CHAPTER XX MISCELLANEOUS ELECTRICAL APPARATUS
HOW ELECTRICITY MAY BE GENERATED FROM HEAT
For the past century there has been on the part of many scientists and inventors a constant endeavor to "harness the sunlight." The power which streams down every day to our planet is incalculable. The energy consumed in the sun and thrown off in the form of heat is so great that it makes any earthly thing seem infinitesimal. We can only feel the heat from a large fire a few feet away, yet the scorching summer heat travels 90,000,000 miles before it reaches us, and even then our planet is receiving only the smallest fractional part of the total amount radiated.
Dr. Langley of the Smithsonian Institute estimated that all the coal in the State of Pennsylvania would be used by the sun in a fraction of a second if it were sent up there to supply energy.
Perhaps, some day in the future, electric locomotives will haul their steel cars swiftly from city to city by means of electricity, generated with "sun power." Perhaps energy from the same source will heat our dwellings and furnish us light and power.
This is not an idle dream, but may some day be an actuality. It has already been carried out to some extent. A Massachusetts inventor has succeeded in making a device for generating electricity from sun energy.
The apparatus consists of a large frame, in appearance very much like a window. The glass panes are made of violet glass, behind which are many hundred little metallic plugs. The sun’s heat, imprisoned by the violet glass, acts on the plugs to produce electricity. One of these generators exposed to the sun for ten hours will charge a storage battery and produce enough current to run 30 large tungsten lamps for three days.
Fig. 303.—How the Copper Wires (C) and the Silver Wires (I) are twisted together in Pairs.
The principle upon which the apparatus works was discovered by a scientist named Seebeck, in 1822. He succeeded in producing a current of electricity by heating the points of contact between two dissimilar metals.
Any boy can make a similar apparatus, which, while not giving enough current for any practical purpose, will serve as an exceedingly interesting and instructive experiment.
Cut forty or fifty pieces of No. 16 B. & S. gauge German silver wire into five-inch pieces. Cut an equal number of similar pieces of copper wire, and twist each German silver wire firmly together with one of copper so as to form a zig-zag arrangement as in Figure 303.
Fig. 304.—Wooden Ring.
Next make two wooden rings about four inches in diameter by cutting them out of a pine board. Place the wires on one of the rings in the manner shown in Figure 305. Place the second ring on top and clamp it down by means of two or three screws.
Fig. 305.—Complete Thermopile. An Alcohol Lamp should be lighted and placed so that the Flame heats the Inside Ends of the Wires in the Center of the Wooden Ring.
The inner junctures of the wires must not touch each other. The outer ends should be bent out straight and be spaced equidistantly. The ring should be supported by three iron rods or legs. The two terminals of the thermopile as the instrument is called, should be connected to binding-posts.
Place a small alcohol lamp or Bunsen burner in the center, so that the flame will play on the inner junctures of the wires. A thermopile of the size and type just described will deliver a considerable amount of electrical energy when the inside terminals are good and hot and the outside terminals fairly good.
The current may be very easily detected by connecting the terminals to a telephone receiver or galvanometer. By making several thermopiles and connecting them in parallel, sufficient current can be obtained to light a small lamp.
HOW TO MAKE A REFLECTOSCOPE
A reflectoscope is a very simple form of a "magic lantern" with which it is possible to show pictures from post-cards, photographs, etc. The ordinary magic lantern requires a transparent lantern slide, but the reflectoscope will make pictures from almost anything. The picture post-cards or the photographs that you have collected during your vacation may be thrown on a screen and magnified to three or four feet in diameter. Illustrations clipped from a magazine or newspaper or an original sketch or painting will likewise show just as well. Everything is projected in its actual colors. If you put your watch in the back of the lantern, with the wheels and works exposed, it will show all the metallic colors and the parts in motion.
Fig. 306.—A Reflectoscope.
The reflectoscope, shown in Figure 306, consists of a rectangular box nine inches long, six inches wide, and six inches high outside. It may be built of sheet-iron or tin, but is most easily made from wood. Boards three-eighths of an inch thick are heavy enough. The methods of making an ordinary box are too simple to need description. The box or case in this instance, however, must be carefully made and be "light-tight," that is, as explained before, it must not contain any cracks or small holes which will allow light to escape if a lamp is placed inside.
