t)i 3 
 
 s 
 
 S 
 ^ ^ 
 
 1 ir" s
 
 A condensed and reliable treatise, giving 
 
 full directions for the construction 
 
 and operation of any kind of 
 
 electrical apparatus
 
 COPYRIGHT 1902 BY GEORGE L. Fowuot
 
 CONTENTS 
 
 CHAP. PAGE 
 
 I ELECTRICITY AND MAGNETISM ... 5 
 
 II STATICAL ELECTRICITY, THE PLATE MACHINE 
 
 AND THE LEYDEN JAR . . . .14 
 
 III CONDUCTORS, CONNECTIONS, INSULATION AND 
 
 BATTERIES 26 
 
 IV ELECTRIC BELLS 47 
 
 V THE ELECTRIC TELEGRAPH . .69 
 
 VI THE TELEPHONE 87 
 
 VII DYNAMOS AND MOTORS 106 
 
 VIII ELECTRIC LIGHTING 123 
 
 IX ELECTRO-PLATING ,.,.-.-, . , .144 
 
 X STORAGE BATTERIES 160 
 
 XI TRANSFORMERS ... . . ,, .... . 172 
 
 XII BURGLAR ALARMS AND GAS LIGHTING . .179 
 
 XIII ELECTRICAL EXPERIMENTS . . . .194 
 
 GLOSSARY 200 
 
 431656
 
 Electricity 
 
 CHAPTER I 
 
 ELECTRICITY AND MAGNETISM 
 
 THE manifestations of electrical phenomena 
 have been known to man ever since he first 
 came to consciousness, in the misty ages of the 
 past. It is quite true that he did not recognize 
 them as such but attributed them to the anger 
 or pleasure of his gods according as they were 
 terrifying or attractive. It is far easier to con- 
 ceive a superstitious cause for natural phenomena 
 than it is to search out the hidden secrets of 
 nature and learn the true reason for the other- 
 wise inexplicable things that occur before our 
 eyes. 
 
 So, while man must have observed the forces 
 that we now know to be merely manifestations 
 
 5
 
 6 Electricity 
 
 of that subtle influence, which we call electricity, 
 from the earliest age^ 01 his existence, the first 
 recorded observance of it cemes to us from the 
 Greeks. 
 
 They had found that the beautiful amber pos- 
 sessed, when rubbed with a cloth or fur, the 
 power of attracting to itself light particles of 
 dust or parchment. Like all other supersti- 
 tious people they attributed this action to the 
 spirit that dwelt within the amber and which 
 was aroused to action by the warmth generated 
 by the friction of the rubbing. It was a slight 
 matter but, nevertheless, it was so invariable in 
 its action and was so peculiar to this one sub- 
 stance that the Greek name for amber or " elec- 
 tron," has been handed down through the cen- 
 turies as that of the wonderfully subtle force 
 that is revolutionizing the world and which bids 
 fair to have an era of its own just as we have 
 had the eras of bronze and iron and silver and 
 gold. 
 
 The manifestations of attraction and repulsion 
 of the amber or electron were noted first as a 
 superstition ; then as an indifferent matter of 
 e very-day occurrence and finally as a subject 
 worthy of scientific investigation and in- 
 quiry.
 
 jeiectdcftE anD /toagnettem 7 
 
 Meanwhile in the heavens above and the earth 
 beneath there were greater and more imposing 
 manifestations of this same force, but on a scale 
 so grand that the untrained minds of the men 
 before whom they appeared could not conceive 
 of the possibility of connecting the one with the 
 other. What possible relationship could exist 
 between the blinding flash of lightning and the 
 deafening roar of the thunder, or the soft scintil- 
 lating light of the aurora borealis and that yellow 
 bit of amber in a woman's hand that silently 
 draws the dust or threads of cotton to itself ? It 
 was far easier to attribute one to the bolts of an 
 angry god or the warfare of the demons of the 
 air, the other to the reflected light from the ban- 
 queting halls of the rulers of earth and sky, and 
 the last to the spirit sleeping within the bit of 
 gum, than connect the three into different mani- 
 festations of one and the same power, differing 
 only in intensity and not in kind. Surely noth- 
 ing could appear more widely different than the 
 flash of the lightning, the scintillation of the 
 northern light and the fluttering of a bit of 
 paper about a piece of amber. Yet we have 
 learned that they are the same in kind and differ 
 only in degree. 
 
 For many centuries the world was quite con-
 
 8 BlectrtcttB 
 
 tent to stand in wonder and awe at what it saw 
 with never a thought of search or investigation. 
 It was not until the sixteenth century that any- 
 thing approaching a scientific inquiry was made 
 into the peculiarities of the manifestations of the 
 rubbed amber. At first progress dragged and 
 nearly three centuries were to elapse before the 
 electric manifestations were to be harnessed so 
 as to do duty in the service of mankind. In fact 
 it was not until the second quarter of the eight- 
 eenth century that there was any clear concep- 
 tion of the electrical properties of different sub- 
 stances. The first step was the discovery of the 
 difference existing when friction was applied to 
 different materials. It led to the division of 
 electricity into two kinds ; the vitreous and res- 
 inous. The former was supposed to be produced 
 when friction was applied to amber, sealing wax 
 or any other resinous substance. Yitreous elec- 
 tricity was excited when friction was applied to 
 glass, rock, crystal or the precious stones. It 
 was also seen that the objects charged with a 
 similar electricity repelled each other and that 
 those charged with dissimilar attracted. The 
 more modern investigations have shown that it 
 is a case of polarity rather than a true difference 
 and that the vitreous electricity corresponds to a
 
 Electricity anD /flbaanetfsm 9 
 
 positive and the resinous to what is known as a 
 negative charge. 
 
 The power of communicating a charge from 
 one substance to another and the conductivity of 
 certain materials by which the electric charge 
 was carried from one point to another followed 
 and it was found that the metals were good con- 
 ductors while glass, porcelain, silk, cotton, hair, 
 etc., were non-conductors or insulators. The fact 
 is, all substances are conductors and it would be 
 impossible to draw a hard and fast line on either 
 side of which could be grouped the conductors 
 and non-conductors. It is a case of more or less 
 resistance to the passage of the electric current. 
 In the case of silver and copper the resistance is 
 so slight that these metals are considered to be 
 the best of conductors. In iron the resistance is 
 greater, but still not so great as to debar it from 
 being considered as a conductor and being almost 
 universally used for telegraph purposes. When, 
 however, we come to glass, porcelain, silk and 
 parafine the resistance is so great that they are 
 said to be non-conductors or insulators, and are 
 used, therefore, as a means of support for those 
 metals that are employed for the conduction of 
 an electric current from one point to another. 
 
 This property of the variation in electrical
 
 10 electricity 
 
 charges and conductivity of metals led to the 
 discovery of the Leyden jar. It had been " ob- 
 served that electrified bodies exposed to the at- 
 mosphere, speedily lost their electric charge, the 
 idea was conceived of surrounding them with an 
 insulating substance, by which it was thought 
 that their electric power might be preserved for 
 a longer time." Water contained in a glass bot- 
 tle was accordingly electrified, but no remark- 
 able results were obtained, till one of the party 
 who was holding the bottle, attempted to dis- 
 engage the wire communicating with the prime 
 conductor of a powerful machine ; the conse- 
 quence was that he received a shock, which, 
 though slight compared with such as are fre- 
 quently taken for amusement from a Leyden jar, 
 his fright magnified and exaggerated in an 
 amusing manner. In describing the effect pro- 
 duced on himself he says " that he felt himself 
 struck in his arms, shoulders and breast, so that 
 he lost his breath and it was two days before he 
 recovered from the effects of the blow and 
 terror, and that he would not take a second 
 shock for the kingdom of France." 
 
 The sparks emitted upon the discharge of a 
 Leyden jar, owing to their peculiar character- 
 istics led Franklin to his famous experiments
 
 Blectrfcftg and /iRagnetism n 
 
 with a kite by which he succeeded in drawing 
 electricity from the clouds and charging a Ley- 
 den jar and thus establishing the identity of the 
 lightning with the gentle manifestation of the 
 attraction of a slip of paper to a piece of rubbed 
 ceiling-wax or amber. 
 
 Another natural phenomena which is closely 
 associated with electricity is that of magnetism, 
 though for centuries it was regarded as en- 
 tirely separate and distinct. The first manifesta- 
 tion of magnetic phenomena to be observed was 
 that of the loadstone or magnetic iron ore. It 
 was found that a piece of this material freely 
 suspended in the air would turn in a certain 
 definite position in which one side was turned 
 towards the north. It was also found that a 
 piece of iron rubbed against this magnetic iron 
 ore acquired the same property and that if it 
 were done with steel the property became a per- 
 manent one. This led to the discovery of the 
 mariner's compass. 
 
 It was not, however, until the nineteenth 
 century that the connection between electricity 
 and magnetism was so thoroughly established 
 that it became possible to convert the manifesta- 
 tions of either one to the other. 
 
 It has been found that if a wire is bent into a
 
 12 
 
 Blectricitg 
 
 coil as shown in Fig. 1, and a current of elec- 
 tricity be made to pass through it it will possess 
 all of the properties of a magnet. The coil here 
 shown is that known as a left hand coil, and if a 
 
 current be pass- 
 ed through in 
 the direction of 
 the arrows from 
 what is marked 
 the positive (-f ) 
 end of the wire 
 
 FIG. I.-THE SOLENOID to the ne g ati ^ 
 
 ( ) end, and it 
 
 be left free to swing, it will stand with its X end to 
 the north and the S end to the south exactly as 
 the compass needle will do. If a similar current 
 be passed through such a coil in the opposite di- 
 rection the poles will be reversed and the posi- 
 tion assumed by the coil when allowed to swing 
 freely will also be reversed. 
 
 If now a bar of soft metal be placed within 
 such a coil it at once becomes magnetized with a 
 strength that depends upon the number of coils 
 and the intensity of the current. In case such a 
 piece of iron is free to move it will travel 
 through the coil under the magnetic influence of 
 the electric current that flows through the wire.
 
 jeiectrfcftg anD flBasnettem is 
 
 As the electric current passing through the 
 wire possesses the power to magnetize a piece of 
 metal that is within it, so a permanent magnet 
 moved through or made to approach or recede 
 from the coil has the power of inducing an elec- 
 tric current through the wire. 
 
 It is upon this mutual interaction of the cur- 
 rent and the magnet upon each other that the 
 whole field of modern electric operation depends. 
 The dynamo and telegraph instrument are the 
 most familiar examples of this action as will be 
 shown later on.
 
 CHAPTEE II 
 
 STATICAL ELECTRICITY, THE PLATE MACHINE 
 AND THE LEYDEN JAR 
 
 WHEN a piece of ambef, resin, ceiling wax or 
 glass is rubbed and an electrical condition in- 
 duced, it is said to be charged with static elec- 
 tricity in distinction from dynamic electricity, 
 which will be explained later. This static elec- 
 tricity is of such a character that if the charged 
 body be brought into contact with another body 
 charged with the opposite kind, the two will flow 
 together, neutralize each other and cause the 
 instant disappearance of every trace of the elec- 
 trical charge. 
 
 While the rubbing of a piece of wax or amber 
 may be quite sufficient to charge the same to an 
 extent that will cause it to attract particles of 
 dust, slips of paper or balls of pith, it will be 
 quite insufficient to give manifestations requiring 
 greater power such as the production of a spark. 
 
 Then, too, it has been found that the electric 
 charge is evenly distributed over the whole sur- 
 14
 
 Statical Electricity 
 
 15 
 
 face of the charged body. As these substances 
 are usually bad conductors the relief of the 
 charge is slow and fails to meet the requirements 
 of experimental or practical work. 
 
 The usual method of generating a charge of 
 statical electricity is by the use of what is known 
 as the plate machine that is shown in Fig. 2. 
 
 This machine 
 consists of a cir- 
 cular plate of 
 glass that is 
 mounted upon a 
 shaft made to ^^ 
 turn in a wooden 
 frame by means 
 of a crank and 
 handle. Press- 
 ed to either side 
 of the glass at 
 the top and bot- 
 tom is a rubber 
 made of cloth, 
 felt or soft leather. About the best material 
 to use for this purpose is a soft chamois leather 
 backed by a cushion so that it exerts an even 
 pressure upon the glass. By placing them at the 
 top and bottom and on both sides of the glass 
 
 FIG. 2. THE PLATE MACHINE
 
 16 BlectrtcftB 
 
 the pressure is equalized and distortion of the 
 glass plate is prevented. 
 
 At right angles to the rubbers on the circle of 
 the plate there is a frame from which a number 
 of sharp points project which are brought up so 
 that they are almost in contact with the plate. 
 These points and the frame to which they are 
 attached are connected by a good conductor to 
 what is known as the prime conductor. The 
 latter is usually made of hollow brass, and it is 
 supported with the frame and its pointers upon 
 glass columns so as to insulate it from the main 
 frame of the machine. 
 
 The operation of such a machine is exceedingly 
 simple. The plate is caused to revolve and the 
 frictional action of the rubbers upon it charges 
 it with electricity. As the successive portions of 
 the plate pass beneath the insulated points the 
 charge is drawn off and carried by them to the 
 prime conductor, from which it can be drawn in 
 turn to the Leyden jar wherein it is to be stored. 
 
 In making such an electrical machine a few 
 necessary precautions must be taken in order to 
 secure the best results. The glass should be of 
 a good quality of plate glass about ^ inch thick, 
 and should be so mounted upon its shaft that 
 when the latter is turned in its bearings the plate
 
 Statical Electricity 17 
 
 will run true and without wabbling. The rub- 
 bers should be cushioned by packing them with 
 some soft, yielding and yet elastic material so 
 that they may exert a constant and even pres- 
 sure against the sides of the plate. The frame 
 upon which this plate with its shaft is mounted 
 should be preferably of wood. This is because 
 wood is a comparatively bad conductor and will 
 tend to prevent an escape of the charge into 
 the earth rather than into the prime conductor 
 whither it is desired that it should go. 
 
 It is a peculiarity of this method of generating 
 electricity that if a piece of glass is rubbed and 
 thereby excited with a charge of positive elec- 
 tricity, the material used as a rubber is, at the 
 same time, charged with negative electricity. 
 Now if the two are kept in contact these oppo- 
 site charges will flow towards each other and 
 become neutralized. In order to prevent this it 
 is necessary that the negative electricity should 
 be removed from the rubbers of the plate machine 
 as rapidly as it is generated. In order to do this 
 it is customary to place a chain in metallic con- 
 tact with the rubbers and allow one end to lie 
 upon the table or floor upon which the machine 
 rests, This enables the positive electricity exist- 
 ing in the earth to approach and flow up to the
 
 18 ^electricity 
 
 rubber and render it inert by neutralizing the 
 charge contained therein. Meanwhile the posi- 
 tive charge is increasing in the prime conductor. 
 
 The form of the prime conductor must also 
 receive consideration. It should be made hollow 
 for the sake of lightness, and because it has been 
 found that an electric charge distributes itself 
 over the outside of a body and does not pene- 
 trate the interior. 
 
 It has also been found that the discharge takes 
 place much more freely from sharp points and 
 angles than it does from rounded surfaces. For 
 this reason, where there is to be a collection, 
 special discharge points are used, while equal 
 care should be exercised in the making of the 
 prime conductor that it should have no exterior 
 angles or sharp projections. 
 
 As for dimensions any diameter of glass can 
 be used, but it will be found that a convenient 
 diameter will lie between 18 inches and 3 feet. 
 
 When operating the machine, the leathers 
 should be occasionally rubbed over with an 
 amalgam of zinc, tin and mercury, or better still 
 with the bi-sulphuret of tin which is one of the 
 most efficient materials for exciting on glass. 
 
 In case of large and powerful machines it is 
 possible to mount two plates upon one shaft.
 
 Statical Blectrfcfts 19 
 
 "When such a machine is well adjusted and is 
 put into motion, the first thing to be noticed is 
 that it produces a crackling noise which can be 
 located at the collecting points. Then if the 
 knuckles of the hand are brought near the prime 
 conductor a spark will leap across the interval 
 between them with a sharp snap, causing a prick- 
 ing sensation. 
 
 If now the room be darkened various mani- 
 festations of light will be observed. Brushes of 
 pale blue light will be seen to emanate from 
 some of the most angular portions of the prime 
 conductor and circles of light will snap along 
 over the face of the glass between the rubbers 
 and the collectors. Then if the working be con- 
 tinued for any length of time, a peculiar odor 
 can be detected due to the presence of ozone 
 that seems to be invariably present at the devel- 
 opment of electricity. 
 
 The peculiar attractive and repellent character- 
 istics of an electric charge can also be made very 
 manifest in connection with the plate machine. 
 By bringing a charged body near another which 
 is not charged there will be an attraction of the 
 opposite electricity to that of the charged body 
 in that end of the uncharged one that is nearest 
 to the charged. If two pith-balls are suspended
 
 20 
 
 Blectricits 
 
 from the end of either body they will be charged 
 with electricity corresponding to that one. Under 
 the influence of this charge they will be repelled 
 from each other. Thus a physical demonstration 
 will be afforded of the attraction of opposite and 
 the repulsion of like charges of electricity. 
 The Leyden jar, which is used for storing or 
 condensing electricity is one of the 
 simplest if not the very simplest of 
 any electrical instrument to make. 
 The common form is shown in 
 Fig. 3. It consists of a glass jar 
 with a large mouth that is coated 
 inside and out for about two-thirds 
 of its height with tinfoil. Through 
 the stopper a brass rod having a 
 knob at the upper end is passed, 
 and the lower end of the same is 
 connected by a chain, or other 
 metallic conductor to the inner coat- 
 ing. In case it is desired to make 
 the jar without going to the trouble of coating 
 the interior surface, equally good results can be 
 obtained by filling the jar about two-thirds full 
 of foil or other metallic clippings. 
 
 The charging of a Leyden jar is exceedingly 
 simple. The plate machine already described is 
 
 FIG. 3. THE 
 LEYDEX JAR
 
 Statical BlectrfcftE 21 
 
 put in motion and the knob of the jar is held in 
 contact with the prime conductor of the machine, 
 the outer coating of the jar being in electrical 
 contact with the earth. It is quite sufficient that 
 the jar is held in the hands as the conductivity 
 of the body of the operator will be equal to 
 the work. "No sensation will be experienced in 
 the hands or body while this work is in progress. 
 
 The intensity of the charge that a Leyden jar 
 is capable of receiving depends upon the extent 
 of the surface of the coating and the distance be- 
 tween the nearest points of metallic or electrical 
 contact between the inner and outer coatings. 
 The greater the surface of the coatings the more 
 intense can the charge be made. If the charge 
 be made too great for the capacity of the jar a 
 spark will leap through the air across the interval 
 between the coatings and the charge will in- 
 stantly disappear. 
 
 "Where it is desired to store a very intense 
 charge several Leyden jars may be used together 
 in a battery. The ordinary method of forming 
 such a battery is to place the desired number of 
 jars together in a box with their outer coatings 
 in metallic contact with each other and the earth. 
 The inner coatings are also electrically connected 
 by a metallic circuit. The whole battery may
 
 22 
 
 then be charged in the same manner as a single 
 jar. For convenience a metallic rod having a 
 ball at each end and a glass or insulated handle 
 is used to carry the charge from the prime con- 
 ductor of the plate machine to the battery. In 
 this way a charge can be stored that will leap 
 across many inches of space. 
 
 There are a few precautions that should be 
 taken in the making and operation of .Ley den 
 jars, in order that satisfactory results may be 
 obtained. 
 
 In the first place a good quality of glass, that 
 is free from air holes, distortions and defects 
 should be used. A poor quality of glass is likely 
 to be perforated by even moderate charges, and 
 then the jar will be useless, for the charge will 
 pass directly through to the outer coating and be 
 dissipated on the earth. But even when the best 
 quality of glass is used an over-charge may 
 pierce the glass. As already stated the differ- 
 ence between a conductor and a non-conductor is 
 a difference in the resistance which they offer to 
 the passage of an electrical current. Glass, for 
 example, is called a non-conductor because the 
 resistance offered by it to the electrical current 
 is very high. 
 
 The passage of a current through any con-
 
 Statical Electricity 23 
 
 ductor causes heat and the greater the re- 
 sistance offered the higher will be the tempera- 
 ture produced. So, when a charge in a Leyden 
 jar is sufficiently intense to cause it to pierce the 
 glass, the resistance offered by the latter pro- 
 duces so high a local temperature that the un- 
 equal expansion of that and the surrounding 
 parts causes a rupture to take place. 
 
 This same resistance and the resulting eleva- 
 tion of temperature is what causes a stroke of 
 lightning to set fire to a building or char the 
 body of a man or animal that is struck. 
 
 With a well constructed battery of Leyden 
 jars, the spark or discharge may be made to leap 
 across many inches of space intervening between 
 the points in contact with the inner and outer 
 coatings of the jars. Observation has shown 
 that this spark possesses the same characteristics 
 that have been observed in a flash of lightning. 
 That is to say, it apparently follows a zigzag 
 course with sharp angles between the straight 
 lines. The duration of such a spark is exceed- 
 ingly short. Just what its actual duration is has 
 not been determined with an accuracy that is ac- 
 cepted as final. It has been shown, however, 
 that the discharging spark from a Leyden 
 jar lasts less than Tsfav of a second and it
 
 24 Electricity 
 
 is very probable that it lasts less than 
 part. 
 
 In the charging and discharging of Leyden 
 jars great caution should be exercised that the 
 discharge does not pass through the body. In 
 the cases of small jars no physical injury will 
 probably result from such an occurrence. The 
 only effect will be the sudden shock and twitch- 
 ing of the muscles through which the discharge 
 takes place. In the case of a large battery, how- 
 ever, that is capable of causing a spark to leap 
 across an interval of from six inches to eight 
 inches, the effect of passing it through the body 
 may be fatal. Such shocks should be especially 
 avoided by all persons who have weak hearts. 
 
 The Leyden jar cannot be used for ordinary 
 electrical operations such as the driving of 
 motors, the ringing of bells and other work of a 
 similar character. Its feature is that it instantly 
 discharges itself and becomes perfectly inert the 
 moment the spark or charge is allowed to leap 
 across the interval separating the inner from the 
 outer coating. This statement needs, however, 
 a slight modification. 
 
 If the jar is allowed to stand for a few mo- 
 ments after the discharge, it will be found that 
 another, but very much fainter discharge can b0
 
 Statical Electrtctts 25 
 
 obtained. This is due to the fact that the main 
 discharge has taken place in such an inconceiv- 
 ably short interval of time that the whole charge 
 has not had time to reach the discharging point 
 before the resistance of the air interval becomes 
 too great to allow it to pass. The remainder 
 therefore spreads itself out over the coating and 
 is ready to produce a smaller and much weaker 
 discharge. This may sometimes be repeated 
 several times, in the case of large and powerful 
 batteries, each succeeding discharge becoming 
 weaker than the preceding. Such charges are 
 known as residual charges. 
 
 As the discharge of a Ley den jar may take 
 place through the glass of the jar itself, so the 
 discharging spark may be made to pierce and 
 perforate any non-conducting material placed be- 
 tween the discharging points. As the spark 
 leaps across the interval it comes into contact 
 with this material of high resistance and instantly 
 enough heat is generated to burn a hole through 
 the substance thus interposed. In this case, too, 
 the fractures resemble those of lightning on a 
 smaller scale.
 
 CHAPTER III 
 
 CONDUCTORS, CONNECTIONS, INSULATION AND 
 BATTERIES 
 
 IT has already been explained in a previous 
 chapter that all substances will conduct electric- 
 ity but with very different degrees of resistance. 
 Where it is desired to conduct an electric current 
 from one point to another a material that offers 
 a low resistance to the passage of the current is 
 used. Silver is probably the best material for 
 electric conductors and it is sometimes used on 
 very delicate and expensive instruments ; but it 
 is too costly for ordinary commercial use. Cop- 
 per stands so high upon the list of good conduc- 
 tors that it is very extensively employed. 
 Where the cost of this metal is too great, iron is 
 used. 
 
 Where it is impossible or undesirable to use a 
 single unbroken piece of metal throughout the 
 whole distance over which it is desired to carry 
 the current or charge, several pieces may be 
 used. When this is done care should be taken 
 
 26
 
 Conductors, Connections 27 
 
 in connecting one of these pieces with the other, 
 to see that the contact between them is intimate 
 and metal to metal so that the resistance to the 
 passage of the current may be reduced to a mini- 
 mum. This union may be effected in several 
 ways. Fig. 4 shows the simplest and easiest 
 method of do- 
 ing this work. 
 The wires FIG. 4. THE AMERICAN TELEGEAPH 
 should first be SPLICE 
 
 scraped until they are bright and then be brought 
 together and tightly twisted. This insures several 
 points of actual metallic contact so that when 
 well made there is little or no loss of energy in 
 the transmission of the current through the 
 wire. 
 
 Other and more troublesome methods consist 
 in bringing the two ends together and either 
 soldering or brazing them. This need only be 
 done where very large conductors are used, 
 where heavy currents are to be transmitted or 
 where it is necessary to economize in space and 
 it is undesirable to increase the diameter of the 
 wire. 
 
 In laying a conductor for the transmission of a 
 current, great care should be taken to see that it 
 is properly insulated. If the earth is used for
 
 28 BlectrtcftE 
 
 the return current the wire should be separated 
 from it by some good non-conductor or an air 
 space of such width that the current cannot leap 
 across the space or gap. 
 
 As to the materials to be used it may be taken 
 that copper is the metal to be used under ordi- 
 nary conditions. This includes all house and 
 outdoor wiring for usual distances. For long 
 distance work, iron may be used to save expense 
 but copper is rapidly coming in for even this 
 purpose on account of the greater efficiency and 
 decreased cost of operation. 
 
 In regard to insulation, for a bare wire, a glass 
 or porcelain support should be used. For small 
 work these supports can be screwed to any part 
 of the wall. The fastening should, however, be 
 secure and strong so as to insure the insulator 
 
 against being torn 
 away by the ten- 
 sion of the wire. 
 A convenient 
 FIG. 5. WIEE AND INSULATOR me thod is shown 
 
 in Fig. 5. This 
 
 consists in laying the main wire up against 
 the insulator and binding it there by a short 
 length of wire twisted about it at either side as 
 shown. The main wire may also be passed
 
 Conductors, Connections 29 
 
 around the insulator so as to form its own fasten- 
 ing. In any case the main wire should be drawn 
 taut so that the sag is reduced to a minimum. 
 The wire must never be allowed to sag so that it 
 will touch anything outside the conductors. 
 
 The difficulty of running bare wires along 
 walls and ceilings for interior work is such that 
 it is never used for that purpose. Insulated wire 
 is invariably used. This consists of a copper wire 
 covered for its whole length with some flexible 
 insulating material. There are various composi- 
 tions used for this purpose adapted to different 
 classes of work. For ordinary interior work 
 such as bell, telegraph and telephone work, a 
 copper wire insulated with a wrapping of cotton 
 thread dipped in parafine is used, with a coating 
 of parafine on the outside to protect the whole 
 from moisture. For electric lighting work, the 
 insulation is usually of some rubber or asphalt 
 composition that is thicker than the cotton wind- 
 ing and less flexible but still sufficiently so to 
 permit of easy adjustment. 
 
 The fastening of insulated wires is less difficult 
 than where bare wires are used. For light 
 wires or where the service is to be but tempo- 
 rary and only light currents are to be used, the 
 cotton-wrapped wires may be attached to the
 
 so jElectrfcftB 
 
 partition or wall by means of ordinary double* 
 pointed tacks. When this method is pursued 
 care should be taken that the tack straddles the 
 wire, that it does not cut into the insulation on 
 either side and that it is not driven home so tightly 
 as to cut into the insulation from the top. If 
 this is done the metal of the tack will be apt to 
 come into contact with the copper of the wire 
 and short-circuiting be the result. Such short 
 circuits are exceedingly difficult to locate and 
 should therefore be avoided in the stringing of 
 the wire in the first place. 
 
 The term short-circuiting is used to express 
 the fact that the current takes a shorter circuit 
 from one pole of the battery to the other. It 
 will always follow the path of least resistance and 
 if there is any way by which it can get across 
 from the outgoing to the return wire without 
 traversing the whole length of the circuit it will 
 do so. Hence any breakage of the insulation 
 that puts the two wires in contact with each 
 other will cause a short circuit and cut the cur- 
 rent off from the point where it was intended 
 that it should do its work. 
 
