118 
MR. HORNER ON THE ALLUVIAL LAND OF EGYPT. 
found, whereas the finer and more argillaceous and calcareous portions are held in 
susjDension and carried out laterally by the gently overspreading waters. 
A transverse section of the valley often presents the following appearance. 
Libyan range. 
Fig. 2. 
The Nile. 
Arabian range. 
In the middle we see the Nile, and on both sides of it elevations of the ground like 
two dams. These run parallel to the river and form its banks. Beyond these, the 
ground again sinks and forms depressions, which, for the most part, are deeper than 
the present bed of the river, so that it flows, as it were, on a great dam. The explana- 
tion of this is, that the Nile accumulates more alluvium in its immediate neighbour- 
hood, and this chiefly consists, though not always, of gravel and sand, whereas in 
places more distant, to which the water never reaches except during the inundation, 
or is conducted by canals, less alluvium is deposited ; but as the water remains long 
there in a tranquil state, it lets fall the more fertilizing mud, and thus the land near 
the desert is the most productive. But in some places the banks of the river consist 
of from 23 to 33 feet of pure mud, sometimes divided by layers of sand. In nume- 
rous places, beds of mud may be seen rising from the level of low-water to the sum- 
mit of the bank, and in digging below the lower level, the mud is frequently found 
to be continued*. Newbold found some banks exhibiting what he considered to be 
stratified annual layers, varying from an inch to a few lines in thickness, in the same 
situation, the upper part of each layer being usually of a lighter colour than the 
lower part, and each separable from that immediately above or below it. But, as 
will hereafter be explained, this appearance was local and the effect of a secondary 
cause, and was not produced by the regular annual inundation. 
The height of the banks of the river generally diminishes from Assouan to the 
Delta, and thence in a greater ratio to the mouths of the river, owing to the wider 
extent over which the mud-charged waters spread below the point of the Nile’s bifur- 
cation below Cairo. About the time of the medium rise of the river the banks below 
Thebes are usually from 20 to 30 feet above the surface of the water, at Cairo from 
15 to 25 feet, at Rosetta from 3 to 12 feet. 
The annual deposit is variable in thickness in different parts of Upper Egypt and 
in the Delta from a variety of causes, and that both in the vicinity of the river and 
at a distance from it. In the vicinity of the river, at particular places, where the 
stream is retarded by the comparative flatness of the country, the deposition is 
greater than in other localities. The deposit of one year is in some places stripped 
off by the flood of the next, and the quantity of earthy matter held in suspension in 
the water is sometimes augmented by portions of the mud cliff falling into the river. 
M. Melly, writing from Tahtah on the 3rd of November 1850, says, “ Le Nil est deja 
* Roziere, Description de I’Egypte, vol. xx. 
