Sfc 
 
P R ACTI C A L 
 
 DYNAMO BUILDING, 
 
 WITH 
 
 DETAIL DRAWINGS AND INSTRUCTIONS FOR WINDING. 
 
 GIVING CORRECT SIZES OF 
 
 WIRE, DIMENSIONS OF IRON, ETC., ETC. 
 
 ALSO 
 
 DIAGRAM FOR HOUSE WIRING. 
 
 BY 
 
 L C. ATWOOD 
 
 ST. LOUIS: 
 
 NIXON -JONES PRINTING Co. 
 1893. 
 
< 
 
 
 Entered according to Act of Congress in the year 1893, by 
 
 L. C. ATWOOD, 
 In the office of the Librarian at Washington, D. C. 
 
ft 
 
 ft? 
 
 R R 
 
 Ever since electric lighting has become a practical success, there has 
 been a desire, on the part of the general public, to know the method of 
 construction of dynamos. There are many able works on the subject, but 
 far too deep and scientific to reach the class most deeply interested. This 
 work is gotten up especially for amateur builders and non-professional men. 
 All measurements and instructions for winding are taken from machines in 
 actual service. Particular attention has been given to every detail of 
 construction, that they may be thoroughly understood. This work will be 
 of great value, not only to those who wish to build dynamos, but to 
 superintendents, engineers and workmen who have the care of present 
 established systems. 
 
 St. Louis, June, 1893. 
 
 (in) 
 
TABLE OF CONTENTS. 
 
 PAGE. 
 
 Introduction 1 
 
 The Construction and Winding of a Siemens Armature 4 
 
 How to Wind a Gramme Ring Armature 9 
 
 Four Light Dynamo 14 
 
 Ten Light Dynamo 21 
 
 Fifteen Light Dynamo 29 
 
 Thirty-five Light Dynamo 39 
 
 Sixty Light Dynamo 45 
 
 One Hundred and Fifty Light Dynamo 52 
 
 One Light Arc Dynamo 61 
 
 Method of Field Winding and House Wiring 67 
 
 Neutral Diameter 70 
 
 Charging of Dynamo 72 
 
 Magnetic Strength of Fields 72 
 
 Speed of the Dynamo 72 
 
 Lines of Force 72 
 
 Causes of Brushes Sparking 73 
 
 Commutator Segments , 75 
 
 Position of the Brushes 76 
 
 How to Test the Dynamo 77 
 
 Wiring for Lamp Circuits 78 
 
 Wiring Tables for Lamps 80,82,83 
 
 Table of Dimensions, Weight and Resistance of Bare Copper Wire 85 
 
 w 
 
vi TABLE OF CONTENTS. 
 
 PAGE. 
 
 Table showing the Weight, Carrying Capacity and Loss in Volts of 
 
 Different Sizes Copper "Wire 84 
 
 Rules and Regulations of the New England Insurance Exchange and 
 
 Boston Fire Underwriters Union for Electric Lighting 86 
 
 Rules and Regulations of the New York Board of Fire Underwriters .... 101 
 
 How the Electric Current is Produced 110 
 
 History of Electricity and Electric Light 115 
 
 The Incandescent System 129 
 
 Storage Batteries 135 
 
 Economy of Electric Lighting 140 
 
INTRODUCTION. 
 
 The time has come when the proper understanding of dynamo building 
 is just as essential as the knowledge of steam engines or any other mechanical 
 appliance. There is hardly any branch of industry but that electricity figures 
 in it in some form. Engineers are called upon to take charge of dynamos and 
 motors in connection with their engineering duties, and many times they are 
 compelled to take positions and run the chances of the machine not getting out 
 of order, and how often are they censured for the apparatus getting out of 
 order when the injunction has been placed upon them not to meddle with any 
 portion of the machine or its adjustments? ~No engineer can take charge of 
 an engine and boilers until he has passed a thorough examination as to his 
 fitness, still machinery far more delicate and liable to get out of order is 
 forced upon him. A mischievous person with a little smattering of electricity 
 can give him no end of trouble when, if the engineer thoroughly understood 
 the machine, he could easily locate or determine the cause. The construction 
 is purely mechanical and in cases of accidents, when the parts are returned to 
 the factory for repairs, those who repair them are perhaps no better workmen 
 than the engineer who had charge of the machine, only they have had a little 
 more experience in that particular line of work. From the mystery that is 
 thrown around that class of work, it is looked upon as something beyond the 
 reach of the ordinary mechanic. The object of this work is to dispel that 
 illusion, and to teach engineers, machinists, non-professional men and school- 
 boys that all that is required to build dynamos is the knowledge of the proper 
 dimensions of iron, correct sizes of wire and a little mechanical skill. The 
 
 (1) 
 
2 PRACTICAL DYNAMO BUILDING. 
 
 principles involved in the generation or production of dynamic electricity are all 
 the same, even if each separate machine is known as a certain system. That 
 magic word has long gone into disuse, and one that thoroughly understands 
 one machine, knows them all, and all that is required to build dynamos for 
 any service, let it be arc or incandescent, continuous or alternating current, 
 high or low potential, is the knowledge of dimensions of iron, sizes of wire 
 and number of windings, for whatever service the machine is intended. If the 
 exact dimensions of iron, the sizes and correct number of windings of wire 
 on the armature and field magnets were given of a large lighting or power 
 generator, it would be impossible to reduce at a regular ratio and construct a 
 dynamo that would give satisfactory results, if any at all. As sizes and styles 
 change, conditions change also. Each machine has its own measurement and 
 sizes of wire for whatever service it is to be used. 
 
 What wonderful changes have been wrought within the last few years in 
 systems that were put on the market as perfect ! Form and quantity of iron 
 have been changed, sizes and quantities of wire have gone through the same 
 transformation, and the end is not yet. The future field is open as wide for 
 electrical developments as the past, and I fully believe that if the fundamental 
 principles of dynamo building were within easy reach of all, it would enable 
 those who are engaged in the care and management of electric plants, to give 
 the owners better service and the machines longer lives. Those who have a 
 desire to engage in the business can do so with a thorough knoAvledge of 
 dynamo construction. 
 
 Practical electric lighting is of very recent date. In 1878 Charles 
 Brush exhibited the first lamps burning in series, and in 1881 Edison installed 
 his first incandescent plant. But how many who are familiar with the workings 
 of dynamos understand their construction? In presenting this little volume to 
 the public, it is the writer's aim to give that information so much desired. The 
 fundamental principles will be so plainly laid down that any one skilled in the 
 use of tools should be able to build all the dynamos in this work, or, with the 
 information it gives, should be able to repair almost any of the present systems. 
 Every dynamo that this work contains has been built and thoroughly tested 
 by the writer, and only information gained by actual practice will be given. 
 
PRACTICAL DYNAMO BUILDING. 3 
 
 Electricity will not be treated scientifically, and no attempt will be made to 
 explain its nature ; neither will we go back to Davenport and Page and rehearse 
 their experiments. No attempt will be made to explain the various systems 
 now in use, as there are but few who have any love for the study of 
 electricity, but have had the opportunity of seeing the different systems 
 working, or have books with cuts of the different machines in use ; but 
 none have given the information so much desired; that is, to tell just how a 
 dynamo is constructed ; how the armature and commutator are made ; how 
 much iron in the pole pieces, and field magnets ; what size of wire on the 
 armature and field magnets, and how many convolutions on each to produce a 
 given current and voltage. That information is the private property of dynamo 
 builders, and the writer will not infringe on their rights, but will confine himself 
 strictly to machines of his own building. While the machines given in this 
 work are small and of low voltage, the principles of construction are as 
 thoroughly incorporated in them as though they were the largest lighting or 
 power generators on the market to-day. It has been the writer's aim in getting 
 up this work to make it as plain as possible for amateur builders, and give 
 information which is of the greatest importance to that class. All technical 
 terms and mathematical formulas have been dispensed with and only plain 
 words and figures used, so that all parts can be readily understood. By 
 carefully following the instructions, there is no reason why any one building a 
 dynamo from this work should not get as good results as the writer. Good 
 workmanship, good material and good insulation are the essential features of 
 success. 
 
 ST. Louis, Mo. L. C. AT WOOD. 
 
THE CONSTRUCTION AND WINDING OF A SIEMENS ARMATURE. 
 
 When the armature core is finished, whether it is a spool of iron wire, or 
 is built up of iron discs, it should be spaced off into the number of sections 
 required. In each end of the core, and on lines parallel with the shaft should 
 be formed equi-distant slots 3 /i6 inch deep and about Vie inch wide. Into these 
 slots are driven pieces of hard wood or vulcanized fiber, which should project 
 sufficiently to keep the coils of copper wire in place, the length of pins varying 
 with the different sizes of wire used on the armature. 
 
 The armature core should now be covered over its entire surface with 
 rubber tape or two or three layers of thin muslin well saturated with shellac 
 varnish. The shaft for a proper distance from the core should also be covered 
 with the same thickness of insulation, and the armature is ready for the copper 
 wire. 
 
 In Fig. I, the wire starts from the commutator end of the armature 
 at 1 ; is carried along the surface of the core between two division pins 
 parallel with the shaft between the pins at the opposite ends ; across the 
 end of the armature core ; then between the pins diametrically opposite those 
 between which the coil started ; then across the commutator end of the core 
 and alongside of the first wire laid on. The wire is carried around the 
 armature core in this manner until the space between one set of pins is filled 
 one layer deep. If two layers of wire are required to each section, go around 
 the armature again in the same manner between the same set of pins, thus 
 winding back to the point of starting. The first layer can be laid all on one 
 side of the shaft and the second layer on the other side, or each coil may be 
 
 (4) 
 
PRACTICAL DYNAMO BUILDING, 
 
 divided, one-half on each side of the shaft as shown in figure (1). Do not 
 cut the wire but leave a loop as shown at 2 sufficiently long to go to the 
 
 FIG. I. 
 
 commutator. After making the loop and securing the wires together close 
 to the armature core, as shown at 2 (which may be done with strong thread, 
 or the wires may be twisted together) , the second section is started between the 
 
6 PRACTICAL DYNAMO BUILDING. 
 
 next set of pins, and proceeded with as the first section until one-half of the 
 sections are laid on the core as shown in Fig. II. All the spaces are now filled, 
 but with only six loops to go to the commutator. The outer layer is now 
 started at 7, going between the pins in the next section and between wire 1 
 and loop 2, as shown in Fig. Ill on the opposite side continuing around the 
 armature core as in the first instance until the outer layer is laid on. The 
 
 FIG. II. 
 
 ending wire of the last layer and the starting wire of the first layer joining 
 together and connecting to the same segment in the commutator. Only three 
 sections of the outer layer are shown in the diagram. If there are two layers 
 of wire to each section, there will be four layers between each set of pins with 
 the lead wires for each section on opposite sides of the armature core. The 
 object of leaving the loops between the sections instead of cutting the wire is 
 
PRACTICAL DYNAMO BUILDING. 7 
 
 to prevent making a mistake in connecting the wires to the commutator, as 
 each loop from the armature connects to a segment in the commutator. To 
 prevent the copper wire from being thrown out against the pole pieces from 
 the centrifugal force, there should be bands of brass wire placed on the outside 
 of the armature ; the number of bands and the size of brass wire will depend 
 upon the size and length of the armature. For the small machines three bands 
 
 FIG. III. 
 
 of No. 26 spring brass wire is large enough, but for the larger machines No. 
 20 or 22 should be used. Between the brass and copper wires should be placed 
 strips of mica, which not only serve as insulation but will prevent the insulation 
 on the copper wire being scorched as the bands are being soldered. 
 
 These cuts are made from a small armature in the course of construction 
 with only twelve sections and one layer of wire to each section. The core is a 
 
g PRACTICAL DYNAMO BUILDING. 
 
 wooden spool filled with iron wire, the division pins are small smooth wire nails 
 with the heads removed. After the armature is wound, the bands placed on 
 the outside, and it is given a coat of shellac varnish, the pins are removed. If 
 the copper wire is well laid on the armature core, there is no danger of the wire 
 coming off, even at a high rate of speed, but in all large armatures the division 
 phis should be of wood or fibre and should remain in the armature. 
 
HOW TO WIND A GRAMME RING ARMATURE. 
 
 The armature core should be first well insulated and spaced off into the 
 desired number of sections that the coils may all be of the same width. The 
 winding is a very simple process as far as the knowledge of the work is 
 concerned, as can be seen by referring to Fig. IV. Starting the first coil at 1, 
 the wire is passed through the interior of the armature core, returning across 
 the outer surface to the point of starting, ending the first section at 2. The 
 second section starts at 3 ending at 4, and so on around the core until the 
 surface of the core is covered. If two or more layers are required to each 
 section, wind back and forth until the desired number of convolutions are laid 
 on. The ending wire of one section and the starting wire of the next section 
 join and go to the same segment in the commutator. As the wires 2 and 3 
 connect and go to one segment in the commutator, 4 and 5 would connect to 
 another segment ; thus when the whole surface was covered, the ending wire 
 of the last section would connect with the starting wire 1 of the first section, 
 forming a complete circuit around the armature core. It is not convenient to 
 leave a loop between the sections to go to the commutator segments as in a 
 Siemens armature, as the wire has to be wound on a shuttle to get it in 
 convenient form to pass through the interior of the armature core. The length 
 of each section should be determined and cut off, for if there should be a few 
 convolutions short in a section, all the wire in that section would have to be 
 taken off again or the wire spliced, which is a dangerous piece of work, as a 
 splice in an armature is liable to come apart, which would open the circuit in the 
 
 (9) 
 
10 
 
 PRACTICAL DYNAMO BUILDING. 
 
 armature, no doubt causing sufficient spark to burn the section in which the 
 break occurred and the adjoining one as well. 
 
 Figs. V and VI are cuts made from a four light armature, which is a 
 
 FIG. IV. 
 GRAMME RING. 
 
 little more convenient to make than the one given in the drawings for a four 
 light dynamo. The armature core is made of iron wire wound on a wooden 
 spool with removable flanges on the ends. When the proper amount of wire is 
 wound on the spool the end of the wire is soldered; the flanges are then 
 
PRACTICAL DYNAMO BUILDING. 
 
 11 
 
 FIG. V. 
 
 no. vi. 
 
12 PRACTICAL DYNAMO BUILDING. 
 
 removed and the wire ring slipped off the wooden spool. The iron ring is then 
 covered with two layers of adhesive rubber tape, then spaced off into eighteen 
 sections and wound four layers deep with "No. 20 double cotton covered magnet 
 wire (B. & S. Gauge). To secure the armature to the shaft, the shaft should 
 be threaded in the center the length of the armature or a little more ; two 
 taper wooden bushings with holes in the centers to admit the armature shaft are 
 placed in the interior of the armature ; with a nut and washer on each end of 
 the shaft, the bushings are forced into place, which will bring the armature 
 central with the shaft if care has been taken in winding the armature so that 
 the copper wire has not been piled up more on one side than the other. After 
 that is done the shaft should be placed in the lathe and turned down to the 
 proper size of the bearings. 
 
 Fig. VI shows the armature finished with commutator in place and 
 bearing turned down. No dimensions of the armature in Figs. V and YI need 
 be given here as they are given in drawing for four light dynamo. Only two 
 styles of armature will be given in this work, the Gramme ring and the 
 Siemens or drum armature, as they are the only ones that can be used with 
 this type of field magnets given. At one time there was quite a difference of 
 opinion as to the relative merits of the two armatures, but the difference 
 existed more in imagination than in the armatures themselves. The agents of 
 the different systems had as much, or in fact, more to do in forming the 
 opinions of users of dynamos than did the machines themselves. In early days 
 of electric lighting ever argument was used to convince a prospective purchaser 
 that theirs was the only system that could be used with any degree of success. 
 Those in favor of a Gramme ring would tell of the slow armature speed, of 
 the hollow core, thereby securing perfect ventilation, and that as each coil was 
 separate and distinct from its neighbor, in case of injury one could be removed 
 without disturbing the others. As all the wire on a Siemens armature is 
 laid on the outside of the armature core, each coil as it is laid on must 
 necessarily cross all previous ones at each end ; the ends of the armature 
 thereby become a perfect network of wires so when one coil burns out, it is 
 generally the first one laid on, and all the wire on the armature must be 
 removed to get to the injured coil. 
 
PRACTICAL DYNAMO BUILDING. 13 
 
 If the wire is properly laid on the core, and is drawn down firmly across 
 the ends, and properly bound and shellaced that the wires may not be thrown 
 out of place from centrifugal force, there is no reason why a Siemens armature 
 of the same electrical output should not run as long and give as good servive as 
 a Gramme ring. When a coil on an armature burns out from fair play, let it 
 be Siemens or Gramme ring, it is time that all the wire on the armature was 
 removed and new wire put on in its place. It requires skill and good workmanship 
 to build either style of armature, and no pains should be spared if good results 
 are expected. As both armatures require the same mechanical horse power to 
 produce a given candle power, it resolves itself into a mere matter of choice 
 which armature is used. 
 
FOUR LIGHT 
 
 These drawings are for a dynamo that will supply current for 4, 16 
 candle power, 35 volts lamps. The machine weighs 25 pounds, and occupies a 
 floor space of 8 x 12 inches ; armature speed 3,200 revolutions per minute, and 
 V2 horse power will be required to drive it. 
 
 Dynamos of this size are much harder to build than larger ones, and 
 the results obtained are not generally as satisfactory. In order to get the 
 required voltage, many turns of fine wire are used on the armature, and a slight 
 variation will cause trouble. If finer wire is used than given here, the armature 
 resistance will be increased. As the resistance of fine wire multiplies very 
 rapidly, that of itself would be sufficient to prevent the machine working. 
 Other obstacles that present themselves are the small polar surfaces and the 
 large air space, and the only way to overcome these difficulties is by a high rate 
 of armature speed and strong fields. 
 
 In Fig. I is shown the upper pole piece (1) ; lower pole piece (3) ; 
 field magnets (2) ; bolts (5) ; and cross section of pole piece extension for 
 supporting the bearings (4). 
 
 The pole pieces should be of soft gray cast iron ; the field magnet cores 
 can be of the same material, but it would be much better to make them of 
 wrought iron as it is very difficult to get solid castings where they are so small ; 
 also the iron is liable to chill, which makes it very hard, thereby increasing the 
 magnetic resistance of the iron, and reducing the efficiency of the machine. 
 
 Too much care can not be taken in putting the machine together. 
 Where the pole pieces join the field magnets the surfaces must be perfectly 
 
 (14) 
 

a 
 
 FIGS. VII. 
 
16 PRACTICAL DYNAMO BUILDING. 
 
 true and smooth, that the whole surface of the iron may be in contact, for if 
 only half of the iron in the field magnets touches the pole pieces, the portion 
 that is not in contact may as well be left out of the machine. There is always 
 a loss at a joint, no matter how well it is made. The best way to put the 
 machine together is to bolt the field magnet cores to the lower pole piece, then 
 place the upper pole piece in position and examine carefully to see that the 
 whole surface is in contact ; if not, the high points should be taken off until 
 it is. Do not depend on the bolts to spring the pole pieces down to make a 
 joint. 
 
 The pole pieces are 7V2 inches long, 3 inches wide, and 3 / inch thick. 
 The field magnet cores are 4 inches long, 3 inches wide, and 3 /4 inch thick. 
 The gap between the pole pieces is ! 3 /4 inches. The diameter of the bore of 
 the machine is about 4 inches, but it should not be bored out until the armature 
 is finished for the reason that the armature may not have worked out to just 
 the size calculated ; if not, the pole pieces can be bored out to suit the 
 armature. 
 
 Fig. II shows the lower pole piece (3) with extensions (4 1 and 4 2 ) 
 for supporting the bearings. The extension (4 1 ) on the pulley side is ! 3 /s 
 inches long ; 1V2 inches wide, and 3 /s inch thick. The extension (4 2 ) on the 
 commutator side is 2V2 inches long, ! J /2 inches wide, and 3 /s inch thick. 
 
 In Fig. Ill is shown the armature drum (1) which can be made of brass 
 or galvanized iron ; it consists of a tube 3 inches long, 2*/2 inches in diameter 
 with flanges on each end 1/2 inch wide. To support the tube is a brass hub 
 with 3 radial arms, as shown at 2 in Fig. IV. The hubs are first drilled, then 
 slipped on the shaft in their proper position ; a pin is then put through the hubs 
 and shaft to securely hold the armature in place. The shaft should then be 
 placed between the centers in a lathe and the ends of the arms turned off until 
 the core will slip over them ; then secure the core to the arms with screws or 
 pins as shown at 3 in Fig. IV. 
 
 The core between the flanges should now be wound full of No. IS 
 annealed iron wire with a layer of paper between each layer of wire. The 
 outer end of the wire should be soldered to prevent its unwinding. The core 
 should be placed on parallel strips and perfectly balanced before it is insulated. 
 
PRACTICAL DYNAMO BUILDING. 17 
 
 This armature is a Gramme ring and as the wire has to pass between the shaft 
 and the core, the inside of the core must be insulated as well as the outside. 
 Great care must be taken in insulating the arms of the hubs where they join 
 the core ; if not, the copper wire will be drawn down so close in these corners 
 that it Avill come in contact with the core, so one-half of the sections in the 
 armature would be cut out, or in other words, the coils would be grounded on 
 the core. A machine in this condition would generate no current though all 
 the other parts were perfect. 
 
 The armature should be spaced off into 12 sections and wound 4 layers 
 deep, 22 convolutions per layer of "No. 20 double covered copper wire (Brown 
 and Sharp gauge). The method of winding and connecting the armature is 
 given in Figs. 4 and 5, page 
 
 The commutator (3) is an important feature ; the success of the machine 
 to a great extent depends upon its construction. The core is of vulcanized 
 fibre 1V4 inches long, and 1 inch in diameter ; a brass ring Vs inch thick is 
 forced over it. The ring is then spaced off into 12 sections, and a screw put 
 through the end of each section into the fiber, as shown at 3 in Fig. IV. 
 Then with a fine hack saw cut through the ring to the fibre between the rows 
 of screws. Be sure that the ring is cut through and all brass cuttings are 
 removed from the slots. The slots can then be filled with fibre, making the 
 commutator solid and smooth on the outside. If any of the brass cuttings are 
 allowed to remain in the slots, thus making a contact between two sections of 
 the commutator, one section of the armature would be cut out or short circuited, 
 reducing the efficiency of the armature. !S"ot only that, but there will be an 
 induced current set up in the coils thus short circuited. The result would be 
 the destruction of that coil, and no doubt the neighboring coils ; the whole 
 armature would then have to be rewound. The cause of all the trouble being 
 in the commutator, if not corrected, the second armature would share the same 
 fate. The joining together of the field magnets and pole pieces, the adjusting 
 of the armature and bearings are secondary considerations compared with 
 the building of the armature and commutator. A little carelessness in the 
 construction of either one will be sufficient to prevent the machine from 
 working ; the work will have to be done over again, which is usually harder 
 
18 PRACTICAL DYNAMO BUILDING. 
 
 to do than to build in the first place, to say nothing of the annoyance and 
 disappointment of the machine not working properly. The writer has a 
 machine now in use from which these drawings are made, and any one 
 building from these instructions should be able to get the same results. 
 
 The pillow-blocks (2) are l : /2 inches wide at the base ; Va inch thick ; 
 from center of shaft to base of pillow-block is 2 3 /s inches. Instead of 
 babbitting the bearings, bushings are used, one of which is shown at 9. 
 They are made of brass 1V4 inches long ; 5 /s inch in diameter with a 3 /s inch 
 hole through center to receive the shaft. It is secured to the pillow block with 
 a screw, as shown at 5, Fig. IV. The screw should go through the bushing 
 instead of pressing on the outside, for in that case there would be danger of 
 compressing the bushing and heating the shaft. The object of using bushings 
 is to facilitate repairs. In case of wear in the bearings, the bushings can be 
 removed and new ones supplied without the danger of getting the armature out 
 of center, as would be the case if the bearings were babbitted. The bushing on 
 the commutator side also serves to hold the yoke and allows it free movement 
 to determine the position of the brushes on the commutator. 
 
 The shaft (11) should be of steel 10 inches long, and 3 /s inch in diameter. 
 The pulley is 2 niches in diameter, 1V4 inch face. It can be made of wood with 
 a metal bushing to secure it to the shaft. 
 
 The brush holder yoke (4) is made of vulcanized fibre 3 inches long ; 
 V4 inch thick; 2 l /z inches between centers of brush holders cut to shape, as 
 shown at 4 in Fig. IV. A brass yoke can be used if preferred like the one 
 shown in the 10 light machine, but insulating bushings and washers will have 
 to be used which will cause a great deal more labor with no better results, as I 
 have found in small machines that a fibre yoke answers all purposes. 
 
 The brush holders (5) are of 3 /g inch square brass ; ! 3 /4 inches long, 
 turned on one end for the distance of 9 /ie inch to go through the yoke and 
 threaded to receive the nut (7) . A brass washer (8) is interposed between the 
 nut (7) and the yoke (4). To the washer are attached the wires from the 
 field magnets and lamp circuits. The other end of the brush holder is slotted 
 to receive the brush (6). A screw (10) is put through the end of the holder 
 to clamp the brush and hold it firmly. 
 
PRACTICAL DYNAMO BUILDING. 19 
 
 The brushes (6) are made of several layers of thin sheet spring 1 copper, 
 thick enough to make a good contact on two sections of the commutator, while 
 the insulation between the sections is passing the brushes. If a good contact is 
 not made by the brushes on the commutator there will be an excessive sparking 
 and a rapid destruction of the brushes and commutator. 
 
 A handle (10) as shown in Fig. IV serves to hold the yoke in place 
 after the position of the brushes has been determined. It is made of wood 
 with a screw in the end. A hole is drilled and tapped in the yoke. The handle 
 should be screwed down sufficiently to hold the yoke, but not enough to 
 compress the bushing, or it will cause the shaft to heat. 
 
THK FIELD MAGNETS. 
 
 On each end of the field magnet cores should be placed a fibre washer 
 Vs inch thick, or 2 thicknesses of cardboard will answer as well. The washers 
 must be well fitted to the magnet cores and held there firmly to prevent the 
 wire from pressing them out of position while the magnet is being wound. The 
 magnet cores should then be covered with two layers of adhesive rubber tape or 
 several layers of muslin or manilla paper well shellaced. They are now ready 
 for the copper wire, which is of double covered 'No. 20 (Brown & Sharp gauge) 
 11 layers deep ; 80 convolutions per layer, making 880 convolutions on each 
 field or 1,760, convolutions on both fields, with a total length of about 1,200 feet, 
 and a resistance of nearly 13 ohms. The length of wire may vary a little 
 from the figures given, caused by the difference in the thickness of insulation, 
 but the variation will not be enough to make any difference with the working 
 of the machine. The method of winding and connecting up the circuits is 
 given in diagram 14, page 68. 
 
 (20) 
 

TEN L-IGHX 
 
 These drawings are for a 10 light, 50 volt, 16 C. P. dynamo; floor 
 space 18x12 inches and 7*/2 inches high, to be run at a speed of 2,200 
 revolutions per minute, weight 75 pounds. It will require one horse power to 
 drive this dynamo. 
 
 In Fig. I is shown the upper pole piece (1) ; lower pole piece (3) ; field 
 magnet cores (2) and cross section of lower pole piece extension for supporting 
 the pillow blocks (4). The pole pieces (1) and (3) are 10 inches long, 4 J /2 
 inches wide, l a /4 inches thick. The gap between the pole pieces is ! 5 /s inches. 
 3 /s inch hexagon cap screws (5) are used to secure the pole pieces (1) and (3) 
 to the field magnet cores (2). Pole pieces are to be bored out to 5 niches. 
 Soft gray cast iron should be used for pole pieces and field magnet cores. 
 Great care must be taken in putting the machine together at the points where 
 the pole pieces and field magnets join. The surface should be planed smooth, 
 then scraped that the whole surface of the iron may be in contact without 
 depending on the screws to make a good joint. The joints are the weakest 
 points in the machine and quite a loss is sustained with the best possible 
 workmanship. 
 
 FIG. II. 
 
 Fig. II shows the lower pole piece (3) with extensions (4) and (4") for 
 supporting the pillow blocks (3). The extension (4') on the pulley side is 3*/2 
 inches long and 2V2 inches wide. On the commutator side, the extension (4") 
 is 5 3 A inches long ; 2V2 inches wide and J /2 inch thick. A. brace or rib is shown 
 in cross section (4) Fig. I. 
 
 (21) 
 
FIG. VIII. 
 
PRACTICAL DYNAMO BUILDING.' 23 
 
 FlG. III. 
 
 Fig. Ill shows the armature core (1) ; shaft (2) and pin (4) through 
 the shaft for holding the commutator in position. The armature spool is made 
 of well seasoned maple wood, 4*/2 inches long ; inside diameter 2V inches ; 
 diameter of flanges 4 3 /s inches ; thickness of flanges 3 /i6 inch. A pin (3) shown 
 by dotted lines, is put through the spool and shaft to securely hold the armature 
 in position. The spool should be finished on the shaft that it may be perfectly 
 true and is then wound full of annealed iron wire with a layer of paper between 
 the layers of wire. The shaft (2) should be made of steel 5 /s inch diameter; 
 17 3 /s inches long. On the commutator side the shaft should extend 6 3 /s inches 
 from the armature core ; on the pulley side, 6V2 inches. 
 
