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, natural 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 present the reader with a suggestive line of experimentation 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  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 modifications. The motors have been selected with regard to their variation from the usual type of “reversible dynamo.” The simple experiments and constructions 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 shortcomings of the current generator.

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 contiguous windings or coils to touch each other, and a 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 intervening 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 windings around the bend.

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.

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 extraordinary 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 under "Magnetizing 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, 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 mandrels.

To make a magnetizing coil a mandrel of any convenient 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 used 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 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 described method is adopted.

A much nicer and more effectual way is to use a solution 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.