Electric toy mak- 
 
 Southern Branch 
 of the 
 
 University of California 
 
 Los Angeles 
 
 Form L 1
 
 This book is DUE on the last date stamped below 
 
 J933 
 
 B'orm L-9-15m-
 
 ELECTRIC TQY MAKING FOR 
 AMATEURS 
 
 IXCLri)/N(,' BATTERIES, MAGNETS, MOTORS, 
 
 MISCELLANEOUS TOYS AND DYNAMO 
 
 CONS TR UCTION 
 
 BY 
 T. O' CO NOR SLOANE E.M., A.M., PH.D. 
 
 UTHOR OF 
 
 " Electricity Simplified," " Arithmetic of Electricity,'' etc., etc. 
 
 Jlllnstrateb 
 
 NEW YORK 
 
 MUNN & CO. 
 1899
 
 COPYRIGHT, 1891, BY 
 NORMAN W. HENLEY & CO.
 
 TK 
 991 \ 
 
 S&3 
 
 PREFACE. 
 
 ELECTRIC TOY MAKING is a very comprehensive 
 title, one which may be made to embrace far more 
 ground than this work pretends to cover. In the 
 realms of amateur work of all kinds mechanics, nat- 
 ural science, and even legerdemain or natural magic 
 electricity can be made to play an important part. 
 The methods of applying it to simple constructions, 
 within the reach and scope of amateurs, constitute 
 the theme of this book. The effort has been to pre- 
 sent the reader with a suggestive line of experimenta- 
 tion and construction, and to open a field within 
 which his own ideas can have indefinite scope and 
 extent. It is believed that little in the way of 
 actual toy making can be done outside of the general 
 limits here defined. Thus, as adjuncts to a static 
 electric machine, Holtz or Winshurst, a quantity of
 
 vi PREFACE. 
 
 pieces of apparatus might have been described, but 
 such appliances do not deserve to be called toys in 
 any sense. 
 
 It is hoped that the work will prove fertile in the 
 suggestive sense. Many things are presented which 
 are susceptible of almost any quantity of modifica- 
 tions. The motors have been selected with regard to 
 their variation from the usual type of " reversible 
 dynamo." The simple experiments and construc- 
 tions given under static electricity are made, as far 
 as possible, independent in action, except as far as an 
 induction or spark coil and battery may be needed to 
 operate some of them. 
 
 As a good workman is known by his tools, so is the 
 electrician judged by his battery. The few hints 
 given as to the use of batteries should tend to put 
 the amateur on a proper footing at the all-important 
 foundation and basis of his operations. "With a well- 
 kept battery the neatly constructed apparatus will 
 appear to double advantage, and its effectiveness will 
 be secured. Apparatus is often blamed for the short- 
 comings of the current-generator.
 
 CONTENTS. 
 
 CHAPTER I. 
 BATTERIES. 
 
 Primary Batteries in General Batteries with Electric 
 Light Carbons A Tomato Can Battery Materials for 
 Battery Cells 9 
 
 CHAPTER II. 
 PERMANENT MAGNETS. 
 
 How to Magnetize Steel Bars Rolling Armatures 
 Mahomet's Coffin Magnetic Jack-straws The Magnetic 
 Top The Magnetic Pendulum Mayer's Floating Needles 
 Magnetic Fishes, and the Magnetic Swan, Boat, etc. ... 23 
 
 CHAPTER III. 
 ELECTRO-MAGNETS. 
 
 Construction of Electro-Magnets Magnetizing Coils 
 The Magic Circle Magnetic Hemispheres 37 
 
 CHAPTER IV. 
 ELECTRIC MOTORS. 
 
 Pendulum Coil Motor Recordon Magnet Motor Multi- 
 polar Motor Page's Rotating Armature The Electric 
 Locomotive . 46
 
 viii CONTENTS. 
 
 CHAPTER V. 
 ELECTRIC BELLS. 
 
 The Tolling Bell The Vibrating Bell The Safe Pro- 
 tector 65 
 
 CHAPTER VI. 
 MISCELLANEOUS TOYS. 
 
 The Electric Dancer The Magic Drum The Electric 
 Hammer Electric Insects The Incandescent Lamp 73 
 
 CHAPTER VII. 
 
 SPARK AND INDUCTION COILS, AND ALLIED SUBJECTS. 
 The Spark Coil The Induction Coil Recordon's Induc- 
 tion Coil The Magneto-GeneratorElectric Artillery- 
 Electric Gymnastics Ano-Kato Simple Experiments in 
 Static Electricity 89 
 
 CHAPTER VIII. 
 
 HAND POWER DYNAMO. 
 
 Page 121 
 
 CHAPTER IX. 
 
 MISCELLANEOUS RECEIPTS AND FOHMUL.E. 
 Page 12U
 
 CHAPTEE I. 
 
 BATTERIES. 
 
 PRIMARY BATTERIES IN GENERAL BATTERIES WITH 
 ELECTRIC LIGHT CARBONS A TOMATO CAN BAT- 
 TERY MATERIALS FOR BATTERY CELLS. 
 Primary Batteries in General. 
 
 THE requirements of a good battery are easier stated 
 than secured. It should be constant, of low resist- 
 ance, and of good electro-motive force. The latter 
 factor should not fall below one volt. For this reason 
 the caustic soda batteries are hardly to be recom- 
 mended unless the amateur is willing to use a large 
 number of cells. 
 
 For constancy and cheapness the sulphate of copper 
 cells lead. The quality of cheapness appertains both 
 to original cost and expense of running. A great ob- 
 jection is their high resistance; for this reason a very 
 large battery may seem to have but little power. If 
 an effort is made to reduce their resistance, by bring- 
 ing the plates closer, copper is deposited on the zinc. 
 
 Tl\e depositi' n of copper on the. positive plates is 
 not only annoying, as exacting scraping and cleaning, 
 but exhausts the solutions. It does not do to bring 
 the plates too close together.
 
 10 ELECTRIC TOY MAKING. 
 
 This is one reason for high resistance, but there is 
 a greater one. It is that the solutions either of zinc 
 or copper sulphate in the cell are never of low resist- 
 ance. Such solutions do not compare with dilute 
 sulphuric acid for conductivity. 
 
 Owing to its constancy and cheapness, the sulphate 
 of copper combinations form favorite batteries with 
 telegraph operators. In the Daniell battery a plate 
 of zinc is contained in a porous cup surrounded by a 
 plate of copper The three are placed in a ghiss 
 jar A solution of zinc sulphate is poured into the por- 
 ous cup; a solution of copper sulphate into the outer 
 jar. In the gravity battery only the glass jar and two 
 plates are used. The copper plate is in the bottom 
 and a gutti-percha covered wire leads from it. The 
 zinc plates are near the top of the jar. To charge it, 
 water is introduced until the zinc is covered. A 
 handful of crystals of copper sulphate are added with 
 a little zinc sulphate solution if necessary. Gravity is 
 here relied on to keep the two solutions separate; the 
 zinc sulphate increases in quantity with the working 
 of the battery, but the copper sulphate solution is 
 kept }'.s strong as possible. After a while the zinc 
 sulphate solution will exceed in specific gravity the 
 copper sulphate solution, when the battery will cease 
 to act properly. Hence, the upper layers of liquid are 
 withdrawn from time to time and replaced by plain 
 water. 
 
 The Leclanche battery, befure the introduction of
 
 BICHROMA TE BATTERIES. 1 1 
 
 the dry batteries, was the great open circuit battery. 
 
 For intermittent work either typo can now be 
 recommended. For constant and heavy work neither 
 is of any utility whatever. 
 
 For heavy work the bichromate cells are the best, 
 all things considered. They are not very constant 
 and with a heavy output soon begin to run down. 
 
 Of them the Bnnsen battery is to be recommended 
 for constant currents of long duration. The cell con- 
 sists, in brief, of a porous cup and outer jar. in on 
 of the divisions an amalgamated zinc plate is con- 
 tained ; in the other division a carbon plate. The car- 
 bon is surrounded by a strong solution of chromic and 
 sulphuric acids. The latter imparts conductivity; the 
 former is the depolarizer. The zinc is surrounded 
 with dilute sulphuric acid. The two solutions inevi- 
 tably diffuse one into the other. The more they are 
 kept distinct the better the condition of the battery is. 
 
 The plain bichromate battery consists of a jar con- 
 taining the amalgamated zinc and carbon plates and 
 charged with the chromic-sulphuric acid solution. 
 This is a defective combination. The chromic acid 
 acts upon the zinc, and the battery rapidly deteriorates 
 when on open circuit. 
 
 The latter trouble is avoided by removing the plates, 
 or, at any rate, the zinc plate, when the cell is_notin 
 use. This practise economizes solution and is by all 
 means to be recommended. Various mechanical con-
 
 13 ELECTRIC TOT MAKING. 
 
 structions have been adopted for raising the plates. 
 Such batteries are termed dip batteries. 
 
 The solution to be used should be carefully 
 prepared. An inferior mixture gives very inferior 
 results. The following is the celebrated Trouve 
 solution and can be highly recommended: 
 
 It requires 
 
 Water 8 pints. 
 
 Powdered Potassium Bichromate 1 2-10 Ibs. 
 
 Concentrated Sulphuric Acid 3610 Ibs. 
 
 The bichromate is added to the water and stirred 
 well through it. The acid is slowly added, with 
 constant stirring. A glass rod, and glass, or well 
 enamelled iron vessels should le used for the mixing. 
 As the acid is added the temperature rises and all, 
 or nearly all, of the bichromate dissolves. Some- 
 times to four parts of water as much as one part of 
 bichromate is added, with nearly two p:irts of sul- 
 phuric acid. All parts are by weight. The secret is 
 in the fine pulverization of the bichromate and in 
 the gradual addition with constant stirring of the 
 acid. 
 
 Great care should be taken in pulverizing the bi- 
 chromate to inhale none of the dust, as it may 
 cause ulcers. 
 
 The above solution may be employed in the car- 
 bon plate division of the Bunsen cell with excellent 
 results.
 
 SAL AMMONIAC BATTERIES. 13 
 
 For" the zinc plate division of the Bunseii cell, one 
 part, by weight, of sulphuric acid to twelve of water 
 is used. 
 
 Very useful little batteries may be constructed by 
 using a mixture of two parts sal ammoniac with one 
 part of mercurous or white mercury sulphate in 
 water as the excitant. Zinc and carbon are the ele- 
 ments and are contained in a single cell. 
 
 A piece of old battery carbon may be bored out for 
 part of its length and used as both the cup and neg- 
 ative element at once. It should be well paraffined by 
 dipping in melted paraffine wax. A zinc rod or wire 
 small enough to enter the hole having some rubber 
 bands wound around it, is inserted as the positive 
 plate. The bands must cover as little of its surface as 
 possible and its bottom must not touch the carbon. 
 The sal ammoniac-mercurous sulphate solution is the 
 excitant. A little of the mixture is placed in the cup, 
 some water is added and mixed with it. The zinc is 
 placed in position, and all is ready for use. 
 
 Such a battery is, of course, more of a curiosity 
 than a practical source of current. 
 
 For working small apparatus the silver chloride 
 cell has been very highly thought of. Although orig- 
 inally of somewhat high cost the silver is not lost and 
 can readily be reconverted into chloride when the 
 battery becomes exhausted. 
 
 A test tube made of extra thick glass will answer 
 for the cell. A piece of sheet zinc is bent so as to fit
 
 14 ELECTRIC TOT MAKING. 
 
 closely in the tube, in contact with its sides. A lug 
 or projecting piece extends up from the zinc. The 
 plate should he nearly as 1< ng as the tube. It must 
 be well amalgamated and put in position. 
 
 Next, a very thin pi<cc of silver foil is wrapped 
 around a rod of wood the size of a lead pencil. A 
 silver wire is soldered or otherwise connected to this 
 to act as terminal. A thick paste of silver chloride 
 and water is spread upon a piece < f blotting paper, 
 which is just long enough to go once around the 
 silver. This is then wrapped around the foil with the 
 chloride paste against the silver. 
 
 A strip of muslin is Avrapped two or three times 
 around the blotting paperand is neaily sewed ortied. 
 
 A thick rubber band, best a section from some 
 rather heavy gas tubing, is put over each end of the 
 silver element. It must fit without squeezing. A 
 perforated slice of cork will answer us well. The 
 silver element is dropped into place, and the tnbe is 
 filled with a solution of sal ammoniac in water. 
 
 Such a cell is without local action, and represents 
 a very small open circuit battery. Two or three will 
 operate a small induction coil. Their durability de- 
 pends on the amount of silver chloride. 
 
 As no gas is generated, the cells may be enclosed 
 hermetically by corks, coated or covered with a thick 
 layer of sealing-wax or cap-cement. They form a 
 convenient pocket battery. Sometimes they are
 
 ELECTRIC LIOHT CARBONS. 15 
 
 made in soft rubber tubing, closed at both ends with 
 corks and cement as above. 
 
 The present work docs not purport to treat of bat- 
 teries, yet it has seemed well to say this much on the 
 subject and to give some examples of the utilization 
 of common material for the purpose in the next 
 sections. 
 
 For temporary purposes a battery of great power is 
 easily made up by using the bichromate solution, with 
 zinc and carbon as the elements, and any convenient 
 porcelain or glass vessels as the cups or jars. For 
 permanent batteries considerable may be done in the 
 way of neat mounting, etc., to make them attractive 
 objects to the eye of the amateur electrician. 
 
 One concluding word must be said : Never attempt 
 to use unamalgamated zincs in a bichromate cell. To 
 amalgamate, place a little globule of mercury in a 
 saucer with some dilute sulphuric acid. Wet the 
 zinc plate with the acid. Then, with a bit of zinc or 
 galvanized iron, rub the mercury well over the sur- 
 face of the zinc plate. 
 
 In the cut of the electric light carbon battery, 
 page 18, the arrangements for amalgamating are 
 shown. The slip of galvanized iron in the saucer is 
 bent so as to fit around the circular zinc rods. 
 Batteries with Electric Light Carbons. 
 
 Electric light carbons make excellent material for 
 the negative plate of batteries. They may be used 
 in various ways as regards their mounting.
 
 16 ELECTRIC TOY MAKING. 
 
 The first thing to be done to them is to remove the 
 copper plating from such portions as are to be im- 
 mersed in the acid or battery fluid. This is easily 
 effected by immersion in dilute nitric acid to the 
 desired depth. A few seconds will generally suffice 
 to strip the metal. * 
 
 The next step depends on how they are to be used. 
 Old rejected pieces, such as the lamp trimmers throw 
 away, may be employed in some constructions. If the 
 pieces are short, an excellent system is the following: 
 
 For each battery jar one long piece is selected. The 
 copper is removed from its lower part, one or two 
 inches at one end being left plated. It is then washed 
 and dried in an oven. To the upper or coppered end 
 while still hot, or if it has cooled, while heated gently, 
 paraffine wax is applied just below the copper, until 
 the porous carbon has absorbed all that it can. 
 
 The smaller pieces of carbon are completely 
 stripped of copper. The long piece is placed upright 
 in a porous cup and the small pieces are packed 
 in around it. This makes the negative element. 
 The wire is wound around the coppered end and 
 may, if desired, be soldered thereto. It is also 
 possible to drill a small hole in the top and screw 
 in a binding post, which may be further secured by 
 soldering. 
 
 The illustration presents another method. To carry 
 it out the carbons must be rather long, according to 
 the average of the rejected pieces. The copper is dis-
 
 NEOA TIVE PL A TES. 1 7 
 
 solved from their lower portions, leaving one or two 
 inches coppered. They are washed, dried and paraf- 
 fined as just described. 
 
 FIG. 1. MAKING NEGATIVE PL&TES FROM ARC LIGHT CARBONS. 
 
 They are next placed on a board and secured as 
 shown by a strip, X. As carbons are often slightly 
 bent, care should be taken to turn them until they lie 
 as fully in contact as possible. A couple of side 
 blocks, abutting against a straight end piece, form a 
 pocket to receive the coppered ends, which are 
 pressed together by the wedge, TV. 
 
 With soldering acid, solder and soldering iron, the 
 ends are now soldered together. The solder is 
 melted into the grooves formed by the contiguous 
 carbons. After cooling, the carbons, now united, are 
 turned over, are again secured as shown and the 
 opposite sides are soldered. 
 
 This gives what is practically a solid battery plate, 
 and which really possesses special advantages in its
 
 18 ELECTRIC TOT MAKING. 
 
 increased area of surface. A binding post can be 
 soldered into one of the grooves. 
 
 Another way of uniting carbons is to cast lead 
 around the ends of a bunch, instead of soldering. 
 This, however, makes a heavy plate only adapted for 
 large batteries. 
 
 FIG. 2. ELECTRIC LIGHT CARBON BATTERY. 
 
 An excellent method is illustrated in the next 
 cut. It is to cut out a circular or square piece of 
 wood to cover or else to simply extend across the
 
 ELECTRIC LIGHT CARBON BATTERIES. 19 
 
 top of the jar. Holes are bored in it through which 
 the carbons are tightly thrust after stripping and 
 paraffining. The ends are brought just flush with the 
 surface of the wood, and a strip of brass or copper is 
 sweated to the plated carbon ends. This is done by 
 first tinning the lower surface of the brass plates, 
 where it is to come in contact with the carbons, and 
 then tinning each carbon top. The strip is now laid 
 in position, and by heating it the two sets of tinned 
 surfaces are caused to unite by the solder running 
 together. The brass plate is pressed down and held 
 so until the solder is partly cooled and has set or 
 ha dened. 
 
 If the ends are not plated a piece of copper foil can 
 be forced into the hole with the carbon, and to this a 
 wire is soldered connecting all the carbons together. 
 The foil can be doubled over the top of the carbons, 
 and the connecting strip of foil used as just described. 
 
 As regards zincs, old Lcclanche battery zincs can be 
 used in a similar way by thrusting them through 
 holes in a board. All the soldering must be done 
 before the zincs are amalgamated. 
 
 A very neat battery is made by cutting out the 
 wood to cover the jar, and giving it a rebate all 
 around its edge, so that it cannot slip. The zincs 
 and carbons are then fastened in holes as just 
 described. For a single fluid battery this is an 
 excellent form of construction. 
 
 The wooden top may be made of pine, or, if a
 
 20 ELECTRIC TO 7 MA KING. 
 
 hard wood is desired, mahogany or maple is good. 
 Ash is not altogether satisfactory, because if the 
 lower surface gets wet Ihe piece warps badly. But 
 this is of less importance, as the greatest care should 
 be taken to avoid such wetting as the acid will cor- 
 rode the connections. 
 
 It will be seen also that a binding post can in this 
 battery be screwed through a hole in the brass or 
 copper strips directly into the wood, and then, if 
 desired, may be soldered. 
 
 A Tomato Can Battery. 
 
 The above designation applies to a simple form of 
 home-made battery in which a discarded tomato can 
 may be made to play a part. It is a battery of con- 
 siderable merit, but of too low voltage. 
 
 The outer vessel for containing the fluids and other 
 parts of the battery is a tomato can or other iron ves- 
 sel. Within it is a porous cap. The annular space 
 between is filled with fine scrap iron, such as turnings, 
 borings and clippings. A zinc plate goes into the 
 porous cup. 
 
