If the muddy waters of the Nile in flood entered a lake 60 to 70 metres deep, the silt would be deposited and remain, for the return flow from the uppermost stratum back into the Nile would disturb none of the Nile mud brought in. After a long succession of such annual deposits, the depth of deposit would be considerable. In the Fayûm entrance we find such a deposit up to R.L. 25·00, and it is to be noted that the Wadi Raiân was supposed by Mr. Cope Whitehouse to have been in working order, as Lake Mœris, after the Fayûm ceased to be so, and therefore there would have been less time for the disappearance of the Nile deposit of the Wadi Raiân than of that of the Fayûm. In the Wadi Raiân, Nile deposit has _not_ been found, though eagerly looked for. I think this fact is fatal to Mr. Cope Whitehouse’s theory of a _direct_ communication between the Wadi Raiân and the Nile or Bahr Yûsuf. Dr. Schweinfurth thus expresses his views as regards fresh-water deposit in the Wadi Raiân:—“The basin (Wadi Raiân) exists, but it comes from geological time, does not belong to the Nile, and offers nowhere in its tracts at some distance from the Fayûm any trace of a fresh-water formation. . . . “The traces of a settlement of water and layers of Nile earth which are said to exist in some parts of the depression are certainly absent. The grey clay-layers of the old sea with shells of fresh water, innumerable fish vertebras, bones of tortoises, &c., are not to be overlooked where they exist. I could prove such fresh-water formations on the road from Talît over Raiân and Medinet-el-Bahrl (27 kilometres to the west of the actual lake) only at a distance of 8 kilometres from the lake (Birket-el-Qurûn). The yellow Eocene marls with stripes of erosion, results of the wind, moving sand, and of periodical rains, are not to be confounded with these lake formations. A man who does that will find traces of old water and Nile earth everywhere in the deserts of Egypt.” Later on in the same letter he says that the question, whether fresh-water formations exist in the basin of Raiân or not, is to be answered in the negative. But supposing an _indirect_ communication with the Nile by way of the Fayûm Lake, it is easy to understand that no Nile deposit would be found in the Wadi Raiân, even if it had been thus repeatedly filled, because the top water only would begin to spill over into it after the Fayûm Lake level had risen above R.L. 26·00, and after the water had travelled at an extremely low velocity to a long distance from the point, at which it first spread itself out in the Fayûm Basin. But I regret, for the sake of Mr. Cope Whitehouse’s feelings, that even this cannot be admitted to have taken place, for in every situation where Nile water has been, fresh-water shells of distinct species are always found, and their total absence in the Wadi Raiân is sufficient proof to geologists that Nile water has never been there.