230 WARREN Ul'HAM, ESQ., ON CAUSES OF THE ICE AGE. 



raiglit be taken at this as tlie rate is known to vary considerably. 

 This estimate would show that the Ice Age came to an end not 

 more than 7,000 to 8,000 years ago. This may give a minimum 

 measure, but it serves at the same time to render more secure the 

 other estimates which are somewhat in excess of this, and which 

 would extend the time to 10,000 years. I cannot but consider 

 these estimates which are founded, as is also my own, upon 

 available geological data as more probably true than that assumed 

 on the astronomical hypothesis. That hypothesis is also entirely 

 discordant with geological facts. It involves the recurrence of a 

 succession of cold periods at geological times of which we have 

 no evidence. 



I do not, however, agree with the author in his opinion as to 

 the cause of the great Ice Age, which he considers due to great 

 continental elevations which would make the glaciated areas of 

 North America to have been 3,000 to 4,000 feet higher than they 

 now are. That there has been a submergence apparently to that 

 extent on the coast of that continent, whereby old glaciated valleys 

 and fiords now form great submarine depressions, are very striking 

 facts. But if it is difficult now to account for the glaciation of 

 mountains 5,000 to 6,000 feet high, what will it be if we have to 

 add to this 3,000 to 4,000 feet more, and to imagine an ice-sheet 

 9,000 to 10,000 feet thick. The author also somewhat damages 

 his case by extending his argument to the tropical regions of 

 Africa and elsewhere. The European area affords no sufficient 

 corroboration. The Rhine, the Thames, and the Severn show no 

 deep submarine valleys. The old Yave is submerged to the depth 

 of 500 feet at Yarmouth, but the Thames and Severn valleys at 

 their entrance show no greater difference of level than 60 to 

 70 feet, and the smaller i-ivers on the Cornish coast of 40 to 50 feet. 

 Still the ca.use of the great Ice Age cannot be different in Europe 

 from Avhat it is in America. That cause has yet, in my opinion, to 

 be discovered. 



Prof. J. Geikie, LL.D., F.R.S., writes :— 



It is a pity that Mr. Upham should have devoted so little space 

 ill his paper towards the explanation of what I have termed the 



