Class I K*S| Book CojpghtN GQRERIGHT DEPOSIT " The vital knowledge — that by which we have grown as a nation to what we are, and which now underlies our whole existence, is a knowledge that has got itself taught in nooks and corners ; while the ordained agencies /or teaching have been mumbling little else but dead fot mulas. ,} i( That which our school courses leave almost entirely out, we thus find to be that which most nearly concerns the business of life. All our industries would cease, were it not for that in- formation which men begin to acquire as they best may after their education is said to be finished. A nd were it not for this information, that has been from age to age accumulated and spread by unofficial means, these industries would never have existed." — Herbert Spencer. COPYRIGHTED, 1896, BY THEO. AUDEL & CO. Press of L. Middled itch Co. EL.ECTROTYPED BY STODDER BROS. NEW Ail CATECHISM ^ OF ELECTRICITY, A Practical Treatise, AWKINS, M. E., Author of Hand Book of Calculations for Engineers ; Maxims and Instructions for the Boiler Room ; Aids to Engineers' Examinations with Questions and Answers ; Steam Engineering Miscellany, Etc., Etc. *«U\ -^ v Relating to The Dynamo and Motor ; Wiring ; The Electric Railway ; Electric Bell Fitting ; Electric Lamps ; Electric Elevators ; Electric Lighting; Electro Plating ; The Telegraph and Tele- phone ; Electric Elevator, Tables and Measurements. THEO. AUDEL & COMPANY, Publishers, 63 Fifth Avenue, Cor. 13th Street, New York. 1896. THOS. A EDISON This work is respectfully dedicated to THOMAS A. EDISON, of Llewellyn Tark, N. J. " From possibilities to realities." PREFACE. What can the autnor of this treatise say in sending it forth to be added to the much more extensive works already published relating to the same subject. He can say this. There are a thousand spoken languages in the world, each mode of speech is more or less perfect, and easily understood. But, outside those born to a particular tribe or nation, al) other tongues save their own are a babel of sound — a literal gibberish. Thus, the Chinaman cannot understand the Italian, nor the Frenchman the German, and so on through the hundreds of dialects; a man who knows six languages is rare, although Elihu Burritt the learned blacksmith was said to be familiar with forty or more. It is the same with the writing of books ; each author must use his own native " lingo " addressed to those born to the same tribe as himself. xii Preface, Now, for many years, a large number of the patrons of the author's other books have signified a desire for him to write a work on Electricity, and the time being ripe, he now sends it forth addressed (only) to those familiar with a common language and animated by a common tie of association and life with himself. Hence, this work is addressed; not to the exper- imenter or to the toy-maker, nor to the scholar in school or college, but to those who have to deal with Electricity as a part of their life work ; to those who hold it in check, like a powerful horse and render serviceable this mysterious force — the rein to hold and guide it is knowledge. Back of the desire for a considerable circulation of the printed book lies the earnest wish that it may be thoroughly useful to that class of men who must perforce use electricity as their bondsman or serve it as an inexorable master. And this is the true office of a book relating to the arts or sciences ; to explain the unvarying laws upon which all true progress is based; to classify and arrange for ready reference this information so that it may be readily available; to furnish hints and suggestions leading to further and thorough re- search in all lines leading from the subjects discussed ; in short to reduce the every-day practice of a thousand skilled workers to an unvarying science; science being defined as the "orderly arrangement of knowledge." Preface. xiii It is also the heartfelt wish of the author that this work may be found to be an introduction of the reader and student to a wide acquaintance with what may be termed electrical literature. In a science which has occupied the whole of very many lives in the investigation of its laws and an immense expenditure of money in experimental tests, it were vain to expect from a single book much more than a limited view of some one part of the subject, or better yet, a work giving the clue to further research and study in many directions. So, in this work the author trusts the student will at least find " the end of the rope " which drawn out will make him master of the principles and practice relating to practical Electricity. And, in the abridge- ment and selection of the ever-widening subject- matter, so present it, that it can at the pleasure or profit of the student, be run out to infinitude in any useful direction. With these few introductory words and added good wishes for the progress and prosperity of the reader, the author thus apologizes (for a preface is usually an apology) for issuing a New Catechism of Electri- city. Introduction. INTRODUCTION. HE great forces of the world are invisible and impalpable ; we cannot grasp or handle them ; and though they are real enough they have the appearance of being very unreal. Electricity and Gravity are as subtle as they are mighty ; they elude the eye and hand of the most skillful philosopher. In view of this, it is well for the average man not to try to fathom, too deeply, the science of either ; neither Edison or Tesla have done that yet. To take the machines and appliances as they are " on the market," and to acquire the skill to operate them, is the long- est step toward the reason for doing it, and why the desired results follow— thus working on the natural method of judg- ing causes from effects. The history of the development of " Practical Electrics" does not cover many years. Not a few -people can easily re- member all the progressive steps from a humble beginning to the time, now, when it has become the leading study of the scientific and engineering world. Introduction. Although electricity was known to the ancient Greeks the uses to which it might be applied have remained unknown for thousands of years. It was reserved for Franklin, Volta, Am- pere, Ohm, and Farraday, with a few others, to discover the laws which govern it. The development of the science in its application to the needs of human life may be considered to date from the time of Farraday, whose career ended in 1867, after a long and brilliant career spent in scientific research. The time has gone by when in answer to the question, " What is Electricity," it can be truly said " It is not known," for as much is now known of its nature an \ source as of the nature and source of Gravity, Heat, Chemical affinity, etc. The following ' ' definitions ' ' carefully written by men high- est in authority, are both interesting and instructive. " There are certain bodies which when warm and dry, ac- quire by friction, the property of attracting feathers, fila- ments of silk or indeed, any light body toward them. This property is called Electricity, and bodies which possess it are said to be electrified." (Linnaeus Cumming.) " The theory of Electricity adopted throughout these les- sons is, that Electricity, whatever its true nature, is one not two; that this Electricity, whatever it may prove to be, is not matter and is not energy ; that it resembles both matter and energy in one respect, however, in that it cannot be created nor destroyed. ' ' (Sylvanus P. Thompson). Note.— When Benjamin Franklin made his discovery of the identity of lightning and electricity, people asked: " Of what use is it?" The philosopher's retort was : 4 4 What is the use of a child ? It may become a man !" Introduction. xvii " Whatever Electricity is, it is impossible to say, but for the present it is convenient to look upon it as a kind of invis- ible something which pervades all bodies.' ' (W. Perrin Maycock). "There is nothing more certain to-day than that Electricity is not a fluid. " (Prof. Rowland). ' * Throughout the nineteenth century this enigma (What is electricity?) has been the object of numerous researches * * * and yet the inner working of electrical phenomena re- mains still a deeper mystery." (A. Stoletow.) These quotations express all that science can give us in a time when there are published every month in the English, French and German languages over 150 issues of periodicals devoted exclusively to electrical subjects, besides which there are probably twice as many more journals devoted to other branches of science and engineering which sometimes have articles on electrical subjects. In 1867 an English mathematician, Maxwell, proved math- ematically that light and electricity were the same. In 1888 Heinrich Hertz proved by experiment that this was true, and the "pointings" of very recent investigations rather confirm the theory that they are one and the same. Note. — One of the dreams of the modern scientist is the direct trans- formation of the radient energy of the sun into electric energy. To what extent this is possible is considered by a well-known electrical writer, who says : " It is a well-known principle in physics that in the last analysis all the forces of Nature are derived from the sun. There are the calorific and luminous vibrations of the sun, which, imprisoned in the coal strata and in combustible vegetation, afford the means of producing steam. When one reflects upon the tendency to utilize these forces in the form of elec- tricity, a problem of first importance is to transfer the solar energy di- rectly into electric energy without the agency of any intermediary." xviii Introduction. Very much the same way in which electricity is concen- trated by the action of the dynamo, so has the sunlight been "concentrated" by a powerful sun glass constructed in France, made under the supervision of the savant, M. de Villette. This glass generated heat sufficient to melt a cop- per coin of the size of our silver 25-cent piece in seven and a half seconds. George Parker, of Fleet street, London, made a glass more powerful ; it was three feet in diameter and so powerful that it was actually m used to melt substances which were too refractory for the furnaces. The best authori- ties on heat say that it had a power of 166.362 degrees Fahr. This is best understood when it is known that it only takes a temperature of 2,787 degrees to melt cast iron so that it will flow like water. It is from those engineers and electricians who are in daily contact with electrical appliances that we are most likely to get the true definition of the subject. They say boldly and to the point, " Electricity is electricity," and motormen are frequently in the habit of describing the electric-current which drives their trolley-car, as "the juice." " Let on the juice ! " or, "Shut off the juice ! " this being always intelli- gable to the most scientific as well as the most illiterate. The competent engineer to-day is expected to combine a practical knowledge of the engine and dynamo room with a proportionate information to be gained only by schools, books and professional instruction, intended to qualify him to oper- ate and manage economically and intelligently, electrical ma- chines ; to install electrical plants ; to perform calculations involving electrical units and to locate and remedy faults in electrical machines in general. Introduction. Not only the competent engineer, but everybody needs to acquire as much information as possible of this universal prop- erty of nature now brought into such close connection with the everyday life of modern civilization. It is the aim of this publication to so present the subject that it may be of wide and useful assistance to the student. Quite recently a distinguished professor of Harvard Univer- sity published an article in which he grouped the engineers now working side by side for the development of our material resources into three classas. First, those men, many of them eminent in the profession, who are the product of the work- shop ; whose experience and education have been obtained entirely in the field or workshop, and from a few available books. Second. Men who have graduated from literary or natural science departments of colleges and have learned engineering after leaving their classes — drawn to it by a strong taste for the profession or by the pressure of circumstances. Third, the younger men, graduated from schools avowedly technical or from the technical departments of universities. These men are gradually supplanting the other two classes, as the demand for greater attainment and better education in- creases, and as competition and the invention of labor saving machinery turns the mechanic into a laborer, and raises the status of the educated engineer. The next generation, the professor believes, will see the men with only workshop or academic training practically cut off from the profession of engineering. Introduction. Happily for the class for whom this work is compiled there is another side to the argument which might show that the men most handicapped in the race for supremacy is the graduate alluded to in class three, for to quote the same kindly author, only, ' ' Occasionally our schools develop a man whose talent and capacity for work will enable him to study and to retain the higher branches of mathematics and physics, and at the same time to grasp their practical applica- tion to the need of modern life." This practically in the end leaves the field for the self- taught, resolute workers, who with one hand execute and the other gather in and assimilate from all sources the scientific or classified knowledge necessary for the best results, eco- nomical, executive and lasting. "Electricity has shown itself capable of in- finite service^ and its field is daily widening. It can bear thought on its rhythmic wings around the globe; carry the human voice hundreds of miles ; deliver messages on board moving trains ; flash into dazzling splendors along city thoroughfares ; light the abyss of the ocean ; operate countless automatic devices; warm us when cold ; fan us when heated, and treasure up and repeat all sounds and harmonies. At the summons of inventive genius it has outwrought the dreams of magic.''' NEW CATECHISM OF ELECTRICITY. ELECTRICITY. While the nature and source of electricity still remains a mystery, and a constant challenge to the philosopher and engineer, many things about it have become positively known — thus — it is posi- tively assured that electricity never manifests itself except when there is some mechanical disturbance in ordinary matter, and every exhibition of elec- tricity in any of its multitudinous ways may always be traced back to a mass of matter. Electricity, it is also conceded, is without weight, and, while electricity is without doubt, one and the same, it is for convenience sometimes classified according to its motion, as 1. Static Electricity, or electricity at rest. 2. Current Electricity, or electricity in motion. 3. riagnetism, or electricity in rotation. 4. Electricity in vibration (Radiation). Note.— Electricity is a name derived from the Greek word Electron— amber. It was discovered more than 2,000 years ago that amber when rubbed possessed the curious property of attracting light bodies. It was discovered after- wards that this property could be produced in jet by friction, and in A. D. 1600 or thereabouts, that glass, sealing-wax, etc., were also affected by rubbing, producing electricity. NEW CATECHISM OF ELECTRICITY. 23 Other useful divisions are into i. Positive and 2. Negative Electricity. And into I . Static, as the opposite of 2. Dynamic Electricity. There are still other definitions or divisions which are in every-day use, such as " Frictional electricity," "Atmospheric electricity," "resinous electricity," "vitreous electricity," "photo-electricity," etc., etc. While it is almost certain that, broadly, magnetism and electricity are one, in practice it is a necessity to use these divisions to explain the various conditions and uses to which they are put and in which they exist. USEFUL DEFINITIONS RELATING TO ELECTRICITY. Static Electricity. This is a term employed to define electricity produced by friction. It is properly employed in the sense of a static charge which shows itself by the attrac- tion or repulsion between charged bodies. When static electricity is discharged, it causes more or less of a current, which shows itself by the passage of sparks or a brush dis- charge; by a peculiar prickling sensation; by a peculiar smell due to its chemical effects ; by heating the air or other sub- stances in its path ; and sometimes in other ways. Note.— Statics is that branch of mechanics which treats of the forces that keep bodies at rest or in equilibrium. Dyuamics treats of bodies in motion. Hence static- electricity is electricity at rest. The earth's great store of electricity is at rest or in equilibrium. That branch of the science which treats of the laws of electricity resid- ing on the surface of bodies, as a charge, is termed electrostatics. 24 NEW CATECHISM OF ELECTRICITY. Current electricity. This may be defined as the quantity of electricity which passes through a conductor in a given time — or, electricity in the act of being discharged, or elec- tricity in motion. An electric current manifests itself by heating the wire or conductor, by causing a magnetic field around the conductor and by causing chemical changes in a liquid through which it may pass. Radiated electricity is electricity in vibration. Where the current oscillates or vibrates back and forth with extreme rapidity, it takes the form of waves which are similar to waves of light. Positive electricity. This term expresses the condition of the point of an electrified body having the higher energy from which it flows to a lower level. The sign which denotes this phase of electric excitement is -f- ; all electricity is either positive or, — , negative. Negative electricity. This is the reverse condition to the above and is expressed by the sign or symbol — . These two terms are used in the same sense as hot and cold. In 1749, Benjamin Franklin observing lightning to possess almost all the properties observable in electric sparks, suggested that the electric action of points, which was discovered by him, might be tried on thunder- clouds, and so draw from them a charge of electricity. He proposed, therefore, to fix a pointed iron rod to a high tower, but shortly after suc- ceeded in another way. He sent up a kite during the passing of a storm, and found the wetted string to conduct electricity to the earth, and to yield abundance of sparks. These he drew from a key tied to the string, a silk ribbon being interposed between his hand and the key for safety. Iyeyden jars could be charged, and all other electrical effects prcduced, by the sparks furnished from the clouds. The proof of the identity was complete. The kite experiment was repeated by Romas, who drew from a metallic string sparks 9 feet long. In 1753, Richmann, of St. Petersburg, who was experimenting with a similar apparatus, was struck by a sudden discharge and killed. NEW CATECHISM OF ELECTRICITY. 25 Atmospheric electricity is the free electricity of the air which is almost always present in the atmosphere. Its exact cause is unknown. The phenomena of atmospheric electricity are of two kinds; there are the well-known manifestations of thunderstorms ; and there are the phenomena of continual slight electrification in the air, best observed when the weather is fine ; the Aurora constitute a third branch of the subject. Dynamic electricity. This term is used to define current electricity to distinguish it from static electricity. This is the electricity produced by the Dynamo. Frictional electricity is that produced by the friction of one substance against another. Resinous electricity. This is a term formerly used, in place of negative electricity. The phrase originated in the well known fact that a certain (negative) kind of electricity was produced by rubbing rosin. Vitreous electricity is a term, formerly used, to describe that kind of electricity (positive) produced by rubbing glass. Magneto ^electricity is electricity in the form of currents flowing along wires ; it is electricity derived from the motion of magnets — hence the name. Voltaic electricity. This is electricity produced by the action of the voltaic cell or battery. Electricity itself is the same thing, or phase of energy by whatever source it is produced and the foregoing definitions are only given as a matter of convenience to aid in its daily application to the service of man. 26 NEW CATECHISM OF ELECTRICITY. Early Experiments in Electricity. " A shock was in this manner sent through a regiment of soldiers. At an early period in the progress of electrical dis- covery, M. Nollet transmitted a discharge through a series of 1 80 men ; and at the convent of Carthusians a chain of men being formed extending to the length of 5,400 feet, by means of metalic wires extended between every two persons compos- ing it, the whole series of persons was affected by the shock at the same instant. Experiments on the transmission of the shock were made in lyondon by Dr. Watson, in the presence of the Council of the Royal Society, when a circuit was formed by a wire carried from one side of the Thames to the other over Westminster Bridge. One extremity of this wire communicated with the interior of a charged jar, the other was held by a person on the oppo- site bank of the river. This person held in his other hand an iron rod, which he dipped in the river. On the other side near the jar stood another person, holding in one hand a wire communicating with the exterier coating of the jar, and in the other hand an iron rod, This rod he dipped in the river when instantly the shock was received by both persons, the electric fluid having passed over the bridge, through the body of the person on the other side, through the water across the river, through the rod held by the other person, and through his body to the exterior coating of the jar. Familiar as such a fact may now appear, it is impossible to convey an adequate idea of the amazement bordering on incredulity with which it was at that time witnessed." NEW CATECHISM OF ELECTRICITY. 27 MAGNETISM AND MAGNETS. ,4 ■;\ v?.':'^$& 5* ... «W.3e.' "- - - Magnetism is that branch of f >, \ science which treats of the na- ture and properties of magnets ?■■:: and magnetic fields. g.v The theory proposed to ac- |g count for the magnetization of g| iron is as follows : Each little £v? particle of iron is supposed to Vji be, and to remain always mag- •;;.>! netic. In an un magnetized iron bar these molecular magnets are arranged irregularly. These little molecules resist being turned out of their usual positions. Hence when a mag- netizing force is brought to bear upon them, the first effect is to turn those little molecules round, whoses axes are already Fig. 10. Note. — The name magnet was given by the ancients to certain hard black stones found in various parts of the world, notably at Magnesia in Asia Minor, which possessed the property of attracting to them small pieces of iron or steel. This magic property, as they deemed it, made the magnet-stone famous; but it was not until the tenth or twelith century that such stones were discovered to have the still more remarkable prop- erty of pointing north and south when hung up by a thread. This prop- erty was turned to advantage in navigation, and from that time the magnet received the name of lodestone (or "leading-stone"). The natural magnet or lodestone is an ore of iron, known to mineralogists as magnetite. This ore is found in quantities in Sweden, Spain, Arkansas, the Isle of Elba and other parts of the world ; it frequently occurs in crystals, the usual form being the regular octahedron. 28 NEW CATECHISM OF ELECTRICITY. MAGNETISM AND MAGNETS. most nearly in the direction of the magnetizing field. As the magnetizing force increases others are turned, increasing thereby the apparent magnetism ; at iast, all are turned with their poles in the direction of the magnetizing field. When this is the case, no further application of magnetiz- ing force, however great, can increase magnetization. This is the point of saturation. It is easily seen that shocks, or heating, or anything which loosens the molecules, tends to facilitate the acquirement of magnetization. On removing the magnetizing force, those molecules which have not been much strained out of their position, fall back to their old di- rections ; but those which have been greatly strained have acquired a permanent magnetic set, and hence remain. In the case of torsion or twisting of a wire, we have a similar behavior. A slight torsion within the limits of elas- ticity disappears when the twisting force is removed, but a violent torsion results in a permanent deformation, which does not disappear when the twisting force is removed. This theory explains how iron can remain, as it were, super-charged or super-saturated with temporary magnetism. In the iron there is very little resistance to magnetization ; that is to say, the molecules do not resist very strongly being turned in similar magnetic directions, and hence when the force is removed, there is very little restoring tendency to make them go back into irregular positions, but a little knock or twist imparts just the necessary disturbance, and causes the regularity to disappear, and with it the apparent magnetism. NEW CATECHISM OF ELECTRICITY. 2Q MAGNETISM AND MAGNETS. Magnetism is like electricity, it cannot be seen ; that it ex- ists is assured by certain effects which it produces. Toy magnets shaped like a horseshoe exhibit the principles upon which magnetism acts; i. e. y magnets attract and hold fast anything that is made of iron and steel, while they have no effect on brass, copper, zinc, gold or silver. A magnetized body cannot be regarded as a source of" energy in itself. Energy must be expended to magnetize the iron, and must also be expended to demagnetize it. Magnetism produces electricity as well as electricity pro- duces magnetism. During the application of the magnetizing force, any blows or shaking tend to facilitate the acquirement of magnetism, but when removed from the field, the same causes tend to re- move it. Heat operates in the same way. If a piece of steel is made red hot, then placed in a strong magnetic field and suddenly cooled, it acquires very strong permanent magnet- ism. Iron at a bright red heat is, however, not affected by a magnet. If a piece of iron, or better still, a piece of hard steel, be rubbed with a lodestone, it will be found to have also acquired the properties characteristic of the magnet ; it will attract light bits of iron and steel. This was all, or nearly all, that was known of the magnet until 1600, when Dr. Gilbert published a large number of magnetic discoveries in his famous work " De Magnete." He observed that the attractive power of a magnet appears to reside at two regions, and in a long-shaped magnet these regions, or poles, are usually at the ends. The portion of the 30 NEW CATECHISM OF ELECTRICITY. MAGNETISM AND MAGNETS. magnet which lies between the two poles is apparently less magnetic, and does not attract iron filings so strongly ; and all round the magnet, halfway between the poles, there is no attraction at all. This region Gilbert called the equator of the magnet, and the imaginary line joining the poles he termed the axis. There is no insulator fcr magnetism. It penetrates every- thing known. The so-called protectors against magnetism are really only excellent conductors which form a short cut for the magnetism around the article to be protected. If a sheet of glass, or wood, or paper, be interposed between a magnet and the piece of iron or steel it is attracting, it will still attract it as if nothing were interposed. A magnet sealed up in a glass tube still acts as a magnet. Lucretious found a magnet put into a brass vase attracted iron filings through the brass. Gilbert surrounded a magnet by a ring of flames, and found it still to be subject to magnetic attraction from without. Across water, vacuum, and all known substances, the mag- netic forces will act; with the single exception, however, that magnetic force will not act across a screen of iron or other magnetic material. If a small magnet is suspended in- side a hollow ball made of iron, no outside magnet will affect it. A hollow shell of iron will therefore act as a magnetic cage, and screen the space inside it fro::i magnetic influences.. All magnetized sub3tances whether permanently or tempo- rarily magnetized have what is called polarity. The pole which tends to point northward when free to move is called the north pole. The other is the south pole. When two NEW CATECHISM OF ELECTRICITY. 31 MAGNETISM AND MAGNETS. magnets are placed near to each other the N. pole of one is found to repel the N. pole and to attract the south pole of the other ; and the reverse. It is pre'cisely by this attraction and repulsion that motive power is produced by the agency of electricity. The magnetic field is the space around the magnet in which the compass needle or other detector of magnetism will be af- fected. The magnetic field is said to be comprised of lines of force. These are infinite in number, and gradually become weaker and weaker, until they disappear as the distance from the magnet is increased. The magnetic circuit is a closed circuit. The lines of force starting from the N. pole and entering again at the S. pole. Magnetic Flux. — This term indicates the number of lines that pass through the magnetic current. It has the same meaning as the term " magnetic flow." Magnetic Lag. — This is the tendency of hard iron and steel to take up magnetism slowly and part with it slowly. " Mag- netic retardation'' has the same meaning, also " magnetic inertia." Magnetic Saturation is the greatest magnetic force which can be permanently imparted to a steel bar. Residual Magnetism. — When a mass of iron has once been magnetized, it becomes a difficult matter to entirely remove all traces when the magnetizing agent has been removed, and, as a general rule, a small amount of magnetism is permanent- ly retained by the iron. The magnetism so retained by the iron is known as residual magnetism^ and it varies in amount NEW CATECHISM OF ELECTRICITY. MAGNETISM AND MAGNETS. with the quality of the iron. Well-annealed, pure, wrought- iron, as a rule, possesses very little residual magnetism, while, on the other hand, wrought-iron, which contains a large percentage of impurities, or which has been subjected to some hardening process, such as hammering, rolling, stamp- ing, etc., and cast-iron possesses a very large amount of resid- ual magnetism. This property of residual magnetism in iron is of great importance in the working of the self-exciting dynamo, and is, indeed, the essential principle of this class of machine. The Magnetic Field. — It is now understood that the phe- nomena of magnetism are due to an atmosphere of magnetic influence which surrounds the poles, and to a lesser, the whole of the magnet. This atmosphere is termed the magnetic field. Magnetic Tick. — When a bar of iron is suddenly magne- tized or demagnetized, it emits a slight sound, called the * ' page sound ' ' or the magnetic tick. Note.— If the North pole of a magnet is presented to the South pole of another magnet, they will attract and hold fast to each other; but, if a South pole is presentedto another South pole or a North pole to a North pole, they will repel each other, and there will be no attraction. NEW CATECHISM OF ELECTRICI'l Y. 33 MAGNETISM AND MAGNETS. Strength of a Magnet. — The "strength " of a magnet is not the same thing as its " lifting power." The strength of a magnet is the strength of its poles. The strength of a magnet pole must be measured by the magnetic force which it exerts. The lifting power of a magnet depends both upon the form of the magnet and on its magnetic strength. A horse-shoe magnet will lift a load three or four times as great as a bar magnet of the same weight will lift. The lifting power is greater if the area of contact between the poles and the arma- ture is iucreased. Also the lifting power of a magnet grows in a very curious and unexplained way by gradually increasing the load on its armature, day by day until it bears a load which at the outset it could not have done. Nevertheless if the load is so increased that the armature is torn off, the power of the magnet falls at once to its original value. The attraction be- tween a powerful electro-magnet and its armature may amount to 200 lbs. per square inch. (See fig. 15, page 46.) Small magnets lift a greater load in proportion to their own weight than large ones. A good steel horse-shoe magnet weighing itself one pound ought to lift twenty pounds' weight. Sir Isaac Newton is said to have possessed a little lode. stone mounted in a signet ring which would lift a piece of iron 200 times its own weight. 34 NEW CATECHISM OF ELECTRICITY. USEFUL DEFINITIONS RELATING TO MAGNETS. Magnets made of steel are usually called permanent mag- nets ; these are of two forms, viz., the "bar magnet " and the " horseshoe magnet," which is merely the bar magnet turned around. Artificial Magnet. —Any magnet not found in nature is an artificial magnet. Horseshoe Magnet. — This is a magnetized bar of iron or steel bent in the form of a horseshoe or letter U. (See Fig. 10.) Natural Magnet is a name sometimes given to a lodestone. Natural magnets are usually of irregular form, although they are sometimes reduced to regular shapes by cutting and grind- ing. Compound Magnets consist of a number of single magnets separately magnetized, and afterwards bound together in bun- dles. Compound magnets are stronger in proportion to their weight than single magnets. Permaneut Magnet. — A magnet of hardened steel which retains its magnetism a long time after being magnetized. A permanent magnet will always attract and hold pieces of iron and steel. Its ends or poles are named North and South. There is usually a loose piece of steel or iron, called an "armature" put across the ends, which has the peculiar property of keeping the magnetism from becoming weaker. A Polarized Electro-Magnet is one whose core is a perman- ent magnet. Such magnets are used in Duplex Telegraphy. The armature of this magnet is released only by a current in a fixed direction. NEW CATECHISM OF ELECTRICITY. 35 ELECTRO MAGNETISM. Fig. 11. Klectro-magnetism is the foundation stone of commercial electricity. A magnet produced by passing! an electric current through a wire conductor coiled around a bar of soft iron is called an electro-magnet ; if the bar be of iron it will be a magnet only so long as the current flows, and electro magnetism is that science which relates to magnetism produced by the electric current, and which treats of the relation between electric currents and magnetism. In 1820 Oerstedt made the important discovery that a con- ductor through which a current of electricity is passing acquires thereby all the properties of a magnet. Note. — The great usefulness of the electro-magnet in its application to electric bells and telegraphic instruments lies in the fact that its mag' netism is under the control of the current ; when circuit is ' ' made " it be- comes a magnet, when circuit is " broken " it ceases to act as a magnet. 36 NEW CATECHISM OF ELECTRICITY. ELECTRO MAGNETISM. Almost immediately after Oerstedt's discovery, Arago and Davy independently discovered how to magnetize iron and steel by causing currents of electricity to circulate round them in spiral coils of wire. The method is shown in the simple diagram of Fig. n where a current from a single cell is passed through a spiral coil of wire, in the hollow of which Fig. 12. is placed a bar of iron or steel, which is thereby magnetized. The separate turns of the coil must not touch one another or the central bar, otherwise the current will take the shortest road open to it and will not traverse the whole of the coils. To prevent such short-circuiting by contact the wire of the coil should be overspun with silk or cotton, or covered with a layer of gutta-percha. NEW CATECHISM OF ELECTRICITY. 37 ELECTRO MAGNETISM. All dynamic-electric machines are based upon that branch of electric science known as Electro Magnetism, hence this discovery marks one of the most important epochs in the progress of practical electricity. This exceedingly important elementary fact in electro magnetism can be shown in a variety of ways. When a wire in which the electric current is flowing is brought near a compass or other magnetic needle, the latter will be affected and tend to change its position and set itself at right angles to the conductor. This proves that an electric current flowing in a wire is in itself a form of a N. of magnet. Lines of Magnetic Force. — If a thin piece of paper is placed over a bar magnet and fine iron filings are sprinkled over it, the particles of iron will arrange themselves in regu- lar curves between the poles and to map out or define lines in the magnetic fields which scientists call lines of force. See Fig. 12. Fig. 10 exhibits the manner in which the filings arrange themselves about the ends of a horse shoe magnet. The forms of the curves show not only the direction of the magnetic force, but they also enable us to draw conclusions as to its intensity. When the force is great the curved lines are thick and sharply defined, and when it is weak the lines are thin aid less plain. The lines of force are also to be found in the neighborhood of wires through which electric currents are passing. They are the outward effect produced by the passage of an electric current, but the most singular fact is that they can also be the cause of an electric current. 38 NEW CATECHISM OF ELECTRICITY. ELECTRO MAGNETISM. Directions of Magnetic Force. — The direction of the mag- netic force in a magnetic field may be defined as the direction in which a small pivoted magnetic needle points when held in the field at that point. If a small suspended magnetic needle or pocket-compass be placed at various points in the magnetic field surrounding a bar magnet, as represented in .> '>^>> / N / \ >. S /■ \ Fig. 13. Fig. 13, it will be found that the needle always points in a definite direction, which direction varies with its position in the field, the direction of the magnetic axis of the needle at any point representing the direction of the magnetic force at that point. If a magnetic needle, similar to that in the above experi- ment, be suspended by means of a thread over a bar magnet, and moved from the north to the south pole of the magnet, as illustrated in Fig. 14, the centre of the needle will trace out curving lines connecting the two poles. The paths or lines followed by the centre of the magnetic needle are NEW CATECHISM OF ELECTRICITY. 39 ELECTRO MAGNETISM. termed lines of magnetic force, and in the modern concep- tion of a magnetic field this latter is assumed to be entirely filled up with these imaginary lines of force. These lines of force are assumed, for reasons to be hereafter understood, to have a certain positive direction, namely that direction in which a small north-seeking magnetic pole would tend to Fig. U. move if placed in the magnetic field ; or, in other words, the lines of force are assumed to stream or flow in a direction from the north to the south pole, as indicated by the arrows in Fig. 14. Points Relating to Electromagnets. Electro-magnets are far more powerful in proportion to their size than steel magnets and can be made of any required size, those made for power stations sometimes weighing scv- ■ eral tons. Electro-magnets are used in nearly all electrical instruments not only because they are stronger than permanent magnets 40 NEW CATECHISM OF ELECTRICITY. ELECTRO MAGNETS. but because they can be made to act instantly by pasing a current of electricity through them at the most convenient moment. The strength of an electro-magnet depends directly on the number of turns of wire and the current flowing through them. In an electro-magnet with an iron core, the grade of the iron also affects the strength — the best soft Swedish iron fur- nishing the strongest magnetism. To increase the amount of magnetism, due to a current in a wire at a certain point, it is only necessary to increase the length of wire about that point — by the operation of this law, the coil form of the magnet is evolved. The Scientific American has given an account of a great electro-magrj t made by Col. King several years ago at Willett's Point fortification, N. Y. The magnet core con- sisted of two old 15-inch guns, weighing 50,000 pounds each. It was turned into a club-footed magnet by the addition of many tons of heavy iron plates. The coil consisted of old torpedo cables 14 miles long, carrying 20 to 25 amperes. The armature consisted of 6 platform plates bolted together. A calculated force of 44,800 pounds was insufficient to tear off the armature, the chain used being broken by the strain. Five cannon balls, Note.— Inasmuch as the field-magnets of dynamos are electro-mag- nets, the iron cores of which are excited by electric currents circulating in surrounding coils, it becomes a matter of primary importance to us to know what is the law that governs the electro-magnet. If we once know the relation that subsists between the exciting current and the magnetism that is produced by it, we can apply this knowledge to the design of dyna- mos ; for such knowledge will enable us to calculate beforehand the size of field-magnet and the number and gauge of coils that will be required in a dynamo that is to furnish any given amount of electric energy. NEW CATECHISM OF ELECTRICITY. 4 1 ELECTRO MAGNETS. of 325 pounds each, were surpended like a chain from the muzzle of the gun. An iron spike placed against the breast of a man standing three or four feet off, with his back to the gun, stood out straight. It required the efforts of two men with a sudden jerk to pull away a 25-pound bar from the gun. The entire mass of iron, including guns, carriages, armature, etc., weighed over 130,000 pounds. At a distance of 71 feet the magnetism of the gun equaled that of the earth, a compass needle being deflected 45 degrees ; at a distance of 300 feet it was deflected 3 degrees. 42 NEW CATECHISM OF ELECTRICITY. ELECTRIC ENERGY, The production of electricity is simply a transformation of energy from one form into another, usually mechanical en- ergy is changed into electrical energy and a dynamo is sim- ply a device for effecting the transformation. Prof. Fessenden truly remarks there are two independent properties of matter— gravity and inertia — and these give us two ways of defining force and energy. It should always be remembered that electricity is some- thing real, although not easily defined. And then, too, while it is not matter and not energy, yet under proper conditions, it having the power of doing work it is convenient to speak of its performance as electric energy. The following ques- tions and answers, although few in numbei may present the subject with considerable clearness. Ques. What is energy? Ans. Energy is the capacity for doing work. Steam under pressure is an example, a spring bent ready to be released is another form. Ques. What is matter ? Ans. Matter is anything occupying space, which is of three dimensions — wide, long, deep — and which prevents other matter from occupying the same space at the same time. Ques. What is the smallest quantity of matter which can exist called ? Ans. An atom. An atom means that which cannot be cut, NEW CATECHISM OF ELECTRICITY. 43 ELECTRIC ENERGY. scratched, or changed inform and that cannot be affected by heat or cold or any known force ; although inconceivably small, atoms possess a definite size and mass. Ques. What is a molecule ? Ans. A molecule is composed of two or more atoms. Ques. Why at this point are definitions most useful of energy and of matter ? Ans. Because, as stated, all electric action is an exhibi- tion of energy, and energy must act through matter as its medium. Ques. What is the difference between electricity and mag- netism ? Ans. The ultimate nature of neither is known. There are, however, some differences. To sustain a current of electricity requires energy. To sustain magnetism requires no energy. Note. — A writer in the New Science Review undertakes to answer the question," What is Electricity?" In order to lead the reader up to the main question, he first considers the natural forces, gravitation and heat. Examples are given of how these forces are manifested, and how energy is changed from one form to another. Every form of force, the author says, should be regarded as a different method in which energy makes itself known to the senses. He calls particular attention to the important fact that the " resistance of one kind or another is always the agent that acts to alter energy from one form to another," and suggests that electricity is simply a form or manifestation that energy may assume under given con- ditions, and generally is a mere transitory stage between the mechanical form and the heat form. " In most operations," he continues, " mechan- ical force passes to the heat form without passing through the electric form ; but whenever magnetism is brought into play as a resistance that must be overcome ; then mechanical power applied to overcome this re- sistance always becomes electricity, if only momentarily in its passage from the mechanical to the heat form." In conclusion, he asks if the question " What is Electricy ?" cannot be answered in a fairly satisfactory way by saying that it is simply a form that energy may assume while un- dergoing transformation from the mechanical or the chemical form to the heat form, or the reverse. 44 NEW CATECHISM OF ELECTRICITY. ELECTRIC ENERGY. A current of electricity is always accompanied by a magnetic field of peculiar form. Magnetism alone cannot produce electricity. Electricity can do work ; magnetism cannot do work in the same sense — and alike with electricity, neither can it exist without contact with matter. Ques. What is it convenient to consider, relating to these minute bodies ? Ans. That they are perpetually in motion with incredible velocities. Ques. How is energy transmitted from one part of material substance to another ? Ans. Gradually and successively. It requires a medium and it requires a certain time. Ques. What is the principal use or function in mechanics of electricity ? Ans. It is purely that of transmission. It corresponds to ropes, shafts and fluids as a medium of conveying and trans- lating power or work. Note.— It is evident that a body in motion has the capacity to do work, and a body at rest may also have the capacity to do work. In the first instance energy is of that kind which is due to the fact that the body is in motion, and has weight, and in the second, energy is due to the po- sition or condition of a body at rest. The ny-wheel of a steam engine in motion possesses kinetic energy ; a heavy weight at the top of a high tower possesses potential energy. Kinetic energy is energy due to matter being actually in motion, or Energy of Motion— Dynamic-energy. Potential or Static energy is a capacity for doing work due to advan- tage of position or other cause. A ten-pound weight supported one foot above a plane has ten foot-pounds of mechanical energy. NEW CATECHISM OF ELECTRICITY. 45 EIectro=Motive Force. The term is employed to denote that which moves or tends to move electricity from one place to another. For brevity we sometimes write it B. M. F. In this particular case, it lit obviously the result of the difference of potential, and pro- portional to it. Just as in water pipes, a difference of level produces a pressure, and the pressure produces a flow so soon as the cap is turned on, so difference of potential produces electro-motive force, and electro-motive force sets up a cur- rent so soon as a circuit is completed for the electricity to flow through. Klectro-motive force, therefore, may often be conveniently expressed as a difference of potential, and vice versa ; but the reader must not forget the distinction. In ordinary acceptance among engineers and practical working electricians, electro-motive force is thought of as pressure, and it is measured in units called volts. The usual standard for testing and comparison is a special form of voltaic cell, called the Clark cell. This is made with great care and composed of pure chemicals. It is accepted as having an K. M. F. of i T Vo 4 o volts at a temperature of 15 degrees C. The term positive expresses the condition of the point hav- ing the higher electric energy or pressure, and, negative^ the lower relative condition of the other point, and the current is forced through the circuit by the (K. M. F.) electric pressure at the generator, just as a current of steam is impelled through pipes by the generating pressure at the steam-boiler. Note. — Care must be taken not to confuse electro-motive force with electric force or electric energy, when matter is moved by a magnet, we speak rightly of magnetic force ; when electricity moves matter, we may speak of eleetric force. But, E). M. F. is quite a different thing, not " force" at all, for it acts not on matter but on electricity, and tends to move it. 46 NEW CATECHISM OF ELECTRICITY. Fig. 15. Lifting Power of Magnets. (See page 33.) NEW CATECHISM OF ELECTRICITY. 47 PRIMARY BATTERIES. An electrical battery is the simplest method of generating electricity for practical use. Batteries all generate electricity by chemical action ; the great variety being caused by the variation of the simple elements used in all. The growing demand for electrical apparatus in work- shops, power plants, office and public buildings and dwellings indicates the needs of plain instructions whereby the en- gineer, electrician or other mechanic can arrange or man- age in a practical way the spe- cial devices ordinarily used. Batteries can be bought from supply houses all com- plete and ready to be set up, but the following pages of description and illustration will be found most useful. Fig. 1.6 represents a simple voltaic cell. The one fundamental fact Fig. 16. on which the electro-chem- ical generation of current depends is that, if a plate of metal is placed in a liquid called an electrolyte, there is a dif- 48 NEW CATECHISM OF ELECTRICITY. PRIMARY BATTERIES. erence of electrical condition produced between them of such sort that the metal either takes a lower or a higher electrical potential than the liquid, according to the nature of the metal and the liquid. If two different metals are placed in one elec- trolytic liquid, then there is a difference of state produced between them, such that, if joined by a wire outside the liquid, a current of electricity traverses this wire. This current pro- ceeds in the liquid from the metal which is most acted upon chemically to that which is least. The term battery is applied to a device in which one or more chemical substances in a fluid mixture act upon a metal and a carbon, or upon two different metals, producing there- by a current of electricity, which will continue as long as there is any action of the chemicals upon the metcl a:ul car- bons, or upon the two metals. Battery connections are formed by two methods ; by the scries method \ as shown in Fig. 17, and the parallel method, Fig. 18. It will be observed that the cells are connected by their electrodes. Note. — " The popular notion of a secondary battery as a contrivance for storing up electricity is quite erroneous. Energy can be stored up but not electricity, and hence, if the term ' accumulator ' is used, it should be in the sense of an accumulator of energy. It is not very easy to draw a distinction between what should be properly called primary and what should be called secondary batteries. In both forms, energy is accumu- lated in a manner capable of being transformed into electric current, and, in both, this ultimately depends on chemical attraction ; but, in the forms of battery, usually called secondary, the chemical processes are such that they can be conveniently and effectively reversed by an external source of current, and so put bick the elements into an active condition, without very serious loss of available energy in so doing." — Flemming. NEW CATECHISM OF ELECTRICITY. 49 PRIMARY BATTERIES. The quantity of electricity generated is precisely the same in each method of connecting up, but the effects are quite different. The series gives high electric pressure and small volume of current, while the parallel gives low electrical pressure and large volume of current. Fig. 17. Ac */ gc W ^ c Fig. 18. Batteries for producing electricity are divided into two classes : 1. Open circuit batteries. 2. Closed circuit batteries. 5° NEW CATECHISM OF ELECTRICITY. PRIMARY BATTERIES. An open circnit battery is one adapted by its construction to maintain a current that shall not run down or exhaust itself when left on open circuit ; for instance, where the electricity is not required constantly without intermission. This system is used in telephones, electric bells, burglar alarms, gas lighting, annunciators, etc. The closed circuit battery is used in electric motors, electric lighting, the electric telegraph, etc., and is adapted by its construction to maintain a current a long time without sensi- ble diminution. The action of the Electrical Battery may be briefly described thus : See (Fig. 19.) V^ ^ffl Place in a glass jar some water having a little sulphuric or other dilute acid added to it. Place in it separately two clean strips, one of zinc (Z) and one of copper (C). This cell is capable of supplying a contin- uous flow of electricity through a wire whose ends are brought into connection with the two strips. When the current flows the zinc strip is observed- to waste away, its consumption in fact furnishes the energy required to drive the current through the cell and the connect- ing wire. The cell may therefore be regarded as a kind of chemical furnace in which the fuel is the zinc. Fig. 19. NEW CATECHISM OF ELECTRICITY. 51 PRIMARY BATTERIES. If the strips are made to touch, or are joined by a pair of metal wires, immediately there is a rush of electricity, through the metal from the copper to the zinc, and a small portion of the zinc is at the same time dissolved away ; the zinc parting with its latent energy as its atoms combine with the acid. This energy is expended in forcing a discharge of electric- ity through the acid to the copper strip, and thence through the wire circuit back to the zinc strip. Fig. 20. The real starting point is in the cell at the surface of the zinc where the chemical action is furnishing energy ; for from this point there are propagated through the liquid certain electro-chemical actions which have the result of constantly renewing the difference of po- tential and supplying electricity to the -f- pole just as fast as that electricity leaks away. ELECTRIC BATTERIES. Smee's Battery is shown in Fig. 21 ; it is frequently termed the Smee Cell. It was devised in the year 1830 by Alfred Smee, an English electrician, and has been very extensively used, and consists of a platinized silver plate for the negative NEW CATECHISM OF ELECTRICITY. :l- JL :!=. 1 ELECTRIC BATTERIES. element, with zinc plates for the positive. The platinized silver plate is usually attached to a wooden bar, and the zinc plates, placed one on each side of it, are kept in position by a metallic cramp passing over the top of the bar. A binding screw, passed through the wooden bar and attached to the silver plate, forms the anode, and a sim- ilar binding screw, on the cramp that holds the zincs to the bar, is the cathode. An earthenware con- taining- vessel is required ; the bat- tery is excited by dilute sulphuric acid (7 volumes of water to one of acid). This battery is admirably adapted for electro-depositing and general galvanic experi- ments ; but it is not suitable for producing electric light, nor Fig. 21. for intensity coils. It is easily managed, tolerably constant, and requires only one exciting fluid ; therefore, porous cells are dis- pensed with. The Bun sen Cell, or Battery, shown in Fig. 22 is a two-fluid cell constructed with zinc and carbon electrodes. The negative plate is carbon, the positive plate amal- gamated zinc. The excitant is a dilute solution of sulphuric acid. The top part of the carbon is sometimes impregnated Fig. 22. NEW CATECHISM OF ELECTRICITY. 53 ELECTRIC BATTERIES. with paraffin wax to keep the acid from creeping up, and electrotyped with copper. The force of the Bunsen increases after setting up for about an hour, and the full effect is not attained until the acid soaks through the porous cell. Carbons are not effected, and last any length of time. The zinc is slowly consumed, through the mercury coating. " With one exception, Bunsen's is the only real producer of voltaic currents that can be cheaply applied and depended upon in the production of electric light. Its current, once started, is almost con- stant for about four hours, and a good light may, with confidence, be depended upon for three hours."— Urquhart. A I i r-" El Xc?fi — ~ Fig. 23. The Leclanche Battery or cell was invented by Leclanche, a French electrician, and was the first battery cell in which sal-ammoniac was used. This form of ^p battery, Fig. 23, is in very general use for electric bells, its great recommen- dation being that, once charged, it retains its power without attention for several years. Two jars are em ployed in its construction ; the outer cne is of glass, contains a zinc rod, and is charged with a solution of am- monium chloride (sal ammoniac). Fig. 24. The inner jar is of porous earthenware, contains a carbon NEW CATECHISM OF ELECTRICITY. ELECTRIC BATTERIES. plate, and is filled up with a mixture of manganese peroxide and broken gas carbon. When the carbon plate and the zinc rod are connected, a steady current of electricity is set up, the chemical reaction which takes place being as fol- lows : The zinc becomes oxidized by the oxygen from the manganese peroxide, and is subsequently converted into zinc chloride by the action of the sal-ammoniac. After the bat- tery has been iii continuous use for some hours, the manga- nese becomes exhausted ot oxygen, and the force of the electrical current is greatly diminished ; but if the battery be allowed to rest for a short time, the manganese obtains a fresh supply of oxygen from the atmosphere, and is again fit for use. After about 18 months* work, the glass cell will probably require recharging with sal-ammoniac, and the zinc rod may also need renewing ; but should the porous cell get out of order, it is better to get a new one entirely than to attempt to recharge it. — Dye^r. Gravity Cells or batteries (see figure 24). Instead of employing a porous cell to keep the two liquids separate, it is possible, where one of the liquids is heavier than the other, to arrange that the heavier liquid shall form a stratum at the bottom of the cell, the lighter floating upon it. Such arrangements are called gravity cells > but the separa- tion is never perfect, the heavier liquid gradually diffusing upwards. In Fig. 24 is shown the method which has been adopted of placing the zinc in the upper part of the cell and the copper in the lower part. The solution of the zinc sulphate which NEW CATECHISM OF ELECTRICITY. 55 ELECTRIC BATTERIES. surrounds the zinc is lighter than the copper sulphate which surrounds the copper. Fig. 25 represents the " Crowfoot " Gravity Battery, largely used for Telegraph and closed curcuit work. After the cell is set up sufficient time must be allowed to form these two sulphates before free action is attained. The Daniell Battery consists of a copper cylinder contain- ing another of porous earthenware, in which is placed a zinc rod ; this latter forms the positive and the copper the negative element. The battery requires 2 excitants — a saturated solution of copper sulphate in the cop- per cylinder, and dilute sulphuric acid (1 volume oil of vitriol to 7 of water) in the porous cell. The walls of the latter keep the solutions separate, while allow ing the electric current to pass through. The cathode and anode are formed by attaching binding screws to the zinc rod and copper cylinder. The battery requires no frame, is effective in use, constant, and gives a current of fair intensity. Latimer Clark's Standard Cell. — A standard cell whose E. M. F. is even more constant than that of the Daniell was suggested by Latimer Clark. This battery is composed of pure mercury, on which floats a paste of mercurous sulphate, a plate of zinc resting on the paste. Contact with the mercury, which acts as the positive pole, is made with a platinum wire. The E. M. F. is 1.436 legal volts. Fig. 25. 