go of the metal grips until the current has been shut off, but in our small shocking machine the handles can be dropped the instant the person holding them wishes to do so.
The shocking machine consists of an induction-coil, an interrupter, and a pair of handles, all of which are easy for a boy to make, and a wet or dry battery of one or two cells to furnish the current.
The Induction-Coil is the first part to make. This is shown in detail in Figs. 188 to 191. The coil has windings
Figs. 188-191.—Details of Induction-Coil.
of two sizes of wire upon an iron core. For the core buy a 5/16-inch carriage-bolt 2½ inches long, and for the wire coils get some No. 20- or 24-gauge electric-bell insulated copper wire, and some No. 30-gauge insulated magnet-wire. To keep the wire from slipping off the ends of the bolt core, cut two cardboard ends about 1½ inches in
