REVIEWS 191 
during the Cretaceous and into the Tertiary period. A subsequent 
period of folding and withdrawal of carbonic acid resulted in the great 
ice age. After several less well-known climatic changes—some geolo- 
gists count as many as six different ice periods—the recent period 
finally arrived with its temperate climate, in which we still live. 
To the fundamental causes here discussed as affecting the climatic 
changes of long duration, a secondary cause may be added, as pointed 
out by Chamberlin, namely, the continued erosion and denudation of 
the continents by precipitation. It is evident that this cause intensifies 
the climatic conditions between ‘cold and warm periods. Ina note 
(p. 375) the author leaves it to the future to decide whether the inter- 
glacial periods are due to changes in the atmosphere, or to changes 
in the inclination of the earth’s axis. 
Since the cooling of the polar regions of the earth have, on the 
whole, always been in advance of the cooling of the tropical and tem- 
perate zones, our greatest mountains lie in these latter zones. The 
polar caps have attained a greater solidity and resistance to pressure, 
and thus the folding has been mostly transferred to other regions. 
The sea has served as a great moderator of the climatic changes of 
long period. Zhe cause of the latter must be sought in the alternate 
contraction and expansion of the earth's crust following changes in the 
mean temperature of the atmosphere. 
The fourth part of the paper has for its subject che changes in the 
inclination of the earth’s axts to the ecliptic and tts influence on climate. 
Here is first given a summary of the evidence of changes in the 
flora and fauna of northern Sweden, since the ice left the peninsula. 
Since the time of the “‘Oak zone,” the average temperature has fallen 
2° C., judging by the fossil distribution of Hazel. Possibly the winter 
temperature was but little different from the present. Accepting the 
archeologist’s figures as to the time of the appearance of paileolithic 
man in Sweden, 7000 to 10,000 years back, the highest temperature of 
the climate of Sweden seems to have occurred at that time. The 
author then proceeds to show that the Quaternary changes of climate 
can be readily and fully accounted for by the “long-periodic” changes 
in the inclination of the earth’s axis. He has tabulated Stockwell’s 
calculations (p. 381). These show the inclination to have been small 
about gooo years ago, and that it has been increasing since then. He 
presents a calculation of the length of the mid-summer day (the sun - 
not setting) for Karesuando, the northernmost meteorological station 
