.) Disconnections or breaks. 
 
 (2.) Partial disconnections or resistance. 
 
 (3.) Escapes. 
 
 (4.) Crosses. 
 
 Ions, Migration of A term em- 
 ployed to express the movement of the ions 
 in an electrolyte during electrolysis. 
 
 The hypothesis of GrOthuss attempts to explain 
 the fact that in electrolysis the anions and kathions 
 do not appear in any part of the electrolyte ex- 
 
 cept at the electrodes, no ions apparently being 
 set free in the liquid. (See Hypothesis, GrOtkuss' . ) 
 
 When copper electrodes are employed in the 
 electrolysis of a solution of copper sulphate, the 
 solution becomes from two to three times weaker 
 at the kathode than at the other electrode. 
 Hittorf explains this fact on the assumption that 
 during the migration the 864 radical moves 
 through the liquid more rapidly than the Cu 
 radical. 
 
 GrOthuss' hypothesis has been objected to be- 
 cause it requires a finite force to bring about the 
 decomposition of the electrolyte, and the experi- 
 ments of Helmholtz prove that the interior of an 
 electrolyte is unable to withstand the slightest 
 electrostatic stress. Clausius has modified GrOt- 
 huss' hypothesis so as to bring it more into 
 accord with the kinetic theory of matter. He 
 believes that some of the moving molecules of the 
 electrolyte are broken up into their constituent 
 ions as a result of occasional molecular impact,, 
 and that it is these separated ions only that appear 
 at the electrodes. Arrhenius asserts that during 
 electrolysis the greater part of the molecules of 
 the electrolyte are thus dissociated. The veloc- 
 ity of the dissociated ions is assumed to be pro- 
 portioned to the potential gradient in the elec- 
 trolyte. According to this theory a continuous 
 movement of positively charged ions occurs 
 towards the negative electrode or kathode and of 
 negatively charged ions towards the positive 
 electrode or anode. 
 
 Iron, Building A heated iron tool, 
 
 by means of which the mould impressed by 
 the printed page, it is desired to electrotype, 
 is built up preparatory to being placed in the 
 electroplating bath. 
 
 A building iron consists essentially of a suitably 
 shaped iron tool which is employed while hot in 
 connection with strips of wax for bringing up or 
 raising the blank spaces in a mould between the 
 pages and paragraphs. 
 
 Iron-Loss in Transformer. (See Ap- 
 pendix Transformer, Iron-Loss in.) 
 
 Isonisation. A term proposed for a de- 
 crease in the strength with which the separate 
 atoms or radicals are held together in the 
 molecules of an electrolyte. 
 
 A term proposed for that modified dis- 
 sociation of a molecule which consists in a 
 
ISO.] 
 
 620 
 
 [Key. 
 
 weakening of the force which holds the ions 
 of the molecules together in an electrolyte. 
 
 The term isonisation does not, as might be 
 supposed, refer to the complete separation of an 
 electrolyte into its ions by electrolysis, but to a 
 preparatory weakening of the bonds which hold 
 the ions together in a solution in which elec- 
 trolysis is about to occur. 
 
 This term was proposed by Fitzgerald for the 
 purpose of covering the peculiar action of elec- 
 trolysis so far as its behavior to aqueous solutions 
 of metallic salts is concerned. 
 
 Isotropic. Homogeneous with respect to 
 direction. 
 
 Employed in reference to the properties of a 
 medium. 
 
 Jack Switch. (See Appendix Switch, 
 Jack) 
 
 Jar, Leyden, Overflow of A term 
 
 sometimes employed for the discharge of a 
 Leyden jar by a disruptive discharge around 
 its edge. 
 
 Joint, End-to-End A term fre- 
 quently employed in place of butt joint. (See 
 Joint, Butt) 
 
 Joint, Sliding An expansion joint. 
 
 (See/iw/, Expansion) 
 
 Joule, International The value 
 
 of the international joule adopted by the Chi- 
 cago Congress of 1893, as equal to io 7 units 
 of work in the C. G. S. system, and which is 
 
 represented sufficiently well for practical use 
 by the energy expended in one second by one 
 international ampere in an international ohm. 
 
 Joule-Meter. Any apparatus capable of 
 measuring energy in joules. 
 
 An energy meter as distinguished from a 
 watt-meter. 
 
 Jumper. A temporary shunt or circuit put 
 around a lamp or loop on a series circuit, to 
 enable it to be readily removed or repaired. 
 
 A jumper usually consists of a piece of wire of 
 sufficient size to carry the current past the faulty 
 lamp or other device which it is desired to tem- 
 porarily remove or repair. 
 
 K. A symbol for moment of inertia. 
 The defining equation is M X L 2 . 
 K (Kappa). A symbol proposed for mag- 
 netic susceptibility. 
 
 1 | 
 
 The defining equation is K = j^- i. e. Q 
 
 cH- n 
 
 kg. An abbreviation for kilogramme, the 
 practical unit of mass. 
 
 kg: cm 2 . An abbreviation proposed for 
 kilogramme per square centimetre, the prac- 
 tical unit of pressure. 
 
 kgni. An abbreviation for kilogrammetre, 
 the practical unit of moment of a couple or 
 of work. 
 
 kgm: s. An abbreviation proposed for 
 kilogrammetre per second, the practical unit 
 of power. 
 
 KR. A contraction for the total capacity 
 of a telephone wire or conductor multiplied 
 by its total resistance. 
 
 KB Law. (See Appendix Law, The 
 KR) 
 
 Kapp Line. (See Appendix Line, 
 Kapp) 
 
 Karsten's Figures. (See Appendix 
 Figures, Karsten's) 
 
 Kathodic Rays of Vacuum Tube. (See 
 Appendix Rays, Kathodic, of Vacuum 
 Tube) 
 
 Kerite Tape. (See Appendix Tape, 
 Kerite) 
 
 Key, Break A key which breaks 
 
 or opens the circuit when depressed. 
 
Key.] 
 
 621 
 
 [Lam. 
 
 Key, Strap A telegraphic key 
 
 formed of a single plate of elastic material. 
 
 The elastic strip of conducting material is 
 fixed at one end. Its motion in one direction is 
 effected by the hand of the operator, and its re- 
 turn in the opposite direction by the elasticity of 
 the material. 
 
 Key, Successive Contact A key so 
 
 arranged as to make or break one contact 
 after another. 
 
 A successive contact key is frequently used in 
 connection with a Wheatstone bridge ; where it 
 is desirable to make or close the battery circuit 
 before making or closing the galvanometer cir- 
 cuit, or to break the battery circuit after break- 
 ing or opening the galvanometer circuit. This is 
 done by means of a successive contact key. A 
 successive contact key is also sometimes called a 
 double contact key. (See Key, Double-Contact 
 Form of Bridge, Spr ague's. Key, Double-Con- 
 tact, Lambert's.) 
 
 Key, Tapper A term sometimes 
 
 employed in place of Morse tapper. (See 
 Appendix Tapper, Morse?) 
 
 Kick of Relay. A momentary effect, 
 more powerful than usual, produced on the 
 armature of a relay by the current of charge 
 on the closing of the circuit. 
 
 The kick varies in its amount or intensity not 
 only with the electrostatic capacity ot the line, 
 but also with its length and with the perfection of 
 its insulation. 
 
 Kilerg. A kilo-erg. 
 
 Kilo-Erg. One thousand ergs. 
 
 Kilo-Volt. One thousand volts. 
 
 Kilometric Capacity of Cable. (See 
 Appendix Capacity, Kilometric, of Cable?) 
 
 Kilometric Insulation of Cable. (See 
 Appendix Insulation, Kilometric, of Cable?) 
 
 Kinematics. That branch of mechanics 
 which treats of motions, irrespective of the 
 mass moved or the forces which produce or 
 oppose its motion. 
 
 Kinetics. That branch of dynamics which 
 treats of the action of forces in producing or 
 modifying motion. 
 
 Krizik's Cores. (See Appendix Cores, 
 Krizik's?) 
 
 L m . A symbol proposed for co-efficient of 
 mutual induction. 
 
 L s . A symbol proposed for co-efficient of 
 self-induction or inductance. 
 
 $ 
 The defining equation is L, = Y 
 
 Lag, Translation 
 
 -A term proposed 
 
 by Elihu Thomson, who defines it as follows : 
 " Lag due to the traverse of a conductor con- 
 veying current past a magnet pole, whereby 
 the action of the current in that conductor 
 becomes displaced in the direction of the 
 motion and produces a moving field, the iron 
 mass or body tending to accommodate itself 
 to the direction of the lines of force in the 
 moving field." 
 
 The phenomena of a shifting field are observed 
 when a coil with an iron wire core is energized 
 by an alternating current so as to produce an 
 
 alternating field, and a wheel made up of iron 
 discs around which is a rim or band of copper 
 overhanging the edges of the disc is placed in 
 such field. On the energizing of the coil, the 
 wheel, which is mounted on pivots, when 
 mechanically started in rotation in either direc- 
 tion, will increase both in speed and torque to a 
 degree depending on the frequency of the current, 
 the friction to be overcome on the alternating 
 field and on the iron and copper of the wheel. 
 (See Field, Magnetic, Shifting. ) 
 
 Lamp, Arc, Striking Mechanism of - 
 
 The mechanism in an arc lamp by means 
 of which the carbons are separated to the 
 distance at which it is desired the arc shall 
 be maintained between them. 
 
 Lamp, Bombardment, Electrical A 
 
 lamp in which the light is produced in a 
 vacuous space by means of the bombard- 
 
Lam.] 
 
 622 
 
 [Law. 
 
 ment of the molecules of the residual gas by 
 the passage of electrical discharges. 
 
 The molecules in their rapid to-and-fro motions 
 are caused to strike against, and thus raise to in- 
 candescence, strips or bars of refractory material, 
 such as carbon, etc. 
 
 Tesla's straight-filament incandescent electric 
 lamp is a form of electric bombardment lamp. 
 (See Lamp, Incandescent, Straight-Filament.} 
 
 Lamp, Burned-Out Incandescent 
 
 A term sometimes employed for an electric 
 incandescent lamp which is no longer able 
 to furnish efficient electric light. 
 
 An incandescent electric lamp is, strictly speak- 
 ing, to be regarded as burned out when it no 
 longer furnishes a suitable light, and this, 
 whether the filament or chamber has been 
 actually destroyed or not. 
 
 Lamp, Electcic, Efficiency of 
 
 Strictly, the ratio of the luminous energy 
 emitted by the lamp, to the energy absorbed 
 by the lamp. 
 
 The term efficiency of a lamp is less accur- 
 ately used to signify its relative watts per candle 
 power. The Edison lamps are of high efficiency 
 if 3.1 watts per c. p., and of low efficiency if 
 greater. 
 
 Lamp, Electric Stopper A term 
 
 now generally em- 
 ployed for an in- 
 candescent elec- 
 tric lamp in which 
 the chamber is 
 stopped, not as 
 formerly by the 
 fusion of the 
 glass, but by the 
 action of a glass 
 stopper hermeti- 
 cally sealed by 
 the use of suit- 
 able cement. 
 
 Fig. 578 shows a 
 lamp of this type. 
 
 Lamp, Glow 
 
 A lamp 
 
 the light of which is produced by glow 
 illumination. (See Appendix Illumination, 
 Glow) 
 
 The term glow lamp is already generally em- 
 ployed in England and Germany for the ordinary 
 incandescent electric lamp. It would appear that 
 the term incandescent lamp generally employed 
 in America is preferable. The term glow-lamp 
 should be limited, as above, to a lamp producing 
 an approximately cold light ; namely, a lamp 
 operating by glow illumination. 
 
 Lamp, Incandescent Bombardment 
 
 An electric lamp in which a refractory 
 material is rendered incandescent by the 
 molecular bombardment produced by the 
 passage of an electric discharge through a 
 rarefied space. 
 
 Most of Tesla's lamps are of the bombardment 
 type and are of a great variety of forms, but in 
 all of them refractory substances like carbon are 
 rendered incandescent by the passage of very 
 rapidly alternating currents through rarefied 
 gases. (See Lamp, Electric, Incandescent Ball. 
 Lamp, Incandescent, Straight Filament. ) 
 
 Lamp, Incandescent Electric, Ageing of 
 
 A term sometimes employed for a 
 
 Fig. 51 8. Electric Stopper 
 Lamp. 
 
 gradual decrease in the economical light 
 emitted by an incandescent electric lamp 
 attending its continued use. 
 
 Lamp, Phosphorescent A lamp 
 
 whose light is obtained by means of the phos- 
 phorescent effects attending the discharges of 
 electricity through a rarefied space. 
 
 In phosphorescent lamps the phosphorescent 
 effects are produced by causing the molecules ot 
 the residual gas to strike against some readily 
 phosphorescent material. Such lamps are some- 
 times called bombardment lamps. But the term 
 bombardment lamp is [perhaps more properly 
 restricted to cases where molecular bombardment 
 raises a substance of high refractory power, such 
 as carbon, to incandescence; while the term 
 phosphorescent lamps is limited to cases where 
 the material so raised to luminescence is a phos- 
 phorescent material. (See Bombardment, Molec- 
 ular.} 
 
 Law, The KR. A generalization 
 
 claimed by some as a law, but denied by 
 most, which assigns a limit to the distance 
 through which intelligible telephonic com- 
 munication can be carried on to cases where 
 the product of K, the capacity of the tele- 
 
Lea.] 
 
 623 
 
 [Lig. 
 
 phone circuit, multiplied by R, its resistance, 
 does not exceed a certain value. 
 
 Preece originally fixed the limits of intelligible 
 communication of speech by means of a telephone 
 to cases where the product of K and R did 
 not exceed 15,000. Preece's figures do not agree 
 with the results of practical telephone work in the 
 United States ; such, for example, as in the case of 
 the line now in actual operation between Boston 
 and Chicago. 
 
 Preece's general method of calculating the K 
 R of a metallic circuit was by multiplying the 
 total capacity of the line by its total resistance 
 and then dividing by four, since the capacity of 
 an insulated loop is taken as one-fourth of the 
 capacity of the entire length of the line measured 
 against the ground. Even when calculated in 
 this way the K R of the Boston-Chicago con- 
 ductor line is nearly 54,000. 
 
 Lead Sulphate of Copper Cell. (See Ap- 
 pendix Cell, Lead Sulphate of Copper?) 
 
 Lead Sulphate of Zinc Cell. (See Ap- 
 pendix Cell, Lead Sulphate of Zinc.) 
 
 Leads, Double-Wire System for Electric 
 
 Light A term employed for a parallel 
 
 or multiple system of leads for electric light. 
 (See Circuit, Parallel. Circuit, Multiple?) 
 
 Leads, Grouping System for Electric 
 
 Light A term sometimes employed 
 
 for series-multiple circuits. (See Circuit, 
 Series-Multiple?) 
 
 Leads, Single Wire System for Electric 
 
 Light A term sometimes employed for 
 
 a circuit in which the current after passing 
 through the lamps is returned by means of 
 the earth or ground. 
 
 This is called the single wire system for electric 
 light leads because but a single wire or con- 
 ductor is employed in the circuit, the return being 
 made through the ground or earth. 
 
 Leak, Telegraphic, Resistance of 
 
 The resistance offered by a leak in a tele- 
 graphic line or circuit. 
 
 Leakance. A word proposed by Heavi- 
 side for leakage conductance. 
 
 It will be seen that the proposed word is an 
 abbreviation or contraction for leakage-conduct- 
 ance. 
 
 Lease, Way A permit obtained from 
 
 the owner of a property for the erection of 
 poles or other attachments for telephonic or 
 telegraphic lines. 
 
 Left -Hand Trolley Switch. (See Ap- 
 pendix Switch, Left-Hand Trolley.) 
 
 Left-Handed Helix. (See Appendix 
 Helix, Left-Handed?) 
 
 Left-Handed Rotation. (See Appendix 
 Rotation, Left-Handed?) 
 
 Left-Handed Spiral. (See Appendix 
 Spiral, Left-Handed?) 
 
 Lever Switch. (See Appendix Switch, 
 Lever?) 
 
 Light, Castor and Pollux A term 
 
 formerly used in place of St. Elmo's fire. 
 
 Light Cell. (See Appendix Cell, Light} 
 
 Light Indicator of Railroad Signal. 
 (See Appendix Indicator, Light, of Rail- 
 road Signal.) 
 
 Light Load. (See Appendix Load, 
 Light.) 
 
 Light, Northern An aurora bore- 
 
 alis. 
 
 Lighting, Vacuum-Tnbe Artificial 
 
 illumination obtained by the passage of elec- 
 tric discharges through vacuum tubes. 
 
 A practical system of electric lighting by means 
 of vacuum tubes was not long ago regarded as an 
 impossibility ; now, however, through the labors 
 of many distinguished men, especially those of 
 Tesla, such a system, which seems to possess 
 many advantages, bids fair in event of certain- 
 difficulties being overcome to become a formid- 
 able rival to the incandescent electric lighting. 
 
 In a system of vacuum-tube lighting, some 
 source of high alternating potential furnishing 
 from 50,000 to 100,000 volts or more is employed. 
 Such discharges are most readily obtained by 
 means of an alternator and disruptive discharges 
 from condensers in connection with an oil trans- 
 former. The oil transformer is employed on ac- 
 count of the high resistance of the oil as a dielec- 
 tric. One of the most important advantages 
 which vacuum-tube lighting possesses over light- 
 ing by means of the ordinary incandescent electric 
 lamp is that it produces a cold light or illumination 
 of the type of glow illumination. (See Appendix 
 Illumination, Glow.) 
 
624 
 
 [Lum. 
 
 Lightning Arrester Board. (See Appen- 
 dix Board, Lightning Arrester?) 
 
 Lightning, Bead A form of light- 
 ning discharge in which the flash produces a 
 discontinuous line of light, thus causing the 
 discharge to assume a bead-like appearance. 
 
 Lightning Tube. (See Appendix Tube, 
 Lightning?) 
 
 Limit, Magnetic A term sometimes 
 
 employed for the temperature at which a 
 magnetic substance loses its magnetism on 
 exposure to heat. 
 
 Line, Eapp A term proposed, but 
 
 not generally adopted, for the English unit of 
 magnetic induction. 
 
 This term, which defines the lines per square 
 inch instead of per square centimetre, does not 
 harmonize with the C. G. S. system of units, 
 and, therefore, should not be encouraged. 
 
 Line, Telegraphic, Charge Current on 
 
 The current produced by the initial 
 
 rush of electricity into a telegraphic line on 
 the closing of the circuit. 
 
 Lines of Magnetization. (See Appen- 
 dix Magnetization, Lines of.) 
 
 Linear Capacity of Cable. (See Appen- 
 dix Cable, Linear Capacity of.*) 
 
 Linear Density of Charge. (See Appen- 
 dix Charge, Linear Density of.) 
 
 Linear Insulation of Cable. (See Ap- 
 pendix Cable, Linear Insulation of.) 
 
 Liquid, Quickening A term some- 
 times applied to a quicking solution. (See 
 Solution, Quicking.) 
 
 Lithanode. A name employed for a solid 
 highly conducting block of lead peroxide pre- 
 pared by a certain process for the plate of a 
 storage cell. (See Cell, Storage?) 
 
 The word lithanode is properjy applied to the 
 product produced by Fitzgerald's process. 
 
 Lithotrity, Electro A term pro- 
 
 posed for a crushing or removing of urinary 
 calculi by means of electrolysis. 
 
 Load. The work thrown upon an electro- 
 magnetic system or machine. 
 
 The load on a dynamo, for example, means 
 the value of its activity or rate of doing work. 
 
 Load Diagram. (See Appendix Dia- 
 gram, Loaa.) 
 
 Load, Full A term indicating the 
 
 condition of running with a comparatively 
 large amount of work. 
 
 Load, Light A term indicating the 
 
 condition of running with a comparatively 
 small amount of work. 
 
 Locomotive, Telpher An electric 
 
 motor by means of which telpher cars are 
 drawn on a telpher line. (See Telpherage.) 
 
 Long-Range Electrometer. (See Appen- 
 dix Electrometer, Long-Range.) 
 
 Loop Test. (See Appendix Test, Loop*) 
 
 Loss, C 2 R A term for the loss of 
 
 energy in a conductor due to the ohmic re- 
 sistance offered by the conductor to its pas- 
 sage. 
 
 The product C 2 R = activity in watts. In 
 this formula, C, is the current in amperes and R, 
 is the ohmic resistance in ohms, and, when multi- 
 plied by the proper factor, it will give the value of 
 the loss in heat units. 
 
 Loss, Core, of Transformer A loss 
 
 of energy in the core of a transformer due to 
 hysteresis and Foucault or eddy currents, etc. 
 
 Low-Frequency Transformer. (See Ap- 
 pendix Transformer, Low-Frequency.) 
 
 Low-Test Fault. (See Appendix Fault, 
 Low- Test?) 
 
 Luminous Disc-Shaped Discharge. (See 
 Appendix Discharge, Luminous Disc- 
 Shaped.) 
 
 Luminous Interference. (See Appendix 
 Interference, Luminous?) 
 
Mac.] 
 
 625 
 
 [Mac. 
 
 9H. A symbol for magnetic moment. 
 The defining equation is 9ft = m /. 
 
 m. An abbreviation for minute, one of 
 the practical units of time. 
 
 m. A. symbol for strength of magnetic 
 pole. 
 
 f he defining equation is F = =r-g- 
 
 m. An abbreviation for metre, the prac- 
 tical unit of length. 
 
 /*. A symbol for magnetic permeability or 
 inductivity. 
 
 OW 
 
 GA2) 
 
 The defining equation is n = -=- - 
 erC 
 
 m 2 . An abbreviation for square metre, 
 the practical unit of surface. 
 
 m 3 . An abbreviation for cubic metre, the 
 practical unit of volume. 
 
 m. a. A contraction for milli-ampere. 
 (See Mzllz- Ampere,) 
 
 m : s. An abbreviation proposed for metre- 
 per-second, the practical unit of velocity. 
 
 m : s 2 . An abbreviation proposed for 
 metre-per-second-per-second, the practical 
 unit of acceleration. 
 
 M. Current. (See Appendix Current, 
 M.) 
 
 M. P. A contraction proposed for man- 
 power. 
 
 M. S. Current. (See Appendix Current, 
 M. S.~) 
 
 Machine, Dynamo-Electric, Arc Lighting 
 
 A dynamo-electric machine suitable 
 
 for supplying current to arc lamps. 
 
 Arc lights are almost invariably connected to 
 the circuit in series. In such cases the series- 
 wound dynamo is preferable for feeding such cir- 
 cuits. (See Machine, Dynamo-Electric, Series- 
 Wound.)- 
 
 Machine, Dynamo-Electric, Compensat- 
 ing-Alternating A term proposed 
 
 for a compensating alternator. (See Appen- 
 dix Alternator, Compensated!) 
 
 Machine, Dynamo-Electric, Direct Cur- 
 rent A term sometimes employed in 
 
 place of continuous current dynamo-electric 
 machine. (See Machine, Dynamo-Electric, 
 Continuous Current?) 
 
 Machine, Dynamo-Electric, for Electro- 
 Plating A dynamo-electric machine 
 
 suitable for use in electro-plating. (See Ma- 
 chine, Dynamo-Electric. Plating, Electro!) 
 
 An electro-plating dynamo-electric machine 
 possesses many advantages over a voltaic battery 
 for the ready production of the current required 
 in electro-plating. By its use the tedious, expen- 
 sive, and often unhealthy charging of a voltaic 
 battery is entirely dispensed with, since the mere 
 running of a belt over a pulley, and the proper 
 speeding of the machine, is all that is required to 
 furnish a suitable current. 
 
 Dynamo-electric machines for electro-plating 
 should be furnished with a device for the purpose 
 of preventing a reversal of the polarity of the 
 dynamo by means of the current produced by the 
 polarization of the electrodes or articles con- 
 nected with the plating bath. The tendency of 
 this current is of course opposed to that of the 
 current furnished to the bath, and, should the ma- 
 chine be continued in use as a source of cur- 
 rent for plating while its polarity is reversed, the 
 metal already deposited on the articles that are 
 being electro-plated will be removed. 
 
 In the early history of the art, considerable 
 difficulty was experienced with series-wound 
 machines due to reversals in the polarity of the 
 dynamos, by means of the current sent back- 
 wards through the dynamo by the counter E. 
 M. F. of the electro-plating bath, whenever, by 
 reason of a decrease of current strength, or a de- 
 crease of the speed of the dynamo, its E. M. F. 
 fell below the counter E. M. F. of the bath. 
 
 Weston prevents such a reversal of the polarity 
 of the dynamo by opening the circuit of the ma- 
 chine as soon as the speed of the machine falls 
 below a certain point. He does this by means 
 of the centrifugal force acting on a small quantity 
 of mercury in a small hollow conical-shaped 
 vessel. 
 
Mac.] 
 
 626 
 
 [Mag. 
 
 Brush first accomplished this same result by 
 means of a shunt which he called a ' ' teaser. ' ' 
 His early plating machine containing this device 
 was the prototype of the compound wound dy- 
 namo-electro machine. In it the coils of the field 
 magnets are excited partly by the main current 
 and partly by a current shunting across the 
 brushes of the machine. A machine so con- 
 .structed possesses the great advantage of render- 
 ing the machine self-regulating under certain 
 circumstances. This additional or shunt circuit 
 takes a variety of forms. (See Machine, Dynamo- 
 Electric^ Compound-Wound.') 
 
 The difficulty of reversed polarity has disap- 
 peared since the introduction of the shunt or 
 compound-wound dynamo, *'. <?., a dynamo whose 
 field is wholly or in part excited by a current 
 shunted across the brushes of the armature. In 
 such a machine, even if the E. M. F. falls below 
 the counter E. M. F. of the bath, the current in 
 the shunt field, and therefore the polarity, re- 
 mains unchanged, and the current reverses only 
 in the armature. 
 
 Machine, Dynamo-Electric, Four-Pole 
 
 A term sometimes employed for a 
 
 dynamo-electric machine in which the field is 
 produced by two separate north poles, and 
 two separate south poles. 
 
 Machine, Dynamo-Electric, Incandescent 
 Lighting A term sometimes em- 
 ployed for a dynamo-electric machine suit- 
 able for furnishing the currents employed for 
 incandescent electric lamps. 
 
 For all cases where the incandescent electric 
 lamps are connected to the leads in multiple-arc, 
 or any of its varieties, any machine capable of 
 producing and maintaining a constant potential 
 at its terminals, notwithstanding changes in the 
 load on it, is suitable for use as an incandescent 
 electric-lighting dynamo-electric machine. Com- 
 pound-wound machines are generally employed 
 for such purposes. (See Machine, Dynamo- 
 Electric, Compound -Wound.) 
 
 Machine, Dynamo-Electric, Separate- 
 Coil Alternating A term sometimes 
 
 employed for a separate coil alternator. 
 (See Appendix Alternator, Separate-Coil.} 
 
 Machine, Dynamo-Electric, Separately 
 Excited Alternating - A term some- 
 times employed for separately excited alter- 
 
 nator. (See Appendix Alternator, Sepa- 
 rately Excited?) 
 
 Machine, Dynamo-Electric, Six-Pole 
 
 A term sometimes employed for a 
 
 dynamo-electric machine in which the field 
 is produced by six poles, i. <?., three separate 
 north poles and three separate south poles. 
 Machine, Dynamo-Electric, Two-Pole 
 
 A term sometimes employed for a 
 
 dynamo-electric machine in which two poles 
 only are employed for producing the field. 
 
 Such a machine is usually called a bi-polar 
 machine. 
 
 Machine, Magneto-Electric, Alternating 
 
 An alternating current dynamo-elec- 
 tric machine, the field of which is produced 
 by permanent magnets. 
 
 A magneto alternator. (See Appendix 
 Alternator, Magneto.) 
 
 Machine, Speeding of Obtaining 
 
 the requisite number of rotations of an arma- 
 ture of a machine per second. 
 
 Machines as ordinarily constructed produce 
 their most economical output for practical pur- 
 poses when a certain speed of rotation has been 
 obtained. 
 
 Machines, Dynamo-Electric, Alternating, 
 
 Parallel Working of The working of 
 
 two or more alternators in parallel. (See 
 Appendix Alternators, Parallel Connection 
 of.) 
 
 Machines, Dynamo-Electric, Alternating, 
 Series- Working The series connec- 
 tion of two or more alternating dynamo-electric 
 machines. (See Appendix Alternators, 
 Series Connection of.) 
 
 Magazine, Magnetic A term some- 
 times employed for a compound magnet. 
 (See Magnet, Compound). (Obsolete.) 
 
 Magne-Crystallic Force. (See Appendix 
 Force, Magne-Crystallic.) 
 
 Magne-Electric Induction. (See Ap- 
 pendix Induction, Magne-Electric} 
 
 Magnet, Choke A term proposed, 
 
 for choking coil. (See Coil, Choking} 
 
 The term choking coil would appear to be 
 preferable. 
 
Mag.] 
 
 627 
 
 [Mag. 
 
 Magnet, Compound A term for- 
 merly applied to an induction coil with two 
 separate circuits. 
 
 The use of this word is inadvisable. The same 
 word is already correctly employed for a mag- 
 net formed of a number of separate magnets. 
 (See Magnet, Compound.) 
 
 Magnet, Deflecting The perma- 
 nent magnet of a magnetometer employed 
 for deflecting a small magnetic needle sus- 
 pended at a definite distance in order to com- 
 pare its influence with that of the earth's 
 horizontal magnetic force. 
 
 Magnet, Differential, Electro A 
 
 differentially wound electro-magnet. (See 
 Appendix Winding, Differential.) 
 
 Magnet, Electro-Compound A 
 
 term formerly applied to an electro-magnet 
 the core of which is wound with two sepa- 
 rate wires or conductors. 
 
 Magnet, Laminated, Permanent 
 
 A term sometimes employed in place of com- 
 pound magnet. 
 
 Magnet, North Pole of, Proposed A. I. 
 E. E. Definition for - The pole of a 
 magnet which seeks the geographical north 
 pole. 
 
 Magnet, South Pole of, Proposed A. I. 
 E. E. Definition for - The pole of a 
 magnet which seeks the geographical south 
 pole. 
 
 Magnet, Theoretical A hypotheti- 
 cal magnet assumed for the purpose of 
 mathematical discussion, as fulfilling the fol- 
 lowing conditions, namely : An infinitely long 
 and thin, uniformly magnetized bar. 
 
 Magnet, Voltaic A term some- 
 times employed for a solenoid or electro- 
 magnetic helix. (See Solenoid.) 
 
 Magnetic Alternator. (See Appendix 
 Alternator, Magnetic.} 
 
 Magnetic Atmosphere. (See Appendix 
 Atmosphere, Magnetic} 
 
 Magnetic Bearing. (See Appendix 
 Bearing, Magnetic.} 
 
 Magnetic Compensator. (See Appendix 
 Compensator, Magnetic?) 
 
 Magnetic Disturbance. (See Appendix 
 Disturbance, Magnetic?) 
 
 Magnetic Effluvia. (See Appendix 
 Effluvia, Magnetic?) 
 
 Magnetic Fluid. (See Appendix Fluid, 
 Magnetic!) 
 
 Magnetic Flux Path. (See Appendix 
 Path, Magnetic Flux?) 
 
 Magnetic Helix. (See Appendix Helix, 
 Magnetic.} 
 
 Magnetic Hysteresis. (See Appendix 
 Hysteresis, Magnetic?) 
 
 Magnetic Limit. (See Appendix Limit, 
 Magnetic?) 
 
 Magnetic Magazine. (See Appendix 
 Magazine, Magnetic} 
 
 Magnetic Phantom. (See Appendix 
 Phantom, Magnetic?) 
 
 Magnetic Shading. (See Appendix 
 Shading, Magnetic} 
 
 Magnetic Source. (See Appendix 
 Source, Magnetic} 
 
 Magnetic Spectrum. (See Appendix 
 Spectrum, Magnetic?) 
 
 Magnetic Spiral. (See Appendix 
 Spiral, Magnetic} 
 
 Magnetic Voltmeter. (See Appendix 
 Voltmeter, Magnetic?) 
 
 Magnetics. That branch of science which 
 treats of the laws and phenomena of mag- 
 netism. 
 
 The use of this term should not be encouraged. 
 
 Magnetician. A word proposed for one 
 skilled in the science of magnetism as known. 
 
 This word appears to be a good one, but is 
 little used. 
 
 Magnetine. A word formerly employed 
 for the principle of magnetism, or for the im- 
 ponderable, hypothetical fluid in which mag- 
 netic phenomena were assumed to take place. 
 
 Magnetisation. (See Magnetization?) 
 
 Magnetisation, Back (See Appen- 
 dix Magnetization, Back} 
 
 Magnetisation, Lines of (See Ap 
 
 pendix Magnetization, Lines of.) 
 
Mag.] 
 
 628 
 
 [Mag. 
 
 Magnetish. Possessing the property of 
 magnetism to a limited degree. 
 
 This term is a bad one, and its use should be 
 avoided. 
 
 Magnetism, Complex-Lamellar,. Distri- 
 bution of The distribution of the 
 
 magnetism of a finite magnet into an infinite 
 number of complex magnetic shells. 
 
 Magnetism, Horizontal Intensity of 
 
 Earth's The force which causes a 
 
 magnetic needle to come to rest in a hori- 
 zontal position in the earth's field. 
 
 The horizontal intensity of the earth's mag- 
 netism can be determined by means of a magnet- 
 ometer. The horizontal intensity at any place is 
 proportional to the square root of the number of 
 oscillations which a needle suspended about a 
 vertical axis performs at that place in a given 
 time, when disturbed from its position of rest in 
 the earth's field. 
 
 Magnetism, Total Intensity of Earth's 
 The entire force of the earth's mag- 
 netism. 
 
 The total intensity of the earth's magnetism 
 is equal to the resultant of the horizontal and 
 vertical intensities, or to the quotient of the hori- 
 zontal intensity by the cosine of the angle of dip. 
 
 Magnetism, Bemanent A phrase 
 
 sometimes used in place of residual magnet- 
 ism. (See Magnetism, Residual?) 
 
 Magnetism, Specific A term pro- 
 posed for the quotient of the magnetic moment 
 of a magnet by its mass. 
 
 Magnetism, Vertical Intensity of Earth's 
 
 The force which tends to cause a 
 
 magnetic needle to assume a vertical position. 
 
 The following formula gives the vertical inten- 
 sity of the earth's magnetism : 
 V = H. tan. 9 
 Where V = vertical intensity. 
 
 H = the horizontal intensity, 
 and = the angle of dip. 
 
 Magnetist A magnetician. 
 
 The word magnetician is preferable. 
 
 Magnetizability. Possessing the ability 
 of becoming magnetized. 
 
 Magnetization, Back A term pro- 
 posed in place of back or backward induc- 
 
 tion. (See Appendix Induction, Back- 
 ward?) 
 
 Magnetization, Circular The mag- 
 netization which exists in a diphase motor 
 in which two alternating magnetic fluxes of 
 equal amplitude are produced in quadrature 
 or at right angles to each other. 
 
 Magnetization, Elliptical Botary 
 The magnetization which exists in a diphase 
 motor in which two alternating magnetic 
 fluxes exist out of phase with each other. 
 
 Magnetization, Lines of A term 
 
 sometimes employed for lines of magnetic in- 
 duction. 
 
 When lines of magnetic force pass through air, 
 the number of lines of induction are the same as 
 the number of lines of magnetizing force ; when, 
 however, the lines of force pass through iron, the 
 number of such lines of induction is greatly in- 
 creased. 
 
 Magnetizee. A word proposed to desig- 
 nate a person who believes he is placed 
 under the power of animal magnetism. 
 
 Magnetizer. A word proposed to desig- 
 nate a person who claims to place another 
 under the power of animal magnetism. 
 
 Magnetizing Helix. (See Appendix 
 Helix, Magnetizing?) 
 
 Magnetizing Spiral. (See Appendix 
 Spiral, Magnetizing?) 
 
 Magneto- Alternator. (See Alternator, 
 Magneto?) 
 
 Magneto-Chemical Cell. (See Appendix 
 Cell, Magneto-Chemical?) 
 
 Magnetod. A word employed by Reichen- 
 bach for the assumed force or principle of 
 animal magnetism. 
 
 Magneto-Electric Alternating Machine. 
 
 (See Appendix Machine, Magneto-Elec- 
 tric Alternating?) 
 
 Magneto-Inductive Capacity. (See Ap- 
 pendix Capacity, Magneto-Inductive?) 
 
 Magnetology. That branch of science 
 which treats of magnetism. 
 ' The word magnetism would appear to bt 
 preferable. 
 
Mag.] 
 
 [Mer. 
 
 Magnetometer, Inclination A 
 
 form of magnetometer suitable for measur- 
 ing variations in the magnetic inclination at 
 Viy place. 
 Magnetometer, Registering Declination 
 
 -- A form of magnetometer in which the 
 
 variations of the declination at any place can 
 be automatically registered. 
 
 Magnetometer, Variation A form 
 
 of magnetometer suitable for measuring 
 changes in the magnetic variation at any 
 place. 
 
 Magneto-Metric. Of or pertaining to 
 the measurement of magnetic force. 
 
 Magnetometry. That branch of science 
 which treats of the measurement of the 
 strength of magnetic fields. 
 
 Magneto-Motor. (See Appendix Motor, 
 Magneto.) 
 
 Magnetophone. A word sometimes used 
 for a magneto telephone. 
 
 Magneto-Tapper. (See Appendix Tap- 
 per, Magneto.) 
 
 Man Power. (See Appendix Power, 
 Man.) , 
 
 Manual Repeater. (See Appendix Re- 
 peater, Manual?) 
 
 Manual Translation. (See Appendix 
 Translation, Manual?] 
 
 Marks, Ripple, Electrical Wave 
 
 marks produced in a fine powder by the dis- 
 charge of a Leyden jar in its neighborhood. 
 
 These ripple marks are due to waves set up in 
 the air by the passage of the discharge. 
 
 The same discharge that produces waves in 
 ether also sets up waves in the surrounding air. 
 It can be shown that the same discharge that can 
 excite ether waves i kilometre in length can 
 excite waves in the air about I millimetre in 
 length. 
 
 Matt. A word employed in electro-plating 
 to designate the appearance presented by an 
 electro-plating of silver in which the deposit 
 is interlaced and closely massed together. 
 (See Plating, Electro?) 
 
 Matter, Electric A term formerly 
 
 applied to the matter which was believed to 
 
 constitute the effluvia formerly assumed to 
 pass off from an electrified body. 
 
 Matter, Fourth State or Condition of 
 
 A term sometimes employed for the 
 
 ultra-gaseous or radiant state of matter. (See 
 Matter, Radiant or Ultra-Gaseous?) 
 
 Matting, Burglar Alarm A mat- 
 ting provided with a number of invisible con- 
 tacts connected with alarm bells whose cir- 
 cuits are closed by treading on the matting. 
 (See Matting, Invisible Electric Floor?) 
 
 Maximum Negative Elongation. (See 
 Appendix Elongation, Maximum Nega- 
 tive?) 
 
 Maximum Positive Elongation. (See 
 Appendix Elongation, Maximum Posi- 
 tive?) 
 
 Maximum Starting Current of Motor. 
 
 (See Appendix Current, Maximum Start- 
 ing, of Motor?) 
 
 Maynooth Voltaic Cell. (See Appendix 
 Cell, Voltaic, Maynooth?) 
 
 Mechanical Replacement of Disc-Indi- 
 cator. (See Appendix Indicator, Disc,. 
 Mechanical Replacement of?) 
 
 Mechanical Telegraphic Interrupter. 
 (See Appendix Interrupter, Telegraphic, 
 Mechanical?) 
 
 Medication, Cataphoric The intro- 
 duction of drugs or other medicaments into 
 the body through its tissues by the cataphoric 
 action of an electric current. (See Cata- 
 phoresis. Osmose, Electric?) 
 
 Medium, Aelotropic A medium 
 
 which manifests different actions in definite 
 directions ; /. e., an eolotropic medium. (See 
 Medium, Eolotropic?) 
 
 Crystallized bodies are in general notably 
 aelotropic, while amorphous substances are gen- 
 erally isotropic. 
 
 An aelotropic substance may be expected to 
 possess different electrostatic elastivity and in- 
 ductive capacity in different directions. 
 
 Melting of Electric Conductor. (See 
 Appendix Conductor, Electric, Melting of.) 
 
 Mercurial Phosphorus. (See Appendix 
 Phosphorus, Mercurial?) 
 
Met.] 
 
 630 
 
 [Mho. 
 
 Metallic Conduction. (See Appendix 
 Conduction, Metallic.} 
 
 Metallic Cross. (See Appendix Cross, 
 Metallic?) 
 
 Metallo-Chromes. Colors which appear 
 when a salt of lead, such as the acetate, is 
 electrolyzed under peculiar circumstances. 
 
 Metallo chromes are produced by electrolytic 
 deposits of peroxide of lead in the neighborhood 
 of the anode. When the thickness of the coating, 
 which is deposited on a plate of polished steel, is 
 properly regulated, a series of brilliant colors 
 appear. 
 
 Gassiot recommends the following process for 
 obtaining metallo-chromes. 
 
 " Place the polished steel plate in a glass basin 
 containing a clear solution of acetate of lead, and 
 over it a piece of card. A small rim of wood 
 should be placed over the card, and on that a 
 circular copper disc. On contact being made 
 from 5 to 20 minutes, with two or three cells of a 
 small constant battery, the steel plate being con- 
 nected with the positive electrode, and the cop- 
 per disc with the negative, the deposit will be 
 effected, and a series of exquisite colors will ap- 
 pear on the steel plate. The colors are films of 
 peroxide of lead thrown down on the surface of 
 the steel, and the varied tints are occasioned by 
 the varying thicknesses of the precipitated film, 
 the light being reflected through them from the 
 metallic surface below. By reflected light every 
 prismatic color is seen ; and by transmitted light 
 a series of prismatic colors complementary to the 
 first series appears, occupying the place of the 
 former series. 
 
 " The colors are seen in the greatest perfection 
 by placing the plate before a window, and inclin- 
 ing a white sheet of paper at 45 degrees over it. " 
 
 Similar colorations are obtained when other 
 substances are electrolytically deposited. Under 
 certain conditions these colorations assume the 
 form of concentric circles, that are sometimes 
 called Nobili's rings. 
 
 Nobili's rings are readily obtained by placing 
 a drop of acetate of copper on a silver plate and 
 touching the middle of the drop with a piece of 
 zinc. Under these circumstances prismatically 
 colored rings are formed, that are disposed 
 concentrically around the point of contact of the 
 zinc. 
 
 Meteorograph, Electric. An apparatus 
 for automatically registering various meteor- 
 
 ological values, such, for example, as the in- 
 dications of a barometer or thermometer, the 
 direction and velocity of the wind, or the 
 value of the rainfall. 
 
 Meteorology. That branch of physics 
 which treats of the phenomena of the atmos- 
 phere. 
 
 Meteorology, Electric That branch 
 
 of meteorology which treats of the electric 
 phenomena of the atmosphere. 
 
 Meter, Coulomb Any form of ap- 
 paratus capable of measuring the number of 
 coulombs that pass in a circuit in a given time. 
 
 Any form of galvanometer which gives the cur- 
 rent in amperes will give the number of coulombs 
 that pass if the time the current is flowing is 
 known. Various forms cf electric meters will 
 therefore give the number of coulombs that pass 
 in a circuit. (See Meter, Electric.) 
 
 Meter, Electrolytic An electro- 
 chemical meter. (See Meter, Electro-Chem- 
 ical?) 
 
 Meter, Quantity A coulomb meter. 
 
 Meter, Telephonic A meter em- 
 ployed for recording the time during which a 
 telephone is in use. 
 
 The telephonic meter, as at present constructed, 
 consists essentially of a clock, the pendulum of 
 which is caught by means of a lever connected with 
 the telephone lever. By such means the clock is 
 stopped while the telephone is out of use or is 
 hung on its hook. 
 
 Method, Accumulation, for Testing 
 
 Joints in Electric Cables A sensitive 
 
 method of testing the insulation of a joint, or 
 of a few feet of gutta-percha core, by allowing 
 the leakage of the joint to accumulate through 
 a condenser for a considerable time and then 
 measuring the condenser discharge. 
 
 Method of Slow Discharge. (See Appen- 
 dix Discharge, Slow, Method of.} 
 
 Mho, Proposed A. I. E. E. Definition for 
 
 A name proposed for the practical 
 
 unit of conductivity. 
 
 A unit of electrical conductance of the 
 value of lo- 9 absolute units; or, in other 
 words, having a value equal to the reciprocal 
 of the ohm. 
 
Mho.] 
 
 631 
 
 [Mot. 
 
 This name for the practical unit of electrical 
 conductance was proposed by a Sub-Committee 
 of the American Institute of Electrical Engineers 
 on Provisional Programme of the International 
 Electrical Congress, held in Chicago, U. S. A., 
 in 1893, on the occasion of the World's Columbian 
 Exposition. 
 
 Milometer. An instrument for measuring 
 the value of conductance in mhos. (See Con- 
 ductance. Mho.} 
 
 Micanite. A name sometimes given to a 
 variety of insulating material made from pure 
 mica bound together by some cementing 
 material. 
 
 Micro-Ohm. The millionth of an ohm. 
 Microphone, Plastic-Circuit A 
 
 microphone in which the ordinary variable 
 contact is replaced by a plastic material of 
 low conducting power. 
 
 The plastic-circuit microphone is the invention 
 of Clammond. In it the ordinary powder form- 
 ing the loose contact is obtained by means of a 
 plastic material composed of a mixture of a good 
 conducting substance with some plastic non-con- 
 ducting material. 
 
 The advantage claimed for the plastic-circuit 
 telephone transmitter is that it has a much greater 
 range of operation than the ordinary contact 
 microphone, being able to transmit either faint or 
 loud tones with equal distinctness. 
 
 Migration of Ions. (See Appendix Ions, 
 Migration of.) 
 
 Mile, Ohm The number obtained 
 
 by multiplying the weight of i mile of wire 
 of a given substance by its resistance. 
 
 The ohm mile of a given substance is the mass 
 of a mile of wire of that substance having the 
 resistance of an ohm. 
 
 Milli-Amnieter. A milli-ampere meter. 
 
 Milli-Aiiipere Meter. (See Meter, Milli- 
 Ampere) 
 
 Mining, Electric Carrying on the 
 
 various operations of mining by means of 
 electric power. 
 
 Electricity has been successfully employed in 
 mining for the driving of percussion or rotary 
 drills, for electric haulage, for pumping, and for 
 purposes of communication, ventilation, power 
 and artificial lighting. 
 
 Minus Charge. (See Appendix Charge, 
 Minus.") 
 
 Molecular Decomposition. (See Ap- 
 pendix Decomposition, Molecular?) 
 
 Molecular Voltaic Couple. (See Ap- 
 pendix Couple, Molecular Voltaic?) 
 
 Monad Atom. (See Appendix Atom, 
 Monad.) 
 
 Monochord. A single stretched wire for 
 measuring the relative number of vibrations 
 produced by different musical notes. 
 
 The instrument takes the name monochord, 
 from the fact that it consists, practically, of a 
 single chord stretched between two points <f 
 support over a resonant case, and provided with 
 means for suitably adjusting its tension so as to 
 produce, when vibrating as a whole, a note of a 
 given musical pitch. When it is required to de- 
 termine the relative number of vibrations existing 
 between the note which the monochord produces 
 and some other note, a sliding bridge is placed 
 in some intermediate part of the wire so as to cut 
 off a part of its length. 
 
 When the length of the original wire has been 
 shortened by means of a sliding bridge, so that 
 it produces a higher note whose pitch is to be 
 compared with that of the wire vibrating as a 
 whole, the relative number of vibrations are then 
 inversely proportional to the lengths of the two 
 wires. 
 
 Mop, Polishing A disc formed of 
 circular pieces of calico, felt, or similar soft 
 material mounted on a shaft and employed, 
 when put in rapid rotation, for polishing 
 articles so as to prepare their surfaces for 
 electro-plating. (See Plating, Electro?) 
 
 For use, mops are charged with fine polishing 
 material; as, rouge, tripoli, etc. 
 
 Mopped. Polished by the action of a mop. 
 (See Appendix Mop, Polishing?) 
 
 Morse Push. (See Appendix Push, 
 Morse?) 
 
 Morse Tapper. (See Appendix Tapper, 
 Morsel] 
 
 Motion, Electrostatic Motion pro- 
 duced by means of an electrostatic field 
 somewhat similar to the motion produced by 
 means of a magnetic field. 
 
Mot.j 
 
 632 
 
 [Mot. 
 
 Electrostatic motion may be produced by vary- 
 ing electrostatic fields placed at right angles to 
 each other. When the force varies in accordance 
 with the sine law, and the difference in phase 
 varies by only 90 degrees, a uniform tendency to 
 rotation is produced. 
 
 Motion, Harmonic A term some- 
 times employed in place of simple-harmonic 
 notion. (See Motion, Simple-Harmonic!) 
 
 Motion, Periodic A term some- 
 times employed in place of simple-periodic 
 motion. (See Motion, Simple-Periodic!) 
 
 Motor, Constant-Potential A 
 
 motor designed for operation by means of a 
 constant potential current. 
 
 Where the motor is to be operated at a constant 
 speed, or by a constant-potential circuit, such, 
 for example, as an incandescent lighting circuit, 
 it is generally made a plain, shunt-wound motor. 
 
 Motor, Diphase A motor which 
 
 requires for its operation two diphase cur- 
 rents. 
 
 The armature of such a motor is always wound 
 either with two separate circuits, or has two 
 separate connections to the same common wind- 
 ing. 
 
 This term would appear preferable to the term 
 two-phase motor. 
 
 Motor, Dynamo A constant cur- 
 rent transformer or dynamotor. (See Ap- 
 pendix Dynamotor!) 
 
 Motor, Efficiency of Electric The 
 
 watts delivered at the motor pulley, divided 
 by the watts supplied. 
 
 Motor, Electric Street Railway, Backing 
 of (See Appendix Bucking!) 
 
 Motor, Electrostatic A motor 
 
 driven by means of the induction of two 
 varied electrostatic fields at right angles to 
 each other. 
 
 Generally, a motor driven by the action of 
 electrostatic fields. 
 
 Motor, Idle Wire of (See Ap- 
 pendix Wire, Idle, of Armature of Motor!) 
 
 Motor, Induction A motor in which 
 
 the magnetic field is produced entirely by the 
 
 working current, ' as distinguished from a 
 motor in which the field magnets are inde- 
 pendently maintained. 
 
 An induction motor consists essentially of coils 
 of wire and laminated iron discs so related to one 
 another that the currents in the moving parts are 
 induced by currents in the stationary parts. 
 
 Motor, Magneto A term formerly 
 
 employed for a voltaic battery coupled in 
 parallel. 
 
 The current furnished by such a battery being 
 capable, when employed with suitable electro- 
 magnets, to produce powerful magnetism, was 
 called a magneto-motor. This word is generally 
 used as below. 
 
 Motor, Magneto A motor whose 
 
 field is produced by permanent magnets. 
 
 Motor-Man. A word generally applied to 
 the person who operates the motor car of 
 street railway systems. 
 
 Motor, Multiphase A term some- 
 times employed in place of polyphase motor. 
 (See Appendix Motor, Polyphase!) 
 
 Motor, Polyphase A motor ope- 
 rated by means of polyphase currents. 
 
 Motor, Polyphase, Unsymmetrical 
 
 An unbalanced polyphase motor; /'. e., a 
 motor where one circuit carries a greater 
 load than the other circuit or circuits. 
 
 Motor, Single-Phase A uni-phase 
 
 motor. 
 
 The term uni-phase is preferable. 
 
 Motor, Synchronous, Self-Starting 
 
 A motor of the synchronous type that is 
 capable of self-starting. 
 
 Motor, Three-Phase A tri-phase 
 
 motor. (See Appendix Motor, Tri-Phase!) 
 
 The term tri-phase motor would appear to be 
 preferable. 
 
 Motor, Tri-Phase A motor which 
 
 requires for its operation three tri-phase cur- 
 rents. 
 
 The armature of such a motor is always wound 
 either with three separate circuits or has three 
 separate connections to a common winding. 
 
 Motor, Two-Phase A diphase 
 
 motor. (See Appendix Motor, Diphase!) 
 
 5 Vol. 2 
 
Mot.] 
 
 633 
 
 [Nip. 
 
 The term diphase motor would appear to be 
 preferable. 
 
 Motor, Uni-Phase A motor which 
 
 requires for its operation a simple alternating 
 current ; i. e., a current which is uni-phase. 
 
 The term uni-phase is preferable to the term 
 single-phase. 
 
 Mounting of Filament. (See Appendix 
 Filament, Mounting- of.) 
 
 Multi-Phase Alternator. (See Appendix 
 Alternator, Multi-Phased) 
 
 Multi-Phase Motor. (See Appendix 
 Motor, Multi-Phased) 
 
 Multiple Auto-reversible Tele-radio- 
 phone. (See Appendix Tele-radiophone, 
 Auto-reversible or Multiple?) 
 
 Multiple-Lightning Flash. (See Ap- 
 pendix Flash, Multiple-Lightning?) 
 
 Multiple-Parallel Circuit. (See Ap- 
 pendix Circuit, Multiple-Parallel!) 
 
 Multiplex Telegraph. (See Appendix 
 Telegraph, Multiplex?) 
 
 Multiplex Telephony. (See Appendix 
 Telephony, Multiplex?) 
 
 Multiplier, Astatic A term some- 
 times employed for an astatic galvanometer. 
 (See Galvanometer, Astatic?). 
 
 Multiplier, Dynamic A term for- 
 merly applied to a self-induction coil. (See 
 Appendix Coil, Induction, Self.} 
 
 Multiplier, Electro-Magnetic A 
 
 term sometimes employed for Sweigger's 
 Multiplier. (See Multiplier, Sweigger's.) 
 
 Municipal System of Incandescent Elec- 
 tric Lighting. (See Appendix System, 
 Municipal, of Electric Lighting?) 
 
 Mutually Induced Currents. (See Ap- 
 pendix Currents, Mutually Induced?) 
 
 N 
 
 n. A symbol sometimes employed for 
 frequency. 
 
 Natural Period. (See Appendix Period, 
 Natural?) 
 
 Needle, Drift of- The failure of the 
 
 needle of a galvanometer to remain at its 
 zero point when no current is passing through 
 its coils, usually due to variation in the 
 magnetic condition of the needle, or to 
 variation in the torsion of the suspending 
 fibre, local causes, etc. 
 
 Needle Telegraph. (See Appendix 
 Telegraph, Needle!) 
 
 Needle, Vertical Magnetic A 
 
 term sometimes employed for a dipping 
 needle. (See Needle, Magnetic, Dipping!) 
 Negative Electrification. (See Appendix 
 Electrification, Negative!) 
 
 Negative Fluid. (See Appendix Fluid, 
 Negative!) 
 
 Negative Spark. (See Appendix Spark, 
 Negat-'v.!) 
 
 Neutral Zone of Electrically Charged 
 Insulated Conductor. (See Appendix 
 Zone, Neutral, of Electrically Charged In- 
 sulated Conductor?) 
 
 Neutral Zone of Magnet. (See Ap- 
 pendix Zone, Neutral, of Magnet?) 
 
 Nipple on Negative Carbon. A small 
 projection formed at the end of the negative 
 carbon directly opposite the positive carbon 
 of a voltaic arc that has been established for 
 some little time. 
 
 The nipple is formed at the end of the nega- 
 tive carbon directly opposite the crater in the op- 
 posing end of the positive carbon by the de- 
 position of volatilized carbon from the positive 
 electrode. The material of the nipple is pure 
 graphite or plumbago. 
 
 If the ends of the carbons, that are thrown away 
 from an electric arc lamp on trimming the lamp, 
 be examined, they will be found to possess either 
 a small crater or a small projection or nipple at 
 their burned end. 
 
Nod.l 
 
 634 
 
 [Osc. 
 
 Either of these ends, but especially the nipple 
 at the negative caroon, is formed of pure graphite 
 sufficiently soft to be readily used for some con- 
 siderable time as a lead pencil. 
 
 Node. A point of comparative rest in a 
 vibrating body. 
 
 Since the position of an anti-node for a funda- 
 mental tone may be the position of the node for 
 one of its harmonics, it is clear that the nodes are 
 often necessarily only points of relative rest. 
 
 Non-Automatic Repeater. (See Appen- 
 dix Repeater, Non-Automatic?) 
 
 Non-Ferric Inductance. (See Appendix 
 Inductance, Non-Ferric?) 
 
 Non-Polar Transformer. (See Appen- 
 dix Transformer, Non-Polar?) 
 
 Northern Light. (See Appendix Light, 
 Northern?) 
 
 o. An abbreviation sometimes used for 
 
 ohm, the practical unit of electric resistance. 
 
 oa. A symbol sometimes used for angular 
 
 velocity. 
 
 V 
 
 The denning equation is 00= =- 
 
 o: cm. An abbreviation proposed for 
 ohm-centimeter, the practical unit of resis- 
 tivity. 
 
 Oersted, Proposed A. I. E. E. Definition 
 
 for A name proposed for the practical 
 
 unit of magnetic reluctance. 
 
 A unit of magnetic reluctance having a 
 value of one absolute unit. 
 
 This name was proposed by a Sub-Committee 
 of the American Institute of Electrical Engineers 
 on Provisional Programme for the International 
 Electrical Congress, held in Chicago, V. S. A., 
 in 1893, on the occasion of the World's Columbian 
 Exposition. 
 
 Ohm, B. A. A resistance of 14.4521 
 
 grammes of mercury in the form of a col- 
 umn of uniform cross-section (one square 
 millimetre) and 104.8 centimetres in height 
 at o degree C. 
 
 The above value of the ohm was adopted as 
 the unit of the British Association at its meeting 
 held in Edinburgh in August, 1892. 
 
 Ohm, International The value 
 
 of the international ohm adopted at the 
 Chicago Congress of 1893, as being the re- 
 sistance column based upon the ohm equal 
 to io 9 units of resistance of the C. G. S. 
 system of electro-magnetic units, and is rep- 
 resented by the resistance offered to an un- 
 
 varying electric current by a column ot 
 mercury at the temperature of melting ice 
 14.4521 grammes in mass, of a constant cross 
 sectional area, and of the length of 106.3 
 centimetres. 
 
 Ohm Mile. (See Appendix Mile, Ohm?) 
 
 Ohm, Proposed A. I. E. E. Definition for 
 The resistance offered at the tempera- 
 ture of melting ice by a column of mercury, 
 14.4521 grammes in mass, of a constant cross- 
 sectional area and of a length of 106.3 centi- 
 metres. 
 
 One-Way Door Trigger. (See Appendix 
 Trigger, One- Way Door?) 
 
 Open-Circuit Transformer. (See Ap- 
 pendix Transformer, Open-Circuit?) 
 
 Opposing Electromotive Force. (See 
 Appendix Force, Electromotive, Opposing?) 
 
 Optical Galvanometer. (See Appendix 
 Galvanometer, Optical?) 
 
 Oscillator, Hertz's A term some- 
 times employed for two insulated metallic 
 plates, to which are attached metallic rods, 
 terminated by rounded knobs or balls separ- 
 ated by an air gap or air space, through which 
 a disruptive discharge passes. 
 
 The metallic plates represent the opposite coat- 
 ing of a Leyden jar. When employed as Hertz's 
 oscillator each plate is connected to the terminal 
 of a Ruhmkorffcoil, and at each discharge elec- 
 trical surgings are produced, which cause waves 
 to radiate from the plates into the surrounding 
 ether. 
 
 Oscillator, Hertz's Axial A term 
 
 sometimes employed for Hertz's linear oscil- 
 
Osc.] 
 
 635 
 
 lator. (See Appendix Oscillator, Hertz's 
 Linear?) 
 
 Oscillator, Hertz's Linear A form 
 
 of Hertz's oscillator in which a straight or 
 linear conductor is employed instead of a 
 plate as in the ordinary oscillator. (See Ap- 
 pendix Oscillator, Hertz's!) 
 
 According to Lodge, a thunder cloud con- 
 nected to the earth by means of a lightning rod 
 forms a linear oscillator. 
 
 Out-Put. The useful energy given out by 
 a machine. 
 
 The out-put is generally taken in connection or 
 in comparison with the in-put. When the use- 
 ful or available electric energy of any source is 
 
 divided by the total electric energy, the value of 
 a ratio, called the efficiency, is obtained. In this 
 case the out-put, when divided by the total in-put, 
 gives the efficiency. (See Efficiency, Electric. ) 
 
 Oven, Baking, Electrical An elec- 
 trically heated oaking oven. 
 
 Almost any form of baking oven can be heated 
 by means of electric heaters suitably placed 
 therein. 
 
 Overflow of Leyden Jar. (See Appendix 
 Jar, Leyden, Overflow of.") 
 
 Overlap Test. (See Appendix Test, 
 Overlap?) 
 
 Over-Maximal Contraction. (See Ap- 
 pendix Contraction, Over-Maximal?) 
 
 P. A symbol proposed for power. 
 
 W 
 
 The denning equation is P = = 
 
 P. A symbol proposed for electric power. 
 
 The same symbol is proposed for mechanical 
 power. 
 The defining equation is P = C E. 
 
 p. A symbol proposed for pressure. 
 
 jr 
 The defining equation is p = -^ 
 
 $. A symbol employed for flux of mag- 
 netic force. 
 The defining equation is $ = g X S. 
 
 Pacinotti Teeth, (See Appendix Teeth, 
 Pacinotti?) 
 
 Page Effect (See Appendix Effect, 
 Page.) . 
 
 Pair, Thermo A thermo couple. 
 
 (See Couple, Ther mo-Electric?) 
 
 Pair, Thermo-Electric A term 
 
 sometimes employed in place of thermo-elec- 
 tric couple. (See Couple, Thermo-Electric.} 
 
 Pair, Voltaic A term sometimes 
 
 employed in place of voltaic couple. (See 
 Couple, Voltaic?) 
 
 Pan, Backing A pan in which the 
 
 copper shell of an electrotype is placed, in 
 order to receive its backing of type metal. 
 
 When the copper shell has been placed in the 
 backing-pan, for the purpose of receiving its 
 backing of type-metal, it has its back covered 
 with sheets of tin-foil. It is then placed along 
 with the backing-pan in the melting-pot, a pot 
 filled with melted type-metal, on which it is per- 
 mitted to float until the covering of tin- foil is 
 melted. It is now removed and placed on a level 
 table where the molten metal from the melting 
 pot is poured over it until a layer of the required 
 thickness is obtained. 
 
 Pan-Telephone. (See Appendix 'Tele- 
 phone, Pan.) 
 
 Parallel-Arc Circuit. (See Appendix 
 Circuit, Parallel-Arc?) 
 
 Parallel Connection of Alternators. 
 
 (See Appendix Alternators, Parallel Con- 
 nection of.) 
 
 Parallel Working of Alternating Dy- 
 namo-Electric Machines. (See Appendix 
 Machines, Dynamo-Electric, Alternating, 
 Parallel Working of?) 
 
 Paramagnetized. Endowed with para- 
 magnetic properties. (See Paramagnetism.) 
 
Pas.] 
 
 636 
 
 [Pha. 
 
 Passive Resistance. (See Appendix 
 Resistance, Passive?) 
 
 Path, Magnetic Flux The path or 
 
 circuit taken by the lines of magnetic force 
 or flux. 
 
 Pear Push. (See Appendix Push, 
 Pear!) 
 
 Peltier's Cross. (See Appendix Cross, 
 Peltier's!) 
 
 Pencil, Carbon A term sometimes 
 
 employed for a carbon rod. 
 
 A rod or cylinder of carbon, as distinguished 
 from a plate. 
 
 Pendant Socket (See Appendix Socket, 
 Pendant?) 
 
 Pendulnni, Electric A term some- 
 times employed for a pith ball electroscope, 
 so arranged as to move to-and-fro like an 
 ordinary pendulum. 
 
 This use of the term is to be avoided, since the 
 word, as primarily employed, signifies either a 
 pendulum driven by electric impulses, or a pen- 
 dulum so arranged as to produce timed impulses. 
 
 The term electroscopic or electrostatic pen- 
 dulum would appear preferable. (See Pendulum, 
 Electric.) 
 
 Pentad Atom. (See Appendix Atom, 
 Pentad.) 
 
 Percentage Conductivity of Wire. (See 
 Appendix Conductivity, Percentage, of 
 Wire.) 
 
 Period. The interval of time between two 
 successive passages of a vibration through 
 a given point of its path taken in the same 
 direetion. 
 
 Period, Natural The period of 
 
 harmonic frequency which brings it to the 
 same value as that of the fundamental fre- 
 quency. 
 
 The natural period, according to Lodge, is 
 represented by the following formula. 
 
 T = 2 ic N/LC X io-3 
 Where T = the period in seconds. 
 
 L = the coefficient of self-induction in 
 
 henries. 
 C = the capacity in micro-farads. 
 
 The natural period can be varied either by 
 varying the self-induction of the circuit or by 
 varying its capacity. 
 
 Period, Variable, of Telegraph Line 
 
 The time required for a current in a tele- 
 graph line to reach a constant strength 
 after the circuit through it is closed. 
 
 Periodic Motion. (See Appendix Mo- 
 tion, Periodic!) 
 
 Periodicity of Alternation. (See Ap- 
 pendix Alternation, Periodicity of.) 
 
 Permanent Laminated Magnet. (See 
 Appendix Magnet, Laminated, Perma- 
 nent!) 
 
 Permanent Telegraphic Signal. (See 
 Appendix Signal, Telegraphic, Perma- 
 nent!) 
 
 Permeation. A word sometimes em- 
 ployed for the number of lines of magnetic 
 force per square centimetre. 
 
 Permittance. A word proposed for 
 dielectric capacity. (See Appendix Capa- 
 city, Specific Dielectric!) 
 
 Electrostatic induction takes place between the 
 two coatings of a condenser, or between two 
 copper conductors across the dielectric between 
 them. Dielectrics differ greatly in their ability 
 to permit this influence to pass through them, and 
 this difference has been called the dielectric 
 capacity, the specific inductive capacity, the in- 
 ductive capacity, or the permittance. (See 
 Capacity, Specific Inductive.) 
 
 Permittivity. A word sometimes em- 
 ployed for specific permittance. (See Ap- 
 pendix Permittance!) 
 
 Phantom, Magnetic A term some- 
 times employed for magnetic figures. (Se* 
 Figures, Magnetic. Field, Magnetic!) 
 
 Phantom Streams. (See Appendix 
 Streams, Phantom!) 
 
 Phase. The fractional part of a period 
 which has passed since a vibrating body last 
 passed through the extreme point of its path 
 in the positive direction. 
 
 Phase Angle. (See Appendix Angle, 
 Phase.) 
 
Pha.] 
 
 637 
 
 [Plu. 
 
 Phase Windings. (See Appendix 
 Winding's, Phase.} 
 
 Phenomena. Plural of phenomenon. 
 
 Phonogram. A dispatch transmitted by 
 means of a telephone. 
 
 The word phonogram corresponds to the word 
 telegram. 
 
 This word is also used for the record produced 
 by a phonograph. 
 
 Phonoplex Telegraph. (See Appendix 
 Telegraph, Phonoplex!) 
 
 Phosphorescent Lamp. (See Appendix 
 Lamp, Phosphorescent!) 
 
 Phosphorus, Mercurial A term 
 
 employed by Hawksbee in 1795 for the light 
 produced by the motion of a column of mer- 
 cury in an exhausted tube. 
 
 The light so produced is due to electricity 
 caused by the friction of the mercury against the 
 walls of the tube. Such a light is often seen in 
 the Torricellian vacuum which exists in the space 
 above the mercurial column in a barometer tube. 
 
 Photo-Electric Alarm. (See Appendix 
 Alarm, Photo-Electric?) 
 
 Photo-Electric Impulsion Cell. (See 
 Appendix Cell, Photo-Electric Impulsion!) 
 
 Photometer, Spectro A form of 
 
 photometer suitable for measuring the rela- 
 tive intensities of lights of different qualities. 
 
 A spectro-photometer consists essentially of 
 means by which the two parallel beams of light 
 that are to be compared are passed side by side 
 through the same prism. The field is then 
 limited to a single color, and the respective 
 intensities of the two lights as regards this par- 
 ticular character of radiation are then compared. 
 
 Photo-Micrography, Electric The 
 
 art of photographing microscopic images by 
 means of the electric light. 
 
 Physiologist, Electro One skilled 
 
 in the art of electro-physiology. (See Physi- 
 ology, Electro!) 
 
 Pins, Core, of Magnet Small pins 
 
 of copper or other non-magnetic material 
 placed in'the cores of an electro-magnet at 
 its poles for the purpose of preventing stick- 
 ing. 
 
 Planer, Electric Deck 
 
 An elec- 
 
 trically driven rotary cutter or planer, adapted 
 for the ready planing of the deck of a ship. 
 
 Fig- 579 shows an electric deck planer. The 
 rotary cutter revolves at some three thousand 
 
 579' -An Electric Deck Planer. 
 
 revolutions per minute, and is so arranged as to 
 be readily adapted for a varying depth of cut. 
 
 Plastic-Circuit Microphone. (See Ap- 
 pendix Microphone, Plastic-Circuit!) 
 
 Plates, Exhausted, of Storage Cell 
 
 A phrase employed to characterize the condi- 
 tion of the plates of a storage battery when 
 they have furnished all the current they are 
 capable of producing without being injured. 
 (See Plates of Secondary or Storage Cell, 
 Forming of!) 
 
 Plates, Field A term sometimes 
 
 applied to the plates of tin-foil, on a Toppler- 
 Holtz influence machine, which act as in- 
 ductors. (See Machine, Toppler-Holtz!) 
 
 Plates, Formed, of Storage Cell 
 
 A phrase employed to characterize the condi- 
 tion of the plates of a new storage battery 
 when they have been prepared for regular 
 service by a preliminary process of charging, 
 or charging and discharging. (See Plates of 
 Secondary or Storage Cell, Forming of!) 
 
 Plating Trough. (See Appendix 
 Trough, Plating!) 
 
 Plug, Attachment A plug for at- 
 taching and connecting a flexible cord to any 
 lamp socket or receptacle. 
 
 Plus Charge. (See Appendix Charge, 
 P!us!\ 
 
Poc.] 
 
 638 
 
 [Pot, 
 
 Pocket Galvanometer.- (See Appendix 
 Galvanometer, Pocket?) 
 
 Point, Indifferent A term some- 
 times employed for the neutral point of a 
 magnet. (See Line, Neutral, of a Magnet?} 
 
 Point, Smashing, of Incandescent Elec- 
 tric Lamps The point in the life of 
 
 an incandescent electric lamp at which it is 
 said to be more economical to replace it by 
 a new lamp than it is to keep it any longer 
 in use. 
 
 The life of an incandescent electric lamp can 
 be preserved for many thousand hours. It is 
 claimed, however, that, so far as economy is con- 
 cerned, it is more economical after a certain 
 number of hours burning to replace it by another 
 than it is to continue it any longer in use. This 
 conclusion, however, is by no means generally 
 accepted. 
 
 The length of life will, of course, depend on 
 the make of the lamp and the potential to which 
 it has been exposed. Cases, however, may fre- 
 quently arise where it will be more economical to 
 use the lamp under an increased difference of po- 
 tential than to cease using it. 
 
 Polar Aurora. (See Appendix Aurora, 
 Polar.} 
 
 Polar Transformer. (See Appendix 
 Transformer, Polar} 
 
 Polarization Battery. (See Appendix 
 Battery, Polarization.} 
 
 Polarization, Gas A term some- 
 times employed for that form of polarization 
 which is due to the collection of a gas, gen- 
 erally hydrogen, on the negative plate. (See 
 Cell, Voltaic, Polarization of} 
 
 Polarized Indicator. (See Appendix 
 Indicator, Polarized.} 
 
 Pole Indicator. (See Appendix Indi- 
 cator, Pole} 
 
 Pole, Magnetic, Blue A term 
 
 sometimes employed for that pole of a mag- 
 net which points approximately towards the 
 geographical south pole. 
 
 The natural confusion arising from this non- 
 descriptive term is still further increased by the 
 fact that some writers use the word blue-pole for 
 
 the pole which points towards the geographical 
 north pole. 
 
 Pole, Magnetic, Red A term some- 
 times employed for the pole of a magnet 
 which points approximately towards the geo- 
 graphical north pole. 
 
 Sometimes used in opposite sense. (See Ap- 
 pendix Pole, Magnetic, Blue.} 
 
 Pole, Magnetic, Unmarked A 
 
 term sometimes employed for the south pole 
 of a magnet. 
 
 Pole, Resultant Magnetic A term 
 
 sometimes employed for a consequent pole. 
 (See Pole, Consequent?) 
 
 Polishing Bob. (See Appendix Bob, 
 Polishing?) 
 
 Polishing Mop. (See Appendix Mop, 
 Polishing.} 
 
 Polyphase Apparatus. (See Appendix 
 Apparatus, Polyphase.} 
 
 Polyphase Armature. (See Appendix 
 Armature, Polyphase.} 
 
 Polyphase Currents. (See Appendix^- 
 Currents, Polyphase?) 
 
 Polyphase Generator. (See Appendix 
 Generator, Polyphase.') 
 
 Polyphase Motor. (See Appendix 
 Motor, Polyphase} 
 
 Polyphase Working. (See Appendix 
 Working, Polyphase.} 
 
 Polyphased Alternating Currents. (See 
 Appendix Currents, Polyphased, Alternat- 
 ing} 
 
 Positive Electrification. (See Appendix 
 Electrification, Positive?) 
 
 Positive Fluid. (See Appendix Fluid, 
 Positive} 
 
 Positive Spark. (See Appendix Spark, 
 Positive.) 
 
 Potash Brush. (See Appendix Brush, 
 Potash} 
 
 Potential, Scalar A potential pos- 
 sessing magnitude and sign without directive 
 signification, as distinguished from a vector 
 potential, which possesses both direction and 
 
Pot.] 
 
 639 
 
 [Pro. 
 
 magnitude. (See Appendix Potential, Vec- 
 tor,} 
 
 Potential, Vector A potential pos- 
 sessing directive properties and one that may 
 be derived by the process of summation 
 from vectors, or elementary directed quanti- 
 ties, as opposed to a scalar potential, which 
 possesses undirected magnitude. (See Ap- 
 pendix Potential, Scalar!) 
 
 Potentiometer, Alternating Current 
 
 A form of potentiometer designed for 
 measuring the differences of potential in al- 
 ternating current circuits. 
 
 Power Factor. (See Appendix Factor, 
 Power.) 
 
 Power, Man A unit of power equal 
 
 to YO horse-power, or about 74^ watts. 
 
 Pressure, Electric A term some- 
 times loosely employed for difference of po- 
 tential or electromotive force. (See Poten- 
 tial, Difference of.) 
 
 The terms potential difference and elec- 
 tromotive force are preferable terms. The use 
 of the term electric pressure can well be aban- 
 doned. The term electric pressure, however, is 
 much to be preferred to the very objectionable 
 term electric tension, or difference of tension. 
 
 Primary Cell. (See Appendix Cell, 
 Primary.) 
 
 Primary Electric Clock. (See Appendix 
 Clock, Primary Electric?) 
 
 Primary Electric Heater. (See Appendix 
 Heater, Primary Electric?) 
 
 Primary Spiral of Induction Coil. (See 
 Appendix Spiral, Primary, of Induction 
 Coil.) 
 
 Process, Building, for Moulds of Elec- 
 trotypes A process for bringing up 
 
 the blank spaces in the mould of an electro- 
 type by the use of wax, melted by a build- 
 ing iron the high places thus built up 
 becoming depressions in the finished plate. 
 
 Process, Coking, for Filament of Incan- 
 descent Electric Lamp A process 
 
 for converting the carbon of an incandescent 
 filament into coke, by subjecting it, while in 
 a vacuum, to the prolonged heating action of 
 a powerful electric current. (See Appendix 
 Filament, Coked.) 
 
 Process, Qnicking A term em- 
 ployed in electro-plating for a process by 
 means of which an article that is to be electro- 
 plated with silver, is previously coated with a 
 layer of mercury by dipping it into a quicking 
 solution, z. e., a solution of salt of mercury. 
 (See Solution, Quicking?) 
 
 Process, Stopping-Off A process 
 
 employed in electro-plating by means of which 
 an article which is to be electro-plated on por- 
 tions only of its surface with one metal, and 
 on other portions with another metal, is first 
 completely covered by an electro-plating of 
 the cheaper metal, and is then stopped-off, by 
 covering with a coating of non-conducting 
 varnish such portions only of its surface as 
 are not to receive the deposit of the dearer 
 metal. (See Stopping-Off?) 
 
 Process, Stopping-Out >A process 
 
 employed in electrotyping by means of which 
 those parts of an electrotype mould that are 
 not to be copied in the electrotype are covered 
 with clean hot wax. 
 
 The stopping-out process is similar to the stop- 
 ping-off process in electro-plating. Wherever the 
 black lead or plumbago surface is covered with 
 clean wax, the copper fails to be deposited. 
 
 Proposed A. I. E. E. Definition for 
 
 Impressed Electromotive Force. (See Ap- 
 pendix Force, Electromotive, Impressed, 
 Proposed A. I. E. E. Definition for?) 
 
 Proposed A. I. E. E. Definition for Gauss. 
 
 (See Appendix Gauss, Proposed A. I. E. 
 E. Definition for?) 
 
 Proposed A. I. E. E. Definition for 
 Henry. (See Appendix Henry, Proposed 
 A. I.E. E. Definition for?) 
 
 Proposed A. I. E. E. Definition for Iu- 
 ductivity. (See Appendix Inductivity, 
 Proposed A. I. E. E. Definition for?) 
 
Pro.] 
 
 640 
 
 [Pul. 
 
 Proposed A. I. E. E. Definition for Mho. 
 
 (See Appendix Mho, Proposed A. I. E. E. 
 Definition for -.) 
 
 Proposed A. I. E. E. Definition for 
 Mutual Inductance. (See Appendix In- 
 ductance, Mutual, Proposed A. I.E. E. Defi- 
 nition for?) 
 
 Proposed A. I. E. E. Definition for North 
 Pole of Magnet. (See Appendix Magnet, 
 North Pole of, Proposed A. I. E. E. Defini- 
 tion for?) 
 
 Proposed A. I. E. E. Definition for 
 
 Oersted. (See Appendix Oersted, Proposed 
 A. I. E. E. Definition for.) 
 
 Proposed A. I. E. E. Definition for Ohm. 
 
 (See Appendix Ohm, Proposed A. I. E. 
 E. Definition for?) 
 
 Proposed A. I. E. E. Definition for Poly- 
 phase Alternating Current. (See Appen- 
 dix Current, Polyphase Alternating, Pro- 
 posed A.I. E. E. Definition for?) 
 
 Proposed A. I. E. E. Definition for Re- 
 luctivity. (See Appendix Reluctivity, 
 Proposed A. I. E. E. Definition for?) 
 
 Proposed A. I. E. E. Definition for Self- 
 Inductance. (See Appendix Inductance, 
 Self, Proposed A. I. E. E. Definition for?) 
 
 Proposed A. I. E. E. Definition for South 
 Pole of Magnet. (See Appendix Magnet, 
 South Pole of, Proposed A. I. E. E. Defini- 
 tion for?) 
 
 Proposed A. I. E. E. Definition for 
 Triphase Alternating Current. (See Ap- 
 pendix Current, Triphase Alternating, 
 Proposed A. I. E. E. Definition for?). 
 
 Proposed A. I. E. E. Definition for Volt. 
 
 (See Appendix Volt, Proposed A. I. E. E. 
 Definition for?) 
 
 Proposed A. I. E. E. Definition for Watt. 
 
 (See Appendix Watt, Proposed A. I. E. 
 E. Definition for?) 
 
 Proposed A. I. E. E. Definition for Web- 
 er. (See Appendix Weber, A. I. E. E. 
 Definition for?) 
 
 Protection, Conduction Lightning 
 
 The protection of any instrument from the 
 passage of a current due to lightning around 
 its coils, and so disturbing the magnetism of 
 the needle. 
 
 Protection, Insulation Lightning 
 
 The protection of any instrument from the 
 jumping of a spark across it from layer to 
 layer. 
 
 Protective Action. (See Appendix Ac- 
 tion, Protective?) 
 
 Protective Throw. (See Appendix 
 Throw, Protective?) 
 
 Protector, Cage, for Lightning Dis- 
 charges A term sometimes employed 
 
 for protecting sheaths for lightning dis- 
 charges. (See Sheath, Protective?) 
 
 The method consists essentially in surrounding 
 the body to be protected by conducting wires in 
 the form of a cage. 
 
 Protector, Conduction Lightning 
 
 A lightning protector by means of which a 
 current is prevented from passing around the 
 coil of a galvanometer or other needle instru- 
 ment, and thus disturbing the magnetism of 
 the needle. 
 
 Protector, Insulation Lightning 
 
 A lightning protector by means of which a 
 discharge is prevented from jumping across 
 the coil of an instrument from layer to layer, 
 and thus damaging the insulation. 
 
 Pull Bell, Circuit Closer for A 
 
 device suitable for attachment to a mechanical 
 door pull, so as to make an electrical contact 
 for the ringing of an electric bell, without pre- 
 venting the original bell from being operated 
 by the mechanical pull. 
 
 Pull-Off, Double Curve In a system 
 
 of electric street railways a hanger supported 
 by a lateral strain in opposite directions, used 
 generally at the ends of both single and 
 double curves and at intermediate points on 
 double track curves. 
 
 A double curve hanger. 
 
 Pull-Off, Single Curve In a system 
 
 of electric street railways a hanger supported 
 
Pill.] 
 
 641 
 
 [Baa. 
 
 in one direction by a lateral strain except at 
 the ends and on the inside curve of double 
 tracks. 
 
 A single curve hanger. 
 
 Puncturation, Electro A term pro- 
 posed for electro-puncture. 
 
 Electro-puncture would appear to be the .pref- 
 erable term. (See, Puncture, Electro.} 
 
 Push, Double-Contact A push pro- 
 vided with two contacts, so arranged that the 
 pressure of the push opens one contact and 
 closes the other. 
 
 Push, Morse A terjn sometimes 
 
 employed in place of double-contact push. 
 (See Appendix Push, Double-Contact!) 
 
 Push, Pear A pear-shaped push 
 
 provided for attachment to a flexible con- 
 ducting cord. 
 
 Push, Sounder An apparatus, con- 
 sisting of a push so combined with a sounder 
 as readily to enable the one pushing it to 
 know whether a distant bell has rung or not 
 on the depression of the push button. 
 
 Push Switch. (See Appendix Switch, 
 Push) 
 
 Pyro-Electric Crystal. (See Appendix 
 Crystal, Pyro-Electric!] 
 
 Pyrogravure. A process for the decora- 
 tion of wood, copper or glass by the burning 
 action of an electrically or otherwise heated 
 tool. 
 
 Q 
 
 Q. A symbol used for quantity of elec- 
 tricity. 
 The defining equation is Q = CT. 
 
 Quad. An abbreviation sometimes em- 
 ployed for a unit of self-inductance. (See 
 Quadrant!) 
 
 The same abbreviation is also employed for 
 quadruplex, but the context will generally pre- 
 vent any confusion. 
 
 Quadmeter. A secohmmeter. (See Sec- 
 ohmmeter!) 
 
 Quadrantal Deviation of Mariner's Com- 
 pass. (See Appendix Deviation, Quad- 
 rantal, of Mariner's Compass!) 
 
 Quadruplex Telegraph. (See Appendix 
 Telegraph, Quadruplex!) 
 
 Quality of Radiation. (See Appendix 
 Radiation, Quality of.} 
 
 Quantity Meter. (See Appendix Meter 
 Quantity!) 
 
 Quick Break. (See Appendix Break, 
 Quick!) 
 
 Quick-Break Switch. (See Appendix 
 Switch, Quick-Break!) 
 
 Quickened. A term employed in electro- 
 plating for a surface which has been prepared 
 for the reception of a deposit of silver, by 
 dipping the article into a quickening liquid. 
 (See Solution, Quicking!) 
 
 Quickening Liquid. (See Appendix 
 Liquid, Quickening!) 
 
 Quickening Solution. A quicking solu- 
 tion. (See Solution, Quicking!) 
 
 Quicking Process. (See Appendix Pro- 
 cess, Quicking!) 
 
 R. A symbol used for resistance. 
 
 E 
 
 The defining equation is R = -^ 
 
 oft. A .symbol proposed for magnetic re- 
 sistance or reluctance. 
 
 The defining equation is f{, = v-^ 
 
 p. A symbol used for specific electrical 
 resistance or reluctivity. 
 
 The symbol v has been proposed for this quan- 
 tity by Hospitalier. 
 
 R. M. S. Current (See Appendix Cur- 
 rent, R. M*. S.} 
 
 Raad. A name formerly given by the 
 
Bad.] 
 
 642 
 
 [Rai. 
 
 Arabians to the torpedo or electrical ray. 
 (See Torpedo, Electric. Ray, Electric.} 
 
 Radial Current. (See Appendix Cur- 
 rent, Radial.} 
 
 Radian. Unit angle. 
 An angle such that its circular arc is equal 
 in length to its radius. 
 Its value in degrees is approximately 57 17' 
 
 45"- 
 
 The radian is not employed in practical appli- 
 cations, since the degree is the unit angle in 
 ordinary use, but in mathematics angles are 
 nearly always discussed in terms of the radian. 
 
 Radian Per Second. Unit angular 
 velocity of a rotating body. 
 
 Radiation, Efficiency of A term 
 
 sometimes employed to represent the ratio of 
 the non-luminous to the luminous radiation in 
 the case of a body emitting light and heat. 
 
 The efficiency of the ordinary sources of arti- 
 ficial light is very low. The efficiency of the 
 radiation of the firefly or glow-worm is very 
 high, practically all its radiation belonging to the 
 luminous type. 
 
 Radiation, Electric The transfer- 
 ence of electric energy by means of waves 
 set up in the surrounding ether. 
 
 During the oscillatory discharge of a Leyden jar, 
 or, in general, during any disruptive discharge, 
 the electricity surges or rushes to and fro, send- 
 ing out or radiating its energy into the surround- 
 ing ether by means of waves. 
 
 It does this until all its energy is either directly 
 dissipated in this manner, or is converted into 
 heat in the conductor, which is afterwards dis- 
 sipated as heat-waves. 
 
 The lengths of the waves thus sent out into 
 space by means of direct radiation of the electri- 
 cal energy depend on a variety of circumstances, 
 the most important of which are : 
 
 (l.) On the capacity of the condensers. 
 
 (2.) On the self-induction of the radiating 
 system. 
 
 Radiation, Intensity of The ratio 
 
 existing between the amount or quantity of 
 radiation and the surface. 
 
 Radiation, Quality of Variations 
 
 in the radiation due to differences, both in the 
 
 various wave lengths present and in the 
 polarization. 
 
 Radiation, Selective Radiation 
 
 limited to waves of a particular wave length. 
 
 The character of the radiation depends. 
 
 (I.) On the nature of the body. 
 
 (2.) On the condition of its surface. 
 
 (3.) On the temperature. 
 
 Langley has shown that in the case of a lumin- 
 ous body the proportion existing between the 
 visible radiation and the invisible radiation varies 
 greatly in different cases. In the case of a gas 
 flame, 2.4% of the radiation is luminous. In the 
 case of the arc light about 10 per cent, is lumin- 
 ous, while in the light emitted by the firefly or 
 the glow-worm practically all the radiation is 
 luminous. 
 
 Radiator, Electric An electric 
 
 heater so placed as to radiate its heat into 
 the room or space to be heated. 
 
 Any electric heater applied to heat the air or 
 space that surrounds it may be regarded as an 
 electric radiator. 
 
 Electric radiators are generally so placed as to 
 prevent direct contact with their heated surfaces. 
 
 Radiophonic Sounds. (See Appendix 
 Sounds, Radiophonic?) 
 
 Railroad, Conductor System for 
 
 A system for the propulsion of cars by 
 means of electricity taken from a conductor 
 placed near the road. (See Railroads, Elec- 
 tric, Dependent System of Motive Power 
 for} 
 
 Railway, Electric, Battery System for 
 
 A system for the propulsion of cars 
 
 by means of electricity derived from storage 
 or secondary batteries placed on the cars. 
 (See Railroads, Electric, Independent Sys- 
 tem of Motive Power for.} 
 
 Railway Generator. (See Appendix 
 Generator, Railway} 
 
 Raindrops, Electrical Aggregation of 
 
 The coalescence of a number of 
 
 separate raindrops into a single drop by the 
 action of electricity. 
 
 Rayleigh has observed the fact that if a verti- 
 cal water-jet is subjected to the influence of an 
 electrified stick of sealing wax held a short dis- 
 
Rat.J 
 
 [Rep. 
 
 tance from the drop, the jet at once shrinks upon 
 itself and greatly changes its appearance, a great 
 number of separate drops collecting into single 
 larger drops. 
 
 Examining the drops by means of intermittent 
 illumination the coalition of the separate drops 
 can be readily seen. When no difference of 
 potential exists between the separate drops they 
 do not unite or coalesce, but when a difference 
 of potential exists, coalescence occurs, and, since 
 such coalescence causes an increased difference of 
 potential, the drops rapidly increase, both in size 
 and potential difference. 
 
 Ratio of Conversion. (See Appendix 
 Conversion, Ratio of.) 
 
 Ratio of Transformation. (See Appen- 
 dix Transformation, Ratio of.) 
 
 Bays, Anodic, of Tacuum Tube 
 
 The rays of light which appear in the neigh- 
 borhood of the anode of a vacuum tube 
 through which a rapid electric discharge is 
 passing. 
 
 Bays, Kathodic, of Vacuum Tube 
 
 The rays of light which appear in the neigh- 
 borhood of the kathode of a vacuum tube 
 through which a rapid electric discharge is 
 passing. 
 
 Reactance. A term proposed by Hospital- 
 ier for a quantity of the same dimensions as 
 the resistance, which does not absorb energy, 
 and the square of which added to the square 
 of the resistance gives the square of the im- 
 pedance to simple harmonic currents. 
 
 Calling Ceff, the effective current, E e ff, the 
 effective electromotive force, a?, the pulsation, or 
 2 TI times the frequency, then 
 
 Eeff 
 
 Ceff = 
 
 The factor in the parenthesis is what Hospital- 
 ier proposes to call the reactance. 
 
 Reaction, Armature The reactive 
 
 magnetic influence produced by the current 
 in the armature of a dynamo or motor upon 
 the magnetic circuit of the machine. 
 
 Red Magnetic Pole. (See Appendix 
 Pole, Magnetic, Red?) 
 
 Redressed. Commuted or caused to take 
 the same direction. 
 
 The commutator redresses or commutes the 
 currents in the armature and causes them to flow 
 in the same direction. 
 
 Regenerative CelL (See Appendix Cell, 
 Regenerative.) 
 Region, Equatorial, of Magnet A 
 
 term sometimes employed for the portions of 
 a magnet which lie near the equator. (See 
 Magnet, Equator of.) 
 
 Registering Declination Magnetometer. 
 
 (See Appendix Magnetometer, Register- 
 ing Declination.) 
 
 Regulating Socket. (See Appendix 
 Socket, Regulating.) 
 
 Relay Contact. (See Appendix Contact, 
 Relay.) 
 
 Relay, Kick of (See Appendix 
 
 Kick of Relay.) 
 
 Relay, Polar, Telegraphic A tele- 
 graphic relay provided with a polarized arma- 
 ture. (See Armature, Polarized.) 
 
 Reluctancy. An alternative word pro- 
 posed for reluctivity. (See Reluctivity. Re- 
 luctance, Magnetic.) 
 
 Reluctivity, Proposed A. I. E. E. Defini- 
 tion for The reciprocal of permea- 
 bility. 
 
 Remanent Magnetism. (See Appendix 
 Magnetism, Remanent^) 
 
 Repeater, Automatic A telegraphic 
 
 repeater which acts automatically. (See Re- 
 peaters, Telegraphic.) 
 
 Repeater, Button A form of 
 
 manual repeater. (See Repeaters, Tele- 
 graphic.) 
 
 Repeater, Electro-Magnetic, Callan's 
 
 A term formerly applied to a variety of 
 vibrating contact breaker. 
 
 Repeater, Manual A telegraphic 
 
 repeater which is operated by hand. (See 
 Repeaters, Telegraphic.) 
 
 Repeater, Non-Automatic A term 
 
 sometimes employed for manual repeater. 
 (See Repeaters, Telegraphic.) 
 
Rep.] 
 
 644 
 
 [Rev. 
 
 Repeating Telegraphic Station. (See 
 
 Appendix Station, Repeating Telegraphic^) 
 
 Repulsion Electrometer. (See Appendix 
 Electrometer, Repulsion?) 
 
 Residue, Electric A term proposed 
 
 for residual charge. 
 
 The term electric residue would appear to be 
 entirely unnecessary. 
 
 Resistance, Apparent A term 
 
 sometimes employed for the impedance of a 
 circuit or the resistance it offers to the pas- 
 sage of an alternating current. 
 
 Resistance, Conduction The re- 
 sistance offered by a conductor to the pas- 
 sage of an electric current. 
 
 Resistance, Conductor A term fre- 
 quently employed for cop per resistance. (See 
 Appendix Resistance, Copper?) 
 
 Resistance, Contact A resistance 
 
 produced by the contact of two surfaces. 
 
 Resistance, Copper A term fre- 
 quently employed for expressing the resist- 
 ance of a telegraphic conductor. 
 
 The value of the copper resistance is generally 
 expressed in ohms-per-mile, ohms-per-knot or 
 ohms-per-kilometre. 
 
 Resistance, Electric, of Metals, Effect of 
 Temperature on A change in the re- 
 sistance of a metal following a given change 
 in temperature. 
 
 At decreasing temperatures an increase occurs 
 in the electric conducting power of the metals. 
 
 Dewar, by means of the intense cold produced* 
 by liquefied oxygen, found that at very low tem- 
 peratures all pure metals increase in their conduct- 
 ing power as the temperature decreases. The 
 temperature curve is such that, the resistivity of 
 pure metals would be zero at, or even before, the 
 absolute zero of temperature. In such a case, 
 if a wire or conductor of pure metal were placed 
 in the approximately absolute zero of inter- 
 stellar space, electricity would pass through it 
 without loss. This must, however, be regarded 
 only as a hypothesis. 
 
 According to Dewar, most non-conducting 
 bodies show a conductivity decreasing with the 
 temperature. 
 
 Resistance of Telegraphic Leak. (Sec 
 Appendix Leak, Telegraphic, Resistance 
 of.) 
 
 Resistance, Passive A term some- 
 times employed for the ohmic resistance of a 
 circuit. (See Resistance, Ohmic.) 
 
 Resistance, Specific Magnetic A 
 
 word proposed for reluctivity. (See Reluc* 
 tivity.) 
 
 Resistance, Transition A term 
 
 formerly employed for the resistance experi- 
 enced by a voltaic cell shortly after closing a 
 circuit. 
 
 The transition resistance was inferred from the 
 decrease in the current strength, and was for- 
 merly attributed to a change in the character of 
 the electrode. It is now generally ascribed to the 
 electromotive force of polarization. 
 
 This term is also employed in a somewhat 
 similar sense in electro-therapeutics. (See Re- 
 sistance, Transition.) 
 
 Resistivity. A term proposed for specific 
 resistance. (See Resistance, Specific) 
 
 Resistivity is the inverse of specific conductivity. 
 
 Resonance, Acoustic The excite- 
 ment or production of waves or vibrations of 
 sound in an elastic body by means of succes- 
 sive impulses received by such body from the 
 sound waves striking it. 
 
 Acoustic resonance is a particular case of sym- 
 pathetic vibrations. Like all cases of such vibVa- 
 tions, there must exist between the sonorous body 
 in which the waves of vibrations are excited, and 
 the body which is producing the exciting waves, 
 an identity of wave length; or, in other words, 
 there must exist between the two strict syn- 
 chronism, so that the effects of timed impulses 
 may be permitted. 
 
 Resonant Circuit. (See Appendix Cir- 
 cuit, Resonant^ 
 
 Resultant Fault. (See Appendix Fault, 
 Resultant.) 
 
 Resultant Magnetic Pole. (See Appendix 
 Pole, Resultant Magnetic.) 
 
 Retarding Disc. (See Appendix Disc, 
 Retarding. 
 
 Reversals. In telegraphy, alternate cur- 
 rent signals transmitted for the purpose of 
 
Key.] 
 
 645 
 
 [Sea. 
 
 adjustment ; as, for example, in obtaining a 
 duplex balance. 
 
 Reversible Heating Effect of Electric- 
 ity. (See Appendix Electricity, Reversible 
 Heating Effect of ".) 
 
 Rheostat, Adjustable An adjustable 
 
 resistance, in a compound-wound dynamo- 
 electric machine, employed to adjust com- 
 pounding for a greater or less than tested 
 speed or a greater or less wiring loss. 
 
 A term sometimes employed for a rheostat, 
 or a resistance that can readily be adjusted 
 or altered. (See Rheostat?) 
 
 Strictly speaking, any rheostat is an adjustable 
 resistance; therefore, this latter use of the term 
 adjustable rheostat would seem to be unnecessary. 
 
 Ribbon Induction Coil. (See Appendix 
 Coil, Induction Ribbon!) 
 
 Right-Hand Trolley Switch. (See Ap- 
 pendix Switch, Right-Hand Trolley?) 
 
 Right-Handed Helix. (See Appendix 
 Helix, Right-Handed?) 
 
 Right-Handed Rotation. (See Appendix 
 Rotation, Right-Handed?) 
 
 Right-Handed Spiral. (See Appendix 
 Spiral, Right-Handed?) 
 
 Ring, (ial vanic A term sometimes 
 
 applied to a galvanic, or, more properly speak- 
 ing, voltaic circuit. (See Circuit, Voltaic?) 
 
 Ripple Marks. (See Appendix Marks, 
 Ripple, Electrical?) 
 
 Rise. In interior house wiring that portion 
 of a conductor which rises vertically from one 
 floor to another. 
 
 Rocking Switch. (See Appendix 
 Switch, Rocking?) 
 
 Rosette, Ceiling A ceiling block of 
 
 ornamental and rosiform design. 
 
 Rotary Converter. (See Appendix Con- 
 verter, Rotary?) 
 
 Rotary Transformer. (See Appendix 
 Transformer, Rotary?) 
 
 Rotation, Electro-Dynamic " The 
 
 rotation of a magnetic field produced as the 
 resultant of two or more magnetic or mag- 
 netizing forces of variable intensity acting at 
 an angle to one another, whose maxima do 
 not coincide, but whose periods are the same." 
 Gutmann. 
 
 Rotation, Left-Handed A rotation 
 
 the direction of which is opposite to that of 
 the hands of a watch when one looks directly 
 at the face of the watch. 
 
 Rotation, Right-Handed A rota- 
 tion the direction of which is the same as 
 that of the hands of a watch when one looks 
 directly at the face of the watch. 
 
 A direction the same as that of an ordinary 
 right-handed screw, when we turn the upper side 
 of the right-hand outwards. 
 
 Rubber Tape. (See Appendix Tape, 
 Rubber?) 
 
 Rumble. A barrel or other hollow box 
 revolved by mechanical power in which small 
 articles that are to be electro-plated are 
 placed for the purpose of polishing them. 
 
 When subjected to the rotation of the barrel 
 the articles became polished by friction against 
 one another. Some dry sawdust is frequently 
 placed in the barrel, to aid in the polishing pro- 
 cess. 
 
 Running Torque of Motor. (See Appen- 
 dix Torque, Running, of Motor.) 
 
 s 
 
 S. A symbol proposed for surface. 
 
 The defining equation is S = L X L. 
 
 8. An abbreviation proposed for second, 
 the C. G. S. unit of time. 
 
 S. N. Telegraphic Instrument. (See Ap- 
 pendix Instrument, S. N., Telegraphic.) 
 
 S. P. Cut-Out. (See Appendix Cut-Out, 
 S.P.) 
 
 Sag of Conductor or Line Wire. (See 
 A ppendix Conductor or Line Wire, Dip of.) 
 
 Scalar Potential. (See Appendix Po- 
 tential, Scalar.) 
 
Sec.] 
 
 646 
 
 [Ser. 
 
 Secondary Spiral of Induction Coil. 
 
 (See Appendix Spiral, Secondary, of In- 
 duction Coil.) 
 
 Section Box. (See Appendix Box, Sec- 
 tion.) 
 
 Segment, Dark, of Aurora A dark 
 
 or non-illumined portion of the sky in the 
 neighborhood of an aurora. 
 
 Segment, Unlighted, of Aurora 
 
 A term employed by Nordenskjold in place of 
 dark segment of aurora. (See Appendix 
 Segment, Dark, of Aurora) 
 
 Selective Emission. (See Appendix 
 Emission, Selective.} 
 
 Selective Radiation. (See Appendix 
 Radiation, Selective.) 
 
 Selective Signal. (See Appendix Sig- 
 nal, Selective.) 
 
 Selective Signalling Apparatus. (See 
 Appendix Apparatus, Selective Signal- 
 ling.) 
 
 Self-Compounding Polyphase Genera- 
 tor. (See Appendix Generator, Self -Com- 
 pounding Polyphase.) 
 
 Self-induction Coil. (See Appendix 
 Coil, Induction, Self.) 
 
 Self-Starting Synchronous Motor. (See 
 Appendix Motor, Synchronous, Self-Start- 
 ing.} 
 
 Semaphoric Electroscope. (See Appen- 
 dix Electroscope, Semaphoric.) 
 
 Semi-Circular Deviation of Mariner's 
 Compass. (See Appendix Deviation, Semi- 
 Circular, of Mariner's Compass?) 
 
 Semi-Conductors. (See Appendix Con- 
 ductor, Semi?) 
 
 Sensitiveness of Telephone. (See Ap- 
 pendix Telephone, Sensitiveness of) 
 
 Separable Conducting Cord Tip. (See 
 Appendix Tip, Conducting Cord, Sep- 
 arable.) 
 
 Separate-Coil Alternator. (See Appen- 
 dix Alternator, Separate-Coil.) 
 
 Separate - Coil Alternating Dynamo- 
 Electric Machine. (See Appendix Ma- 
 
 chine, Dynamo-Electric, Separate-Coil Al- 
 ternating.) 
 
 Separately-Excited Alternating Dynamo- 
 Electric Machine. (See Appendix Ma- 
 chine, Dynamo-Electric, Separately Excited 
 Alternating.) 
 
 Separately-Excited Alternator. (See 
 Appendix Alternator, Separately-Excited) 
 
 Separator, Electro-Magnetic A 
 
 device for separating the useful ore from the 
 dross in low grade finely granulated iron ores. 
 Septum. A wall or diaphragm through 
 which osmotic diffusion can take place. (See 
 Osmose. Osmose, Electric) 
 
 Series, Branched A term some- 
 times employed in place of series-multiple. 
 (See Series-Multiple.) 
 
 Series Connection of Alternators. (See 
 Appendix Alternators, Series Connection 
 of) 
 
 Series, Potential, Dynamos Coupled in 
 
 A term sometimes employed in teleg- 
 raphy for a particular coupling of dynamo- 
 electric machines in series. 
 
 In the application of a number of dynamo-elec- 
 tric machines to the operation of telegraphic lines 
 in a central station, where a number of different 
 lines enter or leave the station, different voltages 
 are required on the different lines. These differ, 
 ent voltages are most readily obtained by coup- 
 ling the machines in what is called potential 
 series. 
 
 In potential-series coupling, the dynamos are 
 connected together in series, that is, the positive 
 brush of one dynamo is connected to the negative 
 brush of another, its positive brush to the nega- 
 tive of another, and so on throughout the series. 
 One terminal of the battery of dynamos is 
 grounded, and the other connected to the line. 
 The terminals of the various telegraphic lines are 
 then connected to points of junction of contiguous 
 dynamos where their opposite brushes are con- 
 nected. By these means the requisite difference 
 of potential is readily obtained. 
 
 Series Working of Alternating Dynamo- 
 Electric Machines. (See Appendix Ma- 
 chines, Dynamo-Electric, Alternating, Serif* 
 Working) 
 
Sen] 
 
 647 
 
 [Sig. 
 
 Service Block. (See Appendix Block, 
 Service. 
 
 Shackle Insulator. (See Appendix In- 
 sulator, Shackle?) 
 
 Shading, Magnetic A term some- 
 times employed for magnetic screening. (See 
 Screening, Magnetic. ) 
 
 Sheath, Closed-Conducting, for Light- 
 ning Protection A form of lightning 
 
 conductor proposed by Maxwell, consisting 
 essentially of a net-work or cage-like con- 
 ductor surrounding the house or building to 
 be protected. 
 
 The theory for the protection of a building by 
 means of a conducting sheath is based on the well 
 known fact that there is no trace of electrostatic 
 charge inside a hollow conductor. 
 
 It is now well known that there are circum- 
 stances under which the closed-conducting circuit 
 does not thoroughly protect a building on which 
 it is placed. If the number of such circuits is suf- 
 ficiently great so as to form a close- meshed cage, 
 the protection thus afforded is excellent. Such a 
 sheath, however, might be dangerous to touch. 
 
 Lodge, who has studied the matter of lightning 
 protection very thoroughly, thus humorously re- 
 marks concerning the system of sheath lightning 
 protection: 
 
 " It would be unpleasant, when you are driven 
 home out of a storm, to find it so highly charged 
 as to knock you down directly you tried to enter. 
 An earth connection is necessary as well." 
 
 Shell, Complex-Magnetic A mag- 
 netic shell whose strength varies from one 
 part to another. 
 
 A complex magnetic shell will result from the 
 overlapping of a number of simple magnetic 
 shells. 
 
 Shell, Copper, of Electrotype A 
 
 thin sheet of electrolytically deposited copper. 
 
 The copper shell is rendered sufficiently rigid 
 for use by being covered with a backing of type 
 metal. 
 
 In order to permit this metal readily to adhere 
 to the back of the shell it is thoroughly cleansed 
 and then covered on the back with sheets of tin- 
 foil, which are melted in the backing-pan pre- 
 paratory to receiving the coating of type metal. 
 
 Shell, Simple Magnetic A mag- 
 netic shell whose strength is everywhere 
 equal. 
 
 Shifting of Spot of Light. A movement 
 of a spot of light on a scale produced by 
 other causes than those acting during the 
 proper operation of the instrument, and caus- 
 ing the spot of light to move away from its 
 true zero position. 
 
 In the case of a galvanometer the spot of light, 
 instead of remaining at the zero point, shifts or 
 moves from one side to another of the zero point. 
 
 This movement is sometimes called the drifting 
 of the zero point. 
 
 The shifting of the spot of light is, of course, 
 caused by the drift of the needle. 
 
 Shunting Air Gap. (See Appendix 
 Gap, Air, Shunting?) 
 
 Shunt-Out. A cut-out device for remov- 
 ing an electro-receptive device from a circuit, 
 without breaking the circuit, by providing a 
 short circuit between its terminals. 
 
 An electro- magnetic cut-out provides a shunt- 
 out of the device it is desired to cut-out It will 
 be seen, however, that all a shunt-out does is to 
 provide a by-path, the resistance of which is so 
 small as compared with the resistance of the de- 
 vice cut-out, that practically all the current flows 
 past the device through the shunt path, thus prac- 
 tically cutting it out from the circuit ; or, more 
 properly speaking, cutting it out from the opera- 
 tive current. 
 
 Side Arms. (See Appendix Arms, 
 Side.) 
 
 Signal, Individual In any system 
 
 of electric communication devices by means 
 of which bells or other signals, at two or 
 more stations electrically connected in the 
 same circuit, are not operated at all of the 
 stations by the calls sent over the line to the 
 call bell at any particular station, but in which 
 each particular bell is only operated by its own 
 call to the exclusion of the other calls. 
 
 Signal, Selective A term some- 
 times employed in place of individual signal. 
 (See Appendix Signal, Individual.) 
 
 Signal, Telegraphic, Audible Tele- 
 graphic signals that can be heard. 
 
Sig.] 
 
 648 
 
 [SoU 
 
 Examples of audible telegraphic signals are to 
 be found in the signals given by various sounders 
 of the Morse type. 
 
 The signals of electric bells are also audible 
 signals. 
 
 Signal, Telegraphic, Evanescent 
 
 Telegraphic signals that leave no permanent 
 record. 
 
 Examples of evanescent telegraphic signals are 
 found in the audible signals produced by most 
 forms of telegraphic sounders. 
 
 Signal, Telegraphic, Permanent 
 
 Telegraphic signals that are recorded by any 
 means which leaves a permanent record. 
 
 The various forms of recording or registering 
 apparatus employed in telegraphy produce per- 
 manent signals. (See Recorder, Morse. Rec- 
 order, Chemical, Bain's. Recorder, Siphon. Reg~ 
 ister, Telegraphic.) 
 
 Signal, Telegraphic, Visual Tele- 
 graphic signals that can be seen. 
 
 Examples of visual telegraphic signals are to be 
 found in the various galvanometric receiving ap- 
 paratus employed in cable telegraphy, or, in gen- 
 eral, in needle telegraphy. The signals received 
 on the siphon recorder, for example, are visible 
 signals. (See Recorder, Siphon.) 
 
 Simple Alternating or Two-Phase Cur- 
 rent. (See Appendix Current, Simple or 
 Two-Phase Alternating?) 
 
 Simple-Magnetic Shell. (See Appendix 
 Shell, Simple-Magnetic?) 
 
 Single-Current Telegraphic Working. 
 (See Appendix Working, Single-Cur- 
 rent, Telegraphic.} 
 
 Single Curve Pull-Off. (See Appendix 
 Pull-Off, Single Curve?) 
 
 Single-Liquid Yoltaic Cell. (See Cell, 
 Voltaic, Single-Fluid?) 
 
 Single-Phase Motor. (See Appendix 
 Motor, Single-Phase?) 
 
 Single-Pole Cut-Out. (See Appendix 
 Cut-Out, Single-Pole?} 
 
 Single-Wire System for Electric Light 
 Leads. (See Appendix Leads, Single- 
 Wire System for Electric Light?) 
 
 Sinusoidal Current. (See Appendix 
 Current, Sinusoidal?) 
 
 Six-Pole Dynamo-Electric Machine. 
 
 (See Appendix Machine, Dynamo-Electric, 
 Six-Pole?) 
 
 Six-Wire System. (See Appendix Sys- 
 tern, Six- Wire?) 
 
 Skew Adjustment of Carbons in Arc 
 Lamp. (See Appendix Carbons, Skew Ad- 
 justment of, in Arc Lamp?) 
 
 Skin Currents. (See Appendix Cur- 
 rents, Skin?) 
 
 Sliding Joint. (See Appendix -Joint, 
 Sliding.} 
 
 Slinging Wires. (See Appendix Wires, 
 Slinging?) 
 
 Slipping of Belt. (See Appendix^//, 
 Slipping of.) 
 
 Smashing Point of Incandescent Elec- 
 tric Lamps. (See Appendix Point, Smash- 
 ing, of Incandescent Electric Lamps.) 
 
 Snapper Sounder. (See Appendix 
 Sounder, Snapper.) 
 
 Socket Base. (See Appendix Base, 
 Socket?) 
 
 Socket, Pendant An attachment to 
 
 a socket provided with a chain or chains for 
 turning on or off a lamp not readily accessi- 
 ble. 
 
 Socket, Regulating A lamp socket 
 
 fitted with an adjustment under control of a 
 key or switch for regulating the degree of 
 incandescence of the filament. 
 
 Socket, Temporary A simple and 
 
 unfinished form of socket for holding a lamp 
 temporarily. 
 
 Solenoid, Anomalous A term 
 
 sometimes applied to a solenoid with conse- 
 quent poles. (See Solenoid, Practical.) 
 
 Solution, Amalgamating A solu- 
 tion of mercury employed for readily amal- 
 gamating the zincs of a voltaic battery. 
 
 Maycock gives the following as a good amalga- 
 mating solution: 
 
 Two pounds mercury. 
 
 Five pounds nitric acid. 
 
 Ten pounds hydrochloric acid. 
 
 The mercury and nitric acid are mixed together, 
 
Son.] 
 
 649 
 
 [Spa. 
 
 and, after the mercury is dissolved, the 10 pounds 
 of hydrochloric acid are added. 
 
 To use this liquid the zincs are first cleansed 
 and then dipped into the solution and afterwards 
 rinsed with clean water. 
 
 Sonometer. A monochord. (See Appen- 
 dix Monochord?) 
 
 Sonometer Interrupter. (See Appendix 
 Interrupter, Sonometer?) 
 
 Sorter, Electro-Magnetic An elec- 
 tro-magnetic separator, sometimes applied to 
 a magnetic separator. (See Appendix Sep- 
 arator, Electro-Magnetic?) 
 
 Sounder Push. (See Appendix Push, 
 Sounder?) 
 
 Sounder, Snapper A sounder for 
 
 producing the sounds corresponding to the 
 Morse characters, as they are heard on a 
 sounder, in which the audible signals are 
 produced by the flexure of a spring. 
 
 A sounder snapper consists essentially of a 
 dented spring plate firmly connected at one end 
 and the other end moved to-and-fro by hand. 
 
 It is used to produce sounds similar to those of 
 the regular electro-magnetic sounder, only, in- 
 stead of being operated by an electric current, it is 
 operated solely by hand. 
 
 Sounder, Telegraphic Box A 
 
 sounder, the receiving magnets of which are 
 enclosed in a hollow box for the purpose of 
 increasing the intensity of the sound by means 
 of resonance. 
 
 Sounds, Radiophonic Sounds re- 
 sulting from the direct action of radiation on 
 certain bodies. (See Sonorescence.) 
 
 It is the photophonic sounds, produced in the 
 receiving instrument of a photophone, that are 
 employed for the transmission of speech or other 
 intelligence. (See Photophone. ) 
 
 Mercadier gives the following conclusions as 
 the result of his experiments on radiophonic 
 sounds: 
 
 (i.) " The radiophone (radiophonic sound) 
 does not appear to be an effect produced by the 
 mass of the receiving plate vibrating transversely, 
 like an ordinary vibrating plate. The nature of 
 the molecules of the receiver and their mode of 
 aggregation do not appear to exercise a predom- 
 inant influence on the production of sounds. 
 
 " The radiophonic phenomena appear to result 
 principally from an action exercised at the sur- 
 face of the receiver, and are amplified when this 
 surface is covered with substances like lamp- 
 black, platinum-black, and the like. 
 
 (2. ) " Radiophonic sounds result from the direct 
 action of radiations on the receivers. Radiophonic 
 sounds are produced principally by the undula- 
 tions of great length of wave, called ' calorific.' 
 
 (3.) " The medium in which radiophonic vi- 
 bration is produced is the layer of condensed air 
 on the surface of the receivers. This layer of air, 
 particularly when the surfaces are smoked, or 
 covered with a substance absorbing heat, is alter- 
 nately heated and cooled by intermittent radia- 
 tions, with the result that periodic and regular 
 dilatations and contractions are set up ; hence a 
 vibratory movement communicated to the ad- 
 jacent gaseous layers, which also vibrate directly 
 under the same influence. 
 
 (4. ) " Radiophonic sounds cannot be produced 
 unless the medium which surrounds the receiving 
 surfaces is gaseous. A liquid or solid medium 
 cannot produce them; but a gaseous medium 
 containing vapor, particularly vapor of am- 
 monia or ether, develops them in a remarkable 
 way : those vapors which have the greatest ab- 
 sorbing thermic power give out the greatest 
 effects." 
 
 Source, Magnetic Any arrangement 
 
 of parts capable of producing lines of mag- 
 netic force. 
 
 A permanent magnet, an electro-magnet, or a 
 circuit through which an electric current is 
 passing, may act as a magnetic source. 
 
 Spark Chronograph. (See Appendix 
 Chronograph, Spark?) 
 
 Spark Discharge. (See Appendix Dis- 
 charge, Spark?) 
 
 Spark, Electric The phenomena 
 
 produced by a disruptive discharge in the air 
 space or gap through which the discharge 
 passes. 
 
 Spark, Negative A spark produced 
 
 by the discharge of a negatively charged con- 
 ductor. 
 
 Spark, Positive A spark produced 
 
 by the disruptive discharge of a positively 
 charged conductor. 
 
Spa v 
 
 650 
 
 [Sta. 
 
 Sparking Terminals. (See Appendix 
 Terminals, Sparking?) 
 
 Speaking Telegraph. (See Appendix 
 Telegraph, Speaking?) 
 
 Speaking-Tube Annunciator. (See Ap- 
 pendix Annunciator, Speaking- Tube?) 
 
 Specific Conductance. (See Appendix 
 Conductance, Specific?) 
 
 Specific Dielectric Capacity. (See Ap- 
 pendix Capacity, Specific Dielectric?) 
 
 Specific Energy. (See Appendix En- 
 ergy, Specific. 
 
 Specific Inductance. (See Appendix 
 Inductance, Specific?) 
 
 Specific Magnetic Resistance. (See Ap- 
 pendix Resistance, Specific Magnetic?) 
 
 Specific Magnetism. (See Appendix 
 Magnetism, Specific?) 
 
 Spectro-Photometer. (See Appendix 
 Photometer, Spectre.) 
 
 Spectrum, Magnetic A term some- 
 times employed in place of magnetic figure 
 or magnetic field. 
 
 The term magnetic spectrum is unfortunate 
 since magnetic figures so produced can hardly be 
 regarded as spectra, but merely as collections 
 of iron filings arranged in the order which the 
 lines of magnetic force take in the space or at- 
 mosphere outside the magnet. 
 
 Speed, Inductance A term pro- 
 posed for the product of a coefficient of self- 
 induction by an angular velocity. 
 
 Speeding of Machine. (See Appendix 
 Machine, Speeding of.) 
 
 Spiral. A term sometimes employed in 
 electricity and magnetism in place of an open 
 coil. (See Coil, Electric.) 
 
 Spiral, Anomalous A term some- 
 times employed in place of an anomalous 
 helix or solenoid. (See Appendix Solenoid, 
 Anomalous.) 
 
 Spiral, Left-Handed A term some- 
 times employed in place of left-handed 
 solenoid. (See Solenoid, Left-Handed. Sole- 
 noid, Practical.) 
 
 Spiral, Magnetic A term some- 
 
 times employed in place of magnetic helix. 
 (See Coil, Electric?) 
 
 Spiral, Magnetizing A term some- 
 times employed in place of a magnetizing 
 helix or coil. (See Coil, Electric?) 
 
 Spiral, Primary, of Induction Coil 
 
 A term sometimes employed for the primary 
 of an induction coil. (See Coil, Induction?) 
 
 Spiral, Right-Handed A term 
 
 sometimes employed in place of right-handed 
 solenoid. (See Solenoid, Right-Handed. 
 Solenoid, Practical?) 
 
 Spiral, Secondary, of Induction Coil 
 
 A term sometimes employed for the sec- 
 ondary of an induction coil. (See Coil, In- 
 duction?) 
 
 Spontaneous Electricity. (See Appendix 
 Electricity, Spontaneous?) 
 
 Spools, Field, of Dynamo-Electric Ma- 
 chine A term sometimes employed 
 
 for the forms on which the field coils are 
 wound. 
 
 Spring Relay Contact (See Appendix 
 Contact, Spring Relay?) 
 
 Spring Voltmeter. (See Appendix 
 Voltmeter, Spring?) 
 
 Standard Clock. (See Appendix Clock, 
 Standard?) 
 
 Standard Trolley Switch. (See Appen- 
 dix Switch, Standard Trolley?) 
 
 Standards. Telegraphic or -telephonic 
 supports placed on the roof of a building for 
 the purpose of supporting telegraphic or 
 telephonic wires or conductors. 
 
 Standards, Dynamo A term ap- 
 plied to the supports for the bearings of a 
 dynamo. 
 
 Starting Box of Shunt-Wound Motor. 
 (See Appendix Box, Starting, of Shunt- 
 Wound Motor?) 
 
 Starting Current of Motor. (See Appen- 
 dix Current, Starting, of Motor?) 
 
 Starting Torque of Motor. (See Appen- 
 dix Torque, Starting, of Motor?) 
 
 Static Transformer. See Appendix 
 Transformer, Static.) 
 
Sta.J 
 
 651 
 
 [Str. 
 
 Station, Repeating Telegraphic 
 
 A station situated at some intermediate 
 point on a long telegraphic line where the 
 currents from the sending station are passed 
 through a relay by means of which they are 
 sent on to the next station by means of a 
 current from a local battery. 
 
 Station, Translating Telegraphic 
 
 A receiving station. 
 
 The station at which the signals are re- 
 ceived. 
 
 Stay-Eye Clips. (See Appendix Clips, 
 Stay-Eye) 
 
 Steeling, Electro The art of cover- 
 ing copper electros with hardened iron. 
 
 Steel-Yard Ammeter. (See Appendix 
 Ammeter, Steel- Yard.) 
 
 Steeps. A word sometimes employed in 
 electro-plating for dips or dipping liquids or 
 solutions. 
 
 Steno - Telegraphy. (See Appendix 
 Telegraphy, Steno.) 
 
 Stereotype, Electro A word some- 
 times employed for electrotype. 
 
 The term electrotype would appear to be 
 preferable. 
 
 Sticking of Magnetic Armature. (See 
 Appendix Armature, Magnetic Sticking 
 of.) 
 
 Stimulation, Unipolar, of a Nerve 
 
 The stimulation of a nerve produced by 
 the application of a single electrode to the 
 nerve. 
 
 This term was proposed by Du Bois Reymond, 
 and is sometimes employed in electro-therapeu- 
 tics. According to Reymond unipolar stimula- 
 tion of a nerve is due to the action of the to- 
 and-fro motions of the electric current between 
 the free ends of the open induction circuit at the 
 moment of induction. 
 
 Stimulus, Electrical, of Nerve 
 
 The effect which electricity produces by its 
 
 passage through a nerve. 
 Landois and Sterling give the following facts 
 
 concerning the electric stimulation of a nerve : 
 The stimulation is more powerful 
 (I.) At the moment the current is completed. 
 
 (2.) At the moment the current ceases. 
 
 (3.) When a constant electric current increases 
 or decreases in its strength. The more rapid the 
 variations, the more energetic the stimulation. 
 
 (4.) To stimulate a nerve, the current must 
 have a certain duration. 
 
 (5.) The electric current is most active when 
 applied to the longer axis of the nerve, and be- 
 comes inactive when applied at right angles to 
 this axis. 
 
 (6.) The greater the length of nerve treated by 
 the current, the smaller is the stimulus that is 
 required. 
 
 Stone, Bologniau A term origin- 
 ally applied to a calcareous substance that 
 became phosphorescent on exposure to light. 
 
 Stoneware Dipping Basket. (See Appen- 
 dix Basket, Stoneware Dipping.) 
 
 Stoneware Dipping Bowl. (See Appen- 
 dix Bowl, Stoneware Dipping.) 
 
 Stopping-Off Process. (See Appendix 
 Process, Stopping-Off?) 
 
 Stopping-Out Process. (See Appendix 
 Process, Stopping-Out.) 
 
 Storage Accumulator. (See Appendix 
 Accumulator, Storage) 
 
 Storage Battery, Formed Plates of - 
 (See Appendix Plates, Formed, of Stor- 
 age Cell?) 
 
 Stove, Plate, Electric A form of 
 
 electric stove in which the heat is imparted 
 to the plate from a suitably shaped resist- 
 ance. 
 
 A form of plate stove is shown in Fig. 580, a 
 
 Fig. 580. Electric Plate Stove. 
 
 part of the top being cut away to show the elec- 
 tric heater. 
 
 Strain. The deformation produced by 
 the action of a stress. 
 
 Strain, Electrostatic A strain or 
 
 deformation produced in any medium by 
 
Str.] 
 
 652 
 
 [Swi. 
 
 means of the stress caused by an electro- 
 static field. 
 
 Stranding of Conductor. (See Appendix 
 Conductor, Stranding of.) 
 
 Strap Key. (See Appendix Key, Strap.) 
 
 Streams, Phantom A term some- 
 times applied to a variety of the Tesla stream- 
 ing discharge. (See Discharge, Streaming.) 
 
 Striking Distance. (See Appendix Dis- 
 tance, Striking.) 
 
 Striking Distance for Yarious Sub- 
 stances. (See Appendix Distance, Strik- 
 ing, for Various Substances.) 
 
 Striking Mechanism of Arc Lamp. (See 
 Appendix Lamp, Arc, Striking Mechan- 
 ism of.) 
 
 Stroboscope. An instrument employed 
 in the study of periodic motion. 
 
 The stroboscope is based on the illumination at 
 frequent intervals of the body whose motion is to 
 be studied. 
 
 Stroboscopic. Of or pertaining to the 
 stroboscope. 
 
 Struck. A word employed in electro- 
 plating to characterize a surface that has 
 been covered with a film of electro-deposited 
 nickel by being placed in a bath and exposed 
 for a few moments to the action of a strong 
 current. 
 
 When the surface of the article to be plated 
 has been struck or covered with a thin film of 
 nickel, the remainder of the coating is deposited 
 on the surface by the action of a weaker current. 
 
 Successive Contact Key. (See Appendix 
 Key, Successive Contact?) 
 
 Surging Circuit. (See Appendix Cir- 
 cuit, Surging.) 
 
 Surgings, Induced Electric Elec- 
 trical surgings induced in neighboring con- 
 ductors by means of electrical surgings or 
 oscillating discharges. (See Discharge, 
 Oscillating) 
 
 Suspension of Compass Needle, Cardan's 
 
 A term sometimes employed for gim- 
 bal suspension. (See Gimbals) 
 
 Sweeping-Out Charge. (See Appen#x 
 Charge, Sweeping-Out.) 
 
 Swinging Annunciator. (See Appendix 
 Annunciafor, Swinging.) 
 
 Switch, Automatic Photo-Electric 
 
 A switch that is automatically opened or 
 closed on the exposure of its face to differ- 
 ences of illumination. 
 
 A selenium cell is so placed in a circuit in com- 
 bination with an electro-magnetic switch that 
 when one of the selenium faces is exposed to the 
 decreasing illumination of approaching night a 
 current is produced by such decrease of light, the 
 direction of which is such as to automatically 
 turn on or light an electric lamp, and conversely, 
 on the approach of daylight and the consequent 
 increase of solar illumination, to turn off the 
 light. 
 
 A contraction for 
 
 (See Switch, Double- 
 
 A contraction for 
 
 (See Switch, Double- 
 
 Switch, D. B. 
 
 double-break switch. 
 Break?) 
 
 Switch, D. P. 
 
 double-pole switch. 
 Pole?) 
 
 Switch, Flush Key A switch whose 
 
 mechanism is contained in a box, the face of 
 which is flush with the wall or other support 
 to which the switch is attached. 
 
 The switch is opened or closed by means of a 
 key. 
 
 Flush Key Switch. 
 
 A form of flush switch is shown in Fig. 581 
 in which a removable key, instead of the ordinary, 
 fixed key, is employed for opening and closing the 
 switch. 
 
Swi.] 
 
 653 
 
 [Sys. 
 
 Switch, Four- Way A term some- 
 times employed in place of four-point switch. 
 (See Switch, Four-Point!) 
 
 Switch, Jack A term sometimes 
 
 employed in place of spring-jack. (See 
 Spring-Jack!) 
 
 Switch, Left-Hand Trolley In a 
 
 system of electric street railways a trolley 
 switch designed for use at a point where a 
 branch trolley leaves the main line to the 
 left-hand side in the going direction. 
 
 Switch, LeYer Any form of switch 
 
 in which the circuit is closed or opened by 
 means of the movement of a lever arm. 
 
 Switch, Push A switch included in 
 
 a push case and operated by means of a push 
 button. 
 
 In push switches successive motions of the but- 
 ton make or break the circuit. 
 
 Switch, Quick-Break A switch by 
 
 means of which a circuit is rapidly or quickly 
 broken. 
 
 Switch, Right-Hand Trolley In a 
 
 system of electric street railways a switch de- 
 signed for use at a point where a branch 
 trolley wire leaves the main line to the right 
 in the going direction. 
 
 Switch, Rocking A form of switch 
 
 operated by means of an electro-magnet by 
 which storage cells are automatically removed 
 from the circuit of the charging dynamo to 
 prevent the battery from discharging through 
 it in case the voltage of the dynamo falls 
 below the E. M. F. of the battery. 
 
 Switch, Standard Trolley In a 
 
 system of electric railways the device em- 
 ployed to hold together the trolley wires at 
 any point where the wire branches, and for 
 automatically guiding a trolley wheel along 
 the wire over the track taken by the car. 
 
 Switch, T. P. A contraction for 
 
 Triple-Pole Switch. (See Appendix Switch, 
 Triple-Poie, 
 
 Switch, Three-Way A term some- 
 times employed in place of three-point switch. 
 (See Switch, Three-Point?) 
 
 Switch, Three- Way Trolley In a 
 
 system of electric street railways, a trolley 
 switch designed for use at a point where the 
 line branches in three directions. 
 
 Switch, Triple-Pole A switch con- 
 sisting of a combination of three separate 
 switches for opening or closing the three cir- 
 cuits at the same instant. 
 
 Symmetrical Electrometer. (See Appen- 
 dix Electrometer, Symmetrical?) 
 
 Symphonance. A word proposed in place 
 of resonance. (See Resonance, Electric?) 
 (See Appendix Resonance, Acoustic?) 
 
 Synchronous-Multiplex Telegraph. (See 
 Appendix Telegraph, Synchronous-Multi- 
 plex?) 
 
 Synthesis, Electro The combina- 
 tion of electro-positive and electro-negative 
 radicals under the influence of electricity. 
 
 Syringe, Battery A syringe ar- 
 ranged to readily transfer the acid or spent 
 liquids from a voltaic cell or batter}' for the 
 introduction of fresh liquid. 
 
 System, Delta Tri-Phase A tri- 
 
 phase system in which the terminal connec- 
 tions resemble in form the Greek letter delta. 
 
 System, Electrically Tuned A 
 
 term sometimes employed for a circuit or 
 system of circuits that has been brought into 
 electrical resonance with another circuit or 
 system of circuits. (See Resonance, Elec- 
 tric.) 
 
 System, Fiye-Wire A system sim- 
 ilar in its arrangements to the three-wire 
 system in which four dynamos are connected 
 to five wires or conductors. (See System, 
 Three- Wire?) 
 
 In such a case there are three wires or con- 
 ductors occupying the position corresponding in 
 general to the neutral wire or conductor in a 
 three-wire system. 
 
 System, Four- Wire A system sim- 
 ilar in its general arrangement to the three- 
 wire system, in which three dynamos are 
 connected to four wires or conductors. (See 
 System, Three-Wire?) 
 
 In such a case there are two wires or conduct- 
 ors occupying in general a position correspond- 
 
Sys.] 
 
 654 
 
 [Tel. 
 
 ing to the neutral wire of the three-wire system. 
 (See System, Three- Wire.) 
 
 System, Municipal, of Electric Lighting 
 
 A series system of incandescent light- 
 ing invented by Edison for use in cities, par- 
 ticularly for street or window lamps, and 
 operated at a total continuous current pressure 
 of 1,000 volts. 
 
 System, Six-Wire A system sim- 
 ilar in general to the three-wire system in 
 which five dynamos are connected to six 
 conductors or leads. (See Appendix Sys- 
 tem, Five- Wire?) 
 
 System, Y Tri-Phase A tri-phase 
 
 system in which the terminal apparatus re- 
 sembles in form the capital letter Y. 
 
 t. A symbol used for time. 
 
 t : m. An abbreviation proposed for revo- 
 lutions per minute, a practical unit of angular 
 velocity. 
 
 T. P. Switch. (See Appendix Switch, 
 T. P.) 
 
 Tap Wire in Quadruples Telegraphy. 
 (See Appendix Wire, Tap, in Quadruplex 
 Telegraphy?) 
 
 Tape, Kerite A kerite covered in- 
 sulating tape. 
 
 Tape, Rubber Insulating tape 
 
 made of rubber. 
 
 Tapper Key. (See Appendix Key, Tap- 
 per.} 
 
 Tapper, Magneto A term some- 
 times employed in place of magneto key. 
 (See Key, Magneto-Electric?) 
 
 Tapper, Morse A form of tele- 
 graphic key provided with two contacts, one 
 in front and the other in the back, arranged 
 so that the depression of the key makes one 
 contact and breaks the other. 
 
 Teeth, Pacinotti A term some- 
 times employed in place of Pacinotti pro- 
 jections. (See Projections, Pacinotti?) 
 
 Telegram. A telegraphic dispatch or com- 
 munication. 
 
 Literally, anything written by means of a tele- 
 graph. 
 
 Telegraph. Any instrument or combina- 
 tion of instruments for conveying a commu- 
 nication or dispatch to a distance by means 
 other than the unassisted voice. 
 
 Telegraph, Acoustic A general 
 
 term embracing the apparatus employed in 
 acoustic telegraphy. (See Telegraphy, 
 Acoustic?) 
 
 Telegraph, Automatic A general 
 
 term embracing the apparatus employed in 
 automatic or machine telegraphy. (See 
 Telegraphy, Automatic?) 
 
 Telegraph, Chemical A general 
 
 term embracing the apparatus employed in 
 chemical telegraphy. (See Telegraphy 
 Chemical?) 
 
 Telegraph, Contraplex A general 
 
 term embracing the apparatus employed in 
 contraplex telegraphy. (See Telegraphy, 
 Contraplex?) 
 
 Telegraph, Dial A general term 
 
 embracing the apparatus employed in dial 
 telegraphy. (See Telegraphy, Dial?) 
 
 Telegraph, Diplex A general term 
 
 embracing the apparatus employed in diplex 
 telegraphy. (See Telegraphy, Diplex?) 
 
 Telegraph, Duplex A general term 
 
 embracing the apparatus employed in duplex 
 telegraphy. (See Telegraphy, Duplex, 
 Bridge Method of. Telegraphy, Duplex, 
 Differential Method of.) 
 
 Telegraph, Electric An electrical 
 
 instrument for conveying a communication 
 or dispatch to a distance by means other than 
 the unassisted voice. 
 
 Electric telegraphs are of a great variety of 
 forms. They may be divided into classes, either 
 according to the number of dispatches they can 
 simultaneously transmit, or according to the 
 
Tel.J 
 
 655 
 
 [Tel. 
 
 method employed for transmitting or receiving 
 the dispatches. 
 
 According to the number of messages they can 
 transmit simultaneously, telegraphs are divided 
 into duplex, diplex, contraplex, quadruplex, 
 multiplex, phonoplex, harmonic, synchronous- 
 multiplex, etc., etc. 
 
 According to the differences in the method of 
 transmitting and receiving the messages, they are 
 divided into the electro-magnetic, the needle, 
 the chemical, the dial, the fac-simile, the writing, 
 the acoustic, the speaking, the induction, the 
 automatic, the fire-alarm, etc., etc. 
 
 Telegraph, Electro-Magnetic A 
 
 general term embracing the apparatus em- 
 ployed in the various systems of electro- 
 magnetic telegraphy. 
 
 Telegraph, Fac-Simile A general 
 
 term embracing the apparatus employed in 
 fac-simile telegraphy. (See Telegraphy, Fac- 
 similed) 
 
 Telegraph, Fire-Alarm A general 
 
 term embracing the apparatus employed in 
 fire-alarm telegraphy. (See Telegraphy, 
 Firt-Alarm.) 
 
 Telegraph, Harmonic A general 
 
 term embracing the apparatus employed in 
 harmonic telegraphy. (See Telegraphy, 
 Gray's Harmonic Multiple?) 
 
 Telegraph, Induction A general 
 
 term embracing the apparatus employed in 
 induction telegraphy. (See Telegraphy, In- 
 duction?) 
 
 Telegraph, Multiplex A general 
 
 term embracing the apparatus employed in 
 multiplex telegraphy. (See Telegraphy, 
 Multiplex.} 
 
 Telegraph, Needle A general term 
 
 embracing the apparatus employed in needle 
 telegraphy. (See Telegraphy, Needle Sys- 
 tem of.) 
 
 Telegraph, Phonoplex A general 
 
 term embracing the apparatus employed in 
 phonoplex telegraphy. (See Telegraphy, 
 Phonoplex.') 
 
 Telegraph, Quadruplex A general 
 
 term embracing the apparatus employed in 
 quadruplex telegraphy. (See Telegraphy, 
 
 Quadruplex, Bridge Method of. Teleg- 
 raphy, Quadruplex, Differential Method 
 of.) 
 
 Telegraph, Speaking A general 
 
 term embracing the apparatus employed in 
 speaking telegraphy. (See Telegraphy, 
 Speaking. Telephone?) 
 
 Telegraph, Synchronous-Multiplex 
 
 A general term embracing the apparatus 
 employed in synchronous-multiplex teleg- 
 raphy. (See Telegraphy, Synchronous- 
 Multiplex?) 
 
 Telegraph, To To write or com- 
 municate at a distance by means of the tele- 
 graph. 
 
 Telegraph, Writing A general 
 
 term embracing the apparatus employed in 
 writing telegraphy. (See Telegraphy, 
 Writing?) 
 
 Telegraphic Box Sounder. (See Appen- 
 dix Sounder, Telegraphic Box?) 
 
 Telegraphic Interrupter. (See Appen- 
 dix Interrupter, Telegraphic?) 
 
 Telegraphic Interruption. (See Appen- 
 dix Interruption, Telegraphic?) 
 
 Telegraphic Polar Belay. (See Appen- 
 dix Relay, Polar, Telegraphic?) 
 
 Telegraphic Spark Coil. (See Appendix 
 Coil, Spark, Telegraphic?) 
 
 Telegraphist. One skilled in the art of 
 transmitting intelligence by means of the tele- 
 graph. 
 
 Telegraphy, Air A term some- 
 times employed for induction telegraphy. 
 (See Telegraphy, Induction?) 
 
 The term air telegraphy has been applied on 
 account of the fact that the electric impulses on 
 one line wire or conductor are transmitted across 
 an air space to a neighboring line wire or con- 
 ductor, *'. e., the air acts as the dielectric through 
 which the induction takes place. 
 
 Telegraphy, Steno A system of 
 
 telegraphy in which the sounds of a word are 
 represented by characters in place of letters. 
 
 Steno-telegraphy differs from ordinary telegra- 
 phy in the same manner that shorthand writing 
 differs from longhand writing. 
 
Tel 
 
 656 
 
 [Ten. 
 
 The object of steno-telegraphy is, of course, to 
 insure increased economy in speed. 
 
 Tele-Indicator. (See Appendix Indi- 
 cator, Tele.) 
 
 Tele-Meteorograph. A form of meteoro- 
 graph. (See Appendix Meteorograph.} 
 
 Telephone Indicator. (See Appendix 
 Indicator, Telephone.) 
 
 Telephone, Pan A word proposed 
 
 for a certain sensitive form of telephone. 
 
 The particular form of telephone for which the 
 name pan-telephone was proposed was an instru- 
 ment with a microphone transmitter. 
 
 Telephone, Sensitiveness of The 
 
 ability of a telephone properly to respond to 
 currents much smaller than those required 
 for the operation of some other telephonic 
 apparatus. 
 
 The telephone is characterized by its extreme 
 sensitiveness, requiring, as it does, for its opera- 
 tion a very small current. It is for this reason 
 that the current produced in the telephone circuit 
 by the induction of neighboring conductors 
 causes the annoying cross-talk in the telephone. 
 
 Telephone, Thermo A telephone 
 
 transmitter consisting of a tense wire, one end 
 of which is connected with the transmitting 
 diaphragm, placed in circuit with a receiving 
 telephone battery, and having a current pass- 
 ing through it of sufficient strength to heat it. 
 
 On speaking near the wire the waves in the 
 air periodically cool the wire, and its resistance 
 varies, and accordingly the current in the line 
 varies. A thermo receiver is made in a similar 
 manner, and the telephone current heats the 
 wire periodically and sets the diaphragm in 
 motion. 
 
 Telephone Time Check. (See Appendix 
 Check, Telephone Time) 
 
 Telephonic Meter. (See Appendix 
 Meter, Telephonic) 
 
 Telephonist. One skilled in the art of 
 telephony. 
 
 Telephony. The art of transmitting intel- 
 ligence by the use of the telephone. (See 
 Telephone) 
 
 Telephony, Duplex A system of 
 
 telephony by means of which a single line 
 
 wire or conductor can be simultaneously used 
 by two subscribers. 
 
 Telephony, Multiplex A system of 
 
 telephony by means of which a single line 
 wire or conductor can be simultaneously 
 used by a number of subscribers. 
 
 Tele-radiophone. A form of radiophone 
 arranged for the simultaneous transmission 
 of telegraphic and telephonic messages. i 
 
 Tele-radiophone, Auto-reversible or Mul- j 
 
 tiple A photo phone so arranged that 
 
 a number of telegraphic communications may 
 be simultaneously sent over a line wire or 
 conductor either all in one direction or part 
 in one direction and the remainder in oppo- 
 site directions. 
 
 The adjectives auto-reversible and multiple refer 
 to the fact that the messages can be transmitted 
 either all in the same direction, or a number in 
 one direction and the remainder in the opposite 
 direction. 
 
 A multiple auto-reversible tele-radiophone is an 
 invention of Mercadier's, based on the electrical 
 properties of selenium. 
 
 A number of selenium cells of variable resist- 
 ance are employed at the sending station, where 
 they are placed in the circuit of a battery of a few 
 elements and of a line wire extending to the re- 
 ceiving station, which is connected with a number 
 of receivers equal to the number of selenium 
 cells of variable resistance. 
 
 When luminous radiations are intermitted so as 
 to have the relative succession and duration of 
 the characters of the Morse alphabet, and these 
 impulses are sent over the line, they affect the 
 receivers at the other end. Each transmitter 
 sends into the line impulses of a definite rate and 
 only affects that receiving instrument at the other 
 end which is tuned in unison with it. The ap- 
 paratus is similar in its general action to Gray's 
 system of multiple harmonic telegraphy. (See 
 Telegraphy, Gray'' s Harmonic Multiple. ~) 
 
 Telpher Locomotive. (See Appendix 
 Locomotive, Telpher) 
 
 Temporary Socket. (See Appendix 
 Socket, Temporary) 
 
 Tension, Difference of An objec- 
 tionable term sometimes employed in place 
 of difference of potential. 
 
Ter.J 
 
 657 
 
 [Tho. 
 
 This use of the term should be strictly avoided, 
 as it is unnecessary and to a great extent mean- 
 ingless. 
 
 Terella. Literally, a little earth. 
 
 A sphere of hardened steel, or, as used by Gil- 
 bert, of loadstone, having marked thereon the 
 poles and equator, and so magnetized that the dis- 
 tribution of its magnetism shall resemble the dis- 
 tribution of the earth's magnetism. 
 
 Terminals, Sparking Terminals 
 
 between which a series of disruptive dis- 
 charges are passed,, 
 
 Sparking terminals are generally provided with 
 rounded or blunt or disc-shaped ends so as to pre- 
 vent a convective discharge from taking place. 
 
 Terrestrial Magnetic Induction. (See 
 Appendix Induction, Magnetic, Terres- 
 trial) 
 
 Tesla Discharge. (See Appendix Dis- 
 charge, Tesla?) 
 
 Tesla Frequencies. (See Appendix Fre- 
 quencies, Tesla.) 
 
 Test, Blavier's A test introduced 
 
 by Blavier for focalizing a single fault in a 
 single telegraphic line or conductor by meas- 
 uring the resistance at one end of the line 
 when the other end is alternately freed and 
 earthed. 
 
 Test Board. (See Appendix Board, 
 Test.) 
 
 Test, Loop A localization test for a 
 
 single fault in a loop of two telegraphic wires, 
 or in a complete metallic circuit. 
 
 Test, Overlap A localization test for 
 
 a single fault in a single telegraphic line by ob- 
 serving the resistance from each end and 
 deducing from the amount to which the sum 
 of the resistances overlap the total conductor 
 resistance of the line. 
 
 Tetrad Atom. (See Appendix Atom, 
 Tetrad.) 
 
 Theoretical Magnet (See Appendix 
 Magnet, Theoretical.) 
 Theory, Contact, of Electricity A 
 
 theory that ascribes the production of elec- 
 tricity in a voltaic cell, and to some extent 
 
 the production of electricity by friction, to the 
 contact of dissimilar substances or surfaces. 
 
 The act of contact is assumed to produce a 
 difference of potential. While mere contact may 
 unquestionably produce a difference of potential, 
 it requires the liberation of the chemical potential 
 energy of the metal of the positive plate of a 
 voltaic couple to maintain such differences of 
 potential as to produce a continuous flow of a 
 current. 
 
 Thermancy, Electro A term pro- 
 posed for that branch of electricity which 
 treats of the effects produced by an electric 
 current on the temperature of a thermo- 
 electric junction. 
 
 Thenno-Chemical Cell. (See Appendix 
 Cell, Thermo-Chemical.) 
 
 Thermo Chemistry. (See Appendix 
 Chemistry, Thermo.) 
 
 Thermo-Electric Generator. (See Ap- 
 pendix Generator, Thermo-Electric?) 
 
 Thermo-Electric Pair. (See Appendix 
 Pair, Thermo-Electric!) 
 
 Thermo-Electrometer. (See Appendix 
 Electrometer, Thermo?) 
 
 Thermo-Multiplier. A thermopile. 
 
 Thermo Pair. (See Appendix Pair, 
 Thermo?] 
 
 Thermo-Phone. An electrical instrument 
 for producing sounds by means of electrically 
 produced heat. 
 
 Thermostatic. Of or pertaining to a 
 thermostat. 
 
 Thermo-Tetephone. (See Appendix 
 Telephone, Thermo?) 
 
 Thermotic, Electro Of or pertain- 
 ing to heat produced by electricity. 
 
 Thimble Brush. (See Appendix Brush, 
 Thimble?) 
 
 Thomson. A name proposed for the unit 
 of conductivity. 
 
 The term mho is to-day generally employed 
 for the unit of conductivity. The plan of em- 
 ploying the names of celebrated deceased elec- 
 tricians is a good one and should not be departed 
 from, no matter how deservedly great the name 
 of the living electrician. 
 
Tho.] 
 
 658 
 
 [Tip. 
 
 Thomson's Bridge. (See Appendix 
 Bridge, Thomson's.} 
 
 Three-Phase Armature. (See Appendix 
 Armature, Three-Phased] 
 
 Three-Phase Currents. (See Appendix 
 Currents, Three-Phased) 
 
 Three-Phase Generator. (See Appendix 
 > Generator, Three-Phased] 
 
 Three-Phase Motor. (See Appendix 
 Motor, Three-Phase^ 
 
 Three-Way Switch. (See Appendix 
 Switch, Three-Way^) 
 
 Three-Way Trolley Switch. (See Appen- 
 dix Switch, Three- Way Trolley?) 
 
 Throw, Concentration A term 
 
 proposed by Squier for the deflection of a 
 magnetic needle by a current produced under 
 certain circumstances by a couple formed of 
 similar plates of iron or other paramagnetic 
 metals when exposed to chemical action while 
 under the influence of a magnetic field. 
 
 The concentration throw is a phenomenon mark- 
 ing the reversal of the direction of current pro- 
 duced by a couple of paramagnetic metals when 
 exposed to the action of a magnetic field. Squier 
 has observed in the case of a couple formed of 
 similar plates of iron exposed to the action of 
 nitric acid while in a ir >gnetic field, that under 
 certain conditions the effect of suddenly putting 
 on a magnetic field was to produce a less rapid 
 deflection of the galvanometer in the opposite 
 direction, so that the electrode which was formerly 
 protected, by being the negative plate of the 
 couple, was now the one acted on by becoming 
 the positive plate. 
 
 It is the above phenomenon for which Squier 
 proposes the term of concentration throw. 
 
 According to Squier, " The ' protective throw ' 
 is due to the actual attraction of the magnet for 
 the ion, and is always in the direction to protect 
 the more strongly magnetized parts, while the 
 ' concentrated throw ' is always in the opposite 
 direction, and depends upon the distribution of 
 the iron salts present in the solution, and the con- 
 vection currents in the liquid. The concentration 
 of the products of the reaction about the point, 
 would tend to produce a ferrous reaction instead 
 of a ferric reaction, and experiments show that a 
 
 higher electromotive force is obtained with cells 
 in which a ferrous reaction takes place than with 
 those in which a ferric reaction occurs, and this 
 change in the character of the reaction produced 
 by the concentration probably accounts, at least 
 in part, for the increased electromotive force at 
 the point." 
 
 Throw, Protective A term pro- 
 posed for the protection afforded by a mag- 
 netic field to paramagnetic metals exposed to 
 chemical action. 
 
 When two similar electrodes of iron, or other 
 paramagnetic metals, are exposed to chemical 
 action while under the influence of a strong mag- 
 netic field, they act as a voltaic couple and the 
 direction of the current produced depends on 
 the direction of the lines of magnetic force. In 
 the case of iron exposed to the action of nitric 
 acid, one electrode being in the shape of a pointed 
 cylinder and the other in the shape of a disc, 
 when the lines of magnetic force of the field coin- 
 cide in the direction with the length of the disc, 
 the current produced passes through the liquid 
 from the disc to the electrode, that is, from the 
 less magnetized electrode, to the more magnet- 
 ized electrode, the presence of the magnetic field 
 determining the direction of the current pro- 
 duced. In this, as in all similar cases of voltaic 
 couples, the negative plate or electrode is pro- 
 tected from the chemical action, the positive plate 
 alone being acted on. 
 
 The name protective throw is proposed by 
 Squier for the protection so afforded, who has 
 studied the phenomena. The proposed term 
 would appear to be an unfortunate one, the pro- 
 tection not being afforded by the throw of the 
 needle. 
 
 Tint-Electro. A term proposed for a 
 method of electric engraving. 
 
 Tip, Conducting Cord A blunted 
 
 or rounded conductor placed at one of the 
 ends of a wire for the purpose of readily in- 
 serting it into a binding post or into a hole in 
 a plate. 
 
 Tip, Conducting Cord, Separable 
 
 A cord and tip arranged so that the tip is 
 readily detachable from the cord. 
 
 The method of attachment can be insured ia 
 a variety of ways. A screw thread forms one of 
 the most obvious. 
 
Ton.] 
 
 659 
 
 [Tra. 
 
 Tonicity, Electro A term some- 
 times employed for electrotonus. (See 
 Electrotonus.) 
 
 Tool, Electric Machine A machine 
 
 tool of any character driven directly by elec- 
 tric power. 
 
 In electric machine tools the motor is generally 
 so placed that the moving power is thus connected 
 directly to the machine instead of transmitted to 
 it by means of belting. Among the many advan- 
 tages possessed by electric machine tools is that 
 such tools do away entirely with lines of shafting. 
 
 Top-Hat Curve. (See Appendix Curve, 
 Top-Hat.) 
 Torque, Running', of Motor The 
 
 torque exerted by a motor while running. 
 
 Torque, Starting-, of Motor The 
 
 torque exerted by a motor at the moment of 
 starting. 
 
 The starting torque in a well-constructed motor, 
 either of the alternating or continuous type, is 
 always in excess of the torque it exerts at full load. 
 
 Total Contact. (See Appendix Contact, 
 Total.} 
 Total Intensity of Earth's Magnetism. 
 
 (See Appendix Magnetism, Total Intensity 
 of Earth's?) 
 
 Touch, Divided A term sometimes 
 
 employed in place of separate touch. (See 
 Touch, Separate?) 
 
 Tourniquet, Electric A term some- 
 times employed in place of electric flyer. (See 
 Flyer, Electric?) 
 
 Transference, Convection The 
 
 transference of electricity in a liquid sub- 
 stance unattended by chemical changes in the 
 liquid. 
 
 Convection transference of electricity appears to 
 partake of the nature of atomic convection, the 
 charge being carried by each atom or group of 
 atoms in the direction in which the electricity is 
 being transferred. 
 
 Transform. To change or convert. 
 
 To convert or change the electromotive 
 force and consequently simultaneously to 
 change the current strength of the circuit by 
 any means. 
 
 Strictly speaking, a transformer is regarded as 
 changing the electromotive force. It therefore 
 produces at the same time changes in the value of 
 the current strength. When we speak of a step- 
 down transformer we refer to a transformer which 
 lowers or decreases the value of the electromotive 
 force, although, of course, at the same time, it 
 is employed to raise or increase the strength of 
 the current. 
 
 Tranformation. The act of transforming 
 or changing. 
 
 Transformation, as of Electromotive 
 
 Force A change in the value of the 
 
 electromotive force by means of an induction 
 coil or transformer. (See Transformer?) 
 
 Electric power is equal to the product of the 
 current by the electromotive force. By the use 
 of a transformer the electromotive force, and con- 
 sequently the current strength, are changed or 
 altered in value. Since in a well-constructed 
 transformer but very little energy is lost in trans- 
 formation, the product of C E, in the primary 
 very nearly equals the product of C' E', in the 
 secondary. It follows, therefore, that as the elec- 
 tromotive force increases in the secondary, the 
 current strength decreases and vice versa. 
 
 In the case of a transformer the transformation 
 is directly proportional to the ratio of the number 
 of turns of the primary and the secondary cir- 
 cuits. 
 
 Transformation, Current The act 
 
 of changing the value of the current in any 
 circuit by changes effected in its electromotive 
 force. (See Transformer?) 
 
 The act of changing the character of the cur- 
 rent, such, for example, as a direct into an alternat- 
 ing current or the reverse, or a single alternating 
 current of short wave length and high frequency 
 into triphase or polyphase currents. 
 
 It will be observed that the term current trans- 
 formation is employed in two distinct senses. 
 
 Transformation of Electric Force. (See 
 Appendix Force, Electric, Transforma- 
 tion of.) 
 
 Transformation, Ratio of The ratio 
 
 between the electromotive force produced in 
 the secondary of an induction coil or trans- 
 former and the electromotive force impressed 
 on the primary. 
 
Tra.] 
 
 660 
 
 [Tra. 
 
 The ratio of transformation depends on the rel- 
 ative number of turns of the secondary and pri- 
 mary coils of the transformer. In a well-con- 
 structed transformer there is very little energy lost 
 in producing a transformation by means of 
 mutual induction. Consequently the energy pro- 
 duced in the secondary must very nearly equal 
 the energy that has been expended in the 
 primary. Suppose, for example, that the number 
 of turns of the secondary of an induction coil is 
 one-fiftieth that of the primary ; then the difference 
 of potential induced in the secondary will be but 
 one-fiftieth that impressed on the primary. In 
 order to make the product of the current strength 
 and the difference of potential in the secondary 
 equal to the product of the current strength and 
 difference of potential in the primary, the cur- 
 rent strength in the secondary will have to be 
 fifty times greater than the current strength in 
 the primary; or, in other words, the product 
 of C and E, in the primary will very nearly 
 equal the product of C' and E' in the secondary, 
 *'. e., C E = C' E' nearly, assuming their lag 
 factors to be equal. 
 
 Transformer, Alternating-Current Ro- 
 tary A term sometimes employed for 
 
 an alternating current motor which at the 
 same time, by means of a suitable commu- 
 tator, delivers continuous currents on a sep- 
 arate circuit. 
 
 Transformer, Closed-Circuit A 
 
 term sometimes employed for closed-iron- 
 circuit transformer. (See Transformer, 
 Closed Iron Circuit!) 
 
 Transformer, Continuous Current 
 
 A term sometimes used for motor-dynamo 
 or dynamotor. (See Transformer, Constant 
 Current!) 
 
 Transformer, Direct-Current Rotary 
 
 A term sometimes employed for a motor- 
 generator. (See Generator, Motor.} 
 
 Transformer, High-Frequency A 
 
 transformer in which the frequency of the 
 currents employed is high. 
 
 Transformer, Iron-Loss in A loss 
 
 of energy in a transformer due to magnetic 
 hysteresis or molecular magnetic friction and 
 to the setting up of eddy or Foucault currents 
 in the iron. 
 
 According to Steinmetz, there is no sensible 
 magnetic viscosity in a transformer up to 204.5 
 complete periods per second. If the eddy or 
 Foucault currents are excluded, the hysteresis loss 
 of a transformer can, up to 200 complete periods 
 per second, be exactly predetermined by calcula- 
 tions based on tests at slow cycles, magnetic 
 viscosity being absent. 
 
 Transformer, Low-Frequency 
 
 A transformer in which the frequency of the 
 currents employed is low. 
 
 Transformer, Non-Polar A term 
 
 sometimes employed in place of closed-iron- 
 circuit transformer. (See Transformer, 
 Closed Iron Circuit!) 
 
 Transformer, Open-Circuit A term 
 
 frequently employed for open-iron-circuit 
 transformer. (See Transformer, Open Iron 
 Circuit!) 
 
 A variety of open-circuit transformer is shown 
 in Fig. 582. 
 
 fig. 58 2. Open- Circuited Transformer, 
 
 Transformer, Polar A term some- 
 
 times employed for open-circuit transformer. 
 (See Appendix Transformer, Open-Cir- 
 cuit!) 
 
 Transformer, Rotary A term gen- 
 erally employed for the combination of a 
 motor and generator in one machine, /. e., 
 one armature and one motor. 
 
 Sometimes employed in place of a con- 
 tinuous current transformer. (See Trans- 
 former, Constant Current. 
 
 The rotary transformer is employed either to 
 transform continuous currents into continuous 
 currents of different potential, in which case its 
 armature contains two windings, the generator 
 
Tra.] 
 
 661 
 
 [Tri. 
 
 winding and the motor winding, and the ratio of 
 transformation is equal to the ratio of the turns 
 of the two windings; or for converting alternate 
 or polyphase currents into continuous currents, 
 in which case if the maximum alternate current 
 potential equals the continuous current potential, 
 it generally contains one armature winding only, 
 which is connected, to the continuous current 
 commutator, and at two, three or four equidistant 
 points to collector rings. 
 
 Such rotary transformers are used extensively 
 in long-distance power transmission for convert- 
 ing the alternating or polyphase currents into 
 continuous currents for railway circuits, or for 
 supplying alternating current circuits, or for elec- 
 tric welding. 
 
 The term rotary transformer should not be con- 
 founded with rotary current transformer. (See 
 Transformer, Rotary Current.) 
 
 Transformer, Static A term some- 
 times employed for an ordinary transformer 
 as distinguished from a rotary transformer. 
 (See Appendix Transformer, Rotary?) 
 
 Transforming. Converting or changing 
 the electromotive force and consequently the 
 current strength in any circuit. 
 
 Transition Resistance. (See Appendix 
 Resistance, Transition?) 
 
 Translating Telegraphic Station. (See 
 
 Appendix Station, Translating Tele- 
 graphic.} 
 
 Translation Lag. (See Appendix Lag, 
 Translation?) 
 
 Translation, Manual In telegra- 
 phy, especially in sub-marine telegraphy, the 
 translation of a message from one circuit 
 directly to another by an operator, who trans- 
 mits to the second circuit, direct from sig- 
 nals received on the first, without writing 
 dowji or transcribing the message. 
 
 Transmitter, Automatic Telegraphic 
 
 An apparatus employed in a system 
 
 of automatic telegraphy for sending or trans- 
 mitting the prepared messages. 
 
 The message for automatic telegraphy is pre- 
 pared by properly punching or perforating a slip 
 or fillet of paper. This fillet is passed through 
 a transmitter so as to transmit automatically. 
 
 Transposition. In telephony a reversal in 
 the relative position of two parallel conductors. 
 
 Transpositions are made in conducting wires 
 in order to neutralize the electromotive forces 
 produced by neighboring currents. 
 
 Trap, Burglar Alarm A spring 
 
 burglar-alarm contact held in an open posi- 
 tion by the pull of a string against the action 
 of a spring. 
 
 The slightest disturbance of the spring 
 draws the contact in one direction, and the 
 destruction of the string permits the spring 
 to draw it in the opposite direction, in 
 either case insuring the closing of a circuit 
 and the ringing of an alarm bell. 
 
 Treated Coked Filament. (See Appen- 
 dix Filament, Treated Coked?) 
 
 Tree Insulator. (See Appendix Insu- 
 lator, Tree?) 
 
 Tregadyne. A term proposed by Houston 
 and Kennelly for a million million dynes, or 
 a million megadynes, or io 12 dynes. 
 
 Trega. A prefix proposed by Houston 
 and Kennelly for a million million or io 12 . 
 
 Tregerg. A term proposed by Houston 
 and Kennelly for a million million ergs, or a 
 million megergs, or io 12 ergs. 
 
 Tregohm. A term proposed by Houston 
 and Kennelly for a million million ohms, or 
 a million megohms, or io 12 ohms. 
 
 Triad Atom. (See Appendix Atom, 
 Triad.} 
 
 Trico. A term proposed by Houston and 
 Kennelly for the million millionth part, or 
 io- 12 . 
 
 Tricofarad. A term proposed by Houston 
 and Kennelly for the millionth part of a 
 microfarad, or io~ 12 farad. 
 
 Trigger, Door 
 
 A device by means 
 
 of which notice is given of the opening or 
 closing of a door or window. 
 
 Trigger, One-Way Door A door 
 
 trigger which operates on the opening of the 
 door only. 
 
 Trigger, Two-Way Door A door 
 
 trigger which operates both when the door is 
 opened and when it is closed 
 
Tri.] 
 
 662 
 
 Trip, Door, Electric A device for 
 
 ringing a bell so as to announce the entrance 
 of a customer. 
 
 The bell is rung only when the door passes the 
 trip, but does not ring when the door is opened, 
 or when it is being closed. 
 
 Tri-Phase Armature. (See Appendix 
 Armature, Tri- Phase?) 
 
 Tri-Phase Current. (See Appendix 
 Current, Tri-Phase?) 
 
 Tri-Phase Generator. (See Appendix 
 Generator, Tri-Phase. } 
 
 Tri-Phase Motor. See Appendix Motor, 
 Tri-Phase. } 
 
 Triphased Alternating Currents. (See 
 
 Appendix Currents, Triphased, Alternat- 
 ing.} 
 
 Turtle-Back Electro. (See Appendix 
 Electro, Turtle-Back?) 
 
 Two-Phase Alternator. (See Appendix 
 Alternator, Two-Phase?) 
 
 Two-Phase Armature. (See Appendix 
 Armature, Two-Phase?) 
 
 Two-Phase Generator. (See Appendix 
 Generator, Two-Phase.} 
 
 Two-Phase Motor. (See Appendix Mo- 
 tor, Two-Phase?) 
 
 Two-Pole Dynamo-Electric Machine. 
 
 (See Appendix Machine, Dynamo-Electric, 
 Two-Pole.) 
 
 Two-Thousand Candle-Power Arc, Defi- 
 nition for (See Appendix Arc, Two- 
 Thousand Candle-Power, Proposed Defini- 
 tion for.} 
 
 Two-Way Door Trigger. (See Appendix 
 Trigger, Two- Way, Door} 
 
 Triple-Pole Switch. (See Appendix 
 Switch, Triple-Pole?) 
 
 Tri-Polar Indicator. (See Appendix 
 Indicator, Tri-Polar} 
 
 Trolley Base Frame. (See Appendix 
 Frame, Trolley Base} 
 
 Trough, Plating A term some- 
 times employed in place of plating bath. 
 (See Bath, Electro-Plating} 
 
 Tube, Lightning A fulgurite. 
 
 (See Fulgurite} 
 
 Tubular Current. (See Appendix Cur- 
 rent, Tubular.) 
 
 Tuning of Electrical Circuit. Altering 
 
 the period of a circuit or varying the capacity 
 or self-induction of the circuit so as to bring 
 it into resonance with another circuit. 
 
 Uui-Phase Armature Winding. (See Ap- 
 pendix Winding, Uni-Phase Armature} 
 
 Uni-Phase Motor. (See Appendix Mo- 
 tor, Um- Phase.} 
 
 Unipolar Stimulation of Nerve. (See 
 Appendix Stimulation, Unipolar, of a 
 
 Nerve} 
 
 Unit, C. G. S., of Volumetric Energy 
 
 (See Appendix Energy, Volumetric, C. G 
 S. Unit of} 
 
 Unlighted Segment of Aurora. (See 
 Appendix Segment, Unlighted, of Aurora} 
 
 Unmarked Magnetic Pole. (See Appen- 
 dix Pole, Magnetic, Unmarked} 
 
 Unsymmetrical Polyphase Motor. (See 
 Appendix Motor, Polyphase, Unsymmet- 
 rical} 
 
 Upper Harmonics of Current. (See 
 Appendix Current, Upper Harmonics of.) 
 
Vac.] 
 
 663 
 
 [Yol. 
 
 T. A symbol used for volt or for volume. 
 The defining equation is V = L X L X L. 
 The same symbol is also employed for volt 
 
 v. A symbol used for velocity. 
 The defining equation is v = 7= 
 
 The same letter is proposed as a symbol for volt. 
 Its use should be limited to one or the other 
 quantity. 
 
 v. A symbol for the ratio between th e 
 units of resistance in the electrostatic and 
 electromagnetic C. G. S. system of measure- 
 ment ; *'. e., for velocity ratio. (See Ratio, 
 Velocity.) 
 
 Yacuum-Tube Lighting. (See Appendix 
 Lighting, Vacuum- Tube.) 
 
 Yariable Period of Telegraph Line. 
 
 (See Appendix Period, Variable, of Tele- 
 graph Line.) 
 
 Variation Magnetometer. (See Appen- 
 dix Magnetometer, Variation?) 
 
 Vector Potential. (See Appendix Po- 
 tential, Vector.} 
 
 Verdet's Constant. (See Appendix Con- 
 stant, Verdet's.) 
 
 Vertical Intensity of Earth's Magnetism. 
 
 (See Appendix Magnetism, Verticalln- 
 tensity of Earth's.) 
 
 Vertical Magnetic Needle. (See Appen- 
 dix Needle, Vertical Magnetic.) 
 
 Vibration Frequency. (See Appendix 
 Frequency, Vibration.) 
 
 Vibrator. An electromagnetic device pro- 
 vided on a siphon recorder for maintaining 
 the siphon in continual vibration so that ink 
 is thrown down upon the fillet of paper be- 
 neath. 
 
 Virtual Current (See Appendix Cur- 
 rent, Virtual.) 
 
 Visual Telegraphic Signal. (See Appen- 
 dix Signal, Telegraphic, Visual.) 
 
 Volatilization of Electric Conductor. 
 
 (See Appendix Conductor, Electric, Vola- 
 tilization of.) 
 
 Volt, International The value of 
 
 the international volt adopted by the Chicago 
 Congress of 1893 as equal to such an electro- 
 motive force that, steadily applied to a con- 
 ductor whose resistance is one international 
 ohm, will produce a current of one interna- 
 tional ampere, and which is represented suffi- 
 ciently well for practical use by y^ff of the 
 electromotive force between the electrodes of 
 the voltaic cell known as Clark's cell, at a 
 temperature of 15 C., and prepared in ac- 
 cordance with certain specifications. 
 
 Volt, Proposed A. I. E. E. Definition ftt 
 
 The product of the A. I. E. E. am 
 
 pere by the A. I. E. E. ohm. 
 
 Volt-Ammeter. A term proposed for any 
 electric instrument capable of measuring 
 either the volts or the amperes in a circuit, or 
 both. 
 
 A measurer of the volt-amperes or the 
 watts. 
 
 A wattmeter. 
 
 The word wattmeter would appear to be pref- 
 erable. 
 
 Volta-Electric. Of or pertaining to voltaic 
 electricity. (See Electricity, Voltaic.) 
 
 Volta-Electricity. Voltaic electricity. 
 (See Electricity, Voltaic.) 
 
 Yolta-Electrometer. A voltameter. (See 
 Voltameter.) 
 
 Volta-Electrometric. Producing voltaic 
 electricity. (See Electricity, Voltaic.) 
 
 Volta-Electromotire Force. (See Ap- 
 pendix Force, Volta-Electromoti-ve.) 
 
 Volta-Plast A word proposed for the 
 voltaic battery employed in electrotyping. 
 
 The use of this word would appear to be en- 
 tirely unnecessary. There is nothing peculiar 
 about this employment of the voltaic battery. 
 
Vol.] 
 
 664 
 
 [VoL 
 
 Volta-Type. A word proposed for elec- 
 trotype. 
 
 The use of this word would appear to be en- 
 tirely unnecessary. The word electrotype is pref- 
 erable. 
 
 Voltagraphy. Electrotypy. 
 The word electrotypy would appear to be far 
 preferable. 
 
 Voltaic Battery, Element of (See 
 
 Appendix Element of Voltaic Battery?) 
 
 Voltaic Bow. (See Appendix Bow, Vol- 
 taic.} 
 
 Voltaic Cell, Callan (See Appen- 
 dix Cell, Voltaic, Callan.) 
 
 Voltaic Cell, Maynooth (See Ap- 
 pendix Cell, Voltaic, Maynooth?) 
 
 Voltaic Electromotive Force. (See Ap- 
 pendix Force, Electromotive, Voltaic?) 
 
 Voltaic Endosmose. (See Appendix 
 Endosmose, Voltaic?) 
 
 Voltaic Heat Cell. (See Appendix Cell, 
 Voltaic Heat?) 
 
 Voltaic Mag-net. (See Appendix Mag- 
 net, Voltaic?) 
 
 Voltaic Pair. (See Appendix Pair, 
 Voltaic?) 
 
 Voltaism. A word sometimes employed 
 in electro-therapeutics for treatment by means 
 of the voltaic current. 
 
 The production of electricity by means of 
 voltaic couples. 
 
 The latter use of this word was the meaning 
 given to it by Sturgeon in 1842, who defined it as 
 follows: "The production of electricity by the 
 association of metals and other organic bodies "by 
 the simple contact of inorganic bodies." 
 
 Voltmeter, Electrometer A volt- 
 meter in which the difference of potential to 
 be measured charges insulated conductors, 
 the electrostatic attractions and repulsions of 
 which produce a deflection of a suitably sus- 
 pended metallic needle. 
 
 A term frequently employed for voltam- 
 eter. (See Electrometer. Voltameter?) 
 
 Voltmeter, Galvanometer Any 
 
 form of galvanometer so arranged as to 
 readily measure difference of potential. 
 
 A term sometimes employed for a galva- 
 nometer. 
 
 Galvanometer-voltmeters may be constructed 
 in a great variety of forms. 
 
 In all such cases, however, the difference of 
 potential is measured by the deflection of a needle 
 of a galvano:-ieter by means of the magnetic field 
 produced by the current which flows through a 
 conductor connecting the two points whose differ- 
 ence of potential is to be measured. 
 
 In any galvanometer- voltmeter a magnetic field 
 produced, as above described, by the difference 
 of potential which is to be measured, may deflect 
 a magnetic needle against the following forces, 
 namely: 
 
 (i.) Against a magnetic field. (See Appendix 
 Voltmeter, Magnetic?) 
 
 (2.) Against the action of a spring. (See Ap- 
 pendix Voltmeter, Spring. ) 
 
 (3.) Against the action of gravity acting on a 
 weight. (See Appendix Voltmeter, Weight.') 
 
 Voltmeter, Magnetic An instru- 
 ment in which the magnetic field of a cur- 
 rent, which is proportional to the difference 
 of potential to be measured, deflects a mova- 
 ble needle against the action of the field of 
 a magnet. (See Voltmeter?) 
 
 Voltmeter, Spring An instrument 
 
 in which the magnetic field of a current, 
 which is proportional to the difference of po- 
 tential to be measured, deflects a movable 
 needle against the action of a spring. (See 
 Voltmeter?) 
 
 Voltmeter, Weight An instrument 
 
 in which the magnetic field of a current, which 
 is proportional to the difference of potential 
 to be measured, deflects a movable needle 
 against the action of a weight. (See Volt- 
 meter?) 
 
 Volume Density of Charge. (See Appen- 
 dix Charge, Volume Density of?) 
 
 Volumetric Energy. (See Appendix 
 
 Energy, Volumetric?) 
 6 Vol. 2 
 
Wan.] 
 
 665 
 
 [Whi. 
 
 W 
 
 W. A contraction used for the physical 
 quantity energy, whether it be electrical, ther- 
 mal, mechanical or chemical, or, in general, 
 to represent the product of the force by the 
 distance. 
 
 W. A symbol used for electric energy. 
 
 The defining equation is W = C E T. 
 
 The same letter is proposed as the symbol for 
 work and moment of a couple. 
 
 W. A symbol proposed for the moment of 
 a couple. 
 
 This letter is also employed as the symbol for 
 work. 
 
 The denning equation is F X D. 
 
 W. h. An abbreviation proposed for watt- 
 hour, the practical unit of electric energy. 
 
 Wand, Electric A term some- 
 times used for an electrophorus in the form 
 of a torch. 
 
 An electric wand is employed for gas lighting 
 by a spark produced by means of a small static 
 machine in the handle upon the electrophorus. 
 
 Watchman's Electric Clock. (See Appen- 
 dix Clock, Electric, Watchman's} 
 
 Water-Gramme Degree. (See Appendix 
 Degree, Water-Gramme!) 
 
 Watt-Efficiency of Secondary Battery. 
 (See Appendix Battery, Secondary, Watt- 
 Efficiency of.) 
 
 Watt, International The value of 
 
 the international watt, adopted by the Chicago 
 Congress of 1893, is equal to io 7 units of 
 power in the C. G. S. system, and which is 
 the work done at the rate of one joule per 
 second. 
 
 Watt, Proposed A. I. E. E. Definition for 
 
 The product of the square of the 
 
 A. I. E. E. ampere and the A. I. E. E. ohm. 
 
 Wares, Hertzian A term sometimes 
 
 employed for electro-magnetic waves. 
 
 Waves in the ether that are produced by oscil- 
 latory discharges passing through a circuit or by 
 a magnetic circuit undergoing variations in its 
 
 magnetic intensity. (See Electricity, Hertz's 
 Theory of Electro-Magnetic Radiation, or 
 Waves.) 
 
 Way Lease. (See Appendix Lease, 
 Way.) 
 
 Weber, A. I. E. E. Definition for 
 
 A name proposed for the practical unit of 
 magnetic flux, 
 
 A unit of magnetic flux having the value of 
 one absolute unit or line. 
 
 This unit is a modification of that proposed by 
 a Sub-Committee of the American Institute of 
 Electrical Engineers on Provisional Programme 
 for the International Electrical Congress held in 
 Chicago, U. S. A., in 1893, on the occasion of the 
 World's Columbian Exposition. 
 
 The term weber was formerly applied to the 
 unit of current; it never, however, came into 
 very extensive use in the United States. 
 
 Wedge Cut-Out -(See Appendix Cut- 
 Out, Wedge.} 
 
 Weeding-Ont of Harmonics. (See Ap- 
 pendix Harmonics, Weeding-Out of.} 
 
 Weeding-Out of Harmonics by Electrical 
 Resonance. (See Appendix Harmonics, 
 Weeding-Out of, by Electrical Resonance?) 
 
 Weight Voltmeter. (See Appendix 
 Voltmeter, Weight) 
 
 Wheel, Barker's A term some- 
 times applied to a Barker revolving contact 
 breaker. (See Appendix Breaker, Contact, 
 Barker's Revolving.} 
 
 Whirl, Contracting Magnetic A 
 
 magnetic whirl which is decreasing or mov- 
 ing in towards the electro-magnet or circuit 
 which is producing it. 
 
 When variations occur in the strength of 
 the magnetism produced by variations in the 
 strength of the current, expanding or contracting 
 whirls are produced around the conductor which 
 move outwards or from the conductor when the 
 strength of the magnetism is increasing, and in- 
 wards or towards the conductor when such 
 strength is decreasing. These whirls produce 
 
Whi.] 
 
 666 
 
 [Wir. 
 
 electro-magnetic waves in the surrounding ether 
 which are called Hertzian electro-magnetic 
 waves. (See Whirl, Expanding Magnetic. 
 Electricity, Hertz's Theory of.) 
 
 Whirls, Electro-Dynamic A whirl- 
 ing or rotary motion produced in a cloud of 
 copper oxide in a voltameter when traversed 
 by a powerful electric discharge while under 
 the influence of a magnetic field. 
 
 The direction of the rotation is opposite to the 
 hands of a watch before a north magnetic pole 
 and in the same direction as the hands of a watch 
 before a south pole. 
 
 Winding, Differential A ny double 
 
 winding of the magnet coils such that the 
 two fields produced thereby are opposed to 
 each other. 
 
 Winding, Single-Phase Armature 
 
 A uni-phase armature winding. (See Ap- 
 pendix Winding, Uni-Phase Armature?) 
 
 Winding, Uni-Phase Armature 
 
 The winding of the armature of a motor such 
 as to enable it to be operated by uni-phase 
 currents. 
 
 Windings, Phase The separate 
 
 windings on the armature of a polyphase 
 motor. (See Appendix Motor, Polyphase?) 
 
 Windmill, Electric A term some- 
 times employed in place of electric flyer. 
 (See Flyer, Electric?) 
 
 Window or Blind Contact (See Appen- 
 dix Contact, Window or Blind?) 
 
 Wire, Annunciator Insulated wire 
 
 suitable for use in connection with annuncia- 
 tors, or other similar purposes. 
 
 Wire, Double Bronze A conduct- 
 ing wire furnished with an aluminium-bronze 
 core and a copper-brass envelope. 
 
 A double bronze wire possesses great tensile 
 strength, extreme toughness, and a comparatively 
 low electrical resistance. 
 
 A No. 1 1 standard gauge double bronze wire 
 has a breaking strain of 850 pounds and a re- 
 sistance of 443 ohms per mile at 60 degrees Fahr. 
 
 Such a wire is so tough that it will stand from 
 eight to ten bends of 180 degrees each in alter- 
 nate directions through a radius of 5 millimetres. 
 
 Wire, Idle, of Armature A term 
 
 sometimes employed in place of dead wire. 
 (See Wire, Dead, of Armature?) 
 
 Wire, Idle, of Armature of Dynamo 
 
 A term applied to that part of the wire on 
 the armature of a dynamo-electric machine 
 in which no useful electromotive force is pro- 
 duced. 
 
 The dead wire on an armature. (See Wire, 
 Dead, of Armature?) 
 
 Wire, Idle, of Armature of Motor 
 
 A term applied to that part of the wire on 
 the armature of a motor in which the field pro- 
 duced by the driving current never exercises 
 useful action in driving the motor, in so far as 
 no counter electromotive force is generated 
 in it. 
 
 Wire or Conductor, Balancing A 
 
 term sometimes employed for a neutral wire 
 or conductor of a three-wire system. 
 Wire, Tap, in Quadruples Telegraphy 
 
 The intermediate wire or conductor, 
 
 in a system of quadruplex telegraphy, which 
 divides the battery into two unequal parts, 
 called respectively the long end and the short 
 end. 
 
 Wires, Equalizing Two wires or 
 
 conductors, one of which is employed for 
 connecting the two positive brushes and the 
 other for connecting the two negative brushes 
 of two compounded dynamos when coupled in 
 parallel. 
 
 In general, wires or conductors employed for 
 equalizing electrical pressure or difference of 
 potential in two or more circuits. 
 
 In the coupling of two compound-wound 
 dynamos, the equalizing wires are connected one 
 to the two positive brushes and the other to the 
 two negative brushes of the coupled machines. 
 By these means the electrical pressure or differ- 
 ence of potential at the terminals of the two dyna- 
 mos is made equal, and consequently the currents 
 in the two fields are also made equal. 
 
 Wires, Slinging A term sometimes 
 
 employed in electro-plating for the wires or 
 conductors by which the articles that are to 
 be electro-plated are hung from the kathode 
 in the plating bath. 
 
Wir.] 
 
 667 
 
 I/on. 
 
 Wiring, Concentric Wiring by 
 
 means of concentric cables. (See Ap- 
 pendix Cable, Concentric.} 
 
 Working Current of Motor. See (Ap- 
 pendix Current, Working, of Motor.} 
 
 Working, Direct, of Telegraphic Sounder 
 
 A term sometimes employed for 
 
 the method in which a telegraphic sounder 
 is operated by means of the current re- 
 ceived from the line wire or conductor 
 from the distant station in contradistinc- 
 tion to the method where the receiving 
 instrument is operated by means of a 
 local battery. 
 
 Working, Double-Current Telegraphic 
 
 A term sometimes employed for 
 
 double-current signaling. (See Signaling, 
 Double Current. ) 
 
 Working Efficiency of Telegraphic Cir- 
 cuit. (See Appendix Circuit, Tele- 
 graphic, Working Efficiency of.) 
 
 Working, Polyphase A general 
 
 term employed to express the actual ap- 
 plication of polyphase currents. 
 
 In polyphase currents the armature of tht 
 motor is provided with separate sets of coils 
 grouped in two's, three's, etc., and put success, 
 ively into action at suitable periods. 
 
 Working, Single-Current Telegraphic 
 
 A term sometimes employed for 
 
 single-current signaling. (See Signaling, 
 
 Single-Current. ) 
 
 
 
 Writiug Telegraph. (See Appendix 
 
 Telegraphy. Writing. 
 
 Y Tri-Phase System. (See Appendix 
 System, Y Tri-Phase.} 
 
 Yards, Ampere The prpduct of 
 
 the current in amperes by the distance in 
 yards through which it passes. (See Feet, 
 Ampere. Turn, Ampere.} 
 
 Zero, Immediate False A term 
 
 employed in Wheatstone bridge measure- 
 ments for an observation made to that 
 position of the galvanometer needle as 
 zero, which is assumed, or which tends 
 to be assumed, immediately after the 
 opening of the circuit of the testing cur- 
 rent. 
 
 Zinc-Lead Accumulator. (See Appendix 
 Accumulator, Zinc-Lead.} 
 
 /one, Neutral, of Electrically Charged 
 
 Insulated Conductor That portion 
 
 of an insulated conductor, charged by 
 electrostatic induction, which lies approx- 
 imately midway between its positive and 
 negative ends. 
 
 Zone, Neutral, of Magnet A term 
 
 sometimes employed for equator of mag* 
 net. (See Magnet, Equator of.} 
 
APPENDIX B. 
 
 A. A symbol for ampere (Partly Interna- 
 tional usage). 
 
 A. or An. A contraction for anode. 
 
 a. A symbol proposed for acceleration. 
 
 a. A symbol for an angle. 
 
 A. B. C. Telegraph Instrument. 
 A step-by-step dial telegraph instrument 
 marked with the letters of the alphabet. 
 
 A. C. A contraction for alternating cur- 
 rent. 
 
 A. C. C. A contraction for anodic closure 
 contraction. 
 
 A. D. C. A contraction for anodic dura 
 
 tion contraction. 
 
 A. H. A contraction for ampere-hour. 
 A. H. E. A contraction for ampere-hour 
 
 efficiency. 
 A. O. C. A contraction for anodic opening 
 
 contraction. 
 
 A. T. A contraction for ampere-turn. 
 A. W. G. A contraction for American 
 
 wire gauge. 
 
 Abnormal Dispersion. Anomalous dis- 
 persion. 
 
 Abnormal Earth-Current. A tempo- 
 rary, stronger, and more variable earth 
 current than usual. 
 
 Abnormal Magnetization. Magnetiza- 
 tion generally in concentric layers of al- 
 ternate polarity, produced by oscillatory 
 or Leyden-jar discharges. (Obsolete.) 
 
 Abnormal Vapor - Densities. Vapor 
 densities whose values do not appear to 
 conform to Avogadro's hypothesis. 
 
 Abreast. Connected in multiple or paral- 
 lel. 
 
 Abscissa. The co-ordinate of a point 
 measured along the axis of abscissas. 
 
 Absolute. (1) Complete in itself. (2) Not 
 dependent on secondary bases. 
 
 Absolute Block System for Railroads. 
 A block system in which one train only 
 is permitted to occupy a given block, or 
 division of the road, at any one time. 
 
 669 
 
 Absolute Calibration. The determina 
 tion of the absolute reading of an electro- 
 meter, galvanometer, voltmeter, am- 
 meter, or other instrument. 
 
 Absolute Electro-Dynamometer. An 
 electro-dynamometer for the measurement 
 of electric currents in C. G. S. units by 
 reference to the moment of a bifllar 
 suspension and constants derived from 
 the winding of the coils. 
 
 Absolute Electrometer. An electrome- 
 ter in which the value of the electromo- 
 tive force is directly determined in abso- 
 lute units from the deflection of its mov- 
 able index. 
 
 Absolute Expansion. The real expan- 
 sion of a liquid, or the expansion it would 
 have independently of any change in the 
 dimensions of its containing vessel. 
 
 Absolute Galvanometer. Any galvano- 
 meter whose indications are directly de- 
 termined in absolute units of current. 
 
 Abs9lute Inductivity. The real indue 
 tivity of a medium as distinguished from 
 the ratio of its inductivity to the induc- 
 tivity of vacuum. 
 
 Absolute Insulation. The total insula- 
 tion of a circuit or conductor without 
 reference to its length. 
 
 Absolute Permittivity. The real per- 
 mittivity of a medium. as distinguished 
 from the ratio of its permittivity to the 
 permittivity of vacuum. 
 
 Absolute Photometric Standard. A 
 term for a fundamental standard of light 
 employed in photometric measurements, 
 in contra-distinction to a secondary 
 standard. 
 
 Absolute Unit of Current. (1) A cur- 
 rent of such a strength that when passed 
 through a wire one centimetre in length, 
 bent in the form of an arc of a circle one 
 centimetre in radius, will act with a force 
 of a dyne on a magnetic pole of unit 
 strength placed at the centre of the arc, 
 (2) A current of 10 amperes. 
 
4-bs.] 
 
 670 
 
 L ACl. 
 
 Absolute Unit of Electromotive 
 Force. (1) The C. G. S. unit of electro- 
 motive force. (2) The one-hundred mil- 
 lionth of a volt. 
 
 Absolute Unit of Inductance. A 
 length equal to one centimetre. (2) The 
 one billionth (10- 9 ) part of a henry. 
 
 Absolute Unit of Induction. A term 
 sometimes used for the absolute unit of 
 inductance. 
 
 Absolute Unit of Magnetomotive 
 Force. A unit of magnetomotive force 
 equal to 4ir multiplied by unit current 
 of one turn. 
 
 Absolute Unit of Resistance. (1) The 
 one thousand millionth of an ohm. (2) A 
 microhm. 
 
 Absolute Units. The centimetre- 
 gramme-second system of units. 
 
 Absolute Vacuum. (1) A space from 
 which all traces of residual gas have been 
 removed. (2) A term sometimes loosely 
 applied to a high vacuum. 
 
 Absolute Zero of Temperature. 
 
 (1) The temperature of a substance in 
 which its molecules are absolutely at rest, 
 or possess no kinetic energy. (2) A tem- 
 perature of approximately 273C. 
 Absorption. The taking in or drinking 
 in of one form of matter by another, such 
 as a gas, a vapor, or a liquid by any sub- 
 stance, usually a solid ; or of energy of 
 sound, light, neat or electricity by ordi- 
 nary matter. 
 
 Absorption Current. The current of 
 diminishing strength which flows into 
 a dielectric under electrification, and 
 which is partly capable of being restored 
 during continued discharge. 
 
 Absorption Dynamometer. The name 
 given to a dynamometer in which me- 
 chanical power is measured and at the 
 same time absorbed, in contradistinction 
 to a transmission dynamometer, in which 
 the power to be measured is all or nearly 
 all transmitted. 
 
 Absorption, Electric. The apparent 
 soaking of an electric charge into the 
 glass or other solid dielectric of a Leyden 
 jar or condenser. 
 
 Absorption of Sound. Acoustic absorp- 
 tion. 
 
 Absorption Spectrum. A spectrum 
 containing gaps or dark spaces due to ab- 
 sorption by some medium which the radi- 
 ation has traversed. 
 
 Absorptive. Possessing the power of ab- 
 sorption. 
 
 Absorptive Power. The power possessed 
 
 by certain substances of taking in and 
 condensing gases within their pores. 
 Acceleration. (1) The time-rate of change 
 of velocity. (2) Increase or decrease of 
 velocity. 
 
 Accumulated Electricity. Stored elec- 
 tricity, as in a condenser. 
 
 Accumulating Electricity .S t o r i n g 
 electricity. 
 
 Accumulation of Electricity. (1) The 
 collection of an electric charge in a Ley 
 den jar or condenser. (2) The increase in 
 an electric charge by devices called ac- 
 cumulators. (3) The production of a 
 charge by an influence machine. (4) The 
 collection of electric energy by storage 
 batteries or accumulators. 
 
 Accumulator. ( 1) A word sometimes ap- 
 plied to a current accumulator. (2) A 
 Leyden jar or condenser. (3) A secondary 
 or storage battery. 
 
 Accumulator Distribution. Distribu- 
 tion of electric energy by means of ac- 
 cumulators. 
 
 Accumulator Traction. Car traction in 
 which the motors are driven by storage 
 batteries carried on the car. 
 
 Acetometer. (1) A hydrometer gradua- 
 ted for determining the strength of com- 
 mercial acetic acid or vinegar. (2) A 
 acidometer. 
 
 Acheson Effect. The change in the elec- 
 tromotive force of the secondary of a trans- 
 former due to changes of temperature in 
 its core. 
 
 Achromatic. Free from false coloration. 
 
 Achromatic liens. A lens capable of 
 
 forming images free from false coloration. 
 
 Achromatic Ocular. An achromatic 
 
 eye-piece. 
 Achromatisable. Capable of being freed 
 
 from false coloration. 
 
 Achromatise. To free from false colora- 
 tion. 
 
 Achromatising. Freeing from false 
 coloration. 
 
 Acidimeter. An acidometer. 
 
 Acidometer. A hydrometer for measur- 
 ing the specific gravity of an acid liquid, 
 and thereby determining its degree of 
 acidity. 
 
 Aclinic. (1) Of or pertaining to no mag- 
 netic inclination. (2) Devoid of magnetic 
 inclination or dip. 
 
 Aclinic Line. (1) A line connecting 
 places on the earth's surface which have 
 no magnetic inclination. (2) The mag- 
 netic equator of the earth. 
 
Aco.] 
 
 671 
 
 [Act. 
 
 Acoustic. Of or pertaining to sound. 
 
 Acoustic Absorption. The absorption 
 by a vibrating body, of the energy of the 
 sound waves produced by another vibrat- 
 ing body. 
 
 Acoustic Interference. Interference of 
 sound waves. 
 
 Acoustic Resonance. (1) The increase 
 in the intensity of the sound emitted by 
 a sonorous body by means of sympathetic 
 vibrations set up in a co-periodic sounding 
 body. (2) The condition by virtue of 
 which a sonorous body is capable of having 
 sympathetic vibrations produced in it by 
 a neighboring sounding body. 
 
 Acoustic Synchronizer. An instrument 
 for indicating the synchronism of two 
 alternating currents or alternators, by an 
 acoustic apparatus in which silence is 
 produced at synchronism. 
 
 Acoustic Telegraph. Any telegraph 
 whose signals are appreciated by the ear, 
 as distinguished from a visual telegraph. 
 
 Acoustic Telegraphy. Sound tele- 
 graphy ; or, any system of telegraphy in 
 which the signals are received by sound, 
 in contradistinction to being received 
 visually. 
 
 Acoustic Tetanus. Tetanus produced by 
 alternating currents from an induction 
 coil, when its contact piece is vibrating 
 with sufficient rapidity to produce a musi- 
 cal note. 
 
 Acoutemeter, Electric. An apparatus 
 for electrically testing the delicacy of 
 hearing. 
 
 Actinic. Of or pertaining to the chemical 
 effect produced by light or other form of 
 radiant energy. 
 
 Actinic Photometer. A photometer in 
 which the intensity of light is measured 
 by the amount of chemical decomposition 
 it produces. 
 
 Actinic Ray. A ray of light, or other 
 form of radiant energy, possessing the 
 power of producing chemical action. 
 
 Actinism. The chemical effects of light. 
 
 Actino-Electricity. Electricity p r o- 
 duced in crystalline substances by the 
 action of radiant energy. 
 
 Actinograph. An apparatus for measur- 
 ing and recording the intensity of the 
 chemical effects of light. 
 
 Actinography. The method of produc- 
 ing records by the chemical effects of 
 light. 
 
 Actinometer. (1) An apparatus for meas- 
 uring the intensity of the chemical effects 
 of light. (2) A pyrheliometer. 
 
 Actinometer, Electric. An apparatus 
 
 for electrically measuring the intensity of 
 
 the chemically active rays present in any 
 
 radiation. 
 Actinpmetry. The science of measuring 
 
 the intensity of the chemical effects of 
 
 radiant energy. 
 Action Currents. Physiological currents 
 
 produced in a muscle or nerve during ita 
 
 activity. 
 
 Active Coil or Conductor. A coil or 
 conductor carrying an electric current. 
 
 Active Component of Exciting Cur- 
 rent. (1) The active current in an alter- 
 nating-current circuit as distinguished 
 from the wattless current. (2; In an 
 alternating-current circuit the component 
 of current which is in phase with the E. 
 M. F. (8) In an alternating-current cir- 
 cuit the product of the E. M. F. and the 
 effective or apparent conductance. 
 
 Active Current. (1) The working com- 
 ponent of a current in an alternating-cur- 
 rent circuit as distinguished from the wat- 
 tless component of current. (2) The com- 
 ponent of an alternating-electric current 
 that is in phase with the impressed electro- 
 motive force. 
 
 Active Electromotive Force. In an al- 
 ternating-current circuit that component 
 of the impressed electromotive force 
 which is expended in overcoming the 
 ohmic resistance, as distinguished from 
 the component which is expended in over- 
 coming the induced C. E. M. F. 
 
 Active Loop. Any single loop in a circuit 
 that is traversed by an electric current. 
 
 Active Mass. In electrolysis the quantity 
 of an electrolyte which is disassociated" 
 into its ions, and which is, therefore, 
 active in conveying the electrolysing cur- 
 rent. 
 
 Active Material of Storage Cell. The 
 substance or substances in a storage or 
 secondary cell, that undergo decompo- 
 sition while charging or discharging, and 
 which serve to store the electric en- 
 ergy. 
 
 Active Molecules. (1) Those molecules 
 in an electrolyte that, during the passage 
 of an electric current, are resolved into 
 their constituent ions and which, there- 
 fore, alone affect the molecular conduc- 
 tivity of the electrolyte. (2) The dis- 
 associated molecules in an electrolyte. 
 
 Active Plate of Voltaic Cell. A name 
 sometimes given to the zinc or other plate 
 of a voltaic or primary cell which is dis- 
 solved during action. 
 
 Active Polar Surface of Magnet. That 
 
Act/ 
 
 672 
 
 [Ady, 
 
 surface oi t, magnet from which the use- 
 ful flux emerges, or into which it enters. 
 
 Active Pressure. In an alternating-cur- 
 rent circuit that component of the im- 
 pressed pressure which is expended in 
 overcoming the olimic resistance. 
 
 Active Pressure A term sometimes em- 
 ployed for the pressure that is effective 
 in producing a current, as distinguished 
 from the impressed pressure. 
 
 Active Wire. That portion of the wire 
 on the armature of a dynamo or motor 
 that is passed through the inducing mag- 
 netic flux as distinguished from the re- 
 mainder of the wire sometimes called 
 " idle wire," which does not pass through 
 such flux. 
 
 Activity. (1) Power. (2) Rate-of-doing- 
 work. (3) The work done per second, in 
 uniform working. 
 
 Actual Cautery. A cautery produced by 
 the agency of a white heat. 
 
 Actual Energy. (1) Energy actually 
 employed in doing work, as distinguished 
 from energy that, though possessing the 
 power of doing work, 'is in the latent or 
 potential state. (2) Kinetic energy. 
 
 Actual Efficiency. Commercial effici- 
 ency. 
 
 Acute Angle. Any angle less than a right 
 angle or 90 degrees. 
 
 Acute-Angled Trolley-Crossing. A 
 contact plate,suspended at the point of in- 
 tersection of* two trolley wires crossing 
 at an acute angle. 
 
 Acyclic Region. (1) A region devoid of 
 cyclosis. (2) A simply connected region. 
 
 Adapter. (1) A screw-nozzle fitted to an 
 incandescent electric lamp and provided 
 with a screw-thread to enable it to be 
 readily placed on a gas bracket, or chan- 
 delier, in the place of an ordinary gas 
 burner. (2) A device whicli permits in- 
 candescent electric lamps of one manufac- 
 ture to be readily placed in the socket of 
 a lamp of another manufacture. (3) Ap- 
 paratus designed to permit the ready use 
 of a continuous-electric current employed 
 for incandescent lighting to produce the 
 feeble continuous currents employed in 
 electro-therapeutic work. 
 
 Adherence. The quality or property of 
 adhesion. 
 
 Adhesion. The mutual attraction which 
 exists between unlike molecules, as dis- 
 tinguished from the attraction of like 
 molecules, or cohesion. 
 
 Adhesion, Electric. The adhesion be- 
 tween surfaces due to the attraction of 
 unlike electrostatic charges. 
 
 Adhesion, Magnetic. The adhesion be- 
 tween surfaces due to magnetic flux. 
 
 Adhesive Tape. A tape covered with in- 
 sulating material and possessing adhesive 
 properties, employed for covering bared 
 conductors, at joints, or other similar 
 places. 
 
 Adiabatic Expansion. The expansion of 
 a gas which neither receives nor gives out 
 heat to the walls of the chamber in which 
 the expansion takes place, as distin- 
 guished from isothermal expansion. 
 
 Adiathermancy. Opacity to heat. 
 
 Adiathermanic. Of or pertaining to 
 adiathermancy. 
 
 Adielectric. (1) Not dilectric. (2) A term 
 proposed for substances, not dielectrics, 
 whose electric conductivity at ordinary 
 temperatures decreases as the temperature 
 increases. 
 
 Adjustable Angle Crossing. A form of 
 trolley crossing in which the angle of in- 
 tersection is adjustable. 
 
 Adjustable Condenser. A condenser 
 whose capacity can be readily varied 
 within certain limits. 
 
 Adjustable Resistance. A resistance 
 whose value can be readily varied within 
 certain limits. 
 
 Adjustable Rheostat. An adjustable re- 
 sistance. 
 
 Adjustable Vacuum Tube. A vacuum 
 tube employed for X-ray work whose 
 vacuum can be decreased by the action 
 of heat on a vaporizable substance. 
 
 Adjustable Wire Clip for Trolley 
 Wire. A clip, capable of adjustment as 
 to its position, inserted in an insulator 
 and designed for holding a trolley wire in 
 place. 
 
 Adjuster for Lamp Pendant. Any de- 
 vice for adjusting or altering the height 
 or position of a pendant lamp. 
 
 Adjusting Cleat. Any cleat that is ca- 
 pable of adjustment as to alignment or 
 height. 
 
 Adjustment. Any regulation of an ap- 
 paratus that will enable it properly to 
 perform its functions. 
 
 Adjustment of Relay. Such a regula- 
 tion of a receiving relay as will permit it 
 to readily respond to signals sent over the 
 line. 
 
 Admittance. (1) The reciprocal of the 
 impedance in an alternating-current cir- 
 cuit. (2) The apparent conductance of 
 an alternating-current circuit or con- 
 ductor. 
 
 Advanced Quadrature. In an alternate 
 
Ady.] 
 
 673 
 
 [Air. 
 
 ing- current circuit the condition of being 
 90 in phase ahead of some particular 
 E. M. F., flux, or current. 
 
 Adynamia System of Currents. A sys- 
 tem of currents so opposed to each other 
 in direction as to neutralize one another's 
 magnetic effects. 
 
 Aeolotropic. Heterogeneous with re- 
 spect to direction. 
 
 Aeolotropic Medium. (1) A medium 
 possessing different properties in different 
 directions. (2) A medium in which equal 
 stresses applied in any direction do not 
 produce equal strains. 
 
 jEpinus' Condenser. An early form of 
 air condenser. 
 
 Aerial Cable. An electric cable sus- 
 pended in the air. 
 
 Aerial Circuit. (1) That portion of a cir- 
 cuit which consists of aerial conductors 
 or lines. (2) A circuit of overhead wire. 
 
 Aerial Conductor. An overhead con- 
 ductor. 
 
 Aerial Line. An overhead line. 
 
 Aerial Telephone Cable. A suitably 
 supported overhead telephone cable. 
 
 Aerodromic Transportation. Trans- 
 portation by means of a balloon-supported 
 car over a suitable support guide. 
 
 Aerodynamics. The science which treats 
 of the forces produced by air in motion. 
 
 Aero-Ferric-Circuit Transformer. An 
 open-circuit transformer. 
 
 Aero-Ferric Inductance. The induct- 
 ance possessed by a coil or coils whose 
 magnetic circuit consists partly of air and 
 partly of iron. 
 
 Aero-Ferric Magnetic Circuit. A 
 magnetic circuit that is completed partly 
 through air and partly through iron. 
 
 Aerolite. A meteorite. 
 
 Aero-Therapeutics. Treatment of dis- 
 ease by means of air under pressures other 
 than that of the atmosphere. 
 
 After Currents. Electric currents pro- 
 duced in nerve or in muscular tissue, on 
 the cessation of a constant current which 
 has been flowing through it. 
 
 After Glow of Exhausted Bulb. A 
 fluorescent glow, observed in an ex- 
 hausted glass chamber, after its with- 
 drawal from electrostatic influence. 
 
 Age-Coating of Electric Incandescent 
 Lamp Chamber. A blackening of the 
 chamber of an electric incandescent lamp 
 due to the deposit thereon, during use, of 
 carbon, or other opaque substance. 
 
 Ageing of Alcohol, Electric. Artifl- 
 43 
 
 cially ageing alcohol by exposing it to tha 
 action of electrically generated ozone. 
 
 Ageing of Electric Incandescent 
 Lamp. A gradual decrease in the effi- 
 ciency of an electric incandescent lamp 
 due either to the age coating of its cham- 
 ber, or to the deterioration of its filament. 
 
 Ageing of Magnet. Treating a perma- 
 nent magnet for the purpose of rendering 
 its magnetic condition more permanent. 
 
 Ageing of Transformer. (1) A decrease 
 in the efficiency of a transformer owing 
 to the ageing of its core. (2) Fatigue of 
 transformer. 
 
 Ageing of Transformer Core. Increase 
 in the hysteretic coefficient in the iron 
 of a transformer core, during the first few- 
 months of its commercial operation, from 
 its continued magnetic reversals at com- 
 paratively high temperature. 
 
 Agglomerate Leclanche Cell. A form 
 of Leclanche cell which dispenses with 
 the porous cup by employing the carbon 
 and black oxide of manganese formed 
 into a solid mass by pressure. 
 
 Agitator for Plating Vat. A device for 
 ensuring a uniformity in the density of 
 the plating solution in a depositing vat, 
 by mechanical stirring. 
 
 Agonal. Of or pertaining to an agone. 
 
 Agone. (1) A line connecting places on 
 the earth's surface where the magnetic 
 needle points to the true geographical 
 north. (2) The line of no declination. 
 
 Agonic. Of or pertaining to an agone. 
 
 Agonic Line. (1) A line connecting ter- 
 restrial points having no declination or 
 variation. (2) The agone. 
 
 Air Battery. A form of voltaic battery 
 whose electromotive force is increased by 
 the direct absorption of oxygen from the 
 air. 
 
 Air Blast for Commutator. A jet of air 
 applied to the surface of the commutator 
 of a dynamo-electric machine to prevent 
 destructive flashing. 
 
 Air-Blast Transformer. A transformer 
 which is cooled by a blast of air. 
 
 Air Churning. The movement of the air 
 that occurs in the vicinity of the arma- 
 ture of a dynamo or motor during rotation 
 resulting in a loss of energy to the machine. 
 
 Air Condenser. A condenser in which 
 air is the dielectric. 
 
 Air-Cooled Transformer. (1) A trans- 
 former which is cooled by the passage 
 through it of convection currents of ait 
 set up by its increase of temperature 
 (2) An air-blast transformer. 
 
Air.] 
 
 674 
 
 [AIL 
 
 Air-Core Solenoid. A solenoid which 
 has no core other than air. 
 
 Air-Core Transformer. A transformer 
 which is destitute of a core other than 
 that of air. 
 
