PiVEROd EH SITS (OF CAUSE VOM GLA CIAL PERIODS —7.53 
contemporaneous, no dogmatic assertion is intended relative 
to the exact contemporaneity of glaciation or to its alternation 
in’ the northern and southern hemispheres, nor respecting the 
doctrine of migration of glaciation in longitude. Observational 
data are yet insufficient to decide these questions. It is obvious, 
however, that the hypothesis under consideration postulates 
essential contemporaneity throughout the globe. 
The constructive pole of the winds.—As a possible factor in the 
localization of glaciation, I venture to offer the suggestion that 
the axis of the earth’s rotation and the axis of the atmosphere’s 
circulation, constructively interpreted, are not identical. By the 
constructive axis of the winds I mean that ideal line about which 
the general currents of the atmosphere would be found to 
revolve if all minor movements were eliminated or equated and 
the aggregate east-west components only were regarded. In 
other words, it is suggested that the planetary system of circu- 
lation is obliquely adjusted to the planet. This was first sug- 
gested to me by a study of the peculiar courses of the arctic 
ice-drift. The polar ice-bearing currents are regarded by experi- 
enced arctic navigators as concrete expressions of the average 
movements of the atmosphere. To be sure, the ice-drift is 
affected by the ocean currents, but these are also, in the main, 
the, results: of the average direction and force of the winds, 
though they do not so immediately and definitely express it as the 
ice-drift, because they are also influenced by more remote agencies. 
If the axis of the currently postulated ‘circumpolar whirl”’ 
of the atmosphere coincided with the axis of the earth, and if it 
were the poleward incurving spiral of the winds that swept the 
surface of the polar sea, the average ice-drift should assume, or 
tend to assume, a corresponding incurving spiral. The ice should 
crowd in toward the pole and rotate upon itself in a direction 
opposite to the hands of a watch. If this were true, the current 
which carried Nansen from east to west should have flowed from 
west to east. 
If the axis of the ‘‘circumpolar whirl” coincided with the 
axis of the earth, and it were the outward-running spiral that 
