It is best to make rain-kites of oil-skin or paraffine paper, as the ordinary paper or cloth becomes saturated with the dampness and very heavy, thus lessening the buoyancy of the line. So penetrating is the dampness of clouds, even without a rain-storm, that the wooden frames sometimes become warped and the paste seams soak open.
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.
THE USE OF KITES IN PHOTOGRAPHY.
One of the most interesting applications of the kite, but a thoroughly practical one, is its use in photography. This has been entirely developed within the past year or two; indeed the first kite-photograph taken on the American continent was one made by Mr. Eddy's camera on May 30, 1895. Although some attempts in this direction had been previously made in Europe, this was the first clearly focused kite-photograph obtained. The previous ones had been blurred, owing to defects in the devices for swinging the camera apparatus from the kite-cord, and for loosening the shutter. Mr. Eddy's apparatus will be better understood from the accompanying cut than from any description. In a general way it is a wooden frame capable of holding the camera, and terminating behind in a long stick or boom, by means of which the camera is made to point in any desired direction or at any angle. This is arranged before sending up the apparatus, the boom being properly placed and held in position by means of guy cords from the main kite-line. A separate line hangs from the spring of the camera shutter, with which is also connected a hollow ball of polished metal supported in such a way that it will drop from its position, five or six feet through the air, when the camera cord is pulled. The purpose of this ball is to allow the operator on the ground to be sure that the camera has responded to his pull and that the desired photograph has been taken. He is assured of this, having given the pull, on seeing the flash made by the polished ball in its fall.
All this being arranged, it is only necessary to send the camera up to any desired altitude and pull the camera cord, in order to get photographs of wide-stretching landscapes, extensive cities, like New York, and panoramas of every description. Such photographs could not but be of the greatest value to geologists, mountain climbers, surveyors, and explorers. And they must possess particular interest for students of geography and for map-makers.
POSSIBLE USE OF KITES IN WAR.
It is obvious, too, that kite-photographs might be of great value in time of war, since a detailed view of an enemy's lines and fortifications might be thus obtained; while at sea a perfected kite-photographing apparatus might be of great value in recording the approach of an enemy's ships. Mr. Eddy regards it as perfectly possible to send up a tandem of kites from the deck of a man-of-war, with a circular camera, such as has already been devised, attached to the main line, and an apparatus for snapping all the shutters simultaneously; and photograph, not only the whole horizon as seen from the deck of a vessel, but, because of the greater elevation, many miles beyond. A battle-ship provided with this photographing device would enjoy as great an advantage as if it were able at will to stretch out its mainmast into a tower of observation a mile high.