250 A JOURNEY IN BRAZIL. 
t 
observations on this subject. Although he has been al- 
most constantly occupied with his collections, he has, 
nevertheless, found time to examine the geological for- 
mations of the neighborhood. The more he considers the 
Amazons and its tributaries, the more does he feel con- 
vinced that the whole mass of the reddish, homogene- 
ous clay, which lie has called drift, is the glacial de- 
V ' * * ^ 
posit brought down from the Andes and worked over by 
the melting of the ice which transported it. According 
to his view, the whole valley was originally filled with 
this deposit, and the Amazons itself, as well as the rivers 
connected with it, are so many channels worn through the 
mass, having cut their way just as the igarape' now wears 
its way through the more modern deposits of mud and sand. 
It may seem strange that any one should compare the for- 
mation of these insignificant forest-streams with that of 
the vast river which pours itself across a whole continent ; 
but it is, after all, only a reversal of the microscopic process 
of investigation. We magnify the microscopically small in 
order to see it, and we must diminish that which transcends 
our apprehension by its great size, in order to understand 
it. The naturalist who wishes to compare an elephant with 
a Coni (Hyrax),* turns the diminishing end of his glass 
upon the former, and, reducing its clumsy proportions, he 
finds that the difference is one of size rather than struc- 
ture. The essential features are the same. So the little 
igarape, as it wears its channel through the forest to-day, 
explains the early history of the great river and feebly 
reiterates the past. 
* It was Cuvier who first ascertained that the small Hyrax belongs to the 
same order as the elephant. 
