But kites are useful for science as well as for sport; and this scientific men are now finding out. Inventors and engineers have discovered that kites present interesting problems for experiment and study. Men who watch the air and the sky find that kites are useful in getting records of what is going on far above the earth's surface. Nearly a hundred and fifty years ago, in 1749, the idea of using kites for a scientific study of the air occurred to two young men in Scotland. They were Alexander Wilson and Thomas Melvill. They made half a dozen large paper kites as strong and as light as the materials would permit. They began by raising the smallest kite, which, being exactly balanced, soon mounted steadily to its utmost limit, carrying up a line, very slender, but of sufficient strength to command it. In the mean time the second kite was made ready. Two assistants supported it in a sloping direction between them, with its face to the wind, while a third person, holding part of the line in his hand, stood at a good distance directly in front. Then the extremity of the line belonging to the kite already in the air was hooked to a loop at the back of the second kite, which, being now let go, mounted superbly. In a little time it took up as much line as could be supported with advantage, thereby allowing its companion to soar at an elevation proportionately higher. All the kites were sent up, one by one, in this manner, the upper kite reaching an amazing height, according to the writer who described the experiment. It disappeared at times among the white summer clouds. The pressure of the breeze upon so many surfaces attached to the same line was found too great for a single person to withstand, and it became necessary to keep the mastery over the kites by additional help. In order to learn about the warmth and the coolness of the air aloft, these young investigators fastened thermometers to the kites. The thermometers had bushy tails of paper, and were let fall from some of the higher kites by gradual singeing of a match-line. However, these young men probably did not learn much in this way, because a thermometer sinking slowly or rapidly to the ground would change its temperature. The kites were found to be capable of useful scientific work, but self-recording instruments to be sent up with the kites were not then invented.
Two years later than the experiment described above, as every boy knows, or ought to know, Benjamin Franklin, by sending up a kite during a thunder-storm, and collecting a charge of electricity, proved that electricity is the same as lightning.
PHOTOGRAPH TAKEN FROM A KITE ABOVE THE BLUE HILL OBSERVATORY, MASSACHUSETTS.
For another hundred years kites were used only as toys. Then came the present age of wonderful inventions, beginning about fifty years ago. For the first time instruments were invented which could be lifted into the air, and could make on a sheet of paper a record of all the changes through which they passed while aloft. In 1883 Mr. E. Douglas Archibald, in England, used kites for sending up instruments to measure how much stronger the wind was aloft than near the ground. In 1890 Mr. McAdie used kites as did Benjamin Franklin, in order to study the electricity in the air. By sending kites tied to a string around which was wound fine copper wire, he found that sparks would fly from the wire to his finger, even when the sky was clear. When a thunder-storm came in sight the sparks became so strong that it was thought best to bring the kites down, on account of the danger. Within the last ten years M. Richard of Paris, and Mr. Fergusson of Blue Hill Observatory, have made instruments so simple and so light that at Blue Hill Observatory we now have instruments weighing less than three pounds, which record on a single sheet of paper how cool or warm the air is, how damp it is, how dense it is, and how fast it moves. One of these instruments, lifted by several kites all tied to the same line is easily sent up a mile or more above the top of the hill from which the kites are flown. On August 1, 1896, an instrument weighing three pounds was sent 6700 feet above the top of Blue Hill, near Boston. It was then 7333 feet above the level of the sea, or more than a thousand feet higher than the fop of Mount Washington, the highest mountain in New England. The highest kite was then higher than the instrument by more than a hundred feet.
Mr. W. A. Eddy, of Bayonne, New Jersey, has used the kites successfully at Blue Hill and at Boston for taking photographs of the surrounding country from a height of several hundred feet in the air. The camera is fastened to the kite-string, and the exposure of the plate is made by pulling a second string which hangs from the camera to the ground. One of the photographs, taken several hundred feet above Blue Hill, is shown here. The picture gives the Blue Hill Observatory and the country for several miles around.
Mr. J. Woodbridge Davis proposed to use kites for sending life-lines to vessels wrecked near the coast, and devised kites for this purpose which could be steered to any point nearly in a line with the wind.
HARGRAVE KITE IN THE AIR.
The largest kite ever built was lately made by Mr. Lamson at Portland, Maine. This kite was built on the plan of Hargrave's kite, shown in one of our pictures, except that the cells were curved, and various other improvements made in construction. This kite was 32 feet long, and had 900 square feet of surface. It weighed about 150 pounds, and lifted a dummy-man weighing 150 pounds several hundred feet into the air. Then the cord broke, and kite and dummy floated off into an adjacent swamp.