155 m. on the
shore of the Mediterranean between Alexandria on the west and Port
Said on the east. The low sandy shore of the Delta, slowly increasing
by the annual deposit of silt by the river, is mostly a barren area of
sand-hills and salty waste land. This is the region of the lagoons and
marshes immediately behind the coast-line. Southwards the quality of
the soil rapidly improves, and becomes the most fertile part of Egypt.
This area is watered by the Damietta and the Rosetta branches of the
Nile, and by a network of canals. The soil of the Delta is a dark grey
fine sandy soil, becoming at times almost a stiff clay by reason of
the fineness of its particles, which consist almost wholly of
extremely small grains of quartz with a few other minerals, and often
numerous flakes of mica. This deposit varies in thickness, as a rule,
from 55 to 70 ft., at which depth it is underlain by a series of
coarse and fine yellow quartz sands, with occasional pebbles, or even
banks of gravel, while here and there thin beds of clay occur. These
sand-beds are sharply distinguished by their colour from the overlying
Nile deposit, and are of considerable thickness. A boring made in 1886
for the Royal Society at Zagazig attained a depth of 375 ft. without
reaching rock, and another, subsequently sunk near Lake Aboukir (close
to Alexandria), reached a depth of 405 ft. with the same result.
Numerous other borings to depths of 100 to 200 ft. have given similar
results, showing the Nile deposit to rest generally on these yellow
sands, which provide a constant though not a very large supply of good
water; near the northern limits of the Delta this cannot, however, be
depended on, since the well water at these depths has proved on
several occasions to be salt. The surface of the Delta is a wide
alluvial plain sloping gently towards the sea, and having an altitude
of 29 ft. above it at its southern extremity. Its limits east and west
are determined by the higher ground of the deserts, to which the
silt-laden waters of the Nile in flood time cannot reach. This silt
consists largely of alumina (about 48%) and calcium carbonate (18%)
with smaller quantities of silica, oxide of iron and carbon. Although
the Nile water is abundantly charged with alluvium, the annual deposit
by the river, except under extraordinary circumstances, is smaller
than might be supposed. The mean ordinary