Crystal
A term applied to the glass of a watch case. Crystals for watches were first used between the years 1615 and 1620.
CUMMING, ALEXANDER. A celebrated clockmaker of England, who was born about 1732 and died at Pentonville in 1814. He was the author of a book called "Elements of Clock and Watch Work," which he published in 1766. There stands in Buckingham Palace to day a clock made by Cumming for George III., which registers the height of the barometer every day throughout the year. He was paid $10,000 for this clock, and received $1,000 per annum for looking after it.