 FIG. IY. 
 
 Fig. IY shows the commutator (1) ; shaft (2) ; pillow blocks (3) ; brush 
 holder yoke (5) ; bushing (6) ; brush holder (7) ; nut (8) ; brass washer (9) ; 
 insulating washer (10) and insulating bushing (11), all in position. (3) is a 
 side view of the pillow block, which is 1 inch thick ; ! 3 /4 inches at shaft. The 
 dotted lines show the bushing (6) and the mode of holding the brush holder 
 yoke (5). The insulating bushing (11) is of vulcanized fibre, or well seasoned 
 maple wood may be used 5 /g inch outside diameter, and Vi inch inside, fitting 
 into yoke (5). Insulating washer (10) can be made of fibre or hard rubber 1 
 inch in diameter ; Vs inch thick with V4 inch hole in center to slip on the 
 holder. (7). One washer is placed on each side of yoke. On the outside of 
 washer (10) is a brass washer (9) serving the two purposes of fastening for the 
 field wires and preventing nut (8) from cutting into insulating washer (10). 
 
 FIG. Y. 
 
 Fig. Y shows end view of pillow block (3) ; side view of brush holder 
 yoke (5) ; handle (4) ; screw (7) for holding bushing (6). The base of pillow 
 block (3) is 2V-2 inches wide and 2 15 /ie inches from center to base. The bushing 
 (6) is fitted into pillow block (3) and screw (7) is put through the head of the 
 
24 PRACTICAL DYNAMO BUILDING. 
 
 pillow block and through the bushing (6) to hold it in position. The object of 
 putting the screw through the bushing is to prevent the compressing of the 
 bushing and causing the shaft to heat. The yoke (5) is made of brass ; it is 
 4Va inches between centers of brush holder (7) . Handle (4) is made of wood 
 with a screw in the end ; the screw to go through yoke (5) and press on bushing 
 (6) . After the position of the brushes on the commutator has been determined, 
 turn the handle until the screw presses tightly on the bushing, but not hard 
 enough to compress the bushing and heat the shaft. 
 
 FIG. VI. 
 
 In Fig. VI is shown the bushing (6) and brush holder (7). The bushing 
 is made of brass 2 l /i inches long ; ~/s inch outside diameter with a 5 /s inch hole 
 to fit the shaft. A flange 1V2 inches in diameter is left on the inside to hold 
 yoke (5) in place. The brush holder (7) is of brass 2 x /2 inches long; J /2 inch 
 square, turned down on one end for the distance of IVs inches to go through 
 yoke and threaded to receive nut. Through the other end is a slot Vs x 3 /4 
 inches to receive brush. The thumb nut (8) holds the brush firmly in place. 
 
 FIG. VII. 
 
 In Fig. VII is shown the construction of the commutator, one of the 
 most essential features of the machine. Take a piece of vulcanized fibre l x/ 2 
 inches long ; ! 5 /s inches in diameter, and force over it a brass ring 3 /i6 inch thick, 
 then space off into 24 sections and put a screw through the end of each section 
 as shown at (12). Then with a fine hack saw cut through the ring between 
 the rows of screws, being careful to cut clear through the ring to the fibre and 
 remove all brass cuttings from the slot. Then fill the slot with thin sheet fibre. 
 The commutator must not be turned off until in position on the shaft. If any 
 of the brass cuttings are allowed to remain in the slots between the sections, it 
 will short circuit the coil attached to that segment ; the result will be an induced 
 current set up in that coil, which would soon destroy it and no doubt the 
 adjoining coils. 
 
THE ARMATURE CONSTRUCTION AND WINDINGS. 
 
 This armature is the Siemens type. When the spool for the armature 
 core is turned to size and secured to the shaft, space off the flanges into 24 
 parts, being 1 careful that the spaces in both flanges are directly in line with the 
 shaft. Then with a fine saw cut into the flanges to the depth of V* inch to 
 receive division pins. The pins may be made of vulcanized fibre or wood, and 
 should project 1 A inch above the flanges. The object of the pins is to keep the 
 layers of copper wire in their proper position. Then wind the spool full of !N"o. 
 18 annealed iron wire with a layer of paper between each layer of wire. The 
 outer end of the iron wire should be soldered to prevent unwinding. Then 
 cover the wire and the shaft at each end of armature for the distance of 2 
 inches with two layers of adhesive rubber tape and the armature is ready for 
 the copper wire, which is No. 18 Brown & Sharp gauge. 
 
 Starting from the commutator end of the armature, the wire is carried 
 along the surface of the armature core between two division pins parallel with 
 the shaft ; then across the end of the armature core between the division pins 
 diametrically opposite those on the other side of the armature ; then across the 
 commutator end of the core and alongside of the first wire, and so on until 
 there are ten convolutions on one side of the shaft; then go around the 
 armature again in the same manner, crossing the ends of the core on the 
 opposite side of the shaft ; then there will be 20 convolutions called 1 section. 
 Do not cut the wire but leave a loop about five inches long to go to the 
 commutator. Those are called lead wires. After making the loop and securing 
 the wires together close to the armature core, lay the wire along armature core 
 in the next space as before. Continue thus until 12 sections are laid on. This 
 
 (25) 
 
9(5 PRACTICAL DYNAMO BUILDING. 
 
 is the inner layer. All the spaces on the core have two layers of wire but there 
 are only twelve lead wires. The outer layer is then started on top of the inner 
 layer and goes around the core as in starting. There will be four layers of wire 
 between each row of pins but only two sections Avith the lead wire for each 
 section on opposite sides of the core. The copper wire all being laid on the 
 core, the next step is to bind the copper wire that it may not be thrown out of 
 place from the high rate of speed the armature has to revolve. The bands 
 should be three in number of ~No. 22 spring brass wire drawn as tightly as the 
 wire will stand without breaking and each should be soldered at several points. 
 A layer of mica or rubber tape should be between the brass and copper wire. 
 
FIELD MAGNETS. 
 
 The field magnets are 5 inches long ; 4 ! /2 inches wide ; I 1 /* inches thick. 
 They should be of soft gray cast iron and should be secured at each end to the 
 pole pieces with two 3 /s inch hexagon cap screws, as shown in Fig. I. At the 
 points where the pole pieces and field magnets join, the parts should be planed 
 smooth, then scraped so that a perfect joint is made and all the iron touches, as 
 there is quite a loss sustained with the best possible joint, and the poorer joint 
 the greater the loss. The best way to put the machine together is to first bolt 
 the field magnets to the lower pole piece, then place the upper pole piece in 
 position and carefully examine the joints to see if the iron touches the whole 
 surface ; if not, it should be made to do so. Do not try to spring them into 
 position with the bolts. On each end of the field magnets should be placed a 
 vulcanized fibre washer 1 /s inch thick extending out from the magnet 5 /s inch. 
 The field magnets should then be covered with two layers of adhesive rubber 
 tape or several layers of muslin thoroughly saturated with shellac. The 
 magnets are then ready to wind. The wire to use is ~No. 20 Brown & Sharp 
 gauge double covered, ten layers to each field magnet with 95 convolutions to 
 each layer, making 1,900 convolutions on both fields, with a total length of 
 wire about 1,900 feet, with a resistance of about 20 Ohms. The length of 
 wire may vary somewhat from the figures given, because of the difference of the 
 thickness of insulation, or the wire may not be laid closely, so that a few turns 
 may be lost ; the variation will not be enough to materially change the output 
 of the machine. Before starting to wind the field magnets coils, a hole should 
 
 (27) 
 
28 PRACTICAL DYNAMO BUILDING. 
 
 be drilled through the fibre washer almost to the iron. The end of the wire 
 should go through the washer that a connection can be made to lead to the 
 brushes. It is better to lead out a flexible wire as there is not so much danger 
 of breaking in handling. If the wire should be broken off close to the fibre, 
 it would necessitate unwinding the whole field to get the end again. 
 
FIFTEEN LIGHT DYNAMO. 
 
 These drawings are for a 15 light, 16 candle power, 50 volt dynamo. 
 The machine will require a floor space of 24 x 14 inches ; is 9 inches high ; 
 armature speed 2,500 revolutions per minute, and will require 1V2 horse power 
 to drive it. 
 
 FIG I. 
 
 Fig. I is a front elevation of the upper pole piece (1) ; lower pole piece 
 (3) ; field magnet cores (2), and cross section of pole piece extension f4). 
 
 The pole pieces are of cast iron 10 3 /4 inches long ; 6 inches wide ; 1V2 
 inches thick ; gap between pole pieces 2 3 /s inches. The bore of the pole piece 
 is 5 x /4 inches. 
 
 It is entirely unnecessary to bore out the pole pieces of these small 
 machines if a close calculation in building the armatures is made, and it 
 corresponds with the circle of the pole pieces. The armature should be finished 
 before the machine is put together and if the circles of the armature and pole 
 pieces are concentric, all that is necessary is to make the proper allowance on 
 the length of the field .magnet cores for the air space between the armature and 
 pole pieces. It will make no difference in the working of the machine whether 
 or not the iron in the pole pieces presents a sand or a finished surface. 
 
 The field magnet cores (2) are of cast iron 5 1 /* inches long ; 6 inches 
 wide and IVa inches thick with the corners rounded off to facilitate winding. A 
 hole is cored through the center to admit a 3 A inch bolt, and a hole is drilled 
 through the end of the upper pole piece to correspond, the lower pole piece 
 
 (29) 
 
30 
 
 PRACTICAL DYNAMO BUILDING. 
 
 FKJ. IX. 
 
PRACTICAL DYNAMO BUILDING. 31 
 
 being drilled and tapped. There will be only one bolt at each end. This 
 makes a very quick and convenient way of putting the machine together. The 
 field magnets should be faced off in a lathe that the ends may be true with the 
 hole in the center. 
 
 FIG. II. 
 
 Fig. II shows a plan view of lower pole piece with extensions for 
 supporting the pillow blocks and bearings. The extension (4 1 ) on the pulley 
 side is 5 inches long ; 3 inches wide with the end rounded off to a radius of l x /2 
 inches. The extension (4 2 ) on the commutator side is 10 7 /s inches long; 3 
 inches wide, and 7 /s inch thick with the end rounded of to the same radius. 
 
 FIG. III. 
 
 Fig. Ill shows a vertical section through armature shaft. 1 is the 
 upper pole piece, and 3 is the lower pole piece showing extensions (4 1 ) and 
 (4 2 ) ; also the method of securing the pillow blocks to the extensions. One 
 bolt can be used as is shown in Fig. Ill, but if it should become loosened from 
 any cause, the shaft would cramp in its bearings and become heated. The 
 better plan is to use two bolts or screws as is shown in Fig. II. 
 
 The distance from top of base to center of shaft is 3 3 /s inches ; the 
 pillow blocks are cored out to receive babbitt metal bearings, as shown at 27. 
 The cap (32), Fig. IV, is secured to the pillow block with two half inch 
 hexagon cap screws (33). 
 
 The shaft (31) should be made of steel 23 inches long and 1 inch in 
 diameter. In the bearings the shaft is turned down to 3 /4 of an inch, leaving a 
 shoulder to prevent endwise play without the use of set collars. The distance 
 between bearings is 13 7 /s inches. 
 
 The armature core is of soft iron wire wound in a spool of well seasoned 
 maple wood (7), 6 inches long. The flanges on each end are 4V2 inches in 
 diameter and 3 /i6 inch thick ; inside diameter of the spool is 2V2 inches. It 
 should be finished on the shaft, that it may be perfectly true. A V inch steel 
 
32 PRACTICAL DYNAMO BUILDING. 
 
 pin should be put through the spool and shaft (as shown at 9) to keep the 
 armature in position and prevent its turning on the shaft. 
 
 Space the flanges into 24 sections and with a fine saw cut a slot to the 
 depth of a quarter of an inch to receive division pins, as shown at 10, Figs. Ill 
 and Y. Before placing the division pins in position, wind the spool full of 
 No. 18 annealed iron wire, as shown, at 8, and the armature is ready for the 
 insulation. The instructions for insulating and winding a Siemens armature 
 are given in Figs. I, II, III, pages 4 and >. 
 
 It may seem to a casual observer that it is a very easy matter to wind a 
 spool of iron wire and have it round, smooth and perfectly balanced, but it is 
 not as easy as it looks. 
 
 It can be done by commencing the layers each time at the same end of 
 the spool, allowing the wire to rest in the grooves of the preceding layer. 
 This will necessitate cutting and soldering the wire at the end of each layer. 
 Or the wire can be wound on continuously by placing heavy stiff paper between 
 each layer of wire to keep it from dropping into the grooves between the 
 convolutions of the Dreceding layer, and giving an even surface on which to 
 wind each layer. 
 
 The commutator (11) is very easy to build and makes a very nice one 
 for a small machine. In place of the brass core with a nut for compressing 
 the segments and holding them in position, 4 bolts are used, as shown at 14. 
 Two brass heads ,(13), turned concave, are shown in section Fig. I, of which 
 13, Fig. YII, is an end view. 12, Fig. YII, shows the end insulation, which 
 can be of fibre rings or mica, either one will readily take the concave form of 
 the brass washers on the ends of the commutator. 8 /32 inch is of sufficient 
 thickness for the end insulation. Mica or fibre insulation Vs2 inch thick is used 
 to insulate the segments from each other. After the segments have all been 
 arranged with the insulation between them well shellaced, an iron band should 
 be forced over the segments to draw them as closely together as possible. The 
 ring should be somewhat smaller than the commutator in its loose condition and 
 forced over by putting it in a vise or with a bolt from the center with a large 
 washer at each end. Put the end washers on the shaft or a mandril the exact 
 size of the shaft with the commutator in the center, then with the bolts set the 
 
PRACTICAL DYNAMO BUILDING. 33 
 
 washers up firmly. Take off the ring from the outside and the commutator is 
 finished with the exception of turning off the outside, which should not be done 
 until the commutator is placed in its proper position on the shaft so it will be 
 perfectly true. 
 
 The lead wires from the armature may be secured to the commutator 
 segments by screws or soldering, whichever is the most convenient. Soldering 
 is far the safer, as there is danger of the screws becoming loosened, breaking 
 off or becoming corroded, causing the brushes to spark, the commutator to 
 burn and greatly increasing the internal resistance of the machine. 
 
 The yoke (16) is of brass 3 /s inch thick, with 5Va inches between centers 
 of brush holders. A hole in center 2 inches in diameter fits on the collar (17) 
 that secures the yoke to the bearing (6) . The handle (34) serves to hold the 
 yoke in position. 
 
 The brush holders (19) are of a style that is quite easy to make as they 
 can be cast in shape and finished with a file with very little labor except wiiere 
 they go through the yoke. They should be turned to 8 /s inch in diameter for 
 the distance of I 1 /* inches and threaded to receive nut (20). An insulating 
 bushing (23-) goes through the yoke and a hard rubber or fibre washer (22) 
 is placed on the brush holder on either side to insulate the holder from the yoke. 
 A brass washer (21) is placed between the nut and outside washer, to which 
 the lamp circuit and field magnet wires are attached. 
 
 FIG. IY. 
 
 Fig. IY shows the bearing on the commutator side with cap (32) and 
 screws (33) ; also the method of attaching the collar (17) for supporting yoke 
 (16). The holes (28) in the pillow block (6) are drilled and tapped. The 
 holes (28) in collar (17) are large enough to permit the screws to pass through 
 freely and are counter sunk so that the screw heads may be flush with the face 
 of the collar. After securing collar (17) to the pillow block, the yoke is 
 placed in position and washer (18) is placed on the outside and held in place 
 with screws (29) . By this arrangement the yoke is allowed to revolve freely 
 around the shaft for the purpose of changing the position of the brushes and 
 
34 PRACTICAL DYNAMO BUILDING. 
 
 at the same time keeping the points of the brushes concentric with the armature 
 shaft, which is a very essential feature. The brushes should touch segments in 
 the commutator that are diametrically opposite each other. There should 
 always be an even number of sections in an armature, that an equal division can 
 be made, as the current divides at the brushes when it enters the armature, and 
 joins again at the other brush. As electricity will always take the path of the 
 least resistance, if there is an unequal number of sections in the armature, or 
 the brushes set so there are two or three sections less on one side, more current 
 will flow through one side than the other, causing the armature to heat, the 
 brushes to spark and the machine to work bad generally, and no doubt in a 
 short time the destruction of the armature would result. 
 
 FIG. Y. 
 
 Fig. Y shows the armature core (7) giving the necessary dimensions, 
 and showing the method of placing the division pins (10). 
 
 FIG. YI. 
 
 Fig. YI shows brush holder yoke (16) which is 5Va inches between 
 centers of brush holders ; 3 inches in diameter in the center, bored out 2 inches 
 to fit collar ; holes in ends l /z inch to receive insulating bushings (23) . The 
 handle (34) can be made of hard wood. 22 is an insulating washer 1 inch in 
 diameter ; 23 is the insulating bushing. Their positions are shown in Fig. III. 
 19 is the brush holder with brush (26) in position. The holder is slotted out to 
 the proper width of a brush. Plate 25 is placed over the brush (26), and 
 screws (24) going through plate (25) into brush holder (19) hold the brush 
 firmly and at the same time admit of easy adjustment of the brushes. The 
 brushes are made of several layers of thin spring sheet copper. They are 4 
 inches long; 1 inch wide and 3 /ic inch thick. The object of using several 
 layers is to get sufficient surface on the commutator and still have the brush 
 elastic. 
 
PRACTICAL DYNAMO BUILDING. 35 
 
 FlG. VII. 
 
 Fig. VII shows the commutator in detail. 11 is the end view ; 15 are 
 the screws for fastening the lead wires to the segments ; 13 the brass heads, 
 and 12 the insulation. 
 
 The proper way to set the armature to have it central in the pole pieces 
 is to have strips of wood or cardboard of the proper thickness and place them 
 at four equi-distant points between the armature and the pole pieces, which will 
 make the air space the same all around the armature. Before the metal is 
 poured in the bearing spaces see that the center of the shaft is in the center of 
 the bearings, when cap 23 is in place. If it is not, the pillow blocks should be 
 raised or lowered as the case may be. Remove cap 23 and after the metal is 
 poured and becomes cool, take out the strips from around the armature and let 
 the shaft rest in the bearings. Put on the caps and babbitt them, then remove 
 the pillow blocks and take off the sharp corners of the metal between the caps 
 and pillow blocks, and cut a groove lengthwise in the babbitt that the oil 
 may circulate the whole length of the bearings. If the work is well done, the 
 shaft should run cool, but if it does not, take off the caps and put a piece of 
 paper between the cap and the bearing. 
 
THE ARMATURE: WIRE AND WINDING. 
 
 The wire on the armature should be No. 15 double covered (Brown & 
 Sharp gauge). There are 24 sections in the armature and 2 layers per section, 
 making the wire on the armature 4 layers deep. The instructions for insulating 
 and winding a Siemens armature are given on page 4, Figs. I, II, III. 
 
 (36) 
 
THE FIELD MAGNETS: WIRE AND WINDING. 
 
 The wire on the field magnets is No. 18 (Brown & Sharp gauge). 
 There are 11 layers on each field, and 93 convolutions to each layer, making 
 the total number of convolutions on both fields 2.046. 
 
 The method of winding and connecting up the machine is shown in dia- 
 gram 14, page 68. 
 
 If a rheostat is needed the instructions for building and connecting are 
 given in the same diagram for winding and connecting the field magnets. 
 
 This machine without changing its construction or armature windings 
 will make one arc light, but in the place of the No. 18 wire on the fields, put 
 No. 11 wire, and connect up in series. When wound and connected in this 
 way it will only require to be run at 1,600 revolutions per minute. The first 
 machine built from these patterns was to supply current for one arc lamp. The 
 field wire was changed and it did equally as good service as an incandescent 
 dynamo, only requiring a higher rate of armature speed. 
 
 (37) 
 
FIG. x. 
 
THIRTY=FIVK LIGHT DYNAMO- 
 
 These drawings are for a 35 light, 50 volt, 16 C. P. dynamo ; floor space 
 20 x 24 inches and 13 inches high, to be run at a speed of 2,200 revolutions 
 per minute, weight 150 pounds. It will require four horse power to drive this 
 dynamo. 
 
 It is unnecessary to go into a thorough detail of construction, as that 
 ground has been thoroughly covered in the 4 and 10 light machines, and only 
 parts that differ from them will be taken up. 
 
 FIG. I. 
 
 In Fig. I is the front elevation. The pole pieces (1) and (2) are 18V4 
 inches long ; 4 inches wide ; 2V4 inches thick, bored out to 8 inches with a gap 
 between pole pieces 3V2 inches. The field magnets are of wrought iron 8 
 inches long ; 3V4 inches diameter, as shown by dotted lines in Fig. II. The 
 ends of the pole pieces are rounded off to a radius of 2 inches and project over 
 the field magnets 3 /s inch on the outside, which is sufficient to hold the 
 insulating washers in place and prevent them from warping. The pole pieces 
 are secured to the field magnets with a single 3 /4 inch cap screw in each end. 
 The pole pieces extensions (4 1 ) and (4 2 ) are 1 inch thick, and 3 J /2 inches wide ; 
 8 inches long on the commutator side ; 5 inches long on the pulley side with 
 braces as shown in cross section in Fig. I and at (16) and (17) in Fig. III. 
 
 The armature is a Gramme ring ; the core is built up of thin iron discs 
 7V4 inches outside diameter ; 4V4 inches inside diameter, making the iron in the 
 
 (39) 
 
40 PRACTICAL DYNAMO BUILDING. 
 
 core 1V2 inches thick. The two outside discs should be of thicker iron to 
 prevent bulging out between the arms of the hub ; also to hold them firm while 
 the armature core is being turned off as it will have to be, as the holes in the 
 discs are not always in the center, which would make the armature out of round 
 and it would be impossible to balance it. The core must be balanced before the 
 copper wire is wound on it and can be done by drilling into the end of the core 
 on the heavy side instead of trying to build up on the outside of the core, as 
 that would make the armature out of round. If the armature were out of 
 round the fields would have to be bored out larger in proportion. That would 
 mean a great loss as it would increase the average distance between the iron in 
 the pole pieces and the armature core. The core is built up of alternating rings 
 of iron and paper until it is 4 inches wide on the face. If the hub is turned up 
 to a good fit so the rings will just slip on and press each one of the arms in the 
 hub firmly, they will require no other fastening, as the friction is sufficient to 
 prevent them from turning. The shaft (16) should be of steel IVd inches in 
 diameter; llVs inches between bearings, but in the bearings it should be turned 
 down to 1 inch so it will leave a shoulder on the inside of the bearings to keep 
 the armature in position without the use of set collars. The shaft should 
 project 4 inches on the outside of bearing to receive the pulley, which should 
 be 5 inches in diameter ; 4 1 /2 inch face to receive a 4 inch belt. 
 
 The commutator (7) is 4Va inches long ; 3 inches in diameter with lugs 
 or projections on each segment 8 /s inch wide ; 8 /4 inch long, the lead wires to be 
 secured to the lugs with screws or the lugs to be slotted and the wires soldered 
 to them. An axial section of the commutator is shown in Fig. VI. (1) is a 
 brass sleeve with a flange on one end, the other end threaded to receive nut (4) . 
 The segments (2) are beveled at each end ; the insulation (3) is concaved to 
 match. There are 42 segments with mica or vulcanized fibre Vs2 inch thick 
 between the segments. The inside diameter of the commutator should be at 
 least Vs inch larger than the core that there may be no danger of the segments 
 and core coming in contact. 
 
 The brush holder yoke (5) as shown in Figs. Ill and VII is of brass 5 /s 
 inch thick and 8 inches between centers of brush holders with 8 /4 inch holes in 
 the ends for insulating bushings (12). The bushings (12) are of vulcanized 
 
PRACTICAL DYNAMO BUILDING. 41 
 
 fibre 3 /4 inch in diameter, 1 /s inch thick. The brush holders are shaped as shown 
 at (II) in Figs. Ill and VIII, and are 4 3 /4 inches long. The end going through 
 the yoke is l /2 inch in diameter for the distance of 1 3 A inches, and is threaded 
 to receive nut (8) . "Vulcanized fibre or hard rubber washers (3) are placed on 
 brush holder to insulate it from yoke (5). A brass washer (14) is placed 
 between the nut and insulating washer to prevent the nut from cutting into the 
 washer, and also for furnishing a means of connecting the lamp circuit and 
 field magnet wires to the brush holder. The other end of the brush holder is 
 slotted as shown in Fig. VIII, the slot being l*/2 x 8 /s inches ; the brush to be 
 1V2 inches wide ; the gib (3) is placed in the slot between the brush and the 
 screw (2) ; the gib presenting a larger surface to the brush, holds it more 
 firmly and prevents the screw from cutting into the brush. The yoke is 
 secured to the bearing with a collar and washer, and handle (10) serves to 
 hold the yoke in place when the position of the brushes has been determined. 
 The pillow blocks (9) are secured to the extension with two */2 inch cap screws 
 going up from the bottom into the bearings. The pillow block and cap are 
 cored out around the shaft, to make room for the babbitt metal bearings, which 
 gives the shaft a wearing surface of 3 inches. From center of shaft to base 
 of pillow blocks is 5V2 inches. Cap (18) is fitted in between projections in the 
 pillow blocks and is held in position with two V2 inch cap screws. In fitting 
 the shaft in the bearings and babbitting them, care should be used that the 
 armature is perfectly central in the pole pieces. The shaft must be allowed 
 to revolve freely to prevent heating, but it should not be loose or the armature 
 will vibrate. 
 
 The hub (2) of the armature should be of brass, secured to the shaft 
 with a pin (3), as shown in Fig. IV. In Fig. V. are given the dimensions 
 of the armature hub with projections for holding the rings in place. The 
 projections (19) are put on with screws that they may be removed to allow 
 the rings to be placed on the hub. 
 
ARMATURE: SIZE OF WIRE AND WINDING. 
 
 There should be 42 sections in the armature with two layers of wire 
 to each section ; three convolutions to each layer of ]^o. 12 double covered 
 copper wire (Brown & Sharp gauge). The winding should start on a line 
 of the arms so there will be three spaces left on the outside of the armature 
 just the width of the arms. It is not a good idea to try to fill those spaces 
 over the spider arms, as it would pile the wire up against the arms on the 
 inside of the core and would be liable to throw the armature out of balance, 
 and if it does not, it will make the armature look badly. With 42 sections, 
 and 6 convolutions per section, the total number of convolutions on the 
 armature would be 252. With about 13 inches per convolution, the length 
 of wire on the armature would be 273 feet. 
 
 (42) 
 
THE FIELD: MAGNETS SIZE OF WIRE AND WINDINGS. 
 
 The size of wire on the field magnets should be No. 18 (B. & S. gauge) 
 10 layers deep ; 135 convolutions per layer, making 2,700 convolutions on both 
 fields with a total length of about 2,900 feet, making the resistance of the field 
 coils about 19.5 ohms. What little variation there will be in the length of wire 
 will not materially affect the machine. The fields are to be connected hi 
 "shunt." This style of machine has been in use for two years. 
 
 (43) 
 
44 
 
 PRACTICAL DYNAMO BUILDING. 
 
 FlQ. XI. 
 
SIXTY LIGHT DYNAMO. 
 
 These drawings are for a 60 light, 16 candle power, 50 volt dynamo ; 
 floor space 20x28 inches, and 13V2 inches high; armature speed 1,600 
 revolutions per minute ; weight 500 pounds. It will require about 5 horse 
 power to drive the dynamo. 
 
 FIG. I. 
 
 Fig. I shows the front elevation. 1 is the upper pole piece ; 3 the lower 
 pole piece ; 2 the field magnet cores, and 4 the cross section, of pole piece 
 extension. 
 
 The pole pieces are 16 3 /4 inches long; 8 inches wide, and 2Va inches 
 thick. The field magnet cores are 8 inches long ; 8 inches wide and 2V2 inches 
 thick in the center, and are rounded off at the corners to facilitate winding. 
 Two holes are cored through the fields to allow the bolts to pass through, as 
 shown by dotted lines. 
 
 In bolting the machine together 4 bolts are used, 2 at each end, the 
 bolts passing freely through the upper pole piece and field magnet cores. The 
 lower pole piece is drilled and tapped to receive them. 
 
 FIG. II. 
 
 Fig. II is a plan view of lower pole piece, showing extensions for 
 supporting the pillow blocks. The extension (4 1 ) on the pulley side is 5V2 
 inches long ; 4V2 inches wide, and 1 inch thick. On the commutator side, the 
 extension (4 2 ) is 10 7 /s inches long; 4V2 inches wide, and 1 inch thick with a 
 
 (45) 
 
46 PRACTICAL DYNAMO BUILDING. 
 
 brace, as shown at (4 2 ) Fig. Ill, to strengthen the extension. Only a fillet 
 is needed on the pulley side, as the bearing is so close to the pole piece. 
 
 FIG. III. 
 