56 NEW CATECHISM OF ELECTRICITY. DEFINITIONS RELATING TO PRIMARY BATTERIES. The Voltaic-cell is very commonly called the voltaic battery after its discoverer, Volta, and more recently named the primary battery, to distinguish it from the secondary or stor- age battery. A cell consists of a vessel containing a liquid in which two elements are immersed. In One Fluid cells both electrodes are immersed in the same solution. In Two Fluid cells each electrode is immersed in a separate solution, one of which is contained in a porous cup which is then immersed in the other liquid. Dry cells are similar in construction to the open circuit, one fluid cell. The only difference being that starch or some other absorbent is mixed with the liquid forming a jelly which is not easily spilled. The dry cell is very efficient, but when once exhausted is of no further use. All dry cells should have vent holes. The Electrodes of a Primary Battery are the plates of metal or other substance immersed in the liquid. The zinc plate is called the generating electrode and the other plate the con- ducting electro. The latter is usually made of carbon, copper being the next most commonly used. Note. — The plates in a galvanic couple are termed elements as the carbon and zinc plates in cell. The plate unattacked by the solution as the carbon plate in the above battery is termed the negative plate or element ; the one attacked, as the zinc plate, is termed the positive plate or element. NEW CATECHISM OF ELECTRICITY. 57 DEFINITIONS-PRIMARY BATTERIES. The Poles of a battery are the parts of the Electrodes which project out of the liquid. They are distinguished from each other by -f- f° r the positive and — for the negative pole. The terms Pole or Terminal apply to the ends of a break in any electric circuit. The Exciling Fluid is the liquid which when plates are placed in it acts upon the plates and produces a current in a wire joining the two plates. The eleclrolyte is another term for the exciting fluid. The Anode is the plate which the current leaves to enter the liquid of the cell as it flows through the circuit of that battery. The Kathode (or Cathode) is the plate the current enters as it leaves the liquid of the cell as it flows through the circuit of that battery. Polarization is the weakening of the battery current" by means of local action ; this is commonly caused by the collec- tion of hydrogen bubbles on the copper plate. Polarization is overcome in two ways, namely, chemically and mechanically. In the first mentioned a solution or substance which will absorb the free hydrogen is introduced in the cell. In the second the plates have a roughened surface and are kept moving in the solution. Local Action. — When the circuit is not closed the current cannot flow, and there should be no chemical action so long as the battery is producing no current. The impure zinc of commerce, however, does not remain quiescent in the acid, 58 NEW CATECHISM OF ELECTRICITY. DEFINITIONS-PRIMARY BATTERIES. but is continually dissolving and giving off hydrogen bubbles, causing local action. The impurities in the zinc consists of particles of iron, arsenic, and other metals. Separating the elements. — Obviously the positive and nega- tive elements of a battery must not be in contact within the exciting fluid ; they should be separated by a space of y% to %, inch. In the case of batteries without porous cells, periodical attention will need to be given to ensure this condition being maintained. Electrolysis is the decomposition of a chemical compound by the electric current. Bichromate Batteries of bottle shape as in Fig. 20, with two carbon plates, a sliding rod and movable zinc plate, are very extensively used by experimenters and lecturers, because they are always ready for being put to work with one motion of the hand, not necessitating any other preparation ; and as soon as the desired result is obtained, the battery can be put out of action with the same facility. NEW CATECHISM OF ELECTRICITY. 59 MANAGEMENT AND CARE OF BATTERIES. Cleanliness in the battery-room is essential to the best results. The jars, before being used, should be coated with parafine wax for an inch or so from the top. This prevents 1 ' creeping" of the salts and consequent weakening cf the battery fluid. Zincs and coppers, or their homologous ele- ments, should be thoroughly cleaned every time the cell is taken out of use. The zinc, after being thoroughly cleaned, should be rubbed with a little mercury. This prevents local action. Porous cups should be soaked in clean water four or five hours and then wiped dry. If the cells are cleaned and put away ready for use, when the emergency does come, the time spent in cleaning will never be regretted. Fig. 26. The Crown of Caps. 6o NEW CATECHISM OF ELECTRICITY. THE MAGNETIC AND ELECTRIC CURRENT. This branch of science comes naturally under the head of Current Electricity, but, To give a definition of the electric current is like attempt- ing Jo describe something which every one knows about ; it can be said to be simply the flow of electric energy from a point of high pressure to that of a lower, yet it must be owned that until we know with absolute certainty what electricity is we cannot expect to know precisely what a current of elec- tricity is. Note — The circuit may be compared to a system of hot- water pipes ; in a hot-water system there is a steam boiler, a flow and a return circulating pipe with pipe coils, at various points for giving off heat where warmth is required. In an electric installation the dyamo or battery replaces the boiler ; flow and return pipes are represented by the two conducting mains and the pipe-coils by lamps, motors and other apparatus. In a hot- water system it is perfectly evident that whatever may be the quantityof water leaving the boiler, the same must return to it and the quantity of water passing through every part of the flow and return pipes in a given time' must be alike. It is so with the electric current ; whatever may be the quantity of the current starting from the dynamo the same quantity comes back to it. Also, the whole of this quantity must pass through the mains, but it is different with the pressure ; this diminishes in proportion to the work done by the current. Consequently the pressure diminishes as the cur- rent advances along its path. Comparing this again with the hot-water system, the analogy is fairly complete ; for the current may be regarding as losing heat (this is often disguised) as it advances, since in losing its pressure it produces heat and the hot water does the same. NEW CATECHISM OF ELECTRICITY. 6l MAGNETIC AND ELECTRIC CURRENT. Ques. — In cases where part of the electricity is transferred from the body originally electrified to the body touched what is this transfer, of electricity called? Ans. — It is called a discharge. Ques. — When does a discharge of electricity become a current ? Ans. — When electricity is supplied to the body as fast as it is taken away. In considering the practical questions relating to the electric current three characteristic effects need to be thought of : i. The chemical. 2. The thermal (heat). 3. The magnetic. All lines of magnectic force from closed circuits and an electric circuit, so called, may be said to be the path in which electricity passes from a given point around a conducting point back again to its starting point. The discovery of electric currents originated with Galvani, a physician of Bologna, who about the year 1786, made a series of curious and important observations upon the convulsive motions produced by the " return shock " and other electric discharges upon a frog's leg. This immortal discovery arose in the most immediate and direct manner, from an indisposition with which a Bolognese lady was affected, for which her medical adviser prescribed frog -broth. Galvani, the husband of the lady, was Professor of Anatomy in the University of Bologna. It happened that several frogs, 62 NEW CATECHISM OF ELECTRICITY. MAGNETIC AND ELECTRIC CURRENT. prepared for cooking, lay upon the table of his laboratory, near to which his assistant was occupied with an electrical machine. On taking sparks from time to time from the con- ductor, the limbs of the frogs were afFeeted with convulsive movements resembling vital actions. This was the effect of the inductive action of the electricity of the conductor upon the highly electroscopic organs of the frogs ; but Galvani was not sufficiently conversant with this branch of physics to comprehend it, and consequently regarded it as a new phenomenon. He proceeded to submit the limbs of frogs to a course of experiments, with the view to ascertain the cause of what appeared to him so strange. For this purpose, he dissected several frogs, separating the legs, thighs, and lower part of the spinal column from the remainder, so as to lay bare the lumbar nerves. He then passed copper hooks through that part of the dorsal column which remained above the junction of the thighs, without any scientific object, but merely for the convenience of suspending them until required for experiment. It chanced, also, that he suspended these copper hooks upon the iron bar of the balcony of his window, when, to his inexpressible astonishment, he found that whenever the wind or any other accidental cause brought the muscles of the leg into contact with the iron bar, that a similar convulsive kick was produced in the frog's leg. Galvani imagined this action to be due to electricity generated by the frog's leg itself. It was, however, proved by Volta, Professor in the University of Pavia, that the electricity arose not from the muscle or nerve, but from the contact of NEW CATECHISM OF ELECTRICITY. 63 MAGNETIC AND ELECTRIC CURRENT. the dissimilar metals. A greater accumulation of electric energy at one point than at another is what causes the electric current. Such a current always flows through a conducting body if the ends are kept at a different electrical pressure. In order that a continuous flow may be kept up there must be a circuit provided. Currents are called continuous if they flow without stopping in one direction. They are called alternate currents if they continually reverse in direction in a regular periodic manner, flowing first in one direction round the circuit and then in the other. The flow would cease unless the difference in electric pressure is maintained ; this can be done by either a battery or dyna- mo. The current is impelled through the circuit by the elec- tric pressure at the battery or dynamo just as a current of steam is impelled through pipes, of whatever form, by the pressure of the steam formed in the boiler. All dynamos, of whatever form, are based upon the discovery made by Faraday in 183 1, that electric currents are generated in conductors by moving them in a magnetic field. Faraday's prin- ciple may be enunciated as follows : " When a conductor is moved in a field of magnetic force in any way so as to cut the lines of force, there is an electromotive-force produced in the . conductor, in a direction at right angles to the direction of the motion, and at right angles also to the direction of the lines of force, and to the right of the lines of force, as viewed from the point from which the motion originates." To understand clearly Faraday's principle — that is to say, how is it that the act of moving a wire so as to cut magnetic 6 4 NEW CATECHISM OF ELECTRICITY. MAGNETIC AND ELECTRIC CURRENT. lines of force can generate a current of electricity in that wire — let us repeat and further explain this. A wire through which a current of electricity is flowing looks in no way different from any other wire. No man has ever yet seen the electricity running along in a wire, or knows -'wmm Fig. 27. precisely what is happening there, but no electrician is in any doubt as to one most vital matter, namely, that when that which is called an electric current flows through a wire, the magnetic forces with which that wire is thereby, for the time, endowed, resides not in the wire at all, but in the space sur- rounding it. Kvery one knows that the space or "field" surrounding a magnet is full of magnetic "lines of force, " NEW CATECHISM OF ELECTRICITY. 65 MAGNETIC AND ELECTRIC CURRENT. and that these lines run in tufts from the N -pointing pole to the S-pointing pole of the magnet, invisible until, by dusting iron filings into the field, their presence is made known, though they are always in reality there (Fig. 27). A view of the magnetic field at the pole of a bar magnet, as seen end-on, would, of course, exhibit merely radial lines, as seen in Fig. 28. Fig. 28. Now, every electric current (so-called) is surrounded by a magnetic field, the lines of which can be similarly revealed. To observe them, a hole is bored through a card or a piece of glass, and the wire which carries the current must be passed up through the hole. When iron filings are dusted into the field they assume the form of concentric circles (Fig. 12), 66 NEW CATECHISM OF ELECTRICITY. Fig. 29. MAGNETIC AND ELECTRIC CURRENT. showing that the lines of force run completely round the wire, and do not stand out in tufts. In fact, every conducting wire is surrounded by a sort of magnetic whirl, like that shown in Fig. 29. A great part of the energy of the so-called electric current in the wire consists in these external magnetic whirls. To set them up requires an expenditure of energy ; and to maintain them requires also a constant expenditure of energy. It is these magnetic whirls which act on magnets and cause them to set as gal- vanometer needles do at right angles to thej conducting wire. Now, Faraday's principle is nothing more nor less than this : that by moving a, wire near a magnet across a space in which, there are magnet lines, the motion of the: wire, as it cuts across those magnetic lines,, sets up magnetic whirls round the moving wire, or, in other language, generates a so- called current of electricity in that wire. It is however necessary that the moving conductor should, in- its motion, so cut the magnetic lines as to alter the number of lines of force that pass through the circuit of which the moving conductor forms part. If a con- ducting circuit — a wire ring or single coil, for example — be moved along in a uniform mag- netic field, so that only the same lines of force pass through it, no current will be generated, see Fig. 30. Or if, again, as in MAGNETIC WHIRL SURROUNDING WIRE CARRYING CURRENT. NEW CATECHISM OF ELECTRICITY. 67 MAGNETIC AND ELECTRIC CURRENT. Fig. 31, the coil be moved by a motion of translation to another part of the uniform field, as many lines of force will be left behind as are gained in advancing from its first to its second position, and there will be no current gener- ated in the coil. If the coil be merely rotated on itself round a central axis, like the rim of a fly-wheel, it will not cut any more lines of force than before, and this motion will generate no current. But if, as in Fig. 32, the coil be tilted in its motion across the uniform field, or rotated round any axis in its own plane, then the number of lines of force that traverse it will be altered, and currents will be generated. These currents will flow round the ring coil in the right- handed direction (as viewed by a person looking along the magnetic field in the direction in which the magnetic lines run ) if the effect of the movement is to diminish the number of lines of force that cross the coil ; they will flow round in the opposite sense, if the effect of the movement is to increase the number of intercepted lines of force. If the field of force be not a uniform one, then the effect of taking the coil by a simple motion of translation from a place where the lines of force are dense to a place where they are less dense, as from position 1 to position 2 in Fig. 32, will be to generate currents. Or, if the motion be to a place where the lines of force run in the reverse direction, the effect will be the same, but even more powerful. 08 NEW CATECHISM OF ELECTRICITY. MAGNETIC AND ELECTRIC CURRENT. Fig. 30. CIRCUIT MOVED WITHOUT CUTTING ANY LINES OF FORCE. Fig. 31. CIRCUIT MOVED SO AS TO ALTER NUMBER OF LINES OF FORCE THROUGH IT. NEW CATECHISM OF ELECTRICITY. 69 MAGNETIC AND ELECTRIC CURRENT. We may now summarize the points under consideration and some of their immediate consequences, in the following manner : (1.) A part, at least, of the energy of an electric current exists in the form of magnetic whirls in the space surround- ing the conductor. Fig. 32. (2.) Currents can be generated in conductors by setting up magnetic whirls round them. (3.) We can set up magnetic whirls in conductors by mov- ing magnets near them, or moving them near magnets. Note. — As a matter of fact, it would be impossible to have a magnetic field exactly like Fig. 32 ; for, in the intermediate part, between the upper and lower fields, the magnetic lines would be of curved complex form. 70 NEW CATECHISM OF ELECTRICITY. MAGNETIC AND ELECTRIC CURRENT. (4.) To set up such magnetic whirls, and to maintain them by means of an electric current circulating in a coil, requires a continuous expenditure of energy, or, in other words, con- sumes power. (5. ) To induce current in a conductor, there must be rela- tive motion between conductor and magnet, of such a kind as to alter the number of lines or force embraced in the circuit. (6.) Increase in the number of lines of force embraced by the circuit produces a current in the opposite sense to de- crease. (7.) Approach induces an electromotive-force in the op- posite direction to that induced by recession. (8.) The more powerful the magnet-pole or magnetic field the higher will be the electromotive-force generated. (9.) The more rapid the motion, the higher will be the electromotive-force. (10.) By joining in series a number of such moving con- ductors, the electromotive-forces in the separate parts are added together ; hence very high electromotive- forces can be obtained by using numerous coils properly connected. (11.) Since the quantity or strength of the currents depends on the resistance of the conductors in the circuit, as well as on the electromotive-force, all unnecessary resistance should be avoided. (12.) Approach being a finite process, the method of approach and recession (of a coil towards and from a mag- NEW CATECHISM OF ELECTRICITY. 7 1 MAGNETIC AND ELECTRIC CURRENT. net pole) must necessarily yield currents alternating in direction. (13.) By using a suitable commutator, all the currents, direct or inverse, produced during recession or approach, can be turned into the same direction in the wire that goes to supply currents to the external circuits ; and if the rotating coils are properly grouped so that before the electromotive-force in one set has died down another set is coming into action, then it will be possible, by using an , appropriate commutator, to combine their separate currents into one practically uniform current. (14.) To the moving conductor which is generating the electromotive-force by cutting the magnetic lines, it makes no difference what the origin of those lines is, whether from a permanent magnet of steel or from an electro-magnet, pro- vided the number of magnet lines so cut is the same. (15.) To the moving conductor it makes no difference what 'the origin of the motion is. Whether the motion be due to a steam engine, or to a gas engine, or to hand driving, or to the driving of an electric current in the wire itself (as in the case of electric motors), it makes no difference to the moving conductor, which provided that the speed and the number of magnet lines given will generate the same electromotive- force. 72 NEW CATECHISM OF ELECTRICITY. ANIMAL ELECTRICITY. Animal Electricity, — Several species of cretures inhabiting the water have the power of producing electric discharges by certain portions of their organism. The best known of these are the Torpedo, the Gytnnotus, and the Silurus, found in the Nile and the Niger. The Klectric Ray, of which there are THE ELECTRIC E£L> three species inhabiting the Mediterranean and Atlantic, is provided with an electric organ on the back of its head, as shown in illustration on this page. This organ consists of laminae composed of polygonal cells to the number of 800 or 1000, or more, supplied with four large bundles of nerve fibres ; the under surface of the fish is — , the upper -(-. In the Suri- nam eel, the electric organ goes the whole length of the body along both sides. It is able to give a most terrible shock, and is a formidable antagonist when it has attained its full length of 5 or 6 feet. NEW CATECHISM OF ELECTRICITY. 73 POINTS " RELATING TO THE ELECTRIC CURRENT. To designate the character of a current, and also a current with reference to its origin, various terms are used. Battery current, dynamo current, earth current, etc. These are terms used to designate the current from a battery, a dynamo or currents flowing through the earth on account of difference of potential at different points. When a difference of electrical force or pressure exists in two places connected by a conductor, or a series of conducting bodies, a current will flow between the two points. The dif- ference of force may be due to several causes, but whatever the cause the current will flow. The two places may be a few inches apart, as in a wire from a primary battery, or miles apart, as in a transmission system, or in the currents of the earth or air. They may be connected by a small copper wire, the rails of a street railway, or by a combination of a large number of conducting bodies. This conductor may be of large capacity, of low resistance, or may be a poor conducting medium. Two kinds of current are generated, distinguished by the di- rection which they flow. The continuous or direct current 74 NEW CATECHISM OF ELECTRICITY. ELECTRIC CURRENT. which flows continuously in one direction, and the alternating reversed current, which alternates the direction of its flow are the currents used, and these two kinds include a number of classes. The alternating current may alternate the direction in which it flows ten thousand times a second, or twenty -five times a second ; this is called the frequency of its alterna- tions. A constant current is an unvarying current. Although the voltage may vary the amount of current does not change. In series arc lighting systems the current is universally constant. The quantity of electricity conveyed by a current is propor- tional to the current and the time it continues to flow. Note. — The telegraphers have made a series of tests for the purpose of ascertaining the actual amount of time which elapses while a signal is be- ing flashed from America to Europe along the Atlantic cable. The tests referred to were made at the McGill University, Montreal, Canada, in June, 1891. In carrying out these experiments a duplex circuit was arranged dii both land and sea along the entire line, which connects Mon- treal with Waterville, Ireland. When the line was '* cleared " a chrono- graph was attached to the observatory wire at Montreal and everything declared in readiness. The instrument clicked off the signal, while the experimenters watched the chronograph with breathless interest. It did not seem to them " like an age of suspense," however, for within one and one-eighth seconds the chronograph recorded the return of the sig- nal, while it slowly dawned upon the interested scientists present that the flash had actually made the round trip from Montreal to Ireland in a pe- riod of time but little greater than one-sixtieth of a minute. In that very short space of time, infinitesimal and almost unthinkable that electric message was flashed a distance almost as great as one-third the circum- ference of the world, or to be exact, 8,022 miles. Other experiments made the same day showed a variation of from one to i.r seconds for the signal to make a round trip. NEW CATECHISM OF ELECTRICITY. 75 ELECTRIC CURRENT. The passage of a current through a conductor cannot be ef- fected without a loss of power i. e. , diminished pressure. Loss of power means work done ; if this work has a useful purpose it is not a loss in the common sense of the word, but in all other cases it is waste. Thus, any pressure of the cur- rent used in a lamp is no loss and nearly the whole pressure of the current, in a well designed installation, may be regarded as utilized in passing through the lamps, motors and other apparatus, a system shown. The electric current, like steam and water flows in the di- rection of the least resistance. This is a general statement, to be modified by the fact that where two or more paths exist some current will pass through each. See page 79, "Divided Currents." The speed of the electric current has been quite accurately determined to be identical with that of light. Experiments have demonstrated the remarkable fact that alternating currents of a tension ten times that which is used in electro execution do not effector injure the human body when passed through the same ; and in fact are hardly per- ceptible in case the currents alternate 100,000 times in a second, that is, change their direction at this almost incom- prehensible velocity. 7 6 NEW CATECHISM OF ELECTRICITY. THE SOLENOID. Fig. 33. BAR MAGNET SHOWING WNES OF FORCE). Fig. 34. n r\ a u n w jQl p" JQ o uhreclurrv of Uli££ offorcoi. # ELECTRO MAGNET SHOWING LINKS OF FORCE. Fig. 35. Current, leaves CurrercU enUrs SOL.ENOID SHOWING LINES OF FORCE. NEW CATECHISM OF ELECTRICITY. 7 7 THE SOLENOID. Solenoids. — If a wire, while being traversed by an electric current, is wound up into a spiral coil, the arrangement becomes a "solenoid." (See Fig. 35.) For with a long closely wound spiral, conveying a current, the lines of force are similar to those of a bar-magnet. (See Fig- 33-) These lines of force must be thought of as closed loops linked with the current. The conductor conveying the current passes through all the loops of force, and these are, so to speak, threaded or slung on the current line of flow. It will be readily inferred that since a solenoid of wire convey- ing a current attracts and repels by its extremities the poles of a magnet, two such spiral conductors conveying currents should attract and repel each other. This is found to be the case. The lines of force form continuous closed curves running through the interior of the coil, and issuing from one end and entering into the other end of the coil, and that the arrange- ment of the external magnetic field is very similar to that of a permanent bar magnet of cylindrical form as represented in Big. 34. A solenoid has north and south poles, and in fact possesses all the properties of an ordinary permanent magnet, with the important difference that the magnetism is entirely under control, for it is found that under all circumstances the strength of the magnetic field of a solenoid is at every point proportional to the strength of the electric current passing through its coils ; if the current is increased, the magnetism is increased in proportion also ; and if the current is stopped, 78 NEW CATECHISM OF ELECTRICITY. THE SOLENOID. all trace of magnetism disappears. The magnetic effect or the magnetising power of a solenoid is also proportional to the number of turns of wire composing the coil. As previously mentioned, the strength of the magnetic field of a solenoid is strictly proportional to the strength of the current flowing in its coils ; this, however, is no longer true when the solenoid is provided with an iron core or becomes an electro magnet, for the reason that the magnetic properties of the iron alters with the strength of the magnetic field. At first, the presence of the iron enormously increases the strength of the field ; after a time, however, as the strength of the current flowing in the exciting coils is increased, the conductibility of the iron for the lines of force appears to decrease, until a point is eventually reached when the pres- ence of the iron core appears to have no effect whatever in increasing the strength of the field. At this stage the iron core may be regarded as being saturated with lines of force, and any further increase of mag- netising power will produce only a slight increase in the strength of the field, any such increase being that due to the effect of the coils alone acting merely as a simple solenoid. Current Sheets — When a current enters a solid conductor it no longer flows in one line but spreads out and flows through the mass of the conductor. When a current is led into a thin plate of conducting matter it spreads out into a ' ' current sheet ' ' and flows through the plate in directions that depend upon the form of the plate and the position of the pole by which it returns to the battery. NEW CATECHISM OF ELECTRICITY. 79 CURRENT SHEETS. Thus, if wires from the two poles of battery are brought into contact with two neighboring points in the middle of a very large flat sheet of tinfoil, the current flows through the foil not in one straight line, but in curving " lines of flow," which start out in all directions and curl round to meet in curves very like those of the " lines of force." that run from the N pole to the S pole of a magnet (Fig. 14). When the earth is used as a return wire to conduct the telegraph currents, a similar spreading of the currents into current "sheets occurs. Divided Circuits. — If a circuit divides into two branches, uniting together again, the current will also be divided, part flowing through one branch part* through the other. The relative strengths of current in the two branches will be pro- portional to their conductivities, i. e., inversely proportional to their resistances. Direction of Lines of Electrical Force. — The direction of the lines of force is found at any spot by holding a small mag- netic test-needle at that point and noting the direction in which it sets, and the direction of its marked or north pole. Various rules have been given for recollecting the direction of the current induced in a conductor when moved so as to cut lines of magnetic force and alter the amount of magnetic induction passing through the circuit. These rules depend generally on some association with the position and motion in swimming, or upon the direction of the cardinal points and the motion of the sun, earth, etc. Apart from the difficulty of recollecting the rules themselves, it requires an effort of NEW CATECHISM OF ELECTRICITY. DIRECTION OF ELECTRIC CURRENT. imagination to apply them to the case of an armature, bar or wire, disc or loop, and as a means of economising time and brain labor the following rule by Prof. Flemming has been found very useful. " If any circuit is being moved in a magnetic field, and it is required to know the direction in which electricity is being urged in any portion of the circuit which is cutting lines of force, proceed as follows : Hold the first and middle fingers and thumb of the right hand in a position as nearly as possible at right angles to each other, so as to represent three axes in space. Make the following associations. Let the direction of the forefinger represent the direction of the ♦lines of force. Let the direction of the thumb represent the direction at right angles to the direction of the field in wich the element of the circuit is moving, then the direction of the middle finger represents the direction of the induced current. ' ' See Fig. 36. In railroad work now becoming of primary importance, i t is always understood that the current flows out on the trolley wire and comes back through the rail or by the return conduc- tor connected to the rail. This return conductor being some- times placed underground and some instances upon poles with underground connection to the rail every six or eight poles. Note. — The following rule gives the relation of the electric current to the lines of magnetic force produced by it. If you look at the positive (or north) end of an electro-magnet, the direction of the current setting up the magnetism is that of positive rota- tion. Similar^, it you imagine a s ction made in a conductor carrying a current and look at the positive end of this conductor ( i. e., the end from which the current is flowing) the direction of lines of force set up about NEW CATECHISM OF ELECTRICITY. FLEMING'S RULE. Fig. 36. Direction of < Right Hand, Y eA Motion. **$£ > X Illustration of Fleming's Rule. Fleming's Rule : " Hold the thumb and the first and the middle fingers of the right hand as nearly as possible at right angles to each other, as in Fig. 36, so as to represent three rectangular axes in space. If the thumb points in the direction of the motion, and the forefinger points along the direction of the magnetic lines, then the middle finger will point in the direction of the induced electro-motive force." 82 NEW CATECHISM OF ELECTRICITY. DIRECTION OF ELECTRIC CURRENT. the conductor in the direction of positive rotation. Conversely, if you look at the negative (south) end of a solenoid, the direction of the current is that of negative rotation, and if you look at the negative end of a conductor (*'. NEW CATECHISM OF ELECTRICITY. I05 ELECTRICAL MEASUREMENTS. Measurement of electric pressure and current volume. The foregoing described instruments belong rather to the experimental and testing departments of electrical science, but the introduction of the dynamo and motor, with their powerful currents have demanded other instruments of greater range and capacity. This has caused the development of in- struments for measuring The Volt. The Ampere. The Ohm. The Volt is the practical unit of measurement of pressure. The Ampere is the practical unit of measurement of rate of flow. The Ohm is the practical unit of measurement of resistance. An Ammeter or ampere meter is a device for measuring the number of amperes which are passing through a current and showing the same by direct reading on a scale. The ammeter is a commercial form of galvanometer in which the deflections (or twistings) of a magnetic needle are valued in amperes. Ammeters are made in various forms based upon several different principles, among which are 1. Permanent-magnet ammeters. 2. Blectro-magnet ammeters. 3. Spring ammeters. 4. Gravity ammeters. io6 NEW CATECHISM OF ELECTRICITY. ELECTRICAL MEASUREMENTS. Fig. 47. THE AMMETER. Fig. 48. THE VOLT METER. NEW CATECHISM OF ELECTRICITY. I07 ELECTRICAL MEASUREMENTS. When electric motive force of one volt passes through a resistance of one ohm it produces one ampere, hence an am- pere is a combination of two things, electric motor force and resistance. An ampere will do a certain amount of work, will decompose a given weight of water, and will deposit .005084 grain of copper per second and in several ways it may be demonstrated what an ampere is. An ampere measurer is just as necessary to all constant current circuits as is a steam guage to a steam plant. Fig. 49. STATION AMMETER. Some ammeters are designed to be used only for standards of comparison and others are intended and so constructed that they can remain continuously in circuit. Each instrument, if well constructed, has considerable range. See Fig. 47. IOS NEW CATECHISM OF ELECTRICITY. ELECTRICAL MEASUREMENTS. The Voltmeter is shown in Fig, 48. It is different from the ammeter in having high resistance and is connected between the two poles or positive and negative wires. The voltmeter measures electric pressure just as the steam guage measures the pressure of steam. In the illustration two scales are shown, the outside one indicating volts and the inner scale one-twentieth of a volt. Fig. 50. THE) WATT METEJR. (i-5th Actual Size.) An instrument that will measure accurately from 1 to 100 volts will not give good results for measuring potentials of 1,000 to 5,000 volts. An ammeter that will measure accur- ately the thousandths of amperes in the current of an indue- NEW CATECHISM OF ELrCTRICITY. ICQ ELECTRICAL MEASUREMENTS. tion coil, will not do at all for measuring ioo or 1,000 am- peres. Fig. 47 shows the standard ammeter and Fig. 49 in- . strument for use to indicate large station output of electricity. The Station Meter. — Electric energy is now supplied in large quantities and distributed for lighting, motive power and heating from large central stations or power-houses. From the power-house distributing mains of copper go out consisting of " feeders" leading into the network of con- ductors. The station meter, illustrated in Fig. 49, is designed to indicate with extreme accuracy the large units being con- stantly produced and utilized. The Watt Meter. — The watt is an electric unit obtained by multiplying the volt, which represents pressure, into the am- pere, which represents volume ; hence, a meter designed to measure electricity sold to customers for motors, lamps and heaters is called a watt-meter or measurer and is illustrated in Fig. 50. The watt- meter consists of two coils of insulated wire, one fine and one coax-se, so arranged in the electric circuit that they act upon each other. These produce a motion in a train of clockwork by which the electric energy is recorded on dials in the same manner as gas consumption is recorded in a gas meter. This record is made in watt hours, being 1 volt X 1 ampere X 1 hour = one watt hour. NEW CATECHISM OF ELECTRICITY. ELECTRICAL MEASUREMENTS. Fig. 51. THE EDISON METER. Note.— This is a chemical meter, the amount of chemical action being proportioned to the ampere hours. NEW CATECHISM OF ELECTRICITY. ELECTRICAL MEASUREMENTS. The Edison Meter is shown in Fig. 51. A glass bottle contains two zinc plates, immersed in a standardized solution of sulphate of zinc. The electric current enters the bottle from the terminal of one plate, passes through the solution and goes out through the terminal of the other plate. In so doing it disintegrates from the "losing plate" particles of zinc and deposits on the " gaining plate " their exact equiva- lent. The amonnt thus transferred is in exact proportion to the amount of current passing through the bottle, according to a well-known physical law. The quantity of current shunted through the bottle is a definite proportion of the quantity going directly into the house, " resistances " within the meter fixing the exact proportions. The exactness of this proportion is verified before the meter is placed on the system, and can be checked at any time by electrical tests on the con- sumer's premises. Kach three wire meter contains two pairs of bottles, one pair on the positive, the other on the negative side of the system. The same amount of current passes through each bottle of the pair and by weighing the " gaining plate " in one bottle and the " losing plate ' ' in the other, a double check is obtained. Note. — After a meter is installed on a customer's premises it is then sealed until the next round of the "meter- wagon." The company's representative unseals the meter, removes the bottles, replacing them by- others whose plate-weights have been carefully recorded, and brings the four bottles in a four-part box back to the Meter Department. Each meter has its proper number ; each bottle-box has an identifying label which bears the record of the bottle-changing and meter-inspection ; and the plates within the bottles are also specifically numbered. NEW CATECHISM OF ELECTRICITY. ELECTRICAL RESISTANCE. Measurements of Resistance. — Unlike the frictional resist- ance of water in pipes, the frictional resistance of the wire is readily computed and measured, making the discussion of the internal action of the electric system much simpler than one of the hydraulic system would be. In fact, we may measure the resistance power in a certain definite unit. The resistances of wires and circuits are measured in prac- tice by comparing them with certain standard "resistance coils," sets of which are often employed arranged in "resist- ance boxes ; " the particular instruments employed in making the comparison being of two kinds, namely, the differential galvanometers and the Wheatstone's bridge. These resistance coils require great accuracy in their measurement, in the insulation of the wire and in the mount- ing of the coils. The wires must be carefully selected and tested. The insulation must be such as will withstand the highest temperature to which it is subjected without change. Silk thread is extensively used for the insulation. The wire is usually wound on spools or in coils so as to occupy as little room as possible, and are mounted in a box, which protects them from injury and places them in convenient form to be carried. The ends of the coils are connected to plates or binding posts in the cover. This, also, must be carefully constructed so that the resistance at the point of conract will be as low as possible. A single coil is sometimes placed in an ebony case, or any number, according as the work for which it is to be used seems to require. When a large number is placed in one NEW CATECHISM OF ELECTRICITY. 113 ELECTRICAL RESISTANCE. box the ends of the wires are usually connected to metal blocks, placed at such a distance apart that a metal plug will make a good connection between any two. The resistance coils being uniform in size, the entire resistance or any part may be used. The Mariner's Compass. — The practical interest of mag- netism (electricity) applied to navigation need not be en- larged upon. The mariner's compass usually consists of a flat circular card, on the under surface of which are secured four to eight light magnetic needles. The card swings in a " com- pass-box " ona pivot placed at its centre, the box having a pointer corresponding to the direction of the ship's head — the box is supported on gimbols — an arrangement for preserving it horizontal while the ship is pitching and tossing. The card is divided into thirty-two points by a star engraved on it, Fig. 52, and it is by these points the course is steered. Fig. 52. N THE MARINER'S COMPASS. 114 NEW CATECHISM OF ELECTRICITY. SYMBOLS, ABBREVIATIONS AND DEFINITIONS. It is well for the reader to memorize the following ques- tions and answers in the same way that the letters of the alphabet or the multiplication are committed to memory, as more or less of them are used upon every page of printed matter relating to electricity. QuKS. What is the meaning of the letters E. M. F. ? Ans. Electro-motive force (abbreviated K. M. F.) is the name given to the force or cause which produces an electric current, see page 45. The fundamental property of matter is, that it cannot impart motion to itself. The inability of matter to put itself in motion is called inertia — that which causes motion is force and that which causes the electric current is electro-motive force (K. M. F.) Ouks. What are the '''-powers of ten " ? ANvS. This system of notation is sometimes called " Index Notation.' ' This consists in using some power of ten as a multiplier in order to avoid the use of long rows of cyphers. NEW CATECHISM OF ELECTRICITY. 115 SYMBOLS, ABBREYIATrONS AND DEFINITIONS. The following examples will show the convenience of the system. The resistance of selenium is about 40,000,000,000, or 4 X io 10 times as great as that of copper ; that of air is about io 36 , or 1 00 , 000 , 000, 000 , 000, 000 , 000, 000, 000 times as great. The velocity of light is about 30,000,000,000 centimetres per second, or 3 X io 10 times. OuKS. What is the C. G. S. system of notation ? Ans. The C. G. S. unit represents the work of a body equal in weight to one gramme, through a space equal to one centimetre in one second. This is the absolute or fundamental unit of electrical work or energy and denominated an erg. QuKS. What is the definition of function ? Ans. This word is derived from a Latin word meaning to perform— hence its general sense is "performance." Note. — The system of units adopted by almost universal consent is the so-called " Centimetre-Gramme-Second " system, in which the funda- mental units are : The Centimetre as a unit of length ; The Gramme as a unit of mass ; The Second as a unit of time. The Centimetre is equal to 0.3937 inch in length. The Gramme is equal to is.ttto or grains. The Second is i-6oth of one minute. All physical quantities, such as electricity, force, velocity, etc., can be expressed in terms of these fundament at quantities : length, mass, and time. Each of these quantities must be measured in terms of its own units. Il6 NEW CATECHISM OF ELECTRICITY. SYMBOLS, ABBREVIATIONS AND DEFINITIONS. Ques. What is an ohm ? Ans.' An ohm is' the practical unit of electric resistance and many researches have been made to determine its work- ing value. For a wire of a certain quality the resistance is in proportion to the length and also in proportion to the cross section or size. QuKS. What is Ohm' s taw f t Ans. The question of relation between volts, amperes and resistance is expressed under one universal law, which is known as Ohm's law, c=^ y in which " C " stands for current, "E" for electro-motive force or volts, and " R " for resistance. Current in amperes equals pressure in volts divided by resistance in ohms, or again, electro-motive force equals resist- ance multiplied by current ; and again, resistance equals electro-motive force divided by the current ; thus it will be seen that these terms are dependent upon each other, and that their relation to each other is expressed by this law. These are written in three wavs : K I. c. — R 2„ K. = CXR, E or 3- R. — C If one volt will force one ampere of current through a cir- cuit having one ohm resistance it will take five volts to force five amperes through the same circuit. If this resistance should be increased to five ohms it would take five times five NEW CATECHISM OF ELECTRICITY. 117 SYMBOLS, ABBREVIATIONS AND DEFINITIONS. amperes for the proper number of volts to force the amperes through, which would be 25 volts. From this it can be seen that it is very easy to obtain any one of these quantities when we have the other two. QuKS. What is a volt ? Ans. The volt represents an electric pressure nearly equal to that of a Daniel battery cell described page 55 ; it is the practical unit of K. M. F. such as may be induced in a con- ductor which cuts lines of magnetic force at the rate of one hundred millions per second. QuES. What is an ampere ? Ans. The ampere is the practical unit of electric current and represents a volume of a current produced by a pressure of one volt flowing through a conductor having a resistance of one ohm. Ques. What symbol is used to indicate battery cells joined up in one row, or as they are said to be " in series." Ans * Jiliiilihlk By tlle use of a s y mbo1 ( see cut ) in n'lM'rrl'j which a short thick line stands for Fig. 53. the zinc and a longer thin line stands for the copper (or carbon). Thus V^ig. 53 represents six cells joined in series. Similar symbols are used for " condensers" in diagrams of electric circuits. IlS NEW CATECHISM OF ELECTRICITY. SYMBOLS, ABBREVIATIONS AND DEFINITIONS. OuKS. What is meant by reluctance ? Ans. The reluctance of a magnetic circuit corresponds with the resistance of an electric circuit. QuES. What is the meaning of ■ ' coil" f Ans. That which is gathered or wound into a ring or circle. . OuES. What is the definition of i ' laminated ' y ? Ans. It means plated — consisting of plates, layers, or scales laid one over the other. QuKS. What is the definition of ' 'periphery " ? Ans. It means the circumference or outside of a circle, ellipsis, or other regular curvilinear figure. OuKS. What is the definition of the zvord "potential" f Ans. This oft-used word means in its primary sense — power to do work — in this connection it denotes power to do electric work. OuKS. What is the definition of ' i shunt ' ' ? Ans. This is a contraction of "shun it." In railways a turning off to a siding that the principal line of rails may be left free — this idea is transferred to electricity literature. Ques. What is the definition of calibration ? Ans. This word comes from one originally meaning " the diameter of a body " and is kindred to the word " calipers." i NEW CATECHISM OF ELECTRICITY. IIQ SYMBOLS, ABBREVIATIONS AND DEFINITIONS. In electrical literature it means to determine the absolute or relative value of the scale divisions or of the indications of any electrical instrument, such as a galvanometer, watt-meter, etc. QuKS. What is meant by periodicity ? Ans. The rate of succession of alternations, or the rate of change in the alternations or pulsations of an electric current. Qu^s. What is staggering f Ans. This term is used when one brush is placed slightly in advance of the other brush so as to bridge over a break in the circuit of the armature wires. QuKS. What is polarity ? Ans. Polarity is that quality possessed by a mineral when it attracts one pole of a magnetic needle and repels the other. OuKS. What is meant by the term "inversely " f Ans. This means to turn into a contrary direction — a change of order so that the last becomes first. QuES. What is meant by permeability ? Ans. Permeability is the conductivity for magnetic lines of force. In other words, it is a measure of the ease with which magnetism passes through any substance. The permea- bility of good soft wrought iron is sometimes 3000 times that of air, varying with the quality of the iron. Note. — The magnetic permeability decreases as the magnetization increases. When a piece of iron has been magnetized up to a certain intensity its substance shows a tendency to reach magnetic saturation. In good iron this is reached at about 125,000 lines of force to the square inch of area of cross section. NEW CATECHISM OF ELECTRICITY. SYMBOLS, ABBREVIATIONS AND DEFINITIONS, QuES. What is the air gap ? Ans. A name given to the part of the magnetic circuit composed of air. Usually the air gap is between the pole pieces and the iron core of the armature. More or less air gap is necessary to provide room for the armature wires and also for mechanical clearance between armature and pole pieces. QUKS. What is the output of a dynamo ? Ans. By the output of a dynamo is meant the electrical activity of the machine in watts, as measured at its terminals; or, in other words, the output is all the available electrical energy. Quks. What is the intake of a dynamo f Ans. The intake of a dynamo is the mechanical activity it absorbs, measured in watts. Quks. What is ' ' torque ' ' t Ans. This is the force which produces the motion around a shaft or axis. It is often expressed as the pounds of " pull ' ' excited at the end of a lever arm one foot long. An example is the "pulling " or turning force of an armature of an electric motor, on its shaft. Quks. What is the definition of "electrical efficiency ' " ? Ans. In a dynamo or generator the relation of total elec- tric energy produced, to the useful, or available electrical energy, thus : if a machine produced but half the work repre- sented by the energy it absorbed, the rest disappearing in NEW CATECHISM OF ELECTRICITY. 121 SYMBOLS, ABBREVIATIONS AND DEFINITIONS. wasteful expenditure — in heating the bearings — in overcoming the resistance of the air, etc., its efficiency would be expressed by Yz or " fifty per cent." Ques. What is a watt ? Ans. This is the unit of electric power, or the T j ¥ of a horse power. It expresses the quantity of work per second, done in any electrical resistance. It is the volt-ampere. QuKS. What is a kilo-watt ? Ans. The name is given to 1,000 watts. One kilo- watt is slightly more than i l /£ horse-power. Kx. — A dynamo of 20 units, or a 20 unit machine, is one capable of giving an output of 20 kilo-watts. QUES. What is a mil? Ans. A mil is one-thousandth part of a lineal inch. It is equal to .025399 millimeter. .000083 °f a foot. .001000 of an inch. A mil is a unit of length. QUKS. What is a circular mil? Ans. A unit of area ; employed in designating the cross- sectional area of wires and other circular conductors. It is equal to .78540 of a square mil. If the diameter of a wire is given in mils the square of its diameter gives its cross-sectional area in circular mils. NEW CATECHISM OF ELECTRICITY. Fig. 54. THK INDIANAPOLIS MACHINE, NEW CATECHISM OF ELECTRICITY. 1 23 THE DYNAMO. The word dynamo, meaning power, is one transferred from the Greek to the English language, hence the primary mean- ing of the term signifying the electric generator is the electric power machine. The word generator, too, is also derived from a word meaning birth-giving, hence also the dynamo is the machine generating or giving birth to electricity. Again, the dynamo is a machine driven by power, generally steam or water power, and connecting the mechanical energy expended in driving it into electrical energy of the current form. Note. — It should be understood that an electric dynamo or battery does not generate electricity, for if it were only the quantity of electricity that is desired, there would be no use for machines, as the earth may be regarded as a vast reservoir of electricity of infinite quantity. But electricity in quantity without pressure is useless, as in the case of air or water, we can get no power without pressure, a flow of currents. As much air or water must flow into the pump or blower at one end as flows out at the other. So it is with the dynamo ; for proof that the current is not generated in the machine, we can measure the current flowing out through one wire, and on through the other, it will be found to be precisely the same. As in mechanics a pressure is necessary to produce a current of air, so in electrical phenomena an electromotive force is necessary to produce a current of electricity. A current in either case can not exist without a pressure to produce it. IL'4 NEW CATECHISM OF ELECTRICITY. THE DYNAMO. Fartaday's great discovery was made in the autumn of 1831, and after various experiments he produced his " new electrical machine " shown in Fig. 55. This piece of apparatus is pre- served and was shown in perfect action by Prof. S. P. Thomp- son in a lecture delivered April nth, 1891, after an interval of sixty years. Its operation is as follows : 1 ' L/et a copper disc be hung on a shaft and so balanced as to turn freely. A horse-shoe magnet is so placed that its Fig. 55. G THE) FARRADAY DYNAMO (A. D. 1831.) inter polar lines of force traverse the disc from side to side. A copper ' i brush ' ' is placed so as to touch the shaft, and one to touch the edge of the wheel. A handle serves to rotate the wheel in the magnetic field. Now let the wheel be rotated clockwise, and if the north pole of the magnet is nearest the reader, the result will be to produce a radial current flowing out at the brush on the edge and back, through the brush on the shaft." In Fig. 56 let D show the dynamos in action and let A B be a long lead with its farther end to earth. L,et the other NEW CATECHISM OF ELECTRICITY. 125 THE DYNAMO. brush or terminal of the dynamo be also connected to earth. The dynamo when in action is just like a cistern of water at a high level, or a pump ; it urges electricity into the lead A B, and at every point a b c in the lead there is a certain electric pressure analogous to the water-pressure in the pipe. The electricity flows in the lead between any two points a and b, in virtue of a difference of electrical pressure between these points ; and the flow or quantity per second, or current strength, is determined by two things ; this difference of pres- sure and the resistance of the piece of lead between the points considered. Along the lead there is a regular fall or gradient of pressure represented by the sloping dotted lines in lower ■oart of Fig. 57. It may thus be seen that the same laws which control the flow of water apply exactly to the electric current. Dynamos, are classified into 1. Unipolar dynamos. 2. Bi-polar (or 2 poles). 3. Multipolar dynamos. This division is caused by their different construction and is treated under the heading * l pole pieces." The dynamo is used for three principal purposes. 1. Incandesent lighting. 2. Arc lighting. 3. For distribution of power. 126 NEW CATECHISM OF ELECTRICITY. THE DYNAMO. Fig. 56. t : 4 fr & ■ £ «i e ? jjj"" a DYNAMO IN ACTION. ■^ 1 Pig. 57. I % J V .-■=_ --'■€-_ — . - "z ' C' c -••« <£' : \\ e' -■\ = : "* f 1 . - ** V' Gs b C :<£ e f £_, \ J? A fc r ^^. FLOW OF WATER UNDER PRESSURE, OR HEAD. NEW CATECHISM OF ELECTRICITY. 12 7 THE DYNAMO. Its various modifications of size and form are designed to meet these, but there is still one other use to which it is put, i. e., for experiments which come outside the limit of this work. When used for power purposes the machine is called a generator, /. e. y it generates electricity to be used through motors. The dynamo in its very simplest form consists of two main portions : (i) an armature, which in revolving induces electromotive-forces in the copper conductor wound upon it; (2) a field-magnet, that is to say a magnet whose function is to provide a field of magnetic lines, to be cut by the armature conductors as they revolve. In all dynamos, whether for .continuous currents or for alternate currents, these two parts can be recognized. In almost all continuous-current machines the field-magnet stands still, and consists of a comparatively simple and massive electromagnet ; whilst the armature, which is a more complex structure, is the portion which rotates. In alternate-current machines the field-magnet is usually multipolar, and in the majority of cases is stationary, whilst the armature rotates ; nevertheless there are many alternators of recent pattern in which the armature stands still and the field-magnet rotates. The criterion as to which portion is properly called " field magnet,' ' and which " armature," is not the question of rota- tion or otherwise. The name of field-magnet is properly given to that part which, whether stationary or revolving, maintains its magnetism steady during the revolution • and the name 128 NEW CATECHISM OF ELECTRICITY. THE DYNAMO. armature is properly given to that part which, whether re- volving or fixed, has its magnetism changed in a regularly repeated fashion when the machine is in motion. In the case of continuous current machines there is another feature of first importance, namely, the apparatus for collect- ing the currents from the revolving armature. This apparatus consists of two essential parts ; the commutator (or collector) attached to the armature and revolving with it, and the brushes. The latter, which are conducting contact pieces held pressed against the surface of the rotating commutator, are provided with special brush-holders mounted upon an adjustable frame or rocker. In the case of alternate-current machines there is no need of a commutator ; but, in general, these machines have to be provided with some device for making a sliding connection. ■ For in those forms in which the armature rotates, its coils must be brought into continuous metallic relation with the conductors of the main circuit ; and in those forms in which the armature is stationary and no such arrangement is needed at that part, there must still be sliding contacts to maintain the coils of the revolving field-magnet part in continuous metallic connection with the auxiliary exciting circuit. In either case the appropriate device consists of a pair of collect- ing rings, against each of which a brush presses. Hence, to summarize, the dynamo-electric generator or the dynamo-electric machine, proper, consists of five principal parts viz.: j. The armature, or revolving, portion. .NEW CATECHISM OF ELECTRICITY. I2Q THE DYNAMO. 2. The field magnates, which produce the magnetic field in w T hich the armature turns. 3. The pole-pieces. 4. The commutator or collector. 