1. On the Resistance of the Air to the Motion of Fans

Extract

The design of this paper is to describe the results of some experiments on “the Resistance of the Air,” which I made under the superintendence of Professor Forbes, in the physical laboratory of the Andersonian University, Glasgow. The apparatus employed resembles somewhat that used by M. le Chevalier de Borda, whose experiments on “the Resistance of Fluids” are recorded in the “Mémoires de l'Académie Royale des Sciences.” It consists essentially of a wooden frame, which was firmly secured to the floor, and supporting a horizontal axis, at one extremity of which is fixed a wooden arm, on to which were bolted the vanes of different forms and sizes, the resistance of which it was desired to ascertain. A cylinder or barrel, about 3 inches in diameter, is fastened to the axis, whereon was wound a cord, which, being acted on by weights, gave a circular motion to the axis, and consequently to the arm, thereby carrying the vanes in the circumference of a circle of 3 feet diameter, and causing them to impinge upon the air with velocities due to the force applied.