An Account of a Large Stone Near Cape Town. In a Letter from Mr. Anderson to Sir John Pringle, Bart. P. R. S.; With a Letter from Sir William Hamilton, K. B. F. R. S. to Sir John Pringle, on Having Seen Pieces of the Said Stone

VI. An Account of a large Stone near Cape Town. In a Letter from Mr. Anderson to Sir John Pringle, Bart. P. R. S.; with a Letter from Sir William Hamilton, K. B. F. R. S. to Sir John Pringle, on having seen pieces of the said Stone. SIR, Cape of Good Hope. Nov. 24, 1776. Read Jan. 15, 1777. THE honour you did me last winter when in London, by approving of the notes I had taken concerning the poisonous effects of some fishes which had been eaten by part of the Resolution's crew in her last voyage, has made me take the liberty to write to you on another subject, which, though perhaps less interesting, is yet curious enough to deserve some attention. What I mean is, a stone of an extraordinary size in this country, which Mr. Masson, whose papers relative to this place were read before the Royal Society, may have mentioned; but it could not be in such a manner as he wished, as it was at his desire that I went to see it: and though neither my time nor abilities were sufficient to observe every particular worth notice, I hope my sincere cere intention of communicating any thing useful or curious will compensate for these deficiencies. The stone is so remarkable, that it is called by the people here 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 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, disposed 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. I have sent a specimen of the rock and of the stratum, which are both what the mineralogists call *saxa conglutinata* or *aggregata*, and consequently are different from the more solid stones which constitute the greatest part of the mountains here; and is likewise another proof of its being a single stone. But it ought to be observed, that the piece of the rock was taken from a thin piece or scale, which the weather may, perhaps, have had some effect upon, so as to change or destroy the cement which keeps the pieces of the different stones together, as it is very friable. It would be needless to attempt to draw any conclusions from this short description; nor indeed am I certain if any useful reasoning could be made from it. I shall, however, leave that to your better judgement, and can only say, as an apology for troubling you, that it astonished me to see its prodigious size; and that, as I had never seen or heard of any thing like it before, I thought it worth mentioning, especially as it had attracted the attention of one who, though he had travelled a great way in this extensive country, had certainly not not seen its equal, or he would not have wished to have this particularly examined. SIR, I RETURN you many thanks for the sight of the stones from the Cape of Good Hope. I have not time to examine them very minutely; but they seem to be both of the same nature, granites, the smaller piece being only of a finer texture. The highest points of the Alps are composed of granite of the same nature, and seem to have been lifted up by exhalations, volcanic explosions, or some such causes. This singular immense fragment of granite most probably has been raised in the same manner. Most of the mountains which are called primitive (which I believe is only a term) are of this texture. I am, &c. W. HAMILTON.