 The exciting solution is a ten per cent, solution of 
 caustic soda. The wires are connected as shown, one 
 to the zinc plate and one to the can itself. 
 
 The battery is liable to polarization, but the large 
 surface of the iron protects it to some extent. 
 
 If it is desired to make it constant or self-depolariz- 
 ing, a quantity of oxide of copper may be placed in the
 
 TOMATO CAN BATTERIES. 21 
 
 bottom of the jar upon a layer of iron borings and the 
 rest of the filling of iron scraps may be dispensed 
 
 FIG. 3. A TOMATO CAN BATTKBT. 
 
 with. This makes it a Lalande-Chaperon battery. 
 The E. M. F. is about .75 volt. 
 
 Materials for Battery Cells. 
 
 Before leaving the subject a word may be said on 
 the cell proper. Porcelain marmalade jars make 
 excellent receptacles for small couples. In selecting 
 a vessel there is one point of special importance. The
 
 22 ELECTRIC TOT MAKING. 
 
 sides should not taper or slope outwards. It is far 
 letter to have a vessel that is smaller at the neck than 
 at the bottom. Self-sealing preserve jars for this 
 reason are very serviceable. 
 
 Wooden battery troughs have been used to a con- 
 siderable extent. These may be made of pine, oak, 
 mahogany or maple. The sides maybe protected from 
 the liquids by baking and, while hot, coating with 
 melted paraffine. Potassium bichromate battery so- 
 lution, however, will in time attack almost anything 
 except glass or porcelain. 
 
 A long trough to contain a number of elements 
 may have its partitions made of glass set in grooves in 
 the sides and secured with cement.
 
 CHAPTER II. 
 PERMANENT MAGNETS. 
 
 HOW TO MAGNETIZE STEEL BARS ROLLING ARMA- 
 TURES MAHOMET'S COFFIN MAGNETIC JACK- 
 STRAWS THE MAGNETIC TOP THE MAGNETIC 
 
 PENDULUM MAYER'S FLOATING NEEDLES 
 MAGNETIC FISHES, AND THE MAGNETIC SWAN, 
 
 BOAT, ETC. 
 
 How to Magnetize Steel Bars. 
 
 A BAR of soft iron held iu a magnetic field, is 
 acted on by the lines of force constituting the field, 
 and becomes a magnet and will attract iron, and 
 act exactly as the permanent magnet does. When 
 remove 1 from the field of force it will show hardly 
 any magnetism. If a piece of steel is treated in the 
 same way, it will also show magnetism when in the 
 field ; but, on removal, will retain some of it. It is 
 a permanent magnet. 
 
 Permanent magnets are easily made of such mater-' 
 ial. The bar of steel should be of good quality, 
 and tempered to a straw color or purple. All the 
 shaping, filing or polishing, which it is proposed to 
 give it, should be done before magnetizing, as the 
 least thing in the way of filing or jarring the mag- 
 net injures its power.
 
 24 
 
 ELECTRIC TOT MAKING. 
 
 It may be magnetized by another magnet, perma- 
 nent or electro or by a magnetizing coil and bat- 
 tery. It is enough to touch one end to the most 
 strongly magnetic part of the field magnet of an 
 active dynamo. This suffices because of the intense 
 polarity of the powerfully excited machine. 
 
 With a single permanent magnet, a bar may be 
 thus magnetized. It is rubbed from the centre to 
 one end, with one pole of the magnet a number of 
 times, the magnet being drawn away from the 
 end and carried back to its centre through the air, 
 and the stroking is rpeated a number of times. Then 
 the same process with the other pole of the magnet 
 is applied to the other half of the bar. It is well to 
 turn it over so as to stroke all sides of it. 
 
 A simplerway is to stroke from one end of the bar 
 to the other, always in the same direction, with one 
 pole of a magnet, returning it through the air. 
 
 Two magnets may be fixed in an inclined position 
 with their poles of opposite name close together, and 
 the bar may be stroked with them as described above 
 for a single magnet. The next cut illustrates this 
 method as well as the process next to be described. 
 
 FIG. 4. MAGNETIZING A BAR OF STEEL. 
 
 An excellent method is to apply the stroking from
 
 MAGNETIZING HORSESHOE BARS. 25 
 
 centre to ends with two magnets simultaneously. A 
 little bit of wood or brass should be used to prevent 
 their ends from coming in contact in the centre of 
 the ' magnet. The cut shows the arrangement, I 
 representing the separating piece, and also shows the 
 bar resting upon the opposite poles of two other mag- 
 nets. The end to be stroked with a north pole should 
 rest upon the north pole of a magnet, and the same 
 applies to the south pole. 
 
 FIG. 5. MAGNETIZING A HORSESHOE MAGNET. 
 
 Magnets are generally either straight or horseshoe 
 in shape. If of the latter description they may be 
 magnetized by touching both poles to opposite poles 
 of a dynamo field magnet. It should be noted that 
 this will reduce for the moment the power of the 
 dynamo. Where a small electro-magnet is at hand 
 the stroking process may be applied as shown in the 
 cut. The bent bar is placed against the poles of the 
 excited electro-magnet, and is drawn downwards as 
 shown by the arrow. This is repeated a number of 
 times and the bent bar, after each stroke, is pulled
 
 26 ELECTRIC TO Y MA KING. 
 
 away from the electro-magnet and is returned to its 
 original position. It is then well to reverse opera- 
 tions; to apply the other face of the bent bar, now 
 partly magnetized, to the electro-magnet, but this 
 time to keep the bend upwards as the opposed poles 
 must be kept in the same relation. The bar is now 
 drawn upwards and away from the electro-magnet a 
 few times and the operation is complete. 
 
 If the electro-magnet has its poles too far apart to fit 
 the horseshoe bar, which it is desired to magnetize, 
 a small block of iron can be placed against one pole 
 to set as an extension. To each pole, if desired, an 
 extension can thus be attached so that a much larger 
 or smaller horseshoe bar can be magnetized. 
 
 If the horseshoe bar is thin in the other direction, 
 so that its edge would come against the faces of the 
 electro-magnet, the inside or outside of the bar 
 should be rubbed, and not the edges. 
 
 To make powerful magnets thin pieces of steel may 
 be magnetized separately and then clamped or screwed 
 together. They must not be rivetted or soldered as 
 either would injure the magnetism. 
 
 Another way, Jacobi's method, to magnetize a 
 horseshoe bar, is to place it with its poles against those 
 of a strong horseshoe magnet. A bar of soft iron, 
 long enough to reach across from outside to outside 
 of the parallel legs is now laid across at or near the 
 ends of the legs of the bar to be magnetized and is 
 drawn along it back to the bend and away from it. It
 
 MAGNETIZING WITH COILS. 27 
 
 is returned through the air and the process repeated 
 a few times on each side of the bar. It is said that a 
 one-pound magnet may thus be made which will carry 
 twenty-six and a half pounds. 
 
 To magnetize with a coil, all that is necessary is to 
 surround a part or all of the bar with a coil of in- 
 sulated wire and to pass a strong current through it 
 for an instant. By Elius' method the coil is moved 
 backward and forward along the bar which it en- 
 circles while the current is passing. The number of 
 passes is of greater importance for weak currents. For 
 strong ones a single pass is ample. 
 
 By another method the bar is armed with two short 
 cylinders of iron, one at each end of three or four 
 times its diameter. These armatures should be of soft 
 iron. It is placed in the axis of a coil that is of the 
 same diameter as the armatures and which is long 
 enough to include both armatures and the bar. A 
 current is passed through the coil and powerful 
 magnetization results. 
 
 To preserve magnets their opposite poles must be 
 connected so as to complete the magnetic circuit. 
 With bar magnets this is best done by placing them, 
 almost touching each other, in pairs with their 
 opposite poles corresponding in direction. Two little 
 bars of soft iron laid across from pole to pole com- 
 plete the circuit. Such bars are termed keepers. If 
 a single magnet is in question a bent piece of soft 
 iron may be used to connect the two poles. A magnet
 
 28 ELECTRIC TOT MAKING. 
 
 may even be left without any keeper, if placed in 
 the magnetic meridian. For horseshoe magnets a 
 single keeper, the armature, suffices to connect both 
 poles. 
 
 In using magnets all jarring must be avoided. It does 
 no harm to pull the armature off if done perfectly 
 steadily and without jar. The re-attraction of the 
 armature with a " click," is what deteriorates a per- 
 manent magnet most rapidly. 
 
 FIG. 6. THE ROLLING 
 
 Rolling Armatures. 
 
 The rolling armature consists of a short cylindrical 
 axis of iron to whose center a wheel is attached. The 
 wheel may be made of lead or other metal. When it 
 is placed as shown upon a horseshoe magnet it will 
 adhere, but if the magnet is properly inclined will roll 
 down to the end. The momentum of the fly-wheel 
 keeps up the motion and the armature rolls across the
 
 ROLLING ARMATURES. 29 
 
 poles and up the other side for a considerable distance. 
 A modification of this armature con- 
 sists of two little bars of iron with 
 brass rollers attached to their ends. 
 They are placed in the position A, 
 as shown in the dotted lines in the 
 cut. On approaching them with 
 the magnet they become polarized 
 both in the same sense and at once 
 
 FIG ;~KBPULSION repel each other and roll away as 
 
 If the horseshoe magnet has parallel sides, and the 
 last described armatures are nicely made, they may be 
 made to roll upon it somewhat as the other rolling 
 armature does. 
 
 By concealing the magnet under a sheet of paper 
 the recession or rolling away from each other of the 
 two bars may be made to seem quite mysterious. 
 Mahomet's Coffin. 
 
 The next cut shows a very pretty magnetic experi- 
 ment which recalls the famous unsupported coffin of 
 Mahomet. A needle, whose point may be broken off, 
 is magnetized by a few strokes with a magnet. On 
 drawing it by a thread, as shown, over the poles of a 
 horseshoe magnet so as to bring like poles over each 
 other, it will lie horizontally and motionless in the 
 air, sustained by an invisible force. As it is drawn 
 forwards and from the further side of the horseshoe 
 magnet it tends to follow the lines of force and rises
 
 ELECTRIC TO 7 
 
 along the line of an arc gradually reaching the 
 position shown. 
 
 With a strong magnet and a little bar of steel, con- 
 
 ^ 
 
 FIG. 8. MAHOMET'S COFFIN. 
 
 tainea in a miniature coffin, the last resting place of 
 the prophet could be well simulated. 
 
 Magnetic Jack-Straivs. 
 
 Magnetic jack-strnws arc an interesting modification 
 of the time-honored 
 game. They are made 
 up of a set of jack- 
 straws to each of which 
 a piece of iron is at- 
 tached. They may be 
 given the usual shapes 
 exactly as in the regular 
 
 
 FIG. 9. MAGNETIC JACK-STRAWS 
 
 straws are drawn out one by one. 
 
 In place of the hook 
 there is substituted a 
 magnet. With this the
 
 THE MAGNETIC TOP. 31 
 
 In the cut a simple way of making the straws is 
 shown. Short pieces of iron or steel wire are used. 
 Some have little blocks of wood fastened to them; 
 others are bent and twisted, others are plain. 
 Different values are assigned to each kind. Each 
 player draws out straws until he shakes or moves one 
 which he is not attempting to remove. He then re- 
 signs to the other player. This is kept up until all 
 are withdrawn. The one getting the highest score, as 
 determined by adding up the value of the straws 
 captured, is the winner. 
 
 The Magnetic Top. 
 
 This amusing toy is easily made. A bar of steel, 
 suitable for the spindle of such a top as shown, is 
 sharpened at one end, and a metallic or heavy wooden 
 disc is fitted to it. The best method of attachment 
 would be by screwing, or by a couple of nuts, one above 
 and one below the disc, the spindle being- threaded 
 in either case. The combination is a top. Before 
 putting it together the spindle is magnetized. 
 All shaping, cutting or filing must precede the mag- 
 netizing. 
 
 FIG. 10. THB MAGNETIC TOP.
 
 32 EL ECTRIC TOT MAKING. 
 
 A supply of short pieces of iron wire is required ; 
 gome of these are bent into different shapes, circles, 
 letter S's, etc; others are straight. When the top 
 is spun by the fingers, and one of the wires is placed 
 on the table against its point, it is slowly carried 
 back and forth in the most curious way. It is well, 
 to make it appear still more mysterious, to use 
 cotton or silk covered wire. 
 
 As the top rotates, the wire is carried by a sort of 
 friction-pulley action along in the direction of its 
 length. As its end reaches the point of the top it 
 changes sides and returns as ib is acted on by the 
 other side of the spindle, and thus goes back and 
 forth, first on one side and then on the other side of 
 the top as long as it spins. 
 
 The Magnetic Pendulum. 
 
 A universal joint is one that admits of movement 
 in all directions. The construction of a perfect 
 joint of this description is far from a simple matter. 
 
 The magnetic pendulum shows how a magnet can 
 be instrumental in producing one. 
 
 The original idea of the apparatus was to show the 
 rotation of the earth by Foucault's well-known ex- 
 periment. A pendulum has fitted to the upper end 
 of its rod, a piece of iron with smoothly rounded 
 upper end. This is suspended from a magnet by 
 simple attraction. Such a pendulum is free to swing
 
 THE MAGNETIC PENDULUM. 
 
 33 
 
 in any or all planes without being restrained by 
 torsion. 
 
 FIG. 11. THE MAGNETIC PENDULUM. 
 
 It is therefore peculiarly well adapted to be used 
 in proving, by its change of plane of oscillation, the 
 rotation of the earth upon its axis.
 
 34 ELECTRIC TOT MAKING. 
 
 It is not to be supposed that the motion is without 
 retardation from its method of suspension. The 
 magnet acting upon the soft iron produces a damp- 
 ing action due to induced currents. The ordinary 
 frictkm can be reduced by having the face of the 
 magnet as smooth as possible, by weighting the pen- 
 dulum until it is barely supported, and by accurate 
 finish of the iron top of the pendulum rod. 
 
 It is obvious that, using a cylindrical armature with 
 horizontal axis, the pendulum could be made to 
 swing always in the same plane. The curvature of 
 the cylindrical surface also could be modified so as 
 to give a cycloidal arc of swing to the pendulum 
 bob. But the isochronisin of the pendulum would 
 be affected by the action of the magnet on the iron, 
 so that a cycloidal pendulum might not prove isochro- 
 nous. 
 
 Mayer's Floating Needles. 
 
 This is an exceedingly pretty experiment, being an 
 improvement on the well-known magnetic fishes. A 
 number of large needles are magnetized, all in the 
 same sense as regards their relation of poles to points 
 or eyes. Each needle is then thrust through a 
 small cork, so that only a little bit of the eye endi 
 projects above one surface of the corks. They are 
 then floated in a vessel of water as shown, the like 
 poles coming above the surface. Under the effect 
 of repulsion and attraction, they float into the most 
 symmetrical shapes, some of which are shown in the
 
 MAGNETIC NEEDLES. 
 
 35 
 
 lower diagrams of the cut. To cause them to separate, 
 a magnet pole of the same name as that of their 
 upper ends may be brought above them. This re- 
 pels them in all directions. 
 
 FIG. 12. MAYER'S MAGNETIC NBEDLBS. 
 
 These floating needles are due to Prof. A. M. 
 Mayer, of the Stevens Institute, N. J., and will well 
 repay investigation. 
 
 Magnetic Fishes and the Magnetic Swan, Boat, etc. 
 
 A few words are enough to describe these well- 
 known toys. The fishes or other objects are m ;de of 
 thin block tin or other non-magnetic material, so
 
 36 ELECTRIC TOY MAKING. 
 
 as to float in water. Bits of iron or of magnetized 
 steel are secured to them in the proper places. Thus, 
 for the fish, a little bit of iron wire projecting from 
 the mouth is proper. For the swan or boat a piece 
 of magnetized steel may be secured in a similar posi- 
 tion. 
 
 By a common magnet attached to a thread with a 
 little stick or rod, the fish may be caught. The 
 swan and boat may be attracted or repelled by one or 
 the other poles of the magnet. 
 
 By using fish to which different values are assigned, 
 or by having the number stamped upon them in a 
 concealed place, a game can be made up. Each 
 player should catch one fish at a time, alternating 
 with the others. The one who catches those aggrega- 
 ing the largest number would be winner. The num- 
 bers of the fish should be concealed, so as to be 
 visible only when out of the water. Thus each 
 player would have to rely on chance for his score.
 
 CHAPTER III. 
 
 ELECTRO-MAGNETS. 
 
 CONSTRUCTION OF ELECTRO-MAGNETS MAGNETIZ- 
 ING COILS THE MAGIC CIRCLE MAGNETIC 
 HEMISPHERES. 
 
 Construction of Electro-Magnets. 
 
 ELECTRO-MAGNETS are almost universally made of 
 the horseshoe type. The core should be, for simple 
 sustaining power, thick and short. The cuts through 
 the book show the regulation shapes which curiously 
 enough are not the most powerful. The core is very 
 conveniently made in three pieces, the two arms 
 being tapped or pinned into the yoke. A simple 
 piece of bent iron, as shown in the electro magnet in 
 Figure 5, will suffice for the full core. It must be, 
 bent into U shape while hot, if of large size. 
 
 The coils may be wound directly on the core, in 
 which case it is well to wrap the latter with paper. 
 Either insulated or bare wire can be used. If the 
 latter, rigorous care must be taken not to permit con- 
 tiguous windings or coils to touch each other, and a
 
 38 ELECTRIC TOT MAKING. 
 
 wrapping of shellacked paper must be employed 
 between each layer of the windings. 
 
 On the whole insulated wire is to be recommended. 
 A common mistake is to wind too much wire around 
 the legs. The proper amount and size is a matter of 
 calculation, all depending upon the battery to be 
 employed, and the length and section of the core and 
 its material. 
 
 The windings upon both legs must be in opposite 
 directions. After winding the straight portion of one, 
 the wire may be carried diagonally across the inter- 
 vening space to the opposite face of the other leg, and 
 the winding may thus be continued. 
 
 The coils may be made separate as will be de- 
 scribed, or may be wound upon bobbins and thrust on 
 as required. 
 
 Nothing is gained in general by carrying the wind- 
 ings around the bend. 
 
 FIG. 13. JOULE'S ELECTRO-MAGNET. 
 
 A very powerful form of magnet is here illustrated.
 
 SOLENOID MAO NETS. 39 
 
 It was devised by Joule, largely on experimental bases, 
 and presents an excellent example of a highly efficient 
 electro-magnet. 
 
 The core is readily made by filing off one side of a 
 piece of gas pipe. No. 1 shows the section of the 
 core, and No. 2 shows the' complete magnet. Here it 
 will be observed the winding is carried around the 
 bend. 
 
 Electro-magnets are used in motors, dynamos and 
 bells, and form a very important element in electric 
 constructions. Their power depends on the current 
 which passes around them and on the number of 
 turns of wire through which the current passes. The 
 lifting power in other words is proportional to the 
 ampere turns. 
 
 Sometimes a straight bar is used as the core, and 
 sometimes the armature is dispensed with, and the 
 drawing into place of the movable core by the fixed 
 coil, or the drawing of the coil by the fixed core is 
 utilized. Thus, if through a coil of wire a sufficiently 
 intense current is passed, a bar of iron brought into or 
 near the opening of the coil will be drawn or sucked 
 in like a plunger into a cylinder. 
 
