R. C. Browne.

The lightning arrester here described can easily be made, and will work well in connection with the wireless-telegraphy apparatus recently described in this magazine. To make it, procure a piece of thick roofing slate, or what is better, a piece of slate from a discarded icechest. It should be 4" long and 2" wide. Slate can be cut with an old saw, and the holes made with a diamond drill. Drill a 1/8" hole in each corner and two holes in the center, 3" apart, the latter to receive the screws in the bases of two binding-posts. Enlarge the holes in the binding-posts to 1/4" diameter, and mount them on the slate with the holes facing each other. Two pieces of 1/4" brass or German silver rod, each 2" long, are needed. Slightly round one end of each piece, and then put them through the holes in the binding-posts with the rounded ends toward each other, but about 1/4" apart, as shown in the illustration. This space is suitable for the wireless-telegraphy apparatus. For other uses it may be lessened.

A Lightning Arrester 255

When made, the instrument is mounted at the point where the wire likely to be charged by lightning enters the building. Under the holes in each corner place small porcelain insulators, and secure to the house with round-headed brass screws. Use care in putting in the screws, as the slate is easily broken at the corners. When in place, connect one end of a heavy copper wire, No. 6 or larger, to the lower binding-post, the other end of the wire being carried on insulators to some good ground, such as a piece of sheet copper 1 square, the wire being soldered to it. The copper plate should be buried deep enough to be in earth which is always moist. The overhead or line wire is connected to the other binding-post before it is carried to the telegraph instruments inside.

Any incandescent electric light will burn under water at any depth if the wires and the lamp are protected from getting wet.