On Drift. 13 



shallow water. And hence we may conclude that Northern Asia 

 was in a state of comparative repose during the period of much 

 greater oscillation, and probably of more frequent and compara- 

 tively violent disturbance of the European area. Again, no traces 

 of former glaciers have been detected on the Ural Mountains, or 

 on the projecting headlands which run out to the northward from 

 the high lands of Northern and Central Asia. This former absence 

 of glaciers during our glacial period, in a region now so much 

 colder than Europe, appears at first sight a great anomaly. It 

 presents, however, no real difficulty, because those very causes 

 which I believe to have produced the glacial cold of Europe would 

 necessarily diminish the cold of Northern Asia, and more especially 

 that portion of it immediately east of the Ural chain, as I have 

 explained in my paper " On the Causes of Changes of Terrestrial 

 Temperature." This effect would be due to the extension of the 

 Atlantic Ocean to the eastward, so that the region of the Ural 

 would become part of the western shores of the old continent, and 

 would experience climatal influences similar, though far less in 

 degree, to those now experienced in our own region. Hence what 

 I have termed the line of 32° F. would be higher in North-western 

 Asia than at present. On tlie other hand, the extension of the 

 ocean to the eastward would lessen the great difference which now 

 exists in Northern Asia between the summer and winter tempera- 

 tures ; and on this account the height of the snow-line above the 

 line of 32° would be diminished. Consequently the absolute 

 height of the snow-line would be increased by the first cause and 

 diminished by the second, and would probably be not very different 

 from its present height, though it might possibly be somewhat 

 less. Now, since the configuration of the mountains was probably 

 very nearly the same at the glacial epoch as now, the existence of 

 glaciers upon them would depend upon the height of the snow- 

 line ; and, that height not being materially altered, there is no 

 more reason why glaciers should have existed there at the more 

 remote than at the present epoch ; and at present we know that 

 there are none in the Ural chain as far as the 70th degree of lati- 

 tude,* and none on the mountains of Northern Asia descending 

 nearly low enough to reach the level of the shallow sea, which we 

 suppose to have covered the low lands of that region during the 

 glacial period. 



This former absence of glaciers, and the comparative repose of 

 Northern Asia during our glacial epoch, are sufficient to account 

 for what appears at first sight extremely anomalous — the fact, that 

 while on the west of the Ural mountains we have a district covered 

 with enormous erratic blocks, there is scarcely a single block to be 

 found on the east of that chain at any distance from its original 



* Geology of Russia. 