 The Litter type of magnet is ordinarily termed a 
 solenoid, not very correctly however. It was used 
 extensively by Dr. Page in his motors in the early 
 days of the science. It is said that very powerful 
 solenoid magnets were exhibited by the old-time 
 lecturers, some sustaining the weight of several men.
 
 40 ELECTRIC TOY MAKING. 
 
 Any magnetizing coil with a bar of iron may be 
 used to illustrate this action. The drawing up of a 
 bar from the table into its axis presents an extraor- 
 dinary appearance when first seen. It is obvious that 
 another version of Mahomet's coffin could be built 
 upon this, the core being.held down by a fine thread. 
 This could be made to present the appearance of a 
 metal bar floating, balloon fashion, at the end of a 
 thread. 
 
 The winding of a magnet may be secured in place 
 by glue or varnish, as will be described iinder "Mag- 
 netizing Coils " more fully. It is enough to wind on 
 all the wire and then apply glue to the finished coil, 
 drying, baking, and varnishing or painting. 
 
 It is obvious that, if a single length of wire is used 
 for winding, and if the legs are wound separately, one 
 end will come next to the core, and the other end will 
 be on the outside of the wire coils and on the other leg. 
 If wound separately on each leg and afterwards joined 
 across the bend, the ends of the wire may be made to 
 come out symmetrically. As regards appearance it is 
 preferable to have them lie next the iron core; for 
 ease of repair they should be on the outside. The 
 latter is to be recommended. 
 
 Magnetizing Coils. 
 
 The construction of magnetizing coils, which have 
 no core to support or carry the wire, and in which 
 the wire must be compact and adherent, layer to layer,
 
 MAGNETIZING COILS. 41 
 
 > 
 
 requires special care. They are wound upon a 
 mandrel, a cylinder generally, which is afterwards 
 withdrawn. It is necessary to arrange so that this 
 withdrawal will be possible; therefore, the mandrel 
 should be slightly tapered, if possible, to facilitate the 
 removal. A glass bottle, a tumbler, or a round ruler 
 or piece of curtain roller are good examples of man- 
 drels. 
 
 F G. 14. MAGNETIZING COIL. 
 
 To make a magnetizing coil a mandrel of any con- 
 venient material is selected. A piece of paper is 
 wrapped around it and on this the insulated wire is 
 wound as neatly as possible. This may be done by 
 hand as regularly as is possible on a lathe, although 
 the use of the latter saves time. Where there are a 
 great number of turns of wire an extemporized 
 winder can easily be put together in a few minutes, 
 the mandrel being usid as axle, with a crank handle 
 attached to one end, and then mounted in a couple 
 of standards. 
 
 The windings of the coil have to be fastened to- 
 gether. For this purpose carpenters' glue may be 
 employed. The glue is applied to each layer as it is
 
 42 ELECTRIC TOY MAKING. 
 
 wound and when the last layer is in place the free end 
 of the wire is kept strained until the glue has 
 hardened, which should be in an hour. The whole 
 can then be slipped off the mandrel and dried over a 
 stove. 
 
 If, on drying it, the surface shows cracks, they can 
 be stopped up by a further coating of glue, followed 
 by drying. 
 
 The coil thus prepared can be painted or varnished 
 with alcoholic solution of shellac, which prevents the 
 glue taking up moisture, and acts to hermetically seal 
 the windings of the coil. 
 
 Additional security may be given by binding with 
 wire, as shown in the cut, but this is unnecessary 
 either when glue is employed or when the next de- 
 scribed method is adopted. 
 
 A much nicer and more effectual way is to use a so- 
 lution of gum copal in ether. This is applied to layer 
 after layer and solidifies the whole mass with a water 
 repelling medium. Alcoholic solution of shellac can 
 be used in the same way. Heating may be necessary, 
 as in the use of glue, to bring about the last degree 
 of solidification. 
 
 The Magic Circle. 
 
 The magic circle next illustrated is designed for 
 use with a small magnetizing coil. It is simply two 
 semi-circles of soft annealed iron, provided with rings 
 or handles exactly at the centre of each piece. The 

 
 THE MAGIC CIRCLE. 
 
 4',} 
 
 faces are planed or filed off so as to fit accurately. A 
 good size is made of one inch round iron, bent into a 
 circle of three inches internal diameter. For such a 
 circle a coil of number eighteen to twenty wire, wound 
 
 Fio. 15. THE MAGIC CIRCLE. 
 
 into forty or fifty turns, suffices. With a current of 
 good strength the attraction the circles will develop 
 is surprising. 
 
 Magnetic Hemispheres, 
 
 A very peculiar form of magnet is shown in the 
 next cut. Although a modification of it is attributed 
 to Prof. Forbes, by Thompson in his recent work on
 
 44 ELECTRIC TOT MAKING. 
 
 the electro-magnet, it is really a very old form. The cut 
 is a reproduction from Davis' Manual of Magnetism, 
 a work copyrighted in 1847. It may aptly be termed 
 the Magdeburgh Hemispheres of Electricity. 
 
 The small sectional figure in the left lower corner 
 shows the construction. Two cylinders of soft iron 
 
 FIG. 1G. THB MAGNETIC HEMISPHERES. 
 
 have cut out an annular groove of size adapted to re- 
 ceive a magnetizing coil. A slot is cut to permit the 
 wires to come out where the two halves are face to 
 face and in contact. 
 
 When the current is turned on and passes through
 
 MAGNETIC HEMISPHERES. 45 
 
 the coil, embedded in the recess, it polarizes the two 
 coils, and if placed together they are strongly at- 
 tracted. No magnetic circuit, it will be observed, is 
 formed. 
 
 The coil may be a movable one, or may be cemented 
 in place with varnish or sealing-wax. Rings should 
 be fitted to both parts. Two persons may be placed 
 in opposition to each other to try to pull them apart. 
 The same magnetizing coil may be used for these 
 as for the magic circle. The metal of the core may be 
 a little heavier than that shown in the cut. These 
 show very little residual magnetism and fall apart 
 easily when the current ceases. The magic circle, 
 on the other hand, retains much residual magnetism 
 even when the current is turntd off. 
 
 When two people pull against each other in their 
 endeavors to draw apart the halves of this apparatus 
 a sudden breaking of the circuit will cause a sudden 
 giving away or perhaps a fall backwards. 
 
 The residual magnetism of the magic circle is so 
 great that to obtain the same sudden separation a re- 
 versal of the direction of the current is necessary. 
 This reversal can be easily made by shifting the ends 
 of the wire by hand so as to connect with the other 
 poles of the battery.
 
 CHAPTER IV. 
 ELECTRIC MOTORS. 
 
 PENDULUM COIL MOTOR RECORDON MAGNET MOTOR 
 MULT1POLAR MOTOR PAGE'S ROTATING ARMA- 
 TURE THE- ELECTRIC LOCOMOTIVE. 
 
 Pendulum Coil Motor. 
 
 A VERY pretty form of slow speed motor is shown 
 in the cut, from which the general features of con- 
 struction can be readily understood. A permanent 
 horseshoe magnet is the basis of c .nstruction. This 
 is attached to a board, as shown, so as to be held an 
 inch or so above its surface. 
 
 A standard rises from the board just at the end of 
 the m;ignet. It carries a horizontal axis on which 
 two coils, such as described under magnetizing coils, 
 swing at the end of short bars. These coils encircle 
 the ends of the magnet. A fly-wheel is carried by 
 two other standards and is connected by pitmen with 
 suspension rods of the coils. 
 
 The coils are thus connected with the terminals or 
 binding-screws seen on the base. 
 
 One terminal connects by the standard and magnet 
 itself with the axis of the fly-wheel. A projecting.
 
 PEND UL UM COIL MOTOR. 47 
 
 segment is attached to this axle, which extends about 
 one-third around the shaft. The two springs seen 
 rising from the base press alternately upon this as the 
 wheel rotates. 
 
 From each spring a wire is carried up the large 
 standard and down one of the vibrating rods to a 
 coil. Each coil has its own spring. The other ends 
 
 FIG. 17. PENDULUM COIL MOTOR. 
 
 of the coils unite and pass down the same standard 
 to the other binding post. 
 
 Thus the current entering at one binding post 
 passes by way of the magnet, standards, and fly-wheel 
 axle. The collar is almost always in contact with one 
 spring. The current passes through this, through
 
 48 ELECTRIC TOY MAKING. 
 
 one of the coils, and leaves it to go to the other bind- 
 ing post, and thence to the battery again. The coil 
 is attracted towards the magnet pole, and as it is 
 drawn thither causes the wheel to rotate. As it 
 reaches the pole and swings beyond it the collar 
 breaks the connection and excites the other coil now 
 most removed from its pole. This is in turn attracted, 
 keeping up the rotation of the wheel. It is also 
 clear that at certain phases both coils may be excited, 
 one swinging to the left and the other to the right. 
 To carry this out two collars may be employed, 
 one for each coil. The other construction is simpler. 
 
 The winding of the coils must be thus arranged : 
 The current in the coil surrounding the north pole 
 of the msignet must go in the direction contrary to 
 that of the hands of a watch, if the observer is sup- 
 posed to be looking directly at the magnet end. The 
 current in the other coil must go in the opposite 
 direction. 
 
 Finally, the permanent magnet might be made of 
 circular section so as to more closely conform to the 
 coils, or the latter may be wound npon a square 
 mandrel. In all such constructions it is important 
 to keep the coils near to the field. 
 
 This motor illustrates one of the solenoid construc- 
 tions already alluded to, where the core is stationary 
 and the coils move. It is further to be noted 
 that two round cores of unmagnetized iron can be 
 used instead of a magnet. In such case the direction
 
 REGORDON MAGNET MOTOR. 49 
 
 of winding of the coils is a matter of indifference. 
 Recordon Magnet Motor. 
 
 A very neat motor is based upon the same type of 
 magnet as that used in the induction coil shown on a 
 later page. In the present illustration B represents 
 such a magnet, mounted in a frame and provided 
 
 FIG. 18. RKCORDON MAGNET MOTOR. 
 
 with two pole pieces, one projecting from each end. 
 The one on the right has hinged to it the armature 
 A. The other pole piece, E, is so shaped as to admit 
 of the armature going within it, and making as close 
 a fit as compatible with the absence of actual contact. 
 An axle with fly-wheel is journaled in the lower part
 
 50 ELECTRIC TOT MAKING. 
 
 of the frame. On the axle are a couple of commu- 
 tator drums, on which two springs, b 1), press. 
 
 The two commutators are of insulating material, 
 wood or ebonite, and one-half of the face of eacli is 
 coated with a slip of brass, which connects with the 
 axle. 
 
 One of the binding screws, by a short piece of wire, 
 connects with the frame of the apparatus, with the 
 axle of the fly-wheel and with the metallic commuta- 
 tor sectors. The other binding post connects with 
 one of the coil terminals. The two springs are in- 
 sulated from the frame, which is effected by using a 
 bar of wood to attach them to. A wire soldered to 
 the screws which attach the springs thereto, runs back 
 of the wood to the other coil terminal. The wire 
 must be insulated from the frame. A pitman is at- 
 tached to the free end of the armature, and its other 
 end receives the crank pin of a crank fastened to the 
 fly-wheel axle. As the axle rotates the armature will 
 rise and fall, and, as the armature is drawn up and 
 down, the fly-wheel will rotate. 
 
 The commutators are so adjusted that when the 
 armature is at its highest point the springs are just in 
 contact with the edge of the metallic segment. This 
 closes the circuit and the armature is attracted and, 
 as it descends, it turns the crank, axle and fly- 
 wheel. It is clear that if the crank turns the wrong 
 way the circuit will at once be broken. For this 
 reason the wheel should be started in the right direc-
 
 RECORDON MOTOR. 51 
 
 tion by hand. The armature is therefore drawn down 
 by the magnet as long as contact of springs and com- 
 mutator sectors last. This ceases just as the arma- 
 ture reaches its lowest point. The momentum of the 
 fly-wheel completes the other half of the revolution, 
 and again closes the circuit through the commuta- 
 tor just as the highest point is reached by the arma- 
 ture. 
 
 The same is repeated over and over again, and the 
 wheel is kept rotating as if by a single acting engine. 
 
 It is in some respects well to set the commutator 
 so that connection will be made only after the arma- 
 ture has descended a very short distance. This will 
 make the motor less apt to start in the wrong direc- 
 tion. 
 
 The extension of the pole pieces gives the magnet 
 a long range of action. The shape is also very com- 
 pact, and the motor suggests possibilities in the way 
 of improvement. The armature might be wound 
 Avith wire and thus be excited also so as to increase 
 the attraction. 
 
 M. Recordon, it is to be noted, makes these mag- 
 nets with hollow cores. The aperture can be seen in 
 the cut just back of the left-hand pole piece. 
 
 Multipolar Motor. 
 
 One of the principal points of merit in a well 
 designed motor is the absence of dead points. The 
 multipolar motor shown in the next illustration,
 
 52 
 
 ELECTRIC TOT MAKING. 
 
 while it has such, on account of their being subdi- 
 vided into six for each revolution, is very constant in 
 its movement. 
 
 The annular frame, A, and base, F, must be made of 
 
 Fio. 19. MULTIPOLAK MOTOR. 
 
 some non-magnetic material, such as brass or wood. 
 Through the frame, at even distances, six bars,C, C, 
 of iron are thrust. 
 
 These constitute armatures. The rotating field is
 
 MULTIPOLAR MOTOR. 53 
 
 built upon a drum, D, which carries six equally 
 spaced radiating cores, carrying coils of wire, B, B. 
 D may be made of brass or even of wood. A non- 
 conducting or insulating collar, E, surrounds one 
 part of it. The latter collar, E, is designed to re- 
 ceive upon its surface one set of terminal wires from 
 the magnetizing coils ; the other terminals go to the 
 surface of the drum, D. 
 
 The magnetizing coils are wound very solidly with 
 insulated wire upon the six cores. They may be 
 further secured by flanges pinned or screwed in 
 place, as the centrifugal force will be considerable. 
 
 The connections of the six field magnets are ar- 
 ranged to carry out this principle. During one-half 
 of the total time of a rotation they must be receiving 
 current, but this again must be divided into six 
 periods, which amounts to saying that they are to be 
 excited during alternate twelfths of each revolution. 
 When in the position shown in the cut they are not 
 excited. After they rotate until one-twelfth of a 
 revolution is accomplished, the magnet cores-are half 
 way betAveen the outer cores or armatures. At this 
 point they are excited and the current continues for 
 the next twelfth of a revolution, to cease again as the 
 magnets pass the armatures. This is "kept up all 
 around the circle. 
 
 The six wires carried to the collar, E, connect with 
 a brass or copper ferrule thereon. Six wires or ribs 
 soldered to the ferrule at equal distances apart lie
 
 54 ELECTRIC TOT MAKING. 
 
 upon the surface of the collar. A copper spring 
 rising from the base presses upon these. The pro- 
 portions are so adjusted that the spring presses upon 
 each wire during one-twelfth of a revolution. This 
 contact period must correspond to the period when 
 the magnets pass from the central point between 
 armatures to the point opposite the same. 
 
 The other six wires run to a ferrule upon the 
 drum D. A second spring presses continually upon 
 this ferrule. 
 
 The wires from the battery, or other source of 
 current, connect with the two springs, one wire with 
 each. 
 
 If the arrangement thus described is studied it will 
 be seen that the current pas-es during contact of the 
 spring with the ribs upon the collar, E, or during the 
 proper portions of the revolution. The magnets 
 are all simultaneously excited in parallel, and are 
 attracted to the cores in advance, referred to the 
 direction of their motion. As soon as they reach 
 them the current ceases and their inertia carries them 
 through the next sixth of a revolution, when they 
 are again excited. 
 
 The speed such a motor will attain is very great, 
 and hence special care has to be taken to guard 
 against centrifugal force displacing the coils. 
 
 Any number of magnets may bo employed with a 
 corresponding number of armatures and commutator 
 connections, as the ribs are termed. It will be found
 
 COMMUTATOR FOR MULTIPOLAR MOTOR. 55 
 
 that the height as well as breadth of the ribs is a 
 factor in determining the period of contact. The 
 more elegant way is to make each rib exactly one- 
 sixth the circle in width and fill the space between 
 the ribs with insulating material flush with the sur- 
 face of the ribs, so as to form a true cylindrical sur- 
 face for the spring to bear against. 
 
 The next cut shows in general the plan of connec- 
 tion, only for seve,n instead of for six magnets. At M is 
 
 FIG. 20. COMMUTATOR OP MULTIPOLAR MOTOR. 
 
 the ferrule upon the drum, against which one spring, 
 C, is constantly pressing. F, F, represent the ribs 
 connected to the collar, against which ribs the other 
 spring, D, bears. Their degree of projection, it- will 
 be seen, determines the time of contact. P and N 
 are the wires from the battery, and B is the base- 
 board. The dotted lines, H, H, indicate the course 
 of two of the wires running to and connected with 
 the ferrule, M. 
 
 A modification of this motor should be here alluded 
 to. The magnets are made stationary and occupy
 
 56 ELECTRIC TOT MAKING. 
 
 the position of the armature bars, while the rotating 
 portion carries only the six armature bars. The 
 commutator bars, springs, and ferrules are identical. 
 One set of terminal wires from the magnets are united 
 and a single larger wire is carried to a binding post. 
 The other ends, in like manner, connect with one of 
 the springs. The other spring connects to the other 
 binding post. Or all the ends of the magnet wires, 
 except those of any two magnets nexb to each other, 
 may be connected so as to bring the magnets in series. 
 The two free ends are connected as described, by 
 means of the springs, one to the commutator, or 
 ferrule, and the other to the binding post. 
 
 Page's Rotating Armature. 
 
 A simple form of motor, which may attain very 
 high speed, is shown in the cut. The great velocity 
 of an electric motor is not to be considered an advan- 
 tage, as it necessitates a reduction of speed by belts 
 and pulleys, or their equivalent. 
 
 Upon a fixed base, a permanent U-shaped magnet, 
 N, S, is secured, above which a horizontal fixed piece 
 is supported, forming the top member of a suitable 
 frame. A set-screw, with a conical hole in its end, 
 passes through the centre of this piece. A support, 
 corresponding to the set-screw, is secured to the base 
 directly below it, as shown. This support is a pin 
 with a conical hole drilled in its top. Between the 
 two coned supports a vertical spindle is carried. By
 
 PAGE'S ROTATING ARMATURE. 
 
 57 
 
 the set-screw the adjustment can be carried out, so 
 as to leave the spindle free to turn, yet without any 
 end shake. 
 
 To the spindle is attached a heavy bar of iron, wound 
 with insulated wire, which is virtually a U-shaped 
 
 FIG. 21. PAGE'S ROTATING ARMATURE. 
 
 electro-magnet. The wire is all wound in the same 
 direction. The ends of the wire are carried to two 
 divisions, i h, of a two-part commutator, which is 
 attached to the spindle directly above the rotating
 
 58 ELECTRIC TOT MAKING. 
 
 magnet, or polarized armature, as it might be called. 
 Two springs, g, f, of copper, brass, or silver, press 
 against the commutator. Each spring is attached 
 to the frame, and each has its own binding post to 
 receive the wires of the actuating circuit. When the 
 current passes the armature and spindle rotate. 
 
