* 
: 
F 
r, 
a 
if 
bs Vi le Re Bs 4 a er yay 
NEWBOLD ON THE GEOLOGY OF EGYPT. 348 
Andreossy, who states* that, after they cease to blow, the sea falls 
back, leaving a shore of about 200 metres wholly uncovered. 
The mud of the delta has been found to imbed human bones at 
considerable depths, remains of persons drowned in the extraordinarily 
high inundations to which the Nile has always been occasionally sub- 
ject. These remains would have been of less rare occurrence had it 
not been a law+ among the ancient Egyptians to take up, embalm, 
and inter the bodies of individuals drowned, and cast up by the Nile. 
Near the mouths of the Nile the alluvium is mingled with marine 
sand, and imbeds existing shells of the Mediterranean with terrestrial 
and fluviatile testacea. Rolled pebbles, but of small size, derived 
chiefly from the plutonic and igneous rocks,-—jaspers, agates, &c.,— 
are found in it in Upper Evypt. 
The finer kind of the mud of the Nile, for instance that of Ghen- 
nah, is, generally speaking, of a dark brown colour passing to lighter 
shades, highly tenacious and retentive of moisture, for which it has 
a great affinity ; it effervesces with acids, and fuses per se with gaseous 
extrication into a greenish glass. It is deposited in regularly stratified, 
annual layers, varying from an inch to a few lines in thickness in the 
same situation. ‘The upper part of each layer is of a lighter colour 
in general than the lower, and each layer is separable from that im- 
mediately above or below it. Exposed to the calorific action of the 
sun’s rays, the surface-layers separate horizontally and peal off in 
curling lamine, and the contracted mass is intersected by deep ver- 
tical fissures, which divide the superficies into shapes usually re- 
sembling the hexagon or pentagon. A similar phenomenon is pre- 
sented by the Indian Regur, or black cotton soil. According to 
Ehrenberg, the mud of the Nile contains an immense number of 
animalcules. 
Thickness of Nile Mud.—I am not aware that the thickness of 
the deposit in the centre of the river’s bed has actually been ascer- 
tained ; but I have measured cliffs of it overhanging the Nile at low 
water, in Upper Egypt, at 40 feet above the water’s level; m Middle 
Egypt they average 30, and at the apex of the delta 18 feet. Sir 
G. Wilkinson{ found that in Upper Egypt, at Elephantine, the de- 
posit had increased, during the last 1700 years, 9 feet ; at Thebes} 
7 feet; at Heliopolis, in Central Egypt, 5 feet 10 mches, diminish- 
ing in a more rapid ratio towards the delta and Mediterranean: it 
appears evident therefore that, as a general rule, the deposit is 
thickest i Upper Egypt. It must however be remarked that, at 
particular places where the stream is retarded by the flatness of 
the country, or from other causes, the deposition is greater than at 
other localities. The deposition of one year is frequently stripped off 
by the flood of the next ; the amount of one year’s deposition varies 
from that of another, while the shifting of the river’s bed from time 
to time renders this fluctuation of amount of deposit still greater, and 
* Memoirs relative to Egypt, p. 200. 
t+ Herod. Euterpe, 90. 
¢ Journal of Royal Geograph. Soc. of London, vol. ix. p. 332. 
2cG2 
