ABSTRACT
Aswan (Syene), but now the term Egypt includes that portion of the Nile valley which lies between the Mediterranean and WadI I;Ialfa, l.e., between 220 and 31° 30' N. latitude. According to Major H. G. Lyons, * DirectorGeneral of Surveys of Egypt, the country consists chiefly of a series of sedimentary deposits of Cretaceous and Tertiary ages, which have been laid down upon the uneven and eroded surface of a great mass of crystalline rocks, which come to the surface on the edge of the eastern desert and also cover large areas of it. The direction of the Nile Valley is generally north and south, and is due to the great earth movements which took place in Miocene times; indeed, the Nile Valley itself has been determined by a line of fracture which is traceable from the sea nearly to the First Cataract. Into this valley in late Miocene or early Pliocene times the sea penetrated at least as far as Esneh, and laid down thick deposits of sand and gravel on the floor of the valley and up to the foot of the cliffs bounding it, while the tributary streams, fed hy a rainfall much heavier than that of to-day, brought down masses of detritus from the limestone plateaux and piled them up along the margins of the valley. A subsequent rise of the area converted this c, fiord" into a river valley, and the deposition of the Nile mud and the formation of cultivable land began. The crystalline rocks occur at Aswan, Kalabsheh, Wadi l:lalfa, and other points further south, forming cataracts and gorges. East and north-east of J}.eneh
their base is a gneiss, overlaid by mica, talc, and chlorite schists, and above these is a thick volcanic series, into which intrudes a gray hornblendic granite, and also a later red granite. The best known of these is the red hornblendic granite of Aswin, which was largely used by the Egyptians for temples, statues, etc., and also the fine porphyry, much used by the Roman emperors. The tops of such rocks rise to the surface of the ground at Aswin, Kalibsheh, and Widi I:Jalfa. In Nubia nearly the whole of the eroded surface of the crystalline rocks has been overlaid by a yellowish sandston!:, which at its base usually becomes a quartz conglomerate. Above these lies a large series of green and gray clays with thick band of soft white limestone. N ext comes an immense thickness of soft white limestone, which forms the cliffs of the Nile Valley from Luxor to Cairo, and furnishes almost the whole of the building stone in Egypt. These strata have been greatly affected by the great earth movements of the Miocene period, which resulted in the formation of the Red Sea, Gulf of Suez, Gulf of Aqaba, the Jordan Vallty, and the Nile Valley, and the salts of the Widi Natrun are due to the shore lagunes when they existed there. As a result of this, thick deposits of sand and gravel were laid down. which to-day underlie the later Nile mud deposits and which furnish a good water supply. After this, climatic conditions analogous to those of to-day seem to have soon set in, and river deposits of dark sandy mud were laid down, which were at levels considerably above the deposits of to-day. Nile mud with shells similar to those now existing occurs in Nubia at 30 metres, and in Egypt at lesser heights, above the present Nile flood level. To-day the Nile is depositing in its bed at the rate of about 0'12 metre per century. At Benha, Mal)allat Rft1,l (in the Tanta district), and I$.alyo.b (all in the Delta), the thickness of the layer of Nile mud is 17, 18, and 12'5 metres respectively; while at Za~azi~, Beni SuwH,
and Suhig (all in the Nile Valley), it is 33'1 I and 17 metres respectively. Between the First and Second Cataracts the proportion of sandstone to granite is about 9 to J, and good granite is only met with at Kalibsheh, where the pass is about 168 yards wide, and the depth of water at loZIJ Nile about 1 I I feet. No fossils whatever are found in the Nubian sandstone. From Abu Simbel northwards the valley is hounded on the left by the high limestone plateau called by the l\rabs Sinn al-Kiddab, which, at this point, is more than 50 miles distant from the river, and it gradually approaches the stream until at Aswin it is only 25 miles distant, and at Gebelen it marches with the river. There is a similar plateau between Gebelen and Esneh. At the First Cataract there is an extensive outcrop of granite and quartz diorite. Between Aswin and a little south of Esneh the river flows between sandstone hills, except at the plains of Kom Ombos and Edru; these plains were originally ancient tleit'ls of rivers coming down from the high ranges which skilt tl}e Red Sea. In the Kom Ombos plain the Nile deposit is about 80 feet above the maximum flood level of to-day. At Ra'amah, about 38 miles north of Aswan, limestone is met with, and immediately north of it is the sandstone of Silsileh. The channel at Silsileh does not represent the original bed of the Nile, for it is only a branch of it; the true channel, which was nearly a mile wide and 50 feet deep, lies on the right of the hill in which the quarries are, and is now lJuried under mud and silt. There was never a cataract at Silsileh. At Luxor the Nile again enters low denuded plains, and a part of the plateau of the Sinn al-Kiddab lies on its left; the plateau again appears at ~eneh, and from this place to Cairo the river flows between limestone hills. At ~eneh the lower Londinian formation dips helow the level of the Nile deposit, and the upper Londinian formation monopolises the whole section of the limestone as far as a point midway
between Asyftt and l\1inyeh; here the lower Parisian strata appear on the tops of the plateaux, and the upper Londinian strata finally disappear a little to the north of Minyeh. The lower Parisian formation is now generally met with as far as Cairo.
