MR. HORNER ON THE ALLUVIAL LAND OF EGYPT, 
131 
Besides the above samples, I, to XVII., Hekekyan Bey distinguishes in his sections 
of the pits layers of soils which are mixtures of the above varieties ; thus we have 
No. 
Nature of the soil. 
XVIII. 
A mixture of black mud with clay, as if they were kneaded together. 
XIX. 
A mixture of compact black mud, clay and river-sand in nearly equal quantities. 
XX. 
Nearly equal proportions of compact black mud, river-sand and fine rubbish. 
XXI. 
River-sand mixed with a little black mud. 
It will be seen that in all the excavations the downward progress was interrupted 
by filtration water. This is mainly derived from the Nile, but occasionally from side 
torrents after rain. As the river rises, the level of the water absorbed by the soil on 
its banks does not keep pace with the rise, for the water takes time to spread late- 
rally, according as the soil is more or less pervious ; and should its descent be im- 
peded by a compact layer, it will continue to spread until it is exhausted at a con- 
siderable distance from the river. When the Nile falls, that portion of the filtration 
water which has not penetrated the soil to a depth below the river’s ebb level, 
returns into the channel ; but the amount returned will also depend upon the more 
or less pervious nature of the soil ; and when retained by a compact layer, it will 
remain for some time at a higher level than the falling surface of the Nile. 
Excavation A. 
Ten men were set to work at this spot. A trench was commenced from a point 
opposite to and 40 feet distant from the north face of the obelisk, and carried 
southwards, descending by steps, so as to form an inclined plane downwards. In 
two days the upper surface of a red sandstone block was reached, being the 
pedestal upon which the granite obelisk immediately rests. The upper surface of 
this block was 5 feet 6 inches below the surface of the ground immediately round 
the obelisk. 
A trench was opened opposite to the southern face of the obelisk, 35 feet distant 
from it, and when carried forward laid bare the pedestal to a depth of 4^ feet from 
its upper surfaee. The filtration water having been reached, it was baled out, and 
it was diseovered that the pedestal rests iinmediately on two layers composed of 
several bloeks of limestone, and under the lower of these white sand was found. The 
pedestal is 6 feet 10| inches in height; the first layer of limestone on which it rests 
is 1 foot 4 inehes, the lower layer 1 foot 3 inches in thickness. The limestone is 
the nummulite limestone of the country ; the sandstone of the pedestal is identical 
with that of the neighbouring hill, Gebel Achmar, that is, the upper sandstone in an 
indurated state. 
An iron bar, 16 feet long and inch in diameter, was worked perpendicularly by 