5. The collecting-brushes that rest on the commutator cylinder and take off the current of electricity generated by the machine. Fig. 58. the: simplest conceivable dynamo. The simplest conceivable dynamo is that shown in Fig. 58, consisting of a single loop of wire C C, rotating or turning on spindle A A between the poles of a large magnet N S. The brushes are represented by B B and the electric circuit by the line B. The lines of force are represented by the dotted lines running between tfye two poles N and S. ISO NEW CATECHISM OF ELECTRICITY. THE DYNAMO. Parts of Dynamo. — The nature and uses of the different parts of a dynamo will be understood by reference to Fig. 59, which represents a complete machine. In this type of dynamo, as in the majority of continuous current dynamos, the mag- netic field is stationary whilst the armature revolves in it. Fig. 59, A COMPLETE DYNAMO. The magnetic field in the particular dynamo illustrated is pro- duced by the iron horse-shoe electro magnet M, which is, excited by the current flowing in the magnetizing coils K B. The ends or poles of the field magnet M are bored out so as to form a circular chamber within which the armature A rotates. This latter consists of an iron core rigidly fixed to a steel shaft NEW CATECHISM OF ELECTRICITY. 13 1 THE DYNAMO. or spindle S, which revolves in the two bearings F F. Upon one end of the shaft is fixed the. driving pulley P. The iron core is overwound with a large number of insulated copper conductors or coils, the ends of which are connected to the circular commutator C. Two stationary metallic brushes, B B, press upon the latter, and convey the current generated in the coils of the armature through the flexible conductors or " leads," L Iv, to the terminals T T, from whence it is con- veyed to the external or working circuit. When the machine is in action, the armature and conductors or coils are caused to rotate within the magnetic field, produced by the electro magnet M, by means of a belt passing over the pulley P. In consequence, K. M. F.s are induced in the conductors, which, on being commutated at the commutator, are transmitted through the medium of the brushes and flexible leads to the two terminals T T, giving rise to a difference of potential be- tween the latter. In the classification of dynamos the two principal divisions are i. Direct current dynamos, and 2. Alternating dynamos, and in each class there are many forms of construction. The direct current dynamos are again divided into three classes, thus, I. Series wound. 2. Shunt wound. 3. Compound wound. 132 NEW CATECHISM OF ELECTRICITY. THE DYNAMO. The manner in which the wiring of the fixed magnets are connected to the armatures gives rise to the foregoing classifi- cation : Series Dynamos. — The manner in which the connections of the series wound dynamo are arranged is shown in Fig. 60. Fig. 60. SERIES WOUND DYNAMO* The coils of the field magnet are wound with a few turns of thick insulated wire, and being joined in series with the armature, the whole of the current generated in the latter passes direct NEW CATECHISM OF ELECTRICITY. 133 THE DYNAMO. through them, and thence to the external circuit. The current in passing through the coils of the field magnet energizes the latter, and creates a magnetic field between the two poles N S, in which the armature revolves. Fig. 61 SHUNT WOUND DYNAMO. Shunt Wound Dynamos. — The shunt wound dynamo differs from the series wound machine, in that an independent circuit is used for exciting its field magnet. This circuit is composed of a large number of turns of fine insulated copper wire, 134 NEW CATECHISM OP ELECTRICITY. THE DYNAMO. which are wound round the field magnet and connected to the brushes, so as to form a shunt or ' ' by pass ' ' to the brushes and external circuit. Fig. 61 shows the connections of the shunt wound dynamo, from which it will be seen that two paths are presented to the current as it leaves the armature, between which it divides in the inverse ratio of the resistance ; whilst one part of the current flows through the magnetizing coils, the other portion flows through the external circuit. In all well designed shunt dynamos, the resistance of the shunt circuit is always very great, as compared with the resistance of the armature and external circuit, and the strength of the current flowing in the shunt coils rarely exceeds 12 amperes in even the largest machines. Compound Wound Dynamos. — These are in fact a combina- tion of the series wound and the shunt wound machines. See Fig. 62. The field magnet of this dynamo is wound with two sets of coils, one set being connected in series, and the other set in parallel, with the armature and external circuit. For the purpose of automatically maintaining a constant pressure in incandescent lighting the compound wound dynamo is now generally employed. Separately Excited Dynamos. — This type of machine is not so extensively used as the self-exciting type, owing principally to the fact that an independent dynamo or battery is necessary for exciting its field magnet. It finds its chiefest application in the electric transmission of power, and in charging accum- NEW CATECHISM OF ELECTRICITY. 135 THE DYNAMO. ulators, and in all cases where a high E. M. F. is required with a varying current. The connections of this dynamo are shown in Fig. 63, where N S are the poles of an electro magnet which is excited by the current generated by the Fig. 62. COMPOUND WOUND DYNAMO. independent dynamo or battery D. The armature A revolves in the space between the two pole pieces, and the two brushes B x B 2 press upon the commutator C, and convey the current generated in the armature to the external circuit E. The 136 NEW CATECHISM OF ELECTRICITY. THE DYNAMO. E. M. F. and output of the dynamo is usually regulated by varying the strength of the magnetizing current (produced by the dynamo or battery D) flowing in the coils of the field mag- net by means of the hand regulator R. Fig. 63. *9 AhR <* WINDING FOR SEPARATELY EXCITED DYNAMO. Note— In the above illustration, as also Figs 60, 61, 62 the external cir- cuit is intended to represent a series of lamps in process of receiving the current, NEW CATECHISM OF ELECTRICITY. 137 Fig. 64. 138 NEW CATECHISM OF ELECTRICITY. THE ARMATURE. The armature should always be considered as a cylindrical magnet having poles in opposite sides of its periphery, and the whole mas 3 of the armature in what is known as the mag- netic flux of the field. The armature is placed where it will be in the strongest magnetic flux and the iron core of the armature acts as a stepping stone between the poles of the field. It is because of this intermediate mass of iron that the flux is so strong. Fig. 65. THE EDISON (BAR) ARMATURE. Note. — There are several ways of arranging the coils upon the arma- ture, and the methods adopted may be classified as follows : — :. Drum Armatures, in which the coils are wound longitudinally upon the surface of a cylinder or drum. Examples : the Siemens and Edison machines. 2. Ring Armatures, in which the coils are wound around a ring, Ex- amples : Gramme and Brush machines. NEW CATECHISM OF ELECTRICITY. 1 39 THE ARMATURE. The types of armature in most extensive use at the present time are the following : — The Ring or Gramme Armature, in. which the coils are arranged upon an iron ring. The Drum or Siemens Armature, in which the coils are arranged upon the surface of an iron cylinder or drum. 3 THOMPSON HOUSTON ARMATURE). Each of these forms of armature has its special advantages, and in a general way it may be said that whilst the ring arma- ture is more suitable for generating small currents at high potentials, the drum is better adapted for producing moderate potentials and large currents. NEW CATECHISM OF ELECTRICITY. THE ARMATURE. Fig. 67. THE WESTERN ARMATURE). Fig. 68. THE WESTERN ARMATURE COMPLETE Fig. FIG. 69 REPRESENTS THE DISC AS BUII/T UP. NEW CATECHISM OF ELECTRICITY. I4I THE ARMATURE. Fig. 66 shows the drum form of armature (Thompson- Houston). Fig. 65 shows the drum armature (Kdison). Fig. 67 represents the uncompleted form of the drum arma- ture and Fig. 68 the same in order for use. Fig. 69 represents the toothed core-disk of which drum armatures are largely built up. These have two advantages over smooth armatures. (1.) The teeth present an excellent means of driving the copper conductors which lie between them. (2). The teeth may be brought very close to the polar surfaces of the field-magnet. To set against these real advantages are the disadvantages of somewhat greater labor required in milling out the channels between the teeth of the assembled core ; the extra difficulty of insulating the core from the conductors ; and the liability of the teeth to set up eddy-currents in the polar faces. The latter can be cured by making the teeth numerous and narrow, also by laminating the polar faces with grooves, and by enlarging the clearance. Or, best of all, by finally serving the entire armature outside the copper conductors with a layer of iron wire. Armatures built up of toothed core -disks have been much used in recent years, particularly for motors. The advantages offered by toothed core-disks are possessed to a still higher degree by core-disks pierced with apertures, for the purpose of ventilation, just within the periphery. Fig. 70 represents the ring or gramme armature. The arrangement of the lines of force in the magnetic field I42 NEW CATECHISM OF ELECTRICITY. THE ARMATURE. between the two poles N and S when the ring is inserted therein, is shown by dotted lines in the figure. If the arma- ture core be rotated in the direction of the arrow, the whole of the conductors, being immovably fixed to the armature, Fig. 70. DIAGRAM OF RING ARMATURK. must necessarily partake of the movement. Owing to this peculiar arrangement a very intense magnetic field is created between the outer surface of the armature core and the pole- faces, while the interior space within the core remains almost entirely free from lines of force. NEW CATECHISM OF ELECTRICITY. 143 -■=-' . . . , — . THE ARMATURE. A broad distinction may be set up between wire wound armatures and those with built up coils consisting of bars and connectors, or of specially constructed portions that are put together instead of being wound on. These are classified as: 1. Wire wound armatures. 2. Bar armatures. Wire-wound armatures are usual for outputs below ioo am- peres, including all arc-lighting machines. For armatures having outputs exceeding 200 amperes bar-armatures are more frequent, owing to the inflexible nature of wires that are thick enough to carry these currents. The two classes com- prise several varieties as under : — Wire-wound Armatures. Bar Armatures. Single round wire. Round bars. Two or more round wires in Rectangular bars. parallel. Rectangular strips. Stranded wire. Rectangular bars of corn- Single square wire. pressed stranded wire. Single rectangular wire. - Special forgings. The armatures of alternators may be of ring, drum, pole, or disk type ; but in all cases the grouping of the windings is different from that which would be adopted for a direct-cur- rent dynamo. The ring armature is considered the most desirable, because it is not so liable to give out ; and if it does, the cost of repairing is less than for a drum armature, and the time lost on account of the damage is less, as a ring armature may 144 NEW CATECHISM OF ELECTRICITY. THE ARMATURE. be put in service as soon as the repairs are made ; and again Fig. 76. when an armature short-circuits, it seldom O burns out more than two or three coils. If it is of the ring type the coils can be readily removed and new ones wound in their places, and if the workman is sufficiently skilled he will not have to disconnect the commutator to make the repairs ; therefore, the cost of replacing the damaged coils will be small. With a drum armature the case is quite different. Armature Cores. — The cores of all practical armatures are now invariably laminated or constructed of iron wire ribbons or disks and are frequently constructed with deep channels or Fig. 72. TOOTHED CORES. grooves in the outer periphery, as shown in Fig. 72, in which the conductors are wound. The projections or teeth in this method of construction present an excellent means of driving NEW CATECHISM OF ELECTRICITY. 145 THE ARMATURE. and protecting the conductors, but the difficulty of insulating the latter from the core is increased by their use, and they also have a tendency to produce eddy currents in the pole pieces of the field magnets, causing a heating of the latter. The latter disadvantage can, however, be obviated to a great extent by making the teeth very narrow and numerous. In most cases notches or keyways are stamped on the inner periphery on the disks as in Fig. 71. Fig. 73. LAMINATED CORE). This core is built up of thin plates of sheet iron of the shape shown at B, Fig. 73. Three of them form a perfect ring with the teeth projecting from the circumference. Upon the inner surface are two hooks which enclose the bolts of the spider. In order to break joints the segments are placed over alternate spaces. This method of building up the core and securing the segments binds the whole firmly together. The 146 NEW CATECHISM OF ELECTRICITY. THE ARMATURE. strain is not thrown in the least on the spider, a fact that allows the spider to be made of smaller cross sections. The winding of the armature is shown at C. It is com- posed of four wires of the form shown. This winding is care- fully insulated before being placed in the slot of the armature core, thus the removal of a coil is an easy matter. The com- mutator connection is made by means of screws which pass through the connector on the end of the winding. Points Relating to the Armature.— -There should be a uniform clearance of at lea«t an eighth of an inch all around between the armature and the pole pieces. They should be perfectly balanced so as to run without jar or vibration. The essential service of the armature is to rotate in the magnetic field, whilst carrying electric currents in its copper coils or conductors. While in the first place power is required to drive the armature, in the second the armature, rotating, becomes a source of power. Most makers test their armatures for balance by laying the journals on two parallel metal rails (or " knife-edges ") and noting whether the armature will remain in any position without tending to roll. It is well indeed to balance them thus on completing the core ready for winding, and again after winding. If the end core-disks have been made of thick iron, holes can be drilled in these to restore perfect balance ; or leaden plugs can be inserted. NEW CATECHISM OF ELECTRICITY. 147 THE ARMATURE. After an armature has been wound trie conductors must be secured in their place by a number of external bands, known as binding wires. These must be very strong, to resist centri- fugal force and to hold the conductors from being dragged aside ; and yet at the Same time must occupy very little radial depth, that the clearance between conductors and pole-face may be as narrow as possible. Some makers use hard-drawn brass, others phosphor-bronze, others steel, for binding wires. Armature cores are usually built up upon an internal frame or skeleton pulley firmly keyed to the shaft. In drum arma- tures this internal supporting frame may be omitted, the core- disks themselves being keyed directly on to the shaft. A drum armature should be allowed to stand for several days, so that the insulating varnish may become thoroughly dry and hard. If the armature is started before it is dry, the wires may shift under the strain of centifugal force, and furthermore, the liquid in the varnish, in most cases, is of low enough resistance to allow the current to break through the insulation and burn out the coils, thus rendering it necessary to make the repairs over a second time. Cores are always laminated, being constructed either of (i) sheet iron disks , (2) iron ribbon, or (3) iron wire. Ribbon is seldom used. For drums and elongated rings, disks stamped out from soft sheet iron are almost universal. The usual thickness is from 40 to 80 mils). They should be of the softest iron. After being stamped out they should be an- nealed, and the burr at the edges removed. Some makers at this stage assemble them upon the shaft, turn them down I48 NEW CATECHISM OF ELECTRICITY. THE ARMATURE. truly in the lathe, then take them apart and remove the burr by grinding lightly on an emery wheel, then remount them. Before being finally mounted on the shaft they must be lightly insulated one from the other. For this purpose it is usual either to cover one face of each core-disk with varnished paper, or to enamel both faces of each core-disk. It is usual to make the two end core-disks of stronger iron, sometimes as much as X~i ncn thick. Wire cores were at one time largely in vogue, having been used by Gramme. The soft iron wire, varnished or slightly oxidized on its surface, was wound on a special former, then removed, taped externally, and wound with the copper wire conductors. Wire cores have disadvantages which have largely stopped their use. OOOO NEW CA'ILCHISM Q> ELECTRICITY. 149 Fig. 74. THE) WKSTINGHOUS3 MACHINE. I50 NEW CATECHISM OF ELECTRICITY. FIELD MAGNETS. The field magnet, the function of which is to produce an intense magnetic field within which the armature revolves, may be either a permanent magnet or an electro magnet. Electro magnets, however, possess such a number of important advantages over permanent magnets, that they are now in- variably used in all machines intended for practical work. The chiefest advantages of the electro magnet, as compared with the permanent magnet, lies in the power of regulating the strength of the magnetic field produced by the former, by suitably adjusting the strength of the magnetizing current flowing through its coils, and also in the greater magnetic effect obtained, weight for weight, from the electro magnet over ihe permanent magnet. The field magnets of a dynamo may be excited, either by the current furnished by an independent dynamo or battery, in which case the machine is said to be " separately excited,' ' or by the current generated in the armature of the machine of which the field magnet forms part, when the machine is said to be self-excited. The latter type of machine depends for its action upon the presence of residual magnetism in its field magnet. Owing to this residual magnetism, a weak magnetic field is always NEW CATECHISM OF ELECTRICITY. 151 FIELD MAGNETS. present Between the pole pieces of a field magnet ; hence, when the armature is rotated in the armature chamber, its conductors cut the lines of force contained in this magnetic field, and a small B. M. F. is set up in the armature in con- sequence. The ends of the magnetizing coils being suitably connected to the brushes, if these latter are in contact with the com- mutator, and a closed circuit through the field magnet wind- ings is formed, this small K. M. F. immediately sends a minute current through the exciting coils ; this immediately increases the strength of the magnetic field, and as a conse- quence an increased K. M. F. is induced in the armature. This results in a stronger current being sent through the exciting coils, and the increase of magnetism which follows results in an increased E). M. F. in the armature. Thus the process goes on, until eventually, for a given speed of rotation of the armature, the E. M. F. reaches a maximum value, beyond which it will not increase with- out a further increase in the speed of rotation ; the exciting current has then arrived at a constant value, and the magnetization of the machine will remain at a constant strength, and maintain the E. M. F. so long as the armature rotates at its normal speed. If the armature ceases to revolve, the field magnets will of course be deprived of their exciting current, and will therefore lose their magnetism ; the iron will, however, retain a sufficient amount of residual magnetism to again start the process when the machine is again started. 152 NEW CATECHISM OF ELECTRICITY. FIELD MAGNETS. Whilst the construction of the armatures of different dynamos may be said to be very much the same, differing in small details only, and being confined to two types, viz., the ring and drum respectively, the construction of the field magnets varies greatly, almost every manufacturer having his own particular form and arrangement. This great variety in the form of the field magnets of different dynamos, is due in a large measure to consideration of economy involved in the manufacture by different makers, and also, to a less extent, to the different conditions under which a machine is required to work. For example, it is sometimes necessary for a machine to give a maximum of output with a minimum of weight, and under such circumstances the field magnet is constructed wholly of wrought-iron, and this necessarily entails an entirely different method of construction and arrangement than if cast-iron were employed. Again, as a rule, the direct coupling of the armature to the engine-shaft involves a different form of field magnet than would be the case if the armature were belt driven. Owing to difficulties of construction, and other considera- tions, field magnets are not in practice usually constructed out of a single-piece of iron, but are usually built up of a combination of parts, and composed either wholly of wrought or cast iron, or of a combination of both. The construction of a typical field magnet is illustrated in Fig. 75, from which it will be seen that it may be divided into five parts, viz.: — the two limbs of cores M M, upon which NKW CATECHISM OF ELECTRICITY. 153 Fig. 75. FIELD MAGNETS. the exciting coils C are wound ; the two end portions P P, called the '.' pole pieces," which are bored out so as to form the " armature chamber" within which the armature revolves ; and the yoke, Y, which serves to connect the two limbs together, and thus complete the magnetic circuit. The permeability of wrought-iron being very much greater than cast-iron, the portions M M of the field magnet, upon which the exciting coils are wound, are frequently constructed of this material ; these portion^ are also usually constructed of a circular section, and thus the amount of wire required for exciting the field magnet is TYPICAI, FIELD MAGNET. [Fig. 76. economized to the ut- most extent. The pole pieces P P and the yoke Y are in many cases of cast-iron, bolted on to the wrought-iron limbs. Although innumer- able forms of field magnets have been devised, they can all be arranged into two groups, viz., those in SALIENT POLE FIELD MAGNET. which the poles are " salient," and those in which the poles 154 NEW CATECHISM OF ELECTRICITY. FIELD MAGNETS. are ''consequent." A salient pole is the term applied to poles, which are produced at the ends of a bar of iron, in distinction to consequent poles, which are produced in a con- tinuous ring of iron. Fig. 77. THE OVERTYPE tflEl/D MAGNET. The salient pole form of field magnet, being least costly to construct, is most frequently met with in practice. Fig. 76 shows its simplest form ; in this arrangement only one mag- netizing coil is required, this being wound upon the yoke NEW CATECHISM OF ELECTRICITY. 155 FIELD MAGNETS. which is usually of wrought iron, let into and bolted to the cast iron pole pieces N S. The paths and directions of the lines of force, with the magnetizing current flowing in the Fig. 78. THB UNTJERTYPB ItlKI/D MAGNET. direction shown, is indicated by the dotted arrow heads and lines. Another form of field magnet which is very exten- sively used, and in which two exciting coils are required, is i 5 6 NEW CATECHISM OF ELECTRICITY. FIELD MAGNETS. shown in Fig. 77. In this type the limbs are usually of wrought-iron, of rectangular section, bolted to the bed place of the machine, which therefore forms the yoke of the mag- net. The magnetizing coils are wound upon bobbins, which Fig. 79. doublk field magnet. are slipped over the limbs, being held in place by the cast iron " horns" C C screwed on at the lower portion of the armature chamber. Consequent Pole Field Magnets.— The leading type 'of consequent pole field magnets are illustrated in Fig. 55. The paths and direction of the lines of force in the field and armature cores are indicated as before by the dotted arrow heads and lines. Fig. 55 may be looked upon as a double NEW CATECHISM OF ELECTRICITY. 157 FIELD MAGNETS. magnet, the exciting coils being wound upon what may be regarded as the yokes of the magnets. The direction of the electric current flowing in the magnetizing coils are such that two similar poles are produced in each pole piece. The form of field magnet illustrated in Fig 77 is known as " the over type ; " when the armature is placed below the field coils and yoke, as represented in Fig. 78, the arrange- ment becomes "the under type." This latter form is very extensively used in large dynamos owing to the low centre of gravity of the revolving armature resulting in increased stability and freedom from vibration ; it is also invariably employed when the armature is to be coupled direct to the engine crank-shaft. In most cases the whole of the field magnet is composed of wrought- iron, the two limbs being formed of rectangular slabs bolted to the yoke. As a rule, this class of field magnet is supported upon a bedplate of cast iron, and therefore it is necessary to magnetically separate its pole pieces therefrom, otherwise they will be magnetically short circuited, or the lines of force will flow through the bed- plate in place of passing through the armature core. To effect this the pole pieces are supported at a suitable distance from the bedplate by "foot steps" S S or brackets of zinc, brass or other non-magnetic substance. Note.— It must always be borne in mind that in all dynamo-electric machines the electro-motive force generated is in proportion to the number of turns of wire in the rotating armature and to the speed of revolution, and the function, or use, of the magnetic field is to produce the proportionate needed lines of force. 158 NEW CATECHISM OF ELECTRICITY. FIELD MAGNETS. Multipolar Field Magnets. — These generally consist of 4, 6, 8 or more poles, arranged in alternate order around the armature. They may be arranged in two classes according as the poles are salient or consequent poles. Fig. 80 represents Fig. 80. ^C A \ p^v\ » 1 iffl * rnr • if, \ 1 MUI/riPOI,AR FlEl,D MAGNET. a very commonly used type of multipolar field magnet ; it consists of a ring of iron, having four pole pieces projecting inwardly, over which the exciting coils are slipped, the ring forming a common yoke for all the poles. As a rule, it is NEW CATECHISM OF ELECTRICITY. 159 FIELD MAGNETS. made in two portions, bolted together horizontally, so that the upper portion may be lifted off for examination of the armature. Following the principles, or underlying laws, of the mag- netic circuit, the relative values of the very many typical forms of the field magnet may be judged by their approach to these general principles : i. Their permeability. 2. Their compactness of form. 3. Their firmness of joints. 4. Their greatness of cross section. 5. The softness of the iron of which they are composed. Fig. 81. I,IN3 WORK. NEW CATECHISM OF ELECTRICITY. Fig. sie^m^ns-hai.ske; machine;. NEW CATECHISM OF ELECTRICITY. COMMUTATORS. Fig. 83. These are collectors, or to use the old name, "com- muters," of the electric current. Their function or use is to collect the currents produced by the cutting of the lines of Torce so as cause them all to concur to a desired result. In general the commutator is formed of alternating sections of con- ducting and non-conducting material running longwise to the axis upon which it turns. Its place is in the shaft of the machine, so that it rotates therewith. Two brushes, or pieces of conducting material, press upon its surface. COMMUTATOR. The apparatus for collecting the currents of dynamo- machines may be divided into three types: First. Direct-current dynamos with closed-coil armatures, as used for incandescent lighting and other work requiring a constant or nearly constant potential, are furnished with a commutator consisting of a considerable number of parallel 162 NEW CATECHISM OF ELECTRICITY. THE COMMUTATOR. bars secured around an insulating hub, and presenting a cylindrical surface, against which press a pair (or in some cases more than one pair) of brushes or sets of brushes. Second. Direct-current dynamos of the open-coil type, as used for arc lighting, and giving a constant or nearly con- stant current, are provided with a commutator consisting of a comparatively small number of segments, each cover- ing a considerable angle, and separated by air-gaps from one another. Third. Alternators with revolving armatures need a pair of collecting rings of metal, each provided with one or more Fig. 84. brushes, or some analogous device to form a sliding con- nection with the circuit. Alternators with revolving field-magnets need a similar device to convey the exciting current to the moving coils. Fig. 84 represents a com- mutator consisting of Lr shaped bars bolted to a disk of slate and arranged so that the segments or parts are separated by an air space. Commutators are made in a great variety of forms. They are used on electric generators, on induction coils and else- where for changing the direction of the electric current* COMMUTATOR WITH AIR GAP. NEW CATECHISM OF ELECTRICITY. 163 THE COMMUTATOR. " Points" Relating to the Commutator. — The number of bars of the commutator depends on the scheme of winding and on the number of sections in which the armature winding is grouped. Increasing the number of bars diminishes the tendency to spark, and lessens the fluctuations of the current. An even number of bars is preferable to an odd number ; and for ring- wound armatures the cores of which are usually carried on three-armed spiders, it is preferable that the num- ber of bars should be a multiple of three. There are, how- ever, two practical reasons against making the number of bars very great. Increasing the number increases the cost. Again, in large machines having but one turn of the armature wind- ing from each bar of tha armature to the next, the number cannot be greatly increased without exceeding the voltage desired. On the other hand, it is found for small dynamos, that if the number of bars is increased, each bar becomes so thin, that a brush of the proper thickness to collect the current would lap over, or bridge, more than two commutator bars at once. The bars should be of a length proportionate to the num- ber of amperes that is to be taken off at them. Modern practice varies somewhat, but it may fairly be represented by some such figure as (1.2) 1 i-5th inches for 100 amperes. The mode of attachment of the bars should be such as to make the greatest amount of length available. 164 NEW CATECHISM OF ELECTRICITY. THE COMMUTATOR. They should also be of considerable thickness to allow them to be turned off occasionally to preserve their round- ness. As for the material most makers use hard drawn copper, made in long lengths of the proper section and cut off to .the length required. It is needful to have a good insulati n be- tween each bar and its neighbors, and a specially good insula- tion between the bars and the sleeve or hub around which they are mounted, and also between the bars and the clamp- ing devices that hold them ; for the difference of potential is small between neighboring bars, and much larger between the bars and other metal-work. The insulating material must not absorb oil or moisture ; hence asbestos and plaster are inadmissible. Vulcanized fibre and paper are not by them- selves adequate, though mechanically strong. Mica is the only satisfactory material. Although the application of the commutator to the coil has the effect of causing the current to flow always in the same direction in the external circuit, it has no effect whatever upon the value of the K. M. F., or the strength of the current, dur- ing a complete revolution of the coil. This still remains as before. The commutator bars are the separated segments or parts upon which the brashes rest. Alternators have no commutator, but they usually need a pair of sliding contacts to convey the currents to and from the rotating part. The usual device is a pair of contact rings NEW CATECHISM OF ELECTRICITY. I65 THE COMMUTATOR. of copper or gun-metal mounted on insulating hubs on the shaft, with one or more brushes to press on each contact-ring. In those alternators in which the revolving part is the arma- ture, great care must betaken to insulate well the two rings from each other, and from the shaft. Commutators with air-gaps between the bars have been used but the difficulty is to keep the gaps from being filled by the metallic dust produced by the wearing of the brushes. Fig. 85. INCANDESCENT UMP SHADE. i66 NEW CATECHISM OF ELECTRICITY. EAU CLAIRE, WIS., MACHINE. NEW CATECHISM OF ELECTRICITY. 167 THE BRUSHES. The brushes bear upon the commutator, and make sliding contact with the armature and working circuits. It is needful that they should have a certain amount of flexibility, in order that they may accommodate themselves to any little in- equality which may occur upon the surface of the commutator, Fig. 87. and also to avoid cutting or scoring the latter ; with these objects, they are usually made of copper or brass gauze, wire, or flexible strip. Gauze Brushes. — This type of brush is now very exten- sively used, owing to its great flexibility and soft and yieldicg nature, resulting in decreased wear of the commutator. It is l68 NEW CATECHISM OF ELECTRICITY. THE BRUSHES. made up of a sheet of copper gauze, folded round several limes, with the wires running in an oblique direction, so as to form a solid flat strip of from X mcn to % mcn m thickness, as shown at A, Fig. 87, the thickness increasing with the volume of the current to be collected. The object of folding the gauze up with the wires running in an oblique direction is to prevent the ends of the brushes fraying or threading out, which would be the case if the gauze was folded up in any other manner. Wire Brushes. — This brush (B. Fig. 87) which was much used previous to the invention of the gauze brush, is made up of a bundle of brass or copper wires, laid side by side and soldered together at one end, being harder than the gauze brush, it is more liable to cut or score the commutator > and it is also more troublesome to trim. Strip Brush. — This is probably the simplest form of brush, but is not very extensively used owing to its lack of flexibility. It consists of a number of strips of copper or brass, laid one upon the other and soldered at one end, as in C, Fig. 87. Carbon Brushes. — When metallic brushes are used upon the commutators of high tension machines, they frequently give rise to excessive sparking, and also heating of the arma- ture, the metallic dust given off appearing to lodge between the segments of the commutator, thus partially short circuit- ing the armature. To obviate this, carbon brushes are fre- quently used on such dynamos, this substance being found very effectual in the prevention of sparking. The brushes NEW CATFXHISM OF ELECTRICITY. 1 69 THE BRUSHES. are usually in the form of oblong blocks placed " butt " end on the commutator, and fed forward as they wear away by means of a spring holder. Wheel Brushes have been employed among the many de- vices for collecting the current. These consist of small wheels, or disks, bearing against and rotating on the surface of the commutator. Lead of the Brushes is the dispacement or lead in advance of, or beyond the position at right angles to the line connect- ing the poles of the field magnet. In a motor the brushes are set back of the right angle or are given a negative lead. The necessity for the lead arises from the counter magnet- ism or the magnetic reaction of the armature. In magnetism the tendency of hard iron, or steel especially, is the cause of the "lag" or magnetic retardation. It is to accommodate this variation that brush holders are provided with devices for moving them backward and forward. Note.— Flexible Carbon Brushes— Carbon commutator brushes, as commonly used, consist of one or two blocks of carbon, pressed against the commutator by a spring to maintain the contact. In the case of street railway motors, subject to violent oscillations, the carbons are often jolted away from the commutator, thus causing sparks and burning of the commutator. In order to dispense altogether with springs and at the same time to maintain the pressure constant, Professor Geo. Forbes of London, has devised a brush of flexible carbon, carbonized cloth, com- pressed into a metal case open at the side, facing the commutator, the case serving both as a holder for the flexible carbon, and also as a ter- minal for the circuit ; owing to its flexibility, it maintains contact with the commutator at an infinite number of points. By this means it is as- serted a much better contact is maintained, which is not broken, or even varied, by the jolting on a railroad car. i7o NEW CATECHISM OF ELECTRICITY. THE BRUSHES. In all well-designed dynamos not less than two brushes are used on each side of the commutator ; this allows of either brush being removed, and examined and trimmed, while the machine is running. It also allows of the brushes being ad- Fig. 88. VARIOUS KINDS OF BRUSHES. justed upon the commutator independently of each other, any uneven wear of the commutator being thus prevented, and better contact made. Brush Holders. — In order to secure sparkless collection of the current, and to prevent undue wear of the commutator, it is needful that the pressure of the brushes upon the latter NEW CATECHISM OF ELECTRICITY. 171 THE BRUSHES. should be capable of being adjusted to meet requirements ; it is also needful that they should be capable of being fed for- ward as required and that they be furnisued with a movement to permit of the brushes being raised from contact with the commutator when necessary. Brush Rockers, — As previously mentioned, when a dynamo is working, the neutral points, or the points upon the com- mutator where sparkless collection of the current can be made, vary in position as the load upon the dynamos varies, moving round in the direction of rotation as the load increases, and vice versa. It is necessary, therefore, in order to avoid sparking, to shift the brushes bodily upon the commutator from time to time, without in any way altering the adjustments of the brush holder springs or breaking the working circuit. To enable this to be effected the brushes with their holders are, in ordinary bi-polar dynamos, usually fixed upon a " rocker" or "yoke." Points relating to Brushes— The brushes must be held firmly, and joined with a good metallic contact to their circuit. Brush-holders must permit brushes to be withdrawn or fed forward as required. Brushes must be held to make contact at proper angle to the surface of the commutator. Brushes must bear with proper pressure upon the com- mutator ; if too light, they will jump and spark ; if too heavy, they will cut the commutator into ruts, 172 NEW CATECHISM OF ELECTRICITY. THE BRUSHES. Brush- holders must permit brushes to be raised from con- tact. They must also permit, by a proper mechanical catch, of the brushes being held raised out of contact. Insulated handles should be provided for all dynamos work- ing above ioo volts, so that the brushes may be raised and adjusted without risk of shocks. The insulation of the brush, or of brush and brush-holder together, must be very thorough. Each maker has his own particular arrangement for giving these essential motions to the brushes and they are best illus- trated in the various ' ' cuts ' ' of dynamos and motors to be found on other pages. NEW CATECHISM OF ELECTRICITY. 1 73 DYNAMO FOUNDATIONS, ETC. "Points" relating to the dynamo. — The place chosen for the dynamo should be dry, free from dust, and preferably where a cool current of air can be had. It should allow a sufficient room for a belt of proper length, unless the dynamo is direct-driven. It is most important to secure good foundations for every dynamo ; and if the dynamo is direct-driven, but is not on the same bed-plate as the engine, a foundation large enough for both together should be laid down. Stone or concrete may be used, or brick built with cement, having a large thick stone bedded at the top. For small dynamos the holding-down bolts may be set with lead or sulphur in holes in the stone top ; but for large dynamos the bolts should be long enough to pass right down to the bottom, where they should be secured into iron plates built in. If long holes are left in the foundations for the holding-down bolts they should be filled in with thin cement after the latter have been put in place. All belt- driven dynamos ought to be provided with tight- ening gear to take up the slack. If the dynamo is not pro- vided with sliding rails under its bed-plate and tightening screws, the less desirable method of employing a tenting pulley, may be used. In any case the bed for dynamo must be quite level, and the shaft set properly parallel with the driving pulley. 174 NEW CATECHISM OF ELECTRICITY. Fig. 89 WINDSOR (CONN.) MACHINE. 1 NEW CATECHISM OF ELECTRICITY. 1 75 CARE AND MANAGEMENT OF THE DYNAMO. When the machine has been securely fixed, and previous to the first starting, the whole of the machine should be care- fully examined to see that all parts are in good order, and have not been damaged. The field magnet circuit should first be inspected to see that none of the wires or connections have been broken or are loose, and that the coils are correctly coupled up. The caps of the bearings should next be taken off, and these and the journals carefully cleaned from all grit and dirt. They should then be oiled, and the caps replaced and screwed up with the hand only. The gaps between the outer surface of the armature and the polar faces should be examined in order to ascertain whether any foreign body, such as a small screw or nail has lodged therein. If such is the case, it should be carefully removed with a bit of wire. The guard plates protecting the armature windings should also be removed, and the windings carefully inspected by slowly rotating the armature, to see that they are not dam- aged, and that the insulation is perfect. The armature should then be finally rotated by hand to see that it revolves freely, and that the bearings are securely fixed. 176 NEW CATECHISM OF ELECTRICITY. CARE AND MANAGEMENT OF THE DYNAMO. The commutator and brushes should next receive atten- tion — the commutator, to see that it is not damaged in any way through one or more of the segments being knocked in, or the lugs being forced into contract with one another ; and the brush-holders and brushes, to see that the latter are clean and make good contact with the brush-holders or flexible leads, and the former to see that they work freely on the spindle, and that the hold-off catches work properly. In the subsequent working of the dynamo it will of course not be necessary to follow the whole of these proceedings every time the machine is started, as it is extremely unlikely that the machine will be damaged from external causes whilst working without the attendant being aware of the fact. Having ascertained that the machine is not injured in any way, and that the armature revolves freely, the adjustment of the brushes should next be proceeded with. Attention to Brushes. — The adjustment of the brushes upon the commutator requires careful attention if sparking is to be avoided. The points upon the commutator at which the tips of the brushes, carried by opposite arms of the rocker, bear upon the commutator, should be, in bi-polar dynamos, at opposite extremities of a diameter. In multipolar dynam: s the positions vary with the number of poles and the nature of the armature winding. In order to facilitate the correct setting of the brushes upon the commutator, setting marks are usually cut in the collar of the commutator next to the bearing. NEW CATECHISM OF ELECTRICITY. 177 CARE AND MANAGEMENT OF THE DYNAMO. In bi-polar dynamos, these setting marks divide the cir- cumference of the commutator into equal parts. In adjusting the brushes, the tips of all the brushes carried by one arm of the rocker are set in correct line with the commutator seg- ment marked out by one setting mark, and the tips of the brushes carried by the other arm or arms are set in correct line with the segments marked out by the other mark or marks. If one or more brushes in a set are out of line with their setting mark, it will be necessary to adjust the brushes up to this mark by pushing them out or drawing them back, as may be required, afterwards clamping them in position. When adjusting the brushes the armature should always be rotated, so that the setting marks are horizontal. The rocker can then be rotated into position, and the tips of both sets of brushes conveniently adjusted to their marks. In those brush- holders provided with an index or pointer for adjusting the brushes the setting marks upon the commutator are absent, length of the pointer being so proportioned that when the tips of the brushes are in line with the extreme tips of the pointers, the brushes bear upon the correct positions on the commutator. Having adjusted the brushes to their correct positions upon the commutator, their tips or rubbing ends should next be examined, whilst in position, to see that they bed accurately on the surface of the commutator. In many instances it will be found that this is not the case, the brushes sometimes J 7 8 NEW CATECHISM OF ELECTRICITY. CARE AND MANAGEMENT OF THE DYNAMO. bearing upon the point or toe, and sometimes upon the heel, so that they do not make contact with the commutator throughout their entire thickness and width. The angle of the rubbing ends will therefore need to be altered by filing to make them lie flat. When the brushes do not bed properly upon the commu- tator, and filing has to be resorted to in order to alter the angle of the brush tips or ends, it will be found necessary to fix the brush in a holder or filing clamp, in order that the correct angle may be conveniently obtained. This, as a rule, is supplied with the machine, and consists of two pieces of metal, both shaped at one end to the correct angle (usually 45 ), to which the brushes must be filed. One of the pieces of metal (the back part) has a groove sufficiently large to accom- modate the brush, which is clamped in position by the other piece of metal and a pinching screw. If the clamp is not supplied, a convenient substitute can be made out of two pieces of wood about the same width as the brush. One end of each piece of wood is sawn to the correct angle, and the brush is placed between the two. In filing, the brush is fixed in the clamp, with the toe or tip pro- jecting slightly over the edge of the clamp, and the latter being fixed in a vice, the brush is filed by single strokes of a smooth file made outwards, the file being raised from contact with the brush when making the back stroke. Having ascertained that the brushes are correctly placed and bedded upon the commutator it remains to adjust their NEW CATECHISM OF ELECTRICITY. I7g CARE AND MANAGEMENT OF THE DYNAMO. pressure upon the latter. This is effected by regulating the tension of the springs provided for the purpose upon the brush-holders. The tension of the springs should be just sufficient to cause the brushes to make a light yet reliable contact with the commutator. The contact must not be too light, otherwise the brushes will vibrate, and thus cause sparking ; nor must it be too heavy, or they will press too hard upon the commutator, grinding and scoring and wearing away the latter and themselves to an undesirable extent, and, moreover, giving rise to great heating and sparking. The correct pressure is attained when the. brushes collect the full strength of current without sparking, while their pressure upon the commutator is just sufficient to overcome any ordinary vibration due to the rotation of the commutator. Adjusting Lubricators. — As a rule, sight feed lubricators are used in all but the smallest machines. Previous to start- ing, these vshould be examined to see that they feed the lubricant properly, and that the oil passages are not clogged. They should then be adjusted to feed an ample supply of oil on to the armature spindle. The amount required will of course depend upon the load and the nature of the oil used, but from 3 to 12 drops per minute of any ordinary heavy hydro carbon oil is generally sufficient for a load varving from 6 to 30 horse-power. Starting Dynamos. — Having attended to the above pre- liminaries, and having cleared all keys, spanners, bolts, &c, out of the immediate neighborhood of the machine, and i8o NEW CATECHISM OF ELECTRICITY. Fig. 90. DAYTON (OHIO) MACHINE. NEW CATECHISM OF ELECTRICITY, l8l CARE AND MANAGEMENT OF THE DYNAMO. having raised the brushes from contact with the commutator by means of the hold-off catches, the dynamo may be started and allowed to run light. Whilst thus running, the bearings should be tested from time to time to ascertain if they heat unduly, and an oppor- tunity is also afforded, while the dynamo is thus running, foi cleaning the commutator, if this is dirty, with finest emery cloth, afterwards wiping clean with a linen rag. The con- nections of the machine and external circuits should be veri- fied, and all terminals, &c, cleaned and examined. If found correct, the brushes should be let down on to the commutator, and their tips adjusted by rotating the rocker into the neutral points. The tips of the brushes carried by one arm of the rocker will, in bi-polar dynamos with vertical field magnets, bear exactly upon the top or highest point of the commutator, while the tips of those carried by the other arm will bear exactly upon the bottom or lowest point of the commutator. In other types of machines, the positions for the brushes will vary according to the class or form of the field magnet and the system of armature winding. If the machine is com- pound or shunt wound, all switches controlling the external circuits should be opened, as the machine excites best when this is the case ; and when the machine is provided with a rheostat or hand regulator and resistance coils, these latter should all be cut out of circuit, or short circuited, until the machine excites, when they can be gradually cut in as the voltage rises. 1 82 NEW CATECHISM OF ELECTRICITY. CARE AND MANAGEMENT OF THE DYNAMO. When the machine is giving the correct voltage, as indi- cated by the voltmeter or pilot lamp, the machine may he switched into connection with the external or working cir- cuits. When the machine is series wound, it is absolutely necessary to have the external circuit closed, otherwise a closed circuit will not be formed through the field magnet windings, and the machine will not excite. Attention to Dynamo after it is started. — When the machine is started and at work, it will need a certain amount of attention to keep it running in a satisfactory and efficient manner. The first point to which attention should be paid is the adjustment of the "lead" of the brushes. If this is neglected, the machine will probably spark badly, and the commutator and brushes will constantly require filing and trimming. The "lead" is the term applied to the slight forward movement which it is found necessary to give to the brushes of most dynamos in order to avoid sparking with an increase of load This lead in all good dynamos is very small, and varies with the load and class of machine. The best lead to give to the brushes can in all cases be found by rotating the rocker and brushes in either direction to the right or left of the neu- tral points, until sparking commences increasing with the movement. The position midway between these two points is the correct position for the brushes, for at this position the least sparking occurs, and it is at this position that the brushes should be fixed by clamping the rocker. NEW CATECHISM OF ELECTRICITY. 1 83 CARE AND MANAGEMENT OF THE DYNAMO. In series dynamos giving a constant current, such as for arc lamps in series, the brushes require practically no lead. In shunt and compound dynamos the lead varies with the load, and therefore the brushes must be rotated in the direc- tion of rotation of the armature with an increase of load, and in the opposite direction with a decrease of load. In cases where the dynamos are subjected to a rapidly varying or fluctuating load, it is of course not possible to con- stantly shift the brushes as the load varies, therefore the brushes should be fixed in the positions where the least sparking occurs at the moment of adjustment. If at any time very violent sparking occurs, which cannot be reduced or suppressed by varying the position of the brushes by rotat- ing the rocker, the machine should be shut down at once, otherwise the commutator and brushes are liable to be de-. stroyed, or the armature burnt up. This especially refers tc high tension machines. As soon as any abnormal sparking is seen at the com mutators of such machines, their speed should be at once, reduced, and the commutator cleaned up, and the brushes readjusted. Another very important point to be looked to is the lubrication of the machine. The lubricators should be inspected from time to time, to see that they feed the lubricant properly, and that none of the waste oil passages are clogged. The oil should on no account be allowed to get on to the commutator or brushes, or into the windings of the armature, as it is liable to cause sparking at the brushes, and to destroy the insulation of the armature. 184 NEW CATECHISM OF ELECTRICITY. CARE AND MANAGEMENT OF THE DYNAMO. Ill filling the lubricators, oil cans made of some non- magnetic material such as copper, brass or zinc, should always be used. If iron cans are used, they are liable to be attracted by the field magnets, and thus possibly catch in the armature, and destroy the insulation of the latter. The bearings, and also the field magnet coils, should be tested at intervals, to see that they do not become unduly heated. When testing the temperature of low tension machines, the hand may be used as a guide forjudging when the machine is running at a safe temperature. If the heat of any portion can be easily borne by the naked hand, it may be taken that the temperatnre of the machine is within safe limits. In the case of high tension machines, however, the naked hand cannot be brought with safety into contact with any portion of the machine, and therefore the only way to ascertain if the windings or other electrical parts are at a safe temperature is to apply a ther- mometer. It may be taken as a safe rule that no part of a working dynamo should have a temperature of more than 8o° Fahr. above that of the surrounding air. Hence, if the temperature of the engine-room is noted before applying the thermometer to the machine, it can at once be seen if the latter is working at a safe temperature. In taking the temperature, the bulb of the thermometer should be wrapped in a woolen rag. The screws and nuts securing the different connections and cables should be examined occasionally, as they frequently work loose through the vibration. NEW CATECHHM OF ELECTRICITY. 185 CARE AND MANAGEMENT OF THE DYNAMO. ' Attention to Brushes and Commutator. — The brushes and commutator are the most troublesome parts of a dynamo and requite most attention. To keep them in a satisfactory work- ing condition, the main thing to be guarded against is the production of sparking at the brushes. If care be taken in the first instance to properly adjust the brushes* to their setting marks, and their pressure upon the commutator, and afterwards to attend to the lead as the load varies, so that little or no sparking occurs, and to keep the brushes and commutator free from dirt, grit, &c, and excessive oil, the surface of the commutator will assume a dark burnished appearance, and all wear will practically cease. Under these circumstances the commutator will run cool, and free from sparking, and will give very little trouble. In order to maintain these conditions it will only be necessary to see that the brushes are properly trimmed and fed forward to their setting marks, as described above, as they wear away, and that the commutator is occasionally polished with the finest emery cloth. If, on the other hand, the pressure of the brushes upon the commutator is too great, or their adjustment is faulty, or the commutator is allowed to get into a dirty con- dition, sparking will inevitably result, and, if not at once attended to and remedied, the brushes will quickly wear away, and the surface of the commutator will be destroyed. If this condition of things is allowed to continue, matters will rapidly get worse. In the earlier stages, the surface of the commutator will become roughened or scored, resulting in jumping of the brushes, and increased sparking ; in the 1 86 NEW CATECHTSM OF ELECTRICITY. CARE AND MANAGEMENT OF THE DYNAMO. later stages, the commutator will become untrue and worn into ruts, and owing to the violent sparking which takes place through this circumstance, the machine will quickly be ren- dered useless for practical purposes. When once started, the only way to remedy this condition of things is to repolish the commutator and readjust the brushes, as directed above. If the commutator is merely scored, a smoth file applied while the armature is revolving, with a final polishing with coarse and fine emery cloth, will generally put things into a satisfactory condition. If, how- ever, the commutator is worn into deep ruts, or is untrue, nothing short of putting the armature in the lathe and re- turning the commutator will make a good job of it. When carbon brushes are used, a little extra special at- tention should be given in keeping the commutator per- fectly clean, otherwise it is liable to heat up through short circuits, caused by carbon dust lodging between the segments. When carbon brushes are working properly, the fact is indi- cated by a uniform greyish tinge being imparted to the com- mutator, with a total absence of heating or sparking of any description. If the surface of the commutator assumes a mottled or streaky appearance, accompanied by small sparks flashing from segment to segment, it is advisable to slow down the machine and clean up the commutator at once. When either metal or carbon brushes are used, the surface of the com- mutator is bound in course of time to undergo a certain NEW CATECHISM OF ELECTRICITY. 187 CARE AND MANAGEMENT OF THE DYNAMO. amount of wear, even when the greatest care is taken to reduce sparking. In order to prevent this wear giving rise to ruts or ridges upon the surfaces of the commutator, it is advisable to shift the brush-holders and brushes upon the rocker arm, if this is possible, from time to time. The unequal wear of the com- mutator may also be prevented by so arranging the brushes carried by one arm of the rocker that they cover the gaps between the brushes carried by the other arm of the rocker. The armature spindle or shaft is also given a little end play in order to prevent this grooving. Lubricant on Commutator. — In most cases it will be found that a little lubricant is needed on the commutator in order to prevent cutting of the latter by the brushes, and this is especially the case when hard strip brushes are used. The quantity of oil so used should be very small — a few drops smeared upon a piece of clean rag, and applied to the commu- tator while running, being quite sufficient. * It is advisable to use mineral oil, such as vaseline, or any other hydro-carbon. Animal or vegetable oils should be avoided, as they have a tendency to carbonize, and thus cause short-circuiting of the commutator, with attendant sparking. Trimming Brushes. — At certain intervals, according to the care taken to reduce sparking, and the length of time the machine runs, the brushes will fray out or wear unevenly, and will therefore need trimming. They should then be removed from the brush-holders, and their contact ends or iS8 NEW CATECHISM OF ELECTRICITY. Fig. 91. AMERICAN GIANT DYNAMO. NEW CATECHISM OF ELECTRICITY. 