 Fig. Ill shows a vertical section through shaft. The shaft (35) is made 
 of steel I 1 /* inches in diameter; 28 inches long; 16 8 /s inches between bearings. 
 In the bearings the shaft is turned down to 1 inch, leaving a shoulder on the 
 inside of the bearings to prevent endwise play. The shaft should revolve freely 
 in the bearing and still not be loose; a little endwise play of the shaft say 
 Vie inch will not do any harm, but if the cap to the bearing does not fit properly 
 and there is a chance for the shaft to vibrate vertically, it will not only cause 
 the whole machine to shake and make a pounding noise, but whatever vibration 
 there is in the bearing will be felt at the brushes ; at every revolution the 
 brushes will be thrown off the commutator, causing an abnormal spark, which 
 will soon destroy the brushes and the commutator as well. A great many 
 machines are working badly to-day from that cause ; that is, machines that 
 have been in use for a long time. The bearings get a little worn and the 
 armature may be a little out of balance and the sparking begins so gradually 
 that it is hard to determine the cause. The result is a continual turning off of 
 the commutator and constant renewal of brushes, which is not only expensive 
 but very annoying. The machine is also in danger while working in such a 
 condition, as the fine particles of copper from the brushes and commutator 
 pervades every portion of the machine. They work in between the lead wires 
 where they connect to the segments of the commutator ; also into the armature, 
 and will eventually short circuit some of the coils, and a burnt-out armature 
 is the result. 
 
 The shaft on the pulley side should extend sufficiently to allow room 
 for a pulley with a 4 J /2 inch face, as it will require a 4 inch belt to drive the 
 machine. 
 
 The bearings (6) are 4 inches wide made of babbitt metal. Before the 
 metal is poured in the bearing spaces the armature must be placed perfectly 
 central in the pole pieces. From center of shaft to base of pillow blocks it 
 
PRACTICAL DYNAMO BUILDING. 47 
 
 is 5Vs inches. The pillow-blocks are secured to the extensions with four 3 /s 
 inch bolts going down through the base of pillow blocks into extensions. 
 
 The hub for the armature core is of brass and is in two parts, as shown 
 at 7 and 8, with three radial arms extending out from the center, as shown in 
 Fig. V. The hubs are first bored out to fit the shaft and the inner surfaces 
 faced off that they may come together without leaving an opening between 
 them. They are then slipped on the shaft in place and a pin put through the 
 hubs and shaft to hold them in position, as shown at 35, Fig. Y. On one side 
 of the arms are solid lugs extending to the height of the core, on the other side 
 the lugs are removable, as shown at 10. 
 
 The core is built up alternately of thin iron discs and paper 7 J /4 inches 
 outside diameter and 4V4 inches inside diameter to form a solid ring 8 inches long. 
 
 The ends of the arms should be turned off so the discs will slip on tight 
 but not sufficiently so to warp them out of shape. The two outer discs should 
 be 3 /ie inch thick. After the discs are placed on the hubs and pressed down, 
 lugs (10) are replaced and held firmly with screws (11). The object of the 
 thicker discs on the outside is to prevent the iron discs bulging out between 
 the arms. If the discs are properly fitted to the arms, they will need no other 
 fastening, as the friction will be sufficient to hold them from turning. 
 
 The shaft should then be put in a lathe and one or two cuts taken off 
 the outside that the outer surface may be perfectly true and smooth. 
 
 The armature should then be placed on parallel strips and perfectly 
 balanced, which can be done by drilling into the end of the core on the heavy 
 side until the armature will come to rest at any point. 
 
 When insulating the armature core, care should be used that the 
 insulation is of the same thickness at all points on the outer surface, for if 
 the insulation is of unequal thickness, the same irregularity will show when 
 the armature is wound, which will necessitate boring out the pole pieces 
 enough larger to accommodate the high places, and it will also throw the 
 copper wire farther from the center in some places than others ; the armature 
 will thus become unbalanced with very poor chances of correcting the 
 difficulty. If good results are expected and a smooth, quiet-running machine 
 is desired, these suggestions must be observed. 
 
48 PRACTICAL DYNAMO BUILDING. 
 
 There are 42 segments in the commutator (12). They are 4 1 /* inches 
 long on the inside ; 3 3 /4 inches on the outside and 1 inch wide ; 13 is the 
 commutator core; 14, fibre insulation; 10, the nut to hold the commutator 
 together; 15, a metal washer interposed between the nut and insulation. If 
 the washer is not used, the friction of the nut on the insulation in tightening 
 up the commutator is sufficient to twist the segments and leave them spiral 
 instead of longitudinal with the shaft as they should be. 38 is the air space 
 between the segments of the commutator (12) and the core (13) ; 37 are the 
 screws for connecting the lead wires to the segments of the commutator. A 
 detail of yoke, brush holder, rod and insulation is given in Fig. VII. 
 
 Brush holders (24) are constructed so that they may be moved on the 
 stud bolts and can be set zig-zag so that the whole surface of the commutator 
 may be in contact and as the commutator wears away, the surface will wear 
 smooth and not in ridges. Four narrow brushes are used instead of two wide 
 ones, which is very essential for machine carrying heavy currents, as it insures 
 better contact on the commutator, and in case the commutator becomes a little 
 rough or uneven the brushes are less liable to spark. 
 
 Brush holders should not be positive on a machine carrying heavy 
 currents, but should be pressed on with springs that the least wear in either 
 brush or commutator may be automatically taken up, which not only relieves 
 the person in charge of a great deal of trouble, but keeps a constant pressure 
 of the brushes on the commutator at all times. The measurements of the 
 brushes and holders are given in Fig. VIII. 
 
 The collar (18) for securing the brush holder yoke to bearing has been 
 thoroughly described in previous machines. A detail is given in Fig. IV. 
 
 FIG. V. 
 
 Fig. V shows end view of armature core (9) with dimensions of rings. 
 Their position is shown at (9) Fig. III. 
 
 FIG. VIII. 
 
 Fig. VIII shows a side and top view of brush holder (24) with brushes 
 (27) in position. This is a very easy and convenient holder to make. The 
 
PRACTICAL DYNAMO BUILDING, 49 
 
 screw (28) that holds the plate that clamps the brush should always be on the 
 top side so it will be an easy matter to adjust the brushes when the machine is 
 running 1 . 
 
 It is not necessary in building machines that each separate one shall be 
 carried out in detail as given in the drawings. There are several different 
 styles of commutators and brush holders given and any one can be used as it 
 suits convenience or fancy, or parts of your own inventing can be applied ; so 
 there is sufficient material used to safely carry the current, and all parts well 
 and substantially constructed. I would not advise any material change in the 
 dimensions of the machine or sizes or quantity of wire, unless you wish to do 
 some experimenting and take these machines as a basis from which to work. 
 The writer found by building and running these machines what their capacities 
 were and gives them here just as he found them. They are no toys but 
 machines that are intended for actual service. The 60 light machine from 
 which these drawings are made has been used for lighting our shop for the 
 last two years, and is giving as good service now as the first day it started. 
 
 All measurements in the dynamo are given finished and in making 
 patterns allowance will have to be made for shrinkage and finishing. 
 
THE ARMATURE WIRE AND WINDINGS. 
 
 The wire on the armature is "No. 12 B. & S. gauge, double cotton 
 covered. There are 42 sections with 2 layers per section, 5 convolutions per 
 layer, making the total number of convolutions on armature 420. 
 
 The method of winding and connecting a Gramme ring is given in 
 Figs. 4 and 5, page 9. 
 
 (50) 
 
The wire on the fields is No. 15 double cotton covered. There are 13 
 layers on each field, with 106 convolutions to each layer; total number of 
 convolutions on both fields, 2,756. 
 
 If a 110 volt dynamo is preferred to a 52, the only change that is 
 necessary in this machine is to put one more layer of wire on the fields ; leave 
 the armature and balance of the machine as given above, and increase the 
 armature speed a little, and you will have a 110 volt dynamo. 
 
 (51) 
 
ISO LIGHT 
 
 These drawings are for a 150 light, 110 volt dynamo ; floor space 25 x 38 
 inches, and 16 3 /s inches high; weight, 1,100 pounds; armature speed 1,350 
 revolutions per minute. The machine will require 15 horse power to drive it. 
 
 FIG I. 
 
 Fig. I is a front elevation of the machine. 1 is the upper pole piece ; 2 
 the lower pole piece, and 3 the field magnet cores. The pole pieces are 22 
 inches long ; 10 inches wide, and 3 inches thick. The field magnet cores are 
 10 8 /s inches long; 10 inches wide, and 3V2 inches thick in the center, and 
 gradually rounded off to the circle of the ends of the pole pieces as shown in 
 Fig. II. The field magnet cores will then have the same cross sectional area 
 as the pole pieces. The lower pole piece (Fig. II) is provided with extensions 
 for supporting the armature bearings. The extension on the pulley side is 6 3 /s 
 niches long, and 6V2 inches wide ; on the commutator side, the extension is 
 IS 1 /* inches long, 6V2 inches wide and IVs inches thick. A chipping strip 5 
 inches wide and V inch thick should be placed on the ends of the extensions 
 for furnishing surfaces for bearings. Two bolts at each end passing through 
 upper pole piece and field magnet cores, threaded into lower pole piece, are 
 required to bolt the machine together. Pole pieces are bored out to lOVie 
 inches ; gap between them 3 x /2 inches. Too much care can not be taken in 
 making the joints. The pole pieces should be planed as smooth as possible, 
 
 (52) 
 
FIG. Xli. 
 
54 PRACTICAL DYNAMO BUILDING. 
 
 then with a fine file and scraper remove all the tool marks that the surface may 
 be perfectly smooth and polished. 
 
 The field magnet cores may be finished in a lathe, but unless a strong- 
 heavy lathe is used and the tool held rigidly, it will spring, and the farther the 
 cut goes from the center the greater the spring of the tool. After the cut is 
 finished and a straight edge is placed on the core, it will show that the center 
 is nearly Vs2 inch lower than the outsides. Those high placed will have to be 
 taken off with a file with danger of getting them out of true. If the machine 
 were put together as the cores came out of the lathe, not V* of the iron would 
 be in contact ; a great loss would be sustained from the increased magnetic 
 resistance ; the joints would become heated, and it is a question if a dynamo 
 working under those conditions could be brought up to its rated capacity 
 without increasing the speed to a dangerous point. 
 
 It may appear to the reader that there is too much stress laid on the 
 forming of the joints of the machine, and that there is too much explaining 
 about them; but as it has cost the writer a great deal of time and expense, and, 
 in fact, a good many changes to get the dynamos described in this work up to 
 the point claimed for them, he can more fully realize the importance of a 
 thorough explanation. To show the effect of poor workmanship, the writer 
 will give an instance of a specially constructed machine for slow speed. The 
 dimensions were as follows : armature (a Gramme ring) 10V2 inches in diameter ; 
 
 3 inches wide ; wound 5 layers deep with ~No. 16 wire ; the pole pieces were of 
 cast iron 3 inches wide at the armature, 4 inches at the field magnets and 2 
 inches thick. The field magnet cores were of wrought iron 14*/2 inches long ; 
 
 4 inches wide ; and l J /2 inches thick. Instead of the machine being bolted 
 together, as shown in drawings, the field magnets were long enough to allow 
 the bolts to go through them into the ends of the pole pieces. Wire on field 
 magnets !N"o. 10 with 720 convolutions on each field; intended speed 600 
 revolutions per minute for an output of 10 amperes at 50 volts pressure. 
 When the machine was tested it was found that at 800 revolutions per minute 
 the output was only 5 amperes at 20 volts pressure. In taking the machine 
 apart to find the trouble it was found that not more than Va of the iron in the 
 pole pieces was in contact with the field magnets. The wire was taken off 
 
PRACTICAL DYNAMO BUILDING. 55 
 
 from the field magnets, perfect joints were made, the wire replaced, and at 600 
 revolutions per minute the machine gave 10 amperes at 65 volts pressure. This 
 shows the importance of good workmanship. 
 
 : 
 
 FIG. III. 
 
 Fig. Ill shows a vertical section through shaft. The shaft should be of 
 machine steel 38 inches long ; I 3 /-* inches in diameter. In the bearings it is 
 turned down to ! J /2 inches, leaving a shoulder inside the bearings to prevent 
 endwise play. Distance between the bearings 21 3 /4 inches. Shaft extends over 
 bearing on pulley side 6 inches. 
 
 The pillow blocks (6) are 6V2x5 inches at the base, and from base to 
 center of shaft 7V inches. They are fastened to extensions with four Va inch 
 hexagon cap screws and lined with babbitt metal, as shown at 27. Length of 
 shaft in bearings 5 inches. 
 
 The hub of the armature core is in two parts, as shown at 7 and 8. 
 They are made of brass with three radial arms extending from the center, of 
 which 7, Fig. V, is an end view. There are lugs on the outside of the arms 
 extending around the core to its outer circumference. Lugs (10) are fastened 
 to the arms with screws (11) so they can be removed to place the iron discs on 
 the hub. The hub should be bored out to fit the shaft and the inside of the 
 arms faced off so they will come together without leaving an opening. Place 
 them on the shaft in position and put a pin through them, as shown at 36, Fig. 
 V. If it is more convenient or preferred a key may be used to hold the hub in 
 place instead of a pin. The ends of the arms should be turned off to 6 inches 
 in diameter. 
 
 The core is built up of thin iron discs (9) 9 3 A inches outside diameter, 
 6 inches inside diameter. The discs should be insulated from each other. It 
 may be done with disc of paper or the iron disc may be covered with a coating 
 of insulating paint or shellac will answer. The discs at each end should be 
 made of J /4 inches iron to prevent the thin iron disc from bulging out between 
 the arms. 
 
 For convenience of insulating, a fibre ring Vie inch thick can be placed 
 
56 PRACTICAL DYNAMO BUILDING. 
 
 on the outside of the iron disc, as the ends of the armature core are the 
 hardest parts to insulate. Fill the hub as full of iron discs as possible, so that 
 it will require clamps or bolts to press them on, then replace lugs (10) and 
 fasten with screws (11). If "No. 22 iron is used to make the disc, it will 
 require about 400 to build the core and as many discs of manilla paper. If the 
 discs are properly fitted to the hub and as many forced on as possible they will 
 require no fastening, as the friction will be sufficient to hold them from turning 
 on the hub. The core should be turned off and perfectly balanced before 
 insulating. 
 
 The commutator has been fully described in previous machines. The 
 only changes necessary are the dimensions and the method of fastening the 
 lead wires to the segments, which is shown at 29 Fig. II and 29 and 30 Fig. 
 "VI. 29 is a copper strip of sufficient carrying capacity let into the lug of the 
 segments and well soldered. The outer end is split, as shown in Fig. Ill, and 
 the parts bent out to form a fork, as in 1 Fig. "VI. The lead wires are laid in 
 and the ends bent over, as shown in 2 and 3, and well soldered. This makes- 
 the most sure and substantial way of fastening the lead wires to the segments, 
 for if the solder were to become loosened the wires would remain in contact 
 with the segments, thus avoiding an open circuit in the armature, but it would 
 undoubtedly cause the brushes to spark, and a burning of the segment at fault 
 from the increased resistance of the poor contact. The machine should not be 
 allowed to run a great while in this way as it would damage the commutator to 
 such an extent as to require turning off. Another difficulty that would arise 
 would be the burning of the points of the brushes sufficiently to change their 
 circle on the commutator. They would have to be refitted. 
 
 Another form of attaching the lead wires to the segments is shown at 
 30, Fig. YI. It is a clip and can be cast in that form. It should be deep 
 enough to permit the wires to lay in it, one above the other, and the sides of 
 the clip bent over the top and well soldered. The clip is fastened to the 
 segments with screws, as shown at 31. This form of connection is equally as 
 good as the other, with the exception of the screws. Unless an extraordinarily 
 good job is done at the joints, the commutator will spark and nothing can be 
 done to remedy it. If the screws become loosened or corroded or dirt works- 
 
PRACTICAL DYNAMO BUILDING. 57 
 
 under them, the resistance will be so greatly increased that a portion of the 
 current will be carried across the insulation to the next segment, and it will 
 invariably produce a spark either at the point of the brush or at the insulation 
 between the segments. 
 
 The core of the commutator is 8 inches long with a projection on the 
 inside for set screws (28) to keep the commutator from moving on the shaft. 
 There are sixty segments in the commutator; diameter finished, 4V2 inches; 
 inside length of segments 6 inches, outside length 5*/2 inches and 1 inch wide. 
 
 The brush holder yoke and method of securing it to the bearing has 
 been fully described in previous machines. A detail is given in Figs. IY 
 and VIII. 
 
 FIG. VII. 
 
 In Fig. VII are shown the brush holders 32 and 33 for carbon brushes. 
 They are made of brass in the form of a box open at each end. They are 3 
 Inches long ; 2V4 inches wide and 5 /s inch thick with a hole through them that 
 will admit a carbon 2 inches wide and 3 /s inch thick. As the end of a carbon 
 brush touches the commutator a spring is used to keep a constant pressure of 
 the brush on the commutator at all times and also to take up the wear of the 
 brush. This style is known as automatic brush holders. Two forms of 
 springs are shown. The spring in 32 is made of sheet spring brass and wound 
 as a clock spring around the screw at the head of the uprights, the outer end 
 projecting down to the brush. As the tendency of the spring is to unwind, 
 it keeps a constant and even pressure on the carbon. 33 is the same pattern as 
 32, only a little different arrangement of the spring. Instead of the flat 
 spring a thin sheet of brass is used with a hinge at the top of the upright ; 
 near the bottom is a hole through which passes a small eyebolt or screw ; on 
 the outside is a thumb nut ; to the other end is attached a spiral spring, so by 
 turning the nut one way or the other, the pressure of the brush on the 
 commutator can be regulated at will. On the lower side of the holder is a 
 boss extending the whole width of the brush holder and through it a 3 A inch 
 hole, so it will slip on the stud (17), then the thumb screws should be 
 
58 PRACTICAL DYNAMO BUILDING. 
 
 tightened to keep holders in place. The brushes should pass freely through 
 the holders, but not too loose, or they will rattle ; not only that, but the 
 vibration will cause sufficient spark to eat away the brush and keep the 
 commutator in a rough and unsightly condition. Unless the commutator is 
 kept in first-class condition, carbon brushes on a low voltage dynamo will 
 give trouble. The commutator should be of a dark-brown or chocolate color 
 when running properly. If it is allowed to spark and become rough the 
 brushes will be so thoroughly insulated from the commutator that the dynamo 
 will not start. The way to correct that trouble is by polishing the commutator 
 with a piece of sand paper fitted into a block of wood the same circle as the 
 commutator ; never use emery cloth, as the particles are liable to cut into the 
 insulation between the segments and short circuit the coils on the armature. 
 
THE ARMATURE : WIRE AND WINDING. 
 
 The armature is wound with Xo. 11 wire (B. & S. gauge), two layers 
 deep, and the layers connected in multiple. So the winding is the same as 
 though a single wire were used and only one layer. In using two small wires 
 it makes it much easier to wind, as one w T ire of sufficient carrying capacity for 
 a machine of this size would be so hard to handle and bend around the ends 
 that it would make a rough and unsightly job ; another serious objection to 
 the large wire is that there would not be as many convolutions on the armature, 
 necessarily requiring a higher rate of speed to get the voltage. There are 60 
 sections in the armature with 8 convolutions per section, total number of 
 convolutions on the armature 480. With 20 feet per section, the total number 
 of feet 1,200, making about 30 pounds. The method of winding a gramme 
 ring armature is given in Figs. 4 and 5, page 9. 
 
 (59) 
 
THE FIELD MAGNETS AND WINDINGS. 
 
 The wire on the field magnets is No. 15 (B. & S. gauge). There are 
 11 layers on each field, with 152 convolutions per layer, making a total number 
 of convolutions on the field magnets 3,344, with an approximate length of 
 6,000 feet, weighing 61 pounds. This machine is connected in shunt. The 
 method of winding, insulating and connecting up is shown in diagram 14, 
 page 68. 
 
 (60) 
 
ONE L-ICHT KRO 
 
 These drawings are for a 1 arc-light dynamo ; will produce 10 amperes 
 at 50 volts pressure; floor space 15V2x22 inches, and 11 inches high; weighs 
 100 pounds ; armature speed 900 revolutions per minute, and will require one 
 horse power to drive it. 
 
 FIG. I. 
 
 Fig. I is a front elevation of the machine ; 1 is the upper pole piece ; 3 
 the lower pole piece ; 2 the field magnet cores and 4 is a cross section of pole 
 piece extensions. 
 
 The pole pieces are of cast iron 4 inches wide ; 1V2 inches thick at the 
 field magnets and 8 /4 inch in the center. The reducing of the pole pieces in 
 the center is not necessary ; it makes the machine a little lighter and perhaps 
 looks a little better, but the machine works as well with the pole pieces solid as 
 cut away, as it has been tried both ways. 
 
 The field magnet cores are of wrought iron 11 inches long, 4 inches 
 wide and 1 inch thick, and bolted flatwise to the ends of the pole pieces 
 instead of end on, as is the usual manner, on account of the small cross 
 sectional area of the field magnets. Where wrought iron field magnet cores 
 are used a provision will have to be made as in this instance, that the whole 
 cross sectional area of the pole pieces shall be in contact with the field magnet 
 cores on account of the high magnetic resistance of the joints and of the 
 small area of their surfaces. As the magnetic resistance of cast iron is 30% 
 greater than wrought, the cross sections of cast iron portions of the machine 
 should be that much larger or the lines of force would be throttled and the 
 
 (61) 
 
FIG. XIII. 
 
PRACTICAL DYNAMO BUILDING. 63 
 
 strength of the field magnets reduced. But if it is preferred to extend the 
 pole pieces across the ends of the field magnet cores, increase the size of the 
 latter to 1V2 inches thick, and the same results will be obtained with cast iron 
 cores as with the present construction and wrought iron. The pole pieces are 
 bored to 8 inches, the gap between them 3 x /2 inches. 
 
 FIG. II. 
 
 Fig. II shows a plan of the lower po.e piece (3) with extensions (4 1 ) 
 and (4 2 ) for supporting the bearings (6). On the pulley side the extension 
 (4 1 ) is 3V2 inches wide, 1 inch thick and 4V4 inches long, rounded on the ends 
 to a radius of ! 3 /4 inches. On the commutator side the extension (4 2 ) is 3V 2 
 inches wide ; 8 3 /s inches long, and rounded on the end to the same radius 
 as (4 1 ). 
 
 FIG. III. 
 
 Fig. Ill shows a vertical section through shaft. The shaft should be 
 made of steel 21V2 inches long; 1M inches in diameter; 9 3 /4 inches between 
 the bearings. In the bearings the shaft is turned down to 1 inch, leaving a 
 shoulder on the inside to prevent endwise play. The pillow blocks (6) are 3V2 
 inches at the shaft and lined with babbitt metal bearings as shown at 27. 
 From top of base to center of shaft is 4 5 /s inches. To secure pillow-blocks to 
 base, bolts (25) are used. 
 
 The hub or spider of the armature core is of brass with six arms 
 extending out radially from the center as shown in Fig. "V, with lugs on the 
 outer ends extending around the core to its outer circumference. The hub is 
 in two parts, as shown at 9 and 10 in Fig. III. The inner surface must be 
 faced off to make a good joint. The hubs are then placed in position on the 
 shaft and pins put through as shown at 30, Fig. V. The shaft should then be 
 put in the lathe and the ends of the arms inside of the lugs turned down to 5 J /4 
 inches in diameter. 
 
 The armature core can be made of thin discs or annealed iron wire. If 
 wire is used, the space between the arms must be filled with wood, then turned 
 
64 PRACTICAL DYNAMO BUILDING. 
 
 off smooth with the inner diameter of the hub. Wooden heads should be 
 placed on the ends to prevent the wire bulging out or breaking down as it is 
 wound on. The space on the inside can now be filled with No. 18 annealed 
 iron wire with a layer of paper between each layer of wire. After the wire is 
 all wound on and the outer end soldered to two or more of the lugs to prevent 
 the wire from unwinding, take off the heads from the ends of the core. The 
 wood between the arms can now be driven out, leaving- the wire on the inside 
 as perfect a circle as on the outside. 
 
 The only difficulty in building an armature in this way is the liability of 
 getting it out of round, unless the wire is cut off at every layer and soldered 
 and started from the same end every time. In winding there must be quite a 
 strain on the wire, that each layer may be perfectly smooth and solid as thread 
 on a spool; if it is rough or uneven and out of balance, you will find it 
 quite a hard matter to balance it. 
 
 If iron rings are used instead of wire for the armature core, the lugs 
 on one end of the arms will have to be attached with screws, and only three 
 arms in the hub are needed, but they should be a little thicker say 3 /s inch. 
 
 This style of commutator (11) has been fully described before. The 
 dimensions are given in Fig. YII. 
 
 The brush holder yoke (17) is the usual pattern. The insulating bushing 
 (21) ; insulating washers (20) ; brass washer (19) and nut (18) are all given 
 with their dimensions in Fig. "VI. 
 
 The brush holder (22) is 2 7 /s inches long ; one end for the distance of 
 IVs inches is turned down to V2 inch, leaving a shoulder that fits up against the 
 insulation (20). In the other end is a slot 1V2 inches long, 3 /s inch wide, to 
 receive the brush. On top of the brush should be a brass plate to prevent the 
 screw (23), Fig. Ill, from cutting into the brush. The brushes are made of 
 several layers of thin sheet spring copper, the outer ends being soldered to 
 keep the layers together. 
 
 The collar for supporting the yoke and method of attaching to pillow 
 block is shown in Figs. IV, and III. 
 
 The pulley (8) , Fig. Ill, should be four inches in diameter ; 3V2 inches 
 face to take a belt 3 inches wide. 
 
The armature is a Gramme ring of 42 sections ; 7 sections between each 
 set of arms. The wire is No. 17, B. & S. gauge, double cotton covered, 4 
 layers deep w r ith 8 convolutions to each layer, making 32 convolutions to each 
 section, with about 32 feet per section, total length of wire on armature 
 1,350 feet. 
 
 It is unnecessary to try to lay the wire on the armature so that the 
 sections will come together over the arms on the outside, as in so doing the 
 wire will be piled up against the arms on the inside, not only making the 
 armature look badly, but this is liable to throw the armature out of balance. 
 In other words, the six groups of sections are to be separated by the spider 
 arms. 
 
 The lead wires from the armature may be fastened to the commutator 
 segments with screws, or slots can be cut in the lugs and the wires soldered 
 in, which, in my judgment, is a far superior method of securing them. The 
 method of winding is given in Figs. IV and V, page 9. 
 
 (65) 
 
THE FIELDS: THEIR WINDINGS AND WIRE. 
 
 The fields should be properly insulated and have insulating- washers on 
 the ends, as shown in diagram 14, page 68. Wire on field is ~No. 11, B. & 
 S. gauge. There are 8 layers on each field core with 72 convolutions per 
 layer, making 1,152 convolutions on both fields with a total length of 1,056 
 feet. The lengths of wire on the armature and field magnets may vary a little 
 from the values given, but this will not make any material difference in the 
 working of the machine, if the proper number of convolutions is obtained. 
 
 This is a series wound dynamo. The whole current generated passes 
 out from the positive brush around the positive field core through the lamp, 
 returning 1 , passes around the negative field core to the negative brush. The 
 whole current generated passes through the field coils, and they are wound and 
 connected as shunt or internal circuit in diagram 14, page 68. 
 
 The machine that these drawings and windings are taken from has been 
 in constant use for over two years ; it was specially built for slow speed and 
 connected directly to the engine ; that is, the armature was on the engine shaft, 
 but if run with a belt and the speed increased to 1,500 revolutions per minute, 
 it will raise the voltage up to 110, easily making a two light machine of it. 
 
 ~No rheostat is used with an arc dynamo ; the strength of current is 
 increased and decreased by the movement of the brushes. If the current is to 
 be reduced, the .brushes should be moved forward, or in the direction of the 
 rotation of the armature'; if the current is to be increased, move the brushes 
 backward. 
 
 (66) 
 
METHOD OF FIELD WINDING AND HOUSE WIRING. 
 
 This diagram shows the method of winding the field magnets and 
 connecting up the fields, rheostat and main line of a shunt wound dynamo. 
 
 Before winding the wire on the field magnets, they should be well 
 insulated with three layers of cotton cloth well saturated with shellac varnish, 
 and at each end should be a washer of vulcanized fibre. The fibre washer is 
 not only an insulation, but serves to hold the wire firmly in its place. On the 
 outside of the fibre washer should be a washer of brass to prevent the fibre 
 washer warping out of shape. As the 4, 10, 15, 35, 60 and 150 light machines 
 are all shunt wound, these instructions will answer for all of them. 
 
 The current leaves the armature at the positive brush, + a portion of the 
 current going through wire (7) in the course indicated by the arrows, through 
 fibre washer as shown by the dotted lines to positive field (11) ; around positive 
 field by the course indicated by the arrows up to rheostat binding post (13) to 
 finger R, to washer S, thence to binding post (14), to wire 8 ; around negative 
 field magnet (12) out through fibre washer to negative brush . At the 
 negative brush the current divides, one-half going around the armature in one 
 direction, the other half in the other direction joining again at positive brush 
 +. This is the internal or field circuit, and no portion of its current goes 
 through the lamps. 
 
 As shunt wound dynamos are not fully self regulating, it would be 
 impossible to decrease the number of lights on the circuit without destroying 
 the remaining ones, unless some means were provided to decrease the magnetic 
 strength of the fields. To produce those results, resistance must be introduced 
 in the field or internal circuit to check the flow of current through them as the 
 
 (67) 
 
DlAGHAM XIV. 
 
