33 ® 
Glacial Period in the 
[July, 
species become more and more separated ; the genera com- 
prise species as far removed from each other as before, but 
these are not connected by the same intermediate forms. 
These gaps become wider and wider as we get farther south, 
until at the extreme end of the continent, where the rocks 
are glaciated from ocean to ocean, isolation, and not affinity, 
is the characteristic of the fauna, which is made up of waifs 
and straj's that appear rather to have struggled in from the 
outside, upon a country that had been depopulated, than to 
have been developed within it. 
In the glaciers of Ceara and northern Nicaragua we find 
the first parallel between the glaciation of the two hemi- 
spheres ; and it is to be noted here, as it may be elsewhere, 
that there appears to have been more ice heaped up on the 
southern half of the world than on the northern, the much 
nearer approach of the glaciers to the Equator in Brazil 
than in Central America being the first evidence of it. This 
was probably due, not to greater cold, but to greater precipi- 
tation, proportional to the vast evaporating area of the 
Southern Ocean. 
Travelling southward, we find that Mr. David Forbes no- 
ticed in Bolivia great accumulations of detritus with grooved 
stones and deeply-furrowed rocks, resembling those that he 
was familiar with in Norway.* And on the opposite side of 
the continent, near Rio Janeiro, Prof. Hartt has described 
moraines left by glaciers that formerly came down from the 
mountains of Tijuca.fi 
Still farther south the evidences of glacial adtion increase. 
For the description of the phenomena of La Plata, Patago- 
nia, and Chile we must still turn to the observations of 
Darwin made more than forty years ago, which, when we 
consider that the glacial theory was in its infancy, evince 
the same rare powers of acute observation and philosophical 
generalisation that have since made his name so famous. 
Ascending the River Santa Cruz, Darwin found, at a dis- 
tance of about ioo miles from the Atlantic and at a height 
of about 1400 feet above the level of the sea, a great abun- 
dance of large angular boulders that had been transported 
from the Cordillera, the nearest slope of which was still 
about 60 miles distant. On both sides of the continent from 
lat. 4i°S. to the southern extremity of it, he considers there 
is the clearest evidence of former glacial adtion in numerous 
immense boulders transported far from their parent source.}: 
* Darwin, Origin of Species, Sixth Edition, p. 335. 
f Geology and Physical Geography of Brazil, p. 26. 
% Origin of Species, Sixth Edition, p. 335. 
