THE GLACIAL PERIOD. 365 
far below the present degree. Northern and Central Asia, 
Europe, and North America from the north pole, were 
covered to a great extent by a connected sheet of ice, which 
in our part of the earth seems to have reached the Alps. 
In a similar manner the cold also advancing from the south 
pole covered a large portion of the southern hemisphere, 
which is now free from it, with arigid sheet of ice. Thus, 
between these vast lifeless ice continents there remained 
only a narrow zone to which the life of the organic world 
had to withdraw. This period, during which man, or at 
least the human ape, already existed, and which forms the 
first period of the so-called diluvial epoch, is now universally 
known as the ice or glacial period. 
The ingenious Carl Schimper is the first naturalist who 
clearly conceived the idea of the ice period, and proved the 
great extent of the former glaciation of Central Europe by 
the help of the so-called boulders, or erratic blocks of stone, 
as also by the “glacier tables.” Louis Agassiz, stimulated 
by him, and considerably supported by the independent 
investigations of the eminent geologist Charpentier, after- 
wards undertook the task of carrying out the theory of the 
ice period. In England, the geologist Forbes distinguished 
himself in this matter, and also was the first to apply it 
to the theory of migrations and the geographical distribu- 
tion of species dependent upon migration. Agassiz, however, 
afterwards injured the theory by his one-sided exaggeration, 
inasmuch as, from his partiality to Cuvier’s theory of cata- 
clysms, he endeavoured to attribute the destruction of the 
whole animate creation then existing, to the sudden coming 
on of the cold of the ice period and the “revolution” con- 
nected with it. 