 Under no circumstances should an attempt be 
 made to hold two wires beneath one and the 
 same tack. They will be almost certain to be
 
 Conductors, Connections 31 
 
 crowded together at some point and cause a 
 great deal of annoyance by the short-circuiting 
 that will result. Always string each wire of a 
 circuit separately if it is desired to avoid such 
 annoyances. 
 
 It is understood that by a circuit is meant 
 the line of wire or electrical connections extend- 
 ing from one pole of a battery to the other and 
 thence through the battery to the original pole. 
 
 This method would not be allowed by the fire 
 underwriters for electric lighting work. Here 
 the insulated wires are themselves held to or 
 clamped between other in- 
 sulators. A common method 
 is to hold the wire clamped 
 between two grooved pieces 
 of wood as shown in Fig. 6. Fia. 6. HOLDING 
 The upper piece rests against CLA MPS FOB INSU- 
 the wall or ceiling and one or LATED WmES 
 two screws can be made to hold the whole in 
 position. Fig. 6 shows the clamp holding two 
 wires ; the outgoing and the return. 
 
 When a length of wire has been used and it is 
 necessary to couple on another length, the work 
 can be done in practically the same manner as 
 with the bare wire as shown in Fig. 4. The 
 insulation is to be cut away for a distance back
 
 32 jeiectricftg 
 
 from the ends of the wires to be joined and they 
 are to be scraped bright and free from all oxidi- 
 zation. They are then t \visted together, after 
 which the bare portion should be tightly wrapped 
 with adhesive insulating tape. The job will be 
 improved if the joint is soldered or brazed before 
 being wrapped. The object is to make such a 
 joint that its conductivity is equal to that of the 
 uncut wire. This avoids all danger of sparking 
 and heating. If this should occur the insulation 
 would be apt to take fire and a disaster be the 
 result. Many serious fires have occurred because 
 of the failure to pay attention to these little de- 
 tails in the original stringing of the wires. 
 
 In addition to the important element of the 
 conductor for the conveyance of the current 
 from one point to another, we have the other 
 still more important one of the generation of the 
 electric current to be carried. We have already 
 seen how an electric charge that may be stored 
 in a Leyden jar may be developed by the rubbing 
 of a glass plate. But this statical form of elec- 
 tricity disappears on the instant of the closing of 
 the circuit leaving the parts inert and dead. 
 
 Where there is to be a continuous manifes- 
 tation of electrical energy there must, therefore, 
 be a continuous development or generation of
 
 Conductors, Connections 33 
 
 the current. At the present time this is accom- 
 plished in two ways, by the use of a battery or a 
 dynamo. The former is used where small quan- 
 tities and low voltages (a term that will be ex- 
 plained later) are required, and the latter where 
 the conditions are reversed, at least so far as 
 quantity is concerned, though the voltage may 
 still be low. 
 
 For such work then as the ringing of bells, 
 the local work of the electric telegraph and tele- 
 phone, the operation of signals and the like, a 
 battery of some form is used. It is less expen- 
 sive to install and as it does not require the con- 
 stant attention that a dynamo does, it is more 
 economical to operate. 
 
 A battery may be defined as an " apparatus 
 arranged to produce a continuous flow of an 
 electric current." 
 
 The forms which this battery may be and have 
 been made to take are innumerable ; but only a 
 few of the more common forms that are easily 
 made will be taken up. . 
 
 The strength of a battery may be said to be 
 almost exactly proportional to the number of 
 cells or elements of which it is composed. The 
 work to be done will, therefore, determine the 
 number of cells to be employed. For example,
 
 34 Electricity 
 
 it is evident that more power is required to 
 operate the hammer of an electric bell than to 
 move the armature of an electric telegraph in- 
 strument. Therefore, with the same length of 
 wire, it may be assumed that more cells of 
 battery will be required in the one case than in 
 the other. 
 
 Batteries may be broadly divided into two 
 general classes, the wet and the dry. The former 
 have the advantage of being more reliable in the 
 development of the current, more constant in 
 operation and more easily replenished and are, 
 therefore, almost universally used when the 
 battery can be placed in some stationary position 
 where it is not likely to be disturbed. The dry 
 battery, on the other hand, possesses the very im- 
 portant advantage of being readily transported 
 from place to place, of having no liquid to be 
 spilled by shocks or jars and of working in any 
 desired position. 
 
 Of the wet batteries the Daniell's cell is one of 
 the easiest to construct and most efficient in 
 operation. It was first brought out in 1836 and 
 is named after its inventor. It has been im- 
 proved from time to time and has now reached a 
 high degree of perfection. 
 
 The general appearance of a battery composed
 
 Conductors, Connections 
 
 35 
 
 of four cells is shown in Fig. 7. It consists of 
 four cells with the positive pole of one connected 
 with the negative pole of the next and in such a 
 way that the current passes from one to another 
 until it reaches the last whence it flows out on to 
 the line. Each cell is made up of six parts, an 
 
 FIG. 7. BATTERY OF DANIELL CELLS AND BELL 
 CIRCUIT 
 
 outside containing jar of glass in which there is 
 set down a thin hollow cylinder of zinc. Within 
 this there is a porous porcelain jar and within 
 this a strip of copper. There are also two liquids 
 used. A saturated solution of the sulphate of 
 copper is placed in the porous jar and in the
 
 36 
 
 outer one there is diluted sulphuric acid. The 
 porosity of the porcelain jar permits the two 
 liquids to communicate and thus form the con- 
 necting link for the generation and passage of 
 the current. 
 
 In the making of such a cell care should be ex- 
 ercised in the selection of the materials used. 
 The glass for the outer jar should be of first- 
 class quality else it will be apt to crack and 
 allow the acid contents to leak out upon sur- 
 rounding objects. 
 
 The porous jars are usually made of porcelain 
 or earthenware as these are less easily affected 
 by the acid than other substances, although it is 
 quite possible to secure a satisfactory efficiency 
 by the use of paper pulp, canvas, pipe clay, 
 wood or carbon, or in fact any material that is 
 not directly and rapidly acted upon by the 
 liquids. 
 
 It has been found that a variation of the 
 amount of porosity in a jar has little or no effect 
 upon the action of the cell as far as resistance is 
 concerned. In consequence of this, experiments 
 seem to point to the desirability of using rather 
 dense than openly porous jars for batteries that 
 are to be kept in continual operation. 
 
 Before using, these jars should be soaked in
 
 Conductors, Connections 37 
 
 water for some time so that the pores may be- 
 come thoroughly filled with moisture. If this is 
 inconvenient, the jar may be placed in position 
 and allowed to stand for a time before the bat- 
 tery is put into action in order to allow the 
 porcelain to become saturated. 
 
 The use of jars that are too porous should be 
 avoided because they permit the liquids to mingle 
 too easily, which will allow the zinc to act 
 directly upon the sulphate of copper and thus 
 cause a deposit of copper to form upon the zinc 
 thereby checking the action of the cell. 
 
 In the preparation of the liquids the sulphate 
 of copper is obtained by placing a crystallized 
 sulphate of copper commonly known as blue- 
 vitriol in water and allowing it to stand until 
 the crystals cease to diminish in size when the 
 solution will be found to be saturated. That is 
 to say the water has taken up all that it is 
 capable of dissolving. The liquid can then be 
 poured off and used in the battery. It is com- 
 mon practice to keep a piece of the vitriol in the 
 battery thus holding the solution up to the satu- 
 ration point at all times. As the liquid decreases 
 in quantity from evaporation or decomposition, 
 water can be added to bring it up to the proper 
 level 431656
 
 38 Blectrfcttg 
 
 The sulphuric acid is merely diluted with 
 about twelve times its own weight of water. 
 Care must be exercised in doing this that it is 
 not done too suddenly or in a vessel of inferior 
 character. The addition of the water to the 
 acid is always accompanied by the development 
 of a considerable amount of heat that will be apt 
 to crack or burst a vessel made of cheap glass. 
 The safe way for the inexperienced person is to 
 add the water slowly, stirring it in and using 
 glazed earthenware for the mixing vessel. 
 
 There is one fault connected with the DanielPs 
 cell that is apt to cause considerable anno} T ance 
 when it is placed in a position where cleanliness 
 is especially desirable. This is what is known as 
 the formation of " climbing salts." 
 
 The action of the battery consists, in part, in 
 the dissolving of the zinc in the sulphuric acid 
 and the formation of the sulphate of zinc. As 
 the liquid becomes saturated with this sulphate. 
 of zinc, the climbing salts appear. They consist 
 of a white salt-like deposit on the surface of the 
 glass and may rise and overrun the whole of the 
 outside and all of the connections. The climb- 
 ing is caused first by some movement produc- 
 ing a wave in the liquid and wetting the glass 
 above the general level. This liquid drys and
 
 Conductors, Connections 39 
 
 leaves a deposit upon the glass. Capillary at- 
 traction then sets in and the liquid is drawn up 
 to evaporate and increase the deposit. 
 
 In one way these deposits are of an advantage 
 in the working of the battery in that they pre- 
 vent a too great concentration of the liquid and 
 a depositing of the salts on the surface of the 
 zinc, both of which tend to increase the resist- 
 ance of the battery as well as lower its effi- 
 ciency. 
 
 These salts are easily detached from the glass 
 by wiping with a rag, but when they accumulate 
 on the porous jar it may take considerable rub- 
 bing to remove them. For this reason that 
 portion which rises above the surface of the 
 liquid should be glazed. When removed the 
 salts should not be put back in the liquid as that 
 would merely intensify the evil. When the bat- 
 tery is placed in an accessible position it can be 
 easily kept clean. 
 
 The formation of climbing salts can be pre- 
 vented by placing a layer of oil on top of the 
 liquid. This is apt to foul the battery, however, 
 and to add to the concentration of the outer 
 liquid, thus raising the resistance and with it 
 lowering the efficiency of the battery. They 
 can, however, be prevented from climbing over
 
 40 jeiectrtcfts 
 
 and passing beyond the limits of the edge of the 
 jar by coating the upper portion of the same 
 with a film of oil or paraffine. 
 
 In the wiring of the cells of a battery the 
 work should be done as indicated in Fig. 7. A 
 wire is led from the zinc of one cell to the copper 
 of the next, from the first to the last and thence 
 back to the first. The metals should be sus- 
 pended in the liquid from a rack set on top of 
 the jars and not allowed to rest on the bottom 
 of the same. These racks may be made of wood 
 or of hard rubber. The porous jar should also 
 be suspended. 
 
 Each metal should be provided with a binding 
 screw for the attachment of the wires. This 
 consists of a threaded bolt soldered or brazed to 
 the zinc and copper and provided with a knurled 
 nut that may be screwed down against a bearing 
 to hold the wire. 
 
 Whenever it becomes necessary to remove the 
 wires for the purpose of cleaning the battery, 
 they and the nut and bearing should be scraped 
 bright so as to insure a metallic contact before 
 replacing. 
 
 In the care of the battery it will be necessary 
 to add a little water from time to time to re- 
 place that lost by evaporation. Otherwise it
 
 Conductors, Connections 41 
 
 will require no attention other than the removal 
 of the salts until it has become exhausted. 
 
 The life of a battery depends upon the service 
 which it is called upon to perform. In telegraph 
 service, where the battery is almost constantly 
 at work, it will be six months or a year before 
 the porous jars will become so clogged with a 
 metallic deposit as to require renewal. 
 
 For household purposes, such as the ringing of 
 bells, the service is intermittent and the battery 
 stands with an open circuit for the greater por- 
 tion of the time, its life may be almost indefi- 
 nitely extended. 
 
 In connecting the battery to the instrument 
 intended to do the work the wiring is very 
 simple. A conductor is attached to the binding 
 post of the zinc at one end of the battery, which 
 is known as the negative pole ; and one to that 
 of the copper at the other end, which is known 
 as the positive pole. If these two wires are 
 brought together so as to complete the metallic 
 contact between the two poles of the battery, 
 the circuit is said to be closed and the current 
 flows in the circuit from the positive pole to the 
 negative and thence through the battery to the 
 positive pole again. 
 
 If then an electric bell were to be connected
 
 42 Electricity 
 
 in this closed circuit it would ring continuously 
 until the battery was exhausted. In order to 
 control the ringing of the bell the wire is broken, 
 as at a, and a push-button or key inserted, by 
 which the circuit can be opened or closed at 
 will. When closed, the battery is instantly set to 
 work and the bell rings. When open, the bell 
 is silent and the battery is at rest, suffering no 
 deterioration other than that due to the evapora- 
 tion of the liquids in the jar. 
 
 There are, as already stated, many forms of the 
 Daniell's cell, intended for the accomplishment of 
 special purposes, but acting on the same principle. 
 Many of these batteries have received a wide ap- 
 plication and have supplanted the simple Daniell's 
 cell. They are, however, usually more difficult to 
 make and maintain and are, therefore, not as well 
 suited to the needs of those who wish to make 
 and care for their own batteries. 
 
 Among such batteries may be mentioned the 
 Leclanche. In this, the glass jar is usually square 
 and is narrowed in at the top so as to just per- 
 mit the removal of the porous jar and thus de- 
 crease the chance of evaporation. The contrac- 
 tion, however, contains a side orifice through 
 which the zinc can be inserted and the jar filled 
 and emptied.
 
 Confcuctors, Connections 43 
 
 One electrode is a cylindrical piece of zinc 
 about a half-inch in diameter, to which a piece 
 of galvanized wire is soldered. The porous 
 jar is filled with a mixture consisting of equal 
 parts of crushed carbon and peroxide of man- 
 ganese ; while, packed in the centre of this mass, 
 is a piece of carbon having a lead cap to which 
 the positive binding post is fastened. 
 
 The liquid in the outside jar consists of one- 
 half water and one-half ammonia-hydrochlorate. 
 The liquid soaks through the porous jar and 
 saturates the mixture of carbon and manganese. 
 
 This form of jar is well adapted for working 
 bells and doing a similar class of work, but 
 owing to the difficulty of making had best be 
 purchased of a dealer when it is desired to 
 use it. 
 
 Finally, a word of caution may be given to the 
 unskilled in the care of a battery. In dismount- 
 ing one for cleaning or renewal it is well to have 
 a little aqua ammonia within reach, into which 
 the fingers may be immersed in case they be- 
 come spattered with the acid, or which may be 
 used to moisten the clothes that have suffered 
 from a similar accident. Always do this work 
 in a well-ventilated room, because the fumes that 
 are apt to arise from the acid of the battery are
 
 44 BlectrtcftB 
 
 not only disagreeable but harmful when taken 
 into the lungs. 
 
 The second class of batteries known as dry are 
 not really dry, but rather moist. In fact as soon as 
 they become thoroughly dried they cease to work. 
 It is upon this principle that some of the fuses used 
 for submarine work operate. So long as the pile 
 is kept dry there is no generation of an electric cur- 
 rent. When water is admitted so as to moisten 
 the parts the electric current is at once generated. 
 
 These batteries are so low-priced that it is not 
 worth the time required to make them. If, how- 
 ever, it is desired to do such a piece of work it 
 may be accomplished as follows : 
 
 Take an unglazed sheet of paper and upon one 
 side of it spread a thin layer of peroxide of man- 
 ganese that has itself been thinned with milk, 
 thin flour paste or water containing a little glue 
 or mucilage. From the paper so prepared cut 
 discs about l}4 inches in diameter and stack 
 them on top of each other to any convenient 
 height. At each end a metallic disc, preferably 
 of copper, of the same diameter, is placed, and 
 these serve to form the poles or electrodes of the 
 battery. The whole is then pressed solidly to- 
 gether and held in that position. 
 
 In order that the outer surface may be smooth
 
 Conductors, Connections 45 
 
 and cylindrical, a hole may be punched through 
 the centre of the discs and an insulated wire be 
 led from the bottom up to the top. 
 
 The whole may be held together by packing 
 in a glass tube of the proper diameter that has 
 been well varnished with shellac on the inside. 
 If a glass tube is undesirable or inconvenient to 
 
 o 
 
 procure, the metallic discs may be made a little 
 larger than the paper ones and pierced around 
 their edges with a number of small holes. 
 Through these holes a lacing of silk cord may 
 be passed from one to the other and the whole 
 bound firmly in place. 
 
 As the action of such a pile depends upon the 
 retention of its moisture it must be hermetically 
 sealed in such a way that it cannot become dry. 
 To do this it had best be given several coatings 
 of shellac varnish, paraffine or sulphur. If the 
 pile is to be set in one place paraffine will be 
 as satisfactory as anything. But if it is to be 
 handled or moved about, the paraffine will be 
 apt to become loosened and scraped off, in which 
 case the shellac should be used. 
 
 While an electric spark can be obtained from 
 these batteries and they can be made to operate 
 a telegraph or other instruments requiring a light 
 current their internal resistance, owing to the
 
 46 Electricity 
 
 great number of elements is enormous, and they 
 are not adapted to long-continued or severe service. 
 
 They are, however, exceedingly convenient for 
 the operation of experimental apparatus that has 
 to be moved from point to point. 
 
 The wiring and operation of these batteries for 
 service is identical with that of the wet batteries 
 previously described. 
 
 It has already been pointed out that the bat- 
 tery is used in places where currents of low in- 
 tensity to be used intermittently are to be used. 
 This applies to the local batteries of all telegraph 
 stations, telephones, and household purposes 
 where they are worked intermittently for ring- 
 ing bells, opening doors or working light signals. 
 For gas lighting on a large scale such as in 
 theatres, public halls and railway stations, where 
 it is merely necessary to produce a spark at the 
 tip of the burner, the friction machine is the 
 most convenient method to employ. With this 
 a Leyden jar is first charged and then discharged 
 over a wire with a gap at each burner. In leap- 
 ing this gap a spark is formed which lights the 
 escaping gas. This machine for such a purpose 
 is more convenient than either a dry or wet bat- 
 tery as it is only required to furnish an instan- 
 taneous current and requires no attention.
 
 CHAPTEE IV 
 
 ELECTKIC BELLS 
 
 THE electric operation of nearly all signals de- 
 pends upon the power of the electric current to 
 convert a bar of soft wrought iron into a magnet 
 of greater or less strength. This is done by pass- 
 ing the current through a wire wound as a helix 
 around the bar of iron. So long as the current 
 is flowing through the wire the bar is a magnet 
 and acts in every way like one ; and, as soon as 
 the current is cut off and ceases to flow the bar 
 jit once becomes inert and, for all practical pur- 
 poses, manifests no magnetic properties at all. 
 
 The condition of the bar while under the in- 
 fluence of the current depends upon the direction 
 of its flow through the wire and the way in which 
 the wire is wound about the bar. That is, these 
 are the controlling factors in the location of the 
 north and south poles of the magnet at opposite 
 ends of the bar. The law of the flow of the cur- 
 rent is that if, in looking at the end of the bar, 
 the current appears to be flowing around it in
 
 48 BlectricttB 
 
 the direction of the movement of the hands of 
 a watch or from left over to right in passing 
 from the positive to the negative pole of the bat- 
 tery, the south pole of the magnet, thus formed, 
 will be toward the observer. If the current is 
 made to flow in the opposite direction or from 
 right over to left, the north pole of the magnet 
 will be toward the observer. This will be more 
 clearly understood from an examination of Fig. 8. 
 
 !\\\\\\\T 
 ^ 
 
 71 
 
 FIG. 8. COMBINATIONS OF ELECTRO-MAGNET COILS 
 
 In this A, B, C and D represent the four combi- 
 nations possible with the two directions of cur- 
 rent and of windings respectively. This property 
 of magnetization is made use of in a wide variety 
 of electrical instruments. 
 
 Eeferring to A and B of Fig. 8, it will be seen 
 that, in each case the north pole of the magnet 
 is at the left-hand end of the bar. The wires 
 are, however, wound with what is known as a
 
 Electric JBells 49 
 
 left and right-hand coil respectively. But the 
 current passes around the bar in the same direc- 
 tion in each case. It is evident, then, from this 
 that the wire can be coiled about the bar from 
 end to end, back and forth, like thread on a spool 
 and still tend to excite the same polarity in a 
 bar. 
 
 In forming a magnet for a bell, it is customary 
 to construct one in the form of a horseshoe, that 
 is one with the north and south poles presented 
 in the same direction. The reason for this is that 
 it makes it possible to use a long armature or 
 movable bar that is excited to correspond to the 
 two poles of the magnet presented to it. In ad- 
 dition to this, it is much more powerful than one 
 in the bar form ; for the former will lift three or 
 four times as much as the latter having the same 
 weight and number of ampere turns. This ex- 
 pression of ampere turns is used to represent the 
 number of turns of wire about the core multi- 
 plied by the number of amperes passing through 
 it. That is to say, if a magnet is surrounded by 
 twenty turns of wire through which a current of 
 one ampere is passing, it is said to have twenty 
 ampere turns. If the current is reduced to one- 
 half an ampere, it will then have ten ampere 
 turns.
 
 50 BlectdcftB 
 
 An ampere is the term used to indicate the 
 quantity or strength of an electric current. The 
 resistance to this current as set up in the wires is 
 measured by ohms and the intensity or pressure 
 of the current is measured in volts. 
 
 It is sometimes difficult to grasp the idea of 
 electrical quantities when no tangible and visible 
 measurement is possible. For that reason the 
 flow of an electrical current is frequently com- 
 pared to that of water in pipes. In the latter 
 there are two elements that control the amount 
 of water that can be delivered by a pipe ; its size 
 and the pressure with which the water is forced 
 through it. It is evident that the larger the pipe 
 the greater the quantity of water that can be made 
 to pass through it when a given pressure per square 
 inch is applied. It is also equally evident that 
 the volume of flow of water will increase as the 
 pressure or head of water is increased. 
 
 The analogy holds good in the case of electric- 
 ity. We may consider the volume of water flow- 
 ing through the pipe as representative of the 
 ampere; the pressure or head with which the 
 water is forced through the pipe as representa- 
 tive of the volt, and the frictional resistance of- 
 fered by the pipe to the flow of the water as 
 representative of the ohm or resistance of the
 
 Electric mile 51 
 
 wire to the flow of the electric current through 
 the same. 
 
 As it is necessary to have a definite mechanical 
 equivalent for the work done by the electric cur- 
 rent, it is referred to what is known as the C. G. 
 S. mechanical unit. This is based on the metric 
 system of measurement and means one gramme 
 (.1452 oz.) lifted through a distance of one centi- 
 meter (.3937 in.) in one second. This was adopted 
 as a basis of measurement by the International 
 Electric Congress that met in Paris in 1881 and 
 1884, and is known as the erg. 
 
 These electric measurements are all inter-re- 
 lated and based on certain definite observations. 
 Thus the ohm is the unit of resistance and is that 
 offered by a column of pure mercury 106 centi- 
 meters (41. Y3 in.) in length and of one square 
 centimeter (.156 sq. in.) in cross-section at a tem- 
 perature of 32 Fahr. This resistance is rep- 
 resented within a small fraction by 1,000,000,000 
 C. G. S. units of resistance or about .024 foot 
 pounds per minute. 
 
 The volt is the unit of electro-motive force and 
 is equal to about that of one Daniell's cell. As 
 this is a variable quantity the volt is legalized at 
 100,000,000 C. G. S. units. 
 
 The ampere is the unit of current strength or
 
 52 Electricity 
 
 volume and is obtained by dividing the volt by 
 the ohm or the electro-motive force by the resist- 
 ance and is, therefore, equal to rV C. G. S. 
 
 The term ampere-hour is frequently used and 
 represents a current of one ampere flowing 
 through a conductor for the space of one hour. 
 
 The meaning of these technical phrases are 
 somewhat difficult to grasp, and the memory 
 will be greatly assisted by referring them to the 
 analogy of water flowing 
 through a pipe as already ex- 
 plained. 
 
 Returning now to the matter 
 
 ^$ 3 L i n hand, attention should be 
 if I 1)1 paid, in the winding of the mag- 
 
 . 9.-OBDiNAiTY net for an electric bell, both 
 
 METHOD OF WIR- to the volume or ampereage 
 
 ING FOE ELECTEO- o f the current to be used and 
 
 MAGNETS the p ro b a bi e resistance of the 
 
 balance of the circuit. As the latter increases 
 so should the windings and the resistance of the 
 wire about the magnet also increase. 
 
 The method, then, to be adopted in the making 
 of the magnet will be to obtain two soft iron 
 cores about one-half inch in diameter and two 
 inches long to which should be added three- 
 eighths of an inch of screw thread to go into a
 
 jSlectrfc JBetle 53 
 
 cross-bar, also of soft iron upon which the two 
 are to be fastened so as to form the U-shaped 
 core as shown in Fig. 9. 
 
 Over each of these cores N" and S two thin 
 wooden bobbins should be snugly fitted. If 
 these are inconvenient to obtain the cores may 
 be heated and wrapped in successive layers of 
 paper. When cooled the paper will slip off, 
 forming a cylindrical core. 
 
 The wire should be wound on the outside of 
 this core and in the direction shown in Fig. 9 ; 
 winding back and forth until a sufficient quantity 
 has been put in position. To do this properly 
 about 6^ oz. of copper wire of size No. 24 of the 
 Birmingham wire gauge should be used. It is 
 essential that the successive coils of this wire 
 should come in contact neither with the iron core 
 nor with each other, else the current will be 
 short-circuited and the effect of the coil nullified. 
 
 Insulated wire must, therefore, be used for this 
 purpose and in order that the coils may be as 
 compact and as neatly arranged as possible it is 
 best to use a wire that is insulated with silk. 
 The ends may be led out at the bottom in a 
 groove cut in the base, to a binding post on the 
 stand to which the magnet is to be secured. This 
 may be of the form shown in Fig. 23.
 
 54 
 
 BlectricttE 
 
 Having formed the magnet there are two forms 
 in which the bell may be put. That is, the bell 
 may be made to ring continuously so long as the 
 circuit is closed or it may be made to give a 
 single stroke with each closing and opening of 
 the same. 
 
 The continuously ringing bell as shown in Fig. 
 10, will be first con- 
 sidered. The mag- 
 net is attached to the 
 base, as shown, by 
 screws. Just above 
 it a bracket A con- 
 taining a binding 
 post is fastened. To 
 the face of this 
 bracket there is 
 
 screwed a spring B 
 FIG. IO.-VIBRATIXG ELECTRIC to the lower end of 
 
 BELL AND CIRCUIT . . , ,. ., . 
 
 which the soft iron 
 
 armature C is attached. This, in turn, is ex- 
 tended down to include the stem D which 
 terminates in hammer E. To the back of the 
 armature C there is also attached the auxil- 
 iary spring K. The spring B is so adjusted that 
 when no current is passing through the wire the 
 armature stands away from the faces of the mag-
 
 Electric JBells 55 
 
 net ends and the spring K is pressed up against 
 the stop F. This stop F should be fitted with an 
 adjusting screw by which the tension on the 
 spring K can be increased or diminished and the 
 armature brought into correct adjustment. The 
 stem D should also be bent to such a shape that, 
 just before the armature comes into contact with 
 the cores of the magnet the hammer should strike 
 against the bell. 
 
 The wiring of this bell is exceedingly simple. 
 One end of the wire forming the coil of the mag- 
 net is led out and fastened in the binding post 
 H. To this same binding post is also led the 
 wire from the positive pole of the battery. This 
 wire also connects with the push button i. 
 
 The other end of the wire of the magnet coil 
 is led out und fastened to the binding post on 
 the bracket A. 
 
 The negative pole of the battery is connected 
 to the binding post G and this in turn, by a wire 
 to the stop F. 
 
 The course of the current then, when the cir- 
 cuit is closed, is from the positive pole of the 
 battery to the push button I, to the binding post 
 H, to and through the magnet coil to the bracket 
 A, to the spring B, to the spring K, to the stop F, 
 to the binding post G, to the negative pole of the
 
 56 BlectrfcftB 
 
 battery and then through the latter to the posi- 
 tive pole. 
 
 The action of the bell in operation is as fol- 
 lows : 
 
 When the push button is pressed to close the 
 circuit, the magnet attracts the armature and 
 draws it to itself, as it does so it draws the spring 
 K away from the stop F. The moment these two 
 are parted the circuit is broken and the magnet 
 ceases to attract the armature. The spring B 
 then throws the armature back to its original 
 position. As soon, however, as the spring K 
 touches the stop F the magnet is again excited 
 and attracts the armature. The hammer is thus 
 kept vibrating to and fro as long as the circuit 
 remains closed at the push button I. 
 
