Dr. Lilienthal, a German, was the first to try scientific wing-sailing. He became a regular air gymnast, running down the sides of an artificial mound until the wings lifted him up and enabled him to float a considerable distance before reaching earth again. His wings had an area of 160 square feet, or about a foot to every pound weight. He was killed by the wings collapsing in mid-air. A similar fate also overtook Mr. Percy Pilcher, who abandoned the initial run down a sloping surface in favour of being towed on a rope attached to a fast-moving vehicle. At present Mr. Octave Chanute, of Chicago, is the most distinguished member of the “gliding” school. He employs, instead of wings, a species of kite made up of a number of small aerocurves placed one on the top of another a small distance apart. These box kites are said to give a great lifting force for their weight. These and many other experimenters have had the same object in view--to learn the laws of equilibrium in the air. Until these are fully understood the construction of large flying-machines must be regarded as somewhat premature. Man must walk before he can run, and balance himself before he can fly. There is no falling off in the number of aërial machines and schemes brought from time to time into public notice. We may assure ourselves that if patient work and experiment can do it the problem of “how to fly” is not very far from solution at the present moment. As a sign of the times, the War Office, not usually very ready to take up a new idea, has interested itself in the airship, and commissioned Dr. F. A. Barton to construct a dirigible balloon which combines the two systems of aerostation. Propulsion is effected by six sets of triple propellers, three on each side. Ascent is brought about partly by a balloon 180 feet long, containing 156,000 cubic feet of hydrogen, partly by nine aeroplanes having a total superficial area of nearly 2000 square feet. The utilisation of these aeroplanes obviates the necessity to throw out ballast to rise, or to let out gas for a descent. The airship, being just heavier than air, is raised by the 135 horse-power motors pressing the aeroplanes against the air at the proper angle. In descent they act as parachutes. The most original feature of this war balloon is the automatic water-balance. At each end of the “deck” is a tank holding forty gallons of water. Two pumps circulate water through these tanks, the amount sent into a tank being regulated by a heavy pendulum which turns on the cock leading to the end which may be highest in proportion as it turns off that leading to the lower end. The idea is very ingenious, and should work successfully when the time of trial comes.