Egypt : handbook for travellers / edited by K. Baedeker.

Date:
1885-1892
Catalogue details

Licence: Public Domain Mark

Credit: Egypt : handbook for travellers / edited by K. Baedeker. Source: Wellcome Collection.

    81/628 (page 57)
    Egypt. The breadth of the cultivable alluvial soil corresponds with the above varying width, but nowhere exceeds 9 miles. The soil deposited by the Nile averages 33-38 ft. deep in Egypt, but near Kalyub at the head of the Delta it increases to about 50 ft., the bottom of it being at places below the level of the sea. The bed of the river is also of considerable depth, and at low water the mud- banks (gef) rise above its surface to a height of 25 ft. in Upper Egypt, and 14 ft. at Cairo. These are also the depths of the various irrigation wells. ‘Throughout the whole (?) of Egypt the Nile mud rests on a hed of sea- sand. The whole country between the first, cataract and the Mediter- ranean was formerly a narrow estuary, which was probably filled by degrees during the pleiocene period with lagoon deposits, washed down from the crystalline Habesh. At a later period, when Egypt had risen from the sea (and after the isthmus had been formed), the river forced its passage through these deposits of mud, sweeping away many of the loose particles at one place and depositing them again farther down’. (Fraas.) The Nile soil is unlike any other in the world in its composi- tion. According to Regnault it contains 63 per cent of water and sand, 18 per cent of carbonate of lime , 9 per cent of quartz, silica, felspar, hornblende, and epidote , 6 per cent of oxide of iron, and 4 per cent of carbonate of magnesia. Nothing certain is known regarding the average increase of the alluvial land, all the calculations regarding it having hitherto been based on erroneous or insufficient data. Thus the Nilometer of antiquity furnishes the depth relatively to the level of the sea, but not absolutely. The thickness of earth accumulated around buildings of known age has also been found a fallacious guide; and lastly local measurements lead to no result, as the river often capriciously washes away what it has deposited in previous years. An approxi- mate calculation might possibly be made if the proportion of solid matter annually brought down by the river could be ascertained, but no investigation of this kind has ever been made. It has some- times been asserted that the desert has begun to encroach upon the cultivated part of the valley, but Sir G. Wilkinson has shown, that, while the sand of the desert may be advancing at places, the cultiv- able bed of the valley is steadily increasing in thickness and width. The Inundation , as is obvious from what has already been said, is more or less favourable according to the greater or less amount of rain that falls among the Abyssinian mountains, for that which falls in Central Africa is a more constant quantity, being regulated by the influence of the trade-winds. Like the waterspouts which descend on equatorial Africa, the overflow al- ways recurs at the same season of the year, varying in its advent by a few7 days only, and in its depth by several yards. At the be- ginning of June the river slowly begins to swell, and between the 15th and 20th of July the increase becomes very rapid. Towards the end of September the water ceases to rise, remaining at the same height for a fortnight or more, but during the first half of October it rises again and attains its highest level (comp. p. 239). After