If the surplus of water upon the Abyssinian mountains had been constant
and uniform, the stream, in its passage across the desert, would have
communicated very little fertility to the barren sands which it
traversed. The immediate banks of the river would have, perhaps, been
fringed with verdure, but the influence of the irrigation would have
extended no farther than the water itself could have reached, by
percolation through the sand. But the flow of the water is not thus
uniform and steady. In a certain season of the year the rains are
incessant, and they descend with such abundance and profusion as almost
to inundate the districts where they fall. Immense torrents stream down
the mountain sides; the valleys are deluged; plains turn into morasses,
and morasses into lakes. In a word, the country becomes half submerged,
and the accumulated mass of waters would rush with great force and
violence down the central valley of the desert, which forms their only
outlet, if the passage were narrow, and if it made any considerable
descent in its course to the sea. It is, however, not narrow, and the
descent is very small. The depression in the surface of the desert,
through which the water flows, is from five to ten miles wide, and,
though it is nearly two thousand miles from the rainy district across
the desert to the sea, the country for the whole distance is almost
level. There is only sufficient descent, especially for the last
thousand miles, to determine a very gentle current to the northward in
the waters of the stream.

Under these circumstances, the immense quantity of water which falls in
the rainy district in these inundating tropical showers, expands over
the whole valley, and forms for a time an immense lake, extending in
length across the whole breadth of the desert. This lake is, of course,
from five to ten miles wide, and a thousand miles long. The water in it
is shallow and turbid, and it has a gentle current toward the north. The
rains, at length, in a great measure cease; but it requires some months
for the water to run off and leave the valley dry. As soon as it is
gone, there springs up from the whole surface of the ground which has
been thus submerged a most rank and luxuriant vegetation.

This vegetation, now wholly regulated and controlled by the hand of man,
must have been, in its original and primeval state, of a very peculiar
character. It must have consisted of such plants only as could exist
under the condition of having the soil in Which they grew laid, for a
quarter of the year, wholly under water. This circumstance, probably,
prevented the valley of the Nile from having been, like other fertile
tracts of land, encumbered, in its native state, with forests. For the
same reason, wild beasts could never have haunted it. There were no
forests to shelter them, and no refuge or retreat for them but the dry
and barren desert, during the period of the annual inundations. This
most extraordinary valley seems thus to have been formed and preserved
by Nature herself for the special possession of man. She herself seems
to have held it in reserve for him from the very morning of creation,
refusing admission into it to every plant and every animal that might
hinder or disturb his occupancy and control. And if he were to abandon
it now for a thousand years, and then return to it once more, he would
find it just as he left it, ready for his immediate possession. There
would be no wild beasts that he must first expel, and no tangled forests
would have sprung up, that his ax must first remove. Nature is the
husbandman who keeps this garden of the world in order, and the means
and machinery by which she operates are the grand evaporating surfaces
of the seas, the beams of the tropical sun, the lofty summits of the
Abyssinian Mountains, and, as the product and result of all this
instrumentality, great periodical inundations of summer rain.

[...]
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Флеш игры стройка.