, just above where the
branches which form the mouths of the Nile separate from the main
stream. All that part of Egypt is flat country, having been formed by
the deposits brought down by the Nile. Such land is called _alluvial_;
it is always level, and, as it consists of successive deposits from
the turbid waters of the river, made in the successive inundations, it
forms always a very rich soil, deep and inexhaustible, and is, of
course, extremely fertile. Egypt has been celebrated for its
unexampled fertility from the earliest times. It waves with fields of
corn and grain, and is adorned with groves of the most luxuriant
growth and richest verdure.

It is only, however, so far as the land is formed by the deposits of
the Nile, that this scene of verdure and beauty extends. On the east
it is bounded by ranges of barren and rocky hills, and on the west by
vast deserts, consisting of moving sands, from which no animal or
vegetable life can derive the means of existence. The reason of this
sterility seems to be the absence of water. The geological formation
of the land is such that it furnishes few springs of water, and no
streams, and in that climate it seldom or never rains. If there is
water, the most barren sands will clothe themselves with some species
of vegetation, which, in its decay, will form a soil that will nourish
more and more fully each succeeding generation of plants. But in the
absence of water, any surface of earth will soon become a barren sand.
The wind will drive away every thing imponderable, leaving only the
heavy sands, to drift in storms, like fields of snow.

Among these African deserts, however, there are some fertile spots.
They are occasioned by springs which arise in little dells, and which
saturate the ground with moisture for some distance around them. The
water from these springs flows for some distance, in many cases, in a
little stream, before it is finally lost and absorbed in the sands.
The whole tract under the influence of this irrigation clothes itself
with verdure. Trees grow up to shade it. It forms a spot whose
beauty, absolutely great, is heightened by the contrast which it
presents to the gloomy and desolate desert by which it is surrounded.
Such a green spot in the desert is called an Oasis. They are the
resort and the refuge of the traveler and the pilgrim, who seek
shelter and repose upon them in their weary journeys over the
trackless wilds.

Nor must it be supposed tha