Palestine; in Persia, in the chinks of rocks, and in strata of gypsum and limestone, or floating upon water. It is found also in America, and at Colebrookdale in England. Kirwan tells us, that petroleum exposed for a long time to the air forms this substance. It is of a viscid consistence; and of a brown, black, or reddish black colour. Sometimes it is indorsus, but generally of a more or less disagreeable smell, particularly when burned. It melts easily, and burns with much smoke and foot, leaving either ashes or a flag according to the heterogeneous matter it contains. It contains a portion of the acid of amber. It gives a bitter salt with mineral alkali, more difficult of solution than common salt, and which, when treated with charcoal, does not yield any sulphur.
II. Elastic Petrol: a very singular kind of fossil met with in some parts of England. This, in colour and consistency, exactly resembles the Caoutchouc, or elastic gum-resin, commonly called Indian rubber, found in South America, and used for rubbing out the traces of black lead pencils from paper. It is of a dark brown colour, almost black; and in some pieces has a yellowish-brown cast like the same gum-resin. It can scarcely be distinguished from the caoutchouc with regard to its elastic property, excepting that the cohesion of its parts is not so great. It burns with a smoky flame, and melts likewise into a thick oily fluid; but emits a disagreeable smell like the Fossil Pitch or Barbadoes tar. "On the whole (says M. Petrole Maxellan), this fossil seems to confirm the opinion of those mineralogists who believe that these oily combustibles derive their origin from the vegetable kingdom. It seems worth trying whether pieces of asphaltum, buried in damp beds of sparry rubbish or other kinds of earth, would take the same elastic consistence." This substance was found in the year 1785 near Casterden in Derbyshire, but in very small quantities. Some of the specimens were of a cylindrical form, like bits of small branches or stalks of vegetables; tho' much more flexible, being perfectly elastic.
III. Hardened rock-oil, or fossil pitch, an inflammable substance dug out of the ground in many parts of the world, and known by the names of petroleum induratum, fix montana, indepoch, bergharz, &c. There are two species. 1. The asphaltum (b), or pure fossil pitch, found on the shores of the Dead Sea and of the Red Sea; also in Sweden, Germany, and France: See ASPHALTUM. It is a smooth, hard, brittle, indorsus substance, of a black or brown colour when looked at; but on holding it up between the eye and the light, appears of a deep red. It swims in water; breaks with a smooth and shining surface; melts easily; and, when pure, burns without leaving any ashes; but, if impure, leaves ashes, or a flag. M. Monet affirms that it contains sulphur, or at least the vitriolic acid. It is slightly and partially acted upon by spirit-of-wine.
(b) This species is found in great quantity in a bituminous lake or plain in the island of Trinidad, of which Mr. Anderson gives the following copious account in the 79th volume of the Philosophical Transactions.
"A most remarkable production of nature in the island of Trinidad, is a bituminous lake, or rather plain, known by the name of Tar Lake; by the French called La Bray, from the resemblance to, and answering the intention of, ship-pitch. It lies in the leeward side of the island, about half-way from the Bocas to the south end, where the mangrove swamps are interrupted by the sand-banks and hills; and on a point of land which extends into the sea about two miles, exactly opposite to the high mountains of Paria, on the north side of the gulf.
"This cape, or headland, is about 50 feet above the level of the sea, and is the greatest elevation of land on this side of the island. From the sea it appears a mass of black vitrified rocks; but, on a close examination, it is found a composition of bituminous scoriae, vitrified sand, and earth, cemented together: in some parts beds of cinders only are found. In approaching this cape, there is a strong sulphurous smell, sometimes disagreeable. This smell is prevalent in many parts of the ground to the distance of eight or ten miles from it.
"This point of land is about two miles broad, and on the east and west sides, from the distance of about half a mile from the sea, falls with a gentle declivity to it, and is joined to the main land on the south by the continuation of the mangrove swamps; so that the bituminous plain is on the highest part of it, and only separated from the sea by a margin of wood which surrounds it, and prevents a distant prospect of it. Its situation is similar to a savannah, and, like them, it is not seen till treading upon its verge. Its colour and even surface present at first the aspect of a lake of water; but it is possible it got the appellation of Lake when seen in the hot and dry weather, at which time its surface to the depth of an inch is liquid; and then from its cohesive quality it cannot be walked upon.
"It is of a circular form, about three miles in circumference. At my first approach it appeared a plain, as smooth as glass, excepting some small clumps of shrubs and dwarf trees that had taken possession of some spots of it; but when I had proceeded some yards on it, I found it divided into areolae of different sizes and shapes: the chaums or divisions anastomosed through every part of it; the surface of the areolae perfectly horizontal and smooth; the margins undulated, each undulation enlarged to the bottom till they join the opposite. On the surface, the margin or first undulation is distant from the opposite from four to six feet, and the same depth before they coalesce; but where the angles of the areolae oppose, the chaums or ramifications are wider and deeper. When I was at it, all these chaums were full of water, the whole forming one true horizontal plane, which rendered my investigation of it difficult and tedious, being necessitated to plunge into the water a great depth in passing from one areola to another. The truest idea that can be formed of its surface will be from the areolae and their ramifications on the back of a turtle. Its more common consistence and appearance is that of pit-coal, the colour rather greyer. It breaks into small fragments of Besides the countries above-mentioned, Brunnich informs us that the asphaltum comes from Porto Principe in the island of Cuba in the West Indies. It is likewise found, according to Fourcroy, in many parts of China; and is used for a covering to ships by Arabs and Indians. 2. The *pax montana impura* contains a great quantity of earthy matter, which is left in the retort after distillation, or upon the charcoal if burnt in the open fire. It coheres like a flag, and is of the colour of black-lead; but in a strong heat this earth is soon volatilised, so that its nature is not yet well known. During the distillation a liquid substance falls into the receiver, which is found to be of the same nature with rock-oil. The substance itself is found in Sweden and several other countries.
