520 Transactions. — Miscellaneous. 



from ordinary glacier-action. Some geologists, who have 

 studied the existing conditions in Greenland, believe that 

 during the ice age a great covering of snow and ice, thou- 

 sands of feet in thickness, overwhelmed wide districts in 

 the regions where these evidences exist, and that by its 

 agency nearly all these effects were produced in America as it 

 accumulated and advanced, or diminished and retired. The 

 geologists oE the United States Geological Survey hold this 

 view, and it is most ably set forth in Dr. Wright's most 

 interesting and comprehensive book. 



The Canadian geologists, with Sir William Dawson at their 

 head, consider that there was a great submergence of the low 

 land in the glaciated regions of North America and Canada 

 during the ice age, and that a great part of the deposits were 

 made by icebergs and shore-ice during this condition of 

 things. 



It seems probable that, as in most such controversies, and 

 as, indeed, Sir William Dawson holds, both sides are partly 

 right, and that submergence of the land and the inroad of 

 cold currents carrying icebergs and depositing their burdens 

 of stones and earth on the sea-bottoms, and compressing and 

 ploughing the shores as they stranded, will account for many 

 of the effects noticed ; but they certainly will not account for 

 all of them, and in many large districts great thicknesses of 

 snow and ice, carrying boulders and stones and earth and 

 other 'things, must have covered the hills and valleys, in the 

 same way as Greenland is covered now, creeping outwards 

 from the highest snow-covered land to immense distances. 



In many places there is no evidence of any extensive 

 glaciation of low lands, but only of the existence of glaciers of 

 greater or less extent on mountain-ranges, and extending 

 down the valleys from them, where no such glaciers now 

 exist. Such seems to have been the case in Tasmania, and, I 

 believe, in New Zealand ; but, whatever the special results in 

 each locality, they all alike indicate a more arctic climate 

 where they occurred than now exists there. 



The third question still demands an answer, What was the 

 cause which produced the last ice age, and why did it cease to 

 act ? 



Some geologists, and eminently Sir William Dawson, the 

 Canadiaii professor, have suggested that an efficient cause may 

 be found in those elevations and depressions of land which are 

 well-known geological facts, and which doubtless may have 

 had considerable climatic influence. 



Sir William Dawson thinks that there is reason to suppose 

 that during the last ice age in North America the Isthmus of 

 Panama was submerged, and thus the Gulf Stream was not 

 thrown northwards as at present ; and also that a consider- 



