The Probert Encyclopaedia of Science & Technology

BALL-COCK

A ball-cock is a kind of self-acting stop-cock opened and shut by means of a hollow sphere or ball of metal or plastic attached to the end of a lever connected with the cock. Such cocks are often employed to regulate the supply of water to cisterns. The ball floats on the water in the cistern by its buoyancy, and rises and sinks as the water rises and sinks, shutting off the water in the one case and letting it on in the other.
Research Ball-cock