CONDITIONS OF CONTINENTAL ICE. 203 



thickness of the Antarctic ice-sheet ? I shall therefore 

 proceed to the consideration of this question. 



In ' Climate and Time,' Chapter XXIII., I have 

 endeavoured to show that the thickness of the ice on 

 the Antarctic continent must be far greater than is 

 generally supposed; that whatever be its thickness at 

 the edge of the continent where it breaks up into 

 bergs, that at the Pole or centre of dispersion it must 

 be of enormous thickness. 



Since the publication of my work, however, Sir 

 Wyville Thomson, Director of the Scientific Staff of 

 the Challenger Expedition, in a lecture on the con- 

 dition of the Antarctic regions delivered at Glasgow 

 some years ago, has come to a totally different 

 conclusion. His conclusion is based chiefly on 

 considerations relating to the principle of regelation 

 and the physical nature of ice ; and, as the same 

 opinion is held by many, I shall examine it at some 

 length. The following quotation from Sir Wyville's 

 lecture will show his views on the subject : — 



" There is one point in connection with the structure of 

 icebergs which is of great interest, but with regard to which 

 I do not feel in a position to form a definite judgment. It 

 lies, however, especially within the province of a distinguished 

 professor in the University of Glasgow, Dr. James Thomson, 

 and I hope he will find leisure to bring that knowledge to 

 bear upon it which has already thrown so much light upon 

 some of the more obscure phenomena of ice. I have 

 mentioned the gradual diminution in thickness of the strata 

 of ice in a berg from the top of the berg downwards. The 

 regularity of this diminution leaves it almost without a 

 doubt that the layers observed are in the same category, 

 and that therefore the diminution is due to subsequent 

 pressure or other action upon a series of beds which were at 

 the time of their deposition pretty nearly equally thick. 



