232 THE VOYAGE. ^TAT. 26. [1835. 



this year's snow had fallen on the road. I do not suppose 

 any of you can be much interested in geological details, but 

 I will just mention my principal results : — Besides under- 

 standing to a certain extent the description and manner of 

 the force which has elevated this great line of mountains, 

 I can clearly demonstrate that one part of the double line is 

 of an age long posterior to the other. In the more ancient 

 line, which is the true chain of the Andes, I can describe the 

 sort and order of the rocks which compose it. These are 

 chiefly remarkable by containing a bed of gypsum nearly 

 2000 feet thick — a quantity of this substance I should think 

 unparalleled in the world. What is of much greater conse- 

 quence, I have procured fossil shells (from an elevation of 

 12,000 feet). I think an examination of these will give an 

 approximate age to these mountains, as compared to the 

 strata of Europe. In the other line of the Cordilleras there 

 is a strong presumption (in my own mind, conviction) that 

 the enormous mass of mountains, the peaks of which rise to 

 13,000 and 14,000 feet, are so very modern as to be con- 

 temporaneous with the plains of Patagonia (or about with 

 the upper strata of the Isle of Wight). If this result shall be 

 considered as proved,* it is a very important fact in the theory 

 of the formation of the world ; because, if such wonderful 

 changes have taken place so recently in the crust of the globe, 

 there can be no reason for supposing former epochs of ex- 

 cessive violence. These modern strata are very remarkable 

 by being threaded with metallic veins of silver, gold, copper, 

 &c. ; hitherto these have been considered as appertaining to 

 older formations. In these same beds, and close to a gold- 

 mine, I found a clump of petrified trees, standing upright, 

 with layers of fine sandstone deposited round them, bearing 

 the impression of their bark. These trees are covered by 

 other sandstones and streams of lava to the thickness of sev- 

 eral thousand feet. These rocks have been deposited be- 



* The importance of these results has been fully recognized by geolo- 

 gists. 



