E. F. Beck.

In experimenting with electricity, one often needs a switch connected in the circuit. It may be a one-point, two-point or a pole-changing switch that is desired. These may be made as follows:

First, get some tops of old battery zincs, A (Fig. 1), which may usually be had for the asking at any telephone central station. Second, a piece of pine wood about 3" square and 1/2" thick. Draw a keystone on it, using the dimensions given in Fig. 2.

Place a dot 1/2" up on the line AB at Z, and with that as a center, describe the two arcs with x and y as a radius, y being 13/4". At the points where the arc, made by the radius y, intersects lines AB and CD, place a dot. The base can now be cut out with a jack-knife. At the three dots, drill holes a little smaller than the screw B (Fig. 1) so that they can be made firm. Take three of the zinc tops and screw them in securely. At the side of each, drill a hole large enough to admit a 10 or 18 gauge wire. Next obtain a piece of brass or other conductive substance about 23/4" long and 1/2" wide. About 1/2" from the one end drill a hole and bend, as shown in Fig. 3. Now bore a hole at Z a little smaller than the screw that is going to hold the brass strip in place. Put a screw through holes H and Z, but before screwing down, put the bare end of a copper wire under the brass strip. It might be well to put a washer on top and be-low the brass strip at H, thus preventing the screw loosening, and insuring a better connection. Then bring the wires up through the three holes and fasten around the grooves in the points. If desired, a hole can be drilled through the other end of the brass strip and a nob attached. Screw holes should be made in the base for the screws that hold it down.

A pole-changing switch will need two strips of brass, three points and a similar base, with few exceptions. The holes drilled on the line CD will be placed further back on the arc (Fig. 2), at the places marked with a cross. Draw a line EF through Z parallel with the back of the switch, and at a point 1/2" each side of Z place a dot. Take the two strips of brass, drill a hole in each a short distance from the end, and bend as Fig. 3, and 1" from the other end drill a small hole in each of the strips. A piece of wood 11/2" long and 1/2" square will serve as a handle. Find the center and bore two small holes 1" apart, and put two round-head brass screws up through the strips into the handle. Now drill two holes on the line Z, at points already marked, and insert screws, as before, through the brass strips into the base, using washers if possible, and putting a wire under each strip. The two outside points must be joined together, forming one line, and the other one will be the wire from the central point. They should be fastened, as before, by twisting around the grooves, and soldered if possible.