Wireless Telegraphy and Telephony

heard the brilliant snapping spark produced by the discharge of a Leyden jar. A Leyden jar in its common form is a glass jar lined inside and out with tinfoil for about two- thirds of its height. A brass rod, terminating in a knob, connects below with the inner coating, usually by means of a loose chain. It may be described as a device which is capable of storing electricity in the form of energy and discharging this energy again in actual electricity. This discharge has been the subject of many interesting investigations of direct interest. Fig. 3.—A static machine connected to a Leyden jar. The inner and outer coatings are connected to the ter- minals of a static electric machine (an apparatus for gener- ating electricity), and the machine set in rotation. After the jar has been charged, the electric machine is discon- nected and one end of a coil of heavy wire connected to the outside coating, while the other end of the wire is made to approach the knob connected with the inner coat- ing. Before the end of the wire reaches the knob a dis- charge occurs through the coil, producing a noisy brilliant spark between the wire and the knob. The discharge ap- pears like a single spark, but in reality it is composed of a great many following each other in rapid succession. The jar discharges its energy, first by a tremendous rush of