THE GYROSCOPE.
This instrument illustrates the law, that the axis of rotation is preserved, in any fixed direction, immovable, while the particles surrounding it are in rapid rotary motion. Hence the humming and the peg-top stand erect, the axis of rotation—the spike or the peg—being kept in a vertical position while in motion; it falls as soon as this motion sinks below a certain rate. This power may be illustrated by placing a disc of wood, or of metal, upon one end of a weighing beam, from which one of the scales has been removed. The disc being equipoised by weights in the opposite scale, place the beam at an angle of 45—the disc being the lowest end—then, by striking the disc, get it into rapid rotation. It will be found that, while spinning, the beam is preserved rigidly in its position; but, as the disc comes to rest, the beam is restored to its horizontal position. Several small weights may be placed in the scale, while the disc is rotating, without disturbing the position of the beam.