 While the construction of the commutator is clear 
 from the perspective view, a small sectional repre- 
 sentation is also given. In it A is the section of the 
 vertical spindle. S, S are the two 
 parts of the commutator. They 
 consist of bent plates of copper, 
 
 Fiu. 22. TWO-PART . rr . 
 
 COMMUTATOR. or brass, or silver, which are in- 
 sulated from the spindle. This insulation may be 
 simply a perforated bit of wood to which the plates 
 are cemented by sealing-wax, with a winding of silk 
 at the ends of the plates to further secure them. The 
 plates must of course not touch each other, and are 
 arranged with the two separations almost in the plane 
 at right angles to the plane of the electro-magnet. 
 In the diagram, W, W represent the springs. 
 
 The general action of the motor is the following : 
 The current, entering by uiie binding posts and springs 
 through the commutator, magnetizes the core of the 
 electro-magnet, which is generally denominated the 
 armature. The magnetization is such that it is 
 attracted in one direction or the other, assuming that 
 the bar does not lie in the plane of the magnet. 
 Yielding to the attraction it turns on its axis and
 
 THE ELECTRIC LOCOMOTIVE. 59 
 
 swings past the poles. As it does this, each spring 
 presses on the other leaf or plate of the commutator. 
 This causes a current, the reverse of the preceding, to 
 pass through the coil, and the bar is at once repelled. 
 As its momentum has carried it past the poles of the 
 magnet it continues its rotation, and is attracted by 
 the distant as well as repelled by the nearer poles. 
 The same action of reversal occurs twice in each revo- 
 lution. 
 
 If the armature lies in the plane of the fixed mag- 
 net the motor will not start, but a touch of the finger 
 will suffice to set it going. 
 
 The name given to this apparatus is that of the 
 celebrated Dr. Page, who, about half a century ago, 
 endeavored to introduce electric motors. As he had 
 no cheap source of current his work was a failure. 
 If the armature in this motor is turned by power it 
 will generate a current ; in other words, the mechan- 
 ism is reversible. 
 
 The Electric Locomotive. 
 
 An electric locomotive, babfed on the use of a motor 
 such as already described under the title of " Page's 
 Rotating Armature" (page 56), is illustrated here. 
 The general construction is clear from inspection of 
 the elevation. The motor is carried horizontally on 
 a little car moving on a railway, and a prolongation 
 of its shaft has on it a worm which gears into a
 
 GO 
 
 ELECTRIC TOT MAKING. 
 
 worm-wheel on the axle of one pair of Avheels. This 
 pair of wheels is attached rigidly to the axle and con- 
 stitute 1ho drivers. 
 
 THE ELECTRIC LOCOMOTIVI 
 
 The current is taken from the rails, the motor act- 
 ing as a bridge across them. The necessary connec- 
 tions for carrying out the plan, and the arrangements 
 for automatically reversing the engine, will be under- 
 stood from the view showing the bottom of the plat- 
 form, the wheels and reversing blocks.
 
 ELECTRIC LOCOMOTIVE. 61 
 
 One pair of wheels, those on the left, are mounted 
 loosely, the axle not rotating. The central or darkly 
 shaded part, M, of the axle, is of wood. A wire from 
 the metallic end of the axle, on which the wheel, K, 
 rotates, runs to a central plate, and thence to a plate, 
 G, which plates are insulated. Near Gr are two plates, 
 E and F, also insulated, except that from each of 
 them a commutator spring, to supply current to the 
 motor, rises. 
 
 It is unnecessary to describe the springs and com- 
 mutator. They are identical with those already 
 described and illustrated (pages 56 to 59). 
 
 An insulated switch, A, turns about the central 
 point between E and F. To its pivot, also insulated, 
 a wire is attached, which connects with the journal 
 of the car-wheel, J. The other car- wheel on the same 
 axle is insulated from it by a wooden or vulcanite 
 piece at L. 
 
 To the switcn pivot a stiff wire with contact piece, 
 C, is soldered. This presses upon E or F, according to 
 the way the switch handle is turned. To the switch 
 handle a second wire is soldered, which is bent so as 
 to bring its two contact pieces, B and D, into the 
 relations shown. 
 
 Both these wires must be of spring temper to ensure 
 electrical contact by pressure between their ends and 
 the plates over which they slide. 
 
 The moving of the switch handle towards the part 
 corresponding to the lower portion of the cut would
 
 62 ELECTRIC TOY MAKING. 
 
 shift the contact pieces, B and C, to the reverse posi- 
 tion, as regards the plates E and F. C would be 
 shifted to E, and B would be shifted to F ; while D 
 would slide along its plate, G-, it would not leave it. 
 
 As the switch is shown in the cut the current 
 would enter by the wheel, K. It would pass to the 
 plate, Gf, thence to the plate, E. It would then go 
 through the coil of the armature of the motor, and, 
 leaving it, would go through the plate, F, contact 
 piece, C, switch journal, and its connection to the 
 journal of the wheel, J, and through that wheel to 
 the other rail. 
 
 This causes the motor to rotate and propels the car 
 along the track always in the same direction. 
 
 Now, if the switch is turned, as already described, 
 so as to reverse the position of the contact pieces, C 
 and B, this will reverse the direction of the current 
 as it goes through the motor, and will reverse the 
 direction in which the car travels. 
 
 This reversal may be automatically effected by 
 switch blocks attached to the roadway, two of which 
 are indicated in the plan by H and I. If such are to 
 be used a pin is inserted in the end of the switch, 
 A, shown in the plan and elevation, which strikes 
 the inclined edge of the switch-blocks and shifts over 
 the switch. In an instant the motor is brought to 
 rest and then starts back reversed. 
 
 The battery connections are shown in the eleva-
 
 LOCOMOTIVE SWITCH CONNECTIONS. 63
 
 G4 ELECTRIC TOT MAKING. 
 
 tion. The rails must be continuous, or must have 
 their abutting ends connected by plates or wires. 
 The two lines of rail must be well insulated from each 
 other. 
 
 Any motor may be used to drive an electric loco- 
 motive. The advantage of those working with a per- 
 manent magnet for field is that they have a fixed 
 direction of movement. 
 
 The elevation shows several details not needing 
 description, such as the set-screws for adjusting the 
 end play of the armature axle. 
 
 The general system of reversing might be applied 
 to any other fixed direction motor. One advantage 
 of the automatic reversing is that it obviates the 
 necessity of a circular or continuous track. An im- 
 provement would also be to start a short up-grade 
 directly beyond the reversing block to aid in stopping 
 and starting back the motor.
 
 CHAPTER V. 
 
 ELECTKIC BELLS. 
 
 THE TOLLING BELL THE VIBRATING BELL THE 
 SAFE PROTECTOR. 
 
 The Tolling Bell 
 
 ELECTRIC bells are generally of the gong type, and 
 produce a sharp ring. The cut shows how a large 
 regulation-shape bell can be made to toll by an elec- 
 tric current. In many cases the use of a gong would 
 be disagreeable from its sound or appearance. In 
 the arrangement illustrated, the ringing apparatus is 
 all contained within the cavity of the bell so as to be 
 pretty well hidden from sight. 
 
 The magnet consists of a perforated iron bobbin 
 with heavy end flanges, of the Recordon type. A 
 couple of pole pieces may be attached to the ends as 
 shown. The magnet is attached to the base of the 
 bell. One of its terminal wires runs through the axis 
 of the extension of the magnet core to the outside of 
 the bell, being insulated from the metal. This obvi- 
 ates the necessity of drilling a special hole in the 
 bell, and possibly impairing its tone. The other 
 terminal wire connects directly with the metal of the 
 bell. A rod, bent into an irregular IT shape, carries
 
 66 
 
 ELECTRIC TOT MAKING. 
 
 at one end an iron ball, and constitutes the clap- 
 per. To the other limb of the rod a flat-faced bar of 
 iron, long enough to reach from outside to outside of 
 the pole pieces, is fastened. This acts as armature. 
 The bent bar is pivoted near its centre, as shown. 
 
 FIG. 25. TUB TOLLING BKLL. 
 
 A circle or ring is comprised within it at the top of the 
 bend, which opening contains the suspension rod or 
 core extension of the magnet. One pin goes through 
 both sides of the ring and the suspension rod in
 
 THE TOLLING BELL. 67 
 
 question. This acts as a very excellent pivoting, 
 preventing lateral shake. 
 
 The bell is hung to a metallic bracket. From the 
 battery one wire runs directly to the bracket. It 
 thus connects with the magnet coil, through the 
 metal of the bracket and bell. 
 
 The other wire from the battery runs to a key, 
 whence another wire connects with the magnet ter- 
 minal wire coming out of the bell spindle. 
 
 The key may be of the simplest construction, as 
 shown in the cut. When it is depressed, thus closing 
 the circuit, the magnet is excited, attracts its arma- 
 ture and rings the bell. 
 
 The peculiar form of the magnet is not only advan- 
 tageous in compactness of shape but is also supposed 
 to give better results than usual in the way of at- 
 tractive power. 
 
 The Vibrating Bell 
 
 The continuously ringing bell is one which will 
 automatically ring as long as the current continues. 
 It is really a motor. A simple form is shown in the 
 cut. 
 
 To a base-board is attached an electro-magnet. A 
 bar of soft iron, which is its armature, is carried by a 
 flat spring which draws it away from the magnet. A 
 contact screw is so arranged as to touch the armature 
 spring when the armature is drawn away from 
 the magnet. To the armature is attached a wire,
 
 ELECTRIC TOY MAKING. 
 
 carrying a ball, which serves as a clapper. A gong is 
 fastened by its central post to the same base-board, 
 which also may carry two binding posts. 
 
 Fio. 26. THE VIBBATING BELL. 
 The connections are shown in dotted lines. From
 
 THE SAFE PROTECTOR. 69 
 
 one binding post a wire runs directly to one of the 
 magnet terminals. From the other terminal of .the 
 magnet the wire connects with the armature spring. 
 From the other binding post a wire runs to the 
 metallic support of the contact screw. 
 
 When no current passes, the armature is drawn 
 back from the bell, and the spring is in contact with 
 the contact screw. If, now, a current is caused to pass, 
 it enters by one of the binding screws and excites the 
 magnet, its course going through the spring and con- 
 tact screw. The magnet attracts its armature, and 
 opens the circuit by drawing the spring away from 
 the contact screw. The attraction of the armature 
 draws the clapper against the bell and gives a ring. 
 As the circuit is opened the armature springs back 
 and again closes the circuit. Again the armature is at- 
 tracted and the bell rings. This operation is repeated 
 over and over again as long as the current is kept up. 
 
 The usual way of turning on the current is by a 
 press-button, which construction is so simple as to 
 need no description. It is seen in section on the left 
 hand of the cut on page 66. Any form of switch 
 will answer the same purpose. 
 
 The Safe Protector. 
 
 This apparatus is what may be termed a combined 
 electrical and mechanical safe protector. The illus- 
 tration shows its application and principle. 
 
 In Fig. 2 the ordinary bell, such as described in its
 
 70 
 
 ELECTRIC TOY MAKING. 
 
 proper place (page 67), with battery, switch-box or 
 "thief detector/' and safe are shown. From the 
 safe two wires, I J, are carried to the switch-box. 
 Within the safe is a spring-switch, which, when 
 pressed, maintains an open circuit, and when released 
 
 FIG. 27. THE SAFE PROTECTOR. 
 
 by the opening of the safe door, closes the circuit. 
 Such a switch is so simple that enlarged description 
 is not required. This switch is actuated by the safe
 
 THE SAFE PROTECTOR. 71 
 
 door. When closed, the door keeps the circuit open 
 by pressing on the switch. When the door is opened the 
 circuit closes, as the gwitch is released from pressure. 
 
 Two wires from the battery and bell circuit lead to 
 the switch-bo*x, connecting with the binding screws, 
 E, F, Fig. 1, on top of the box, A B C D. Within 
 the box each wire bifurcates as shown, and has its two 
 terminals connected to the two pairs of pins, O 1 , 3 
 and 0, 4 respectively. On the pins, 0, O 1 , two 
 springs, R, R 1 , work, to whose outer ends the safe 
 wires are attached. These wires draw the springs 
 down until they press against the steady-pins 1 
 and 2. 
 
 If, now, the safe is opened the circuit closes and the 
 bell rings. If the burglar, before opening the safe, 
 noticing the wires, I, J, cuts one of them to secure 
 himself from detection, the spring R or R 1 , as the 
 case may be, springs up and makes contact with the 
 stud, 3 or 4, on the opposite bell and battery terminal. 
 This, of course, closes the circuit, also, and the bell 
 rings. The same is the case if both wires are cut. 
 Both springs then fly up and the circuit is closed just 
 as before. 
 
 It will, of course, be an object to hide the switch- 
 box, because if one or both of the leads from bell and 
 battery are severed, the apparatus will become inop- 
 erative. The wires, I, J, must also be so fixed as to 
 appear like ordinary electric leads. They must be 
 perfectly free for their entire lengths.
 
 72 ELECTRIC TOY MAKING. 
 
 If the burglar understood the construction all he 
 would have to do would be to secure the wires, I J, 
 by staples or by tying, and theu to cut them off be- 
 low the staples. This would prevent the bell from 
 ringing and would enable the safe to be opened. It 
 is assumed, however, that the natural course of cut- 
 ting one or both of the wires will be followed by any 
 illicit operator, who attempts to prevent the electric 
 alarm from operating.
 
 CHAPTER VI. 
 MISCELLANEOUS TOYS. 
 
 THE ELECTRIC DANCER THE MAGIC DRUM THE 
 ELECTRIC HAMMER ELECTRIC INSECTS THE 
 INCANDESCENT LAMP. 
 
 The Electric Dancer. 
 
 THIS amusing toy originally was produced to be 
 operated entirely by hand. The electrical modifica- 
 tion is based upon the principle of the vibrating bell, 
 and needs but a short description. The cuts show 
 one construction very clearly. 
 
 A box contains the motive mechanism. This con- 
 sists of an electro-magnet with a soft iron armature 
 carried by a spring. A wire from the battery goes 
 directly to the magnet. The other terminal of the 
 magnet connects with the armature spring at L 1 . 
 The other end of the spring is bent at right angles 
 at L 2 , and carries a platform on a support L 3 . This 
 is the dancing platform. A contact spring, S S, is 
 carried by the armature spring. A contact screw, C, 
 is adjustable as regards its contact with the spring 
 S S. From it a wire runs to the binding post, B, to 
 which the other battery wire is attached.
 
 74 ELECTRIC TOT MAKING. 
 
 The magnet may have as cores round iron bars f 
 inch in diameter, 1 inch long, and wound to 1 
 inch diameter, with No. 26 silk covered wire. 
 
 FIG. 28. THE ELECTRIC DANCER. ELEVATION. 
 
 The action of a current on such mechanism is to 
 keep the platform in constant vibration, which may
 
 THE ELECTRIC DANCER. 75 
 
 be regulated and modified over quite a range of action 
 by the screw, C. 
 
 The figure is made of wood, with very loose joints, 
 and is suspended by a curved arm, so that its feet 
 
 A 
 
 8 
 
 
 
 
 
 o 
 
 
 
 
 C 
 
 D 
 
 
 FIG. 29. THE ELECTRIC DANCKB. PLAN. 
 
 just touch the stage. When a current passes, the 
 lignre begins to dance, and keeps it up as long as the 
 battery supplies enough energy. 
 
 Another way of working it is to make the figure 
 do the making and breaking of the circuit. For 
 this end, the binding post, B, should be connected to 
 the curved suspension-rod, instead of connecting 
 with the contact screw, C. Jointed wires are carried 
 through the figure, and the ends are soldered to light 
 brass, or copper plates, on the soles of the feet. The 
 armature spring is in electrical contact with the top 
 of the dancing platform, which must have a metallic 
 surface. Very thin sheet brass, or copper, may be 
 used for this. 
 
 In the last construction, the screw, C, and spring,
 
 76 ELECTRIC TOT MAKING. 
 
 S S, may be retained, but there must be no connec- 
 tion between them and the binding post, B. 
 
 Tims arranged, the feet will make and break the 
 circuit. The jointed wires of one side are shown in 
 the cut. The height must be accurately fixed, so that 
 only slight adjustment need be made by the screw, C. 
 
 The wire by which the figure is suspended, should 
 have plenty of spring to it. The figure may be sus- 
 pended by a spiral wire spring, or even by an India 
 rubber spring. In the latter case, if the figure is to 
 make and break the circuit, by its feet, one or two 
 wire conductors must be used independently of the 
 rubber springs. 
 
 Two or three Leclanche cells will work the figure 
 for a short time for larger periods a more constant 
 type of generator must be used. 
 
 The Magic Drum. 
 
 The magic drum has been exhibited by many pro- 
 fessional magicians. When it is shown on a stage, far 
 from the eyes of the audience, it can be easily manipu- 
 lated, with little refinement, as far as concealment of 
 its mode of action is concerned. The trick is doubt- 
 less familiar to our readers. A drum is hung, by one 
 or two cords, from the top of the proscenium arch, or 
 ceiling, and, in response to the performer's orders, 
 plays, raps, etc. 
 
 The newer construction here illustrated, due to 
 Mr. Geo. M. Hopkins, is superior, as it requires only
 
 THE MAGIC DRUM. 
 
 one suspending cord, and, without close inspection, 
 it is far from obvious how the result is brought about. 
 The drum must contain some apparatus for mak- 
 ing a sound. As shown in No. 2, the apparatus con- 
 sists of a magnet and armature, D, both secured firmly 
 
 FIG. 30. THE MAGIC DRUM. 
 
 to the body of the drum. The armature should be 
 as close to the poles of the magnet as possible, with- 
 out touching, even when the current is turned on. 
 
 A sudden exciting or releasing from excitement of 
 the magnet will produce a sound, on the general 
 principle of the make and break sounds in a tele- 
 phone.
 
 V8 ELECTRIC TOT MAKING. 
 
 The advantage of this apparatus is that it can be 
 so small and light as to be impossible of detection by 
 the closest inspection. Placed close to the embou- 
 chure of the drum it will fall outside of the line of 
 sight of any one looking into the interior. 
 
 If preferred, any form of rapping device, such as 
 described for bells, can be used. These will be more 
 easily detected. 
 
 From the magnet the two terminal wires run to 
 opposite ends of the drum, and are provided with two 
 ostensible suspending cords, A B, as shown in No. 1. 
 These are, of course, really the conductors, and end 
 in metallic hooks. They are hooked into a ring, C, 
 which is hooked on the end of the suspending cord. 
 
 The ring is shown in detail in No. 3. It is of 
 ebonite, or other non-conductor, and has two metallic 
 strips, indicated by the unshaded areas, a b, within its 
 interior. The main suspending cord, which includes 
 two wires concealed in it, and insulated, one from the 
 other, terminates in a hook, also of two insulated 
 pieces of metal, whose section is seen at E. Each 
 piece of this hook is connected with one of the two 
 wires in the suspending cord. 
 
