It is difficult to keep track of each preceding turn, while winding, because of the fineness of the wire, and on this account it is a good scheme to coat each layer with bluing after it has been wound on, so that each turn of the following layer will show plainly against the stained layer beneath it. Figure 190 shows the complete induction-coil.
Cut a base block 5 inches wide and 7 inches long, bevel the top edges to give it a trim appearance, and mount the induction-coil to one side of the center (Fig. 187), strapping it in place by means of two tin straps similar to that shown in Fig. 191, cut from a tin can.
The projecting ends of the primary-coil connect with the battery, while the two ends of the secondary-coil connect with the handles. Make three binding-post plates out of folded pieces of tin, similar to plates B and C, in Fig. 182. Tack two of these to the end of the base and connect the secondary-coil wires to them (Fig. 187), and tack the third near one end of the induction-coil and connect one primary-coil wire to it (Fig. 187).
For the Handles take two pieces of broom-handle 34 inches long, and cover each with a piece of tin (Fig. 192). The pattern for the tin covering (Fig. 193) shows how tabs are prepared on the ends and holes punched through them for connecting with the induction-coil. The connecting wires should be 5 or 6 feet long. Flexible wire is better than bell-wire for these, because it is more easily handled in passing the handles around. Tack the tin covering to the pieces of broom-handle.