 Air-Expansion Lightning Arrester. 
 A form of lightning arrester in which the 
 arc, when formed, is blown out by the 
 expansion of a mass of confined air under 
 the influence of the heat of the arc. 
 
 Air Field. That portion of a magnetic 
 field in which the magnetic flux passes 
 through air only. 
 
 Air Film of Lamp Chamber. A film of 
 condensed air that tends to remain on the 
 walls of an exhausted lamp chamber after 
 the action of the air pump. 
 
 Air Gap. In a magnetic circuit, any gap 
 or opening containing air only. 
 
 Air Gap of Commutator. The air space 
 between contiguous segments in an air- 
 insulated commutator. 
 
 Air Insulation. An insulation obtained 
 by air, or by the action of air. 
 
 Air Ley den. An air condenser. 
 
 Air-Line Wire. That portion of a circuit 
 which consists of overhead wires, in con- 
 tradistinction to the portion which passes 
 through underground conduits, or 
 through a submarine cable. 
 
 Air Magnetic Circuit. A magnetic 
 circuit in which the flux passes wholly 
 through air. 
 
 Air Path. The path a disruptive discharge 
 takes through the air. 
 
 Air Pump. A device for removing air or 
 other gas from a containing vessel. 
 
 Air Reluctance. The reluctance of that 
 portion of a magnetic circuit which con- 
 sists of air. 
 
 Air Resistance of Dynamo. The me- 
 chanical resistance to the rotation of a 
 dynamo due to the surrounding air. 
 
 Air Space. (1) The space that exists be- 
 tween the surface of an armature and the 
 polar surface within which it rotates. 
 (2) The space between opposed surfaces 
 of a comb lightning-arrester. 
 
 Air-Space Cut-Out. A modified form of 
 paper cut-out in which the disc of paper 
 or mica is replaced by an air-space. 
 
 Air-Space Submarine Cable. A mul- 
 tiple-conductor submarine cable, having 
 a core in which an internal air space is 
 provided for separating the conductors. 
 
 Air Telegraphy. (1) Aerial telegraphy. 
 (2) Induction telegraphy. (3) Wireless tel- 
 egraphy. 
 
 Air- Washing of Lamp Filament. A 
 
 deleterious effect produced on the fila- 
 ment of an incandescent electric lamp by 
 the molecular bombardment of the resid- 
 ual gaseous atmosphere of its chamber. 
 Alarm, Electric. (1) Any automatic elec 
 trie device by which attention is calle* 
 to the occurrence of certain events, suck 
 as the opening of a door or window, the 
 stepping of a person on a mat or stair- 
 case, the rise or fall of temperature be- 
 yond a certain predetermined point, etc., 
 by the closing or opening of an electric 
 circuit. (2) A device for calling a person 
 to a telegraphic or telephonic instru- 
 ment. 
 
 Alarm Point. In a system of fire teleg- 
 raphy, any point from which an alarm 
 is sent out. 
 
 Alarm Wires of Submarine Cable. 
 Extra insulated wires imbedded in the 
 fibrous serving of a submarine cable, be- 
 tween the sheathing wires and the con- 
 ductor core, and capable of giving an 
 alarm when their insulation is affected 
 through injury to the cable, before the 
 working conductor or central core may 
 be injured. 
 
 Aligned Magnetomotive Force. The 
 magnetomotive force in a magnetic cir- 
 cuit containing iron, due to the aligning 
 of the molecular magnets of the iron 
 under the influence of the impressed 
 magnetic force or prime flux. 
 
 " Alive." (1) A name sometimes given 
 to a live wire or circuit. (2) An active 
 wire or circuit. 
 
 All-Day Efficiency of Transformer. 
 
 The ratio of the energy commercially 
 supplied by a transformer in 24 hours to 
 the energy absorbed by it from the mains 
 during that time. 
 
 All-Night Arc Lamp. A double-carbon 
 arc lamp. 
 
 Allotropic. Of or pertaining to allo- 
 tropism. 
 
 Allotropic State. A modification of a 
 substance by means of which, without 
 any change in chemical composition, it 
 acquires physical or chemical properties 
 differing from those it ordinarily pos- 
 sesses. 
 
 Allotropism. The state or condition re- 
 sulting from acquiring the allotropic 
 state. 
 
 Allotropy. The property of, or capacity 
 for, acquiring the allotropic state. 
 
 Alloy. A combination or homogeneous 
 mixture of two or more metallic sub- 
 stances. 
 
All]. 
 
 675 
 
 [Alt. 
 
 Alloy. To form a combination or homo- 
 geneous mixture of two or more metallic 
 substances. 
 
 Alphabetic Telegraph. (1) A telegraph 
 in which the letters of the message to be 
 sent are spelled out in succession from a 
 dial. (2) An A, B, C, telegraph. 
 
 Alteration Theory of Muscular or 
 Nerve Currents. A theory which 
 traces the origin of electric currents in 
 the nerves or muscular fibres to an alter- 
 ation from their original condition. 
 
 Alternate Currents. Alternating cur- 
 rents. 
 
 Alternating. Periodically changing in 
 direction. 
 
 Alternating Arc. (1) An alternating-cur- 
 rent arc. (2) An arc supplied from an 
 alternating-current circuit. 
 
 Alternating Continuous-Current Com- 
 mutating Machine. A secondary gen- 
 erator for transforming from alternating 
 to continuous currents by the aid of a 
 commutator. 
 
 Alternating-Current Arc. A voltaic arc 
 produced by alternating electric currents. 
 
 Alternating-Current Armature- Wind- 
 ing. A.n armature winding suitable for 
 the production of alternating currents. 
 
 Alternating - Current Dynamo - Elec- 
 tric Machine. A dynamo-electric ma- 
 chine producing alternating currents in 
 its external circuit. 
 
 Alternating-Current Electric Motor. 
 A motor driven by alternating electric 
 currents. 
 
 Alternating-Current Electro-Magnet. 
 An electro-magnet whose coils are 
 traversed by alternating Currents, and 
 which, although constantly reversing in 
 magnetism, yet possesses a continued at- 
 traction for its armature. 
 
 Alternating - Current Phase - Meter. 
 An apparatus for measuring the differ- 
 ence between the phases of two alternat- 
 ing currents. 
 
 Alternating - Current Potentiometer. 
 A potentiometer suitable for measuring 
 the difference of pressure in an alternat- 
 ing-current circuit. 
 
 Alternating-Current Power. (1) Elec- 
 tric power supplied through the medium 
 of alternating currents. (2) The product 
 of the effective alternating-current 
 strength, the effective pressure under 
 which that current is supplied, and the 
 power factor. (3) With sinusoidal elec- 
 tromotive forces and currents, the pro- 
 duct of the effective current strength, 
 
 the effective pressure under which that 
 current is supplied, and the cosine of the 
 phase-difference between the two. 
 
 Alternating-Current Pressure Indi- 
 cator. An alternating - current volt- 
 meter. 
 
 Alternating-Current Regulator. (1) A 
 regulator for maintaining constant the 
 pressure of an alternating-current gen- 
 erator. (2) A regulator for controlling 
 the strength of an alternating current. 
 
 Alternating-Current Rotary Trans- 
 former. A rotary transformer for 
 transforming alternating into continu- 
 ous-currents, or vice-versa. 
 
 Alternating-Current Transmission. 
 Transmission of power or energy by 
 means of alternating currents. 
 
 Alternating-Current Rush. (1) A term 
 sometimes applied to the first rush or 
 wave of alternating current passing into 
 the primary coil of a transformer at the 
 moment it is connected to the mains. (2) 
 A term sometimes applied to the oscilla- 
 tory discharge of a condenser. 
 
 Alternating-Current Working. Feed- 
 ing lamps, motors, or other receptive 
 devices by means of alternating cur- 
 rents. 
 
 Alternating Currents. (1) Currents 
 which flow alternately in opposite direc- 
 tions. (2) Currents whose directions are 
 periodically reversed. 
 
 Alternating Discharge. (1) A dis- 
 charge which periodically changes its 
 direction. (2) An oscillatory discharge. 
 
 Alternating Dynamo - Electric Ma- 
 chine. An alternating-current dynamo- 
 electric machine. 
 
 Alternating Electromotive Forces. 
 Electromotive forces whose directions 
 are periodically reversing. 
 
 Alternating Electrostatic Field. A 
 field of electrostatic flux whose direction 
 is periodically reversing. 
 
 Alternating Electrostatic Potential. 
 An electrostatic potential whose value is 
 periodically changing sign. 
 
 Alternating Influence Machine. An 
 electrostatic influence machine which de- 
 livers periodically alternating electric dis- 
 charges or currents. 
 
 Alternating Magnetic Field. A mag- 
 netic field the direction of whose flux 
 periodically changes. 
 
 Alternating Magnetic Potential. A 
 magnetic potential whose value is period- 
 ically changing sign. 
 
 Alternating Magnetic Call-Bell. A 
 
Alt]. 
 
 676 
 
 call-bell operated by the uncommuted 
 currents of a magneto-electric machine. 
 Alternating Magneto - Electric Ma- 
 chine. A magneto-electric generator 
 that produces alternating currents in its 
 external circuit. 
 
 Alternating Potential. A potential, 
 whether electrostatic, electric, or mag- 
 netic, that is periodically changing in 
 sign. 
 
 Alternating Sparking Distance. The 
 air space across which an alternating- 
 current disruptive-discharge would pass. 
 
 Alternation. (1) A change in direction. 
 (2) A change or reversal in the direction 
 of an electromotive force or current. (3) 
 A single vibration or oscillation as distin- 
 guished from a complete cycle or double 
 vibration. 
 
 Alternation of Current. A change in 
 the direction of a current. 
 
 Alternations. Successive changes in the 
 direction of a current or electro-motive 
 force. 
 
 Alternative Air-Path of Magnetic 
 Flux. In a ferric magnetic circuit a 
 field, outside the iron of the circuit, 
 through which a portion of the magnetic 
 flux passes. 
 
 Alternative Path. The path or circuit 
 taken by an impulsive discharge through 
 an insulator in preference to a conducting 
 path or circuit, of enormously smaller 
 ohmic resistance, open to the discharge. 
 
 Alternator. The name generally given 
 to an alternating-current dynamo or gen- 
 erator. 
 
 Amalgam. A combination or mixture of 
 a metal with mercury. 
 
 Amalgam, Electric. A substance with 
 which the rubbers of the ordinary fric- 
 tional electric machine are covered. 
 
 Amalgamate. To form into an amalgam. 
 
 Amalgamating. Forming into an amal- 
 gam. 
 
 Amalgamating Solution. A solution 
 of a salt of mercury employed for readily 
 amalgamating the zincs of a voltaic 
 battery. 
 
 Amalgamation. The act of forming into 
 an amalgam or effecting the combina- 
 tion of a metal with mercury. 
 
 Amalgamation of Zinc. Coating the 
 surface of the zinc of a voltaic cell with 
 mercury. 
 
 Amalgamator, Electric. An electrically 
 driven amalgamator for the treatment of 
 gold or silver ores with mercury. 
 
 Amazite. The name given to a particular 
 kind of insulating material. 
 
 Amber. A resinous substance generally 
 of a transparent yellow color. 
 
 American Morse Code. The Morse tele- 
 graphic code employed in America, as 
 distinguished from that employed in 
 other parts of the world. 
 
 American System of Telegraphy. 
 The Morse system of telegraphy as em- 
 ployed in America. 
 
 American Telegraphic Code. The 
 American Morse code of telegraphic sig- 
 nals. 
 
 American Twist Joint. A joint between 
 two conducting wires in which each end 
 is twisted around the other. 
 
 American "Wire Gauge. The name gen- 
 erally given to the Brown and Sharpe 
 wire gauge, in which the largest wire, 
 No. 0000, has a diameter of 0.46", the wire 
 No. 36, 0.005", and all other diameters are 
 in geometrical progression. 
 
 Ammeter. Any form of galvanometer 
 which is capable of measuring current 
 strength directly in amperes. 
 
 Ammeter Panel of Switchboard. In a 
 
 central station the panel of the switch- 
 board which carries the principal amme- 
 ter or ammeters. 
 
 Ammunition Hoist, Electric. An elec- 
 trically operated hoist employed for rais- 
 ing ammunition to the gun deck or turret 
 of a ship. 
 
 Amorphous. Possessing no definite crys- 
 talline form. 
 
 Amperage. The number of amperes pass- 
 ing in a cirquit in a given time. 
 
 Ampere. (1) The practical un , of electric 
 current. (2) A rate of flow of electricity 
 transmitting one coulomb per second. (3) 
 The current of electricity which would 
 pass through a circuit whose resistance is 
 one ohm, under an electro-motive force 
 of one volt. (4) A current of such a 
 strength as will deposit 1.118 milli- 
 grammes of silver per second from a spe- 
 cifically prepared solution of silver ni- 
 trate. 
 
 Ampere-Arc. A single conductor, bent 
 in the form of an arc of a circle, and used 
 in an electric balance for measuring cur- 
 rent. 
 
 Ampere-Balance. A balance form of 
 ammeter which measures currents of a 
 few amperes, or which determines a cur- 
 rent strength of one ampere. 
 
 Ampere-Centimetre. A proposed unit 
 of magnetic flux equal to the flux pro* 
 
Amp.] 
 
 677 
 
 [An*. 
 
 duced by one ampere flowing through a 
 circuit one centimetre in length. 
 
 Ampere-Foot. A unit of current strength 
 multiplied by the distance to which said 
 current is carried, employed in calculat- 
 ing the fall of electric pressure in distri- 
 buting mains. (2) The magnetic flux or 
 flux density developed in a coil. 
 
 Ampere-Hour. (1) A unit of electrical 
 quantity equal to the quantity of elec- 
 tricity conveyed by one ampere flowing 
 for one hour. (2) A quantity of elec- 
 tricity equal to 3600 coulombs. 
 
 Ampere-Hour Efficiency of Storage 
 Battery. (1) In a cycle of charge and 
 discharge, the ratio between the ampere- 
 hours taken out of a storage battery and 
 the ampere-hours put into it. (2) The 
 quantity efficiency of a storage battery 
 as distinguished from the energy effi- 
 ciency. 
 
 Ampere-Hour Meter. A meter which is 
 capable of measuring an electric supply 
 in ampere-hours. 
 
 Ampere-Hour Output of Storage Bat- 
 tery. The amount of useful electric 
 quantity produced by a storage battery 
 in ampere-hours. 
 
 Ampere-Meter. An ammeter. 
 
 Ampere-Minute. A unit of electrical 
 quantity equal to the electric quantity 
 conveyed by one ampere in one minute. 
 
 Ampere-Ring. A word sometimes used 
 for ampere-turn. 
 
 Ampere-Second. (1) A unit -of electric 
 quantity equal to the quantity of elec- 
 tricity conveyed by one ampere flowing 
 for one second. (2) A coulomb. 
 
 Ampere-Stream in Armature. The ag- 
 gregate current in amperes produced by 
 all the conductors on a dynamo armature. 
 
 Ampere-Tap. In a system of electric dis- 
 tribution a tap provided in a branch cir- 
 cuit for carrying off a current of one am- 
 pere. 
 
 Ampere-Turn. A unit of magneto-motive 
 force equal to that produced by one am- 
 pere flowing around a single turn of wire. 
 
 Ampere- Volt. A word sometimes used 
 for volt-ampere, cr watt. 
 
 Ampere-Yard. A proposed unit of elec- 
 tric current multiplied by distance 
 through which said current is carried, 
 sometimes employed in calculations. 
 
 Ampere-Winding. A word sometimes 
 used for ampere-turn ; i. e, , a single wind- 
 ing or turn through which one ampere 
 passes. 
 
 Ampere-per-Square-Centlmetre. A 
 
 unit of density of current expressed in 
 amperes-per-square-centimetre of normal 
 cross-section of conductor. 
 
 Ampere-per-Square-Inch. A unit of 
 density of current expressed in amperes 
 per-square-inch of area of normal cross- 
 section of conductor. 
 
 Ampere's Rule for Deflection of Nee- 
 dle. The north-seeking pole of a mag- 
 netic needle is deflected by a current to 
 the left-hand of an observer who is sup- 
 posed to be swimming in the current 
 while facing the needle. 
 
 Ampere's Theory of Magnetism. A 
 theory or hypothesis which ascribes the 
 cause of magnetism to the presence of 
 electric currents in the ultimate particles 
 of a magnet. 
 
 Amperian Currents. The electric cur- 
 rents that are assumed, in the Amperian 
 theory of magnetism, to flow in closed 
 circuits around the ultimate particles of 
 a magnet. 
 
 Amphigenic Charge. A name proposed 
 for an electric charge, whose surface den- 
 sity varies in sign. 
 
 Amplitude of Galvanometer Swing. 
 
 (1) In a series of ballistic galvanometer 
 deflections, the half sum of the deflection 
 or elongation from zero, on one side of the 
 scale, and the means of the preceding and 
 following elongations on the other side. 
 
 (2) When referred to radian measure the 
 ratio of the above quantity to the distance 
 of the scale from the mirror. 
 
 Amplitude of Simple-Harmonic Mo- 
 tion. The maximum cyclic value of a 
 simple-harmonic or simple-periodic vibra- 
 tion ; or, the distance in a straight line 
 from the median position to the position 
 of greatest elongation. 
 
 Amplitude of Vibration or "Wave. 
 The extent of the excursion of a simply 
 vibrating particle on either side of its vi- 
 brating point or point of rest. 
 
 Amyl-Acetate Standard. (1) A photo- 
 metric standard lamp of definite dimen- 
 sions burning amyl-acetate. (2) The- 
 Hefner-Alteneck standard lamp. 
 
 Amyloid. (1) A substance employed in 
 the manufacture of incandescent lamp 
 filaments produced by the action of sul- 
 phuric acid on cellulose. (2) Parchment- 
 ized cellulose. 
 
 Amyloid Filament. An incandescent 
 lamp filament made from amyloid. 
 
 Anaemic Cataphoresis. Cataphoretio 
 medication accompanied by the applica- 
 tion of bandages to retard local circula- 
 tion in the parts treated. 
 
An*.] 
 
 678 
 
 [Ang. 
 
 Anaesthesia. Insensibility to pain. 
 
 Anaesthesia, Electric. Nervous insen- 
 sibility obtained by electrical means. 
 
 Analogous Pole. In a pyro-electric sub- 
 stance like tourmaline, the pole that ac- 
 quires a positive electrification while the 
 temperature of the crystal is rising. 
 
 Analysis. The determination of the com- 
 position of a compound substance by sep- 
 arating it into the elementary substances 
 of which it is composed. 
 
 Analysis, Electric. The determination 
 of the composition of a compound sub- 
 stance by electric means. 
 
 Analyzable. Capable of being analyzed. 
 
 Analyze. To separate into component 
 parts. 
 
 Analyzer, Electric. A gridiron of me- 
 tallic wires which is transparent to per- 
 pendicularly incident electro-magnetic 
 waves, when the length of the wires is 
 perpendicular to the electric oscillations, 
 but is opaque to them, that is, possesses 
 the ability to absorb or reflect them, when 
 rotated 90 from its former position : i. e., 
 when parallel to the electric oscillations. 
 
 Analyzing. Separating into component 
 parts. 
 
 Anaphoresis. A term sometimes applied 
 for the electric osmose which occurs in 
 the neighborhood of the anode. 
 
 Anchor. In a trolley system the diagonal 
 tie wires which bind the trolley wire 
 longitudinally to adjacent poles in order 
 to maintain a uniform degree of tension 
 in the trolley wire. 
 
 Anchor Log. A log partially buried in the 
 ground and serving as an anchor for a tel- 
 egraphic pole. 
 
 Anchor Platform. A frame-work at- 
 tached to an anchor-pole by means of 
 which the pole is solidly set in the earth. 
 
 Anchor Pole. (1) A pole for overhead 
 wires of sufficient stiffness to take the en- 
 tire tension at points where an abrupt 
 angle occurs, or where the conductors 
 enter underground conduits. (2) A ter- 
 minal pole. 
 
 Anchor-Ring Core. A toroidal core. 
 
 Anchor Strain-Ear. In an overhead 
 trolley system a trolley ear or insulator 
 employed for anchoring the trolley wire, 
 or maintaining it taut, so as to ensure 
 good and continuous contact with the 
 trolley wheel. 
 
 Anchored. (1) Kept in position by means 
 of an anchor strain -ear. (2) Kept in posi- 
 tion by means of an anchor, as a buoy or 
 ship. (3) Maintained in a given position. 
 
 Anchored Filament. An incandescent 
 lamp filament supported at its centre 'to 
 prevent injury to it by excessive vibra- 
 tie" 
 
 Aneiectric. A word formerly applied to 
 conducting substances which it was be- 
 lieved could not be electrified by friction. 
 (Obsolete.) 
 
 Anelectrotonic State. The state or con- 
 dition of electrotonus. 
 
 Anelectrotonic Zone. The polar zone. 
 
 Anelectrotonus. The decreased func- 
 tional activity which occurs in a nerve in 
 the neighborhood of the anode or positive 
 electrode. 
 
 Anemograph. A recording anemometer. 
 
 Anemograph, Electric. An electrically 
 recording anemometer. 
 
 Anemometer. An apparatus for record- 
 ing the intensity and direction of the 
 wind. 
 
 Anemometer, Electric. An apparatus 
 for electrically recording the intensity 
 and direction of the wind. 
 
 Anemometry. The measurement of the 
 direction and intensity of the wind. 
 
 Anemoscope. An instrument which in- 
 dicates but does not measure the inten- 
 sity, or record the direction of the wind. 
 
 Aneroid. Devoid of liquid. 
 
 Aneroid Barometer. An apparatus for 
 measuring atmospheric pressure, which 
 operates by the to-and-fro movements of 
 one of the walls of a partially exhausted 
 elastic metallic box. 
 
 Angle. The deviation of direction be- 
 tween two intersecting lines or planes. 
 
 Angle Cathetometer. A cathetometer 
 suitable for measuring angular deviation. 
 
 Angle of Declination. (1) The angle 
 which measures the deviation of the mag- 
 netic needle to the east or west of the true 
 geographical north. (2) The angle of va- 
 riation of a magnetic needle. 
 
 Angle of Dielectric Hysteretic Lag. 
 In a condenser traversed by an alterna- 
 ting current the angle whose tangent is 
 equal to the ratio of the hysteretic con- 
 ductance to the hysteretic susceptance of 
 the condenser, or to the angle whose co- 
 tangent is the ratio of the hysteretic re- 
 actance of condensance to the hysteretic 
 resistance of the condenser. 
 
 Angle of Dip. (1) The angle which a 
 magnetic needle, free to move in both a 
 vertical and horizontal plane, makes with 
 the horizontal line passing through its 
 point of support. (2) The angle of inclina* 
 tion of a magnetic needle. 
 
Aug.] 
 
 679 
 
 [Ann. 
 
 Angle of Hysteretic Advance of Phase. 
 The angle by which the equivalent sine 
 wave of exciting current leads the sine 
 wave of magnetism, in a transformer or 
 choking coil containing iron. 
 
 Angle of Inclination. The angle of dip. 
 
 Angle of Lag. The angle of lag of a dy- 
 namo-electric machine. 
 
 Angle of Lag of Current. (1) An angle 
 whose tangent is equal to the ratio of the 
 
 inductive to the ohmic resistance in a cir- 
 cuit. (2) An angle whose cosine is equal 
 to the ohmic resistance divided by the 
 impedance of a circuit. (3) An angle 
 whose cosine is the ratio of the real to the 
 apparent power in an alternating-current 
 circuit. 
 
 Angle of Lag of Dynamo-Electric Ma- 
 chine. (1) The angle through which the 
 axis of magnetization of the armature of 
 a dynamo-electric machine is shifted by 
 reason of the resistance its core offers to 
 cyclic reversals of magnetization. (2) 
 The angle through which the axis of 
 magnetization of the armature of a dyna- 
 mo-electric machine is shifted by reason 
 of both hysteresis and armature reaction. 
 (3) The backward angular deviation from 
 the normal of the brushes of a motor in 
 order to secure sparkless commutation. 
 
 Angle of Lead. The forward angular de- 
 viation from the normal position which 
 must be given to the collecting brushes 
 on the commutator of a continuous-cur- 
 rent generator in order to obtain quiet 
 commutation. 
 
 Angle of Maximum Sensitiveness of 
 Galvanometer. The angle of deflection 
 at which a given small alteration in the 
 current strength produces the greatest 
 deflection of the change in the needle. 
 
 Angle of Polar Span. The angular dis- 
 tance which the pole pieces extend cir- 
 cumferentially around the armature bore. 
 
 Angle of Variation. The angle of de- 
 clination of the magnetic needle. 
 
 Angular. Of or pertaining to an angle. 
 
 Angular Acceleration.. The time rate 
 of change of angular velocity. 
 
 Angular Couple . The angular force. . 
 
 Angular Currents. Currents flowing 
 through circuits which intersect one an- 
 other at any angle. 
 
 Angular Energy. The product of one- 
 half the square of the angular velocity 
 and the moment of inertia. 
 
 Angular Force. The force which causes 
 the rate pf change of angular momentum. 
 
 Angular Momentum. The product of 
 
 the moment of inertia at any instant and 
 the angular velocity. 
 
 Angular Torque. The angular twist or 
 couple. 
 
 Angular Velocity. (1) The velocity of a 
 point moving relatively to a centre of 
 rotation or to some selected point, and 
 usually measured in degrees per second, or 
 in radians per second. (2) In a sinusoidal- 
 current circuit the product of 6.2832 and 
 the frequency of the current. 
 
 Angular Wire Gauge. A wire gaug^e 
 measurer formed of a metallic strip con- 
 taining a tapering, or acute-angled slot 
 with graduated edges. 
 
 Animal Electricity. Electricity pro- 
 duced in the bodies of animals during 
 life. 
 
 Animal Magnetism. A term sometimes 
 applied to hypnotism or artificial som- 
 nambulism. 
 
 Anion. The electro-negative ion or radical 
 of a molecule. 
 
 Anisptropic Conductor. A conductor 
 which though homogeneous in structure 
 possesses different conductivities in dif- 
 ferent directions. 
 
 Anisotropic Medium. (1) A medium 
 in which equal stresses do not produce 
 equal strains when applied in different 
 directions. (2) An eolotropic medium. 
 
 Annealing. The art of softening metals 
 by heating and subsequent gradual cool- 
 ing. 
 
 Annealing, Electric. A process for an- 
 nealing metals in which electric heat is 
 substituted for ordinary heat. 
 
 Annual Inequality of Earth's Mag- 
 netism. (1) A variation in any of the 
 elements of the earth's magnetism de- 
 pendent upon the relative position of the 
 sun and earth. (2) Annual variations in 
 the earth's magnetism. 
 
 Annual Load-Factor. (1) The ratio be- 
 tween the mean output of a central station 
 in one year, and the maximum output at 
 any time during the year. (2) The ratio 
 between the mean daily output of a cen- 
 tral station in one year, and the mean 
 daily maximum output in the same year. 
 
 Annual Variations of Magnetic 
 Needle. Variations in the magnetic de- 
 clination that occur at regular periods of 
 the year. 
 
 Annunciator Board. A board on which 
 annunciator drops are placed. 
 
 Annunciator Clock, Electric. A clock 
 employed in connection 'with an an- 
 nunciator for automatically disconnect- 
 
Ann.] 
 
 680 
 
 [Ant. 
 
 ing certain circuits at certain predeter- 
 mined times. 
 
 Annunciator Drop. An annunciator 
 signal whose dropping indicates the clos- 
 ing or opening of the circuit of a partic- 
 ular electro-magnet connected therewith. 
 
 Annunciator Wire. A class of insulated 
 wire prepared for use in annunciator 
 circuits. 
 
 Anodal. Of or pertaining to the anode. 
 
 Aiiodal Diffusion. A word sometimes 
 * used for cataphoretic medication. 
 
 A.node. (1) The conductor or plate of a 
 decomposition cell connected with the 
 positive terminal of a battery or other 
 electric source. (2) The terminal of an 
 electric source out of which the current 
 flows into the electrolyte of a decompos- 
 ing cell or voltameter. (3) In a vacu- 
 um tube, electrolytic cell, bath, or re- 
 ceptive device, the terminal at which the 
 current enters, as distinguished from the 
 cathode, at which the current leaves. 
 
 Anodic. Of or pertaining to the anode. 
 
 Anodic Closure Contraction. The 
 muscular contraction produced by the 
 closing of a voltaic circuit, the anode of 
 which is placed over a nerve, and the 
 cathode at some other part of the body. 
 
 Anodic Contraction. The muscular con- 
 traction produced in the neighborhood of 
 the anode, either on opening or closing 
 the circuit. 
 
 Anodic Currents. In a polarized voltaic 
 couple immersed in acidulated water, 
 the electric currents produced by the 
 agitation of the plate connected with the 
 anode. 
 
 Anodic Duration Contraction. The 
 time during which a muscle continues 
 contracted on the opening or closing of a 
 circuit whose anode is placed over the 
 part contracted. 
 
 Anodic Electro-Diagnostic Reactions. 
 The characteristic reactions which oc- 
 cur at the anode of an electric source 
 placed over any part of a living body. 
 
 Anodic Opening Contraction. The 
 muscular contraction produced by the 
 opening of a voltaic circuit the anode of 
 which is placed over a nerve and the 
 cathode at some other part of the body. 
 
 Anodic Rays. The radiation claimed to 
 emanate from the anode of an X-ray tube. 
 
 Anodic Zone. The zone or region sur- 
 rounding the anode when employed as a 
 therapeutic electrode. 
 
 Anodograph. A word proposed for a 
 radiograph. 
 
 Anomalous. (1) Irregular. (2) Not in 
 accordance with the ordinary rule. 
 
 Anomalous Dispersion. An abnormal 
 dispersion in which the order of the wave 
 frequencies is inverted as regards their 
 order in ordinary dispersion. 
 
 Anomalous Helix. A helix wound so as 
 to produce an anomalous magnet. 
 
 Anomalous Magnet. A magnet possess- 
 ing more than two free poles. 
 
 Anomalous Magnetization. (1) The 
 magnetization produced by the oscillatory 
 discharge of a condenser or Leyden jar. 
 (2) Magnetization which produces more 
 than two free poles in a magnet. 
 
 Anomalous Pole. A name sometimes 
 given to those poles of an anomalous 
 magnet which consist of two similar 
 adjacent poles. 
 
 Anomalous Solenoid. An anomalous 
 helix. 
 
 Anomalous Spiral. An anomalous helix. 
 
 Answer Back Signal. A return signal. 
 
 Answering Call-Box. A call-box at 
 which an answering signal is obtained, 
 indicating that the call has been received 
 at the central station. 
 
 Answering Board. In a telephone 
 switchboard the board holding the an- 
 swering jacks. 
 
 Answering Jacks. In any panel of a 
 telephone switchboard the jacks con- 
 nected with the subscribers whose calling 
 drops are placed in that panel, so that 
 each call may be immediately answered 
 at an adjacent jack. 
 
 Answering Key. In a telephone switch- 
 board a lever contact key which enables 
 the operator to bring her head telephone 
 into connection with any subscriber. 
 
 Anti-Cathode of X-Ray Tube. (1) A 
 deflection plate placed opposite the ca- 
 thode of an X-ray tube. (2) A platinum 
 plate supported inside an X-ray tube to 
 receive the cathodic bombardment. 
 
 Anti-Conical System of Distribution. 
 A system of conical conductors employed 
 in anti-parallel feeding. 
 
 Anti-Hum. A device for lessening the 
 humming sound due to the vibration of 
 an aerial wire. 
 
 Anti-Induction. Opposing or preventing 
 induction and its effects. 
 
 Anti-Induction Cable. A cable whose 
 conductors are so arranged as to avoid 
 the effects of induction, either from them- 
 selves or from neighboring conductors. 
 
 Anti-Induction Conductor. A con 
 
Ant.] 
 
 681 
 
 [App. 
 
 ductor cQnstructed so as to avoid injur- 
 ious inductive effects from neighboring 
 circuits. 
 
 Anti-Induction Telephone Cable. 
 (1) A telephone cable in which the con- 
 ductors are so arranged as to neutralize 
 the effects of induction produced by 
 neighboring circuits. (2) A telephone cable 
 in which the effects of electrostatic in- 
 duction from neighboring circuits is 
 avoided by a metallic covering or sheath- 
 ing that is grounded at suitable inter- 
 vals. 
 
 Antilogous Pole. The pole of a pyro- 
 electric substance like tourmaline, which 
 acquires a negative electrification while 
 the temperature of the crystal is rising. 
 
 Antimonious Lead. An alloy of lead 
 and antimony employed for the grid of a 
 storage battery because it is not acted on 
 by the charging current. 
 
 Antinode. The point in a vibrating string, 
 wire, or plate, midway between adjacent 
 nodes. 
 
 Anti-Parallel Feeding. A method of 
 feeding in a system of parallel distribu- 
 tion in which the pressure at the ter- 
 minals of all the translating devices is 
 kept approximately uniform by employ- 
 ing mains tapering in opposite directions ; 
 that is, with their large ends connected 
 to the generator terminals or bus-bars, 
 and the mains proceeding in opposite 
 directions around the circuit to be sup- 
 plied. 
 
 Anti-phase. (1) A phase relation be- 
 tween two periodic currents such that 
 they, tend to decrease the amplitude of 
 the motion. (2) Phase opposition. 
 
 Anvil of Telegraph Key. The front 
 stop of a Morse telegraph key, upon which 
 the lever descends in signalling. 
 
 Aperiodic. (1) Not characterized by 
 periodicity. (2) Devoid of periodicity. 
 (3) Coming to rest steadily without oscil- 
 lations. 
 
 Aperiodic Galvanometer. (1) A gal- 
 vanometer whose needle comes to rest 
 without any oscillation. (2) A dead- 
 beat galvanometer. 
 
 A-Pole. A telegraph double-pole shaped 
 like a letter A. 
 
 Apparent Electromotive Force. The 
 E. M. F. apparently acting in a circuit as 
 measured by the drop of pressure due to 
 the resistance of the circuit and the cur- 
 rent strength passing through it. 
 
 Apparent Coefficient of Induction. 
 A term 'sometimes used for the apparent 
 inductance in a circuit which either en- 
 
 velops iron, or is inductively associated 
 with secondary circuits. 
 
 Apparent Coefficient of Magnetic In- 
 duction. The apparent permeability of 
 a substance as expressed by the amount 
 of magnetic flux that passes through it 
 per unit of normal cross-sectional area, 
 differing from the true value on account 
 of the presence of eddy currents. 
 
 Apparent Conductor-Resistance. The 
 impedance of a conductor which forms 
 part of an alternating-current circuit con- 
 taining both resistance and reactance. 
 
 Apparent Efficiency of Alternator. 
 
 The ratio of the electric activity delivered 
 at the terminals of an alternator, as the 
 product of volts and amperes supplied, to 
 the activity mechanically absorbed at its 
 pulley or shaft ; in contradistinction to 
 the efficiency determined from the true 
 electric activity delivered. 
 
 Apparent Efficiency. The efficiency of 
 a generator, motor, or other apparatus, in 
 an alternating-current circuit based upon 
 the volt-amperes or apparent power as dis- 
 tinguished from efficiency based on real 
 power. 
 
 Apparent Efficiency of Alternating- 
 Current Motor. The ratio of the power 
 mechanically delivered by the motor to 
 the apparent activity it receives at its ter- 
 minals ; as distinguished from the effi- 
 ciency based upon the real electric activity 
 received. 
 
 Apparent Energy. (1) The product of 
 the effective current and the effective 
 pressure in an alternating-current circuit. 
 (2) Apparent activity, as opposed to true 
 activity. (3) In a sinusoidal-current cir- 
 cuit, or simple alternating-current circuit, 
 the product of effective volts and effective 
 amperes uncorrected for the cosine of the 
 angle of their phase difference. 
 
 Apparent Expansion. The increase in 
 the volume of a liquid by expansion irre- 
 spective of the expansion of its con- 
 taining vessel. 
 
 Apparent Insulation. The insulation 
 resistance of a circuit, uncorrected for 
 the effect of leakage in the measuring 
 current. 
 
 Apparent Impedance. (1) In an alter- 
 nating-current circuit the virtual imped- 
 ance in a primary circuit due to the 
 presence of an associated secondary cir- 
 cuit. (2) The joint impedance of a net- 
 work of impedances. 
 
 Apparent Insulation of Telegraphic 
 
 Line. The insulation of a telegraph line 
 
App.] 
 
 682 
 
 [Arc. 
 
 uncorrected for its conductor resistance, 
 or for the drop in testing potential at the 
 more remote portions. 
 
 Apparent Magnetization. The magnet- 
 ization due to the superposition of two 
 separate magnetizations. 
 
 Apparent Power. In an alternating- 
 current circuit, the apparent watts, or the 
 product obtained by multiplying the volts 
 by the amperes, as read directly from a 
 voltmeter and ammeter. 
 
 Apparent Reluctance. The reluctance 
 of a magnetic circuit, or portion thereof, 
 under the influence of a complex of such 
 superposed magnetic fluxes as may prac- 
 tically be developed, as distinguished 
 from its reluctance under a single mag- 
 netising force. 
 
 Apparent Resistance. The impedance 
 in an alternating-current circuit or por- 
 tion thereof. 
 
 Apparent Torque Efficiency. In an 
 alternating-current motor, the ratio of the 
 torque actually developed to the torque 
 which it would give at the same volt- 
 ampere or apparent electric input in volt- 
 amperes if there were neither internal 
 losses nor phase displacement in the motor. 
 
 Apparent Watts. The apparent power 
 in an alternating-current circuit as dis- 
 tinguished from the real power. 
 
 Apron Grapnel. A form of grapnel for 
 grappling a cable in which the prongs are 
 protected from breakage on rocks by an 
 apron or covering, only a sufficient space 
 being left between the apron and the 
 prongs for the entrance of the cable. 
 
 Aqueous Solution. A solution of a salt 
 or other substance in water. 
 
 Arago's Disc. A disc of copper or other 
 non-magnetic metallic substance which, 
 when rapidly rotated under a magnetic 
 needle supported independently of the 
 disc, causes the needle to be deflected in 
 the direction of rotation, and, when the 
 velocity of the disc is sufficiently great, to 
 rotate with it. 
 
 Arborescent Discharges. Disruptive 
 discharges obtained from a high-potential 
 discharge of a series-connected battery. 
 
 Arborescent Deposits. Tree-shaped 
 electro-metallurgical deposits. 
 
 Arc. (1) A voltaic arc. (2) A portion of a 
 circle, or other plane conic section. 
 
 Arc. To discharge in the form of a voltaic 
 arc. 
 
 Arc Ammeter. An ammeter on an arc 
 circuit. 
 
 Arc Blow-Pipe, Electric. A blow-pipe 
 
 in which the air-blast is obtained by a 
 convective discharge. 
 
 Arc-Circuit Cut-Out. A cut-out placed 
 in a series arc-light circuit to prevent the 
 extinguishment of any lamp from break- 
 ing the entire circuit. 
 
 Arc-Circuit Cut-Out Box. A box fo\ 
 holding an arc-circuit cut-out. 
 
 Arc-Circuit Indicator. A device in the 
 form of a simple galvanometer which in- 
 dicates when the current is passing 
 through an arc-light circuit. 
 
 Arc Crater Photometric Standard. A 
 
 photometric standard based on the inten- 
 sity of light normally emitted from a 
 definite area of the crater of a carbon 
 voltaic arc. 
 
 Arc, Electric. A term sometimes em- 
 ployed for the voltaic arc. 
 
 Arc-Lamp, Electric. (1) An electric lamp 
 whose source of light is the voltaic arc. 
 (2) An incandescent electric lamp, em- 
 ployed to illumine the circles of telescopes 
 or other instruments in an observatory. 
 
 Arc-Lamp Compensator. A reactive or 
 choking coil, placed in the circuit of a 
 lamp or lamps for the purpose of auto- 
 matically regulating the amount of cur- 
 rent passing through the lamp or lamps. 
 
 Arc-Lamp Globe. A glass globe sur- 
 rounding the arc of an arc lamp. 
 
 Arc-Lamp Hand-Board. An arc-lamp 
 hanger-board. 
 
 Arc-Lamp Hanger. A board from which 
 an arc lamp is suspended, provided with 
 electric connections for readily short-cir- 
 cuiting the lamp. 
 
 Arc-Lamp Spark-Arrester. A gauze 
 chimney surrounding the arc and em- 
 ployed for the purpose of preventing fires 
 when arc lamps are placed near com- 
 bustible materials, .as in shop windows. 
 
 Arc-Lamp Suspension-Board. (1) A 
 board for suspending an" arc lamp. (2) 
 an arc-lamp hanger-board. 
 
 Arc-Light . The light of the carbon 
 voltaic arc. 
 
 Arc-Light Circuit. (1) A circuit in 
 which arc-lights are placed. (2) Gen- 
 erally, a series-connected circuit. 
 
 Arc-Light Cut-Out. A switch for short- 
 circuiting an arc-lamp and so cutting it 
 out of the circuit. (2) A cut-out which 
 automatically removes an arc-lamp from 
 the circuit. 
 
 Arc-Light Diffuser. Any diffuser for 
 scattering or diffusing the light from an 
 arc light so as to avoid the production of 
 intense shadows. 
 
Arc.] 
 
 683 
 
 [Arm, 
 
 Arc-Light Generator. A dynamo-elec- 
 tric machine that furnishes current for 
 arc-light circuits. 
 
 Arc-Light-Points. The carbon pencils 
 between which the arc is maintained in 
 an arc light. 
 
 Arc- Light Projector. An arc lamp pro- 
 vided with a reflector for obtaining a 
 beam of approximately parallel rays of 
 light. 
 
 Arc-Light Meter. A form of electric 
 current timer. 
 
 Arc-Light Regulator. A device, gene- 
 rally automatic, for maintaining the car- 
 bons of an arc-lamp a constant distance 
 apart during the operation of the lamp. 
 
 Arc-Light Tower. A tower employed in 
 out-door illumination for supporting a 
 number of arc lamps. 
 
 Arc-Light Transformer. A transfor- 
 mer which supplies alternating currents 
 to arc-lamps. 
 
 Arc-Lighter. An arc-light generator. 
 
 Arc-Lighting. Artificial illumination 
 obtained by means of arc lights. 
 
 Arc-Lighting Dynamo-Electric Ma- 
 chine. An arc-light generator. 
 
 Arc Plug-Switchboard. A switchboard 
 provided with spring-jack contacts con- 
 nected with the terminals of different 
 circuits, and plug switches connected with 
 the dynamo terminals, by means of which 
 any dynamo can be connected with any 
 circuit ; or a number of circuits connected 
 with the same dynamo ; or a number of 
 separate dynamos placed in the same 
 circuit. 
 
 Arc Micrometer. An apparatus for 
 measuring the length of a voltaic arc by 
 means of a micrometer. 
 
 Arc Standard of Light. A photometric 
 standard based on the intensity of the 
 light emitted by a given area of crater of 
 the positive carbon in a carbon arc. 
 
 Arc Switchboard. An arc plug-switch- 
 board. 
 
 Arcing. Discharging by means of voltaic 
 arcs. 
 
 Areometer. An instrument for readily 
 determining the specific gravity of 
 liquids. 
 
 Areometry. The measurement of the 
 specific gravity of liquids by means of 
 areometers. 
 
 Argand Electric Burner. An Argand 
 burner provided with a device for elec- 
 trically igniting the gas. 
 
 Argand Electric Lighter. An Argand 
 electric burner. 
 
 Argand Valve-Burner or Lighter. 
 An Argand burner provided with means 
 . whereby the gas can be both turned on 
 and lighted electrically. 
 
 Argymometry. The art of determining 
 the weight of electrically deposited silver. 
 
 Arithmetical Mean Value of Periodic 
 Current of E. M. P. Wave. The arith- 
 metical average of all the instantaneous 
 values during one complete period. 
 
 Arm of Balance or Bridge. One of the 
 resistances of an electric balance 01 
 bridge. 
 
 Arms of Balance or Bridge. Two sepa- 
 rate resistances, the value of one of which 
 is usually a decimal multiple of the other, 
 employed in an electric bridge or balance, 
 in connection with a known resistance, 
 to determine the value of an unknown 
 resistance. 
 
 Armature. (1) A mass of iron or other 
 magnetizable material placed on or near 
 the poles of a magnet. (2) The armature 
 of a dynamo-electric machine. 
 
 Armature Bars. (1) Heavy copper bars 
 of rectangular or trapezoidal cross-sec- 
 tion, or of imbricated rectangular strips, 
 or of rectangular bars of compressed 
 stranded wire, or of special forgings, em- 
 ployed on large drum armatures in place 
 of the ordinary wire windings. (2) Heavy 
 conductors employed for armature wind- 
 ings. 
 
 Armature Binding Wires. Coils of 
 wire bound on the outside of the armature 
 wires for the purpose of preventing their 
 separating from the armature core by 
 centrifugal force. 
 
 Armature Bore. The space between the 
 pole-pieces of a dynamo or motor provided 
 for the rotation of the armature. 
 
 Armature Chamber. (1) The armature 
 bore. (2) An armature pocket. 
 
 Armature Chambers. Spaces left in the 
 armature core for the reception of the 
 armature coils. 
 
 Armature Core-Discs. The thin discs 
 of sheet-iron that form, when assembled, 
 the laminated core of the armature of a 
 dynamo or motor. 
 
 Armature Core of Dynamo. The masa 
 of laminated iron on which the armature 
 coils or conductors of a dynamo or motoi 
 are placed. 
 
 Armature Covering. A covering of can- 
 vas or other suitable material placed on 
 an armature for the purpose of protecting 
 its conductors from injury or dirt. 
 
Arm.] 
 
 C84 
 
 [Art. 
 
 Armature Hole.- (1) The armature bore. 
 (2) A hole made in the core for the recep- 
 tion of an armature coil or winding. 
 
 Armature Inductors. The bars, strips, 
 or coils, placed on the dynamo armature 
 core, in which electromotive forces are 
 induced by rotation. 
 
 Armature Loop. The single conducting 
 coil or loop on a dynamo or motor arma- 
 ture. 
 
 Armature of Cable. The sheathing or 
 protective coat placed on the outside of a 
 cable. 
 
 Armature of Condenser. A term some- 
 times applied to the metallic plates or 
 coatings of a condenser or Leyden jar. 
 
 Armature of Dynamo. (1) Coils of in- 
 sulated wire together with the iron core 
 on or around which such coils are wound. 
 (2) That part of a dynamo in which useful 
 differences of potential or useful currents 
 are generated. (3) Generally that part of 
 a dynamo which is revolved between the 
 pole-pieces of the field magnets. (4) That 
 member of a dynamo in which the mag- 
 netic flux is caused to successively fill 
 and empty the coils and thereby gener- 
 ate E. M. Fs. 
 
 Armatures of Holtz Machine. The 
 pieces of paper that are placed on the 
 stationary plate of a Holtz, or other simi- 
 lar electrostatic induction machine, near 
 the openings in the same. 
 
 Armature Pinion. A toothed wheel 
 . placed on the armature shaft of a street- 
 car motor for engaging the teeth of the 
 reducing gear. 
 
 Armature Pockets. Spaces provided in 
 an armature core for the reception of the 
 armature coils. 
 
 Armature Projections. Those portions 
 of the armature core between which the 
 armature slots, pockets, or chambers are 
 situated. 
 
 Armature Reaction. The reactive mag- 
 netic influence produced, by the current 
 in the armature of a dynamo or motor, 
 on the magnetic circuit of the machine. 
 
 Armature Segment. That portion of an 
 armature winding, or armature inductor, 
 whose circuit is included between two 
 contiguous segments of the commutator. 
 
 Armature Slots. Slots provided in an 
 armature ' core for the reception of the 
 armature coils. 
 
 Armature Spider. A metal frame-work, 
 keyed to the armature shaft, and pro- 
 vided with radial arms for firmly holding 
 the armature core. 
 
 Armature Stampings. Stampings of 
 
 soft sheet iron intended for the core discs 
 
 of a laminated armature core. 
 Armature Turns. The separate turns of 
 
 conductors on the armature of a dynamo 
 
 or motor. 
 
 Armature Varnish. An insulating var- 
 nish sometimes applied to armature wind- 
 ings for the purpose of increasing theil 
 powers of resisting moisture and friction. 
 
 Armature Winding-Space. Longitu- 
 dinal grooves or spaces left in the arma- 
 ture core for the reception of the arma- 
 ture coils. 
 
 Armed Magnet. A magnet provided 
 with an armature. 
 
 Armor of Cable. The protecting sheath- 
 ing or metallic covering of a submarine 
 or other electric cable. 
 
 Armored. Provided with armor, as of the 
 protective sheathing of a cable. 
 
 Armored Cable. A cable provided with 
 a protective sheathing or armor. 
 
 Armored Conductor. A conductor pro- 
 vided with a protective sheathing or 
 armor. 
 
 Army Telegraph. The telegraphic ap- 
 paratus employed in field service in the 
 army. 
 
 Arrester Plate of Lightning Protec- 
 tor. The ground -connected plate of a 
 comb lightning-arrester. 
 
 Arrester Plates. A term sometimes ap- 
 plied to the two plates of an ordinary 
 comb lightning-protector. 
 
 Arrival Curve of Current in Sub- 
 marine Cable or Telegraphic Cir- 
 cuit. A curve showing the gradual 
 increase in the strength of current reach- 
 ing the receiving end of a submarine 
 cable under a given condition of signal- 
 ling. 
 
 Articulate Speech. The successive tones 
 of the human voice that are necessary to 
 produce intelligible words. 
 
 Artificial Cable. A circuit containing 
 associated resistance and capacity, and 
 employed in a system of duplex sub- 
 marine telegraphy corresponding to the 
 artificial line in duplex aerial line tele- 
 graphy. 
 
 Artificial Cable Leak. A leak purpose- 
 ly introduced at some point in the circuit . 
 of an artificial cable employed in duplex 
 cable telegraphy. 
 
 Artificial Carbons. Carbons obtained 
 by the carbonization of a mixture of pul- 
 verized carbon with a carbonizable liquid. 
 
Art.] 
 
 685 
 
 [AtOa 
 
 Artificial Fault in Cable. A fault pur- 
 posely made in an artificial cable for the 
 purpose of studying its behavior under 
 tests. 
 
 Artificial Illumination. The employ- 
 ment of artificial sources of light. 
 
 Artificial Line. In duplex telegraphy a 
 combination of resistance coils and con- 
 densers which serves to balance an actual 
 telegraph line. 
 
 Artificial Magnet. A magnet produced 
 by induction from another magnet or 
 from an electric current. 
 
 Asbestos Porcelain. A porous sub- 
 stance, somewhat resembling ordinary 
 porcelain, employed for the porous cells 
 of voltaic batteries. 
 
 A-Side of Quadruplex Table. That 
 side of a quadruplex system which is 
 worked by means of reversed currents. 
 
 Asphyxia. Suspended respiration event- 
 ually resulting in death from non-aeration 
 of the blood. 
 
 Assumed Direction of Flow of Cur- 
 rent. A convention which regards the 
 current as leaving an electric source at 
 its positive pole, and returning to it at its 
 negative pole. 
 
 Assymmetrical. Devoid of symmetry. 
 
 Assymmetrical Resistance. A resist- 
 ance which is claimed to be greater to a 
 flow of current in one direction than in 
 another. 
 
 Astatic. Devoid of magnetic directive 
 power. 
 
 Astatic Circle. A term sometimes used 
 for astatic circuit. 
 
 Astatic Circuit. A circuit, consisting of 
 two closed curves enclosing equal sur- 
 faces, which is not deflected by the 
 earth's field on the passage of a current 
 through it. 
 
 Astatic Couple. Two magnets of equal 
 strength so placed one above the other in 
 a vertical plane as completely to neutral- 
 ize each other's effects. 
 
 Astatic Galvanometer. A galvanometer 
 provided with an astatic needle or cir- 
 cuit. 
 
 Astatic Multiplier. An astatic galvano- 
 meter. 
 
 Astatic Needle. (1) A compound mag- 
 netic needle of great sensibility, possess- 
 ing little or no directive power. (2) An 
 astatic needle consisting of two separate 
 needles rigidly connected and placed par- 
 allel one directly over the other with 
 opposite poles opposed. 
 
 Astatic Pair. An astatic couple. 
 
 Astatic System. An astatic combination 
 
 of magnets. 
 
 Astaticizing. Rendering a system astatic. 
 Astigmatism. A defect in the lenses of 
 
 the eye which prevents horizontal and 
 
 vertical lines from being in focus at the 
 
 same time. 
 Astronomical Meridian. A great circle 
 
 passing through any point of the heavens 
 
 and the north and south poles of the 
 
 heavens. 
 
 Asymptote of Curve. A straight line 
 which continually approaches a curved 
 line, but which meets it only at an in- 
 finite distance. 
 
 Asynchronism. Devoid of synchronism. 
 
 Asynchronous. Occurring or acting 
 non-simultaneously. 
 
 Asynchronous Alternating-Current- 
 Motor. A motor whose speed is not 
 synchronous with that of its driving gen- 
 erator, both machines having the same 
 number of poles. 
 
 Atmosphere. (1) A unit of gaseous or 
 fluid pressure equal to 14'73 pounds per 
 square inch. (2) The ocean of air which 
 surrounds the earth. 
 
 Atmospheric. Of or pertaining to the 
 atmosphere. 
 
 Atmospheric Cathode Discharge. An 
 X-ray discharge which is assumed to ac- 
 company and form part of the sun's 
 radiation. 
 
 Atmospheric Electricity. The free 
 electricity which is present in the atmos- 
 phere. 
 
 Atom. (1) An ultimate particle of mat- 
 ter. (2) The smallest quantity of ele- 
 mentary or simple matter that can exist. 
 
 Atom of Electricity. A quantity of 
 electricity equal in amount to that pos- 
 sessed by any chemical monad atom. 
 
 Atomic. Of or pertaining to the atom. 
 Atomic Attraction. (1) The attraction 
 
 which causes the atoms to combine. (2) 
 
 Chemical affinity. 
 Atomic Capacity. The equivalence or 
 
 valency of an atom. 
 
 Atomic Currents. A term sometimes 
 employed instead of molecular or Ampe- 
 rian currents. 
 
 Atomic Energy. Chemical potential 
 energy. 
 
 Atomic Heat. A constant product ob- 
 tained by multiplying the specific heat of 
 an elementary substance by its atomic 
 weight- 
 
Ato.] 
 
 686 
 
 [Aut. 
 
 Atomic Weight. The relative weight of 
 the atoms of elementary substances. 
 
 Atomicity. (1) The combining capacity 
 of the atoms. (2) The relative equiva- 
 lence of the atoms, or their atomic ca- 
 pacity. 
 
 Atomization. The act of obtaining li- 
 quids in a spray of finely divided parti- 
 cles. 
 
 Atomize. To separate into a spray by 
 means of an atomizer. 
 
 Atomizer. An apparatus for readily ob- 
 taining a finely divided jet or spray of 
 liquid. 
 
 Attachment Plug. A plug provided for 
 insertion in a screw socket or spring jack, 
 for the ready connection of a lamp or 
 other receptive device to a circuit. 
 
 Attract. To draw together. 
 
 Attracted-Disc Electrometer. A form 
 of electrometer in which the force is 
 measured by the attraction existing be- 
 tween two charged discs. 
 
 Attracting. Drawing together. 
 
 Attraction. Literally the act of drawing 
 together. 
 
 Attraction of Gravitation. (1) Mass at- 
 traction ; or, the attraction which causes 
 masses of matter to tend to move towards 
 one another. (2) The attraction which 
 causes bodies to fall to the earth. (3) Molar 
 attraction. 
 
 Attractions and Repulsions of Cur- 
 rents. The tendency of active circuits 
 to be attracted to or repelled from one 
 another by the mutual action of their 
 magnetic fields. 
 
 Audible Code. A term employed in rail- 
 way signalling for a code of audible sig- 
 nals in railway service. 
 
 Audible Telegraphic Signal. A signal 
 which is received by the ear in contra- 
 distinction to a visual signal or one re- 
 ceived by the eye. 
 
 Audiometer. A form of induction bal- 
 ance or sonometer employed in testing 
 the acuteness of hearing. 
 
 Audiphone. A thin plate of hard rubber 
 held in firm contact with the teeth and 
 maintained at a certain tension by strings 
 attached to one of its edges, employed for 
 the purpose of aiding the hearing. 
 
 Auger. A boring tool for cutting holes 
 for telegraph poles. 
 
 Aura, Electric. A term sometimes ap- 
 plied to an electric brush or convective 
 discharge. 
 
 Aural Electrode. An electrode suitably 
 
 shaped for the therapeutic treatment of 
 the ear. 
 
 Aurora. (1) Luminous sheets, columns, 
 arches, or pillars of pale flashing light, 
 generally of a reddish color, seen in the 
 Northern and Southern heavens. (2) The 
 Northern and Southern lights. 
 
 Aurora Australis. (1) The Southern 
 light. (2) A name given to an appear- 
 ance in the Southern heavens similar to 
 that of the aurora borealis. 
 
 Aurora Borealis. The Northern light. 
 
 Aurora Glory. A term proposed for the 
 almost constant crown or crowns of light, 
 which occupy a nearly fixed position in 
 the heavens during the continuance of 
 an aurora. 
 
 Aurora Polaris. A general name for the 
 aurora borealis or the aurora australis. 
 
 Auroral. Of or pertaining to an aurora. 
 
 Auroral Arch. An arch-like form some- 
 times assumed by the auroral light. 
 
 Auroral Bands. Approximately parallel 
 streams of light that are sometimes seen 
 during the prevalence of an aurora. 
 
 Auroral Coronse. Crown-shaped appear- 
 ances sometimes assumed by the auroral 
 light. 
 
 Auroral Curtain. A curtain-shaped 
 sheet of auroral light. 
 
 Auroral Plashes. (1) Sudden variations 
 in the intensity of the auroral light. 
 (2) Intermittent flashes of auroral light. 
 
 Auroral Light. The light given off by 
 an aurora. 
 
 Auroral Storm. An unusual prevalence 
 of auroras. 
 
 Auroral Streams. Auroral streamers. 
 
 Auroral Streamers. Flashing columns 
 or pillars of light that are emitted from 
 portions of the sky during the prevalence 
 of an aurora. 
 
 Austral. Of or pertaining to the South. 
 
 Austral Fluid. A term formerly em- 
 ployed for that magnetic fluid which was 
 supposed to exist around or to emanate 
 from the austral pole of a magnet. 
 
 Austral Magnetic Pole. (1) The name 
 formerly employed in France for the 
 north-seeking pole of a magnet. (Not in 
 general use.) (2) That pole of a magnet 
 which points to the earth's geographical 
 north. (Not in general use.) 
 
 Auto-Car. -(I) An automobile car. (2) 
 A car provided with storage batteries. 
 
 Auto-Converter. (1) A choking coil con- 
 nected across a circuit and tapped at va- 
 rious points to enable a reduced E. M. F. 
 
Aut.J 
 
 687 
 
 [Aut. 
 
 to be obtained. (2) An auto-transformer. 
 (3) A choking coil connected to an induc- 
 tion motor by a switch in such a manner 
 as to facilitate the starting of the motor 
 under load. 
 
 Auto-Excitation. Self-excitation. 
 
 Auto-Exciting. Self -exciting. 
 
 Autographic Telegraphy. (1) Fac- 
 simile telegraphy. (2) A writing tele- 
 graph. 
 
 Auto-Induction. A word sometimes em- 
 ployed instead of self-induction. 
 
 Auto-Kinetic System of Fire Telegra- 
 phy. A system of fire telegraphy in 
 which the transmitters are connected in 
 series in a pair of circuits, so that, when 
 an alarm is being transmitted from one 
 alarm point, no other alarm, received at 
 the same time, will be transmitted until 
 the first has been recorded. 
 
 Automatic Annunciator Drop. An 
 annunciator drop which on the closing of 
 a distant circuit falls and holds the cir- 
 cuit closed until the drop is raised. 
 
 Automatic Answer-Back. An auto- 
 matic return-signal call-box. 
 
 Automatic Argand Burner. An Ar- 
 
 gand burner furnished with a device by 
 means of which it can be either auto- 
 matically lighted or extinguished at a 
 distance. 
 
 Automatic Gas Cut-Off. A device for 
 automatically cutting out the battery 
 from an electric gas-lighting circuit, on 
 the accidental grounding of the circuit. 
 
 Automatic Guard for Series-Con- 
 nected Incandescent Lamps. (1) 
 An automatic cut-out, placed on a series- 
 connected incandescent lamp, for the 
 purpose of short-circuiting the holder 
 should the lamp filament break. (2) A 
 film cut-out. 
 
 Automatic Indicating-Grapnel. A 
 grapnel which automatically completes 
 the circuit of an electric bell or indicator 
 on a cable ship, as soon as the cable is 
 hooked. 
 
 Automatic Indicator. Any automatic 
 device for electrically indicating the 
 number of times a circuit has befin opened 
 or closed, thus showing the number of 
 times any operation has occurred, which 
 has caused the opening or closing of the 
 circuit. 
 
 Automatic Indicator for Grapnel. 
 An apparatus employed with a grapnel 
 for indicating when the grapnel conies 
 off the sea bottom. 
 
 Automatic Inker. An ink- writing Morse 
 
 recorder which is automatically self- 
 starting upon its operation by telegraphic 
 currents. 
 
 Automatic Interrupter. An automatic 
 contact-breaker. 
 
 Automatic Locking-Switch. A com- 
 bined key and switch employed in sub- 
 marine cables, whereby the switch is 
 automatically locked and thus prevented 
 from being left for sending, when it 
 should be left for receiving, or vice-versa. 
 
 Automatic Make-and-Break. A device 
 whereby the to-and-f ro movements of the 
 armature of an electro-magnet are caused 
 to automatically make and break its cir- 
 cuit. 
 
 Automatic Multiple-Transmitter. In 
 a telegraphic signalling or calling system, 
 the means whereby the requisite number 
 of spacing and electric impulses for any 
 of a number of different calls, is auto- 
 matically sent over a line, in order to pro- 
 duce a given signal, such for example, in 
 a system of police telegraphy, as a call for 
 an ambulance, a call for a squad, etc. 
 
 Automatic Oiler. An oil cup or reservoir 
 that automatically spreads oil over the 
 bearing of a machine in motion. 
 
 Automatic Overload-Switch for Stor- 
 age Battery. An automatic electro- 
 magnetic switch, inserted in the discharg- 
 ing circuit of a storage battery, by means 
 of which, when the discharging current 
 exceeds a certain safe limiting strength, it 
 is automatically opened. 
 
 Automatic Paper-Winder. An appa- 
 ratus for carrying and automatically 
 winding the paper fillet or strip used on 
 telegraphic registers. 
 
 Automatic Photo-Electric Switch. 
 A switch that is automatically opened or 
 closed on the exposure of its face to 
 differences of illumination. 
 
 Automatic Regulation of Dynamo- 
 Electric Machine. Such a regulation 
 of a dynamo-electric machine as will 
 automatically preserve constant, either 
 the current strength or the potential dif- 
 ference at its terminals. 
 
 Automatic Regulation of Motor. Such 
 a regulation of a motor as will maintain 
 constant its speed, or its torque. 
 
 Automatic Regulator. A device for 
 securing automatic regulation of a dy- 
 namo or motor, as distinguished from 
 hand regulation. 
 
 Automatic Repeater. A telegraphic re- 
 peater which is automatically operated, in 
 contradistinction to a manual repeatei 
 which is operated or controlled by hand. 
 
Aut.] 
 
 688 
 
 Automatic Rheostat. An automatic 
 variable resistance. 
 
 Automatic Rheotome. An automatic 
 contact-breaker. 
 
 Automatic Ringing - Through. A 
 means by which in junction telephone 
 working the attention of the distant ex- 
 change can be secured by the act of estab- 
 lishing connection at the originating ex- 
 change without the necessity of calling up 
 the distant exchange after connection 
 has been made. 
 
 Automatic Search-Light. A search- 
 light in which a parallel, or slightly 
 divergent beam of light, is caused au- 
 tomatically to sweep the horizon and thus 
 disclose the approach of a torpedo boat or 
 other similar danger. 
 
 Automatic Signalling. Telegraphic 
 transmission by machine-made contacts as 
 distinguished from telegraphic signalling 
 by hand. 
 
 Automatic-Call-Box. A form of tele- 
 phone call-box by means of which the 
 service of a telephone exchange can be ob- 
 tained by a payment made into a box, 
 thus dispensing with the services of an 
 attendant. 
 
 Automatic Chemical Telegraphy. 
 
 Automatic telegraphy in which the sig- 
 nals are recorded on a fillet or band of 
 chemically prepared paper. 
 
 Automatic Circuit-Breaker. A device 
 for automatically opening a circuit when 
 the current passing through it is exces- 
 sive. 
 
 Automatic Clearing Indicator. (1) A 
 self-restoring drop. ( 2 ) A clearing indica- 
 tor at a telephone exchange on a junction 
 line, which automatically indicates when 
 the conversation has terminated. 
 
 Automatic Contact-Breaker. A device 
 for causing an electric current to rapidly 
 make and break its own circuit. 
 
 Automatic Counter. In railway block- 
 signalling, an electro-magnetic device 
 for recording and indicating the signals 
 of an audible code. 
 
 Automatic Curb-Sender. In subma- 
 rine telegraphy, a transmitter in which 
 each signal is curbed automatically ; i. e., 
 each signal is followed by one or more 
 alternately directed impulses before earth- 
 ing, for the purpose of clearing the line 
 of its static charge. 
 
 Automatic Cut-in. Any arrangement 
 of parts that will automatically introduce 
 a translating device or an electric source 
 into a circuit on the occurrence of any 
 predetermined event. 
 
 Automatic Cut-Out. Any arrangement 
 of parts that will automatically cut-out 
 or remove a translating device or an elec- 
 tric source from a circuit on the occur- 
 rence of a predetermined event. 
 
 Automatic Cut-Out for Storage Bat- 
 tery. An automatic electro-magnetic 
 switch, inserted into the charging cir- 
 cuit of a storage battery, so arranged that 
 if the charging current falls below a safe 
 limiting strength the charging circuit 
 will be opened. 
 
 Automatic Cut-Out for Multiple-Con- 
 nected Electro-Receptive Devices. 
 (1) A device for automatically cutting 
 an electro-receptive device, such as a 
 lamp, out of a circuit. (2) A safety catch 
 or safety base. 
 
 Automatic Cut-Out for Series-Con- 
 nected Electro-Receptive Devices. 
 Means whereby an electro-receptive de- 
 vice, such as an arc lamp, is to all intents 
 and purposes automatically cut-out of, or 
 removed from, a circuit, by means of a 
 shunt of low resistance which permits the 
 greater part of the current to flow past 
 the lamp. 
 
 Automatic Cut-Out of Magneto. A 
 cut-out switch for automatically remov- 
 ing the armature of a magneto from the 
 telephone circuit by the action of a spring, 
 as soon as the handle is released. 
 
 Automatic Drop. An automatic annun- 
 ciator drop. 
 
 Automatic Electric Alarm-Bell. An 
 electric alarm-bell furnished with an 
 automatic contact-breaker. 
 
 Automatic Electric Bell. (1) A trem- 
 bling or vibrating bell. (2) An auto- 
 matic electric alarm-bell. 
 
 Automatic Electric Gas-Burner. An 
 
 electric device for both turning on the 
 gas and lighting it, and turning the gas off, 
 and thus extinguishing the light, by alter- 
 nately touching different buttons. 
 
 Automatic Electric Safety System for 
 Railroads. A system for automatically 
 preventing tne approach of two trains, 
 whatever their speed, beyond a pre- 
 determined distance from each other. 
 
 Automatic Fire- Alarm. An instrument 
 for automatically telegraphing an alarm 
 of fire from any locality on its increase in 
 temperature beyond a certain predeter- 
 mined point. 
 
 Automatic Fire- Annunciator. An an- 
 nunciator for automatically indicating 
 the point from which a fire-alarm has 
 been sent. 
 
 Automatic Steam- Whistle, Electric.^ 
 
Aut.J 
 
 689 
 
 [Aux. 
 
 A steam-whistle employed in absolute 
 block systems for railroads, whereby, 
 during fogs or snow-storms, when the 
 signals are hidden from view, the loco- 
 motive, on passing over a portion of the 
 road at a convenient distance from the 
 signal, is caused to make a succession of 
 electric contacts, whereby a steam whis- 
 tle is blown' on the moving train. 
 Automatic Switch. (1) A switch which 
 is automatically opened or closed on the 
 occurrence of certain predetermined 
 events. (2) In double-current telegraphy 
 an electro-magnetic switch which enables 
 the distant station to stop the sending 
 operator at the home station. 
 
 Automatic Switch for Incandescent 
 Electric Lamps. (1) A safety fuse or 
 safety cut-out. (2) Any switch by means 
 of which incandescent lamps can be 
 lighted or extinguished at a distance. (3) 
 A device for automatically closing the 
 circuit of a lamp or lamps on the opening 
 of a door, or passage of a barrier. (4) A 
 device for automatically opening the cir- 
 cuit of a lamp or lamps after the expira- 
 tion of a predetermined time or at the 
 closing of a door. 
 
 Automatic Telegraph. A general term 
 embracing the apparatus employed in 
 automatic or machine telegraphy. 
 
 Automatic Telegraph-Sounder. A 
 form of automatic telegraphic transmit- 
 ter. 
 
 Automatic Telegraph-Transmitter. 
 (1) A device for automatically transmit- 
 ting signals by means of embossed or per- 
 forated slips drawn under suitable con- 
 tact devices. (2) A transmitter employed 
 in automatic telegraphy for sending pre- 
 pared messages. 
 
 Automatic Telegraphy. A system of 
 telegraphy by means of which a tele- 
 graphic message is automatically trans- 
 mitted over a line by the motion of a pre- 
 viously perforated fillet of paper, the 
 perforations of which are arranged in the 
 order and length required to form the 
 characters to be transmitted. 
 
 Automatic Telephone-Exchange. A 
 system of telephony in which the sub- 
 scribers are able to secure selective inter- 
 communication without the aid of an 
 exchange operator. 
 
 Automatic Telephone Hook. An auto- 
 matic telephone switch, operated by hang- 
 ing up the telephone used in connection 
 with it. 
 
 Automatic Telephone Switch. (1) A 
 device for automatically transferring the 
 connection of the main line from the tele- 
 4-1 
 
 phone to the call-bell by the weight of 
 the telephone when hung up. (2) A 
 switch operated by the act of hanging up 
 or taking down a telephone from a hook 
 and employed to introduce or remove a 
 call-bell from the line. 
 
 Automatic Time Cut-Out. A device 
 which automatically cuts a translating 
 device or an electric source from a circuit 
 at a certain predetermined time, or after 
 the lapse of a predetermined time. 
 
 Automatic Variable Resistance. A 
 resistance the value of which can be auto, 
 matically varied. 
 
 Automatically Regulable. Capable of 
 automatic regulation. 
 
 Automatically Regulate. To regulate 
 in an automatic manner. 
 
 Automobile. (1) Self -movable. (2) Con- 
 taining the power necessary for its own 
 motion. 
 
 Automobile Carriage. A horseless car- 
 riage. 
 
 Automobile Torpedo. A torpedo which 
 contains the power required for its pro- 
 pulsion. 
 
 Automobile Vehicle. An automobile 
 carriage. 
 
 Auto-Reversible Tele-Radiophone. 
 
 (1) A photophone arranged so that a num- 
 ber of telegraphic communications may 
 be simultaneously sent either all in the 
 same direc f ion, or part in one direction, 
 and the remainder in the opposite direc- 
 tion. (2) A multiple tele-radiophone. 
 
 Auto-Starter. (1) A self -starting mech- 
 anism. (2) A self-starting ink-writer. 
 (3) A self-starting motor. 
 
 Auto-Telephone System. A system of 
 multiple-circuit telephony in which a 
 single battery is employed, whereby a 
 number of telephone stations can be con- 
 nected by a single cable without the use 
 of a distributing board, or exchange. 
 
 Auto-Transformer. A one-coil trans- 
 former consisting of a choking coil con- 
 nected across a pair of alternating-current 
 mains, and so arranged that a current or 
 pressure differing from that supplied by 
 the mains can be obtained from it by 
 tapping it at different points. 
 
 Auxiliary Bus. A central-station bus- 
 bar connected to an auxiliary pressure ; 
 i. e., a pressure different from the main- 
 station pressure. 
 
 Auxiliary Alarm Telegraph. In a sys- 
 tem of fire-alarm telegraphy, where an 
 alarm received in any one circuit is auto- 
 matically repeated over all the other cir 
 
Ave.] 
 
 690 
 
 [Bac, 
 
 cults, means whereby the repetition of 
 the signals are prevented from interfering 
 with the incoming signals of any of the 
 other circuits. 
 
 Average Efficiency of Motor. (1) The 
 efficiency of an electric motor based on 
 its average or mean load. (2) The ratio 
 of all the work that a motor delivers in a 
 given time to the electric energy it has 
 absorbed in that time. 
 
 Average Electromotive Force. The 
 mean electromotive force. 
 
 Average Life of Incandescent Lamp. 
 The mean time during which a number 
 of incandescent lamps will continue to 
 burn without breaking when connected 
 with a circuit of given pressure. 
 
 Average Value of Periodic Current 
 or E. M. F. The arithmetical mean 
 value of a periodic current or E. M. F., 
 with respect to magnitude and without 
 respect to sign or direction. 
 
 Avogrado's Hypothesis. Equal vol- 
 umes of different gases measured at the 
 same temperature and pressure contain 
 the same number of molecules. 
 
 Axes of Co-Ordinates. A vertical and a 
 horizontal line, usually intersecting each 
 other at right angles, and called respec- 
 tively the axes of ordinates and abscissas, 
 from which the ordinates and abscissas 
 are measured. 
 
 'Axial. Of or pertaining to an axis. 
 
 Axial Current. In electro-therapeutics, 
 
 a current flowing in a nerve in the oppo. 
 
 site direction to the normal impulse oi 
 
 the nerve. 
 Axial Magnet. A name sometimes given 
 
 to a solenoid with a straight core. 
 Axis of Abscissae or Abscissas. The 
 
 horizontal line in the axes of co-ordinates. 
 Axis of Magnetic Needle. A straight 
 
 line drawn through a magnetic needle, 
 
 and joining its poles. 
 
 Axis of Ordinates. The vertical line in 
 the axes of co-ordinates. 
 
 Azimuth. In astronomy, the apgle sub- 
 tended at an observer between the plane 
 of an azimuth circle and the plane of the 
 meridian. 
 
 Azimuth Circle. The arc of a great 
 circle passing through" the zenith, or the 
 point of the heavens directly overhead, 
 and the nadir, or the point directly be- 
 neath. 
 
 Azimuth Compass. (1) A compass used 
 for measuring the horizontal angular dis- 
 tance of any distant object from the mag- 
 netic meridian. (2) The mariner's com- 
 pass. 
 
 Azimuth Telegraph. On a war-ship a 
 telegraph for indicating at any or all 
 guns the azimuth of a target. 
 
 Azimuth and Range Telegraph. On 
 a war-ship a combined telegraph to the 
 guns of the azimuth and range of a target. 
 
 B 
 
 &. A symbol for magnetic intensity, or 
 induction density, usually expressed in 
 C. G. S. units per normal square centi- 
 metre. (Partly International usage. ) 
 
 B. (1) A symbol for magnetic induction, or 
 the amount of flux per normal square 
 centimetre of the magnetized material. 
 (2) A symbol for susceptance in alter- 
 nating-current circuits. 
 
 B. A. Ampere. The British Association 
 ampere in a circuit whose resistance is 
 one B. A. ohm under an E. M. F. of 
 one B. A. volt. 
 
 B. A. Balance. A type of balance or 
 bridge, originally employed by the British 
 Association Committee in duplicating B. 
 A. ohms. 
 
 B. A. Ohm. (1) The British Association 
 ohm. (2) The resistance of a column of 
 mercury one square millimetre in area of 
 normal cross-section, and 104.9 centi- 
 metres in length, at the temperature of 
 zero centigrade. 
 
 B. A. U. A contraction for British Asso- 
 ciation unit or ohm. 
 
 B. A. Unit. The British Association unit 
 of resistance or ohm. 
 
 B. S. G-. A contraction for British stand- 
 ard gauge. 
 
 B. & S. W. G-. A contraction for Brown 
 and Sharpe's wire gauge. 
 
 B. T. U. (1) A contraction for Bi'itish 
 thermal unit. (2) A contraction for Board 
 of Trade unit. 
 
 B. W. G. A contraction for Birmingham 
 wire gauge. 
 
 Back Ampere-Turns. Ampere-turns on 
 a dynamo armature which tend to oppose 
 the flux produced by the field magnets. 
 
 Back Electromotive Force. A term 
 
 sometimes used for counter-electromotive 
 
 force. 
 Back Induction. An induction opposed 
 
 to the field and tending to weaken or 
 
 neutralize it. 
 
Bac.] 
 
 691 
 
 [Bal. 
 
 Back Magnetization. A term some- 
 times used for backward or back induc- 
 tion. 
 
 Back Magnetization of Armature. 
 Counter-magnetomotive forces acting in 
 the main magnetic circuit of the field 
 coils, and tending to reduce the useful 
 flux passing through the armature. 
 
 Back of Electro-Magnet. The yoke of 
 an electro-magnet. 
 
 Back Pitch. The backward pitch of the 
 armature windings. 
 
 Back Stroke of Lightning. The return 
 stroke of lightning. 
 
 Back Stop of Key. A stop placed on the 
 back of a telegraph key in order to limit 
 its motion in the direction of release. 
 
 Back-Turns of Armature. (1) Those 
 turns on an armature whose current 
 tends to demagnetize the field. (2) The 
 back ampere-turns. 
 
 Backing Metal. An alloy that is placed 
 on the back of the copper shell of an elec- 
 trotype in order to stiffen it. 
 
 Backing Pan. The pan in which the cop- 
 per shell of an electrotype is placed in 
 order to receive its backing of type 
 metal. 
 
 Backward Induction of Dynamo Ar- 
 mature. The component of the arma- 
 ture induction that opposes the induction 
 of the field magnets. 
 
 Backward Pitch of Armature Wind- 
 ings. A pitch which is always left- 
 handed, or counter-clockwise, when re- 
 garded from the commutator side. 
 
 Backward Waves. In a closed circuit 
 supplied by a dynamo or other source of 
 electromotive force, a wave of potential 
 that is assumed to start from the negative 
 pole of the dynamo and travel around 
 the circuit in the opposite direction to the 
 forward wave of positive potential from 
 the positive pole of the dynamo. 
 
 Bad Earth. A term sometimes applied to 
 a bad ground, or a connection to earth 
 whose electric resistance is comparatively 
 high. 
 
 Bain Telegraph Code. An old form of 
 telegraphic alphabet originally employed 
 in connection with the Bain printing 
 instrument. 
 
 Bain's Chemical Recorder. An appa- 
 ratus for recording the dots and dashes of 
 a telegraphic despatch on a sheet of chemi- 
 cally prepared paper. 
 
 Bain's Chemical Solution. Bain's print- 
 ing solution. 
 
 Bain's Printing Solution. (1) The so- 
 lution used in Bain's chemical recorder. 
 (2) A solution of potassium f erro-cyanide 
 and water. 
 
 Baking Oven, Electric. An electrically 
 heated baking oven. 
 
 Balance Arm. One of the arms of an 
 electric balance. 
 
 Balance Arms. The arms of an electric 
 balance. 
 
 Balance, Electric. A term sometimes 
 used for an electric bridge. 
 
 Balance Galvanometer. A dynamo gal- 
 vanometer employed for indicating when 
 the pressure of the dynamo is equal to 
 the pressure on the bus-bars. 
 
 Balance Indicator. Any device for indi- 
 cating when an electric balance has been 
 obtained. 
 
 Balance Indicator of Three-Wire Sys- 
 tem. A device for indicating when a 
 balance is obtained between the positive 
 and negative leads of a three-wire system 
 of distribution. 
 
 Balance of Induction in Cable. The 
 neutralization of induction in a cable by 
 the presence of equal and opposite effects. 
 
 Balance of Telegraphic Circuit. The 
 condition of a duplexed telegraph line 
 when the home relay ceases to respond to 
 the home key. 
 
 Balance Photometer. A photometer 
 based on the decomposition of iodide of 
 nitrogen by the action of light. 
 
 Balanced Armature. (1) An armature 
 whose weight is symmetrically distributed 
 as regards its axis of rotation. (2) An 
 armature that has been so adjusted by 
 the addition of weights that its weight is 
 symmetrically distributed with reference 
 to its axis of rotation. 
 
 Balanced Circuit. A telephonic, tele- 
 graphic, or other circuit which has been 
 so erected and adjusted as to be free 
 from mutual inductive disturbances from 
 neighboring circuits. 
 
 Balanced Load. A load which is sym- 
 metrically divided between two or more 
 generating units, as in the three-wire, 
 five-wire, multiple, or polyphase systems 
 of distribution. 
 
 Balanced Magnetic Circuits of Arma- 
 ture. The magnetic circuits traversing 
 the armature of a dynamo-electric ma- 
 chine through which the magnetic fluxes 
 produced by the field are symmetrically 
 distributed in regard to flux density, total 
 flux, and geometrical distribution. 
 
 Balanced Metallic Circuit. A metallic 
 
Bal.] 
 
 692 
 
 [Ban. 
 
 circuit, the two sides of which have sim- 
 ilar electric properties. 
 Balanced Polyphase System. A poly- 
 phase system all the branches of which 
 are symmetrical in regard to their electro- 
 motive force, current, and phase. 
 
 Balanced Reaction Coil. A coil em- 
 ployed in a system of distribution by 
 alternating-current transformers for 
 maintaining a constant current in the sec- 
 ondary circuit or circuits despite changes 
 in the load placed therein. 
 
 Balanced Resistance. A resistance so 
 placed in a bridge or balance as to be bal- 
 anced by the remaining resistances in the 
 bridge. 
 
 Balanced System. An electric system 
 of distribution or communication which 
 is so adjusted as to be free from mutual 
 inductive disturbances from neighboring 
 systems. 
 
 Balancing. Rendering a metallic tele- 
 phone circuit free from inductive dis- 
 turbances from other lines. 
 
 Balancing Coil of Armature. An aux- 
 iliary field-winding in series with an 
 armature, and having its magnetomotive 
 force equal and opposite to that of the 
 armature current, so that their total mag- 
 netic effect upon the field is zero, and the 
 field flux remains unchanged at all loads. 
 
 Balancing of Telegraph Line. In du- 
 plex or quadruplex telegraphy the opera- 
 tion of adjusting the balance between 
 the real and artificial lines, whereby the 
 home signals do not affect the receiving 
 instruments. 
 
 Balancing Relay .A differentially wound 
 relay. 
 
 Balancing Resistance for Dynamos. 
 A regulating resistance that possesses a 
 sufficient range to balance one dynamo 
 against another with which it is operated 
 in parallel. 
 
 Balancing Thermopile. (1) A double 
 thermopile. (2) A differential thermo- 
 pile. 
 
 Balancing Wire or Conductor. A term 
 sometimes employed for the neutral wire 
 or conductor of a three-wire system. 
 
 Balata. An insulating material. 
 
 Ball Lightning. A name sometimes 
 given to globular lightning. 
 
 Ballistic Curve. The curve actually de- 
 scribed by a projectile thrown through 
 the air in any other than a vertical direc- 
 tion. 
 
 Ballistic Galvanometer. (1) A galvano- 
 meter designed to measure the total quan- 
 
 tity of electricity in a discharge lasting for 
 a brief interval, as, for example, the cur- 
 rent caused by the discharge of a conden- 
 ser. (2) A galvanometer, in which the 
 movable part is as little damped as pos- 
 sible, suitable for measuring electric 
 charges or discharges, and usually ad- 
 justed to have a long period of vibration 
 or slow swing. 
 
 Ballistic Pendulum. A pendulum with 
 a heavy bob employed to determine the 
 velocity of a projectile fired into it. 
 
 Balloon Buoy. A buoy used in submarine 
 cable work somewhat resembling a bal- 
 loon in shape. 
 
 Balloon, Electric. (1) A balloon or air- 
 ship provided with electric power so as to 
 be capable of being started or moved 
 against the direction of the wind. (2) An 
 electrically dirigible balloon. 
 
 Balloon Signalling for Military Pur- 
 poses. Transmitting intelligence, as of 
 the movements of an enemy's army, 
 from observations made in balloons by 
 means of telephone circuits directly 
 connected with the balloons. 
 
 Band Arc Lamp. An arc lamp in which 
 the feeding of the carbons is effected 
 through the movements of a band of cop- 
 per, which carries the upper carbon holder 
 and conducts the current into the arc. 
 
 Band or Banded Spectrum. The con- 
 dition assumed by the spectrum of a com- 
 pressed gas or vapor when sufficiently 
 heated, in which the lines of the ordinary 
 spectrum are broadened into bands. 
 
 Banjo. A wooden drum fastened upon a 
 kite-shaped board, employed for tighten- 
 ing a pole-strung telephone or telegraph 
 wire. 
 
 Bank Board. A small switchboard con- 
 taining a bank of lamps used in an alter- 
 nating-current series-incandescent system 
 of street lighting, and usually supplied 
 with an ammeter and switch for intro- 
 ducing one or more relief lamps. 
 
 Bank of Lamps. A group of electric 
 lamps collected together in a common 
 structure, usually for the purpose of ob- 
 taining a load. 
 
 Bank of Transformers. A group of 
 transformers collected together in a com- 
 mon structure usually either for the pur- 
 pose of obtaining a load, or for readily 
 varying the pressure. 
 
 Banked Battery. A term sometimes 
 applied to a battery from which a num- 
 ber of separate circuits are supplied with 
 current. 
 
 Banking Transformers. (1) Grouping 
 
Bar.] 
 
 693 
 
 [Bat. 
 
 transformers in a common structure either 
 for the purpose of obtaining a load, or 
 for readily varying the pressure. (2) As- 
 sociating transformers in parallel. (3) 
 Associating transformers in series. 
 
 Bar Armature. An armature whose con- 
 ductors are formed of bars. 
 
 Bar Electro-Magnet. An electro-mag- 
 net, the core of which is in the foi-m of a 
 straight bar or rod. 
 
 Bar Windings. Armature windings 
 composed of copper bars. 
 
 Bar-Wound Armature. An armature 
 in which the conductors have the form of 
 bars. 
 
 Barad. (1) A unit of intensity of pressure. 
 (2) A dyne per square centimetre. 
 
 Bare Arc-Light Carbons. Arc-light car- 
 bons or pencils unprovided with an elec- 
 tro-plating of copper or other conducting 
 metal. 
 
 Bare Carbons. Arc-light or battery car- 
 bons, unprovided with an electro-plating 
 of copper. 
 
 Barker's Wheel. An early form of reac- 
 tion water wheel. 
 
 Barlow's Wheel. A wheel or disc of 
 metal, capable of rotation on an axis, 
 that is set into rotation when placed be- 
 tween the poles of magnets and traversed 
 between its centre and circumference by 
 a current of electricity, 
 
 Barometer. An apparatus for measuring 
 the atmospheric pressure. 
 
 Barometric Column. A column, usually 
 of mercury, approximately 30 inches in 
 vertical height, sustained in a barometer 
 or other tube by the atmospheric pres- 
 sure. 
 
 Barometric Gradient. The drop or fall 
 of atmospheric pressure per unit of dis- 
 tance as measured between two adjacent 
 isobars. 
 
 Barrel of Jack. In telephony a conduct- 
 ing cylinder in a jack for making con- 
 tact with the sleeve of a plug. 
 
 Barrow-Reel. A reel supported on a 
 barrow for convenience in paying out an 
 overhead conductor during its installa- 
 tion. 
 
 Bar Winding of Armature. A winding 
 consisting of insulated copper bars con- 
 nected at their extremities. 
 
 Base Frame of Generator. The frame 
 on which a generator is supported. 
 
 Basis Metal of Electro-Plating. The 
 
 metal on whose surface an electro-plating 
 is to be deposited. 
 
 Batch Working. In telegraphy a method 
 of operating consisting in "sending a 
 plurality of messages in one direction over 
 a line, and then a plurality of messages 
 in the opposite direction, as distinguished 
 from up-and-down working. 
 
 Bathometer. An instrument for obtain- 
 ing deep-sea soundings without the use 
 of a sounding-line. 
 
 Battery. A name frequently used for an 
 electric-battery. 
 
 Battery. (1) To place a storage battery 
 on a storage-battery car. (2) To supply 
 a battery to a station or circuit. 
 
 Battery Car. A storage-battery car. 
 
 Battery, Electric. A general name ap- 
 plied to the combination, as a single 
 source, of a number of separate electric 
 sources. 
 
 Battery Gauge. A form of portable gal- 
 vanometer suitable for ordinary battery 
 testing work. 
 
 Battery Jar. A jar provided for holding 
 the electrolyte of each of the separate 
 cells of a primary or secondary battery. 
 
 Battery Lamp. An incandescent lamp 
 of such low voltage as to be readily oper- 
 ated by the ordinary voltage of a battery 
 of a few series-connected cells. 
 
 Battery Motor. An electric motor so 
 wound as to be properly operated by the 
 comparatively low electromotive force Of 
 an ordinary battery. 
 
 Battery of Alternators. A number of 
 separate alternators so connected as to be 
 capable of acting as a single alternator. 
 
 Battery of Generators. A number of 
 separate generators so connected as to be 
 capable of acting as a single generator. 
 
 Battery Pole-Changer. A form of trans- 
 mitter employed in duplex telegraphy for 
 readily reversing the direction of the 
 main battery so as to send signals to the 
 line. 
 
 Battery Solution. The exciting liquid 
 or electrolyte of a primary or secondary 
 cell. 
 
 Battery Stand. The insulating or insu- 
 lated stand provided for holding a pri- 
 mary or secondary battery. 
 
 Battery Syringe. A syringe for either re- 
 moving the acid or spent liquids from a 
 voltaic battery, or for introducing fresh 
 liquid. 
 
 Battery System for Electric Railroads. 
 
 A system for the propulsion of street cars 
 by means of storage batteries. 
 Battery Transformer. A step-up trans- 
 former so wound as to be readily operated 
 
Bat.] 
 
 694 
 
 [Bic. 
 
 by a primary battery of a few series-con- 
 nected cells. 
 
 Battle Circuit. A circuit on a warship, 
 connected with the conning tower and 
 provided for use during action. 
 
 Battle Lantern. A form of safety lantern 
 for use in action on board a warship. 
 
 Bead. Areometer. A form of hydrometer 
 suitable for rapidly testing the density of 
 the exciting liquid in a storage cell. 
 
 Bead Chain. A chain of metallic beads 
 sometimes employed for the pull in a 
 pendant electric-burner. 
 
 Bead Hydrometer. A bead areometer. 
 
 Bead Lightning. A form of lightning 
 discharge in which the flashes produce a 
 discontinuous line of light possessing a 
 bead-like appearance. 
 
 Beaded Cable. A form of cable employed 
 for high-tension transmission, provided 
 with a sheathing of strung porcelain 
 beads. 
 
 Bec-Carcel. The carceL or French photo- 
 metric standard. 
 
 Becquerel Radiation. An invisible ra- 
 diation, discovered by Becquerel, emitted 
 by certain salts, especially those of ura- 
 nium, capable both of penetrating many 
 media opaque to ordinary light, and 
 affecting a photographic plate. 
 
 Becquerel Bays. Becquerel radiation. 
 
 Bed-Plate of Dynamo-Electric Ma- 
 chine. The base or frame of a dynamo- 
 electric machine. 
 
 Bega. A prefix for a billion, one thousand 
 million, or 10 9 . 
 
 Begadyne. One billion dynes, or roughly, 
 the earth's gravitational force on a ton 
 of matter. 
 
 Beg-Erg. One billion ergs ; or, 73.7 foot- 
 pounds, approximately. 
 
 Beg-Ohm. One billion ohms, or one thou- 
 sand megohms. 
 
 Begohm Galvanometer. A galvano- 
 meter which gives unit deflection through 
 a resistance of one begohm in circuit with 
 one volt. 
 
 Bell Box. In telephony a box containing 
 or designed to contain a telephone bell. 
 
 Bell Hanger's Joint. A careless form of 
 telegraphic or telephonic joint in which 
 the ends of the wires are merely looped 
 into each other. 
 
 Bell Mouth of Cable Tank. A circular 
 aperture provided in the top of a cable 
 tank, through which a cable is led into 
 or taken out of the tank. 
 
 Bell Pull, Electric. Any circuit-closing 
 device operated by a pull. 
 
 Bell-Shaped Magnet. A modified form 
 of horse-shoe magnet in the form of a 
 split tube, and in which the approached 
 poles are semi circular in shape. 
 
 Bell Switch. A switch connected with a 
 telephone alarm-bell for the purpose of 
 throwing it in or out of circuit. 
 
 Belt Circuit. A series lighting circuit 
 extending in the form of a wide loop, 
 belt, or circle, as opposed to a circuit 
 formed of two closely associated parallel 
 wires. 
 
 Belt-Driven Generator. A generator 
 driven by means of belting, as distin- 
 guished from a direct-driven or rope- 
 driven generator. 
 
 Belt-Driving or Coupling. Driving or 
 
 coupling by means of belts. 
 Belt, Electric.^A belt suitably shaped 
 so as to be capable of being worn on the 
 body, consisting either of imaginary or 
 real voltaic or thermo-electric couples, 
 and employed for its alleged therapeutic 
 effects. 
 
 Belt of Current. The total current gen- 
 erated by an armature at any moment, 
 assumed as making a single turn around 
 the armature. 
 
 Belt Speed. The velocity of translation 
 or linear speed of a belt in the transmission 
 of power. 
 
 Bessel's Functions. A series of mathe- 
 matical functions often connected with 
 problems in electricity and satisfying a 
 certain relation first enunciated by Bessel 
 in connection with an astronomical prob- 
 lem. 
 
 Bias of Relay Tongue. A term em- 
 ployed to signify such an adjustment of 
 a polarized relay that on the cessation 
 of a working current the relay tongue 
 shall always rest against the insulated 
 contact, and not against the other con- 
 tact, or vice versa. 
 
 Bichromate Voltaic Cell. A zinc-car- 
 bon couple employed with a solution of 
 bichromate of potash and sulphuric acid 
 in water. 
 
 Bicro. A prefix for one billionth, one 
 thousand millionth, or 10- 9 . 
 
 Bicro-Ampere. The billionth of an am- 
 pere. 
 
 Bicro-Farad. The billionth of a farad. 
 Bicro-Henry. The billionth of a henry. 
 Bicron. A unit of length equal to the 
 
 billionth of a metre, and indicated by the 
 
 symbol pp. 
 
Bic.] 
 
 695 
 
 [Bi-T. 
 
 Bicycle Car. An electrically propelled 
 car whose weight rests on a single rail, 
 and which is kept in position by a guide 
 rail supported vertically above the main 
 rail. 
 
 Bicycle Electric Lamp. An incandes- 
 cent lamp suitable for use on a bicycle 
 and usually operated by a small voltaic 
 battery. 
 
 Bifllar Control of Galvanometer 
 Needle. The control of a galvanometer 
 needle whereby it returns to its position 
 of rest, on the removal of the deviating 
 force, by the operation of a bifilar sus- 
 pension. 
 
 Bifilar Suspension. S u s p e n s i o n by 
 means of parallel vertical wires or fibres 
 as distinguished from suspension by a 
 single wire or fibre. 
 
 Bifllar Winding. The method of wind- 
 ing employed in resistance coils to obviate 
 the effects of self-induction, in which the 
 wire, instead of being wound in one contin- 
 uous It^igth, is doubled on itself before 
 winding. 
 
 Bight of Cable. A single loop or bend 
 of cable. 
 
 Bimetallic Accumulator. An accumu- 
 lator or storage cell whose positive and 
 negative plates are formed respectively 
 of two different metals. 
 
 Bimetallic Helix. A compound helix of 
 two metals of different expansibilities, 
 such as copper and steel, firmly riveted 
 or soldered together, so that the helix is 
 twisted or moved in one direction by un- 
 equal expansion, and in the opposite direc- 
 tion by unequal contraction. 
 
 Bimetallic Thermometer. A thermom- 
 eter whose operation depends on the ex- 
 pansion and contraction of a bimetallic 
 helix. 
 
 Bimetallic Thermostat. A form of ther- 
 mostat employed for opening or closing a 
 circuit by the expansions and contractions 
 of a bimetallic arc-shaped spring. 
 
 Bimetallic Wire. A compound tele- 
 phone or telegraph wire consisting of a 
 steel core and a copper envelope, suitable 
 for long-span overhead-construction. 
 
 Binary Compound. A compound 
 formed by the union of two different 
 elements. 
 
 Binding Coils. Coils of wire, wound on 
 the outside of the armature coils and at 
 right angles thereto, to prevent the loosen- 
 ing of the armature coils during rotation 
 by centrifugal force. 
 
 Binding Post. A metallic binding screw, 
 rigidly fixed to some apparatus or support, 
 
 and employed for conveniently making 
 firm electric connections. 
 
 Binding Screw. A name sometimes ap- 
 plied to a binding post. 
 
 Binding Wire for Telegraph Lines. 
 
 (1) The wire employed for securing a tele- 
 graph wire to the insulator which sup- 
 ports it. (2) A tie wire. 
 
 Binnacle Compass. A compass on board 
 ship placed in a binnacle for use in steer- 
 ing or directing the vessel. 
 
 Biograph. An apparatus for obtaining on 
 a screen, from a rapid succession of suit- 
 able pictures, the appearance of the actual 
 movements of natural objects. 
 
 Bioplasm. (1) Any form of living matter 
 possessing the power of reproduction. 
 
 (2) Living protoplasm. 
 Bioscope. A biograph. 
 
 Bioscopy, Electric. The determination 
 of the presence of life or death by the 
 passage of electricity through the nerves 
 or muscles. 
 
 Bipolar. Having two poles. 
 
 Bipolar Armature. An armature suit- 
 able for use in a bipolar field. 
 
 Bipolar Armature-Winding. Any ar- 
 mature winding suitable for use in a 
 bipolar field. 
 
 Bipolar Bath. An electro-therapeutic 
 bath, the current supplied to which enters 
 at one part of the bath-tub and leaves 
 at another. 
 
 Bipolar Dynamo-Electric Machine. 
 A dynamo-electric machine with a bi- 
 polar field. 
 
 Bipolar Generator. A bipolar dynamo- 
 electric machine. 
 
 Bipolar Magnetic Field. A magnetic 
 field formed by two opposite magnetic 
 poles. 
 
 Bird Cage, Electric. A bird-cage-shaped 
 wire screen employed by Hertz in his in- 
 vestigations on the propagation of electro- 
 magnetic waves for screening the spark 
 micrometer. 
 
 Bird Cage. In submarine cable-work, a 
 mechanical distortion of the sheathing 
 in which the wires are locally bulged out- 
 wards leaving the serving or core visible 
 or exposed. 
 
 Birmingham Wire Gauge. An En- 
 glish wire gauge. 
 
 Bismuth Spiral. A flat spiral of bismuth 
 wire employed for the measurement of 
 strong magnetic fields. 
 
 Bi-Telephone. A term sometimes ap- 
 plied to a double telephone receiver ar- 
 
Biv.] 
 
 696 
 
 [Bol. 
 
 ranged so as to permit the ready applica- 
 tion of both ears of the listener to the 
 receiving instruments. 
 
 Bivalent. (1) Possessing an atomicity or 
 valency of two. (2) Divalent. 
 
 Bitite. A variety of insulating material. 
 
 Black Electro-Metallurgical Deposit. 
 A dark electro-metallurgical deposit that 
 is thrown down from the metal in a plat- 
 ing bath when too strong a current is 
 employed. 
 
 Black Lead. Plumbago or graphite. 
 
 Black Leading Machine for Electro- 
 Types. A machine for covering the 
 printing surface of the wax impression 
 employed in electro-typing with an elec- 
 trically conducting surface of black lead. 
 
 Black Light. Non-luminous radiation. 
 
 Blake Telephone Transmitter. A 
 
 form of carbon telephone transmitter. 
 
 Blank Panel. A panel on a switchboard 
 provided for the support of extra circuit 
 connections or instruments. 
 
 Blasting, Electric. The electric ignition 
 of powder or other explosive material in 
 a blast. 
 
 Blavier's Formulae. The formulae em- 
 ployed in the Blavier test. 
 
 Blavier's Test. A test introduced by 
 Blavier, for localizing a single fault in a 
 single telegraph line or conductor, by 
 measuring the resistance at one end of 
 the line, when the other end is succes- 
 sively freed and earthed. 
 
 Bleaching, Electric. A bleaching pro- 
 cess in which the bleaching agents are 
 liberated as required by electrolytic de- 
 composition. 
 
 Block. To stop or check by means of a 
 block system. 
 
 Block-Facing. In a system of electric 
 distribution mains a section of conductors 
 extending in front of a city block-facing. 
 
 Block System for Railroads. A sys- 
 tem for avoiding the collision of moving 
 railroad trains, by dividing the road into 
 a number of separate blocks or sections of 
 a given length, and so maintaining tele- 
 graphic communication between towers 
 located at the ends of each of such blocks, 
 as to prevent, by the display of suitable 
 signals, more than one train or engine 
 from being on the same block at the same 
 time. 
 
 Block Wire. The line or wire employed 
 in block systems for railroads connecting 
 each block tower with the next tower on 
 each side of it. 
 
 Blooms. Masses of wrought or cast metal, 
 generally rectangular in shape and ap- 
 proximately six inches square and three 
 or four feet in length, from which wires 
 are obtained by rolling. 
 
 Blow. To melt or fuse a safety fuse. 
 
 Blow-Pipe, Electric. A blow-pipe in 
 which the air-blast is obtained by a con- 
 vective electric discharge. 
 
 Blower, Electric. An electrically driven 
 blower. 
 
 Blowing a Fuse. The fusion or volatili- 
 zation of a fuse wire or safety strip by 
 the current passing through it. 
 
 Blowing Point of Fuse. The current 
 strength at which a fuse blows or melts. 
 
 Blue Magnetic Pole. A term sometimes 
 employed for the south-seeking magnetic 
 pole. 
 
 Bluestone Gravity Cell. A voltaic cell 
 consisting of a zinc-copper couple whose 
 elements are immersed respectively in 
 electrolytes of zinc sulphate & nd copper 
 sulphate. 
 
 Board of Trade Unit. (1) A unit of elec- 
 tric supply, or the energy contained in a 
 current of 1.000 amperes flowing for one 
 hour under a pressure of one volt. (2) A 
 kilowatt-hour. 
 
 Boat, Electric. An electrically propelled 
 boat. 
 
 Bobbed. A word employed to character- 
 ize a surface that has been polished by 
 the action of a bob. 
 
 Bobbin, Electric. A coil of insulated 
 wire suitable for the passage of an elec- 
 tric current for any purpose, as, for ex- 
 ample, energizing an electro-magnet. 
 
 Body -Protector, Electric. A device for 
 protecting the human body against the 
 accidental passage through it of an electric 
 discharge. 
 
 Boiler-Feed, Electric. A device for 
 electrically opening a boiler-feed appa- 
 ratus when the water in the boiler falls 
 to a certain predetermined point. 
 
 Boiling of Secondary or Storage Cell. 
 
 A term sometimes applied to the gassing 
 
 of a storage cell. 
 Bole. A unit of momentum, proposed by 
 
 the British Association, equal to one 
 
 gramme-kine. 
 Bolognian Stone. A name formerlygiven 
 
 to a calcareous substance that becomes 
 
 phosphorescent on exposure to light. 
 
 Bolometer. (1) An apparatus for electri- 
 cally measuring small differences of 
 temperature. (2) A fine wire or thin strip 
 
Bol.] 
 
 697 
 
 [Bra. 
 
 of metal whose resistance is altered by 
 incident radiant energy. 
 
 Bolometric Spectrum. The luminous 
 and non-luminous spectrum obtained by 
 the use of a rock-salt prism, or a diffraction 
 grating, for the measurement of radia- 
 tion in the bolometric spectrometer. 
 
 Bolometric Spectrometer. A spectro- 
 meter designed for the measurement of 
 radiation, luminous or otherwise. 
 
 Bolt. A lightning discharge. 
 
 Bombardment, Electric. M o 1 e c u 1 a r 
 
 bombardment. 
 
 Bombardment Incandescent Lamp, 
 Electric. An electric lamp in which re- 
 fractory material is rendered incandes- 
 cent by molecular bombardment produced 
 by the passage of an electric discharge 
 through a rarefied space. 
 
 Bonded Bails. In any electric system 
 where the rails are used as a part of the 
 circuit, as in a trolley system, rails con- 
 nected at their joints by suitable bonds 
 for the purpose of bringing them into 
 good electric contact with one another. 
 
 Bonding Resistance of Bail. The resist- 
 ance offered in a rail circuit at the 
 bonded joints. 
 
 Bonsalite. An insulating substance. 
 
 Bony Current. The electric current re- 
 sulting from the difference of potential 
 existing between the different parts of a 
 bone in a recently killed animal. 
 
 Booster. A dynamo, inserted in a special 
 feeder or group of feeders in a distribu- 
 tion system, for the purpose of raising the 
 pressure of that feeder or group of feed- 
 ers, above that of the rest of the system. 
 
 Boreal Fluid. A term formerly applied 
 to the fluid that was supposed to exist 
 around, or to emanate from, the boreal 
 pole of a magnet. 
 
 Boring, Electric. Forming holes in 
 metajs or minerals by the heat of the 
 voltaic arc. 
 
 Bot. A contraction sometimes used for 
 Board of Trade unit of electric supply, or 
 the kilowatt -hour. 
 
 Boucherize.- To subject to the boucher- 
 izing process. 
 
 Boucherizing. A process for preserving 
 wooden telegraph poles, or railroad sleep- 
 ers, by injecting a solution of copper sul- 
 phate into the pores of the wood. 
 
 Bougte-Decimale. (1) The standard 
 French candle. (2) A standard of lumi- 
 nous intensity equal to the l-20th of that 
 of the Yiolle molten-platinum standard. 
 
 Bougie-Metre. A unit of illumination 
 
 7_ 
 
 equal to the normal illumination from 
 a bougie-decimale at the distance of one 
 metre, sometimes called a lux. 
 
 Bound Charge. The condition of a charge 
 on a conductor placed near another con- 
 ductor, but separated from it by a me- 
 dium through which electrostatic induc- 
 tion can take place. 
 
 Bow Gear. The gear placed at the bow of 
 a cable ship for the ready handling of a 
 cable or the ropes used in cable work. 
 
 Box Balance. A box form of electric 
 bridge. 
 
 Box Bridge. A commercial form of elec- 
 tric bridge or balance in which both the 
 arms of the bridge and the known resist- 
 ances consist of standardized resistance 
 coils placed in a suitable box. 
 
 Box-Sounding Belay. A relay whose 
 magnet is surrounded by a resonant case 
 of wood, for the purpose of increasing the 
 intensity of the sounds made by the ar- 
 mature of the magnet. 
 
 Boxing the Compass. Naming consec- 
 utively all the different points or rhumbs 
 of a compass from any one of them. 
 
 Bracket- Arm. An arm supported by a 
 bracket for carrying a line insulator. 
 
 Bracket- Arm Hanger. A hanger for an 
 overhead trolley line supported on a 
 bracket arm. 
 
 Bracket Pole. In a system of overhead 
 wires, a pole employed for the support 
 of the brackets provided for the suspen- 
 sion of the overhead wires or conductors. 
 
 Bracket Suspension-Ear. A trolley ear 
 supported on a bracket arm, designed for 
 the suspension of an overhead trolley 
 wire. 
 
 Brake Arm. An arm or lever connected 
 with the brake shoe, and by which the 
 brake power is applied. 
 
 Brake Disc. An electro-magnet in the 
 form of a disc, employed in an electric 
 street-car brake. 
 
 Brake Handle. A handle projecting 
 above the dasher of a car for the opera- 
 tion of the hand brake mechanism. 
 
 Brake Shoe. A mass of metal whose out- 
 line conforms to the tread of a car wheel, 
 which is pressed against the circumfer- 
 ence of the wheel on the operation of 
 the brake mechanism, for the purpose of 
 stopping the car. 
 
 Braided Wire. A wire covered with a 
 braiding of insulating material. 
 
 Branch. (1) In a system of parallel distri- 
 bution, any conductor from which outlets 
 
 Vol. 2 
 
Bra.] 
 
 698 
 
 [Bre. 
 
 are taken or taps made. (2) One of the 
 divisions of a divided conductor. 
 
 Branches. (1) Conductors connected to 
 the submains or supply conductors in a 
 system of incandescent lighting. (2) 
 Wires tapped to mains. 
 
 Branch. Block. A porcelain block pro- 
 vided with suitable grooves in which the 
 terminals or conductors are placed for 
 connecting a pair of branch wires to the 
 mains. 
 
 Branch Box. A box containing a branch 
 block. 
 
 Branch Circuits. (1) Additional circuits 
 provided at points of a circuit where the 
 current branches or divides, part of the 
 current flowing through the branch, and 
 the remainder flowing through the origi- 
 nal circuit. (2) A shunt circuit. 
 
 Branch Conductor. (1) A conductor 
 placed in a branch or shunt circuit. 
 (2) A smaller or sub-conductor tapping a 
 main. 
 
 Branch Coupling Box. In a system of 
 street mains a coupling box suitable for 
 connecting a house service connection 
 with the incandescent mains supplying 
 the house. 
 
 Branch Cut-Out. A safety fuse or cut- 
 out, inserted between a pair of branch 
 wires and the mains supplying them. 
 
 Branch Fuse. A branch cut-out or safety 
 fuse. 
 
 Branch of Multiple Circuit. Any of 
 the separate circuits that are connected 
 between the mains in a multiple circuit. 
 
 Branch Point of Circuit. Any point of 
 a circuit from which a branch is taken 
 off. 
 
 Branch-Wire Terminal Telephone 
 Switchboard. A three-wire multiple 
 switchboard for a telephone in which the 
 jacks for any one subscriber are connected 
 in successive panels in parallel instead of 
 in series. 
 
 Branched Magnetic Circuit. A mag- 
 netic circuit in which the flux sub- 
 divides into a number of separate mag- 
 netic circuits. 
 
 Branched Series. A term sometimes em- 
 ployed for series-multiple. 
 
 Branching Boards. Multiple telephone 
 switchboards connected on the branching 
 or multiple system. 
 
 Branching Telephone System. (1) A 
 system of multiple telephone switchboards' 
 employing the branching or three-wire 
 switchboard. (2) A system of multiple 
 telephone switchboard in which the vari- 
 
 ous jacks on one line are connected in 
 parallel instead of in series. 
 
 Branding, Electric. The process where- 
 by a branding tool is heated to incan- 
 descence by an electric current instead 
 of by ordinary means. 
 
 Bread-and-Butter Cable. A name 
 given to a form of light submarine cable 
 in which the sheathing consists alter- 
 nately of yarns and wires. 
 
 Breadth Coefficient of Armature Coil. 
 
 The ratio of the effective electromotive 
 force induced in an armature coil to the 
 effective electromotive force which would 
 be induced if the coil had no breadth ; i. e. , 
 if all its wire could be compressed into 
 the space occupied by a single turn. 
 
 Breadth of Coil. The angular distance to 
 which a coil extends circumferentially 
 around an armature core. 
 
 Break. Any lack of conducting continuity 
 in a circuit. 
 
 Break-Down Switch. A panel switch 
 employed in small three-wire systems, 
 for connecting the positive and negative 
 bus-bars so as to convert the system into 
 a two-wire system, and thus, in case of 
 a break-down, to permit the system to 
 be supplied with current from a single 
 dynamo. 
 
 Break-Induced Current. (1) The cur- 
 rent induced in an active circuit by 
 breaking or opening that circuit. (2) The 
 current induced in a secondary circuit on 
 the breaking of the circuit of the pri- 
 mary. 
 
 Break Key. A key which opens or breaks 
 the circuit when depressed. 
 
 Break Shock. A term sometimes em- 
 ployed in electro-therapeutics for the 
 physiological shock produced on the open- 
 ing or breaking of an electric circuit. 
 
 Break Signal. In telegraphy a name 
 given to the signal which separates the 
 preamble from the text of a message, or 
 the text from the signature. 
 
 Breaking Capacity of Switch. The 
 strength of current which can be safely 
 and effectively interrupted by a switch, 
 as distinguished from the carrying capac- 
 ity of the same. 
 
 Breaking Down of Dielectric. Such a 
 weakening of a dielectric subjected to 
 electric pressure as permits disruptive 
 discharges to pass through its substance. 
 
 Breaking Down of Insulation. The 
 failure of an insulating material, as evi- 
 denced by the disruptive passage of an 
 electric discharge through it. 
 
Ere.] 
 
 G99 
 
 [Bri. 
 
 Breaking In. (1) An interruption in the 
 sending of a telegraphic despatch by an 
 intermediate operator who endeavors to 
 simultaneously use the line. (2) Introduc- 
 ing a key into a telegraph circuit by open- 
 ing its switch. (3) Interrupting the con- 
 tinuity of a circuit. 
 
 Breaking the Primary. Opening or 
 breaking the circuit of the primary of an 
 induction coil or transformer. 
 
 Breaking Weight of Wire. The weight 
 required to be hung on the end of a wire 
 in order to break it. 
 
 Breast Plate. The breast support for the 
 microphone transmitter of a central 
 telephone station operator. 
 
 Breast Telephone Transmitter. A 
 telephone transmitter supported for con- 
 venience on a plate placed on the breast 
 of the operator. 
 
 Breath Figures, Electric. Faint figures 
 of condensed vapor produced by electrify- 
 ing a coin or other conducting object, 
 placing it momentarily on the surface of 
 a clean, bright, glass sheet, and then 
 breathing gently on the spot where the 
 coin was placed. 
 
 Breeze, Electric. A brush discharge em- 
 ployed in electro-therapeutics. 
 
 Breguet's Manipulator. A sending in- 
 strument employed by Breguet in his 
 system of step-by-step, or dial telegraphy. 
 
 " Bridge." A word sometimes employed 
 for multiple-arc. 
 
 Bridge Arms. The arms of an electric 
 bridge or balance. 
 
 Bridge Balance of Telegraph Line. 
 Such a balance of a duplexed telegraph 
 line, obtained by an electric bridge, in 
 which the home relay ceases to respond 
 to the home key. 
 
 Bridge Duplex. The bridge method of 
 duplex telegraphy, as distinguished from 
 the differential method. 
 
 Bridge, Electric. (1) A device whereby 
 an unknown electric resistance is readily 
 measured. (2) A device for measuring 
 an unknown resistance by comparison 
 with two fixed resistances and an adjust- 
 able resistance. 
 
 Bridge Method of Duplex Teleg- 
 raphy. (1) A system whereby two 
 telegraphic messages can be simultane- 
 ously transmitted over a single wire in 
 opposite directions, when a bridge balance 
 of the line has been obtained. (2) A sys- 
 tem of duplex telegraphy by means of a 
 single-bridge duplex-system. 
 
 Bridge of a Fuse. A small gap at a fuse 
 
 in a metallic circuit filled with a semi- 
 conducting compound in which heat is 
 developed by a current. 
 
 Bridge System of Quadruplex Teleg- 
 raphy. A system of quadruplex telegra- 
 phy by means of a bridge duplex system. 
 
 Bridges. Heavy copper wires suitably 
 shaped for connecting a dynamo-electric 
 machine in an incandescent lighting sta- 
 tion to the bus- bars. 
 
 Bridge- Wire. The wire in a Wheat- 
 stone's Bridge in which the galvanometer 
 is inserted. 
 
 Bridge with Secondary Conductors 
 A form of Wheatstone bridge employ- 
 ing an additional pair of resistances, and 
 suitable for measuring very low Resist- 
 ances. 
 
 Bridging Bell. A polarized electric bell 
 permanently connected across the circuit 
 employed in the bridging-bell system of 
 telephony. 
 
 Bridging-Bell Telephone System. A 
 system of telephone communication in 
 which the call bells are placed in multiple- 
 arc, permanently bridging the two line 
 conductors of metallic circuits, or legged 
 to the ground in grounded circuits, so 
 that, when a call is sent out, every bell 
 in the line rings, the particular station 
 needed being indicated by a suitable code 
 of signals. 
 
 Bridging Coils. In telephony, coils which 
 are connected across a telephone circuit, 
 as distinguished from coils placed in 
 series in the circuit. 
 
 Bridging Indicator. In telephony, an 
 indicator connected in shunt across a 
 circuit instead of in series. 
 
 Bridging Relay. In telephony or tele- 
 graphy, a relay which is connected in 
 shunt across a circuit instead of in series, 
 
 Bridle Chain. In submarine cable work, 
 the chain on a buoy which is connected 
 to the buoy rope, and by which the buoy 
 rope maybe picked up when the buoy 
 is released at the slip chain. 
 
 Bridle "Wires. (1) Wires connecting the 
 separate line wires with a cable box or 
 tower. (2) Wires for looping a telegraph 
 station into a line or lines. 
 
 Bright Deposit. In the electro-plating of 
 silver a bright surface of deposited metal 
 produced by a special final process in the 
 plating. 
 
 Bright Dipping. Cleansing a metal sur- 
 face by dipping it in acid liquids for the 
 purpose of ensuring a bright electro- 
 metallurgical coating. 
 
Bri.] 
 
 700 
 
 [Bui. 
 
 Bright Dipping Liquid. The liquid em- 
 ployed in bright dipping. 
 
 Brilliancy of Light. (1) The brightness 
 of a luminous source. (2) The quantity 
 of light that is emitted normally from 
 unit surface of a luminous source. (3) 
 The intrinsic intensity of a luminous 
 source. 
 
 Britannia Joint. A telegraphic or tele- 
 phonic joint in which the ends of the 
 wires are laid side-by-side, bound to- 
 gether, and subsequently soldered. 
 
 British Association Unit. A term for- 
 merly applied to the British Association 
 unit of resistance or ohm. 
 
 Broiler, Electric. An electrically heated 
 broiler. 
 
 Broken Circuit. (1) An open circuit. 
 (2) A circuit whose electric continuity 
 has been disturbed, and through which 
 the current has, therefore, ceased to pass. 
 
 Brother-in-Law. A bell whose sound is 
 the same as that of the car indicator, con- 
 cealed by a dishonest conductor for the 
 purpose of avoiding ringing the bell of 
 the car indicator when a fare has been 
 collected. 
 
 Brush-and-Spray Discharge. -A stream- 
 ing form of high-potential discharge pos- 
 sessing the appearance of a spray of 
 silvery white sparks, or of a branchbf thin 
 silvery sheets around a powerful brush, 
 obtained by increasing the frequency of 
 the alternations. 
 
 Brush Contact-Surface. (1) That portion 
 of a commutator surface which is in con- 
 tact with the brushes at any moment of 
 time. (2) The surface area of a brush 
 applied to a contact surface. 
 
 Brush Discharge. The faintly luminous 
 discharge which takes place from a 
 positively charged pointed conductor. 
 
 Brush Electrode. A conducting brush- 
 shaped electrode employed in electro- 
 therapeutic treatment. 
 
 Brush-Holder Cable. A stranded con- 
 ductor or cable employed in a dynamo 
 or motor for direct connection to the 
 brushes. 
 
 Brush Holders for Dynamo-Electric 
 Machine. Devices for supporting the 
 collecting brushes of a dynamo-electric 
 machine. 
 
 Brush Pressure. (1) The electric pressure 
 at the brushes of a dynamo-electric ma- 
 chine. (2) Mechanical pressure on a 
 brush. 
 
 Brush Rocker. In a dynamo or motor 
 any device for shifting the position of the 
 Pushes on the commutator cylinder. 
 
 Brush Shifting Device. A modified 
 form of brush rocker. 
 
 Brushes of Dynamo-Electric Ma- 
 chines. Strips of metal, bundles of wire 
 or wire gauze, slit plates of metal, or 
 plates of carbon, that bear on the com- 
 mutator cylinder of a dynamo, and carry 
 off the current generated. 
 
 B-Side of Quadruples Table. That 
 side of a quadruplex table which is 
 worked by means of strengthened cur- 
 rents. 
 
 Bucking. A term employed in the opera- 
 tion of street-railway passenger cars for a 
 sudden stopping of the car as if by a col- 
 lision, due to opposition between two 
 motors. 
 
 Buckled Diaphragm. A fault in a 
 telephonic transmitter or receiver due to 
 a dent or warping in the diaphragm. 
 
 Buckling. The warping or irregularities 
 produced in the surface of the plates of 
 storage cells by a too rapid discharge. 
 
 Buffing. Preparing surfaces for the re- 
 ception of electro-plating by subjecting 
 them to the polishing action of a revolv- 
 ing wheel covered with a buff, on the 
 surface of which rouge has been spread. 
 
 Bug. (1) A term employed in quadru- 
 plex telegraphy to designate any fault in 
 the operation of the apparatus. (2) Gen- 
 erally, a fault in the operation of any 
 electric apparatus. (3) A particular fault 
 or difficulty in quadruplex telegraphy 
 consisting of an interference between the 
 A and B-sides. 
 
 Bug-Trap. A device employed to over- 
 come the bug in quadruplex telegraphy. 
 
 Building-Iron. A heated iron tool by 
 means of which, the mould impressed by 
 a printed page, which it is desired to 
 electro-type, is built up preparatory to its 
 being placed in the plating bath. 
 
 Building Knife. A heated knife-shaped 
 tool employed in removing the wax that 
 has been forced up around the sides of 
 the matrix during the taking of the im- 
 pression. 
 
 Building Process for Electro-Type 
 Metals. A process for bringing up the 
 blank spaces in the mould of an electro- 
 type by the addition of wax plates melted 
 
 , into place by the building-iron, the high 
 spaces thus built-up becoming depressions 
 in the finished plate. 
 
 Building Switch. A switch provided 
 with an insulating handle for cutting a 
 building in or out of an electric circuit, 
 usually, a series circuit. 
 
 Building Tool. A form of building iron 
 
Bui.] 
 
 701 
 
 [Bus 
 
 " Building-Up " of Dynamo. The ac- 
 tion whereby a dynamo-electric machine 
 rapidly reaches its maximum E. M. F. 
 after starting. 
 
 " Built-in " Underground Conductor. 
 An underground conductor which, in- 
 stead of being placed in the duct of a 
 conduit or tube so as to be capable of re- 
 moval therefrom, at any time, is perma- 
 nently "built in" or surrounded by the 
 insulating and protective material. 
 
 "Built-Up" Magnet. A composite per- 
 manent magnet. 
 
 Bullet Probe. A probe containing elec- 
 trical conductors, so arranged that the 
 contact of the probe with a bullet closes 
 an electric circuit and operates an electric 
 signal. 
 
 Bunched Cable. A cable containing 
 more than a single wire or conductor. 
 
 Bunsen Screen. The screen of a Bunsen 
 or translucent-disc photometer. 
 
 Bunsen Voltaic Cell. A zinc-carbon 
 couple whose elements are immersed 
 respectively in electrolytes of dilute sul- 
 phuric and strong nitric acids. 
 
 Buoy, Electric. A buoy on which elec- 
 trically produced luminous signals are 
 displayed. 
 
 Burette. A graduated glass tube em- 
 ployed for readily measuring the volume 
 of a liquid. 
 
 Burglar-Alarm, Electric. An electric 
 device for automatically announcing the 
 opening of a door, window, closet, drawer 
 or safe, or the passage of a person through 
 a hallway, or on a stairway. 
 
 Burglar-Alarm Annunciator, Elec- 
 tric. An annunciator used in connec- 
 tion with a system of burglar-alarms. 
 
 Burglar-Alarm Contacts. Contacts fit- 
 ted to windows, doors, tills, safes, floors, 
 etc. , so that the movements of the various 
 parts from their natural positions, sound 
 an alarm. 
 
 Burglar-Alarm Matting. A matting 
 provided with a number of invisible con- 
 tacts connected with an alarm bell, whose 
 circuits are closed by treading on the 
 matting. 
 
 Buried Cable or Conductor. An un- 
 derground cable or conductor placed di- 
 rectly in the earth, in contra-distinction 
 to one placed in a conduit or subway. 
 
 Buried Transformer. A transformer, 
 provided with a water-tight cover and 
 placed below the surface of the ground. 
 
 Burn-Out. The destruction of an arma- 
 ture, or any part of an electric apparatus, 
 
 by the passage of an excessive current 
 due to short-circuit or other cause. 
 
 Burned-Out Incandescent Lamp. An 
 incandescent lamp which through con- 
 tinued use is no longer able to furnisb 
 electric light. 
 
 Burner, Electric. A gas-burner that is 
 capable of being electrically lighted. 
 
 Burnetize. To subject to the burnetizing 
 process. 
 
 Burnetizing. A method adopted for the 
 preservation of wooden telegraph poles, 
 by injecting a solution of zinc-chloride 
 into the pores of the wood. 
 
 Burning at Commutator of Dynamo. 
 An arcing at the brushes of a dynamo- 
 electric machine, due either to their im- 
 perfect contact or improper position, re- 
 sulting in the loss of energy to the circuit, 
 and the destruction of the commutator 
 segments, or of the brushes. 
 
 Burnishing. A process by means of 
 which surfaces are prepared for electro- 
 plating by subjecting them to the action 
 of burnishing tools. 
 
 Burnt Electro-Metallurgical Deposit. 
 The black deposit of metal which is 
 thrown down when the intensity of the 
 depositing current is too strong. 
 
 Bus. A word generally used instead of 
 omnibus. 
 
 Bus-Bar Connectors. Connectors em- 
 ployed for connecting or joining the ends 
 of bus-bars. 
 
 Bus-Bar Stand. A bus-bar support on a 
 switchboard. 
 
 Bus-Bar Voltmeter. A voltmeter em- 
 ployed in a central station for measuring 
 the pressure between the bus-bars. 
 
 Bus-Bars. Heavy bars of conducting 
 metal connected directly to the poles of 
 one or more dynamo-electric machines, 
 and, therefore, receiving the entire cur- 
 rent produced by the machines. 
 
 Bus Field-Excitation. Excitation of the 
 field of a generator by current taken 
 directly from the bus-bai's. 
 
 Bus-Rods or Wires. Terms frequently 
 used for bus-bars. 
 
 Bushing of Socket. A sleeve or cylinder 
 of insulating material inserted at the 
 entrance of a lamp socket for the pro- 
 tection of the entering conductors. 
 
 Busy-Back. A jack at a central telephone 
 exchange connected with a battery and 
 vibrator, in such a way that the operator 
 by inserting the plug of an incoming line 
 into this jack can notify a calling operator 
 that the subscriber desired is busy. 
 
Bus.] 
 
 702 
 
 [Cab. 
 
 Busy Test. A simple test whereby a tele- 
 phone operator at a multiple switchboard 
 can readily tell whether any wire or cir- 
 cuit connected with the switchboard is 
 or is not in use at any moment of time. 
 
 Butt Joint. (1) An end-to-end joint. (2) 
 A joint effected in wires by placing the 
 wires end on and subsequently soldering 
 or welding them. 
 
 Butt Prop. A tool sometimes called a 
 "dead man," used in the erection of 
 telegraph poles. 
 
 Button Repeater. A manual telegraphic 
 repeater whereby the proper connections 
 
 are made for repeating a message in 
 either direction, by turning a button. 
 
 Buzzer, Electric. (1) A call, not as loud 
 as that of an electric bell, employing a 
 humming sound by the use of a suffi- 
 ciently rapid automatic contact-breaker. 
 (2) A telephone receiver for morse circuits 
 employing a vibrating contact key. 
 
 Buzzing of Bell. An improper action of 
 an electric bell, whereby it produces a 
 buzzing sound instead of its proper ring- 
 ing. 
 
 By-Pass of Discharge. A term some- 
 times employed for alternative path. 
 
 C. A contraction for Centigrade. 
 
 C. A contraction for current. 
 
 C. A symbol for capacity. (Partly inter- 
 national usage.) 
 
 C.- -A symbol for coulomb. 
 
 C. E. M. F. A contraction for counter 
 electromotive force. 
 
 C. G-. S. A contraction for centimetre- 
 gramme-second. 
 
 C. c. A contraction for cubic centimetre, 
 the C. G. S. unit of volume. 
 
 cm. An abbreviation for centimetre, the 
 C. G. S. unit of length. 
 
 cm 2 . An abbreviation for square centi- 
 metre, the C. G. S. unit of surface. 
 
 cm 3 . An abbreviation for cubic centi- 
 metre, the C. G. S. unit of volume. 
 
 C. M. M. Jfi 1 . A contraction for counter- 
 magnetomotive force. 
 
 C. P. A contraction for candle-power. 
 
 C. 38,. A contraction for conductor-resist- 
 ance. 
 
 C 2 H Activity. (1) The PR activity. 
 (2) That portion of the electric activity 
 which is expended in heating the con- 
 ductor, and due to the ohmic resistance 
 offered by the conductor to the passage 
 of the current. (3) The thermal activity 
 of a circuit expressed in watts, and equal 
 to the square of the current strength in 
 amperes multiplied by the resistance in 
 ohms. 
 
 Loss. The loss of energy in a con- 
 ductor due to the ohmic resistance and 
 the current strength. 
 
 'C. G. S. Units. The centimetre-gramme- 
 second units. 
 
 Cabinet Seat Contact. A contact 
 placed in a silence telephone cabinet, 
 underneath a seat, and closed by the 
 weight of a person on the seat. 
 
 Cable. (1) An electric cable. (2) A mes- 
 sage transmitted by means of an electric 
 cable. 
 
 Cable. To send a telegraphic despatch by 
 means of a cable. 
 
 Cable Alphabet. The code or telegraphic 
 alphabet employed in cable signalling. 
 
 Cable Box. A box provided for the re- 
 ception and protection of a cable head. 
 
 Cable Buoy. A buoy generally secured 
 by a mushroom anchor and provided for 
 temporarily holding or securing an end of 
 a cable during its laying or repair. 
 
 Cable Casing. The metallic sheathing of 
 a cable. 
 
 Cable Cell. A voltaic cell formed by an 
 exposed broken end of a submarine copper 
 conductor and the iron sheathing of the 
 cable. 
 
 Cable Clearing-House System. A 
 system whereby every message sent over 
 a submarine cable is returned to the head 
 office and a comparison effected between 
 the original message, as received for 
 transmission, and the final message, as 
 delivered to the addressee. 
 
 Cable Clip. A term sometimes used for 
 cable hanger. 
 
 Cable Closing Machine. A machine for 
 covering a cable with its sheathing. 
 
 Cable Code. (1) A cable alphabet.. 
 (2) A cable cipher. 
 
 Cable Core. (1) The insulated conducting 
 wires of an electric cable. (2) The elec- 
 trically essential portion of a cable as dis- 
 tinguished from its sheath or protection. 
 
 Cable Cross-Connecting Board. In a 
 telephone exchange, where a number of 
 cables enter the building from the outside, 
 a distributing board, placed in a termi- 
 nal room to facilitate the work that ia 
 
Cab.] 
 
 703 
 
 [Cab. 
 
 constantly going on of making and chang- 
 ing the connections of the subscribers' 
 lines to the switchboard cables. 
 
 Cable Currents. (1) Various currents that 
 exist in a submarine cable and interfere 
 with the testing, consisting of earth cur- 
 rents, electrostatic charge and discharge 
 currents, and polarization currents due to 
 a fault or break. (2) A current flowing 
 through a cable in the absence of any im- 
 pressed E. M. F. (3) The current which 
 tends to flow in a broken cable from the 
 exposed copper conductor at the fracture 
 to the iron sheathing through the ap- 
 paratus at the station. 
 
 Cable Despatch. A despatch sent by 
 means of a cable. 
 
 Cable Drum. (1) In cable machinery, a 
 drum on which cable is wound for coil- 
 ing, shipping, laying, or turning over. 
 (2) A drum or reel on which cable is 
 wound for transport. 
 
 Cable, Electric. A combination of an 
 extended length of a single insulated elec- 
 tric conductor, or of two or more sepa- 
 rately insulated electric conductors, cov- 
 ered externally with a metallic sheathing 
 or armor. 
 
 Cable Fault. Any failure in the proper 
 working of a cable due either to a total 
 or partial fracture of the cable, or to a 
 heavy electric leakage. 
 
 Cable Float. A float employed for tem- 
 porarily relieving the tension on a cable 
 while it is being paid out. 
 
 Cablegram. A telegraph message re- 
 ceived by cable. 
 
 Cable Grapnel. A heavy pronged iron 
 hook provided for picking up a cable by 
 grappling. 
 
 Cable Grip. (1) The grip provided for 
 holding the end of an underground cable 
 while it is being drawn into a duct. 
 (2) In a cable road the grip by means of 
 which a car is driven by the moving 
 cable. 
 
 Cable Ground. The locality of a cable 
 operation or repair. 
 
 Cable Hanger. A hanger or hook suit- 
 ably secured to a cable and designed to 
 sustain its weight by intermediately sup- 
 porting it on an iron or steel wire strung 
 above the cable. 
 
 Cable Hanger Tongs. Tongs provided 
 with long handles for attaching the 
 hangers of an aerial cable to the suspend- 
 ing wire or rope. 
 
 Cable Head. A rectangular board pro- 
 vided with binding posts and fuse wires 
 
 for the purpose of receiving the wires of 
 overhead lines where they enter a cable. 
 
 Cable House. A hut provided for secur- 
 ing and protecting the end of a submarine 
 cable when it is landed. 
 
 Cable Hut. A cable house. 
 
 Cable Joint. An insulated electric con- 
 nection made between the cores of two 
 separate lengths of cable. 
 
 Cable Junction-Box. A junction box for 
 holding and protecting the insulated 
 connections or joints between cables. 
 
 Cable Laid-TJp-in-Layers. A cable all 
 of whose conducting wires are in layers. 
 
 Cable Laid-Up-in-Reverse-Layers. A 
 cable the alternate layers of whose con- 
 ductors are twisted in opposite directions. 
 
 Cable Laid-up-in-Twisted-Pairs. A 
 cable every pair of whose wires is twisted 
 together. 
 
 Cable Land Line. (1) A land line com- 
 posed of cable. (2; A land line connected 
 to a cable. 
 
 Cable Laying. The process of placing a 
 cable on the sea-bottom. 
 
 Cable Lead. A lead formed of a cable 
 of several stranded conductors, as dis- 
 tinguished from a lead containing a 
 single conductor. 
 
 Cable Message. A cable despatch. 
 
 Cable Office. An office connected with a 
 cable. 
 
 Cable Protector. (1) A device for the 
 safe discharge of the charge induced in 
 the metallic sheathing of a cable, or in 
 the conductors surrounding or adjacent 
 to the cables, consequent on changes in 
 the electromotive force applied to the 
 conducting core of the cable. (2) A fuse 
 device provided for the protection of each 
 of the wires of an aerial cable, placed in 
 the cable head at the junction where an 
 aerial line enters the cable head. 
 
 Cable Rack. A rack placed at the back 
 of a multiple telephone switchboard f^r 
 supporting the cabled switchboard con- 
 ductors and providing ready access to the 
 same. 
 
 Cable Repairing. The process of repair- 
 ing a broken or faulty cable. 
 
 Cable Resistor. A form of float or buoy 
 provided for lessening the strain on a 
 cable while paying it out. 
 
 Cable Road. A system of car propulsion 
 in which the cars are drawn by the 
 movement of an underground cable to 
 which the moving cars are attached by a 
 suitable grip. 
 
704 
 
 [Cal. 
 
 Cable Sending-Key. A key employed 
 for readily sending the positive and nega- 
 tive current impulses required to trans- 
 mit the cable alphabet or code. 
 
 Cable Serving. A covering of hemp or 
 jute spun around the insulated core of a 
 cable in order to protect it from the pres- 
 sure of the iron wire armor or sheathing 
 of the cable. 
 
 Gaol Ship. A ship provided with the 
 apparatus required for laying or repairing 
 submai'ine cables. 
 
 Cable Signals. Signals received over the 
 circuit of a cable. 
 
 Cable Speaking-Set. The apparatus 
 used in signalling over a cable. 
 
 Cable Spinning-Jenny. A device for 
 readily binding an aerial cable to a sup- 
 porting wire. 
 
 Cable Splice. A connection between the 
 sheathing or armor of two lengths of 
 cable. 
 
 Cable Stopper. A flexible grip applied 
 to a cable to keep it from moving or 
 slipping. 
 
 Cable Suspender. A device for suspend- 
 ing an aerial cable. 
 
 Cable Switchboard. A switchboard to 
 which the cable conductors are connected. 
 
 Cable Tank. A strong water-tight tank 
 
 E laced on a cable ship and provided for 
 olding a coiled section of cable that is 
 ready for laying. 
 
 Cable Telegraph. A general term in- 
 cluding all the apparatus employed in 
 cable telegraphy. 
 
 Cable Telegraphy. Telegraphic com- 
 munication carried on over a submarine 
 cable. 
 
 Cable Terminal. A water-tight covering 
 provided at the free end of a telephone 
 cable to prevent injury to the cable's in- 
 sulation by the moisture of the air. 
 
 Cable Terminal-Pole. The terminal pole 
 of an aerial line provided where the ends 
 of an aerial line are connected with an 
 underground cable for the support of the 
 cable head. 
 
 Cable Terminal - Switchboard. A 
 
 board in a cable head where the wires 
 are spread out and connected in proper 
 order to a number of binding posts which 
 in their turn are connected through fuse 
 wires to binding posts receiving the ends 
 of overhead wires. 
 
 Cable Transformer. An alternating- 
 current transformer in which the pri- 
 mary and secondary conductors have the 
 
 form of a cable overlaid by an iron 
 sheath or magnetic circuit. 
 
 Cable Vault. A vault provided in a 
 building where cables enter from under- 
 ground conduits, and where the cables 
 are opened and connected to fusible plugs 
 or safety catches. 
 
 Cable Testing. The process or methods 
 of trying or measuring the electric or 
 mechanical capabilities of a cable. 
 
 Cable Well. A cable tank. 
 
 Cable Winder. A cable spinning-jenny. 
 
 Cable Work. Any operation connected 
 with the manufacture, shipping, laying, 
 testing, or repair of cables. 
 
 Cable Worming. A central core of hemp 
 or jute around which are wrapped the 
 several separate conductors of any cable 
 that contains more than a single con- 
 ductor. 
 
 Cabled. Transmitted by means of cable 
 
 telegraphy. 
 Cabling. Transmitting by means of cable 
 
 telegraphy. 
 
 Cadmium Standard Cell. A standard 
 voltaic cell of very low temperature 
 coefficient of variation in E. M. F. , em- 
 ploying a cadmium-zinc couple. 
 
 Cage Lightning-Protector. A term 
 sometimes employed for a lightning pro- 
 tector consisting of wires in the form of 
 a cage surrounding the body to be pro- 
 tected. 
 
 Calamine, Electric. A crystalline va- 
 riety of silicate of zinc that possesses pyro- 
 electric properties. 
 
 Calculagraph. A machine employed in 
 long-distance telephony for registering 
 the time during which the use of a line 
 by a subscriber continues. 
 
 Gal-Electric Generator. A generator 
 whose operation depends on the produc- 
 tion of electricity in the secondary coil of 
 a transformer by changes of temperature 
 in its iron core. 
 
 Gal-Electricity. Electricity produced by 
 changes of temperature in the iron core 
 of a transformer. 
 
 Calibrate. To determine the absolute or 
 relative values of the scale divisions, or of 
 the indications of any electrical instru- 
 ment, such as a galvanometer, electro- 
 meter, voltmeter, wattmeter, or other 
 similar instrument. 
 
 Calibrating. Determining or marking off 
 the values or readings of a galvanometer, 
 electrometer, voltmeter, wattmeter, or 
 other similar electrical instrument. 
 
 Call. (1) In telephony, the signal or call of 
 
Cal.] 
 
 705 
 
 [au. 
 
 a subscriber for connection to some other 
 subscriber. (2) In telegraphy, the signal 
 for attention, or the call for response from 
 the distant operator. 
 
 Call-Bell, Electric. An electric bell used 
 to call the attention of an operator to the 
 fact that his correspondent wishes to 
 communicate with him. 
 
 Call-Key. Any suitable key for sending 
 an electric call. 
 
 Callaud Voltaic Cell. A name some- 
 times given to the blue-stone gravity cell. 
 
 Calling Circuit. In the Law system of 
 telephony, a common calling- wire circuit 
 connecting the centi'al exchange through 
 all the subscribers' offices in a given 
 group, and employed for sending calls to 
 the central office. 
 
 Calling Drops. In an isolated-station 
 switchboard, drops employed for indicat- 
 ing the particular subscriber calling. 
 
 Calling Plug. That plug of a pair of 
 plugs, at a central telephone switchboard, 
 which is inserted in the jack of the sub- 
 scriber wanted and through which that 
 subscriber is called up. 
 
 Calling Side of Telephone Circuit. 
 That side of a telephone circuit over 
 which a call arrives. 
 
 Calling Station. Any station that desires 
 to be placed in communication with an- 
 other station. 
 
 Calling Wire. A wire forming the call- 
 ing circuit in a system of telephony. 
 
 Call Signal. In telegraphy, the signal or 
 group of signals indicating the particular 
 station called. 
 
 Call Wire. (1) A speaking wire. (2) A 
 wire connecting two telephone exchanges, 
 for the purpose of transmitting instruc- 
 tions, as distinguished from a wire em- 
 ployed for establishing communication 
 between subscribers. (3) A wire employed 
 for calling the attention of a central- 
 station operator by a subscriber, as dis- 
 tinguished from the wires through which 
 he communicates with other subscribers. 
 
 Call- Wire Key. A subscriber's key em- 
 ployed to call the operator at a central 
 telephone station. 
 
 Call- Wire Switchboard. A switchboard 
 at a telephone station auxiliary to a 
 multiple switchboard in a call-wire 
 system, and employed for suitably divid- 
 ing up call-wires among the operators, 
 so as to equalize their work. 
 
 Call-Wire System. A system of tel- 
 ephony in which special wires are em- 
 
 45* 
 
 ployed to call the operator at the central 
 station. 
 
 Calorescence. The transformation of ob- 
 scure heat rays into luminous rays on 
 impact with certain solid substances. 
 
 Caloric. A term formerly applied to the 
 assumed fluid that was believed to be the 
 cause or essence of heat. 
 
 Calorie. (1) A heat unit. (2) The quantity 
 of heat required to raise 1 gramme of 
 water 1 centigrade. 
 
 Calorific Intensity. The temperature at- 
 tained in combustion. 
 
 Calorimeter. An instrument for measur- 
 ing the amount of heat contained in, or 
 developed by, a given body. 
 
 Calorimeter, Electric. An instrument 
 for measuring the heat developed, in a 
 given time, in any conductor, by an elec- 
 tric current. 
 
 Calorimetric. Of or pertaining to the 
 calorimeter. 
 
 Calorimetric Conductivity. Specific 
 heat transference, or the conductivity of 
 a substance based on the quantity of heat 
 transferred in a given time, independently 
 of the temperature attained. 
 
 Calorimetric Measurement. The meas- 
 urement of heat energy by means of a 
 calorimeter. 
 
 Calorimetric Photometer. A photo- 
 meter in which the light to be measured 
 is absorbed by the face of a thermo-pile, 
 and its photometric intensity estimated 
 from the strength of the electric current 
 thereby produced. 
 
 Calorimetry. The art of measuring heat 
 energy by means of a calorimeter. 
 
 Calorimotor. (1) A deflagrator. (2) A 
 word formerly employed for a number of 
 series-connected voltaic cells. (Obsolete.) 
 
 Calory. A less preferable orthography 
 sometimes employed for calorie. 
 
 Canalization. (1) A network of conduct- 
 ors. (2) A system of electric mains. 
 
 Candle. (1) A unit of photometric inten- 
 sity. (2) The photometric intensity which 
 would be produced by a standard candle 
 burning at the rate of two grains per 
 minute. 
 
 Candle Balance. A balance support pro- 
 vided for the standard candle of a photo- 
 meter, so arranged as continuously to 
 weigh the candle and so determine its rate 
 of consumption while in use. 
 
 Candle, Electric. A Jablochkoff candle. 
 
 Candle-Foot. A unit of illumination 
 
 equal to that normally produced by a 
 
Can.] 
 
 706 
 
 [Cap. 
 
 standard British candle, at a distance of 
 one foot, and sometimes called a lux. 
 
 Candle-Power. (1) The intensity of light 
 emitted by a luminous body estimated in 
 standard candles. (2) The photometric 
 intensity of one standard candle . 
 
 Canopy. (1) In a multiple telephone ex- 
 change, an overhanging frame suitably 
 supported from above, and containing 
 plugs and drops. (2) An ornamental 
 metallic covering employed in incandes- 
 cent lighting for an electrolier or pendant 
 outlet. 
 
 Canopy Switch. An overhead switch 
 placed at each end of a trolley car for the 
 purpose of permitting the motorman to 
 turn the current on or off the car as de- 
 sired, when, for example, he wishes to in- 
 spect a fuse block or controller without 
 pulling down the trolley pole. 
 
 Cant Hook. A tool employed in the erec- 
 tion of telegraph poles consisting of a pole 
 furnished with a curved pivoted hook 
 employed for turning or rolling a telegraph 
 pole. 
 
 Caoutchouc. (1) A resinous substance 
 possessing high powers of electric insula- 
 tion, obtained from the milky juice of cer- 
 tain tropical trees. (2) India rubber. 
 
 Cap Wire. An overhead wire carried on 
 the summit of a pole, as distinguished 
 from an overhead wire carried on a cross 
 arm. 
 
 Capability of Dynamo - Electric Ma- 
 chine. The maximum theoretical activ- 
 ity of a dynamo as expressed by the square 
 of its electromotive force divided by its 
 resistance. 
 
 Capacitance. (1) A term proposed in 
 place of capacity. (2) The reactance of 
 a condenser in an alternating-current 
 circuit. 
 
 Capacity Balance of Duplex System. 
 The balance of capacity in duplex teleg- 
 raphy as opposed to a balance of resist- 
 ance. 
 
 Capacity Circuit. A circuit containing 
 capacity but no inductance. 
 
 Capacity Current of Cable. (1) The 
 current in a cable due to its capacity. 
 (2) The charging or discharging current 
 in a cable. 
 
 Capacity Load. The apparent load or 
 current of a high-tension generator due 
 to the capacity of the distributing con- 
 ductors as distinguished from the load or 
 current usefully distributed. 
 
 Capacity of Accumulator. The avail- 
 able output of a storage battery expressed 
 either in ampere-hours, or in watt-hours. 
 
 Capacity of Cable. (1) The quantity of 
 electricity required to raise a given length 
 of cable to a given potential, divided by 
 the potential. (2) In a multiple cable, the 
 amount of charge at unit potential which 
 any single conductor will take up, the 
 rest of the conductors being grounded. 
 (3) The ability of a conducting wire or 
 cable to permit a certain quantity of 
 electricity to be passed into it before ac- 
 quiring a certain potential. 
 
 Capacity of Cable Tank. The accom- 
 modation of a cable tank expressed either 
 voluminally in cubic feet, or in relation 
 to the number of miles of a given type of 
 cable which can be practically stowed 
 away in it. 
 
 Capacity of Condenser. (1) The quan- 
 tity of electricity a condenser is capable 
 of holding in coulombs when charged to 
 a pressure of one volt. (2) The ratio be- 
 tween the quantity of electricity in cou- 
 lombs on one coating of a condenser and 
 the potential difference in volts between 
 the two coatings. 
 
 Capacity of Leyden Jar. The quantity 
 of electricity a Leyden jar will take under 
 unit difference of potential. 
 
 Capacity of Line. The ability of a line 
 to act as a condenser, and, therefore, like 
 it, to possess capacity. 
 
 Capacity of Polarization of Voltaic 
 Cell. The capacity of becoming polar- 
 ized when subjected to a steady discharge. 
 
 Capacity of Secondary or Storage Cell. 
 The capacity of an accumulator. 
 
 Capacity Pressure. (1) In a condenser 
 connected with a source of alternating 
 currents, a pressure in phase with the 
 condenser current. (2) A pressure due 
 to a capacity. (3) The pressure at the 
 terminals of a condenser. 
 
 Capacity Reactance. (1) The reactance 
 of a condenser due to its capacity. 
 (2) The condensance. (3) The capacitance. 
 
 Capacity Resistance. (1) A term pro- 
 posed for the resistance which a conden- 
 ser or other substance possessing electric 
 capacity offers to the passage of an alter- 
 nating electric current. (2) The impe- 
 dance of a condenser. 
 
 Capillarity. The elevation or depression 
 of liquids in tubes of small internal diam- 
 eter. 
 
 Capillary. Of small or hair-like diameter 
 or size. 
 
 Capillary Attraction. The molecular 
 attractions concerned in capillary phe- 
 
Cap.] 
 
 Capillary Contact-Key. A form of fluid 
 contact-key in which the circuit is closed 
 or broken by means of a wire which is 
 dipped into or removed from the surface 
 of a mass of mercury. 
 
 Capillary Electrometer. An electro- 
 meter in which difference of potential 
 is measured by the movements of a drop 
 of sulphuric acid in a tube filled with 
 mercury. 
 
 Capsizing Thermometer. A thermom- 
 eter employed in deep sea soundings for 
 cable work, which is caused to record the 
 temperature at the moment the lead 
 commences to ascend from the bottom, 
 by causing the thermometer to be re- 
 versed or capsized. 
 
 Car Annunciator. An annunciator 
 placed in a car for the purpose of calling 
 a waiter or porter. 
 
 Car Barn. A covered shed provided with 
 tracks in which trolley cars are stored 
 when not in use. 
 
 Car Body. The wooden framework of a 
 street-railway car which encloses the 
 space provided for the passengers. 
 
 Car-Brake, Electric. A car-brake that 
 is operated by the electric current pro- 
 duced by the motor acting as a generator 
 when the current is turned off and the 
 car is rapidly moving. 
 
 Car-Brake Mechanism. The mechan- 
 ism for applying the brake to a car- wheel. 
 
 Car Controller. (1) A device placed at 
 each end of the platform of a trolley car, 
 under the control of the motor man for 
 starting, stopping, reversing or changing 
 the velocity of a trolley car. (2) A series- 
 parallel car-controller. 
 
 Car-Heater, Electric. An electric heat- 
 er consisting essentially of suitably sup- 
 ported coils of insulated wire traversed 
 by an electric current. 
 
 Car-Lamp, Electric. An incandescent 
 lamp generally provided with an anchored 
 filament, suitable for use in street-railway 
 cars. 
 
 Car-Propulsion, Electric. The propul- 
 sion of cars by means of electric motors. 
 
 Car Truck. The part of a car on which 
 the car body rests. 
 
 Car Wiring. The distribution of conduct- 
 ors on an electric street car. 
 
 Carbon. An elementary substance which 
 occurs naturally in three distinct allo- 
 tropic forms : graphite, charcoal and the 
 diamond. 
 
 Carbon Arc. A voltaic arc formed be- 
 tween carbon electrodes. 
 
 rOT [Car. 
 
 Carbon Brushes for Electric Motors 
 or Generators. Plates of artificial car- 
 bon employed as the brushes of dynamos 
 or motors. 
 
 Carbon Button. A button-shaped carbon 
 mass whose resistance varies with press- 
 ure. 
 
 Carbon Cell. (1) A silvered plate of glass 
 
 Erovided on its silvered side with a num- 
 er of zigzag furrows filled with carbon 
 soot, and employed as the receiving in- 
 strument in a photophone. (2) A voltaic 
 cell employing carbon as one of its ele- 
 ments. 
 
 Carbon Clutch or Clamp for Arc 
 Lamps. A clutch or clamp attached to 
 the lamp rod or the support of the positive 
 or upper carbon of an arc lamp, provided 
 for gripping or holding the carbon. 
 
 Carbon Diaphragm of Telephone. 
 A thin sheet of carbon employed as the 
 diaphragm in certain forms of telephone 
 transmitters. 
 
 Carbon Electrodes for Arc Lamps. 
 The carbons of an electric arc lamp be- 
 tween which the arc is maintained. 
 
 Carbon Holder. A device employed in 
 an arc lamp for supporting the lower or 
 negative carbon. 
 
 Carbon Megohm. A resistance of ap- 
 proximately one megohm composed of a 
 thin film or strip of graphite. 
 
 Carbon Motor Brush. A carbon brush 
 employed on a motor. 
 
 Carbon Pencils. A word sometimes used 
 for the carbons employed in arc lamps. 
 
 Carbon-Point Lightning- Arrester. A 
 lightning arrester in which the disruptive 
 discharge occurs between opposed carbon 
 points. 
 
 Carbon Points. The carbon rods or pen- 
 cils employed in arc lamps. 
 
 Carbon B,heostat. An adjustable resist- 
 ance formed of carbon plates or powder 
 whose resistance can be varied by pres- 
 sure. 
 
 Carbon Telephone Transmitter. A 
 telephone transmitter whose operation is 
 dependent on variations in the resistance 
 of a carbon button, or of a mass of loose 
 granulated carbon, on the to-and-fro 
 movements of the diaphragm. 
 
 Carbon Tongs. A pair of tongs suitable 
 for gripping arc-light carbons. 
 
 Carbon Transmitter. A carbon tele- 
 phone transmitter. 
 
 Carbons. A general term applied to the 
 carbons or negative elements of voltaio 
 cells. 
 
Car.] 
 
 708 
 
 [Cat. 
 
 Carbonic Acid Gas. A gaseous substance 
 formed by the union of one atom of car- 
 bon with two atoms of oxygen. 
 
 Carboning Lamps. Placing carbons in 
 electric arc lamps. 
 
 Carbonizable. Capable of being carbon- 
 ized. 
 
 Carbonization. The act of carbonizing. 
 
 Carbonize. To reduce a carbonizable sub- 
 stance to carbon. 
 
 Carbonized Cloth Discs for High Re- 
 sistance. Discs of cloth carbonized by 
 heating to an exceedingly high temper- 
 ature while out of contact with air. 
 
 Carbonizer. Any apparatus suitable for 
 reducing a carbonizable material to car- 
 bon. 
 
 Carbonizing. Subjecting a carbonizable 
 substance to the process of carbonization. 
 
 Carbonizing Box. A box prepared for 
 holding the carbon filaments of incandes- 
 cent lamps during their carbonization. 
 
 Carbonizing Frame. A suitably shaped 
 block of carbon prepared for winding the 
 cotton threads, or other plastic carboniz- 
 able material, employed for the filaments 
 of incandescent lamps, before submitting 
 them to the carbonizing process. 
 
 Carcass of Dynamo-Electric Machine. 
 A term sometimes used for the iron f rame- 
 work of a dynamo. 
 
 Carcel. (1) A French photometric stand- 
 ard of light. (2) The light emitted by 
 a lamp of definite dimensions burning 
 42 grammes of Colza oil in an hour, with 
 a flame 40 millimetres in height. 
 
 Carcel Lamp. An oil lamp employed in 
 France as a photometric standard. 
 
 Carcel Standard. The carcel. 
 
 Carcel Standard Gas-Jet. A lighted 
 gas jet employed for determining the can- 
 dle-power of gas by measuring the height 
 of a jet of gas, burning under certain 
 conditions, when used in connection with 
 the light of a larger gas-burner burning 
 under similar conditions, for a photo- 
 metric measurement of electric lights. 
 
 Cardan Suspension of Compass 
 Needle. The gimbal suspension of a 
 compass needle. 
 
 Cardew Voltmeter. A voltmeter whose 
 indications are obtained by the expansion 
 of a long fine wire by the passage through 
 it of the current to be measured. 
 
 Carnot's Cycle. A cycle of steps or oper- 
 ations proposed by Carnot for convenience 
 in studying the transformation of heat 
 into work. 
 
 Carriers of Replenishes The moving 
 conductors of a replenisher which carry 
 the charges and thus permit an accumu- 
 lation of such charges. 
 
 Carrying Capacity. The maximum cur- 
 rent strength that any conductor can 
 safely transmit. 
 
 Carrying Capacity of Safety Fuse. 
 The maximum current strength which a 
 fuse wire or block can carry without 
 melting. 
 
 Carrying Hooks. A pair of curved hooks 
 pivoted together and provided with han- 
 dles, for carrying telegi'aph poles. 
 
 Cascade Charging of Leyden Jars or 
 Condensers. A method of charging 
 Leyden jars or condensers by means of 
 the electricity liberated by induction 
 from one coating when a charge is pass- 
 ing into the other coating. 
 
 Cascade Connection. A term sometimes 
 employed for series connection. 
 
 Cascade Connection of Condensers. 
 A term sometimes employed for a series- 
 connection of condensers. 
 
 Case-Hardening, Electric. S u p e r- 
 ficially hardening a piece of metal by 
 means of electrically generated heat. 
 
 Case Wiring. A wiring in which the elec- 
 tric conductors are held in place on the 
 walls or ceilings of a room by means of 
 continuous cleats. 
 
 Casings. Grooves or panelled channels 
 for carrying wires in a house. 
 
 Cast Rail-Bond. A method for bonding 
 the successive track rails, in a system of 
 trolley propulsion, by casting molten 
 iron around all except the upper portions 
 of the joint. 
 
 Casting, Electric. A process for casting 
 metals, in which the metals are fused by 
 means of heat of electric origin. 
 
 Castor and Pollux Light. A term for- 
 merly used for the St. Elmo's fire. 
 
 Catalisis. An objectionable orthography 
 sometimes employed for catalysis. 
 
 Catalysis. The influence produced on 
 chemical combination or decomposition, 
 by the presence of certain substances 
 which, without undergoing any changes 
 themselves, produce changes in the affini- 
 ties of other substances by their mere 
 contact or presence. 
 
 Catalytic. Of or pertaining to catalysis. 
 
 Cataphoresis. Electric osmose. 
 
 Cataphoretic. Of or pertaining to cata- 
 phoresis. 
 
 Cataphoretic A c t i o n. Cataphoretic 
 medication or demedication. 
 
Cat.] 
 
 709 
 
 [Cei. 
 
 Cataphoretic Demedication. A means 
 whereby material is removed from differ- 
 ent parts of the body by means of cata- 
 phoresis. 
 
 Cataphoretic Electrode. (1) An elec- 
 trode containing in solution the drug or 
 medicament that is to be introduced into 
 the body by cataphoresis. (2) The anode. 
 
 Cataphoretic Medication. The intro- 
 duction of a drug or medicament into the 
 body by means of cataphoresis. 
 
 Cataphoric. Of or pertaining to cata- 
 phoresis. 
 
 Catelectrotonus. An orthography some- 
 times employed for cathelectrotonus. 
 
 Catenary. A catenary curve. 
 
 Catenary Curve. The curve described 
 by the sagging of a wire, under its own 
 weight, when stretched between two 
 points of support. 
 
 Cathelectrotonic. Of or pertaining to 
 cathelectrotonus. 
 
 Cathelectrotonic State. The condition 
 of increased functional activity of a 
 nerve in the neighborhood of the cathode 
 to whose influence it is subjected. 
 
 Cathelectrotonic Zone. A name some- 
 times given to the peripolar zone. 
 
 Cathelectrotonus. In electro-therapeu- 
 tics the condition of increased functional 
 activity that occurs in a nerve in the 
 neighborhood of the cathode or negative 
 electrode. 
 
 Cathetometer. An instrument for the 
 accurate measurement of small heights 
 or distances. 
 
 Cathion. The electro-positive ion, atom, 
 or radical, into which the molecule of an 
 electrolyte is decomposed by electrolysis. 
 
 Cathodal. Of or pertaining to the 
 cathode. 
 
 Cathode. (1) The conductor or plate of 
 an electro-decomposition cell connected 
 with the negative terminal of a battery 
 or other electric source. (2) The terminal 
 of an electric source into which the cur- 
 rent flows from the electrolyte of a de- 
 composition cell or voltameter. (3) The 
 electrode of a bath, tube, body, or device 
 by which the current leaves the same. 
 (4) The negative electrode. 
 
 Cathode Cup. (1) A cup-shaped cathode 
 of an X-ray tube. (2) A concave mirror 
 attached to the cathode of an X-ray or 
 other high-vacuum tube. 
 
 Cathode Pictures. X-ray or Roentgen- 
 ray pictures. 
 
 Cathode Bay Spectrum. A succession 
 of light and dark phosphorescent bands 
 
 produced on a screen, in an exhausted 
 Crookes tube, by magnetically deflected 
 cathode rays. 
 
 Cathode Rays. Radiation emitted from 
 the cathode or negative electrode of a 
 Crookes or X-ray tube. 
 
 Cat ho die. Of or pertaining to the 
 cathode. 
 
 Cathode Streams. Cathode rays. 
 
 Cathodic Current. In a polarized vol- 
 taic couple immersed in acidulated water, 
 the current produced by the agitation of 
 the plate connected with the cathode. 
 
 Cathodic Electro-Diagnostic Reac- 
 tions. The reactions which occur at the 
 cathode placed on or over any part of a 
 living body. 
 
 Cathodic Rays. The cathode rays, 
 
 Cathodic Streamings. Cathode rays. 
 
 Cathodogram. A Roentgen or X-ray 
 picture. 
 
 Cathodograph. A radiograph. 
 
 Cation. An orthography sometimes em- 
 ployed for cathion. 
 
 Catoptrics. That branch of optics which 
 treats of the reflection of light. 
 
 Cauterization. The act of cauterizing or 
 burning with a heated, solid or caustic 
 substance. 
 
 Cauterization, Electric. Subjecting to 
 cauterization by means of an electrically 
 heated wire. 
 
 Cauterize. To subject to cauterization. 
 
 Cauterizer, Electric. A name some- 
 times given to an electric cautery. 
 
 Cautery Battery. A term sometimes 
 employed in electro-therapeutics for a 
 multiple-connected voltaic battery adapt- 
 ed for producing incandescence for cau- 
 tery effects. 
 
 Cautery Cabinet. A cabinet containing 
 a cautery battery, switchboard, cautery 
 knives and other necessaries for electric 
 cauterization. 
 
 Cautery Cell. A cell suitable for use in 
 a cautery battery. 
 
 Cautery, Electric. The application to 
 the human body of variously shaped plat- 
 inum wires, heated to incandescence by 
 the electric current, for removing dis- 
 eased growths, or for stopping hemor- 
 rhages. 
 
 Cautery Knife-Electrode. A knife- 
 shaped electrode that is rendered incan- 
 descent by the passage through it of an 
 electric current. 
 
 Ceiling Block. An attachment fastened 
 to the ceiling for suspending flexible 
 
Cei.] 
 
 710 
 
 [Can. 
 
 cords, and connecting them with the sup- 
 ply wires of an incandescent system. 
 Ceiling Board. An arc -light hanger 
 board. 
 
 Ceiling Bracket. (1) A ceiling canopy. 
 (2) A bracket for supporting an insulated 
 wire or wires to a ceiling. 
 
 Ceiling Cut-Out. A cut-out placed in a 
 ceiling block. 
 
 Ceiling Fan. An electrically driven fan 
 
 suspended from the ceiling. 
 Ceiling Rose. An ornamental ceiling 
 
 plate from which an electric conductor 
 
 passes. 
 
 Ceiling Rosette. An ornamental, rose- 
 shaped ceiling block. 
 
 Cell of Primary or Secondary Battery. 
 A jar of a primary or secondary battery 
 containing a single couple and its elec- 
 trolyte. 
 
 Celluloid Lamp-Filament. A lamp 
 filament made by carbonizing celluloid, 
 a modified form of cellulose. 
 
 Celluvert Fibre. A variety of insulating 
 material. 
 
 Centi. A prefix for the one hundredth 
 part. 
 
 Centi- Ampere. The hundredth of an 
 ampere. 
 
 Centi- Ampere Balance. An ammeter in 
 the form of a balance, capable of measur- 
 ing current strengths readily expressed in 
 centi-ampei'es (i. e., from 1 ff ampere to 
 1 ampere). 
 
 Centigrade Thermometer Scale. A 
 thermometer scale in which the length 
 of the thermometric tube, between the 
 melting point of ice and the boiling point 
 of water, is divided into one hundred 
 equal parts or degrees. 
 
 Centigramme. The hundredth of a 
 gramme ; or, 0. 1543 grains avoirdupois. 
 
 Centilitre. The hundredth of a litre ; or, 
 0.6102 cubic inch. 
 
 Centimetre. The hundredth of a metre ; 
 or, 0.3937 inch. 
 
 Centimetre-Gramme-Second System. 
 A system based on the centimetre as the 
 unit of length, the gramme as the unit of 
 mass, and the second as the unit of time. 
 
 Centimetre-Gramme-Second Units. 
 The units of the centimetre-gramme- 
 second system. 
 
 Centipede Cable-Grapnel. A grapnel 
 whose projecting prongs give it an ap- 
 pearance somewhat resembling a centi- 
 pede. 
 
 Central. A name given to any central 
 telephone exchange or office. 
 
 Central Galvanization. A variety of 
 general galvanization in which the 
 cathode is placed over the epigastrium 
 and the anode moved over the body. 
 
 Central Lighting-Station. A station 
 where the generators and distributing 
 apparatus are placed for producing the 
 current which lights the lamps in a given 
 district. 
 
 Central-Station Burglar- Alarm. A 
 burglar-alarm whose contacts, situated at 
 the place to be protected, are connected 
 by suitable circuits with alarms placed in 
 a centrally located station. 
 
 Central-Station Lighting. The lighting 
 of a number of houses or other buildings 
 from a single centrally located station. 
 
 Central - Station Multiple - Switch- 
 Board. A switchboard employed in a 
 central telephone exchange, in which 
 each subscriber's jack appears in more 
 than a single panel. 
 
 Central Telephone Exchange. (1) A 
 central telephone office connected with 
 a plurality of subscribers or telephone 
 stations. (2) A central exchange con- 
 nected with a plurality of local exchanges. 
 
 Central - Telephone - Exchange Mul- 
 tiple-Switchboard. Any form of 
 switchboard employed in a central tele- 
 phone exchange, by means of which 
 numerous subscribers connected there- 
 with can be readily connected to one 
 another. 
 
 Centrally Grounded Wire of Railway 
 Circuit. A conductor or wire extending 
 along the roadbed, parallel to the rails of 
 a pair of tracks, connected to the bond 
 wires, and itself grounded at intervals. 
 
 Cement-Lined Conduit. A conduit of 
 wood, stone or metal, the surfaces of 
 whose ducts are lined with cement. 
 
 Centre-Pole Trolley Line Construc- 
 tion. A form of aerial line construction 
 in which the trolley wires are suspended 
 from poles placed in the middle of the 
 street or road. 
 
 Centre of Distribution. In a system of 
 incandescent distribution any point at 
 which the supply current is branched or 
 radially distributed to mains, to sub- 
 mains, or to translating devices. 
 
 Centre of Gravity. The centre of weight 
 of a body. 
 
 Centre of Oscillation. A point in a body 
 swinging like a pendulum, which is 
 neither accelerated nor retarded, during 
 its oscillations, by the portions of the pen- 
 
Ceil.] 
 
 711 
 
 [Che. 
 
 dulum that are situated above or below 
 it. 
 
 Centre of Percussion. That point in a 
 body, suspended so as to move as a pen- 
 dulum, at which a blow perpendicular to 
 the radius would produce no pressure 
 at the axis. 
 
 Centre-Pole Construction. In a double- 
 track trolley system, especially on broad 
 streets, a system of pole construction in 
 which poles are placed between the two 
 tracks, provided with bracket arms ex- 
 tending over each track for the support 
 of the trolley wire. 
 
 Centre Railway Line A trolley line of 
 centre-pole construction. 
 
 Centrifugal Force. That force which is 
 supposed to urge a rotating body directly 
 away from the centre of rotation. 
 
 Centrifugal Governor. A device for 
 maintaining constant the speed of a steam 
 engine or other prime mover, despite 
 certain changes in its load or work. 
 
 Centrifuge. (1) An apparatus for separat- 
 ing solids from liquids or liquids of differ- 
 ent density from one another by centri- 
 fugal forces. (2) A centrifugal separator. 
 
 Centrifuge, Electric. A centrifuge 
 driven by an electromagnetic motor. 
 
 Centripetal. Seeking the centre. 
 
 Cerebration. The action of the brain in 
 producing thought. 
 
 Chafe. A weak or worn place in the 
 sheathing of a submarine cable due to 
 attrition. 
 
 Chaflng-DishjElectric. An electrically- 
 heated chafing dish. 
 
 Chain Cable-Grapnel. A grapnel whose 
 prongs are attached to the linky of a 
 chain. 
 
 Chain Lightning. A variety of light- 
 ning flash in which the discharge assumes 
 a rippling, chain-like appearance. 
 
 Chain Pull. A pendant chain attached to 
 a pendant burner for the movement of 
 the wipe-spark spring and the ratchet in 
 an electrically-lighted gas-burner. 
 
 Chamber of Incandescent Lamp. The 
 glass bulb or chamber of an incandescent 
 lamp provided for maintaining a high 
 vacuum, and for the reception of the 
 filament. 
 
 Change-Over Switch. A switch pro- 
 vided in a central station for transferring 
 a working circuit from one dynamo to 
 another, or from one battery of dynamos 
 to another. 
 
 Change , Ratio of Transformer. The 
 ratio of transformation. 
 
 Changing Switch. A change - over 
 switch. 
 
 Characteristic Curve. (DA diagram 
 in which a curve is employed to represent 
 the relation of certain varying values. 
 (2) A curve indicating the characteristic 
 properties of a dynamo-electric machine 
 under various phases of operation. (3) A 
 curve indicating the electromotive force 
 of a generator, as a variable dependent on 
 the excitation. 
 
 Characteristic Curve of Dynamo. A 
 curve showing the pressure at the ter- 
 minals of a dynamo at different field ex- 
 citations. 
 
 Characteristics of Sound. (1) The pe- 
 culiarities that enable different musical 
 sounds to be readily distinguished from 
 one another. (2) The tone or pitch, in- 
 tensity or loudness, and the quality or 
 timbre of sounds. 
 
 Charge Accumulator. A word some- 
 times given to a Leyden jar or condenser. 
 
 Charge Current onTelegraphic Line. 
 
 The current produced by the initial rush 
 of electricity into a telegraph line on the 
 closing of the circuit. 
 
 Charge, Electric. The quantity of elec- 
 tricity that exists on the surface of an 
 insulated electrified conductor. 
 
 Charged Body. A body containing an 
 electric charge. 
 
 Charged Cell. A cell of a storage battery 
 that has been acted on by a charging cur- 
 rent. 
 
 Charging Accumulators or Storage 
 Batteries. Sending an electric current 
 into storage batteries or accumulators for 
 the purpose of enabling them to act as 
 electric sources. 
 
 Charging Current. The current em- 
 ployed in charging a storage battery or 
 accumulator. 
 
 Chatterton's Compound. An insulat- 
 ing compound for cementing together the 
 alternate coatings of gutta-percha em- 
 ployed on a cable conductor, or for filling 
 up the space between the stranded con- 
 ductors. 
 
 Checking Action. A term sometimes 
 employed for a dampening action. 
 
 Checking Instrument. An instrument 
 in a cable station for recording sending or 
 out-going signals on a recorder slip. 
 
 Chemical Affinity. (1) Atomic attrac- 
 tion. (2) The force that causes atoms to 
 unite and form molecules. 
 
 Chemical Annunciator. A term some- 
 
Che.] 
 
 712 
 
 [Ckr. 
 
 times employed for electrolytic annun- 
 ciator. 
 
 Chemical Battery. A name sometimes 
 given to a voltaic telegraph battery as 
 distinguished from a dynamo. 
 
 Chemical Change. Any change in mat- 
 ter resulting from atomic combination 
 and the consequent formation of new 
 molecules. 
 
 Chemical Effect. (1) Any effect occa- 
 sioned by atomic combination, in which 
 the substances entering into combination 
 lose all those properties and peculiar- 
 ities by which they are ordinarily recog- 
 nized. (2) Atomic combination result- 
 ing in the formation of new molecules. 
 
 Chemical Equivalent. (1) The quotient 
 obtained by dividing the atomic weight 
 of an elementary substance by its atom- 
 icity. (2) The ratio between the quantity 
 of an element and the quantity of hy- 
 drogen it is capable of replacing. (3) The 
 quantity of an elementary substance that 
 is capable of combining with or replacing 
 one atom of hydrogen. 
 
 Chemical Galvano-Cautery. A term 
 sometimes applied to electro-puncture or 
 the application of electrolysis to the treat- 
 ment of diseased growths. 
 
 Chemical Generator of Electricity. 
 A term sometimes employed in place of a 
 voltaic pile or battery. 
 
 Chemical Phosphorescence. A variety 
 of phosphorescence in which the emitted 
 light is produced by the actual combus- 
 tion of a specific chemical substance by 
 the oxygen of the air, as in the phosphor- 
 escence of the fire-fly, or the glow-worm. 
 
 Chemical Photometer. A photometer 
 in which the intensity of light to be meas- 
 ured is determined by the amount of 
 chemical action produced in a given time. 
 
 Chemical Potential Energy. The po- 
 tential energy possessed by the element- 
 ary chemical atoms. 
 
 Chemical Recording Meter. A meter 
 which records by means of electrolysis 
 the quantity of electricity supplied in a 
 given time. 
 
 Chemical Separation. Chemical decom- 
 position. 
 
 Chemical Telegraph. A general term 
 for the apparatus employed in chemical 
 telegraphy. 
 
 Chemical Telegraphy. A system of 
 telegraphy, in which the dots and dashes 
 of the Morse alphabet, or other telegraphic 
 code, are recorded on a fillet of moistened 
 paper by the electrolytic action of the 
 
 current on some chemical substance with 
 which the paper is impregnated. 
 
 Chemical Telephone. The name given 
 to a telephone operating on the principles 
 of the electro-motograph. 
 
 Chemical Velocity. The ratio of the 
 amount of substance transformed in any 
 chemical process to the time required for 
 its transformation. 
 
 Chemism. A word sometimes employed 
 for chemical affinity. 
 
 Chief Operator. The senior operator on 
 duty in a telegraph or telephone office. 
 
 Chimes, Electric. A chime of bells rung 
 by the attractions and repulsions of elec- 
 trostatic charges. 
 
 Chimney Bracket. A bracket for sup- 
 porting an overhead wire fastened to a 
 chimney corner. 
 
 Chloride Storage Cell. A name given 
 to a storage-cell in which the plates are 
 formed of grids of antimonious lead, cast 
 around pastilles or buttons of fused chlo- 
 ride of lead, which, when properly sub- 
 jected to the charging current, are con- 
 verted into spongy metallic lead and lead 
 peroxide, on the negative and positive 
 plates respectively. 
 
 Choke Coil. A name sometimes given to 
 a choking coil. 
 
 Choke Magnet. A word sometimes used 
 for choking coil. 
 
 Choking Coil. A coil of wire so wound 
 on a core of iron as to possess high self- 
 induction when used on alternating-cur- 
 rent circuits. 
 
 Choking Effect. The effect produced 
 by a choking coil in obstructing or cut- 
 ting off an alternating current with a 
 smaller loss of power than would its use 
 as a mere ohmic resistance. 
 
 Chord Armature Windings. (1) Ar- 
 mature windings partly formed by chords 
 of arcs on the periphery to which they 
 are applied. (2) An armature winding 
 in which the wire is carried from one 
 point on the surface to another along a 
 chord of the included arc. 
 
 Chromosphere. An intensely hot gaseous 
 envelope surrounding the central lumin- 
 ous nucleus or photosphere of the sun. 
 
 Chronograph, Electric. An electric ap- 
 paratus for automatically measuring and 
 registering small intervals of time. 
 
 Chronograph Record. A record ob- 
 tained oy means of a chronograph. 
 
 Chronometer, Electric. An electrically 
 controlled and operated mechanism for 
 indicating and recording time. 
 
Clir.] 
 
 713 
 
 [Cir. 
 
 Chronoscope, Electric. (1) An appa- 
 ratus for electrically indicating but not 
 measuring small intervals of time. (2) An 
 electrically operated device by which 
 small intervals of time can be measured. 
 
 Cigar-Lighter, Electric. An apparatus 
 for electrically lighting a cigar. 
 
 Cinematograph. A biograph. 
 
 Cipher Code. A code in which a number 
 of words or phrases are represented by 
 single words, or by arbitrary words or 
 syllables. 
 
 Cipher Message. A code message. 
 
 Circle of Reference. A circle by refer- 
 ence to which simple-harmonic motion 
 may be studied by comparison with uni- 
 form motion around such circle. 
 
 Circuit Breaker. Any device for open- 
 ing or breaking a circuit. 
 
 Circuit Closer. Any device for making 
 or closing a circuit. 
 
 Circuit-Closer Bell-Pull. A device, 
 suitable for attachment to a mechanical 
 door pull, which makes a contact for the 
 ringing of an electric bell, without pre- 
 venting the original bell from being 
 operated by the mechanical pull. 
 
 Circuit, Electric. The path in which 
 electricity circulates or passes from a 
 given point around or through a conduct- 
 ing path back again to its starting-point. 
 
 Circuit Indicator. A rough form of gal- 
 vanometer employed to indicate the pres- 
 ence and direction of a current in a cir- 
 cuit, and, in some cases, to roughly indi- 
 cate its strength. 
 
 Circuit Loop-Break. A device for in- 
 troducing a loop into any part of an 
 aerial line circuit. 
 
 Circuit Loop-Break Insulator. An in- 
 sulator employed in a circuit loop-break. 
 
 Circuital. (1) Of or pertaining to a cir- 
 cuit. (2) Flowing or passing in a closed 
 circuit. 
 
 Circuital Flux. (1) A term sometimes 
 employed for circular flux. (2) The flux 
 surrounding any circuit. (3) Flux com- 
 pleting a closed circuit. 
 
 Circuital G-aussage. The gaussage as 
 measured once completely around a 
 closed magnetic circuit. 
 
 Circuital Vector. A vector quantity 
 which does not terminate in space but 
 forms a closed curve or endless chain. 
 
 Circuital Voltage. The voltage as meas- 
 ured around a closed circuit. 
 
 Circuitation. The line integral of a 
 vector quantity taken around a circuit. 
 
 Circular Bell. A term sometimes applied 
 to a bell so constructed that all of its 
 moving parts are contained in the gong. 
 
 Circular Current. A current flowing 
 through a circular path. 
 
 Circular Flux. (1) A term sometimes 
 employed for the concentric circular flux 
 which surrounds an active cylindrical 
 wire or conductor. (2) Generally, cir- 
 cuital flux. 
 
 Circular Magnetic Flux. Circular flux. 
 
 Circular Magnetism. (1) The magnet- 
 ism of a cylindrical rod of iron or steel one 
 of whose poles extends circumferentially 
 around the rod while the other pole is 
 situated at and around its centre. (2) A 
 circular distribution of magnetic flux. 
 
 Circular Magnetization. The magnet- 
 ization producing circular magnetism. 
 
 Circular Mil. (1) A unit of area employed 
 in measuring the cross-section of wires, 
 equal, approximately, to 0.7854 square 
 mils. (2) The area of a circle one mil in 
 diameter. 
 
 Circular Millage. The areas of cross- 
 sections of wires or conductors expressed 
 in circular mils. 
 
 Circular Scratch Brush. A scratch 
 brush of circular shape, 'suitable for 
 being set in rapid rotation by a lathe. 
 
 Circular Touch. A method of magnet- 
 ization by touch in which four bars are 
 placed in the form of a rectangle and the 
 magnetizing magnet is placed in contact 
 at any point, drawn around the rectangle 
 a number of times, and removed at the 
 point where its motion began. 
 
 Circular Type of Periodically Alter- 
 nating E. M. F. A periodically alter- 
 nating E. M. F. having a curve whose 
 values in different parts of a cycle are 
 such that when plotted in a curve they 
 will produce a circular outline. 
 
 Circular Units of Area. Various units 
 employed for measuring areas of cross- 
 section by reference to the area of a unit 
 circle, such, for example, as the circular 
 mil. 
 
 Circulating Power. A term employed 
 by Hopkinson for the method of taking 
 power out of a machine as a motor and 
 utilizing this power to drive the generator 
 with which it is connected. 
 
 Circumferential Speed. The speed of 
 any point on the circumference of a ro- 
 tating wheel or armature. 
 
 Circumflux. A term sometimes employed 
 for the product of armature current and 
 the total number of armature conductors 
 divided by the number of poles. 
 
Cla.] 
 
 714 
 
 [Clo. 
 
 Clamp for Arc Lamps. (1) A device for 
 gripping the lamp rod of an arc-lamp. 
 (2) The carbon clutch or clamp of an arc- 
 lamp. 
 
 Clamp Splicing-Ear. A trolley splicing 
 ear in which the two ends of the wire are 
 placed in the jaws of a clamp and then 
 pressed together and secured by a bolt. 
 
 Clamp Terminals. Simple screw-clamps 
 serving as terminals for connecting the 
 ends of flexible cords or other wires. 
 
 Clark Element. A name sometimes 
 given to a Clark standard voltaic cell. 
 
 Clark's Compound. A bituminous and 
 siliceous compound employed on the 
 outer casing of the sheathing of a sub- 
 mai'ine cable. 
 
 Clark's Standard Voltaic Cell. A form 
 of zinc-mercury couple employed, in con- 
 nection with electrolytes of mercurous 
 sulphate and zinc sulphate, as a standard 
 cell. 
 
 Clay Electrode. A therapeutic electrode 
 of clay shaped so as to fit the part of the 
 body to be treated. 
 
 Clearance. The gap space between the 
 surface of a rotating armature and the 
 opposed polar surface of the field magnets 
 of a dynamo or motor. 
 
 Clearance Space. The clearance. 
 
 Clearing. In telephony, the operation of 
 disconnecting subscribers who have been 
 in connection, and restoring the lines to 
 their normal conditions. 
 
 Clearing-Out Drops. (1 ) Electro-mag- 
 netic drop-shutters placed in a telephone 
 exchange in circuit with a pair of com- 
 municating subscribers, so that the fall- 
 ing of the shutter when they " ring off " 
 indicates that the conversation is ended. 
 (2) Ring-off drops. 
 
 Clearing-Out Relays. Relays provided 
 for operating clearing-out drops. 
 
 Clearing Signal. (1) A ring-off signal. 
 
 . (2) A signal in a telephone exchange to 
 indicate that a telephonic conversation 
 lias ended. 
 
 Cleat Wiring. Placing or establishing 
 electric conductors or wires on walls or 
 ceilings by means of suitably shaped in- 
 sulating cleats. 
 
 Cleat, Electric. A suitably shaped piece 
 of wood, porcelain, hard-rubber or other 
 non-conducting material used for fasten- 
 ing and supporting electric conductors to 
 ceilings and walls. 
 
 Cleavage Electricity. Electrification 
 produced by the cleavage of crystalline 
 substances. 
 
 Clepsydra, Electric. An instrument for 
 measuring time by the escape of water or 
 other liquid under electric control. 
 
 Click Wire. (1) A wire of a multiple 
 telephone switchboard employed for the 
 engaged test, by which a click is heard 
 in the operator's telephone when the sub- 
 scriber asked for is busy. (2) The busy 
 test wire. 
 
 Clip. A slight break in signalling where- 
 by a signal is unduly shortened, that is 
 likely to occur with an imperfect adjust- 
 ment of duplex or quadruplex telegraphy. 
 
 Clip Switch. A switch in which the 
 switch-lever enters the base of a clip. 
 
 Clipping of Telegraphic Signal. The 
 curtailing of a telegraph signal due to 
 defective adjustments or to disturbances 
 on the line. 
 
 Clock, Electric. A clock the works of 
 which are moved, controlled or regulated, 
 either entirely or partially, by the electric 
 current. 
 
 Clock Meter. An electric meter in which 
 clock-work is employed. 
 
 Clock Register. A register employed 
 in connection with a clock for recording 
 the time of an occurrence. 
 
 Clockwise Motion. A rotary motion 
 whose direction is the same as that of the 
 hands of a clock, viewed from the face. 
 
 Clockwork Feed for Arc Lamps. An 
 arc-lamp mechanism in which one or both 
 carbons are fed by trains of wheel 
 work. 
 
 Closed Car-Wheel. A car-wheel in 
 which the portion of the wheel between 
 the flange and the axle is formed of an 
 imperforate mass. 
 
 Closed Circuit. A completed circuit. 
 
 Closed - Circuit Burglar-Alarm. A 
 burglar alarm that is normally on closed 
 circuit, and which operates on the open- 
 ing of the circuit by the opening of the 
 contacts. 
 
 Closed-Circuit Signalling. A system 
 of single-circuit signalling in which the 
 sending batteries are placed at each end 
 of the line and are so connected as to 
 remain always in circuit. 
 
 Closed-Circuit Thermostat. A ther- 
 mostat maintained normally on closed 
 circuit. 
 
 Closed-Circuit Transformer. A term 
 sometimes employed for closed iron-cir- 
 cuit transformer. 
 
 Closed-Circuit Voltaic Cell or Bat- 
 tery. A voltaic cell or battery that can 
 be left for a considerable time on a closed 
 
Clo.] 
 
 715 
 
 [Cod. 
 
 circuit of comparatively small resistance 
 without serious polarization. 
 Closed-Circuit Voltmeter. A volt- 
 meter intended to be in permanent con- 
 nection with the pressure it is designed 
 to measure. 
 
 Closed-Circuited. Placed in a closed or 
 completed circuit. 
 
 Closed-Circuited Conductor. A con- 
 ductor connected in a closed or completed 
 .circuit. 
 
 Closed-Circular Current. A current 
 flowing in a circular circuit. 
 
 Closed-Circular Solenoid. A circular 
 solenoid closed upon itself so as to form a 
 tore. 
 
 Closed-Coil Armature. (1) An armature 
 the coils of which are never on open cir- 
 cuit during rotation. (2) A dynamo ar- 
 mature whose coils are grouped in sec- 
 tions and connected with successive bars 
 of a commutator, so as to be continuously 
 connected together in a closed circuit. 
 
 Closed-Coil Winding. Any winding 
 by which the armature coils are connect- 
 ed in closed circuit during the operation 
 of the machine. 
 
 Closed-Conducting Sheath for Light- 
 ning Protector. A method for light- 
 ning protection consisting in forming a 
 wire-sheathing or netting around the ob- 
 ject to be protected. 
 
 Closed Iron -Circuit Transformer. 
 
 (1) A transformer, the core of which forms 
 a completed magnetic circuit. (2) An 
 iron-clad transformer. 
 Closed Iron - Magnetic Circuit. A 
 magnetic circuit all of whose path is 
 completed by iron. 
 
 Closed Loop. A single loop of wire or 
 conductor placed on a closed circuit. * 
 
 Closed - Loop Parallel - Circuit. A 
 variety of parallel circuit in which both 
 the leading and returning conductors form 
 closed loops, between which the trans- 
 lating devices are bridged. 
 
 Closed Magnetic Circuit. A magnetic 
 circuit which lies wholly in iron or other 
 substance of high magnetic permeability. 
 
 Closed Magnetic Circuit of Atom. A 
 closed magnetic circuit whose flux is 
 supposed to lie entirely within the atom. 
 
 Closed-Magnetic Circuit of Molecule. 
 A closed magnetic circuit assumed to 
 lie wholly within the molecule. 
 
 Closed Magnetic Core. A magnetic 
 core so shaped as to provide a complete 
 iron path or circuit for the magnetic flux 
 of its field. 
 
 Closet System of Parallel Distribu- 
 tion. A system of parallel distribution 
 and house wiring in which the various 
 receptive devices are collected in groups 
 each of which is supplied with a separate 
 and independent supply circuit back to 
 the service ; as distinguished from a tree 
 system. 
 
 Closed Trolley Car. A trolley car en- 
 closed from the outer air as distinguished 
 from an open or summer car. 
 
 Closure. The completion of an electric 
 circuit. 
 
 Clown's Hat Curve. A curve of current 
 or electromotive force in which the pres- 
 sure generated increases or decreases at 
 a rapid rate of change, and whose 
 shape is somewhat similar to the shape of 
 a peaked hat or a clown's hat. 
 
 Club - Footed Electro-Magnet. An 
 
 electro-magnet whose core is in the form 
 of a horse-shoe and is provided with a 
 magnetizing coil on one pole only. 
 Cluster Call. A globe of metal from 
 which a cluster of incandescent lamps 
 radiate. 
 
 Clutch for Arc Lamps. A carbon 
 clutch or clamp for arc lamps. 
 
 Clutching Device. (1) Any device em- 
 ployed for clutching or holding the car- 
 bons in an arc-lamp. (2) A device for 
 clutching or holding any object subjected 
 to occasional motion. 
 
 Coarse Winding of Field Magnets. 
 The series-winding of a compound-wound 
 machine. 
 
 Co-acting. Acting simultaneously or to- 
 gether. 
 
 Coating. An adherent layer or covering. 
 
 Coating of Condenser. A sheet of tin 
 foil placed on ona side of a Leyden jar or 
 condenser, directly opposite a similar sheet 
 on the other side, for the purpose of 
 receiving and collecting an electric 
 charge. 
 
 Coatings of Leyden Jar. The sheets of 
 tin foil or other conductor placed on op- 
 posite sides of a Leyden jar or condenser. 
 
 Code Name. In telegraphy, the symbol, 
 word, or group of letters, standing for, 
 or representing the name of some person, 
 association, or thing, according to a pre- 
 arranged code. 
 
 Code or Coded Telegraphy. A system 
 of telegraphy employed for sending de- 
 spatches in which the time required for 
 transmitting is considerably decreased 
 by employing code words instead of the 
 actual words of the message. 
 
Cod.] 
 
 716 
 
 [Coi. 
 
 Coded Telegraph Messages or Code 
 Messages. Messages that are sent by 
 the use of prearranged words, any one of 
 which may stand for a group of words, 
 a phrase, or a complete sentence. 
 
 Code Time. In telegraphy, the code sig- 
 nals in the preamble of a message which 
 signify and indicate the time at which the 
 message was received for transmission. 
 
 Coefficient of Electro-Magnetic Iner- 
 tia. A term sometimes employed in 
 place of the coefficient of inductance or 
 self-inductance of a circuit. 
 
 Coefficient of Expansion. The frac- 
 tional increase in the length of a bar or 
 rod, when heated from 32 to 33 degrees 
 Fahr. , or from to 1 degree Cent. 
 
 Coefficient of Hysteresis. (1) The work 
 expended hysteretically in a cubic-centi- 
 metre of iron, or other magnetic substance, 
 in a single cycle of unit magnetic flux 
 density. (2) The coefficient which multi- 
 plied by the volume of iron, the frequency 
 of alternation, and the l-6th power of the 
 maximum flux density gives the hyster- 
 etic activity. 
 
 Coefficient of Inductance. (1) A con- 
 stant quantity such that, when multiplied 
 by the current strength passing through 
 any coil or circuit, will numerically rep- 
 resent the flux linkage with that coil or 
 circuit due to that current. (2) A term 
 sometimes used for coefficient of self-in- 
 duction. (3) The ratio of the C. E. M. F. 
 of self-induction in a coil or circuit to 
 the time-rate-of-change of the inducing 
 current. 
 
 Coefficient of Induction. A term some- 
 times used for coefficient of magnetic in- 
 duction. 
 
 Coefficient of Magnetic Induction. 
 (1) A term sometimes used instead of 
 magnetic permeability. (2) The ratio 
 between the quantity of magnetic flux 
 that passes through any area of normal 
 cross-section of a magnetic circuit and 
 
 ' the magnetizing force producing that 
 flux. 
 
 Coefficient of Magnetic Leakage. 
 
 (1) The ratio of the flux through a leakage 
 path to the flux through an armature. 
 
 (2) The ratio of the mutual induction in 
 a transformer as reduced by magnetic 
 leakage to the mutual induction in the 
 absence of magnetic leakage. 
 
 Coefficient of Magnetization. A num- 
 ber representing the intensity of magneti- 
 zation produced in a magnetizable body 
 divided by the magnetizing force, and 
 usually represented by the symbol K. 
 
 Coefficient of Mutual Inductance. 
 
 (1) The ratio of the electromotive force 
 induced in a circuit to the rate-of -change 
 of the inducing current in a magnetically 
 associated circuit. (2) The ratio of the 
 total flux-linkage with a circuit proceed- 
 ing from an associated inducing circuit, 
 to the strength of current flowing in the 
 latter. 
 
 Coefficient of Mutual Induction. The 
 
 coefficient of mutual inductance. 
 
 Coefficient of Potential. (1) A co- 
 efficient which multiplied into the charge 
 of a body gives its potential. (2) The ratio 
 of the potential of an electrified body to 
 its charge, when all neighboring bodies 
 are uncharged. 
 
 Coefficient of Reflection. The percent- 
 age value expressing the ratio of the 
 intensity of the reflected ray to the in- 
 tensity of the incident ray. 
 
 Coefficient of Self-induction. (1) Self- 
 inductance. (2) The ratio in any circuit 
 of the flux induced by and linked with a 
 current, to the strength of that current. 
 (3) The ratio in any circuit of the E. M. 
 F. of self-induction to the rate-of-change 
 of the current. 
 
 Coercitive Force. A name sometimes 
 employed for coercive force. 
 
 Coercive Force. (1) The power of resist- 
 ing changes in magnetization. (2) In 
 cyclic magnetization the demagnetizing 
 force which must be applied to a mag- 
 netic substance in order to completely 
 demagnetize it. 
 
 Coherer. A detector of electro-magnetic 
 waves consisting of conducting particles 
 forming a semi-conducting bridge be- 
 tween two electrodes. 
 
 Coil and Plunger for Electro-Magnet. 
 A movable iron core which is attracted 
 into a hollow coil or solenoid when a cur- 
 rent passes through said coil. 
 
 Coil, Electric. (1) A convolution of insu- 
 lated wire through which an electric 
 current may be passed. (2) A number of 
 turns of wire, or a spool of wire, through 
 which an electric current may be passed. 
 
 Coil-Heater, Electric. A heater whose 
 heat is obtained by the passage of an 
 electric current through a suitably sup- 
 ported coil of wire. 
 
 Coil Winding. Loop or lap winding. 
 
 Coil Winding of Alternator. (1) A 
 form of winding applied to the armature 
 of an alternator in which the wire is 
 made into coils that are laid upon the 
 surface of the armature core. (2) A term 
 sometimes used for loop winding. 
 
Coi.] 
 
 717 
 
 [Com. 
 
 Coiling Space of Cable Tank. The 
 space provided in a cable tank for the re- 
 ception of a cable. 
 
 Coked Core of Incandescent Filament. 
 An incandescent lamp filament formed 
 of a core -of electrically coked carbon 
 whose surface is covered with a deposit 
 of carbon by the flashing process. 
 
 Coked Filament. A carbon filament for 
 an incandescent lamp that has been so sub- 
 jected to electrical heating in a vacuum 
 as not only to be thoroughly freed from 
 its occluded gases but also to have its car- 
 bon changed into a variety of coke. 
 
 Coking, Electric. Subjecting carbon to 
 the coking process. 
 
 Coking of Filament. Subjecting a fila- 
 ment to the coking process. 
 
 Coking Process for Filament of In- 
 candescent Lamp. A process for 
 converting the carbon of an incandescent 
 filament into coke by subjecting it, while 
 in a vacuum, to the prolonged heating 
 action of a powerful electric current. 
 
 Cold Light. (1) Luminous radiation 
 unaccompanied by obscure radiation. 
 (2) Radiation confined within the limits of 
 the visible spectrum. (3) The light of a 
 fire-fly or glow-worm. 
 
 Collapsing Drum. A visual-signal drum 
 capable of manual distension and collapse. 
 
 Collation. The repetition of a message or 
 important parts of the same by an oper- 
 ator at a telegraph station who has re- 
 ceived it over the line, to the transmitting 
 operator at the sending station. 
 
 Collecting Ammeter An ammeter in a 
 central station which collects, and, there- 
 fore, indicates the total current received 
 from two or more separate generators, 
 and usually employed to indicate the total 
 current output of a station. 
 
 Collecting Brushes of Dynamo-Elec- 
 tric Machine. Conducting brushes 
 which bear on the commutator cylinder 
 of a dynamo and carry off the current 
 generated by the E. M. F. in the armature 
 coils. (2) The brushes which bear on 
 the collecting rings of an alternator 
 armature. 
 
 Collecting Combs. The collecting points 
 of a frictional electric machine, or of an 
 electrostatic induction machine. 
 
 Collecting Panel. A panel in a switch- 
 board which collects all the current sup- 
 plied by the generators connected to that 
 switchboard. 
 
 Collecting Rings for Alternators. 
 
 Metallic rings connected with the ter- 
 minals of the armature coils of an alter- 
 
 nator on which brushes rest to carry off 
 the alternating currents. 
 Collectors, Electric. Devices employed 
 for collecting electricity from a moving 
 electric source. 
 
 Collectors of Alternators. The collect- 
 ing rings. 
 
 Collectors of Dynamo-Electric Ma- 
 chine. The brushes that rest on the 
 commutator cylinder and carry off the 
 current generated on the rotation of the 
 armature. 
 
 Collectors of Frictional Electric Ma- 
 chine. The metallic points that collect 
 the charge from the glass plate or cylin- 
 der of a frictional electric machine. 
 
 Colloids. One of the two classes into 
 which substances are separated by dial- 
 ysis. 
 
 Colombin. An insulating substance con- 
 sisting of a mixture of sulphates of barium 
 and calcium placed between the parallel 
 carbons of the Jablochkoff candle. 
 
 Column, Electric. A term formerly ap- 
 plied to a voltaic pile. 
 
 Colza Oil. The oil employed in the Carcel 
 standard lamp. 
 
 Comazant. (1) A term formerly applied 
 to a St. Elmo's fire. (2) A corposant. 
 
 Collector Rings. The collecting rings 
 of an alternator. 
 
 Comb Lightning-Arrester. A form of 
 lightning-arrester in which the line wires 
 are connected to two metallic plates pro- 
 vided with serrations like the teeth of a 
 comb, and placed near to another ground- 
 connected plate, which may or may not 
 be furnished with similar serrations. 
 
 Comb of Storage Battery. The grid of 
 a storage battery. 
 
 Comb Protector. A comb lightning-ar- 
 rester. 
 
 Combination Anchor-Poles. (1) An 
 anchor pole intended for the support of 
 both aerial wires and aerial cables. (2) A 
 composite anchor-pole. 
 
 Combination Bracket. (1) A bracket 
 for supporting a pair of insulators side by 
 side. (2) A bracket for supporting both 
 a gas lamp and an incandescent lamp. 
 
 Combination Fittings for Chandeliers. 
 Fittings that provide for the use of both 
 gas and electricity. 
 
 Combination Gas-Fixtures. Combina- 
 tion fittings. 
 
 Combination Lightning-Protector. 
 
 A form of combined film and fuse light- 
 ning-protector employed on telephone 
 
Com.] 
 
 718 
 
 [Com. 
 
 circuits, arranged so as to ground the cir- 
 cuit either under the action of high pres- 
 sures, or under the action of an unduly 
 strong current. 
 
 Combination Line-Protector. A com- 
 bination lightning-protector. 
 
 Combination Protector. A combination 
 lightning-protector. 
 
 Combination Rheostat. A form of box 
 rheostat, or resistance box, which con- 
 tains within its cover several separate 
 series of resistance coils. 
 
 Combination Triphase- Winding. A 
 triphase winding combining both the star 
 winding and the triangular winding. 
 
 Combined Fibre and Spring Suspen- 
 sion. A suspension of a needle by the 
 combined use of a spiral spring and a 
 single fibre. 
 
 Combined Tangent and Sine Galvano- 
 meter. A galvanometer furnished with 
 two magnetic needles of different lengths, 
 one a small needle for tangent measure- 
 ments, and the other a long needle for 
 sine measurements. 
 
 " Come Along." A small portable vise 
 capable of ready attachment to an aerial 
 telegraph or telephone cable, and used in 
 connection with a line dynamometer to 
 pull up the wire to its proper tension. 
 
 Commercial Efficiency. The useful or 
 available energy produced by any ma- 
 chine or apparatus divided by the total 
 energy it absorbs. 
 
 Commercial Efficiency of Dynamo, or 
 Generator. The ratio of the output of 
 a dynamo, or the useful and available 
 electric energy delivered at its terminals, 
 divided by its intake, or the mechanical 
 energy required to drive it. 
 
 Commercial Efficiency of Motor. The 
 ratio between the mechanical activity 
 developed at a motor pulley and the elec- 
 tric activity absorbed at its terminals. 
 
 Common Arc of Aurora Glory. The 
 inner or common arc of an aurora glory. 
 
 Common Return. A return conductor 
 common to several circuits. 
 
 Common Side of Quadruplex System. 
 In quadruplex telegraphy, the neutral or 
 No 2. side, as distinguished from the polar 
 or No 1. side. 
 
 Communicator, Electric. A term for- 
 merly employed for a telegraphic key. 
 
 Commutating Machine. A rotary 
 transformer. 
 
 Commutation. The act of commuting or 
 causing a number of electromotive forces 
 
 or currents to take one and the same 
 direction. 
 
 Commutation Fringe. A term em- 
 ployed for the induction produced by an 
 edge or fringe of the magnetic flux at the 
 pole tip, under which commutation takes 
 place. 
 
 Commutator. (1) Any device for chang- 
 ing in one portion of a circuit the direc- 
 tions of electromotive forces or currents 
 in another portion. (2) A device for 
 changing alternating into continuous 
 currents, or vice versa. 
 
 Commutator. A name sometimes given 
 to a universal switch or pin switchboard. 
 
 Commutator Bar. One of the insulated 
 segments of a commutator. 
 
 Commutator Coils. Coils wound around 
 an armature core for the purpose of pre- 
 venting sparking, connected at one of 
 their ends to the main windings at points 
 between the coil sections, and at the 
 other end to the commutator segments. 
 
 Commutator Motor. An alternating, 
 current motor in which the armature is 
 provided with a commutator. 
 
 Commutator of Dynamo-Electric Ma- 
 chine. The device employed to cause 
 the electromotive forces generated in an 
 armature, on its rotation in the magnetic 
 field, to take one and the same direction 
 
 externally. 
 
 Commutator Press Button. A press 
 button employed in a system of telephony, 
 at a subscribers' station, for calling the 
 central station by reversing a battery. 
 
 Commutator Segments or Strips. The 
 insulated bars of a commutator. 
 
 Commutatorless. Devoid of a commu- 
 tator. 
 
 Commutatorless Continuous-Current 
 Dynamo. (1) A dynamo that furnishes 
 continuous currents without the aid of a 
 commutator. (2) The so-called unipolar 
 dynamo. 
 
 Commuted. Caused to take one and the 
 same direction. 
 
 Commuted Currents or Electromotive 
 Forces. Currents or electromotive 
 forces that have undergone commutation. 
 
 Commuted Magneto-Generator. A 
 magneto-generator whose currents are 
 commuted. 
 
 Commutated. Commuted. 
 
 Commutating. Commuting. 
 
 Commuting. Changing direction. 
 
 Commuting Transformer. A rotarj 
 commutator. 
 
Com.] 
 
 719 
 
 [Com. 
 
 Companion Loops. A pair of telegraphic 
 loop-circuits, connecting a pair of branch 
 offices with the main office, in which there 
 is a duplex set, so connected therewith, 
 that the instruments at the branch offices 
 are made the virtual duplex instruments 
 of the main station ; one branch office 
 sending while the other is receiving. 
 
 Comparator. An apparatus for compar- 
 ing standards of lengths or gauges. 
 
 Compartment Man-Hole of Conduit. 
 A man-hole provided with suitably sup- 
 ported shelves or compartments that pro- 
 tect different cable sections. 
 
 Compass. A mariner's compass. 
 
 Compass Card. A card used in a mari- 
 ner's compass on which are marked the 
 four cardinal points of the compass ; 
 North, South, East and West, and again 
 sub-divided into 32 points called rhumbs, 
 and also frequently divided circumferen- 
 tially into degrees. 
 
 Compass Sights. Small holes or narrow 
 slits made in opaque plates, affixed to the 
 compass box, for use in taking bearings. 
 
