ON VOLCANIC ACTION, 



357 



sphere Were more frequent, acting upon a greater 

 number of points, and when the tendency to establish 

 these communications gave rise, in the line of the 

 long crevices, to the cordilleras of the Andes and 

 Himmaleh mountains, the chains of less elevation, 

 and the ridges whose undulations embellish the land- 

 scape of our plains. Our author then mentions, as 

 proofs of these protrusions, the sandstone formations 

 which extend from the plains of the Magdalena and 

 Meta, almost without interruption, over platforms 

 having an elevation varying from 8950 to 10,232 feet ; 

 and the bones of antediluvian animals intermingled 

 on the summit of the Uraiian chain of northern Asia 

 with transported deposites, containing gold, dia- 

 monds, and platina. Another evidence of this sub- 

 terranean action of elastic fluids, which heave up 

 continents, domes, and mountain-chains, displace 

 rocks and the organic remains which they contain, 

 and produce eminences and depressions, is the great 

 sinking of the ground which occurs in the west of 

 Asia, of which the Caspian Sea and the Lake Aral 

 form the lowest part (320 and 205 feet beneath the 

 level of the ocean), but which extends far into the 

 interior of the continent, stretching to Saratov and 

 Orenburg on the Jaik, and probably to the south-east 

 as far as the lower course of the Sihon (Jaxartes) and 

 the Amou (the Oxus of the ancients). This depres- 

 sion of a continental mass extending to more than 

 320 feet below the surface of the ocean, he continues, 

 has not hitherto obtained the necessary considera- 

 tion which its importance demands, because it was 

 not sufficiently known. It appears to him to have an 

 intimate connexion with the upheaving of the Cau- 

 casian Mountains, those of Hindoo-kho, and of the 

 elevated plain of Persia, which borders the Caspian 

 Sea and the Mavar-ul-Nahar to the south ; and, per- 

 haps, more to the eastward, with the elevation of the 

 great mass of land which is designated by the vague 

 and incorrect name of the central plain of Asia. 



