The shores have widened here, and fall off in an angle of 45° to 50°: though they appear on this account lower, yet it is plainly visible by the steeper places, that they always become higher. It is only below in the places where the river beats against, that the bluish clay is seen: the remaining part of the shores has, apparently, merely constituents of the same, as is the case in most places where the high water has not washed away the crust of humus crumbling from above and covering the base of the surface; for the original soil discloses itself immediately under the covering of earth, as is seen in precipices, and clefts in rocks caused by water. The river has also thrown or deposited thick layers on the shores. We must not be deceived here by observing various strata of earth mixed above and below with sand; this is a later alluvial deposit. A pure layer of clay is never to be seen, however, in these tracts of strata, so far as I have remarked here and on the Nile. If it does appear, it lies either as the foundation of the whole, below on the banks of the water, as on the Nile; for all the ground there is alluvial and earthy deposits, gained when the high water is drawn off; or it rises, as in the Sobàt, with the talus of the shores to the surface, which is covered with a crust of humus. The Sobàt dug a bed for itself in firm clay-ground that resisted the water, and remained tolerably constant in the trench opened by it, without having altered its course, for no gohrs are seen on dry ground; but perhaps, in some places, it has flowed over its bed, and formed channels. On the contrary, the White Stream wallowed for a long time in the deep slime of an emptied lake, before it threw up solid dams, on which there are marshy forests, as on the old shores. This long valley-basin lies also on a layer of clay. The Sobàt may be considered as a further boundary of the peninsula of Sennaar, and have given to the latter the name of Gesira. Certainly it has been, like the Blue Nile, a main-road for the tribes of the highlands of Ethiopia to the valleys of these countries; and this must have been especially the case because it has no accompanying marsh-lakes. Such nations could not have wound down from the mountains of Bari and the highlands there, by reason of the many marshes; for we are not to suppose that nomadic tribes can provide themselves and families with a stock of provisions for a long journey, or stow entire herds in their hewn-out trunks of trees (canoes); and it is impossible that the cattle could have been driven along the shore for their use.