 Trouble is frequently experienced with the 
 failure of these vibrating continuous bells to 
 work. This failure is usually credited to the 
 battery which may be in first-class condition. 
 The difficulty can usually be traced to the mech- 
 anism of the bell. If the adjustment at the 
 stop F is not properly made the bell will not 
 ring. It is evident that if the hammer strikes 
 the gong before the spring K leaves the stop F 
 and thus breaks the circuit, the latter will not be 
 broken at all and the magnet will continue to
 
 Electric WellB 57 
 
 attract the armature and there will be but one 
 stroke given by the hammer on the gong. 
 
 On the other hand, if the stop F is drawn so 
 far back that the spring K does not touch it 
 when the hammer is thrown back to its full ex- 
 tent by the spring B, the circuit will always re- 
 main open and there will be no possibility of 
 exciting the magnet. Or if the spring K just 
 touches the stop F so that it is drawn away as 
 soon as the armature starts forward, the circuit 
 will be broken too soon before sufficient mo- 
 mentum has been given to the hammer to cause 
 it to overcome the resistance of the spring B and 
 reach the gong. 
 
 The proper adjustment of the stop F is ob- 
 tained when the contact between it and the 
 spring K ceases just before the hammer comes 
 into contact with the gong. To be precise in the 
 matter : Suppose the hammer stands three- 
 quarters of an inch from the gong when at rest. 
 The circuit should be broken when it has reached 
 a point from one-eighth to three-sixteenths of an 
 inch from the gong. 
 
 It is also necessary to see to it that the points 
 of contact between the stop F and the spring K 
 are kept bright and clean. 
 
 These bells are usually placed high on the
 
 58 Blectrfctts 
 
 wall, and frequently in damp and dusty places. 
 An accumulation of dust or rust, however slight, 
 may be quite sufficient to break the circuit at F 
 and hold it open at all times. All of these 
 things should be carefully looked to before at- 
 tributing a failure to work to the battery, and 
 they can be readily attended to and the adjust- 
 ments made by any householder without going 
 to the annoyance and delay of sending for an 
 outside electrician. 
 
 The remaining 
 piece of mechanism 
 
 ^ ^_ to be described in 
 
 'tfM^fcWMfa connection with the 
 FIG. 11. PUSH BUTTON bell is the push-but- 
 ton that is shown in 
 
 section in Fig. 11. These push-buttons are very 
 simple in construction. The wires from the bat- 
 tery and from the bell are led in as shown. One 
 terminates in a flat spiral spring B and the other 
 in the flat plate C. By pressing upon the porcelain 
 button A, the spring is forced down against the 
 plate and the circuit is closed. 
 
 Another type of bell operated by electricity is 
 the single stroke bell. That is to say when the 
 circuit is closed the hammer is thrown down 
 against the gong and strikes a single blow, re-
 
 Electric ffietls 
 
 59 
 
 maining in that position until the circuit is 
 again opened, to repeat the blow upon closing 
 again. 
 
 The construction of such a bell is similar to 
 that of the vibrating bell. The difference is in 
 the method of wiring. A bell of this character 
 is shown in Fig. 12. The wires from the coil of 
 the magnet are led off to the two binding posts 
 
 FIG. 12. SINGLE STROKE ELECTRIC BELL 
 
 A and B from which the wires are led to the bat 
 tery in exactly the same manner as in the bell 
 shown in Fig. 10. The armature F, to which the 
 stem and hammer are attached is held by the 
 spring E. There is, however, no auxiliary 
 spring but the screw D, of the stop C is brought 
 to bear directly against the armature and pre- 
 vents it from, being thrown too far back away
 
 60 ^electricity 
 
 from the core of the magnet. Neither does the 
 armature form any part of the electric circuit by 
 which the bell is operated; From this it will be 
 seen that, when the cores are magnetized by the 
 passage of the current the armature is drawn 
 forward once and held until released by the 
 opening of the circuit. 
 
 The adjustments to be made for the operation 
 of this bell are as follows : The armature should 
 come up against a stop, as at G just before the 
 hammer strikes the gong. The momentum of 
 the former will then cause it to be thrown ahead 
 to deliver a quick blow and then spring back 
 clear of the gong to permit the latter to vibrate 
 as would not be the case were the hammer to be 
 held in contact. 
 
 ' If desired, the stop G can be dispensed with in 
 the making of the bell, and the armature be al- 
 lowed to strike directly against the core of the 
 magnet instead. When this is done the armature 
 or the ends of the cores should be given a coat- 
 ing of copper plating, to prevent sticking. Or, 
 if the plating is inconvenient, a piece of thin 
 copper may be interposed. 
 
 The reason for the sticking is that, after the 
 circuit by which the core is magnetized has been 
 broken, there will still remain enough residual
 
 JElectrtc Bells 61 
 
 magnetism to hold the armature and prevent a 
 quick reaction. For this reason the armatures of 
 bells and telegraph instruments are not allowed 
 to come into contact with the cores but have 
 their forward motion checked by an adjustable 
 stop with a screw, like that shown in Fig. 12. 
 
 In fitting up an electric call bell, either of the 
 vibrating or single stroke type, the error is fre- 
 quently made of attempting to economize in the 
 number of cells that are put into the battery. 
 This false economy will invariably result in an 
 amount of annoyance that will far more than 
 offset any small saving that may be effected. If 
 any mistake is to be made in this regard let it 
 be, by all means, on the side of providing more 
 battery power than is really needed. This power 
 will depend, of course, upon the size of the gong 
 in the bell to be operated, because, the larger the 
 gong the greater the length of wire in the mag- 
 nets, and with it the greater the resistance. 
 Then, too, while the making of the core for the 
 single stroke bell is the same as for the vibrat- 
 ing, the size of the core and the quantity of wire 
 needed should be greater. Thus the magnet de- 
 scribed in the early part of this chapter is suited 
 for a vibrating bell with a gong 4 inches in 
 diameter. For a similar single stroke bell the
 
 63 Electricity 
 
 core should be lengthened to 2^ inches and tl\ 
 amount of wire used increased to 9^ oz. For a 
 smaller gong of 2^ inches diameter the cores 
 may be ^ inch in diameter and 1^ inches 
 long, upon which 3 ounces and 3^ ounces of 
 wire respectively should be wound for the two 
 types of bells. 
 
 Two cells of battery can be made to work such 
 bells, but it will be found to be far better to 
 allow an ample margin and put in three cells for 
 the small bell and four for the large, increasing 
 this to six in case the circuit is long or several 
 bells are to be operated. Where the 
 work done is constant and heavy, 
 even a larger number of cells will be 
 advisable, in order to prevent a 
 rapid deterioration and exhaustion 
 FIG. 13. SIM- of the battery. 
 PLEBELLCIB- The arrangement of the cells may 
 
 CUIT , j- ! j A U A 1 
 
 be divided into what is known as 
 multiple and series. For the working of a 
 single bell or for bells that are used infre- 
 quently, the series arrangement should be used. 
 The disposition of the battery of three cells 
 and the wiring for a single bell, is shown in 
 Fig. 13. The three cells of the battery are rep- 
 resented by the lines at A, B and C. These
 
 Electric JBells 63 
 
 .cells are said to be in series. That is the current 
 passes through the series of the three, one after 
 the other. This arrangement increases the ten- 
 sion or voltage of the current above that of the 
 single cell. 
 
 Should the service on the line be constant or 
 increased by the addition of more bells, the 
 quantity or ampereage of electricity may be in- 
 creased while the voltage remains 
 the same by adding more cells and 
 arranging them in multiple series. 
 This is shown in Fig. 14. Here, it 
 will be seen, the positive poles at 
 one end of each series of cells, are 
 united ; and the same is done for p IG H.B 
 the negative poles at the other end. CIRCUIT WITH 
 These two wires are then united BATTERIES IN 
 through the circuit. The voltage is PARALLEL 
 the same as in Fig. 13, but the ampereage is 
 doubled. 
 
 When there is but a single bell worked by a 
 single battery and rung from a single push 
 button, the wiring should be done as shown in 
 Fig. 13. It is, however, frequently desirable to 
 ring one bell from two different rooms ; or, it 
 may be desired to ring bells separated from each 
 other from push buttons located at one point.
 
 64 Electricity 
 
 The latter occurs in the case of apartment houses 
 where the call bells are rung in each separate 
 apartment from the street door. 
 
 There is one simple principle underlying the 
 wiring for bells that must always be borne in 
 mind. It is that the circuit from the battery 
 to the bell must be unbroken except at the par- 
 ticular push button by which it 
 is to be operated, and that, 
 when the latter is closed, the 
 current must flow direct to the 
 FIG. 15. BELL CIR- point of application and not be 
 CUIT WITH Two liable to diversion and applica- 
 PUSH BUTTONS elsewhere 
 
 Fig. 15 has been drawn in accordance with 
 this principle to show the method of wiring to 
 be followed where a single bell is to be worked 
 by either one of two separated push buttons. It 
 will be seen that in case either of the buttons is 
 pressed the circuit is closed and the mere fact 
 that there are some feet of wire attached that 
 run out into space, will have no effect upon the 
 ringing of the bell. 
 
 Fig. 16 illustrates a case of the wiring of an 
 apartment house of five flats, with a bell in each 
 apartment and the push button at the street 
 door. Here each one of the five push buttons
 
 Electric Bells 65 
 
 controls the corresponding bell, and none other 
 and yet all of the buttons and all of th bells are 
 
 FIG. 16. FIVE BELL CIRCUITS LEADING FROM 
 A SINGLE BATTERY 
 
 connected to the battery by a common wire 
 while a separate and distinct one runs from each 
 button to its own particular bell. Take No. 5 
 as an example. When the circuit is closed at 
 this point, the current flows out from the battery 
 to that button thence to bell No. 5 and back to 
 the battery. It cannot enter and operate any of 
 +,he other four bells because their circuits are 
 open at their respective push buttons. 
 
 One more combination will be shown in which 
 a single battery is used to operate two bells 
 worked from two push buttons, the bells to be 
 located at the opposite button. This require- 
 ment frequently arises where it is desired to 
 transmit signals to and fro between separated 
 points. 
 
 In this case, Fig. 17, three wires are used to
 
 66 Electricity 
 
 carry two complete circuits, for if the button A' 
 is pressed the bell A will be rung, while the bell 
 B' is rung from B. 
 
 FIG. 17. DOUBLE BELL AND CALL CIRCUIT 
 
 This principle carried out into a greater elabo- 
 ration of detail will serve as a guide for the anal- 
 ysis of much that is apparently intricate in the 
 wiring of electric bells and signals. It holds 
 true of that mass of wires running out from the 
 large enunciator of a hotel to each of the indi- 
 vidual bedrooms whereby signals and calls are 
 transmitted to and fro without requiring the use 
 of a messenger. The one prime requisite for the 
 proper working of the system being that the 
 wires shall be thoroughly insulated from each 
 other and that the circuit when closed shall not 
 be diverted to other points than that at which it 
 is desired that it shall act. 
 
 Like all other pieces of mechanism the electric 
 bell requires some attention and is subject to 
 some ills. The care that should be bestowed 
 upon the battery has already been mentioned in
 
 Electric JBells 67 
 
 a previous chapter and need not be recapitulated 
 here. Theoretically there should never be any 
 trouble with the wires after they have once been 
 properly located. As a matter of practical ex- 
 perience they will frequently get out of order. 
 Mice and rats will obtain access to them and 
 gnaw off the insulation and the accidental 
 dropping of a nail, or the accumulation of mois- 
 ture may serve to either short circuit or shut off 
 enough of the current to prevent the ringing of 
 the bell. 
 
 Disuse will also prevent a metallic contact 
 from taking place between the moving parts. A 
 little rust accumulating on the metal portions of 
 a push button will serve to hold them apart and 
 prevent the flow of the current. This rust is 
 quite apt to accumulate where the button simply 
 drops into contact. It is always better to have 
 two such surfaces come together with a rubbing 
 action, as this tends to keep them bright and in- 
 sures that they touch metal to metal. In addi- 
 tion to these, the bells are liable to disarrange- 
 ment through the loosening of the screws in the 
 binding posts and the shifting of the adjustable 
 stops for the armature. It may, therefore, be 
 necessary to make quite an exhaustive examina- 
 tion of the whole system from the battery to the
 
 68 Electricity 
 
 bell before a trouble can be located. But how- 
 ever troublesome this may be and however much 
 time it may consume, the investigator may rest 
 assured that there is never anything mysterious 
 about these electrical difficulties. They may be 
 troublesome to detect but when found they will 
 usually be seen to be very simple. In fact it 
 most frequently occurs that a very slight defect, 
 just sufficient to prevent the proper acting of the 
 bell or signal, is far more difficult to detect than 
 one of greater proportions, just as a gnat crawl- 
 ing on the ground is not as manifest to the eye 
 as the big tumble bug of a beetle.
 
 CHAPTEE Y 
 
 THE ELECTRIC TELEGRAPH 
 
 IT is quite beyond the bounds of possibility to 
 estimate the benefit that has accrued to mankind 
 from the application of the electric current to 
 the conveyance of messages by telegraphy. As 
 the name implies it is the writing by lightning, 
 and a writing by lightning both in the means 
 employed and the speed of transmission. Yet 
 like all other things that have acquired a wide 
 and almost universal adoption the mechanism 
 of the electric telegraph is, in itself, exceedingly 
 simple. 
 
 The motive power was, for many years, the 
 battery such as we have seen employed for the 
 ringing of bells and the transmission of simple 
 signals. In fact it is in itself the transmission of 
 the simplest of signals. 
 
 The instrument used is nothing but a variation 
 of the single stroke bell, or rather it would be 
 more proper to say that the single stroke bell is 
 a mere variation of the ordinary telegraph in- 
 strument or sounder.
 
 70 Electricity 
 
 Such an instrument is shown in Fig. 18, and 
 is of such simplicity in detail that its construc- 
 tion will be readily understood. In the first 
 place it should be mounted upon a hardwood 
 base, A, which may be screwed or fastened to the 
 operating table. To this is attached the base B 
 of the instrument itself, which should be of brass 
 and drilled with holes in the proper places 
 
 FIG. 18. TELEGRAPH SOUNDER 
 
 through which small countersunk machine screws 
 are inserted to hold the various parts in their 
 proper positions. 
 
 The magnet is, of course, of the first impor- 
 tance. This is built up in exactly the same way 
 as that used and already described in connection 
 with electric bells. The cores need not be more
 
 Cbe Blcctrfc ^Telegrapb 71 
 
 than one-half inch in diameter and two inches 
 long, but the amount of wire should be varied 
 according to the distance over which the line is 
 to be worked. "With 8 ozs. of No. 26 wire a 
 sounder can be made that will work well in con- 
 nection with a line wire fifteen miles long. For 
 short circuits the amount used in the winding 
 can be considerably less. Five or six ounces will 
 be quite sufficient for short circuits or where the 
 instrument is to be used for experimental pur- 
 poses only. , 
 
 The armature D is made of a flat bar of soft 
 iron from A inch to y& inch in thickness and long 
 enough to reach out to the outer edges of the 
 cores of the magnet. It should be equal to the 
 diameter of the core in width. This may be 
 fastened by a single small machine screw to the 
 armature or sounder lever E. This lever is 
 pivoted on points at the end of the screw F 
 which passes through the yoke G and is held 
 from turning by the check-nut H. 
 
 All parts of the sounder should be of a good 
 quality of brass with the exception of the mag- 
 net cores and armature which are to be of soft 
 iron, and the wiring of the magnet which must 
 be of well-insulated copper wire. 
 
 If restricted only by the main portions of the
 
 72 Electricity 
 
 instrument, the armature lever, which vibrates 
 on two screw points similar to F entering from 
 either side, would be able to move up until it 
 struck the reversed portion of the frame I at A, 
 and down until the armature lay against the 
 cores of the magnets. To prevent this range of 
 motion, which would be far too great, two ad- 
 justing screws K and L are used. Their con- 
 struction is very clearly shown from an examina- 
 tion of the engraving. The screw L passes 
 through the lever E and has a bearing against 
 the main portion of the frame I. It is so ad- 
 justed that, when against the frame, the armature 
 D is just clear of the cores of the magnet. The 
 upward motion is likewise limited by the screw 
 K to what may be required under the varying 
 conditions of battery strength to produce a 
 sharp clear sound to indicate the motions of the 
 armature. 
 
 The lever E has a downwardly projecting am 
 against which a spring is made to bear, and 
 whose tension is regulated by means of an ad 
 justing screw. This spring tends to lift the lever 
 and hold it up against the stop K. 
 
 The wires from the winding of the magnets are 
 led out and connected to two binding posts M, 
 only one of which can be seen in the engraving;
 
 TTbe Electric Gelegtapb 73 
 
 the other being on the opposite corner and con- 
 cealed by the instrument itself. The connection 
 of the wires is made at the bottom beneath the 
 base N. These binding posts have a small hole 
 B near the top in which the wire from the battery 
 is inserted. This wire is then firmly clamped in 
 position by the screw N. 
 
 It will thus be seen that the sounder is exceed- 
 ingly simple and can be made by any mechanic 
 with ordinary tools at his command. 
 
 The wiring for the sounder is similar in every 
 respect to that used for the electric bell. The 
 difference between the two is that, in the case of 
 the bell, the circuit is broken when it is not in 
 use, whereas in the case of the telegraph the 
 circuit is kept closed. The immediate result of 
 this is that the battery used for the maintenance 
 of the telegraph circuit is exhausted very much 
 more rapidly than is that used for the operation 
 of a bell. In the one case there is a constant flow of 
 current and in the other an intermittent one, that 
 is at work only when the bell is actually ringing. 
 
 The necessity for this changed condition will 
 be readily understood when the requirements of 
 the two cases are considered. With the bell it 
 is usually controlled from one or more points 
 always acting on the same bell, hence the closing
 
 74 
 
 BlectrfcitB 
 
 of the circuit at these points accomplishes the 
 purpose of doing the ringing. In the case of the 
 telegraph it is necessary to operate instruments 
 from two widely separated points over one and 
 the same wire. The method of doing this work 
 will be more readily understood from an ex- 
 amination of the engraving Fig. 19, in which the 
 arrangement of a telegraph line is diagrammatic- 
 ally represented. 
 
 FIG. 19. TELEGRAPH CIRCUIT 
 
 The battery is located at S and is connected 
 through its negative pole with the earth. The 
 wire from the positive pole is led first through 
 the coil of wire of the first instrument at I. 
 This instrument is usually of a type known as a 
 relay and will be explained later. 
 
 From the relay I it goes to the first operating 
 key C, and thence on through the successive ke} 7 s 
 C', C" and relays I' and I" to the earth. The 
 keys are kept closed at all times except when in
 
 Electric tTelegrapb 
 
 75 
 
 use, so that the operator at each station can con- 
 trol the working of the line. Thus, suppose the 
 operator at I' wishes to send a message to I", he 
 opens his key and by making and breaking the 
 circuit, is able to cause the armatures of the re- 
 lays to click back and forth between their stops. 
 As he does so the armatures at I, V and I" are 
 operated simultaneously so that the message can 
 be read at any station along the line. While the 
 
 clicking of an 
 instrument is a 
 notification to 
 the operator at 
 any point that 
 the line is in use. 
 
 FIG. 20. TELEGEAPH OPERATING KEY ^ U 
 
 for the working 
 
 of a telegraph circuit is shown in Fig. 20. The wire 
 enters and is attached to the point A, which is insu- 
 lated from the frame and other portions of the key. 
 The operating lever B is pivoted between two screw 
 points and to it is attached the other wire lead- 
 ing on out over the line. The lever carries a 
 point that stands opposite to A and which may 
 be brought into contact with the latter by press- 
 ing down upon the button-head C. When the 
 key is not in use the lever D is pushed beneath
 
 76 jeiectrfcttB 
 
 the contact-point A, as shown in the engraving, 
 and thus establishes an electrical contact between 
 it and the frame and with it to the lever ; thus 
 closing the circuit. When the key is to be 
 worked the lever D is first moved out to break 
 the contact at A, when the opening and closing of 
 the circuit is controlled by the working of the lever. 
 The signals of the electric telegraph are con- 
 veyed through a series of clicks on the sounder 
 instruments known as dots and dashes, because 
 they were originally inscribed as such on a mov- 
 ing strip of paper. These signals are made in 
 accordance with what is known as the Morse 
 code and are , as follows for the several letters 
 of the alphabet: 
 
 A. K . U .. 
 
 B ... L v ... 
 
 C . . . M W . 
 
 D . . N . X . . . 
 
 E . O . . Y . . . . 
 
 F . . P Z .. . . 
 
 G . Q..-. &.... 
 
 H . . . . R . . . ... 
 
 I .. S ... ? .. 
 
 J . . T , . . 
 
 1 . . 5 9 . . 
 
 2 . . . . 6 10 
 
 3 ... . 7 .. 
 
 4 . ,. 8 ...
 
 Gbe Blectrfc GeleQtapb 77 
 
 These letters will be seen to vary from each 
 other in some cases by the mere intervals and 
 lapses of time between the dots and dashes. 
 Thus H, Y, Z and & are formed by four dots, 
 spaced and sounded at different intervals apart. 
 
 Originally all telegraphic signals were regis- 
 tered upon a moving strip of paper as already 
 stated. The method is shown diagrammatically 
 in Fig. 21. The strip of paper R was moved at 
 a uniform speed, by 
 clock-work beneath 
 the roller C, while 
 a stylus point, at- 
 tached to the arm- 
 
 ature of the instru- FlQ 21> _ TELEGRAPH REGISTEE _ 
 ment, was brought ING APPARATUS 
 
 into contact with it. 
 
 This method has now been abandoned and the 
 reading is done entirely by sound. This has 
 added very materially to the work of becoming 
 a telegraph operator. It should be quite pos- 
 sible for an industrious person to learn to send 
 an intelligible message in from five to six days, 
 whereas it might take as many months to learn 
 to receive one with certainty and accuracy. 
 
 This reception of messages by ear has necessi- 
 tated the use of the relay instrument already
 
 78 jeiectrtcfts 
 
 referred to. The current passing over a tele- 
 graph line is usually so weak that the click of 
 the armatures on the relay instruments on the 
 main line, is so indistinct as to be heard with diffi- 
 culty. In order to increase the noise made by 
 the instrument a sounder operated by a local 
 battery is used. The strength of this battery is 
 such that the armature of the sounder is brought 
 against its stops with sufficient force to give 
 
 out a distinctly 
 audible sound. 
 The movement 
 
 of the armature 
 FIG. 22. TELEGRAPH RELAY AND , u , 
 
 SOUNDER f the rela y 
 
 is, therefore, 
 
 merely used to open and close the circuit of the 
 local battery by which the sounder is operated. 
 
 The method of wiring for the relay and sounder 
 is shown diagrammatically in Fig. 22. 
 
 A is the relay instrument, which is exactly 
 like the sounder except that it is so constructed 
 that its armature can be made to close and open 
 an electric circuit. B and C are the positive and 
 negative wires of the main line as they enter 
 and leave the coils of the relay magnet. D is 
 the armature of the relay and is made to con- 
 nect electrically with one pole of the battery F.
 
 Gbe Electric Gelesrapb 79 
 
 The sounder coil E has one wire leading to 
 the stop G for the relay armature, and the other 
 to one of the poles of the battery F. From the 
 other pole of the battery a wire is led to the 
 insulated armature of the relay. It is evident, 
 then, that, as the armature D moves back and 
 forth under the influence of its magnet, it will 
 make and break the circuit of the sounder and 
 cause the armature of the latter to move to and 
 fro between its stops and give the desired signals 
 to the receiving operator. 
 
 In regard to the amount of current used upon 
 telegraph lines, it is very weak and is hardly 
 perceptible when passed through the body. For 
 the main line it amounts to from forty to fifty 
 thousandths of an ampere, or, as it is technically 
 expressed, to from forty to fifty milliamperes. 
 At times it may even drop to fifteen milliamperes 
 and still give good and satisfactory service in 
 working. 
 
 The tension or voltage of the current is, how- 
 ever, quite high. Owing to the distances over 
 which the ordinary telegraph line is operated, 
 the resistance of the wires is very great and the 
 voltage must be increased in almost direct pro- 
 portion to the distance in order to overcome this 
 resistance. For this reason a large and powerful
 
 so ^Electricity 
 
 battery must be employed. Xo fixed rule can 
 be given for the determination of the strength 
 of current to be used, as it will depend upon 
 local conditions such as climate, the character of 
 the line, number and kind of instruments and 
 the like. A roughly broad statement may be 
 made to the effect that ordinarily one DanielFs 
 cell can be depended upon to give one volt, and 
 that the voltage should be equal to the number 
 of miles between terminals. 
 
 Thus for a line one hundred and fifty miles 
 long a battery of one hundred and fifty cells will 
 be required, and the voltage will touch the same 
 figure. It is customary, however, to duplicate 
 this battery by placing one of the strength named 
 at each end of the line. This is in order to ob- 
 tain a margin of excess to insure the proper work- 
 ing of the line under all of the adverse conditions 
 to which it may be subjected. 
 
 There is always more or less leakage of the 
 current from a line of any length owing to bad 
 insulation and changing weather conditions. A 
 heavy rainstorm by which the wires, insulators 
 and poles are wet will cause a very serious leak- 
 age of the current as a result of the deposited 
 moisture, since water is of itself a fairly good 
 conductor. It is, therefore, well to bear in mind
 
 Gbe Electric Gelearapb 81 
 
 the caution given in connection with electric 
 bells to always provide an excess of current over 
 that which the actual requirements of the case 
 make necessary. This applies with especial force 
 to private telegraph lines. 
 
 As for the battery required to operate a 
 sounder, two Daniell's cells are all that will be 
 needed. This is practically the standard number 
 that is used in all stations. 
 
 In erecting a telegraph line, but one wire is 
 used, the return current being carried by the 
 ground as shown in Fig. 19. It is necessary in 
 establishing the ground, as it is called, that the 
 wires should be carried down below the point of 
 permanent moisture and that they should be put 
 in close and intimate electrical contact with the 
 soil. 
 
 It will not do, then, to merely push the wire 
 down into the ground. It should be brazed to a 
 copper plate and the latter should be buried 
 below the water or moisture line and the earth 
 firmly packed about it. The wires may also be 
 fastened to gas or water pipes or the plate may 
 be buried near a stream of water or even lowered 
 into a well. 
 
 If the wires are to be attached to water or gas 
 pipes the latter should be filed clean and bright
 
 82 ^electricity 
 
 before the connection is made. Even then they 
 may prove to be an unsatisfactory ground be- 
 cause of some insulating or highly resisting ma- 
 terial having been used to form their own joints. 
 
 It may be taken as an axiom that many if not 
 most of the troubles experienced with private 
 telegraph lines arise from an improper or insuffi- 
 cient grounding of the wires. 
 
 For short lines it will usually be found to be 
 inadvisable to attempt to use the earth for the 
 return circuit. The added expense of putting in 
 an extra wire to complete the circuit will be 
 amply repaid by the convenience and freedom 
 from annoyance due to the failure of the current, 
 that would otherwise occur and the facility with 
 which all parts of the circuit can be inspected 
 and repaired. 
 
 From what has been said it will be seen that 
 the operation of long circuits involves the use of 
 very large and proportionately heavy batteries. 
 As the cell of a Daniell's battery for such a serv- 
 ice should be in a glass jar at least five inches in 
 diameter by six inches deep, the weight and bulk 
 of batteries, numbering cells by the hundreds, is 
 a matter of serious importance, which is not less- 
 ened by the trouble and expense of maintenance. 
 
 This difficulty has been obviated by the appli-
 
 Gbe Electric Gelegrapb 83 
 
 cation of the dynamo to the generation of the- 
 current used for telegraphic purposes. The 
 method ordinarily employed is to connect several 
 dynamos in series exactly as the batteries have 
 already been described as being connected, and 
 increasing the voltage from one to the other by 
 this means. The voltage used on long circuits is 
 somewhat less per mile than that previously given 
 in the rough statement of what should be pro- 
 vided for. It has been found that two hundred 
 and forty volts is sufficient for a circuit of four 
 hundred miles. 
 
 As far as the operators and the working of the 
 line are concerned there is no difference between 
 the using of a current generated by batteries or 
 dynamos. The advantages possessed by the lat- 
 ter are greater compactness, decreased cost of 
 installation and maintenance and increased re- 
 liability. 
 
 There are some precautions that should be 
 taken in the installation of any telegraph line, no 
 matter how short, where the wires are stretched 
 out of doors and are exposed to the elements. 
 
