Page:Popular Science Monthly Volume 56.djvu/262

248 existence of two fluids. He was led to this belief by observing that he obtained a larger spark between two oppositely electrified bodies than from either to the earth.

From this time on there appears upon the scene a host of workers in this field, one of the most prominent being the distinguished American, Benjamin Franklin. Somewhat previous to his remarkable work, or about 1750, Boze made certain discoveries in the matter of the surface tension of conducting liquids being diminished by electrification, and Mowbray and Nollet ascertained that the vegetation of flowers and of vegetating seeds was hastened by electrifying them.

Franklin (born 1706, died 1790) made the important discovery of the active discharge of electricity from an electrified body by points as well as the converse of it—i. e., that electricity was rapidly abstracted from a charged atmosphere by points. This enabled him to increase the efficiency of the electrical machine by adding a combshaped series of points to the collector of the prime conductor.

Up to this time, although the identity of lightning with electricity had long been suspected, it had not been at all established, and to Franklin may be said to belong the honor of doing so, although in this, as in the case of the invention of the Leyden jar, there appears to have been successful contemporaneous research elsewhere. Before performing his great experiment Franklin published a book strongly supporting the belief in the identity of the two. Once having conceived the idea of drawing electricity from the upper atmosphere, he unfortunately lost some time through waiting for the completion of the spire of a certain church in Philadelphia, from the top of which he hoped to be able to collect electricity by means of a wire, but finally hit upon the device which now fills much the same place in connection with his memory that the classical cherry tree does with Washington's—the lightning-collecting kite. This apparatus was very simply constructed, and had a pointed wire projecting a short distance above the framework. It was controlled, and electrical connection made, by an ordinary string which terminated in a short length of silk ribbon to protect the person from possible injury, and to give electricity a chance to accumulate in the system, by insulating the "line." At the end of the string proper Franklin fastened a metallic key. In company with his son he flew the kite during a thunderstorm which occurred in June, 1752; for some time no electric disturbance approached the neighborhood, and he was on the point of abandoning the experiment when he observed what he had been waiting for—the outer fibers of the string standing out from the latter by repulsive force—and, applying his knuckle to the key, he drew a spark. Subsequently, when the rain soaked the string and caused it to conduct much better, there was a fine supply