Silver plated table clock with plate and ball. A very nice reproduction of the Congreve Roller Ball - made in China. Instead of a pendulum, the movement is made by a ball that moves back and forth along a plate, the "rolling ball". The ball moves 12 seconds forward and 12 seconds back. A superb clock and a real collector's item.Wooden base 30 cm x 27 cm. Total height 40 cm. The running ball clock was patented by Sir William Congreve in 1808. The basic concept is that the ball slides between 12 and 30 seconds to travel the zigzag track, which causes the escapement to move. This reverses the angle of the plate and the hands move forward accordingly. The mechanism is mounted on a wooden console with three adjustable spherical feet. Ideally, the ball should always have the same running time on the track, but this is not the case. Friction, dust, will prevent the ball from rolling and slow it down. In addition, the metal expands or contracts with changes in temperature, which changes the length of the path and the size of the ball. Adjusting the accuracy, which will be relative, is done by changing the angle of inclination of the plate. Therefore, the clock will never run exactly on time. The watch is accompanied by a winding key.