In 1887, prior to his removal to Washington as Secretary of the Smithsonian Institution, Langley began his experiments in aerodynamics at the old observatory in Allegheny--now a part of the city of Pittsburgh. His chief apparatus was a whirling table, sixty feet in diameter, and with an outside speed of seventy miles an hour. This was at first driven by a gas engine,--ironically named "Automatic,"--for which a steam engine was substituted in the following year. By means of the whirling table and a resistance-gauge (dynamometer chronograph) Langley studied the effect of the air on planes of varying lengths and breadths, set at varying angles, and borne horizontally at different velocities. At times he substituted stuffed birds for the metal planes, on the action of which under air pressure his scientific deductions were based. In 1891 he published the results of his experiments. These proved--in opposition to the teaching of some very distinguished scientists--that the force required to sustain inclined planes in horizontal locomotion through the air diminishes with increased velocity (at least within the limits of the experiment). Here a marked contrast is shown between aerial locomotion on the one hand, and land and water locomotion on the other; "whereas in land or marine transport increased speed is maintained only by a disproportionate expenditure of power, within the limits of experiment in such _aerial horizontal transport, the higher speeds are more economical of power than the lower ones_." Again, the experiments demonstrated that the force necessary to maintain at high velocity an apparatus consisting of planes and motors could be produced by means already available. It was found, for example, that one horse-power rightly applied is sufficient to maintain a plane of two hundred pounds in horizontal flight at a rate of about forty-five miles an hour. Langley had in fact furnished experimental proof that the aerial locomotion of bodies many times heavier than air was possible. He reserved for further experimentation the question of aerodromics, the form, ascent, maintenance in horizontal position, and descent of an aerodrome (ἀεροδρόμος, traversing the air), as he called the prospective flying machine. He believed, however, that the time had come for seriously considering these things, and intelligent physicists, who before the publication of Langley's experiments had regarded all plans of aerial navigation as utopian, soon came to share his belief. According to Octave Chanute there was in Europe in 1889 utter disagreement and confusion in reference to fundamental questions of aerodynamics. He thought Langley had given firm ground to stand upon concerning air resistances and reactions, and that the beginning of the solution of the problem of aerial navigation would date from the American scientist's experiments in aerodynamics.