An instance in point may here be given from Leo Africanus, who tells us that three castles were accidentally discovered, far in the desert of Libya, about eighteen years before the time when he related the following story:—“The guide of a caravan (whose name was Hámar) had missed the usual track, in consequence of a complaint in his eyes; and there being no other person in the whole caravan who knew the road they ought to take but himself, he went on, upon his camel, in advance of the party, and at every mile they made he caused a handful of sand to be presented to him, which he smelt, and then continued his journey. In this manner the caravan continued to advance till they came within forty miles of the castles above mentioned, near which there were five or six little hamlets, and a profusion of excellent dates. The guide then addressed himself to those who were about him, and assured them that they were in the neighbourhood of some inhabited place, but few of the party believed what he said, for as they were at least four hundred and eighty miles from Egypt, it was imagined, if indeed the assertion should be true, that they must have moved back upon Augela.” “On the third day, however, after this notice, they came in sight of the three castles above mentioned; and the people of the place, surprised and alarmed at the appearance of so many strangers, retreated to the castles, where they shut themselves up, and refused to supply the caravan with water, of which they were greatly in need. As the wells were within the fortifications, there was nothing left for the caravan, under these adverse circumstances, but to carry the forts, and to supply themselves by force, or to continue their journey across the desert, at the risk, perhaps the certainty, of perishing with thirst. They soon determined to make an attack upon the castles, which, after a slight engagement, they succeeded in carrying; and having obtained from the wells as much water as was necessary, they proceeded on their route across the desert[22].” In many of the forts which we visited in the Syrtis, one or two, and sometimes more, wells were still visible within the works (although, for the most part, they were filled up with mud and sand, or with the rubbish of the fallen materials of the buildings); and it is probable that all of them were originally provided with a convenience so essential to the garrison. In some cases we found wells decidedly without the works, in places which appeared to be wholly undefended; except we may suppose them to have been within range of the archers and slingers from the walls, which did not always appear to have been the case. In such instances, however, we must not conclude that there were originally no wells within the forts, because none are found there at present; for a single century of neglect would in many cases be sufficient to account for the disappearance of a well altogether.