covering to the surface of bodies are various. There are several varieties of this ore among them, Native or Virgin Silver, which has a rich metallic lustre, resembling tin. Ruby Silver, so denominated from its red colour, is the most beautiful of the ores of this metal. Horn Silver, so called from its resemblance to that substance, and consequently very unlike the metallic appearance of the former kinds, is generally sufficiently soft to be indented by the nail.

SUGAR.

A sweet substance obtained from the juice extracted from a cane; or, according to chemists, an essential salt capable of crystallization, of a sweet and agreeable flavour, and contained in almost every species of vegetable, but most abundantly in the Sugar Cane. Next to the cane the American Maple (57) yields Sugar the most prolifically. The juice is obtained from the tree by tapping, and this being collected is boiled and converted into Sugar. Sugar has also been obtained in Germany from beet root, and in France from grapes. Potatoes, wheat, barley, &c. contain this saccharine quality, indeed scarcely any vegetable is destitute of it. The Sugar Cane is the principal production of the West Indies, and the chief article of commerce. It is a jointed

P

reed, generally growing to the height of 7 or 9 feet, and sometimes rising to 12 feet; when ripe it is of a yellow straw colour producing leaves. The joints on one stalk are 40 or 50 in number, and each root has numerous stalks. It requires a rich soil, and that of St. Christopher and Jamaica appears to suit it best. The autumnal months are the season for planting it, and it is propagated by the shoots which are cut from the tops of the old canes. The upland plantations suffer greatly from monkeys, and the lowlands from rats, and both are likewise subject to a disease called the blast, occasioned by a small insect. The crops do not ripen precisely at stated periods. The canes are cut about a yard in length, tied in bundles, and carried to the mill, where they are bruised and the juice extracted from them, which after being duly prepared is sent to Europe, and subsequently refined. After this purification it is called Lump or Loaf Sugar, it being usually made in moulds of a conical form. The art of refining Sugar was introduced to the Europeans by a Venetian about 1659. The tops of the canes when cut are given to the cattle for food, and the upper shoots are reserved for planting. It is supposed to be the sweet cane mentioned in Jeremiah, and seems to have been early known to the Indians and Chinese, but was not used in Europe until after the discovery of America. In a pure form Sugar is one of the

most nutritive substances derived from the vegetable kingdom, and being antiseptic a great number of organic substances are preserved from decay by its use (58).

SULPHUR, OR BRIMSTONE.

An inflammable substance, found in the neighbourhood of volcanoes, combined with earths and metals, from which it is separated by sublimation in furnaces. It is insoluble in water, almost devoid of smell, except when heated or by friction, of a yellow colour, and faint taste. It is found native in many parts of the world, and is usually imported in irregular masses, which are melted into rolls, with the addition of coarse resin, flour, &c. Sulphur is of great utility in the arts, and is much used in bleaching, dissolving metals, particularly iron, &c. under the name of Sulphuric Acid or Oil of Vitriol, which liquid is obtained from Sulphur converted into an acid by combustion in the open air, during which process silk, wool, &c. become whitened by being exposed to the fumes. By other processes are obtained what are called Flowers and Liver of Sulphur. Sulphur is used medicinally.

SPERMACETI.

A flaky, white, unctuous substance, glossy, and semi-transparent; in taste something like butter,

and in scent rather resembling tallow. It is sometimes prepared from oil, but chiefly from the brain of a species of whale, called Physeter Macrocephalus, purified from the oily matter; and our best oil is obtained from the blubber of the same fish. Spermaceti is employed in the making a superior kind of candle, also medicinally. It is indissoluble with caustic alkalies, and cannot consequently be employed in the formation of soaps, like other oily matters. It is quite soluble in oils, and in a liquid state unites with wax and resins.

SALT.

Soda, combined with muriatic acid, forms Salt, of which there are several descriptions. Sea Salt is an artificial preparation, extracted from the waters of the great ocean. The manufacturing it is carried on in buildings near the sea, called Salterns, and is very simple. Water is drawn off from a cistern where it had been previously left for the sand and mud to settle, and placed in a heated furnace. It is then clarified either with whites of eggs or blood. After being skimmed with thin ash boards, clear sea water is added, and this is repeated three or four times, when the crystals begin to form, and, adhering to each other, sink to the bottom; they are then raked to the sides, when the greater part of the liquor is evaporated and left to drain

from the brine, after which it is put into store-houses to dry, and in a few days is ready for sale. The saline liquor which drains from the Salt is called bittern, from its sharp and bitter taste. There is a fine white calcareous earth, found in a powdered form, which separates from the sea water during its coction, which is called powder scratch; and a similar substance adheres to the bottom and sides of the pan, which is termed stone scratch. This is frequently removed, or it would soon destroy the pan. The process of preparing Salt is generally performed in twenty-four hours. Salt is in very great request, being used for correcting the insipidity of food, and for preserving organic substances from corruption. Salted meats and fish, however, are unwholesome, if eaten frequently; but Salt is considered to assist digestion, if not taken too plentifully. Rock Salt is clear and transparent, or coloured red and brown, rarely blue; it is situated in basins of gritstone, though it is considered to belong to the Gypsum formation; it is surrounded in this country by sandstone, indurated clay, and marl, always attended by Gypsum, and sometimes by thin beds of limestone. It forms a considerable article of commerce. Salt is made from brine springs in some parts of England; and in Northwich there is a mine, which, from the peculiar arrangement of the Salt, presents a most singular spectacle, appearing