196 THOMAS C. CHAMBERLIN AND ROLLIN T. CHAM BERLIN 



local differentiating agency. Acting on rain, wind increases the 

 amount per unit area that strikes the surface of an eminence on 

 its windward side; it also somewhat increases the force of the 

 impact on that side. On the other hand, wind tends to drive 

 falling and fallen snow around the wind-swept side of the eminence 

 into its lee and to heap it up in the eddies there, and on the areas 

 protected from the wind. Thus the snowfall that, in the absence 



Fig. i. — Snow lodgment on the side of the summit ridge of Mt. Victoria, Canadian 

 Rockies. This ridge forms the continental divide. The snow has lodged on the 

 Eastern or Albertan side in the lee of the crest. Photo, by R. T. C. 



of wind, would come to rest on the windward and lateral slopes of 

 an eminence and later must drain away on these slopes is, under 

 the action of wind, concentrated notably in patches in the lee. 

 Considered therefore in detail, rain action is somewhat intensified 

 on the windward side of prominences, while snow lodgment, leading 

 on toward glacial action, is more markedly concentrated on their 

 leeward slopes. 



The field use of this distinctive localization of rain-work and 

 of snow-work respectively is qualified by the fact that, while the 



