8' Thickness of the Antarctic Ice, and its f January, 
The testimony from icebergs may therefore be regarded 
as decisive against the opinion that the Antarctic ice cannot 
be more than 1400 feet thick. 
That 1000 or 2000 feet cannot be the limits of thickness 
attained by continental ice is amply proved by the geological 
evidence, which goes to show that during the Glacial Epoch 
the ice in some places much exceeded 1400 feet. Prof. Dana, 
for example, has proved that during the period in question 
the thickness of the ice on the American continent must 
in many places have been considerably above a mile. 
He has shown that over the northern border of New 
England the ice had a mean thickness of 6500 feet, while 
its mean thickness over the Canada water-shed, between 
St. Lawrence and Hudson’s Bay, was not less than 
12,000 feet, or upwards of 2J- miles (see “ American Journal 
of Science and Arts ” for March, 1873). Prof. Erdmann 
and Mr. Amund Helland have shown that the ice in some 
parts of Scandinavia was at least 6000 feet thick. It has 
been proved, by M. Guyot and others, that the Great 
Valley of Switzerland was formerly filled with a mass 
of ice between 2000 and 3000 feet in thickness. Mr. 
Jamieson found that the isolated mountain of Schiehallion, 
in Perthshire, 3500 feet high, is marked near its top as well 
as on its flanks, and this not by ice flowing down the side 
of the hill itself, but by ice passing over it from the north. 
Dr. James Geikie has shown* that the ice between the 
mainland and the Outer Hebrides was as much as 3700 feet 
in thickness. The great mass of ice from Scandinavia, 
filling the Baltic and the North Sea during the Glacial Epoch, 
must have been over 3000 feet thick at least. t 
The Temperature of the Antarctic Ice. 
In examining the physical reasons which have been ad- 
vanced for the limit assigned to the thickness of the Antarctic 
ice-cap, we must first consider the probable temperature of 
the ice ; for not only does the thickness of the sheet depend, 
as we shall see, to a considerable extent on the temperature 
of the ice, but misapprehensions on this point will tend to 
vitiate all our reasoning on the subject. 
There are but three quarters from which the ice-cap can 
receive an appreciable amount of heat, viz., (1) the air 
above ; (2) the earth beneath ; and (3) the work of com- 
pression. Other sources can yield little, if any at all. For 
* Quait. Journ. Geol. Soc., vol. xxxiv., p. 861. 
t Climate and Time, Chap. XXVII. 
