142 
ISLAND LIFE. 
[part I. 
that of Greenland, is, according to Meech, one-half that received 
at the equator. The heat received by Greenland from the sun, 
if none were cut off by the atmosphere, would therefore melt 
fifty feet of ice per annum, or fifty times the amount of snow 
which falls on that continent. What then cuts off the ninety- 
eight per cent of the sun’s heat ? ” The only possible answer 
is, that it is the clouds and fog during a great part of the 
summer, and reflection from the surface of the snow and ice 
when these are absent. 
South Temperate, America as illustrating the influence of Astro- 
nomical Causes on Climate. — Those persons who still, doubt the 
effect of winter in aphelion with a high degree of excentricity 
in producing glaciation, should consider how the condition of 
south temperate America at the present day is explicable if 
they reject this agency. The line of perpetual snow in the 
Southern Andes is so low as 6,000 feet in the same latitude as 
the Pyrenees ; in the latitude of the Swiss Alps mountains only 
6,200 feet high produce immense glaciers which descend to the 
sea-level ; while in the latitude of Cumberland mountains only 
from 3,000 to 4,000 feet high have every valley filled with 
streams of ice descending to the sea-coast and giving off 
abundance of huge icebergs. 1 Here we have exactly the con- 
dition of things to which England and Western Europe were 
subjected during the latter portion of the glacial epoch, when 
every valley in Wales, Cumberland, and Scotland had its glacier; 
and to what can this state of things be imputed if not to the 
fact that there is now a moderate amount of excentricity, 
and the winter of the southern hemisphere is in aphelion ? 
The mere geographical position of the southern extremity of 
America does not seem especially favourable to the production 
of such a state of glaciation. The land narrows from the tropics 
southwards and terminates altogether in about the latitude of 
Edinburgh; the mountains are of moderate height; while during 
summer the sun is three millions of miles nearer, and the heat 
received from it is equivalent to a rise of 20° F. as compared 
with the same season in the northern hemisphere. The only 
1 See Darwin’s Naturalist’s Voyage Round the World, 2nd Edition, pp. 
244-251. 