 Compensated Alternator. An alterna- 
 tor employed for sustaining a uniform 
 voltage at some point of its circuit under 
 varying loads, whose field magnets are 
 excited partly by constant currents taken 
 from a separate generator, and partly by 
 currents supplied by the load current in 
 the armature. 
 
 Compensated Excitation of Alterna- 
 tor. The excitation of an alternating- 
 current dynamo whose field is partly sep- 
 arately excited, and partly excited from 
 the main circuit of the machine. 
 
 Compensated Galvanometer. A dif- 
 ferential- galvanometer for indicating 
 pressure at a distant point of a continu- 
 ous-current circuit, having one coil in 
 shunt and the other in series with said 
 circuit. 
 
 Compensated Meter-Bridge. A meter- 
 bridge so arranged that its indications 
 are compensated for the effects of tem- 
 perature. 
 
 Compensated Besistance-Coil. A re- 
 sistance-coil so arranged as to be compen- 
 sated for the effect of temperature upon 
 its resistance. 
 
 Compensated System of Currents. 
 In telegraphy with the Wheatstone auto- 
 matic apparatus, a system of double-cur- 
 rent signalling in which both the initial 
 and final currents are weakened before 
 removal by the interposition of a resist- 
 ance in the battery circuit. 
 
 Compensated Voltmeter. A central- 
 
 station voltmeter connected to the bus- 
 bars in such a manner that its indications 
 are automatically corrected for the drop of 
 pressure in some particular feeder or group 
 of feeders, so that its readings correspond 
 to the pressure supplied to the mains. 
 
 Compensated "Wattmeter. A watt- 
 meter so wound as to be compensated for 
 the effect of reactance in its shunt circuit. 
 
 Compensated Coils. A term sometimes 
 applied to the series coils placed on a 
 shunt- wound machine. 
 
 Compensated Condenser. A condenser 
 employed in duplex telegraphy to give to 
 the artificial line a static capacity equal 
 to that of the main line. 
 
 Compensated Potential-Indicator. A 
 compensated voltmeter. 
 
 Compensating Line. An artificial line 
 employed in duplex telegraphy. 
 
 Compensating Magnet. A magnet 
 placed over a galvanometer or other 
 needle, for the purpose of varying the di- 
 rection and intensity of the earth's mag- 
 netic force on such needle. 
 
 Compensating Pole. A small bar elec- 
 tro-magnet, or electro-magnetic coil, 
 placed perpendicularly between the pole- 
 pieces of a dynamo to compensate for the 
 cross magnetization of the armature cur- 
 rents. 
 
 Compensating Wire. In a system of 
 differential duplex telegraphy, the arti- 
 ficial line or wire, as distinguished from 
 the real line or wire. 
 
 Compensation Photometer. (1) A pho- 
 tometer in which the illumination of the 
 two parts of the photometer screen is 
 equalized by diminishing the intensity of 
 the pencil of light by polarization. (2) A 
 polarization photometer. 
 
 Compensator. An auto-transformer. 
 
 Compensator for Alternating-Current 
 Lamps. A choking coil or compensator, 
 placed in circuit with the lamps in an 
 alternating-current circuit, for the pur- 
 pose of automatically regulating the cur- 
 rent strength in the lamps. 
 
 Compensator System. A system of al- 
 ternating-current electric distribution 
 from high-pressure mains to low-pressure 
 translating devices, in which the latter 
 are connected in derived circuits between 
 sections of choking coils connected across 
 the mains. 
 
 Complement of Angle. What an angle 
 lacks to make its value equal to 90, or 
 a right angle. 
 
 Complete Fault. Any fault which com- 
 pletely interrupts telegraphic or telephon- 
 
Com.] 
 
 720 
 
 [Com. 
 
 ic communication as distinguished from a 
 partial fault. 
 
 Complete Wave. (1) Two successive al- 
 ternations, or a double alternation of a 
 periodically-alternating quantity. (2) A 
 cycle. 
 
 Completed Circuit. (1) A closed cir- 
 cuit. (2) A circuit whose conducting 
 continuity is unbroken. 
 
 Completing a Circuit. Closing a circuit. 
 
 Complex Distribution of Lamellar 
 Magnetism. A distribution of the mag- 
 netism of a finite magnet into an infinite 
 number of complex -magnetic shells. 
 
 Complex-Harmonic Motion. Motion 
 resulting from the superposition or co- 
 action of a plurality of simple-harmonic 
 motions. 
 
 Complex-Harmonic Alternating E. M. 
 F.s. Electromotive forces resulting 
 from the combination of a fundamental- 
 harmonic electromotive force and its 
 harmonics. 
 
 Complex-Harmonic 
 
 rents produced by 
 electromotive forces. 
 
 Currents. Cur- 
 complex-harmonic 
 
 Complex - Harmonic Electromotive 
 Forces . Com plex-harmonic alternating 
 electromotive forces. 
 
 Complex-Magnetic Shell. (1) A mag- 
 netic shell whose strength varies from 
 one part to another of its surface. (2) A 
 distribution of magnetization equivalent 
 to an association or superposition of a 
 number of separate magnetic shells of 
 arbiti'ary strength and area. 
 
 Complex Quantities. Any quantity 
 made up of two parts, one of which is 
 measured along an axis of reference, and 
 the other in a direction at right angles to 
 such axis, these axes being sometimes 
 described as the real and imaginary axes 
 respectively. 
 
 Component. One of the two or more 
 separate forces into which any single 
 force may be resolved ; or, conversely, the 
 separate forces which together produce 
 any single resulting force. 
 
 Component Currents. The two or more 
 currents into which it may be conceived 
 that a single current may be divided so 
 as to be the equivalent "of that single 
 current. 
 
 Component Electromotive Forces. 
 The two or more E. M. F.s into which 
 any given E. M. F. may be resolved. 
 
 Component Inductions. The two or 
 more inductions into which any given 
 magnetic flux may be resolved so as to be 
 its equivalent. 
 
 Components of Impedance. The ener- 
 gy component or effective resistance, and 
 the wattless component or effective re- 
 actance. 
 
 Composite Anchor-Pole. A combina- 
 tion anchor-pole. 
 
 Composite Balance. A balance with two 
 pairs of fixed coils of coarse and fine wire 
 respectively, employed for measuring 
 strong or feeble currents as desired. 
 
 Composite Dynamo. A compound- 
 wound dynamo. 
 
 Composite Excitation. Any excitation 
 of the field magnets of a dynamo in which 
 more than a single winding is employed, 
 such as a shunt and a series winding. 
 
 Composite Field. The field of a com- 
 positely-excited dynamo. 
 
 Composite-Field Dynamo. (1) A dy- 
 namo whose field has a composite excita- 
 tion. (2) A dynamo whose field is com- 
 pound wound. 
 
 Composite Grid. A storage-battery grid 
 made of a number of sheets of lead foil 
 covered with graphite, placed between 
 two plates of sheet lead which are held 
 together with lead rivets. 
 
 Composite Horse-Shoe Magnet. A 
 
 compound horse-shoe magnet. 
 
 Composite Kilo-Ampere Balance. A 
 
 balance form of ammeter, provided with 
 coarse and fine windings, so arranged that 
 the instrument will serve as a kilo-ampere 
 meter, as a centi-ampere meter, or, as a 
 voltmeter. 
 
 Composite Wire. (1) A wire provided 
 with a steel core and an external copper 
 sheath, possessing sufficient tensile 
 strength to enable it to be ued in long 
 spans without excessive sagging. (2) A 
 bimetallic wire. 
 
 Compositely-Excited Dynamo. (1) A 
 compound-wound dynamo. (2) A com- 
 posite-field dynamo. 
 
 Composition of Forces. Finding the 
 direction and intensity of a single force 
 which represents the total effect of two 
 or more forces that are acting simultane- 
 ously on a body. 
 
 Compound. An asphaltic composition 
 employed in the sheathing of submarine 
 cables. 
 
 Compound Alternator. A compound- 
 wound alternator. 
 
 Compound Arc. An arc formed of mora 
 
 than two separate electrodes. 
 Compound Battery. A term formerly 
 
 employed for a battery of voltaic cells, as 
 
t'om.] 
 
 721 
 
 [Con. 
 
 contradistinguished from a single cell. 
 (Obsolete.) 
 
 Compound Cable. A multiple-core cable. 
 
 Compound Circuit. A circuit contain- 
 ing more -than a single source, or more 
 than a single electro-receptive device, or 
 both. (Not in general use.) 
 
 Compound Condenser. (1) A name 
 sometimes given to subdivided condenser. 
 (2) A composite condenser. 
 
 Compound Electro-Magnet. A word 
 formerly employed for an electro-magnet 
 consisting of an iron core wound with 
 two or more separate magnetizing cir- 
 cuits. (Not in general use.) 
 
 Compound Magnet. A number of single 
 magnets placed parallel, side by side, 
 and with their similar poles adjacent. 
 
 Compound Radical. (1) A group of un- 
 satura ted atoms. (2) A group of elemen- 
 tary atoms some of whose bonds are in- 
 terconnected or joined with the bonds of 
 other atoms. 
 
 Compound Receiver. A telephone re- 
 ceiver employed by an operator at a 
 central station, and composed of two 
 separate telephone receivers united into 
 one common frame or receptacle with a 
 single ear- piece, for the purpose of afford- 
 ing a separate distinct circuit and dia- 
 phragm, independently of the speaking 
 circuit and diaphragm. 
 
 Compound Telegraph-Wire. A bi- 
 metallic telegraph wire. 
 
 Compound Winding. A method of 
 winding dynamos or motors in which 
 both shunt and series coils are placed on 
 the field magnets. 
 
 Compound - Wound. (1) Having asso- 
 ciated shunt and series windings. 
 (2) Compositely wound. 
 
 Compound-Wound Alternator. An 
 alternator whose fields are compound- 
 wound. 
 
 Compound-Wound Continuous-Cur- 
 rent Generator. A continuous-current 
 generator whose fields are compound- 
 wound, for the purpose of maintaining 
 the pressure constant under all loads. 
 
 Compound- Wound Field. A field pro- 
 vided with compound windings. 
 
 Compound-Wound Motor. A motor 
 whose field is compound wound, for the 
 purpose of maintaining its speed constant 
 under all loads. 
 
 Compound- Wound Voltmeter. (1) A 
 compensated voltmeter. (2) A voltmeter 
 having more than one winding. 
 
 Concealed Wiring. Interior wiring 
 46 
 
 placed out of sight, and either built in 
 the plaster of a room or carried through 
 suitable conduits placed therein. 
 Concentration of Lines of Force. 
 Any increase in the intensity of a mag- 
 netic flux. 
 
 Concentration Throw. The deflection 
 of a magnetic needle by a current, pro- 
 duced under certain circumstances by a 
 couple formed of plates or iron or other 
 paramagnetic metal, when exposed to 
 chemical action while in a magnetic field. 
 
 Concentric Cable. (1) A cable provided 
 with both a leading and return conductor 
 insulated from each other, and forming 
 respectively the central core or conductor, 
 and the enclosing tubular conductor. 
 (2) A cable having concentric conductors. 
 
 Concentric-Carbon Electrodes. Con- 
 centric-carbon electrodes employed in a 
 modified form of Jablochkoff candle. 
 
 Concentric Conductors. Cylindrical 
 coaxial conductors insulated from each 
 other. 
 
 Concentric-Cylindrical Carbons . A 
 cylindrical rod of carbon placed inside a 
 hollow cylinder of carbon, but separated 
 from it either by an air space, or by some 
 refractory insulating material, employed 
 in a form of Jablochkoff candle. 
 
 Concentric Mains. Mains employing 
 concentric cables. 
 
 Concentric Wiring. Wiring by means 
 of concentric cables. 
 
 Condensance. Capacity reactance. 
 
 Condenser. (1) A device for increasing 
 the capacity of an insulated conductor 
 by bringing it near another earth- 
 connected conductor but separated there- 
 from by any medium that will permit 
 electrostatic induction to take place 
 through its mass. (2) Any variety of 
 electrostatic accumulator. 
 
 Condenser Capacity. The capacity of a 
 condenser. 
 
 Condenser Circuit. Any circuit in which 
 a condenser is inserted. 
 
 Condenser Lightning- A r r e s t e r. A 
 form of lightning arrester whose opera- 
 tion depends on the connection of a con- 
 denser with some part of the circuit to be 
 protected. 
 
 Condenser Pressure. The difference of 
 potential at the terminals of a condenser. 
 
 Condenser Rheostat. A rheostat in the 
 circuit of a condenser in an artificial 
 line of a duplex or quadruplex system. 
 
 Condenser Signalling. Any form of 
 
Con.] 
 
 722 
 
 [Con. 
 
 telegraphic or telephonic signalling in 
 which condensers are employed. 
 
 Condenser Working. Condenser signal- 
 ling. 
 
 Condensing Electroscope. An electro- 
 scope provided with a condenser for 
 the purpose of rendering evident feeble 
 charges. 
 
 Conduct. (1) To pass electricity through 
 conducting substances. (2) To carry, or 
 to possess the power of carrying, an elec- 
 tric current. 
 
 Conductance. (1) A word sometimes 
 used in place of conducting power. 
 (2) The reciprocal of resistance. (3) In 
 a continuous-current circuit the ratio of 
 the current strength to the E. M. F. 
 (4) In an alternating-current circuit the 
 quantity whose square added to the' square 
 of the susceptance is equal to the square 
 of the admittance. 
 
 Conductance, Electric. Conducting 
 power for electricity. 
 
 Conductance Leak. A leak in a cable or 
 circuit produced by conduction as dis- 
 tinguished from a leak possessing induc- 
 tion. 
 
 Conductibility. (1) Possessing the 
 power of conducting electricity. (2) Con- 
 ductivity. 
 
 Conducting Cord. A small insulated 
 flexible cable usually consisting of a 
 stranded conductor or conductors. 
 
 Conducting Cord Tip. A blunted or 
 rounded conductor placed at one of the 
 ends of a cord or wire for the purpose of 
 readily inserting it into a binding post or 
 into a plug hole. 
 
 Conducting Loop. A loop of wire or 
 other electric conductor. 
 
 Conducting Power. The ability pos- 
 sessed by a given length and area of 
 normal cross-section of a substance for con- 
 ducting light, heat, electricity, or mag- 
 netism, as compared with that possessed 
 by an equal length and area of normal 
 cross-section of some other substance 
 taken as a standard. 
 
 Conducting Power for Electricity. 
 The ability possessed by a given length 
 and area of normal cross-section of a sub- 
 stance to conduct electricity, as compared 
 with that possessed by an equal length 
 and area of normal cross-section of some 
 other substance taken as a standard, 
 such, for example, as pure copper. 
 
 Conducting Power for Heat. The 
 
 ability possessed by a substance to trans- 
 mit heat through its mass. 
 
 Conducting Power for Lines of Mag- 
 netic Force. (1) Permeability. (2) In- 
 due tivity. 
 
 Conduction Current. The current that 
 passes through a metallic or other con- 
 ducting substance, as distinguished from 
 one produced in a non-conductor or 
 dielectric. 
 
 Conduction, Electric. (1) The so-called 
 flow or passage of electricity through a 
 metallic or other similar substance. 
 (2) The ability of a substance to determine 
 the direction in which electric energy 
 shall be transmitted through the ether 
 surrounding it. (3) The ability of a sub- 
 stance to determine the direction in which 
 a current of electricity shall pass from 
 one point to another. 
 
 Conduction Lightning-Protection. 
 The protection of any instrument from 
 the passage of a current due to lightning 
 through its coils. 
 
 Conduction Lightning-Protector. A 
 lightning protector by means of which a 
 current is prevented from passing through 
 the coils of a galvanometer, or other 
 needle instrument, and thus injuriously 
 disturb the magnetism of the needle. 
 
 Conduction Besistance. The resistance 
 offered by a conductor to an electric 
 current. 
 
 Conductive. Possessing the power of 
 conducting. 
 
 Conductive Discharge. A discharge 
 effected by leading the charge off through 
 a conductor placed in contact with the 
 charged body, as opposed to a convective 
 or disruptive discharge. 
 
 Conductivity, Electric. (1) The recip- 
 rocal of electric resistivity. (2) The con- 
 ductance of a substance referred to unit 
 dimensions. 
 
 Conductivity Resistance. The resist- 
 ance offered by a substance to electric 
 conduction, or to the passage of elec- 
 tricity through its mass. 
 
 Conductor. (1) Any substance which 
 will permit the so-called passage of an 
 electric current. (2) A substance which 
 possesses the ability of determining the 
 direction in which electric energy shall 
 pass through the ether in the dielectric 
 surrounding it. 
 
 Conductor Resistance. A term fre- 
 quently employed for copper resistance. 
 
 Conductor System. A net-work of in- 
 terconnected conductors employed for 
 distributing electricity. 
 
 Conduit Cables. A cable conductor of 
 set of conductors laid in a conduit. 
 
Con.] 
 
 723 
 
 [Con. 
 
 Conduit Conductors. Conductors in- 
 tended for use in underground circuits, 
 provided with an insulation suitable to 
 maintain the electric integrity of the 
 separate circuits. 
 
 Conduit, Electric. An underground 
 space, either single or provided with a 
 number of separate spaces called ducts, 
 employed for the reception of electric 
 wires or cables. 
 
 Conduit Trolley-System. A single or 
 double-trolley system in which the trolley 
 wire or wires are placed in an under- 
 ground slotted conduit, the trolley wheel 
 being replaced by a plow or sled pushed 
 or drawn through the slot. 
 
 Coned Plunger for Electromagnetic 
 S o 1 e n o i d. A cone-shaped core, em- 
 ployed in connection with a solenoid in- 
 stead of the ordinary cylindrical core, for 
 the purpose of obtaining a comparatively 
 uniform pull through a fairly extended 
 movement of the core. 
 
 Conflict, Electric. A term proposed for 
 the magnetic field surrounding an active 
 conductor. 
 
 Congelation. The act of freezing, or the 
 change of a liquid into a solid on loss of 
 heat. 
 
 Conical Conductor. (1) A cone-shaped 
 conductor, which gradually increases or 
 decreases in diameter, thus assuming the 
 form of a tapering cone, employed to 
 obtain an approximately constant current 
 density through a system of parallel dis- 
 tribution. (2) In practice, a cylindrical 
 conductor that tapers by sections, the 
 diameter being reduced in each succeed- 
 ing length. 
 
 Conjoined E. M. P.'s. A number of elec- 
 tromotive forces simultaneously acting 
 in one circuit. 
 
 Conjugate Coils. Two coils whose con- 
 ductors are conjugate to each other. 
 
 Conjugate Conductors. (1) In a con- 
 ducting net-work, two conductors so re- 
 lated that the introduction of an E. M. F. 
 in one produces no current in the other. 
 (2) Two conductors so placed as regards 
 each other that an interruption of the 
 current in one, produces no induced cur- 
 rent in the other. 
 
 Conjugate Functions. The real and im- 
 aginary components of a function of a 
 complex variable. 
 
 Connect. To place or bring into electric 
 contact. 
 
 Connecting. Placing or bringing into 
 electric contact. 
 
 Connecting Bars. Metallic bars at a 
 call-wire multiple-switchboard, for con- 
 necting the operator's set with the call- 
 wire jacks through a cord. 
 
 Connecting In "Bridge." A phrase 
 sometimes employed for connecting in 
 multiple arc or parallel. 
 
 Connecting Jack. A jack for introduc- 
 ing a loop into a telephone circuit. 
 
 Connecting Peg. A metallic block for 
 bridging an air gap and so making an 
 electric connection. 
 
 Connecting Screws. A term sometimes 
 employed indifferently for connectors or 
 for binding posts. 
 
 Connecting Side of Telephone Switch- 
 board. That side of a telephone switch- 
 board at which connections are made 
 with subscribers wanted, as distinguished 
 from the side at which calls are received. 
 
 Connecting Sleeve. A metallic sleeve 
 employed as a connector for readily join- 
 ing the ends of two or more wires. 
 
 Connecting-Up. (1) In telegraphy, join- 
 ing up. (2) The operation of establishing 
 an electric circuit. 
 
 Connection. The act of placing in electric 
 or magnetic contact. 
 
 Connection Board of Transformer. A 
 board usually located in an accessible 
 place in a transformer case, and provided 
 with binding posts for conveniently mak- 
 ing or changing the connections of the 
 transformer coils with the external cir- 
 cuits. 
 
 Connection for Intensity. A phrase 
 formerly employed for connection in 
 series. (Nearly obsolete.) 
 
 Connection for Quantity. A phrase 
 formerly employed for connection in mul- 
 tiple. (Nearly obsolete.) 
 
 Connection in Cascade. A term some- 
 times employed for connection in series. 
 
 Connection in Sequence. A term some- 
 times used for connection in series. 
 
 Connection of Battery for Intensity. 
 A term formerly employed for the series- 
 connection of the cells in a battery. (Ob- 
 solete.) 
 
 Connection of Battery for Quantity. 
 A term formerly employed for a multiple 
 or parallel connection of the cells in a bat- 
 tery. (Obsolete.) 
 
 Connector. A device for readily connect- 
 ing or joining the ends of two or more 
 conductors. 
 
 Conning Tower. A shell-proof tower 
 from which the commander on a turreted 
 
Con.] 
 
 724 
 
 [Coil. 
 
 war-ship directs its movements when in 
 action. 
 
 Consequent Points. The points or places 
 in an anomalous magnet where its conse- 
 quent poles are situated. 
 
 Consequent Pole. (1) A magnet pole 
 formed by two free north or two free 
 south poles placed together. (2) A mag- 
 net pole developed at some point of a 
 magnet other than its extremities. 
 
 Consequent Poles of Dynamo. 
 
 (1) Dynamo poles formed by the juxtapo- 
 sition of two similar magnetic poles. 
 
 (2) Dynamo poles developed at polar pro- 
 jections unprovided with magnetizing 
 coils. 
 
 Consequent Resistance. A term pro- 
 posed for the apparent resistance of a 
 conductor traversed by alternating cur- 
 rents, as modified by the skin effect, and 
 as distinguished from its ohmic resist- 
 ance or its inductive resistance. 
 
 Conservation of Energy. (1) A term 
 indicative of the fact that energy can 
 never be annihilated, so that if it disap- 
 pears in one form, it must reappear in 
 some other form. (2) The indestructi- 
 bility of energy. 
 
 Consonance. (1) A phase agreement be- 
 tween two simple-periodic waves or vibra- 
 tions. (2) The reinforcement of sound 
 waves, or their increase in intensity, by 
 means of vibrating bodies that are not in 
 resonance with, or are tuned to vibrate 
 in unison with, the sounding body. 
 
 (3) Forced unison. 
 
 Consonance, Electric. In an alternat- 
 ing-current circuit the co-phasing of the 
 impressed E. M. F. with the primary cur- 
 rent, due to the influence of capacity in 
 an inductively associated secondary cir- 
 cuit. 
 
 Consonant Electric Circuit.-^!) An 
 alternating-current circuit containing re- 
 sistance and inductance, and inductively 
 associated with a secondary circuit con- 
 taining resistance, inductance, and capac- 
 ity, in such a manner that the secondary 
 inductance and capacity neutralize the 
 inductance of the primary circuit. (2) A 
 primary alternating-current circuit devoid 
 of reactance or choking effect, owing to 
 the presence of a condenser in a secondary 
 circuit, as distinguished from the effect 
 of a condenser inserted in the primary 
 circuit directly. 
 
 Consonator. Any body capable of rein- 
 forcing sound by consonance. 
 Constant. Possessing an invariable value. 
 
 Constant Cell. Any voltaic cell which, 
 under certain circumstances, is capable of 
 furnishing a constant electromotive force 
 and current. 
 
 Constant Current. (1) A direct current, 
 or one that always flows in the same di- 
 rection. (2) A current whose strength is 
 unvarying. 
 
 Constant - Current Alternating - Cur- 
 rent Dynamo. An alternator which 
 supplies a constant effective current 
 strength in its circuit. 
 
 Constant-Current Arc-Lamp. A series- 
 connected arc-lamp. 
 
 Constant-Current Circuit. A circuit 
 whose current strength is maintained 
 constant notwithstanding changes in its 
 resistance. 
 
 Constant-Current Dynamo. A con- 
 stant-current generator. 
 
 Constant-Current Generator. A term 
 applied to a generator intended to pro- 
 duce a constant strength of current de- 
 spite changes in its load. 
 
 Constant-CurrentTransformation. A 
 
 change or transformation in the strength 
 of a constant current. 
 Constant-Current Transformer. (1) A. 
 transformer which is intended to raise or 
 reduce a current strength in a given con- 
 stant ratio. (2) A transformer designed 
 to maintain a constant strength of current 
 in its secondary circuit, despite changes 
 of load. 
 
 Constant Inductance. (1) The induc- 
 tance of a circuit immersed in or wholly 
 surrounded by a material of constant 
 magnetic permeability. (2) An induc- 
 tance which does not vary with the cur- 
 rent strength. 
 
 Constant-Potential Alternating-Cur- 
 rent Dynamo. (1) An alternator which 
 supplies a constant effective pressure at 
 its terminals. (2) A compounded alter- 
 nator. 
 
 Constant-Potential Arc-Lamp. An 
 arc lamp employed on constant-potential 
 or incandescent mains. 
 
 Constant-Potential Circuit. (1) A cir- 
 cuit whose potential is maintained ap- 
 proximately constant. (2) A multiple-arc 
 or parallel-connected circuit. 
 
 Constant-Potential Dynamo. (1) A 
 dynamo that furnishes an approximately 
 constant difference of potential or elec- 
 tromotive force despite changes in its re- 
 sistance or load. (2) A shunt or com- 
 pound-wound dynamo. 
 
 Constant-Potential Generator. A con- 
 stant-potential dynamo. 
 
Con.] 
 
 725 
 
 [Con. 
 
 Constant-Potential Motor. (1) A motor 
 designed for operation by means of a con- 
 stant-potential current. (2) Generally, a 
 shunt-wound or compound-wound motor. 
 
 Consumer. One who receives electric 
 supply. 
 
 Consumer's Terminals. In a system of 
 electric distribution the terminals of a 
 house service, the property of the house, 
 and at which the electric supply is de- 
 livered by the supply company. 
 
 Consumption Circuit. Any circuit in 
 which an electro-receptive device is 
 placed. 
 
 Contact Breaker. A device for breaking 
 or opening an electric circuit. 
 
 Contact Electromotive Force. Elec- 
 tromotive force produced by the mere 
 contact of dissimilar metals. 
 
 Contact Electricity. Electricity pro- 
 duced by contact electromotive forces. 
 
 Contact Force. A contact electromotive 
 force. 
 
 Contact Lamp. A name sometimes given 
 to a semi-incandescent lamp. 
 
 Contact Resistance. Resistance pro- 
 duced at the contact of two or more sur- 
 faces. 
 
 Contact Ring of Telephone Plug. A 
 plug in a multiple telephone switchboard 
 carrying an insulated metal ring or sleeve 
 establishing a circuit for the busy test. 
 
 Contact Rings of Alternator. The col- 
 lector rings of an alternator. 
 
 Contact Series. A series of metals ar- 
 ranged in such an order that each becomes 
 positively electrified by contact with the 
 one that follows it. 
 
 Contact Screw. A screw the end of 
 which is provided with a platinum or 
 other contact, employed to close the 
 circuit of any electric device in whose 
 circuit it is placed. 
 
 Contact Theory of Electricity. A the- 
 ory that ascribes the production of elec- 
 tromotive forces, or of electricity, to the 
 contact of dissimilar substances or sur- 
 faces. 
 
 Contact Theory of Voltaic Cell. The 
 contact theory of electricity applied to 
 the production of electricity in a voltaic 
 cell. 
 
 Contacts. (1) Conducting pieces or plates 
 introduced into electric circuits at points 
 where it is desired to open and close the 
 circuit. (2) A variety of fault occasioned 
 in any circuit by the accidental contact 
 of any part of the circuit with a conduct- 
 ing body. (3) A metallic cross or faulty 
 
 connection between two telegraphic or 
 telephonic circuits. 
 
 Containing Cell. (1) A jar provided for 
 holding or containing the solution or 
 electrolyte employed in connection with 
 a primary or secondary voltaic couple. 
 (2) A jar or receptacle for containing any 
 liquid or solution, as in an electro-plating 
 bath. 
 
 Continental Telegraphic-Code. A tele- 
 graphic-code employed in Europe gener- 
 ally. 
 
 Continuator. A constant-current dyna- 
 mo. (Not in use.) 
 
 Continuity of Circuit. The uninter- 
 rupted conducting condition of a circuit. 
 
 Continuity -Preserving Transmitter. 
 A transmitter employed in duplex teleg- 
 raphy, so arranged that the line wire 
 may be transferred from the battery to 
 the earth without any break in the conti- 
 nuity of the circuit. 
 
 Continuous- Alternating Transformer. 
 
 (1) A secondary generator for transform- 
 ing continuous into alternating currents. 
 
 (2) A dynamotor, motor-dynamo, or ro- 
 tary transformer. 
 
 Continuous Current. (1) An electric 
 current which flows in one and the same 
 direction. (2) A direct current. 
 
 Continuous-Current Arc. A voltaic arc 
 produced by a continuous current, as dis- 
 tinguished from one produced by alternat- 
 ing currents. 
 
 Continuous-Current Armature- Wind- 
 ings. Armature windings suitable for 
 use in continuous-current generators. 
 
 Continuous-Current Dynamo-Electric 
 Machine. A continuous-current gener- 
 ator. 
 
 Continuous-Current Generator. Any 
 generator capable of furnishing contin- 
 uous currents. 
 
 Continuous-Current Motor. A motor 
 operated by continuous or direct currents. 
 
 Continuous-Current Transformer. (1) 
 A dynamotor or motor-dynamo. (2) A 
 transformer from one continuous pressure 
 and current to another. 
 
 Continuous E. M. F.'s. Electromotive 
 forces whose direction and value remain 
 constant. 
 
 Continuous - Sounding or Ringing 
 Electric-Bell. (l)An electric bell, which 
 on completion of its circuit continues 
 sounding until stopped. (2) A trembling 
 bell. 
 
 Continuous Spectrum. (1) A luminous 
 spectrum that is devoid of the Fraunhofer 
 
Coil.] 
 
 726 
 
 [Con. 
 
 dark lines, or which contains all the phys- 
 iologically effective luminous frequencies. 
 (2) The spectrum of a sufficiently heated 
 incandescent solid. 
 
 Continuous- Surf ace Commutator. A 
 dynamo commutator, whose surface con- 
 tains no breaks in the gaps between con- 
 tiguous commutator bars ; i. e., whose 
 gaps are tilled with an insulating material 
 instead of being left with air spaces. 
 
 Continuous Trolley Wire. An un- 
 jointed trolley wire. 
 
 Continuous Winding. A term fre- 
 quently employed for wave winding or 
 undulatory winding of an armatui'e. 
 
 Continuous Wire or Conductor. An 
 unjointed wire or conductor. 
 
 Continuously Insulated Cable. A 
 length of cable extending continuously 
 between two points without any taps. 
 
 Contracting Magnetic Whirls. Mag- 
 netic whirls which are decreasing or mov- 
 ing in towards the electro-magnet or cir- 
 cuit producing them. 
 
 Contractures. In electro-therapeutics 
 prolonged muscular spasms or tetanus 
 caused by the passage of electric currents. 
 
 Contraplex Telegraph. A general term 
 embracing the apparatus employed in 
 contraplex telegraphy. 
 
 Contraplex Telegraphy. Duplex teleg- 
 raphy in which transmissions are simul- 
 taneously made from opposite ends of the 
 lino. 
 
 Controlled Clock. A clock whose works 
 are controlled or regulated either entirely 
 or partially, by an electric current. 
 
 Controller. (1) The magnet employed in 
 a system of automatic constant-current 
 regulation, whose coils are traversed by 
 the main current, employed automatically 
 to throw a regulator magnet into or out 
 of the main circuit on changes of the cur- 
 rent passing. (2) Any electric mechanism 
 for controlling a circuit or system. (3) An 
 electric switching mechanism for control- 
 ling the speed of a motor or motors. (4) A 
 street-railway car-controller. 
 
 Controller Resistance. Resistance em- 
 ployed in connection with street-car con- 
 trollers for starting or stopping the mo- 
 tors, or for varying their speed. 
 
 Controller Switch. (1) The switch oper- 
 ating the switch cylinder of a street-car 
 controller. (2) Any switch employed in 
 connection with a street-car controller. 
 
 Controlling Box. The box holding any 
 controlling rheostat or controller. 
 
 Controlling Block, Electric. In a sys- 
 tem of time-telegraphy, the master clock 
 
 whose impulses move or regulate the 
 secondary clocks. 
 
 Controlling Magnet. (1) Any magnet 
 which controls some particular action, 
 as, for example, the attraction of a needle 
 in a galvanometer. (2) A name some- 
 times given to the controller in an auto- 
 matic system of current regulation. 
 
 Controlling Stand. The support or stand 
 provided for holding the apparatus em- 
 ployed for controlling a motor. 
 
 Convection Currents. Currents pro- 
 duced by the bodily carrying forward of 
 static charges in convection streams. 
 
 Convection, Electric. The air streams 
 which are thrown off from points on the 
 surface of a charged insulated conductor. 
 
 Convection of Heat, Electric. (1) A 
 term employed to express the dissymmet- 
 rical distribution of temperature that 
 occurs when an electric current is sent 
 through a metallic wire, the middle of 
 which is maintained at one constant tem- 
 perature, and the ends at another constant 
 temperature. (2) Distribution of heat 
 which attends the passage of an electric 
 current through an unequally heated con- 
 ductor. 
 
 Convection Streams. Streams of elec- 
 trified air, or other gaseous or vaporous 
 particles, given off from sharp points on 
 the surface of highly charged insulated 
 conductors. 
 
 Convection Transference. The trans- 
 ference of electricity by means of convec- 
 tion streams. 
 
 Convective Discharge. The discharge 
 which occurs from the points of a highly 
 charged conductor, through the electro- 
 static repulsion of similarly charged air 
 particles, which thus carry off minute 
 charges. 
 
 Converging Magnetic Flux. Magnetic 
 flux that converges or radiates from a 
 point or points. 
 
 Conversion of Electromotive Force. 
 Any increase or decrease in the value of 
 an electromotive force produced by means 
 of a transformer. 
 
 Convert. To transform or change an elec- 
 tromotive force or current. 
 
 Converted Currents. Electric currents 
 whose strengths have been increased or 
 decreased by means of a transformer. 
 
 Converter. A name sometimes given 
 to a transformer. 
 
 Converter Bracket. (1) A bracket for 
 holding a pair of insulators and a single 
 light converter and shunt box in an alter- 
 nating-current series-system of street light- 
 
Con.] 
 
 727 
 
 [Cop. 
 
 ing. (2) A bracket for supporting an al- 
 ternating-current converter. 
 
 Converter Fuse. A safety fuse connect- 
 ed with the circuit or circuits of a 
 converter or transformer, and usually 
 mounted in the transformer case. 
 
 Converting. Transforming or changing 
 an electromotive force or current. 
 
 Converting Currents. (1) Changing the 
 value of the current strength by means 
 of transformers. (2) Changing a contin- 
 uous into an alternating current, or vice 
 versa. 
 
 Converting Station. (1) A transform- 
 ing station. (2) A station containing 
 transformers. 
 
 Conveyer, Electric. An electrically op- 
 erated or controlled system of transport- 
 ing material. 
 
 Convolutions of Wire. The separate 
 loops or turns in a helix or coil. 
 
 Cooling-Box of Hydro-Electric Ma- 
 chine. A box provided in Armstrong's 
 hydro-electric machine for the steam to 
 pass through before leaving the nozzle. 
 
 Cooling Surface. The surface from 
 which a hot body can dissipate its heat 
 energy. 
 
 Cooling Surface of Armature. That 
 portion of an armature surface from 
 which it can dissipate into the surround- 
 ing air, the heat energy produced in it 
 by the passage of the currents generated 
 during its rotation. 
 
 Cooling Tubes. Tubes inserted in the 
 frame or casing of an alternating-current 
 transformer for the supply of cold water 
 from an external pump or source. 
 
 Co-Periodic. Possessing the same peri- 
 odicity. 
 
 Co-Periodic E. M. F.'s, Currents or 
 Fluxes. Electromotive forces, currents 
 or fluxes, possessing the same periodicity. 
 
 Co-Phasal. Possessing the same phase. 
 
 Co-Phasal Alternations. Alternations 
 possessing the same phase. 
 
 Co-Phase. (1) Coincidence in phase of 
 co-periodic motions. (2) Such a phase 
 relation between two periodic but non- 
 co-periodic quantities as tends to increase 
 the amplitude of the motion. 
 
 Copper Arc. An arc formed between 
 copper electrodes. 
 
 Copper Bath. An electrolytic bath 
 containing an electrolyzable solution of a 
 copper salt, and a copper plate forming 
 the anode, and placed in an electrolyte 
 near the object to be electroplated, which 
 forms the cathode. 
 
 Copper Battery. A battery employed in 
 sending copper currents to line. 
 
 Copper Conductivity Standard. (1) 
 According to rules of the British Institu- 
 tion of Electrical Engineers, a metre- 
 gramme wire of standard conductivity, 
 whose resistance is 0.1519 international 
 ohm at!5C., corresponding to Matthies- 
 sen's standard for hard copper. (2) Ac- 
 cording to a committee of the American 
 Institute of Electrical Engineers, a copper 
 metre-gramme, of Matthiessen standard 
 soft copper conductivity, whose resistance 
 is 0.1501 ohm at 15C. 
 
 Copper Connector. (1) A particular 
 form of connector employed in the grav- 
 ity voltaic cell for connecting the copper 
 element to the circuit wire or conductor. 
 (2) A special form of coupler for con- 
 necting large wires or conductors. 
 
 Copper Current. A term sometimes 
 used in telegraphy for a positive current. 
 
 Copper Efficiency. The ratio of the 
 electric energy delivered by a copper con- 
 ducting system, to the energy delivered 
 to that system. 
 
 Copper Fuse- Wire Terminals. Copper 
 terminals provided for connection with 
 the terminals of fuse wires or safety 
 catches. 
 
 Copper Heat. The heat which appears 
 in a copper conductor due to the passage 
 through it of an electric current. 
 
 Copper-Lead Accumulator. An ac- 
 cumulator or storage battery consisting 
 of plates of copper and lead immersed in 
 a solution of copper sulphate. 
 
 Copper Loss. The total loss of energy 
 produced by the passage of a current 
 through the copper wire of a dynamo, 
 motor, or conducting system generally. 
 
 Copper Magnetic Circuit. That portion 
 of a magnetic circuit which is completed 
 through copper. 
 
 Copper Plating. Electro - plating with 
 copper. 
 
 Copper Resistance. In submarine tel- 
 egraphy, conductor resistance. 
 
 Copper Resistivity. The specific re- 
 sistance of copper of Matthiessen soft cop- 
 per standard referred to the resistance of 
 a cube one centimetre in length of edge, 
 such a cube offering between parallel 
 faces a resistance of 1.594 microhms at 
 C. (2) The resistivity of a copper wire. 
 
 Copper Ribbon. A variety of strap cop- 
 per. 
 
 Copper Shell of Electro - Type. The 
 thin electrolytic deposit of copper which, 
 when stiffened by the backing metal and 
 
Cop.] 
 
 728 
 
 [Cos. 
 
 suitably mounted on a block, forms the 
 electro-type. 
 
 Copper Strap. Copper conductors in the 
 form of straps or flat bars. 
 
 Copper Tape. Rectangular straps or bars 
 of copper employed for armature wind- 
 ings. 
 
 Copper Voltameter. A voltameter 
 whose indications are dependent on the 
 electrolysis of a solution of a copper salt. 
 
 Copper-Zinc Accumulator. An accu- 
 mulator or storage cell consisting of a 
 plate of copper and a plate of zinc im- 
 mersed in a solution of zinc sulphate. 
 
 Coppered Arc-Light Carbons. Carbons 
 employed in arc-lamps, covered electro- 
 lytically with copper. 
 
 Coppered Carbons. Carbons for arc- 
 lamps, or batteries, that are electrolyti- 
 cally coated with copper. 
 
 Coppered Plumbago. Powdered plum- 
 bago coated with copper for use in the 
 metallization of objects to be electro- 
 plated. 
 
 Copying Telegraph. A fac-simile or 
 automatic telegraph. 
 
 Cord Adjuster. A device for adjusting 
 the length of a pendant cord. 
 
 Cord, Electric. A flexible, insulated elec- 
 tric conductor, generally containing two 
 parallel wires. 
 
 Cord Peg. A cord to which a connecting 
 peg is attached. 
 
 Cord-Peg Connection. Connection in a 
 switchboard by means of a cord peg. 
 
 Cord Pendant. A flexible or stranded 
 conductor employed for a lamp pendant. 
 
 Cord Shelf. A shelf provided for the 
 holding of the cord pegs of a telephone 
 switchboard. 
 
 Core Discs. Stampings or cuttings of 
 sheet iron, employed, when suitably as- 
 sembled, for the laminated core of a 
 dynamo or motor armature, or other 
 dynamo-electric apparatus. 
 
 Core Losses. The hysteresis and the 
 Foucault or eddy-current losses of the 
 core of a dynamo, motor, or transformer. 
 
 Core Losses of Transformer. (1) The 
 hysteresis and Foucault-current losses in 
 the core of a transformer. (2) The iron 
 losses in a transformer. 
 
 Core of Cable. (1) The insulated wires em- 
 ployed for the transmission of the current 
 through a conducting cable. (2) The elec- 
 tric conductor and insulator as distin- 
 guished from the mechanical serving and 
 sheathing of a cable. 
 
 Core Pins of Magnet.- -Pins in the cores 
 of a magnet for securing their firm 
 mechanical union with the yoke. 
 
 Core Ratio of Cable. The ratio between 
 the diameter of the core of a cable and the 
 mean diameter of the conductor strand. 
 
 Core Transformer. (1) A transformer in 
 which the iron forms the core or central 
 portion on which the wire windings are 
 placed. (2) A transformer possessing a 
 core capable of insertion or removal. 
 
 Cored Carbons. Arc-light carbons pro- 
 vided with a soft centre of carbon. 
 
 Cored Electrodes. Cored arc-light car- 
 bons. 
 Coreless. Devoid of a core. 
 
 Coreless Armature of Dynamo or 
 Motor. An armature of a dynamo or 
 motor unprovided with the usual core 
 of iron. 
 
 Corn-Plaster Fuse. A strip of fusible 
 metal rolled up with an asbestos tape in 
 the form of a cylinder and employed as 
 a safety catch in a telephone switchboard. 
 
 Cornice Bracket. A form of insulator 
 bracket for use on the under side of cor- 
 nices. 
 
 Corposant. A name sometimes given by 
 sailors to the St. Elmo's fire. 
 
 Coronse. (1) Crown - shaped masses of 
 light sometimes seen during the preva- 
 lence of aurorse. (2) Auroral coronee. 
 
 Corpuscle. (1) An ultimate particle in an 
 assumed highly tenuous substance that 
 was formerly believed to be emitted by 
 highly heated bodies. (2) Any of the 
 ultimate particles of the matter into 
 which it has been assumed that the ulti- 
 mate elementary atoms may be divided. 
 
 Correcting Factor of Wattmeter. 
 The correction which must be applied to 
 the readings of an alternating-current 
 wattmeter when the reactance in its 
 shunt circuit cannot be neglected. 
 
 Correcting Relay .(1) A relay employed 
 in the Delaney system of synchronous- 
 multiplex telegraphy to aid in obtaining 
 synchronism. (2) In a quadruplex sys- 
 tem, a relay intermediate between the 
 polarized receiving relay and its sounder, 
 for the purpose of preventing false signals 
 or kicks. 
 
 Correlation of Energy. A term some- 
 times applied to the different phases under 
 which energy may appear. 
 
 Corrugated Reflector. A reflector 
 formed of silvered corrugated glass. 
 
 Cosine. (1) One of the trigonometrical 
 functions. <8) The ratio of the base to 
 
Cos.] 
 
 7:>9 
 
 [Cou. 
 
 the hypothenuse of a right-angled triangle 
 in which the hypothenuse is the radius 
 vector, and the angle between the base 
 and hypothenuse the angle whose cosine 
 is considered. 
 
 Cosine Law of Illumination. The in- 
 tensity of illumination, of a surface 
 illumined by a single-point source, varies 
 as the cosine of the angle of the rays 
 incident upon the surface from that 
 source. 
 
 Oosinusoid. A curve of cosines. 
 
 Cotangent. (1) One of the trigonometrical 
 functions. (2) The reciprocal of the tan- 
 gent of an angle. 
 
 Coulomb. (1) The practical unit of elec- 
 tric quantity. (2) Such a quantity of 
 electricity as would pass in one second 
 through a circuit conveying one ampere. 
 (3) The quantity of electricity contained 
 in a condenser of one farad capacity, 
 when subjected to the E. M. F. of one 
 volt. 
 
 Coulomb Meter. A meter for measuring 
 in coulombs, the quantity of electricity 
 which passes through any circuit. 
 
 Coulomb's Electric Balance. A tor- 
 sion balance for measuring the forces of 
 electric 01 magnetic repulsion. 
 
 Coulomb's Torsion Balance. An ap- 
 paratus for measuring the force of elec- 
 tric or magnetic repulsion between two 
 similarly charged bodies, or between two 
 similar magnet poles, by opposing to such 
 forces the torsion of a thin wire. 
 
 Coulomb- Volt. A word sometimes em- 
 ployed for the volt-coulomb or joule. 
 
 Counter-Clockwise Motion. A rotary 
 motion whose direction is opposed to that 
 of the hands of a clock, as viewed from 
 the clock face. 
 
 Counter Communication Telephone 
 Switch. A switch arranged in a tele- 
 phone system in connection with a silence 
 cabinet, whereby a person occupying the 
 cabinet is unable to call up the exchange 
 without the sanction and assistance of an 
 attendant in the office outside the cabinet. 
 
 Counter, Electric. (1) A device for 
 counting and registering such quantities 
 as the number of fares collected, gallons of 
 water pumped, sheets of paper printed, 
 votes polled, revolutions of an engine per 
 second, etc. (2) Any counting device 
 operated or controlled by electricity. 
 
 Counter Electro-Dynamic Force. The 
 electro-magnetic force which is set up in 
 a dynamo armature opposing the im- 
 pressed driving force. 
 
 8 
 
 Counter-Electromotive Force. (1) An 
 opposed or reverse electromotive force 
 which tends to set up a current in the 
 opposite direction to that actually pro- 
 duced by a source. (2) In an electric 
 motor, an electromotive force produced 
 by the rotation of the armature and op- 
 posed to that produced by the driving 
 current. 
 
 Counter-Electromotive Force Cell. 
 (1) An electrolytic cell inserted in the 
 charging circuit of a storage battery to re- 
 duce the charging current strength, usu- 
 ally composed of opposed plates or grids of 
 antimomous lead from the surfaces of 
 which gases are disengaged by electrol- 
 ysis. (2) Additional cells, generally with- 
 out active material, employed with a stor- 
 age battery which has to be charged at a 
 pressure above the normal pressure, and 
 inserted between the dynamo and the 
 mains to maintain their pressure normal. 
 
 Counter-Electromotive Force Light- 
 ning- Arrester. (1) A lightning-arrester 
 in which the passage of a discharge 
 through the instruments to be protected 
 is opposed by a counter electromotive 
 force generated by induction on the pas- 
 sage of the lightning discharge. (2.) A 
 choking-coil lightning-arrester. 
 
 Counter-Electromotive Force of Arc. 
 
 An electromotive force produced during 
 the formation of a carbon voltaic arc op- 
 posed to that which maintains the arc. 
 
 Counter-Electromotive Force of Con- 
 vecti /e Discharge. Resistance to the 
 passage of an electric discharge through 
 a high vacuum, somewhat of the nature 
 of a counter electromotive force. 
 
 Counter-Electromotive Force of Elec- 
 trolysis. A counter electromotive force 
 produced by electrolysis in the plating 
 bath of an electrolytic cell. 
 
 Counter-Electromotive Force of In- 
 duction. The counter electromotive 
 force of self or mutual induction. 
 
 Counter-Electromotive Force of Mut- 
 ual Induction. (1) Counter-electro- 
 motive force produced by mutual induc- 
 tion between neighboring circuits. (2) 
 Counter-electromotive force in the pri- 
 mary circuit of a transformer produced by 
 the mutual induction from the current 
 in the secondary circuit. 
 
 Counter-Electromotive Force of Polar- 
 ization. Electromotive force developed 
 in a voltaic cell or plating bath by polar- 
 ization, and opposed to that which pro- 
 duces the current of the cell. 
 
 Counter-Electromotive Force of Self- 
 induction. The counter-electromotive 
 
 Vol. 9. 
 
Cou.] 
 
 730 
 
 [Cri, 
 
 force produced in the primary circuit of an 
 induction coil by the action thereon of an 
 alternating electromotive force. 
 
 Counter-Electromotive Force of Self- 
 induction of the Primary. The 
 counter-electromotive force produced in 
 the primary circuit of a transformer by 
 the action of induction of the primary 
 current on itself, as distinguished from 
 that produced by mutual induction .from 
 the secondary current. 
 
 Counter-Electromotive Force of Self- 
 induction of the Secondary. The 
 counter-electromotive force produced in 
 the secondary by periodic variations in 
 the effective electromotive force in the 
 secondary circuit. 
 
 Counter-Electromotive Force of Stor- 
 age Battery. The electromotive force 
 in a storage battery which opposes the 
 electromotive force employed in charging. 
 
 Counter-Electromotive Force of Volt- 
 aic Cell. The counter-electromotive 
 force in a voltaic cell due to its polariza- 
 tion. 
 
 Counter Inductive Effect. An opposal 
 of current or charge by means of an elec- 
 tromotive force produced by induction. 
 
 Counter Pressure. A term sometimes 
 used for counter-electromotive force. 
 
 Couple. (1) In mechanics, two equal and 
 parallel, but oppositely directed forces, 
 not acting in the same line, and tending to 
 produce rotation. (2) The two elements 
 in a voltaic cell or thermo-electric cell. 
 
 Coupled Cells. A number of separate 
 cells so connected or coupled as to form 
 a battery or single electric source. 
 
 Coupling Box for Electric Tubes. A 
 
 box provided for the ready connection of 
 the conductors in the separate lengths 
 of underground electric tubes. 
 
 Coupling Clamp for Underground Con- 
 ductors. An electric coupling between 
 two lengths of underground conductors. 
 
 Coupling Joint for Underground 
 Tubing. A joint for the separate con- 
 ductors in an underground tubing, con- 
 sisting generally of a flexible conductor 
 and connectors for ready attachment to 
 the ends of the conductor. 
 
 Coupling of Voltaic Cells or Other 
 Electric Sources. Connecting a num- 
 ber of separate voltaic cells, or other sep- 
 arate electric sources, so as to enable them 
 to act as a battery or single electric 
 source. 
 
 Coupling Transformer. A transformer 
 which employs polyphasal coupling of 
 magnetic circuits. 
 
 Cradle Dynamometer. A dynamometer 
 in which the dynamo to be tested is sup- 
 ported in a cradle, and the mechanical 
 energy it receives or transmits is measured 
 by the torque developed by the cradle 
 about its axis. 
 
 Cradle Suspension of Street-Car Mo- 
 tor. A method of supporting a street- 
 car motor on its truck upon a spring 
 cradle. 
 
 Crater in Positive Carbon. A depression 
 in the end of the positive carbon of an 
 arc-lamp, which occurs after the arc has 
 been maintained for some little time. 
 
 "Creep" of Belt. A term sometimes 
 used for the slip of a belt. 
 
 Creepage. The residual elastic torsion of 
 a suspension fibre. 
 
 Creeping, Electric. A term sometimes 
 applied to the creeping of a current. 
 
 Creeping in Voltaic Cell. The formation 
 by efflorescence of salts on the sides of 
 the porous cup of the voltaic cell, on the 
 binding posts, or on the walls of the 
 vessel containing the electrolyte. 
 
 Creeping of Belt. (1) An action of a driv- 
 ing belt due to its retractility, whereby the 
 driving pulley travels somewhat faster 
 than the driven pulley. (2) Belt slip. 
 
 Creeping of Current. (1) A term some- 
 times employed for a change in the direc- 
 tion of the path of a current from a direct 
 line between the points of connection with 
 the source. (2) Electrification or polariza- 
 tion currents in an electrolyte. (3) The 
 extension of a glow or streamer discharge 
 over the surface of a dielectric. 
 
 Creosoting. A process employed for the 
 preservation of wood, such, for example, 
 as telegraph poles, by injecting creosote 
 into the pores of the wood. 
 
 Crevasse. A narrow gap or slit effected, 
 or imagined, in a magnet or magnetized 
 substance, for the purpose of determining 
 the magnetic forces on a small needle. 
 
 Crith. A proposed unit of mass, or the 
 weight of one litre or cubic decimetre of 
 hydrogen at Centigrade, and 760 mil- 
 limetres barometric pressure. 
 
 Critical Angle. The angle of incidence at 
 which a ray of light falling upon the 
 surface of a body ceases to be reflected 
 and is wholly absorbed or internally re- 
 flected and refracted. 
 
 Critical Current. The current strength 
 at which a certain critical result is 
 reached. 
 
 Critical-Current of Dynamo. That 
 value of the current of a dynamo at which 
 
Cri.] 
 
 731 
 
 [Cro. 
 
 its characteristic curve begins to depart 
 from a nearly straight line. 
 
 Critical-Current of Magnetization. 
 The current strength at which a small 
 increase in the magnetizing current pro- 
 duces a great increase in the magnetiza- 
 tion of an iron core. 
 
 Critical-Distance of Lateral Discharge 
 through an Alternative Path. The 
 distance at whicli a discharge will take 
 place through an air space of given di- 
 mensions, in preference to passing through 
 a metallic circuit of comparatively small 
 ohmic resistance. 
 
 Critical Pressure of a Gas or Vapor. 
 (1) The lowest pressure at which a sub- 
 stance in the liquid state cannot be par- 
 tially vaporized by increase of temper- 
 ature, but changes wholly into a gas. (2) 
 The lowest pressure at which a gaseous 
 substance when cooled is condensed to a 
 liquid in the presence of its vapor. (3) 
 The pressure above which no amount of 
 chilling will liquefy a gaseous substance. 
 
 Critical-Speed of Compound- Wound 
 Dynamo. The speed at which both the 
 series and shunt coils of a dynamo give 
 the same difference of potential when the 
 full load is on the machine, as the shunt 
 coil would have if used alone on open- 
 circuit. (2) The speed at which a 
 dynamo commences to build up its ex- 
 citation. 
 
 Critical Temperature of a Gas or 
 Vapor. (1) The temperature of a vapor 
 at a given pressure above which no pres- 
 sure, however great, can convert the 
 vapor into liquid. (2) The temperature 
 above which a vapor is essentially a per- 
 manent gas. 
 
 Critical Temperature of a Substance. 
 
 (1) The temperature above which no 
 pressure applied to the substance in the 
 gaseous form will effect liquefaction. 
 
 (2) The temperature below which a gase- 
 ous substance is a vapor, and as such cap- 
 able of liquefaction by pressure. 
 
 Critical Volume of a Gas or Vapor. 
 The volume of a substance at the critical 
 temperature and pressure. 
 
 Crookes' Dark-Space. A dark space 
 surrounding the negative electrode in a 
 rarified space through which electric dis- 
 charges are passing. 
 
 Crookes' Effect. The effect produced in 
 high-vacuum tubes due to the charac- 
 teristic motions possessed by heated or 
 electrified molecules when in the ultra- 
 gaseous or radiant state. 
 
 Crookes' Electric Radiometer. A ra- 
 diometer in which the repulsions of the 
 
 molecules of the residual atmosphere take 
 place from electrified instead of from 
 heated surfaces. 
 
 Crookes' Layer. The dark space or layer 
 enveloping the cathode of an excited 
 Crookes' tube. 
 
 Crookes' Radiometer. An apparatus 
 for demonstrating the action of radiant 
 matter in producing motion, from the 
 effects of the reaction of a stream of 
 molecules thrown off from a number of 
 easily moved, unequally heated surfaces. 
 
 Crookes' Tubes. (1) Glass tubes contain- 
 ing high vacua, provided with platinum 
 leading-in wires terminating in suitably 
 shaped metallic surfaces, employed in 
 demonstrating the peculiarities of the 
 radiant or ultragaseous condition of mat- 
 ter. (2) A name frequently given to 
 X-ray tubes. 
 
 Cross. (1) A connection or contact between 
 two telegraph circuits. (2) A contact be- 
 tween two conductors or circuits which 
 should be insulated from each other. 
 
 Cross- Ampere Turns. (1) Ampere turns 
 on a dynamo armature possessing u cross- 
 magnetizing tendency to distort the mag- 
 netic field. (2) Ampere turns whicli tend 
 to produce a cross magnetization, at right- 
 angles to that produced by the field- 
 magnets. 
 
 Cross Arm. (1) A horizontal beam at- 
 tached to a pole for the support of the 
 insulators of telegraph, electric light, or 
 other electric wires. (2) A telegraphic 
 arm. 
 
 Cross-Arm Bolts. Bolts employed for 
 attaching the cross-arms to a pole. 
 
 Cross-Arm Brace. Galvanized iron 
 braces whose ends are respectively con- 
 nected to the pole and the cross-arm for 
 the purpose of stiffening them. 
 
 Cross Bonding. In an electric railway 
 the bonding between the ground feeder 
 and the track for the purpose of ensuring 
 a good conducting return circuit. 
 
 Cross-Connected Dynamo. A dynamo 
 the ends of whose armature coils are con- 
 nected to corresponding segments all 
 around the commutator. 
 
 Cross-Connecting Board. In a system 
 of telegraphic or telephonic communica- 
 tion, a board to which the line terminals 
 are run, before entering the switchboard, 
 so as readily to place any line in connec- 
 tion with any desired section of the switch- 
 board. 
 
 Cross-Connecting Conductors. (1) The 
 conductors on a cross-connecting board 
 which serve to connect the sections of a 
 
Croo 
 
 732 
 
 LCry. 
 
 switch-board with the wires leading to a 
 cable. (2) The conductors which connect 
 corresponding commutator segments in a 
 cross-connected armature. 
 
 Cross-Connecting Telephone Switch- 
 board. A telephone distributing board. 
 
 Cross-Connecting Trough. A trough 
 dividing a telephone test board from a 
 distributing board, formed for holding the 
 joints in the cross-connections between 
 them. 
 
 Cross-Connection of Armature Wind- 
 ings. Armature windings in which the 
 wires are interconnected at the corre- 
 sponding segments of the commutator. 
 
 Cross-Connection of Commutator. 
 The interconnection of the armature coils 
 to corresponding commutator segments. 
 
 Cross Current. Current passing between 
 the armatures of alternating current 
 generators, or motors, operated in parallel, 
 and due to differences in the phase or 
 magnitude of the E. M. Fs. in the ma- 
 chines. 
 
 Cross Fire. (1) A term employed in tel- 
 ephony or telegraphy for an escape or leak- 
 age of current from one line to another, 
 due to defective insulation. (2) Cross talk. 
 
 Cross, Electric. (1) A connection, gen- 
 erally metallic, accidentally established 
 between two conducting lines. (2) A de- 
 fect in a telegraph, telephone, or other 
 circuit, caused by two wires coming into 
 contact by crossing each other. 
 
 Cross Induction. (1) An induction pro- 
 duced by the armature current whose 
 magnetization is at right-angles to that 
 produced by the field. (2) Cross magneti- 
 zation. 
 
 Cross-Induction of Dynamo Arma- 
 ture. Cross magnetization produced by 
 a dynamo armature. 
 
 Cross Magnetization. A magnetization 
 set up by the currents circulating in the 
 armature turns, which is at right-angles 
 to the magnetization set up by the field 
 flux. 
 
 Cross-Over Block. A device to permit 
 the safe crossing of one wire over another 
 in moulding or cleat wiring. 
 
 Cross System. A system of running over- 
 head wires for the purpose of preventing 
 mutual inductive disturbances, which con- 
 sists in crossing or transposing the position 
 of wires on the pole arms at suitable in- 
 tervals, as distinguished from the twist 
 system. 
 
 Cross-Talk. (1) Cross-fire conversation 
 over one telephone circuit which is heard 
 in neighboring telephone circuit. (2) In- 
 
 terference between neighboring tele- 
 phone circuits. 
 
 Cross- Wire-Suspension for Arc Lamp. 
 
 Suspension of an arc-lamp by means of 
 a pulley and cord, attached to a block and 
 tackle suspended from a suitably sup- 
 ported cross wire. 
 
 Crossing Cleat. A cleat so arranged as 
 to permit the crossing of one pair of wires 
 under or over another pair without con- 
 tact with each other. 
 
 Crossing Prog. A frog sometimes em- 
 ployed in place of a trolley cross-over. 
 
 Crossing Wires. (1) A device employed 
 in telegraphic circuits whereby a faulty 
 conductor is cut out of the line circuit, by 
 crossing it over to a neighboring less- 
 used line. (2) In telegraphy, interchang- 
 ing sections of wire between two way 
 stations, so as to remove a fault from a 
 circuit or to rearrange a circuit passing 
 through the stations. 
 
 Crow-Foot Zinc. A crpw-foot-shaped 
 zinc employed in the gravity voltaic cell. 
 
 Crown Telephone Receiver. A tele- 
 phone receiver in which a number of 
 permanent steel magnets are arranged in 
 the form of a crown, all the poles of the 
 same name centring at the soft-iron pole- 
 piece carrying the coil, and the opposite 
 coils being joined to the rim of the dia- 
 phragm. 
 
 Crucible, Electric. (1) A crucible suit- 
 able for electro-metallurgical operations. 
 (2) A crucible in which the heat of a vol- 
 taic arc, or of electric incandescence, is 
 employed, to perform difficult fusions, to 
 effect the reduction of metals from their 
 ores, or to form alloys. 
 
 Crystal. A solid body bounded by sym- 
 metrically disposed plane faces. 
 
 Crystalline Electro-Metallurgical De- 
 posit. A non-adherent, non-coherent 
 film of electrolytically deposited metal. 
 
 Crystallization. Solidification from solu- 
 tion or fusion in definite forms. 
 
 Crystallization by Electrolytical De- 
 composition. Crystalline deposition of 
 various metals by the passage, under cer- 
 tain conditions, of an electric current 
 through solutions of their salts. 
 
 Crystallize. To separate from a liquid or 
 vapor in the form of a crystalline solid. 
 
 Crystalloid. Those portions of a mixed 
 substance subjected to dialysis, that are 
 capable of crystallization. 
 
 Cryptoscope. (1) An apparatus consist- 
 ing of a fluorescent screen placed at one 
 end of a light-tight pasteboard. tub, and 
 
Cry.] 733 
 
 viewed at the other end through an eye- 
 piece. (2) A fluoroscope. 
 
 Cryptoscopic Screen. (1) The screen 
 employed in cryptoscopy. (2) A fluores- 
 cent screen. 
 
 Cryptoscopy. The art of examining the 
 body by means of a cryptoscope. 
 
 Cube Knot. A unit of volume sometimes 
 employed in calculations of insulation 
 resistance of submarine cables. 
 
 Cubic Energy. A term sometimes em- 
 ployed for voluminal energy. 
 
 Cup Brush. A brush suitably shaped for 
 polishing the interior surface of a cup or 
 other similar surface of an object that is 
 to be electroplated. 
 
 Cupric Electrolysis. In electro-thera- 
 peutic treatment, electrolysis performed 
 with copper electrodes whereby a salt of 
 copper is carried into the tissues under 
 the anode by cataphoric action. 
 
 Curb Key. A telegraphic key employed 
 in curb signalling. 
 
 Curb Sender. An automatic transmitter 
 employed in submarine telegraphy, which 
 is operated by a punched paper strip and 
 which sends curbed signals into the cable. 
 
 Curb Signalling. In cable telegraphy, a 
 system for reducing the effects of retarda- 
 tion and increasing the speed of signal- 
 ling, by following each signalling current 
 with a definite sequence of reversed cur- 
 rents or earthings. 
 
 Curbed Signals. Signals sent by means 
 of a curb key. 
 
 Curbing. Employing curb signalling. 
 
 Curl. (1) The vector part of the nabla of a 
 vector point-function. (2) The line inte- 
 gral of a vector once around any closed 
 loop, and equal to the surface integral of 
 a related vector passing through the loop. 
 (3)The rotation or spin of a vector point- 
 function. (4) A vector which indicates by 
 its direction the plane, and by its length 
 the magnitude, of the maximum vector 
 rate-of-change of a vector point-function 
 in the neighborhood of a given point. 
 
 Current Accumulator. Any apparatus 
 in which the strength of an electric cur- 
 rent is increased by the motion past it of 
 a conductor, the currents produced in 
 which tend to strengthen and increase 
 the current which causes the induction. 
 
 Current Balance. A general name given 
 to a variety of ampere balance which 
 gives readings in various decimals or mul- 
 tiples of amperes, and which determines 
 the strength of current passing, through 
 its action on a movable ring or coil placed 
 between two fixed rings or coils. 
 
 [Cur. 
 
 Current Calorimeter. An electric ca- 
 lorimeter. 
 
 Current Commuter. (1) Any device that 
 causes alternating currents to flow in one 
 and the same direction. (2) A commu- 
 tator. 
 
 Current-Conveying Helix. An active 
 helix. 
 
 Current Density. (1) The current 
 strength which passes in any part of a cir- 
 cuit, divided by the area of cross-section 
 of that part of the circuit. (2) The ratio 
 of the current strength through any 
 surface of section of active conductor to 
 the area of that surface, assumed perpen- 
 dicular to the current. 
 
 Current Distribution. The spreading or 
 ramification of electric currents through 
 a conducting mass or network. 
 
 Current Direction-Indicator. An in- 
 strument for insertion in an arc or other 
 circuit to indicate whether the proper 
 direction of current is maintained. 
 
 Current Diverter for Electric Bail- 
 ways. A term sometimes given to the 
 rheostat employed in starting and regulat- 
 ing a street-car motor. 
 
 Current Efficiency of Storage Battery. 
 
 The ratio between the total useful elec- 
 tric quantity delivered by a charged stor- 
 age battery to the working circuit, to the 
 total electric quantity employed in charg- 
 ing the battery. 
 
 Current, Electric. (1) The quantity of 
 electricity per-second which passes 
 through any conductor or circuit, when 
 the flow is uniform. (2) The rate at which 
 a quantity of electricity flows or passes 
 through a circuit. (8) The ratio, ex- 
 pressed in terms of electric quantity per- 
 second, existing between the electro- 
 motive force causing a current and the 
 resistance which opposes it. 
 
 Current Equalizer for Storage Bat- 
 tery. A device for controlling the 
 strength of the charging or discharging 
 circuit of a storage battery. 
 
 Current Filaments. A term sometimes 
 employed in place of current streamlets. 
 
 Current Governor. (1) A current regu- 
 lator. (2) Any device, whether auto- 
 matic or non-automatic, for maintaining 
 constant the current strength in any 
 circuit. 
 
 Current Induction. A term sometimes 
 used for voltaic induction. 
 
 Current Meter. (1) Any form of current 
 galvanometer. (2) An indicating amme- 
 ter or recording ampere-hour meter, 
 
Cur.] 
 
 734 
 
 [Cut, 
 
 Current Recording-Meter. A record- 
 ing ammeter. 
 
 Current Retarder. A term sometimes 
 employed for rheostat. 
 
 Current Reverser. (1) A switch or other 
 apparatus designed to reverse the direc- 
 tion of a current. (2) A current changer. 
 
 Current Rush.. The impulsive rush of 
 current that occurs when a transformer 
 is first switched on, or connected with, an 
 alternating-current circuit. 
 
 Current Sheet. The area of active con- 
 ducting surface carrying a current con- 
 sidered as though the current existed as 
 a material sheet. 
 
 Current Spiral. A conducting helix or 
 spiral provided for the passage of a cur- 
 rent. 
 
 Current Streamlets. A conception of a 
 series of parallel current streams or cur- 
 rent filaments flowing through a solid con- 
 ductor. 
 
 Current Strength.-^!) In a direct-cur- 
 rent cii'cuit the quotient of the total elec- 
 tromotive force divided by the total re- 
 sistance. (2) The time-rate-of-flow in a 
 circuit expressed in amperes, or coulombs 
 per second. (3) In an alternating current 
 the quotient of the total electromotive 
 force divided by the impedance. 
 
 Current System of Induction Teleg- 
 raphy. A system of induction teleg- 
 raphy on railroads, depending on current 
 induction between a fixed circuit along 
 i the roadway, and a parallel circuit on the 
 moving train. 
 
 Current Teaser, Electric. A coil of 
 thin wire placed on the field magnets of 
 a dynamo-electric machine in addition to 
 the series coils wound thereon, and con- 
 nected as a shunt across the main cir- 
 cuit. 
 
 Current Transformation. (1) The act 
 of changing the strength of a current by 
 changes effected in its electromotive force. 
 (2) The act of changing a direct into an 
 alternating current, or the reverse, or a 
 Uniphase-alternating current into a mul- 
 tiphase-alternating current. 
 
 Current Transformer. A device for 
 changing in one circuit the strength of 
 current which flows in another. 
 
 Current Turns. (1) The product of the 
 number of turns in a coil by the current 
 flowing through them. (2) A word some- 
 times used for ampere-turns. 
 
 Current Wave. (1) The progressive elec- 
 tro-magnetic disturbance in the ether sur- 
 rounding a conducting wire forming part 
 of a circuit. (2) The progressive disturb- 
 
 ance of electric flow traversing a con- 
 ducting circuit, under the influence of 
 a variation in its impressed electromotive 
 force. 
 
 Current Weigher. (1) A current bal- 
 ance. (2) An ammeter in which the 
 electro-magnetic force of the current is 
 compared with the earth's gravitational 
 force on a mass. 
 
 Currents of Motion. A term sometimes 
 employed in electro-therapeutics for the 
 electric currents that are asserted to 
 traverse healthy muscle or nerve tissue, 
 during the sudden contraction or relaxa- 
 tion of such muscle and nerve. 
 
 Currents of Rest. A term sometimes 
 employed in electro-therapeutics for the 
 electric currents that are asserted to trav- 
 erse healthy muscle or nerve tissue while 
 the muscles are passive. 
 
 Curve Guy-Poles. Anchor poles or pull- 
 offs, employed in an overhead-trolley 
 system, placed at a curve or turn-out, to 
 which are attached the wire guys em- 
 ployed to preserve the proper tension for 
 the conductor at these points. 
 
 Curve of Sines. (1) A curve representing 
 at continuous successive positions the 
 successive values of the sines of a pro- 
 gressively varying angle. (2) A sinusoid. 
 (3) When drawn to rectangular co-ordi- 
 nates, a curve successively rising above 
 and falling below the axis of abscissas cor- 
 responding to the sines of angles measured 
 along said axis. 
 
 Curve of Cross-Over System. In a sys- 
 tem of transposition for overhead wires, 
 in order to avoid the effects of induction, 
 the short bend of wire which effects the 
 transposition at a pole cross-arm. 
 
 Cushioning Chamber. In a dead-beat 
 mirror galvanometer, a chamber before 
 or behind a suspended mirror, for the 
 
 Eurpose of dampening the motions of the 
 itter. 
 
 Cut-In. To introduce an electro-receptive 
 device into the circuit of a source by 
 completing or closing the circuit through 
 it. 
 
 Cut-In. (1) A term sometimes employed 
 for filament cut-out. (2) An automatic 
 guard cut-out. 
 
 Cut-Off. Any device for cutting a battery 
 or other electric source from a circuit, or 
 from part of a circuit. 
 
 Cut-Out. To remove an electro-receptive 
 device or loop from the circuit of an elec- 
 tric source. 
 
 Cut-Out. (1) A device for removing an 
 electro-receptive device or loop from the 
 
Cut.] 
 
 735 
 
 [D. P, 
 
 circuit of an electric source. (2) A safety 
 fuse.. 
 
 Cut-Out Board. A board supporting a 
 number of fuse cut-outs. 
 
 Cut-Out Block. A block containing a 
 fuse wire or safety catch. 
 
 Cut-Out Box. A box containing a cut- 
 out. 
 
 Cut-Out Cabinet. Any enclosed space 
 provided in a building for the reception 
 of cut-outs or fuses. 
 
 Cut-Out Switch. A short-circuiting 
 switch by means of which an arc-light 
 is cut out from its feeding circuit. 
 
 Cutting and Holding Grapnel. In 
 submarine telegraphy, a grapnel which, 
 after engaging a cable on the sea bottom, 
 automatically grips the cable, and cuts it 
 beyond the grip. 
 
 Cutting Lines of Magnetic Force. 
 Passing a conductor through lines of 
 magnetic force or flux, or passing mag- 
 netic lines of force or flux through a con- 
 ductor, so as to cut or intersect such lines 
 or such flux. 
 
 Cycle. (1) A succession of events which 
 periodically recur, reckoning from any 
 stage of the disturbance to the moment 
 at which that stage next occurs. (2) A 
 complete recurrence of any periodic 
 change. 
 
 Cycle of Alternations. The cycle of 
 a periodically-alternating electromotive 
 force, current or flux. 
 
 Cycle of Magnetization. A single com- 
 plete passage of any magnetic substance 
 through the successive stages of a period- 
 ically-recurring magnetic change. 
 
 Cyclic. Of or pertaining to a cycle. 
 
 Cyclic Magnetization. Magnetization 
 produced in a magnetic substance when 
 subjected to periodic cyclic changes in 
 the magnetizing force. 
 
 Cyclic Magnetic Variations. Secular 
 magnetic variations occurring during 
 great cycles of time. 
 
 Cyclic Motion. Any motion which re- 
 occurs in a cycle. 
 
 Cyclic Stability. (1) In an alternating- 
 current circuit the condition of uniform 
 periodic motion in alternating quantities, 
 such as pressure and current, attained 
 after a definite number of cycles from the 
 starting of the motion ; as distinguished 
 from the variable state of motion when 
 the circuit is first closed. (2) The per- 
 manent state in an alternating-current 
 circuit. 
 
 Cyclometer. An instrument for record- 
 ing the number of turns completed by 
 a wheel, shaft, drum, or other rotating 
 device, or for indicating the distance 
 traversed by its periphery. 
 
 Cyclosis. The existence of independent 
 cycles in a diagram. 
 
 Cyclotrope. A word proposed for trans- 
 former or converter. (Not in use.) 
 
 Cylindrical Armature. A term some- 
 times applied to a drum armature. 
 
 Cylindrical Carbon Electrodes. Car- 
 bon cylinders employed for the electrodes 
 of arc lamps or for battery plates . 
 
 Cylindrical Core. (1) A cylindrical- 
 shaped mass of iron employed for the 
 core of a solenoid or helix. (2) A cylin- 
 drical-shaped mass of soft carbon em- 
 ployed in cored electrodes. 
 
 Cylindrical Electro-Magnet. An elec- 
 tro-magnet whose core consists of a 
 hollow cylinder provided with a slot 
 extending parallel to its axis. 
 
 Cylindrical Magnet. A cylindrically 
 shaped magnet. 
 
 Cylindrical Ring-Armature. A ring 
 armature whose core has the shape of 
 a long cylinder. 
 
 Cylindrical Vibrator. A weight in the 
 form of a cylinder supported by a suspen- 
 sion for the purpose of measuring its 
 torsional rigidity. 
 
 Cymogene. An extremely volatile liquid 
 hydrocarbon given off from crude coal-oil 
 during the early stages of its distillation. 
 
 Cystoscopy, Electric. The examination 
 of the human bladder by electric illu- 
 mination. 
 
 D 
 
 d. A symbol for diameter. 
 
 D. B. Switch. A contraction for double- 
 break switch. 
 
 D. C. A contraction for direct current. 
 D. E. M. I 1 . A contraction for direct- 
 electromotive force. 
 "D." Operator. A term employed in 
 
 mathematics for the operator which ef- 
 fects the total differentiation of a func- 
 tion with respect to time. 
 
 D. P. Cut-Out. A contraction for double- 
 pole cut-out. 
 
 D. P. Switch. A contraction for double- 
 pole switch. 
 
D.Q.] 
 
 [Dea. 
 
 D. Q. In submarine telegraphy, a signal 
 serving to separate the address from the 
 text of the message. 
 
 Daily Variation of Magnetic Needle. 
 The diurnal variation of the magnetic 
 needle. 
 
 Damped Galvanometer. A galvano- 
 meter whose movable part i. e.. whose 
 needle or coil when moved, comes to rest 
 as quickly as possible. 
 
 Damped Magnetic Needle. A magnetic 
 needle so placed as to come quickly to 
 rest after it has been set in motion. 
 
 Damped Vibrations. (1) Vibrations that 
 occur under circumstances in which the 
 vibratory or swinging motions can be at 
 once brought to rest, instead of repeatedly 
 swinging to-and-fro, on the removal of the 
 force causing the vibration. (2) Vibra- 
 tions of successively diminishing ampli- 
 tude. 
 
 Dampening Factor. The property of an 
 oscillatory alternating-current circuit of 
 diminishing the amplitude of its oscilla- 
 tions owing to the influence of electric 
 resistance or of radiation. 
 
 Damper. (1) A metallic cylinder so ar- 
 ranged as to partially or completely sur- 
 round the iron core of an induction coil 
 for the purpose of varying the intensity 
 of the currents produced in the secondary. 
 (2) A dash-pot, or similar apparatus, pro- 
 vided for preventing the too sudden 
 movements of a lever or other part of 
 a moving device. (3) Any device em- 
 ployed for damping a magnetic needle. 
 
 Damping. (1) The act of stopping a sudden 
 vibratory motion without waiting for it 
 to cease after repeated swingings to-and- 
 fro. (2) The act of causing a periodically 
 moving body to lose its energy of motion 
 by the application of retarding forces. 
 
 Damping Coil for Galvanometer. 
 (1) An auxiliary coil employed with a gal- 
 vanometer for receiving transient electric 
 currents from a key under the control of 
 an observer, for the purpose of checking 
 the motion of the needle. (2) A short-cir- 
 cuited coil, on or near a movable electro- 
 magnetic system, for the purpose of 
 damping its oscillations by the action of 
 electric currents induced therein. 
 
 Damping, Electric. A term sometimes 
 employed for the decrease in the intensity 
 of the electric oscillations produced in a 
 resonant circuit by electric resistance, 
 under circumstances where some of the 
 higher overtones are set up in the circuit. 
 
 Damping Magnet. Any magnet em- 
 ployed for the purpose of checking the 
 motions of a moving body or magnet. 
 
 Damping Suspension. A suspension 
 which is rendered dead-beat, or aperiodic, 
 by the application of any retarding force 
 or damping mechanism. 
 
 Damping Tube. (1) A tube fitted with a 
 glass cap and placed in an instrument to 
 diminish the cavity in which a movable 
 system swings, and thus damp its motion. 
 (2) A conducting tube attached to a 
 movable system and placed in the vicin- 
 ity of fixed permanent magnets, in order 
 to damp the vibrations of the system. 
 
 Damping Vessel. A dash-pot. 
 
 Dani ell's Voltaic Cell. A zinc-copper 
 couple whose elements are immersed re- 
 spectively in electrolytes of dilute sul- 
 phuric acid and a saturated solution of 
 copper sulphate. 
 
 Dark Discharge. A term applied by 
 Faraday to that portion of the convective 
 discharge which occurs, under certain cir- 
 cumstances, in the rarefied gas of an 
 exhausted chamber between the positive 
 and negative electrodes. 
 
 Dark-Light Frequencies. Ether vibra- 
 tions of the nature of light whose 
 frequencies are too low to produce 
 physiologically effective light. 
 
 Dark-Segment of Aurora. A dark or 
 non-illumined portion of an aurora glory, 
 or crown of auroral light. 
 
 Dash-Pot. A mechanical device for pre- 
 venting a too sudden motion in the 
 movable part of any apparatus. 
 
 Day Load. A load on an apparatus, 
 machine, or central station, occurring 
 during the daytime as distinguished from 
 a night load. 
 
 Day of Magnetic Disturbance. A day 
 during which the mean departure of the 
 reading of a declinometer at any place, 
 from the normal monthly value at that 
 place, is at least one and one-half times 
 the average. 
 
 Daylight Color-Values. Such values of 
 luminous frequencies as correspond to 
 those present in ordinary sunlight or day- 
 light. 
 
 Dead - Beat. (1) Heavily damped. (2) 
 Aperiodic. (3) Such a motion of a gal- 
 vanometer needle, or other suspension 
 system, in which the needle moves sharply 
 from point to point and comes quickly to 
 rest. 
 
 Dead-Beat Discharge. A non-oscilla- 
 tory discharge. 
 
 Dead-Beat Galvanometer. (1) An aperi- 
 odic galvanometer, or one whose needle 
 comes quickly to rest instead of repeat- 
 
Dea.] 
 
 737 
 
 [Dee. 
 
 edly swinging to-and-fro. (2) A heavily 
 damped galvanometer. 
 Dead Beatness. Possessing the property 
 of aperiodicity. 
 
 Dead Dipping. Dipping in acid liquids 
 for the purpose of obtaining a dead or 
 unpolished surface on an electro-metal- 
 lurgical coating or deposit. 
 
 Dead Earth. (1) A fault in a telegraphic 
 or other line, in which the line is thor- 
 oughly grounded or connected with earth. 
 (2) A total earth. (3) An earth of inap- 
 preciable or insignificant resistance. 
 
 Dead-Ended Conductor or Wire. A 
 conductor or wire whose end is deliber- 
 ately left open or insulated, as, for ex- 
 ample, by being wound around an 
 insulator. 
 
 Dead Ending. Leaving a conductor 
 dead-ended. 
 
 Dead Ground or Grounding. Such a 
 grounding as will ensure a ground of 
 negligible resistance. 
 
 Dead Man. A support for raising a pole 
 and supporting it in place while securing 
 it in the ground. 
 
 Dead Points of Motor Armature. Any 
 positions of a motor armature when at 
 rest, in which the driving current cannot 
 start it. 
 
 Dead Resistance for Testing Bank. 
 
 (1) A resistance for a testing bank devoid 
 of inductance. (2) An inductionless re- 
 sistance. 
 
 Dead Wires. (1) Any disused wires or 
 abandoned wires, generally aerial. (2) A 
 term applied to that portion of the wire on a 
 dynamo which produces no electromotive 
 force on its movements through the field 
 flux. (3) That part of the wire on a motor 
 which produces no useful effect on the 
 passage through it of a driving current. 
 
 Dead Wires of Dynamo Armature. 
 
 The wires on the armature of a dynamo 
 or motor which produce no useful elec- 
 tromotive force or resulting current on 
 the movement of the armature through 
 the field of the machine. 
 
 Dead Wires on Motor Armature. The 
 wires on the armature of a motor which 
 produce no useful torque on the passage 
 through them of an electric current. 
 
 Death, Electric. Death resulting from 
 the passage of an electric discharge or cur- 
 rent through the human body. 
 
 Decalescence. An absorption of sensible 
 heat that occurs at a certain time during 
 the heating of a bar of steel. 
 47 
 
 Decay of Waves. The diminution in the 
 amplitude of waves due to obstruction of 
 any kind. 
 
 Deci. A prefix for the one-tenth part. 
 
 Deci-Ampere. One-tenth of an ampere. 
 
 Deci- Ampere Balance. A balance form 
 of ammeter whose scale is graduated to 
 give direct readings in deci-amperes. 
 
 Deci-Lux. The one-tenth of a lux. 
 
 Deci-Polar Dynamo. A dynamo whose 
 field is produced by ten magnet poles. 
 
 Decimal Candle. A photometric stand. 
 
 ard equal to the twentieth part of the 
 
 Violle platinum standard. 
 Deck Cable-Lead. Guide pulleys or 
 
 leads, placed at suitable intervals on the 
 
 deck of a cable ship, extending from a 
 
 tank to the bow or stern sheaves, to aid in 
 
 laying a submarine cable. 
 Deck-Planer, Electric. An electrically 
 
 driven rotary cutter or planer, suitable 
 
 for planing the deck of a ship. 
 
 Deflection of Magnet. The variation of 
 a magnetic needle from the true geograph- 
 ical North. 
 
 Deflection Compass. A declinometer. 
 
 Declinometer. A magnetic needle suita- 
 bly arranged for the measurement of the 
 magnetic declination or variation of any 
 place. 
 
 Decohere. To restore or regain the nat- 
 ural condition of a coherer. 
 
 Decomposition. The separation of a 
 molecule into its constituent ions or radi- 
 cals, or into its ultimate atoms. 
 
 Decomposition, Ulectric. Chemical de- 
 composition effected by means of an elec- 
 tric discharge or current. 
 
 Decomposition, Electrolytic. The sep- 
 aration of a molecule into its consti- 
 tuent ions or radicals by the action of an 
 electric current. 
 
 Decorative Series Lamps. Series-con- 
 nected incandescent lamps employed to 
 obtain decorative effects. 
 
 De-Energize. To deprive an electro- 
 receptive device of its operating current. 
 
 De-Energizing. Depriving an electro- 
 receptive device of its operating current. 
 
 Deep Sea-Cable. That portion of a sub- 
 marine cable which is laid in the deep 
 water, at a distance from the coast or 
 shore. 
 
 Deep - Seated Eddy - Currents. The 
 
 eddy currents that are set up in the mass 
 of a conductor subjected to electro- 
 dynamic induction, as distinguished 
 
Dee.] 
 
 738 
 
 [Dem. 
 
 from the superficially -seated eddy -cur- 
 rents. 
 
 Deep- Water Submarine-Cable. A deep 
 sea cable. 
 
 Defective-Loop Repeater. <1) A device 
 for employing the good wire of a defective 
 loop to an office, to receive and transmit 
 alternately, on a duplex, or on the com- 
 mon side of a quadruplex set. (2) A re- 
 peater connecting a branch office with a 
 duplex or quadruplex set at a main 
 office, and arranged to operate on a single 
 wire of a pair or loop to said branch office 
 when the other wire becomes defective. 
 
 Deflagration. A violent but not explo- 
 sive combustion of a substance. 
 
 Deflagration, Electric. The fusion and 
 volatilization of metallic substances by 
 the passage through them of an electric 
 current. 
 
 Deilagrator. The name given to a partic- 
 ular voltaic battery of small internal 
 resistance, employed, in the early history 
 of the voltaic battery, for the electric de- 
 flagration of metallic substances. 
 
 Deflecting Magnet. (1) The permanent 
 magnet of a magnetometer, employed for 
 deflecting a small magnetic needle sus- 
 pended at a definite distance, in order to 
 compare its influence with that of the 
 earth's horizontal magnetic force. (2) The 
 compensating magnet of a galvanometer. 
 
 Deflection Method. A method employed 
 in electrical measurements in which, as 
 distinguished from the zero method, the 
 amount of the deflection produced on any 
 instrument, by a given current or a given 
 charge, is utilized for determining the 
 value of that current or charge. 
 
 Deflection of Cable Dynamometer. 
 (1) The sag, or distance to which a cable 
 dynamometer sheave descends below the 
 horizonal line corresponding to infinite 
 tension. (2) The sag of a dynamometer 
 sheave which increases as the strain on 
 the cable diminishes. 
 
 Deflection of Magnetic Needle. The 
 movement of a needle out of a position of 
 rest, either in the earth's magnetic field, 
 or in the field of another magnet, by the 
 action of the flux of an electric current or 
 of a magnet. 
 
 Deformation. (1) Any displacement of 
 the particles of a solid with reference to 
 one another, produced by the action of a 
 stress. (2) A strain. 
 
 Degeneration of Cell. Such a change 
 in the muscular or cellular structure of a 
 cell that incapacitates it from performing 
 its ordinary functions. 
 
 Degeneration of Energy. A degrada- 
 tion of energy. 
 
 Deka. A prefix signifying ten times. 
 
 Deka- Ampere. Ten amperes. 
 
 Deka- Ampere Balance. A balance-form 
 
 of ammeter measuring tens of amperes 
 
 (0 to 100 amperes. ) 
 
 Deliquescence. The solution of a crys- 
 talline solid arising from its absorption of 
 the vapor of water from the atmosphere. 
 
 Delivered Power. In a system of elec- 
 trical transmission, the power that is 
 delivered at one end of a line as distin- 
 guished from the power sent into the line 
 at its other end. 
 
 Delta Connection. The connection of 
 circuits employed in a delta triphase- 
 systern. 
 
 Delta Current. (1) The current between 
 adjacent wires or terminals of a triphase- 
 system. (2) The ring current. 
 
 Delta Potential of Triphase System. 
 
 (1) The effective difference of potential, 
 or voltmeter pressure, between adjacent 
 wires or terminals of a triphase-sj^stem. 
 
 (2) The ring potential. 
 
 Delta Triphase-System. A triphase 
 system in which the terminal connections 
 resemble the Greek letter delta, or 
 triangle. 
 
 Demagnetizable. Capable of being de- 
 prived of magnetism. 
 
 Demagnetization. The act of depriving 
 a magnet of its magnetism. 
 
 Demagnetization by Successive Re- 
 versals. A process for removing the 
 magnetism from a mass of steel, as in a 
 watch, by subjecting it to many success- 
 ive magneto-motive forces alternating 
 in direction and gradually diminishing to 
 zero. 
 
 Demagnetize. To deprive of magnetism. 
 Demagnetizing. Depriving of magnet- 
 ism. 
 
 Demagnetizing Current. The current 
 which serves to remove the magnetization 
 of some magnetic device. 
 
 Demagnetizing Lines of Flux. Mag- 
 netic flux produced by a magnetized bar 
 in a direction opposite to the magnetizing 
 force, and tending, therefore, to demag- 
 netize the bar. 
 
 Demand Recording-Meter. A meter 
 which registers the maximum demand 
 for electric energy, usually a meter which 
 registers the maximum current strength 
 supplied through it, in addition to the 
 total quantity of electricity delivered. 
 
Dem.] 
 
 739 
 
 [Dia. 
 
 Demarcation Current. A term some- 
 times applied to the electric current ob- 
 tained from an injured muscle. 
 
 Density, Electric. The quantity of free 
 electricity on any unit of area of surface 
 of a charged body. 
 
 Density of Charge. The quantity of 
 electricity per-unit-of-area at any part of 
 a charged surface. 
 
 Density of Current. The quantity of 
 current that passes per-unit-of-area of 
 cross-section in any part of a circuit. 
 
 Density of Electrification. The density 
 of an electrostatic charge. 
 
 Density of -Field. The quantity of mag- 
 netic flux that passes through any field 
 per-unit-of-area of cross-section. 
 
 Dentiphone. An audiphone. 
 
 Dephased. (1) Differing in phase. (2) 
 Caused to differ in phase. 
 
 Depolarization. The act of reducing or 
 removing the polarization of a voltaic 
 cell or battery. 
 
 Depolarize. To deprive of polarization. 
 
 Depolarizer. The material employed in 
 voltaic cells for the purpose of depolar- 
 izing them. 
 
 Depolarizing. Depriving of polarization. 
 
 Depolarizing Fluid or Liquid. An 
 electrolytic fluid or liquid employed in a 
 voltaic cell for the purpose of preventing 
 or lessening polarization. 
 
 Depositing Cell or Vat. Any electro- 
 lytic cell in which an electro-metallur- 
 gical deposit is made. 
 
 Deposition, Electric. The deposit of a 
 substance, generally a metal, by the action 
 of electrolysis. 
 
 Deprez-D' Arson val Galvanometer. A 
 
 form of dead-beat galvanometer. 
 Derivation. (1) A shunt or derived cir- 
 cuit. (2) A leak. 
 
 Derivative or Derived Current. The 
 current that flows through a branch or 
 derived circuit. 
 
 Derived Circuit. (1) A branch or shunt 
 circuit. (2) A derivation. 
 
 Derived-Circuit Arc-Lamp. The name 
 sometimes employed for a differential arc- 
 lamp. 
 
 Derived Units. Various secondary units 
 obtained or derived from the fundamental 
 units of length, mass, and time. 
 
 Desk Loop. (1) In telegraphy, a loop or 
 circuit, running to a desk in a telegraph 
 office, and connecting the apparatus on 
 such desk with main-line apparatus at 
 some other table. (2) A circuit connect- 
 
 ing an operator at one desk with a duplex 
 or quadruplex set of apparatus at another 
 desk for convenience in handling the 
 traffic. 
 
 Desk Push. An electric push attached 
 to a desk for the purpose of ringing a call- 
 bell, or closing some other electric circuit. 
 
 Desk Set. Telephone apparatus arranged 
 for use on a desk. 
 
 Destructive Distillation. The action of 
 heat on an organic substance while out of 
 contact with air, resulting in the decom- 
 position of the substance into simpler and 
 more stable compounds. 
 
 Detector Galvanometer. Any rough 
 form of galvanometer or galvanoscope 
 employed for detecting the presence of 
 electric currents. 
 
 Detector Peg. A peg used in connection 
 with a detector galvanometer. 
 
 Detonating Fuse. (1) A fuse that is ex- 
 ploded by a percussion or blow. (2) A 
 percussion fuse. 
 
 Detorsion Bar. A bar placed in a mag- 
 netic declinometer for the purpose of re- 
 moving the torsion on the suspending 
 thread of the magnet. 
 
 Developed Winding. A winding of a 
 dynamo-electric machine developed . or 
 expanded upon a drawing or plane. 
 
 Devil Claws. A device employed in 
 stringing overhead wires. 
 
 Dextrorsal Helix. A name sometimes 
 applied to a dextrorsal solenoid. 
 
 Dextrorsal Solenoid. A solenoid whose 
 winding is right-handed. 
 
 Diacritical Current. Such a strength of 
 a magnetizing current as produces a mag- 
 netization of an iron core equal to one- 
 half saturation. 
 
 Diacritical Number. Such a number of 
 ampere turns at which a given core would 
 receive a magnetization equal to one- 
 half saturation. 
 
 Diacritical Point of Magnetic Satu- 
 ration. A term proposed for such a 
 value of the co-efficient of magnetic satu- 
 ration that its core is magnetized to ex- 
 actly one-half of its possible maximum 
 magnetization. 
 
 Diagometer. An apparatus in which an 
 attempt is made to determine the chemi- 
 cal composition, and consequent purity, of 
 certain substances by their electrical con- 
 ducting powers. 
 
 Dial Bridge or Rheostat. A resistance 
 bridge or rheostat whose contact points 
 are arranged in the shape of a dial. 
 
Dia.] 
 
 740 
 
 [Die. 
 
 Dial Telegraph. A general term embrac- 
 ing the apparatus employed in dial teleg- 
 raphy. 
 
 Dial Telegraphy. A system of teleg- 
 raphy in which the messages are received 
 by the movements of a needle over a dial 
 plate. 
 
 Dialysis. The act of separating a liquid 
 mixture into its crystalloids and colloids 
 by passing the liquid through a mem- 
 brane. 
 
 Dialyzing. Subjecting to the process of 
 dialysis. 
 
 Diamagnetic. The property possessed by 
 substances like bismuth, phosphorus, 
 antimony, zinc and others, of being ap- 
 parently repelled when placed between 
 the poles of powerful magnets. 
 
 Diamagnetic Permeability. The per- 
 meability to magnetic flux possessed by 
 diamagnetic substances. 
 
 Diamagnetic Polarity. A polarity, the 
 reverse of ordinary magnetic polarity, the 
 existence of which was assumed to ex- 
 plain the phenomena of diamagnetism. 
 
 Diamagnetically. In a diamagnetic 
 manner. 
 
 Diamagnetism. A name sometimes given 
 to the magnetism of diamagnetic bodies. 
 
 Diamagnetized. Subjected to the action 
 of so-called diamagnetism. 
 
 Diamagnetometer. A magnetometer 
 designed for the study of diamagnetism. 
 
 Diamagnets. Diamagnetic substances 
 subjected to magnetic induction, and 
 formerly called diamagnets in contra- 
 distinction to ordinary or paramagnets. 
 
 Diameter of Commutation. (1) The 
 diameter of the commutator cylinder of a 
 dynamo at which the brushes are applied. 
 (2) That diameter on the commutator 
 cylinder of an open-circuited armature, 
 which joins the points of contact of the 
 collecting brushes. 
 
 Diaphragm. (1) A sheet of an elastic 
 solid, generally circular in shape, securely 
 fastened at its edges and capable of being 
 set into vibration. (2) The porous wall or 
 septum of an endosmometer. (3) The 
 porous partition of a voltaic cell. (4) A 
 disc of blackened metal provided with 
 a circular aperture and employed for 
 cutting off all the light from a lens except 
 that falling on its central portions. 
 
 Diaphragm Currents. Electric currents 
 produced by forcing a liquid through the 
 capillary pores of a diaphragm. 
 
 Diaphragm of Voltaic Cell. (1) The 
 porous partition or plate of a voltaic cell. 
 (2) Generally, a porous cell. 
 
 Diaphragm Photometer. A photometer 
 which depends on the equality of the 
 brightness obtained on the two halves of a 
 diaphragm or screen, either by varying 
 the distances of the lights from the screen 
 or by varying the inclination of the 
 luminous rays thereon. 
 
 Dice-Box Insulator. A name sometimes 
 applied to a double-cone insulator. 
 
 Dielectric. Any substance which permits 
 electrostatic induction to take place 
 through its mass. 
 
 Dielectric Absorption. The absorption 
 of a charge or current by a dielectric. 
 
 Dielectric Capacity. A term employed 
 in the same sense as specific ijiductive 
 capacity. 
 
 Dielectric Circuit. A circuit formed in 
 whole or in part through a dielectric as 
 opposed to a conducting circuit. 
 
 Dielectric Constant. A term sometimes 
 employed in place of specific inductive 
 capacity. 
 
 Dielectric Current. (1) The rate-of -in- 
 crease of the polarization of a dielectric 
 produced by a change in the polariza- 
 tion through the circuit. (2) A displace- 
 ment current. 
 
 Dielectric Density of a Gas. A term 
 sometimes employed instead of dielectric 
 strength of a gas. 
 
 Dielectric Displacement. (1) Electric 
 displacement taking place through a die- 
 lectric. (2) The electromotive intensity in 
 a dielectric multiplied by 4?r and divided 
 by the dielectric co-efficient. 
 
 Dielectric Elasticity. (1) The reciprocal 
 of the dielectric co-efficient. (2) The 
 measure of the electric force that must be 
 exerted upon a dielectric in order to effect 
 unit displacement. 
 
 Dielectric Energy Current. That com- 
 ponent of an alternating current passing 
 through a condenser which is in phase 
 with the impressed E. M. F. at its termi- 
 nals. 
 
 Dielectric Hysteresis. (1) A variety of 
 molecular friction, analogous to magnetic 
 hysteresis, produced in a dielectric under 
 changes of electrostatic stress. (2) That 
 property of a dielectric by virtue of which 
 energy is consumed in reversals of electri- 
 fication. 
 
 Dielectric Hysteretic Admittance. 
 (1) In an alternating-current circuit the 
 apparent component of admittance due to 
 dielectric hysteresis. (2) In a condenser 
 traversed by an alternating current the 
 admittance, which is the geometrical sum 
 of the hysteretic conductance and the hy 
 
Die.] 
 
 
 741 [Dif. 
 
 steretic susceptance, or whose reciprocal is 
 the vector hysteretic impedance. 
 
 Dielectric Hysteretic Impedance. In 
 an alternating-current circuit, the ap- 
 parent component of impedance due to 
 dielectric hysteresis. 
 
 Dielectric Hysteretic Lag. Lag in an 
 alternating-current circuit due to dielec- 
 tric hysteresis. 
 
 Dielectric Medium. Any medium ca- 
 pable of acting as a dielectric. 
 
 Dielectric Polarization. (1) The polari- 
 zation of a dielectric by means of which 
 electric induction takes place. (2) Dielec- 
 tric displacement. 
 
 Dielectric Resistance. (1) The resist- 
 ance which a dielectric offers to mechan- 
 ical strains produced by electrification. 
 (2) The resistance of a dielectric to dis- 
 placement currents. 
 
 Dielectric Static Hysteresis. Hystere- 
 sis occurring in a dielectric under succes- 
 sive electric reversals, and due to a quasi- 
 electrostatic friction independent of the 
 rate of reversal, as distinguished from 
 dielectric viscous hysteresis which varies 
 with the frequency of cyclic electric re- 
 versals. 
 
 Dielectric Strain. (1) The strained con- 
 dition of the glass or other dielectric of a 
 condenser produced by the charging of 
 the condenser. (2) The deformation of a 
 dielectric under the influence of an elec- 
 tro-magnetic stress. 
 
 Dielectric Strength of Gas. The elec- 
 tromotive intensity a gas is capable of 
 bearing without permitting a disruptive 
 discharge to pass through it, and capable 
 of measurement in volts per centimetre. 
 
 Dielectric Stress.-^(l) The electro-mag- 
 netic force producing a deformation or 
 strain in a dielectric. (2) Electromotive 
 intensity. 
 
 Dietrine. A name given to a variety of 
 insulating material. 
 
 Difference of Potential. That quanti- 
 tative property in space by virtue of 
 which work is done when a mass of any 
 kind is moved from one point to another. 
 
 Difference of Electric Potential. 
 (1) That quantitative property in space 
 whereby work is done when an electric 
 charge is moved therein. (2) The electric 
 work done on a unit charge in an excur- 
 sion between two points. 
 
 Difference of Magnetic Potential. 
 (1) That quantitative property in space 
 whereby work is done when a magnetic 
 pole moves therein. (2) The magnetic 
 
 work done on a unit magnetic pole in an 
 excursion between two points. 
 Difference of Tension. A term some- 
 tunes incorrectly employed for difference 
 of potential. 
 
 Difference of Thermal Pressure. A 
 phrase sometimes employed for the dif- 
 ference of temperature between any two 
 points in a conducting substance that 
 is assumed to cause the flow of heat 
 through that conductor from the higher 
 to the lower temperature. 
 
 Difference Theory of Muscle and 
 Nerve Currents. A theory proposed 
 to explain the cause of the electric cur- 
 rents in living tissues, by an alteration or 
 change in the protoplasm, by injury, by 
 differences of temperature, or by polari- 
 zation. 
 
 Differential Coils. Coils that are differ- 
 entially wound, or that act differentially. 
 
 Differential Compound Motor. (1) 
 A compound motor in which the mag- 
 neto-motive force of the working current 
 is opposed to the magneto-motive force of 
 the shunt excitation, for the purpose of 
 maintaining the speed constant under all 
 loads. (2) A compound-wound contin- 
 uous-current motor. 
 
 Differential Electric Arc-Lamp. A 
 term formerly employed for a derived- 
 circuit arc-lamp, in which the lifting 
 magnet either consists of a core or sole- 
 noid wound with series and shunt coils, 
 or of two separate and opposed cores, one 
 of which contains the series and the other 
 the shunt winding. 
 
 Differential Electric Bell. An electric 
 bell whose magnetizing coils are differ- 
 entially wound. 
 
 Differential Electro-Dynamometer. 
 (1) A double dynamometer with two mov- 
 ing coils rigidly connected and oppositely 
 acted on, so that the movement of the sus- 
 pension system can be reduced to zero by 
 electrical adjustments made while the in- 
 strument is under operation. (2) A dyna- 
 mometer for measuring the difference 
 between two electro-dynamic forces. 
 
 Differential Electro-Magnet. A differ- 
 entially-wound electro-magnet. 
 
 Differential Equation. An equation 
 connecting quantities into which one 01 
 more differential coefficients or differ- 
 entials enter. 
 
 Differential Galyanometer. A gal- 
 vanometer containing two coils, so wound 
 as to tend to deflect its needle in opposite 
 directions. 
 
Dif.] 
 
 742 
 
 [Dil. 
 
 Differential Induction Coil. (1) An in- 
 duction coil employed in duplex and quad- 
 ruplex telegraphy, ' having two differ- 
 entially-wound primary coils, one of 
 which is placed in the main line of the 
 circuit, and the other in the circuit of an 
 artificial line. (2) In telephony, an induc- 
 tion coil which sometimes forms part of 
 the equipment of a multiple switchboard 
 operator. 
 
 Differential Inductometer. A galvano- 
 metric apparatus for measuring the mo- 
 mentary currents produced by the dis- 
 charge of a cable. 
 
 Differential Magnetometer. A mag- 
 netometer having a divided magnetic cir- 
 cuit and a needle differentially acted upon 
 by the branches. 
 
 Differential Method of Duplex Teleg- 
 raphy. A system of duplex telegraphy 
 in which the coils of the receiving and 
 transmitting instruments are differenti- 
 ally wound. 
 
 Differential Method of Quadruplex 
 Telegraphy. A system of quadruplex 
 telegraphy by means of a double-differ- 
 ential duplex system. 
 
 Differential Permeability. The differ- 
 ential coefficient of flux density to mag- 
 netizing force in a substance undergoing 
 magnetization. 
 
 Differential Relay. A telegraphic relay 
 containing two differentially wound coils 
 of wire on its magnet core. 
 
 Differential Speed. In an induction 
 machine, the angular velocity of the field 
 relatively to the rotor. 
 
 Differential Susceptibility. The differ- 
 ential coefficient of the magnetic intensity 
 to the magnetizing force in a substance 
 undergoing magnetization. 
 
 Differential Thermo-Pile. A thermo- 
 pile whose two opposite faces are exposed 
 to the action of two nearly equal sources 
 of heat, in order to determine accurately 
 the difference in the thermal intensities 
 of such sources of heat. 
 
 Differential Voltmeter. A voltmeter 
 consisting of two separate decomposition 
 cells, one placed in a circuit of known 
 resistance, and the other in a circuit 
 whose resistance is to be determined. 
 
 Differential Winding. Such a double 
 winding of magnet coils that the two 
 poles produced thereby are opposed to 
 each other. 
 
 Differential Winding of Field. (1) 
 A field-magnet winding in which two ex- 
 citing currents exert opposing magneto- 
 motive forces. (2) A form of winding 
 
 in which the magnetizing flux of the 
 series coil is opposed by the magnetizing 
 flux of the shunt coils. 
 
 Differentially- Wound Dynamo-Elec- 
 tric Machine. A compound-wound 
 dynamo-electric machine. 
 
 Differentially-Wound Motor. A com- 
 pound-wound motor, in which the current 
 in the shunt coils opposes, in its magnet- 
 izing effects, the current in the series coil, 
 so that the efficient magnetizing effect 
 produce-d is the difference between the 
 magnetizing effects of the two coils. 
 
 Differentially Wound Translator. 
 In telephony, a translator having one 
 primary and two equal secondary coils, 
 employed in duplex working. 
 
 Diffraction Grating. A plate containing 
 a series of parallel linear openings, slits or 
 scratches, separated by opaque or smooth 
 spaces, employed for producing spectra 
 by diffraction or interference. 
 
 Diffusing Globes for Electric Lights. 
 Globes so constructed as to ensure a dif- 
 fusion of the light around which they are 
 placed. 
 
 Diffusion Creep. A term sometimes used 
 for the diffusion of an electric current. 
 
 Diffusion of Electric Current. The 
 flow of an electric current in the portions 
 of a conducting substance that lie outside 
 the parts in the direct line between the 
 points where the terminals of an electric 
 source are applied, so that a difference 
 exists in the density of the current at dif- 
 ferent points of such substance. 
 
 Diffusion of Electric Waves. (1) The 
 scattering of electric waves, or their 
 deviation from a parallel beam. (2) The 
 transmission of electric waves through a 
 medium. 
 
 Diffusion of Electro-Therapeutic Cur- 
 rent. The differences in the density of 
 current in different portions of the human 
 body, lying between electro-therapeutic 
 electrodes. 
 
 Diffusion of Lines of Force. The diffu- 
 sion of magnetic flux. 
 
 Diffusion of Magnetic Flux. The 
 lateral deflection of magnetic flux from 
 the direct path between the poles that 
 produce it. 
 
 Digging Spoon. A spoon-shaped shovel 
 used in digging holes for telegraph poles. 
 
 Dilation, Electric. Electric expansion, 
 or an increase in volume, produced in a 
 body by an electric charge. 
 
 Dilatometer. An instrument resembling 
 a thermometer, employed in measuring 
 the expansion of a liquid by heat. 
 
Dim.] 
 
 743 
 
 [Dip. 
 
 Dimensions of Electro-Magnetic 
 Units. The conventional exponential 
 values of electro-magnetic units in terms 
 of the fundamental units of length, mass, 
 and time. 
 
 Dimensions of Electrostatic Units. 
 The exponential values given convention- 
 ally to the units of the electrostatic 
 system, in terms of the fundamental 
 units of length, mass, and time. 
 
 Dimensions of Magnetic Units. The 
 exponential values given conventionally 
 to the units of the magnetic system, in 
 terms of length, mass, and time. 
 
 Dimensions of Units. The exponential 
 values given conventionally to units in 
 terms of length, mass, and time. 
 
 Diminished Electric Irritability. A 
 decrease in the irritability of nervous or 
 muscular tissue produced by a suitable 
 electric current. 
 
 Dimmer. A clicking coil employed in an 
 alternating-current system of distribution 
 for regulating the current strength pass- 
 ing through incandescent lamps. 
 
 Diode Working. A term employed for 
 the two-way mode of telegraphic working 
 established by the Delany Synchronous 
 Multiplex Telegraphic System. 
 
 Diopter. A unit of the refracting or focal 
 power of a lens. 
 
 Dioptre. An orthography commonly em- 
 ployed for diopter. 
 
 Dioptric. An orthography sometimes 
 employed for diopter. 
 
 Dioptric. Of or pertaining to dioptrics. 
 
 Dioptric Shade. A shade for a luminous 
 source made of refractive material, which 
 prevents the light from passing, in cer- 
 tain directions, by reason of its refractive 
 power. 
 
 Dioptrics. The science which treats of 
 the refraction of light. 
 
 Dioptry . An orthography frequently em- 
 ployed for diopter. 
 
 Dip. The inclination of a magnetic needle. 
 Dip Circle. A dipping needle provided 
 
 with means for accurately measuring the 
 
 angle of dip. 
 
 Dip of Line- Wire or Conductor. The 
 sag, due to its weight, of an aerial con- 
 ductor between any two of its adjacent 
 supports. 
 
 Diphase - Alternating Currents. (1) 
 Two separate alternating electric currents 
 whose phase difference is a quarter of a 
 cycle. (2) Two-phase currents. (3) 
 Quarter-phase currents. 
 
 Diphase- Alternating E. M. F's. (l)Two 
 separate alternating-electromotive forces 
 whose phase difference is a quarter of a 
 cycle. (2) Two-phase E. M. F.'s. (3) Quar- 
 ter-phase E. M. F.'s. 
 
 Diphase Alternator. An alternator that 
 produces diphase E. M. F.'s. 
 
 Diphase Armature. The armature of a 
 diphase alternator, or diphaser. 
 
 Diphase Armature- Winding. Any ar- 
 mature winding capable of furnishing 
 diphase currents. 
 
 Diphase Circuit. A circuit, consisting 
 either of three or four separate wires, em- 
 ployed for the transmission of diphase 
 currents. 
 
 Diphase Field. A diphase magnetic field. 
 Diphase Generator. (1) A generator 
 
 capable of producing diphase E. M. F.'s. 
 
 (2) A diphase alternator. 
 
 Diphase Inter-Connected Circuit. 
 (1) A diphase circuit consisting of two 
 outgoing conductors, one for each phase or 
 side of the system, and a single return- 
 conductor common to both. (2) A di- 
 phase system in which the two diphase cir- 
 cuits are not electrically separated or in- 
 dependent. 
 
 Diphase Magnetic-Field. A magnetic 
 field produced by diphase currents. 
 
 Diphase Motor. A motor suitable for use 
 with diphase electric currents. 
 
 Diphase Rotary-Field. (1) A magnetic 
 field produced by four or more magnet 
 poles whose coils are so wound that their 
 polarity not only alternates with changes 
 in the direction of the current, but acts 
 as though the field rotated. (2) A rotat- 
 ing magnetic field produced by diphase 
 currents. 
 
 Diphase Transformer. A polyphase 
 transformer suitable for use with diphase 
 currents. 
 
 Diphase - Triphase Transformer. A 
 
 transformer for converting diphase into 
 
 triphase currents. 
 Diphaser. A word sometimes used for 
 
 diphase alternator. 
 Diplex Circuit. The circuit, including 
 
 the line wire and apparatus, employed in 
 
 any diplex system. 
 
 Diplex Telegraph. A general term em- 
 bracing the apparatus employed in diplex 
 telegraphy. 
 
 Diplex Telegraphy. Any method by 
 which two telegraphic messages can be 
 simultaneously sent in the same direction 
 over a single wire. 
 
Dip.] 
 
 744 
 
 [Dh\ 
 
 Diplex Telephony. Any method by 
 which two telephone messages can be 
 simultaneously sent in the same direction 
 over the same wire. 
 
 Diplex Transmission. The simulta- 
 neous telegraphic or telephonic transmis- 
 sion of two messages in the same direction 
 over a single wire. 
 
 Dipolar. (1) Possessing two poles. (2) Bi- 
 polar. 
 
 Dipping. (1) An electro-metallurgical 
 process whereby a thin coating or depos- 
 it of metal is obtained on the surface of 
 another metal by dipping it in a solution 
 of a readily decomposable metallic salt. 
 (2) Cleansing surfaces for electro-plating, 
 by immersing them in various acid 
 liquors. 
 
 Dipping Basket. A perforated basket 
 of non-corrosive material, employed in 
 electro-plating, for the reception of 
 articles that are to be cleansed by dip- 
 ping. 
 
 Dipping Hook. A metallic hook em- 
 ployed in electro-plating for holding ar- 
 ticles that are to be cleansed by dipping. 
 
 Dipping Magnetic-Needle. (1) A mag- 
 netic needle suspended so as to be free to 
 move in a vertical plane only, and em- 
 ployed to determine the angle of dip or 
 magnetic inclination. (2) An inclination 
 compass. 
 
 Dipping Needle. A term sometimes used 
 for a dipping magnetic needle. 
 
 Dipping "Wire. The wire employed in 
 electro-metallurgy for suspending small 
 articles that are to be cleansed by dip- 
 ping. 
 
 Dips. Acid liquors employed in dipping. 
 
 Direct-Coupled Dynamo. A dynamo 
 whose armature shaft is directly coupled 
 to the driving shaft. 
 
 Direct Coupling. Coupling the shaft of 
 a dynamo armature directly to the driv- 
 ing or engine shaft. 
 
 Direct-Current. (1) A current whose di- 
 rection is constant, as distinguished from 
 an alternating current. (2) A continuous 
 current. 
 
 Direct-Current Dynamo-Electric Ma- 
 chine.-~Any dynamo-electric machine 
 capable of furnishing direct currents. 
 
 Direct-Current Electric Motor. An 
 electric motor driven by means of direct 
 or continuous currents, as distinguished 
 from a motor driven by alternating cur- 
 rents. 
 
 Direct- Current Rotary Transformer. 
 (1) A term sometimes employed for a ro- 
 
 tating secondary generator of continuous 
 currents. (2) A motor-dynamo or dyna- 
 motor. 
 
 Direct-Current Transformer. (1) A 
 transformer intended to vary the strength 
 of continuous currents. (2) A direct-cur- 
 rent secondary -generator. 
 
 Direct-Driven Dynamo of Generator. 
 A direct-coupled dynamo or generator. 
 
 Direct-Deflection Method of Measur- 
 ing Resistance. A method of measur- 
 ing resistance based on the deflection of 
 a galvanometer in circuit with a resist- 
 ance and a battery. 
 
 Direct-Electromotive Force. (1) An 
 
 electromotive force acting on a circuit in 
 the same direction as another electromo- 
 tive force already existing in that circuit. 
 (2) The electromotive force acting on any 
 circuit in contra-distinction to the coun- 
 ter-electromotive force set up in such cir- 
 cuit. (3) A continuous-electromotive 
 force as distinguished from an alternat- 
 ing-electromotive force. 
 
 Direct Excitation. (1) The excitation of 
 a muscle, resulting from the placing of an 
 electrode directly on the muscle itself. 
 (2) The excitation of a dynamo electric 
 machine by a separate source of direct 
 currents, as distinguished from its excita- 
 tion by commuted currents taken from 
 its own armature. 
 
 Direct-Induced Current. The break in- 
 duced current. 
 
 Direct Inker. An ink-writing Morse re- 
 corder, wound for insertion in a tele- 
 graphic line, as distinguished from one 
 wound for a local circuit. 
 
 Direct Lightning-Discharge. The act- 
 ual lightning discharge, as distinguished 
 from the back or return-stroke or dis- 
 charge. 
 
 Direct-Reading Galvanometer. A gal- 
 vanometer in which the absolute value of 
 the deflection and current strength are in- 
 dicated directly, or without computation. 
 
 Direct Sounder.^-A telegraphic sounder 
 wound for a line circuit and not for use in 
 the local circuit of a relay. 
 
 Direct-Reading Potentiometer. A po- 
 tentiometer which indicates directly on 
 its scale the pressure measured at its ter- 
 minals. 
 
 Direct Working of Telegraphic 
 Sounder. The working of a telegraphic 
 sounder without the use of a telegraphic 
 relay. 
 
 Directed Streaming-Discharge. A 
 Tesla or high-frequency discharge which 
 
Dir.] 
 
 745 
 
 [Di? 
 
 assumes the shape of a highly luminous 
 cone. 
 
 Directing Clock. A controlling or mas- 
 ter clock. 
 
 Directing Magnet. A controlling or com- 
 pensating magnet. 
 
 Direction of Electric Current. A con- 
 vention whereby an electric current is 
 regarded as leaving a source at its positive 
 pole, and re-entering it at its negative 
 pole. 
 
 Direction of Electrostatic Flux. A 
 convention whereby it is assumed that 
 electrostatic flux leaves a positively 
 charged body at its positive pole, and ter- 
 minates on a negatively charged body. 
 
 Direction of Lines of Force. The direc- 
 tion of magnetic or electrostatic flux. 
 
 Direction of Magnetic Flux. A con- 
 vention whereby it is assumed that mag- 
 netic flux issues from a magnet at its 
 north-seeking pole, and returns to it at its 
 south-seeking pole. 
 
 Direction of Negative Rotation. In 
 
 the conventionally adopted system of 
 kinetics, a clock-wise rotation about an 
 axis as viewed from the front side of the 
 clock. 
 
 Direction of Positive Rotation. In the 
 conventionally adopted system of kinet- 
 ics the counter-clockwise direction of 
 rotation about an axis as viewed from 
 the front face of the clock. 
 
 Directive Tendency of Magnetic 
 Needle. The tendency of a magnetic 
 needle to come to rest in the direction of 
 the earth's magnetic flux. 
 
 Disc Armature. (1) The armature of a dy- 
 namo-electric machine whose windings 
 consist of flat coils supported on the sur- 
 face of a disc. (2) An armature having 
 the form of a disc. 
 
 Disc Electrodes. Disc-shaped carbon 
 electrodes formerly employed in long- 
 burning or all-night arc-lamps. 
 
 Discharge. (1) The equalization of the 
 difference of potential between the ter- 
 minals of a condenser or source, on their 
 connection by a conductor. (2) The re- 
 moval of a charge from a conductor by 
 connecting the conductor to the earth or 
 to another conductor. (3) The removal 
 of a charge from an insulated conductor, 
 by means of a stream of electrified air 
 particles. 
 
 Discharge. To equalize differences of 
 potential by connecting them by a con- 
 ductor. 
 
 Discharge Key. A key employed to pass 
 the discharge from a condenser or cable 
 through a galvanometer. 
 
 Discharge of Magnetism of Field 
 Magnets. A term sometimes employed^ 
 for the unbuilding of a dynamo, or Or 
 gradual failure to produce current on tin 
 loss of magnetism of its field magnets. 
 
 Discharging Rate. The strength of the- 
 discharging current of a storage cell or 
 battery. 
 
 Discharge Resistance. The resistance 
 that is placed in the path or circuit of a 
 discharge. 
 
 Discharging Rod. A jointed metallic 
 rod, blunted at both ends, capable of 
 adjustment as to the distance of the ends 
 from each other, and provided with in- 
 sulating handles, employed for the dis- 
 ruptive discharge of Leyden batteries or 
 condensers. 
 
 Discharging Tongs. A pair of discharg- 
 ing I'ods with an insulating handle, con- 
 nected together by a rivet like a pair of 
 tongs, for effecting the disruptive dis- 
 charge of a Leyden jar or condenser. 
 
 Discoidal Ring- Armature. A term 
 sometimes used for disc armature. 
 
 Discoidal Winding. The flat-ring wind- 
 ing employed in a disc armature. 
 
 Disconnect. (1) To break or open an eleo 
 trie circuit. (2) To remove an electro- 
 receptive device from a circuit. 
 
 Disconnecting. The act of opening or 
 breaking a circuit, or of removing elec- 
 tro-receptive devices therefrom. 
 
 Disconnecting Plug. An infinity plug. 
 
 Disconnection. (1) A general term des- 
 ignating a variety of faults caused by the- 
 accidental breaking or disconnection of a 
 circuit. (2) The intentional opening or 
 breaking of a circuit, or the removal of an. 
 electro-receptive device therefrom. (3 ) A. 
 discontinuity in a circuit. 
 
 Disconnector. A key or other device for 
 opening or breaking an electric circuit, or 
 for removing an electro-receptive device- 
 therefrom. 
 
 Discontinuity Plug. A name sometimes 
 employed for an infinity plug. 
 
 Discriminating Lightning- Arrester. 
 The name sometimes applied to a non- 
 arcing continuous-current lightning-ar- 
 rester. 
 
 Diselectriflcation. A general term em- 
 ployed for the act of causing a charged 
 body to lose its electric charge. 
 
 Disguised Electricity. Dissimulated 6t 
 latent electricity. 
 
Dis.j 
 
 746 
 
 [Dis. 
 
 Disintegration of Storage Battery 
 Plate. The gradual loosening or separa- 
 tion of the active material of a storage 
 battery plate from the perforations of the 
 grid. 
 
 Disjunctor. A device employed in a sys- 
 tem for the distribution of electric en- 
 ergy by means of continuous currents in 
 connection with condensers, for periodi- 
 cally reversing the constant current sent 
 over the line. 
 
 Dispersing Pad-Electrode. A thera- 
 peutic pad-electrode, suitable for use with 
 strong currents, applied directly to the 
 body, for diffusing the therapeutic current 
 through a large tract thereof. 
 
 Dispersion Photometer. A photometer 
 in which the light to be measured is de- 
 creased in intensity by a known amount, 
 so as to be more readily compared with a 
 standard light of much smaller intensity. 
 
 Displacement Current. (1) Therate-of- 
 change of electric displacement. (2) An 
 electric current produced in a dielectric 
 by electric displacement, as opposed to a 
 conduction cm-rent. 
 
 Displacement, Electric. A displace- 
 ment of electricity in a uniform non- 
 crystalline dielectric when electrostatic 
 flux passes through it. 
 
 Displacement Flux. (1) The flux of elec- 
 tric displacement. (2) The surface inte- 
 gral of displacement effected through the 
 surface. 
 
 Displacement Lines. The lines along 
 which displacement flux moves. 
 
 Displacement Waves. Waves produced 
 in the ether by means of electric displace- 
 ments. 
 
 Disruptive Discharge. A sudden and 
 more or less complete discharge that 
 takes place across an intervening non- 
 conductor or dielectric. 
 
 Disruptive Electric-Conduction . The 
 conduction of electric energy which ac- 
 companies a disruptive discharge. 
 
 Disruptive Strength of Dielectric. 
 The strain a dielectric is capable of bear- 
 ing without suffering disruption, or with- 
 out permitting a disruptive discharge to 
 pass through it. 
 
 Dissipation Function. (1) A function 
 expressing the rate at which heat is 
 produced by the passage of an electric 
 current through a conductor. (2) A 
 function, which, when differentiated 
 with respect to a velocity as the inde- 
 pendent variable., gives the applied 
 " force required to overcome the dissipa- 
 tive resistance to motion. 
 
 Dissipation of Charge. The gradual 
 but final loss of charge by leakage which 
 occurs even in a well insulated conductor. 
 
 Dissipation of Energy. The expendi- 
 ture or loss of available energy. 
 
 Dissipativity. The time-rate of dissipat- 
 ing energy as heat per-unit- volume of a 
 substance. 
 
 Dissimulated Electricity. (1) A term 
 sometimes applied to the condition of an 
 electric charge when placed near an op- 
 posite charge, as in a Leyden jar or con- 
 denser. (2) A bound charge. 
 
 Dissociate. To separate a compound sub- 
 stance into its constituent parts. 
 
 Dissociation. The separation of a com- 
 pound substance into its constituents. 
 
 Dissonance, Electric. (1) Electrical dis- 
 agreement. (2) A term employed in con- 
 tradistinction to electric consonance, to 
 alternating electromotive forces, fluxes 
 or currents, whose phases are in opposi- 
 tion. 
 
 Dissymmetrical Alternating-Electro- 
 motive Forces. Alternating-electro- 
 motive forces, in which an alternating 
 semi-wave, when reversed in sign, does 
 not reduplicate the preceding or suc- 
 ceeding semi-wave. 
 
 Dissymmetrical Induction of Arma- 
 ture. Any induction produced in the 
 armature of a dynamo that is unequal in 
 amount, in opposite or symmetrically dis- 
 posed portions of the armature. 
 
 Dissymmetrical Magnetic Field. A 
 field whose flux is not symmetrically dis- 
 tributed. 
 
 Dissymmetry of Commutation. A 
 commutation in which the neutral line 
 does not coincide with the diameter of 
 commutation. 
 
 Distant Battery. A battery employed 
 in any telegraphic system at the distant 
 receiving end of the line. 
 
 Distant Station. A term applied by a 
 telegraph operator to the distant end of 
 the line, in order to distinguish it from 
 his own, or the home end. 
 
 Distillation, Electric. The distillation 
 of a liquid in which the effects of heat 
 are aided by the electrification of the 
 liquid. 
 
 Distorsion. The change in the shape 
 or configuration of a medium, or an en- 
 tity, produced by the action of a stress 
 or disturbance. 
 
 Distorsion of Magnetic Field. A 
 change in the direction or distribution of 
 the magnetic flux in the field of a dynamo 
 
Dis.j 
 
 747 
 
 [Dis. 
 
 armature, produced by the magnetomo- 
 tive force of the armature current. 
 Distorsional Elasticity. Elasticity in a 
 body, due to its distorsion or deformation. 
 
 Distorsionless Cable. A cable that 
 forms part of a distorsionless circuit. 
 
 Distorsionless Circuit. (1) A telegraph- 
 ic circuit in which leakage and con- 
 ductor resistance are so balanced as to 
 leave no tailings. (2) A telegraphic cir- 
 cuit in which there is no distorsion of 
 signals or electric waves. 
 
 Distributed Capacity. The capacity of 
 a circuit considered as distributed over 
 its entire length, so that the circuit may 
 be considered as shunted by an infinite 
 number of infinitely small condensers, 
 placed infinitely near together, as distin- 
 guished from localized capacity, in which 
 the capacity is distributed in discrete 
 aggregations. 
 
 Distributed Inductance. Inductance 
 distributed throughout the entire length 
 of a circuit or portion thereof, as distin- 
 guished from inductance interposed, in a 
 circuit in bulk at some one or more points. 
 
 Distributed Winding of Dynamo Elec- 
 tric Armature. A winding disposed 
 regularly over the surface of the armature 
 as distinguished from a pole winding, or a 
 winding composed of a few localized coils. 
 
 Distributing Board. <1) A term some- 
 times employed in a system of telephonic 
 or telegraphic communication, to a cross- 
 connecting board. (2) A board at which 
 the wires or cables from a telephone 
 switchboard terminate and at which con- 
 nections are made with the circuit wires. 
 (3) An insulating board provided with 
 screw connecting-pieces for readily con- 
 necting branch circuits to mains in a dis- 
 tributing system, with or without fuse 
 cut-outs. 
 
 Distributing Box. (1) A box containing 
 means for readily changing the connec- 
 tions of distribution circuits with their 
 source of supply. (2) A device by means 
 of which both arc and incandescent lights 
 may be simultaneously employed on the 
 same constant-current circuit. (3) A 
 device for cutting into or out of an arc 
 circuit, at will, a group of series incan- 
 descent lamps. 
 
 Distributing Box of Conduit. A name 
 sometimes given to a man-hole of a con- 
 duit. 
 
 Distributing Brushes of Motor. The 
 brushes which rest on the commutator of 
 an electric motor and carry the driving 
 current to it. 
 
 Distributing Mains. The mains env 
 ployed in a feeder system of parallel dis- 
 tribution. 
 
 Distributing Ppint. A point, usually at 
 the junction of risers and mains, or mains 
 and sub-main's, where all the fuses or 
 safety catches, belonging to that part of 
 the system, are collected. 
 
 Distributing Station. (1) A station from 
 which electricity is distributed. (2) A 
 central station. 
 
 Distributing Switch. A switch for clos- 
 ing a plurality of distributing circuits at 
 will upon the source of supply. 
 
 Distributing Switchboard. (1) A mul- 
 tiple switchboard. (2) A device for dis- 
 tributing electricity over any of a number 
 of circuits. 
 
 Distributing Box. A box placed at a 
 distributing point for holding all the f usea 
 belonging to that portion of the distribut- 
 ing system. 
 
 Distributing Box for Arc-Light Cir- 
 cuits. A device by means of which both 
 arc and incandescent lights may be sim- 
 ultaneously employed on the same line 
 from a constant-current dynamo-electric 
 machine. 
 
 Distributing Centre. (1) In an electrical 
 distribution system a centre or sub-centre 
 of distribution. (2) A ramifying point. 
 
 Distribution of Charge. The diffusion 
 or dispersion of an electric charge over 
 the surfaces of electrified bodies. 
 
 Distribution of Electricity. The divi- 
 sion and transmission of electric energy 
 by means of various combinations of elec- 
 tric sources, circuits and electro-receptive 
 devices, so arranged that the electricity 
 generated by the sources is carried or dis- 
 tributed to more or less distant electro- 
 receptive devices, by means of the various 
 circuits connected therewith. 
 
 Distribution of Electricity by Alter- 
 nating Currents. A system of electric 
 distribution in which the Jamps, motors 
 or other receptive devices, are operated 
 by means of alternating currents that 
 are sent over the line or lines, in many 
 cases after they have been modified by 
 apparatus called transformers. 
 
 Distribution of Electricity by Alter- 
 nating Currents by Means of Con- 
 densers. A system of alternating-cur- 
 rent distribution in which condensers are 
 employed to transform currents of high 
 potential, received from an alternating- 
 current dynamo, to currents of low poten- 
 tial which are fed to the lamps or other 
 electro-receptive devices. 
 
Dis.] 
 
 748 
 
 [Div, 
 
 Distribution of Electricity by Com- 
 mutating Transformers. A system of 
 electric distribution in which motor gen- 
 erators are used, but neither their field- 
 magnets nor armatures are revolved, a 
 .special commutator being employed to 
 change the polarity of the magnetic cir- 
 cuits. 
 
 Distribution of Electricity by Con- 
 stant-Currents. Any system of elec- 
 tric distribution employing direct cur- 
 rents, as distinguished from one employ- 
 ing alternating currents. 
 
 Distribution of Electricity by Con- 
 stant Potential-Circuits. A system 
 of electric distribution in which the re- 
 ceptive devices are placed in multiple or 
 multiple-series across constant-potential 
 mains. 
 
 Distribution of Electricity by Con- 
 tinuous Currents by Means of Con- 
 densers. A system of distribution in 
 which a continuous current is conducted 
 to certain points in a line, where a dis- 
 junctor is employed to reverse it period- 
 ically, the reversed currents so obtained 
 being directly used to charge condensers 
 in the circuit of which induction coils 
 are employed. 
 
 Distribution of Electricity by Con- 
 tinuous Currents by Means of 
 Transformers. A system for the trans- 
 mission of electric energy by means of 
 continuous or direct currents that are sent 
 over the line to suitably located stations 
 where motor-dynamos are used for trans- 
 formers. 
 
 Distribution of Electricity by Motor- 
 G-enerators. A system of electric 
 distribution in which a continuous high- 
 potential current, distributed over the 
 main line, is employed at the point where 
 its energy is to be utilized for driving a 
 motor, which in turn drives a dynamo 
 whose current is employed to energize 
 the electro-receptive devices. 
 
 Distribution of Power, Electric. Any 
 system in which mechanical energy is 
 first converted into electro-magnetic en- 
 ergy and then distributed over a line wire 
 or circuit to electric motors, which again 
 change the electro-magnetic energy into 
 mechanical energy. 
 
 Distributor. A word sometimes applied 
 to the distributing mains in a parallel 
 system of distribution. 
 
 District Call-Box. A box by means of 
 which an electric signal is automatically 
 sent over a telegraph line and received 
 by an electromagnetic device at the other 
 end of the line. 
 
 Diurnal Currents. Earth currents 
 through telegraph circuits of normal 
 strength and executing diurnal cycles. 
 
 Diurnal Inequality of Earth's Mag- 
 netism. Diurnal variations in the value 
 of the earth's magnetic variation or in- 
 clination. 
 
 Diurnal Load-Factor. (1) The ratio be- 
 tween the total number of units sent out 
 from a station in twenty-four hours, to 
 the amount which would have been sent 
 out in the same time if the plant were 
 working at its maximum load for the 
 whole twenty-four hours'. (2) The ratio of 
 daily average to daily maximum load. 
 
 Diurnal Variation. An approximately 
 regular variation of the magnetic needle 
 which occurs at different hours of the 
 day. 
 
 Divalent. (1) Possessing an atomicity or 
 valency of two. (2) Bivalent. 
 
 Divergence. (1) The integral of outward- 
 ly directed flux over the surface of an ele- 
 ment of volume divided by that volume. 
 (2) The opposite of convergence. 
 
 Divergent Flux. (1) Flux that diverges 
 or diffuses as it proceeds. (2) Flux that 
 decreases in intensity along its path. 
 
 Divergent Vector Quantity. A vector 
 point function in space having diver- 
 gence. 
 
 Diverging-Lens Photometer. A pho- 
 tometer in which the intensity of the 
 light to be measured is decreased by 
 means of a diverging lens. 
 
 Diverging Magnetic Flux. Magnetic 
 flux that decreases in intensity and di- 
 verges or diffuses in direction along its 
 path. 
 
 Diversity Factor. A term proposed for 
 the ratio of the average supply of electric 
 power to a consumer to the maximum 
 power supplied. 
 
 Diviance. A term proposed for resistance 
 to the flow of magnetic induction. 
 
 Divided Circuit. (1) A branched or bifur- 
 cated circuit. (2) A term sometimes 
 employed for multiple circuit. 
 
 Divided Core. A laminated core. 
 
 Divided Magnetic Circuit. A mag- 
 netic circuit which bifurcates or divides. 
 
 Divided Telephone-Switchboard. A 
 multiple telephone switchboard. 
 
 Divided Touch. A term used in place 
 of magnetization by separate touch. 
 
 Divided Trolley Line. A term some- 
 times used for a sectional trolley line. 
 
 Dividing Engine. (1) A mechanical de- 
 vice for dividing a thermometric, galvanos* 
 
Div.] 
 
 749 
 
 [Dou, 
 
 metric, or other scale, into equal parts. 
 (2) A device for dividing a tube or a 
 scale into equal parts of a length, consist- 
 ing essentially of a horizontal screw by 
 means of which a carriage carrying suit- 
 able marking gear can be moved along a 
 parallel prismatic guide. 
 
 Division Operator. A railway telegraph- 
 operator in charge of a telegraph division 
 or section of railway telegraph. 
 
 Doctor for Plating. A device employed 
 in electro-plating for coating surfaces 
 that are too extended to be immersed at 
 once in the plating bath. 
 
 Dolly. A polishing brush employed in 
 electro-plating, consisting of a number ol 
 calico rings suitably clamped together 
 in a wooden holder for attachment to a 
 lathe. 
 
 Domestic Telephone-Switchboard. 
 (1)A telephone switchboard located in a 
 house for readily connecting different 
 rooms. (2) A local telephone switchboard 
 for connecting apartments in a residence. 
 
 Door-Bell Pull, Electric. A circuit- 
 closing device attached to a bell-pull and 
 operated by the ordinary motion of the 
 pull. 
 
 Door-Contact Lamp. A contact which 
 lights a lamp and permits it to remain 
 lighted only while the door operating its 
 circuit remains in a certain position. 
 
 Door-Opener, Electric. An electro- 
 magnetic device for opening a door from 
 a distance. 
 
 Door Push. A contact closed or opened 
 by the opening or shutting of a door to 
 give a notice of the movement at a dis- 
 tance, as in a burglar-alarm system. 
 
 Door Trigger. A device by means of 
 which notice is given of the opening or 
 closing of a door or window. 
 
 Dot-and-Dash Code. A term sometimes 
 employed for the Morse telegraphic code. 
 
 Dotting Contact. An electric contact 
 obtained by the approach of one contact 
 point towards another. 
 
 Double Alternation. (1) A complete 
 cycle or double vibration. (2) A com- 
 plete to-and-fro movement. 
 
 Double Armature "Windings. Two 
 separate armature windings applied sym- 
 metrically to a core, and whose ends are 
 connected respectively to alternate com- 
 mutator bars. 
 
 Double-Balance Relay. In a closed-cur- 
 rent system of alarm telegraphy, a pair 
 of relays connected in series, one of which 
 will close a local circuit if the main line 
 current appreciably weakens, and the 
 
 other of which will close a local circuit 
 if the main line current appreciably 
 strengthens. 
 
 Double-Bar Switch. A switch or re- 
 verser consisting of a pair of parallel 
 metallic bars or strips which move to- 
 gether upon independent centres so as to 
 make contact simultaneously upon one or 
 more pairs of contacts. 
 
 Double-Block Duplex System. A 
 system of duplex telegraphy in which a 
 condenser exists in both arms of the 
 duplex bridge. 
 
 Double-Break Knife-Switch. (1) A 
 knife switch which breaks a circuit at two 
 points. (2) A knife switch provided with 
 a contact for botli poles. 
 
 Double-Break Switch. A term some- 
 times used for double-pole switch. 
 
 Double-Bracket Pole. A pole employed 
 in an overhead line for the support of a 
 double bracket. 
 
 Double-Bracket Trolley Suspension. 
 In a double-track trolley road, a pole pro- 
 vided with two brackets, one extending 
 over each track, and provided for holding 
 the two trolley wires. 
 
 Double-Block Duplex System. A du- 
 plex system on the Wheatstone bridge 
 system, employing a condenser in each 
 arm of the bridge. 
 
 Double-Break Switch. (1) A double- 
 pole switch. (2) A switch which breaks 
 a circuit in two places, as distinguished 
 from a switch which breaks a circuit at a 
 single point only. 
 
 Double-Bronze Wire. A conducting 
 wire possessing great tensile strength, 
 provided with an aluminium-bronze core, 
 and a copper-brass envelope. 
 
 Double-Carbon Arc-Lamp. An arc- 
 lamp which will burn all night without 
 recarboning, containing two sets of car- 
 bon electrodes so arranged that, when one 
 set is practically consumed, the current is 
 automatically switched to the other set. 
 
 Double-Circuit Dynamo. A dynamo- 
 electric machine provided with two sepa- 
 rate circuits. 
 
 Double-Conductor Cable or Wire. A 
 cable or wire provided with two separate 
 insulated conductors. 
 
 Double-Cone Insulator. An insulator 
 in which the line wire passes through and 
 is supported by means of a tube consist- 
 ing of two inverted, truncated cones, 
 joined at their vertices. 
 
 Double-Connector. A form of binding 
 screw suitable for readily connecting two 
 wires together. 
 
Dou.] 
 
 750 
 
 [Dou. 
 
 Double-Contact Key. A key suitable 
 either for making two separate succes- 
 sive contacts, or for closing either of two 
 circuits. 
 
 Double-Contact Push. A push provided 
 with two contacts so arranged that the 
 pressure of a push opens one contact and 
 closes the other. 
 
 Double-Contact Push Button. A push- 
 button provided with two contacts. 
 
 Double-Cord Multiple-Switchboard. 
 A multiple telephone switchboard in 
 which connections are made by plugs and 
 cords having two twin wires, as opposed 
 to a switchboard in which single cord 
 plugs are used. 
 
 Double - Cord Switchboard. (1) A 
 switchboard employing twin-wire or 
 double-conductor connections. (2) A 
 switchboard in which each connection is 
 established through a pair of cords, as 
 distinguished from a single-cord switch- 
 board. 
 
 Double-Cup Insulator. (1) An insulator 
 consisting of two funnel-shaped cups,' 
 placed in an inverted position on the sup- 
 porting pin, and separated from each other 
 by a Free air-space except at the ends 
 which are connected. (2) A double-petti- 
 coat insulator. 
 
 Double-Curb. A device for increasing 
 the speed of telegraphic signalling by 
 ridding the line of its charge before the 
 next signal is sent, by sending more than 
 one reversal of current with or without 
 grounding the line, as distinguished from 
 a single-curb. 
 
 Double-Curb Signalling. Signalling by 
 means of a double curb. 
 
 Double-Current Signalling. (1) Signal- 
 ling by means of currents that alternately 
 change their direction. (2) Signalling in 
 which the marking currents have one 
 direction and the spacing currents the 
 opposite direction. 
 
 Double-Current Telegraphic - Work- 
 ing. Telegraphing or operating by means 
 of double currents. 
 
 Double-Current Translation. (1) The 
 automatic repetition of a telegraphic mes- 
 sage by means of double currents. (2) 
 Telegraphic translation employing double 
 currents. 
 
 Double-Current Translator. A tele- 
 graphic translator or repeater designed to 
 operate on double-current transmission. 
 
 Double-Current Transmitter. A trans- 
 mitting instrument employed in a system 
 of telegraphy in which the direction of 
 the line current is alternately changed, 
 
 according to whether the key rests on its 
 front or on its back stop. 
 Double-Current Working. A method 
 of telegraphic working or transmission by 
 means of double currents. 
 
 Double-Curve Pull-Off. A double-curve 
 hanger. 
 
 Double-Curve Trolley Hanger. A 
 
 hanger provided for holding an overhead 
 trolley wire, supported by a lateral strain 
 in opposite directions, and employed, gen- 
 erally at the end of both single and double 
 curves, and on intermediate points on 
 double-track curves. 
 
 Double-Curve Trolley-Suspension. 
 
 Suspension by means of a double-curve 
 trolley hanger. 
 
 Double-Deck Switchboard. A switch- 
 board arranged in two rows placed one 
 above the other. 
 
 Double-Dielectric Refraction. Double 
 electric refraction produced in a dielectric 
 by the action of an electro-magnetic 
 stress. 
 
 Double-Duplex Block. In submarine 
 telegraphy, duplex transmission obtained 
 by the aid of a condenser inserted in each 
 arm of a Wheatstone's balance. 
 
 Double-Filament Lamp. (1) An incan- 
 descent lamp, frequently employed for 
 the side-light of a ship, and provided with 
 two carbon filaments so arranged that 
 should one break, the other will continue 
 burning. (2) A twin-filament lamp. (3) 
 An incandescent lamp having two fila- 
 ments connected in series, and, therefore, 
 requiring twice the electric pressure of an 
 ordinary lamp. 
 
 Double-Flexible Conductor. A con- 
 ductor consisting of two separate stranded 
 flexible conductors, provided with an in- 
 sulating covering common to both. 
 
 Double-Fluid Electrical Hypothesis. 
 A hypothesis which endeavors to explain 
 the causes of electrical phenomena by the 
 assumption of the existence of two dif- 
 ferent electric fluids. 
 
 Double-Fluid Voltaic Cell. (1) A vol- 
 taic cell in which two separate fluids or 
 electrolytes are employed. (2) A two-fluid 
 voltaic cell. 
 
 Double-Focus X-Ray Tube. An X-ray 
 tube, suitable for use with alternating 
 electric currents, in which two anti- 
 cathodes are employed, so arranged that 
 they act as a common source of X-rays. 
 
 Double-Hatchet Switch. A term some 
 timer used for a double-knife switch. 
 
Don.] 
 
 751 
 
 [Dou t 
 
 Double-Horseshoe Field-Magnet. A 
 multiple field-magnet of a dynamo formed 
 by two separate electro-magnets. 
 
 Double Insulation. Insulation of a con- 
 ductor effected at two distinct points, so 
 that if one insulation should fail the other 
 will serve. 
 
 Double-Key Tapper. A key used in a 
 system of needle telegraphy to send elec- 
 tris impulses through the line in alter- 
 nately opposite directions. 
 
 Double-Liquid Voltaic Cell. A double- 
 fluid voltaic cell. 
 
 Double-Loop. (1) In telegraphy, any pair 
 of associated loops. (2) A pair of loops 
 connecting a pair of branch offices with a 
 central office. 
 
 Double-Loop Repeater. In telegraphy, 
 a pair of loops connecting a pair of branch 
 offices with a central office, and so con- 
 nected with a duplex set, or with the 
 common side of a quadruplex set, in the 
 main office, that one branch office can send 
 messages on the duplexed line while the 
 other office is receiving. 
 
 Double-Magnet Dynamo-Electric Ma- 
 chine. A term sometimes applied to a 
 dynamo-electric machine, whose field 
 magnets have two consequent poles. 
 
 Double-Needle Telegraphy. A system 
 of needle telegraphy in which two sepa- 
 rate and independently operated needles 
 are employed on two separate circuits. 
 
 Double-Peg. A split peg which closes two 
 separate contacts, when inserted in the 
 switchboard to which it belongs. 
 
 Double-Pen Telegraphic-Register. A 
 telegraphic register provided with two 
 separate styluses or pens for recording 
 the message on a paper fillet. 
 
 Double-Petticoat Insulator. (1) A 
 double insulator, placed one within and 
 beneath the other, to reduce the electric 
 leakage over the surface. (2) A double- 
 cup insulator. 
 
 Double-Plug. A double peg. 
 
 Double-Plug Key. A plug key made in 
 two separate parts that are insulated from 
 each other. 
 
 Double-Pole Bell. An electro-magnetic 
 bell having a polarized armature which 
 plays between a pair of electro-magnetic 
 poles. 
 
 Double Pole. (1) A double telegraph 
 pole. (2) Two telegraph poles placed 
 side-by-side and braced together. (3) An 
 H-pole. 
 
 Double-Pole Cut-Out. (1) A cut-out 
 which provides in a single operation the 
 
 cutting out of both the positive and the 
 negative leads. (2) Two safety fuses, 
 mounted on the same holder, and con- 
 nected respectively to the positive and 
 negative mains. 
 
 Double-Pole Fusible Cut-Out. A term 
 sometimes used for double-pole cut-out. 
 
 Double-Pole Safety-Fuse. An auto- 
 matic double-pole cut-out. 
 
 Double-Pole Switch. A switch which 
 simultaneously breaks the circuit of both 
 positive and negative leads. 
 
 Double-Pole Telephone-Receiver. A 
 
 telephone receiver in which both poles of 
 a small electro-magnet are presented to 
 the diaphragm. 
 
 Double Pull-Off. (1) A pull-off employed 
 on curves to hold a trolley wire in posi- 
 tion when strain in both directions is nec- 
 essary to hold it in place. (2) A double- 
 curve pull-off. 
 
 Double-Reduction. A gear wheel veloc- 
 ity reducer employing two gear wheels 
 and two pinions, or oneintermediate shaft. 
 
 Double-Reduction Car-Motor. A car- 
 motor provided with a double-reduction, 
 or with one intermediate gear shaft be- 
 tween the motor shaft and car wheel. 
 
 Double-Reflection Tube. A term some- 
 times employed for a double-focus X-ray 
 tube. 
 
 Double-Refraction. The property pos- 
 sessed by certain transparent substances 
 of splitting up a ray of light passed 
 through them into two separate rays. 
 
 Double-Refraction, Electric. The prop- 
 erty of doubly refracting light acquired 
 by some transparent substances when 
 subjected to the stress of an electrostatic 
 or electro-magnetic field. 
 
 Double Ringing-Key. In a multiple tel- 
 ephone switchboard, a pair of keys form- 
 ing part of an exchange operator's set, 
 employed in ringing up. 
 
 Double-Shackle Insulator. A form of 
 insulator employed in shackling a wire, 
 consisting of two single-shackle insulators. 
 
 Double-Shed Insulator. A double-cup 
 insulator. 
 
 Double-Speaking Telegraph. A term 
 sometimes employed for the duplex tele- 
 graph as employed on submarine cables* 
 
 Double-Style Printing Apparatus. A 
 double Morse receiver employing two 
 printing levers or styluses marking dots 
 in parallel lines, one responding to posi- 
 tive currents and representing dots, and 
 the other responding to negative currents 
 and representing dashes. 
 
Don.] 
 
 752 
 
 [Dow. 
 
 Double-Successive Contact-Key. A 
 
 key so arranged as to successively close 
 two separate circuits. 
 
 Dpuble Tapper Key. A key employed 
 in a system of needle telegraphy to send 
 electric impulses over the line in alter- 
 nately opposite directions. 
 
 Double Telegraphic Transmission. 
 Any method of simultaneously sending 
 two messages over a single line wire or 
 conductor. 
 
 Double Telegraphy. A term sometimes 
 employed for duplex telegraphic working. 
 
 Double-Throw Switch. (1) A switch 
 capable of being thrown into either of 
 two contacts or pairs of contacts. (2) A 
 switch which has three positions. (3) A 
 throw-over switch. 
 
 Double-Touch. Magnetization by double 
 touch. 
 
 Double-Transmission. (1) The simul- 
 taneous sending of two messages over a 
 single wire in opposite directions. (2) Du- 
 plex or contraplex telegraphy. 
 
 Double-Transmitter for Engine Tele- 
 graph. A transmitter on board a twin- 
 scre%v steamer for communicating orders 
 electrically to the engine-room for both 
 engines simultaneously. 
 
 Double-Trolley. Two separate trolleys 
 placed on the same car, and moving over 
 two separate trolley wires which form a 
 metallic circuit, in any double-overhead 
 system. 
 
 Double-Trolley Line. A metallic-circuit 
 trolley line employing two trolleys, one 
 connected with the positive conductor and 
 the other with the negative conductor. 
 
 Double-Trolley System for Electric 
 Railroads. An electric railroad system 
 employing double trolley wires and double 
 trolleys so as to provide a complete metal- 
 lic circuit. 
 
 Double-Truck Car. A car supported on 
 two separate single trucks, and employed 
 with long cars for safety and ease in turn- 
 ing around sharp curves. 
 
 Double Vibration. (1) A to-and-fro or 
 complete vibration. (2) A complete cycle 
 of vibratory motion. 
 
 Double- Winding of Armature. An 
 armature winding provided with two 
 separate windings or sets of coils, in which 
 the separate windings are insulated from 
 each otner and connected to the com- 
 mutator at alternate segments, so that the 
 brushes rest coincidently upon segments 
 that are connected with each winding, 
 thus permitting each winding to furnish 
 half the current strength with an attend- 
 
 ant decrease in the inductance of each 
 circuit. 
 
 Double-Wire Circuit. A metallic cir- 
 cuit. 
 
 Double- Wire Cleat. A cleat for support- 
 ing a pair of wires. 
 
 Double-Wire Moulding. A moulding 
 for containing two wires, each in a sepa- 
 rate groove. 
 
 Double-Wire System for Electric- 
 Light Leads. On board ship, a system 
 of electric-light wiring, in which going 
 and returning conductors are provided, 
 as distinguished from a single-wire system 
 in which the hull of the vessel is em- 
 ployed as a common return. 
 
 Double-Wire Telephone-Switchboard. 
 A switchboard in a central telephone ex- 
 change, employing metallic circuits, in 
 which each subscriber is connected by 
 an independent double wire or metallic 
 circuit. 
 
 Double-Word. In telegraphy, a word of 
 more than the prescribed length and, 
 therefore, counted and charged as two. 
 
 Do able -Wound Gramme King. A 
 
 gramme ring provided with two inde- 
 pendent and symmetrically interspersed 
 windings. 
 
 Double-Wound Wire. Wire provided 
 with a double winding of cotton, silk, or 
 other insulating thread. 
 
 Doubler of Electricity. An early form 
 of continuous electrophorous. 
 
 D9ubly He-Entrant Armature- Wind- 
 ing. (1) A winding in which the armature 
 is provided with two separate windings 
 or conducting paths, each of which is in- 
 dependently re-entrant. (2) A double- 
 wound armature, each winding of which 
 is re-entrant. 
 
 Doubly-Wound Resistance Coils. A 
 resistance coil wound, as is usual, with 
 the wire doubled on itself, in order to 
 minimize self-induction. 
 
 Douche, Electric. An electrified shower- 
 bath. 
 
 Down-Contact of Switch. A contact 
 which is made by the downward move- 
 ment of a switch. 
 
 Down-Lines. In the United Kingdom of 
 Great Britain and Ireland, telegraphic 
 lines on the side remote from the prin- 
 cipal station of the circuit, as distin- 
 guished from up-lines. 
 
 Down-Side. In Great Britain, that side 
 of a telegraphic circuit further from the 
 metropolis or principal town of the cir- 
 cuit, as distinguished from the up-side. 
 
Dra.] 
 
 753 
 
 [Dro. 
 
 Drag. In submarine cable operations, a 
 haul made with a gi-apnel across a line of 
 cable in ths hope of hooking said cable. 
 
 Drag of Magnetic Field. A word some- 
 times employed for the torque or electro- 
 dynamic force produced by a magnetic 
 field on an active conductor placed in it. 
 
 Draw-Bar. In a locomotive, the link 
 or bar which connects it with its load. 
 
 Draw-Bar Pull. The pull delivered by a 
 locomotive at its draw-bar, as distin- 
 guished from the pull exerted by its motor. 
 
 Drawbridge Frog. A trolley frog for use 
 at the point of overhead contact with a 
 drawbridge wire. 
 
 Draw Tongs. A species of vise employed 
 in connection with a light block-and- 
 tackle for obtaining the required tension 
 on an aerial line wire. 
 
 Draw Vise. (1) A device employed in 
 stringing overhead wires. (2) A portable 
 vise for holding and drawing up an over- 
 head wire. 
 
 Drawing-In-and-Out Conduit. A con- 
 duit provided with ducts, so as to readily 
 permit the wires or conductors to be 
 placed in the conduit or removed from 
 after they have been placed therein. 
 
 Drawing-In Box. A flush box. 
 
 Drifting of Needle. (1) The failure of the 
 needle of a galvanometer to remain at its 
 zero point when no current is passing 
 through its coils, due usually to variation 
 in the condition of the magnetic needle, 
 to variation in the torsion of the suspend- 
 ing system, or to local or other causes. 
 (2) Elastic fatigue in the suspension of a 
 magnetic system. 
 
 Drifting of Zero Point. A term fre- 
 quently employed for the shifting of the 
 zero point. 
 
 Drilling, Electric. (1) A term sometimes 
 employed for the use of the voltaic arc 
 in perforating a mass of metal or mineral. 
 (2) Drilling by means of an electrically 
 operated tool. 
 
 Drip Loop. A loop inclined upwards at 
 the point where outside conductors enter 
 a building, so that the rain-water flows 
 along said loop from the building, instead 
 of towards it. 
 
 Driven Circuit of Transformer. The 
 secondary circuit of a transformer. 
 
 Driven Coil of a Transformer. The 
 secondary coil of a transformer. 
 
 Driven Pulley. A pulley which receives 
 its motion from a driving shaft. 
 
 Driven Pulley of Dynamo. The pulley 
 connected with the armature shaft of a 
 dynamo. 
 
 Driven Shaft. The shaft worked by a 
 belt from the driving pulley. 
 
 Driving Circuit of Transformer. The 
 primary circuit of a transformer. 
 
 Driving Coil of a Transformer. The 
 primary coil of a transformer. 
 
 Driving Current of Motor. The cur- 
 rent which operates an electric motor. 
 
 Driving E. M. F. The impressed or 
 
 - working E. M. F. 
 
 Driving Gear of Magneto. The gear 
 wheels connecting a magneto telephone- 
 transmitter armature with the driving 
 handle, whereby the speed of revolution 
 of the armature is increased. 
 
 Driving Horns. In a smooth-cored ar- 
 mature, mechanical projections for hold- 
 ing the armature wires in place, and com- 
 municating their electro-magnetic force 
 to the armature. 
 
 Driving Pressure. The driving or im- 
 pressed E. M. F. 
 
 Driving Pulley. That pulley of a ma- 
 chine which is mounted on the driving 
 shaft. 
 
 Driving Pulley of Motor. The pulley 
 attached to the shaft -of a motor, or the 
 pulley through which a motor furnishes 
 its mechanical power. 
 
 Driving Shaft. The shaft connected di- 
 rectly with a prime mover. 
 
 Driving Spider. The radial arms or 
 spokes connected to the armature of a dy- 
 namo, and keyed to its shaft, so as to act 
 as a driving wheel for the armature. 
 
 Drop. (1) A word frequently used for drop 
 of potential, pressure, or electromotive 
 force. (2) The fall of potential which 
 takes place in an active conductor by 
 reason of its resistance. 
 
 Drop. A shutter, or falling armature, of 
 a drop annunciator. 
 
 Drop Annunciator. An electro-mag- 
 netic annunciator, which, on being en- 
 ergized, releases a shutter and allows the 
 same to drop. 
 
 Drop-Handle. In single-needle teleg- 
 raphy, a form of transmitter handle. 
 
 Drop Indicator. A drop annunciator. 
 
 Drop of Magnetic Potential. A fall of 
 magnetic potential. 
 
 Drop of Potential. The fall of potential, 
 equal in any part of a circuit to the pro- 
 duct of the current strength and the re- 
 sistance of that part of the circuit. 
 
 Drop of Telephone Switchboard. A 
 small electro-magnetic annunciator in- 
 serted in the line of each subscriber, 
 
Pro,] 
 
 754 
 
 [Dup. 
 
 whereby any current received from a sub- 
 scriber attracts the armature of the elec- 
 tro-magnet and releases the shutter, there- 
 by indicating the number of the particu- 
 lar subscriber calling. 
 
 Drop of Voltage. The drop or difference 
 of potential of any part of a circuit. 
 
 Drop Relay -Contact. A form of relay- 
 contact in which, on the passage of a cur- 
 rent, the attraction of an armature releases 
 a drop and thus completes a local circuit,' 
 which remains closed until the drop is 
 reset. 
 
 Drop-Shutter of Annunciator. The 
 drop of an electro-magnetic annunciator. 
 
 Drop-Trolley. A particular form of trol- 
 ley wheel and pole which employs a 
 swivel joint and springs forcing the trol- 
 ley against the wire. 
 
 Drop-Trolley Stand. A support for a 
 trolley pole or mast provided with a swivel 
 joint and suitable springs for ensuring a 
 firm pressure of the trolley wheel against 
 the trolley wire. 
 
 Drum. A reel for holding wire or cable. 
 
 Drum Armature. A dynamo armature 
 whose coils are wound longitudinally over 
 the surface of a cylinder or drum. 
 
 Drum Armature- Winding. The wind- 
 ing employed on a drum armature. 
 
 Dry Battery. (1) A number of separate 
 dry voltaic cells, connected so as to act as 
 a single source. (2) A dry pile. 
 
 Dry Cable. A dry-core cable. 
 
 Dry Cell. A dry voltaic cell. 
 
 Dry-Core Cable. A cable whose core is 
 wrapped with paper or cotton which is 
 not afterwards filled with paraffine, gutta- 
 percha, or other insulating material, and, 
 consequently, whose dielectric consists 
 largely of dry air. 
 
 Dry Distillation. A species of destruc- 
 tive distillation. 
 
 Dry Electrode. A therapeutic electrode 
 applied in a dry state. 
 
 Dry Front of Microscopic Objective. 
 That front of a microscopic object glass 
 which is turned towards the object, but 
 is separated from it by a short distance or 
 air gap, in contradistinction to an immer- 
 sion lens. 
 
 Dry Gelatine Cell. A type of dry voltaic 
 cell in which the fluid electrolyte is ab- 
 sorbed by, or combined with, a suitable 
 gelatinous substance. 
 
 Dry Pile. A dry battery. 
 
 Dry Transformer. An air-insulated 
 transformer, as distinguished from an oil- 
 insulated transformer. 
 
 Dry Voltaic Cell. (1) A misnomer for a 
 voltaic cell in which the fluid electrolyte 
 is held in suspension by saw-dust, gelatine, 
 or other suitable material. (2) A sealed 
 voltaic cell, which can, therefore, be in- 
 verted without danger of spilling liquid. 
 
 Dual Electrolysis. A term sometimes 
 employed to denote the double decom- 
 position that attends the electrolysis of a 
 metallic salt ; viz. that of the salt and its 
 solvent. 
 
 Dub's Laws. A set of experimentally es- 
 tablished laws relating to the tractive and 
 attractive magnetic forces developed by 
 electro-magnets under various conditions, 
 of which the following are two : ' ' The 
 attraction of V-shaped electro-magnets, 
 with an equal number of windings, ispro- 
 
 ' portional to the square of the magnetiz- 
 ing current strength." "The attraction 
 of V-magnets is, with equal currents, pro- 
 portional to the square of the number of 
 windings of the magnetizing spirals." 
 
 Duct. A space left in an underground 
 conduit for a separate wire or cable. 
 
 Duct of Conduit. The space provided in 
 a conduit for a conductor or cable. 
 
 Dumb-Bell Vibrator. An electric vi- 
 brator consisting of two spheres con- 
 nected by a straight conductor contain- 
 ing an air-gap. 
 
 Dummy Moulding. A moulding not in- 
 tended for the reception of a wire, but as 
 part of an ornamentation, the moulding 
 being symmetrically arranged on the ceil- 
 ing with an electrolier as a centre, with 
 only one or a few of the mouldings actu- 
 ally having wires placed in them. 
 
 Duopod. A two-legged screw support for 
 a pendant or upright. 
 
 Duplex Balance. The condition of a 
 duplex telegraphic line, in which the 
 home instruments are unaffected by the 
 sending signals, and are, therefore, ready 
 to respond to the received signals. 
 
 DupLex Cable. A cable containing two 
 separate conductors placed parallel to- 
 each other. 
 
 Duplex Circuit. (1) A circuit arranged 
 for duplex transmission. (2) A metallic 
 circuit. 
 
 Duplex Cut-Out. A cut-out so arranged 
 that when one bar or strip is fused or 
 melted by an abnormal current, another 
 can be immediately substituted for it. 
 
 Duplex Electrolysis. A term some- 
 times used for dual electrolysis. 
 
 Duplex Flat-Cable. A flat laid-up cable 
 containing two wires. 
 
 Duplex Loop. A loop or pair of wires 
 
Dup.] 
 
 755 
 
 [Dyn. 
 
 leading to a branch office, whereby a 
 branch office can be brought into con- 
 nection with a duplex set placed at the 
 main office, for the duplex sending and re- 
 ception of messages at said branch office. 
 Duplex Telegraph. A general term 
 embracing the apparatus employed in 
 duplex telegraphy. 
 
 Duplex Telegraphic Insulator. A 
 
 double telegraph insulator. 
 
 Duplex Telegraphy. A system of tel- 
 egraphy whereby two messages can be 
 simultaneously transmitted in opposite 
 directions over a single wire. 
 
 Duplex Telephony. Duplex telephonic 
 transmission. 
 
 Duplex Transmission. The sending of 
 two telegraphic or telephonic messages 
 simultaneously in opposite directions over 
 the same wire. 
 
 Duplex Wire. An insulated conductor 
 containing two separate parallel wires. 
 
 Duplex Working. Duplex transmis- 
 sion. 
 
 Duplexed-Diplex Telephony or Tel- 
 egraphy. Quadruplex telephony or tel- 
 egraphy. 
 
 Duplicate Arc. A multiple arc contain- 
 ing but two branches. 
 
 Duration of Electric Discharge. The 
 time required to effect a complete dis- 
 ruptive discharge. 
 
 Dust Telephone - Transmitter. (1) A 
 form of microphone transmitter in which 
 finely granulated carbon or carbon dust is 
 contained within a suitably shaped box, 
 connected with the terminals of the trans- 
 mitter. (2) A granular telephone trans- 
 mitter. 
 
 Dyad. (1) A chemical element which has 
 two bonds by which it can unite or com- 
 bine with other elements. (2) A biva- 
 lent element. 
 
 Dyad Atom. An atom whose valency, 
 atomicity, or combining power, is two. 
 
 Dyeing, Electric. The application of 
 electricity either to the reduction or to 
 the oxidation of the salts used in dyeing. 
 
 Dynamic Electricity. A term some- 
 times employed for current electricity, in 
 contradistinction to static electricity. 
 (Obsolete.) 
 
 Dynamic Induction. (1) A term some- 
 times employed for mutual induction. 
 (2) Kinetic induction. 
 
 Dynamic Multiplier. (1) A term some- 
 times employed for a self-induction coil 
 or a coil possessing self-induction. (2) A 
 spark coil. 
 
 Dynamic System of Induction Teleg- 
 raphy. A term sometimes used for the 
 current system of induction telegraphy, 
 as distinguished from an electrostatic 
 system of induction telegraphy. 
 
 Dynamics. That branch of mechanics 
 which treats of the action of a force in 
 producing motions or pressures. 
 
 Dynamo. A dynamo-electric machine or 
 generator. 
 
 Dynamo Armature-Coils. The coils, 
 employed on the armature of .a dynamo- 
 electric machine. 
 
 Dynamo Balancing-Rheostat. An ad- 
 justable rheostat whose range is sufficient 
 to balance the current of one dynamo 
 against that of another, with which it is 
 required to operate in parallel. 
 
 Dynamo Battery. The combination of 
 several separate dynamos to act as a 
 single electric source. 
 
 Dynamo Brush-Holders. Devices for 
 supporting the collecting brushes of dy- 
 namo-electric machines. 
 
 Dynamo Brush-Trimmer. A device for 
 rapidly ensuring the accurate trimming 
 of dynamo brushes. 
 
 Dynamo Changing-Switch. A switch 
 designed to throw a dynamo from one 
 circuit to another. 
 
 Dynamo-Electric Generator. A dy- 
 namo-electric machine. 
 
 Dynamo-Electric Machine. (1) A ma- 
 chine for the conversion of mechanical 
 energy into electric energy, by means of 
 electro-dynamic induction. (2) A dy- 
 namo. 
 
 Dynamo-Electric Machine Battery. 
 A dynamo battery. 
 
 Dynamo or Motor Frame. The iron 
 body of a dynamo or motor, including the 
 pole-pieces and standards, but excluding 
 the base-plates and bearings. 
 
 Dynamo or Motor Standards. The sup- 
 ports on which a dynamo or motor arma- 
 ture rests. 
 
 Dynamo Pole-Changer. A pole-chang- 
 ing transmitter employed in a system of 
 duplex or quadruplex telegraphy. 
 
 Dynamo Power. The power of a motor 
 to act as a generator. 
 
 Dynamo Power of a Motor. (1) A power 
 possessed by an electric motor of produc- 
 ing counter-electromotive force. (2) 
 The number of volts of counter-electro< 
 motive force produced by a motor per- 
 revolution per-second. 
 
Dyn.] 
 
 756 
 
 [Ear. 
 
 Dynamo Regulator. A name given to a 
 form of rheostat employed in the regula- 
 tion of a dynamo. 
 
 Dynamo Resistance Box. A form of 
 rheostat employed in the regulation of 
 a dynamo. 
 
 Dynamo Terminals. The main termi- 
 nals of a dynamo. 
 
 Dynamograph. A term sometimes ap- 
 plied to a typewriting telegraph that 
 records the messages in typewritten char- 
 acters, both at the receiving and trans- 
 mitting ends of the line. 
 
 Dynamograph, Electric. A device for 
 electrically recording the work done by 
 any machine. 
 
 Dynamometer. A general name given 
 to a variety of apparatus for measuring 
 power. 
 
 Dynamometric Governor. A dyna- 
 mometer employed on the shaft of an 
 
 electric motor for the purpose of operat- 
 ing a regulating apparatus. 
 
 Dynamotor. (1) A particular type of 
 rotary transformer. (2) A motor-gener- 
 ator, in which a generator and motor 
 armature-winding are rotated through a 
 common magnetic field. 
 
 Dynamotor Windings. Windings re- 
 quired for the armatures of the dynamo 
 and motor of a dynamotor. 
 
 Dyne. (1) The C. G. S. unit of force. 
 
 (2) The force which in one second can 
 
 impart a velocity of one centimetre-per- 
 
 second to a mass of one gramme. 
 Dyne-cm. An abbreviation proposed for 
 
 a dyne-centimetre, the C. G. S. unit of 
 
 work. 
 Dyne : cm-. An abbreviation proposed 
 
 for a dyne-per-square-centimetre, the C. 
 
 G. S. unit of pressure. 
 
 Dyne-Centimetre-Per-Second. The C. 
 G. S. unity of activity. 
 
 E 
 
 E. or e. A symbol for electromotive 
 force. 
 
 E. A contraction sometimes used for 
 earth. 
 
 E. H. P. A contraction for electrical 
 horse-power. 
 
 E. M. P. A contraction for electromotive 
 force. 
 
 E. M. P. of Self-induction. The E. M. 
 F. generated in a loop of wire during the 
 filling or emptying of that loop by mag- 
 netic flux from its own current. 
 
 Ear. (1) A metal piece supported by an 
 insulator to which the trolley wire is 
 fastened. (2) A trolley ear. 
 
 Ear Piece. A circular opening into an 
 air chamber placed over the diaphragm 
 of a telephone, suitably shaped to per- 
 mit the ready application of the listener's 
 ear. 
 
 Earth. (1) A fault in a telegraphic or other 
 line caused by the accidental contact of 
 the line with the ground or earth, or 
 with some other ground-connected con- 
 ductor. (2) That part of the earth or 
 ground which forms a part of an electric 
 circuit. 
 
 Earth-Battery Current. A current on 
 a telegraph line caused by voltaic action 
 between two dissimilar earth plates, as 
 distinguished from a true earth current. 
 
 Earth Cell. A term frequently applied to 
 a variety of voltaic cell, consisting of any 
 voltaic couple buried in a comparatively 
 moist stratum of earth. 
 
 Earth Circuit. A circuit in which the 
 ground or earth forms part of the con- 
 ducting path. 
 
 Earth-Circuited Conductor. A con- 
 ductor connected to the ground or to an. 
 earth-connected circuit. 
 
 Earth Coil for Magnetic Measurement. 
 A coil capable of being moved about a 
 fixed axis, or fixed axes, employed for 
 generating a measurable E. M. F. from 
 the earth's magnetic field. 
 
 Earth Connection. A conductor which 
 establishes a connection between any 
 apparatus or circuit and ground. 
 
 Earth Currents. Electric currents flow- 
 ing through the earth, caused by the 
 difference of potential of its different 
 parts. 
 
 Earth Currents of Cable. Currents in 
 a cable due to natural causes, such as 
 climatic conditions or magnetic disturb- 
 ances, as distinguished from the current* 
 sent through the cable for the transmis- 
 sion of messages. 
 
 Earthenware Conduit. A conduit, gen- 
 erally multiduct, made of glazed earthen- 
 ware. 
 
Ear.] 
 
 757 
 
 [Edu 
 
 Earth-Grounded Wire. A wire one ter- 
 minal of which is grounded or put to 
 earth, so that the earth forms a part of 
 the circuit in which it is placed. 
 
 Earth Indicator. An instrument suitable 
 for the accurate determination of the 
 magnetic inclination and the calibration 
 of ballistic galvanometers. 
 
 Earth Overlap Test. A localization test 
 for the position of a partial earth in a 
 telegraph line, conducted alternately by 
 observers at each end of the line, the line 
 being grounded at one end while its re- 
 sistance is measured at the other, and 
 resistance is added to one end until the 
 fault is brought to the centre of the cir- 
 cuit. 
 
 Earth Plates. Plates of metal, buried in 
 the earth or in water, connected to the 
 terminals of earth wires. 
 
 Earth Return. That portion of a ground- 
 ed circuit in which the earth forms its 
 conducting path. 
 
 Earth Strip. In a multiple telephone 
 switchboard a strip of metal, or top plate 
 of a series of jacks, permanently connect- 
 ed to earth through a battery, to furnish 
 connections for the busy test. 
 
 Earth-Switch for Telephone. (1) In a 
 single-cord multiple telephone-switch- 
 board, a device for maintaining a ground- 
 connection with the shank of a plug when 
 out of use, by supporting the plug, friction 
 tight, against a ground-connected bar. 
 (2) A switch at a telephone switchboard 
 for automatically grounding the sleeve of 
 a plug when out of use. 
 
 Earth Wires. The wires that lead an 
 earth-grounded circuit to the earth plates. 
 
 Earth's Field. The magnetic field pro- 
 duced in any place by the earth's flux. 
 
 Earth's Flux. The magnetic flux pro- 
 duced by the earth by virtue of its mag- 
 netized condition. 
 
 Earthed. Connected to earth or ground. 
 
 Earthing. Connecting a line or conductor 
 to earth or ground. 
 
 Earthing Device. An instrument for 
 automatically making connection be- 
 tween a system of wiring and the earth, 
 should the potential between them rise be- 
 yond a certain predetermined safe limit. 
 
 Earthkin. A terella. 
 
 Easement. A permit obtained from the 
 owner of a property for the erection of 
 poles or attachments for telephone, tele- 
 graph, or other aerial lines. 
 
 Ebonite. (1) A hard, tough, black sub- 
 stance, composed of India rubber and 
 
 sulphur, possessing both high powers of in- 
 sulation and high specific inductive capac- 
 ity. (2) Vulcanite. 
 
 Economic Coefficient. The ratio be- 
 tween the net electric power, or the out- 
 put of a dynamo, and the gross electric 
 power, or power actually converted in the 
 dynamo. 
 
 Economic Coefficient of Dynamo-Elec- 
 tric Machine. (1) The ratio between 
 the electric power produced by a dyna- 
 mo at its terminals, and the mechanical 
 power expended in driving it. (2) A 
 term sometimes employed for the ratio of 
 the useful electric power at the termi- 
 nals to the total electric power developed 
 in the machine. 
 
 Economy Coil. A choking coil employed 
 for the purpose of reducing the pressure 
 on arc lamps fed by step-down trans- 
 formers. 
 
 Eddy Conduction-Currents. (1) Eddy 
 currents. (2) Foucault currents. 
 
 Eddy-Current Loss. The loss of energy 
 in a dynamo, motor, transformer, or simi- 
 lar apparatus, due to the presence of 
 eddy currents. 
 
 Eddy Currents. Useless currents pro- 
 duced in the pole-pieces, armature, and 
 field-magnet cores of dynamos or motors, 
 or in metallic masses generally, either by 
 their motion through magnetic flux, or 
 by variations in the strength of electric 
 currents flowing near them. 
 
 Eddy Displacement-Currents. Eddy 
 currents produced in the mass of a di- 
 electric or insulator, by the passage 
 through it of electrostatic or magnetic 
 flux. 
 
 Edgewise System. A system of mount- 
 ing central-station switchboard instru- 
 ments, in which, for the purpose of econo- 
 mizing space, their scales are presented 
 edgeways vertically to the switchboard 
 face. 
 
 Edison Distributing-Box. A distribut- 
 ing box employed in the Edison three- 
 wire system of distribution. 
 
 Edison Effect. An electric discharge 
 which occurs between one of the termi- 
 nals of the incandescent filament of an 
 electric lamp and a metallic plate placed 
 near but disconnected from the filament 
 as soon as a certain difference of poten- 
 tial is reached between the lamp terminals. 
 
 Edison Electric-Tubes. The under- 
 ground tubes employed in the Edison, 
 three- wire system of distribution. 
 
 Edison - Lalande Cell. A zinc-copper 
 couple in which the copper is covered 
 
Eel.] 
 
 758 
 
 with a depolarizing layer of copper-oxide, 
 and the couple immersed 'n an electrolyte 
 of caustic soda zr r~tasr:. 
 Eel, Electric. (1) Ai: eel possessing the 
 power of giving powerful electric shocks. 
 (2) The gymnotus electricus. 
 
 Effective Ampere-Turns. O The re- 
 sultant magnetizing force v- a magnetic 
 circuit. (2) The square root, of the mean 
 square of the ampere-turr.s in a periodi- 
 cally-varying magnetizing force. 
 
 Effective Conductance. (1) The ratio in 
 an alternating-current circuit of the real 
 electric power, or real activity, to the 
 square of the effective pressure. (2) The 
 virtual conductance of a circuit. (3) In 
 an alternating-current circuit the ratio of 
 the energy component of current to the 
 total E. M. F. 
 
 Effective Current-Strength. (1) The 
 strength of an alternating or sinusoidal- 
 electric current, determined by its heat- 
 ing effect ; or, in other words, the therm- 
 ally effective current strength. (2) That 
 value of the current strength of a sinusoi- 
 dal or alternating current which is equal 
 to the square root of the mean square 
 of the instantaneous values of the current 
 during one or more cycles. (3) The square 
 root of the time average of the square of 
 the current. 
 
 Effective Electromotive Force. (1) 
 The difference between the direct and the 
 counter-electromotive force. (2) The 
 square root of the time average of the 
 square of the E. M. F. (3) The virtual 
 E. M. F. 
 
 Effective M. M. P. The square root of 
 the time average of the square of a peri- 
 odically-alternating M. M. F. 
 
 Effective Reactance. (1) In an alternat- 
 ing-current circuit, the ratio of the watt- 
 less component of an electromotive force 
 to the total current. (2) Apparent react- 
 ance. 
 
 Effective Resistance. In an alternat- 
 ing-current circuit, the ratio between the 
 energy component of an electromotive 
 force and the total current. 
 
 Effective Secondary - Electromotive 
 
 Force. (1) The vector difference be- 
 tween the direct and counter-electromo- 
 tive force in the secondary of an induc- 
 tion coil. (2) The E. M. F. in a secondary 
 circuit expended in overcoming resist- 
 ance. (3) The square root of the time aver- 
 age of the square of a secondary E. M. F. 
 Effective Starting-Current of Motor. 
 The indicated value of the starting cur- 
 rent of a motor as observed on an am- 
 - meter. 
 
 Effective Susceptance. (1) In an alter- 
 nating-current circuit, the ratio between 
 the wattless component of a current and 
 its total electromotive force. (2) Apparent 
 susceptance. 
 
 Efficiency. The ratio between an effect 
 produced and the expenditure required 
 to produce that effect. 
 
 Efficiency of Voltaic Battery. (1) The 
 ratio between the actual ampere-hour out- 
 put per gramme of zinc dissolved, and the 
 theoretical ampere-hour output. (2) The 
 ratio of the energy delivered at the ter- 
 minals of a battery to the theoretically 
 computed energy liberated within it elec- 
 trochemically. (3) The ratio of the en- 
 ergy at terminals to the total electric en- 
 ergy. 
 
 Effective Value of Periodic Current or 
 E. M. F. (1) The square root of the 
 mean square of the current or E. M. F. 
 extended over one or more complete cy- 
 cles. (2) The virtual current or E. M. F. 
 
 Efficiency, Electric. The useful or avail- 
 able electric energy delivered by any 
 source to its external circuit, divided by the 
 total electrical energy within the-source. 
 
 Efficiency of Dynamo, Electric. The 
 electrical output of a dynamo, divided by 
 the total electric activity in its armature 
 circuit. 
 
 Efficiency of Conversion. The ratio be- 
 tween the enei'gy present in any result 
 and the energy expended in producing 
 that result. 
 
 Efficiency of Conversion of Dynamo. 
 The total electric energy developed by a 
 dynamo, divided by the total mechanical 
 energy required to drive the dynamo. 
 
 Efficiency of Distribution. The ratio 
 of the units of electric quantity or elec- 
 tric energy sold, or distributed to consum- 
 ers from a central station, to the units 
 generated in that station. 
 
 Efficiency of Electric Lamp. (1) The 
 ratio of the luminous energy emitted by 
 an incandescent lamp to the energy ab- 
 sorbed by the lamp. (2) The ratio of the 
 number of candles which can be obtained 
 from an electric lamp to the electric ac- 
 tivity in the lamp expressed in watts. (3) 
 A term in common but inaccurate use for 
 the ratio of the number of watts con- 
 sumed by a lamp to the number of can 
 dies it produces, expressed in watts pei 
 candle. 
 
 Efficiency of Electric Motor. (1) The 
 ratio of the power delivered at a motor 
 pulley to the electric power supplied at 
 its terminals. (2) The ratio between the 
 useful mechanical power delivered by a 
 
Elf.] 
 
 759 
 
 [Ele. 
 
 motor and the electrical power put in to 
 drive it. 
 
 Efficiency of Radiation. The ratio of 
 the luminous activity of a luminous body 
 to its radiation activity. 
 
 Efficiency of Secondary Battery. (1) 
 The ratio of the electric quantity of dis- 
 charge in ampere-hours to the electric 
 quantity in a charge. (2) The ratio of the 
 electric energy of discharge in watt-hours 
 to the electric energy of charge. 
 
 Efficiency of Transformer or Con- 
 verter. The ratio of the power supplied 
 at the secondary terminals of a trans- 
 former or converter to the power supplied 
 at its primary terminals. 
 
 Efflorescence. (1) Pulverulence or crum- 
 bling of crystalline salts, due to the loss 
 of their water of crystallization on drying. 
 (2) A term loosely applied to the deposi- 
 tion of solid matter above the line of liquid 
 on the surface of a vessel containing a va- 
 porizing saline solution, by the crystalli- 
 zation of the salt. 
 
 Effluvia. The name given to a variety of 
 assumed highly tenuous imponderable 
 forms of matter that were formerly be- 
 lieved to be given off by electrified or 
 magnetized bodies. 
 
 Effluvium, Electric. A term employed 
 in the early history of electricity for the 
 supposed highly-tenuous, imponderable 
 matter given off from an electrified body, 
 which was assumed to be the cause of 
 electric phenomena. 
 
 Efflux. The flow or quantity of liquid es- 
 caping in a given time from an orifice in 
 a containing vessel. 
 
 Egg, Electric. An egg-shaped vessel con- 
 taining a partial vacuum through which 
 an electric discharge is passed, for the 
 purpose of producing luminous effects. 
 
 Elastance. (1) The reciprocal of the elec- 
 trostatic capacity. (2) The reciprocal of 
 permittance. 
 
 Elastic. (1) Of or pertaining to elasticity. 
 (2) Possessing elasticity. 
 
 Elasticity. That property of a body in vir- 
 tue of which its original configuration or 
 form is regained, after a strain or distor- 
 tion has been produced in it by the action 
 of a stress. 
 
 Elasticity, Electric. The quotient aris- 
 ing from dividing the electric strain by 
 the electric stress. 
 
 Elastivity. The reciprocal of permit- 
 tivity. 
 
 Elbow Connection. A connection at an 
 angle more or less approaching 90. 
 
 Elbow Connector. A connector suitable 
 for connecting conductors at an elbow. " 
 
 Electrepeter. An old term for switch, 
 key, or pole-changer. (Obsolete.) 
 
 Electret. (1) A name proposed for a sub" 
 stance possessing natural or inherent elec- 
 trization. (2) A permanently polarized 
 body. 
 
 Electric. Of or pertaining to electricity. 
 
 Electrical. An orthography for electric. 
 
 Electrically. In an electrical manner. 
 
 Electrically Conducting. Transferring 
 electricity by electric conduction. 
 
 Electrically Controlled Clock. A clock 
 that is controlled, either wholly or par- 
 tially, by electricity. 
 
 Electrically Discharging. Equalizing 
 differences of potential by connecting 
 them with a conductor. 
 
 Electrically Energizing. Causing elec- 
 tricity tc produce any effect in an electro- 
 receptive device. 
 
 Electrically Illumined Buoy. An elec- 
 trically lighted buoy. 
 
 Electrically Retarded. Decreased speed 
 of telegraphic signalling by means of 
 electrostatic induction. 
 
 Electrically Tuned System. Any cir- 
 cuit or system of circuits that have been 
 brought into electric resonance with an- 
 other circuit or system of circuits. 
 
 Electrician. One versed in the principles 
 and applications of electricity. 
 
 Electricity. The name given to the un- 
 known cause of electric phenomena. 
 
 Electricity Driving-Force. A term 
 sometimes used for electromotive force. 
 
 Electricity Meter.; (1) A coulomb meter. 
 (2) A term sometimes used for electric 
 meter. 
 
 Electrics. A term formerly applied to 
 
 substances capable of becoming electrified 
 
 by friction. (Obsolete.) 
 Electrifiable. Capable of being endowed 
 
 with electric properties. 
 Electrification. The production of an 
 
 electric charge. 
 
 Electrified. Endowed with an electric 
 charge. 
 
 Electrified Body. A charged body. 
 
 Electrify. To endow with electric prop- 
 erties. 
 
 Electrlne. Of or pertaining to electrum 
 or amber. 
 
Ele.] 
 
 760 
 
 [Ele. 
 
 Electripherous. An unnecessary word 
 proposed for anything capable of bearing 
 or transmitting electricity. 
 
 Electrization. Electrification. 
 
 Electrize. To electrify or endow with an 
 electric charge. 
 
 Electrizer. Anything which electrifies or 
 charges a body with electricity. 
 
 Electro - Anaesthesia. Insensibility to 
 pain produced by the use of electricity. 
 
 Electro-Ballistics. The application of 
 electricity to the determination of the 
 velocity of projectiles. 
 
 Electro-Bath.. The liquid or fluid em- 
 ployed in electro-plating. 
 
 Electro-Biological. Pertaining to elec- 
 tro-biology. 
 
 Electro-Biologist. One skilled in electro- 
 biology. 
 
 Electro-Biology. That branch of electric 
 science which treats of the condition of 
 living animals and the effects of electric- 
 ity upon them. 
 
 Electro-Bioscopist. One skilled in elec- 
 tro-bioscopy. 
 
 Electro-Bioscopy. The determination of 
 the existence of life or death by the pas- 
 sage of electricity through the muscles 
 and nerves. 
 
 Electro-Brassing. (1) The electrolytic 
 deposition of brass from a solution con- 
 taining salts of zinc and copper. (2) Coat- 
 ing a surface with a layer of brass by 
 electro-plating. 
 
 Electro-Calorimetry. The art of meas- 
 uring the quantity of heat developed in 
 any conductor or circuit by an electric 
 current. 
 
 Electro-Capillarity. The science which 
 treats of the mutual effects between elec- 
 tricity and capillarity. 
 
 Electro-Capillary. Of or pertaining to 
 electro-capillarity. 
 
 Electro - Capillary Electrometer. A 
 capillary electrometer. 
 
 Electro-Capillary Light. A bright light 
 obtained by the discharge of an induction 
 coil through a narrow capillary tube pro- 
 vided with aluminium or copper elec- 
 trodes, and filled with air at ordinary 
 pressures. 
 
 Electro-Capillary Phenomena. Elec- 
 tric phenomena observed in capillary 
 tubes at the contact surfaces of two 
 liquids. 
 
 Electro-Capillary Telephone. A tele- 
 phone transmitter whose operation de- 
 pends on the electric currents produced 
 
 by forcing a liquid through a bundle of 
 capillary tubes, by the to-and-fro move- 
 ments of the diaphragm. 
 Electro-Chemical. Of or pertaining to 
 electro-chemistry. 
 
 Electro-Chemical Accumulator. A 
 
 storage battery. 
 
 Electro-Chemical Actinometer. (1) An 
 actinometer employing electrolytic ac- 
 tion. (2) An electric actinometer. 
 
 Electro-Chemical Decomposition. 
 
 Electrolytic decomposition. 
 
 Electro-Chemical Filtration. A term 
 formerly employed in place of electric 
 end osmose. 
 
 Electro-Chemical Meter. An electric 
 meter in which the current passing is 
 measured by the amount of electrolytic 
 decomposition it effects. 
 
 Electro-Chemical Telephone. A name 
 sometimes given to the Edison electro- 
 motographic telephone. 
 
 Electro-Chemical Series. A list of 
 chemical elements so arranged that each 
 will displace from its compounds any 
 element lower in the list than itself. 
 
 Electro - Chemically. In - an electro- 
 chemical manner. 
 
 Electro - Chemist. One skilled in the 
 science of electro-chemistry. 
 
 Electro-Chemistry. (1) That branch of 
 electric science which treats of electric 
 combinations and decompositions effected 
 by the electric current. (2) The science 
 which treats of the relation between the 
 laws of electricity and chemistry. 
 
 Electro-Chromic Rings. (1) A term 
 sometimes applied to metallochromes. 
 (2) Nobilli's rings. 
 
 Electro-Chronographic. Of or pertain- 
 ing to the electric chronograph. 
 
 Electro-Chronometric Counter. An 
 apparatus employed in a system of elec- 
 tric clocks to enable the master clock 
 electrically to control or operate a num- 
 ber of separate or secondary clocks. 
 
 Electro - Coppering. Electro - plating 
 with copper. 
 
 Electro-Crystallization. Crystallization 
 effected during electrolytic deposition. 
 
 Electro-Culture of Plants. Stimulating 
 the growth of plants by electricity. 
 
 Electro-Deposit. A coating or electro- 
 plating of metal. 
 
 Electro-Depositer. One who practises 
 the art of electro-deposition. 
 
 Electro - Deposition. (1) The deposit, 
 usually of a metallic substance, by means 
 
761 
 
 [Ele. 
 
 of electrolysis. (2) Electrolytic deposi- 
 tion. 
 
 Electro-Deposits. Electrolytic deposits. 
 
 Electro-Diagnosis. Diagnosis by means 
 of the exaggeration or diminution of the 
 reaction of the excitable tissues of the 
 body when subjected to the varying in- 
 fluences of electric currents. 
 
 Electro-Diagnostic. Of or pertaining to 
 electro-diagnosis. 
 
 Electro-Diapason. An electro-magnet- 
 ically operated tuning-fork. 
 
 Electro-Dynamic Attraction. The mu- 
 tual attraction existing between electric 
 currents, or between conductors through 
 which electric currents are passing. 
 
 Electro-Dynamic Balance. A balance 
 form of electro-dynamometer. 
 
 Electro-Dynamic Capacity. A term 
 sometimes employed for self-induction. 
 
 Electro-Dynamic Force. A mechanical 
 force exerted on the substance of a wire 
 or conductor due to the dissymmetrical 
 distribution of magnetic flux in its neigh- 
 borhood. 
 
 Electro-Dynamic Induction. Electro- 
 motive forces set up by induction in con- 
 ductors which are either actually or prac- 
 tically moved so as to cut magnetic flux. 
 
 Electro-Dynamic Interrupter. An in- 
 terrupter for the primary circuit of an 
 induction coil, consisting of an elastic 
 wire stretched, like the wire of a sono- 
 meter or inonochord, between the poles 
 of a permanent horse-shoe magnet. 
 
 Electro-Dynamic Machinery. Any ap- 
 paratus designed for the production, 
 transference, utilization, or measurement 
 of energy by the medium of electricity. 
 
 Electro-Dynamic Motor. (1) A motor 
 operated by electro-dynamic force. (2) 
 An electric motor. 
 
 Electro-Dynamic Potential. An elec- 
 tric potential produced by electro-dyna- 
 mic induction. 
 
 Electro-Dynamic Repulsion. The mu- 
 tual repulsion between two electric cir- 
 cuits whose currents are flowing in op- 
 posite directions. 
 
 Electro-Dynamic Rotation. (1) The ro- 
 tation of a magnetic field produced as the 
 resultant of two or more magnetic fields 
 or magnetizing forces of variable inten- 
 sity, acting at right angles to one another, 
 whose maxima and minima do not coin- 
 cide, but whose periods are the same. (2) 
 Rotation produced electro-dynamically. 
 
 Electro-Dynamic Screen. A conduct- 
 ing scr.een employed for intercepting the 
 
 9 
 
 transmission of varying electro-magnetic 
 forces. 
 
 Electro-Dynamic Whirls. Whirlings, 
 or rotary motions produced in a cloud of 
 copper oxide in a voltameter, when the 
 electrolyte is traversed by a powerful 
 discharge, while under the influence of 
 magnetic flux. 
 
 Electro-Dynamics. That branch of elec- 
 tric science which treats of the action of 
 electric currents on one another, on 
 themselves, or on magnets. 
 
 Electro-Dynamical. Of or pertaining to 
 electro-dynamics. 
 
 Electro-Dynamometer. A form of gal- 
 vanometer suitable for the measurement 
 of electric currents. 
 
 Electro - Dynamometer Balance. A 
 name sometimes given to a current bal- 
 ance. 
 
 Electro-Etching. A term sometimes em- 
 ployed for electric engraving. 
 
 Electro-Extraction of Ores. Various 
 electric processes for extracting metals 
 from their ores. 
 
 Electro-Filtration. A term sometimes 
 employed for electric osmose or cata- 
 phoresis. 
 
 Electro-Genesis. A word proposed for 
 the production of electricity. (Not in 
 use.) 
 
 Electro-Genie. Producing electricity. 
 (Not in use.) 
 
 Electro-Gild. To cover with a metallic 
 coating of gold by electro-plating. 
 
 Electro-Gilder. One who practises the 
 art of electro-gilding. 
 
 Electro-Gilding. (1) Electric gilding. 
 (2) Electro-plating with gold. 
 
 Electro-Gilt. Gilded by means of elec- 
 tricity. 
 
 Electro-Graphy. Galvanography. 
 
 Electro-Inductive Repulsion. Repul- 
 sion between bodies due either to the 
 influence of electrostatically induced 
 charges, or electromagnetically induced 
 currents. 
 
 Electro-Kinetic. Of or pertaining to elec* 
 tro-kinetics. 
 
 Electro-Kinetic Energy. Electrical 
 energy that is actually engaged in doing 
 work. 
 
 Electro-Kinetic Units. A term some- 
 times used for C. G. S. electro-magnetic 
 units. 
 
 Electro-Kinetics. A term sometimes ap- 
 plied to the phenomena of electric cur- 
 rents, or electricity in motion, as dis- 
 Vol. 2 
 
file.] 
 
 762 
 
 tinguished from electrostatics, or the 
 phenomena of electric charges, or elec- 
 tricity at rest. 
 
 Electro-Lithotrity. A term proposed for 
 the removal of urinary calculi by elec- 
 trolysis. 
 
 Electro-Magnet. (1) A magnet produced 
 by the passage of an electric current 
 through a circuit of insulated wire. (2) A 
 magnetizing coil surrounding a soft iron 
 core, that is capable of being magnetized 
 and demagnetized instantly on the clos- 
 ing and opening of the circuit. 
 
 Electro-Magnetic. Of or pertaining to 
 an electro-magnet or to electroTinag- 
 netism. 
 
 Electro-Magnetic Ammeter. A form of 
 ammeter in which a magnetic needle is 
 moved against the field of an electro- 
 magnet by the field of the current it is 
 measuring. 
 
 Electro-Magnetic Annunciator. An 
 electro-magnetic device for automatically 
 indicating the points or places at which 
 one or more electric contacts have been 
 closed. 
 
 Electro-Magnetic Attraction. The mu- 
 tual attraction existing between the un- 
 like poles of electro-magnets. 
 
 Electro-Magnetic Bell. An electro- 
 magnetically operated bell. 
 
 Electro-Magnetic Bell-Call. A bell-call 
 operated by an electro-magnet. 
 
 Electro-Magnetic Brake. A brake for 
 car wheels, whose braking power is 
 either entirely derived from electro-mag- 
 netism, or is thrown into action by elec- 
 tro-magnetic devices. 
 
 Electro-Magnetic Cam. A form of mag- 
 netic equalizer which depends for its 
 operation on the lateral approach of a 
 suitably shaped polar surface. 
 
 Electro-Magnetic Capacity of Line. 
 A term sometimes used for the self-induc- 
 tion or inductance of a line. 
 
 Electro-Magnetic Cut-Out. A cut-out 
 operated by means of an electro-magnet. 
 
 Electro-Magnetic Dental Mallet. A 
 mallet for filling teeth, the blows of which 
 are struck by means of an electro-mag- 
 netically driven mechanism. 
 
 Electro-Magnetic Drill. A drum em- 
 ployed in blasting and mining operations, 
 operated by means of electricity. 
 
 Electro-Magnetic Drum. A drum used 
 in feats of legerdemain operated by 
 means of an automatic electro-magnetic 
 contact-breaker. 
 
 Electro-Magnetic Engine. An electric 
 motor. 
 
 Electro-Magnetic Explorer. An appa- 
 ratus operated by means of induced cur- 
 rents, and formerly employed for the pur 
 pose of locating bullets, or other foreign 
 metallic substances in the human body. 
 
 Electro-Magnetic Eye. (1) A term ap- 
 plied to a certain form of spark micro- 
 meter, employed by Hertz in his experi- 
 ments on electro-magnetic radiation. 
 (2) A term sometimes applied to a co- 
 herer. 
 
 Electro-Magnetic Field. The field pro- 
 duced either by an electro-magnet or by 
 an electric current. 
 
 Electro-Magnetic Flux. Magnetic flux 
 produced by means of an electro-magnet 
 or by an electric current. 
 
 Electro-Magnetic Gyroscope. An elec- 
 tro-magnetically driven gyroscope. 
 
 Electro-Magnetic Helix. An electro- 
 magnetic solenoid. 
 
 Electro-Magnetic Impulse. An im- 
 pulse produced in the ether surrounding a 
 conductor by the action of an impulsive 
 discharge, or by a pulsating field. 
 
 Electro-Magnetic Induction. A va- 
 riety of electro-dynamic induction in 
 which electric currents are produced by 
 the motion either of electro-magnets, or 
 electro-magnetic solenoids. 
 
 Electro-Magnetic Inertia. A term 
 sometimes employed for the inductance 
 or self-induction of a current. 
 
 Electro-Magnetic Interference. The 
 interference of electro-magnetic waves. 
 
 Electro-Magnetic Intermitter. An 
 electro-magnetic vibrator. 
 
 Electro-Magnetic Medium. Any me- 
 dium in which electro-magnetic phe- 
 nomena occur, or through which electro- 
 magnetic waves are transmitted. 
 
 Electro-Magnetic Meter. An electric 
 meter in which the current passing is 
 measured by the electro-magnetic effects 
 it produces. 
 
 Electro-Magnetic Mine-Exploder. A 
 
 small magneto-electric machine employed 
 in the direct firing of blasts. 
 Electro-Magnetic Momentum. T h e 
 product of the inductance of a circuit and 
 the current strength it carries. 
 
 Electro-Magnetic Motor. An electric 
 motor. 
 
 Electro-Magnetic Multiplier. A term 
 sometimes employed for Schweigger's 
 multiplier. 
 
Ele.] 
 
 res 
 
 [Ele, 
 
 Electro-Magnetic Optical-Strain. Any 
 
 optical strain produced by electro-mag- 
 netic stress. 
 
 Electro-Magnetic Pop-Gun. A mag- 
 netizing coil, provided with a tubular 
 space for the insertion of a core much 
 shorter than the length of the coil, which 
 is violently projected when the coil is en- 
 ergized by a current. 
 
 Electro-Magnetic Radiation. The radi- 
 ation, from any conductor through which 
 oscillatory discharges are passing, of 
 electro-magnetic waves similar in all re- 
 spects to those of light, save in their much 
 greater wave length. 
 
 Electro-Magnetic Repeater. A word 
 formerly employed for a form of vibrating 
 contact-breaker. 
 
 Electro-Magnetic Repulsion. The mu- 
 tual repulsion produced by two similar 
 electro-magnetic poles. 
 
 Electro-Magnetic Resonator. A term 
 sometimes applied to a Hertz spark micro- 
 meter, in which electro-magnetic waves 
 are produced by electric resonance. 
 
 Electro-Magnetic Retardation. A re- 
 tardation in the magnetization or demag- 
 netization of a substance. 
 
 Electro-Magnetic Rotation. Rotation 
 obtained by electro-magnetic attractions 
 and repulsions. 
 
 Electro-Magnetic Separator. (1) A de- 
 vice for separating iron ore from the 
 dross, in finely-pulverized, low-grade iron 
 ores. (2) A device for magnetically re- 
 moving particles of iron from brass filings 
 or other non-magnetic material, and thus 
 freeing such material from impurities. 
 
 Electro-Magnetic Shunt. (1) In a sys- 
 tem of telegraphic communication, an 
 electro-magnet whose coils are placed in 
 a shunt circuit around the terminals of 
 the receiving instrument. (2) Any shunt 
 coil provided with a magnetic core. 
 
 Electro-Magnetic Solenoid. (1) A cy- 
 lindrical coil of wire, each convolution of 
 which is circular. (2) An electro-mag- 
 netic helix. (3) A cylindrical current 
 sheet. 
 
 Electro-Magnetic Sorter. An electro- 
 magnetic sepai'ator. 
 
 Electro-Magnetic Strain. The effect 
 produced by an electro-magnetic stress. 
 
 Electro-Magnetic Stress. The force or 
 pressure in an electro-magnetic field 
 which produces a strain or deformation in 
 a piece of glass or other substance placed 
 therein. 
 
 Electro-Magnetic Telegraph. A gen- 
 eral term embracing the apparatus em- 
 ployed in a system of electro-magnetio 
 telegraphy. 
 
 Electro-Magnetic Telegraphy. (1) A 
 system of telegraphy employing or based 
 upon electro-magnetism. (2) The ordi- 
 nary Morse telegraphy. 
 
 Electro-Magnetic Temperature-Regu- 
 lator. A temperature regulator whose 
 operation is dependent on the action of 
 an electro-magnet which is thrown into 
 operation by the expansion or contraction 
 of a solid liquid or gas. 
 
 Electro-Magnetic Twist or Pull. The 
 torque of an electro-magnetic motor. 
 
 Electro-Magnetic Units. (1) A system 
 of C. G. S. units employed in electro-mag- 
 netic measurements. (2) Units based on 
 the attractions and repulsions capable of 
 being exerted between two unit magnetic 
 poles at unit distance apart, or between 
 a unit magnetic pole and a unit electric 
 current. 
 
 Electro-Magnetic Vibrator. A name 
 sometimes given to an automatic contact- 
 breaker. 
 
 Electro-Magnetic Waves. Waves in the 
 ether, given off from a circuit through 
 which an oscillatory discharge is passing, 
 or from a magnetic circuit undergoing 
 variations of magnetic intensity. 
 
 Electro-Magnetic Voltmeter. A form 
 of voltmeter in which the difference of po- 
 tential is measured by the movements of a 
 magnetic needle in the field of an electro- 
 magnet. 
 
 Electro-Magnetics. That branch of elec- 
 tric science which treats of the relations 
 that exist between electric circuits and 
 magnets. 
 
 Electro - Magnetism. Magnetism pro- 
 duced by means of electric currents. 
 
 Electro-Magnetist. One skilled in the 
 art of electro-magnetism. (Not in use.) 
 
 Electro - Massage. The application of 
 electricity to the body during its mas-' 
 sage. 
 
 Electro-Mechanical Alarm. A mechan- 
 ically operated alarm, that is started or 
 set in operation by means of an electric 
 current. 
 
 Electro-Mechanical Bell. A bell whose 
 striking apparatus is mechanically oper- 
 ated, when called into action by an electro- 
 magnet. 
 
 Electro - Mechanical Gong. A gong 
 struck or operated by mechanical force, 
 at times which are dependent on the pas- 
 sage of an electric current. 
 
Ele. 
 
 764 
 
 [Ele. 
 
 Electro-Mechanical Indicator. A me- 
 chanical indicator that is started or set 
 into action by electricity. 
 
 Electro-Medical. Of or pertaining to 
 electricity employed electro-therapeuti- 
 cally. 
 
 Electro-Medical Apparatus. A general 
 term for any apparatus employed in elec- 
 tro-therapeutic treatment. 
 
 Electro - Metallurgical Circuit . An 
 electric circuit employed in electro-metal- 
 lurgical processes. 
 
 Electro-Metallurgical Galvanization. 
 A process of covering any conducting 
 surface with a metallic coating by elec- 
 trolytic deposition, such, for example, as 
 the thin copper coating deposited on the 
 carbon electrodes used in arc-lights. 
 
