Why there should be so much vegetation on the Kalahari may be explained by the geological formation of the country.  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.  The want of vegetation is as true of some parts too in the centre of South America as of Australia; and the cause of the difference holds out a probability for the success of artesian wells in extensive tracts of Africa now unpeopled solely on account of the want of surface water.  We may be allowed to speculate a little at least on the fact of much greater vegetation, which, from whatever source it comes, presents for South Africa prospects of future greatness which we can not hope for in Central Australia.  As the interior districts of the Cape Colony are daily becoming of higher value, offering to honest industry a fair remuneration for capital, and having a climate unequaled in salubrity for consumptive patients, I should unhesitatingly recommend any farmer at all afraid of that complaint in his family to try this colony.  With the means of education already possessed, and the onward and upward movement of the Cape population, he need entertain no apprehensions of his family sinking into barbarism.