Many obstacles exist to the erection of any permanent marks by which the roads of the desert might be distinguished. Yet I have observed that the people of our caravan, in such places as afforded stones for the purpose, used to collect four or five large ones, thus raising small heaps at proper distances from each other. This affords them some satisfaction at their return; but in many places, where the sand is loose and deep, it becomes impracticable. They are then obliged to rely on the facility acquired by habit, of distinguishing the outline and characteristic features of certain rocks, as they are perfectly ignorant of the compass, and very little informed as to the fixed stars. Though the names of the constellations be little known to them, yet they distinguish such as may guide them in their course during the night. With all these aids however their deviations from the true line are not infrequent. Three times, in the course of our journey, the whole caravan was quite at a loss for the road, though some of the members of it had made ten or twelve different journies to and from Dar-Fûr. During the whole of my route I had reason to suspect that the accounts in books of travels, which have generated such terrific notions of the moving sands of Africa, are greatly exaggerated. While we remained at Leghea, indeed, a violent gale sprang from the North-west, and raised a cloud of sand. At that time I placed a wooden bowl, capable of containing about two gallons, in the open air. Thirty minutes had elapsed when it appeared completely filled with sand. Our companions indeed affected to relate various stories of caravans that had been overwhelmed. But as neither time nor place were adduced, it would seem not unreasonable to doubt the truth of the assertion. If caravans have been thus buried on their road, it may be presumed that accident can only have happened after they have been deprived of the power of moving, by the influence of a hot wind, want of water, and other causes. A number of men, and other animals, found dead, and covered with sand, would be sufficient ground for succeeding native travellers to believe, as they are strangers to ratiocination, or, though not entirely persuaded, to relate, as they delight in the marvellous, that the persons they had found had been overwhelmed on their march; when in fact this accumulation had not happened till they were already dead. But perhaps the matter scarcely merits this discussion.