66 
TRAVELS IN 
very great depth below the general furface of the country ; fo 
that whenever the heavy rains defcend, the waters fubfide into 
thefe deep channels, which, on account of their narrownefs, 
almoft inftantaneoufly become filled to the very brink. The 
impetuofity with which fuch torrents rufh towards the fea is 
irrefiftible. 
. Whether the deep excavations, that form the beds of thefe 
rivers, may be fatisfaftorily 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 fear- 
city of fprings, the invention is naturally exercifed in endeavour- 
ing to account for a phenomenon fo unufual. The following 
qbfervations may perhaps afHft 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 confiderably above the gene- 
ral furface of the country, and fometimes its tapper 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 
inftance of Table Mountain, where, on every fide, copious 
ilreams of pure limpid water, filtered through the immenfe 
raafs 
