very great depth below the general furface of the country; fo
that whenever the heavy rains defcend, the waters fuhfide into
thefe deep channels, which, on account of their narrowneis,
aim oft inftantaneoufly become filled to the very brink. The
impetuofity with which fuch torrents ruih towards the fea is
irrefiftible.
"Whether the deep excavations, that form the beds of thefe
rivers, may be fatisfadorily explained by fuppofing the texture
of the adjacent materials to have been of a loofe and incoherent
nature ; or, whether a greater antiquity than to many, parts of
the globe may not be affigned to the continent of South Africa,
on the whole furface of which there appears to be a remarkable
fimilarity, is a queftion on the merits of which one would he-
fitate to give a prompt decifion. But, on comparing the great
quantity of rain that annually falls at the Cape, a quantity far
exceeding that in moft parts of Europe, with the general fcar-
city of fprings, the invention is naturally exercifed in endeavouring
to account for a phenomenon fo unufual. The following
obfervations may perhaps afiift in explaining it:
All the continued chains of mountains in Southern Africa are
compofed of fandftone refting upon a bafe of granite. This
granite bafe is fometimes elevated eonfiderably above the general
furface of the country, and fometimes its upper part is
funk as far beneath it. In fituations where the former happens
to be the cafe, numerous fprings are fure to be found, as in the
inilance of Table Mountain, where, on every fide, copious
jftreams of pure limpid water, filtered through the immenfe
mafs
mafs of fuperincumbent fandftone, glide over the impenetrable
furface of granite, furnifhing an ample fupply to the whole
town, the gardens, and the adjacent farms. But in all thofe
places where the fandftone continues to defcend below the furface,
and the upper part of the granite bafe is funk beneath the
general level of the country, the fprings that make their appearance
are few and fcanty.
The reafoning that fuggefts itfelf on thefe fads will lead to
the following conclufion :— that the citterns or cavities in the
fandftone mountains, being corroded and fretted away, in the
lapfe of ages, to a greater depth than the openings or conduits
which might, perhaps, at one time have given their waters
vent, the fprings can no longer find their way upon the furface,
but, oozing imperceptibly between the granite and the
fandftone, below the general level of the country, glide in fub-
terraneous ftreams to the Tea.
I am the more inclined to this opinion from the experience
of feveral fails. When Admiral Sir Roger Curtis direded a
fpace of ground, between the Admiralty-houfe and the fhore of
Table Bay, to be enclofed as a naval yard, the workmen met
with great impediment from the copious fprings of pure freih.
water that ruihed out of the holes, which they found neceflary
to fink in the fand, for receiving the upright pofts. It is a
well known fad, that on almoft every part of the ifthmus that
conneds the mountainous peninfula of the Cape to the continent,
freih water may be procured at the depth of ten or twelve
feet below the fandy furface. Even in the fide of. the Tyger
Hills,