t high. Their surfaces
are nearly smooth, without chink or fissures; and they are found to be a
species of granite, different from that which composes the neighbouring
mountains."

Mr Anderson having, with his letter to Sir John Pringle, also sent home
a specimen of the rock, it was examined by Sir William Hamilton, whose
opinion is, that "this singular, immense fragment of granite, most
probably has been raised by a volcanic explosion, or some such cause."
See his Letter to Sir John Pringle, annexed to Mr Anderson's, in the
Philosophical Transactions.--D.]

"Its circumference, I think, must be at least half a mile, as it took us
above half an hour to walk round it, including every allowance for the
bad road, and stopping a little. At its highest part, which is the S.
end, comparing it with a known object, it seems to equal the dome of St
Paul's church. It is one uninterrupted mass of stone, if we except some
fissures, or rather impressions, not above three or four feet deep, and
a vein which runs across near its N. end. It is of that sort of stone
called, by mineralogists, _Saxum conglutinatum_, and consists chiefly of
pieces of coarse quartz and glimmer, held together by a clayey cement.
But the vein which crosses it, though of the same materials, is much
compacter. This vein is not above a foot broad or thick; and its surface
is cut into little squares or oblongs, disposed obliquely, which makes
it look like the remains of some artificial work. But I could not
observe whether it penetrated far into the large rock, or was only
superficial. In descending, we found at its foot a very rich black
mould; and on the sides of the hills some trees of a considerable size,
natives of the place, which are a species of _olea_.[89]

[Footnote 89: "It is strange that neither Kolben nor de la Caille should
have thought the Tower of Babylon worthy of a particular description.
The former [vol. ii. p. 52, 53, English translation] only mentions it as
a high mountain. The latter contents himself with telling us, that it
is a very low hillock, _un tres bas monticule. Voyage de la Caille_, p.
341. We are much obliged to Mr Anderson for his very accurate account of
this remarkable rock, which agrees with Mr Sonnerat's, who was at the
Cape of Good Hope so late as 1781. His words are, "La Montagne de la
_Perle_, merite d'etre observee. C'est un des plus hautes des environs
du Cap. Elle n'est composee que d'un seul bloc de granit crevasse da