1 89 CARE AND MANAGEMENT OF THE DYNAMO. faces examined. If not truly square, they should be filed or clipped with a pair of shears, the course of treatment differing with the type of brush. If metal strip brushes, the feathered-out ends should' be clipped square with a pair of shears, the ends thoroughly cleaned from any dirt or carbonized oil, and replaced in their holders. Gauze and wire brushes require a little more atten- tion. When their position on the commutator has *been well adjusted and looked after, so that little or no sparking has taken place, it will generally be only found necessary to wipe them clean, and clip off the fringed edges and corners with the shears, or a pair of strong scissors. If, however, the ma- chine has been sparking, the faces will be worn or burnt away, and probably fused. If such is the case, they will need to be put in the filing clamp, and filed up square and true, as directed above. If the contact faces of the brushes are very dirty and cov- ered with a coating of carbonized oil, &c, it will be necessary to clean them with benzoline or soda solution before replacing. The handiest way of trimming carbon brushes, or of bedding a complete new set of metal brushes, is to bind a piece of emery cloth or sand paper, face outwards, around the com- mutator after the current has been shut off, and then mount the carbon or metal brushes in the holders, adjusting the ten- sion of the springs so that the brushes bear with a moderately strong pressure upon the emery cloth or sand paper. Then let the machine run slowly until the ends of the brushes are ground to the proper form. Care should be taken, I9O NEW CATECHISM OF ELECTRICITY. CARE AND MANAGEMENT OF THE DYNAMO. however, that the carbon or metal dust given off does not get into the commutator connections or armature windings, or short circuiting will result. If it becomes necessary, through sparking or other causes, to trim the brushes while the ma- chine is working, one brush at a time should be removed from the holders. The brush to be removed should first be raised carefully from the commutator ; then, if excessive sparking or heating occurs, the brush should be let down again, and the tension of the springs of the brushes temporarily increased until the brushes are trimmed. This of course only applies to machines provided with at least two brushes to each set. If only one brush is provided, the machine must be stopped before the brushes can be trimmed. SHUTTING DOWN DYNAMO. When shutting down a machine, the load should first be gradually reduced, if possible, by easing down the engine ; then, when the machine is supplying little or no current, the main switch should be opened. This reduces the sparking at the switch contacts, and prevents the engine racing. NEW CATECHISM OF ELECTRICITY. igi CARE AND MANAGEMENT OF THE DYNAMO. When the voltmeter almost indicates zero, the brushes should be raised from contact with the commutator. This prevents the brushes being damaged in the event of the engine making a backward motion, which it often does, particu- larly when it is a gas-engine. On no account, however, should the brushes be raised from the commutator while the machine is generating any considerable voltage ; for not only is the insulation of the machine liable to be damaged by this, proceeding, but in the case of large shunt dynamos an ex- ceedingly violent shock is liable to be administered to the person lifting the brushes. When the dynamo is at rest, or only revolving slowly, and the brushes are raised from the commutator, the latter should be cleaned up, if this is necessary. In dusty places, such as flour mills, sugar works, cement works, &c, it will probably be necessary to clean off the commutator with benzoline, and finally with finest emery cloth, at the end of every run. In places free from dust, it will only be necessary to wipe the revolving surface perfectly clean, or until it will not soil a white rag, and occasionally to apply a little fine emery cloth before stopping. When the machine is stopped it should be thoroughly cleaned up. The armature should be dusted with a pretty stiff brush from any adherent copper dust, dirt, &c, and the other portions of the machine should be thoroughly cleaned with linen rags. Waste should not be used, as it is liable to leave threads, fluff, &c, on the projecting parts, terminals 192 wew catechism of electricity. CARE AND MANAGEMENT OF THE DYNAMO. and other parts of the machine, and on the windings of the armature, which is very difficult to remove. The brushes-should be examined, and if necessary trimmed and adjusted, and all terminals, screws, bolts, &c, carefully cleaned and screwed up ready for the next run. The brush- holders should receive special attention, as when dirty they are liable to stick and cause sparking. All dirt and oil should be removed from the springs and contacts, and pivots and other working parts, It is advisable at stated intervals to entirely remove the brush-holders from the rocker arms, and give them a thorough clean up, by taking them to pieces, and cleaning each part separately with emery cloth and benzoline or soda solution. Another point to which particular attention should be given is the cleaning of the brush rocker. This being com- posed wholly of metal, and the two sets of positive and nega- tive brushes being only separated from it by a few thin insulating washers, it follows that if any copper dust given off by the brushes is deposited in the neighborhood of these washers, there is considerable liability for a dead short circuit of the machine to occur, by the dust bridging across the insulation. These particular parts should therefore be kept scrupulously clean and free from any conducting matter. It is a good plan, when the machine has been thoroughly cleaned up and all connections made secure, to occasionally test the insulation of the different parts. If a record is kept of these tests, any I NEW CATECHISM OF ELECTRICITY. 193 CARE AND MANAGEMENT OF THE DYNAMO. deterioration of the insulation of the machine can at once be detected, localized and remedied before it has got far enough to cause a breakdown. As a means of protecting the machine from any moisture, dirt, &c, while standing idle, it is advisable to cover it, up with a suitable waterproof cover. PRACTICAL RULE FOR COUPLING UP FIELD MAGNET COILS. Iu coupling up the coils of either salient or consequent pole field magnet coils, assume each of the pole pieces to have a certain polarity ( in bi-polar dynamos two poles only, a north and south pole respectively, are required ; in multipolar dy- namos the poles must be arranged in alternate order around the armature, the number of N and S poles being equal), then apply the rule given on page 81 to each of the coils, and ascer- tain the direction in which the magnetizing current must flow in each in order to produce the assumed polarity in each of the pole pieces. Having marked these directions on the coils, the coils can be coupled up in either series or parallel accord- ing to requirements, so that the current flows in the necessary direction in each. 194 NEW CATECHISM OF ELECTRICITY. CARE AND MANAGEMENT OF THE DYNAMO. Connecting Up Dynamos. — The manner in which the con- nections of the field magnet coils, and brnshes, and terminals,, are connected to one another, depends entirely upon the class of dynamo. The field magnet shunt coils of shunt and com- pound wound dynamos, are invariably arranged in series with one another, and then connected as a shunt to the brushes or terminals of the machine, as represented in Figs. 61 and 62. The series coils of series and compound wound machines, are arranged either in series or in parallel with one another, ac- cording to circumstances, and the amount of current given by the machine, and then connected in series to the armature and external circuits upon the principle shown in Figs . 60 and 61. Fig. 92. WATER METER FOR POWER STATIONS,. NEW CATECHISM OF ELECTRICITY. I95 SYMBOLS, ABBREVIATIONS AND DEFINITIONS. Quks. What is the meaning of the terms "bug" and "bug trap" ? Ans. The term bug is used to a limited extent to designate any fault or trouble in the connections or working of electric apparatus. The "bug trap" is the arrangement or connec- tion for overcoming the * ' bug. ' ' These terms are said to have originated in quadruplex telegraphy and been transferred to all electric apparatus. QuKvS. What is the meaning of l ' synchronous ' ' f Ans. It means the occurrence of two events at the same time ; caused to act together or occur simultaneously. Quks. Where and how is the word used ? Ans. It is used in telegraphy — in the ' * step-by-step " system ; with alternating current dynamos, where two are used together, it is necessary that they are " synchronized " — i. e., act together, since otherwise the machine may suffer. Motors of the "synchronous type," are so called because they run at the same speed or in a certain proportion to the speed of the generator. Note. — See page 114. 196 NEW CATECHISM OF ELECTRICITY. Fig. 93. NEW CATECHISM OF ELECTRICITY. I97 REGULATING DYNAMOS. Means of governing the performance of dynamos are needed, not only for keeping the pressure at some constant number of volts or for keeping current at some constant number of amperes, but also for such purposes as to enable the voltage of any one dynamo to be raised in order that it may feed into some distant point of a distributing network. The output of a dynamo may be regulated or varied by any of the following methods, or by a combination of the same: (i) Variation of speed of armature. (2) Variation of strength of magnetic field. (3) Variation of position of brushes on commutator. (4) Variation of resistance in dy- namo circuit. The application of these methods of regula- tion to the various classes of dynamos is considered in the succeeding paragraphs. Regulating Separately Excited Dynamos. — The voltage and output of this class ot machine is most commonly gov- erned by varying the strength of the magnetizing current flowing through its field magnet coils. When the magnetiz- ing current is furnished by a battery or accumulator, this is I98 NEW CATECHISM OF ELECTRICITY. REGULATING DYNAMOS. effected either by means of a hand regulator or rheostat inserted in the exciting circuit (as represented in Fig. 94), or by varying the number of cells in circuit, this latter being the most economical plan. In most cases, however, a smaller dynamo is used for the purpose. In this case the strength of the magnetizing current flowing in the coils of the main dy- namo may be regulated by either of two methods : (a) by means of a hand regulator inserted in the field circuit as be- fore ; or (b) by varying the voltage of the smaller exciting dynamo. This latter may be effected either by varying the speed of the armature, or by varying the strength of the magnetic field, by regulating the strength of the magnet- izing current flowing in the field coils by means of a hand regulator. It is, however, usual to provide the field circuit of each individual dynamo with a hand regulator, so that its pressure may be adjusted independently of the others. Hand regulators when applied to the regulation of dyna- mos, consist of multiple contact switches, so arranged that either the resistance of the field magnet circuit may be varied, by inserting or removing resistance in series with the latter, or one or more of the exciting coils may be cut into or out of circuit, or short circuited. ' When arranged for per- forming the former operation, the regulator is usually com- bined with a set of resistance coils. A combination of this description being illustrated in Fig, 94. It consists of two cast-iron end frames, rigidly connected together by means of two iron rods bolted into the ends of the frames. The two end frames are hollow, and each con- NEW CATECHISM OF ELECTRICITY. IQ9 Fig. 94. REGULATING DYNAMOS. tain a slate slab, securely fixed in place by means of screws or bolts passing through the slabs, and screwing into the iron frames. The projecting edges of the slate slabs are provided with a number of brass studs or bolts, on to which are fixed the ends of spiral coils of German silver, platinoid, or iron wire. These spiral coils are all joined in series, being formed of a con- tinuous length of wire, which passes up and down between the slate slabs. The connections of the spiral coils to the external circuit are made by means of two terminals, and a number of contacts fixed in the slate slab, in the f^-l f jj i' i." i" ±" r a' * : J, '*^l bottom end frame. The terminal """ V\( ^ shown on the left of the figure is con- nected to the extreme left hard spiral coil, the terminal on the right being connected to the lever of the multiple contact switch or regu- lator, shown at the bottom of the figure. This is composed of twelve contacts, each contact being electrically connected to the bottom j unction of a spiral coil. By altering the position of the lever of the regulator the coils can be cut in or out of circuit, and the resistance varied, as may be required. When the regulator is arranged for performing the latter operation, the switch is not combined with a resistance, but the exciting coils of the field magnets are divided up into groups, and the ends are connected to the contacts or terminals in place of the NEW CATECHISM OF ELECTRICITY. REGULATING DYNAMOS. resistance coils, so that by varying the position of the lever each of the exciting coils may be cut into or out of circuit, and the strength of the magnetic field adjusted accordingly. Regulating Series Dynamos. — The series dynamo is ordi- narily used for operating series arc lamp circuits, and for the electric transmission of power, its regulation being effected by any of the following methods : (i) Variation of strength of magnetic field. (2) Variatiou of speed of armature. (3) Variation of position of brushes on commutator. (1.) Regulation by Variation of Strength of Magnetic Field. — Although theoretically there are several different methods of varying the strength of the magnetic field of a series dynamo, in practice, the method of shunting the ex- citing current in the field coils is invariably followed. The essential principle of this method consists in establishing a shunt of variable resistance across the field coils, so that a portion of the armature current is shunted through the resis- tance, the remainder being used for exciting the field mag- nets. The strength of the magnetic field being proportional (within certain limits) to the strength of the magnetizing current flowing in the exciting coils, it follows that the E. M. F. of the machine will vary in proportion to the resistance of the shunt. By reducing the resistance of the latter, a larger proportion of the total current will flow through it, and the strength of the current flowing in the field coils being thus reduced, the voltage of the machine will be reduced also, or NEW CATECHISM OF ELECTRICITY. REGULATING DYNAMOS. vice versa. The alteration in the resistance of the shunt can be effected by hand, with the aid of a rheostat or hand regu- lator, similar in principle to that represented in Fig. 96. When used for this purpose, however, the hand regulator is usually so arranged that all the resistance coils can be cut out of circuit, and the field coils short-circuited thus allow- ing of the voltage of the machine being adjusted from zero to the maximum value. Automatic Regulation. — In cases where an approximately constant current is to be maintained in a circuit, as in series arc circuits, the adjustment of the resistance of the variable shunt is, as a rule, effected automatically by means of some electro-magnetic device, actuated by solonoids placed in the main circuit. Regulation by Variation of Speed of Armature. — The vol- tage and output of series dynamos can be governed to some extent by varying the speed of the armature, by opening or closing the stop-valve of the steam engine, or other motor driving the dynamo. This method of regulation is, however, only applicable in cases where the fluctuations of the load are small, since it involves constant attendance on the* en- gine. Regulation by Variation of Position of Brushes on Com- mutator. — In both ring and drum armatures, when rotating in a bi- polar field, there are two points situated at opposite extremities of a diameter of the commutator, at one of which the potential is a maximum, and at the other a mini- NEW CATECHISM OF ELECTRICITY. Fig. ^Ss2 THE TROY (N. Y.) MACHINE. NEW CATECHISM OF ELECTRICITY. 203 REGULATING DYNAMOS. mum, and it is at these points that the brushes must be placed, in order to obtain the greatest difference of pressure. From the point of maximum potential to the point of mini- mum potential either way round the commutator, the pres- sure gradually decreases in value. Hence, if the brushes make contact at points on the commutator other than the neutral points or points of highest and lowest potential, the pressure between the brushes will vary in proportion to their distance from the neutral points, increasing as they approach the neutral points, and decreasing as they recede from them, until when making contact at points situated at about 90 from the neutral points, they will be at nearly the same po- tential. From this it follows that by merely rocking the brushes round the commutator, the pressure at the terminals of the machine may be varied and regulated as required. Such a method of regulation cannot, however, be used with advan- tage in ordinary dynamos, owing to the very destructive sparking which takes place at the brushes when they are moved any considerable distance from the neutral points. Special dynamos have been designed to meet the special requirements of this method of regulation, and in which the sparking at the brushes is obviated at all loads within the range of the machine, but as these have not come into gene- ral use they need not be further considered here. Regulation of Shunt Dynamos. — In parallel incandescent lighting, it is absolutely necessary to maintain the pressure 204 NEW CATECHISM OF ELECTRICITY. REGULATING DYNAMOS. at the lamps at a constant value. When the lamps are situ- ated at a considerable distance from the machine, as in town lighting, this necessitates a constantly varying pressure at the machine in order to make up for the fall of pressure in the mains connecting the machine to the lamps, which fall is dependent on the amount of current flowing in the mains. The ease with which this variation of pressure can be effected in the shunt dynamo causes this class of machine to be ordi- narily used in central stations for incandescent lighting, the regulation being effected by either of the following methods, or by both in conjunction : (i) Variation of strength of magnetizing current. (2) Variation of speed of armature. (1.) Regulation by Variation of Strength of Magnetizing Current.— This is the only thoroughly efficient method of regulation for a shunt dynamo. The variation in the strength of the magnetizing current is effected by means of a hand regulator or rheostat, similar to that represented in Fig. 94, which is inserted in the shunt circuit of the machine, as shown diagramatically in Fig. 96. In this system of regula- tion, the resistances of the field magnet shunt windings and of the regulator coils are so proportioned that, when no load is on the dynamo, and all the coils of the regulator are in cir- cuit with the shunt, the machine generates the normal pres- sure required at the lamps. As more and more lamps are switched on, the voltage at the lamps has a tendency to decrease, and therefore the pressure at the machine must be raised in proportion. This is effected by moving the lever of the regulator (r), so that fewer resistance coils- are included NEW CATECHISM OF ELECTRICITY. 205 REGULATING DYNAMOS. in the shunt circuit ; the resistance of the latter being thus decreased, the exciting current and voltage of the machine is increased correspondingly. This method of regulation is common with all in which resistances are included in the cir- cuit, wastes energy to a certain extent, but the quantity so Fig. 96. REGULATION FOR A SHUNT-DYNAMO. wasted is so small in proportion to the whole that it may be considered as of little moment, especially when the advan- tages of the system are taken into account. Regulation by Variation of Speed of Armature. — A much less satisfactory method of regulation for shunt dynamos is that of varying the speed of the armature. For small varia- 206 NEW CATECHISM OF ELECTRICITY. REGULATING DYNAMOS. tions of pressure, the alteration of speed can be readily effected by means of an adjustable governor, the speed of the armature being varied by increasing or diminishing the ten- sion of the governor spring, according to the pressure required at the terminals of the machine. For larger variations, how- ever, the only effective method of regulation is by means of the stop-valve ; that is to say, the main stop-valves of the engines are opened or closed in proportion to the pressure re- quired. When a number of dynamos are running in parallel, the disadvantages of this system, as compared with the method of varying the strength of the magnetic field, become especially prominent, since, in place of a number of easily adjusted hand regulators, fixed in some central position, and operated by a single attendant, this method involves the regulation being effected by probably as many men as there are engines, each regulating the stop- valve of a particu- lar engine. Furthermore, the regulation is not nearly so effective, owing to the difficulty of expeditiously adjusting the valves to give the pressure required. In connection with this particular system of regulation, a special type of voltmeter is generally employed, this being of extraordinary large dimen- sions, with the index or pointer about 18 inches in length, so that its indications may be seen all over the engine-room. Regulating Compound Dynamos. — A carefully com- pounded dynamo will, when run at the speed for which it was designed, regulate itself perfectly, and maintain a con- stant difference of potential at its terminals under any varia- NEW CATECHISM OF ELECTRICITY. 20? REGULATING DYNAMOS. tion of load within its range. In practice, however, it is not always possible to work a dynamo under these exact condi- tions, and, moreover, in the case of large machines,' the effect of temperature upon the resistance of* the machine has ari appreciable effect upon the voltage. Means for regulating the latter are desirable. The voltage may be varied to a certain extent by suitably adjusting the governor of the driving engine, increasing or decreasing the speed ; but in many cases this is not very desirable or possible, and a much better method of obtaining the desired variation of voltage is to insert a variable resistance or hand regulator in the shunt circuit of the machine, the resistance of the shunt being suitably proportioned to give the requisite margin for regulation. Regulating Over-Compounded Dynamos, — It is sometimes desirable, as in central light and power stations, to have a dynamo which will maintain a constant pressure at a point some distance from the machine. In this case the dynamo is over-compounded, or the series coils are wound with a greater number of turns, in order to raise the pressure at the termi- nals of the machine as the load increases, and thus compen- sate for the fall of pressure in the mains. As it is well to vary the degree of over-compounding, the series coils of such dynamos are usually so proportioned as to give from 10 per cent, to 20 per cent, of over- compounding, and a strip or ribbon of German silver or copper is arranged as a shunt to the series coils. By suitably including a greater 208 NEW CATECHISM OF ELECTRICITY. Fig. 97. AN AI/TERNATOR. NEW CATECHISM OF ELECTRICITY. 200, REGULATING DYNAMOS. or lesser length of ribbon in the circuit, the resistance of the variable shunt and the amount of current flowing in the series coils can be varied, and the percentage of over-com- pounding adjusted accordingly. Regulation of Motors. — It is extremely important that electric motors should be so arranged as to run at a uniform speed, no matter what their load may be. For example, in driving lathes, and many other kinds of machinery, it is essential that the speed should be regular, and that the motor should not "race " as soon as the stress of the working load is removed. It will be evident that the employment of certain combina- tions for the field magnets, under the condition of a constant potential, when driven at a constant fpeed, regulate the dynamo. Now it is not hard to see that this problem may be applied conversely, and that motors may be built with a combination of arrangements for their field-magnets, such that, when sup- plied with currents under the standard condition of constant potential in the distributing mains, their speed shall be con- stant whatever the load. It will be evident that the windings must oppose one another— one must tend to demagnetize the field magnet, the other to magnetize. This effect is based upon the important electrical law that if a current is passed through a dynamo the armature will rotate. In all cases the rotation is in such a direction as to induce in the armature an electro-motive force opposed to that of the driving current. 2IO NEW CATECHISM OF ELECTRICITY. Fig. 98. four pole; ring dynamo. NEW CATECHISM OF ELECTRICITY. COUPLING OF DYNAMOS. When it is needful to generate a large and variable amount of electrical energy, as is the case in large installa- tions and central generating stations, apart from the question of liability to breakdown, it is neither economical or desir- able that the whole of the energy should be furnished from a single dynamo. Since the efficiency of a dynamo is depends ent upon its output at any moment, or the load at which it is worked, the efficiency varying from 95 per cent, at full load to 80 per cent, at half load, it is obviously advisable in order to secure the greatest economy in working, to operate any dynamo as far as possible at full load. Under the above cir- cumstances, when the whole of the output is generated by a single dynamo this can evidently not be effected, for the load will naturally fluctuate up and down during the working hours, as the lamps, motors, etc., are switched into and out of circuit ; and hence, although the dynamo may be working at full load during a certain portion of the day, at other times it may probably be working below half load, and therefore the efficiency and economy in working in such an arrange- ment is very low. In order to secure a maximum efficiency ^ it is usual in such cases to divide up the generating plant into a number of units, varying in size, so that as the load fluctu- NEW CATECHISM OF ELECTRICITY. COUPLING OF DYNAMOS. ates it can either be shifted from one dynamo to another as the exigencies of the case requires ; or when the load exceeds the capacity of the largest dynamo in the plant, the output of one can be added to that of another, and thus the dynamos actually at work at any moment can be operated as nearly as possible at full load. As it is necessary to take certain pre- cautions in ccnnecting one dynamo to another, in order that the other dynamos may not be affected by the change, and that they may work satisfactorily together, it is well to consider these in connection with the different types of machines. Series and Parallel Connections, — Since the output of a dynamo is made up of two factors, viz. : the pressure and the current respectively, it follows that the output of a machine may be increased by increasing either the one or the other, or both at the same time. As, however, the systems of distri- bution in use at the present time involve the maintenance of either a constant current or a constant pressure in a circuit, the methods of coupling dynamos together resolve them- selves into two kinds, corresponding to the systems of distri- bution, viz.: parallel and series connections. In coupling two or more machines in parallel, the pressures of all the ma- chines are kept at a constant value, while the output of the plant is increased in proportion to the current capacities of the machines in circuit. In the series coupling, the current capacity of the plant is kept at a constant value, while the output is increased in proportion to the pressures of the ma- chines in circuit. NEW CATECHISM OF ELECTRICITY. 213 COUPLING OF DYNAMOS. Shunt Dynamos in Series.— The simplest operation in con- nection with, the coupling of dynamos, and the one used probably more frequently in practice than any other, is the coupling of two or more shunt dynamos to run either in 214 NEW CATECHISM OF ELECTRICITY. COUPLING OF DYNAMOS. series or in parallel. When connected in series, the positive terminal of one machine is joined to the negative of the other, and the two outer terminals are connected through the ammeter A, fuses F x F 2 , and switch S, to the two main con- conductors or omnibus bars as represented in Fig. 99. The machine will operate when the connections are arranged in this manner, if the ends of the shunt coils are connected to the terminals of the respective machines ; but a better plan is to put both the coils in series with one another, so that they form one long shunt between the two main conductors, as shown in Fig. 99. When arranged in this way, the regula- tion of both machines may be effected simultaneously by inserting a hand regulator (r) in series with the shunt circuit, as represented. Shunt Dynamos in Parallel. — The coupling of two or more shunt dynamos to run in parallel is effected without any difficulty, and is probably an operation more frequently performed than any other, it being daily practiced in central generating stations on the low tension system. Fig. 100 illus- trates diagramatically the method of arranging the connec- tions. The positive and negative terminals of each machine are connected respectively to two massive insulated copper bars, shown at the top of the diagram, and called omnibus bars, through the double pole switches S x S 2 , and the double pole fuses F x F 2 . Ammeters, A x A 2 , are inserted in the main circuit of each machine, and serve to indicate the amount of current generated by each. An automatic switch or cutout, AC X AC 2 , is also shown as being included in the NEW CATECHISM OF* ELECTRICITY. 215 COUPLING OF DYNAMOS. main circuit of each of the machines, although this appli- ance is sometimes dispensed with. The pressure of each of H the machines is regulated independently by means of the hand regulators R x R 2 , inserted in series with the shunt cir- cuit. 216 NEW CATECHISM OF ELECTPICITY. COUPLING OF DYNAMOS. The shunt circuits are represented as being connected to the positive and negative terminals of the respective ma- chines, but in many cases, where the load is subjected to sud- den variations, and when a large number of machines are connected to the bus bars, the shunt coils are frequently con- nected direct to these ; and in such circumstances this method is preferable, as by means of it the fields of the idle dynamos can be excited almost at once direct from the bus bars by the current from the working dynamos, and hence if a heavy load should come on suddenly, no time need be lost in building up a new machine previous to switching it into parallel. The pressure of the lamp circuit is given by a voltmeter, whose terminals are placed across the omnibus bars ; and the pres- sure at the terminals of each of the machines is indicated by separate voltmeters or pilot lamps, the terminals of which are connected to those of the respective machines. Switching Dynamo into and out of Parallel. — In order to put an additional dynamo into parallel with those already working, it is necessary to run the new dynamo up to full speed, and, where it excites, regulate the pressure by means of a hand regulator until the voltmeter connected to the terminals of the machines registers one or two volts more than the voltmeter connected to the lamp circuit, and then close the switch. The load upon the machine can then be adjusted to correspond with that upon the other machines by means of the hand regulator. In this class of machine there is little or no danger of overloading an armature when con- necting it to the bus bars, and therefore the pressure need not NEW CATECHISM OF ELECTRICITY. 21 7 COUPLING OF DYNAMOS. be adjusted with very great accuracy ; in fact, it is common practice in central stations to judge of the voltage of the new dynamo merely by the appearance of its pilot lamp. When shutting down a machine, the load or current must first be reduced, by gradually closing the stop-valve of the engine, or inserting resistance into the shunt circuit by means of the hand regulator ; then when the ammeter indicates nine or ten amperes, the main switch is opened, and the engine stopped. By following this plan, the heavy sparking at the switch contacts is avoided, and the tendency for the engine to race reduced. Great care, however, has to be taken that the current is not reduced too far, or otherwise there is a risk of the machine being stopped, receiving a back current from the other dynamos, resulting in heavy sparking at the com- mutator, and in the machine being driven as a motor. To obviate this danger, and to render these precautions needless, shunt dynamos when running in parallel are frequently pro- vided with automatic cutouts, set so as to automatically switch out the machine when the current falls below a certain mini- mum value. Dividing Load. — If a plant composed of shunt dynamos running in parallel be subjected to variations of load, gradual or instantaneous, the dynamos will, if they all have similar characteristics, each take up an equal share of the load ; if, however, as is sometimes the case, the characteristics of the dynamos are dissimilar, the load will not be shared equally ; the dynamos with the most drooping characteristics taking less than their share with an increase of load, and more than 2l8 NEW CATECHISM OF ELECTRICITY. COUPLING OF DYNAMOS. their share with a decrease of load. If the difference is slight, it may readily be compensated by means of the hand regula- tor increasing or decreasing the pressures of the machines, as the load varies or fluctuates. If, however, the difference is considerable, and the fluctuations of load very rapid, it be- comes practically impossible to evenly divide the load by this means so that each dynamo takes up its proper share of the work. Under such circumstances, the pressure at the bus bars is liable to great variations, and there is also great liability for the fuses of the overloaded dynamos to be blown, thus precipitating a general breakdown. To cause an equal divis- ion of the load amongst all the dynamos, under such circum- stances, it is needful to insert a small resistance in the armature circuits of such dynamos as possess the straightest characteristics, or of such dynamos as take more than their share of an increase of load. By suitably adjusting or pro- portioning the resistances, the pressures at the terminals of all the machines may be made to vary equally under all varia- tions of load, and each of the machines will then take up its proper share of the load. Automatic Cutouts. — Shunt and other dynamos are always liable when working to have the pressure at their terminals reduced, either through a fault in the armature or field cir- cuits, or through a hot bearing or other cause. When a num- ber of shunt dynamos are running in parallel, and the pressure of one falls below that of the others, the load is transferred from the machine having the lower pressure to NEW CATECHISM OF ELECTRICITY. 2ig Fig. 101. COUPLING OF DYNAMOS. the machine with the higher pressure, until when the pres- sure falls below a certain minimum value a reverse current is sent through the armature of the machine whose pressure has been reduced by the machines having the higher pressure. This results in the machine being driven as a motor, and in great sparking at the commuta- tors of all the dynamos, and also in an overload of the driving dynamos, and probably in the blowing out of all the fuses. In order to prevent this occurring, shunt dynamos when running in parallel are each as a rule provided with an automatic switch, placed between one or both of the machine ter- minals and the omnibus bars, whose duty it is to switch off automatically the machine in the event of a reduction of its voltage from any of the above-mentioned causes. The principle and action of this instrument will be understood by reference to Fig. 101. Briefly described, the instrument consists of an electro-magnet, fixed upon a slate base, and shown in the upper portion of the figure, and an iron armature fixed to the ends of the pivoted levers of the switch, shown in the lower portion of the figure. AUTOMATIC SWITCH. 220 NEW CATECHISM OF ELECTRICITY. COUPLING OF DYNAMOS. The electro-magnet is included in series with the switch and armature circuit, and while the pressure of the machine to which the instrument is connected remains at its normal value, the current flowing in its coils Is sufficiently strong to enable it to hold up the iron armature against its pole pieces. If from any cause the voltage of the machine is reduced, the current flowing in its armature is decreased also, until when it falls below a certain minimum value at which the automatic switch is arranged to act, the strength of the electro-magnet has been so far diminished that it can no longer hold up the armature against the weight of the levers, and these latter therefore drop and switch the machine out of circuit. A fusible cutout is shown in the centre of the figure, which, when the current exceeds the safe capacity of the machine, melts, and cuts out the armature, thus saving it from destruc- tion. , Coupling Series Dynamos in Series. — Series wound dyna- mos will run satisfactorily together without special precau- tions when coupled in series, if the connections are arranged as in Fig. 102. The positive terminal of one dynamo is con- nected to the negative terminal of the other, and the two outer terminals are connected directly to the two main con- ductors or bus bars through the ammeter A, fuse F, and switch S. If it be desired to regulate the pressure and out- put of the machines, variable resistances, or hand regulators R L R 2 , may be arranged as shunts to the series coils, as represented, so as to divert a portion or the whole of the cur- rent therefrom. NEW CATECHISM OF ELECTRICITY. 221 COUPLING OF DYNAMOS. Series Dynamos in Parallel. — Simple series wound dyna- mos not being well adapted for the purpose of maintaining a ^"^^^^ o _^^> O oS ***^^*^ no mistake can obviously be made ; when two or more coils are used, however, it is possible to so arrange the connections that poles are produced in the yokes or other por- tions of salient pole field magnets ; or in case of consequent pole field magnets, the connections may be so arranged that the coils neutralize each other, and no external field whatever is produced in the manner in which the coils of the various types of salient and consequent pole field magnets are coupled. 26o NEW CATECHISM OF ELECTRICITY. DISEASES OF DYNAMOS. Taken as a whole, an electric machine is remarkably dur- able, and the cost of maintenance very small. There are only three parts that can really wear away — these are the two journals and the commutator. The shafts in nearly all machines are made of steel, and in some are even hardened and ground. Therefore the wear in the journals takes place mostly on the boxes, and these, being interchangeable, can be replaced in a few minutes and at small expense when worn out. The commutators, if they run without sparking, should last several years. k As there are virtually only three parts that really wear out, it might be supposed that the renewal of these parts would be all that would be required to keep the machine in perfect running order. But experience shows that such is not the case. At least four-fifths of the mishaps and break-downs that occur with dynamos arise from causes more strictly within the province of the engineer than in that of the electrician. On the other hand, many of the mechanical faults that develop themselves in the machine might have been avoided had the engineer been possessed of a better knowledge of the electric and magnetic conditions which obtain in the running of the machine. NEW CATECHISM OF ELECTRICITY. 26l DISEASES OF DYNAMOS. In the practical operation of dynamos and motors as well the following is a list which covers nearly everything which should be first considered as faults or diseases : First. — Failure to excite or generate, i. e. y when the ma- chine is running the current does not flow. Second. — Heating .of armature, field magnets, commutator or brushes, or heating of the bearings. Third. — Sparking at commutator. Fourth. — Too high or too low speed. Fifth. — Excessive noise or vibration. Sixth. — Variation of voltage. Each of these classes is distinct from the others, and when the "trouble" has been located, it will be seen that the remedying of one of the above list is nearly always all that is required — hence the importance of some study before apply- ing the cure. It is impossible to give complete direction for each occa- sion, but the lists will greatly aid the prompt and intelligent attendant. FAILURE TO EXCITE. The first point to be observed, if the machine fails to ex- cite, is the position of the brushes upon the commutator. If these are not on or near the neutral points, the whole of the E. M. F. of the armature will not be utilized, and will prob- ably be insufficient to excite the machine. If in doubt as to 262 NEW CATECHISM OF ELECTRICITY. FAILURE TO EXCITE. the correct positions, the brushes should be rotated by means of the rocker into various points on the commutator, sufficient time, say five minutes, being given the machine to excite be- fore moving them into a new position. If the different points of contact of the connections of the machine are not kept thoroughly clean and free from oil, etc., it is probable that such resistance will be interposed in the path of the exciting current as to prevent the machine build- ing or exciting. Kach of the contacts should, therefore, be examined, and cleaned, and screwed up tight. The chief point to which attention should be given is the contact faces of the brushes arid surface of the commutator. These are very frequently covered with a slimy coating of oil and dirt, which is quite sufficient to prevent the machine exciting. In shunt and compound dynamos there is a certain critical speed below which they will not excite. If the normal speed of the machine is known, it can at once be seen whether the failure to excite arises from this cause, by measuring the speed of the armature with a speed indicator. In all cases it is advis- able, if the machine does not excite in the course of a few min- utes, to increase the speed to a certain extent. As soon as the voltage rises, the speed may be rednced to its regular amount. Insufficient residual magnetism is a fault, although not of frequent occurrence, and it is almost impossible for it to take place if the field magnets are of cast-iron. It always occurs when the dynamo is a new one, or when the field magnets have been taken apart for repairs, etc. It may be remedied by passing the current from a few storage cells, or another NEW CATECHISM OF ELECTRICITY. 263, FAILURE TO EXCITE. dynamo, for some time in the proper direction through the field coils. If a heavy current, such as is obtainable from a storage battery, is not available, and the machine is shunt or compound wound, a few Leclanche or dry cells will generally effect the purpose. Reversed magnetism in fields is a fault of infrequent occurrence. It may be caused by the proximity of other dynamos, but is generally due to reversed connections of the field coils. Under such conditions the field coils tend to pro- duce a polarity opposed to the magnetization to which they owe their current, and, therefore, the machine will refuse to excite until the field connections are reversed, or a current is sent from another dynamo or a battery through the field coils in a direction to produce the correct polarity in the pole pieces. A dynamo may refuse to excite through some portion of its windings or connections being short circuited, for the reason that the field magnets are deprived of the necessary current required for building the machine. Short circuits most frequently occur in terminals, brush-holders, commu- tator, armature coils, field coils. The terminals of the various circuits of the machine are liable to be short circuited, either through metallic dust bridging across the insulation, or through the terminals mak- ing direct contact with the frame of the machine. The various terminals should be examined, and if the fault cannot be located by inspection, they should each be disconnected from their circuits and tested with a battery and galvanometer. 264 NEW CATECHISM OF ELECTRICITY. EXCESSIVE HEATING OF DYNAMOS The excessive heating of the constituent parts of a dynamo is probably the most common and at the same time the most annoying fault which arises in the working of the dynamo. It may be due to various causes, electrical or mechanical ; and may occur in any one or more of the component parts of the dynamo : (1.) Connections. (2.) Armature, commutator, brushes. (3.) Field magnets. (4.) Bearings. It may be detected by applying the hand to the different portions of the machine if low tension, or a thermometer if high tension, and also by a smell of over-heated insulation and paint or varnish. When this last indication is felt, it is advisable to stop the machine at once, otherwise the insula- tion is liable to be destroyed. 1. Heating of Connections. — This may proceed from either or both of the following causes : (a) Excessive Current. — The terminals and connections will be excessively heated if a larger current passes through them than they are designed to carry. This nearly always NEW CATECHISM OF ELECTRICITY. 265 EXCESSIVE HEATING OF DYNAMOS. proceeds from an overload of the dynamo, and if this is rectified as directed in (4) "Overload of Dynamo," the heat- ing will disappear. (b) Bad Contacts. — If the contacts of the different con- nections of the dynamo are not kept thoroughly clean and free from all grit, oil, etc., and the connections themselves are not tightly screwed up, great heating will result, and they may even be unsoldered. 2. Heating of Armature, Commutator and Brushes. — When excessive heating occurs in these portions of the dy- namo, it may proceed from any of the following causes : (a) Excessive current ; (b) Heated bearings ; (c) Short cir- cuits in armature or commutator ; (d). Moisture in armature coils ; (e) Disconnections in armature coils ; (f) Eddy cur- rents in armature core or conductors. (a) Excessive Current. — When the dynamo is overloaded the temperature of the armature will rise to a dangerous ex- tent, depending upon the degree the safe capacity of the machine is exceeded, and heavy sparking of the brushes will also result. If the overload is not removed as directed in (4) "Overload of Dynamo," the insulation of the armature may be destroyed. (b) Heated Bearings. — If the bearings are heated, the heat may be conducted along the armature shaft and core, thus giving rise to excessive heating of the armature. (c) Short Circuits in Armature or Commutator. — This fault results in sparking at the brushes, and in excessive 266 NeW catechism of electricity. EXCESSIVE HEATING OF DYNAMOS. heating of one or the whole of the armature coils, and even in the burning up of the latter if a bad case. When the armature is overheated, and the defect does not proceed from an overload or the causes mentioned below, the dynamo should be immediately stopped and tested for this fault. (d) Moisture in Armature Coils. — The effect of this fault being to practically short circuit the armature, a heating of the latter results. In bad cases steam or vapor is given off. (e) Disconnections in Armature Coils. — This fault results in local heating of the armature, for the reason that resist- ance is interposed in the path of the current at the fracture. It always results in sparking at the brushes, and the heating being confined to the neighborhood of the disconnection. (/) Eddy Currents in Armature Core or Conductors — When the construction of the armature core and conductors does not fulfil the necessary conditions required for the pre- vention of Eddy currents, such as the laminations not being sufficiently insulated or numerous enough, a great heating of the whole of the armature results, which may even extend to the bearings. There is no remedy for this defect other than the purchase of a new armature, or the entire reconstruction of the old. The fault may be detected by exciting the field magnets and running the machine on open circuit, with the brushes raised off the commutator for some time, when the armature will be found to be excessively heated. 3. Heating of Field Magnets. — When the field magnets are found to be excessively heated, they should be tested for NEW CATECHISM OF ELECTRICITY. 267 EXCESSIVE HEATING OF DYNAMOS. the following faults in the order given : (a) Excessiv e excit- ing current ; (b) Moisture in field coils ; (c) Short circuits in field coils ; (d) Kddy currents in pole pieces. (a) Excessive Exciting Current. — When the excessive heating arises from this cause, all the exciting coils will be heated equally. It may be due to excessive voltage, in the case of shunt dynamos ; or to an overload in the case of compound and series dynamos. In either case it may be remedied by reducing the voltage or overload as directed in (4) " Overload of Dynamo." If due to the coils being incor- rectly coupled up, i. e., coupled up in parallel in place of series, it will be necessary to rectify the connections or insert a resistance in series. (b) Moisture of Field Coils. — As in the armature, the presence of damp or moisture in the field coils tends to de- crease the insulation resistance, thus in effect producing a short circuit with its- attendant heating. The fault may easily be detected by applying the hand to the field coils, when they will be found to be damp, and in addition steam or vapor will be given off where the machine is working The fault may be remedied by drying and varnishing the coils. (c) Short Circuits in Field Coils. — This fault is character- ized by an unequal heating of the field coils. If the coils are connected in series, the faulty coil will be heated to a less ex- tent than the perfect coils. If, on the other hand, they are connected in parallel, the faulty coil will be heated to a 2 63 NEW CATECHISM OF ELECTRICITY. Fig. 121. BARRIER MACHINE (N. Y.) NEW CATECHISM OF ELECTRICITY. 25a. EXCESSIVE HEATING OF DYNAMOS. greater extent than the perfect coils. The faulty coil can thus be easily located by this indication. (d) Eddy Currents in Pole Pieces. — This fault may be due to defective design or construction of the armature. Toothed core armatures are particularly liable to cause this fault, if the teeth and air gap are not properly proportioned. The defect may also be occasioned by variation in the strength of the exciting current. If due to this latter cause, it will be accompanied by sparking at the brushes. If a shunt dynamo, insert an am- meter into the shunt circuit, and note if the deflection is steady. If this is not the case, the variation in the current most probably proceeds from imperfect contacts thrown into vibration. 4. Heating of Bearings. — The heating of the bearings is of frequent occurrence in the working of dynamos, and is probably the most troublesome fault to which they are sub- ject, as its origin is, as a rule, obscure. When the bearings heat excessively, so that the heat cannot be borne by the naked hand, and such simple remedies as the supply of fresh lubricant, or slacking back the caps of the bearings or the belt fails to remedy the trouble, the dynamo should be stopped, as it indicates something radically wrong. The use of water on heated bearings has been recom- mended, but its use is questionable. No doubt it cools the bearings for the time being, and allows of the machine being run for a short time longer ; but when the bearings are in 270 NEW CATECHISM OF ELECTRICITY. EXCESSIVE HEATING OF DYNAMOS. such condition as to need the application of water, probably as much damage is done to the journals and liners, through scoring, etc., as more than counterbalances any slight gain secured through running the machine while the bearings are heated. Removing the lubricators, and flooding the bear- ings and journals with ordinary or castor oil, tends to re- duce the heating ; or the effect of sulphur mixed with oil, and applied direct to the bearings, after removing the lubri- cators, should be tried. If these remedies fail, the machine should be stopped, and the cause of the heating ascertained. As a rule, heating of the bearings is due to — (a) Defective lubrication or bad oil; (b) Journals too tight; (c) Belt too tight ; (d) Dirt, grit, etc., in bearings ; (e) Rough or badly fitted journals or bearings ; (/) Bent or badly turned shaft ; (g) End pressure of shaft against bearings ; (k) Armature incorrectly placed in armatnre chamber ; (i) Badly propor- tioned bearings ; (j ) Bearings out of line ; (k) Conduction of heat from armature. (a) Defective Lubrication or Bad Oil. — When the bearings heat up, first examine the lubricators to see that they are full, and that they feed the lubricant properly, and that none of the feed or waste oil passages are clogged. It is advisable to pass the end of a piece of wire down each of the passages occasionally to clear them. The quality of the oil supplied to the lubricators should be of the best mineral oil, perfectly clean and free from grit. It is advisable not to use the waste oil for the dynamo again ; but if used, see that it is well filtered. In some instances, hot bearings, due to defective NEW CATECHISM OF ELECTRICITY. 271 EXCESSIVE HEATING OF DYNAMOS. lubrication, have been remedied by cutting grooves ob* liquely in the face of the liners for the better circulation of the Oil. (b) Journals too tight. — If the caps of the bearings are screwed up too tight, the hearings are bound to heat up. As the armature spindle or shaft is not subjected to any recip- rocal stresses, it is only needful to have the caps of the bear- ings screwed up hand tight. If the top brass does not bear upon the bottom brass, it may be necessary to scrape open the bearing a little, or insert a liner between the top and bottom brasses, until the spindle revolves freely by hand. (c) Belt too tight. — Heating of the bearings may be due to too great a tension of the belt, caused either by an over- load of the dynamo, or through too narrow a belt being used for the work, thus necessitating the dynamo being screwed up tightly upon the slides. When this is the case, the bear- ing next the pulley will be heated more than the other. The remedy is to reduce the load upon the dynamo, as directed in B (4) " Overload of Dynamo," or get a broader belt and pulley and run with some slack on the belt. (d) Dirt y Grit, Etc., in Bearings. — The presence of the smallest quantity of grit in the lubricant or bearings will re- sult in great heating of the latter, and in scoring of the shaft and liners, if not removed quickly. The machine should be stopped if possible, and the caps of the bearings taken off and the armature taken out of the bearings, and the latter carefully cleaned and scraped up smooth. 272 NEW CATECHISM OF ELECTRICITY. EXCESSIVE HEATING OF DYNAMOS. If the journals are scored to any extent, it will be neces- sary to put the armature in the lathe and carefully file them up with a dead-smooth file before replacing. If the machine cannot be stopped at once, the lubricators should be made to feed very fast, or removed entirely, and the bearings continu- ously flooded with oil by means of an oil can until the ma- chine can be conveniently stopped. (e) Rough or Badly Fitted Journals or Bearings. — To ensure cool running, the journals should be perfectly smooth and true, and bear upon the surface of the liners throughout their entire length and width. To ascertain if this is the case, the caps of the bearings should be removed, and a little i ' marking, ' ' composed of red lead or other coloring matter and ordinary oil, rubbed upon the journals. The caps should then be replaced, and the nuts screwed up to working pressure, and the armature rotated a few times. The caps- should then be again re- moved, and the armature taken out, and the bearings exam- ined. If the journals are bearing all over the surface of the liners, the fact will be indicated by the marking being dis- tributed equally all over. If this is not the case, the project- ing portions of the liners, as indicated by the marking, should be carefully scraped up and the armature put back again, and the bearings tested from time to time until the journals bear all over as indicated by the marking being equally distributed all over the surface of the liners. {/} Bent or Badly Turned Shaft. — A bent shaft can be detected by rotating it with the hand. If bent, it will NEW CATECHISM OF ELECTRICITY. 273 EXCESSIVE HEATING OF DYNAMOS. "bind " at some portion of the revolution. If only slightly bent, the shaft should be placed in the lathe and carefully sprung back approximately straight, a light cut being taken off the journals to finally true it. The bearings will then need to be carefully refitted, as directed above. If badly bent, the only remedy is a new one. A badly turned shaft may be detected by means of the calipers and marking, as described above. If not truly circular, the marking will be unequally distributed over the journals. (g) End Pressure of Shaft against Bearings. — This may be caused either by the shaft not being truly level, or through the belt not being truly aligned, or through there being no "end play." In the former case, carefully test the journals with a spirit-level, and pack up the dynamo or slide rails until perfectly level. If the belt does not run true upon the pulleys, it will be necessary to align the machine by moving it upon the sliding bedplate until the centre of the belt runs upon the centre of the pulley. If no end play exists, the shaft will be bound between the collars and the bearings, and the defect will be visible to the eye. The correct amount of end play required varies with the size of the dynamo and method of driving adopted. In di- rect driven dynamos, it the collars of the journals are clear of the ends of the bearings, no end play is needed. In belt- driven dynamos, it is necessary to have from one-eighth to three-eighths of an inch of end play. In all cases it may be ascertained if the correct amount of end play is present by running the dynamo and observing, when slight pressure is •2 74 NEW CATECHISM OF ELECTRICITY. EXCESSIVE HEATING OF DYNAMOS. applied to one end of the shaft, if any end motion is pro- duced. If no end motion is obtained, or a strong pressure is needed to obtain the latter, the face of the collar or end of the bearing against which the shaft bears should be filed or turned down, until the correct amount is obtained, when the machine is running. (h) Armature Incorrectly Placed in Armature Chamber. — When the field magnet of a dynamo is Excited, it has a tendency to attract the iron core of the armature. The di- rection and intensity of the attractive force varies with the type of field magnet and the position of the armature core in the armature chamber or bore. In vertical horse-shoe mag- nets of the over-type form (Fig. 77), if the armature is placed exactly in the centre of the armature chamber, there is a tendency for the armature to be attracted downwards, the in- tensity of the attraction varying with the strength of the field magnets. In large dynamos this attractive force may even amount to some thousands of pounds, and therefore, if the armature core is not placed in the armature bore in such position as to balance or nullify the attractive force, the bear- ings are liable to heat up through the excessive pressure brought to bear upon them. To counterbalance the attractive force, it is necessary in such dynamos to place the armature slightly above the centre of the armature chamber. In field magnets of the undertype form (Fig. 78), the attraction is in an upward direction, and therefore, as the weight of the core is lifted off the bearings, the latter are not so liable to heat up as in the case with the overtype form. In horizontal field NEW CATECHISM OF ELECTRICITY. 275 EXCESSIVE HEATING OF DYNAMOS. 