SOUTHERN AFRICA. 
6i 
mafs of fuperincumbent fandftoiie, glide over the impenetrable 
fuiface 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 fur- 
face, and the upper part of the granite bafe is funk beneath the 
general level of the country, the fprings that make their appear- 
ance are few and fcanty. 
The reafoning that fuggefts itfelf on thefe fa£ls will lead to 
the following conclufion : — that the cifterns 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 fur- 
face, but, oozing imperceptibly between the granite and the 
fandftone, below the general level of the country, glide in fub- 
terraneous ftreams to the fea. 
I am the more inclined to this opinion from the experience 
of feveral fads. When Admiral Sir Roger Curtis directed 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 frefh 
water that rufhed out of the holes, which they found neceifary 
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 conti- 
nent, frefli water may be procured at the depth of ten or twelve 
feet below the fandy furface. Even ia the fide of the Tyger 
Hillsj 