PRACTICAL DYNAMO BUILDING. 69 
 
 magnetic strength of the fields increase and decrease in proportion to the 
 amount of current flowing through the wire around them. By the aid of the 
 rheostat the operator is enabled to keep the lamps burning at their proper 
 candle power or to increase and decrease their brilliancy at will. 
 
 The rheostat consists of a box containing a suitable number of coils of 
 German silver wire. For convenience only a few coils are shown. On the 
 outside of the box are twelve brass plates set in a perfect circle insulated from 
 each other. This may be done by putting fibre or mica between them, as in 
 building a commutator, or the plates may be set Vie inch apart, which will 
 answer fully as well. To these plates are attached wires leading from the 
 German silver coils as the numbers indicate. In the center of this circle is 
 brass plate (S) ; to it is attached the finger (R) in such a manner that it may 
 be allowed to revolve freely around the whole circle. In the position that 
 finger R is now, no current would pass through the German silver coils, but if 
 the finger were moved over to plate 2, the current would flow through wire 15 ; 
 through coil !S r o. 1 ; through finger R to plate S, returning through wire 8 to 
 negative field 12. Thus, if the finger R were to be moved around the whole 
 circle of plates, all the coils in the rheostat would be in circuit with the 
 field coils. 
 
 The number of coils in a rheostat and size of wire in them will depend 
 wholly upon the size of the machine, the amount of current that is required to 
 energize the fields and to what per cent of lights it is desired to regulate the 
 machine. If only two or three amperes of current are allowed to pass through 
 the field coils, No. 16 wire is large enough; for three to five amperes of current 
 use No. 14 wire. 
 
 The ends of the rheostat box through which the German silver coils 
 pass must be made of slate. The sides may be made of wood but lined with 
 asbestos paper. If it is fastened to a wooden partition, porcelain knobs 
 must be placed between the box and the partition with a sheet of asbestos 
 intervening; or the box may be set on brackets several inches from the 
 woodwork. The coils in the rheostat sometimes get sufficiently heated to ignite 
 wood, and unless these rules are observed, a fire may be the result. 
 
NKUTRAL DIAMETER. 
 
 As the neutral point of a shunt wound dynamo changes with the change 
 of load, it is the resultant of two factors, namely : the magnetism generated by 
 the current flowing through the armature, and the magnetism of the field 
 magnates generated by the current flowing through the field coils. Should the 
 magnetism in the armature become greater than in the field coils ; or that in the 
 field magnets greater than in the armature, the polar lines will shift back or 
 forward as the case may be. This is brought about by the varying conditions 
 under which the machine works. 
 
 To prevent sparking and secure a maximum amount of work from 
 dynamo electric machines, the brushes should always be kept at or near the 
 neutral line. The brushes, therefore, must be shifted to secure this result, or 
 some means devised to prevent the shifting of the neutral line. The travel or 
 change of the neutral line is forward or in the direction of the rotation of the 
 armature, as the load increases, the reverse as the load decreases. In an arc 
 machine it is practical to follow the neutral line with the brushes as it oscillates 
 back and forth with the change of loads. As the current is very light and 
 constant, or nearly so, the changing of the position of the brushes is more to 
 regulate the voltage than the quantity of current. The increase and decrease 
 of current in an arc dynamo is very slight, but the voltage is raised and 
 lowered according to the number of lamps burning on the circuit. But the 
 conditions under which an incandescent dynamo works are very different. The 
 brushes remain positive and means must be devised to compensate for change 
 of load and keep the neutral lines as near one position as possible. 
 
 (70) 
 
PRACTICAL DYNAMO BUILDING. 71 
 
 There are several means devised for producing these results. In some 
 dynamos coils of wire surrounding the armature and connected in series with 
 the main line are used. Others have coils wound around the field magnets at a 
 given point and produce the same results. A single layer of wire in addition 
 to the shunt coils on the field magnets of the cross sectional area of the main 
 line and connected in series with the armature will to a certain extent make the 
 dynamo self -regulating. The last named winding is known as compound ; that 
 is, series and shunt coils on the field magnets. The author has a device in the 
 form of a horseshoe magnet let into the pole pieces (but insulated therefrom) 
 as near the neutral line as possible. These magnets are wound with the line 
 wire and connected in series with the armature. The object is to exert 
 sufficient influence at that point to keep the neutral line permanent. All these 
 devices are supposed to make an incandescent dynamo self-regulating without 
 the aid of a rheostat, and, in fact, they do to a certain per cent of the load, but 
 for absolute regulation, a rheostat must be used. 
 
A DYNAMO MUST BE CHARGED BEFORE IT WILL WORK. 
 
 After the dynamo is finished and the field wires properly connected, a 
 current from another dynamo should be sent through the field coils and 
 armature to magnetize the iron, or the dynamo will not start. If it is not 
 convenient to get a dynamo current either continuous or alternating, several 
 strong batteries may be used. After a dynamo has once started to work it will 
 never have to be charged again as there will always be sufficient magnetism 
 retained in the iron to make the dynamo self-exciting. 
 
 THE MAGNETIC STRENGTH or FIELDS. There is a limit to the 
 magnetization of the fields for two reasons. The first is that beyond a certain 
 amount of wire in the field coils the internal resistance of the dynamo is being 
 increased without producing any effective lines of force. Second, with too 
 much current going through the field coils, they will be magnetized so strongly 
 that they will be beyond the proper range of regulation, and it will be almost 
 impossible to keep the lamps burning at a fixed candle power with a variable 
 load. Field magnets in that condition are called over-saturated. As little 
 current as possible should be used to energize the field magnets, as all current 
 that passes through the field coils that is not needed is wasted. A dynamo to 
 work properly should just be able to carry the full load with all the coils in the 
 rheostat cut out. 
 
 SPEED OF THE DYNAMO. Another essential feature in producing good 
 light is steady speed, for the candle power of the lamps will vary as the speed 
 varies. 
 
 LINES OF FORCE . It will be seen from the construction of this type of 
 dynamo that all lines of force generated in the field magnets are brought into 
 
 (72) 
 
PRACTICAL DYNAMO BUILDING. 73 
 
 direct action with the armature ; no lines of force are wasted. As all lines of 
 force that are generated in the field magnets and miss the armature, are not 
 only a loss, but a detriment to the machine, as well as a loss of power to 
 produce them. 
 
 CAUSES OF THE BRUSHES SPARKING. It would be a matter of 
 impossibility to name the different causes of the brushes sparking and 
 give a remedy which the operator could apply and get instant relief. A 
 chapter might be written on the subject, but how would the operator know 
 which remedy to apply? If from any cause he has allowed any portion of the 
 machine to get out of adjustment, or has allowed dirt to accumulate in the 
 armature, or the lead wires to become loose from the segments of the 
 commutator, the brushes to change their position, or get so badly worn out of 
 shape that only a portion of them is in contact with the commutator, or has 
 allowed the commutator to become rough and uneven, he should be able to see 
 those causes of sparking, and remedy them without any printed instructions ; 
 but if he does not, he should be given another position and a closer observer 
 placed in charge of the dynamo, as there is no excuse for allowing a dynamo to 
 get in such a condition. A dynamo may be in perfect condition and then spark 
 at the brushes, the cause being an overload ; but still the dynamo may not be 
 working up to its rated capacity. The rated capacity does not always 
 determine its carrying capacity, as there are hardly two machines of the same 
 build and winding that will carry exactly the same number of lights. The first 
 thing to find out is the actual carrying capacity of the dynamo and then keep it 
 at its proper load, regardless of its rated capacity. 
 
 The different carrying capacity of machines of the same size and 
 winding is due to several causes. First, the wire used in their construction 
 may vary slightly in size, or if the same sized wire is used, it may be of higher 
 resistance in one machine than the other. Second, the difference in the 
 thickness of the insulation on the wire may be the means of allowing several 
 convolution o more on the field magnets and armature in one machine than the 
 other. Third, the iron in one dynamo may be harder than in another, which 
 increases the resistance and retards the travel of the magnetic lines of force, for 
 the harder the iron, the higher the magnetic resistance, and consequently the 
 
74 
 
 PRACTICAL DYNAMO BUILDING. 
 
 slower the iron to magnetize and demagnetize, causing the dynamo to heat, 
 and all undue heating represents that much loss. Fourth, the air space in one 
 dynamo may be greater than in the other, and as all lines of force generated in 
 the field magnets, have to leap across the air space to the iron in the armature 
 core, and as air is about seven hundred times higher resistance than iron, the 
 weakening effect of unnecessary air space can readily be seen. In small 
 machines Vie inch clearance between the binding wire on the armature and the 
 pole pieces is sufficient, and in the larger ones not over 3 /32 inch is needed. In 
 the large machine 3 /32 inch space between the armature and the pole pieces 
 looks very small, but it is just as good as though the pole piece were J /4 inch 
 away, for all there is to guard against is the expansion of the armature by 
 heating. 
 
 It is very important that the armature should be perfectly round, for if 
 there is one high place, the pole pieces will have to be bored out that much 
 larger to accommodate it, thus increasing the air space and reducing the 
 efficiency of the dynamo in proportion. 
 
 FIG. XV. 
 
PRACTICAL DYNAMO BUILDING. 75 
 
 COMMUTATOR SEGMENTS. It is generally supposed that the proper way 
 to build a commutator is to have a solid ring of the proper size cast, turned to 
 the proper shape, and cut into segments of the desired width. That will do 
 very well for a small commutator when the segments are small and narrow, but 
 for a large commutator it is far more convenient, and also more accurate to cast 
 the segments separately. But in order to have the segments all of the same 
 thickness, they must be cast from a gate, as shown in the Fig. 15. If an 
 attempt were made to cast enough segments for a commutator one at a time, 
 there would hardly be two of the same thickness, which would require a great 
 deal of work with a file to bring them all to gauge ; but with a gate on which 
 there are six or eight segments, the moulder being reasonably careful, all the 
 filing required would be the taking off of the sharp points and corners, and the 
 commutator is ready to be put together. If possible use mica insulation 
 between the segments as it is hard and will wear as long as the segments 
 themselves ; fibre may be used, but it will not give as good service as mica. 
 The insulation between the ends of the segments and the commutator heads 
 may be of fibre if of sufficient thickness, as there is no wear on them, and their 
 requirements are no greater than those of the insulation between the copper 
 wire and the iron core of the armature. 
 
POSITION OF THE BRUSHES. 
 
 The brushes should be set at a non-sparking point ; but the exact 
 position cannot be determined until after the machine is in operation. 
 Theoretically they are in their right positions in diagram 14, supposing the 
 neutral diameter to be in position shown. But after the machine is started and 
 the brushes spark, they should be moved forward or in the direction of the 
 course of rotation of the armature, although with the brushes at a non-sparking 
 point, the machine is not always the strongest. Great care should be taken 
 in fitting the brushes to the commutator that all the leaves, if copper, are in 
 contact the whole width of the brush ; if not, it will cause a spark and the 
 longer the machine is allowed to run in this condition, the worse it will get; the 
 commutator will become rough and uneven, which will necessitate taking the 
 armature out and turning the commutator off in the lathe. A little care and 
 judgment must be used, for when the commutator begins to spark, there is 
 something radically wrong, and the defect should be remedied at once. If a 
 copper brush is allowed to spark and burn, those parts become insulated, 
 reducing the carrying capacity at point of contact, thereby increasing the spark 
 and destroying the brushes and commutator. The copper cuttings will be 
 flying around the machine, getting in and around the connections and 
 armature, and will work into the insulation, short circuit the coils and 
 eventually burn out the armature. 
 
 (76) 
 
HOW TO TEST THE 
 
 As the coils are being wound on the armature they should be frequently 
 tested with a magneto to see that none of the wires are in contact with the iron 
 core. If there is any place on the armature that has been slighted while 
 insulating, especially on the edges or in the corners where the arms of the 
 spiders join the core, it is a very easy matter to draw the copper wire down 
 close enough to cut through the insulation and bring the wire and iron core in 
 contact. If there were several places on the armature where this had 
 happened, the machine would not work ; the wire would have to be taken off 
 and the defect remedied. So it would be much better to test the armature as it 
 is being wound than to have to take it all apart to correct it. 
 
 The commutator must also be tested, before it is connected with the 
 armature, to see that the segments are all properly insulated from each other 
 and from the core as well. 
 
 The fields must be tested in like manner, but for the first and second 
 layers only, for if they are clear, there will be no chance of the outer layers 
 coming in contact with the iron. The only real danger of the field wire 
 coming in contact with the iron is where the insulation of the core comes up 
 against the fibre washers. After the field is wound, unless care has been used 
 in holding the fibre washers in their proper places, they are liable to spring off 
 and allow the wire to draw into the crevice and come in direct contact with the 
 iron. 
 
 If these instructions are closely followed, it will be the means of saving 
 a great deal of work and annoyance ; otherwise the machine would probably 
 have to be torn apart and the work done over again. 
 
 (77) 
 
WIRING FOR LAMP CIRCUITS. 
 
 Although this work contains the rules and requirements for electrical 
 wiring adopted by the Boston and !N^ew York Board of Fire Underwriters, a. 
 reference to the accompanying diagram will give one a far better idea than the 
 printed instructions, as a plan of the work is before him. 
 
 Before leaving the dynamo with the main line, a fuse block must be 
 placed as shown at 5 with a fuse of sufficient carrying capacity for the whole 
 current, and no more, to protect the dynamo in case of a short circuit on the 
 main line. Wires may be supported on porcelain knobs or wood cleats may be 
 used, but for heavy wires porcelain knobs are preferable. Tie wires must be 
 insulated as well as conductors. Wherever a loop is taken from the main line, 
 a branch block must be placed, as shown at unless the wire is very large, then 
 fuse blocks will be allowed to be placed as shown at 1 and 2, but as close to the 
 main line as possible. Whenever a loop is taken from the main line, and a 
 branch taken from that loop, a branch block must be placed as shown at 3 and 
 4. Whenever the size of wire is reduced from one loop or branch to another 
 a branch block must be used. All fuse and branch blocks must be double 
 pole ; that is, have a fuse in both wires. 
 
 Wherever a lamp is placed in a loop or branch, a double pole porcelain 
 cut-out must be used to protect the lamps from grounds as well as abnormal 
 voltage. 
 
 All loops leaving the main line or branches where branch blocks are not 
 used, must be well soldered and covered with adhesive rubber tape. Where 
 one wire crosses another so they touch, hard rubber tubing must be used. The 
 
 (78) 
 
PRACTICAL DYNAMO BUILDING. 79 
 
 course the current takes ' through the wires and lamps is indicated by the 
 arrows. The ends of the main line and all loops and branches must be left 
 open. 
 
 The following are wiring tables arranged by E. A. Sperry for 50, 70, 
 and 110 volts, 16 candle power lamps, and by consulting them it is a very easy 
 matter for any one to determine the correct size of wire for any number of 
 lamps for any distance. 
 
80 
 
 PRACTICAL DYNAMO BUILDING. 
 
 WIRING TABLE FOR 50 VOLT, 16 CANDLE POWER LAMPS. 
 
 LOSS OF 1 VOLT. 
 
 Arranged by E. A. SPERRY. 
 
 V. 
 
 p 
 
 o 
 
 H 
 
 
 
 3 
 f 
 
 Distance in Feet to Center of 
 Wire Sizes are indicated belo\v in B. & S. Gauge. 
 Distribution. 
 
 20' 
 
 25' 
 
 30' 
 
 35' 
 
 40' 
 
 45' 
 
 50' 
 
 60' 
 
 70' 
 
 80' 
 
 90' 
 
 100' 
 
 120' 
 
 140' 
 
 160' 
 
 180' 
 
 200' 
 
 1 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 2 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 15 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 11 
 
 10 
 
 3 
 
 16 
 
 16 
 
 16 
 
 16 
 
 16 
 
 15 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 4 
 
 16 
 
 16 
 
 16 
 
 15 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 5 
 
 16 
 
 16 
 
 15 
 
 14 
 
 13 
 
 13 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 16 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 7 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 1] 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 8 
 
 15 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 9 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 10 
 
 14 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 12 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 14 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 16 
 
 12 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 18 
 
 11 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 20 
 
 11 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 25 
 
 10 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 80 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 
 
 
 
 00 
 
 35 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 00 
 
 00 
 
 000 
 
 40 
 
 8 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 00 
 
 000 
 
 000 
 
 000 
 
 45 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 00 
 
 00 
 
 000 
 
 0000000 
 
 50 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 00 
 
 000 
 
 000 
 
 00000000 
 
 55 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 
 
 00 
 
 00 
 
 000 
 
 0000 
 
 0000 
 
 0000 
 
 60 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 1 
 
 
 
 
 
 00 
 
 00 
 
 000 
 
 000 
 
 0000 
 
 
 
 65 
 
 *_/ 
 
 5 
 
 f_/ 
 
 5 
 
 ^t 
 
 4 
 
 n 
 
 3 
 
 *j 
 
 3 
 
 2 
 
 2 
 
 1 
 
 o 
 
 o 
 
 00 
 
 00 
 
 000 
 
 0000 
 
 0000 
 
 
 
 \ju 
 
 70 
 
 tj 
 
 4 
 
 vj 
 
 4 
 
 JL 
 
 4 
 
 <_J 
 
 3 
 
 t/ 
 
 2 
 
 2 
 
 4U 
 
 1 
 
 1 
 
 o 
 
 00 
 
 00 
 
 000 
 
 000 
 
 0000 
 
 0000 
 
 
 
 \* 
 
 75 
 
 jC. 
 
 4 
 
 JL 
 
 4 
 
 TI 
 
 3 
 
 t_J 
 
 3 
 
 Mrf 
 
 2 
 
 0U 
 
 i 
 
 JL 
 
 1 
 
 o 
 
 00 
 
 00 
 
 000 
 
 000 
 
 0000 
 
 0000 
 
 
 
 
 1 U 
 
 80 
 
 \ 
 
 3 
 
 7X 
 
 3 
 
 o 
 
 3 
 
 Cf 
 
 2 
 
 Al 
 
 2 
 
 _i_ 
 
 1 
 
 JL 
 
 1 
 
 \j 
 
 o 
 
 \J\J 
 
 00 
 
 00 
 
 000 
 
 000 
 
 0000 
 
 0000 
 
 
 
 
 V-J\y 
 
 90 
 
 fj 
 
 3 
 
 U 
 
 3 
 
 tJ 
 
 2 
 
 M 
 
 2 
 
 M 
 
 1 
 
 i 
 
 o 
 
 00 
 
 00 
 
 000 
 
 000 
 
 0000 
 
 0000 
 
 
 .... 
 
 
 
 *J w 
 
 100 
 
 U 
 
 2 
 
 t_J 
 
 2 
 
 Al 
 
 2 
 
 Al 
 
 1 
 
 JL 
 
 1 
 
 JL 
 
 
 
 \J 
 
 
 
 \J\J 
 
 00 
 
 000 
 
 000 
 
 0000 
 
 0000 
 
 
 
 
 
 
 
 
 
 
 
PRACTICAL DYNAMO BUILDING. 
 
 81 
 
 CARRYING CAPACITY IN AMPERES AND 16 C. P. LAMPS OF COMMERCIAL 
 
 COPPER WIRE. 
 
 Arranged by E. A. SPERRY. 
 
 2% DROP PER 100 FEET OF CIRCUIT. 
 
 American 
 Gauge. 
 Biovvn & 
 sliarpc's 
 Number. 
 
 Circular Mils, (d 2 .) 
 
 Amperes. 
 
 3 
 Watt 
 Lamps. 
 
 Amperes. 
 
 3-5 
 Watt 
 Lamps. 
 
 Amperes. 
 
 4 
 Watt 
 
 Lamps. 
 
 0000 
 
 211600.00 
 
 197.75 
 
 205 
 
 296.35 
 
 396 
 
 395.50 
 
 618 
 
 000 
 
 167805.00 
 
 156.82 
 
 150 
 
 235.02 
 
 317 
 
 313.64 
 
 490 
 
 00 
 
 133079.40 
 
 124.37 
 
 126 
 
 186.38 
 
 252 
 
 248.74 
 
 388 
 
 
 
 105592.50 
 
 98.68 
 
 101 
 
 147.89 
 
 199 
 
 197.36 
 
 309 
 
 1 
 
 83694.20 
 
 78.22 
 
 81 
 
 117.22 
 
 157 
 
 156.44 
 
 243 
 
 2 
 
 66373.00 
 
 62.03 
 
 64 
 
 92.96 
 
 125 
 
 124.00 
 
 194 
 
 3 
 
 52634.00 
 
 49.19 
 
 50 
 
 73.71 
 
 99 
 
 98.38 
 
 153 
 
 4 
 
 41742.00 
 
 39.01 
 
 40 
 
 58.46 
 
 79 
 
 78.02 
 
 122 
 
 5 
 
 33102.00 
 
 30.93 
 
 32 
 
 46.36 
 
 62 
 
 61.87 
 
 97 
 
 6 
 
 26250.50 
 
 24.53 
 
 26 
 
 36.76 
 
 50 
 
 49.06 
 
 76 
 
 7 
 
 20816.00 
 
 19.45 
 
 19 
 
 29.15 
 
 39 
 
 38.90 
 
 61 
 
 8 
 
 16509.00 
 
 15.42 
 
 16 
 
 23.12 
 
 31 
 
 30.85 
 
 47 
 
 9 
 
 13094.00 
 
 12.23 
 
 12 
 
 1835 
 
 25 
 
 24.47 
 
 38 
 
 10 
 
 10381.00 
 
 9.70 
 
 11 
 
 14.54 
 
 19 
 
 19.40 
 
 30 
 
 11 
 
 8234.00 
 
 7.69 
 
 8 
 
 11.53 
 
 15 
 
 15.38 
 
 24 
 
 12 
 
 6529.90 
 
 6.10 
 
 6 
 
 9.14 
 
 12 
 
 1220 
 
 19 
 
 13 
 
 5178.40 
 
 4.84 
 
 5 
 
 7.25 
 
 9 
 
 9.68 
 
 15 
 
 14 
 
 4106.80 
 
 3.84 
 
 4 
 
 5.75 
 
 7 
 
 7.68 
 
 12 
 
 15 
 
 3256.70 
 
 3.04 
 
 3 
 
 4.56 
 
 6 
 
 6.08 
 
 9 
 
 16 
 
 2582.90 
 
 2.41 
 
 2 
 
 3.61 
 
 4' 
 
 4.82 
 
 7 
 
 17 
 
 2048.20 
 
 1.91 
 
 2 
 
 2.87 
 
 4 
 
 3.83 
 
 6 
 
 18 
 
 1624.30 
 
 1.51 
 
 2 
 
 2.27 
 
 3 
 
 3.03 
 
 5 
 
 19 
 
 1252.40 
 
 1.17 
 
 1 
 
 1.75 
 
 2 
 
 2.34 
 
 3 
 
 20 
 
 1021.50 
 
 .95 
 
 1 
 
 1.43 
 
 2 
 
 1.90 
 
 3 
 
82 
 
 PRACTICAL DYNAMO BUILDING. 
 
 WIRING TABLE FOR 70 VOLT, 16 CANDLE POWER LAMPS, 
 
 LOSS OF l^j. VOLTS. 
 
 Arranged by B. A. SPEBBY. 
 
 
 
 p. 
 
 s 
 
 "o 
 
 6 
 'A 
 
 Distance in Feet to Center of 
 Wire Sizes are indicated below in B. & S. Gauge. 
 Distribution. 
 
 20' 
 
 25' 
 
 30' 
 
 35' 
 
 40' 
 
 45' 
 
 50' 
 
 60 
 
 70' 
 
 80' 
 
 90' 
 
 100' 
 
 120' 
 
 140' 
 
 160' 
 
 180' 
 
 200' 
 
 I 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 16 
 
 15 
 
 15 
 
 14 
 
 2 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 16 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 13 
 
 12 
 
 11 
 
 
 
 O 
 
 17 
 
 17 
 
 17 
 
 17 
 
 17 
 
 16 
 
 16 15 
 
 14 
 
 14 
 
 13 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 4 
 
 17 
 
 17 
 
 17 
 
 16 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 5 
 
 17 
 
 17 
 
 16 
 
 15 
 
 14 
 
 14 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 H 
 
 6 
 
 17 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 8 
 
 16 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 9 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 10 
 
 15 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 12 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 14 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 16 
 
 13 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 18 
 
 12 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 20 
 
 12 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 25 
 
 11 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 30 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 1 
 
 1 
 
 1 
 
 
 
 35 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 
 
 00 
 
 40 
 
 9 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 00 
 
 00 
 
 00 
 
 45 
 
 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 
 
 00 
 
 00 
 
 000 
 
 50 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 00 
 
 00 
 
 000 
 
 000 
 
 55 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 00 
 
 000 
 
 000 
 
 000 
 
 60 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 1 
 
 1 
 
 
 
 o 
 
 00 
 
 00 
 
 000 
 
 
 
 65 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 00 
 
 000 
 
 000 
 
 
 
 70 
 
 5 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 
 
 00 
 
 00 
 
 000 
 
 000 
 
 
 75 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 o 
 
 00 
 
 00 
 
 000 
 
 000 
 
 
 
 
 t-/ 
 
 80 
 
 4 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 o 
 
 00 
 
 00 
 
 000 
 
 000 
 
 
 
 
 v-*vy 
 
 00 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 o 
 
 
 
 00 
 
 00 
 
 000 
 
 000 
 
 
 
 
 
 103 
 
 3 
 
 n 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 00 
 
 00 
 
 000 
 
 000 
 
 
 
 
 
 
 
 
 
 
 
PRACTICAL DYNAMO BUILDING, 
 
 83 
 
 WIRING TABLE FOR 110 VOLT, 16 CANDLE POWER LAMPS, 
 
 LOSS OF 2-fff VOLTS. 
 
 Arranged by E. A. SPEBRY. 
 
 o5 
 
 s 
 
 03 
 
 O 
 ^0 
 
 Distance in Feet to Center of 
 Wire Sizes are indicated below in B. & S. Gauge. 
 Distribution. 
 
 20' 
 
 25' 
 
 30' 
 
 35' 
 
 40' 
 
 45' 
 
 50' 
 
 60' 
 
 70' 
 
 80' 
 
 90' 
 
 100' 
 
 120' 
 
 140' 
 
 160' 
 
 180' 
 
 200' 
 
 1 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 18 
 
 17 
 
 17 
 
 16 
 
 2 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 18 
 
 18 
 
 17 
 
 16 
 
 16 
 
 15 
 
 15 
 
 14 
 
 13 
 
 3 
 
 19 
 
 19 
 
 19 
 
 19 
 
 19 
 
 18 
 
 18 
 
 17 
 
 16 
 
 16 
 
 15 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 4 
 
 19 
 
 19 
 
 19 
 
 18 
 
 18 
 
 17 
 
 16 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 5 
 
 19 
 
 19 
 
 18 
 
 17 
 
 16 
 
 16 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 6 
 
 19 
 
 18 
 
 17 
 
 16 
 
 16 
 
 15 
 
 15 
 
 14 
 
 14 
 
 13 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 7 
 
 18 
 
 17 
 
 16 
 
 16 
 
 15 
 
 15 
 
 14 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 18 
 
 17 
 
 16 
 
 15 
 
 15 
 
 14 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 9 
 
 8 
 
 8 
 
 9 
 
 17 
 
 16 
 
 15 
 
 15 
 
 14 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 10 
 
 17 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 12 
 
 16 
 
 15 
 
 14 
 
 14 
 
 13 
 
 J3 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 14 
 
 15 
 
 14 
 
 13 
 
 13 
 
 12 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 16 
 
 15 
 
 14 
 
 13 
 
 12 
 
 12 
 
 11 
 
 11 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 18. 
 
 14 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 20 
 
 14 
 
 13 
 
 12 
 
 11 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 25 
 
 13 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 30 
 
 12 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 3 
 
 2 
 
 35 
 
 11 
 
 10 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 40 
 
 11 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 1 
 
 1 
 
 1 
 
 45 
 
 10 
 
 9 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 50 
 
 9 
 
 9 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 ' 4 
 
 3 
 
 3 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 55 
 
 9 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 
 
 
 
 60 
 
 8 
 
 8 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 f V 
 
 
 
 65 
 
 8 
 
 8 
 
 7 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 1 
 
 
 
 
 
 
 
 70 
 
 7 
 
 7 
 
 7 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 
 
 75 
 
 7 
 
 7 
 
 6 
 
 6 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 80 
 
 6 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 o 
 
 
 
 
 90 
 
 6 
 
 6 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 2 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 
 LOO 
 
 5 
 
 5 
 
 5 
 
 4 
 
 4 
 
 3 
 
 3 
 
 2 
 
 1 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
84 
 
 PRACTICAL DYNAMO BUILDING. 
 
 TABLE SHOWING THE WEIGHT, CARRYING CAPACITY AND LOSS IN VOLTS 
 OF DIFFERENT SIZES OF COPPER WIRE. 
 
 Arranged by E. A. SPERRY. 
 
 Brown & 
 Sharpe's 
 Gauge No. 
 
 Diameter. 
 
 Lbs. per 1,000 
 feet bare wire. 
 
 Approximate 
 Weight 
 Underwriter's 
 Insulation 
 per 1,000 feet. 
 
 Safe current in 
 Amperes. 
 
 Loss in Volts 
 per 
 Ampere per 
 100 feet of line 
 (2 wire). 
 
 0000 .... 
 
 .46 
 
 640.5 
 
 825 Ibs. 
 
 312. 
 