 One of these precautions is the protection of 
 the instruments from injury by lightning. 
 Wherever a bare wire is out of doors it is sub- 
 jected to the influence of the electrical condition
 
 84 
 
 of the atmosphere. As it is usually a far better 
 conductor than the other objects with which it is 
 surrounded and as it is usually led to a direct 
 connection with the ground, it becomes a light- 
 ning rod of great extent ready to receive and 
 convey any discharge that may be delivered to it. 
 
 It has already been pointed out that the con- 
 veyance of an electrical current through any 
 wire whatsoever is always accompanied by the 
 development of more or less heat. The stronger 
 the current and the greater the resistance of the 
 wire the higher will be the temperature devel- 
 oped in the wire. 
 
 As the wire used in the coils of a telegraph in- 
 strument is smaller than that used out upon the 
 line, its resistance is greater and the amount of 
 heat developed in it with the passage of a given 
 amount of current will also be greater. It fol- 
 lows, then, that a current, which might have no 
 appreciable effect upon a line wire might heat to 
 redness and destroy the wiring of an instrument. 
 
 To prevent such an accident from occurring as 
 the result of a lightning discharge, lightning 
 arresters should be placed in the circuit. The 
 simplest form which this can take is that of 
 a fine piece of wire of high resistance. As soon, 
 therefore, as the intensity of the current rises
 
 Gbe Blectric Getegrapb 85 
 
 above that which it is desired that the wires 
 shall carry, this small wire is melted and is 
 broken, thus opening the circuit and preventing 
 the excess current, with which the line is charged, 
 from passing through the instruments and injur- 
 ing them. This is the easiest method for pri- 
 vate lines that are to be erected and operated by 
 the owner. 
 
 For regular telegraphic service more elaborate 
 provisions are made with regularly constructed 
 lightning arresters. Some of these are arranged 
 to automatically cut out with a spring as soon as 
 the voltage exceeds a certain predetermined 
 figure. Others are provided with a plug which 
 may be withdrawn whenever the dancing of the 
 armature of the instrument shows that the line 
 is subjected to outside electrical influences at 
 some point along it. 
 
 It is always well to provide even short private 
 lines with one of these plugs so that the instru- 
 ments may be entirely disconnected, whenever it 
 is known that the line is not to be used for any 
 length of time. This makes it possible to dis- 
 connect at night during the season of electrical 
 storms. There are several ways in which this 
 plug can be made, the simplest being that of 
 placing two binding posts like Fig. 23, in the
 
 86 
 
 circuit and connecting these with a strong cop- 
 per wire, which may be easily removed by the 
 slackening of one of the set-screws. 
 
 This plug should not be used to the 
 exclusion of the fusible wire, but 
 merely as a protection to the latter and 
 to avoid the annoyance of replacing the 
 same when the danger of its destruc- 
 tion begins to manifest itself. 
 
 No attempt has been made in this 
 chapter to deal with the intricacies of 
 duplex and quadruplex telegraphy, by 
 means of which two messages may be 
 sent in opposite directions over one wire at the 
 same time, but merely to handle the matter in its 
 simplest form, and in a way to guide those who 
 wish to use it on a small scale.
 
 CHAPTEE VI 
 
 THE TELEPHONE 
 
 THE telephone strictly speaking is au instrtu 
 ment with which sounds can be conveyed from 
 one point to another by means of the electric 
 current. There are, however, other instruments, 
 improperly called telephones, by which the same 
 object may be attained and in which no electrical 
 current is used at all. 
 
 As these so-called mechanical telephones are 
 very frequently made and installed for private 
 use it may be well to give a brief description of 
 their construction and principle of operation. 
 
 Sound is a form of wave motion which may be 
 imparted to solids, liquids or gases, and which, 
 when impinging on the drum of the ear, pro- 
 duces the sensation which we know by that 
 name. That the sound waves can be carried 
 through solids and liquids as well as gases is evi- 
 denced by the loud apparent noise made by the 
 striking of stones together when the head of the 
 listener is below water. The same phenomena is 
 
 87
 
 88 Electricity 
 
 manifested by the conveyance of sound waves 
 along pipes that are struck with a hammer. 
 
 The principle, then, upon which a mechanical 
 telephone may be made to operate is that of the 
 conveyance of a sound through the metal of a 
 wire. Means must be supplied of imparting the 
 sound vibrations to one end of the wire and of 
 receiving them from the same at the other. 
 Owing to the resistance of the metal to the pas- 
 sage of these wave motions, the distance over 
 which they can be carried is limited. As a mat- 
 ter of fact it is somewhat difficult to get a me- 
 chanical telephone to work when the distance is 
 more than a mile between terminals. 
 
 The construction of a mechanical telephone for 
 household or office purposes is very simple. The 
 most satisfactory working can be obtained by 
 using a drumhead or piece of parchment 
 stretched over a frame and held firmly in the 
 position it is to occupy. A piece of steel wire is 
 let through the centre of the drumhead and 
 fastened to a small button, which may thus be 
 held firmly against the head. The wire is car- 
 ried to another similar drumhead and similarly 
 fastened. It should be carried as direct as pos- 
 sible with the minimum number of bends and 
 none of them short ones.
 
 Gbe Gelepbone 89 
 
 A person standing in front of such a drum- 
 head and speaking, can be heard at the other. 
 Attention may be called by tapping on one head 
 with the finger. The transference of conversa- 
 tion over the line can be prevented by merely 
 hanging a curtain loosely before the receiving 
 drumhead. The diaphragms or drumheads may 
 be replaced if desired by a piece of ferrotype, 
 such as the so-called tintype pictures are made upon. 
 
 The true telephone, on the other hand de- 
 pends upon an electric current "for the transfer- 
 ence of the sound waves from one point to an- 
 other, and the connecting wire is not, in any 
 way subjected to their vibrations. 
 
 Before taking up the construction of the tele- 
 phone, a few words regarding magnetism and its 
 influences will be needed. In the first chapter it 
 was explained that a magnet has the power to 
 attract to itself small iron filings with which it 
 may be brought into contact. If a magnet be 
 placed beneath a sheet of paper and iron filings 
 be first scattered over the top and the paper then 
 slightly jarred, they will arrange themselves 
 along certain lines of force as shown in Fig. 24. 
 They will cluster most densely about the poles 
 of the magnet and lead out and back in diverg- 
 ing lines from one pole to the other.
 
 90 
 
 jeiectrfcftB 
 
 It has been shown that, if an electric current 
 be made to pass in a coil around a bar of iron, 
 
 the latter will become 
 magnetized. The 
 converse of this is 
 equally true, that if 
 a magnet be moved 
 through a coil of 
 FIG. 24. MAGNETIC FIELD wire, an electric cur- 
 rent will be gen- 
 erated and made to pass through the wire pro- 
 vided the ends are brought together so as to form 
 a closed circuit. 
 
 These simple phenomena lie at the base of the 
 operation of the electric telephone as well as that 
 
 FIG. 25. SECTION OF BELL TELEPHONE RE- 
 CEIVER 
 
 of all dynamos and motors and will be more 
 fully explained later. 
 
 Fig. 25 is a sectional engraving of the double- 
 pole Bell telephone receiver.
 
 Gbe ftelepbone 91 
 
 The working parts consist of a horseshoe mag- 
 net A, two soft iron cores wound as magnets B 
 and C and a diaphragm D. 
 
 The horseshoe magnet is permanent and car- 
 ries the soft iron cores which are in metallic con- 
 tact with it and which thus form short polar ex- 
 tensions. The wires are led out from the wind- 
 ings to the binding posts at the farther end to 
 which the wires to complete the circuit to the 
 other instrument are fastened. 
 
 The operation of the instrument is as simple 
 as its .construction. A noise, such as speaking, 
 made in front of the diaphragm, causes the latter 
 to vibrate just as in the case of the mechanical 
 telephone. This vibration causes a variation in 
 the number and intensity of the magnetic lines 
 of force cutting the coils around the soft iron 
 cores. This variation of intensity and number 
 has the same effect as a moving of the core 
 through the coils, as may be inferred from an 
 examination of Fig. 24. The result of this is 
 that an electric current is generated and caused 
 to pass through the coil of wire about the cores. 
 
 If now these wires are carried out and con- 
 nected to another similar receiver so that the 
 wire from B leads to the coil corresponding to C, 
 and vice versa, the current generated at the first
 
 92 jeiectricfts 
 
 diaphragm will cause a variation of the intensity 
 of the magnetism in the cores in front of the 
 second diaphragm. 
 
 In explanation of this statement the reader 
 will remember that the intensity of the electric 
 current passing through a coil controls the 
 strength of the magnet. So, in this case, the 
 strength of the cores is varied by the variation 
 of the current produced by the vibration of 
 the first diaphragm. This causes corresponding 
 change to take place in the attraction of the 
 cores for the diaphragm; in harmony with the 
 vibrations of the transmitting diaphragm, causing 
 it to emit similar though somewhat weaker 
 sounds. 
 
 From this it appears that an instrument like 
 that shown in Fig. 25 may be used both as a 
 transmitter and receiver. The former is the 
 term applied to the instrument at which the 
 message is started, and the latter to that at which 
 it is received. 
 
 In the construction of the instrument the 
 screw E, at one end, is a holding and adjusting 
 screw only. It holds the permanent horseshoe 
 magnet in position and serves to adjust it so that 
 the ends of the cores will be at the proper dis- 
 tance from the diaphragm in order to produce
 
 Gbe Gelepbone 93 
 
 the best results. The diaphragm itself is held 
 by a cap screwed down over it and clamping it 
 around the edge. 
 
 In practice it has been found to be preferable 
 to use separate instruments for the transmitting 
 and reception of telephone messages. 
 
 The transmitter that has received the widest 
 application is the one known as the Blake, prob- 
 ably because it was the first satisfactory one pro- 
 duced. It is dependent for its action upon the 
 fact that, if an electric current is made to pass 
 through two non-oxidizable substances in loose 
 contact with each other, and these are put into 
 vibration, the resistance offered to the passage of 
 that current is subject to wide variations. This 
 is due to the increase and decrease in intimacy 
 of contact, by which the resistance is correspond- 
 ingly increased or diminished. 
 
 Thus, in the Blake transmitter, the current is 
 made to pass through a piece of hard carbon that 
 is in loose contact with a piece of platinum. 
 
 The construction of this transmitter is shown 
 in section in Fig. 26. The diaphragm A is carried 
 by an insulating ring clamping and holding it at 
 its edge. Against the centre of this diaphragm 
 there is brought to bear a platinum point B. 
 This latter is held by a thin spring C which is
 
 94 
 
 Blectricfts 
 
 held by a piece of insulation to the upper arm of 
 the heavy lever D. This latter is itself carried 
 by the spring E and adjusted to position by the 
 screw F. Dropping down from 
 the upper end of the lever is a 
 spring G to the lower end of 
 which the carbon button H al- 
 ready referred to is attached. 
 This is in contact with the 
 platinum point. 
 
 The wiring from the electric 
 circuit enters through the insula- 
 tion at the top of the lever D 
 and is led out from the bottom 
 of the same. The course of the 
 FIG. 26. SECTION current through the transmitter is 
 OF BLAKE TELE- first over the spring C to the 
 PHONE TRANS- platinum point B, to the carbon 
 button H, to the spring G, to the 
 lever D and out at the bottom of the bracket as 
 shown. 
 
 The action of the transmitter is as follows : 
 The speaker in front of the diaphragm causes 
 it to vibrate in unison with the pitch of the 
 utterance. This vibration is communicated to 
 the platinum point and by it to the hard carbon 
 button. The tension of the spring by which the
 
 Gbe Gelepbone 95 
 
 latter is supported is varied by this vibration caus- 
 ing a variation in the pressure of contact be- 
 tween the two parts thus producing a correspond- 
 ing variation in the resistance to the current 
 already indicated. 
 
 It will be noticed that in this transmitter the 
 horseshoe magnet and soft iron cores are missing 
 and that the generation of an electric current by 
 the variation of the lines of force of a magnet 
 does not take place. 
 
 This transmitter 
 is known as the 
 
 microphone trans- 
 
 mitter and is a Fl0 ' 27 -- SllfGLE TELEPHONE Cte- 
 
 CUIT 
 
 modification of the 
 
 Hughes microphone, whose action is dependent 
 upon the principle already explained regarding 
 the variation of the resistance to an electric cur- 
 rent by the vibration of two loose pieces in contact. 
 This instrument, then, depends upon some out- 
 side source of electricity for the operating cur- 
 rent and merely changes the amount of flow of 
 this current to produce the desired effect upon 
 the receiver. This current may be furnished by 
 an ordinary Daniell's or Leclanche battery and 
 the wiring for a simple circuit would be done as 
 shown in Figs. 26 and 27.
 
 96 
 
 Blectrfcfts 
 
 In this the current starts from the battery and 
 flows out over the wire to the transmitter, thence 
 to the coils of the receiver and on back to the 
 battery. 
 
 With such a combination as that given in this 
 illustration, the transmission of sound would be 
 in one direction only, namely from the trans- 
 mitter to the receiver. Though the action of the 
 receiver might send back some sound it could not 
 be made available. 
 
 In order, then, 
 that the tele- 
 phone circuit 
 may be used to 
 transmit sound 
 FIG. 28. SIMPLE TELEPHONE CIRCUIT in both direc- 
 WITH RECEIVER AXD TRANSMITTER t i ons and thus 
 
 be employed for conversational purposes, there 
 should be a receiver and transmitter at each end 
 of the line. 
 
 The wiring for such a combination is very sim- 
 ple and consists in putting the extra transmitter 
 and receiver into the circuit as shown in Fig. 28. 
 Here two batteries are used just as in a telegraph 
 circuit for the sake of having an ample current 
 available and not because a battery at one end of 
 the line could not be made to do the work. The
 
 ttbe Gelepbone 97 
 
 'line is also shown with a return wire, which, as 
 in the case of the telegraph should always be 
 used on short lines, owing to the difficulty of 
 securing a satisfactory ground return. 
 
 As the distance between the transmitter and 
 receiver of a telephone circuit increases, the 
 greater is the resistance offered by the line 
 wires, the greater the current required to operate 
 it and the less the influence of the transmitter in 
 causing a variation of the intensity of that cur- 
 rent. After a time the distance would become 
 so great that the proportional variation of resist- 
 ance set up at the transmitter as compared with 
 the total resistance of the line would be so slight 
 as to be inappreciable. When this point was 
 reached there would be no perceptible effect at 
 the receiver and no sound would be heard at that 
 point. 
 
 In order to obviate this difficulty recourse is 
 had to the induction coil. 
 
 Just as we have seen the magnet to be sur- 
 rounded by lines of force that will cause iron 
 filings to arrange themselves in certain definite 
 positions on a sheet of paper ; so a wire, through 
 which a current of electricity is passing, is sur- 
 rounded by corresponding lines of force that 
 have a direct influence on other wires in their
 
 98 ^electricity 
 
 own neighborhood. This influence causes an in- 
 duced electrical current in the second wire. Thus, 
 if two wires are laid side by side and an electric 
 current be made to pass, from the positive pole 
 of a battery, over one of the wires from right to 
 left, an induced current will appear in the second 
 wire flowing from left to right. 
 
 In like manner if the wire carrying the primary 
 current, or the one generated by the battery, is 
 wound about a soft iron core, the latter will be- 
 come magnetized to a degree dependent upon 
 the number of ampere turns. A second coil, 
 carried around this same core, will have an in- 
 duced or secondary current passing through it. 
 
 Advantage is taken of these facts to cause the 
 transmitter to so influence the current of the 
 main line that the proper effect is produced at 
 the receiver. The practical working of this ar- 
 rangement is that the primary current, or the 
 one generated direct by the battery is compara- 
 tively large and the undulations are not of great 
 magnitude. In the secondary current, on the 
 other hand, owing to the greater number of 
 windings in the coil, the intensity is higher and 
 the fluctuations correspondingly greater. 
 
 The modification that should be made in the 
 connections shown in Fig. 28, consist in the in-
 
 Gbe ftelepbone 99 
 
 troduction of the induction coil into the circuits 
 of the two local batteries. The method by which 
 this is accomplished is clearly shown in Fig. 29. 
 
 As far as the local battery is concerned it will 
 be seen that its circuit is confined strictly to its 
 own transmitter. Thus, take the connections at 
 the station A . The current flows from the battery 
 B to the transmitter and thence through the in- 
 duction coil D and back to the battery. At the 
 
 FIG. 29. TELEPHONE CIRCUIT WITH IN- 
 DUCTION COILS 
 
 station C there is a similar connection for the 
 transmitter. There is no direct connection of 
 the primary current with the receiver either at 
 its own or the opposite end of the telephone cir- 
 cuit. This connection is made by means of the 
 induced current. 
 
 Starting from the induction coil at D the cur- 
 rent goes out over the line wire to the induction 
 coil of the station C, thence to the receiver of
 
 ioo Blectrfcfts 
 
 that station, back to the receiver of station A and 
 finally completes the circuit by entering the in- 
 duction coil D. 
 
 This is the simple arrangement in accordance 
 with which the speaking telephone is constructed 
 and worked. There are some complications and 
 delicacies of adjustment that might make it diffi- 
 cult for the amateur to meet were he to attempt 
 to make one for his own use, but there is nothing 
 intricate in the erection and maintenance of the 
 same when the operating parts have once been 
 obtained. 
 
 The instrument as thus described is by no 
 means a complete and perfect telephone, for even 
 ordinary use. In addition to the apparatus that 
 is merely capable of transmitting spoken words 
 from one point to another, there must be some 
 means of attracting the attention of the parties 
 located at one instrument when those at the 
 other wish to speak to them. 
 
 The ordinary method of doing this is by the 
 use of a call bell. This may be independent of 
 the telephone but using the same line wire and 
 may take the form of the ordinary bell described 
 in a preceding chapter. Such an arrangement is, 
 however, seldom used, but in its stead the mag- 
 neto switch bell or a battery bell is used.
 
 Ebe Gelepbone 101 
 
 In the former a small dynamo is placed within 
 the telephone case, and is t/u-rh^d by a .handle 
 upon the outside. The principles underlying the 
 construction of the dynamo* wilj be f.uHy a^piaiiied 
 in the chapter on Dynamos and Motors. 
 
 Suffice it, for the present, to say that the cur- 
 rent generated by this small dynamo is led out 
 over the line wire to the further end where it is 
 made to ring the call bell. The introduction of 
 this magneto bell adds a little more to the com- 
 plication in that it is desirable that the trans- 
 mitter and receiver should be out of the circuit 
 when the instrument is not in use, and that the 
 bell should be in circuit. This is accomplished 
 by the weight of the receiver pulling down the 
 lever upon which it is carried, when not in use 
 and cutting out the transmitter and receiver and 
 putting the bell in circuit. The removal of the 
 receiver from the hook allows a spring to lift the 
 lever, a movement which cuts out the bell and 
 puts the transmitter and receiver into the circuit. 
 
 The battery switch bell is in itself constructed 
 like the vibrating bell already described. The 
 ringing is accomplished by the pressing of a 
 push button on the side of the case while the re- 
 ceiver is still hanging upon its hook at the side. 
 On removal of the receiver a spring lifts the
 
 102 Blectrfcftg 
 
 lever and, as in the previous instance, throws the 
 bell out -of and the -receiver and transmitter into 
 circuit. 
 
 These are tb.3 principles irpon which the whole 
 telephonic circuit are worked and, like all other 
 electrical instruments, they are exceedingly 
 simple in theory. 
 
 Owing, however, to the contracted limits of a 
 telephone case into which it is desired to stow a 
 considerable mass of wiring and apparatus, the 
 whole scheme will appear upon first examination, 
 to be a complicated and chaotic tangle. But this 
 is far from being the case, and the recommenda- 
 tion of dissection is made to the student of the 
 telephone, just as it is made to the student of 
 human anatomy. 
 
 It is quite necessary that a word of caution 
 should be added, in the closing of this chapter, 
 regarding the stringing of telephone wires. In 
 the ordinary electrical circuit where some visible 
 work is to be done like the ringing of a bell or 
 the moving of an armature or a telegraph instru- 
 ment the current must be of considerable in- 
 tensity and variations in that intensity are un- 
 noticed, provided only that it is, in itself, strong 
 enough to do the work desired. In the telephone 
 circuit, on the other hand, the current is very
 
 Gbe Gelepbone 103 
 
 feeble and is dependent for its efficiency upon 
 these same variations that are of no moment in 
 other classes of work. 
 
 We have seen how a current can be induced by 
 placing one wire near another that is already 
 carrying a current from a primary battery. It 
 follows, then, that the same law must hold good 
 at all points of the line, and the proximity of 
 telegraph or electric lighting wires to a telephone 
 wire may set up induced currents in the latter, 
 that may have such an overpowering effect as 
 not only to prevent the transmission of speech 
 from one end of the line to the other, but to 
 cause the receivers to ring with noises emanating 
 from remote sources. Indeed it was these in- 
 duced currents that, in the early days of tele- 
 phony, caused the most serious trouble to the 
 companies and their patrons. 
 
 The telephone wire seems to be particularly 
 sensitive to the influences of induction, and dis- 
 tances of several feet, that would ordinarily be 
 considered quite sufficient to protect a wire are 
 totally inadequate in telephone work. 
 
 It may be laid down as a fixed basis of opera- 
 tion that telephone wires should not be placed 
 parallel to those carrying stronger currents. If 
 approximate parallelism is not to be avoided, the
 
 104 Electricity 
 
 outgoing and return wires should zigzag on their 
 poles so that first one and then the other shall be 
 the nearer to the wire with the stronger current. 
 This minimizes the effects of the induction by ex- 
 citing currents in opposite directions in the same 
 circuit ; currents which thus serve to neutralize 
 and counteract each other. 
 
 Where telegraph or electric lighting wires are 
 to be crossed by a telephone circuit, it should al- 
 ways be done at right angles. Such a crossing 
 obviates the trouble of induction entirely. 
 
 As for the return wire in a telephone circuit 
 the rule given for telegraph wires can be used 
 and for the same reasons : where the distances 
 are short and especially where they are limited 
 to the confines of a single building, use a wire 
 for a return circuit. This applies also to the 
 confines of a factory. For greater distances the 
 earth may be used for the return. 
 
 The most satisfactory wire for private line 
 work will be found to be No. 16, made of hard 
 drawn copper or phosphor bronze. It should be 
 well insulated and drawn taut. For inside work 
 it should be covered, but may be bare out-of- 
 doors. 
 
 After the instruments have been set up they 
 should be carefully tested to see that the ad-
 
 Gbe Gelepbone 105 
 
 justment is all right. The first thing to do is to 
 take down a receiver and, holding it to the ear, 
 breathe into the transmitter. A distinct sound 
 should be heard. If this can be done, an as- 
 sistant can be sent to the other end to ring up 
 and, if a conversation can be carried on, the in- 
 struments are all right. 
 
 In case the second instrument fails it should 
 be examined and adjusted until the breathing 
 test gives an audible sound. 
 
 The location of faults and failures of the tele- 
 phone is sometimes a tedious piece of work, and 
 can only be touched upon here. But trouble may 
 occur in the springs by which the pressure be- 
 tween the platinum point and the carbon is regu- 
 lated. In the receiver, it may arise from the 
 accumulation of dust that dampens the action of 
 the diaphragm. It is only by a careful exami- 
 nation of the whole apparatus that the defects 
 can always be placed, and the rapid location of 
 faults cannot be done except by an experienced 
 person.
 
 CHAPTEK YII 
 
 DYNAMOS AND MOTOKS 
 
 DURING the last thirty years of the nineteenth 
 century the practical application of electricity to 
 the uses of man advanced by leaps and bounds ; 
 and it is safe to say that so great a proportion of 
 this advancement, as to leave but an insignificant 
 remainder, is due to the development of the 
 dynamo and the discovery of its convertibility 
 into a motor. The dynamo has rendered it pos- 
 sible to produce currents of an intensity pre- 
 viously undreamed of and at an expense so far be- 
 low that of a similar generation by batteries as 
 to put the latter entirely out of consideration as 
 a competitor. It is the dynamo that is now de- 
 pended upon for the generation of all currents 
 aside from the light and isolated instances that 
 we have been heretofore considering. 
 
 The dynamo has converted the generation of 
 
 the electric current from a matter of chemical 
 
 combinations to the mere mechanics of motion. 
 
 While the practical working of the dynamo has 
 
 100
 
 Bgnamos ant) /factors 107 
 
 developed many difficulties and troubles which it 
 has taken some time and considerable ingenuity 
 to overcome, the fundamental principles of its 
 operation are exceedingly simple. 
 
 It has already been shown that if a magnet be 
 made to approach toward or recede from a coiled 
 wire, or to pass through the opening of its coils, 
 an electric current will be generated and made 
 to pass through the wire. And, further, that the 
 strength of this current will depend upon the 
 power of the magnet and the form and number 
 of the coils. Hence it must be apparent that if 
 a coil of wire be made to approach and recede 
 from a magnet or, in other words, to move to 
 and fro in a magnetic field, the result will be the 
 same as though the coil were to be held station- 
 ary and the magnet moved. 
 
 As revolution about a shaft in a magnetic field 
 is the easiest method of accomplishing this result, 
 this is the way in which the work has been done. 
 The dynamo, then, is so constructed that coils of 
 wires are revolved in front of the faces of pow- 
 erful magnets. The effect of this work done in 
 the magnetic field is to generate the currents 
 which are then led off and made to perform use- 
 ful work. 
 
 In order to obtain the maximum results with
 
 108 jeiectricits 
 
 machinery of the most compact form, several 
 coils of wire are moved in unison between the 
 faces of two magnets that are set opposite to 
 each other. The result of this is that there are 
 always two coils, (those nearest the faces of the 
 magnets) in which the maximum currents are be- 
 ing generated. 
 
 If now we conceive of a coil of wire moving 
 between two magnets whose north and south 
 poles are presented to each other, it will be ap- 
 parent that it will be subjected to different in- 
 fluences as it passes next to the two poles respect- 
 ively. This difference of influence will produce 
 different results, which are simply that the cur- 
 rent generated in the coil will flow in one direc- 
 tion in front of one pole and in the other direc- 
 tion in front of the other pole. If this is so, there 
 must be some point where the current changes 
 its direction of flow, and this must occur twice in 
 each revolution of the coil. 
 
 It has also been shown that the intensity of 
 the current depends upon the intensity of the 
 magnetic field, and as this is most intense directly 
 in front of the centre of the pole, it naturally 
 follows that the current in the coil gradually in- 
 creases in intensity from one neutral point to the 
 point of maximum intensity and then as grad-
 
 2>Enamos anfc dfcotors 109 
 
 ually dies away to the other neutral point, where 
 reversal takes place to repeat the same phenom- 
 enon back to the original neutral point. 
 
 Having generated the current it remains to 
 lead it off and make it available, and this is 
 purely a problem of mechanics. 
 
 The coils are wound about a soft iron core as 
 shown in Fig. 30. If there are two coils on this 
 core there will be two breaks in the current at 
 each revolution. If, however, four segments or 
 coils are used the current will be continuous in 
 the sense that there is no actual break but there 
 will be a variation in the intensity dependent 
 upon the point occupied by the coils in the rev- 
 olution. This variation is lessened by increasing 
 the number of coils, still more, thus holding the 
 current at a constant degree of intensity. 
 
 As it is impossible to graphically represent the 
 wiring of a large number of segments or coils as 
 they are put upon a single armature, attention is 
 particularly directed to the two-coil arrangement 
 shown in Fig. 30. 
 
 The current generated in the top coil, for ex- 
 ample, flows in the direction indicated by the 
 arrows, and out at the block A of the commutator. 
 This block is connected to the block B by 
 the brushes and the line wire so that the cur-
 
 110 
 
 Electricity 
 
 rent is entering from B and flowing into the 
 coils. 
 
 The commutator is formed of a large number 
 of copper segments placed 
 radially to the shaft and in- 
 sulated from it and from 
 each other. 
 
 They are, in fact, the 
 terminals of the armature 
 coils. They are connected 
 to each other and the circuit 
 thus closed through the in- 
 termediary of the brushes. 
 These brushes consist of 
 blocks of hard carbon or 
 copper that can be adjusted 
 to come into contact with the commutator at 
 the proper point and, while insulated from the 
 body of the machine, are electrically connected 
 to the line wires to which they deliver the cur- 
 rent generated in the armature. 
 
