An instrument for illustrating the nature of the centripetal and centrifugal forces. The disposition which bodies have to fly off from the axis round which they revolve, may be beautifully exhibited, by employing a small bucket filled with water, and attaching it to the hand by a flexible cord, it may be whirled round without destroying the equilibrium of the fluid, or causing any portion of it to be spilled. Precisely in the same way are the bodies which revolve round the sun, kept from falling into that luminary by the centrifugal force which is generated. Now the whirling-table is employed to exhibit the amount of this force, and, by a combination of weights and pulleys, a variety of bodies are made to revolve with different degrees of speed. The apparatus usually consists of a frame furnished with a large wheel, round which a band passes, and gives motion to two smaller ones. On one of these a rod is attached for balls to slide, and on the other a flat table of mahogany; and these may be put into motion with different degrees of speed.

The whole apparatus is exceedingly valuable to the teacher of astronomy.