 .0098 
 
 000.... 
 
 .40964 
 
 508.5 
 
 610 " 
 
 262. 
 
 .0123 
 
 00.... 
 
 .3648 
 
 402.8 
 
 458 " 
 
 220. 
 
 .0155 
 
 0.... 
 
 .32495 
 
 319.6 
 
 385 " 
 
 185. 
 
 .0196 
 
 1.... 
 
 .2893 
 
 253.4 
 
 308 " 
 
 156. 
 
 .0247 
 
 2 
 
 .25763 
 
 201.0 
 
 249 " 
 
 131. 
 
 .0311 
 
 3.... 
 
 .22942 
 
 159.3 
 
 201 " 
 
 110. 
 
 .0392 
 
 4.... 
 
 .20431 
 
 126.4 
 
 163 " 
 
 92.3 
 
 .0495 
 
 5.... 
 
 .18194 
 
 100.2 
 
 133 " 
 
 77.6 
 
 .0624 
 
 6.... 
 
 .16202 
 
 79.46 
 
 109 " 
 
 65.2 
 
 .0787 
 
 7.... 
 
 .14428 
 
 63.01 
 
 90 " 
 
 54.8 
 
 .0992 
 
 8.... 
 
 .12849 
 
 49.98 
 
 74 " 
 
 46.1 
 
 .125 
 
 9.... 
 
 .11443 
 
 39.64 
 
 62 " 
 
 38.7 
 
 .158 
 
 10.... 
 
 .10189 
 
 31.43 
 
 52 " 
 
 32.5 
 
 .199 
 
 11.... 
 
 .090742 
 
 24.93 
 
 43 " 
 
 27.3 
 
 .251 
 
 12.... 
 
 .080808 
 
 19.77 
 
 36 " 
 
 23. 
 
 .316 
 
 13.... 
 
 .071961 
 
 15.68 
 
 30 " 
 
 19.3 
 
 .399 
 
 14 .... 
 
 .064084 
 
 12.43 
 
 25 " 
 
 16.2 
 
 .503 
 
 15.... 
 
 .057068 
 
 9.86 
 
 21 " 
 
 13.6 
 
 .634 
 
 16.... 
 
 .05082 
 
 7.82 
 
 18 " 
 
 11.5 
 
 .799 
 
 17.... 
 
 .045257 
 
 6.20 
 
 15 " 
 
 9.6 
 
 1.088 
 
 18.... 
 
 .040303 
 
 4.92 
 
 13 " 
 
 8.1 
 
 1.271 
 
TABLE OF DIMENSIONS, WEIGHT AND RESISTANCE OF BARE COPPER WIRE. 
 
 BROWN & SHARPE'S GAUGE THE STANDARD. 
 
 American Gauge, I 
 Brown & Sharpe's 
 Number. 
 
 Diameter, Mils. 
 
 AKEA. 
 
 WEIGHT AND LENGTH, 
 sp. gr. 8.9. 
 
 RESISTANCE AT 75 F. 
 
 Circular 
 mils. (d2) 
 1 mil. = 
 .001 in. 
 
 Square in. 
 (d2 x .7854) 
 
 Lbs. per 
 1,000 ft. 
 
 Lbs. per 
 mile. 
 
 Feet 
 per Ib. 
 
 R 
 
 Ohms 
 per 
 1,000 feet. 
 
 Ohms 
 per mile. 
 
 Feet 
 per Ohm. 
 
 Ohms per Ib. 
 
 OOCO 
 
 too 
 
 00 
 
 460 000 
 409.640 
 364.800 
 
 211600.00 
 167805 01 
 133079.40 
 
 166190. 
 131790. 
 ! 104520. 
 
 639.33 
 507.01 
 402.09 
 
 1 3375.7 
 2677.0 
 2123.0 
 
 1.56 
 1 97 
 2.49 
 
 .04906 
 .06186 
 .07801 
 
 .25903 
 .32664 
 .41187 
 
 20383. 
 16165. 
 12820. 
 
 .000076736 
 .00012039 
 .00019423 
 
 
 1 
 o 
 
 324 950 
 
 289 300 
 257.630 
 
 105592.50 
 83(194 2 
 66373.0 
 
 82932. 
 65733. 
 52130. 
 
 319.04 
 252.88 
 200.54 
 
 1684 5 
 1335.2 
 1058.8 
 
 3.13 
 3.95 
 4.99 
 
 .09831 
 .12404 
 .15640 
 
 .51909 
 .65490 
 .82582 
 
 10409. 
 8062.3 
 6393 7 
 
 .00030772 
 .00048994 
 .00078045 
 
 3 
 4 
 5 
 
 229.420 
 204 310 
 181.910 
 
 52634 00 
 41742.00 
 33102.00 
 
 41339 
 32784. 
 25998. 
 
 159.03 
 126.12 
 100.01 
 
 839.68 
 665 91 
 528.05 
 
 6.29 
 
 7.93 
 10.00 
 
 .19723 
 .24869 
 .31361 
 
 1.0414 
 1.3131 
 1.6558 
 
 5070.2 
 41)21.0 
 3188.7 
 
 .0012406 
 .0019721 
 .0031361 
 
 6 
 7 
 
 8 
 
 12 020 
 
 144.2SO 
 128 400 
 
 26250.50 
 20816.00 
 16509. 01) 
 
 20617. 
 16349. 
 12966. 
 
 79 32 
 62.90 
 
 49.88 
 
 418.81 
 332 11 
 263.37 
 
 12.61 
 15.90 
 20.05 
 
 .39:>46 
 .49871 
 .62881 
 
 2.08S1 
 2.6331 
 3.3201 
 
 2528.7 
 2003.2 
 1590.3 
 
 .0049868 
 .0079294 
 .012608 
 
 9 
 10 
 11 
 
 114.430 
 101.890 
 90.742 
 
 13594.00 
 10381.00 
 8234.00 
 
 10-284. 
 8153.2 
 6467.0 
 
 39.56 
 31.37 
 
 24.88 
 
 208 88 
 165.63 
 137.37 
 
 25.28 
 31.38 
 40.20 
 
 .79281 
 1. 
 1.2607 
 
 4 1860 
 5.2800 
 6.6568 
 
 1261.3 
 
 1000.0 
 793.18 
 
 .020042 
 .031380 
 .050682 
 
 12 
 13 
 14 
 
 80.808 
 71.961 
 64.084 
 
 6529 90 
 5178.40 
 4106.80 
 
 5128.6 
 4067.1 
 3146.9 
 
 19.73 
 15.65 
 12.41 
 
 104.18 
 82.632 
 65.525 
 
 50.69 
 63.91 
 
 80.59 
 
 1.5898 
 2.0047 
 2.5908 
 
 8.3940 
 10.585 
 13.680 
 
 629.02 
 498 83 
 385.97 
 
 .080585 
 12841 
 .20880 
 
 15 
 16 
 17 
 
 57.068 
 50.820 
 45.257 
 
 3256.7 
 2582.9 
 2048.2 
 
 2557.8 
 2028.6 
 1608.6 
 
 9.84 
 
 7.81 
 6.19 
 
 51.956 
 41 237 
 32.683 
 
 101.63 
 128.14 
 161.59 
 
 3.1150 
 4 0191 
 5.0683 
 
 16.477 
 21 221 
 26.761 
 
 321 02 
 248.81 
 197.30 
 
 .31658 
 .51501 
 .81900 
 
 18 
 19 
 20 
 
 21 
 22 
 23 
 
 40.303 
 35.390 
 31.961 
 
 1624.3 
 1252.4 
 1021.5 
 
 1275.7 
 
 983.64 
 802.28 
 
 4.91 
 3.78 
 3 09 
 
 25.925 
 20 051 
 16.315 
 
 203.76 
 264.26 
 324.00 
 
 6 S911 
 8.2889 
 10.163 
 
 33.745 
 
 43.765 
 53.658 
 
 156.47 
 120.64 
 98.401 
 
 1.3023 
 2.1904 
 3.2926 
 
 28.462 
 25.347 
 22.571 
 
 810.10 
 642.70 
 509.45 
 
 636.25 
 504.78 
 400 12 
 
 2.45 
 1.94 
 1.54 
 
 12 936 
 10 243 
 8.1312 
 
 408.56 
 515 15 
 649 66 
 
 12.815 
 16.152 
 20.377 
 
 67.660 
 85.283 
 107.59 
 
 78.037 
 61.911 
 49.087 
 
 5 2355 
 8 3208 
 13.238 
 
 24 
 
 25 
 26 
 
 20.100 
 17.900 
 15.940 
 
 404.01 
 320 40 
 254.01 
 
 317 31 
 251 64 
 199.50 
 
 1.22 
 .97 
 
 .77 
 
 6.4416 
 5.1216 
 4.0656 
 
 819.21 
 1032.96 
 1302.61 
 
 25.695 
 32 400 
 40.868 
 
 135.67 
 171 07 
 215.79 
 
 38.918 
 30 864 
 24.469 
 
 21.050 
 33.466 
 35.235 
 
 27 
 
 28 
 29 
 
 14.195 
 12.641 
 11.257 
 
 201 50 
 159.79 
 126.72 
 
 158 26 
 125.50 
 99.526 
 
 .61 
 
 .48 
 .38 
 
 3.2208 
 2.5344 
 2.0064 
 
 1642.55 
 2071 22 
 2611.82 
 
 51.519 
 64.966 
 81.921 
 
 272 02 
 343.02 
 432.54 
 
 19.410 
 15.393 
 12.207 
 
 84.644 
 134.56 
 213.96 
 
 30 
 81 
 32 
 
 10.025 
 
 8.928 
 7.950 
 
 100.5 
 79.71 
 63.20 
 
 78.933 
 62.604 
 49.637 
 
 .30 
 .24 
 .19 
 
 1.5840 
 1.2672 
 1.0032 
 
 3293.97 
 4152 22 
 5236.66 
 
 103.30 
 127.27 
 164.26 
 
 545.39 
 871.69 
 
 867.27 
 
 9. 6812 
 7.8573 
 6.0880 
 
 340.25 
 528.45 
 860.33 
 
 33 
 34 
 35 
 
 7.0SO 
 6 304 
 5.614 
 
 50.13 
 39.74 
 31.52 
 
 39 372 
 31 212 
 24.756 
 
 .15 
 .12 
 
 .10 
 
 .7920 
 .63:56 
 .5280 
 
 6602.71 
 8328.30 
 10501.35 
 
 207.08 
 261.23 
 329 35 
 
 1093.4 
 1379.3 
 1738.9 
 
 4 8290 
 3 8281 
 3.0363 
 
 1367.3 
 2175.5 
 3458.5 
 
 36 
 37 
 38 
 
 5.000 
 4.453 
 3.965 
 
 25.00 
 19 83 
 15.72 
 
 19.635 
 15.567 
 12.347 
 
 .08 
 .06 
 .05 
 
 .4224 
 
 .3168 
 .2640 
 
 13238.83 
 16691.06 
 20834.65 
 
 415.24 
 523 76 
 66U.67 
 
 2192 5 
 2765.5 
 
 3486.7 
 
 2.4082 
 1.9093 
 1.5143 
 
 5497.4 
 8742.1 
 13772. 
 
 39 
 
 40 
 
 3.531 
 3.144 
 
 12.47 
 9. 89 
 
 9.7939 
 7.7676 
 
 .04 
 .03 
 
 .2112 
 .1584 
 
 26302 23 
 33175.94 
 
 832.48 
 1049.7 
 
 4395 5 
 5342.1 
 
 1.2012 
 .9527 
 
 21896. 
 34823. 
 
RULES AND REGULATIONS 
 
 Or THE NEW ENGLAND INSURANCE EXCHANGE AND BOSTON FIRE 
 
 UNDERWRITERS' UNION FOR ELECTRIC LIGHTING. [ADOPTED 
 
 APRIL 15TH, 1889, AND SUPERSEDING ALL PREVIOUS RULES.] 
 
 ARC SYSTEM. 
 
 OUTSIDE WIRES. 
 
 All outside overhead wires must be covered with some material of high 
 insulating power, not easily abraded ; they must be firmly secured to properly 
 insulated and substantially built supports. All tie wires must have an 
 insulation equal to that of the conducting wires. 
 
 2. All joints must be so made that a perfectly secure and unvarying 
 connection, fully equal to the cross-section of the conducting wire, will be 
 secured and they should be soldered. Resin should not be used as a flux. 
 Nothing but an acid solution should be used, and any excess should be washed 
 off before the splice is covered. This also applies to inside wires. All joints 
 must be securely wrapped with an approved tape. 
 
 The following formula for soldering fluid is recommended, viz. : 
 
 Saturated solution of zinc 5 parts. 
 
 Alcohol 5 " 
 
 Glvcerine 1 
 
 / 
 
 3. Care must be taken that conducting wires are not placed in such 
 position that it would be easy for water, or any liquid, to form cross connection, 
 between them, and they should not approach each other nearer than one foot. 
 
 (86) 
 
PRACTICAL DYNAMO BUILDING. 87 
 
 4. The wires must never be allowed in contact with any substance 
 other than air, and their proper insulating supports. 
 
 5. Conducting wires carried over or attached to buildings, must be at 
 least seven feet above the highest point of flat roofs, and one foot above the 
 ridge of pitch roofs. Lines constructed subsequent to the adoption of these 
 regulations should not be run over and attached to buildings other than those in 
 
 O < - > 
 
 which the light or power is being, or is to be used, but should be on separate 
 poles, or structures, where they can be easily reached for inspection. 
 
 6. When they are in proximity to other conducting wires, or any 
 substance likely to divert any portion of the current, dead, insulated guard-irons 
 must be placed so as to prevent any possibility of contact in case of accident to 
 the wires, or their supports. The same precautions must be taken where sharp 
 angles occur in the line wires, and also where any wires (telegraph, telephone 
 or others) could possibly, owing to their position, come in contact with the 
 electric light wires. 
 
 7. Overhead wires from the main circuit or pole in the street to the 
 terminal insulators attached to buildings, and at the point where they enter a 
 building, must not be less than twelve inches apart. They must be rigidly 
 and neatly run, and supported by glass or porcelain insulators, or rubber 
 hooks. The rubber hooks must be of an approved pattern, i. e., with 
 the rubber insulation free from flaws, and projecting over the hook in cup 
 form. 
 
 8. Service blocks must be protected by at least two coats of water-proof 
 paint over their entire surface ; and when used to support rubber hooks, must 
 have at least one inch of wood between the inner end of the hook and the back 
 of the block. 
 
 9. For entering buildings, wires with an extra heavy water-proof 
 insulation must be used from the terminal insulators outside to the inside of a 
 building. They must loop down, so that water may drip off, without entering 
 the building, and the holes through which they enter should, where possible, 
 slant upward. If an approved glass insulator for bushing the hole be used, the 
 extra heavy water-proof insulation will not be required. 
 
 10. Service wires must come in contact with nothing save air, and their 
 
88 PRACTICAL DYNAMO BUILDING. 
 
 insulating supports, except in unavoidable cases, when a wire with an extra 
 heavy insulation suitable for the purpose must be used. 
 
 11. The use of porcelain knobs, as insulators, except in perfectly dry 
 places, or for the support of specially insulated wire, will not be accepted unless 
 of some approved .shape. 
 
 12. ]S"one but an approved tubing will be accepted as a durable 
 water-proof insulation. 
 
 13. Wires must enter and leave the building through an approved 
 cut-out switch. 
 
 14. The cut-out switch must be " double contact," and should 
 effectually close the main circuit, and cut off the ulterior when turned " off." 
 It must be so constructed that there shall be no arc between the points when 
 thrown "on" or " off." It should be automatic in its action in either 
 direction, not stopping between points when once started. It should indicate 
 upon inspection whether current be "on" or " off." 
 
 15. It must be mounted on a non-conducting base, kept free from 
 moisture, and easy of access to firemen and police. 
 
 INSIDE WIRING. 
 
 16. Wires must not be concealed ; they must be run in plain sight so as 
 to be open to inspection at any time. They should be kept apart at least 
 twelve inches. 
 
 17. In perfectly dry places wires may be supported by cleats of wood 
 (filled to prevent the absorption of moisture) or porcelain. Cleats should be so 
 made as to separate the wire at least one-fourth of an inch from the building. 
 
 18. In places liable to dampness, wires must be separated at least one 
 and one-half inches, they must be thoroughly and carefully put up, and 
 supported upon porcelain or glass insulators, or hard rubber hooks. They 
 should also be provided with an approved insulation covering. 
 
 19. When wires pass through walls, floors, partitions, etc., in-doors, 
 glass insulators, or an extra covering of hard rubber, should be used. Wires 
 must never be left exposed to disturbance or mechanical injury. 
 
PRACTICAL DYNAMO BUILDING. 
 
 ARC LAMPS. 
 
 20. The frames and other exposed parts of arc lamps must be carefully 
 insulated from the circuit. 
 
 21. Each lamp must be provided with a proper hand switch, and also 
 with an automatic switch that will shunt the current around the carbons, should 
 they fail to feed properly. 
 
 22. Stops of some kind must be provided to prevent the carbons from 
 falling- out in case their clamps fail to hold them ; and these stops must always 
 be in place when the lamp is burning. 
 
 23. For inside use the light must be surrounded by a globe resting in a 
 tight stand, so that no particles of melted copper or heated carbon can escape. 
 When inflammable material is near or under the lamp, the globe must be 
 protected by a wire netting. Unless a very high globe, which closes in as far 
 as possible at the top, be used, it must be provided with some protector or spark 
 arrester, reaching to a safe distance above the light. Broken or cracked globes 
 must be replaced by perfect ones immediately. (By inflammable material is 
 meant such as dry goods, clothing, millinery and the like in stores ; flyings or 
 goods in fabric factories, shavings and saw-dust in w r ood- working shops, or any 
 other substance that can be readily ignited by droppings or flyings from the 
 lamp.) 
 
 24. Electrical connection between the conducting wires and lamps must 
 be made through a suitable "hanger-board" and rods on which the lamp is 
 hung. 
 
 INCANDESCENT LAMPS ON ARC-LIGHT CIRCUITS. 
 
 25. The rules for running wires for arc lamps apply also to incandescent 
 lamps run in series. 
 
 26. These must be provided with a proper hand switch, and also with 
 an approved automatic device which will shunt the circuit around the carbon 
 filament should it break. ~No electro-magnet device will be accepted for this 
 purpose. 
 
 27. Any method of distributing current to incandescent lamps on 
 
90 PRACTICAL DYNAMO BUILDING. 
 
 arc-light circuits, other than as above provided for, must receive the approval 
 of this Exchange before being put into use. 
 
 DYNAMOS AND MOTORS. 
 
 28. They must be located in dry places, not exposed to the flyings of 
 combustible material, and must be insulated upon dry wood, filled to prevent 
 absorption of moisture. They must be kept thoroughly clean and dry. They 
 must be provided with a reliable automatic regulating device, or a competent 
 person must be in attendance near the machine whenever it is in operation. In 
 wiring for motive power, the same precautions should be taken as with a 
 current of the same volume and potential for lighting. 
 
 29. The wires leading to motors should be separated at least twelve 
 inches from each other, and must be provided with an approved cut-out switch 
 at the point where they enter the building. The same precautions must be 
 observed in entering the building that are required for lighting circuits. 
 
 TESTING. 
 
 30. All circuits should be tested at least twice a day with a suitable 
 magneto, or other approved device, in order to discover any escapes to ground 
 that may exist. One test should be made in the morning, and another in 
 ample time before starting, to remove any defect, should it be found to exist. 
 The rules for testing should be observed in any separate or isolated plant the 
 same as in Central Stations. 
 
 31. The JSTew England Insurance Exchange reserves the right at any 
 time to add to, change or modify these rules, and to enforce such modifications, 
 changes, etc., as it shall deem necessary for safety; and it will use all 
 reasonable efforts to promptly notify all electric light companies of any change. 
 
 32. The signing of these rules by an electric light company, or persons 
 controlling electric lights, shall be considered a guaranty on their part that 
 they will have the testing performed on their circuits or lines as above required. 
 
INCANDESCENT SYSTEM. 
 
 OUTSIDE WIRES. 
 
 1. All outside overhead wires must be covered with some material of 
 high insulating power, not easily abraded, and they must be firmly secured to 
 properly insulated and substantially built supports. All the wires must have 
 an insulation equal to that of the conducting wires. 
 
 2. All joints must be so made that a perfectly secure and unvarying 
 connection, fully equal to the cross-section of the conducting wire, will be 
 secured and they should be soldered. All joints must be securely wrapped 
 with an approved tape. 
 
 3. Care must be taken that conducting wires are not placed in such 
 position that it would be easy for water, or any liquid, to form cross connection 
 between them, and main conductors or feeders should not approach each other 
 nearer than one foot. 
 
 4. The wires must never be allowed in contact with any substance other 
 than air, and their proper insulating supports. 
 
 5. Conducting wires carried over or attached to buildings, must be at 
 least seven feet above the highest point of flat roofs, and one foot above the 
 ridge of pitch roofs. Lines constructed subsequent to the adoption of these 
 regulations should not be run over and attached to buildings other than those 
 in which the light or power is being, or is to be, used, but should Jbe on 
 separate poles, or structures, where they can be easily reached for inspection. 
 
 G. When they are in proximity to other conducting wires, or any 
 substance likely to divert any portion of the current, dead, insulated guard- irons 
 must be placed so as to prevent any possibility of contact in case of accident to 
 the wires or their supports. The same precautions must be taken where sharp 
 
 (91) 
 
92 PRACTICAL DYNAMO BUILDING. 
 
 angles occur in the line wires, and also where any wires (telegraph, telephone, 
 or others) could possibly, owing to their position, come in contact with the 
 electric light wires. 
 
 7. Wires from main circuit to main cut-out inside of buildings, must be 
 separated by a distance of not less than six inches, for currents having an 
 electro-motive force of 250 volts or less, and this distance must be increased for 
 currents of higher potential. 
 
 8. They must also be rigidly and neatly run, and must be supported by 
 glass or porcelain insulators, or by rubber hooks. Rubber hooks must be of 
 an approved pattern; i. e., with the rubber insulation free from flaws, and 
 projecting over the hook in cup form. 
 
 9. Service blocks must be protected by at least two coats of water-proof 
 paint over their entire surface ; and, when used to support rubber hooks, must 
 have at least one inch of wood between the inner end of the hook and the back 
 of the block. 
 
 10. For entering buildings, wires of extra heavy and durable 
 water-proof insulation, protected by an outside covering not easily abraded, 
 must be used from the terminal insulator outside, to the main cut-out inside of 
 the building. They must loop down, so that water may drip off without 
 entering the building, and the holes through which they enter should, where 
 possible, slant upward. If an approved glass insulator for bushing the holes be 
 used the extra heavy insulation will not be required. 
 
 11. Service wires must come in contact with nothing save air, and their 
 insulating supports, except in unavoidable cases, when a wire with an extra 
 heavy insulation, suitable for the purpose, must be used. 
 
 12. The use of porcelain knobs as insulators, except in perfectly dry 
 places, or for the support of a specially insulated wire, will not be accepted, 
 unless of some approved shape. 
 
 TTNDERGROUND SERVICE. 
 
 13. Where underground service conductors, enclosed in a metal tube, 
 enter a building, special care must be taken at the point where the conductors 
 leave the tube, and thence to the main cut-out, to protect them in such a 
 
PRACTICAL DYNAMO BUILDING. 93 
 
 manner that they can not come in contact with each other, nor with the tube, 
 nor be acted upon by falling moisture, nor disturbed by anything being moved 
 against them, etc. 
 
 14. This service must not end in any place where it would be unsafe or 
 undesirable to place a cut-out, but should be continued by means of specially 
 insulated conductors (and a space of ten inches should be maintained between 
 them) to a suitable location. 
 
 INSIDE WIRING. 
 
 15. Copper wire used for incandescent lighting must be procured from 
 manufacturers whose products have been found, by reliable tests, to be at least 
 95 per cent, conductivity. Samples of wire to be used, or in actual use, must 
 be submitted to this Exchange, for tests of conductivity, at any time when 
 required. Samples of wire must also be submitted for tests of insulation, at 
 any time when required. 
 
 For inside work, no wires smaller than "No. 16 " B. & S." or ISTo. 18 
 "B. W. G." will be approved. 
 
 16. Permission will not be granted for the use of the lights unless the 
 wire come fully up to the standard of conductivity, no matter how well the 
 wiring may be done. 
 
 17. All parties, firms or corporations proposing to do construction work 
 or wiring, either outside or inside, must fully satisfy this Exchange of their 
 ability to do the work in a safe and acceptable manner. 
 
 18. Before using any new form of insulation, the approval of this 
 Exchange for its use under the proposed circumstances must be secured. 
 
 19. The use of lead-covered wire, or wire the covering of which 
 contains paraffine, is prohibited. 
 
 20. Mouldings with open grooves laid against the walls or ceilings will 
 not be approved. A wood moulding having a backing of at least one-fourth 
 inch thickness to intervene between the wire and the wall or ceiling of the 
 building, the backing to be protected by at least two coats of water-proof 
 paint, and the moulding of such shape as to protect the wire from moisture, 
 will be approved. 
 
94 PRACTICAL DYNAMO BUILDING. 
 
 21. When wires are run in new buildings, and are to be concealed from 
 view by walls and ceilings, care must be taken to separate them ten inches or 
 more, whenever it be possible to do so, by running them singly on separate 
 timbers, studding, etc. Cleats are not desirable for concealed work. All 
 concealed wires should be supported on insulators, such as porcelain knobs, or 
 other equally good, non-combustible, insulating substance. Wires should, 
 where it be possible, be kept from contact with any part of the building by 
 means of such insulators, rather than to depend upon the insulation covering. 
 Where complete separation from the building by air space and insulators be 
 not possible, an approved insulation covering, that shall be water-proof 
 and non-combustible, will be required. Wires run in non-combustible and 
 water-proof tubes, made of a suitable insulating material, will be approved. 
 
 Care must be taken to keep the wires away from metal pipes and other 
 conductors. Outlet wires should be left in such a way as not to be injured by 
 plasterers. They should not, as a rule, be brought through the same opening 
 with gas-pipes, but must be carefully insulated from them. 
 
 22. Approval will not be given to any work where the wires have been 
 " fished" any great distance. 
 
 23. Moulding must not be used in wet places. 
 
 24. In dye-houses, paper and pulp mills, and other buildings specially 
 liable to moisture, all wires (except when used for pendants) must be separated 
 at least six inches. The wire must be thoroughly and carefully put up, and 
 must be supported by glass or porcelain insulators, or by rubber hooks. 
 
 25. In crossing any metal pipes, or any other conductor, wires must be 
 separated from the same by an air space of at least one-half inch, where 
 possible, and so arranged that they can not come in contact with each other by 
 accident. Wires should go over water-pipes where possible. 
 
 26. Where wires pass through partitions, floors, etc., glass insulators, 
 or an outer covering of hard rubber should be used to protect them. 
 
 27. Wires must never be left exposed to mechanical injury, or to 
 disturbance of any kind. 
 
 28. Metallic staples must never be used ; when staples are used they 
 must be of an approved insulating material. 
 
PRACTICAL DYNAMO BUILDING. 95 
 
 29. None but an approved tubing will be accepted as a durable 
 water-proof insulation. 
 
 30. Wires of the same polarity, but belonging to different circuits, or 
 leading to and from a double-pole switch, must not run in one groove through 
 the same tube, nor in the same slot in a cleat. 
 
 31. Cleats should be made of well-seasoned hardwood (filled to prevent 
 the absorption of moisture), porcelain or other approved material, and so made 
 as to separate the wire at least one-fourth inch from the building. When, 
 secured by cleats not over four feet apart and tightly stretched in the same 
 horizontal plane, wires having a difference of potential of 120 volts or less, 
 should be separated at leaet one and one-half inches ; when they are confined 
 in moulding a half-inch space is sufficient. This rule applies only to small 
 mains, taps, etc., mains carrying currents of large volume should be separated a 
 greater distance. 
 
 32. The dividing strip between grooves in moulding must never be 
 reduced below one-half inch in thickness by cutting out to admit ioints in 
 wires. 
 
 33. Where exposed to acid fumes, vapors of ammonia, etc., wires 
 should be provided with an insulation that will not be injured thereby, and 
 should be put up in the manner described in Rule 24. 
 
 34. All splices in wires must be soldered ; a soldering-bolt should be 
 used for this purpose, if possible. Care must be taken not to render the wire 
 brittle by over-heating. Resin should not be used as a flux. Nothing but an 
 acid solution should be used, and any excess should be washed off before the 
 splice is covered. 
 
 35. The insulation of any joint must be equal to that of the other parts 
 of the same wire. 
 
 SAFETY CUT-OUTS AND SWITCHES. 
 
 36. Every system of conductors must be protected by safety cut-outs 
 that will interrupt the passage through the conductors of a current stronger 
 than they can safely carry. The carrying capacity (in amperes) of a fusible 
 metal must be less than that of the smallest conductor it is designed to protect. 
 
96 PRACTICAL DYNAMO BUILDING. 
 
 Conductors include wire, cord, binding-screws, contact points of switches, 
 sockets, cut-outs, etc. 
 
 Any fuse must melt immediately with any excess of the amperes which 
 it is marked to carry. 
 
