From its always remaining fluid in the temperate climates of the earth, it was, however, not considered as a true metal; for the ancients had no means of ascertaining that at the low temperature of -39° Fahr., it becomes malleable and assumes the solid form. The Greeks called it Hydrargyros or _water-silver_, from its fluidity and argentine colour; the Romans, ‘argentum vivum,’ or live silver, from which our ‘quicksilver’ has been derived, and in the Middle Ages the alchemists gave it the planetary name of Mercury, which has been generally adopted in modern scientific language. At a very early age cinnabar (sulphide of mercury), the beautiful scarlet ore from which it is chiefly obtained, was employed by the ancients as a colouring material for imparting a florid complexion to triumphant generals or to guests at the festive board. The extent to which this cosmetic was used may be inferred from the facts mentioned by Pliny, that the Greeks imported red cinnabar from Almaden 700 years before the Christian era, and that Rome in his time received 700,000 pounds from the same mines. As the alchemists considered quicksilver as the fittest substance for transmutation into gold, it became the subject of innumerable experiments; and though these manipulations had not the desired effect, they accidentally led to the discovery of several of its combinations, which soon became known as powerful medicines. But it was reserved for modern times to appreciate and understand the full importance of mercury, and to extend the field of its utility to a variety of uses unknown to former ages. Alloyed with tin-foil, it forms the reflecting surface of looking- glasses; and by its ready solution of gold and silver, and subsequent dissipation by a moderate heat, it becomes the great instrument of the arts of gilding and silvering copper and brass. The same property makes it available in extracting these precious metals from their ores. To science it is a substance of paramount value. Its great density, and its regular rate of extension and contraction by increase and diminution of temperature, give it the preference over all liquids for filling barometer and thermometer tubes, so that without mercury we should know but little indeed about the laws of caloric and of atmospherical pressure. In chemistry it furnishes the only means of collecting and manipulating, in the pneumatic trough, such gaseous bodies as are condensible over water. To its aid, in this respect, the modern advancement of chemical discovery is pre-eminently due, and without its assistance many a branch of industry which now greatly adds to the wealth of the nation could never have existed.