FAZENDA LIFE. 99 
the Union and Industry road. The journey to Jniz 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 
G2 
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, 
