An apparatus comprising a coil, an interrupter, or armature, and a switch may be set on one block, and the arrangement of the several parts is clearly shown in the drawing of the complete galvano-faradic apparatus (Fig. 11). The block should be six inches long, four inches wide, and seven-eighths of an inch in thickness.
The coil is made as described for Fig. 8, the spool being three inches long and one inch and a quarter in diameter. A carriage-bolt three inches and a half long and five-sixteenths of an inch in diameter, with a bevelled head, is made fast in the spool, and this coil is strapped to the block with two metal bands and screws. Two binding-posts (A and B of Fig. 11) are arranged at the upper corners, and to these the ends of the secondary coil wires are attached. Two more binding-posts (C and D of Fig. 11) are arranged at the lower side and provided with a switch to open and close the circuit. One of the primary coil wires is made fast to C, and the other one to a block which contains the set-screw that bears against the vibrating armature. Its arrangement and the wire connection is explained in Fig. 9 B.
An armature of thin brass or tin is made and attached to a block (E in Fig. 11). At the loose end that is opposite the bolt-head several wraps of tin are made and soldered fast, or a small block of soft iron may be riveted to the armature. It must be of iron or tin, however, so as to be attracted by the electro-magnetized bolt-head. This arrangement may be seen in Fig. 12. Attach a thick piece of paper over the bolt-head, so that the lug at the end of the armature will not adhere to it through residual magnetism.
In regular galvano-faradic machines the current regulator is formed of a hollow cylinder which is drawn from the core of the coil; but in this simple machine the water-jar regulator may be connected between a pole of the battery and the binding-posts (D or E of Fig. 11). The wires of the handles are attached to posts (A and B of Fig. 11), and when all the wires are in place and the current turned on by means of the switch, the vibrator begins to work and the shocking-current is felt through the handles. By means of the regulating-screw that bears on the armature, the number of vibrations may be increased or diminished, but for faradic purposes the vibrations should be as quick as possible. Much amusement may be had with this apparatus, and a large number of people may be given a shock by getting them to join hands when standing or sitting in a circle.