380	THE DIAMOND
	are situated, therefore, where vegetation is or has been extremely luxurious. Some of these sections in this age, elevated and denuded of soil, are almost barren, though the surface of the Karoos in South Africa, con­sisting chiefly of ferruginous reddish sands and clays which bake hard in time of drought, rests on a slaty rock which retains the rain water and keeps alive the bulbous and other alkali plants until the wet season transforms the country, with tropical rapidity, to oceans of blossoms. A large part of the South African plateau lying within the hills of the west coast, the Bokkeveldts in the South, and the Drakenberg mountains which skirt it on the east coast and turning westward form a northern interior frontier in the Transvaal south of the Limpopo river, probably held at one time lacustrine basins interspersed with great stretches of the rankest vegetation, which deposited during the ages immense stores of carbonaceous material. If by any means, ver­tical fissures were opened in such an area of the earth's surface, there would be a great in-pouring of this material into the cavities, sufficient one might think reasonably, to supply an abundance of the carbon necessary to pro­duce the very small proportion diamonds constitute of the mass contained in the diamond chimneys. As stated, this high plateau of the diamond-bearing part of South Africa appears to have been raised to its present elevation, from whatever cause or by what­ever means, either by one uplift, or by a gradual exer­cise of force which did not break up and distort the trend of the strata. In Brazil and elsewhere, the strata in which the diamondiferous deposits occur are broken and often folded. In many places they are raised to a