A round hole from two and one-half to three inches in diameter is cut in the center of one of the faces of the box.
The exact diameter cannot be given here because it will be determined by the lens which the experimenter is able to secure for his reflectoscope. Only one lens is required. It must be of the "double-convex" variety, and be from two and one-half to three inches in diameter. A lens is very easily secured from an old bicycle lantern. It should be of clear glass.
Fig. 307.—How the Lens is Arranged and Mounted.
A tube, six inches long and of the proper diameter to fit tightly around the lens, must be made by rolling up a piece of sheet-tin and soldering the edges together. This tube is the one labeled "movable tube" in the illustrations. A second tube, three inches long and of the proper diameter to just slip over the first tube, must also be made. A flat ring cut from stiff sheet-brass is soldered around the outside of this second tube, so that it may be fastened to the front of the case by three or four small screws in the manner shown. The hole in the front of the box should be only large enough to receive the tube.
The lens is held in position near one end of the movable tube by two strong wire rings. These rings should be made of wire that is heavy and rather springy, so that they will tend to open against the sides of the tube. It is a good plan to solder one of them in position, so that it cannot move, and then put in the lens. After the lens is in position, the second ring should be put in and pushed down against the lens. Do not attempt to put the lens in, however, until you are sure that the metal has cooled again after soldering, or it will be liable to crack.
Fig. 308.—A View of the Reflectoscope from the Rear, showing the Door, etc.
The back of the box contains a small hinged door about four inches high and five and one-half inches long. The pictures that it is desired to project on the screen are held against this door by two small brass clips, as shown in Figure 308.
Fig. 309.—A View of the Reflectoscope with the Cover removed, showing the Arrangement of the Lamps, etc.
The light for the reflectoscope is most conveniently made by two 16-candle-power electric incandescent lamps. Figure 309 shows a view of the inside of the box with the cover removed, looking directly down. The lamps fit into ordinary flat-base porcelain receptacles, such as that shown in Figure 310. Two of these receptacles are required, one for each lamp. They cost about ten cents each.
Fig. 310.—A Socket for holding the Lamp.
The reflectors are made of tin, bent as shown in Figure 311. They are fastened in position behind the lamps by four small tabs.
It is possible to fit a reflectoscope with gas or oil lamp to supply the light, but in that case the box will have to be made much larger, and provided with chimneys to carry off the hot air.
The interior of the reflectoscope must be painted a dead black by using a paint made by mixing lampblack and turpentine. The interior also includes the inside of the tin tubes.
The electric current is led into the lamps with a piece of flexible lamp-cord passing through a small hole in the case. An attachment-plug is fitted to the other end of the cord, so that it may be screwed into any convenient lamp-socket.
Fig. 311.—The Tin Reflector.
The pictures should be shown in a dark room and projected on a smooth white sheet. They are placed under the spring clips on the little door and the door closed. The movable tube is then slid back and forth until the picture on the screen becomes clear and distinct.
The lantern may be improved considerably by using tungsten lamps of 22 c. p. each in place of ordinary c. p. carbon filament lamps.
If four small feet, one at each corner, are attached to the bottom of the case, its appearance will be much improved.
Very large pictures will tend to appear a little blurred at the corners. This is due to the lens and cannot be easily remedied.
HOW TO REDUCE THE 110-v. CURRENT SO THAT IT MAY BE USED FOR EXPERIMENTING
Oftentimes it is desirable to operate small electrical devices from the 110-v. lighting or power circuits. Alternating current can be reduced to the proper voltage by means of a small step-down transformer, such as that described in Chapter XIII. Direct current may be reduced by means of a resistance. The most suitable form of resistance for the young experimenter to use is a "lamp bank."
A lamp bank consists of a number of lamps connected in parallel, and arranged so that any device may be connected in series with it.
The lamps are set in sockets of the type known as "flat-base porcelain receptacles," such as that shown in Figure 310, mounted in a row upon a board and connected as shown in Fig. 312.
