A B, in the annexed engraving, is a glass tube fixed at one end in a wooden handle. The rubber, with its flap, D, carries a little Leyden jar, the end of which is visible at F. This jar is coated inside and out with a resinous insulating compound, and the metallic lining of the inside of the jar is in contact with the brass collecting-ring, E. The handle being held in one hand and the rubber in the other, when the tube is rubbed the little ring and jar rapidly collect electricity. A 1/2 inch spark and smart shock may be readily obtained from this apparatus, the length of the spark depending upon the amount of rubbing each time before the jar is discharged. When it is not desired to take the shock through the human body, the jar may be discharged by means of the metallic cord, H.

A Simple Electrical Machine