 37. A cut-out must be placed where the underground or overhead 
 service joins the inside wires, and at every point where a change is made in 
 the size of the wire (unless the cut-out in the larger wire be intended to protect 
 the smaller) . 
 
 38. Cut-outs, switches, and other devices which occasion a break in the 
 circuit, must be so arranged that leakage of electricity from them is impossible, 
 and should be mounted on non-conbustible material ; must not be put in places 
 liable to become damp; must be protected from rubbish, etc., and should be 
 easy of access. 
 
 39. "Where it be necessary to use cut-outs and switches in damp places, 
 great care must be taken to protect them from moisture, and to use only such 
 as are provided with bases that will not absorb moisture. 
 
 40. When necessary, cut-out devices must be covered 'with some 
 fire-proof and water-repelling material. 
 
 41. All cut-outs must be double-pole. 
 
 42. The plug or other device for enclosing or supporting the fusible 
 strip or wire should be incombustible and moisture-proof, and so constructed 
 that an arc can not be maintained across its terminals by the fusing of its 
 metals. 
 
 43. ~No lead or composition strips carrying more than ten amperes 
 before melting shall be used, unless provided with contact surfaces of some 
 harder metal having perfect electrical connection with the fusible part of the 
 strip. 
 
 44. All switches must have a firm and secured contact that will make 
 and break readily, and that will not stick between "full on" and "off," nor 
 get out of repair easily in other ways. The points of contact must not be 
 allowed to scrape or rub the entire surface of an insulating material between 
 the contact strips an air space must intervene. The carrying capacity of the 
 different parts must be sufficient to prevent heating. 
 
PRACTICAL DYNAMO BUILDING. 97 
 
 45. Where points varying widely in potential are brought near each 
 other by means of cut-outs, or switches, hard rubber, lava or other approved 
 material must be used in the construction of the cut-outs and switches. 
 
 46. Switches should be double-pole, and they must be when the circuits 
 "which they operate are connected to fixtures attached to gas-pipes. 
 
 47. On any combination fixture, no group of lamps requiring a current 
 of seven amperes or over shall be ultimately dependent on one cut-out. 
 
 FIXTURE WORK. 
 
 48. In all cases where wires are concealed within, or attached to 
 fixtures, the latter must be insulated from the gas-pipe by some device 
 approved by this Exchange. An exception to this rule will sometimes be 
 made in the case of a wall gas-bracket wired for one or two lights. 
 
 49. When holes are drilled in fixtures, all burs or fins must be removed 
 from the edge of the holes before the conductors are drawn through. 
 
 50. When wired outside, the conductors used must be so secured as 
 not to be cut or abraded by the pressure of the fastenings or motion of the 
 fixture. 
 
 51. All wire used for fixture work must have an insulation that is 
 durable, and not easily abraded, and must not in any case be smaller than No. 
 18 " B. & S." or No. 20 " B. W. G." 
 
 52. Each fixture must be tested for possible " contact" between wire 
 and fixture, and for " short circuit," before current is turned on. 
 
 53. The tendency to condensation within the pipes or fixtures should be 
 guarded against by sealing the upper end. 
 
 54. No combination fixture with less than one-fourth inch clear space 
 between the inside pipe and the outside casing will be approved. 
 
 PENDANTS AND SOCKETS. 
 
 55. No portion of the lamp-socket exposed to contact with outside 
 objects will be allowed to come into electrical connection with either of the 
 conducting wires. 
 
98 PRACTICAL DYNAMO BUILDING. 
 
 56. Cord pendants must be protected by hard rubber bushing, or 
 something equally good, where they enter the socket. 
 
 57. The use of paraffined insulation for pendants will not be approved. 
 
 58. Key sockets must not be used with wire pendants, unless the wire 
 be composed of strands, i. e., flexible. 
 
 59. When exposed to the weather, or used in wet rooms, care must be 
 taken to keep moisture from the inside of sockets. 
 
 60. The weight of every socket and lamp suspended by a cord must be 
 borne by a ceiling block, rosette, or cleat, and by a knot under the bushing in 
 the socket, in order to take all strain from the joints and binding-screws. 
 
 61. Flexible cord must not be used except for pendants, wiring of 
 fixtures, portable lamps, and "mill work." 
 
 62. The two conductors of flexible cord must not have an insulation 
 composed of an inflammable water-proof compound between them, but should 
 be separated by a fibre insulation, or the like. If a water-proof insulation be 
 necessary, it must be placed outside the two conductors, and must in all cases 
 be covered with a non-inflammable outside coating, to prevent cord from 
 carrying fire. 
 
 DYNAMOS AND MOTORS. 
 
 63. They must be located in dry places, not exposed to flyings of 
 combustible material, and must be insulated upon dry wood, filled to prevent 
 absorption of moisture. They must be kept thoroughly clean and dry. They 
 must be self -regulating, or a competent person must be in attendance near the 
 machine whenever it be in operation. In wiring for motive power, the same 
 precautions should be taken as with a current of the same volume and potential 
 for lighting. The motor (and resistance box) should be protected by a cut-out 
 and controlled by a switch. 
 
 SECONDARY GENERATORS OR CONVERTERS. 
 
 64. Converters must not be placed inside of any building. They may 
 be placed on the outer walls when in plain sight and easy of access, but must 
 be thoroughly insulated from them. If placed on wooden walls, or the 
 
PRACTICAL DYNAMO BUILDING. 99 
 
 woodwork of stone or brick buildings, the insulation must be fire-proof. 
 When an underground service be used, the converter may be put in any 
 convenient place that is dry and does not open into the interior of the building ; 
 this location must have the approval of the inspector before the current is 
 turned on. 
 
 65. The converter should be enclosed in a metallic or non-combustible 
 case. 
 
 66. If for any reason it become necessary that the primary wires 
 leading to and from the converter should enter a building, they must be kept 
 apart a distance of not less than twelve inches, and the same distance from all 
 other conducting bodies. The insulation of the wire must be of the very best. 
 
 67. Safety fuses must be placed at the junction of all feeders and 
 mains, and at the junction of mains and branches where necessary, also in both 
 the primary and secondary wires of the converter, in such manner as not to 
 be affected by the heating of the coils. Secondary wires, after leaving the 
 converter, will be subject to rules already given for services, inside wiring, etc. 
 
 68. Any provision for grounding the secondary circuit by means of 
 "film cut-out" or other approved automatic device, will be approved. A. 
 permanent ground will not be approved. 
 
 MISCELLANEOUS. 
 
 69. Companies or individuals furnishing electricity from central stations 
 must enter into an agreement with this Exchange, binding themselves to 
 maintain at all times in their stations some approved device to indicate any 
 escape to earth, which may tend to develop leakage to water or gas pipes, or 
 other earth connections within buildings. This approved means of testing 
 shall also apply to separate or isolated plants, where special conditions of 
 moisture exist, or in buildings subject to mechanical changes of piping, etc. 
 
 70. The signing of these Rules and Requirements shall constitute and 
 be considered an agreement on the part of the signer that such approved 
 device or tell-tale shall at all times be employed on their circuits. 
 
 71. The wiring in any building must test free from " grounds " before 
 the current be turned on. This test may be made with a magneto that will 
 
100 PRACTICAL DYNAMO BUILDING. 
 
 ring through a resistance of 10,000 ohms, where currents of less than 200 
 volts potential are used. 
 
 72. All incandescent work should be inspected before being concealed, 
 and notice should be given this Exchange as soon as work be commenced. 
 
 73. The New England Insurance Exchange reserves the right at 
 any time to add to, change or modify these Rules, and to enforce such 
 modifications, changes, etc., as it shall deem necessary for safety; and it will 
 use all reasonable efforts to promptly notify all Electric Light Companies 
 of any change. 
 
 74. Any additional loading of wires, either in a building as a whole, 
 or in any department thereof, without the previous approval of the Exchange, 
 or the inspector, shall be deemed a sufficient cause for the suspension of permits 
 until such approval be secured. (See Form F, Inspector's Certificate.') 
 
 NOTES. 
 
 A certificate for all new work or changes in old work (Form C for Arc. 
 Form F for incandescent) should be signed by the party installing or 
 controlling any apparatus. The certificate should be filed with the Secretary 
 of the Local Board of Fire Underwriters having jurisdiction, if there be 
 such, otherwise with the Secretary of the New England Insurance Exchange, 
 Boston. 
 
 This certificate is relied upon as a guarantee until the work can be 
 inspected. Permits for the use of the light or power may be granted as soon 
 as the certificate be duly filed. 
 
 Concealed work should be inspected before being covered up, and, as a 
 rule, incandescent work generally should be inspected before current be 
 turned on. 
 
 The above Rules and Requirements are jointly adopted by the New 
 England Insurance Exchange, " Associated Factory Mutuals," and Boston 
 Fire Underwriters' Union, and are applicable^ to all Electric Lighting and 
 Power work in New England, exclusive of buildings in the State of New 
 Hampshire not insured by the " Associated Factory Mutuals." 
 
 [Also adopted by the New York State Board.] 
 
NEW YORK BOARD OF FIRE UNDERWRITERS. 
 
 AMENDED STANDARD FOR ELECTRIC EQUIPMENTS, ADOPTED FEBRUARY 
 
 27, 1889. 
 
 CONDUCTORS. 
 
 CAPACITY OF WIRES. 
 
 1. The conducting wires must be of copper and must have a weight 
 per running foot at least equal to that of the wire (or parallel group of wires) 
 constituting the main circuit of the magnetic regulator of the electric lamps 
 (arc lamps), or of the armature of the machine employed, whichever of these 
 be greatest. 
 
 JOINTS OR SPLICES. 
 
 2. All joints on wires must be so made as to secure perfect and durable 
 contacts, which shall always maintain a degree of conductivity at the joint, at 
 least equal to that of the wire generally. 
 
 3. The joint must be so made as in the ordinary "telegraph splice" 
 that it be mechanically secure against motion or displacement, and must then 
 be further electrically connected by solder so applied as to leave no corrosive or 
 otherwise injurious substance on the connection. After joining and soldering, 
 the joint must be covered with insulating material in such a way as to make the 
 insulation of the joint as good as that of the rest of the line. 
 
 4. A joint made by the process of electric welding would be the 
 
 (101) 
 
102 PRACTICAL DYNAMO BUILDING. 
 
 equivalent of one made as indicated above, but no joint depending upon solder 
 for its mechanical integrity, either wholly or in part, will be allowed. 
 
 WIRES EXTERIOR TO BUILDINGS. 
 
 5. Outside wires must be covered with at least two coatings, one of 
 insulating material impervious to water, next to the wire, and the other of some 
 substance fitted to resist abrasion or like mechanical injury, and must be firmly 
 secured to substantial approved insulators, adequately supported. All "tie 
 wires" or those used to secure the conductors to the "insulators" must be 
 themselves covered with water-proof insulating and mechanically resistant 
 material similar to that used on the conductors themselves. 
 
 6. Overhead conducting wires must be supported on poles as far as 
 possible, so that they can be easily reached for inspection, and when this 
 cannot be done, and special permit be granted allowing them to be carried over 
 attached to buildings, they must be supported at least seven feet above the 
 general level of the roof and at least one foot above the ridge of " pitch roofs." 
 
 7. Where wires approach buildings to enter them they should be so 
 located as not to be readily reached by the occupants of such buildings, and in 
 the case of arc light systems must maintain a minimum distance of ten inches 
 and for incandescent systems of six inches except where the wires are carried in 
 conduits. 
 
 8. When these exterior electric light wires are near other conductors of 
 any kind capable of carrying off a part of the current if contact should be 
 made, dead insulated guard-irons must be placed so as to prevent any such 
 contact in case of accident affecting the wires or their supports. 
 
 9. Like precautions must be taken where acute angles occur in the line 
 wires. 
 
 10. Overhead wires from the main circuit or pole lines in the street to 
 the insulators attached to the buildings which they enter, must not be less than 
 ten inches apart for arc wires or six inches for incandescent wires carrying- 
 currents of 250 volts E. M. F. as a maximum. They must be securely and 
 rigidly supported on "insulators' 1 of glass, porcelain or other approved 
 material. 
 
PRACTICAL DYNAMO BUILDING, 103 
 
 WIRES ENTERING BUILDINGS. 
 
 11. Whenever electric light wires enter buildings through their exterior 
 walls the wires must be firmly supported and incased in tubes of non-conducting 
 material not liable to absorb moisture (e. g. porcelain or glass) and so placed 
 as to prevent the entrance of rain water along the wires (e. g. the tubes must 
 slope upward as they pass inward through the wall). 
 
 12. Both the ingoing and return wires should enter the building at the 
 same location, and pass through an approved manual " cut-out box" or switch, 
 which must be placed where it will be easy of access to firemen and the police. 
 
 HIGH POTENTIAL WIRES WITHIN BUILDINGS. 
 
 13. In the interior of buildings wires for arc lights, besides being 
 covered with an insulating covering, such as has already been described, must 
 be in all cases securely attached and supported by insulators which shall keep 
 them out of contact with any wall, partition, ceiling or floor, so as to secure an 
 air space of at least one-quarter inch between the wire and any adjacent wall, 
 partition or floor, and whenever the wires cross or come near to any other 
 wires, pipes or other conductors, the wires must all be rigidly secured and 
 separated from each other or any other conductors by means of some rigid 
 non-conducting material. 
 
 14. Arc wires of opposite polarities (i. e. the incoming and outgoing 
 wires from each lamp or of each circuit) must be kept at a distance not less 
 than eight inches from each other except within the structure of lamps or on 
 switch-boards, cut-out boxes or the like, where a nearer approach is necessary. 
 
 15. In exceptional cases, however, where the wires are so rigidly 
 secured and insulated that contact or connection between them is quite 
 impossible, they may be allowed to approach nearer, (e. g. If each wire or 
 conductor be covered with a thick and undisplaceable insulation, which in turn 
 is covered by a leaden sheath or pipe and then two or more such pipes are 
 inclosed in an iron pipe in such manner that injury to. the lead-covered cables 
 be impossible, this would be an allowable substitute for the eight inches of 
 absolute separation called for in the general rule.) 
 
104 PRACTICAL DYNAMO BUILDING. 
 
 16. Whenever wires are carried through walls, partitions or floors 
 within a building, they must be surrounded by a special rigid insulating tube or 
 casing impervious to water, and must be so attached and supported as to be 
 secure from abrasion or other mechanical injury. 
 
 NOTE. Rubber tubing will not meet the above requirements as an 
 insulation. 
 
 ARC LAMPS. 
 
 17. The exterior frames and other exposed parts of arc lamps must be 
 securely insulated from the electric circuit, and all such lamps must have glass 
 globes surrounding the light and inclosed below, so as to prevent the fall of 
 ignited particles. Where inflammable materials are placed below such lamps 
 the globe must be surrounded by a wire netting capable of keeping the parts of 
 the globe in place if it be fractured in use. 
 
 NOTE. Broken globes must be replaced as soon as practicable by new 
 ones. 
 
 18. In show windows and other places where inflammable materials are 
 displayed and in factories or wood-working establishments where "flyings' 1 
 may be present in the air, each lamp must be provided with " spark arresters." 
 
 19. Each lamp must be provided with a hand-switch and also with an 
 automatic switch which shall shunt the current round the carbons before the arc 
 between them reaches a dangerous length. 
 
LOW POTENTIAL SYSTEMS. 
 
 . 
 
 DIRECT SYSTEMS. 
 
 20. Iii direct incandescent systems, the rules as to the capacity, 
 location and arrangement of conductors are substantially the same as has been 
 already stated, with the following exceptions : 
 
 21. In case the difference of potential at the positive and negative 
 posts of the dynamo or dynamos developing the current is not more than 250 
 volts the positive and negative wires in aerial lines and elsewhere which would 
 otherwise be required to maintain a minimum distance of ten inches, may be 
 brought to within six inches of each other. Also underground conductors may 
 be inclosed both in the same tube, and if rigidly and securely supported, and 
 surrounded by and imbedded in a solid insulating substance, may lie within 
 one-quarter inch of each other. 
 
 22. "When underground-service conductors enter a building care must 
 be taken that they be at once separated to the required distance (see below) 
 and are adequately and permanently insulated from each other and from the 
 pipe in which they were inclosed, if they were inclosed in a metallic pipe or 
 conduit. 
 
 23. They must also be adequately protected from mechanical injury, 
 and must be so located that a cut-out can be safely and conveniently located 
 close to the end of the service pipe or conduit by which they are brought in. 
 
 LOW POTENTIAL WIRES WITHIN BUILDINGS. 
 
 24. In the distribution of the conductors through buildings " concealed 
 work," such as the placing of wires under floors or within partitions, walls or 
 ceilings should be avoided as much as possible. 
 
 (105) 
 
106 PRACTICAL DYNAMO BUILDING. 
 
 25. In perfectly and securely dry localities an approved insulated wire 
 without water-proof covering may be used, provided the wires are not concealed 
 and are supported by cleats or insulators. 
 
 26. Wherever the wires are to be in any way covered up they must be 
 coated with an approved water-proof insulation. 
 
 27. In all cases of concealed work the company proposing to introduce 
 the same will be required to furnish the Board with a detailed diagram of the 
 work, showing the kind and size of wire used at the different branches, with 
 particulars as to the insulation and in what materials embedded, location of 
 cut-outs, switches, etc. The diagram to be signed and sworn to by an officer 
 of the company and filed with the Board for reference. 
 
 28. If wires be embedded in the plaster of walls, ceilings or partitions, 
 they must be separated not less than ten inches from each other, in addition to 
 being insulated as above described. 
 
 29. In buildings in course of construction, terminal wires must be so 
 arranged as to be secure from injury by the plasterers. 
 
 30. Wires insulated as above may be covered by or embedded in 
 mouldings in dry locations, but in breweries, paper-mills, dye-houses, and other 
 like places where they are exposed to moisture, they must be carried out of 
 contact with the walls, ceilings and the like on approved " insulators." 
 
 SECONDARY SYSTEMS. 
 
 31. In these systems where alternating currents of high electro-motive 
 force are used on the main lines, and secondary currents of low electro-motive 
 force are developed in local "converters" or "transformers," it is important 
 that the entire primary circuit and the transformers should be excluded from 
 any insured building, and be confined to the aerial line (the transformers being 
 attached to the poles or the exterior of the buildings) or to underground 
 conduits, if such be used, or placed in fire-proof vaults or exterior buildings. 
 
 32. In those cases, however, where it may not be possible to exclude 
 the transformers and entire primary from the building, the following precautions 
 must be strictly observed. 
 
PRACTICAL DYNAMO BUILDING. 107 
 
 33. The transformer must be constructed with or inclosed in a 
 fire-proof or incombustible case, and located at a point as nearly as possible 
 to that at which the primary wires enter the building. Between these points 
 the conductors must be heavily insulated with a coating of approved 
 water-proof material, and, in addition, must be so covered in and protected 
 that mechanical injury to them, or contact with them, shall be practically 
 impossible. 
 
 34. These primary conductors, if within a building, must also be 
 furnished with a double-pole switch, or separate switches on the ingoing and 
 return wires and also with automatic double-pole cut-out where they enter the 
 building or where they leave the main line, on the pole or in the conduit. The 
 switches above referred to should, if possible, be inclosed in secure and 
 fire-proof boxes outside the building. 
 
 35. In the case of isolated plants using the secondary system, the 
 transformers must be placed as near to the dynamos as possible, and all primary 
 wires must be protected in the same manner as is indicated in the second 
 paragraph above. 
 
 INSULATION". 
 
 36. Where there ia a possible exposure to water, the first or second 
 coating must be impervious to the fluid. 
 
 37. For incandescent lamp fixtures and electroliers, exceptions may be 
 made to the foregoing rule in which the wires can be placed nearer than the 
 prescribed distance to each other, or to other conductors, provided the fixture 
 is fully insulated at the base from house and ground piping, and further 
 provided that a double-pole safety catch is placed at the base of each fixture, 
 or at the nearest branch connection, as may be required by the Inspector of 
 the Board. 
 
 38. In all cases when combination (gas and electric) fixtures are used, 
 extra precaution must be used to secure complete and continuous insulation 
 from the gas piping. 
 
108 PRACTICAL DYNAMO BUILDING. 
 
 INSULATION IN GENERAL. 
 
 39. It is to be understood as a general or universal rule that all 
 machines, lamps, wires and other parts of electric systems, are to be so 
 constructed, mounted and secured as to insure complete and continuous 
 insulation ; with such exceptions only as are hereinbefore stated, and that in 
 no case shall ground circuits be employed, or any part of the system be allowed 
 to come in contact with the earth through gas or water pipes or the like. 
 
 AUTOMATIC SHUNT. 
 
 40. Wherever a current of such high electro-motive force be employed 
 that if concentrated on one lamp or motor of the series it would produce an arc 
 capable of destroying or fusing parts of such lamp, an automatic switch must 
 be introduced in each lamp or motor by which it will be thrown out of circuit 
 before the arc approaches any such dangerous extent. 
 
 41. Means by which those in charge of the dynamo electric machines 
 will be warned of any excessive flow of current, or means whereby the same 
 will be automatically checked, must in all cases be provided. 
 
 FUSIBLE OR OTHER AUTOMATIC CUT-OUTS FOR LOW POTENTIAL CIRCUITS. 
 
 42. Wherever a connection is made between a larger and smaller 
 conductor at the entrance to or within a building, some approved automatic 
 device must be introduced into the circuit of the smaller conductor at or close 
 to its junction, by which it shall be interrupted whenever the current passing 
 is in excess of its safe carrying capacity. 
 
 43. The safe carrying capacity of a wire is the current which it will 
 convey without becoming painfully warm when grasped for a minute in the 
 closed hand. 
 
 CUT-OUT BOXES OR SWITCHES. 
 
 44. All cut-out boxes or switches which shift, transmit, or break a 
 current must be mounted on incombustible bases, and so arranged as to close 
 
PRACTICAL DYNAMO BUILDING. 109 
 
 one circuit before they open another, and operate in such a manner that no arc 
 can be formed between the contact surfaces when thrown " on " or "off." 
 It must be so far positive in its action that it can not stop between its extreme 
 positions. It must indicate on inspection whether current is "on" or off." 
 This rule applies to isolated plants as well as to those connected with central 
 stations. 
 
 MOTORS. 
 
 45. The rules and regulations under the head of capacity of wires, 
 insulation, automatic cut-outs, and switches shall be observed, where electric 
 motors are used, and in addition the motor frames must be properly insulated, 
 and so mounted as to be free from grounds, and each motor shall be provided 
 with an approved switch to prevent an excessive flow of current. 
 
 STORAGE BATTERIES. 
 
 46. When the current for lights or power is taken from storage 
 batteries, the same general regulations are to be observed. 
 
 MEANING OF TECHNICAL TERMS, ETC. 
 
 47. HIGH POTENTIAL CIRCUITS OR WIRES. This term includes all 
 wires arranged with the view of carrying currents of more than 250 volts 
 difference of potential between any two parts of the system, even if such 
 current be used to run incandescent lamps. 
 
 48. Low POTENTIAL CURRENTS OR WIRES are such as do not carry 
 currents of more than 250 volts. 
 
 49. Companies furnishing electricity from central stations must enter 
 into an agreement with the New York Board of Fire Underwriters, binding 
 themselves to test their lines for ground connections at least onee every day 
 (and preferably three times per day), and to report the result of such tests 
 to the Board weekly. 
 
 50. The rules and regulations of the Board of Electrical Control and 
 all existing regulations of the local authorities in reference to stringing of 
 wires must be strictly observed. 
 
HOW THE ELECTRIC CURRENT IS PRODUCED. 
 
 Elsewhere we give some details in regard to how the electric current is 
 produced, but perhaps not in a manner that may be readily comprehended by 
 all. The trouble in describing the operation is in obtaining a level of common 
 understanding, which is very hard to do when there is no common ground to 
 stand on ;-for electricity, in the strict form of comparison, can hardly be likened 
 to any other form of energy. The Electrician several months ago made an 
 ingenious attempt to so simplify and explain the theory of the generation of a 
 current of electricity by mechanical means that it might be understood by any 
 one, no matter how unskilled he was. It is much easier to understand 
 electricity, says the paper in question, when we assume it to be a fluid, than in 
 any other way ; and as the fluid theory answers every purpose, we will assume 
 it to be such, and the machinery for producing the current, merely as a pump 
 for pumping or forcing electricity through the wires and carbons, as water may 
 be forced through a pipe or valve. A pump for forcing water through a pipe 
 consists of a cylinder or barrel, inside of which there is a movable air-tight 
 partition that separates the inside of the cylinder into two parts ; this is called a 
 piston. This piston is connected with a rod which extends outside of the 
 cylinder, and enables the piston to move from the outside. If this piston is 
 moved it draws water in at one end of the cylinder and forces it out at the 
 other; and when valves are properly arranged and pipes attached, the pump is 
 complete. When all the valves, pipes, and chambers are completely filled with 
 water, if the suction and discharge pipes are connected together, and the pump 
 operated, it will pump or force the same water over and over again around a 
 
 (110) 
 
PRACTICAL DYNAMO BUILDING. Ill 
 
 complete circuit. If a valve is placed in a pipe and partially closed j it will be 
 found that much more power is required to work the pump. Where does all 
 this power go? It is expended in friction in passing the partly closed valve ; 
 this may be called resistance. Now suppose that a force equal to lifting all the 
 water in the pump and pipes seven hundred and seventy -two feet high were 
 exerted, the friction would heat the water just one degree. If this pumping 
 were continued with sufficient force for an hour or more, the water would boil^ 
 and could be converted into steam ; in fact, all the force exerted on the pump 
 would be converted into heat, which would be confined to the pump and its 
 connections. In this manner mechanical energy is said to be converted into 
 heat. 
 
 Now suppose that we take this same pump and so arrange the valves 
 that we allow steam to enter one end of the cylinder and at the same time allow 
 a free escape at the other end, what is the result? The piston will be moved 
 by the steam until it reaches the extreme end of the cylinder. Now, if we 
 allow the steam to enter the other end, it will push the piston in the other 
 direction to the opposite extremity, and when we have so connected this 
 reciprocating motion, through the agency of a connecting rod and crank to a 
 shaft, that the shaft will be turned by the motion of the piston and make an 
 attachment that will open and close the valves at the proper time, we have 
 constructed a complete steam engine, and this is said to be a machine for 
 converting heat into force, power or dynamic energy. The steam in passing 
 through the engine is cooled down and condensed just in proportion to the 
 work done. 
 
 It is therefore shown that a mechanical force applied or exerted in 
 moving a piston in a cylinder can be made to circulate a current of fluid 
 through pipes, and that the fluid is heated just in proportion to the work or 
 force exerted. Conversely, a current or a fluid in a pipe may be made to 
 move a piston, and this piston made to give off force or power and the fluid 
 cooled just in proportion to the work or power developed. 
 
 So with electricity. If a strong magnet is moved inside a coil of 
 insulated wire it produces a current of electricity in the wire composing such 
 coils, very much in the same manner that the moving of a piston in a pump 
 
112 PRACTICAL DYNAMO BUILDING. 
 
 cylinder produces a current of water in the pipes, which may be regarded as an 
 extension of the cylinder. It is also found that it requires power to move a 
 magnet inside of a coil of wire, and that this power bears a certain relation to 
 the current of electricity produced, and also that if there is placed a resistance 
 in the wire to correspond to the valve in the water pipes, that this resistance 
 becomes heated, also that the heat represents the same amount of force that 
 the heat in the water did. This is called a machine for converting dynamic 
 energy into electrical energy. If, now, we connect the wires of the above coil 
 with a battery and allow a current of electricity to pass through the wire, the 
 magnet will be drawn into the coil with considerable force, but only while the 
 current is passing, and it will also be found that the work done by this pulling 
 of the magnet has weakened the flow of electricity in the coil just in proportion 
 to the work done. When this magnet is properly connected to a rotating shaft 
 by the agency of a connecting rod and crank, and is provided with a suitable 
 attachment that will let on and shut off the flow of electricity at the proper 
 time, we have an electrical engine, and this is said to be a machine for 
 converting electrical energy into dynamic energy. It is, therefore, shown 
 that the moving of a magnet in an insulated coil produces a current of 
 electricity in such coil, that force is required to move the magnet, and that 
 this force or power is converted into a relative amount of electrical current 
 or energy ; conversely, that a current of electricity may be made to move a 
 magnet and develop power, and the power so developed represents a certain 
 and definite amount of electrical energy. It is not, however, necessary to 
 move a magnet in a coil of wire to produce a current of electricity. The coil 
 may be moved on the magnet, or the magnetism may be moved in the magnet, 
 or the polarity of the magnet may be changed from north to south and vice 
 versa. Indeed, any disturbance, movement, strengthening, weakening or 
 change whatsoever in the magnet produces a current in the wire about it, the 
 strength of which depends upon the degree and rapidity of such change or 
 motion. When a piece of soft iron is brought near a strong magnet it, too, 
 becomes a magnet. If, for instance, a common nail has its point brought near 
 the north pole of a magnet, the head of the nail will at once become a north 
 pole and its point a south pole. If the position of the nail is reversed, the 
 
PRACTICAL DYNAMO BUILDING. 113 
 
 magnetism will remain the same as relates to the magnet, but not to the nail. 
 The nail may be said to have turned round on its magnetism. If, now, this 
 nail should have a small shaft passed through perpendicular to its axis, and 
 mounted so as to be revolved with rapidity while in this position, the magnetism 
 in the nail would change at each turn, the end nearest the magnet always being 
 a south pole. This is called a change in polarity. If on this nail a fine coil 
 of insulated wire be placed, and the outside and inside ends connected together, 
 a strong pulsation of electricity will take place in the wire of the coil at each 
 half-turn. When the ends of the wire are separated and brought down to 
 the shaft, so that the current may be taken off through a commutator to a 
 stationary conductor, we have a complete magneto -electric machine, which has 
 only to be enlarged to produce an electric light. 
 