The current from the power line enters through a switch and a fuse and then passes through the lamps before it reaches the device it is desired to operate. The switch is for the purpose of shutting the current on and off, while the fuse will "blow" in case too much current flows in the circuit.
The amount of current that passes through the circuit may be accurately controlled by the size and number of lamps used in the bank. The lamps may be screwed in or out and the current altered by one-quarter of an ampere at a time if desirable.
The lamps should be of the same voltage as the line upon which they are to be used. Each 8-candle-power, 110-v. carbon lamp used will permit one-quarter of an ampere to pass. Each 16-candle-power, 110-v. lamp will pass approximately one-half an ampere. A 32-candle-power lamp of the same voltage will permit one ampere to flow in the circuit.
Fig 312.—Top View of Lamp Bank, showing how the Circuit is arranged. A and B are the Posts to which should be connected any Device it‘s desirable to operate.
AN INDUCTION MOTOR
An Induction Motor is a motor in which the currents in the armature windings are induced. An induction motor runs without any brushes, and the current from the power line is connected only to the field. The field might be likened to the primary of a transformer. The currents in the armature then constitute a secondary winding in which currents are induced in the same manner as in a transformer.
An induction motor will operate only on alternating current.
A small motor such as that shown in Figure 267, and having a three-pole armature, is the best type to use in making an experimental induction motor.
Remove the brushes from the motor and bind a piece of bare copper wire around the commutator so that it short-circuits the segments.
A source of alternating current should then be connected to the terminals of the field coil. If you have a step-down transformer, use it for this purpose, but otherwise connect it in series with a lamp bank such as that just described.
Place a switch in the circuit so that the current may be turned on and off. Wind a string around the end of the armature shaft so that it may be revolved at high speed by pulling the string in somewhat the same manner that you would spin a top. When all is ready, give the string a sharp pull and immediately close the switch so that the alternating current flows into the field.
If this is done properly, the motor will continue to run at high speed, and furnish power if desirable.
Most of the alternating-current motors in every-day use for furnishing power for various purposes are induction motors. They are, however, self-starting, and provided with a hollow armature, which contains a centrifugal governor. When the motor is at rest or just starting, four brushes press against the commutator and divide the armature coils into four groups. After the motor has attained the proper speed, the governor is thrown out by centrifugal force and pushes the brushes away from the commutator, short-circuiting all the sections and making each coil a complete circuit of itself.
ELECTRO-PLATING
Water containing chemicals such as sulphate of copper, sulphuric acid, nitrate of nickel, nitrate of silver, or other metallic salts is a good conductor of electricity. Such a liquid is known as an electrolyte.
It has been explained in Chapter IV that chemical action may be used to produce electricity and that in the case of a cell such as that invented by Volta, the zinc electrode gradually wastes away and finally enters into solution in the sulphuric acid.
It is possible exactly to reverse this action and to produce what is known as electrolysis. If an electrolyte in which a metal has been "dissolved" is properly arranged so that a current of electricity may be passed through the solution, the metal will "plate out," or appear again upon one of the electrodes.
Electrolysis makes possible electro-plating and thousands of other exceedingly valuable and interesting chemical processes.
More than one-half of all the copper produced in the world is produced electrolytically.
Practically all plating with gold, silver, copper and nickel is accomplished with the aid of electricity.
These operations are carried out on a very large scale in the various factories, but it is possible to reproduce them in any boy’s workshop or laboratory, with very simple equipment.
The proper chemicals, a tank, and a battery are the only apparatus required. The current must be supplied by storage cells or a bichromate battery because the work will require five or six amperes for quite a long period.
A small rectangular glass jar will make a first class tank to hold the electrolyte.
The simplest electro-plating process, and the one that the experimenter should start with is copper-plating.
Fill the tank three-quarters full of pure water and then drop in some crystals of copper-sulphate until the liquid has a deep blue color and will dissolve no more.
Obtain two copper rods and lay them across the tank. Cut two pieces of sheet copper having a tongue at each of two corners so that they can be hung in the solution, as shown in Figure 313. Hang both of the sheets from one of the copper rods. Connect this rod to the positive pole of the battery. These sheets are known as the anodes.
