22 MERCURY. Uses. This metal is used in lhe construction of barometers and thermometers ; also for collecting gases absorbable in water; and its property of amalgamating, enables th^ metallurgist to extract, at a small expence, minute por tions of gold and silver from poor ores *. When amal gamated with tin, it is used for silvering mirrors : amal gams of gold and silver are employed for plating other metals -(•; and the amalgam of mercury and bismuth is used for the rubbers of electrical machines. In the oxi dated and saline states, it acts as a powerful medicine. Observations. 1. The greater part of the mercury of commerce is obtained by distilling native cinnabar, not from native mercury, which occurs but in small quantity. 2. When rendered solid by artificial freezing mixtures, it is found to be malleable, and to crystallise in octahe drons. 3. The fracture of congealed mercury is hackly. 1 2. Native. * The amalgamation of gold and silver appears to have been known to the ancients—Vid. Plin. Hist. Nat. xxiiii.; Vitruv. viii. 8. f The process of gilding is mentioned by Piiny.—Vid. Plin. I. c. cd. Bit). p. 101.