witch ball, a hollow glass sphere, sometimes as large as 7 inches (18 cm) in diameter. Witch balls are made in several colours, among which green and blue predominate. Its name is possibly a corruption of the 18th-century term watch ball.

References to witch balls are found from the 18th century onward, but their origin is probably older. In England many examples, striped and spattered with enamel colours, have been attributed to the Nailsea works near Bristol; but they were also made elsewhere in England and, from the 19th century, in the United States. Having some kinship with the glass balls used by fishermen to float their nets, witch balls have been associated with sea superstitions; it has also been suggested that they were originally hung in windows to ward off misfortune. It seems likely, however, that those that are silvered inside, made from the mid-19th century onward, were hung up for their reflective qualities; they could reflect a whole room in the manner of a convex mirror. They are sought after as curios, and modern examples are still made.