WAEEEN UPHAM^ ESQ., ON CAUSES OF THE ICE AGE. 229 



dnced, wliicli Avould wash away the debris caused by glaciation, and 

 this would spread over the phxins considerably beyond the fi-inge 

 of the northern ice. Thus we may, I think, get a very rational 

 conception of what is commonly called the Ice Age, without 

 drawing upon our imagination for that extraordinary state of 

 tilings which is pictured by so many, and we can do this without 

 requiring" an increase of the cold or heat of the globe taken as a 

 whole, which I do not believe to have practically altered from the 

 time of the Cambrian period. An elevation of a portion of the earth's 

 surface to the extent of 3,000 feet may seem enormous ; but what 

 is it compared with the diameter of the globe ? It is just i ^^oc^^^? 

 which is really a very slight swelling of the surface, and might be 

 produced in certain cases by the expansion of the substance of 

 the globe by altered local thermal conditions. As to the pressure 

 of ice producing depression, I do not consider that the pressure of 

 any possible accumulation of ice would produce depression on the 

 surface of the globe ; cold however causes contraction, and heat 

 expansion. And it is to these agencies I look as having caused 

 changes of level in the past ; similar changes are occurring at the 

 present period. 



The meeting Avas then adjourned. 



REMARKS ON THE FOREGOING PAPER. 



Sir Joseph Peestwich, D.C.L., F.R.S.,* wrote : — 

 Two questions of great interest are raised by Mr. Upham's 

 paper — the cause of the great Ice Age and the date measured 

 fi'om our own time at which it came to an end. In this country, 

 owing to the prevailing belief in Croll's hypothesis, the date of 

 the last event was placed at 80,000 years ago. My own opinion 

 has long been that 10,000 to 12,000 years was a more probable 

 estimate. The American geologists, upon entirely different and 

 independent data, have arrived at a similar conclusion. Among 

 the reasons assigned by the author, one is the rate of erosion of 

 some of the great water-falls on that continent. Exception 



* The last communication receiveu from this author ere liis decease. — Ed. 