 It is obvious that, if the drum is suspended as J 
 shown, the two wires of the suspending cord may, at 
 their further end, be attached to an electric circuit. 
 If the current is turned on and off, a sound will be 
 produced each time. 
 
 The single suspension cord, and the single hook
 
 THE ELECTRIC HAMMER. 79 
 
 thereon, with the intermediate ring, and apparent 
 absence of any sounding apparatus within the interior 
 of the drum, enhance the mystery above the ordinary. 
 The drum may even be passed around for inspec- 
 tion. If this is to be done, it is well to remove the 
 short suspending ends, A B, so that only a couple of 
 rings for hanging it will be visible. In such case, the 
 cords, A, B, should have hooks at both ends. 
 
 The Electric Hammer. 
 
 This toy, although, if made small, it is only a sort 
 of model of a steam hammer, can be made quite 
 powerful enough to be of some service. For the 
 latter end, it would be well to vary the construction 
 a little, and to use a polarized hammer spindle. 
 Simplicity is favored by the construction described. 
 
 As shown in the cut, it comprises a solenoid or deep 
 magnetizing coil, mounted on a suitable frame and 
 base. Under the axis of the core is placed an anvil. 
 
 A bar of soft iron nearly fits the opening in the 
 centre of the coil. The lower end of the bar is fitted 
 with an enlargement to represent the hammer head. 
 
 One battery wire connects directly with one of the 
 coil terminals. The other battery wire is attached to 
 a flat rubbing plate of ebonite, or hard wood, which 
 is secured by a single screw to the frame, so that it 
 can be swung up or down, as desired. The attach- 
 ment of the wire thereto is effected by a screw screwed 
 into the plate, and through which its point extends.
 
 80 
 
 ELECTRIC TOY MAKING. 
 
 The point is then filed off so as to be exactly flush 
 with the face of the plate. 
 
 Fie. 31. THE ELECTRIC HAMMER. ELEVATION.
 
 THE ELECTRIC HAMMER. 
 
 81 
 
 The second terminal of the coil is soldered to the 
 metallic frame at any convenient point. 
 
 FIG. 32. PLAN OF CONNECTIONS op ELECTRIC HAMMER. 
 
 To the frame a swinging arm is pivoted, the same 
 pivot serving for it and for the contact plate. It is 
 bent so as to pass back of the stem of the hammer, 
 and has two striking pins extending from it. A pin 
 attached to the hammer stem, strikes one of these 
 pieces, as the hammer rises, and another as it falls. 
 
 The action of the hammer, when connected to a 
 battery, is as follows : The current passes by the 
 contact screw, vibrating or swinging arm, and frame 
 to the magnet, and leaves it by the regular connec- 
 tion. 
 
 The solenoid attracts and draws up the hammer. 
 As it rises, the striking pin encounters the upper pro- 
 jection on the swinging arm, and raising it, displaces 
 its end from the contact pin. This opens the circuit, 
 stops the current, and the hammer falls. As it nearly 
 reaches the anvil the pin again strikes the lower pro- 
 jection on the swinging arm, and, pressing it down, 
 brings its end over the contact screw, thus closing the
 
 82 ELECTRIC TOT MAKING. 
 
 circuit and again exciting the solenoid. The ham- 
 mer is lifted and the same succession of movements 
 occurs over and over again, with considerable rapidity. 
 The contact or rubbing plate may be adjusted by 
 moving up or down, in order to regulate the motion 
 of the hammer. As the latter falls by gravity only, 
 its blows are not very heavy. 
 
 Electric Insects. 
 
 The base of the interesting toy next described, and 
 due to Mr. Geo. M. Hopkins, is an electro- magnet, 
 which is made to constitute the body of an insect. 
 The first insect to be spoken of is the electric butter- 
 
 %. 
 
 The sectional views of the body show a straight, 
 soft iron core, to which an arched pole piece, h, is 
 attached at the front of the insect's thorax. The 
 back of the butterfly is a thin plate of iron attached 
 to the other end of the core by the screw, g. To this 
 plate two small armatures, i i, are pivoted at /, as 
 shown, which extend down and over the ends of the pole 
 piece, li. To these armatures the wings are attached. 
 In making these there is room for artistic taste. 
 
 The armatures are made so much heavier than th(-[ 
 wings th;it the latter stand erect. It is, however, a 
 simple matter to introduce a fine German silver or 
 brass wire spring to keep the armatures away from 
 the pole piece. 
 
 The core is wrapped with No. 24 silk-covered wire,
 
 ELECTRIC INSECTS. 
 
 83 
 
 and the terminals are made to represent, or are carried 
 through or back of two of the insect's legs. The con- 
 
 
 FIG. 33. ELECTRICAL BUTTERFLY. 
 
 structor must not forget to put on the head with 
 proper adjuncts. 
 
 When a current is passed through the insect the 
 wings Avill be depressed. They will rise again on being 
 released. The current may be turned on by hand, 
 or an automatic circuit breaker, such as shown in 
 the next cut, may be used.
 
 ELECTRIC TOT MAKING. 
 
 This consists of a pendulum, whose motion is 
 maintained by electricity. Near its top the rod 
 carries an armature. The lower end 
 of the rod, which must be of metal, 
 and should terminate in a platinum 
 point, passes, in its motion, through 
 a globule of mercury. An electro- 
 magnet is fixed near the armature. 
 The circuit, which includes the but- 
 terfly, or several of its kindred, and 
 a battery, n, runs tli rough the cur- 
 rent breaker, thus : 
 
 One terminal goes to the electro- 
 magnet, k, and thence connects by 
 its suspension bracket, with the pen- 
 dulum rod ; going through this, the 
 current passes through the globule 
 
 Fio. 34. PENDULUM 
 
 CIRCUIT BREAKER, of mercury on m, to the other ter- 
 minal which is connected therewith. 
 
 Thus the butterfly and the pendulum magnet are 
 both excited, and the pendulum is attracted. If the 
 pendulum is started swinging, it will, as it leaves 
 the mercury globule, open the circuit, and the butter- 
 fly will move its wings ; at the same time the magnet 
 ceases to pull it. It swings back, and as it passes 
 through the globule, is attracted by the magnet as 
 the circuit closes, and the butterfly again moves its 
 wings in the reverse direction. 
 
 This can be kept up as long as desired. The exact
 
 ELECTRIC INSECTS. 86 
 
 position of the mercury globule, to give ti good swing, 
 must be determined by experiment. The plumb-bob 
 
 FIG. 35. ELECTRICAL DRAGON-FLY AND BEE. 
 
 is also made adjustable, so as to allow of varying the 
 time of movement of the insect's wings. 
 
 The dragon-fly and bee are more independent. 
 They are by nature quicker in their motions than
 
 86 ELECTRIC TOT MAKING. 
 
 the butterfly, and are constructed to rapidly move or 
 "buzz" their wings. 
 
 The core is bent at right angles at the head as 
 shown in the section of the dragon-fly. The arma- 
 ture, J, of soft iron, is carried by a spring fastened 
 at c to the core of the magnet. This is wound also 
 with No. 24 silk-covered wire. One terminal is 
 connected to the spring at c. From the armature an 
 extension of the spring reaches down over the insect's 
 front, and is bent to receive a contact screw, d, best 
 tipped with platinum. A contact piece, e, connects 
 with a wire running through, or by, one of the legs. 
 The other terminal of the magnet wire runs by 
 another leg. Thence the two are carried to a battery. 
 
 The whole arrangement, it will be seen, is an 
 automatic circuit breaker, and as long as the current 
 ; s turned on, will keep the armature in vibration. 
 
 Properly shaped wings made of mica, and painted 
 to represent the veins, are attached in any desired 
 position to the armature. The current causes these 
 to rapidly vibrate. 
 
 A very nice way to mount the insects is to place 
 them on some artificial flowers in a flower pot, which 
 latter contains a Leclanche battery. 
 
 One of the battery terminals connects with the 
 insect. The other runs to the base of the flower pot. 
 Here it nearly meets one of the terminal wires from 
 the insect. A globule of mercury is so disposed as to 
 leave the circuit open, if all is on a level table. If
 
 THE INCANDESCENT LAMP. 87 
 
 lifted, or tipped a little, the mercury shifts and 
 makes contact with both wires, closing the circuit 
 and making the insects start into seeming life. 
 
 The Incandescent Lamp. 
 
 The amateur should not attempt to make incandes- 
 cent carbon filament lamps. These are for sale, of all 
 descriptions and sizes. A platinum wire lamp, un- 
 regulated, is easily made, and with a carefully regu- 
 lated current is very good as a toy, but is of little 
 practical value. The end of a test tube may be used 
 to represent the bulb, and a bent loop of fine platinum 
 wire to represent the filament. The ends of the plati- 
 num are soldered to two copper wires considerably 
 thicker than themselves. The copper wires are 
 thrust through a cork which closes the end of the tube. 
 
 The platinum wire should be fine, No. 28 to 30. 
 The copper wire should be not less than No. 25. 
 
 The next cut shows a regulated platinum lamp, 
 which might render real service, although it would 
 never be as efficient as the carbon filament lamp, with 
 its almost perfect vacuum. 
 
 A base carries two binding posts and a glass 
 shade or bulb, and the mechanism of the lamp. 
 From the binding posts wires run to a post, B, and a 
 short screw at C. The latter screw holds down 
 against the base a high arched piece. To the post, B, 
 a rocker, A, is pivoted. From the arched piece to 
 the rocker a platinum wire, P, extends.
 
 88 ELECTRIC TOT MAKING. 
 
 As shown in the cut, the current entering by one 
 post passes through the wire and out by the other 
 post. As the wire expands with the heat, the left 
 end of the rocker descends. The adjustment is such 
 that contact is made before the platinum is hot enough 
 
 FIG. 36. SKLF-REGULATING PLATINUM LAMP. 
 
 to melt. This short circuits the wire, and the heat 
 falls ; as the wire contracts, it breaks the contact and 
 again grows hot. These operations in practise suc- 
 ceed each other so rapidij and are of such slight 
 degree, that all appears perfectly stationary, and no 
 vibration is perceptible.
 
 CHAPTER VII. 
 
 SPARK AND INDUCTION COILS, AND ALLIED 
 SUBJECTS. 
 
 THE SPARK COIL THE INDUCTION -COIL RECORD- 
 OX'S INDUCTION COIL THE MAGNETO-GENERA- 
 TOR ELECTRIC ARTILLERY ELECTRIC GYM- 
 NASTICS ANO-KATO SIMPLE EXPERIMENTS IN 
 
 STATIC ELECTRICITY. 
 
 The Spark Coil. 
 
 FOR the production of a simple spark for lighting 
 gas, firing an explosive mixture, and the like, a spark 
 coil may be employed. It is simpler in construction 
 than an induction coil. It practically represents a 
 single coil, either primary or secondary, of the more 
 complicated apparatus. 
 
 To construct one, a core of iron wire is first made. 
 This may be a bundle of pieces of wire of gauge No. 20, 
 or thereabouts. The pieces composing it should be 
 about eight inches long, and the bundle should repre- 
 sent a cylinder about f inch in diameter. 
 
 A very good plan is to put the pieces of wire in a 
 coal fire in the evening, and to allow them to become
 
 90 ELECTRIC TOT MAKING. 
 
 red hot. They are left in the fire over night until 
 it has grown cold. This anneals them and leaves 
 them covered with a thin film of oxide. The latter is 
 a non-conductor of electricity, and its presence acts to 
 break up the continuity of the core. 
 
 On this the coil is wound. It may be made of No. 
 20 wire, insulated with cotton. What is sold as 
 magnet wire will answer perfectly. This should be 
 wound on until the whole is about three times the 
 diameter of the core. The wire windings should cover 
 as nearly as possible the whole of the core. 
 If such a coil is placed in circuit with a battery, 
 the parallel component windings of wire act one upon 
 the other, when the current is turned on or off, and 
 produce a high potential difference. This causes the 
 production of a spark. The spark is strongest when 
 the current is suddenly shut off by breaking the cir- 
 cuit. As the coil is normally on an open circuit, and 
 as the operation of producing a spark consists in 
 suddenly depressing and releasing a key, thus open- 
 ing and closing the circuit in quick succession, a 
 double spark or discharge is produced. 
 
 The battery for operating a spark coil should be, as 
 a general rule, arranged in series. This gives as a 
 starting point the highest attainable potential differ- 
 ence, which again is magnified or increased by the 
 self-induction of the coil. 
 
 The tendency of the day is to use coils for high 
 tension effects. Regular induction coils are to be
 
 THE IND UCTION COIL. 9 1 
 
 recommended for powerful tension, but where a spark 
 suffices, the spark-coil answers every purpose. 
 
 So true is this that, on an emergency, any electro- 
 magnet, such as is used in a telegraph sounder, or 
 for lifting weights, and the like, can be made to do 
 service as a spark-coil. The ready production of a 
 spark on opening a circuit goes to prove that it in- 
 cludes a high potential battery, or that electro- 
 magnets, or some form of coil, are actuated by it. 
 
 The Induction Coil. 
 
 The induction coil is, in general terms, an apparatus 
 for converting a current of one intensity into a current 
 of a greater or less intensity. Conversely with the 
 change of intensity there is an inverse change in the 
 potential difference of such parts of the circuit as 
 represent the entering and outgoing terminals of 
 the coil. To bring about this change a steady cur- 
 rent cannot be directly used if such is the one to be 
 acted upon it must first be converted into an irregular 
 or varying one. The first, or unconverted current, is 
 called the primary current. The converted current, 
 produced by the action of the coil, is called the 
 secondary current ; it is always an interrupted cur- 
 rent, and of the type known as alternating. 
 
 An induction coil may be very easily constructed. 
 As a toy, for giving shocks and similar uses, it may 
 be quite small. But as the size increases the difficul- 
 ties of construction increase. The very large coils,
 
 92 ELECTRIC TOT MAKING. 
 
 giving from twelve to forty-two inch sparks, require 
 the highest skill of the apparatus maker. 
 
 For the amateur the induction coil will generally 
 be designed to increase potential difference at the 
 expense of intensity. The illustrations show the 
 features of construction of a simple coil designed to 
 do this. 
 
 Before going further it should be understood that 
 nothing absolute can be said of the size of a coil, or 
 of the wire composing it. All this is a matter of 
 calculation, and depends upon the current to be used, 
 and upon the current to be obtained from the coil. 
 
 The coil proper of the drawing consists of the 
 core, A, primary coil, B, insulating coating, C, and 
 secondary coil, D. The wires of the secondary coil 
 are kept insulated from the primary, and the greatest 
 care must also be taken to keep the different wind- 
 ings of both secondary and primary insulated from 
 each other. 
 
 The core consists of a bundle of iron wires, about 
 No. 18. These are laid together so as to form a cylin- 
 der. They may be annealed and oxidized as described 
 for the spark coil. After wrapping the core with 
 some shellacked paper, the primary wire is wound on 
 as compactly as possible. It should be insulated wire, 
 and it is well, if it is cotton covered, to paint over 
 the successive layers with alcoholic solution of shellac. 
 
 For ordinary coils No. 18 wire is a good size, and 
 two wrappings around the core may be employed.
 
 THE INDUCTION COIL. 93 
 
 A paste-board tube such as used for mailing draw- 
 ings or papers which are not to be folded, serves to 
 
 FIG. 37. INDUCTION COIL. 
 
 cover the primary coil a-ud core. On this the second- 
 ary core is wound. The tube must be well paraf- 
 fined. 
 
 Here, far more precautions in the way of insulating 
 the wire have to be taken. The wire itself is much 
 finer. If the potential is to be raised to one thousand 
 times the original diffeience, the wire will answer if 
 of one-thousandth the section of the primary. Turns 
 enough must then be given to it to ensure this ratio. 
 
 As a matter of practise the secondary is often made 
 of coarser wire than is required under the above sup-
 
 94 ELECTRIC TOT MAKING. 
 
 position. Very fine wire is expensive, and is difficult 
 10 work, as it is liable to break very easily when being 
 wound. No. 36 wire is fine enough for all ordinary 
 purposes. 
 
 Either bare, or insulated, or covered wire may be 
 used. In any case the number of turns it takes 
 around the core and primary must be equal to the 
 turns of the primary multiplied by the factor express- 
 ing the desired ratio of increase of potential diffrr- 
 ence. 
 
 Suppose a coil is to produce one thousand times as 
 great voltage as that existing between the primary 
 terminals, and that the primary has fifty turns. Then 
 the secondary must have fifty thousand turns. 
 
 If bare wire is used a layer is wound upon the in- 
 sulating tube, C, the successive turns lying as close as 
 possible without touching. Then a piece of paper is 
 wound over the wire, and is shellacked, and the wind- 
 ing is continued over it. This goes on until the 
 desired number of turns are obtained. As this in- 
 volves a long piece of winding it is best to do it on 
 the lathe. 
 
 An excellent plan is to wind only a half inch in 
 length of the secondary at a time, but to wind each 
 half inch to the full thickness before beginning the 
 next. To execute this, a bit of thin board with a 
 hole the size of the insulating tube in it is needed. 
 This is thrust up to within half an inch of the end 
 of the coil, and the space between it and the end is
 
 THE INDUCTION COIL. 
 
 95 
 
 wound to the full thickness ; then it is shifted half 
 an inch and the winding is thus continued until done. 
 In any case a temporary flange of some kind is 
 needed at the ends to keep the coils square. 
 
 Fia. 38. END PIECE OF FRAME OF INDUCTION COIL. 
 
 From time to time the wire should be tested for 
 continuity, as it is very apt to break. If it does part, 
 it may be carefully twisted together, and it is well to 
 solder it. This can be done in the flame of an alco- 
 hol lamp. In testing its continuity an ordinary 
 compass can be utilized as the galvanometer. If a 
 dozen turns of the wire are taken around it a slight 
 current will deflect the needle. The compass must
 
 96 ELECTRIC TO T MAKING. 
 
 be so placed that the coils lie in the magnetic merid- 
 ian. As battery, a copper coin and a bit of galvan- 
 ized iron, immersed for the moment in dilute sul- 
 phuric acid, will answer if the galvanometer is sensi- 
 tive enough. It is sufficient to discern the smallest 
 possible change of direction of the compass-needle. 
 
 If insulated wire is used, it should be shellacked 
 from time to time as wound, and the paper between 
 the layers should always be used as described. 
 
 When all is wound it is mounted in a frame as 
 shown, the coil being carried by two end pieces, H, 
 H, one of which is shown in side elevation on a larger 
 scale than that of the illustration of the coil. 
 
 The terminals of the secondary lead to and are 
 soldered to two binding posts, E, E. The terminals 
 of the primary, K, K, connect with a source of cur- 
 rent which must be very variable, intermittent, or 
 alternating. 
 
 If to the secondary terminals, or binding posts, a 
 couple of pieces of wire are attached, the ends of 
 which are held in the hands, and if then an inter- 
 mittent current is passed through the primary, a 
 series of shocks will be experienced. 
 
 For this purpose it is best to attach handles of 
 brass tubing, about half an inch in diameter, to the 
 ends of the wires, in order to give a larger surface of 
 contact. Wet sponges may, with advantage, be used 
 on the tubing, although as this is not necessary and 
 is rather unpleasant, it is not generally done.
 