2nagnets (Fig. 79, etc.), the attractive forces act in op- posite directions, and are therefore balanced ; and in such dynamos the armature core may be placed exactly in the cen- tae of the armature bore. A heating of the bearings is also liable to be occasioned through the attractive forces devel- oped by the centre of the armature core not being parallel with the centre of the armature chamber or bore, or through the core being nearer one pole piece thau the other. This may result from unequal wearing of the bearings, and there- fore the bearings should either be re-lined or the bolt holes of the bearings readjusted, or the bearings packed up until the armature is correctly centred. (i) Badly Proportioned Bearings, — The bearings will heat up if the wearing and bearing surfaces are not suitably pro- portioned for the work they have to perform. In such cases the bearings will heat at the first run of the machine. The only remedy is to put in new or larger bearings, or an ad- ditional one, if the shait is long enough, and arrangements can be made to admit of this being done. (J) Bearings out of Line. — This will be indicated by an unequal wear of the liners, and by the shaft binding or seizing. The remedy is to draw the bolt holes of the bearings until the bearings are correctly aligned with each other and with the armature bore. (k) Conduction of Heat from Armature. — The bearings are liable to heat up through the heat developed by an overload or short circuit of the armature, or the production of eddy currents in the core being conducted along the shaft, 276 NEW CATECHISM OF ELECTRICITY. A CHAPTER OF "DON'TS." 44 Don't " use waste on commutators. 44 Don't" allow copper brushes to remain in contact with with commutators when the machine is at rest. *' Don't" get rattled at all the wires, cables and instru- ments at the switch board ; they are all useful and most of them absolutely necessary, and they are no more complicated than the piping about your plant with which you are now familiar. 44 Don't " fail to remember when the belts are put on the machines they are designed to run like any other piece of mechanical apparatus of similar weight and speed. " Don't " forget to ask the man who is to set up new appa- ratus to give you printed or verbal directions for running it. If he is a ' ' square man ' ' he will cheerfully do this. 44 Don't" fail to read the following, written by an engi- neer to a party seeking information. Note. — "You will find that there is an armature made to revolve between two or more * fields," and that as the latter become magnetized they have an attraction that tends to hold the armature from turning, but the belt knows a * good thing ' and 'pushes it along,' thus generating current which the winding carries to the commutator, where it is picked off by the brushes and passed along to the circuit. If your circuit is kept whole and the machine in good order, there is less need of trouble with it than with a buzz saw." NEW CATECHISM OF ELECTRICITY. 277 FLASHING OR SPARKING. In all good dynamos there are certain positions upon the commutator for the brushes at which there will be absolutely no sparking so long as the commutator is kept clean and in good condition. In other dynamos, badly designed or con- structed, sparking occurs at all positions, no matter where the brushes are placed, and in such dynamos it is therefore impossible to prevent sparking at the brushes, no matter how well they are adjusted. When sparkiug occurs at the brushes of a good dynamo, two kinds may generally be distinguished by the practised eye, viz., those sparks due to bad adjustment of the brushes, generally of a bluish color, small when near the neutral points, and increasing in violence and brilliancy as the brushes recede from the correct positions upon the commutator ; and those due to dirty and neglected state of the commutator and brushes, these being distinguished by a reddish color and a spluttering or hissing. When due to this last-mentioned cause, it is impossible to suppress the sparking until the com- mutator and brushes have been cleaned up. In the former case, the sparks will disappear as soon as the brushes have been rotated into the neutral points. Another class of sparks appear when there is some more or less developed fault, such as a short circuit, or disconnection Fig. 122. EQUALIZER CONNECTION AT k W RHEOSTAT KJ FOUR POI,K MACHINE WITH CONNECTIONS. NEW CATECHISM OF ELECTRICITY. 279 SPARKING AND FLASHING. in the armature or commutator. These are similar in character to those produced by bad adjustment of the brushes, but are distinguished from the latter by their not decreasing in violence as the brushes are rotated towards the neutral points. Having distinguished the classes of sparks which appear at the commutator of a dynamo, it remains to enumerate the causes tending to produce sparking. These are • (r.) Bad adjustment of brushes. (2.) Bad condition of brushes , (3 ) Bad condition of commutator. (4.) Overload of dynamo. (5.) lyoose connections, terminals, &c. (6.) Disconnections in armature circuit. (7.) Short circuits in armature circuit. (8. Short circuits or disconnections in field magnet circuit. 1. Bad Adjustment of Brushes. — When sparking is pro- duced by bad adjustment of the brushes, it may be detected by rotating or shifting the rocker, by the indication that the sparking will vary with each movement. To obtain good adjustment of the brushes, it will be necessary to rock them gently backwards and forwards, until a position is found in which the sparking disappears. If a position cannot be found at which the sparking disappears, it is probable that the brushes are not placed diametrically apart upon the commu- tator, or that the neutral points are not situated in their true theoretical positions upon the commutator through some defect in the winding, &c. In this last- mentioned case, the 28o NEW CATECHISM OF ELECTRICITY. SPARKING AND FLASHING. brushes may be strictly adjusted to their theoretically correct positions before starting the machine ; then, when the machine is started and the load put on, violent sparking occurs, which cannot be suppressed by shifting the rocker. If, however, one set of brushes only is observed, it will gener- ally be found that, at a certain position, the sparking at the set of brushes under observation ceases or is greatly reduced, while sparking still occurs at the other set. When this position is found, the rocker should be fixed by the clamping screw, and the brushes of the other set at which sparking is still occurring adjusted by drawing them back or pushing them forward in their holders until a position is found at which the sparking ceases, at which they should be fixed. Correct position of the brushes upon the commutator and the suppression of sparking is a matter of great importance, and any time spent in carefully adjusting will be amply repaid by the decreased attention and wear of the brushes and com- mutator. 2. Bad Condition of Brushes — If the contact faces of the brushes are fused or covered with carbonized oil, dirt, &c, there will be bad contact between the brushes and commutator, and consequently great heating and sparking. Simple exam- ination will generally reveal whether this is the case. The remedy is to remove the brushes, one at a time if the machine is running, clean, file if necessary, trim, and readjust. If the brushes are exceedingly dirty, or saturated with oil, it will be necessary to clean them with turpentine, benzoline, or soda solution, before replacing. MEW CATECHISM OF ELECTRICITY. 28l SPARKING AND FLASHING. 3. Bad Condition of Commutator. — If the surface of the commutator is rough, worn into grooves, or excentric, or had one or more segments loose, or set irregularly, the brushes will be thrown into vibration, and sparking will result. A simple examination of the commutator will readily detect these defects. The remedy for a rough commutator is to file it up while running with a dead-smooth file, afterwards polish- ing with finest emery cloth. If the commutator is untrue, the fact will be indicated when the machine is slowed down by a visible excentricity, or by holding the hand, or a stick in the case of high tension machines, against the surface while revolving, when any irregularity or excentricity will be ap- parent by the vibration or movement of the stick. The only remedy for an excentric commutator is to re-turn it as directed in the succeeding paragraph. Loose or high or low segments may be detected by the same means. The remedy for high segments is to tap them gently down with a small hammer or mallet, and if possible tighten up the clamping cones at the ends of the commutator. If it is im- possible to hammer the segments down, they should be filed down level with the rest of the commutator, or the commu- tator, re-turned. For low segments, the only remedy is to pull out the segments, or turn commutator down to their level. Re-turning Commutator. — In re-turning the commutator, the armature should first be carefully taken out of the armature chamber, avoiding knocks or blows of any kind. The whole of the windings should then in order to prevent any particles 282 NEW CATECHISM OF ELECTRICITY. SPARKING AND FLASHING. of metal finding their way on to the surface of the armature at the time the commutator is being turned, be entirely wrapped in calico or canvas before the armature is put into the lathe. The armature should on no account be rolled upon the floor, or subjected to blows or knocks while being put into the lathe, the winding is liable to be ruined if this takes place. In re- turning the commntator, a sharp-pointed tool should be used with a very fine feed. A broad-nosed tool ought not to be used, as it is liable to burr over the segments. After turning, the commutator should be lightly filed up with a dead-smooth file, and finally polished with coarse and fine emery cloth. After the commutator has been turned and polished, the insulation between the segments should be lightly scraped with the tang of a small file to remove any particles or burrs of metal which may be likely to short circuit the commutator. The points where the armature wires are soldered to the lugs should also be carefully cleaned with a brush from any adherent copper dust, and should then receive a coat or two of shellac varnish. While the commutator is being turned, care should be taken that the setting marks for the adjustment of the brushes are not turned out if these are present. The same care should be used in putting the armature back into the armature chamber as was used in tak- ing it out, otherwise the insulation is liable to be seriously damaged. 4. Overload of Dynamo. — It may happen through some cause or other that a greater output is taken from the machine i NEW CATECHISM OF ELECTRICITY. 283 SPARKING AND FLASHING. than it can safely carry. When this is the case, the fact is indicated by excessive sparking at the brushes, great heating of the armature and other parts of the dynamo, and possibly by the slipping of the belt (if a belt-driven machine), result- ing in a noise. The causes most likely to produce overload are :— (a) Excessive voltage ; (b) Excessive current ; (c) Re- versal of polarity of dynamo ; (d) Short circuits or grounds in dynamo, or external circuits. {a) Excessive Voltage. — This will be indicated by the voltmeter, and by the brightness of the pilot lamp. It may be caused either by excessive excitaiton of the field magnates, or by excessive speed. In the former case, resistence should be introduced into the field circuit to diminish the current flowing therein if a shunt machine ; or if a series machine, a portion of the cur- rent should be shunted across the field coils by means of a resistance arranged in parallel with the series coils ; or the same effect may be produced in both cases by reducing the speed of the armature if this is possible. If due to excessive speed, which will be indicated by a speed indicator, the natural remedy is to reduce the speed of the motor driving the dynamo, or, if this is not possible, insert resistance into the dynamo circuit, as described above. (b) Excessive Current. — This will be indicated by the ammeter. If the dynamo is supplying arc lamps, the excessive current may possibly be caused by the bad feeding of the. lamps. If this is the case, the fact will be indicated by the oscillations of the ammeter needle; and by the unsteadiness 284 NEW CATECHISM OF ELECTRICITY. SPARKING AND FLASHING. of the light. If incandescent lamps are in circuit, the fault may be caused by there being more lamps in circuit than the dynamo is designed to carry. Under such circumstances, another dynamo should be switched into circuit in parallel, or, if this is not possible, lamps should be switched off until the defect is remedied. When electro-motors are in circuit, sparking frequently results at the dynamo commutator, owing to the fluctuating load. In such cases the brushes should be adjusted to a position at which the least sparking occurs with the average load. (c) Reversal of Polarity of Dynamos. — When com pound or series wound dynamos are running in parallel, their polarity is occasionally reversed while stopping by the current from the machines at work. Under such conditions, when the machine is again started, the B. M. F. of one is added to that of another, or the machines are connected in series, so that a closed circuit is formed, and as a consequence an enormous current results. Before the machine can be again coupled in parallel, it will be necessary to send a current through the field coils in the reverse direction. (d) Short Circuits or Grounds in Dynamo or External Circuits.— A dynamo is liable to be overloaded through bad insulation of the dynamo or external circuits, resulting in a considerable leakage of current, in which case the ammeter will probably not indicate the fact. To ascertain if this is the case, connect a piece of insulated wire to one of the terminals NEW CATECHISM OF ELECTRICITY. 285 SPARKING AND FLASHING. of the machine while running, and then make short momen- tary contacts with the ground through a water pipe, or frame of the dynamo, or other body in good connection with the earth. If a flash occurs, it proves that the insulation is defective somewhere. This test should be applied to each of the terminals in turn. The fault should next be located by taking the mains -to the external circuit out of the terminals of the machine, and again testing as before. If a flash again occurs, it proves that the defect exists in the dynamo, which should be stopped, and the terminals, etc., tested with a battery and galvanometer. It must be clearly understood that a fault of this description is just as likely to occur in the external circuit, and therefore, if after removing the mains from the terminals of the machine, and again testing, the flash disappears, it may be taken that the fault is in the ex- ternal circuit, which should be tested in a similar manner to the dynamo. (5.) Loose Connections, Terminals, c2fc. — When any of the connecting cables, terminal screws, etc. , securing the dif- ferent circuits are loose, sparking at the brushes, as a rule, results, for the reason that the vibration of the machine tends to continually alter the resistance of the various circuits to. which they are connected. When the connections are excessively loose, sparking also results at their points of con- tact, and by this indication the faulty connections may be readily detected. When this sparking at the contacts is absent, the whole of the connections should be carefully examined and tested. 2 86 NEW CATECHISM OF ELECTFICITY. SPARKING AND FLASHING. (6. ) Disconnections in Armature Circuit.— 1£ there is a broken circuit in the armature, as sometimes happens, through a fracture of the armature connections, &c, there will be serious flashing or sparking at the brushes, which cannot be suppressed by adjusting the rocker. As a rule it results in the production of " flats" upon one or more bars of tl^e com- mutator. If it is impossible to stop the machine, the spark- ing may be much reduced by placing one of the brushes in each set a little in advance of the others, so as to bridge across the disconnection. If the machine is only provided with one brush on each side of the commutator, a bit of copper wire may be fixed in each holder, so as to project slightly in front of the brushes, and thus bridge over the broken circuit. (7.) Short Circuits in Armature Circuit.— -This fault is in- dicated by sparking at the commutator, and in bad cases by an excessive heating of the armature, dimming of the light, and slipping of the belt, and in the case of drum armatures by a sudden cessation of the current. (8. ) Short Circuits or Disconnections in Field Magnet Cir- ^•/.—Either of these faults is liable to give rise to sparking at the commutator. If one of the coils is short circuited, the fact will be indicated by the faulty coil remaining cool while the perfect coil is overheated. The fault may arise through some of the connections to the coils making contact with the frame of the machine or each other. To ascertain this, ex- amine all the connections, and test with a battery and gal- vanometer. A total disconnection in one or more of the field coils may readily be detected by means of the battery and NEW CATECHISM OF ELECTRICITY. 287 SPARKING AND FLASHING. galvanometer. A partial disconnection is not, however, so readily discovered, for the reason that the coil wires may be in sufficiently close contact to give a deflection of the gal- vanometer needle. The only methods of detecting this fault is by measuring the resistance of the coils with an Ohmeter or Wheatstone Bridge, or by placing an ammeter in circuit with each coil in turn, and comparing the amount of current flowing in each. If the short circuit is not accessible, the only way to remedy the fault is to rewind the coil, and the same applies to a disconnection if in the interior of the coil. 288 NEW CATECHISM OF ELECTRICITY. LIST OF PARTS. i. Armature (Ring Type). 2. Left Hand Field. 3. Right Hand Field. 4. Pulley Leg. 5. Commutator I,eg. 6. Field Rods. 7. Pulley. 8. Automatic Regulator. 9. Air Blast. 10. Commutator. Fig. 123. ARC LIGHT GENERATOR. 11. Brushes. 12. Brush Holders. 13. Pulley Bearing Cap. 14. Oil Rings. 15. Commutator Bearing Cap. 16. Yokes. 17. Regulator and Yoke Connection 18. Vulcanite Connection Block. 19. Binding Post an d Machine Con nections. . . 20. Armature Short Circuitir Switch. NEW* CATECHISM OF ELECTRICITY. Fig. 124. THOMPSON-HOU$TON ARC-LIGHT GENERATOR (PARTS). 29O NEW CATECHISM OF ELECTRICITY. VARIATION OF SPEED. This will be indicated by the dynamo failing to excite, or by a decrease of the voltage if the machine is working. The fault mav proceed from the undermentioned causes : — (1.) Reduced speed of driving engine; (2.) Overload of dynamo. (3.) Defective bearings. (4.) Short circuits in armature. (5.) Armature rubbing against pole pieces. (6.) Slack or dirty belt. 1. Reduced Speed of Driving Engine. — It can readily be* ascertained whether the alteration in speed of the dynamo> proceeds from this cause by counting the revolutions of the engine with a speed counter. If at any time it is necessary to. run an engine driving a shunt or compound dynamo at ai lower speed than the normal, the voltage and output of the dynamo can generally be maintained at their ordinary value by coupling up the shunt coils in parallel, thus increasing the strength of the current flowing in the shunt circuit and the strength of the field correspondingly. Care should be taken, however, that the coils do not overheat with the increased current. NEW CATECHISM OF ELECTRICITY. 29I VARIATION OF SPEED. 2. Overload of Dynamo. — When the reduction in speed proceeds from this cause, it is accompanied by excessive sparking at the brushes, and heating of the bearings and armature, and slipping of the belt. If the overload be re- moved as directed in Overload of Dynamo, the speed will again attain its normal value. 3. Defective Bearings. — When due to this cause, the bear- ings will be excessively heated, and the shaft will " bind " or "seize," making a noise. It generally proceeds from de- fective lubrication, and may be remedied as directed in (4) Heating of Bearings. 4. Short Circuits in Armature. — This practically amounts to an overload of the dynamo, and is accompanied by spark- ing at the brushes, heating of dynamo, and reduction of speed. The short circuit should be localized and repaired. 5. Armature Rubbing Against Pole Pieces, — This will result in a diminution of speed if not remedied. 6. Slack or Dirty Belt. — If the driving belt is not kept in good order, and free from oil, dirt, &c, a considerable amount of power will be lost in transmission. This will also be the case if the tension of the belt is not properly adjusted. If the motor driving the dynamo is a steam engine, turbine, or other steady running motor, the belt should in all cases be as tight as possible, consistent with the heating of the bearings. In the case of gas or oil engines, however, it will be necessary to have a certain amount of slack on the belt to allow of a little slip on the dynamo pulley, the amount varying with the irregularity of speed of the driving motor. 292 NEW CATECHISM OF ELEC'i KICITT. VARIATION OF VOLTAGE. The pressure at the terminals of either shunt, series, or compound dynamos is liable to vary or fluctuate from various causes. In plain shunt or series wound dynamos a variation of pressure under a varying load follows as a consequence to the construction of the machine. A distinction, therefore, needs to be drawn between this natural variation of pressure and an abnormal fluctuation, which also affects compound dynamos, which may occur from time to time in the working of such machines. The causes tending to produce a fluctua- tion of voltage are : — (1.) Irregularities of speed. (2.) Bad joints in belt. (3.) Short circuits or disconnections in armature cir- cuit. (4.) Short circuits or disconnections in field magnet circuit. (5.) Incorrect connections. 1. Irregulariiies of Speed. — Any cause tending to produce a variation in the speed of the dynamo is responsible for a variation of voltage. Steam engines, turbines, &c, give as a rule very little trouble in regard to irregularities of speed. In the case of gas and oil engines, however, an unsteadiness of NEW CATECHISM OF ELECTRICITY. 293 VARIATION OF VOLTAGE. speed is always present, owing to their mode of action and construction. Before such motors can be used successfully in driving dynamos, this unsteadiness of speed needs to be re- duced and compensated as far as possible. With this object, such engines, when used for driving dynamos, are therefore fitted with extra heavy fly-wheels, and a fly-wheel is also fitted upon the armature spindle of the dynamo. In driving with such engines, the governors and valves are adjusted, if possible, to give an explosion at every revolution of the fly- wheel, and any little irregularity of speed is then compensated by varying the tension and slip of the belt on the dynamo pulley. 2. Bad Joints in Belt. — If the belt is not jointed in a suit- able manner, it will cause a fluctuation of voltage, and a flick- ering of the light as the joint passes over the pulley. The belt should in all cases be soft and pliable, and made endless by a long spliced joint, or a butt joint with fasteners, or an endless link belt should be used. I^apped joints should on no account be used. 3. Short Circuits or Disconnections in Armature Circuit. — When either of these faults is present, a periodical fluctuation of voltage will be set up, accompanied by sparking at the brushes. When this occurs- the machine should be stopped at once and the fault located and repaired. 4. Short Circuits or Disconnections in Field Magnet Cir- cuit:— -Kither of these faults will give rise to a dimiuution or increase of voltage. To locate the faults, the entire field cir- cuit should be tested and examined. 2Q4 NEW CATECHISM OF ELECTRICITY. VARIATION OF VOLTAGE. 5. Incorrect Connections. — If on starting a machine for the first time, or after repairs, the voltage is either above or below its normal value, it is possible the variation may be the result of incorrect connections. The whole of the connections, in- cluding the armature, brushes, flexible leads, and field coil connections, should therefore be examined and verified. EXCESSIVE NOISE OR VIBRATION. The causes tending to produce excessive noise or vibration in a dynamo are : — (1.) Bad foundations. (2.) I/Oose screws, connections, &c. (3.) Belt joints. (4.) Bad adjustment of brushes. (5.) Knocking of shaft or pulley against bearings. (6.) Armature out of balance. (7. ) Armature knocking or rubbing against pole pieces. (8.) Straining of shaft couplings. These reasons for noise and vibration are self -explaining and the mere reading of them will suggest the appropriate remedy— but perhaps the more readily with the following paragraphs : NEW CATECHISM OF ELECTRICITY. 295 EXCESSIVE NOISE. Excessive vibration can only be due to want of proper bal- ance in the armature. Vibration of another kind may nevertheless be disastrous to the dynamo, even in a well balanced machine, and this is caused by its not being firmly attached to a proper founda- tion. Continuous-current machines should run practically si- lently ; the belt will make far more noise than any part of the dynamo. Alternators do not usually run silently for the coils of all disk armatures churn the air between the poles. A case is recorded of a remarkable instance of an alternator, which emitted a sustained howling sound of piercing loud- ness. The cause was an accidental coincidence between the number of alternations and the natural vibration period of some of the solid iron parts. 296 NEW CATECHISM OF ELECTRICITY. WINDINGS OF ARMATURES. Fig. 125. Figs. 125 and 126 are simple diagrams showing the way in which wire is wound on drum and ring armatures, respec- tively. In both figures the coils are shown separated to more readily illustrate the prin- ciple. A little examina- tion of the figures will show that each section of the coil is connected to the next in order to it ; the whole of the windings constituting, therefore, a single closed coil. DRUM WINDING. Also the end of each section and the beginning of the next are both connected with a segment of the commutator. Fig. 126. RING WINDING. NEW CATECHISM OF ELECTRICITY. 297 WINDING OF ARMATURES. Let it be remembered that in closed-coil armatures, whether of the "ring" or the "drum" type, there are usually as many segments to the commutator as there are sections or groups of coils in the circuit of the armature. In the case of open-coil armatures y the separate coils are not connected up together in series, and a special form of commutator is used instead of the usual arrangement of a large number of parallel bars. The principle of the ring or gramme armature is shown in Fig. 70. An iron ring capable of revolving upon an axis is arranged in the magnetic field between the poles N and S of an electro magnet. Upon this ring is wound a number of coils or loops of insulated copper wire, so as to cover the whole of the surface of the iron ring. The ends of each of the coils are connected to the ends of the adjacent coils, so that a con- tinuous closed spiral is formed all around the ring ; and, at the points where connection is made between the coils, con- nection is also made to strips of copper, which are insulated from each other and arranged around the axis of rotation into a circular commutator, as shown in the figure, against the two strips situated at opposite ends of a diameter press, two metallic brushes, Bi, B2, which, remaining stationary, serve to convey the current generated in the coils of the arma- ture to the external circuit K. The arrangement of the lines of force in the magnetic field between the two poles N and S, when the ring is inserted therein is shown in the dotted lines in the figure. 2g8 NEW CATECHISM OF ELECTRICITY. WINDING OF ARMATURES. From this it will be seen that the lines of force issuing from the north pole pass by way of the armature core to the south pole of the magnet, one-half of the lines passing through the upper portion of the core and the other half passing through the lower portion of the core. Owing to this peculiar arrangement, a very intense magnetic field is created between the outer surface of the armature core and the polar faces, whilst the interior space within the core remains almost en- tirely free from lines of force. The drum or Siemen's type of armature differs essentially from the ring armature only in the manner in which the con- ductors are arranged upon the iron core. In the ring arma- ture the core consists of a ring, and is overwound with con- ductors passing along the outer surface and through the interior ; in the drum armature, the core is in most cases a ring also, or may be regarded as a ring, and is overwound with conductors passing along the outer surface, but in place of passing through the interior the conductors are carried completely around it axially, in the manner represented in Fig. 127. This shows a drum armature in perspective, upon which only two adjacent conductors or coils have been wound. Since the windings of the drum armature pass over the ends of the core, it is impossible to represent the whole of them in perspective, and, therefore, they are exhibited diagramatically in Fig. 128, which illustrates what is known as a right-handed winding, with eight-part commutator (see in cut a, b, c, d, etc.). In the figure shown, the windings are supposed to be i NEW CATECHISM OF ELECTRICITY. 299 WINDING OF ARMATURES. viewed from the commutator or front end of the armature. The windings passing along the length of the drum are represented by the small circles upon which are marked the dots and crosses de- \ L X. Fig. 127. noting the direction of the K. M. F., as in the ring armature. The con- nections passing across the back end of the drum are represented by the dotted lines ; those upon the front end by full lines. 300 NEW CATECHISM OF ELECTRICITY. WINDING OF ARMATURES. The manner in which the individual loops or coils are arranged will be rendered clear by following the course of a single loop or coil upon the armature. Starting from the commutator segment (a) upon which the positive brush is resting at the upper portion of the armature, the conductor proceeds up the face of the drum to b, thence along the top and across the back end to the lowest part of the drum, from whence it proceeds across the bottom of the drum to 15. From 15 the conductor is brought around the face of the drum and connected to the commutator section (h), next to the one from which it started. Another coil starts from the segment (h) and follows a similar course upon the surface of the armature, and is con- nected to the segment (g), from which another coil starts, and so on all around the armature. A continuous closed spiral is thus formed all around the armature, in a somewhat similar manner to the ring armature. The arrangement of the line of force in the magnetic field, when the armature is inserted therein, is similar to that of the ring armature, and with the armature rotating in the direction indicated by the arrow, it will be seen that the K. M. F.s and currents induced in the conductors, on either side of the armature, have the same relative directions as those induced in the conductors arranged upon the outer surface of the ring armature, the only differ- ence being that the current flows across each end of the drum in place of flowing through the interior ; the conductors at the ends being thus the only idle portions of the winding in the drum armature. NEW CATECHISM OF ELECTRICITY. 3OI WINDING OF FIELD MAGNETS. Field Magnet Windings. — The insulated wires used for the excitation of the field magnets, not being subjected to any of the detrimental influences experienced by the armature conductors, are in most cases of solid copper. As a rule, the wires are wound upon insulated spools, which are afterwards slipped over the limbs of the magnet ; in some cases, however, they are wound direct upon the core of the field magnet, this latter being previously insulated with vulcanized fibre or other insulating material. In general, the wires used for the exciting coils of shunt wound dynamos are very thin ; hence, when this is used for making connection to the terminals of the machine, it is very liable to break off near the flanges of the reel upon which it is wound. Several plans are adopted to prevent this occurring : in some cases the ends of the shunt coils are soldered to stouter wires within the flanges of the bobbins, these wires being afterwards connected to the terminals of the machine ; in other cases, the ends of the coils are soldered to large termin- als fixed upon the flanges of the bobbins, these terminals being afterwards suitably connected together by strips of copper. Ring Windings. — When a ring core is to be wound, it is frequent to stencil upon the end faces a number of radial lines corresponding in breadth to the separate sections, so as to guide the winder in his work. 302 KEW CATECHISM OF ELECTRICITY. Fig. 129. RING WINDINGS. For ring-windings there is, in general, little trouble. Nevertheless, some care must be exercised. The separate " sections" of the coil are almost invariably wound on the cores separately, leaving the ends projecting, secured tempor- arily with string, and these ends subsequently connected to- gether and to the commutator. An inexperienced workman may easily connect up wrongly ; making a left-handed winding instead of a right-handed one, or vice versd. Hence, it is well to provide him with some such working drawing as Fig. 129, which relates to a right- handed winding having four turns in each section. The wire marked " o " is the last or outer end of the section previous to that considered. This end will eventually be brought down to a bar a of the commutator, and from this bar will go out the beginning or left-bottom end, marked L, B, of the section in question. L/Ooking at this diagram the winder will see that the wire ly B must pass under the core to the far end and then return over the top, thus making turn No. 1. It will then bend down to the right, be threaded through again, and make turn No. 2 ; again, and make turn No. 3 ; but as the inner space is narrower than the outer space, turn No. 4 will probably have to ride on, or partly bed between, the turns already wound. The right-top end, marked R T, will eventu- Winding Diagram. Armature. NEW CATECHISM OF ELECTRICITY.. 303 RING WINDINGS, ETC. ally be joined to bar h of the commutator. If the winder is shown that the right- top wire of one section joins the left- bottom turn of the next section at the commutator, he will have no excuse for mistakes. The winding of multipolar rings is absolutely similar, provided as many brushes are applied to the commutator as there are poles. For arc-lighting armatures, and in general those which have numerous convulutions of wire to each section, it is con- venient to prepare the wire in separate lengths sufficient for each section, and to coil each length on small shuttles each length being wound upon two shuttles, which are alternately used for successive layers. By this device both ends of the wire that constitutes a section are brought to the outside in- stead of one of them leading directly down to the bottom layer, as in ordinatry bobbin winding. Winding Diagrams. — If one tries to draw all the con- nectors of a drum winding the lines cross and occasion con- fusion. There is therefore a great advantage in adopting a mode of representation, originally suggested by Herr Fritsche, of Berlin, in which the armature winding is considered as though the entire structure had been developed out on a flat surface. If one was to attempt in a picture to show twenty or more conductors and their respective connections, the drawing would be unintelligible. Accordingly we have to imagine ourselves placed at the centre, and the panorama of the four 304 NEW CATECHISM OF ELECTRICITY. ARMATURE WINDINGS. Fig. 130. DEVELOPMENT OF WINDING EOR FOUR POLE MACHINE. NEW CATECHISM OF ELECTRICITY. 305 ARMATURE WINDINGS. WINDING FOR FOUR POLK MAGNET TO CORRESPOND TO FIG. 130. 306 NEW CATECHISM OF ELECTRICITY. ARMATURE WINDINGS. poles laid out flat, as in Fig. 130. It will be noticed that the faces of the N and S poles are shaded obliquely for distinc- tion. Now in an actual machine there are many armature con- ductors spaced symmetrically around, and these have to be grouped together by connecting wires. In the case of ring windings the wires which connect the active conductors in the gap-space pass through the central aperture in the ring when they are removed from the magnetic field. Suppose, for simplicity we have a ring armature of only 12 turns and 12 bars to the commutator. If this is opened out from the in- side we shall have the form shown in Fig. 130, where the dotted lines are the inactive parts of the spiral winding that pass through the inside of the ring. By tracing the arrows it will be seen that there must be two positive and two negative brushes. Fig. 131 gives an end view diagram of the same winding by which the two modes of presentation may be compared. It is usual to couple the positive brushes together, and the negative brushes together. A 6-pole machine would require six brushes, and so forth. When the brushes of the same sign are thus connected together the electromotive-force of the whole armature is simply that of any of the sets of coils from one -|- brush to the adjacent — brush. Lap Winding and Wave Winding. — This distinction arises in the following manner. Since the conductors that are passing a north pole generate electromotive-forces in one NEW CATECHISM OF ELECTRICITY. 307 ARMATURE WINDINGS. direction, and those that are passing a south pole generate electromotive -forces in the opposite direction, it is clear that a conductor in one of these groups ought to be connected to one in nearly a corresponding position in the other group, so that the current may flow down one and up the other in agreement with the directions of the electromotive -forces. If now we examine Fig. 132 we shall see that at the back of the armature (or end distant from the commutator) each con- ductor is united to one five places further on — No. 1 to No. 6, No. 3 to No. 8 — and that at the front end the winding, after having made one " element " (as for example d-j-12-e), then forms a second element (^-9-14-/"), which laps over the first ; and so on all the way round until the winding returns on itself. Now contrast with this Fig. 133, in which, though the connections at the back end are the same, those at the com- mutator end are different. . It will be seen that when the winding returns back toward the commutator, instead of lapping back toward the part from which it started, it is turned the other w r ay. The winding d-y-12 does not return at once to e, but goes on to /, whence another element z-17-4-^ goes on in a sort of zig-zag wave. These are both drum windings, the corresponding winding tables being as shown in Figs. 134 and 135. Note. — As each and every armature must needs have its own especial winding— based, of course, upon both experience and calculations, it will be understood that these few pages are given to explain the general practice— and in no other sense. 303 NEW CATECHISM OF ELECTRICITY. ARMATURE WINDINGS. Fig. 133. NEW CATECHISM OF ELECTRICITY. 309 ARMATURE WINDINGS, § I is I Fig. 133. 3io NEW CATECHISM OF ELECTRICITY. ARMATURE WINDINGS. Figs. 134 and 135 represent tables such as are furnished the practical workmen by the designers of the machines. These greatly facilitate the work and add accuracy to the building of the dynamo. (Wave- winding. ) F B F a 1 « 1 / f 11 10 b b 8 (I — 9 13 IS c c 5 10 h h 15 2 a d 7 12 i i 17 4 e + e - 9 14 a Fig. 134. (Lap- winding} F B F -%-a 1 6 b b 3 8 c ~*~ c 5 10 d a 7 12 e + e 14 f f 11 10 — v 13 18 h h 15 2 i i 17 4 a Fig. 135. NEW CATECHISM OF ELECTRICITY. 311 TESTING FOR CONDUCTIVITY AND INSULATION. Testing for Conductivity. — In making this test, the instru- ments are connected as represented in Fig. 136. B is the bat- tery, G the galvanometer, and S is a coil of wire being tested for electrical continuity or conductivity. As will be seen, the Fig. 136. positive pole -|- of the battery is connected to one terminal of the galvanometer, and the other or negative pole is connected to one of the ends of the coil under test. The other terminal of the galvanometer is connected to the other end of the zoil. If the connecting wires are making good electrical contact 312 NEW CATECHISM OF ELECTFICITY. TESTING FOR CONDUCTIVITY. with the respective terminals, and the wire of the coil being tested is unbroken, the needle of the galvanometer will be de- flected as soon as a closed circuit is made by the end of the coil coming into contact with the galvanometer terminal. If the wire of the coil is broken in some part or the ends of the con- Fig. 137. *Hi I I I I h 6 necting wires do not make good electrical contact with the ter- minals, the needle will not be deflected. In order to prevent mis- takes, it is advisable to test the battery and galvanometer con- nections and contacts by short circuiting or bringing the ends of the wire connecting the terminal of the galvanometer and negative pole of the battery together before starting to test the circuit or coil. If the needle is deflected, the connections are all right ; if undeflected, there is a bad contact some- where, which must be made good before the test can proceed. NEW CATECHISM OF ELECTRICITY. 313 TESTING FOR CONDUCTIVITY. Testing for Insulation. — The o1>ject of this test is to ascer- tain whether the insulation of a circuit or of the wire wound upon a metal spool or core, such as a magnet core, has broken down or is in good order. In making the test, the instru- ments and connections are arranged as shown in Fig. 137. The battery and galvanometer are connected to one another, as in the conductivity test described above. The unconnected terminal of the battery is connected to one end of the coil under test, the other end of the coil remaining free and unconnected. Some portion of the metal core, say the end, is then cleaned bright with a knife or emery cloth, and the unconnected terminal of the galvanometer is brought into contact with this bright or clean part of the core. If then some portion of the insulation of the wire has been abraded or destroyed, thus bringing the bare wire into contact with the metal core, as at A in the figure, the needle of the galvano- meter will be deflected since a closed circuit is formed through the core and wire. If on the contrary the insulation is per- fect, the needle will be undeflected. It will thus be seen that in the conductivity test it is necessary that the needle should be deflected, or turned, to prove that all is right, while in the insulation test the converse holds good ; if the needle is de- flected, it proves that the insulation is broken down. NEW CATECHISM OF ELECTRICITY. Fig. 138. NEW CATECHISM OF ELECTRICITY. 315 THE ALTERNATOR. A dynamo constructed without a commutator for making the current direct, produces an alternating current, and such a machine is called an alternator. A great many kinds of alternators have been constructed. They may be thus classi- fied : 1. Those with a stationary field magnet and rotating ar- mature. 2. Those with rotating field magnet and stationary arma- ture. 3. Those with both field magnet and armature part station- ary. In the latter class, the amount of magnetic induction from the armature to the field is caused to vary or alternate in direction by the revolution of appropriate pieces of iron called inductors. Still another division rests on whether they give one simple alternating current, a two-phase current, or whether they give multiple currents. In alternate-current working machines, the current is rapidly reversed, rising and falling in a succession of impulses or waves. Electricity is, in fact, oscillating backwards and 3l6 NEW CATECHISM OF ELECTRICITY. THE ALTERNATOR. forwards through the line with enormous rapidity, under the influence of a rapidly-reversing electromotive-force. The adjectives alternate, oscillatory, periodic, undulatory and harmonic have all been used to describe such currents ; the term wave-currents is more apt. The properties of alternate-curreuts differ somewhat from those of direct or continuous currents. They are affected not only by the resistance of the circuit but also by its inertia it self-induction, which diminishes the amplitude of the waves and retards their phase. The alternating current enables us to take advantage of an effect called induction, which is only exerted when the cur- rent is suddenly broken or changed in direction. The ordinary alternator has three or more pairs of poles instead of a single pair, and the armature carries as many coils as there are poles. These coils are coupled in series or in parallel so as to act as a single coil, the large number of poles increasing the number of alternations or cycles per second. Since alternating currents are used largely for light- ing, it is necessary to have at least forty complete alternations per second in order to avoid flickering of the incandescent or arc lights. Note. — The alternating current machine may be built to give directly a pressure up to 2,000 or 3,000 volts, and in certain types as high as 5,000 volts. If this is insufficient for the purpose, the voltage may be still further increased by the use of transformers. NEW CATECHISM OF ELECTRICITY. 317 THE ALTERNATOR. Also, the transformers would have to be much larger if the frequency of alternations were less. For the systems in gen- eral use, sixteen thousand single alternations (eight thousand complete alternations or cycles) per second have been adopted as giving the most desirable frequency, the recent tendency being to reduce this to a considerably lower number. With a single coil armature revolving in a two-pole field, this would involve excessively high speed, hence the necessity for the mnltipolar field. Multiphased currents are two or more separate and dis- tinct currents not differing in any way from the current de- rived from an ordinary "single phase" alternator. Their peculiarity lies, not in the nature of the currents themselves, but in the fact that they have different strengths at a given instant of time. In the two-phased system, for instance, when one of the currents is at zero value, the other has its maximum value, or the currents are displaced in phase, whence the expression two-phased. If two identical simple alternators have their armature shafts coupled in such a manner, but when a given armature coil on one is directly under a field pole, the corresponding coil on the other is midway between two poles of its field, the two currents generated will differ in phase by a half- alternation, and will be two-phased currents; similarly, three- phased currents could be generated by coupling the armatures of three simple alternators so that the corresponding coils on each are equally " staggered " with respect to each other. 318 NEW CATECHISM OF ELECTRICITY. THE ALTERNATOR. By the introduction of what is known as the tnulti- phase systems all difficulties have been overcome and alternating current motors are now manufactured which are equal to the best direct current motors in efficiency and starting torque, and which have the additional advantage of having no com- mutator or moving contacts of any kind. Two-phase and three-phase currents differ in this respect ; the two-phase system requires four wires to connect the gen- erators with the motors and their action is that of two distinct and separate circuits through which are passing simple alter- nating currents of electricity which act upon the revolving part of the motor like the two cranks on a cross connected engine at right angles to one another, or one 90 degrees in advance of the other. The three-phase method of employing the alternating cur- rent requires only three wires and for transmitting electrical energy in large amounts long distances for power purposes, it is an ideal system. The Monocyclic System. — The " monocyclic " system is that in which three wires are used, but the main or energy current is conveyed by two of the wires, while the third one serves as an auxilliary and is necessary for starting the motor. The motors are of the class called "induction motors " from the fact that the current in the armature or revolving part is in- duced by an alternating current in a stationary coil outside of the armature and at an angle to the field, instead of being con- Note. — The Fig. on the next page is intended to show the "wave motion ' ' of the different alternations. NEW CATECHISM OF ELECTRICITY. 319 THE ALTERNATOR. ducted into the armature through sliding contacts as in the more familiar direct current motor. Motors constructed upon this principle have the advantage of great starting power, and are able to stand temporary over- loads without damage. They can be made smaller than the direct current type, are cylindrical in shape and adapted to be put in any position. They are almost as simple as a grind- stone, and having self-oiling bearings, require scarcely any attention at all. The monocyclic in its broadest sense is a combination of the single-phase and three-phase systems. Three-phase cur- rents are produced from single-phase currents by means of a specially wound armature which may be operated as a motor- generator at the point where energy for motors is to be dis- tributed, or the main generator may be provided with a special armature arranged to produce the necessary difference of phase between the ordinary two-wire circuit and a third wire. 320 NEW CATECHISM OF ELECTRICITY. MOTORS. Very nearly all that has been said upon the subject of dynamos applies to the motor and needs not to be repeated. Motors are, however, divided into two general classes : i. Those for use with continuous currents. 2. Those for use with alternating currents. The real development of the motor as a transmission of power machine came after the commercial introduction of Gramme's dynamos in 1871, as engineers began to understand how two of these machines could be used — one as generator, the other as motor — to transmit power through a line. All the earlier attempts to introduce electric motors came to nothing, for at that time there was no economical method of generating electric currents known. But, motors are also classified the same as dynamos, as series wound, shunt wound, compound wound, bipolar and multipolar motors. The motor being intended for the distri- bution and application of the power generated by the dynamo Note.— A glance at the early history of the electric motor brings out the striking fact that this machine was invented eight years before the dynamo, and for several decades it was considered of more importance, both scientifically and practically. NEW CATECHISM OF ELECTRICITY. 321 MOTORS. is usually a much smaller machine — thus a dynamo of 1,000 horse power will furnish the necessary force for nine or ten 100 horse power motors. In construction, the dynamo and motors are essentially the same, but in their action are exactly the reverse. Fig. 139. GENERATOR. MOTOR. Motors depend for their operation on the tendency to motion in a magnetic field. If the conducting wire, while situated in the magnetic field, is actually conveying an electric current (from whatever source) it experiences a side thrust, tending to move it forci- bly, parallel to itself, across the magnetic lines, and so enables it to exert power and to do work. This is illustrated in Fig. 322 NEW CATECHISM OF ELECTRICITY. MOTORS. 140, where the small arrows exhibit the movement of the cur- - rent and the large arrow the resulting push or magnetic force. This action is the principle of the dynamo used as a motor. . Two points are vital to the right understanding of the* action of electric motors: (1) the propelling drag, (2) the- Counter electromotive-force. The first is that the real driving- force which propels the revolving armature is the drag which the magnetic field exerts upon the armature wires through which the current is flowing (or, in the case of deeply-toothed armatures, on the protruding teeth): the second is that the revolving armature generates a counter electromotive force as its moving wires cut the magnetic lines. Fig. 140. The Propelling Drag. — In a generator the drag acts in a, direction which opposes the rotation, and is, in fact, a counter- force or reaction against the driving force. In a motor the : drag is the driving-force, and produces the rotation. The Counter Electromotive-force. — Let it be remembered that wherever in an electric circuit, current flows through some portion of the circuit in which there is an electromotive- NEW CATECHISM OF ELECTRICITY. 323 DYNAMO AND MOTOR BELTS. force, the current will there either receive or give up energy according to whether the electromotive-force acts with the current or against it. This will be made clearer by Fig. 139, representing a circuit in which there are a dynamo and a motor. Each is rotating right-handedly, and therefore gen- erates an electromotive-force tending upwards from the lower brush to the higher. In each case the upper brush is the posi- tive one. But in the dynamo, where energy is being supplied to the circuit, the electromotive-force is in the same direction as the current ; whilst in the motor where work is being done, and energy is leaving the circuit, the electromotive-force is in a direction which opposes the current. DYNAMO AND MOTOR BELTS. " Points" relating to Dynamo and Motor Belts, — No sub- ject relating to motors will be found of more practical interest than the following : 1. Dynamo belts should make a straight run through the air and over the pulleys without wabbling ; they should main- tain an even and perfect contact with that part of the pulley with which they come in contact. In order to do this they should be kept soft, pliable, and have no abrasions or rough places — the belt should be first-class — as near perfection as possible, for they must do their work so the light burns with- 324 NEW CATECHISM OF ELECTRICITY. DYNAMO AND MOTOR BELTS. out flicker. When belt fasteners give way there is too much strain upon belt. The greatest amount of slack in a belt is found when it leaves the driving pulley, hence the tightener should be near the driving pulley, as it takes up the slack, prevents vibration and diminishes strain on belts and bear- ings. More than no° of heat is injurious to belts. 2. The double belt should always run with the splices, and not against them. One-quarter turned belts should be made of two-ply leather, so as to avoid so much side strain. Slow- motion belts should be made of two-ply leather, as they receive hard labor and strains. 3. The electric generators of the alternating system require special belts, as they are run at great velocity. Belts for the alternating system should be endless, perfectly smooth, even in texture and thickness. If too much power is added to the stick- ing or adhesive qualities of a belt the friction will cause loss. 4. Friction is greatest when the pulleys are covered with leather. Friction depends upon pressure, but adhesion depends upon the surface contact ; for instance, two square feet of adhesion will hold twice as much as one square foot, hence, the more a belt adheres to pulley surface without straining, through too much tightening, the better the driving power. Wet days produce slipping because the leather absorbs dampness. 5. A leather-covered pulley will produce more resistance than polished or rough iron ones. A good belt dressing makes a smooth, resisting surface, and as it contains no oils, which NEW CATECHISM OF ELECTRICITY. 325 DYNAMO AND MOTOR BELTS. create a slippery surface to belts, it increases belt adhesion. The friction of leather upon leather is five times greater than leather upon iron. 6. Moisture and water distend the fibres, change the properties of the tanner's grease and softening compounds. Repeated saturation and drying will soon destroy leather. Leather well filled with tanner's grease or animal oil, if allowed to hang in a warm room for several months without handling, will dry out, become harsh, and will readily crack. 7. Many things have been used to make belts stick to the pulleys, some of considerable value. A careful study of all the parts that work together is required in order to get full power transmission. Suitable belt dressing will overcome many serious questions that arise, but it must be properly applied. 8. A running belt is stretched and relaxed at different times, and unless there is perfect elasticity in all its parts there will not be uniform distension. Whatever relieves the strain upon belts prolong their life. There should be 25 per cent, margin allowed for adhesion before a belt begins to slip. 9. The adhesion between the surface of belt and pulley must produce more friction than the pull or tension. When great tension or stretching is required it evidences the fact that the belt is not properly proportioned, or that it is oil soaked and there is too much oil on the pulleys. 10. An endless belt will always give the best results, as lacing produces a momentary flicker in the lights at each revolution. 326 NEW CATECHISM OF ELECTRICITY. ELECTRICAL POWER TRANSMISSION. As compared to any other known method of transmitting power it may be said that electricity is an ideal agent, for as it has been well said — Fig. 144. LINK WORK. Electricity never stretches, never breaks, weighs nothing, can be subdivided indefinitely with great ease, can turn corners without loss. It can transmit large amounts of energy at pressures easily controlled along wires of mod- erate size, and it never freezes. Its loss by friction is comparatively insignificant, and its other losses in compariscn with every other known agent are almost nothing. The period of planning the schemes of transmission, of designing the dynamos, and of construction is now ended and all criticism as to dividends on the cost of electric works has been swept away by the results achieved. The efficiency of each type of machine and system is now greater than has been attained before. and definite results are assured. NEW CATECHISM OF ELECTRICITY. 327 ELECTRIC POWER TRANSMISSION, A system for the transmission of electric energy embraces: First, a conducting circuit between the two stations. Second, a battery or dynamo arranged to furnish the current. Third, the motor for changing the electric back into mechanical energy. Electric transmission can be used to advantage with standard forms of machines as follows : First, where a large waterpower is available at a considera- ble distance from the mill which is in need of more power than can be obtained from the water privilege at the mill itself. Second, where owing to the separation of mill buildings, or peculiar local requirements, it is desired to transmit power Note. — The waters of the American River, which have been running to waste, are now utilized for lighting Sacramento's streets, propelling her cars, operating her factories and cooking the food of her citizens. Years have been spent on the work here. An immense masonry dam was thrown across the American River at Folsom, California, creating a reservoir three miles long and furnishing a flow of 85,000 cubic feet a minute. The water, after passing through four horizontal shaft double turbine wheels, is used for irrigation purposes, and 300,000 acres of land will be supplied. The turbine wheels are 30 inches in diameter, and under a head of 55 feet develop 1,300 horsepower each. The shafts of the wheels are coupled direct to the shafts of four three-phase alternating current generators of the General Electric type, each capable of develop- ing 1,000 horse-power. These dynamos weigh about forty tons each. The electric current is passed through " step-up " or raising transformers which raise the voltage to 16,000 volts, and it is then transmitted by over- head copper wires to this city. Two separate lines have been built as a precaution against accident or shutdowns for repairs. One line will always be held in reserve. It is calculated that 50 per cent of the electric power generated at Folsom will be transmitted twenty-four miles to Sacramento, 328 NEW CATECHISM OF ELECTRICITY. ELECTRIC POWER TRANSMISSION. further than can be done by belting in order to avoid the instalment of individual steam plants in each building. Third, where small water privileges are available at various points on a stream, but in order to become useful the power must be concentrated at one point without too great expense for maintenance and operation of the individual parts of the system. Fourth, where for various reasons in securing a mill site it is desirable to locate at a considerable distance from the source of power on account of the fact that the land immed- iately adjacent to the privilege is not suitable for location. Fifth, where for special reasons it is important to do away with shafting throughout the mill. Electric motors in the machine shop work so satisfactorily for power transmission and effect such evident savings in the cost of manufacturing that they are utilized in many ways. The motors used average about 3 H. P. and are connected by insulated wires strung to switches located at convenient points about the shop. No pains are taken to fasten the motors while they are at work, as their own weight is amply sufficient to hold them in position and keep the belt tight. The great convenience of moving tools and placing them in any desired position is a great advantage of the new system. Note.