Then if a piece of carbon, or some metallic object is hung from the other rod and connected to the negative pole of the battery, the electro-plating will commence. The apparatus should be allowed to run for about half an hour and then the object hung from the rod connected to the negative pole of the battery should be lifted out and examined. It will be found thickly coated with copper. It is absolutely necessary to have the poles of the battery connected in the manner stated, or no deposit of copper will take place.
Objects which are to be electro-plated must be free from all traces of oil or grease and absolutely clean in every respect, or the plating will not be uniform, because it will not stick to dirty spots.
Fig. 313.—A Glass Jar arranged to serve as an Electro-Plating Tank.
Such articles as keys, key-rings, tools, etc., can be prevented from rusting by coating with nickel.
Nickel-plating is very similar to copper-plating. Instead, however, of having two copper sheets suspended from the rod connected to the positive pole of the battery, they must be made of nickel.
The electrolyte is composed of one part of nickel-sulphate dissolved in twenty parts of water to which one part of sodium-bisulphate is added.
This mixture is placed in the tank instead of the copper-sulphate. The objects to be plated are hung from the copper rod connected to the negative pole of the battery.
When the nickel-plated articles are removed from the bath they will have a dull, white color known as "white nickel." When white nickel is polished with a cloth wheel revolving at high speed, and known as a buffing-wheel, it will assume a high luster.
HOW TO MAKE A RHEOSTAT
It is often desirable to regulate the amount of current passing through a small lamp, motor, or other electrical device operated by a battery.
This is accomplished by inserting resistance into the circuit. A rheostat is an arrangement for quickly altering the amount of resistance at will.
A simple rheostat is easily made by fitting a five-point switch such as that shown in Figure 95 with several coils of German-silver resistance wire. German silver has much more resistance than copper wire, and is used, therefore, because less will be required, and it will occupy a smaller space.
A five-point switch will serve satisfactorily in making a rheostat, but if a finer graduation of the resistance is desired it will be necessary to use one having more points.
Two lines of small wire nails are driven around the outside of the points, and a German-silver wire of No. 24 B. & S. gauge wound in zig-zag fashion around the nails from one point to the other.
Fig. 314.—A Rheostat.
The rheostat is placed in series with any device it is desirable to control. When the handle is on the point to the extreme left, the rheostat offers no resistance to the current. When the lever is placed on the second point, the current has to traverse the first section of the German-silver wire and will be appreciably affected. Moving the handle to the right will increase the resistance.
If the rheostat is connected to a motor, the speed can be increased or decreased by moving the lever back and forth.
In the same manner, the light from a small incandescent lamp may be dimmed or increased.
A CURRENT REVERSER OR POLE-CHANGING SWITCH
A pole-changing or current reversing switch is useful to the experimenter. For example, if connected to a small motor, the motor can be made to run in either direction at will. A motor with a permanent magnet field can be reversed by merely changing the wires from the battery so that the current flows through the circuit in the opposite direction. If the motor is provided with a field winding, however, the only way that it can be made to run either way is by reversing the field. This is best accomplished with a pole-changing switch.
Such a switch may be made by following the same general method of construction as that outlined on pages 107 and 108, but making it according to the design shown in Figure 315.
Motors such as those illustrated can be made to reverse by connecting to a pole-changing switch in the proper manner.
The two outside points or contacts (marked D and D) should both be connected to one of the brushes on the motor. The middle contact, C, is connected to the other brush.
One terminal of the field is connected to the battery. The other terminal of the field is connected to the lever, A. B connects to the other terminal of the battery.
Fig. 315.—A Pole-Changing Switch or Current Reverser. The Connecting Strip is pivoted so that the Handle will operate both the Levers, A and B.
When the switch handle is pushed to the left, the lever A should rest on the left-hand contact, D. The lever B should make contact with C. The motor will then run in one direction. If the handle is pushed to the right so that the levers A and B make contact respectively with C and D (right-hand), the motor will reverse and run in the opposite direction.
A COMPLETE WIRELESS RECEIVING SET
Many experimenters may wish to build a wireless receiving set which is permanently connected and in which the instruments are so mounted that they are readily portable and may be easily shifted from one place to another without having to disturb a number of wires.
