in natural history, a distinct genus of stones, composed of separate and very large concretions rudely compacted together; of great hardness, giving fire with steel, not fermenting with acids, and slowly and imperfectly calcinable in a great fire.

Of this genus there are three species: 1. The hard white granite, with black spots, commonly called moorstone. This is a very valuable kind, consisting of a beautiful congeries of very variously constructed and differently coloured particles, not diffused among or running into one another, but each pure and distinct, though firmly adhering to whichever of the others it comes in contact with, and forming a very firm mass. It is much used in London for the steps of public buildings, and on other occasions where great strength and hardness are required. 2. The hard red granite variegated with black and white, and common in Egypt and Arabia. 3. The pale whitish granite, variegated with black and yellow. This is sometimes found in strata, but more frequently in loose nodules, and is used for paving the streets.

Some of these kinds of stones are found in almost every country, and in many places they are found of immense bigness. The largest mass of this kind in the known world, lying as an unconnected stone, is found near the Cape of Good Hope in Africa, and of which we have the following description in the Philosophical Transactions, vol. 68, p. 102, given by Mr Anderson in a letter to Sir John Pringle. "The stone is so remarkable, that it is called by the people there the Tower of Babel, and by some the Pearl Diamond. It either takes the last name from a place near which it is situated, or it gives name to the tract of cultivated land called the Pearl. It lies upon the top of a ridge of low hills, beyond a large plain, at..." Granite. the distance of about thirty miles from the Cape Town; beyond which, at a little distance, is a range of hills of a much greater height. It is of an oblong shape, and lies north and south. The south end is highest; the east and west sides are steep and high; but the top is rounded, and slopes away gradually to the north end, so that you can ascend it by that way, and enjoy a most extensive prospect of the whole country.

I could not precisely determine its circumference, but it took us above half an hour to walk round it; and by making every allowance for the rugged way, and stopping a little, I think the most moderate computation must make it exceed half a mile. The same difficulty occurred with respect to knowing its height: but I think, that, at the south end, it is nearly equal to half its length: or, were I to compare it to an object you are acquainted with, I should say it equalled the dome of St Paul's church.

"I am uncertain whether it ought to be considered as the top of the hill, or a detached stone, because there is no positive proof of either, unless we were to dig about its base; but it would certainly impress every beholder, at first sight, with the idea of its being one stone, not only from its figure, but because it is really one solid uniform mass from top to bottom, without any interruption; which is contrary to the general character of the high hills of this country, they being commonly divided, or composed of different strata, at least if we may judge from the rows of plants or shrubs which grow on the sides of the steepest, and, as I suppose, are produced from the small quantity of earth interposed between them. It has indeed a few fissures, or rather impressions, which do not reach deeper than four or five feet; and near its north end a stratum of a more compact stone runs across, which is not above twelve or fourteen inches thick, with its surface divided into little squares, or oblongs, uponed obliquely. This stratum is perpendicular; but whether it cuts the other to its base, or is superficial, I cannot determine. Its surface is also so smooth, that it does not appear to have formerly been joined to, or separated from, any other part by violence, as is the case with many other large fragments; but enjoys the exact situation where it was originally placed, and has undergone little change from being exposed for so many successive ages to the calcining power of a very hot climate."—A part of this stone being examined by Sir William Hamilton, he determined it to be a granite, and of the same nature with the tops of some of the Alps; and supposes both of them to have been elevated by volcanic explosions.

genus of stones of the order of petrae, belonging to the class of saxa. The principal constituent parts of this stone are felt-spar or rhombic quartz, mica, and quartz. These ingredients constitute the hardest sort of granite, and that most anciently known. That into which schorl enters is more subject to decomposition. They never have any particular texture or regular form, but consist of enormous shapeless masses extremely hard. In the finer granites the quartz is transparent; in others generally white or grey, violet or brown. The felt-spar is generally the most copious ingredient, and of a white, yellow, red, black, or brown colour. The mica is also grey, brown, yellow, green, red, violet, or black; and commonly the least copious. The schorl is generally black, and abounds in the granites that contain it. Hence the colour of the granites depends principally on that of the spar or schorl. The red granites consist commonly of white quartz, red felt-spar, and grey mica; the grey ones of white quartz, grey or violet felt-spar, and black mica. The black granites commonly contain schorl instead of felt-spar; and the green usually contain green quartz.

On exposing granite to the flame of a blow-pipe, the component ingredients separate from one another. Mr Gerhard having melted some in a crucible, found the felt-spar run into a transparent glass; below it the mica lay in form of a black flag, the quartz remaining unaltered. It melted somewhat better when all the three were powdered and mixed together; though even then the quartz was still discernible by a magnifying glass. Hence we may explain the reason why grains of a white colour are sometimes found in volcanic lavas. The mixture of mica prevents the flake or quartz from splitting or cracking; and hence its infusibility and use in furnace-building.

Granites are seldom flatly or laminated. In those which are of a close texture, the quartz and schorl predominate. They take a good polish; for which reason the Egyptians formerly, and the Italians still work them into large pieces of ornamental architecture, for which they are extremely fit, as not being liable to decay in the air. Farber, in his letters from Italy, mentions a kind of stone named granitone, composed of felt-spar and mica; a substance of this kind, which moulders in the air, is found in Finland; which is said to contain salt-petre, and sometimes common salt. In that country it is called rapakivi. Wallerius describes 18 species of granites, besides many others akin to this genus. Those described by Cronstedt are, 1. Loose or friable, which comes from France, and is used at the brass works for casting that metal in. 2. Hard or compact, of which there are two varieties, red and grey. The former is met with of two kinds; viz. fine-grained from Swappari in Lapland, or coarse-grained from the province of Dalarne in Sweden. The grey, with other colours, is met with on the coast round Stockholm and Norland in Sweden.