DRAWING DOWN ELECTRICITY BY A KITE-STRING.
The scientific kite-flyer will find much to tempt him into the field of electricity; and will be able, not only to duplicate Dr. Franklin's historic experiment of bringing down sparks from the heavens, but may go far beyond this, taking advantage of the greater knowledge of electricity at his disposal and the superior apparatus. In the summer of 1885, Alexander McAdie, at the Blue Hills Observatory, got strong sparks at the earth's surface from a wire connected with a kite whose surface had been coated with tinfoil so as to form an electric collector. He also, by the brightness and increased lengths of the sparks obtained, proved that the electric force in the atmosphere is very greatly increased with the approach of thunder clouds; and also that this force increases steadily as the kites reach greater altitude, and vice versa. Indeed Mr. Eddy and others who have conducted similar experiments, have found the electric force so strong at certain altitudes as to make the manipulation of the conducting wire a source of considerable danger.
On October 8, 1892, Mr. Eddy made an important advance in electrical experiments with kites, by using a collector quite separate from the kites themselves, which were merely used in tandem to support the line on which the collector was swung and raised to any desired altitude. By this arrangement any accident that might befall one of the kites is less likely to ruin the whole experiment.
Much experience with the kite-collector has convinced Mr. Eddy that there is always in the air overhead, at all times of the year and in all weathers, an abundant, practically a boundless, supply of electricity. It has never yet happened to him to send his collector up to even so low a height as four hundred feet without getting a spark in his discharge-box at the earth. He has discovered, however, that the greater the amount of moisture in the air, the greater is the height to which he must send the collector before getting the first spark. There is no doubt that large quantities of electricity might be obtained by hoisting large collectors, supported by strong flying tandems, to considerable altitudes, and drawing off the supply at the earth by means of a system of transformers which would lower the electricity from the dangerously high tension at which it discharges down the wire, to a voltage that could be handled with safety. In his experiments thus far, Mr. Eddy has discharged the copper wire leading from his collector into a wooden box containing a pasteboard wheel with darning-needle axle and tinfoil edges. The axle is grounded, and the copper wire from the collector placed near the tinfoil periphery of the wheel, so as to discharge its sparks through the intervening distance, and by the shock cause the wheel to turn.