J. Croll—Geological Climatology. 267 
ice are due to a different cause. Here the snowfall is great 
and the amount of heat cut off enormous; but this alone 
would not account for the non-disappearance of the snow and 
ice, For, notwithstanding this, the heat received is certainly 
more than sufficient to melt all the snow which falls, great as 
that amount may be. The real cause is that the heat received 
is not sufficiently intense to raise the temperature to the melt- 
ing point. More heat is actually received by the snow than is 
required to melt it, but it is dissipated and lost before it can 
Manage to raise the temperature of the snow to the melting 
point; consequently the snow is not melted. Here snow falls 
In the very middle of summer, but snow would not fall unless 
the temperature were near the freezing poiit. 
Loregoing principles applied to the case of the Glacial 
epoch.—Let us now apply the foregoing principles to the case 
of the Glacial epoch. As winter then occurred in aphelion 
during a high state of eccentricity, that season would be muc 
€quinox and summer was approaching the consequent rise of 
temperature would be accompanied by an increase in the 
Snowfall. A melting of the snow would also begin, but 
and Scandinavia. Before the end of autumn, however, it 
would again begin to fall. Next year would bring a repeti- 
tion of the same process, with this difference, however, that 
the snow line would descend to a lower level than on the pre- 
vious year. Year by year the snow line would continue to 
descend till all the high grounds became covered with perma- 
nent snow. 