The receiving set shown in Figure 316 is made up of some of the separate instruments described in Chapter XIV, and illustrates the general plan which may be followed in arranging an outfit in this manner.
COMPLETE RECEIVING SET, CONSISTING OF DOUBLE SLIDER TUNING COIL, DETECTOR AND FIXED CONDENSER.
COMPLETE RECEIVING SET, CONSISTING OF A LOOSE COUPLER IN PLACE OF THE TUNING COIL, DETECTOR AND FIXED CONDENSER.
The base is of wood, and is nine inches long, seven inches wide, and one-half of an inch thick.
A double-slider tuning coil, similar to that shown in Figure 203, is fastened to the back part of the base by two small wood-screws passing upwards through the base into the tuner heads.
Fig. 316. A Complete Wireless Receiving Outfit.
The fixed condenser is enclosed in a rectangular wooden block which is hollowed out underneath to receive it and then screwed down to the base in the forward right-hand corner.
The detector is mounted in the forward left-hand part of the base, and in the illustration is shown as being similar to that in Figure 210. Any type of detector may, however, be substituted.
The tuning coil may be replaced by a loose coupler if desirable, but in that case the base will have to be made larger.
The telephone receivers are connected to two binding-posts mounted alongside the detector.
The circuit shown in Figure 218 is the one which should be followed in wiring the set. The wires which connect the various instruments should be passed through holes and along the under side of the base so that they are concealed.
HOW TO BUILD A TESLA HIGH-FREQUENCY COIL
A Tesla high-frequency coil or transformer opens a field of wonderful possibilities for the amateur experimenter. Innumerable weird and fascinating experiments can be performed with its aid.
When a Leyden jar or a condenser discharges through a coil of wire, the spark which can be seen does not consist simply of a single spark passing in one direction, as it appears to the eye, but in reality is a number of separate sparks alternately passing in opposite directions. They move so rapidly that the eye is unable to distinguish them. The time during which the spark appears to pass may only be a fraction of a second, but during that short period the current may have oscillated back and forth several thousand times.
If the discharge from such a Leyden jar or a condenser is passed through a coil of wire acting as a primary, and the primary is provided with a secondary coil containing a larger number of turns, the secondary will produce a peculiar current known as high-frequency electricity. High-frequency currents reverse their direction of flow or alternate from one hundred thousand to one million times a second.
Fig. 317.—Illustrating the Principle of the Tesla Coil. A Leyden Jar discharges through the Primary Coil and a High-Frequency Spark is produced at the Secondary.
High-frequency currents possess many curious properties. They travel only on the surface of wires and conductors. A hollow tube is just as good a conductor for high-frequency currents as a solid rod of the same diameter. High-frequency currents do not produce a shock. If you hold a piece of metal in your hand you can take the shock from a high-frequency coil throwing a spark two or three feet long with scarcely any sensation save that of a slight warmth.
The Tesla coil described below is of a size best adapted for use with a two-inch or three-inch spark coil, or a small high-potential wireless transformer. The purpose of the spark coil or the transformer is to charge the Leyden jars or condenser which discharge through the primary of the Tesla coil.
Fig. 318.—Details of the Wooden Rings used as the Primary Heads.
If the young experimenter wishes to make a Tesla coil which will be suited to a smaller spark coil, for instance, one capable of giving a one-inch spark, the dimensions of the Tesla coil herein described can be cut exactly in half. Instead of making the secondary twelve inches long and three inches in diameter, make it six inches long and one and one-half inches in diameter, etc.
The Primary consists of eight turns of No. 10 B. & S. gauge copper wire wound around a drum. The heads of the drum are wooden rings, seven inches in diameter and one-half inch thick. A circular hole four and one-half inches in diameter is cut in the center of each of the heads.
Fig. 319.—Details of the Cross Bars which support the Primary Winding.
The cross bars are two and one-half inches long, three-quarters of an inch thick and one-half of an inch wide. Six cross bars are required. They are spaced at equal distances around the rings and fastened by means of a brass screw passing through the ring. When the drum is completed it should resemble a "squirrel cage."
Small grooves are cut in the cross bars to accommodate the wire. The wires should pass around the drum in the form of a spiral and be spaced about five-sixteenths of an inch apart.
