CONDITIONS OF CONTINENTAL ICE. 205 



uniformity in the thickness of the ice-sheet is maintained ; 

 that, in fact, ice at the temperature at which it is in contact 

 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 physical 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 subject 

 in somewhat 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 deter- 

 mined by direct 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. Direct 

 measurements, and some other facts 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 



* "Condition of the Antarctic Region," p. 23. "Nature," vol, 

 xv., p. 122. 



