1879O 
Relations to that of the Glacial Epoch. 
3 
with the surface of the earth’s crust within the Antarctic 
regions, cannot support a column of itself more than 
1400 feet high without melting.”* 
The subject is one of very considerable importance, not 
merely in relation to the Antarctic regions at the present 
day, but also in its bearings on the condition of things 
generally during the Glacial Epoch. For if Sir Wyville 
Thomson’s conclusions in reference to the thickness of the 
Antarctic ice be true, they must hold equally true for the 
ice of the Glacial Epoch, and consequently would modify 
to a large extent prevailing conceptions regarding the phy- 
sical condition of our country during that epoch. 
They are therefore conclusions worthy of discussion, and, 
as they are diametrically opposed to those arrived at by 
myself, I have thought of considering the subjedb in some- 
what fuller detail, the more so as new elements in the 
question have since been introduced. 
At the very outset of the inquiry it must be observed that 
the question of the thickness of the ice covering the 
Antarctic continent is one which cannot be determined by 
diretft observation. No one, as yet, has ever been able to 
set his foot on that continent ; and the perpendicular wall 
forming the outer edge of its icy mantle is nearly all that 
has been seen of it. Diredt measurements, and some other 
fadts to which we shall shortly refer, show with tolerable 
certainty what is the probable average thickness of the ice- 
sheet at its outer circumference ; but observation can tell 
us nothing whatever about the thickness of the ice in the 
interior, which is the question at issue. This has to be de- 
termined by purely physical and mechanical considerations, 
based, it is true, on data derived from observation. A visit 
to tbe Antarctic regions may indeed enable us to become 
acquainted with data which we might not have known 
otherwise, but this acquaintance would not aid us in 
drawing the proper inference from those data. 
It fortunately happens, however, that the very circum- 
stances that render the region so difficult to get at are those 
which at the same time tend to simplify the problem. The 
Antarctic region is the most inaccessible on the globe, but 
of all regions it is the one where the physical conditions 
are most uniform and least under the influence of con- 
tingent circumstances, such as those resulting from the 
presence of warm ocean currents in one place and cold 
currents in another, or of great masses of land in one part 
* Condition of the Antarctic Region, p. 23. Nature, vol. xv., p. 122. 
