CHAPTER V 
THE ICE AGE 
GEOoLoaIcaL research has revealed traces of more than one 
ice age, or glacial period, in both the Northern and South- 
ern Hemispheres, far back in the earth’s remote past, 
countless ages before the appearance of man. However, 
the one which we generally have in mind when we speak 
of the Ice Age, and with which we are here concerned, oc- 
curred but yesterday, geologically speaking, and pro- 
foundly influenced the development of man. There is no 
doubt whatever that man existed long before it began, but 
the vicissitudes and hardships to which he was then ex- 
posed had a great deal to do with the shaping of his later 
destinies and therefore the Glacial Period deserves our 
attention here. 
Many explanations have been suggested of the causes 
that produce an ice age or lead to its disappearance. One 
surmise pictures the solar system, in its journey through 
space, as having passed through a “cold region” which 
lowered the temperature of our earth enough to cause 
enormous expansion of the polar ice caps. But this theory 
lacks the support of any real evidence. 
Again, the English astronomer, Croll, argued for varia- 
tions in the shape of the earth’s orbit as the cause of an 
ice age. We all know that the path of our planet around 
the sun does not form a true circle but an ellipse. This 
changes its shape through the ages at a rate that can be 
calculated astronomically. Croll suggested that the Ice 
Age corresponded to the last period of great eccentricity 
of the orbit of the earth, when the latter attained its 
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