Cut the base block A 1½ inches wide and 2½ inches long. Make the shaft B 2¾ inches long and of a diameter equal to the hole in a thread spool; and prepare the crank C to fit on the end, and drive a brad into it for a handle. Fasten the crank to the shaft with glue, or by driving a small brad through the two. The shaft supports D should be prepared as shown in Fig. 196, 1¼ inches wide across the bottom, ⅝ inch wide at the top, and 1¾ inches high. Bore a hole through each, a little below the top, and large enough so the shaft will turn easily, and fasten these supports with brads to the sides of base A. Drive eight brads into a thread spool, spacing them equidistant from one another, and mount this spool upon the shaft (E, Fig. 194), first slipping the shaft through one support, then through the spool, and then through the other support. Drive the spool brads a trifle into the shaft to hold the spool in position.
The projecting arm F (Fig. 194) is a strip of tin cut from a can, and must be long enough so each nail-head will strike its end when spool E is revolved. Drive a nail into base A, at G, and, after bending strip F as shown in Fig.198, fasten it with brads upon the top of an upright made similar to H (Fig. 197), and nail this upright to the end of base A. The upper end of strip F must be bent so it will bear down upon the head of nail G.
The wire from the primary-coil which is as yet not connected should be attached to nail G, and one battery wire should be connected to a binding-post plate I fastened to
