THE HUMAN SPECIES. 105 



explained; an. if this observation is accepted with respect to 

 brute mammals, it surely implies that man, at least in some 

 degree, may have had to encounter similar contingencies. 



In jrder to appreciate the great changes proved, or asserted 

 to have occurred, let us take a short review of those which are 

 the most prominent in the physical history of the earth. 



ASIA. 



Asia, apparently the most ancient integral continent of the 

 earth, it may be surmised, is held aloft by the agency of great 

 subterrene volcanic trunks, whose direction is externally mani- 

 fested by the huge mountain range, which, passing longitudi- 

 nally from east to west, nearly beneath its centre, forms the gen- 

 eral water shed to the south and to the north, and constitutes the 

 hinge, the axis of nutation, to the whole of both its planes towards 

 the two oceans. In the east, the chain forms two or more paral- 

 lel ridges, widening until an elevated table-land, of prodigious 

 extent, is included between them. This plateau forms, chiefly, 

 the Gobi desert ; its northern boundary consisting of the Altaic 

 chain facing Siberia, and the southern, overlooking the great 

 peninsula of India, contains, in the Himalaya system, the 

 highest mountains of the world.* To the westward, it is con- 

 tinued by the Hindu Koh, which is the real Caucasus, and 

 perhaps the Paropamissus of the ancients. Further on, the 

 chain of Elburs overhangs the southern shore of the Caspian ; 

 then succeeds Western Caucasus, and the mountain groups of 

 Asia Minor and the Crimea, anciently known by the names of 

 Taurus and Tauris ; this, crossing the Hellespont about Con- 



* That this lofty chain was hove up at a much more remote period, is 

 sufficiently proved by the presence of banks of oyster shells, discovered 

 by Dr. Gerrard at 16,000 feet above the level of the sea; ard in Thibet, 

 shells fallen from cliffs, still higher, were taken up at the height of 

 17,000 feet. In Asia Minor, oyster beds are not more than 3000 feet 

 above the sea. 



