WOODWORTH: GEOLOGICAL EXPEDITION TO BRAZIL AND CHILE. S89 
cyclones of the existing atmospheric circulation over the glacial fields. 
The distribution of land and sea in the Southern Hemisphere was then 
so different from what it now is, particularly in the Atlantic and 
Indian regions, that, while we may freely speculate upon a different 
system of distribution of aqueous vapor, it is at present impossible to 
construct an unassailable theory. 
‘The “pendulationstheorie” of H. Simroth (1907) which is but a 
modification of the idea of a shifted axis of rotation does not better 
than the original conception explain the phenomena of distribution 
of Permian glaciation for the reason that no shifting of polar climates 
will bring the glacial deposits in the polar regions. Dr. Wilh. R. 
Eckardt (1910, p. 125-127) has well observed in connection with the 
above mechanical hypothesis that Sumatra, assumed to be one of the 
fixed equatorial poles of pendulation in this speculation, is placed on 
the borders of the principal area of Permian glaciation and hence no 
essential shift is accomplished. 
The recently elaborated hypothesis that glaciation may be brought 
about through the temporary reduction of the amount of carbon in 
the earth’s atmosphere appears to fail as an adequate explanation of 
the phenomena of glacial periods since the view does not explain the 
succession of epochs of glaciation and deglaciation in the Pleistocene 
period. our times in this period the ice-sheets apparently came on 
and went off. If the abstraction of carbon in the form of coal and 
limestones in the preglacial period led to the first ice accumulation 
and advance, the hypothesis leaves unexplained the shortly succeeding 
ice advances between whose dates no corresponding appreciable 
reduction in the carbon is registered by rock-making in the earth’s 
crust. 
As we do not know with any certainty the cause of the latest glacial 
periods so near our own times, it is evident that the geographical 
conditions of the Permian must be thoroughly ascertained before we 
can construct a plausible explanation of a glacial period so remote and 
taking place on lands whose contours are as yet drawn with too much 
conjecture. Certain lights appear however to be burning as guides 
to the path which shall lead to the discovery of the probable cause of 
Permian glaciation. These may be briefly summarized as follows: — 
The axis of the earth appears to have lain in Permian times where 
it does now. ‘This excludes a favorite group of hypotheses. 
The glaciated lands of south Brazil and German southwest Africa 
were in Permian time at or near sea-level. This does not exclude the 
extrusion of glaciers from highlands to the sea-border provided the 
highlands lay over the site of the Atlantic basin. 
