VALLEY OF THE AMAZONS. 
171 
Thus in its main features the Valley of the 
Amazons, like that of the Mississippi, is a 
cretaceous basin. This resemblance suggests 
a further comparison between the twin conti¬ 
nents of North and South America. Not only 
is their general form the same, but their frame¬ 
work, as we may call it, that is, the lay of their 
great mountain-chains and of their table-lands, 
with the extensive intervening depressions, 
presents a striking similarity. Indeed, a zo¬ 
ologist, accustomed to trace a like structure 
under variously modified animal forms, cannot 
but have his homological studies recalled to 
his mind by the coincidence between certain 
physical features in the northern and southern 
parts of the Western hemisphere. Yet here, 
as throughout all nature, these correspond¬ 
ences are combined with a distinctness of in¬ 
dividualization, which leaves its respective 
character not only to each continent as a 
whole, but also to the different regions circum¬ 
scribed within its borders. Tn both, however, 
the highest mountain-chains, the Rocky Moun¬ 
tains and Coast Range with their wide inter¬ 
vening table-land in North America, and the 
chain of the Andes with its lesser plateaus in 
