258 LOUIS AGASSIZ. 



offered to defray the expenses of tlie expedition, and authorized him to 

 take with him, as assistants, six uaturaUsts. The Emperor of Brazil, 

 the Secretary of the Navy of the United States, the president of the 

 Pacific Mail Steamship Company, each contributed in large measure to 

 the success of this exxjedition, which had been joined by some distin- 

 guished naturalists as voluntary recruits. On the 1st of Ai)ril, ISQo, 

 Agassiz embarked, taking with him Mrs. Agassiz, who kept the journal; 

 her husband communicated to her the scientific results as they were ob- 

 tained, and thus was composed the book known under the name of "A 

 Journey to Brazil." We refer to this volume any of our readers who 

 desire to follow the American savans along the borders of the Amazon 

 and explore with them the vast basin they undertook to study. 



Agassiz, during this voyage, made immense collections. These have 

 already been, in part, studied and described, and will give rise to works 

 which will make better known to us the fauna of the extraordinary re- 

 gion. He observed, also, many general facts of natural history. The 

 account of the expedition manifests the great talent he possessed of 

 noting every peculiarity offered to his observation in the zoological 

 character of the animals he discovered, in the ichthyological fauna of the 

 Amazon, in the geographical distribution of the terrestrial and aquatic 

 animals, and in the physical and geological characteristics of the great 

 valley he traversed. 



One of the points which fixed his attention and to which he constantly 

 refers in the history of the vo^rage, is the nature and the distribution of 

 the drift of this region. This deposit, which is of great thickness and 

 immense extent, for it is estimated to bo some thousand miles in length 

 and six or seven hundred in width, could not have been formed by the 

 sea, since there were no traces found of marine shells. It is, then, a fresh- 

 water deposit. If a lake had occupied this vast space the basin must 

 have been closed ; otherwise, this material would have been carried into 

 the sea. Agassiz attributed this phenomenon to the ancient extension 

 of the glaciers. An immense glacier, according to him, descended from 

 the Cordilleras, augmented hy tributaries from Guiana and from Brazil, 

 and covered the valley of the Amazon. It accumulated at its lower 

 edge a moraine of colossal dimensions, forming thus a gigantic embank- 

 ment, which bars the mouth of the basin. 



It is true that polished and scratched surfaces are not found; the 

 rocks are too soft to have retained such traces, but the rounded rocks 

 Agassiz observed in some localities, the blocks of the Erere, the nature 

 of the deposit in the valley, the character of which is analogous to that 

 of the material accumulated under the glaciers ; the resemblance of the 

 upper formation of this country to the drift of liio, the glacial origin 

 of which seemed to him beyond a doubt; the tact that the basin of 

 fresh water must have been closed on the side of the ocean by a power- 

 ful barrier, appeared to him sulticient arguments to establish the exist- 

 ence of this glacial period. Later there was a rupture in the exterior 