- The great adaptability of this system was well shown in the case of a factory which was almost completely destroyed by fire, neverthe- less a few uninjured tools in a remote end of the building were operated successfully by means of electric motors within two days after the fire. NEW CATECHISM OF ELECTRICITY. 329 ELECTRIC POWER TRANSMISSION. Practically the only objection which can be urged against the electric system of transmission is the fact that the first cost of installation is greater than with ordinary belting and shafting, but even this is questionable, since while it might seem that the electric system would actually consume more power than the ordinary plan since it involves two transformations of energy. In most cases, however, if the power has to be distributed to a number of machines, particularly if they are located at any distance from the engine, the loss of power is less with electric transmission. This is explained by the high efficiency of the dynamo and motor compared with the low efficiency of belt transmission as ordinarily practiced. Perhaps the greatest saving, however, of the electric system is due to the fact that the consumption of* energy entirely ceases when the tool stops. This stoppage in the case of the busiest tools amounts to at least 25 per cent, of the nominal working hours throughout the year and with large or special tools which are not used so steadily, the stoppage is often as high as 50 to 75 per cent, since there are many whole days when they are not used at all. Wherever electric motors can be substituted for a number of small engines scattered about, the saving in power is very great not only because of the low efficiency of small steam engines, but also by the avoidance of condensation in long steam pipes. Perhaps the most important advantage gained by the electric system is in the increased output since the cost of power is a very small item. This increased output is secured 33° NEW CATECHISM OF ELECTRICITY. ELECTRIC POWER TRANSMISSION. by the greater convenience and promptness in starting and stopping as well as in regulating the speed of the machinery. The workman can, for example, temporarily increase the speed, when conditions are favorable, thereby saving consid- erable time. The ordinary type of motor used in factories is the plain shunt wound machine fed with constant potential current. The motor is started and varied in speed by means of a rheostat in the armature circuit. This simple arrangement answers very well in most cases, but for variable speed between wide limits a series wound motor controlled by a rheostat as in electric railway practice may be preferable. In other cases some special method of regulation such as the Leonard system, or the " boost and retard " plan may be adopted. Electrical Transmission in Mines. — It is predicted that the day is not far distant when every large mine in the country will have adopted electric power, and that such adoption, in view of superior advantages for continuous service, as shown in the record of the Mammoth mine outfit, will result in the more general use of convenient water power. The utilization of water power electrically transmitted for mine operation is becoming more popular among mining men, as each installation demonstrates not only the feasibility of the system but also the economy which every such installa- tion shows when compared with pre-existing systems which it displaces or which are in similar operation elsewhere, NEW CATECHISM OF ELECTRICITY. 33I ELECTRIC POWER TRANSMISSION. Long Distance Electrical Transmission. — In a general way, at the usual price of coal, the transmission of power from cheap water power, up to ten or fifteen miles, will nearly always pay, if the amount be reasonably great, a few hundred or a thousand horse power ; while the current can readily be transmitted over enormously great distances — several hundred miles — practically speaking, such transmissions will probably be exceedingly rare for many years to come. Admitting that power can be transmitted satisfactorily, the next point is as to the economy of this electric transmission. In the cost of a water privilege at a distance, where the problem is to transmit power in bulk for a few thousand feet or more, the practical question is simply one of cost of power delivered on the ground by steam. The cost of power de- livered to the motors, of course, depends upon the value of the water privilege, its cost to electrical apparatus and local conditions. Note. — The project is now discussed in England to supply electric power from central stations built in the centre of the coal fields and transmit it to the great industrial centres, including I/mdon, where transmitting and storage stations could be erected. The electric energy- could be sold to the different distributing companies at a little over two cents per kw hour and to the small factory owner for about $25 per 3,000 working hours for one H. P.; in I^ondon this costs at present about twice as much ; the system enables valuable chemical constituents to be re- covered from the coal, which at present cannot be done in the smal steam power plants ; one of these constituents is sulphate of ammonia ; it is estimated that one H. P. hour can be obtained for %. pound of coal, the average consumption at present being 5 pounds ; the loss in trans- mission from the coal fields to London is about 33 per cent. ; for trans- mitting 10,000 H. P., three bare conductors for the positive and three for the negative would be used and run on oil insulators ; 30,000 volts are to be used. 332 NEW CATECHISM OF ELECTRICITY. ELECTRIC POWER TRANSMISSION. As regards the difficulties which have to be encountered in electrical power transmission, the principal ones centre about the transmission line. Speaking from an electrical stand- point, it is sometimes difficult to get and maintain insulation against the voltages put to use for long distance work. Physically the maintenance and guarding of a long line against accidents, or malicious injury, is not altogether easy to be paid. The difficulties include such things as severe storms, which tear down the line, or blow down trees across it, accidental or malicious breaking of insulators and the like, to say nothing of the ordinary wear and tear to which over- head lines are subjected. Quite aside from such special causes of damage, the generation and utilization of power is all clear sailing. Economy of Electric Locomotives. — Under certain condi- tions no doubt exists as to the economy of electrical appli- ances. In the saving in repairs it is stated on the authority of Siemens that the electric locomotives on the underground railway in I/ondon ran 60,000 miles without needing repairs of any kind. In the wear of tracks, in lighter road-beds and bridges and in steeper grades, the economies from this stand- point are beyond peradventure. The building of electric power stations of smaller capacity than the aggregate capacity Note. — 5,000, 10,000 or 15,000 volts is within the range of fair practi- cability if the climatic conditions are favorable. I would not hesitate to make it 30,000, 40,000 or 50,000 volts, in a climate like that of some parts of Mexico, while I would shun half of this, in a stormy or damp climate- Prof. Bell. NEW CATECHISM OF ELECTRICITY. 333 ELECTRIC POWER TRANSMISSION. of locomotives, and the saving in coal consumption by work- ing steam economically in large cylinders are placed in the favor of electric traction. These remarks apply very nearly to all forms of electric transmission. The Niagara Falls Power Plant. — No enterprise of modern times has attracted greater attention from the engineers of the world and the public in general than the work which was undertaken some years ago by the Niagara Kails Power Com- pany for the utilization of a portion of the power of the Niagara, Falls through electric-motors operated by turbine water wheels. About 275,000 cubic feet of water pass over the falls each second, falling from the crest of the falls 165 feet, furnishing, as it has been estimated, not less than seven million of horse power. The surface canal starts from a point about one and one- half miles above the falls and runs inland 1,700 feet, with a depth of 12 feet, the main tunnel being 7,000 feet long, 19 feet wide and 21 feet high. This artificial waterway has a capacity sufficient to develop 100,000 horse-power. This great work is under construction in what are called " units " of 5,000 electric horse power, several of which are in most successfnll operation. 334 NEW CATECHISM OF ELECTRICITY. THE DYNAMOTOR. A dynamotor is an electrical apparatus in which two ma- chines, a dynamo and a motor, are placed on the same shaft, one of the machines receiving current, and the other gene- rating current, usually of a different voltage. In one form two armatures are mounted on one shaft in a single field or in separate fields ; one is a motor armature driven by the original current ; the other generates new cur- rent. This is a "motor-dynamo," and it can transform con- tinuous currents up or down. Continuous current transformers have attained an effi- ciency of 83 per cent, at full load. Another form of dynamotor is called the continuous alter- nating transformer. This is arranged so as to change a con- tinuous into an alternating current or the reverse. As the driven and driving parts of the dynamotor are contained in one rotating part, their friction is very slight. Note. — The long distance transmission lines for a certain railway are connected to step-down transformers, transforming the current from 6,000 volts on the line to 400 volts at the secondaries. The secondaries are connected to the three collector rings on one side, and the current is thus brought into the armature of the rotary converter or dynamotor. The alternating current at 400 volts is then converted in this machine into direct current at 500 volts at no load and 550 volts at full load delivered from the commutator side. This is given as example of the utility of the dynamotor. NEW CATECHISM OF ELECTRICITY. 335 TRANSFORMERS. For the sake of economizing the cost of the metallic con- ductors, distribution of the electric current is effected at a high electric pressure from the central generators, and is re- Fig. 142. ceived at different points by apparatus known as transformers, which transform the electric energy supplied to them, and give it out again at a lower pressure. 336 NEW CATECHISM OF ELECTRICITY. TRANSFORMERS. To comprehend fully the bearing of the matter, it must be remembered that the energy supplied per second is the pro- duct of two factors, the current and the pressure at which that current is supplied ; the magnitudes of the two factors may vary, but the value of the power supplied depends only on the product of the two ; for ex- ample, the energy furnished per second by a current of 10 amperes supplied at a pressure of 2000 volts is exactly the same in amount as that furnished per second by a cur- Fig. I4d. rent of 400 amperes supplied at a pressure of 50 volts ; in each case the product is 20,000 watts. Now the loss of energy that occurs in transmission through a well-insulated wire depends also on two factors, the current and the resistance of the wire, and in a given wire is propor- tional to the square of the cur- rent. In the above example the current of 400 amperes, if trans- mitted through the same wire as the 10- ampere current, would, Fig. 144. because it is forty times as great, waste sixteen hundred times as much energy in heating the wire. Or, to put it the other way round, for the same NEW CATECHISM. OF ELECTRICITY. 337 TRANSFORMERS. loss of energy one may nse, to carry the io-ampere current at 2000 volts, a wire having only T ^th of the sectional area of the wire used for the 400-ampere current at 50 volts. The cost of copper conductors for the distributing lines is therefore very great- ly economized by em- ploying high pressures for distribution of small currents. ^- 1 i 11 Hill 1 fiflH si i 1 1 111 Fig. 145. Operation of the Transformer.- -If we wind two separate coils of wire on an iron bar, and pass a direct current through one coil, no effect is produced in the other coil except at the mo- ment of turning on the current, but if an alter- nating current is used instead, a current is at once produced and maintained in the sec- Fig. 146. ond coil. By a very simple law the pressure or voltage of the two coils are in proportion to the number of turns in each. Thus, if the primary coil is supplied with current of 1,000 volts, and the secondary coil has one-tenth as many turns, the pressure in the secondary will be 100 volts. 338 NEW CATECHISM OF ELECTRICITY, TRANSFORMERS. By the proper proportion of the primary and secondary coils, the voltage may be raised to any pressure which can be safely transmitted. Fig. 142 exhibits the transformer with its connecting wires and insulated. A transformer of the latest pattern may be said to have these points of excellence : High efficiency, close regulation, small leakage, quiet running, attractive appearance, convenient arrangement, separable core, removable coil, reliable fuse device. Fig. 145 and 146 represent two methods of procuring the necessary structure of laminated iron, the parts in this case being stamped from sheet iron. This is done to secure good magnetic circuit with ample ventilation. Fig. 143 is a representation of Farraday's first induction coil and is thoroughly typical of all transformers. Fig. 144 is another form of the cylindrical transformer and the one utilized by Ruhmkorfr is his special machine else- where described. For transforming from high pressures to low, several kinds of apparatus are known, namely : — 1. Storage Batteries. — A large number of these to be charged in series at a high potential ; the series afterwards divided up or rearranged so as to discharge larger currents at lower pressure. This system is applicable to direct-current working only, not to alternate currents, and has the advantage of storing the consumer's supply. These will be treated on in a separate section. NEW CATECHISM OF ELECTRICITY. 339 TRANSFORMERS. 2. Induction Coils ', also called for this purpose Secondary Generatars, or Transformers, or Converters. — This system will only answer with alternating currents, which being trans- mitted through the distributing mains at high pressure, and traversing the primary wires of the induction-coils, set up in the secondary wires currents which feed the separate circuits of lamps at the desired low pressure. 3. Motor-Generators as previously described. 4. Commuting -Transformers. — These are a variety of the last, but neither armature nor field-magnet revolves, the polarity of the magnetic circuit being caused to vary by special commutators. 5. Condensers. — It is theoretically possible to employ con- densers for transforming alternate currents, but their use is not yet practical. 34° NEW CATECHISM OF ELECTRICITY. Fig. 147. INDUCTION COII.. Fig. 148. RUHMKORFF COIL,. NEW CATECHISM OF ELECTRICITY. 34I THE CONDENSER. This is a form (see Fig. 150) of accumulator which resulted from the discovery of the Ley den-jar. It is made of a num- ber of sheets of tin foil insulated from each other by sheets of paper soaked in parafine. The insulation may also be effected by the use of sheets of mica, oiled silk, etc. The telegraphic condenser consists of a box packed full of sheets of tin foil, the alternate sheets of which are connected with each other and each set has its own binding post. The tin foil is used in condensers because it is the cheapest for any two conductors which are near together and insulated from each other, acts as a condenser. The iron frame of a dynamo or motor and the wire wound upon the fields and armature act as the two surfaces of a condenser, and one may sometimes get a severe shock by touching both at the same time. A long insulated wire buried in the earth or in the water forms a condenser on account of the surface of the wire and the surface of water or earth outside being so large and so close together. Note. — The object of the condenser is, firstly, to make the break of circuit more sudden by preventing the spark due to self-induction in the primary circuit from leaping across the interrupter ; and, secondly, to store up the electricity of this self-induced extra-current at break for a brief instant, and then discharge it back through the primary coil so as to augment the induced direct electromotive-force in the secondary coil. 342 NEW CATECHISM OF ELECTRICITY. Fig. 149. ADJUSTABLE WATER RESISTANCE. Fig. 150. CONDENSER. NEW CATECHISM OF ELECTRICITY. 343 INDUCTION COILS, An induction coil comprises three principal parts — the core, the primary coil, and the secondary coil. Induced currents have in general enormously high electro- motive-forces, and are able to spark across spaces that ordinary battery currents cannot possibly cross. The induction coil consists of a cylindrical bobbin having a central iron core surrounded by a short inner or (i primary " coil of stout wire, and by an outer " secondary " coil consisting of many thou- sand turns of very fine wire, very carefully insulated between its different parts. This arrangement is illustrated in Fig. 147. The fundamental law of induction may be thus stated : " Any variation or cessation of a current of electricity flowing in one conductor will induce a momentary current in an adjacent conductor ; and if the secondary conductor be an insulated wire coiled around the first conductor, also a coil of insulated wire, the effect is heightened." In the Ruhmkorff coil (see Fig. 148) which is an applica- tion of the above laws, the primary coil is of large wire and the secondary coil of extremely fine wire, of a length many thousand times greater than the wire of the primary coil. Note.— Fig. 149 represents an adjustable water resistance, available for use as an artificial load either for arc-lighting machines or the alternators. 344 NEW CATECHISM OF ELECTRICITY. Fig. 151. ELECTRIC LIGHT PLANT, STEAMER " BAY STATE. NEW CATECHISM OF ELECTRICITY. 345 ELECTRIC LIGHTING. There are two systems of electric lighting in common use : i. Arc Lighting. 2. Incandescent Lighting. Candle Power, by which these are measured, is the amount of light given by the standard candle. The legal English and standard Ameri- can candle is a sperm candle burning "two grains a minute." It should have burned some FlG * ten minutes before use and the wick should be bent over and have a red tip. Otherwise its readings or indications are useless. A ''sixteen can die-power " lamp means a lamp giving the light of sixteen candles. The candle-power is a universal unit of illuminating power. Note. — According to some recent experiments made by the Govern- ment of the United States, a i candle-power white light is visible at a distance a little more than a mile, one of 3 candle-power is visible at two miles ; on an exceptionally clear night a white light of 3.2 candle-power was readily distinguished at three miles ; one of 5.6 candle-power at four miles, and one of 12.2 candle-power at five miles ; a green or red 2 candle- power light was visible at one mile, 15 candle-power at two miles, 51 candle-power at three miles and 106 candle-power at four miles. 346 NEW CATECHISM OF ELECTRICITY. ELECTRIC LIGHTING. The Arc-light. — If two pointed pieces of carbon are joined by wires to the terminals of a generator of electric currents, and are brought into contact for a moment and then drawn apart to a short distance, a kind of electric flame called the arc or the voltaic arc is produced between the points of car- bon, and a brilliant light is emitted by the white hot points of the carbon electrodes. Th'.s phenomenon was first noticed by Humphrey Davy in 1800, and its explanation appears to be the following : Before contact the difference of potential between the points is insufficient to permit a spark to leap across even T oiroo" °f an i n ch of air- space, but when the carbons are made to touch, a current is established. On separat- ing the carbons the momentary extra-current due to self-induction of the circuit, which possesses a high electromotive-force, can leap the short distance, and in doing so vola- tilizes a small quantity of carbon between the points. Carbon vapor being a partial conductor allows the current to continue to flow across the gap, provided it be not too wide ; but as the carbon vapor has a very high resistance, it becomes intensely heated by the passage of the current, and the carbon points also grow hot. Since, however, solid matter is a better radiator than gaseous matter, the carbon points emit far more light than the arc itself, though they are not so hot. In the arc the most infusible substances, such as flint and diamond, melt ; Fig. 153. NEW CATECHISM OF ELECTRICITY. 347 ELECTRIC LIGHTING. and metals such, as gold and platinum are even vaporized readily in its intense heat. When the arc is produced in the air the carbons slowly burn away by oxidization. It is observed, also, that particles of carbon are torn away from the -f- electrode, which becomes hollowed out to a cup- shape, and some of these are deposited on the — electrode, which assumes a pointed form. In the alternating current arc lamp, since the current flows alternately in each direction, the carbons burn away with uniform rapidity and the ends assume about the same form. The light will be thrown up and then down as the di- rection of the current changes, and for this reason reflectors are placed above the arc to catch the upward rays. The familiar prism and spectrum experiment shows that all ordinary "white" light is made up of colors, shades of red, yellow, green and blue. The quality of any light will depend upon both the presence and intensity of these com- ponent color-groups. When the incandescent lamp burns low the red and yellow rays are mainly present ; as it grows hotter the greens and blues are added, until, when all are present in correct proportion, the light is pure white. Analy- sis of the components of ordinary lights shows that the candle and oil flames are made up mainly of red and yellow, with some green and faint blue rays. The two pencils in the modern arc lamp are separated by a distance of from one-sixteenth to three-sixteenths of an 343 NEW CATECHISM OF ELECTRICITY. Fig. 154. Fig. 155. RHEOSTAT. Fig. 156. double; knife; switch. single; kniee; switch. inch. The electricity, in overcoming the resistance of this air gap, generates such an amount of heat that the tips are kept at a white glow. The carbon toward the positive pole of the machine will be found to be cone-shaped with a depress- ion at the top, whence it derived the name " arc- light " — the crater in the cone assuming the form ( NEW CATECHISM OF ELECTRICITY. 349 ELECTRIC LIGHTING. an arc or part of a circle. The other carbon will be found slightly rounded with a little pyramid just beneath the crater of the upper carbons. Under these conditions, it will be noticed that the positive carbon, or one nearest the positive brush of the dynamo, will burn away much faster than the other, and because the greater amount of light is desired below the lamp, the positive carbon is placed above the other. Long before the incandescent electric light had been in- vented, the arc light made by an electric arc formed between * Note. — It was about this time that popular explanations begun to be made of the nature and source of electricity ; on the installation of a 4,000 candle light arc lamp, one man who had gathered a crowd around him thus proclaimed, calling attention to the solenoid at the top of the lamp : " That is the can that holds the oil," and, speaking of the side rod of the lamp, " That is the tube which conducts the oil from the can to the burner." This season also witnessed the introduction of the arc light into ' ' Wannamaker's " at Philadelphia. One gentleman on that occasion looked the whole apparatus over very carefully, perhaps a half hour, sized it up, and then, pointing to the line wire, he said, " How large is the hole in that wire that the electricity flows through ? " Another gentleman, one connected with a great manufacturing company, observed in complete silence the machine running for perhaps five minutes. Then he fully digested the whole thing, and was ready to tell all about it. He said, "The electricity in that thing is generated by that revolving busi- ness there, rubbing the air up against these iron blades (meaning the magnets;, just as you get sparks when you rub a cat's back." In the following year, 1879, the Cincinnati Exposition Buildings were lighted, and an expert from New York City was sent out to make matters go smooth, but one distressful night he failed to appear, and a self-exam- ined engineer was put in charge, but the lamps would not "illumine " — so the next morning Mike was sent for. "Well, Mike, why didn't your light burn last night? " " Sure, sir, I don't know. I do be thrying to do me part ; it's more than the full of a box of matches I spint a-thrying to light thim two bla^k sticks, and dev'l a light could I get." The great pile of burnt matches under the lamp bore evidence of the truth of Mike's assertion. 350 NEW CATECHISM OF ELECTRICITY. Fig. 157. Fig. 158. LAMP SOCKETS. Fig. 159. SWITCH BOARD. NEW CATECHISM OF ELECTRICITY. 351 ELECTRIC LIGHTING. the ends of two carbon pencils, was used for illuminating purposes. At first a dynamo was used to run a single light, but, in the year 1878, Mr. Chas. F. Brush invented and devel- oped the modern series arc lamp with the shunt coil, which may justly be considered the birth of the electric lighting industry of the world. It is worthy of permanent record, as stated by Mr. Foree Bain, that "in 1879 the Maxim Electric I^ight Company of New York took the contract to light the exposition building in Cincinnati with arc lights. The plant consisted of ten twenty-thousand candle power lamps and ten separate dyna- mos for these lamps, and seven ten-thousand candle power lamps and seven corresponding dynamos, that is, a dynamo for each lamp. " The dynamos were of the gramme ring type, with wrought-iron field magnets, stationary brush holders. The lamps were made almost entirely of brass, and were beautiful in design and finish, but they required new adjustment with each change of the current value. " The dynamos were marked 15 webbers. " The circuit consisted of copper wire on one side, and gas pipes on the other side, when they were available. The cop- per wire was plain and uncovered, and was procured of the tinners and hardware stores. " All of the dynamos and all of the lamps were connected in parallel between the outgoing conductors and the gas 352 NEW CATECHISM OF ELECTRICITY. ELECTRIC LIGHTING. Fig. 160. To Fit Thomson-Houston Socket. INCANDESCENT LAMPS. NEW CATECHISM OF ELECTRICITY. 353 ELECTRIC LIGHTING. pipes. It is true the gas pipes did get quite warm, but I thought that that was an indication that the business was working well. " In this plant I didn't have a socket, a switch, a piece cf insulated wire, a fuse, an automatic cut-out, a switchboard, a ground detector, a voltmeter, an ammeter, nor an inspector's certificate. Yet the plant ran for thirty nights without a ' hitch.'" The light of the arc lamp approaches nearest to that of sunlight ajf any of the artificial lights used. It is used not only for the general purposes of illumination but also exten- sively in photography. The arc light per candle power is much cheaper than the incandescent light, but up to the present time the arc lamp has not been successfully made in as small units. In the field of electric lighting, there is a much greater chance for extraordinary improvements than in that of the application of power. In an "arc" light, less than ten per cent, of the energy applied is converted into light ; the balance passes off in the form of heat. In incandescent lights the efficiency is still lower, being about four or five per cent. Incandescent Lighting. — The device, with the arc light, has, more than any other, introduced electricity as an in- dustrial agent to public approval is the incandescent lamp. From the time of the perfection of the now familiar pear- shaped globe, with its thread-like strip of carbon, capital has 354 NEW CATECHISM OF ELECTRICITY. ELECTRIC LIGHTING. freely flowed forth from its strong vaults to the accomplish- ment of thousands of projects for the utilization of the electric force. It has been an illustration of the proverb that ' i seeing is belie ving." The history of the development of the incandescent lamp is one of the most interesting to be found in the literature of inventions. Its successful accomplishment was akin to the taming a wild horse to docile service. The first strictly incandescent lamp was invented by de Molyens of Chelten- ham, England, in 1841 ; its foundation principle was the pro- duction of a white light by the high resistance of a platinum wire to the passage of the electric current ; in 1845 J. W. Starr of Cincinnati first proposed the use of carbon. Experi- ments soon demonstrated the great advantages of the carbon over the platinum or any other metal. Many different forms of incandescent lamps have been made, but all are nearly of the same principle of construction,, making use of the carbon filament. In 1880 Edison patented the lamp of which millions have been put into use. The manufacture of incandescent lamps has developed into en- ormous proportions owing to the fact that the value of the entire device is destroyed the instant the slender filament is broken — it is here as in many other manufactured articles,, "the weakness of the goods is the strength of the trade." Lamp Circuits. — An electric pressure being available, it is necessary, in order to have an electric flow, to provide a con- tinuous conducting path from the point of positive potential NEW CATECHISM OF ELECTRICITY. 355 ELECTRIC LIGHTING. to the point of negative potential. This path, whether com- posed simply of wires, or of lamps, motors, or other applica- tions of electric power is called a circuit, and circuits may be divided into two kinds, viz.: series circuits, and parallel or shunt circuits. In the series circuit (Fig. 161), the wires, lamps, etc. , are arranged end to end, so as to form one continuous conducting path connecting the two points of higher and lower potential, and the current in flowing between these points passes in succession through each of the lamps or other appliances composing the circuit. In the parallel or shunt circuit (Fig. 162), two main wires or leads M x M 3 are connected to the points of higher and lower potential, and the lamps, wires, etc., are connected across the two mains, or arranged side by side so as to form a number of independent paths or branches, and the current, in flowing from the higher to the lower potential, divides itself amongst these branches in in- verse proportion to their resistance. It will be apparent that the total resistance of the parallel arrangement is less than that of any of its branches, for these, being arranged side by side, are equivalent to one having a cross section equal to the cross section of the branches. If the resistances of all the branches are equal, the total resistance of the circuit will be equal to the resistance of one branch divided by the number of branches. The total resistance of the series circuit is evidently equal to the sum of the resistances of each of its separate parts, since these are included in one continuous path ; and, for the same reason, the strength of the current flowing in a 356 NEW CATECHISM OF ELECTRICITY. ELECTRIC LIGHTING. Fig. 161. +•— © — -€> — ©■ -•— (9 — © — & SERIES CIRCUIT. Fig. 162. +va PARAIvWL, CIRCUIT. NEW CATECHISM OF ELECTRICITY. 357 ELECTRIC LIGHTING. series circuit is obviously everywhere the same. A circuit is said to be " closed " when it forms a continuous conducting path, and to be ' ' open ' ' when a discontinuity occurs in some portion such that an electric current cannot flow. When a circuit is connected or bridged across in such a manner, by some conducting material, so as to offer a resistance less than its normal working resistance, it is said to be cross-circuited or short-circuited. Systems of Distribution. — The several methods for arrang- ing the distribution of the electric current may be thus classi- fied : 1. The multiple arc system. 2. The multiple series system. 3. The three- wire system. 4. The alternating transformer system. The multiple arc system is illustrated in Fig. 163, which will readily show the method of distribution. This is also called the parallel system. The multiple series system is represented in Fig. 164. This is a combination of the series with the parallel systems ; that is, several series in parallel with each other. The three-wire system is also illustrated in Fig. 164, where A A represent two dynamos, which are connected in such a manner that, while the total voltage of the system is 220, the lamps being connected to a third or neutral wire receive only 358 NEW CATECHISM OF ELECTRICITY. ELECTRIC LIGHTING. Fig. 163. V V V V \ v \ *' ®« TWO WIRE INCANDESCENT SYSTEM. Fig. 164. ZEUL "«- TTTTT THREE) WIRE INCANDESCENT SYSTEM. FiG. 165. g?*" 1**4 i i M 4 I ALTERNATING SYSTEM. NEW CATECHISM OF ELECTRICITY. 359 ELECTRIC LIGHTING. 1 10. By this means the voltage is doubled and the cost of copper accordingly reduced to one-fourth, or, practically, taking the central wire into consideration, to not more than three-eighths. The alternating transformer system is shown in Fig. 165. The transformer or converter in the circuit is represented by the two letters C C. In the alternating current system, for distribution in the open air, a high potential current is used, from 1,000 to 10,000 volts being maintained at the central station ; two leads un- connected at the end lead from the station. Where current is desired, a converter is placed, whose primary is connected to the two leads, bridging the interval between them. From the secondary the house leads are taken with alow induced initial potential, in some cases of 50 volts. By the insurance rules, the converters are kept outside of buildings. The Switchboard. — With the exception of the automatic regulation of the generator, there is nothing so important in stations operating arc lights, as the switchboard. In Fig. 159 is shown the arc plug switchboard, by the use of which any combinations either of circuits or machines are easily effected without danger of personal injury to the operator, or of dis- turbing or extinguishing the lights. Note. — Edison's discovery of the high resistance filiment solved the problem and made it possible to use a voltage of about 1 10 for distributing purposes. Even this was found inadequate for large areas, and he after- wards devised the three-wire system. 360 NEW CATECHISM OF ELECTRICITY. ELECTRIC LIGHTING. The Electric Lamp of the Future, — Neither of the two forms of lamp now in common use for electric lighting yields all the results that could be desired. The arc concentrates the illumination too much ; the incandescent burner, while sub-dividing it, is wasteful of energy. It develops heat, and this is a net loss. The phosphorescent lamp at present re- quires current of too high potential and frequency of altera- tion to be economical. The arc lamp is yet to be touched up to more perfectly uniform action ; the glow lamp is to be cheapened. Vacuum Tube Electric Lamps. — Partial vacuum tubes known as Geisler's and Crooke's have been in use for years as a source of light in which, as is generally known, the light is produced by the passage of the electric discharge through the rarefied gas of the tube. In such light there is no com- bustion and only very little heat. Tubes five or Six feet long, three or four inches in diam- eter, and of any shape, may be lighted, and shine with a bluish white light, vastly brighter than any have been lighted before. The electric terminals for these tubes are not wires sealed into them, but metallic caps upon their ends. These act inductively upon and through the residual air contained in the hermetically sealed tube. This form of lighting has been attempted before, but the results for practical purposes have not been satisfactory. The light has not been obtained in sufficient quantity, and the apparatus necessary for producing it has been expensive and NEW CATECHISM OF ELECTRICITY. 361 ELECTRIC LIGHTING. somewhat complicated, and the current employed difficult to insulate. The apparatus has now been greatly simplified and an unusual volume of light obtained from the tubes, while the current employed is under comparatively low potential. A Geisler Tube is a glass tube containing two platinum wire terminals passing through the glass and having the air exhausted so as to leave a partial vacuum. Electric dis- charges or sparks pass between the two wires much more easily in a vacuum than in ordinary air. The passage of the Fig. 166. Type 1 3 4 5 G GEISI,KR TUBKS. € discharge causes the air or other gas to become dimly lumin- ous. The color of the light depends upon the kind of glass and upon the gas enclosed. Geisler tubes are sometimes made in beautiful designs. The incandescent lamp is the most common form of the Geisler tube. 362 NEW CATECHISM OF ELECTRICITY. ELECTRIC LIGHTING. Crooke' } s Tube f or Crooke's Radiometer. — This is a device similar to the f< Geisler " tube and produces the most power- ful rays known to physicists. The rays, however, do not come from the visible illumina- tion. Prof. Roentgen calls them X rays, for want of any other name. They cannot be seen. They are mysterious and unknown, except that they are proven to exist. The remarkable property of the X rays is the power to penetrate objects opaque to the human eye, as a block of wood, the human body and thousands of other things. The rays falling upon an opaque object do not render it translu- cent in the sense that the eye can then see within or beyond it. The manner in which it is proved that the rays penetrate the opaque object is to make a photograph of the interior of the object. It is quite a different process from ordinary photography. The object to be photographed, a lead pencil for instance, is placed between the Roentgen light and a sensitized plate. The X rays penetrate the wood and whiten the plate. They fail to penetrate the lead within the wood, and that is shown in black relief upon the plate. So with the hand. The hand is put between the light and the plate. The X rays pass through the flesh and whiten the plate, but the rays cannot penetrate the bones, so the bones are shown in black shadow on the plate. Standard Incandescent Lamp Sockets. — This is a question for immediate agreement among makers. It is thought the NEW CATECHISM OF ELECTRICITY. 3^3 ELECTRIC LIGHTING. most practical and satisfactory solution is a form of base or mount so inexpensive that when the lamp is destroyed the base may be allowed to go with it as in itself a thing of no value. In view of the fact that high tension lamps are in all probability to be the lamp of the future, the question of a safe socket acquires vast importance. Porcelain will no doubt come largely into use for this purpose, which will greatly modify the conditions governing the selection of both a base and socket. See Figs. 157, 158, 160. ORNAM3NTAI, LAMP. 364 NEW CATECHISM OF ELECTRICITY. MODKL. ELECTRIC LIGHTING DYNAMO. NEW CATECHISM OF ELECTRICITY. 365 Whatever the source of electrical energy and whatever devices may be used to convert it into its destined purpose the transference is made by the means of wire. Gas, water, etc., are distributed for all sorts of purposes and the laws governing them are similar to those governing electricity. Bach trade has, of course, some elements which have to be considered that are neglected in others, but the main laws are common to all and do not require different interpretations except possibly in degree. Note. Size for size, a thread of spider silk, it is said, is decidedly tougher than a bar of steel. An ordinary thread will bear a weight of three grains. This is just about fifty per cent, stronger than a steel thread of the same thickness. 366 NEW CATECHISM OF ELECTRICITY. WIRING. A habit of studying the distribution of electricity as is done with the distribution of steam, gas, water, etc., soon make all the problems easy to understand. The use of wire has been traced back to the earliest Egypt- ian history. Specimens are in existence which can be proven to date to 1700 B. C. Kensington Museum has a specimen which was made in Minera, 800 years B. C. Ancient literature contains many references to wire. From the ruins of Hercu- laneum metal heads have been exhumed on which the hair is represented by wire. There is no question that this ancient wire was made by hammering out the metal, which was always bronze or of the precious group. This held true of all made previous to the fourteenth century, during which the process of forming wire by drawing or elongating the metal by forcing it through a conical orifice, made in some substance harder than the metal treated, was invented. The subject naturally divides itself into : Klectric bell wiring, including fire and burglar alarms. Wiring for incandescent, or glow, lamps. 3. Wiring for arc lights. 4. Wiring for telephones and telegraphs. Wiring for railway and power plants, including over- head wiring, car wiring, and station wiring. A good wiring installation should have the following attri- butes ; NEW CATECHISM OF ELECTRICITY. 367 Fig 161. WIRING. First, it should supply the lamps with current, and provide appropriate means of controlling che lights. Second, the current should be distributed to the lamps at a constant pressure. That is, the voltage of the dynamo being constant, and also the n amber of lamps, the voltage from socket to socket should not vary beyond a certain amount. Third, the wiring should comply with the insurance rules in force in the locality in which the work is done. Fourth, a minimum amount of copper should be used in the accomplishment of the result. wire;. Prof. S. P. Thompson says what is wanted is a mode of running- the wires and fixing the switches and other accessories, that they shall not only be electrictight, but shall be watertight, gastight, airtight, oil- tight and rattight, Fig. 162. and he adds that all of the above requirements; and more, are filled by a properly insulat- ed conductor in- closed in an injury- resisting metal pipe. Fig. 163. 5 PORCELAIN ROSETTE. e BINDING POST. 368 NEW CATECHISM OF ELECTRICITY. WIRING. List of Tools useful for small inside wiring : Corner Brace as shown in Fig. 164. Several sizes of small Bits. I2 7/ and 24 7/ Twist Point Bell Hangers. Gimlet for */*" hole. Metre Box. Combination Handle with set of small tools. Rat Tail File. Small Screw Driver. Flat Chisel. Medium Size Hammer. Key-hole Saw. NEW CATECHISM OF ELECTRICITY. 369 FUSES. Fuse wire is a safety device designed to break the electric circuit when an excessive current passes, and it breaks the circuit because it is heated to a point at which it melts. Other designations are " Safety Cutouts," l ' Safety Fuses, ' ' " Fuse Blocks" and " Safety Catches." The main object of fuses is a protection against fire, as the fuse melts at such a low temperature that it will not set lire to inflammable material. If a short circuit was to occur on a cir- cuit unprotected by fuse the copper would become red hot and finally melt, and if in contact with wood or other combustible material, or should the melted copper fall on anything inflam- mable it would be cause of a fire. Fuses should be placed wherever the size of wire changes or wherever there is a branch of smaller size wire connected, unless the next fust on the main or larger wire is small enough to protect the branch or small wire, but more lights may be added on the large wire, making it necessary to put in a larger. The illustrations on page 370 show the different forms and patterns of the device. 37o NEW CATECHISM OF ELECTRICITY. SAFETY FUSES. Fig. 165. Fig. 166. Fig. 167. Fig. 168. Fig. 169. NEW CATECHISM OF ELECTRICITY. 37 l SAFETY FUSES. " Points ' ' relating to the Safety Fuse. Covered fuses are more sensitive than open ones. A fuse wire should be rated for its carrying capacity for the ordinary lengths employed. On important circuits fuses should be frequently renewed. Fuses up to five amperas should be at least ?.% ins. long, Y2 m. to be added for each increment of five amperes capacity. Round fuse wires should not be employed in excess of thirty amperes capacity. For higher currents flat ribbons of lour inches and upwards should be used. Experiments have shown that for large fuses, a multiple fuse is more sensitive than a single one. A one hundred ampere fuse may be made by taking four wires of twenty-five amperes capacity. Unless a fuse be long and quite heavy, its carrying capacity is practically the same whether it be placed vertically or hori- zontally. Experience seems to show that the best alloy for a fuse is one of lead and tin, the lead being considerably in excess. If too much lead is used, the fuses deteriorate rapidly and coat with the white film. A fuse block may be overloaded, not because the metal of the terminals is not of sufficient cross-section to carry the current, but because of insufficient area of, or loose contact of, fuse, or wires, and this heating is very frequently the cause of fuses melting. 372 NEW CATECHISM OF ELECTRICITY. SAFETY FUSES. Wires and fuses should be screwed up tight, as it is fre- quently the case the area of contact of wires or fuse is not sufficient to prevent heating when there is a full load on the wires. The area of contact should be several times the cross- section of the wires connected and for that reason, in the case of large size wires, the ends should be flattened if connected under the head of a binding screw. A leading question now is the automatic circuit breaker versus the fuse wire. Both these devices are excellent in themselves, but each requires judgment in selection and use. The automatic circuit breaker is to be preferred for switch board use and motor service. A circuit breaker placed in plain sight on the front of the board is to be preferred in all cases. For lighting circuits, it is doubtful if any simpler and bet- ter device than the fuse wire can be used. In spite of all that has been said against it, when properly used and taken care of, it leaves little or nothing to be desired ; yet there is noth- ing about the plant that is more dangerous when ignorantly or carelessly used. NEW CATECHISM OF ELECTRICITY. 373 IMPORTANT. The National Code is said to be the wiremen's Bible ; it says "Thou shalt not use this, and thou shalt not do that/' and it also contains for him who will study it, the principles which enable him to decide what he ought to do. The code is not intended to be a cast-iron set of regulations or a complete specification of how to do construction, but it is designed to serve as the common law of electrical construction, to indicate what things must always be done, what must never be done, and to set forth the principles which should be observed in order to secure safety. It is the spirit of the code, even more than the letter, that should be studied by the archi- tect and the engineer. It is impossible to conceive a set of regulations which would describe all the necessary requirements of good work, but an observance of the principles underlying these rules will enable us to determine what material and construction is suit- able and what is best for each particular case. 374 NEW CATECHISM OF ELECTRICITY. WIRING RULES AND REQUIREMENTS. National Board Pire Underwriters. RULES AND REQUIREHENTS Of the National Board of Fire Underwriters for the Installation of Wiring and Apparatus for Electric Light and Power as Recommended by the Under- writers' and National Electric Association. The use of wire ways for rendering concealed wiring permanently accessible is most heartily endorsed and recom- mended ; and this method of accessible concealed construction is advised for general use. Architects are urged, when drawing plans and specifica- tions, to make provisions for the channeling and pocketing of buildings for electric light or power wires, and in specifica- tions for electric gas lighting to require a two-wire circuit, whether the building is to be wired for electric lighting or not, so that no part of the gas fixtures or gas piping be allowed to be used for the gas lighting circuit. Class A. Central Stations for Light or Power. These Rules also apply to Dynamo Rooms in Isolated Plants, connected with or detached from buildings used for other purposes ; also to all varieties of apparatus therein of both high and low potential. New catechism of electricity. 375 WIRING RULES AND REQUIREMENTS. 1. Generators : a. Must be located in a dry place. b. Must be insulated on floors or base frames, which must be kept filled, to prevent absorption of moisture, and also kept clean and dry. c. Must never be placed in a room where any hazardous process is carried on, nor in places where they would be exposed to inflammable gases, or flyings of combustible material. d. Must each be provided with a waterproof covering. 2. Care and Attendance : A competent man must be kept on duty in the room where generators are operating. Oily waste must be kept in approved metal cans and removed daily. 3. Conductors : From generators, switchboards, rheostats or other instruments, and thence to outside lines, conductors — a. Must be in plain sight and readily accessible. b. Must be wholly on non-combustible insulators, such as glass or porcelain. c. Must be separated from contact with floors, partitions or walls through which they may pass, by non-combustible insulating tubes, such as glass or porcelain. d. Must be kept rigidly so far apart that they cannot come in contact. e. Must be covered with non-inflammable insulating material sufficient to prevent accidental contact, except that (s bus bars " may be made of bare metal. 376 NEW CATECHISM OF ELECTRICITY. NATIONAL BOARD FIRE UNDERWRITERS. f. Must have ample carrying capacity, to prevent heat- ing. (See Capacity of Wires Table.) 4. Switchboards : a. Must be so placed as to reduce to a minimum the danger of communicating fire to adjacent combustible material. b. Must be accessible from all sides when the connections are on the back ; or may be placed against a brick or stone wall when the wiring is entirely on the face. c. Must be kept free from moisture. d. Must be made of non-combustible material, or of hard wood in skeleton form, filled to prevent absorption of moisture. e. Bus bars must be equipped in accordance with Rule 3 for placing conductors. 5. Resistance Boxes and Equalizers : a. Must be equipped with metal, or other non-com- bustible frames. (See Definitions.) b. Must be placed on the switchboard, or, if not thereon, at a distance of a foot from combustible material, or separated therefrom by a non-inflammable, non-absorptive, insulating material. 6. Lightning Arresters : a. Must be attached to each side of every overhead circuit connected with the station. b. Must be mounted on non-combustible bases in plain sight on the switchboard, or in any eqtially accessible place, away from combustible material. NEW CATECHISM OF ELECTRICITY. 377 WIRING RULES AND REQUIREMENTS. c. Must be connected with at least two " earths " by separate wires, not smaller than No. 6 B. & S., which must not be connected to any pipe within the building, and must be run as nearly as possible in a straight line from the arresters to the earth connection. d. Must be so constructed as not to maintain an arc after the discharge has passed. 7. Testing : a. All series and alternating circuits must be tested every two hours while in operation, to discover any leakage to earth, abnormal in view of the potential and method of operation. b. All multiple arc low potential systems (300 volts or less) must be provided with an indicating or detecting device, readily attachable, to afford easy means of testing where the station operates continuously. c. Data obtained from all tests must be preserved for examination by insurance inspectors. These rules on testing to be applied at such places as may be designated by the association having jurisdiction. 8. Motors : a. Must be wired under the same precautions as with a current of the same volume and potential for lighting. The motor and resistance box must be protected by a double pole cut-out and controlled by a double-pole switch, except in cases where one- quarter horse-power or less is used on low tension circuit, a single pole switch will be accepted. 37$ NEW CATECHISM OF ELECTRICITY. NATIONAL BOARD FIRE UNDERWRITERS. b. Must be thoroughly insulated, mounted on filled dry wood, be raised at least eight inches above the surrounding floor, be provided with pans to prevent oil from soaking into the floor, and must be kept clean. c. Must be covered with a waterproof cover when not in use, and, if deemed necessary by the Inspector, be inclosed in an approved case. (See Definitions.) 9. Resistance Boxes : a. Must be equipped with metal or other non-com- bustible frames. (See Definitions.) b. Must be placed on the switchboard, or at a distance of a foot from combustible material, or separated therefrom by a non-inflammable, non-absorptive, insulating material. Class B. High Potential Systems, over 300 Volts. Any circuit attached to any machine, or combination of machines, which develop over 300 volts difference of potential between any two wires, shall be considered as a high potential circuit and coming under that class, unless an approved trans- forming device is used, which cuts the difference of potential down to less than 300 volts. 10. Outside Conductors — Ali, Outside, Overhead Con- ductors (Including Services) : - a. Must be covered with some approved insulating material, not easily abraded, firmly secured to properly insulated and substantially built supports, all tie wires having an insulation equal to that of the conductors they confine, (See Definitions.) NEW CATECHISM OF ELECTRICITY. 379 Fig. 170. MICROMETER WIRE GUAGE. 3 SO NEW CATECHISM OF ELECTRICITY. WIRING RULES AND REQUIREMENTS. b. Must be so placed that moisture cannot form a cross connection between them, not less than a foot apart, and not in contact with any substance other than their insulating supports. c. Must be at least seven feet above the highest point of flat roofs, and at least one foot above the ridge of pitched roofs over which they pass or to which they are attached. d. Must be protected by dead insulated guard irons or wires from possibility of contact with other conducting wires or substances to which current may leak. Special precautions of this kind must be taken where sharp angles occur, or where any wires might possibly come in contact ^ 'th electric light or power wires. e. Must be provided with petticoat insulators of glass or porcelain. Porcelain knobs or cleats and rubber hooks will not be approved. f. Must be so spliced or j oined as to be both mechanically and electrically secure without solder. The joints must then be soldered, to insure preservation, and covered with an insula- tion equal to that on the conductors. (See Definitions. ) g. Telegraph, telephone and similar wires must not be placed on the same cross-arm with electric light or power wires. ii. Service Blocks : Must be covered over their entire surface with at least two coats of waterproof paint. 12. All Interior Conductors : a. Must be covered where they enter buildings from outside terminal insulators to and through the walls, with NEW CATECHISM OF ELECTRICITY. 38 1 NATIONAL BOARD FIRE UNDERWRITERS. extra waterproof insulation, and must have drip loops outside. The hole through which the conductor passes must be bushed with waterproof and non-combustible insulating tube, slanting upward toward the inside. The tube must be sealed with tape, thoroughly painted, and securing the tube to the wire. b. Must be arranged to enter and leave the building through a double contact service switch, which will effectually close the main circuit aud disconnect the interior wires when it is turned ' ' off. ' ' The switch must be so constructed that it shall be automatic in its action, not stopping between points when started, and prevent an arc between the points under all circumstances ; it must indicate on inspection whether the current be"on" or " off," and be mounted in a non-com- bustible case, and kept free from moisture, and easy of access to police or firemen. So-called " snap switches" shall not be used on high potential circuits. c. Must be always in plain sight, and never encased, except when required by the Inspector. d. Mus'; be covered in all cases with an approved non- combustible material that will adhere to the wire, not fray by friction, and bear a temperature of 150 F. without softening. (See Definitions.) e. Must be supported on glass or porcelain insulators, and kept rigidly at least eight inches from each other, except within the structure of lamps or on hanger-boards, cut-out boxes, or the like, where less distance is necessary. f. Must be separated from conctact with walls, floors, timbers or partitions through which they may pass by non- combustible insulating tube. 382 . NEW CATECHISM OF ELECTRICITY. WIRING RULES AND REQUIREMENTS. g. Must be so spliced or joined as to be both mechanically and electrically secure without solder. They must then be soldered, to insure preservation, and covered with an insulation equal to that on the conductors. 13. Arc L/Amps — In Every Case : a. Must be carefully isolated from inflammable material. b. Must be provided at all times with a glass globe surrounding the arc, securely fastened upon a closed base. No broken or cracked globes to be used. c. Must be provided with an approved hand-switch, also an automatic switch, that will shunt the current around the carbons should they fail to feed properly. (See Definitions. ) d. Must be provided with reliable stops to prevent carbons from falling out in case the clamps become loose. e. Must be carefully insulated from the circuit in all their exposed parts. f. Must be provided with a wire netting around the globe, and an approved spark arrester above to prevent escape of sparks, melted copper, or carbon, where readily inflammable material is in the vicinity of the lamps. It is recommended that plain carbons, not copper-plated, be used for lamps in such places. (See Definitions.) g. Hanger-boards must be so constructed that all wires and current-carrying devices thereon shall be exposed to view and thoroughly insulated by being mounted on a waterproof non-combustible substance. All switches attached to the same must be so constructed that they shall be automatic in their action, not stopping between points when started, and pre- venting an arc between points under all circumstances. NEW CATECHISM OF ELECTRICITY. 383 NATIONAL BOARD FIRE UNDERWRITERS. h. Where hanger boards are not used, lamps to be hung from insulated supports other than their conductors. 