326 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
Mountains and Valleys.—From the generally horizontal stratifi- 
cation of the rocks covering the greater part of Egypt, it is difficult 
to trace in them any particular lines of elevation. Mural cliffs, as 
has been already observed, flank the valley of the Nile im a northerly 
direction to the vicinity of Cairo, where they deviate severally towards 
the east and west. A similar range of cliffs, though not so abrupt 
in character, flanks both shores of the Red Sea. This formation is 
traversed by. valleys and ravines that cross each other at right angles, 
running nearly north and south and east and west. Through the 
most considerable of the first of these classes of valleys flows the 
Nile ;. while the latter have long formed channels of communication 
and commerce between the valley of the Nile, the Red Sea, and the 
countries to the eastward of it. They are termed Wadis by the 
Arabs, and the deepest of the transverse valleys or ravines, Makna’t, 
or places on which from their depth the sun cannot shine. In the 
eastern desert of Upper Egypt I traced these valleys to an anticlinal 
line running nearly north and south, and caused by plutonic rocks 
rising from the aqueous strata to the height of more than 1000 feet 
above the sea’s level. Their upheaval forms the key to the systems 
of valleys by which Egypt is mtersected, and illustrates forcibly the 
truth of Mr. Hopkins’s observations on the laws of fracture, caused 
by expansive subterranean forces operating on strata under certain. 
conditions. The aqueous deposits, though evincing considerable dis- 
turbance at the junction-line with the plutonic rocks and associated 
hypogene schists, have evidently, from their slightly inclined position 
at a considerable distance from them, been elevated to their present 
position above the ocean’s bed, with no more force and abruptness 
than was necessary to produce in them the fissures by which they 
are intersected ; and it is worthy of remark, that in proportion as the 
strata recover their horizontal position, the fissures become less fre- 
quent, deep and extensive. 
Some of these fissures,—the valley of Kossier for instance, 
which has its origin in a line of dislocation,—appear to have been 
widened by aqueous causes no longer in operation. Others seem 
altogether formed by them, as for instance the Waterless river, the 
Bahr bila Maieh of the Arabs, westward of the delta, and the valley 
separating the petrified wood formation from the Red mountain, or 
Gebel Ahmar, near Cairo, as will be mentioned in a subsequent part 
of this paper when treating of ‘‘ the petrified forest.” The surface 
of these valleys is, for the most part, covered with drifted gravel, 
composed not only of the detritus of rocks in the vicinity, but of 
rolled pebbles of other formations transported from great distances, 
for whose presence the action of existing streams is not adequate to 
account, as these pebbles often rest on ledges and hills much elevated. 
above the general draimage-level. The limestone valley of Kossier, 
near the Red Sea, is covered with a gravel—great part of which 
consists of pebbles from the plutonic rocks and hypogene schists in 
the interior. Few of these pebbles are found near the Nile west of 
the sites of the parent rocks, a fact indicating the easterly course of 
the retiring waters or current which transported them. 
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