When, from the summit of the rocks which fence round and bristle over the Desert of Erosion, we perceive for the first time the _Desert of Sand_, the impression is very similar to that which we derive from the sight of ocean. M. Martins had already become sensible of this peculiar effect when, from the Col de Sfa, he had gazed down upon the Desert of the Plateaux. "A grand circular arch," he says, "extended before us, bounding a violet surface, smooth as the sea, and blending at the horizon with the azure of heaven; it was the Sahara. The arc eastward rested against the chain of the Aurès; westward, against that of the Zibans, some of whose offshoots, in the neighbourhood of Biskra, arose like reefs upon that sea which seemed to have been frozen suddenly into immobility. The actual sea ever trembles and shivers on the surface; a light wavering, imperceptible to the eye, propels towards the shore the expiring wave, fringed with a border of foam. Here, nothing like this may be seen; it is a motionless, a congealed sea, or, rather, it is the smooth bed of a sea whose waters have disappeared. Science teaches us that such is the fact; and now as ever the expression of the reality is more picturesque, more eloquent than all the comparisons created by the imagination."[56] An eminent French artist, M. Fromentin, whose skill with the pen equals his talent with the brush, has also painted this "congealed sea" in grand and poetic language. "The first impression," he says, "produced by this glowing lifeless picture, composed of the sun, space, and solitude, is keen, and cannot be compared to any other. Little by little, however, the eye grows accustomed to the grandeur of the lines, to the emptiness of space, to the denudation of the earth; and if anything can still astonish, it is that one becomes sensible to effects which change so little, and is so powerfully affected by spectacles in reality of the simplest character."[58] I must also enumerate among the "artists in words" who have painted the wonders of the Sahara, General Daumas, not one of the least distinguished of the Franco-Algerine warriors. He describes it in the following language:--"It is a naked and barren immensity,--this sea of sand, whose eternal waves, agitated to-day by the _choub_, will to-morrow be heaped up immovable, and which are slowly furrowed by those fleets called caravans." General Daumas, it is evident, confines himself to the scientific realism, which M. Martins prefers to the glowing and inexact imagery of the poets, and conveys in a few words an accurate yet very picturesque idea of that arid sea, where the wind stirs up rolling waves of sand instead of foaming billows, and which the Arabs call _Falat_. I shall place before the reader, however, the description given by M. Martins himself, for it represents both the _ensemble_ and the details of the picture.