Having made the cases for the magnets, now make the mouthpieces. Procure two wooden boxes such as boot-buttons are sold in, and glue one to the end of each of the wooden tubes you have just made, cutting a hole in the bottom of the box to correspond with the bore of the case. In [Fig. 1a] you will see the work, so far as you have completed it, shown in section. In the lid of the box cut a clean hole the size of a dime right in the center, but this lid must not be fastened to the box just yet.
The next things to be made are two bobbins upon which to wind the wire—one for each instrument. Cut a piece of fairly strong cardboard about 1⁄4-inch wide and just large enough in circumference to fit the marked end of the magnets tightly. Divide your No. 36 wire into two equal lengths, and wind each piece around the bobbins, leaving the two ends free to the length of about two inches.
Next slip the magnet, M, into the groove, and push it through so that the bobbin, L, is contained in the box C, [Fig. 2]. Make two holes in the bottom of this box, pass the ends of the wires through them and fasten them with binding screws, as in the illustration H, [Fig. 2].
The thin plate which vibrates with the voice must next be made. Obtain a smooth piece of very thin sheet-iron—of just such a texture as is used by photographers for ferrotypes. Take the greatest care to keep this perfectly flat. Cut two round pieces large enough to cover the mouthpieces as you will see in P, [Fig. 3], where it is shown in section. Take the lid in which you have already cut the circular hole and fasten it to the box in such a way that it keeps the iron plate in position (Q, [Fig. 3]).
Fig. 2.—Arrangement of magnet.
Fig. 3.—Section of completed instrument.
Fig. 4.—Connection with battery.