The site selected for the great Nile dam was at the head of the First Cataract above Assuan.
There are two important rapids and one cataract on the lower 300 m.
Three and a half miles above the town, at the beginning of the Cataract, the Assuan Dam stretches across the Nile.
But, owing to the cataract, the main route for traffic with the south was by land along the eastern shore.
His sight, however, failed, and in 1811 he had an operation for cataract, which proved unsuccessful.
He considered the horizontal strata of this hyperboloid as always in motion, while the remainder of the water was in a state of rest, and imagined that there was a kind of cataract in the middle of the fluid.
At the cataract) in 30 m, is manifestly a watercourse of very modern origin; for a large river would now have a thoroughly matured valley had it long followed its present course; the same is true of the St Lawrence, which in its several rapids and in its subdivision into many channels at the Thousand Islands, presents every sign of youth.
Assuan (q.v.), pop. 12,618, is at the foot of the First Cataract and 551 m.
Farther south are the stupendous ruins of Thebes on both sides of the river, the temple of Esna, the ruins and tombs of El Kab, the temple of Edfu, the quarries of Silsila and the temple of Ombos, followed by the inscribed rocks of the First Cataract, the tombs and quarries of Assuan and the temples of Philae.
Red granite was obtained from the First Cataract, breccia and diorite were quarried from very early times in the Wadi Hammamat, on the road from Coptos to the Red Sea, and porphyry was brought, chiefly in Roman times but also in the prehistoric age, from the same region at Jebel Dokhn.
Raided south Palestine and Ethiopia, and at Semna beyond the second cataract set up a stela of conquest that in its expressions recalls the stelae of Sesostris in Herodotus: Sesostris may, therefore, be the highly magnified portrait of this Pharaoh.
The auditorium is little less perfect than that of Aspendus and very nearly as large; but the scena wall has collapsed over stage and proscenium in a cataract of loose blocks.
At the Shoshone Falls the river makes a sudden plunge of nearly 200 ft., and the Falls have been compared with the Niagara and Zambezi; a short distance back of the main fall is a cataract of 125 ft., the Bridal Veil.
Long, goes past the cataract region and ends at Stanley Pool, whence the Congo is navigable to Stanley Falls, a distance of 980 m.
And the Nile shall cease to exist from the Lower Cataract downwards."
The natural geographical and ethnical southern frontier of Egypt is the First Cataract; Egyptian scribes of the Old Empire recognized this truth no less clearly than Diocletian, and Juvenal anticipates the verdict of every modern observer when he describes the " porta Syenes " as the gate of Africa.
Similarly while the exploration of the Egyptian colonies south of the First Cataract has added many details to our knowledge of political history, of local cults and provincial organization, yet with one exception it has not affected the known outlines of the history of civilization.
- Ruins of pyramids, temples, churches and other monuments are found along both banks of the Nile almost as far south as the Fourth Cataract, and again in the " Island of Meroe."
Here the Nile narrows and passes the Semna cataract, and graven on the rocks are ancient records of " high Nile."
Opposite Hannek at the Third Cataract on Tombos Island are extensive ancient granite quarries, in one of which lies an unfinished colossus.
Some one throws himself over a cataract or leaps into the crater of a volcano, and immediately a score or two follow.
Alike in volume and in beauty these take a very high place among European waterfalls; the cataract has a total descent of about 650 ft., in three leaps of 65, 330 and 190 ft.
Of these the largest is the cataract of Niagara, about 1 m.
Between the Guaviare and the Meta the Orinoco is obstructed by the famous Maipures cataract, where, in several channels, it breaks.
By the treaty of 1872 the Brazilian frontier was drawn up the Parana from the mouth of the Iguassu or Y-Guazu (25° 30' S.) to the Salto Grande or Great Cataract of La Guayra (24° 7'), thence west along the watershed of the Sierra de Maracayu, north along the Sierra de Ambaya to the sources of the Apa, and down that stream to its junction with the Paraguay.
Above the town is the second cataract, and on the west bank of the Nile opposite Halfa are the ruins of the ancient Egyptian city of Buhen (Bohon).
Deepand Assuan (First Cataract), the course of the river is interrupted by outcrops of granites and other crystalline rocks, which have been uncovered by the, erosion of the overlying sandstone, and to-day form the mass of islands, with numerous small rapids, which are described not very accurately as cataracts; no good evidence exists in support of the view that they are the remains of a massive barrier, broken down and carried away by some sudden convulsion.
Egypt normally included the whole of the Nile valley from the First Cataract to the sea; pure Egyptians, however, formed the population of Lower Nubia above the Cataract in prehistori.c times; at some periods also the land was divided into separate kingdoms, while at others Egypt stretched southward into Nubia, and it generally claimed the neighboring Libyan deserts and oases on the west and the Arabian deserts on the east to the shore of the Red Sea, with Sinai and the Mediterranean coast as far as Rhinocorura (El Arish).
There are the forts and temples above the second cataract at Semna and Kumma.
South of the Cataract, within the Dodecaschoenus) were built under the Ptolemies.
The Napo is navigable for steamboats for some distance above the mouth of the Coca, and thence for canoes as far as the Cando cataract, 3332 ft.
This was the resolution adopted by the Egyptian government to extend the great reservoir at the First Cataract by raising the height of the Aswan dam.
PHILAE, an islet in the Nile above the First Cataract, of great beauty and interest, but since the completion of the Assuan dam in 1902 submerged except for a few months yearly during High Nile (July to October), when the water is allowed to run freely through the sluices of the Assuan dam.
Its lowest one, the Itaboca cataract, is about 130 m.
Here is the great cataract of Itamaraca, which rushes down an inclined plane for 3 m.
Soon after his return to St Petersburg a cataract formed in his left eye, which ultimately deprived him almost entirely of sight.
ASSUAN, or Aswan, a town of Upper Egypt on the east bank of the Nile, facing Elephantine Island below the First Cataract, and 590 m.
By the end of the month the gunboats had surmounted the 4th cataract and reached Abu Hamed.
He considered it necessary to hold Dongola, and he reported that he was distributing this army along the left bank of the Nile, on the open reach of water between the Hannek cataract and Abu Dom, opposite Merawi.
The railway up the right bank of the Nile was continued to Kerma, in order to evade the difficulties of the 3rd cataract; but the sirdar had conceived the bold project of cutting off the great angle of the Nile from Wadi Haifa to Abu Hamed, involving nearly 600 m.
Including the 4th cataract, by constructing a railway across the Nubian desert, and so bringing his base at Wadi Haifa within a few hours of his force, when it should have advanced to Abu Hamed, instead of ten days.
A successful operation for cataract restored his eyesight in June 1900, and notwithstanding his 81 years he resumed to some extent his former political activity.