 The effect would be very much heightened, however, if the nail were 
 bent in the form of a ring with a shaft secured into it, like the shaft in a 
 wheelbarrow wheel, and the coil divided up into twenty or more sections, each 
 section ending in an independent copper strip in the commutator. Another 
 improvement would result from revolving it between two magnets of opposite 
 polarity, or between the opposite poles of a horse-shoe magnet. The chance 
 for enlargement on this basis will be obvious. Machines embodying this 
 principle have been carried to a great degree of perfection. "While the 
 machine is not in motion, we may consider all the w r ires in or about it to 
 be full of electricity, as a pump and its pipes may be full of water. When 
 starting on the first turn of the armature a slight current is produced by the 
 induction from the residuary magnetism. The current of electricity may be 
 said to draw or suck in through the bottom brush into the armature, where 
 it divides into two equal currents, one passing up on one side while the other 
 passes up on the opposite side and against the motion. The impelling or 
 pushing forward of the current all takes place in the armature, the two 
 currents induced in the armature unite on the top side and escape through 
 the commutator to the top brush ; from here it passes through one of the 
 electro-magnets, and from thence to the lamp, where the friction or resistance 
 offered to it in passing the space filled only with gaseous matter between the 
 two carbons is so great that an enormous degree of heat is produced. With 
 
114 PRACTICAL DYNAMO BUILDING. 
 
 a current of water, the heat would be taken along with the water j but with 
 electricity it is left at the point of friction, and communicating with the 
 carbon points, heats them to a degree unknown to any other agency ; the 
 heated points of the carbons are the source of the light. After passing 
 through the lamp, the current is taken back to the machine, where it goes 
 through the wire of the other electro-magnet and to the bottom brush, this 
 completing the circuit. These machines require power to drive them just in 
 proportion to the electricity produced, and are called dynamo-magneto-electro 
 machines, as they convert dynamic energy into electrical energy by the agency 
 of magnets. 
 
 It is a very common error to confound the current of electricity produced 
 by a magneto machine with that produced by the common friction or plate 
 machine. The plate machine produces a current of electricity of very great 
 tension, but there is very little of it. It may be compared to a discharge of 
 water from a pipe the size of the finest hair, but under a pressure of many 
 millions of pounds per square inch ; while the current produced by a magneto 
 machine may be compared to the discharge of water from a pipe ten feet in 
 diameter and under a very low pressure. A current of electricity, like a current 
 of water, has both quantity and pressure ; only the pressure of electricity is 
 called tension, while the rest is electro-motive force when in action. American, 
 Electrical Directory, 1SS5. 
 
HISTORY OF ELECTRICITY AND THE ELECTRIC LIGHT. 
 
 The name "electricity" is derived from elektron, the Greek name for 
 amber. The ancients were well acquainted with the fact that certain bodies, 
 when rubbed, acquire the power of attracting light particles of matter. 
 Thales, of Miletus, the founder of the Ionic philosophy, and one of the seven 
 wise men of Greece, who flourished some six hundred years before the Christian 
 era, developed this attractive property in amber by friction, and concluded that 
 the substance was animated by an unknown spirit or element. Theophrastus, 
 some time later, observed the same attractive property in a crystal termed the 
 lyncurium, now supposed to be tourmaline. Pliny and other naturalists refer 
 to the attractive power of amber as something well known, but say nothing to 
 lead us to suppose that the knowledge of electrical phenomena went beyond 
 the discoveries of the old philosophers. The first attempt towards a 
 generalization of electrical phenomena was made near the close of the 
 sixteenth century, by Dr. William Gilbert, physician to Queen Elizabeth, of 
 England, in a treatise on the magnet. 
 
 The earlier electricians, in the prosecution of their researches, used 
 simple glass tubes, or rods of sulphur, which were held in the hand and excited 
 by friction with silk or flannel. The first idea of a machine originated with 
 the celebrated Otto von Guericke, of Madgeburg, Germany, who mounted a 
 globe of brimstone on an axis and caused it to revolve rapidly against the palm 
 of the hand. This was in 1660. He was the first to notice a peculiar light, or 
 rather a phosphorescent glow, as one of the effects of this friction. For the 
 globe of brimstone, Dr. Hawksbee, of England, afterwards substituted a globe 
 of glass ; and Professor Winkler, of Leipsic, rendered the instrument much 
 
 (115) 
 
116 PRACTICAL DYNAMO BUILDING. 
 
 more useful and convenient by affixing a cushion of soft leather stuffed with 
 horse-hair, so that, by the pressure of a spring, it might rub against the 
 revolving globe. Later on, a hollow cylinder or a plate of glass came into 
 general use for lecture room experiment in electricity. 
 
 The peculiar glow seen by Von Guericke was some years afterwards (in 
 1680) more closely observed and described by an Englishman, Dr. Wall, who 
 obtained electricity by rubbing a stick of amber with a woolen cloth. While 
 grasping the amber strongly during friction, he heard a number of little 
 " cracklings," as he quaintly called them, which were accompanied by flashes 
 of light. This light and these discharges, says the doctor, " resemble thunder 
 and lightning." Boyle, Newton and others, accumulated many new facts, but 
 these were not of a nature to lead to the discovery of general principles. The 
 electric spark, it appears, was first noticed by Dr. Wall. In the early part of 
 the eighteenth century, Dr. Ilawksbee made many electrical experiments, and 
 besides ascertaining that glass w r as a substance which could be readily electrified 
 by friction, found that some other bodies, especially metals, treated in the same 
 manner, manifested no electrical power whatever. In 1728, Mr. Stephen Grey, 
 a pensioner at the Charter House, England, performed a number of experiments 
 which led to the discovery of electrical conduction, and to the classification of 
 bodies into conductors and non-conductors. 
 
 The conclusions arrived at by Grey were firmly established by the 
 brilliant researches of Du Fay, a French philosopher, to whom we are indebted 
 for the discovery that there are two opposite states of electrical excitation, 
 in which forces are developed attractive to each other. In 1745 and 1716 
 numerous attempts were made to confine electricity in glass vessels containing 
 water or mercury (here we may see the first idea of the storage battery) ; 
 and, almost simultaneously, Yon Kleist, in Germany, and Cunaeus, in 
 Holland, became acquainted with the disagreeable effects of the electric 
 shock. Muschenbrock, of Leyden, repeated the experiments of Cunaeus, 
 and published a wonderful report of the effects of the shock received from 
 the apparatus which is still known as the Leyden jar. The discoveries of 
 Franklin followed soon after and greatly advanced the science of electricity. 
 By a series of beautiful experiments with a common kite this celebrated 
 
PRACTICAL DYNAMO BUILDING. 117 
 
 philosopher ascertained, what had been before conjectured, that lightning was 
 an electrical phenomenon. Cavendish, of England, afterwards entered with 
 great zeal into the field of electrical research and thoroughly investigated the 
 conditions of bodies charged with electricity. 
 
 About the year 1789, Galvani, of Bologne, Italy, discovered that the 
 mere contact of metals with the muscles and nerves of a frog recently killed 
 produced convulsive motions; and by repeating Galvani' s experiments, the 
 celebrated Alexander Yolta, a professor of natural philosophy in the University 
 of Pavia, Italy, was led to the discovery of the apparatus now known as the 
 "Voltaic pile, a discovery which gave rise to a new branch of electrical science 
 which is termed galvanism, or more correctly, voltaic electricity. It was in 
 March of the year 1780 that Prof. Yolta announced to Sir Joseph Banks, 
 President of the Royal Society of Great Britain, the construction of his first 
 pile. That date may well be said to be the most memorable in the annals of 
 science, for it marks the beginning of an era of unparalleled activity, discovery 
 and invention. Humphrey Davy, then a young man of twenty-two years, was 
 just beginning to attract public notice. 
 
 In February, 1801, he obtained the appointment of assistant lecturer 
 in the recently founded Royal Institution. His first thoughts were naturally 
 for his favorite subject, and he eagerly applied the new source of power to 
 the investigation of the properties of the elements. In the course of his 
 experiments he made some important discoveries, one being the obtaining 
 from caustic potash, by powerful battery current, the metal potassium, and a 
 few days later he reduced, by a similar process, sodium from its hydrate soda. 
 In 1808, through the liberality of a few members of the Royal Institution, 
 Davy was enabled to construct a new battery consisting of 2,000 cells (the 
 batteries previously in the Institution combined being only 500 cells), arranged 
 in two hundred porcelain troughs, one of which may still be seen at the Royal 
 Institution. The fluid was a mixture of sixty parts of water with one of 
 nitric and of sulphuric acid. The plates were zinc and copper, square in form 
 and thirty-two inches in surface. Such was the battery from which the first 
 flashes of the electric light were obtained. 
 
 It is not difficult to believe that the effects were "brilliant and 
 
118 PRACTICAL DYNAMO BUILDING. 
 
 impressive." Sir Humphrey Davy himself has left a brief description of his 
 celebrated experiment, which was made before the members of the Royal 
 Institution in 1810. "When pieces of charcoal," says he, "about an inch 
 long- and one-sixth of an inch in diameter were brought near each other 
 (within the thirtieth or fortieth of an inch), a bright spark was produced, 
 and more than half the volume of the charcoal became ignited to whiteness ; 
 and, by withdrawing the points from each other, a constant discharge took 
 place through the heated air in a space equal at least to four inches, producing- 
 a most brilliant ascending arch of light, broad and conical in form in the 
 middle." The carbons used by Davy were pencils of common charcoal. As 
 such they must have wasted away rapidly, and, no regulating apparatus 
 having been devised for adjusting the distance between them, the light must 
 necessarily have been of short duration. In fact, it remained for thirty-four 
 years a brilliant but sterile laboratory experiment. 
 
 It was not until 1844 that Leon Foucault replaced the soft friable 
 charcoal by the hard, compact carbon found in gas retorts, and availing himself 
 of the newly invented and powerful battery of Prof. Bunsen, succeeded in 
 producing a steady, continuous light. It was publicly exhibited in Paris by 
 M. Deleuil, and now its fitness was recognized by illuminating public works, 
 squares, theatres, and lighthouses. Foucault found it serviceable even for 
 photographic purposes. Its general introduction was, however, retarded by 
 the inconveniences attending the manipulation of powerful galvanic batteries,. 
 such as the labor of charging and discharging, the weakening of the current, 
 and the evolution of deleterious gases ; indeed, it may be questioned whether 
 (says Mr. M. F. O'Reilly, from whose graphic account of the discovery of 
 " The Voltaic Arc," forming the third of the papers in the first section of Vol. 
 I of Dredge's excellent work on "Electric Illumination," the foregoing facts 
 of this sketch commencing with Yolta's discovery, are taken), without the 
 development of Faraday's grand discovery of magneto induction, it would 
 ever have become a grand commercial success. 
 
 The first really practical application of electric light was made in 1846. 
 An electric sun shone in the opera of " The Prophet" in Paris. Towards the 
 close of 1847, Mr. "W. E. Staite gave a public exhibition of the electric light 
 
PRACTICAL DYNAMO BUILDING. 119 
 
 at Sunderland, England, this being the first public exhibition of the kind given 
 in that country. During four years Mr. Staite exhibited his light in various 
 cities of England. In 1852 the Dock Commissioners of Liverpool built a high 
 tower for the purpose of placing an electric light upon it, but Mr. Staite died 
 in that year and his idea seemed to have died with him. Two Frenchmen 
 Lacassagne and Thiers took out a patent for a new regulator in 1855. In 
 this system the carbon rested on a column of mercury, which lifted it by a 
 special mechanism as combustion progressed. They lighted the Quai des 
 Celestins at Lyons, in June, 1855, and the papers of the period were very 
 enthusiastic in their descriptions of the peculiar effects of the dazzling light. 
 The great difficulty experienced at this time consisted in the means for 
 producing electricity. 
 
 In point of fact, the reason why inventors of the early period were 
 baffled, despite their ingenuity, was because they had no cheap and practical 
 mode of generating the current necessary for the production of light, and 
 were obliged to obtain their power from batteries. "Yet even in this 
 direction," says Mr. James Dredge in his preface to " Electric Illuminations," 
 "something had been effected. A great deal of very suggestive work was 
 done in view of utilizing battery currents to generate motive power ; whereas, 
 the very machines constructed for this purpose would have converted 
 mechanical energy into electricity. Thus Elias, in 1844, did not dream of 
 generating currents, but only of utilizing them, although the motor he devised 
 might have been available for the former far more useful purpose. Pacinotti, 
 again, devised his celebrated machine rather as a motor than as a generator 
 of electricity. 
 
 "It is a fact, however, that the idea of converting mechanical into 
 electrical energy occupied the minds of inventors at quite an early date ; thus, 
 King and Poole, in 1846, Dujardin in 1847, Henley in 1849, and many others, 
 realized the possibility of generating useful currents by making coils revolve 
 in close proximity to permanent magnets. Most of these inventions were 
 imitations, more or less close, of Pixii and his followers, Clarke, Saxton, 
 Page and Stohrer, and it was not until 1854 that we find any record of an 
 entirely new departure. In that year Soren Hjorth patented a generator in 
 
120 PRACTICAL DYNAMO BUILDING. 
 
 which the principle of augmenting the power of electric currents by the 
 reaction of electro-magnets upon each other is described so clearly that it 
 is evident the inventor appreciated the value of the dynamic principle, and 
 thus anticipated by about thirteen years the practically simultaneous discoveries 
 of Varley, AVheatstone and Siemens." 
 
 "With this brilliant exception, and that of another inventor, who in 
 1858 also proposed "to employ the electro-magnet in obtaining induced 
 electricity which supplies wholly or partially the electricity necessary for 
 polarizing the electric magnets, which electricity would otherwise be required 
 to be obtained from batteries and other known sources," inventors confined 
 themselves for the next ten years to the perfection of magneto-electric 
 machines. It will be seen from the necessarily brief accounts here given 
 that most of the early attempts, however ingenious, at mechanical productions 
 of electric currents, proved unpractical ; some few bearing the stamp of genius 
 are clearly anticipatory of later and successful developments ; others, again, 
 dating from this early period, have steadily developed into the practical types 
 of to-day. But, with few exceptions, the interest attaching to the inventions 
 and propositions prior to 1870 is mainly historical. With that date, however, 
 the problem of producing electrical currents by mechanical means enters a 
 new phase, and with the first patent of Gramme this branch of science 
 commences a fresh epoch. 
 
 The honor of devising a practical generator, yielding absolutely 
 continuous currents, belongs, without doubt, to M. Zenobie Theophile 
 Gramme, of Paris. His first patent was taken out in 1870; and his first 
 machine was submitted to the Academy of Science in July, 1871, when it 
 elicited warm commendations from the members of that learned body. 
 Adopting the sof.t iron ring of Paciriotti, he wrapped around it consecutive 
 lengths of insulated wire, thus forming a number of short distinct coils. 
 The ends of these were brought out and formed into one circuit, by joining 
 with metallic sectors, which were themselves connected with the novel 
 commuting arrangements of the machine. Gramme afterwards made several 
 improvements on his original machine, but it would be impossible to give 
 their details in this sketch in a way to be generally understood. 
 
PRACTICAL DYNAMO BUILDING. 121 
 
 Suffice it to say, that from this new departure of Gramme has directly 
 sprung our present methods of producing electricity at a cost, even now, 
 below the price for which the same quantity of light from gas can be furnished 
 the public. Thus we see that while machines furnished with permanent steel 
 magnets succeeded chemical batteries for the production of electric light, these 
 in their turn were succeeded by machines (now generally known as dynamos) , 
 containing electro-magnets of soft iron, which have been found to be capable 
 of holding twenty times as much magnetism as permanent magnets. The 
 accumulation of electricity by means of a dynamo machine is based upon two 
 principles : 
 
 First. That when a wire is moved across a magnet through a space 
 surrounding the magnet, and known as " the field of force," the power exerted 
 against the attraction of the magnet is converted into electricity. 
 
 Second. When an electric current is passed through insulated wires, 
 coiled around a piece of iron, the iron is magnetized. 
 
 In treating of the subsequent discoveries of Siemens and Wheatstone, 
 Prof. Tyndall, in a discourse delivered at the Royal Institution of Great 
 Britain, January 17th, 1879, said: " On the 4th of February, 1867, a paper 
 was received by the Royal Society from Mr. William Siemens, bearing the title, 
 ' On the Conversion of Dynamic into Electrical Force without the use of 
 Permanent Magnetism.' On the 14th of February, a paper from Sir Charles 
 Wheatstone was received, bearing the title, i On the Augmentation of the 
 Power of a Magnet by the Reaction Thereon of Currents Induced by the 
 Magnet Itself.' Both papers, which dealt with the same discovery and which 
 were illustrated by experiments, were read upon the same night, viz., the 14th 
 of February. The whole field of science hardly furnishes a more beautiful 
 example of the interaction of natural forces than that set forth in these two 
 papers. You can hardly find a bit of iron you can hardly pick up an 
 old horse-shoe, for example that does not possess a trace of permanent 
 magnetism; and from such small beginnings Siemens and Wheatstone have 
 taught us to rise by a series of interactions between magnet and armature to a 
 magnetic intensity previously unapproached . Conceive the Siemens armature 
 placed between the poles of a suitable electro-magnet. Suppose the latter to 
 
122 PRACTICAL DYNAMO BUILDING. 
 
 possess at starting the faintest trace of magnetism ; when the armature rotates 
 currents of infinitesimal strength are generated in its coil. Let the ends of 
 the coil be connected with the wire surrounding the electro-magnet. The 
 infinitesimal current generated in the armature will then circulate round the 
 magnet augmenting its intensity by an infinitesimal amount. The strengthened 
 magnet instantly reacts upon the coil which feeds it, producing a current of 
 greater strength. This current again passes around the magnet, which 
 immediately brings its enhanced power to bear upon the coil. By this play of 
 mutual give and take between magnet and armature the strength of the former 
 is raised in a very brief interval from almost nothing to complete magnetic 
 saturation. Such a magnet and armature are able to produce currents of 
 extraordinary power ; and if an electric lamp be introduced into the common 
 circuit of magnet and armature, we can readily obtain a most powerful light. 
 By this discovery, then, we are enabled to avoid the trouble and expense 
 involved in the employment of permanent magnets ; we are also enabled to 
 drop the exciting magneto-electric machine, and the duplication of electric 
 magnets. By it, in short, the electric generator is so far simplified and reduced 
 in cost as to enable electricity to enter the lists as the rival of our present 
 means of illumination." 
 
 Since the discoveries of Siemens and Wheatstone there have been many 
 improvements made in dynamo -electric generators, and the number of different 
 inventions made is very large. In Europe the number is far greater than 
 here. In America the best know are the Brush, Edison, Excelsior, Fuller, 
 Heisler, Jenney, Maxim, Sperry, Thomson-Houston, Van Depoele and 
 Weston. 
 
 In the line of conductors for arc lamps great progress has been made. 
 It is not more than eight or nine years since the separation of generator and 
 light was made to any extent, 150 to 200 yards being the maximum. But 
 gradually the divisibility of the electric light in separating the lamps fed 
 from the same generator, resulted in the necessary consequence of extending 
 the radius of operations of one installation, and consequently the length of 
 the conductors became more and more extended. This led to a search for 
 the best and most available material for conductors and silver was found to 
 
PRACTICAL DYNAMO BUILDING 123 
 
 be the best. Its cost, however, precluded its use, and copper the next 
 metal in conductibility was selected. The size of the copper wires or 
 conductors is varied according 1 to the kind of electric light supplied through 
 them. The conductors for the incandescent system must be comparatively 
 large, for the volume of electricity is greater in it than in the arc system. 
 
 The arc lights, which require a more intense current, do not need so 
 large conductors, though some require or use larger wires than others. These 
 arc light wires are carefully covered with an insulating material to prevent 
 the current from being deflected from its intended course. There are various 
 substances used in coating or insulating conductors, among them being 
 gutta-percha, rubber, asphaltum, etc. 
 
 Perhaps it may not be out of place here to state that the first 
 fundamental law of electric currents is that discovered by Dr. G. S. Ohm, 
 and known as Ohm's law. It sums up the two causes which affect the 
 strength of an electric current in the following statement: The strength of 
 a current is directly proportional to the electro-motive force that tends to 
 drive the current through the wires of the circuit and it is inversely 
 proportioned to the resistance which the whole circuit offers to the passage 
 of the current. 
 
 The law may be illustrated in this way: Suppose either a dynamo- 
 electric generator or a battery of voltaic cells be employed to send a current 
 through a long line of wire and a series of lamps which offer a certain 
 considerable resistance to the flow ; to keep this flow going in spite of the 
 resistance requires a continued steady pressure, as it were, behind. The name 
 of ' l electro-motive force ' ' is given to this particular power of the generator 
 or battery, by virtue of which it tends to urge electricity through the circuit. 
 If, through the same circuit, it is desired to send a current of double strength, 
 then twice as great an electro-motive force must be applied, and we must do 
 this either by driving our generator at double speed or by using a larger 
 and more powerful generator; or, in the case of a battery, doubling the 
 number of cells. The standard by which electro-motive force is measured is 
 called "one volt;" it corresponds in practice very nearly to the electro- 
 motive force of a single Daniells cell. The dynamo-electric generators in 
 
124 PRACTICAL DYNAMO BUILDING. 
 
 use for electric lights urge the currents forward with electro-motive forces 
 that vary from fifty volts to two hundred volts, according to their construction, 
 etc. Within certain limits the electro-motive force for a machine of given 
 construction is proportional to the speed at which it is driven. 
 
 The standard hy which electric resistance is measured is, as we have 
 seen, denominated "one Ohm," which is approximately as great a resistance 
 as that offered by about one hundred yards of ordinary telegraph wire. The 
 arc or flame electric lamp may offer, according to circumstances, from one 
 to ten times. 
 
 The resistance of incandescent lamps, such as those of Swan and 
 Edison, ranges from thirty-five ohms in the former to one hundred and thirty 
 ohms in the latter. The unit or standard in which currents of different 
 strength are expressed is the "ampere." An electro-motive force of one 
 volt, when applied to drive electricity through a circuit whose resistance is 
 one ohm, produces therein a current whose strength is one ampere. For 
 producing an arc light the current must not be less than about two amperes, 
 and may be as great as fifty or more amperes. The current in incandescent 
 lamps is usually a little more than one ampere in strength. Ohm's law may 
 be expressed exactly as follows : the strength of the current in amperes is 
 found by dividing the number of volts of electro-motive force by the number 
 of ohms of resistance in the circuit. 
 
 Before electric conductors were perfected the arc lamp was the subject 
 of invention and improvement. The first arc lamp was patented by Thomas 
 Wright, of England, in 1845. In this the electrodes were made in form of 
 discs rotated by clock-work, with the slow continuous motion. In 1847 Mr. 
 W. E. Staite brought out a lamp in which the length of the arc was 
 regulated by mechanical devices. He employed carbon rods as his electrodes, 
 and arranged them vertically one over the other, making the feeding of them 
 dependent on the current traversing the circuit. From this time up to March, 
 187G, when Jablochkoff secured his patent for his electric candle, there were 
 a great number of arc lamps invented in England, France, Germany, Russia 
 and the United States for which patents were obtained. 
 
 The discovery of M. Jablochkoff involved the suppression of all the 
 
PRACTICAL DYNAMO BUILDING. 125 
 
 mechanism then usually employed in ordinary electric lamps. The so-called 
 candle consisted of two carbons fixed parallel to each other, a slight distance 
 apart, and separated by an insulating material which was consumed at the 
 same rate as the carbons themselves. An even consumption of the carbons 
 was secured by alternating the direction of the flow of the current from the 
 generator by reversing its motion. This form of lamp was afterwards 
 improved, but it has not found equal favor with some others. 
 
 In a dynamo machine the magnets, when at rest, are but very feebly 
 magnetized ; but when the armature is revolved it generates an electric 
 current which passes through the wires around the magnets, increasing their 
 strength and enabling them to produce a stronger current in the armature ; 
 and this in turn adds to the strength of the magnets, the armature and the 
 magnets reacting on each other, until the limit of the capacity of the magnet 
 is reached, after several hundred revolutions of the armature. When the 
 motion of the armature is stopped the magnets lose nearly all their magnetism, 
 as soft iron will not retain magnetism like steel. 
 
 Electricity for lighting might be furnished by galvanic batteries, but 
 the cost would amount to twenty-five or thirty times as much as when 
 generated by a dynamo. 
 
 It may be further explained that an electric current, flowing in a 
 circuit of wire, may be regarded as a magnetic whirl in the space surrounding 
 the wire. If, then, by moving the coil of wire past a magnet we set up 
 magnetic whirls in the space surrounding the coil, we set up electric currents 
 in the wires themselves. Dynamo-electric generators are machines for moving 
 coils of wire past poles of magnets, there being special arrangements, first, 
 to procure the setting up of very powerful magnetic whirls around the coils 
 of wire, and, therefore, of very strong electric currents in the wires themselves ; 
 and secondly, to turn all these currents into one direction, so as to flow in 
 one steady stream through the circuit. 
 
 Now, in regard to the relation of electric currents to the work they 
 can do, and to the energy expended in their production, it is laid down as a 
 fundamental principle that to do work of any kind, whether mechanical or 
 electrical, requires the expenditure of an equivalent amount of energy. Just 
 
126 PRACTICAL DYNAMO BUILDING. 
 
 as a steam engine cannot work without using fuel, or a laborer without food, 
 so an electric current cannot go on flowing, nor an electric light keep on 
 shedding its beams, without a supply of energy from somewhere or other. 
 
 Thus, although magnets are used in order to generate currents of 
 electricity in rotating coils of wire, a magnet is not in itself a source of power. 
 It will not do work for us until we have done an equal amount of work on it. 
 "We must pull its keeper away from it before it can pull the keeper back to do 
 work. Then it yields us in its kind. It transmutes our energy into another 
 form of force that can produce either light, power, or heat, according as we 
 desire to utilize it. It is just the same with other forces. An iron weight, for 
 example, is not in itself a source of power. It will not do work for us it 
 will not even drive a clock until we do some work on it. In generating 
 electric currents from electro-magnets in the manner explained, as practiced 
 by all the electric light companies of the day, we (our steam engines) have to 
 supply the necessary energy. We spend this energy in moving something in 
 opposition to a resisting force. This something happens to be a coil of wire, 
 or a combination of such coils. The force in this case happens to be a 
 magnetic force, and the result of the motion happens to be (by the particular 
 arrangements of the coils and magnets) the setting up of magnetic whirls 
 around the wire, or what we otherwise call an electric current in the wire. 
 But it is we (or our engines) that do the work. 
 
 There are two methods of converting electricity into light. The arc 
 light is chiefly due to the glowing of the tips of the carbons, caused by the 
 high temperature produced by the current overcoming the resistance offered by 
 the space between the carbon poles, whereby the energy of the electricity is 
 converted into heat. The carbons are slowly volatilized and partially burned. 
 The intensely heated vapor adds to the illumination ; but the combustion of the 
 burning carbon interferes with the light. The incandescent light is produced 
 by the current overcoming the resistance offered by a filament of carbon and 
 raising it to a temperature sufficient to render it luminous. The immediate 
 destruction of the carbon of the incandescent system is prevented by regulating 
 the quantity of the current and inclosing the carbon in a glass bulb, and 
 exhausting the air, so that it can not burn. Both the arc and incandescent 
 
PRACTICAL DYNAMO BUILDING. 127 
 
 lights are due to the glowing of intensely heated carbon. In the arc light the 
 incandescence is, in a measure, destructive to the carbon ; but with thoroughly 
 homogeneous material in the carbons, and an accurate and sensitive mechanical 
 system of feeding, this waste can be so regulated and anticipated that no 
 aberrations in the illumination in the arc can occur. In the arc light, where 
 the carbon is heated to destruction, the total quantity of light for a given 
 expenditure of electricity is about nine times what it is in an incandescent light 
 working at a commercial rate. 
 
 Sir William Armstrong has found that six horse-powers would supply 
 thirty-seven incandescent lights, giving altogether the illumination of nine 
 hundred and twenty-five candles, while the same power applied to arc lights 
 would give more than six thousand candles. In the arc light the terminals of 
 the carbons are different, the lower carbon consuming to a sharp point, while 
 the upper one is blunt and the end concave. The light emitted from these 
 ends is not alike; the upper carbon having the most heated surface, about 
 nine-tenths of the light is thrown downward below a horizontal plane. This 
 gives the arc light advantages as an illuminant of large halls, parks, streets, 
 factories, etc., where it can be suspended overhead, to manifest advantage in 
 the distribution of the light which can all be utilized. The power of arc lights 
 as generally estimated, is that of the strongest rays which are thrown down at 
 an angle of forty-five degrees, which is about twice the brilliancy of the 
 average light. The temperature of the upper carbon, according to experiments 
 made in France, in 1879, in an electric light, is estimated at six thousand 
 degrees Fahrenheit, and the lower one at four thousand five hundred degrees, 
 but this estimate refers only to the special light experimented with, which used 
 small carbons ; and the general result to-day, in the opinion of electricians 
 is probably greater than the one given above. 
 