 Electro-Metallurgical Deposit. A me- 
 tallic deposit thrown down on a conduct- 
 ing surface by electrolysis. 
 
 Electro-Metallurgical Dipping. A pro- 
 cess for obtaining an electro-metallurgi- 
 cal deposit on a metallic surface by dip- 
 ping it in a solution of a readily decom- 
 posable metallic salt. 
 
 Electro-Metallurgical Galvanization. 
 The electro-therapeutic effects produced 
 on nerves or muscles by the passage of an 
 electric current. 
 
 Electro-Metallurgy. (1) That branch of 
 electric science which relates to the elec- 
 tric reduction or treatment of metals. (2) 
 Electro-metallurgical processes effected 
 by the agency of electricity. (3) Electro- 
 plating or electro-typing. 
 
 Electro-Motion. Motion produced by 
 electricity. 
 
 Electro-Motor. A term sometimes em- 
 ployed for a voltaic couple. 
 
 Electro-Muscular. Of or pertaining to 
 the influence of electricity on the mus- 
 cles. 
 
 Electro-Muscular "Excitation. In elec- 
 tro-therapeutics, the galvanic or farad ic 
 excitation of a muscle, or its excitation 
 by the continuous current from a voltaic 
 battery, or by the alternating currents 
 from an induction coil. 
 
 Electro-U egative. (1) In such a state as 
 regards electricity as to be repelled by 
 bodies negatively electrified, and attracted 
 by those positively electrified. (2) The 
 ions or radicals which appear at the anode 
 or positive electrode of a decomposition 
 cell. 
 
 Electro-Negative Ions. (1) The negative 
 ions, or groups of atoms or radicals, which 
 appear at the anode or positive terminal 
 of a decomposition cell. (2) The anions. 
 
 Electro-Negative Radicals. The elec- 
 tro-negative ions. 
 
 Electro-Negatively. In an electro-neg- 
 ative manner. 
 
 Electro-Negatives. (1) The anions or 
 electro-negative ions of a radical. (2) The 
 atoms or radicals that appear at the anode, 
 or positive terminal of any source, during 
 electrolysis. 
 
 Electro-Nervous Excitability. The 
 electro-therapeutic excitation of a nerve. 
 
 Electro-Nickeling. Electro-plating with 
 nickel. 
 
 Electro-Optics. That branch of science 
 which treats of the general relations ex- 
 isting between light and electricity. 
 
 Electro-Pathic. Of or pertaining to elec- 
 tro-pathology. 
 
 Electro-Pathology. Diagnosis by means 
 of electricity. 
 
 Electro-Percussion Drill. (1) A drill 
 employed for quarrying or mining in 
 which a reciprocating motion for the drill 
 is obtained by sending an electric current 
 alternately through one or the other of a 
 pair of solenoids of which the drill stock 
 forms the core. (2) Any reciprocating 
 drill operated electrically. 
 
 Electro-Photometer. An instrument for 
 measuring the intensity of light by means 
 of electricity. 
 
 E 1 e c t r o-Photo-Micography. Photo- 
 graphy of the magnified images of micro- 
 scopic objects illumined by the electric 
 light. 
 
 Electro-Physiological. Of or pertain- 
 ing to electro-physiology. 
 
 Electro-Physiologist. One skilled in 
 electro-phy siology . 
 
 Electro-Physiology. The study of elec- 
 tric phenomena of living animals and 
 plants. 
 
 Electro-Plating. The process of covering 
 any conducting surface with a metal, by 
 the aid of an electric current. 
 
 Electro-Plating Bath. A tank contain- 
 ing a metallic solution in which articles 
 are placed to be electro-plated. 
 
 Electro-Pneumatic. Of or pertaining to 
 the combined action of electricity and 
 air pressure. 
 
 Electro-Pneumatic Block System. A 
 block system for railroads in which the 
 semaphores are operated pneumatically 
 under the control of electro-magnetically 
 operated valves. 
 
 Electro-Pneumatic Signals . Signals 
 operated by diaphragms or piston? 
 
Ele.] 
 
 765 
 
 [Ele. 
 
 moved by compressed air, under electric 
 control. 
 
 Electro-Pneumatic Thermostat. An 
 instrument for automatically indicating 
 the existence of a given temperature by 
 the closing of an electric circuit, on the 
 expansion or contraction of a gas. 
 
 Electro-Polar. Possessing electric poles. 
 
 Electro-Positive. (1) In such a state, as 
 regards an electric charge, as to be at- 
 tracted by a body negatively electrified, 
 and repelled by a body positively electri- 
 fied. (2) The ions or radicals which ap- 
 pear at the cathode or negative electrode 
 of a decomposition cell. 
 
 Electro-Positive Ions. The cathions or 
 groups of atoms or radicals which appear 
 at the cathode of a decomposition cell. 
 
 Electro-Positively. In an electro-posi- 
 tive manner. 
 
 Electro-Positives. (1) The cathions or 
 electro-positive ions of radicals. (2) The 
 atoms or radicals that appear during elec- 
 trolysis at the cathode, or negative elec- 
 trode. 
 
 Electro-Positive Radicals. The electro- 
 positive ions. 
 
 Electro-Potential Energy. Electric en- 
 ergy possessing the power of doing work, 
 but not actually doing work. 
 
 Electro-Prognosis. In electro-therapeu- 
 tics a prognosis, or prediction of the fatal 
 or non-fatal termination of a disease, from 
 an electro-diagnosis based on the exagger- 
 ated or diminished reactions of the ex- 
 citable tissues of the body, when subjected 
 to the varying influences of electric cur- 
 rents. 
 
 Elect ro-Puncturation. Electro-punct- 
 ure. 
 
 Electro -Puncture. The application of 
 electrolysis to the treatment of aneurisms 
 or diseased growths. 
 
 Electro-Pyrometer. An apparatus for 
 the determination of temperature by the 
 measurement of the electric resistance 
 of a platinum wire exposed to the tem- 
 perature which is to be measured. 
 
 Electro-Receptive Devices. (1) Vari- 
 ous devices suitable for being placed in 
 an electric circuit and energized by the 
 passage of an electric current through 
 them. (2) Translating devices. 
 
 Electro-Reciprocating Drill. An elec- 
 tro-percussion drill. 
 
 Electro-Refining. Various processes for 
 the electric refining of metals. 
 
 Electro-Skiagraph. A term proposed for 
 a radiograph or X-ray picture. 
 
 Electro-Semaphore. A semaphore oper- 
 ated by means of electricity. 
 
 Electro-Sensibility. An effect produced 
 on a sensory nerve by its electrization. 
 
 Electro-Siliceous Light. An effect ob- 
 tained by the discharge of a powerful 
 rheostatic machine, through a glass tube 
 traversed by a platinum wire, and plunged 
 in salt water, the heat of the discharge 
 not only melting and volatilizing the 
 wire, but also raising the glass tube to 
 brilliant incandescence. 
 
 Electro-Silvering. Covering a surface 
 with an adherent coating of silver, by 
 electro-plating. 
 
 Electro-Smelting. The separation or re- 
 duction of metallic substances from their 
 ores, by means of the heat developed by 
 electric currents. 
 
 Electro - Statics. That branch of elec- 
 tric science which treats of the phenomena 
 and measurement of electric charges. 
 
 Electro-Steeling. (1) The art of covering 
 copper electrodes with a thin coating of 
 hardened iron. (2) Covering a printing 
 surface of an electro with a thin deposit 
 of copper, for the purpose of hardening it. 
 
 Electro-Ster^ttype. A word sometimes 
 employed for electro-type. 
 
 Electro-Stereotyping. Electro-typing. 
 
 Electro-Synthesis. The chemical com- 
 bination of electro-positive and electro- 
 negative radicals under the influence of 
 electricity. 
 
 Electro-Technics. The science which 
 treats of the technical applications of elec- 
 tricity and the general principles involved 
 therein. 
 
 E 1 e c t r o-Telegraphy. Electric teleg- 
 raphy. 
 
 Electro-Therapeutic Bath. A bath fur- 
 nished with suitable electrodes for use in 
 the therapeutic applications of electricity. 
 
 Electro-Therapeutic Breeze. An elec- 
 tric breeze or convection current in air 
 produced by the electrification of metallic 
 points. 
 
 Electro-Therapeutic Diffusion of Cur- 
 rent. The difference in the density of a 
 current in different parts of the human 
 body between electrodes applied thera- 
 peutically. 
 
 Electro-Therapeutic Dosage . Propor- 
 tioning the strength of an electro-thera- 
 peutic current and the duration of its ap- 
 plication to the body. 
 
 Electro-Therapeutic Electrode. The 
 electrode mainly concerned in the electro 
 
Ele.] 
 
 766 
 
 [Ele. 
 
 therapeutic treatment or diagnosis of 
 diseased or disordered parts of the body. 
 Electro - Therapeutic Electrodes. 
 Electrodes of various shapes employed in 
 electro-therapeutics. 
 
 Electro-Therapeutic Galvanization. 
 In electro-therapeutics, the effects pro- 
 duced on nervous or muscular tissue by 
 the passage of a voltaic current. 
 
 Electro - Therapeutic Head-Breeze. 
 A form of electric breeze or convective 
 electric discharge applied to the head. 
 
 Electro-Therapeutic Polarizing - Cur- 
 rent. The current which produces the 
 phenomena of electro-tonus. 
 
 Electro-Therapeutic Electrician. An 
 electro-therapist. 
 
 Electro-Therapeutics. (1) The applica- 
 tion of electricity to the human body for 
 the curing of disease or the improvement 
 of health. (2) Electro-therapy. 
 
 Electro-Therapeutist. An electro-ther- 
 apist. 
 
 Electro-Therapist. (1) One skilled in 
 electro-therapy. (2) An electro-medical 
 practitioner. 
 
 Electro-Therapy. A word sometimes 
 used instead of electro-therapeutics. 
 
 Electro-Thermal Meter. An electric 
 meter in which the current is measured 
 by means of the heat generated by the 
 passage of the current through a resist- 
 ance. 
 
 Electro-Thermancy . That branch of 
 electricity which treats of the effects 
 produced by an electric current on the 
 temperature of a thermo-electric junc- 
 tion. 
 
 Electro-Thermic. Of or pertaining to 
 the generation of heat by means of elec- 
 tricity. 
 
 Electro-Thermic Lightning-Arrester. 
 A lightning arrester operated by the ex- 
 pansion of a high-resistance shunt wire 
 permanently connected to the circuit. 
 
 Electro-Thermotic. Of or pertaining to 
 heat generated by electricity. 
 
 Electro-Tinning. Covering a substance 
 with a coating of tin by electro-plating. 
 
 Electro-Tint. An etching obtained by 
 
 electricity. 
 Electro-Tinting. A term proposed for a 
 
 method of electric engraving. 
 Electro-Type. To produce a fac-simile 
 
 by electrolytically depositing metals in 
 
 a mould. 
 
 Electro-Type. A cast or impression of 
 type obtained by means of electro-metal- 
 lurgy. 
 
 Electro-Type Process. The process of 
 electro-typing. 
 
 Electro-Typic. Of or pertaining to elec- 
 tro-typy. 
 
 Electro-Typing. Obtaining casts or 
 copies of pages of type by depositing 
 metals in moulds, by the agency of elec- 
 tric currents. 
 
 Electro-Typographic. Pertaining to 
 printing by means of electricity. 
 
 Electro-Typy. The art of producing 
 electro-types. 
 
 Electro-Vection. A term sometimes 
 employed for electric endosmose. 
 
 Electro-Vital. Pertaining to the rela- 
 tions between electricity and vitality. 
 
 Electrocesis. A word proposed for curing 
 disease by electricity. (Not used.) 
 
 Electro Compound-Magnet. A term 
 formerly applied to an electro-magnet 
 whose core was wound with two separate 
 wires or conductors. (Obsolete.) 
 
 Electro Contact-Mine. A submarine 
 mine that is automatically fired on the 
 completion of the current of a battery 
 placed on shore, on the closing of floating 
 contact points by passing vessels. 
 
 Electrocution. Capital punishment by 
 means of electricity. 
 
 Electrode. (1) Either of the terminals of 
 an electric source. (2) Either of the 
 terminals of an electric source that are 
 placed in a solution in which electrolysis 
 is taking place. (3) Either of the electro- 
 therapeutic terminals of an electric 
 source. 
 
 Electrodes. The positive and negative 
 terminals of an electric source, at their 
 points of application to a receptive de- 
 vice. 
 
 Electrodeless Discharge. The dis- 
 charge obtained through the rarified gas 
 of any vacuum tube that is unprovided 
 with electrodes. 
 
 Electrogen. A name sometimes applied 
 to the unknown cause of electricity. (Not 
 in general use.) 
 
 Electrograph. (1) A curve produced by 
 a recording electrometer. (2) A word 
 sometimes used for radiograph. 
 
 Electrographics. (1) The science of geo- 
 metrically solving electrical problems by 
 graphical methods. (2) The science 
 which treats of the graphical representa- 
 tion of electric quantities. 
 
Ele.] 
 
 767 
 
 [Ele. 
 
 Electrolier. A chandelier for holding 
 electric lamps, as distinguished from a 
 chandelier for holding gas burners. 
 
 Electrolier Arm. An electric fixture 
 employed for attaching incandescent elec- 
 tric lamps to gas fixtures or electroliers. 
 
 Electrolier Cut-Out. Any cut-out con- 
 nected in the circuit of an electrolier. 
 
 Electrolier Switch. A switch conven- 
 iently located for lighting or extin- 
 guishing lamps in an electrolier. 
 
 Flectrization. The act of being electri- 
 fied, or electrifying. 
 
 Electrologist. An unnecessary word 
 proposed for electrician. 
 
 Electrologist. One skilled in the science 
 of electricity. (Not in general use.) 
 
 Electrology. That branch of science 
 which treats of electricity. (Obsolete.) 
 
 Electrolysis. (1) Chemical decomposi- 
 tion effected by means of an electric cur- 
 rent. (2) The decomposition of the mol- 
 ecule of an electrolyte into its ions or 
 radicals. (3) Electrolytic decomposition. 
 
 Electrolysis by Means of Alternating 
 Currents. Electrolytic decomposition 
 effected, under certain circumstances, by 
 alternating currents. 
 
 Electrolysis of Salts. The electrolytic 
 decomposition of a salt into its constit- 
 uent ions or radicals. 
 
 Electrolyte. <1) Any compound liquid 
 which is separable into its constituent 
 ions or radicals by the passage of elec- 
 tricity through it. (2) The exciting 
 liquid in a voltaic cell. 
 
 Electrolytic. Of or pertaining to elec- 
 trolysis. 
 
 Electrolytic Accumulator. A word 
 sometimes applied to a secondary or stor- 
 age battery. 
 
 Electrolytic Analysis. A term some- 
 times used for electric analysis. 
 
 Electrolytic Annunciator. An annun- 
 ciator consisting of a number of separate 
 electrolytic cells, provided with a trans- 
 parent cover, and so arranged that on the 
 closing of the circuit of any particular 
 cell by a distant push-button, a chemical 
 decomposition is effected in the liquid 
 of the electrolytic cell and a reddish- 
 brown film formed over the surface of the 
 electrode connected therewith. 
 
 Electrolytic Assaying. Assaying by 
 
 means of electrolysis. 
 
 Electrolytic Bath. An electrolytic cell. 
 Electrolytic Cell. (1) A cell or vessel 
 
 containing an electrolyte in which elec- 
 
 trolysis is carried on. (2) A plating cell 
 or vat. 
 
 Electrolytic Clock. A timepiece in. 
 which the rotation of the clock-work is 
 obtained by the rotation of a delicately 
 pivoted and well balanced wheel by the- 
 difference in weight of its two halves im- 
 mersed in an electrolytic bath, on the- 
 passage of an electrolyzing current. 
 
 Electrolytic Condenser. A condenser 
 consisting of a number of iron plates im- 
 mersed in a solution of carbonate of soda, 
 and inserted in a branch circuit for the 
 purpose of giving the current in that cir- 
 cuit a lead, by increasing the capacity. 
 
 Electrolytic Conduction. A term some- 
 times employed to indicate the passage of 
 electricity through an electrolyte by 
 means of charges imparted to its free 
 ions or radicals. 
 
 Electrolytic Conductivity. The recip- 
 rocal of the electrolytic resistance. 
 
 Electrolytic Convection. A term pro- 
 posed for explaining the apparent con- 
 duction of electricity by an electrolyte, 
 without decomposition. 
 
 Electrolytic Corrosion. The corrosion 
 by electrolytic action of water-pipes, gas- 
 pipes, or other masses of metal, buried in 
 moist earth. 
 
 Electrolytic Coulomb-Meter. A cou- 
 lomb-meter whose operation depends on 
 electrolytic decomposition. 
 
 Electrolytic Diaphragm. A diaphragm 
 in an electro-plating bath. 
 
 Electrolytic Decomposition. The sep- 
 aration of a molecule into its constituent 
 ions or radicals by the action of an elec- 
 tric current. 
 
 Electrolytic Dissociation. Electrolytic 
 decomposition. 
 
 Electrolytic Epilation. The removal of 
 hair by electrolysis. 
 
 Electrolytic Etching. (1) Etching by 
 means of electrolytic corrosion. (2) A 
 form of electric etching. 
 
 Electrolytic Exchange. Electrolysis. 
 
 Electrolytic Generator. A continuous- 
 current dynamo-electric generator de- 
 signed for supplying electricity for elec- 
 trolytic purposes. 
 
 Electrolytic Heating. A method of elec- 
 tric heating consisting in plunging the 
 metal to be heated beneath the surface of 
 a conducting liquid, while held in a metal 
 clamp that is connected to the negative 
 pole of a continuous-current source, while 
 the positive pole of such source is con- 
 nected, to the metal lining of the vessel 
 containing the conducting liquid. 
 
Ele.l 
 
 768 
 
 [Ele. 
 
 Electrolytic Hydrogen. Electrolytical- 
 ly liberated hydrogen. 
 
 Electrolytic Meter. An electro-chemical 
 meter. 
 
 Electrolytic Moulding. A term some- 
 times employed for electro-typing. 
 
 Electrolytic Refining. The refining of 
 metals by electrolysis. 
 
 Electrolytic Removal of Hair. Elec- 
 trolytic epilation. 
 
 Electrolytic Separation. Molecular dis- 
 sociation produced by electrolysis. 
 
 Electrolytic Synthesis. Synthesis of a 
 substance by electrolytic means. 
 
 Electrolytic "Writing. Imprinting writ- 
 ten characters on cloths or other textile 
 fabrics by the electrolytic decomposition 
 of a dyeing substance with which they 
 are. impregnated. 
 
 Electrolytically. In an electrolytic man- 
 ner. 
 
 Electrolyzability. Possessing the power 
 of being electrolyzed. 
 
 Electrolyzable. Capable of being elec- 
 trolyzed or decomposed by means of elec- 
 tricity. 
 
 Electrolyzation. The act of electroly- 
 zing. 
 
 Electrolyze. To separate or decompose 
 by means of electricity. 
 
 Electrolyzed. Separated or decomposed 
 by means of electricity. 
 
 Electrolyzer. (1) One who, or that 
 which, causes electrolysis. (2) An elec- 
 trolyzing apparatus. 
 
 Electrolyzing. Causing or producing 
 electrolysis. 
 
 Electrolyzing Cell. An electrolytic cell. 
 
 Electrolyzing Chamber. A chamber or 
 space in which electrolysis occurs. 
 
 Electrometer. An apparatus for measur- 
 ing differences of electric potential. 
 
 Electrometer Fatigue. The failure of 
 the needle of an electrometer to return to 
 the zero point, due to the elastic fatigue 
 of its suspension. 
 
 Electrometer Gauge. A device em- 
 ployed in connection with some hetero- 
 static electrometers, to ascertain whether 
 the needle connected with the layer of 
 acid, that acts as the inner coating of a 
 Leyden-jar used in connection therewith, 
 is at its normal potential. 
 
 Electrometer- Voltmeter. A voltmeter 
 in which the differences of potential to 
 be measured are employed to charge in- 
 sulated conductors, the electrostatic at- 
 tractions and repulsions of which result 
 
 in the deflection of a suitably suspended 
 metallic needle. 
 
 Electrometric. Of or pertaining to an 
 electrometer. 
 
 Electrometrical. (1) Of or pertaining to 
 the measuring of electrical forces. (2) Of 
 or pertaining to an electrometer. 
 
 Electromotive Arrangement or De- 
 vice. An electromotive source. 
 
 Electromotive Force. (1) The force 
 which starts or tends to start electricity 
 in motion. (2) The maximum or total 
 generated difference of potential which 
 exists in a circuit. 
 
 Electromotive Force of Induction. 
 
 The electromotive force developed by any 
 inductive action. 
 
 Electromotive Impulse. An impulse 
 producing an impulsive rush of elec- 
 tricity. 
 
 Electromotive Intensity. The vector 
 electric force at a point, as measurable by 
 the mechanical force that would be ex- 
 erted upon a unit electric charge at that 
 point. 
 
 Electromotive Series. A name some- 
 times given to a contact series. 
 
 Electromotive Source. Any source such 
 as a dynamo, or voltaic cell, capable of 
 producing an electromotive force. 
 
 Electromotograph. An apparatus in 
 which the friction of a platinum point 
 against a rotating cylinder of chalk is re- 
 duced by electrolytic action, consequent 
 on the passage of an electric current. 
 
 Electromotographic Telephone. A 
 loud-speaking telephone operating on the 
 principle of the electromotograph. 
 
 Electron. (1) A word formerly used for 
 amber. (2) The electric atoms whose pro- 
 jection from the cathode of a high-vacu- 
 um tube is supposed to constitute the 
 cathode rays or streamings. (3) An alloy 
 of gold and silver. 
 
 Electronecrosic. Pertaining to capital 
 punishment by means of electricity. 
 
 Electronecrpsis. A word proposed for 
 capital punishment by means of electric- 
 ity. (Not in use.) 
 
 Electronome. A name proposed for a 
 measurer of electricity. (Not in use.) 
 
 Electropath. One skilled in the art of 
 electro-therapy. 
 
 . A word sometimes em- 
 
 Electropathy 
 ployed for ele 
 
 ectro-therapeutics. 
 
 Electrophanic. Pertaining to capital 
 punishment by means of electricity. 
 
Ele.] 
 
 769 
 
 [Ele. 
 
 Electrophanical. Pertaining to capital 
 punishment by means of electricity. 
 
 Electrophanize. To inflict capital pun- 
 ishment by means of electricity. 
 
 Electrophany. A word proposed for cap- 
 ital punishment by means of electricity. 
 (Not in use.) 
 
 Electrophila. A word proposed for capi- 
 tal punishment by means of electricity. 
 (Nut in use.) 
 
 Electrophobia. A word proposed for un- 
 necessary fear of electricity. 
 
 Electrophone. A word proposed for a 
 carbon-contact telephone transmitter. 
 
 Electrophor. An orthography sometimes 
 employed for electrophorous. 
 
 Electrophoric. Of or pertaining to an 
 electrophorous. 
 
 Electrophoric Medium. A word some- 
 times employed for a dialectric medium. 
 
 Electrophorous. A simple form of elec- 
 trostatic induction apparatus. 
 
 Electropoion Liquid. An exciting 
 liquid, consisting of one part of bichro- 
 mate of potash dissolved in ten parts of 
 water, to which two and a half parts of 
 sulphuric acid have been gradually added. 
 
 Electroscope. An apparatus for showing 
 the presence of an electric charge, or de- 
 termining its character, whether positive 
 or negative, but not for measuring its 
 amount or value. 
 
 Electroscopic Gauge. A term formerly 
 applied to an early form of discharging 
 gold-leaf electroscope. 
 
 Electroscopically. By means of an elec- 
 troscope. 
 
 Electroscopy. The art of determining, 
 by means of an electroscope, the character 
 of an electric charge. 
 
 Electrostatic. Of or pertaining to elec- 
 trostatics. 
 
 Electrostatic Attraction. The mutual 
 attraction existing between unlike elec- 
 tric charges. 
 
 Electrostatic Aurora. Luminous phe- 
 nomena attending the production of an 
 electrostatic corona. 
 
 Electrostatic Balance. A form of bal- 
 ance employed for. the measurement of 
 high, direct, or alternating electromotive 
 forces, by the electrostatic effects pro- 
 duced by their charges. 
 
 Electrostatic Capacity. The quantity 
 of electricity which must be imparted to 
 a given conductor as a charge, in order 
 to raise its potential to unity, all neigh- 
 boring conductors being at zero potential. 
 49 
 
 Electrostatic Capacity of a Line. The 
 power possessed by an electric line wire 
 or conductor to act as a condenser. (2) The 
 capacity of a line or conductor for holding 
 an electric charge, as a condenser. 
 
 Electrostatic Charge-Current of Cable. 
 A momentary and violent rush of cur- 
 rent that occurs on the application of an 
 electromotive force to a submarine cable. 
 
 Electrostatic Circuit. A circuit formed 
 bylines of electrostatic flux with an elec- 
 tric source. 
 
 Electrostatic Corona. A luminous effect 
 produced on the surface of a thin sheet 
 of mica, or other insulating material, when 
 placed between two electrodes, subjected 
 to a compai'atively high difference of po- 
 tential. 
 
 Electrostatic Current. The time-rate- 
 of-flow of electrostatic flux. 
 
 Electrostatic Difference of Potential. 
 The difference of potential due to elec- 
 tric charges. 
 
 Electrostatic Discharge. A term some- 
 times employed for a disruptive dis- 
 charge. 
 
 Electrostatic Field. (1) The region of 
 electrostatic influence surrounding a 
 charged body. (2) A region traversed by 
 electrostatic flux. 
 
 Electrostatic Flux. A stress in the 
 ether which proceeds from a charged 
 body along definite curved lines or paths. 
 
 Electrostatic Flux-Paths. The paths 
 traversed by electrostatic flux. 
 
 Electrostatic Force. The force which 
 produces the attractions or repulsions of 
 charged bodies. 
 
 Electrostatic Generator. A general 
 term applied to various forms of influence 
 machines. 
 
 Electrostatic Hysteresis. (1) The en- 
 ergy consumed in an alternating-electro- 
 static field by the dielectric medium. (2) 
 Dielectric hysteresis. 
 
 Electrostatic Indicator. A name some- 
 times applied to an electrometer. 
 
 Electrostatic Induction. The induction 
 of an electric charge produced in a con- 
 ductor brought into an electrostatic field. 
 
 Electrostatic Induction-Machine. (1) 
 A machine in which a small initial charge 
 produces a greatly increased charge by 
 its inductive action on a rapidly rotated 
 disc of glass or other dielectric. (2) An 
 electrostatic influence machine. 
 
 Electrostatic Influence. A term some- 
 times used instead of electrostatic induc- 
 tion. 
 
Ele.] 
 
 770 
 
 [Ele. 
 
 Electrostatic Leakage. The gradual dis- 
 sipation of a charge due to insufficient in- 
 sulation. 
 
 Electrostatic Lines of Force. (1) Lines 
 of force produced in the neighborhood of 
 a charged body, by the presence of the 
 charge. (2) Lines extending in the direc- 
 tion in which the force of electrostatic at- 
 traction or repulsion acts. 
 
 Electrostatic Motion. Motion produced 
 by an electrostatic field somewhat simi- 
 lar to motion produced by a magnetic 
 field. 
 
 Electrostatic Motor. (1) A motor driven 
 by means of the induction of two varying 
 electrostatic fields at right angles to each 
 other. (2) Generally, a motor driven by 
 the interaction of two or more electro- 
 static fields. 
 
 Electrostatic Optical Strain. A strain 
 or deformation produced in an optical 
 medium by the stress of an electrostatic 
 field. 
 
 Electrostatic Potential. (1) The power 
 of doing electric work possessed by a unit 
 quantity of positive electricity residing 
 on the surface of an insulated body. (2) 
 That property in space by virtue of which 
 work is done when an electric charge is 
 moved therein. 
 
 Electrostatic Repulsion. The mutual 
 repulsion produced by two similar elec- 
 trostatic charges. 
 
 Electrostatic Resistance. The resist- 
 ance offered by any medium to the passage 
 of an electrostatic flux or an electrostatic 
 current. 
 
 Electrostatic Retardation. Retardation 
 in signalling, on long telegraphic lines, 
 due to electrostatic capacity. 
 
 Electrostatic Screening. Screening or 
 shielding from the inductive effects of an 
 electrostatic charge. 
 
 Electrostatic Strain. Strain produced 
 by the stress of an electrostatic field. 
 
 Electrostatic Stress. The force or pres- 
 sure in an electrostatic field which pro- 
 duces electrostatic strain in any sub- 
 stance placed therein. 
 
 Electrostatic Time, Constant. In an 
 
 electric circuit or condenser, possessing 
 
 capacity and resistance, the product of 
 
 k the capacity and the resistance, usually 
 
 expressed in seconds or farad-ohms. 
 
 Electrostatic Units. Units based on the 
 attractions or repulsions of two unit 
 charges of electricity at unit distance 
 apart. 
 
 Electrothanasing. Producing accidental 
 death by means of electricity. 
 
 Electrothanasis. A word proposed for 
 accidental death produced by electricity. 
 (Not in use.) 
 
 Electrothanasise. To produce accidental 
 death by electricity. 
 
 Electrothanatose. A word proposed for 
 capital punishment inflicted by means of 
 electricity. (Not in use.) 
 
 Electrothanatosic. Of or pertaining to 
 capital punishment by means of elec- 
 tricity. 
 
 Electrothanatosing. A word proposed 
 for execution by electricity. 
 
 Electrotisis. A word proposed for capital 
 punishment by means of electricity. (Not 
 in use.) 
 
 Electrotome. A term sometimes applied 
 to an automatic contact-breaker which 
 vibrates with sufficient rapidity to pro- 
 duce a musical sound. 
 
 Electrotonic. Of or pertaining to electro- 
 tonus. 
 
 Electrotonic Currents. In electro-ther- 
 apeutics, a current due to the internal 
 polarization of a nerve fibre between the 
 conducting core of the nerve and its en- 
 closing sheath. 
 
 Electrotonic Effect. An altered con- 
 dition of excitability produced in a nerve 
 when in the electrotonic state. 
 
 Electrotonic Excitability. The actual 
 excitability of a nerve when in the elec- 
 trotonic state. 
 
 Electro-Tonicity. A term sometimes 
 employed for electrotonus. 
 
 Electrotonus. The condition of altered 
 functional activity which occurs in a 
 nerve when subjected to the action of an 
 electric current. 
 
 Electrozemia. A word proposed for cap- 
 ital punishment by means of electricity. 
 (Not in use.) 
 
 Electrum. A name given by the ancients 
 to various substances that could be readily 
 electrified by friction. 
 
 Element. (1) Any kind of matter which 
 cannot be decomposed into simpler mat- 
 ter. (2) Matter that is formed or com- 
 posed of but one kind of atoms. 
 
 Element of Current. A term employed 
 in mathematical discussions to indicate 
 a very small part of a current, for ease in 
 considering its actions. 
 
 Element of Storage Battery. (1) A 
 single set of positive and negative plates 
 of a storage cell, so connected as to be 
 ready for placing in the acid liquid of the 
 containing jar or vessel. (2) A term some- 
 
Ele.] 
 
 771 
 
 [End. 
 
 times applied to one of the storage cells 
 of a battery. 
 
 Element of Voltaic Cell. Either of the 
 substances forming the couple of a voltaic 
 cell. 
 
 Elements of Armature Winding. The 
 separated conductors forming the parts of 
 an armature winding. 
 
 Elementary Matter. Matter which can- 
 not be decomposed into simpler matter. 
 
 Elevator Annunciator. An annunciator 
 connected with an elevator to indicate 
 the floor from which a signal is sent. 
 
 Elevator, Electric. An elevator oper- 
 ated by means of an electric motor. 
 
 Elevator Switch. A switch operated 
 from an elevator for controlling the op- 
 eration of the elevator motor. 
 
 Elliptical Rotary-Magnetization. The 
 magnetization which exists in a diphase 
 motor when two alternating-magnetic 
 fluxes coexist while out of phase with 
 each other. 
 
 Elliptical Rotation. A rotation as of a 
 point on an ellipse. 
 
 Elliptically Rotating Magnetic Field. 
 (1) A magnetic field which is subject to 
 elliptical rotation. (2) The rotation of 
 magnetic flux produced by two diphase 
 currents of unequal intensity, or of equal 
 intensity, but not of 90 phase difference, 
 
 Elongated Ring-Core. A hollow cylin- 
 drical core of comparatively great length. 
 
 Elongation of Needle. A phrase some- 
 times used for the maximum angular 
 deflection of a needle, or the maximum de- 
 flection of the spot of light on a galva- 
 nometer scale, when making one or more 
 swings. 
 
 Embedded Coils. (1) Coils or windings 
 placed in grooves or perforations on the 
 armature of a dynamo or motor. (2) Iron- 
 clad armature coils. 
 
 Embossing Telegraphic Instrument. 
 A registering telegraphic instrument in 
 which the signal is recorded in embossed 
 characters on a paper fillet. 
 
 Emergency Brake.-^-(l) A brake on a ve- 
 hicle employed only in emergency. (2) In 
 an electrically propelled vehicle a brake of 
 greater power than the ordinary brake, 
 and used only in emergency, as, for ex- 
 ample, a reversing switch to reverse the 
 direction of rotation of the motors. 
 
 Emergency Cable. A small, compara- 
 tively inexpensive and easily handled 
 cable, employed in the case of breaks in a 
 pole line due to floods, railroad wrecks. 
 
 etc., for opening up communication dur 
 ing repairs of the break. 
 
 Emergency Crew. A crew or gang in a 
 power distribution system for service in 
 case of a break-down, emergency, or fault 
 on the line. 
 
 Emergency Switch. An accessory 
 switch placed on a car controller for 
 reversing the motion of a car when 
 necessary. 
 
 Electrotisic. Pertaining to capital pun- 
 ishment by means of electricity. 
 
 Electrotising. Inflicting capital punish- 
 ment by means of electricity. 
 
 Emissivity. The specific radiating power 
 of a surface, or its ability to emit or throw 
 out radiant energy, usually expressed in 
 ergs per sq. cm. 
 
 Emissivity of Filament. The ability of 
 a filament to emit or radiate light and 
 heat when traversed by an electric cur- 
 rent. 
 
 Emmetropic Eye. The normal human 
 eye, or the human eye in its normal adjust- 
 ment and capability of accommodation. 
 
 Empanelled Wires. Wires placed inside 
 mouldings, or behind panels. 
 
 Emptied. A term sometimes applied to a 
 discharged secondary or storage battery, 
 or to a discharged condenser. 
 
 Enamelled Rheostat. A rheostat whose 
 coils consist of wires imbedded in a mass 
 of enamel, in close juxtaposition to a mass 
 of iron or other heat-conducting material. 
 
 Enclosed Arc-Lamp . An arc-lamp 
 whose carbons are enclosed by a closely fit- 
 ting globe, so as to maintain an atmosphere 
 around the arc practically devoid of oxy- 
 gon, thus diminishing the rate of con- 
 sumption of the carbons. 
 
 Enclosure of Magnetic Flux. (1) Link- 
 age of magnetic flux. (2) Confining mag- 
 netic flux in a ferric magnetic circuit. 
 
 End Connections. End windings. 
 
 Endlessness. The condition of a closed 
 ring of uniform cross-section in which the 
 magnetizing coils are wound uniformly 
 all around it, and a practically endless or 
 uniform magnetic field is obtained 
 throughout the length of the ring. 
 
 Endoscopie Lamp. A lamp provided for 
 the examination of a bodily cavity 
 through its natural outlet. 
 
 Endosmometer. An apparatus for meas- 
 uring the strength of endosmotic currents. 
 
 Endosmose. The unequal mixing of two 
 different liquids or gases through the 
 pores of an interposed medium. 
 
End.] 
 
 772 
 
 [Ent. 
 
 Endosmose, Electric. (1) The unequal 
 mixing of two liquids through the pores of 
 an interposed septum on. the passage of 
 an electric current through the septum. 
 (2) The transfer of liquid through an im- 
 mersed septum traversed by an electric 
 current. 
 
 Endosmosis. A word frequently employ- 
 ed in place of endosmose. 
 
 Endosmotic Equivalent. The ratio be- 
 tween the amount of water that passes 
 through a porous membrane into a saline 
 solution, and the amount of salt that 
 passes in the opposite direction. 
 
 Endothactic Cut-out. A cut-out ar- 
 ranged to throw a device into a circuit. 
 
 Endothactic Switch.. A switch which is 
 arranged to cut a device into a circuit. 
 
 Endothermic. Of or pertaining to the 
 absorption of beat. 
 
 Endothermic Reaction. A chemical ac- 
 tion attended with the absorption of heat. 
 
 End-to-End Joint. A term frequently 
 employed in place of butt-joint. 
 
 End Windings. (1) End connections. 
 (2) Conductors for connecting up bar 
 windings at the end of an armature. 
 
 Energetics. That branch of mechanics 
 which treats of the transfer of energy or 
 of its transformation. 
 
 Energy. The power of doing work. 
 
 Energy Component of Current. (1) In 
 an alternating-current circuit the com- 
 ponent of current which is in phase with 
 the impressed E. M. F. (2) In an alter- 
 nating-current circuit, the product of the 
 E. M. F. and the effective conductance. 
 
 Energy Component of E. M. F. (1) In 
 an alternating-current circuit the com- 
 ponent of E. M. F. which is in phase with 
 the current. (2) In an alternating-cur- 
 rent circuit, the product of the current 
 and the effective resistance. 
 
 Energy Current. (1) A term sometimes 
 used for active component of current in 
 an alternating-current circuit, as dis- 
 tinguished from the wattless component 
 of current. (2) The product in an alter- 
 nating-current circuit of the effective con- 
 ductance and the E. M. F. 
 
 Energy Efficiency of Storage Battery. 
 The watt-hour efficiency. 
 
 Energy, Electric. The power which 
 electricity possesses of doing work. 
 
 Energy Electromotive Force. (1) The 
 energy component of E. M. F. in an alter- 
 nating-current circuit. (2) The compon- 
 ent of E. M. F. which is in phase with the 
 current strength. 
 
 Energy Flux. (1) A stream of energy 
 transfer. (2) A surface integral of energj 
 transferred through a surface. 
 
 Energy Meter. A term sometimes ap- 
 plied to a wattmeter. 
 
 Energy of Motion. A word sometimes 
 used for kinetic energy. 
 
 Energy of Position. A word sometimes 
 
 used for potential energy. 
 Energy of Strain. A term sometimes 
 
 used for potential energy of deformation 
 
 elasticity. 
 
 Energy Resistance. In an alternating- 
 current circuit, the energy component of 
 impedance. 
 
 Energy Storage-Capacity. The total 
 amount of energy which a storage cell 
 can store up expressed in watt-hours. 
 
 Energy Transforming-Deviee. Any 
 device which will transform or change 
 energy from one form to another. 
 
 Engaged Test. (1) In telephony, the busy 
 test. (2) A test made by the operator at a 
 central exchange to ascertain whether the 
 subscriber desired is already engaged in 
 telephonic communication. 
 
 Engine. In telephony, a name sometimes, 
 used for a ringer or magneto-generator. 
 
 Engine Dynamo. A direct-connected 
 dynamo. 
 
 Engine Plane Signal. In a system of 
 mine signalling a circuit containing a 
 battery and bell at the engine house, and 
 a pair of uncovered iron wires along the 
 engine plane, or hoist run. for the purpose 
 of giving signals to the man at the engine. 
 
 Engine-Room Indicator. An indicator 
 placed in an engine-room. 
 
 Engine-Room Tachometer. A tacho- 
 meter suitable for permanent attachment 
 to an engine, dynamo, or other rotating 
 machine situated in an engine-room. 
 
 Engine Telegraph. A telegraph on board 
 ship for communicating orders to the 
 engine-room. 
 
 English Heat Unit. <1) The British heat 
 unit. (2) The heat necessary to raise a 
 pound of water 1 F. 
 
 Engraving, Electric. A method for elec- 
 trically etching or engraving a metallic 
 plate by covering it with wax, tracing 
 the design on the wax so as to expose the 
 metal, connecting the, metal with the 
 positive terminal of a battery, and placing 
 it in a bath opposite another plate of metal, 
 so that it will be electrically corroded on 
 its exposed parts. 
 
 Entering Current of Telegraphic Cir- 
 cuit. A term employed to designate the- 
 
Ent.] 
 
 773 
 
 [Equ. 
 
 current on a telegraphic line or conductor 
 near the battery. 
 
 Entrefer. (1) The gap of non-magnetic 
 material through which the field flux has 
 to pass at the surface of the armature 
 of a dynamo-electric machine, composed 
 either of an air-gap or of air and copper. 
 (2) The width of the non-magnetic gap, 
 as distinguished from the width of the 
 clearance or simple air-gap of a smooth 
 cored armature. 
 
 Entropy. (1) In thermo-dynamics the 
 non-available energy in any system. 
 (Clausius and Mayer.) (2) In thermo- 
 dynamics the available energy in any 
 system. (Tait, Thomson, Maxwell.) 
 
 Entropy, Electric. A term proposed by 
 Maxwell for use in thermo-electric phe- 
 nomena, to include the doctrine of entropy 
 in electric science. 
 
 Environment. The accompaniments or 
 surroundings of any thing or condition. 
 
 Eolotropic. (1) Heterogeneous with re- 
 spect to direction. (2) A medium in which 
 equal stresses applied in different direction 
 do not produce equal and similar strains. 
 
 Eolotropic Dielectric. A dielectric pos- 
 sessing eolotropic properties. 
 
 Eolotropic Medium. Any medium pos- 
 sessing eolotropic properties. 
 
 Eolotropic "Wire-Grating. An eolo- 
 tropic screen employed by Hertz in his 
 experiments on electric radiation. 
 
 Eolotropism. The possession of eolo- 
 tropic properties. 
 
 Eolotropy.-The doctrine, theory, or condi- 
 tion of eolotropism. 
 
 Epoch. In the case of a vibrating body, 
 the time or the angle reckoned from the 
 point of starting to the point of maximum 
 positive elongation. 
 
 Equal Arms Electric Balance. An 
 
 electric Wheatstone bridge or balance em- 
 ploying equal arms. 
 
 Equal Deflection Method. A method 
 of measuring a resistance, electromotive 
 force or current which consists in obtain- 
 ing the same deflection on a galvanometer 
 in the circuit with a given shunt. 
 
 Equalizer. (1) An equalizing bar. (2) A 
 term employed for an equalizer wire. (3) 
 A device for equalizing electric pressure 
 over a system. 
 
 Equalizer Feeder. A feeder whose sole 
 or principal purpose is to equalize the 
 pressure between the ends of two or more 
 other feeders, as distinguished from sup- 
 plying current to feeding points. 
 
 Equalizer Feeder-Switch. A switch 
 employed to throw a feeder equalizer in 
 or out of circuit. 
 
 Equalizer S witch. A switch governing 
 a resistance suitable for feeder regulation. 
 
 Equalizer Wire. (1) An equalizing bar. 
 (2) A wire connecting the series windings 
 of two or more compound-wound genera- 
 tors operated iii parallel. 
 
 Equalizing Bar. A bar joining the series 
 coils of two parallel-connected, compound- 
 wounds generators, so that any excess of 
 current supplied by the armature of one 
 machine must necessarily excite the 
 other machine to the same extent. 
 
 Equalizing Current. The current pass- 
 ing through an equalizing bar between 
 two dynamos. 
 
 Equalizing Dynamo. A dynamo em- 
 ployed in systems of three or five-wire 
 distribution to supply one pair of mains 
 which may be unduly loaded so as to 
 equalize the pressure. 
 
 Equalizing Resistance-Coils. Resist- 
 ance coils employed in a system of feeder 
 regulation. 
 
 Equalizing Wires.-^(l) Two wires or con- 
 ductors, one of which is employed for 
 connecting the positive brushes and 
 the other for connecting the negative 
 brushes of compound-wound dynamos, 
 when connected in parallel. (2) Wires 
 connecting corresponding segments in a 
 multipolar armature winding. 
 
 Equator of Magnet. (1) A point ap- 
 proximately midway between the poles 
 of a straight bar magnet, or nearly mid- 
 way from the poles of a horse-shoe mag- 
 net, if measured along the bar from each 
 pole. (2) A line of neutral points on a 
 magnet. 
 
 Equatorial. Of or pertaining to the 
 equator. 
 
 Equatorial Region of Magnet. The 
 portions of a magnet which lie near the 
 magnetic equator. 
 
 Equatorially. In the direction of the 
 equator. 
 
 Equiangular Impedances. Imped- 
 ances which have the same angle. 
 
 Equilibrium. The condition of a body 
 on which several forces are acting, so that 
 their resultant is zero. 
 
 Equilibrium of Radiation. The condi- 
 tion of a radiating body in which the 
 radiant energy it absorbs is equal to that 
 which it emits. 
 
 Equimolecular Solutions. Solutions 
 which contain, in the same quantity of 
 
Equ.] 
 
 774 
 
 [Eth. 
 
 tlie solvent, quantities of the dissolved 
 substance proportional to their molecular 
 weights. 
 
 Equipotential. Of or pertaining to an 
 equality of potential. 
 
 Equipotential Electrostatic-Surfaces. 
 (1) Surfaces on or surrounding charged 
 bodies, all points of which are at the same 
 electric potential. (2) Electric surfaces 
 perpendicular to the lines of electric 
 force, over which a quantity of electricity, 
 considered as being concentrated at a 
 point, may be moved without doing work. 
 
 Equipotential Magnetic-Surfaces. 
 Surfaces surrounding the poles of a mag- 
 net or system of magnets, where the 
 magnetic potential is the same. 
 
 Equivalent Air-Gap. An air-gap which 
 would have the same magnetic resist- 
 ance as a joint, assuming the permeabil- 
 ity of the metal to be unaffected by the 
 cutting. 
 
 Equivalent Conductance. (1) A con- 
 ductance such that if inserted in a sinu- 
 soidal-current circuit would absorb en- 
 ergy at the same rate as the actual 
 conductance in a non-sinusoidal current 
 circuit. (2) Virtual conductance. (3) 
 The effective conductance of an alternat- 
 ing-current system or conductor. 
 
 Equivalent Conductivity. The mole- 
 cular conductivity of a solution divided 
 by the valency. 
 
 Equivalent Impedance. Such an im- 
 pedance in a simple-harmonic-current cir- 
 cuit as would, with the same effective 
 current strength, absorb energy at the 
 same rate as an actual impedance in a 
 complex-harmonic-current circuit. 
 
 Equivalent Heactance. Such a react- 
 ance in a simple-harmonic-current circuit 
 as would permit energy to be absorbed, 
 with the same effective current strength, 
 at the same rate as an actual reactance 
 in a complex-harmonic-current circuit. 
 
 Equivalent Resistance. (1) A single 
 resistance which may replace a number 
 of resistances in a circuit without alter- 
 ing the current traversing it. (2) Such a 
 resistance in a simple-harmonic-current 
 circuit as would permit energy to be ab- 
 sorbed, with the same effective current 
 strength, at the same rate as an actual re- 
 sistance in a complex-harmpnic-current 
 circuit. (3) The effective resistance of an 
 alternating-current system or conductor. 
 
 Equivalent Resistance and Induct- 
 ance. In an alternating-current circuit, 
 or system of circuits, such a resistance 
 and inductance as would, if substituted 
 for the actual system, cause the same 
 
 strength and activity of current to pusa 
 through the conducting leads. 
 
 Equivalent Resistance and Reactance. 
 Such a resistance and reactance in a 
 simple alternating-current circuit, as 
 would cause the same current both in 
 magnitude and phase to flow in the main 
 leads, as when a number of multiple arc 
 circuits are connected to them. 
 
 Equivalent Sinusoid. A curve repre- 
 senting a sinusoid, which, for purposes of 
 analytical investigation, has been takenas 
 the equivalent in power of a curve ol 
 pressure or current which is not sinu- 
 soidal. 
 
 Equivolt. A term proposed for unit ot 
 electric energy applied especially to 
 chemical decomposition. (Not in general 
 use.) 
 
 Erb's Standard Size of Electrodes. 
 Standard sizes of electrodes, generally 
 adopted in electro-therapeutics. 
 
 Erg. (1) The 1 C. G. S. unit of work, or 
 the work done when unit C. G. S. force 
 is overcome through unit C. G. S. dis- 
 tance. (2) The work accomplished when 
 a body is moved through a distance of 
 one centimetre with the force of one 
 dyne. (3) A dyne-centimetre. 
 
 Erg-Meter. (1) An apparatus for meas- 
 uring the work of an electric current in 
 ergs. (2) An energy-meter. 
 
 Ergometer. An erg-meter. 
 
 Erg : s. An abbreviation proposed for erg- 
 per-second, the C. G. S. unit of power. 
 
 Erg-Ten. (1) A term proposed for ten mil- 
 lion ergs ; 10 10 ergs, or one erg multiplied 
 by low. ( 2 ) A kilo-joule. 
 
 Error. In telegraphy, a blunder or inac- 
 curacy either of transmitted signals, as in 
 sending a message, or of deciphered, re- 
 transmitted, or recorded signals, as in re- 
 ceiving a message. 
 
 Escape, Electric. (1) A partial loss of 
 current to earth by imperfect insulation. 
 (2) A loss of charge on an insulated con- 
 ductor. 
 
 Escapement, Electric. An electrically 
 actuated clock escapement. 
 
 Essential Resistance. A term some- 
 times used for internal resistance. 
 
 Etching, Electric. A term sometimes 
 used for electric engraving. 
 
 Ether. The highly tenuous, elastic fluid 
 that is assumed to fill all space, and by 
 whose vibrations or waves, light, radiant 
 heat, and electro-magnetic radiation are 
 transmitted. 
 
Eth.] 
 
 775 
 
 [Exp. 
 
 Ether Flow Vortices. Vortices in the 
 ether upon whose alleged existence is 
 based a hypothesis for the explanation of 
 magnetic phenomena. 
 
 Ether Path of Reluctivity. A concep- 
 tion employed in studying the reluctivity 
 of a magnetic medium which regards the 
 magnetic flux as taking two multiple- 
 connected paths, one the path of metallic- 
 reluctivity through the mass of the sub- 
 stance, and the other the path of ether- 
 reluctivity, through its associated ether. 
 
 Ether Streamings. Streamings that are 
 assumed to exist in the ether around a 
 magnet, or around a charged conductor. 
 
 Ethereal. Of or pertaining to the ether. 
 
 Eudiometer. (1) A voltameter in which 
 separate graduatedvesselsare prepared for 
 the reception and measurement of the 
 gaseous products evolved during electro- 
 lysis. (2) A graduated glass tube for hold- 
 ing and measuring the volume of the 
 evolved gas. 
 
 Eudiometric. Of or pertaining to an 
 eudiometer. 
 
 Eudiometrically. By means of an eudio- 
 meter. 
 
 Evanescent Telegraphic Signal. Any 
 telegraphic signal which is not perma- 
 nently recorded. 
 
 Evaporation. The change from the liquid 
 to the vaporous state. 
 
 Evaporation, Electric. The formation 
 of vapors on the surfaces of solid or 
 liquid substances by the influence of neg- 
 ative electrification. 
 
 Even Harmonics. In a complex harmon- 
 ically-varying quantity, the harmonics 
 whose frequencies are even multiples of 
 the, fundamental frequency. 
 
 Ewing's Theory of Magnetism. A 
 theory of magnetism proposed by Ewiug, 
 based on the assumption of originally 
 magnetized particles. 
 
 Excitability of Nerve or Muscular 
 Fibre, Electric. The effect produced 
 by an electric current in stimulating a 
 nerve of a living animal, or in producing 
 an involuntary contraction of a muscle. 
 
 Excitant. (1) That which excites. 
 
 (2) The electric or magnetic force which 
 energizes a receptive device. 
 
 Excitation. (1) The production of elec- 
 trification by any means. (2) The pro- 
 duction of magnetism by any means. 
 
 (3) The energizing of any electro or mag- 
 neto-receptive device. (4) The produc- 
 tion of the magnetic field in a dynamo 
 
 or motor. (5) The stimulation of a 
 muscle or nerve fibre. 
 
 Exciter. Anything which causes an ex- 
 citation. 
 
 Exciter Dynamo. A dynamo used for 
 the separate excitation of another dynamo. 
 
 Exciter of Field. A dynamo, or othel 
 electric source, employed in the separate 
 excitation of tne field of a dynamo. 
 
 Exciting Ampere-Turns. The ampere- 
 turns in the field-winding of a generator 
 or motor employed for the excitation of 
 its field. 
 
 Exciting Fluid or Liquid of Voltaic 
 Cell. The electrolyte of a voltaic cell. 
 
 Execution, Electric. Inflicting capital 
 punishment by electricity. 
 
 Exhaust Fan, Electric. An electrically 
 driven exhaust fan. 
 
 Exhaust Wheel, Electric. An electri- 
 cally driven rotary device Tor drawing or 
 exhausting the air from an apartment. 
 
 Exhausted Storage Cell. An emptied 
 storage cell. 
 
 Exhausted Voltaic Cell. A voltaic cell 
 in a state of exhaustion. 
 
 Exhaustion, Electric. Physiological ef- 
 fects resembling those produced by sun- 
 stroke, resulting from prolonged exposure 
 to powerful voltaic arcs. 
 
 Exhaustion of Primary Voltaic Cell. 
 The inability of a primary voltaic cell 
 to furnish any further current, unless 
 fresh electrolyte, or new positive ele- 
 ments, or both, are supplied to it. 
 
 Exhaustion of Secondary Voltaic 
 Cell. The inability of the cell to furnish 
 any further current until again acted on 
 by a charging current. 
 
 Exosmosis. The osmotic current which 
 is directed towards the lower level. 
 
 Exothactic Cut-Out. A cut-out de- 
 signed to remove a device from a circuit. 
 
 Exothatic Switch. A switch designed to 
 cut a device out of circuit. 
 
 Exothermic. Of or pertaining to an exo- 
 thermic reaction. 
 
 Exothermic Reaction. A chemical re- 
 action attended by the evolution of heat. 
 
 Expanding Magnetic Whirls. Mag- 
 netic whirls sent out from a conductor 
 through which a current of gradually in- 
 creasing strength is passing, or from a 
 magnet whose magnetism is gradually in- 
 creasing. 
 
 Expanding of Magnetic Field. The 
 increase in the strength of a magnetic 
 flux and of the region traversed by it. 
 
Exp.] 
 
 776 
 
 [Eye. 
 
 Expansibility. (1) The quality of being 
 expansible. (2) Possessing the capacity 
 for expansion. 
 
 Expansion. The act of increasing in 
 length, surface, or volume. 
 
 Expansion, Electric. The increase in 
 volume produced in a body by giving it 
 an electric charge. 
 
 Expansion Joint. A joint suitable for 
 tubes or pipes exposed to considerable 
 changes of temperature, in which a slid- 
 ing joint is provided to safely permit a 
 change in length on expansion or contrac- 
 tion. 
 
 Expended Energy. The energy em- 
 ployed to produce any result. 
 
 Exploder, Electric. A small magneto- 
 electric machine used to produce a high 
 electromotive force, employed in the 
 direct firing of blasts. 
 
 Exploration of Magnetic Field. 
 
 Mapping out the location and density of 
 a magnetic field by any suitable means. 
 
 Explorer, Electric. An apparatus oper- 
 ated by means of induced currents for 
 the purpose of locating bullets and other 
 foreign metallic substances in the human 
 body. 
 
 Exploring Needle. (1) A form of ex- 
 ploring probe. (2) A magnetic needle 
 employed in exploring a magnetic field. 
 
 Explosive Distance. A term sometimes 
 employed for sparking distance. 
 
 Extension Bell. (1) An extension call- 
 bell. (2) A call-bell situated at a distance 
 from the apparatus to which it calls at- 
 tention. 
 
 Extension Call-Bell. An additional bell 
 connected with the call-bell of a telephone 
 or other device, and placed in some other 
 portion of a building, for the purpose of 
 calling the subscriber to the instrument 
 when he may be in a distant part of the 
 house. 
 
 Extension Plates for Poles. Double 
 plates forming between them a loop for 
 an upper extension or branch of a guy- 
 rod supporting a pole. 
 
 Extension Push-Button. An auxiliary 
 push-button placed at a distance from a 
 main push-button. 
 
 Extensometer. A form of apparatus for 
 measuring the elongation of a substance 
 under stress. 
 
 External Armature Generator. A 
 generator in which the armature is ex- 
 ternal to the field frame. 
 
 External Characteristic of Dynamo. A 
 curve showing the E. M. F. at the termi- 
 nals of a dynamo under varying currents, 
 as distinguished from an internal charac- 
 teristic showing the internal E. M. F. 
 
 External Circuit. That part of a circuit 
 with which an electric source is con- 
 nected that is external to that electric 
 source. 
 
 External Magnetic Circuit. (1) That 
 portion of a magnetic circuit which lies 
 outside the magnetic source. (2) That 
 portion of the circuit of a magnet which 
 lies outside its mass or core. 
 
 External Magnetic Field. That portion 
 of a magnetic field which lies outside the 
 body of a magnet. 
 
 External - Secondary Resistance. In 
 the secondary circuit of a transformer, 
 the resistance external to the transformer. 
 
 Extra-Current Direct. A term some- 
 times employed for the current produced 
 in the primary of a transformer on, the 
 breaking of its circuit. 
 
 Extra-Current Inverse. A term some- 
 times employed for the current produced 
 in the primary current of a transformer 
 on the making of its circuit. 
 
 Extra-Current Neutralize!*. A device 
 for reducing electro-magnetic retardation 
 which consists of a shunted condenser in- 
 serted in the main circuit. 
 
 Extra Currents. Currents produced in a 
 circuit by self-induction. 
 
 Extra-High-Potential System. In the- 
 National Electric Code a potential above 
 3000 volts. 
 
 Extra-High-Potential "Wires. Wires 
 suitable for use in extra-high-potential 
 systems. . 
 
 Extraneous Field. A leakage magnetic 
 field. 
 
 Extraordinary Resistance. A term 
 sometimes used for external resistance. 
 (Not in use.) 
 
 Extra-European Message. In Europe a 
 message sent to or received from some 
 point beyond the geographical limits of 
 Europe. 
 
 Extra-Polar. Lying beyond or outside 
 the poles. 
 
 Extra-Polar Region. In electro-thera- 
 peutics, the region which lies outside or 
 beyond the therapeutic electrodes. 
 
 Eye-Piece. The ocular of a telescope o* 
 microscope. 
 
*] 
 
 777 
 
 [Fan. 
 
 F. A symbol proposed for farad, the prac- 
 tical unit of capacity. 
 
 F. A symbol proposed for force. 
 
 of. A symbol for magnetomotive force. 
 (Partly international usage.) 
 
 f. A symbol proposed for force. (Partly 
 international usage.) 
 
 P. M. A contraction for field magnets. 
 
 F. W. G-. A contraction for French wire 
 gauge. 
 
 Fac-Simile Telegraph. A general term 
 embracing the apparatus employed in 
 fac-simile telegraphy. 
 
 Fac-Simile Telegraphy. (1) A system 
 whereby a fac-simile or copy of a chart, 
 diagram, picture, or signature, is tele- 
 graphically transmitted from one station 
 to another. (2) Pan-Telegraphy. 
 
 Factor. Each of the several quantities 
 which are multiplied together to form a 
 product. 
 
 Factor of Safety. (1) The ratio of the 
 computed or measured strength of a 
 structure to the maximum strength it 
 will be called upon to exert. (2) An 
 amount by which the breaking load or 
 stress in any system must be divided in 
 order to obtain the safe load or stress. (3) 
 A multiple of the calculated strength re- 
 quired of a structure adopted to ensure 
 safety. 
 
 Factor of Safety of Demagnetization. 
 The ratio of the demagnetizing force in 
 an aero-ferric magnetic circuit corre- 
 sponding to an actually existing residual 
 flux density, to the actually existing 
 mean demagnetizing force. 
 
 Fahrenheit Thermometric Scale. The 
 thermometric scale in which the length of 
 the thermometer tube, between the melt- 
 ing point of ice and the boiling point of 
 water, is divided into 180 equal parts or 
 degrees. 
 
 Fall-Back Indicator. A term sometimes 
 employed for drop indicator. 
 
 Fall of Potential. The drop of poten- 
 tial. 
 
 Fall of Pressure. The drop of pressure. 
 
 Fall of Pressure in Active Conductor. 
 The fall of pressure due to the passage 
 of the current, and equal to the product 
 of the current strength by the resistance. 
 
 False. (1) Untrue. (2) Provisionally as- 
 sumed. 
 
 False Discharge of Submarine Cable. 
 An oscillatory discharge produced in a 
 cable as distinguished from an aperiodic 
 discharge. 
 
 False Electric Current. A virtual elec- 
 tric current distribution which has no ac- 
 tual existence, but which is assumed in 
 order to comply with the' conditions of 
 an electro-magnetic field. 
 
 False Electrification. A virtual electri- 
 fication having no real existence, but 
 which may be assumed in order to deter- 
 mine a given distribution of electro-mag- 
 netic energy in a medium. 
 
 False Magnetic Currents. Virtual mag- 
 netic currents having no real existence 
 but assumed for the purpose of conform- 
 ing to the requirements of a given electro- 
 magnetic distribution. 
 
 False Magnetic Poles of Earth. A 
 term proposed to designate the place or 
 places on the earth which apparently act 
 as magnetic poles, in addition to two true 
 magnetic poles in the neighborhood of 
 the earth's geographical poles. 
 
 False Resistance. A resistance arising 
 from a counter electromotive force, and 
 not directly from the dimensions of the 
 circuit, or from its specific resistance. 
 
 False Zero. (1) A zero of a measuring in- 
 strument accepted at the position it nat- 
 urally assumes under the action of forces 
 other tha.n those impressed in the meas- 
 urement. (2) A zero taken midway be- 
 tween two unequal and opposite deflec- 
 tions of a measuring instrument. (3) Iu 
 Wheatstone-Bridge measurement, the po- 
 sition of the galvanometer needle natu- 
 rally assumed under the influence of E. 
 M. F. in the bridge before the application 
 of the testing battery. (4) In cable test- 
 ing the position of the spot of light when 
 the testing battery is disconnected and the 
 galvanometer short-circuit key is open. 
 (5) A cable zero, or zero to the existing 
 current in a cable. (6) The natural zero. 
 
 Fan Guard. A wire guard placed around 
 an electric fan, to prevent the revolving 
 blades from coming in contact with sur- 
 rounding objects. 
 
 Fan Motor. (1) An electric motor suit- 
 
Far.] 
 
 778 
 
 [Fee. 
 
 able for driving a fan. (2) An electric 
 motor carrying a fan. 
 
 Far-Leading Dynamo. A motor-dyna- 
 mo placed as a shunt across a pair of long 
 mains, to compensate for their drop in 
 voltage. 
 
 Farad.-^-(l) The practical unit of electric 
 capacity. (2) Such a capacity of a con- 
 ductor or condenser that one coulomb of 
 electricity is required to produce therein 
 a difference of potential of one volt. 
 
 Faraday Effect. The rotation of the 
 plane of polarization of a beam of plane 
 polarized light on its passage along a 
 magnetic field. 
 
 Faraday's Cube. An insulated room or 
 cube covered on the inside with tin-foil, 
 which, when charged on the outside, gives 
 no electrical indications to an observer on 
 the inside even to delicate instruments. 
 
 Faraday's Dark Space. The gap in the 
 continuity of the luminous discharges 
 that occur between the positive and nega- 
 tive electrodes. 
 
 Faraday's Disc. A metallic disc movable 
 in a magnetic field on an axis parallel to 
 the direction of the flux. 
 
 Faraday's Net. An insulated net of cot- 
 ton, gauze, or other similar conducting 
 material, capable of being turned inside 
 out without being thereby discharged, 
 and employed for demonstrating the fact 
 that the charge of an insulated conductor 
 is limited to its outer surface. 
 
 Faradic. Of or pertaining to Faraday. 
 
 Faradic Adapter. A device for readily 
 permitting commercial incandescent- 
 light circuits to be employed for electro- 
 therapeutic work, with an induction 
 coil. 
 
 Faradic Battery. A term erroneously 
 used for a faradic coil, or induction coil. 
 
 Faradic Brush. A brush-shaped elec- 
 trode employed in the medical applica- 
 tion of electricity. 
 
 Faradic Coil. A term sometimes used for 
 a faradic machine, or medical induction 
 coil. 
 
 Faradic Current. (1) In electro-thera- 
 peutics, a current produced by an induc- 
 tion coil, or magneto-electric machine. 
 (2) A rapidly alternating current, as dis- 
 tinguished from a direct current. 
 
 Faradic Excitability. Muscular or ner- 
 vous excitability produced by the em- 
 ployment of faradic currents. 
 
 Faradic Excitation. The excitement of 
 muscle or nerve fibre by faradio cur- 
 rents. 
 
 Faradic Induction Apparatus. An in- 
 duction coil apparatus for producing fara- 
 dic currents. 
 
 Faradic Irritability. Muscular contrac- 
 tions produced by the action of faradia 
 currents on a nerve. 
 
 Faradic Machine. Any machine for 
 producing faradic currents. 
 
 Faradism. A word sometimes employed 
 for faradization. 
 
 Faradization. In electro-therapeutics, 
 
 the effects produced on the nerves or 
 
 muscles by the use of faradic currents. 
 Faradization of Skin. Treatment of the 
 
 skin by faradic currents. 
 Fast Repeater. A telegraphic repeater 
 
 or translator especially designed for rapid 
 
 signalling. 
 Faradometer. A term proposed for an 
 
 instrument designed for the measurement 
 
 of faradic currents. 
 Fast-Speed Telegraphy. Automatic or 
 
 machine telegraphy. 
 Fathom. (1) A unit of length equal to six 
 
 feet or two yards. (2) Approximately, the 
 
 one-thousandth part of a nautical mile. 
 
 Fault. Any defect in the proper working 
 of a circuit, due to ground contacts, cross 
 contacts, or disconnections. 
 
 Fault Resistance. The resistance of a 
 fault. 
 
 Fault Searcher. An instrument em- 
 ployed in connection with a telephone or 
 other sensitive current-detector, for de- 
 termining the moment when a portion of 
 the cable containing the fault comes 011 
 board ship, while the same is being picked 
 up for purposes of repair. 
 
 Feather Edge. A strip of wood laid by 
 the side of a layout of cable in a cable 
 tank to protect it from the pressure of 
 superincumbent flakes. 
 
 Feed. (1) To supply with an electric cur- 
 rent. (2) To move or regulate one or 
 both of the carbon electrodes in an arc- 
 lamp. 
 
 Feed-Line. A feeder. 
 
 Feed- Wire Insulator. An insulator em- 
 ployed for the support of a feed-wire. 
 
 Feeder. One of the conducting wires 
 through which the current is distributed 
 to the main conductors, as distinguished 
 from a conductor which supplies trans- 
 lating devices directly. 
 
 Feeder-and-Main System of Distri- 
 bution. A system for the transfer of 
 electric energy in which, for the pur- 
 pose of preventing too great a drop of 
 
Fee.] 
 
 
 779 
 
 [Fer. 
 
 pressure on the mains, they are connected 
 at suitable points to the feeder wires, in- 
 stead of to the generator or generators. 
 
 Feeder Ammeter. An ammeter placed 
 in the circuit of a feeder, usually at a 
 switchboard. 
 
 Feeder Block. A block containing a 
 feeder cut-out. 
 
 Feeder Box. A distribution box supplied 
 by a feeder, into which a feeder enters to 
 receive its distributing connections. 
 
 Feeder Clamp. Any clamping device for 
 connecting or fastening a feeder wire to a 
 trolley wire or to a main. 
 
 Feeder Cleat. A clamp furnished with a 
 device whereby a feeder wire may be 
 readily connected to a trolley wire. 
 
 Feeder Distribution. A feeder - and- 
 main system of distribution. 
 
 Feeder Equalizer. A resistance coil in- 
 serted in the circuit of a feeder, with or 
 without means for adjustment, for the 
 purpose of equalizing the pressure at the 
 feeding points. 
 
 Feeder - Equalizer Resistance. A 
 feeder regulator. 
 
 Feeder-Equalizer Switch. An equa- 
 lizer switch employed in feeder systems. 
 
 Feeder for Trolley Conductor. A wire 
 or conductor of low resistance employed 
 for transmitting elec.tric pressure direotly 
 from the power station to some distant 
 point of the trolley wire, for the purpose 
 of maintaining the potential at that point. 
 
 Feeder-Mechanism for Arc-Lamps. 
 
 An arc-lamp feeding mechanism. 
 
 Feeder Panel of Switchboard. A panel 
 of a switchboard, furnished with the 
 necessary switches, voltmeters, ammeters, 
 and safety devices, to which the feeder 
 wires are connected. 
 
 Feeder Plug. A metallic bolt which, 
 when inserted in a trolley car in place of 
 an insulated bolt, establishes connection 
 between the trolley wire and a feeder 
 through the span wire. 
 
 Feeder Potential. (1) The electric poten- 
 tial of any feeder relatively to ground. (2) 
 The difference of potential between any 
 pair of feeder conductors. 
 
 Feeder Regulators. (1) Artificial re- 
 sistances introduced into the circuit of 
 idle feeders, so as to increase the drop of 
 pressure existing in them. (2) A form of 
 special transformer, whose primary is con- 
 nected across the mains and its secondary 
 is in series with one feeder wire, and is 
 employed to produce a pressure which, 
 by means of a suitable reversing switch, 
 
 either aids or opposes the alternating pres- 
 sure on the mains. (3) A term sometimes 
 applied to boosters. 
 
 Feeder Switch. Any switch placed on a 
 feeder panel that is connected with the 
 separate feeders and employed for the 
 purpose of connecting or disconnecting a 
 generator with such feeder. 
 
 Feeder System. A system of distribution 
 in which the service wires are connected 
 by means of feeders to certain centres of 
 distribution. 
 
 Feeder Tubes. Underground tubes pro- 
 vided for the reception of the feeder wires. 
 
 Feeders. Wires supplying currents to 
 main conductors at different points, to 
 equalize their potential under load, as 
 distinguished from wires supplying cur- 
 rents directly to the load. 
 
 Feeding Centre. (1) A centre of distri- 
 bution supplied by a feeder. (2) A feed- 
 ing point. 
 
 Feeding Conductors or Wires. Feed- 
 ers. 
 
 Feeding Device or Mechanism for 
 Electric Arc-Lamps. A device for 
 maintaining the carbon electrodes of an 
 arc-lamp at a constant distance apart dur- 
 ing their consumption. 
 
 Feeding Point. (1) A point of connection 
 between a feeder and the mains. (2) A 
 feeding centre. 
 
 Fender. A device placed in front of a 
 street car for preventing accidental in- 
 jury to pedestrians passing in front of the 
 moving car. 
 
 Ferranti Effect. (1) An increase in the 
 electromotive force or difference of po- 
 tential of mains or conductors carrying 
 alternating currents,which exists towards 
 the end of the same furthest from the 
 terminals that are connected with the 
 source. (2) A negative drop in pressure. 
 
 Ferric Circuit. A ferric-magnetic cir- 
 cuit. 
 
 Ferric Inductance Coil. An inductance 
 coil provided with an iron core. 
 
 Ferric Magnetic Circuit. A magnetic 
 circuit composed wholly of iron. 
 
 Ferric Path of Reluctivity. That por- 
 tion of the flux paths through iron or 
 other magnetic material, in which the 
 flux passes through the metal proper, as 
 distinguished from that which is assumed 
 to pass through the ether lying within 
 such material. 
 
 Ferro-Magnet. A word sometimes em- 
 ployed for an ordinary magnet made of 
 paramagnetic material, as distinguished 
 
Fer.] 
 
 780 
 
 [Fil. 
 
 from a diamagnet, or one formed of dia- 
 magnetic material. 
 
 Ferro-Magnetic. A word sometimes em- 
 ployed for paramagnetic. 
 
 Ferro-Magnetic Substances. Para- 
 magnetic substances. 
 
 Ferrp-Magnetism. Magnetism possessed 
 by iron or other paramagnetic substances. 
 
 Ferro-Manganese Alloys. Various al- 
 loys employed for the wires of resistance 
 coils, whose electric resistance is not sen- 
 sibly affected by changes of temperature. 
 
 Fibre Suspension. Suspension of a 
 needle or other system by a fibre of un- 
 spun silk, quartz or other suitable ma- 
 terial. 
 
 Fibrone. A variety of insulating ma- 
 terial. 
 
 Fictive Layers. Layers in a dielectric 
 possessing equipotential surfaces due to 
 the accumulation of charges insufficient 
 to produce a constant potential within the 
 dielectric, but, nevertheless, capable of 
 modifying its potential. 
 
 Fiducial Point. (1) A fixed point or refer- 
 ence point in the scale or indications of 
 a galvanometer or other measuring in- 
 strument. (2) A temporary zero point. 
 
 Field. (1) A term sometimes used for a 
 magnetic field. (2) A term sometimes 
 used for an electrostatic field. 
 
 Field Coils. The field-magnet coils of a 
 dynamo-electric machine or motor. 
 
 Field, Electric. A term sometimes used 
 in place of electrostatic field. 
 
 Field Frequency. The frequency of 
 revolution in a rotating magnetic-field. 
 
 Field-Magnet Coils. The magnetizing 
 coils on the field magnets of a dynamo or 
 motor. 
 
 Field-Magnet Regulating Box. (1) 
 The field regulating box. (2) A resistance 
 box inserted in the circuit of the field 
 magnets. 
 
 Field Magnets. The magnets which pro- 
 duce the magnetic field or flux in which 
 the armature of a dynamo or motor ro- 
 tates. 
 
 Field of Force. (1) The space traversed 
 by electrostatic or magnetic flux. (2) An 
 electrostatic or magnetic field. 
 
 Field of Vortex Ring. The field of in- 
 fluence possessed by a vortex ring. 
 
 Field Poles. The poles of the field mag- 
 nets of a dynamo or motor. 
 
 Field-Regulating Box.; (1) A resistance 
 box, inserted in series with the field mag- 
 net coils, for the purpose of varying the 
 
 strength of the magnetizing current. (2) 
 A regulating box or rheostat connected 
 with the field circuit of a generator, for 
 the purpose of controlling its pressure. 
 
 Field Rheostat. A field-regulating box. 
 
 Field Spools of Dynamo or Motor. 
 The magnetizing coils of the field-mag- 
 nets of a dynamo or motor. 
 
 Field Strength. The magnetic intensity 
 of a field. 
 
 Field Telegraph Line. A semi-perma- 
 nent telegraph line employed in army 
 telegraphy, connecting headquarters with 
 the divisional generals, and such other 
 stations as may be required. 
 
 Field Windings of Induction Motor. 
 
 Field windings so arranged as to produce 
 a rotating magnetic field when supplied 
 by multiphase or uniphase currents. 
 
 Fieldless Motor. A form of motor in 
 which the torque is obtained by the mu- 
 tual attraction of separate armatures. 
 
 Figure-of-Eight Wire. A trolley wire 
 whose cross-section resembles in outline 
 the figure 8. 
 
 Figure of Merit of Galvanometer. 
 
 The reciprocal of the current strength re- 
 quired to produce a deflection of a gal- 
 vanometer needle through one division of 
 the scale. 
 
 Figures, Electric. Figures of various 
 shapes produced on electrified surfaces 
 by the arrangement of dust particles, or 
 vapor vesicles, under the influence of elec- 
 tric charges. 
 
 Filament. A slender thread or fibre. 
 
 Filament of Incandescent Lamp. The 
 incandescing conductor of an incandes- 
 cent electric lamp. 
 
 Filament Shadows. Markings produced 
 on the inner surface of an incandescent 
 lamp chamber by the deposition thereon 
 of carbon from the filament. 
 
 Filamentous Armature Core. A lam- 
 inated armature core formed of iron 
 wire. 
 
 Filar Micrometer. A micrometer ocular 
 in which an angular or linear distance is 
 measured by the movement of a fibre 
 across the field of view, under the control 
 of a screw adjustment. 
 
 Film. (1) A thin pelicle or layer. (2) A 
 name sometimes given to an electro-plat- 
 ing or deposit. 
 
 Film Cut-Out. (1) A cut-out in which a 
 film or sheet of paper, or mica, is inter- 
 posed between a line plate and the earth 
 plate, which, when punctured by a spark, 
 short-circuits the instruments on the 
 
Fil.] 
 
 781 
 
 [Fiv. 
 
 line. (2) A cut-out for a series incan- 
 descent lamp, in which a film of paper or 
 other insulator is interposed between the 
 lamp terminals, so that when the filament 
 breaks, the pressure rises at the termi- 
 nals, and both punctures and short cir- 
 cuits the film, thus cutting out the broken 
 lamp. 
 
 Film Lightning-Arrester. A film-cut- 
 out lightning-arrester. 
 
 Filter Pump. A pump employed for in- 
 creasing the rapidity of filtration of a 
 liquid by atmospheric pressure. 
 
 Filtration. The separation of a liquid 
 from an undissolved solid or solids me- 
 chanically suspended therein. 
 
 Final Cable Test. (1) The test made 
 after a cable is laid, to ascertain if the 
 electrical specifications have been met. 
 
 Final Cable Splice. (1) The splice in a 
 cable which completes it. (2) The last 
 splice. 
 
 Finding Earth. In telegraphy, making 
 earth. 
 
 Finishing Brushes. In electro-plating, 
 finer brushes than scratch brushes, em- 
 ployed for polishing. 
 
 Fire-Alarm Annunciator. An annun- 
 ciator used in connection with a system 
 of fire alarms. 
 
 Fire-Alarm Contact. A contact so ar- 
 ranged that an alarm is automatically 
 given when a predetermined temperature 
 is reached. 
 
 Fire-Alarm Signal-Box. A signal box 
 placed in a street, or other convenient 
 position, by means of which an alarm of 
 fire can be sent. 
 
 Fire-Alarm Telegraph. A general term 
 embracing the apparatus employed in 
 fire-alarm telegraphy. 
 
 Fire-Alarm Telegraphy. A system of 
 telegraphy by means of which alarms can 
 be sent to a central station, or to the fire- 
 engine houses in a district, from call-boxes 
 placed on the line, or from automatic fire- 
 alarm contacts. 
 
 Fire Ball. A term sometimes applied to 
 globular lightning. 
 
 Fire Cleansing. Removing grease by the 
 action of fire from articles that are to be 
 electro-plated. 
 
 Fire Extinguisher, Electric. A ther- 
 mostat or mercurial contact, which auto- 
 matically completes a circuit and thus 
 turns on a water jet for extinguishing a 
 fire, on a certain predetermined increase 
 of temperature. 
 
 Fire-Fly Radiation. Any form of lumi- 
 nous radiation containing a small propor- 
 tion of non-luminous frequencies, and, in 
 this respect, similar to the radiation of 
 the fire-fly or glow-worm. 
 
 Fire-Glow. A term employed by the an- 
 cients for an aurora. 
 
 Fire Telegraph. A fire-alarm telegraph. 
 
 Firing Battery. A battery employed 
 in mining, in military, or in naval opera- 
 tions for firing a fuse. 
 
 Firing Filament. (1) Subjecting suitably 
 shaped carbonizable material to the car- 
 bonizing process, so as to prepare it for 
 use as the filament of an incandescent 
 lamp. (2) Carbonizing a filament. 
 
 Firing Rheostat. A rheostat in the firing 
 circuit of a fuse detonator. 
 
 Fish Plate. In a system of electric rail- 
 roads, the plate connecting contiguous 
 rails by bolts. 
 
 Fished Wires. Wires that have been in- 
 troduced into ducts by the application of 
 the fishing process. 
 
 Fishes, Electric. Various fishes, such as 
 the eel and the ray, which possess the 
 ability of either protecting themselves, or 
 securing their prey, by giving electric 
 shocks to the objects touching them. 
 
 Fishing Box. A term sometimes used 
 for junction box. 
 
 Fishing Conductors. The process of 
 threading conductors through the spaces 
 left for them in floors, walls, tubes, or 
 conduits by securing their ends to the 
 end of a convenient length of wire and 
 hauling the latter through in advance. 
 
 Fishing Process. The process employed 
 for the fishing of wires. 
 
 Fishing of Wires. The process of draw- 
 ing a wire into its place in a building 
 through floors, walls, or ceilings by 
 placing a wire in a hole at one end and 
 engaging it by a hook from the other, so 
 as to draw it through. 
 
 Fiske's Electric Range-Finder. A de- 
 vice by means of which the distance of an 
 object can be readily obtained. 
 
 Fiske's Electric Range-Finder . A de- 
 vice by means of which the exact distance 
 of an enemy's ship or other target can be 
 readily determined. 
 
 Fittings. {!) The sockets, holders, arms, 
 etc., required for holding and supporting 
 incandescent electric lamps. (2) Incan- 
 descent light fixtures. 
 
 Five-Point Jack. In a multiple tele- 
 phone switchboard, a jack having five 
 separate contact points. 
 
Fiv.] 
 
 782 
 
 [Fie, 
 
 Piye-Point Branching Jacks. In a mul- 
 tiple telephone branching switchboard, 
 five-point jacks connected in parallel to 
 a subscriber's line. 
 
 Five- Wire System. A system, similar 
 in its arrangement to the three-wire sys- 
 tem, in which four series-connected dy- 
 namos are suitably connected to five 
 wires or conductors. 
 
 Fixed Call-Boxes. District call-boxes so 
 arranged with burglar-alarm circuits, that 
 the alarm is sent to the district station 
 connected therewith. 
 
 Fixed Electric Lamp. A stationary in- 
 candescent lamp as distinguished from a 
 portable lamp. 
 
 Fixed Resistance. A resistance whose 
 value is approximately constant, as dis- 
 tinguished from a regulable resistance. 
 
 Fixed Secondary. The secondary of an 
 induction coil that, as is common in such 
 coils, is fixed, in contradistinction to a 
 movable secondary. 
 
 Fixture Cut-Out. A cut-out or safety 
 plug attached to an electric lamp. 
 
 Fixture Electric. (1) Fittings for electric 
 light. (2) A support or electrolier for one 
 or more incandescent lamps rigidly fas- 
 tened to a wall or ceiling. (3) Any elec- 
 tric apparatus forming part of a perman- 
 ent installation. 
 
 Fixture Wire. A class of insulated wire 
 suitable for use in electric fixtures. 
 
 Flag of Balance. A small arm pivoted 
 friction-tight upon the movable coils of 
 an electro-dynamometer balance, and 
 capable of adjustment for the purpose of 
 obtaining a correct initial balance. 
 
 Flag Signalling. A system of semaphoric 
 signalling in which a light flag, held in 
 the hand, is waved to the left for the 
 dots, and to the right for the dashes, of 
 the Morse or Continental Code. 
 
 Flake of Cable. A single horizontal layer 
 of a coiled cable. 
 
 Flame. A mass of imflammable gas in a 
 state of combustion. 
 
 Flaming Discharge. The white, flam- 
 ing, arc-light discharge that occurs be- 
 tween the terminals of a high-frequency, 
 high-potential induction coil, when the 
 current through the primary is increased 
 in strength beyond that required for the 
 sensitive-thread discharge. 
 
 Flaming of Carbon Arc. An irregular 
 burning of a voltaic arc, which occurs 
 when the carbons are too far apart, and 
 the current strength somewhat exceeds 
 the normal. 
 
 Flash Signalling. A method of sema 
 phoric signalling by means of a lantern, 
 or torch. 
 
 Flashed Carbon Filaments. Carbon 
 filaments that have been subjected to the 
 flashing process. 
 
 Flashing. Subjecting carbons to the 
 flashing process. 
 
 Flashing Lights. (1) Lights employed 
 in light -house illumination, that are 
 periodically shaded, so as to produce an 
 intermittence of the light, and thus to 
 permit such light to be readily distin- 
 guished from adjacent lights. (2) Any 
 light whose intensity is periodically in- 
 termitted. 
 
 Flashing of Dynamo - Electric Ma- 
 chine. A name given to long flashing 
 sparks at the commutator of a dynamo, 
 due to the short-circuiting of the external 
 circuit at the commutator. 
 
 Flashing Process for Carbon Fila- 
 ments. A process for improving the 
 electrical homogeneity of carbon fila- 
 ments by the deposit of carbon in their 
 pores and over their surfaces, by exposing 
 the filaments to a gradually increasing 
 electrical incandescence, while surround- 
 ed by a carbonaceous gas or liquid. 
 
 Flat Board. A multiple telephone- 
 switchboard whose surface lies in a hor- 
 izontal plane, as distinguished from a 
 vertical board. 
 
 Flat Cable. A cable the separate con- 
 ductors of which are laid up side-by-side, 
 so as to form a flat-conductor. 
 
 Flat Commutator-Segment. A com- 
 mutator segment that has, through wear 
 or otherwise, acquired a flat surface. 
 
 Flat Duplex-Cable. A flat cable con- 
 taining two separate conductors which 
 are laid up side-by-side. 
 
 Flat-Iron, Electric. An electrically 
 heated flat-iron. 
 
 Flat-Ring Armature. An armature 
 whose core has the shape of a short cylin- 
 drical ring. 
 
 Flats. Those parts of commutator seg- 
 ments, the surfaces of which, through wear 
 or otherwise, have become lower than the 
 other portions. 
 
 Fleeting Knife of Cable Gear. The 
 adjustable guide on the drum of a cable 
 machine, which leads the cable to the sur- 
 face of the drum. 
 
 Flexible. Capable of being readily flexed 
 or bent. 
 
 Flexible Cable. A stranded cable, of 
 one which can be readily flexed or bent. 
 
Fie.] 
 
 783 
 
 [Flu. 
 
 Flexible Conduit-System. A system 
 of conduits for underground wires, so 
 constructed that the conductors or cables 
 it is to cozitain can be introduced at any 
 time after its completion. 
 
 Flexible Electric Heater. An electric 
 heater made of flexible material, so as to 
 permit its local application to different 
 parts of the body. 
 
 Flexible Electric-Light Pendant. 
 A pendant for an incandescent lamp, 
 formed by its flexible supporting conduc- 
 tors. 
 
 Flexible Lamp-Cord. (1) A flexible cord 
 provided for supporting an incandescent 
 lamp. (2) A flexible cord maintaining 
 electric connection with a semi-portable 
 incandescent lamp. 
 
 Flexible Lead. A conductor that is 
 stranded for the purpose of obtaining 
 flexibility. 
 
 Flexible Twin-Lead. A lead containing 
 two separate parallel stranded conduc- 
 tors. 
 
 Float Dynamometer. A dynamometer 
 for measuring the mechanical activity of 
 a dynamo or motor in which the machine 
 is supported in a floating cradle and con- 
 nected to its driver or load through a flex- 
 ible coupling. 
 
 Floor-Contact. A contact placed on the 
 floor and arranged so as to be readily 
 operated by the foot. 
 
 Floor Push. A form of floor contact. 
 
 Flow. (1) The quantity of liquid escaping 
 from an orifice in a given time. (2) The 
 quantity of a fluid that flows past a given 
 point in a given time. 
 
 Flow, Electric. Electric current. 
 
 Flow of Energy. The transmission of 
 energy through the medium or dielectric 
 surrounding a conductor, now regarded 
 as causing the current of electricity which 
 was formerly assumed to flow through 
 the conductor. 
 
 Flow Of Electrostatic Flux. The trans- 
 ference of electrostatic flux which con- 
 stitutes, in reality, the so-called flow of 
 electric current through a conductor. 
 
 Flow of Heat. The quantity of heat 
 which passes through a thermal conductor 
 when subjected to a certain difference of 
 temperature. 
 
 Flow of Magnetic Flux. (1) The quan- 
 tityof magnetic flux which passes through 
 any magnetic circuit, under a given mag- 
 neto-motive force, against a given mag- 
 netic reluctance. (2) The time-rate of 
 change of magnetic flux through a mag- 
 netic circuit. 
 
 Flow of Magnetic Induction. The 
 
 transmission of magnetic flux from one 
 point of a magnetic circuit to another. 
 Fluctuating Electromotive Force or 
 Current. An electromotive force or 
 current which varies periodically in mag- 
 nitude. 
 
 Fluid. (1) Any substance which readily 
 flows. (2) A liquid or a gaseous sub- 
 stance. 
 
 Fluid Depolarizer. A fluid substance 
 employed in a voltaic cell as a depolar- 
 izer. 
 
 Fluid, Electric. Either of the assumed 
 fluids which were formerly believed to be 
 the cause of electric excitement. 
 
 Fluid Insulator. An oil insulator. 
 
 Fluidity. Possessing the properties of 
 fluids. 
 
 Fluorimeter. A fluoroscope. 
 
 Fluoresce. To become luminous when 
 exposed to radiant energy. 
 
 Fluorescence. The property possessed 
 by certain solid and liquid substances of 
 becoming luminous when exposed to 
 radiant energy. 
 
 Fluorescent. Possessing the capability 
 of fluorescing. 
 
 Fluorescent Screen. A screen covered 
 with fluorescent materials. 
 
 Fluorescing. Emitting fluorescent light. 
 
 Fluorograph, Electric. A visible X-ray 
 
 picture obtained on a fluorescent screen. 
 
 Fluoroscopic Examination. An X-ray 
 examination of the human body by means 
 of a fluorescent screen. 
 
 Fluoroscopic Screen. A screen covered 
 with fluorescent material, and used in 
 connection with the X-rays for fluoro- 
 scopic examination. 
 
 Fluoroscopy. The art of examining the 
 body by X-rays in connection with a 
 fluoroscopic screen. 
 
 Flush. Box. A box or space, flush with 
 the surface of a roadbed, provided, in a 
 system of underground wires or conduits, 
 to facilitate the introduction of a con- 
 ductor into the conduit, or the examina- 
 tions of the conductors. 
 
 Flush Key-Switch. A key switch that 
 is flush with, or does not project beyond, 
 the surface of the wall in which it is 
 placed. 
 
 Flush of Current of Arc-Lamp. The 
 current that flows into an arc-lamp on 
 starting, and which greatly exceeds in 
 strength that which flows after the 
 normal arc has been established. 
 
.Flu.] 
 
 784 
 
 [Foo. 
 
 Plush Plate. A plate on which flush 
 push-buttons are mounted. 
 
 Plush Push. A push the upper surface 
 of whose button or buttons are flush 
 with the surface of the wall or plate in 
 which it is placed. 
 
 Plush Switch. Any switch sunk in a 
 wall, so that its plane outer surface is 
 flush with the surface of the wall. 
 
 Fluviograph, Electric. An apparatus 
 for electrically registering the varying 
 height of water in a tidal stream, or in 
 the ocean, or, in general, for any differ- 
 ences of water level. 
 
 Flux. (1) Magnetic or electric flux. (2) A 
 surface integral of a vector quantity. 
 
 Plux Density. The quantity of magnetic 
 flux per unit of area of normal cross- 
 section. 
 
 Plux Density per-Square-Centimetre 
 or per-Square-Inch. The quantity of 
 magnetic flux passing through a circuit 
 per square inch or square centimetre of 
 area of normal cross-section. 
 
 Plux of Displacement. The surface in- 
 tegral of electric displacement passing 
 through a closed curve. 
 
 Plux, Electric. Electrostatic flux. 
 
 Plux Horn. A term proposed for the 
 leading horn or polar edge of a generator 
 which supplies the magnetic flux neces- 
 sary for reversing the current in the 
 armature coil under commutation. 
 
 Plux Intensity. (1) The density of a 
 flux. (2) The surface density of a vector 
 quantity at a point. 
 
 Plux Leakage. Any failure of flux to 
 pass through its proper receptive device. 
 
 Plux Lines of Electrostatic Force. 
 The lines or paths traversed by electro- 
 static force. 
 
 Plux of Heat. The flow of heat per unit 
 of time through a given area. 
 
 Plux of Light. (1) The total quantity of 
 light emitted through a given area by a 
 luminous source. (2) The total quantity 
 of light emitted from a point source. 
 
 Plux of Magnetic Induction. The flow 
 of magnetic induction. 
 
 Plux of Magnetism. (1) The flow of 
 magnetic induction. (2) The surface in- 
 tegral of magnetic induction through a 
 given surface. 
 
 Plux Oscillations. Oscillations in the 
 intensity of electrostatic or of magnetic 
 flux. 
 
 Plux Phase. The phase of a simple-har- 
 monic magnetic flux. 
 
 Ply or Flyer, Electric. A light wire 
 wheel provided with pointed radial arms, 
 which is set into rapid rotation by the 
 escape of convection streams from its 
 points, when connected with a charged 
 body. 
 
 Plying Break of Armature Conductor. 
 A discontinuity in an armature wire that 
 can only be detected when the armature 
 is rotating, owing to the influence of 
 centrifgual force. 
 
 Plying Soundings. Approximate sound- 
 ings, in depths not exceeding two hundred 
 fathoms, obtained without decreasing the 
 speed of the ship below five or six knots 
 per hour. 
 
 Pocal Length. (1) The distance of a focus 
 from a lens. (2) When not otherwise 
 specified, the principal focal length of a 
 lens or mirror. (3) The distance from 
 the optical centre of a mirror or lens at 
 which parallel rays are brought to a 
 focus. 
 
 Pocometer. An apparatus for readily de- 
 termining the focus of a lens or optical 
 combination. 
 
 Focus. A point before or back of a mir- 
 ror or lens, where all the rays of light 
 coming from the lens or mirror either 
 meet, or seem to meet. 
 
 Focusing. Altering the distance between 
 an object, and a lens or mirror, in order 
 to obtain a sharp image of the object. 
 
 Focusing Arc-Lamp. An arc-lamp de- 
 signed for use in connection witli a re- 
 flector or lens, whose mechanism feeds 
 both carbons, and so permits the arc to 
 be maintained at the focus of the reflector 
 or lens. 
 
 Fog, Electric. A dense fog which some- 
 times occurs when there is an unusually 
 large quantity of free electricity in the 
 atmosphere. 
 
 Foiled Conductor. A term applied to a 
 conductor whose insulating coating is 
 covered by a thin coating or layer of tin 
 foil or lead. 
 
 Following Edges of Pole-Pieces of 
 Motor. Those edges of the pole-pieces of 
 a motor which the armature is leaving. 
 
 Following Horns of Pole-Pieces or 
 Dynamo. Those edges or terminals of 
 the pole-pieces of a dynamo which the 
 armature is leaving. 
 
 Foot-Candle. A unit of illumination 
 equal to the normal illumination pro- 
 duced by a standard candle at the dis* 
 tance of one foot. 
 
 Foot-Grain. A standard for comparing 
 the resistances of wires at a given tern- 
 
Too.] 
 
 785 
 
 [Foil. 
 
 perature, the length of the wire being one 
 foot, and its weight one grain. 
 
 Foot-Pound. <1) A unit of work. (2) The 
 amount of work required to raise one 
 pound vertically through a distance of a 
 foot. 
 
 Foot-Pound-per-Second.-^-{l) A unit of 
 activity. (2) A rate-of -doing-work equal 
 to the expenditure of one foot-pound per 
 second. 
 
 Foot-Switch. A switch capable of being 
 
 readily operated by the foot. 
 Force. Anything which changes or tends 
 
 to change the condition of rest or motion 
 
 in a body. 
 
 Force, Electric. The force exerted be- 
 tween electrostatic charges. 
 
 Force of Field. The force in a magnetic 
 or electric field independent of the im- 
 pressed magnetic or electric force. 
 
 Force of Flux. The total magnetic or 
 electric force in a magnetic or electric 
 field, as distinguished from the impressed 
 magnetic or electric forces or from the 
 force of a field. 
 
 Force Pump. A pump provided with a 
 solid piston, and employed for raising 
 liquids through greater vertical heights 
 than that through which such liquids 
 could be raised directly by atmospheric 
 pressure. 
 
 Forced Electromagnetic Vibrations. 
 
 Electro-magnetic vibrations that are set 
 up in a system independently of its elec- 
 tro-magnetic dimensions. 
 
 Forced Vibrations. A term employed 
 for vibrations set up in a body independ- 
 ently of its nature and form, and other 
 than the free vibrations which the body 
 would acquire, if disturbed and then left 
 to itself. 
 
 Forge, Electric. A forge in which the 
 metal to be operated on is electrically 
 heated. 
 
 for Trolley Wheel. The mechan- 
 ism which connects the trolley wheel to 
 the trolley pole. 
 
 Forked Circuits. (1)A term used in teleg- 
 raphy for a number of circuits that ra- 
 diate from a given central point. (2) In 
 telegraphy, a circuit which divides into 
 two branches, thus connecting three ter- 
 minal stations. 
 
 Forked Lightning. A variety of light- 
 ning flash, in which the discharge, on 
 meeting the earth or other object, divides 
 into two or more branches. 
 
 Form Factor of Alternating-Current 
 Curve. A factor equal to the square 
 50 
 
 root of the mean square divided by the true 
 mean value of the alternating electro- 
 motive force or current. 
 
 Formal Inductance of Circuit. That 
 part of the counter-electromotive force of 
 a circuit which depends on the form of 
 the circuit. 
 
 Formed Armature- Windings. Arma- 
 ture coils that are wrapped on a suitable 
 form and afterwards placed on the arma- 
 ture core. 
 
 Formed Plates of Secondary Cell. 
 Plates that have been submitted to the 
 forming process. 
 
 Formers. The forms employed in obtain- 
 ing formed armature or other windings. 
 
 Forming Block. A block for holding the 
 jack connections of a set or row in a mul- 
 tiple telephone switchboard, for conveni- 
 ence in soldering their contacts with cable 
 conductors, before inserting the set in the 
 switchboard panel. 
 
 Forming Storage - Battery Plates. 
 Obtaining thick coatings of peroxide of 
 lead and of spongy lead respectively, on 
 the lead plates of a storage battery, by 
 repeatedly sending the charging current 
 between them in alternately opposite 
 directions, while immersed in dilute sul- 
 phuric acid. 
 
 Formulae. Mathematical expressions for 
 some general law, rule, or principle. 
 
 Forward Induction. An induction in 
 the field of a motor or dynamo, in which 
 the current in the armature coils produces 
 an induction which assists the field, in 
 centra-distinction to the back induction, 
 which opposes the field. 
 
 Forward Lead of Dynamo Brushes. 
 A displacement of the brushes on the 
 commutator of a dynamo in the direction 
 of rotation of the armature. 
 
 Forward Pitch of Armature Winding. 
 A pitch which is always directed right- 
 handedly, or clockwise, when viewed from 
 the commutator side. 
 
 Forward Waves. In a closed-current 
 circuit supplied by a dynamo giving a 
 harmonic-alternating electromotive force, 
 the wave of induced potential that is as- 
 sumed to travel through the circuit, from 
 the positive pole of the dynamo to its 
 negative pole. 
 
 Foucault Currents. (1) A name some- 
 times applied to eddy currents, especially 
 when in armature cores. (2) Useless cur- 
 rents developed in a conducting mass, 
 through which varying magnetic flux is 
 moving. 
 
Fou.] 
 
 786 
 
 [Fre. 
 
 Foucault Losses. Losses of energy in a 
 dynamo or motor, due to Foucault cur- 
 rents. 
 
 Foundation Trench. A trench dug to 
 receive the masonry employed in a foun- 
 dation. 
 
 Fountain, Electric. A fountain oper- 
 ated by electric motors, provided with a 
 variety of jets that are electrically illu- 
 mined by different colored lights. 
 
 Fountain Projector. An arc-light pro- 
 jector employed in illumining the jets of 
 an electric fountain. 
 
 Four-Conductor Cord. A flexible oord 
 containing four separate insulated con- 
 ductors. 
 
 Four-Pole Switch. (1) A switch em- 
 ployed for making or breaking four con- 
 tacts. (2) A switch employed to open or 
 close a pair of diphase circuits. (3) A 
 double double-pole switch for diphase cir- 
 cuits, one double-pole switch being pro- 
 vided for each circuit. 
 
 Fourier's Series. A series of sines or of 
 cosines of multiple arcs. 
 
 Four-Piece Electro-Magnet. An elec- 
 tro-magnet -constructed in four pieces ; 
 namely, two cores, a yoke and an arma- 
 ture. 
 
 Four-Point Switch. (1) A switch whose 
 circuit can be completed through four 
 points, either singly, or simultaneously. 
 (2) A four-pole switch. 
 
 Four-Pole Dynamo-Electric Machine. 
 A dynamo-electric machine whose mag- 
 netic field is produced by four magnet 
 poles. 
 
 Four-Speed Regulator. A regulator 
 provided with a motor by which four dif- 
 ferent speeds can be obtained. 
 
 Four- Way Splice-Box. A splice-box 
 provided with four ways or tubular con- 
 duits. 
 
 Four- Way Switch. A four-point switch. 
 
 Four - Wire Diphase - Circuit. A di- 
 phase circuit, employing four wires in 
 contradistinction to a three-wire diphase 
 circuit. 
 
 Four- Wire System. A system similar 
 in its general arrangement to the three- 
 wire system, in which three dynamos are 
 connected to four wires or conductors. 
 
 Four- Wire Transmission. A system of 
 electric transmission employing four con- 
 ductors. 
 
 Fourth State or Condition of Matter. 
 The ultra-gaseous or radiant condition of 
 matter 
 
 Fractional Distillation. (1) A method 
 adopted for the separation of two or more 
 liquids in solution, by first raising the 
 liquid to the boiling point of the most 
 volatile liquid, and retaining that temper- 
 ature until all that liquid is evaporated, 
 and then raising the temperature to that 
 of the next most volatile liquid, and so on 
 throughout. (2) The successive separa- 
 tion by distillation of liquids that volatil- 
 ize at different temperatures. 
 
 Fractional Electrolysis. Successive 
 electrolysis of different substances by 
 gradually raising the E. M. F. 
 
 Fracture of Cable. A parting or rupt- 
 ure of a submarine cable. 
 
 Frame of Dynamo or Motor. A dy- 
 namo or motor frame. 
 
 Franklinic Alternating E. M. F.'s. 
 Alternating - electromotive forces ob- 
 tained by means of a frictional or electro- 
 static-induction machine. 
 
 Franklinic Currents. The currents pro- 
 duced by a frictional or electrostatic-in- 
 duction machine. 
 
 Franklinic Electricity. A term some- 
 times employed in electro-therapeutics 
 for the electricity produced by a frictional 
 or electrostatic-induction machine. , I 
 
 Franklinism. A word sometimes em- 
 ployed for franklinization. 
 
 Franklinization. A term employed in 
 medical electricity for electrization by 
 means of a frictional machine, as distin- 
 guished from faradization or electrization, 
 by means of an induction-coil. 
 
 Franklin's Kite. The kite employed by 
 Franklin in demonstrating the identity of 
 lightning and electricity. 
 
 Fraunhofer's Dark Lines. Spaces in 
 the otherwise continuous spectrum of the 
 sun where certain frequencies are absent. 
 
 Free Charge. The condition of an elec- 
 tric charge on a conductor isolated from 
 other conductors. 
 
 Free Ether. A term sometimes em- 
 ployed for the ether that exists in the 
 inter-planetary spaces, as distinguished 
 from the inter-molecular or inter-atomic 
 ether. 
 
 Free Electricity. (1) In the old double- 
 fluid hypothesis, a term employed for 
 either the positive or the negative 
 electricity when it is freed from the in- 
 fluence of the other. (2) A term some- 
 times employed for a charge on an insu- 
 lated conductor that is isolated from 
 other conductors. (3) A term sometimes 
 employed for the electricity contained in 
 a free charge. 
 
Fre.J 
 
 787 
 
 [Ful. 
 
 Free Insulated. The condition of a tele- 
 graph wire when it is disconnected from 
 its apparatus and left insulated. 
 
 Free Magnet Pole^ A pole in a piece of 
 iron or other paramagnetic substance 
 which acts as if it existed as one magnetic 
 pole only. 
 
 Free Magnetism. (1) In the theory of 
 magnetic matter, magnetism resident 
 upon the polar surface of a magnet and 
 not neutralized by opposite polarity. (2) 
 That portion of the imaginary magnetic 
 matter of a magnet that is distributed 
 over the surface of the magnet. 
 
 Free Path. That path of a gaseous mol- 
 ecule in which it does not collide or strike 
 against another molecule. 
 
 Free Vibrations. Vibrations dependent 
 on the elasticity and shape of a body ac- 
 quired when the body is acted on by a 
 disturbing force and then left to itself. 
 
 Freezing. Congealing or assuming the 
 solid state by loss of heat. 
 
 Freezing Mixtures. Various mixtures, 
 such as salt and ice, which melt or dis- 
 solve on being mixed, and thus absorb 
 sensible heat from themselves, or from 
 surrounding substances. 
 
 Freezing of Shaft in Bearing. The fix- 
 ing of a shaft in its bearing by the lique- 
 fication and subsequent cooling of its 
 anti-friction metal. 
 
 Freezing Point. The point of congela- 
 tion of a liquid. 
 
 French Measures and Weights. A 
 system of measures and weights em- 
 ployed generally in physical science, 
 based on the metre as the unit of length, 
 and the gramme as the unit of weight. 
 
 French Standard Candle. The bougie- 
 decimale or the twentieth part of a Violle. 
 
 Frequency of Alternation. (1) The 
 number of cycles or periods executed by 
 an alternating current in unit time. 
 (2) The periodicity. (3) The number of 
 alternations or half -cycles executed by an 
 alternating current in a second or in a 
 minute. 
 
 Frequency Setter. In an alternating- 
 current circuit having induction ma- 
 chines, an alternator which supplies them 
 with a definite frequency. 
 
 Frequency Teller. A device for deter- 
 mining the frequency of an alternating 
 current. 
 
 Friable. Easily crumbled or pulverized. 
 Friction. Resistance to the sliding or 
 rolling motion of one body over another. 
 
 Friction Brake. (1) A Prony brake. 
 (2) Any form of brake dependent for its 
 operation on friction. 
 
 Fringe of Lines of Force. A term some- 
 times used for fringe of magnetic field. 
 
 Friction, Electric. A term sometimei 
 employed for electric resistance. 
 
 Frictional Electric Machine. A ma- 
 chine for the development of electricity 
 by friction. 
 
 Frictional Electricity. The electricity 
 developed by friction. 
 
 Frictional Torque. (1) Torque developed 
 by friction. (2) In a motor the torque 
 necessary to exert on the armature in 
 order to overcome its friction. 
 
 Fringe of Magnetic Field. The lateral 
 extension or diffusion of magnetic flux 
 from the edge of a pole piece whereby 
 the field is not restricted to the space 
 covered by the pole, but extends with 
 diminishing intensity to a greater area. 
 
 Frog. (1) A metallic guide placed on one 
 side of a single track, where a car has to 
 be driven from one track to another, so as 
 to guide the car in the required direction. 
 (2) A grooved piece of metal, serving as 
 a guide, at the intersection of two rails 
 in a track-crossing. (3) A trolley frog. 
 
 Front Door Pull. A circuit-closing de- 
 vice operated by a pull at a front. 
 
 Front Stop of Key. A stop placed on the 
 front of a telegraphic key in order to re- 
 strict its motion in a downward direction. 
 
 Frost Alarm. An electric alarm sounded 
 or set in operation by means of a mechan- 
 ism operated by a fall of temperature to 
 or below the freezing point of water. 
 
 Frying of Arc. The frying sound .that 
 accompanies a voltaic arc when the car- 
 bons are too near together. 
 
 Fulgurite. A tube of vitrified sand be- 
 lieved to be formed by a lightning dis- 
 charge into the ground. 
 
 Full Battery. A complete battery em- 
 ployed in the quadruplex system, as dis- 
 tinguished from a reduced battery. 
 
 Full Contact. A complete contact. . 
 
 Full Load. (1) An entire load. (2) The 
 maximum load which a machine is de- 
 signed to carry permanently. 
 
 Full-Load Current. The current of 
 maximum load of a source or station. 
 
 Full-Load Efficiency of Motor. The 
 efficiency of a motor when operating at 
 full load. 
 
 Full-Load Efficiency of Transformer. 
 The efficiency of a transformer, or the 
 ratio of the power yielded at secondary 
 
Ful.] 
 
 788 [Gal. 
 
 terminals to the power absorbed at pri- 
 mary terminals, when operating at full 
 load. 
 
 Full Metallic -Contact. A contact 
 which, from its small resistance, estab- 
 lishes a complete connection. 
 
 Fuller Voltaic Cell. A zinc-carbon cou- 
 
 Ele immersed in a solution of electropoion 
 quid and provided with a layer of mer- 
 cury around the lower part of the zinc. 
 Fulminate. A name given to a class of 
 highly explosive compounds. 
 
 Fundamental Frequency. The nominal 
 or lowest frequency of a complex har- 
 monic electromotive force, flux or current. 
 
 Fundamental Tone. The lowest or dom- 
 inant tone, or that on which the pitch of 
 a musical note is dependent. 
 
 Fundamental Units. (1) The units of 
 length, time, and mass, to which all other 
 quantities can be referred. (2) Units of 
 length, time, and mass, as distinguished 
 from their derivations, or derived units. 
 
 Furnace, Electric. A furnace in which 
 electrically generated heat is employed 
 for effecting difficult fusions, for the 
 extraction of metals from their ores, or 
 for other metallurgical operations. 
 
 Fuse Block. A block containing a safety 
 fuse or fuses. 
 
 Fuse Board. A board of slate, or other 
 infusible material, on which the safety 
 
 fuses in a given installation are assem- 
 bled. 
 
 Fuse Box. (1) A box containing a safety 
 
 fuse. (2) A box containing fuse wires. 
 Fuse Carrier. A fuse block. 
 
 Fuse, Electric. (1) A device for elec- 
 trically igniting a charge of powder, by 
 the heat generated in a small strip, wire 
 or mass of poorly conducting material. 
 (2) A safety wire or catch. 
 
 Fuse Holder. A device for holding or 
 protecting a safety fuse. 
 
 Fuse Links. Strips or plates of fusible 
 metal in the form of links employed for 
 safety fuses. 
 
 Fuse Panel. A panel in a switchboard 
 provided for the support of safety fuses. 
 
 Fuse Ribbons, Strips, or Wires. Ma- 
 terial for safety fuses in the form of ru> 
 bons, strips, or wires. 
 
 Fused Electrolytic Bath. An electroly- 
 tic bath in which the electrolyte is main- 
 tained in a state of fusion during elec- 
 trolysis by means of heat. 
 
 Fusible Arrester. A safety catch. 
 
 Fusible Plug. A term sometimes applied 
 to a safety plug. 
 
 Fusible Protector. A safety fuse which 
 acts as a line protector. 
 
 Fusing Current. A term sometimes ap- 
 plied to the current which causes a fuse 
 to blow or melt. 
 
 G 
 
 g. (1) An abbreviation or symbol for the 
 gravitation constant, or the force with 
 which the earth acts upon unit mass at any 
 locality. (2) An abbreviation proposed for 
 gramme, the unit of mass in physical in- 
 vestigations. 
 
 g. In telegraphy, an abbreviation for " go 
 ahead." 
 
 g. cm 2 . An abbreviation proposed for the 
 gramme centimetre-squared, the centi- 
 metre-gramme-second unit of moment of 
 inertia. 
 
 G. M. D. A contraction for geometrical 
 mean distance. 
 
 G. M. T. A contraction for Greenwich 
 mean time, the standard time used in 
 submarine telegraphy. 
 
 G. P. A contraction for gutta-percha. 
 
 Gain Plate of Copper Voltameter. The 
 plate of a copper voltameter that increases 
 in weight due to the deposition on it of 
 metallic copper. 
 
 Gains. The spaces cut in the faces of tel- 
 egraph poles for the support and placing 
 of the cross arms. 
 
 Galvanic Adapter. An apparatus for 
 obtaining from an electric light circuit 
 feeble continuous currents such as are 
 used in electro-therapeutic applications. 
 
 Galvanic Arc. A term sometimes used 
 for a voltaic arc. (Not in general use.) 
 
 Galvanic Battery. An unadvisable term 
 sometimes used in place of voltaic battery. 
 
 Galvanic Cabinet. A suitably shaped 
 box provided with a voltaic battery and 
 all the accessories necessary for its use in 
 electro-therapy. 
 
 Galvanic Cautery. A term sometimes 
 used in place of electric cautery. 
 
 Galvanic Cell. A name sometimes used 
 in place of voltaic cell. 
 
 Galvanic Chain. A galvanic circuit. 
 
Gal.] 
 
 789 
 
 [Gal. 
 
 Galvanic Circle. A term sometimes used 
 for galvanic circuit. 
 
 Galvanic Circuit. A name sometimes 
 used for voltaic circuit. 
 
 Galvanic Couple. A name sometimes 
 given to a voltaic couple. 
 
 Galvanic Dosage. A name sometimes 
 given to electro-therapeutic dosage. 
 
 Galvanic Electricity. A.n unadvisable 
 term sometimes used in place of voltaic 
 eler tricity. 
 
 Galvanic Etching. A term sometimes 
 used for electric engraving. 
 
 Galvanic Excitability. A term some- 
 times used for electric excitability of nerv- 
 ous or muscular fibre. 
 
 Galvanic Induction. A term sometimes 
 used for voltaic induction. 
 
 Galvanic Irritability. Muscular con- 
 tractions produced by the action of vol- 
 taic currents. 
 
 Galvanic Multiplier. A term formerly 
 applied to a galvanometer. 
 
 Galvanic Polarization. A term some- 
 times applied to the polarization of a vol- 
 taic cell. 
 
 Galvanic Ring. A term sometimes ap- 
 plied to a voltaic circuit. 
 
 Galvanic Taste. The sensation of taste 
 produced when a voltaic current is passed 
 through the tongue. 
 
 Galvanism. An inelegant term some- 
 times employed to express the effects pro- 
 duced by voltaic electricity. 
 
 Galvanist. One skilled in the art of gal- 
 vanism. (Obsolete.) 
 
 Galvanized. (1) Subjected to the influ- 
 ence of galvanism. (2) Covered with a 
 coating of zinc by immersion in a bath of 
 molten zinc. 
 
 Galvanized Iron. Iron coated with zinc. 
 
 Galvanized Iron Wire. A zinc-coated 
 iron wire. 
 
 Galvanizing. (1) Covering iron with an 
 adherent coating of zinc by dipping it 
 in a bath of molten metal. (2) Subject- 
 ing a nerve or muscle to the action of gal- 
 
 Galvanizing Wire. Covering wire with 
 a coating of zinc by dipping it in a bath 
 of molten metal. 
 
 Galvano. A word sometimes used in place 
 of electro, either for an electro-type or for 
 an article reproduced in copper by electro- 
 metallurgy. 
 
 Galvano-Caustic Loop. (1) A loop of 
 platinum wire suitably supported, so as to 
 be shortened at will, and employed for re- 
 
 moving diseased growths by drawing it, 
 while heated to electric incandescence, 
 through the parts to be removed. (2) An 
 electric cautery. 
 
 Galvano-Caustics. A term sometimes 
 employed for the destruction of diseased 
 tissues by electrolysis. 
 
 Galvano-Causty. A term sometimes em- 
 ployed for galvano-cautery. 
 
 Galvano-Cautery. An electric cautery. 
 Galvano-Electric Cautery. An electric 
 cautery. 
 
 Galvano-Faradization. (1) In electro- 
 therapeutics, the simultaneous excitation 
 of a nerve or muscle, by both a voltaic and 
 a faradic current. (2) A pulsating, con- 
 tinuous current. 
 
 Galvanoglyphy. A word proposed for 
 the process of producing an electro-type. 
 (Not in use.) 
 
 Galvanography . The process of building 
 up a picture in colored varnish, whose 
 varying thickness gives the necessary gra- 
 dations of light and shade ; subsequently 
 black-leading the picture, and depositing 
 a layer of copper by electro-plating, and 
 employing the finished picture as an en- 
 graved plate for printing. 
 
 Galvano-Magnet. A word sometimes 
 used for electro-magnet. (Not in use.) 
 
 Galvano-Magnetic. A word proposed 
 for electro-magnetic. (Not in use.) 
 
 Galvano-Magnetism. A word proposed 
 for electro-magnetism. (Not in use.) 
 
 Galvanometer. (1) An apparatus for 
 measuring the strength of an electric 
 current by the deflection of a magnetic 
 needle. (2) A current measurer. 
 
 Galvanometer Constant. (1) The con- 
 stant of calibration of the galvanometer 
 scale. (2) The numerical factor connect- 
 ing a current passing through a galvan- 
 ometer with the deflection produced by 
 such current. (3) The value of one divi- 
 sion of the galvanometer scale in terms of 
 resistance or current strength. 
 
 Galvanometer Shunt. A shunt placed 
 around a sensitive galvanometer in order 
 to protect it from the effects of a strong 
 current, or for reducing its sensibility. 
 
 Galvanometer Switch. A switch em- 
 ployed with a dynamo balance-galvan- 
 ometer. 
 
 Galvanometer Voltmeter. Any form 
 of galvanometer arranged so as to readily 
 measure a difference of potential. 
 
 Galvanometric. Of or pertaining to a 
 galvanometer. 
 
Gal.] 
 
 790 
 
 [Gea. 
 
 Galvanometrical. Of or pertaining to a 
 gal vanometer. 
 
 Galvanometrically. In the manner of a 
 galvanometer. 
 
 Galvanometry . The determination of the 
 current strength by means of a galvan- 
 ometer. 
 
 Galvano-Plastic Adhesion. Adhesion 
 to surfaces produced by a galvano-plastic 
 deposit between them. 
 
 Galvano-Plastic Bath. A plating bath. 
 
 Galvano-Plastic Matrix. A mould in 
 which a galvano-plastic deposit is made. 
 
 Galvano-Plastic Soldering. Uniting 
 two metallic surfaces by a metallurgical 
 deposit. 
 
 Galvano-Plastics. (1) A term some- 
 times employed for eleotrotyping, or for 
 producing an electrolytic deposit suffi- 
 ciently thick to permit of its ready sep- 
 aration from the object on which it has 
 been deposited. (2) Literally, the cold 
 moulding or shaping of metals by electro- 
 typing. 
 
 Galvano-Plasty. Galvano-plastics. 
 
 Galvano-Puncture. A term sometimes 
 used for electro-puncture. 
 
 Galvanoscope. (1) A galvanometer in- 
 tended to show the existence of a current 
 rather than to measure its strength. (1) 
 A crude or simple form of galvanometer. 
 
 Galvanoscopic Prog. The hind legs of 
 a recently killed frog, employed as an 
 electroscope or galvanoscope, by sending 
 electric currents from the nerves to the 
 muscles. 
 
 Galvano-Therapeutics. An objection- 
 able term sometimes employed for elec- 
 tro-therapeutics. 
 
 Galvano-Thermal Cautery A term 
 sometimes used for electric cautery. 
 
 GalvanotomiS. A term proposed for the 
 state of tetanus produced in a muscle 
 that has been over-stimulated electrically. 
 
 Galvanotropism. Movements produced 
 in living organisms by the passage of 
 electricity through them. 
 
 Gap Space. The air-gap or entrefer. 
 
 Gap Wire Gauge. A form of wire gauge 
 in which a gap or set of gaps is left in a 
 plate of metal which may be bridged or 
 filled by the wire to be measured. 
 
 Gas Battery. A battery formed of gas 
 cells. 
 
 Gas-Burner, Electric. An electric gas- 
 burner that can be electrically turned on 
 and lighted, or electrically lighted after 
 it has been turned on by hand. 
 
 Gas Cell. A voltaic couple formed of 
 
 metals in the presence of gases instead of 
 
 solids as usual. 
 Gas Engine. An engine whose motive 
 
 power is derived from the heat of burning 
 
 gas. 
 
 Gas-Flame Photometric-Standard. A 
 
 gas-jet photometer. 
 
 Gas- Jet Photometer. A photometer in 
 which the standard of light is a gas jet 
 burning with or without a diaphragm at a 
 definite height under standard conditions 
 of volume and pressure. 
 
 Gas-Lighting, Electric. The electric 
 ignition of a gas jet from a distance. 
 
 Gas-Lighting Torch. A gas-lighting ap- 
 pliance, consisting of the combination of 
 a portable voltaic battery and a spark 
 coil. 
 
 Gas Polarization. A term sometimes 
 employed for that form of polarization 
 which is due to the collection of hydrogen 
 gas on the negative plate of a voltaic 
 cell. 
 
 Gas Voltameter. A voltameter whose 
 indications are based on the volume of 
 gas liberated at a fixed pressure and 
 temperature. 
 
 Gassing. The evolution of gas from the 
 plates of a secondary or storage battery. 
 
 Gastroscope, Electric. An electric ap- 
 paratus for the illumination and inspec- 
 tion of the human stomach. 
 
 Gastroscopy. The examination of the 
 stomach by the gastroscope. 
 
 Gauge, Electric. Any form of portable 
 galvanometer suitable for ordinary test- 
 ing work. 
 
 Gauss. (1) The name proposed in 1894 by 
 the American Institute of Electrical En- 
 gineers for the C. G. S. unit of magnetic 
 flux density. (2) A unit o'f intensity of 
 magnetic flux, equal to one C. G. S. unit 
 of magnetic flux per-square-centi metre of 
 area of normal cross-section. (3) A name 
 proposed for the C. G. S. unit of magnetic 
 potential or magnetomotive force by the 
 British Association in 1895. 
 
 Gaussage. (1) The value of the magnetic 
 intensity in gausses. (2) A name proposed 
 for the value of the M. M. F. in gausses. 
 
 Gauze Brushes for Dynamo or Motor. 
 
 Dynamo or motor brushes formed of wire 
 
 gauze, or of bundles of parallel plates 
 
 of thin woven wire. 
 Gear Clutch Arc-Lamp. An arc-lamp 
 
 provided with a gear clutch. 
 Gearless Car Motor. A motor whose 
 
 speed is such as to permit it to be con- 
 
Oei.] 
 
 791 
 
 [Glo. 
 
 nected directly, without intermediate 
 gearing, on the car-wheel axle. 
 Geissler Mercurial Pump. A mercurial 
 air pump in which the exhaustion is ob- 
 tained by the aid of a Torricellian vac- 
 uum. 
 
 Geissler Tubes. Glass tubes, provided 
 with platinum electrodes passed through 
 and fused into the glass, containing the 
 residual atmospheres of gases at a com- 
 paratively low vacuum, either with or 
 without fluorescent liquids, or solids, or 
 both, employed to obtain various luminous 
 effects on the passage of electric dis- 
 charges. 
 
 General Alternating- Current Trans- 
 former. Any form of alternating-cur- 
 rent apparatus ift which secondary cur- 
 rents are induced, such as an induction 
 motor or induction generator, as well the 
 ordinary transformer. 
 
 General Faradization. A method of 
 employing the faradic current similar to 
 its use in general galvanization. 
 
 General Galvanization. A method of 
 employing an electric current therapeut- 
 ically by the use of electrodes of suffi- 
 cient size to direct the current practically 
 through the entire body. 
 
 Generator. A dynamo-electric machine. 
 Generator Ammeter. An ammeter 
 
 measuring the total current output of a 
 
 generator. 
 
 Generator Bus-Bars. The bus-bars 
 which receive the total generated pressure 
 of a number of dynamos, or of a station. 
 
 Generator Panels of Switchboard. 
 That panel or set of panels of a central- 
 station switchboard which contains the 
 generator bus-bars, and supports the gen- 
 erator ammeters voltmeters and switches. 
 
 Generator Switch. A switch provided 
 for the purpose of connecting or discon- 
 necting a generator from the bus-bars. 
 
 Generator Unit. (1) A dynamo-electric 
 generator in a central station. (2) One 
 of a number of independent generating 
 machines in a central station. 
 
 Generator Voltmeter. A voltmeter con- 
 nected with the circuit of a generator, 
 and employed to measure its pressure. 
 
 Geographical Equator. The great circle 
 of the earth midway between its poles. 
 
 Geographical Meridian. Any great 
 
 circle of the earth passing through its 
 
 poles. 
 Geomantic Lines of Force. the lines 
 
 of the earth's magnetic force. (Not in 
 
 general use.) 
 
 German-Silver Alloy. An alloy, em- 
 ployed for the wires of resistance coils, 
 usually consisting of fifty parts of copper, 
 twenty-five of zinc and twenty-five of 
 
 . nickel. 
 
 Gig, Electric. An electrically propelled 
 gig- 
 
 Gilb. A name proposed for the gilbert. 
 
 Gilbert. (1) A name proposed for the C. 
 G. S. unit of magnetomotive force. 
 (2) A unit of magnetomotive force equal 
 to that produced by j^ of one ampere- 
 turn. 
 
 Gilbertage. The value of the magneto- 
 motive force of a circuit expressed in 
 gilberts. 
 
 Gilding, Electric. Electro-plating with 
 gold. 
 
 Gilt Plumbago. Powdered plumbago 
 whose conducting power for electricity 
 has been increased by electro- plating it 
 with gold, used for rendering non-con- 
 ducting surfaces electrically conducting. 
 
 Gimbals. Concentric rings of brass, sus- 
 pended on pivots in a compass box, on 
 which the compass is so supported, as to 
 enable it to remain horizontal notwith- 
 standing the movements of the ship. 
 
 Girder Armature. An armature with 
 an H or girder-shaped core. 
 
 Girder Joint for Rail Bond. A name 
 given to a joint in steel rails consisting of 
 two side-clamped girders supporting a tee- 
 bar and double clamped. 
 
 Glass-Bead Hydrometer. A bead areo- 
 meter. 
 
 Glass Fuse. A fuse contained in a glass 
 tube with metallic ends. 
 
 Glass Screw Insulator. A glass in- 
 sulator provided with an inside screw 
 thread for attachment to the insulator 
 pin. 
 
 Globe Holder for Arc-Lamp. A sup- 
 port provided for holding the globe of an 
 arc-lamp. 
 
 Globe Net for Arc-Lamp. A thin wire 
 netting placed on the outside of an arc- 
 light globe. 
 
 Globe Strain - Insulators. Insulators 
 provided for the support of the strain 
 wires in an overhead trolley system. 
 
 Globular Lightning. A rare form of 
 lightning in which a globe of fire ap- 
 pears quietly floating in the air for a 
 while and then explodes with great vio- 
 lence. 
 
Glo.] 
 
 792 
 
 [Gra. 
 
 Globular Spark. An experimentally 
 produced globular discharge obtained 
 from a large condenser. 
 
 Glow Discharge. A form of convective 
 discharge. 
 
 Glow Illumination. (1) A term pro- 
 posed for an illumination similar to that 
 of a glow-worm ; that is, luminous radia- 
 tion unaccompanied by non-luminous 
 radiation. (2) A term sometimes used 
 for illumination by incandescent electric 
 lamps. 
 
 Glow-Lamp, Electric. (1) A lamp whose 
 light is produced by glow illumination. 
 (2) A term sometimes used for incandes- 
 cent lamps. 
 
 Glow- Worm Radiation. (1) The radia- 
 tion of the glow-worm or fire-fly. (2) Ra- 
 diation that is practically confined 
 within the limits of the visible spectrum. 
 
 Glowing of Electric Conductor. The- 
 incandescence of an electric conductor. 
 
 Glue-Pot, Electric. An electrically heat- 
 ed glue-pot. 
 
 Glyphography. The art of forming an 
 electro-type block, whose impressions will 
 produce relief outlines on a flat sur- 
 face, by covering a flat copper plate 
 with a suitable insulating material, cut- 
 ting through the same until the copper is 
 exposed, and then coating the surface 
 with plumbago and electro-plating. 
 
 Gnomon, Electric. A term formerly ap- 
 plied to a variety of pith-ball electro- 
 meter. 
 
 Gold Bath. An electrolytic bath consist- 
 ing of a readily electrolyzable solution of 
 a gold salt, a gold plate acting as the 
 anode and placed in the liquid opposite 
 the object to be electroplated, which forms 
 the cathode. 
 
 Gold-Leaf Electroscope. An electro- 
 scope in which a pair of leaves of beaten 
 gold is employed to detect the presence 
 of an electric charge, or to determine its 
 character, whether positive or negative. 
 
 Gold-Plating. Electroplating with gold. 
 Gong Signalling for Railroads. A 
 
 system of railroad signals employing a 
 
 code dependent on the sounds produced 
 
 by gongs. 
 Good Earth. (1) Total or dead-earth. 
 
 (2) An earth connection whose resistance 
 
 is negligibly small. 
 
 Goose-Neck Double-Pull-Off. An in- 
 sulator with a support shaped like a goose 
 neck provided with two points for the 
 attachment of the strain wires and em- 
 
 ployed on curves to hold the trolley wire 
 in position. 
 
 Goose - Neck Pull - Off. An insulator, 
 with a support shaped like a goose neck, 
 employed on curves to hold the trolley 
 wire in position, and provided with a 
 single point for the attachment of the 
 strain wire. 
 
 Governor, Electric. A device for elec- 
 trically controlling the speed of a steam 
 engine, the direction of a current in a 
 plating bath, the speed of an electric 
 motor, the resistance of an electric cir- 
 cuit, the flow of a liquid or gas into or 
 from a containing vessel, or for other 
 similar purposes. 
 
 Graded Cyclic-Magnetization. A reg- 
 ularly expanding or contracting cylic 
 magnetization . 
 
 Graded Winding of Galvanometer. 
 A galvanometer winding composed of 
 more, than one size of insulated wire 
 provided with a view to increasing the 
 sensibility of the galvanometer, and in 
 which the finest wire is placed nearest 
 the axis of the coil. 
 
 Gradient. (1) The increase or decrease of 
 an elevation or quantity with reference to 
 some constant quantity. (2) The space- 
 rate-of -change in a quantity. 
 
 Gradient, Electric. (1) The rapidity of 
 increase or decrease of the strength of an 
 electromotive force or current. (2) The 
 vector space-rate of descent of electric 
 potential at any point. 
 
 Graduators. Devices, generally electro- 
 magnetic, employed in systems of simul- 
 taneous telegraphic and telephonic trans- 
 mission over the same wire, so inserted 
 in the line circuit as to gradually ob- 
 tain the makes and breaks required in a 
 system of telegraphic communication, 
 so that they fail sensibly to influence the 
 diaphragm of a telephone placed in the 
 same circuit. 
 
 Gramme. (1) A unit of mass equal to 
 15.43235 grains. (2) The mass of a cubic 
 centimetre of water at the temperature 
 of its maximum density. 
 
 Gramme Armature - Winding. The 
 winding originally employed by Gramme 
 on the armature of his dynamo-electric 
 machine. 
 
 Gramme Atom. Such a number of 
 grammes of any elementary substance 
 as is numerically equal to the atomic 
 weight of that substance. 
 
 Gramme-Calorie. (1) The amount of 
 heat required to raise a gramme of water 
 one degree Centigrade. (2) The gramme- 
 degree-Centigrade. 
 
Gra.J 
 
 793 
 
 [Gro. 
 
 Gramme Equivalent. Such a number 
 of grammes of any substance as is nu- 
 merically equal to the electro-chemical 
 equivalent of that substance. 
 
 Gramme Molecule. A weight of any 
 substance, taken in grammes, numerical- 
 ly equal to its molecular weight. 
 
 Gramme-Ring Transformer. (1) A 
 transformer whose primary and secondary 
 coils are placed on a closed iron ring. (2) A 
 transformer resembling a Gramme-ring 
 armature. 
 
 Gramaphone. An apparatus for record- 
 ing and reproducing articulate speech. 
 
 Gramaphone Record. A record of ar- 
 ticulate speech obtained by means of a 
 gramaphoue. 
 
 Granular -Carbon Telephone - Trans- 
 mitter. A dust telephone transmitter. 
 
 Granular Telephone. A word some- 
 times used for a granular carbon tele- 
 phone transmitter. 
 
 Graphite. A variety of soft carbon suit- 
 able for writing on paper or on similar 
 surfaces. 
 
 Grapnel Toes. The prongs of a grapnel 
 employed in grappling for a submarine 
 cable. 
 
 Graphophone. A form of apparatus for 
 recording and reproducing articulate 
 speech. 
 
 Graphophone Record. A record of ar- 
 ticulate speech received on a graph- 
 ophone. 
 
 Grappling. Recovering a sunken object, 
 such as a cable, by means of a grapnel. 
 
 Grapnel. A device for hooking and re- 
 covering a submerged object, such as a 
 cable. 
 
 Gratings. A plate of glass or metal cov- 
 ered with closely-ruled, parallel lines, 
 employed for obtaining diffraction spec- 
 tra. 
 
 Gravitation. Mutual attraction produced 
 between two masses of matter by the 
 force of gravity. 
 
 Gravity. The force which causes masses 
 of matter to move or to tend to move 
 towards one another. 
 
 Gravity Ammeter. A form of ammeter 
 in which the magnetic needle is moved 
 against the force of gravity by the mag- 
 netic influence of the current it is measur- 
 ing. 
 
 Gravity Annunciator-Drop. An an- 
 nunciator drop which is operated by 
 gravity under the influence of an electric 
 current. 
 
 10- 
 
 Gravity-Drop Annunciator. An a 
 nunciator whose signals are operated by 
 the fall of a drop. 
 
 Gravity -Feed Arc-Lamp. An arc-lamp 
 in which the upper or positi'*d carbon is 
 fed, or permitted to drop towards the 
 negative carbon under the influence of 
 gravity, on the operation of the feeding 
 mechanism. 
 
 Gravity Needle-Drop. A needle annun- 
 ciator furnished with a gravity drop. 
 
 Gravity Voltaic Cell. A blue-stone 
 gravity cell. 
 
 Gravity Voltmeter. A form of volt- 
 meter in which the potential difference 
 is measured by the movement -of a mag- 
 netic needle against the pull of a weight. 
 
 Grease-Spot Photometer. (1) A translu- 
 cent-disc photometer. (2) A Bunsen 
 photometer. 
 
 Greater Calorie. The amount of heat 
 required to raise the temperature of one 
 kilogramme of water from Centigrade 
 to 1 Centigrade. 
 
 Green Candle. A standard candle em- 
 ployed in connection with a screen o! 
 green glass in order more readily to com- 
 pare the light of an arc with that of a 
 standard candle. 
 
 Grenet Voltaic Cell. A name sometimes 
 given to the bichromate cell. 
 
 Grid Indicator. (1) In telephony, , 
 clearing indicator in which the armaturo 
 is painted with alternate white and black 
 horizontal stripes and fronted by a bras;? 
 grid. (2) A form of telephone visual 
 clearing indicator. 
 
 Grid. (1) A lead plate provided with per- 
 forations or other irregularities of sur- 
 face, and employed in storage cells for 
 the support of the active material. 
 (2) The support provided for the active 
 material on the plate of a secondary or 
 storage cell. 
 
 Grid Plugs. Plugs of active material, or 
 of material that is readily rendered active 
 by a charging current, inserted in the 
 perforations of a grid for the purpose of 
 decreasing the time required for the 
 forming of the plates of a storage cell. 
 
 Grip of Belt. The hold of a belt on the 
 driving pulley. 
 
 Grothuss' Hypothesis. A hypothesis 
 proposed to account for the electrolytic 
 phenomena that occur on closing the cir- 
 cuit of a voltaic cell. 
 
 Ground. A general term for the eaivh 
 
 when employed as a return conductor. 
 Vol. 2 
 
Gro.J 
 
 794 
 
 <3round Circuit. A circuit in which the 
 ground forms part of the path through 
 which the current passes. 
 
 Oround Coil. A small rheostat employed 
 in duplex telegraphy at the home station, 
 for the purpose of obtaining the balance 
 of the line at that station. 
 
 Ground Detector. ^{1) In a system of in- 
 candescent-lamp distribution, a device 
 placed in a central station for indicating, 
 by the brightness of a lamp, the existence 
 of a ground on the system. (2) An instru- 
 ment for detecting or measuring grounds 
 or leaks. 
 
 Ground Indicator. (1) A tell-tale device 
 employed on a line carrying a current, to 
 instantly indicate any fault in the insu- 
 lation. (2) An apparatus for detecting a 
 loss of insulation. 
 
 Ground Plate of Lightning Arrester. 
 That plate of a comb lightning-arrester 
 which is connected to the ground or earth. 
 
 ground-Return. (1) A general term 
 used to indicate the use of the ground or 
 earth for part of an electric circuit. 
 (2) The earth or ground which forms part 
 of the return path of an electric circuit. 
 
 Ground Shield of Transformer. (1) A 
 metallic plate or shield in a transformer 
 separating the primary and secondary 
 coils and connected to ground so as to 
 protect the secondary circuit from any 
 possibility of becoming crossed with the 
 primary. (2) A cylinder of slotted copper 
 placed between the primary and secon- 
 dary windings of a transformer, so that 
 there can be no accidental contact be- 
 tween the high pressure and the low pres- 
 sure circuits. 
 
 Ground Wire. The wire or conductor 
 leading to 6r connected with the ground 
 or earth in a grounded circuit. 
 
 Grounded Circuit. A circuit, part of 
 whose path is completed through the 
 ground. 
 
 Grounded Dynamo. A dynamo whose 
 circuit is accidentally or intentionally 
 grounded. 
 
 Grounding. (1) A word sometimes em- 
 ployed in electro-metallurgy for the pre- 
 paratory process of burnishing. (2) Con- 
 necting a circuit to earth or ground. 
 
 Group Incandescent Switch. A switch 
 which governs a portion or group of the 
 lamps on an electrolier, or in a room. 
 
 Grouping System for Switchboard 
 Circuits. A system of central-tele- 
 phone-station distribution in which the 
 subscribers are divided into a convenient 
 
 number of groups, and each group given 
 to the charge of a single operator. 
 
 Growth of Lines of Force. The expan- 
 sion of lines of force. 
 
 Grove's Voltaic Cell. A zinc-platinum 
 couple immersed respectively in electro- 
 lytes of sulphuric and nitric acid. 
 
 Guard Arm. In telegraphic pole-setting, 
 a short upright secured to a pole croos- 
 arm so as to catch a wire should it become 
 detached from the pole. 
 
 Guard Ring of Electrometer or Con- 
 denser. A conducting ring constructed 
 to form the annular extension of a plate 
 or disc in an air-condenser, for the purpose 
 of preventing any disturbance of electric 
 flux-distribution at the edge of such disc 
 or plate. 
 
 Guard Suspension Wire. In a trolley 
 system, a wire supported on the tops 
 of opposite poles for the suspension of a 
 running guard wire, or guard- wires. 
 
 Guard Wire. A wire hung above any 
 active conductor, such as a trolley wire, 
 in order to prevent it from coming into 
 electric contact with falling wires. 
 
 Guard-Wire Hanger. A hanger em- 
 ployed for the suspension of a guard wire. 
 
 Gutta-Percha. A resinous gum obtained 
 from a tropical tree, and valuable elec- 
 trically for its high insulating powers and 
 for its indestructibility when employed 
 in submarine cables. 
 
 Gutter of Insulator. A channel on the 
 side of an insulator, designed to carry off 
 the rain water. 
 
 Guy. A rod, chain, rope or wire employed 
 for supporting or stiffening any structure 
 such as a telegraph pole. 
 
 Guy-Rod Bands. Bands by which a guy- 
 rod is fastened to a pole. 
 
 Guy Rods. Metallic rods employed as 
 guys. 
 
 Guy Rope. A rope employed as a guy. 
 Guy Stubs. (1) A stub or anchor to 
 
 which a guy is secured. (2) The stub of 
 
 a pole set in the earth at an angle away 
 
 from the pole to be guyed. 
 Guy Wire. A wire employed as a guy. 
 Guying. Stiffening by means of guys. 
 Guys. Stays, suitably secured to a posl -> 
 
 anchor, for the purpose of steadying *n 
 
 overhead wire system. 
 Gymnoticus Electricus. The electric 
 
 eel. 
 Gyration. The act of turning around an 
 
 axis. 
 Gyrometer. A rotary speed-indicator. 
 
Gyr.] 
 
 795 
 
 [Man. 
 
 Gyroscope, Electric. A gyroscope 
 driven by an electro-magnetic motor. 
 
 Gyrostat. (1) A revolving flywheel de- 
 signed to display gyrostatic action. (2) A 
 flywheel possessing considerable moment 
 of inertia, suitably supported on pivots 
 within a case, so as to permit of being 
 carried about, and employed to show the 
 
 resistance which rotating bodies offer to 
 changing their plane of rotation. 
 Gyrostatic Action of Dynamo on Ship- 
 board. The action which occurs at the 
 bearings of a dynamo running on board a 
 tossing ship, whereby gyrostatic stresses- 
 are produced. 
 
 H 
 
 H. A symbol for the horizontal intensity 
 of the earth's magnetism. 
 
 H. A contraction for the henry or practi- 
 cal unit of self induction. 
 
 H. A contraction for the magnetizing 
 force that exists at any point ; or, gen- 
 erally, for the intensity of magnetic 
 force. 
 
 II . A symbol for field intensity. 
 
 3C. A symbol proposed for magnetizing 
 force. (Partly international usage.) 
 
 h. An abbreviation for hour, a practical 
 unit of time. 
 
 "H. B." Curves. (1) Curves indicating 
 the relations between magnetizing force 
 and magnetic flux density in a magnetic 
 substance. (2) A term sometimes em- 
 ployed for magnetization curves. 
 
 H.P. or St. A contraction for horse- 
 power. 
 
 H.R. A contraction for high resistance. 
 
 H- Armature Core. (1) An armature 
 core in the shape of the letter H. (2) A 
 girder, shuttle, or I-armature. 
 
 H-Poles. In telegraphy a pair of parallel 
 vertical poles braced together to form one 
 structure, resembling the letter H. 
 
 Hsematocrit, Electric. An electrically 
 driven device for separating the white 
 blood corpuscles from the red corpuscles 
 by centrifugal force. 
 
 Half-Deflection Method. A method of 
 measuring an electromotive force, current 
 or resistance, by adjusting the circuit in 
 such a way as to halve the galvanometer 
 deflection. 
 
 Half-Gate. The condition of a turbine 
 when operating with the gate half open. 
 
 Half-Hoop Magnet. A magnet in the 
 form of a semi-circle. 
 
 Half-Load Efficiency. The efficiency 
 which a device possesses at half its full 
 load. 
 
 Half-Shade for Incandescent Lamp. 
 A reflecting shade whose outline conforms 
 
 to that of the lamp chamber, and covers 
 but half of its surface. 
 
 Half- Wire Guard for Incandescent 
 Lamp. A wire guard which covers but 
 half of an incandescent lamp. 
 
 Hall Effect. A transverse electromotive 
 force produced by a magnetic field in 
 substances undergoing electric displace- 
 ment. 
 
 Halleyan Lines. A term sometimes used 
 for isogonal lines. 
 
 Halpine-Savage Torpedo. A form of 
 torpedo in which electricity is both the 
 propelling and the directing power, and 
 in which the electric source furnishing 
 the propelling current is contained within 
 the torpedo. 
 
 Hand-Brake Mechanism. A car brake 
 operated by hand. 
 
 Hand Dynamo Machines. A hand gen- 
 erator. 
 
 Hand Generator. (1) A hand-driven dy- 
 namo. (2) A hand-driven telephone mag- 
 neto generator. 
 
 Hand-Hole of Conduit. A box or open- 
 ing, communicating with an underground 
 cable, provided for readily tapping the 
 cable, and of sufficient size to permit the 
 introduction of the hand. 
 
 Hand-Lighting Electric Burner. A 
 name sometimes applied to a plain pen- 
 dant burner. 
 
 Hand-Operated Alarm. Any electric 
 alarm operated by hand, as distinguished 
 from an automatically operated electric 
 alarm. 
 
 Hand Regulation. Any regulation of a> 
 dynamo effected by the hand, in contradis- 
 tinction to automatic regulation, such as 
 will preserve constant either the current; 
 or the potential. 
 
 Hand Regulator. A resistance box, 
 whose separate coils can be readily placed 
 in or removed from the circuit by means 
 of a hand-operated switch. 
 
 Hand Scratch-Brush. A scratch brush. 
 
Han.] 
 
 796 
 
 [Hea. 
 
 operated by hand, as distinguished from 
 one operated by means of a lathe. 
 Hand-Signalling. Telegraphic signal- 
 ling by hand, as distinguished from auto- 
 matic or machine signalling. 
 
 Hand Telegraphic Transmission. 
 Manual telegraphic transmission. 
 
 Hand Telephone. (1) A telephone re- 
 ceiver held in the hand, as distinguished 
 from a head telephone receiver. (2) An 
 ordinary telephone receiver. 
 
 Hanger Board. A form of board provided 
 for the ready replacement or removal of 
 an arc-lamp from a circuit. 
 
 Hanger Cut-Out. A cut-out switch for 
 an arc lamp placed under a hanger. 
 
 Hard-Drawn Copper Wire. <1) Copper 
 wire that is hardened by being drawn 
 three or four times without annealing. 
 (2) Copper wire not annealed after leaving 
 the die. 
 
 Hard Porous Cell. A hard-baked porous 
 cell, whose use in a voltaic cell renders 
 its resistance comparatively high, but 
 which is better able to stand the disinte- 
 grating action arising from the crystalli- 
 zation of saline substances present in the 
 battery. 
 
 Hardening. Increasing the hardness of 
 certain metals by heating them to a high 
 temperature and then suddenly cooling. 
 
 Hardness. That property of a body in 
 virtue of which it resists scratching or 
 cutting. 
 
 Harmonic Analyzer. (1) A device for 
 automatically resolving a complex har- 
 monic into its simple-harmonic com- 
 ponents. (2) A harmonic receiver. (3) A 
 receiving instrument responding to a sin- 
 gle harmonic frequency and which selects 
 that frequency from a complex-harmonic 
 current. 
 
 Harmonic Capacity. The capacity of a 
 condenser to a charge or current received 
 from a harmonically varying E. M. F. 
 
 Harmonic Currents. (1) Periodically al- 
 ternating currents varying harmonically. 
 (2) Currents which are harmonic functions 
 of time. (3) Sinusoidal currents. 
 
 Harmonic Electromotive Forces. 
 (1) Periodically alternating E. M. F.'s vary- 
 ing harmonically ; or harmonic functions 
 of time. (2) Sinusoidal E. M. F.'s. 
 
 Harmonic Frequencies. A series of 
 frequencies whose values are integral 
 multiples of the frequency of their 
 fundamental. 
 
 Harmonic Motion. (1) Simple-harmonic 
 motion. (2) Simple-periodic motion. 
 
 Harmonic Receiver. (1) The receiver em- 
 ployed in systems of harmonic telegraphy, 
 consisting of an electro-magnetic rod 
 tuned to vibrate to a single note or rate 
 only. (2) A receiver designed to respond 
 to a single harmonic frequency in a com- 
 plex-harmonic current. 
 
 Harmonic Telegraph. A general term 
 embracing the apparatus employed in 
 harmonic telegraphy. 
 
 Harmonic Telegraphy. (1) A system for 
 the simultaneous transmission of a num- 
 ber of separate and distinct musical 
 sounds over a single wire, employed for 
 simultaneously transmitting an equal 
 number of telegraphic messages. (2) A 
 system of telegraphy employing harmonic 
 currents. 
 
 Harmonic Vibrations. The over-tones 
 or higher vibrations into which a com- 
 plex-periodic vibration may be resolved. 
 
 Harmonics. The higher component tones 
 into which any complex tone can be re- 
 solved. 
 
 Harmonics, Electric. Currents of higher 
 frequencies into which any complex-har- 
 monic current may be resolved. 
 
 Harmonics of Current. The harmonic 
 currents into which a complex-harmonic 
 current may be resolved. 
 
 Harmonics of Sound Waves. The over- 
 tones or harmonics into which any com- 
 plex tone may be resolved. 
 
 Harmonograph. A mechanical device 
 for compounding any number of simple- 
 harmonic motions of different amplitudes 
 and phases. 
 
 Harness. (1) The head and breast equip- 
 ment of an exchange operator. (2) A term 
 used by telephonists. 
 
 Harpoon, Electric. A harpoon contain- 
 ing a bomb that is electrically fired or 
 exploded by the harpooner after the im- 
 bedding of the harpoon. 
 
 Harveyizing. A method of superficially 
 hardening a steel plate. 
 
 Haulage, Electric. Locomotion of a 
 vessel or car by the agency of electricity. 
 
 Head - Bath, Electric. A variety of 
 electric breeze applied therapeutically to 
 the head of a patient. 
 
 Head-Gear Telephone. A telephone 
 receiver held to the ear by means of a 
 suitable head supporting-gear, thus leav- 
 ing the hands of the operator free. 
 
 Head-Board of Dynamo. An insulating 
 board of a dynamo-electric machine for 
 the reception of terminals or switches. 
 
 Head-Board of Motor. A switchboard 
 
Hea.] 
 
 797 
 
 [Hel. 
 
 connected with a motor for use in start- 
 ing it. 
 
 Head Guy. A guy attached to the top of 
 a pole. 
 
 Head Guying. A method of pole guying 
 for checking lateral vibrations, in which 
 the top of each pole is guyed to the 
 bottom of the next succeeding pole for 
 a distance of several poles. 
 
 Head-Lamp. An electric lamp placed 
 in the focus of a reflector supported on 
 the head. 
 
 Head-Light, Electric. An electric light 
 placed in the focus of a parabolic reflector 
 in front of an engine or car. 
 
 Head of Liquid. (1) The vertical distance 
 from the level of a liquid in a containing 
 vessel to the centre of gravity of an orifice 
 placed therein. (2) Difference of liquid 
 elevation or level. 
 
 Head Receiver. A head-gear telephone- 
 receiver. 
 
 Hearing Tubes. Tubes connecting a 
 telephone receiver with the ears of the 
 listener. 
 
 Heat. (1) A form of energy. (2) A mode of 
 motion. (3) A vibratory motion impressed 
 on the molecules of matter by the action 
 of any form of energy. (4) A wave mo- 
 tion impressed on the universal ether by 
 the action of some form of energy. 
 
 Heat Alarm. A temperature alarm. 
 
 Heat Coil. (1) A form of protector for 
 switchboards or receptive apparatus gen- 
 erally, consisting of a coil of fine German 
 silver wire wrapped around a small me- 
 tallic plug, held in its place by a drop of 
 readily fusible solder, and so arranged 
 that on the melting of the solder a spring 
 is permitted to act so as to dead-ground 
 the system. (2) A form of sneak-current 
 arrester. 
 
 Heat, Electric. The heat developed by 
 the passage of an electric current through 
 a conductor. 
 
 Heat Insulator. Any non-conductor of 
 heat. 
 
 Heat Lightning. A variety of lightning 
 flash unaccompanied by audible thunder, 
 in which the discharge lights up the sur- 
 faces of neighboring clouds. 
 
 Heat Unit. (1) The quantity of heat re- 
 quired to raise a given mass of water 
 through one degree of the thermometric 
 scale. (2) The calorie. 
 
 Heat Units. Units based on the quantity 
 of heat required to raise a given mass of 
 a substance, generally water, through 
 one degree of the thermometric scale. 
 
 Heater, Electric. A device for the con- 
 version of electricity into heat, employed 
 for purposes of artificial heating. 
 
 Heating Effects of Current. The heat 
 generated by the passage of an electric 
 current through any circuit. 
 
 Heavy Escape. A term employed for a 
 rapid loss of current on a telegraphic line, 
 due to its accidental connection with the 
 ground, as distinguished from a slight 
 loss of current. 
 
 Hedgehog Transformer or Converter. 
 A name applied to a particular form of 
 open-circuited iron-core transformer, in 
 which a core of iron wire projects diver- 
 gingly from each end of the coil. 
 
 Heeling Error of Compass Needle. 
 The error in a ship's compass needle due 
 to the induced and permanent magnet- 
 ism of the ship in a vertical plane, which 
 produces no influence upon the needle 
 until the ship heels over, either under a 
 press of canvas, or from any other cause. 
 
 Hefner-Alteneck Amyl-Acetate Stan- 
 dard. (1) The arayl-acetate standard of 
 luminous intensity. (2) A standard lamp 
 of definite dimensions consuming amyl- 
 acetate. 
 
 H e f n e r-A 1 1 e n e c k Amyl-Acetate 
 Lamp. The lamp employed in the Hef- 
 ner-Alteneck amyl-acetate standard. 
 
 Heilmann Locomotive. An electrically 
 propelled locomotive which carries not 
 only the steam plant necessary for the 
 operation of the dynamo that furnishes 
 its driving current, but also the motor 
 propelling the truck. 
 
 Hekto. A prefix for one hundred. 
 Hekto-Ampere. One hundred amperes. 
 
 Hekto- Ampere Balance. A balance 
 
 form of ammeter measuring hundreds of 
 
 amperes. 
 Hekto-Watt Hour. (1) One hundred 
 
 watt-hours. (2) A unit of work equal to 
 
 one hundred watt-hours. 
 Helical Coil. A wire coil containing a 
 
 number of convolutions or spirals. 
 
 Heliograph. (1) An instrument for tele- 
 graphic communication, that operates by 
 employing flashes of sunlight to repre- 
 sent the dots and dashes of the Morse 
 alphabet. (2) A portable instrument for 
 visual telegraphic communication con- 
 sisting essentially of a mirror supported so 
 as to reflect a beam of sunlight to the dis- 
 tant station, and means to intercept the 
 beam at intervals corresponding to Morse 
 code signals. 
 
 Heliographic Transmission. A system 
 
Hel.] 
 
 798 
 
 [Met. 
 
 of telegraphic communication employing 
 the heliograph. 
 
 Heliography. (1) A description of the 
 sun. (2) A term sometimes applied to the 
 fixing of images in the camera obscura. 
 (3) Transmitting or receiving telegraphic 
 signals by means of the heliograph. 
 
 Holiostat. A mirror mounted on an axis 
 parallel to the axis of the earth and so 
 rotated by clock-work as to keep a beam 
 of light reflected from its surface in a 
 constant position, notwithstanding the 
 rotation of the earth. 
 
 Heliotropism. A bending and twisting 
 action produced on the growth of stalks 
 and stems by their exposure to any source 
 of light. 
 
 Helix. A word sometimes used in place 
 of coil or solenoid. 
 
 Holm Indicator. An electrical indicator 
 on board ship for indicating the position 
 at which the helm or rudder stands. 
 
 Helmholtz's Galvanometer. A double- 
 ring tangent-galvanometer, whose two 
 ring coils are parallel to each other, and 
 so placed on opposite sides of the mag- 
 netic needle that their magnetic field at 
 the needle may be as nearly uniform as 
 possible, and much more nearly uniform 
 than a single-coil ring can produce. 
 
 Hemihedral Crystal. A crystal whose 
 shape or form has been modified by the 
 replacement of half of its edges or solid 
 angles. 
 
 Hemispherical Pole-Pieces. Pole- 
 pieces of a dynamo-electric machine that 
 provide between them a spherical space 
 for the revolution of an armature. 
 
 Hen. A word proposed for henry. (Not 
 in use.) 
 
 Henley's Quadrant Electroscope. 
 A form of swinging-pendulum electro- 
 scope formerly employed for indicating 
 powerful charges of electricity. 
 
 Henry. (1) The practical unit of self-in- 
 duction. (2) An earth-quadrant, or 10 9 
 centimetres. 
 
 Henry's Coils. A number of separate in- 
 duction coils sp'connected that the cur- 
 rents induced in the secondary of the first 
 coil, induce currents in the secondary of 
 the second coil with whose primary it is 
 connected in series, and so on throughout 
 all the coils. 
 
 Heptad Atom. An atom whose valency, 
 atomicity, or combining power, is seven. 
 
 Hercules' Stone. A name given by the 
 ancients to the lodestone. 
 
 Hermetical Seal. A seal obtained in a 
 
 glass vessel by the fusion of its walls, so 
 as to enable it to hold either a vacuum or 
 a pressure greater or less than that of the 
 atmospheric pressure. 
 
 Hertzian Waves. (1) Electro-magnetic 
 waves given off by an electro-magnet 
 whose intensity is undergoing rapid pe- 
 riodic variations, or by a current whose 
 strength is undergoing rapid periodic 
 variations. (2) Electro-magnetic waves 
 given off from a circuit through which 
 an oscillatory discharge is passing. 
 
 Hertz's Axial Oscillator. A term some- 
 times employed for Hertz's linear oscil- 
 lator. 
 
 Hertz's Linear Oscillator. A form of 
 Hertz's oscillator in which a straight or 
 linear conductor is employed instead of a 
 plate as in the ordinary oscillator. 
 
 Hertz's Oscillator. A term sometimes 
 employed for two insulated metallic 
 plates to which are attached metallic 
 rods, terminated by rounded poles or 
 knobs, and separated by an air-gap or 
 space through which disruptive dischar- 
 ges pass. 
 
 Hertzian Oscillations. Hertzian waves. 
 
 Heterochromatic Photometry. (1) 
 Photometric measurements made when 
 the light chosen as a photometric standard 
 emits rays whose frequencies differ from 
 that of the light which is to be measured. 
 (2) Photometry not restricted to light of 
 one color as distinguished from mono- 
 chromatic photometry. 
 
 Heterogeneous Conductor. (1) A con- 
 ductor which does not possess the same 
 power of electric conduction in all direc- 
 tions. (2) A non-isotropic conductor, or 
 non-homogeneous conducting medium. 
 
 Heterogeneous Dielectric. A non- 
 homogeneous dielectric, or one which 
 possesses different powers of induction in 
 different directions. 
 
 Heteropolar Dynamo. (1) A dynamo 
 whose conductor moves successively past 
 opposite magnet poles. (2) A bipolar or 
 multipblar dynamo, as distinguished from 
 a commutatorless dynamo. 
 
 Heterostatic. (1) Diversely electrified. 
 (2) A term employed to distinguish a form 
 of electrometer in which the electrifica- 
 tion is measured by determining the 
 mutual influence of the attraction exerted 
 by the charge to be measured, and the 
 attraction of a fixed charge imparted to 
 the instrument by a source independent 
 of the charge to be measured. 
 
 Heterostatic Electrometer. (1) An 
 electrometer in which the electrification 
 
flex.] 
 
 799 
 
 [Hig. 
 
 to be measured is not the only electrifica- 
 tion employed. (2) An electrometer pro- 
 vided with an independent charge. 
 
 Hexad Atom. An atom whose valency 
 or atomicity is six. 
 
 Hexode Working. A term employed for 
 a six- way mode of working by the Delany 
 synchronous multiplex telegraph. 
 
 Hick's Automatic Button Repeater. 
 A manual form of telegraphic repeater. 
 
 High-Admittance Motor. An alternat- 
 ing-current induction motor characterized 
 by high admittance. 
 
 High Commutator Bars. A term ap- 
 plied to those commntator segments, or 
 parts of commutator segments, which, 
 through less wear, faulty construction, or 
 looseness, are higher than the adjoining 
 segments. 
 
 High-Economy Lamp. Any lamp of 
 high efficiency. 
 
 High Frequency. Any frequency much 
 higher than that ordinarily employed. 
 
 High-Frequency Currents. Currents 
 produced by electromotive forces of high 
 frequency. 
 
 High-Frequency Induction Motor. 
 An induction motor operated by high- 
 frequency currents. 
 
 High - Frequency Transformer. A 
 transformer suitable for employment in 
 connection with high-frequency electro- 
 motive forces or pressures. 
 
 High Insulation. An unusually good in- 
 sulation. 
 
 High-Potential Current. A term loose- 
 ly applied for a current produced by high 
 electromotive forces. 
 
 High-Potential Insulator. An insula- 
 tor suitable for use on high-potential cir- 
 cuits. 
 
 High-Potential Push-Button. A push 
 button provided for safe use on a high- 
 pressure system. 
 
 High-Potential Switch. A switch suit- 
 able for use on high-pressure circuits. 
 
 High-Potential System. In the Na- 
 tional Electric Code, any pressure of from 
 300 to 3,000 volts. 
 
 High-Potential Testing Transformer. 
 An alternating-current transformer for 
 obtaining from an ordinary alternating- 
 current circuit, a high alternating pres- 
 sure suitable for testing insulation. 
 
 High-Potential Wires. Circuit wires 
 provided with high insulation, and, there- 
 fore, suitable for connection with high- 
 potential sources. 
 
 High Resistance. A resistance for any 
 circuit or apparatus, much higher than 
 that ordinarily employed on such circuit 
 or apparatus. 
 
 High-Resistance Arrester. A form of 
 lightning arrester consisting of a number 
 of thin metallic plates separated from one 
 another by means of thin sheets of mica, 
 or other refractory insulating substance. 
 
 High-Resistance Magnet. A term some- 
 times used for a long-coil magnet of fine 
 wire, possessing a high electric resistance. 
 
 High-Resistance Telephone. A tele- 
 phone having an unusually high resist- 
 ance. 
 
 High-Pressure Incandescent Lamp. 
 An incandescent lamp provided with 
 long, thin filaments whose electric resist- 
 ance is high, and which, therefore, re- 
 quires a comparatively high pressure for 
 its operation. 
 
 High-Reactance Motor. An alternating- 
 current induction motor possessing com- 
 paratively high primary reactance. 
 
 High-Speed Electric Motor. (1) An or- 
 dinary electric motor, as distinguished 
 from a motor designed to run at a slow 
 speed. (2) A motor which has its greatest 
 efficiency when running at high speed. 
 
 High-Susceptance Motor. An alter- 
 nating-current motor possessing compara- 
 tively high susceptance. 
 
 High-Tension Accumulator. An ac- 
 cumulator consisting of a number of 
 series-connected secondary cells. 
 
 High-Tension Bus. A bus-bar supplied 
 by a high pressure. 
 
 High-Tension Cable. A cable possessing 
 high insulation and, therefore, suitable 
 for bearing high electric pressures. 
 
 High-Tension Circuit. A circuit em- 
 ployed in connection with high electric . 
 pressures. t 
 
 High-Tension Fuse. A fuse for igniting 
 an explosive, that is operated by the 
 heating power of an electric discharge of 
 high tension. 
 
 High-Tension Switch. A switch suit- 
 able for use in high-tension circuits. 
 
 High Vacuum. (1) A space from which 
 nearly all traces of air or residual gas have 
 been removed, as distinguished from a low 
 or imperfect vacuum. (2) Such a vacuum 
 that the length of the mean free-path of 
 the molecules of the residual atmosphere 
 is equal to or exceeds the dimensions of the 
 containing vessel. (3) A nearly perfect 
 vacuum. 
 
 High- Voltage Electro-Magnetic Gen- 
 
Hig.] 
 
 800 
 
 [Hor. 
 
 erator. An electro-magnetic generator 
 arranged so as to produce a high electro- 
 motive force. 
 
 High- Voltage Incandescent Lamps. 
 Incandescent lamps constructed for more 
 than the usual pressure ; usually lamps for 
 more than 120 volts. 
 
 Hissing Arc. A voltaic arc that emits a 
 hissing sound, due to its carbons being 
 too near together. 
 
 " Hitching Up." A term sometimes em- 
 ployed for boosting. 
 
 Hittorf Effect. The effect produced by a 
 Hittorf tube. 
 
 Hittorf Rays. The rays emitted by a 
 Hittorf tube. 
 
 Hittorf Tubes. Various forms of high- 
 vacuum tubes employed by Hittorf in his 
 researches in electrical discharges through 
 high vacua. 
 
 Hold-Off Spring. A spring which acts to 
 keep one thing away from another, in op- 
 position to some force tending to keep it 
 in contact with such thing. 
 
 Hold-On Spring. A spring which acts to 
 keep one thing against or in contact with 
 another, in opposition to some force tend- 
 ing to pull it away from such thing. 
 
 Holder for Incandescent Lamp. An 
 incandescent lamp-socket. 
 
 Holder for Safety Fuse. A support, 
 generally of porcelain or other infusible 
 material, employed for holding a safety 
 fuse and for catching the metal when 
 fused. 
 
 Holders for Brushes of Dynamo-Elec- 
 tric Machine. Devices for holding the 
 collecting brushes of a dynamo-electric 
 machine. 
 
 Holohedral Crystal. A crystal whose 
 shape or form has been modified by the 
 replacement of all its edges or solid an- 
 gles. 
 
 Holophane. A form of glass globe or 
 enclosing chamber for a source of light, 
 which has its external surface cast into 
 lenticular ridges for the more general 
 diffusion of the emerging light. 
 
 Holophotometer. A photometer based 
 on the employment of a Bunsen screen 
 with a system of mirrors, so combined as 
 to avoid errors due to the movements 
 which the lights undergo while being 
 compared. 
 
 Holtz Influence Machine. A particular 
 form of electrostatic influence machine. 
 
 Home Battery. The battery in a sending 
 station on a telegraphic line, as distin- 
 guished from a distant battery. 
 
 Home Station. The near or sending sta- 
 tion on a telegraphic line, as distinguished 
 from a distant or receiving station. 
 
 Homogeneous Conductor. A c o n - 
 ductor possessing the same resistivity 
 throughout its length. 
 
 Homogeneous Current-Distribution. 
 Such a distribution of current through a 
 conductor in which there is an equal 
 density of current in all parts of a nor- 
 mal cross-section of the conductor. 
 
 Homogeneous Dielectric. (1) A die- 
 lectric possessing similar properties in all 
 directions. (2) A uniform dielectric. 
 
 Homogeneous Light. (1) A light con- 
 sisting practically of but a single fre- 
 quency. (2) Monochromatic light. 
 
 Homopolar Dynamo. (1) A dynamo 
 whose conductor moves continuously past 
 poles of one polarity only. (2) A com- 
 mutatorless dynamo. (3) A so-called 
 unipolar dynamo. 
 
 Hood for Arc Lamp. A hood provided 
 for the double purpose of protecting the 
 body of an arc lamp from the weather, 
 and for throwing its light in a downward 
 direction. 
 
 Hood Suspension for Arc Lamp. A 
 
 suspension of an arc lamp from a hanger- 
 board placed inside a suitably supported 
 hood. 
 
 Hop System of Space Relations. A 
 
 system of space relations, employed 
 by some electrical writers, which "fol- 
 lows the hop tendril ; i. e., which consid- 
 ers advance accompanied by left-hand ro- 
 tation as positive ; or that a rotation is 
 positive when accompanied by transla- 
 tion in the manner of a female screw : or, 
 that clockwise rotation is positive when 
 viewed from the front of the clock. 
 Horizontal Candle Power. (1) The 
 intensity of light emitted by any source 
 in a horizontal direction. (2) Tlie lumin- 
 ous intensity of a source taken in a hori- 
 zontal direction, as measured in units of 
 luminous intensity. 
 
 Horizontal Component. That portion 
 of a force which acts in a horizontal 
 direction. 
 
 Horizontal Component of Earth's Mag- 
 netism. (1) That portion of the earth's 
 directive force which acts in a horizontal 
 direction. (2) That portion of the earth's 
 magnetic force which acts to produce 
 motion in a compass needle free to move 
 in a horizontal plane only. 
 
 Horizontal Force of Needle. The hori- 
 zontal component of the earth's magnetic 
 force or magnetism. 
 
Hor.] 
 
 
 801 
 
 [Hug. 
 
 Horizontal Intensity of Earth's Mag- 
 netism. (1) The horizontal component 
 of the earth's magnetic intensity at any 
 point. (2) The earth's horizontal mag- 
 netic force upon a unit magnetic pole. 
 
 Horizontal Intensity of Light. (1) The 
 intensity of a light measured in a horizon- 
 tal direction. (2) The flux of a light con- 
 tained in a small horizontal beam issuing 
 from a source, divided by the solid angle 
 of the beam. 
 
 Horizontal Slit Photometer. A form of 
 spectro- photometer whose slit is horizon- 
 tal, lying in a straight line joining the 
 sources of light. 
 
 Horns of Pole-Pieces of Dynamo. 
 
 (1) The edges or terminals of the pole-pieces 
 of a dynamo towards or from which the 
 armature is carried during its rotation. 
 
 (2) The following or leading horns of the 
 pole-pieces of a dynamo. 
 
 Horology, Electric. That branch of 
 electric science which treats of the appli- 
 cation of electricity to the regulation and 
 operation of electric clocks. 
 
 Horse. A support for a dynamo-armature 
 in the process of winding it. 
 
 Horseless Carriage. An automobile car- 
 riage. 
 
 Horse-Power. (1) A commercial unit of 
 power, activity, or rate-of-doing-work. 
 (2) A rate-of-doing-work equal to 33,000 
 pounds raised one foot-per-minute, or 550 
 pounds raised one foot-per-second. (3) A 
 rate-of-doing-work equal to 4,562 kilo- 
 grams raised one metre per minule. 
 
 Horse-Power, Electric. Such a rate-of- 
 doing electrical work as is equal to 746 
 watts, or 746 volt-coulombs per second. 
 
 Horse-Power-Hour. (1) A unit of work 
 equal to the work done by one horse- 
 power acting for an hour. (2) 1,980,000 
 foot-pounds. 
 
 Horseshoe Electro-Magnet. An elec- 
 tro-magnet whose core has the shape of a 
 horseshoe, or the letter U. 
 
 Horseshoe Magnet. A magnetized bar of 
 steel or hardened iron, bent in the form 
 of a horseshoe, or letter U. 
 
 Hot Saint Elmo's Fire. A term proposed 
 by Tesla for a form of flaming brush-dis- 
 charge between the secondary terminals 
 of a high-frequency, high-potential induc- 
 tion coil. 
 
 Hot - Wire Ammeter. An ammeter 
 whose readings are based on the expan- 
 sion of a wire due to an increase of tem- 
 perature, by the passage through it of 
 the current that is to be measured. 
 
 5* 
 
 Hot- Wire Thermometer. A thermom- 
 eter whose indications are dependent on 
 the expansion of a bi-metallic wire or 
 spiral. 
 
 Hot - Wire Voltmeter. A voltmeter 
 whose indications are based on the in- 
 crease in the length of a metallic wire 
 placed in the circuit of the electromotive 
 force that is to be measured. 
 
 Hotel Annunciator. An annunciator 
 connected with the different rooms of a 
 hotel. 
 
 House Annunciator. An annunciator 
 connected with the different rooms of a 
 house. 
 
 House Mains. The conductors connect- 
 ing the service wires with the street 
 mains, in a system of multiple-incandes- 
 cent lamp distribution. 
 
 House Regulator. An alternating-cur- 
 rent apparatus for insertion in the circuit 
 of a group of lamps in a house for the 
 purpose of controlling the candle-power 
 of that group. 
 
 House-Service Conductor. In a system 
 of multiple-incandescent lamp distribu- 
 tion, that portion of the service wire 
 which is included between the street 
 mains and the cut-out within the house. 
 
 House Telephone System. (1) A do- 
 mestic telephone system. (2) A system 
 for establishing telegraphic communica- 
 tion between different places in a house. 
 
 House Wiring. The wiring in a house 
 for distributing electric currents therein. 
 
 House Wires. The circuit wires em- 
 ployed in a house in a system of distribu- 
 tion. 
 
 Howler. A term sometimes used for a 
 loud buzzer. 
 
 Hughes' Electro-Magnet.- (1) An elec- 
 tro-magnet in which a U-shaped perma- 
 nent magnet is provided with pole-pieces 
 of cast iron on which only are placed the 
 magnetizing coils. (2) A quick-acting 
 electro-magnet whose magnetizing coils 
 are placed on soft-iron pole-pieces that are 
 connected with and form the prolonga- 
 tion of the pole-pieces of a permanent 
 horseshoe magnet. 
 
 Hughes' Induction-Balance. An ap- 
 paratus for the detection of the presence 
 of a metallic conducting substance in the 
 body by the aid of induced electric cur- 
 rents. 
 
 Hughes' Theory of Magnetism. A 
 theory proposed to account for the phe- 
 nomena of magnetism by the presence of 
 originally magnetized particles or mole- 
 cules. 
 
Hum.] 
 
 802 
 
 [Hys. 
 
 Hummer, Electric. A word sometimes 
 employed for an electric buzzer. 
 
 Hunning's Transmitter. The original 
 form of dust telephone transmitter. 
 
 Hunting of Parallel-Connected Alter- 
 nators. (1) Aperiodic increase and de- 
 crease in the speed of alternators, when 
 running under certain conditions in paral- 
 lel connection as motors or dynamos. (2) 
 Imperfect synchronous running. 
 
 Hydraulic Gradient. (1) The gradient 
 representing the drop of pressure between 
 the surface of a liquid in a containing 
 vessel and a discharging orifice connected 
 therewith. (2) The rate-of-drop of pres- 
 sure in a hydraulic system of distribution. 
 
 Hydraulic Power Dynamometer, 
 Any dynamometer suitable for measuring 
 hydraulic power. 
 
 Hydraulic Storage. A method of 
 storage of energy consisting in forcing 
 water into elevated reservoirs. 
 
 Hydraulic Transmission. The trans- 
 mission of power by means of pipes con- 
 taining water under pressure. 
 
 Hydraulics. That branch of science 
 which treats of the transmission of water 
 through pipes and the apparatus required 
 for raising or moving water. 
 
 Hydro-Carbon Treatment of Fila- 
 ments. Treatment of incandescent lamp 
 filaments by means of the flashing pro- 
 cess. 
 
 Hydro-Dynamics.: That branch of nat- 
 ural philosophy which treats of the con- 
 ditions of rest and motion in fluid bodies. 
 
 Hydro-Electric Bath. An electro-thera- 
 peutic bath in which one electrode is ap- 
 plied to the metallic lining of the bath 
 tub, and the other to the body of the pa- 
 tient. 
 
 Hydro-Electric Generator. A term 
 sometimes used for voltaic battery. 
 
 Hydro-Electric Machine. A term 
 sometimes used for a machine in which 
 electricity is developed by the friction of 
 a jet of steam over a water surface. 
 
 Hydro-Electro-Therapeutics. Cura- 
 tive processes combining electro-pathic 
 and electro-therapeutic treatment. 
 
 Hydrogen Voltmeter. A voltmeter 
 whose indications are based on the quan- 
 tity of hydrogen evolved under a constant 
 pressure and temperature. 
 
 Hydro-Generator, Electric. An appa- 
 ratus for the electrical development of 
 the nascent hydrogen employed in the 
 electrical rectification of alcohol. 
 
 Hygrometer. (1) An apparatus for de- 
 
 termining the specific gravity of liquids.. 
 (2) An areometer. 
 
 Hydrometric Telegraph. A form of in- 
 strument by means of which signals ar 
 transmitted by means of water pressure. 
 
 Hydro-Plastics. The art of electrically 
 shaping or depositing metals in the wet, 
 by electro-plating. 
 
 Hydro-Plasty. The art of hydro-plastics. 
 
 Hydro-Platinum Rheostat. A water 
 rheostat furnished with platinum elec- 
 trodes. 
 
 Hydrostatic Wire-Testing Machine. 
 A machine, operated by hydraulic pres- 
 sure, for testing the tensile strength of 
 wires. 
 
 Hydrotasimeter, Electric. An elec- 
 trically operated apparatus designed to 
 show at a distance the exact position of 
 any water level. 
 
 Hydrometer. An apparatus for deter- 
 mining the amount of moisture present 
 in the atmosphere. 
 
 Hydrometrical. Of or pertaining to a 
 hygrometer. 
 
 Hydrometrically. In the manner of a 
 hygrometer. 
 
 Hyperphosphorescence. (1) A nam 
 applied to a variety of phosphorescence in 
 which, after due stimulus, the body ex- 
 hibits a persistent emission of invisible 
 rays, not included in the hitherto recog- 
 nized spectrum. (2) A phosphorescence 
 accompanied by the emission of the 
 Becquerel rays. 
 
 Hypothesis. A provisional assumption of 
 facts or causes, the real nature of which 
 is still unknown, for the purpose of study- 
 ing their effects. 
 
 Hypothetical. Of or pertaining to a hy- 
 pothesis* 
 
 Hypsometer. (1) An apparatus for deter- 
 mining the height of a mountain or other 
 elevation by ascertaining the temperature 
 at which water boils on such elevation. 
 (2) a hydro-barometer. 
 
 Hypsometrical. Of or pertaining to a 
 hypsometer. 
 
 Hypsometrically. In the manner of a 
 hypsometer. 
 
 Hysteresial Dissipation of Energy. 
 The dissipation of energy by means of 
 hysteresis. 
 
 Hysteresis. (1) A lagging behind of 
 magnetization relatively to magnetizing 
 force. (2) Apparent molecular friction 
 due to magnetic changes of stress. (3) A 
 retardation of the magnetizing or demag- 
 netizing effects as regards the causes 
 
Hys.] 
 
 803 
 
 [Ice. 
 
 which produce them. (4) That quality 
 of a paramagnetic substance by virtue of 
 which energy is dissipated on the reversal 
 of its magnetization. 
 
 Hysteresis Coefficient. (1) The hystere- 
 tic coefficient. (2) The energy dissipated 
 in a cubic centimetre of magnetic ma- 
 terial by a single cyclic reversal of unit 
 magnetic density. 
 
 Hysteresis Conductance. The effec- 
 tive conductance in a transformer or 
 condenser due to the effects of hysteresis. 
 
 Hysteretetic Constant. The hysteretic 
 coefficient. 
 
 Hysteresis Loop. The looped curve 
 which forms the outlines of the graphic- 
 ally represented hysteretic cycle to rec- 
 tangular co-ordinates of magnetizing 
 force and magnetic intensity or magneti- 
 zation. (2) A cyclic magnetization curve, 
 forming a closed loop. 
 
 Hysteresis Losses. Losses of useful 
 energy due to hysteresis. 
 
 Hysteresis Measurer. An apparatus 
 for conveniently estimating or measuring 
 the hysteretic coefficient of a magnetic 
 material. 
 
 Hysteresis Meter. A hysteresis meas- 
 urer. 
 
 Hysteresis Tester. A hysteresis meas- 
 urer. 
 
 Hysteretic Activity. Activity expended 
 in producing hysteretic effects. 
 
 Systeretie Coefficient. The activity in 
 watts which would be expended in one 
 cubic centimetre of a metal when magnet- 
 ized and demagnetized to a flux density 
 of one gauss at one 'complete cycle or 
 double-reversal per second. 
 
 Hysteretic Condensance. In a con- 
 denser traversed by an alternating 
 current, the apparent reactance of the 
 condenser, due to or modified by hyster- 
 esis. 
 
 Hysteretic Conductance. In a con- 
 denser traversed by an alternating cur- 
 rent, the apparent conductance of the 
 condenser, due to or modified by hyster- 
 esis. . 
 
 Hysteretic Cycle. A cycle of complete 
 magnetization and reversal. 
 
 Hysteretic Energy Current. The com- 
 ponent of current in phase with the im- 
 pressed E. M. F. at the primary terminals 
 of a transformer representing the power 
 expended in hysteresis. (2) The energy 
 component of the exciting current of a 
 transformer. 
 
 Hysteretic Energy Electromotive 
 Force. The energy component of the 
 E. M. F. of excitation in a transformer. 
 
 Hysteretic Lag. The lag in the magnet- 
 ization of a transformer due to hysteresis. 
 
 Hysteretic Resistance. In a condenser 
 traversed by an alternating current, the 
 apparent resistance of the condenser due 
 to or modified by hysteresis. 
 
 Hysteretic Susceptance. In a con- 
 denser traversed by an alternating cur- 
 rent, the apparent susceptance of the 
 condenser, due to or modified by hys- 
 teresis. 
 
 Hysteretic Torque. That portion of the 
 torque of a dynamo-electric machine due 
 to the influence of hysteresis, whereby 
 mechanical work must be expended in de- 
 veloping hysteretic energy as heat in the 
 iron undergoing magnetic reversal. 
 
 I 
 
 I. (1) A symbol for strength of current. 
 (2) A symbol for intensity of magneti- 
 zation. 
 
 <D. A symbol for intensity of magneti- 
 zation. (Partly international usage.) 
 
 I. H. P. A contraction for indicated horse- 
 power. 
 
 I. I. In telegraphy, a signal serving to 
 separate the text of a message from the 
 signature, or the name of the sender. 
 
 I. B. A contraction for India rubber. 
 
 I, B. A contraction sometimes employed 
 for the drop in an electric circuit, equal to 
 the product of the current in amperes by 
 the resistance in ohms. 
 
 I. 8. W. Gr. A contraction for Imperial 
 
 standard wire gauge. 
 I. W. Gr. A contraction for Indian wire 
 
 gauge. 
 
 I. 2 B. Activity. (1) The activity expended 
 in a circuit, equal to the square of the 
 current strength in amperes by the resist- 
 ance in ohms. (2) The C 2 R. activity. 
 
 I. 2 B. Loss. (1) The loss of power in any 
 circuit equal to the square of the current 
 in amperes by the resistance in ohms. 
 (2) The C 2 R. loss. 
 
 I- Armature. An I, or H-shaped armature. 
 
 Ice Clearer for Trolleys. A trolley 
 
He.] 
 
 804 
 
 I IMIII. 
 
 wheel designed to remove aggregations of 
 ice from a trolley-wire. 
 
 Ideal Solenoid. A solenoid consisting of 
 a cylinder built up of a number of true 
 circular currents, all independent of one 
 another, and all of whose faces of like 
 polarity are similarly directed. 
 
 Identical-Electrode Cell. A term some- 
 times employed for a double-fluid voltaic 
 cell, both of whose electrodes' are formed 
 of the same metal, and whose electro- 
 motive forces are dependent on the col- 
 lection of unlike ions around such plates. 
 
 Idio-Electrics. A term formerly applied 
 to such bodies as amber, resin, or glass, 
 which are readily electrified by friction, 
 and which were then supposed to be elec- 
 tric in themselves. (Obsolete.) 
 
 Idiostatic. Possessing one kind of elec- 
 trification only. 
 
 Idiostatic Electrometer. An electro- 
 meter in which the electrification is whol- 
 ly due to the potential difference to be 
 measured, as distinguished from a heter- 
 ostatic electrometer, in which an auxiliary 
 charge is employed from an independent 
 source. 
 
 Idle Coil. (1) Any coil through which 
 for the time no current is passing. (2) 
 Any coil which is not passing through 
 a magnetic field or generating an E. M. F. 
 
 Idle Current. A wattless current. 
 
 Idle Current of Alternating-Current 
 Dynamo.^ The wattless current of an 
 alternating-current circuit, as distin- 
 guished from the active or working cur- 
 rent. 
 
 Idle Plug. In a telephone switchboard, a 
 plug not in use. 
 
 Idle Poles. Poles or electrodes in Crookes' 
 tubes between which no discharge is tak- 
 ing place. 
 
 Idle Wire. (1) Any wire through which 
 either no current at all, or no useful cur- 
 rent, is passing. (2) Any open-circuited 
 armature wire not generating an E. M. F. 
 
 Idle-Wire of Armature. A term some- 
 times employed in place of dead wire. 
 
 Idle Wire of Armature of Dynamo. 
 (1) That part of the wire on a dynamo 
 armature in which no useful electro- 
 motive force is produced. (2) The dead 
 wire of an armature. 
 
 Idle- Wire of Armature of Motor. 
 That part of the wire on the armature of 
 a motor in which the field produced by 
 the driving current exercises no useful 
 action in driving the motor, since no 
 counter-electromotive force is generated 
 in it. 
 
 Igniter. A carbonaceous material placed 
 between the free ends of a Jablochkoff 
 candle, which becomes incandescent on 
 the passage of the current and so enables 
 the arc to be formed. 
 
 Ignition, Electric. The explosion of a 
 powder, or the lighting of a combustible 
 substance, by electrically generated heat. 
 
 Illuminant. Any source of light. 
 
 Illuminated. A somewhat inelegant or- 
 thography for illumined. 
 
 Illuminated Dial Instrument. An in- 
 strument for engine-room or central- 
 station use, provided with a translucent 
 dial illumined from the back to render 
 the position of the pointer visible at a 
 great distance. 
 
 Illuminating Power. The amount of 
 illumination produced by any luminous 
 source. 
 
 Illumination. The quantity of light re- 
 ceived on a surface per-unit-of-area, 
 either directly from a luminous source or 
 indirectly by reflection and diffusion from 
 surrounding objects. 
 
 Illumined. Lighted up or rendered vis- 
 ible by means of light. 
 
 Illumined-Dial Measuring Instru- 
 ment. A name applied to any electri- 
 cal measuring instrument whose dial is 
 so illumined that its scale divisions can be 
 readily seen at a distance. 
 
 Illumined Electrode. That electrode of 
 a selenium cell which on exposure to 
 light develops an E. M. F. 
 
 Illuminometer. An instrument for 
 measuring the illumination of a surface. 
 
 Image. The picture of an object formed 
 by rays from its several points, brought 
 or focused by any suitable means, either 
 on the retina, or on a screen, so as to per- 
 mit the image to become visible. 
 
 Image, Electric. (1) A term sometimes 
 applied to the charge produced on a 
 neighboring surface by induction from a 
 known charge. (2) An electrified point, 
 or system of points, on one side of a sur- 
 face, which would produce on the other 
 side of that surface the same electrical 
 action that the actual electrification of 
 the surface really produces. 
 
 Imbibition Currents. Currents pro- 
 duced in tissues by the imbibition or 
 absorption of a fluid. 
 
 Immediate False Zero. A term em- 
 ployed in Wheatstone-bridge measure- 
 ments in an observation made with ref- 
 erence to that position of the galvano- 
 meter needle, as zero, which is assumed, 
 
I 111 111.] 
 
 805 
 
 [Imp. 
 
 or which tends to be assumed, immedi- 
 ately after the application of the testing 
 E. M. F. 
 
 Immersion Front of Microscopic Ob- 
 ject Glass. That front of a high-power 
 or immersion objective, to which the 
 object is attached, by a drop of transpar- 
 ent liquid. 
 
 Immersion Gilding. A gilding or elec- 
 tro-plating obtained by a process of sim- 
 ple immersion in a suitable solution of 
 gold. 
 
 Immersion Objective. An object glass 
 of high magnifying power. 
 
 Impact. A shock or collision caused by 
 the meeting of two bodies when one or 
 both are in motion. 
 
 Impedance. (1) Generally, opposition to 
 current flow. (2) The sum of the ohmic 
 resistance, and the spurious resistance of 
 a circuit, measured in ohms. (3) In a 
 simple-harmonic current circuit the 
 square root of the sum of the squares of 
 the resistance and reactance. (4) The 
 apparent resistance of a circuit contain- 
 ing both resistance and reactance. 
 
 Impedance Circuit. A circuit contain- 
 ing impedance. 
 
 Impedance Coils. A term sometimes 
 applied to choking coils, reactance coils, 
 or economy coils. 
 
 Impedance Factor. The ratio of the im- 
 pedance of a conductor or circuit to its 
 ohmic resistance. 
 
 Impedance Bush. (1) The rush of cur- 
 rent produced on closing an inductive 
 circuit. (2) An impulsive current rush. 
 
 Impediment. A term proposed for the 
 apparent resistance of a circuit contain- 
 ing resistance, self-induction, and capac- 
 ity. 
 
 Impenetrability. That property which 
 prevents any two particles of matter 
 from occupying the same space at the 
 same time. 
 
 Imperfect Earth. Partial earth. 
 
 Imperfect Linkage. (1) Magnetic flux 
 linkage between two coils or circuits, such 
 that some linkage of one circuit is not 
 associated with the other circuit. (2) 
 Coils or circuits possessing mutual induc- 
 tion but also possessing magnetic leakage. 
 
 Imperfect Magnetic Circuit. A term 
 sometimes employed for a magnetic cir- 
 cuit in which, from the magnetizing coils 
 being placed on one part of the core 
 only, the intensity of the flux is greater 
 through some portions of the ferric cir- 
 cuit than through others, so that some of 
 
 the lines of induction complete their cir- 
 cuits by passing through the space sur- 
 rounding the core instead of through the 
 core itself. 
 
 Impermeability. The reciprocal of the 
 permeability. 
 
 Impermeance. The reciprocal of the per- 
 meance. 
 
 Imponderable. (1) Possessing no weight. 
 (2) A term formerly applied to the lumi- 
 niferous or universal ether. 
 
 Impressed. Caused to act or forced upon. 
 
 Impressed Electromotive Force. 
 (1) The electromotive force brought to 
 act in any circuit to produce a current 
 therein. (2) In an alternating-current 
 circuit, the impressed electromotive force 
 due to an impressed source, in contradis- 
 tinction to the effective electromotive 
 force, or that which is active in produc- 
 ing current, or the electromotive forces 
 due to, or opposed to, self or mutual induc- 
 tion. (3) An applied E. M. F. as distin- 
 guished from a resultant, active, or watt- 
 less E. M. F. 
 
 Impressed Field. An electric or mag- 
 netic field brought to bear upon any sub- 
 stance or space as distinguished from sec- 
 ondary fields thereby set up. 
 
 Impressed Pressure. The impressed 
 electromotive force. 
 
 Impulse. (1) Any single or momentary 
 force acting on a body. (2) The motion 
 produced by a suddenly communicated 
 force. 
 
 Impulse of Couples. The product of the 
 magnitude of a couple, and the time it is 
 acting. 
 
 Impulsion Cell. A photo-electric cell 
 whose sensitiveness to light may be re- 
 stored or destroyed by slight impulses 
 given to the plate, either by mechanical 
 blows or taps, or by electro-magnetic im- 
 pulses. 
 
 Impulsion Effect. The restoration or 
 loss of sensitiveness of a photo-electric 
 cell to the action of light, produced by 
 means of an impulse, such as a mechan- 
 ical tap or blow, or an electro-magnetic 
 impulse. 
 
 Impulsive. Communicated by an im- 
 pulse. 
 
 Impulsive Current-Rush in Inductive 
 Circuit. An abnormal rush of current 
 which sometimes occurs when a trans- 
 former is suddenly switched on to an 
 active main. 
 
 Impulsive Discharge. A discharge pro- 
 duced in conductors by suddenly created 
 differences of potential. 
 
Imp.] 
 
 806 
 
 [Inc. 
 
 Impulsive Impedance. The impedance 
 encountered by an oscillatory discharge. 
 
 Impulsive Inductance. The apparent 
 inductance of a conductor or circuit when 
 subjected to an impulsive discharge. 
 
 Impulsive Permittance. The apparent 
 permittance of a conductor or circuit 
 through which an impulsive discharge is 
 passing. 
 
 Impulsive-Rush Discharge. An im- 
 pulsive discharge. 
 
 " In Bridge." In multiple to a circuit, as 
 distinguished from being inserted in 
 series with a circuit. 
 
 Inactive Molecules. (1) Those molecules 
 of an electrolyte which, during the pas- 
 sage of an electric current, are not re- 
 solved into their constituent ions, and 
 which, therefore, have no effect on the 
 molecular conductivity of the electrolyte. 
 (2) The non-dissociated molecules of an 
 electrolyte. 
 
 Incandesce. To glow or shine by means 
 of incandescence. 
 
 Incandescence. The shining or glowing 
 of a substance, usually a solid, by reason 
 of its elevation to a sufficiently high tem- 
 perature. 
 
 Incandescence, Electric. The shining 
 or glowing of a substance, generally a 
 solid, by means of heat of electric origin. 
 
 Incandescent. Shining or glowing with 
 heat. 
 
 Incandescent-Ball Electric Lamp. An 
 incandescent electric lamp in which the 
 light is produced by a sphere or ball of 
 carbon placed in an exhausted glass 
 chamber and subjected to electrostatic 
 waves of high frequency. 
 
 incandescent Bombardment-Lamp. 
 An electric lamp in which a refractory 
 material is rendered incandescent by the 
 molecular bombardment produced by the 
 passage of an electric discharge through 
 a rarefied space. 
 
 Incandescent Circuit. A circuit pro- 
 vided for the operation of incandescent 
 electric lamps. 
 
 Incandescent-Cut-Out. (1) A cut-out 
 suitable for use in an incandescent light 
 circuit. (2) A safety-fuse cut-out. 
 
 Incandescent Filament. The incandes- 
 cing conductor of an incandescent electric 
 lamp, whether of small or of compara- 
 tively large cross-section, though gener- 
 ally of the former. 
 
 Incandescent Electric Lamp. An elec- 
 tric lamp whose light is produced by the 
 electric incandescence of a strip or fila- 
 
 ment of some refractory substance, almost 
 invariably carbon. 
 
 Incandescent Electric Lighting. 
 Artificial lighting obtained by means of 
 incandescent, electric lamps. 
 
 Incandescent Generator. A dynamo- 
 electric machine suitable for operating 
 incandescent lamps. 
 
 Incandescent Lamp. An incandescent 
 electric lamp. 
 
 Incandescent Lamp-Base. The base of 
 an incandescent electric lamp. 
 
 Incandescent Lamp-Cord. A flexible 
 lamp cord containing two separate con- 
 ductors, suitable for use with a pendant 
 incandescent electric lamp. 
 
 Incandescent Lamp-Shade. A shade 
 provided for use in connection with an in- 
 candescent electric lamp. 
 
 Incandescent Lamp-Socket. A socket 
 provided for the reception of an incan- 
 descent lamp. 
 
 Incandescent Lighting. Artificial 
 lighting produced by the use of incandes- 
 cent lamps. 
 
 Incandescent Lighting Dynamo-Elec- 
 tric Machine. An incandescent gener- 
 ator. 
 
 Incandescent Mantle-Burner. (1) A 
 gauze skeleton, or mantle, employed for 
 artificial illumination, made of refractory 
 materials and rendered incandescent by 
 the heat of a Bunsen flame. (2) The man- 
 tle of a Welsbach burner. 
 
 Incandescing. Producing light by incan- 
 descence. 
 
 Incandescing Filament. A lamp fila- 
 ment that is producing light by incandes- 
 cence. 
 
 Incandescing Lamp. (1) An incandes- 
 cent lamp that is actually producing light. 
 (2) An incandescent lamp emitting light. 
 
 Inclination Chart. A map or chart on 
 which the isoclinic lines are marked. 
 
 Inclination Compass. (1) A magnetic 
 needle, free to move in a single vertical 
 plane only, and employed for determining 
 the angle of dip at any place. (2) An in- 
 clinometer or dipping circle. 
 
 Inclination Magnetometer. An incli- 
 nation compass or inclinometer. 
 
 Inclination Map. A map or chart on 
 which isogonal lines, or lines connecting 
 places which have the same magnetic dip 
 or inclination, are drawn. 
 
 Inclination of Magnetic Needle. (1) 
 The deviation of a mechanically balanced 
 magnetic needle from a horizontal posi- 
 tion. (2) The dip of a magnetic needle. 
 
lue.J 
 
 807 
 
 [lud. 
 
 Inclinometer. An inclination compass. 
 (2) A word sometimes used for a dipping 
 circle. 
 
 Incoming Call. A call received at an ex- 
 change from a subscriber or from another 
 exchange, as distinguished from an out- 
 going call. 
 
 Incoming Call Trunk Line. A trunk 
 line entering a central telephone station 
 and employed for the reception of calls, 
 as distinguished from an outgoing call 
 trunk line upon which calls are trans- 
 mitted. 
 
 Incoming End. The end of a junction 
 telephone wire at which calls are received. 
 
 Incoming Junction Board. A switch- 
 board at a central exchange at which in- 
 coming junction wires are received and 
 distributed. 
 
 Incoming Lines. Lines at a telephone 
 exchange at which calls are received, as 
 distinguished from outgoing lines. 
 
 Incoming Signals. The signals that are 
 received at the home end of a telegraphic 
 circuit. 
 
 Incoming Wires. Wires leading into a 
 building, room, switchboard, or other de- 
 vice. 
 
 Incomplete Circuit. An open or broken 
 circuit. 
 
 Inconductivity. A word sometimes used 
 for non-conductivity. 
 
 Increased Electric Irritability. Irrita- 
 bility of nervous or muscular tissue pro- 
 duced' by a much weaker electric current 
 than that required to produce it in nor- 
 mal tissue. 
 
 Increment Key. A telegraphic key so 
 connected that an increase or increment 
 in the line current occurs -whenever the 
 key is depressed, as distinguished from a 
 key which opens or closes a circuit. 
 
 Increment Key of Quadruples Tele- 
 graphic System. A key employed to 
 increase the strength of a current and so 
 operate one of the distant instruments in 
 a quadruples system, by an increase in 
 the strength of the current. 
 
 Independent Circuits. (1) Separate cir- 
 cuits or those which have no electric con- 
 nection with other circuits. (2) Circuits 
 in electric connection, but acting inde- 
 pendently, as though insulated from each 
 other. 
 
 "In-Current" of Telephone Relay. 
 The current which is received by a tele- 
 phone relay, for transmission to another 
 circuit. 
 
 Independent-Biphase System. A 
 
 phrase sometimes used for the four-wire 
 diphase system. 
 
 Indestructibility of Energy or Mat- 
 ter. A theory which assumes that 
 energy or matter can never be destroyed, 
 and that, consequently, when either dis- 
 appears in one form or phase, it must re- 
 appear in some other form or phase. 
 
 Index of Refraction. (1) The ratio of 
 the sine of the angle of incidence to the 
 sine of the angle of refraction for the 
 light passing from a vacuum into a mate- 
 rial medium. (2) A quantity represent- 
 ing the amount of deviation of a ray of 
 light from its original course, on its pas- 
 sage from a standard medium, or vacuum, 
 to another of different density. (3) A 
 quantity representing the ratio of the 
 velocity of wave-propagation in a vacuum 
 to the velocity in a material medium. 
 (4) In the electro-magnetic theory of light 
 the geometric mean of the specific induc- 
 tive capacity and the magnetic induc- 
 tivity of a medium to electro-magnetic 
 waves of a given frequency. 
 
 India Rubber. (1) A resinous substance 
 obtained from the milky juices of a 
 tropical tree. (2) Caoutchouc. 
 
 Indicating Bell. An electric bell which, 
 in order to distinguish between different 
 bells in the same office, is provided with 
 an annunciator drop which is released by 
 each bell when it rings. 
 
 Indicating-Bell Annunciator. An an- 
 nunciator provided for an indicating bell. 
 
 Indicating Lamp. A lamp connected 
 with a circuit, which is lighted or extin- 
 guished, or the intensity of whose light 
 is caused to vary, on the occurrence of a 
 predetermined change in the pressure or 
 resistance of the circuit. 
 
 Indicating Push Button. A push but- 
 ton which leaves an indication of its 
 having been depressed. 
 
 Indicating Switch. A switch provided 
 with an indicator which shows whether 
 the circuit of the switch is closed or open. 
 
 Indicator. A term sometimes employed 
 for annunciator. 
 
 Indicator Card. The card of a steam- 
 engine indicator, on which are traced the 
 curves of pressure, by means of which the 
 indicated horse-power of the engine may 
 be calculated. 
 
 Indicator Dial, Electric. In a system 
 of railway block signalling by electricity, 
 an electro-magnetic indicator having a 
 dial which shows the condition of a sec- 
 tion of railway. 
 
 Indicator, Electric. (1) A general terra 
 
Ind.] 
 
 808 
 
 [Ind. 
 
 applied to various devices operated by the 
 deflection of a magntic needle, or the 
 ringing of a bell, or by both, for indicat- 
 ing, at some distant point, the condition 
 of an electric circuit, the strength of cur- 
 rent passing through any circuit, the 
 head of water or other liquid, the pressure 
 on a boiler, the temperature, the speed of 
 an engine or lines of shafting, the work- 
 ing of a machine, or other similar events 
 or occurrences. (2) A term sometimes 
 used in place of annunciator. (3) Any 
 electric or magnetic signalling apparatus. 
 
 Indicator Flap. A light metal disk or 
 cover, hinged over a self-restoring indi- 
 cator, in a branching multiple telephone 
 switchboard. 
 
 Indifferent Electrode. In electro-thera- 
 peutics, the electrode that is employed to 
 merely complete the circuit through the 
 organ or part of the body subjected to the 
 electric current, and not directly con- 
 cerned in the treatment or diagnosis of 
 the diseased part, and which, therefore, 
 may be located at any convenient point. 
 
 Indifferent Point. A point in the intra- 
 polar regions of a nerve, where the ane- 
 lectrotonic and cathelectrotonic regions 
 meet, and where the excitability is, there- 
 fore, unchanged. 
 
 Indirect Distribution. A system of 
 electric distribution in which intermedi- 
 ate contrivances for the transformation 
 or accumulation of electric energy are 
 employed between the generator and the 
 receptive devices. 
 
 Indirect Electrolysis. Chemical react- 
 ions effected as a consequence of electro- 
 lytic action, as distinguished from electro- 
 lytic actions themselves. 
 
 Indirect Excitation. The excitation of 
 a muscle obtained by placing an electrode 
 on its nerve instead of directly on the 
 muscle. 
 
 Indirect Welder. A step-down trans- 
 former employed in electric welding. 
 
 Individual Electric Motors. A term 
 sometimes employed for electric motors 
 that are coupled directly to the shaft of 
 each machine to be driven or operated. 
 
 Individual Signal. A selective signal, or 
 one in which a given signal only is sound- 
 ed a.t a distant point on a circuit with 
 which more than one signal is connected. 
 
 Individual Signalling Apparatus. 
 Signalling apparatus provided with indi- 
 vidual signals. 
 
 Individual Telephone Switchboard. 
 A single section of a multiple switch- 
 board. 
 
 Individual Transformer. A transform- 
 er employed solely for the supply of some 
 particular translating device or group of 
 devices, as distinguished from a trans- 
 former which supplies a number of cir- 
 cuits or groups. 
 
 " In-Door " Transformer. A trans- 
 former designed for use inside a building. 
 
 Induced. (1) Set up or caused by induc- 
 tion. (2) Not produced by metallic com- 
 munication. 
 
 Induced Atomic or Molecular Cur- 
 rents. Currents supposed to be induced 
 in the atoms or molecules of a magnetiz- 
 able substance when brought into mag- 
 netic flux. 
 
 Induced Circuit. An inductive circuit. 
 
 Induced Current. A current produced 
 by electro-dynamic induction. 
 
 Induced Current of Transformer. A 
 term sometimes employed for the second- 
 ary current of a transformer. 
 
 Induced Direct-Current. (1) The cur- 
 rent produced in an active circuit on the 
 breaking of such circuit, having the same 
 direction as the active current and tend- 
 ing to prolong and strengthen it. (2) The 
 break-induced current. 
 
 Induced Electromotive Forces. E. M. 
 F.'s set up by electro-dynamic induction. 
 
 Induced Electric Surgings. Electric 
 surgings induced in neighboring conduct- 
 ors by means of electric surgings, oscilla- 
 tory discharges, or impulsive current- 
 rushes in their vicinity. 
 
 Induced Electrostatic Charge. A 
 charge produced by bringing a body inta 
 an electrostatic field. 
 
 Induced Lightning Discharge. (1) A 
 lightning discharge produced in a sub- 
 stance by induction from a neighboring 
 lightning flash. (2) A back or return 
 lightning stroke. 
 
 Induced M. M. F. (1) Any magneto- 
 motive force produced by induction. (2) 
 The aligned or structural magneto-motive 
 force, as distinguished from the prime 
 magneto-motive force. 
 
 Induced Magnetic Flux. Magnetic 
 flux produced in any body by induction. 
 
 Induced Reverse Currents. (1) The 
 currents induced in an active conductor 
 at the moment of making or closing the 
 circuit in the opposite direction to the in- 
 ducing current, and, therefore, tending to 
 check its flow. (2) The current induced 
 in the secondary on making or breaking 
 the circuit of the primary. 
 
Ind.] 
 
 809 
 
 [Ind. 
 
 Induced Spiral or Conductor. A term 
 sometimes used for the secondary spiral or 
 conductor of a transformer. 
 
 Inducing. Producing electromotive 
 forces, currents, or fluxes, by means of in- 
 duction. 
 
 Inducing Circuit. Any circuit which 
 causes induction. 
 
 Inducing Current of Transformer. A 
 term sometimes employed for the primary 
 current of a transformer. 
 
 Inducing Magnet. The permanent mag- 
 net of a relay. 
 
 Inducing Spiral or Conductor. A term 
 sometimes used for the primary spiral or 
 conductor of a transformer. 
 
 Inductance. (1) The capacity for induc- 
 tion possessed by an active circuit on itself, 
 or on neighboring circuits. (2) Self-in- 
 duction. (3) That property, in virtue 
 of which a finite electromotive force 
 impressed on a circuit does not im- 
 mediately generate the full current due 
 to the resistance of the circuit, and 
 which, when the electromotive force 
 is withdrawn, requires a finite time 
 for the current strength to fall to its 
 zero value. (4) A property, by virtue of 
 which the passage of an electric current 
 is necessarily accompanied by the absorp- 
 tion of electric energy in producing a 
 magnetic field. (5) A constant quantity 
 in a circuit at rest, and devoid of iron, de- 
 pending only upon its geometrical ar- 
 rangement, and usually expressed in 
 henrys, or in centimetres. 
 
