Democratic Sentinel, Volume 9, Number 20, Rensselaer, Jasper County, 12 June 1885 — Foucault’s Experiment. [ARTICLE]

Foucault’s Experiment.

This famous experiment was made by M. Foucault, a French scientist, to visibly demonstrate the rotation of the earth on its axis, as follows: One end of a fine steel wire was firmly fastened to the under surface of a high ceiling; on the lower end of the wire a heavy copper ball was hung, which carried below it a steel pointer. This pendulum swung over a place so hollowed out that the pointer would move just over its surface; about the edge of the hollow was laid a ridge of fine sand, which the pointer would pass through at every vibration. In order that the pendulum might not he moved by any other impulse than the simple attraction of the earth, it was drawn aside from its vertical position and tied by a thread; and when it was perfectly still the thread was burned off, and the ball began to oscillate. As the po nter passed through the ridges of sand it was seen that at each vibration it crossed a little to the right, looking from the center of the place where it crossed before. Now, the theory of the experiment is this: When the pendulum begins to swing, drawn by tho earth’s attraction only, it must necessarily move in a plane containing three points—the point of suspension, the point from which it started, and the center of the earth. It can not of itself leave this plane of vibration, and there is no force without to cause it to turn aside; it must,, therefore, go on therein, to the end of the vibration. The next vibration begins in tbe same plane and ends in it, and so with each subsequent vibration. The point to which the pendulum is suspended has, of course, the motion of the earth at the place where the experiment is performed; but as the wire is fastened so that no rotary or twisting motion can be imparted to it, the forward motion of the point of suspension only carries the plane of vibration forward without twisting it to the right or left. The ball, therefore, does not move toward the right; its apparent motion makes visible the actual motion of the earth beneath it toward the left; that is, toward the east. Theoretically, as the pendulum is moved by the attraction of the earth only, a persistent force, its vibration would be perpetual. But, practically, the friction of the atmosphere retards and after a time overcomes its motion. This experiment has been performed in the Pantheon at Paris, in the Bunker Hill monument near Boston, and in the Exposition Building at' Chicago, and at several other important places in this country and Europe. —lnter Ocean.