Rolling ball clock in a glass case on a wooden foot in a chrome/silver finish. Bought as vintage reproduction – most are made of brass. The clock stands on a wooden base and is enclosed within a glass case with open door. This clock has a fascination for mechanically minded people. The Congreve clock is a clock type that instead of a pendulum uses a ball that rolls along a zigzag trail to drive the timekeeping. Based on the original work by Sir William Congreve from 1808. The ball needs between 15 seconds and a full minute to complete the zigzag track, after which it stumbles over the escapement which in turn reverses the tilting direction of the zigzag plate while at the same time causing the hands of the clock to move forward. Thus the angle of the plate is flipped and the hands move forward one to four times a minute. The original work can be admired in the British Museum. This clock is in excellent condition, although the accuracy of every Congreve clock depends on many factors, including standing fully level, and so the ball and track being clean as well as temperature and humidity levels all have clear influences on its workings. The clock needs to be adjusted before it can run.