Since the two remaining divisions of the five concerned in the problem of flight had been already solved by Lilienthal, it seemed that it only remained for some scientist to combine this complete knowledge in the proper way to produce a practical flying-machine--one that would fly through the air, and continue to fly until the power was exhausted. It was not a startling announcement to the scientific world, therefore, when about three years later the news was flashed that Prof. S. P. Langley had produced such an apparatus. [Illustration: FLYING MACHINES OF THE MONOPLANE TYPE. Upper figure, the aeroplane of M. Robert Esnault-Pelterie. Middle figure, the aeroplane of M. Blériot. Lower figure, the Vuia aeroplane, a bat-like machine of freakish structure which had no large measure of success. A modification of the boat-like machine shown in the upper figure gained celebrity through its use by M. Latham in the first attempt (in July, 1909) to fly across the English Channel. M. Blériot's aeroplane as finally developed became a very successful flying machine. With its aid M. Blériot was first to accomplish the feat of flying across the English Channel (from Calais to Dover in about 23 minutes) on the morning of July 25th, 1909. These pictures are reproduced from the London Graphic of January 25th, 1908.] Professor Langley described this really wonderful machine, which he called the "aerodrome," as follows: "In the completed form there are two pairs of wings, each slightly curved, each attached to a long steel rod which supports them both, and from which depends the body of the machine, in which are the boilers, the engines, the machinery, and the propeller wheels, these latter being not in the position of an ocean steamer, but more nearly amidships. They are made sometimes of wood, sometimes of steel and canvas, and are between three and four feet in diameter. "The hull itself is formed of steel tubing; the front portion is closed by a sheathing of metal which hides from view the fire-grate and apparatus for heating, but allows us to see a little of the coils of the boiler and all of the relatively large smokestack in which it ends. There is a conical vessel in front which is simply an empty float, whose use is to keep the whole from sinking if it should fall in the water. "This boiler supplies steam for an engine of between one and one-half horse-power, and, with its fire-grate, weighs a little over five pounds. This weight is exclusive of that of the engine, which weighs, with all its moving parts, but twenty-six ounces. Its duty is to drive the propeller wheels, which it does at rates varying from 800 to 1,200, or even more, turns a minute, the highest number being reached when the whole is speeding freely ahead.