 Inductance Box. A box containing a 
 number of graded inductances, and em- 
 ployed for the measurement of the in- 
 ductance of a circuit. 
 
 Inductance Bridge. An apparatus 
 similar to a Wheatstone's bridge, for 
 measuring the inductance of a circuit. 
 
 Inductance Coil. (1) An impedance, re- 
 actance, or choking coil. (2) A coil placed 
 in a circuit, for the purpose of prevent- 
 ing an impulsive current-rush in that 
 circuit, by means of the counter-electro- 
 motive force developed in the coil on 
 being magnetized. 
 
 Inductance-Reactance. The reactance 
 of a self-inductive coil, as distinguished 
 from the reactance of a condenser, or a 
 capacity-reactance. 
 
 Inductance-Resistance. Reactance. 
 
 Inductance Speed. (1) A term proposed 
 for the product of the co-efficient of self- 
 induction by an angular velocity, corre- 
 sponding to a simple-harmonic frequency. 
 (2) In an alternating-current circuit, the 
 
 product of an inductance and STT times the 
 frequency. 
 
 Inductanceless. Devoid of inductance. 
 
 Inductariceless Circuit. (1) A circuit 
 practically devoid of inductance. (2) A 
 circuit whose magnetic field is negli- 
 gible, such, for example, as an ordinary 
 incandescent lamp, or a double-wound re- 
 sistance coil. 
 
 Inducteous Body. A term proposed by 
 Faraday for a body in which a charge is 
 induced by the action of a neighboring 
 charge. 
 
 Induction. (1) The influence exerted by 
 a charged body, or by a magnetic field, 
 on neighboring bodies without apparent 
 communication. (2) The influence pro- 
 duced through a dielectric by the action 
 of electrostatic or magnetic flux. 
 
 Induction Alternator. A name some- 
 times given to an inductor alternator. 
 
 Induction Booster. An ordinary induc- 
 tion m'otor whose field coils are in series 
 with the mains, employed in an alternat- 
 ing-current circuit as a booster or feeder 
 regulator. 
 
 Induction Bridge. (1) A balance in 
 which electro-magnetically induced cur- 
 rents are equilibrated. (2) An induct- 
 ance bridge. 
 
 Induction Coil. An apparatus consisting 
 of two associated coils of insulated wire 
 employed for the production of currents by 
 mutual induction. 
 
 Induction Factor. In an alternating- 
 current circuit the ratio of the wattlesa 
 component of current to the total current 
 strength. 
 
 Induction-Finder. A term sometime* 
 used for a magnetic explorer. 
 
 Induction Flux. Total magnetic flux iir 
 any portion of a magnetic circuit. 
 
 Induction Generator. (1) A generator 
 supplying currents which are received 
 from the line and reinforced within its 
 coils. (2) A generator which operates by 
 induction from currents in a short-cir- 
 cuited armature. (3) An induction-motor- 
 driven above synchronism. (4) An alter- 
 nating-current dynamo itself incapable of 
 generating currents but becoming excited 
 y currents received from the line. 
 
 Induction Killer. Any anti-inductioa 
 device. 
 
 Induction Motor. (1) An asynchronous 
 alternating-current motor, in which cur- 
 rents are induced in a short-circuited ele- 
 ment or armature. (2) A polyphase or 
 uniphase motor operating by the action 
 
Ind.] 
 
 810 
 
 [Ind. 
 
 of a rotary magnetic field upon a short- 
 circuited armature. " 
 
 Induction Multiphase-Motor. An al- 
 ternating-current induction, or .asynchro- 
 nous motor, operated by multiphase cur- 
 rents. 
 
 Induction Plates of Condenser. The 
 metallic plates of a condenser on which 
 the charges reside. 
 
 Induction Regulator. A term some- 
 times employed for an alternating-current 
 regulator. 
 
 Induction Resistance. An inductive 
 resistance. 
 
 Induction Rotary. A term sometimes 
 employed for a rotary converter without 
 field excitation. 
 
 Induction Screen. (1) A plate of metal 
 placed between two adjacent electrified 
 bodies, or magnetic coils, for the purpose 
 of preventing or modifying the inductive 
 action they exert on one another. (2) A 
 conducting screen wholly or -partially 
 opaque to inductive action. 
 
 Induction Telegraph. A general term 
 embracing the apparatus employed in in- 
 duction telegraphy. 
 
 Induction Telegraphy. (1) A system for 
 telegraphing, between moving trains and 
 fixed stations on a railroad, by means of 
 impulses transmitted by induction be- 
 tween the car and a wire parallel with 
 the track. (3) Wireless telegraphy. 
 
 Induction Top. A top consisting of a 
 copper disc supported on a vertical axis, 
 which, when spun before the poles of a 
 steel magnet, assumes an inclined posi- 
 tion, by reason of the currents produced 
 therein. 
 
 Induetional Igniting Device. A de- 
 vice for producing ignition by an induced 
 electric discharge. 
 
 Inductionless. Devoid of induction. 
 
 Inductionless Circuit. A circuit devoid 
 of induction. 
 
 Inductionless Resistance. <1) A resist- 
 ance devoid of self-induction. (2) A 
 double-wound resistance. 
 
 Inductive. Capable of producing induc- 
 tion. , 
 
 Inductive Capacity of Line. The elec- 
 trostatic capacity of a line. 
 
 Inductive Circuit. Any circuit in which 
 induction occurs. 
 
 Inductive Connection. A connection of 
 one circuit with another by means of in- 
 duction only, as distinguished from me- 
 tallic connection. 
 
 Inductive Disturbance. Any disturb- 
 
 ance in the operation of a telephone o* 
 telegraph line produced by induction. 
 
 Inductive Electromotive Force. An 
 
 electromotive force produced by induc- 
 tion. 
 
 Inductive Interference. Inductive dis- 
 turbance on a line. 
 
 Inductive Leak. A leak containing in- 
 ductance provided in a cable or circuit as 
 distinguished from a leak containing re- 
 sistance only. 
 
 Inductive Leakance. (1) Leakage tak- 
 ing place through inductive shunts. (2) 
 Leakage artificially produced in a tele- 
 graph or telephone circuit through in- 
 duction coils. 
 
 Inductive Pole. An induced pole. 
 Inductive-Reactance. Reactance due to 
 
 self induction as distinguished from re- 
 
 a ctance due to a condenser. 
 
 Inductive Retardation. A retardation 
 in the appearance of a signal, at the dis- 
 tant end of a cable or circuit, produced 
 by the action of induction. 
 
 Inductive Resistance. (1) A resistance 
 possessing self-induction. (2) The react- 
 ance of a circuit. 
 
 Inductive Resistance Regulator. Any 
 regulator suitable for altering the imped- 
 ance of a circuit or conductor by varying 
 its inductance. 
 
 Inductivity. (1) A word proposed for 
 specific inductance. (2) Magnetic perme- 
 ability. 
 
 Inductivity. (1) The magnetic perme- 
 ability of a magnetic medium. (2; The 
 dielectric constant of an electric medium. 
 
 Inductively Associated Circuit. Such 
 a position of a circuit as regards another 
 circuit, that any electric change in one 
 circuit produces a corresponding change 
 in the other circuit by induction 
 
 Inductize. To subject a body to the effects 
 of induction. 
 
 Inductometer. An instrument capable 
 of measuring inductance. 
 
 Inductpphone. A device for obtaining 
 electric communication between moving 
 trains and fixed stations by means of in- 
 duction currents. 
 
 Inductor Alternator. (1) An inductor 
 dynamo for alternating currents. (2) An 
 alternator in which both armature and 
 field are fixed, but in which a rotating 
 frame is so placed in relation to each as to 
 generate E. M. F.'s in conducting loops 
 or coils on the armature. 
 
 Inductor Alternating Generator. An 
 alternator in which neither the field coils 
 
Incl.] 
 
 811 
 
 Tins. 
 
 nor the armature rotates, but an iron 
 frame rotates in such a manner as to 
 periodically fill and empty the armature 
 loops with magnetic flux. 
 Inductor Dynamo. (1) A generator in 
 which the field and armature coils are 
 stationary, and the magnetic flux through 
 them is altered by the motion of inductors 
 past them. (2) A dynamo-electric gener- 
 ator in which the differences of potential 
 causing the currents are obtained by mag- 
 netic changes in the cores of the armature 
 and field coils by the movements of in- 
 ductors past them. 
 
 Inductor Generators. Inductor alter- 
 nators or dynamos. 
 
 Inductors of Electrostatic Machine. 
 The electrified parts of an electrostatic 
 influence machine, which exert inductive 
 influence. 
 
 Inductors. The laminated masses of iron 
 employed in inductor dynamos for the 
 purpose of producing variations in the 
 magnetic flux of the core and armature. 
 
 Inductprium. A name sometimes given 
 to an induction coil. 
 
 Inductoscope. Any apparatus for de- 
 tecting the presence of induction between 
 two circuits. 
 
 Inductric. Capable of producing induc- 
 tion. 
 
 Inductric Body. A term proposed by 
 Faraday for the body containing the in- 
 ducing electric charge. 
 
 Inefficiency of Incandescent Lamp. 
 The number of watts that have to be sup- 
 plied to an incandescent lamp per-candle- 
 power emitted, very commonly, but inac- 
 curately, called the'efficiency of the lamp. 
 
 Inertia. The inability of a body to change 
 its condition of rest or motion until some 
 rorce acts on it. 
 
 Inertia, Electric. A term sometimes 
 used for electro-magnetic inertia. 
 
 Inertia Factor. The factor in a 'dynami- 
 cal system in virtue of which the moving 
 system possesses kinetic energy. 
 
 Inferred Zero. (1) A zero deduced or 
 inferred from the deflection produced by 
 a charge that is to be measured, by com- 
 parison with the value of the deflection 
 obtained by a known charge. (2) A zero 
 on the scale^of an instrument, too remote 
 to be mechanically obtainable, but as- 
 sumed as virtually existing for the pur- 
 poses of calculation. 
 
 Infinity Plug. (1) A plug provided for 
 a hole in a resistance box in which the 
 two pieces of brass the plug connects are 
 not connected by any resistance coil, and 
 
 which, therefore, when withdrawn, leaves 
 an open circuit of a practically infinite 
 resistance. (2) A discontinuity plug. 
 Inflection. The bending by diffraction of 
 rays of light or radiant energy on their 
 passage past a sharp edge. 
 
 Inflexible Conduit System. A conduit 
 system which will not permit the intro- 
 duction or removal of its conductors, 
 after the structure is completed. 
 
 Influence. A word sometimes used in- 
 stead of electrostatic induction. 
 
 Influence Charge. A charge produced 
 by electrostatic induction. 
 
 Influence, Electric. Electrostatic induc- 
 tion. 
 
 Influence Machine. A name sometimes 
 used for an electrostatic-induction ma- 
 chine. 
 
 Infra-Red Frequencies. Frequencies 
 lower or smaller in Dumber than those of 
 red light. 
 
 Infra-Bed Light. A term applied to radi- 
 ation frequencies below the reds of the 
 spectrum. 
 
 Infra-Red Spectrum. That portion of 
 the spectrum which lies below the red, or 
 whose frequencies are smaller than those 
 of the red. 
 
 Initial. Placed or occurring at the be- 
 ginning. 
 
 Initial Magnetization. Magnetization 
 originally produced or imparted. 
 
 Injection of Telegraph Poles. Impreg- 
 nating telegraph poles with any preser- 
 vative liquid. 
 
 Injector. An apparatus for the introduc- 
 tion of a condenser or other device into an 
 electric circuit at a definite moment and 
 for a definite interval of time. 
 
 Inners. In telephony, the internal pair of 
 springs of a jack. 
 
 In-Put. The power absorbed by any ma- 
 chine in causing it to perform a certain 
 amount of work. 
 
 Inside Box-Brush. A brush suitably 
 shaped for polishing the inside of tubular 
 surfaces, for the purpose of cleansing such 
 surfaces so as to prepare them for electro- 
 plating. 
 
 Inside Wiring. (1) In a system of incan- 
 descent lighting, the conductors that lead 
 to the interior of a house or other building 
 to be lighted. (2) Any conductors placed 
 inside a building. 
 
 Inside Work. Indoor wiring. 
 
 Insulation, Electric. A term sometimes 
 employed for electric sun-stroke or elec- 
 trie prostration. 
 
Ins.] 
 
 812 
 
 [Ins. 
 
 .Inspection Boxes. Man-holes provided 
 for the inspection of electric mains. 
 
 -Installation. (1) A general term embrac- 
 ing the entire plant and accessories re- 
 quired to perform any specified work. 
 (2) The act of placing, arranging or erect- 
 ing a plant or apparatus. 
 
 Installation, Electric. (1) The establish- 
 ment of any electric plant. (2) A plant. 
 
 Instantaneous. Occurring at an instant. 
 
 Instantaneous-Contact Method. A 
 method of determining the form of an 
 alternating-current wave by making con- 
 tacts with the circuit at definite instants 
 in each cycle. 
 
 Instantaneous Current. The current 
 strength taken at any given moment of 
 time. 
 
 Instantaneous Electromotive Force. 
 The value of the electromotive force taken 
 at any given instant of time. 
 
 Instantaneous Efficiency of Trans- 
 former. The efficiency of a transformer 
 taken at any instant of time, as distin- 
 guished from its mean efficiency, or its 
 efficiency extending over a fairly consid- 
 erable time. 
 
 Instantaneous Pressure. The instan- 
 taneous electromotive force. 
 
 Instantaneous Value of Periodic Cur- 
 rent or E. M. P. The value of a peri- 
 odic current or E. M F. at any given in- 
 stant of time as distinguished from an 
 average or effective value. 
 
 Instantaneous Values. Values meas- 
 ured at a given instant of time, as dis- 
 tinguished from average values. 
 
 Instrument Bars. In a multiple tele- 
 phone switchboard the conducting bars 
 connected to an operator's set. 
 
 Instrument Zero. The true zero of an 
 instrument scale, as distinguished from a 
 zero selected at some other point or a 
 false zero. 
 
 Insulate. To so insulate a body as to pre- 
 vent electricity from being conducted to 
 or removed from it. 
 
 Insulated Body. A body supported on 
 or surrounded by an insulator, or non- 
 conductor of electricity. 
 
 Insulated Conductors. Conducting 
 wires provided with an insulating coating 
 or covering. 
 
 Insulated. A term sometimes employed 
 in telegraphy for a free wire, or a wire 
 that is disconnected from its apparatus 
 and left insulated. 
 
 Insulated Pliers. A pair of pliers whose 
 
 handles are encased in insulating ma- 
 terial. 
 
 Insulated Trolley-Crossing. A cross- 
 ing placed at the intersection of two 
 streets where trolley wires cross each 
 other, provided with an insulating mate- 
 rial to prevent the contact of the crossing 
 wires. 
 
 Insulated Turn-Buckle. (1) A turn- 
 buckle carrying a shackle insulator at one 
 end. (2) A device supported by suitable 
 insulators employed on overhead circuits' 
 for straightening the wires by increasing 
 the stress on them. 
 
 Insulated Wires. Wires provided with 
 insulating coverings or coatings. 
 
 Insulating. Providing with insulation. 
 
 Insulating Bushing. A bushing made 
 of insulating material. 
 
 Insulating Cements. Various mixtures 
 of gums, resins and other substances pos- 
 sessing the ability not only of binding two 
 or more substances together, but also of 
 electrically insulating them from one 
 another. 
 
 Insulating Coating. A coating or cover- 
 ing of insulating material. 
 
 Insulating Covering. An insulating 
 coating. 
 
 Insulating Joint. A joint in an insulat- 
 ing material or covering in which the 
 continuity of the insulating material is 
 ensured. 
 
 Insulating Sleeve. A sleeve formed of 
 insulating material, and provided for 
 covering splices in an insulated con- 
 ductor. 
 
 Insulating Stool. A stool provided with 
 insulating supports of vulcanite, or simi- 
 lar high-insulating substance, employed 
 to afford a convenient insulating stand or 
 support. 
 
 Insulating Tape. A ribbon of flexible 
 material impregnated with okonite, rub- 
 ber, or other similar material, and gen- 
 erally containing some adhesive sub- 
 stance, employed for insulating wires or 
 electric conductors at joints, or other ex- 
 posed places. 
 
 Insulating Tube. (1) A tube of insulat- 
 ing material provided for covering a splice 
 in an insulated conductor. (2) A tube 
 of insulating material provided for slii> 
 ping over an insulated conductor where it 
 passes through a partition, and employed 
 for preventing the abrasion of the insu- 
 lating material at that point. 
 
 Insulating Varnish. An electric varnish 
 formed of any good insulating material. 
 
Ins,] 
 
 813 
 
 Insulating Washer. A washer formed 
 of insulating material. 
 
 Insulation. Any medium or material 
 that will prevent a body from gaining or 
 losing light, heat, electricity, etc. 
 
 Insulation Bracket. A bracket of insu- 
 lating material, provided with an insu- 
 lator. 
 
 Insulation Break-Down. Any failure 
 of the insulation which prevents it from 
 insulating. 
 
 Insulation, Electric. A non-conducting 
 material so placed with respect to a con- 
 ductor as to prevent either the loss of its 
 charge, or the leakage of its current. 
 
 Insulation Joint. A joint in an insu- 
 lating material or covering in which con- 
 tinuity is preserved both in the conducting 
 and in the insulating substance. 
 
 Insulation Lightning-Protection. The 
 protection of an instrument by means of 
 an insulating lightning-protector from the 
 jumping of a spark across it from layer 
 to layer. 
 
 Insulation Lightning-Protector. A 
 lightning protector by means of which a 
 discharge is prevented from jumping 
 across the coils of an instrument from, 
 layer to layer, and thus damaging its 
 insulation. 
 
 Insulation Materials. (1) Materials 
 whose resistivity is high. (2) Non-con- 
 ductors. 
 
 Insulation Resistance. (1) The resist- 
 ance existing between a conductor and 
 the earth, or between two conductors 
 in a circuit through insulating materials 
 lying between them. (2) The resistance 
 taken between a line or conductor and 
 the earth through the insulators, or be- 
 tween two separate wires of a cable 
 through the insulating materials separ- 
 ating them. (3) A terin sometimes applied 
 to the resistance of the insulating ma- 
 terial of a covered wire or conductor. 
 (4) The resistance of any insulation. 
 
 Insulator. Any device employed for in- 
 sulating a wire or other body. 
 
 Insulator Bracket. A frame of wood or 
 metal for holding the insulator of an 
 overhead wire, and of such simple form 
 as to be readily attached to a wall or 
 support. 
 
 Insulator Cap. A cover or cap placed 
 some distance above an insulator, but 
 separated from it by an air space. 
 
 Insulator Pin. The bolt by which an 
 insulator is attached to a bracket, pole- 
 arm, or support. 
 
 Intaglio. (1) An engraving in which the 
 
 surface is so hollowed out that an im 
 pression therefrom would give the ap- 
 pearance of a bas-relief. (2) The copy ol 
 a coin or other similar object obtained 
 in an electro. 
 
 Intake. A word sometimes used instead 
 of input. 
 
 Intake of Dynamo. The mechanical 
 activity which a dynamo absorbs when 
 running. 
 
 Intake of Machine. The activity re- 
 quired to operate a machine. 
 
 Intake Wires. The wires which feed a 
 distribution box. 
 
 Integrating Meter. Any meter which 
 leaves a record of, and sums up, or inte- 
 grates, some quantity with respect to 
 time. 
 
 Integrating Wattmeter. (1) A watt- 
 hour meter, or a meter which integrates 
 the power which passes through it with 
 respect to time. (2) An energy meter. 
 
 Integrator. An apparatus for automat- 
 ically performing the operation of inte- 
 gration, or th.e continuous summing up 
 of instantaneous values. 
 
 Intensity. (1) The surface density of a 
 vector or directed quantity. (2) The de- 
 gree of concentration with which a num- 
 ber of forces act. 
 
 Intensity Armature. A term formerly 
 employed for an armature with coils of 
 many turns, and, consequently, of a com- 
 paratively high resistance. (Obsolete.) 
 
 Intensity Current. A term formerly 
 employed for the current produced by a 
 series-connected battery. (Obsolete.) 
 
 Intensity of Current. (1) A term taken 
 from the French language to indicate cur- 
 rent strength. (2) Current density, or cur- 
 rent strength per-unit-area of normal 
 cross-section. 
 
 Intensity of Field. The strength or 
 density of a magnetic field as measured 
 by the quantity of magnetic flux that 
 passes through it per-unit-of-area of nor- 
 mal cross-section. 
 
 Intensity of Illumination. The quan- 
 tity of light received per-unit-of -surface . 
 
 Intensity of Light. (1) In a given direc- 
 tion of emission, the ratio of the flux of 
 light in a small solid angle containing 
 that direction to the solid angle. (2) The 
 candle-power of a light. 
 
 Intensity of Magnetic Flux.; (1) The 
 quantity of magnetic flux per-unit-of-area 
 of normal cross-section. (2) The density 
 of magnetic flux. 
 
 Intensity of Magnetization. (1) A 
 
Int.] 
 
 quantity which represents the intensity 
 of magnetization produced in a sub- 
 stance. (2) A quantity which represents 
 the intensity with which a magnetizable 
 substance is magnetized. (3) Magnetic 
 moment per-unit-volume. (4) The sur- 
 face density of imaginary magnetic mat- 
 ter on any surface normal to the direc- 
 tion of magnetization. 
 
 Intensity of Radiation. (1) The ratio 
 existing between the amount or quantity 
 of radiation, and the surface from which 
 that radiation takes place. (2) The ratio 
 of the flux of energy in any small solid 
 angle of a beam to the solid angle. 
 
 Interactance. In an induction coil oper- 
 ated on a simple alternating-current 
 circuit, the product of the mutual in- 
 ductance and the angular velocity cor- 
 responding to the frequency of the cur- 
 rent, and expressible in ohms. 
 
 Inter Air-Space. A term sometimes 
 employed for the air-space or entrefer. 
 
 Inter-Atomic Ether. A term sometimes 
 used for the ether existing between the 
 constituent atoms of the molecules. 
 
 Tnter-Connected Armature-Winding. 
 (1) Such a connection of the separate 
 circuits in a multipolar armature as will 
 permit a single pair of brushes to be 
 employed on the commutator. (2) A 
 cross-connected armature. 
 
 Inter-Connection. The cross-connection 
 of an armature. 
 
 Inter-Crossing. In a system of tele- 
 phonic circuits, a device for avoiding the 
 disturbing effects of induction, by 
 alternately crossing equal sections of the 
 line wires. 
 
 Inter-Exchange Working. (1) Tele- 
 phonic communication effected through 
 the medium of more than a single ex- 
 change (2) Telephone communication 
 passing between two exchanges, or be- 
 tween two subscribers connected there- 
 with. 
 
 Interference of Electro-Magnetic 
 Waves. Interference effects, similar to 
 those produced in the case of light and 
 sound, observed in electro-magnetic 
 waves when two systems of waves of equal 
 frequency simultaneously act, in opposed 
 phases, on the same medium. 
 
 Inter-Ferric Gap. (1) An air-gap in an 
 aero-ferric magnetic circuit between iron 
 and iron. (2) The entrefer. 
 
 Inter-Ferric Space. An inter-ferric gap. 
 
 Interflange. The distance between the 
 two flanges of a bobbin, measured par- 
 allel to the bobbin's axis, and represent- 
 
 814 [Int. 
 
 ing the length of the cylindrical spaca 
 which may be occupied by wire w hen tha 
 bobbin is wound. 
 
 Inter-Induction. Mutual induction. 
 
 Interior Conduit. (1; A conduit provided 
 inside the walls of a house, or in other 
 convenient spaces within a house, for the 
 reception of the house wires. (2) A con- 
 duit in the walls or floors of a building, 
 provided for accommodating electrio 
 conductors. 
 
 Interior-Conduit Junction-Box. The 
 box provided in a system of interior con- 
 duits to receive the terminals of the feed- 
 ers, and in which connection is made 
 between the feeders and the mains, or 
 the mains and branches. 
 
 Interior-Pole Dynamo. A dynamo hav- 
 ing field poles in the interior of a cylin- 
 drical or Gramme-ring armature. 
 
 Inter-Linked Diphase-System. A 
 
 three-wire diphase-system. 
 
 Inter-Linked Polyphase-System. A 
 
 polyphase system of conductors so inter- 
 connected that one wire serves as the 
 return for another, and distinguished 
 from a polyphase system in which each 
 phase is provided with a separate circuit. 
 
 Inter-Locking Apparatus. A device for 
 mechanically operating railroad switcheg 
 and semaphoric signals from a" distant sig- 
 nalling tower, for the purpose of indicat- 
 ing the position of such switches, by 
 means of a system of inter-locking levers, 
 so inter-locked as to render it impossible, 
 af !;er a route has once been set and a sig- 
 nal given, to clear a signal for a route 
 that would conflict with the one previ- 
 ously set up. 
 
 Inter-Locking Magnet. A magnet em- 
 ployed in a system of electric railroad 
 signals for crossings, whereby a gong ig 
 caused to ring at the crossings on the ap- 
 proach of a train, and is automatically 
 stopped by the same train after it has 
 passed the crossing. 
 
 Intermediate Cable. A type of cable 
 intermediate between a shore-end cable 
 and a deep-sea cable. 
 
 Intermediate Station. Any station be- 
 tween the terminal stations of a telegraph 
 line. 
 
 Intermediate Switch. A switch em- 
 ployed at an intermediate telephone 
 station for communicating with either 
 terminal station at will, without inter- 
 rupting the line. 
 
 Intermittent. (1) Acting at interval* 
 only. (2) Fluctuating or pulsating. 
 
Int.] 
 
 815 
 
 Intermittent Contact. The occasional 
 contact of a telegraphic or other line 
 with other wires or conductors, by swing- 
 ing, or by alternate contractions and ex- 
 pansions, occasioned by changes of tem- 
 perature. 
 
 Intermittent Cross. (1) An accidental 
 contact, generally metallic, occasioned by 
 wires being brought into occasional con- 
 tact with one another, or with some other 
 conductor by the intermittent action of 
 the wind. (2) A swinging cross. 
 
 Intermittent Current. A current that 
 does not flow continuously, but which . 
 flows and ceases to flow at intervals, so 
 that electricity is practically alternately 
 present and absent from the circuit. 
 
 Intermittent Currents of Wheatstone 
 System. In the Wheatstone automatic 
 system the transmission of short initial 
 and final currents in each signal. 
 
 Intermittent Disconnection. Any 
 fault in a line which occurs at intervals 
 or intermittently. 
 
 Intermittent Electromotive Force. 
 An electromotive force which acts inter- 
 mittently. 
 
 Intermittent Earth. (1) A fault in a 
 telegraphic or other line in which, by the 
 action of the wind, or by occasional ex- 
 pansion by heat, the line is brought 
 into intermittent contact with the earth. 
 (2) A swinging earth. 
 
 Intermittent Integrating Meter. A 
 meter which does not take a reading of 
 the current or .power continucusly, but 
 at regular intervals, and then adds up 
 the result. 
 
 Intermittent System of Currents. A 
 system of currents employed in teleg- 
 raphy, in which the initial and final 
 currents are separated by an interval or 
 insulation. 
 
 Intermitter. An interrupter. 
 
 Inter-Molecular. Between the mole- 
 cules. 
 
 Inter-Molecular Ether. A term some- 
 times used for the ether that exists be- 
 tween the molecules of matter. 
 
 Internal Armature Generator. A gen- 
 erator in which the armature is situated 
 within the field-poles, as distinguished 
 from a generator whose armature is exter- 
 nal to the field. 
 
 Internal Characteristic of Dynamo. 
 A curve showing the E. M. F. generated 
 in a dynamo under varying excitation, as 
 distinguished from the external charac- 
 teristic showing the E. M. F. at terminals. 
 
 Internal Circuit. That part of a circuit 
 which is included within the electric 
 source. 
 
 Internal Magnetic-Circuit. A term 
 sometimes employed for that part of a 
 magnetic circuit which lies within the 
 magnetic core. 
 
 Internal Magnetic-Field. That portion 
 of 'a magnetic field produced by a magnet 
 which lies within the magnetic core. 
 
 Internal Polarization of Moist Body. 
 A polarization exhibited by such moist 
 bodies as nervous or muscular fibres, 
 the juicy parts of vegetables and animals, 
 or in general, by all bodies possessing a 
 firm structure and filled with a liquid, on 
 the passage through them of a strong 
 electric current. 
 
 Internal Poles of Dynamo. (1) The in- 
 wardly projecting field poles of a dy- 
 namo. (2) Magnetic field-poles internal 
 
 to an armature. 
 
 International Ampere. (1) The value 
 of the ampere as adopted by the Inter- 
 national Congress of 1893, at Chicago. 
 (2) The value of an ampere equal to the 
 one-tenth of a unit of current in the C. 
 G. S. system of electro-magnetic units, 
 and represented with sufficient accuracy 
 for practical purposes, by the unvarying 
 current, which, when passed through a 
 solution of nitrate of silver in water, in 
 accordance with certain specifications, 
 deposits silver at the rate of 0.001118 of a 
 gramme-per-second. 
 
 International Coulomb. (1) The value 
 of the coulomb as adopted by the Inter- 
 national Electrical Congress of 1893, at 
 Chicago. (2) The quantity of electricity 
 equal to that transferred through a cir- 
 cuit by a current of one International 
 ampere in one second. 
 
 International Farad. (1) The value of 
 the farad as adopted by the International 
 Electrical Congress of 1893, at Chicago. 
 (2) The capacity of a conductor charged 
 to a potential of one International volt by 
 one International coulomb of electricity. 
 
 International ?Tenry. (1) The value of 
 the henry as adopted by the International 
 Electrical Congrest. cf 1893, at Chicago. 
 (2) The value of the induction in a circuit, 
 when the electromotive force induced in 
 the circuit is one International volt, and 
 the inducing current varies at the rate of 
 one ampere per second. 
 
 International Joule. (1) The value of 
 the joule as adopted by the International 
 Electrical Congress of 1893, at Chicago. 
 (2) A value equal to 10 7 units of work of 
 
Int.] 
 
 816 
 
 [Iny. 
 
 the C. G. S. system and represented with 
 sufficient accuracy for practical purposes 
 by the energy expended in one second by 
 one ampere in one International ohm. 
 
 -International Morse Code. A term 
 sometimes employed for the International 
 telegraphic alphabet, as distinguished 
 from the American Morse Code. 
 
 International Ohm. (1) The value of 
 the ohm as adopted by the International 
 Electrical Congress of 1893, at Chicago. 
 (2) A value of the ohm equal to 10 9 units 
 of resistance of the C. G. S. system of 
 electro-magnetic units,and represented by 
 the resistance offered to an unvarying 
 electric current by a column of mercury 
 at the temperature of melting ice, 14.4521 
 grammes in mass, of a constant cross-sec- 
 tional area, and of the length of 106.3 
 centimetres. 
 
 International Telegraphic Code. The 
 International Morse Code. 
 
 International Unit of Activity. The 
 
 International watt. 
 
 International Unit of Work. The In- 
 ternational joule. 
 
 International Volt. (1) The value of the 
 volt as adopted by the International 
 Electrical Congress of 1893, at Chicago. 
 (2) Such an electromotive force that 
 steadily applied to a conductor whose 
 resistance is one International ohm, will 
 produce a current of one International 
 ampere, and which is represented with 
 sufficient accuracy for practical use by 
 ^4$ of the electromotive force between 
 the poles or electrodes of the voltaic cell 
 known as Clark's cell, at a temperature of 
 15 Cent, when prepared in accordance 
 with certain specifications. 
 
 International Watt. (1) The value of 
 the watt as adopted by the International 
 Electrical Congress of 1893, at Chicago. 
 (2) A value equal to 10 7 units of activity 
 in the C. G. S. system, and equal to the 
 work done at the rate of one joule-per- 
 second. 
 
 Inter-Node. The space between two ad- 
 jacent nodes. 
 
 Inter-Polar. Between the poles. 
 
 Inter-Polar Gap. An air-gap or space 
 between the faces of opposing pole-pieces. 
 
 Inter-Polar Space. The inter-polar gap. 
 
 Interpolated Commutator Segments. 
 Blank commutator segments. 
 
 Interrupted. Broken or opened. 
 
 Interrupted Current System. A sys- 
 tem of electric distribution effected by 
 the aid of periodically interrupted contin- 
 uous currents. 
 
 Interrupter. Any device for interrupt- 
 ing or breaking a circuit. 
 
 Inter-Urban Communication. Tele 
 graphic or telephonic communication be- 
 tween adjacent cities. 
 
 Inter-Urban Electric Railway. An 
 
 electric railway suitable for use between 
 
 adjacent cities. 
 Inter - Urban Telephony. Telephonic 
 
 communication carried on between adja- 
 
 cent cities. 
 Intra-Molecular. (1) Inter-molecular, 01 
 
 between the molecules. (2) Within the 
 * confines of a molecule. 
 
 Intra-Polar Electrolysis. Electrolytic 
 action taking place in the region between 
 the electrodes, as distinguished from that 
 which occurs in their immediate vicinity. 
 
 Intrinsic Brilliancy of Luminous 
 Source. (1) At any point of a luminous 
 surface the ratio of the luminous intensity 
 along the normal to the small surface area 
 from which it is emitted. (2) Luminous 
 intensity per-unit-area of normal lumi- 
 nous surface. 
 
 Intrinsic Electrization. A term pro- 
 posed for permanent impressed electriza- 
 tion in a substance from internal causes. 
 
 Intrinsic Intensity of Light. The 
 quantity or flux of light emitted normally 
 from a unit of surface of a luminous 
 source. 
 
 Intrinsic Magnetization. Magnetiza- 
 tion due to impressed magnetic force, as 
 distinguished from magnetization due to 
 electric currents. 
 
 Intrinsic Radiation of Luminous 
 Source. (1) The radiation of a luminous 
 source expressed in lumens-per-square- 
 centimetre. (2) The flux density of light 
 issuing normally from a luminous source. 
 
 Invariable Calibration of Galvano- 
 meter. In a galvanometer with absolute 
 calibration, a method for preventing the 
 occurrence of variations in the intensity 
 of the field of a galvanometer, due to the 
 neighborhood of masses of iron. 
 
 Inverse Current. (1) The current which 
 tends to be produced by a current in its 
 own circuit on making or closing the cir- 
 cuit. (2) The current produced in the 
 secondary of an induction coil on the mak- 
 ing or completion of the circuit of the 
 primary. (3) The make-induced current. 
 
 Inverse Electromotive Force. An elec- 
 tromotive force which acts in the oppo- 
 site direction to another already existing 
 electromotive force. 
 
 Inverse Secondary Current. Thn 
 make-induced current. 
 
IllV.] 
 
 817 
 
 [Iro, 
 
 Inversion, Electric. The determination 
 of electric disti'ibution over the surfaces of 
 neighboring electrified conductors by the 
 geometrical method of inversion. 
 
 Invert Insulator. An insulator support- 
 ed in an inverted position. 
 
 Inverted Arc. An inverted arc-lamp. 
 
 Inverted Arc-Lamp. An electric arc- 
 lamp in which the positive carbon is 
 lowermost, or inverted, as compared with 
 its position in the ordinary arc-lamp. 
 
 Inverted Dynamo. A dynamo whose 
 armature bore or chamber is placed below 
 the field-magnet coils. 
 
 Inverted Induction-Coil. A term some- 
 times employed for a step-down trans- 
 former. 
 
 Invisible Electric-Contact Matting. 
 A matting or other floor covering, pro- 
 vided with a series of invisible electric 
 contacts, which are closed by a person 
 walking over them. 
 
 Invisible Spectrum. That portion of the 
 spectrum which is incapable of affecting 
 the eye as light. 
 
 Ionic. Of or pertaining to the ions. 
 
 Ions. The groups of atoms or radicals into 
 which a molecule is separated by electro- 
 lytic decomposition. 
 
 Ionic Attraction. The mutual ( attrac- 
 tion produced by the cathions and the 
 anions. 
 
 Ionic Conductivities. Specific conduc- 
 tivities of ions, so selected that their sums 
 give molecular conductivities for any 
 combination of ions. 
 
 lonisation. (1) The decrease in the 
 strength with which the separate atoms 
 or radicals are held together in the mole- 
 cules of an electrolyte. (2) A modified 
 dissociation of the molecule of an elec- 
 trolyte which consists in the weakening 
 of the force which holds together its ions 
 or radicals. 
 
 Iron-Armored Conduit. (1) A conduit 
 provided with an exterior iron casing or 
 covering. (2) A conduit in which each 
 duct has an iron casing or covering. 
 
 Iron-Clad. Surrounded by iron. 
 
 Iron-Clad Armature. (l)The armature of 
 a dynamo or motor, whose insulated coils 
 are entirely or nearly surrounded by the 
 iron of the armature core. (2) An arma- 
 ture in which the conductors are buried 
 in slots, grooves, or tunnels below the 
 surface of the armature core. 
 
 Iron-Clad Armature Windings. Ar- 
 mature windings that are entirely or 
 nearly surrounded by iron. 
 
 52 
 
 Iron-Clad Coil. An iron-clad magnet. 
 Iron - Clad Drop. An annunciator o 
 
 telephone drop whose electro-magnet is 
 
 iron-clad. 
 
 Iron-Clad Dynamo. (1) A dynamo whose 
 armature is iron -clad. (2) An iron-en- 
 cased dynamo. 
 
 Iron-Clad Electro-Magnet. An electro- 
 magnet whose magnetizing coil is almost 
 entirely surrounded by iron in some 
 cases to increase its portative power, i 
 others to increase its inductance, and i> 
 yet others to shield its magnetic varia- 
 tions. 
 
 Iron-Clad Generator. An iron-clad dy- 
 namo. 
 
 Iron-Clad Inductance. An inductance 
 associated with a ferric or aero-ferric mag' 
 netic circuit, as distinguished from an 
 inductance associated with a non-ferric 
 magnetic circuit. 
 
 Iron-Clad Magnet. (1) An electro-mag- 
 net whose magnetic resistance is lowered 
 by a casing of iron connected with the 
 core, and provided for the passage of the 
 magnetic flux. (2) An iron-clad electro- 
 magnet. 
 
 Iron-Clad Motor. A motor whose ar- 
 mature is iron-clad. (2) An iron-encased 
 motor. 
 
 Iron-Clad Rheostat. A rheostat whose 
 resistance coils are provided with an 
 enamelled insulation, and imbedded in a 
 mass of iron. 
 
 Iron Core. The mass of iron on which 
 
 are placed the magnetizing coils of an 
 
 electro-magnet or solenoid. 
 Iron-Core Loss. The hysteretic and Fou- 
 
 cault losses due to the presence of an iron, 
 
 core. 
 Iron Covered Cable. A submarine 
 
 cable provided with an iron sheathing. 
 
 Iron-Enclosed Electro-Magnet. An 
 iron-clad electro-magnet. 
 
 Iron-Loss in Transformer. The loss of 
 energy in a transformer due both^to mag- 
 netic hysteresis or magnetic friction, and 
 to the setting up of eddy or Foucault 
 currents in the iron. 
 
 Iron Magnetic Circuit. A ferric mag- 
 netic circuit. 
 
 Iron Reluctance. (1) The reluctance in 
 a magnetic circuit due to the presence of 
 iron in that circuit. (2) Reluctance in 
 iron. 
 
 Iron- Work Fault of Dynamo. A 
 ground or connection between the circuit 
 of a dynamo and any part of its iron 
 frame. 
 
Irr.] 
 
 818 
 
 [Iso.. 
 
 Irrationality of Dispersion. A lack of 
 proportionality in the dispersions of spec- 
 tra produced by different refractive media. 
 
 Irreciprocal Conduction. (1) Conduc- 
 tion in which the magnitude of the cur- 
 rent is altered when its direction is re- 
 versed. (2) The electric conduction in 
 an assymmetrical resistance. 
 
 Irregular Magnetic Flux. Magnetic 
 flux which is not uniform, but is either 
 converging or diverging, as distinguished 
 from uniform magnetic flux. 
 
 Irregular Variation. Any variation of 
 the magnetic needle which occurs at ir- 
 regular intervals. 
 
 Irreversible Heat. (1) Heat produced in 
 a homogeneous conductor by the passage 
 of electricity through it in any direction. 
 (2) In an electric circuit, the joulean heat- 
 ing effect as distinguished from the 
 Peltier effect. (3) In an electric circuit 
 any development of heat by the current, 
 which does not depend upon its direction. 
 
 Iridescence. Interference effects pro- 
 ducing rainbow-colored tints by the re- 
 fraction of light from thin, transparent, 
 finely striated surfaces. 
 
 Irritability, Electric. The irritability 
 of nerves or muscles produced by an elec- 
 tric current or discharge. 
 
 Irrotational Stress. (1) Stress unac- 
 companied by rotation. (2) A stress de- 
 void of curl. 
 
 Isobaric Lines. Isobars. 
 
 Isobarometric Lines. The isobaric lines. 
 
 Isobars. (1) Lines connecting places on 
 the earth's surface which simultaneously 
 have the same barometric pressure. 
 (2) The isobaric lines. 
 
 Isochasmen Curves. Curves drawn on 
 the earth's surface between zones having 
 equal frequency of auroral discharges. 
 
 Isochronism. Equality of time-vibration 
 or motion. 
 
 Isochrqnize. To produce equality of time- 
 vibration or motion. 
 
 Isqchronizing. Producing equality of 
 time- vibration or motion. 
 
 Isochronous Oscillations. Isochronous 
 vibrations. 
 
 Isochronous Vibrations. Vibrations 
 or oscillations which perform their to- 
 and-fro motions on either side of the 
 position of rest in equal times. 
 
 Isoclinal. Possessing the same inclina- 
 tion. 
 
 Isoclinal Lines. Lines connecting places 
 
 on the earth's surface which have tha 
 
 same magnetic inclination or dip. 
 Isoclinal Chart. A map or chart on 
 
 which isoclinal lines are marked. 
 Isoclinic. Of or pertaining to the 
 
 isoclinals. 
 
 Isodynamic. Possessing equal force. 
 Isodynamic Chart or Map. A map or 
 
 chart on which isodynamic lines are 
 
 marked. 
 
 Isodynamic Lines. Lines connecting 
 places which have the same total mag- 
 netic intensity. 
 
 Iso-Electric Points. A term sometimes 
 used in electro-therapeutics for points of 
 equal potential. 
 
 Isogonal. Of or pertaining to the isogonal 
 lines. 
 
 Isogonal Chart or Map. A chart or 
 map on which the isogonal lines are 
 marked. 
 
 Isogonal Lines. Lines connecting places 
 on the earth's surface which have the 
 same magnetic declination. 
 
 Isqgonic. Of or pertaining to the isogonal 
 lines. 
 
 Isolated Electric Lighting. Electric 
 lighting in which the plant is located on 
 the premises that are to be lighted, as 
 distinguished from a plant located at a 
 station, central either to a number of 
 buildings, or to an extended area to be 
 lighted. 
 
 Isolated Plant. An electric plant or dis- 
 tribution system confined to a building 
 or group of buildings as distinguished 
 from a central-station system. 
 
 Isolated-Station Telephone Switch- 
 board. A switchboard established for 
 the inter-communication of a number of 
 telephoners, where the distance separating 
 them is considerable, or where privacy 
 in the communication is essential. (2) A 
 small sub-station telephone switchboard. 
 (3) A domestic telephone switchboard. 
 
 Isqlatine. A variety of insulating mate- 
 rial. 
 
 Isolating Switch for Lamps. A short- 
 circuiting switch designed to cut a lamp 
 completely out of connection with a cir- 
 cuit and without opening or breaking the 
 circuit of other lamps. 
 
 Isolux.-j (1) A line connecting points of 
 equal illumination on any illumined sur- 
 face. (2) A line of equal illumination. 
 
 Isothermal Expansion of Gas. The ex- 
 pansion of a gas whose temperature is 
 maintained constant. 
 
ISO.] 
 
 [Joe. 
 
 Isomorphism. The quality of possessing 
 the same crystalline form. 
 
 Isomerism. A state or condition of com- 
 pound substances which, though identical 
 in composition, yet possess entirely dif- 
 ferent properties. 
 
 Isothermal Surfaces. Surfaces on a 
 body, all points of which have the same 
 temperature. 
 
 Lsothermals. Lines connecting places on 
 the earth's surface which have the same 
 mean annual temperature. 
 
 Isotropic. Possessing equal elasticity in 
 all directions. 
 
 Isotropic Conductor. (1) A substance 
 which possesses the same powers of elec- 
 tric conduction in all directions. (2) An 
 electrically homogeneous conducting 
 medium. 
 
 Isotropic Dielectric. A dielectric pos- 
 sessing the same powers of inductive 
 capacity in all directions. 
 
 Isotropic Medium. A medium possess- 
 ing the same properties in all directions. 
 
 Isotropism. The quality of possessing 
 equal elasticity in all directions. 
 
 Isthmus Method of Magnetization. 
 A method of obtaining an exceedingly 
 strong magnetization by so placing the 
 body to be magnetized that it forms a 
 narrow isthmus between the pole-pieces 
 of a powerful electro-magnet. 
 
 Isynchronous Vibrations. (1) Vibra- 
 tions possessing equality of time of vibra- 
 tion or motion. (2) Isochronous vibra- 
 tions. 
 
 J. A contraction proposed for joule. 
 
 JablochkofF Candle. An electric arc 
 light in which the two carbon electrodes 
 are placed parallel to each other, and 
 maintained at a constant distance apart 
 by means of a strip of an insulating sub- 
 stance placed between them. 
 
 Jablochkoff 's Igniter. A small strip of 
 carbon or carbonaceous material that is 
 readily rendered incandescent by a cur- 
 rent, placed between the free ends of the 
 parallel carbons of a Jablochkoff candle, 
 for the formation of an arc on the passage 
 of the current. 
 
 Jack Hole. In a telephone switchboard 
 
 the hole leading into a jack. 
 Jack Panel. The panel of a telephone 
 
 switchboard provided for the support of 
 
 the jacks. 
 Jack Switch. A switch operated by 
 
 means of a spring jack. 
 Jacketed Magnet. A term sometimes 
 
 applied to an iron-clad magnet. 
 Jacobi's Law. The maximum activity is 
 
 performed by an electric motor when its 
 
 counter-electromotive force is equal to 
 
 one-half of the impressed electromotive 
 
 force. 
 
 Jacobi's Unit of Current. Such a cur- 
 rent that when passed through a volta- 
 meter will liberate a cubic centimetre of 
 oxygen and hydrogen per second at zero 
 Cent., and 760 millimetres barometric 
 pressure. 
 
 Jacobi's Unit of Resistance. (1) The 
 
 electric resistance of 25 feet of a certain 
 copper wire weighing 345 grains. (2) The 
 resistance of a copper wire one metre in 
 length and one millimetre in diameter of 
 cross-section. 
 
 Jar, Electric. A name formerly given to 
 a Leyden jar. 
 
 Jar of Secondary Cell. The jai in 
 which the electrolyte and plates of a sec- 
 ondary cell are placed. 
 
 Jaws of Switch. The metallic clips pro- 
 vided for the reception of the knife-blades 
 of a switch. 
 
 Jet Photometer. An apparatus for de- 
 termining the candle-power of an illu- 
 minating gas by means of the height of a 
 jet of such gas when burning under con- 
 stant conditions of pressure and tempera- 
 ture. 
 
 Jewelry, Electric. Minute incandescent 
 lamps substituted for gems in articles of 
 jewelry. " 
 
 Jockey Gear. The cable gear through 
 which a cable has to pass when entering 
 or leaving a picking-up or paying-out 
 drum, and in which it passes under 
 weighted wheels, called jockey wheels, 
 for the purpose of maintaining a uniform 
 tension of the cable upon the drum so as 
 to prevent slip. 
 
 Jockey of Relay. A form of extension 
 tongue pivoted friction-tight upon the 
 tongue of a sensitive relay employed in 
 submarine telegraphy. 
 
 Jockey Wheel. A weighted wheel riding 
 over a cable on a grooved wheel in a 
 
Joi.] 
 
 820 
 
 [Jun. 
 
 cable ship for the purpose of preserving 
 uniformity of tension in the cable. 
 Joining-Tip. (1) Connecting in series or 
 multiple-arc. (2) Generally, connecting 
 or placing in a circuit. 
 
 Joining-Up a Wire. Connecting a wire 
 to an apparatus or circuit after it has 
 been disconnected or grounded. 
 
 Joint. (1) The junction of two or more 
 pieces or conductors. (2) The place 
 where the junction of two or more pieces 
 or conductors is effected. 
 
 Joint Admittance. The total or com- 
 bined admittance of a number of separate 
 admittances connected in parallel. 
 
 Joint Conductance. The combined con- 
 ductance of a number of separate con- 
 ductances connected in parallel. 
 
 Joint-Cooling Tray. A tray employed 
 for cooling a cable core-joint by a cooling 
 mixture. 
 
 Joint Magnetomotive Force. The re- 
 sultant magnetomotive force of a number 
 of simultaneously acting magnetomotive 
 forces. 
 
 Joint Reluctance. The combined reluc- 
 tance of a number of parallel-connected 
 reluctances. 
 
 Joint Reluctivity. The reluctivity of a 
 number of parallel-connected reluctivi- 
 ties. 
 
 Joint Resistance. The combined resist- 
 ance of a number of parallel-connected 
 resistances. 
 
 Joint Trough. A trough of water or 
 cooling solution in which a submarine 
 cable joint is submerged for cooling. 
 
 Jointless Conductor. A conductor in 
 a single length and without joint. 
 
 Joulad. A term proposed for joule. (Not 
 in use.) 
 
 Joule. (1) A volt-coulomb or unit of 
 electric energy or work. (2) The amount 
 of electric work required to raise the 
 potential of one coulomb of electricity 
 one volt. (3) Ten million ergs. 
 
 Joule Effect. The heating effect pro- 
 duced by the passage of an electric cur- 
 rent through a conductor, arising from 
 its resistance only. 
 
 Joulean Effect. A word sometimes used 
 for joule effect. 
 
 Joule Meter. (1) Any apparatus capable 
 of measuring energy in joules. (2) An 
 energy meter, as distinguished from a 
 wattmeter. 
 
 Joule-Per-Second. A unit of activity, 
 
 equal to the expenditure of one joule in 
 each second. 
 
 Joule's Cylindrical Electro-Magnet.^ 
 An electro-magnet provided with a hoi* 
 low cylindrical core. 
 
 Joule's Equivalent. The mechanical 
 equivalent of heat. 
 
 Joule's Law. The heating power of a 
 current is proportional to the product of 
 the square of its strength and the resist- 
 ance of the circuit through which it 
 passes. 
 
 Journal. That portion of a shaft which 
 revolves on a bearing. 
 
 Journal Friction. Friction produced by 
 the rotation of a shaft on a bearing. 
 
 Jumper. A temporary shunt or short cir- 
 cuit put around a source, lamp or receptive 
 device on a series-connected circuit, to en- 
 able it to be readily removed or repaired. 
 
 Jump Spark. A disruptive spark ob- 
 tained between two opposed conducting 
 surfaces, as distinguished from a spark 
 obtained by or following a wiping contact. 
 
 Jump-Spark Burner. A term some- 
 times applied to a gas burner in which the 
 issuing jet is ignited by means of a high- 
 tension spark obtained between two op- 
 posed points. 
 
 Junction. In telephony, a wire or circuit, 
 connecting two exchanges. 
 
 Junction Board. In telephony, a switch- 
 board at which junction wires terminate. 
 Junction Box. A moisture-proof box 
 
 Provided in a system of underground con- 
 uctors to receive the terminals of the 
 feeders, and in which connection is made* 
 between the feeders and the mains, and 
 through which the current is distributed 
 to the individual consumers. 
 
 Junction Calls. Telephonic calls arriving 
 on a junction line. 
 
 Junction Circuit. In telephony, a line 
 connecting a trunk circuit with a local 
 subscriber. 
 
 Junction Line. (1) In telephony, a junc- 
 tion. (2) A line connecting two telephone 
 exchanges. 
 
 Junction-Line Plug. In a central tele- 
 phone exchange, a plug connected with a 
 junction line. 
 
 Junction Lines. Lines connecting two: 
 or more telephone exchanges, as dis- 
 tinguished from subscribers' lines. 
 
 Junction Operator. In telephony, an 
 operator at a junction board. 
 
Jan.] 
 
 821 
 
 [Key. 
 
 Junction Surface of Voltaic Cell. The 
 contact surface between the elements of 
 a voltaic cell and the electrolyte. 
 
 Junction Wires. Junction lines. 
 
 Junction Working. Inter-exchange 
 
 telephone working. 
 Just Non-Oscillatory Discharge. A 
 
 discharge which is just non-oscillatory. 
 
 K 
 
 K. A symbol for electrostatic capacity. 
 
 K. A symbol for moment of inertia. 
 
 K. A symbol for magnetic susceptibility. 
 
 K. C. C. A contraction for cathodic clos- 
 ure contraction. 
 
 K. D. C. A contraction for cathodic dura- 
 tion contraction. 
 
 K. W. A contraction for kilowatt, 
 kg. An abbreviation for kilogramme, a 
 practical unit of mass. 
 
 kg : cm 2 . An abbreviation for kilo- 
 gramme-per-square-centimetre, a practi- 
 cal unit of pressure. 
 
 kgm. An abbreviation for kilogramme- 
 metre, a practical unit of the moment of 
 a couple or of work. 
 
 kgm : s. An abbreviation proposed for 
 kilogramme-meter-per-second, a practical 
 unit of power. 
 
 KB,. A contraction for the total capacity 
 of a telegraph or telephone wire or con- 
 ductor, multiplied by its total resistance. 
 
 KB Law. (1) A well-recognized law that 
 the limiting speed of signalling through 
 a submarine cable, assuming a given re- 
 ceiving and sending apparatus in uniform 
 adjustment, varies inversely as the KR of 
 the cable. (2) A generalization claimed 
 as a law by some, but denied by most, 
 which assigns the distance through which 
 intelligible telephonic communication can 
 be carried, to cases where the product of 
 K, the capacity of the telephone circuit 
 and R, its resistance, does not exceed a 
 certain value. 
 
 Kaolin. A variety of white clay some- 
 times employed for insulating purposes. 
 
 Kapp Lines. A term proposed for unit 
 lines of magnetic force or flux. 
 
 Karsten's Figures. A name sometimes 
 applied to electric breath figures. 
 
 Kartavert. A variety of insulating mate- 
 rial. 
 
 Katalysis. An orthography sometimes 
 employed for catalysis. 
 
 Katelectrotonus. Catelectrotonus. 
 
 Kathelectrotonic State. The cathelec- 
 trotonic state. 
 
 Kathelectrotonus Zone. Cathelectro- 
 tonic zone. 
 
 Kathelectrotonus. Cathelectrotonus. 
 
 Kathetometer. A cathetometer. 
 
 Kathion. A cathion. 
 
 Kathodal. Cathodal. 
 
 Kathode. A cathode. 
 
 Kathodic. Cathodic. 
 
 Kathodic Electro-Diagnostic Beac- 
 tions. Cathodic electro-diagnostic reac- 
 tions. 
 
 Kathodic Bays. Cathodic rays. 
 
 Kations. Cathions. 
 
 " Keeper " of Inductor Alternator. A 
 word sometimes employed for inductor. 
 
 Keeper of Magnet. A mass of soft iron 
 applied to the poles of a magnet, and 
 through which its magnetic flux passes. 
 
 Kelvin. (1) A word proposed, but not 
 adopted, for a kilowatt-hour or one thous- 
 and watt hours. (2) A word proposed for 
 the Board of Trade unit. 
 
 Kelvin Balance. A form of electro-dyna- 
 mometer balance designed by Lord Kelvin. 
 
 Kerite. A variety of insulating material. 
 
 Kerite Tape. A kerite-covered insulating 
 tape. 
 
 Kerr Effect. The elliptical polarization 
 of a beam of plane polarized light, pro- 
 duced by its passage across an electrized 
 dielectric. 
 
 Key-Board. Any board to which electric 
 keys or switches are connected. 
 
 Key-Board Transmitter. The trans- 
 mitter employed in a step-by-step or print- 
 ing telegraph. 
 
 Key Lamp-Socket. A lamp-socket pro- 
 vided with a key for lighting or extin- 
 guishing the lamp. 
 
 Keyless. Devoid of a key. 
 
 Keyless Fire- Alarm Box. A fire-alarm 
 box covered with a glass window which 
 requires to be broken in order to send the 
 alarm. 
 
 Keyless Lamp-Socket. A lamp-socket 
 unprovided with a key, and whose lamp, 
 therefore, requires to be lighted and ex* 
 tinguished by a switch placed elsewhere* 
 
Key.] 
 
 822 
 
 [Kuo. 
 
 Keyless Wall-Socket. A socket placed 
 on a wall, provided for the reception of a 
 plug switch for the introduction of a 
 lamp. 
 
 Kick. A recoil. 
 
 Kick of Coil. The discharge from an elec- 
 tromagnetic coil. 
 
 Kick of Relay. An impulse communicat- 
 ed to the tongue of a relay by a discharge 
 from the line. 
 
 Kicking Coil. A choking coil. 
 
 Kicks. In telegraphy, sudden impulses of 
 a mirror spot, or siphon, due to a momen- 
 tary earth current or discharge. 
 
 Kilerg. One thousand ergs. 
 
 Killing Wire. (1) A method formerly ad- 
 opted for removing kinks, bends and flaws 
 in iron by stretching it on the line in long 
 lengths. (2) A method of straightening 
 wire by subjecting it to tension. (3) A 
 term sometimes applied to loss of elasti- 
 city of contact springs of switches, due to 
 their over-heating by the current. 
 
 Kilo. A prefix for one thousand times. 
 
 Kilo-Ampere. One thousand amperes. 
 
 Kilo- Ampere Balance. A balance form 
 of ammeter which measures thousands of 
 amperes. 
 
 Kilo-Dyne. One thousand dynes. 
 
 Kilo-Erg. One thousand ergs. 
 
 Kilo -Gauss. One thousand gausses. 
 
 Kilogramme. One thousand grammes, or 
 2.2046 pounds avoirdupois. 
 
 Kilogramme-Metre. A unit of work 
 equal at Washington, D.C., to 9.81 multi- 
 plied by 10 1 ergs. 
 
 Kilo-Henry. One thousand henrys. 
 
 Kilo-Joule. One thousand joules. 
 
 Kilo-Lines. One thousand lines of force. 
 
 Kilometre. One thousand metres. 
 
 Kilometric Capacity of Cable. The ca- 
 pacity of a cable in micro-farads per kilo- 
 metre. 
 
 Kilometric Insulation of Cable. The 
 insulation of a cable measured in meg- 
 ohm-kilometres, or the average insulation 
 of one kilometre in megohms. 
 
 Kilo-Volt. One thousand volts. 
 
 Kilo-Watt. One thousand watts. 
 
 Kilo- Watt-Hour. (1) The amount of 
 work equal to that performed by an activ- 
 ity of one kilowatt maintained steadily 
 for one hour. (2) An amount of work 
 equal to 3.600,000 joules. 
 
 Kilo-Watt Hour Meter. A form of re- 
 cording watt-meter. 
 
 Kilo- Weber. One thousand webers. 
 
 Kine. A unit of velocity, proposed by the 
 British Association, equal to a centimetre- 
 per-second. 
 
 Kinematics. That branch of science 
 which treats of motion, irrespective ot 
 the mass moved, or of the forces which 
 produce or oppose the motion. 
 
 Kinetic Energy. Energy producing mo- 
 tion, as distinguished from potential 
 energy, or energy capable of producing 
 motion. 
 
 Kinetic Induction. Dynamic or mutual 
 induction. 
 
 Kinetic Theory of Matter. A theory 
 which assumes that the molecules of mat- 
 ter are in a constant state of motion or 
 vibration towards or from one another, in 
 paths that lie within the spheres of their 
 mutual attractions or repulsions. 
 
 Kinetics. That branch of dynamics 
 which treats of the action of forces in 
 producing or modifying motion. 
 
 Kinetoscope. A means for obtaining the 
 effect of moving objects by means of a 
 rapid succession of suitable pictures. 
 
 Kinetograph. (1) A term at one time 
 applied to a device proposed for the simul- 
 taneous reproduction of a distant stage 
 and its actors under circumstances such 
 that the actors can be heard at any dis- 
 tance from the theatre. (2) An apparatus 
 for reproducing on a screen the image of 
 a moving object. 
 
 KirehofPs Laws. The Laws for the pres- 
 sures and currents in branched or divided 
 circuits. 
 
 Kneading Tools. Tools for shaping hot 
 gutta-percha laid on a joint between gut- 
 ta-percha covered wires. 
 
 Knife-Break Switch. A knife switch. 
 
 Knife-Edge Suspension. The suspen- 
 sion of a needle or system on knife-edges, 
 supported on steel or agate plates. 
 
 Knife-Edge Switch. A term sometimes 
 used for knife-switch. 
 
 Knife-Switch. (1) A switch which is 
 opened or closed by the motion of a knife 
 contact between parallel contact plates. 
 (2) A knife-edge switch or knife switch. 
 
 Knob Insulator. An insulator shaped 
 like a knob and divided into two parts 
 suitable for supporting a single wire when 
 clamped together by its supporting 
 screw. 
 
 Knot. (1) A nautical mile, or 6087 feet. 
 (2) A length equal to one minute of arc in 
 terrestrial latitude. (3) A unit of velocity 
 at sea equal to one naut per hour, ob- 
 
Kno.] 
 
 823 
 
 [Lam. 
 
 tained from an observation of a knotted 
 log-cord thrown overboard. 
 
 Knot-Pound. A standard of conductivi- 
 ty of copper referred to a length of one 
 knot and a conductor weight of one 
 pound, and sometimes employed in sub- 
 marine telegraphy. 
 
 Kohlrausch's Law. In electrolytic con- 
 duction, the rate of motion of each atom 
 in a given liquid is independent of the 
 element with which it may have been 
 combined. 
 
 Krizik's Bars or Cores. Iron bars or 
 
 cores of various shapes, provided for sole- 
 noids, in which the distribution of the 
 metal is so proportioned as to ensure a 
 nearly uniform attraction or pull in dif- 
 ferent positions of the solenoid. 
 
 Kruss' Optical Scale. A scale employed 
 for measuring the height of a flame. 
 
 Kyanized. Subjected to the kyanizing 
 process. 
 
 Kyanizing. A process employed for the 
 preservation of wooden telegraph poles, 
 or railroad ties or sleepers, by injecting a 
 solution of corrosive sublimate into the 
 pores of the wood. 
 
 Ii. A symbol for coefficient of inductance. 
 
 L. A contraction for length. 
 
 L. A symbol for the coefficient of induc- 
 tance or self-induction. (Partly inter- 
 national notation.) 
 
 Lm. A symbol proposed for coefficient of 
 mutual-induction, or mutual inductance. 
 
 Ls. A symbol proposed for coefficient of 
 self-induction, or self-inductance. 
 
 Labile Galvanization. A term employed 
 in electro-therapeutics, in contra-distinc- 
 tion to stabile galvanization, to designate 
 the method of applying the current by 
 keeping one electrode at rest, in firm con- 
 tact with one part of the body, and con- 
 necting the other electrode to a sponge 
 which is moved over the parts of the 
 body that are to be treated. 
 
 Lag. (1) Falling behind. (2) To fall be- 
 hind. 
 
 Lag of Motor Brushes. A movement of 
 the brushes of a motor to a position on 
 the commutator, in the opposite direction 
 to its rotation, in order to obtain freedom 
 from sparking. 
 
 Lag of Resultant Flux. The displace- 
 ment in phase of the magnetic flux in an 
 induction motor behind the impressed 
 magneto-motive force. 
 
 Lagging Electromotive Force. An 
 electromotive force or component of elec- 
 tromotive force lagging behind a current 
 or flux. 
 
 Lagging Current. A periodic current 
 lagging behind the impressed electromo- 
 tive force which produces it. 
 
 Lagging of Current. An alternating 
 current; which is retarded in phase be- 
 hind the pressure which produces it. 
 
 Tagging of Magnetization. (1) A re- 
 
 tardation in the magnetization as com- 
 pared with the magnetizing electromotive 
 force. (2) A cyclic retardation of mag- 
 netization in a transformer due to hys- 
 teresis. 
 
 Lambert's Discharge Key. A highly 
 insulated form of double-contact key, 
 used in testing. 
 
 Lamellar. Composed of parallel plates or 
 laminae. 
 
 Lamellar Distribution of Magnetism. 
 
 (1) The distribution of magnetism in 
 magnetic shells. (2) Such a distribution 
 of magnetism in a thin plate that the 
 magnetized particles are arranged with 
 their greatest lengths in the direction of 
 the thickness of the plate, so that all the 
 poles are situated at or near the faces of 
 the plate, and, consequently, the extent 
 of such polar surfaces is great when com- 
 pared with the thickness of the plate. 
 Lamellar Magnet. A magnet whose 
 magnetism is characterized by lamellar 
 distribution, 
 
 Laminated. Built up or composed of 
 laminae. 
 
 Laminated Core. An iron core that has 
 been sub-divided in planes parallel to its 
 magnetic flux-paths, in order to avoid the 
 injurious production of Foucault or eddy 
 currents. 
 
 Laminated Magnet. A magnet provided 
 with a laminated core. 
 
 Laminating. Sub-dividing into laminae. 
 Lamination. The sub-division of an iron 
 core into laminae. 
 
 Lamination of Armature Core. The 
 sub-division of the iron core of a dynamo 
 or motor armature into a number of in- 
 
Lam.] 
 
 824 
 
 [Lam. 
 
 sulated parallel strips or plates, for the 
 purpose of avoiding eddy currents. 
 Lamination of Conductors. (1) The 
 division of a conductor into a number of 
 parallel strands or wires, for the purpose 
 either of lessening the eddy currents pro- 
 duced in its mass, or for reducing the 
 skin effect when alternating currents are 
 employed. (2) A stranded conductor. 
 
 Lamp Adapter.-; (1) A device which 
 permits an electric lamp to replace an or- 
 dinary gas burner on a gas bracket or 
 chandelier. (2) A device which permits 
 an electric lamp base of one manufacturer 
 to be readily inserted in the socket of an- 
 other manufacturer. 
 
 Lamp Base. The portion of an incandes- 
 cent lamp chamber through which the 
 leading-in wires are passed, provided with 
 two metallic plates or parts, suitably in- 
 sulated from one another, and electrically 
 connected to the ends of the leading-in 
 wires. 
 
 Lamp Bracket, Electric. A device 
 similar to that employed for a gas burner, 
 suitable for the support of an incandes- 
 cent lamp. 
 
 Lamp Bulb. The chamber or globe in 
 which the filament of an incandescent 
 lamp is placed. 
 
 Lamp Cap. The base of an incandescent 
 lamp. 
 
 Lamp Chamber. The bulb of an incan- 
 descent lamp. 
 
 Lamp Circuit. A circuit containing an 
 electric lamp or lamps. 
 
 Lamp Clamp. A suitable grip for hold- 
 ing the rod that supports the electrode of 
 an arc-lamp. 
 
 Lamp Contacts. Metallic plates or rings 
 placed in an incandescent lamp base, and 
 connected to the terminals of the filament. 
 
 Lamp Cord. A flexible cord containing 
 two separately insulated wires suitable 
 for use in connection with an incandescent 
 lamp. 
 
 Lamp Cut-Out. (1) A device so arranged 
 as to automatically cut a series-con- 
 nected arc-lamp out of the circuit, as soon 
 as the carbons are entirely consumed. 
 (2) A safety catch or safety fuse con- 
 nected with the circuit of a multiple-con- 
 nected incandescent lamp. 
 
 Lamp Dimmer. A reactive coil, em- 
 ployed on an 'alternating circuit for the 
 purpose of varying the intensity of incan- 
 descent lights connected with such 
 circuit. 
 
 Lamp Efficiency. (1) Commonly, but 
 
 illogically, the watts consumed by a lamp 
 per candle-power delivered. (2) More 
 nearly correctly, the reciprocal of this ; or 
 the number of candles obtained from an 
 incandescent lamp per watt supplied to 
 it. 
 
 Lamp Feet. (1) In a conducting loop, cir- 
 cuit, or system, the product of the number 
 of lamps supplied and the distance at 
 which they are supplied ; each lamp being 
 multiplied by its distance, and the sum of 
 such products being taken. (2) A quan- 
 tity sometimes used in computing dis- 
 tribution systems of electric lighting. 
 
 Lamp Filament. The filament of an in- 
 candescent lamp. 
 
 Lamp Fittings. (1) The.sockets, holders, 
 brackets, etc., required for holding, or 
 supporting, incandescent electric lamps. 
 (2) Lamp fixtures. 
 
 Lamp Frame. The frame of an arc-lamp 
 provided for the support of the feeding 
 mechanism, globe, etc. 
 
 Lamp Hanger. A device provided for 
 the suspension of an arc-lamp. 
 
 Lamp Hood. A hood employed to protect 
 an arc-lamp from rain or snow, and gen- 
 erally so arranged as to throw its light in 
 a downward direction. 
 
 Lamp-Hour. (1) Such a service of 
 electric current as is required to main- 
 tain one electric lamp during one hour. 
 (2) Such a quantity of electricity, or of 
 electric energy, as will maintain one 
 standard lamp in normal operation for 
 one hour. 
 
 Lamp Indicator. (1) An apparatus e*m- 
 ployed in a central station to indicate the 
 presence of the proper voltage, or poten- 
 tial difference, on the mains. (2) A 
 lamp employed on a telephone switch- 
 board to indicate when the subscriber is 
 calling, or when he has rung off. (3) A 
 pilot lamp. (4) Any indicating apparatus 
 employing an electric lamp as signalling 
 device. 
 
 Lamp Pendant. A flexible cord em- 
 ployed for the support of a pendant 
 lamp. 
 
 Lamp Pillar. (1) A pillar supporting one 
 or more lamps. (2) A lamp post. 
 
 Lamp Posts. Posts provided for the sup- 
 port of lamps. 
 
 Lamp Protector. A lamp hood, cover or 
 guard. 
 
 Lamp Receptacle. (1) A lamp socket 
 or holder. (2) A receptacle for a flex- 
 ible connection leading to a lamp. 
 
 Lamp Bod, (1) The rod provided in an 
 
Lam.] 
 
 825 
 
 [Law. 
 
 ordinary arc-lamp for the support of the 
 positive carbon. (2) In a focussing 
 lamp, the rods provided for the support 
 of the two carbons. 
 
 Lamp Socket. A support provided for 
 the reception of an incandescent lamp, so 
 arranged that the introduction of the 
 lamp therein, automatically connects the 
 lamp terminals with the terminals of the 
 supply wires. 
 
 Lamp-Socket Rheostat. A regulable re- 
 sistance placed in the socket of an incan- 
 descent lamp for the purpose of altering 
 the quantity of light it emits. 
 
 Lamp -Socket Switch. (1) A switch 
 
 E laced in the socket of an incandescent 
 imp, provided for lighting and extin- 
 guishing the lamp. (2) A lamp-socket key. 
 
 Lamp Switches. Switches placed in the 
 circuit of a group of incandescent lamps, 
 either in the branches, or in the mains, 
 for the purpose of simultaneously lighting 
 or extinguishing a number of lamps. 
 
 Land Line. (1) A telegraph line on land, 
 either aerial or buried, as distinguished 
 from a submarine cable. (2) An aerial 
 telegraph line. (3) That portion of a sub- 
 marine-cable circuit which extends over 
 the land. 
 
 Lantern Lamp. An incandescent lamp 
 provided with a lantern-shaped chamber 
 surrounding the lamp chamber. 
 
 Lantern Projector. A focussing arc-lamp 
 employed in connection with a projecting 
 apparatus. 
 
 Lap Joint. (1) The joint effected by over- 
 lapping short- portions near the ends of 
 the things to be joined, and securing 
 them to each other while in that posi- 
 tion. (2) A joint between the ends of two 
 conducting wires in which the two ends 
 after being laid together, side by side, are 
 lapped firmly together by a piece of separ- 
 ate wire. 
 
 Lap-Joint for Wires. A joint between 
 two wires, made by over-lapping their 
 ends and subsequently soldering. 
 
 Lap Winding. A winding for a drum 
 armature, in which the successive con- 
 ducting loops are arranged on the surface 
 of the armature over-lapping one an- 
 other. 
 
 Large Calorie. (1) A term sometimes used 
 for the great calorie. (2) A kilogramme- 
 degree-centigrade. (3) One thousand 
 lesser calories. 
 
 Latent. Hidden, concealed. 
 
 Latent Electricity. A term formerly 
 
 applied to bound electricity. 
 Lateral. Ah offset from a conduit system 
 
 11 
 
 for connecting services with the con- 
 ductors of a conduit. 
 
 Lateral Bracket. A form of bracket for 
 running wires from corner to corner of 
 buildings, and for supporting an insulator 
 in an upright position. 
 
 Lateral Discharge. (1) A Leyden-jar or 
 other impulsive discharge occurring be- 
 tween parts of the circuit not in the 
 direct path of the main discharge. (2) A 
 discharge occurring through an alterna- 
 tive path. 
 
 Lateral Induction. (1) Induction occur- 
 ring between closely-approached portions 
 of a circuit, through which an impulsive 
 discharge is passing. (2) The induction 
 produced by an impulsive discharge as 
 manifested in a lateral discharge. 
 
 Lateral Magnetic-Leakage. (1) The 
 failure of magneto flux to pass in ap- 
 proximately parallel paths through a bar 
 of iron or other magnetizable material, 
 which has come to rest in a field in which 
 it is free to move. (2) The escape of 
 magnetic flux from the sides of a bar 
 magnet, or other similar magnet, instead 
 of from the poles at its ends. 
 
 Lattice Pole. A form of structural-iron 
 pole designed for the support of overhead 
 wires or conductors, made in the form of 
 a light, strong lattice. 
 
 Lattice Work of Pole. A composite 
 pole whose upper portion consists of 
 structural lattice work, employed in cases 
 where the stresses produced on the top of 
 the pole are excessive by reason of the 
 weight of the cables, or the number of 
 lines or aerial wires supported thereon. 
 
 Launch, Electric. A launch whose mo- 
 tive power is electric. 
 
 Law. (1) In physics, any relation existing 
 between natural phenomena and their 
 causes. (2) The invariable manner in 
 which physical causes produce their 
 effects. (3) Any observed relation of 
 sequences in the universe. 
 
 Law of Electro-Chemical Equiva- 
 lence. The amount of electrolytic libera- 
 tion produced by an electric current 
 passed through various chemical sub- 
 stances is proportional to the chemical 
 equivalent of each substance, that is, to 
 its atomic weight divided by its valency. 
 
 Law of Illumination. The illumination 
 produced by a single-point source of light, 
 varies inversely as the square of the dis- 
 tance from that source. 
 
 Law of Ohm. (1) The law of non-varying 
 current strength in a circuit not subject 
 to variation. (2) Ohm's law. 
 Vol. 2 
 
Law.] 
 
 826 
 
 [Lea. 
 
 Law of Volta. (1) The law of contact 
 series. (2) Volta's law. 
 
 Laws of Becquerel. Laws for the mag- 
 neto-optic rotation of the plane of polari- 
 zation. 
 
 Laws of Coulomb. Laws for the force 
 of attraction and repulsion existing be- 
 tween charged bodies, or between neigh- 
 boring magnet poles. 
 
 Laws of Faraday. Laws of electrolytic 
 decomposition . 
 
 Laws of Joule. Laws expressing the de- 
 velopment of heat in a circuit by an 
 electric current. 
 
 Laws of Reflection. (1) The angle of in- 
 cidence is equal to the angle of reflection. 
 (2) Both the incident and the reflected 
 rays lie in the same plane. 
 
 Lay. The helical disposition of wires in a 
 strand or sheath, in which each wire 
 makes a complete revolution about the 
 axis. 
 
 Lay Torpedo. A moving torpedo, in 
 which the motive power is either carbonic 
 acid gas or compressed air, and the guid- 
 ing power electricity. 
 
 Layer. A name sometimes applied to an 
 electro-plating deposit. 
 
 Lay-Outof Cable in Tank. (1) The 
 starting of a new flake in coiling a cable 
 in a tank, by proceeding from the eye at 
 the end of the finished flake, directly out- 
 ward to the edge of the tank. (2) That 
 part of a cable which connects the inside 
 of one flake with the outside of the suc- 
 ceeding flake in a cable tank. 
 
 Laying-Up Cables. Placing or disposing 
 separate cables or conductors in a bunched 
 cable. 
 
 Lead. (1) An insulated conductor leading 
 to or from an electric source. (2) In 
 telegraphy , an insulated conductor leading 
 to an instrument, battery, circuit, or sta- 
 tion. (3) In a multiple or parallel-con- 
 nected circuit, a conductor or main con- 
 nected to the positive terminal of the 
 source. (4) In a system of electric distri- 
 bution, an insulated conductor leading to 
 a main, feeder, source, station, testing 
 apparatus, or device. (5) A connecting 
 wire. 
 
 Lead Accumulator. An accumulator or 
 storage cell which has been formed from 
 two plates of lead immersed in dilute 
 sulphuric acid. 
 
 Lead Burning. Effecting a metallic 
 junction between two lead plates or strips 
 by partially fusing them together. 
 
 Lead-Covered Conductors. Insulated 
 conductors sheathed in lead. 
 
 Lead-Encased Cable. A cable provided 
 with a sheathing or coating of lead on its 
 external surface. 
 
 Lead of Brushes of Dynamo-Electric 
 Generator. An angular deviation from 
 the normal position, forwards, or in the 
 direction of rotation of the 'armature, 
 which is given to the brushes on the 
 commutator, in order to obtain sparkless 
 commutation. 
 
 Lead of Current. An advance in the 
 phase of an alternating current beyond 
 that of the electromotive force producing 
 the current. 
 
 Lead of Motor Brushes. The angular 
 displacement from the normal position 
 in the direction contrary to that of the 
 rotation of the armature, which it is 
 necessary to give the brushes on an elec- 
 tric motor, when its load is increased, in 
 order to obtain freedom from sparking. 
 
 Lead Scoring Tool. A tool for readily 
 scoring the surface of a lead-covered 
 cable, for the purpose of obtaining a clean 
 surface preparatory to making a joint. 
 
 Lead Sheathing. The coating of lead 
 placed on the outside of a lead-covered 
 cable. 
 
 Lead Sleeve. A lead tube provided for 
 making a joint in a lead-covered cable. 
 
 Lead-Tin Alloys. Alloys of lead and tin, 
 of low melting point, employed for safety 
 fuses. 
 
 Lead Tree. An arborescent deposit of 
 lead obtained by the electrolysis of a solu- 
 tion of a lead salt. 
 
 Lead Voltameter. A voltameter consist- 
 ing of lead electrodes immersed in a dilute 
 solution of sulphuric acid and water. 
 
 Leaded Cable. A cable provided with a 
 lead sheathing. 
 
 Leading Current. An alternating-cur- 
 rent wave or component, in advance of 
 the electromotive force producing it 
 
 Leading Edge of Pole-Pieces of Arma- 
 ture. Those edges or terminals of the 
 field-magnet pole-pieces which the arma- 
 ture is approaching in its rotation. 
 
 Leading Horn of Pole-Pieces of Dy- 
 namo. Those edges or terminals of the 
 field-magnet pole-pieces towards which 
 the armature of a dynamo-electric ma- 
 chine is carried during its rotation. 
 
 Leading-In Insulator. The insulator 
 provided for the support of the wires 
 leading into a building from an aerial cir- 
 cuit. 
 
 Leading-In Tube.y-(l) A tube of insulat- 
 ing material provided for the reception 
 
Lea.] 
 
 827 
 
 [Lef. 
 
 of the leading-in wires in a building. 
 (2) An insulating tube. 
 
 Leading-In Wires .-^(1) The wires that 
 pass from an aerial circuit into a house or 
 building. (2) The wires or conductors 
 which lead the current through an in- 
 candescent electric lamp; i.e., into and 
 out of a lamp. (3) Wires leading a cir- 
 cuit into a house, room, box, or apparatus. 
 
 Leading Pole of Dynamo or Motor. 
 
 The pole of a dynamo or motor approached 
 by points on the surface of the revolving 
 armature which lie between the poles at 
 any instant. 
 
 Leading-Up Wires. Wires employed 
 for raising an aerial cable to the cable 
 hangers. 
 
 Leads. (1) In a system of parallel distri- 
 bution. the conductors connected to the 
 positive and negative terminals of a 
 source. (2) Generally, the conductors in 
 any system of electric distribution. (3) 
 Conductors which lead the current to or 
 from any source, circuit or device. (4) 
 In electric testing the insulating conduc- 
 tors leading the testing current to the cir- 
 cuit or conductor tested. 
 
 Leak. (1) Any loss or escape by leaking. 
 (2) The point or place where a leak occurs. 
 
 Leakage. A loss or escape by leaking. 
 
 Leakage Conductance. Insulation con- 
 ductance, or the reciprocal of the insula- 
 tion resistance. 
 
 Leakage Conductor. (1) A conductor 
 placed on a telegraphic circuit for the 
 purpose of preventing the disturbing ef- 
 fects of leakage into a neighboring line 
 by providing a direct path for such leak- 
 age to the earth. (2) A conductor placed 
 on a telegraphic line for the purpose of 
 lessening the retardation of the line by 
 assisting in its discharge. 
 
 Leakage Current of Primary .^(1) The 
 magnetizing current which flows into the 
 primary circuit of a transformer when 
 the secondary circuit is open, (2) A cur- 
 rent employed in magnetizing only, as 
 distinguished from a current usefully 
 transformed. 
 
 Leakage Current of Transformer. (1) 
 The current which flows into the primary 
 circuit of a transformer when the secon- 
 dary circuit is opened. (2) The mag- 
 netizing current. 
 
 Leakage Drop. The drop produced in a 
 circuit by leakage. 
 
 Leakage, Electric. The gradual dissipa- 
 tion of a charge or current due to insuf- 
 ficient insulation. 
 
 Leakage Factor. In a dynamo-electric 
 machine, the ratio of the total flux, which 
 passes through the field-magnet cores of 
 a dynamo or motor, to the total useful flux 
 passing from them through the armature. 
 
 Leakage Flux. (1) That portion of the 
 field flux which does not pass through the 
 armature of a dynamo or motor, and 
 which, therefore, produces no useful ef- 
 fect. (2) The stray flux, or that from 
 which no useful effect is obtained. 
 
 Leakage Indicator.-^!) A magnetic ex- 
 plorer. (2) An electric testing apparatus 
 for revealing the presence of leakage in 
 any circuit or system. 
 
 Leakage Interference. Interference be- 
 tween two or more circuits due to their 
 mutual leakage. 
 
 Leakage Magnetic Resistance. The re^ 
 luctance to leakage magnetic flux. 
 
 Leakage Method of Measuring Insu- 
 lation. A method of measuring the in- 
 sulation of a conductor or condenser by 
 determining the rate at which it loses 
 charge by leakage. 
 
 Leakage Paths. The paths traversed by 
 leakage magnetic flux. 
 
 Leakance. A term proposed for leakage- 
 conductance in a circuit. 
 
 Leclanche's Voltaic Cell. A zinc-car- 
 bon couple whose elements are used in 
 connection with a solution of sal-ammo- 
 niac, and a quantity of finely divided 
 black oxide of manganese surrounding 
 the carbon. 
 
 Lecture Galvanometer. A'form of gal- 
 vanometer suitable for showing the 
 movements of a galvanometer needle to 
 an audience at a considerable distance 
 from the instrument. 
 
 Left-Hand Trolley-Frog. A trolley- 
 frog so arranged as to switch a car to the 
 left. 
 
 Left-Hand Trolley-Switch. A switch 
 arranged to divert a car to the left of a 
 main line. 
 
 Left-Handed Armature-Windings. 
 Armature windings applied to the core 
 in a left-handed or sinistrorsal helix. 
 
 Left-Handed Dynamo. A dynamo 
 which runs left-handedly, or counter- 
 clockwise, when regarded from the pulley 
 end. 
 
 Left-Handed Helix. (1) A left-handed 
 solenoid. (2) A helix wound left-hand- 
 edly, or counter-clockwise. 
 
 Left-Handed Motor. A motor which 
 runs left-handedly, or counter-clockwise, 
 when regarded from the pulley end. 
 
Lef.] 
 
 828 
 
 [Ley. 
 
 Left-Handed Rotation. A rotation in a 
 positive or counter-clockwise direction. 
 
 Left - Handed . Solenoid. A solenoid 
 whose winding is left-handed, or counter- 
 clockwise. 
 
 Left-Handed Spiral. A left-handed 
 helix. 
 
 Left-Handed Winding. The winding of 
 a solenoid or helix in a counter-clockwise 
 direction. 
 
 Leg. In a system of telephonic exchange, 
 where a ground-return is used, a single 
 wire ; or, where a metallic circuit is em- 
 ployed, two wires, provided for connect- 
 ing the subscriber with the main switch- 
 board, so that any subscriber may be 
 placed directly in circuit with two or 
 more other subscribers. 
 
 Leg Key. A Morse telegraphic key having 
 long screw in its base for passing through 
 a table. 
 
 Leg of Circuit. (1) A branch of a bifur- 
 cated or divided circuit. (2) A loop or 
 offset in a series circuit. 
 
 Leg of Electro-Magnet. One of the 
 cores of an electro-magnet. 
 
 Legal Earth Quadrant. (1) A practical 
 unit of inductance as denned by the Elec- 
 trical Congress of 1884, at Paris, and as 
 distinguished from the true earth quad- 
 rant. (2) The legal quadrant. 
 
 Legal Ohm. (1) An ohm whose value is 
 in accordance with the definition of the 
 Electrical Congress of 1884, in Paris. (2) 
 The resistance of a uniform column of 
 mercury one square millimetre in area 
 of cross-section, and 106 centimetres in 
 length, at the temperature of Cent., or 
 32 Fahr. (3) The concrete standard ohm 
 as defined by the Electrical Congress of 
 1884, at Paris, as distinguished either from 
 the B. A. ohm, the true ohm, or the In- 
 ternational ohm. 
 
 Legal Quadrant. (1) The legal earth 
 quadrant. (2) The unit of self-induction 
 based upon the definitions of the Electrical 
 Congress of 1884, in Paris. 
 
 Legged. Placed in a circuit by means of 
 a leg. 
 
 Legging Key-Board. A key-board em- 
 ployed for the purpose of legging an oper- 
 ator into a circuit containing two or more 
 subscribers. 
 
 Legless Key. (1) A name sometimes given 
 to a Morse telegraphic key provided with 
 a flat base. (2) A self-closing key. 
 
 Length of Spark. The air distance trav- 
 ersed by a disruptive discharge. 
 
 Lenard Effect. The effect produced by 
 
 the Lenard Rays, in causing fluorescence, 
 and in passing through some substances 
 that are opaque to light. 
 
 Lenard Rays. The peculiar radiation 
 emitted from that external portion of a 
 Lenard tube that is directly opposite the 
 cathode. 
 
 Lenard Tube. A form of high-vacuum 
 tube provided with an aluminium plate, 
 hermetically sealed in that portion of the 
 wall of the tube lying directly opposite 
 the cathode, and employed for producing 
 Lenard rays. 
 
 Lens. A medium, transparent to radiant 
 energy, provided with a curved face or 
 faces, and employed to bring a beam or 
 pencil of light to a single point or focus. 
 
 Lens Lamp. A.n incandescent lamp pro- 
 vided with a small lens hermetically fixed 
 in a portion of its wall, opposite a suitably 
 placed reflector. 
 
 Lens-Mirror Projector. A form of pro- 
 jector whose operation is dependent on 
 the combined action of a mirror and a lens. 
 
 Lenz's Laws. Laws for determining the 
 direction of currents produced by electro- 
 dynamic induction. 
 
 Lesser Calorie. (1) The small calorie. 
 (2) The therm. (3) The water-gramme- 
 degree-centigrade . 
 
 Letter-Box, Electric. A device that 
 announces tho deposit of a letter in a box 
 by the ringing of a bell, or by the moving 
 of a needle or index. 
 
 Letter Printing Instrument. A type- 
 printing telegraphic instrument. 
 
 Level, Electric. An equipotential elec- 
 tric surface. 
 
 Level of Earth, Electric. A term some- 
 times employed for the potential of the 
 earth. 
 
 Lever Brake for Car. A form of car 
 brake operated by means of a brake 
 handle. 
 
 Lever Hook. (1) The hook in an auto- 
 matic telephone switch on which a tele- 
 phone receiver is hung when not in use. 
 (2) A contact lever provided with a hook 
 for supporting a telephone. 
 
 Lever Switch. (1) A switch mounted 
 upon a fulcrum axis like a lever. (2) A 
 switch operated by the movements of a 
 lever. (3) A telephone switch of a multi- 
 ple telephone switch-board, operated by 
 a lever. 
 
 Leyden-Jar. A condenser in the form of 
 a jar, in which the metallic coatings are 
 
 ' placed opposite each other respectively on 
 the outside and inside of the jar. 
 
Ley.] 
 
 829 
 
 I Urn. 
 
 Leyden-Jar Battery. The combination 
 of a number of separate Leyden jars so as 
 to act as a single jar. 
 
 Leyden-Jar Discharge. (1) The dis- 
 ruptive discharge produced by a Leyden 
 jar. (2) A name sometimes given to an 
 oscillatory discharge. 
 
 Leydic Resistance. A term proposed for 
 the resistance offered by various metallic 
 circuits to condenser discharges. 
 
 Lichtenberg's Dust-Figures. Figures 
 obtained by writing on a sheet of shellac 
 with the knob of a charged Leyden jar, 
 and then sprinkling over the sheet, dried, 
 powdered sulphur and red lead, which 
 have been previously mixed together and 
 are thereby rendered respectively nega- 
 tive and positive. 
 
 Lichtenberg's Electric Figures. A 
 term sometimes applied to Lichtenberg's 
 dust-figures. 
 
 Life Curve of Incandescent Electric 
 Lamp. A curve in which the life of an 
 incandescent electric lamp is represented 
 by means of abscissae and ordinates that 
 are respectively equal to the life in hours 
 and the candle-power at constant pressure, 
 or the pressure at constant candle-power. 
 
 Life of Electric Incandescent Lamp. 
 The number of hours that an incandes- 
 cent electric lamp will continue to fur- 
 nish a good commercial light when oper- 
 ated at normal pressure. 
 
 Lift, Electric. An electrically operated 
 lift or elevator. 
 
 Light. (1) That particular form of radiant 
 energy by means of which objects are 
 rendered visible. (2) The flow or flux of 
 light emitted from a luminous source. 
 
 Light Bath, Electric. A form of electro- 
 therapeutic bath in which the patient is 
 exposed to the radiation of a number of 
 incandescent lamps. 
 
 Light Cell. A term sometimes employed 
 for a photo-electric cell. 
 
 Light, Electric. Light produced by the 
 action of electric energy. 
 
 Light Escape. A partial ground or 
 earth. 
 
 Light-House Illumination, Electric. 
 The application of the electric arc-light 
 to light-houses. 
 
 Light Indicator of Railroad Signal. 
 A device by means of which an indica- 
 tion is given electrically, at a distance, as 
 to whether a signal lamp is lighted or not. 
 
 Light Load of Machine. A partial load, 
 or a load which is small by comparison 
 with the capacity of the machine. 
 
 Light Cable, Electric. A cable em- 
 ployed for furnishing the current required 
 for the maintenance of electric lights. 
 
 Lighting Circuits. Any electric circuit 
 for the distribution of light. 
 
 Lightning. A spark or discharge that 
 results from the disruptive discharge of a 
 cloud to the ground, or to a neighboring 
 cloud. 
 
 Lightning Arrester. A device by means 
 of which the apparatus placed in any- 
 electric circuit is protected from the de- 
 structive effects of a flash or discharge of 
 lightning. 
 
 Lightning - Arrester Board. The 
 board to which the lightning arresters of 
 a system of telephonic or telegraphic 
 communication are connected. 
 
 Lightning-Arrester Earth. The earth 
 provided for the grounding of the earth- 
 plate of a lightning arrester. 
 
 Lightning Bolt. A lightning flash or dis- 
 charge. 
 
 Lightning Conductor. A lightning rod. 
 
 Lightning Deviator. A term sometimes 
 used for lightning arrester. 
 
 Lightning Discharger. A term some- 
 times used for lightning protector. 
 
 Lightning Flash. A lightning discharge. 
 
 Lightning Guard. A term sometimes 
 used for lightning rod. 
 
 Lightning Jar. A Leyden-jar whose 
 coatings consist of metallic filings in the 
 gaps between which an irregular series 
 of sparks, somewhat resembling a light- 
 ning flash, appear on the discharge of the 
 jar. 
 
 Lightning Rod. A rod, strap, wire, or 
 stranded cable, of good conducting mate- 
 rial, placed on the outside of a house or 
 other structure, in order to protect it 
 from the effects of a lightning discharge. 
 
 Lightning Rods for Ships. A system of 
 rods or conductors designed to afford 
 electric protection for vessels at sea. 
 
 Lightning Stroke. (1) A disruptive dis- 
 charge occurring between two oppositely 
 charged clouds, or between a cloud and 
 the earth. (2) A lightning flash. 
 
 Lightning Tube. A fulgurite. 
 
 Lime Light. A source of light obtained 
 by the incandescence of a cylinder of 
 lime under the influence of the oxy-hy- 
 drogen blow-pipe. 
 
 Limit Switch. A small automatic switch 
 on an electric street car, connected in series 
 with the brake discs, and so arranged as 
 to be capable of cutting out the fields ot 
 
Lim.] 
 
 830 
 
 [Lin. 
 
 both motors when the braeking current is 
 excessive. 
 
 Limiting Distance of Speech. (1) The 
 length of circuit, or the distance to which 
 a circuit may be carried in a straight line, 
 at which telephonic conversation is just 
 practicable. (2) The limiting length of 
 line to which telephonic speech can be 
 carried successfully, depending upon the 
 electric conditions of the circuit, and the 
 nature of the apparatus employed. 
 
 Limiting Speed of Cable. The speed 
 to which the transmission of signals 
 through a cable is limited, by reason of its 
 electrostatic capacity and resistance. 
 
 Limiting Stop. A stop set so as to limit 
 the motion of an electrically vibrating or 
 oscillating bar to any pre-determined 
 extent. 
 
 Limiting Temperature-Elevation. A 
 temperature elevation of any apparatus 
 which is not to be exceeded during its 
 prolonged operation. 
 
 Line. Generally, a wire or conductor 
 connecting any distant points or stations. 
 
 Line Adjuster. An instrument employed 
 for overcoming the effects of leakage on 
 the adjustment of the relays in a tele- 
 graphic circuit. 
 
 Line Arrester. The lightning arrester 
 connected to a line or circuit. 
 
 Line Circuit. (1) The wires or other 
 conductors in the main line of a tele- 
 graphic or other circuit. (2) A trans- 
 mission circuit for electric energy. 
 
 Line Crosses. Electric crosses occurring 
 on lines. 
 
 Line Crossing. (1) The place where two 
 overhead trolley conductors cross each 
 other. (2) A metallic plate uniting the 
 ends of trolley wires, where one wire 
 crosses another. 
 
 Line Cross-Over. (1) A trolley crossing. 
 (2) A trolley cross-over. 
 
 Line Drop. In a telephone switchboard, 
 an electro-magnetic drop connected to a 
 line. 
 
 Line Dynamometer. A dynamometer 
 employed during the erection of an over- 
 head line, in order to determine whether 
 it has been pulled up to its proper tension. 
 
 Line Insulator. An insulator employed 
 for the support of an aerial line. 
 
 Line Integral. A continuous summing 
 up of some instantaneous quantity exe- 
 cuted or conducted along a continuous 
 line. 
 
 Line Jacks. In a telephone switchboard, 
 a jack connected to a line. 
 
 Line of Least Sparking. The diameter 
 
 of sparkless commutation. 
 
 Line Peg. A peg or plug in a switchboard 
 connecting the line with translating 
 devices or with another line. 
 
 Line-Pressure Compensator. A device 
 for attachment to a voltmeter in an alter- 
 nating-current system, whereby the volt- 
 meter indications are compensated for 
 the drop of pressure in the feeder, and 
 are such as would be obtained if the 
 instrument were directly connected to 
 the mains. 
 
 Line Reactance. The reactance of a line 
 conductor. 
 
 Line Section of Electric Railroad. 
 
 Any part of a trolley, or other railroad 
 line, so insulated from other parts as to 
 permit of the separate control of its sup- 
 ply of electric power. 
 
 Line Selector. A wire selector. 
 
 Line Wire. In telegraphy, the wire that 
 connects the different stations with one 
 another. 
 
 Line-Wire Tier. A tie wire of soft 
 copper or soft iron employed for holding 
 the line wire to the insulator. 
 
 Lines of Electric-Displacement. Lines 
 of electric flux, along which electric dis- 
 placement takes place. 
 
 Lines of Electric-Induction. The lines 
 along which electric induction takes 
 place. 
 
 Lines of Electrostatic-Flux. The lines 
 along which electrostatic flux passes. 
 
 Lines of Electrostatic-Force. (1) Lines 
 of force produced in the neighborhood of 
 a charged body by the presence of the 
 charge. (2) Lines extending in the direc- 
 tion in which the force of electrostatic 
 attraction or repulsion acts. 
 
 Lines of Inductive- Action. Lines of 
 electrostatic force. 
 
 Lines of Magnetic-Force. (1) Lines in 
 which magnetic force acts. (2) Lines 
 extending in the direction in which the 
 force of magnetic attraction or repulsion 
 acts. 
 
 Lines of Magnetic-Induction. (1) Mag- 
 netic flux-paths. (2) The lines in which 
 magnetic induction proceeds. 
 
 Lines of Magnetization. (1) A term 
 sometimes applied for lines of magnetic 
 induction. (2) A term sometimes applied 
 to those portions of the lines of magnetic 
 force which lie within the magnetized 
 substance. 
 
 Lineants. A term proposed as a unit of 
 magnetic flux in place of webers, and 
 
Lin.] 
 
 831 
 
 [Loc. 
 
 equal to the pressants divided by the 
 resistants, or to the magneto-motive force 
 divided by the reluctance. (Not used.) 
 
 Linear Capacity. The quotient of the 
 capacity of a line or conductor by its 
 length. 
 
 Linear Capacity of Cable. The electro- 
 static capacity of a cable per-unit-of- 
 length. 
 
 Linear Coefficient of Expansion. The 
 increase in a unit length of a substance 
 when subjected to unit difference of tem- 
 perature. 
 
 Linear Density, Electric. The amount 
 of electrification per unit of length. 
 
 Linear Density of Charge. The density 
 of charge per-unit-of-length. 
 
 Linear Insulation. The product of the 
 total insulation of a line by its length. 
 
 Linear Insulation of Cable. The prod- 
 uct of the insulation resistance of a cable 
 by its length. 
 
 Linear Spectrum. A spectrum consist- 
 ing of a few isolated frequencies. 
 
 Line-Man. One who puts up and repairs 
 line circuits, and attends to the receptive 
 devices connected therewith. 
 
 Link-Fuse. A link-shaped leaden plate, 
 provided with suitable ends for connection 
 with the copper fuse- wire terminals. 
 
 Link-Fuse Cut-Out. A cut-out employ- 
 ing a link-fuse. 
 
 Linkages. In a coil traversed by a cur- 
 rent, the sum of the magnetic flux due to 
 that current linked with the coil, obtained 
 by considering the quantity of flux linked 
 with each turn, separately and succes- 
 sively, and adding the fluxes so obtained. 
 
 Linked Magnetic and Electric Cir- 
 cuits. A phrase sometimes employed to 
 represent the interlinked condition of 
 magnetic and electric circuits. 
 
 Liquid Compass. A form of ship's com- 
 pass in which the compass-needle is sus- 
 pended, not only by the usual gimbals, but 
 is also so arranged that its oscillations are 
 checked by a surrounding liquid. 
 
 Liquid Flow. The quantity of liquid 
 that escapes from an orifice, or passes 
 through any cross-section of a pipe or 
 channel, in a given time. 
 
 Liquid-Level Alarm, Electric. A de- 
 vice for electrically sending an alarm 
 when a liquid level differs materially 
 from a given level. 
 
 Liquid Resistance Load. An artificial 
 load for a dynamo consisting of a mass 
 of liquid interposed between suitable 
 electrodes: 
 
 Liquid Thermostat. A thermostat 
 whose operation depends on the expan- 
 sion of a liquid. 
 
 Liquefaction. The conversion of a solid 
 into a liquid by the addition of heat, or 
 of a gas into a liquid, either by the removal 
 of heat, or by the combined influence of 
 low temperature and pressure. 
 
 Listening Cam. In a telephone system a 
 metallic cam or lever-key by means of 
 which an operator readily places her tele- 
 phone in circuit with a subscriber. 
 
 Listening Key. In a telephone switch- 
 board, a listening cam. 
 
 Lithanode. Highly conducting lead per- 
 oxide in a solid form suitably prepared for 
 the plate of a storage cell. 
 
 Line Trolley-Crossing. (1) The point or 
 plate where two trolley wires cross each 
 other at a street crossing. (2) A line 
 crossing. 
 
 Live Wire. (1) A wire through which 
 current is passing. (2) A wire connected 
 with an electric pressure or source. 
 
 Liverpool Repeater. A name given to 
 a form of telephone repeating induction 
 coil in which the iron core is constructed 
 of thin wires bent around over the coils, 
 so as to overlap at the ends, and form a 
 complete magnetic circuit. 
 
 Load. The work thrown on any machine. 
 
 Load-Diagram of Station. A curve 
 which represents the output of a station 
 for a given time, say for the twenty-four 
 hours of the day. 
 
 Load-Factor. The ratio of the average 
 to the maximum load. 
 
 Load of Dynamo. The current delivered 
 by a dynamo. 
 
 Load-Panel. The panel of a central- 
 station switchboard provided with appa- 
 ratus for indicating the total station-load. 
 
 Loadstone. An objectionable orthogra- 
 phy sometimes employed for lodestone. 
 
 Local Action of Dynamo-Electric Ma- 
 chine. The loss of energy in a dynamo 
 by the establishment of eddy currents in 
 its pole-pieces, cores, or other conducting 
 masses. 
 
 Local Action of Voltaic Cell. An irreg- 
 ular consumption of the zinc, or positive 
 element of a voltaic cell, by the fluid or 
 electrolyte when the circuit is opened or 
 broken, as well as when it is closed or in 
 regular action. 
 
 Local Battery. A voltaic battery thrown 
 into or out of action by a relay and em- 
 ployed at a station on a telegraphic line, 
 
Loc.] 
 
 832 
 
 [Lon. 
 
 to operate a sounder, or a registering or 
 recording apparatus, at that point only. 
 Local Battery Circuit. The circuit in a 
 telegraphic system in which is placed the 
 local battery, as distinguished from the 
 main battery. 
 
 Local Calls. At a central telephone ex- 
 change, a call received from a subscriber 
 connected directly therewith, as distin- 
 guished from a call received from another 
 exchange. 
 
 Local Currents. A term sometimes used 
 for eddy currents. 
 
 Local Faradization. A method of thera- 
 peutically applying the voltaic current, 
 similar in general to that employed in 
 local galvanization. 
 
 Local Galvanization. The application 
 of galvanization to portions of the body 
 only, in contradistinction to general gal- 
 vanization. 
 
 Local Jack. In a multiple telephone 
 switchboard, an answering jack corre- 
 sponding to a local line drop, or a jack 
 separated from the main body of the 
 switchboard and set in a local row for the 
 convenience of the operator in answering 
 calls. 
 
 Localization of Faults. Determining 
 the position of a fault on a telegraphic line 
 or cable by electrical tests applied at one 
 or both ends. 
 
 Localization Test. A test of a faulty cir- 
 cuit made to determine the position of 
 the fault. 
 
 Localized Capacity. Capacity inserted 
 in a circuit in one or more condensers, as 
 distinguished from distributed capacity, 
 or that which is present throughout the 
 entire circuit. 
 
 Localized Inductance. Inductance in- 
 serted in a circuit at one or more points, 
 as distinguished from distributed induct- 
 ance which is present throughout the 
 entire circuit. 
 
 Localized Vector. (1) A vector function 
 of space. (2) A vector point-function. 
 (3) A vector quantity which is a property 
 of every point of a region. 
 
 Locally Inter-Connected Switchboard. 
 
 A switchboard sub-divided into sections, 
 each provided with auxiliary jacks which 
 are interconnected among the different 
 sections. 
 
 Lock, Electric. A lock that is automati- 
 cally released by the aid of a distant push- 
 button. 
 
 Locomotive, Electric. (1) A locomotor 
 whose motive power is electricity. (2) An 
 electrically-driven locomotive engine. 
 
 Locomotive Head-Light, Electric. An 
 
 electric light placed in the focus of a par- 
 abolic reflector in front of a locomotive 
 engine. 
 
 Locomotor. A travelling motor, as dis- 
 tinguished from a stationary motor. 
 
 Locomotor, Electric. An electrically 
 driven locomotor. 
 
 Lodestone. A name given to a piece of 
 naturally magnetized iron ore. 
 
 Lodge's Standard Voltaic Cell. A 
 
 standard form of Daniell's cell. 
 
 Log, Electric. An electric device for 
 measuring the speed of, or the distance 
 traversed by, a vessel. 
 
 Logarithm. The exponent, or the power 
 to which it is necessary to raise a fixed 
 number called the base, in order to pro- 
 duce a given number. 
 
 Logarithmic. Of or pertaining to a loga- 
 rithm. 
 
 Logarithmic Curve. A curve in which 
 the rate of increase or decrease of the or- 
 dinate is proportional to the ordinate it- 
 self. 
 
 Logarithmic Decrement of Galvano- 
 meter .- (!) In a series of galvanometer 
 swings or deflections, the ratio of any 
 pair. of successive amplitudes. (2) The 
 ratio of any two successive total swings 
 or deflections of a galvanometer needle. 
 
 Logging Motor, Electric. (1) An elec- 
 tric locomotor employed for hauling logs. 
 (2) A form of telpher motor moving over 
 a cable way, usually over a swamp, for 
 hauling logs out of the same. 
 
 Long- Arc System of Electric Lighting. 
 A system of arc lighting employing long 
 arcs and, consequently, high electro-mo- 
 tive forces. 
 
 Long-Closed Circuit. A series circuit in 
 which all the devices are included as dis- 
 tinguished from a series circuit in which 
 some of the electro-receptive devices are 
 cut-out. 
 
 Long-Coil Magnet. (1) An electro-mag- 
 net whose magnetizing coil consists of 
 many turns of fine wire. (2) A high- 
 resistance magnet. 
 
 Long-Connection Armature-Winding. 
 Such a connection of a two-circuit arma- 
 ture winding that in each circuit electro- 
 motive forces are produced by field pole& 
 of one polarity only. 
 
 Long Connection of Two-Circuit 
 Gramme-Windings. A form of 
 Gramme winding in which the two cir- 
 cuits from brush to brush consist of con- 
 ductors that are influenced by only one- 
 half the poles. 
 
Ion.] 
 
 833 
 
 [Loo. 
 
 Long-Core Electro-Magnet. An electro- 
 magnet with a long core. 
 
 Long-Distance Carbon Telephone 
 Transmitter. A form of microphonic 
 telephone transmitter suitable for use on 
 long-distance circuits. 
 
 Long-Distance Telephone Cabinet. 
 An approximately sound-tight cabinet 
 employed for convenience and secrecy in 
 telephonic communication. 
 
 Long-Distance Transmission. Trans- 
 mission of electric energy over fairly con- 
 siderable distances. 
 
 Long End of Quadruplex Battery. 
 The end of a quadruplex battery that is 
 further from the point of intermediate 
 connection than the short end. 
 
 Long-Range Electrometer. An electro- 
 meter the range of whose scale is compar- 
 atively long. 
 
 Long-Shunt Compound-Winding. A 
 compound winding of a dynamo-electric 
 machine in which the shunt coil is con- 
 nected directly, or through resistance, 
 with the terminals of the machine, as dis- 
 tinguished from a short-shunt compound- 
 winding. 
 
 Long-Shunt Compound-Wound Dy- 
 namo-Electric Machine. A com- 
 pound-wound dynamo, in which the 
 shunt-field magnet coils form a shunt to 
 the binding posts of the machine. 
 
 Longitudinal Magnetization. Such a 
 magnetization of a bar or rod, that its 
 separate magnetic particles are arranged 
 with their axes lying in the direction of 
 the length of the bar. 
 
 Longitudinal Vibrations. Vibrations 
 set up in an elastic medium in the direc- 
 tion of propagation or transmission, as dis- 
 tinguished from transverse vibrations 
 which occur at right angles to the direc- 
 tion of propagation. 
 
 Loom, Electric. An electrically operated 
 loom , in which the Jacquard cards of the 
 ordinary loom are replaced by simple per- 
 forated metal plates, whose perforations 
 correspond to those in the Jacquard cards. 
 
 Loop Bracket. (1) A insulating bracket 
 from which a conducting loop can con- 
 veniently be run so as to include a source 
 or translating device. (2) A bracket for 
 holding two insulators and wires, such as 
 might form a loop. 
 
 Loop-Break. A device for introducing a 
 loop in a break made at any part of a cir- 
 cuit. 
 
 Loop-Circuit. (1) A term sometimes ap- 
 plied to a circuit in parallel or multiple- 
 arc. (2) A metallic circuit. (3) A circuit 
 
 53 
 
 having two wires, one out-going and the 
 other returning, as distinguished from an 
 earth-return circuit. 
 
 Loop Cut-Out. A cut-out placed in a 
 loop. 
 
 Loop, Electric. A portion of a main cir- 
 cuit consisting of a wire going out from 
 one side of a break in the main circuit and 
 returning to the other side of the break. 
 
 Loop-Mile. (1) A mile of going and 
 return conductor in a loop circuit. (2) A 
 mile of double conductor. (3) A double 
 mile of conductor. (4) A distance of one 
 mile traversed by a pair of conductors. 
 
 Loop or Spreader Bracket. A bracket 
 used on cross-arms for taking off loops 
 that are to be carried to service wires, 
 branch mains, or transformers. 
 
 Loop Switch. A switch for opening or 
 closing a loop, or for throwing a loop into 
 or out of a main circuit. (2) A switch 
 for connecting a branch office with a du- 
 plex or quadruplex switch at a main of- 
 fice, so that the branch office assumes 
 control of one set of apparatus ; i. e., 
 sends and receives messages on the duplex 
 or quadruplex system. 
 
 Loop System of Distribution. A system 
 of distribution employed in the early his- 
 tory of electric lighting, in which each of 
 a number of lamps was furnished with cur- 
 rent through a single machine by means 
 of a separate and independent loop or cir- 
 cuit connected with the terminals of such 
 machine. 
 
 Loop-System of Parallel Distribution. 
 A system of parallel distribution in 
 which a pair of mains is connected to a 
 generator in a manner designed to equal- 
 ize the drop of pressure ; one main being 
 connected at the home end directly to 
 the generator, and the other being con- 
 nected at its distant end to the generator 
 through a separate wire. 
 
 Loop Test. A localization test for a fault 
 in a loop of two telegraphic wires, or in a 
 complete metallic circuit. 
 
 Loop Winding. A term sometimes used 
 for lap-winding. 
 
 Loop-Winding of Alternator. (1) Coil 
 winding. (2) An alternator armature- 
 winding in which the wire is laid on the 
 surface of the armature core in loops or 
 coils. 
 
 Loops of Force. A term sometimes ap- 
 plied for lines of force. 
 
 Loops of Induction. A term sometimes 
 applied for lines of magnetic induction. 
 
 Loops of Mutual-Induction. Loops or 
 lines of induction produced in any cir- 
 
Loo.] 
 
 834 
 
 [Lum. 
 
 cuit by variations in the intensity of the 
 current flowing in a neighboring circuit. 
 Looping-In. A term sometimes employed 
 for a method adopted in grounded tele- 
 phone or telegraph circuits for connect- 
 ing Several instruments in series in a loop 
 in that circuit, so that any conversation 
 must be transmitted through all the in- 
 struments which happen to be in the cir- 
 cuit between the parties connected. 
 
 Loss Plate of Voltameter. (1) That plate 
 of a voltameter from which the metal 
 is electrolytically dissolved during the 
 passage of the current. (2) The plate con- 
 nected with the anode or positive ter- 
 minal. 
 
 Loose Carbon Transmitter. (1) A tele- 
 phone transmitter employing loose car- 
 bon or carbon dust. (2) A dust telephone 
 transmitter. 
 
 Loose Contact. A contact effected by 
 two or more surfaces that rest loosely on 
 one another, or by means of their weight 
 only. 
 
 Loose-Handle Switch. A form of switch 
 in which the handle after it has been 
 moved a short distance falls into a new 
 position of equilibrium. 
 
 Loss of Continuity. A disconnection or 
 interruption of a circuit. 
 
 Loud-Speaking Telephone. (1) A name 
 given to any telephone characterized by 
 the intensity of the sounds produced by 
 its receiver. (2) A name sometimes given 
 to the electro-motographic telephone. 
 
 Loudness. That quality of a sound which 
 depends on the amplitude of its vibra- 
 tions. 
 
 Low-Frequency. (1) A frequency of but 
 comparatively few alternations per sec- 
 ond. (2) Any frequency lower than that 
 usually employed. 
 
 Low-Frequency Trans forme r. A 
 transformer designed for operation on a 
 low-frequency circuit. 
 
 Low-Potential Current. A term some- 
 times used for a current on a low-pressure 
 circuit. 
 
 Low-Potential System. In the National 
 Electric Code, a system having a pressure 
 less than 300 volts. 
 
 Low Pressure. A comparatively small 
 pressure or electromotive force. 
 
 Low-Pressure Circuit. A circuit de- 
 signed for use in connection with low 
 electric pressure. 
 
 Low-Pressure Incandescent Lamp. 
 An incandescent lamp whose filament is 
 short and thick, and, consequently, of 
 
 low electric resistance suited for a lo\* 
 pressure. 
 
 Low-Resistance Magnet. A magnet 
 wound with low-resistance magnetizing 
 coils. 
 
 Low-Speed Electric Motor. An elec- 
 tric motor designed to run normally at 
 low speeds. 
 
 Low Tension. A term sometimes used 
 
 for low pressure. 
 Low-Tension Bus. In a central station 
 
 any bus-bar connected witli a low-tension 
 
 generator. 
 
 Low-Tension Electric Fuse. A fuse 
 that is ignited by heating a wire to in- 
 candescence by the passage of an electric 
 current of low pressure, as distinguished 
 from a high-tension fuse. 
 
 Low-Tension Switch. A switch de- 
 signed for use on low-tension circuits. 
 
 Low Vacuum. (1) A vacuum in which 
 the mean-free-path of the molecules of 
 the residual gas is small as compared with 
 the dimensions of the containing vessel. 
 (2) A space from which only a portion ot~ 
 the air or residual gas has been removed. 
 
 Loxodograph. An apparatus for elec- 
 trically recording on paper the actual 
 course of a ship, by the combined action 
 of magnetism and photography. 
 
 Lubricating. Reducing friction by 
 means of lubrication. 
 
 Lubrication. The reduction of friction 
 between surfaces, by rendering them 
 slippery. 
 
 Luces. A plural of lux. 
 
 Lumen. (1) A unit of flux-of-light equal 
 to the light received by a square metre of 
 spherical surface, from a point source of 
 unit intensity, placed at the centre of a 
 sphere one metre in radius. (2) The flux 
 of light through a steradian from a point 
 source, whose intensity is one pyr. (3) A 
 pyr-steradian. 
 
 Lumen-Meter. An instrument for meas- 
 uring the flux of light. 
 
 Lumen-Second. A rad. 
 Lumination. A term proposed for il- 
 lumination. (Not in use.) 
 
 Luminescence. A limited power for 
 emitting light possessed by certain bodies 
 which have previously acquired potential 
 energy by exposure to light or radiant 
 energy. 
 
 Luminescence Lamp. (1) A fluorescent 
 lamp. (2) A lamp rendered luminescent 
 by bombardment. (3) An X-ray lamp. 
 (4) A vacuum-tube lamp. 
 
Lum.] 
 
 835 
 
 [Mac. 
 
 Luminiferous. Bearing or carrying 
 
 light. 
 Luminosity. A term sometimes used for 
 
 the brightness of a source. 
 Luminous Absorption. The absorption 
 
 of luminous energy in its passage through 
 
 bodies. 
 Luminous Efficiency. The ratio which 
 
 the luminous radiation emitted by a source 
 
 bears to the total radiant energy emitted 
 
 by such source in a given time. 
 Luminous Flux. A phrase sometimes 
 
 employed for flow of light. 
 
 Luminous Frequencies. Physiological- 
 ly effective frequencies, or those capable 
 of producing the sensation of light. 
 
 Luminous Heat. Heat radiation accom- 
 panied by or containing physiologically 
 effective frequencies. 
 
 Luminous Intensity. The amount of 
 visible radiation emitted from a luminous 
 source per-unit-of-area of surface. 
 
 Luminous Interference. Interference 
 produced by light waves of the same 
 frequency when out of phase with each 
 other. 
 
 Luminous Radiation. Radiation capa- 
 ble of affecting the eye. 
 
 Lummer-Brodhun Screen. A form of 
 photometric screen requiring the use of 
 
 but one eye, thus eliminating any errors 
 due to the varying sensibility of the two 
 eyes, each of the two sources of light 
 that are being compared illumining its 
 own field only, and these two fields 
 being presented to the eye as a disc and 
 circle respectively, the latter surround- 
 ing the former, and yet having a sharp 
 line of separation from it. 
 
 Lunar-Inequality of Earth's Magnetic 
 Variation. Small changes in the value 
 of the magnetic variation or inclination, 
 dependent on the position of the moon 
 as regards the magnetic meridian. 
 
 Lunar-Inequality of Earth's Magnet- 
 ism. Small variations in the value of 
 the earth's magnetic elements dependent 
 on the position of the moon as regards 
 the magnetic meridian. 
 
 Lux. (1) A unit of illumination equal to 
 the light received on each square metre of 
 the interior of a sphere whose radius is 
 one metre, from a bougie-decimale placed 
 at its centre. (2) An illumination equal 
 to a lumen-per-square-metre. (3) The 
 normal illumination produced by one 
 carcel at a distance of a metre. 
 
 Lux-Second. (1) The time-illumination 
 of one lux during one second. (2) A unit 
 of time-illumination employed in photo- 
 graphy. (3) A phot. 
 
 M 
 
 M. A contraction sometimes employed to 
 
 express a pressure of the millionth of an 
 
 atmosphere. 
 
 m. A symbol for magnetic moment. 
 m. A symbol for strength of magnetic 
 
 pole. 
 m. An abbreviation for metre, a practical 
 
 unit of length. 
 m. An abbreviation for minute, a practical 
 
 unit of time. 
 p. A symbol for magnetic permeability or 
 
 inductivity. (International notation.) 
 ft. A symbol for micron, the millionth of a 
 
 metre, or one thousandth of a millimetre. 
 
 pp. A symbol for bicron, the millionth of 
 a millimetre, or thousandth of a micron. 
 
 m 2 . An abbreviation for square metre, a 
 practical unit of surface. 
 
 m 3 . An abbreviation for cubic metre, a 
 practical unit of volume. 
 
 m.a. A contraction for milli-ampere. 
 
 m : s. An abbreviation proposed for metre- 
 per-second, a practical unit of velocity. 
 
 m : s 2 . An abbreviation proposed for 
 metre-per-second-per-second, a unit of 
 acceleration. 
 
 mm. A contraction for millimetre. 
 
 M. Current. A term proposed for mean 
 current. 
 
 M. M. F. A contraction for magneto- 
 motive force. 
 
 M. P. A contraction for man-power. 
 
 M. P. H. A contraction sometimes em- 
 ployed in railroad work for miles-per- 
 hour. 
 
 M. S. Current. A term proposed for 
 mean-square-current. 
 
 Mac or Mack. A term at one time pro- 
 posed for the practical unit of self-induct- 
 ance, after Maxwell. 
 
 Machine Seal of Lamp Chamber. A 
 hermetical seal effected mechanically be- 
 
Mac.] 
 
 836 
 
 [Mag. 
 
 tween the glass support of an incandes- 
 cent lamp and the walls of the lamp 
 chamber. 
 
 Machine Telegraphic Transmission. 
 High-speed telegraphic transmission ef- 
 fected by means of an automatic tele- 
 graphic transmitter. 
 
 Machine Telegraphy. Automatic or 
 high-speed telegraphy. 
 
 Machine Tool, Electric. An electrically 
 driven machine tool. 
 
 Made Circuit. A completed circuit. 
 
 Magazine Fuse. A safety fuse contain- 
 ing a number of spare fuses, so arranged 
 as to readily permit the replacement of 
 the fuse when blown, either automatic- 
 ally, or by hand. 
 
 Magic Pane. A condenser formed of a 
 sheet of glass, covered on one side with 
 pieces of tin-foil, with small spaces left 
 between them disposed in some design on 
 the glass, which design becomes lumin- 
 ous on the discharge of the condenser. 
 
 Magne-Crystallic Action. A term pro- 
 posed by Faraday to express differences 
 in the action of magnetism on crystalline 
 bodies in different directions. 
 
 Magne-Crystallic Force. The force 
 which produces magne-crystallic actions. 
 
 Magne-Electric Induction. A variety 
 of electro-dynamic induction in which 
 electric currents are produced by the 
 motion of permanent magnets past con- 
 ductors, or of conductors past permanent 
 magnets. 
 
 Magnes Stone. An old name for mag- 
 netite or for a natural magnet. 
 
 Magnet. (1) Any body producing mag- 
 netic flux. (2) A body possessing the 
 power of attracting the unlike pole of an- 
 other magnet, or of repelling the like 
 pole, or of inducing magnetism in mag- 
 netizable bodies. 
 
 Magnet Coil. A coil of insulated wire 
 surrounding the core of an electro-mag- 
 net, through which the magnetizing cur- 
 rent is passed. 
 
 Magnet Cores. Bars or cylinders of iron 
 on which the magnetizing coils of wire 
 are placed. 
 
 Magnet Operation. The use of a magnet 
 for the purpose of removing particles of 
 iron from the eye. 
 
 Magnetic or Magnetical. Of or pertain- 
 ing to a magnet. 
 
 Magnetic A-B-C-Instrument. A step- 
 by-step dial telegraph instrument employ- 
 ing magneto-induced currents. 
 
 Magnetic Adherence. Adhesion be- 
 
 tween surfaces, due to their mutual mag- 
 netic attractions. 
 
 Magnetic Aelotropy. A difference in 
 the magnetic susceptibility of a mass of 
 iron in different directions. 
 
 Magnetic Air-Circuit. That portion of 
 a magnetic circuit which passes wholly 
 through air. 
 
 Magnetic Air-Gap. Any gap in an aero- 
 ferric magnetic circuit filled with air. 
 
 Magnetic Alternator. A magneto-alter- 
 nator. 
 
 Magnetic Atmosphere. (1) A term for- 
 merly employed for a space filled with 
 the assumed magnetic effluvia. (2) A 
 magnetic field. 
 
 Magnetic Attraction. The mutual at- 
 traction exerted between unlike magnetic 
 poles. 
 
 Magnetic Axis. (1) The line along which 
 a magnetic needle, free to move, but 
 which has come to rest in a magnetic 
 field, can be turned without changing the- 
 direction in which it comes to rest. (2) 
 The line connecting the poles of a bar 
 magnet or needle. 
 
 Magnetic Axis of Straight Needle. 
 A straight line drawn through a mag- 
 netic needle joining its poles. 
 
 Magnetic Azimuth. (1) The arc inter- 
 cepted on the horizon, between a mag- 
 netic meridian and a great circle passing 
 through the observed body. (2) A mag- 
 netic bearing. 
 
 Magnetic Battery. The combination of 
 a number of separate magnets so as to be 
 capable of acting as a single magnet. 
 
 Magnetic Bearing. The horizontal angle 
 included between a horizontal line from 
 an observer's eye to an object and the 
 observer's magnetic meridian. 
 
 Magnetic Bearing Compass. A com- 
 pass provided with means for taking bear- 
 ings. 
 
 Magnetic Belting. A method of driving 
 machinery in which the belt is provided 
 at frequent intervals with strips of sheet 
 iron riveted to it perpendicularly to its 
 length and the iron driving pulley mag- 
 netized, so that the magnetic attraction 
 increases the friction or grip on the pulley. 
 
 Magnetic Blow-Out. (1) A device for 
 extinguishing an arc by an electro-mag- 
 net. (2) A device employed for extin- 
 guishing an arc formed between the con- 
 tact pieces of a street-car controller, or 
 other similar device, by means of the flux 
 produced by an electro-magnet which i& 
 placed in the circuit of the current pro- 
 ducing the arc. 
 
Mag.] 
 
 837 
 
 [Mag. 
 
 Magnetic Blow-Out Lightning-Ar- 
 rester. A lightning arrester in which 
 the arc, when formed, is blown out by 
 the action of the flux of an electro-mag- 
 net placed in the circuit of the arc. 
 
 Magnetic Bridge. An apparatus for 
 measuring magnetic resistance, similar 
 in principle to Wheatstone's electric 
 bridge. 
 
 Magnetic Centre of Gravity. A con- 
 ception respecting the existence of a 
 point from which the magnetic flux pro- 
 ducing a magnet pole issues, similar to 
 the conception of a centre of gravity in 
 an unequally loaded plane. 
 
 Magnetic Circuit. The path through 
 which magnetic flux passes. 
 
 Magnetic Circuit-Breaker. A circuit 
 breaker operated by means of an electro- 
 magnet. 
 
 Magnetic Circuit-Closer. A circuit 
 closer operated by means of an electro- 
 magnet. 
 
 Magnetic Closed-Circuit. A ferro-mag- 
 netic circuit. 
 
 Magnetic Clutch. (1) A form of clutch 
 in which magnetic attraction is substi- 
 tuted for ordinary mechanical force, to 
 obtain the friction required in the clutch. 
 (2) A clutch operated electro-magnetic- 
 ally. 
 
 Magnetic Coercivity. A term some- 
 times used for coercive force. 
 
 Magnetic Compensator. A device for 
 neutralizing the effects produced by the 
 local magnetism of a ship on a magnetic 
 needle. 
 
 Magnetic Concentration. The separa- 
 tion of the useful ore from the dross in 
 low-grade ores, by the use of an electro- 
 magnetic separator. 
 
 Magnetic Conduction - Current. ( 1 ) 
 Time-rate of increase of magnetic flux 
 through a boundary. (2) Time-rate of 
 flow of magnetism. 
 
 Magnetic Conductivity. Magnetic per- 
 meability. 
 
 Magnetic Connection. (1) A term some- 
 times employed for inductive connection. 
 (2) The connection of one circuit with 
 another by means of inter-linked mag- 
 netic flux. 
 
 Magnetic Control of Galvanometer 
 Needle. The alteration in the sensibility 
 of a galvanometer needle effected by 
 means of a compensating magnet. 
 
 Magnetic Couple. The couple which 
 turns or tends to turn a magnetic needle, 
 placed in the earth's field, into the plane 
 of the magnetic meridian. 
 
 Magnetic Creeping. A term used for 
 a gradual increase in the magnetization, 
 following a sudden increase in magnet- 
 izing force. 
 
 Magnetic Cross-Flux of Transformer. 
 A magnetic flux across the direction of 
 main or working flux and representing 
 magnetic leakage. 
 
 Magnetic Current. The time-rate of in- 
 crease of magnetic flux through a sur- 
 face. 
 
 Magnetic Curve-Tracer. An instru- 
 ment for graphically recording the varia- 
 tions of magnetic intensity in a mass of 
 iron subjected to cyclic variations of mag- 
 netizing force. 
 
 Magnetic Curves. (1) Curved lines ex- 
 tending in the direction of the flux-paths 
 of a magnetic field, obtained by gently 
 tapping a sheet of paper or glass sprinkled 
 with iron filings and held in the field. (2) 
 Magnetic figures. 
 
 Magnetic Cycle. A cycle of magnetiza- 
 tion. 
 
 Magnetic Day of Disturbance. A day 
 of magnetic disturbance. 
 
 Magnetic Declination. The variation of 
 a magnetic needle from the true geo- 
 graphical north. 
 
 Magnetic Deep-Sea Thermometer. A 
 deep-sea thermometer containing small 
 steel maximum and minimum limit 
 markers which are reset by a permanent 
 magnet. 
 
 Magnetic Density. The strength of 
 magnetism as measured by the amount of 
 magnetic flux which passes through unit 
 area of normal cross-section. (2) Inten- 
 sity of magnetic induction. 
 
 Magnetic Deviation. (1) The local mag- 
 netic variation due to the presence of 
 iron in the vicinity, as distinguished from 
 the true magnetic variation of the local- 
 ity considered. (2) On board ship, that 
 part of the total magnetic variation due 
 to iron in or on board the ship. 
 
 Magnetic Diffusion. Magnetic leakage. 
 
 Magnetic Dip. (1) The deviation of a 
 freely suspended magnetic needle from a 
 true horizontal position. (2) The mag- 
 netic inclination. 
 
 Magnetic Discontinuity. The more or 
 less marked change in the permeability 
 of a magnetic circuit produced by any 
 joint in such circuit. 
 
 Magnetic Displacement. (1) An imag- 
 inary stress in the ether when subjected 
 to magnetization and corresponding to 
 electric displacement in electrostatics. 
 (2) Magnetic induction. 
 
Mag.] 
 
 838 
 
 [Mag. 
 
 Magnetic Dissymmetry. (1) A lack of 
 uniformity of the magnetic flux in a 
 magnetic circuit, or in portions of that 
 circuit. (2) A lack of uniformity pro- 
 duced in the flux through the armature 
 core of a dynamo or motor during its op- 
 eration. 
 
 Magnetic Disturbance. A term some- 
 times employed for temporary variations 
 in the intensity of the earth's magnetism. 
 
 Magnetic Divining Rod. A small dip- 
 ping needle employed for the purpose of 
 locating approximately the position of 
 beds of iron ore. 
 
 Magnetic Effluvia. (1) A term employed 
 in the early history of magnetism for 
 assumed imponderable effluvia which 
 were supposed to be given off by magnets. 
 (2) Magnetic flux. 
 
 Magnetic Elements of a Place. The 
 values of the magnetic intensity, the 
 magnetic declination or variation, and 
 the magnetic inclination or dip of any 
 place. 
 
 Magnetic Equalizer. A device for 
 equalizing the otherwise unequal force 
 exerted between a magnet pole and its 
 armature at varying distances. 
 
 Magnetic Equator. (1) The line con- 
 necting places on the earth's surface where 
 a magnetic needle remains horizontal, 
 when suspended so as to be free to move in 
 a vertical as well as in a horizontal plane, 
 (2) An irregular line passing around the 
 earth, approximately midway between 
 its magnetic poles. 
 
 Magnetic Excitation. Magnetization. 
 
 Magnetic Explorer. (1) A small flat 
 coil of insulated wire, used, in connection 
 with the circuit of a galvanometer or 
 telephone, to determine the position and 
 extent of the magnetic leakage of a 
 dynamo, or other similar apparatus. (2) A 
 search coil so connected to a ballistic 
 galvanometer that its movements through 
 magnetic flux will be indicated by the 
 galvanometer. 
 
 Magnetic Fatigue. An increase in the 
 hysteretic coefficient of iron due to an 
 assumed fatigue after many cyclic re- 
 versals. 
 
 Magnetic Fatigue of Transformer. 
 (1) An increase in the hysteretic loss of a 
 transformer with time. (2) The ageing 
 of a transformer core. 
 
 Magnetic Field. (1) The region of mag- 
 netic influence surrounding the poles of 
 a magnet. (2) The space or region trav- 
 ersed by magnetic flux. (3) A space 
 traversed by magnetic flux in which a 
 
 magnet needle, free to move, will assume 
 a definite position. 
 
 Magnetic Figures. A name sometimes 
 applied to the groupings of iron filings 
 obtained when a sheet of paper or glass, 
 sprinkled with filings, is so held in a mag- 
 netic field as to permit the filings to be 
 grouped or arranged under the influence 
 of the magnetic flux. 
 
 Magnetic Filament. A polarized line or 
 chain of ultimate magnetic particles. 
 
 Magnetic Flow. A term sometimes em- 
 ployed for magnetic flux. 
 
 Magnetic Fluids. A term formerly em- 
 ployed for the assumed fluids which were 
 believed to be the cause of magnetic 
 phenomena. 
 
 Magnetic Austral Fluid. The assumed 
 
 magnetic fluid existing at the south pole 
 
 of any magnet. 
 Magnetic Boreal Fluid. The assumed 
 
 magnetic fluid existing at the north pole 
 
 of any magnet. 
 
 Magnetic Flux. (1) The streamings that 
 issue from and return to the poles of a 
 magnet. (2) The total number of lines 
 of magnetic force in any magnetic field. 
 (3) The magnetic flow that passes through 
 any magnetic circuit. 
 
 Magnetic Flux-Density. The quantity 
 of magnetic flux in any part of a mag- 
 netic circuit per-unit-of-area of normal 
 cross-section. 
 
 Magnetic Flux-Intensity. The density 
 of magnetic flux. 
 
 Magnetic Flux-Paths. Paths taken by 
 magnetic flux in any magnetic circuit. 
 
 Magnetic Force. The force which causes 
 the attractions and repulsions of mag- 
 netic poles. 
 
 Magnetic Friction. A term sometimes 
 used for magnetic hysteresis. 
 
 Magnetic Fringe at Edge of Dynamo 
 Pole-Pieces. The lateral dispersion or 
 diffusion of magnetic flux through the 
 air space which produces an apparent 
 fringe of magnetic flux in the air sur- 
 rounding the poles. 
 
 Magnetic Gearing. A form of friction 
 gearing employing magnetic adhesion. 
 
 Magnetic Generator. A magneto-elec- 
 . trie generator. 
 
 Magnetic Helix. A magnetizing coil. 
 
 Magnetic Hysteresis. (1) Apparent mo- 
 lecular friction due to magnetic change 
 of stress. (2) A lagging of magnetization 
 behind the magnetic force producing it. 
 (3) That quality of a magnetic substance 
 
Mag.] 
 
 839 
 
 [Mag. 
 
 in virtue of which energy is absorbed on 
 the reversal of its magnetization. 
 
 Magnetic Image. The analogue in mag- 
 netism of an electric image in electro- 
 statics. 
 
 Magnetic Impermeability. A term 
 sometimes used for magnetic reluctivity. 
 
 Magnetic Inclination. (1) The angular 
 deviation from a horizontal position of 
 a freely suspended magnetic needle. 
 
 (2) Magnetic dip. 
 
 Magnetic Inductipn. (1) In air, the 
 density of magnetic force ; in iron or 
 other magnetic material the sum of the 
 prime flux, or magnetic force, and the 
 magnetic flux thereby produced in the 
 iron. (2) Total magnetic flux-density. 
 
 (3) The production of magnetism in a 
 magnetizable substance on its being 
 brought into magnetic flux. 
 
 Magnetic Inertia. The inability of a 
 magnetic core to instantly lose or acquire 
 magnetism. 
 
 Magnetic Intensity. (1) Magnetic flux- 
 density. (2) The quantity of magnetic 
 flux per-unit-of-area of normal cross-sec- 
 tion. (3) Magnetic induction. 
 
 Magnetic Joint. A joint effected be- 
 tween contiguous pieces of iron forming 
 portions of a magnetic circuit. 
 
 Magnetic Lag. (1) Magnetic viscosity 
 manifested by the sluggishness with 
 which a magnetizing force produces its 
 magnetizing effects in a mass of iron. 
 (2) The tendency of an iron core to resist, 
 and, therefore, to retard its magnetiza- 
 tion. (3) Hysteresis in iron. 
 
 Magnetic Lag Motor. A form of motor 
 whose torque depends on magnetic lag or 
 hysteresis. 
 
 Magnetic Latitude. (1) The meridional 
 angular distance of a place north or south 
 of the magnetic equator. (2) The lati- 
 tude as deduced from the magnetic dip. 
 
 Magnetic Leakage. (1) A useless disper- 
 sion of magnetic flux of a dynamo or 
 motor by its failure to pass through the 
 armature. (2) Any useless dispersion of 
 magnetic flux by its failure to pass 
 through a magneto-receptive device 
 placed in the magnetic circuit. 
 
 Magnetic Leakage Factor. The ratio 
 of the total flux generated in a magnetic 
 circuit to the quantity usefully passing 
 through an armature or magneto-recep- 
 tive device. 
 
 Magnetic Lightning-Arrester. (1) An 
 electro-magnetic blow-out lightning-ar- 
 rester. (2) Any lightning-arrester em- 
 ploying an electro-magnet. 
 
 Magnetic Limbs. (1) Magnetic cores. 
 (2) Magnetic, arms. 
 
 Magnetic Limit. A term sometimes em- 
 ployed for the temperature at which a 
 magnetic substance loses its magnetism 
 on exposure to heat. 
 
 Magnetic Line-Protector. An electro- 
 magnetic device placed on a telegraphic 
 or other line for the purpose of protect- 
 ing its instruments from lightning dis- 
 charges. 
 
 Magnetic Lines of Force. (1) Lines of 
 magnetic force. (2) Flux paths. (3) The 
 lines along which a free magnetic pole 
 would be urged. 
 
 Magnetic Magazine. A term sometimes 
 employed for a compound magnet. (Ob- 
 solete.) 
 
 Magnetic Mass. The quantity of mag- 
 netism or imaginary magnetic mattei 
 resident on a polar surface. 
 
 Magnetic Memory. (1) That deviation 
 of a magnetic condition of a magnetic 
 substance from the complete response to 
 an impressed magnetic force which is a 
 function of antecedent magnetic states. 
 (2) A term proposed for magnetic reten- 
 tivity. (3) The . power possessed by a 
 magnetic substance, in virtue of hyster- 
 esis, to retain in any magnetic state, the 
 history of antecedent states. 
 
 Magnetic Meridian. (1) The great circle 
 which passes through a place and through 
 the poles of a magnetic needle at that 
 place, when in a position of rest under the 
 free influence of the earth's magnetism. 
 (2) The terrestrial great circle coinciding 
 in plane with the direction of the earth's 
 local magnetic force. 
 
 Magnetic Moment. (1) The product of 
 the strength of one of the poles of a mag- 
 net into the distance between them. 
 (2) The sum of the two forces of the 
 directive couple of a magnet multiplied by 
 half the perpendicular distance between 
 the directions of these forces. (3) The 
 length of a magnet multiplied by the in- 
 tensity of one of its poles. 
 
 Magnetic Needle. (1) A magnetized 
 steel needle, or thin straight strip or rod. 
 (2) A straight bar of magnetized steel, 
 supported at or above its centre of grav- 
 ity, and free to move in a horizontal 
 plane only, in a vertical plane only, or in 
 both. 
 
 Magnetic North. That point of the hori- 
 zon which is indicated by the north-seek- 
 ing pole of a magnet. 
 
 Magnetic Observatory. An observatory 
 in which observations are made of the 
 
Mag.] 
 
 840 
 
 [Mag. 
 
 variations in the direction and intensity 
 of the earth's magnetic field. 
 
 Magnetic Oscillation. A magnetic vi- 
 bration, or to-and-fro variation. 
 
 Magnetic Output. The product of the 
 magnetic flux produced by any source and 
 its magneto-motive force. 
 
 Magnetic Parallels. Lines connecting 
 places on the earth's surface at right 
 angles to the isogonal lines, or lines of 
 equal declination or variation. 
 
 Magnetic Permeability. (1) Conductiv- 
 ity for magnetic flux. (2) The ratio be- 
 tween the magnetic induction produced 
 in a magnetic substance, and the magnet- 
 izing force producing such magnetic in- 
 duction. 
 
 Magnetic Permeance. Magnetic perme- 
 ability. 
 Magnetic Permeation. The passage of 
 
 magnetic flux through any permeable 
 
 substance. 
 Magnetic Perturbations. Abnormal 
 
 magnetic variations, or disturbances. 
 Magnetic Phantom. A term sometimes 
 
 employed for magnetic figures. 
 Magnetic Points of Cbnvergence. The 
 
 magnetic paths of the earth around which 
 
 the isogonic lines are drawn. 
 Magnetic Polar-Area. The active area 
 
 of the pole-pieces of a magnet. 
 
 Magnetic Polar-Intensity. The intens- 
 ity of the magnetic flux produced at the 
 pole-pieces of a magnet. 
 
 Magnetic Polarization. That condition 
 of a magnetizable substance when it is 
 subjected to polarization. 
 
 Magnetic Polar-Surface. The magnetic 
 polar area. 
 
 Magnetic Polarity. Polarity acquired 
 by a magnetizable substance when 
 brought into magnetic flux. 
 
 Magnetic Poles. Those parts of a mag- 
 netic source from or at which the flux 
 emerges or enters. 
 
 Magnetic Potential. (1) That property 
 of any space by virtue of which magnetic 
 work is done when a magnet pole is 
 moved therein. (2) The amount of work 
 required to bring up a unit north-seeking 
 magnetic pole from an infinite distance 
 to a given point in a magnetic field. 
 (3) The line integral of magnetic force on 
 a unit pole in coming from an infinite 
 distance to the point considered. 
 
 Magnetic Proof-Piece. A magnetized 
 ellipsoidal or square rod employed for as- 
 certaining the distribution of magnetism 
 
 over a magnet by the force required to 
 detach the same. 
 
 Magnetic Proof-Plane. A small coil of 
 wire placed in the circuit of a delicate 
 galvanometer, and used for exploring a 
 magnetic field. 
 
 Magnetic Reactance. In an alternating- 
 current circuit the reactance of a coil as 
 distinguished from the reactance of a 
 condenser. 
 
 Magnetic Reluctance. The resistance 
 offered by a medium to the passage 
 through it of magnetic flux. 
 
 Magnetic Remanence. The magnetic 
 flux-density left in iron or other magnetic* 
 substance after the removal of a mag- 
 netizing force. 
 
 Magnetic Repulsion. Mutual repulsion 
 exerted between two similar magnet 
 poles. 
 
 Magnetic Resistance. A term formerly 
 used for magnetic reluctance. 
 
 Magnetic Resistivity. (1) Magnetic re- 
 luctivity. (2) The reluctance of a medium 
 referred to the reluctance offered between 
 parallel faces of a unit cube. (3) The 
 magnetic analogue of electric resistivity. 
 
 Magnetic Retardation. A retardation 
 in the magnetization or demagnetization 
 of a substance due to magnetic lag. 
 
 Magnetic Retentiveness. A name some- 
 times applied to magnetic retentivity. 
 
 Magnetic Retentivity. (1) The resist- 
 ance a body offers to change of mag- 
 netization. (2) Hysteretic retention of 
 magnetism when the magnetizing force 
 is changed or wholly withdrawn. (3) 
 That quality of iron or other magnetic 
 substance in virtue of which it retains its 
 magnetic flux after the withdrawal of the 
 magnetizing force. (4) Magnetic rema- 
 nence. 
 
 Magnetic Ringer. A magnetic call-bell. 
 
 Magnetic Rotary - Polarization. (1) 
 Rotary polarization of a beam of plane 
 polarized light, produced by its passage 
 through magnetic flux. (2) Magneto- 
 optic rotation. 
 
 Magnetic Safety Factor. The factor of 
 safety of demagnetization. 
 
 Magnetic Saturation. (1) The maximum 
 magnetization which can be imparted to 
 a magnetic substance. (2) The condition 
 of iron, or other magnetic substance, when 
 its intensity of magnetization is so great 
 that it fails to be further magnetized by 
 any magnetizing force, however great. 
 
 Magnetic Screen. (1) A hollow box 
 whose sides are made of thick iron placed 
 
Mag.] 
 
 841 
 
 [Mag. 
 
 around a magnet or other body, so as 
 to shield its interior from a magnetic 
 field external to the box. (2) A magnetic 
 shield. 
 
 Magnetic Screening. Preventing mag- 
 netic induction from taking place by in- 
 terposing either a thick iron plate,or a plate 
 of good conducting material, between 
 the body producing the magnetic field and 
 the body to be magnetically screened. 
 
 Magnetic Self-induction. (1) Electro- 
 magnetic self-induction. (2) The power 
 possessed by a magnet of inducing an op- 
 posite polarity in its own particles. (3) Self- 
 demagnetizing power in a magnet. 
 
 Magnetic Sense. A name sometimes ap- 
 plied to the assumed sense by means of 
 which magnetic influences are claimed to 
 be perceived. 
 
 Magnetic Shade. A term sometimes used 
 for a magnetic screen. 
 
 Magnetic Shells. Sheets or layers con- 
 sisting of magnetic particles in each of 
 which all the north poles are situated in 
 one of the flat surfaces of the layer, and 
 all the south poles in the opposite surface. 
 
 Magnetic Shield for Watches. A hol- 
 low case of iron in which a watch is per- 
 manently kept in order to partially shield 
 it from the influence of external magnetic 
 flux. 
 
 Magnetic Shunt. An additional path of 
 magnetic material provided in a magnetic 
 circuit for the passage of magnetic flux. 
 
 Magnetic Shunt-Circuit. An additional 
 or branch circuit through which some of 
 the flux is diverted from the main mag- 
 netic circuit. 
 
 Magnetic Shunt-Transformer. (1) A 
 transformer provided with a magnetic 
 shunt of regulable value, for the purpose 
 of regulation. (2) A transformer situated 
 in a magnetic shunt. 
 
 Magnetic-Siren Telephone-Call. A 
 magnetophone employed as a telephone 
 call. 
 
 Magnetic Solenoid. A spiral coil of wire, 
 which acts like a magnet when an electric 
 current is sent through it. 
 
 Magnetic Sounds. Faint clicks heard on 
 the magnetization and demagnetization 
 of a readily magnetizable substance. 
 
 Magnetic Source. Anything capable of 
 producing magnetic flux. 
 
 Magnetic Spectrum. (1) A term some- 
 times employed in place of magnetic 
 figures or a magnetic field. (2) The suc- 
 cession of bright and dark fluorescent 
 bands produced upon a suitable screen in 
 
 a Crookes tube when the cathode rays 
 are deflected by magnetic flux. 
 
 Magnetic Spin. A term sometimes em- 
 ployed for magnetic field. 
 
 Magnetic Spiral. A magnetizing spiral 
 or helix. 
 
 Magnetic Sticking of Armature. The 
 magnetic adhesion of the armature to the 
 magnet poles under the influence of hys- 
 teresis. 
 
 Magnetic Storm. (1) Any unusually 
 marked irregularity occurring in the dis- 
 tribution of the earth's magnetism result- 
 ing in a variation in the value of its mag- 
 netic elements. (2) A comparatively 
 violent and widespread temporary pertur- 
 bation of the earth's magnetic elements in 
 some way associated with solar disturb- 
 ances and electric earth currents. 
 
 Magnetic Strain. The result of subject- 
 ing any medium to magnetic stress or 
 magnetic flux. 
 
 Magnetic Stream-Lines. (1) Magnetic 
 flux-paths. (2) Lines of magnetic flux. 
 (3) The curved paths along which a free 
 magnetic pole would be urged in different 
 parts of the field. 
 
 Magnetic Stress. (1) The mechanical 
 stress exerted by the attraction of magnet- 
 ized bodies. (2) That property of flux 
 which produces magnetic strain or mag- 
 netic phenomena in bodies subjected to its 
 influence. 
 
 Magnetic Susceptibility. (1) The ratio 
 existing between the induced magnetiza- 
 tion and the magnetizing force producing 
 such magnetization. (2) The intensity of 
 magnetism divided by the magnetic force. 
 
 Magnetic Telephone. (1) A name some- 
 times given to an electro-magnetic tele- 
 phone. (2) A magneto telephone. 
 
 Magnetic Telephone-Transmitter or 
 Receiver. A magneto-telephone-trans- 
 mitter or receiver. 
 
 Magnetic Theodolite. An apparatus for 
 measuring the declination or variation of 
 the magnetic needle at any place. 
 
 Magnetic Tick. (1) A metallic click heard 
 on the magnetization and demagnetiza- 
 tion of a bar of iron or steel. (2) The Page 
 effect. 
 
 Magnetic Time-Constant. In an electric 
 circuit or conductor, the ratio of the 
 inductance to the resistance, usually ex- 
 pressed in henrys per ohm, or seconds. 
 
 Magnetic Traction. (1) Tractive or sup- 
 porting power exerted by a magnet. 
 (2) Hauling or carrying effected magneti- 
 cally. 
 
842 
 
 [Mag. 
 
 Magnetic Unit Pole. An imaginary free 
 magnetic pole situated at a point, of such 
 strength that it would act with a force of 
 a dyne on a similar unit pole distant from 
 it one centimetre. 
 
 Magnetic Units. (1) Units based on the 
 force exerted between magnet poles. 
 (2) Units employed in dealing with mag- 
 nets and magnetic phenomena. (3) The 
 magnetic system of C. G. S. electro- 
 magnetic units, as distinguished from the 
 electrostatic system. 
 
 Magnetic-Vane Ammeter. An am- 
 meter in which the strength of a magnetic 
 field produced by the current that is to be 
 measured is determined by the repulsion 
 exerted between a fixed and a movable 
 iron vane placed inside the field and 
 magnetized thereby. 
 
 Magnetic-Vane Voltmeter. A volt- 
 meter in which the potential difference is 
 measured by the repulsion exerted be- 
 tween a fixed and a movable vane of soft 
 iron placed within the field of the mag- 
 netizing coil. 
 
 Magnetic Variations. Variations in the 
 value of the magnetic elements of a place. 
 
 Magnetic Variation-Transit. An ap- 
 paratus for measuring the magnetic decli- 
 nation or variation at any place. 
 
 Magnetic Variometer. An instrument 
 for comparing the horizontal component 
 of the earth's magnetism at different 
 localities. 
 
 Magnetic Viscosity. A property of iron 
 or other paramagnetic substance in virtue 
 of which a certain time is required before 
 a given magnetizing force can produce 
 its full effects. 
 
 Magnetic Voltmeter (1) An instrument 
 in which the magnetic field of a current 
 proportional to the difference of potential 
 to be measured deflects a movable needle 
 against the action of the field of a magnet. 
 (2) A voltmeter employing a permanent 
 magnet. 
 
 Magnetic Vortices. Imaginary vortices 
 in the ether postulated to account for 
 magnetic phenomena. 
 
 Magnetics. A word sometimes used for 
 that branch of science which treats of the 
 laws and phenomena of magnetism. 
 
 Magnetician. A word proposed for one 
 skilled in the science of magnetism. 
 
 Magnetification. The production of 
 magnetism in any body. 
 
 Magnetine. A word formerly applied for 
 the assumed principle of magnetism ; i.e., 
 the imponderable, hypothetical fluid to 
 
 the presence of which magnetic pheno- 
 mena were believed to be due. 
 
 Magnetisation. An orthography some- 
 times used for magnetization, and in 
 similar words where the z is replaced by s. 
 
 Magnetish. Possessing the property of 
 magnetism to a limited degree. (Very 
 rarely used.) 
 
 Magnetism. (1) That property or condi- 
 tion of matter which accompanies the 
 production of magnetic flux. (2) Mag- 
 netic.flux or streamings. (3) That branch 
 of science which treats of the nature and 
 properties of magnets and of magnetic 
 flux. 
 
 Magnetism of Rotation. A conception 
 at one time entertained that revolving 
 bodies became magnetized, as a deduction 
 from Arago's experiment. 
 
 Magnetist. A magnetician. (Seldom 
 used.) 
 
 Magnetite. A name given to mineral 
 
 magnetic oxide of iron. 
 Magnetizability. Possessing the ability 
 
 of becoming magnetized. 
 
 Magnetizable. Capable of being mag- 
 netized. 
 
 Magnetization. The act of imparting or 
 acquiring magnetization. 
 
 Magnetization by Double-Touch. - 
 
 A magnetization effected by placing two 
 magnets with their opposite poles to- 
 gether on the middle of the bar to be 
 magnetized, moving them to one end of 
 the bar, then moving them over the sur- 
 face of the bar to the other end, and 
 continuing these to-and-fro movements a 
 number of times, observing to stop in the 
 middle of the bar, and when the mag- 
 netizing magnets are moving in the oppo- 
 site direction to that in which they began 
 to move. 
 
 Magnetization by Separate-Touch. 
 Magnetization obtained by placing two 
 magnetizing bars with their opposite 
 poles at the middle of the bar to be mag- 
 netized, drawing them away from each 
 other towards its ends, returning them 
 through tire air to the middle of the 
 magnet, and repeating this a number of 
 times. 
 
 Magnetization by Touch. The produc- 
 tion of magnetic poles in a magnetizable 
 substance by touching it with a magnet. 
 
 Magnetization Curves. Curves which 
 graphically represent the relation of a 
 magnetizing force to the intensity of 
 magnetization or to the magnetic flux. 
 
 Magnetization Cycle. (1) A cycle of 
 magnetization. (2) A succession of mag- 
 
843 
 
 [Mag. 
 
 netic states which terminate in the 
 original state. 
 
 Magnetize. To endow with the property 
 of magnetism. 
 
 Magnetized. Endowed with the property 
 of magnetism. 
 
 Magnetizee. A word proposed to desig- 
 nate a person who believes he is placed 
 under the power of animal magnetism. 
 
 Magnetizer. (1) One who, or that which, 
 magnetises. (2) A word proposed to desig- 
 nate a person who claims that he can 
 place another under the power of his 
 animal magnetism. 
 
 Magnetizing. Endowing a body with 
 magnetic qualities. 
 
 Magnetizing Ampere-Turns. The am- 
 pere-turns of a magnetizing coil. 
 
 Magnetizing Currents. Currents that 
 are employed in producing magnetization. 
 
 Magnetizing Flux. Flux which is in- 
 tended to magnetize a body, or to keep it 
 magnetized, as distinguished from mag- 
 netic flux which performs any other 
 functions. 
 
 Magnetizing Force, (1) The vector 
 space- rate of descent of magnetic poten- 
 tial. (2) The prime flux-density impressed 
 upon a body, and which may induce 
 magnetism in the same. (3) The force at 
 any point with which a unit magnetic 
 pole would be acted on. (4) The impressed 
 flux-density of a field as distinguished 
 from the total flux-density. 
 
 Magnetizing Helix. A magnetizing 
 spiral or solenoid. 
 
 Magnetizing Spiral. A magnetizing 
 helix or solenoid. 
 
 Magnetizing Turn. A single turn in a 
 magnetizing coil. 
 
 Magneto. (1) A magneto-generator. 
 (2) A small magneto-electric dynamo 
 machine. 
 
 Magneto-Alternator. An alternator 
 whose field flux is produced by perma- 
 nent magnets. 
 
 Magneto-Blasting Machine. A mag- 
 neto-electric machine employed for gen- 
 erating the currents used in electric 
 blasting. 
 
 Magneto Call-Bell. A call-bell operated 
 by a magneto-electric machine. 
 
 Magneto-Chemical Cell. A cell, the 
 voltaic couple of which consists of two 
 magnetized steel bars, whose north and 
 south poles are respectively immersed in 
 a solution of oxalic acid. 
 
 Magnetod. A name employed by Reich- 
 
 enbach for the assumed force or principle 
 of animal magnetism. 
 
 Magneto-Dynamic Force. The force 
 exerted between magnets, or between 
 magnets and electric currents. , 
 
 Magneto-Dynamics. That branch of 
 dynamics which treats of the influence of 
 magnet poles on one another. 
 
 Magneto - Electric Alternating Ma- 
 chine. A magneto-alternator. 
 
 Magneto-Electric Bell. An electric bell 
 whose actuating current is obtained from 
 a magneto-electric machine. 
 
 Magneto-Electric Brake. (1) A device 
 for checking the swing of a galvanometer 
 consisting of means for sending slight 
 inverse currents through the coils of the 
 galvanometer. (2) An electro-magnetic 
 brake. 
 
 Magneto-Electric Call-Bell. A call 
 bell operated by a magneto-electric ma- 
 chine. 
 
 Magneto-Electric Dynamo. A dynamo- 
 electric machine whose field magnets are 
 formed of permanent magnets. 
 
 Magneto-Electric Faradic- Apparatus. 
 A small magneto-electric machine em- 
 ployed in electro-therapeutics for produc- 
 ing faradic currents. 
 
 Magneto-Electric Force. A theoreti- 
 cally-assumed mechanical force exerted 
 between a magnetic current and an elec- 
 tric field, corresponding to the electro- 
 magnetic force known to be exerted be- 
 tween an electric current and a magnetic 
 field. 
 
 Magneto-Electric Generator. A mag- 
 neto-generator. 
 
 Magneto-Electric Induction. A va- 
 riety of electro-dynamic induction in 
 which electric currents are produced by 
 the motion of pel-man ent magnets past 
 conductors, or of conductors past perma- 
 nent magnets. 
 
 Magneto-Electric Key. A telegraphic 
 key so arranged that a coil of wire on an 
 armature connected with a- key lever, 
 through the movements of the key to- 
 wards and from the poles of a permanent 
 magnet, produces currents that are sent 
 into the line. 
 
 Magneto-Electric Machine. A mag- 
 . neto-generator. 
 
 Magneto-Electrical Medical Appara- 
 tus. A small magneto-alternator em- 
 ployed in medical electricity for the pro- 
 duction of alternating or pulsating cur- 
 rents. 
 
 Magneto-Electric Multiplier. An early 
 form of induction coil employed by Page. 
 
Mag.] 
 
 844 
 
 [Mai. 
 
 Magneto-Electricity. (1) Electricity 
 produced by the motion of magnets past 
 conductors or of conductors past magnets. 
 (2) Electricity produced by magneto- 
 electric induction. 
 
 Magneto-Generator. A dynamo-electric 
 machine whose field flux is obtained from 
 permanent magnets. 
 
 Magnetogram. Any automatic record 
 obtained by means of a magnetic instru- 
 ment. 
 
 Magnetograph. A permanent record ob- 
 tained by the action of a self-recording 
 magnetometer. 
 
 Magneto-Induction Key. A magneto- 
 electric telegraph transmitter so arranged 
 that the movements of a key produce the 
 electric currents that are sent into the 
 line. 
 
 Magneto-Inductor. An inductor con- 
 sisting of a permanent magnet as distin- 
 guished from an inductor consisting of 
 an electro-magnet. 
 
 Magneto-Inductive Capacity. A term 
 sometimes employed for magnetic per- 
 meability. 
 
 Magneto Instrument. (1) A name for- 
 merly applied to a magneto machine. 
 (2) In telegraphy, a name sometimes em- 
 ployed for a machine . operating or oper- 
 ated by magnetically-induced currents. 
 
 Magnetology . (1) A name sometimes ap- 
 plied to the science of magnetism. (Not 
 in general use.) (2) That branch of 
 science which treats of magnetism. (Very 
 seldom used.) 
 
 Magnetometer. (1) An apparatus for the 
 measurement of magnetic force. (2) Any 
 apparatus for measuring the elements of 
 the earth's magnetic force. 
 
 Magnetometric. Of or pertaining to a 
 magnetometer. 
 
 Magnetometry. That branch of science 
 which treats of the measurement of the 
 strength of magnetic fields. 
 
 Magn eto-Motive. Producing magnetic 
 effects. 
 
 Magneto-Motive Force. (1) The force 
 which produces magnetic flux. (2) The 
 force that moves or tends to move mag- 
 netic flux. 
 
 Magneto-Motive Intensity. A term 
 sometimes used for the slope of magneto- 
 motive force. 
 
 Magneto-Motor. (1) A term formerly ap- 
 plied to a voltaic battery coupled in par- 
 allel. (2) A motor whose field is pro- 
 duced by permanent magnets. 
 
 Magneto-Optic Rotation. A rotation of 
 
 the plane of polarization of a beam of 
 plane polarized light on its passage 
 through a transparent medium, when 
 placed in a strong magnetic field in the 
 direction of the beam. 
 
 Magnetophone. A species of magnetic 
 siren with which sounds are produced in 
 a telephone by the periodic currents pro- 
 duced in its coils by the rotation of a per- 
 forated metallic disc in a magnetic field. 
 
 Magneto-Pointer. A dial of a printing 
 telegraph. 
 
 Magneto-Polar. Possessing magnetic 
 polarity. 
 
 Magneto-Receptive Device. A device 
 
 that is capable of being energized when 
 
 placed in magnetic flux. 
 Magnetoscope. Any apparatus for the 
 
 detection of the presence of magnetism, 
 
 but not for measuring it. 
 
 Magneto-Signals. Any signals operated 
 by a magneto-electric machine. 
 
 Magneto-Static Ammeter. An ammeter 
 whose magnet is acted on by a uniform 
 field of force with two coils, while at- 
 tracted by two systems of powerful per- 
 manent magnets. 
 
 Magneto-Static Current-Meter. A 
 magneto-static ammeter. 
 
 Magneto-Static Screening. Screening 
 from the inductive effects of a stationary 
 magnetic field. 
 
 Magneto-Statics. The science which 
 treats of magnetic forces at rest. 
 
 Magneto-Tapper. (1) A term sometimes 
 employed for a magneto-key. (2) Aeon- 
 tact key which closes the circuit of a 
 magneto. 
 
 Magneto-Telephone Transmitter. A 
 
 telephone transmitter formed of a power- 
 ful compound magnet provided with a 
 coil of insulated wire supported in front 
 of one of its poles, and an iron core form- 
 ing the pole-piece of the magnet. 
 
 Magneto-Therapy. Alleged electro- 
 therapeutic effects produced by the ap- 
 plication of magnets to the human body. 
 
 Magnet Wire. Insulated wire suitable 
 for winding magnets and usually cotton- 
 covered. 
 
 Magpie Cable. A name given to a form 
 of telephone cable in which the wires or 
 conductors are arranged in double pairs. 
 
 Main Battery. The battery employed in 
 telegraphic systems for sending the signals 
 over the main line, as distinguished from 
 a battery employed for any other work. 
 
 Main-Battery Circuit. ( 1 ) A term some- 
 times used for line circuit. (2) The cir- 
 
Mai.] 
 
 845 
 
 [Man. 
 
 cult of the main battery in any conduct- 
 ing system. 
 
 Main-Circuit Fuse. A safety fuse pro- 
 vided for the protection of the main cir- 
 cuit. 
 
 Main-Circuit Switch. A switch inserted 
 in a main circuit. 
 
 Main Cut-Out. Any cut-out placed in 
 the circuit of a main. 
 
 Main Feeder. (1) The feeder to which 
 the standard pressure-indicator is con- 
 nected, and whose pressure controls the 
 pressure at the ends of all the other 
 feeders. (2) A standard feeder. (3) A 
 principal feeder supplying a group of sub- 
 feeders. 
 
 Main Fuse. A main-circuit fuse. 
 
 Main- Line-Circuit Switch. A main 
 switch. 
 
 Main-Line Cut-Out. A main cut-out. 
 
 Main-Line Relay. A relay suitable for 
 use in connection with a main telegraphic 
 line. 
 
 Main-Line Sounder. A sounder suitable 
 for use in connection with a main tele- 
 graphic line. 
 
 Main Switch. (1) A switch connected 
 with the electric mains, (2) A principal 
 switch controlling a group of subsidiary 
 switches. (3) A main-line-circuit switch. 
 
 Main Telegraphic-Circuit. The princi- 
 pal or line telegraphic circuit. 
 
 Main Telegraphic-Current. The cur- 
 rent employed on a main telegraphic line 
 or circuit. 
 
 Main Terminals of Machine. (1) The 
 principal terminals of a machine. (2) The 
 terminals connected with the external cir- 
 cuit of a machine. 
 
 Main-to-Dynamo Bonding. A phrase 
 employed for a method of bonding the 
 rails in an electric car system, in which 
 the bonding is between a positive water 
 main, or buried metallic system, and the 
 negative terminal of the dynamo. 
 
 Main-to-Track Bonding. A phrase em- 
 ployed for a method of bonding of the rails 
 in an electric car system in which the 
 bonding is between a positive water main 
 and a negative track. 
 
 Main-Trunk Telephone-Line. (1) A 
 main telephone line connecting two cities 
 and usually erected with considerable 
 care, as to conducting power, insulation, 
 and freedom from electrical disturbance, 
 so as to serve as a general link of com- 
 munication either for communication be- 
 tween those cities, or for communication 
 through those cities. (2) A term used in 
 
 contradistinction to a local telephone line 
 connecting two stations. 
 
 Main Tubes. The tubes in an under- 
 ground system, provided for the mains. 
 
 Main Voltmeter. (1) A voltmeter in a 
 central station connected with the mains. 
 (2) A principal or standard voltmeter. 
 
 Main Wire. (1) Wire used in or intended 
 for electric mains. (2) Wire constituting 
 part of an electric main. (3) The prin- 
 cipal electric conductor in a distribution 
 or conducting system. 
 
 Mains. (1) In a parallel system of distri- 
 bution the parallel conductors carrying 
 the main current, and to which translat- 
 ing devices are connected. (2) In a sys- 
 tem of parallel distribution, the principal 
 conductors which extend from the risers, 
 or service wires, along the corridors or 
 passages along the floor to be lighted. 
 
 Mains of Electric Railroads. The 
 mains from which the driving current is 
 supplied to the cars. 
 
 Make. To complete or close a circuit. 
 
 Make-and-Break. The operation of al- 
 ternately completing and opening a cir> 
 cuit. 
 
 Make-Induced Current. (1) The cur 
 rent produced by self-induction on tin 
 making or closing of a circuit. (2) Thu 
 current produced by mutual induction in 
 the secondary of an induction coil or 
 transformer, on the making or comple- 
 tion of the circuit of the primary. 
 
 Making Earth. In telegraphy, ground- 
 ing. 
 
 Making the Primary. Closing the cir- 
 cuit of the primary. 
 
 Making-Up Batteries. Joining voltaic 
 cells in series or in parallel. 
 
 Manganin. A high-resistivity metal of 
 very low resistivity temperature-coeffi- 
 cient. 
 
 Mangin Projector. A special form of 
 search-light projector. 
 
 Mangin Reflector. A special form of 
 dioptric reflector employed in connection 
 with the Mangin projector, consisting of 
 a circular glass reflector, silvered at the 
 back, and whose inner and outer or front 
 and back surfaces are both spherical. 
 
 Manganin Resistance. A resistance 
 made of manganin wires, strips, or sheets. 
 
 Man-Hole Compartment of Conduit. 
 A man-hole provided in a conduit for 
 affording access to the same. 
 
 Man-Hole of Conduit. An opening com- 
 municating from the surface of the road* 
 
Man.] 
 
 846 
 
 Mas. 
 
 bed with an underground conduit, of suf- 
 ficient size to admit a man. 
 
 Manometer. An apparatus for measur- 
 ing the tension or pressure of gases. 
 
 Manometric. Of or pertaining to a mano- 
 meter. 
 
 Man-Power. A unit of power equal to 
 the one-tenth of a horse-power, or about 
 75 watts. 
 
 Manual Alarm. A fire alarm operated 
 by hand-power. 
 
 Manual Igniting Device. (1) A pen- 
 dent electric gas-lighting burner. (2) An 
 electric gas igniter operated by hand. 
 (3) A manual mine exploder. 
 
 Manual Repeater. A telegraphic re- 
 peater which is controlled or operated by 
 hand, as distinguished from an automatic 
 repeater. 
 
 Manual Telegraphic Transmission. 
 Transmission by hand, as distinguished 
 from automatic or machine transmission. 
 
 Manual Translation. The translation, 
 especially in submarine telegraphy, of a 
 message from one circuit to another, by 
 an operator who transmits to the second 
 circuit, direct from signals received on the 
 first, without writing down or transcrib- 
 ing the messages. 
 
 Marconi Rays. Electro-magnetic waves 
 employed in the Marconi system of wire- 
 less telegraphy. 
 
 Marconi "Waves. Electromagnetic 
 waves employed in the Marconi system 
 of wireless telegraphy. 
 
 Margin of Relay Adjustment. The 
 range of alteration permissible in the ad- 
 justment of the armature of a relay with- 
 out interfering with the working of the 
 instrument. 
 
 Marine Galvanometer. (1) A form of 
 Thomson reflecting galvanometer, heavily 
 encased in iron, devised for use on steam- 
 ships where the motion of magnetized 
 masses of iron would seriously disturb 
 the reading of ordinary instruments. 
 (2) Any form of galvanometer suitable 
 for use on board ship. 
 
 Marine Junction-Box. A water-tight 
 junction box for effecting junctions be- 
 tween mains, or mains and branches, on 
 board ship. 
 
 Marine Lamp-Socket. A form of spring 
 socket for flexibly supporting an incan- 
 descent lamp on board ship. 
 
 Marine Search-Light or Lamp. An 
 electric search-light suitable for use at 
 sea. 
 
 Marine Switch. A water-tight switch in 
 
 an incandescent lamp, fixture, or circuit, 
 on board ship. 
 
 Marine Voltmeter. A form of voltmeter 
 suitable for use on a ship. 
 
 Mariner's Compass. (1) A compass 
 mounted in such a manner as to be service- 
 able on board ship. (2) A name often ap- 
 
 plied to an azimuth compass. 
 
 Mark Buoy. In submarine cable work, a 
 buoy moored to the bottom of the sea by a 
 mushroom anchor, and placed to mark 
 a certain position, ,as distinguished from 
 a cable buoy which is moored to the end 
 of a cable. 
 
 Marked End of Magnet. A name for- 
 merly applied to the north-seeking pole of 
 a magnet. 
 
 Marked Pole of Magnet. A term some- 
 times applied to the north-seeking pole 
 of a magnet. 
 
 Markers. Colored flags or signal lights, 
 usually green, displayed in systems of 
 block railroad-signalling, in order to avoid 
 accident from the train breaking in two. 
 
 Marking Current. The current em- 
 ployed in automatic telegraphy to produce 
 the dots and dashes of the Morse alphabet, 
 as distinguished from the spacing current 
 or that employed to leave spaces between 
 such characters. 
 
 Marking Disc. In a Morse ink-writer, 
 the rotating inking disc, which marks the- 
 signals. 
 
 Mass. The quantity of matter contained 
 in a body. 
 
 Mass Attraction. The mutual attraction 
 exerted between masses of matter. 
 
 Mass Specific-Resistance. (1) Specific 
 resistance referred to unit mass instead of 
 unit volume. (2) The resistance taken be- 
 tween the ends of a cylindrical wire of 
 definite length, usually one metre, con- 
 taining a mass, usually a gramme. (3) 
 The resistance of a metre-gramme. 
 
 Massage. The treatment of the body by 
 kneading, rubbing or friction, for the 
 purpose of effecting changes in its general 
 nutrition. 
 
 Mass, Electric. A mathematical concep- 
 tion for quantities of electricity which are 
 so distributed as to produce electrostatic 
 forces in conformity with the laws of 
 gravitational forces, and, therefore, cor- 
 responding to material masses. 
 
 Mass Specific Resistance. (1) The re- 
 sistance of a known mass of a material ; 
 namely, one gramme, in the form of a 
 circular sectioned wire one metre in 
 length. (2) The resistance of a foot-grain. 
 
Mas.] 
 
 847 
 
 [Mea. 
 
 Mast-Arm for Arc-Lamp. A movable 
 arm or bracket provided at the top of a 
 pole for the support of a lamp arranged 
 for the ready lowering of the lamp for 
 re-carboning. 
 
 Mast Compass. A compass secured to the 
 mast of a ship, at an elevation sufficient 
 to considerably reduce the component of 
 local attraction from the ship's magnetiza- 
 tion. 
 
 Master Clock. A central or controlling 
 clock employed in a system of electric 
 time distribution, from which time is 
 transmitted to the secondary clocks in its 
 circuit. 
 
 Mate of Wire in Twisted Pair. (1) One 
 of the wires of a twisted pair. (2) The 
 conjugate member of a wire in a twisted 
 pair. 
 
 Matt. (1) A word employed in electro- 
 plating to designate the appearance pre- 
 sented by an electro-plating of silver in 
 which the deposit is interlaced and closely 
 massed together. (2) A fused mass of im- 
 pure copper employed as the raw material 
 in electrolytic refinement. 
 
 Matter. Anything which occupies space 
 in three dimensions and prevents other 
 matter from simultaneously occupying 
 the same space. 
 
 Matter, Electric. A term formerly ap- 
 plied to the matter which was believed to 
 constitute the effluvia formerly assumed 
 to pass off from an electrified body. 
 
 Matteucci's Muscular Pile. A pile 
 formed by arranging a series of muscles 
 so that their exterior and interior surfaces 
 are alternately connected. 
 
 Matthiessen's Metre-Gramme-Stand- 
 ard.. 0) A standard of resistivity or con- 
 ductivity in metallic wires. (2) The re- 
 sistance of a wire one metre in length, 
 and of such a diameter as would cause the 
 wire to weigh one gramme. (3) Accord- 
 ing to the American Institute of Electrical 
 Engineers Committee, the standard estab- 
 lished by Matthiessen for a metre-gramme 
 of soft copper, 0.1417 international ohm at 
 C., or 0.1501 international ohm at 15 C. 
 
 Matthiessen's Mile-S t a n d a r d. A 
 standard of resistance equal to the resist- 
 ance of one mile of pure copper wire one- 
 sixteenth of an inch in diameter, at 15.5 
 Cent. (No longer used.) 
 
 Matthiessen's Unit of Resistance. 
 Matthiessen's mile-standard. 
 
 Maturing of Call. In a system of tele- 
 phony where a number of calls have been 
 received at an exchange and recorded for 
 
 execution in order, the time at which any 
 particular call is reached in its order. 
 
 Maximum. (1) Possessing the greatest 
 value. (2) In a continuous succession of 
 values, a value greater than that which 
 precedes or follows it. 
 
 Maximum Activity of Motor. <1) The 
 activity of a motor when working at its 
 greatest possible rate, or the activity when 
 the useful work done is equal to half the 
 energy expended. (2) The full-load ac- 
 tivity of a motor. (3) The maximum 
 available activity of a motor. 
 
 Maximum Efficiency of Transformer. 
 
 The highest efficiency obtainable from a 
 transformer. 
 
 Maximum Horizontal Intensity of 
 Light. The greatest intensity of light 
 . emitted by a source in a horizontal direc- 
 tion. 
 
 Maximum Magnetization. A term 
 sometimes used for magnetic saturation. 
 
 Maximum Negative-Elongation. The 
 position of a vibrating body when it is at 
 the extremity of its path on the negative 
 side. 
 
 Maximum Positive-Elongation. The 
 
 position of a vibrating body when it is at 
 the extremity of its path on the positive 
 side. 
 
 Maximum Starting-Current of Motor. 
 The highest value the starting current 
 of a motor attains. 
 
 Maximum Traction Truck. A form of 
 double car-truck. 
 
 Maxwell's Electro-Magnetic Theory 
 of Light. (1) A hypothesis for the cause 
 of light based on the relations existing 
 between the phenomena of light and 
 those of electro-magnetism. (2) A hy- 
 pothesis that regards light as a purely 
 electro-magnetic phenomenon. 
 
 Mclntire's Parallel-Sleeve-Telegraph- 
 ic Joint. A joint for telegraphic or other 
 wires, in which the ends to be joined are 
 slipped into sleeves or parallel tubes, which 
 are afterwards filled with solder. 
 
 Mean. (1) Average. (2) A quantity hav- 
 ing an intermediate value between others. 
 
 Mean Annual Station-Current. The 
 average current delivered by a station 
 throughout the year. 
 
 Mean Current. (1) The time average of 
 a current strength. (2) In an alternating- 
 current circuit, the time average of a cur- 
 rent strength without regard to sign or 
 direction. 
 
 Mean Electromotive Force. (1) The 
 average electromotive force. (2) In an 
 
Mea.] 
 
 848 
 
 [Med. 
 
 alternating-current circuit, the time aver- 
 age of the E. M. F. without regard to sign 
 or direction. 
 
 Mean Horizontal Intensity of Light. 
 The average intensity of light in a hori- 
 zontal plane containing the source. 
 
 Mean Illumination. The average illu- 
 mination. 
 
 Mean Load-Current. The average load- 
 current. 
 
 Mean Spherical Candle-Power. (1) An 
 average candle-power numerically equal 
 to the total quantity of light emitted by 
 a point source divided by 12.566. (2) The 
 average candle-power of a source taken 
 at all points of the surface of a sphere. 
 
 Mean Spherical Intensity of Light. 
 The mean spherical candle-power. 
 
 Mean Quadratic Current. A term pro- 
 posed for the effective strength of an 
 alternating current. 
 
 Mean Thermal Capacity for Heat. The 
 
 average capacity for heat. 
 Measurement of Resistance. The de- 
 termination of the value of an electric 
 resistance by any suitable means. 
 
 Measurements, Electric. Determina- 
 tions of the values of the electromotive 
 force, resistance, current, capacity, 
 energy, etc., in any electric circuit or 
 instrument. 
 
 Measuring Current. (1) The current by 
 which an electrical measurement is made. 
 (2) A testing current. 
 
 Mechanical Air Pump. A mechanical 
 device for exhausting or removing the air 
 from any vessel. 
 
 Mechanical Characteristic of Motor. 
 A term sometimes employed for the curve 
 of the torque and speed of a motor as co- 
 ordinates. 
 
 Mechanical Circuit-Closer. (1) Any 
 circuit-closer not operated electrically. 
 (2) An automatic circuit-closer not oper- 
 ated electrically. 
 
 Mechanical Closer. A mechanical cir- 
 cuit-closer. 
 
 Mechanical Cut-Out (1) Any cut-out 
 not operated electrically. (2) An auto- 
 matic cut-out not operated electrically. 
 
 Mechanical Depolarizer of Voltaic 
 Cell. A method for removing the gas 
 collected on the negative plate of a voltaic 
 cell by the mechanical agitation of the 
 liquid. 
 
 Mechanical Equivalent of Heat. The 
 
 amount of mechanical energy converted 
 into heat that would be required to raise 
 the temperature of a unit mass of water 
 
 one degree of the thermometric scale. 
 
 (2) The quantity of energy mechanically 
 
 equivalent to one heat unit. 
 Mechanical Equivalent of Light. The 
 
 quantity of energy contained in one unit 
 
 of light. 
 Mechanical Frictions of Dynamo. 
 
 The journal, brush and air frictions of a 
 
 dynamo. 
 
 Mechanical Magnet Lightning - Ar- 
 rester. A mechanical device operated 
 by an electro-magnet for the extinguish- 
 ment of the arc established by a light- 
 ning flash. 
 
 Mechanical Mine. A submarine mine 
 that is fired when struck by a passing 
 ship through the action of some contriv- 
 ance contained within the torpedo itself, 
 and having no connection whatever with 
 the shore. 
 
 Mechanical Recording Meter. A me- 
 chanically operated recording meter. 
 
 Mechanical Seal. A mechanically made 
 seal of the chamber of an incandescent 
 lamp. 
 
 Mechanical Telegraph. Any form of 
 telegraphy by which communication is 
 established by mechanical means. 
 
 Mechanical Telegraphic Interrupter. 
 A form of mechanical telegraphic 
 sounder for learners, where no battery is 
 required. 
 
 Mechanical Telephone. A wire or 
 string telephone, operated by longitudinal 
 vibrations transmitted through a wire or 
 string. 
 
 Mechanical Throwback - Indicator. 
 An annunciator drop provided with a 
 drop that is mechanically replaced. 
 
 Mechanical Torpedo. A torpedo that 
 is exploded by percussion against any 
 obstacle. 
 
 Mechanical Vibrator. (1) A mechani- 
 cally operated contact-breaker. (2) A 
 mechanical means for obtaining the ejec- 
 tion of the ink from the siphon in a siphon 
 recorder. 
 
 Mechanical Work. (1) The product of a 
 force by the distance through which the 
 force acts. (2) The expenditure of energy 
 required for any change in the configura- 
 tion of a material system. 
 
 Medical Battery. A medical induction 
 coil. 
 
 Medical Electrician. An electro-thera- 
 pist. 
 
 Medical Induction-Coil. An induction 
 
 coil used for medical purposes. 
 Medical Magneto-Electric Apparatus. 
 
Meg.] 
 
 849 
 
 [Met. 
 
 A terra applied to small magneto-electric 
 machines employed in electro-therapeutics 
 for the production of uncommuted or far- 
 adic currents. 
 
 Meg or Mega. A prefix for one million 
 times. 
 
 Mega-Dyne. One million dynes. 
 
 Mega- Joule. One million joules. 
 
 Mega-Lines. One million lines. 
 
 Megalascope, Electric. An apparatus 
 for the medical exploration of the cavi- 
 ties of the body. 
 
 Mega- Volt. One million volts. 
 
 Mega- Weber. One million webers. 
 
 Megerg. One million ergs. 
 
 Megohm. One million ohms. 
 
 Megohm Box. A resistance box contain- 
 ing a resistance or resistances equal to a 
 megohm. 
 
 Megohm Galvanometer. A galvano- 
 meter which gives unit deflection through 
 a resistance of one megohm in circuit 
 with one volt. 
 
 Megohm Mile. A unit of linear insula- 
 tion resistance equal in value to the pro- 
 duct of a megohm by a mile, and such as 
 is possessed by a mile of wire, the insula- 
 tion of which is one megohm. 
 
 Melting Points of Metals. Tempera- 
 tures at which metals fuse. 
 
 Membrane Diffusion. Osmose. 
 
 Membrane Telephone-Receiver. An 
 early form of telephone receiver whose 
 diaphragm was formed of a sheet of gold- 
 beater's skin. 
 
 Mercurial Air-Pump. (1) A device for 
 obtaining a high vacuum by the use of 
 mercury. (2) The Geissler or Sprengel 
 mercury pumps. 
 
 Mercurial Connection. A form of read- 
 ily adjustable connection obtained by 
 providing the poles of one piece of appa- 
 ratus with cups or cavities filled with 
 mercury, in which the terminals of anoth- 
 er piece of apparatus are dipped, in order 
 readily to place them in circuit with each 
 other. 
 
 Mercurial Contact. An electric contact 
 effected through the medium of mercury. 
 
 Mercurial Phosphorescence. A term 
 formerly employed for the light produced 
 by the motion of a column of mercury in 
 an exhausted tube. 
 
 Mercurial Temperature - Alarm. An 
 instrument for automatically telegraph- 
 ing an alarm by means of a mercurial 
 contact, on a pre-determined change of 
 temperature. 
 
 ,54 
 
 Mercurial Thermostat. A thermostat 
 operating by the expansion of a mercury 
 column. 
 
 Mercury Break. A form of circuit 
 breaker operated by the removal of a con- 
 ductor from a mercurial surface. 
 
 Mercurial Commutation. A change in 
 the direction of a current obtained by 
 means of a mercurial connection. 
 
 Mercury Cup. A cup partly filled with 
 mercury employed as a mercurial contact. 
 
 Mercury Gauge. A vacuum or pressure 
 gauge whose indications are dependent 
 on the height of a mercury column. 
 
 Mercury Piezometer. An instrument 
 employed in cable work for measuring 
 the depth of the ocean, by recording the 
 pressure at the lowest . point reached by 
 the sounding lead, and used as a check 
 upon the length of sounding line. 
 
 Mercury Switchboard. A switchboard 
 in which connections are effected by mer- 
 curial contacts. 
 
 Mercury Tube. (1) A sealed glass tube 
 containing mercury arranged to emit 
 fluorescent light when agitated. (2) A 
 resistance formed of a thread of mercury 
 contained in a tube. 
 
 Meridional. Of or pertaining to a meri- 
 dian. 
 
 Mesh Grouping of Polyphase Circuit. 
 A triangular or delta-connection of three- 
 phase coils as distinguished from a star 
 connection. 
 
 Message Wire. A line or wire employed 
 in block systems for railroads extending 
 along the road and used for local tele- 
 graphic business. 
 
 Messenger Call-Box. A district call- 
 box. 
 
 Messenger Rope. (1) In cable- work a 
 rope drive for operating a drum or winch 
 at a distance. (2) A rope supporting 
 guide sheaves. 
 
 Messenger Strand. A strand in a mes- 
 senger wire. 
 
 Messenger Wire of Aerial Cable. The 
 supporting wire or rope from which the 
 cable clips employed in the suspension of 
 an aerial cable are supported. 
 
 Metal-Cased Blake Transmitter. A 
 form of telephone transmitter provided 
 with a metallic covering. 
 
 Metallic. Of or pertaining to a metal. 
 
 Metallic Arc. An arc formed between 
 metallic electrodes. 
 
 Metallic Circuit. A circuit which is 
 metallic throughout, in contradistinction 
 to an earth-return circuit. 
 
Met.] 
 
 850 
 
 [Met. 
 
 Metallic-Circuit Plug. In a telephone 
 switchboard, a plug which makes contact 
 both at its tip and at its sleeve, so as to 
 close a double or metallic circuit con- 
 nected therewith by a twin cord. 
 
 Metallic Coating. An electrolytically 
 deposited coating of metal. 
 
 Metallic Connection. Connection by 
 means of a metallic conductor. 
 
 Metallic Conducting Joint. A joint in 
 a conductor in which a continuity of con- 
 ducting power is secured. 
 
 Metallic Conduction. The conduction 
 of electricity through a metal, in contra- 
 distinction to its conduction through an 
 electrolyte. 
 
 Metallic Conductor. A conductor 
 formed of a metal. 
 
 Metallic Contact. (1) A contact of a 
 metallic conductor obtained by bringing 
 it into firm connection with another 
 metallic conductor. (2) Contact between 
 metal and metal. 
 
 ]V Metallic Contact of Cable. A complete 
 "cntact between the copper conductor of a 
 s marine cable and its metallic sheath. 
 
 Metallic Cross. A fault due to the actual 
 contact between two or more wires or 
 conductors, so that the current from one 
 line passes to another. 
 
 Metallic Electric Conduction. (1) A 
 conduction of electric energy by means 
 GJ. metallic substances. (2) Metallic con- 
 duction. 
 
 Metallic Electrodes. Variously shaped 
 pieces of metal employed for electro- 
 therapeutic electrodes. 
 
 Metallic Electrolysis. A form of cata- 
 phoretic medication in which a metallic 
 electrode, connected to the positive pole 
 of a continuous-current source, is 
 brought into contact with the part to be 
 treated, while the negative pole is applied 
 to some other part of the body, and the 
 metallic salt formed by electrolysis at the 
 anode is cataphoretically driven into the 
 tissues beneath the electrode. 
 
 Metallic Filament. A metallic wire em- 
 ployed as a filament of an incandescent 
 lamp. 
 
 Metallic Reluctivity. (1) The reluc- 
 tivity of a metallic substance. (2) In a 
 magnetic substance the reluctivity of the 
 substance as considered independently of 
 the reluctivity of the ether in its mass. 
 
 Metallic Resistance. A term some- 
 times applied to the resistance of wires 
 or conductors, in contradistinction to 
 the resistance of insulating materials. 
 
 Metallic Resistivity. The resistivity of 
 a metallic substance. 
 
 Metallic Solution. A solution of a 
 metallic salt. 
 
 Metallization. Rendering a non-conduct- 
 ing surface electrically conducting by 
 covering it with a metallic coating so as 
 to enable it to be readily electro-plated. 
 
 Metallizing. Subjecting to the process of 
 metallization. 
 
 Metallo-Chromes. (1) A name some- 
 times given to Nobili's rings. (2) Pris- 
 matic colors which appear when a salt of 
 lead, such as an oxide, is electrolyzed 
 under certain circumstances. 
 
 Metallurgy. That branch of science 
 which treats of the reduction or treat- 
 ment of metallic ores or metals. 
 
 Metamerism. (1) A variety of isomerism. 
 (2) The quality possessed by some chem- 
 ical substances, differing in their proper- 
 ties, although similar in their quantita-. 
 tive composition, owing to a difference of 
 molecular construction or arrangement of 
 atoms in the molecule. (3) A term used 
 in distinction to polymerism. 
 
 Meteorites. Fragmentary eolids that 
 when attracted to the earth become in- 
 candescent on their passage through its 
 atmosphere. 
 
 Meteorograph, Electric. An appa- 
 ratus for automatically registering by 
 electricity various meteorological values 
 such as the indications of a barometer or 
 thermometer, the direction and velocity 
 of the wind, the value of the rain-fall, 
 etc. 
 
 Meteorology. That branch of physics 
 which treats of the phenomena of the 
 atmosphere. 
 
 Meteorology, Electric. That branch 
 of physics which treats of the electric 
 phenomena of the atmosphere. 
 
 Meter, Electric. Any apparatus for meas- 
 uring commercially the quantity of elec- 
 tricity that passes in a given time through 
 a consumption circuit. 
 
 Meter-Motor. (1) A small motor em- 
 ployed in operating an electric meter. 
 (2) A meter comprising a small motor. 
 
 Meter Sealing Tool. A tool for stamping 
 a leaden seal which prevents the unin- 
 dicated opening of a meter by an un- 
 authorized person. 
 
 Method of Recoil. A method of measur- 
 ing a discharge through a ballistic gal- 
 vanometer by reversing the direction of 
 its swing. 
 
 Method of Slow Discharge. An insu 
 
Met.] 
 
 
 851 
 
 [Mic, 
 
 lation test for a telegraphic line, based on 
 the rate at which a charge leaks out 
 when the conductor is left insulated. 
 
 Methven Carburetter. A device employ- 
 ed in connection with a Methven screen, 
 consisting of troughs of fine wire gauze 
 filled with gasoline, so that the gas pas- 
 sing through becomes charged with the 
 vapor. 
 
 Methven' s Screen. A vertical rectangu- 
 lar metallic screen used in connection with 
 a standard Argand burner as a photomet- 
 ric standard. 
 
 Metre. A unit of length equal, approxi- 
 mately, to one ten-millionth part of a 
 quadrant of a meridian of the earth taken 
 through Paris ; or, approximately, to 
 39.37 inches, 
 
 Metre-Bridge. A slide form of Wheat- 
 stone's bridge in which the slide wire is 
 one metre in length. 
 
 Metre-Candle. (1) The illumination pro- 
 duced by a standard candle at the distance 
 of one metre. (2) A unit of illumination. 
 
 Metre-Gramme. (1) A unit of resistance 
 equal to that of the resistance of a wire 
 one metre in length weighing one 
 gramme. (2) A standard of comparison 
 of resistivity or conductivity. (3) Mat- 
 thiessen's metre-gramme standard of 
 copper wire, which for soft copper wire, 
 according to the committee of the Ameri- 
 can Institute of Electrical Engineers, is 
 0.1501 International ohm at 15 C. 
 
 Metre-Millimetre. A resistance stan- 
 dard, consisting of a length of wire or 
 other conductor, one metre long and 
 having a diameter of one millimetre. 
 
 Metric Factors. The factors employed 
 for the conversion of the metric system 
 units into those of other systems. 
 
 Metric Horse-Power. A unit of power 
 in which the rate-of -doing-work is equal 
 to 75 kilogramme-metres per second. 
 
 Metric System of Weights and Meas- 
 ures. A system of weights and meas- 
 ures based on the metre and the 
 gramme. 
 
 Mho. (1) The practical unit of conduct- 
 ance. (2) Such a conductance as is equal 
 to the reciprocal of one ohm. (3) A unit 
 of electric conductance of the value of 
 10- 9 absolute units. 
 
 Mho-Box. A conductance box, or box 
 containing adjustable conductance, 
 graduated in mhos. 
 
 Mhometer. An insti-ument for measur- 
 ing the value of a conductance in mhos. 
 
 Mica. (1) A refractory, mineral substance 
 employed as an insulator. (2) A double 
 
 ilicate of alumina or magnesia and 
 potash or soda. 
 
 Micanite. A variety of insulating 
 material made from and built up of small 
 mica sheets bound together by some in- 
 sulating cement. 
 
 Micro. A prefix for the one-millionth. 
 
 Micro- Ampere. The millionth of an am- 
 pere. 
 
 Micro-Coulomb. The millionth of a 
 coulomb. 
 
 Micro-Farad. The millionth of a farad. 
 
 Micro-Gilb. A contraction for micro- 
 gilbert. 
 
 Micro-Gilbert. The millionth of a gilbert. 
 
 Micro Glow-Lamp. A miniature incan- 
 descent lamp. 
 
 Micro-Graphophone. A modification of 
 the phonograph, in which a number of 
 separate non-metallic diaphragms are 
 caused to act on a single diaphragm, for 
 the purpose of obtaining stronger vibra- 
 tions of the same. 
 
 Micrometer Caliper. A micrometer wire 
 gauge. 
 
 Micrometer Eye-Piece. An eye-piece of 
 a telescope, microscope or other optical 
 apparatus provided with a micrometer. 
 
 Micrometer Microscope. A microscope 
 provided with a micrometer eyepiece. 
 
 Micrometer Wire-Gauge. A sensitive 
 form of wire gauge, usually constructed 
 with a fine thread screw, having a gradu- 
 ated head for close measurements of wire 
 diameters. 
 
 Micron. A unit of length equal to the 
 millionth part of a meter. 
 
 Microhm. The millionth of an ohm. 
 
 Microphone. A form .of contact tele- 
 phone-transmitter employed in connec- 
 tion with a telephone for rendering faint 
 or distant sounds distinctly audible. 
 
 Microphone Induction-Coil. An in- 
 duction coil employed in connection with 
 a mici'ophonic telephone transmitter. 
 
 Microphone Relay. A device for auto- 
 matically repeating a telephonic message 
 over another wire. 
 
 Microphonic. Of or pertaining to the 
 microphone.- 
 
 Microphonic Contact. A loose contact 
 capable of being employed for a telephone 
 transmitter. 
 
 Microscope. An optical instrument for 
 the examination of objects too minute 
 to be seen by the unaided eye. 
 
 Microscopic. (1) Of or pertaining to the 
 
me.] 
 
 852 
 
 [Mix. 
 
 microscope. (2) Of very minute dimen- 
 sions. 
 
 Microscopy. The art of microscopic ex- 
 amination. 
 
 Micro-Seismograph. An electric appa- 
 ratus for graphically recording the direc- 
 tion and intensity of faint earthquake 
 shocks or earth tremors. 
 
 Micro - Tasimeter. An apparatus in- 
 vented by Edison for measuring minute 
 differences of temperature, or of moisture, 
 by the resulting differences of pressure 
 upon a carbon button. 
 
 Micro-Telephone. (1) A convenient 
 form of writing table-set telephone used 
 by some exchange operators in quiet ex- 
 changes, or in busy exchanges, at night. 
 (2) A form of combined transmitter and 
 receiver. (3) A small semi-portable tele- 
 phone set. 
 
 Micro-Volt. The one-millionth of a volt. 
 
 Migration of Ions. A term employed to 
 express the movement of the ions in an 
 electrolyte undergoing electrolysis. 
 
 Migration Values of Ions. The veloci- 
 ties of the ions. 
 
 Mil. A unit of length used in measuring 
 the diameter of wires equal to the one- 
 thousandth of an inch. 
 
 Milammeter. A milli-ammeter. 
 
 Mild Steel. A term employed for soft 
 steel. 
 
 Mil-Foot. (1) A resistance standard con- 
 sisting of a foot of wire, or other con- 
 ducting material, one mil in diameter. 
 (2) A standard of comparison of resistiv- 
 ity or conductivity of wires. 
 
 Milli. A prefix for the one-thousandth 
 part. 
 
 Milli- Ammeter. A milli-ampere meter. 
 
 Milli-Ampere. The thousandth of an 
 ampere. 
 
 Milli-Ampere Meter. An ampere meter 
 graduated to read in milli-amperes. 
 
 Milli-Calorie. (1) The thousandth of a 
 
 calorie. (2) The small calorie. 
 Milli-Oersted. The thousandth of an 
 
 oersted. 
 
 Milli-Volt. The thousandth of a volt. 
 Mimosa Sensitiva. A sensitive plant 
 
 whose leaves fold or shut up, either when 
 
 touched, or when traversed by electric 
 
 currents. 
 Mine Explorer, Electric. A small 
 
 magneto-electric generator employed in 
 
 the direct firing of blasts. 
 Miniature Incandescent Lamp. A 
 
 very small incandescent lamp, suitable for 
 
 decorative, microscopic, dental or surgical 
 purposes. 
 
 Mining, Electric. The application of 
 electricity to mining. 
 
 Milling Locomotive, Electric. An elec- 
 tric locomotive employed in mining opera- 
 tions. 
 
 Minotto's Voltaic Cell. A form of Dan- 
 iells' cell employing a flat copper plate at 
 the bottom of the cell beneath a mass of 
 copper sulphate crystals, the cell being 
 then filled with wet sand, or wet sawdust, 
 on which rests the zinc plate. 
 
 Minus Charge. A negative charge. 
 
 Miophone. An apparatus, based on the 
 use of the microphone, employed for the 
 medical examination of the muscles. 
 
 Mirror Galvanometer. A galvanometer 
 whose readings are obtained by the move- 
 ments of a spot of light reflected from 
 a mirror attached to the needle or its sus- 
 pension system. 
 
 Mirror Magnetometer. A magneto- 
 meter whose needle or suspension system 
 is provided with a mirror. 
 
 Mirror Receiver in Cable Telegraphy. 
 In cable telegraphy, a mirror galvano- 
 meter employed as a receiver. 
 
 Mirror Receiving-Instrument. (1) A 
 receiving signalling instrument employed 
 in submarine telegraphy, whose needle or 
 suspension system is provided with a 
 mirror. (2) A mirror galvanometer mod- 
 ified for use in telegraphing. 
 
 Mirror Speaking - Instrument. A 
 mirror receiving-instrument. 
 
 Mixed Charge Test for Capacity. A 
 test employed for determining the capac- 
 ity of a submarine cable, in which an 
 unknown capacity is charged to one po- 
 tential, a known capacity is charged to 
 an opposite potential, and the two charges 
 are then mixed with the object of neutral- 
 ization. 
 
 Mixed Circuit. (1) In telephony, a circuit 
 partly metallic and partly earth-circuited. 
 (2) A term sometimes applied to the com- 
 bination of a series and a multiple circuit. 
 
 Mixed-Circuit Board. (1) A telephone 
 switchboard arranged for the reception 
 and inter-connection of metallic circuits 
 and ground-return circuits. (2) A mixed- 
 circuit switchboard. 
 
 Mixed-Circuit Switchboard. A tele- 
 phone switchboard connected with mixed 
 circuits or circuits of which some are 
 metallic and others are provided with 
 ground return. 
 
 Mixed Distribution. (1) A distribution 
 
Mix.] 
 
 853 
 
 [MoU 
 
 of electric energy which combines both 
 series and parallel distribution. (2) 
 Series-parallel or parallel-series distribu- 
 tion. 
 
 Mixing Key. The key employed in simul- 
 taneously charging a cable and a con- 
 denser for producing the mixed charge 
 employed in the mixed-charge test for 
 capacity. 
 
 Mixture Photometer. A photometer 
 combining the principles of the compensa- 
 tion and the polarization photometer. 
 
 Moderate-Speed. Generator. A gener- 
 ator designed to be run at a moderate 
 speed, as distinguished from a slow-speed 
 generator. 
 
 Moderate-Speed Motor. A motor de- 
 signed to work at a moderate speed, as 
 distinguished from a slow-speed motor. 
 
 Modulus of Elasticity . (1) The ratio of 
 the simple stress required to produce a 
 small elongation or compression in a rod 
 of unit area of normal cross-section, to 
 the proportionate change of length pro- 
 duced. (2) Young's modulus. 
 
 Moist Electrode. A therapeutic elec- 
 trode moistened with water or some other 
 liquid. 
 
 Moist Voltaic Cell. A form of the so- 
 called dry voltaic cell. 
 
 Moisture-Proof Insulation. (1 ) Water- 
 proof insulation. (2) A type of insulation 
 which is not strictly water-proof, but 
 which is capable of being immersed for 
 a short time without suffering serious loss 
 of insulation. 
 
 Molar Attraction. (1) Mass attraction, 
 as distinguished from molecular attrac- 
 tion or cohesion. (2) Gravitation. 
 
 Molar Vibration of Telephone Dia- 
 phragm. The mass vibration of a tele- 
 phone diaphragm, as distinguished from 
 molecular vibration. 
 
 Molecular. Of or pertaining to the mole- 
 cules. 
 
 Molecular Accommodation. A re- 
 arrangement of the molecules of a para- 
 
 ' magnetic substance resulting, by constant 
 repetition, in a decrease in the hysteretic 
 friction in cyclic magnetization. 
 
 Molecular Agitation. Rapid mechanical 
 vibration given to a mass of iron for the 
 purpose of reducing its magnetic hyster- 
 esis. 
 
 Molecular Attraction. (1) The mutual 
 attraction existing between neighboring 
 molecules. (2) Cohesion or adhesion. 
 
 Molecular Bombardment. (1) The col- 
 lisions which occur between neighboring 
 
 molecules, and which are accentuated and 
 accelerated by heat. (2) The forcible rec- 
 tilinear projection from the negative 
 electrode of the residual gaseous molecules 
 in an exhausted vessel, on the heating of 
 the same, or on the passage through it of 
 an electric discharge. 
 
 Molecular Chain. A polarized chain of 
 molecules that is assumed by Grothuss* 
 hypothesis to exist in an electrolyte during 
 its electrolytic decomposition, or in a vol- 
 taic cell on the closing of the circuit. 
 
 Molecular Conductance. The conduct- 
 ance offered by a mass of an electrolyte 
 equal to its molecular weight in grammes, 
 when contained in an insulating vessel 
 furnished with two opposite parallel con- 
 ducting sides or faces, distant one centi- 
 metre apart. 
 
 Molecular Conductivity of Electro- 
 lyte. (1) The conductance possessed by 
 one gramme-molecule of an electrolyte 
 when placed between electrodes one 
 centimetre apart. (2) A term sometimes 
 used for molecular conductance. 
 
 Molecular Configuration. A term for 
 the molecular groupings or the relative 
 position of the molecules in a magnetizable 
 substance. 
 
 Molecular Currents. (1) A term some 
 times employed for Amperian currents. 
 (2) Atomic currents. 
 
 Molecular Decomposition. Decomposi- 
 tion of a molecule. 
 
 Molecular Dissociation. (1) Molecular 
 decomposition. (2) The disruption of 
 molecules into ions, or atoms. 
 
 Molecular Encounter. A collision be- 
 tween two molecules of a gaseous sub- 
 stance that takes place during the to-and- 
 fro movements they describe in accord- 
 ance with the kinetic theory of gases. 
 
 Molecular Heat. The number of calories 
 of heat required to raise one gramme- 
 molecule of a substance one degree Cen- 
 tigrade. 
 
 Molecular Kinetics. The kinetics of the 
 molecules. 
 
 Molecular Magnetomotive Forces. 
 (1) The magnetomotive forces inherently 
 possessed by the molecules. (2) The 
 aligned or structural-magnetomotive 
 force as distinguished from the prime 
 magnetomotive force. 
 
 Molecular Magnetism. (1) The mag- 
 netism resulting from molecular magneto- 
 motive forces. (2) The inherent magnetic 
 flux in a molecule of a magnetic substance. 
 
 Molecular Magnetization. The in- 
 
Mol.] 
 
 854 
 
 [Mou. 
 
 herent magnetization possessed by the 
 molecules. 
 
 Molecular Magnets. The inherently 
 magnetized molecules. 
 
 Molecular Oscillations. To-and-fro 
 movements or oscillations of the mole- 
 cules. 
 
 Molecular Range. The distance at which 
 the molecules of matter continue to exert 
 a sensible attraction on one another. 
 
 Molecular Repulsion. The mutual re- 
 pulsion existing between molecules arising 
 from their kinetic energy. 
 
 Molecular Resistance. (1) The resistance 
 offered by a mass of an electrolyte equal 
 to its molecular weight in grammes, when 
 contained in an insulating vessel having 
 two opposite parallel conducting faces 
 distant one centimetre apart. (2) The re- 
 sistance of one gramme-molecule of an 
 electrolyte when brought between two 
 electrodes one centimetre apart. 
 
