remains perfectly sound.—Shagreen is employed principally in the manufacture of cases for mathematical instruments, watches, &c. though it is sometimes used for covering books.
SHALE is a black, slaty substance, or a species of clay concreted into a stony consistence, and impregnated with a considerable quantity of bituminous matter. It is of various degrees of hardness, but does not emit sparks when stricken against steel; and, on being heated, it exhales a strong smell.
Large strata of this mineral are dug out in Derbyshire, as well as in those counties which contain fossil coal. On calcination, an acid is evolved, that combines with the argillaceous particles, and forms Alum. The shale is next immersed in water, in consequence of which, the alum thus obtained is dissolved; and, after undergoing various processes, is formed into the masses usually met with in the shops.—It is computed by Doctor Watson (Chemical Essays, vol. ii.) that 120 tons of the calcined shale will produce one ton of alum.
Shallot. See Eschallot.
SHARK, or Squalus, L. genus of fish, comprehending 32 species, of which the following are the most remarkable:
1. The Canicula, Spotted Shark, or Dog-fish, inhabits almost every sea, and grows to the length of 4 feet: it attains a considerable age, is extremely voracious, and chiefly subsists on fishes. The skin of this species is beautifully spotted, like that of a leopard; when stripped off, it is manufactured into Shagreen, and is likewise employed in a dry state, for polishing wood, and for other purposes.
2. The maximus, Basking Shark, or Sun-fish, abounds in the Irish Channel, and on the Western Coast of Scotland. It is of a prodigious size, measuring sometimes 27 feet and upwards in length: it has been observed to derive great pleasure from basking on the surface of the ocean, during the heat of the day. Its liver is valuable, on account of the great quantity of oil which it contains: those of the larger kind yielding, upon an average, eight barrels each. The catching of the basking shark, and melting down its liver, afford employment to many industrious families:—the oil thus procured, is not only pure, sweet, and fit for lamps, but is also much used externally for relieving bruises, burns, and rheumatic pains.
3. The Carcharias, Great White Shark, or Requin, is the most formidable and destructive enemy of the mariner. It sometimes infests the British seas, but generally those of hot climates, where it grows to the length of 30 feet, and weighs from 3 to 4000 lbs. According to Funke, however, its weight occasionally amounts to 10,000 lbs. and the fish measures ten feet in circumference. An entire horse has been found in the stomach of this monster. And as it is probable, from the large teeth (glossopetræ) sometimes dug out ot the earth, that the requin, in former ages, must have been a still more bulky creature, naturalists have conjectured that such a fish, and not a whale, swallowed Jonah. The Great White Shark is particularly dangerous to swimmers, who have often lost one or more of their limbs, and not unfrequently been devoured entire. This fish is principally valued for its oil; as its flesh,
