Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/207

Rh commercial part of arithmetic, by which the commodities are properly calculated and equalled, by computing the respective value of the different articles offered for exchange.

The proper way of ascertaining the difference of prices in barter would be, to find the price of one of the commodities, and an equivalent quantity of the other, either by practice, or by the rule of three.  BASALTES, in natural history, a hard stone of a black, grey, or sometimes greenish colour; and on account of its constituent parts, and resemblance to lava, generally classed among the volcanic productions. Its specific gravity is to that of water, as three to one. The component parts of basaltes are in the following proportion: siliceous earth 50, argillaceous 15, calcareous 8, magnesia 2, and iron 25. It is remarkable, that this fossil is disposed either in solid or jointed columns; the former consisting of five or six pillars, either of an uniform size, or conical, and generally standing close to each other perpendicularly, of different, and sometimes equal length, as if they had been arranged by a skilful artist. The Hebridic island of Staffa is entirely composed of lofty and capacious basaltic columns, the most curious arrangement of which, perhaps on the whole globe, is the celebrated Fingal's cave. In Germany, also, there are several basaltic mountains; for instance, those on the Rhine, and near Freyberg, in Saxony, where basaltes is frequently found of an oval or spherical figure. Spain, Russia, Poland, and Silesia, also produce various basaltic rocks. Great quantities of this fossil are deposited in the neighbourhood of Mount Etna, in Sicily; of Hecla, in Iceland, &c. But the largest mass yet discovered are, what is called the Giant's Causeway, in Ireland.

As naturalists differ in their opinion concerning the origin of this curious substance, whether it be the production of volcanos arising from subterraneous fires, or derive its origin from crystallization by water, we shall state only the result of M. 's inquiry into this subject, as his explanation appears to be conclusive. He asserts, that both fire and water contribute to form basaltes, and it cannot be doubted that there has been some connection between the basaltic pillars and subterraneous fire, as they are found mixed with lava, and other substances, produced by that element.

Uses.—Basaltes is an excellent material for building houses, and paving streets: it is also employed by lapidaries and statuaries for various productions of art; as well as by artists working in gold and silver, for touch or test-stones. Gold-beaters and book-binders, on the continent, make their anvils of this firm and massy stone; which is also used as an ingredient in the manufacture of glass, especially for producing the common window-glass, and green bottles.  BASILICON OINTMENT, in pharmacy, a preparation consisting of eight parts of hog's lard; five of white resin; and two of yellow wax: or, according to the London College, of nearly equal parts of yellow resin, bees wax, and olive oil.—The former ingredients, prescribed by the Edinburgh College, are cheaper and equally efficacious.

This ointment is generally 