 Molecular Rigidity. The resistance 
 offered by the molecules of a substance 
 to rotation or displacement. 
 
 Molecular Shadows. The comparatively 
 dark spaces on those portions of the walls 
 of a Crookes tube, which have been pro- 
 tected by molecular bombardment by 
 suitably interposed screens. 
 
 Molecular Streams. Rectilinearly di- 
 rected streams of molecules, thrown off 
 from the cathode of a high-vacuum tube, 
 under the influence of heat or electric 
 discharges. 
 
 Muscular Theory of Muscle and 
 Nerve Currents. A theory which re- 
 gards every muscle or nerve fibre as 
 formed of a number of series-connected 
 electromotive molecules surrounded by a 
 neutral conducting fluid. 
 
 Molecular Transfer of Heat. The 
 transfer of heat by means of molecular 
 vibrations. 
 
 Molecular Vibration of Telephone 
 Diaphragm. The molecular vibration 
 of a telephone diaphragm under the in- 
 fluence of the changes in the magnetiza- 
 tion of the telephone magnet, as distin- 
 guished from its molar vibration. 
 
 Monochromatic Photometry. (1) The 
 photometry of monochromatic lights. 
 (2) Photometry in which the spectra or the 
 compositions of the lights to be compared 
 are similar. 
 
 Molecular Voltaic-Couple. A voltaic 
 couple formed of the atoms or radicals of 
 a molecule. 
 
 .Molecular Vortices. The vortices in the 
 ether which, according to a particular 
 
 theory, are assumed to constitute the 
 molecules, atoms or ultimate particles of 
 matter. 
 
 Molecule. (1) The smallest quantity of a 
 compound substance that can exist as such. 
 (2) A group of atoms whose chemical bonds 
 or affinities are completely satisfied. 
 
 Molten-Platinum Lamp. The violle or 
 molten platinum standard. 
 
 Molten-Platinum Standard of Light. 
 
 (1) The violle. (2) The practical standard 
 of white light adopted at the Electrical 
 Congress of Paris, in 1884, and defined as 
 the total quantity of light emitted by a 
 square centimetre of molten platinum at 
 the temperature of its solidification. 
 
 Moment. (1) Torque. (2) The product of 
 any quantity, directed with respect to an 
 axis, and the perpendicular distance of its 
 direction from that axis. 
 
 Moment of a Couple. (1) The torque or 
 effective power of a couple. (2) The in- 
 tensity of one of the forces in a couple, 
 multiplied by the perpendicular distance 
 between the direction of the forces. 
 
 Moment of a Magnet. The polar length 
 of a magnet multiplied by the intensity 
 of magnetism of one of its poles. 
 
 Momentary Current. (1) A current that 
 continues flowing but for a short time. 
 
 (2) A current of brief duration. 
 
 Momentum. (1) The product of the mass 
 of a moving body by its velocity. (2) 
 Quantity of motion in a system. 
 
 Monad Atom. An atom whose valency 
 or atomicity is one. 
 
 Moniyalent. (1) Possessing a valency or 
 atomicity of one. (2) Univalent, or mono- 
 valent. 
 
 Monochord. A sonometer. 
 
 Monocular. An eye-piece or glass, pro- 
 vided for a single eye. 
 
 Monophotal Arc-Light Regulator. 
 A term sometimes employed for an elec- 
 tric are-lamp in which the whole current 
 passes through the arc-regulating mech- 
 anism, and which is usually operated 
 singly in circuit with a dynamo. 
 
 Monocycler. A monocyclic generator. 
 
 Monocyclic. Of or pertaining to a mono- 
 cycler, or to a monocyclic system. 
 
 Monocyclic Alternator. A monocyclic 
 generator. 
 
 Monocyclic Armature. The armature 
 of a monocyclic generator, provided with 
 two sets of windings, one of which con- 
 stitutes the main winding and corresponds 
 to that of an ordinary uniphaser, while 
 
Mon.] 
 
 855 
 
 [Mot. 
 
 the second is of smaller cross-section and 
 fewer turns, and is connected to the centre 
 of the main winding in diphase relation 
 to it. 
 
 Monocyclic Circuit. The circuit of a 
 monocyclic generator. 
 
 Monocyclic Generator. A form of 
 polyphase generator provided with a mo- 
 nocyclic armature. 
 
 Monocyclic Motor. A form of induc- 
 tion motor suitable for use on monocyclic 
 circuits. 
 
 Monocyclic System.; (1) A system of 
 alternating-current distribution suitable 
 for electric lighting with the additional 
 capability of operating triphase induction 
 motors. (2) A system for the distribution 
 of alternating currents employing three 
 wires, between two of which an ordinary 
 uniphase pressure is maintained, while 
 between either of them and the third, 
 there is a diphased pressure. 
 
 Monogenic Charge. A name proposed 
 for such a distribution of an electric 
 charge in which the sign of the surface 
 density is everywhere the same. 
 
 Monophase Generator. An alternator 
 producing uniphase or monophase cur- 
 rents. 
 
 Monophase Motor. A uniphase motor. 
 
 Mooring Chain. A chain employed for 
 the mooring of a cable buoy. 
 
 Mopped. Subjected to the action of a pol- 
 ishing mop. 
 
 Mordey Effect. A decrease in the value 
 of the hysteresis in the iron of a dynamo 
 armature at full load. 
 
 Morse Alphabet. The Morse telegraphic 
 alphabet. 
 
 Morse Code. The Morse telegraphic al- 
 phabet. 
 
 Morse Embosser. A Morse register. 
 
 Morse Ink-Writer. The name some- 
 times given to a Morse inker. 
 
 Morse Inker. A form of telegraphic ink- 
 writer printing signals in the Morse code. 
 
 Morse Push. A term sometimes employed 
 for a double-contact push. 
 
 Morse Recorder. An apparatus for au- 
 tomatically recording the dots and dashes 
 of the Morse telegraphic dispatch, on a 
 fillet of paper drawn under an indenting 
 or marking point on a striking lever con- 
 nected with the armature of an electro- 
 magnet, as distinguished from a Morse 
 inker. 
 
 Morse Register. A Morse recorder. 
 
 Morse System of Telegraphy. A sys- 
 
 tem of telegraphy in which makes and 
 breaks, occurring at intervals corre- 
 sponding to the dots and dashes of the 
 Morse alphabet, are received by an electro- 
 magnetic sounder, or other receiver. 
 Morse Tapper. A form of telegraphic 
 key provided with two contacts, one in 
 front, and another on the back, so arranged 
 that the depression of the key makes one 
 contact and breaks the other. 
 
 Morse Writer. A form of telegraphic 
 Morse ink-writer. 
 
 Morse Telegraphic- Alphabet. Various 
 groupings of dots and dashes or deflec- 
 tions of a needle to the right and left, em- 
 ployed for representing the letters of the 
 alphabet or other signs. 
 
 Morse Telegraphic-Sounder. An elec- 
 tro-magnet, the movements of whose ar- 
 mature lever produce the audible sounds 
 corresponding to the dots and dashes of 
 the Morse code. 
 
 Motional Electric Force. The electric 
 force induced by the motion of magnetic 
 flux, or of the medium supporting the 
 flux. 
 
 Motional Magnetic Flux. Magnetic 
 flux produced by the motion of an elec- 
 trostatic charge, or of electrostatic flux. 
 
 Motorneer. A word proposed for motor- 
 man. (Not in general use.) 
 
 Motor Armature. The armature of an 
 electric motor. 
 
 Motor Car, Electric. An electrically 
 propelled car. 
 
 Motor Circuit. A circuit containing an 
 electric motor. 
 
 Motor-Controlling Rheostat. A rheo- 
 stat connected with a motor, and em- 
 ployed for starting the motor or for 
 regulating its speed. 
 
 Motor Cut-Out. A cut-out provided in 
 the circuit of a motor for the purpose of 
 throwing it out of circuit. 
 
 Motor - Dynamo. (1) An electrically 
 driven motor, rigidly connected to the 
 armature of a dynamo, and employed for 
 transforming or changing the pressure of 
 a direct-current circuit. (2) The combi- 
 nation, in a continuous-current generator 
 of a motor and a dynamo, in separate 
 structures, mechanically connected to 
 form a single machine or structure. 
 
 Motor-Electromotive Force. A term 
 proposed for the counter-electromotive 
 force of a motor. 
 
 Motor, Electric. A device for transform- 
 ing electric power into mechanical power. 
 
 Motor-Generator. (1) A motor coupled 
 
Mot.] 
 
 856 
 
 [Mul. 
 
 to a generator. (2) A motor-dynamo. 
 (3) A form of secondary generator. 
 
 Motorman. The man who operates a 
 trolley car. 
 
 Motor-Meter. (1) An electric meter whose 
 operations depend on the movements of 
 an electric motor. (2) A meter con- 
 nected with the supply circuit of an elec- 
 tric motor. 
 
 Motor Slip. The deviation of an induc- 
 tion motor from synchronous speed, or 
 the proportional loss of synchronous speed 
 due to load and losses of energy. 
 
 Motor Standards. The supports for the 
 bearing of an electric motor. 
 
 Motor Starter. A term proposed for a 
 motor starting-rheostat. 
 
 Motor Starting-Box. A box containing 
 a starting rheostat or controller. 
 
 Motor Starting-Rheostat. An adjusta- 
 ble rheostat provided for preventing an 
 abnormal rush of current through a shunt- 
 wound motor, on the starting of the same. 
 
 Motor Suspension. The suspension pro- 
 vided for the electric motors on a street- 
 car truck. 
 
 Motor Switch. A switch provided for 
 the control of a motor. 
 
 Motor Telegraph Printing System. 
 A printing telegraph system in which 
 two motors, one at the transmitting, and 
 one at the receiving end of the line, are 
 maintained in synchronous rotation. 
 
 Motor Torque. The rotary effort de- 
 veloped by an electric motor. 
 
 Motor-Transformer. (1) A transformer 
 or secondary generator operated by a 
 motor. (2) A motor-generator, dynamo- 
 tor, or rotary-transformer. (3) A dyn- 
 amo-electric machine having two arma- 
 ture windings, one to receive current as a 
 motor, and the other to deliver current to 
 a secondary circuit as a generator. 
 
 Motor Truck. The truck of an electric 
 car provided with supports for the sus- 
 pension of an electric motor or motors. 
 
 Motoring at Brushes. A term proposed 
 for flashing at the brushes of a motor. 
 
 Moulded Carbons. Artificial carbons 
 made by moulding mixtures of carbona- 
 ceous substances under pressure. 
 
 Moulded Filaments. The formation of 
 an incandescent filament by moulding a 
 suitable carbonaceous paste by hydraulic 
 pressure. 
 
 Moulded Mica. An insulating substance 
 consisting of finely divided mica, made 
 into a paste with some f used insulating 
 
 material, and moulded into the desired 
 shape before cooling. 
 
 Moulding Wiring. Electric conductor* 
 or wires that are held in place on the 
 walls or ceiling of a room by means of 
 suitably-shaped mouldings. 
 
 Mouldings, Electric. Mouldings of 
 dried non-conducting wood, provided 
 with longitudinal grooves for the recep- 
 tion and support of insulated wires. 
 
 Mounted Filament. The filament of an 
 incandescent lamp placed on its support, 
 ready for introduction into the lamp 
 chamber. 
 
 Mounting of Filament. Providing the 
 filament and leading-in wires of an incan- 
 descent lamp with a suitable glass sup- 
 port ready for introduction into the 
 chamber of an incandescent lamp, and 
 its hermetical sealing therein. 
 
 Mouse-Mill Dynamo. A form of dyna- 
 mo-electric machine employed to drive a 
 replenisher or influence machine. 
 
 Mouse-Mill Machine. A form of induc- 
 tion machine employed as a replenisher 
 or high-tension source. 
 
 Mouth-Pieces. Circular openings into 
 air chambers, placed over the diaphragms 
 of telephones, phonographs, gramophones, 
 or graphophones, to permit the ready 
 application of the mouth in speaking, 
 so as to set the diaphragm in vibration. 
 
 Movable. Capable of being moved. 
 
 Movable Secondary. The secondary of 
 an induction coil, which, instead of being 
 fixed, as in most coils, is movable. 
 
 Multi - Cellular Electrostatic Volt- 
 meter. An electrostatic voltmeter in 
 which a series of fixed and movable plates 
 are employed, instead of the single pair of 
 plates of the quadrant electrometer. 
 
 Multi-Circuit Arc-Dynamo. A dynamo 
 whose armature is provided with several 
 circuits designed to avoid too high an 
 electromotive force on any single circuit. 
 
 Multi-Circuit Arc-Light Generator. 
 (1) An arc-light generator designed to 
 supply, several series-connected arc-cir- 
 cuits, as distinguished from a generator 
 designed to supply a single circuit. (2) A 
 multi-circuit arc dynamo. 
 
 Multi-Coil Alternating-Current Ar- 
 mature-Winding. An alternator arma- 
 ture-winding containing on its surface 
 more than one coil or group of conduc- 
 tors per pole of the field frame, as distin- 
 guished from a uni-coil winding. 
 
 Multi-Conductor Cable. A cable pro- 
 vided with a plurality of conducting 
 circuits. 
 
Mul.] 
 
 
 857 
 
 [Mul.. 
 
 Multi-Duct Conduit. A conduit con- 
 taining a plurality of ducts. 
 
 Multi-Periodic Current. (1) A current 
 composed of a number of associated com- 
 ponent currents of different frequencies. 
 (2) A complex-harmonic current. 
 
 Multiphase. Containing more than a 
 single phase. 
 
 Multiphase Alternating- Currents . A 
 number of separate alternating currents 
 which differ in phase by a fixed amount. 
 
 Multiphase Alternator. An alternator 
 capable of producing multiphase cur- 
 rents. 
 
 Multiphase Apparatus. A general term 
 for multiphase alternators, motors, or 
 other receptive apparatus, suitable for 
 use on multiphase circuits. 
 
 Multiphase Circuits. The circuits em- 
 ployed in a system of multiphase distri- 
 bution. 
 
 Multiphase Dynamo. A multiphase 
 alternator. 
 
 Multiphase Generator. A multiphase 
 alternator. 
 
 Multiphase Induction-Motor. An in- 
 duction motor suitable for use in con- 
 nection with multiphase currents, and 
 operated by rotating magnetic fields. 
 
 Multiphase Synchronous-Motor. A 
 synchronous alternating-current motor 
 supplied with multiphase currents as dis- 
 tinguished from an asynchronous or in- 
 duction multiphase motor. 
 
 Multiphase System. A system for the 
 distribution of energy by multiphase cur- 
 rents. 
 
 Multiphaser. A multiphase alternator. 
 
 Multiple-Arc Circuit. A term often 
 used for multiple circuit. 
 
 Multiple- Arc-Connected Electro-Re- 
 ceptive Devices. Electro-receptive de- 
 vices connected with the driving circuit 
 in multiple arc. 
 
 Multiple- Arc-Connected Sources. A 
 battery of multiple-connected sources. 
 
 Multiple-Arc-Connected Translating 
 Devices. Multiple-arc connected elec- 
 tro-receptive devices. 
 
 Multiple- Arc Resistance Box. A re- 
 sistance box whose resistances are capable 
 of being inter-connected in multiple arc. 
 
 Multiple Armature-Windings. (1) A 
 term sometimes used for multiple-circuit 
 armature-windings. (2) A term some- 
 times used for multiple-wound armature 
 windings. 
 
 Multiple Cable. A cable containing 
 
 12 
 
 more than a single conducting wire or 
 circuit. 
 
 Multiple Cable-Core. A cable contain- 
 ing more than a single conducting wire 
 or core. 
 
 Multiple Call-Box. A call-box capable 
 of automatically transmitting a number 
 of different calls. 
 
 Multiple Circuit. A circuit in which a 
 number of separate sources or separate 
 receptive devices, or both, have all their 
 positive poles connected to a single posi- 
 tive lead or conductor, and all their neg- 
 ative poles connected to a single negative 
 lead or conductor. 
 
 Multiple - Circuit Multiple - Wound 
 Armature. An armature providing a 
 plurality of circuits between the brushes, 
 and also a plurality of independent wind- 
 ings connected to symmetrically inter- 
 spersed independent commutator bars. 
 
 Multiple Circuit Winding of Arma- 
 ture. Such a winding as provides a mult- 
 iplicity of circuits in parallel through an, 
 armature. 
 
 Multiple Conduit. A conduit provided 
 with a number of separate ducts. 
 
 Multiple - Connected. Connected in 
 multiple-arc. 
 
 Multiple-Connected Battery. A bat- 
 tery whose separate cells are connected 
 in multiple-arc. 
 
 Multiple - Connected Electro - Recep- 
 tive Devices. Multiple-arc-connected 
 translating devices. 
 
 Multiple- Arc-Connected Sources. A 
 number of separate sources connected in 
 multiple-arc, so as to act as a single 
 source. 
 
 Multiple Connection. Connection in 
 parallel or in multiple-arc. 
 
 Multiple-Contact Carbon Telephone 
 Transmitter. (1) A telephone trans- 
 mitter provided with a number of sep- 
 arate contacts. (2) A dust telephone- 
 transmitter. 
 
 Multiple Converter. A multiple trans- 
 former. 
 
 Multiple Electric Gas-Lighting. A 
 system of electric gas-lighting in which 
 a number of gas jets are ignited by high 
 electromotive force discharges obtained 
 from a Ruhmkorff coil or static induction 
 machine. 
 
 Multiple Electrode Telephone. A 
 telepnone transmitter possessing a plural- 
 ity of active contacts. 
 
 Multiple Electrolysis. Electrolysis pro- 
 Vol. 2 
 
Mul.] 
 
 858 
 
 [Mul. 
 
 ducing or accompanied by secondary 
 chemical reactions. 
 
 Multiple - Harmonic Telegraph. A 
 general term embracing the apparatus 
 employed in multiple-harmonic teleg- 
 raphy. 
 
 Multiple - Harmonic Telegraphy. A 
 
 system for the simultaneous transmission 
 of a number of separate and distinct mus- 
 ical notes over a single wire, which 
 separate notes are utilized for the simul- 
 taneous transmission of an equal number 
 of independent telegraphic messages. 
 
 Multiple Jacks. The reduplicating jacks 
 of a multiple telephone switchboard. 
 
 Multiple Lightning Flash. Several 
 lightning flashes apparently coming from 
 the same cloud, 
 
 Multiple-Pair Brush-Rocker. A term 
 sometimes used for multiple-pair brush- 
 yoke. 
 
 Multiple-Pair Brush-Yoke. A device 
 for holding a number of pairs of brushes 
 on the commutator; so that they can all be 
 simultaneously moved oj- rotated thereon. 
 
 Multiple-Parallel Circuit. A term 
 sometimes employed for a multiple of 
 parallel circuits. 
 
 Multiple Quadruples. A system of re- 
 peating from more than one quadruplex 
 circuit to a brancli office, or repeating 
 from one quadruplex circuit to another. 
 
 Multiple Resonance. The partial re- 
 sonance of a primary conductor devoid of 
 a definite period of oscillation, and, there- 
 fore, capable of performing all possible 
 oscillations lying within wide limits. 
 
 Multiple Rheostat. A form of rheostat 
 whose resistances are capable of being 
 thrown into a circuit in multiple, so that 
 the carrying capacity increases as the re- 
 sistance is decreased. 
 
 Multiple Running. The operation of 
 generators in parallel. 
 
 Multiple-Series. A multiple connection 
 of series groups. 
 
 Multiple-Series Circuit. A circuit in 
 which a number of separate sources, or 
 receptive devices, or both, are connected 
 in a number of separate groups in series, 
 and these separate groups subsequently 
 connected in multiple. 
 
 Multiple-Series Condenser. (1) An ar- 
 rangement of groups of condensers in 
 series, which groups are connected in 
 multiple. (2) A condenser divided into 
 parts capable of being connected either 
 in multiple, or in series, or in both. 
 
 Multiple-Series-Connected Receptive 
 or Translating Devices. A number of 
 
 receptive or translating devices connected 
 in multiple-series. 
 
 Multiple-Series-Connected Sources. 
 A number of separate electric sources so 
 connected in multiple-series, as to be 
 capable of acting as a single source. 
 
 Multiple-Series Connection. Connec- 
 tion in multiple-series. 
 
 Multiple Switch. A switch provided 
 with a number of separate contact plates 
 for controlling a plurality of circuits. 
 
 Multiple Switchboard. A switchboard 
 to which the numerous circuits employed 
 in systems of telegraphy, telephony, an- 
 nunciators, or electric light and power 
 circuits, are connected. 
 
 M u 1 1 i p 1 e-Tablet Switchboard. A 
 switchboard provided with a number of 
 separate tablets or panels. 
 
 Multiple Telegraphic - Repeater. A 
 
 telegraphic repeater which repeats from 
 one circuit to two or more Morse circuits. 
 Multiple Telegraphy. A system for the 
 simultaneous telegraphic transmission 
 over the same wire of more than a single 
 message in the same direction. 
 
 Multiple Telephone Receiver. (1) A 
 telephone receiver in a multiple tele- 
 phone circuit. (2) A composite tele- 
 phone receiver. 
 
 Multiple Telephone Switchboard. A 
 switchboard consisting in reality of a 
 number of separate switchboards, each 
 provided with separate operators and 
 bearing transmitter keys, switches and 
 generators, employed when the number 
 of subscribers connected with the switch- 
 board exceed a number such as can be 
 handled by a single switchboard. 
 
 Multiple Telephony. The simultaneous 
 transmission over the same wire of a num- 
 ber of separate telephonic despatches, in 
 the same direction. 
 
 Multiple Transformer. (1) Any form of 
 transformer the coils or circuits of which 
 are connected in multiple. (2) The or- 
 dinary alternating-current transformer 
 connected across a supply circuit, as dis- 
 tinguished from a series transformer. 
 
 Multiple Transmission. The simulta- 
 neous sending of two or more messages 
 over a single conductor in the same direc- 
 tion. 
 
 Multiple Unit System of Railway 
 Traction. A system of electric railways 
 in which each traction unit is provided 
 with its own independent motors, in such 
 a manner that all the units may be oper- 
 ated collectively from a single point. 
 
Mul.] 
 
 859 
 
 [Mus. 
 
 Multiple Valued Function. A func- 
 tion which has more than one value for a 
 single value of its variable. 
 
 Multiple Wheel Printing Telegraph. 
 A printing telegraph instrument pro- 
 vided with a plurality of printing wheels. 
 
 Multiple Windings. Independent wind- 
 ings symmetrically disposed upon the 
 same armature, insulated from each other, 
 but brought to different segments of the 
 commutator. 
 
 Multiple-Wound Multiple-Circuit 
 Armature. A multipolar armature 
 having a plurality of windings, and each 
 
 winding having a plurality of circuits 
 between the brushes. 
 
 Multiple- Wound Two-Oircuit Arma- 
 ture-Windings. A multipolar arma- 
 ture having a plurality of windings, each 
 winding having two circuits between the 
 brushes. 
 
 Multiple Working of Dynamo-Elec- 
 tric Machines. A term sometimes used 
 for parallel working of dynamo electric 
 machines. 
 
 Multiples. The jacks in the various sec- 
 tions of a multiple-telephone switchboard, 
 which are connected to the same line or 
 subscriber. 
 
 Multiplex Telegraph. A general term 
 embracing the apparatus employed in 
 multiplex telegraphy. 
 
 Multiplex Telegraphy. (1) A system of 
 telegraphy for the simultaneous transmis- 
 sion in opposite directions of more than 
 two separate messages over a single wire 
 from each end. (2) A term sometimes used 
 for multiple telephony or simultaneous 
 transmission of more than one message 
 in the same direction over a single wire. 
 
 Multiplex Telephony. A system of tele- 
 phony for the simultaneous transmission 
 in opposite directions of more than two 
 separate messages over a single wire from 
 each end. 
 
 Multiplex Working. Multiplex trans- 
 mission. 
 
 Multiplicatpr. A term sometimes used 
 for multiplier. 
 
 Multiply. In a multiple telephone switch- 
 board to reduplicate or to repeat at each 
 section of the switchboard. 
 
 Multiply Re-Entrant Armature- Wind- 
 ing. An armature-winding provided 
 with a plurality of separate conducting 
 paths or windings, each of which is in- 
 dependently re-entrant. 
 
 Multiplying Power of Shunt. A quan- 
 tity by which the current flowing through 
 
 a galvanometer or other device provided 
 with a shunt, must be multiplied, in order 
 to give the total current. 
 Multi-Point Secondary. A secondary 
 coil arranged so that it can be readilj 
 tapped at different points. 
 
 Multipolar Armature. An armature 
 suitaole for use in a multipolar field. 
 
 Multipolar - Drum Armature - Wind- 
 ings. Windings of a drum armature 
 suitable for a multipolar field ; i. e. pro- 
 ducing more than two poles on the arma- 
 ture surface. 
 
 Multipolar Dynamo. A dynamo pro- 
 vided with a multipolar field. 
 
 Multipolar Electric Bath. An electro- 
 therapeutic bath in which more than two 
 electrodes are employed. 
 
 Multipolar Field. A field produced by 
 more than two separate magnet poles. 
 
 Multipolar Generator. A multipolar 
 dynamo. 
 
 Multipolar Motor. A motor whose field- 
 magnets contain more than two separate 
 magnet poles. 
 
 Multipolar Railway - Generator. A 
 generator having a multipolar field, em- 
 ployed for furnishing current to trolley 
 cars. 
 
 Multipolar-Ring Armature- Winding. 
 The winding of a ring armature adapted 
 to a multipolar field. 
 
 Multipolar Winding. A winding suit- 
 able for use in multipolar generators or 
 motors. 
 
 Multi-Slot Armature - Winding. A 
 multi-coil armature winding. 
 
 Multi-Slot Alternating-Current Iron- 
 Clad- Armature. An iron-clad arma- 
 ture having more than one slot per field 
 pole and furnishing alternating currents. 
 
 Municipal Series Circuit. A series cir- 
 cuit employed for the distribution of in- 
 candescent lights and suitable for lighting 
 streets. 
 
 Municipal System of Incandescent 
 Electric Lighting. A system for the 
 distribution of incandescent electric 
 lights, in which the separate lamps are 
 connected to the circuit in series, each 
 lamp being provided with a film or other 
 automatic cut-out. 
 
 Muscle Currents. In electro-therapeu- 
 tics the electric currents flowing through 
 a muscle during its stimulation or ac- 
 tivity. 
 
 Muscular Pile. Matteucci's muscular 
 pile. 
 
Jttus.] 
 
 860 
 
 [Nat. 
 
 Mushroom Anchor. An anchor resem- 
 bling a mushroom in form and used for 
 mooring buoys in submarine cable-work, 
 so as to resist dragging along the sea-bot- 
 tom and yet avoid becoming tightly en- 
 gaged in rocks. 
 
 Mushroom Deposit on Negative Car- 
 bon. A flat deposit of graphitic carbon 
 of a mushroom shape, that forms on the 
 negative carbon of an enclosed arc-lamp. 
 
 Musket, Electric. A gun whose charge 
 is ignited by a platinum wire rendered 
 incandescent by the action of a battery 
 placed in the stock of the gun. 
 
 Mutual Flux of Transformer. The 
 
 magnetic flux which passes through both 
 coils in a transformer as distinguished 
 from magnetic flux which may traverse 
 one coil, when excited to the exclusion of 
 the other. 
 
 Mutual Inductance. (1) The coefficient 
 of mutual induction between two con- 
 ductors. (2) The flux linkages in one 
 circuit due to unit current in the other. 
 
 Mutual Induction. (1) Induction pro- 
 duced on each other by two neighboring 
 circuits through the mutual inter-con- 
 nection of their magnetic fluxes. (2) In- 
 duction produced in neighboring 
 charged conductors by the inter-connec- 
 tion of their electrostatic fluxes. 
 
 Myograph. An instrument for measur- 
 ing nervous sensibility. 
 
 Myopia. Near-sightedness. 
 
 Myopic. Of or pertaining to near-sighted- 
 ness. 
 
 Myria. A prefix for ten thousand times. 
 
 N 
 
 N. A symbol for the whole number of lines 
 of magnetic flux or induction in any mag- 
 netic circuit- 
 
 N. In submarine telegraphy, a code signal 
 at the end of a message to indicate that 
 there are no more messages to follow. 
 
 N. A contraction for north-seeking mag- 
 netic pole. 
 
 n. (1) A symbol employed for frequency. 
 (2) A contraction for a number. 
 
 N. H. P. A contraction for nominal horse- 
 power. 
 
 Name Plate. A plate fastened to a 
 dynamo-electric machine and bearing the 
 name of the maker and other particulars 
 such as the speed, power, weight, pres- 
 sure, and current of the machine. 
 
 Narrow-Gauge Street-Railway Mo- 
 tor. A street-railway car motor of less 
 breadth than usual, suitable for use on 
 narrow-gauge tracks. 
 
 Nasal Electrode. An electrode suitable 
 for introduction into the nostril for its 
 therapeutic treatment. 
 
 Nascent State. A term used in chemistry 
 to express the state or condition of an 
 elementary atom or radical when just 
 liberated from chemical combination, 
 when it possesses chemical affinities or 
 attractions more energetic than after- 
 wards. 
 
 Natural Current from Fault in Cable. 
 The feeble current originating from the 
 voltaic couple formed at a break or fault 
 in a cable. 
 
 Natural Currents. A term sometimes 
 applied to earth currents. 
 
 Natural-Draught Transformer. (1) An 
 alternating-current transformer in which 
 an air-space is left between the primary 
 and secondary coils, through which a con- 
 vection current of air passes on the heat- 
 ing of the coils. (2) A transformer cooled 
 by radiation and convection, as distin- 
 guished fi'om an air-transformer. 
 
 Natural Electret. A body whose mole- 
 cules are inherently electrized, as distin- 
 guished from a body whose molecules be- 
 come electrized by induction. 
 
 Natural Law. (1) A law of nature. 
 (2) An observed co-relation of phenomena 
 such that when one phenomenon or group 
 of phenomena occurs in a certain definite 
 way, another phenomenon or group of 
 phenomena invariably follows. 
 
 Natural Magnet. The name sometimes 
 given to a lodestone. 
 
 Natural Period. (1) The time in which 
 a cyclic phenomenon naturally completes 
 itself. (2) The time of complete free os- 
 cillation of a vibrating substance or con- 
 dition, when not subjected to external 
 restraint. 
 
 Natural Resultant Fault. In any cir- 
 cuit, a fault which is the electrical equiv- 
 alent in position and magnitude of all the 
 actual small faults or leakages which may 
 be present in that circuit. 
 
 Natural Unit of Electricity. (1) A 
 term sometimes used in place of an atomic 
 
Nat.] 
 
 
 861 
 
 [Neg. 
 
 charge of electricity. (2) The quantity of 
 electricity carried by a single monad atom 
 of any elementary substance. 
 
 Natural Unit of Quantity of Electric- 
 ity. The quantity of electricity pos- 
 sessed as a charge by any elementary 
 monad atom. 
 
 Naut. A nautical mile. 
 
 Nautical Mile. (1) A knot or naut, or a 
 distance of 6,087 feet ; or nearly 1.15 stat- 
 ute miles. (2) The ^iJ^th of the earth's 
 equatorial circumference, or / ff th of a de- 
 gree of longitude at the equator. 
 
 Nautical Telegraphy. Telegraphy con- 
 ducted at sea or over the sea, either be- 
 tween different vessels or on board a 
 single vessel, 
 
 Near-Sightedness. (1) Inability to see 
 objects distinctly unless they are com- 
 paratively near the eye. (2) Myopia. 
 
 Nebula. A misty appearance in the 
 heavens often resolved by a telescope in- 
 to clusters of innumerable stars. 
 
 Needle. A word frequently used for a 
 magnetic needle. 
 
 Needle Annunciator. An annunciator 
 whose indications are obtained by the 
 movements of a needle, instead of by the 
 fall of a drop. 
 
 Needle Electrode. A needle-shaped 
 therapeutic-electrode employed for elec- 
 trolytic treatment. 
 
 Needle Instrument. A single-needle 
 instrument. 
 
 Needle of Oscillation. A small mag- 
 netic needle employed for measuring the 
 intensity of a magnetic field by the num- 
 ber of oscillations it makes in a given 
 time when disturbed from its position of 
 rest in such field. 
 
 Needle System of Telegraphy. A sys- 
 tem of telegraphy in which the letters of 
 the alphabet and numerals are indicated 
 by the to-and-fro movements of a mag- 
 netic needle. 
 
 Needle Telegraph. A general term em- 
 bracing the apparatus employed in needle 
 telegraphy. 
 
 Needle Telegraphy. The needle system 
 of telegraphy. 
 
 Negative Brush of Dynamo. The brush 
 connected with the negative terminal of 
 a dynamo. 
 
 Negative Brush of Motor. The brush 
 connected with the negative terminal of 
 the driving source. 
 
 Negative Bus-Bars. The negative om- 
 nibus bars. 
 
 Negative Charge. (1) According to the 
 double-fluid hypothesis, a charge of nega- 
 tive electricity. (2) According to the 
 single-fluid hypothesis, any deficit of an 
 assumed electric fluid. (3) An electric 
 charge of the same character as that pro- 
 duced on silk when rubbed by glass. 
 
 Negative Conductor. The conductor 
 connected to the negative terminal of an 
 electric source. 
 
 Negative Currents. In telegraphy, a 
 term applied to the currents sent over a 
 line from the negative pole of the battery. 
 
 Negative Direction of Electrical Con- 
 vection of Heat. A direction in which 
 heat is transmitted by electric convection, 
 through an unequally heated conductor 
 opposite to that of an electric current. 
 
 Negative Direction of Simple-Har- 
 monic Motion. Simple-harmonic mo- 
 tion in which the generating circle is 
 moved over in the negative direction. 
 
 Negative Electricity. (1) One of the 
 phases of electric excitement. (2) The 
 kind of electric charge produced on resin 
 when rubbed with cotton. 
 
 Negative Electromotive Force. Such 
 an E. M. F. as is produced at the free pole 
 of a battery or other source whose posi- 
 tive pole is grounded. 
 
 Negative Electrification. (1) The 
 charging of a body with negative electric- 
 ity. (2) A negative charge. 
 
 Negative Electrode. The electrode con- 
 nected with the negative terminal of a 
 source. 
 
 Negative Element of Electrolyte. 
 
 (1) The element which in electrolysis ap- 
 pears at the positive electrode. (2) The 
 cathion. 
 
 Negative Element of Voltaic Cell. 
 
 (1) That element of a voltaic couple 
 which is,not acted on by the electrolyte. 
 
 (2) The element which forms the positive 
 pole of the cell above the surface of the 
 electrolyte. 
 
 Negative Feeders. The feeders con- 
 necting the negative mains with the 
 negative poles of the generators. 
 
 Negative Fluid. (1) A specific fluid 
 which was formerly believed by the ad- 
 vocates of the double-fluid electric 
 hypothesis to be the cause of negative 
 excitement. (2) A deficit of an assumed 
 single electric fluid. 
 
 Negative Inductance. A capacitance. 
 
 Negative Lightning. A name given to 
 a variety of lightning discharge whose 
 existence is apparent in some photo- 
 
862 
 
 [Neiu 
 
 graphic negatives of lightning flashes, 
 as black branches coming out from the 
 main-lightning stem. 
 
 Negative Omnibus-Bar. The bus-bar 
 connected to the negative terminals of 
 the generators. 
 
 Negative Phase of Electrotonus. A 
 decrease in the electromotive force of a 
 nerve, produced by sending an electric 
 current through the nerve in the opposite 
 direction to the nerve current. 
 
 Negative Plate of Storage Cell. (1) 
 That plate of a storage cell which is con- 
 verted into or partly covered with a coat- 
 ing of spongy lead by the action of the 
 current. (2) That plate of a storage cell 
 which is connected with the negative 
 terminal of the charging source, and 
 which is, therefore, the negative pole of 
 the cell on discharging. 
 
 Negative Plate of Voltaic Cell. (1) 
 The electro-negative element of a voltaic 
 couple. (2) That element of a voltaic 
 couple which is negative in the electro- 
 lyte of the cell. (3) That portion of the 
 pla,te of a voltaic cell above the liquid, 
 which becomes the positive pole of the 
 cell. 
 
 Negative Pole of Receptive Device. 
 That pole of a receptive device which is 
 connected to the negative pole of a 
 source. 
 
 Negative Pole of Source. That pole of 
 an electric source through which the 
 current is assumed to enter, or flow back 
 into the source, after having passed 
 through the circuit connected to the 
 source. 
 
 Negative Potential. (1) A potential such 
 as determines a tendency of electricity to 
 flow towards it from the earth or from 
 any point of positive potential. (2) Gen- 
 erally, the lower potential or lower level. 
 (3) That property of a point in space by 
 virtue of which electric work is done by 
 the movement of a small positive charge 
 to that point from an infinite distance. 
 
 Negative Rays. The molecular streams 
 given off at the negative electrode or 
 cathode of an induction tube, on the pas- 
 sage of electric discharges through the 
 tube. 
 
 Negative Resistance. A property of a 
 circuit or conductor containing an E. M. 
 F. , whereby a current flowing through the 
 conductor rises in pressure instead of 
 falling. 
 
 Negative Rotation. Right-handed or 
 clockwise rotation, as viewed from in 
 ront of the clock. 
 
 Negative Side of Circuit. (1) The side 
 of a circuit opposite to the positive sides. 
 (2) That side of a circuit bent in the form 
 of a circle, from which, if an observer 
 stood with his head in the negative region, 
 he would see the current pass around him 
 clockwise, or right-handedly. (3) The 
 side of a circuit connected with the 
 negative pole of the source. 
 
 Negative Spark. The spark produced 
 by the discharge of a negatively charged 
 conductor. 
 
 Negative Terminal. (1) The terminal 
 of a voltaic cell connected with the posi- 
 tive plate or element. (2) The terminal 
 of a source connected with the negative 
 pole. (3) The terminal of a translating 
 device connected with the negative pole 
 of the source. 
 
 Negative Wire. (1) A wire charged, or 
 intended to be charged, negatively. (2) 
 A wire connected with the negative pole 
 of a source. (3) A wire of negative 
 potential. 
 
 Negatively Excited. Endowed with a 
 negative charge. 
 
 Net Efficiency. The final or ultimate 
 efficiency of a series of machines or 
 translating devices, through which en- 
 ergy, or any other quantity, has to suc- 
 cessively pass, as distinguished from the 
 separate efficiency of each machine or 
 device. 
 
 Netted Globe. A globe surrounding an 
 arc-lamp and provided with an external 
 netting. 
 
 Netting Wire. A wire net-work-shield 
 inclosing the globe of an arc-lamp, both 
 to protect it from mechanical injury and 
 to prevent glass from falling in case of 
 fracture. 
 
 Network of Conductors. A term ap- 
 plied to a number of interconnected con- 
 ductors which may resemble a net in ap- 
 pearance. 
 
 Network of Currents. A term some- 
 times applied to a number of shunts or 
 derived circuits, or to the currents which 
 flow in a network of conductors. 
 
 Neutral Armature. A non-polarized 
 armature. 
 
 Neutral Ampere-Meter. An ampere- 
 meter connected with the neutral bus-bar 
 in a three- wire system of distribution. 
 
 Neutral Conductor. The neutral wire 
 in a three- wire system. 
 
 Neutral Feeder. In a three-wire system 
 a feeder connected with the neutral bus- 
 bar. 
 
Neu.] 
 
 863 
 
 [Nip. 
 
 Neutral-Line of Magnet. The equator 
 of a magnet. 
 
 Neutral-Line of Commutator Cylin- 
 der. A line on the commutator cylin- 
 der of a dynamo connecting the neutral 
 points or points of zero potential. 
 
 Neutral-Line of Dynamo Armature. 
 
 (1) A line passing through the armature, 
 symmetrically disposed as regards its 
 entering and emerging flux. (2) A line of 
 zero polarity. 
 
 Neutral Omnibus-Bar, or Bus-Bar. 
 In a three- wire system of distribution, 
 the bus-bar connected with the neutral 
 dynamo terminals, or the terminals unit- 
 ing the positive and negative dynamos. 
 
 Neutral Point. A term sometimes em- 
 ployed in electro-therapeutics for indiffer- 
 ent point. 
 
 Neutral Points of Magnet. (1) Points 
 approximately midway between the poles 
 of a magnet. (2) Points of zero polarity. 
 
 Neutral Points of Dynamo-Electric 
 Machine. (1) Two points situated on 
 the commutator cylinder at opposite ends 
 of its diameter at which the collecting 
 brushes must rest in order to obtain 
 sparkless com mutation. (2) Points of zero 
 potential on a commutator. 
 
 Neutral Points of Thermo-Electric 
 Diagram. (1) The points on a thermo- 
 electric diagram where the lines repre- 
 senting the thermo-electric powers of any 
 two metals cross each other. (2) A mean 
 temperature for any two metals in a 
 thermo-electric series, at which, if their 
 two junctions are slightly over or slightly 
 under the mean temperature, the one 
 as much above as the other is below, no 
 effective electromotive force is developed. 
 
 Neutral Relay-Armature. (1) A relay 
 armature consisting of a piece of soft iron 
 which closes a local circuit whenever its 
 electro-magnet receives an impulse over 
 the main line. (2) A normally unmag- 
 netized relay armature. 
 
 Neutral Section of Magnet. A section 
 passing through the neutral line or equa- 
 tor of a magnet. 
 
 Neutral Salt. A salt possessing neither 
 
 acid nor basic properties. 
 Neutral Solution. A solution of neutral 
 
 salt. 
 
 Neutral Wire. (1) In a three-wire system 
 of electric distribution the wire con- 
 nected to the neutral dynamo-terminal. 
 
 (2) The balance wire of a three- wire 
 system. 
 
 Neutral- Wire Ampere-Meter. An am- 
 
 pere meter placed in the circuit of a 
 neutral wire, in a three-wire system, for 
 the purpose of showing the excess of cur- 
 rent passing over one side of the system 
 as compared with the other side, when a 
 balance between the two is no longer 
 maintained. 
 
 Neutral Zone of Charged Insulated 
 Conductor. That portion of an insu- 
 lated conductor, charged by electrostatic 
 induction, which lies approximately mid- 
 way between its positive and negative 
 end. 
 
 Neutral Zone of Magnet. A term some- 
 times employed for equator of magnet. 
 
 Neutralization. The act or quality of 
 rendering neutral, as in the discharge of 
 an electrified body. 
 
 New Ohm. A term sometimes used for 
 the international ohm. 
 
 Nib on Carbon Electrode. A term 
 sometimes employed for the graphitic 
 deposit on one side of the negative carbon, 
 when the arc has been maintained be- 
 tween the sides of two parallel carbon 
 electrodes. 
 
 Nickel Bath. An electrolytic bath con- 
 taining a readily electrolyzable salt of 
 nickel, a plate of nickel acting as the 
 anode of the battery, and placed in a 
 liquid near the object to be coated, which 
 forms the cathode. 
 
 Nickel Facing of Electro-Type. A 
 thin electro-plating of nickel deposited on 
 the surface of an electro-type for the pur- 
 pose of hardening it. 
 
 Nickel Plating. Electro-plating with 
 nickel. 
 
 Niello-Work. An enamelling process in 
 which a pattern is traced upon a bright 
 silver surface with a silver sulphide, or 
 with mixtures of lead, copper and silver 
 sulphide, artificially prepared, and which 
 is afterwards fixed, by heating to the 
 fusion point. 
 
 Nigger. A term sometimes employed for 
 a fault in any electric apparatus or sys- 
 tem. 
 
 Night-Bell. In a hotel or telephone ex- 
 change, a bell switched into connection 
 with a shunted circuit of an annunciator 
 case, and intended, by its constant ring- 
 ing, to call the attention of the night 
 operator to the falling of a drop. 
 
 Night-Switch for Telephone. A switch 
 so arranged that, when turned to the on- 
 position, any or all of the drops will, on 
 falling, ring a bell, and thus call the atten- 
 tion of the operator. 
 
 Nipple of Negative Carbon. A tiny 
 
No.] 
 
 864 
 
 [Noil. 
 
 projection of graphitic carbon, deposited 
 during the maintenance of the arc, on 
 the surface of the negative carbon oppo- 
 site the crater of the positive carbon. 
 
 No. 1 Side of Quadruples System. 
 That side of the quadruplex system which 
 is employed in operating the polar duplex 
 system. , 
 
 No. 2 Side of Quadruplex System. 
 That side of a quadruplex system which 
 contains the increment key and neutral 
 relay. 
 
 Nobili's Rings. Metallo-chromes. 
 
 Nodal Point. A point in a vibrating 
 string or wire free from vibration. 
 
 Node. A nodal point. 
 
 Nodes, Electric. (1) Points in a circuit 
 or conductor through which electric 
 oscillations are passing, which possess 
 a constant value of potential, while the 
 potential at the internode alternates be- 
 tween two fixed limits. (2) Points in a 
 conductor where the strength of the in- 
 duced oscillatory current is equal to zero. 
 
 Ifodular Electro - Metallurgical De- 
 posit. A coherent electro-metallurgical 
 deposit, of irregular outline, which occurs 
 whenever the current density falls below 
 its normal value. 
 
 Noise. (1) Any discordant assemblage of 
 musical tones. (2) Any sound of too short 
 duration to permit its pitch to be readily 
 distinguished. 
 
 Noisy Arc. A voltaic arc whose mainte- 
 nance is attended by frying, hissing or 
 spluttering sounds. 
 
 Nominal Candle-Power. A term some- 
 times applied to the candle-power of a 
 luminous source taken in a favorable 
 direction. 
 
 Non-Arcing Arrester. A non-arcing 
 lightning arrester. 
 
 Non-Arcing Fuse. A fuse wire formed 
 of non-arcing metal, which, therefore, 
 blows without the formation of a voltaic 
 arc. 
 
 Non-Arcing Metal. An alloy formed of 
 mixtures of a certain group of metals, 
 which, under certain conditions, will not 
 permit the maintenance of an alternating- 
 current ai'c between them. 
 
 Non-Arcing-Metal Lightning- Arrest- 
 er. A lightning arrester employing 
 electrodes of non-arcing metals. 
 
 Non- Arcing Metals. Metals forming 
 non-conducting oxides such that an 
 alternating-current arc is interrupted 
 between them under certain conditions. 
 
 Non-Automatic Repeater. A manual 
 repeater. 
 
 Non-Automatic Variable Resistance. 
 A resistance, the value of which is regu- 
 lated by hand. 
 
 Non-Conductor. Any substance whose 
 conductivity is low, or whose electric re- 
 sistance is great. 
 
 Non-Coperiodic. (1) Non-synchronous. 
 (2) Devoid of coperiodicity. (3) Not 
 isochronous. (4) Having a period differ- 
 ing from the period considered. 
 
 Non-Coperiodic Electromotive Forces, 
 Currents and Fluxes. Electromotive 
 forces, currents, or fluxes that are of dif- 
 ferent periods or frequencies. 
 
 Non-Electrics. A term formerly applied 
 to substances like the metals or other 
 good conductors, which appeared not to 
 be capable of electrification by friction. 
 
 Non-Ferric. Devoid of iron. 
 
 Non-Ferric Inductance. (1) The in- 
 ductance possessed by a circuit which 
 does not contain, or is not magnetically 
 associated with, iron. (2) The inductance 
 of a coil with a non-magnetic core. 
 
 Non-Ferric Inductance-Coil. An in- 
 ductance coil devoid of iron. 
 
 Non-Ferric Magnetic Circuit. (1) A 
 magnetic circuit devoid of iron. (2) A mag- 
 netic circuit containing only air, wood, 
 copper or other non-magnetic materials. 
 
 Non-Homogeneous Current-Distribu- 
 tion. (1) A distribution of current pass- 
 .ing through a conductor, in which there 
 is an unequal density of current over any 
 cross section of the conductor. (2) The 
 skin effect. 
 
 Non-Illumined Electrode. That elec- 
 trode of a selenium cell which is pro- 
 tected from the direct action of light. 
 
 Non-inductive Load. (1) An induction- 
 less load. (2) A load consisting of re- 
 sistance. 
 
 Non-Interfering Fire Telegraph. A 
 system of fire-alarm telegraphy in which 
 two calls, simultaneously delivered, are 
 incapable of interfering with each other. 
 
 Non-Interfering Street Signal Box. 
 A street signal box connected with a cen- 
 tral station for the delivery of an alarm, 
 in such a manner that two signals given 
 at the same time from two different boxes 
 will not interfere with each other. 
 
 Non-inductive Resistance. A resist- 
 ance devoid of self-induction. 
 
 Non-Isotropic Expansion. A property 
 possessed by some crystalline substance of 
 unequal expansion along different axes. 
 
Non.] 
 
 865 
 
 [Nos. 
 
 Non-Luminous Radiation. Radiation 
 incapable of affecting the eye. 
 
 Non-Luminous Heat Radiation. (1) 
 Heat radiation devoid of frequencies ca- 
 pable of exciting or producing the sensa- 
 tion of light. (2) Heat radiation devoid 
 of luminous frequencies. 
 
 Non-Magnetic Steel. Certain alloys of 
 iron, such as manganese steel, or nickel 
 steel, that are practically devoid of the 
 ability of being magnetized. 
 
 Non-Multiple Telephone Switch- 
 board. (1) A telephone switchboard 
 which is either not so large as to have 
 rendered reduplication necessary, or 
 which operates upon a system in which 
 reduplication is dispensed with. (2) A 
 single telephone-switchboard. 
 
 Non-Oscillatory. (1) Not characterized 
 by oscillations. (2) Maintaining the same 
 direction of motion throughout. 
 
 Non-Oscillatory Charge. A charge ob- 
 tained by means of non-oscillatory electro- 
 motive forces or currents. 
 
 Non-Oscillatory Charging. Charging 
 uniformly by currents which are always 
 of the same direction, as opposed to charg- 
 ing with oscillations in which the currents 
 alternate. 
 
 Non-Oscillatory Current. (1) A cur- 
 rent that is devoid of periodic oscillation. 
 (2) A uniform current. 
 
 Non-Oscillatory Discharge. A steady 
 discharge, or one characterized by free- 
 dom from periodic oscillation. 
 
 Non-Oscillatory Intermittent - Cur- 
 rent. A current which is intermittent, 
 but always in the same direction, as dis- 
 tinguished from an oscillatory current 
 whose direction alternates. 
 
 Non- Overlapping Winding of Alter- 
 nator. A winding in which the coils 
 are mechanically separate and do not 
 overlap. 
 
 Non-Periodic Alternating-Current. 
 An alternating current whose intensity 
 varies non-periodically. 
 
 Non-Periodically Varying - Current. 
 A continuous current whose strength is 
 subject to non-periodical oscillations. 
 
 Non-Polar Transformer. A term some- 
 times used for a closed iron-circuit trans- 
 former. 
 
 Non-Polarizable. Incapable of polariza- 
 tion. 
 
 Non-Polarizable Electrodes. Electro- 
 therapeutic electrodes constructed so as 
 to avoid the effects of polarization. 
 
 Non-Polarized Armature. An arma- 
 55 
 
 ture of soft iron which is attracted to- 
 wards the poles of an electro-magnet on 
 the completion of the circuit, no matter 
 in what direction the current passes 
 through the coils. 
 
 Non-Reactive Circuit. A circuit which 
 possesses neither inductance nor capacity, 
 and, therefore, has ohmic resistance only. 
 
 Non-Sinusoidal Currents. Alternating 
 currents that are not of the true sinusoi- 
 dal type. 
 
 Non-Synchronous Motor. (1) An asyn- 
 chronous motor. (2) An alternating-cur- 
 rent motor capable of starting at any 
 load. (3) An induction motor. (4) An 
 alternating-current motor which is not 
 compelled to run in synchronism with its 
 driving current. 
 
 Non-Uniform Magnetic Flux. Mag- 
 netic flux whose density varies in differ- 
 ent portions of the magnetic circuit. 
 
 Non-Vibrating Filament Lamp. An 
 incandescent lamp with an anchored fila- 
 ment. 
 
 Normal. (1) Perpendicular to. (2) In 
 accordance with rule. (3) Regular. 
 
 Normal Current. The current strength 
 at which a system or apparatus is de- 
 signed to be operated. 
 
 Normal Earth-Current. The usual earth 
 current. 
 
 Normal Magnetic-Day. A day during 
 which the values of the earth's magnetic 
 elements do not vary greatly from their 
 mean value. 
 
 Normal Voltage. The voltage at which 
 a system or apparatus is designed to be 
 operated. 
 
 Normal Voltaic-Arc. A voltaic arc 
 whose characteristic properties are those 
 possessed by the ordinary arc. 
 
 North Magnetic Pole. That pole of a 
 magnetic needle which points approxi- 
 mately to the earth's geographical north. 
 
 North-Seeking Magnetic Pole. (1) The 
 north magnetic pole. (2) That pole of a 
 magnet which turns towards and approx- 
 imately points to the north geographical 
 pole of the earth. 
 
 Northern Lights. (1) Luminous sheets, 
 columns, arches or pillars of pale, flash- 
 ing light, generally of a reddish color, 
 seen in the northern heavens. (2) The 
 aurora borealis. 
 
 Nose Suspension of Motor. The sus- 
 pension of a motor in a car truck by a 
 projecting hook or nose from above, as 
 distinguished from a suspension by a bar 
 and spring from beneath. 
 
Nul.] 
 
 866 
 
 [Ohm. 
 
 Null or Zero Method. (1) Any method 
 employed in electrical measurements in 
 which the values are determined by bal- 
 ancing against them equal similar values, 
 and ascertaining such equality not by the 
 deflection of the needle, but by the ab- 
 sence of such deflection. (2) Any method 
 of 'measurement in which the criterion is 
 no indication on the instrument em- 
 ployed, as distinguished from a method 
 
 depending upon the amounts or quantita- 
 tive values of such indications. 
 Null Point. (1) Such a point on a micro- 
 meter circuit that when joined or con- 
 nected with the secondary circuit of an 
 induction coil, the sparks in the micro- 
 meter circuit are either very greatly de- 
 creased, or are entirely absent. (2) A 
 nodal point. . 
 
 o 
 
 O. An abbreviation for ohm, the practical 
 unit of resistance. 
 
 O. K. A telegraphic signal of acquiescence 
 meaning "all right," and said to be a 
 perversion of the initial letters of the 
 phrase " all correct." 
 
 Q. A contraction for megohm. 
 
 u. A contraction for ohm. 
 
 o. A symbol sometimes employed for an- 
 gular velocity. 
 
 O. cm. An abbreviation proposed for 
 ohm-centimetre, a standard of resistivity 
 or conductivity. 
 
 Oblique Induction. In the air gap of a 
 dynamo, magnetic induction which is 
 deflected from the perpendicular to the 
 polar surface by armature reaction. 
 
 Obscure Heat. Non-luminous heat. 
 
 Observation Mine. A variety of sub- 
 marine mine that is fired from a distant 
 point when an enemy's vessel is observed 
 to be within its destructive area. 
 
 Obtuse Angle. Any angle whose value, 
 is greater than 90. 
 
 Occluded-Gas Process. A process for 
 the removal of the residual atmosphere 
 from a vacuum tube, or from the cham- 
 ber of an incandescent electric lamp, 
 consisting in heating the same to a high 
 temperature while connected with the 
 pumps, before sealing off. 
 
 Occlusion of Gas. The absorption or 
 condensation of a gas in the pores or on 
 the surfaces of various substances. 
 
 Ocean Cable. A submarine cable. 
 
 Octo-Polar Dynamo. A multi-polar dy- 
 namo whose field has eight poles. 
 
 Octo-Polar Field. A field produced by 
 the flux of eight separate magnet poles. 
 
 Od. The name given by Reichenbach to 
 the assumed force which he claimed to 
 be the cause of animal magnetism. 
 
 Odd Harmonics. In a complex harmon- 
 ically varying quantity, the harmonics 
 
 whose frequencies are odd multiples of 
 the fundamental frequency. 
 
 Odorscope. An apparatus in which the 
 determination of an odor was attempted 
 by the measurement of the effect its vapor 
 or effluvia produced on a contact resist- 
 ance. 
 
 Odylic. Of or pertaining to the od force. 
 
 Odylic Rays. Rays accompanying the 
 od force, which, according to Reichen- 
 bach, were emitted from magnet poles, 
 and various other bodies, and were capa- 
 ble of producing faint luminous sensa- 
 tions in people sufficiently sensitive to 
 their influence. 
 
 Oersted. (1) The name proposed for the 
 C. G. S. unit of magnetic reluctance. 
 (2) The reluctance offered to the passage 
 of magnetic flux by a cubic centimetre of 
 air when measured between parallel faces. 
 
 Off Position of Switch. (1) That posi- 
 tion of a switch in which it throws a 
 device or a portion of a circuit off from 
 the working circuit. (2) The break posi- 
 tion of a switch. 
 
 Office Cable. (1) A cable of insulated 
 wires suitable for indoor office-work. 
 (2) A cable leading to a telegraph office. 
 
 Office Loop. (1) In telegraphy, a loop, or 
 two wires running to an office. (2) In 
 telegraphy, a loop or pair of wires running 
 from a circuit in an office to some desk in 
 the same office, as distinguished from a 
 loop running to some distant point. 
 
 Offset. A side connection, or lateral, taken 
 from a conduit or cable for connection to 
 a service. 
 
 Ohm. (1) The practical unit of electric 
 resistance. (2) Such a resistance as would 
 limit the flow of electricity under an 
 electromotive force of one volt, to a cur- 
 rent of one ampere, or one-coulomb-per- 
 second. (3) A value equal to 10 9 or 
 1,000,000,000 absolute electro-magnetic 
 units. (4) A value which is represented 
 
Ohm.] 
 
 
 867 
 
 [Ope. 
 
 conventionally in C. G. S. units by a veloc- 
 ity of 10 9 or 1,000,000,000 centimetres per 
 second. 
 
 Ohmage. The value of an electric resist- 
 ance expressed in ohms. 
 
 Ohmic. (1) Of or pertaining to the ohm. 
 (2) Having the nature of an electric re- 
 sistance. 
 
 Ohmic Drop. The drop in pressure due 
 the olimic resistance. 
 
 Ohmic Resistance. (1) The true resist- 
 ance of a conductor due to its dimensions 
 and conductivity, as distinguished from 
 the spurious resistance produced by 
 counter-electromotive force. (2) A re- 
 sistance such as would be measurable in 
 ohms by the usual methods of continuous- 
 current measurement. 
 
 Ohm-Meter. A commercial galvanome- 
 ter employed for practically measuring, 
 by the deflections of a magnetic needle, 
 the resistance of any part of a circuit to 
 which it is connected, and through which 
 a current flows. 
 
 Ohm Mile. (1) A standard of conductivity 
 of wires one mile in length and having a 
 resistance of one ohm at a standard tem- 
 perature. (2) The product of the weight 
 of a mile of wire and its resistance in 
 ohms at a given temperature. (3) Such 
 a mass of a substance, at a standard tem- 
 perature, as would enable a uniform wire 
 of that substance, one mile in length, to 
 offer a resistance of one ohm. 
 
 Ohm's Law. The strength of a continuous 
 electric current in any circuit is directly 
 proportional to the electromotive force 
 acting on that circuit, and inversely pro- 
 portional to the resistance of the circuit. 
 
 Oil-Cooled Transformer. A trans- 
 former that is cooled by means of oil. 
 
 Oil Cup. A cup filled with lubricating 
 oil, so supported that its oil is slowly fed 
 to a shaft and bearing, or in general, to 
 the rubbing parts of a machine. 
 
 Oil Guard. (1) A guard of sheet metal sup- 
 ported so as to catch any drops of oil that 
 may be thrown upon its surface, and thus 
 protect any person or apparatus. (2) A 
 guard placed over a direct-driven dynamo, 
 to prevent oil from being thrown on it 
 by the revolving engine. 
 
 Oil-Insulated. Insulated by means of oil. 
 
 Oil Insulator. A fluid insulator con- 
 taining oil. 
 
 Oil Insulator for Storage Battery. An 
 oil insulator provided for the support of 
 a storage battery. 
 
 Oil Paper. An insulating material con- 
 
 sisting of paper that has been soaked in 
 an insulating oil. 
 
 Oil Transformer. (1) A transformer im- 
 mersed in oil in order to ensure and 
 maintain high insulation. (2) An oil- 
 insulated transformer. 
 
 Okonite. A variety of insulating material. 
 
 Olivette Box. A box containing an arc= 
 lamp provided with an aperture closed by 
 colored glass, and employed for the pur- 
 pose of obtaining a uniform field of color 
 over a large surface, such as a stage scene. 
 
 Omnibus Bars. (1) Heavy bars of cop- 
 per connected directly to the poles of a 
 dynamo in a central station, and, there- 
 fore, receiving their entire current. 
 (2) Main conductors common to two or 
 more dynamos in an electrical generating 
 plant. 
 
 Omnibus Wires. 'A word sometimes 
 used for bus-bars. 
 
 On Position of Switch. (1) That posi- 
 tion of a switch in which it throws a de- 
 vice, or portion 'of a circuit, on to a work- 
 ing circuit. (2) The make position of a 
 switch. 
 
 One-Coil Transformer. A word some- 
 times employed for auto-transformer. 
 
 One-Fluid Voltaic Cell. A name some- 
 times given to a single-fluid voltaic cell. 
 
 One-Layer Armature- Winding. (1) An 
 armature winding consisting of but a 
 single layer of wire. (2) A winding 
 which, although it may consist of several 
 layers, would be possible of application 
 in a single layer, as distinguished from a 
 two-layer armature which must be laid 
 in two layers. 
 
 One-Metal Cell. An identical electrode 
 cell. (2) A cell in which both elements 
 are composed of one metal. 
 
 One- Way Door-Trigger. A door-trigger 
 which operates on the opening of the door 
 only. 
 
 Opacity. Possessing the property of non- 
 transparency to radiation. 
 
 Open-Arc. A non-enclosed voltaic arc. 
 
 Open-Box Conduit. A conduit consist- 
 ing of an open box of wood placed in a 
 trench and closed with a wooden cover, 
 after the introduction of the cable. 
 
 Open Car- Wheel. A form of car-wheel 
 in which the space between the flange 
 and the axle is provided with symmetri- 
 cal perforations. 
 
 Open Circuit. A broken circuit, or a cir- 
 cuit whose conducting continuity is 
 broken. 
 
 Open-Circuit Battery. A voltaic bat- 
 
Ope.] 
 
 868 
 
 [Ope. 
 
 tery which is normally on open circuit, 
 and which is used continuously on closed 
 circuit only for comparatively small por- 
 tions of time. 
 
 Open-Circuit Burglar-Alarm. A bur- 
 glar alarm whose battery is normally on 
 open circuit, and is brought into action 
 on the closing of such circuit as a door, 
 window, or other point. 
 
 Open-Circuit Current of Transformer. 
 A term sometimes employed for the leak- 
 age current of a transformer. 
 
 Open-Circuit Electric Oscillations. 
 Electric oscillations produced in open cir- 
 cuits by the presence of electric surgings 
 in neighboring circuits. 
 
 Open-Circuit Induction. The induction 
 produced in an open circuit by means of 
 electric surgings in. neighboring circuits. 
 
 Open-Circuit of Triphase Connections. 
 The star-connection of triphase circuits. 
 
 Open-Circuit Single-Current Signal- 
 ling. A system of single-current signal- 
 ling in which the sending batteries placed 
 at each station are in circuit during sig- 
 nalling only. 
 
 Open-Circuit Thermostat. A thermo- 
 stat maintained normally on an open-cir- 
 cuit. 
 
 Open-Circuit Transformer. (1) A trans- 
 former whose magnetic circuit is partly 
 completed through air. (2) An aero-fer- 
 ric-circuit transformer. 
 
 Open-Circuit Voltaic Cell. A voltaic 
 cell that cannot be kept on closed circuit 
 with a comparatively small resistance, 
 for any considerable time, without seri- 
 ous polarization. 
 
 Open-Circuit Voltmeter. (1) A volt- 
 meter in which the points of a circuit 
 where the potential difference is to be 
 measured, are connected with an open- 
 circuit to give indications by means of 
 the charges so produced. (2) An electro- 
 meter- voltmeter. 
 
 Open-Circuited. Provided with an open 
 or broken circuit. 
 
 Open-Circuited Conductor. (1) A con- 
 ductor not forming a closed circuit. (2) 
 A conductor not closed on itself, and 
 whose metallic continuity, therefore, is 
 not complete, but through which an 
 oscillatory discharge is capable of passing. 
 
 Open - Circuited Discharge. A dis- 
 charge taking place through a circuit 
 whose metallic continuity is incomplete. 
 
 Open-Circuited Oscillation. An elec- 
 tric oscillation or surging taking place in 
 an open-circuited conductor. 
 
 Open-Circuit Thermostat. A thermo- 
 stat maintained normally on an open-cir- 
 cuit. 
 
 Open - Circuited Transformer. An 
 aero-ferric-circuit transformer. 
 
 Open-Coil Armature. An armature, 
 some of whose coils are on open-circuit 
 during a portion of the rotation of the 
 armature. 
 
 Open-Coil Armature- Windings. The 
 windings of an open-coil dynamo arma- 
 ture. 
 
 Open - Coil Disc Dynamo - Electric 
 Machine. (1) A disc- wound dynamo- 
 electric machine whose armature coils are 
 open-circuited during part of each revo- 
 lution. (2) An open-coil dynamo-elec- 
 tric machine, the armature of which is 
 disc shaped. 
 
 Open - Coil Drum Dynamo - Electric 
 Machine. An open-coil dynamo-electric 
 machine, the armature of which is drum- 
 wound. 
 
 Open-Coil Dynamo. A dynamo pro- 
 vided with an open-coil armature. 
 
 Open - Coil Ring Dynamo - Electric 
 Machine. An open-coil dynamo-electric 
 machine, the armature of which is ring- 
 wound. 
 
 Open - Iron - Circuit Converter. An 
 open-iron-circuit transformer. 
 
 Open-Iron-Circuit Transformer. An 
 aero-ferric transformer. 
 
 Open-Iron-Magnetic Circuit. An aero- 
 ferric magnetic circuit. 
 
 Open Magnetic Core. Any iron core 
 which forms a portion of an aero-ferric 
 circuit. 
 
 Open Trolley-Car. A trolley-car open 
 on the sides and ends. 
 
 Open-Wire Symmetrical Twist. A 
 system of stringing aerial telephone wives, 
 so as to avoid cross talk, in which all the 
 wires on a pole are helically twisted right- 
 handedly along the line, one step being 
 taken at each successive pole. 
 
 Open Wiring. (1) Wiring that has been 
 purposely left exposed to view. (2) Wir- 
 ing supported on cleats or insulators as 
 distinguished from channelled, panelled, 
 or covered wiring. 
 
 Open Work. Open wiring. 
 
 Opening a Circuit. Breaking a circuit. 
 
 Opening Shock. The physiological shock 
 produced on opening or breaking an elec- 
 tric circuit containing self-induction. 
 
 Operator's Head Telephone. A head- 
 gear telephone. 
 
Ope.j 
 
 
 869 
 
 [Osc. 
 
 Operator's Position. The space or posi- 
 tion allotted to each operator in front of 
 a multiple telephone switchboard. 
 
 Operator's Set. A telephone set at a 
 central station employed by the operator. 
 
 Operator's Shelf. A shelf at, on, or 
 above a multiple telephone switchboard 
 for supporting the apparatus used by the 
 operators. 
 
 Ophthalmoscope. An apparatus for ex- 
 amining the living retina. 
 
 Ophthalmoscopic. Of or pertaining to 
 the ophthalmoscope. 
 
 Opposed Electromotive Forces. Elec- 
 tromotive forces that are opposed either 
 to each other or to some other already 
 existing electro-motive force. 
 
 Opposed Magnetomotive Forces. 
 
 Magnetomotive forces that are opposed 
 either to each other, or to some other al- 
 ready existing magnetomotive force. 
 
 Optic Angle. The angle contained be- 
 tween the optical centres of both eyes at 
 any point to which they may be directed. 
 
 Optic Axis. (1) The right line passing 
 through the eye, so that the eye is sym- 
 metrical on all of its sides. (2) The axis 
 of symmetry of a crystal. (3) The prin- 
 cipal axis of the eye, or its axis of figure. 
 
 Optic Nerve. The nerve of vision. 
 
 Optics. That branch of physics which 
 treats of -the properties and phenomena of 
 light. 
 
 Optical Bench. A graduated support em- 
 ployed for varying the distance between 
 fixed and movable optical appliances. 
 
 Optical Efficiency of Light. The ratio 
 between the obscure and the luminous 
 radiation. 
 
 Optical Galvanometer. A galvanometer 
 whose indications are based on the mag- 
 netic rotary power of liquids. 
 
 Optical Strain. A deformation produced 
 in a plate of glass, or other transparent 
 medium, by the action of a stress, attended 
 by a change in some of the optical prop- 
 erties of such medium. 
 
 Optical Telegraph. A name sometimes 
 applied to a semaphore. 
 
 Oral Annunciator. An electric annun- 
 ciator that is operated by a puff of breath 
 transmitted through an ordinary speak- 
 ing tube. 
 
 Ordinary Jacks. In a multiple tele- 
 phone-switchboard, the reduplicated jacks 
 of each subscriber appearing successively 
 in each section, as distinguished from the 
 local or answering jack, which appears 
 at a single panel. 
 
 Ordinary Lines. The lines used for con- 
 versation in a call-wire system of tel- 
 ephony, as distinguished from the wires 
 employed for calling. 
 
 Ordinate. In graphics, a distance taken 
 on a line called the axis of ordinates 
 
 Ordinary Relay. A non-polarized relay. 
 
 Organ, Electric. A wind organ in which 
 the escape of air into the different pipes 
 is electrically controlled, or propelled. 
 
 Orientation of Magnetic Needle. The 
 coming to rest of a magnetic needle in 
 the direction of the earth's magnetic flux. 
 
 Originating Call. The call t>f the sub- 
 scriber who asks to be connected with 
 some other subscriber, as distinguished 
 from any other call which may follow in 
 the process of securing connection. 
 
 Originating Operator. In telephonic 
 communication passing through more 
 than one exchange, the operator who is 
 nearest to the calling subscriber, and con- 
 sequently the operator who first delivered 
 the call, as distinguished from other oper- 
 ators whose assistance may have been 
 called in. 
 
 Oscillating Current. (1) An oscillatory 
 current. (2) A periodically alternating 
 current usually of diminishing ampli- 
 tude. 
 
 Oscillating-Current Transformer. A 
 transformer operated by an oscillating 
 current. 
 
 Oscillating Discharge. An oscillatory 
 discharge. 
 
 Oscillating Needle. A needle of oscilla- 
 tion. 
 
 Oscillation. A to-and-f ro motion or vibra- 
 tion. 
 
 Oscillation of a Function. The differ- 
 ence between the greatest and the least 
 values which a function assumes in a 
 given interval. 
 
 Oscillations, Electric. (1) The series of 
 partial intermittent discharges of which 
 the apparent instantaneous disruptive dis- 
 charge of a Leyden jar, through a small 
 resistance, consists. (2) Free electric 
 vibrations of a disturbed electric system. 
 (3) Electric surgings. 
 
 Oscillator. Any device for producing 
 oscillations. 
 
 Oscillator, Electric. A device for pro- 
 ducing electric currents of a constant 
 period, independently of variations in its 
 driving force. 
 
 Oscillatory. Vibratory, or characterized 
 
 by periodic to-and-fro movements. 
 Oscillatory Charging. Charging by 
 
Osc.] 
 
 870 
 
 [Out. 
 
 means of an oscillatory electromotive 
 force or current. 
 
 Oscillatory Current. A current which 
 oscillates or performs periodic vibrations 
 usually of diminishing amplitude. 
 
 Oscillatory Discharge. (1) An appar- 
 ently instantaneous discharge of a Ley den 
 jar or condenser, which in reality consists 
 of a number of successive discharges. (2) 
 A discharge which periodically decreases 
 by a series of oscillations. 
 
 Oscillatory Dynamo. A dynamo whose 
 armature coils have electromotive forces 
 generated.in them by a vibratory or oscil- 
 latory motion through a magnetic field, 
 instead of the usual rotary motion. 
 
 Oscillatory Electric Displacement. A 
 displacement of an oscillatory character 
 produced in a dielectric. 
 
 Oscillatory Electric Inductance. Os- 
 cillatory inductance. 
 
 Oscillatory Electromotive Force. A 
 rapidly periodic electromotive force, 
 usually rapidly diminishing in amplitude. 
 
 Oscillatory Generator. An oscillatory 
 dynamo. 
 
 Oscillatory Inductance. Inductance in 
 the circuit of electric oscillations. 
 
 Oscillatory Induction. A name some- 
 times applied to open-circuit induction. 
 
 Oscillatory Intermittent Currents. 
 Intermittent currents which are oscillat- 
 ory in character, such as the oscillatory 
 discharges of a static machine. 
 
 Oscillograph. (1) An instrument for re- 
 cording rapid variations of an electrical 
 current or pressure, usually consisting of 
 a combination of a suitable form of gal- 
 vanometer with a photographic recording 
 apparatus. (2) A cathode-ray tube in 
 which the cathode rays are deflected by 
 the application of a magnetic field. 
 
 Osmometer. An apparatus for measuring 
 osmose. 
 
 Osmose. An unequal mixing of liquids of 
 different densities through the pores of a 
 separating medium. 
 
 Osmose, Electric. The unequal differ- 
 ence of diffusion between two liquids 
 placed on opposite sides of a diaphragm, 
 produced by the passage of an electric 
 current through the diaphragm. 
 
 Osmosis. A term sometimes used for 
 osmose. 
 
 Osmotic. Of or pertaining to osmose. 
 
 Osmotic Pressure. (1) The pressure pro- 
 duced by osmose. (2) The virtual gas- 
 eous pressure of a dissolved substance. 
 
 Osmotic Pressure. (1) Pressure produced 
 
 by osmose. (2) Pressure in a solution 
 due to the presence of a dissolved sub- 
 stance. 
 
 Osteotome, Electric. An electrically 
 propelled circular saw employed in the 
 surgical cutting of bones. 
 
 Outboard Bearing. (1) A journal bearing 
 projecting beyond the base frame of a 
 machine for giving adequate support to a 
 long or heavy shaft. (2) A separate 
 journal bearing supported outside the 
 frame of a machine. 
 
 Outboard Bearing of Dynamo-Electric 
 Machine. (1) A bearing projecting be- 
 yond the base frame of a dynamo-electric 
 machine for the purpose of adequately 
 supporting the rotor. (2) A bearing for 
 the shaft of a dynamo rotor supported 
 independently of the base of the dynamo. 
 
 " Out-Current " of Telephone Relay. 
 The current which is sent out by a tele- 
 phone relay or repeater. 
 
 "Out-Door" Transformer. A trans- 
 former placed outside a building on the 
 sides of its walls, or on suitably selected 
 posts. 
 
 Outers. (1) The outside conductors of a 
 three-wire system as distinguished from 
 the neutral conductor. (2) In telephony, 
 the external pair of springs of a telephone 
 jack. 
 
 Outgoing Call. A call issued from an ex- 
 change, as distinguished from an incom- 
 ing call. 
 
 Outgoing-Call Trunk-Line. A trunk 
 line terminating at a central telephone 
 station and conveying calls which are 
 transmitted from the station, as distin- 
 guished from an incoming call line on 
 which such calls are received. 
 
 Outgoing Current. The current sent out 
 over a line from a station as distinguished 
 from the received current, or the return- 
 ing current. 
 
 Outgoing End. The end of a junction 
 telephone wire at which calls are trans- 
 mitted. 
 
 Outgoing Lines. (1) Lines in a tele- 
 phone exchange on which calls are for- 
 warded or transmitted, as distinguished, 
 from incoming lines. (2) Outgoing 
 wires. 
 
 Outgoing Side of Telephone Switch- 
 board. (1) The side of a switchboard at 
 which the conductors leave it. (2) The 
 side of a switchboard to which calls are 
 transferred or from which calls are trans- 
 mitted. 
 
 Outgoing Signals. Signals sent out over 
 
Out.] 
 
 871 
 
 [Ove. 
 
 a telegraphic line by the outgoing cur- 
 rents. 
 
 Outgoing "Wires. Wires by means of 
 which the current is led out from a gen- 
 erator or station. 
 
 Outlet. (1) A place where branch wires 
 come out in a wall or ceiling for connec- 
 tion to a switch, lamp or other device. 
 (2) In a system of incandescent-lamp dis- 
 tribution, the places in a building where 
 the fixtures or lamps are attached. 
 
 Outlet Block. (1) A fuse block placed at 
 or near an outlet. (2) A block containing 
 an outlet fuse wire. 
 
 Outlet Box. A box placed at or near an 
 outlet for the ready making or changing 
 of electric connections with the outlet 
 conductors. 
 
 Outlet Insulator. Any insulator em- 
 ployed at an outlet. 
 
 Output. The useful energy or activity 
 given out by any machine. 
 
 Output of Dynamo-Electric Machine. 
 (1) The electric power of the current 
 developed by a dynamo-electric generator 
 or transformer, at its delivery terminals 
 expressed in volt-amperes, watts, or kilo- 
 watts. (2) The available mechanical 
 power developed by a motor, or the power 
 delivered at its pulley or shaft. 
 
 Output Wires. Wires connected with a 
 distribution box which take their supply 
 from the box. 
 
 Outrigger. An arm horizontally fastened 
 to a pole for the purpose of trussing it. 
 
 Outrigger for Arc-Lamp. A device for 
 suspending an electric arc-lamp so as to 
 cause it to stand out from the wall of a 
 building. 
 
 Outrigger Torpedo. A pole or spar tor- 
 pedo. 
 
 Outside Wiring. (1) Any wiring for a 
 circuit outside of a house or other build- 
 ing. (2) Out-door wiring. 
 
 Outside Work. Out-of-door wiring. 
 
 Over-Compounded. Such a compound- 
 ing of a dynamo-electric machine as pro- 
 duces under an increase of load an increase 
 of voltage at its terminals. 
 
 Over-Compounded Dynamo. A dy- 
 namo in whicli the magneto-motive force 
 of its series coils not only compensates 
 for the drop in the armature, but also for 
 the drop in a conductor leading from the 
 generators to the motors or translating 
 devices, thus permitting the external 
 conductors to be regarded electrically as 
 forming an extension of the armature 
 winding, and thus permitting the genera- 
 
 tor to deliver a constant pressure at its 
 final terminals at the motor or device. 
 Overflow of Leyden Jar. A term 
 sometimes employed for the discharge of 
 a Leyden jar by a disruptive discharge 
 around its edge. 
 
 Overhead Conductor. An aerial con- 
 ductor. 
 
 Overhead Feeders. Aerial feeders, as 
 distinguished from buried or under- 
 ground feeders. 
 
 Overhead Lines. A term applied to 
 aerial telegraph, telephone, electric light 
 or power lines, that run overhead, in con- 
 tradistinction to similar underground 
 lines. 
 
 Overhead Mains. Any system of aerial 
 mains. 
 
 Overhead Switch. (1) A switch con- 
 trolling an overhead circuit. (2) A can- 
 opy switch. (3) A switch placed over- 
 head. (4) A switch placed above a motor- 
 man on a car so as to be within his reach. 
 
 Overhead Trolley-System. (1) An aerial 
 trolley wire system. (2) A system of 
 electric-street-car propulsion in which the 
 required current is taken from an over- 
 head trolley- wire. 
 
 Overhead Trolley- Wire. An ordinary 
 aerial trolley wire. 
 
 Overhead Trolley. A trolley employed 
 in an overhead trolley-system. 
 
 Overhead Wires. Aerial wires. 
 
 Overland Telegraph. Any telegraphic 
 circuit provided with aerial conductors, 
 as distinguished from a submarine or an 
 underground telegraph. 
 
 Overlap Test. A localization test for a 
 single fault in a single telegraph line, by 
 observing the resistance from each end 
 and deducting therefrom half of the 
 amount, by which the sum of these resist- 
 ances overlap the total conductor resist- 
 ance of the line, to determine the posi- 
 tion occupied by the fault. 
 
 Overlap Splice. A splice of a rope or 
 cable in which the strands of one part 
 overlap the parts of the other, as distin- 
 guished from a splice in which the strands 
 of both parts interlace. 
 
 Overlapping Block System. An elec- 
 trically operated block system in which 
 the signals automatically delivered by a 
 train occupying one section, appear at a 
 considerable distance behind the train on 
 the preceding section. 
 
 Overlapping Winding of Alternator 
 Armature. A winding in which the 
 successive coils overlap, as distinguished 
 
Ove.] 
 
 872 
 
 [Pac. 
 
 from a winding in which successive coils 
 are mechanically separated. 
 Overload. (1) Any load whose value ex- 
 ceeds that of the normal. (2) An exces- 
 sive load. 
 
 Overload of Electric Motor. (1) A 
 load greater than that which an electric 
 motor can carry with its greatest effi- 
 ciency of operation. (2) Any load which 
 causes injurious heating of a motor. (3) 
 Any load exceeding the full load for 
 which a motor is designed. 
 
 Overload Storage-Battery Switch. 
 A switch placed in a discharging circuit 
 of a storage battery, arranged so as to 
 automatically break the circuit of the 
 battery should the discharge become ex- 
 cessive. 
 
 Overload Switch. A switch designed to 
 automatically open a circuit upon the 
 occurrence of an overload. 
 
 Over-Load Switch of Accumulator. 
 (1) A switch inserted in the circuit of a 
 storage battery which automatically 
 opens or introduces resistance into the 
 circuit when the current becomes exces- 
 sive. (2) An overload storage-battery 
 switch. 
 
 Overloaded Conductor. A conductor 
 carrying any electric current heavier 
 than the normal current for which it was 
 intended. 
 
 Over-Maximal Contraction. An in- 
 crease in the electric stimulation of a 
 motor nerve beyond the point where an 
 apparent maximum stimulus has been 
 reached. 
 
 Over-Running of Incandescent 
 Lamps. The operation of incandescent 
 lamps at a pressure above the normal. 
 
 Over-Running Trolley. An overhead 
 trolley, as distinguished from an under- 
 ground trolley. 
 
 " Overshoot." To err in compensation 
 by exceeding in adjustment, so as to over- 
 pass the limit. 
 
 Overtone Currents. Electric currents 
 of harmonic frequencies accompanying a 
 fundamental periodic current. 
 
 Overtones. Additional faint tones of 
 higher frequency than the fundamental, 
 and some multiple thereof, associated 
 with the fundamental and tending to give 
 it its characteristic quality. 
 
 Overtones, Electric. Electric upper har- 
 monics or rates of alternation higher than 
 the fundamental rate. 
 
 Overtype Dynamo. A dynamo-electric 
 machine whose armature bore or cham- 
 ber is placed above the field-magnet coils 
 instead of below them. 
 
 Overtype Magnet. A form of horseshoe 
 bi-polar electro-magnet, standing verti- 
 cally over the armature between its poles. 
 
 Over-Winding of Series Motor. A 
 series motor whose series-field winding is 
 unduly strong. 
 
 Over-Wound Motor Field. (1) A motor 
 field so wound that its full strength is 
 nearly attained with considerably less 
 than the normal current. (2) A term 
 sometimes employed for an over-com- 
 pounded motor field. 
 
 Oyster Pitting. A form of incandescent 
 lamp-fitting employed on board a ship for 
 water-tight bulkheads which cannot be 
 pierced. 
 
 Ozite. A form of insulating material. 
 
 Ozokerite. A form of insulating material. 
 
 Ozone. An allotropic modification of oxy- 
 gen which possesses more powerful oxy 
 dizing properties than ordinary oxygen, 
 and formed by electric discharges in air. 
 
 Ozonizer. An apparatus for producing 
 ozone by means of electric discharges. 
 
 P. A symbol for power. 
 
 P. A symbol for electric power. 
 
 P. A symbol proposed for pressure. 
 
 4>. A symbol for quantity of magnetic flux. 
 
 P. C. A contraction for primary current. 
 
 P. D. or p. d. A contraction frequently 
 employed for potential difference. 
 
 P. P. D. A contraction for primary po- 
 tential difference. 
 
 Pacinotti Projections. Radial projec- 
 
 tions or teeth, in an armature core, so ex- 
 tending from the central shaft as to form 
 slots, pockets or armature chambers, for 
 the reception of the armature coils. 
 
 Pacinotti Ring. A ring-shaped arma- 
 ture-core provided with projections em- 
 ployed by Pacinotti to receive the arma- 
 ture windings in his generator. 
 
 Pacinotti Teeth. A term sometimes used 
 for Pacinotti projections. 
 
 Packing of Telephone Dust Transmit- 
 
Pag.] 
 
 873 
 
 [Par. 
 
 ter. The partial cohering of the parti- 
 cles of granulated carbon in a dust trans- 
 mitter into a solid cake, thus seriously in- 
 juring the delicacy of the apparatus. 
 
 Page Effect. Faint sounds produced 
 when a piece of iron is rapidly magnet- 
 ized and demagnetized. 
 
 Palladium. A metal of the platinum 
 group. 
 
 Palladium Alloys. Various alloys of 
 palladium with other metals, some of 
 which are entirely devoid of paramag- 
 netic properties, and are, therefore, em- 
 ployed for the hair-springs of watches, in 
 order to render them free from the dis- 
 turbing influence of strong magnetic 
 fields. 
 
 Palette Combination Wire-Gauge. A 
 wire-gauge measurer consisting of a 
 graduated cam pivoted in a frame hook, 
 so that the wire to be measured is gripped 
 between the hook and cam. 
 
 Pan-Cake Armature-Coil. A flat arma- 
 ture coil applied to and secured upon the 
 surface of an armature. 
 
 Panel Board. A switchboard which is 
 not prepared in one piece, but which is 
 constructed and connected in panels. 
 
 Panel Feeder. The feeder connected 
 with the bus-bars of any particular panel 
 on a switchboard. 
 
 Panel Fuse. A fuse placed in the circuit 
 of a particular panel on a switchboard. 
 
 Panel of Switchboard. One of the sep- 
 arate vertical sub-sections of a composite- 
 ly constructed switchboard. 
 
 Panel Pressure. The pressure which is 
 maintained at a particular switchboard 
 panel. 
 
 Panel Reflector. A reflector composed 
 of strips or panels of silvered glass, or 
 other good reflecting material. 
 
 Panelled Conductors. Conductors 
 placed in mouldings. 
 
 Panelled "Wire. Wire placed inside 
 mouldings or panels. 
 
 Pan-Telegraphy. Fac-simile or auto- 
 matic telegraphy. 
 
 Pan-Telephone. A name proposed for a 
 certain sensitive form of telephone. 
 
 Paper Cable.-^-(l) A paper-insulated cable. 
 (2) A cable in which paper is the solid 
 insulator employed. 
 
 Paper Carbons. Incandescent lamp fila- 
 ments formed of carbonized paper. 
 
 Paper Condenser. A condenser in which 
 sheets of paper covered by some good in- 
 sulating material are employed as a 
 dielectric. 
 
 Paper Cut-Out. A term sometimes used 
 
 for film cut-out. 
 Paper-Film Cut-Out. A paper or film 
 
 cut-out. 
 
 Paper Insulation. Insulation obtained 
 by paper. 
 
 Paper Perforator. An apparatus em- 
 ployed in automatic telegraphy for punch- 
 ing in a strip of paper, the circular or 
 elongated spaces that produce the dots 
 and dashes of the Morse alphabet. 
 
 Paper Telephone Cable. A paper-insu- 
 lated telephone cable. 
 
 Parabolic. Of or pertaining to a parabola. 
 
 Parabola. A conic section formed by the 
 intersection of a right cone by a plane 
 parallel to any side. 
 
 Parabolic Reflector. (1) A reflector or 
 mirror the surface of which is a parabo- 
 loid, or such as would be obtained by the 
 revolution of a parabola around its axis. 
 (2) A reflector employed in connection 
 with electro-magnetic radiation of which 
 the section perpendicular to the long axis 
 has the form of a parabola, the focus of 
 which is occupied by the electric oscil- 
 lator. 
 
 Paradox. (1) Something which seems to 
 contradict the ordinary laws of nature, 
 but which is in reality the expression 
 of such law. (2) A seeming inconsistency, 
 or self-contradiction. 
 
 Paraffine. A solid hydro-carbon possess- 
 ing high insulating powers. 
 
 Paraffined Wire. Wire wrapped or 
 braided with some textile material and 
 afterwards coated with paraffine. 
 
 Paraffining. Coating or covering with 
 paraffine. 
 
 Paragrele. A French term for a light- 
 ning rod, intended to protect a field 
 against the destructive action of hail. 
 
 Parallax. The apparent displacement of 
 the position of an object, relatively to 
 points in front or behind it, due to a dif- 
 ference in the point of view. 
 
 Parallax Error. An error in reading the 
 position of a pointer on a scale due to par- 
 allax. 
 
 Parallel Arc-Circuit. A word sometimes 
 used for multiple circuit. 
 
 Parallel Circuit. A term sometimes used 
 for multiple circuit. 
 
 Parallel Conical Conductors. A sys- 
 tem of conical conductors, or of conduc- 
 tors successively diminishing in diameter, 
 employed in parallel distribution. 
 
 Parallel Connected Sources. A num- 
 ber of separate sources connected in 
 
Par.] 
 
 874 
 
 [Par. 
 
 parallel, so as to be capable of acting as a 
 single source. 
 
 Parallel-Connected Triphasers. Two 
 or more triphasers connected in parallel 
 to a common .set of triphase bus- bars or 
 mains. 
 
 Parallel-Connections of Alternators. 
 A number of alternators connected to 
 a single pair of leads or bus-bars in paral- 
 lel or multiple-arc. 
 
 Parallel Coupling. A term sometimes 
 employed for the parallel connection of 
 alternators. 
 
 Parallel Distribution. A distribution 
 of electric energy in which the receptive 
 devices are arranged between one or more 
 pairs of parallel conductors, extending 
 to the limits of the system. 
 
 Parallel Feeding. (1) Furnishing the 
 current required for the operation of a 
 number of receptive devices connected 
 in parallel. (2) Multiple-arc distribution 
 in which a pair of mains is supplied at 
 one end as distinguished from an anti- 
 parallel system. 
 
 Parallel-Series. A term sometimes ap- 
 plied to a multiple-series connection. 
 
 Parallel Transformer. (1) A trans- 
 former connected with a parallel-system 
 of distribution. (2) A transformer that 
 is connected to mains in parallel. (3) A 
 transformer whose secondary coils are 
 connected in parallel. 
 
 Parallel Tree-Circuit. A system of 
 parallel distribution in which the dis- 
 tributing mains diverge and ramify from 
 a common centre or central station, di- 
 minishing in size as they proceed. 
 
 Parallel- Wire Stretcher. A clamping 
 tool for gripping and stretching wire. 
 
 Parallel-Working of Dynamo-Electric 
 Machines. The working of two or more 
 dynamos in pai'allel. 
 
 Parallelogram of Forces. A parallo- 
 gram whose sides represent in length and 
 direction the intensity and direction of two 
 co-acting forces, and whose intermediate 
 diagonal represents the resultant force. 
 
 Paramagnet. (1) A magnet produced by 
 iron or other magnetic substance. (2) A 
 ferromagnet. 
 
 Paramagnetic. (1) Possessing the proper- 
 ties ordinarily recognized as magnetic. 
 (2) Possessing the power of concentrat- 
 ing lines of magnetic force. (3) Ferro- 
 magnetic. 
 
 Paramagnetic Permeability. Perme- 
 ability to magnetic force. 
 
 Paramagnetic Polarity. Magnetic po- 
 
 larity, or the polarity possessed by para- 
 magnetic substances. 
 
 Paramagnetically. In a paramagnetic 
 manner. 
 
 Paramagnetism. The magnetism of 
 paramagnetic substances. 
 
 Parasitical Currents. A name some- 
 times applied to eddy currents. 
 
 Paratonnere. A French term for light- 
 ning rod, sometimes employed in English 
 technical works. 
 
 Parcel of Wire. A word sometimes em- 
 ployed for any quantity of manufactured 
 wire presented at one time and in one 
 piece for examination or testing. 
 
 Parchmentized-Thread Filament. A 
 filament for an incandescent lamp made 
 from the carbonization of parchmentized 
 thread. 
 
 Parchmentizing Process. A process for 
 converting cellulose thread into artificial 
 parchment by treating it with dilute sul- 
 phuric acid. 
 
 Partial Contact. (1) A high-resistance 
 or imperfect contact between two tele- 
 graphic lines or circuits. (2) An incom- 
 plete contact. 
 
 Partial Disconnection. (1) A partial 
 discontinuity. (2) A loss of complete 
 metallic connection. (3) An imperfect 
 metallic contact. 
 
 Partial Earth. The fault in a telegraphic 
 or other line in which the line is in par- 
 tial connection with the earth. 
 
 Partial Fault. In telegraphy or tele- 
 phony, a fault due to an imperfect ground- 
 contact, a cross-contact or a disconnec- 
 tion, as distinguished from a complete 
 fault or one that interrupts communica- 
 tion. 
 
 Partial Reaction of Degeneration. 
 That form of alteration to electric stim- 
 ulation in which the nerves show no ab- 
 normal reaction to electric stimulation, 
 while the muscles, when directly stimu- 
 lated by a constant current, exhibit the 
 reaction of degeneration. 
 
 Partial Vacuum. An incomplete vac- 
 uum. 
 
 Partially Overlapping Winding of 
 Alternator Armature. A winding in 
 which some of the coils overlap each 
 other and some of the coils do not over- 
 lap. 
 
 Parting of Cable. A complete rupture 
 or breaking of a submarine cable. 
 
 Party Lines for Telephone Service. 
 (1) Lines which connect several sub- 
 scribers in one circuit, as opposed to lines 
 
Par.] 
 
 
 875 
 
 [Pen. 
 
 devoted to a single subscriber. (2) Lines 
 connecting permanently together several 
 telephonic stations, as distinguished from 
 lines connecting each telephone station 
 through an exchange. 
 
 Partz Gravity Cell. A zinc-carbon 
 couple employed with electrolytes of sul- 
 phate of magnesia or common salt, and 
 sulpho-chromic salt, in which the liquids 
 are kept apart by their difference of 
 density. 
 
 Passive Resistance. A term sometimes 
 used for ohmic resistance. 
 
 Passive State. A condition of a metallic 
 substance in which it may be placed in 
 liquids that would ordinarily combine 
 with it, without being attacked or cor- 
 roded. 
 
 Paste Joint for Lamp Filament. A 
 form of joint between the leading-in 
 wires and the ends of the lamp filament 
 obtained by the employment of a moist 
 hydro-carbon paste which is subsequently 
 carbonized. 
 
 Pasted Secondary Cell. A secondary 
 cell in which the active material is applied 
 to the surface of the grid or support in 
 the form of a paint, paste, or cement. 
 
 Path of Magnetic Leakage. A side 
 path taken by deviating magnetic flux, 
 as distinguished from the main path of 
 usefully employed flux. 
 
 Patrol Alarm-Box. In a system of sig- 
 nal telegraphy or telephony, a box from 
 which a call, communication, or alarm 
 can be given by a patrol. 
 
 Paying-Out. The operation of passing 
 submarine cable out of the ship while 
 laying it. 
 
 Paying-Out Drum. A drum employed 
 in laying a submarine cable and over 
 which the cable takes several turns, 
 whereby, by means of brakes, tension may 
 be applied to the cable as it leaves. 
 
 Paying-Out Leg. In a bight of cable at 
 the bows of a cable ship, that side or leg 
 which is paid out, as distinguished from 
 the side or leg which is held stationary or 
 picked up. 
 
 " Pea " Lamp. A term sometimes given 
 to a particular form of miniature incande- 
 scent lamp. 
 
 Peaked Type of Periodically-Alter- 
 nating Electromotive Force. A type 
 of electromotive force whose curve of 
 graphical representation has a peaked 
 shape, as opposed to a smooth or a flat 
 shape. 
 
 Pear Push. A pear-shaped push-contact, 
 
 usually provided with a flexible cord 
 pendant. 
 
 Pedestal of Armature. A supporting 
 pillar for an armature bearing. 
 
 Peg-Circuit. A circuit that is opened 
 or closed by means of metallic pegs. 
 
 Peg-Switch. (1) A switch that is opened 
 or closed by means of a peg. (2) A pin 
 switch. 
 
 Peg-Switchboard. A switchboard whose 
 circuits are capable of being variously 
 inter-connected by means of peg switches. 
 
 Peltier Effect. The heating effect pro- 
 duced by the passage of an electric cur- 
 rent across a thermo-electric junction, or 
 surface of contact between two different 
 metals, as distinguished from a Joulean 
 effect or heat due to resistance merely. 
 
 Peltier's Cross. A cross, made by placing 
 two plates of dissimilar metals in contact 
 at right-angles to each other, employed 
 for the study of the Peltier effect. 
 
 Pen Carriage. The carriage in an elec- 
 tric chronograph which carries the pen 
 and moves over the sheet of paper on 
 which the record is made. 
 
 Pen, Electric. A device for manifold 
 copying, in which a sheet of paper is made 
 into a stencil by minute perforations ob- 
 tained from a needle driven by a small 
 electric motor, the stencil being after- 
 wards employed in connection with an 
 ink roller for the production of any re- 
 quired number of copies. 
 
 Pencil Microphone. A carbon micro- 
 phone in which the loose carbon is in the 
 form of one or more pencils. 
 
 Pendant Argand. An Argand burner so 
 arranged as to be lighted or extinguished 
 by the pulling of a pendant. 
 
 Pendant Cord. A flexible conductor pro- 
 vided for conveying the current to a 
 pendant lamp or push. 
 
 Pendant, Electric. A hanging fixture 
 provided with 'a socket for the support 
 either of an incandescent lamp, or of a 
 contact. 
 
 Pendant Electric-Lamp. An incandes- 
 cent lamp supported on a pendant cord. 
 
 Pendant Pull-Switch. A switch which 
 is operated by pulling upon a pendant 
 cord or loop. 
 
 Pendant Socket. An attachment pro- 
 vided with a chain or chains for turning 
 on or off a lamp not readily accessible. 
 
 Pendulum Annunciator. (1) An an- 
 nunciator whose indicating arm consists 
 of a pendulous or swinging arm which, 
 when at rest, assumes a vertical position, 
 
Pen.] 
 
 876 
 
 [Per. 
 
 and which is moved to the right or left 
 by the action of the current. (2) A 
 swinging annunciator. 
 Pendulum, Electric. (1) A pendulum 
 so arranged that its to-and-fro motions 
 send electric impulses over a line, either 
 by making or breaking contacts. (2) An 
 electric tuning fork whose to-and-fro 
 movements are maintained by electric 
 impulses. 
 
 Pendulum Indicator. A term sometimes 
 employed for a pendulum annunciator. 
 
 Pendulum Myograph. An electric 
 pendulum employed for physiological 
 and chronographic purposes. 
 
 Pendulum Selector. In a system of se- 
 lective telephony, a pendulum which is 
 adjusted to vibrate at different rates and 
 thereby actuate the call-bell of some par- 
 ticular station selectively. 
 
 Pendulum Signaller. A pendulum 
 armed with a contact maker for closing 
 a circuit and transmitting signals. 
 
 Pentad Atom. An atom whose valency 
 or atomicity is five. 
 
 Pentane Standard. A standard source 
 of light obtained from the burning of 
 pentane, and used in photometric meas- 
 urements in place of a Methven screen. 
 
 Penthode Working. A five-way mode 
 of telegraphic working obtained by the 
 use of the Delany synchronous multi- 
 plex telegraph. 
 
 Penumbra. A region of partial shadow 
 surrounding the umbra or complete 
 shadow, obtained when the source of 
 light causing the shadow has an appreci- 
 able area. 
 
 Percentage Conductivity. The conduc- 
 tivity of a wire expressed in percentage 
 of the conductivity of Mathiessen's 
 standard. 
 
 Percentage Conductivity of Wire. 
 (1) The conductivity of a wire in terms of 
 the conductivity of pure copper. (2) The 
 conductivity of a particular copper wire 
 compared with the conductivity of a 
 standard wire of the same dimensions. 
 (3) The conductivity of a wire referred 
 to Matthiessen's standard of conductivity 
 for copper. 
 
 Perfect Linkage. Linkage of magnetic 
 flux between two associated coils or cir- 
 cuits unaccompanied by magnetic leak- 
 age, or such that all of the flux is linked 
 with all the turns of each circuit. 
 
 Perforated Armature. An armature 
 provided with perforations for the in- 
 sertion of the coils. 
 
 Perforated Core-Discs. The separate 
 core discs of a laminated armature core 
 provided with perforations for the in- 
 sertion of armature wires. 
 
 Perforator. (1) A paper perforator. (2) In 
 automatic telegraphy, an apparatus for 
 perforating paper. 
 
 Perforator Mallet. A mallet used with 
 a perforator for striking its keys. 
 
 Perforator Slip. The slip of paper pre- 
 pared for use in a perforator. 
 
 Period. (1) The interval of time between 
 two successive passages of a vibration 
 through a given point of its path taken in 
 the same direction. (2) The time occu- 
 pied in performing a complete cycle. 
 
 Period of Open-Circuit Oscillation. 
 The time in which the oscillation set up 
 in an open circuit by electric resonance 
 requires to make one complete to-and-fro 
 motion. 
 
 Period of Simple-Harmonic Motion. 
 
 The interval of time which elapses be- 
 tween two successive passages of a moving 
 particle over the same point in the same 
 direction. 
 
 Period of Vibration. The time occupied 
 
 in executing one complete vibration or 
 
 motion to-and-fro. 
 
 Periodic. Of or pertaining to a period. 
 Periodic Alternating Electromotive 
 
 Force. An electromotive force whose 
 
 direction periodically varies. 
 
 Periodic Current. (1) A current whose 
 strength and direction periodically vary. 
 (2) A simple harmonic or sinusoidal cur- 
 rent. (3) A periodically alternating cur- 
 rent. 
 
 Periodic Discharge. (1) An electric dis- 
 charge which periodically changes its 
 direction. (2) An alternating discharge. 
 
 Periodic Governor. A form of governor 
 for an electric motor, in which the cur- 
 rent is automatically cut off for a certain 
 portion of each revolution. 
 
 Periodic Motion. A term sometimes em- 
 ployed for simple-periodic motion. 
 
 Periodically Alternating Discharge. 
 An alternating discharge. 
 
 Periodically Decreasing Discharge. 
 An oscillatory discharge whose successive 
 oscillations decrease in intensity. 
 
 Periodicity. (1) The number of periods 
 executed per second by a periodically 
 alternating quantity. (2) The number of 
 cycles executed in unit time by an alter- 
 nating current. (3) The frequency of an 
 alternating current. 
 
 Periodicitv of Alternation. (1) The 
 
Per.] 
 
 
 number of alternations per second. (2) 
 The frequency. (3) The number of alter- 
 nations executed per second or per minute. 
 
 Periodicity of Auroras, Magnetic 
 Storms, and Sunspots. Coincidences 
 between the occurrence of auroras, mag- 
 netic storms and sun-spots. 
 
 Peripheral Speed. The speed of a point 
 on the circumference of a rotating cylin- 
 der or wheel. 
 
 Peripheral Velocity. (1) The rate of 
 linear peripheral speed. (2) The tan- 
 gential velocity at a periphery. 
 
 Periphratic Region. A region which 
 encloses other regions within itself. 
 
 Peripolar Zone. The zone or region sur- 
 rounding the polar zone on the body of 
 a patient undergoing electro-therapeutic 
 treatment. 
 
 Periscopic Eye-Piece of Microscope. 
 An eye-piece consisting of a triple eye- 
 lens and a single field-lens, possessing a 
 very large and flat field. 
 
 Permanency, Electric. The property 
 possessed by most metallic substances, 
 while in a solid state, of retaining a con- 
 stant electric conducting power at the 
 same temperature. 
 
 Permanent Charge by Induction. An 
 induced charge permanently communi- 
 cated to a conductor, as distinguished 
 from a temporarily induced charge. 
 
 Permanent Currents of Wheatstone 
 System. (1) In the Wheatstone auto- 
 matic system the use of a signalling cur- 
 rent during the whole period in which a 
 signal is transmitted. (2) The continued 
 application of current in one or other 
 direction oil the line. 
 
 Permanent Current Telephone Work- 
 ing. A system of telephony employing 
 a constant normal strength of current 
 on the line. 
 
 Permanent Electret. A body whose 
 molecules are permanently and inherently 
 electrized, as distinguished from a body 
 whose molecules are only inherently elec- 
 trized while under the influence of some 
 change of state. 
 
 Permanent Intensity of Magnetiza- 
 tion. A term employed for the intensity 
 of a permanent magnetism produced in 
 hard steel, as distinguished from the 
 magnetization produced temporarily in 
 soft iron. 
 
 Permanent Laminated - Magnet. A 
 term sometimes employed in place of 
 compound-magnet. 
 
 Permanent Magnet. A name sometimes 
 
 877 [Per. 
 
 given to a magnet composed of hardened 
 steel, whose magnetic retentivity is high. 
 Permanen t-Magnet Voltmeter. A 
 form of voltmeter in which difference 
 of potential is measured by the movement 
 of a magnetic needle under the combined 
 action of a coil and a permanent magnet, 
 against the pull of a spring. 
 
 Permanent Magnetism. M agnetism 
 possessed by permanent magnets. 
 
 Permanent Magnetization. (1) A term 
 employed for the magnetization produced 
 in a mass of steel or hardened iron when 
 brought into a magnetic field. (2) The 
 magnetization of a permanent magnet. 
 
 Permanent Magneto-Motive Force. 
 The magneto-motive force of a permanent 
 magnet. 
 
 Permanent State of Charge on Tele- 
 graphic Line. (1) The condition of the 
 charge on a telegraphic line during the 
 time the current passing is at full strength 
 in all parts. (2) The charge in a telegraph 
 line when insulated at one end and con- 
 nected to an E. M. F. at the other. 
 
 Permanent System of Currents. (1) A 
 term sometimes used in telegraphy to 
 represent the current sent into a line by 
 a double-current key. (2) In a Wheat- 
 stone's automatic telegraph system the usf 
 of double currents, whereby a current is 
 always flowing on the line. 
 
 Permanent Telegraphic Line. A term 
 employed for a telegraphic line that is in- 
 tended to remain in use for an indefinite 
 time, in contra distinction to a semi-per- 
 manent line which is only designed for 
 use during a comparatively limited time. 
 
 Permanent Telegraphic Signals. Tele- 
 graphic signals that are permanently re- 
 corded as distinguished from transient or 
 unrecorded signals. 
 
 Permeability Bridge. A device for 
 measuring the magnetic permeability of 
 a medium, operating on the principle of 
 a Wheatstone bridge. 
 
 Permeability Curve. A curve repre- 
 senting the permeability of a magnetic 
 substance. 
 
 Permeameter. An apparatus for deter- 
 mining magnetic permeabilities by the 
 measurement of the tractive force re- 
 quired to detach a mass of soft iron 
 having a plane surface, from a magnetic 
 pole whose magnetic flux passes perpen- 
 dicularly through the surface. 
 
 Permeance, Magnetic. (1) The recipro- 
 cal of magnetic reluctance. (2) The con- 
 ductance of a medium to magnetic flux. 
 
 Permeating. (1) The passage of mag- 
 
Per.] 
 
 878 
 
 [Pha. 
 
 netic flux through a magnetizable sub- 
 stance, or of electrostatic flux through a 
 dielectric. (2) Intimately traversing the 
 depths of a medium. 
 
 Permeation. The passage of magnetic 
 flux through any permeable substance. 
 
 Permissive Block-System for Rail- 
 roads. -A block-system in which two or 
 more trains are, under certain conditions, 
 permitted to occupy the same block sim- 
 ultaneously. 
 
 Permissivity. A word frequently used 
 for permittivity. 
 
 Permittance. (1) Electrostatic capacity. 
 (2) The capability of a condenser or di- 
 electric to hold a charge. 
 
 Permittivity. (1) Specific permittance. 
 (2) The dielectric constant. 
 
 Perpendicular. (1) At right angles to. 
 (2) A line at right angles to one or more 
 other lines. 
 
 Persistence of Energy. The indestruc- 
 tibility of energy. 
 
 Personal Equation. A constant obser- 
 vational error peculiar to an observer, and 
 depending upon his psychological condi- 
 tion. 
 
 Perviability. A word proposed for per- 
 meability to electrostatic flux. 
 
 Perviance. (1) Conductance to electric 
 lines of force. (2) The reciprocal of divi- 
 ance. 
 
 Petticoat Insulator. (1) An insulator 
 provided with a petticoat, or deep internal 
 groove, around its lower extremity, or 
 stalk. (2) A line-wire vertical insulator 
 provided with an insulating inverted cup 
 having a form resembling a petticoat. (3) 
 An ordinary telegraph or telephone single- 
 cup insulator. 
 
 Pflugers Law. A given tract of nerve is 
 stimulated by the appearance of cathelec- 
 trotonus and the disappearance of anelec- 
 trotonus, but not by the disappearance of 
 cathelectrotonus and the appearance of 
 anelectrotonus. 
 
 Phantom Circuit. (1) Any of the addi- 
 tional circuits established on a telegra- 
 phic line by means of any variety of mul- 
 tiplex telegraphy. (2) An imaginary cir- 
 cuit virtually created by multiplexing a 
 telegraph circuit. 
 
 Phantom Streams. A term sometimes 
 applied to a variety of the Tesla streaming 
 discharge. 
 
 Phantom Wires. (1) A term sometimes 
 applied to the virtual additional circuits 
 or wires obtained in any single wire or 
 conductor by the use of any multiplex 
 
 telegraphic system, 
 cuits. 
 
 (2) Phantom cir- 
 
 Phase. The fractional part of a period, 
 which has elapsed since a vibrating body 
 last passed through the extreme point of 
 its path in the positive direction. 
 
 Phase Angle. The angle of phase, in 
 a simple-harmonic motion, or the angular 
 distance through which the corresponding 
 circularly moving point has passed from 
 the point of last maximum positive elonga 
 tion. 
 
 Phase Detector. A device for determin- 
 ing the phase of an alternating current, 
 electromotive force, or flux. 
 
 Phase Diagram. A diagram representing 
 the magnitude and relative phase position 
 of electric pressures or currents. 
 
 Phase-Difference Measurer. A device 
 for measuring difference of phase, be- 
 tween any periodically alternating quan- 
 tities. 
 
 Phase Indicator. (1) A device for indi- 
 cating when the pressure of an alternator 
 is in phase and synchronism with the 
 pressure of the circuit with which it is 
 to be connected. (2) A term sometimes 
 
 - employed for a synchronizer. 
 
 Phase Meter. A phase-difference meas- 
 urer. 
 
 Phase Modification. The alteration of 
 the phase of any periodically alternating 
 quantity. 
 
 Phase of Simple-Harmonic Motion. 
 
 The angle through which the correspond- 
 ing circularly moving point has moved 
 from the point of maximum positive elon- 
 gation. 
 
 Phase of Vibration. (1) The position 
 of the particles in motion in a wave or 
 vibration at any instant of time during 
 the wave period, as compared with their 
 mean position. (2) The phase angle of 
 vibration considered as simple-harmonic 
 motion. 
 
 Phase Regulation. The regulation of the 
 phase or phases of alternating currents 
 or E. M. F.'s. 
 
 Phase-Splitter .-7(1) Any apparatus which 
 so acts upon an incoming alternating cur- 
 rent that the same current goes out in 
 different branches as a plurality of cur- 
 rents differing in phase. (2) A device for 
 producing a difference of phase between 
 two currents, so as to enable a single-phase 
 induction-motor to be self -star ting. (3) A 
 device for making an alternating current 
 split into two or more dephased compo- 
 nents. 
 
 Phase Splitting. The quality or opera' 
 
Pha.] 
 
 879 
 
 [Pho. 
 
 tion cf causing a single alternating cur- 
 rent to split into a plurality of relatively 
 dephased components. 
 
 Phase Transformation. A change of 
 phase obtained by a transformer whereby 
 two-phase currents may be transformed 
 into three-phase currents, or vice-versa. 
 
 Phase- Windings. The separate wind- 
 ings on the armature of a polyphase 
 motor. 
 
 Phasing Current. The current produced 
 between two dynamos when thrown into 
 parallel, which arises from their being 
 either not perfectly in phase, or not per- 
 fectly equal in pressure, or both. 
 
 Phasing or Wattless-Component. A 
 
 component of alternating current, 90 out 
 of phase with respect to a pressure, and, 
 therefore, indifferent to it in respect to 
 energy. 
 
 Phasing Transformer. (1) A trans- 
 former capable of effecting a change of 
 phase. (2) A transformer for the supply 
 of multiphase secondary-currents from 
 Uniphase primary-currents, or, vice-versa. 
 
 Phelp's Stock Printer. A form of print- 
 ing telegraph employed in sending stock 
 quotations telegraphically. 
 
 Phenakistoscope. An optical toy de- 
 pending on the persistence of a retinal 
 image, in which the appearance of life is 
 obtained from a succession of suitable 
 pictures that are caused to rapidly pass 
 before the eye. 
 
 Phenomenon. Any event observed or 
 known to occur in nature. 
 
 Pherope. A name sometimes applied to a 
 telephote. 
 
 Philosopher's Egg. A name given to 
 the ovoid or egg-shaped mass of light, that 
 appears when a convective discharge is 
 taken between two electrodes in a partial 
 vacuum. 
 
 Phonautograph. An apparatus for the 
 automatic production of the visible trac- 
 ings of the vibrations produced by any 
 sounds. 
 
 Phone. (1) A contraction frequently em- 
 ployed for telephone. (2) A message sent 
 by telephone. 
 
 Phone. To send a message by telephone. 
 
 Phoned. Communicated by telephone. 
 
 Phonic Wheel. A wheel maintained in 
 synchronous rotation by timed electric 
 impulses sent over a telegraphic line, and 
 employed in the Delany synchronous 
 multiplex telegraph system. 
 
 Phoning. Communicating by telephone. 
 
 Phonogram. A term proposed for a de- 
 
 spatch transmitted by means of a tele- 
 phone. 
 
 Phonograph. An apparatus for the re- 
 cording and reproduction of articulate 
 speech, or of sounds of any character, at 
 any time after their occurrence, and for a 
 number of times. 
 
 Phonograph Record. A record obtained 
 
 by means of a phonograph. 
 Phonographic. Of or pertaining to the 
 
 phonograph. 
 
 Phonophore. A modified form of har- 
 monic telegraph. 
 
 Phonoplex. A general term embracing 
 the apparatus employed in phonoplex 
 telegraphy. 
 
 Phonoplex Telegraphic-Receiver. A 
 
 special form of telephone receiver em- 
 ployed in phonoplex telegraphy, which 
 responds to brief current impulses but 
 not to prolonged impulses. 
 
 Phonoplex Telegraphy. A system of 
 double telegraphic transmission, in which 
 telephonic currents, superposed on the 
 ordinary Morse currents, actuate a modi- 
 fied telephonic receiver, and thus permit 
 the simultaneous transmission of two 
 separate messages over a single wire 
 without interference. 
 
 Phonoplex Transmission. Double tele- 
 graphic transmission obtained by the 
 superposition of telephonic and Morse 
 currents. 
 
 Phonozenograph. An instrument de- 
 vised to indicate the direction of a distant 
 sound. 
 
 Phosphoresce. To emit phosphorescent 
 light. 
 
 Phosphorescence. The power of emit- 
 ting light, or becoming luminous by 
 simple exposure to radiant energy. 
 
 Phosphorescence, Electric. Phosphor- 
 escence caused in a substance by the 
 passage of an electric discharge. 
 
 Phosphorescent. Possessing the quality 
 of phosphorescence. 
 
 Phosphorescent Glow. A phosphores- 
 cent light emitted by the residual atmos- 
 phere of a vacuum tube several seconds 
 after an electric discharge has ceased to 
 pass through it. 
 
 Phosphorescent Lamp. A lamp whose 
 light is obtained by means of the phos- 
 
 Shoresceut effects attending electrical 
 ischarges through a rarified space. 
 Phosphorescing. Emitting phosphor- 
 escent light. 
 Phosphoroscope. An apparatus fol 
 
Pho.J 
 
 880 
 
 [Pho. 
 
 measuring the phosphorescent power of 
 any substance. 
 
 Phot. (1) A unit of time-illumination, or 
 the total illumination produced by one 
 hi* for one second of time. (2) The lux- 
 second. 
 
 Photo-Chemical. Relating to photo- 
 chemistry. 
 
 Photo-Chemical Effect. Chemical ef- 
 fects produced by the action of radiant 
 energy. 
 
 Photo-Chemistry. The chemistry of the 
 effects of radiant energy. 
 
 Photo-Chronograph. An electric instru- 
 ment for automatically recording the 
 transit of a star across the meridian. 
 
 Photo-Electric. Pertaining to the com- 
 bined action of light and electricity. 
 
 Photo-Electric Alarm. (1) An alarm 
 operated by means of a photo-electric cell. 
 (2) A selenium cell proposed for use in 
 connection with the circuit of an electric 
 source and suitable electro-receptive de- 
 vices, so as to cause the sounding of an 
 alarm on the exposure of one of the faces 
 of the cell to light. 
 
 Photo-Electric Battery. Several pho- 
 to-electric cells so combined as to be 
 capable of acting as a single source. 
 
 Photo-Electric Cell. A cell capable of 
 producing difference of potential when its 
 opposite faces are unequally exposed to 
 radiant energy. 
 
 Photo-Electric Impulsion-Cell. A 
 photo-electric cell whose sensitiveness to 
 light may be restored by slight impulses, 
 such as mechanical blows or taps, or by 
 electro-magnetic impulses. 
 
 Photo-Electricity . Difference of electric 
 potential produced by the action of light. 
 
 Photo-Electromotive Force. An elec- 
 tro-motive force produced by the action 
 of light. 
 
 Photo-Engraving. Engraving effected 
 by the agency of light. 
 
 Photo-Fluoroscopy. The photography 
 of the image obtained on a fluoroscopic 
 screen. 
 
 Photographic Meter. An electric meter 
 producing a photographical record. 
 
 Photographic Negative . A photo- 
 graphic picture whose lights and shadows 
 are reversed with reference to the 
 original. 
 
 Photographic Positive. A photographic 
 picture whose lights and shadows corres- 
 pond to those in the natural object. 
 
 Photometer. An apparatus for measur- 
 ing the intensity of the light emitted by 
 any luminous source. 
 
 Photometer Bar. A graduated horizon- 
 tal bar designed to carry a photometer 
 screen and to indicate by the distance of 
 the screen from the sources of light, the 
 relative intensities of the lights com- 
 pared. 
 
 Photometer Bench. A photometer bar, 
 with or without accessory photometric 
 apparatus. 
 
 Photometer Box. A darkened box in 
 which is placed the photometer screen or 
 disc. 
 
 Photometer Disc. The photometer 
 screen. 
 
 Photometer, Electric. An electric in- 
 strument for measuring the intensity of 
 light or illumination. 
 
 Photometer Gallery. A name some- 
 times given to a photometric bench. 
 
 Photometer Screen. An opaque or trans- 
 lucent screen, employed in a photometer 
 for measuring the intensity of light, and 
 which receives the two illuminations to 
 be compared. 
 
 Photometric. Of or pertaining to a pho- 
 tometer. 
 
 Photometric - Surface of Luminous 
 Source. A surface formed by the locus 
 of points at the ends of lines, obtained by 
 laying off lines in various directions pas- 
 sing through the luminous source, whose 
 lengths measure the intensity of the rays 
 emitted in these directions. 
 
 Photometrically. In a photometric man- 
 ner. 
 
 Photo-Micrography. The photography 
 of microscopic objects. 
 
 Photo-Micrography, Electric. The art 
 of photographing microscopic images by 
 means of the electric light. 
 
 Photophone. An instrument for the tele- 
 phonic transmission of articulate speech 
 along a ray of light instead of along a 
 conducting wire. 
 
 Photophone Transmitter. The trans- 
 mitter employed in radiophony, in con- 
 nection with the photophone. 
 
 Photophore. An apparatus in which the 
 light of a small incandescent lamp is em- 
 ployed for purposes of medical explora- 
 tion. 
 
 Photosphere. The luminous envelope 
 which surrounds the sun, and which is the 
 source of its luminous radiation. , 
 
 Photo-Telegraphy. (1) Telegraphic com- 
 munication carried on by means of light. 
 (2) Heliography. (3) Radiophony. 
 
 Photo-Voltaic Cell. A photo-electric- 
 cell. 
 
Pho.] 
 
 881 
 
 [Pis. 
 
 Photo- Voltaic Effect. A change in the 
 resistance of selenium or other substance 
 produced by its exposure to light. 
 
 Physical Change. Any change in matter 
 resulting from a re-arrangement of its 
 molecular groupings, without the forma- 
 tion of new molecules, as distinguished 
 from a chemical change. 
 
 Physical Equator. The geographical 
 equator. 
 
 Physical Phosphorescence . Phosphor- 
 escence produced in matter by the impact 
 of light waves, resulting in a vibratory 
 motion of the molecules, of a rapidity suf- 
 ficient to cause them to emit light. 
 
 Physical. (1) Of or pertaining to nature. 
 (2) Natural. 
 
 Physiological. Of or pertaining to phy- 
 siology. 
 
 Physiological Coefficient of Illumina- 
 tion. The illuminating value of one watt 
 of activity at frequencies within visible 
 limits of the spectrum. 
 
 Physiological Rheoscope. A sensitive 
 nerve-muscle preparation employed to 
 determine the presence of an electric cur- 
 rent. 
 
 Physiologically. In a physiological man- 
 ner. 
 
 Physiologically - Effective Flux of 
 Light. The physiologically-effective il- 
 lumination received by any surface. 
 
 Physiologically-Effective Radiation. 
 That portion of the radiation which con- 
 sists of physiologically active or luminous 
 frequencies. 
 
 Physiology, Electro. The study of the 
 electric phenomena of living animals and 
 plants. 
 
 Piano, Electric. A piano whose strings 
 are struck by hammers actuated by 
 means of electro-magnets. 
 
 Picking-TJp Gear. The gear provided in 
 a cable ship for the recovery of a sub- 
 merged cable. 
 
 Pickle. An acid solution in which metal- 
 lic objects are dipped in order to thor- 
 oughly cleanse their surfaces before being 
 electro-plated. 
 
 Piece of Wire. A single length of wire 
 without a joint or splice of any descrip- 
 tion. 
 
 Pierced-Core Armature. A perforated 
 armature core. 
 
 Piezo-Electricity. Electrification pro- 
 duced in certain crystalline substances by 
 pressure. 
 
 Piezometer. An apparatus for determin- 
 ing the compressibility of a liquid. 
 $6 
 
 Pike Pole. A straight pole armed at one 
 end with a metal point or pike, for use in 
 setting up telegraph poles. 
 
 Pile. (1) A word frequently used for voltaic 
 or thermo-electric pile, though more fre- 
 quently for the former. (2) A voltaic or 
 thermo-electric battery. 
 
 Pilot Brush. A small accessory brush 
 placed on the commutator cylinder for 
 the purpose of determining the variations 
 in the electromotive force produced in 
 various segments. 
 
 Pilot-Hquse Controlling-Gear. Gear 
 placed in the pilot house for the control 
 of a search-light projector. 
 
 Pilot Lamp. (1) A lamp connected across 
 the terminals of a dynamo to show roughly 
 the pressure which it is producing. (2) A 
 lamp placed in a central station, generally 
 on the dynamo itself, to indicate the dif- 
 ference of potential at the dynamo ter- 
 minals by means of the intensity of the 
 emitted light. 
 
 Pilot Motor. (1) A small motor which 
 goes ahead of and serves to set in opera- 
 tion a larger or working motor. (2) A 
 small motor whose sole duty is to actuate 
 contacts for controlling the operation of 
 a large motor. 
 
 Pilot Transformer. A small transformer 
 placed at any desired portion of a line in 
 order to determine its pressure. 
 
 Pilot Wires. (1) The wires leading di- 
 rectly to the generating station from dif- 
 ferent parts of the mains, in order to de- 
 termine the difference of potential at 
 such parts. (2) Wires provided for con- 
 nection to a pilot lamp, or other device 
 for indicating the maintenance of normal 
 pressure. 
 
 Pins. Wooden pegs for supporting pole 
 line insulators. 
 
 Pin Plug. A plug consisting of a single 
 metallic pin with or without an insulat- 
 ing head, for bridging a discontinuity in 
 a resistance box or switchboard. 
 
 Pipe Conduit. A conduit formed of suit- 
 ably prepared metallic pipes surrounded 
 either on the interior or the exterior with 
 a cementing compound. 
 
 Pipe Pole. (1) A pole for aerial wires, 
 formed of iron pipes, usually in lengths or 
 sections of tapering diameter. (2) A pole 
 of iron or steel in tubular form. 
 
 Pipette. A glass tube suitable for holding 
 and removing small quantities of liquid 
 for analytical or other purposes. 
 
 Piston Manometer. A manometer 
 whose operation is dependent on the prin- 
 ciple of hydraulic pressure. 
 
Pit.] 
 
 882 
 
 [Pla. 
 
 Pitch.-^(l) The frequency of vibration of 
 a musical tone. (2) The* frequency of an 
 electrically produced tone. (3) The dis- 
 tance between successive corresponding 
 points of symmetry in a mechanical sys- 
 tem, such as of screw threads or propeller 
 blades. (4) The distance between succes- 
 sive corresponding conductors on a dyna- 
 mo armature. (5) In an armature wind- 
 ing divided into coils or segments, the 
 number of coils through which advance 
 must be made in making end connections 
 between the coils. 
 
 Pitch Line. (1) A circle upon the periph- 
 ery of which the pitch is measured. 
 (2) A circle drawn around the external 
 surface of an armature through the mid- 
 dle of the length of the inductors placed 
 thereon. 
 
 Pitch, of Poles. The distance measured 
 along the pitch line between the centres 
 either of a pair of poles of opposite sign, 
 or of a pair of poles of the same sign. 
 
 Pitch of Windings. (1) In alternators, 
 usually the distance measured along the 
 pitch line between the centres of a pair of 
 successive poles of opposite sign ; or, in 
 some alternators, half this distance. (2) , 
 In a continuous-current armature, the 
 pitch. 
 
 Pitch-Ratio of Alternator. The ratio of 
 the width of a pole-piece, or an armature 
 coil, to the pitch of the machine, or dis- 
 tance between successive field-pole cen- 
 tres as measured on the pitch line. 
 
 Pith. A light cellular substance that 
 forms the central portions of the stalls of 
 certain plants. 
 
 Pith Balls. Two balls of pith, suspended 
 from an insulated conductor by conduct- 
 ing threads of cotton, or other semi-con- 
 ducting substance, and employed for 
 showing the presence of a charge on the 
 same by their mutual repulsion. 
 
 Pith-Ball Electroscope. An electro- 
 scope whose indications are obtained by 
 the attractions or repulsions of pith balls. 
 
 Pivot Suspension. Suspension of a 
 needle by means of a jewelled cup and a 
 metallic pivot. 
 
 Pivotal Trolley. A trolley stand in 
 which the pole is supported on a pivot, so 
 as to be capable of rotation, for the pur- 
 pose of reversing the direction. 
 
 Plain-Pendant Argand Electric Burn- 
 er. A plain-pendant electric burner 
 suitable for lighting an Argand gas 
 burner. 
 
 Plain-Pendant Electric Burner. A gas 
 burner provided with a pendant for the 
 
 purpose of lighting the gas by means of a 
 spark, after the gas has been turned on 
 by hand. 
 
 Plaited Electrode Accumulator. A 
 form of storage cell or accumulator, in 
 which the electrodes consist of plaited 
 strips or ribbons of lead. 
 
 Plane Angle. (1) An angle contained 
 between two straight lines. (2) An angle 
 lying in a plane. 
 
 Plane of Polarization of Light. (1) The 
 plane of incidence in a ray of light polar- 
 ized by reflection. (2) A plane perpen- 
 dicular to the plane of vibration of plane 
 polarized light. 
 
 Plane Vector. A quantity which pos- 
 sesses not only magnitude but also direc- 
 tion in a single plane. 
 
 Planimeter. An instrument for auto- 
 matically integrating the areas of plane 
 curves, around the contour of which a 
 fiducial point on the instrument is carried. 
 
 Piano-Concave. Flat on one side and 
 concave on the other. 
 
 Piano-Convex. Flat on one side and con- 
 vex on the other. 
 
 Plant. An installation. 
 
 Plant Efficiency. (1) The efficiency of a 
 plant or electric installation. (2) The ef- 
 ficiency of a plant as distinguished from 
 the distribution system which it operates* 
 or by which it may be operated. 
 
 Plant Efficiency of Motor. The effi- 
 ciency of a motor, as distinguished from 
 the efficiency of the system with which 
 it is connected. 
 
 Plant Electricity. Electricity produced 
 by plants during their growth. 
 
 Plastic. Possessing the property of plas- 
 ticity. 
 
 Plastic-Circuit Microphone. A micro- 
 phone which operates by varying the re- 
 sistance of a plastic circuit. 
 
 Plastic Rail-Bond. In street-railway 
 systems, a rail-bond in which contact is 
 secured with the rail-ends by^ sodium 
 amalgam, or other conducting material 
 applied in a plastic condition. 
 
 Plasticity. (1) The property of readily 
 changing form under continuous stress. 
 (2) The property of possessing small re- 
 sistance to distortional stress. 
 
 Plate Condenser. (1) A condenser, the 
 metallic coatings of which are placed on 
 suitably supported dielectric plates. (2) A 
 condenser made up of one or more pairs of 
 conducting plates separated by a plate or 
 plates of non-conducting material. 
 
Pla.] 
 
 
 883 
 
 [Pin. 
 
 Plated. Electro-plated, or covered with 
 an electro-metallurgical coating. 
 
 Platform Controller. An electrical car- 
 controller placed on the platform of a car 
 for the purpose of starting, stopping and 
 regulating the speed of the car. 
 
 Platform Coupling. An electric coup- 
 ling connecting two cars and placed on 
 or beneath the platform of the cars. 
 
 Platinating. Covering a conducting sur- 
 face electrolytically with platinum. 
 
 Plating. A word frequently used for elec- 
 tro-plating. 
 
 Plating Balance. An automatic device 
 for disconnecting the current from an 
 article to be plated, as soon as a certain 
 Increase in weight has been reached. 
 
 Plating Dynamo. A dynamo employed 
 for furnishing the current required for a 
 plating process. 
 
 Plating Trough. A term sometimes em- 
 ployed for plating bath. 
 
 Platinoid. An alloy consisting of German 
 silver with one or two per cent, of metal- 
 lic tungsten, whose electric resistivity is 
 only slightly affected by changes of tem- 
 perature. 
 
 Platinum. A heavy, refractory and not 
 readily oxydizable metal of a tin-white 
 color. 
 
 Platinum Alloy. An alloy of platinum, 
 commonly a platinum-silver alloy. 
 
 Platinum Black. Finely divided plati- 
 num that possesses in a marked degree 
 the power of absorbing or occluding 
 gases. 
 
 Platinum Fuse. A thin platinum wire 
 rendered incandescent by the passage of 
 an electric current, and employed for the 
 ignition of a charge of powder. 
 
 Platinum-Iridium Alloy. An alloy of 
 platinum and iridium employed for the 
 manufacture of wire sometimes used in 
 resistance coils on account of its low tem- 
 perature coefficient of resistivity. 
 
 Platinum Lamp. (1) A lamp whose in- 
 candesjcent filament is formed of a plati- 
 num wire. (2) A lamp of molten plati- 
 num. (3) A violle. 
 
 Platinum-Silver Alloy. A name usually 
 applied to a particular alloy of one part 
 of platinum and two parts of silver, pos- 
 sessing a low temperature-coefficient of 
 resistivity. 
 
 Platinum Standard Light, (1) The 
 luminous intensity emitted perpendicu- 
 larly by a surface of platinum one square 
 centimetre in area, at its temperature of 
 fusion. (2) The Violle standard. 
 
 Platinum Sulphuric Acid Voltameter. 
 A platinum voltameter. 
 
 Platinum Voltameter. (1) A voltameter 
 employing platinum electrodes. (2) A 
 voltameter furnished with platinum elec- 
 trodes immersed in a dilute solution of 
 sulphuric acid and water. 
 
 Platining. (1) Covering a surface elec- 
 trolytically with platinum. (2) Platinum 
 plating ; or, electro-plating with plati- 
 num. 
 
 Platinizing. (1) Obtaining a platinum 
 coating of a conducting surface by simple 
 immersion in a solution of a platinum salt. 
 (2) Platining. 
 
 Platymeter. An instrument employed 
 for comparing the capacity of two con- 
 densers, or the specific inductive capaci- 
 ties of two dielectrics. 
 
 Plow. A term sometimes employed for 
 the sliding contact and its support that is 
 pushed before a car, along the trolley 
 conductors in an underground trolley 
 system. 
 
 Plow, Electric. An electrically propelled 
 plow employed in agriculture. 
 
 Plucker Tube. A modification of a 
 Geissler tube employed for studying the 
 stratification of the light, and the pecul- 
 iarities of the space adjoining the nega- 
 tive electrode. 
 
 Plug. (1) A suitably-shaped metallic key 
 provided with an insulating handle and 
 employed for closing or making contacts. 
 (2) An incompetent telegraph operator. 
 
 Plug Cut-Out. A cut-out employing 
 fuse-plugs. 
 
 Plug Hole. The hole provided in a plug 
 switch for the introduction of a plug. 
 
 Plug Key. A key-shaped plug. 
 
 Plug Operator. A term of contempt 
 sometimes applied to an inefficient tele^ 
 graphic operator. 
 
 Plug Resistances. (1) A number of separ- 
 ate resistances that can be introduced into 
 a circuit by unplugging. (2) The resist- 
 ances of the ordinary resistance box. 
 
 Plug Sleeve. The contact cylinder on 
 the surface of a telephone-switchboard 
 plug- 
 Plug Switch. A switch operated by the 
 insertion of a metallic plug between two 
 insulated metallic segments connected to 
 a circuit, and separated by air-spaces for 
 the reception of the plug key. 
 Plug Switchboard. A switchboard 
 whose various circuits are inter-connected 
 by means of plug keys. 
 Plugging. (1) Completing a circuit by 
 
Plu.] 
 
 884 
 
 [Pol. 
 
 means of plugs. (2) In a telephone 
 switchboard, the operation of making 
 the connections by inserting plugs in the 
 proper jacks. 
 
 Plumbago. (1) An allotropic modifica- 
 tion of carbon. (2) Graphite. 
 
 Plunge Battery. The couples of a vol- 
 taic battery so supported on a horizontal 
 bar as to be capable of being simultane- 
 ously placed in or removed from the ex- 
 citing liquid. 
 
 Plunger Door-Contact. A form of elec- 
 tric contact for doors in which the closing 
 of the door forces in a small plunger 
 against the tension of a spring, thereby 
 either making or breaking an electric 
 alarm circuit. 
 
 Plunger Floor - Contact. A form of 
 plunger contact suitable for being placed 
 on the floor and operated by the foot. 
 
 Plunger Switch. A switch, the operat- 
 ing lever cylinder of which passes through 
 a bushing in a switchboard, so as to make 
 and break contacts at the back of the 
 switchboard. 
 
 Plus Charge. A positive charge. 
 
 Pneumatic. Of or pertaining to pneuma- 
 tics. 
 
 Pneumatic Car-Brake Mechanism. A 
 car-brake operated by air-pressure. 
 
 Pneumatic Perforator. A paper perfor- 
 ator operated by compressed air. 
 
 Pneumatic Rodding. A method of in- 
 troducing a cable or wire into the duct of 
 a conduit by the movement of a dart 
 driven through the duct by air pressure. 
 
 Pneumatic Telegraph. A form of in- 
 strument for transmitting signals by 
 means of air pressure. 
 
 Pneumatic Transmission. Transmis- 
 sion of objects or of power, effected by 
 means of compressed air. 
 
 Pneumatics. That branch of physics 
 which treats of the properties of gases 
 either at rest or in motion. 
 
 Pocket Galvanometer. A galvanometer 
 suitable for carrying in the pocket. 
 
 Pocket Gauge, Electric. A rough form 
 of pocket galvanometer. 
 
 Pocket Telegraphic-Relay. A relay 
 sufficiently small to be readily carried in 
 the pocket. 
 
 Pockets in Inside Wiring System. 
 Hollow spaces provided in the walls, 
 floors or ceilings of a building for draw- 
 ing wires in, for making connections, or 
 for inserting safety devices. 
 
 Poggendorff's Voltaic Cell. The name 
 sometimes given to the Grenet cell. 
 
 Point Discharge. A term sometimes ap- 
 plied to a convective discharge. 
 
 Point of Origin. (1) In graphics, the 
 point where the axes of co-ordinates start. 
 (2) The point at which a curve starts. 
 
 Points on Lightning Rod. Points of 
 unoxydizable metal placed on lightning 
 rods to effect the quiet discharge of a 
 cloud by convection streams. 
 
 Points of Compass. (1) The thirty-two 
 points into which the edge or periphery 
 of a compass card is divided. (2) The 
 rhumbs of a compass. 
 
 Polar. Of or pertaining to a pole. 
 
 Pointer Telegraph. A term sometimes 
 used for a dial telegraph. 
 
 Polar Aurora. A general term for the 
 Northern or Southern light. 
 
 Polar Bore of Field Frame. The bore 
 or cylindrical hollow space excavated in 
 a field frame for the reception of an ar- 
 mature. 
 
 Polar Duplex. A system of differential 
 duplex-telegraphy employing polar-re- 
 ceiving relays. 
 
 Polar Duplex-Telegraphy .Telegraphic 
 communication obtained by means of a 
 differential duplex in which the current 
 flowing from the home battery to line is 
 reversed when the home key is depressed. 
 
 Polar Electrolysis. (1) A form of elec- 
 trolysis attended by destruction of the 
 tissues. (2) Galvano- Caustics. 
 
 Polar Relay. In telegraphy, a relay hav- 
 ing a normally polarized armature, as 
 distinguished from a neutral relay, in 
 which the armature is normally in neu- 
 tral magnetic condition. 
 
 Polar Surface of Magnet. (1) The sur- 
 faces of one or both poles of a magnet. 
 (2) A surface of magnetic material from 
 which or into which magnetic flux 
 passes. 
 
 Polar Tips. The free ends of the field- 
 magnet pole-pieces of a dynamo-electric 
 machine. 
 
 Polar Transformer. A term sometimes 
 employed for an open-circuit transformer. 
 
 Polar Variation Diagram. A diagram 
 drawn to polar co-ordinates and represent- 
 ing some relation between periodically 
 varying quantities. 
 
 Polar Zone. The zone or region in the 
 human body surrounding a therapeutic 
 eleotrode. 
 
 Polariscope, Electric. An electric ap- 
 paratus for polarizing electro-magnetic 
 waves and for revealing the presence of 
 polarization. 
 
Pol., 
 
 885 
 
 [Pol. 
 
 Polarity. (1) The possession of poles, or 
 of opposite properties, at opposite ends. 
 (2) The condition of electric or magnetic 
 differentiation between properties of elec- 
 tric or magnetic flux depending on and 
 inherent in the direction of such flux. 
 
 Polarity Indicator. Any device for de- 
 termining the direction of a current or 
 the polarity of a magnet. 
 
 Polarization Battery. A term some- 
 times employed for a secondary or storage 
 battery. 
 
 Polarization Current. In electro-thera- 
 peutics the constant current which, when 
 passed through a nerve, produces therein 
 the electro-tonic state. 
 
 Polarization Current from Fault in 
 Cable. A current due to the polarization 
 of a fault or break in a cable under the 
 action of a testing current. 
 
 Polarization, Electric.--(l) In dielectrics, 
 the condition of being subjected to elec- 
 trification. (2) In dielectrics, the condi- 
 tion of containing or restoring a residual 
 charge. (3) In electrolysis, the condi- 
 tion of having free ions liberated at the 
 electrodes, whereby a C. E. M. F. is set up. 
 
 Polarization Fault-Current of Cable. 
 A current produced in a cable due to the 
 counter-electromotive force set up in a 
 fault under the action of a signalling, 
 testing, or natural current. 
 
 Polarization of Dielectric. (1) A molec- 
 ular strain produced in the dielectric of 
 a Leyden jar, or other condenser, by the 
 attraction of the electric charges on its 
 opposite faces, or by electrostatic stress. 
 (2) A term sometimes employed for elec- 
 tric displacement. 
 
 Polarization of Electrolyte. An as- 
 sumed formation of molecular groups or 
 chains in which the poles of all the mole- 
 cules of any chain are turned in the same 
 direction, that is with their positive poles 
 facing the negative plate, and their nega- 
 tive poles facing the positive plate. 
 
 Polarization of I^ight. The condition of 
 a ray of light in which the vibrations of 
 the ether by which the light is propagat- 
 ed are all limited to a single plane, the 
 plane perpendicular to which is called the 
 plane of polarization. 
 
 Polarization of Voltaic Cell. The col- 
 lection of a gas, generally hydrogen, on 
 the surface of the negative element of a 
 voltaic cell. 
 
 Polarization Battery. A term some- 
 times used for secondary or storage bat- 
 tery. 
 
 Polarization Photometer. A photo- 
 
 meter in which the illumination of the 
 stronger of two luminous sources to be 
 compared is reduced by polarization. 
 
 Polarized Armature. An armature 
 which possesses a polarity independently 
 of that imparted by the working cur- 
 rent. 
 
 Polarized Bell. An electro-magnetic 
 bell provided with a polarized armature. 
 
 Polarized Indicator. Any electro-mag- 
 netic indicator employing a polarized 
 armature. 
 
 Polarized Ink-Recorder. An ink-re- 
 corder employing a polarized armature. 
 
 Polarized Radiation. Any radiation 
 whose waves are polarized, or restricted 
 to a particular plane of vibration. 
 
 Polarized Relay. (1) A telegraphic re- 
 lay provided with a permanently magnet- 
 ized armature in place of the ordinary 
 soft-iron armature. (2) A polar relay. 
 (3) A non-polarized or neutral relay, as 
 distinguished from a polarized relay. 
 
 Polarized Ring-Off Drop. A ring-off 
 drop in a telephone switchboard having 
 a polarized armature. 
 
 Polarized Sounder. A telegraphic 
 sounder employing a polarized armature. 
 
 Polarizing Current. A current which 
 produces polarization. 
 
 Polarizing Spectro-Photometer. A 
 spectro-photometer employing a polari- 
 scope. 
 
 Pole Armature. (1) An armature whose 
 coils are wound on separate poles that 
 project from the periphery of a disc, 
 drum, or ring armature. (2) An armature 
 having polar projections. 
 
 Pole Bands. Metallic bands placed 
 around a pole for the purpose of support- 
 ing guy-rods or brackets. 
 
 Pole - Changing and Interrupting 
 Electrode Handle. A handle provided 
 for the ready insertion of the electro- 
 therapeutic electrodes, containing means 
 for interrupting or changing the direction 
 of the current. 
 
 Pole Changer. (1) A switch or key for 
 reversing the direction of a current. 
 (2) A reverser. (3) A generator of alter- 
 nating currents at a telephone exchange, 
 consisting of an electro-magnetically 
 driven pendulum which periodically re- 
 verses a call battery. 
 
 Pole-Changing Key. (1) A pole changer. 
 (2) A key which effects a reversal. 
 
 Pole-Changing Switch. A switch em- 
 ployed for changing the direction of the 
 current in any circuit. 
 
Pol.] 
 
 886 
 
 [Pol. 
 
 Pole Clamp. An iron clamp on a pole 
 
 employed for the support of span wires or 
 
 brackets. 
 Pole Climbers. Devices employed by 
 
 line-men for climbing wooden telegraphic 
 
 poles. 
 
 Pole Clip. A pole clamp. 
 
 Pole Counter. A hand-operated register- 
 ing device employed for counting tele- 
 graph or other poles. 
 
 .Pole Guys. A guy employed for the stif- 
 fening of a pole. 
 
 Pole Hood. A hood or cover placed at 
 the top of a pole. 
 
 Pole Indicator. Any device for readily 
 determining the polarity of a pole, of a 
 magnet, or of an electric source. 
 
 Pole-Pieces of Dynamo or Motor. 
 A mass of iron or steel connected with the 
 poles of the field-magnets of a dynamo 
 or motori and shaped to conform to the 
 outline or contour of the armature. 
 
 Pole Platform. A platform, capable of 
 supporting one or more men, placed on a 
 terminal pole, and provided with a cable 
 box for the purpose of affording a ready 
 means of inspecting and arranging the 
 conductors in the box. 
 
 Pole Roof. A metallic cap or roof of a 
 telegraph or telephone pole. 
 
 Pole Shoe. A plate of iron or steel 
 mounted on, and forming the pole-piece 
 of a field magnet, and sometimes used 
 for supporting a field coil. 
 
 Pole Steps. Steps permanently fastened 
 to a wooden or iron pole to facilitate 
 climbing. 
 
 Pole Support for Arc-Lamps. A sup- 
 port placed on the top or end of a pole for 
 the reception of an arc-lamp. 
 
 Pole Tips. A name sometimes employed 
 for the horns of a dynamo field pole. 
 
 Pole Top. A fixture for the top of an 
 aerial pole provided with a number of 
 arms and insulators for the support of 
 additional aerial circuits. 
 
 Poles of Condenser. The terminals of a 
 condenser. 
 
 Poles of Magnetic Intensity. The 
 earth's magnetic poles as determined by 
 means of observations of magnetic inten- 
 sity. 
 
 Poles of Magnetic Verticity. The 
 earth's magnetic poles as determined by 
 means of a dipping needle. 
 
 Poling Boards. Short rough boards laid 
 vertically against the sides of an excava- 
 tion, in packed soil, and kept in place by 
 cross struts. 
 
 Polishing Bob. A disc of tough wood 
 provided on its edge with a ring or rim of 
 leather or hide, on which finely divided 
 emery is placed, employed, when mounted 
 on a shaft and put in rapid rotation, for 
 polishing articles so as to prepare them 
 for electro-plating. 
 
 Polishing Mop. A disc formed of circu- 
 lar pieces of calico, felt, or other similar 
 soft material, mounted on a shaft and em- 
 ployed, when put in rapid rotation, for 
 polishing surfaces for electro-plating. 
 
 Polycyclic System. A multiphase sys- 
 tem. 
 
 Polymerism. A species of isomerism in 
 which chemical compounds of the same 
 proportional constitution, as determined 
 by analysis, have different properties, due 
 to having different numbers of atoms in 
 their molecules. 
 
 Polymorphic Instrument. A term 
 sometimes used for a polymorphic ma- 
 chine. 
 
 Polymorphic Machine. An apparatus 
 capable of effecting the transformation of 
 alternating-currents from one species to 
 another. 
 
 Polyphasal Coupling of Magnetic Cir- 
 cuits. The inter-linking of magnetic 
 circuits traversed by polyphase magnetic 
 fluxes. 
 
 Polyphase. Possessing more than a single 
 phase. 
 
 Polyphase Alternator. An alternator 
 capable of supplying polyphase currents. 
 
 Polyphase Apparatus. Apparatus oper- 
 ated by polyphase currents. 
 
 Polyphase Armature. An armature so 
 wound as either to produce polyphase cur- 
 rents, or to be operated by such currents. 
 
 Polyphase Armature- Windings. 
 Windings of polyphase generators. 
 
 Polyphase Asynchronous Motor. (1) 
 An asynchronous motor operated by mul- 
 tiphase currents. (2) A multiphase in- 
 duction motor. 
 
 Polyphase Choking-Coil. (1) A choking 
 coil in a polyphase system. (2) A click- 
 ing coil operated by polyphase currents. 
 
 Polyphase Circuits. The circuits em- 
 ployed in polyphase-current distribution. 
 
 Polyphase Currents. Currents differing 
 in phase from one another by a definite 
 amount, and suitable for the operation of 
 polyphase motors or similar apparatus. 
 
 Polyphase Dynamo. A polyphase gen- 
 erator. 
 Polyphase Generator. An alternator 
 
Pol.] 
 
 887 
 
 [Pos. 
 
 which delivers two or more alternating 
 currents definitely differing in phase. 
 
 Polyphase Inductor - Alternator. An 
 inductor alternator suitable for producing 
 polyphase currents. 
 
 Polyphase Inductor-Generator. (1) A 
 polyphase genei'ator of the inductor type 
 in which no conductor or winding is 
 rotated. (2) A polyphase inductor-alter- 
 nator. 
 
 Polyphase Motor. A motor operated by 
 means of polyphase currents. 
 
 Polyphase Power. Power transmitted 
 by means of polyphase currents. 
 
 Polyphase Rotary - Converter. A ro- 
 tary converter operated by or producing 
 polyphase currents. 
 
 Polyphase Switchboard. A switch- 
 board suitable for controlling polyphase 
 circuits. 
 
 Polyphase Synchronous - Motor. A 
 synchronous motor operated by polyphase 
 currents. 
 
 Polyphase Transformer. A transform- 
 er suitable for use in connection with 
 polyphase circuits. 
 
 Polyphase Transmission. Transmis- 
 sion of power by means of polyphase 
 currents. 
 
 Polyphase Working. A general term 
 employed to express the application of 
 polyphase currents. 
 
 Polyphased Alternating-Currents. A 
 term employed for polyphase currents. 
 
 Polyphaser. (1) A term sometimes em- 
 ployed for a polyphase alternator, or 
 generator. (2) A multiphaser. 
 
 Polyphotal Arc-Light Regulator. A 
 regulator for arc-lamps suitable for use 
 in a number of series-connected arc 
 lamps. 
 
 Poacelet. A name proposed for a unit of 
 activity equal to 100 kilogramme-metres 
 per second ; or, approximately, one kilo- 
 watt. 
 
 Pondermotive Force. The force re- 
 quired for the movement of gross matter. 
 
 Pony Insulators. A name given to a par- 
 ticular type of glass telegraph insulator. 
 
 Pony Telegraphic Relay. A name ap- 
 plied to a particular form of telegraphic 
 relay. 
 
 Porcelain. A variety of insulating sub- 
 stance, made from kaolin. 
 
 Porcelain Insulator. Any insulator of 
 porcelain for supporting a wire. 
 
 Porcelain Wire-Tube. A porcelain tube 
 
 employed for passing an electric wire 
 through a partition. 
 
 Porosity. A property of matter in virtue 
 of which spaces or pores are left between 
 its constituent atoms and molecules. 
 
 Porous Cell. A jar of unglazed earthen- 
 ware employed in a double-fluid voltaic 
 cell to mechanically separate the two 
 electrolytes. 
 
 Porous Cup. A porous cell. 
 
 Porous Insulation. An insulating ma- 
 terial containing air or other gas. 
 
 Porous Jar or Pot. A porous cell. 
 
 Porret's Phenomenon. An increase in 
 the diameter of a nerve fibre in the neigh- 
 borhood of the positive pole, when trav- 
 ersed by a voltaic current. 
 
 Portable Conductors. Flexible cords 
 containing insulated wires suitable for 
 use with portable lamps, motors, or other 
 devices. 
 
 Portable Electrometer. A form of read- 
 ily transportable Thomson electrometer. 
 
 Portable Igniting Device. (1) A porta- 
 ble electric mine-exploder. (2^ A porta- 
 ble electric gas-igniter. 
 
 Portable-Lamp Guard. A guard pro- 
 vided for the protection of a portable 
 lamp. 
 
 Portable Tachometer. A portable speed 
 indicator. 
 
 Portative Power of Magnet. The lift- 
 ing or sustaining power of a magnet. 
 
 Portelectric. (1) An electric carrier. (2} 
 A system of electric transportation by 
 means of the successive attractions of a 
 number of hollow helices of insulated 
 wire on a moving iron core. 
 
 Portrait, Electric. A portrait formed on 
 paper by the electric volatilization of gold 
 or other metal. 
 
 Position-Finder, Electric. An electric 
 device by means of which the position of a 
 distant object can be determined. 
 
 Positive Brush of Dynamo. The brush 
 of a dynamo out from which flows the 
 current generated in the armature. 
 
 Positive Brush of Motor. The brush 
 connected to the positive terminal of a 
 driving source. 
 
 Positive Carbon. That carbon of a vol- 
 taic arc out from which the current flows 
 into the arc. 
 
 Positive Charge. (1) According to th 
 double-fluid hypothesis, a charge of posi- 
 tive electricity. (2) According to the 
 single-fluid hypothesis, any excess of an 
 assumed electric fluid. (3) A charge of 
 electricity having a positive potential. 
 
Pos.] 
 
 [Pot. 
 
 Positive Currents. A term employed in 
 telegraphy for currents sent over a line 
 from the positive pole of a battery. 
 
 Positive-Direction of Lines of Mag- 
 netic Force. The direction in which a 
 free north-seeking pole would move along 
 the lines of force when placed in a mag- 
 netic field. 
 
 Positive - Direction of Simple - Har- 
 monic Motion. The motion which a 
 body moving with simple-harmonic mo- 
 tion has, when its corresponding circularly 
 moving point moves counter-clockwise. 
 
 Positive-Direction of Electric Con- 
 vection of Heat. A direction in which 
 heat is transmitted through an unequally 
 heated conductor by electric convection 
 during the passage of electricity through 
 the conductor, the same as that of the 
 current. 
 
 Positive-Direction Round a Circuit. 
 In a plane circuit looked at from the posi- 
 tive side, a direction opposed to that of 
 the hands of a clock. 
 
 Positive-Direction Through a Circuit. 
 In a plane circuit carrying a positive cur- 
 rent, a direction through the circuit simi- 
 lar to that of the advance of a corkscrew 
 which is twisted round in the direction 
 of the current. 
 
 Positive Electricity.^ (1) One of the 
 phases of electric excitement. (2) That 
 kind of electric charge produced on cot- 
 ton when rubbed against resin. 
 
 Positive Electrification. (1) The charge 
 of a body with positive electricity. (2) A 
 positive charge. (3) An electrification of 
 positive potential. 
 
 Positive Electrode. The electrode con- 
 nected with the positive pole of an elec- 
 tric source. 
 
 Positive Electromotive Force. An 
 E. M. F. which will communicate a posi- 
 tive charge. 
 
 Positive Feeders. The feeders that are 
 connected with the positive terminal of 
 a dynamo. 
 
 Positive Fluid. (1) The specific fluid that 
 was formerly believed by the adherents 
 of the double-fluid electric hypothesis to 
 be the cause of electric excitement. (2) 
 The surplusage of an assumed single 
 electric fluid. 
 
 Positive Lead. In a system of parallel 
 distribution, a lead connected with the 
 positive generator-terminal, or with the 
 positive bus-bars. 
 
 Positive Omnibus-Bars. The bus-bars 
 that are connected with the positive ter- 
 minal of a dynamo. 
 
 Positive Phase of Electrotonus. An 
 increase in the electromotive force of a 
 nerve produced by sending a current 
 through the nerve in the same direction 
 as the nerve current. 
 
 Positive Plate of Storage Cell. (1) That 
 plate of a storage cell which is converted 
 into, or covered by, a layer of lead peroxide 
 by the action of the charging current. 
 (2) That plate of a storage cell which is 
 connected with the positive terminal of a 
 charging source, and which is, therefore, 
 the positive pole* of the cell on dis- 
 charging. 
 
 Positive Plate of Voltaic Cell. (1) The 
 electro-positive element of a voltaic 
 couple. (2) That element of a voltaic 
 couple which is positive in the electrolyte 
 of the cell. (3) The plate which forms 
 above the surface of the electrolyte, the 
 negative pole of the cell. 
 
 Positive Pole. That pole of an electric 
 source out of which the current is as- 
 sumed to flow. 
 
 Positive Potential. (1) That potential in. 
 a circuit external to a source from which 
 the electric current flows. (2) The higher 
 potential or higher electric level. 
 
 Positive Rotation. Left-handed or coun- 
 ter-clockwise rotation. 
 
 Positive Side of Circuit. That side of a 
 circuit bent in the form of a circle in 
 which, if an observer stood with his head 
 in the positive region, he would see the 
 current pass around him counter-clock- 
 wise. 
 
 Positive Spark. A spark produced by 
 the disruptive discharge of a positively 
 charged conductor. 
 
 Positive Terminal. The terminal con- 
 nected with the positive pole of a source. 
 
 Positive Wire. The wire connected with 
 the positive pole of a source. 
 
 Positively Excited. Charged with posi- 
 tive electricity. 
 
 Pot Operator. (1) The operator which i 
 the double inverse of the curl operator. 
 (2) The operator which acting upon a 
 point function in space produces its vector 
 potential. 
 
 Potash Brush. A brush employed in 
 cleansing, by the use of a caustic solution, 
 surfaces which are to be electro-plated. 
 
 Potential Dynamometer. An electro- 
 dynamometer suitably arranged for the 
 measurement of electric potential differ- 
 ences. 
 
 Potential, Electric. (1) The power of 
 doing electric work. (2) Electric level. 
 
Pot.] 
 
 889 
 
 [Pra. 
 
 Potential Energy. (1) Stored energy. 
 
 (2) Potency or capability of doing work. 
 
 (3) Energy possessing the power or potency 
 of doing work, but not actually perform- 
 ing such work. 
 
 Potential Function. A point function 
 of space, whose space differentiation 
 gives a vector point-function. 
 
 Potential Galvanometer. A term some- 
 times applied to a voltmeter. 
 
 Potential Gradient. (1) The rate-of-fall 
 of potential at a point. (2) A line repre- 
 senting the fall of potential in a circuit. 
 
 Potential Indicator. An apparatus for 
 indicating potential difference. 
 
 Potential of Conductors. (1) The rela- 
 tion existing between the quantity of 
 electricity in a conductor and its ca- 
 pacity. (2) That property of a conductor 
 whereby electric work is done when an 
 electric charge is moved towards it. 
 
 Potential Beceptacle. A receptacle in 
 a switchboard, wall, cover, base, or other 
 device, for receiving a plug connected to 
 a potential-indicator, or voltmeter. 
 
 Potentiometer. An apparatus for the 
 galvanometric measurement of electro- 
 motive forces, or differences of potential, 
 by a zero method, and by relation to a 
 standard E. M. F. 
 
 Potentiometer Voltmeter. A voltmeter 
 operating on the potentiometer principle 
 and employing a standard voltaic cell as 
 its basis of measurement. 
 
 Potentiometer Wire. A graduated wire 
 employed in a potentiometer for the pur- 
 pose of securing proportionate linear re- 
 sistances and thereby proportional poten- 
 tial differences. 
 
 Pounds-Per-Mile-Ohm. (1) A standard 
 of conductivity of telegraph or telephone 
 wires. (2) The weight of a uniform wire 
 offering one ohm per mile at standard 
 temperature. 
 
 Poundal. (1) The -weight of a pound, or 
 the earth's attraction upon the mass of a 
 pound of matter, at any terrestrial locality. 
 (2) A gravitational unit of force. 
 
 Power. (1) Rate-of-doing-work, express- 
 ible in watts, joules-per-second, foot- 
 pounds-per-hour, etc. (2) Activity. 
 
 Power Cable. A cable employed for the 
 electric transmission of power. 
 
 Power Circuits. Circuits employed for 
 the electric transmission of power. 
 
 Power Coefficient. (1) In an alternat- 
 ing-current circuit, the ratio of the 
 power component of electromotive force 
 to the power component of current. (2) 
 
 13 
 
 The apparent resistance of an alternating- 
 current circuit. 
 
 Power Cylinder. The commutating 
 cylinder of a street-car controller as dis- 
 tinguished from the reversing cylinder. 
 
 Power, Electric. Power developed by 
 means of electricity. 
 
 Power Electromotive Force. A term 
 sometimes employed for that component 
 of the E. M. F. acting in the same direc- 
 tion with the current, or in phase with it, 
 and expended in overcoming effective or 
 ohmic resistance. 
 
 Power Factor. The ratio of the true 
 watts to the apparent volt-amperes in an 
 alternating-current conductor, circuit, or 
 device. 
 
 Power-Factor of Transformer. The 
 ratio of the true watts absorbed by a 
 transformer under a given load to the ap- 
 parent watts absorbed. 
 
 Power Generator. A generator of alter- 
 nating currents at a central telephone ex- 
 change. 
 
 Power-House. A house provided with 
 the plant necessary for the production of 
 the electric power required in a system 
 of electric distribution. 
 
 Power Measurer, Electric. A watt- 
 meter. 
 
 Power Meter. A wattmeter. 
 
 Power of Periodic Currents. With 
 simple-harmonic currents, the product of 
 effective current strength, the driving 
 effective pressure, and the cosine of the 
 difference of phase between them. 
 
 Power-Wire of Monocyclic System. 
 The wire or circuit of a monocyclic sys- 
 tem employed for supplying currents for 
 the operation of triphase electric motors. 
 
 Poynting's Law. At any point in space, 
 electro-magnetic energy moves perpen- 
 dicularlv to the plane containing the lines 
 of electric force and the lines of magnetic 
 force, and the amount of energy per second 
 crossing the unit area of this plane is 
 equal to the product of the intensities of 
 the two forces, multiplied by the sine of 
 the angle between them, and divided by 
 
 4T. 
 
 Practical Current. A term sometimes 
 employed for the effective current in an 
 alternating-current circuit. 
 
 Practical Solenoid. A name applied to 
 an ordinary solenoid, in order to distin- 
 guish it from an ideal solenoid. 
 
 Practical Unit of Inductance. (1) A 
 unit of length equal to the earth's quad- 
 rant, or 10 9 centimetres. (2) The henry. 
 Vol. 2 
 
Pra.] 
 
 890 
 
 [Pri. 
 
 Practical Unit of Magneto-Motive 
 Force. A value of magneto-motive force 
 equal to 4?r multiplied by an ampere of one 
 turn, or equal to one-tenth of an absolute 
 unit of M. M. F. 
 
 Practical Unit of Self-induction. A 
 term frequently used for the practical 
 unit of inductance. 
 
 Practical Units. Definitely related mul- 
 tiples or sub-multiples of the absolute or 
 centimetre-gramme-second units. 
 
 Preamble. In telegraphy, the opening 
 words of a despatch containing the names 
 of the sending and delivery stations, the 
 number of words in the message, the 
 code time, and other service instructions, 
 as distinguished from the text of the mes- 
 
 Prefix. In telegraphy, a code letter or 
 group of letters prefixed to a message to 
 indicate its nature or relative importance. 
 
 Prepayment Meter. A device whereby 
 a certain electric service is given by 
 means of an electric penny-in-the-slot ap- 
 paratus. 
 
 Presbyopic. Far-sighted. 
 
 Press Button. A push-button. 
 
 Press Message. (1) A message directed 
 to a newspaper or daily publication. (2) 
 A news message. 
 
 Press Telegram. A press message. 
 
 Pressant. A name proposed for a unit of 
 magneto-motive force. 
 
 Pressel. (1) A press switch or push con- 
 nected to the end of a flexible pendant 
 conductor. (2) A pendant press-button. 
 
 Pressure, Electric. A term sometimes 
 employed for difference of potential, or 
 electromotive force. 
 
 Pressure Equalizer. (1) An automatic 
 device employed in connection with a 
 storage battery to maintain a uniform 
 pressure at its terminals under different 
 loads. (2) A regulating device employed 
 in a system of electric distribution for 
 maintaining the pressure uniform. 
 
 Pressure Indicator. Any device for in- 
 dicating the electric pressure in a circuit. 
 
 Pressure Panel of Switchboard. That 
 panel in a switchboard which contains 
 apparatus for measuring the mean electric 
 pressure in the power house. 
 
 Pressure Recording-Gauge. Any form 
 of recording voltmeter. 
 
 Pressure .Wires. Small insulated copper 
 conductors, employed in a system of un- 
 derground street mains, extending from 
 points of junction between the feeders 
 and the mains to the central station, to 
 
 indicate in the central station the pres- 
 sure supplied to the mains. 
 
 Pricking Wires. A method sometimes 
 adopted for locating a wire, by connect- 
 ing a battery with one pole to earth and 
 the other pole to the wire sought for, by 
 means of a brad-awl or needle inserted 
 through the gutta-percha insulating ma- 
 terial. 
 
 Primary Admittance. The admittance 
 of the primary coil or coils of an alternat- 
 ing-current transformer or induction ma- 
 chine. 
 
 Primary Ampere-Turns. The ampere- 
 turns in the primary coil of a transformer. 
 
 Primary Battery. The combination of a 
 number of separate primary cells to form 
 a single electric source. 
 
 Primary Cell. A term sometimes em- 
 ployed for a voltaic cell. 
 
 Primary Coil of Transformer. (1) That 
 coil of an induction coil or transformer 
 on which the primary electromotive force 
 is impressed. (2) The driving coil of a 
 transformer. (3) The coil which receives 
 energy prior to transformation. 
 
 Primary Currents. Currents flowing in 
 a primary circuit, as distinguished from 
 currents flowing in a secondary circuit. 
 
 Primary Cut-Out. A cut-out placed in 
 the primary circuit of a transformer. 
 
 Primary Electric Clock. A term some- 
 times employed in place of controlling or 
 master clock. 
 
 Primary Electric Heater. A term pro- 
 posed for the main electric heater in a 
 building. 
 
 Primary Electromotive Force. The 
 electromotive force applied to the pri- 
 mary coil of a transformer. 
 
 Primary Element of Induction Motor. 
 The element connected with the line or 
 lines, as distinguished from the element- 
 closed upon itself. 
 
 Primary Fuse Box. A fuse box placed 
 in the primary circuit of an induction 
 coil or transformer. 
 
 Primary Impedance. (1) The imped- 
 ance of the primary coil of a transformer, 
 or of an induction machine. (2) The 
 impedance 'of the primary coil of a trans 
 former, or of an induction machine, in- 
 dependent of the reactance of mutual 
 inductance, or the C. E. M. F. of mutual 
 linkage. 
 
 Primary Plate of Condenser. That 
 plate of a condensing transformer in 
 which the inducing charge is placed in 
 order to induce a charge of different 
 potential in the secondary plate. 
 
Pri.] 
 
 891 
 
 [Pro. 
 
 Primary Spiral of Induction Coil. The 
 primary of an induction coil or trans- 
 former. 
 
 Prime Conductor. The positive conduc- 
 tor of a frictional electric or electrostatic 
 machine. 
 
 Prime Flux-Density. The magnetic 
 density of the prime magnetic flux in a 
 ferric circuit. 
 
 Prime Magneto-Motive Force. The 
 magneto-motive force due to the magnet- 
 izing current in a ferric circuit. 
 
 Prime Magnetic Flux. (1) A term em- 
 ployed for the flux produced in a ferric 
 circuit by the prime magneto-motive 
 force, as distinguished from the induced, 
 aligned, or structural magneto-motive 
 force. (2) Magnetizing force as distin- 
 guished from magnetic induction. 
 
 Prime Motor. A prime mover. 
 
 Prime Mover. A motor which drives the 
 secondary motors or movers. 
 
 Primordial Atoms. The atoms or com- 
 pounds into which it has been assumed 
 that the so-called elementary atoms of 
 ordinary matter are broken up by means 
 of the cathode rays. 
 
 Principal Circuit. A main circuit as dis- 
 tinguished from a derivation circuit. 
 
 Principal Current. A main current as 
 distinguished from a derivation current. 
 
 Principal Telegraphic Circuit. A term 
 sometimes used for the main circuit. 
 
 Principal Telegraphic Current. A 
 term sometim.es employed for the main 
 current. 
 
 Printing Telegraphy. A system of teleg- 
 raphy in which the messages received 
 are printed on a paper fillet. 
 
 Prism Error of Compass. The error in 
 a magnetic bearing due to an inaccurate 
 setting of the prism relatively to the com- 
 pass card. 
 
 Probable Error of an Observation. A 
 magnitude of accidental error in the re- 
 peated observation of a quantity, such 
 that it is just as probable that the real 
 accidental error is greater as that it is less 
 than this magnitude. 
 
 Probe, Electric. A metallic conductor 
 inserted in the body of a patient in order 
 to ascertain the position of a bullet or 
 other foreign metallic substance. 
 
 Process of Carbonization. Means for 
 carbonizing carbonizable material. 
 
 Production of Cold by Electricity. 
 The absorption of energy, and consequent 
 reduction of temperature at a thermo- 
 electric junction, by the passage of an 
 
 electric current in a certain direction 
 across such junction. 
 
 Production of Electricity by Light. 
 The production of electric difference of 
 potential by the action of light. 
 
 Prognosis, Electric. A prognosis or pre- 
 diction of the fatal or non-fatal termina- 
 tion of a disease from an electric diagno- 
 sis, based on the exaggerated or dimin- 
 ished reactions of the excitable tissues of 
 the body, when subjected to the varying 
 influences of electric currents. 
 
 Progression of Magnetic Flux. In a 
 polyphase motor, the circular motion of 
 the magnetic flux around the field or 
 armature. 
 
 Projecting Power of Magnet. (1) The 
 range within which a magnet produces 
 sensible attraction or repulsion. (2) The 
 power of an electro-magnet to repel a 
 suitably placed armature. 
 
 Projection Arc-Lamp. An arc- lamp 
 suitable for use in a projector or search- 
 light. 
 
 Projector, Electric. A projector or 
 search-light provided with an electric arc- 
 light at its focus. 
 
 Projection Armatures. Slotted arma- 
 tures in which the width of the slot is suf- 
 ficiently great to leave a distinct projec- 
 tion in the armature surface as distin- 
 guished from tunnel armatures in which 
 the slot is very narrow. 
 
 Prony Brake. A mechanical device for 
 measuring the power of a driving shaft 
 by the application of a brake to the periph- 
 ery of a wheel firmly keyed on the shaft. 
 
 Proof-Plane. A small insulated conduc- 
 tor employed to take and carry electric 
 charges from the surfaces of insulated 
 charged conductors. 
 
 Proportional Coils. Pairs of resistance 
 coils, generally of 10, 100 and 1,000 ohms 
 each, forming the proportional arms of 
 a balance or bridge, and employed in the 
 box or commercial form of Wheatstone's 
 bridge. 
 
 Proportionate Arms. The two resist- 
 ances or arms of an electric bridge, whose 
 relative or proportionate resistances only 
 are required to be known, in order to de- 
 termine in connection with a known re- 
 sistance, the value of an unknown resist- 
 tance placed in the remaining arm of the 
 bridge. 
 
 Proposed Definition for 2,000 Candle- 
 Power Arc. (1) Such an arc as will re- 
 quire at ordinary pressures 450 watts ac- 
 tivity to maintain it. (2) A 450- watt arc. 
 
Pro.] 
 
 892 
 
 [Puin. 
 
 Propulsion, Electric. A general term 
 for driving by electric power. 
 
 Prostration, Electric. Physiological ex- 
 haustion or prostration, resembling that 
 produced by sun-stroke, resulting from 
 exposure to an unusually powerful arc. 
 
 Protecting Battery. In submarine cable 
 telegraphy, a battery permanently con- 
 nected to a faulty cable through a high re- 
 sistance, for the purpose of sending a 
 negative current through the fault in 
 order to keep the exposed surface of the 
 conductor free from corrosion salts. 
 
 Protection of Houses, Ships or Build- 
 ings, Electric. Means for protection 
 from the destructive effects of a lightning 
 discharge, consisting essentially in the 
 use either of lightning-rods or of an en- 
 closing conducting shell. 
 
 Protection of Metals, Electric. The 
 protection of a metal from corrosion by 
 placing it in connection with another 
 metal, which, when exposed to the cor- 
 roding liquid, vapor or gas, will form 
 with the surrounding liquid the positive 
 element of a voltaic couple and will, 
 therefore, alone be corroded. 
 
 Protection of Ship's Sheathing, Elec- 
 tric. Attaching pieces of zinc to the 
 copper sheathing of a ship for the purpose 
 of preventing the corrosion of the copper 
 by the water. 
 
 Protective Action. (1) The electric pro- 
 tection of metals. (2) The protection of 
 structures from lightning by lightning 
 protectors. 
 
 Protective Sheath. A device attached 
 to a transformer or converter, consisting 
 of a copper strip or plate connected to 
 the earth and interposed between the 
 primary and secondary windings, to pre- 
 vent any connection from taking place 
 between the high-potential primary and 
 the low-potential secondary circuit. 
 
 Protective Throw. A term proposed for 
 the protection afforded by a magnetic 
 field to paramagnetic metals exposed to 
 chemical action. 
 
 Protoplasm. Bioplasm. 
 
 Psychrometer. A form of recording hy- 
 grometer. 
 
 Public Supply Instruments. Electric 
 meters designed for registering the cur- 
 rent or energy supplied to a consumer. 
 
 Pull. A contact-maker similar in general 
 construction to a push-button, but oper- 
 ated by a pull instead of by a push. 
 
 Pull Contact. Any contact that is ef- 
 fected by the movement of a pendant or 
 pull. 
 
 Pulley. A wheel placed on a shaft for the 
 driving of the same by means of a belt. 
 
 Pull-Off. (1) An insulator employed on 
 curves to hold the trolley wire in proper 
 position. (2) A steel wire attached to a 
 trolley wire through an insulator, and 
 employed to pull the trolley wire into 
 position over a curve in the track. 
 
 Pull-Off Pole. A pole provided for the 
 suspension of a pull-off wire, or wires. 
 
 Pulsating Current. A pulsatory current. 
 
 Pulsating Electromotive Force. An 
 electromotive force whose direction is 
 pulsatory. 
 
 Pulsating Motor. A motor employing a 
 reciprocating movement in its armature 
 as opposed to the ordinary rotary motion. 
 
 Pulsation. (1) A quantity of the nature 
 of an angular velocity, equal to 2 TT mul- 
 tiplied by the frequency of the oscillation, 
 or to 2 TT divided by the duration of a 
 single period. (2) In a simple-harmonic 
 current circuit, the angular velocity of 
 the corresponding circularly moving 
 point. 
 
 Pulsation, Electric. An electric pulse 
 or oscillation. 
 
 Pulsation of Reactance. Variations 
 periodically occurring in the apparent 
 reactance of an alternating-current cir- 
 cuit or machine. 
 
 Pulsation of Resistance. Periodic vari- 
 ations in the apparent resistance of an 
 alternating current circuit or apparatus. 
 
 Pulsatory Continuous-Current. A 
 current whose direction remains constant, 
 but whose intensity is subject to steady 
 changes. 
 
 Pulsatory Electromotive Force. An" 
 electromotive force whose value is sub- 
 ject to pulsatory changes. 
 
 Pulsatory Magnetic-Field. A field 
 whose strength pulsates in such a man- 
 ner as to induce oscillatory currents in 
 neighboring circuits. 
 
 Pulsatory Magnetism. Magnetism pro- 
 duced by pulsatory currents. 
 
 Pulse, Electric. (1) An electric oscilla- 
 tion. (2) A momentary flow of electricity 
 through a conductor which gradually 
 varies from zero value to the maximum, 
 and then to zero value again, like a pulse 
 or vibration in an elastic medium. 
 
 Pumping of Alternating-Current Dy- 
 namo. A pulsation in the motion of a 
 synchronously-running alternating-cur- 
 rent generator or motor, due to imperfect 
 synchronism. 
 
 Pumping of Electric Lights. A term 
 
Pun.] 
 
 893 
 
 sometimes applied to a pulsatory or peri- 
 odic increase or decrease iu the brilliancy 
 of lights. 
 
 Punched - Clip Switch. A form of 
 switch in which the clips are punched out 
 of sheet metal. 
 
 Puncher. In automatic telegraphy, a per- 
 forator. 
 
 Punning of Telegraph Pole. The proc- 
 ess of packing the earth around the base 
 of a telegraph pole. 
 
 Pupillary Photometer. A photometer 
 whose operation is dependent on the 
 diminution of the diameter of the pupil 
 of the eye with the intensity of the light 
 striking the eye. 
 
 Pure Spectrum. A single spectrum or 
 distribution of luminous frequencies as 
 distinguished from a spectrum which is 
 formed by the superposition of a number 
 of .spectra slightly displaced with refer- 
 ence to one another. 
 
 Push. A term sometimes applied to a 
 push button. 
 
 Push Box. A box provided for the recep- 
 tion of the mechanism of a push button 
 or push. 
 
 Push Button. A device for closing an 
 electric circuit by the movement of a 
 button. 
 
 Push-Button Battler. (1) A device con- 
 nected with a push-button to show that a 
 bell connected at a distant point in the cir- 
 cuit of the button rings when the button 
 is pressed. (2) A push-button combined 
 with an electro-magnetic vibrator. 
 
 Push-Button Socket. A socket provided 
 with a push-button for the closing of a 
 circuit. 
 
 Push-Button Socket-Key. An incan- 
 descent lamp-socket so provided with a 
 push-button key as to permit the lamp to 
 be readily lighted or extinguished by the 
 same hand that holds it. 
 
 Push-Button Switch. A switch oper- 
 ated by a push-button. 
 
 Push Contact. A name sometimes ap- 
 plied to a push button. 
 
 Putting Straight. The operation of re- 
 storing the normal condition of wires 
 which have been crossed at two way 
 stations. 
 
 Pyknometer. A term sometimes used 
 
 for a specific gravity bottle, employed in 
 determining the specific gravity of a 
 liquid. 
 
 Pyr. (1) A bougie-decimale. (2) A pro- 
 posed unit of luminous intensity equal to 
 the one-twentieth of the Violle standard. 
 (3) A proposed name for the one-twen- 
 tieth of the Violle standard. 
 
 Pyrheliometer. An apparatus for meas- 
 uring the energy of solar radiation. 
 
 Pyro-Electric. Pertaining to pyro-elec- 
 tricity. 
 
 Pyro-Electric Crystal. Any crystalline 
 substance capable of producing pyro- 
 electric phenomena on being unequally 
 heated. 
 
 Pyro-Electricity. Electricity produced 
 in certain crystalline bodies by their un- 
 equal heating or cooling. 
 
 Pyrogravure. A process for the decora- 
 tion of wood, copper, or glass, by the burn- 
 ing action of an electrically or otherwise 
 heated tool. 
 
 Pyro-Magnetic. Of or pertaining to 
 pyro-magnetism. 
 
 Pyro-Magnetic Electric Device. Any 
 device operated by or employing pyro- 
 magnetism. 
 
 Pyro-Magnetic Generator or Dynamo. 
 An apparatus for producing electricity 
 directly from the heat derived from 
 burning fuel. 
 
 Pyro-Magnetic Motor. A motor con- 
 sisting of an armature formed of a disc 
 or ring of thin steel, which is set in mo- 
 tion when unequally heated, by reason of 
 the difference in the coercive force so 
 produced. 
 
 Pyro-Magnetism. A term sometimes 
 applied to the phenomena of the com- 
 bined effects of magnetism and heat. 
 
 Pyrometer. An instrument for deter- 
 mining temperatures higher than those 
 which can be readily measured by ther- 
 mometers. 
 
 Pyrometer, Electric. A device for de- 
 termining the temperature of a body by 
 the measurement of the electric resist- 
 ance of a platinum wire exposed to the 
 heat to be measured. 
 
 Pyr-Steradian. (1) The flux of light cor- 
 responding to the luminous intensity of 
 one pyr extending over the solid angle of 
 one steradian. (2) A term sometimes 
 used for lumen. 
 
Q.] 
 
 894 
 
 [Qua. 
 
 Q or q. A contraction for electric quantity. 
 
 Quad. (1) A contraction for quadruplex 
 telegraphy. (2) An abbreviation some- 
 times employed for the quadrant or the 
 unit of self-inductance. 
 
 Quad-Meter. (1) A secohm meter. (2) 
 An instrument for measuring inductance. 
 
 Quadrant. A term proposed for the earth 
 quadrant or practical unit of self-induc- 
 tion, now officially recognized as the 
 henry. (2) The length of the arc, from 
 the pole to the equator, on a terrestrial 
 meridian circle extending through Paris, 
 or very nearly 10,000 kilometers. 
 
 Quadrant Electrometer. An electro- 
 meter in which an electrostatic charge is 
 measured by the attractive and repulsive 
 force exerted by four plates or quadrants 
 on a light needle of aluminium suspended 
 between them. 
 
 Quadrantal Deviation of Mariner's 
 Compass. (1) The deviation of a mag- 
 netic needle due to the induced mag- 
 netism in the iron of a ship acting as a 
 mass of soft iron, and not as a permanent 
 magnet. (2) The deviation of a compass 
 needle on board ship which changes sign 
 once in each quadrant. 
 
 Quadrantal Error. The quadrantal de- 
 viation of a mariner's compass as dis- 
 tinguished from either the semicircular or 
 the heeling error. 
 
 Quadrature. A term applied to express 
 the fact that one simple-harmonic quan- 
 tity lags 90 behind another. 
 
 Quadruplex Circuit. A circuit em- 
 ployed in quadruplex telegraphy. 
 
 Quadruplex Connector. Any connec- 
 tor suitable for connecting the four ends 
 of four wires. 
 
 Quadripolar Dynamo or Generator. 
 A multipolar dynamo having four poles 
 in its field frame, or four magnetic cir- 
 cuits through its armature. 
 
 Quadripolar Field. A field produced by 
 four separate magnet poles. 
 
 Quadruplex. Of or pertaining to quad- 
 ruplex telegraphy. 
 
 Quadruplex Balance. The balance ob- 
 tained in a quadruplex circuit in order to 
 permit quadruplex transmission. 
 
 Quadruplex Circuit. Any single circuit 
 over which four separate messages can 
 be simultaneously transmitted, two in one 
 
 direction and the remaining two in the 
 opposite direction, 
 
 Quadruplex Telegraph. A general 
 term embracing the apparatus employed 
 in quadruplex telegraphy. 
 
 Quadruplex Telegraphy. A system for 
 the simultaneous transmission of four 
 messages over a single wire, two in one 
 direction, and two in the opposite direc- 
 tion. 
 
 Quadruplex Telephony. The simulta- 
 neous transmission of four telephonic 
 messages, two in one direction and the re- 
 maining two in the opposite direction. 
 
 Quadruplex Transmission. Tele- 
 graphic or telephonic transmission ef- 
 fected by means of a quadruplex system. 
 
 Quadruplex "Working. Operating a 
 telegraph or telephone line by quadruplex 
 apparatus. 
 
 Quadruplex Re-Entrant Armature 
 Winding. An armature provided with 
 four independent conducting paths or 
 windings, each of which is independently 
 re-entrant. 
 
 Qualitative Analysis. A chemical an- 
 alysis which merely ascertains the kind* 
 of elementary substances present. 
 
 Quality of Musical Sound. (1) That 
 property of a musical note which enables 
 it to be distinguished from another which 
 possesses the same wave length and am- 
 plitude ; i. e., the same pitch and loudness. 
 (2) The timbre of sound. 
 
 Quality of Radiation. The character of 
 radiation in regard to the frequency and 
 amplitude of the vibration it contains. 
 
 Quantitative Analysis. Chemical an- 
 alysis which ascertains the different pro- 
 portions in which the component sub- 
 stances enter into a compound substance. 
 
 Quantity Armature. An old term for an 
 armature wound with a few coils and of 
 comparatively low resistance. 
 
 Quantity Connection for Condensers. 
 A term formerly employed for the mul- 
 tiple connection of a number of con- 
 densers. 
 
 Quantity Current. An old term for a 
 current pi'oduced by a voltaic battery con- 
 nected in multiple-arc. 
 
 Quantity Efficiency of Storage Bat- 
 tery. (1) The ratio of the number of 
 ampere-hours taken out of a storage bat- 
 
Qua.] 
 
 895 
 
 [Raa. 
 
 tery to the number of ampere-hours put 
 in the battery in charging it. (2) The 
 ampere-hour efficiency. 
 Quantity, Electric. The amount of elec- 
 tricity present in any current or charge. 
 
 Quantity Meter, Electric. A coulomb 
 meter. 
 
 Quantity of Light. (1) Flux of light. 
 (2) The product of the luminous intensity 
 and the solid angle through which it is 
 emitted. 
 
 Quantivalence. A general term for the 
 combining capacity of the elements. 
 
 Quarter-Load Efficiency of Trans- 
 former. The efficiency of a transformer 
 at quarter -load. 
 
 Quarter-Period. The time in which a 
 vibrating body, or alternating quantity, 
 completes one quarter of its cycle. 
 
 Quarter - Phase. The condition of di- 
 phase relationship or the separation of 
 two alternating quantities by a quarter 
 period. 
 
 Quarter-Phase Armature. A polyphase 
 armature which will produce quarter- 
 phase currents. 
 
 Quarter-Phase Armature-Winding. 
 Such a winding of a polyphase armature 
 as will permit it to produce quarter-phase 
 currents. 
 
 Quarter-Phase Bar- Winding for Ar- 
 mature. A form of bar winding em- 
 ployed in the armature of a quarter-phase 
 generator. 
 
 Quarter-Phase System. A two-phase 
 system of alternating-current distribution 
 employing two currents dephased by a 
 quarter period. 
 
 Quartz Fibre. A suspension fibre ob- 
 tained by drawing a thread from a fused 
 crystal of quartz. 
 
 Quasi-Resonance. (1) Imperfect reso- 
 nance. (2) The production of resonance in 
 a primary alternating-current circuit by 
 
 the adjustment of a secondary circuit or 
 circuits. 
 
 Quega. A prefix for a quintillion, or 10 15 . 
 
 Quegohm. A quintillion ohms, or a thou- 
 sand million megohms. 
 
 Quick. To cover with an adherent film of 
 mercury. 
 
 Quick-Break. A break of a circuit ob- 
 tained by means of a quick-break switch. 
 
 Quick-Break Switch. A switch by 
 means of which a circuit may be rapidly 
 broken. 
 
 Quickened. A term employed in electro- 
 plating for a surface which has been pro- 
 vided for the reception of a deposit of 
 silver by dipping the article in a quicken- 
 ing liquid. 
 
 Quickening Liquid. A term sometimes 
 applied to the quickening solution. 
 
 Quickening Process. A process em- 
 ployed in quickening. 
 
 Quickening Solution. A solution of a 
 salt of mercury in which objects to be 
 electro-plated are dipped after cleansing, 
 just before being placed in a plating 
 bath. 
 
 Quicking. Subjecting to the quicking 
 process. 
 
 Quicking Solution. A quickening solu- 
 tion. 
 
 Quiet Arc. A noiseless arc. 
 Quiet Commutation. Commutation de- 
 void of sparking. 
 
 Quiet Discharge. A name given to a 
 convective discharge in order to distin- 
 guish it from a noisy disruptive discharge. 
 
 Quintuple Harmonic. A harmonic of 
 five times the frequency of the funda- 
 mental. 
 
 Quivering of Magnetic Field. The pul- 
 sation of magnetic flux either under the 
 leading pole-piece of a generator, or the 
 trailing pole-piece of a motor, due to the 
 successive commutations of the advan- 
 cing armature coils. 
 
 R. A contraction for ohmic resistance. 
 
 R. A symbol proposed for magnetic resist- 
 tance or reluctance. 
 
 r. A symbol for radius. 
 
 p. A symbol for specific electric resistance 
 or resistivity. 
 
 R. M. S. Current. (1) A term proposed 
 
 for the square root of the mean square of 
 
 the current. (2) The effective current. 
 R. P. M. An abbreviation for revolutions 
 
 per minute. 
 R. Q. In submarine telegraphy, a request 
 
 for repetition of a doubtful word, phrase, 
 
 or sentence. 
 Raad. A name formerly given by the 
 
 Arabians to the torpedo or electric ray. 
 
Rac.} 
 
 896 
 
 [Rad. 
 
 Raceway. A continuous space provided 
 in a conduit for the insertion or removal 
 of a conductor or conductors. 
 
 Racing of Dynamo. A general term for 
 any excessive speed produced in a dynamo- 
 electric machine by the sudden removal of 
 its load, as by the breaking of a belt. 
 
 Racing of Motor. An increase in the 
 speed of an electric motor when the load 
 is suddenly removed. 
 
 Rack-Rail-Incline Electric Railway. 
 A means adopted for the passage of a 
 trolley or other car over a steep grade by 
 the use of a rack rail to be operated by 
 the ordinary incline system where the 
 line is too long. 
 
 Racking of Armature Conductors. A 
 term sometimes applied to a sudden drag 
 exerted on the armature conductors of a 
 dynamo or motor during operation. 
 
 Rad. (1) A unit quantity of time-flux of 
 light. (2) A lumen-second or one lumen, 
 maintained during one second. (3) A 
 name proposed for the lumen-second. 
 
 Radial Armature. A term sometimes 
 used for pole armature. 
 
 Radial Current. A term proposed for a 
 current which radiates from a centre. 
 
 Radial Photometer. A photometer 
 whose bench is movable about a vertical 
 axis, so as to be readily turned into any 
 azimuth, and employed to determine the 
 intensity of the light emitted by a lum- 
 inous source in various directions. 
 
 Radial Truck. A triple-truck support for 
 a car-body, in which the car is supported 
 on the centres of the end trucks in such a 
 manner that they may swivel freely, 
 carrying the middle truck between them. 
 
 Radially-Laminated Armature. An 
 armature core whose iron consists of thin 
 discs suitably supported on the shaft. 
 
 Radian.-^(l) A unit angle. (2) An angle 
 whose circular arc is equal in length to 
 its radius ; or. approximately, 57 17' 45". 
 
 Radian-per-Second. A unit of angular 
 velocity of a rotating body. 
 
 Radiant Efficiency. The ratio of the 
 light-giving radiation to the total radia- 
 tion. 
 
 Radiant Energy. Energy transferred or 
 charged on the universal ether. 
 
 Radiant Matter. (I) That condition of 
 the gaseous matter that constitutes the 
 residual atmosphere of high vacua. (2) 
 Ultra-gaseous matter. 
 
 Radiant Vector. A vector point-func- 
 tion which represents the rate and direc- 
 
 tion at and in which energy is being trans- 
 ferred in space. 
 
 Radiophonic Transmission. (1) Trans- 
 mission by means of a photophone. (2) 
 Transmission of articulate speech along 
 rays of light. 
 
 Radiate. (1) To transfer energy by means 
 of waves. (2) To issue radially, or by 
 rectilinear divergence, from a common 
 centre. 
 
 Radiating. (1) Transferring energy by 
 means of waves. (2) Issuing radially. 
 
 Radiation. (1) A transference of energy 
 by means of waves. (2) Issuing radially 
 from a common centre. 
 
 Radiation Constant. The amount of 
 heat lost by radiation in unit time when 
 the temperature of the radiating body is 
 one degree of the thermometric scale 
 above that of the surrounding air. 
 
 Radiation, Electric. (1) The transfer- 
 ence of electric energy by means of elec- 
 tro-magnetic waves set up in the surround- 
 ing ether. (2) That property of a rapidly 
 oscillating or alternating-current circuit 
 by virtue of which energy is expended 
 by the circuit in the form of electro-mag- 
 netic waves. 
 
 Radiation Meter. (1) An instrument 
 for measuring radiation. (2) A meter 
 employed for the measurement of the 
 radiation emitted by an electric oscilla- 
 tion, whose operation is dependent on the 
 elongation produced in a stretched wire 
 by the heat developed therein by cur- 
 rents induced by the rapidly oscillating 
 field of force. 
 
 Radiation of Electricity. The radiation 
 of electric energy by means of electro- 
 magnetic waves. 
 
 Radiation of Magnetic Flux. (1) The 
 passage of magnetic flux out of the north- 
 seeking pole of a magnet or solenoid. (2) 
 The issue of magnetic flux from a mag- 
 netic pole in approximately radial paths. 
 
 Radiator, Electric. (1) An electric 
 heater so placed as to radiate its heat into 
 a room or other space to be heated. (2) An 
 electric circuit which radiates or produces 
 electro-magnetic oscillations or waves. 
 
 Radicals. (1) Unsaturated atoms or groups 
 of atoms, in which one or more of the 
 bonds are, left open or free. (2) Ions. 
 
 Radiograph. The word now generally 
 employed for a picture taken by means of 
 X-rays. 
 
 Radiography. (1) The process of taking 
 radiographs, or X-ray pictures. (2) X-ray 
 photography. 
 
Kad.] 
 
 897 
 
 [Rat. 
 
 Radiometer. (1) A word frequently em- 
 ployed for the Crookes radiometer. (2) 
 An instrument in which the rotation of 
 a light set of vanes is produced in an 
 ultragaseous space, by radiant energy. 
 
 Radio-Micrometer. An electric appara- 
 tus for measuring the intensity of radiant 
 heat. 
 
 Radiophone. A name sometimes given 
 to a photophone. 
 
 Radiophonic. Of or pertaining to the 
 radiophone. 
 
 Radiophonic Sounds. Sounds resulting 
 from the direct action of radiation on cer- 
 tain bodies. 
 
 Radiophony. The production of sound 
 by a body capable of absorbing radiant 
 energy, when an intermittent beam of 
 heat or light falls on it. 
 
 Radius of Gyration. In a rotating body, 
 a radial distance from the centre of rota- 
 tion at which, if the entire mass of the 
 body were collected, its moment of inertia 
 would remain the same. 
 
 Rail-Bond, Electric. Any device where- 
 by the ends of contiguous rails are placed 
 in good electrical contact with one 
 another, so that the resistance of the rails, 
 employed as a portion of the return- 
 circuit, may be as small as possible. 
 
 Rail Bonding. Connecting rails by elec- 
 tric bonds, for the purpose of effecting in- 
 timate electric contact between them. 
 
 Rail Joint. A rail bond. 
 
 Railroad, Electric. A railroad or rail- 
 way on which the cars are driven or pro- 
 pelled by means of electric motors placed 
 on the cars, or on locomotives. 
 
 Railroad Switchboard. A switchboard 
 employed in a railroad power-house, to 
 which the generator and feeder terminals 
 are attached. 
 
 RailwayCircu.it. A circuit for operating 
 an electric railway. 
 
 Railway Current-Controller. (1) A 
 term formerly given to a form of switch- 
 board employed for controlling the output 
 of an electric power-house. (2) A rail- 
 road motor-controller for starting and 
 stopping the cars, and for varying their 
 speed. 
 
 Railway, Electric. An electric railroad. 
 
 Railway Generator. A dynamo-electric 
 machine which develops the current em- 
 ployed in systems of electric railways. 
 
 Railway Line-Crossing. (1) Means pro- 
 vided for supporting the separate trolley 
 wires at places where two or more wires 
 cross one another. ^ A trolley crossing. 
 ' 57 
 
 Railway Line-Section. One of the in- 
 dependent divisions into which the trolley 
 wire and its feeder system are divided by 
 means of section insulators, for the pur- 
 pose of preventing an accidental ground 
 at one point from interrupting the traffic 
 over a considei-able portion of the road. 
 
 Railway Motor. An electric motor em- 
 ployed for the propulsion of an electric 
 street or trolley car. 
 
 Railway Power-Generator. A term 
 sometimes used for railway generator. 
 
 Railway Return Circuit. (1) A term 
 frequently employed for the ground-re- 
 turn of a trolley system. (2) The return 
 circuit, generally a grounded circuit, em- 
 ployed in trolley systems. 
 Railway Return- Wire. (1) A copper 
 . wire employed for the purpose of aiding 
 and re-inforcing the ground-return, so as 
 to decrease the wasteful expenditure of en- 
 ergy due to the poor quality of the rail 
 and track, with its numerous joints, as a 
 conductor. (2) A term sometimes em- 
 ployed for a railway return-circuit. 
 
 Railway Section-Insulators. Insulators 
 employed for the purpose of dividing the 
 trolley wire or line into a number of inde- 
 pendent sections. 
 
 Railway Turn-Out. (1) In a single-track 
 road, an extra track provided to permit 
 the passage of a car in the opposite direc- 
 tion. (2) A local section of track into 
 which a car can be run, so as to leave the 
 main line clear. 
 
 Range Finder, Electric. Fiske's electric 
 range finder. 
 
 Range Indicating System. On war- 
 ships a telegraphic indicating-system for 
 announcing, at any or all of the guns, the 
 range or distance of the target as signalled 
 from the range finder. 
 
 Ratchet -Pendant Argand Electric 
 Gas-Burner. A ratchet-pendant electric 
 burner adapted for lighting an Argand 
 gas burner. 
 
 Ratchet-Pendant Electric Gas-Burner. 
 A gas burner in which one pull on a 
 pendant turns on the gas and ignites it by 
 means of an electric spark from a spark 
 coil, and the next pull turns it off. 
 
 Ratchet - Pendant Electric Candle 
 Burner. A pendant for both lighting 
 and extinguishing a candle gas-jet. 
 
 Rate-of-Doing-Work. (1) Activity. (2) 
 Power. 
 
 Rated Candle - Power. A nominal 
 candle-power. 
 
 Ratio Arms of Bridge. A name some- 
 
Rat.] 
 
 898 
 
 [Rea. 
 
 times given to the proportionate arms of 
 a bridge. 
 
 Ratio of Conversion. A. term sometimes 
 employed instead of ratio of transforma- 
 tion. 
 
 Ratio of Transformation. The ratio be- 
 tween the electromotive force produced 
 at the secondary terminals of an induc- 
 tion coil, or transformer, and the electro- 
 motive force impressed on the primary 
 terminals. 
 
 Ray. (1) A term sometimes employed for 
 a single line of light or other form of radi- 
 ant energy, as distinguished from a pen- 
 cil of rays or a beam. (2) A line of radiant 
 energy flux. 
 
 Ray, Electric. (1) A species of fish 
 which possesses the power of producing 
 electricity. (2) A single line of electric 
 flux-energy. 
 
 Rayleigh's Current-Weigher. A form 
 of electro-dynamometer balance. 
 
 Rayleigh's Form of Clark's Standard 
 V oltaic Cell. A modified form of 
 Clark's standard voltaic cell. 
 
 Reactance. (1) The inductance of a coil 
 or circuit multiplied by the angular ve- 
 locity of the sinusoidal current passing 
 through it. (2) A quantity whose square 
 added to the square of the resistance 
 gives the square of the impedance, in 
 a simple-harmonic current circuit. 
 
 Reactance Factor. The ratio of the re- 
 actance of a coil, conductor, or circuit, 
 to its ohmic resistance. 
 
 Reactance of Condenser. (1) The recip- 
 rocal of the product of the capacity of a 
 condenser, and the angular velocity of 
 the simple-harmonic pressure with which 
 it may be connected. (2) A quantity 
 which divided into the alternating-cur- 
 rent pressiire at condenser terminals, 
 gives the current strength in the con- 
 denser. 
 
 Reactance of Mutual Inductance. In 
 an alternating-current circuit, the prod- 
 uct of a mutual inductance and the an- 
 gular velocity. 
 
 Reacting Inductive Electromotive 
 Force of Primary Circuit. (1) The C. 
 E. M. F. of self-induction in a primary 
 alternating-current circuit. (2) The C. 
 
 E. M. F. of mutual-induction in a primary 
 alternating-current circuit, or the C. E. M. 
 
 F. due to current in the secondary circuit. 
 
 Reaction. In electro-therapeutics, mus- 
 cular contractions following the closing 
 or opening of an electric circuit through 
 the nerves or muscles. 
 
 Reaction Coil. (1) A magnetizing coil 
 
 surrounded by a conducting covering of 
 sheathing which opposes the passage of 
 rapidly alternating currents less when 
 directly over the magnetizing coil than 
 when a short distance from it. (2) A 
 choking coil. 
 
 Reaction Machine. An induction ma- 
 chine. 
 
 Reaction Motor. An induction motor. 
 
 Reaction of Degeneration. An altera- 
 tion in the behavior of nerves and muscles 
 under electric stimulation, due to disease. 
 
 Reaction of Exhaustion. A condition 
 of nervous or muscular irritability to 
 electric excitation, when a certain reac- 
 tion produced by a given current strengtli 
 cannot be reproduced without an increase 
 in current strength. 
 
 Reaction Principle of Dynamo-Elec- 
 tric Machine. The mutual interaction 
 between the current generated in the 
 armature coils and the field coils of a con- 
 tinuous-current dynamo-electric machine, 
 each strengthening the other until the 
 full-working current which the machine 
 is capable of developing is produced. 
 
 Reaction Telephone. An electro-mag- 
 netic telephone in which the currents in- 
 duced in a coil of fine wire attached to 
 the diaphragm are passed through the 
 coils of an electro-magnet, each thus re- 
 acting on and strengthening the other. 
 
 Reaction Time. The time required for 
 the effects of an electric current to pass 
 from a nerve to a muscle. 
 
 Reaction- Wheel, Electric. A wheel 
 driven by the reaction of a convective 
 discharge. 
 
 Reactive Circuit. A circuit containing 
 either inductance or capacity alone, or 
 both inductance and capacity. 
 
 Reactive Coil. A reaction coil. 
 
 Reactive Drop. The drop in a circuit or 
 conductor "due to its reactance, as dis- 
 tinguished from the drop due to its ohmio 
 resistance. 
 
 Reactive Effect. The choking effect of 
 reactance in an alternating-current cir- 
 cuit. 
 
 Reactive Electromotive Force. In an 
 alternating-current circuit, that com- 
 ponent of the electromotive force that is 
 in quadrature with the current and is 
 employed in balancing the C. E. M. F. of 
 inductance. 
 
 Reading Microscope. A form of micro- 
 scope employed for the measurement of 
 very small distances. 
 
 Reading Telescope. A telescope em 
 
Kea.] 
 
 899 
 
 [Rec. 
 
 ployed in electric measurements for read- 
 ing the deflections of a galvanometer. 
 
 Real Cable. In duplex submarine cable- 
 telegraphy the actual cable, as distin- 
 guished from the artificial cable. 
 
 Real Efficiency of Storage Battery. 
 (1) The ratio of the number of watt-hours 
 taken out of a storage battery to the 
 number of watt-hours put into the bat- 
 tery in charging it. (2) The energy effi- 
 ciency, or watt-hour efficiency, of a stor- 
 age battery, as distinguished from its 
 quantity efficiency, or ampere-hour effi- 
 ciency. 
 
 Real Hall Effect. A transverse electro- 
 motive force produced by magnetic flux 
 through conductors conveying electric 
 currents in a manner somewhat similar 
 to that in which the Faraday effect is 
 produced. 
 
 Real Image. (1) An image formed by 
 rays of light that actually meet in the 
 various visible points, as distinguished 
 from a virtual image. (2) An image 
 which is capable of being received on a 
 screen. 
 
 Rebabbitting. The operation of replac- 
 ing the Babbitt metal in the b earings of 
 a machine. 
 
 Recalescence. A property possessed by 
 a bar or a mass of cooling incandescent 
 steel, of again becoming incandescent 
 after having cooled sufficiently to no 
 longer emit luminous heat. 
 
 Recalibration. A new calibration of an 
 instrument. 
 
 Received Current. A term used in teleg- 
 raphy to distinguish the currents that 
 come in over a line from a distant station, 
 from those that are sent out to a distant 
 station. 
 
 Receiver. A name sometimes given to a 
 receiving instrument of a gramophone, 
 graphophone, telephone, or telegraph in- 
 strument. 
 
 Receiver Magnet. A receiving magnet. 
 
 Receiving End of Line. That end of a 
 line at which the currents arrive, as dis- 
 tinguished from the end at which they 
 are sent out. 
 
 Receiving Leg of Telegraphic Loop. 
 The wire of a telegraphic loop upon 
 which messages are received, as distin- 
 guished from the sending leg. 
 
 Receiving Magnet. (1) A name some- 
 times given to the relay of a telegraphic 
 system. (2) In general, any magnet used 
 directly in the receiving apparatus at the 
 receiving end of a telegraph or telephone 
 line- 
 
 Receiving Signaller. (1) A receiving 
 operator. (2) An operator engaged in re- 
 ceiving a telegraphic message. 
 
 Receiving Transformer. A transformer 
 at the receiving end of a circuit. 
 
 Receptacle. In incandescent lighting a 
 permanent device for receiving an at- 
 tachment plug. 
 
 Receptive Device. (1) A translating de- 
 vice. (2) In electrotechnics, a magneto- 
 or electro-receptive device. (3) A device 
 for receiving energy and utilizing or 
 transforming it. 
 
