In America the pioneer who did most to further the science of human flight was Professor Samuel Pierpont Langley, of the Smithsonian Institute, in Washington. He was well known as an astronomer before ever he took up with aeronautics. From 1866 to 1887 he was professor of astronomy at the Western University of Pennsylvania, at Pittsburg. During his later years there he built a laboratory for aerial investigations, and carried out his famous experiments. His whirling table, with an arm about thirty feet long, which could be moved at all speeds up to seventy miles an hour, was devised to measure the lifting power of air resistance on brass plates suspended to the arm. In 1891 he published his _Experiments in Aerodynamics_, which embodied the definite mathematical results obtained by years of careful research. It would be difficult to exaggerate the importance of this work. The law which governs the reaction of the air on planes travelling at various speeds and various angles of incidence had been guessed at, or seen in glimpses, by earlier investigators; but here were ascertained numerical values offered to students and inventors. The main result is best stated in Professor Langley's own words: 'When the arm was put in motion I found that the faster it went the less weight the plates registered on the scales, until at great speed they almost floated in the air.... I found that only one-twentieth of the force before supposed to be required to support bodies under such conditions was needed, and what before had seemed impossible began to look possible.... Some mathematicians, reasoning from false data, had concluded that if it took a certain amount of power to keep a thing from falling, it would take much additional power to make it advance. My experiment showed just the reverse ... that the faster the speed the less the force required to sustain the planes, and that it would cost less to transport such planes through the air at a high rate of speed than at a low one. I found further that one horse-power could carry brass plates weighing two hundred pounds at the rate of more than forty miles an hour in horizontal flight.'