FAZEXDA LIFE. 99 



the Union and Industry road. The journey to Juiz de Fora, 

 though we had made it once before, had lost nothing of its 

 beauty by familiarity, and had gained in interest of another 

 kind ; for his examination of the erratic drift at Tijuca has 

 given Mr. Agassiz the key to the geological constitution of 

 the soil, and what seemed to him quite inexplicable on 

 our first excursion over this road is now perfectly legible. 

 It is interesting to watch the progress of an investigation of 

 this character, and to see how the mental process gradually 

 clears away the obscurity. The perception becomes sharp- 

 ened by dwelling upon the subject, and the mind adapts 

 itself to a difficult problem as the eye adapts itself to dark- 

 ness. That which was confused at first presently becomes 

 clear to the mental vision of the observer, who watches and 

 waits for the light to enter. There is one effect of the 

 atmospheric influence here, already alluded to in the 

 previous pages, which at first sight is very deceptive. 

 Wherever there is any cut through drift, unless recently 

 opened, it becomes baked at the surface so as to simulate 

 stone in such a way as hardly to be distinguished from 

 the decomposed rock surfaces in place, unless by a careful 

 examination. This, together with the partial obliteration 

 of the stratification in many places, makes it, at first glance, 

 difficult to recognize the point of contact between the 

 stratified rock and the drift resting above it. A little 

 familiarity with these deceptive appearances, however, 

 makes it as easy to read the broken leaves of the book 

 of nature here as elsewhere, and Mr. Agassiz has now 

 no more difficulty in following the erratic phenomena in 

 these Southern regions than in the Northern hemisphere. 

 All that is wanting to complete the evidence of the actual 

 presence of ice here, in former times, is the glacial writing, 



