40 Journal of Travel and Natural History 



believes to be unquestionable) and on his views of the physical 

 history of the valley in general. These require the explanation of 

 two phenomena : the filling of the basin of the Amazons with 

 clays and sandstone to the height of more than 800 feet above 

 the sea, with no seaward barrier of rock ; and the subsequent 

 denudation of the country to its present level. Mr Agassiz thought 

 the valley of the Amazons was an immense cretaceous basin filled 

 with recent deposits, and that the history of its formation was 

 briefly this : 



isf. The filling of the whole valley with a glacier, which extended 

 from the high lands of Guiana to those of central Brazil. 2d. The 

 formation of a vast terminal moraine, which, upon the retreat of 

 the glacier, shut out the sea and eventually left an immense fresh- 

 water lake. 3</. The partial melting of the glacier, during which 

 time the lower stratified layers were deposited, the coarse materials 

 falling to the bottom, ^th. The disintegration of the whole body 

 of ice, at which period more or less regular beds of sand were 

 deposited to the depth of 800 feet. 5M. The breaking through of 

 the morainal barrier and the extensive denudation of the whole 

 country ; which was followed by, 6th, a period of quiet accumula- 

 tion of ochraceous sandy clay with boulders brought by floating 

 ice at the close of the ice period. 7///. A second drainage, caused 

 by the total destruction of the seaward barrier and a reduction of 

 the waters to their present level, ^th. The gradual encroachment 

 of the sea upon the river-bed, destroying all traces of a delta, and 

 causing the former affluents near its mouth to flow into the sea. 



This volume, from portions of which we have given this brief 

 preliminary notice, consists almost entirely of Mrs Agassiz' diary, 

 written from day to day, in the hope that, "some use might be 

 made of the thread of the narrative in knitting together the scientific 

 reports of the journey." The work is appropriately inscribed to 

 Mr Nathaniel Thayer, who, with unusual munificence, bore the 

 entire expense of six regular assistants. 



Mr Vogeli, Professor in the Military Institute at Rio, and sent 

 to Boston by the Emperor of Brazil, is translating the work into 

 Portuguese and French. It will appear at an early day in Rio and 

 Paris. 



S. ScuDDER, Boston. 