The pith-asphaltum is of a mean consistence between the asphaltum and the common petroleum. Mongez says that it is the same with the bitumen collected from a well named *De la Pege*, near Clermont Ferrand in France.
The people of mount Ciaro, in Italy, have some years since found out a much easier way of finding petroleum than that which they formerly had been used to. This mountain abounds with a sort of greyish salt, which lies in large horizontal beds, mingled with strata of clay, and large quantities of a spar of that kind called
a cellular appearance, and glossy, with a number of minute and shining particles interposed through its substance; it is very friable, and, when liquid, is of a jet black colour. Some parts of the surface are covered with a thin and brittle scoria, a little elevated.
As to its depth, I can form no idea of it; for in no part could I find a substratum of any other substance: in some parts I found calcined earth mixed with it.
Although I smelt sulphur very strong on passing over many parts of it, I could discover no appearance of it, or any rent or crack through which the steams might issue; probably it was from some parts of the adjacent woods: for although sulphur is the basis of this bituminous matter, yet the smells are very different, and easily distinguished, for its smell comes nearest to that of pitch of any thing I know. I could make no impression on its surface without an axe: at the depth of a foot I found it a little softer, with an oily appearance, in small cells. A little of it held to a burning candle makes a hissing or cracking noise like nitre, emitting small sparks with a vivid flame, which extinguish the moment the candle is removed. A piece put in the fire will boil up a long time without suffering much diminution: after a long time's severe heat, the surface will burn and form a thin scoria, under which the rest remains liquid. Heat seems not to render it fluid, or occupy a larger space than when cold; from which, I imagine, there is but little alteration on it during the dry months, as the solar rays cannot exert their force above an inch below the surface. I was told by one Frenchman, that in the dry season the whole was an uniform smooth mass; and by another, that the ravines contained water fit for use during the year. But neither can I believe: for if, according to the first assertion, it was an homogeneous mass, something more than an external cause must affect it to give it the present appearances; nor without some hidden cause can the second be granted.
Although the bottoms of these ramified channels admit not of absorption, yet from their open exposure, and the black surface of the circumjacent parts, evaporation must go on amazingly quick, and a short time of dry weather must soon empty them; nor from the situation and structure of the place is there a possibility of supply but from the clouds. To show that the progress of evaporation is inconceivably quick here, at the time I visited it there were, on an average, two-thirds of the time incessant torrents of rains; but from the afternoon being dry, with a gentle breeze (as is generally the case during the rainy season in this island), there evidently was an equilibrium between the rain and the evaporation; for in the course of three days I saw it twice, and perceived no alteration on the height of the water, nor any outlet for it but by evaporation.
I take this bituminous substance to be the *bitumen alphaltum Linnei*. A gentle heat renders it ductile; hence, mixed with a little grease or common pitch, it is much used for the bottoms of ships, and for which intention it is collected by many; and I should conceive it a preservative against the borer, so destructive to ships in this part of the world.
Besides this place, where it is found in this solid state, it is found liquid in many parts of the woods; and at the distance of 20 miles from this about two inches thick in round holes of three or four inches diameter, and often at cracks or rents. This is consequently liquid, and smells stronger of tar than when indurated, and adheres strongly to any thing it touches; grease is the only thing that will divest the hands of it.
The soil in general, for some distance round La Bray, is cinders and burnt earths; and where not so, it is a strong argillaceous soil; the whole exceedingly fertile, which is always the case where there are any fulphureous particles in it. Every part of the country, to the distance of 30 miles round, has every appearance of being formed by convulsions of nature from subterraneous fires. In several parts of the woods are hot springs; some I tried, with a well-graduated thermometer of Fahrenheit, were 20° and 22° hotter than the atmosphere at the time of trial. From its position to them, this part of the island has certainly experienced the effects of the volcanic eruptions, which have heaped up those prodigious masses of mountains that terminate the province of Paria on the north; and no doubt there has been, and still probably is, a communication between them. One of these mountains opposite to La Bray in Trinidad, about 30 miles distant, has every appearance of a volcanic mountain: however, the volcanic efforts have been very weak here, as no traces of them extend above two miles from the sea in this part of the island, and the greater part... called by the Germans *selenites*; which is the common fort, that ferments with acids, and readily dissolves in them, and calcines in a small fire. They pierce these slates in a perpendicular direction till they find water; and the petroleum which had been dispersed among the cracks of those slates is then washed out by the water, and brought from all the neighbouring places to the hole or well which they have dug, on the sur- face of the water of which it swims after eight or ten days. When there is enough of it got together, they lade it from the top of the water with bras basins; and it is then easily separated from what little water is taken up with it. These wells or holes continue to furnish the oil in different quantities for a considerable time; and when they will yield no more, they pierce the slates in some other place.
It is never used among us as a medicine; but the French give it internally in hysteric complaints, and to their children for worms: some also give it from 10 to 15 drops in wine for suppressions of the menes. This, however, is rather the practice of the common people than of the faculty.