708 TNC: CHAM B EIAIEEN: 
This discussion of the present circulation, too protracted for 
this place, yet too brief for its purpose, has seemed necessary to 
make clear the conception entertained respecting the agencies 
of localization. It has previously been urged in this paper that 
a reduction of the carbonic acid in the atmosphere and the con- 
sequent reduction of its heat-absorbing capacity must intensify 
the influence of all surface features. In the discussion of exist- 
ing glaciation I have endeavored to connect the present great 
ice-fields genetically with the two great areas of low pressure, 
and to associate them with an oblique disposal of the great circu- 
latory features. The chief centers of present glaciation lie on 
the borders of the American continent. The chief Pleistocene 
glaciations, were concentrically arranged about these centers. 
As has been pointed out by other students of Pleistocene glacia- 
tion, the yreat northeasterly ice-sheet had its western, southern 
and southeastern limits almost coterminous with the predomi- 
nant paths of northern migrant cyclones. To complete the 
hypothesis of localization it is therefore only necessary to assume 
an intensification of the present oblique system of circulation, 
with a further shifting of the centers of depression in the direc- 
tion of the present displacement, accompanied by a sufficient 
depression of temperature. And these are the effects assigned 
to a reduction of the atmosphere’s thermal capacity due to loss 
of carbonic acid. 
Suggestion relative to migrant cyclones—One further feature 
deserves notice. If the constructive pole of the winds hes some- 
where between the earth’s pole and the American continent, the 
frictional action of the earth will affect the two sides of the eddy 
in opposite senses. On the western side ( from the American 
point of view) the friction will tend to drag the bottom air 
toward the cyclonic center and crowd the isobars upon each 
other. As the lines of the wind circulation and the earth rota- 
tion cross each other obliquely, a predisposition to form gyratory 
or cyclonic eddies may be inferred, and this may be one of the 
sources of migrant cyclones which may be regarded as small 
eddies in the grander cyclonic movements. 
