Egypt is a valley bounded on the right and left by very rugged mountains; it must, therefore, occur to any one that the Nile, being a torrent falling from very high ground in Ethiopia, were this valley concave, the violent rapidity, or motion, would be much likelier to carry away mud and soil, than to leave it behind in a state to accumulate.
The land of Egypt slopes gently from the middle of the valley to the foot of the mountains on each side, so that the center is really the highest part of the valley, and in the middle of this runs the Nile[140]. At right angles with the stream large trenches are cut to the foot of the mountains, in which canals the water enters, and insensibly flows down to the end of these trenches, where it diffuses itself over the level ground.
As the river swells, these canals fill with water, which goes seeking a level to the foot of the mountains; so that now the flood, which begins to restagnate towards the bank of the river, acquires no motion, as the calishes are formed at right angles to the stream. Sometimes, indeed, the river is so high, when the rains in Ethiopia are excessive, that the back-water joins the current of the Nile, when immediately it communicates its motion to the stagnant water, and sweeps away every thing that is planted into the sea. It is a mistake then to assert,—the fuller the Nile, the better for Egypt.
It has been said by various authors, that it was necessary Egypt should be measured every year, on account of the quantity of mud which the Nile brought down by its inundation, which so covered the land-marks, that no proprietor knew or could discover the limits of his own farm, and that this annual necessity first gave rise to the science of Geometry[141]. How or when Geometry was first known and practised, is not my business in this place to inquire, though I think the origin here given is a very probable one. The land of Egypt was certainly measured annually: it is as certainly so at this very time; and if so, the present reason for this is probably the very one which first gave rise to it; but that this is not owing to the mud of the Nile, will appear on the slightest consideration; for if Egypt increase a foot in a hundred years, one year’s increase of soil could be but the one hundredth part of a foot, which could hide no land-mark whatever; and we see to this day those in Egypt were huge blocks of granite often with gigantic heads at the end of them; which the Nile, at the rate Herodotus fixes, of a foot in 100 years, as being added to the soil, would not cover in several thousand years.
It is absurd to suppose that the Nile is to bring down an equal quantity of soil every year from the mountains of Abyssinia; whatever was the case at first when this river began to flow, we are sure now, that almost every river and brook in Abyssinia runs in a bed of hard stone, the earth having been long removed; and the rivers now cannot furnish from their rocky beds what they first did from their earthy bottoms, when Egypt was supposed, according to Herodotus, to have its foundation laid in the floods; and therefore, on the first consideration, this annual and equal increase must be impossible.
At Basboch, before the Nile enters Sennaar, I made several hundred trials upon its sediment, as it then came down from the cultivated country of Abyssinia; I thereby found this sediment surprisingly small, being a mixture of fat earth, and a small quantity of sand. At the junction of the Nile and Astaboras I did the same, taking up the water from the middle of the stream, and, having evaporated it afterwards, I found little more sediment than at Sennaar; the water was indeed whiter, and the greatest part of the sediment was sand. I repeated this experiment at Syené with the utmost attention, where the Nile leaves Nubia, and enters Egypt, and I found the quantity of sediment fully nine times increased from what it was at Sennaar, and in it only a trifle of black earth, all the rest being sand. The experiment at Rosetto was not so often repeated as the others; but the result was, that, in the strength of the inundation, the sediment consisted mostly of sand, and, towards the end, was much the greater part of earth. I think these experiments conclusive, as neither the Nile coming fresh from Abyssinia, nor the Atbara, though joined by the Mareb, likewise from the same country, brought any great quantity of soil from thence.
It was at Syené that the water should have been most charged with mud, for all the accession it was to bring to Egypt was then in its stream; but there the chief part of the sediment was sand, fanned and ventilated with perpetual hot winds, and spread on the surface of the burning desert, never refreshed with the dew of heaven. In that dreary desert, between Gooz and Syene, we saw huge pillars of this light sand; their base in the earth, and heads in the clouds, crossing the wide expanse in various directions, and, upon its becoming calm in the evening, falling to pieces, and burying themselves in the Nile, with whose stream they mixed like an impalpable powder, and were hurried down the river, to compose the many sandy islands we see in the course of it.
It seems to be an established fact, that water of every sort, fresh and salt, that of rivers, and what is stagnant, has from early times sensibly diminished through the whole world; if then the land of Egypt has been continually rising every year, while the quantity of water that was to cover it has become less, or at least not increased, dearth in these latter years must have been frequent in Egypt, for want of the Nile’s rising to a proper height; but this is so far from being the case, that, in these last 34 years[142], there has not been one season of scarcity from the lowness of the Nile, although the rise having been too great, and the waters too abundant, have thrice in that time occasioned famine by carrying away the millet.
If the land of Egypt increased (as Herodotus says) one foot in 100 years, this addition must have appeared in the most ancient public monuments: now, the very base of all the obelisks in Upper Egypt, are bare and visible, and even the paved plane, laid visibly on purpose to receive the Gnomonical shade, is not covered, nor scarcely out of its level, and these small deviations are apparently owing to the falling of neighbouring buildings. There are in the plain, immediately before Thebes, two Colossal statues[143], obviously designed for Nilometers, covered with hieroglyphics, as well as more modern inscriptions; these statues are uncovered to the lowest part of their base; whereas we should have now been walking on ground nearly equal in height to their heads. The same may be said of every public monument, if there had been any truth in the surface of Egypt increasing a foot in a hundred years.
It appears, at least as far as Hadrian’s time, that if the pecus of the Greeks be the peek of the present Egyptians, the same quantity of water overflowed Egypt as now.