; Naphtha: the arilli coalited and monospermous. There are two species; both of them with perennial roots, composed of many thick fleshy fibres, which strike deep into the ground, and are connected at the top into large heads; the stalks grow to seven or eight feet high, producing white flowers, tubulous at bottom, but spreading open at top, and dividing into five obtuse segments. Both these plants are natives of Virginia and other parts of North America: from the bark of some of the Indian kinds a sort of fine hemp might be procured, capable of being woven into very strong cloth. They are easily propagated by seed, which will thrive in any situation.an inflammable substance of the bituminous kind, of a light brown colour, and incapable of decomposition, though frequently adulterated with heterogeneous mixtures. By long keeping it hardens in the air into a substance resembling a vegetable resin; and in this state it is always of a black colour, whether pure or mixed with other bodies. According to Mongez, there are three kinds of naphtha, the white, reddish, and green or deep-coloured; and it is in fact a true petrol or rock oil, of which the lightest and most inflammable is called naphtha. It is said to be of an extremely fragrant and agreeable smell, though very different in this respect from vegetable oils. It is also transparent, extremely inflammable, dissolves resins and balsams, but not gum-resins nor elastic gums. It dissolves in the essential oils of thyme and lavender, but is insoluble in spirit of wine and ether. It burns with a bluish flame, and is as inflammable as ether; like which it also attracts gold from aqua-regia.

Naphtha, according to Cronstedt, is collected from the surface of some wells in Persia; but Mr Kirwan informs us, that it issues out of white, yellow, or black clays, in Persia and Media. The finest is brought from a peninsula in the Caspian Sea, called by Kempfer okhira. It issues out through the earth into cisterns and wells, purposely excavated for collecting it at Baku in Persia. Different kinds of this substance are also found in Italy, in the duchy of Modena, and in Mount Ciaro, 12 leagues from Plaisance.

The formation of naphtha and petroleum is by most naturalists and chemists ascribed to the decomposition of solid bitumens by the action of subterranean fires; naphtha being the lightest oil, which the fire disengages first; what follows gradually acquiring the colour and consistence of petrol. Lastly, the petrolea, united with some earthy substances, or altered by acids, assume the appearance of mineral pitch, pila-phaltum, &c. This opinion seems to be supported by the phenomena attending the distillation of amber; where the first liquor that rises is a true naphtha; then a petroleum of a more or less brown colour; and lastly, a black substance like jet, which being farther urged by the fire, leaves a dry friable matter, &c. It is further observed, that nature frequently produces all the different kinds of petrolea near the same spot; of which we have an instance at Mount Testin in the duchy of Modena in Italy. Some, however, are of opinion, that these mineral oils or bitumens are formed from the vitriolic acid, and various oily and fat substances found in the bowels of the earth.