while aerodrome is the name given to the flying-ground from which it starts. The success of his machine became widely known, and in 1898 the War Department of the United States, having ascertained that Langley was willing to devote all his spare time to the work, allotted fifty thousand dollars for the development, construction, and test of a large 'aerodrome', big enough to carry a man. The construction was long delayed by the difficulty of finding a suitable engine. This difficulty hampered all early attempts at flight. The internal-combustion engine was by this time pretty well understood, and, with the will to do it, might have been made light enough for the purpose. But it was almost an axiom with engineering firms that a very light engine could not wear well and was untrustworthy in other ways. One horse-power to the hundredweight was what they regarded as the standard of solid merit. Further, they were prejudiced against that extremely rapid movement of the parts which is necessary if the crank-shaft is to revolve more than a thousand times a minute. They were asked to depart from all their cherished canons and to risk failure and break-down in order that man should achieve what many of them regarded as an impossibility. It was with Langley as it was with Pilcher and the Wrights; he had to make his own engine. By 1901 he had completed with the aid of his assistants an engine of fifty-two horse-power, weighing, with all its appurtenances, less than five pounds to the horse-power. A year and a half more was spent in adapting and co-ordinating the frame and appliances, and in carrying out the shop tests. At last, on the 7th of October 1903, from a house-boat moored in the Potomac river, about forty miles below Washington, the first trial was made. The machine caught in the launching mechanism, and fell into the river, where it broke. It was repaired, and a second trial was made on the 8th of December 1903. Again the machine failed to clear the launching car, and plunged headlong into the river, where the frame was broken by zealous efforts to salve it in the dark. Nine days after this final failure the Wrights made their first successful power-driven flight, at Kitty Hawk, on the coast of North Carolina. Langley was almost seventy years old when his last and most ambitious machine failed. He lived for two years more. If his contributions to the science of flight, which are his chief title to fame, were ruled out of the account, he would still be remembered as something more than a good astronomer--a man of many sciences, who cared little for his own advancement, and much for the advancement of knowledge.