20 
Thickness of the Antarctic Ice , and its [January, 
thickening of others, — just such an appearance as might 
be expected to result from the occasional drifting of large 
beds of snow before they have time to become consolidated.” 
The comparative absence of stones, gravel, or earth on 
the southern icebergs shows likewise the flat nature of the 
Antarctic ice-covering. “ We certainly never saw,” says 
Sir Wyville, “ any trace of gravel or stones, or any foreign 
matter necessarily derived from land, on an iceberg.” 
But supposing we should make the extravagant assump- 
tion that in this comparatively flat and uniform sheet the 
pressure by some unexplained means is not evenly distri- 
buted, but that, on the contrary, it is all brought to bear on 
certain points and consumed in melting the ice, and that 
the total quantity of ice melted is the exaCt equivalent of 
the work performed by gravity ; and let us further assume 
that the entire mass of the ice is already at the melting- 
point, and that, therefore, no work is required to raise its 
temperature ; then the total quantity of ice melted would be 
, *9 
ot course — — or 
142 
1 
158 
of the entire mass. Gravity could 
perform only of the amount of work required to melt 
If we suppose the sheet to be 1400 feet 
of this thickness will be equal to 9 feet. 
the entire sheet 
1 
thick, then 
i5« 
A layer of ice about 9 feet in thickness, therefore, is the 
total amount that gravity could under any circumstances 
have melted. 
But more than this, it must be borne in mind that these 
9 feet represent the total quantity which could be melted 
during the whole time the sheet was being formed ; that is, 
from the time the bottom layer fell in the form of snow on 
the surface down to the present day. We have no means 
of ascertaining the length of this period. If we assume 
it to be 10,000 years, and this is probably an underestimate, 
then 9 feet of ice melted during that period would amount 
1 
to only 1 inch in ninety-two years, or “ of an inch 
annually. But whether the period be 10,000 or 5000 years 
the quantity is so trifling that it may be practically dis- 
regarded in the present inquiry. 
Nor is this all, for if the great mass of the ice be as much 
as 2 0 below the freezing-point, which it undoubtedly is, the 
total amount of heat generated by compression and friction 
during the 10,000 years would not suffice to raise the tem- 
perature of the ice even to the melting-point. 
