Speculum Metal, an alloy used for the specula or mirrors of reflecting telescopes. The best is composed of 126 parts of copper and 58.9 of tin. It takes a fine polish and is not easily tarnished unless exposed to damp. Glass with a film of metallic silver deposited upon it is now taking the place of speculum metal for these mirrors. The silvered glass is equally serviceable and less costly. See TELESCOPE.
Speculum Metal,
Chambers's Encyclopaedia, Volume 9: Bound to Swansea, p. 619
Source scan(s): p. 0638