At the present time it is not necessary for any man to take a small boy with him as a species of lightning-rod to ward off ridicule when he flies a kite. I have been one of a committee on kite-flying at which some of the most learned and serious men in England were my colleagues in investigating the subject. The behaviour of kites is certainly very puzzling to those who do not thoroughly understand the subject. A kite may be made with the greatest degree of perfection, and placed in the hands of one of considerable experience; nevertheless, it may behave very badly, diving suddenly to the ground without any apparent cause. Then, again, this same kite will sometimes steadily mount in the air until it reaches a height difficult to account for. If the surface of the earth should be perfectly smooth, and the wind should always blow in a horizontal direction, kites would not show these eccentric peculiarities, but, as a matter of fact, the air seldom moves in a horizontal direction; it is always influenced by the heat of the surface of the earth. Heated air is continually ascending in some places only to be cooled and to descend in other places. If one is attempting to fly a kite where the air is moving downwards, he will find it an extremely difficult matter, whereas, if he is fortunate enough to strike a current of air which is rising, the kite will mount much higher in the air than can be accounted for, except we admit of the existence of these upward draughts of air. On one occasion many years ago, I was present when a bonded warehouse in New York containing 10,000 barrels of alcohol was burnt. It was nine o’clock at night, and I walked completely around the fire, and found things just as I had expected. The wind was blowing a perfect hurricane through every street in the direction of the fire, although it was a dead calm everywhere else; the flames mounted straight in the air to an enormous height, and took with them a large amount of burning wood. When I was fully 500 feet from the fire, a piece of partly burnt 1-inch board, about 8 inches wide and 4 feet long, fell through the air and landed very near me, sending sparks in every direction. This board had evidently been taken up to a great height by the tremendous uprush of air caused by the burning alcohol. It is very evident that a kite made of boiler iron could have been successfully flown under these conditions providing that it could have been brought into the right position. [Illustration: Fig. 7.--The circulation of air produced by a difference in temperature.]