 Reciprocal. The quotient arising from 
 dividing any quantity into unity. 
 
 Reciprocating Motor. A motor with, a 
 reciprocating action, or with a motion 
 alternately in opposite directions, as dis- 
 tinguished from a rotary motor. 
 
 Reciprocal Vectors. Two vectors whose 
 product is equal to the numeric unity. 
 
 Recoil Circuit. A term sometimes ap- 
 plied to the circuit that lies in the alter- 
 native path of a discharge. 
 
 Recoil Kick of Disruptive Discharge. 
 A kick or reaction produced by a disrup- 
 tive discharge. 
 
 Recorder. A word sometimes used for 
 either a telegraphic recorder, or a siphon 
 recorder. 
 
 Recorder Ammeter. An ammeter whose 
 indications are permanently recorded. 
 
 Recorder Battery. The local battery 
 supplying the magnets, or mouse-mill, of 
 a siphon recorder. 
 
 Recorder Circuit. The circuit of a 
 siphon recorder. 
 
 Recorder Coil. The receiving coil of a 
 siphon recorder. 
 
 Recorder Magnets. The magnets which 
 supply the magnetic flux in which moves 
 the receiving coil of a siphon recorder. 
 
 Recorder Shunt. A shunt of low resist- 
 ance placed across the terminals of the 
 coil of a siphon-recorder during sending. 
 
 Recorder Signals. Signals received on a 
 siphon recorder by the projection of ink 
 upon a moving strip of paper from a small 
 glass siphon connected with the receiving 
 coil. 
 
 Recorder Slip. The strip of paper re- 
 cording, or prepared for recording, siphon- 
 recorder signals. 
 
 Recorder Switch. The switch employed 
 in connection with a siphon recorder for 
 changing from sending to receiving con- 
 nections. 
 
 Recorder - Vibrator. An electronic- 
 
Rec.] 
 
 900 
 
 [Red. 
 
 chanical vibrator for forcing an inter- 
 mittent flow of ink from the siphon of a 
 recorder on to a band of paper moving 
 beneath it. 
 
 Recording Compass. A compass so ar- 
 ranged as to record the directions of 
 the needle, and to sound an alarm in case 
 the course of the vessel deviates any pre- 
 determined number of degrees. 
 
 Recording Drum. A cylindrical drum 
 covered by a sheet or strip of paper on 
 which a chronographic or other record, is 
 made. 
 
 Recording Meter. Any form of electric 
 meter that records its indications. 
 
 Recording Voltmeter. A voltmeter 
 whose indications are permanently re- 
 corded. 
 
 Recording Wattmeter. (1) A recording 
 form of wattmeter. (2) A dial watt-hour 
 or kilowatt-hour meter. 
 
 "Recovery" of Condenser. The con- 
 dition of a condenser whose dielectric has 
 regained its neutral condition after having 
 been strained by a charge. 
 
 Rectal Electrode. An electrode suita- 
 ble for the treatment of the rectum. 
 
 Rectangular Curve. A curve whose out- 
 line approximates or conforms to a rec- 
 tangular shape. 
 
 Rectangular Type of Periodically Al- 
 ternating Electromotive Force. An 
 electromotive force whose variations of 
 strength are represented by a curve of 
 rectangular outline. 
 
 Rectangular Variation - Diagram . A 
 diagram drawn to rectangular co-ordi- 
 nates, and representing the variation of 
 any quantity or quantities. 
 
 Rectification of Alcohol, Electric. A 
 process whereby the bad taste and odor 
 of alcohol, due to the presence of alde- 
 hydes, are removed by the electrical con- 
 version of the aldehydes- into true alcohol 
 through the addition of hydrogen atoms. 
 
 Rectified. Commuted, or caused to tako 
 one and the same direction. 
 
 Rectified Currents. Commuted cur- 
 rents. 
 
 Rectifier. A name sometimes given to a 
 commutator. 
 
 Rectilinear Co-Ordinates. Co-ordi- 
 nates measured from two rectilinear axes 
 intersecting in the plane of delineation 
 at a point called the origin. 
 
 Rectilinear Current. A current flowing 
 through a straight or rectilinear portion 
 of a circuit. 
 
 Rectifying Commutator. A term some- 
 times applied to a commutator which 
 commutes alternating into direct cur- 
 rents. 
 
 Red Candle. A photometric candle em- 
 ployed in connection with a red glass 
 screen, for the purpose of enabling the 
 unpracticed eye to more readily compare 
 it with the source whose intensity is to be 
 measured. 
 
 Red Heat. The temperature at which a 
 body begins to glow or to emit red rays 
 of light. 
 
 Red Hot. Possessing the temperature of 
 red heat. 
 
 "Red" Magnetism. A name formerly 
 applied to the magnetism at the north 
 pole of a magnet, as distinguished from 
 the so-called ''blue" magnetism at the 
 south pole. 
 
 Redressed. A word sometimes employed 
 for commuted. 
 
 Redressed Currents. Commuted cur- 
 rents. 
 
 Reduced Battery. A portion only of a 
 main-line battery employed in quadruplex 
 telegraphy. 
 
 Reduced Deflection Method. A 
 
 method of measuring electromotive force, 
 resistance or current, by determinations 
 based upon an observed reduction in 
 current strength, and resulting deflection 
 of a galvanometer in the circuit. 
 
 Reducing Clamp for Underground 
 Tubing. A clamp at a coupling box 
 clasping an underground tube, of such 
 dimensions as to permit of a change in 
 the diameter of the next succeeding tube. 
 
 Reducing Coupling. A flexible coupling 
 connecting two conductors of different 
 diameters. 
 
 Reducing Switch.- -A switch so con- 
 nected with a circuit as to bring a reduced 
 or lowered pressure upon a sub-circuit. 
 
 Reducteur Resistance for Volt-Meter. 
 
 (1) A coil of known resistance as com- 
 pared with the resistance of the coils of 
 a voltmeter, that is connected with them 
 in series for the purpose of increasing the 
 range of the instrument. (2) A multi- 
 plying coil, or multiplier of a voltmeter. 
 
 Reducteur Shunt for Ammeter. (1) 
 A shunt coil connected in multiple with 
 the coils of an ammeter for the purpose 
 of changing the value of its readings. 
 
 (2) A multiplier. 
 
 Reduction Factor of Galvanometer. 
 The ratio between the horizontal inten- 
 sity of the field of a galvanometer and 
 the galvanometer constant. 
 
Red.] 
 
 901 
 
 [Reg. 
 
 Reduction Gear. Gear employed on a 
 street-car for suitably reducing the speed 
 of the car below that of the motor which 
 drives it. 
 
 Reed Interrupter. A form of automatic 
 make-and-break contact, operated by the 
 vibrations of a reed. 
 
 Reel Insulator. An insulator resembling 
 a reel in shape, and suitable for use in 
 connection with an engine plane signal 
 system. 
 
 Re-Enforcement of Sound. An increase 
 in the intensity of sound by the use of 
 sounding boards, resonators, or reflectors. 
 
 Re-Entrancy. The intersection of a curve 
 by itself. 
 
 Re-Entrancy of Armature Winding. 
 
 The condition or property of an armature 
 winding, by virtue of which the conduct- 
 ing path through the armature repeats 
 itself or re-enters itself. 
 
 Re-Entrant Armature- Windings. Ar- 
 mature windings, which, when followed 
 in either direction, lead back to the start- 
 ing point. 
 
 Refining, Electric. The refining of 
 metals by the application of electrolysis. 
 
 Reflect. To throw off from a surface ac- 
 cording to the laws of reflection, as of 
 waves in an elastic medium. 
 
 Reflecting. Throwing off from a surface 
 in accordance with the laws of reflection. 
 
 Reflecting Galvanometer. A term 
 sometimes applied to a mirror galvano- 
 meter. 
 
 Reflection. The throwing back of a body 
 or wave from a surface at an angle equal 
 to that at which it strikes the surface. 
 
 Reflection of Electro-Magnetic Waves. 
 The reflection of electro-magnetic 
 waves that occurs from the surfaces of 
 certain substances placed in the path of 
 the waves. 
 
 Reflector. A reflecting surface suitably 
 shaped to reflect rays of light in any de- 
 sired direction. 
 
 Reflector Bracket. A bracket for sup- 
 porting two insulators and for holding 
 the support of a street lamp, with or with- 
 out a reflector. 
 
 Reflector Search-Light. A search-light 
 consisting of a focussing lamp placed at 
 the focus of a suitable reflector. 
 
 Reflector Shade. A shade surrounding 
 an arc-lamp, a portion of whose surface 
 is covered with reflecting material. 
 
 Refract. To change the direction of 
 waves in any elastic media in accordance 
 with the laws of refraction. 
 
 Refracting. Changing the direction of 
 waves in elastic media in accordance 
 with the laws of refraction. 
 
 Refraction. The bending of a ray of light, 
 heat, or electro-magnetism, at the inter- 
 face of any two transparent media, whose 
 elasticity and density differ. 
 
 Refractive Energy. A value equal to the 
 index of refraction minus unity. 
 
 Refractory. (1) Possessing the power of 
 resisting fusion by heat. (2) Fusible only 
 at extraordinarily high temperatures. 
 
 Refreshing Action of Current. The 
 restoration, after fatigue, of muscular 
 and nervous excitability obtained by the 
 action of voltaic alternatives. 
 
 Regenerable Cell. A regenerative cell. 
 
 Regenerated Cell. A cell which has had 
 its ability for producing current restored 
 by a charging process. 
 
 Regenerative Armature. A word pro- 
 posed for the armature of a dynamo that 
 is capable of producing its own magnetic 
 field-flux, when commuted with a back- 
 ward lead. 
 
 Regenerative Cell. (1) A name some- 
 times given to an early form of of storage 
 cell. (2) Any cell which can have its 
 energy restored by the action of a charg- 
 ing current. 
 
 Regional Magnetic Disturbances. A 
 term proposed for magnetic disturbances 
 that are apparently confined to limited 
 regions of the earth's surface. 
 
 Register. A word frequently employed 
 for any registering apparatus. 
 
 Registering Apparatus, Electric. De- 
 vices for obtaining permanent records by 
 electrical means. 
 
 Registering Declination-Magnetome- 
 ter. A magnetometer employed for au- 
 tomatically registering the magnetic de- 
 clination. 
 
 Registering Electrometer. An electro- 
 meter whose indications are automatically 
 registered. 
 
 Registering Photometer. (1) A photo- 
 meter which registers not the photometric 
 but the actinic or chemical action of light. 
 (2) A recording photometer. 
 
 Regulating Box. (1) A rheostat inserted 
 in the field circuit of a generator or 
 motor for regulating the current passing 
 through the field-magnet coils. (2) A 
 rheostat. 
 
 Regulating Cell for Storage Battery. 
 A counter-electromotive force cell. 
 
 Regulating Lamp-Socket. (1) A lamp 
 socket containing a device controlled by 
 
Beg.] 
 
 902 
 
 [Rem. 
 
 a key or switch for regulating the degree 
 of incandescence of the filament. (2) A 
 general term for any form of lamp socket 
 which will permit the light to be econo- 
 mically turned down or lowered in in- 
 tensity. 
 
 Regulating Wires. Adjusting the ten- 
 sion of overhead line wires. 
 
 Regulation of Dynamo. Such an ad- 
 justment of a dynamo as will preserve 
 constant either its current or its pres- 
 sure. 
 
 Regulation of Motor. Such an adjust- 
 ment of a motor as will preserve constant 
 its speed, or its torque, or both. 
 
 Regulator for Dynamo. Any device by 
 means of which the regulation of a dy- 
 namo is effected. 
 
 Regulator for Motor. Any device by 
 means of which the regulation of a motor 
 is effected. 
 
 Regulator Magnet. (1) A magnet whose 
 function is to automatically effect any 
 desired regulation. (2) In a system of 
 automatic constant-current dynamo-reg- 
 ulation, the magnet by the movements of 
 whose armature the commutator brushes 
 are automatically shifted to such posi- 
 tions on the commutator as will main- 
 tain the current practically constant, 
 despite changes in the resistance of the 
 circuit external to the machine. 
 
 Reguline Electro-Metallurgical De- 
 posit. A flexible, adherent and strongly 
 coherent film of electrolytically deposited 
 metal. 
 
 Rejuvenation of Luminescence. Re- 
 imparting, by exposure to light or other 
 suitable means, the power of lumines- 
 cence to a substance after it has lost this 
 power. 
 
 Relative Inductivity. The ratio of the 
 inductivity of a medium to the induc- 
 tivity of vacuum. 
 
 Relative Permittivity. The ratio of the 
 permittivity of a medium to the permit- 
 tivity of vacuum. 
 
 Relaxation Distance. The distance in 
 which an electro-magnetic wave travel- 
 ling along the surface of a conductor, 
 diminishes in amplitude in a ratio whose 
 Naperian logarithm is unity. 
 
 Relaxation Time. The time during 
 which a logarithmically diminishing 
 quantity diminishes in a ratio whose Na- 
 perian logarithm is unity. 
 
 Relay. In telegraphy, an electro-magnet 
 provided with contact points placed on a 
 delicately supported armature, the move- 
 
 ments of which open or close a local re- 
 ceiver circuit. 
 
 Relay Bell. An electric bell in which a 
 relay magnet is employed to switch a 
 local battery into the circuit of the bell. 
 
 Relay Contact. (1) A term frequently 
 applied to a form of electro-magnetic in- 
 strument by means of which a local cir- 
 cuit is completed on the passage of a cur- 
 rent. (2) The contact point of a relay. 
 
 Relay Magnet. (1) A term sometimes 
 given to a relay. (2) The permanent 
 magnet of a polarized relay. (3) The 
 electro-magnet of a relay. 
 
 Relief Lamp. (1) An incandescent lamp 
 whose socket is provided with a spring 
 cut-out, so arranged that on the breaking 
 of the lamp the circuit is automatically 
 closed. (2) An incandescent lamp held in 
 reserve for insertion in a series system to 
 take the place of a lamp that has been 
 cut out. 
 
 Relief Operators. In telegraphy or tele- 
 phony, operators coming on duty to re- 
 lieve the operators at work. 
 
 Relief Photometer. The name given to 
 a class of photometers in which the two 
 divisions of the screen are not placed in 
 the same plane but at right angles to each 
 other, the quality of the illumination 
 being readily determined since the whole 
 screen then appears as a single plane il- 
 lumined surface, in which the edge of a 
 dihedral angle of the screen is no longer 
 perceptible. 
 
 Relievo. (1) The opposite of intaglio. (2) 
 A stone, electro, or other solid body, in 
 which a figure is so represented that its 
 outlines project or stand out from the 
 surface. 
 
 Reluctance. (1) A term applied to mag- 
 netic resistance. (2) In a magnetic cir- 
 cuit the ratio of the M. M. F. to the total 
 magnetic flux. , 
 
 Reluctancy. -fir term proposed for re- 
 luctivity. 
 
 Reluctivity The specific magnetic re- 
 sistance of a medium. 
 
 Reluctivity Constants. The constants 
 which, wh en applied according to a form- 
 ula to the magnetic force or magnptic 
 flux density in iron or steel, give the re- 
 luctivity of the iron or steel. 
 
 Remaining Sockets. The sockets of a 
 multiple telephone switchboard in circuit 
 with any particular socket. 
 
 Remanence. (1) Magnetic retentivity. 
 (2) The property of magnetic substances 
 to retain part of their magnetism owing 
 to hysteresis. (3) The magnetic flux 
 
Rem.] 
 
 density in a magnetic substance when 
 the magnetic force is reduced to zero. 
 
 Remanent Flux. Renianent magnetism. 
 
 Remanent Magnetism. A phrase some- 
 times used in place of residual mag- 
 netism. 
 
 Remanent Polarization. (1) A term 
 proposed to describe the condition of a 
 voltameter when a certain number of 
 discharges having traversed it, all in the 
 same direction, and a series of discharges 
 exactly equal to the preceding have been 
 established in the opposite direction, the 
 currents of polarization are less in- 
 tense in the second than in the first. (2) 
 Residual polarization of immersed elec- 
 trodes after a passage of the current. 
 
 Removable Key-Switch. A plug 
 switch. 
 
 Removable Pole-Step. A pole step cap- 
 able of being inserted into and removed 
 from a socket for the equipment of a line- 
 man, to enable a lineman to reach the 
 permanent steps. 
 
 Renovation of Secondary or Storage 
 Cell. The recharging of a run-down or 
 discharged storage cell. 
 
 Renter. A term sometimes used for sub- 
 scriber. 
 
 Reofore. A rheophore. 
 
 Repair- Wagon for Trolley Line. A 
 wagon provided with a tower or telescopic 
 support employed for the repair of trolley 
 lines. 
 
 Repeater. The name sometimes given to 
 a telegraphic repeater, or translator. 
 
 Repeating Relay. (1) A relay employed 
 in a repeater. (2) The relay in a tele- 
 graph circuit which repeats the signals 
 into another circuit. 
 
 Repeating Sounder. A telegraphic 
 sounder whicn repeats a telegraphic 
 despatch into another circuit. 
 
 Repeating Telegraphic Station. A 
 station situated at some intermediate 
 point on a long telegraphic line which is 
 divided into sections, where the currents 
 received on one section are passed 
 through a repeater by means of which 
 they are sent on or repeated into the other 
 section. 
 
 Repeating Telephone Coil. An induc- 
 tion coil provided with two windings, 
 usualh r of an equal number of turns, each 
 winding being connected to a telephone 
 circuit, so that the two circuits are placed 
 in intimate inductive association. 
 
 Replenisher. A static influence machine 
 employed for charging a quadrant elec- 
 trometer or other electrostatic device. 
 
 903 
 
 [Res. 
 
 Repulsion, Electric. The mutual driv- 
 ing apart, or tendency to mutually drive 
 apart, which exists between two similarly 
 charged bodies, or between two similar 
 electric charges. 
 
 Repulsion Electrometer. An electro- 
 meter in which the differences of poten- 
 tial are measured by means of the repul- 
 sion existing between two similarly 
 charged bodies. 
 
 Repulsion Motor. (1) An electric motor 
 deriving its power from the repulsion be- 
 tween electric charges. (2) An alternat- 
 ing-current motor deriving its power 
 from the repulsion between electric cur- 
 rents. (3) An alternating-current motor 
 in which the armature is provided with 
 temporarily short-circuited windings by 
 means of a commutator and brushes. 
 
 Reserve-Cell Switch. A switch em- 
 ployed in a storage-battery installation 
 for the purpose of maintaining the pres- 
 sure of discharge by introducing reserve 
 cells into the circuit. 
 
 Residual Atmosphere. The traces of 
 air or other gas remaining in a space 
 which has been nearly exhausted of its 
 gaseous contents by a pump or other 
 means. 
 
 Residual Charge. The charge remain- 
 ing in a Leyden jar after it has been dis- 
 ruptively discharged. 
 
 Residual Flux. Residual magnetic 
 flux. 
 
 Residual Magnetic-Flux. (1) Rema- 
 nence. (2) Magnetic flux remaining in a 
 magnetic circuit by virtue of hysteresis 
 after the withdrawal of the magnetizing 
 force. 
 
 Residual Magnetism. (1) The magnet- 
 ism remaining in a core of an electro- 
 magnet on the opening of the magnetiz- 
 ing circuit. (2) The small amount of 
 magnetism retained by soft iron when re- 
 moved from any magnetic flux. 
 
 Residue, Electric. A term proposed for 
 residual charge. 
 
 Resilience. (1) A word sometimes em- 
 ployed for elasticity. (2) The work done 
 in deforming a bar up to the elastic 
 limit. 
 
 Resin. A general term applied to a 
 variety of dried juices of vegetable 
 origin. 
 
 Resinous Electricity. A term formerly 
 employed in place of negative electri- 
 city. 
 
 Resinous Electrification. A name for- 
 merly applied to an electrification pro- 
 duced in resin by its friction. 
 
Res.] 
 
 904 
 
 [Res. 
 
 Resistance. (1) A word sometimes used 
 for electric resistance. (2) Obstruction 
 to flow. (3) Obstruction to force. 
 
 Resistance Balance. A duplex or quad- 
 ruplex balance adjusted for the resistance 
 of a line by means of a rheostat. 
 
 Resistance Balance of Duplex System. 
 
 (1) A balance obtained in a duplex system 
 by inserting in the artificial line a resist- 
 ance corresponding to that of the sum 
 of the resistances of the main-line wire, 
 the distant relays, and the distant battery. 
 
 (2) A balance of resistance in duplex tele- 
 graphy as opposed to a balance of capac- 
 ity. 
 
 Resistance Board. A general term for a 
 board on which resistances are so placed 
 as to be capable of ready adjustment, con- 
 nection, introduction, or removal from a 
 circuit. 
 
 Resistance Box. A term employed for a 
 box containing graduated resistance coils. 
 
 Resistance Bridge. A name frequently 
 employed for a Wheatstone's resistance 
 balance. 
 
 Resistance Bridge-Box. A box form of 
 Wheatstone's bridge. 
 
 Resistance Coefficient. The resistance 
 factor. 
 
 Resistance Coil. (1) A coil of wire, strip, 
 or conductor, possessing electric resist- 
 ance. (2) A coil of wire, of known elec- 
 tric resistance, employed for measuring 
 an unknown electric resistance. 
 
 Resistance Column. A name given to a 
 particular form of resistance coil or 
 rheostat. 
 
 Resistance Conductivity. The resist- 
 ance offered by a substance to electric 
 conduction , or to the passage of electricity 
 through its mass. 
 
 Resistance, Electric. (1) The ratio be- 
 tween the electromotive force of a circuit 
 and the current that passes therein. (2) 
 The reciprocal of electric conductance. 
 
 Resistance Factor. The coefficient of 
 frictional resistance to the movements of 
 a suspended or oscillatory system. 
 
 Resistance Losses. (1) Losses in any 
 system for the transmission or the trans- 
 ference of energy occasioned by friction. 
 (2) Losses in an electrical distribution 
 system due to resistance. 
 
 Resistance of Human Body, Electric. 
 The ohmic resistance which the human 
 body offers to the passage of an electric 
 discharge or current. 
 
 Resistance of Human Skin, Electric. 
 The ohmic resistance of the skin. 
 
 Resistance of Liquid, Electric. The 
 ohmic resistance of a mass of liquid. 
 
 Resistance of Telegraphic Leak. The 
 resistance offered by a leak in a tele- 
 graphic line or circuit. 
 
 Resistance of Voltaic Arc. Resistance 
 offered by a voltaic arc to the passage of 
 a current. 
 
 Resistance Slide. (1) A rheostat in which 
 the separate resistances or coils are placed 
 in or removed from a circuit by means of 
 a sliding contact or key. (2) Apparatus 
 employed in telegraphy for charging a 
 conductor to a given fraction of the max- 
 imum potential of a battery, so as to adjust 
 its charge in order to balance the vary- 
 ing charge of the cable. (3) A set of coils 
 by which a potential difference applied to 
 the terminals is virtually divided into 
 10,000 parts, so that any ratio may be in- 
 stantly selected. 
 
 Resistance Thermometer, Electric. A 
 thermometer whose indications are based 
 on the change in the electric resistance of 
 a metallic substance with changes of 
 temperature. 
 
 Resistance to Shearing. The quotient 
 of the shearing stress by the shear pro- 
 duced. 
 
 Resistants. Bodies possessing the power 
 of resistance. 
 
 Resister. A name sometimes given to a 
 float or buoy connected with a cable while 
 it is being paid out, in order to diminish 
 the risk of injury from tension. 
 
 Resisting Torque. (1) The torque which 
 it is necessary to give to a motor in order 
 to enable it to move. (2) The torque of 
 retarding or opposing forces. 
 
 Resistive. (1) Possessing the property of 
 resistance. (2) Offering resistance. 
 
 Resistivity. (1) The specific resistance of 
 a substance referred to the resistance of 
 a cube of unit volume. (2) Specific re- 
 sistance, or the inverse of specific con- 
 ductivity. (3) A quantity in the C. G. S. 
 electro-magnetic system represented di- 
 mensionally in square centimetres per 
 second. 
 
 Resolution of Force. The separation of 
 a single force acting with a given inten- 
 sity in a given direction, into a number of 
 separate forces acting in other directions. 
 
 Resonance. (1) In a simple-harmonic cur- 
 rent, circuit, or branch, containing both 
 inductance and capacity, the neutraliza- 
 tion or annulment of inductance-reactance 
 by capacity-reactance, whereby the imped- 
 ance of the circuit or branch is reduced to 
 the ohmic resistance. (2) In an alternat- 
 
Res.] 
 
 
 905 
 
 [Ret. 
 
 ing-current circuit, or branch, containing 
 localized inductance and capacity, the re- 
 enforcement of condenser pressure, in- 
 ductance pressure, or current strength, 
 due to the mutual neutralization or oppo- 
 sition of inductance and capacity-react- 
 ances. (3) In an alternating-current 
 circuit, or branch, the attunement of a 
 circuit containing a condenser to the same 
 natural undamped frequency of oscil- 
 lation as the frequency of impressed E. M. 
 F. whereby the circuit responds to this 
 frequency more than to any other. (4) In 
 an alternating-current circuit, or branch, 
 the annulment of inductance-reactance by 
 capacity-reactance, whereby the imped- 
 ance of the circuit or branch is not only 
 reduced to its ohmic resistance, but its 
 current is in phase with its impressed 
 E. M. F. (5) In a secondary alternating- 
 current circuit containing localized in- 
 ductance and reactance, the attunement 
 of the natural undamped frequency of 
 oscillation to the frequency of the pres- 
 sure impressed upon the primary circuit, 
 whereby the secondary impedance is re- 
 duced to its ohinic resistance, the second- 
 ary current is a maximum for any given 
 primary current strength, and the second- 
 ary current is in phase with the induced 
 secondary E. M. F. 
 
 Resonant Capacity. The capacity of a 
 resonant circuit, or such a capacity as 
 will render an alternating-current circuit 
 resonant. 
 
 Resonant Circuit. (1) A circuit whose 
 dimensions are such as to bring it into 
 resonance with a neighboring circuit. 
 (2j A circuit containing distributed in- 
 ductance and capacity, in which resonant 
 effects are thereby produced. 
 
 Resonant Inductance. The inductance 
 of a resonant circuit, or the inductance 
 which will render it resonant. 
 
 Resonant Rise of Potential. A rise of 
 potential in a circuit due to its resonance. 
 
 Resonator, Electric. (1) An open-cir- 
 .cuited conductor whose dimensions are 
 such that electro-magnetic waves or 
 pulses are propagated through it at the 
 same rate as they are taking place in a 
 neighboring circuit, and which, conse- 
 quently, has electro- magnetic pulses set up 
 sympathetically in it by resonance. (2) A 
 circuit tuned to oscillate in synchronism 
 with another oscillating or alternating 
 circuit. 
 
 Rest.-^l) Freedom from motion. (2) The 
 condition of a body in which it maintains 
 an unchanged relative position with re- 
 spect to neighboring bodies. 
 
 Restoring-Coil Battery. In a telephone 
 exchange the battery which operates the 
 self-restoring annunciators. 
 
 Restoring-Coil Circuit. In a telephone 
 switchboard, the local circuit of the coil 
 of a self-restoring annunciator. 
 
 Restored Cell. A charged storage cell. 
 
 Resultant. In mechanics, a single force 
 that represents in direction and intensity 
 the effects of two or more separate forces, 
 
 Resultant Fault. The apparent position 
 and magnitude of a fault in a cable due 
 to the resultant of all its leakage, or faults 
 compounded by the rules of parallel 
 forces, or as represented by finding the 
 centre of gravity of an unequally loaded 
 rod. 
 
 Resultant Induction. The magnetic 
 induction in an armature of a dynamo or 
 other magnetized body which is the re- 
 sultant of several components of magnetic 
 induction. 
 
 Resultant Magnetic Field. A single 
 magnetic field produced by two or more 
 co-existing magnetic fields. 
 
 Resultant Magnetic Field of Dynamo. 
 The magnetic field which is the result 
 of both the field due to the field magnets 
 and to the current passing through the 
 armature coils. 
 
 Resultant Magnetic Pole. A term 
 sometimes employed for a consequent 
 pole. 
 
 Resultant Reactance. The total react- 
 ance in a circuit or conductor. 
 
 Resuscitating Power of Secondary or 
 Storage Cell. The ability possessed by 
 a storage cell to regain its normal condi- 
 tion under the influence of the charging 
 current. 
 
 Retardance. In a telephone circuit, a 
 quantity alleged to represent the limita- 
 tion of "the circuit in regard to the trans* 
 mission of speech, and equal to the prod- 
 uct of the total capacity of the line andi 
 the total ohmic resistance. 
 
 Retarding Coil. A choking coil. 
 
 Retarding Disc. A copper disc supported' 
 on a rotating shaft so placed as to cut 
 magnetic flux, and be thereby retarded 
 in its speed of rotation. 
 
 Retardation. A decrease in the speed of 
 telegraphic signalling caused by distrib- 
 uted electrostatic induction and resist- 
 ance. 
 
 Retardation Coil. (1) A term sometimes 
 used for choking coil. (2) An induction 
 coil. (3) A retarding coil. 
 
 Retardation, Electric. A retardation in. 
 
Ret.] 
 
 906 
 
 [Rev. 
 
 the starting or stopping of an electric 
 current due to self-induction. 
 
 Retarded Quadrature. In a simple- 
 harmonic-current circuit the condition of 
 lagging in quadrature, or of phase differ- 
 ence amounting to 90 in lag. 
 
 Retentiveness. Possessing the property 
 of retentivity. 
 
 Retentivity. Possessing the power of re- 
 taining magnetization or of resisting de- 
 magnetization. 
 
 Retort Carbon. Carbon obtained from 
 a deposit on the interior of a gas retort, 
 and formerly used for the production of 
 arc-light carbons. 
 
 Return-Call Annunciator. An annun- 
 ciator connected with an answering call- 
 box for showing that a call sent out has 
 been received at the central station, 
 
 Return Charge. (1) A charge produced 
 by an oscillatory return or back stroke of 
 lightning. (2) A charge produced induc- 
 tively by a lightning discharge. 
 
 Return Circuit. That part of a circuit 
 by which an electric current returns to 
 the source. 
 
 Return Conductor. The return wire. 
 
 Return Current. In telegraphy the elec- 
 trostatic discharge from a cable or under- 
 ground wire. 
 
 Return Current. The discharge current 
 from a telegraph line passing to ground 
 at the sending end. 
 
 Return Feeders. (1) The feeders through 
 which a current returns to a central sta- 
 tion. (2) Negative feeders. (3) The 
 feeders connected with the track in a 
 trolley system. (4) Ground feeders. 
 
 Return Feeders for Railway Circuits. 
 Copper conductors employed in rail- 
 way circuits for re-enforcing ground-re- 
 turn circuits, and usually insulated. 
 
 Return Ground. (1) That part of the 
 ground employed as a return. (2) The 
 ground-return. 
 
 Return-Signal Call-Box . An answer- 
 ing call-box. 
 
 Return Stroke of Lightning. An 
 electric discharge induced by the direct 
 discharge of a lightning flash, as distin- 
 guished from the direct discharge itself. 
 
 Return-Track Feeder. A feeder in a 
 trolley system connected to the track. 
 
 Return Wire. The wire or conductor by 
 means of which the current returns to 
 the electric source after having passed 
 through the electro-receptive devices. 
 
 Returns. In a system of distribution, 
 those conductors through which the cur- 
 
 rent flows back from the electro-receptive 
 devices to the sources. ' 
 
 Reversal. (1) A change in direction. 
 (2) A semi-wave. 
 
 Reversal of Phase. A change in the 
 phase of a current due either to the re- 
 versal of the current or of the conductor 
 in which it is produced. 
 
 Reversals. In telegraphy, alternate-cur- 
 rent signals transmitted for the purpose 
 of adjustment or for clearing the line of 
 a charge. 
 
 Reverse - Current Working. Teleg- 
 raphic transmission by means of reverse 
 currents, or double currents. 
 
 Reverse Currents. (1) A name some- 
 times applied to alternating currents. 
 (2) A name sometimes applied to double- 
 currents. 
 
 Reverse-Induced Current. (1) The cur- 
 rent induced by a current in its own cir- 
 cuit at the moment of making or closing 
 the circuit. (2) The current induced in a 
 secondary circuit on making or clos- 
 ing a primary circuit. 
 
 Reverser. Any device for reversing or 
 changing the direction of a current. 
 
 Reverser Bars. The commutator con- 
 nection employed in Sayer's armature 
 winding which carries the current during 
 the short time that the corresponding 
 sections are passing under the brushes. 
 
 Reversible Bridge. A bridge or balance 
 so arranged that the proportionate coils 
 can be readily interchanged, thus per- 
 mitting the bridge coils to be readily 
 tested by reversing. 
 
 Reversible Electric Motor. (1) A mo- 
 tor whose direction of motion is readily 
 reversed. (2) A motor which is so ar- 
 ranged as to be readily operated as a gen- 
 erator. 
 
 Reversible Heat. The heat produced in 
 a heterogeneous conductor by the passage 
 through it of an electric current. 
 
 Reversible Heating Effect of Elec- 
 tricity. A term sometimes employed in 
 place of the Peltier effect. 
 
 Reversible Regenerative Armature. 
 A regenerative armature that is capable 
 of generating electromotive forces when 
 the direction of its rotation is reversed. 
 
 Reversibility of Dynamo. The ability 
 of a dynamo to operate as a motor when 
 traversed by an electric current. 
 
 Reversing. Changing any direction to its 
 opposite. 
 
 Reversing a Current. Changing the di- 
 rection of a current. 
 
Rev.] 
 
 
 907 
 
 [Bib, 
 
 Reversing Cell. A voltaic cell whose 
 couple and electrolyte are contained in a 
 hermetically closed vessel so arranged 
 that when the cell is placed in one posi- 
 tion the electrolyte does not touch the 
 couple, and when reversed the electrolyte 
 surrounds the couple. 
 
 Reversing Controlling-Box. A motor 
 controlling-box which enables the direc- 
 tion of rotation of the motor to be re- 
 versed. 
 
 Reversing Cylinder. (1) The cylinder in 
 a motor-controlling apparatus carrying 
 the reversing contacts. (2) The contact 
 cylinder of a reversing switch. 
 
 Reversing-Gear of Electric Motor. 
 Apparatus for obtaining a reversal in the 
 direction of rotation of a motor. 
 
 Reversing-Handle of Car Controller. 
 (1) A switch handle placed on a car con- 
 troller for the purpose of changing its 
 direction of motion. (2) The handle of 
 an emergency switch in a street-car con- 
 troller. 
 
 Reversing Key. (I) A key inserted in 
 the circuit of a galvanometer for obtain- 
 ing deflections of the needle on either side 
 of the galvanometer scale. (2) A key 
 which serves to reverse the current sup- 
 plied to a circuit. 
 
 Reversing Key of Quadruplex Tele- 
 graphic System. The key in a quadru- 
 plex system which reverses the direction 
 of the current and so operates one of the 
 distant instruments. 
 
 Reversing Magnetic-Field. That por- 
 tion of the field of a dynamo produced by 
 the field-magnet coils, in which the cur- 
 rents flowing in the armature coils are 
 stopped or reversed after the coil has 
 passed its theoretical position of neu- 
 trality. 
 
 Reversing Switch. A switch employed 
 in reversing a circuit or current. 
 
 Revolving Primary of Induction 
 Motor. (1) A rotor primary. (2) In an 
 induction motor, a revolving element 
 connected with the line. 
 
 Revolving System. The twist system of 
 erecting telegraph or telephone wires, so 
 as to avoid induction. 
 
 Rheocord. A word formerly employed 
 for rheostat. (Obsolete.) 
 
 Rheometer. A word formerly employed 
 for any device for measuring the strength 
 of a current. (Obsolete.) 
 
 Rheomotor. A word formerly employed 
 to designate any electric source. (Obso- 
 lete.) 
 
 Rheophore. A word formerly employed 
 
 to indicate a portion of a circuit convey- 
 ing a current and capable of deflecting a 
 magnetic needle placed near it. (Obso- 
 lete.) 
 
 Rheoscope. A word formerly employed 
 in place of galvanoscope. (Obsolete.) 
 
 Rhebscopic Limb. A word sometimes 
 employed for a physiological rheoscope, 
 such as the galvanoscopic frog. 
 
 Rheostat. An adjustable resistance. 
 
 Rheostat Frame. A perforated frame or 
 casing in which the separate resistances 
 of a rheostat are placed. 
 
 Rheostat Handle of Car-Controller. 
 The main switch of a car-controller. 
 
 Rheostat Panel. A panel in any switch- 
 board to which the rheostat circuits are 
 connected. 
 
 Rheostatic Machine. A machine de- 
 vised by Plante in which continuous static 
 effects of considerable intensity are ob- 
 tained by charging a number of con- 
 densers from storage cells connected in 
 multiple-arc, and then discharging the 
 condensers in series. 
 
 Rheotome. A word formerly employed 
 
 for interrupter. (Obsolete. ) 
 Rheotometer. A compound bridge and 
 
 rheostat. 
 
 Rheotrope. A word formerly employed 
 for commutator or current reverser. 
 
 Rhigolene. A highly volatile hydro-car- 
 bon obtained during the distillation of 
 coal-oil, and sometimes employed in the 
 flashing treatment of incandescent lamp 
 filaments. 
 
 Rhumbs of Compass. The points of a 
 mariner's compass. 
 
 Ribbed Armature-Core. A cylindrical 
 armature core provided with longitudinal 
 projections or ribs which serve as grooves 
 for the reception of the armature coils. 
 
 Ribbon Conductor. A flat, ribbon- 
 shaped conductor. 
 
 Ribbon Copper. A copper strip or rib- 
 bon-shaped copper conductor. 
 
 Ribbon Core. A form of laminated core 
 
 made by iron ribbons. 
 Ribbon Fuse. A fuse in the shape of a 
 
 ribbon. 
 
 Ribbon Induction-Coil. An induction- 
 coil whose primary and secondary circuits 
 are formed of metallic ribbons instead of 
 wires. 
 
 Ribbon Vibrator. An electro-magnetic 
 contact-breaker consisting of a horizontal 
 steel ribbon, the rate of vibration of 
 
908 
 
 [Kin. 
 
 which can be varied by varying its ten- 
 sion. 
 
 Bight - Angled Trolley - Crossing. A 
 trolley crossing placed at a point where 
 two streets intersect at right angles. 
 
 Bight-Hand Trolley-Prog. A trolley 
 frog used at a point where a branched 
 trolley wire leaves the main line on the 
 right hand in the direction of advance. 
 
 Bight-Hand Trolley-Switch. A term 
 sometimes used for a right-hand trolley 
 frog. 
 
 Bight-Handed Armature Winding. 
 An armature winding applied to the core 
 in a right-handed or dextrorsal helix. 
 
 Bight-Handed Dynamo. A dynamo 
 whose proper direction of rotation is 
 right-handed regarded from the pulley 
 end. 
 
 Bight-Handed Helix. (1) A right- 
 handed solenoid. (2) A helix wound 
 right-handedly when regarded from either 
 end. 
 
 Bight-Handed Motor. A motor ar- 
 ranged to run right-handedly or clock- 
 wise when regarded from the pulley end. 
 
 Bight-Handed Botation. (1) A direction 
 of rotation which is the same as that of 
 the hands of a watch, when one looks 
 directly at the face of the watch. (2) Neg- 
 ative rotation. 
 
 Bight-Handed Solenoid. A dextrorsal 
 solenoid or one whose winding is right- 
 handed. 
 
 Bight-Handed Spiral. A term some- 
 times used for right-handed solenoid. 
 
 Bight-Handed Winding. A winding 
 applied in a right-handed direction. 
 
 Ring Armature. An armature provided 
 with a ring-shaped core. 
 
 Bing-Armature Core. A ring-shaped 
 armature core. 
 
 Bing Clutch. A form of clutch employed 
 for gripping the lamp rod of an arc-lamp 
 when slightly moved from a horizontal 
 position. 
 
 Bing Clutch for Arc-Lamp. A ring- 
 shaped clutch embracing the lamp rod, 
 which grips or holds the rod when tilted 
 or inclined, but permits it to fall when in 
 a horizontal position. 
 
 Bing-Connected Armature. An arma- 
 ture provided with ring connections. 
 
 Bing-Connected Generator. A gener- 
 ator provided with an armature winding, 
 in which corresponding points are con- 
 nected to ring conductors for the purpose 
 of equalizing the magnetic flux and the 
 current distribution around the armature. 
 
 Bing Connections of Armature Con- 
 ductors in the form of rings in a multi- 
 polar armature to each of which are con- 
 nected corresponding points of the arma- 
 ture winding for the purpose of equaliz- 
 ing the current and magnetic flux in the 
 machine. 
 
 Bing Core. A ring-armature core. 
 
 Bing Current of Triphase System. 
 The current flowing between adjacent 
 wires or terminals of a triphase system. 
 
 Bing Magnet. A uniformly magnetized 
 rod bent into a closed ring. 
 
 Bing Main. A ring-shaped distributing 
 main. 
 
 Bing-Off. A term employed for a signal 
 sent by a telephone correspondent when 
 the conversation is finished. 
 
 Bing-Off Drop. (1) A telephone drop re- 
 leased by a ring-off signal. (2) A drop 
 placed at a central telephone station, and 
 operated by a subscriber when he rings 
 off or hangs up his telephone. 
 
 Bing-Off Signal. A signal given by a 
 subscriber at the close of his conversation, 
 to inform the central station that the 
 connection may be discontinued. 
 
 Bing-Off Telephone-Indicator. Any 
 
 indicator on a telephone switchboard that 
 is operated by a ring-off signal. 
 
 Bing Potential of Triphase System. 
 The effective difference of potential or 
 voltmeter pressure between adjacent 
 lines or terminals of a triphase system. 
 
 Bing-Up. (1) In telephony, to actuate the 
 call-bell of a subscriber wanted. (2) To 
 call up an operator at an exchange or a 
 distant subscriber. 
 
 Bing Windings. Windings suitable for 
 use in a ring-wound armature. 
 
 Bing - Wound Armature. An arma- 
 ture consisting of a ring core with coils of 
 wire wound thereon. 
 
 Binger. A telephone magnet. 
 
 Binger Coils. The coils or winding of a 
 telephone magneto. 
 
 Binger Magnet. A permanent magnet 
 employed in a telephone magneto or 
 ringer. 
 
 Binging Keys. In a telephone switch- 
 board, keys for closing a generator upon 
 a subscriber's circuit to ring his bell. 
 
 Binging Key. In a telephone switch- 
 board, a key employed to ring up a sub- 
 scriber. 
 
 Binging Key-Bars. In a telephone 
 switchboard, metallic bars connecting the 
 ringing keys with the instrument bara 
 and generator. 
 
Kin.] 
 
 909 
 
 [Roo. 
 
 Kings, Electric. A term sometimes used 
 instead of Nobili's rings. 
 
 Ripple Marks, Electric. Wave marks 
 produced in a fine powder by a neighbor- 
 ing Leyden-jar discharge. 
 
 Risers. (1) Supply wires which lead the 
 current from the service wires to the dif- 
 ferent floors of a building. (2) The supply 
 wires which rise to the various floors, as 
 distinguished from floor mains, submains, 
 or branches, which run along each floor. 
 
 River Cable. (1) A cable suitable for use 
 in a river. (2) A form of sub-aqueous 
 cable. 
 
 Riveted Railway-Joint. A rail-bond in 
 which the connection between two con- 
 tiguous rails is obtained by riveting spe- 
 cially heavy fish-plates to each end of the 
 rail. 
 
 Riveting Apparatus. Electric. A rivet- 
 ing apparatus employing electrically gen- 
 erated heat. 
 
 Roaring of Arc. A roaring sound attend- 
 ing the formation of a powerful voltaic 
 arc when the carbons are too near to- 
 gether. 
 
 Rock-Drill, Electric. An electrically 
 operated rock-drill. 
 
 Rocker Arm. An arm on which the 
 brushes of a dynamo or motor are mount- 
 ed for the purpose of shifting their posi- 
 tion on the commutator. 
 
 Rocker-Arm Circle. The frame of a 
 dynamo-electric machine which supports 
 the brush arms and is capable of adjust- 
 ment in angular position. 
 
 Rocking Switch. An automatic throw- 
 over switch. 
 
 Rod Clamp. A clamp employed in the 
 lamp-rod of an arc-lamp. 
 
 Rod Clutch. The clutch .employed for 
 gripping an arc-lamp rod. 
 
 Rod Switch. A switch provided for 
 lighting and extinguishing a lamp, so ar- 
 ranged that it can readily be pushed to its 
 off or on position by means of a rod. 
 
 Rodding a Conduit. The process of in- 
 troducing a drawing-in wire through the 
 ducts of an underground conduit by 
 pushing a number of short sections of 
 jointed rods through such ducts. 
 
 Roentgen Effects. The peculiar effects 
 produced by Roentgen or X-rays. 
 
 Roentgen Ether Waves. A term some- 
 times employed for Rontgen rays. 
 
 Roentgen Radiograph. A word pro- 
 posed for radiograph. 
 
 Roentgen-Ray Picture. A word pro- 
 posed for radiograph. 
 
 Roentgen-Ray Screen . ( 1 ) A screen cov- 
 ered with fluorescent material intended 
 to receive a visible Roentgen picture. 
 (2) A fluoroscopic screen. 
 
 Roentgen Ray Transformer. An alter- 
 nating-current transformer suitable for 
 operating a Roentgen ray tube. 
 
 Roentgen-Ray Tube. A vacuum tube 
 for the production of Roentgen rays, or 
 X-rays. 
 
 Roentgen Rays. A peculiar radiation 
 emitted in the neighborhood of that por- 
 tion of a high vacuum tube on which the 
 cathode rays fall. 
 
 Roentgen Shadow Print. A radio- 
 graph. 
 
 Roentgen Streams. (1) Roentgen or 
 X-rays. (2) A term applied to the Roent- 
 gen rays, by those who regard them 
 as consisting of actual streams of matter 
 thrown off, either from the cathode, or 
 from the residual atmosphere of the 
 vacuum tube. 
 
 Roentgen Tube. Any high-vacuum tube 
 capable of producing Roentgen rays. 
 
 Roentgengram. A word proposed for 
 radiograph. 
 
 Roentgengraph. A word proposed for 
 radiograph. 
 
 Roget's Spiral. (1) A spiral, helix or 
 solenoid, freely suspended at its upper 
 end so that its lower end shall dip in a 
 mercury surface, which when traversed 
 by a sufficiently powerful current will 
 break its own circuit by the attraction 
 produced by its adjacent convolutions 
 when by its weight it will complete the 
 circuit, and thus be alternately opened 
 and closed. (2) A form of automatic con- 
 tact-breaker. 
 
 Roman Vitriol. A name formerly applied 
 to blue-stone or copper sulphate. 
 
 Rontgram. A word proposed for radio- 
 graph. 
 
 Rontgraph. A word proposed for radio- 
 graph. 
 
 Rontgraphy. A word proposed for radio- 
 graphy. 
 
 Roof Box of Push. A term sometimes 
 employed for the upper covering of the 
 box of a push-button. 
 
 Roof Bracket. (1) An insulator bracket, 
 either straight or offset for attachment to 
 a roof. (2) A form of house fixture pro- 
 vided for the support of overhead wires. 
 
 Roof Standard. A form of house fixture 
 provided for overhead wires. 
 
Roo.] 
 
 910 
 
 [Rub. 
 
 Room Call, Electric. Any device placed 
 in the room of a hotel for the purpose of 
 automatically sending calls to the office. 
 
 Hope Transmission. Transmission of 
 power by means of ropes or cables. 
 
 Rosette. (1) An ornamental plate pro- 
 vided with service wires and placed in a 
 , wall or ceiling for the ready attachment 
 of an electric lamp or electrolier. (2) A 
 word sometimes used in place of ceiling 
 rose. 
 
 Rosette Cut-Out. A rosette for an elec- 
 trolier, provided with a cut-out. 
 
 Rotary Converter. A secondary gener- 
 ator for transforming alternating into 
 continuous currents or vice-versd, con- 
 sisting of an alternating-current machine 
 whose armature winding is connected 
 with a commutator ; or of a continuous- 
 current machine, whose armature is 
 tapped at symmetrical points and con- 
 nected to collector rings ; so that, when 
 the armature runs it is an alternator on 
 one side and a direct current machine on 
 the other. (2) A rotary transformer. 
 
 Rotary Current. (1) A name applied to 
 any system of polyphase currents which 
 are capable of producing a rotary field. 
 (2) A rota ting-current distribution. 
 
 Rotary-Current Transformer. A 
 transformer capable of being operated by 
 a rotary current. 
 
 Rotary Electric Field. A rotary elec* 
 trostatic field. 
 
 Rotary Electro-Type. (1) A term some- 
 times used for a turtle-back. (2) Any 
 electro-type with a curved surface suit- 
 able for printing in a cylinder press. 
 
 Rotary-Field Induction-Motor. An 
 induction motor operated by a rotary 
 field. 
 
 Rotary -Field Motor. A rotary-field in- 
 duction-motor. 
 
 Rotary Induction Transformer. A 
 rotary-current transformer. 
 
 Rotary-Magnetic Field. (1) A field 
 produced by a rotary current. (2) A mag- 
 netic field in which a set of magnet 
 poles is produced, whose successive posi- 
 tions are such that a rotation of the field 
 is effected. 
 
 Rotary -Magnetic Polarization. The 
 rotation of the plane of polarization of a 
 beam of plane-polarized light, consequent 
 on its passage through a medium sub- 
 jected to the stress of a magnetic field. 
 
 Rotary Magnetism. The magnetism 
 produced by a rotary magnetic field. 
 
 Rotary-Phase Alternating-Currents. 
 Rotary-phase currents. 
 
 Rotary-Phase Currents. A term some- 
 times employed for a rotating electrio 
 current distribution. 
 
 Rotary -Phase Dynamo. A term some- 
 times employed for a rotating-current 
 dynamo. 
 
 Rotary Transformer. (1) A term gener- 
 ally employed for the combination of a 
 motor and generator in one machine 
 having a single armature-winding trav- 
 ersed both by alternating and continuous 
 currents. (2) A secondary generator for 
 transforming from alternating to contin- 
 uous currents or vice-versd. (8) A rotary 
 converter. 
 
 Rotating Brushes of Dynamo. (1) Eo- 
 tating discs of metal employed in place of 
 the ordinary brushes for carrying off the 
 current from the armature of a dynamo. 
 (2) Brushes revolved around the periphery 
 of a commutator. 
 
 Rotating Current. (1) A term applied 
 to the current which results by combining 
 a number of alternating currents, whose 
 phases are definitely displaced with re- 
 spect to one another. (2) A polyphase or 
 multiphase current. 
 
 Rotating-Current Field. A magnetic 
 field produced by a rotating current. 
 
 Rotating-Current Motor. A motor 
 operated by a rotating current. 
 
 Rotating-Current Transformer. A ro- 
 tary-current transformer. 
 
 Rotating Transformer. (1) A rotary 
 transformer. (2) An induction motor. 
 
 Rotating Vector. A line or vector 
 quantity which rotates about a fixed 
 point. 
 
 Rotometer. A form of cyclometer at- 
 tached to a drum for measuring the 
 amount of cable passing over the drum in 
 picking up or paying out a submarine 
 cable. 
 
 Rotor. That portion of a dynamo-electric 
 machine which rotates. 
 
 Rotor Armature. An armature which 
 rotates. 
 
 Rotor Circuit. The circuit of a rotor. 
 
 Rotor Coils. The coils placed on a rotor. 
 
 Rotor Currents. The currents produced 
 in the rotor coils. 
 
 Rotor Field. The field of a rotor. 
 
 Round Wire-Gauge. A. wire gauge con- 
 sisting of a circular plate provided on its 
 circumference with slots of various sizes. 
 
 Rubber of Electric Machine. That 
 portion of a frictional machine which 
 produces the electricity by rubbing against 
 a disc or plate. 
 
Rul).] 
 
 
 911 
 
 [Saf. 
 
 Rubber Tape. A form of adhesive, in- 
 sulating tape made of rubber. 
 
 Rubbing Contact. A contact effected 
 by means of a rubbing motion. 
 
 Rubbing Contact Key. A key provided 
 with a rubbing contact. 
 
 Ruhmkorff Coil. (1) An early form of 
 induction coil or step-up transformer. 
 (2) An induction coil having an iron-wire 
 core, and a fine wire secondary coil of 
 many turns for the production of power- 
 ful induced E. M. F.'s, usually excited 
 from a battery or continuous - current 
 source through a suitable current breaker. 
 
 Ruhmkorff Commutator. A com- 
 mutator employed in a Ruhmkorff coil 
 for reversing the direction of the current 
 through the primary. 
 
 Rumble. A barrel, or hollow box, rotated 
 by mechanical power, in which small 
 articles are prepared for electro-plating 
 by the polishing obtained by their attrition 
 against one another, or against hard ob- 
 jects placed therein. 
 
 Run-Down Cell. An exhausted cell. 
 
 Running-Board. A device employed in 
 the construction of a heavy overhead line, 
 
 . consisting in placing a number of reels 
 of wire, usually ten or more, on a spindle, 
 and arranging a piece of wood as a cross- 
 arm to which ten or more wires are at- 
 tached, harnessing horses to the cross- 
 piece, and then dragging the running 
 board away as the wires are paid out 
 from the reels, and passing them over 
 their appropriate cross-arms, where they 
 are at once secured to the insulators by 
 line-men. 
 
 Running Guard- Wire. A wire provided 
 in a system of aerial trolley circuits, ex- 
 tending parallel to and immediately above 
 the trolley wire, intended to intercept any 
 wire falling on the line from above. 
 
 Running Position of Street-Car Con- 
 troller. A position of the switch-handle 
 of a street-car controller at which current 
 is supplied to the car-motors and they are 
 
 . kept in I'otation, as distinguished from a 
 position in which the current is cut-off. 
 
 Running Rope. A rope attached to the 
 running-board employed in the stringing 
 of aerial wires. 
 
 Running Torque of Motor. The torque 
 exerted by a motor while running, as 
 distinguished from the starting torque. 
 
 S. A contraction proposed for surface. 
 
 S. A contraction proposed for second. 
 
 8. An abbreviation for second, the C. G. S. 
 unit of time. 
 
 S. C. A contraction for secondaiy current. 
 
 S. G. In submarine telegraphy, the prefix 
 for a service message, or a message relat- 
 ing to the business of the company only. 
 
 S. H. M. A contraction for simple-har- 
 monic motion. 
 
 S. P. D. A contractive for secondary pot- 
 ential difference. 
 
 S. N. Code. A contraction for single- 
 needle code. 
 
 S. N. Telegraphic-Instrument. A con- 
 traction employed for single-needle tele- 
 graphic instrument. 
 
 S. P. Cut-Out. A contraction for single- 
 pole cut-out. 
 
 S. R. G. A contraction for standard rail- 
 road gauge or 4'.8i''. 
 
 S. W. G. A contraction for the British 
 standard wire gauge. 
 
 S. W. G. A contraction for Stubb's wire 
 gauge. 
 
 Saddle Bracket. A bracket holding an 
 insulator and fastened to the top of a tele- 
 graph or telephone pole. 
 
 Safe Alarm. An electro-magnetic alarm 
 connected with a safe and designed to 
 give notice of an attempt to force the same. 
 
 Safe Carrying Capacity of a Conduc- 
 tor. The maximum electric current a 
 conductor will carry without becoming 
 unduly heated. 
 
 Safety Catch. A safety fuse. 
 
 Safety-Catch Holder. A holder for a 
 safety fuse. 
 
 Safety Cut-Out. A safety fuse. 
 
 Safety Device. Any device by means of 
 which a circuit is automatically opened 
 or short-circuited when the current pass- 
 ing through it exceeds certain pre-deter- 
 mined limits. 
 
 Safety Device for Arc-Lamps or Series 
 Circuit. Any mechanical device which 
 automatically provides a path for a cur- 
 rent around a lamp, or other faulty re- 
 ceptive device in a series circuit, and thus 
 prevents the opening of the entire circuit 
 on the failure of such device. 
 
912 
 
 [Sea. 
 
 Safety Device for Multiple Circuit. 
 
 (1) A safety fuse. (2) A fuse wire or strip. 
 (3) Any device for protecting a branch 
 circuit, instrument or conductor from an 
 excessive current. 
 
 Safety Factor of Transformer. The 
 ratio of the voltage with which a trans- 
 former has been tested, to the voltage at 
 which it is operated. 
 
 Safety Fuse. A wire, bar, plate or strip 
 of readily fusible metal, capable of con- 
 ducting, without fusing, the current or- 
 dinarily employed on the circuit, but 
 which fuses and thus automatically 
 breaks the circuit on the passage of an 
 abnormally strong current. 
 
 Safety Fuse-Block. A block provided 
 for the reception of a safety fuse. 
 
 Safety Lamp, Electric. (1) An incan- 
 descent lamp, provided with thoroughly 
 insulated leads,employed in mines or other 
 similar places, where the explosive effects 
 of readily ignited substances are to be 
 feared. (2) A portable electric incandes- 
 cent lamp and battery for use in mines 
 where explosive gases may be found. 
 
 Safety Link. A link-shaped safety-fuse. 
 
 Safety Plug. (1) A safety fuse. (2) An 
 insulating screw-plug containing a safety 
 fuse, which by its insertion in a suitably 
 prepared socket, automatically closes the 
 circuit through such fuse. 
 
 Safety Strip. A strip of fusible metal 
 employed as a safety fuse. 
 
 Sag of Conductor or Line Wire. The 
 dip of an aerial wire or conductor, be- 
 tween two adjacent supports, due to its 
 weight. 
 
 Sag Error. (1) Any error in installing an 
 serial wire due to insufficient allowance 
 for sag with change of temperature. (2) 
 Any error in computing the length of an 
 aerial wire due to insufficient allowance 
 for sag. 
 
 Saint Elmo's Fire. Tongues of faintly 
 luminous flame which sometimes appear 
 on the pointed ends of earth-connected 
 bodies, such as the tops of church stee- 
 ples, or the masts of ships. 
 
 Salient Magnetic Poles. A term some- 
 times applied to the single poles located 
 at the extremities of an anomalous mag- 
 net, in order to distinguish them from 
 the double or consequent poles formed by 
 the juxta-position of two similar mag- 
 netic poles. 
 
 Salimeter. A form of hydrometer suit- 
 able for measuring the density of a saline 
 solution. 
 
 Saline Creeping. The fonnation,by efflo- 
 
 rescence, of salts on the walls of a solid 
 immersed in a saline solution. 
 
 Saline Solution. A solution of a salt in 
 a liquid. 
 
 Sand-Barrel Setting for Pole. A stout 
 barrel or cask, placed in the bottom of 
 an excavation in a loose, sandy soil, as a 
 pole foundation in which the butt of the 
 pole is placed, and a firm loam or clay 
 tightly packed into the barrel around the 
 pole. 
 
 Sand-Box for Electric Car. A box em- 
 ployed for holding sand, so arranged as 
 to distribute it over a track as desired, 
 for the purpose of increasing the friction. 
 
 Sanding Device. A device employed for 
 sprinkling sand over a car-track. 
 
 Sandy Electro-Metallurgical Deposit. 
 A non-coherent electro-metallurgical de- 
 posit, which occurs when the current 
 density exceeds its normal value. 
 
 Sash Lines. Ropes employed in raising 
 telegraph poles to the vertical position. 
 
 Saturated Solution. A solution in 
 which as much of the solid has been dis- 
 solved as the solvent will take at a given 
 temperature. 
 
 Saturating Flux. The flux required to 
 produce magnetic saturation in any cir- 
 cuit. 
 
 Saw, Electric. An electrically operated 
 saw. 
 
 Saw - Tooth Lightning - Arrester. A 
 name sometimes applied to a comb light- 
 ning-arrester. 
 
 Sayers Armature Winding. An arma- 
 ture winding provided with additional 
 coils called commutator coils which are 
 subjected to the influence of an auxiliary 
 pole and which are introduced into the 
 main circuit to obtain sparkless commu- 
 tation. 
 
 Scalar. The name given to a quantity 
 which has no directive property, or which 
 has numerical magnitude only, such as 
 temperature, or energy, as distinguished 
 from a vector quantity. 
 
 Scalar Potential. A potential possessing 
 magnitude and sign without direction, as 
 distinguished from a vector potential 
 which possesses both direction and mag- 
 nitude. 
 
 Scale Zero. (1) An instrument zero. (2) 
 A zero selected at the zero mark of a scale. 
 
 Scarf Joint of Conductors. A joint be- 
 tween the ends of conductors in which 
 the ends are prepared by filing them diag- 
 onally, so that when laid together and 
 soldered, the joint is cylindrical in shape, 
 
Sch. 
 
 
 913 
 
 [Sec. 
 
 presents no rough edge, and, unlike a 
 butt joint, extends over an appreciable 
 length. 
 
 Schiseophone. An electro - mechanical 
 appliance for detecting flaws or internal 
 defects in rails or other metallic masses. 
 
 Schweigger's Multiplier. A name 
 formerly given to a coil consisting of a 
 number of turns of insulated wire, pro- 
 vided for the purpose of increasing the 
 strength of the magnetic field produced 
 by an electric current, and so increasing 
 the amount of its deflecting power on a 
 magnetic needle. 
 
 Sciagraph. A word proposed for radio- 
 graph. 
 
 Sciagraphic Print. A word sometimes 
 used for radiograph. 
 
 Sciagraphy. A word proposed for radi- 
 ography. 
 
 Scintillating Jar. A Ley den jar whose 
 coatings, instead of being formed of con- 
 tinuous sheets of tin-foil, are formed of 
 small pieces, placed at regular intervals 
 on the glass or dielectric, so as to leave a 
 small space between them. 
 
 Scratch Brush. A brush made of wires, 
 or of stiff bristles, employed for cleansing 
 the surfaces of metallic objects before sub- 
 jecting them to the electro-plating proc- 
 ess. 
 
 Scratch Brushing. Cleansing the sur- 
 faces of articles to be electro-plated by 
 friction with a scratch brush. 
 
 Screen, Electric. A closed conductor 
 placed over a body in order to protect or 
 screen it from the effects of external 
 electro-static fields. 
 
 Screening. Protecting a body from the 
 effect of an electrostatic or electro-mag- 
 netic field by means of a screen. 
 
 Screening Effect of Eddy Currents. 
 
 A term sometimes used for the effect pro- 
 duced by eddy currents in a solid mass of 
 iron or steel, of shielding the interior of 
 the mass from an externally applied 
 alternating magnetic field. 
 Screw Block-Fuse. (1) A form of plug 
 cut-out. (2) A screw-plug in a receptacle 
 or block containing a fuse. 
 
 Screw Cleat. A cleat provided with a 
 screw for its ready attachment to wood- 
 work. 
 
 Sea Cell Test. In a sub-marine system of 
 electric torpedoes, a circuit test by means 
 of a single voltaic cell in which sea water 
 is the electrolyte. 
 
 Sea Telegraphy. (1) Submarine Teleg- 
 58 
 
 raphy. (2) Telegraphy carried on at 
 sea either between neighboring vessels or 
 between different parts of the same ves- 
 sel. 
 
 Seal of Meter. A leaden seal placed on a 
 meter, after it has been properly installed, 
 for preventing its being tampered with. 
 
 Sealing-In of Filament. Effecting a 
 hermetical seal between the support of 
 the filament of an in candescent lamp and 
 the lamp chamber in which it is placed. 
 
 Sealing-Off of Lamp Chamber. Her- 
 metically closing a lamp chamber while 
 it is connected with the pumps, by the 
 fusing of the glass. 
 
 Sealing Tools. Tools employed for place 
 ing a seal on a meter. 
 
 Sealing Wires. Wires employed for 
 forming part of the seal of a meter. 
 
 Search-Light, Electric. A focussing 
 arc light placed in front of a reflector 
 or lens, for the purpose of obtaining an 
 approximately parallel beam of light for 
 lighting the surrounding space. 
 
 Searching Coil. A term sometimes ap- 
 plied to an exploring coil. 
 
 Secohm. (1) The practical unit of self- 
 induction, or of inductance. (2) A length 
 equal by definition to that of an earth 
 quadrant, or very nearly 10 9 centimetres. 
 
 (3) A henry. 
 
 Secohmmeter. An apparatus for measur- 
 ing the self-inductance, the mutual in- 
 ductance, or the capacity of conductors. 
 
 Secondary. A word frequently employed 
 for the secondary coil of a transformer or 
 induction coil. 
 
 Secondary Accumulator. A storage- 
 cell accumulator. 
 
 Secondary Ampere-Turns. Ampere- 
 turns in the secondary of a transformer 
 or induction coil. 
 
 Secondary Admittance. The admit- 
 tance of a secondary circuit. 
 
 Secondary Battery. A word frequently 
 used for storage battery. 
 
 Secondary Cell. A word frequently used 
 for storage cell. 
 
 Secondary Clock. Any clock in a system 
 of time telegraphy that is controlled by 
 a master clock. 
 
 Secondary Coil of Transformer. 
 
 (1) The coil of a transformer into which 
 energy is transferred from the primary 
 line and primary coil. (2) The secondary 
 winding of a transformer or induction 
 coil. (3) The driven coil of a transformer. 
 
 (4) The coil in the external circuit of 
 
Sec.] 
 
 914 
 
 [Sec. 
 
 which there is no directly impressed E. 
 M. F. 
 
 Secondary Currents. (1) The currents 
 produced in the secondary of a trans- 
 former. (2) The currents produced by 
 secondary batteries. (3) Currents in any 
 secondary circuit. 
 
 Secondary Electromotive Forces. A 
 name sometimes given to the electromo- 
 tive forces produced by a secondary cell 
 or battery. 
 
 Secondary Element of Induction 
 Motor. Those portions of an induc- 
 tion motor, closed upon themselves, in 
 which currents are induced. 
 
 Secondary Frequency of Induction 
 Motor. The frequency of the alternat- 
 ing currents induced in the secondary 
 circuits of an induction motor, compris- 
 ing only a small fraction of the frequency 
 in the primary circuit or circuits. 
 
 Secondary Fuse-Box. A fuse box placed 
 in the secondary circuit of a transformer 
 or induction coil. 
 
 Secondary Generator. (1) A generator 
 which is not a prime source of energy, 
 but receives its energy from some other 
 electrical circuit either at some anteced- 
 ent period, as in the case of a storage cell, 
 or coincidently, as in the case of a trans- 
 former. (2) A term sometimes employed 
 for transformer. 
 
 Secondary Generator. A device em- 
 ployed in alternating-current circuits for 
 obtaining the working pressure on one 
 circuit by induction from a neighboring 
 circuit. 
 
 Secondary Impressed Electromotive 
 Force. The E. M. F. impressed upon a 
 secondary circuit, as distinguished from 
 the E. M. F. that is active in producing 
 current, or the E. M. F. exerted in over- 
 coming self-induction. 
 
 Secondary Impedance. In a secondary 
 circuit, the impedance, either of part, or 
 of all of the circuit. 
 
 Secondary Movers. The driven shafts 
 or machines, as distinguished from the 
 driving shafts or machines. 
 
 Secondary Plate of Condenser. That 
 plate of a condenser in which a charge is 
 induced by the presence of a charge on 
 the opposite plate. 
 
 Secondary Primary. A winding on an 
 induction coil intermediate between the 
 secondary and primary windings, ar- 
 ranged with the aid of revolving contacts 
 to serve, in each cycle, first as a secondary, 
 and next as a primary winding, for the 
 purpose of reducing the sparking at the 
 
 contact wheel of the primary coil when 
 excited from an incandescent-lighting 
 continuous-current circuit. 
 Secondary Resistance. The resistance 
 of a secondary coil or circuit. 
 
 Secondary Spiral of Induction Coil. 
 A term sometimes employed for the sec- 
 ondary winding of an induction coil. 
 
 Secondary Standard of Light. Any 
 standard of photometric intensity of light 
 that is not a fundamental standard, but 
 which is used as an intermediary to, or 
 with reference to, a fundamental stand- 
 ard. 
 
 Secret Telephone System. A domestic 
 telephone system arranged so that tele- 
 phonic communication can be obtained 
 between any two stations without being 
 overheard by a person at any other sta- 
 tion, and without the aid of an attendant 
 or exchange. 
 
 Secretion Current. A current following 
 electric stimulation of the secretoiy 
 nerves. 
 
 Section. (1) Apart. (2) A cutting plane. 
 
 (3) A graphical representation of the ap- 
 pearance that is, or would be, presented by 
 a body when exposed at a cutting plane. 
 
 (4) In a trolley system, a portion or length 
 of trolley conductor insulated from ad- 
 jacent portions. 
 
 Section Box. In a trolley system, a box 
 containing the connection to a section 
 and the switch by which it is connected 
 to a feeder. 
 
 Section Circuit-Breaker. A magnetic 
 circuit-breaker controlling a trolley-wire 
 section. 
 
 Section of Multiple Switchboard. A 
 complete division or reduplicating unit of 
 a switchboard, in which every jack ap- 
 pears once. 
 
 Section of Switchboard. A term some- 
 times used for a panel or a part of a 
 panal of a switchboard. 
 
 Section Insulator. An insulator in a 
 trolley-wire system, which electrically 
 disconnects one trolley section from an- 
 other. 
 
 Sectional Feeding-Point. In a street- 
 railway system, a point where a feeder 
 connects with a section of trolley wire or 
 main-supply conductor. 
 
 Sectional Plating. Plating an article 
 with a greater thickness of metal at cer- 
 tain points than at the rest of the surface. 
 
 Sectional Plating-Frame. A frame em- 
 ployed for holding an object to be electro- 
 plated so that it shall receive a greater 
 
Sec.] 
 
 
 915 
 
 [Sel. 
 
 depth of deposit on certain portions of its 
 surface than elsewhere. 
 
 Sectional Trolley-Line. A system of 
 trolley wires divided into sections. 
 
 Sectioned Coils for Magnet. (1) A term 
 employed for a method of winding a 
 magnetizing coil, in separate compart- 
 ments. (2) Dividing a winding space 
 into short axial sections, and filling each 
 with wire. 
 
 Secular. Of or pertaining to cycles of 
 time. 
 
 Section Switch. In a system of railway 
 or power-distribution, a switch control- 
 ling and supplying a section. 
 
 Secular Variation. A variation in the 
 magnetic declination, which occurs at 
 cycles or great intervals of time, as op- 
 posed to diurnal or annual variations. 
 
 Seebeck Effect. A term sometimes em- 
 ployed for thermo-electric effect. 
 
 See-Sawing. A term employed to char- 
 acterize the condition of two parallel-con- 
 nected alternators when they do not syn- 
 chronize properly. 
 
 See-Sawing of Parallel-Connected 
 Generators. (1) A term sometimes ap- 
 plied to the hunting of generators. (2) 
 Imperfect synchronism between gener- 
 ators. 
 
 Segment Switch. A switch in which a 
 pivoted strip or lever moves over the arc 
 of a circle divided into insulating seg- 
 ments. 
 
 Segments! Core-Disc. A dynamo core- 
 disc which, instead of being made in one 
 piece, is formed of suitable joined seg- 
 ments. 
 
 Seismic Photo-Chronograph. A chro- 
 nograph that photographically records 
 seismic disturbances. 
 
 Seismograph, Electric. An apparatus 
 for electrically recording the direction 
 and intensity of earthquake shocks. 
 
 Selectance. The property by virtue of 
 which resonant electric circuits respond 
 more to one frequency of alternating cur- 
 rent than to another. 
 
 Selective Absorption. The absorption 
 of a particular or selected character of the 
 waves of sound, light, heat or electricity. 
 
 Selective Consonance. That property 
 of a consonant alternating-current circuit 
 by virtue of which it responds more to 
 one frequency than to another. 
 
 Selective Emission. Selective radia- 
 tion. 
 
 Selective Opacity. (1) Opacity limited to 
 
 certain frequencies only. (2) Selectivity 
 as regards transparency. 
 Selective Radiation. (1) Radiation 
 limited to certain frequencies. (2) Selec 
 tivity as regards radiation. 
 
 Selective Resonance. The property of a 
 resonant circuit which renders it selective 
 to a definite frequency of alternating 
 current. 
 
 Selective Signal.-^l) A term sometimes 
 employed for an individual signal. (2) 
 A signal which affects one only of a 
 plurality of translating devices connected 
 to a circuit. 
 
 Selective-Signal Pendulum. A system 
 of selective signalling in which the re- 
 ceiving bells respond each to a single 
 alternating-current frequency, and the 
 transmitting frequency is adjusted cor- 
 respondingly by altering the virtual 
 length of a pendulum swinging in the 
 transmitter. 
 
 Selective Signalling - Apparatus. A 
 term sometimes employed for individual 
 signalling-apparatus. 
 
 Selectivity. (1) The capability for devel- 
 oping selective action. (2) The degree 
 of capability for effecting selection. 
 
 Selenium. A comparatively rare element, 
 generally found associated with sulphur, 
 the electric resistance of which is affected 
 by light. 
 
 Selenium Battery. A number of sepa- 
 rate selenium cells connected so as to 
 form a single cell or battery. 
 
 Selenium Cell. A cell consisting of a 
 mass of selenium fused in between two 
 conducting wires or electrodes of platin- 
 ized silver, or other suitable metal. 
 
 Selenium Eye. A rough model of the 
 human eye in which a selenium resist- 
 ance takes the place of 'a retina and two 
 slides the place of the eyelids. 
 
 Selenium Photometer.^-(l) A photo- 
 meter in which the intensity of the light is 
 estimated by the comparison of the 
 changes in the resistance of a selenium 
 resistance, successively exposed under 
 similar conditions to the light to be 
 measured and to a standard light. (2) A 
 photometer employing the photo-electric 
 properties of selenium. 
 
 Selenium Resistance. A mass of sele- 
 nium employed as a resistance, whose 
 value varies with the variations in the in- 
 tensity of the light to which it is exposed. 
 
 Self-Acting Make-and-Break. A term 
 sometimes employed for an automatic 
 make-and-break. 
 
 Self- Aligning-Bearings. Journal bear- 
 
Sel.] 
 
 916 
 
 [Sel. 
 
 ings so constructed and adjusted as to 
 permit of a slight angular range of move- 
 ment in order to conform to the surface of 
 the shaft. 
 
 Self-Cleaning Contact Key. A. name 
 sometimes given to a key provided with a 
 rubbing contact. 
 
 Self-Closing Telegraphic Key. A tele- 
 graphic key provided with an automatic 
 switch in its knob, so that pressing the 
 key opens the switch, and releasing the 
 key automatically closes the switch. 
 
 Self-Compounding Polyphase Gen- 
 erator. A polyphase generator whose 
 field magnets are compound-wound, and 
 which supplies the series winding with 
 currents conductively or inductively as- 
 sociated with those in the line. 
 
 Self-Contained Engine or Machine. 
 An engine or machine all of whose work- 
 ing parts are within the said engine or 
 machine. 
 
 Self-Cooling Transformer. (1) A trans- 
 former which maintains its temperature 
 within the necessary safe limits by natural 
 radiation and conduction, without the use 
 of any external cooling apparatus. (2) 
 An oil or air-insulated transformer in 
 which no forced circulation of the air or 
 oil is employed. 
 
 Self-Demagnetizing Force. The force 
 exerted by a permanent bar magnet tend- 
 ing to demagnetize itself, owing to the 
 passage of some of its flux back through 
 the bar in the opposite direction to the 
 magnetization through the substance of 
 the steel. 
 
 Self-Excitation. An excitation of the 
 field magnets of a generator obtained 
 by leading a portion or all of its own cur- 
 rent through its field coils, as distin- 
 guished from separate excitation. 
 
 Self-Excited. Excited by means of its 
 own current. 
 
 Self-Excited Alternator. An alternator 
 whose fields are self -excited. 
 
 Self-Excited Dynamo. A dynamo 
 whose field is self-excited. 
 
 Self-Excited Series-Wound Contin- 
 uous-Current Generator. A contin- 
 uous-current generator having a series- 
 wound field which is excited by the cur- 
 rent supplied from the armature of the 
 generator. 
 
 Self-Excited Shunt-Wound Contin- 
 uous-Current Generator. A contin- 
 uous-current generator having a shunt- 
 wound field which is excited by a small 
 part of the current supplied by the arma- 
 
 ture and diverted from the external cir- 
 cuit for that purpose. 
 
 Self-Induced Current. A current in- 
 duced in a circuit, on the opening or 
 closing of the circuit, by changes in its 
 own strength. 
 
 Self-induction. Induction produced in 
 a circuit by the induction of the current 
 on itself at the moment of starting or 
 stopping the current therein. 
 
 Self-induction Coil. (1) A coil of wire 
 possessing self-induction. (2) A choking 
 coil. 
 
 Self-Locking Annunciator Drop. 
 A name sometimes given to a self-restor- 
 ing telephone drop. 
 
 Self-Locking Pole Ratchet. A ratchet- 
 winder for raising and lowering an arc- 
 lamp on a pole, and provided with a self- 
 locking attachment. 
 
 Self-Oiling Bearings. (1) Bearings pro- 
 vided with automatic oilers. (2) Bear- 
 ings which lubricate themselves when 
 the shaft is rotating. 
 
 Self-Oiling Journal. A journal pro- 
 vided with automatic oilers. 
 
 Self-Polarizing Relay. A relay provided 
 not only with the ordinary set of magnet- 
 izing coils, but also with an additional 
 magnetizing coil for the magnetization of 
 its tongue, so that the magnetism of the 
 tongue is reversed when the current re- 
 verses. 
 
 Self-Recording Magnetometer. A 
 magnetometer which is capable of con- 
 tinuously recording the daily and hourly 
 variations of the earth's magnetic field. 
 
 Self-Registering Tachometer. A ta- 
 chometer that provides a permanent re- 
 cord of the varying speed of the machine 
 to which it is connected. 
 
 Self-Registering Wire-Gauge. A wire- 
 gauge arranged so as to register the dia- 
 meter of the wire to be measured. 
 
 Self-Regulating Dynamo. A self-regu- 
 lating generator. 
 
 Self-Regulating Generator. A gener- 
 ator so wound as to automatically main- 
 tain either a constant-current in the cir- 
 cuit, or a constant difference of potential 
 between its terminals, despite changes in 
 the resistance of its load. 
 
 Self-Regulating X-Ray Tube. An X- 
 ray tube provided with an automatic 
 means of adjusting the degree of vacuum, 
 and, therefore, the electric pressure at 
 its terminals. 
 
 Self-Regulation. Any form of automatic 
 regulation. 
 
Sel.] 
 
 917 
 
 [Sen. 
 
 Self-Restoring Annunciator Drop. 
 An annunciator drop so arranged as to be 
 capable of replacing itself, thus dispens- 
 ing with a manual replacement. 
 
 Self-Restoring Indicator. (1) An in- 
 dicator which will automatically resume 
 its proper position. (2) A self-restoring 
 drop or annunciator. 
 
 Self- Starting Alternating - Current 
 Motor. (1) An alternating-current mo- 
 tor which is capable of starting at any 
 normal load. (2) A non-synchronous 
 motor. 
 
 Self-Starting Synchronous Motor. 
 . An alternating-current synchronous mo- 
 tor which is in any way enabled to be 
 self -starting when connected with the 
 mains. 
 
 Self-Winding Clock. A clock that is 
 automatically wound at regular intervals 
 by the action of a small electro-magnetic 
 motor, contained within the clock, and 
 operated by one or more voltaic cells con- 
 cealed in the case of the clock. 
 
 Semaphore. A variety of visual signal 
 apparatus employed in railroad block sys- 
 tems. 
 
 Semaphore Arm. A movable arm of a 
 signal apparatus employed in block sys- 
 tems for railroads, for the purpose of in- 
 dicating the condition of the road as re- 
 gards other trains. 
 
 Semaphore Indicator. (1) An annunci- 
 ator in which a gravity drop or shutter is 
 caused to fall by the action of an electric 
 cmrent, thus exposing a number or other 
 signal back of the drop or shutter. (2) 
 An indicator employed in a semaphoric 
 signalling apparatus. (3) The movable 
 shutter or drop employed in a semaphore. 
 
 Semaphoric Electroscope. A name 
 sometimes given to a particular form of 
 quadrant electroscope. 
 
 Semi-Circular. Of or pertaining to a 
 semi-circle or half a circle. 
 
 Semi-Circular Deviation of Mariner's 
 Compass. A term employed in contra- 
 distinction to the quadrantal deviation 
 for the deviation of a magnetic needle, 
 due to the permanent magnetism of the 
 ship, having its resultant in a horizontal 
 plane, and changing sign twice in a 
 complete" revolution of the ship. 
 
 Semi - Circular Error of Compass 
 Needle. The semi-circular deviation of 
 the mariner's compass. 
 
 Semi-Conductor. A name applied to a 
 group of bodies whose conducting power 
 is, roughly, midway between that of good 
 conductors and insulators. 
 
 Semi-Incandescent Electric Lamp. 
 An electric lamp in which the light is due 
 to the combined effects of an electric aro 
 and of incandescence. 
 
 Semi-Period. (1) A half period. (2) Th 
 time occupied by a reversal or alterna- 
 tion. 
 
 Semi -Permanent Telegraph Line. 
 In military telegraphy, a line interme- 
 diate in character and method of con- 
 struction between a permanent line and a 
 temporary line. 
 
 Semi-Permeable Septum. A septum 
 which will permit the passage through it 
 of a solvent, but not of the dissolved sub- 
 stance. 
 
 Sending End of Line. The end of a 
 telegraphic line from which the signals 
 are sent. 
 
 Sending Leg of Telegraphic Loop. 
 The wire of a telegraphic loop upon which 
 messages are sent, as distinguished from 
 the receiving leg. 
 
 Sending Signaller. The operator on a 
 telegraphic line who is sending the sig- 
 nals as distinguished from one at the 
 other end who is receiving them. 
 
 Sense of Magnetic Force. A word some- 
 times used for direction of magnetic 
 force. 
 
 Sensibility of Galvanometer. (1) The 
 readiness and degree to which the needle 
 of a galvanometer will respond to the pas- 
 sage of an electric current through its 
 coils. (2) The reciprocal of the current 
 required to produce a definite small angu- 
 lar deflection. (3) The deflection pro- 
 duced by a definite small current strength. 
 (4) The figure of merit of a galvanometer. 
 
 Sensitive Flame. A flame which alters its 
 shape or size on the sounding of notes 
 possessing the same frequency as that 
 which it is capable of producing. 
 
 Sensitive Discharge. A thin, thread-like 
 discharge that occurs between the termi- 
 nals of a high-frequency induction coil. 
 
 Sensitive Telephone. A telephone that 
 is able to properly respond to currents 
 smaller than those ordinarily employed 
 in telephone apparatus. 
 
 Sensitive Tube. A coherer. 
 
 Sensitiveness of Wheatstone's Bal- 
 ance. The minimum change in the 
 measured resistance which, under the con- 
 ditions of the test and with the apparatus 
 employed, is capable of either being de- 
 tected, or of producing the unit of scale 
 deflection in the galvanometer. 
 
 Sent Current. The current employed u 
 transmitting a signal. 
 
Sep.] 
 
 918 
 
 [Ser. 
 
 Separable Conducting Cord Tip. A 
 telephone plug arranged for ready con- 
 nection with, or disconnection from, a 
 flexible conducting cord. 
 
 Separable Iron Core. An iron core 
 which can be removed from the appara- 
 tus in which it is used. 
 
 Separate-Circuit Dynamo. (1) A term 
 sometimes employed for a self-exciting 
 dynamo in which a special or separate 
 armature circuit is connected to the fields. 
 (2) A dynamo capab'e of supplying a plur- 
 ality of separate circuits. 
 
 Separate-Circuit Motor. A term some- 
 times applied to a motor whose armature 
 is provided with two windings having two 
 separate commutators, the main one be- 
 ing supplied with the driving current. 
 
 Separate-Coil Alternator. An alterna- 
 tor whose field magnets are excited by 
 means of current taken from the coils of 
 the armature after it has been commuted. 
 
 Separate-Coil Dynamo-Electric Ma- 
 chine. A term sometimes used for a sep- 
 arate-coil alternator. 
 
 Separate-Coil Machine. (1) A machine 
 in which the armature coils are mechani- 
 cally separated from each other, as dis- 
 tinguished from a machine in wiiich the 
 coils are interlaced. (2; A dynamo-elec- 
 tric machine in the armature of which 
 there exists a separate coil or winding for 
 the special purpose of exciting the field 
 magnets. 
 
 Separate Excitation. The excitation of 
 the field magnets produced by a source 
 external to the machine. 
 
 Separate Touch. A phrase sometimes 
 employed for magnetization by separate 
 touch. 
 
 Separately -Excited Alternator. An 
 alternator whose field magnets are sep- 
 arately excited. 
 
 Separately-Excited Dynamo-Electric 
 Machine. A dynamo-electric machine 
 whose field coils are separately excited. 
 
 Separately-Excited Field. The field of 
 a dynamo that receives its magnetizing 
 current from a source outside or separate 
 from the dynamo. 
 
 Separator. A corrugated and perforated 
 insulating sheet of ebonite or other simi- 
 lar substance, shaped so as to conform to 
 the outlines of the plates of a storage bat- 
 tery, and placed between them at suitable 
 intervals in such a manner as to prevent 
 their short-circuiting, but without imped- 
 ing the free circulation of the liquid. 
 
 Septum. The porous partition of an en- 
 dosmometer. 
 
 Series and Magneto Dynamo-Electric 
 Machine. A compound-wound dynamo 
 in which the armature circuit of a mag- 
 neto-electric machine is connected with 
 and excites the fine winding on the field 
 magnets. 
 
 Series-and-Separately-Excited Dyna- 
 mo-Electric Machine. A compound- 
 wound dynamo whose field-magnet cores 
 are wound with two separate circuits, one 
 connected in series with the field magnets 
 and the external circuit, and the other 
 with some source by means of which it is 
 separately excited. 
 
 Series - and - Shunt - Wound Dynamo- 
 Electric Machine. A compound- 
 wound dynamo whose field magnets are 
 wound with two separate coils, one in 
 series with the armature and the external 
 circuit, and the other in shunt with the 
 armature. 
 
 Series-Arc Cut-Out. A device for auto- 
 matically providing a short-circuit past a 
 faulty lamp in a series-connected circuit, 
 so that the failure of a lamp to operate 
 may not interfere with the operation of 
 the rest of the lamps. 
 
 Series Board. A series-connected multi- 
 ple telephone switchboard. 
 
 Series Circuit. A circuit in which the 
 separate sources or separate electro-recep- 
 tive devices, or both, are so placed that 
 the current produced in it or passed 
 through it passes successively through the 
 entire circuit from the first to the last. 
 
 Series-Connected Battery. A battery 
 of series-connected cells. 
 
 Series-Connected Incandescent 
 Lamps. A number of lamps connected 
 to a circuit in series and provided with a 
 film or other similar cut-out, to prevent 
 the failure of a single lamp from extin- 
 guishing all the rest. 
 
 Series-Connected Electro-Receptive 
 Devices. A number of electro- receptive 
 devices connected to a circuit in series. 
 
 Series-Connected Sources. A number 
 of separate sources so connected in series 
 as to act as a single source. 
 
 Series-Connected Translating Devices. 
 A term sometimes used for series-con- 
 nected electro-receptive devices. 
 
 Series-Connected Voltaic Cells. A 
 number of voltaic cells so connected in 
 series as to be capable of acting as a single 
 source or battery. 
 
 Series Connection. Such a connection 
 of a number of separate electric sources 
 or electro-receptive devices or circuits 
 
Ser.] 
 
 919 
 
 [Ser. 
 
 that the current passes successively from 
 
 the first to the last in the circuit. 
 Series-Connection for Condensers. 
 
 The connection of a number of condensers 
 
 in series. 
 Series-Connection of Alternator s . The 
 
 connection of two or more alternators in 
 
 series. 
 
 Series Converter. A series transformer. 
 
 Series Distribution. A distribution of 
 electric energy in which the receptive 
 devices are placed one after another in 
 succession upon a single conductor, ex- 
 tending throughout the entire circuit 
 from pole to pole. 
 
 Series Dynamo. A series-wound dynamo. 
 
 Series Field-Terminals of Motor. The 
 terminals of a compound-wound motor 
 which are connected to the ends of a series 
 field-winding. 
 
 Series Grouping of Armature Con- 
 ductors. (1) A two-circuit multipolar 
 winding. (2) A winding for a multipo- 
 lar armature in which only two paths 
 are provided for the current between the 
 brushes. 
 
 Series Incandescent Lamp. An incan- 
 descent lamp suitable for use in a series 
 circuit. 
 
 Series Incandescent Lighting System. 
 A system of incandescent lighting in 
 which the lamps are connected in series, 
 as distinguished from a multiple system 
 in which they are connected in parallel. 
 
 Series Motor.-^l) A motor suitable for use 
 in a series circuit. (2) A series-wound 
 motor. 
 
 Series-Multiple. A series-multiple con- 
 nection. 
 
 Series-Multiple Car-Controller. A 
 controller provided for starting and stop- 
 ping a double motor car, for varying its 
 speed, or the torque of its motors, by con- 
 necting the motors either in series or in 
 parallel with or without resistances. 
 
 Series-Multiple Circuit. A compound 
 circuit in which a number of separate 
 sources, or separate electro-receptive 
 devices, or both, are connected in a 
 number of separate groups in multiple 
 arc, and these separate groups sub- 
 sequently connected in series. 
 
 Series-Multiple-Connected Electro- 
 Receptive Devices. A connected sys- 
 tem in which a number of separate elec- 
 tro-receptive devices are joined in parallel 
 in separate groups, and all of these groups 
 subsequently connected in series. 
 
 Series-Multiple-Connected Sources. 
 The connection of a number of separate 
 
 electric sources so as to form a single 
 source, in which the separate sources are 
 connected in a number of separate mul- 
 tiple groups or circuits, and these groups 
 or circuits separately connected together 
 in series. 
 
 Series-Multiple-Connected Translat- 
 ing Devices. Series-multiple-connected 
 electro-receptive devices. 
 
 Series-Multiple Connection. Such a 
 connection of a number of separate electro- 
 receptive devices that the devices are 
 placed in multiple groups or circuits and 
 these separate groups afterwards con- 
 nected with one another in series. 
 
 Series-Multiple Switchboard. A tele- 
 phone switchboard, in which a subscriber's 
 jacks are connected in series, while plug 
 connections are made in parallel or across 
 the circuit. 
 
 Series-Parallel Controller. A series- 
 multiple car-controller. 
 
 Series Tranformer. A term sometimes 
 applied to a converter whose primary coil 
 is connected in series with the primary 
 coils of other similar transformers in the 
 primary circuit. 
 
 Series Turns of Dynamo - Electric 
 Machine. The magnetizing field-mag- 
 net coils of a dynamo that are connected 
 in series with the armature circuit. 
 
 Series Winding. A winding of a dynamo 
 electric machine in which a single set of 
 magnetizing coils are placed on the field- 
 magnet cores and connected in series with 
 the armature and the external circuit. 
 
 Series- Wound Dynamo-Electric Ma- 
 chine. A dynamo-electric machine in 
 which the field circuit and the external 
 circuit are connected in series with the 
 armature circuit, so that the armature 
 current passes through the field winding 
 into the external circuit. 
 
 Series- Working of Dynamo-Electric 
 Machines. Such a coupling of several 
 dynamo-electric machines as will deliver 
 in series the current supplied by them. 
 
 Series- Wound Field. The field of a dyn- 
 amo in which the armature current passes 
 through the magnetizing coil. 
 
 Series- Wound Laminated Synchro- 
 nous Motor. A series-wound syncho- 
 nous motor provided with a laminated 
 core. 
 
 Series- Wound Motor. A motor provided 
 with a series- wound field. 
 
 Serrated Lightning Arrester. A terra 
 sometimes applied to a saw-tooth light- 
 ning arrester. 
 
Ser.j 
 
 920 
 
 [She. 
 
 Service. A conductor or set of conductors 
 supplying electric energy from electric 
 mains to the premises of a consumer. 
 
 Service Block. (1) A block connected 
 with service wires. (2) A block for sup- 
 porting and connecting service wires. 
 
 Service Conductors. Service wires. 
 
 Service Line. (1) A service wire. (2) 
 In telephony, a line or circuit connecting 
 a switchboard with a subscriber. 
 
 Service Tube. A tube provided for the 
 introduction of service wires. 
 
 Service Wires. (1) The wires which lead 
 into a building and which are connected to 
 the supply mains or supply circuit. (2) 
 The wires through which service is given 
 to a consumer. (3) Delivery wires. 
 
 Serving Mallet. A tool employed for 
 placing the tarred yarn serving on a cable 
 splice. 
 
 Serving of Cable. The bedding of tape, 
 yarn, jute or compound in a cable as dis- 
 tinguished from the core or the sheathing. 
 
 Serving Tool. A tool employed in placing 
 the serving on a cable. 
 
 Seven-Point Jacks. In a multiple tele- 
 phone switchboard, jacks having each 
 seven different points of contact. 
 
 Sextant. An optical device consisting of 
 a fixed and movable mirror, employed for 
 measuring the angular distance between 
 any two objects. 
 
 Sextaplex Telegraph. A general term 
 embracing the apparatus used in sex- 
 taplex telegraphy. 
 
 Sextaplex Telegraphy. A system of 
 telegraphy whereby six distinct messages 
 can be simultaneously transmitted over 
 the same line, three in one direction and 
 three in the opposite direction. 
 
 Sextaplex Transmission. Transmitting 
 intelligence by means of sextaplex teleg- 
 raphy. 
 
 Sextipolar. Possessing six poles. 
 
 Sextipolar Dynamo. A dynamo posses- 
 sing a sextipolar field. 
 
 Sextipolar Field. A field produced by 
 six magnet poles. 
 
 Sextuple Telegraph. A general term for 
 the appratus employed in sextuple teleg- 
 raphy. 
 
 Sextuple Telegraphy. A system of 
 telegraphic communication in which six 
 separate messages are simultaneously sent 
 over a line in the same direction. 
 
 Sextuple Transmission. The transmis- 
 sion of intelligence by sextuple teleg- 
 raphy. 
 
 Sextuply Re-Entrant. An armature 
 provided with six separate conducting 
 paths or windings, each of which is inde- 
 pendently re-entrant. 
 
 Shackle Insulator. A term applied to 
 any form of insulator used for shackling 
 a wire, as distinguished from an insulator 
 which merely supports a wire. 
 
 Shackling a Wire. (1) Inserting an insu- 
 lator between the two ends of a cut wire. 
 (2) Securing the end of a telegraph or 
 telephone wire to a shackle. 
 
 Shaded. (1) Cut off or screened from the 
 effects of an electro-static or magnetic 
 field. (2) Screened. 
 
 Shaded-Pole Motor. An alternating- 
 current motor in which the rotary effort 
 is obtained by placing short circuited 
 coils on a portion of the polar faces. 
 
 Shade-Holder. A ring or circle clamped 
 to the socket of an incandescent lamp for 
 supporting a shade. 
 
 Shading Coil of Alternating-Current 
 Motor. A conducting coil or loop cover- 
 ing part of one or more poles in an alter- 
 nating-current motor, for the purpose of 
 retarding the magnetic flux through that 
 portion of the pole, and thereby exerting 
 a tangential drag on the armature. 
 
 Shadow, Electric. A term sometimes 
 used for molecular shadow. 
 
 Shadowgram. A term sometimes used 
 for radiograph. (Not in general use.) 
 
 Shadowgraph. A word frequently used 
 for radiograph. 
 
 Shadow Photometer. A photometer in 
 which the intensity of the light to be 
 measured is estimated by a comparison of 
 the distance at which it and the standard 
 light produce shadows of the same inten- 
 sity. 
 
 Shallow- Water Submarine Cable. A 
 submarine cable intended for use in shal- 
 low water, where the cable is apt to be 
 injured by friction against a rocky bot- 
 tom, and therefore provided with heavier 
 armor than a deep-sea cable. 
 
 Shear. A strain consisting of an extension 
 in one direction combined with an equal 
 compression perpendicular thereto. 
 
 Shearing Stress. A stress producing a 
 shear. 
 
 Sheathing of Cable. The armor or pro- 
 tecting covering employed for surround- 
 ing the core of a cable. 
 
 Sheathing Wires. The metallic wires 
 which form the armor of a submarine 
 cable. 
 
She.] 
 
 921 
 
 [Sho. 
 
 Shed of Insulator. A petticoat or in- 
 verted cone of a telegraph insulator. 
 
 Sheer. The curve which the line of ports 
 or the deck of a ship presents to the eye, 
 when observed from one side. 
 
 Sheet Lightning. A variety of lightning 
 flash, unaccompanied by thunder audible 
 to an observer, in which the surfaces of 
 clouds are illumined. 
 
 Shell of Arc-Lamp. The outside casing 
 of an arc-lamp. 
 
 Shell of Commutator. A term some- 
 times employed for the commutator form, 
 separated from its shaft. 
 
 Shell of Fixture. A light ornamental 
 metallic casing covering some part of an 
 electrolier. 
 
 Shell Transformer. (1) A transformer 
 whose primary and secondary coils are 
 laid on each other, and the iron core is 
 then wound through and over them, so as 
 to completely enclose them. (2) A form 
 of iron-clad transformer. 
 
 Shellac. A resinous substance obtained 
 from the roots and branches of certain 
 tropical plants, which possesses high insu- 
 lating powers, and high specific inductive 
 capacity. 
 
 Shifting Magnetic Field. (1) A magnet- 
 ic field whose lines of magnetic force are 
 changing position with respect to the 
 axis of the magnet pole from which they 
 emanate. (2) A rotary magnetic field. 
 
 Shifting of Phase of Alternating Cur- 
 rent. In an alternating-current circuit 
 the changes in the phase relation of cur- 
 rent strengtli to impressed E. M. F. de- 
 pending upon variations in the frequency 
 or in the impedance. 
 
 Shifting of Spot of Light. Any move- 
 ment of a spot of light on a scale causing 
 that spot to move away from its true zero 
 position, produced by causes other than 
 those acting during the proper operation 
 of the instrument. 
 
 Shifting Zero.-^l) A zero that changes or 
 shifts its position. (2) A false zero in 
 measuring instruments. 
 
 Ship Dynamometer. A dynamometer 
 employed on board a cable ship for the 
 purpose of indicating the strain on a 
 grappling rope or on a cable. 
 
 Ship Return-Circuit System. A name 
 applied to a single- wire system or form of 
 circuit in which the hull of the ship forms 
 the return wire. 
 
 Shock. (1) Objectively, a concussion or 
 blow. (2) Subjectively, a violent nervous 
 stimulus. 
 
 14- 
 
 Shock, Electric. A physiological shock 
 produced in an animal by an electric dis- 
 charge. 
 
 Shoe of Contact for Street Railway. 
 The metallic contact piece which rubg 
 against a surface rail or conduit rail in a 
 street railway system. 
 
 Shoe Plug. A form of sliding contact- 
 plug for insertion in a jack of a telephone 
 switchboard. 
 
 Shore-End of Telegraphic Cable. (1) 
 A shallow-water section of submarine 
 cable. (2) The end of a submarine cable 
 landed on a shore. 
 
 Short Arc System of Electric Light 
 ing. A system of electric lighting in 
 which short voltaic arcs are maintained 
 between carbon electrodes. 
 
 Short Circuit. (1) A shunt or by-path of 
 negligible or comparatively small resist- 
 ance, placed around any part of an 
 electric circuit through which so much of 
 the current passes as to virtually cut out 
 the parts of the circuit to which it acts as 
 a shunt. (2) An accidental direct con- 
 nection between the mains or main ter- 
 minals of a dynamo or system producing 
 a heavy overload of current. (3) To cut 
 out of circuit by a short conductor. (4) 
 To accidentally produce a short circuit. 
 
 Short-Circuit-Key. A key which in its 
 normal position short-circuits a galvan- 
 ometer, or other device with which it is 
 connected. 
 
 Short-Circuited. (1) Placed on a short- 
 circuit. (2) Cut out by means of a short- 
 circuit. 
 
 Short-Circuited Conductor. A con- 
 ductor which has a short-circuit estab- 
 lished past it. 
 
 Short Circuiting. (1) Cutting out of 
 circuit by means of a short-circuit. (2) 
 Establishing a direct connection between 
 the terminals of a source or device, or 
 between mains connected to them. 
 
 Short-Circuiting a Dynamo-Electric 
 Machine. (1) Cutting out the external 
 circuit of a dynamo by means of a short- 
 circuit. (2) Connecting the poles or ter- 
 minals of a dynamo by a circuit of negli- 
 gibly small resistance. (3) Greatly over- 
 loading a constant-potential machine, and 
 underloading a constant-current ma- 
 chine. 
 
 Short-Circuiting Plug. (1)A plug which 
 when inserted in its receptacle short cir- 
 cuits the device connected therewith. 
 (2) A plug employed in short-circuiting a 
 coil or other resistance. 
 
 Short-Closed Circuit. In a series dis* 
 -Vol. 2 
 
Sho.] 
 
 922 
 
 [Shu. 
 
 tribution circuit, the condition of 'having 
 short-circuited devices, as distinguished 
 from a long-closed circuit from which all 
 short circuits have been removed. 
 Short-Coil Magnet. A magnet whose 
 magnetizing coil consists of a few turns 
 of short thick wire. 
 
 Short Connection of Two-Circuit 
 G- r a m m e-W i n d i n g. A form of 
 Gramme winding in which the circuits 
 from brush to brush consist of conduc- 
 tors influenced by all the poles, so that the 
 E. M. F.'s generated in the two circuits 
 are necessarily equal. 
 
 flhort-Connection Two-Circuit Arma- 
 ture Winding. (1) Such a two-circuit 
 winding that in each circuit between the 
 brushes electromotive forces are induced 
 by each and all the poles of the field 
 frame. (2) Such a type of two-circuit 
 winding as connects coils together lying 
 in adjacent fields. 
 
 Short-Core Electro-Magnet. An elec- 
 tro-magnet provided with a short core. 
 
 Short-End of Quadruplex Battery. 
 The end of a quadruplex battery, the 
 smaller portion of which is always in 
 circuit, as opposed to the end of the extra 
 battery thrown in circuit by the depres- 
 sion of the increment key. 
 
 Short-Shunt Compound- Winding. A 
 compound winding of a dynamo-electric 
 machine in which the shunt coil is connect- 
 ed directly, or through resistance, with 
 the armature brushes, as distinguished 
 from a long-shunt com pound- winding. 
 
 Short-Shunt Compound-Wound Dy- 
 namo - Electric Machine. A com- 
 pound-wound dynamo whose field-magnet 
 eoils form a shunt to the armature only, 
 as distinguished from a shunt to the 
 armature and series coils combined. 
 
 Short-Sightedness. (1) The condition of 
 ' the eye in which distinct images are 
 formed of those objects only which are 
 near to the eye. (2) Myopia. (3) The 
 condition of sight pertaining to an elon- 
 gated eyeball. 
 
 Short Timber. A term applied to 
 timber that has been improperly subjected 
 to preservative processes, and has thereby 
 been rendered brittle. 
 
 Short Wire Repeater. A repeater be- 
 tween a duplex or quadruplex and a 
 branch office wire. 
 
 Shower-Bath, Electric. A device for 
 carrying an electric charge to the body of 
 a patient by the falling water. 
 
 Shunt. An additional, or by-path estab- 
 
 lished for the passage of an electric cur- 
 rent or discharge. 
 
 Shunt. To establish an additional, or by- 
 path for the passage of an electric current 
 or discharge. 
 
 Shunt - and - Separately - Excited Dy- 
 namo - Electric Machine. A com- 
 pound-wound dynamo in which the field 
 is excited both by means of a shunt to the 
 armature circuit, and by a current pro- 
 duced by a separate source. 
 
 Shunt Bell, Electric. An electric bell 
 whose magnetizing coils are connected to 
 the line wire in shunt. 
 
 Shunt Breaking Resistance. A re- 
 sistance for insertion in the field of a 
 shunt dynamo, before breaking its circuit, 
 to prevent the production of a dangerously 
 powerful induced pressure. 
 
 Shunt - Circuit. (1) A derived circuit. 
 
 (2) A branch or additional circuit, pro- 
 vided in any part of a circuit, through 
 which the current branches or divides, 
 part flowing in the original circuit and 
 part through the new branch or shunt. 
 
 (3) A circuit for diverting or shunting a 
 portion of the current. 
 
 Shunt Coil. A coil placed in a shunt 
 circuit. 
 
 Shunt Dynamo. A shunt-wound dy- 
 namo-electric machine. 
 
 Shunt-Field Terminals of Motor. The 
 terminals of the shunt field coils of an 
 electric motor. 
 
 Shunt for Ammeter. (1)A shunt coil con- 
 nection in multiple with the coils of an 
 ammeter for the purpose of changing the 
 value of the readings. (2) A reducteur. 
 
 Shunt Spool. A spool or coil of insulated 
 wire placed in a shunt circuit. 
 
 Shunt Street-Car Motor. A shunt- 
 wound car motor. 
 
 Shunt Ratio. (1) The ratio existing 
 between a shunt and the circuit it shunts. 
 (2) The ratio existing between the total 
 current strength and the current strength 
 in the branch to which the shunt is ap- 
 plied. 
 
 Shunt Rheostat. A rheostat placed in a 
 shunt-circuit. 
 
 Shunt Turns of Dynamo. The ampere 
 turns in the shunt circuit of a shunt- 
 wound or compound-wound dynamo. 
 
 Shunt Winding. A term sometimes em- 
 ployed for the shunt field coils on a shunt- 
 wound dynamo or motor. 
 
 Shunt- Wound Dynamo-Electric Ma- 
 chine. A dynamo - electric machine 
 whose field-magnet coils are placed in 
 
Shu.] 
 
 
 923 
 
 [Sie. 
 
 shunt with the armature circuit, so that 
 only a portion of the current generated 
 passes through the field-magnet coils, but 
 all the difference of potential of the 
 armature acts at the terminals of the 
 field circuit. 
 
 Shunt-Wound Field. The field of a 
 dynamo in which the field-magnet coils 
 are placed in shunt with the armature 
 and external circuit. 
 
 Shunt- Wound Motor. A motor whose 
 field-magnet coils are placed in shunt to 
 the armature circuit. 
 
 Shunted. Provided with a shunt. 
 
 Shunting. Providing with a shunt. 
 
 Shunting Air-Gap . (1) An air-gap in a 
 circuit placed around a galvanometer or 
 other instrument, for the purpose of pro- 
 tecting it from the effects of a powerful 
 disruptive discharge. (2) An air-gap 
 shunt in a magnetic circuit. 
 
 Shutter Apparatus. In a system of 
 visual telegraphy, an apparatus for sud- 
 denly displaying and obscuring a light 
 by means of hand-controlled shutters. 
 
 Shutter Indicator Armature. The ar- 
 mature of an electro-magnet so arranged 
 that when released it displays an in- 
 dicator on an annunciator. 
 
 Shuttle Armature. (1) A variety of 
 drum armature in which a single coil of 
 wire is wound in an H-shaped groove 
 formed in a bobbin-shaped core. (2) The 
 old form of Siemens' armature. 
 
 Shuttle- Wound Armature. An ar- 
 mature whose coils are placed on its core 
 by first winding the wire on a shuttle and 
 passing the same through the opening or 
 gap provided for the coil. 
 
 Side A of Quadruples Table. That 
 side of a quadfuplex system which is 
 worked by means of reversed currents.' 
 
 Side B of Quadruples Table. That side 
 of a quadruplex system which is worked 
 by means of strengthened currents. 
 
 Side-Bar Suspension of Motor. In a 
 street railway car truck, a method of sup- 
 porting the motors which consists in em- 
 ploying a pair of bars or light girders 
 mounted on springs parallel to the side 
 frames and supporting the motors from 
 these bars. 
 
 Side Bracket. A particular form of 
 single insulator bracket. 
 
 Side Commutator. The commutator of 
 a dynamo-electric machine placed on the 
 side of the revolving armature. 
 
 Side Current. A term applied by Hertz 
 to the current produced in the side cir- 
 cuit of a micrometer. 
 
 Side Plash. A sparking or lateral dis- 
 charge taking place from the sides of a 
 conductor through which an impulsive 
 rush of electricity is passing. 
 
 Side-Lights, Electric. Red or green 
 lanterns placed on permanent fixtures on 
 either side of a ship. 
 
 Side of Three-Wire System. <1) A term 
 applied to the positive or negative con- 
 ductors or leads in the three-wire system 
 of distribution. (2) The positive or the 
 negative half of a three-wire system. 
 
 Side Pole. A trolley-wire pole mounted 
 at the side of a track as distinguished from 
 a central pole. 
 
 Side Pole Line. An aerial line supported 
 from poles placed on the side of a street 
 or road, as distinguished from a centre 
 pole line or from one supported from 
 poles placed in the centre of the street or 
 road. 
 
 Side-Pole Trolley-Line Construction. 
 A method for the suspension of aerial 
 trolley lines in which the trolley and feed 
 wires are suspended from poles placed on 
 one side of the street or road. 
 
 Side Suspension of Motor. A side-bar 
 suspension of a motor in a truck. 
 
 Side Telegraphic Eepeater. A tele- 
 graphic repeater which operates adja- 
 cent circuits from a main line. 
 
 Sides of Three-Wire System. (1) The 
 portions of a three-wire system which have 
 respectively positive and negative poten- 
 tials. (2) The positive and negative por- 
 tions of a three-wire system. 
 
 Siderial. Of or pertaining to the stars. 
 
 Sidero-Magnetic. A term proposed for 
 ferro-magnetic. 
 
 Siemens Armature Electro-Magnetic 
 Bell. A form of electro-magnetic bell, 
 the movements of whose armature are 
 obtained by the reversal of polarity that 
 occurs when alternating currents are 
 passed through a single-coil Siemens ar- 
 mature. 
 
 Siemens Differential Voltameter. 
 A form of voltameter employed by 
 Siemens for determining the resistance 
 of the platinum spiral used in his electro- 
 pyrometer. 
 
 Siemens Electro - Dynamometer. A 
 form of galvanometer employed for the 
 measurement of electric currents. 
 
 Siemens Electro-Pyrometer. An ap- 
 paratus for the determination of temper- 
 ature by the measurement of the electric 
 resistance of a platinum wire exposed to 
 the source of heat, the temperature of 
 which is to be measured. 
 
Sie.] 
 
 924 
 
 [Sim. 
 
 Siemens-Halske Voltaic Cell. A zinc- 
 copper couple whose elements are em- 
 ployed with dilute sulphuric acid and a 
 saturated solution of copper sulphate re- 
 spectively. 
 
 'Siemens Water Pyrometer. A pyro- 
 meter employed for determining the tem- 
 perature of a furnace or other intense 
 source of heat, by the increase in the tem- 
 perature of a known weight of water to 
 which a metal cylinder of a given weight 
 has been put, after exposure for a given 
 time to the som - ce of heat to be measured. 
 
 Signal Arm. A semaphore arm. 
 
 .Signal-Service System for Electric 
 Railroad. A system of electric signals 
 used on railroads for ascertaining the 
 condition of the road, sending instruc- 
 tions to engineers, and conveying intelli- 
 gence generally from stations along the 
 road to running trains. 
 
 Sight-Feeding Oiler. A glass oil-cup 
 which permits the visible feeding of lu- 
 bricating oil to the journal bearings. 
 
 Signature. In telegraphy, a name of the 
 sender of a message as it appears upon the 
 same. 
 
 Silence Telephone Cabinet. A long- 
 distance telephone cabinet. 
 
 Silent. A switch device for preventing 
 the action of an electric alarm by short- 
 circuiting it. 
 
 Silent Discharge. A name sometimes 
 given to a convective discharge, in order 
 to distinguish it from the more noisy dis- 
 ruptive discharge. 
 
 Silhougraph. A word proposed for ra- 
 diograph. 
 
 Silver Bath. An electrolytic bath con- 
 taining a readily electrolyzable salt of sil- 
 ver, and a plate of silver acting as the 
 anode, placed in the liquid near the 
 object to be coated which forms the 
 cathode. 
 
 Silver Chloride Voltaic Cell. A zinc- 
 silver couple immersed in electrolytes of 
 sal-ammoniac or common salt, and silver 
 chloride, respectively. 
 
 Silver-Palladium Alloy. An alloy of 
 silver with palladium and other metals, 
 employed for the hair-springs, escape- 
 ments and balance-wheels of watches, on 
 account of its non-magnetic properties. 
 
 Silver Plating. Covering the surfaces of 
 the baser metals with an adherent coating 
 of silver by the electric current. 
 
 Silver Voltameter. A voltameter in 
 which the quantity of electricity passing is 
 determined by the weight of silver depos- 
 ited. 
 
 Silvered Plumbago. Powdered plum- 
 bago covered with metallic silver, for use 
 in the metallization of objects to be elec- 
 tro-plated. 
 
 Silurus Electricus. The electric eel. 
 
 Similars. Conductors in the secondary 
 winding of an induction machine which 
 are similar to each other in respect to 
 the magnitude of their induced electro- 
 motive forces at any instant, and sym- 
 metrically disposed relatively to the ro- 
 tating poles. 
 
 Simple Alternating-Currents. (1) Sin- 
 usoidal-alternating currents. (2) Simple- 
 harmonic currents. 
 
 Simple Arc. A voltaic arc formed be- 
 tween two electrodes. 
 
 Simple Circuit. A term sometimes em- 
 ployed for a circuit containing a single 
 electric source and a single electro-recep- 
 tive device. 
 
 Simple Electric Candle Burner. A 
 
 plain-pendant electric burner. 
 
 Simple-Harmonic Currents. (1) Cur- 
 rents whose flow is variable both in 
 strength and duration, and in which the 
 quantity of electricity passing by any sec- 
 tion of conductor may be represented by 
 a simple-harmonic curve. (2) A current 
 of such a nature that the continuous va- 
 riation of the flow of electricity past any 
 area of cross-section of the conductor, or 
 the continuous variations in electromotive 
 force, may be expressed by a simple-har- 
 monic curve. 
 
 Simple-Harmonic Curve. The curve 
 which results when a simple-harmonic 
 motion in one line is compounded with 
 uniform motion in a straight line at right 
 angles thereto. 
 
 Simple-Harmonic. Electromotive 
 Forces. Electi'omotive forces which 
 vary in such a manner as to produce 
 simple-harmonic currents ; or, electromo- 
 tive forces whose variations can be cor- 
 rectly represented by a simple-harmonic 
 curve. 
 
 Simple-Harmonic Motion. (1) Motion 
 which repeats itself at regular intervals 
 in one line, taking place backwards or 
 forwards, and which is the orthogonal 
 projection of the path of a point moving 
 uniformly in a plane circle upon a diame- 
 ter of the circle. (2) Motion which is a 
 simple-periodic function of the tim. (3) 
 Simple-periodic motion. 
 
 Simple-Harmonic Variation. A varia- 
 tion of current or electromotive force 
 which takes place in accordance with 
 simple-harmonic law. 
 
Sim.] 
 
 925 
 
 [Sin. 
 
 Simple Immersion. A term sometimes 
 employed for an electrolytic deposit ob- 
 tained by merely dipping a metal in a so- 
 lution of a metallic salt. 
 
 Simple Magnet. A simple magnetized bar. 
 
 Simple Magnetic Shell. A magnetic 
 shell whose strength is everywhere the 
 same. 
 
 Simple - Periodic Currents. A term 
 sometimes used for simple-harmonic cur- 
 rents. 
 
 Simple-Periodic Curve. A simple-har- 
 monic curve. 
 
 Simple-Periodic Electromotive Force. 
 A simple-harmonic electromotive force. 
 
 Simple-Periodic Motion. Simple-har- 
 monic motion. 
 
 S i m p 1 e-Periodic Variation. Simple- 
 harmonic variation. 
 
 Simple Radical. (1) An unsaturated 
 atom with its bond or bonds free. (2) A 
 single unsaturated atom, as distinguished 
 from an unsaturated group of atoms. 
 
 Simple Rigidity. (1) In an isotropic 
 body the ratio of shearing stress to the 
 resulting shear. (2) Resistance to shear- 
 ing. (3) In an isotropic body the edges 
 of a unit cube to which tangential shear- 
 ing stresses are applied, the ratio of the 
 tangential force to the angular distortion 
 effected in the cube. 
 
 Simple Shunt. A coil arranged as a 
 
 shunt, and unprovided with an iron core. 
 Simple-Sine Motion. A term sometimes 
 
 employed for simple-harmonic motion. 
 Simple Voltaic Cell. A term sometimes 
 
 used for a single-fluid cell. 
 Simplex Telegraph. A general term 
 
 embracing the apparatus employed in 
 
 simplex telegraphy. 
 
 Simplex Telegraphy .A system of teleg- 
 raphy in which a single message only can 
 be sent over the line wire. 
 
 Simplex Working. (1) Transmitting 
 messages by simplex telegraphy. (2) A 
 word sometimes employed for simple 
 telegraphic transmission: 
 
 Sims-Edison Torpedo. A special form 
 of torpedo in which electricity is both the 
 propelling and directing power, but the 
 electric source is situated outside the tor- 
 pedo, and is connected with the same by 
 a light cable. 
 
 Sine Galvanometer. A galvanometer 
 whose deflecting coil is placed in a verti- 
 cal plane movable about a vertical axis, 
 so that it can be made to follow the mag- 
 netic needle in its deflections. 
 
 Sine Law. (1) A law of magnitude de- 
 
 nned by the sines of angles. (2) A mag- 
 nitude which follows the sines of succes- 
 sive angles. 
 
 Single Brush-Rocker Arm. A device 
 by means of which a single pair of brushes 
 are so situated on a dynamo or motor as 
 to be capable of being readily shifted into 
 the desired position on the commutator 
 cylinder. 
 
 Single-Brush Yoke. A term sometimes 
 used for single brush-rocker arm. 
 
 Single-Circuit. An undivided circuit. 
 
 Single-Contact Carbon Telephone. 
 A form of microphonic telephone trans- 
 mitter, in which a single contact is em- 
 ployed. 
 
 Single-Contact Key. Any key which 
 makes a single contact only. 
 
 Single-Cord Multiple-T elephone 
 Switchboard. (1) A multiple telephone 
 switchboard employing a single conduct- 
 ing cord in establishing connections. 
 (2) A multiple-telephone switchboard in 
 which the circuits are all ground-return- 
 circuits, and the subscribers' jacks are all 
 connected in series. 
 
 Single-Cord Switchboard. (1) A tele- 
 phone switchboard in which an inter-con- 
 nection between two subscribers is ef- 
 fected through a single cord. (2) A tele- 
 phone switchboard in which each line 
 terminates in a plug. 
 
 Single-Cord Telephone Switchboard. 
 A telephone switchboard employing 
 single conducting cords. 
 
 Single-Cup Insulator. An insulator 
 consisting of a single inverted cup. 
 
 Single Curb. A device for increasing the 
 speed of telegraphic signalling by ridding 
 the line of its previous charge by means 
 of a single reversed current sent through 
 it after each signal, before connecting to 
 the ground, as distinguished from a 
 double curb in which a succession of two 
 reversed currents follow each signal. 
 
 Single-Curb Signalling. Signalling by 
 means of a single curb. 
 
 Single-Current Signalling. Signalling 
 by means of makes or breaks in the cir- 
 cuit of a single current. 
 
 Single-Current Closed-Circuited Sig- 
 nalling. A method of telegraphic sig- 
 nalling in which the line circuit is nor- 
 mally closed, being only broken by the 
 sending operator, while the current in the 
 circuit has only one direction. 
 
 Single-Current Key. A key employed 
 in single-current signalling. 
 
 Single-Current Open-Circuit Signal- 
 
Sin,] 
 
 926 
 
 [Sin. 
 
 ling. A method of telegraphic signalling 
 in which the main-line batteries are fixed 
 at each station, and are in circuit only 
 when signalling. 
 
 Single-Current Telegraphic Working. 
 A term sometimes used for single-current 
 signalling. 
 
 Single-Current Translator. A tele- 
 graphic translator suitable for use in 
 single-current working. 
 
 Single-Curve Suspension. (1) A sus- 
 pension suitable for the support of a trol- 
 ley wire at a single curve in the line, or 
 single-track curve. (2) A form of suspen- 
 sion having a single curved holder or 
 support. 
 
 Single-Curve Trolley Hanger. (1) A 
 hanger supporting a single curve wire or 
 single-track curve wire. (2) A trolley 
 hanger supported by a single curved 
 holder. 
 
 Single-Curve Trolley-Suspension. 
 (1) Suspension of a trolley wire by a single- 
 curve trolley-hanger. (2) A single-track 
 trolley-suspension at a curve in the track. 
 
 Single-Coil Field Dynamo. A dynamo 
 whose magnetic field is obtained from a 
 single magnetizing coil. 
 
 Single Field-Coil Multipolar Dynamo. 
 A multipolar dynamo having a single 
 field coil on a single core provided with a 
 plurality of polar projections. 
 
 Single-Fluid. Pertaining to the single- 
 fluid hypothesis of electricity or magnet- 
 ism. 
 
 Single -Fluid Hypothesis of Elec- 
 tricity. A hypothesis which endeavors 
 to explain the cause of electrical phenom- 
 ena by the assumption of the existence of 
 a single electric fluid. 
 
 Single-Fluid Voltaic Cell. A voltaic 
 cell in which but a single fluid or electro- 
 lyte is used. 
 
 Single-Focus X-Ray Tube. An X-ray 
 tube suitable for use in connection with 
 pulsatory currents, and provided with a 
 single deflecting plate or anticathode op- 
 posite the cathode. 
 
 Single-Line Repeater. In telegraphy, a 
 repeater from a single circuit into an- 
 other. 
 
 Single-Liquid Voltaic Cell. A single- 
 fluid voltaic cell. 
 
 Single-Loop Armature. An armature 
 consisting of a closed conducting circuit 
 containing a single loop, so placed as to 
 be capable of revolving in a magnetic 
 field, as to cut its magnetic flux. 
 
 Single-Magnet Dynamo-Electric Ma- 
 
 chine. A term sometimes used for a 
 single field-coil dynamo. 
 Single-Needle Telegraphy. A system 
 of telegraphy in which the transmitted 
 signals are received by the movements of 
 a vertical needle suitably suspended be- 
 fore a dial. 
 
 Single-Pair Brush-Rocker. A term 
 sometimes used for single-pair brush yoke. 
 
 Single-Pair Brush Yoke. A device for 
 so holding a single pair of collecting 
 brushes of a dynamo-electric machine 
 that they can be readily moved or rotated 
 on the commutator cylinder. 
 
 Single-Pair Yoke. A single-pair brusk 
 
 yoke. 
 
 Single Peg. A peg provided with but a 
 
 - single contact. 
 
 Single Phase. (1) Uniphase. (2) Mono- 
 phase. (3) Pertaining to ordinary alter- 
 nating currents in a simple alternating- 
 current system as distinguished from 
 multiphase currents. 
 
 Single-Phase Alternating Current. 
 A uniphase alternating current. 
 
 Single-Phase Alternator. An alter- 
 nator capable of producing simple r 
 single-phase currents. 
 
 Single-Phase Armature Windings. 
 Windings employed on the armature of a 
 single-phase alternator. 
 
 Single-Phase Armature Windings. 
 Armature windings of single-phase ge- 
 erators. 
 
 Single-Phase Asynchronous Motor. 
 A single-phase alternating-current motor 
 capable of running otherwise than in 
 synchronism with the current supplied to 
 it from the circuit. 
 
 Single-Phase Bar - Armature Wind- 
 ings. Such a bar armature winding of 
 an alternator as is capable of producing 
 single-phase currents. 
 
 Single-Phase Dynamo. A single-phaj* 
 alternator. 
 
 Single-Phase Generator. A single- 
 phase alternator. 
 
 Single-Phase Motor. A uniphate 
 motor. 
 
 Single-Phase Induction Motor. An 
 induction motor operated by uniphase 
 currents. 
 
 Single-Phase Induction Motor. An in- 
 duction motor operated or intended to be 
 operated on a single-phase alternating- 
 current circuit. 
 
 Single-Phase Synchronous Motor. A 
 synchronous motor capable of being opei* 
 ated by uniphase currents. 
 
Sin.] 
 
 927 
 
 [Sin. 
 
 Single-Phase Transformer. A transfor- 
 mer suitable for supplying or transform- 
 ing single-phase currents. 
 
 Single-Phase Winding. A single-phase 
 armature winding. 
 
 Single-Phaser. (1) An alternating-cur- 
 rent generator of single-phase currents. 
 (2) A uniphaser. 
 
 Single-Pole Cut-Out. A cut-out by 
 means of which the circuit is broken or 
 cut in one of the two leads only. 
 
 Single-Pole Safety -Fuse. A single pole 
 cut-out operated by a safety fuse. 
 
 Single-Pole Switch. A switch which 
 opens or closes a circuit at one of its 
 leads only. 
 
 Single-Pole Telephone Receiver. (1) 
 A bar-magnet telephone with a coil on 
 one end of the bar. (2) A telephone re- 
 ceiver in which only one magnetic pole is 
 presented to the diaphragm, as distin- 
 guished from a receiver in which a pair of 
 poles, each surrounded by a coil, is pre- 
 sented to the diaphragm. 
 
 Single-Pole Telephone Switch. A 
 fcingle-pole switch employed on a tele- 
 phone circuit. 
 
 Single Pull-Off. <!)' A trolley pull-off 
 supported on a single-curve holder. (2) 
 A single-curve pull-off. (3) A trolley 
 pull-off on a single-track curve. 
 
 Single-Reduction. (1) Having but a 
 single gear wheel for reducing speed. 
 (2) A gearing in which but a single re- 
 duction of speed takes place as opposed 
 to a double gearing in which two separate 
 reductions are effected. 
 
 Single-Reduction Street-Car Motor. 
 A street-car motor which requires a 
 single reduction gear connected with the 
 car axle to reduce the motion of the car 
 axle as opposed to i motor geared with 
 the car axle through two successive gear 
 wheels and therefore one intermediate 
 shaft. 
 
 Single-Reflection Tube. A term some- 
 times applied to an X-ray tube contain- 
 ing but a single deflecting plate or anti- 
 cathode. 
 
 Single-Shackle Insulator. <1) A form 
 of insulator employed in shackling a 
 single wire. (2) A form of single shackle 
 to which two wires can be fastened at 
 different points and left insulated. 
 
 Single-Shed Insulator. An insulator 
 provided with a single inverted cup. 
 
 Single-Stroke Electric Bell. An elec- 
 tric bell that gives a single stroke only for 
 each closure of the circuit. 
 
 Single-Throw Switch. A switch having 
 but two positions, one for opening, and the 
 other for closing the circuit it controls, 
 as distinguished from a double-throw 
 switch. 
 
 Single-Touch. A phrase sometimes em* 
 ployed for magnetization by single 
 touch. 
 
 Single-Track Bracket Trolley-Suspen- 
 sion. A form of single-track trolley- 
 wire suspension, in which a bracket is 
 supported from a pole placed on one side 
 of the street. 
 
 Single-Trolley System. A trolley 
 system in which a single conducting 
 over-head wire is employed, the track 
 and ground being used for a return. 
 
 Single-Trolley System Electric-Rail- 
 road. An electric railroad operated by a 
 single trolley. 
 
 Single-Truck Car. A car whose body is 
 supported on a single truck. 
 
 Single- Valued Function. A function 
 which has only a single value for each 
 value of the variable. 
 
 Single- Wire Cable. A cable whose core 
 contains a single conducting wire only. 
 
 Single- Wire Circuit. A term sometimes 
 used for a grounded circuit. 
 
 Single-Wire Line. A term sometimes 
 used for a single-wire circuit. 
 
 Single -Wi r e Multiple Telephone 
 Switchboard. (1) A single-cord mul- 
 tiple telephone switchboard. (2) A 
 switchboard connecting ground-return 
 subscribers' lines, the jacks of which are 
 all in series in each line. 
 
 Single-Wire Spring-Jack. A spring- 
 jack suitable for use in a single-wire 
 switchboard. 
 
 Single -Wire Switchboard. (1) A 
 switchboard devoted to the connections 
 of a single line with various sets of appa- 
 ratus. (2) A telephone switchboard con- 
 nected to ground-return circuits. 
 
 Single -Wire System for Electric 
 Light Leads. A term sometimes em- 
 ployed for a ground-return electric light 
 circuit. 
 
 Single- Wire Telephone Switchboard. 
 A form of telephone switchboard connect- 
 ing ground-return circuits. 
 
 S i ng 1 e- Wound Gramme Ring. A 
 Gramme ring provided with a single 
 winding, the number of whose coils is a 
 multiple of the number of poles, and th 
 number of whose commutator segments 
 is equal to the number of poles. 
 
 Single-Wound Multiple-Circuit Mul 
 
Sin.] 
 
 928 
 
 [Ski, 
 
 tipolar Drum-Armature. A drum 
 armature wound for a multipolar field in 
 a single winding and affording a plur- 
 ality of paths or circuits between its 
 brushes. 
 
 Single-Wound Two-Circuit Drum- 
 Armature. A drum armature, wound 
 for a multipolar field, with a single wind- 
 ing and affording two conducting paths 
 or circuits between the brushes. 
 
 Single-Wound Two-Circuit Multipo- 
 lar Ring- Armature. A ring armature 
 wound for a multipolar field, with a single 
 winding, which affords but two conduct- 
 ing paths or circuits between the brushes. 
 
 Single-Wound Wire. Wire wound or 
 covered with a single layer of insulating 
 material. 
 
 Singly Re-Entrant Armature- Wind- 
 ing. (1) A single-winding which re-en- 
 ters itself. (2) An armature provided 
 with a single- winding which is re-entrant. 
 
 Singular Polarization. A term applied 
 to the polarization of a voltaic cell when 
 the depolarizing current is many times 
 stronger than the primary current. 
 
 Sinistrorsal Helix. A sinistrorsal sole- 
 noid. 
 
 Sinistrorsal Solenoid. A solenoid whose 
 
 winding is left-handed. 
 Sinuous Current. A term sometimes 
 
 applied to a current flowing through a 
 
 sinuous conductor. 
 
 Sinusoid. A name frequently given to a 
 curve of sines. 
 
 Sinusoidal. Of or pertaining to a sinu- 
 soid. 
 
 Sinusoidal Alternating Electromotive 
 Forces. (1) Alternating electromotive 
 forces whose variations in strength 
 are correctly represented by a sinusoidal 
 curve. (2) Simple-harmonic E. M. F.'s. 
 (3) E. M. F.'s which are simple-harmonic 
 functions of time. 
 
 Sinusoidal Alternator. An alternator 
 capable of producing sinusoidal electro- 
 motive forces. 
 
 Sinusoidal Currents. Simple-periodic 
 currents whose strengths are correctly 
 represented by sinusoids. 
 
 Sinusoidal-Current Circuit. A circuit 
 conveying sinusoidal currents. 
 
 Sinusoidal Curve. (1) A curve of sines. 
 (2) A sinusoid. (3) A curve which to 
 rectangular co-ordinates has an ordinate 
 at each point proportionate to the sine of 
 an angle proportionate to the abscissa. 
 
 Sinusoidal Flux. A flux which varies 
 
 sinusoidally or according to a simple- 
 harmonic law. 
 
 Sinusoidal Generator. A sinusoidal al- 
 ternator or generator capable of deliver- 
 ing a simple-harmonic E. M. F. 
 
 Sinusoidal Magnetic Flux. A sinu- 
 soidally varying flux. 
 
 Sinusoidal Magnetomotive Force. 
 A magnetomotive force varying sinw- 
 soidally. 
 
 Sinusoidal Variation. Such a variation 
 of an electromotive force, current, or flux, 
 as may be correctly represented by a sin- 
 usoid. 
 
 Sinusoider. A name sometimes given to 
 a sinusoidal alternator. 
 
 Siphon, Electric. A siphon in which 
 the stoppage of the flow of the liquid due 
 to the gradual accumulation of air, is 
 prevented by electrical means. 
 
 Siphon Recorder. An apparatus for re- 
 cording in ink on a strip of paper a mes- 
 sage received over a cable by means of a 
 jet of ink thrown out from a fine glass 
 tube supported on a fine wire. 
 
 Siphon-Recorder Vibrator. A device 
 employed in a siphon recorder to obtain 
 the vibrations required for the ejection 
 of the ink from the siphon by mechanical 
 means instead of by electrical means. 
 
 Siphon Writing. A record obtained by 
 means of a siphon recorder. 
 
 Siren. An acoustic apparatus employed 
 for measuring the frequency of sound 
 waves. 
 
 Six-Pole Dynamo-Electric Machine. 
 
 A sextipolar dynamo. 
 
 Six- Wire System. A system of distribu- 
 tion similar in general to the three-wire 
 system, in which five dynamos are con- 
 nected to six conductors or leads. 
 
 Six- Wire Triphase System. A system 
 for the production of triphase currents, 
 in three separate circuits, each having two 
 wires. 
 
 Skew Adjustment of Carbons in Arc- 
 Lamps. The adjustment of the carbons 
 of an arc lamp by means of which the 
 positive carbon is placed a short distance 
 in front of, but out of the vertical line 
 with the negative carbon. 
 
 Skiagraph. A word proposed for radio- 
 graph. (Not in general use.) 
 
 Skiasmogram. A word proposed for 
 radiograph. (Not in use.) 
 
 Skidding of Car Wheels. A term ex- 
 pressing the sliding of the wheels of a cal 
 in place of their proper rolling motion. 
 
Ski.] 
 
 929 
 
 [Slo. 
 
 Skin Currents. A term applied to rapid- 
 ly alternating currents which are limited 
 to the surface of a conductor. 
 
 Skin Electromotive Force. The E. M. 
 F. which is active in producing the skin 
 effect in a conductor. 
 
 Skin Effect. The tendency of rapidly 
 alternating currents to avoid the central 
 portions of solid conductors and flow, for 
 the greater part, through the superficial 
 portions. 
 
 Skipping of Pointer of Telegraph In- 
 strument. In a dial telegraph, the fail- 
 ure of the dial to point to the letter in- 
 tended, and caused by its skipping one or 
 more of the letters. 
 
 Skodogram. A term proposed for 
 radiograph. (Not in use.) 
 
 Skotograph. A term proposed for radio- 
 graph. (Not in use.) 
 
 Slack. Excess. 
 
 Slack Cable. Extra cable, or cable paid 
 out in excess of the distance covered, 
 in order to permit of the subsequent re- 
 covery of the cable without undue strain, 
 and also to allow of its accommodating 
 itself to irregularities in the contour of 
 the sea-bottom. 
 
 Sled. A sliding contact drawn after a 
 moving railroad car through the slotted 
 conduit containing the wires or conduc- 
 tors from which the driving current is 
 taken. 
 
 Sleeve Joint. A junction of the ends of 
 conducting wires obtained by passing 
 them through tubes, and subsequently 
 twisting and soldering. 
 
 Sleeve of Plug. A conducting cylinder 
 upon a telephone plug, making contact 
 with the barrel or socket of a telephone 
 jack. 
 
 Slide Bridge. A bridge whose propor- 
 tionate arms are formed of a single thin 
 wire, of uniform diameter and of compar- 
 atively high resistance, of some material 
 whose temperature coefficient is low. 
 
 Slide Contact Piece. A contact piece in 
 which the circuit is completed by means 
 of a sliding or wiping joint. 
 
 Slide Form of Electric Bridge. A slide 
 bridge. 
 
 Slide Resistance. (1) A rheostat whose 
 separate resistances or coils are placed in 
 or removed from a circuit by means of a 
 sliding contact. (2) An apparatus em- 
 ployed in telegraphy consisting of a pair 
 of slide rheostats actually subdivided into 
 100 parts each, but forming jointly a 
 rheostat virtually subdivided into 10,000 
 parts. 
 
 59' 
 
 Slide Switchboard. A telephone switch- 
 board in which the connections are made 
 by sliding contacts. 
 
 Slide Wire. A wire of uniform diameter 
 employed in Wheatstone's electric bridge 
 for the proportionate arms of the bridge. 
 
 Sliding Bed-Plate. A bed-plate of a 
 belt-driven dynamo, motor, or other sim- 
 ilar apparatus, provided with means for 
 moving it, so as to tighten the belt. 
 
 Sliding Contact. A contact connected 
 with one part of a circuit that closes or 
 completes that circuit by being slid over 
 a conductor connected \vith another part 
 of such circuit. 
 
 Sliding Contact-Key. A key employed 
 in the slide form of Wheatstone's bridge 
 to make contact with the sliding wire. 
 
 Sliding Joint. An expansion joint. 
 
 Slings. Bright copper wires employed for 
 hanging an object to be electro-plated to 
 the negative rod in the depositing vessel. 
 
 Slinging Wires. Erecting wires on 
 aerial poles. 
 
 Slip. To release a buoy, rope, anchor etc., 
 in cable work. 
 
 Slip of Induction Motor. The propor- 
 tional difference between the speed of the 
 rotary magnetic field which drives the 
 motor and the speed of the rotor. 
 
 Slip of Rotor. The proportional differ- 
 ence between the speed of a rotary 
 magnetic field and the speed of the rotor. 
 
 Slip Thimble. In cable work, a device for 
 readily disengaging a buoy from the side 
 of a vessel or from its buoy rope. 
 
 Slippage. The ratio, subtracted from 
 unity, of the speed of a rotor divided by 
 the speed of a rotatory magnetic field. 
 
 Slipping of Belt. The loss of speed of a 
 revolving belt on its pulley due to slip- 
 ping. 
 
 Slope of Magneto-Motive Force. A 
 term sometimes used for magnetizing 
 force. 
 
 Slope of Potential. A phrase some.times 
 used for drop of potential. 
 
 Slots on Armature Core. Slots or 
 grooves provided in an armature core for 
 the reception of the armature coils. 
 
 Slot- Wound Armature. (1) An arma- 
 ture in which the windings are buried in 
 slots. (2) An ironclad armature. 
 
 Slotted Armature. (1) An armature pro- 
 vided with slots or grooves for the recep- 
 tion of the wires. (2) An iron-clad arma- 
 ture. 
 
 Slotted Armature-Core. An armature 
 core provided with longitudinal grooves. 
 
Slo.] 
 
 930 
 
 [Sof. 
 
 Slotted Conduit. An underground con- 
 duit provided with a slot extending to 
 the surface of the road-bed, through 
 which a travelling conductor can carry 
 off the current from one or more con- 
 ductors supported in the conduit. 
 
 Slow-Speed Electric Motor. (1) An 
 electric motor which is capable of efficient 
 operation at a comparatively slow speed. 
 (2) A motor designed to run at a com- 
 paratively slow speed. 
 
 Slow-Speed Generator. A generator 
 designed to be run at a slow speed. 
 
 Sluggish Magnet. A magnet that ac- 
 quires or loses its magnetism sluggishly. 
 mashing Point of Incandescent 
 Electric Lamp. Such a period in the 
 life of an incandescent lamp which has 
 become blackened, when it will be more 
 economical to break the lamp, or remove 
 it from the circuit and replace it by a 
 new one, than to continue its operation. 
 
 Smee Voltaic Cell. A zinc-silver couple 
 employed in connection with an electro- 
 lyte of dilute sulphuric acid. 
 
 Smelting of Phosphorus, Electric. 
 The electric separation of phosphorus from 
 any of its compounds. 
 
 Smooth-Body Generator. A dynamo or 
 generator provided with a smooth-core 
 armature. 
 
 Smooth -Core Armature. (1) An ar- 
 mature which presents a continuously 
 smooth cylindrical surface before the ar- 
 mature coils are wound on it. (2) A sur- 
 face-wound armature as distinguished 
 from an iron-clad armature. 
 
 Snap Switch. A switch in which the 
 transfer of the contact points from one 
 position to another is accomplished by a 
 quick motion obtained by the operation 
 of a spring. 
 
 Snap Welding of Bails. A welding 
 joint for a rail bond in which the rails are 
 clamped at their short projections, the 
 ends heated as rapidly as possible and 
 then firmly squeezed together when the 
 welding temperature has been reached. 
 
 Snapper. A device in a sounding-lead 
 consisting of a pair of metallic jaws which 
 are open when the lead is lowered but 
 which automatically close when the sea 
 bottom is reached, for the purpose of 
 securing samples of the sea bottom. 
 
 Snapper Sounder. A mechanical device 
 for producing, by the flexure of a spring, 
 sounds corresponding to Morse characters 
 as heard from a Morse sounder. 
 
 Sneak Current. (1) A relatively weak 
 current accidentally introduced into a 
 
 telephonic or telegraphic circuit, which 
 would do no immediate harm, but which 
 continuing to circulate in a bell or annun- 
 ciator coil would generate enough heat 
 in a comparatively short time to burn it 
 out. (2) A current of sufficient strength 
 to be dangerous if maintained, but insuf- 
 ficiently strong to melt the usual safetj 
 fuses. 
 
 Sneak-Current Arrester. A sneak-cur- 
 rent protector or coil. 
 
 Sneak-Current Coil. A coil of German- 
 silver wire inserted in a telephone circuit 
 to become sufficiently heated by a sneak- 
 current, or current of dangerous strength, 
 to melt a drop of fusible metal placed 
 within it, and thereby cut the telephone 
 apparatus out of circuit. 
 
 Sneak-Current Protector. A form of 
 protector in which a fine fusible wire is 
 inserted between the end of a line andtha 
 instruments. 
 
 Snow-Sweeper, Electric. A form of 
 snow-sweeper operated by means of a*, 
 electric motor. 
 
 Soakage. A term sometimes employed 
 for residual charge. 
 
 Spaking-In. A term sometimes employed 
 for the gradual penetration of an electria 
 charge through a dielectric. 
 
 Soaking-Out. A term sometimes em- 
 ployed by telegraphers to represent th 
 gradual discharge which occurs after 
 the first discharge when a charged cabl 
 conductor is put to earth. 
 
 Socket. (1) In a telephone switchboard a 
 jack or receptacle for a plug. (2) Th 
 barrel of a jack, as distinguished from th 
 contact of the jack placed behind tht 
 barrel. 
 
 Socket-Base. A lamp base provided witk 
 means for ready introduction into a lamp 
 socket. 
 
 Socket for Electric Lamp. A support 
 for the reception of an incandescent 
 lamp. 
 
 Socket Key. A key provided in a lamp 
 socket for lighting or extinguishing th 
 lamp. 
 
 Socket Lamp. A lamp provided with a 
 socket. 
 
 Socket Switch. A socket key. 
 
 Soft-Drawn Copper Wire. Copper wire 
 that is softened by annealing after being 
 drawn. 
 
 Soft Porous Cell. A soft baked poroua 
 cell, whose use in a voltaic cell renders its 
 internal resistance comparatively low. 
 
 Softness. That property of a body in 
 
Sol.] 
 
 931 
 
 [Sou. 
 
 virtue of which it is readily scratched, or 
 its molecules displaced. 
 
 Solar Telegraph. A name sometimes ap- 
 plied to a heliograph. 
 
 Solarizatioii. A term used in photogra- 
 phy for the effect produced by exposure 
 to the sun. 
 
 Solder Ear. An ear or hanger in a trolley 
 system to which the trolley is secured by 
 solder. 
 
 Soldering, Electric. A process for ob- 
 taining metallic joints, in which electri- 
 cally generated heat is employed to melt 
 the solder. 
 
 Soldering Flux. Any chemical suitable 
 for use in connection with solder to cleanse 
 the surfaces of the articles to be soldered. 
 
 Soldering Furnace. A portable furnace 
 for melting solder and heating soldering 
 irons. 
 
 Solenoid. (1) A cylindrical coil of wire 
 whose convolutions are circular. (2) An 
 electro-magnetic helix. (3) Theoretically, 
 a series of coaxial conducting circles 
 placed side by side. 
 
 Solenoid Core. A core, usually of soft 
 iron, placed within a solenoid and mag- 
 netized by the magnetic flux of the ma'g- 
 netizing current. 
 
 Solenoid Galvanometer. A galvano- 
 meter whose needle consists of a solenoid 
 core. 
 
 Solenoidal. Of or pertaining to a solenoid. 
 
 Solenoid al Blow-Out. A magnetic 
 blow-out in which the magnet is a solenoid 
 devoid of an iron core. 
 
 Solenoidal Distribution. A space dis- 
 tribution of a vector quantity devoid of 
 convergence. 
 
 Solenoidal Distribution of Magnetism. 
 
 A term sometimes applied to such a dis- 
 tribution of magnetism in a bar that its 
 particles are arranged with their poles in 
 the direction of the length of the bar, the 
 ends of which are of opposite magnetic 
 polarities, and the extent of whose surface 
 is small as compared with the length of 
 the bar. 
 
 Solenoidal Magnet. A magnet possess- 
 ing a solenoidal distribution of magnetism. 
 
 Solid Angle. (1) The opening between 
 three or more planes at their point of 
 common intersection. (2) 'The area of a 
 portion of spherical surface of unit radius 
 as traced by a central radius vector which 
 traces the outline of the solid angle. 
 
 Solid Arc-Light Carbons. (1) Carbon 
 electrodes for arc lights unprovided with 
 a core of softer carbon. (2) A carbon 
 
 which is of uniform composition through- 
 out as distinguished from a cored carbon. 
 Solid-Back Telephone Transmitter. 
 A term applied to a form of microphone 
 transmitter, largely employed in long- 
 distance telephony. 
 
 Solid Carbons. Solid arc-light carbons. 
 
 Solid Conduit. A conduit in which the 
 insulating material is cast or placed around 
 the wires or conductors so that they can- 
 not be removed from the conduit with- 
 out breaking. 
 
 Solid Depolarizer. Any solid substance 
 employed in connection with the negative 
 plate of a voltaic cell for the purpose of 
 effecting its depolarization. 
 
 Solid Thermostat. A thermostat whose 
 operation depends on the expansion of a 
 solid, or on the unequal expansion of two 
 different solids. 
 
 Solid Wires. Any conductor formed of 
 a single wire, as distinguished from a 
 stranded conductor, or one formed of a 
 number of parallel wires. 
 
 Soluble Electrodes. Electrodes em- 
 ployed in metallic electrolysis, made of 
 copper, iron or other metals which are 
 converted into metallic salts during elec- 
 trolysis. 
 
 Solution. A liquid in which a solid, gas 
 or another liquid is dissolved. 
 
 Sonometer. A single wire stretched at 
 its ends, provided with a movable bridge 
 for the purpose of determining the rela- 
 tion existing between the frequencies of 
 the successive tones of any gamut. 
 
 Sonometer Interrupter. A term some- 
 times employed in place of electro-dyna- 
 mic interrupter. 
 
 Sonorescence. A word proposed for the 
 sounds produced when a piece of vulcan- 
 ite, or other solid substance, is exposed to 
 a rapid succession of flashes of light. 
 
 Sonorous. Sounding or producing sound. 
 
 Soot Cell. In radiophony, a name some- 
 times given to .a carbon cell. 
 
 Sound. (1) The sensation produced on the 
 brain through the ear by the vibrations 
 of a sonorous body. (2) The sound waves 
 that are capable of producing a sensation 
 of sound on the brain through the ear. 
 
 Sound Error. In telegraphy, an error 
 made by mistaking the sound of a signal, 
 syllable, word or phrase, as distinguished 
 from an error made by mistaking the 
 sight of a written character or word. 
 
 Sound Wavos. Waves produced in the 
 air or other elastic medium by the vibra- 
 tions of a sonorous body. 
 
Sou.] 
 
 932 
 
 [Spa, 
 
 Sounder Resonator. (1) A name some- 
 times given to a sounder surrounded by a 
 resonant case, for the purpose of increas- 
 ing the intensity of its sound by reso- 
 nance. (2) A box-sounding relay. 
 
 Sounding Board. An elastic board em- 
 ployed in a stringed musical instrument 
 for the purpose of increasing the intensity 
 of the sounds by resonance. 
 
 Sounding Belay. A box-sounding relay. 
 
 Sounding Tube. A tube employed in a 
 deep-sea sounding-lead for the purpose of 
 securing a sample of the sea bottom. 
 
 Source, Electric. Any arrangement ca- 
 pable of maintaining a difference of po- 
 tential or electromotive force. 
 
 Southern Light. The aurora australis. 
 
 South Magnetic Pole. (1) That pole of 
 a magnetic needle which points approxi- 
 mately to the earth's geographical south. 
 (2) The south-seeking pole of a magnetic 
 needle. 
 
 South-Seeking Magnetic Pole. The 
 south magnetic pole. 
 
 Spacer. In a double-current Morse trans- 
 lator, an electro-magnet in the local cir- 
 cuit, sending zinc, negative, or spacing 
 currents on the circuit to which the cur- 
 rent is being delivered. 
 
 Spacing Battery. A battery in double- 
 current telegraphy employed to send spac- 
 ing currents. 
 
 Spacing Current. (1) The current em- 
 ployed in automatic telegraphy for the 
 purpose of leaving a space on the record- 
 ing paper, as distinguished from the 
 marking current, or the current that is 
 intended to record a dot or dash on the 
 paper. (2) In double-current telegraphy, 
 the currents in one direction which effect 
 and correspond to spaces as distinguished 
 from those in the other direction which 
 effect and correspond to marks or signals. 
 
 Spacing of Armature Conductors. The 
 
 pitch of an armature \vinding. 
 
 Span Cable- Way. An- overhead cable 
 suspended from poles, and intended for 
 supporting an electric locomotor in a sys- 
 tem of electric haulage or telpherage. 
 
 Span Guard-Wire. A wire strung across 
 the street over a trolley wire for the pur- 
 pose of preventing a wire from falling on 
 the trolley wire, as distinguished from 
 running guard wires which overhang and 
 follow a trolley wire along the street. 
 
 Span Wires. Wires tightly stretched 
 across a street from pole to pole, for the 
 purpose of supporting trolley wires. 
 
 Span- Wire Hangers. The hangers which 
 
 suspend the trolley wires from the span 
 wires. 
 
 Span -Wire Trolley Line Construction. 
 A method for the suspension of an aerial 
 trolley line, in which the trolley and feed 
 wires are suspended from span wires sup- 
 ported on poles placed opposite to one 
 another on each side of the street or road. 
 
 Spanish Spoon. A name given to a form 
 of shovel employed for lifting soil out of 
 a hole in the ground excavated for a tele- 
 graph pole. 
 
 Spar Torpedo. A torpedo attached to 
 the end of a spar and designed to be ex- 
 ploded by percussion against the side of 
 an enemy's vessel when thrust against it. 
 
 "Spare" Machine. An extra dynamo, 
 motor or other machine reserved in an in- 
 stallation for use in case of accidental 
 break down. 
 
 Spark Arrester. A device for preventing 
 an arc lamp from scattering sparks or 
 particles of incandescent carbon. 
 
 Spark Chronograph. A form of electric 
 chronograph in which the record is made 
 of the time of a certain event by means 
 of a spark from a Ruhmkorff or spark 
 .coil. 
 
 Spark Coil. A coil of insulated wire con- 
 nected with the main circuit in a system 
 of electric gas lighting, whose extra spark 
 produced on breaking the circuit is em- 
 ployed for electrically igniting gas jets. 
 
 Spark Discharge. (1) An electric dis- 
 charge effected by a spark. (2) A dis- 
 ruptive discharge. 
 
 Spark, Electric. A term sometimes ap- 
 plied to a disruptive discharge. (2) The 
 phenomena produced by a disruptive dis- 
 charge in the air-space or gap through 
 which the discharge passes. 
 
 Spark G-ap.-Kl) The air-space or gap 
 through which a disruptive discharge 
 passes. (2) A gap forming part of a cir- 
 cuit between two opposing conductors 
 and filled with air or other dielectric, 
 across which a spark passes when a cer- 
 tain difference of potential has been 
 reached. 
 
 Spark Micrometer. A spark gap capable 
 of delicate adjustment and measurement. 
 
 Spark Tube. A high-vacuum tube across 
 which the epark from an induction coil 
 will not pass, if the vacuum is sufficiently 
 high. 
 
 Sparking. Discharging by means of dis- 
 ruptive sparks. 
 
 Sparking Discharge. A disruptive di& 
 charge. 
 
Spa.] 
 
 933 
 
 [Spe. 
 
 Sparking Distance. The distance 
 through which electric sparks will pass 
 across an intervening air-gap. 
 
 Sparking of Dynamo-Electric Ma- 
 chine. An irregular and injurious oper- 
 ation of a dynamo attended with sparks 
 at its collecting brushes. 
 
 Sparking Terminals. (1) The terminals 
 of a spark-gap. (2) The points or ends of 
 a spark-gap. 
 
 Sparkless Commutation. Commuta- 
 tion of a dynamo accomplished without 
 sparking at the brushes. 
 
 Spasmodic Governor. A name given to 
 a form of governor for electric motors, in 
 which the current is automatically cut 
 off in proportion as the work is cut off. 
 
 Speaking Battery. In telegraphy or 
 telephony, the battery employed for 
 speaking or signalling. 
 
 Speaking Key. (1) In telegraphy, a key 
 employed in speaking. (2) A signalling 
 key as distinguished from a testing key. 
 
 Speaking Mirror. A simple form of 
 mirror galvanometer employed in cable 
 telegraphy for the reception of the cur- 
 rent impulses or signals. 
 
 Speaking Mirror Plug. A closed tube 
 or plug for insertion into a speaking mir- 
 ror instrument, and containing a sus- 
 pended mirror and magnet. 
 
 Speaking Switch. In telegraphy, a 
 switch employed in speaking or signalling. 
 
 Speaking Telegraph. A term sometimes 
 employed for the telephone. 
 
 Speaking Telegraphy. A term some- 
 times employed for telephony. 
 
 Speaking-Tube Annunciator. An oral 
 annunciator. 
 
 Speaking-Tube Mouth-Piece Alarm, 
 Electric. A mouth-piece for a speaking- 
 tube, so arranged that the movement of 
 a pi voted plate covering the mouth-piece 
 automatically rings an electric bell atthe 
 other end of the tube. 
 
 Speaking-Tube Telephone System. A 
 name sometimes employed for a system 
 of telephone communication by means of 
 which a number of offices can be con- 
 nected without the use of a central switch- 
 board. 
 
 Speaking Wire. In a system of tele- 
 phony, a wire connecting two exchanges 
 for the purpose of communicating: instruc- 
 tions between operators, as distinguished 
 from a wire through which a subscriber 
 may be connected. 
 
 Specific Capacity. Specific inductive 
 capacity. 
 
 Specific Conductance. A term some- 
 times used for specific conductivity. 
 Specific Conduction Resistance. 
 
 (1) Resistivity. (2) A term sometimes 
 used for specific resistance. 
 
 Specific Conductivity. (1) The partic- 
 ular conductivity of a substance for elec- 
 tricity. (2) The specific or particular re- 
 sistance of a given length and area of 
 cross-section of a substance, as compared 
 with the same length and area of cross- 
 section of some standard substance. 
 (3) Conductivity with reference to Mat- 
 thiessen's standard conductivity. 
 
 Specific Dielectric Capacity. A term 
 sometimes employed in place of specific 
 inductive capacity. 
 
 Specific Energy. (1) Volumetric energy. 
 
 (2) Energy per unit of volume. 
 Specific Gravity. The weight of a given 
 
 volume of a substance, as compared with 
 an equal volume of some standard sub- 
 stance, such as water. 
 
 Specific Heat. The capacity of a sub- 
 stance for heat, as compared with an 
 equal quantity of some other substance 
 taken as unity. 
 
 Specific Heat of Electricity. A term 
 proposed to indicate the analogies exist- 
 ing between the absorption and emission 
 of heat in purely thermal phenomena, 
 and the absorption and emission of heat 
 in thermo-electric phenomena. 
 
 Specific Hysteretic Dissipation. 
 
 (1) The loss of energy by hysteresis in a 
 particular substance, per unit of volume. 
 
 (2) The hysteretic loss of energy in a sub- 
 stance under given conditions compared 
 with the similar loss in a standard sub- 
 stance. 
 
 Specific Inductive Capacity. (1) The 
 ability of a dielectric to permit induction 
 to take place through its mass as compar- 
 ed with the ability possessed by a vacuous 
 space of the same dimensions, under pre- 
 cisely the same conditions. (2) The rela- 
 tive power of bodies for transmitting elec- 
 trostatic stresses and strains, analogous 
 to permeability in metals. (3) The ratio 
 of the capacity of a condenser whose coat- 
 ings are separated by a dielectric of a 
 given substance, to the capacity of a 
 similar condenser whose plates are sep- 
 arated by a vacuum . (4) The ratio of the 
 permittivity of a substance to the permit- 
 tivity of vacuum. 
 
 Specific Magnetic Capacity. (1) A 
 term sometimes employed in the sense of 
 magnetic permeability. (2) A word em- 
 ployed for conductibility for magnetic 
 
Spe.] 
 
 934 
 
 [Spe. 
 
 flux, in the same sense that specific capac- 
 ity is conductibility for electrostatic flux. 
 
 Specific Magnetic Conductivity. The 
 specific or particular permeability of a 
 substance to magnetic flux. 
 
 Specific Magnetic Induct! vity. A term 
 sometinies used for specific magnetic con- 
 ductivity. 
 
 Specific Magnetic Reluctance. A 
 term sometimes used for specific magnetic 
 resistance. 
 
 Specific Magnetic Resistance. A term 
 sometimes used for reluctivity. 
 
 Specific Magnetism. A term proposed 
 for the quotient of the magnetic moment 
 of a magnet by its mass. 
 
 Specific Molecular Conductivity. 
 Molecular conductivity as referred to that 
 of some standard substance. 
 
 Specific Reluctance. A term sometimes 
 used for reluctivity. 
 
 Specific Resistance. (1) The particular 
 resistance a substance offers to the pas- 
 sage of electricity through it, compared 
 with the resistance of some standard sub- 
 stance. (2) In absolute measurements, the 
 resistance in absolute units between op- 
 posed faces of a centimetre cube of a 
 given substance. (3) In the practical 
 system, the above resistance in ohms. (4) 
 Resistivity, expressed in electro-magnetic 
 absolute units as square-centimetres per 
 second. 
 
 Specific Resistance of Liquid. 
 (I) Tha resistance of a given length and 
 area of cross-section of any liquid as com- 
 pared with the resistance of an equal 
 length and cross-section of pure copper 
 or other standard conductor. (2) Resis- 
 tivity of a liquid. 
 
 Spectrograph. A word proposed for 
 radiograph. 
 
 Spectrophone. An instrument employed 
 for the exploration of the ultra- red por- 
 tion of the spectrum. 
 
 Spectro-Photometer. (1) A form of 
 photometer suitable for measuring the 
 relative intensities of lights of different 
 qualities. (2) A photometer which com- 
 pares luminous intensities in successive 
 ' portions of spectra, frequency by fre- 
 quency. (3) A spectroscope so arranged 
 as to readily permit of the comparison as to 
 brightness, wave-length by wave-length, 
 of rays from two different luminous 
 sources. 
 
 Spectro-Photometric. Of or pertaining 
 to the spectro-photometer. 
 
 Spectro-Photometry. Photometry by 
 means of the spectro-photometer. 
 
 Spectroscope. An optical instrument for 
 determining the composition of a body 
 by the character of the light it emits, as 
 determined by its component frequencies. 
 
 Spectroscopic. Of or pertaining to the 
 spectrum. 
 
 Spectrum. A band of multicolored light 
 or radiant energy of different frequencies, 
 obtained by dispersion in a prism or by a 
 diffraction grating. 
 
 Speed Constant. In submarine teleg.a- 
 phy, a constant quantity which divided 
 by the product of the capacity and resist- 
 ance of a cable gives the working speed 
 of the cable in letters per minute. 
 
 Speed Counter. Any apparatus for deter- 
 mining the number of revolutions of a 
 shaft. 
 
 Speed and Direction Indicator. A 
 telegraph on board ship for indicating the 
 speed of revolution of the propeller shaft 
 and the direction of its movement. 
 
 Speed Indicator. A form of speed 
 counter. 
 
 Speed of Rotation. (1) The number of 
 revolutions per second, per minute, hour 
 or unit of time generally. (2) The dis- 
 tance passed over in a given time by the 
 circumference of a rotating wheel or 
 pulley. (3) The angular velocity of rota- 
 tion in degrees or radians per unit of 
 time. 
 
 Speed Recorder. (1) An apparatus for 
 recording the instantaneous values of the 
 speed of any machine. (2) An instru- 
 ment for both indicating and recording 
 the speed of a trolley car from moment 
 to moment. 
 
 Speeding. (1) Varying the number of 
 revolutions per second. (2) Increasing a 
 speed of rotation. 
 
 Speeding of Dynamo. Varying the 
 speed of a dynamo, for the purpose of ob- 
 taining the proper speed required to oper- 
 ate an electro-receptive device placed in 
 its circuit. 
 
 Spelter. A name sometimes given to com- 
 mercial zinc. 
 
 Spent Acid. A battery or other acid that 
 has, through use, become too weak for 
 efficient action. 
 
 Spent Liquor. Any liquor such as that 
 used in an acid or other bath, that has 
 through use become too weak for efficient 
 action. 
 
 Spewing of Cable Core. The mechani- 
 cal derangement of a cable, whereby the 
 sheathing opens and the core appears OB 
 the surface. 
 

 935 
 
 [SplL 
 
 Spherical Aberration. A defect where- 
 by a lens or mirror with spherical faces 
 fails to produce in its images the correct 
 outlines of objects, owing to the fact that 
 the curvature of one or both of its faces 
 should slightly depart from the true 
 spherical form in order to produce a true 
 image. 
 
 Spherical Armature. An armature for 
 a dynamo, the coils of which are wound 
 on a spherical iron core. 
 
 Spherical Bougie Decimale. (1) A unit 
 of luminous flux equal to that which 
 would be produced by a point source 
 having an intensity of one bougie deci- 
 male in all directions. (2) A luminous 
 flux equal to 12.566 lumens. 
 
 Spherical Candle-Power. (1) The total 
 flux of light emitted by a luminous source 
 divided by 12.566. (2) The candle-power of 
 a point-source, which emits with uniform 
 intensity in all directions, as much light 
 as does an actual lamp. (& The average 
 candle-power of a luminous source taken 
 in all directions, or considered over the 
 entire surface of an enveloping sphere. 
 
 Spherical Candle-Power Measurer. 
 An instrument for measuring, or ena- 
 bling to be measured, the mean spherical 
 candle-power of a source of light from a 
 single observation. 
 
 Spherical Candle-Power Photometer. 
 (1) A photometer designed to measure 
 the mean spherical candle-power of a 
 lamp. (2) A photometer designed to 
 measure the mean spherical candle-power 
 of a luminous source from a single ob- 
 servation. 
 
 Spherical Harmonics. Homogeneous 
 functions of rectilinear space-co-ordinates 
 which satisfy Laplace's equation. 
 
 Spherical Strain Insulator. An insu- 
 lator for a guy-wire or trolley pull-off, 
 spherical in form. 
 
 Spherorneter. An apparatus for readily 
 measuring the curvature of a sphere. 
 
 Sphygmogram. A record made by a 
 sphygmograph. 
 
 Sphygmograph. An instrument for re- 
 cording the movements of the pulse, usu- 
 ally of the radial artery at the wrist. 
 
 Sphygmograph, Electric. An instru- 
 ment for electrically recording the pecul- 
 iarities of the pulse. 
 
 Sphygmophone. An apparatus employ- 
 ing a microphone for the medical exam- 
 ination of the pulse. 
 
 Sphygmoscope. An apparatus for de- 
 tecting, but not recording, the peculiari- 
 ties of the pulse. 
 
 Spider. A radial bracket or support fot 
 supporting an armature or machine on a 
 revolving shaft. 
 
 Spider Arm. One of the projections of a 
 spider support. 
 
 Spin. (1) The curl of a vector point- 
 function. (2) Eotation. (3) Vorticity. 
 
 Spiral. (1) A helix. (2) A word some- 
 times employed in electricity and mag- 
 netism for an open conducting coil. 
 
 Spiral Accumulator. An accumulator 
 whose plates consist of two parallel plates 
 of lead insulated from each other and 
 rolled into a close spiral. 
 
 Spiral Loop System of Parallel Distri- 
 bution. A modified form of loop system 
 for parallel distribution. 
 
 Spiral Loop System of Distribution. 
 
 A name given to a variety of parallel 
 distribution adopted for obtaining a com- 
 paratively uniform distribution of poten- 
 tial, in which the parallel conductors are 
 extended in the arcs of spirals from the 
 generating station throughout the district 
 to be served, both spirals extending from 
 one pole of the generator nearly to the 
 other pole. 
 
 Spiral Winding. A S9lenoidal winding. 
 
 Spiralled Fours of Cable. A defect In 
 the winding of a telephone cable, in which 
 any four wires are so wound about the 
 core that one pair is not on the average 
 midway between the other pair, so that 
 cross-talk is sure to result. 
 
 Splice Bar. A fish plate employed for 
 connecting together the ends of a rail. 
 
 Splice Box. A box provided for holding 
 splice joints and loops so arranged as to 
 be readily accessible for examination, re- 
 arrangement, cross-connection, etc. 
 
 Splicing. Connecting the sheathings of 
 the two ends of a cable at a joint. 
 
 Splicing Ear. (1) A trolley ear for uniting 
 the ends of a trolley wire. (2) A splicing 
 suspension ear. 
 
 Splicing Mallet. A mallet used in a sub- 
 marine cable splice for laying on a serv- 
 ing of yarn under tension. 
 
 Splicing Sleeve. A tube of conducting 
 material employed for covering a splice 
 in a conducting wire. 
 
 Splicing Suspension Ear. A metal 
 piece suitably supported on an insulator 
 and provided in a system of overhead 
 trolley wires for connecting two separate 
 ends of the trolley line. 
 
 Splicing Tool. A tool employed in 
 making a cable splice, for forcing the 
 sheave wires around the cable in their 
 
Spli.] 
 
 936 
 
 [Spr. 
 
 proper spiral position corresponding to 
 that which they have on other parts of 
 the cable. 
 
 Splicing Tube. A name sometimes given 
 to a connector employed in making a 
 joint in a trolley wire. 
 
 Split Battery. A voltaic battery connect- 
 ed in series and having one of its middle- 
 plates connected to the ground. 
 
 Split Condenser. (1) A condenser so ar- 
 ranged that its different sections can be 
 readily inter-connected in the same cir- 
 cuit or employed in different circuits as 
 may be required. (2) A subdivided con- 
 denser. 
 
 Split Current. (1) A divided current. 
 (2) A current tapped from a main tele- 
 graph wire. 
 
 Split Dynamometer. A dynamometer 
 employed in connection with alternating 
 currents provided with two coils, so ar- 
 ranged that separate currents of the same 
 frequency can be passed independently 
 through each. 
 
 Split Lead-Tee. A T-shaped lead tube 
 that is split for readily covering a joint at 
 a branch in a cable. 
 
 Split Phase. A difference produced be- 
 tween the phased of two or more alter- 
 nating currents into which a Uniphase 
 alternating current has divided. 
 
 Split-Phase Motor. (1) A multiphase 
 motor operated from a uniphase alternat- 
 ing-current circuit by the introduction of 
 a phase-splitting device. (2) A multiphase 
 motor in which the multiphase currents 
 are locally produced from a single-phase 
 circuit. 
 
 Split-Pin Plug. A plug having two 
 halves or two sleeves insulated from each 
 other, employed for readily introducing a 
 loop into a circuit. 
 
 Split-Ring Magnet. A ring-core magnet 
 provided with an air-gap. 
 
 Split-Secondary of Induction Coil. 
 The secondary of an induction coil which 
 is divided into two equal portions. 
 
 Spluttering of Arc. A spluttering sound 
 attending the formation of a voltaic arc. 
 
 Spokes of Armature Core. Radial pro- 
 jections on a spider in an armature core, 
 on which coils are sometimes wound. 
 
 Sponge Electrode. A therapeutic elec- 
 trode provided with a sponge. 
 
 Spontaneous Electricity. A term for- 
 merly employed for the electricity pro- 
 duced by the melting of sulphur. 
 
 Spot. The reflected image or luminous 
 
 patch of light on a mirror galvanometer 
 scale. 
 
 Spotty Filament. The filament of an 
 incandescent lamp possessing such local 
 variations in resistance that when ren- 
 dered luminous by the passage of the cur- 
 rent, it possesses points of unequal brill- 
 iancy. 
 
 Spreader Bracket. A name sometimes 
 given to a loop bracket. 
 
 Spreader for Arc Wires. A form of 
 loop bracket employed on arc circuits. 
 
 Spreading of Magnetic Field. A term 
 sometimes employed for divergence of a 
 magnetic field. 
 
 Sprengel Mercury Pump. A mercurial 
 air pump in which the vacuum is obtained 
 by means of the fall of a stream of 
 mercury through a tube in such a manner 
 as to entangle portions or bubbles of 
 residual air. 
 
 Spring Ammeter. A form of ammeter 
 in which a magnetic core or needle is 
 moved against the action of a spring by 
 the field of the current it is measuring. 
 
 Spring Clips of Switch. Spring jaws of 
 a switch which grasp the blade or blades 
 in the closed position. 
 
 Spring Contact. (1) A contact which 
 either opens or closes under the action of 
 a spring. (2) A spring-supported contact, 
 connected with one part of a circuit, that 
 completes the circuit on being moved so 
 as to touch another contact connected 
 with the other part of the circuit. (3) A 
 circuit-closing or circuit-opening device 
 normally maintained in one position and 
 condition by the action of a spring. 
 
 Spring Dynamometer. A dynamometer 
 whose operation is dependent on the 
 action of a spring. 
 
 Spring Jack. A form of spring contact 
 provided with a hole for the insertion of 
 a plug. 
 
 Spring- Jack Cut-Out. A cut-out operat- 
 ed by a spring jack. 
 
 Spring-Jack Telephone Switchboard. 
 A form of telephone switchboard pro- 
 vided with calling drops, clearing out 
 drops, and spring jacks, so arranged as to 
 readily enable a number of subscribers to 
 be placed in inter-communication. 
 
 Spring Manometer. A manometer 
 whose operation is dependent on the de- 
 formation of an elastic solid. 
 
 Spring Relay-Contact. A form of relay 
 contact which is interrupted by the action 
 of a spring as soon as the circuit is 
 broken. 
 
Spr.] 
 
 937 
 
 [Sta. 
 
 Spring-Snag Lever-Switch. A form of 
 switch operated by a spring snap lever. 
 
 Spring - Suspended Street- Bail way 
 Motor. A street-railway car motor sus- 
 pended from the car truck by means of 
 springs. 
 
 Spring Voltmeter. A form of voltmeter 
 in which the potential difference is 
 measured by the movement of a magnetic 
 needle, coil, or core, against the pull of a 
 spring. 
 
 Spurious Hall Effect. An apparent 
 transverse electromotive force in conduc- 
 tors carrying electric currents in magnet- 
 ic fields, by changes, produced by magnet- 
 ism, in the conductivity of the metals 
 and the consequent production of local 
 disturbances in the electrical flow, thus 
 resulting in an apparent transverse elec- 
 tromotive force. 
 
 Spurious Resistance. A false or ap- 
 parent resistance arising, from the devel- 
 opment of a counter-electromotive force. 
 
 Square Conductor. A form of power 
 conductor with rectilinear cross-section. 
 
 Square Mil. (1) A unit of area employed 
 in measuring the areas of cross-section of 
 wires, equal to .000001 square inch. 
 (2) A unit of area equal to 1.2732 circular 
 mils. 
 
 " Squeeze." In electro-typing the im- 
 pression obtained by subjecting a type, or 
 woodcut, to a plate or mass or soft wax. 
 
 Squeezer. A device for testing the duc- 
 tility of a wire, consisting in a receptacle, 
 somewhat resembling a lemon squeezer, 
 in which the wire is placed and clamped 
 and the device opened and closed until 
 the wire breaks. 
 
 Squirted Filament. A filament for an 
 incandescent lamp made by the carboni- 
 zation of a carbonaceous paste, that is 
 shaped by being squirted by pressure 
 through a suitably shaped die hole. 
 
 Stabile Galvanization. A term em- 
 ployed in electro-therapeutics in which 
 the current is caused to pass continuously 
 and steadily through the portions of the 
 body undergoing galvanization. 
 
 Stable Equilibrium. (1) The equilib- 
 rium of a body supported on a base, such 
 that in order to overturn it, its centre of 
 gravity must be raised. (2) The equilib- 
 rium of a body so supported that any 
 small displacement raises its centre of 
 gravity. 
 
 Stable Period 9f Circuit. (1) That 
 condition of a circuit in which the cur- 
 rent- passing through it has reached its 
 
 full strength, and is no longer undergoing 
 variations. (2) The permanent state. 
 
 Stage Regulator. A controller of incan- 
 descent lamps in a theatre, placed near 
 the stage, whereby they may be lighted, 
 extinguished, or dimmed. 
 
 Staggered Armature. An armature in 
 which the conductors do not lie on ita 
 surface in a direction parallel to the axis 
 of rotation, but cross its surface diag- 
 onally. 
 
 Staggering of Dynamo Brushes. A 
 term sometimes applied to the position of 
 the brushes on a commutator cylinder, in 
 which one brush is placed slightly in ad- 
 vance of the other, so as to wear the 
 commutator surface smoothly, and pre- 
 vent the formation of grooves. 
 
 Stalk of Insulator. The support or inner 
 metal cylinder of an aerial line insulator. 
 
 Standard. A metallic pole supported on 
 the roof of a house for carrying overhead 
 wires. 
 
 Standard Candle. (1) A candle of defi- 
 nite composition, which, when burned at 
 the rate of two grains per minute, will 
 produce a light of a definite and fixed 
 brightness. (2) A legal standard of light 
 in Great Britain. 
 
 Standard Cell. A standard voltaic cell. 
 
 Standard Clock. A clock employed for 
 the comparison of other clocks. 
 
 Standard Coil. A standard resistance 
 coil. 
 
 Standard Compass. A compass on board- 
 ship which is used as a standard and by 
 which other compasses may be checked- 
 or compared. 
 
 Standard Cross-Arms. Wooden cross- 
 arms of standard dimensions for support- 
 ing aerial wires on poles. 
 
 Standard Earth - Quadrant. (1) A- 
 length approximately equal to 10,000 
 kilometres. (2) One quarter of the mend* 
 ian circle of the earth taken through Paris, 
 (3) A standard unit of inductance. 
 
 Standard Feeder. A term sometimes 
 applied to a principal feeder, operated at 
 standard pressure. 
 
 Standard Luminous Intensity. 
 (1) Any unit of luminous intensity em- 
 ployed as a standard. (2) A luminous 
 intensity of one violle, bougie-decimale, 
 Hefner- Alteneck, carcel, British standard 
 candle, etc. 
 
 Standard Megohm. A resistance equal 
 to one million ohms, employed as a. 
 standard. 
 
 Standard Ohm. A length of wire having 
 
Sta.] 
 
 a resistance of the value of one ohm, em- 
 ployed in standardizing resistance coils. 
 
 Standard Quadrant. (1) The standard 
 earth quadrant. (2) A standard induct- 
 ance equal to one quadrant. 
 
 Standard Resistance. A known resist- 
 ance used for comparison with, or deter- 
 mination of, an unknown resistance. 
 
 Standard Resistance Coil. A coil whose 
 resistance is that of a standard ohm or 
 some multiple or sub-multiple thereof. 
 
 Standard Telephone Switchboard. 
 A name applied to a foi-m of multiple 
 switchboard commonly employed in the 
 United States. 
 
 Standard Time. Mean solar time used 
 in telegraphy, and referred either to the 
 meridian of Greenwich, or to some other 
 meridian west of Greenwich, an exact 
 number of hours. 
 
 Standard Voltaic Cell. A voltaic cell 
 whose electromotive force is practically 
 constant, and which can, therefore, be 
 used as a standard in the measurement of 
 an unknown electromotive force. 
 
 Standard Wire Gauge. A wire gauge 
 adopted by the National Telephone Ex- 
 change Association and the National 
 Electric Light Association of America. 
 
 .Standards. (1) Telegraphic or telephonic 
 supports placed on the roof of a building 
 for the purpose of supporting the wires or 
 conductors. ^ (2) A general term for a 
 resistance coil, voltaic cell or other stand- 
 ard employed for purposes of comparison. 
 (3) A term applied to the support of the 
 bearings of a dynamo or motor. 
 
 Standardized Resistance Coil. A coil 
 whose resistance has been carefully ob- 
 tained by comparison with a standard. 
 
 Standardizing a Voltaic Cell. Deter- 
 mining the exact value of the electromo- 
 tive force of a voltaic cell, in order to 
 permit it to be used as a standard in ob- 
 taining the electromotive force of any 
 electric source. 
 
 Standing Torque. Starting torque. 
 
 Star Current in Polyphase System. 
 (1) A current between any line or terminal 
 of a polyphase system and the neutral 
 point. (2) The current in any branch of 
 a star polyphase system. 
 
 Star Grouping of Polyphase Circuits. 
 A method of grouping a triphase circuit 
 consisting of making a common junction 
 at one point and branching them star- 
 wise. 
 
 Star Potential in Polyphase System. 
 The effective difference of potential or 
 
 [Sta. 
 
 voltmeter pressure between any line or 
 terminal of a polyphase system and tka 
 neutral point. 
 
 Star Triphase- Winding. A connectio* 
 of three triphase windings in which all 
 three are connected together at a common 
 point or junction point, and the three 
 free ends connected to the terminals. 
 
 Star Triphaser. A triphaser possessing 
 a star triphase winding. 
 
 Starting Box. A name sometimes applied 
 to a starting resistance. 
 
 Starting Box for Electric Motor. A 
 resistance provided for starting an elec- 
 tric motor. 
 
 Starting Box of Shunt- Wound Motor. 
 A box provided with a rheostat of variable 
 resistance, introduced into the armature 
 circuit of a shunt-wound motor for the 
 purpose of preventing the rush of current 
 made on first connecting the motor with 
 the driving-circuit. 
 
 Starting Coil of Motor. A coil employed 
 as a starting resistance for an electric 
 motor. 
 
 Starting Current of Motor. The cur- 
 rent traversing the coils of a motor at 
 its moment of starting. 
 
 Starting Motor for Synchronous 
 Motor. A small electric motor some- 
 times employed for bringing the arma- 
 ture, of a synchronous singlerphase motor 
 up to its proper speed before connecting 
 it with the driving-current circuit. 
 
 Starting Position of Street-Car Con- 
 troller. (1) The position of a street-car 
 controller switch at which the current is 
 cut off from the motors. (2) The position 
 of a street-car controller switch, at which 
 the current is first admitted to the motors 
 when starting. 
 
 Starting Resistance. A resistance em- 
 ployed in the starting box for an electric 
 motor. 
 
 Starting Rheostat. Coils of wire mount- 
 ed in a suitable manner, and so connected 
 as to be successively placed in the circuit 
 of a motor while it is being started. 
 
 Starting Torque of Motor. (1) The 
 torque required in starting a motor. (2) 
 The torque developed by a motor in start- 
 ing. 
 
 Static Balance. A duplex or quadruplex 
 balance ad justed for the capacity of a line 
 by the use of a condenser. 
 
 Static Balance of Duplex System. 
 
 (1) The capacity balance of a duplex sys- 
 tem as distinguished from the resistance 
 balance. (2) A balance for charging and 
 
Sta.] 
 
 939 
 
 [Sta. 
 
 discharging as distinguished from a bal- 
 ance for steady currents. 
 Static Breeze. An electric breeze ob- 
 tained by a cpnvective discharge or an 
 electrostatic discharge. 
 
 Static Compensating Condenser. A 
 condenser employed in the artificial line 
 of duplex or quadruplex telegraphy. 
 
 Static Compensator. A condenser em- 
 ployed for compensating the electro-static 
 capacity of a line in the duplex system. 
 
 Static Discharge. A name sometimes 
 given to a disruptive discharge. 
 
 Static Electricity. A term applied to 
 electricity produced by friction. 
 
 Static Electro-Motor. An electro-motor 
 operated by the repulsion of electric 
 charges. 
 
 Static Energy. (1) A term used to ex- 
 press the energy possessed by a body at 
 rest, resulting from its position as regards 
 other bodies, in contradistinction to ki- 
 netic energy, or the energy possessed by a 
 body whose atoms, molecules and masses 
 are in actual motion. (2) Potential en- 
 ergy. 
 
 Static Hysteresis. (1) A term sometimes 
 applied to that quality in iron or other 
 paramagnetic substance, by virtue of 
 which energy is dissipated during every 
 reversal in its magnetization, in contra- 
 distinction to viscous hysteresis. (2) Elec- 
 trostatic dielectric hysteresis. 
 
 Static Induction. A term sometimes 
 employed for electrostatic induction. 
 
 Static Insulation. A term employed in 
 electro-therapeutics for a method of treat- 
 ment by convection streams or discharges, 
 in which the patient is seated on an insu- 
 lated stool connected to one pole or elec- 
 trode of an influence machine, while the 
 other pole or electrode is connected to the 
 ground. 
 
 Static Magnetic Induction. The in- 
 duction which takes place in the field of 
 a magnet whose flux is stationary as re- 
 gards the body in which the induction is 
 occurring. 
 
 Static Shock. (1) A term employed in 
 electro-therapeutics for a mode of apply- 
 ing Franklinic currents or discharges by 
 placing the patient on an insulating stool 
 and applying one pole of a static machine 
 provided with small condensers or Leyden 
 jars, while the other pole is connected to 
 the body of the patient. (2) An electro- 
 static shock. 
 
 Static System of Induction Teleg- 
 raphy. A system of induction teleg- 
 raphy depending on static induction be- 
 
 tween the sending and the receiving in- 
 strument. 
 
 Static Time Constant. The electrostatic 
 time constant of a circuit. 
 
 Static Transformer. A term sometimes 
 employed for an ordinary transformer, 
 to distinguish it from a rotary trans- 
 former. 
 
 Static Voltmeter. (1) A voltmeter oper- 
 ating by electrostatic action, as opposed 
 to a voltmeter operating electro-magneti- 
 cally. (2) A voltmeter in which the mov- 
 ing system is displaced by electrostatic 
 forces. (3) A voltmeter of the electro- 
 scope or electrometer type. 
 
 Statics. (1) That branch of science which 
 treats of the relations that must exist be- 
 tween the points of application of forces 
 and their direction and intensity, in order 
 that equilibrium may result. (2) The 
 science of forces at rest. 
 
 Station Circuit - Breaker. A circuit- 
 breaker in a central station. 
 
 Station Indicator. (1) A name some- 
 times given to a station voltmeter. (2) 
 Any indicator situated at a central station. 
 
 Station Load. The total load existing on 
 a central station at any time. 
 
 Station Load-Curve. A curve repre- 
 senting the station load at different 
 times. 
 
 Station Panel. (1) A panel in a central- 
 station switchboard. (2) A load panel in 
 a central-station switchboard showing the 
 total load of the station. (3) A panel in 
 a central-station switchboard connecting^ 
 a feeder running to some other station or 
 sub-station. 
 
 Station Recording- Wattmeter. A 
 wattmeter suitable for use in a central 
 station for recording the energy delivered 
 bv the station. 
 
 Station Switch. (1) A switch in a sta- 
 tion. (2) A switch for connecting an 
 auxiliary station to a system. (3) A 
 switch supplying an auxiliary station. 
 (4) A switch for connecting the lighting 
 or other local wires in a central station to 
 the system of distribution. 
 
 Station Transformer. (1) A transform- 
 er placed in a central station. (2) A 
 transformer which supplies a load in a 
 station. (3) A transformer intended to 
 supply current to lamps and potential 
 indicators on the switchboard in the 
 station. 
 
 Stationary Transformers. A word 
 sometimes applied to ordinary alternat- 
 ing-current transformers, in contradis- 
 tinction to rotary transformers. 
 
:Sta.] 
 
 940 
 
 [Ste. 
 
 Stationary Electric Motor. An electric 
 motor that is fixed to the floor or ground, 
 in contradistinction to a travelling or 
 locomotor. 
 
 ^Stationary Fare-Register for Street 
 Car. A register placed permanently in 
 a car, for the purpose of recording the 
 fare received by a conductor. 
 
 Stationary Floor-Key. A name some- 
 times applied to a floor push. 
 
 Stationary Hook of Telephone. A 
 fixed hook provided for holding a tele- 
 phone. 
 
 Stationary Motor. A motor that is fixed 
 in place, in contradistinction to a loco- 
 motor. 
 
 Stationary Secondary of Induction 
 Motor. An induction motor whose sec- 
 ondary coils form the stator. 
 
 Stationary Tachometer. Any tacho- 
 meter employed for indicating the num- 
 ber of revolutions per minute of a snaft 
 in a stationary rotating machine. 
 
 Stationary Torpedo. A term sometimes 
 employed for a submarine mine. 
 
 Stator. That part of a dynamo or motor, 
 whether the armature or the field, which 
 remains at rest or stands still during the 
 operation of the machine, as distinguished 
 from the rotor or part which rotates. 
 
 Stator Armature. (1) An armature of a 
 dynamo or motor that remains at rest 
 during the operation of the machine. 
 (2) An immovable element of a machine 
 which is also its armature. 
 
 Stator Circuit. The circuit of the stator 
 coils. 
 
 Stator Coils. The coils placed on the sta- 
 tor of a dynamo or motor. 
 
 Stator Currents. Currents that flow in 
 the stator of a dynamo or motor. 
 
 Stator Field. A field of a dynamo or mo- 
 tor that remains at rest during operation. 
 
 Statute Mile. A length employed in 
 Great Britain equal, by statute, to 5280 
 feet. 
 
 Stauroscope. A form of polariscope for 
 investigating the effects of polarized light 
 on crystals. 
 
 Stay-Eye Clip. An iron band rigidly 
 clamped to roof beams or other strong 
 supports and carrying an iron ring for the 
 attachment of a stay -rod. 
 
 Stay Rod. A rod of iron or steel, used to 
 stay or support a telegraph or telephone 
 pole. 
 
 Stay Tightner. A swivel for taking up 
 slack in a stay. 
 
 Steady Current. A current whose 
 strength does not vary from time to time. 
 
 Steam Dynamo. (1) A name applied to 
 a steam-turbine dynamo. (2) A dynamo 
 direct-connected to a steam engine. 
 
 Steam Governor, Electric. A device 
 used in connection with a valve to so 
 electrically regulate the supply of steam 
 to an engine that the engine shall be 
 driven at such a speed as will maintain 
 either a constant current, or constant 
 potential. 
 
 Steam-Turbine Dynamo. A high-speed 
 dynamo whose armature is driven by 
 means of a steam turbine. 
 
 Steaming Lights, Electric. A term 
 sometimes applied to the side lights of a 
 ship. 
 
 Steam's Relay Shunt. A shunt em- 
 ployed in the differential method of du- 
 plex telegraphy to short-circuit the relay 
 and then permit the line current to be cut 
 off directly after it has completed its work 
 in closing the local circuit. 
 
 Steel Facing of Electro-Type. A thin 
 electrolytic deposit of iron placed on the 
 surface of an electro-type for the purpose 
 of hardening it. 
 
 Steel-Yard Ammeter. A form of am- 
 meter in which the strength of a current 
 is measured by means of the electro-mag- 
 netic forces applied to one extremity of a 
 steel-yard lever, provided with sliding 
 weights for balancing these forces. 
 
 Steeps. A word sometimes employed in 
 electro-plating for dips or dipping liquids 
 or solutions. 
 
 Steering Compass. A compass employed 
 for the steering of a ship. 
 
 Steering, Electric. Steering effected 
 electrically. 
 
 Steering Telegraph. A telegraph on 
 board ship for communicating steering 
 orders from some point such as the bridge 
 or conning tower. 
 
 Steno-Telegraphy. A system of tele- 
 graphy in which the sounds of a word are 
 represented by characters instead of by 
 letters. 
 
 Step-by-Step Annunciator. An an- 
 nunciator operated on the step-by-step 
 principle. 
 
 Step-by-Step Telegraphy. (1) A sys- 
 tem of telegraphy in which the signals 
 are registered by the movements of a 
 needle over a dial on which the letters of 
 the alphabet are marked. (2) Dial teleg- 
 raphy. 
 
Ste.J S 
 
 Step-Down Converter. A step-down 
 transformer. 
 
 Step-Down Transformer. (1) A trans- 
 former in which a small current of com- 
 paratively great difference of potential is 
 converted into a large current of com- 
 paratively small difference of potential. 
 (2) An inverted Rulimkorff induction coil. 
 
 Step-Up Converter. A step-up trans- 
 former. 
 
 Step-Up Transformer. A transformer 
 in which a large current of comparatively 
 small difference of potential is converted 
 into a small current of comparatively 
 great difference of potential. 
 
 Steradian. (1) A unit of solid angle. (2) 
 The solid angle subtended at the centre 
 of a sphere of unit radius by a unit of 
 spherical area, or unit of surface on the 
 sphere. 
 
 Stereopticon. A lantern apparatus for 
 projecting on a screen a stereoscopic 
 picture. 
 
 Stereoscope. An optical apparatus for 
 obtaining from two photographic pic- 
 tures, taken in slightly different positions, 
 pictures correctly representing solid ob- 
 jects. 
 
 Stereoscopic. Of or pertaining to a ster- 
 eoscope. 
 
 Stereotype. A fac-simile or duplication 
 of a page of movable types or of engrav- 
 ings, effected by obtaining a moulding of 
 the original in some suitable material, and 
 then immersing the mould in melted type 
 metal. 
 
 Sterilization, Electric. Sterilizing a so- 
 lution by depriving it, by means of elec- 
 tric currents, of whatever germs it may 
 contain. 
 
 Stern Sheave. (1) A large sheave on the 
 stern of a cable-ship for paying out cable. 
 (2) Any sheave at the stern of a boat or 
 vessel used in paying out cable. 
 
 Stethoscope. An instrument for ascer- 
 taining the condition of the organs of cir- 
 culation and respiration by the sounds 
 they produce. 
 
 Sticking. (1) A name given by teleg- 
 raphers to the failure of a relay arma- 
 ture to leave the magnet pole and break 
 contact on the cessation of the current. 
 (2) Undue adhesion between the contacts 
 of a relay. 
 
 Sticking of Magnetic Armature. The 
 adherence of the armature of any electro- 
 magnet to its poles after the current has 
 ceased to pass through the magnetizing 
 coils. 
 
 [Sto. 
 
 " Stiff Field." A magnetic field of com- 
 paratively high density. 
 
 Stilography. A modified form of glyph- 
 ography. 
 
 Stimulus of Nerve, Electric. The effect 
 which electricity produces by its passage 
 through a nerve. 
 
 Stock Ticker. A step-by-step printing 
 telegraphic instrument, employed in 
 transmitting stock quotations to brokers' 
 offices from stock exchanges. 
 
 Stock-Ticker Service. A term em- 
 ployed for the transmission of stock quo- 
 tations from stock exchanges to sub- 
 scribers. 
 
 Stoneware Dipping-Bowl. A perfo- 
 rated bowl made of stoneware, in which 
 articles are placed that are to be subjected 
 to the dipping process in electro-metal- 
 lurgy. 
 
 Stoneware Dipping-Basket. A stone- 
 ware dipping bowl. 
 
 Stopped-Off. Subjected to the stopping- 
 off process. 
 
 Stopper Incandescent Lamp. An in- 
 candescent lamp in which the mounted 
 filament, instead of being hermetically 
 sealed in the lamp chamber, is placed 
 therein by means of a tightly fitting 
 stopper. 
 
 Stopper Lamp. A stopper incandescent 
 lamp. 
 
 Stopping-Off A process employed in 
 electro-plating,in which a metallic article, 
 
 . already electro-plated over its entire sur- 
 face, is electro-plated with another metal 
 over certain parts only. 
 
 Stopping-Off Process. A process em- 
 ployed in electro-plating by means of 
 which an article which is to be electro- 
 plated on portions of its surface only with 
 one metal, and on other portions with 
 another metal, is first completely covered 
 by an electro-plating of the cheaper metal, 
 and then stopped-off by covering, with a 
 coating of non-conducting varnish, such 
 portions only of its surface as are not to 
 receive the deposit of the more precious 
 metal. 
 
 Stopping-Off Varnish. A varnish used 
 in electro-plating to cover portions which 
 are not to receive the metallic coating. 
 
 Stopping-Out Process. A process em- 
 ployed in electro-typing, by means of 
 which those parts of an electro-type 
 mould that are not to be copied in the 
 electro-type are covered with clean hot 
 wax. 
 
 Storage Accumulator. A term some- 
 tunes used for storage battery. 
 
Sto.] 
 
 942 
 
 [Str. 
 
 Storage Battery. A number of separate 
 storage cells connected so as to form a 
 single electric source. 
 
 Storage-Battery Car. An electric car 
 which carries the storage battery em- 
 ployed for its propulsion. 
 
 Storage-Battery Meter. A meter con- 
 nected with a storage battery for the pur- 
 pose of indicating the electric quantity, 
 or energy, left in the same. 
 
 Storage-Battery Traction. Electric car 
 traction obtained by means of storage 
 batteries. 
 
 Storage Capacity. The capacity of a 
 storage battery, as measured in ampere- 
 hours. 
 
 Storage Cell. (1) Two relatively inert 
 plates of metals or metallic compounds 
 immersed in an electrolyte incapable of 
 acting on them until after an electric cur- 
 rent has been passed through the liquid 
 from one plate to the other, and has thus 
 changed their chemical relations. (2) 
 One of the cells required to form a sec- 
 
 ondary battery. () A term sometimes 
 given to the jar containing a single cell. 
 
 Storage-Cell Tester. A convenient form 
 of electrode provided for ready attach- 
 ment to the individual cells of a storage 
 battery, for the purpose of ascertaining 
 their electromotive forces from time to 
 time. 
 
 Storage of Electricity. A term improp- 
 erly employed to indicate such a storage 
 of energy as will enable it to directly re- 
 produce electric energy. 
 
 Storage of Energy. The change from 
 any form of kinetic energy to any form 
 of potential energy. 
 
 Storm, Electric. (1) Any unusual con- 
 dition of the atmosphere as regards the 
 quantity or distribution of its free elec- 
 tricity. (2) A thunder storm. 
 
 Stove-Plate, Electric. An electrically 
 
 heated stove-plate. 
 Straggling Flux. Leakage flux. 
 Straight Connector. A connector for 
 
 coupling two wires in the same straight 
 
 line. 
 Straight- Filament Incandescent 
 
 Lamp. An incandescent lamp provided 
 
 with a straight filament. 
 Straight-Line Insulator. An insulator 
 
 employed for a trolley line, where the 
 
 conductor is supported by transverse 
 
 wires from poles placed on either side of 
 
 the roadway. 
 Straight-Line Suspension . Suspension 
 
 by means of a straight-line trolley hanger. 
 
 Straight-Line Trolley Hanger. A trol- 
 ley hanger employed on a straight trolley 
 line, suitably supported by a span wire sa 
 as to have a vertical strain only. 
 
 Straightaway Bunched Cable. A 
 bunched cable, the separate conductors 
 of which are placed in successive layers, 
 and extend in the direction of the length 
 of the cable without any twisting, as dis- 
 tinguished from a helically wound cable. 
 
 Strain. The deformation produced by the 
 action of a stress. 
 
 Stranded Conductor. A conductor 
 formed of a number of smaller interlaced 
 or twisted conductors, either for the pur- 
 pose of reducing self-induction, or eddy 
 currents, or for increasing its flexibility. 
 
 Stranded Core. A core whose conductor 
 is stranded, as opposed to a core whose 
 conductor is a solid wire. 
 
 Stranded Feeder Conductor. A feeder 
 conductor formed of stranded wires. 
 
 Stranded Line. A line formed of a 
 stranded conductor. 
 
 Stranding of Conductor. Forming a 
 conductor of a number of separate con- 
 ductors or strands. 
 
 Strap Coppers. Copper conductors 
 formed of bars or straps, employed in con- 
 nection with a bar-armature winding. 
 
 Strap-Driven. A term sometimes em- 
 ployed for belt-driven. 
 
 Strap Key. A Tjey made from an elastic 
 strip or strap of metal. 
 
 Strap Switch. A switch made from a 
 strip or strap of metal. 
 
 Straps and Climbers. A device em- 
 ployed by line-men for climbing wooden 
 telegraph poles. 
 
 Stratham's Electric Fuse. A form of 
 fuse in which the ignition is effected by 
 an electric spark. 
 
 Stratification Tube. A vacuum tube 
 whose residual atmosphere displays alter- 
 nate dark and light striae, or stratifications, 
 on the passage through it of an induction- 
 coil discharge. 
 
 Stratified. Arranged in separate layers 
 or strata. 
 
 Stratified Discharge. The alternate 
 light and dark spaces assumed by the dis- 
 charge of an induction coil through a 
 partially exhausted gas. 
 
 Stray Chain. In submarine cable-work, 
 a length of chain which attaches the end 
 of a buoyed cable to the mushroom anchor 
 mooring chain. 
 
 Stray Currents. A term sometimes used 
 for eddy currents. 
 
Stp.] 
 
 943 
 
 [Str. 
 
 Stray Field.y-(l) Leakage magnetic flux. 
 
 (2) That portion of a magnetic field which 
 
 does not pass through an armature or 
 
 other magneto-receptive device. 
 Stray Flux. The flux of a stray field. 
 Stray Power. That portion of the power 
 
 applied to drive a machine which is lost 
 
 by various frictions. 
 Stream-Lines of Escaping Fluid. 
 
 Lines which show the actual paths of the 
 
 particles of an escaping fluid. 
 Streamers. Pillars or parallel flashing 
 
 columns of light frequently seen during 
 
 the prevalence of an aurora. 
 
 Streaming Discharge. A form assumed 
 by a flaming discharge between the sec- 
 ondary terminals of an induction coil, 
 when the frequencies of the alternations 
 increase beyond a certain limit, and the 
 potential is consequently increased. 
 
 Streamings. (1) A term sometimes em- 
 ployed for electrostatic or electro-mag- 
 netic flux. (2) X-ray streamings. 
 
 Street Call-Point in Fire Telegraphy. 
 Any point in a street where an alarm 
 call-box is placed. 
 
 Street- Car Controller. (1) An electric 
 switching apparatus contained in a box 
 placed on the platform of an electric 
 street-car, and employed to control the 
 speed of the car. (2) A car-controller. 
 
 Street-Car Lamp. An incandescent lamp 
 provided with an anchored filament, suit- 
 able for use in a street-car. 
 
 Street-Car Motor. A motor employed 
 for the propulsion of a trolley car. 
 
 Street-Car Recording Watt-Meter. A 
 
 wattmeter designed for use on a street- 
 car for registering the amount of electric 
 energy delivered to a car in a given time. 
 
 Street Load-Diagram. A diagram show- 
 ing the electric load on each street of any 
 particular district of electric supply. 
 
 Street Mains. In any system of electric 
 distribution, the conductors extending 
 through the streets from junction box to 
 junction box, through which the current 
 is distributed from the feeders, and from 
 which service wires are taken. 
 
 Street Railway, Electric, (1) Any elec- 
 trically propelled street railway. (2) The 
 ordinary trolley system of electric car 
 propulsion. 
 
 Street Service. <1) In a system of in- 
 candescent-lamp distribution that portion 
 of the circuit which is included between 
 a main and the service cut-out. (2) That 
 portion of service conductors which lies 
 outside of the building served. (3) In a 
 
 system of electric distribution including 
 street lighting, service wires supplying 
 street lamps. 
 
 Strength of Current. (1) A general term 
 for the magnitude of the current in a cir- 
 cuit. (2) Amperage. 
 
 Strength of Magnetic Field. The mag- 
 netic force acting on a free unit magnetic 
 pole placed in any magnetic field. 
 
 Strength of Magnetism. A term some- 
 times used for intensity of magnetization. 
 
 Stress. The pressure, pull or other force, 
 producing a deformation or strain. 
 
 Stress Flux. (1) A general term for the 
 flux producing any stress. (2) The sur- 
 face integral of stress passing through a 
 surface. 
 
 Stretching Insulator. An insulator of 
 extra mechanical strength provided with 
 means for carrying a short extra length 
 of wire, twisted around a stem such that 
 the excess can be employed for making a 
 joint, o.r for other purposes. 
 
 Striae, Electric. Parallel streaked bands, 
 consisting of alternate light and dark 
 spaces, produced in low-vacuum tubes by 
 an electric discharge through them. 
 
 Striking. Subjecting an article to ttie 
 action of a striking bath. 
 
 Striking an Arc. Separating the carbon 
 electrodes for the formation of an arc be- 
 tween them. 
 
 Striking Bath. A bath containing less 
 silver and a greater proportion of free 
 cyanide, employed in silver plating, for 
 obtaining an almost instantaneous deposit 
 of silver before subjecting the object to 
 the regular plating bath. 
 
 Striking Distance. A term sometimes 
 employed for sparking distance, or the 
 distance through which a disruptive dis- 
 charge will pass. 
 
 Striking Mechanism of Arc Lamp. 
 The mechanism employed in an arc-lamp 
 to separate the carbons on the establish- 
 ment of the arc. 
 
 Stringing Wires. Placing aerial wires on 
 poles or other supports. 
 
 Strip Commutator. A commutator 
 formed of plates or flat strips as opposed 
 to a commutator whose segments are 
 strips placed edgewise. 
 
 Strip Fuse. A name sometimes applied 
 to a safety strip. 
 
 Strip Resistance. A resistance formed 
 of strip or strap conductors. 
 
 Stripping?. Dissolving the metal coating 
 from a silver, gold or other plated article 
 
Str.] 
 
 944 
 
 [Sub. 
 
 Stripping Bath. A bath employed for 
 removing an electro-plating of gold, silver 
 or other metal, either by simple dipping 
 or by electric action. 
 
 Stripping Liquid.^(l) The liquid em- 
 ployed in a stripping bath. (2) The 
 liquid employed to remove the coating of 
 one metal from the surface of another 
 without affecting the other metal. 
 
 Stroboscope. An instrument employed 
 in the study of periodic motion. 
 
 Stroboscopic. Of or pertaining to the 
 stroboscope. 
 
 Stroboscopic Disc. A disc employed in 
 a stroboscope. 
 
 Strong-Current Arrester. Any form of 
 arrester suitable for protecting a line 
 from a strong current produced by ac- 
 cidental contact with a trolley, power or 
 lamp circuit. 
 
 Struck. A word employed in electro-plat- 
 ing to characterize a surface that has been 
 covered with a film of electrolytically de- 
 posited silver or nickel, by being placed 
 in a bath and exposed for a few moments 
 to the action of a strong current. 
 
 Structural Carbon. A term applied to a 
 carbon lamp-filament obtained by the car- 
 bonization of any structural carbonizable 
 material such as bamboo. 
 
 Structural Magnetic Flux. (1) Mag- 
 netic flux produced by the alignment of 
 the individual molecular magnets in iron, 
 steel or other magnetic substance. (2) 
 Magnetic flux produced by means of a 
 structural magneto-motive force. (3) 
 Magnetic flux produced by iron or other 
 magnetic metal as opposed to flux pro- 
 duced by electric currents. 
 
 Structural Magneto-Motive Force. 
 (1) A name sometimes given to an aligned 
 or induced magneto-motive force, in order 
 to distinguish it from the prime magneto- 
 motive force. (2) A magneto-motive 
 force produced by aligning or structurally 
 arranging the molecular magneto-motive 
 forces inherent in iron, steel, or other 
 magnetic substance. 
 
 Structureless Carbons. A term some- 
 times applied to carbon filaments that are 
 obtained by the carbonization of a struct- 
 ureless material, such as tamadine or 
 celluloid. 
 
 Struts for Telegraph Poles. Inclined 
 wooden or iron props applied to telegraph 
 poles in order to resist thrusts or pressures. 
 
 Sturgeon's Wheel. A name sometimes 
 applied to Barlow's wheel. 
 
 Sub- Aqueous. Under water. 
 
 Sub-Aqueous Cable. (1) A cable em- 
 
 ployed for use under water, generally 
 under fresh water, as in crossing a river. 
 (2) A river cable as distinguished from a 
 sea cable. 
 
