There Is A Rim Or Fringe
Of Ancient Rocks Round A Great Central Valley, Which, Dipping Inward,
Form A Basin,
The bottom of which is composed of the oldest silurian rocks.
This basin has been burst through and filled up
In many parts
by eruptive traps and breccias, which often bear in their substances
angular fragments of the more ancient rocks, as shown in the fossils
they contain. Now, though large areas have been so dislocated
that but little trace of the original valley formation appears,
it is highly probable that the basin shape prevails over
large tracts of the country; and as the strata on the slopes,
where most of the rain falls, dip in toward the centre, they probably
guide water beneath the plains but ill supplied with moisture from the clouds.
The phenomenon of stagnant fountains becoming by a new and deeper outlet
never-failing streams may be confirmatory of the view that water is conveyed
from the sides of the country into the bottom of the central valley;
and it is not beyond the bounds of possibility that the wonderful river system
in the north, which, if native information be correct, causes a considerable
increase of water in the springs called Matlomagan-yana (the Links),
extends its fertilizing influence beneath the plains of the Kalahari.
The peculiar formation of the country may explain why there is
such a difference in the vegetation between the 20th and 30th
parallels of latitude in South Africa and the same latitudes
in Central Australia.
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