THE PREHISTORIC MAST 169 



great floods which in the rainy season pour down from 

 the mountains of Abyssinia. 



This outlet has been available and has been in 

 process of erosion by running water from a period 

 long anterior to the advent of man, and with this 

 early prehuman history belonging to the miocene 

 and pliocene periods of geology we have no need to 

 meddle, except to state that it was closed by a great 

 subsidence, that of the pleistocene or glacial period, 

 when the land of North Africa and Western Asia 

 was depressed several hundred feet, when Africa was 

 separated from Asia, when the Nile valley was an 

 arm of the sea, and when sea-shells were deposited on 

 the rising grounds of Lower Egypt at a height of two 

 hundred feet or more. 1 Such raised beaches are found 

 not only in the Nile valley but on the shores of the 

 Red Sea, and, as we shall see, along the coast of 

 Palestine ; but, so far as known, no remains of man 

 have been found in connection with them. This 

 great depression must, however, geologically speaking, 

 have been not much earlier than the advent of man, 

 since m many parts of the world we find human re- 

 mains in deposits of the next succeeding era. 



This next period, that known to geologists as the 

 post-glacial or early modern, was characterised by 

 an entire change of physical conditions. The con- 

 tinents of the northern hemisphere were higher and 



1 Hull, Geology of Palestine and adjacent Districts, Palestine 

 Exploration Fund. Dawson, Modern Science in Bible Lands, p. 311 

 and Appendix. References will be found in these works to the labours 

 of Fraas, Schweinfurth, and others. 



