(From the Hebrew term metil, a hard substance). Metals, or metallic substances, are distinguished by their splendour, their opacity, their fusibility, specific gravity, conducting power, hardness, elasticity, malleability, ductility, tenacity, and com-bustibilitv. From their hardness and elasticity."hey are adapted for the construction of different instruments en.ployed by surgeons; and these properties lit them for discovering solid bodies by the vibrations they convey to the hand, as a stone in the bladder, or a bullet under the muscles. Their splendour is connected with their opacity, for all metals are impervious to light; and the green rays, which seem to pass through the thinnest gold leaf, are seemingly owing to light transmitted through an accidental fracture.

All metals are fusible; and mercury even retains its fluidity in our greatest colds. The specific gravity of the lightest metal, arsenic, is more than five times greater than water, and much more considerable than the densest stone, which is not suspected to be metallic. The metals arc the best conductors of electricity, and it has been supposed that the electrical fluid is conveyed through our system more readily by the small proportion of iron which the blood contains. This is, however, improbable, as the electrical shock follows more closely the course of the nerves than of the arteries.

Metallic substances are also called perfect or imperfect. The first arc not permanently altered by the greatest heat of our furnaces; while the second, when exposed to a strong heat, with the access of free air, are changed by a process similar to burning, and in some instances with an actual flame, into an earthy substance called calx, which is heavier than the metal from which it was produced, though its specific gravity is less. This arises from the union of vital air, which converts some metals into acids. If the calx of a metal be exposed to a strong heat in a closed vessel, with some inflammable matter, styled a flux, it recovers its metallic state. This is called reduction, or reviving of the metal.

All metals are imperfect, except gold, silver, and platina. The imperfect metals are, mercury, lead, copper, iron, tin; and the semimetals, bismuth,nickel, arsenic, cobalt, zinc, antimony, manganese, molybdae-na, tellurium, titanium, chronium, columbium, osmium, iridium, and uranite, with some others whose nature is not yet accurately ascertained. As the appellations arsenic, antimony, manganese, wolfram, and mo-iybda^na, are given to the ores, the term of regulus is often employed to distinguish the metal, though modern chemists often use the terms indiscriminately.

The heaviest metal is gold, then follow platina, mercury, lead, silver, copper, iron, and tin. The most malleable also is gold, followed by silver, copper, tin, iron, lead, platina, zinc, bismuth, antimony. The force of cohesion is greatest 'in gold, next in iron, silver, brass, and copper, successively: tin is far below copper, and lead still less cohesive. The order of fusibility is the following, tin, bismuth, lead, zinc, antimony, silver, copper, cobalt, nickel, gold, iron,manganese, and platina. Different proportions of tin and lead are still more fusible; and, if bismuth be added, this property is increased. Five parts of tin, three of bismuth, and two of lead, become soft in boiling water. This last property renders such metallic mixtures highly useful as injections for anatomical preparations.

All the metals dissolve in acids. See Affinity; and in these solutions the metal is in a state of calx. - Neumann, Chaptal, Fourcroy, and Thompson's Chemistry.