WAERE'N UPHAMj ESQ., ON CAUSES OF THE ICE AGE. 223 



changes in temperature, linniidity, and snowfoll, were de- 

 monstrably very rapid, the Avhole duration of this glacial 

 lake being probably only about 1,000 years.* The vicissi- 

 tudes of the general glacial retreat seem to me to have been 

 due thus chiefly to variations of snowfall, some long terms 

 of years having much snoAV and prevailingly cool tem- 

 perature, therefore allowing considerable glacial re-advance, 

 while for the greater part other series of years favoured 

 rapid melting and retreat. 



44 Under this view we may, T think, account for all the ob- 

 servations which have been held in America and Europe as 

 proofs of iuterglacial epochs, without assuming that there 

 Avas either any far re-advance of the ice-border or any 

 epeirogenic movements attending the glacial retreat of such 

 magnitude as to induce the fluctuations of which the forest 

 beds and marginal moraines bear witness. The Ice age 

 seems to me to have been essentially continuous and single, 

 Avith important fluctuations, but not of epochal significance, 

 both during its advance and decline. 



The President (Sir G. G. Stokes, Bart., D.Sc, F.R.S.).— I will 

 ask you to return your thanks both to the author of this paper, 

 and also to Professor Hull for so ably reading it. (Applause.) I 

 now invite remarks on the subject, which presents considerable 

 difficulty. 



Professor E. Hull, LL.D., F.R.S., F.G.S.— I think this is one 

 of the most interesting and valuable contributions, to account for 

 the production of the Ice Age of the Quaternary Period, that we 

 have had for a long time. 



There is a great freshness about it — a quality which applies to 

 many of the American papers. Fortunately America has produced 



* Geol. and Nat. Hist. Survey of Canada, Annual Eeport, new seiies, 

 vol. iv, for 1888-89, p. 51 E. 



Q 



