If deserts _have_ a fault (which their present biographer is far from admitting), that fault may doubtless be found in the fact that their scenery as a rule tends to be just a trifle monotonous. Though fine in themselves, they lack variety. To be sure, very few of the deserts of real life possess that absolute flatness, sandiness and sameness, which characterises the familiar desert of the poet and of the annual exhibitions--a desert all level yellow expanse, most bilious in its colouring, and relieved by but four allowable academy properties, a palm-tree, a camel, a sphinx, and a pyramid. For foreground, throw in a sheikh in appropriate drapery; for background, a sky-line and a bleaching skeleton; stir and mix, and your picture is finished. Most practical deserts one comes across in travelling, however, are a great deal less simple and theatrical than that; rock preponderates over sand in their composition, and inequalities of surface are often the rule rather than the exception. There is reason to believe, indeed, that the artistic conception of the common or Burlington House desert has been unduly influenced for evil by the accessibility and the poetic adjuncts of the Egyptian sand-waste, which, being situated in a great alluvial river valley is really flat, and, being the most familiar, has therefore distorted to its own shape the mental picture of all its kind elsewhere. But most deserts of actual nature are not all flat, nor all sandy; they present a considerable diversity and variety of surface, and their rocks are often unpleasantly obtrusive to the tender feet of the pedestrian traveller. A desert, in fact, is only a place where the weather is always and uniformly fine. The sand is there merely as what the logicians call, in their cheerful way, 'a separable accident'; the essential of a desert, as such, is the absence of vegetation, due to drought. The barometer in those happy, too happy, regions, always stands at Set Fair. At least, it would, if barometers commonly grew in the desert, where, however, in the present condition of science, they are rarely found. It is this dryness of the air, and this alone, that makes a desert; all the rest, like the camels, the sphinx, the skeleton, and the pyramid, is only thrown in to complete the picture.