MIRROR, a reflecting surface, usually made of glass, lined at the back with a brilliant metal, so as strongly to reflect the image of any object placed before it. When mirrors were invented is not known, but the use of a reflecting surface would become apparent to the first person who saw his own image reflected from water; and probably for ages after the civilization of man commenced, the still waters of ponds and lakes were the only mirrors; but we read in the Pentateuch of mirrors of brass being used by the Hebrews. Mirrors of bronze were in very common use among the ancient Egyptians, Greeks, and Romans, of which many specimens are preserved in museuras. Praxit cies taught the use of silver in the manufacture of mirrors in the year 328 B.C. Mirrors of glass were first made at Venice in 1300; and judging from those still in existence—of which one may be seen at Holyrood palace, in the apartments of queen Mary—they very rude contrivances, compared with modern ones. It was not until 1673 that the making of mirrors was introduced into England. It is now a very, important manufac ture; and mirrors can be produced:of any size to which plate can be cast. After the plate of glass is polished on both sides, it is laid on a perfectly level table of great strength and solidity, usually of smooth stone, made like a billiard Mile, with raised edges; a sheet or sheets of tin foil sufficient to cover the upper surface of the glass are then put on, and rubbed down smooth, after which the whole is covered with quick silver. which immediately forms an amalgam with the tin. The superfluous mercury is
then run off, and a woolen cloth is spread over the whole surface, and square iron weittlits are applied. After this pressure has been continued a day and night, the weights and the cloth are removed,and the glass is removed to another table of wood, with a movable top, which admits of gradually increasing inclination until the unamalgannited quick silver has perfectly drained away, and only the surface of perfect amalgam aemains coat ing the glass, and perfectly adherent to it.
Heat is reflected like light; so that a concave mirror maybe used to bring rays of heat to a focus. In this way combustible substances may be set on fire at a distance from the reflector whence they receive their heat. Thus used, a mirror is called a burning-mir ror.