LIFE IN RIO CONTINUED. 89 



to a new geological agency, thus far not discussed in our 

 geological theories. It is obvious here (and to-day with 

 the pouring rain which keeps me in doors I have satis- 

 factory evidence of it) that the warm rains falling upon the 

 heated soil must have a very powerful action in accelerating 

 the decomposition of rocks. It is like torrents of hot water 

 falling for ages in succession upon hot stones. Think of 

 the effect, and, instead of wondering at the large amount 

 of decomposed rocks which you meet everywhere, you will 

 be surprised that there are any rocks left in their primitive 

 condition. It is, however, the fact, that all the rocks you 

 see are encased, as it were, in a lining of the decomposed 

 part of their surface ; they are actually covered with a 

 rotten crust of their own substance. 



" Ever truly yours, 



" L. AGASSIZ." 



Among the objects of special interest which we have 

 seen here for the first time are the colossal fruits of the 

 Sapucaia-tree, a species of Lecythis, belonging to the same 

 family as the Brazilian nuts. These fruits, of which there 

 are a number of species, vary from the size of an apple to 

 that of an ordinary melon ; they resemble an urn closed 

 with a lid, and contain about fifty seeds as large as almonds. 

 The woods all over these Tijuca hills are beautiful and 

 wonderfully luxuriant ; but I lack names for the various 

 trees. We are not yet familiar enough with the aspect 

 of the forest to distinguish readily its different forms of 

 vegetation ; and it is besides exceedingly difficult here to 

 ascertain the common names of plants. The Brazilians do 

 not seem to me observant of nature in its details ; at all 

 events, I never get a satisfactory answer to the question I 