 THE IND UCTION COIL. 97 
 
 Sparks may also be taken from the coil by bringing 
 the ends of two conductors from the secondary ter- 
 minals sufficiently close. A very small coil, two or 
 three inches long, will give a one- eighth inch spark, 
 and some of the large ones will give a spark several 
 feet long, one which will pierce a glass plate two 
 inches or more in thickness. 
 
 The primary circuit may be broken by hand. One 
 of the old methods consisted in connecting one end 
 of the primary to the battery, and the other to a very 
 
 FIG. 39. CIRCUIT BREAKER. 
 
 coarse cut file. The teeth of the file might be an 
 eighth of an inch apart, and as high as possible. 
 Then the other wire from the battery was drawn
 
 98 ELEGTR1G TOY MAKING. 
 
 across the file, and, as it jumped from tooth to tooth, 
 effected the desired "make and break." 
 
 Another way of doing it by hand is shown in the 
 cut. A cog-wheel from an old clock, or elsewhere, is 
 mounted on a metallic frame, which is in connection 
 with one of the battery wires. A spring wire presses 
 against the teeth as the wheel rotates. This spring 
 is in connection with one of the primary terminals of 
 the coil. The other primary terminal is in direct 
 connection with the battery. Thus the make and 
 break is obtained by turning the wheel. 
 
 The coil itself may be made to do the making and 
 breaking. As shown in the cut it is thus arranged : 
 On the base are two binding posts, which are the 
 primary terminals. One of the primary terminal 
 wires, K, K, runs directly to one of the binding posts. 
 The other primary terminal wire runs to the base of 
 the vertical spring, F. At its top this spring carries 
 a block of soft iron which acts as an armature. The 
 other binding post seen in the elevation connects 
 with the metallic standard, G. An adjustable con- 
 tact screw, with platinum point, goes through the top 
 of the standard. The spring normally presses against 
 this screw. It is well to rivet a little bit of platinum 
 on the spring at the point of contact. 
 
 When the terminals from a battery are attached to 
 the binding screws the action is obvious. The spring, 
 F, making contact through G with the battery, closes 
 the primary circuit and a current goes through the
 
 THE INDUCTION COIL. 9i> 
 
 primary. This magnetizes the core and the armature 
 on the spring is attracted. It draws the spring away 
 from the contact screw and breaks the circuit. The 
 core ceases to be magnetic and the spring flies back 
 and renews the contact. This action is kept up as 
 long as connection with the battery is maintained, 
 the makes and breaks succeeding each other with 
 great rapidity. 
 
 As thus described, the induction coil is far from 
 perfect. A violent sparking action takes place at the 
 make and break contact and there is considerable 
 waste of energy. Both these bad features can be 
 diminished by the use of a condenser, whose construc- 
 tion will be next explained. 
 
 It would consist, in its simplest plan, of two leaves 
 of tin-foil separated from each other, one connected 
 to the spring, F, and the other to the standard, G. 
 The area must be quite large so that as a matter of 
 convenience it is best built up of small pieces of tin- 
 foil laid in a pile that fits the base of the instrument, 
 which is made into a box to contain them. The con- 
 nections and general features of the condenser are 
 best shown in the plan view. 
 
 Each piece of foil is cut with projecting ears, A, B, 
 at one of the corners. The shape is seen in the plan 
 view given here. A piece of paper, saturated with 
 paraffine wax, is placed between each two sheets. In 
 piling up the sheets of tin-foil the ears, A, or B, of 
 each sheet are placed at the opposite corners as
 
 100 
 
 ELECTRIC TOT MAKING. 
 
 indicated in the plan. It is now evident that if the 
 projecting ears are bent down or pressed together, 
 each set of leaves of tin-foil will be insulated 
 from the other, but all the leaves of each set will 
 be in electrical connection with each other. To 
 
 FIG. 40. PLAN VIEW OF INDUCTION COIL. 
 
 ensure all this, the paper should be cut an eighth of 
 an inch longer and wider than the tin-foil. The 
 paper can be easily waxed or paraffined by applying 
 the wax in shavings and melting it with a hot sad- 
 iron, or in an oven or over a stove. 
 
 Referring now to the plan, in it E denotes one of 
 the binding posts to which the battery wire is to be 
 connected. H is the primary coil. From E a wire is 
 carried to and connects at D with one of the termi- 
 nals of H. The other terminal of H, denoted by C, 
 connects with the spring (F, in the elevation), whose 
 base is shown in the plan. The other binding post 
 which, it will be remembered, is in connection with the
 
 THE INDUCTION COIL. 101 
 
 contact screw post (G, of the elevation), is shown at F 
 in the plan. From this contact screw post a wire 
 connects with one set of tin-foil sheets, A, while from 
 the spring u wire connects with the other set of 
 sheets, B. 
 
 The action of the condenser is apparent in the 
 reduction of the size of the spark between the make 
 and break surfaces, and in the lengthening of the 
 other secondary spark. In other words, a condenser 
 greatly improves the action of an induction coil, and 
 should always be used. 
 
 As an example of a miniature coil the following 
 data may be given : Core, 4 inches long, and as 
 thick as a lead pencil. Length between end pieces, 3 
 inches. Primary coil, two ounces of No. 18 wire. 
 The secondary wound to within % inch of the insu- 
 lating tube, with two ounces of No. 36 wire. The con- 
 denser, twenty pieces tin-foil, each 3 inches square. 
 
 An excellent way of making the insulating tube is 
 to saturate a piece of blotting paper with paraffine 
 wax. A wooden mandrel is wrapped with a piece of 
 writing paper, whose free end is pasted down to the 
 paper. This must be free to slide on and off. The 
 mandrel must be of the diameter of the primary. On 
 this the blotting paper is wound, being pressed into 
 place with a hot iron. This solidifies it by melting 
 the wax. It should be one-twentieth of an inch 
 thick. 
 
 The tension of the shocks may be graduated by
 
 102 
 
 ELECTRIC TOY MAKING. 
 
 Bulling the core out or pressing it in. Its removal 
 greatly reduces the intensity of action. Or else a 
 space may be left between the secondary and pri- 
 mary, and a brass tube may be arranged to slide in 
 and out of this space. The removal of the tube 
 increases the energy of action. 
 
 Recor don's Induction Coil. 
 
 A very good form of induction coil is shown in the 
 next cut which at least possesses the merit of novelty. 
 
 FIG. 41. RECOUDON'S INDUCTION COIL. 
 
 It is disadvantageous in not admitting the convenient 
 use of a wire core. 
 
 The core which is hollow, is made of soft, annealed
 
 RECORDON'S INDUCTION COIL. 103 
 
 iron, turned so as to represent a spool or bobbin with 
 deep flanges at eacli end. It is mounted as shown, 
 wound with primary and secondary coil, B, as de- 
 scribed for the other form of coil. The secondary con- 
 nects with two binding posts on the base, one of which 
 is seen at N. Of the primary terminals, one connects 
 with the standard, D, the other with the binding 
 post, b. From the binding post, 5 1 , a wire runs to the 
 standard, C. 
 
 To the top of the standard, D, a spring is screwed 
 to which an iron block, A, is attached. The stand- 
 ard, C, carries a contact screw with platinum point. 
 The iron block, A, acts as the armature of the mag- 
 net. The piece, P, is simply designed to regulate 
 the period of vibration and prevent too rapid a 
 succession of makes and breaks. The battery con- 
 nects with the binding posts, J 1 and b, 
 
 When the current passes to the primary coil 
 through the standard, C, contact screw, spring and 
 standard, D, it excites the core, which becomes a 
 magnet. The armature, A, is attracted and draws 
 the spring away from the contact screw. This opens 
 the circuit. The core ceases to attract the armature 
 and it springs back. The contact screw again 
 comes in contact with the spring, and the current 
 again passes. Thus the make and break is effected 
 practically as in the case of the other coil. 
 
 Although shown without a condenser, it will work 
 far better if it has one.
 
 104 ELECTRIC TOT MAKING. 
 
 This coil may be fitted with a regulator. To do 
 this the barrel should be turned down so as to be very 
 thin. It may even be made of sheet iron, bent into 
 a tube and soldered along its seam, and to the heavy 
 flanges. A bundle of iron wires is then arranged to 
 fit into the tube, and to be slid in or out as desired. 
 The more there are within the tube the greater will 
 be the effect of the coil. 
 
 The dimensions of the coil illustrated are as fol- 
 lows : Diameter of coil, 3 T y 7 inches; thickness of 
 flanges, T %- inch ; exterior diameter of core, 1 T V inch ; 
 interior diameter of flange, 1^- inch ; distance be- 
 tween flanges, 1^ inch. Primary wire, -^frlb. avoir- 
 dupois No. 18 wire ; secondary wire (in 31 layers), 
 j^j- Ib. avoirdupois No. 32 wire. There is, of course, 
 nothing absolute in these dimensions. 
 
 The Magneto- Generator. 
 
 A very powerful and compact form of magneto- 
 generator is the subject of the next cut. As arranged 
 it is designed to give rapid alternating shocks. 
 
 Two powerful horseshoe magnets are mounted as 
 shown. A pair of bobbins, such as those used on the 
 legs of horseshoe electro-magnets, arc carried by a 
 vertical spindle so as to rotate between the opposing 
 poles. The letters, N and S, seen on the magnet ends, 
 denote the north and south poles respectively. The 
 bobbins have, as cores, two bundles of iron wire, 
 which should be annealed and oxidized. Each piece
 
 THE MAGNETO-GENERATOR. 
 
 105 
 
 of wire should be long enough to nearly reach from 
 face to face of the magnets. 
 
 As wire, Nos. 30 to 36 may be used. The bobbins 
 may be two inches long, and wound with enough 
 wire to fill them up to a diameter of one inch. Be- 
 tween every layer of winding a piece of paraffined 
 paper must be smoothly wound. Shellacked paper 
 
 FIQ. 42. MAGNBTO-GENKBATOB. 
 
 may be used instead, and each of the layers may then 
 be varnished with alcoholic solution of shellac. The 
 general precautions observed in winding the secondary 
 of an induction coil must be followed here. 
 
 In laying on the windings the greatest care must be 
 taken to avoid kinks, or sudden bends. From time 
 to time the part wound should be tested with a gal- 
 vanometer, as in the case of the induction coil, to see 
 if it passes a current. If the wire breaks, the ends 
 must be soldered after neat twisting together.
 
 106 ELECTRIC TOT MAKING. 
 
 The wire on the bobbins must be wound in opposite 
 directions, one right and the other left handed, ex- 
 actly as in a horseshoe electro-magnet. 
 
 On the upper end of the spindle are an insulated 
 collar and an insulated crown-wheel. The bobbins 
 are connected together so as to give the current an 
 opposite direction in each one. The connecting wire 
 is made to lead diagonally from front of one to rear 
 of the other. This leaves two free terminals. One is 
 soldered to the collar, the other to the crown-wheel. 
 
 Two springs of copper, brass, or silver, press, one 
 against the collar, the other against the teeth of the 
 crown-wheel. Multiplying gear is applied to drive 
 the mechanism, by turning the bobbins rapidly 
 around in the magnetic field created by the magnets. 
 
 The springs are secured to insulated binding posts, 
 to each of which flexible wire, or conducting cord, 
 is connected. The other ends of the pieces have 
 handles. 
 
 If, now, the hand-wheel is rapidly turned, while the 
 handles are held one in each hand, or are applied to 
 different parts of the body, a succession of rapidly 
 succeeding shocks will be felt. 
 
 Should it be desired to have the impulses all run 
 in the same direction, the commutator shown and 
 described on page 58, must be used, instead of the 
 collar and crown-wheel. 
 
 A well made magneto-generator, such as described, 
 will give powerful shocks. If wound with coarser
 
 ELECTRIC ARTILLERY. 107 
 
 wire, No. 25, or thereabouts, and if provided with the 
 commutator just alluded to, it will give quite cur- 
 rent enough to heat fine platinum wire and decom- 
 pose water. 
 
 Electric Artillery. 
 
 Explosions of gunpowder, or of hydrogen, or of coal 
 gas, mixed with oxygen or air, can 
 be produced by the electric spark, 
 or by an incandescent wire. The 
 cut shows what may be termed an 
 electric mortar. It may be made of 
 metal or of wood. Two wires, in- 
 
 FIG. 43. ELECTRIC , , , .. , , , . , , , , 
 
 MORTAR. sulated from the material of the 
 
 mortar, if the latter is of metal, are arranged as 
 shown, approaching close to each other, but not 
 touching within the cavity of the mortar. 
 
 Such a mortar may be charged with powder, and if 
 a spark from a Leyden jar, induction or spark 
 coil, is passed through it, the powder will explode. A 
 ball placed on the mouth, which is countersunk to 
 receive it, will be shot into the air. A magneto- 
 generator may be used to produce the spark. 
 
 The ignition by a spark is not always certain. It is 
 a common practice to include in the circuit, if a 
 Leyden jar is employed, a piece of wet cord, which 
 makes the spark more efficient. The spark may be 
 taken also directly from an electric machine. 
 
 It is better to produce these explosions by a wire 
 heated by a current. For such, the simplest method
 
 108 ELECTRIC TOT MAKING. 
 
 is to fit the barrel with a plug, which screws tightly 
 into it, and through which the two wires, well insu- 
 lated, pass as shown in the cut. 
 
 The wires protrude a little on the inner side, and 
 
 1 
 
 FIG. 44. ELECTRIC OR VOLTAIC PISTOL. 
 
 across from end to end of them a very fine wire, of 
 platinum or of iron, is carried. It must be in good 
 electrical connection with both, which is best insured 
 by soldering. The copper wires may be No. 20 or 
 thereabouts. What is the simplest, and really the 
 best construction, is to make a plug of some non-con- 
 ducting material, such as hard wood, and to thrust 
 the bare wires through holes which, if in wood, may 
 be bored with a brad-awl. The connecting wire 
 should be very fine and the shorter it is the hotter it 
 will get. If too great a current is employed the 
 wire will be melted. It is well to test, by experiment, 
 how many cups of the experimenter's battery are re- 
 quired to heat it to redness.
 
 ELECTRIC ARTILLERY. 109 
 
 All this is a subject of calculation, and those who 
 wish can readily work out the problem for them- 
 selves. 
 
 Such an apparatus may be called an electric 
 primer. A pinch of gunpowder can be ignited by 
 passing a current through the wire, immersed in or 
 covered by it. 
 
 The voltaic pistol simply consists of a tube of brass 
 with a handle and a side connection into which the 
 plug screws. By holding it mouth downwards for a 
 second or two, some inches above and over an open 
 unlighted gas-burner, it will be charged with a mix- 
 ture of air and gas. A cork is now thrust into its 
 mouth ; it is held pointed in the right direction, and 
 a current is passed through the cap. The mixture ex- 
 plodes and drives the cork out. To produce a strong 
 explosion, the proper mixture is about six of air to 
 one of gas. Such a mixture may be made in a test 
 tube or even in a bottle. One sixth of its volume of 
 water is introduced and the tube or bottle is inverted, 
 without loosing any water, into a basin of water with 
 its mouth under the surface ; the rest of the bottle 
 is now filled by bubbling gas into it. 
 
 The pistol barrel is filled with water ; it is inverted 
 in the basin, and the contents of the bottle are intro- 
 duced, bubbling through the water. It is removed, 
 mouth downwards, and quickly corked, and all is 
 ready for the explosion. 
 
 For an extremely violent report, a mixture of one
 
 110 ELECTRIC TOT MAKING. 
 
 volume of oxygen to two volumes of hydrogen gas 
 may be used. 
 
 It is obvious that many variations can be intro- 
 duced in this experiment. A bottle may take the 
 place of the pistol. The wires may be thrust through 
 the cork, which will take the place of both the cap 
 and cork. The bottle is best filled over water to se- 
 cure the right mixture. On turning on the current 
 the cork will be driven up to the ceiling. 
 
 In the same way India rubber balloons may be ex- 
 ploded. They must be partially inflated with oxy- 
 gen evolved under pressure, and then about twice the 
 volume of hydrogen is introduced directly from the 
 
 FIG. 45. FIBE CRACKER EXPLOSIONS. 
 
 generating flask. A very small cork is arranged with 
 the exploding wire connection. As the balloon is 
 filled its neck is pinched with the finger well up from 
 the end, and the cork is dexterously introduced. 
 Common fire crackers may be used as presented in
 
 ELECTRIC GYMNASTICS. Ill 
 
 the cut to illustrate electric fuses. All that is neces- 
 sary is to twist a fine wire around the projecting fuse 
 of the cracker, as shown in the cut at a, or to trans- 
 fix the cracker with a piece of fine wire, as shown at 
 J. "When a strong enough current is sent through 
 the wire the explosion of the fire cracker will follow. 
 In " rain-making " experiments, conducted in the 
 arid zone in the western United States, in the 
 season of 1891, large balloons of combustible gas 
 and oxygen were exploded by electricity in the hope 
 of producing rain. 
 
 Electric Gymnastics. 
 
 A very clever idea has taken shape in the produc- 
 tion of gymnastic apparatus, which in its use pro- 
 duces and administers electric shocks. The type of 
 apparatus is of the weight-lifting kind, in which 
 s'pade handles attached to ropes are pulled by the 
 gymnast. The strings run over pulleys and weights 
 are attached to their ends. By varying the weights 
 the exercise may be made more or less severe, and by 
 different movements a great variety of exercise may 
 be derived from the comparatively simple apparatus. 
 
 The idea of applying electricity is to cause these 
 movements to tie productive of shocks. This can be 
 effected in several ways. The first way to be 
 described is by a magneto-generator. 
 
 The cords of the apparatus have wires running 
 through them. The handles are metallic and are in
 
 112 ELECTRIC TOY MAKING. 
 
 electric or metallic communication with the wire. 
 The magneto-generator has already been described. 
 In the ordinary gymnastic apparatus the pulleys 
 are fastened about six feet from the floor. At this 
 point the generator is to be secured. From the pulley 
 spindle a horizontal axle runs along parallel with 
 the wall. The generator is placed in such a position 
 that this axle comes in the prolongation of its own 
 axle and three or four inches out from the wall. The 
 axle passes through two strong journal brackets or 
 pillars. Two pulleys with deep, wide grooves have 
 fastened to them the handle cords. A third pulley 
 has the weight-cord fastened to and wound around 
 it a number of times. 
 
 Under this arrangement it is clear that, when the 
 weight is up, the handles will be free to be pulled 
 out to the full extent. If the weight descends it 
 will unroll its own cord, and roll up the other two. 
 
 In these movements, the bobbin of the generator 
 will turn with greater or less velocity, according to 
 the way in which the apparatus is handled. If the 
 wire handle-cords are connected to the terminals from 
 the bobbin, the one who manipulates the apparatus 
 will receive a series of electric shocks. This will be 
 more violent as he works the apparatus more ener- 
 getically. 
 
 The connection is easily managed. Perhaps the 
 simplest way is by springs, which bear against insu- 
 lated metal-coated drums or collectors.
 
 ELECTRIC O TMNAST1CS. 1 1 3 
 
 For this method two collars of wood, or other insu- 
 lating material, are fastened to the axle, one for each 
 handle- cord. The collars have a ring of brass around 
 their peripheries. Each wire from a handle-cord is 
 soldered, or driven firmly under the brass on one of 
 the collars. 
 
