Page:Various Forces of Matter.djvu/25

Rh oscillates to and fro—that pendulum bob as it is sometimes called. Observe, if I hold the straight stick horizontally, as high as the position of the balls at the two ends of its journey, you see that the ball is in a higher position at the two extremities than it is when in the middle. Starting from one end of the stick, the ball falls towards the centre, and then rising again to the opposite end, it constantly tries to fall to the lowest point, swinging and vibrating most beautifully, and with wonderful properties in other respects—the time of its vibration and so on—but concerning which we will not now trouble ourselves.

If a gold leaf, or piece of thread, or any other substance, were hung where this ball is,