26 NATURAL HISTORY OF 



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 manifested by the huge moun- 

 tain range, which, passing longitudinally from east to 

 west, nearly beneath its centre, forms the general 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 parallel 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 continued by the Hindu Koh, which is 

 the real Caucasus, and perhaps the Paropamissus of 

 the ancients., Further on, the chain of Albars over- 



* 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 ; and 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. 



