The experiments which I have devised and here describe, are made with one specific object, namely, to elucidate the dynamic principles lying at the basis of the aerial mechanical flight of bodies denser than the air in which they move, and I have refrained as a rule from all collateral investigations, however important, not contributing to this end. These experiments, then, are in no way concerned with ordinary aeronautics, or the use of balloons, or objects lighter than the air, but solely with the mechanical sustentation of bodies denser than the air, and the reader will please note that only the latter are referred to throughout this memoir when such expressions as planes, models, mechanical flight, and the like, are used.

The experiments in question, for obtaining first approximations to the power and velocities needed to sustain in the air such heavy inclined planes or other models in rapid movement, have been principally made with a very large whirling table, located on the grounds of the Allegheny Observatory, Allegheny, Pa. (lat. 40 27 ? 41.6 ?; long. 5 ^h 20 ^m 2.93 ^s; height above the sea-level, 1,145 feet).

The site is a hill on the north of the valley of the Ohio and rising about 400 feet above it. At the time of these observations the hill-top was bare of trees and of buildings, except those of the observatory itself. This hill-top is a plane of about three acres, of which the observatory occupies...