14. Incandescent l,amps in Series Circuits having a Maximum Potential oe 300 Volts or over : a. Must be governed by the same rules as for arc lights, and each series lamp provided with an approved hand spring switch and automatic cut-out. b. Must have each lamp suspended from a hanger-board by means of a rigid tube. c. No electro-magnetic device for switches and no system of multiple series or series multiple lighting will be approved. d. Under no circumstances can series lamps be attached to gas fixtures. Class C. Low Potential Systems, 300 Volts or less. 15. Outside Overhead Conductors : a. Must be erected in accordance with the rules for high potential conductors. b. Must be separated not less than 12 inches, and be provided with an approved fusible cut-out, that will cut off the entire current as near as possible to the entrance to the building and inside the walls (See Definitions.) 16. Underground Conductors : a. Must be protected against moisture and mechanical injury, and be removed at least two feet from combustible material when brought into a building, but not connected with the interior conductors. 384 NEW CATECHISM OF ELECTRICITY. WIRING RULES AND REQUIREMENTS. b. Must have a switch and a cut-out for each wire between the underground conducters and the interior wiring when the two parts of the wiring are connected. These switches and fuses must be placed as near as possible to the end of the underground conduit, and connected therewith by specially insulated conductors, kept apart not less than two and one-half inches. (See Definitions.) c. Must not be so arranged as to shunt the current through a building around any catch -box. 17. Inside Wiring— General Rules : At the entrance of every building there shall be an approved switch placed in the service conductors by which the current may be entirely cut off. (See Definitions.) 18.. Conductors : a. Must have an approved insulating covering, and must not be of sizes smaller than No. 14 B. & S., No. 16 B. W. G., or No. 4 B. S. G., except that in conduit installed under Rule 22, No. 16 B. & S., No. 18 B. W. G., or No. 4 B. S. G. may be used. (See Definitions.) b. Must be protected when passing through floors ; or through walls, partitions, timbers, etc., in places liable to be exposed to dampness by waterproof, non-combustible, insulating tubes, such as glass or porcelain. Must be protected when passing through walls, partitions, timbers, etc., in places not liable to be exposed to dampness by approved insulating bushings specially made for the purpose. (See Definitions.) NEW CATECHISM OF ELECTRICITY. 385 Fig. 171. ^^JLiLil BIRMINGHAM WIRE GUAGE) (B. W, G, ) 386 NEW CATECHISM OF ELECTRICITY. NATIONAL BOARD FIRE UNDERWRITERS. c. Must be kept free from contact with gas, water or other metallic piping, or any other conductors or conducting material which they may cross (except high potential conduc- tors) by some continuous and firmly fixed non-conductor- creating a separation of at least one inch. Deviations fromi this rule may sometimes be allowed by special permission.. d. Must be so placed in crossing high potential conduc- tors that there shall be a space of at least one foot at all points* between the high and low tension conductors. ower station or on the electric railway. This is notably true in the development of the electric rail- way, where new experiences and new problems are coming up continually. These problems are being solved in many cases by the engineers in the "inner circle" of the large compa- nies, and the knowledge is confined to the favored few. Many of the same difficulties and problems come also to the men directly in charge of the motors ; men who do not under- stand much theory, and who are not informed of what is well known to the favored few. In view of this withholding of necessary knowledge, the reader, especially if connected with the electric railway ser- NEW CATECHISM OF ELECTRICITY. 423 THE ELECTRIC RAILWAY. vice, is seriously advised to acquire a knowledge of the gen- eral principles of electricity, of the dynamo and motor and to then apply them to the special line here explained. Briefly, the system of electric car propulsion consists in the production of the electric current by mechanical means, its transmission through conductors to the electric motors on the cars, where it is again transformed into mechanical energy, which gives the motion to the car. The current which drives the motors may be derived from two sources : i, from an accumulator carried with the car ; 2, by a current from a dynamo placed by the side of the con- ducting lines, hence outside th^ car. The accumulator will be mentioned and described here- after. The line system may be divided into three divisions ; 1. The trolley, or overhead system. 2. The underground system. 3. The surface system. Note. — A, novel plan of making use of both these systems is a combi- nation of electric trolley and storage battery in operation upon a suburban railway in Hanover, where, after a long trial, it has been adopted. Elec- tric accumulators are placed beneath the seats of the cars. The r^ad is equipped with trolley wires and motors on one section only. While the car is traveling over the trolley section the accumulators are charged, receiving a current through the same feed wire as the trolley. When the end of the trolley is reached, which is at the city limits, within which the overhead wires are prohibited, the car continues on its way over a track that was formerly used as a horse car line, relying absolutely for power upon the electric energy stored in the accumulators during the trip over the trolley road. 424 NEW CATECHISM OF ELECTRICITY. THE ELECTRIC RAILWAY. The surface system (3) which is not much used consists in an arrangement where the iron or steel tracks are used for conductors. The underground system (2) is still somewhat in an experi- mental stage. It calls for the use of underground * ' conduits ' y very similar to those in use in connection with the cable-car system of propulsion — but, Conduits themselves are exceedingly expensive to con- struct, and cannot be operated unless there is a system of sew- erage in connection with them, and in case of damage are exceedingly difficult to repair. Hence the system known as the " Trolley " line has come into such general favor that nearly one thousand million dollars have already been invested in the system in the United States alone. The Trolley Wheel is represented in Fig. 239 ; there are various forms of it, but usually they are made of brass, about five inches in diameter, mounted on the end of a pole about 12 feet long, bent over as shown in Figs. 195 and 197. The end of this pole sets in a frame attached to the car roof, and springs acting on the lower end press the wheel against the trolley wire. The pole may be of wood or steel. The action of the wheel is such that it does not increase the sag of the wire but tends to push it up a little in its pass- age. NEW CATECHISM OF ELECTRICITY. 425 Fig. 197. r ^ \ —I % X OVERHEAD TRANSMISSION. 426 NEW CATECHISM OF ELECTRICITY. THE ELECTRIC RAILWAY. The practical operation of the trolley system is shown in full page figure, where the current, as shown by the arrows, is taken from the dynamo to the switch board, thence directly to the trolley wire or conductor, passing along in the direction shown by the arrows, a portion being conducted off at the points T T (the remainder going on to supply the other cars), where it passes down through the trolley arm, along the wires concealed in the car to the motors, through the motors, thence to the rails as indicated on the diagram, back to the switch board and through the various appliances used there to the dynamo, thus making a complete circuit. Where long lines are used wires are run out from the sta- tion and connected to the overhead trolley wire at suitable points, in order that the electrical pressure may be kept prac- tically constant. These wires are known as " feeder wires." The Motor.-^-The electric motor for street car propulsion is simply an appliance for the transmission of electrical into mechanical energy, and in action is just opposite to a dynamo machine (see Fig. 198). One end of the armature shaft of the motor is provided with a pinion which communicates its motion by means of a large gear to an auxiliary shaft provided with a pinion which in turn communicates its motion to another large gear placed upon the car axle. In order to insure the parallelism of these gears and pinions one end of the motor is fastened directly to the car axle, the other end is supported by springs, which NEW CATECHISM OF ELECTRICITY. 427 THE ELECTRIC RAILWAY. Fig. 198. STREET: CAR MOTOR. 428 NEW CATECHISM OF ELECTRICITY. THE ELECTRIC RAILWAY. permits of a movement of the motor and does away with the jar and strain which would otherwise occur on the starting and stopping of the car. The Railway Motor Controllers now in use are in many respects, the most perfect devices ever employed for the pur- pose. They are the result of a gradual development from the earliest types, and in details of construction, perfection of workmanship and certainty of action they are undoubtedly enormously superior to all of the original styles. There are several methods of governing the speed of the electric motor. In some systems a rheostat or resistance is connected in series with the armature, this rheostat being governed by mechanism placed at each end of the car, known as the " controller stand." This controller stand is provided with a handle, by means of which the amount of current which flows through the motor and the speed may be easily regulated. Fig. 199 shows very clearly the interior of the type K2 as now made by the General Klectric Co. At the left of the center of the figure, extending from the top downward, the main controlling contact is shown, consisting of arcs or seg- ments of circles, each of which terminates in a removable copper contact tip. The twelve contact fingers are shown at the left. Above, at the right, are shown the eight fingers and contacts of the reversing cylinder. Near the bottom of the controller at the left are the two cut-out handles, the raising of which cuts out either No. 1 or NEW CATECHISM OF ELECTRICITY. 429 Fig. 199 c RAILWAY MOTOR CONTROLLER. 430 NEW CATECHISM OF ELECTRICITY. THE ELECTRIC RAILWAY. No. 2 motor as may be desired, at the same time locking the main controlling drum so that it can not be turned to the points corresponding to the parallel combination, no matter which motor may be cut out of the circuit. Near the bottom at the right is the main terminal board with its fifteen main terminals and just above is seen the heavy electro-magnet, designed for blowing out the arcs formed at the tips of the contact fingers. The magnet is connected in on the main circuit, and what- ever current is being used by the car at any time passes through its coil, so that the heavier the current and the con- sequent tendency to arc, the stronger is the field magnetism of the magnet and its corresponding power for blowing out the arc. One pole of the magnet is hinged and swings out- ward, exposing the fingers, as it is shown outlined against the cover of the controller. When closed this pole is directly over the finger tips, the other pole being formed by the heavy iron casting composing the back of the controller. • Each car is provided with a revervsing switch, by means of which the direction of the current may be changed, which results in changing the direction of the rotation of the arma- ture, thus entirely obviating the necessity of turntables, or anything of like nature, and checking the car in a case of great emergency to avoid accident or collision. Kach car is also provided with lightning arresters embodying the same principles as those used in the power station, by means of which all danger from lightning discharges is obviated. Kew catechism of electricity. 431 THE ELECTRIC RAILWAY. The Electric Locomotive. — The most interesting develop- ment of the overhead (trolley) system is, of course, the 96- ton electric locomotive. The following data, relating to the machine are given by the builders of the electrical part of the locomotive, the General Electric Company : Number of trucks, 2 ; number of motors, 4 ( 2 to each truck) ; weight on driving wheels, 192,000 pounds (96 tons) ; number of driving wheels, 8 ; drawbar pull, 42,000 pounds ; starting drawbar pull, 60,000 pounds ; gauge, 4 feet 8)4 inches ; diameter of drivers, 62 inches outside of tires ; length over all, 35 feet ; height to top of cab, 14 feet 3 inches. This machine has been in operation since August 4th, 1895, at Baltimore, hauling the entire northbound freight ser- vice of the B. and O. railroad. Every train has been handled promptly and the locomotive has been ready at any and all hours during the day, causing no delay to traffic. Up to the present time no train which would hold together has been found heavy enough to cause the electric locomotive to slip its wheels under ordinary fair conditions. The capacity of the locomotive has been by no means reached. Note. — Test was made to learn its capacity for running a loaded train on an up grade. For this purpose a train consisting of two steam locomo- tives, not working, and 27 loaded freight cars, was brought to a stop while going north through the tunnel. Here the grade is 42 feet to the mile, and the rails were damp and greasy. The weight of the train alone was 1 125 tons, or 1221 including the electric locomotive. Every drawbar was tight, no slack occurring throughout the the length of the train. In this condition current was turned into the motors and movement was immedi- ately communicated to the train. At the end of one minute the train was moving at a speed often and one-half miles an hour, and at this point the speed was increased to the usual rate. 432 NEW CATECHISM OF ELECTRICITY. LINEMEN'S CONSTRUCTION TOOLS. Fig. 200. Fig. 201. pole SUPPORT. CONNECTORS. Fig, 202. CONNECTORS. Fig. 203. )^S8 1 ipra ^giliCi 01 POLK RATCHET. NEW CATECHISM OF ELECTRICITY. 433 LINE WORK. Instructions and Cautions for Linemen. -When cutting wire, grip the line with the cutting jaws of the pliers and move up and down at right angles with the wire two or three times, so that you cut the insulation part of the way round on both sides ; then hold your pliers firmly, bend the wire once or twice 'up and down with your left hand and the wire will break. Never try to break the wire by twisting your pliers, unless you first move the line out of the cutting jaws. There is no excuse for nicks in the cutting jaws of Stub's pliers, and careful line- men rarely have it happen. In stripping the endsof wire to make a connection, always cut along the wire towards the end, in much the same manner as if whittling a stick. Never cut round the wire with the edge of the knife or pliers, except when cutting the wire. In making joints, be careful never to let the cutting jaws or edge of your tools "score" the wire. If you do, don't cover it up, but make a new joint. After a joint is made with not less than four turns each side of the connectors, dip or moisten with acid. If you are on the ground, dip the joint in melted solder and hold it there a few seconds to thoroughly heat the joint, then take it out. If well "tinned," dip it in water to remove any acid which may be on the ends of the wire near the insulation. NOTE _ For very much of the following pages relating to practical electric Railroading we are indebted to Jas. I. Ayer, General Manager, St. L,ouis, Mo. 434 new catechism of electricity. LINEMAN'S CONSTRUCTION TOOLS. Fig. 205. Fig. 204. DIGGING SHOVEL. ! SPOON SHOVEL;. Fig. 20S. Fig. 206. 1 TAMPING BAR. Fig. 207 DIGGINC BAR. SAFETY wire; CUTTERS. NEW CATECHISM OF ELECTRICITY. 435 LINE WORK. If where you cannot dip the joint, but have to use the ladle, pour the solder frequently over the joint until it leaves a thin, smooth coating on the wire. It is not properly done if the solder is in lumps or on in a thick layer. If you are obliged to use a " blow pot," hold the joint in the flame until the solder will easily melt when held against the wire after the flame is removed. When this is accom- plished, apply the solder with the flame, and not before. Solder is put on the joints to keep them from corroding, thereby insuring good contact where the two wires come together, and is of no use if not well applied. After the joint is well cleaned of acid after being soldered, paint it thoroughly with insulating compound, then cover with a layer of tape, which you will start on one side of the joint, against the insulation of the wire, but not over it. Have the first layer cover the joint and bare wire only. When this is done, paint it, then start back over the joint and tape until you have run over the line insulation about two inches, then wrap two more layers, painting each when done. In wrapping tape, cover what you have half, or lap one- half. After four layers are on, paint the whole thoroughly. Whenever you find a break in the insulation on the line anywhere, paint it first, then tape and paint it. Don't forget this. In " tying in, " never draw the tie wire so as to bend a kink in the line or cut through the insulation with the tie. A tie will properly hold the wire in place without drawing it so tight as to do either. 43& NEW CATECHISM OF ELECTRICITY. LINEMAN'S CONSTRUCTION TOOLS. Fig. 309. Fig. 310. 'CUMBERS. " CUMBERS." Fig. 211. LINEMAN'S PUERS. NEW CATECHISM OF ELECTRICITY. 437 LINE WORK. In u g pulley blocks on the line, avoid the use of * ' come- alongs ' ' when possible, by taking a series of half-hitches, or making a " noose wrap " with a small line on the wire to hook the block to. If you do use " come-alongs, ' ' see that you do not score, cut or kink the wire, and always paint and tape broken insulation. Groundmen are especially cautioned to watch the line in " paying out ' ' and prevent "kinking." Should a short kink get pulled into the line, cut it out rather than take the risk of its breaking, though you should straighten it out. Never use porcelain knobs where exposed to moisture or the weather, and never use them anywhere else if glass can possibly be used. Porcelain knobs circuit breaks may be used where neces- sary, providing not more than two lamps are on the loop. In making them, paint and insulate with tape the joints in con- necting wire of loop. In making house connections where wires enter building, be sure to have not less than six inches clearance from cor- nices of walls. All wiring running over cornices or other building projections must be protected with rubber tubing, thoroughly taped and painted at the end. Never let a wire, however well protected, come in contact with any outside por- tion of the building. In placing tubing on wire, carefully paint and tape at the upper end, leaving the lower end open, so that moisture could escape if it got in. NEW CATECHISM OF ELECTRICITY. Fig. 212. LINEMAN'S TOOLS. Fig. 213. REEL; AND STAND. Fig. 214. REEL AND STAND. Fig. 215. BLOCK AND FALLS WITH " COME-ALONGS. McINTlRE SPLICING TOOL (FIG. 212.) NEW CATECHISM OF ELECTRICITY. 436, LINE WORK. Always run wires in straight parallel lines, and make square turns where possible. Twelve inches between wires is the proper space for arc lighting circuits, where practicable. Never fasten a cut-out box against the wall. Always place glass or porcelain knobs between the box and the wall. Never fail to put in "drip-loops" in line where entering building. In all electrical work, remember where insulation is desired it can never be too good, or when contact is desired, you can never make it too good or strong. In removing lamps ordered out, always close the loop at the line where it was originally cut in, and remove all dead wire. Never leave dead or unnecessary wire in circuit. Always use iron pins on arms where wires turn a corner or leave the line. Never screw an insulator on iron pin or bracket very tight, nor without first putting inside the glass a strip of paper folded twice or three times . This will prevent the glass being broken , as iron expands with heat nearly twice as rapidly as glass, and unless there is room enough, the difference in temperature between winter and summer would burst insulators in summer which were placed in winter. In connecting line to lamps hung from suspension wire, put on safety loops by making a half-connection with a short flexible wire on each side of the insulators at the pole and on the lamp hood. Solder and tape same as other joints. Arrange the length of wires leading to lamp so the lamp will not shadow the roadway of either street. 440 NEW CATECHISM OF ELECTRICITY. LINE APPLIANCES. Fig. 216. Fig. 220. WMMlMtfiiiiU^^UiUUiiilteHtti WOOD PIN. GLOBE INSULATOR. Fig. 217. WOOD BRACKET. Fig. 221. TREE INSULATOR. Fig. 218. THREE POINT FROG. Fig. 222. INSULATOR. Fig. 219. TROLLEY EROG. Fig. 223. INSULATED PLUG. NEW CATECHISM OF ELECTRICITY. 441 INSTRUCTIONS AND CAUTIONS. Do not handle any electric light apparatus while you are standing on the ground. Never use both of your hands while handling dynamos, or anything pertaining to same, while said dynamos are being used. Fig. 224. UNEMAN'S SAE^Y B£l/T. Do not touch a water pipe, iron post, or any stone, brick or iron structure while in contact with a lamp, line, dynamo, or anything connected with the electric light apparatus at the same time, unless you are provided with rubber gloves or other insulating material. When your business necessitates your going through the station, keep as far as possible from the machinery and belt- ing, and do not meddle with anything unless you are ordered by the man in charge, and then only after receiving careful instructions. 442 NEW CATECHISM OF ELECTRICITY. LINE APPLIANCES. Fig. 225. TE)RMINAI-wM rrn rrn tcp cor ...A ~IQ COT RAIX, JOINTS, NEW CATECHISM OF ELECTRICITY. 443 LINE WORK. No one is permitted to in any manner work on the switch- boards except when directed so to do by the man in charge of dynamo room, and then only after receiving careful instruc- tions. Keep away from the lightning arresters and wires leading to them. I/inemen or others operating on lines, must handle each and every wire at all times as if it were charged with the elec- tric lighting current and grounded. When obliged to pass over, under, or by an electric wire, avoid touching it in any manner, and especially with any uncovered portion of your person. Damp or wet clothing makes chance contact with wire dangerous. Tools used by linemen and others who ..have occasion to work on lamps or apparatus which may be charged with the current, must have handles well covered with rubber or other insulating material, and it shall be the duty of every lineman to look after his tools and see that they are in good condition for use, and especially as to the insulation of the handles. If it is at any time necessary to stand on the ground or any surface not insulated from the ground while handling electric wires or apparatus, heavy gum boots or an insulated stool must be used ; and under no circumstances allow yourself to make contact between two or more wires at the same time. Lamp trimmers and others engaged in taking care of and trimming lamps, must see that the switch on the board from which the lamp hangs is closed before they proceed to handle the lamp. Instructions laid down in these rules must be observed in connection with the work of handling the lamps. 444 NEW CATECHISM OF ELECTRICITY. LINE APPLIANCES. Fig. 331. TREE INSULATORS. Fig. 233. Fig. 234. Fig. 235. Fig. 232. Fig. 236. FEEDER LINE "EARS." NEW CATECHISM OF ELECTRICITY. 445 LINE WORK. In the event of any one in any manner being caught on live wires, where it is possible to get to them, pull the one caught away by grasping any portion of his clothing or body protected by clothing. There would be no possible danger to the one rendering help, no matter where you may be standing. If the one caught should be on a pole or ladder, he could usually release himself by kicking himself loose from the supports, or drawing up his knees, thereby causing the body to fall. It is understood that employees will wear and use their safety belts when working above ground on poles or ladders, especially when handling wires. In working on lines, all circuits must at all times be regarded as alive and grounded. With the hundreds of miles of wire throughout the city, some of which are carrying heavy current at all times, many using ground return, the line you are on may p come alive " at any time — be careful. Always avoid temporary work. When working on poles, be careful to stand so, if you should slip or get a shock, you would fall on your belt rather than on the wires. Avoid leaning over or crowding through wires when possi- ble, and do not put yourself in a position where you would fall on wires, should an accident occur. Always in making connection on poles, work from below rather than above, when possible. Examine cross arms and see that they are sound and firmly fastened before trusting your weight on them. 446 NEW CATECHISM OF ELECTRICITY. LINE APPLIANCES. Fig. 237. GLASS INSULATOR. NEW CATECHISM OF ELECTRICITY. 447 LINE WORK. Be careful that all tools are securely fastened in your belt when working on pole or ladder, and, in handling wires .and lines on poles, have a proper regard for the safety of those walking or driving below. When working on poles, always use your safety belt, as well as other safety devices which you are requested to use. It takes but a little time to make yourself safe, and many weeks to mend a broken bone. Never lay tools down when above the ground. See that all wires leading out of transformers and out of fuse boxes are well taped and painted where they leave the transformers, and all transformers must be placed so far from doors, balconies, windows and other openings, and sufficiently high above ground and roof, as to prevent accidental contact, in other words, out of reach. Instructions and Cautions for the Dynamo Room. — All station employees are requested to study the circuit maps and become familiar with the locations of the different circuits. On receipt of telephone or other message to cut out any circuit for the protection of life and property, do so promptly. On an arc circuit, always run the brushes up before pulling plugs on switch-board. On incandescent by cutting in resist- ance at switch-board to kill the dynamo, then open the switch. When a live circuit opens during a run, the dynamo must be cut out at once and left out until the trouble is located and O. K'd by lineman or inspector. Circuits ordered open must be marked on board with col- ored chalk. All other circuits must be marked " 0. K." with 448 NEW CATECHISM OF ELECTRICITY. LINE APPLIANCES. Fig. 238. " COM3-A-I,ONG. ' Fig, 239. TRO^^Y WHEJKlf. NEW CATECHISM OF ELECTRICITY, 449 LINE WORK. white chalk. This must be done only by those authorized so to do, and must be reported to man in charge in dynamo room. Never "try " a circuit with dynamo that opens during a run, until the trouble is located, no matter if it " rings' ' closed. Never connect dynamo to a circuit on which men are at work, without instructions from the men to do so. When an arc light or motor circuit is reported " O. K." after it has been open, build up current very slowly at dynamo by hand, and take about five minutes to put full current on, because it frequently happens that linemen will leave their work and start out on a circuit looking for trouble, without first notifying the station. By starting the circuit in this manner, should they be in a position where they might feel the current, they would likely have warning before current reached a dangerous intensity. Never run two machines in series. Doing this will be sufficient cause for dismissal. No excuse will be accepted for disobedience of this rule. Rubber mats and gloves must be used when working the switch-board. The same rule applies to work on dynamos when running. An arc made by electricity can frequently be blown or whipped out with a towel, on continuous current circuits, and should be extinguished in that manner, if the connections which occasion the arc cannot be easily separated. 45o NEW CATECHISM OF ELECTRICITY. LINE APPLIANCES. Fig. 240. CIRCUIT BREAKER. Fig. 241. CIRCUIT BREAKER. Fig. 242. RUBBER HOOK INSULATOR. NEW CATECHISM OF ELECTRICITY. 451 LINE WORK. In the event of a short circuit on alternating lines or switches in station, the current can be safely shut off by cut- ting in resistance on exciter at switch-board. Water will not extinguish an electric arc or fire when pro- duced only by the current. Large canvas covers are available, which should be quickly spread over the dynamos if water is used to extinguish fire on the floor above. Fire buckets must be kept filled with both sand and water on each floor in machine building above engine room. In many cases sand will prove more useful than water in extin- guishing a fire. The hose on each floor must be kept connected and ready for use. In using sand or water, remember that a little well directed is better than quantities thrown wildly. Use no more of either than is absolutely necessary, as it is easy to do more damage with them than would be likely by fire. Any faulty lamps, wires, belts or anything else reported to this department, must have immediate attention from the man in charge.* No joints are permitted to be made and left without being soldered. When placing guard wires on street crossings, always use iron pins and glass insulators to attach both ends of guard wires to. Never tie on cross arm pole. In stormy weather, when they may be of use, they would be dangerous every way. Yj"- NEW CATECHISM OF ELECTRICITY. LINE WORK. Location of Trolley Wire, — On straight line work the wire should be over the center of the track. At curves the wire should be placed on the inside of the curve, its distance from the center of the track depending on the degree of curvature. The Repair Shop. — Near the car house, if not under the same roof, should be placed the shop for such repairing as is profitable for the company to do themselves. The few tools— a lathe, drill press, etc. — may be conveniently run by a sta- tionary electric motor. In the repair shops, perhaps even more than other parts of the plant, order and neatness should be the rule. The arma- tures should be kept in racks and not on the floors. The winders and their supply of wire should be kept away from litter of any kind. The floor should be well swept especially of all metal filings. Each kind of supply should have a special bin, etc., etc. Fig. 253. In Fig. 253 is con- tained a suggestion. As each tool should have a place it is well, if conven- ient, to have a little ' ' sil- houette ' ' drawing made just under the place a tool should be hanging. When the tool is away this is a reminder to put it back. NEW CATECHISM OF ELECTRICITY. 453 CARE AND MANAGEMENT OF THE STREET CAR MOTOR. The motor should have exceptionally good care. This can only be given by frequent and careful inspection. The dynamo and engine in the power house are carefully watched and oiled. They are well located and have every advantage ; on the same principle the street car motor needs very much more care, due to its unfavorable location. Washers, carbon dust, bits of gravel, sand, pieces of carbon brushes, and other matter capable of doing serious damage, have been found in the motor cases of some of the best types. The time for inspection is usually brief, but everything must be noted. Spare parts should be at hand and no armature or field coil in which a defect is suspected to exist should be allowed to go on a trip. Loose nuts, hot boxes, burnt commutator bars, and matters of a kindred nature, should be carefully sought for. Dust or mud should not be allowed to accumulate. The screws of the motor support should receive minute inspection. Kvery screw on the truck is liable to be jarred loose and the dropping of the motor into the street is almost certain to wreck the greater part of the equipment, both mechanically and electri- cally. 454 NEW CATECHISM OF ELECTRICITY. LINE APPLIANCES. Fig. 243. WINDING MACHINE. Fig. 244. Fig. 245. BARN OR BRIDGE HANGER. Fig. 246. TROLLEY CROSS-OVER. NEW CATECHISM OF ELECTRICITY. 455 CARE OF THE MOTOR. The motorman should be present when his motor is taken apart and inspected. By this means he will become familiar with the various parts and their diseases. The motor is under his care the greater part of the time and therefore the more he knows of its construction the fewer accidents there will be. The car should be provided with a monkey wrench, a few duplicates of the most important bolts and nuts, a pair of pliers, some rubber tape and a supply of insulated copper wire about No. 8 B. & S. With these simple toolaand mater- ials vexatious delays can often be avoided. Run carefully over curves, crossings and switches and thus save both them and the motors. With a little practice the motorman can accustom himself to the ordinary sights, sounds and smells on and about a car equipment and anything unusual will at once be detected. The one thing that is most liable to derange the mechanical portion of a car equipment is vibration. This is largely met by a properly designed truck, but a careful motorman can also do much to reduce this evil. Feeder Wires. — In electric railways the feeder wire sup- plies the current from the generator, to the trolley wires. In lighting systems it is the main wire coming from the dynamo. Feeder cables are always made of stranded — or more than one wire, 45$ NEW CATECHISM OF ELECTRICITY. LINE APPLIANCES. Fig. 248. Fig. 351. hanger" and "ear." Fig. 249. SINGLE "PULL-OFE" AND EAR. FIG. 250. Fig. 252. DOUBLE "PULT,-0FE" AND EAR. WIRE TIES. NEW CATECHISM OF ELECTRICITY. 457 STORAGE BATTERIES. These are also known as accumulators from the fact that they accumulate or store electric energy ; they are also called secondary batteries in distinction to primary batteries described on page 47. These various terms are applied either to a single cell or to a collection of cells electrically connected together. Secondary batteries are in no sense generators of electricity but are employed to accumulate, or store, a given quantity of electric energy, the quantity of which is estimated by the numbers of hours required to dis- Fig. 254. charge it at a given rate. While the electric energy may be produced by a primary battery, it is usually stored by the use of a dynamo, as shown in Fig. 255. During the " charging" process the electric energy is accumulated and during the discharge the chemical processes are reversed, the electric energy flowing from the battery until the materials are restored to their original chemical condition. 45^ NEW CATECHISM OF ELECTRICITY. STORAGE BATTERIES. Accumulators are coming into rapid application in many different ways. Following is a list of some, in which accumu- lators are giving highly satisfactory results : Electric locomotives for hauling in factories and mines. Carriage propulsion. Electric launch propulsion. Train lighting. Yacht lighting. Carriage lighting. Bic3'cle lighting. Miners' lamps. Medical, surgical and laboratory work. Phonographs. Sewing machine motors. Fan motors. Electric fire-alarm. Heat regulating. Railroad signal apparatus. For portable use, in connection with phonograph and other small motor work and small electric lamps, chloride accumulators are put up in sealed rubber jars, enclosed in neat hardwood cases, provided with handles and binding posts. Various capacities are furnished 'for batteries complete, filled with acid, and charged up ready for immediate use. But, it is in connection with electric railways and electric light and power companies that the greatest advances are being made ; in Europe especially, great attention is being NEW CATECHISM OF ELECTRICITY. 459 STORAGE BATTERIES. paid to the subject ; eight years' experience in German cen- tral station practice have indicated that the use of storage batteries insured a reduction of 33^ per cent, in the engine 478 NEW CATECHISM OF ELECTRICITY. THE TELEGRAPH. a covering for wires inside the finer instruments. For the handles or knobs to the various instruments hard rubber is generally used. The operation of a telegraph is not, as many people sup- pose, a complicated or difficult matter to understand. The apparatus employed is quite simple, and easily understood. The battery is the first essential part of a telegraphic apparatus, as it is by the chemical action in the battery that the electric current is first generated. In practical telegraphy this current is made to traverse long or short distances through the conducting medium of metallic wires, and by means of the proper instruments, made to give out tangible results. The basis of the entire telegraphic mechanism is the Klectro-magnet and the transmitting "Key," (see Fig. 271.) The Klectro-magnet is constructed as follows : two bars of soft iron, having round heads of hard rubber, thus making spools of each, are joined together by means of a short flat bar of iron similarly soft. The round bars in the spool of the magnet are called cores, the flat connecting bar at the back is called the "back bar/' or "heel piece." The movable flat piece of iron in front, which is to be attracted by magnetism to the cores, or withdrawn by the spring when no magnetism excites the cores, is called the armature, A silk or cotton-covered wire is wound in continuous turns about the cores, until the diameter of about an inch and a half is attained, and each core or spool of the magnet contains , NEW CATECHISM OF ELECTRICITY. 479 THE TELEGRAPH. a great number of turns of trie wire around it. Now, if a cur- rent of electricity be sent through this wire, it will, by its passing through the numerous turns, cause the iron cores within to become magnetic and to possess the power of attracting with considerable force any piece of iron brought near to their ends. THE MORSE TELEGRAPH ALPHABET. h" i ^j_ Bf_ l Ijsl Ja OP Q R S T U mm ■■••■§ « m um iiii m «• « w • • m t u rn n » • «*■» ..y_ ..jy_ .J*.. .. Y .. ..?.'.4 6 .. Numerals. ._*_. _.JL §— - .--4 JL_ 6 7 8 9 -•»•«»•>« mm mmamm m m mmmmm m mnm m mrnarn m m ■ n i n m Punctuation. Per iod, Comma, Semi -c olon. Quotation. Exclamation* Inte rrogation: Parenthesis. Parag raph. The Morse alphabet consists of what are called dots, dashes and spaces. Combinations of these make intelligible signals. Many of the characters will be found to be the reverse of others : such as A is the reverse of N ; B of V ; D of U ; C of R ; Q of X ; Z of & ; so if the formation of one of these letters be obtained, its reverse is easily mastered. C, K, H, I, O, P, R, S, Z, Y, are merely represented by dots and spaces, and, if due regard be given to them, they will be found very easy to commit to memory, 480 NEW CATECHISM OF ELECTRICITY. THE TELEGRAPH. The first step is to memorize the alphabet, so that each character can be called to mind at will ; thus, A, dot and dash; B, dash and three dots ; C, two dots, space, dot, etc. The period is the only punctuation mark in frequent use. A dot (K) is made by a single instantaneous, downward stroke of the key. A short dash (T) is made by holding the key down as long as it takes to make three dots. A long dash (Iv or cipher) is made by holding down as long as required to make five dots. A cipher is prolonged so as to occupy about the time required for seven dots. The intervals between dots or dashes in the same letter are called breaks. A space in letters should occupy the time required for a dot and break. The space between letters should occupy the time required for two dots and breaks. The space between words should occupy the time required for three dots and breaks. In letters that do not contain spaces, the dots and dashes should follow each other as closely as possible. The armature of the magnet is attached to a lever, and this lever, which swings on* a pivot in the middle, is provided at the end with a pointed pin or screw, which is caused to press upwards against a strip of paper whenever the magnet attracts, and to return to its former position when the attraction ceases. Meanwhile the paper is kept moving steadily forward, so that if the lever-pin is pressed against the paper, for only an instant of time, a short mark or dot appears pressed or embossed into Fig. 272. THE MORSE KEY. Fig. 273. KEY BOARD, Fig. 274. TElfEORAPH KEY AND RET, AIT. 482 NEW CATECHISM OF ELECTRICITY. THE TELEGRAPH. the paper. If for a longer time, the mark would be propor- tionately longer, or a dash. If alternately, the marks would come consecutively, and have spaces between them. As the Morse Alphabet consists entirely of dots, dashes, spaces, and' extra long dashes, the letters and numerals are easily made; with these marks and their combinations. So that as the: hand of the operator, on the key at a distant point, makes, short or long strokes, dots or dashes, or spaces, these same marks appear on the paper as it comes from the Register, and. being based on the formation given by the Morse Alphabet,, are as easily understood by the receiving operator as though they appeared in the well-known Roman characters. It should be remembered that there is no change in the tone of a sounder, the letter being determined solely by the * ' time or times ' ' the lever is up or down. The key is provided with screws for the purpose of regu- lating its play to suit the hand of the operator. A little practice will enable the learner to judge best for himself as to how this should be set. The Key is a simple contrivance for making or breaking the contacts which control the passage of the current — a steel lever, swung on a pivot, having a rubber handle, which the operator grasps lightly with the thumb and forefingers. On pressing the lever downward, a platina point projecting under the lever is brought into contact with another platina point set into an insulation of rubber in the base of the key, so that there can be no electrical connection between them unless the NEW CATECHISM OF ELECTRICITY. 483 THE TELEGRAPH. key is pressed down, or " closed, " as it is termed. A conduct- ing wire being separated at any point, and one of its ends connected with the lever or base of the key, and the other end with the metal set into the rubber insulation, would con- vey the current while the key was closed, and cease to do so the moment it was opened. Platina is used at the points where the electrical contacts are made and broken, because it does not readily fuse or tarnish. An extra lever at the side of the key is called the " circuit-closer, ' ' and is used as a means of keeping the circuit closed when the hand of the operator is not on the key. When the circuit-closer is pushed into its closed position, it makes contact with a brass Hp, which latter is fastened to the rubber along with the lower platina point. This, then, has the same effect as though the key was pressed downward and contact made at the points. Duplex Telegraphy. — There are two distinct methods of arranging telegraphic apparatus so as to transmit two messages through one wire, one from each end, at the same time. The ikst of these, known as the differential method, involves the use of instruments wound with differential coils, and is appli- cable to special cases. The second method of duplex working, known as the Wheatstone's Bridge Method, is capable of much more general application. The Relay. — In working over long lines, or where there are a number of instruments on one circuit, the currents are often not strong enough to work the recording instrument directly. In such a case there is interposed a relay or repeater. 484 NEW CATECHISM OF ELECTRICITY. THE TELEGRAPH. This instrument consists of an electromagnet round which the line current flows, and whose delicately poised armature, when attracted, makes contact for a local circuit in which a local battery and the receiving Morse instrument are included. The principle of the relay is, then, that a current too weak to do the wo**k itself may set a strong local current to do its work for it. Another term for this instrument is ' ' the relay magnet. ' ' The use of the relay is especially required in the Morse system of telegraphy in order to cause the sounder to be more distinctly heard ; the use of the relay permits much smaller currents to be used than could otherwise be done. Faults in Telegraph Lines. — Faults may occur in telegraph lines from several causes : either from the breakage of the wires or conductors, or from the breakage of the insulators, thereby short-circuiting the current through the earth before it reaches the distant station, or, as in overhead wires, by two conducting wires touching one another. Various modes for testing the existence and position of faults are known to tele- graph engineers ; they depend upon accurate measurements of resistance or of capacity. Thus, if a telegraph cable part in mid-ocean it is possible to calculate the distance from the shore end to the broken end by comparing the resistance that the cable is known to offer per mile with the resistance offered by the length up to the fault, and dividing the latter by the former. NEW CATECHISM OF ELECTRICITY. 485 THE TELEGRAPH. Submarine Telegraphs. — Telegraphic communication be- tween two countries separated by a strait or ocean is carried on through cables, sunk to the bottom of the sea, which carry conducting wires carefully protected by an outer sheath of insulating and protecting material. The conductor is usually of purest copper wire, weighing from 70 to 400 lbs. per nauti- cal mile, made in a sevenfold strand to lessen risk of breaking. In the Atlantic cable, which is of the usual type of cable for long lines, the core is protected first by a stout layer of gutta- percha, then by a woven coating of jute, and outside all an external sheath made of ten iron wires, each covered with hemp. The shore ends are even more strongly protected by external wires. (See Fig. 42, page 97.) Culley states that when a current is sent through an Atlantic cable from Ireland to Newfoundland no effect is pro- duced on the most delicate instrument at the receiving end for two-tenths of a second, and that it requires three seconds for the current to gain its full strength, rising in an electric wave which travels forward through the.cable. The«strength of the current falls gradually also when the circuit is broken . 486 NEW CATECHISM OF ELECTRICITY. ELECTRIC BELLS. The electric bell is a bell rung by electricity. Generally it is worked by a current exciting an electro- magnet attracting or releasing an armature which is attached Fig. 275. to the vibrating or pivoted tongue of the bell. T*his is done alternately so that the tongue beats against the bell. NEW CATECHISM OF ELECTRICITY. 487 ELECTRIC BELLS. The arrangements of the instrument are shown in Fig 276, in which B is the electro -magnet and H the hammer. A battery consisting of one or two Leclanche cells placed at some convenient point of the circuit, provides a current when required. By touching the i ' push ' ' P, the circuit is com- pleted, and a current flows along the line and round the coils of the electro-magnet, which forthwith attracts a small piece of soft iron attached to the lever, which terminates in the hammer H. The lever is itself included in the circuit, the current entering it above and quitting it at C by a contact- breaker, consisting of a spring tipped with platinum resting against the platinum tip of a screw, from which a return wire passes back to the zinc pole of the battery. As soon as the lever is attracted forward the circuit is broken at C by the spring moving away from contact with the screw ; hence the current stops, and the electro-magnet ceases to attract the armature. The lever and hammer therefore fall back again establishing contact at C, whereupon the hammer is once more attracted forward, and so on. The push P is shown in section on the right of Fig. 277. It usually consists of a cylindrical knob of ivory or porcelain capable of moving loosely through a hole in a circular support of porcelain or wood, and which, when pressed, forces a platinum-tipped spring against a metal pin, and so makes electrical contact between the two parts of the interrupted circuit. The bell may be worked by a distant switch or press button ringing once for each movement of the distant switch or it may be of the— 4 8& NEW CATECHISM OF ELECTRICITY. ELECTRIC BELLS. Vibrating Bell Type. — When the current is turned on in this system it attracts the armature. As this moves towards the poles of the magnet it breaks the circuit by drawing the " contact spring " away from the " contact point." This opens the circuit as before explained and causes the continual ringing. Fig. 376. Fig. 27t. DEFECTS OF ELECTRIC BELL. The possible defects of electric bells may be classed under four heads, viz.: ist, bad contacts ; 2d, bad adjustment of the parts ; 3rd, defective insulation ; 4th, warpage or shrinkage of base. Many operators are content with simply turning the NEW CATECHISM OF ELECTRICITY. 469 ELECTRIC BELLS. terminal wires round the base of the binding-screws. Unless the binding-screws are firmly held down on to the wires by means of a back nut, a great loss is sure to occur at these points, as the wires may have been put on with sweaty hands, when a film of oxide soon forms, which greatly lowers the conductivity of the junction. Again, at the junction points of the wires with the contact angle brass and contact pillar, some workmen solder the junctions, using " killed spirits" as a flux. If solder be used at any parts, let resin be used as a flux. Even if any excess of resin remain on the work, it does no harm and does not destroy the insulation of any of the other portions. Another point where bad contact may arise is at the platinum contacts. Platinum is a metal which does not rust easily, even under the influence of the electric spark given at the point of contact. Therefore it is preferred to every other metal (except, perhaps, iridium) for contact breakers. As to bad adjustment ; it is evident that the magnets and the armature must stand at a certain distance apart to give the best effects with a given battery power. The distance varies from ^ T ¥ in. in the very smallest, to ^ in. in large bells. Sometimes the armature adheres to the poles of the electro- magnet ; this is due to residual magnetism^ and points to hard or unannealed iron in the cores or armature. As a make-shift, this defect may be partially remedied by passing a thin piece of paper over that surface of the armature which faces the poles of the electro-magnets. 4^o NEW CATECHISM OF ELECTRICITY. Fig. 278. Fig. 279. CO IhQ r*^ 2 c p CQ -■© CQ 6 M V NEW CATECHISM OF ELECTRICITY. 493 ELECTRIC BELLS. bring the parts too close together and jamb the magnets, the armature, and the contact pillar into an unworkable position. No bell that is set to do real work should be fitted up without a cover or case. The dust which is sure to accumu- late, not to speak of damp and fumes, etc., will certainly militate against good contacts and good action if this important point be neglected. ~ JOINING TWO WIRES. Ete. 284. J01NING-0N A BRANCH WIRE. To make a good joint, the following method of procedure should be adopted : — Strip the ends of the wires to be joined of their insulation for a length of about i % inches, and scrape clean with a knife or brighten with emery paper. Then (taking one wire in each hand) twist the wires together as shown in Figs. 283 and 284 (Fig. 284 is a branch wire), and tighten up with the plier. Now get ready the articles required for soldering, which' should consist of the following : — A small copper bit, filed wedge shape with an ]/% inch groove cut across one face; a small spirit lamp for heating the bit, a stick of solder, and lastly, a piece of composite candle or 494 NEW CATECHISM OF ELECTRICITY. ELECTRIC BELLS, rosin. The best "blow-pipe" solder should be used, the quality of which may be tested by holding it up to the ear and bending it, when, if it is good, a peculiar crackling noise will be heard, which is known as the ' ' cry of the tin. " To solder the joint, heat the bit, previously tinned, in a spirit lamp or fire, and wipe with a piece of clean rag, and then, holding it with the grooved side upward^ fill the groove with solder. Now rub some composite candle or powdered rosin on the joint, and lay it in the groove, turning it over till the solder runs completely round, when quickly wipe with a piece of rag, and the result will be a strong, clean joint. CONNECTING UP. The following diagrams, 279 to 282, show several ways of connecting up bells, indicators, etc., and though the methods most usually required are shown, nearly every instance may require some little special modification. Simple Bell Circuit.- -Pig. 279 shows a simple circuit, con- sisting of push, battery, and bell. The cover of the push P has been removed, showing the connections to the contact springs, ©ne of which, for the purpose of distinction, is shown darker than the other. The bell B (shown in detail in Fig- 275) has its cover on ; thus none of the movement is visible. Z and C are the respective poles of the battery D. On the two springs of the push being pressed together the NEW CATECHISM 6F ELECTRICITY. 4^5 ELECTRIC BELLS. current flows from the positive pole C of the battery to the terminal Iy, through the bell to the terminal K, and thence by the wire and push-springs to the negative pole Z. Both in this and the following figures the Z or return wire is shown thicker, in order to make the diagrams clearer. Simple Bell Circuit with "Earth." — Fig. 280 is a simple bell circuit with " earth " connections, the circuit being com- pleted between the two plates K K by the earth; the wire from the zinc of the battery, and one of the wires from the push being fastened to the water-pipe or gas-pipe. Two or more Pushes to ring same Bell. — Fig. 281 shows the method of connecting two or more pushes so as to ring the same bell. The pushes are here shown with their covers on, the buttons being represented by the black dots. Pressing the button of either of the pushes a, b> c> d completes the circuit, causing the bell B to ring. Two Bells to ring simultaneously from one Push. — Fig. 282 shows an arrangement by means of which two bells can be rung simultaneously from one push, the bells being some dis- tance apart, as in separate rooms. On the button of the push P being pressed in, the current flows from the positive pole C of the battery through the push, and along the wire a to d, where it divides, half (if the bells are of equal resistance) pass- ing through the bell B, and half through the bell W. When bells are arranged parallel like this, care should be taken to insure the resistance of the coils of each bell being as near 49 6 NEW CATECHISM OF ELECTRICITY. ELECTRIC BELLS. alike as possible, or else to put the bell with the lowest resist- ance the furthest from the battery, so that the resistance of the line compensates for its lower resistance. If there are many bells, care must also be taken to provide sufficient bat- tery power, the largest sized cells being used. The practice of splitting up a battery of smaller cells into two halves, and connecting the halves in parallel, is not advocated, unless absolutely necessary, it being far preferable to employ larger sized cells. Push Buttons.— These are switches (see Figs. 285 and 286) for closing a circuit by means of pressure applied to a button. The button is applied to a spring so that when pushed in and released it springs back ; thus the circuit is closed only as long as the button is pressed. Pulls.— These are switches for closing a circuit when pulled. Magneto Bell and Generator.- -Fig. 278 shows a small magneto bell and generator, there being also a switch hook at the bottom, since the generator is mainly used for tele- phony, which is the chief field of the magneto bell. The generator is, it will be seen/ fixed in the body of the case, while the bell is on the lid. The hammer-head, projecting through a hole, works between the two gongs. The apparatus required for signalling by the method men- tioned above consists of two parts— the generator and the bell. The principle on which the generator acts is the same NEW CATECHISM OF ELECTRICITY. 497 ELECTRIC BELLS. as that on which is based the action of all dynamos, and, in fact, the generator finds in the dynamo almost its exact counterparts. The Electric Buzzer is a very useful instrument for use in places where the ringing of a bell would be an annoyance. It operates on the same principle as the electric bell and can be adjusted to emit a musical and pleasing hum instead of the ordinary ringing. The direction of the current cuts no figure in this class of work ; connect the opposite ends of the circuit to the opposite ends of the circuit to the opposite poles of the battery and the circuit is complete. Wiring plans and specifications should be worked out by electrical engineers rather than architects or builders, as the problems of wastage of current and the danger to life and property are extremely difficult to work out under all the varying conditions. " Diagrams " should be made showing in detail the con- nections actually required, and these should be provided at an early stage of any installation. 498 New catechism of electricity, ELECTRIC BELLS. Explanation of Technical Terms used in Electric=beII Work. Battery.-The combination of cells which furnish the current of electricity for working the bells, indicators, &c. C*//._Bach outer jar of the battery, with its two elements and exciting fluids constitutes a cell. Fig. 285. Fig. 386. Circuit.— The wires, bells, indicators, batteries, &c, form- ing the path for the electricity. Defledion.-The angle or number of degrees through which the needle of the detector moves during the passage of a current round the coils. Earth return.-The use of the earth as part of the circuit. Earth wire.-The wire from the bell, battery, &c., leading to the water or gas pipes. NEW CATECHISM OF ELECTRICITY. 499 ELECTRIC BELLS. Fault. — Any break or interruption of the circuit by which some of the operations are interfered with. Line. — The wire joining one station with another. Line Battery. — The battery which is used to send the currents to line. Local battery. — The battery placed near the bell or appara- tus required to be worked which continues the ringing of the bell after it has been once started by the current from the line battery. Local circuit — The circuit through which the current of the local battery flows. Metallic circuit. — The use of another wire for return instead of earth. To connect up. — To join the bells, indicators and other apparatus included in the circuit. To disconnect. — To remove the ends of the wires from the terminals of the instrument, thus cutting it out of the circuit. To make " earth.'" — To connect the wire to earth. A short-circuit. — A fault caused by two wires coming together so as to form a shorter path for the current, diverting the whole or greater part of it from its proper course. To short-circuit a cell. — To join the terminals with a piece of wire. 71? short-circuit an instrument. — To join the terminals of the bell, &c, with a piece of wire. 500 NEW CATECHISM OF ELECTRICITY. ELECTRIC PUMPS. Pumps suitable for all services are built to be driven by electric motors, and special designs have been made to cover the requirements of hydraulic elevator service, mine service, water works supply, irrigation purposes, fire protection, or in short any service where electric motive power can be used to advantage. The great variety in style and size of these pumps now in successful use assures the extension and enlargement of the application of electric motors to all k inds of pumping machin- ery. Fig. 28y~shows a motor attached to a pump with govern- ing arrangement which is very simple in construction. The pulley of the switch is connected by a chain to a float resting upon the water in the tank, so that when the water falls the wheel is revolved until the starting point is reached, when it causes the switch arm to pass slowly over the contacts until the full current is cut in, and the motor runs at full speed. As the water rises, through the action of the pump, the pulley is turned in the opposite direction, finally making a quick break, shutting off the current and stopping the motor. This switch is positive in action, and cannot fail to work at all times and under all circumstances. It prevents the tank from overflowing or becoming empty through neglect of the attendant. NEW CATECHISM OF ELECTRICITY. 50I ELECTRIC PUMPS. Fig. 287. EI3CTRIC PUMP AND AUTOMATIC TANK SWITCH. 