Page:Popular Science Monthly Volume 38.djvu/791

Rh upon the subject. Gyration has nothing to do with it; centrifugal force has no application to it, except when turning corners, or otherwise changing abruptly the direction of the movement; balancing is a detriment rather than an assistance; and rapid motion alone accounts for nothing. Some other explanation is needed; this I shall now attempt to give.

Regarded mathematically as a machine for the application of force, the bicycle is a very simple affair. The weight (Figs. 6 and 7) is applied at the saddle, A, and is so great that the center of



gravity of the whole is very close to that point. A B and A are the lines of force, B marking the point where the fore wheel rests on the ground, and C where the rear one. In discussing the forces that act on the machine we need consider only these lines, all the other parts being merely for convenience or ornament. It is evident that A can not of itself tilt either backward or forward, since a vertical line from it falls between B and C. In