During these travels, I always endeavoured to conceal myself while writing, lest I should awaken the suspicion of the Moslems: I always endeavoured to get into a wood, or placed myself under the shade of a bush or a rock, when I wished to commit what I thought worthy of remark to writing.[6] From the tower I had an extensive view over an immense plain of white sand, on which nothing grows except a few stunted shrubs, the _mimosa ferruginea_, and where the uniformity of the picture is only here and there broken by some scattered hills or banks of sand. I could not help contemplating with astonishment the extraordinary city before me, created solely by the wants of commerce, and destitute of every resource except what its accidental position as a place of exchange affords. The western quarter of the mosque seems very ancient, but the whole façade on that side is in ruins. There are also some vaulted arcades, from which the whole of the plaster facing is detached. This mosque is constructed of sun-dried bricks, of nearly the same form as those made in Europe. The walls are rough-cast with a kind of coarse sand, similar to that of which the bricks are made, mixed with the gluten of rice. In some parts of the desert there is found a very hard ash-coloured earth, in which sand predominates. This earth has been used in making the bricks for the mosque. The rest of the edifice appears to have been built after the western part was in ruins. Though the new part is very well for a people ignorant of architecture, it is greatly inferior to the ancient remains. I was surprised to find in the ancient part three galleries, each supported by ten arcades, as well built as if they had been the work of a skilful architect. The arches are six feet wide and ten high; there the plaster is in an excellent state, and appears to have been white-washed. The style and the position of this building connect it with the ruins. I am inclined to think that the mosque consisted originally of this part only, and that additions were afterwards made to it.