PYROMETER (Gr. iri p,

See also:

• FIRE (in O. Eng. f j'r; the word is common to West German languages, cf. Dutch vuur, Ger. Feuer; the pre-Teutonic form is seen in Sanskrit pu, pavaka, and Gr. irup; the ultimate origin is usually taken to be a root meaning to purify, cf. Lat. purus)

fire, µErpov, a measure)  , an instrument for measuring high temperatures . The term was first used by Musschenbroek to denote an instrument wherein the expansion of a metal rod measured the temperature . Discontinuous thermoscopes, depending on the fusion of a metal or salt, are also employed . Prinsep prepared a series of alloys of silver and gold, and of gold and platinum, whose melting points, as determined by accurate instruments, covered a range of temperature from 954 to 1775°, at intervals of from 25° to 3o° . By placing ingots in a furnace and observing which one melted a fair idea of the temperature was obtained . Carnelley and Williams employed certain salts of known melting point; whilst the Seger's cones, employed in porcelain manufacture, depend on the fusion of small cones made of clay .