Early Radiosonde – Scientific kite-flying

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No branch of science has made such rapid strides within the last quarter of a century as that of kite-flying; indeed, it is not going too far to say that during the last decade the modern kite has done more in the exploration of the air than its contemporary, the balloon. Kites are now extensively flown both on the Continent and in America for obtaining meteorological observations. Numerous kite flying stations have been opened in France, Germany, and the United States. Some of them are under the control of the respective Governments, while others are purely private institutions.

By far the largest and most interesting of these is Blue Hill Observatory, a private institution, near Boston, Massachusetts, U.S.A. Here kites may daily be seen far away on the horizon, almost out of sight. Before describing the present method of flying these little air-ships, it is interesting to recall the ancient history of the toy that is now being put to such practical and scientific purposes.

The type of kite in general use at the various meteorological stations is the Hargrave or Cellular kite. It was invented by Mr. Lawrence Hargrave, of Sydney, Australia. It consists of two light boxes, without tops or bottoms, fastened some little distance one above the other. The wind exercises its lifting force chiefly upon the front and rear sides of the upper box, the lower box, which inclines to the rear and so receives less pressure, preserving the balance, while the ends of the boxes, being in line with the wind, keep the kite steady.

The Hargrave is undoubtedly the most perfect kite ever designed, next to which comes the Malay form of kite, invented by that well-known kite-flier, Mr. William A. Eddy, of Bayonne, New Jersey. Until four years ago the little air-ships were drawn in by hand. Now, however, the kites are brought down by machinery. Through the kindness of Mr. A. Lawrence Botch, Director of the Blue Hill Observatory, I am enabled to reproduce a photograph of this clever piece of mechanism, and incidentally other photographs showing the methods of kite-flying at this interesting station.

The pull of the kites during ascent is sufficient to unreel the wire, which, by means of a pulley, is delivered to the kites as required, an attached wheel meanwhile recording the pull on the line and the length paid out. A fine steel music-wire is employed, weighing only fifteen pounds to the mile, and capable of withstanding a pull of three hundred pounds. Kites are usually drawn in by the machine at the rate of three to six miles an hour.

The kites carry up a meteorograph, which is virtually a combination of a barometer, a thermometer, and a hygrometer, all of which record their readings automatically on one cylinder turned by clockwork. These little instruments are the invention of M. Richard, of Paris, are made of aluminium, and weigh three pounds. By flying two or more kites, a greater lifting power is obtained, while there is also less risk of the kites breaking away and getting lost. Indeed, often five, six, and more kites are attached to the same line, when it is desired to lift a heavy instrument into the air, while there is a record of twelve kites having been attached to the same rope.

The kites at Blue Hill vary in height from five to twelve feet and more, and are fairly heavy. The larger ones contain about seventy square feet of supporting surface and exert a pull of from seventy to a hundred pounds. It would be impossible to manage such an air-ship by hand, but by means of the steam windlass or reeling apparatus referred to they are kept under control.

In the summer of 1897, a kite at Blue Hill attained the then record height of 11,716 feet. It was regarded as a remarkable achievement. Since then the distance has been gradually increased, the present record height being 15,800 feet above the level of the sea an ascent of over three miles and exceeding the highest scientific balloon ascent in America. When this unique record was achieved,. a combined weight of a hundred and seventy-five pounds was lifted into the air. Six kites of the improved Hargrave type were used. They had curved flying-surfaces modelled after the wings of a bird. The length of wire paid out to the kites was over five miles.

According to the recording instruments, the temperature at the highest point attained was fifteen degrees below freezing-point, and the wind velocity was about twenty-five miles an hour. Flights have been made at Blue Hill in gales, in rain, and in snow-storms, but never in a thunder-storm. The high flights occupy ten or twelve hours.

Occasionally the kites are left out all night. Few men in this country have given more time and thought to the subject than Major B. Baden-Powell, brother of the celebrated Defender of Mafeking. He is said to possess the largest kite ever made. It stands thirty-six feet in height and has an area of five hundred square feet. Major Baden-Powell experimented with it at Pirbright Camp a few years ago, when the giant easily lifted a man in the air.

Not only have kites proved to be the cheapest and most reliable instruments for securing meteorological records, but they are useful also for signalling purposes. Mr. W. A. Eddy has recently invented a device for telephoning by means of kites. Many know of the wonderful success accomplished in kite-photography, and it would seem that the modern kite in the hands of a scientist is a weather-chart, a photographer, a signalling apparatus, a telephone, a collector of electricity, a parcel- and letter-carrier, and a medium for lifting man into space.

The Sketch - Wednesday 04 December 1901

Image © Illustrated London News Group