Pendulum Autographs

Abstract

IT may interest some of your readers to know that they can for themselves observe in the most accurate manner the motion of the compound pendulum described by Mr H. Airy^* by merely attaching the ends of a fine thread to two points in the ceiling of a room, and suspending a leaden bullet by means of a second thread tied to the middle point of the former, so that the bullet may just escape the floor. Lay underneath a large sheet of white paper ruled with two dark lines at right angles to each other to correspond to the two axes of vibration. It is Mr. Airyapos;s experiment with the hoop on an extended scale. The motion of the bullet, unimpeded by contact of pencil with paper, is graceful and accurate in the extreme.