Abyssinia, as we have seen, was probably drier than at present, but further south the rainfall must have been considerably greater. Lake Kioga stood 600 feet above its present level and was connected with Lake Victoria. Lake Victoria and the smaller lakes were twice their present size, and most of the broad valleys were filled with water. Lake Magadi is the attenuated relic of a vast sheet of water, and other great lakes have disappeared entirely. One of these, in the Rift valley, south of Lake Naivasha, has been mapped by Professor Gregory and named after Professor Suess. Part of this decrease of the lakes has undoubtedly taken place within historic times, and part may be attributed to changes in the drainage, but there remains enough evidence to show that some time in the Ice Age the great lakes were very much larger than the present. Mr. E. J. Wayland, the Government Geologist of Uganda, informs me that in the old basin of Victoria Nyanza there are masses of gravel which may be two or three miles in breadth, the surface of which forms two terraces at different levels. Above the level of these is an old peneplain with ancient beach gravels. Mr. Wayland considers that this peneplain was formed probably during the Pliocene by the first Victoria Nyanza occupying a basin between folds. The initial high level was due to the want of an outlet, but may have been amplified by other causes. The level of the lake then sank gradually to a considerably lower level, after which it rose again nearly to its old level and remained there for a considerable time. During this period the great gravel deposits were formed; they contain flood deposits, especially near their base. The level of the lake then sank again and this part of the basin was converted into a valley occupied by a river. Subsequently the level rose again sufficiently to carve out the lower terrace in the gravels. Mr. Wayland considers that the upper terrace may also represent a stage distinct from that in which the gravels were actually deposited, but the upper terrace may be the original surface of the gravels. Thus there is evidence of two Pluvial periods in central Africa, of which the first, probably corresponding with the great extension of the mountain glaciers, was the greater. From the archæological evidence it appears to correspond with the Mindelian glaciation of Europe.