When things were in their natural state, undisturbed by man, the Birket el Keiroon was a lake, as it is now. In those days, as in our own, it was supplied with water, just as the pool within the enclosure of Karnak, and other pools, and all the wells in Egypt, by natural infiltration; for the water of the river percolates readily through the porous strata, and flows into any sufficiently deep depressions, or excavations. The existence of the oases also in the desert must be accounted for in this way. The Bahr Jusuf Canal had, at some unrecorded date, been brought along the foot of the Libyan range. Starting from Diospolis Parva, by the air-line forty miles below Thebes, it had traversed the whole of the rest of the valley; then, passing through the Delta, it had reached the sea, somewhere in the neighbourhood of modern Alexandria; a distance, again, in the air-line of 400 miles; though, of course, this falls very far short of giving the measure of its ceaseless sinuosities. This Grand Canal of old Egypt now carries off about a twenty-eighth part of the water that passes over the cataract of Philæ. In its course it flows along the depressed range that forms the eastern boundary of the Faioum. In this depressed range there is a ravine through which in early days, at the season of the inundation, some of the overflow of the Bahr Jusuf found its way to the top level of the Faioum. It is not easy now, to decide whether it got through naturally at first, or whether the ravine was canalized to enable it to pass through. At all events it is evident that, if there had originally been a natural passage, it was levelled and enlarged by man availing himself of natural fissures and depressions. But however this might have been, the inundation having found its way on to the upper level of the Faioum, appears to have formed there an immense morass. The first condition, then, of the district had been a dry desert, precisely resembling any other part of the desert, except that it slanted from what may be spoken of as the rim of its mussel-shell-like depression down to the spring-fed Birket el Keiroon. Its second condition, that now before us, is what was brought about by the water of the inundation, that had in some way or other been let into the district: it formed wherever it was retained, and chiefly on the upper plateau, a vast extent of morasses. We have the evidence of geology for the former—for we see that the original surface of the district consisted of thin layers of limestone, alternating with layers of clay—and of tradition for the latter.