SUPPOSED GLACIATION OF BRAZIL. 769 



a single scratch either upon the rocks in place or upon a boulder, 

 cobble, or pebble, that could, by any legitimate stretch of the 

 imagination, be attributed to glacial action. And it is but just 

 to recall the fact that both Agassiz and Hartt recognized this as 

 the one piece of evidence, above all others, lacking for their 

 Brazilian glacial theory. How diligently Agassiz searched for 

 such evidence one can judge from the story of his journey as 

 told by Mrs. Agassiz and himself, and I know that Hartt left no 

 stone unturned and no locality unexplored that he thought might 

 afford him the long-sought striae. They both explained the 

 absence of such marks by supposing that they had been oblit- 

 erated by the decomposition of the rocks, and Agassiz believed 

 that in the Amazon region there were no rock surfaces exposed. 1 

 But it cannot be considered credible that glacial striae should 

 have been preserved in Asia, Africa and Australia since Carboni- 

 ferous times, 2 but entirely obliterated in Brazil, both from the 

 bed rocks and from the conglomerates deposited in post-tertiary 

 times, or as has already been mentioned, that the pitted and 

 water-worn faces should have been preserved in these materials 

 while the ice marks should have been obliterated. 



James E. Mills, a professional geologist and a former pupil 

 of Agassiz at Harvard, spent nearly two years in Brazil in the 

 ^tates of Rio Grande do Sul, Rio de Janeiro, and Minas Geraes. 

 He expresses his views of the subject of glaciation in that 

 country as follows: 3 "In those portions of Brazil which came 

 within my field of observation there is no glacial drift, and there 

 are no glaciated rock surfaces or glacial topography or other 

 signs of the existence of glaciers." 



Agassiz points out the weakness of his own theory regarding 

 Brazilian glaciation very nicely in his letter to Professor Pierce, 



1 Journey, 426. There are plenty of rock surfaces in the Casaquiari region, on the 

 Araguary, the Tocantins, the Tapajos and in hundreds of other places away from the 

 immediate alluvial plain of the Amazon. 



2 Geological Magazine, 1886, 492-495. For the literature of the subject see C. D. 

 White in Amer. Geologist, May, 1889, 299-330. 



3 American Geologist, III., 361. 