The ends of the wire should be fastened to binding-posts mounted on the heads.
The Secondary is a single layer of No. 26 B. & S. silk- or cotton-covered wire wound over a cardboard tube, twelve inches long and three inches in diameter.
The tube should be dried in an oven and then given a thick coat of shellac, both inside and out, before it is used. This treatment will prevent it from shrinkage and avoid the possibility of having to rewind the tube in case the wire should become loose.
Fig. 320.—The Secondary Head.
The secondary is fitted with two circular wooden heads just large enough to fit tightly into the tube, having a half-inch flange, and an outside diameter of three and seven-eighths inches.
The Base of the coil is fifteen inches long and six inches wide and is made of wood.
The coil is assembled by placing the primary across the base and exactly in the center. Two long wood-screws passing through the base and into the primary heads will hold it firmly in position.
The secondary is passed through the center of the primary and supported in that position by two hard rubber supports, four inches high, seven-eighths of an inch wide and one-half of an inch thick. A brass wood-screw is passed through the top part of each of the supports into the secondary heads so that a line drawn through the axis of the secondary will coincide with a similar line drawn through the axis of the primary.
A COMPLETE COHERER OUTFIT AS DESCRIBED ON PAGE 274.
THE TESLA HIGH FREQUENCY COIL.
The supports are made of hard rubber instead of wood, because the rubber has a greater insulating value than the wood. High-frequency currents are very hard to insulate, and wood does not usually offer sufficient insulation.
A brass rod, five inches long and having a small brass ball at one end, is mounted on the top of each of the hard-rubber supports. The ends of the secondary winding are connected to the brass rods.
Fig. 321.—End View of the Complete Tesla Coil.
The lower end of each of the hard-rubber supports is fastened to the base by means of a screw passing through the base into the support.
In order to operate the Tesla coil, the primary should be connected in series with a condenser and a spark-gap as shown in Figure 324. The condenser may consist of a number of Leyden jars or of several glass plates coated with tinfoil. It is impossible to determine the number required ahead of time, because the length of the connecting wires, the spark-gap, etc., will have considerable influence upon the amount of condenser required. The condenser is connected directly across the secondary terminals of the spark coil.
When the spark coil is connected to a battery and set into operation, a snappy, white spark should jump across the spark-gap.
If the hand is brought close to one of the secondary terminals of the Tesla coil, a small reddish-purple spark will jump out to meet the finger.
Fig. 322.—The Complete Tesla Coil.
Adjusting the spark-gap by changing its length and also altering the number of Leyden jars of condenser plates will probably increase the length of the high-frequency spark. It may be possible also to lengthen the spark by disconnecting one of the wires from the primary binding-posts on the Tesla coil and connecting the wire directly to one of any one of the turns forming the primary. In this way the number of turns in the primary is changed and the circuit is tuned in the same way that wireless apparatus is tuned by changing the number of turns in the tuning coil or helix.
Fig 323.—Showing how a Glass-Plate Condenser is built up of Alternate Sheets of Tinfoil and Glass.
The weird beauty of a Tesla coil is only evident when it is operated in the dark. The two wires leading from the secondary to the brass rods and the ball on the ends of the rods will give forth a peculiar brush discharge.
If you take a piece of metal in your hand and hold it near one of the secondary terminals, the brushing will increase. If you hold your hand near enough, a spark will jump on to the metal and into your body without your feeling the slightest sensation.
If one of the secondary terminals of the Tesla coil is grounded by means of a wire connecting it to the primary, the brushing at the other terminal will increase considerably.
Make two rings out of copper wire. One of them should be six inches in diameter and the other one four inches in diameter. Place the small ring inside the large one and connect them to the secondary terminals. The two circles should be arranged so as to be concentric, that is, so that they have a common center.
The space between the two coils will be filled with a pretty brush discharge when the coil is in operation.
Fig. 324.—A Diagram showing the Proper Method of Connecting a Tesla Coil.
There are so many other experiments which may be performed with a Tesla coil that it is impossible even to think of describing them here, and the young experimenter wishing to continue the work further is advised to go to some library and consult the works of Nikola Tesla, wherein such experiments are fully explained.
