Even now, illusion often recalls, in the obscurity of night, these images of a former age. For when the guiding constellations illumine the margin of the plain with their rapidly rising and setting beams, or when their flickering forms are reflected in the lower stratum of undulating vapour, a shoreless ocean seems spread before us[3]. Like a limitless expanse of waters, the Steppe fills the mind with a sense of the infinite, and the soul, freed from the sensuous impressions of space, expands with spiritual emotions of a higher order. But the aspect of the ocean, its bright surface diversified with rippling or gently swelling waves, is productive of pleasurable sensations,—while the Steppe lies stretched before us, cold and monotonous, like the naked stony crust of some desolate planet[4]. In all latitudes nature presents the phenomenon of these vast plains, and each has some peculiar character or physiognomy, determined by diversity of soil and climate, and by elevation above the level of the sea. In northern Europe the Heaths which, covered by one sole form of vegetation, to the exclusion of all others, extend from the extremity of Jutland to the mouth of the Scheldt, may be regarded as true Steppes. They are, however, both hilly and of very inconsiderable extent when compared with the Llanos and Pampas of South America, or even with the Prairies on the Missouri[5] and Copper River, the resort of the shaggy Bison and the small Musk Ox. The plains in the interior of Africa present a grander and more imposing spectacle. Like the wide expanse of the Pacific, they have remained unexplored until recent times. They are portions of a sea of sand, which towards the east separates fruitful regions from each other, or incloses them like islands, as the desert near the basaltic mountains of Harudsch[6], where, in the Oasis of Siwah, rich in date-trees, the ruins of the temple of Ammon indicate the venerable seat of early civilization. Neither dew nor rain refreshes these barren wastes, or unfolds the germs of vegetation within the glowing depths of the earth; for everywhere rising columns of hot air dissolve the vapours and disperse the passing clouds. Wherever the desert approaches the Atlantic Ocean, as between Wadi Nun and the White Cape, the moist sea-air rushes in to fill the vacuum caused by these vertically ascending currents of air. The navigator, in steering towards the mouth of the river Gambia, through a sea thickly carpeted with weeds, infers by the sudden cessation of the tropical east wind[7], that he is near the far-spreading and radiating sandy desert.