1866.] s SENATE— No. 67. 9 



study of the erratic phenomena, and it is not strange that 

 those who seem familiar with the country should entertain the 

 idea that the surface rocks are everywhere decomposed and that 

 there is no erratic formation nor drift here. But upon close 

 examination it is easy to see that while the decomposed rocks 

 consist of the small particles of the primitive rocks, which they 

 represent, with their dykes and all other characteristic features, 

 there is not a trace of larger or smaller boulders in them ; 

 while the superincumbent drift, consisting of similar parts, 

 does not show the slightest sign of the indistinct stratification 

 characteristic of the decomposed metamorphic rocks below it, 

 nor any of the decomposed dykes, but is full of various kinds 

 of boulders of different dimensions. The boulders have not 

 yet been traced to their origin ; the majority consist of a 

 kind of greenstone, composed of nearly equal amounts of a 

 greenish black hornblende and feldspar; this greenstone is 

 said by mining engineers to be found in Entre Rios, on the 

 Parahyba, where iron mines are worked in a rock like these 

 boulders. Thus far the only evidence furnished of the action 

 of glaciers is the extensive accumulation of drift, similar in its 

 characteristics to northern drift. No trace has been found of 

 glacial action, properly speaking, such as polished surfaces, 

 scratches and furrows. 



The decomposition of the surface rocks and the extent to 

 which it takes place in Brazil is very remarkable, and points to 

 a new geological agency, thus far not noticed in our geological 

 theories. It is obvious that the warm rains falling upon 

 the heated soil must have a very powerful action in accumulat- 

 ing the decomposition of rocks ; and, as these rains have fallen 

 for ages in succession upon hot stones, instead of wondering at 

 the amount of decomposed rocks, we should rather wonder that 

 there are any rocks left in their primitive condition. All the 

 rocks being, however, encased in a lining of the decomposed 

 part of their surface, they are thus protected by a rotten crust 

 from further decomposition. 



As the expedition is almost entirely composed of young men 

 formerly working at the Museum, the force left to carry on our 

 operations at home has been greatly reduced, and consequently 

 less has been done than in former years for the arrangement 

 of the collection ; but it is hoped that on the return of the 



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