INTRODUCTION. 
vii 
stumps of trees of eonsiderable size occur, indicating that in some parts, at least, in 
the neighbourhood of the water the country was wooded. Later, within the historic 
period (XII. Dynasty, beginning about 2778 B.c.*), the lake was converted into an 
artiticially-controllcd reservoir. Lake Mocris, and was employed to regulate the supply 
of water in years of exceptionally high or low Nile floods. At this date, though smaller 
than the earlier Pleistocene lake, the water-covered area was far greater than at the 
present time, indications of its former extent being found in old shore-lines, still 
fringed with the stumps of tamarisk-bushes, and in the ruins of temples and cities 
{e.g. Qasr-el-Sagha). These remains are now separated from the water by miles of 
desert. Later still, probably in Ptolemaic times, the lake ceased to be used as a 
reservoir, and the quantity of water admitted to the Fayum was limited, so far as 
possible, to the amount actually required for the irrigation of the district. The 
consequence of this was that the lake received only such surplus water as drained 
from the cultivated lands, and its level began to fall until, within the last year or two, 
it reached its smallest dimensions. Since then the more abundant supply of water 
resulting from the vast irrigation-works in the Nile Valley has led to a considerable 
area being reclaimed, and the consequent increase in the amount of water draining 
into the lake has brought about a slight rise in its level. 
The cultivated land lies to the south and east of the lake, while on the north the 
desert extends down almost to the water’s edge, from which it is separated by a 
belt of sand-dunes and swamp of varying width, covered with scanty vegetation, 
consisting mainly of tamarisk and reeds. Along the whole of the north margin 
also there is a band of lacustrine deposits widening out towards the east. These 
beds overlap the edge of the Middle Eocene strata which form the lower parts of 
the depression. 
With only one or two exceptions, the whole of the vertebrate remains described in 
the present volume are derived from the Middle and Upper Eocene deposits lying 
on the northern side of the lake, and it will only be necessary here to give a brief 
account of the geological structure of that region. Looking northwards from a 
suitable point of view on the southern side of the lake, the northern slope of the 
depression can be seen rising in a series of escarpments of varying height (see Map 
and Section), and running roughly parallel to one another from about E.N.E. to 
W.S.W. ; the terraces between the successive steps vary in width from mere ledges 
to plains some kilometres wide. There are three main escarpments, of which the 
* Flinders Petrie, ‘A Historj'of Egypt,’ vol. i. p. 147. 
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