192 DISCUSSIONS IN CLIMATOLOGY. 



rush over both, leaving a covering of mud as the water sub- 

 sided. Part of this fixed ice, but not the whole, might be 

 thawed away during summer, and next winter a fresh layer 

 of ice with a fresh supply of animal remains might be formed 

 over the former stratum ; and so the peculiar position and 

 perfect state of preservation of this immense collection of 

 extinct animals may be accounted for without having recourse 

 to the somewhat improbable theory that a very great and 

 sudden change had taken place in the climate of that 

 region/' * 



Dr. Rae lived some years on the banks of two of the 

 great rivers of America, near to where they enter 

 Hudson's Bay, and also on the Mackenzie River, which 

 flows into the Arctic Sea, and had good opportunities 

 of observing what takes place on these streams, all of 

 which have large alluvial deposits, forming flats and 

 shallows at their mouths. 



Arctic America during Interglacial times. — We 

 have seen that the eastern continent in Pleistocene 

 times enjoyed in the Arctic regions interglacial 

 conditions of climate. It is true that on the western 

 continent we have not in Arctic regions such clear and 

 satisfactory evidence of an interglacial period. But it 

 would be rash to infer from this that the western 

 continent was, in this respect, less favoured than the 

 eastern. That we should find less evidence at the 

 present day of former interglacial periods in Arctic 

 America than in Arctic Asia, is what is to be expected, 

 for the glaciation which succeeded interglacial periods 

 has been far more severe in the former region than in 

 the latter. The remains of the mammoth have, how- 

 ever, been found in Arctic America, in ice-cliffs at 

 Kotzebue Sound, under conditions exactly similar to 

 those of Siberia. 



* ''Phil. Mag." July, 1874, p. 60. 