CONCLUSION
Unless the average boy has materially changed his habits, in recent years, it matters not what the preface of a book may contain, for it will be unceremoniously skipped with hardly more than a passing glance. With this in mind, the author has tried to "steal a march" on you, and instead of writing a longer preface, and including some material which might properly belong in that place, has added it here in the nature of a conclusion, thinking that you would be more likely to read it last than first.
Some time ago, when in search for something that might be described in this book, I thought of some old boxes into which my things had been packed when I had dismantled my workshop before going away to college. They had been undisturbed for a number of years and I had almost forgotten where they had been put. At last a large box was unearthed from amongst a lot of dusty furniture put away in the attic. I pried the cover off and took the things out one by one and laid them on the floor. Here were galvanometers, microphones, switches, telegraph keys, sounders, relays, and other things too numerous to mention. They had all been constructed so long ago that I was considerably amused and interested in the manner in which bolts, screws, pieces of curtain rod, sheet-iron, brass, and other things had been taken to form various parts of the instruments. The binding-posts had almost in every case seen service as such on dry cells before they came into my hands. The only parts that it had been necessary to buy were a few round-headed brass screws and the wire which formed the magnets. In several instances, the latter were made so that they might be easily removed and mounted upon another instrument. The magnets on the telegraph sounder could be removed and fitted to form part of an electric engine or motor.
One particular thing which struck me very forcibly was the lack of finish and the crudeness which most of the instruments showed.
Of course it was impossible to avoid the clumsy appearance which the metal parts possessed, since they were not originally made for the part that they were playing, but I wished that I had taken a little more care to true up things properly or to smooth and varnish the wood, or that I had removed the tool-marks and dents from the metal work by a little filing.
If I had done so, I should now be distinctly proud of my work. That is not to say that I am in the least ashamed of it, for my old traps certainly served their purpose well, even if they were not ornamental and were better back in their box. Perhaps I might be excused for failing in this part of the work through lack of proper tools, and also because at that time there were no magazines or books published which explained how to do such things, and when I built my first tuning coils and detectors nothing on that subject had ever been published. I had to work out such problems for myself, and gave more thought to the principles upon which the instruments operated than to their actual construction.
The boys who read this book have the advantage of instructions showing how to build apparatus that has actually been built and tested. You know what size of wire to use and will not have to find it out for yourself. For that reason you ought to be able to give more time to the construction of such things. The purpose of this conclusion is simply a plea for better work. The American boy is usually careless in this regard. He often commences to build something and then, growing tired before it is finished, lays it aside only to forget it and undertake something else. Finish whatever you undertake. The principle is a good one. Remember also that care with the little details is what insures success in the whole.
If in carrying out your work, you get an idea, do not hesitate to try it. A good idea never refused to be developed. It is not necessary to stick absolutely to the directions that I have given. They will insure success if followed, but if you think you can make an improvement, do so.
Of course, such a book as this cannot, in the nature of things, be exhaustive, nor is it desirable, in one sense, that it should be.
I have tried to write a book which, considered as a whole, would prove to be exhaustive only in that it treats of almost every phase of practical electricity.
The principle in mind has been to produce a work which would stimulate the inventive faculties in boys, and to guide them until face to face with those practical emergencies in which no book can be of any assistance but which must be overcome by common sense and the exercise of personal ingenuity.
The book is not as free from technical terms or phrases, as it lay in my power to make it, because certain of those terms have a value and an every-day use which are a benefit to the young experimenter who understands them.
Any one subject treated in the various chapters of the "Boy Electrician" may be developed far beyond that point to which I have taken it. The railroad system could be fitted with electric signals, drawbridges, and a number of other devices.
Many new ideas suggest themselves to the ready-witted American boy. I shall always be pleased to hear from any boy who builds any of the apparatus I have described, and, if possible, to receive photographs of the work. I should be glad to be of any assistance to such a lad, but remember that some of the drawings and text in this book required many hours even to complete a small portion, and therefore please do not write to ask how to build other apparatus not described herein. And, as the future years bring new inventions and discoveries, no one now knows but that, some day, perhaps I will write another "Boy Electrician."
THE END.
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