502 NEW CATECHISM OF ELECTRICITY. ELECTROMETALLURGY. The applications of electro-chemistry to the industries are three-fold. Firstly, to the reduction of metals from solutions of their ores, a process too costly for general application, but one useful in the accurate assay of certain ores, as, for exam- ple, of copper ; secondly, to the copying of types, plaster casts, and metal-work by cathode deposits of metal ; thirdly, to the covering of objects made of baser metal with a thin film of another metal, such as gold, silver, or nickel. All these operations are included under the general term of electro- metallurgy. In 1836 De La Rue observed that in a Daniell's cell the copper deposited out of the solution upon the copper plate which served as a pole took the exact impress of the plate, even to the scratches upon it. In 1839, Jacobi, Spencer, and Jordan independently developed out of this fact a method of obtaining, by the electrolysis of copper, impressions (in reversed relief) of coins, stereotype plates, and ornaments. A further improvement, due to Murray, was the employment of moulds of plaster or wax, coated with a film of plumbago in order to provide a conducting surface upon which the deposit could be made. Electro Plating or Electro Deposition. — The full details of the many processes for electro plating cannot be given on account of their length ; the general principle includes a bat- NEW CATECHISM OF ELECTRICITY. 503 ELECTROMETALLURGY. tery or source of electric current (say a dynamo of suitable size, etc., as shown and explained in connection with illustra- tion 288. ) For Rapid Boiler Repairs the electric arc is most efficient. It enables a patch to be applied in difficult places, Adhere riv- eting would be impossible without partly taking the boiler to pieces. For instance, parties had an upright boiler wasted by corrosion at one point of the outer shell. When the defect was cut away, there was a hole 5% in. by $% in. A piece of mild steel plate was cut to fit over the hole, with 1 1-2 in* lap all around. It was then laid in position, and the electric arc struck upon the junction, so as to thoroughly incorporate the patch with the shell. The whole job, including testing by hydraulic pressure, was completed in 10 hours. In another case, the internal bottom corners of the fire-box of a locomotive type boiler were badly wasted. The defects were repaired by building on and melting into the recesses small pieces of mild steel, and thoroughly incorporating the new pieces with the old. The leaks were stopped, and no fur- ther trouble experienced during eight months which have since elapsed. Note.— The extreme hardness of armor plates has one great disad- vantage, it is impossible to cut or drill them, and to do so is often very necessary, To exactly locate proposed holes, in order that they may be drilled before the surface of the plate is hardened, is a very expensive undertaking. For a long time there was no known method of drawing the temper from the metal in a circumscribed area, for no matter how heat was applied, the large mass of metal produced such rapid cooling as to reteraper the spot. By means of electricity, however, the problem has been solved, and a small section of a plate, where it is desired to drill a hole, may be heated to 1,000 degrees and very slowly cooled, thus drawing the temper satisfactorily. 504 NEW CATECHISM OF ELECTRICITY. ELECTROMETALLURGY. Fig. 288k Fig. 288 represents the operation of plating, the position of the anode and cathode, the battery and the bath. The battery has its centre or positive plate connected to a rod extending across the trough, to which are suspended the anodes, a y a> a> of gold, silver or copper, or whatever other metal from which to obtain a deposit. The other plates of the battery, or the nega- tive elements, are connected with the remaining rod across the trough, to which are suspended the articles to be plated, b, b> b. Electricity in Drilling. — The electric current is now used extensively to aid in drilling hardened steel. By this* meahlT the steel is softened in a very limited space by sending the current, of sufficient strength, through the metal at the required point. The terminal of one of the conductors is placed at the point where it is required to drill the hole and the terminal of the other conductor on the opposite side where the drill is intended to pass through. The application of cur- rent between these points will soften the metal in a direct line between the terminals without affecting a greater area than is desired. The metal being thus softened no great difficulty is experienced in drilling it afterward (see Note, page 503.) NEW CATECHISM OF ELECTRICITY. 505 ELECTROMETALLURGY. Sharpening Files by Electrical Process. — The dull and dirty files are first placed for 12 hours iu a cold solution of caustic soda of 15 to 20 per cent. ; they are then cleaned with a scratch brush and after another immersion are again cleaned with a scratch brush and a 5 to 6 per cent, soda solution. They are then placed in the following bath : six parts nitric acid of 40 degrees ; 3 parts of sulphuric acid ; 100 parts of water. It is said to be very important to see that this bath is properly proportioned in order that the action is not too rapid. They are inserted in this bath, and connected to plates of car- bon immersed close to them, by means of a copper plate con- necting all the carbons and the files at the top. This produces a short-circuited battery which generates gas on the surface of the files. The gas formed creates bubbles which adhere to the points of the files, and protect them from being eaten away, while the rest of the file is being etched. They are taken out every five minutes and washed in water so as to remove the oxide which collects. They are then placed for half an hour in lime water made of one part by weight of slacked lime and 50 parts water ; this is to remove the acid. They are then dried in sawdust and to prevent rusting are rubbed with a mixture of oil and turpentine. It is said that it requires but 20 to 30 minutes in the electrolytic bath to sharpen the files. Note.— The " Elek. Zeitschrift " states that the method of sharpening files, described some years ago, is meeting with great favor, especially in England and France, where it is used very largely. Baths are in use for treating 300 to 400 files at a time. One workman can attend to two such baths. Experience has shown that one man can in this way sharpen 400 files a day working 10 hours. The process can be repeated several times without injuring the files. This same method is also used to sharpen knives used in beet sugar factories. For this purpose it is said to give very good results and does not require any skilled labor, while at the same time it represents a considerable saving in the cost of sharpening knives. 506 NEW CATECHISM OF ELECTRICITY. Fig. ELECTRIC ELEVATOR, NEW CATECHISM OF ELECTRICITY. 507 THE ELECTRIC ELEVATOR. The electric elevator — or as it is described in England, the Electric Lift — is a combination of the regular elevator with the electric motor ; i. e. y the power applied to raise and lower, is the electric current, as against water pressure or steam pressure. The adaptability of electricity to all service where power is required was never so apparent as in its application to passen- ger elevators ; the success of the electric hoist seems destined to develop a field the extent of which has not yet been calcu- lated. The essential features of the electric elevator are : (1) high speed, (2) absolute safety, (3) completely under control of operator, (4) applicable to the current to be supplied by the lighting mains, (5) low cost of operation and maintenance. In the hydraulic pumping system as well as in the hydraulic street pressure system, it is noteworthy that just as much water is required to carry up the empty car as to carry up a full load, and — If a steam pump is used it is necessary to keep the fire burning under the boiler and to keep the steam up all the time, although the pump in most cases runs only a small por- tion of the time, so that the consumption of coal is many times larger in proportion to the power used than in ordinary steam engines of equal power, but — 508 NEW CATECHISM OF ELECTRICITY, THE ELECTRIC ELEVATOR. If electricity is used in connection with a proper motor, the consumption of current stops when the work stops, which insures great economy of operation whether the current sup- ply is obtained from a central station or from owner's dynamos. The advantages of the device as summarized are as follows : Advantages of the Electric Elevator. i. As compared with hydraulic elevators. No frozen or burst water pipes. No flooded cellars. No piston to pack and grease. No leaking valves or cylinders. No air to cause runaways. No excessive weight to bring car down. No heavy or unsightly tanks on rj^of or pressure tanks occupying valuable space. No creeping of car away from landing, if left for a few minutes. No water pipes to fill up or corrode, thereby reducing power and speed. 2. As compared with steam elevators. No odors or heat. No ashes, dust, or dirt. No boiler insurance. No costly space occupied. No vibration of building or disagreeable noises. No consumption of coal while elevator is at rest. No waiting to get up steam. NEW CATECHISM OF ELECTRICITY. 509 Fig. 290. ELECTRIC elevator. 5IO NEW CATECHISM OF ELECTRICITY. THE ELECTRIC ELEVATOR. 3. General advantages. Prompt and easy start. Smooth running. Quick and smooth stop, regardless of load, speed, or skill. Requires minimum attention. Speed practically uniform under all loads. Large margin of power. Minimum operating expense. Extreme simplicity, few moving and wearing parts. Most approved safety devices. "Points" relating to the Electric Elevator: The satisfactory working of an electric elevator depends largely upon the devices by which it is started, stopped, and reversed ; an automatic switch and rheostat (or regulator) should be provided, by which these changes can always be made properly without strain on the apparatus, with perfect smoothness and without the exercise of skill on the part of the operator. Pulling the rope downwards as far as possible causes the car to ascend. A slight pull in the opposite direction opens the switch, allows the brake to apply and the car comes to a stop. Pulling the rope upwards as far as possible causes the car to descend. The same effect is produced by the turning of a hand wheel— forwards or backwards. Any apparatus will wear in time, and therefore elevators should be equipped with the most reliable and improved forms of safety appliances, NEW CATECHISM OF ELECTRICITY. 51 1 THE ELECTRIC ELEVATOR. The advantages of the automatic method of control can hardly be overstated ; with it any person can run the elevator without danger of injuring the mechanism. It is impossible to start or stop with disagreeable suddenness. Car Safeties. — Bach bottom guide shoe of the cage should be provided with a steel safety dog with rods connecting them with the cables, by means of levers in the cross head, so that in case the lifting cables break or slacken, the dogs will throw in at once and lock the car to the guides. Slack Cable Stop. — The winding machine should be pro- vided with an effective device to stop the machine and prevent the slacking of the cables upon the drum in case the car is obstructed in any manner in its descent. Without such device the cables might become entangled with the machine and injured. Automatic Terminal Stops. — Stop balls should be securely fastened to the hand rope by which the switch is operated, in case the operator forgets or fails to pull the rope at terminal landings, so the car stops itself by means of these balls. The winding machine should be provided with a substan- tial and effective device that will accomplish this same result in case the stop balls should fail, from any cause, to do it. Safety Speed Governor. — The winding machine of high speed passenger elevators should be provided with a centrifugal governor, which applies a heavy auxiliary brake to the drum, in case of excessive speed due to any cause, bringing the whole apparatus to a stop. 512 NEW CATECHISM OF ELECTRICITY. Fig. 291. ELECTRIC ELEVATOR FOR PASSENGERS. NEW CATECHISM OF ELECTRICITY. 513 THE ELECTRIC ELEVATOR. Safety Switch. — With some elevators if the electric current is interrupted by breaking of wires or by any other means while the motor is in operation, the car will run down too rapidly for safety ; a switch so constructed as to make this impossible should be provided. Electric Hoist. — A hoist does its heaviest work in starting its load. A steam hoist having two engines with cranks at right angles can only be depended upon at this time for one- half of its rated capacity, as one of the engines may be on a dead center. An electric motor, on the other hand, has no dead centers, and a heavy current in excess of the normal, can be turned into the armature for a few moments without danger. This important advantage is of great value, and gives elec- tric hoists a greater capacity, other things being equal, than a steam hoist. The simplicity, too, is very apparent ; instead of two link motions, we have a simple reversing switch, and the only parts subject to wear in the motor are the two bear- ings and the commutator. (See Fig. 108, page 235.) The power is transmitted to the hoist through an intermedi- ate gear and pinion, which is nicely covered with an iron guard, protecting it from dust, dirt, and liability of accidents. They are particularly convenient where an electric current is easily supplied, and very often they can be run much more economically than with steam. They are also very useful for contractors and railroad work when it is inconvenient to move boilers about the line. The electric wires can easily be run by ordinary workmen, and are always ready to tap at any point. 5 M NEW CATECHISM OF ELECTRICITY. Fig. 292. ELECTRIC ELEVATOR WITH HOIST. NEW CATECHISM OF ELECTRICITY. 515 ELECTRIC TROUBLE" OF WATCHES. There are two well known laws of magnetism that apply- to watches. The first is that any so-called magnetic metal, placed in the field of a magnet, will itself become a magnet, and will retain this magnetism in a more or less marked degree when removed from the field. Steel is an excellent example of such metals. The second law is that similar magnetic poles repel, and dissimilar poles attract, each other. By applying these laws we arrive at a full understanding of the effect of magnetism on a pocket watch of the usual construction, and an explana- tion of its loss of value as a timekeeper. A watch, in the field of a magnet strong enough to stop it, will usually, when removed, at once commence running again, but its time-keep- ing qualities will have been ruined. The parts affected by magnetism are the balance and springs. The balance in an ordinary watch moves five times a second ; 18,000 times an hour, and 432,000 times each day. But a slight change in the forces that move it are necessary to make a difference of several minutes each day. As the balance moves back and forth the magnetism of the main-spring is pulling or pushing it. If this force was constant and always 5l6 NEW CATECHISM OF ELECTRICITY. "ELECTRIC TROUBLE" OF WATCHES. in the same direction the watch would run uniformly. Such, however, is not the case. When the main- spring is tightly- wound its magnetic poles are in a certain direction and in unwinding they are constantly changing, so that the direction of this force is also constantly changed. The effect on the balance is such as to cause the watch to run too fast sometimes and too slow other times. Non-magnetic watches are made with these parts of a non- magnetic metal so that they are not influenced by electric machinery. The very hard steel used for the cylinder wheel of ordinary watches is apt to become "highly magnetized when brought near dynamos running ; and this magnetization, combined with the earth's magnetism, always causes the watch to get slow, and often to stop altogether. In order to annihilate this magnetization, a natural magnet or a powerful electro-magnet must be placed in a horizontal position — on a table, for instance, and the watch held horizon- tally about half a yard off on a level with the magnet. The watch must then be brought slowly nearer the magnet, while being turned slowly, and at the same time as regularly as possible, between the fingers, as on a vertical axis. When the poles of the magnets are reached, the turning of the watch is to be continued, while being gradually withdrawn until the starting point is reached. This simple method has often been adopted with the desired result. NEW CATECHISM OF ELECTRICITY. 517 ELECTRIC CLOCKS. Electric Clocks. — Electrically controlled clocks, governed by a standard central clock, have proved a more fruitful invention. In these the standard timekeeper is constructed so as to complete a circuit periodically, once every minute or half minute. The transmitted currents set in movement the hands of a system of dials placed at distant points, by causing an electromagnet placed behind each dial to attract an arma- ture, which, acting upon a ratchet wheel by a pawl, causes it to move forward through one tooth at each specified interval, and so carries the hands round at the same rate as those of the standard clock. TYPES OF DYNAMOS AND MOTORS- Scattered through this volume will be seen illustrated different types of dynamos and motors. The place of manu- facture of these various machines are given as well as — in some instances — of the name of the makers. It were vain to attempt, within the limits of this volume, to explain the differences, special advantages, and applications of each machine. Every reputable maker of electrical machines, and there are now very many such, stands back, by warranty written or implied, of the promised performance of his product, so each manufacturer is alert to improve by additions or changes his special designed machine. 51 8 NEW CATECHISM OF ELECTRICITY. ACCIDENTS AND EMERGENCIES. The introduction of electricity as an industrial and useful agent has been attended with many distressing accidents, causing great suffering and frequently loss of life. Three instances are given of the latter to emphasize the necessity of constant care and skill in those in attendance on electrical apparatus: 14 Charles Gruive, 30 years old, night electrical engineer of the East River Electric Light Company, was shocked to death at 10:30 o'clock las fc night in the company's plant at 425 East 24th street, New York. He had been standing for several minutes near one of the great dynamos on the second floor, when he was heard by a workman standing close by to utter a slight cry. He fell to the floor, and the workman, run- ning immediately to him, found him unconscious. Physicians from Bellevue Hospital tried a number of methods of resuscitation— artificial respiration, hypodermic injections, etc. — but to no avail. An examination of the body by Dr. Hoyt showed only two burus across the hand, so slight that they would not have been noticed in any other case. The face of the dead man showed no sign of pain, nor was any part of the body distorted. One of the workmen in the building said that the number of volts from the dynamos on that floor was something over 1,200. Gruive lived in Hoboken with a wife and three children, and had been employed for a long time by the company, being considered a care- ful and clever man. He went on duty at 6 o'clock last night in perfect health and in good spirits." " Louis Wentz, a press boy in the Times office, Leavenworth, Kansas, was instantly killed this morning by taking hold of a poorly insulated electric-light wire. The pressroom lights had gone out, and in attempting to regulate them, holding the wire in his left hand, his right hand NEW CATECHISM OF ELECTRICITY. 519 ACCIDENTS AND EMERGENCIES. touched a screw coupling a circuit. The pressman tried to pull the boy away from the wire and received a shock which knocked him senseless for a time." "George Sullivan, a plumber, who was engaged in making repairs at the Birmingham Company's power house, Pittsburgh, Penn., was killed by a live wire at noon to-day. With a fellow workman he mounted a ladder to make a connection near the ceiling. His companion held the pipe, and Sullivan began to drive a nail into the wall to hold it. In strik- ing at the nail he missed it and struck a live wire. An awful flash resulted. Sullivan fell backward, striking another live wire with the back of his neck. He was thrown into the air, and then fell to the floor, dead." Happily, while these accidents are becoming less frequent, none the less it is important to both know and observe the rules for safety so constantly repeated. Reference is again particularly and emphatically made to the "cautions" printed under the heading of Electric Rail- ways, pages 441 and 447 inclusive, as well as to what follows. The Electric Shock. — Currents of electricity passed through the limbs affect the nerves with certain painful sensations, and cause the muscles to undergo involuntary contractions. Note.—' ' A rat in the City Electrical Iyight Works of Baltimore played havcc. He stepped from one brass terminal to another, with his front feet on one pole and his hind fett on the other, thus being subjected to 2, 700 volts. In an instant there was a flash, a heavy ironstone piece of insulation was smashed, the net-work of wires blazed up, setting fire to the wooden frames of the switchboard, and hundreds of houses were plunged in darkness. The hair of the rat was completely burned off and the body became rigid as if suddenly frozen in the act of stepping across the terminals. Although the hair was burned off and even the skull bone protrnded, the body being instantly carbonized and rendered rigid, its attitude, when discovered, was life-like." " Some time ago a tame leopard escaped from its keepers at Bridgeport, Conn., and climbed an electric light pole and began monkeying with the wires. Not being posted in electric science the leopard got knocked out. The skin was presented to a museum." 520 NEW CATECHISM OF ELECTRICITY. ACCIDENTS AND EMERGENCIES. The effect experienced by the discharge of electricity with high potential difference through the animal system is that of a sharp and painful shock ; pain and violent muscular con- traction accompany it. The voltage is the main element of shock, amperage has also some direct influence. Of currents, an alternating current is reputed worse than a direct current, in producing a dangerous shock. Electric Prostration. — The voltaic arc (arc light) is the source of the most intense heat and brightest light producible by man ; too great exposure to its rays in its more powerful forms causes symptoms resembling those of sunstroke. The skin is sometimes affected to such a degree as to come off after a few days. The throat, forehead and face suffer pains, and the eyes are irritated. These effects only follow exposure to very intense sources of light, or for very long times. The condition of the body after death by electric shock corresponds exactly with that found after death by asphyxia. The electric shock paralyzes or destroys the nerve centre which controls the respiratory movements ; the passage of venous blood into the arterial system causes contraction of the arterioles, and finally stoppage of the heart exactly as in death by drowning or suffocation. There is, therefore always hope of resuscitation, except when the respiratory nerve centre has been destroyed. M. D'Arsonval mentions a case in which a workman was stunned by being subjected, for a short time, to a pressure of 4,500 volts. About a quarter of an hour after the accident, assistance arrived, and artificial NEW CATECHISM OF ELECTRICITY. 521 ACCIDENTS AND EMERGENCIES. respiration was practised. In two hours the man was able to speak, and finally was completely restored. The D'Arsonville Hethod of Resuscitation. The proof of the efficacy of this method is now so compler% that no one following electrical pursuits in which there is danger from electric shocks, is justified in neglecting to make himself familiar with it. First, it must be appreciated that accidental shocks seldom result in absolute death unless the victim is left unaided for too long a time, or efforts at resuscitation are suspended too early. In the majority of instances the shock is only sufficient to suspend animation temporarily, owing to the momentary and imperfect contact of the conductors, and also on account of the indifferent parts of the body submitted to the influence of the current. It must be appreciated also that the body under the conditions of accidental shocks seldom receives the full force of the current in the circuit, but only a shunt current, which may represent a very insignificant part of it. When an accident of this nature occurs, the following rules should be promptly adopted and executed with due care and deliberation : i . — Remove the body at once from the circuit by breaking contact with the conductors. This may be accomplished by using a dry stick of wood, which is a non-conductor, to roll the body over to one side, or to brush aside a wire, if that is conveying the current. When a stick is not at hand, any dry 522 NEW CATECHISM OF ELECTRICITY. Fig. 294. ACCIDENTS AND EMERGENCIES. piece of clothing may be utilized to protect the hand in seiz- ing the body of the victim, unless rubber gloves are conven- ient. If the body is in contact with the earth, the coat- tails of the victim, or any loose or detached piece of clothing, may be seized with impunity to draw it away from the con- ductor. When this has been accom- plished, observe Rule 2. 2. — Turn the body upon the back, loosen the collar and cloth- ing about the neck, roll up a coat and place it under the shoulders, so as to throw the head back, and then make efforts to establish artificial Long Acid Glove. respiration (in other words, make him breathe), just as would be done in case of drowning. To accomplish this, kneel at the subject's head, facing him, and seizing both arms draw them forcibly to their full length over the head, so as to bring them almost together above it, and Note. — Linemen's rubber gloves (see illustration) are designed to prevent the frequent and often fatal accidents occurring to linemen from shock while handling electric light wires or other wires in contact with the same, and also the dangers of line work from lightning in stormy weather. The gloves are also useful in handling the strong acids of bat- teries, being impervious to the same. NEW CATECHISM OF ELECTRICITY. 523 ACCIDENTS AND EMERGENCIES. hold them there for two or three seconds only. (This is to expand the chest and favor the entrance of air into the lungs). Then carry the arms down to the sides and front of the chest, firmly compressing the chest walls, and expel the air from the lungs. Repeat this manoeuvre at least sixteen times per minute. These efforts should be continued unremittingly for at least an hour, or until natural respiration is established. 3. — At the same time that this is being done, some one should grasp the tongue of the subject with a handkerchief or piece of cloth to prevent it slipping, and draw it forcibly out when the arms are extended alove the head, and allow it to recede when the chest is compressed. This manoeuvre should likewise be repeated at least sixteen times per minute. This serves the double purpose of freeing the throat so as to permit air to enter the lungs, and also, by exciting a reflex irritation from forcible contact of the under part of the tongue against the lower teeth, frequently stimulates an involuntary effort at respiration. If the teeth are clenched and the mouth cannot be opened readily to secure the tongue, force it open with a stick, a piece of wood, or the handle of a pocket knife. While this is being done, a physician should be summoned. Electric Protector. — This is a protective device for guarding the human body from destructive or injurious electric shocks. In one system, Delany's, the wrists and ankles are encircled by conducting bands, which, by wires running along the arms, back and legs, are connected. A discharge, it is assumed, received by the hands will thus be short circuited around the body and its vital organs. 524 NEW CATECHISM OF ELECTRICITY. CAUTION. Quotation. — " Of nearly all accidents arising from contact with electric wires and electric machines it may be said it is more the want of care than the want of knowledge." The Fig. 295 is a reminder of the necessity for constant care and watchfulness upon the part of all who have aught to do with electricity. DAXGEli SIGNAL. I N DEX Abbreviations, 114, 195. Accidents and Emergencies, 518. Accumulator, Chloride, 461. Adjusting lubricators, 179. Air Gap, Def. of, 120. Alphabet, Morse Telegraph, 479. Alternating Dynamos, 131. Transformer System, 359. Wire System (Ills.), 358. Alternator (Ills.), 208. Machine (Ills.), 314, 315. Alternators with Revolving Arma- tures, 162. Amber, Greek word for, 22. American Giant Dynamo, 188. Ammeter, the, 105. Illustration, 106. Station, 107. Ampere, the, 105 ; def., 117. Animal Electricity, 72. Anode, Def. of, 57. Arc Lamps, Underwriters' Rules Relating to, 382. Lighting, 345, 346; (Ills.), 98. Armature, 127, 128 ; (Ills.), 238. Bar, 143, 138. Core, Laminated (Ills.), 144, 145. Diagram of Ring, 142. Armature, Drum, 138. Ring, 138, 139. Faults in, 231. Grounds in, 241. Heating of, 265. Incorrectly placed in Chamber, 274. '• Points " Relating to, 146. Rubbing against Pole Pieces, 291. Armatures, Short Circuits in, 231, 291. Short Circuits between Sections through Frame or Core, 239. Thomson-Houston (Ills.)^ 139, 141. Western (Complete), (Ills.), 140, 141. Winding of, 296. Winding (Note), 307. Wire Wound, 143. Armor Plates, Electric Drilling of (Note), 503. Arresters, Lightning, Underwriters' Rules for, 376. Atmospheric Electricity, 25. Atom, Definition of, 42. Attention to Brushes, 176. Cutouts, 218. 526 NEW CATECHISM OF ELECTRICITY. Automatic Regulation of Dynamos, 201. Switch (Ills.), 219, 226. Terminal Stops, 511. B. & S., Definition of, 229, 419. Ball and Wood Engine and Dyna- mo (Ills.), 196. Bar Armatures, 143. Bar, Digging (Ills.), 434. Barriett Machine (N. Y.), 268. Battery, Definition, 48, 498. Gauge, 104. Closed Circuit, 49, 50. DanielPs, 55. Leclanche, 53. Smee's, 51. Batteries, Bichromate, 58. Definitions Relating to Primary, 47, 56. Electric, 51. Management and Care of, 59. Open Circuit, 49, 50. Storage, 457. Underwriters' Rules for Pri- mary and Storage, 400, 408. Bearings, Defective, 271, 275, 291. Heating of, 269. Out of Line, 275. Bell Circuits (Ills.), 490, 492. Electric, 486. Magneto (Ills.), 471. Pulls, 496. Telephone (Ills.), 470. Belt, Slack or Dirty, 291. Belt, Safety (Ills.), 441. Too Light, 270. Belting, 323, 325. Belts, Bad Joints in, 293. Bennett's Electroscope, 103. Bible, Wireman's, 373. Bichromate Batteries, 58. Binding Post (Ills.), 367. Bi-polar Dynamo, 125. Birmingham Wire Gauge, 385, 419. Bi-telephone, 474. Block and Falls with ,4 Come- alongs" (Ills.), 438. Blowpots, how to use, 435. Board, Switch (Ills.), 350. Bohenberger's Electroscope, 103. Boiler Repairs, Electric, 503. Booster, Definition of, 228. Boston Machine (Ills.), 245. Bracket, Wood (Ills.), 440. Brown & Sharp Wire Gauge (Ills.), 391. Brush, Rockers, 171. Holders, 170. Brushes, 167, 176. Bad Condition of, 279, 280. Carbon, 168. Heating of, 265. Lead of, 169. 44 Points" Relating to, 171. Strip, 168. Trimming, 187. Wheel, 169. Wire, 168. 44 Bug " and ,4 Bug Trap," Def. of, 195. INDEX. 527 Bunsen Cell, 52. Buttons, Push, 496. Buzzer, Electric, 496. B. W. G., Definition of, 229. C. G. S. System of Notation, 115. Cable Stop, 511. Sub-marine (Ills.), 97. Supporter, 90. Calibration, Definition of, 118. Calculations of Watt Meter, 109. Calculations of " Power of 10," 114. Candle Power, 345. Carbon Brushes, 168. Telephone, 474. Care and Management of the Dyna- mo, 175, 375. Street Car Motor, 453. Car Houses (U. Rules), 400. Safeties, 511. Wiring (U. Rules), 400. Cathode, Definition, 57. Cautions for the Dynamo Room, 447. For Linemen, 433, 524. Cell, Definition of, 56, 498. Bunsen, 52. Faure, 461. Gravity, 54. Latimer Clark's Standard, 55. Plantes, 460. Centimetre-Gramme-Second Sys- tem, 115. (Central Station Testing (U. Rules), 412. Chapter of u Don'ts," 276. Chemical Meter, 110. Chloride Accumulator, 461. Cincinnati Machine (Ills.), 240. Circuit Breakers (Ills.), 450. Circuit, Definition, 498. Moved so as to alter number of lines of force through it (Ills.), 68. Moved without cutting any lines of force (Ills.), 68. Circuits, Bell, 494, 495. Divided, 79. Lamp, 354, 355 ; (Ills.), 356. Circular Mil, 121. Clamps, Guy (Ills.), 442. Clark's Standard Cell, 55. Classification of Dynamo, 131. Cleat and Cover (Ills.), 409. Cleat, Wood (Ills.), 397. Climbers (Ills.), 436. Clocks, Electric, 517. Closed Circuit Battery, 49, 50. " Code," National, of Wiring, 373. Coil, Definition of, 118. Coils, Coupling up Field Magnet, 259. Induction, 339 ; (Ills.), 340, 468. Collecting Brushes, 129. Collector, 129. "Come-along" (Ills.), 448. Commutator, 129. Bad Condition of, 281. Commutator and Brushes, Attention to, 185. Commutators, 161. 528 NEW CATECHISM OF ELECTRICITY. Commutator Lubricant, 187. Heating of, 265. Returning of, 281. Short Circuit in, 246. With Air Gap (Ills.), 162. Flats on, 244. Commuting Transformers, 339. Compass, Mariner's, 113. Needle (Note\ 100. Compound Dynamos in Parallel, 224. Compound Magnets, 34. Wound Dynamos, 134. Condensers, 339, 341 ; (Ills.), 342. Condensing Electroscope, 103. Conductivity, Testing for, 311. Conductors and Non-Conductors, 91. Conductors, Underwriters' Rules Relating to, 384, 405, 406, 411. Conduit Junction Boxes, 415. Conduits, Underwriters' Rules for Wiring, 407, 411. Conduits and Tubes, Note Relating to, 388. <4 Connecting Up" Dynamos, 194. Connections, 212, 285, 294. Connectors (Ills.), 418, 432. Consequent Pole Field Magnet, 156. Controllers, Railway Motor, 428. Converters (U. Rules), 396. Cooking Apparatus (U. Rules), 414. Cooking and Heating Electric Ap- paratus, 413. Copper (Note), 93. Cord, Flexible U. Rules Relating to, 395. Cores, Armature, 144. Counter Electromotive Force, 322. Coupling Compound Dynamos in Series, 224. Coupling of Dynamos, 211. Coupling Series Dynamos in Series, 220. Coupling up Field Magnet Coils, 259. Crooke's Tube, 362. Crown of Cups (Ills.), 59. Cumming, Linnaeses, Quotation from, 16. Current, Electric, 22, 24, 60, 69. (Note), 69. "Points" relating to Electric, 73. Current Sheets, 78. Current, Excessive, 283. Currents, Eddy, 258. Cutouts, Automatic, 218. Line (Ills.), 397. Safety 369. Underwriters' Rules for, 408. Daniell Battery, 55. D'Arsonville Method of Resuscita- tion, 521. Dayton (Ohio) Machine (Ills.), 180. Decorative Series Lamps (U. Rule), 396. Defective Bearings, 291. Defects of Electric Bells, 488. Definitions, 114, 195, 228. Of the National Board of F. U., 402. Relating to Primary Batteries,56. INDEX. 529 Deflection, Definition of, 229, 498. Derivation of the word Magnet, (Note), 27. Designing a Dynamo, 252. Diagram of Ring Armature, 142. Diagram Winding (Ills.), 302, 303. Dialectrics, Definition of, 228. Diaphragm Telephone, 469. Direct Current Dynamos, 131. Direction of Iyines of Electrical Force, 38, 79. Disconnections in Armature Circuit, 243, 286. Diseases of Dynamos, 260. Disc, Built up (Ills.), 140, 141. Discharge, Definition of a, 61. Distortion of Magnetic Field in the Dynamo, 256. Divided Circuits, 79. Dividing I^oad, 217. " Don'ts," Chapter of, 276. Double Field Magnet, 156. Double Pointed Tacks (Ills.), 409. Drag, Propelling, of Motors, 322. Drilling, Electricity in, 504. Drum Armature, 138. Drum Winding (Ills.), 296. Dry Cells, Definition of, 56. Duplex Telegraphy, 483. Dynamics, Definition, 23. Dynamic Electricity, 23, 25. Dynamo, Barriett, 268. Alternating, 131. American Giant, 188. Attention to, after it is started,182. Dynamo, Bi-polar, 125. Boston (Ills.), 245. Care and Management of, 175. Cincinnati (Ills ), 240. Classification of, 125, 131. Complete (Ills.), 130. Definition of, 123. Designing a, 252. Direct Current, 131. Distortion of Magnetic Field in the, 256. Erie (Ills.), 256. Farraday's, 124. Foundations, 173. Four Pole Ring (Ills.), 210. Four Pole with, Connections, 278. General Electric (Ills.), 137. In Action (Ills.), 126. Intake of a, 120. Model Electric lighting (Ills.), 364. Multipolar, 125 ; (Ills.), 230. Overload of, 282, 291. Output of a, 120. Parts of, 127, 128, 129, 130. Parts of Arc Ivight, 288. Philadelphia (Ills.), 246. 41 Points " Relating to, 172. Regulation for a Shunt (Ills.), 205. Simplest Conceivable, 129. Switching a new one into Par- allel, 227. Shutting Down, 190. Troy, N. Y. (Ills.), 202. 530 NEW CATECHISM OF ELECTRICITY. Dynamo, Unipolar, 125. Dynamo-room, Instructions and Cautions for, 447. Dynamos and Motors, Types oi } 517. Compound in Parallel, 224. Compound Wound, 134. Connecting up, 194. Coupling Compound, in Series, 224. Dynamos,Coupling Series, in Series, 211, 220. Diseases of, 260. Excessive Heating of, 264. Regulating, 197. Regulating Compound, 206. Regulating Over Compounded, 207. Regulating Series, 200. Reversal of Polarity of, 284. Separately Excited, 134. Series, 132. Series, in Parallel, 221. Shunt, in Series, 213. Shunt, in Parallel, 214. Shunt Wound, 133 Starting the, 179. Switching into and out of Par- allel, 216. Dynamotor, 334. Early Experiments in Electricity,26. Earth Return, 498. "Earth, to Make," Definition, 499. Wire, 498. Eddy Currents, 258. Eddy Currents in Armature Cores, 266. In Pole Pieces, 269. Edison (Bar) Armature, 138. Bi-polar Generator (Ills), 254. Conduit Junction Box (Ills.), 415. Edison Lamp Socket (Ills.), 352. Edison Meter (Ills.), 110. Eel, Electric (Ills.), 72. Efficiency, Electrical, 120. Electric Batteries, 51. Bell, 486; (Ills.), 486. Bells, Connecting up, 494. Bells, Defects of, 488. Clocks, 517. Current (Note), 60. Current, Experiment (Note), 74. Currents, Summary of Principle, 69. Eel (Ills.), 72. Elevator, 507. Elevator (Ills.), 506, 509, 512 : 514. Energy, 42. Gas Lighting (U. Rules), 395. Heaters, Ranges and Stoves, 413. Hoist, 513. Hoisting Machine (Ills.), 235. Lamp (Ills.), 253. Lighting, 345. Lights and Motors in General Storage Stores, 412. Light Plant Str. "Bay State," 344. Locomotive, 431. Locomotive, Economy of, 332. INDEX. 531 Electric Power Transmission, 326, (Note) 327. Power Transmission for I/mg Distances, 331. Prostration, 520. Protector, 523. Pumps, 500. Pump and Automatic Tank Switch (Ills.), 501. Railway, 422. Shock, 519. Trouble of Watches, 515. Electrical Battery, Action of, 50. Efficiency, Definition of, 120. Machine, Indianapolis(llls.), 122. Measurements, 99. Resistance, 87. Electricity and Magnetism, Differ- ence between, 43. Electricity, Definition, 16, 22, 25. Definition of (Note), 43. Animal, 72. Atmospheric, 25. Current, 22, 24. Derivation of Name (Note), 22. Dynamic, 23. Early Experiments in, 26. Frictional, 25. In Drilling, 504. In Rotation, 22. In Vibration, 22, 24. Magneto, 25. Negative, 23, 24. Positive, 23, 24. Resinous, 25. Electricity, Static, 22, 23. Vitreous, 25. Voltaic, 25. Electrodes, Definition of, 56. Electrolysis, Definition of, 58. Electrolyte, Definition of, 57. Electro Magnets (Note), 40; (Ills.), 76. Ammeters, 105. Magnetic Induction, 83. Magnetism, 35. Meter, 103. Electrometallurgy, 502. Electro-Motive Force, 45. Counter, 322. Electron, Definition, 22. Electro Plating, 504. Electro Statics, 23. Electroscope, 103. Elements, Separating the, 58. Elevator, Electric, 507. Advantages of, 508. Electric (Ills.), 506, 509, 512, 514. "Points " Relating to, 510. E. M. F., Definition of, 114. Emergencies and Accidents, 518. Energy, Definition of, 42. Electric, 42. Kinetic, Potential, Static (Note), 44. Equalizing I^oad, 227. Exciting Fluid, 57. Exchange, Telephone, 474. F., Meaning of, 229. 532 NEW CATECHISM OF ELECTRICITY. Failure to Excite, 261. Fa rra day's Discovery, 63. Dynamo (Ills.), 124. Faults in Armatures, 231. Telegraph Lines, 484. Faure Cell, 461. Feeder Line " Ears " (Ills.), 444. Wires, 455. Field Magnets, 127, 129, 150 ; (Ills.), 153. Heating of, 266. Rule for Connecting up, 193. Field Magnet Windings, 301. Field, Magnetic, 31, 32. Files, Sharpening by Electrical Process, 505 ; (Note), 505. Fixture Work, Underwriter's Rules, 393. Flashing or Sparking, 277. Flats on Commutator, 244. Flemming's Rule, 80. Flow of Water under Pressure or Head (Ills), 126. Flux, Magnetic, 31. Force, Direction of Lines of Elec- trical, 79. Direction of Magnetic, 38. Electro-Motive, 45. Lines of Magnetic, 37. Foucault Currents, Definition of, 229. Foundations for Trolley Pole, 421. Of Dynamos, 173. Four Pole Dynamo with Connec- tions, 278. Franklin's Experiment (Note), 24. Frictional Electricity, 25. Frog's Leg, Discovery, 61. Function, Definition of, 115. Fuse and Connections (Ills.), 454. Blocks, 369. Fuses, 369. "Points" Relating to Safety, 371. Safety (U. Rules), 390; (Ills.), 370. Galvaniscope, 102. Galvani's Discovery,[61. Galvanism, 61. Galvanometer, 101-103. Gauge, Battery, 104. Brown & Sharpe Wire (Ills.), 391. Birmingham Wire (Ills), 385. Micrometer Wire (Ills.), 379. Standard Wire, (Ills.), 391. Gauges, Wire, 419. Geisler Tube, 361. General Electric Dynamo (Ills.), 137. Generator, Edison Bi-polar (Ills.), 254. List of Parts of Edison Bi-polar (Ills.), 255. Generators, Motor, 339. Rules for, 375. Glass Insulator (Ills.), 446. Globe Insulator (Ills ), 440. Glove, Safety (Ills.), 522. Glue-pots, Electric, Underwriters' Rules Relating to, 414. Gold Leaf Electroscope, 103. INDEX. 533 Governor, Safety Speed Elevator, 511. Gravity Ammeters, 105. Cells, 54. Grounds in Armature, 241. Guy Clamp (Ills.), 442. Hanger and Ear (Ills.), 146. Barn or Bridge (Ills.), 454. Heat, Conduction from Armature, 275. Heating and Cooking Apparatus, Electric (U. Rules), 413. Heating of Armature, Commutator, and Brushes, 265. Of Bearings, 269. Of Connections, 264. Of Dynamos, 264. Of Field Magnets, 266. Hoist, Electric, 513. Holders, Brush, 170. Horseshoe Magnet, 34. Houses, Car (U. Rules), 406. How to Use the Telephone, 472. Incandescent Lamps in Series Cir- cuit (U. Rules), 383. Lighting, 345, 353. Index Notation, 114. Induction Coil (Ills.), 340, 471. Coils, 339, 343, 468. Electric Magnetic, 83. Inertia, 114. Inside Wiring (Ills.), 409. Instructions and Cautions for the Dynamo Room, 447. Instructions and Cautions for Line- men, 433, 441. Insulated Wire (Ills.), 471. Insulation, Testing for, 311, 313. Insulator, Glass (Ills.), 446. Globe Strain (Ills ), 89. Rubber Hook, 450. Insulators (Ills.), 440. Porcelain (Ills.), 397. Tree (Ills.), 444. 44 Intake" of a Dynamo, 120. Introduction, 15. Inversely, Definition of, 119. Joints, Direction for Making Good, 493. Making, 433. Journals, Too Tight, 270 ; Badly Fit- ted, 272. Kathode (or Cathode), Definition of, 57. Key and Relay, Telegraph (Ills.), 481. Board (Ills ), 481. Transmitting Telegraph, 476. Kilo Watt, Definition of, 121. Kinetic Energy (Note), 44. Knife Switches, 348. Lag, Magnetic, 31. Laminated Armature Core (Ills.), 145. Definition of, 118. Lamps, Arc (U. Rule), 405. 534 NEW CATECHISM OF ELECTRICITY. Lamp Circuits, 354, 355 ; (Ills.), 356. Decorative Series (XL Rule), 396. Electric, of the Future, 360. Electric (Ills.), 253, 363. Standard Incandescent, "62. Lamp Sockets, 350 ; (Ills.), 352. Lap Winding, 306; (Ills.), 308. Laws of Klectrical Resistance, 88. Lead of Brushes, 169. Leclanche Battery, 53. Lifting Power of Magnets (Ills.), 46. Lightning Arresters, U. Rules for, 376. Lighting, Electric, 345. Electric (Note), Curious Re- marks, 349. Line Appliances, 442, 444. Battery, 499. Cutout (Ills.), 397. Lines of Magnetic Force, 37. Line Work, 433. Lineman's Pliers (Ills.), 436. "Climbers" (Ills ), 436. Construction Tools, 432, 434, 436, 438, 440. Safety Belt (Ills.), 441. Linemen, Instructions and Cautions for, 433. Load, Equalizing, 227. Local Action, Definition of, 57. Battery, 499. Locomotive, Electric, 431. Electric, Economy of, 332. Long Distance Telephone Trans- mitter (Ills.), 468. Lubricant on Commutator, 187. Lubrication, Defective, 270. Lubrications, Adjusting, 179. Machine, Dayton, Ohio (Ills.), 180. Eau Claire, Mo. (Ills.), 166. Electric Hoisting, 235. Siemens-Halske (Ills.), 160. Westinghouse (Ills.), 149. Windsor (Conn.), 174. Magnet, Artificial, 34. Bar (Ills.), 76 Consequent Pole Field, 156. Derivation of the word (Note), 27. Double Field, 156. Horseshoe, 34. Multipolar Field, 158. Natural, 34. Overtype Field (Ills.), 154. • Polarized Electro, 34. " Relay," 483. Salient Pole Field (Ills.), 153. Strength of, 33. Typical Field (Ills.), 153. Undertype Field (Ills.), 155. Magnetic and Electric Current, 60. Field, 31, 32. Flux, 31. Lag, 31. Permeability, 119. Saturation, 31. " Tick, "32. Whirl (Ills.), 66. Magnetism and Magnets, 27. Definition, 22. INDEX. 535 Magnetism, Electro, 35. Residual, 31. Magneto Bell (Ills.), 471. Bell and Generator (Ills.), 490. Electricity, 25. Testing Instrument (Ills.), 473. Magnets and Magnetism, 27. Magnets, Compound, 34 Lifting Power of (Ills.), 46. 11 Points" Relating to Electro, 39. Useful Definitions Relating to,34. "Make and Break," Definition of, 229. Management and Care of Batteries, 59. Mariner's Compass, 113. Matter, Definition of, 42. Maycock, W. Perrin, Quotation from, 17. Mclntire Sleeve and Joint (Ills.), 118. Splicing Tool (Ills.), 438. Measurements, Electrical, 99. Measurement, Method of, 248. Measurement of Electric Pressure, 105. Current Volume, 105. Measurements of Resistance, 112. Mechanical Clip (Ills.), 454. Meter, Chemical, 110. Edison (Ills.), 110,111. Station, 109. Watt, 109. Method of Measurement, 248. Micrometer Wire Gauge, 419 ; (Ills.), 379. Mil, Definition of, 121. Circular, 121. Mines, Electrical Transmission in, 330. Mirror, Galvanometer, 103. Molecule, Definition of, 42. Monocyclic System, 318, 319. Morse Key (Ills.), 481. Telegraph Alphabet, 479. Motor, Care and Management of the Street Car, 453. Motor-Generators, 339. Motor, Street Car (Ills.), 427. Motors, 320, 426 ; (Ills.), 321. Alternating Current, 320. Continuous Current, 320. In Storage Houses (U. Rule), 412. Propelling Drag of, 322. Types of Dynamos and, 517. Regulation of, 209. Underwriters' Rules for Wiring, etc., 377. Mouldings Underwriters' Rules Re- lating to, 388. Mouth Piece, Telephone (Ills.), 468. Multiphase Currents, 317. Multipolar Field Magnets, 158. Dynamo (Ills.), 230. Dynamo, 125. Multiple Series System, 357. Arc System, 357. National Board Fire Underwriters' Rules, 374. Code of Wiring, 373. 536 NEW CATECHISM OF ELECTRICITY. Natural Magnet, 34. Needle, Compass (Note), 100. Negative Electricity, 23. Energy, 45. New York Board of Fire Underwrit- ers Addenda to other Rules, 411. Niagara Falls Electric Power, 333. Non-Conductors and Conductors, 91. Ohm, the, 105. Definition of, 116. Ohm's Law, 116. Open Circuit Batteries, 49, 50. " Output" of a Dynamo, 120. Overhead Transmission (Ills.), 425. Overload of Dynamo, 282, 291. Overtype Field Magnet (Ills.), 154. Parts of Arc Light Generator, 288. Of Dynamo, 127-130. Of Edison Bipolar Generator, (Ills.), 255. Periodicity, Definition of, 119. Periphery, Definition of, 118. Permanent Magnet Ammeters, 105. Permeability, 119. Pith Ball Electroscope, 103. Plante's Cell, 460. Plug, Insulated (Ills.), 440. " Points " Relating to the Armature, 146. Relating to Brushes, 171. Relating to the Commutator, 163-165. " Points " Relating to the Dynamo, 172. Relating to Electric Current, 13. Relating to Electric Elevator, 510. Relating to Electro-Magnets, 39. Relating to Safety Fuse, 371. Polarity, Definition of, 119. Polarization, Definition of. 57. Polarized Electro Magnet, 34. Poles, Definition of, 57. Pole Pieces, 129. Ratchet (Ills.), 432. Support (Ills.), 432. Positive Electricity, 23. Energy, 45. Potential, Definition of, 118. Energy (Note), 44. Power, Candle, 345. Powers of Ten, 114. Practical Operation of the Tele- phone, 470. Preface, 11. Press Buttons (Ills ), 498. Pressure, Electrical, Unit of, 105. Primary Batteries, 47. Propelling Drag of Motors, 322. Prostration, Electric, 520. Protector, Electric, 523. Protectors, U. Rule for Wire, 410. Pull-off and Ear (Ills.), 456. Pulls, Electric Door, 496. Pumps, Electric, 500; (Ills.), 501. Push Buttons, 496. 537 Quadrant Electrometer, 103. Electroscope (Henly), 102. Quotation Relating to Danger, 524. Rail Joints (Ills.), 442. Railway, Electric, 422. Motor Controllers, 428; (Ills.), 429. Ratchet, Pole (Ills.), 432. Receiver, Telephone, 469 ; (Ills.), 468. Reel and Stand (Ills.), 438. Regulating Compound Dynamos, 206. Dynamos, 197. Series Dynamos, 200. Regulation for a Shunt Dynamo (Ills.), 205. Of Dynamos, Automatic, 201. Of Motors, 209. Relay, Telegraph, 483. Reluctance, Definition of, 118. Repair Shop, 452. Residual Magnetism, 31. Resinous Electricity, 25. Resistance Boxes, Definition of, 404. Resistance Boxes and Equalizers, Underwriters' Rules, 376. Resistance, Electrical, 87. Electrical, Unit of, 105. Water (Ills.), 342. Resuscitation, D'Arsonville Method of, 521. Reversal of Polarity of Dynamos, 284. Rheostat and Armature (Ills.), 242, 348. Ring Armature, 138, 139. Ring Windings, 301 ; (Ills.), 296. Rockers, Brush, 171. Rosette, Porcelain (Ills.), 367. Rowland, Prof., Quotation from, 17. Rubber Hook Insulator (Ills.), 450. Tubing (Ills.), 403. Ruhmkorff Coil (Ills.), 340, 343. Rule, Flemming's (Ills.), 81. Rule for Coupling up Field Magnet Coils, 193. Rules and Fecommendationsof Fire Underwriters, 374. Sad-Irons, Electric, etc , U. Rules Relating to, 416. "Safeties," Car, 511. Safety Belt (Ills.), 441. Catches, 369. Fuses, Underwriters' Rules Re- lating to, 390 ; (Ills.), 370. Speed Elevator Governor, 511. Switch, 513. Salient Pole Field Magnet (Ills.), 153, 154. Saturation, Magnetic, 31. Sawyer-Mann I,amp Socket (Ills.), 352. Secondary Batteries (Note), 48. Segments, Loose or Knocked in, 247. Separately Exciter! Dynamos, 134. Series and Parallel Connections, 212. Series Dynamos, 132, 221. Service Blocks (U. Rules), 380. 538 NEW CATECHISM OF ELECTRICITY. Shafting, Bent or Badly Turned, 272. End Pressure of, 273. Sheets, Current, 78. Shock, Electric, 519. Short Circuits between Adjacent Coils, 236. . In Armatures, 231, 239, 291. In Armature Circuit, 286. In Commutator, 246. Or Disconnections in Armature Circuits, etc., 293. In Coils, 232. Shunt, Definition of, 118. Dynamos in Parallel, 214. Dynamos in Series, 213. Wound Dynamos, 133. Shutting Down Dynamo, 190. Siemens Armature, 139. Siemens-Halske Machine (Ills.), 160. Sleeve, 418. Smee's Battery, 51. Sockets, Electric Lamp, Underwrit- ers' Rules Relating to, 395. Lamp, 350. Solenoids, 77. Sparking or Flashing, 277. Speed of Electric Current (Note), 74. Speed, Reduced, of Driving Engine, 290. Irregularities of, 290, 292. Splicing Tool (Ills.), 438. Spring Ammeters, 105. Staggering, Definition of, 119. Standard Wire Gauge (Ills.), 391. Starting Dynamos, 179. Static Electricity, 22, 23. Energy (Note), 44. Station Ammeter, 107. Meter, 109. Station, U. Rules for Power, 408. Steamer " Bay State " Electric Light Plant, 344. Stoletow, A., Quotation from, 17. "Stop," Slack Cable, 511. Stops, Automatic Terminal, 511. Storage Batteries, 338, 457; (Ills.),462. Storage Batteries (Note) 460. Storage or Primary Batteries (U. Rules\ 400. Street Car Motor (Ills.), 427 Strength of a Magnet, 33. Submarine Telegraph, 485. Supporter, Cable, 90. Surface System, Electric Railway f 424. Switch (Ills.), 471. Automatic (Ills ), 219, 226. Automatic Tank and Electric Pump (Ills.), 501. Safety Elevator, 513. Switchboard, 359, 474. Switchboards, 404 ; (Ills.), 350. Underwriters' Rules for, 376. Switches (Ills.), 348. Underwriters' Rules Relating to, 392. Switching a New Machine into Parallel, 227. Dynamos Into and Out of Par- allel, 216. 539 Symbols, Abbreviations and Defini- tions, 114, 195, 228. Synchronous, Definition of, 195. System, Alternating Transformer, 359. Multiple Arc, 357. Multiple Series, 357. Surface Electric Railway, 424. Three-wire, 357. Underground Electric Railway, 424. Of Lamp Distribution, 357. Table of Capacity of Wires, 390. Table Showing the Relative Dimen- sions of Pure Copper Wire, 464. Tacks, Double Pointed (Ills.), 409. Tamping Bar (Ills.), 434. Telegraph Lines, Faults in, 484. Telegraph, 476, 477. Submarine, 485. Telegraphy, Duplex, 483. Telephone, 466. Bell (Ills.), 470. Bi-, 474. Carbon, 474. Exchange, 474; (Note), 474. How to Use the 472. Practical Operation of the, 470. N. Y. System (Note), 469. Terminals (Ills ), 442. Testing Central Stations, U.Rule,412. Circuits, Underwriters' Rule for, 377. Testing for Conductivity, 311. For Insulation, 311. Thomson-Houston Arc Light Gen- erator (Ills.), 289. Armature (Ills.), 139. Lamp Socket (Ills.), 352. Thompson, S. P., Quotation from, 16. Three-wire Incandescent System, (Ills.), 358. Three-wire System, 357. Tick, Magnetic, 32. Tools, Care of (Ills.), 452. Linemen's Construction, 432, 434, 436, 438, 440. List of, for Small Inside Wiring, 368. Torque, Definition of, 120. Tower Wagon (Ills.), 86. Transformer, Operation of, 337. Transformers, 335. Commuting, 339. Transmission (Electric), in Mines, 307. Overhead (Ills.), 425. Power, 326. Transmitter and Receiver (Ills.), 468. Telephone, 469. Transmitting Key (Ills.), 476. Tree Insulators (Ills.), 444. Trimming Brushes, 187. Trolley Cross Over (Ills.), 454. Car (Ills), 420. Frog (Ills.), 440. Wheel 424 ; (Ills.), 448. 540 NEW CATECHISM OF ELECTRICITY. Trolley Wire, Pole, Connections and Foundations (Ills ), 421. Wire, Location of, 452. Wires (U. Rules), 399 Tubing, Rubber (Ills.), 403. Twophase Current, 317. Two- Wire Incandescent System, (Ills.), 358. Types of Dynamos and Motors, 517. Underground System, Electric Rail- way, 424. Undertype Field Magnet (Ills.), 155. Underwriters' Rules and Recom- mendations, 374, 384. Relating to the Alternating Sys- tem, 396. Electric Power Stations, 399. High Potential System, 378. Low Potential Systems, 383. Wiring in Special Places, 388. For Outside Wiring, 386. Unipolar Dynamo, 125. Unit of Pressure, 105. Of Rate of Flow, 105. Of Resistance, 105. Useful Definitions Relating to Mag- nets, 34. Vacuum Tube Electric Lamps, 360. Variation of Speed, 290. Vibrating Electric Bells, 488. Vibration, 295. Electricity in, 22, 24. Vitreous Electricity, 25. Volt, the, 105, 117. Voltaic Electricity, 25. Voltage, Excessive, 283, 292. Voltaic Cell, Definition of, 56. Volta's Discovery, 62. Voltmeter, 108 ; (Ills.), 106. Watches, Electric Trouble of, 515. Water, Illustration of Flow, 126. Resistance (Ills.), 342 Meter for Power Stations (Ills.), 194. Watt, Definition of, 121. Meter, 109 ; (Ills.), 109. Wave Winding, 306 ; (Ills.), 309, 310. Western Armature (Ills ) , 140, 141. Western Union Wire Joint (Ills.), 418. Westinghouse Machine (Ills.), 149. Wheel, Trolley, 424. Brushes, 169. Winding Armature (Note), 307. Diagram (Ills.), 302, 303. Drum (Ills.), 296. For Four Pole Machine (Ills.), 304, 305. For Separately Excited Dynamo (Ills.), 136. L-ap, 306; (Ills.), 308. Machine (Ills.), 454. Of Armatures, 296. Ring, 301 ; (Ills.), 296. Wave, 306 ; (Ills.), 309, 310. Windings, Field Magnet, 301. Wire, Covered (Ills.), 409, 471, 342. 541 Wire, Direction for Making Good Joints, 493. Cutters (Ills.). 434. Gauges, 419. Protectors, U. Rule for, 410. Table Showing the Relative Di- mensions of Pure Copper Wire, 464. Ties (Ills.), 456. Wire Wound Armatures, 143. Wireman's Bible, 373. Wires, Feeder, 455. Ground Return (U. Rules), 400. Table of Capacity, 390. Trolley, Underwriters' Rules Relating to, 399. Wiring, 365. Car (U. Rules), 400. Inside (Ills.), 409. Rules and Requirements, 375. Underwriters' Rules for Special, 407. Wood Bracket (Ills.), 440. Cleat (Ills.), 397. Pin (Ills.), 440. Fig. /HAWKAN'SV, ;:;;i:...:,^..,.,-':;.-- v ---' '■' THE END. 14 Received the set of books O. K. — thought I would go over them thoroughly before expressing my opinion— now I will say I would not be without them. They are a great help to me, aud no engineer or fireman should be without them." KBKNKZER CARTER, Engineer of the Board for the Examination Denver, Col., Jan. 3, '96. of Stationary Engineers. HAWKINS' WORKS Hand-Book of Calculations For Engineers, Machinists and Steam Users, $2- 50 Maxims and Instructions for the Boiler Room, $2- 50 Aids to Engineers' Examinations WITH QUESTIONS AND ANSWERS, $2 New Catechism of Electricity, A PRACTICAL TREATISE, $2 Sent Prepaid to any part of the world upon receipt of price. THEO. AUDEL & CO., 63 SHSJSr N. Y. 543 HAWKINS' New Catechism of Electricity. A PRACTICAL TREATISE. This work is designed to supplement the author's other works. It is bound in red leather, pocket-book form, with titles and edges in gold. It contains 544 pages with 295 illustrations with numerous explanatory notes. The principal subjects upon which it treats are : The Nature Source and History of Elec- tricity; Electric Current ; Primary and Secondary Batteries. The Dynamo ; the Motor ; Electric lighting ; Wiring ; Electric Railways ; Bell Fitting ; Tele- graph and Telephone ; Electric Transmission ; Electric Symbols, Terms and Abbreviations ; Electric Elevators ; Electric Pumps ; Electric Appliances and Tools ; Electric Measurements ; Accumulators ; Cautions for the Dynamo Room ; Cautions to Iyinemen ; Accidents and Emergencies. All these subjects are treated in the plainest and most simple manner, and each subject is profusely illustrated and quite up to date. The price of this work is $2.00, sent to any part of the world upon receipt of amount. THEO. AUDEL & CO., 63 HZStffe N. Y. 544 HAWKINS' Aids to Engineers' Examination WITH QUESTIONS AND ANSWERS. This work has passed through several editions and is revised and thoroughly up-to-date. It contains 224 pages and is bound in red crimson leather with titles and edges in gold — exceedingly handsome and strong. The book contains information not elsewhere obtainable, the main subjects treated, upon which are given detailed in- formation with Questions and Answers are as follows :— - The Steam Boiler, Boiler Braces, Incrustation and Scale, Firing of Steam Boilers, Water Circulation in Boilers, Construction and Strength of Boilers, The Steam Engine, Engine and Boiler Fittings, Pumps, The Injector, Electricity and Electric Machines, Steam Heating, Refrigeration, Valve Setting, etc. It tells exactly what an engineer will have to go through in getting a license, with much kindly and helpful advice to the applicant for a license. It gives a short chapter on the " Key to Success " in obtaining knowledge necessary for ad- vancement in engineering. This is very important. Price, $2.00 to any part of the world. 44 Aids to Engineers' Examinations," with Questions and Answers, by N. Hawkins, M. H. 44 This is a work useful to anyone intending to apply for an engineer's license. Its twelve pages of index shows its wide sc^pe in the treatment of the subject. Each section, as the steam engine, pumps, electricity, refrigeration, etc., are preceded by explanatory paragraphs, stating the underlying principles and laws which govern their practical application; there are also many valuable foot notes and tables. The author, Mr. Hawkins, is already favorably known. The book makes a handsome addition to any library."— American Engineering, July, 1895. THE0.AUDEL4C0.,63^,rJ.N.Y. 545 HAWKINS' Maxims and Instructions FOR THE BOILER ROOM. This volume is uniform in size, binding and illustrations with the " Calculations," by the same author. It is 6 x 9 inches ; weighs 2^ lbs., has nearly 200 illustrations, 331 pages, and is bound in green silk cloth. The " make-up of this book is unique inas- much as it contains a thousand homely "points " of direction for the care and management of the steam producing department of the steam plant ; it also gives all information necessary for the planning, riveting and setting of steam boilers. It also deals with the care and management of steam pumps, injectors, water meters, steam gauges, pipes and piping, steam heating, plumb- ing, etc., etc. The work gives many valuable tables relating to steam, water, strength of materials and rules for figuring the strength of the steam boiler, etc. This book has also been endorsed by the satis- factory purchase of many editions by superintend- ents, chief engineers, steam users, or owners of " steam plants," as well as thousands of firemen, who find in the volume information to them of incalcul- able importance. Send for special descriptive matter. Price, prepaid, $2.50 THEO. AUDEL& CO., 63 3ELS£ N. Y. 546 HAWKINS' Hand-Book of Calculations. 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