 Copper or brass springs are attached to the base- 
 board carrying the apparatus, which lies flat against 
 the wall. There is one spring for each collar, and 
 each presses against the metal coating of the collar. 
 These springs are in electric communication with 
 the terminals of the magneto-generator. 
 
 Thus arranged the generator terminals are in con- 
 stant connection with the handles, and the person 
 operating receives the desired electrical excitement. 
 It is also possible to dispense with the commutator of 
 the generator and simply connect the terminals from 
 the rotating bobbins directly to the handle-wires. 
 This gives, however, rather a slow succession of 
 shocks. 
 
 Another way of arranging the system is to use an 
 induction coil. Then the working of the apparatus 
 is caused to make and break the primary circuit. 
 
 For this end, the general features of a rotating 
 axle, with handle cord and weight-cord pulleys, is 
 preserved. The same collars and springs are em- 
 ployed also. Upon the back-board an induction coil 
 is mounted. Its secondary terminals are carried to
 
 114 
 
 ELECTRIC TOY MAKING. 
 
 the two springs, thus being in electric connection 
 with the handles. 
 
 The axle which rotates back and forth carries an 
 insulated circuit breaking wheel of the general type 
 of the one shown in the cut. As it has to work in 
 
 CIRCUIT BREAKER. 
 
 both directions of rotation, the wire that strikes the 
 teeth must be so bent and shaped as to work whichever 
 way the wheel may rotate. Two springs press, one 
 against the teeth, the other against the face or frame 
 of the wheel, and connect wilh battery and primary. 
 A better arrangement is to mount a regular smooth 
 surfaced commutator on the axle. This may consist 
 of a wooden cylinder, to which are secured a number
 
 ELECTRIC GYMNASTICS. 115 
 
 of slips of thin brass lying parallel with the axis. 
 These should be so thin as to lie flush with the wood, 
 or they may be inlaid, or embedded in it. Two 
 small screws will fasten each piece. A ring of brass 
 goes around one end of the commutator drum, being 
 in good electrical connection with all the slips. 
 
 One spring is attached to the base so as to bear 
 against the ring. Another spring bears against the 
 drum to one side of the ring. From one spring a 
 wire goes to one of the primary terminals of the coil. 
 From the other spring a wire runs to the battery, 
 and the other battery wire runs to the other primary 
 terminal of the coil. 
 
 It Avill be understood, of course, that the coil is 
 unprovided with an automatic circuit breaker, and 
 that the manipulation of the apparatus by the gym- 
 nast, makes and breaks the primary circuit. This 
 induces a current in the secondary, which, by the 
 spring connections, wires and metallic handles, finds 
 its way to the hands. 
 
 The coil should be provided with a movable core, or 
 brass shielding tube, or else some arrangement for rais- 
 ing and lowering the battery plates should be provided 
 in order to vary the strength of the induced currents. 
 
 The magneto-generator gives shocks varying in in- 
 tensity as well as in frequency. The induction coil 
 gives shocks of uniform intensity, varying in fre- 
 quency. The objection to the latter is that it needs a 
 battery.
 
 llfi ELECTRIC TOT MAKING 
 
 It is also to be noted that the magneto-generator 
 may be made to supply the proper current to the 
 primary of an induction coil, and that the collecting 
 collars may connect with the secondary of the coil. 
 In this method, the characteristic alternating current 
 of the generator works the induction coil to advantage, 
 without any mechanical make and break device. 
 
 The primary of the coil thus used should have a 
 large number of turns, from one-eighth to one-fourth 
 as many as are in the secondary wire. The bobbins 
 of the generator should be wound of the same sized 
 wire as the primary of the coil. No. 24 wire would 
 be a good size for both. 
 
 Thi^ disposition will increase the tension of the 
 circuit, and will give more powerful effects, as the 
 apparatus is more rapidly moved. 
 
 AnoKato. 
 
 The words ANO, KA.TO, are taken from the Greek, 
 and mean up, down, and allude to the motions of the 
 objects seen in the box. The cut shows its general 
 features of construction. It is a shallow box whose 
 bottom and interior sides are coated with tin-foil. A 
 number of objects are made out of the lightest pith- 
 
 The latter may be of the pith of cornstalks, of 
 elder pith, or, what is still better, of the pith of the 
 dry stalks of the sunflower. Little men with jointed 
 legs and arms, insects, jointed snakes, etc., are made 
 out of the pith, and may be colored with a little red
 
 ANO-KATO. 
 
 117 
 
 and black ink. The box is covered with u piece of 
 glass. 
 
 If the glass is rubbed with a proper rubber, it be- 
 comes electrically excited, and attracts the objects in 
 the box. As they ri^e, they touch the glass ; and as 
 
 FIG. 47. ANO-KATO. 
 
 they lie against it, becoming charged with the same 
 electricity, are quickly repelled. They fall into the 
 box and are discharged by coming against the tin- 
 foil, which, for high potential difference, may be con- 
 sidered to be iu electrical communication with the 
 earth. 
 
 This operation goes on as long as the rubbing is 
 kept up. 
 
 For the rubber, a pad of hair, or other material, 
 around which a piece of kid glove is tied, is employed.
 
 118 
 
 ELECTRIC TO Y MAKING. 
 
 This may be made much more efficient by the use of 
 some amalgam such as that used on electric machines. 
 
 Simple Experiments in Static Electricity. 
 Some simple experiments in static electricity are 
 next illustrated. The first cut shows a modification 
 
 r 
 
 PIG. 48. GLASS SHOW-CASE EXPERIMENT. 
 
 of Ano-Kato. It is supposed to be especially adapted 
 for use on the interior of a glass case. 
 
 A short silk thread, o, is stuck with a little bit of 
 sealing-wax to the interior of a glass case, so as to 
 hang down as shown in the full line. If, now, the 
 exterior of the glass is excited by rubbing with a silk 
 handkerchief, or other electrically efficient rubber, 
 such as the pad just mentioned, the thread will be
 
 EXPERIMENTS IN STATIC ELECTRICITY. 119 
 
 agitated and drawn in one or the other direction aa 
 shown by the dotted lines, I, c, following sometimes 
 the finger. It is needless to remark that the move- 
 ments thus excited, may, in their way, be very curious 
 and amusing.' 
 
 The next cut gives a view of India rubber balloons, 
 
 Fio. 49. EXPERIMENT WITH BALLOONS. 
 
 electrically excited. By striking these with a rubber 
 of animal fibre, or tissue, such as a feather duster, 
 they will become highly excited, and will tend to 
 separate from each other. The balloons are the ordin- 
 ary India rubber ones sold in the streets by peddlers.
 
 120 ELECTRIC TOT MAKING. 
 
 It is said that three of them may be so excited ihat 
 one will adhere to the ceiling, and carry the other 
 two as shown. The latter are represented as repelling 
 each other under the same excitement. 
 
 But of these simple experi- 
 ments, one of the best is shown 
 in the next illustration. A 
 bunch of fine India rubber 
 threads is required. These 
 may be procured at a suspender 
 factory, or other place, where 
 India rubber interwoven fabrics 
 are made. The threads may be 
 quite long six or eight feet is 
 not too much. 
 
 The bunch of threads is held 
 in one hand, by the end, as 
 shown, if not too long, or 
 otherwise are suspended to the 
 
 FIG. 50 E X PK BIMENTWIT H ceiling, and are gently stroked 
 RUBBER THREADS. down with a feather duster. 
 They all become charged with the same kind of elec- 
 tricity, and hence, each thread repels its neighbor, 
 and the whole bunch separates. The separation is 
 quite persistent, and may last a long time.
 
 CHAPTER VIII. 
 HAND POWER DYNAMO. 
 
 A HAND power dynamo is necessarily a rather feeble 
 machine. But the construction of one is compara- 
 tively easy, and will give good practice, the benefits 
 of which will be felt if a larger one is ever attempted. 
 
 For the sake of simplicity the well known "H" 
 armature is adopted m the machine to be described, 
 and the whole construction is designed to embody a 
 very few parts. 
 
 In the illustration, the diagonally shaded parts 
 show the section of the field magnet, wound with two 
 coils of wire, as shown by the vertical lines near its 
 base. The general construction or design is best 
 seen in the cut. The following may be taken as gen- 
 eral dimensions : Extreme length of field magnet, 4 
 inches ; height, including feet, 4 inches ; width, 2 
 inches. The elevation may be taken as on a scale of 
 one-fourth the natural size. 
 
 As shown in the cut, an arm is cast on the magnet 
 to hold the driving wheel. It is obvious that the arm 
 can be dispensed with and a special standard used for 
 this purpose.
 
 122 ELECTRIC TOY MAKING. 
 
 Holes are drilled in the foot-flanges of the field- 
 magnet, and it is screwed down to a base board about 
 twelve inches long and six inches wide. 
 
 The field proper, or area within Ihe pole pieces, 
 the space in which the armature rotates, must be as 
 exact a circle as practicable. The iron should be of 
 
 FIG. 51. HAND POWER DYNAMO. 
 
 good quality and as soft as possible. Good cast iron 
 will answer all requirements. 
 
 The interior surface of the pole pieces is sometimes
 
 HAND POWER DYNAMO. 123 
 
 coated with tape, glued on. The portion to be wound 
 with wire is smoothly coated in the same way. All 
 is then ready for the winding. 
 
 One and one-half pounds of No. 21 silk-covered 
 wire is used to wind the two field-magnet coils. The 
 wire is weighed accurately and may be divided into 
 two equal portions, each temporarily on its own reel. 
 Otherwise it may be wound directly on one of the 
 cores from a single reel, and the remainder weighed 
 from time to time to ascertain when one-half has 
 been employed. Then the other half is wound on 
 the other core. 
 
 In either case the top core is first wound over the 
 top and away from the operator, and as- closely and 
 evenly as possible. When partly wound, at short 
 intervals, the winding is tested with a galvanometer 
 and battery. One terminal of the battery is con- 
 nected through a galvanometer with the coil ter- 
 minal. The other battery terminal is touched to the 
 iron of the field-magnet. If any deflection is pro- 
 duced the winding- is defective in insulation, and is 
 in electric contact with the field-magnet. It must be 
 unwound and the trouble found and rectified. 
 
 In winding the superimposed layers, two pieces of 
 tape, about one inch longer than the space wound, are 
 to be laid on. After two or three thicknesses or lay- 
 ers of wire have been wound over it, the ends are 
 turned in and over to be secured by the next 
 winding. This is repeated so as to give a good wind-
 
 124 ELECTRIC TOT MAKING. 
 
 ing surface and especially to prevent the under layers 
 spreading. After a coil is wound it should be gently 
 flattened down by blows with a wooden stick or 
 mallet. 
 
 The second or lower coil is wound in the opposite 
 direction over the top and towards the operator. If 
 the wire with which the winding is done is in two 
 pieces, two of the ends, the last of the upper and first 
 of the lower coil must be connected by twisting and 
 soldering, leaving two ends free. The latter go 
 through holes in the base-board to two binding 
 screws, one of which onlv is shown in the cut. 
 
 The armature is of " H " section and its spindle is 
 journaled in two strips, which are screwed or bolted 
 to the sides of the field-magnets. The places of 
 attachment of one of these strips are indicated in the 
 cut of the dynamo by two white rectangles with a 
 bolt hole in the centre of each. These strips must be 
 of brass or some non-magnetic material, and on no 
 account of iron or steel. 
 
 The end view of the armature, giving also its cross 
 section, is shown in the next cut. It may be of 
 soft cast iron. It is far preferable, if possible, to 
 build it up of washers of thin sheet iron annealed and 
 oxidized, or with thin shellacked paper placed between 
 each. In such case each piece must be perforated, 
 but with a square or rectangular aperture, and strung 
 upon a spindle which it closely fits. In such case 
 special pieces must be used at the ends to secure the
 
 HAND POWER DYNAMO. 125 
 
 necessary projections or horns shown more clearly in 
 the next cut, which represents the end view of the 
 armature. 
 
 The edges of the armature are filed or smoothed 
 off if necessary, and it is wound with one half-pound 
 
 Fiu. 52. END VIKW OP ARMATURE. 
 
 of the same wire. The surface to be wound must be 
 covered with tape, glued on. The winding is led or 
 made to begin from the commutator end of the arma- 
 ture, and is interrupted where the spindle comes as 
 shown in the cut of the dynamo, Fig. 51. 
 
 The commutator shown on the left of the spindle 
 is a block of hard wood about throe-quarters of an 
 inch in diameter, and three-eighths of an inch 
 deep. A tube of brass is driven over it and is screwed 
 fast with short screws, which must not reach 
 the spindle. The commutator is driven on to the 
 shaft. The brass tube, after being screwed in place, is 
 cut with two oblique and narrow cuts completely 
 separating it into two halves. One of these cuts is 
 shown on the commutator in Fig. 53.
 
 126 ELECTRICAL TOT MAKING. 
 
 The two terminals of the armature winding are 
 soldered each to one of the commutator divisions. 
 
 A driven pulley one inch in diameter is fastened 
 on the proper end of the armature spindle. 
 
 All these parts must be rigidly secured together. 
 
 FIG. 53. ELEVATION AND JOURNALISING OF AKMATUKK, COMMUTATOR 
 AND DRIVING PULLET. 
 
 The armature spindle is two and one-quarter inches 
 long, -j^- inch diameter, and the ends are turned 
 down to -j^- inch for the bearings. It must turn 
 freely in the space between the pole pieces with a 
 clearance of about -fa inch. This will exact very 
 accurate centering. It is well to turn a fine groove in 
 the centre of the cylindrical sectors of the armature 
 and to wrap a few turns of wire around the windings,
 
 HAND POWER DYNAMO. 127 
 
 and within the groove to stop the windings from 
 displacement by centrifugal force. 
 
 Two springs or " brushes " of spring-tempered 
 copper, about one-half an inch wide, are attached to 
 the base board and bear against the opposite sides of 
 the commutator. From each spring a wire may be 
 carried to a binding-post. This gives a.shunt wound 
 machine. Or only one of the field-magnet terminals 
 may be carried to a binding-post, the other connect- 
 ing with one of the commutator brushes. The other 
 commutator brush connects with the other binding 
 post. This is a series wound machine. 
 
 The driving pulley is about ten inches in diameter, 
 and like the driven pulley is grooved to receive a 
 sewing machine belt. 
 
 The proper position of the commutator is found by 
 trial, twisting it back and forth until the best results 
 are obtained. 
 
 Such a dynamo, if properly constructed, will, at 
 1,600 revolutions, or at two and one-half turns of the 
 driving-wheel per second, give about ten volts poten- 
 tial difference, and over an ampere of current. Two 
 or three cells of bichromate battery will operate it as 
 a motor, the driving belt being removed.
 
 CHAPTER IX. 
 MISCELLANEOUS RECEIPTS AND FORMULAE. 
 
 Kookogey's' Battery Solution. Potassium bichro- 
 mate, 221 parts; water, boiling, 1,134 parts; while 
 boiling, add concentrated sulphuric acid, very care- 
 fully and slowly 1,588 parts; allow it to cool and to 
 precipitate, decant for use. All parts arc by weight. 
 
 Electropoion Fluid.-M.ix one gallon sulphuric acid, 
 concentrated, and three gallons of water. In a sepa- 
 rate vessel dissolve six pounds of potassium bichro- 
 mate in two gallons of boiling water. Mix the two 
 solutions. Use only when perfectly cold. 
 
 Solution, for Amalgamating Zinc. Dissolve one 
 part of mercury in a mixture of two parts nitric and 
 four parts hydrochloric acid. After solution, add 
 six parts more of hydrochloric acid. A few seconds 
 immersion will amalgamate ordinary zincs, which 
 may then be washed in clean water, and well rubbed. 
 Amalgamation by rubbing with metallic mercury 
 and dilute acid is generally simpler. 
 
 High Potential Battery. Positive Element: Sodium 
 amalgam in caustic soda solution. 
 
 Negative Element : A carbon plate in chloride of 
 iodine.
 
 MISCELLANEOUS. 129 
 
 The electromotive force of this battery is said to be 
 about 4 volts. (See "Electric World," Vol. 6, 
 No. 16). 
 
 Chloride of Iron Battery. This battery corres- 
 ponds in construction with the Bunsen battery^ 
 except that ferric chloride is used as the depolarizer 
 in place of chromic acid. After it becomes polarized, 
 by redaction of the ferric to ferrous chloride, it will 
 recuperate on standing, as the air oxidiz< s the iron 
 salt. As this action i^ slow, bromine was added to 
 the depolarizing mixture. This gave a disagreeable 
 odor. Another improvement was to add potassium 
 chlorate with a little hydrochloric acid, which had 
 very little odor and was found to work very well. 
 The List combination is described by Thomas Moore, 
 in the London Chemical News. 
 
 Potassium Permanganate Cell. By using a solu- 
 tion of potassium permanganate and ammonium 
 chloride in water as exciting fluid, with carbon and 
 amalgamated zincs ;is the dements, a good open cir- 
 cuit battery is obtained. A warm and concentrated 
 solution of potassium permanganate may be poured 
 into exhausted and drained porous cells of Leclanche 
 batteries to regenerate them. 
 
 Dry Battery. A good mixture for dry batteries is 
 made up of : Plaster of Paris, 4 parts ; zinc oxide, 
 1 part; saturated solution of zinc chloride, enough to 
 make a thick paste. The Carl Gassncr, Jr., patent
 
 130 ELECTRIC TOT MAKING. 
 
 specifies : Sal ammoniac, 1 part; plaster of Paris, 
 3 parts; zinc chloride, one part; water, two parts. 
 All parts are by weight. A zinc can may be used as 
 at once the cup and positive element ; a rod of carbon 
 is the negative element. 
 
 Smee's Battery. This battery consists of amalga- 
 gamated zinc positive and platinized silver negative 
 plates, in a single vessel with a ten per cent, solution 
 of sulphuric acid. To platinize the negative plate, 
 dissolve a little platinum bichloride in water with a 
 little hydrochloric acid, and decompose the solution 
 by a battery, using a platinum plate as anode 
 and the silver plate as cathode. This produces a 
 deposit of platinum on the silver which facilitates 
 the escape of hydrogen gas. 
 
 Platinized Carbon for Smee Batteries (WALKER). 
 The carbon plates are first purified by soaking them 
 for some days in sulphuric acid diluted with time to 
 four times its volume of water ; a tinned copper con- 
 ductor is then fastened to one by tinned copper rivets. 
 The carbon is then platinized by electrolysis, the car- 
 bon plate being used as the cathode, the anode being 
 either a platinum or carbon plate. The solution used 
 is thus prepared : sulphuric acid, diluted with ten 
 times its volume of water, is taken, and crystals of 
 platinum chloride are added until the solution be- 
 comes of a beautiful straw yellow color. After the 
 current has passed for about twenty minutes the plate
 
 MISCELLANEOUS. 131 
 
 is finished ; it may be tested by using it as a cathode 
 in the electrolysis of water ; it ought to allow the 
 hydrogen to escape freely, without sticking to it in 
 the form of bubbles. 
 
 Porous Pots. Minimum leakage with distilled 
 water at 14C., 15 per cent, in twenty-four hours. 
 
