Fig. 4.—Hammer of Contact-breaker.
P, Platinum foil.
I, Soft iron fastened to opposite side.
A piece of sheet brass is taken 1½ inches long by about ⅜ of an inch at one end, gradually tapered up till it comes to a point about ⅛ of an inch broad at the other; it must be very thin, and must act as a spring when fastened tightly at one end. A small piece of soft iron is soldered to the small end of this to be attracted by the core when working. The next thing is to fasten a small piece of platinum foil about ¼ of an inch square on the opposite side of the brass to the soft iron, and a little below it (Fig. 4). This is rather a difficult operation, as it is such a small object to solder, and the best way is to get it done by a tinsmith, unless you are skilled in the use of the soldering bit.
Fig. 5.—Screw of Contact-breaker.
F, Flange of paper-fastener soldered to upright brass strip.
P, Platinum tip to screw.
Fig. 6.—Plan of Coil Complete.
A, Coil.
B B B B, Binding screws.
C, Strip of brass supporting spring.
D, Strip of brass supporting screw.
S, Screw to adjust position of soft iron, I.
Current travels from the binding-screw to C, from C to S, thence to D and round the coil by the wire, returning to battery by screw in opposite corner.