On issuing from these gorges, we enter upon the Desert proper by a sandy plain which the Djellahs have named the "River without Water," and which, very low at first, slowly rises into a plateau of very slight elevation, intersected by some veins of a sandstone similar to that of the conical mountains. Then the plain declines anew, and we emerge upon the Sea of Sand, where the pulverized sandstone alternates with fields of rotted or broken pebbles, and mounds of porphyry and granite. At the foot of one of these mounds, the _Tallat-el-Guindé_, flourish a few wretched vegetables, among others some gum-trees and doum-palms. The latter trees are also found in solitary mournfulness scattered about the plain. Otherwise the _Desert of Korosko_ is wholly deprived of vegetable life, of "The glory in the grass, and the splendour in the flower." As for water, it must needs be content with that of a few brackish wells, grouped, about twelve in number, at a spot called _El-Mourath_. It is there only that the caravans can fill their ill-tanned leather-bottles, in which the already nauseating liquid grows hot, and quickly becomes putrid. Its stench and its taste are then so disgustful that the very camels reject it several times before they can constrain themselves to drink of it. [Illustration: RAVINES OF KOROSKO.] * * * * * The _Desert of Bahiouda_, situated in about the same latitude as that of Korosko, but on the other bank of the Nile, is of a less absolute aridity and nakedness. Water is more abundant and less brackish; vegetation is less scanty; and one meets on every side with giraffes, gazelles, wild cattle, and even, it is said, with lions and elephants. Great numbers of reptiles, lizards, serpents, and tortoises inhabit the sand and the crevices of the rocks. * * * * * South of the above-named Deserts, towards 17° N. lat., is placed the limit of the Rainless District. Under the 18th parallel the rains do not last above one or two months in the year, and in some years are absolutely wanting; but when they _do_ fall, it is generally in impetuous torrents. As we advance towards the Equator they become more regular, and last for longer periods. According to Humboldt, the average yearly rainfall in 19° N. lat. measures 80 inches; under the equator, 96 inches. In these tropical climes the year is divided into two seasons--one of excessive drought, and one of excessive rain. During the former, the sky is ever cloudless; during the latter, completely overcast.