 Dr. "W. H. Preece estimates the temperature of the lower or negative 
 carbon to be about 5,702 degrees Fahrenheit, while the upper or positive 
 carbon has a temperature of 7,052 degrees, the arc itself being 8,672 degrees 
 Fahrenheit. This high temperature also furnishes much more light rays from 
 a given amount of heat than a lower temperature would give. Dr. Charles "W. 
 Siemens, in an address delivered before the British Association, in York, 
 
128 PRACTICAL DYNAMO BUILDING. 
 
 England, two years ago, stated " that in a gas burner only one per cent of the 
 calorific energy of combustion produced light, while in the incandescent light 
 it was three and seven-tenths per cent, and in the arc light it amounted to 
 thirty-three per cent." This will give an idea of the relative economy of the 
 three systems. The incandescent light exceeds gas by nearly four to one, while 
 the arc light exceeds gas by thirty times, and the incandescent light by eight 
 times, besides giving a white, clearer and purer light than either gas or electric 
 incandescence. Indeed, the pure white of the electric light, compared with the 
 dim yellow of gas, the ability to distinguish colors, the absence of heat and 
 injurious effect to clothing, pictures, etc., the cleanliness and purity of the air 
 in halls and factories under its use, all tend to make it the most desirable of the 
 artificial illuminants. American Electrical Directory, 1885. 
 
THE INCANDESCENT SYSTEM. 
 
 In Dredge's work on "Electric Illumination" Mr. Conrad "W. Cooke 
 gives the history of the various systems of incandescent lighting. Regarding 
 the Swan system and, incidentally, the Edison, we outline the most salient 
 features. The first published notice of the Swan incandescent lamp, according 
 to Mr. Cooke, appeared in the issue of the Photographic Journal for June, 
 1880, but Mr. Swan had publicly exhibited a carbon filament lamp, which had 
 given excellent results, twelve months before the above named date at the 
 conclusion of a lecture he delivered in Newcastle, Sir William Armstrong 
 having presided at this meeting. It is, therefore, an historical fact that the 
 Swan carbon filament incandescent lamp had been brought to a practical 
 form and was publicly exhibited in the autumn of 1879. 
 
 As an actual fact of much interest, Mr. Swan had been laboring at 
 this work of incandescent lighting for many years, one of the earliest forms 
 he adopted in those comparatively remote days having been a horse-shoe of 
 carbonized paper placed beneath a glass bell which was more or less exhausted 
 of air. The small arch of carbonized paper was about an inch high and half 
 an inch across, the lower ends were clamped to small blocks of carbon and 
 the bell was exhausted as far as possible of air. When an electric current 
 of sufficient strength was passed through this carbon strip it was, owing to 
 its high resistance, brought rapidly to a state of incandescence, but, naturally, 
 such a device had but a very short duration in service. The filament became 
 hotter on the inner than on the outer edge and under this unequal influence 
 began to curl over, rapidly bending more and more until the crown of filament 
 would touch the base of the lamp and break up. This, however, was in the 
 
 (129) 
 
130 PRACTICAL DYNAMO BUILDING. 
 
 early days of Mr. Swan's experiments, which he appears to have abandoned 
 for a considerable time, resuming them, however, with great ardor since 1877. 
 Early in 1879 he realized the fact that, to obtain a durability of carbon 
 filament, it was necessary to maintain it at as high or a higher temperature 
 during the process of exhausting the air from the glass bulb than it would 
 have subsequently to sustain in actual work. 
 
 It was just about this time that Mr. Edison was conducting a remarkable 
 series of parallel experiments with platinum and its alloys, and the results 
 he obtained of the changed physical properties of metal wire, raised to 
 incandescence in vacuo, corresponded strictly to those obtained by Mr. Swan 
 with carbon filaments treated in a similar way. It was on the 19th of June, 
 1879, that Mr. Edison took out his patent in Great Britain for the application 
 of this principle he had discovered, for the manufacture of incandescent electric 
 lamps, with prepared platinum or alloyed platinum luminous loops ; but he, like 
 inventors twenty years before him, abandoned metallic, and availed himself of 
 vegetable filaments. Mr. Swan, on the other hand worked with the latter from 
 the beginning, and the evolution of his system from the first imperfect and 
 rapidly failing horseshoe of carbonized paper, to his permanent metal-like 
 filament of carbonized thread, is an interesting one to follow. In this 
 connection it may be advisable to point out, in the clearest possible manner, the 
 great radical distinction between the Edison lamp and the Swan lamp of the 
 most recent type. Edison insists upon using a "structural carbon," because 
 he says that such carbons alone possess the qualities of the highest possible 
 resistance in a very small bulk, and are capable of resisting the disintegrating 
 effects of intense heat, and the absence of atmospheric pressure. He further 
 says, that by structural carbon he means "a carbon wherein the natural 
 structure, cellular or otherwise, or the original material is preserved unaltered, 
 that is, not modified by any treatment which tends to fill up the cells or porse 
 with unstructural carbon, or to increase its density, or alter its resistance." 
 
 To obtain such carbons, therefore, Mr. Edison is obliged to resort to 
 raw material, such as natural fibre, and now exclusively to bamboo strips, 
 which are subjected to a series of beautiful processes. Mr. Swan's object, on 
 the other hand, is to obtain a material suitable for the carbon filament which 
 
PRACTICAL DYNAMO BUILDING. 131 
 
 shall be as far as possible devoid of structure ; he could not, therefore, make 
 use of any vegetable fibre in its natural state. Paper he quickly found was 
 unsuitable, even when prepared by his special process, and he ultimately 
 adopted cotton thread, which is susceptible to the parchmentizing operation 
 that had enabled him to obtain such promising results with paper prepared in 
 the same manner. Steeping cotton in a solution of sulphuric acid and water 
 until the tissue is destroyed, produces, when properly washed and dried, a 
 horny, homogeneous filament of very considerable strength. To increase the 
 density and uniformity of the filament thus obtained, it is passed between 
 compressing rollers and flattened, so that a somewhat increased area of 
 incandescent surface is thus obtained. From the great practical success 
 attending both the Edison and the Swan systems, it is evident that a 
 " structural" carbon is no more absolutely necessary than is a structureless 
 one ; but this is one of the leading points of difference in the two systems. Mr. 
 Swan made other improvements in his carbons, such as making horse-shoes for 
 his lamps out of cardboard, soaked in dilute sulphuric acid, and washed and 
 dried ; and also by carbonizing vegetable parchments, upon which he took out 
 patents. He also made great improvements in the glass bulbs used by him. 
 
 The Maxim is another of the incandescent lamps, which has points of 
 excellence worthy of notice. In this form of lamp, Mr. Maxim made use of a 
 strip of carbonized paper, which is rendered durable by covering its surface 
 with a hard deposit of carbon. This is effected by heating the filament to 
 incandescence within a closed chamber filled with the vapor of gasoline. The 
 degree of incandescence of a filament varying with the resistance to the 
 current, it follows that the thinner and more imperfect parts of the paper strips 
 become more highly heated than the remainder, and the deposit of carbon on 
 those parts is more active. In this way it is intended to obtain a perfectly 
 homogeneous filament, which shall be durable and at the same time one in 
 which the light shall be uniform. The Maxim lamp appears to fulfill both 
 these requirements to a high degree. 
 
 The Lane-Fox lamp is another which may be of interest to note, as it 
 is the one which Mr. Edison claims is an infringement upon his. It is the 
 invention of Mr. St. George Lane-Fox, an Englishman, and in its present 
 
132 PRACTICAL DYNAMO BUILDING. 
 
 shape represents the latest form of the lamp first described, and patented by 
 him in 1878, which, like the Edison lamp of that date, was intended for 
 metallic incandescence. The filament employed in the improved Lane-Fox 
 lamp is made from grass fibre, preferably that known as French whisk or bass 
 broom, and used in making certain kinds of carpet brushes. The fibre is 
 iirst cleaned by boiling in a strong solution of caustic soda or potash, and 
 the outer skin scraped off. The soda or potash is then boiled out of it, 
 and a number of fibres are stretched round a mold or shape of plumbago, 
 .and are then baked in a plumbago crucible at a white heat. After being 
 baked in this manner, the fibres are furthur carbonized by depositing' carbon 
 upon them from a rich hydrocarbon gas, such as benzole. Instead of 
 employing the electric current in this operation, Mr. Lane-Fox carbonizes 
 his filaments by raising the benzole receptacle to a white heat in a furnace. 
 His light, like the others, is produced in an exhausted glass bulb. 
 
 The Bernstein incandescent lamp was a lamp of low resistance. Its 
 carbon was hollow and presented a large surface for incandescence, hence its 
 property of giving light with a current of very low tension. But it was very 
 frail, and liable at the slightest jar to break, and was not, under the most 
 favorable conditions, of long life. The company controlling this invention 
 after a time adopted the ordinary carbon loop and an approach to the higher 
 resistance of ordinary incandescent lamps was made. 
 
 The Brnsh-Swan incandescent lamp is only an imitation of the English 
 Swan lamp, already mentioned. 
 
 The Crookes incandescent lamp is another variety, which, however, is 
 not known in this country, being in use principally in England. Mr. Crookes, 
 the inventor, may be called the father of the high vacuum in the glass globes 
 used in the incandescent systems, for without his experiments and investigations 
 in this direction, both Edison and the other inventors of incandescent lamps 
 would have found their road to success a far more difficult one than it has 
 been. Crookes lamps are quite largely used in England. For his filaments 
 lie uses a homogeneous structureless cellulose, which he has made or invented. 
 This is produced from cotton dissolved in ammonium cuperate, the material 
 being afterwards deposited in sheets of any thickness desired. The substance 
 
PRACTICAL DYNAMO BUILDING. 133 
 
 is a new and very interesting- product, presenting the appearance of an almost 
 transparent horn-like sheet. This material, after being dried, is cut into 
 threads of uniform cross sections. These are cut to the desired length, and 
 molded into the form of the filaments that may be desired and then carbonized 
 at a high temperature, giving a filament thoroughly homogeneous and of 
 uniform conducting power, not subject to warping or twisting under the 
 action of heat because of the absolute uniformity of substance and absence 
 of fibrous structure, which Edison, as we have shown, at first regarded as a 
 necessary condition of structure for the carbon filament. 
 
 The Stanley and Thompson lamp is the joint invention of William 
 Stanley, Jr., of Englewood, N". J., and Edward P. Thompson, M. E., of 
 ~New York, and it is now manufactured under rights owned by the Union 
 Switch and Signal Company, of Pittsburgh, Pa. The principal part of the 
 invention consists in such a chemical treatment of animal substances that 
 they may be used as the carbonizable material from which the carbon 
 filaments are manufactured, in a dense flexible and elastic condition. It is 
 well known that all forms of animal matter, such as catgut, skin, silk, hoofs 
 of animals, etc., becomes disintegrated into a fine powder during the process 
 of destructive distillation. This is due to the presence of a large quantity 
 of water and nitrogen, which, under the influence of heat, causes a rupture 
 of the natural structure of the material. It is found, however, that by soaking 
 these materials in a solution of soluble carbon compound, such as sugar, 
 starch, etc., in dilute sulphuric acid, for several weeks, the chemical nature 
 of the substance becomes radically different. This mixture of chemicals is 
 not washed away, but the prepared filaments are simply dried and put into 
 the furnace after being wound upon suitable forming blocks. During the 
 heating of the filaments the chemicals slowly continue their action, so that 
 the structure is not only not destroyed, but, also, the pores are filled with all 
 the carbon from the carbon compound which is put into solution in the 
 dilute sulphuric acid. Another important part of the invention is that of 
 being able to carbonize a large number of carbon filaments in a very small 
 space. The prepared filament is wound helically upon a block whose 
 cross-sectional shape is that which it is desired the carbon filament shall be. 
 
134 PRACTICAL DYNAMO BUILDING. 
 
 The two ends are held temporarily by wax and then a ligature, such as 
 ordinary string 1 or cord is wound helically at right angles to the winding of 
 the filament and the ends are tied. This ligature serves to hold the filament 
 upon the block permanently and yet allows the latter to shrink. The 
 shrinkage is allowed to take place also by severing the filament along one 
 end of the forming block. The Stanley and Thompson lamp was among the 
 four standard lamps exhibited at the International Electrical Exhibition at 
 Philadelphia in 1884, and this description is a brief of a valuable paper on 
 the " Chemistry of the Carbon Filament," by Edward P. Thompson, M. E., 
 read at the Philadelphia meeting of the American Institute of Electrical 
 Engineers. American Electrical Directory, (1885). 
 
What are known as secondary currents of electricity were observed at 
 the very beginning of the present century, and almost immediately succeeding 
 the invention of the electric battery by Volta. One of the earliest methods of 
 measuring a current of electricity was by plunging conductors, connected with 
 the terminals of a voltaic battery, into a vessel containing slightly acidulated 
 water, and collecting the gases evolved, whose volume was an indication of the 
 quantity of electricity given off by the battery. Gautherot, a French scientist, 
 discovered as early as 1801, that if the terminals used in the water were of 
 platinum or silver, after the battery had been removed these terminals 
 possessed the property of giving off, from themselves, a feeble current of short 
 duration, if connection were made between the two sides. In 1803, Hitter, of 
 Jena, observed the same phenomenon with the terminals of gold wire, and 
 constructed the first secondary battery by piling a series of golden plates one 
 on top of the other, separated by bits of woolen cloth, wetted in salt water. 
 Inactive itself, this battery, after having been submitted to the action of a 
 voltaic battery whose elements were greater in number than its own, was 
 capable of giving off, during a few seconds, a current in the opposite direction 
 to that of the voltaic battery ; this current received the name of * ' secondary 
 current." 
 
 After the announcement of the discovery the phenomena were 
 investigated and explained correctly by such scientists as Yblta, Marianmi 
 and Becquerel, who demonstrated that this current came from the formation 
 of acid and basic deposits on the metallic discs, caused by the decomposition of 
 the primary current of the salt with which the bits of cloth were soaked. It 
 
 (135) 
 
136 PRACTICAL DYNAMO BUILDING. 
 
 remained, however, for the distinguished Frenchman, Gaston Plante, to fully 
 investigate and make clear the principles governing the phenomena. He 
 commenced his researches in 1855 and investigated with zeal and patience 
 until 1879, when he published the result of his work. He made secondary 
 batteries in many forms and of many metals, and finally concluded that lead 
 was the best material. He took of the sheet lead of commerce two sheets of 
 equal size, each having a tail piece in one corner. Laying one sheet on a table 
 he placed the second over it, with its tail at the opposite end to that of the first 
 sheet, separating the two sheets by strips of hard rubber, so they would not 
 touch. Then he rolled them up into a scroll. This was then placed in a glass 
 vessel, the tail pieces pulled through the cover and the vessel filled with water, 
 slightly acidulated with sulphuric acid, so as to make it a better conductor. 
 When the current from a battery of two or three Bunsen cells was connected 
 with these tail pieces, the water in the battery was decomposed, oxygen going 
 to the positive anode and hydrogen to the negative cathode. As commercial 
 lead has a slight coating of oxide of lead on its surface, this oxide on the anode 
 was made a peroxide by the addition of oxygen, and the oxide coating on the 
 cathode was reduced to metallic lead in fine granular form by the action of 
 hydrogen. By charging his battery, first in one direction, and then, after 
 discharging it, charging it again in the opposite direction, and repeating this 
 for a considerable time, it was found the coatings on the plate grew thicker 
 and thicker, until a point was reached beyond which no additional storage 
 strength could be gained, when the plates were "formed." These plates 
 were capable of holding considerable charges. M. Plante never took out a 
 patent. M. Faure, another Frenchman, conceived the idea of painting the 
 lead plates with a paste made of red oxide of lead, covering them with felt 
 to keep the paste in place, and in that condition putting them in the acidulated 
 water, just as Plante did. He can thus spread on more of a coating than 
 would be formed on the plates by a life-time of charging and recharging. 
 Hence his battery (which he has patented in Europe and America) is 
 proportionately stronger than Plante' s, and has been put to practical use. 
 It is thus evident that the Faure battery is nothing more than the old Plante 
 battery, the claim of its patentee resting solely upon the method of preparing 
 
PRACTICAL DYNAMO BUILDING. 137 
 
 the plates to be charged. Now, we recognize the fact that there is a field for 
 the incandescent as well as for the arc electric light, a field of usefulness 
 broad enough for all, and that possibly the storage batteries may also find 
 a use in the future. Indeed, the progress already made in that direction has 
 been, all things considered, really quite wonderful. But there is still something 
 lacking in it that makes it halt short of success. The truth is, that no matter 
 how desirable the end in view would be for the world at large, the best system 
 of storage that we know of has not got beyond the experimental stage, and 
 even at this stage it is threatened with the complications of law suits. These 
 latter would be against its general adoption, even if it were the perfect, 
 economical system which is claimed for it, for people are not generally prone 
 to purchase law suits if they know it. Besides, it appears from the most 
 careful experiments made, that the loss of electrical energy in the storage and 
 delivery of the current by these secondary batteries range from forty to fifty 
 per cent, which of itself alone would seem to constitute a fatal objection to 
 their use. Mr. "Woodbury says: " The so-called 'storage' of electricity is a 
 subject which is the object of much interest. Electricity alone, of all forms of 
 energy, is used from hand to mouth so that the dynamo must be equal to the 
 greatest demand upon the system at any one instant. All form of electric 
 lights require uniformity in the speed of the dynamo, and the incandescent 
 lights are especially sensitive to variations in the speed, so that it is frequently 
 advisable to have a separate engine solely on that account. Such uniform 
 speed would not be essential for the dynamo used in charging secondary 
 batteries. In a storage battery the electricity is not accumulated in any 
 manner, as is sometimes assumed, but a certain chemical action is produced by 
 passing an electric current through the battery, and later on a counter-chemical 
 action produces electricity, when the battery is discharged. The Faure storage 
 battery consists of sheets of lead, coated with red-lead and covered with sheets 
 of felt. The whole is inclosed in a box, and covered with dilute sulphuric acid. 
 On passing an electric current through the battery, the red-lead on the negative 
 side loses its oxygen, which combines with the red-lead on the positive side, the 
 result being that one coating of red-lead is reduced to pure lead, and the other 
 side changed to peroxide of lead. When the battery is put in use the theory 
 
138 PRACTICAL DYNAMO BUILDING. 
 
 is that this atom of oxygen leaves the peroxide of lead on one side, and rejoins 
 the spongy lead on the other side, producing the secondary current; but 
 difficulty has been experienced from losses due to various kinds of local action 
 in the battery, such as the deposition in the sulphate of lead, and the injury to 
 the sheets of felt ; so that the electricity regained has not been as much as is 
 desired. There are several forms of secondary batteries, all of which are 
 similar in principle ; and one free from the faults due to local action would be 
 a great boon to all users of incandescent lamps, for then the apparatus would 
 be permanent, and its efficiency such as would insure commercial success." 
 
 Such tests of the Faure battery as we have seen reported seem to 
 indicate that a higher efficiency than fifty per cent can not be safely relied 
 upon in practice. That is, only about one half the current expended in 
 charging the battery can be recovered in useful work, and even this efficiency 
 would probably be considered impaired unless the battery were used within a 
 comparatively short time after charging it. Aside from the loss of current, 
 the expense of the battery appears to be quite a serious item. Taking, for 
 instance, the plant at the theatre des Yarietes at Paris, it is stated that two 
 hundred and sixty-five Swan lamps are used and are supplied by about a 
 hundred Faure batteries. The total weight of the batteries it is stated to be 
 fourteen tons, ten tons of which are active material. 
 
 No doubt in certain exceptional cases such batteries will prove 
 extremely useful, but for general use in a system of distribution from central 
 stations, we think the advantages have been largely overestimated. It is 
 true that the conductors for distributing the current may be considerably 
 reduced in size, but the cost of constructing and maintaining the secondary 
 batteries would, in a large measure, make up for this advantage, if not entirely 
 counterbalance it. The advantages claimed by way of reducing the capacity 
 of engines and dynamos has also been considerably overrated. Experience 
 seems to show that no machinery can be relied on for constant use, working 
 anything like twenty-four hours a day. Considerable time must be allowed 
 for making necessary repairs and overhauling machinery, and very reputable 
 mechanical engineers have expressed the opinion that no practical advantage 
 could be gained by running engines and machines more than twelve hours 
 
PRACTICAL DYNAMO BUILDING, 139 
 
 per day, as the increased wear and tear and the liability of accident would 
 counterbalance the saving in the cost of the plant. It is obvious, also, that 
 the introduction of the storage battery largely increases the complication of 
 the system. sTo doubt there would be considerable demand for a really 
 efficient secondary battery for use in places where expense is not a controlling 
 consideration, but we by no means share the sanguine views of those who 
 believe that such a battery would effect a revolution in present methods of 
 lighting. 
 
 It is a fact, nevertheless, that in certain situations and under peculiar 
 conditions the storage system may answer an end that no other form of 
 electricity or electric conversion can as well do. This would be where power 
 was cheap or running to waste, perhaps, though in such a case it might, 
 perhaps, be more economical to build a higher dam, store up the water and 
 convert its force directly into electricity for use as needed. The great 
 objections to the storage system are the great cost of the batteries, the 
 necessity of employing experts to operate them, which is expensive, and the 
 very considerable loss of the primary current in discharging them, and the 
 consequently diminished delivery of the current. Thus there is a great loss 
 both in charging, conversion and in discharging. Another difficulty is that 
 an overcharge of these batteries may destroy them, and. call for a renewal 
 of the plates, which would of course be attended with considerable expense. 
 They have to be very delicately and very skillfully handled or they will soon 
 get out of order. On the whole, therefore, it would seem as if the promise 
 of the storage battery is no nearer fulfillment than it was five years ago. 
 American Electrical Directory, 1885. 
 
THE ECONOMY OF ELECTRIC LIGHTING. 
 
 A few years ago there were very grave doubts in the minds of the 
 majority of people concerning the possibility of really economical lighting by 
 electricity ; it was even said that while the quality and quantity of electric light 
 would leave little to be desired, it could not be produced at a price to compete 
 on favorable terms with gas. At this time such a statement would be 
 immediately recognized as fallacious, for there are very many places where 
 electric energy is sold at a price that puts gas quite in the background as an 
 economical illuminant. A 16 candle power electric incandescent light is the 
 equivalent of a five foot gas jet consuming the average quality of gas. In 
 other words, we can in making a comparison between these two artificial 
 lights reckon 200 electric lamp hours as the equivalent of 1,000 feet of gas. 
 Consequently at the prevailing central station rate of one cent per lamp hour 
 electric lighting costs an amount equivalent to $2 a thousand feet for gas, 
 while it possesses the great advantage of giving out relatively little heat and 
 burning no oxygen out of the air. At the generally prevailing price for gas 
 the two illuminants are so nearly on an equal footing that small accidents of 
 situation are enough to control the question of relative economy. But it is 
 not my purpose to discuss the somewhat worn question of electricity vs. gas, 
 but to call attention to what can be done in the way of domestic lighting by 
 electricity, even when it has to compete with kerosene lamps. It may appear 
 somewhat absurd to take the position that kerosene may in many cases cost as 
 much as, or more than, electric lighting at the usual rates ; nevertheless such 
 is the fact. Of course where one is content with a comparatively small amount 
 of light not at all equivalent to what would be secured by electricity or gas, 
 
 (140) 
 
PRACTICAL DYNAMO BUILDING. 141 
 
 the oil lamp owns no competitor, but if the problem in hand is to light a 
 residence in a thoroughly satisfactory manner the conditions are very much 
 changed. I shall take a concrete case drawn from my own observation, by 
 way of illustration. The field of operations was a 10-room modern house in a 
 suburban town, occupied by half a dozen adults. The lighting throughout 
 was by kerosene lamps, 13 being in regular use, part of them having duplex 
 burners, the other the simple flat wick. During a period covering the latter 
 part of November and the first half of December 52 gallons of oil were 
 consumed in 24 days. The price of oil being 13 cents per gallon, the daily 
 cost of illumination was a small fraction over 32 cents. It may be added that 
 the oil barrel had a lock faucet, so that unwarranted use of oil was prevented. 
 To render the comparison with electric lighting more easy, we may reduce this 
 figure to monthly consumption, and obtain $9.70 as the monthly lighting bill. 
 Not all of the 13 lamps were lighted on every night, but they may be counted 
 as being in regular use. Now what could be done under similar conditions 
 with the incandescent lamp? On a liberal estimate, wiring the house for 15 
 lights would have given an illumination at least equivalent to that obtained by 
 oil. It then appears that incandescent lamps at 64 cents per month would have 
 been actually as cheap as oil, with the additional great advantages of no care, 
 no danger of fire and no pollution of the air. It may be replied, however, 
 that the month taken as the basis of estimate was probably the one requiring 
 the most light, so that there would be a saving in oil during other parts of 
 the year so great as to render the fixed charge for electricity anything but 
 economical. This, of course, is in a measure true, but the number of 
 incandescent lamps was deliberately taken larger than was necessary, to allow 
 of fixed lamps in places where oil lamps are occasionally carried; and, further, 
 64 cents per month is not a specially low rate for incandescent lamps in 
 domestic service. In selling by contract the prices, of course, vary 
 enormously from place to place. A few figures may, however, be of 
 interest, particularly as they relate to small plants such as might be found 
 in towns of very moderate size. In one small city the charge for domestic 
 lighting is 60 cents per lamp per month, the number of lights connected being 
 less than 1,000, on the direct current system, coal being the fuel used at the 
 
142 PRACTICAL DYNAMO BUILDING. 
 
 station. Another direct current plant, having only 500 lights and burning coal 
 obtained at a low rate on account of favorable situation, charges only 20 cents 
 per month for domestic service, provided at least six lights are wired. Still 
 another, situation in a location where coal is about as expensive as in New 
 York City, and furnishing 700 lights, charges for regular use 80 cents per 
 month, and for occasional lamps 50 cents per month. As the class includes 
 all lamps in sleeping apartments, and other rooms not constantly inhabited, 
 the average price would fall to something like 60 cents per month. At contract 
 price, however, low water mark is probably touched in a certain water power 
 plant where the charges for lamps in regular use averaged 30 cents a month, 
 and for those in occasional use, such as mentioned above, are furnished at 12 x /2 
 cents per month. 
 
 Where any considerable number of lamps are used, as in large suburban 
 towns, they can be furnished at a good profit at 50 cents a month for domestic 
 service ; this, however, does not apply to commercial lighting or other cases 
 where lamps are to be used regularly. But for the service we are discussing 
 the price is such as very many companies would be only too glad to get. 
 So much for light supplied by contract. It is tolerably evident from what I 
 have previously said that the difference in cost between oil and electricity 
 for equal service may be merely nominal and not infrequently in favor of 
 electricity. 
 
 Where incandescent lamps are supplied by meter the case is even 
 more favorable. Assuming the standard central station charge of one cent 
 per lamp hour the house above mentioned could unquestionably have been 
 lighted as cheaply by electricity as by oil, for 32 lamp hours per night would 
 t>e quite adequate for the service required; and here the comparison would 
 be a fair one throughout the year as only the electricity used is paid for- 
 Unless in unfavorable situations one cent per lamp hour is a profitable selling 
 price for incandescent lights, and this fact is attested by its being the charge 
 made very frequently by city central stations, and even by small companies 
 doing precisely the kind of work of which we are speaking. As a final 
 contribution to the economy of this particular case we are considering it 
 should be mentioned that the price for gas in the town spoken of was $2.85 
 
PRACTICAL DYNAMO BUILDING. 143 
 
 per thousand feet, which makes it distinctly more expensive than electric 
 lighting at the rate last named. It is far from my purpose to contend that 
 everywhere and under all circumstances electricity is the cheapest illuminant, 
 but I hope that I have successfully shown that in many cases it could replace 
 not only gas but oil lamps without increasing, and even in some places 
 diminishing the cost of illumination. Of course the weak point of the oil 
 lamp, so far as economy is concerned, is the necessity for keeping it burning' 
 when the electric light or even gas would be extinguished. A lamp is not 
 lighted without inconvenience, and therefore in rooms which will be 
 occasionally visited during an evening oil is being constantly consumed 
 where gas gets or incandescent lamps would be turned off. If one wishes 
 to go to the trouble of extinguishing and relighting these lamps a considerable 
 saving might be effected ; but for residences where plenty of light is desired 
 and convenience somewhat consulted, the consumption of oil rises to an 
 amount that gives gas and electricity an excellent chance for competition. 
 
 To sum up, where incandescent lamps can be obtained at one cent per 
 lamp hour, or an equivalent contract price, they will compete on favorable 
 terms not only with gas, but with oil, supposing equal illumination in each 
 case. Aside from this the greater cleanliness and convenience of the 
 incandescent lamps should commend it even where it is slightly at a 
 disadvantage. It is a great pity that more suburban towns do not take 
 advantage of electricity for house to house lighting, particularly since at the 
 price mentioned an electric light plant is in most situations a very good 
 investment. This statement should not be understood as applying to localities 
 where coal is very high, or where from an isolated situation or local 
 circumstances the cost of operation rises to an amount considerably above 
 the general average. Dr. Louis Bell in Electrical World. 
 
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