LIFE IN RIO CONTINUED. 87 



a good photograph. This locality afforded me at once an 

 opportunity of contrasting the decomposed rocks which 

 form a characteristic feature of the whole country (as far 

 as I have yet seen it) with the superincumbent drift, and 

 of making myself familiar with the peculiarities of both 

 deposits ; so that I trust I shall be able hereafter to dis- 

 tinguish both, whether they are in contact with one another 

 or found separately. These decomposed rocks are quite a 

 new feature to me in the structure of the country. Imagine 

 granite, gneiss, mica slate, clay slate, and in fact all the 

 various kinds of rocks usually found in old metamorphic 

 formations, reduced to the condition of a soft paste, ex- 

 hibiting all the mineralogical elements of the rocks, as 

 they may have been before they were decomposed, but 

 now completely disintegrated and resting side by side, as 

 if they had been accumulated artificially in the manner 

 you have seen glass cylinders filled with variously colored 

 sands or clays to imitate the appearance of the beds of 

 Gay-Head. And through this loose mass there run, here 

 and there, larger or smaller dikes of quartz-rock or of 

 granite or other rocks equally disintegrated ; but they 

 retain the arrangement of their materials, showing them 

 to be disintegrated dikes in large disintegrated masses of 

 rock ; the whole passing unmistakably to rocks of the 

 same kind in which the decomposition or disintegration 

 is only partial, or no trace of it visible, and the whole 

 mass exhibiting then the appearance of an ordinary meta- 

 morphic set of rocks. 



" That such masses forming everywhere the surface of tbe 

 country should be a great obstacle to the study of the 

 erratic phenomena is at once plain, and I do not therefore 

 winder that those who seem familiar with the country 



