Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/730

706 E G Y P T [THE NILE. it assumes a green colour for more than a fortnight, owing to the quantity of vegetable matter which it brings down from its upper course. It then resumes its turbid character for the period of the rise, and retains it, though in a less degree, for the remaining portion of the year, until the following midsummer. The water is extremely sweet, particularly in its turbid state. A careful nitration destroys its peculiar flavour, and the best method is to allow it to settle in the porous jars manufactured in the country. It is very wholesome, except during the short period at which it is green. The turbid appearance, great est during the rise and inundation, is owing to the presence of large quantities of earthy matter, which are annually deposited. This deposit or mud of the Nile has been analyzed by M. Regnault. The specimen was dry, and taken from a canal which conducted the waters of the iiuui- datioii. lie obtained the following results : Water -11 Carbon ...: -09 Oxide of iron "06 Silica -04 Carbonate of magnesia 04 Carbonate of lime 18 Alumeii 48 1. Regnault remarks that the quantities of silica and alumen vary according to the places whence the mud is taken, and that on the banks of the Nile it contains much sand, but when carried by the waters of the inundation to distant tracts it loses a quantity of sand in propor tion to the distance, so that, when the distance is very con siderable, the argillaceous matter is nearly pure ; and thus the soil presents this matter in the different degrees of purity which the arts of pottery and brick-making require (Dexcr. de I Effypte, xx. 162-164). The Nile shows the first signs of rising in Egypt about the time of the summer solstice. At Khartoom, where the White and Blue Niles join, the beginning of the increase is observed early in April (Clot-Bey, Aper^u, i. p. 36, 37). The slowness of the rise in the earlier stage causes this difference. Usually the regular increase does not begin in Egypt until some days after the summer solstice, and the inundation begins about two months after that solstice. The river attains its greatest height at, or not long after, the autumnal equinox, and then, falling more slowly than it had risen, sinks to its lowest point at the end of nine months, when it remains stationary for a few days, until it begins again to increase. The inundation continues rather longer than it naturally would do, because the waters are retained for some time upon the lands by closing the mouths of the canals (see the table, Descr. de I Efjypte, xviii. i. 630, seqq., for the details of the state of the Nile, from July 2, 1799, to April 10, 1800). The river s banks being a little higher than the rest of the cultivable soil, the water is conveyed by canals or cuttings, and does not pour over the banks. The inundations vary considerably, and, by either failing or rising to too great a height, cause much damage and distress. In the Description de VEijypte (xviii. i. 626-629) there is a table of 66 inundations, of which 11 were very high, 30 good, 16 feeble, and 9 insufficient. This table was taken from the official records of the Nilometer on the island of Er-R6dah, near Cairo, and comprehends the in undations of A.II. 1150-1215 (A.D. 1737-1800). The Nile rises about 40 feet at the First Cataract, about 36 at Thebes, about 25 at Cairo, and about 4 at the llosetta and Danu etta mouths during a good inundation (Englishwoman in Egypt, i. 89; Descr. de CEyypte, xviii. i. 576, 577). When it is said, however, that the river has attained to a certain height in feet or cubits, the height at the Nilometer of Er-lloduh above-meiitkmed is meant; and by ancient writers, that of the river at Memphis, which was situate on the western bank, a little higher than Er- Rodah. If the river do not attain a greater height than 18 or 20 feet, the rise is scanty ; if only 2 or 4 feet more, insufficient; if it attain to 24 feet, or a greater height, not exceeding 27 feet, the inundation is good ; but a higber rise must be characterized as a destructive flood (Descr. de iEr/ypte, xviii. i. 616). Sometimes the inundation has failed altogether ; as for seven years (A.M. 457-464) in the reign of the Fatimee caliph El-Mustansir bi-llah, when there was a seven-years famine (see below, page 752); and low inundations always cause dearths. Excessive inundations, on the other hand, produce, or at least foster, the plague and murrain ; so that a variation of a few feet is productive of the most serious consequences. The current, when the Nile is low, has been estimated at about 2 miles in the hour, and at about 3 miles an hour when it is high. The volume of water which the Nile pours into the Mediterranean in 24 hours is as follows, according to M. Linant: Cubic Metres. by the Kosetta Branch, 79,532,551,728 by the Damietta Branch, 71,033,810,040 150,566,392,368 . . ,, , . , ,.-., I by the Rosetta Branch, 478,317,838,960 During the high Sale, ) b j. thc VauntM* Branch, 227,196! 8^ 480 .During tlie low Kile, 705,514,667,440 -(Clot-Bey, Apergu, i. 41). Although the water is abundantly charged with alluvium throughout the year, and especially during the inunda tion, the annual deposit by the river, except under extra ordinary circumstances, is very much smaller than might be supposed. Various computations have been made as to the exact deposit left in a century on the land, but they have not usually differed above an inch. If, however, we com pare the quantity of deposit on certain very ancient struc tures, of which we know the date, we shall find that the amount has materially differed in various places. Such dif ferences are the natural results of irregularities in the river s course, of the strength or weakness of the current at parti cular places, of the nature of the country, and many other disturbing causes. The mean ordinary rate of the increase of the soil of Egypt has been calculated by Mr Lane as about k inches in a century. M. Girard, in the Descr. de rEgypte, makes it "very nearly" 126 millimetres, or 4 960 English inches. (For a remarkable instance of rapid deposit, see the Englishwoman in Egypt, i. 132-134, and plan, p. 126.) The cultivable land of Egypt must be regarded as wholly the deposit of the Nile, but it is vain to attempt a calcula tion of the period at which this process began, since we cannot conclude that the same rate has always obtained, and we must suppose that the causes at first in operation were very different from those which now regulate the phenomenon. At the time of the French occupation of Egypt it was found that the cultivable soil occupied only 6921 square miles, or somewhat more than two-thirds of the whole spuco included between the deserts; but the quantity actually under cultivation did not exceed 5500 square miles, or six- elevenths of the entire surface. This proportion has since not materially changed. It was not always so, and the deficiency of the population is the principal cause that so large a proportion of the soil which might possibly bo brought into a state of culture is left uncultivated. Throughout Egypt the cultivable soil does not present any very great difference, being always the deposit of the river; it contains, however, more sand near the river than

at a distance from it. Towards the Mediterranean, its