 This current is also led, either in whole or in 
 part through the field magnets, as those magnets 
 between which the armature is revolved is called, 
 and which therefore serve for their own excita- 
 tion. 
 It might properly be asked, if the genera- 
 
 FIG. 30. DIAGRAM OF 
 ARMATURE WIND- 
 INGS FOR DYNAMOS
 
 JDgnamos anfc Motors in 
 
 tion of the current is due to the presence of a 
 magnet outside the armature, how it happens, if 
 this magnet depends upon the current for its own 
 existence, that the current can be started in the 
 first place. The reason lies in the fact that there 
 are traces of magnetism to be found in all pieces 
 of iron, and especially those that have once been 
 magnetized, known as residual magnetism, and it 
 is this faint trace that serves to generate the first 
 feeble currents that make themselves manifest 
 when the armature is set in revolution. These 
 at once serve to increase the magnetic properties 
 of the field magnets and by the time the machine 
 is running at its normal speed the full current 
 for which it was wound is being generated. 
 
 In order to understand the construction and 
 operation of the dynamo, it will be well to pass 
 in brief review the materials that are used and 
 the methods that are followed in its construction. 
 
 The armature shaft should be of steel and of 
 ample strength to withstand the torsional stresses 
 that are put upon it. And it must be remem- 
 bered that this armature shaft has real work to 
 do and real resistances to overcome. The coils 
 of the armature exert a push contrary to their 
 motion, which must be overcome, and all of the 
 work which the electric current generated by the
 
 112 ^Electricity 
 
 dynamo may afterwards be called upon to per- 
 form, such work as the driving of machinery or 
 the moving of street cars, must be done and 
 done with a loss of about 35 per cent, by the ar- 
 mature shaft. 
 
 As in all other electrical appliances with 
 which we have had to deal, copper wire is used 
 for the winding of the armature. This wire is 
 invariably insulated with some covering that is 
 not likely to become injured by heat or friction. 
 A good cotton-covered wire of about 16 guage is 
 a suitable one for small dynamos. In the laying 
 of this wire about the cores the utmost care must 
 be taken that it is immovably packed and held in 
 position. There is nothing more disastrous to 
 the working of the armature than loose wires. 
 We have already seen how the coils oppose a re- 
 sistance to the motion of revolution that is im- 
 parted to them, and this opposition characterizes 
 the action of each individual wire, with the re- 
 sult that it tends to crowd back and rub upon its 
 fellow. Then, when rubbing does take place, 
 the insulation is soon worn away, the wires of 
 the coil come into contact with each other, short 
 circuiting and heating take place and in a flash 
 the armature is frequently ruined. 
 
 The core of the armature should invariably be
 
 Dynamos anfc /footers 113 
 
 made of the softest and purest iron that is ob- 
 tainable. Cast iron will not do at all and forged 
 wrought iron will not give satisfactory results. 
 The best method of forming the core is to build 
 it up of thin plates cut out of refined sheet iron. 
 The reason for this lies partly in the greater 
 purity of the metal obtainable and partly from 
 the fact that the several parts can be insulated 
 from each other. Wires may also be successfully 
 used for the building up of the armature core, 
 but the mechanical difficulties of handling, join- 
 ing and insulating them makes the flat plate pref- 
 erable. 
 
 The solid iron cores are objectionable princi- 
 pally upon the ground of their tendency to heat, 
 and the facility with which they permit of the 
 formation of electrical eddies, known as Fou- 
 cault currents within their confines. 
 
 The commutator to which the ends of the coils 
 are attached is formed of a number of copper 
 segments set radially about the shaft and insu- 
 lated from it and from each other. They are 
 equal in number to the coils in the armature 
 core. 
 
 The brushes have taken almost every conceiv- 
 able form and still show wide variations, de- 
 pendent upon the ideas of the manufacturer or
 
 114 BlectrtcftB 
 
 designer of the machine. They may be a bundle 
 of copper wires, soldered together at one end, or 
 thin plates of the same metal also fastened to- 
 gether at one end, or a plate split into several 
 tongues by slots cut into the end or pieces of 
 hard carbon with an electro-plated covering at 
 the end and extending well down to the point of 
 contact with the commutator, where bj the re- 
 sistance of the mass to the flow of the electric 
 current is greatly diminished. 
 
 The field magnets are usually of cast iron 
 though sometimes they are forged. They must 
 be wound with a well-insulated wire which may 
 be somewhat larger than that used on the ar- 
 mature. In the winding, the coils should be 
 carefully packed but there is not the same tend- 
 ency to move to be guarded against as in the 
 armature. As a matter of detail it is well to put 
 more wire about the central portion than at the 
 ends, as contributive to a greater uniformity of 
 current. 
 
 The principle of action of the dynamo has 
 been seen to be that of the generation of an elec- 
 tric current by the movement of a coil of wire 
 through a magnetic field, a principle that was 
 discovered by Faraday in 1831. 
 
 The converse of this is also true that if an
 
 Dynamos an& dBotors us 
 
 electric current be passed through a coil standing 
 in a magnetic field there will be a tendency to 
 move. This movement will take place, however, 
 in a direction opposite to that in which it would 
 be necessary to move the coil in order to gener- 
 ate a current similar to the one referred to. 
 
 This converse action is the reason for what is 
 known as the reversibility of the dynamo. 
 Hence if, instead of revolving the armature by 
 some outside power, and thus generating a cur- 
 rent, that same current be sent into the armature, 
 through the brushes and commutator, it will re- 
 volve in the opposite direction from that in 
 which it would itself have to be moved when 
 acting as a dynamo or generator. 
 
 The dynamo can, then, be used as a motor or 
 the motor as a dynamo without any change 
 whatever in construction. As a matter of fact, 
 however, slight changes are made in the details 
 of construction of the two, in order that each 
 may be best adapted to the purposes which it is 
 called upon to serve. The principle, neverthe- 
 less, remains unchanged and is merely an ex- 
 ample of reciprocal action. 
 
 Any one who expects to operate a motor or 
 dynamo should have this elementary knowledge 
 of their construction and mode of action in order
 
 116 Blectrfcfts 
 
 that they may be handled intelligently. This is 
 necessary because, like all other machinery, the 
 dynamo and motor have their ills and the person 
 who has charge of them should so thoroughly 
 understand their construction that it will be pos- 
 sible to analyse the trouble and either apply a 
 remedy or make the repairs without calling in 
 outside assistance. 
 
 As the dynamo and motor are so nearly iden- 
 tical, they will be considered collectively here- 
 after under the general title of " machine." 
 
 In the selection of an electric machine, the 
 same advice may be given as in the case of the 
 battery. Be sure and secure one that has an 
 ample margin of excess above the calculated re- 
 quirements of the work in hand. It is a peculiar 
 property of the machine that, whether working 
 as a generator or a motor, it automatically ad- 
 justs itself to the amount of work that it has to 
 do. Thus the dynamo will generate no more 
 current than is being drawn off from the line, 
 and it will generate as much as the demand re- 
 quires, even to the point of overheating and 
 burning out. So, too, the motor will take in 
 only the amount of current required for its 
 work, but when the latter is increased too far 
 beyond its rated capacity, it, too, will struggle
 
 2>namo6 anb Motors 117 
 
 to meet the demand, even to the point of a col- 
 lapse. 
 
 For these reasons it is well to have an excess 
 of power in reserve, that overloading may be 
 avoided. As a matter of fact it is probable that 
 in nine cases out of ten, a machine will run more 
 economically when its output is twenty per cent, 
 less than its rated capacity than when run up to 
 the limits of that capacity. 
 
 Another point in the selection of the machine 
 should be borne in mind and that is that there 
 is no economy in the purchase of cheap, light 
 machines. The purity of the metal required in 
 their construction and the care that must be 
 taken in the workmanship makes them more ex- 
 pensive to manufacture than other classes of ma- 
 chinery of the same weight. Hence a low price 
 usually means the neglect of some essentials. 
 
 Weight, besides being of value from an elec- 
 trical standpoint, is also an advantage in that it 
 serves to steady the running ; and this is a most 
 important factor in the operation of any elec- 
 trical machine. 
 
 After the machine has been selected it should 
 be carefully located and set. The principal point 
 in this is to see that the foundation or base upon 
 which it is placed, is solid and unyielding. If
 
 118 BiectrfcttB 
 
 the machine is a small one, there will be no need 
 to build a special foundation. But, even though 
 it be merely a desk fan, it should be put where 
 it will be steady and not subjected to jars. Large 
 machines should be placed upon special masonry 
 foundations. 
 
 The direction of rotation of a motor depends 
 upon the direction of the flow of current through 
 it. This must be evident from the principles of 
 its action as already laid down. A current flow- 
 ing in one direction through its coils will tend to 
 move them in one direction, and in another if it 
 is reversed. 
 
 Ordinarily, electric machines are intended to 
 run right-handed, that is, from left over to right, 
 or in the direction of the movement of the hands 
 of a watch, when the observer is standing at the 
 pulley end of the armature shaft. They can, 
 however, be made to run in the opposite direc- 
 tion by merely reversing the position of the 
 brushes. When this is done on an ordinary 
 two-pole machine, no other connection need be 
 changed. This merely changes the direction of 
 rotation and the position of the brushes. 
 
 It must not be thought that changing the con- 
 nection of the wires will effect the same result. 
 This, to be sure, changes the direction of the
 
 an& /footers 119 
 
 current in the coils, but it does the same thing 
 for the field magnets thus changing their polarity, 
 or converting what was the north pole to the 
 south pole and vice versa, and thus keeping the 
 direction of rotation the same. The only way 
 in which this can be done is to change the direc- 
 tion of the flow of the current in the field or the 
 coils alone. 
 
 Before starting any electric machine it should 
 be thoroughly inspected to make sure that it is 
 in perfect working order. This means that, first 
 of all, it should be clean. All dust and grit and 
 especially all metallic particles should be wiped 
 off, lest they cause a short circuiting, and above 
 all should this be done in connection with the 
 commutator and brushes. 
 
 The actual starting should be done slowly and 
 with a watchfulness that will make it possible to 
 stop at once, if anything goes wrong. The shaft 
 should be examined to see that it moves freely 
 in its bearings, and the lubricators be adjusted 
 to feed the oil properly. 
 
 A word of caution may be interjected here to 
 those who are called upon to handle electric cur- 
 rents. Do not touch a conductor with the bare 
 hands. Do not attempt to manipulate conductor 
 wires with ordinary tools. Always wear rubber
 
 120 Electricity 
 
 gloves, and rubber shoes are also a wise extra 
 precaution. Always use tools that have insul- 
 ating handles when at work about electric ma- 
 chines or wires where the voltage is high. It is 
 well, also, to work with one hand only, so that 
 in case of accidental contact the current will not 
 pass from one side to the other of the body. 
 
 After a machine has been at work for some 
 time it frequently happens that it causes a good 
 deal of trouble by sparking at the brushes. This 
 sparking may take the form of a vivid flash of 
 light that hovers constantly about the point of 
 contact as a bluish flame or it may be inter- 
 mittent. There are several causes for this, one 
 of the principal being failure of contact between 
 the brush and the commutator. This may be 
 due to an unevenness in the surface of the com. 
 mutator as the result of wear ; or the brush itself 
 may be so hard that it will not work down to a 
 good surface ; or the machine may be vibrating 
 to such an extent that the jar is communicated 
 to the brushes. Sparking may also result from 
 the brushes being out of position, a broken cir- 
 cuit in the armature, weak field magnetism or a 
 high resistance in the brush. 
 
 There is then an apparently wide field for in- 
 vestigation when, sparking occurs at the brushes
 
 Bgnamos and /footers 121 
 
 though each of the mechanical difficulties show 
 at once whether or not they are the causes of the 
 trouble. In a well-designed and well-built ma- 
 chine that has been well cared for and not over- 
 loaded, the chances are that, in ninety-nine cases 
 out of a hundred, the cause will be found in some 
 trouble with the brushes or unevenness in the 
 worn surface of the commutator. 
 
 Owing to the character of the insulation used, 
 it is very desirable that the armature and field 
 magnets should run cool, and they must be care- 
 fully watched to see that this condition is main- 
 tained. The heating of the armatures may result 
 from moisture that has soaked in among the 
 coils, from an excess current passing through it 
 or from short circuiting. The Foucault currents 
 due to a solid ring construction will also produce 
 this result, and it sometimes happens that, in 
 winding an armature, one or more coils are con- 
 nected in the wrong direction. When either of 
 these constructional difficulties is the cause of 
 the heating, there is no remedy other than in a 
 rebuilding of the armature. Heating of the 
 field magnets may also be due to moisture in the 
 coils, excess of current or Foucault currents. 
 The first can be cured by drying, in the second 
 it may be due to a short circuit in one coil, thus
 
 122 Electricity 
 
 sending an excess into the other, and in the last 
 the remedy again lies only in reconstruction. 
 
 These are merely a few of the more prominent 
 troubles that are apt to arise in the care of elec- 
 trical machinery. But, like all apparatus of its 
 kind there are always unexpected developments 
 that must be met with a knowledge of the prin- 
 ciples in accordance with which the machine is 
 constructed. And, while this is simple in itself, 
 there are so many outside variables that come in 
 to influence its action that . the result is one of 
 some complication, though by no means impos- 
 sible of solution by any one who will take the 
 pains to examine into the several phenomena as 
 they manifest themselves in the course of ex- 
 perience. 
 
 It is due to the dynamo and its reversibility as 
 a motor that the electrical progress of the last 
 quarter o.f a century is due and the former has 
 stepped in to supply electric currents on a scale 
 that would be utterly impracticable were reliance 
 to be placed upon batteries. It has enabled the 
 telegraph companies to meet the demands that 
 have been made upon them for an increase of 
 service, while the applications for the develop 
 ment of light, heat and power may be numbered 
 by the thousands.
 
 CHAPTEE VIII 
 
 ELECTEIC LIGHTING 
 
 IT has been shown in a previous chapter that 
 all substances offer a certain definite amount of 
 resistance to the passage of the electric current. 
 This resistance is least in silver, a trifle more in 
 copper, still more in iron and the increase con- 
 tinues on through other substances, being very 
 great in glass and air. In overcoming these re- 
 sistances heat is generated and this heat is in pro- 
 portion to the resistance and the intensity of the 
 current. With the good conductors such as 
 copper and iron the temperature is rarely raised 
 to such a degree that the metal becomes red hot 
 except in the case of currents of great in- 
 tensity. 
 
 This generation of heat is shown in the results 
 of a stroke of lightning, where buildings may be 
 set on fire on account of the resistance of the ma- 
 terial to the passage of the current. 
 
 This principle is made use of in all systems of 
 electric lighting whether it be arc or incandes- 
 
 123
 
 124 
 
 cent. The practical method by which the re- 
 sults are obtained, is to interpose some substance 
 of such high resistance, that it is heated by the 
 passage of the current to an incandescent condi- 
 tion. The development of heat invariably pre- 
 cedes the appearance of light and the time re- 
 quired is also a matter of material and strength 
 of current. 
 
 The material that is apparently best adapted 
 for use in the electric lamp seems to be some 
 form of carbon. In what is known as the arc 
 light there is an actual consumption of the car- 
 bon ; whereas, in the incandescent system, there 
 is theoretically no such consumption. 
 
 The fact that an intensely bright light could be 
 produced by the passage of an electric current 
 through two carbon points was discovered by 
 Sir Humphrey Davy in 1813, who used a battery 
 of 2,000 voltaic cells for the generation of his 
 current, and two sticks of common wood char- 
 coal for the electrodes. 
 
 The carbon used for the present arc light is a 
 manufactured article that is very hard. The 
 original carbons used by Davy were soft and 
 were rapidly wasted away in service. It there- 
 fore became necessary to secure something that 
 would retain its shape and burn slowly. This has
 
 JElectrfc SLfsbtfns 125 
 
 been found in the Carre carbons which may be 
 made as follows : 
 
 " Fifteen parts of pure coke finely pulverized 
 and five parts of calcined lamp-black, are mixed 
 with seven to eight parts of a syrup made of 
 cane sugar and gum arabic, in the proportion of 
 thirty parts of sugar to ten parts of gum. The 
 mixture is then pulverized, made into paste with 
 water, forced under heavy pressure into a die 
 form required for the carbons, and baked re- 
 peatedly at a very high temperature. After 
 each baking the carbons are immersed in a con- 
 centrated syrup of burnt sugar, maintained at a 
 boiling temperature, so as to fill the pores with the 
 sugar, the process being facilitated by intervals 
 of cooling ; and the superfluous syrup being washed 
 from their surfaces with boiling water previous to 
 each baking. When the required density has been 
 obtained, the carbons are slowly dried for about 
 fifteen hours at a temperature of about 340 Fahr., 
 and they are then ready for use." 
 
 The carbons are then given a coating of copper 
 by electro-plating so as to reduce the resistance 
 over a greater portion of the stick from that of 
 carbon to copper. When so made they are very 
 strong and are used in lengths of from 18 inches 
 to 20 inches.
 
 126 
 
 Great as may be the resistance of the carbon^ 
 that of the air is still greater and it is necessary, 
 in order to produce an arc light that the two 
 pieces should first be in contact and then, after 
 the flow of the current is established, be drawn 
 apart. The current thus started while the car- 
 bons are in contact leaps across the air space in- 
 terposed when they are drawn apart and the 
 intensity of the heat thus generated maintains 
 the light. 
 
 For convenience the carbons are usually set in 4 
 a vertical position with the current entering at 
 the upper one, which thus becomes the positive 
 electrode of the lamp. As this upper carbon 
 burns away it assumes the form of a truncated 
 cone or crater, while the lower one becomes 
 pointed. The space between is filled with a 
 mixture of carbon vapor and air, which, at the 
 high temperature at which it is maintained, has 
 a much lower resistance than the air at ordinary 
 temperatures. Both points are maintained at a 
 white heat and it is the radiation from these in- 
 candescent tips that produces the light. Of the 
 two, the condition of the upper one is the most 
 intense and is really the source of about sixty- 
 five per cent, of all the light radiated by the 
 lamp.
 
 Electric Xfgbtfng 
 
 127 
 
 Of course it is necessary that the bringing of 
 the carbons into contact in an extinguished lamp 
 and their separation, immediately the flow of 
 current has been started, should be done automat- 
 ically. There have been a great variety of 
 lamps brought out for this purpose in which ad- 
 vantage is taken of the variation in the resistance 
 offered by car- 
 bons in contact / " X. ^ / n / 
 and apart. Some >\ T^>3mm~^ " / 
 of these lamps 
 are of compli- 
 cated construc- 
 tion and involve 
 the use of more 
 or less clock- 
 work. Among 
 the simplest is 
 the Brush lamp that will serve to show the 
 method of operation employed. 
 
 This lamp depends for its working upon the 
 action of a solenoid, or a soft iron core free to 
 move in a coil of wire through which an electric 
 current is passing. 
 
 The construction of the Brush lamp is shown 
 in Fig. 31. The carbons are represented by A-j- 
 and A respectively. The terminals of the line 
 
 FIG. 31. DIAGEAM OF BRUSH ABC 
 LAMP
 
 128 Blectticfts 
 
 circuit are at B and C. The lower carbon is held 
 in a stationary frame that is in direct electrical 
 contact with the terminal C. The upper carbon 
 is held in a washer D that is clutched by an ex- 
 tension from the base of the solenoid E. The 
 main wire leading oif from the terminal B is 
 divided into three parts. One part F leads down 
 through the resistance coil E- to the armature G of 
 the magnet H, whose uses will be explained later. 
 The other two branches I and K pass through the 
 coils L and M of the solenoids and then uniting 
 are led to a contact with the upper carbon at N. 
 
 In addition to this a main wire is led down 
 from the terminal C to the coil H and ends in the 
 contact O. 
 
 Another finer wire P is led between the ter- 
 minals B to C, around the coils H, L and M, but in 
 an opposite direction to these coils. This wire 
 is what is known as a shunt circuit and, owing 
 to its greater resistance, carries only about one 
 per cent, of the total current, but by giving it a 
 greater number of coils about H, L and M it serves 
 to materially modify and counteract the magnet- 
 izing properties of those coils. 
 
 When the lamp is to be lighted a current is 
 allowed to pass from the terminal B to C. In 
 doing so it flows through the coils L and M and
 
 Electric Xisbting 129 
 
 the two carbons. The resistance of the latter 
 being comparatively little the solenoid cores rise 
 through the coils L and M and separate the car- 
 bons producing the light. As the distance of this 
 separation increases so does the resistance, thus 
 checking the flow of the current and correspond- 
 ingly weakening the strength of the solenoid. 
 The latter then drops back until it reaches the 
 point where the weight and strength of the 
 solenoid are balanced, and the lamp continues to 
 work in this its normal position. 
 
 The wire F leading to the resistance coil K is 
 to enable the lamp to automatically close the 
 circuit between B and C in case of accident and 
 thus prevent other lamps, that are in circuit in 
 series with it, from becoming extinguished. 
 When an accident resulting in the permanent 
 extinguishment of the lamp ocpurs this circuit so 
 magnetizes the core of H that the armature G is 
 attracted and the contact points O are brought 
 together, thus permitting a direct flow of the 
 current from B to C through the resistance coil li 
 which now takes the place of the lamp in inter- 
 posing the proper resistance into the circuit. 
 
 The arc lamp properly constructed is capable 
 c? emitting an intense light ranging from an or- 
 dinary lamp of 1,200 candle power to the most
 
 130 Electricity 
 
 powerful search lights of 50,000 candle power or 
 more. The current of course varies with the in- 
 tensity of the light and is approximately about 
 one two-hundredths of the same. Thus for a 
 1,200 candle power light about 6.8 amperes of 
 current will be required ; for 2,000 candle power 
 about 10 amperes and so on, decreasing slightly 
 in proportion to the increase of light. 
 
 At present the current used for electric 
 lighting is generated by the dynamo, and indeed 
 it was the discovery and development of the 
 latter that has rendered the method possible. 
 "While it is quite feasible to generate a current 
 with batteries alone, that are capable of main- 
 taining an arc light, their bulkiness, first 
 cost and expense of maintenance place them 
 quite outside the pale of any commercial con- 
 siderations. 
 
 As the arc lamp continues in use, the carbons 
 gradually waste away and must be renewed 
 after a certain length of time. In fact they are 
 consumed at an approximate rate of about \y 2 
 inches per hour. 
 
 In the incandescent lamp we have, on the 
 other hand, an example of a resistance coil pure 
 and simple. There is, to be sure, a slow wasting 
 away and gradual deterioration of the carbon but
 
 Electric ILfgbttns isi 
 
 no consumption that is comparable to that of the 
 arc lamp. 
 
 The incandescent system of lighting involves 
 the placing of a section of high resistance in the 
 circuit. The current, in passing through this 
 section heats it and raises it to such a^ condition 
 of incandescence that it emits light. In order 
 that this resisting section may be made small and 
 light and that it may not be, at the same time, 
 burned by contact with the oxygen of the air, 
 when in this glowing condition, it is enclosed in 
 an air-tight bulb from which the air has been ex- 
 hausted so that the work is done in a partial 
 vacuum away from the destructive influences of 
 the oxygen. 
 
 The filaments, as these resisting sections pro- 
 ducing the light are called, are usually made of 
 fine threads of carbon. They are exceedingly 
 delicate and are instantly dissipated if a crack or 
 leak in the glass bulb admits ever so small a 
 quantity of air. 
 
 The development of the incandescent light has 
 required a great deal of experimenting in order 
 to secure the best possible material for use in the 
 making of these filaments ; and the several manu- 
 facturers have each a material that is used for 
 the particular lamp made. Edison uses a bain-
 
 132 Blcctcicits 
 
 boo fibre taken from the interior of the plant ; 
 the Lane-Fox carbons are made from a grass 
 fibre known as bass broom ; the Cruto carbons 
 are made by depositing the carbon upon a fine 
 platinum wire ; the Weston carbons are made of 
 cotton as are also the Swan. 
 
 The filament is almost invariably made in the 
 form of a horseshoe, and great care must be ex- 
 ercised in their manufacture. Its resistance de- 
 pends, to a great extent, upon its length and 
 diameter. An ordinary filament would be about 
 5 inches long and .005 inch in diameter, and this 
 would be suitable for a lamp of sixteen candle 
 power. The wastage of the filament is due to 
 the actual burning away of the carbon caused by 
 the presence of a small amount of oxygen that re- 
 mains within the glass on account of the impos- 
 sibility of producing a perfect vacuum. There is 
 also a certain amount of wastage as the result of 
 incandescence in which infinitesimal portions of 
 the carbon are given off as vapor to settle again 
 on the interior of the glass, whither they are at- 
 tracted by the difference in what is termed the 
 potential. This is the cause of the darkening 
 that takes place in incandescent light glasses 
 after they have been in use for a time. 
 
 It may be explained here that the term " dif-
 
 Electric Hfgbttng 133 
 
 ference of potential" is used to express technic- 
 ally the reason for the flow of the electric cur- 
 rent. At the positive pole of the battery or 
 dynamo, it is supposed that there is a higher 
 pressure or potential than at the negative. This 
 difference causes a flow of the current from one 
 pole to the other. It is analogous to the flow of 
 water through a pipe which takes place from the 
 point of greatest pressure to the least. 
 
 The voltage used in incandescent lighting 
 covers a wide range of from 50 to 120 volts, with 
 from 90 to 100 as an approximation to average 
 practice. "With this voltage the durability of a 
 lamp or the filament will be from 600 to 1,000 
 hours of service. The glass or bulb is so fitted 
 with the contact points that when it is screwed 
 into its socket it automatically makes its own 
 connections and places the filament in the circuit. 
 
 The methods to be employed in the placing of 
 electric lights and the wiring for the same are 
 matters of interest to all users. All wiring for 
 residences, offices or factories should be done on 
 one of the two systems known as the multiple 
 arc and three-wire systems. 
 
 The first is represented in Fig. 32. Here the 
 current generated by the dynamo at A flows out 
 at the positive pole and over the wire B. This
 
 134 jeiectrtcfts 
 
 wire is connected to the return wire C, leading to 
 the negative pole of the dynamo, by a number of 
 special wires in each of which there is placed an 
 
 incandescent 
 
 0111111111111 lamp. Each of 
 mmHHH these Umpa 
 
 + e , . -j 
 
 FIG. 32. MULTIPLE ARC SYSTEM OF IN- 
 
 CANDESCENT LIGHTING pendently of all 
 
 of the others 
 
 and may burn out or become destroyed without 
 affecting the action of the others in any way. The 
 two essential conditions for the use of this system 
 are that the dynamo should maintain a constant 
 voltage in the wires, regardless of the number of 
 lamps in use ; and that only lamps intended for 
 the same voltage shall be used. 
 
 The working of this system is explained as fol- 
 lows : The current generated by the dynamo 
 flows out upon the wire and a certain portion of 
 it cuts across to the return wire through each of 
 the lamp circuits, the total output of the dynamo 
 corresponding to the number of lamps in service. 
 
 In order to lessen the work of the dynamo and 
 for other reasons it is sometimes desirable to cut 
 out certain lines of wire, and for this purpose 
 switches are used. In electrical parlance a switch 
 may be defined as a means for opening or closing
 
 Electric 3U0btfng 135 
 
 a circuit. They are invariably located close to 
 the dynamo in the power house so that the cur- 
 rent can be cut off from or turned into certain 
 lines. It is always well to have them arranged 
 to open and close quickly and they must possess 
 ample capacity to carry the full current of the 
 line. A satisfactory form is the knife switch in 
 which a blade of copper is made to enter between 
 two others thus 
 closing the con- 
 nection ; and if 
 the moving part 
 is made so as to 
 be started by FJG> 33< _ THEEE . WIEE SYSTEM OF IN- 
 hand and be CANDESCENT LIGHTING 
 
 then driven in 
 
 by a spring it will be better on account of the 
 rapidity of its movement. Similar switches 
 should also be placed in the wires as they enter 
 buildings and at all points beyond which the in- 
 stallation may be considered as separate. This 
 makes it possible to examine and repair such 
 parts of the installation, without interfering in 
 any way with the working of other parts. 
 
 The three-wire system is shown in Fig. 33. 
 The advantage of this method is one that affects 
 the producer rather than the consumer, in that
 
 136 Electricity 
 
 its advantage lies in the reduced quantity of wire 
 required for the mains. 
 
 The dynamos are connected in series as shown, 
 and the lamps are placed in a circuit interposed 
 between the positive and negative wires A and B, 
 and a neutral wire C. When an equal number of 
 the lamps in the two lines D and E are lighted the 
 current flows out at A, cuts across to the return 
 wire B through the lamps and so back to the 
 dynamos. If, however, an unequal number are 
 in use in the two lines, the third wire, which was 
 neutral before, now comes into action and acts as 
 a positive or negative wire according as the 
 greater number of lamps are burning in the line 
 E or D. This method makes it possible to use 
 three-eighths the amount of copper in the mains 
 that the two- wire or multiple arc system would 
 require for the same number of lamps. 
 
