Page:Africa by Élisée Reclus, Volume 1.djvu/89

 over a lofty granite ledge. The desert east of the rapids is intersected by an old branch of the river running at several yards above the present high-water level. Even the most superficial observer of natural phenomena cannot fail to perceive that he is travelling in a now abandoned watercourse. Ho still perceives the windings of the stream between rocks covered with hieroglyphic inscriptions; he observes its old cliffs and banks, and here and there the alluvia are still revealed under the billows of sand drifting before the winds from the desert. The records deciphered by archaeologists describe the march of armies along this old river bod, from the times of Thotmes and Rameses down to the present day. According to the observations made by Lepsius at Semne above the second cataract, it is probable that, from the beginning of Egyptian history, this dried-up channel was once flooded by a branch of the Nile. During the reign of Amenemha III., some 4,700 years ago, the watermarks engraved on the rocks at this place show that the flood level exceeded by many yards that of the present time: the highest watermark exceeds by 25 feet, the lowest by 13 feet, the corresponding levels of modem days. On the right bank of the Hannek cataract also M. de Gottberg has found alluvial deposits 10 feet above the level of the highest modem floods. May not the waters have been thus arrested by the cataracts, and forced to flow into the now dried-up valley which serves as a highway between Egypt and Nubia? Above the Batn-el-Hagur rapids are to be seen many tracts formerly cultivated but now quite sterile, since the waters of the floods no longer reach them. Like all river valleys whose beds are regulated by the action of running waters, that of the Nile establishes its equilibrium by falling in Nubia and again rising in Lower Egypt. M. de Gottberg accoimts for the lowering of the water- level in Nubia through the disappearance of cataracts formerly existing between "Wadi-Halfa and Asuan, traces of which are still visible. The rocks forming these cataracts consist of schists, which, unlike the crystalline reefs, yielded to the destructive force of the stream. The granite rocks themselves also yield to the same action, but much more gradually. Below the granite ledge washed by the waters of the first cataract, the cliffs lining the river bank are composed of layers of sandstone, succeeded farther on by limestone rocks. Historic Egypt begins at the foot of this rocky barrier, which is covered on either side by tertiary deposits. North of Asuan the banks of the river are at first separated only by a space of from two to three miles. The fields and plants hemmed in between the escarpments and the stream present on either side nothing but a narrow strip of verdure winding along the foot of the grey or yellow rocks, which glitter like burnished gold in the sun. The cultivated zone lies chiefly to the west, along the so-called "Libyan" bank, which is most exposed to the solar rays. Like most other rivers of the northern hemisphere, the Nile bears chiefly towards its right bank, the current skirting the foot of the rocks, which at some points rise sheer above the stream. The towns stand mostly on the left bank.