A white oxide (21) prepared from zinc, was, some years ago, proposed as a substitute for white lead in house painting. This oxide is not dangerous in its application; and does not become yellow when mixed with oil. But these advantages are counterbalanced by some defects, which have hitherto caused it to be rejected. It is lighter than white lead: does not cover the surface so equally, nor so well; and is of considerably higher price. CALAMINE.—The principal use of calamine is in the manufacture of brass (230); and the mines of Derbyshire, and of Limbourg in the Netherlands, supply with this mineral nearly all the brass works in Europe. After the calamine is dug out of ground, it is reduced to pieces not in general larger than a nut. It is then roasted for five or six hours, in what is called a reverberating furnace. The large pieces are separated, and the small ones are passed through a sieve. It is washed; and, when dry, is ground in a mill. In this state it is sold. The principal demand for it is at Birmingham, for the different brass founderies in that town. The use of calamine in the composition of brass was known at a very early period. It is mentioned by Aristotle, who also makes a distinction between the compound resulting from the mixture of copper and calamine or brass, and that resulting from the mixture of copper and tin or bronze. ──────────────────────────────────────────────────────────────────────── ORDER II.—BRITTLE METALS, OR SUCH AS ARE NOT CAPABLE OF BEING FLATTENED OR ELONGATED BY THE HAMMER WITHOUT TEARING OR BREAKING. 242. ARSENIC, _in a metallic state, has a bluish white colour, and considerable brilliancy; it is remarkably brittle, is the softest of all known metals, and is somewhat more than eight times heavier than water._ _It is found nearly pure, and in considerable abundance, in different parts of Germany; usually occurring in masses of various shapes, and in combination with a small portion of iron, gold, or silver._ _The arsenic sold in the shops, and too well known for its poisonous qualities, is an oxide (21) of this metal artificially prepared._ In some mines on the Continent arsenic is very abundant, and is found extremely injurious to the workmen. Being very volatile, its fumes affect and destroy the lungs, and occasion death in a short time to many of them. One of its ores, _arsenical pyrites_, is found abundantly in Cornwall and Devonshire, accompanying ores of copper and tin; and, in combination with other metals, it occurs, in a greater or less proportion, in almost all mines.