woodworth: geological expedition to brazil and chile. 121 



If one reads Chapter X on the Plains and valleys of Chile in Dar- 

 win's Geological observations, he will find the author convincing 

 himself that the sea rather than the rivers now coming out of the 

 Andes is accountable for nearly every detail of the land form, — not 

 only the passes in the mountains and the valleys sculptured in the 

 mountain mass but also the plains of waterworn detritus particularly 

 where rounded pebbles are found. 



This statement tallies with the general belief of the school of 

 geologists of the period in which Darwin formed his concepts. It was 

 naturally easy for him to admit terraces of any origin and marine 

 shells on the surface at lower levels along the coast of Chile as evidence 

 of elevation when he had found to his own satisfaction that the sea 

 had beaten against the high Andes where no recent marine shells are 

 found. This much is necessary for the reader to understand in weigh- 

 ing the conclusions which may be presented concerning the elevation 

 of the coast of Chile. 



It is only just to Darwin, however, to show from his own writings 

 how he abandoned the views he entertained concerning topographic 

 signs of elevation on the coast of South America when in later years 

 similar problems came to his attention in the British Islands. 



Darwin (Francis Darwin, 1903, 2, p. 191) wTote Lyell in 1861,— 

 "I return Jameson's capital letter. I have no comments, except to 

 say that he has removed all my difficulties, and that now and for 

 evermore I give up and abominate Glen Roy and all its belongings. 

 It certainly is a splendid case, and wonderful monument of the old 

 ice period .... How many have blundered over those horrid shelves!" 

 Again in 1868, Darwin (Francis Darwin, 1903, 2, p. 211) wrote 

 Croll, — " I was formerly a great believer in the power of the sea in 

 denudation, and this was perhaps natural, as most of my geological 

 work was done near sea-coasts and on islands. 



" But it is a consolation to me to reflect that as soon as I read ]Mr. 

 Whittaker's paper on the escarpments of England, and Ramsay and 

 Juke's papers, I gave up in my own mind the case; but I never realized 

 the truth until reading your papers just received. How often have 

 I speculated in vain on the origin of the valleys in the chalk platform 

 round this place, but now all is clear." Still he clung to his interpreta- 

 tion of terraces and of shells on the surface in South America. As late 

 as 1872, Darwin wrote Lyell (Francis Darwin, 1903, 2, p. 164-165),— 

 " It seems to me very cool in Agassiz to doubt the recent upheaval 

 of Patagonia, without having visited any part of it; and he entirely 

 misrepresents me in saying that I infer upheaval from the form of the 

 land, as I trusted entirely to shells embedded and on the surface. 