 Sub-Branch. A term sometimes em- 
 ployed for a branch taken out of or tapped 
 from a branch. 
 
 Sub-Centre Transformer. A trans- 
 former placed at, and supplying secondary 
 circuits radiating from, a sub-centre of 
 distribution. 
 
 S u b-D ivided Conducto r. (1) A 
 
 stranded conductor. (2) A compositely 
 formed conductor. (3) A multiple-wire 
 conductor. 
 
 Sub-Divided Transformer. (1) A trans- 
 former having subdivisions in its primary 
 or secondary coils. (2) A transformer 
 having a sub-divided magnetic circuit. 
 
 Sub-Exchange for Telephones. A 
 local exchange in connection with a cen- 
 tral exchange. 
 
 Sub-Mains. (1) Conductors which branch 
 off from the mains. (2) Mains which are 
 themselves branches of mains. 
 
 Sub-Marine. Under the sea. 
 
 Sub-Marine B^at, Electric. A boat 
 capable of being propelled and steered 
 while under water. 
 
 Sub-Marine Board.- (1) A complete set 
 of sub-marine cable telegraphic instru- 
 ments mounted on a board. (2) A sub- 
 marine cable testing board. 
 
 Sub-Marine Cable. A cable designed for 
 use under water, generally under the 
 ocean. 
 
 Sub-Marine Finder. A form of induc- 
 tion balance proposed for the location of 
 torpedoes, anchors, iron ships or other 
 metallic submerged articles. 
 
 Sub-Marine Fuse. A fuse employed for 
 the ignition of a sub-marine mine. 
 
 Sub-Marine Key. A key suitable for use 
 in sub-marine telegraphy. 
 
 Sub-Marine Mine. A mass of gun-cot- 
 ton or other explosive material contained 
 in a water-tight vessel and placed under 
 water so as to explode on the passage of 
 an enemy's vessel over it. 
 
 Sub-Marine Search Light. A.n incan- 
 descent light employed for sub-marine 
 exploration. 
 
 Sub-Marine Sentry. A device sometimes 
 employed in sub-marine cable work for 
 indicating the presence of very shallow 
 water, and consisting of a water kite 
 which is below the vessel and which rises 
 to the surface when it strikes the sea-bot- 
 tom. 
 
Sub.] 
 
 945 
 
 [Sup. 
 
 Sub-Marine Telegraph. A general term 
 for the apparatus employed in sub-marine 
 telegraphy. 
 
 Sub-Marine Telegraphy. (1) A system 
 of telegraphy in which the line wire con- 
 sists of a sub-marine cable. (2) A system 
 of telegraphy across oceans. 
 
 Sub-Marine Telephony. Telephony 
 carried on by means of sub-marine cables. 
 
 Sub-Permanent Magnetism. A term 
 sometimes employed for the character 
 of the magnetism in an iron ship, as dis- 
 tinguished from that of a magnetized steel 
 bar, and as indicating that the perman- 
 ence in the magnetism of the former is 
 not as marked as in that of the latter. 
 
 Subscriber's Indicator. In a telephone 
 switchboard, the indicator or drop con- 
 nected in a subscriber's circuit and oper- 
 ated by his call. 
 
 Subsidiary Distributing Board. A dis- 
 tributing board auxiliary to a multiple 
 telephone switchboard, and from which 
 the subscribers' lines are portioned to the 
 local spring jacks for the various opera- 
 tors, in order to equally distribute their 
 work. 
 
 Sub-Station. An auxiliary station. 
 
 Sub-Station Accumulator. An accum- 
 ulator employed at sub-stations, or aux- 
 iliary centres of distribution. 
 
 Sub-Station Transformer. A trans- 
 former employed at an auxiliary station 
 or sub-station. 
 
 Substitute Primary Coil.-^l) A secon- 
 dary-primary coil. (2) An intermediate 
 coil in a transformer which alternately 
 takes the part of a secondary and primary. 
 
 Substitution Method. A method of 
 measuring resistances, currents, electro- 
 motive forces, etc., by removing them 
 from a circuit and replacing them by a 
 known or adjustable corresponding resist- 
 ance, current or electromotive force. 
 
 Subterranean. Under the earth. 
 
 Subterranean Mine. An underground 
 mass of gunpowder, or gun-cotton or 
 other high explosive, placed in suitable 
 vessels for protection against moisture, 
 provided with an electrically connected 
 fuse, which is either exploded automati- 
 cally on the movement of an enemy over 
 it, or by a distant operator. 
 
 Sub-Transformer Station. In a system 
 of electric distribution by alternating cur- 
 rents, an auxiliary station at which trans- 
 formers are placed for local secondary dis- 
 tribution. 
 
 Sub-Trunk Telephone Line. (1) An 
 60 
 
 auxiliary trunk telephone line. (2) A 
 trunk line connecting telephone ex- 
 changes and used for making connections 
 with trunk lines. 
 
 Suburban Communication. Tele- 
 phonic or telegraphic communication be- 
 tween the suburbs and central portions of 
 a city. 
 
 Suburban Electric Railway. An elec- 
 tric railway connecting the centre of a 
 city with the suburbs. 
 
 Subway, Electric. An accessible under- 
 ground way or passage provided for the 
 reception of electric-light wires or cables. 
 
 Successive-Contact Key. Any form of 
 key employed to make two or more suc- 
 cessive contacts. 
 
 Sugg. A name sometimes given to a stand- 
 ard British candle. 
 
 Sulphating. A name applied to one of the 
 sources of loss in the operation of a stor- 
 age cell, by means of the formation of an 
 inert coating of lead sulphate on the sur- 
 face of the battery plates. 
 
 Summer Lightning. A name sometimes 
 given to heat lightning. 
 
 Sunflower Commutator. (1) A com- 
 mutator resembling a sunflower in ap- 
 pearance. (2) A form of flat or disc com- 
 mutator. 
 
 Sun-Light Color- Values. Such lumin- 
 ous frequencies in a source of artificial 
 light as will give to its light the same 
 effects as are produced by sunlight. 
 
 Sunshine. The luminous radiant energy 
 emitted by the sun. 
 
 Sun-Spot Disturbance. Any disturb- 
 ance due to, attributed to, or accompany- 
 ing, the presence of spots on the sun. 
 
 Sun-Spots. Dark spaces, varying in num- 
 ber and position, which appear on the sur- 
 face of the sun. 
 
 Sun-Stroke, Electric. (1) Electric pros- 
 tration produced by exposure to the light 
 of an electric arc. (2) Physiological ef- 
 fects similar to those produced by ex- 
 posure to the sun, experienced by those 
 exposed for a long time to the intense light 
 and heat of the voltaic arc. 
 
 Sun Telegraph. A name sometimes ap- 
 plied to the heliograph. 
 
 Sunk Winding. (1) A name sometimes 
 employed for an iron-clad winding. (2) 
 A winding sunk below the surface of an 
 armature or other device. 
 
 Superficial Eddy-Currents. Eddy cur- 
 rents produced in conducting substances 
 that are limited to the outer layers 
 thereof. 
 
Sup,] 
 
 946 
 
 [Sus, 
 
 Superficial Field. A field produced by 
 the super-position of two or more sep- 
 arate fields. 
 
 Superposed Magnetism. A term ap- 
 plied to a magnetism impressed on an 
 already magnetized substance. 
 
 Super-Saturation. A condition of a 
 solution which has been allowed to cool, 
 while out of contact with air, below its 
 point of crystallization or solidification. 
 
 Super-Saturation of Solution. The 
 condition assumed by a warmed saturated 
 solution of a salt when placed in a closed 
 vessel out of contact with the air, and al- 
 lowed to cool, without being shaken. 
 
 Supervising Operators. In telephony, 
 or telegraphy, operators whose duty it is 
 to supervise the work of other operators. 
 
 Supplement of Angle. What an angle 
 needs to bring its value to 180. 
 
 Supplementary Dynamo. A word 
 sometimes used for a booster dynamo. 
 
 Supply Conductors. (1) A term some- 
 times applied to the sub-mains in a system 
 of incandescent light distribution. (2) 
 Conductors which convey electric energy. 
 
 Supply Mains. A term sometimes ap- 
 plied to the mains in a system of incan- 
 descent light or power distribution. 
 
 Supply Meter, Electric. A meter which 
 indicates or measures the electricity or 
 electric energy supplied to a given cus- 
 tomer or machine. 
 
 Supply Unit. A name proposed for the 
 Board of Trade unit. 
 
 Support Plate of Storage Cell. A term 
 sometimes employed for the grid of a 
 storage cell. 
 
 Surface Action. Any action limited to 
 a surface. 
 
 Surface Contact of Street-Railway 
 Car. A contact, flush with the surface 
 of a street, and intended for use in con- 
 nection with the electric propulsion of a 
 street-railway car. 
 
 Surface Contact-Resistance between 
 Metal and Liquid. The resistance in- 
 troduced into a primary or secondary cell 
 at the contact between the metal and 
 liquid. 
 
 Surface Contact Street Railway Sys- 
 tem. A system of street-railway pro- 
 pulsion employing surface contacts. 
 
 Surface Density. The quantity of elec- 
 tricity-per-unit-of-area at any point on a 
 charged surface. 
 
 Surface-Efficiency of Filament. (1) 
 The efficacy of a particular character of 
 surface for luminous radiation. (2) The 
 
 luminous efficiency of a particular charac- 
 ter of surface in a filament. 
 Surface Integral. (1) The sum of all 
 the products of a point function and its 
 associated element of area, lying on a 
 surface, when the elements are all in- 
 definitely small. (2) The integral of a 
 quantity taken over a surface. 
 
 Surface Integral of Magnetic Induc- 
 tion. The total magnetic flux passing 
 through a surface. 
 
 Surface Magnetization. In the distri- 
 bution of imaginary magnetic matter, 
 the magnetism residing on a surface, or 
 the so-called free magnetism. 
 
 Surface-Wound Armature. (1) An ar- 
 mature wound on its surface, as distin- 
 guished from an iron-clad armature. (2) 
 An armature in which the conductors lie 
 over the surface of the core, instead of 
 being placed in grooves or slots formed 
 therein. 
 
 Surfusion. A word sometimes employed 
 for super-saturation. 
 
 Surgical Lamp. A lamp employed in 
 surgical exploration, examination, or oper- 
 ation. 
 
 Surging Circuit. Any circuit through 
 which a surging discharge is passing. 
 
 Surging Discharge. (1) A discharge ac- 
 companied by electric surgings. (2) An 
 oscillatory discharge. 
 
 Surgings, Electric. (1) Electric oscilla- 
 tions set up in a conductor that is under- 
 going rapid discharging, or in neighbor- 
 ing conductors that are being rapidly 
 charged and discharged. (2) Electric 
 oscillations, direct or induced. 
 
 Susceptance. In an alternating-current 
 circuit, branch, or conductor, the quan- 
 tity whose square added to the square of 
 the conductance is equal to the square of 
 the admittance. 
 
 Susceptibility. A word sometimes used 
 for magnetic susceptibility. 
 
 Suspended Cable-Way. A modification 
 of the telpherage system, in which a car- 
 riage provided with one or more grooved 
 wheels is electrically driven over a sus- 
 pended cable. 
 
 Suspended-Coil Galvanometer. Any 
 form of galvanometer in which the cur- 
 rent passing is measured by the move- 
 ments of a suspended coil. 
 
 Suspended Trolley-Way. (1) A sus- 
 pended cable- way. (2) A form of tele- 
 pherage system. 
 
 Suspender. A word sometimes used fof 
 a cable suspender. 
 
Sus.] 
 
 947 
 
 [Swi. 
 
 Suspender for Telephone Cable. (1) 
 A word sometimes employed for cable 
 hanger. (2) A hook or support for a 
 telephone cable. 
 
 Suspending Hook for Telephone 
 Cable. A cable hanger. 
 
 Suspending Wire of Aerial Cable. (1) 
 The wire from which an aerial cable is 
 strung or suspended. (2) A messenger 
 wire. 
 
 Suspension. (1) The mechanism for sus- 
 pending a thing, with or without the 
 thing suspended. (2) The means employed 
 in suspending any system, such as a 
 needle, a pendulum, or a car motor. 
 
 Suspension for Car-Motor. The means 
 employed for supporting a car-motor on 
 a car truck. 
 
 Sustained Currents, Electromotive 
 Forces or Fluxes. Any electromotive 
 force, current or flux, whose effect is con- 
 tinued, as distinguished from one whose 
 effect is temporary. 
 
 Swage. A particular form of anvil on 
 which highly heated metallic plates are 
 shaped by hammering them into forms 
 the same as that of the anvil on which 
 they are placed. 
 
 Swage. To fashion heated metallic plates 
 by hammering them into the form of the 
 anvil on which they are supported. 
 
 Swaging. Fashioning highly heated me- 
 tallic plates into any desired form by ham- 
 mering, while on suitable dies. 
 
 Swaging, Electric. Forming or shaping 
 of metallic plates by hammering them 
 against suitable anvils or dies while soft- 
 ened by electric heat. 
 
 Sweating. A term employed for the proc- 
 ess of soldering together the ends of 
 electric-light cables. 
 
 Swelling Current. In electro-thera- 
 peutics, a current that begins weak and 
 is then periodically made stronger and 
 weaker. 
 
 Swelling Faradic-Currents. A term 
 employed in electro-therapeutics for 
 Faradic currents that are caused to grad- 
 ually increase in strength and then to 
 gradually decrease to zero strength. 
 
 Sweep, (1) In submarine cable work, a 
 drag. (2) In submarine cable work, a 
 haul made with a grapnel across a line of 
 cable. 
 
 Sweeper, Electric. A term employed 
 for an electrically -driven sweeper. 
 
 Sweeping-Out Charge. A phrase em- 
 ployed in double-current signalling for 
 freeing the line from a charge produced in 
 
 sending one signal, by reversing the di- 
 rection of the current through the line 
 before sending the next signal. 
 
 Swinging Annunciator. A pendulum 
 annunciator. 
 
 Swinging Cross. A term sometimes 
 
 given to an intermittent cross. 
 Swinging Earth. A name sometimes 
 
 given to an intermittent earth. 
 Swinging Voltmeter. A voltmeter 
 
 mounted upon a swinging bracket of a 
 
 switchboard, so as to be capable of being 
 
 read from any direction. 
 
 Swiss Commutator Switchboard. A 
 
 switchboard having cross-bars after the 
 type of a Swiss commutator. 
 Switch. (1) Any device for readily open- 
 ing or closing an electric circuit. (2) -In 
 telephony, a name sometimes given to a 
 switchboard. 
 
 Switch-Bell. (1) A bell switch. (2) A 
 combination of a bell and switch. 
 
 Switch Blade. A conducting strip or 
 knife-blade of a switch. 
 
 Switch-Board. (1) A board, base, slab or 
 frame of insulating material, upon which 
 are supported conducting bars, pieces, 
 frames or masses, with or without switches 
 and instruments, for the ready establish- 
 ment of electrical connections between 
 circuits connected therewith. (2) A board 
 carrying switches and instruments for 
 controlling a distribution system and the 
 generators connected therewith. (3) A 
 board provided with a switch or switches 
 by means of which electric circuits con- 
 nected therewith may be opened, closed 
 or interchanged. (4) In a central station 
 for telegraphy, telephony, light or power 
 distribution, the electric controlling me- 
 chanism. 
 
 Switch Cord. An insulated conducting 
 cord connected with a switch. 
 
 Switch-Board Arrester. A device in- 
 tended for use on switchboards, consist- 
 ing either of some form of lightning ar- 
 i ester or of a sneak-current arrester. 
 
 Switch-Board Bolt. A bolt for mechan- 
 ically fastening apparatus to a switch- 
 board or the panels of a switchboard to a 
 frame. 
 
 Switch-Board Bracket. A bracket on a 
 switchboard for supporting an incandes- 
 cent lamp or other device. 
 
 Switch-Board Cable. Any cable con- 
 nected with a switchboard. 
 
 Switchboard Fittings. A general term 
 embracing the connectors, set screws, 
 wire-holders or bus-bar connections, em 
 
Swi.] 
 
 948 
 
 [Syn. 
 
 ployed in placing the different apparatus 
 on a switchboard. 
 
 Switch-Board Protector. (1) A pro- 
 tector provided with a suitable electro- 
 magnetic safety device, or with a fuse wire 
 or safety catch, placed at cable heads, at 
 the junction between aerial-land and un- 
 derground lines, for the purpose of pro- 
 tecting the cable from a too powerful 
 electric discharge or current. (2) Any 
 lightning, or circuit protector, placed on 
 a switchboard. 
 
 Switchboard Transformers. Trans- 
 formers on an alternating-current switch- 
 board for locally supplying alternating- 
 currents of reduced pressure. 
 
 Switch-Board Wattmeter. A wattme- 
 ter placed on a switchboard to determine 
 the out-put, or the intake, of some circuit 
 connected therewith. 
 
 Switch-Box. Any box containing one or 
 more switches. 
 
 Switch-Finger. A contact-finger, or pro- 
 jecting metallic contact on the cylinder 
 of a street-car controlling-switch, or on 
 similar apparatus. 
 
 Switch-Handle, Electric. In electric 
 railway block-signalling, a miniature rail- 
 way electric switch handle for closing 
 and opening an electric circuit. 
 
 Switch Hole. A hole provided in a 
 switch key for the insertion of a plug. 
 
 Switch Hook. (1) An automatic tele- 
 phone hook. (2) A hook which serves 
 the purpose of a switch. 
 
 Switch Jack. A spring jack. 
 
 Switch Pin. A metallic pin or plug pro- 
 vided for insertion in a switchboard. 
 
 Switch Room. The room or hall in a 
 central telephone exchange in which a 
 switchboard is placed. 
 
 Switch Spring. A spring placed in a 
 switch for its mechanical operation, or for 
 securing electric connection. 
 
 Switched-In. Thrown into a circuit by 
 means of a switch. 
 
 Switched-Out. Removed from a circuit 
 by means of a switch. 
 
 Swivel Clevis. A device consisting es- 
 sentially of a nut and bolt, by means of 
 which any slack in a guy -rod may be taken 
 up. 
 
 Symmetrical Alternating Current. 
 Any alternating current whose successive 
 semi-periods, waves, or alternations pos- 
 sess opposite but equal values, or corre- 
 spond in all respects save in direction. 
 
 Symmetrical Alternating Electro- 
 motive Forces. Electromotive forces 
 
 whose successive semi-waves or alterna- 
 tions possess equal but opposite values, or 
 correspond in all respects save in direc- 
 tion. 
 
 Symmetrical Induction of Armature. 
 (1) An induction produced by the sim- 
 ultaneous passage of the same quantity 
 of magnetic flux through adjoining 
 halves of the armature. (2) A sym- 
 metrical magnetization in an armature. 
 
 Symmetrical Magnetic Field. A field 
 whose magnetic flux is symmetrically 
 distributed. 
 
 Symmetrical Polyphase System. 
 A polyphase system symmetrically ar- 
 ranged in regard to conductors, pressures, 
 currents and loads. 
 
 Sympathetic Electric Vibrations. 
 (1) Electric vibrations produced in a cir- 
 cuit by the electro-magnetic waves given 
 off by a neighboring circuit. (2) Electric 
 vibrations that are produced by reso- 
 nance. 
 
 Sympathetic Generator. An induction 
 generator. 
 
 Sympathetic Vibrations. Vibrations 
 set up in bodies, and having the same 
 frequency as that produced by the excit- 
 ing body. 
 
 Symphonance. A word proposed in place 
 of resonance. 
 
 Synchronism. (1) Unison of frequencies 
 in alternating-current systems or appara- 
 tus. (2) The simultaneous occurrence of 
 any two events. (3) Generally, the co- 
 periodicity and co-phase of two periodi- 
 cally recurring events. (4) The coinci- 
 dence in cyclic recurrence of two or more 
 periodic variables, without regard to am- 
 plitude. 
 
 Synchronizable. Capable of being syn- 
 chronized. 
 
 Synchronize. (1) To cause to occur or 
 act simultaneously. (2) To bring two 
 alternating-current machines into unison 
 or co-periodicity, and into practical coin- 
 cidence of phase, so that they may be con- 
 nected together. 
 
 Synchronized. Caused to occur or act 
 simultaneously. 
 
 Synchronizer. (1) Anything causing or 
 tending to cause synchronism. (2) A 
 phase indicator. (3) A device for indi- 
 cating when synchronism is attained be- 
 tween alternators that are to be connect- 
 ed in parallel. 
 
 Synchronizing Dynamo-Electric Ma- 
 chines. Adjusting the frequencies and 
 phases of two alternating-current dyna- 
 
949 
 
 [Tai. 
 
 mos so as to permit of their being coupled 
 or joined in parallel. 
 
 Synchronizing Torque. The torque of 
 an alternating-current generator or motor 
 armature tending to bring it into syn- 
 chronism with some other armature oper- 
 ated with it. 
 
 Synchronograph. A name given to a 
 record obtained by a polarizing photo- 
 electric apparatus. ' 
 
 Synchronous. (1) Occurring simulta- 
 neously in point of time. (2) Generally, 
 co-periodic and co-phasal, as distin- 
 guished from isochronous, which connotes 
 agreement in period only. 
 
 Synchronous Generator. A generator 
 of alternating currents, operating or 
 capable' of operating in synchronism with 
 another generator. 
 
 Synchronous Motor. A form of alter- 
 nating-current motor which requires to be 
 brought into step with the driving cur- 
 rent before it will properly operate. 
 
 Synchronous Multiphase Motor. 
 A multiphase motor designed to operate 
 in isochronism with the generator or gen- 
 erators connected with it. 
 
 Synchronous Multiplex Telegraph. 
 A general term for the apparatus em- 
 ployed in synchronous multiplex teleg- 
 graphy. 
 
 Synchronous Multiplex Telegraphy. 
 A system of simultaneous telegraphic 
 transmission in which a number of mes- 
 sages, either all in the same direction, or 
 part in one and the remainder in the op- 
 posite direction, can be simultaneously 
 transmitted over a single line wire. 
 
 Synchronous Reactance. (1) The ap- 
 parent reactance of a synchronous motor 
 armature under working conditions 
 (2) The combined apparent reactance of 
 self-induction and armature reactance of 
 a synchronous motor armature under 
 working conditions. 
 
 Synchronous Speed. The speed of a 
 motor or generator at which it is in syn- 
 chronism with the current in the system 
 to which it is connected. 
 
 Synchronous Vibrations. Vibrations 
 produced by two or more separate sys- 
 tems that exactly coincide, both in fre- 
 quency and in phase. 
 
 Synthesis. (1) Indirect analysis or the 
 formation of a chemical substance by the 
 combination of its constituent parts. 
 (2) The building-up or combination of 
 atoms into molecules. 
 
 System of Electric Lighting. (1) A 
 term sometimes applied to an electric 
 light installation. (2) An electric light 
 plant. 
 
 t. A symbol employed for time, 
 t : m. An abbreviation for turns-per-min- 
 ute, a practical unit of angular velocity. 
 
 T. P. Switch. A contraction for triple- 
 pole switch. 
 
 T-Connector. A connector provided for 
 connecting a wire with two branch wires, 
 and resembling the letter T in shape. 
 
 T-Shaped Spark. A variety of three- 
 branched spark obtained by the discharge 
 of a Leyden jar through a peculiar form 
 of induction coil. 
 
 Table-Key. A key placed on the table of 
 a telephone exchange for effecting the 
 connections with an operator. 
 
 Table Push. A push-button connected 
 with a table for ease in ringing a call-bell. 
 
 Table Switch. A switch on the table of 
 a telephone switchboard. 
 
 Tablet Board. A switchboard divided 
 into panels or tablets. 
 
 Tablet Check. In telegraphy, a tabulat- 
 ed form upon which messages sent and 
 
 received are checked off for the purpose 
 of recording the traffic and ensuring 
 against the loss of a message. 
 
 Tachograph. An apparatus for recording 
 the number of revolutions per minute of 
 a machine or shaft. 
 
 Tachometer. (1) An apparatus for indi- 
 cating at any moment on a dial the num- 
 ber of revolutions per minute of a shaft 
 or machine with which it is connected. 
 (2) A speed indicator. 
 
 Tachyphore. (1) A name proposed for a 
 system of electric transportation in which 
 a carriage formed of magnetic material is 
 propelled by the sucking action of sole- 
 noids placed along the tracks, and ener- 
 gized in succession during the passage of 
 the car. (2) A port-electric system. 
 
 Tail Light. A light displayed at the rear 
 of a train, in order to avoid rear-end col- 
 lisions. 
 
 Tail of Mercury. An elongation or tail, 
 of grayish color, due to the presence of 
 
Tai.] 
 
 950 
 
 [Tea, 
 
 oxides, left behind a drop of impure mer- 
 cury, when moved over smooth surface. 
 
 Tailings. (1) In telegraphy, residual dis- 
 charges from the line through the receiv- 
 ing instrument, following each signal, and 
 thus tending to make the signals run to- 
 gether. (2) Residual or return charges or 
 currents in the transmission of electro- 
 magnetic waves through a dielectric. 
 
 Talantoscope. A low-vacuum tube em- 
 ployed in connection with a Hertzian os- 
 cillator to determine when it is sending 
 forth waves, and when it is under the in- 
 fluence of undirectional discharges and 
 is not sending forth waves. 
 
 Talking Circuit. In telephony, a circuit 
 employed by a subscriber during conver- 
 sion, as distinguished from a calling cir- 
 cuit. 
 
 Tamadine. A modified form of tri-nitro 
 cellulose, employed, when cut into suit- 
 able shapes and subsequently carbonized, 
 for the filaments of incandescent lamps. 
 
 Tangent. (1) One of the trigonometrical 
 functions. (2) In a right-angled triangle 
 formed by a radius-vector, base, and per- 
 pendicular, the ratio of the perpendicular 
 to the base. 
 
 Tangent and Sine Galvanometer. A 
 galvanometer furnished with two mag- 
 netic needles of different lengths, the 
 small one being used for tangent meas- 
 urements, and the long one for sine 
 measurements of current strength. 
 
 Tangent Galvanometer. An instrument 
 in which the deflecting coil consists of a 
 coil of wire within which is placed a 
 needle, supported at the centre of the 
 coil, and very short by comparison with 
 the diameter of the coil. 
 
 Tangent Scale. A scale designed for use 
 with a tangent galvanometer on which 
 the values of the tangents are directly 
 marked, instead of degrees of the circle 
 as ordinarily, thus avoiding the necessity 
 of finding from tables, tangents corre- 
 sponding to the degrees. 
 
 Tangentially - Laminated Armature 
 Core. An armature core consisting of a 
 closely-coiled ribbon of sheet iron. 
 
 Tank-Heater, Electric. A form of elec- 
 tric heater for heating liquids, consisting 
 essentially of a heating coil immersed in 
 a liquid contained in a tank. 
 
 Tanning, Electric. The application of 
 electric currents to the tanning of leather. 
 
 Tap. (1) A conductor attached as a shunt 
 to a larger conductor. (2) A derived 
 circuit for carrying off a share of the 
 main current. (3) A wire taken from the 
 
 junction between the short and long sec- 
 tions of a quadruplex battery. 
 
 Tap Wire in Quadruplex Telegraphy. 
 The intermediate wire or conductor in a 
 system of quadruplex telegraphy, which 
 divides the battery into two unequal 
 parts, called respectively the long side 
 and the short side. 
 
 Tap Wires. The wires or conductors em- 
 ployed in trolley systems to carry the 
 current from the feeders or mains at a 
 pole to a near point on the trolley wire. 
 
 Taped Conductor. A taped wire. 
 
 Taped Wire. (1) A conducting wire cov- 
 ered witli an insulating material in the 
 shape of a tape. (2) A wire covered with 
 an insulating material and subsequently 
 taped. 
 
 Tapered Mains. Mains in the tree sys- 
 tem whose diameters diminish in succes- 
 sive sections. 
 
 Taping. (1) Covering a wire or a joint 
 with an insulating tape. (2) A covering 
 of tape applied to a cable sheathing. 
 
 Tapers. Wires tapering in diameter for 
 the purpose of effecting a splice between 
 two different types of submarine cables. 
 
 Tapper Bell. A single-stroke electric 
 bell provided with a suitable key for sig- 
 nalling purposes. 
 
 Tapper Key. A term sometimes em- 
 ployed in place of a Morse tapper. 
 
 Tapper Signal. In a system of mining 
 signals, signals sent or received by meaas 
 of tapper bells. 
 
 Tapping a Circuit. Introducing a loop 
 or branch in a telegraphic or telephonic 
 circuit, for the purpose of intercepting 
 the messages sent over the circuit. 
 
 Taps. A general term employed, in a sys- 
 tem of incandescent lamp distribution, 
 for branches or sub-branches that are 
 carried from the mains into the rooms ef 
 a building or to the fixtures in the halls. 
 
 Target, Electric. A target in which the 
 point struck by the ball is automatically 
 registered by means of electric devices. 
 
 Tasimeter. An apparatus designed by 
 Edison for the purpose of detecting 
 minute heat changes by variations in the 
 resistance of a soft-carbon disc, resulting 
 from changes of pressure due to the ex- 
 pansion of a substance exposed to the 
 heat to be measured. 
 
 Teaser. An electric current teaser. 
 
 Teaser, Electric. (1) A coil of fine 
 wire placed on the field magnets of a 
 dynamo in a shunt across the main cir* 
 cuit, in addition to the field magnet series 
 
Tea, ] 951 
 
 coil. (2) A series coil placed on a field 
 magnet, in addition to a regular shunt 
 field, for the purpose of preliminary ex- 
 citation. 
 
 Teaser "Winding. An additional coil 
 wound on the armature of a monocyclic 
 generator of smaller cross-section and 
 fewer turns than the main winding, one 
 end of which is connected at the centre 
 of the main winding, and the other to a 
 collecting ring. 
 
 Tee Box for Underground Cables or 
 Conductors. A box, shaped like a letter 
 T, and containing a joint or joints between 
 a main line and an offset, branch, lateral, 
 or service conductor. 
 
 Tee Connector. A T-shaped connector 
 employed for readily connecting a wire 
 at right angles to another wire. 
 
 Teeth of Armature. Polar projections 
 or ridges on the surface of an armature- 
 core, between which lie the armature 
 windings or conductors. 
 
 Tele-Anemograph. A device for record- 
 ing the indications of an anemograph at 
 a distance. 
 
 Tel-Autogram. A recorded message ob- 
 tained by means of a tel-autograph. 
 
 Tel-Autograph. A telegraphic system 
 for the fac-simile reproduction of writing 
 at a distance. 
 
 Tele- Autograph. An orthography some- 
 times employed for tel-autograph. 
 
 Tele-Barograph. A device for recording 
 the indications of a barometer at a dis- 
 tance. 
 
 Tele-Barometer, Electric. An electric 
 recording barometer, for indicating and 
 recording barometric pressures at a dis- 
 tance. 
 
 Telegram. Any despatch received by 
 means of a telegraph. 
 
 Telegraph. (1) A general name for the 
 instrument or combination of instru- 
 ments employed for conveying a commu- 
 nication or despatch to a distance by 
 means other than that of the unassisted 
 voice. (2) A general term for any appa- 
 ratus employed in telegraphy. 
 
 Telegraph. To transmit a message by 
 means of a telegraph. 
 
 Telegraph Circuit. (1) An electric cir- 
 cuit employed in telegraphy. (2) An in- 
 sulated line apparatus at one or more tele- 
 graph stations and a ground return cir- 
 cuit. 
 
 Telegraph, Electric. A general term 
 for any apparatus employed in electric 
 telegraphy. 
 
 Telegraph Line-Adjuster. A general 
 term given to apparatus by means of 
 which the adjustment of a telegraph line 
 is facilitated. 
 
 Telegraph Loop. A pair of wires ex- 
 tending from a telegraphic station to a 
 branch office. 
 
 Telegraph Posts. A term sometimes 
 employed for telegraph poles. 
 
 Telegrapher. A telegraphic operator. 
 
 Telegrapher's Cramp. An affection of 
 the hand of a telegrapher, due to con- 
 tinuous excessive use of the same muscles, 
 somewhat similar to the disease known as 
 writer's cramp. 
 
 Telegraphic. Of or pertaining to a tele- 
 graph. 
 
 Telegraphic Alarm. An alarm bell for 
 calling the attention of an operator to a 
 telegraphic instrument when the latter is 
 of the non-acoustic or needle type. 
 
 Telegraphic Alphabet. The code em- 
 ployed for letters and other characters in 
 telegraphy. 
 
 Telegraphic Arm. A cross-arm placed 
 on a telegraphic pole for the support of 
 the insulators. 
 
 Telegraphic Box-Sounder. A sounder 
 whose receiving magnets are enclosed in 
 a hollow box, for the purpose of increas- 
 ing the intensity of the sound by reso- 
 nance. 
 
 Telegraphic Bracket. A support or 
 cross-piece placed on a telegraph pole, 
 tree, wall or roof, for the support of a 
 telegraphic line-insulator. 
 
 Telegraphic Cable. A cable designed 
 to establish telegraphic communication 
 between different points. 
 
 Telegraphic Clock. A name sometimes 
 applied to a master clock. 
 
 Telegraphic Code. The pre-arranged 
 system of signals employed in any system 
 of telegraphy. 
 
 Telegraphic Cross- Arm. A term some- 
 times employed for telegraphic arm. 
 
 Telegraphic Dial. A dial board contain- 
 ing letters of the alphabet and figures, 
 employed in dial telegraphy. 
 
 Telegraphic Dynamo. A dynamo em- 
 ployed for generating the currents used 
 in telegraphic transmission. 
 
 Telegraphic Earth-Circuit. That por- 
 tion of a telegraphic circuit which is com- 
 pleted through the earth or ground. 
 
 Telegraphic Embosser. An apparatus 
 for recording a telegraphic message on a 
 paper strip in raised or embossed char- 
 acters. 
 
Tel,] 
 
 952 
 
 TTel. 
 
 Telegraphic Fixtures. A term gener- 
 ally limited to the various supports pro- 
 vided for the attachment of telegraphic 
 wires. 
 
 Telegraphic Ground-Circuit. An earth 
 circuit used in any system of telegraphy. 
 
 Telegraphic House-Top Fixtures. 
 Telegraphic fixtures placed on the roofs 
 of buildings for the support of the lines. 
 
 Telegraphic Ink- Writer. (1) A device 
 employed for recording the dots and 
 dashes of a telegraphic message in ink on 
 a strip of paper. (2) A Morse inker. 
 
 Telegraphic Insulator. An insulator 
 employed on telegraphic lines. 
 
 Telegraphic Interrupter. (1) A device 
 for making and breaking a circuit at a 
 definite rate. (2) A telegraphic key, or 
 other analogous device. 
 
 Telegraphic Interruption. (1) Any 
 fault in a line or apparatus which pre- 
 vents telegraphic transmission. (2) A 
 term sometimes employed in telegraphy 
 for faults in general. (3) A break or 
 total stoppage of signals in a submarine 
 cable. 
 
 Telegraphic Joint. A permanent con- 
 tact or junction between the ends of two 
 electric conductors. 
 
 Telegraphic Key. The key employed 
 for sending over the line the successive 
 makes-and-breaks corresponding to the 
 dots and dashes of the Morse alphabet, or 
 to the deflections of the needle in a needle 
 telegraph. 
 
 Telegraphic Line. A conducting circuit 
 employed in any telegraphic system for 
 the transmission of electric impulses or 
 currents. 
 
 Telegraphic Line-Circuit. The conduc- 
 tor or line connecting different tele- 
 graphic stations. 
 
 Telegraphic Needle. A needle em- 
 ployed in telegraphy to represent by its 
 movements to the right or left, respec- 
 tively, the dots and dashes of the Morse 
 alphabet. 
 
 Telegraphic Paper-Winder. An appa- 
 ratus for winding or coiling the paper 
 fillet used on a telegraphic register. 
 
 Telegraphic Photography. A term 
 sometimes used for means whereby an 
 image of a photographic object may be 
 telegraphically transmitted to a distant 
 station. 
 
 Telegraphic Pocket-Belay. A form of 
 telegraphic relay of such small dimen- 
 sions as to permit it to be readily carried 
 in the pocket. 
 
 Telegraphic Polar - Belay . A tele- 
 graphic relay provided with a polarized 
 armature. 
 
 Telegraphic Pole. A wooden or iron 
 pole provided with suitable insulators for 
 the support of an overhead telegraphic 
 line or lines. 
 
 Telegraphic Begister. (1) An apparatus 
 employed at the receiving end of a tele- 
 graphic line for the purpose of obtaining 
 a permanent record of the telegraphic 
 despatch. (2) A Morse register. 
 
 Telegraphic Begistering Apparatus. 
 
 (1) A name sometimes given to a tele- 
 graphic recorder. (2) A Morse register. 
 
 Telegraphic Bepeater. (1) Any telegra- 
 phic device whereby the relay, sounder or 
 registering apparatus is caused to repeat 
 into another circuit the signals received. 
 
 (2) An apparatus for maintaining telegra- 
 phic communication between two circuits 
 not in conductive connection. 
 
 Telegraphic Saddle. A bracket of spe- 
 cial shape, placed astride, on the top of 
 a telegraph pole, for the support of an 
 insulator. 
 
 Telegraphic Splice. A sheath connec- 
 tion made between two cable ends, and 
 overlying a joint. 
 
 Telegraphic Stay-Bods. Guy rods sup- 
 porting telegraph poles. 
 
 Telegraphic Stock-Printer. A form of 
 printing telegraph employed for printing 
 on a strip of paper the quotations of stocks, 
 received from a stock exchange. 
 
 Telegraphic Switchboard. (1) A device 
 employed at a telegraphic station, by 
 means of which any one of a number of 
 telegraphic instruments in use at that 
 station may be placed in or removed 
 from any line connected with the station, 
 or by means of which one wire may be 
 connected to another. (2) A switchboard 
 for conveniently effecting and changing 
 telegraphic connections. 
 
 Telegraphic Through-Traffic. A gen- 
 eral term for the telegraphic messages 
 sent directly between the terminal sta- 
 tions, as distinguished from way traffic, 
 which includes some intermediate sta- 
 tion. 
 
 Telegraphic Time-Service. (1) Any 
 telegraphic distribution of time. (2) The 
 telegraphic distribution of time to jewel- 
 lers, railroad time-keepers, or others in 
 need of frequent imfprmation as to the 
 precise time, in which electric signals 
 are sent out from a standard clock, through 
 relays, at two second intervals, with spe- 
 cial signals at minute, five-minute, and 
 hour intervals. 
 
Tel.] 
 
 
 953 
 
 [Tel. 
 
 Telegraphic Transmitter. A tablet 
 having suitable contact marks placed on 
 its surface, such that by moving a metal- 
 lic rod over it proper signals are sent. 
 
 Telegraphic Translator. A term some- 
 times applied to a telegraphic repeater. 
 
 Telegraphic Way-Traffic. Telegraphic 
 messages sent from one ofKce to another, 
 as distinguished from messages between 
 terminal offices only. 
 
 Telegraphic Wire. The wires employed 
 
 in telegraphic line circuits. 
 Telegraphical. Of or pertaining to the 
 
 telegraph. 
 
 Telegraphically. In a telegraphic man- 
 ner. 
 
 Telegraphing. Sending a communica- 
 tion by means of a telegraph. 
 Telegraphist. A telegraphic operator. 
 
 Telegraphone. An instrument whereby 
 the indentations on the cylinder of a graph- 
 ophone can be reproduced upon another 
 cylinder, at the same time that the vocal 
 sounds represented by the indentations 
 are being rendered audible. 
 
 Telegraphy. Any system by means of 
 which a communication or despatch is 
 transmitted to a distance, by means other 
 than that of the unassisted voice. 
 
 Tele - Hydro - Barometer. An in stru- 
 ment for indicating and recording at a 
 distance the height of water or other 
 liquid in a vessel or reservoir. 
 
 Tele-Hydro-Barometer, Electric. An 
 
 apparatus for electrically transmitting to, 
 and recording at a distant station, the 
 height of water or other liquid. 
 
 Tele-Indicator. A term sometimes em- 
 ployed for telemeter. 
 
 Tele-Intensity of Projector. The ap- 
 parent luminous intensity of a search 
 light at a distance. 
 
 Tele-Manometer, Electric. A gauge 
 for electrically indicating and recording 
 pressures at a distance. 
 
 Tele-Meteorograph. A form of meteor- 
 ograph, registering at a distance by the 
 aid of electricity. 
 
 Telemeter. An apparatus for electrically 
 indicating and recording at a distance 
 the pressure on a gauge, the reading of a 
 thermometer, or the indications of a 
 similar instrument. 
 
 Tele-Metric. Of or pertaining to a tele- 
 meter. 
 
 Telephone. To communicate by means 
 of a telephone. 
 
 15 Vol. 
 
 Telephone. An instrument for the elec- 
 tric transmission of articulate speech. 
 
 Telephone Battery. Any form of open- 
 circuit battery, suitable for use in connec- 
 tion with a telephone. 
 
 Telephone Booth. A telephone cabinet 
 booth. 
 
 Telephone Cabinet-Booth. A silence 
 telephone cabinet. 
 
 Telephone Cable. (1) A cable, either 
 aerial or subterranean, suitable for the 
 transmission of telephonic despatches. 
 (2) Generally, a cable whose conductors 
 are twisted in pairs, for the purpose of 
 avoiding the disturbance produced by 
 cross-talk. 
 
 Telephone Call-Bell. A bell employed 
 in connection with a telephone circuit 
 for calling a correspondent at the other 
 end of the line to his telephone. 
 
 Telephone Call-Wire. (1) A wire em- 
 ployed in certain telephone systems, by 
 the subscriber, for the purpose of calling 
 the central office. (2) A special calling 
 wire in a telephone system. 
 
 Telephone Circuit. An electric circuit 
 for the transmission of telephonic mes- 
 sages. 
 
 Telephone Cords. (1) Flexible conduc- 
 tors provided for use in connection with a 
 telephone. (2) Flexible conducting cords 
 provided with a telephone switchboard 
 for making connections between sub- 
 scribers. 
 
 Telephone Cross-Talk. A disturbance 
 produced in a telephone circuit by induc- 
 tion or leakage from a neighboring circuit. 
 
 Telephone Drop. An annunciator drop 
 used on a telephone switchboard. 
 
 Telephone Exchange. A central office 
 provided with circuits, switches and other 
 devices, by means of which any one of a 
 number of subscribers, connected either 
 directly or indirectly with the exchange, 
 may be placed in communication with 
 any other subscriber, or with some other 
 exchange. 
 
 Telephone-Exchange Switchboard. 
 A switchboard employed in a central 
 telephone exchange for the purpose of 
 readily placing any subscriber in connec- 
 tion with any other subscriber connected 
 with that system. 
 
 Telephone Galvanometer. A high- 
 resistance galvanometer consisting of ail 
 electro-magnet, provided with a soft-iron 
 disc delicately mounted between its poles, 
 and permanently bridged across a tele- 
 phone circuit for the purpose of giving a 
 visual call-signal. 
 2 
 
Tel.i 
 
 [Tel. 
 
 Telephone Head-Gear. Any apparatus 
 placed on the head for readily attaching 
 a telephone receiver to the ear of the 
 operator. 
 
 "Telephone Indicator. (1) An indicator 
 employed on a telephone circuit to in- 
 dicate the number of the correspondent 
 calling. (2) A telephone drop annuncia- 
 tor. 
 
 Telephone Indicator-Coil. A coil em- 
 ployed on a telephone indicator. 
 
 Telephone Meter. (1) An apparatus em- 
 ployed on telephone circuits for register- 
 ing the number of connections between 
 subscribers and the time or duration of 
 the same. (2) A calculagraph. 
 
 Telephone Relay. An electro-magnetic 
 relay employed to close an indicator cir- 
 cuit or a call-bell circuit in a telephone 
 system. 
 
 Telephone Repeating-Coil. (1) A form 
 of induction coil employed for repeating 
 a telephonic message. (~) An induction 
 coil having two insulated windings, one 
 in each of the two telephone circuits to 
 be connected. 
 
 Telephone Set. A general term for the 
 apparatus employed by a telephone sub- 
 scriber at his office. 
 
 Telephone Side Tone. The tone obtained 
 in a telephone receiver by talking to or 
 tapping at its own transmitter. 
 
 Telephone Subscriber. A term applied 
 to a person who is connected with a cen- 
 tral telephone station. 
 
 Telephone Subway. A subway provided 
 for the reception of telephone cables or 
 wires. 
 
 Telephone Switch. (1) Any switch em- 
 ployed in connection with a telephone. 
 (2) A switch employed to place either a 
 call-bell or a telephone in a telephone 
 circuit. 
 
 Telephone Test-Board. A board pro- 
 vided in a central-telephone exchange 
 for the leading-in and orderly arrange- 
 ment of the line wires, between the out- 
 side line and the switchboard, for identi- 
 fication and testing. 
 
 Telephone Time-Check. A clock in a 
 telephone exchange by means of which 
 a drop shutter is automatically released, 
 at a particular trunk- wire indicator, at 
 the expiration of the allotted time that a 
 subscriber is given the use of the trunk 
 line, and by which the central-station 
 operator's attention is called to the fact 
 01 such expiration. (2) A telephone 
 meter. 
 
 Telephone Tinnitus. (1) A professional 
 
 neurosis of the auditory mechanism as- 
 cribed to the constant use of the tele- 
 phone. (2) A nervous auditory disorder 
 attributed to constant use of the tele- 
 phone. 
 
 Telephone Transformer. (1) An appa- 
 ratus for repeating into one circuit a 
 telephonic message received on another 
 circuit. (2) A telephone repeating coil. 
 
 Telephone Translator. A telephone re- 
 peater. 
 
 Telephoner. (1) A term sometimes ap- 
 plied to a person at one end of a simple 
 telephone line, in contradistinction to a 
 telephone subscriber at the end of a cir- 
 cuit connected with any telephone ex- 
 change. (2) Any one carrying on a con- 
 versation by means of a telephone. 
 
 Telephonic. Of or pertaining to a tele- 
 phone. 
 
 Telephonic Alarm. (1) An alarm bell 
 for calling a correspondent to his tele- 
 phone. (2) A call bell. 
 
 Telephonic Cable. A telephone cable. 
 
 Telephonic Cross-Connection. Tele- 
 phonic transposition. 
 
 Telephonic Exchange. A telephone ex- 
 change. 
 
 Telephonic Insulator. Any insulator 
 employed in connection with a telephone 
 line. 
 
 Telephonic Line. The line wire or cir- 
 cuit employed in telephonic transmission. 
 
 Telephonic Joint. A joint effected be- 
 tween the ends of two wires in a tele- 
 phone circuit. 
 
 Telephonic Meter. A telephone meter. 
 
 Telephonic Receiver. (1) The instru- 
 ment employed in receiving a telephonic 
 message. (2) The instrument held to the 
 ear for the purpose of receiving a tele- 
 phonic message. 
 
 Telephonically. By means of a tele- 
 phone. 
 
 Telephonist. Any one employing a tele- 
 phone. 
 
 Telephony. The art of transmitting ar- 
 ticulate speech by means of a telephone. 
 
 Telephote. (1) An apparatus for the 
 telegraphic transmission of pictures by 
 means of the action of light on selenium. 
 (2) The pherope. 
 
 Tele-Photography. A system of fac- 
 simile transmission by dots and dashes 
 transmitted by means of a continuous cur- 
 rent, whose intensity is varied by a trans- 
 mitting instrument containing a selenium 
 resistance. 
 
Tel.] 
 
 955 
 
 [Tern. 
 
 Tele-Radiophone. A form of radiophone 
 arranged for the simultaneous transmis- 
 sion of telegraphic and telephonic mes- 
 sages. 
 
 Telescope. An optical instrument for 
 rendering distant objects visible by en- 
 larging their apparent dimensions and by 
 increasing the amount of the light emitted 
 by them that reaches the eye. 
 
 Telescopic. Of or pertaining to the tele- 
 scope. 
 
 Telescriptor. A name given to a particu- 
 lar form of printing telegraph. 
 
 Teleseme. A self-registering hotel an- 
 nunciator by means of which a dial 
 operated in a room indicates the charac- 
 ter of the service required. 
 
 Telestereoscope. An optical instrument 
 for causing distant objects to appear in 
 relief. 
 
 Tele-Thermograph. (1) A registering 
 tele-thermometer. (2) The record made 
 by a tele-thermometer. 
 
 Tele-Thermometer, Electric. An elec- 
 trical recording thermometer, for indicat- 
 ing and recording temperature at a dis- 
 tance. 
 
 Telluric Magnetic Force. A term some- 
 times employed for the earth's magnetic 
 force. 
 
 Telluric Mines. Explosive mines under- 
 ground , as distinguished from sub-aqueous, 
 or sub-marine explosive mines. 
 
 Telpher. A general name for the appara- 
 tus employed in systems of telpherage. 
 
 Telpher Line. The electric circuit em- 
 ployed in a telpherage system. 
 
 Telpher Locomotion. The transporta- 
 tion of merchandise by means of a telpher 
 system, or telpherage. 
 
 Telpher Locomotive. An electric motor 
 by means of which telpher cars are drawn 
 on a telpher line. 
 
 Telpherage. A system for the convey- 
 ance of carriages suspended from electric 
 conductors, driven by means of electric 
 motors, that take the current required to 
 energizo them directly from the conduct- 
 ors on which they are suspended. 
 
 Temper. To obtain the requisite degree 
 of hardness and elasticity of a metal by 
 cooling IT; while heated. 
 
 Temperature. The thermal condition of 
 a body considered with reference to its 
 capability to communicate heat to other 
 bodies. 
 
 Temperature Alarm, Electric. An 
 electric alarm automatically operated by 
 a change of temperature. 
 
 Temperature Coefficient. <1) A coef- 
 ficient of variation in a quantity, per de- 
 gree of change in temperature. (2) The 
 coefficient by which a change of tempera- 
 ture must be multiplied in order to arrive 
 at the change in a quantity due to the 
 change of temperature. 
 
 Temperature Elevation. (1) The excess 
 of temperature of a heated body over the 
 temperature of its environment. (2) The 
 excess of temperature acquired by a con- 
 ductor traversed by a current over the 
 surrounding air. 
 
 Temperature Gradient. (1) A line rep- 
 resenting the rate-of-change of tempera- 
 ture in a body through which heat is flow- 
 ing. (2) A space-rate-of-change in tem- 
 perature. (3) A rate-of-change in any 
 quantity varying with temperature. 
 
 Temperature Regulating-Switch for 
 Electric Car Heater. A switch em- 
 ployed in systems of car heating, whereby 
 the separate heaters may be connected in 
 series, or in parallel groups, between the 
 trolley and the track, or by means of 
 which one or more of the heaters may be 
 removed at will. 
 
 Tempering. Obtaining a change in the 
 hardness and elasticity of a metal by sud- 
 denly cooling it while heated. 
 
 Tempering, Electric. A process for 
 temperii g metals in which heat of electric 
 origin is. employed instead of ordinary 
 heat. 
 
 Temporary. Lasting but for a while. 
 Temporary Charge by Induction. An 
 
 electric charge of a temporary character 
 
 produced on a conductor by induction, as- 
 
 distinguished from a permanent charge 
 
 so obtained. 
 Temporary Currents. Currents that 
 
 continue but for a brief interval of time. 
 Temporary Electromotive Forces. 
 
 Electromotive forces which continue but 
 
 for a brief interval of time. 
 
 Temporary Intensity of Magnetiza- 
 tion. The intensity of the magnetization, 
 temporarily induced in a bar of soft iron, 
 as distinguished from permanent mag- 
 netization induced in hard steel. 
 
 Temporary Magnetization. (1) A word 
 employed for the magnetization produced 
 in a mass of soft iron, when brought into 
 a magnetic field. (2) Magnetization which 
 is temporary in character. 
 
 Temporary Magneto-Motive Forces. 
 
 Magneto-motive forces that continue but 
 
 for a brief interval of time. 
 Temporary Socket. A socket provided. 
 
Ten.} 
 
 956 
 
 [Tes. 
 
 for an incandescent lamp that is not in- 
 tended to be permanently installed. 
 
 Tenacity. (1) The stress required to pro- 
 duce a rupture in a mass of given cross 
 section of any material. (2) The power of 
 a material to resist rupture. 
 
 Tension.-^-(l) An elongating stress. (2) 
 The strain produced in a substance by the 
 action of a stress. (3) The pressure pro- 
 duced by a confined gas against the walls 
 of the containing vessel, due to molecular 
 impact. 
 
 Tension, Electric. A term loosely ap- 
 plied to signify indifferently surface den- 
 sity, electromotive force, electromotive" 
 intensity, dielectric stress, or difference 
 of potential. 
 
 Tension-Ratchet. A name sometimes 
 given to a line-dynamometer. 
 
 Terminal Board. A switchboard situat- 
 ed on a dynamo. 
 
 Terminal Branch Cut-Out. A cut-out 
 for a branch taken from the end of a main 
 line. 
 
 Terminal Electromotive Force. The 
 
 electromotive force of a dynamo taken at 
 the terminals of the machine. 
 
 Terminal Insulator. (1) An insulator 
 at the terminus of a line. (2) A telegraph 
 line insulator provided with two grooves 
 for the reception of two ends which may 
 be kept insulated from each other. 
 
 Terminal Pole. (1) The last pole of a line. 
 (2) A pole of greater dimensions and more 
 securely anchored than the rest, erected 
 at the end of a telegraphic, telephonic, 
 trolley, or power line, or where aerial wires 
 join subterranean cables, and intended to 
 safely resist the lateral tension of the line. 
 
 Terminal Pressure. The pressure at the 
 terminals of any electric apparatus. 
 
 Terminal Reflection. A term applied 
 to the reflection of electro-magnetic waves 
 from the end of an open-circuited con- 
 ductor. 
 
 Terminal Telegraphic Station. The 
 telegraphic station at either terminus of 
 a line. 
 
 Terminal Voltage. The terminal elec- 
 tromotive force. 
 
 Terminals. A name indifferently applied 
 to the poles or to the electrodes of a vol- 
 taic battery. 
 
 Terra-Cotta Conduit. An earthenware 
 conduit. 
 
 ** Terra Voltaism." The operation of a 
 telegraph system by a single voltaic ele- 
 ment, consisting of a pair of dissimilar 
 
 metals buried in the earth at opposite 
 ends of the line. 
 
 Terella. A sphere of hardened steel, or of 
 lode-stone, magnetized so that the distri- 
 bution of its magnetism shall resemble 
 that of the earth. 
 
 Terrestrial Electricity. A term pro* 
 posed for atmospheric electricity. 
 
 Terrestrial Magnetic Induction. The 
 production of magnetism by the action of 
 the earth's field. 
 
 Terrestrial Magnetism. A name ap- 
 plied to the magnetism of the earth. 
 
 Tesla Coil. A form of oil-insulated in- 
 duction coil or transformer. 
 
 Tesla Discharge. A variety of high-fre- 
 quency, high-pressure discharge. 
 
 Tesla Frequencies. A term sometimes 
 applied to frequencies which are much 
 higher than those ordinarily employed. 
 
 Tesla Transformer. A step-up, oil-in- 
 sulated transformer, employed by Tesla 
 in obtaining high-frequency discharges. 
 
 Test Board. (1) A board employed in a 
 telegraphic, telephonic, or transmission cir- 
 cuits, generally, provided with the measur- 
 ing instruments required for testing its 
 insulation and other electrical properties. 
 (2) A board in a telephone station to 
 which telephone lines are connected, for 
 the purpose of quickly connecting the 
 testing instruments to such lines. 
 
 Test Cell. A voltaic cell employed for 
 the busy or engaged test in a multiple 
 telephone switchboard. 
 
 Test Circuit. In a multiple-telephone 
 switchboard the circuit for the busy test. 
 
 Test Clerk. A clerk to whom the duties 
 of testing the telephone lines are assigned. 
 
 Test Loop. A loop running to a test 
 board. 
 
 Test Plugs. (1) Plugs used in testing. 
 (2) Plugs for insertion in testing jacks. 
 
 Test Ring. (1) A call made by the central 
 station to each subscriber to ascertain 
 whether the line is in good operating con- 
 dition. (2) A ring in front of each jack 
 in a multiple telephone switchboard, and 
 supplying a contact for the busy test. 
 
 Test Room. A testing room. 
 
 Test Thimble. A thimble at a central 
 telephone exchange carrying a contact, 
 and employed for making a busy test at 9> 
 multiple telephone switchboard. 
 
 Test Wire for Multiple Switchboard. 
 A wire running to a multiple switchboard 
 and connecting all the jacks of the same 
 number in the different sections for the- 
 
Tes,] 
 
 957 
 
 [The. 
 
 purpose of enabling the operator to ascer- 
 tain whether the subscriber needed is 
 busy. 
 
 Test Wire of Metallic Circuit. (1) The 
 return-wire of a metallic circuit. (2) In 
 telephony, that wire in a subscriber's me- 
 tallic-circuit loop which serves for the 
 
 ' busy test at the switchboard. 
 
 Test Wires. (1) The wires in a multiple 
 telephone switchboard, by which the 
 busy test is made. (2) Any wires or cir- 
 cuits used in making a test. (3) Wires 
 to be tested or undergoing a test. 
 
 Testing. (1) Submitting to trial for elec- 
 tric capabilities. (2) Determining the 
 value of the current strength, the dif- 
 ference of potential, the resistance, the 
 coulombs, the farads the joules, the watts, 
 etc., in any circuit. (3) Making electrical 
 measurements, generally. 
 
 Testing Bank. A bank of lamps, or otner 
 inductionless resistances, employed in 
 testing a circuit. 
 
 Testing Board. A board employed in a 
 telephone switchboard for the purpose of 
 testing the condition of the lines. 
 
 Testing Car for Railway Circuits. 
 
 An electric trolley-car provided for mak- 
 ing electric tests along a line of street 
 railway while the car is in motion. 
 
 Testing Jacks. In a multiple telephone 
 switchboard, or distributing board, special 
 jacks sometimes inserted in any circuit 
 for testing such circuit. 
 
 Testing Magneto. A magneto-electric 
 machine employed to produce the high 
 electromotive force required in testing 
 high-resistance circuits. 
 
 Testing of Joints. (1) Determining the 
 insulation or conductor resistance of a 
 joint in any circuit. (2) Ascertaining the 
 resistance of the insulating material 
 around a joint in a cable. 
 
 Testing Point of Spring Jack. The 
 tip of a spring jack. 
 
 Testing Pole. A term sometimes em- 
 ployed in electro-therapeutics for the in- 
 different pole or electrode. 
 
 Testing Posts. Hollow posts provided 
 with a door, placed above an underground 
 cable, into which the wires are sometimes 
 led, employed for ease in opening and 
 testing. 
 
 '1'esting Rod. An insulated conducting 
 rod employed in testing insulators for 
 dipping into the liquid contained in their 
 sheds, when inverted in a testing bath. 
 
 Testing Room. (1) A room on board a 
 cable-ship provided with instruments for 
 
 cable testing and signalling. (2) A room 
 fitted with tables and apparatus for mak- 
 ing electrical tests. (3) In a telephone 
 exchange, a room usually near the switch 
 room through which all telephone lines 
 pass and arranged for conveniently test- 
 ing such lines. 
 
 Testing Switch. In a quadruples tele- 
 graphic system, a switch for throwing 
 the line from the sending battery to 
 ground through a suitable resistance, for 
 the purpose of enabling the distant sta- 
 tion to obtain a balance. 
 
 Testing Transformer. (1) A transformer 
 employed in any system of distribution 
 for the purpose of testing for grounds, for 
 the condition of the line, for drop of po- 
 tential, etc. (2) A transformer employed 
 in testing. 
 
 Tetanus. Continuous spasmodic contrac- 
 tion of the muscles. 
 
 Tetrad Atom. An atom whose valency 
 or atomicity is four. 
 
 Tetrivalent. Possessing a valency or 
 atomicity of four. 
 
 Tetrode Working. A term applied to a 
 four-way mode of working the Delany 
 synchronous multiple telegraph. 
 
 Thaumatrope. An optical toy depending 
 on the persistence of the retinal image, 
 in which two different pictures placed 
 upon the opposite sides of a card are 
 caused, by the rapid rotation of the card, 
 to appear as a single picture. 
 
 Theatre Dimmer. (1) A dimmer employ- 
 ed in theatres for varying the intensity of 
 the illumination. (2) A rheostat or chok- 
 ing coil employed in a theatre-lighting 
 circuit. 
 
 Theatre Dimming Rheostat. A rheo- 
 stat employed in connection with a theatre 
 dimmer. 
 
 Theatrophone. A sytem of telephonic 
 communication between theatres or opera- 
 houses and subscribers. 
 
 Theodolite. An instrument employed for 
 measuring angles in vertical or horizon- 
 tal planes. 
 
 Theoretical Magnet. A hypothetical 
 magnet, assumed for the purpose of 
 mathematical discussion as possessing in- 
 finite length and thinness, and uniform 
 magnetization. 
 
 Therapeutic Adapter. An adapter em- 
 ployed in electro-therapeutic work. 
 
 Therapeutical Electrization. Subject- 
 ing different parts of the human body to 
 the action of electric currents for the cure 
 of a diseased condition. 
 
The.] 
 
 958 
 
 [The. 
 
 Therm. (1) A heat unit equal to the 
 amount of heat required to raise the tem- 
 perature of a gramme of water, at the 
 temperature of its greatest density, one 
 degree Centigrade. (2) The smaller 
 calorie. 
 
 Therm Calorie. A word sometimes used 
 for the smaller calorie. 
 
 Thermsethesiometer. An instrument 
 employed in electro-therapeutics for test- 
 ing the temperature sense in nervous 
 diseases. 
 
 Thermal. Of or pertaining to heat. 
 
 Thermal Absorption. The absorption of 
 heat energy during its passage through a 
 body. 
 
 Thermal Activity. (1) The activity pos- 
 sessed by a body, arising from its heat 
 energy. (2) The rate of doing thermal 
 work. (3) The rate of generating heat. 
 
 Thermal Balance. (1) A differential 
 galvanometer employed for determining 
 small differences of temperature. (2) The 
 bolometer. 
 
 Thermal Batteries. (1) Thermo-piles. 
 (2) Thermo-electric batteries. (3) An elec- 
 tric source operated by heat energy. 
 
 Thermal Cautery. A cautery heated by 
 ordinary heat, as distinguished from an 
 electric cautery, or one heated by heat of 
 electric origin. 
 
 Thermal Circuit Closer. A circuit- 
 closer operated by changes of tempera- 
 ture. 
 
 Thermal Coil of Resistance Box. A 
 coil of wire inserted in a resistance box, 
 and possessing a high temperature suffi- 
 cient, for the purpose of indicating by its 
 resistance the temperature within the 
 box. 
 
 Thermal Current. A heat current, or 
 one due to the flow or transference of 
 heat through a conductor. 
 
 Thermal Current-Strength. The quan- 
 tity of heat per second transmitted across 
 any area of normal cross-section of a con- 
 ductor. 
 
 Thermal Diffusiyity. A term proposed 
 for thermometric conductivity, or the 
 ratio of the calorimetrical conductivity 
 to the specific heat per unit volume. 
 
 Thermal Electromotive Force of Re- 
 sistance Coils . A thermo-electric 
 couple inserted in a resistance box, for 
 the purpose of determining the tempera- 
 ture within it. 
 
 Thermal Equivalent of Work. The 
 equivalent, in heat units, of a given 
 quantity of mechanical work. 
 
 Thermal Incandescence. The shining 
 or glowing of a substance, generally a 
 solid, by means of heat other than that ot 
 electric origin. 
 
 Thermal Resistance. The resistance 
 . offered by a substance to the passage of 
 heat. 
 
 Thermal Resistivity. (1) Specific ther- 
 mal resistance. (2) The specific thermal 
 resistance of a substance referred to the 
 thermal resistance of a unit cube between 
 any pair of parallel faces. 
 
 Thermally Effective Value. (1) In an 
 alternating-current circuit, the effective 
 values from thermal measurements or 
 considerations. (2) The square-root-of- 
 mean-square values. 
 
 Thermic Balance. A bolometer. 
 
 Thermic Interrupter. A device operat- 
 ed by the expansion of a metallic wire 
 employed for the purpose of preventing 
 more than a certain number of arc-lamps 
 being used in a circuit where the current 
 is paid for by the number of lights, rather 
 than by the current supplied. 
 
 Thermo-Barometer. (1) A device for 
 
 . determining the elevation of a mountain 
 by observing the temperature at which 
 water boils on that elevation. (2) A 
 hypsometer. 
 
 Thermo-Battery. A term sometimes ap- 
 plied for a thermo-electric battery. 
 
 Thermo-Call. A thermo-electric call. 
 
 Thermo-Cell. A thermo-electric cell. 
 
 Thermo-Chemical Cell. An electric 
 cell, in which a difference of potential is 
 produced by the combined action of heat 
 and chemical action. 
 
 Thermo-Chemistry. That branch of 
 chemistry which treats of the measure- 
 ment of chemical energy in thermal units. 
 
 Thermochrosy. (1) A word expressive 
 of the fact that ordinary radiant heat, 
 like light, consists of an assemblage of 
 waves of different frequencies. (2) Heat 
 coloration. 
 
 Thermo-Electric Battery. A combina- 
 tion, as a single thermo-electric source, of 
 a number of separate thermo-electric cells 
 or couples. 
 
 Thermo-Electric Call. An instrument 
 for electrically sounding an alarm when 
 the temperature rises above or falls below 
 a fixed point. 
 
 Thermo-Electric Cell. A name applied 
 to a thermo-electric couple. 
 
 Thermo-Electric Couple. Any two dis- 
 similar metals which, when connected at 
 their ends only, so as to form a complete 
 
The.] 
 
 959 
 
 [The. 
 
 electric circuit, will produce an electric 
 current when one end is more highly 
 heated than the other. 
 
 Thermo-Electric Current. A current 
 produced by a thermo-electromotive 
 force. 
 
 Thermo-Electric Diagram. A diagram 
 in which the thermo-electric power be- 
 tween different metals is given for dif- 
 ferent temperatures. 
 
 Thermo-Electric Effect. The produc- 
 tion of an electromotive force at a thermo- 
 electric junction by reason of the differ- 
 ence of temperature between that junc- 
 tion and the other junction of the couple. 
 
 Thermo-Electrio Electromotive Force 
 of Voltaic Cell. The thermo-electro- 
 motive force produced by a voltaic couple. 
 
 Thermo-Electric Element. A name ap- 
 plied to either of the metals that form a 
 thermo-electric couple. 
 
 Thermo-Electrio Force. (1) The force 
 produced by a thermo-electric couple. 
 (2) The electromotive force of a thermo- 
 electric circuit. 
 
 Thermo-Electric Generator. A ther- 
 mo-electric pile. 
 
 Thermo-Electric Inversion. An inver- 
 sion of the thermo-electromotive force of 
 a couple at certain temperatures. 
 
 Thermo-Electric Junction. A junction 
 of a thermo-electric couple. 
 
 Thermo-Electric Neutral Point. A 
 temperature at which two thermo-elec- 
 tric forces are equal. (2) A temperature 
 at which a junction of two metals has no 
 thermal E. M. F. 
 
 Thermo-Electric Pair. A thermo-elec- 
 tric couple. 
 
 Thermo-Electric Pile. A thermo-elec- 
 tric battery. 
 
 Thermo -Electric Potential-Difference. 
 Difference of potential produced by a 
 thermo-electric cell or pile. 
 
 Thermo-Electric Power. A number 
 which, when multiplied by the difference 
 of temperatures of a thermo-electric 
 couple, will give the difference of poten- 
 tial generated thereby. 
 
 Thermo-Electric Series. A list of 
 metals, so arranged as to their thermo- 
 electric powers, that each in the series is 
 electro-positive to any lower in the list. 
 
 Thermo-Electricity. (1) The electro- 
 motive forces developed by a thermo- 
 electric cell or battery. (2) Electricity 
 produced by differences of temperature 
 at the junction of dissimilar metals. 
 
 Thermo-Electriflcation. E lectrifica- 
 
 tion produced by differences of tempera- 
 ture in a thermo-electric couple. 
 Thermo-Electrometer. A name some- 
 times, though not happily, given to an 
 electric thermometer. 
 
 Thermo - Electromotive Force. An 
 
 electromotive force or difference of poten- 
 tial produced by differences of tempera- 
 ture at a thermo-electric junction. 
 
 Thermo-Element. A name sometimes 
 employed for a thermo-couple 
 
 Thermo-Galvanometer. A galvanome- 
 ter employed in connection with a thermo- 
 pile for the purpose of showing difference, 
 of temperature by means of the currents 
 developed. 
 
 Thermo-Luminescence. Luminescence 
 produced in a substance by heat at a 
 temperature below that of luminosity. 
 
 Thermolysis. The decomposition of a 
 molecule by heat. 
 
 Thermo-Magnetic Generator. (1) A de- 
 vice for producing electricity by the com- 
 bined influence of heat and magnetism. 
 (2) A pyro-magnetic generator. 
 
 Thermo-Magnetic Motor. A pyro- 
 magnetic motor. 
 
 Thermometer, Electric. A device for. 
 determining the effects of an electric dis- 
 charge by the movements of a liquid 
 column due to the expansion of a con- 
 fined mass of air through which the dis- 
 charge is passed. 
 
 Thermometric Conductivity. The. 
 ratio of the calorimetric conductivity to, 
 the specific heat of unit volume. 
 
 Thermometric Heat. A term proposed 
 for heat in gross matter, as distinguished 
 from radiant heat, or wave motion in the. 
 ether. 
 
 Thermometric Resistance Coil. A coil 
 whose resistance is known at a given 
 temperature, and employed to determine, 
 an unknown temperature to which it is 
 exposed, from the change in its resistance. 
 
 Thermometry. That branch of science 
 which treats of the determination of 
 temperature. 
 
 Thermo-Multiplier. (1) A word some- 
 times used for thermo-pile. (2) A form 
 of low-resistance galvanometer suitable 
 for use in connection with a thermo-pile. 
 
 Thermo-Pair. A thermo-electric couple. 
 
 Thermophone. (1) An electric instru- 
 ment for producing sound by means of 
 electricity. (2) Any instrument by means, 
 of which sounds are produced by the ab- 
 sorption of radiant energy. 
 
 Thermo-Pile. A thermo-electric battery.^ 
 
The.] 
 
 960 
 
 [Thr. 
 
 Thermo-Pile Galvanometer. A form 
 of galvanometer for detecting small dif- 
 ferences of temperature, in which the 
 thermo-pile is placed within the instru- 
 ment. 
 
 Thermoscopie Receiver. A name some- 
 times given to a microphonic receiver. 
 
 Thermostat. An instrument for auto- 
 matically maintaining a given tempera- 
 ture by closing an electric circuit through 
 the expansion of a solid or liquid. 
 
 Thermostatic Alarm, Electric. Any 
 electric alarm operated by the action of a 
 thermostat. 
 
 Thermostatic. Of or relating to a ther- 
 mostat. 
 
 Thermostatic Regulation. Any regula- 
 tion, such as in the temperature of a room, 
 effected by the action of a thermostat. 
 
 Thermostatic Regulator. A regulator 
 whose action is dependent on a ther- 
 mostat. 
 
 Thermo - Telephone. (1) A telephone 
 transmitter consisting of a continuous 
 wire,one end of which is connected with a 
 transmitting diaphragm placed in circuit 
 with the receiving telephone battery, and 
 having a current passed through it of 
 sufficient strength to heat the wire. (2) A 
 telephone receiver in which the dia- 
 phragm is set in vibration by thermally- 
 produced changes in the length of an at- 
 tached wire. 
 
 Thermo-Tropic Battery. A name pro- 
 posed for a form of carbon batteiy, in 
 which the E. M. F. is produced by the ac- 
 tion of heat. 
 
 Thermo-Tropic Current. The currents 
 produced by a thermo-tropic battery. 
 
 Thief Alarm. A term sometimes em- 
 ployed for a burglar alarm. 
 
 Third -Rail Electric Railway. An 
 electric street-car railway in which a third 
 rail, insulated from the track, is employed 
 for one side of the circuit, the outside 
 rails, together with return feeders, being 
 employed for the other side of the circuit. 
 
 Thimble Brush. A suitably shaped 
 brush employed for cleansing such sur- 
 faces as the inside of a thimble, and so 
 preparing them for electro-plating. 
 
 Thomson. A name proposed, but not 
 adopted, for a unit of electric conduc- 
 tivity. 
 
 Thomson Effect. (1) The production of 
 an electromotive force in unequally 
 heated homogeneous conducting sub- 
 stances. (2) The increase or decrease in 
 the differences of temperature in an un- 
 
 equally heated conductor, produced by 
 the passage of an electric current through 
 the conductor. 
 
 Thomson's Bridge. A modified form of 
 Wheatstone's bridge employed for the 
 measurement of very small resistances. 
 
 Three Ammeter Method of Measure- 
 ment. A method of measuring activity 
 in an alternating-current circuit by the 
 combined use of three ammeters in a 
 main and branch circuits respectively. 
 
 Three-Bearing Generator. (1) A belt- 
 driven dynamo-electric generator, pro- 
 vided with a third shaft bearing situated 
 between the armature and the pulley. 
 (2) A generator whose rotor shaft has 
 three bearings. 
 
 Three-Bearing Motor. (1) A belt-driv- 
 ing motor provided with a third shaft 
 bearing between the pulley and the ar- 
 mature. (2) A motor whose rotor shaft 
 has .three bearings. 
 
 Three-Bearing Railway Generator. 
 A railway-generator having three bear- 
 ings for its rotor shaft. 
 
 Three-Bladed Switch. (1) A switch 
 provided with three blades. (2) A switch 
 closing three circuits simultaneously. 
 
 Three-Branched Spark. A form of 
 branched spark obtained by the discharge 
 of a Leyden jar through a peculiar form 
 of induction coil. 
 
 Three - Circuit Way - Telegraphic 
 Switchboard. A form of telegraphic 
 switchboard suitable for use at a way 
 station. 
 
 Three-Coil Armature Winding of Al- 
 ternator. An armature winding pro- 
 viding three coils in a ring armature or 
 three slots in a drum armature for each 
 and every pole in the field frame. 
 
 Three-Coil Armature Winding of 
 Multiphase Alternator. An armature 
 winding providing three coils in a ring 
 armature or three slots in a drum arma- 
 ture, per phase, for each and every pole 
 in the field frame. 
 
 Three Corner Telegraphic Repeater. 
 A telegraphic repeater which repeats from 
 one circuit to two circuits. 
 
 Three-Current Test to Instrumental 
 Zero. A localization submarine cable 
 test, in which three separate measure- 
 ments of resistance are made with differ- 
 ent current strengths in succession, the 
 Wheatstone bridge balance being taken 
 to instrument zero. 
 
 Three-Filament Incandescent Lamp 
 for Triphase Circuits. An incandes- 
 cent lamp intended for use on triphas* 
 
Thr.] 
 
 961 
 
 [Thr. 
 
 circuits provided with three leading-in 
 wires connected to the free ends of three 
 filaments which are connected in a com- 
 mon joint. 
 
 Three-Part Commutator. A commuta- 
 tor made up of three insulated segments. 
 
 Three-Phase Armature. An armature 
 possessing a three-phase winding. 
 
 Three-Phase Armature- Winding. An 
 armature winding such as will enable it 
 to produce three-phase currents. 
 
 Three-Phase Bar- Winding for Arma- 
 ture. A bar winding for an armature, 
 such as will enable it to produce three- 
 phase currents. 
 
 Three-Phase Circuit. Any circuit suit- 
 able for the transmission of three-phase 
 currents. 
 
 Three-Phase Coil-Winding for Arma- 
 ture. A coil winding for an armature, 
 such as will enable it to produce three- 
 phase currents. 
 
 Three - Phase Continuous - Current 
 Commutating Machine. A trans- 
 former from triphase alternating to con- 
 tinuous currents, employing a revolving 
 armature provided with a commutator. 
 (2) A triphase rotary transformer. 
 
 Three-Phase Currents. Three alternat- 
 ing-currents differing in phase from one 
 another by one-third of a cycle. 
 
 Three-Phase Dynamo. A three-phase 
 generator. 
 
 Three-Phase Generator. Any generator 
 capable of producing three-phase cur- 
 rents. 
 
 Three-Phaser. A three-phase generator. 
 
 Three-Phase Meter. A meter suitable 
 for operation on a three-phase system, for 
 recording the energy delivered on all 
 three branches. 
 
 Three-Phase Motor. Any motor suitable 
 for operation by three-phase currents. 
 
 Three-Phase Rotary-Converter. A ro- 
 tary converter suitable for use in connec- 
 tion with three-phase currents. 
 , Three - Phase Rotating - Magnetic 
 Field. A rotating field produced by the 
 action of a three-phase current. 
 
 Three-Phase System. A system for the 
 transmission of electric energy by means 
 of three-phase currents. 
 
 Three-Phase Transformer. Three sep- 
 arate transformers employed for the 
 transformation of triphase currents. 
 
 Three-Phase Transmission. Transmis- 
 sion by means of three-phase currents. 
 
 Three-Phase Two-Phase Transformer. 
 An alternating-current transformer for 
 transforming from three-phase currents 
 to two-phase currents. 
 
 Three-Phase Working. Three-phase 
 transmission. 
 
 Three-Phaser.-y<l) A three-phase gener- 
 ator. (2) A triphaser. 
 
 Three-Point Switch. (1) A switch by 
 means of which a circuit can be com- 
 pleted through three different contact 
 points. (2) A switch designed to make 
 three distinct contacts. 
 
 Three-Point Trolley Switch. A trolley 
 switch provided for a bifurcation in a 
 road, or where a road divides into three 
 branches. 
 
 Three-Voltmeter Method of Measure- 
 ment. A method of measuring activity 
 in an alternating-current circuit, employ- 
 ing three voltmeters simultaneously. 
 
 Three- Way Frog. A three-way trolley 
 frog. 
 
 Three- Way Plug. A multiple telephone 
 switchboard plug making three contacts 
 at sleeve, ring and tip respectively. 
 
 Three-Way Switch. A three-point 
 switch. 
 
 Three-Way Trolley -Frog. A trolley 
 frog used where a trolley line branches 
 in three directions. 
 
 Three- Way Trolley-Switch. (1) A 
 trolley switch designed for use at a point 
 where the line branches in three direc- 
 tions. (2) A trolley switch with three 
 connections. 
 
 Three- Wire Circuit. (1) A circuit em- 
 ployed in a three-wire system. (2) A 
 three-wire diphase system. (3) A three- 
 wire triphase system. 
 
 Three- Wire Diphase. A form of diphase 
 circuit containing three wires, in which 
 one of the wires is usually provided with 
 a greater area of cross-section and is em- 
 ployed as the common return. 
 
 Three-Wire Distribution Board. A 
 
 distribution board in a three-wire system. 
 
 Three-Wire Mains. The mains employed 
 in a three-wire system of distribution. 
 
 Three-Wire Meter. A meter suitable 
 for operation on a three-wire system for 
 recording the power delivered on both 
 sides of the system. 
 
 Three-Wire Moulding. Moulding em- 
 ployed in a three- wire distribution system. 
 
 Three-Wire Multiple Switchboard. 
 A multiple telephone switchboard in 
 which the jacks in a subscriber's line are 
 
Thr.] 
 
 962 
 
 [Tinu 
 
 connected in multiple, and in which three 
 wires run to all jacks. 
 
 Three-Wire Switchboard. (1) A tele- 
 phone switchboard with three wires to 
 each jack. (2) A switchboard employed 
 in a three-wire system of electric distri- 
 bution. 
 
 Three- Wire Switchboard. A switch- 
 board suitable for use in connection with 
 a three-wire system of distribution. 
 
 Three-Wire System. A system of elec- 
 tric distribution for lamps or other mul- 
 tiple-connected translating devicas, in 
 which three conductors are employed in 
 connection with two dynamos connected 
 in series, the central or neutral conductor 
 being connected to the junction of the 
 dynamos, and the two other conductors to 
 the remaining free terminal of each. 
 
 Three- Wire Transmission. (1) Trans- 
 mission by the three-wire system. (2) 
 Transmission by means of the three-wire 
 diphase or three-wire triphase systems. 
 
 Three- Wire Telephone Switchboard. 
 A branched terminal telephone switch- 
 board. 
 
 Throttling. Partially or completely cut- 
 ting off. 
 
 Throttling of Lines of Magnetic Force. 
 Any decrease in the density of magnetic 
 flux due to a magnetic joint, or to any 
 decrease in the magnetic permeability of 
 any portion of a circuit. (2) Saturation. 
 
 Through.-^-(l) In communication with, 
 telegraphically. (2) Directly connected 
 telegraphically, without intermediate 
 stations. (3) Completed or ended. 
 
 Through Circuit. A telephonic or tele- 
 graphic circuit that has been completed 
 through to a given station, by cutting out 
 interruptions or breaks in a line, by the 
 connection together of sections of dif- 
 ferent wires. 
 
 Through Line. A line extending be- 
 tween two terminal stations, as distin- 
 guished from a line containing way sta- 
 tions. 
 
 Through Telephone Tablets. Panels 
 placed in a telephone switchboard for 
 connecting subscribers on different 
 switchboards. 
 
 Throw. A term sometimes employed for 
 the excursion or throw of a needle. 
 
 Throw of Needle. A phrase sometimes 
 employed for the angular deflection of a 
 needle, particularly when the needle 
 makes its first swing. 
 
 Throw-Back-Indicator, Electric. An 
 annunciator with a drop that is automati- 
 cally replaced. 
 
 Throw-Over Reversing Switch. A re- 
 versing switch which is operated by 
 throwing it over from one side to the 
 other. 
 
 Throw- Over Starting Switch. A 
 throw-over switch employed for starting 
 an electric motor. 
 
 Throw-Over Switch. (1) A switch for 
 readily and rapidly changing a circuit 
 from one source to another or one system 
 to another. (2) A switch which is 
 thrown over from one set of contacts to 
 another, by movement about an axis. 
 
 Thumb-Cock Electric Burner. An 
 
 electric gas-burner in which the turning 
 of an ordinary thumb-cock turns on the- 
 gas and ignites it by a spark produced by 
 a wiping contact, actuated by the motion 
 of the thumb-cock. 
 
 Thunder. The loud noise accompanying 
 a disruptive lightning discharge. 
 
 Thunder Bod. A term formerly em- 
 ployed for lightning rod. 
 
 Thunder Storm. A rain storm accom- 
 panied by thunder and lightning. 
 
 Ticker. A word sometimes employed for 
 stock ticker, or printing telegraph. 
 
 Ticket Operator. In telephony, an oper- 
 ator at a central exchange whose duty it 
 is to record calls on tickets for that pur- 
 pose. 
 
 Tie Bar. A bar extending across the track 
 at suitable intervals between two opposite 
 rails, and employed to prevent the spread- 
 ing of the rails. 
 
 Tie Feeder. A feeder connecting two 
 stations, two feeders, or two feeding 
 points. 
 
 Tie Line. (1) In an electric distributing 
 system, a conductor free from translating 
 devices and employed to equalize poten- 
 tial. (2) A conductor connecting two 
 points in a distributing system for the 
 purpose of equalizing their potentials. 
 
 Tie Sleeper. A sleeper laid transversely 
 to a track and serving to retain in place 
 the rails which are fastened to it. 
 
 Tie Wire. (1) Binding wire of an insu- 
 lator. (2) Wire which binds an overhead 
 wire to the groove of its insulator. 
 
 Time Annunciator. An alarm clock. 
 
 Time-Ball, Electric. A ball suspended in 
 a prominent position on a tall pole and 
 caused to fall at the exact hour of noon, 
 or at any other pre-determined time, for 
 the purpose of giving a visual signal of 
 correct time to an entire neighbor hood. 
 
 Time Constant. (1) Irf an electric circuit 
 the ratio of the inductance to the con 
 
Tim.] 
 
 963 
 
 [Too. 
 
 ductor resistance. (2) In an electric cir- 
 cuit containing a condenser the product 
 of the capacity of the condenser, and the 
 resistance of its discharging circuit. 
 
 Time-Constant of Circuit. (1) The time 
 in which a current will fall in a circuit 
 when the E. M. F. is suddenly removed, in 
 a ratio whose Naperian logarithm is unity. 
 (2) The ratio of the inductance of a cir- 
 cuit to its resistance. 
 
 Time-Constant oi Condenser. The time 
 in which the charge of a condenser falls 
 in a ratio whose Naperian logarithm is 
 unity. 
 
 Time-Constant of Electro-Magnet. 
 The time required for the current to fall, 
 when the E. M. F. is suddenly withdrawn, 
 to a ratio whose naperian logarithm is 
 unity. 
 
 Time Cut-Out. An automatic cut-out ar- 
 ranged so as to permit a translating de- 
 vice to operate for a certain time, after 
 which it is cut cu , of the circuit. 
 
 Time Detector, Electric. An electri- 
 cally operated v .tchman's clock. An ap- 
 paratus for electrically registering the 
 time at which a watchman visits one or 
 more stations and closes or opens a cir- 
 cuit connected with the register. 
 
 Time Fall ot Electromotive Force of 
 Secondary Cell. A gradual decrease in 
 the potential difference of a secondary or 
 storage cell observed during its discharge. 
 
 Time Flow. The ratio expressed in ergs- 
 per-square-centi metre, of the amount of 
 energy which is passed through a normal 
 area of cross -section, to that cross-section. 
 
 "Time Gun. A gun that is automatically 
 fired by a standard clock, for the purpose 
 of giving a time signal to an entire neigh- 
 borhood. 
 
 Time Hysteresis. A term sometimes in- 
 correctly employed for magnetic creep- 
 ing. 
 
 Time-Illumination. (1) A given illumi- 
 nation that is continued for a given time. 
 (2) The effect produced by an illumina- 
 tion continued for a time. (3) The pro- 
 duct of illumination and time. 
 
 Time-Lag of Magnetization. (1) A lag 
 which appears to exist between the time 
 of the action of the magnetizing force, 
 and the appearance of the rriagnetism. 
 \2) In an alternating-current choking-coil 
 or transformer, the lag of magnetization 
 due to hysteresis, expressed as a time or 
 fraction of a period. 
 
 Time Meter, Electric. An electric meter 
 whose operation is based on a record of 
 
 time during which an electric current ia 
 passing. 
 
 Time of Oscillation. The time of vi- 
 bration. 
 
 Time of Vibration. The time required 
 for a complete to-and-fro motion of the 
 particles of an elastic medium. 
 
 Time Register. Any device for register- 
 ing a lapse of time. 
 
 Time Register for Railroads. A tele- 
 graphic apparatus or register designed to 
 record a telegraphic message transmitted 
 over a line. 
 
 Time Relay. (1) A relay employed in a 
 form of stock ticker for momentarily de- 
 laying the releasing of a clutch and the 
 closing of a transmitter, until the print- 
 ing of a given letter has been assured. 
 (2) A relay employed in a system of time 
 signalling. 
 
 Time-Rise of Electromotive Force of 
 Secondary Cell. A gradual increase in 
 the potential difference of a secondary or 
 storage cell observed during charge. 
 
 Time Switch. (1) A switch arranged to 
 open or close a circuit at a certain time 
 or after the lapse of a certain time 
 (2) An automatic switch in which a pre- 
 determined time is required either to in- 
 sert a resistance into or remove it from 
 a circuit. 
 
 Time Telegraph. A general term for the 
 apparatus employed in time telegraphy. 
 
 Time Telegraphy. A system for the tel- 
 egraphic transmission of time. 
 
 Tinned Wire. Wire electro-plated with 
 tin. 
 
 Tinning Metal. The solder employed in 
 joining electrotype shells or for preparing 
 their backs for the reception of the back- 
 ing metal. 
 
 Toe of Grapnel. A prong of a cable 
 grapnel. 
 
 Toll Station. A pay telephone or tele- 
 graph station. 
 
 Toll System. A system of charging for 
 telephone communications based upon 
 telephone calls, as distinguished from a 
 charge based upon rental. 
 
 Tone. Any musical note of a definite fre- 
 quency. 
 
 Tongue of Relay. The tip or extremity 
 of the armature, carrying a contact point. 
 
 Tooling. The operation of shaping a 
 gutta-percha covered joint by the appli- 
 cation of a warm tool to its surface. 
 
 Toothed-Core Armature. A laminated 
 armature-core whose toothed discs pro- 
 
Too.] 
 
 964 
 
 [Toil. 
 
 vide longitudinal grooves on the surface 
 of the armature for the reception of the 
 armature coils. 
 
 Toothed-Core Discs. The discs employed 
 in a toothed-core armature. 
 
 Toothed-Drum Armature. A drum- 
 shaped form of toothed-core armature. 
 
 Toothed-Ring Armature. A ring- 
 shaped form of toothed-core armature. 
 
 Top-Hat Curve. A curve of electro- 
 motive force, current or flux which lias 
 the shape of a top hat, that is, in which 
 the value is fairly constant for a consid- 
 erable time at its maximum rise and fall. 
 
 Topler-Holtz Machine. A form of elec- 
 trostatic induction, or influence, machine. 
 
 Torch Signalling. A form of flash sig- 
 nalling. 
 
 Tore. A toroid. 
 
 Toroid. A solid of revolution bounded by 
 a surface generated by revolving any 
 closed plane curve about an axis in its 
 plane which does not cut it. 
 
 Toroidal Coil. <1) A coil wound in the 
 form of a toroid. (2) A closed circular 
 solenoid. 
 
 Toroidal Current-Sheet. A uniform 
 current-sheet having the form of a 
 toroid. 
 
 Torpedo Boat. A boat used for carrying 
 and discharging torpedoes. 
 
 Torpedo Cable. (1) A cable in the circuit 
 of which a torpedo fuse is placed. (2) A 
 cable designed for use with a torpedo. 
 
 Torpedo, Electric. (1) A name some- 
 times given to an electric ray. (2) An 
 electrically operated torpedo. 
 
 Torpedo Nets. Steel-wire netting sus- 
 pended from or attached to a ship's side 
 for the purpose of ensuring protection 
 against moving torpedoes. 
 
 Torque. (1) The moment of a force ap- 
 plied to a dynamo or other machine which 
 causes its rotation. (2) The mechanical 
 rotary or turning force which acts on the 
 armature of a dynamo-electric machine, 
 or motor, and causes it to rotate. (3) The 
 ratio of the mechanical activity of a 
 motor, at its belt or pulley, to the angular 
 velocity. 
 
 Torque Efficiency. The ratio of the 
 torque exerted by a motor at a given in- 
 put or terminal electric activity, to the 
 torque it would exert if it were a perfect 
 machine and had no loss of energy. 
 
 Torqueless Stress. A twistless stress, or 
 stress which produces no torque. 
 
 Torricellian Vacuum. The vacuum 
 which exists above the surface of the 
 
 mercury in a barometer tube, or other 
 vessel over thirty inches in vertical 
 height, which has been filled with boiled 
 mercury and inverted below the, surface 
 of the mercury in a vessel. 
 
 Torsibility. Possessing the ability of be- 
 ing torsed or twisted. 
 
 Torsion. The twisting of a body by the 
 application of a torsional force. 
 
 Torsion Galvanometer. A galvanom- 
 eter in which the strength of a deflecting 
 current is measured by the torsion exerted 
 on the suspension system. 
 
 Torsional Rigidity of Fibres. The 
 elastic couple set up in a fibre per unit of 
 twist. 
 
 Torsional Vibration. The vibration pro- 
 duced in a solid body by torsion. 
 
 Total Candle-Power. A term some- 
 times used for the total quantity of 
 light emitted by any luminous source. 
 
 Total Contact. A full or metallic contact. 
 
 Total-Current-Panel of Switchboard. 
 That panel of a switchboard which is pro- 
 vided with devices for measuring and con- 
 trolling the total current generated by a 
 station. 
 
 Total Disconnection. (1) Any discon- 
 nection effected by the opening of a 
 switch or the actual breaking of a circuit. 
 (2) A complete loss of continuity in a cir- 
 cuit. 
 
 Total Earth. A term sometimes used for 
 dead earth. 
 
 Total Efficiency of Luminous Source. 
 The ratio of the luminous rays to the 
 total energy expended. 
 
 Total Intensity of Earth's Magnetism. 
 
 (1) The resultant or entire force of the 
 earth's magnetism, as distinguished from 
 the horizontal or vertical components. 
 
 (2) The flux density of the earth's mag- 
 netism. 
 
 Total Magnetic Induction. (1) The 
 number of lines of magnetizing force 
 which pass through any space where 
 magnetizable material is ,_iaced. to- 
 gether with the lines added by the mag- 
 netization of the magnetic material. 
 (2) Total magnetic intensity, or in- 
 duction density, in a magnetized sub- 
 stance. 
 
 Total Resistance. The sum <A Mie re- 
 sistances of a circuit. 
 
 Tourmaline. A crystalline body consist-- 
 ing of natural silicates and borates of 
 alumina, lime, iron, etc. , possessing pyro- 
 electric properties. 
 
Tou.] 
 
 965 
 
 [Tra. 
 
 Tourniquet, Electric. A term some- 
 times used for an electric flyer. 
 
 Tower, Electric. A high tower, provided 
 in systems of tower illumination, for the 
 support of a number of electric arc-lamps. 
 
 Tower-System of Electric Lighting. 
 
 The lighting of extended areas by means 
 of arc lights placed on the tops of tall 
 towers. 
 
 Tower Wagon. The repair wagon em- 
 ployed on trolley lines, and provided with 
 a structure for enabling the workmen to 
 conveniently reach the trolley wires. 
 
 Towing, Electric. Electric hauling of 
 canal boats. . 
 
 Towing Torpedo. A torpedo arranged 
 to be towed after a vessel, and exploded 
 when it strikes the side of an enemy's 
 vessel. 
 
 Track Bond. A rail bond. 
 
 Track Instrument. An electric contact 
 capable of being closed by a train moving 
 over it, placed by the side of a railroad 
 track, and employed to sound an alarm 
 or indicate at a distance the presence of 
 the train. 
 
 Track Joint. A rail joint. 
 
 Track Switch. (1) A switch for leading a 
 car from one track to another. (2) A 
 mechanical switch in the rail of a street- 
 car track for changing the route of a car. 
 
 Track-to-Dynamo Bonding. A method 
 of bonding in which a track of positive 
 polarity is bonded to the negative side of 
 a dynamo. 
 
 Traction, Electric. The propulsion of a 
 car, or other vehicle, by the action of an 
 electric motor. 
 
 Trailer. (1) An ordinary car attached to 
 a trolley car and drawn after it. (2) Any 
 car hauled by a motor car. 
 
 Trailer Grapnel. A second or following 
 grapnel attached to and travelling behind 
 an ordinary grapnel. 
 
 Trailing Pole. (1) The following pole 
 edges of a dynamo-electric machine. (2) 
 The pole edges of a dynamo-electric ma- 
 chine, from which a point on the surface 
 of the armature moves when midway be- 
 tween the poles. 
 
 Train Describer. (1) An electric contriv- 
 ance arranged for automatically indicat- 
 
 , ing the position of trains on a railroad. 
 (2) In a system of block signalling by 
 electricity, an instrument for indicating 
 at a distance the character of a train 
 which is being sent along the line. 
 
 Train Wire. A line wire connected with 
 the general despatcher's office, employed 
 
 in a block system of railroads, and used 
 for sending train orders only. 
 
 Trajectory. (1) The curve described by a 
 pi'ojectile thrown obliquely upwards. (2) 
 A curve which cuts, according to a given 
 law, a system of curves obtained by vary- 
 ing a parameter. 
 
 Tramcar, Electric. A term applied to 
 an electric trolley car. 
 
 Tramway, Electric. A term applied tc 
 an electric railway . 
 
 Trans-Continental 1'elephony. Tele- 
 phonic communication established across 
 a continent. 
 
 Transfer Board. In telephony, a switch- 
 board at which calls are transferred from 
 one junction line to another. 
 
 Transfer Bus-Bar. A bus-bar that is em- 
 ployed to gradually transfer a feeder 
 from one bus-bar to another, without the 
 sudden variation of potential which 
 would occur if it were thrown over di- 
 rectly. 
 
 Transfer Operator. In telephony, an op- 
 erator at a transfer board. 
 
 Transform. (1) To change or convert. 
 (2) To change or convert the electromo- 
 tive force, and, consequently, the current 
 strength in a circuit, by any means. (3) 
 To change the type of a current, as from 
 an alternating into a continuous current. 
 
 Transformation. The act of transform- 
 ing or changing. 
 
 Transformation of Electromotive 
 Force or Current. A change in the 
 value of an electromotive force or current 
 by any means. 
 
 Transformation of Electric Force. 
 (1 ) Transformation of electromotive 
 force. (2) Transformation of electric en- 
 ergy into some other form of energy. 
 
 Transformation of Heat. Transforma- 
 tion of heat energy into any other form, 
 of energy. 
 
 Transformer. An induction coil em- 
 ployed either for raising or for lowering 
 electric pressure. 
 
 Transformer Connection Board. A 
 board employed on a transformer for ease 
 in changing or inter-connecting its cir- 
 cuits. 
 
 Transformer Controller. (1) An appa- 
 ratus for operating or controlling a trans- 
 former. (2) A controller of pressure op- 
 erated on the principle of an alternating* 
 current transformer. 
 
 Transformer Fuse. A fuse employed 
 either in the primary or secondary circuit 
 of a transformer. 
 
Tra.] 
 
 966 
 
 [Tra. 
 
 Transformer Fuse-Block. A fuse-block 
 in or near a transformer case. 
 
 Transformer Guard. (1) A transformer 
 lightning-guard. (2) Any device for 
 automatically grounding the secondary of 
 a transformer on its accidental contact 
 with the primary. 
 
 Transformer Indicator-Diagram. A 
 
 set of diagrams automatically recorded on 
 a card, which give the instantaneous 
 values of the current and electromotive 
 force of a transformer circuit. 
 
 transformer Lightning- Arrester. A 
 form of lightning arrester designed for 
 the protection of transformers. 
 
 Transformer Lightning Guard. A 
 transformer lightning-arrester. 
 
 Transformer Motor. An induction mo- 
 tor. 
 
 Transformer Secondary Connection 
 Board. A separate transformer connec- 
 tion board provided for its secondary 
 circuits. 
 
 Transformer Stampings. Sheet steel 
 stampings of such shape as is suitable for 
 building up the laminated core of a trans- 
 former. 
 
 Transformer Sub-Station. A sub-sta- 
 tion where a number of transformers are 
 grouped, designed as a sub-centre of dis- 
 tribution. 
 
 Transforming. (1) Changing electric en- 
 ergy from lower pressure and higher cur- 
 rent to higher pressure and lower current 
 or vice-versA. (2) Changing the charac- 
 ter of a current. 
 
 Transforming Currents. Changing the 
 value of the current strength in any 
 circuit, with a corresponding opposite 
 change in pressure. 
 
 Transforming Down. Lowering the 
 pressure in a distribution circuit by means 
 of a step-down transformer. 
 
 Transforming Station. (1) In a system 
 of distribution by transformers, a station 
 other than a central station, where a num- 
 ber of transformers are placed in order to 
 supply a group of houses in that neighbor- 
 hood. (2) A transformer sub-station. 
 
 Transforming Up. Raising the pressure 
 in a distribution circuit, by means of a 
 step-up transformer. 
 
 Transient. (1) Momentary. (2) Lasting 
 or enduring but for a short time. 
 
 Transient Currents. Currents that are 
 of but momentary duration. 
 
 Transient Magnetomotive Force. (1) 
 A momentary magnetomotive force. (2) 
 
 A magneto-motive force produced by the 
 momentary passage of an electric current. 
 
 Trans-Illumination. Such an illumina- 
 tion of an interior cavity of the body as 
 to permit it to be visible through the in- 
 tervening portions of the body as a trans 
 lucent screen. 
 
 Transition Layer. A layer marking the 
 separation of two homogeneous bodies at 
 which the electric or magnetic proper- 
 ties pass with great rapidity from one 
 value to another. 
 
 Transition Resistance. (1) A term 
 sometimes used in electro-therapeutics 
 for a change in the value of a resistance 
 caused by polarization. (2) Resistance 
 residing in the contact surface between a 
 solid and a liquid, or between two solids. 
 
 Translator. A telegraphic translator or 
 repeater. 
 
 Translating Commutator. A term 
 sometimes used for translation commu- 
 tator. 
 
 Translating Device. A name frequently 
 given to an electro-receptive device. 
 
 Translating Telegraphic Station. 
 (1) A receiving station. (2) Any station 
 at which a telegraphic message is auto- 
 matically repeated into another circuit. 
 
 Translation Commutator. A name 
 sometimes given to a switch on a trans- 
 lating board. 
 
 Translation Lag. A lag due to the 
 traverse of an active conductor past a 
 magnet pole, whereby the current in the 
 conductor is displaced in the direction of 
 the motion, and produces a moving field, 
 the iron mass or body tending to accom- 
 modate itself to the direction of the flux 
 in the moving field. 
 
 Translator. An orthography for tran- 
 slator. 
 
 Translator Keys. Keys employed in a 
 translator for signalling on either circuit. 
 
 Translucence. Possessing the property 
 of transmitting light but of preventing 
 the outlines of objects from being seen. 
 
 Translucent. Possessing the property of 
 translucence. 
 
 Translucent-Disc Photometer. A 
 photometer in which the light to be meas- 
 ured is placed on one side of a partly 
 translucent and partly opaque disc, and 
 the standard candle, or other photometric 
 standard, is placed on the opposite side, 
 the intensity of the light being estimated 
 by the distance of the lights from the disc, 
 when an equal illumination is obtained 
 over both surfaces. 
 
Tra.] 
 
 967 
 
 [Tre. 
 
 Transmission Circuit, Electric. The 
 circuit employed to receive the apparatus 
 necessary in any transfer of electric en- 
 ergy from the generators to the receptive 
 devices. 
 
 Transmission Dynamometer. A dyna- 
 mometer in which the mechanical power 
 that is measured is transmitted to some 
 machine, as distinguished from a dyna- 
 mometer which measures and at the same 
 time absorbs the energy. 
 
 Transmission, Electric. The transfer- 
 ence of energy from one po^nt to another 
 by means of electric currents. 
 
 Transmission Insulator. (1) An insu- 
 lator employed on transmission lines. (2) 
 A high-tension insulator. 
 
 Transmission Line. A transmission cir- 
 cuit. 
 
 Transmission of Energy. The trans- 
 ference of energy from one point to an- 
 other. 
 
 Transmission of Electric Energy. The 
 transference of electric energy from one 
 point to another. 
 
 Transmitted Power. Power that is 
 transferred from one point to another. 
 
 Transmitter, Electric. (1) A general 
 name applied to the various electric ap- 
 paratus employed in telegraphy or tele- 
 phony to transmit or send electric im- 
 pulses over a line wire or conductor. 
 (2) Any electric-transmitting instrument, 
 as distinguished from a receiving instru- 
 ment. 
 
 Transmitting Magnet. The magnet em- 
 ployed in any transmitting instrument. 
 
 Transmitting Station. A station from 
 which any electric signals or impulses are 
 sent. 
 
 Transposing. In a system of telephonic 
 communication, a device for avoiding the 
 bad effects of mutual induction, by alter- 
 nately crossing equal lengths of consecu- 
 tive sections of the line. 
 
 Transposition. The transposing of a tele- 
 graph or telephone circuit. 
 
 Transposition Insulator. A special 
 form of insulator provided for the ready 
 transposition of a telephone circuit. 
 
 Transposition Joints of Telephone 
 Circuit. The joints employed on a tele- 
 phone circuit at the transposition in- 
 sulators. 
 
 Transverse Electromotive Force. An 
 electromotive force excited by a magnetic 
 field in a substance in which electric dis- 
 placement is occurring. 
 
 Transverse Vibration. A vibration in 
 
 an elastic medium in which the successive 
 particles move at right angles to the direc- 
 tion in which the wave is progressing 
 through the medium. 
 
 Travelling Derrick. A derrick sup- 
 ported on guideways, on a platform over 
 which it is movable, provided for shifting 
 or moving heavy masses through short 
 distances. 
 
 Travelling Dynamo. A dynamo mount- 
 ed on a movable platform. 
 
 Travelling Motor. (1) A motor placed 
 on a movable car or carriage, as distin- 
 guished from a stationary motor. (2) A 
 locomotor. 
 
 Travelling of Arc. An unsteadiness pro- 
 duced in the light of a carbon arc occa- 
 sioned by the shifting of the position of 
 the arc between the electrodes. 
 
 Traversing Motor, Electric. (1) A mo- 
 tor which moves regularly to-and-fro, 
 through a limited distance. (2) In an 
 electrically operated crane, the motor 
 which operates the traverse. 
 
 Tread of Car Wheel. The running face 
 of a car wheel, or the part that comes in 
 contact with the surface of the track. 
 
 Treated Coke Filament. A coke fila- 
 ment of an incandescent lamp that has 
 been subjected to the flashing process. 
 
 Tree-System of Parallel Distribution. 
 A system of parallel distribution of in- 
 candescent lamps, in which the main 
 conductors of the system resemble the 
 trunk of a tree, and the auxiliary leads 
 branch in various directions, somewhat 
 after the fashion of a spreading tree, the 
 lamps occupying the place of the twigs, 
 leaves and fruit. 
 
 Tree Insulator. (1) An insulator placed 
 on a tree for the support of an aerial wire. 
 (2) A variety of insulator suitable for at- 
 tachment to trees, and designed so as to 
 keep the conductor in normal position, 
 despite the movement of the tree. 
 
 Tree Wire. A special form of insulated 
 wire designed to resist the abrasion of 
 the insulating substance, when rubbed 
 against a rough surface, like the bark of 
 a tree. 
 
 Trega. A prefix for a trillion, or one mil- 
 lion millien, or 10 12 . 
 
 Tregadyne. A trillion dynes, or roughly 
 the weight of a thousand tons. 
 
 Tregerg. One trillion ergs, or 73,730 foot- 
 pounds at Greenwich ; or, approximately. 
 33 foot-tons. 
 
 Tregohm. One trillion ohms, or one mil- 
 lion megohms. 
 
Tre.J 
 
 968 
 
 [Tri. 
 
 Tregohm Galvanometer. A galvano- 
 meter which gives unit deflection through 
 a resistance of one tregohm, in circuit 
 with one volt. 
 
 Trembler. A name sometimes applied to 
 a trembling bell. 
 
 Trembler Bell. A trembling bell. 
 
 Trembling Bell. A form of vibrating or 
 automatic make-and-break contact bell. 
 
 Trevelyan Effect. A musical note 
 emitted under certain circumstances 
 when a mass of heated copper is supported 
 on thin edges on a block of cold lead. 
 
 Triad Atom. An atom whose valency or 
 atomicity is three. 
 
 Triangular Trip base Winding. A 
 word sometimes employed for the inter- 
 linked or three-wire triphase. 
 
 Triangular Triphaser. A triangularly 
 wound triphaser. 
 
 Tricro. A prefix signifying one trillionth 
 part, or 1CM 2 . 
 
 Tricro- Ampere. The one trillionth of an 
 ampere. 
 
 Tricro-Farad. The one trillionth of a 
 farad. 
 
 Tricron. One trillionth of a metre, or 
 KM 2 metre. 
 
 Tricrohm. The one trillionth of an ohm. 
 
 Trifilar Suspension. A suspension sup- 
 ported by three parallel fibres. 
 
 Trigonometrical. Of or pertaining to 
 trigonometry, or the science of angles, 
 their relations, and properties. 
 
 Trigonometrical Functions. Certain 
 quantities definitely related to angles 
 considered as independent variables. 
 
 Trigonometrically. In a trigonometri- 
 cal manner. 
 
 Trigonometry. That branch of mathe- 
 matical science which treats of angles and 
 their properties, in triangles or otherwise. 
 
 Trimmer. A name sometimes given to a 
 man who recarbons electric arc-lamps. 
 
 Trimming a Lamp. Re-carboning an 
 arc lamp. 
 
 Trimming a Wire. (1) Preparing a wire 
 for jointing or connecting to an instru- 
 ment. (2) Baring a wire of insulation 
 and cleansing its conducting surface. 
 
 Triode Working. A three-way mode of 
 telegraphic working by the Delany syn- 
 chronous multiplex telegraphic system. 
 
 Trip Indicator. A form of indicator in 
 which the indicator arm or drop is disen- 
 gaged by the tripping action produced by 
 
 the movement of the armature of an elec 
 tro-magnet. 
 
 Triphase. A word frequently employed 
 for three-phase. 
 
 Triphase Armature. A three-phase 
 armature. 
 
 Triphase Armature- Windings. Three- 
 phase armature windings. 
 
 Triphase Circuit. A three-phase circuit. 
 Triphase-Current. A three-phase cur- 
 rent. 
 
 Triphase Dynamo. A dynamo capable 
 
 of producing three-phase currents. 
 Triphase Generator. A triphase 
 
 dynamo. 
 Triphase Motor. A motor capable of 
 
 being operated by triphase currents. 
 Triphase Rotary-Field. A rotary field 
 
 produced by the simultaneous action of 
 
 triphase currents. 
 
 Triphase Rotary-Transformer. A ro- 
 tary transformer operated by, or produc- 
 ing three-phase currents. 
 
 Triphase Rotating-Magnetic Field. 
 A triphase rotary field. 
 
 Triphase Transformers. (1) Three sep- 
 arate transformers employed for chang- 
 ing the pressure on triphase circuits. 
 
 (2) A single transformer having three 
 separate triphase windings. 
 
 Triphase Alternating-Currents. 
 Three uniphase alternating-currents 
 whose phases are displaced with regard 
 to one another by one-third of a cycle. 
 
 Triphaser. A triphase generator. 
 
 Triple-Carbon Arc-Lamp. An arc- 
 lamp in which three carbon electrodes 
 are used. 
 
 Triple Connector. A connector suitable 
 for uniting the ends of three wires. 
 
 Triple Petticoat Insulator. An aerial 
 line insulator provided with a triple pet- 
 ticoat. 
 
 Triple-Pole Single-Throw Switch. 
 A single-throw switch having three 
 blades, and intended for closing three 
 circuits simultaneously. 
 
 Triple-Pole Switch. (1) A switch consist- 
 ing of a combination of three separate- 
 switches for opening or closing three cir- 
 cuits at the same instant. (2) A switch 
 employed to open or close three contacts. 
 
 (3) A switch employed to open or close 
 triphase circuits. 
 
 Triple-Truck Support. (1) A support 
 for a car body, consisting of three sep 
 rate trucks. (2) A radial-truot supportt 
 
Tri,] 
 
 969 
 
 [Tro, 
 
 Triplex Telephony. (1) The simultan- 
 eous telephonic transmission of three 
 distinct messages over the same wire in 
 the same direction. 
 
 Triply He-Entrant Armature Wind- 
 ing. An armature winding provided 
 with three independent conducting paths 
 or windings each of which is separately 
 re-entrant. 
 
 Tripod Roof Support. A roof-top sup- 
 port for a telegraph line, in the shape of 
 a tripod. 
 
 Tripping Coil. A coil forming part of the 
 mechanism of a circuit-breaker on the 
 switchboard of a central railroad station, 
 so arranged that when the current has 
 reached a certain predetermined value, 
 limited by the action of a spring, the trip- 
 ping mechanism is operated, thus break- 
 ing the circuit. 
 
 Trivalent. Possessing an atomicity or 
 valency of three. 
 
 Trolley. A rolling contact-wheel that 
 moves over a trolley line and carries off 
 the current required to drive the motor 
 cars. 
 
 Trolley Base. A base provided for the 
 support of a trolley pole, and furnished 
 with springs to preserve a firm contact 
 between the trolley and the trolley wire, 
 and also provided with a swivel joint for 
 readily reversing the direction of the 
 trolley pole. 
 
 Trolley Base-Frame. A trolley base. 
 
 Trolley Bus-Bar. In a railway power 
 station, the bus-bar connected with the 
 trolley system, as distinguished from the 
 bus-bar connected with the ground. 
 
 Trolley Car. A motor car in a system of 
 electric railroads employing a trolley 
 system. 
 
 Trolley Car-Controller. (1) A series-par- 
 allel controller. (2) A car-controller. 
 
 Trolley-Contact. The contact secured 
 between a trolley and the trolley wire. 
 
 Trolley-Cord. The cord attached to the 
 trolley pole or mast for removing it from 
 and placing it on the line. 
 
 Trolley-Crossing. (1) An insulating de- 
 vice, placed at the crossing of two trolley 
 wires, by which the trolley, while run- 
 ning on one line may cross the other with- 
 out coming into electrical contact with it. 
 (2) A plate supported at the crossing of 
 two trolley wires with guides to assist 
 the trolley wheel across it. 
 
 Trolley Crossing-Ear. An ear employed 
 at a trolley crossing. 
 
 Trolley Cross-Over. (1) An arrangement 
 
 for suspending the trolley wires at a 
 trolley crossing. (2) A trolley crossing. 
 Trolley Ear. A metal piece supported by 
 an insulator, to which the trolley wire ia 
 fastened. 
 
 Trolley Fork. The mechanism which 
 mechanically connects the trolley wheel 
 to the trolley pole. 
 
 Trolley Frog. (1) The device to which 
 the trolley wire is attached, employed for 
 causing a car to deviate from one line to 
 another. (2) A name given to the device 
 employed in fastening or holding together 
 the trolley wires at any point where the 
 wires branch, and properly guiding the 
 trolley along the trolley wire on the 
 movement of the car over the track, 
 under the action of the track switch. 
 
 Trolley Guard. A trolley wire guard. 
 
 Trolley Hanger. A device for support- 
 ing and properly insulating a trolley wire. 
 
 Trolley Harp. The metallic frame placed 
 on a trolley fork for supporting the trolley 
 wheel. 
 
 Trolley Ice-Clearer. A form of trolley 
 wheel suitable for removing ice or sleet 
 from a trolley wire. 
 
 Trolley Insulator. A name sometimes 
 applied to a trolley ear. 
 
 Trolley Insulated Crossing. An insu- 
 lated trolley crossing. 
 
 Trolley Mast. A term frequently used 
 for trolley pole. 
 
 Trolley Mechanism. (1) The device em- 
 ployed for carrying the current from the 
 trolley line to the motor in the car. (2) 
 A general mechanism, including the 
 trolley base, pole, wheel and rope. 
 
 Trolley Pole. A pole, or mast, of wood 
 or metal supporting the trolley and em- 
 ployed to carry a conductor from the car 
 to the trolley wire. 
 
 Trolley Section. (1) A single continuous 
 length of trolley wire. (2) A portion of a 
 trolley line insulated from adjoining por 
 tions and furnished with separate feed 
 wires. 
 
 Trolley Railway. An electrically oper 
 ated railroad employing a trolley. 
 
 Trolley Stand. (1) A word sometimes 
 used for a trolley base. (2) A support 
 provided for a trolley pole. 
 
 Trolley Strain-Insulator. An insulator 
 provided for the support of the strain 
 wires. 
 
 Trolley Strain- Wires. Wires employed 
 for attachment to lugs in the anchor 
 strain ear, for the purpose of maintaining 
 the trolley line taut. 
 
Tro.J 
 
 970 
 
 LTru, 
 
 Trolley Switch. (1) A switch placed on a 
 track for the purpose of changing the 
 car from one track to another. (2) An 
 overhead switch provided at a turn of a 
 trolley road for guiding the trolley to 
 another line when the frogs on the track 
 beneath have thrown the wheels of the 
 car into another track. 
 
 Trolley Three-Way Prog. A trolley 
 frog used where the line branches in 
 three directions. 
 
 Trolley Traction. Electric traction by 
 the trolley system. 
 
 Trolley Truck. The truck supporting 
 a trolley car and containing the car 
 motors. 
 
 Trolley Two-Way Frog. The ordinary 
 V-shaped trolley frog. 
 
 Trolley Wheel. (1) A metallic wheel 
 connected with the trolley pole and moved 
 over the trolley wire, for the purpose of 
 taking therefrom the current required 
 for driving the motor car. (2) The trolley. 
 
 Trolley Wire. The bare overhead wire 
 employed in a trolley system for supply- 
 ing the driving current to the car motors 
 through the intervention of the trolley 
 mechanism. 
 
 Trolley Wire Insulator. The insulator 
 provided for the support of a trolley wire. 
 
 Trolley Wire Splice. A joint or splice 
 employed in joining two ends of trolley 
 wires, consisting essentially in slipping 
 the ends in a tubular conductor and 
 then brazing them. 
 
 Trop. A proposed unit of entropy equal 
 to the quotient of one joule divided by one 
 degree Centigrade. 
 
 Truck for Car Motor. A support pro- 
 vided with wheels, and employed either 
 singly, or in connection with one or more 
 similar trucks, for the support of the car 
 body. 
 
 True Contact Force. The force or effect, 
 distinguished from the voltaic effect 
 which exists at the points of contact be- 
 tween two dissimilar metals. 
 
 True Galvanometer Constant. The 
 intensity of the field produced at the 
 centre of a galvanometer coil by a unit 
 current flowing through the coil. 
 
 True Ohm. (1) An ideal ohm having the 
 true theoretical value. (2) A term some- 
 times applied to the International ohm in 
 contradistinction to the B. A. or legal 
 ohm. 
 
 True Power. In an alternating-current 
 circuit the power which is represented 
 by the true watts, as distinguished from 
 
 the apparent power, or that represented by 
 the apparent watts. 
 
 True Resistance. The resistance which 
 a conductor offers to the passage of a cur- 
 rent, by reason of its dimensions and 
 resistivity, as distinguished from the 
 spurious resistance produced by a counter 
 electromotive force. 
 
 True Watts. The activity in an alternat- 
 ing-current circuit, as given by the read- 
 ing of a correctly calibrated wattmeter 
 connected with such circuit. 
 
 True Zero. An instrument or scale zero, 
 as distinguished from a false zero of a 
 galvanometer. 
 
 Trumpet, Electric. An electro-magnetic 
 buzzer whose sound is strengthened by a 
 trumpet- shaped resonator. 
 
 Trunion Screws. A pair of screws whose 
 opposed points form the pivots of a mov- 
 able shutter, armature, or other rotating 
 device. 
 
 Trunk Call. A telephone call transmitted 
 through a trunk wire. 
 
 Trunk Connection. A telephonic con- 
 nection established through a trunk wire. 
 
 Trunk Junction -Board. A junction 
 telephone switchboard for trunk wires. 
 
 Trunk-Line Wires. (1) Through wires 
 extended between two distant stations, 
 provided with receiving and transmitting 
 instruments a j . their ends only. (&) In 
 telephony,main line wires connecting two 
 terminal offices for connection to sub- 
 offices or subscribers. (3) A main line 
 wire connecting two important terminals 
 for receiving telephone traffic. 
 
 Trunk-Line Working. Telephone work- 
 ing embracing the use of trunk lines be- 
 tween central stations, as distinguished 
 from lines connecting a central station 
 with subscribers. 
 
 Trunk Operator. In telephony, an oper- 
 ator at a trunk switchboard. 
 
 Trunk Switchboard. In telephony, a 
 switchboard at which trunk lines termi- 
 nate. 
 
 Trunk Wire. (1) A trunk line wire. (2) 
 A main telephone wire. (3) A connect- 
 ing wire running from town to town, or 
 exchange to exchange, as distinguished 
 from a wire connected permanently tc a 
 subscriber. 
 
 Trunk Working. Telephonic or tele- 
 graphic transmission by means of trunk 
 line-wires. 
 
 Trunking - Out Telephone Switch- 
 board. A form of telephone switch* 
 board employed in long-distance working, 
 
Tru.] 
 
 971 
 
 [Twi. 
 
 Trunking Switchboard. A switchboard 
 in which a few subscribers only are con- 
 nected to the operator, thus enabling him 
 to obtain any other subscriber by means 
 of trunk wires extending to other sec- 
 tions. 
 
 Trunking Telephone System. (1) A 
 system of telephony employing trunk 
 wires. (2) A system of telephony in which 
 multiple switchboards are dispensed with, 
 and all calls are trunked from the in- 
 coming to the outgoing panel. 
 
 Trussed Pole. A pole which has been 
 strengthened against lateral pull by the 
 use of an outrigger and stays. 
 
 Trussed Standard. A standard which 
 has been strengthened to resist lateral 
 stresses by the use of an outrigger and 
 stays. 
 
 Tube of Flow. A word sometimes used 
 for a tube of force. 
 
 Tube of Force. An imaginary tube in 
 electrified or magnetized space, bounded 
 by lines of electrostatic or magnetic force, 
 and intersected by equipotential surfaces. 
 
 Tube of Induction. In a space occupied 
 by magnetic induction, an imaginary tube 
 of induction flux bounded by induction 
 lines. 
 
 Tube of Magnetic Force. In magnet- 
 ized space, a tube bounded by lines of 
 magnetic force. 
 
 Tubular Annunciator Drop. A special 
 form of telephone annunciator-drop in 
 the shape of a tube, and provided with 
 an iron-clad magnet. 
 
 Tubular Braid. A braid of fibrous insu- 
 lating material, woven in the form of a 
 tube, and provided for drawing over a 
 joint after the two wires have been con- 
 nected. 
 
 Tubular Conductors. Conductors in the 
 shape of tubes. 
 
 Tubular Connectors. Connectors in the 
 shape of tubes. 
 
 Tubular Current. (1) A term sometimes 
 applied to the current that traverses the 
 superficial portions only of a solid con- 
 ductor. (2) A current flowing through a 
 tube, or having a distribution such as 
 would be produced by flow through a 
 tube. 
 
 Tubular Electro-Magnet. An electro- 
 magnet of a tubular form. 
 
 Tubular Magnet. (1) A magnet in which 
 a single coil enclosing a core is surrounded 
 by an iron cylinder connected to the core 
 at one end by an iron base or yoke. (2) 
 A form of iron-clad magnet. 
 
 Tumbler Switch. A switch provided 
 with a double-contact knife-blade which 
 can be readily depressed by the movement 
 of a bolt lever placed at the top. 
 
 Tumbling Box. (1) A rotating box in 
 which metallic articles that are to be 
 electro-plated are placed, so as to be 
 polished by attrition against one another. 
 (2) A rotating box in which rough cast- 
 ings are placed for smoothing their sur- 
 faces by attrition. 
 
 Tuning-Fork Dynamo. An oscillatory 
 dynamo. 
 
 Tuning-Fork Interrupter. A reed in- 
 interrupter. 
 
 Tuning of Electric Circuit. Altering 
 the period of a circuit, or varying either 
 its capacity or self-induction, so as to 
 bring it in resonance with another circuit. 
 
 Tunnel Armature. An armature of a 
 dynamo-electric machine in which the 
 conductors are placed in holes, or nearly 
 closed grooves, beneath the external 
 surface of the core. 
 
 Turnbuckle. (1) An appliance for strain- 
 ing span wires. (2) A screw tightener 
 for a rod, guy, or line. 
 
 Turn-Out. (1) A short section of single 
 track which allows two cars to pass one 
 another on a single track line . (2) A short 
 side section placed at a station on a single- 
 track road for switching a car off the main 
 line so as to leave it clear. 
 
 Turn-Table, Electric. A table suitable 
 for show-windows revolved around a ver- 
 tical axis by means of an electric motor. 
 
 Turret-Turning Motor. A motor em- 
 ployed on board a war-ship for turning a 
 gun turret. 
 
 Turtle-Back Electro. A curved electro- 
 type employed for use in cylindrical 
 presses. 
 
 Twigs. (1) A term sometimes applied te 
 the branches or conductors connected 
 with the sub-mains in a system of incan- 
 descent distribution. (2) Sub-branches, 
 
 Twin-Carbon Arc-Lamp. A double-car- 
 bon arc-lamp. 
 
 Twin Conductors. Two parallel con- 
 ductors, laid side-by-side, and covered by 
 a simple coating of braid. 
 
 Twin Filament Lamp. A double-fila- 
 ment lamp. 
 
 Twin Wire. A conductor consisting of 
 two separate conductors bound together 
 by an insulating covering. 
 
 Twin- Wire Circuit. A circuit formed 
 of twin conductors. 
 
Twi.] 
 
 972 
 
 [Two. 
 
 Twist System. A system of running 
 overhead wires for the purpose of destroy- 
 ing mutual inductive disturbances, and 
 consisting in giving to the wires a helical 
 twist as they run. 
 
 Twist in Armature Leads. A displace- 
 ment of the ends of the armature wires 
 connected with the commutator seg- 
 ments, as regards the position of the coils 
 on the armature, for the purpose of ob- 
 taining a more convenient position for 
 the diameter of commutation, and, con- 
 sequently, for the points of contact of the 
 collecting brushes on the commutator. 
 
 Twist in Leads. A twist given at regu- 
 lar intervals, to the leads of twin con- 
 ductors, for the purpose of avoiding the 
 effects of induction. 
 
 Twisted Bunched-Cable. A bunched 
 cable, the separate conductors of which 
 consist of twisted pairs placed in succes- 
 sive layers. 
 
 Twisted Double-Conductors. A pair 
 or a number of pairs of twisted twin con- 
 ductors. 
 
 Twisted Pair Cable. A cable contain- 
 ing one, several, or many twisted pairs of 
 conductors, suitable for metallic circuits. 
 
 Twisted Pairs of Conductors. An 
 assemblage of twisted pairs of con- 
 ductors, for metallic circuits. 
 
 Twisted Strip- Voltmeter. A voltmeter 
 consisting of a twisted strip of platinum- 
 silver, and operating by the tendency of 
 the strip to coil or uncoil when its tempera- 
 ture is changed by the passage through 
 it of the current to be measured. 
 
 Twisted Wire-Clip. A clip formed of a 
 twisted wire. 
 
 Twisted Wires. A term sometimes em- 
 ployed for transposed aerial telephone 
 wires. 
 
 Twisting Force. A term sometimes used 
 for torque. 
 
 Two-Bearing Generator. A generator 
 whose rotor is provided with but two 
 bearings, as distinguished from a three- 
 bearing generator. 
 
 Two-Bearing Motor. A motor whose 
 rotor is provided with but two bearings, 
 as distinguished from a three-bearing 
 motor. 
 
 Two-Circuit Armature-Winding. An 
 armature winding which provides only 
 two circuits through an armature be- 
 tween the commutator brushes, no matter 
 how great may be the number of poles. 
 
 Two-Circuit Dynamo. A dynamo pro- 
 vided with a two-circuit armature wmdr 
 ing. 
 
 Two-Circuit Multiple - Winding. A 
 multiple winding on an armature, each 
 component of which offers two circuits 
 to the current. 
 
 Two-Circuit Single-Wound Armature. 
 A single-wound armature possessing two 
 circuits independently of the number of 
 poles and distinguished by the fact that 
 the pitch is always forward. 
 
 Two-Coil Armature- Win ding of Alter 
 nator. A winding providing two slots 
 in drum armatures or two coils in ring 
 armature, for each and every pole in the 
 field frame. 
 
 Two-Coil Armature- Winding of Mul- 
 tiphase Alternator. A winding pro- 
 viding two slots in drum armatures, or two 
 coils in ring armatures, per phase, for 
 each and every pole in the field frame. 
 
 Two-Fluid Voltaic Cell. A double-fluid 
 voltaic cell. 
 
 Two-Layer Amature- Winding. (1) A 
 winding which is essentially applied in 
 two layers. (2) A winding having more 
 than two layers, but which would be 
 capable of application in two layers only. 
 
 Two-Liquid Cell. A term sometimes 
 used for double-fluid cell. 
 
 Two-Part Commutator. A commutator 
 containing two segments suitable for com- 
 muting currents in a single coil rotated 
 in a bipolar field. 
 
 Two-Phase Alternator. A diphase al- 
 ternator. 
 
 Two-Phase Armature. A diphase arma- 
 ture. 
 
 Two-Phase Circuit. A diphase circuit. 
 Two-Phase Dynamo or Generator. 
 A diphase generator. 
 
 Two-Phase Motor. A diphase motor. 
 Two-Phase Rotary - Transformer. A 
 
 diphase rotary transformer. 
 
 Two-Phase-Three-Phase Transformer. 
 An alternating-current transformer for 
 transforming from two-phase currents to 
 three-phase currents. 
 
 Two-Phase Transformer. A diphase 
 transformer. 
 
 Two-Phase Working. Transmitting 
 electric power by means of diphase cur- 
 rents. 
 
 Two-Phaser. (1) A generator of diphase 
 or quarter-phase alternating-currents. 
 (2) A diphaser. 
 
 Two-Point Switch. A switch by means 
 of which a circuit can be completed 
 through two different contact points. 
 
 Two-Point Trolley Switch. A trolley 
 
Two.J 
 
 973 
 
 [Unb. 
 
 switch provided for a bifurcation in a 
 road. 
 
 Two-Pole Dynamo-Electric Machine. 
 A dynamo-electric machine whose field 
 is produced by two poles. 
 
 Two, Three, or Pour-Conductor Cable. 
 A cable containing two, three or four 
 separate conducting wires. 
 
 Two-Way Door-Trigger. A trigger 
 which operates both when the door is 
 opened and when it is closed. 
 
 Two- Way Splice-Box. A splice box 
 provided with two tubular conduits or 
 ways. 
 
 Two- Way Switch. A switch provided 
 with two contacts connected with two 
 separate and distinct circuits. 
 
 Two- Wire Distributing Board. A dis- 
 tributing board for metallic circuits. 
 
 Two- Wire Incandescent Lighting. 
 Incandescent lighting from a single pair 
 of mains, as distinguished from three- 
 wire incandescent lighting. 
 
 Two-Wire Mains. A name for the 
 mains employed in the ordinary system 
 of multiple distribution, as distinguished 
 
 from a three-wire main, or that used in a 
 three-wire system. 
 
 Two- Wire Moulding. A moulding pro- 
 vided with two grooves, and employed for 
 the reception of two-wire mains or bran- 
 ches. 
 
 Two-Wire Multiple-Switchboard. A 
 multiple telephone switchboard in which 
 the jacks of a subscriber's circuit are con- 
 nected by two wires. 
 
 Two- Wire Switchboard. A telephone 
 switchboard with two-wire connections. 
 
 Tying-In of Line Wire. Securing aline 
 wire to its insulator. 
 
 Type-Printing Telegraphy. Printing 
 telegraphy. 
 
 Type-Printing Telegraphic Transmit- 
 ter. A transmitter employed in printing 
 telegraphy. 
 
 Typewriter, Electric. A typewriting 
 machine in which the keys are only in- 
 tended to make the contacts of circuits 
 of electro-magnets, the attractions of 
 whose armatures cause the movement of 
 the type levers required for the work of 
 printing. 
 
 u 
 
 TJ. A contraction sometimes employed for 
 
 unit. 
 Ultimate Capacity of Switchboard. 
 
 The total number of subscribers that a 
 
 multiple telephone switchboard can be 
 
 made to accommodate. 
 
 Ultimate Optical Efficiency. A term 
 sometimes employed for the conditions 
 required to ensure the greatest efficiency 
 in the observation of small angular de- 
 flections of a suspended mirror by prop- 
 erly proportioning the dimensions of dif- 
 ferent parts of the system. 
 
 Ultra-Gaseous Matter. (1) The peculiar 
 condition of the matter which consti- 
 tutes the residual atmospheres of high 
 vacua. (2) Radiant matter. 
 
 Ultra-Incandescent Lamp. An incan- 
 descent lamp in which the filament is 
 covered with oxides of thorium, etc., so 
 that their radiative powers are utilized 
 by the glowing filament. 
 
 Ultra-Thermal Lightning Arrester. 
 An arrester for protecting instruments 
 from unduly powerful currents, operated 
 by the expansion of a metallic wire placed 
 in the line circuit. 
 
 Ultra-Ultra- Violet. A term proposed If ot 
 luminous frequencies far beyond the vio- 
 let in the spectrum. 
 
 Ultra- Violet Bays. A term proposed 
 for rays whose frequencies are greater 
 than that of violet light. 
 
 Ultra-Violet Spectrum. That portion 
 of the spectrum which lies beyond the 
 violet, or whose frequencies are greater 
 than that of the violet. 
 
 Umbrella Type of Generator. A type 
 of generator in which an umbrella-shaped 
 rotor is revolved around the stator or 
 stationary element. 
 
 Umbrella Springs. In telephone switch- 
 board plugs, contact-springs pressing out 
 sideways from the plug, like umbrella 
 springs. 
 
 Unbalanced Load. In a system of elec- 
 tric distribution, a load whose distribu- 
 tion is unsymmetrical. 
 
 Unbalanced Polyphase System. A 
 polyphase system in which the load and, 
 therefore, the pressures and currents, are 
 not symmetrically distributed. 
 
 Unbattery . <1) To disconnect from a bat 
 tery. (2) To remove a battery from a car. 
 
Unto.] 
 
 974 
 
 [Und. 
 
 carriage, boat, building, device or recep- 
 tacle. 
 
 Unbuilding of Dynamo. The loss of 
 magnetization of a dynamo field. 
 
 Undemagnetizable. A term applied to 
 an electro-magnetic railroad signal, whose 
 signals are unreversible by atmospheric 
 causes. 
 
 Underframe. A truck of an electric mo- 
 tor car. 
 
 Underground Cable. A cable suitable 
 for being placed underground. 
 
 Underground-Cable Support. (1) Any 
 support provided in a subway for holding 
 an underground cable. (2) A support 
 provided for holding a cable where it 
 passes around the side of a manhole, un- 
 derground conduit, or other similar loca- 
 tion. 
 
 Underground-Cable Terminal. (1) The 
 place where an underground cable 
 emerges from the ground. (2) A cross- 
 connecting or distributing board placed 
 where an underground cable enters or 
 leaves the ground, in order to facilitate 
 the making and changing of the connec- 
 tions. 
 
 Underground Conductor. An electric 
 conductor placed underground, either by 
 actual burial, or by passing it through 
 underground conduits or subways. 
 
 Underground Electric Conduit. 
 (1) An underground pipe or tube provided 
 with a number of separate ways or ducts 
 for the reception of electric wires or 
 cables. (2) An underground passage- way 
 or space provided for the reception of 
 electric wires or cables. 
 
 Underground Electric Tube. An iron 
 pipe containing three insulated conduc- 
 tors separated from one another and from 
 the pipe by means of a bituminous insul- 
 ating substance, employed in connection 
 with the Edison three-wire system of dis- 
 tribution. 
 
 Underground Railway. A name some- 
 times applied to an under-running trolley 
 system. 
 
 Underground Telegraph. (1) A tele- 
 graph, a large portion of whose circuit 
 consists of underground wires or conduc- 
 tors. (2) A telephone cable provided for 
 use underground. 
 
 Underground Telephone Cable. A 
 subterranean telephone cable, as distin- 
 guished from an aerial telephone cable. 
 
 Underground Trolley System. A 
 system of car propulsion in which the 
 trolley wheel is replaced by a plow or 
 sled that is pushed before, or drawn after, 
 
 the car along a trolley wire placed inside 
 a slotted underground conduit. 
 
 Underground Tube. An underground 
 electric tube. 
 
 Under-Running of Cable. The opera- 
 tion of passing a shallow-water cable over 
 a boat, barge or vessel for the purposes of 
 examination, by hauling the cable in at 
 the bows, and allowing it to pass out at 
 the same time over the stern ; or, simply 
 allowing it to run over a sheave while the 
 boat is urged along the line of cable. 
 
 Under -Running of Incandescent 
 Lamps. The operation of incandescent 
 lamps at a pressure below the normal. 
 
 Under-Running Sheave. A supported 
 sheave for the admission of a bight of 
 cable, and suitable for use in underrunning 
 as distinguished from a sheave through 
 which an end must be passed. 
 
 Under-Running Trolley. (1) A trolley 
 wheel running under a wire in the usual 
 way. (2) A word sometimes used for un- 
 derground underrunning trolley. 
 
 Under-Running Trolley. A system of 
 street-car propulsion in which the trolley 
 wire is suitably supported in an under- 
 ground slotted conduit, the current being 
 taken off by means of a sled or shoe, 
 pushed before or drawn after the car. 
 
 Undertaker. (1) One who supplies elec- 
 tric energy to consumers. (2) A word 
 sometimes used in electric lighting litera- 
 ture for those who are ready to deliver 
 electric energy to consumers. 
 
 Under-Type Magnet. A horse-shoe 
 magnet of the vertical type, whose arma- 
 ture is placed near the lower end. 
 
 Undulating Current. (1) A name some- 
 times given to an undulatory current. (2) 
 V current of constant direction but contin- 
 uously varying strength. 
 
 Undulation. A wave or vibration, es- 
 pecially electric. 
 
 Undulator. A form of rotating commu- 
 tator employed for the use of transform- 
 ers on continuous-current circuits. (2) A 
 commutating device for the operation of 
 alternating-current apparatus from a 
 continuous-current circuit. 
 
 Undulatory Currents. Currents of con- 
 stant direction whose strength gradually 
 changes. 
 
 Undulatory Discharge. (1) A discharge 
 whose strength gradually changes with- 
 out change of direction. (2) A term 
 sometimes used for an oscillatory dis- 
 charge. 
 
 Undulatory "Winding. A name fre- 
 quently given to a wave winding. 
 
line. 
 
 975 
 
 [Uni. 
 
 Unevenly Distributed Armature 
 Winding. A winding in which the 
 slots do not recur at equal intervals 
 around the periphery of the armature. 
 
 Unflashed Filament. A lamp filament 
 that has not been subjected to the flashing 
 process. 
 
 Hnfooting. A layer of broken stone, 
 gravel and concrete, placed in layers and 
 rammed, and employed at the bottom of a 
 foundation trench for receiving the ma- 
 sonry work. 
 
 TTngilding Bath. A stripping bath suit- 
 able for the removal of a coating of gold. 
 
 Uni-Coil Alternating-Current Arma- 
 ture-Winding. A winding providing 
 one slot or coil on the armature for each 
 and every pole in the field frame. 
 
 Uni-Coil Multiphase Armature- Wind- 
 ing. A multiphase armature winding 
 providing one slot or coil per phase for 
 each and every pole in the field frame. 
 
 Uni-Directed Currents. (1) Currents 
 that have been caused to take the same 
 direction by means of a commutator. 
 (2) Commuted currents. 
 
 Uni-Directed Electromotive Forces. 
 
 Unidirectional electromotive forces. 
 Unidirectional. Possessing the same 
 direction. 
 
 Unidirectional Discharge. An electric 
 discharge which preserves the same direc- 
 tion from the beginning to the end of the 
 discharge. 
 
 Unidirectional Electromotive Forces. 
 Similarly directed electromotive forces. 
 
 Unidirectional Leak. A gradual loss 
 or leakage of electricity which takes place 
 in the same direction. 
 
 Unifilar Suspension. Suspension by 
 means of a single wire or thread. 
 
 Uniform Density of Field. A field in 
 which the density is the same in all equal 
 areas of similar cross-section, 
 
 Uniform Flux. Uniform magnetic-flux. 
 
 Uniform Magnetic-Field. (1) A field 
 of uniform density. (2) A field traversed 
 by the same number of lines of magnetic 
 flux in all portions of area of normal 
 cross-section. (3) Magnetic flux in 
 straight lines and of uniform density. 
 
 Uniform Magnetic Filament. A term 
 sometimes applied to a magnetic fila- 
 ment. 
 
 Uniform Magnetic Flux. (1) A mag- 
 netic flux whose density is everywhere 
 the same. (2) The flux of a uniform 
 magnetic-field. 
 
 Uniform Magnetization. Such a mag- 
 netization of a rectangular or cylindrical 
 bar that equal areas of normal cross- 
 section are traversed by the same quan- 
 tity of magnetic flux. 
 
 Uniform Potential. (1) A potential 
 whose value does not vary from point to 
 point. (2) A constant potential. 
 
 Uniformly Distributed Current. (1) A 
 term sometimes employed in the sense of 
 a steady current. (2) A current having 
 the same density at all points in a cross- 
 section of a conductor. 
 
 Unigraph. A portable form of sending 
 and receiving Morse instrument in one 
 piece. 
 
 Uninsulated Return. (1) A return which 
 employs the earth only as a return cir- 
 cuit. (2) An earth-return. 
 
 Uni-Periodic Current. An alternating 
 current of a single frequency, as distin- 
 guished from a multi-periodic current. 
 
 Uniphase. Single phase. 
 
 Uniphase Alternator. An alternator 
 that produces uniphase currents. 
 
 Uniphase Armature. The armature of 
 a uniphase alternator. 
 
 Uniphase Armature-Winding. Such 
 an armature-winding as will produce uni- 
 phase alternating-currents. 
 
 CJniphase Circuit. Any circuit through 
 which uniphase or single-phase currents 
 are passing. 
 
 Uniphase Dynamo. A uniphase alter- 
 nator. 
 
 Uniphase Generator. A uniphase al- 
 ternator. 
 
 Uniphase Motor. An electric motor 
 capable of being operated by uniphase 
 currents. 
 
 Uniphaser. A term sometimes employed 
 for a uniphase alternator. 
 
 Uniplanar. Confined to a single plane. 
 
 Unipolar. Possessing a single pole. 
 
 Unipolar Alternator. An alternator 
 provided with a so-called single magnetic 
 pole. 
 
 Unipolar Armature. A dynamo-electric 
 machine armature whose polarity is not 
 reversed during its rotation in the field of 
 the machine. 
 
 Unipolar Dynamo. (1) A dynamo pro- 
 vided with a unipolar armature. (2) A 
 commutatorless, continuous-current dy- 
 namo. 
 
 Unipolar Electric Bath. An electro- 
 therapeutic bath in which the water 
 forms one of the electrodes of the source. 
 
Uni.] 
 
 976 
 
 [Uni, 
 
 and the other electrode is attached to a 
 metal rod fixed at a convenient height 
 above the body. 
 
 Unipolar Induction. (1) A term some- 
 times applied to the induction that occurs 
 when a conductor is so moved through a 
 magnetic field as to continuously cut its 
 lines of force. (2) The induction that 
 occurs in a commutatorless, continuous- 
 current dynamo. 
 
 Unipolar Magnet. A term proposed for 
 a magnet in the shape of a long bar, one 
 pole of which lies in the axis of rotation, 
 the axis being placed near to the other 
 pole which is balanced by a counterpoise. 
 
 Unipolar Stimulation of Nerve. The 
 stimulation of a nerve produced by the 
 application of a single electrode to that 
 nerve. 
 
 Uni-Slot Armature- Winding or Al- 
 ternator. An alternator armature- 
 winding in which a single slot is provided 
 for each and every pole in the armature 
 frame. 
 
 Unit Angle. (1) A radian. (2) An angle 
 equal to 57.29578 ; or, 57 17' 44.8" nearly. 
 (3) A degree, minute, second, grad, radian 
 or other unit of angular measure. 
 
 Unit Angular Velocity. (1) A radian 
 per second. (2) The velocity under which 
 a particle moving in a circular path 
 whose radius is equal to unity, would 
 traverse unit angle in unit time. (3) Any 
 angular velocity which describes a unit 
 angle in unit time. 
 
 Unit Difference or Potential of Elec- 
 tromotive Force. (1) Such a differ- 
 ence of potential between two points that 
 requires the expenditure of one erg of 
 work to bring a unit of positive electricity 
 from one of these points to the other, 
 against the electric force. (2) In the 
 practical system of units, the volt. 
 
 Unit Jar. A small Leyden jar sometimes 
 employed to measure, approximately, the 
 quantity of electricity passing into a Ley- 
 den battery or condenser. 
 
 Unit Magnetic-Pole. (1) A magnetic 
 pole whose strength is such that it would 
 act on a similar pole at a distance of one 
 centimetre with a force of a dyne. (2) 
 A magnetic pole of unit strength. 
 
 Unit of Acceleration. That accelera- 
 tion which will give to a body unit ve- 
 locity in unit time, as for example, a 
 centimetre-per-second per-second. 
 
 Unit of Activity. (1) A rate-of-doing- 
 work that will perform one unit of work 
 in each second. (2) In the C. G. S. sys- 
 
 tem, an activity of one erg-per-second. 
 (3) In the practical system, the watt. 
 
 Unit of Diviance. A term proposed for 
 unit of resistance to lines of electrostatic 
 force. 
 
 Unit of Electric Quantity. (1) A unit 
 quantity of electricity. (2) The quantity 
 of electricity conveyed by unit current 
 per second. (3) In the practical system 
 of units, the coulomb. 
 
 Unit of Electric Supply. (1) A unit, 
 provisionally adopted in England by the 
 Board of Trade, equal to a supply of one 
 thousand amperes flowing for one hour 
 under an electromotive force of one volt. 
 
 (2) The Board of Trade unit, or kilowatt- 
 hour. (3) An amount of electric energy 
 equal to 3,600,000 joules. 
 
 Unit of Electric Work. The joule. 
 
 Unit of Electrostatic Capacity. (1) 
 Such a capacity of a condenser, or con- 
 ductor, that an electromotive force of one 
 volt will charge it with a quantity of 
 electricity equal to one coulomb. (2) 
 The farad. 
 
 Unit of Force. (1) A force which acting 
 for one second on a mass of one gramme 
 will give it a velocity of a centimetre-per- 
 second. (2) In the C. G. S. system, the 
 dyne. 
 
 Unit of Heat. (1) The quantity of heat 
 required to raise a given weight of water 
 through one degree of the thermometric 
 scale. (2) The British, thermal unit or 
 the pound-degree-Fahrenbeit ; i. e., the 
 amount of heat required to raise one 
 pound of water one degree Fahrenheit. 
 
 (3) The greater calorie, or the amount of 
 heat required to raise the temperature of 
 one thousand grammes of water one de- 
 gree centigrade. (4) The smaller calorie, 
 or the amount of heat required to raise 
 the temperature of one gramme of water 
 one degree centigrade. (5) The joule ; or 
 the quantity of heat energy developed in a 
 second by the passage of a current of one 
 ampere through the resistance of one 
 ohm. 
 
 Unit of Illumination. The lux. 
 
 Unit of Inductance. (1) A unit of 
 length equal to one centimetre. (2) In 
 the practical system of units, a secohn? or 
 quadrant. (3) The henry. 
 
 Unit of Light. Such a light that collect- 
 ed at a single point, would produce unit 
 illumination at unit distance from such 
 point. 
 
 Unit of Luminous Intensity. The 
 British candle : or the intensity of light 
 emitted by a candle, of definite dimen- 
 
Uni.] 
 
 977 
 
 [Up-C. 
 
 sions and composition, burning at the 
 rate of two grains per minute. 
 Unit of Magnetic-Flux. The weber ; or, 
 the amount of flux which would pass 
 through a magnetic circuit whose reluc- 
 tance is one oersted, under a magne to- 
 motive force of one gelbert. 
 
 Unit of Magnetic Intensity. The gauss ; 
 or, a flux density of one weber-per-square- 
 centimetre of normal cross-section. 
 
 Unit of Magnetic Reluctance. The 
 oersted; or, the reluctance which is offered 
 to the passage of magnetic flux by a cubic 
 centimetre of air, when measured between 
 parallel faces. 
 
 Unit of Magneto-Motive Force. The 
 gilbert ; or, the magneto-motive force 
 which is required to act on a circuit in 
 order to cause one weber of flux to pass 
 through it against a reluctance, or mag- 
 netic resistance of one oersted. 
 
 Unit of Mass. The quantity of matter 
 in a standard gramme. 
 
 "Unit of Out-Put of Dynamo-Electric 
 Machine. (1) The unit of electric power 
 furnished by the current of a dynamo- 
 electric machine. (2) The kilowatt. 
 
 Unit of Photometric Intensity. The 
 intensity of light produced by a candle of 
 given dimensions and composition that 
 consumes two grains per minute. 
 
 Unit of Resistance. (1) Such a resistance 
 that unit difference of potential is re- 
 quired to cause the passage of unit cur- 
 rent strength through it. (2) In the 
 practical system of units, the ohm. 
 
 Unit of Self-induction. The unit of in- 
 ductance. 
 
 Unit Quantity of Electricity . (l)Such 
 a quantity of electricity as would pass 
 in one second through a circuit whose re- 
 sistance is one ohm under an electromotive 
 force of one volt. (2) The coulomb. 
 
 Unit Strength of Current. (1) Such a 
 strength of current that when passed 
 through a circuit one centimetre in length 
 arranged in an arc of a circle one centi- 
 metre in radius, will exert a force of one 
 dyne on a unit magnetic pole placed at 
 the centre. (2) In the practical system 
 of units, the ampere. (3) In the C. G. S. 
 system of units, ten amperes. 
 
 Unit of Power. Any unit which meas- 
 ures the rate at which energy is expended, 
 such as the erg-per-second, the foot- 
 pound-per-minute, the kilogramme- metre- 
 per-minute, the horse-power, etc. 
 
 Unit of Twist of a Fibre. Such a twist 
 that in unit of length of fibre a unit 
 angular twist is produced. 
 62 
 
 Units of Work. (1) The erg. (2) A dyne- 
 centimetre, or the amount of work done 
 when a force of one dyne acts through 
 a distance of one centimetre. (3) A foot- 
 pound, or the amount of work required to 
 raise one pound vertically through the 
 distance of one foot. 
 
 Univalent. (1) Possessing a valency or 
 atomicity of one. (2) Monovalent. 
 
 Universal Battery System. In teleg- 
 raphy or telephony, a system of employ- 
 ing one battery for the supply of a plur- 
 ality of circuits. 
 
 Universal Discharger. An apparatus 
 for sending the discharge of a Leyden 
 jar, or condenser, through any desired 
 circuit. 
 
 Universal Ether. (1) The luminiferous 
 ether. (2) The ether. 
 
 Universal Switch. A pin switchboard 
 composed of horizontal and vertical me- 
 tallic bars capable of inter-connection by 
 means of pins. 
 
 Unlighted Segment of Aurora. A term 
 frequently applied to the dark segment of 
 an aurora. 
 
 Unmarked End of Magnet. A name 
 formerly applied to the south-seeking pole 
 of a magnet. 
 
 Unmarked Pole of Magnet. The south- 
 seeking pole of a magnet. 
 
 Unmarked Magnet Pole. A name some- 
 times given to the south pole of a magnet. 
 
 Unplugging. Introducing the resistance 
 of a resistance box into a circuit by the 
 removal of the plug keys, 
 
 Unpolarized. Devoid of polarization. 
 
 Unsilvering Bath. A stripping bath, 
 suitable for the removal of a coating of 
 silver. 
 
 Unsymmetrical Polyphase Motor. A 
 polyphase motor provided with unsym- 
 metrical windings. 
 
 Untreated Filament. The filament of an 
 incandescent lamp that has not been sub- 
 jected to the flashing process. 
 
 Unvaring Current. (1) A current whose 
 strength does not vary from time to time. 
 (2) A current of constant strength and 
 direction. 
 
 Up-and - Down - "Working. In teleg- 
 raphy, a method of operating consisting 
 of sending a message over the line from 
 each end alternately, as distinguished 
 from batch working. 
 
 Up-Contact of Switch. A contact which 
 is made by the upward movement of a 
 switch. 
 
Up.] 
 
 978 
 
 [Tar. 
 
 Tip Lines. In Great Britain, lines in the 
 direction of the principal station on a 
 circuit, as distinguished from the down 
 lines. 
 
 Tip Side. In telegraphy in Great Britain, 
 that side nearer to the principal station of 
 a circuit, as distinguished from the down 
 side. 
 
 Upper Harmonics of Current. The 
 higher frequencies of a simple-periodic or 
 alternating current. 
 
 Upright Board. A telephone switch- 
 board whose surface is vertical, as dis- 
 tinguished from a flat board. 
 
 Upright Galvanometer. A galvano- 
 meter whose needle moves in a vertical 
 plane. 
 
 Uranium Rays. A phrase sometimes 
 employed for Becquerel rays. 
 
 Urban Telephony. Telephonic com- 
 munication between different portions of 
 the same city. 
 
 Urethral Electrode. An electro-thera- 
 peutic electrode suitable for treatment of 
 the urethra. 
 
 Useful Current. A name proposed for 
 the effective current in an alternating- 
 current circuit. 
 
 Useful Life of Incandescent Lamp. 
 The time during which an incandescent 
 lamp can furnish practical and operative 
 illumination. 
 
 Utilizing Apparatus. Any device by 
 means of which energy may be utilized. 
 
 V. A contraction for volt. 
 
 V. A contraction for volume. 
 
 V. A contraction sometimes used for ve- 
 locity. 
 
 v. (1) A symbol employed for the ratio 
 existing between the units of resistance 
 in the electrostatic and magnetic C. G. S. 
 system of units. (2) A velocity ratio. 
 
 V. A. A contraction sometimes used for 
 voltaic alternatives. 
 
 Vacuum. A space from which all, or 
 nearly all, traces of gas have been re- 
 moved. 
 
 Vacuum Lightning-Discharger. A 
 vacuum lightning protector. 
 
 Vacuum Lightning -Protector. A 
 lightning protector employing a vacuum 
 tube for carrying off high-pressure dis- 
 charges. 
 
 Vacuum Manometer. Any manometer 
 whose operation is independent of at- 
 mospheric pressure. 
 
 Vaccuum Pump. An air pump. 
 
 Vacuum -Tube Lighting. Artificial 
 illumination obtained by the passage of 
 electric discharges through vacuum 
 tubes. 
 
 Vacuum Tubes. (1) Glass tubes in 
 which the air or other gas has been par- 
 tially removed, and through which electric 
 discharges are passed for the production 
 of luminous effects. (2) A name some- 
 times applied to Crookes, Roentgen, or 
 other high-vacuum tubes. 
 
 Vaginal Electrode. An electro-thera- 
 
 peutical electrode suitably shaped for the 
 treatment of the vagina. 
 Valency. The combining value of a 
 chemical atom, as regards its power of 
 displacing other atoms in chemical com- 
 pounds. 
 
 Valve, Electric. An electrically-con- 
 trolled or operated valve. 
 
 Vapor. A gaseous substance produced by 
 the action of heat, or by reduction of pres- 
 sure, on a vaporizable liquid. 
 
 Vapor Globe of Incandescent Lamp. 
 A glass globe surrounding the chamber 
 of an incandescent lamp, for the purpose 
 of enabling it to be safely employed in an 
 explosive atmosphere, or to permit it to 
 be exposed in places where water is liable 
 to fall on it. 
 
 Vapor Pressure. The pressure at which 
 a liquid changes into a vapor. 
 
 Vaporization. The conversion of a vola- 
 tile liquid into a vapor, either as in evap- 
 oration at the surface of a liquid, or 
 throughout its mass, as in ebullition. 
 
 Variable Condenser. A term sometimes 
 employed for an adjustable condenser. 
 
 Variable Inductance. (1) The induc- 
 tance of a substance whose magnetic per- 
 meability is not constant. (2) An adjust- 
 able inductance. 
 
 Variable Period of Electric Circuit. 
 That period during whicli the current 
 strength is rising or falling in a circuit, 
 after the making or breaking of the same, 
 until the current strength is reached or 
 
Tar.] 
 
 979 
 
 [Ten. 
 
 until the line has been completely dis- 
 charged. 
 
 Variable Period of Electric Current. 
 The time which is required for an electric 
 current to reach its full strength after 
 the circuit is made, or for reaching zero 
 strength when its circuit has been opened. 
 
 Variable Period of Telegraph Line. 
 The time required for the current in a 
 telegraphic line to reach a constant 
 strength after the circuit through it has 
 been closed. 
 
 Variable Ratio Transformer. An alter- 
 nating-current transformer whose ratio of 
 transformation is subject to variation. 
 
 Variable Resistance. (1) A resistance, 
 the value of which can be readily varied 
 or changed. (2) An adjustable resist- 
 ance. 
 
 Variable State of Charge on Telegraph 
 Line. The condition of the charge on a 
 telegraph wire, while the strength of the 
 current is increasing up to its full 
 strength in all parts, or diminishing to 
 zero. 
 
 Variation Chart or Map. (1) A chart or 
 map on which the variations of the earth's 
 magnetism are marked. (2) An isogonic 
 chart. 
 
 Variation Magnetometer. A form of 
 magnetometer suitable for measuring 
 changes in the earth's magnetic variation 
 at any place. 
 
 Variation of Declination. A variation 
 in the magnetic declination of the earth 
 at any place. 
 
 Variation of Earth's Magnetism. Any 
 variation in the value of the magnetic 
 declination or inclination that occurs 
 simultaneously over all parts of the earth. 
 
 Variation of Magnetic Needle.^-(l) The 
 angular deviation of the magnetic needle 
 from the true geographical north. (2) The 
 declination of the magnetic needle. 
 
 Variometer. (1) An instrument for com- 
 paring the horizontal component of the 
 earth's magnetism in different localities. 
 (2) The magnetic variometer. 
 
 Varnish, Electric. A varnish formed of 
 any good insulating material. 
 
 Varley's Photometer. A form of pho- 
 tometer in which the intensity of the 
 light to be measured is determined from 
 the relative openings of two concentric 
 circular diaphragms placed in two rotat- 
 ing discs through which the standard light 
 and the light to be measured respectively 
 pass. 
 
 Varley's "Unit of Resistance. The re- 
 sistance of one statute mile of a special 
 
 copper wire ^th of an inch in diameter. 
 (No longer in use.) 
 
 Varying Continuous - Current. A di- 
 rect current whose strength varies from 
 time to time. 
 
 Varying Undirectional - Current. A 
 varying continuous or direct current. 
 
 Vector. (1) A directed quantity. (2) A 
 quantity possessing both direction and 
 magnitude. 
 
 Vector Diagram. A diagram represent- 
 ing the relations of vector quantities. 
 
 Vector Equations. Equations connect- 
 ing vector quantities. 
 
 Vector Formula. A formula containing 
 vector quantities. 
 
 Vector Impedance. The impedance of 
 an alternating-current circuit considered 
 as a vector or directed quantity. 
 
 Vector Potential. A potential possessing 
 direction, as well as magnitude, derived 
 by the process of summation of vectors 
 or elementary directed quantities, as op- 
 posed to a scalar potential, or one pos- 
 sessing undirected magnitude. 
 
 Vector Quantity. A quantity possessing 
 both direction and magnitude. 
 
 Vector Sum. The geometrical sum of 
 two or more vector quantities. 
 
 Vectorial Algebra. The algebra of vec- 
 tors or directed quantities. 
 
 Vehicle, Electric. (1) An electrically- 
 propelled vehicle. (2) An automobile 
 carriage. 
 
 Velocimeter. Any apparatus for measur- 
 ing the speed of a machine, or velocity 
 generally. 
 
 Velocity. The distance traversed by a 
 body in any time. 
 
 Velocity of Discharge. (1) The veloc- 
 ity with which a liquid or gas escapes 
 from an orifice in a given time. (2) The 
 time required for the passage of a dis- 
 charge from a given length of conductor. 
 
 Velocity of Transmission of Signal- 
 ling. The apparent speed of transmis- 
 sion of signals over a telegraph circuit. 
 
 Velocity Ratio. (1) A ratio of the na- 
 ture of a velocity that exists between the 
 dimensions of the electrostatic and elec- 
 tro-magnetic units. (2) The ratio between 
 the velocities of two mutually associated 
 or interconnected bodies or parts in 
 a machine. 
 
 Vena-Contracta. A contracted vein or 
 conical jet that exists in a jet of ^ water 
 escaping from a circular orifice in the 
 wall of a containing vessel. 
 
Ven,] 
 
 980 
 
 [Yir. 
 
 Ventilated Armature- Windings. Ar- 
 mature windings provided with means 
 for cooling by forcing currents of air over 
 them. 
 
 Ventilating Duct. A ventilating space. 
 Ventilating Groove. A ventilating space 
 or duct in an armature core. 
 
 Ventilation of Armature of Dynamo 
 or Motor. The renewal of air in the 
 armature chamber, due to the passage 
 through it of a stream of air employed 
 for the purpose of preventing too high a 
 temperature elevation during operation. 
 
 Verdet's Constant. The magneto-optic 
 constant of a transparent magnetized 
 substance, expressed in angular rotation 
 of the plane of polarization, for a lumin- 
 ous ray of definite frequency at a definite 
 temperature, between points on the ray 
 path whose magnetic potential differs by 
 unity. 
 
 Veriscope. A form of bioscope. 
 
 Vernier. A device for the more accurate 
 measurement of smaller differences of 
 length or angle than could be detected by 
 the eye alone, by means of the direct read- 
 ing of the position of a mark on a slid- 
 ing scale. 
 
 Vernier Caliper. A caliper possessing a 
 vernier scale provided for greater precis- 
 ion in observation. 
 
 Vernier Slides. A pair of resistance 
 slides one of which is connected in shunt 
 to a pair of contacts on the other. 
 
 Vernier Wire-Gauge. A micrometer 
 wire-gauge. 
 
 Vertical Component of Earth's Mag- 
 netism. That component of the earth's 
 directive force which acts in a vertical 
 direction. . 
 
 Vertical Electrostatic Voltmeter. 
 A form of voltmeter the needle of which 
 moves in a vertical instead of in a hori- 
 zontal plane. 
 
 Vertical Galvanometer. A galvanome- 
 ter whose needle is capable of motion in 
 a vertical plane only. 
 
 Vertical Intensity of Earth's Mag- 
 netism. (1) The vertical component of 
 the earth's magnetism. (2) The -force 
 which tends to cause a magnetic needle 
 to assume a vertical position. 
 
 Vertical Magnetic Needle. A magnetic 
 needle free to move in a vertical plane 
 only. 
 
 V. Frog. A trolley frog shaped like a 
 letter V. 
 
 Vibrating. Periodically moving to-and- 
 fro. 
 
 Vibrating Bell. A name sometimes 
 given to a trembling bell. 
 
 Vibrating Contact. (1) A spring con- 
 tact connected with one part of a circuit, 
 and so supported as to be able to vibrate 
 towards and from another part of the 
 circuit, thus automatically closing and 
 opening the same. (2) A form of auto- 
 matic contact-breaker. 
 
 Vibrating Electric Doublet. A source 
 of electro-magnetic waves consisting of 
 two equal and opposite oscillating charges 
 concentrated on two small conductors 
 whose distance from each other is indefi- 
 nitely small in comparison with the dis- 
 tance at which the resulting wave disturb- 
 ance is considered. 
 
 Vibrating Electrotome. An auto- 
 matic circuit-breaker producing a musi- 
 cal note. 
 
 Vibration. A complete to-and-fro move- 
 ment of a vibrating body. 
 
 Vibration Frequency. The number of 
 vibrations produced per second. 
 
 Vibration Needle. A tube containing 
 cylindrical weights for attachment to a 
 suspension for measuring the torsional 
 rigidity of the same. 
 
 Vibration Period. The period of a single 
 or whole vibration in a conductor in 
 which an oscillatory vibration is being 
 produced. 
 
 Vibrator. An electro-magnetic device 
 provided on a siphon recorder for main- 
 taining the siphon in continual vibra- 
 tion, so that ink is thrown from it on a 
 fillet of paper beneath. 
 
 Villari Critical Point. A term proposed 
 for that strength of magnetic field at 
 which the reversal of the effects of ten- 
 sion occurs. 
 
 Vine System of Space Relations. A 
 system of space relations, usually adopted 
 by electrical writers, which follows the 
 vine tendril ; i. e., which considers ad- 
 vance in the direction of a right-handed 
 rotation as positive. 
 
 Violle. A unit of luminous intensity pro- 
 duced in a perpendicular direction by one 
 square centimetre of platinum at the tem- 
 perature of its solidification. 
 
 Violle Lamp. The violle. 
 Virgin Iron. Iron that has never been 
 subjected to magnetization. 
 
 Virtual Amperes. (1) Amperes meas- 
 ured in an alternating-current as the 
 square root of the mean square of the 
 current, and determined by an ammeter 
 
Vir.] 
 
 981 
 
 [Vol. 
 
 calibrated by constant currents. (2) Ef- 
 fective amperes. 
 
 Virtual Conductance. A term some- 
 times employed for equivalent conduct- 
 ance. 
 
 Virtual Counter Electromotive Force. 
 Effective C. E. M. F. in an alternating- 
 current circuit. 
 
 Virtual Current. The virtual amperes. 
 
 Virtual Resistance. The apparent re- 
 sistance of a circuit. 
 
 Virtual Voltage. Voltage measured in 
 an alternating-current circuit as the 
 square root of the mean square of the 
 value in volts, as obtained by a voltmeter 
 calibrated by continuous currents. 
 
 Virtual Work. In a system of bodies or 
 material points, the amount of work 
 which would be done by the force acting 
 upon the bodies in an indefinitely small 
 displacement, and which work vanishes 
 when the system is in equilibrium. 
 
 Viscous Hysteresis. (1) The time lag 
 observed in magnetizing a bar of iron 
 which is neither referable to the induc- 
 tion in the iron nor to self-induction in 
 the magnetizing current, but to the mag- 
 netic viscosity of a substance. (2) A 
 sluggishness exhibited by iron for mag- 
 netization or demagnetization, due to 
 magnetic viscosity. 
 
 Visual. Of or pertaining to vision. 
 
 Visual Angle. An angle subtended be- 
 tween two lines drawn from an eye to 
 opposite extremities of an object. 
 
 Visual Clearing-Indicator. (1) An in- 
 dicator at a telephone exchange for in- 
 forming the operator that a conversation 
 has ended, by the lighting up of a little 
 incandescent lamp through a relay con- 
 tact. (2) A clearing indicator appealing 
 to the eye, as distinguished from an in- 
 dicator which releases a drop. 
 
 Visual Telegraphic Signals. Telegra- 
 phic signals that can be seen, as distin- 
 guished from those which can be heard. 
 
 Visual Telegraphy. (1) Any system of 
 telegraphy whose receiving instruments 
 give visual signals. (2) Needle telegraphy. 
 
 Vis- Viva. (1) The energy stored in a mov- 
 ing body. (2) The measure of the amount 
 of work that must be perfonned in order 
 to bring a moving body to rest. 
 
 Vitreous. Of or pertaining to glass. 
 
 Vitreous Electricity. A term formerly 
 employed for positive electricity. 
 
 Vitreous Electrification. A term for- 
 merly employed for positive electrifica- 
 tion. 
 
 Vitrite. A variety of insulating sub- 
 stance. 
 
 Volatilization, Electric. (1) A term 
 sometimes used instead of electric evap- 
 oration. (2) The volatilization of a con- 
 ductor under the influence of heat of 
 electric origin. 
 
 Volatilization of Electric Conductor. 
 The deflagration of an electric conductor 
 by electrically generated heat. 
 
 Volcanic Lightning. The lightning dis- 
 charges that attend most volcanic erup- 
 tions. 
 
 Volt. (1) The practical unit of electro- 
 motive force. (2) Such an electromotive 
 force as is induced in a conductor which 
 cuts lines of magnetic flux at the rate of 
 100,000,000 per second. (3) Such an elec- 
 tromotive force as would cause a current 
 of one ampere to flow against a resistance 
 of one ohm. (4) Such an electromotive 
 force as would charge a condenser of the 
 capacity of one farad with a quantity of 
 electricity equal to one coulomb. (5) 
 10 8 absolute electro-magnetic units of elec- 
 tromotive force. 
 
 Volt-Ammeter. (1) A name sometimes 
 given to any instrument capable of meas- 
 uring either the volts or the amperes in a 
 circuit, or both. (2) The measurer of the 
 volt-amperes or watts. (3) A wattmeter. 
 
 Volt- Ampere. The watt. 
 
 Volt Box. The name sometimes given to 
 a divided wire placed across the terminals 
 of a voltmeter to be tested. (2) A name 
 sometimes given to a resistance divided 
 into such sections that any suitable frac- 
 tional drop in potential in the entire re- 
 sistance can be readily measured by a po- 
 tentiometer. 
 
 Volt Indicator. A name sometimes given 
 to a voltmeter. 
 
 Voltage. The value of the electromotive 
 force or difference of potential of any part 
 of a circuit, expressed in volts. 
 
 Volta-Electric. Of or pertaining to volta- 
 electricity. 
 
 Volta-Electric Induction. A term 
 sometimes used for voltaic induction. 
 
 Volta-Electricity. A word sometimes 
 used for voltaic electricity. 
 
 Volta-Electrometer. A word sometimes 
 used for voltameter. 
 
 Volta -Electrometric. Of or pertaining 
 to a voltameter or to voltaic electricity. 
 
 Volta-Electr emotive Force . Voltaic 
 electromotive force. 
 
 Volta-Force. Contact force between dif- 
 ferent metals. 
 
Vol.] 
 
 982 
 
 [Vol. 
 
 Volta-Plast. An unnecessary word pro- 
 posed for a voltaic battery, used in electro- 
 plating. 
 
 Volta-Type. An unnecessary word pro- 
 posed for electro-type. 
 
 Volta's Law. The difference of potential 
 between any two metals is equal to the 
 sum of the difference of potential between 
 the intervening substances in the contact 
 series. 
 
 Voltagraphy. An unnecessary word 
 sometimes used for electro-typing. 
 
 Voltaic Accumulator. A term some- 
 times used for a secondary cell. 
 
 Voltaic Alternatives. (1) A term used 
 in medical electricity for the sudden re- 
 versals in the polarity of the electrodes of 
 a voltaic battery employed in electro- 
 therapeutics. (2) An alternating current 
 obtained from a voltaic battery by the use 
 of a suitable commutator. 
 
 Voltaic Arc. (1) A brilliant arc or bow of 
 light which appears between the elec- 
 trodes or terminals of a sufficiently power- 
 ful source of electricity, when placed in 
 contact and then separated a short dis- 
 tance from each other. (2) The source of 
 light of the electric arc-lamp. 
 
 Voltaic Balance. An apparatus employed 
 to measure the voltaic energy present in 
 any aqueous solution by balancing the 
 electromotive forces produced by two 
 small zinc-platinum couples immersed in 
 water and placed in series with the circuit 
 of a sensitive galvanometer, so as to bal- 
 ance one another, and then applying a solu- 
 tion of the substance whose energy is to be 
 measured to the liquid in one of the solu- 
 tions. 
 
 Voltaic Battery. The combination as a 
 single source of a number of separate vol- 
 taic cells. 
 
 Voltaic Battery Indicator. A device for 
 indicating the condition of a voltaic bat- 
 tery. 
 
 Voltaic Battery Protector. A device 
 for automatically opening the circuit of a 
 voltaic battery, whenever it becomes 
 accidentally grounded. 
 
 Voltaic Bow. A word sometimes used 
 for a voltaic arc. 
 
 Voltaic Capacity of Accumulator. A 
 term sometimes applied to the storage 
 capacity of an accumulator. 
 
 Voltaic Cell. (1) The combination of two 
 metals, or of a metal and a metalloid, 
 which , when dipped into a liquid or liquids 
 called electrolytes, and connected by a 
 conductor, will produce a current of elec- 
 
 tricity. (2) A voltaic couple and ita 
 accompanying electrolytes. 
 
 Voltaic Circle. A name formerly em- 
 ployed for voltaic cell or circuit. 
 
 Voltaic Circuit. The patli through which 
 the current flows from a voltaic cell or 
 battery through the translating devices 
 and back again through the cell or 
 battery. 
 
 Voltaic Couple. Any two materials, gen- 
 erally dissimilar metals, which are capa' 
 ble of acting as an electric source wheii 
 dipped into an electrolyte. 
 
 Voltaic Coupler. Any device by means 
 of which voltaic cells may be readily 
 coupled or connected in different varieties 
 of circuits. 
 
 Voltaic Effect. The difference of poten- 
 tial observed at the point of contact of 
 dissimilar metals. 
 
 Voltaic Electricity. The difference of 
 potential produced by a voltaic cell or 
 battery. 
 
 Voltaic Electromotive Force. A term 
 sometimes used for the electromotive 
 force generated at the electrodes of an 
 electrolytic cell in contradistinction to 
 the counter-electromotive force produced 
 at such electrodes before polarization. 
 
 Voltaic Elements. Two metals or sub- 
 stances which form a voltaic couple. 
 
 Voltaic Endosmose. A term sometimes 
 used for electric osmose or endosmose. 
 
 Voltaic Force. A word sometimes used 
 for voltaic electromotive force. 
 
 Voltaic Heat Cell. A cell by means of 
 
 which heat energy is changed or converted 
 
 into electric energy. 
 Voltaic Impulse. A word sometimes 
 
 used for the electromotive impulse of a 
 
 voltaic couple. 
 Voltaic Induction. A word sometimes 
 
 used for current induction. 
 
 Voltaic Magnet. An unnecessary term 
 sometimes employed for a solenoid or 
 electro-magnetic helix. 
 
 Voltaic Pair. A voltaic couple. 
 
 Voltaic Pile. A word sometimes used 
 for voltaic battery. 
 
 Voltaism. (1) A word sometimes em- 
 ployed in electro-therapeutics for treat- 
 ment by means of the voltaic current. 
 (2) The production of electricity by means 
 of voltaic couples. 
 
 Voltameter. An electrolytic cell em- 
 ployed for measuring the quantity of 
 electric current passing through it, by 
 the amount of chemical decomposition 
 affected in a given time. 
 
Vol.] 
 
 983 
 
 [Wai. 
 
 Voltameter Law. The amount of chemi- 
 cal action produced by electrolysis in any 
 electrolyte is proportional to the quantity 
 of electricity which passes through that 
 electrolyte. 
 
 Volta's Condensing Electroscope. An 
 electroscope whose leaves are charged by 
 means of a condenser, employed for the 
 detection of feeble charges. 
 
 Voltmeter. Any instrument employed 
 for measuring differences of potential. 
 
 Voltmeter Panel of Switchboard. The 
 panel of a switchboard containing a volt- 
 meter or voltmeters. 
 
 Voltmeter Switch. A switch for readily 
 and safely connecting a voltmeter with 
 any one of a number of circuits whose 
 pressures may have to be measured. 
 
 Volume Density, Electric. The amount 
 of electricity per unit of volume. 
 
 Volume Density of Charge. The elec- 
 tric volume-density. 
 
 Volume of Illumination. A term pro- 
 posed for a total quantity of illumination 
 comprised between a surface on a hori- 
 zontal plane, and the locus of the extremi- 
 ties of ordinates drawn vertically to each 
 part of that surface, in values represent- 
 ing the intensity of illumination at that 
 point. 
 
 Volume Specific Resistance.-^!) The 
 electric resistance of a cubic centimetre of 
 material measured between opposite faces 
 of the cube, and expressed in the C. G. S. 
 absolute system of units. (2) Volume re- 
 sistivity. (3) Specific resistance by vol- 
 ume as compared with the volume resist- 
 ance of a standard substance. 
 
 Volume Voltameter. A voltameter in 
 
 which the quantity of current passing is 
 determined by the volume of gas evolved. 
 
 Volumetric Energy. (1) Energy per 
 unit of volume. (2) The energy in any 
 substance or space divided by the volume 
 of the substance or space. 
 
 Vortex Atom. A hypothetical vortex in 
 the ether constituting an atom of a ma- 
 terial substance. 
 
 Vortex Cylinder. A cylindrically shaped 
 vortex ring. 
 
 Vortex Ether. An ether possessing in- 
 ertia and capable of forming vortices like 
 a frictionless liquid. 
 
 Vortex Ring. (1) A ring of vertically 
 moving matter. (2) A name sometimes 
 given to a motion in the air or other gross 
 matter, similar to that which is supposed 
 to constitute a vortex atom. 
 
 Vortex-Ring Field. The field of influ- 
 ence possessed by a vortex ring. 
 
 Vortex Stream Lines. Stream lines in 
 the ether or matter, constituting a vortex 
 atom or ring. 
 
 Vulca. A variety of insulating material. 
 
 Vulcabeston. A variety of insulating 
 substance composed of asbestos _ and rub- 
 ber. 
 
 Vulcanite. (1) A variety of vulcanized 
 rubber, possessing high powers of insula- 
 tion and specific inductive capacity. (2) 
 Ebonite. 
 
 Vulcanized Fibre. A variety of insulat- 
 ing material suitable for purposes requir- 
 ing the highest insulation. 
 
 Vulcanizing Wooden Poles. Subject- 
 ing poles to the action of heat while in a 
 closed cylinder. 
 
 w 
 
 W. A contraction for watt. 
 
 "W. A contraction for work. 
 
 W. A contraction for weight. 
 
 W. A contraction for physical energy, 
 whether electrical, thermal, mechanical 
 or chemical ; or, in general, for the pro- 
 duct of the force acting, and the distance 
 through which it acts. 
 
 W. A symbol for electric energy. 
 
 W. A symbol proposed for moment of a 
 couple. 
 
 W. H. E. A contraction for watt-hour 
 
 efficiency. 
 W. P. A contraction for waterproof. 
 
 w. h. An abbreviation for watt-hour, a 
 practical unit of electric energy. 
 
 Wall Box for Flush Switch. A box 
 sunk in a wall for the reception of a flush 
 switch. 
 
 Wall Bracket. (1) An insulator bracket 
 attached to a wall.- (2) A more or less 
 ornamental support for one or more in- 
 candescent lamps attached to the wall of 
 a room, hall, or corridor. 
 
 Wall Frame for Flush Switch. A term 
 sometimes used for the wall box of a flush 
 switch. 
 
 Wall Plug. A plug provided for the in- 
 sertion of a lamp or other electro-recep- 
 
Wai.] 
 
 984 
 
 [Wat. 
 
 tive device in a wall socket, thus connect- 
 ing it with the lead. 
 
 Wall Set. Telephone apparatus arranged 
 for use when supported on or against a 
 wall. 
 
 Wall Socket. A socket placed in a wall 
 and provided with openings for the inser- 
 tion of a wall plug with which the ends 
 of a flexible twin-lead are connected. 
 
 Wand, Electric. A term sometimes used 
 for an electrophorus in the form of a torch. 
 
 Wandering of Electric Spark. A dis- 
 charge possessing the appearance of a 
 brilliant luminous globule, which moves 
 slowly, in an irregular path, over the sur- 
 face of the tin-foil on a condenser to 
 which the terminals of a powerful rheo- 
 static machine is placed, when a portion 
 of the mica plate in the condenser is ac- 
 cidentally pierced. 
 
 Wanted Station. A word sometimes em- 
 ployed for a station that is desired by a 
 telephone subscriber. 
 
 Ward. A term proposed for a line and 
 direction in a line. 
 
 Waring Anti-Induction Cable. A 
 form of lead-covered anti-induction cable. 
 
 Washer Plate. A buried metallic plate 
 for supporting the tension of a stay-rod. 
 
 Waste Magnetic Field. A term fre- 
 quently employed for stray field. 
 
 Watch-Case Telephone Beceiver. A 
 name sometimes given to a small tele- 
 phone receiver in the shape of a watch- 
 case. 
 
 Watchman's Electric Clock. A name 
 sometimes given to a watchman's electric 
 register. 
 
 Watchman's Electric Register. A 
 clock device for permanently recording 
 the time of a watchman's visit to each of 
 the different localities he is required to 
 visit at stated intervals. 
 
 Water Battery. A battery formed of 
 zinc-copper couples immersed in an elec- 
 trolyte of ordinary water. 
 
 Water-Cooled Transformer. A trans- 
 former that is cooled by the forced circu- 
 lation of water through it. 
 
 Water-Dropping Accumulator. A de- 
 vice tor increasing the difference of po- 
 ; tential between two electric charges, by 
 the dropping of water through electrified 
 funnels. 
 
 , Water-Dropping Collector. A term 
 sometimes employed for a water-drop- 
 ping accumulator. 
 
 Water-Gramme-Degree Centigrade. 
 (1) A heat unit equal to the quantity of 
 
 heat required to raise a gramme of water 
 one degree Centigrade. (2) The small 
 calorie. 
 
 Water Horse-Power. A term employed 
 by the Indian Government for a horse- 
 power developed by falling water, and 
 estimated as being equal to 15 cubic feet 
 of water falling per second, through a dis- 
 tance of one foot. 
 
 Water Telephone Transmitter. A 
 
 telephone transmitter consisting of a jet 
 of water issuing vertically downwards 
 from a small orifice. 
 
 Water-Level Alarm, Electric. (1) A 
 device for electrically sounding an alarm 
 when a water level varies materially from 
 a given level. (2) A liquid-level alarm. 
 
 Water-Pipe Besistance. The resistance 
 which any pipe offers to the flow of water 
 through it. 
 
 Water-Proof Wire. Wire covered by a 
 water-proof material. 
 
 Water Pyrometer. A pyrometer em- 
 ployed for determining the temperature 
 of a furnace, or other intense source of 
 heat, by the increase in temperature of a 
 known weight of water, into which a 
 metal cylinder of a given weight has 
 been put, after having been exposed for a 
 given time to the source of heat to be 
 measured. 
 
 Water Bheostat. A rheostat whose resist- 
 ance is obtained by means of a mass of 
 water of fixed dimensions. 
 
 Water-Tube Dead-Beat Suspension. 
 A dead-beat suspension obtained for the 
 mirror of a sensitive galvanometer by the 
 resistance offered by water in a tube to 
 the movement of a vane attached to the 
 suspension axis. 
 
 Water Voltaic Cell. A cell consisting 
 of a couple immersed in ordinary water. 
 
 Water Voltameter. A name sometimes 
 given to a dilute sulphuric acid volta- 
 meter. 
 
 Watt. (1) A unit of electric power. (2) A 
 volt-ampere. (3) The power developed 
 when 44.25 foot pounds of work are done 
 in a minute, or 0.7375 foot-pound of work 
 is done in a second. 
 
 Watt Arc. A voltaic arc, the electric 
 power of which is estimated in watts. 
 
 Watt Balance. A form of electric balance 
 suitable for measuring in watts the elec- 
 tric energy developed in any circuit. 
 
 Watt Generator. A term sometimes em- 
 ployed for the power in watts that any 
 electric source is capable of producing. 
 
 Watt-Hour. (1) A unit of electric work. 
 
Wat.] 
 
 985 
 
 (2) A term employed to indicate the ex- 
 penditure of an electric power of one 
 watt for an hour. 
 
 Watt-Hour Efficiency of Storage Bat- 
 tery. The ratio between the amount of 
 electric work in watt-hours a battery 
 will yield after being charged, and the 
 amount of work in watt-hours expended 
 in charging it. 
 
 Watt-Hour Meter. A form of recording 
 watt-meter. 
 
 Wattless Component. A component 
 of E. M. F. or current, in quadrature with 
 the working component. 
 
 Wattless Component of Current. (1) 
 In an alternating-current circuit that 
 component of the current which is in 
 quadrature with the impressed E. M. F. 
 and which, therefore, takes from or gives 
 no energy to the circuit. (2) In an alter- 
 nating-current circuit the product of the 
 
 E. M. F. and the effective susceptance. 
 
 Wattless Component of Electromo- 
 tive Force. (1) In an alternating-cur- 
 rent circuit, that component of the E. M. 
 
 F. which is in quadrature with the cur- 
 rent strength, and, therefore, does no 
 work on the current. (2) In an alternat- 
 ing-current circuit the product of the 
 current and the effective reactance. 
 
 Wattless Current. (1) That component 
 of an alternating electric current which is 
 in quadrature with the pressure and 
 which, therefore, does no work. (2) The 
 idle current. (3) In an alternating-cur- 
 rent circuit the product of the effective 
 susceptance and the E. M. F. 
 
 Wattless E. M.F. (1) The wattless com- 
 ponent of E. M. F. in an alternating-cur- 
 rent circuit. (2) The reactive E. M. F., 
 as distinguished from the active E. M. F. 
 of an alternating-current circuit. (3) In 
 an alternating-current circuit, the pro- 
 duct of the E. M. F. and the effective or 
 apparent conductance. 
 
 Wattless Magnetizing Current. (1) A 
 component of the magnetizing current 
 which consumes no power on the average. 
 (2) That component of the current which 
 flows through the primary of a trans- 
 former, which serves for magnetizing 
 only, and which is in quadrature with the 
 pressure, as distinguished from the com- 
 ponent of magnetizing current which 
 expends energy in the iron core. 
 
 Wattmeter. An instrument for measur- 
 ing the power in any circuit. 
 
 Watt-Minute. (1) A unit of electric 
 work. (2) An expenditure of electric 
 power of one watt for one minute. 
 
 16 
 
 Watt-Second. (1) A unit of electric work. 
 (2) An expenditure of electric power of ! 
 one watt for one second. (3) A joule. 
 
 Wave. An oscillatory motion in an elastic' 
 medium, periodic in time. 
 
 Wave Bisector. An electric chronograph 
 for determining the current or potential 
 in a telegraph circuit or line at any given 
 small interval of time after the applica- 
 tion of the sending current. 
 
 Wave, Electric. An electric periodic dis- 
 turbance in an elastic medium. 
 
 Wave Form of Alternating Current. 
 Any particular type of an alternating- 
 current wave. 
 
 Wave Form of Alternating Current. 
 A graphical type of an alternating-cur- 
 rent wave. 
 
 Wave Winding. (1) Undulatory wind- 
 ing. (2) Continuous winding. (3) A wind- 
 ing which, when developed, has the form 
 of a wave. 
 
 Waves of Condensation and Rarefac- 
 tion. (1) The alternate spheres of con- 
 densed and rarified air by means of which 
 sound is propagated. (2) Sound waves. 
 
 Way. A term sometimes employed for 
 cable way. 
 
 Way Lease. A permit obtained from the 
 owner of a property for the erection of 
 poles or other attachments for telephonic 
 or telegraphic lines. 
 
 Way Leave. A word sometimes used for 
 way lease. 
 
 Way Leave. (1) A right of way. (2) 
 An easement. 
 
 Way Line. A line communicating with 
 way stations. 
 
 Way Office Cut-Out. A cut-out em- 
 ployed for inserting or removing a way 
 office in a telegraphic line, by the aid of 
 a plug. 
 
 Way Telegraphic Station. Any station 
 intermediate between the terminal sta- 
 tions. 
 
 Ways for Dynamo-Electric Machine. 
 Slides on the base of a dynamo-electrio 
 machine for moving part of its frame. 
 
 Weather Contact. (1) A weather cross. 
 (2) A partial contact between wires ow- 
 ing to leakage in bad weather. 
 
 Weather Cross. A contact or leak occur- 
 ring in a telegraphic or other line during 
 wet weather, from a defective action of 
 the insulators. 
 
 Weather Proof Insulation. A trade- 
 name for a character of insulation con- 
 sisting of one or more layers of braided 
 Vol. 2 
 
Wea.] 
 
 986 
 
 [Wim. 
 
 material soaked in an insulating com- 
 pound. 
 
 "Weather-Proof Wire. A wire provided 
 with weather-proof insulation. 
 
 Weber. (1) The practical unit of magnetic 
 flux. (2) A unit of magnetic flux having 
 the value of one absolute unit or line. 
 (3) A term formerly employed for unit of 
 current, but now replaced by ampere. (4) 
 A term proposed by Clausius and Siemens, 
 but not adopted, for a magnetic pole of 
 unit strength. 
 
 Weber Turns. Flux linkages in C. G. S. 
 units of flux and the turns through which 
 they pass. 
 
 Weber's Theory of Diamagnetism. A 
 theory which endeavors to account for the 
 phenomena of diamagnetism on the as- 
 sumption of originally magnetized parti- 
 cles, molecules, or atoms. 
 
 Wedge Battery.- In a telegraph station, 
 a battery whose terminals are connected 
 with a wedge for insertion in a jack. 
 
 Wedge Cut-Out. A form of cut-out em- 
 ployed on telegraphic circuits. 
 
 Weeding-Out of Harmonics by Elec- 
 tric Resonance. Gradually removing 
 the upper harmonics from a complex- 
 harmonic current by altering the natural 
 period of the system, until it is in unison 
 or resonance with the fundamental fre- 
 quency. 
 
 Weight of Observations. The relative 
 numerical reliability of observations. 
 
 Weight Efficiency of Transformer. 
 The specific output or activity of a trans- 
 former. 
 
 Weight Voltameter A voltameter in 
 which the quantity of current passing is 
 determined by the difference of weight of 
 the instrument after the current has 
 passed for a given time. 
 
 Weight Voltmeter. A voltmeter in 
 which the potential difference to be meas- 
 ured is determined by the movement of 
 a magnetic needle under the influence of 
 the current, against the action of a 
 weight. 
 
 Weight-Per-Mile-Ohm. (1) A standard 
 of conductivity of wires. (2) The weight 
 per mile of a wire, multiplied by its re- 
 sistance per mile at a given temperature. 
 
 Welded Bail Bond. A rail bond ef- 
 fected by electrically welding together 
 the ends of the rails. 
 
 Welder. A name sometimes applied to an 
 electric welder 
 
 Welding. Uniting, generally at a high 
 
 temperature, two pieces of metal in one 
 without the appearance of a junction. 
 
 Welding Converter. A welding trans- 
 former. 
 
 Welding, Electric. Effecting the weld- 
 ing union of metals by means of heat of 
 electric origin. 
 
 Welding Transformer. A step-down 
 transformer employed in electric welding. 
 
 Welsbach Burner. A form of incandes- 
 cent mantel burner whose light ig due to 
 the incandescence under the action of a 
 Bunsen flame of a mantel covered with 
 refractory materials. 
 
 Western Union Splice. A term some- 
 times employed for an American wire 
 joint. 
 
 Wheatstone's Electric Balance. A 
 name sometimes given to an electric 
 bridge or balance. 
 
 Wheatstone's Electric Bridge. A 
 
 Wheatstone's electric balance. 
 Wheel Brush. A name given to any 
 
 rotary brush. 
 Wheel Printing Telegraph. A printing 
 
 telegraph in which a printing wheel is 
 
 employed. 
 Whip. A vibrating contact-maker. 
 
 Whirl, Electric. (1) A term employed to 
 indicate the circular directions of the 
 lines of magnetic fcrce surrounding a 
 conductor conveying an electric current. 
 (2) A magnetic whirl. 
 
 Whistle, Electric. An automatic electric 
 whistle. 
 
 Whistling Effect. (1) An effect produced 
 with a carbon transmitter and telephone 
 receiver in a line, such that if the trans- 
 mitter be close to the receiver and then 
 slightly jarred, a musical note will be 
 emitted by the receiver which will react 
 upon the transmitter and produce similar 
 sounds in other receivers on the same 
 circuit. (2) A means sometimes em- 
 ployed to call a subscriber's attention 
 when his receiver has been accidentally 
 left in the line circuit, instead of the bell. 
 
 White. Containing all the frequencies of 
 the sun's radiation. 
 
 White Heat. A temperature of a heated 
 body, at which it emits all visible fre 
 quencies from the red to the violet, and 
 therefore glows with a white light. 
 
 Wig- Wag Signalling. A term sometimes 
 used for torch signalling. 
 
 Wimshust's Electrostatic Machine. A 
 form of influence electric machine. 
 
Win.] 
 
 987 
 
 [Woo. 
 
 Wind and Water Line of Telegraph 
 Pole. The surface of a telegraph pole at 
 the level of the ground, where it is ex- 
 posed to the destructive action of air and 
 water. 
 
 Wind, Electric. The convection streams 
 of air particles produced at the extremi- 
 ties of points attached to the surface of 
 charged insulated conductors. 
 
 Windage of Dynamo Armature. A 
 term proposed for the air-gap between 
 the armature and the pole-pieces of a 
 dynamo. (Not ill general use.) 
 
 Winding Space. The space provided on 
 an armature or magnet core for its mag- 
 netizing coils. 
 
 Windings. A .general name applied to 
 the coils placed on an armature of a 
 dynamo or motor, or on the core of an 
 electro-magnet. 
 
 Wind-Mill Electric. A term sometimes 
 used for an electric flyer. 
 
 Wind-Mill Meter. An alternating-cur- 
 rent meter whose operation is dependent 
 on the motion of a wind-mill, by currents 
 of air set up by the heat emitted from a 
 conductor through which the current to 
 be measured is passing. 
 
 Window Contact. A variety of burglar- 
 alarm contact, by means of which an 
 alarm bell is rung by a slight pressure 
 against a blind contact, on any attempt 
 from without, after the breaking of the 
 glass in the window. 
 
 Window-Tube Insulator. A tube of 
 vulcanite, or other insulating material, 
 provided for the insulation of a wire 
 entering a room through a window. 
 
 Wings. The conducting plates, flaps, or 
 extensions, of an electric resonator or 
 oscillator. 
 
 Wipe Spark. A spark obtained from a 
 spark coil by the wiping contact of a 
 spring. 
 
 Wiped Joint. (1) A wiped solder or 
 plumber's joint. (2) A joint in the lead 
 sheathing of a cable formed by adding free 
 surface metal, as in a plumber's joint in 
 lead pipes. 
 
 Wiping Contact. A contact obtained by 
 a wiping movement of one conductor 
 against another. 
 
 Wippe. An orthography sometimes em- 
 ployed for whip. 
 
 Wire. (1) To provide with a conduct- 
 ing circuit. (2) To send a telegram. 
 
 Wire. (1) A conductor that forms part of 
 a circuit. (2) A telegram. 
 
 Wire Core. A form of laminated core ob- 
 
 tained by the use of a number of iron 
 wires. 
 
 Wire Drum. A drum for holding over- 
 head wires in process of erection. 
 
 Wire Dynamometer. A line dynamo- 
 meter. 
 
 Wire Finder. Any form of galvanometer 
 used to locate or find the corresponding 
 ends of different wires in a bunched cable. 
 
 Wire-Grating Polarizer. A series of 
 parallel wires set in a frame and em- 
 ployed for polarizing electro-magnetic 
 waves. 
 
 Wire Guard. A wire netting placed over 
 an incandescent lamp chamber, acting as 
 a guard or protection for it. 
 
 Wire Holder. (1) A form of insulator 
 suitable for holding or supporting a wire. 
 (2) A reel or cross suitable for holding a 
 roll of wire. 
 
 Wire Joint. (1) Any joint connecting 
 two pieces of line wire. (2) A telegraphic 
 joint. 
 
 Wire Rail-Bond. A bond between con- 
 tiguous or opposite rails effected by 
 means of a conducting wire. 
 
 Wire Selector. A wire finder. 
 
 Wire Shade-Guard. A wire guard pro- 
 vided for the shade of an incandescent 
 lamp. 
 
 Wire Shield for Incandescent Lamp. 
 A wire lamp-guard. 
 
 Wire Splice. A splice effected between 
 two pieces of wire. 
 
 Wire Terminals. Metal eyes for solder- 
 ing to the ends of wires and for connec- 
 tions to switchboards. 
 
 Wire- Wound Armature. An armature 
 which is wound with wire, as distin- 
 
 fuished from an armature wound with 
 ars. 
 
 Wired. Provided with a conducting wire 
 or wires. 
 
 Wireless Telegraphy. (1) A general 
 term for any form of telegraphic com- 
 munication which can be effected with- 
 out wire circuits. (2) Induction teleg- 
 raphy. (3) Conduction telegraphy through 
 the medium of the earth. 
 
 Wiring. (1) Placing or installing the 
 wires required in any circuit. (2) Col- 
 lectively, the wires or electric conductors 
 employed in any circuit of electric dis- 
 tribution. 
 
 Wood Mouldings, Electric. Mouldings 
 of dried non-conducting wood provided 
 with longitudinal grooves for the recep- 
 
Woo.] 
 
 988 
 
 [X-Ra. 
 
 tion and support of electric wires or con- 
 ductors. 
 
 Wood's Button-Repeater. A form of 
 manual telegraphic repeater. 
 
 "Work. The product of the force by the 
 distance through which it acts. 
 
 Work, Electric. (1) The joule. (2) A 
 volt-coulomb, or the work done by the 
 passage of one conduct through one volt. 
 
 Work-Meter. A word sometimes used 
 for energy meter. 
 
 Working Current. (1) In an alternating- 
 current circuit, a name sometimes given 
 to an active current, or that component 
 of the current which is in phase with the 
 pressure. (2) Any current in a circuit, 
 which does work. (3) A current operat- 
 ing a translating device. 
 
 Working Current of Motor. The active 
 current of an alternatirg-current motor. 
 
 Working Efficiency of Telegraphic 
 Circuit. The variation or margin be- 
 tween the joint resistance of the line 
 conductor and the resistance of the in- 
 sulators supporting such conductor. 
 
 Working Galvanometer-Constant. A 
 term sometimes employed for galvano- 
 meter constant. 
 
 Wprking Position of Switch.. The po- 
 sition of a switch when closed. 
 
 Working Speed of Cable. A term em- 
 ployed for the number of signals that can 
 be sent over a cable in a given time. 
 
 Working Substance of Storage Bat- 
 tery. A name sometimes given to the 
 active material of a storage battery. 
 
 Woven-Wire Dynamo or Motor 
 Brushes. Gauze brushes for dynamos 
 or motors. 
 
 Wrapped Wire. Wire covered with a 
 wrapping of insulating material. 
 
 Wrecking Wagon for Trolley Line. A 
 word sometimes used for repair wagon. 
 
 Writing Error. In telegraphy an error 
 made in writing a message. 
 
 Writing Telegraph. A general name 
 for the apparatus used in writing tele- 
 graphy. 
 
 Writing Telegraphy. A species of fac- 
 simile telegraphy, by means of which the 
 motions of a transmitting pen so vary 
 the resistance of two lines connected with 
 the receiving instrument, as to cause 
 a receiving pen or stylus to reproduce 
 them. 
 
 X 
 
 X-G-raph. A word sometimes employed 
 for radiograph. 
 
 X-Radiation. A term sometimes used 
 for Roentgen radiation. 
 
 X-Ray Field. The field of activity of 
 X-rays. 
 
 X-Ray Pluoroscopy. The study of flu- 
 oroscopic effects obtained by means of 
 the X-rays. 
 
 X-Ray Lamp. A lamp consisting essen- 
 tially of a high-vacuum tube, the inner 
 walls of which are covered with crystals 
 of calcium tungstate or other fluorescent 
 substance, which emits fluorescent light 
 when exposed to X-rays. 
 
 X-Ray Photograph. A term sometimes 
 employed for radiograph. 
 
 X-Ray Photography. Photography ef- 
 fected by means of the X-rays. 
 
 X-Ray Picture. A term sometimes em- 
 ployed for radiograph. 
 
 X-Ray Source. Any source capable of 
 producing X-rays. 
 
 X-Ray Transformer. A transformer 
 employed for obtaining the high-potentia', 
 discharges employed in Roentgen or X 
 ray tubes. 
 
 X-Ray Transformer-Coil. A form of 
 induction coil employed for the produc- 
 tion of X-rays. 
 
 X-Ray Tube. A name sometimes given 
 to a Roentgen ray tube. 
 
 X-Rays. ^(1) A name frequently given to 
 X-radiation. (2) The invisible rays emit- 
 ted by an electrically excited Crookes 
 tube, and which are capable of penetrat- 
 ing many substances opaque to light, and 
 of producing actinic or fluorescent effects. 
 (3) The unknown rays emitted by an X- 
 ray tube from some point, generally op- 
 posite the cathode, which receives cath- 
 ode-ray bombardment. 
 
Y-Co,] 
 
 [Zin. 
 
 Y-Connection of Three-Phaser. (1) The 
 connection, resembling the letter Y, of the 
 three circuits of a triphaser to a common 
 junction. (2) Star connection. 
 
 Y-Connected Three-Phaser Armature. 
 (1) A triphase armature having three cir- 
 cuits connected to a common point. (2) A 
 star-connected triphase armature. 
 
 Y-Connector. A connector resembling 
 the letter Y in shape for joining a con- 
 ductor to two branch wires. 
 
 Y-Current. The current between any 
 wire of a triphase system and the neutral 
 point. 
 
 Y-Guy for Telegraph Pole. A Y-shaped 
 guy attached to a telegraph pole for pre- 
 venting it from bending near the top. 
 
 Y-Potential of-Triphase System. The 
 effective difference of potential or volt- 
 meter pressure between one terminal or 
 
 conductor of a triphase system and the 
 neutral point. 
 
 Y-Shaped Spark. A variety of three- 
 branched spark obtained by the discharge 
 of a Ley den jar through a peculiar form 
 of induction coil. 
 
 Yale-Lock-Switch Burglar-Alarm. 
 An apparatus whereby the opening of a 
 door by an authorized party provided with 
 a regular key, will not sound an alarm, 
 but any other opening will sound an alarm. 
 
 Yacht-Tender, Electric. An electrically 
 propelled tender provided for use in con- 
 nection with a yacht. 
 
 Yoke. That portion of the iron of an elec- 
 tro-magnet that joins the two cores. 
 
 Yoke Horse-Shoe Electro-Magnet. A 
 horse-shoe electro-magnet whose two 
 straight limbs are formed of two straight 
 rods or bars connected together at one 
 pair of ends by a yoke. 
 
 Z. A symbol sometimes employed in elec- 
 tro-therapeutics for muscular contraction. 
 
 Z. A symbol for electro-chemical equiv- 
 alent. 
 
 Z-Insulator. A simple form of single- 
 shed earthenware overhead line insul- 
 ator. 
 
 Zamboni's Dry Pile. A form of dry pile 
 consisting of discs of paper, silvered on 
 one side and tinned on the other, placed 
 together alternately with slightly moist- 
 ened bin-oxide of manganese. 
 
 Zeeman Effect. The broadening of the 
 lines in the spectrum of a heated sub- 
 stance when placed in the flux of a power- 
 ful magnetic field. 
 
 Zero Method. (1) Any method employed 
 in electrical measurement, in which the 
 value of the electromotive force, the resist- 
 ance, current, or other similar quantities, 
 are determined by balancing against such 
 quantities equal values of the same units, 
 and ascertaining the equality, not by the 
 deflection of a needle of a galvanometer or 
 electrometer, but by the absence of such 
 deflections. (2) A null method. 
 
 Zero Potential. (1) An arbitrary poten- 
 tial-level from which electric levels are 
 measured. (2) The earth's potential. 
 
 Zigzag Electro-Magnet. A multipolar 
 electro-magnet whose magnetizing coils 
 are separately wound in grooves cut in 
 the face of straight or curved bars. 
 
 Zigzag Electromotive Force. An elec- 
 tromotive force, the curve of which would 
 have the general form of a zigzag. 
 
 Zigzag Lightning. (1) A common vari- 
 ety of lightning flash, in which the dis- 
 charge assumes a forked or zigzag ap- 
 pearance. (2) Forked lightning. 
 
 Zigzag Periodic Electromotive 
 Force. A zigzag alternating electro- 
 motive force. 
 
 Zigzag Type of Periodically Alter- 
 nating Electromotive Force. An 
 alternating electromotive force whose 
 graphic representation is a zig-zag curve. 
 
 Zinc Battery. A battery employed in 
 sending zinc currents to line, 
 
 Zinc-Carbon Voltaic Cell. A voltaic 
 cell consisting of a zinc-carbon couple 
 immersed in a suitable electrolyte. 
 
 Zinc-Copper Voltaic Cell. A voltaic 
 cell consisting of a zinc-copper couple im- 
 mersed in a suitable electrolyte. 
 
 Zinc-Lead Accumulator. A secondary 
 cell employing plates of lead and zinc. 
 
Zin.] 
 
 990 
 
 [Zon. 
 
 Zinc Currents. A term sometimes used 
 for negative currents. 
 
 Zinc-Lead Voltaic Cell. A voltaic cell 
 consisting of a zinc-lead couple immersed 
 in a suitable electrolyte. 
 
 Zinc Plating. Electro-plating with zinc. 
 
 Zinc Sender. A device employed in tele- 
 graphic circuits in order to counteract 
 the retardation produced by the charge 
 given to the line, in which a momentary 
 reverse current is sent into the line after 
 each signal. 
 
 Zincs. A general term applied to the zino 
 elements of voltaic cells. 
 
 Zincode of Voltaic Ceil. A name for- 
 
 merly given to the zinc terminal or elec- 
 trode of a voltaic cell. 
 
 Zootrope. An optical toy depending on 
 the persistence of vision, in which a num- 
 ber of pictures of animals are so caused 
 to pass before the eye as to produce the 
 appearance of the motions of life. 
 
 Zonal Harmonic. A zonal surface har- 
 monic. 
 
 Zonal Surface Harmonic. A spherical 
 harmonic which is symmetrical about an 
 axis. 
 
 Zone Lamp. A lamp provided with a 
 lens-shaped chamber so as to cause it to 
 throw out its light in a single zone only. 
 
IBtS 
 
UNIVERSITY OF CALIFORNIA LIBRARY