332 PROFESSOR E. HULL, LL.D., F.R.S., F.G.8., ON THE 
basin-like depressions already referred to in the Libyan 
Desert, of which the Fayim and Rayan are the most 
important examples. 
We have already seen the effect which this refrigeration 
of the climate at the commencement of the Glacial period 
had upon the animals of the Europasian continent in driving 
them southwards into Africa; this was at a time of land- 
elevation, and of lowering of the Mediterranean waters. The 
period of submersion, now being discussed, succeeded to 
this, and may have to some extent continued while the 
climate was undergoing amelioration after the epoch of 
intense cold. With the melting of the snows and the 
accompanying copious rainfall, the river valleys would 
become channels of large streams. Hence, this may well be 
designated the “ Pluvial period,” coextensive with the later 
glacial stages of the European area, and gradually passing 
into that of recent times, and the dawn of ancient Egyptian 
civilisation.* 
(5.) Silting up of the Nile Valley and Plain of the Delta.— 
During the Pluvial period the waters of the Nile, independent 
of the periodic floods of Abyssinia, probably carried down 
larger quantities of sediment than at the present day, and 
partially filled up the great gulf formed during the period of 
elevation. This precipitation of sediment, no doubt, con- 
tinued during the rising of the sea-bed, and after Lower 
Egypt had been converted into a fluviatile plain with its 
seven rivers.t Within historic times, there is every reason to 
believe the waters of the Red Sea extended far north of 
their present limits at Suez, as places far north of that town 
* A sketch map of this region during the Pluvial period will be found 
in the Phys. Geol. and Geog. of Arabia Petrea, dc. p. 72. The Pluvial 
period of the Eastern Hemisphere is representative, at least in part, of 
the Champlain period of American geologists; on which subject see 
paper by Prof. J. D. Dana, Amer. Journ. Sci., vol. xxiii (1882). 
+ The following is an account of the strata passed through at the deep 
boring made at Rosetta, communicated to the Royal Society by Col. 
Maitlani, I.E. :— 
1. Alluvial mud and clay _.... ws. 30 feet. 
2. Sands and clays _.... ee. wage FOL eS 
3. Hard clay in lumps ais sire Ona 
4. Sand and clay alternating... yeah Os ay 
5. Coarse sand with pebbles... ane, Go 
Total .... aa Vy See Os te a 
The pebbles above stated may possibly be concretions. 
