The Wimshurst machine illustrated herewith (Fig. 196) was made very cheaply out of such materials as came to hand. The frame is of oak and the bosses of nine. The two glass disks are 12 inches in diameter. The sectors were made of brass foil with brass hemispheres (tack heads) soldered on them. Sixteen sectors are used on each disk. The Leyden jars consist of Welsbach lamp chimneys (the straight kind) to which the tinfoil was applied at the center, keeping it 1 1/2 inches from each end. The posts that support the combs and terminals pass through the chimneys. The posts are of hard rubber, and each has a hole bored in the end to receive the stem of the brass ball, which connects the comb and the terminal to it. The stems were made fast by pouring melted sulphur into the holes around them. The combs are connected to the inner coating of the Leyden jars. In place of simply connecting the outer coatings of the jars with wire, two tubes are fitted into the frame in such manner that they can be connected by putting a plug in one tube, and be disconnected by putting it into the other, and then hand holes or any other form of terminals may be attached to them.

The device is used for a display design by placing in the circuit a tinfoil strip cut away at the points where sparks are wanted to make the design or letters, etc. When the outer coatings are connected, a 1 1/2-inch spark is obtained. The machine is driven by means of oak pulleys and a leather cord belt.

Fig. 196 - A home-made Wimshurst machine.

The accompanying photograph of the machine and the spark was made as follows; Winn the camera had been focused on the machine, the room was darkened by drawing the shades; then while the plate was exposed, the machine was operated to give several sparks. The camera was now closed and, after the shades were raised, a second exposure was made without disturbing the machine or the camera. - I