Fig. 7.—Oriental tailless Kites.
From historical researches that have been stimulated by the recent practical applications of kites, it appears that their first use for scientific purposes was in 1749, when Dr. Alexander Wilson of Glasgow, and his pupil, Thomas Melvill, used kites to lift thermometers. Their kites, from four to seven feet in height, and covered with paper, were fastened behind one another, each kite taking up as much line as could be supported, thereby allowing its companion to soar to an elevation proportionally higher. It is related that "the uppermost one ascended to an amazing height, disappearing at times among the white summer clouds, whilst all the rest, in a series, formed with it in the air below such a lofty scale, and that too affected by such regular and conspiring motions, as at once changed a boyish pastime into a spectacle which greatly interested every beholder…. To obtain the information they wanted they contrived that thermometers, properly secured, and having bushy tassels of paper tied to them, should be let fall at stated periods from some of the higher kites, which was accomplished by the gradual singeing of a match-line." How the thermometers were prevented from changing their readings while falling to the ground is not explained. The account concludes: "When engaged in these experiments, though now and then they communicated immediately with the clouds, yet, as this happened always in fine weather, no symptoms whatever of an electrical nature came under their observation. The sublime analysis of the thunderbolt, and of the electricity of the atmosphere, lay yet entirely undiscovered, and was reserved two years longer for the sagacity of the celebrated Dr. Franklin." Hence it seems that Franklin's famous experiment of collecting the electricity of a thunder-cloud by means of a kite, performed at Philadelphia in 1752, was not its first scientific application, and therefore America can claim only the later and most remarkable development of this means of exploring the air.
About 1837 there existed in Philadelphia an organization called the Franklin Kite Club that flew kites for recreation. Espy, the eminent meteorologist, was a member, and he states "that on those days when columnar clouds form rapidly and numerously the kite was frequently carried upward nearly perpendicularly by columns of ascending air," a phenomenon which is often observed to-day. Espy calculated the height at which clouds should form by the cooling of the air to its dew-point, and then employed kites to verify his calculations of the heights of the clouds. It will be remembered that both these methods are utilized in the measurements of cloud-heights at Blue Hill. Kites were employed to get temperatures a hundred or more feet above the Arctic ocean early in the present century, and in 1847 W. R. Birt flew a kite at Kew Observatory, with which he hoped to obtain measures of temperature, humidity, wind velocity, etc. This kite, hexagonal in shape, required three divergent strings attached to the ground to keep it steady, and the instruments were to be hoisted up to the kite by a pulley.
Perhaps the first person to soar aloft on a kite was a lady, who, more than fifty years ago, was lifted some hundred feet by a great kite constructed by George Pocock, an Englishman, to serve as an aërial observatory in warfare, and also to drag carriages along the ground. It was proposed afterwards to make use of kites in shipwrecks to take persons or life-lines ashore, and in 1865 Sir George Nares invented a storm-kite, so called, with a tail made up of hollow cones. This form of tail, subsequently used for both kites and balloons, is very efficient, since it offers increasing resistance as the wind becomes stronger.
In 1882 Mr. Douglas Archibald in England revived the use of kites for meteorological observations, and outlined a comprehensive scheme of exploring the air with kites which included almost all that has been done since, but his actual work, performed during the next three years, was limited to ascertaining the increase of wind velocity with height. To do this, he attached registering anemometers at four different points on the kite-wire, but since the total wind movements only were registered from the time the anemometers left the ground until they returned, it was impossible to obtain simultaneous records near the ground and at the kite, as is done to-day. Still, Archibald got differential measurements of the velocity of the wind up to the height of 1200 feet. The kites he employed were diamond-shaped, covered with silk, and were flown tandem, with the hollow cones, already mentioned, attached to the tails. Although copper and iron wire had been used for flying kites many years before, yet Archibald was the first to substitute steel pianoforte wire for the string, thereby increasing the strength while diminishing the weight, size, and cost of the line. Mr. Archibald in 1887 took the first photograph from a kite, a method which MM. Batut and Wenz developed in France, and Messrs. Eddy and Woglom in the United States.
The subsequent progress of kite-flying for meteorological purposes has taken place in the last-named country, and may be chronologically stated as follows: in 1885 Mr. Alexander McAdie (later of the U. S. Weather Bureau) repeated Franklin's kite experiment on Blue Hill, with the addition of an electrometer; in [1891], and again in 1892, he measured simultaneously the electric potential at the base of Blue Hill, on the hill, and with kites as collectors several hundred feet above the hill-top, about the same time that Dr. Weber, in Breslau, Germany, was making a more extensive use of kites for the same purpose. It was no doubt William A. Eddy of Bayonne, N. J., who turned the attention of American scientific men to kite-flying, and created the widespread interest in kites which exists to-day. About 1890 Mr. Eddy lifted thermometers with an ordinary kite, but soon afterwards devised a tailless kite, resembling the Java kite except that the horizontal cross-piece is nearer the top of the vertical stick, and its ends are bent backward in a bow and connected by a cord. This kite starts upward on being held in the wind at the end of a taut line, and continues to rise until the increasing wind-pressure on the portion above the cross-stick balances the pressure on the larger lower portion. The kite is kept from falling to one side by the looseness of the covering on either side of the backbone, and if there is more material on one side than on the other, or if the covering is too tight to form pockets in the wind, the kite requires a tail.[1]