This oil is principally used as a vehicle for mixing the ingredients of some kinds of fire-works; and, although it is employed in that way, yet it has also an effect in combustion, having similar properties with liquid bitumen. It enters into the composition of some of the preparations, and perhaps is equally good as liquid bitumen. Indeed, the oil of spike, as sold in the shops, and used principally by farriers as an embrocation for horses, is an artificial preparation, made by mixing together about five ounces of Barbadoes tar, with a pint of the spirit of turpentine. _Sec. XIV. Of Amber._ Amber, succinum, karabe, the electron of the ancients, which are synonimous terms, is very inflammable. A piece of it, put on the point of a knife, and set on fire, will burn entirely away, emitting, at the same time, a white smoke, and a somewhat agreeable odour. It is used in the composition of fire-works, and particularly in some kinds of rockets. All the preparation it undergoes, when thus used, is to reduce it to powder in a mortar, and to pass it through a fine sieve. It also forms a part of the composition of odoriferous fire; but the formulæ for the latter are various. Amber is of various colours, either yellowish, white, or honey-yellow. It is translucent, and sometimes transparent. It may be turned or polished. It occurs in grains or in irregular masses. Alluvial deposites of sand, gravel, &c. frequently contain it. It is also found with bituminous wood, brittle lignite, or jet, and with other substances. It has been discovered in New-Jersey, near Trenton, in alluvial soil. Naturalists believe, that amber was once a resinous juice. Masses weighing 20 lbs. have been found. Sometimes it contains insects. It is formed into beads and the like. As amber becomes electric by friction, and the ancients called it electron, the term electricity is derived from it. By distillation, it yields both an acid, (the succinic), and an oil. Jet is usually considered black amber. We may introduce here a few remarks respecting ambergris: Ambergris is a substance, which has a peculiar fragrance, and for that reason is used as a perfume, and may be employed like similar substances in odoriferous fire. As to its origin, we have no certain account; but it seems, from its general properties, to be formed in the same manner as bituminous substances, although it is mostly found on the sea-shore, where it has been probably washed up from the sea. Ambergris is found principally on the shores of Ceylon, and is known to be good, by laying some of it on a very hot knife, when, if pure, it will not only melt and run like wax, but entirely evaporate, leaving no residue. Ambergris, on account of its price, (the retail price in London being a guinea per ounce), is frequently adulterated with various mixtures of benzoin, labdanum, meal, &c. scented with musk. But pure ambergris, when heated, has a greasy feel, and appearance, and is soluble in hot ether and alcohol.