Page:The journal of the Royal Geographic Society of London. Volume 34, 1864. (IA s572id13663720).pdf/417

Rh A. G. Bain, as well as from the explorations of Livingstone, and the observations of Richard Thornton. From Mr. Thornton’s journals, copies of which have been placed in my hands, I find that granitic, syenitic, felspathic, and porphyritic rocks of igneous origin, with highly metamorphosed, schistose, and quartzose rocks of great age, occur on the banks of the Zambesi. He also describes near the rapids and falls above Tete various beds of coal in old sandstones, shales, and conglomerates. It is therefore evident that the older or palæozoic rocks of geologists form the nucleus of the continent. At the same time there is no evidence of the existence of any of the younger fossiliferous marine rocks in Inner Africa. My belief is, that the superficial deposits which there exist have been alone formed by disintegration of the old rocks, and that the accumulation of sand, clay, and pebbles, which diversify the surface, are purely of terrestrial or lacustrine or fluviatile origin. This view is indeed to be inferred by simply referring to Mr. Bain’s excellent memoir on the geological structure of Southern Africa, which shows that the crystalline and palæozoic rocks were succeeded in the very ancient days of the bidental reptiles, by lacustrine deposits only.

Whatever rocks have since been examined in the interior and to the north, such as sandstones and clays, often ferruginous, and tufas arising from calcareous springs,—every known feature indicates that terrestrial and fluviatile conditions only prevailed throughout those wide regions and during enormously long periods. The only striking fossil shell, indeed, which Speke found in a ridge at a great distance from the coast, proved to be a large Achatina, similar in form to the A. perdix now living in South Africa, and with it was associated a small shell like a Potamides.

The observations of other travellers,—whether made by Livingstone in his first journey across South Africa, between St. Paul de Loanda and the mouth of the Zambesi, or in his recent explorations up the Shiré (in which he was accompanied by Dr. Kirk and his brother Charles Livingstone), when he examined the shores of the Nyassa Lake, or by Burton and Speke, and Speke and Grant, in their respective journeys,—have all equally failed in discovering any inland formation or deposit in which are imbedded fossil marine remains of secondary or tertiary age.

On the contrary, with sandstones, often ferruginous, resting on granites and a very few other rocks, whether quartzose, argillaceous,