 Where the wires for the electric lighting of a 
 building are to be run after the building has been 
 erected the most common and cheapest method 
 of doing the work is to use cleats. These cleats 
 consist merely of short strips of wood with 
 grooves cut across one face of a proper size to 
 receive a wire and hold it firmly when the cleat 
 is nailed or screwed against a ceiling or partition. 
 The same precautions as to the tightening of the
 
 Electric ftigbting 137 
 
 wires that are to be observed in other classes of 
 wiring must be followed in this. 
 
 The use of the cleat leaves all of the wires ex- 
 posed to view. If it is desired to have them con- 
 cealed it will be necessary to cut holes in the 
 plaster at the point where it is desired to place 
 the lamp and run the wires between the sides of 
 the partitions and between the floors and ceilings 
 to the source of supply. To do this successfully 
 will require some time and patience. 
 
 Through the hole in the wall, which should be 
 clear of the studding, drop a length of No. 19 
 jack chain to which a strong string is attached. 
 Locate its position on the ceiling by jouncing it 
 with the string and then bore a hole through an 
 adjacent base board and fish for it with a piece 
 of wire having a hook on the end. Move it along 
 from point to point in this way and draw after 
 it the wires for the lamp. 
 
 It need hardly be said that the wire used for 
 all electric lighting purposes must be covered 
 with some good insulation. Some one of the 
 compositions of rubber is the material that is 
 usually used for this purpose. The greatest earn 
 must be exercised, in the running of the wires 
 that the insulation is not injured in any way. 
 This is particularly true of concealed work. If
 
 138 Blectricfts 
 
 the wires are placed after the completion of the 
 building, they must be cautiously handled lest 
 the insulation be broken or torn from the wire 
 while it is being drawn into place. If the work 
 is done on an uncompleted building, eternal 
 vigilance alone will serve to guard it against the 
 carelessness or wilful maliciousness of the work- 
 men engaged in the construction. The cotton- 
 wrapped wire that can be used for bell work 
 should not be employed for electric lighting 
 owing to the danger of fire. 
 
 In additition to the insulation covering the 
 wire, other safety devices must be introduced 
 into the system. One of these is the use of the 
 safety plug or fuse. 
 
 There is always present the possibility of an 
 abnormal increase in the voltage on an electric 
 lighting circuit, which might heat the wires to a 
 temperature sufficient to set fire to the insulation 
 or other materials with which they are in con- 
 tact. The fuse may be attached to the wires by 
 binding screws, so as to be easily replaced if 
 melted, and are so constructed that they will 
 melt and thus break the circuit, before the wires 
 will become sufficiently hot to do any damage, 
 and this should be limited to 150 Fahr. 
 
 Again, wherever a current enters a building
 
 Electric Xfgbtfns 139 
 
 there should be a switch where the connection 
 can be broken and the wires thus be made dead 
 so that they can be handled with impunity for 
 repairs. 
 
 Wherever wires are to be joined the splice 
 should be made in accordance with the direc- 
 tions given in connection with Fig. 4 on page 27. 
 After the splice has been made it should be 
 carefully wrapped and thoroughly protected by 
 means of adhesive insulating tape, wound tightly 
 about it. This should be carried out to a suffi- 
 cient thickness to form a thorough insulation, 
 and for that purpose should be somewhat thicker 
 than the regular insulation about the wire. The 
 joints should also be soldered before winding. 
 
 When the wires pass through a wall, partition 
 or joist an extra insulation should be used. This 
 usually takes the form of a hard rubber or com- 
 position tubing which may be procured at any 
 supply store. 
 
 The size of the wire used must also receive its 
 due amount of attention. Copper is, of course, 
 the only material to b.e considered. The larger 
 the wire the greater the number of lamps that it 
 will carry. Thus a No. 18 wire will carry 7 
 lamps of 55 volts and 14 of 110 volts. With a 
 No. 14 wire, we find that 15 of the 55-volt and
 
 140 Electricity 
 
 30 of the 110-volt lamps can be carried. With a 
 Ko. 8 wire, these figures are increased to 40 and 
 80 lamps respectively. 
 
 The determination of the size of wire suited 
 for use in an installation is a matter that can be 
 readily calculated. The resistance of a wire is 
 dependent upon its size, and this is usually ex- 
 pressed in terms of " circular mils." A circular 
 mil may be defined as the sectional area of a 
 wire w T hose diameter is one-thousandth of an 
 inch. As the sectional areas of w r ires vary as 
 the squares of their diameters, it follows from 
 this that a wire % inch in diameter will contain 
 62,500 circular mils. 
 
 The problem of determining the size of wire 
 to be used lies in so adjusting its resistance plus 
 that of the lamps, that the voltage of the dynamo 
 will overcome this resistance. It is a problem 
 that can be attacked from many sides. 
 
 In the first place the resistance of the copper 
 wire of the conductor may be taken to be its 
 length in feet multiplied by 10.79 and divided 
 by its sectional area in circular mils. Thus a 
 mile (5,280 ft.) of J^ inch copper wire would 
 offer a resistance of
 
 Electric %fgbtfns 141 
 
 A transposition of the formula enables us to 
 get the length, when size of wire and resistance 
 are given, or the size of wire for a given re- 
 sistance and length. 
 
 The determination of the size of the wire suit- 
 able for any circuit depends upon the resistances 
 to be overcome in that circuit. In calculating 
 these resistances it must be borne in mind that, 
 where the lamps are in multiple as in Fig. 32, 
 the total resistance is lessened with an increase 
 in the number of lamps, due to the increased 
 facilities offered to the passage of the current. 
 
 Suppose now we have 25 lamps, each with a 
 resistance of 150 ohms. The total resistance is, 
 therefore, 
 
 150 
 
 = 6 ohms. 
 <*o 
 
 Further, if it is decided that a drop of 10 per 
 cent, in potential can be allowed in a wire 200 
 feet long, we will have 90 per cent, of the total 
 current available for overcoming lamp resistance 
 and the other 10 for that of the wire. The total 
 resistance of lamps and conductors is, therefore, 
 6 .9 = 6.66 ohms, and T V of this, or 0.66 ohm, 
 is attributable to the conductor alone. The prob- 
 lem has now resolved itself into the determina-
 
 142 jeiectricitB 
 
 tion of the size of wire that, in a length of 209 
 feet, will give a resistance of 0.66 ohm. 
 
 Taking our first formula and transposing we 
 will have 
 
 200 X 10.79 
 ^ = 3,268 circular mils. 
 
 Extracting the square root of this quotient we 
 have 
 
 1/3268 = 57, 
 
 or the diameter of the wire sought is .057 inch, 
 corresponding to No. 15 of the American wire 
 gauge. 
 
 It will be seen from this that the resistance to 
 be overcome is of the first moment in settling 
 upon the size of wire to be used, and with that 
 in hand the solution of the problem is rapid and 
 easy. 
 
 The wiring for electric lighting that has thus 
 far been described relates to the incandescent 
 system only. It differs essentially from that 
 used in arc lighting in that, in the latter, the 
 lamps are usually connected in series. So while 
 in the incandescent lamp only enough current 
 passes through it for its own uses, with the arc . 
 lamp the whole current sent out to the circuit 
 passes through each and every lamp in that circuit.
 
 Blectrfc Xigbtfns 143 
 
 The wiring and connections are made as when 
 a number of cells are coupled in series as in Fig. 
 13. That is to say a wire is led from the nega- 
 tive terminal of one lamp to the positive of the 
 next and so on through the series back to the 
 negative terminal of the dynamo. 
 
 The calculations as to the sizes of wires to be 
 used are made in exactly the same way and the 
 same or even greater precautions must be taken 
 in the matter of insulation. Wiring for arc cir- 
 cuits must be heavier and more substantial than 
 in incandescent work on account of the greater 
 voltage to be protected, but in other respects the 
 principles of the insulation remain the same. 
 
 It will thus be seen that the wiring and main- 
 tenance of an electric lighting system is a simple 
 matter like other things electrical, but they do 
 require thoughtful care and attention, else the 
 results obtained may not only be poor but dis- 
 astrous.
 
 CHAPTER IX ' 
 
 ELECTRO-PLATING 
 
 IN the chapter treating on the construction 
 and operation of batteries it was shown that the 
 electric current was generated by the chemical 
 decomposition of some of the materials that enter 
 into the battery. It has also been found that 
 the decomposition of the sulphate of copper, that 
 is placed in the porous jar, is followed by the de- 
 position of an equivalent amount of copper upon 
 the electrode. This electrode, therefore, con- 
 tinually increases in size and weight by succes- 
 sive accretions of this metal. It is therefore, a 
 case of plating a metal with itself by means of 
 electric deposition. 
 
 A practical application of this principle is to 
 be found in the art of electro-plating in which 
 an electric current is made to pass through a 
 solution of a metal with which it is desired to 
 coat another object. The solution thus treated 
 is decomposed and the metal thus set free gathers 
 upon one of the electrodes or terminals of the cir- 
 144
 
 145 
 
 cult. This electrode is the object to be coated 
 and is immersed in the liquid or bath. 
 
 The work is done for both ornamental and 
 practical purposes and usually consists in depos- 
 iting an expensive metal upon a cheaper one, 
 whereby the appearance of the expensive one is 
 obtained with the weight and cost of the cheap 
 one. The metals that are most frequently used for 
 electro-plating are copper, nickel, silver and gold. 
 Other metals that may be deposited, with more 
 or less ease, are zinc, tin, lead, cobalt, platinum 
 and iron, though it is difficult to do good work 
 with the latter. These metals are of compara- 
 tively little interest to the electro-plater, and at- 
 tention will, therefore, be limited in this chapter 
 to the four metals first mentioned. 
 
 The solutions most commonly used for electro- 
 plating are, for copper, the sulphate of copper ; 
 for nickel, the double sulphate of nickel and 
 ammonium ; for silver, the double cyanide of 
 silver and potassium ; and for gold, the double 
 cyanide of gold and potassium. The prepara- 
 tion of these solutions will be considered later. 
 
 In nearly all electrical experiments and in the 
 early stages of practical electrical development, 
 as we know it to-day, the current for electro- 
 plating work was generated by batteries. But,
 
 146 Blectrictts 
 
 as the dynamo has supplanted the battery in 
 other classes of work, so now it is exclusively 
 used where large quantities are to be done. Yet, 
 where the amount of plating to be done is small, 
 is done intermittently or a current from a dynamo 
 is not available it is upon the battery that the 
 electro-plater is still obliged to rely. 
 
 The selection of a battery for this class of 
 work is a matter of somewhat greater impor- 
 tance than it is where it is merely desired to 
 secure a current of sufficient intensity to ring a 
 bell or operate a telegraph instrument. There, 
 so long as the work is done it matters little as 
 far as practical results are concerned, what may 
 be the internal resistance of the battery itself. 
 In electro-plating, on the other hand, it is unde- 
 sirable to use a battery having a high internal 
 resistance. The three qualities that are desired 
 for doing first-class electro-plating work are high 
 electromotive force, constancy of voltage and 
 low internal resistance, and these seem to be 
 best embodied in what is known as the Bunsen 
 cell. 
 
 Like the DanielFs the Bunsen is an acid battery 
 but using different materials for electrodes and 
 liquids. The four elements of the cell are carbon 
 and zinc for the electrodes and sulphuric and
 
 ^Electroplating 147 
 
 nitric acid for the liquids. It is usually preferred 
 to use glazed earthenware for the outer jar 
 though glass can be used for the work where the 
 battery is to be put in one place and not moved. 
 The sulphuric acid diluted with from seven to 
 fifteen parts of water is placed in the outer jar 
 and in it is immersed the bar or rod of zinc. The 
 inner jar contains nitric acid of full commercial 
 strength and in this the carbon electrode is im- 
 mersed. The latter is made of baked coke dust 
 firmly compressed. The zinc should be amalga- 
 mated in order to insure a proper working of the 
 battery, and this can be done as follows : First 
 scrape it until it is perfectly clean and bright, 
 and free from all oxidization. The further de- 
 tails of the process are taken from Niaudet. 
 
 " The zincs are placed on end in a bucket of 
 water containing one-tenth of sulphuric acid, 
 They stand out of the liquid about half an inch, 
 so that they may be lifted out without immersing 
 one's fingers in the acid. Three zincs are placed 
 at one time in the bucket, in order that each may 
 remain in the cleansing solution the length of 
 time required for the amalgamation of the other 
 two." For one-half of the time that each zinc re- 
 mains in the solution its position should be 
 inverted in order that the projecting portion
 
 148 Blectrfcits 
 
 may also be subjected to the action of the 
 acid. 
 
 " The vessel containing the mercury for amal- 
 gamation should be cylindrical and a little longer 
 than the zincs to be amalgamated. This per- 
 mits the use of the smallest quantity of mercury. 
 The zincs are carefully immersed in the mer- 
 cury and turned slowly once or twice to in- 
 sure the amalgamation of the entire surface. 
 When removed they should be held at an angle 
 to permit the superfluous mercury to run off. 
 They are then placed in an empty trough ; where, 
 after a time, a quantity of mercury, that has run 
 off will be found at the bottom." 
 
 The zincs must be reamalgamated every time 
 the battery is cleaned and the work should be 
 done only a short time before charging so that 
 the surface may be fresh when first placed in the 
 acid. The zinc will also be maintained in a bet- 
 ter condition while the battery is at work if a 
 little mercury is kept in the bottom of the cell. 
 
 Such a battery when carefully adjusted can be 
 depended upon to furnish a constant current of 
 about 1.8 volts with a low internal resistance 
 thus fully meeting the three requirements of such 
 a battery as already set forth. 
 
 The Bunsen battery possesses nevertheless, one
 
 149 
 
 serious disadvantage. While at work it emits 
 fumes of nitrous oxide that are very injurious to 
 ,he health of persons inhaling them. For this 
 reason it should never be located in the room 
 where the work is being done, but should be put 
 in a closet that can be entirely shut off from the 
 workroom and is itself provided with an ample 
 and separate ventilation. This closet should be 
 dry and cool and yet not subjected to a freezing 
 temperature. 
 
 The number of these cells to be used will be 
 dependent upon the work to be done and the 
 metal to be deposited. For copper and nickel 
 there should be used three or more cells coupled 
 in series ; for silver, two should be employed and 
 for gold one will answer. 
 
 In the preparation of the object to be electro- 
 plated the first and all-important essential is 
 cleanliness. This cleanliness must be understood 
 in a chemical and not a mechanical sense. The 
 surface must be free from every trace of dust, 
 oil, vegetable or animal matter, and from all rust 
 or tarnish. Thus an article polished ever so 
 brightly and wiped, will have some particles of 
 dust adhering to it that will prevent a suitable 
 deposition of the plating metal. Or, if an article 
 were to be made clean and were afterwards
 
 150 Blectrfcfts 
 
 touched with the naked hand the contact of the 
 latter would soil it to an extent that would re- 
 sult in the peeling off of such plating as might 
 afterwards be put upon it. 
 
 In the same category as cleanliness must also 
 be placed the surface condition of the article to 
 be plated. The electro deposition is exceedingly 
 sensitive and will faithfully reproduce any 
 blemishes that may exist on the surface of the 
 metal. Thus, for example if there are any 
 scratches, pitting or imperfections on the original, 
 they will appear on the plating and what is 
 more, they cannot be removed by subsequent 
 polishing and burnishing. Hence perfection of 
 surface condition must be added to cleanliness. 
 
 The several materials that are used as the base 
 for electro-plating require somewhat different 
 treatments in order to secure the necessary clean- 
 liness prior to the immersion in the bath. 
 
 The alloys of copper, tin and nickel, whatever 
 special name they may be passing under can all 
 be treated as belonging to the same class. If the 
 surface is in good mechanical condition so far as 
 scratches and imperfections are concerned the 
 article to be plated may be immersed or " dipped " 
 in a hot solution of caustic potash. This will 
 remove all traces of grease and dirt. If, in addi-
 
 ^electroplating 151 
 
 tion to this, there is some oxidization on the sur- 
 face, the article must be dipped in an acid bath. 
 This may be composed of one gallon of water, 
 two quarts of sulphuric acid and one quart of 
 nitric acid or proportional quantities. If this 
 does not work, add an ounce of hydrochloric acid 
 at intervals until the desired result has been ob- 
 tained. 
 
 After dipping, the articles must be thoroughly 
 washed in a superabundance of fresh water. 
 There must be no scrimping of this commodity, 
 for, if the slightest particle of acid is left upon 
 the metal, oxidation will set in at once and the 
 surface be spoiled for plating work. 
 
 A word of caution must also be added regard- 
 ing the use of these dips. While the articles are 
 submerged within them they give off very in- 
 jurious and poisonous fumes. The work should, 
 therefore, either be done out of doors with the 
 operator upon the windward side of the vessel or 
 in a room provided with a special ventilating 
 hood and shaft beneath which the dip is placed 
 and through which a strong up draft is created. 
 
 Cast iron should be cleaned in the same way 
 as that followed for the ordinary pickling proc- 
 ess by which the hard scale and burnt sand with 
 which it is coated is frequently removed prior to
 
 152 Electricity 
 
 machining. This pickle can be made by putting 
 one part of sulphuric acid into twenty-one parts 
 of water which is about six ounces to the gallon. 
 The metal must be allowed to remain in the 
 pickle until the scale is loosened and can be 
 easily scraped off with a wire brush. If it is 
 particularly obstinate, the work can be facilitated 
 by the addition of a little muriatic acid. 
 
 When taken out of the pickle the surface must 
 be at once scoured with wet silver sand, then 
 rinsed in cold water and placed in a cold potash 
 solution ; after which it must be again rinsed in 
 clean water and instantly placed in the plating 
 bath. 
 
 Kough wrought iron and steel may be treated 
 in the same way though it is not necessary that 
 they should remain in the pickling solution for 
 so long a time. Where a bright surface is re- 
 quired, it can be obtained by any of the usual 
 methods of polishing, after which it should be 
 dipped in a hot potash solution to remove all 
 traces of grease. 
 
 Rapidity of execution is one of the chief req- 
 uisites in the preparation of all iron or steel 
 articles for electro-plating. The tendency to 
 rust or oxidize when exposed to the air is so 
 great and takes place with such rapidity, and a
 
 , ^electroplating 153 
 
 coating that would be invisible to the eye is so 
 detrimental to the adherence of the plating that 
 the utmost precautions are necessary in order to 
 secure the proper surface for deposition. 
 
 As the replating of old articles- constitutes one 
 of the chief sources of revenue of a jobbing shop, 
 and the principal occupation of the amateur, 
 their preparation is a matter of some moment. 
 
 In the first place it is necessary that they 
 should be freed from all traces of previous coat- 
 ing since, from what has already been said, it is 
 evident that a satisfactory piece of work cannot 
 be done over patches and possibly loose pieces of 
 old plating. 
 
 Gold may be removed by dissolving it in a 
 solution of the cyanide of potassium. This is 
 done by immersing it in the solution and passing 
 a strong current of electricity through it. In 
 making the battery connections connect the 
 article itself direct to the positive pole of the 
 battery and immerse a piece of carbon in the 
 liquid and connect this to the negative pole. 
 Silver may also be stripped in the same way. 
 
 Nickel may be removed by immersion in a 
 bath consisting of one part water, one part nitric 
 acid and four parts sulphuric acid. Great care 
 must be exercised in the preparation of this
 
 154 BlectrfcftB 
 
 mixture as it is accompanied by the development 
 of high temperatures. The work should be done 
 in a lead-lined vessel of iron, as glass or earthen- 
 ware would be almost sure to be broken by the 
 sudden development of heat. 
 
 The article should be carefully watched while 
 it is in the stripping liquid and removed the in- 
 stant the coating has been completely dissolved. 
 The time required to effect this will depend upon 
 the thickness of the original coating and may 
 range from a minute or two to half an hour. 
 This should be done either in the open air or 
 under a ventilating shaft. 
 
 "With the old coating stripped off the work 
 should proceed in the same way as with new 
 articles. 
 
 Having prepared the piece for plating, it now 
 remains to place it in a suitable bath and make 
 the proper electrical connections for the deposi- 
 tion of the metals. Mr. J. T. Sprague gives the 
 following as the best alkaline copper solution : 
 " Dissolve eight ounces of copper sulphate in one 
 quart of hot distilled water, and allow it to cool. 
 Then add liquid ammonia, stirring in with a glass 
 rod until a green precipitate has been formed. 
 Then add more ammonia until the whole mixture 
 has assumed a blue tint. Dilute this with an
 
 Electroplating . 155 
 
 equal bulk of cold distilled water and add enough 
 solution of potassium cyanide to destroy the blue 
 color and give a brown color to the solution. 
 Let it stand for a few hours and then pass it 
 through a calico filter, and then add enough dis- 
 tilled water to make one gallon of the solution." 
 
 The solution must then be placed in a suitable 
 vat, which can best be made of enameled iron, 
 the size of which will depend upon the extent of 
 the operations and the size of the articles to be 
 plated. It is well also to have some means of 
 heating the liquid, as it will give the best results 
 when worked at a temperature of from 115 to 
 130 Fahr. 
 
 The articles to be plated are slung from a bar 
 extending across the top of the vat, but separated 
 from it. This bar is directly connected to the 
 negative pole of the battery. The wires used 
 for slinging the various objects to be plated 
 should be of copper of a size dependent upon the 
 weight to be carried. Ordinarily a ISTo. 22 wire 
 will answer every purpose. 
 
 The positive pole of the battery is connected 
 to a similar rod from which a piece of pure 
 copper is suspended in the solution. This copper 
 gradually wastes away as the deposits gather 
 upon the plated article.
 
 156 jeiectrfcitg 
 
 With one ampere of current, copper can be de- 
 posited at the rate of about 18.16 grains per 
 hour. The thickness of the deposit rests upon 
 the basis that about 2.25 grains are required for 
 a thickness of one-thousandth of an inch per 
 square inch of surface. Knowing the surface, it 
 is then an easy matter to estimate the time re- 
 quired to make a deposit of any desired thickness. 
 
 For nickel-plating the double sulphate of 
 nickel and ammonium is used. This may be pre- 
 pared by dissolving the crystals of the double 
 sulphate in hot water and then filtering. 
 
 It has already been noted that the current for 
 depositing nickel must be somewhat stronger 
 than that required for the other metals and it is, 
 therefore well to surround large objects with 
 anodes or positive pole connections so that the 
 deposition may be uniform over all parts of the 
 surface. 
 
 Even with this stronger current the rate of 
 deposition is somewhat slower than with copper, 
 being at the rate of about 16.9 grains per ampere 
 hour, and it requires about 2.22 grains to coat 
 one square inch of surface with a thickness of 
 one-thousandth of an inch. It is also necessary 
 that, in nickel plating, the process should proceed 
 continuously from the start to the finish.
 
 157 
 
 The electric connections are the same as in the 
 care of copper and nickel of course replaces that 
 metal as the anode or positive pole. The resist- 
 ance offered to the passage of the electric cur- 
 rent also makes it desirable to suspend the anode 
 close to the article to be plated. 
 
 Silver plating is done by means of the double 
 cyanide of silver and potassium and the solution 
 can best be formed by merely dissolving that 
 salt in pure water. This solution may be rich 
 or attenuated according to the class of work to 
 be done. It must simply be borne in mind that 
 the attenuated solution offers a greater resistance 
 to the passage of the current than the richer ; 
 and, therefore, calls for a more powerful battery. 
 
 Bonney gives the following instructions for 
 the preparation of a gilding solution of the 
 double cyanide of gold and potassium : 
 
 " Procure five pennyweights of pure gold leaf 
 or wire, and divide it into two parts ; three 
 pennyweights of pure white ninety-eight per cent, 
 cyanide of potassium and one quart of distilled 
 water. Dissolve the cyanide of potassium in the 
 distilled water made hot in a good enameled 
 saucepan, and keep it at nearly scalding heat 
 while making and working the gilding solution. 
 Make up a battery of two Bunsen or three
 
 158 Electricity 
 
 Daniell cells in series. Hang one strip of gold 
 from the wire leading to the negative pole of the 
 battery and the other from the wire leading to 
 the positive pole. Get a small clean white 
 porous battery cell, nearly fill it with the cyanide 
 of potassium solution, place it in the saucepan, 
 and suspend in the porous cell the strip of gold 
 connected to the negative pole of the battery. 
 Immerse the other strip of gold in the outer 
 cyanide solution and pass the current of the 
 battery from one to the other for two or three 
 hours. During that time the gold will have dis- 
 solved off the anode or positive strip and entered 
 into combination with the cyanide of potassium 
 solution to form the double cyanide of gold and 
 gilding bath." 
 
 The rate of deposition per ampere hour for 
 gold and silver is about 37.73 and 52.1 grains 
 respectively. 
 
 When iron, steel, lead, tin, zinc, pewter or 
 Britannia metal are to be gold or silver plated, it 
 will be well to give them a preliminary coating 
 of copper since this metal can be made to adhere 
 firmly and gold and silver cannot ; whereas the 
 latter can be readily put upon the copper. 
 
 After the requisite amount of plating has been 
 done the first step, whether the work be done
 
 159 
 
 with gold, silver, nickel or copper is to wash the 
 article thoroughly in clean water and then dry 
 in warm boxwood sawdust as that has been 
 found to be best adapted for the purpose. 
 
 The proper finishing of articles requires the 
 use of a polishing lathe with an outfit of scratch 
 brushes, formed of fine stiff brass wire and of 
 mops made of calico stitched together to form a 
 wheel and with which rouge, crocus and tripoli 
 can be applied for polishing. The final burnish- 
 ing may be done by hand and consists in the rub- 
 bing down of the compact and hardened surface 
 with a smooth burnishing tool. 
 
 Thus, it will be seen, that while the work of 
 electro-plating may call for a considerable elab- 
 oration of detail, the underlying principle is the 
 same as that by which the sulphate of copper is 
 decomposed and deposited on the copper electrode 
 of an ordinary Daniell cell.
 
 CHAPTER X 
 
 STORAGE BATTERIES 
 
 THE storage battery differs from the ordinary 
 battery that has been heretofore considered in 
 the essential peculiarities of its operation. The 
 action of an ordinary battery depends upon the 
 presence of materials arranged in a certain juxta- 
 position, by which they are enabled to maintain 
 the generation of an electric current for a definite 
 period until they have been consumed or con- 
 verted into other chemical compositions than 
 those in which they were originally used. When 
 this change has taken place they are said to have 
 been consumed, and it is not economical to at- 
 tempt to reconvert them to their original condi- 
 tion. It is a case analogous to the steam, boiler, 
 where fuel is burned and converted to carbonic 
 acid gas, from which it would be uneconomical 
 to attempt to extract the carbon to use it over 
 again. 
 
 The storage battery, on the other hand, is 
 similar in its action to the weight of a clock. 
 
 160
 
 Storage JBattetfe0 lei 
 
 When the latter is at the bottom of the case it 
 can exert no influence to propel the works ; but, 
 when raised to the top, it possesses the so-called 
 potential energy of being able to keep the clock 
 in motion by its own descent. This descent may 
 require a longer or a shorter time, but through- 
 out the whole period of its duration the clock 
 runs at a uniform speed. The timepiece is thus 
 kept in motion by the repeated lifting of the 
 weight by some external force. 
 
 The storage battery presents an analogous 
 case. As first put together the several elements 
 have no such affinity for each other as to lead to 
 the formation of different chemical compositions, 
 and thus generate an electrical current. They 
 are inert relatively to each other. 
 
 If now an electrical current be made to pass 
 through such a battery, a change of chemical 
 composition of some of the elements takes place, 
 and when this has been done the new combina- 
 tions bear the same relationship to each other 
 that is borne by the elements of the primary bat- 
 tery heretofore considered. They stand ready to 
 change back to the original composition and 
 generate an electrical current. 
 
 When this reconversion is complete the battery 
 is said to be exhausted and it is in precisely the
 
 162 Blectrfctts 
 
 same condition as a clock that has run down and 
 which must be wound up again before it can go 
 on. 
 
 As compared with the simple primary battery, 
 the secondary or storage battery, or accumulator 
 as it is frequently called, possesses the advantage 
 of being able to yield a very much greater out- 
 put of current for the same weight and size. This 
 feature alone makes it available for many pur- 
 poses where the primary battery could not be 
 considered, such as the propulsion of automobiles, 
 the lighting of railway cars, and the propulsion 
 of street cars. 
 
