NOME XXI. BITUMINOUS ROCKS. The chief bituminous substances are naphtha, or pure rock oil, as fluid and transparent as water; petrol, which is less fluid and pure, when it is yet more impure it becomes mineral tar. Of mineral pitch there are three diversities: Maltha, of a brownish colour and earthy construction; Asphalt, pure and black; and the elastic, or mineral Caoutchou. All the bitumens belong more strictly to the province of chemists, who now arrange them after the vegetable substances, from which, like coal, they all seem to be derived. They are most commonly found in the proxi- Gangarts. mity of that mineral, and in its most usual attendant rocks, limestone and sandstone. In Siberia, bitumen has even been observed in balls of chalcedony. It sometimes also appears in veins, that traverse that argillaceous glutenite called grauwack; and in veins of calcareous spar in basalton, or the transitive grunstein of Werner. The asphalt occurs in mineral veins, like the caoutchou. The chief bituminous rocks, however, are limestone and sandstone; the for L2 Naptha of mer being generally black, as at Sefeld, in Tyrol. The grandest appearance of that nature is at Baku, on the western side of the Caspian Sea; whence it is supposed that this substance was brought to Constantinople, where it formed the chief ingredient of the noted composition called the Grecian fire; which, burning with increased intensity under water, became a most formidable instrument against an inimical fleet. From the description given by Hanway, it would appear that the rock is limestone. His account of this singular phenomenon deserves to be here repeated. "The earth round this place, for above two miles, has this surprising property, that, by taking up two or three inches of the surface, and applying a live coal, the part which is so uncovered immediately takes fire, almost before the coal touches the earth: the flame makes the soil hot, but does not consume it, nor affect what is near it with any degree of heat. Any quantity of this earth carried to another place, does not produce this effect. Not long since, eight horses were consumed by this fire, being under a roof where the surface of the ground was turned up, and by some accident took flame. "If a cane or tube, even of paper, be set about two inches in the ground, confined and close with the earth below, and the top of it touched with a live coal, and blown upon, immediately a flame issues, without hurting either the cane or paper, provided the edges be covered with clay; and this method they use for light in their houses, which have only the earth for the floor: three or four of these lighted canes will boil water in a pot, and thus they dress their victuals. The flame may be extinguished in the same manner as that of spirits of wine. The ground is dry and stony; and the more stony any particular part is, the stronger and clearer is the flame; it smells sulphureous, like naptha, but not very offensive. "Lime is burnt to great perfection by means of this phenomenon; the flame communicating itself to any distance, where the earth is uncovered to receive it. The stones must be laid on one another, and in three days the lime is completed. Near this place brimstone is dug, and naptha springs are found. "The chief place for the black or dark grey naptha, is the small island Wetoy, now uninhabited, except at such times as they take naptha from thence. The Persians load it in bulk in their wretched vessels, so that sometimes the sea is covered with it for leagues together. When the weather is thick and hazy, the springs boil up the higher; and the naptha often takes fire on the surface of the earth, and runs in a flame into the sea in great quantities, to a distance almost incredible. In clear weather the springs do not boil up above two or three feet; in boiling over, this oily substance makes so strong a consistency, as by degrees almost to close the mouth of the spring; sometimes it is quite closed, and forms hillocks that look as black as pitch; but the spring which is resisted in one place, breaks out in another. Some of the springs, which have not been long opened, form a mouth of 18 or 10 feet diameter. "The people carry the maptha, by troughs, into pits or reservoirs; drawing it off from one to another, leaving in the first reservoir the water, or the heavier part with which it is mixed when it issues from the spring. It is unpleasant to the smell, and used mostly amongst the poorer sort of the Persians, and other neighbouring people, as we use oil in lamps, or to boil their victuals; but it communicates a disagreeable taste. They find it burn best with a small mixture of ashes: as they find it in great abundance, every family is well supplied. They keep it at a small distance from their houses, in earthen vessels, under ground, to prevent any accident by fire, of which it is extremely susceptible. "There is also a white naptha on the peninsula of Apcheron, of a much thinner consistency; but this is found only in small quantities. The Russians drink it both as a cordial and a medicine, but it does not intoxicate: if taken internally, it is said to be good for the stone, as also for disorders of the breast, and in venereal cases, and sore heads; to both the last the Persians are very subject. Externally applied, it is of great use in scorbutic pains, gouts, cramps, &c.; but it must be put to the part affected only; it penetrates instantaneously into the blood, and is apt for a short time to create great pain. It has also the property of spirits of wine, to take out greasy spots in silks or woollens; but the remedy is worse than the disease, for it leaves an abominable odour. They say it is carried into India as a great rarity; and, being prepared as a japan, is the most beautiful and lasting of any that has yet been found. Not far from hence are also springs of hot water, which boil up in the same manner as the naptha, and very thick, being impregnated with a blue clay; but it soon clarifies. Bathing in this warm water is found to strengthen and procure a good |