Page:The American Cyclopædia (1879) Volume XII.djvu/466

452 NILE branches, of which only three appear to have been of much size, the Pelusiac or eastern arm, the Oanopic or western, and the Sebennytic or middle. The river now enters the Mediter- ranean by two outlets, the Rosettalbranch on the west and the Damietta branch on the east, with their mouths in lat. 31 36' N., sepa- rated from each other by 95 m. of seacoast. The Pelusiac branch is now dry. On the E. side of it, not far from the apex of the delta, was Heliopolis, the On of Scripture, of whose ruins only an obelisk remains. Forty miles lower down was Bubastis; and still lower, near the sea, though its remains are now sev- eral miles inland, was Pelusium, from which the arm derived its name. The ancient Se- bennytic branch had its mouth where the lake of Boorlos now lies. It has been par- tially renewed in a free wide canal, which starts midway between the two modern branches, and continues as far as Tanta, about half way between Cairo and the sea. The Canopic branch is represented by the first Eart of the present Rosetta branch as far as it. 31, whence it turned to the west and entered the sea near the bay of Aboukir. The W. or Rosetta branch is the usual chan- nel of communication between Alexandria and Cairo, and is navigated by small steamers at regular intervals ; it is 1,800 ft. broad, and has in the dry season a depth of about 5 ft. The Damietta branch is 900 ft. wide, and its depth when the river is lowest is about 8 ft. In the ordinary state of its waters the Nile has not depth sufficient for vessels of more than 60 tons burden, but during the height of the inun- dation the depth of water is 40 ft., and large vessels can ascend to Cairo. The river begins to rise as early as April in its upper branches, but not until the latter part of June in Egypt, where it reaches its greatest height between Sept. 20 and 30, when it is usually at Cairo 24 ft. above the low-water level, and at Thebes 36 ft. About the middle of October it begins to fall, and in Egypt is at the lowest about the middle of May. The rise sometimes reaches 30 ft., and the overflow then does great damage ; on the other hand, when it falls short of 18 ft., the harvests fail, and Egypt experiences a famine. Of the 66 inundations between 1735 and 1801, 11 were very high, 30 good, 16 feeble, and 9 insufficient. The water of the river is charged with mud, which it deposits over the cultivated land of Egypt to an average depth of not more than the 20th part of an inch each year. Not- withstanding its turbidness, the water is sweet and wholesome, and is freely drunk by the peo- ple, among whom the saying is proverbial that he who has drunk of the Nile will always long to return and drink of it again. On the island of Rhoddah, near Cairo, is the celebrated nilome- ter for indicating the height of the Nile during the annual inundation. It consists of a square well or chamber, in the centre of which is a graduated pillar, divided into cubits of about 22 in. each. A nilometer existed at Memphis in the times of the Pharaohs, and during the reigns of the Ptolemies there was one at Ili- thyia, and another at Elephantine in the reigns of the early Roman emperors. That at Rhod- dah is attributed to the caliph Amin, who reigned from 809 to 833. During the inunda- tion four criers proclaim every morning in the streets of Cairo the height to which the water has risen. When it has reached 18 cubits the canals are opened and it is allowed to flow over the land. In 1847 the French engineer Linant commenced the construction of a barrage or great dam, just below the apex of the delta, whereby it was intended so to regulate the flow of water as to produce two inundations in a year ; but after 62 beautiful arches had been thrown across the Rosetta branch, the work was abandoned in consequence of the practical difficulties which were encountered. As the extent of the Nile basin is not definitely known, no accurate estimate of its area can be given ; but it may safely be stated as at least 500,000 sq. m. Its approximate length, throughout all its windings, from the limit of steam naviga- tion above Gondokoro, in lat. 4 37' N., is 3,000 m., which gives an average descent in the river of 9 in. per mile. The average fall per mile from Asswan to Cairo, 555 m., is 6-4 in. The additional length of the river between the point we have mentioned and its exit from the Albert N'yanza can scarcely be less than 200 m. According to Lyell, not only the fertility of the alluvial plain above Cairo, but the very existence of the delta below that capital, are due to the power possessed by the Nile of transporting mud from the interior of Africa and depositing it on its inundated plains. The following is the composition of the Nile mud, which is generally found unstratified: silica, 42'50 ; alumina, 24'25 ; carbonate of lime, 3 '85 ; peroxide of iron, 13'65; magnesia, T05; car- bonate of magnesia, 1'20; humic acid, 2'80; water, 10'70. The investigations, conducted under the auspices of the royal society of Eng- land, for the purpose of ascertaining the rate of accumulation, indicate a mean increase of 3 in. in a century; but this result requires verification, especially as there are geological reasons for believing that a slow subsidence of the land in Egypt has taken place within the historic period. The ibis, the hippopotamus, and the crocodile are characteristic animals of the Nile fauna, all frequenting the upper por- tion of the river, though formerly common in the northern latitudes. The lotus and the papy- rus are equally distinctive representatives of the flora. The Nile abounds with fish, among which are large eels, white trout, and a large species of salmon. The course of the White Nile above its junction with the Blue Nile at Khartoom was first explored in 1827 by M. Linant, who ascended the stream as far as El- Ais in lat. 13 23' N. A few years afterward Mehemet Ali, pasha of Egypt, determined to have the river explored to its sources. Accord- ingly, between 1839 and 1842, three expedi-