 The principle of the storage battery was dis- 
 covered early in the nineteenth century in con- 
 nection with the decomposition of water by 
 means of the electric current. It is now a com- 
 mon and well-known laboratory experiment to 
 pass a current of electricity through a body of 
 water and thereby effect its decomposition. If 
 such a current is worked it will be found that 
 oxygen gas will arise in bubbles from the wire 
 leading to the positive pole of the battery and 
 hydrogen from the one leading to the negative. 
 Suppose, now the terminals of the wires used be 
 made of platinum so that the gas evolved shall 
 be free from oxides, and these gases be collected
 
 Storage ;atterfe0 163 
 
 in bell jars inverted over the respective terminals 
 and the gases evolved thus separately collected ; 
 and, after the. connections to the battery have 
 been broken, the gases themselves be connected 
 by a wire, it will be found that a current of elec- 
 tricity will be generated, flowing in an opposite 
 direction from that by which the decomposition 
 was affected. As this continues the oxygen and 
 hydrogen will unite to form water until they 
 have entirely disappeared; when the flow of 
 electricity will cease. 
 
 From this as a basis, other gas batteries were 
 constructed, and finally working along the same 
 lines Gaston Plante in 1859 found that it was 
 possible to produce practically the same results 
 with lead plates. 
 
 The original Plante plates consisted of two 
 lead plates with two sheets of gutta-percha laid 
 between them and the whole rolled together and 
 immersed in a jar of water acidulated with sul- 
 phuric acid. The formation of the plates, as it is 
 called, required a long time and consisted in 
 alternately charging and discharging. 
 
 This method of forming the plate was im- 
 proved upon by Faure who substituted a plate 
 coated with a paste composed of the oxide of 
 lead. This was done for the purpose of securing
 
 164 Electricity 
 
 a more rapid formation of the cell. In fact it is 
 ready for service after two or three chargings. 
 Considerable difficulty was at first experienced 
 by the peeling off of the paste but this was over- 
 come by making the plates in the form of a grid 
 and pressing the paste into the holes from the 
 opposite sides so that it was interlocked and thus 
 held in position. This paste is made of red lead 
 and sulphuric acid. 
 
 The action of the electric current in the charg- 
 ing of a Faure plate is to convert the paste on 
 one plate to the peroxide of lead and to spongy 
 lead on the other. 
 
 The liquid employed is a mixture consisting of 
 four volumes of distilled water and one of pure 
 sulphuric acid. In accordance with the caution 
 already given, this mixture should not be made 
 in the battery cell on account of the heat that is 
 developed. It should be put together in a sep- 
 arate vessel and poured into the jar when it has 
 become cool. The tops of the plates should be 
 about 1 yz inches below the surface of the liquid/ 
 
 The range of usefulness of the storage battery 
 is extending from day to day and small batteries 
 are being rapidly introduced for portable lamps 
 and household purposes. The ordinary voltage 
 of such cells can be depended upon to be about
 
 Storage ^Satterfce 165 
 
 two. Hence a battery that is to be called upon 
 to furnish eight volts would have to be provided 
 with four cells. 
 
 In the formation of such a cell a sheet of lead 
 plate may be used measuring about 8 inches by 
 6 inches by % inch. This must be perforated 
 with as large a number of holes ^ inch in di- 
 ameter as can be drilled or punched in it and 
 still leave room for countersinking on each face. 
 There should be at least seven of these plates for 
 each cell and they should be set into the acid or 
 bath and so coupled that the negative and posi- 
 tive plates alternate, two negative being on the 
 outside as the odd number would indicate. A 
 better and stronger form of plate or grid can be 
 obtained by casting as the metal can then be dis- 
 posed in the most satisfactory manner. 
 
 It will somewhat facilitate the preparation of 
 the plates if the negatives are filled with pre- 
 cipitated lead crystals formed by placing strips 
 of zinc in acetate of lead. These crystals are 
 quite adhesive and will remain in position if they 
 are pressed firmly into the holes in the grids 
 from opposite directions. The jars for such cells 
 should have an inside measurement of at least 
 11 inches by 8 inches by 4^ inches. This will 
 permit the bottom of the plates to be raised 1
 
 166 
 
 inch above the bottom of the jar, and to stand 
 1 inch from the sides at their edges and y 2 inch 
 at their faces. The jar itself may be of glass or 
 gutta-percha. 
 
 Care must be exercised that the plates do not 
 touch each other when in position. They can 
 best be held by hard wood racks that have been 
 saturated with hot paraffine. These are simply 
 blocks about an inch wide made to fit across the 
 bottom of the jars and notched to receive the 
 plates, whose faces should be about j^ inch apart. 
 These serve to steady and hold the bottom of the 
 plates and the tops should be held in a similar 
 manner by a rack laid across them and clamped 
 down to prevent its floating away. 
 
 In charging, owing to internal resistances and 
 the losses invariably accompanying all trans- 
 formations of energy, a somewhat higher voltage 
 must be used than that of the expected output 
 of the cells. It should, in fact, be about 25 per 
 cent, in excess so that a current of about 2.5 volts 
 per cell should be used. Care must also be exer- 
 cised not to crowd the charging too rapidly and 
 for a cell like the one just described the rate 
 should not be more than four amperes. This 
 may be increased for larger cells in proportion to 
 the increase of surface on the positive plates.
 
 Storage JSattcrfes 167 
 
 While the charging can be done by means of 
 a battery consisting of Bunsen cells like that 
 previously described, it is a slow and expensive 
 process and should never be used where a current 
 from a dynamo circuit is available. 
 
 Where it is possible to get access to one it will 
 be found to be advantageous to make connections 
 with an incandescent electric lighting circuit. 
 Before making such a connection it will be neces- 
 sary to determine which is the positive and which 
 the negative wire. 
 
 The simplest way of doing this will be to im- 
 merse the two in a bowl of water, keeping them, 
 at the same time, some distance apart. It has 
 already been shown that the passage of an elec- 
 tric current through water in this way, serves to 
 decompose it into its constituent gases, oxygen 
 and hydrogen. As water is formed by the union 
 of one atom of oxygen with two of hydrogen it 
 follows that the bubbles of hydrogen arising 
 from the negative wire will be greatly in excess 
 of the oxygen arising from the positive. The 
 wires are, therefore, readily distinguished. 
 
 The voltage of these mains is, however, usu- 
 ally greatly in excess of that allowable for the 
 charging of so small a number of cells as that in- 
 dicated. If the line is charged with a 100-volt
 
 168 BlectrtcftB 
 
 current and it is desired to cut it down to the 
 ten volts needed for the charging of the four 
 cell battery similar to that which we have had 
 under consideration, it can be done by inserting 
 incandescent lamps of different voltages into the 
 circuit. They should be adapted for different 
 voltages and be placed in the positive wire. 
 Fig. 34 shows the scheme of the wiring by which 
 
 this may be 
 done. This can 
 be changed by 
 
 arranging the 
 FIG. 34. METHOD OF CHARGING Low 1rt A ? 
 
 lamps diner- 
 VOLTAGE STORAGE BATTERY 
 
 ently and using 
 
 those for different voltages in a way that will 
 readily suggest itself. 
 
 In connecting the battery for charging, the 
 positive wire of the circuit must be connected to 
 the positive plate of the battery. 
 
 The charging must be continued until gas rises 
 freely from the plates. 
 
 The time required to do this will depend upon 
 the capacity of the battery and the current used. 
 The four cell battery above described, for ex- 
 ample will have a capacity of about twenty am- 
 pere-hours. That is to say it will furnish a cur- 
 rent of one ampere for twenty hours, or of two
 
 Storage ^Batteries 169 
 
 amperes for ten hours. The time required for 
 charging may be obtained by dividing their ca- 
 pacity by the ampereage of the current supplied 
 to them. 
 
 Probably more damage is done to the plates of 
 a storage battery by rapid discharging than by 
 any other means. Such a process tends to buckle 
 or bend the plates and, when this occurs to such 
 an extent that the positive and negative plates 
 come into contact, the battery is practically 
 ruined. Much damage of this kind is done by 
 making direct connections between the positive 
 and negative poles, in order to ascertain by the 
 production of a spark whether the cell is charged 
 or not. This short-circuits the cell and a few rep- 
 etitions will be apt to produce buckling. If 
 this information relative to the condition of the 
 cell is desired, it can be best obtained by the use 
 of a two volt lamp placed in the circuit between 
 the two poles. 
 
 When the discharging of the battery is begun 
 the voltage, for cells like those described will be 
 about 2J^. It will soon drop to 2 volts and will 
 remain practically constant at that point until 
 the cell is nearly exhausted. As soon, then, as 
 it drops to 1.8 volts which may be detected by 
 the dimming of the lamps if it is used for
 
 170 BlectricftB 
 
 lighting, the discharging should be stopped and 
 recharging be begun as soon thereafter as pos- 
 sible. 
 
 In the case of a storage battery it may be re- 
 membered that far less damage is done by over- 
 charging than by allowing it to stand in an ex- 
 hausted condition. Where a battery is to be out 
 of service for any length of time, it should first 
 be fully charged and then recharged at intervals 
 of three or four weeks to make up for leakage 
 losses. 
 
 If allowed to stand neglected for any length 
 of time, white patches are apt to appear on the 
 surface of the plates and these can only be gotten 
 rid of by scraping and then overcharging. Their 
 reappearance may then be prevented by the 
 addition of a little caustic soda to the electrolyte 
 or liquid. 
 
 In addition to the evolution of the gases that 
 denote the completion of the charging of a bat- 
 tery, the colors of the plates are also changed. 
 The positive plate becomes brown and the nega- 
 tive a pale slate color. 
 
 As in other instances that have been mentioned 
 in connection with electrical work, the storage 
 battery, when in use and being charged, emits some 
 fumes or gases that are detrimental to health.
 
 Storage Batteries 171 
 
 They should, therefore, be kept in a well-ventilated 
 apartment. Metal work of any kind that is sub- 
 jected to the action of these gases will be rapidly 
 corroded and, for that reason, all of the metallic 
 connections, such as binding posts and the like, 
 that must necessarily be used about the battery, 
 should be given a coating of paraffine for pro- 
 tection. And, as a final precaution, let it be 
 understood that no attempt must ever be made 
 to charge these batteries in the wrong direction. 
 Such a proceeding will be sure to result in heat- 
 ing and a buckling of the plates. Indeed buck- 
 ling has been one of the most serious difficulties 
 to be overcome in the use and construction of 
 this type of battery. It appears however, that 
 when a battery has been well made and is well 
 cared for it improves rather than deteriorates with 
 age. This has been the experience of those who 
 use them for the development of large powers 
 such as the propulsion of street cars and as 
 auxiliaries in power stations. They are, in fact, 
 like any other article intended for use. They 
 must be well cared for or they cannot be de- 
 pended upon to render an efficient service. But 
 when given the proper amount of attention 
 they are among the most reliable sources for the 
 production of the electric current.
 
 CHAPTER XI 
 
 TRANSFORMERS 
 
 IT has already appeared that an electric cur- 
 rent in one wire may induce a current in an ad- 
 jacent wire. This induction, however, takes 
 place only during the period of an increase or 
 decrease in the intensity of the current. 
 
 It has also been shown in earlier chapters, that 
 the resistance of a circuit or wire to the passage 
 of the electric current is dependent upon its 
 length, and that long lines, such as are used for 
 telegraphic purposes, require a stronger battery 
 for their operation than do short ones. This 
 fact of the increased resistance of long lines is 
 one of the principal causes that militate against 
 the conveyance of electric currents over great 
 distances. If the current is of low voltage it 
 does not have sufficient intensity to overcome the 
 resistance of the line unless the latter is made 
 very low ; and this low resistance cannot be ob- 
 tained unless large masses of copper are used as 
 conductors. The excessive cost of such con- 
 
 172
 
 {Transformers 173 
 
 ductors makes their adoption impossible for com- 
 mercial reasons. 
 
 The other alternative for long distance trans- 
 mission is the use of a small wire and a high 
 voltage. Here again a practical difficulty is en- 
 countered in the fact that these excessively high 
 voltages cannot be used in ordinary electrical 
 apparatus and that they are exceedingly danger- 
 ous both from the standpoint of risk to life and 
 as a cause of fires. 
 
 The means employed to overcome both of 
 these serious difficulties is to use a small wire and 
 transmit a current over it at an excessively high 
 voltage, and then, at the point of utilization, 
 insert a transformer into the circuit, whereby the 
 voltage is greatly decreased and brought down 
 to a point where it can be used in incandescent 
 lighting circuits and for motor propulsion. 
 
 These circuits are usually of the alternating 
 type. 
 
 It will be remembered that, in the chapter de- 
 voted to dynamos and motors, it was explained 
 that, as the coils of wire constituting the arma- 
 ture, passed successively through the magnetic 
 fields of the two field magnets, electric currents 
 were set up in opposite directions respectively ; 
 and that it was the method of connecting the
 
 174 BlectrfcttB 
 
 wires to the commutator that served to hold the 
 outflow of these currents in a constant direction, 
 despite their change of direction with each pas- 
 sage of the coil through the neutral point. 
 
 Where these excessively high voltages (10,000 
 and upwards) are to be carried the wiring of the 
 dynamo is so arranged that the commutator does 
 not charge the polarity of the current but the re- 
 versal does occur in the outgoing line just as it 
 does in the armature coil itself. Such a current 
 is called an alternating one. 
 
 This alternation provides the very conditions 
 that are needed for the successful generation of 
 an induced current and it is produced by the use 
 of the transformer. 
 
 Electrical apparatus of this class has assumed 
 a great variety of forms, by which attempts have 
 been made to overcome the electrical and me- 
 chanical difficulties inherent in their construction. 
 They are usually enclosed in water-proof cases 
 and are placed out of doors, so as to obviate the 
 necessity for carrying the high tension currents 
 into a building. 
 
 The making of a transformer suited for the 
 conversion of these high tension currents to low 
 tension is a matter involving great care both in 
 the mechanical work to be done and the elec-
 
 {Transformers 
 
 175 
 
 trical calculations. A transformer may, how- 
 ever, be said to consist merely of one coil of wire 
 placed within and carefully insulated from an- 
 other coil. Within the inner coil there is a soft 
 iron core, similar to that of an electro magnet. 
 In the transformer, however, this core is made 
 up of a number of plates or wires. A simple 
 form of transformer can be made, that is adapted 
 to light experi- 
 mental work, by 
 using two coils of 
 wire as shown in 
 Fig. 35. It con- 
 sists merely of an 
 inner coil with its 
 wires connected to 
 the source of the 
 primary current. 
 If this inner coil 
 be made up of 
 about 100 feet of No. 16 insulated copper wire 
 and the outer of a smaller wire of much greater 
 length, that is of -1,500 feet of No. 35, the in- 
 duced current will be very perceptible even 
 though the primary one be weak. 
 
 For rapidly making and breaking the circuit 
 in the primary wire, a convenient method will be 
 
 FIG. 35. INDUCTION COIL
 
 176 Blectrfcitg 
 
 found to attach one wire to a coarse file and to 
 draw the end of the other rapidly to and fro over 
 the teeth. 
 
 The type of transformer just described is what 
 is known as a Ruhmkoff coil and is intended to 
 give a current of greater potential or higher 
 voltage in the secondary coil than existed in the 
 primary. It is what might be technically called 
 a step-up transformer, or one by which the volt- 
 age from the primary to the secondary current 
 is increased. 
 
 The method of transformer construction that 
 is followed at the present is, however, that which 
 originated with Faraday and which may be said 
 to consist of a ring of iron, serving as a core, 
 upon which successive coils of wire are placed. 
 These coils placed side by side form the primary 
 and secondary coils of the transformer. The ad- 
 vantage possessed by this ring or closed circuit 
 transformer is that its magnetic resistance is very 
 much less and its efficiency higher. 
 
 In the construction of a transformer core, par- 
 ticular attention should be paid to the selection 
 of the iron from which it is made. As in the 
 case of the ordinary magnet core, the purest iron 
 that is obtainable should be used. That is to 
 say, it should be as free as possible from carbon,
 
 177 
 
 silicon, phosphorus, etc. Sometimes a very 
 mild steel is used but pure iron will be most 
 satisfactory. A high quality of soft Swedish 
 iron is probably the best, and even this had bet- 
 ter be in the form of sheets, as in that form the 
 mechanical i m- 
 purities can be thor- 
 oughly worked out 
 of the metal. 
 
 An example of 
 transformer con- 
 struction is shown 
 diagrammatically in 
 Fig. 36. It is the 
 plan of construction 
 of the Dick and 
 Kennedy transform- 
 er. The central core FIG. 36. DIAGRAM OF THE DICK 
 A is built up of a AND KENNEDY TRANSFORMER 
 number of soft iron plates and is wound with 
 the two coils of wire C C' and D D', one serving 
 as the primary and the other as the secondary 
 coil. The outside of the core is wound with 
 several layers of thin sheet iron B. This was an 
 expensive and cumbersome apparatus but serves 
 to show the principle of construction. 
 
 The transformer, then, acting on the principle
 
 178 Electricity 
 
 of induction that has been known for so many 
 years ; with no moving parts and liable to no 
 deterioration beyond that incidental to natural 
 decay, unless overheated, serves as the means by 
 which the high tension currents generated by 
 some cheap source of power, can be conveyed to 
 distant points and there converted to voltages 
 that are utilizable. 
 
 With it is concluded the description of the 
 several classes of electrical machinery that have 
 been developed and it serves to emphasize the 
 fact of the simplicity of all of the fundamental 
 principles of the art. The transformer handling 
 currents of thousands of volts, and the magnet of 
 the telephone receiver with its inappreciable ten- 
 sion are acting upon one and the same principle, 
 differing only in degree.
 
 CHAPTEE XII 
 
 BURGLAR ALARMS AND GAS LIGHTING 
 
 THE burglar alarm is intended to cause a bell 
 to ring whenever a door or window in any part 
 of a house is opened or moved. The apparatus 
 that is installed for the purpose is frequently 
 
 FIG. 37. WIRING FOE BURGLAR ALARM 
 
 quite elaborate in the details of its perfection, t 
 but the principle of action is as simple as in 
 many other seemingly intricate pieces of elec- 
 trical apparatus. 
 
 The clearest way to explain the workings of 
 the system is by reference to the diagram Fig. 37. 
 
 179
 
 180 BlectrfcftB 
 
 Here, in order not to introduce too great a 
 mass of lines, representative of the wires used, 
 which might be apt to lead to confusion, only 
 four points are shown as protected. 
 
 At each of these four points contacts are placed 
 that will be closed whenever a door or window, 
 or whatever other movable piece may need pro- 
 tection, is moved. The simplest form of contact 
 consists of a brass slide that is made to pass over 
 another as the door opens. In order to avoid 
 the necessity of using a loose wire to follow the 
 movements of the part, two strips of brass may 
 be set a short distance apart and connected re- 
 spectively to the two poles of the battery. Thus, 
 for example, in protecting a window, lay two 
 strips of brass side by side from the top of the 
 lower sash to the top of the window casing 
 The contact between them may be formed by an 
 adjustable piece of brass to be fastened to any 
 desired point on the sash. This will enable the 
 latter to be set to open any desired amount 
 . before the ringing of the alarm will be started. 
 
 The annunciator is the most complicated part 
 of the apparatus. It is intended to show at a 
 glance the point at which the contact has been 
 made and where the attempt to enter the house 
 is to be looked for. In order to understand its
 
 JSurcUar alarms anO Gas Xtgbting 181 
 
 construction thoroughly it will be well to con- 
 sider it in connection with the wiring of the 
 building to be protected and the several points 
 from which the alarm is to be sounded. 
 
 In Fig. 37, the annunciator is shown as con- 
 nected to four points only, namely : two win- 
 dows and two doors. The bell E at the top of 
 the annunciator is of the vibrating type, exactly 
 like that described in Chapter IV and illustrated 
 on page 54. The battery F may consist of any 
 number of cells, not less than three, and increased 
 in number according to the length of the circuit 
 to be operated. Within the annunciator there are 
 four magnet coils with an armature, correspond- 
 ing to the four points to be protected. In addi- 
 tion to the armature there is also a drop that is 
 held up by a catch on the same and which is 
 loosened when the armature is raised by the ex- 
 citation of the magnet. 
 
 Let these four magnets with their armatures 
 be indicated by 0, 5, c and d. 
 
 At the two ends of the annunciator case there 
 are the binding posts G and II. From the post G 
 a wire is led along the top of the case and a 
 branch is carried off from it and connected to 
 one end of each of the magnet windings #, J, c 
 and d, while a fifth branch runs up and connects
 
 182 Electricity 
 
 to one of the binding posts of the bell E. The 
 binding post G is also connected direct to one of 
 the poles of the battery by a wire that has no 
 other connections. A wire is also led direct 
 from the other pole of the battery to the bind- 
 ing post H. This wire, however, has branches 
 )c /, g and h leading off to the four protected 
 points A, B, C and D. Each of these wires termi- 
 nates in a contact at the four points mentioned 
 respectively. 
 
 One end of the coil wires of the magnets of <z, 
 #, c and d have been said to be connected to the 
 binding post G. The other ends are extended 
 through the wires *', &, I and m to the second con- 
 tact points at the four respective protected places 
 A, B, C and D. 
 
 In the interior of the annunciator there are also 
 other connections for the operation of the bell. 
 
 The several armatures of <z, J, c and d are made 
 to hold the drops up when not in use. These 
 drops are each insulated and connected by wire 
 to the other binding post of the bell opposite to 
 that to which the wire from g is led. Beneath 
 each of the drops there is a contact point, which 
 is connected to the binding post H. 
 
 Let us now look into the wiring of the system. 
 
 When it is at rest there is no complete circuit.
 
 JBurglar Blatms anfc (3a5 Xfgbtfng 183 
 
 Everything is open. Following the lines from 
 the battery we go to the binding post G, thence 
 through the several coils a, 5, c and 6?, and thence 
 out through their respective wires *', &, I and m 
 to the four points A, B, C and D, where the circuit 
 is broken, while from the same point the wires 
 fyfy 9 an d h lead back to the opposite pole of the 
 battery from that at which we started on our 
 outer tracing. 
 
 Suppose now the door at D is opened. The 
 connection between the wires m and h is closed 
 and the current flows from the positive pole of 
 the battery to G, through the coil d and over the 
 wires in and h back to the negative pole of the 
 battery. In doing so it excites the magnet d, 
 which lifts its armature letting fall the drop. 
 When this occurs a contact is made uniting the 
 wire leading from the binding post H to the drop d 
 and that leading from the binding post of the bell 
 to the same point. The bell circuit is thus closed 
 and a current flows from the positive pole of the 
 battery to the binding post G to the bell E, to the 
 drop d, to the binding post H and thence back to 
 the negative pole of the battery. The latter 
 must, therefore, be strong enough to work the 
 main circuit to the protected point as well as the 
 shunt circuit through the bell.
 
 It will be seen that, with this system of wiring 
 and connections, the ringing of the bell, when 
 once started, continues independently of the 
 opening or closing of the contact at the sev- 
 eral protected points. Hence, if the intruder, 
 alarmed by the ringing, hastily closes the opened 
 door or window, it does not silence the bell, 
 which continues to sound until the drop is lifted 
 to engage with its catch on the armature, and 
 thus break the connection between the binding 
 post H and that on the bell. 
 
 Modifications in the working of the bell can 
 be made by having it rung by a spring which is 
 released by the falling of the drop. In this case 
 there are, of course, no electric connections to 
 the bell. Another method is the use of a sepa- 
 rate battery for its working. In that case the 
 arrangement should be the same as that described 
 in Chapter IV, and the connections should be from 
 the battery to one side of the bell and to the 
 binding post II. When this is done, there should 
 be no connection between the negative pole of 
 the battery F, and the binding post H, all other 
 connections remaining the same. 
 
 In order that the annunciator may not operate 
 at every opening and closing of the door during 
 the day when it is not needed, a switch should
 
 3Bur0lar Blarms an& Gas Xtgbttng 185 
 
 be placed in the wire between the binding post G 
 and the positive pole of the battery, close to the 
 former. This switch can be opened in the morn- 
 ing, thus making the closing of the circuit im- 
 possible, and left so during the day, and closed 
 the last thing at night thus at once throwing all 
 connections into possible working. 
 
 Such a piece of apparatus as this should be fre- 
 quently tested to see that it is in good working 
 order. Where the parts are allowed to stand 
 idle for any length of time, the contact points 
 are apt to become slightly oxydized and may fail 
 to effect an electrical contact at the crucial mo- 
 ment. Therefore, at least once a week the 
 switch should be closed during the day, and the 
 contact made at each protected point to see 
 whether the bell will be properly sounded or not. 
 
 The arrangement of an annunciator for a hotel 
 or office is nearly the same. The contacts at the 
 several protected points correspond to the several 
 push buttons in the rooms of the guests. The 
 bell, however, is not arranged to ring continu- 
 ously but only so long as the circuit is closed by 
 the pressure on the button. 
 
 The wire from the binding post of the bell is, 
 therefore, led direct to the post H and the circuit 
 through the coils #, , c and d thus becomes a
 
 186 BlectrtcftB 
 
 shunt circuit that is just sufficient to release the 
 drop and expose the number of the room from 
 which the call was sounded. The bell then 
 ceases to ring the instant the push button is re- 
 leased, but the drop having fallen leaves the 
 room number exposed until it is again raised at 
 the annunciator. In the construction of the lat- 
 ter very light magnetic coils may be used, and 
 the catches for holding the drops are easily ar- 
 ranged so that by giving enough leverage a very 
 slight pull on the armature is quite sufficient to 
 release them. 
 
 There is one more application of electricity to 
 domestic and household purposes that, a luxury 
 at first, soon becomes a necessity, and that is its 
 adaptation to gas lighting. In a previous chap- 
 ter a brief outline of the use of the plate machine 
 for the production of an electric spark for gas 
 lighting was given. Such work, however, is 
 rarely done except in the case of large installa- 
 tions where a great number of burners are to be 
 lighted or where they are placed in inaccessible 
 locations such as the ceilings of theatres, public 
 halls and the like. 
 
 The convenience of electricity for domestic 
 purposes lies in its adaptability to use on single 
 burners or on a small number. The burners
 
 Burglar Btarms anD Gas Xigbtfng 187 
 
 themselves may be fitted to be either merely 
 lighted by electricity or to both turn on the gas 
 and light it at the same time. 
 
 In fitting up any method of this sort two 
 things must be borne in mind ; that the source of 
 electrical supply must be sufficient to cause spark- 
 ing and that the sparking occurs when the circuit 
 is broken and at the point of 
 rupture and not when it is closed. 
 
 One of the simplest forms of 
 electric gas lighting attachments 
 is to be found in the ratchet 
 burners shown in Fig. 38. The 
 gas is turned on by the ordinary FIG. 38. 
 key and a pull given to the pendant. RATCHET GAS 
 This throws the wire connected to 
 the lever extending out to the left up into contact 
 with the one shown clamped about the tip with 
 a piece of asbestos insulating material beneath. 
 The touching of these two pieces of wire closes 
 the circuit and as they separate a spark is pro- 
 duced in the stream of gas, issuing from the tip, 
 which ignites it. The gas is extinguished by 
 closing the cock in the ordinary manner. 
 
 Such a burner is suited for use in kitchens, 
 stables and other places where they are apt to be 
 used by careless or ignorant persons, as there is
 
 188 Electricity 
 
 little danger of the gas being left turned on un- 
 lighted. 
 
 A more convenient form of burner is the auto- 
 matic whose general appearance is shown in Fig. 
 39. With this burner the gas is both turned on 
 and lighted by electricity, and it 
 is especially convenient for use in 
 cellars and hallways where an oc- 
 casional light is required and where 
 
 1 I it is desired to have the burner 
 
 t==J located at some distance from the 
 L -J entrance. 
 
 **" The burner contains within itself 
 
 FIG. 39. Au- ..!_., ,. X T , 
 
 TOMATIC GAS kt n the means of opening the cock 
 
 LIGHTEB in the 'gaspipe and the sparking 
 
 arrangement for lighting. 
 
