PHYSICAL AND CLIMATAL CONDITIONS. 79 



tions of great magnitude would be produced of the same 

 general nature with those of the Missouri coteau. These, 

 of course, now constitute the great " terminal moraine " * 

 which has l^een so carefully traced by the geologists of 

 the United States. 



Comparing a map of America in the Pleistocene with 

 that of the same region in the later Cretaceous and early 

 Eocene, it will be at once seen how, in the one case, the 

 arctic conditions must have been transferred to temperate 

 regions, and how, in the other, temperate conditions must 

 have been carried north to Greenland. 



It may be well here to notice shortly the contention 

 often made that the weight of the ice upon the parts of the 

 continents loaded with it must have been itself a cause of 

 the Pleistocene depression. No one has, I believe, con- 

 tended more strenuously than the writer, in connection 

 both with the carboniferous deposits and those of the 

 deltas of great rivers,f in favour of the instability of the 

 crust of the earth when loaded with great weights or 

 when these are removed ; but it must be observed that 

 such weights are usually due to the deposition of sediment 

 in the sea. The effect of accumulations of ice on high 

 lands is less certainly known. If, however, we imagine 

 that the continental period of the later Pliocene was 

 closed by a differential depression, submerging the plains 

 and leaving the mountains elevated, the resulting geogra- 

 phical conditions would be favourable to accumulation of 



* I need scarcely say that the reference of this terminal moraine to 

 a land glacier is absurd on physical grounds ; and there is no modern 

 exatnple of such a thing, as even the Greenland neve discharges by 

 local glaciers. 



t "Acadian Geology," "Modern Science in Bible Lands," Presi- 

 dential Address to Brit. Association, 1886. 



