470 RECENT ADVANCES IN GEOLOGY. 
This compound movement, the precession of the equinoxes 
and the shifting of the line of apsides, it is claimed, exerts 
a marked influence in the distribution of the earth’s tempera- 
ture. While the Great Winter prevails at the north pole, 
the refrigeration is so excessive that the heats of summer are 
insufficient to melt the snow and ice precipitated during the 
winter, and hence, year after year and century after century, 
they go on accumulating, until the cireumpolar region is in 
a state of glaciation, and the added weight becomes sufficient 
to displace the centre of gravity, which would be equivalent 
to a subsidence at one pole and an elevation at the other. 
M. Adhemar has even caleulated the extent of this move- 
ment, and states that it would amount to about 5,500 feet. 
Now, let it be borne in mind that Professor Ramsey has 
shown that in Wales the submergence of the land during the 
Drift Epoch amounted to 2,300 feet, and our own observa- 
tions show that in the northern portions of this country the 
glacial action proper may be traced to the height of 2,000 
feet; although there were mountains which served as radi- 
ating centres, on whose flanks the Drift action may be traced 
much higher. These. geographical points, roughly esti- 
mated, are about midway between the equator and the pole, 
and the extent of the subsidence would correspond very well 
with the calculations before referred to. 
In the year 1248, the Great Winter terminated at the 
south pole, where for 10,500 years the aceumulation of snow 
and iee had been going on, attended with the phenomena 
which we have described. “Here then,” says M. Julien, an 
advocate of this theory, "is an irresistible foree which, fol- 
lowing the invariable law of the irregular precession of the 
equinoxes, must make the earth's centre of gravity periodi- 
cally oscillate.” 
Mr. Croll, an English physicist, has elaborately discussed 
this question in a series of papers in the “Edinburgh New 
Philosophical Magazine,” which have excited profound atten- 
tion. With great labor he has prepared tables showing the 