 When at rest, the two terminals that are shown 
 leading up to the tjp beside the burner are in con- 
 tact. Within the case there are two sets of mag- 
 nets and an armature that is moved by one or 
 the other alternately. When the current is first 
 turned on the gas valve is opened and the arma- 
 ture raised and turned so as to be caught by a 
 hook that holds the valve open. As it does so it 
 strikes against a lever by which the contact 
 points beside the burner are separated thus pro- 
 ducing a spark. This break of the circuit puts
 
 alarms and <3as Xfsbtins 189 
 
 an end to the attraction of the magnet and the 
 armature drops, allowing the terminals beside the 
 burner to come together again. Such contact 
 again closes the circuit and energizes the mag- 
 nets, lifting the armature only to separate the 
 contact points and produce another spark. This 
 vibrating action continues just as it does in the 
 case of the vibrating electric bell, producing a 
 series of sparks so long as the push button is kept 
 closed. This button is naturally released when 
 the gas ignites. 
 
 The gas is turned off by pressing another but- 
 ton whereby the armature is brought under the 
 influence of the other or extinguishing magnet. 
 
 The common practice is to place the push 
 buttons near the entrance to the cellar or hall- 
 way that is to be lighted and to use white for the 
 lighting button and black for the extinguishing. 
 
 In residences, where the hall gas is to be 
 lighted, the lighting button may be placed near 
 the front door, and the extinguished at the head 
 of the stairway ; so that the gas may be lighted 
 upon entering and extinguishing when the sec- 
 ond-story has been reached. It is also possible 
 to have two or more lighting and extinguishing 
 buttons at any convenient locations. 
 
 As for the battery, the same rule as that pre-
 
 190 
 
 Electricity 
 
 viously laid down for other classes of work holds 
 good here. Be sure and use enough cells to in- 
 sure the working. The number will depend 
 upon the kind of automatic burner used, but 
 ordinarily four should be sufficient. They should 
 be connected in series, and the arrangement of 
 the wires may be made 
 in accordance with the 
 diagrammatic scheme 
 shown in Fig. 40. 
 
 The negative pole of 
 the battery may be 
 
 i|l|l|!|f "" = 
 
 connected directly to 
 the gaspipe in the im- 
 FIG. 40. WIEING FOE AUTO- mediate neighborhood 
 MATIC GAS LIGHTEE o f j ts own location ; 
 care being taken to first file the pipe until it is 
 bright and free from rust and then wrapping the 
 copper wire tightly about it. 
 
 The wires from the positive pole are led to the 
 two push buttons and from them separately to 
 the burner as shown. 
 
 It is quite possible to operate a number of 
 burners from one and the same battery and the 
 same leading wires may be used. It is merely a 
 matter of properly locating the push buttons at 
 those points where it is desired to close the cir-
 
 Blarms and <3as XtQbting 191 
 
 cults. The same leading wires can be used for 
 this multiplicity of connections just as it was 
 done for the operation of the burglar alarm from 
 several different points as detailed in the early 
 part of this chapter. 
 
 There is one more method of gas lighting in 
 common use, and that is the induction coil. 
 
 It was shown in Chapter XI, Fig. 35, that an 
 induction coil can be so constructed as to raiso 
 the voltage of the secondary coil above that of 
 the primary. This principle is applied to gas 
 lighting. A coil is built up along the lines de- 
 scribed for Fig. 34, and the wires led off and 
 over each one of a number of gas jets that are 
 arranged in one group. 
 
 At each jet there are two platinum terminals 
 sot a short distance (about T V inch) apart over 
 the burner. The current from the induction coil 
 has sufficient energy to leap across this gap pro- 
 ducing a spark and igniting the escaping gas. 
 In order to work this successfully, all of the 
 burners in a group are left open and the gas is 
 turned on from a cock. As soon as it is flowing 
 from the jets the spark from the induction coil 
 is used to ignite it. 
 
 The general arrangement of such an induction 
 coil is shown in Fig. 41. The coil itself is at A
 
 192 
 
 BlectrfcttB 
 
 and is formed by a comparatively small number 
 of turns of heavy wires for the primary current 
 from the battery ; and a greater number of turns 
 
 of fine wire for 
 the secondary 
 current. The 
 latter is led to 
 the sparkling 
 tips of the gas 
 jets at B, C and 
 D representing 
 the group to be 
 lighted. 
 
 The current 
 from the primary battery E is carried first 
 to a reversing box F, when the direction of 
 the flow of the current through the wires 
 G and H can be reversed. From F the primary 
 current goes to the coil by way of a circuit 
 breaker at I, which is constructed on the same 
 principle as the vibrating bell described in 
 Chapter IY and illustrated by Fig 10. The 
 armature K, under the influence of the core of 
 the magnet, which should be formed in this case, 
 of a bundle of wires, makes and breaks the cir- 
 cuit exactly as in the case of the bell. This 
 action in the primary circuit causes the sparks 
 
 FIG. 41. SPARK COIL FOE GAS LIGHT- 
 ING
 
 alarms anfc <5as XfQbtins 193 
 
 to appear at the gas jets in the secondary cir- 
 cuit. 
 
 At M a wire comes down from K and I to a 
 condenser. This is really a form of Ley den jar 
 and is made up of alternate layers of tin foil and 
 paraffine paper. This condenser serves to prevent 
 a spark from leaping across the interval between 
 K and I in the primary current when the circuit 
 is broken and also to weaken the secondary cur- 
 rent when the circuit is closed. 
 
 The intensity of the current in the secondary 
 coil depends upon the relative number of turns 
 in the primary and secondary coils and the 
 strength of .the battery that is used and these 
 may be varied between wide limits.
 
 CHAPTER XIII 
 
 ELECTRICAL EXPERIMENTS 
 
 WITH the instruments and apparatus that have 
 been described in the foregoing chapters, there 
 are a large number of most interesting experi- 
 ments that may be made ; a few of which will 
 be indicated in the pages to follow. 
 
 First, we may start with what was known as 
 the earliest manifestations of electricity devel- 
 oped by friction. Take a piece of sealing wax 
 or better a hard rubber comb and rub it briskly 
 for a moment or two with a silk handkerchief. 
 It will then be found to possess the property of 
 lifting small slips of paper by attracting them to 
 itself. 
 
 Another manifestation is produced by taking 
 a sheet of writing paper and drying it thoroughly 
 at a fire. Then lay it on the table and rub it 
 with india-rubber. It will adhere to the surface 
 upon which it is laid and, if it is peeled off, will 
 emit a crackling sound and sparks can be seen. 
 
 Hang two pith balls near each other by silk 
 194
 
 JElectrical ^Experiments 195 
 
 threads and touch them successively with a piece 
 of excited rubber or sealing wax and they will 
 immediately recede from each other and the 
 threads will stand out at an angle from the 
 vertical. 
 
 Touch a piece of pith so- suspended with an 
 excited (i. e., rubbed) glass rod and it will imme- 
 diately recede from the rod but will be attracted 
 to an excited rod of sealing wax. 
 
 Similarly a number of pith balls suspended in 
 pairs at intervals along a brass rod, that is in- 
 sulated from the floor and held in front of the 
 prime conductor of a plate machine (Fig. 2), will 
 manifest a like repulsion for each other. Those 
 at the ends of the rod will separate and their 
 threads will stand out at an angle, while those at 
 the centre will hang inert and manifest neither 
 attraction nor repulsion. 
 
 The plate machine can also be used to give an 
 imitation of a lightning stroke. Let it be turned 
 rapidly and a conductor connected to the floor 
 be brought, close to the prime conductor. Sparks 
 will leap across the interval and if a sheet of 
 paper be placed in the space it will be pierced 
 with fine holes burned through it. 
 
 By coupling several Leyden jars together and 
 charging them a longer and more powerful dis-
 
 196 Electricity 
 
 charge and spark can be obtained. A space of 
 six inches may be crossed. A thin piece of wood 
 held in the path of such a spark may be pierced 
 and shattered in exactly the same way as a tree 
 is shattered by a stroke of lightning. 
 
 Electrical shocks can also be obtained and ad- 
 ministered by the use of the plate machine and 
 a Leyden jar. The simplest and lightest form of 
 such a shock will be to hold the knuckles in front 
 of the prime conductor while the machine is in 
 motion. Sparks will leap across the interval and 
 a prickling sensation will be experienced in the 
 hand and arm. 
 
 Severer shocks may be administered by charg- 
 ing a Leyden jar and then discharging it by 
 touching the outer coating and the knob at the 
 same time. Or the same shock can be adminis- 
 tered to a number of persons at once. Let 
 any number form a line by clasping hands, 
 and let the two at the ends touch the outer coat- 
 ing and knob of the charged jar at the same 
 time respectively. The jar will then be dis- 
 charged through the whole line. 
 
 It has been shown how the spark from the 
 plate machine or from the discharge of the Ley- 
 den jar can be used to light gas at a distance. A 
 favorite experiment on the part of lecturers on
 
 Electrical Experiments 197 
 
 electricity is to use the spark to fire a small 
 charge of powder at a distance from the speaker. 
 To do this, procure a small cannon and drill two 
 touch holes and line them with some insulating 
 material. Bring to them the two wires that are 
 to lead to the outer coating and knob of the jar 
 respectively, but do not allow them to touch. 
 Load the cannon and then by touching the wires 
 to the knob and outer coating of the jar, the 
 latter will be discharged and the spark produced 
 in the mass of powder, will fire it. 
 
 A very beautiful electrical effect can also be 
 produced by laying wires on the surface of an 
 insulator such as a piece of wood. These wires, 
 or wire, may be led back and forth over the sur- 
 face in parallel lines. Then cut the wire in such 
 a way that the points where this is done will, 
 when taken as a whole, form a design, letters or 
 words. By connecting the ends of the wire to 
 the prime conductor and earth chain of the plate 
 machine and then rotating the latter, sparks will 
 appear at each point where the wire was cut and 
 the design will stand out in fire against the insu- 
 lating background. This is very effective when 
 performed in the dark. 
 
 A very simple gas lighter can also be made 
 with a Ley den jar. Simply charge the jar and
 
 198 Blectrfcitg 
 
 grasping it in the hand turn on the gas and touch 
 the edge of the tip with the knob of the jar. 
 The resulting spark will ignite the gas. 
 
 One of the most interesting experiments that 
 can be performed with a battery is that of the 
 decomposition of water. It has been shown that 
 if an electrical current be passed through a basin 
 of water oxygen will be evolved from the posi- 
 tive terminal and hydrogen from the negative. 
 
 These two gases can be easily collected. Pro- 
 cure two bell jars, fill them with water, invert 
 them and submerge their edges in the water of 
 the basin through which the current is to be 
 made to pass. The atmospheric pressure will 
 keep them filled. Place the two terminals be- 
 neath the jars, one under each, and turn on the 
 current. The gases evolved will rise into the 
 jars and displace the water. 
 
 "With the gases thus obtained a number of in- 
 teresting phenomena can be shown. If they are 
 brought together at a burner they may be ig- 
 nited and burned with an intensely hot flame. 
 Or an extinguished candle, with a spark on the 
 wick, when plunged into the oxygen jar will 
 burst into flame. A piece of red hot iron dipped 
 into the same jar will glow and burn like tinder 
 in the air.
 
 Electrical Experiments 199 
 
 Magnetism also affords a wide scope for ex- 
 perimental work. The formation of a permanent 
 magnet is easily accomplished by simply laying a 
 piece of steel across the two poles of a magnet, 
 like that used on electric bells. In this way a 
 very efficient compass needle may be produced. 
 
 A magnet thus formed and placed beneath a 
 sheet of paper upon which iron filings are scat- 
 tered will cause them to arrange themselves 
 along the lines shown in Fig. 23. 
 
 These few experiments will serve as sugges- 
 tions for many others that can be performed by 
 the utilization of the various properties of elec- 
 trical phenomena. 
 
 In conclusion, attention is once more directed 
 to the small number of really fundamental prin- 
 ciples that enter into the manifestation and con- 
 trol of electrical phenomena. But, few as these 
 may be, it is readily seen that they may be made 
 to play a great variety of roles according to the 
 circumstances under which they are obliged to 
 act. If, however, the rules that have been laid 
 down are thoroughly understood and carefully 
 followed, there is practically no limitation to the 
 wide variety of applications to which the electric 
 current may be put.
 
 GLOSSAKY 
 
 THE following are the definitions of a few 
 electrical terms used in the foregoing chapters. 
 
 Ammeter. An instrument for measuring the 
 strength of an electric current. The readings 
 are given in amperes. 
 
 Ampere. The "unit of current strength. 
 Named after Ampere. One ampere deposits 
 4.0248 grammes of silver per hour. It is equal to 
 the voltage divided by the resistance in ohms. 
 
 Armature. The revolving portion of a dynamo 
 or motor, containing the wires in which the cur- 
 rent is generated in the former or through which 
 it is made to pass in order to give motion in the 
 latter. 
 
 Battery. An apparatus arranged to furnish a 
 continuous flow of an electric current. 
 
 Binding Post. A means of fastening the 
 wires through which an electric current is to pass 
 to a battery or other apparatus. It usually con- 
 sists of a case and screw by which the wire may 
 be held. 
 300
 
 201 
 
 Cell. A jar containing any arrangement of 
 substances for the purpose of obtaining a con- 
 tinuous current of electricity. 
 
 Charge. An accumulation of electricity which, 
 when the proper means are used, may be again 
 discharged. 
 
 Circuit. The pathway for an electric current 
 from one pole of a battery or dynamo to the 
 other. 
 
 Commutator. That portion of a dynamo or 
 motor that periodically interrupts the electric 
 current and serves to transmit the current gene- 
 rated in the armature to the main circuit. 
 
 Conductor. A substance that offers but slight 
 resistance to the passage of the electric current. 
 
 Coulomb. The unit of quantity of current. 
 Named after Coulomb. It is the quantity of 
 electricity flowing in a current of one ampere for 
 one second. It is equal to 10 1 C. G. S. (centi- 
 meter, gramme, second) units. 
 
 C. G. S. The unit of electrical measurement. 
 It represents the work done by the movement of 
 one gramme, through a distance of one centi- 
 meter in one second. 
 
 Current. The flow of electricity. The pas- 
 sage of electricity from one pole of a battery, pile, 
 coil or dynamo to the other.
 
 202 BlectrtcftB 
 
 Dynamic Electricity. Electricity whose cur- 
 rent has a continuous flow, though not neces* 
 sarily in one direction. 
 
 Dynamo. An apparatus for generating an 
 electric current by the transformation of me- 
 chanical motion. 
 
 Electrolysis. The decomposition of chemical 
 compounds by electricity. 
 
 Electro-magnet. A bar of soft iron rendered 
 temporarily magnetic by the passage of a current 
 of electricity through a coil of wire by which it 
 is surrounded. 
 
 Erg. The work represented by one C. G. S. 
 
 Farad. The electric unit of capacity. Named 
 after Faraday. It represents the storage of one 
 coulomb in a condenser. 
 
 Field Magnet. The magnets through whose 
 magnetic fields of influence, the armature of a 
 dynamo or motor is made to pass. 
 
 Galvanic Electricity. An electric current 
 generated by a battery. Synonymous with 
 dynamic electricity. Named after Galvani. 
 
 Henry. The unit of induction. Named after 
 Henry. It represents the induction in an electric 
 circuit, when the induced electro-motive force is 
 one volt and the inducing current varies at the 
 rate of one ampere per second. Its value is
 
 203 
 
 10 9 0. G. S. (centimeter, gramme, second) 
 units. 
 
 Induction. The action which electrified bodies 
 exert at a distance on bodies in a natural state. 
 The generation of a current in a circuit insulated 
 from that through which an electric current is 
 passing. 
 
 Insulator. A substance which offers a high 
 resistance to the passage of an electric cur- 
 rent. 
 
 Joule. The electric unit of heat. Named 
 after Joule. It represents the heat developed in 
 a conductor by one watt in one second. 
 
 Magnetic Field. The region or space affected 
 by a magnet. 
 
 Motor. An apparatus for converting an elec- 
 tric current into mechanical motion. The reverse 
 of a dynamo. 
 
 Negative Pole. That pole or terminal of a 
 battery or dynamo towards which the electric 
 current is supposed to flow. 
 
 Ohm. The unit of electrical resistance. 
 Named after Ohm. The resistance offered by a 
 column of pure mercury 106 centimeters long, 
 and one square centimeter in cross-section at a 
 temperature of 32 Fahr. It is equal to 10 9 ; 
 G. G. S. units of resistance.
 
 204 BlectricitB 
 
 Ohmmeter. An instrument for measuring the 
 resistance of a circuit. 
 
 Pile. A series of elements " piled " upon each 
 other forming an electric generator. First made 
 by Yolta and called a Voltaic pile. 
 
 Pole. The terminal points of a battery, pile 
 or dynamo from and to which the electric cur- 
 rent is supposed to flow. The two points at op- 
 posite ends of a magnetic bar where the attrac- 
 tion is the greatest. 
 
 Positive Pole. That pole or terminal of a 
 battery or dynamo from which the electric cur- 
 rent is supposed to flow. 
 
 Potential. Electric intensity. A term hold- 
 ing the same relation to electricity that level 
 does to gravity. 
 
 Resistance. The opposition offered by a con- 
 ductor to the passage of an electric current. 
 
 Short Circuit. A circuit through which a cur- 
 rent is enabled to pass and whose resistance is 
 less than that of the circuit through which it is 
 intended to pass. 
 
 Solenoid. A coil of wire through which a 
 current of electricity is made to pass, and which 
 is thus made to possess many of the properties of 
 a magnet. 
 
 Statical Electricity. Electricity developed by
 
 (Blossarg 205 
 
 frictional contact between bodies, as distinguished 
 from that generated by chemical means. 
 
 Terminal. The ends of a battery or dynamo 
 to which the wires of the circuit are attached. 
 Usually applied to the clamping screw placed in 
 that position. 
 
 Torque. The torsional stress put upon a 
 motor shaft in its effort to turn under the in- 
 fluence of the electric current. 
 
 Volt. The unit of electro-motive force. 
 Named after Volta. It is equal to 10 8 C. G. S. 
 units. 
 
 Voltmeter. An instrument used to measure 
 the electro-motive force or voltage of batteries 
 and dynamos. 
 
 Watt. The unit of electric power, Named 
 after Watt. It is equal to one volt multiplied 
 by one ampere or 10 7 C. G. S. units. 
 
 Wattmeter. An instrument for measuring the 
 number of watts or amount of electric power 
 passing over a circuit.
 
 POPULAR HAND-BOOKS 
 
 COME books are designed foi , 
 
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 tion. C[ This series combines both 
 features. The information is not only 
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 and readable. In this busy, bulling 
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 Qoth, each 50 cents 
 
 THE PENN PUBLISHING COMPANY 
 923 Arch Street, Philadelphia
 
 ETIQUETTE There is no passport to good society 
 bv A S nes ft. Morton Hke good manners. Ever, though one 
 possess wealth and intelligence, his suc- 
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 LETTER WRITING Why do most persons dislike to 
 
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 QUOTATIONS A clever compilation of pithy quota- 
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 EPITAPHS Even death has its humorous side. 
 
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 stones," but when they are tombstones 
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 PROVERBS The genius, wit, and spirit of a nation 
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 THINGS WORTH Can you name the coldest place in 
 KNOWING the United States or tell what yeai 
 
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 i
 
 A DICTIONARY OF Mast of us dislike to look up * 
 
 MYTHOLOGY mythological subject because 
 
 By John H. Bechtel * *^ e time required, fl This 
 
 book remedies that difficulty 
 
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 fl It is comprehensive, convenient, condensed, and the infor- 
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 something found in few other works. 
 
 SLIPS OF SPEECH Who does not make them? 
 
 By John H. Bechtel The best of us do. <! Why not 
 
 avoid them ? Any one inspired 
 
 with the spirit of self-improvement may readily do so. <J No 
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 Style. 
 
 HANDBOOK OF What is more disagreeable 
 
 PRONUNCIATION *nan * faulty pronunciation? 
 
 By John H. Bechtel No other defect so clearly 
 
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 t
 
 PRACTICAL A new word ft a new tool J This 
 
 SYNONYMS book will not only enlarge your vocabu- 
 
 By John H. Bechtcl I ar y but will show you how to express 
 
 the exact shade of meaning you have 
 
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 AFTER-DINNER The dinner itself may be ever so 
 
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 TOASTS Most men dread being called upon to 
 
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 i
 
 THE DEBATER'S There is no greater ability than 
 
 TREASURY the power of skillful and forcible 
 
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 J There is also a list of over 200 questions for debate, with 
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 PUNCTUATION Few persons can punctuate properly; 
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 ORATORY Few men ever enjoyed a wider ex- 
 
 By Henry Ward Beecher penence or achieved a higher repu- 
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 of true oratory* 
 
 *
 
 CONVERSATION Some people ate accused of talk 
 
 3y J. P. Mahaffy ing too much. But no one is ever 
 
 taken to task (or talking too well 
 
 H Of all the accomplishments of modem society, that of 
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 READING The ability to read aloud well, 
 
 AS A FINE ART whether at the fireside or on the 
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 9 The work is especially recommended to teachers and 
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 CONUNDRUMS Conundrums sharpen our wits and 
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 I
 
 MAGIC There is no more delightful form of entei^ 
 
 fty Ellis Stanyon tainment than that afforded by the per- 
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 q Fully illustrated. 
 
 HYPNOTISM There is no more popular or 
 
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 WHIST "According to Cavendish" is now 
 
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 ASTRONOMY : Can you tell what causes 
 
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 Few books contain as much valuable material so pleasantly 
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 BOTANY: The scientific study of 
 
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 9
 
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 HOW to GrOW Them but few succeed in growing 
 
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 ject of flowers is quite thoroughly covered, the style used is 
 plain, simple, and free from all technicalities. 
 
 DANCING A complete instructor, beginning with 
 
 By Marguerite Wilson ^ e nnft positions and steps and leading 
 up to the square and round dances, 
 fl It contains a fufl list of calls for all of the square dances, 
 and the appropriate music for each figure, the etiquette of 
 the dances, and 1 00 figures for the german. fl It is unusu- 
 ally well illustrated by a large number of original drawings. 
 J Without doubt the best book on the subject. 
 
 ASTROLOGY If yu wish to obtain a horoscope of 
 By M. M. Macgregor y ur entire ^ e or $ y u would lie to 
 know in what business or profession you 
 will best succeed, what friends you should make, whom you 
 should marry, the kind of a person to choose for a business 
 partner, or the time of the month in which to begin an enter- 
 prise, you will find these and hundreds of other vital ques- 
 tions solved in this book by the science of Astrology,
 
 GRAPHOLOGY : Do you know that every 
 
 How to Read Character time you write five or 
 from Handwriting Hnes vour j"* 1 a 
 
 By Clifford Howard COmplete , reC A rd f * 
 
 character ? Anyone who 
 
 understands Graphology can tell by simply examining your 
 handwriting just what sort of a person you are. CJ There is 
 no method of character reading that is more interesting, more 
 trustworthy, and more valuable than that of Graphology, 
 and it is the aim of this volume to enable, anyone to become 
 a master of this most fascinating art. 
 
 PRACTICAL PALMISTRY. The hand shows the 
 
 By Henry Frith man ^ ut manv who be- 
 
 lieve in palmistry have 
 
 found no ready access to its principles. J This little guide 
 to it is complete, trustworthy, and yet simple in arrangement. 
 C| With this book and a little practice anyone may read 
 character surely, recall past events, and forecast the future. 
 I Fully illustrated. 
 
 CIVICS : This book answers a multi- 
 
 What Every Citizen tu< ^ e of questions of interest to 
 Should Know everyone, fl It gives intelli- 
 
 By George Lewis ? e nt ' coneise ' an< * com P lete 
 
 information on such topics as 
 
 the Monroe Doctrine, Behring Sea Controversy, Extradition 
 Treaties, Basis of Taxation, and fully explains the meaning 
 of Habeas Corpus, Free Coinage, Civil Service, Australian 
 Ballot, and a great number of other equally interesting subjects. 
 II
 
 LAW, AND HOW TO ^*>st legal difficulties arise 
 KEEP OUT OF IT from ignorance of the minor 
 
 By Paschal H. Coggins, Esq. P of law - fl T^ 5 book 
 
 furnishes to the busy man and 
 
 woman knowledge of just such points as are most likely to 
 arise in every-day affairs, and thus protects them against 
 mental worry and financial loss. ][ Not only is this informa- 
 tion liberally given, but every point is so explained and illus- 
 trated that the reader will not only understand the law on 
 the subject, but cannot fail to remember it. 
 
 CLASSICAL DICTIONARY All literature abounds 
 By Edward S. Ellis, A. M. in classical allusions, but 
 
 many do not understand 
 
 their meaning. ][ The force of an argument or the beauty 
 of an illustration is therefore often lost. ^ To avoid this, 
 everyone should have at hand a complete dictionary such as 
 this, fl It contains all the classical allusions worth knowing, 
 and they are so ready of access as to require little or no 
 time in looking up. 
 
 PLUTARCH'S LIVES Plutarch was the most famou, 
 
 By Edward S. Ellis. A. M. biographer and one of the most 
 
 delightful essayists who ever 
 
 lived. ^[ To him we are indebted for an intimate acquaint- 
 ance with many famous Greeks and Romans who made 
 history and who still live. J This book is a condensed form 
 of the original " Lives." CJ All the personages likely to be 
 inquired about are mentioned, and what is told of them is 
 just what one most wishes to know.
 
 GOLF Golf, to-day, is a synonym for "out- 
 
 By Horace Hutchfnson doors" to thousands of busy people. 
 fl This standard book gives a com- 
 plete history of the game, together with instructions for the 
 selection of implements, and full directions for playing. 
 J Much interesting information relating to celebrated links 
 and famous players is presented. C[ A convenient glossary, 
 together with the rules and etiquette of the game, is 
 appended. 
 
 FIRST AID Lives can be saved and much 
 
 TO THE INJURED suffering prevented by the 
 
 By F. J. Warwick study of this work. <J What 
 
 to do in all kinds of accidents, 
 
 as well as in the first stages of illness, with a brief and simple 
 statement of the human anatomy, constitute the chief features 
 of the book. [ It is written in a plain and simple way, 
 easily understood, and its value is further increased by its 
 copious illustrations. 
 
 NURSING Every household has its serious illnesses, 
 
 By S. Virginia Levls kut ^ ew f am & es ca n afford a profes- 
 sional nurse, fl This book is the next 
 best thing, better in some respects, as anyone can easily 
 follow its instructions, and when once learned they are 
 always available. [ The fullest particulars are given for the 
 care of the sick in all the simple as well as the serious ail- 
 ments of Hf e. 
 
 *
 
 ELECTRICITY An interesting and thoroughly reliable 
 By George L Fowler presentation of the subject for the ama- 
 teur or skilled electrician. C[If you wish 
 to install an electric door-bell, construct a telephone, wire a 
 house, or understand the workings of a dynamo, this volume 
 will furnish the required information. CJ A practical book of 
 inestimable value to everyone. 
 
 PHYSIOGNOMY How can we judge whether a man 
 
 By Leila Lomax may be trusted to handle money for 
 
 us ? C[ How can a woman analyze 
 
 a man who would marry her ? fl Partly by words, partly 
 by voice, partly by reputation, but more than all by looks 
 the shape of the head, the set of the jaw, the line of the 
 mouth, the glance of the eye. | Physiognomy as ex- 
 plained in this book shows clearly how to read character 
 with every point explained by illustrations and photographs. 
 
 THE DOG Every dog owner should know how to 
 By John Maxtee choose a dog, how to house and feed him, 
 how to exercise and train him, and how to 
 get him back to condition if he is out of sorts. J All the 
 essentials of dog keeping are here, from kennel to show- 
 bench, and from biscuits to flea-bane. J For the one who 
 wants a cheap but expert dog encyclopedia in little space 
 this is the only book. 
 
 14
 
 HEALTH 1 : HOW TO What is the use of dumb 
 
 GET AND KEEP IT bells every morning and 
 
 By Walter V. Woods, M. D. rigid dieting three times a 
 
 day when there is an open 
 
 drain in the cellar ? <J Why shield the baby from draughts 
 and then feed him on infecfted milk ? ^ Do you know the 
 things that make for Health ? proper exercise, resl, bath- 
 ing, eating, ventilation, and good plumbing these are only 
 a few of them. CJ This book tells what Health is, what 
 makes it, what hurts it, and how to get and how to keep it. 
 
 CURIOUS FACTS Why do you raise your hat to a 
 
 By Clifford Howard lady ? and why are you always 
 
 careful to offer the right hand and 
 
 not the left? t| Is there a good reason for the buttons on 
 the sleeve of your coat ? ^ How did your family name 
 originate ? tj Is it true that it takes nine tailors to make a 
 man, and if so, why, forsooth ? fl These and scores of 
 equally interesting questions find answers here. Open it at 
 any page and you will see something you have wanted to 
 know all your life.
 
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