PHYSICAL AND CLIMATAL CONDITIONS. 83 



promote the production of snow and ice. But this could 

 not affect the interior of Eussia or of Asia, so long as their 

 plains reiijained above water. 



" 5. The submergence of the plains must be a necessary 

 condition of the general glaciation of the higher lands. 



" 6. Astonomical changes do not affect this result. 

 With a great eccentricity of the orbit and the winter in 

 aphelion the colder winters and hotter summers would 

 produce more powerful monsoons, while on the opposite 

 condition the interior of the continents would have 

 warmer winters and cooler summers and weaker monsoons. 

 In either case the conditions for continental glaciers would 

 not be improved. 



" 7. These considerations show that general coverings of 

 ice stretching from the Pole to perhaps 45° are impossible. 

 Under conditions of submergence of the plains the sea 

 must keep open, in order to afford material for snow on 

 the remaining high lands, and with large continental 

 plains the climate will be too dry for glaciers. Thus 

 there must always be seas free from ice, or continental 

 plains free of ice, and under most supposable conditions 

 there must be both." 



The following comments by the writer accompanied the 

 above abstract in 1882 : 



Applying these very simple geographical truths to the 

 North American continent, it is easy to perceive that no 

 amount of refrigeration could produce a continental 

 glacier, because there could not be sufficient evaporation 

 and precipitation to aflbrd the necessary snow in the 

 interior. The case of Greenland is often referred to, but 

 this is the case of a high mass of cold land with sea 

 mostly open on both sides of it, giving, therefore, the con- 

 ditions most favourable to precipitation of snow. If 



