It remains for us now to make brief mention of how men have tried, and are still trying, to imitate the soaring or gliding flight of birds without the use of machinery to assist them. We have seen how an albatross can, when the wind is blowing, convert itself, as it were, into a kite, and keep aloft in the air for a while without moving its wings. Similarly many people have attempted, by attaching themselves to a large supporting surface or aeroplane, and casting themselves off from a height, to glide with the wind across wide stretches of country. In this mode of soaring flight some have made considerable progress. Herr Lilienthal, a German, was perhaps for a time the most successful. He started from small beginnings, jumping off a spring board a few feet high, and gradually increasing the height as he became more accustomed to his apparatus. Later he had a large artificial mound made specially for him, and from the top of this he would throw himself into the air, and with a favourable wind sail a distance of four hundred yards at a considerable height above the ground. Lilienthal’s experiments, however, came to a sad end. On August the 11th, 1896, after he had glided along in the air for about two hundred yards, a sudden gust of wind caught the wide-spread wings of his apparatus, and tilted it upwards. This caused him to lose his balance, and he fell from a height of sixty feet and broke his spine. A similar accident also caused the death, a few years later, of a young Englishman, Mr. Percy S. Pilcher, who had been following up Lilienthal’s experiments. The greatest difficulty now to be overcome in solving the problem of human flight, whether with soaring apparatus or flying machine, may be summed up in one word--“balance.” Every schoolboy knows that the great art of kite-flying consists in so adjusting the point of attachment of the string and the length of the tail that his kite is properly balanced, and is not liable to turn over or “dip” when in the air. Every observer of birds, too, has noticed how largely the question of balance enters into their flying. A bird in the air is continually and instinctively adjusting its wings to its position, and to every puff of wind, even as a man on a bicycle is continually, though unconsciously, adjusting his handle-bar to the inequalities of the road; and as a cyclist requires practice before he can ride his machine, or a skater before he can keep his feet on the ice, so even a bird has to learn how to balance itself before it can use its wings.