 Ebonite. To keep ebonite in good order it should 
 be occasionally washed with a solution of ammonia 
 in water. 
 
 Non- Corrosive Soldering Fluid. Mix water, 8 
 parts; glycerine, 1 part; lactic acid, 1 part. All by 
 weight. 
 
 Low Temperature, Solder. For use when the parts 
 to be soldered will not stand a high temperature. 
 Finely divided copper (obtained by precipitating a 
 solution of copper sulphate with zinc) is mixed with 
 concentrated sulphuric acid in a porcelain mortar. 
 30 to 36 parts of copper are taken, according to the 
 degree of hardness desired, and 70 parts of mercury 
 are stirred in. When the amalgam has completely 
 formed, it is washed with hot water till all traces of 
 acid are removed. It is then allowed to cool. 
 
 When this composition is to be used, it is heated 
 until it is of the consistency of wax, so that the sur- 
 faces to be joined may be readily smeared with it. 
 When cold, they adhere very strongly. 
 
 To purify Mercury which has been used for amal- 
 gamating Zincs. If one of the new low pressure
 
 132 ELECTRIC TOT MAKING. 
 
 distilling apparatus be not at hand, put the mercury 
 in a deep vessel, put plenty of dilute sulphuric acid 
 over it, and place a piece of carbon (a bit of an electric 
 light carbon answers very well) into the mercury; 
 weight it or tie it down so that there is good contact 
 with the mercury ; this arrangement sets up local 
 action, and dissolves out all metallic impurities ; do 
 not carry the action too far, as you may dissolve some 
 of the mercury in the form of mercury sulphates. 
 
 Gilt Plumbago (TABAUBET). For giving a con- 
 ducting surface to electrotype moulds, .10 gr. of chlo- 
 ride of gold is dissolved in one litre of sulphuric 
 ether, 500 to 600 gr. of plumbago (in fine powder) 
 is thrown in, the whole is poured out into a large 
 dish, and exposed to air and light. As the ether 
 evaporates, the plumbago is stirred and turned over 
 with a glass spatula. The drying is finished by a 
 moderate heat, and the plumbago put by for use. 
 
 Soldering Wires (GULLET). To solder iron wires 
 together, dissolve chloride of zinc (or kill spirit of 
 salt with zinc), add a little hydrochloric acid (spirit 
 of salt) to clean the wire. The rain soon washes off 
 the excess of chloride of zinc. To solder iron and 
 copper wires together the excess of chloride must be 
 washed off, and the joint covered with paint or resin, 
 or solder with resin. 
 
 For unanncalcd wires, solder at as low a tempera- 
 ture as possible.
 
 MISCELLANEOUS. 133 
 
 The zinc solution, or spirit of salt, should never be 
 used except for overhead out-door lines. AH joints 
 in covered wire, whether run underground or above 
 ground, and all joints within doors, either in covered 
 or uncovered wire, should be made with resin. No 
 spirit of salt, either pure or killed with zinc, should 
 ever be allowed in an instrument maker's shop or 
 dynamo factory. Workmen will use it, if not watched. 
 Its presence may often be detected by holding an 
 open bottle of strong solution of ammonia (liquor 
 p.mmoniae) under a newly made joint; if it becomes 
 surrounded with a slight white cloud or mist, spirit 
 of salt in some form has been used. 
 
 Red Varnish. For wood, interior of electro-mag- 
 net coils, galvanometers, etc., dissolve sealing-wax in 
 alcohol at 90; apply it with a pencil when cold in 
 four or five coats, until the desired thickness is 
 attained. It is better to use many coats than to 
 make the varnish thick. 
 
 Covering of the External Wires of Large Electro- 
 Magnets. Large electro-magnets are generally wound 
 with copper wire, covered with a double layer of 
 cotton. The outside layer is hardened by painting it 
 with cold, thick gum-lac varnish. It is gently roasted 
 before a charcoal brazier. The layer thus formed 
 is extremely hard. It is filed smooth, polished with 
 flax and fine pumice powder, and finally varnished. 
 
 Cement for Induction Coils. The proportions vary
 
 134 ELECTRIC TOT MAKING. 
 
 very much but generally approximate to the following 
 formula: 
 
 Resin, .... 2 parts. 
 
 Wax, 1 " 
 
 For hot countries slightly increase the proportion 
 of resin. 
 
 Insulation of Wires for Telegraphy and Telephony 
 (C. WiEDEMANK)-Prepareabath of potassium plum- 
 bate by dissolving 10 gr. of litharge in a litre of 
 water, to which 200 gr. of caustic potash have been 
 added, and boil for about half an hour ; it is allowed 
 to settle and decanted. The bath is now ready for 
 use. The wire to be insulated is attached to the 
 positive pole of a battery or electroplating dynamo, 
 and a small plate of platinum attached to the nega- 
 tive pole is dipped into the bath. The peroxide of 
 lead is formed on the wire, and passes successively 
 through all the colors of the spectrum. The insula- 
 tion becomes perfect only when the wire assumes its 
 last color, which is a brownish-black. 
 
 This perfect insulation may be utilized for gal- 
 vanometers or other apparatus. 
 
 Chatterton's Compound. For cementing together 
 the layers of gutta-percha in cable cores, an excellent 
 insulator of fairly low inductive capacity. 
 
 Stockholm Tar, ... 1 part. 
 
 Resin, . . . . . 1 " 
 
 Gutta-percha, . . . . 3 "
 
 MISCELLANEOUS. 135 
 
 Is also used for filling up the interstices of shore- 
 end cables. Its density is about the same as that of 
 gutta-percha, but its inductive capacity is less. 
 
 Joints of Gutta-percha Covered Wire (GULLET). 
 Exact perfect cleanliness. Eemove the gutta-percha 
 for about four centimetres, clean the wire with emery 
 paper, twist the wires together for about two centi- 
 metres, cut the ends off close, so as to leave no point 
 sticking out. Solder with resin and good solder con- 
 taining plenty of tin. The gutta-percha is then split, 
 and turned back for about 5 centimetres, the soldered 
 joint is covered with Chatterton's compound, and the 
 gutta-percha on each side of it is warmed and manip- 
 ulated until the two sides join. The joint is finished 
 with a hot soldering iron, taking care to smooth it off 
 well, without burning it ; it is then covered with 
 another layer of Chatterton's compound. A sheet of 
 gutta-percha is then taken, warmed at a spirit lamp, 
 and drawn out carefully so as slightly to dimmish its 
 thickness. "Whilst both gutta-percha and Chatterton's 
 compound are warm, the sheet is laid on the joint, 
 and moulded around it with the thumb and forefinger. 
 The joint is then trimmed with scissors ; the edges 
 kneaded in and smoothed down with a hot iron. 
 When the joint is cold, another coating of Chatter- 
 ton's compound is applied, and covered with a longer 
 and broader piece of sheet gutta-percha. The whole 
 is then covered with a final coating of Chatter- 
 ton's compound, spread with the iron, and polished
 
 136 ELECTRIC TOY MAKING. 
 
 by hand when cold, taking care to keep the hand 
 well moistened. It is indispensable to obtain inti- 
 mate and perfect union between the new gutta- 
 percha and that which covers the wire. A much 
 neater and cleaner joint cnn be made by introducing 
 the two wires into a little sleeve of tinned iron, fixing 
 it to the wires by compressing it as a metal tag is fixed 
 lo a lace, and afterwards soldering; no points are 
 then left sticking out at the ends of the joint. 
 
 Cement used by Gaston Plante for his Secondary 
 Batteries is run hot on the corks and connecting 
 strips of the secondary cells to prevent the acid from 
 creeping. 
 
 Turner's Cement, . . 1,000 parts. 
 
 Tallow, or Beeswax, . . 100 " 
 
 Powdered Alabaster, . . 250 " 
 
 Lampblack (to color it black), . 2.5 " 
 
 Waterproofing Wooden Battery Cells (SPRAGUE). 
 When the boxes are quite dry and warm, they arc 
 smeared over inside with a hot cement, composed 
 of four parts of resin and one part of gutta-percha, 
 with a little boiled oil. 
 
 It may be noted that the addition of boiled oil 
 improves all substances used for this purpose which 
 contain pitch, marine glue, or other viscous solid, 
 tending to prevent them from flowing. 
 
 Watertight Decomposition Cells for Elec f rotyping 
 (E. BERTHOUD). A wtll made vat of oak may last
 
 MISCELLANEOUS. 137 
 
 for twelve or fifteen years, if it be smeared inside with 
 the following composition : 
 
 Burgundy Pitch, . . 1.500 parts. 
 
 Old Gutta-percha in small shreds, 250 " 
 
 Finely Powdered Pumice-stone, 750 " 
 
 Melt the gutta-percha, and mix it well with the 
 pumice-stone. Then add the Burgundy pitch. 
 When the mixture is hot, smear the inside of the vat 
 with it. Lay it on in several coats. Eoughness and 
 cracks are smoothed off with a hot soldering iron. 
 The heat of the iron makes the cement penetrate into 
 the pores of the wood, and increases its adhesion. 
 The vat will stand sulphate of copper baths, but not 
 baths containing cyanide. 
 
 Cap Cement. For joining glass tubes to brass caps 
 and fittings, and for similar purposes, cap cement 
 is thus made : Five parts, by weight, of resin are 
 melted with one part of yellow wax; one part of finely 
 powdered Venetian red is stirred into the melted 
 mass. To apply, both surfaces are warmed enough 
 to melt the cement, but not too hot. 
 
 Electrical Cement. For similar purposes to those 
 to which" Cap Cement" is applied, the following 
 (Singer's formula) cement may be used: Eosin, five 
 parts ; beeswax and red ochre, of each 1 part; plaster 
 of Paris, ^ part. A cheaper formula gives rosin, 14 
 parts; red ochre, 2 parts; plaster of Paris, 1 part. 
 
 Com position for Cushions of Ano-Kato, andof Fric- 
 tional Electric Machines. Canton advises the use of
 
 1P>8 ELECTRIC TOT MAKING. 
 
 an amalgam of zinc and tin. Kienmayer gives the 
 following formula : equal parts of zinc and tin ; melt, 
 and add twice the weight of alloy of mercury. When 
 the rubbed plate or cylinder is of vulcanite, the amal- 
 gam must be softer than when it is of glass. In 
 France they gent-rally use mosaic gold (bisulphide of 
 tin). The amalgam must be reduced to fine powder, 
 and applied by the aid of a little hard grease. 
 
 Solution for Paper for Chemical Telegraphs. One 
 part saturated solution of ferrocyanide of potassium, 
 one part saturated solution of nitrate of ammonium, 
 two parts water.
 
 INDEX. 
 
 PAGE 
 
 ALARM or safe protector ..... 69-72 
 Amalgamation of zincs in bat- 
 
 teries ......................... 15 
 
 Ano-Kato .................. 116-118 
 
 Ano-Kato in show case .. .118,119 
 Armature, Page's rotating. . . .56-59 
 
 Armature, Page's rotating, its 
 
 commutator ................ 58 
 
 Armatures, rolling ............ 28 29 
 
 Artillery, electric ......... 107-111 
 
 BALLOONS, experiment wilh 
 rubber ................... 119, 120 
 
 Bars, steel, to magnetize ...... 23-28 
 
 Batteries ....................... 9-22 
 
 Batteries, bichromate ....... 11,12 
 
 Batteries, copper sulphate ...... 9, 10 
 
 Batteiics, dip ................. 11,12 
 
 Batteries, miniature, from elec- 
 tric light carbons ............ 13 
 
 Batteries, primary, in general.. 9 
 Batteries, sal ammoniac ........ 13 
 
 Batteries with electric light car- 
 bons ........................ 15-20 
 
 Battery from a tomato can ____ 20, 21 
 
 Battery, gravity ............... 10 
 
 Battery, Lalande Chaperon... 21 
 Battery, Leclanche" ....... _____ 10, 11 
 
 Battery, silver chloride ........ 13-15 
 
 Buttery solution, Trouve's ..... 12 
 
 Battery troughs of wood ..... 22 
 
 Bells, electric .............. 65-72 
 
 Bell, the tolling ............... 65-67 
 
 Bell, the vibrating ............. 67-69 
 
 Boat. Magnetic ................ 36 
 
 lar alar 
 
 Burgla 
 
 larm ................ 69-72 
 
 CARBONS, applying parafflne to. 16 
 Carbons, electric light in bat- 
 
 teries ....................... 15-20 
 
 Cells, materials for ... ........ 21 . 22 
 
 Circle, the magic ............. 42, 43 
 
 Circuit breaker, pendulum. . . 83-85 
 Circuit breakers for induction 
 
 coils ....................... 97,98 
 
 Coil, pendulum motor ......... 46-49 
 
 Coils, induction and spark .... 89-104 
 
 Coils, induction, condensers 
 
 of ....... ................. 99-101 
 
 Coils, magnetizing, to make. . .40-42 
 Coils, spark and induction.. . .89-104 
 
 PA6E 
 
 Coil to magnetize with 27 
 
 Condensers of induction coils 
 
 99-101 
 
 Copal gum for coils 42 
 
 Copper oxide in battery 20, 21 
 
 Core of coils, how made 89,90 
 
 DANCER, the electric 73-76 
 
 Dancer, the electric, battery re- 
 quired for 76 
 
 Drum, the magic 76-79 
 
 Dynamo, hand power 121-127 
 
 ELECTRIC artillery 107-111 
 
 Electric bell, key for 67 
 
 Electric bells 65-72 
 
 Elec'ric dancer 73-76 
 
 Electric dancer, battery required 
 
 for 7fi 
 
 Electric gymnastics 111-116 
 
 Electric hammer 79-82 
 
 Electric insects 82-87 
 
 Electric insects, circuit breaker 
 
 . for 83-85 
 
 Electric insects, mercury switch 
 
 for 86,87 
 
 Electric light carbons in batter- 
 ies 15-20 
 
 Electric locomotive 59-64 
 
 Electric mortar 107-1 1 1 
 
 Electric motors 46-64 
 
 Electric Pistol 108-1 10 
 
 Electro-magnet from gas-pipe 
 
 Electro-magnet, Joule's 38, 39 
 
 Electro-magnets 37^45 
 
 Electro-magnet, solenoid 39, 40 
 
 Electro-magnets, their construc- 
 tion 37-10 
 
 FIRE CRACKER explosions and 
 
 fuses 110,111 
 
 Fishes, magnetic 36 
 
 Force, lines of, followed bv 
 
 polarizf-d needle 29, 30 
 
 Formulas and receipts, miscel- 
 laneous 128 
 
 Foncanlt's experiment 32-34 
 
 Fuses, fire cracker 110, 111 
 
 GENERATOR, the magneto. .104-107 
 
 Gluing Coils 41.42 
 
 Gymnastics, electric 111-116
 
 140 
 
 INDEX. 
 
 PAGE 
 
 HAMMER, the electric 79-82 
 
 Hemispheres, magnetic 43-45 
 
 Hopkin's electric insects 82-87 
 
 Hopkin's magic drum 76-79 
 
 INCANDESCENT lamp 87,88 
 
 Induction coil, Recordon's. .102-104 
 
 Induction coils 91-104 
 
 Induction coils, condensers of 
 
 99-101 
 
 Insects, electric 82-87 
 
 Insects, electric, circuit breaker 
 
 83-85 
 
 Insects, eleciric, mercury switch 
 
 for 86,87 
 
 Iron scraps in battery 20 
 
 JACK-STRAWS, magnetic 30,31 
 
 Joule's electromagnet 38,39 
 
 KEEPERS of magnets 27,28 
 
 Key for electric b?ll 67 
 
 LALANDE-Chaperon battery 21 
 
 Lamp, incandescent 87,88 
 
 Lamp, platinum, self-regulating 
 
 Locomotive, ihe electric. . . . . . .59'-64 
 
 MAGIC circle 42,43 
 
 Magic drum 76-79 
 
 Magnetic fishes, swan, boat, etc. 3fi 
 
 Magnetic hemispheres 43-45 
 
 Magnetic jack-straws 30.31 
 
 Magnetic pendulum 32-34 
 
 Magnetic swan 36 
 
 Magnetic top 31,32 
 
 Magnetizing by a dynamo 25 
 
 Magnetizing by an electro mag- 
 net 25.26 
 
 Magnetizing by a permanent 
 
 magnet.... 24.25 
 
 Magnetizing coils, to make. . . .40-42 
 Magnetizing, Elia's method .... 27 
 Magnetizing. Jacobin method .26. 27 
 
 Magnetizing steel bars 23,28 
 
 Magneti/.ing with a coil 27 
 
 Magneto-generator 104-107 
 
 Magnets, compound 26 
 
 Magnet*, ill effects of jariing 
 
 and filing 28 
 
 Magnets, permanent 23-36 
 
 Magnets, to preserve 27, ?8 
 
 Mahomet's coffin 29,30 
 
 Mahomet's coffin with solenoid. 40 
 
 Mayer's floating needles 34, 35 
 
 Miscellaneous formulas and 
 receipts 138-138 
 
 PAGE 
 
 Miscellaneous toys. ... 73 88 
 
 Mortar, electric 107, 108 
 
 Motor, multipolar 51-56 
 
 Motor, multipolar, its commuta- 
 tor .. 53-55 
 
 Motor, pendulum coil 46-49 
 
 Motor, Recordon magnet 49-5 1 
 
 Mnltipolar motor 51-56 
 
 Multipolar motor, its commuta- 
 tor 53-55 
 
 NEEDLES, Mayer's floating 34, 35 
 
 OXIDE of copper in battery 20,21 
 
 PAGE'S rotating armature 56-59 
 
 Page's rotating armature, its 
 
 commutator 58 
 
 Page's solenoid magnets 39 
 
 Paraffine. applying to carbons.. 16 
 
 Pendulum circuit breaker 83-85 
 
 Pendulum coil motor 46-49 
 
 Pendulum, the magnetic 32-34 
 
 Pistol, electric or voltaic .... 108-1 10 
 RECEIPTS and formulas, miscel- 
 laneous 128-138 
 
 R ('cordon's induction coil. . .102-104 
 
 Recordon magnet motor 49-M 
 
 Rolling armatures 28, 29 
 
 Rolling armatures, repulsion of. 29 
 Rotating armature, Pag* 's.... 56-59 
 Rotating armature, Page's, its 
 
 commutator 58 
 
 Rubber balloon experiment. 119, 120 
 Rubber thread experiment. ... 120 
 
 SAFE protector ... 09-72 
 
 Show case. Ano-Kato 118,119 
 
 Soda, caustic, in battery 20 
 
 Solenoid electro-magnet 39. 40 
 
 Solenoid of electric hammer.. .81. 82 
 
 Spark coils 89, 91 
 
 Static electricity, simple experi- 
 ments in 1)8-120 
 
 Steel bars, to magnetize 23-28 
 
 S ivan, magnetic 36 
 
 Switch, mercury, for electric in- 
 sects 86.87 
 
 TOLLING bell r.5-07 
 
 Top, the magnetic 31-83 
 
 Toys, miscellaneous 73-88 
 
 Trouve, battery solution 12 
 
 VIBRATING bell 07-69 
 
 Voltaic pistol 108-110 
 
 Zmc, amalgamation of, in bat- 
 teries..., . 15
 
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