A few miles above Memphis the Libyan range is divided by a depression. This cleft leads from the Nile into a spacious urn-shaped valley, now called Fayum, of which the western part is filled by a large lake. On the ruins near this lake, the name of King Amenemha III. is frequently read. If we remember that the careful observations of the rise of the Nile from the reign of this king tend to show that he was busily engaged with the irrigation of the land, that the Egyptians call this lake the lake of inundation (_meri_), and that the king Moeris of the Greeks owes his name to this title (_suten en meri_), we may regard Amenemha III. as the author of the wonderful hydraulic structures at Fayum. The great reservoir, which he constructed, is no longer in existence, but the remains of it can be traced in dams and in the modern lake of Fayum, the Birket-el-Kerun. The urn-shaped valley of Fayum offered a situation for a basin near the Nile, which might receive and preserve part of the inundation, and the depression in the Libyan range secured a natural path for the canal, required to feed the basin from the Nile, and the Nile from the basin. For the site of the basin the nearest part of the valley was selected; it was enough that the bed of the reservoir was not lower than the lowest level of the Nile. No deep excavations were needed; all that was required was to enclose a large part of the valley with strong dams; and the earth necessary for erecting these could be taken out of the enclosed space. These dams must have been massive enough to retain a large body of water, and prevent it from breaking out into the western, and far lower part of the valley, and at the same time of sufficient height to prevent any overflow even in the times of the highest inundations. At the eastern entrance into Fayum we find running from the valley of the Nile the remains of long, rectilinear, and very massive banks, in which modern research has recognised the original enclosure of the lake of Moeris. The breadth of the dams appears to have been carried to 150 feet; whereas the height can hardly have exceeded thirty feet.[167] When Herodotus tells us that the depth of the basin in the deepest part was fifty fathoms, it is obvious that the statement rests on the computation that the two pyramids in the middle of the lake were of the same height under as above the surface. The same authority allows a circuit of about 450 miles for the lake, but from the remains we cannot allow a greater circuit than 150 miles.[168] The Egyptians were sufficiently skilled in the erection of strong dams, and structures of such an extent could not be in excess of the resources of a country which had erected the great pyramids. Finally, when Herodotus asks what had become of the earth dug out of this great lake, the answer is that there was no complete excavation, but merely the enclosure of a certain space of land, and what was taken out of this was at once applied to the