PERIOD OF CHANGES. 359 



There is something extremely fascinating in the view chapter 

 thus afforded us of the great worlc-shop and laboratory of ^^VI^IL 

 nature as it may be justly called. We see the volcanic 

 powers of the central earth at work, their hidden fires Central 

 fusing and changing the materials of which it is com- P°w*^''*' 

 posed, and the elastic fluids traversing the oxidated and 

 solidified crust of the globe, intersecting this crust with 

 crevices, and injecting it with masses and veins of basalt, 

 metallic substances, and other matters, introduced after 

 the solidiiicating of the planet had been completed. The 

 period of the great geological changes which we are now Period of 

 considering, is shown to have been that when the com- chlngea 

 munication of the fluid interior of the planet and its at- 

 mosphere were frequent, and gave rise, in the line of the 

 long crevices, to the cordilleras of the Andes and Him- 

 malaya Mountains, and the ridges whose indulations em- 

 bellish the landscape of tamer scenery. It is as proofs 

 of these protrusions that Humboldt refers to the sand- EWdence of 

 stone formations which extend from the plains of the P'''^''^'"'"'^- 

 Magdalena and Meta, over platforms having an elevation 

 varying from 8950 to 10,232 feet ; and to the bones of 

 antediluvian animals intermingled on the summit of the 

 Uralian chain of North Asia with transported deposites, 

 containing gold, diamonds, and platina. Another evi- 

 dence of this subterranean action of elastic fluids is the 

 great depression of the land already referred to, which 

 occurs in the west of Asia, of which the Caspian Sea and Great Asiatic 

 the Lake Aral form the lowest part many feet beneath '-P'^^^"''* 

 the level of the ocean, but which extends far into the in- 

 terior of the continent, stretching to Saratov and Oren- 

 burg 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 depression of a 

 continental mass extending to 80 feet below the surface 

 of the ocean in its mean state of equilibrium, has not 

 hitherto obtained the necessary consideration which its 

 importance demands, because it was not suflBciently 

 known. 



