SNOW- WAVES AND SNOW-RIPPLES 121 



being smooth except where transverse grooves are 

 cut in the partially consolidated material which is 

 exposed during the turning over of the wave. In 

 this respect waves of snow differ from those of 

 sand, for the resistance of the larger sand-grains 

 produces rippling on the surface of the sand- 

 waves. 



On the prairie around Winnipeg, however, there 

 lay during January and February a good deal of 

 altered snow, composed of rounded icy grains, 

 which varied in size from ^L inch to f inch 

 in diameter, the former being the size of 

 somewhat coarse sand, the latter of the " lag 

 gravel," which is rolled along by wind but not 

 ordinarily thrown into suspension. This snow-sand, 

 as I shall call it, fell into ripples of great regu- 

 larity, much resembling those in sand. I lingered 

 on at Winnipeg in the hope of observing the for- 

 mation of this snow-sand, but was unable to do 

 so. It is, however, certain that it is sometimes 

 produced by the breaking up of the ice formed 

 by re-freezing of melted snow. The doubtful point 

 is whether there is any other way in which it is 

 produced. Snow merely consolidated by pressure 

 did not ripple. I watched the action of wind upon 

 the material when it was composed of fairly 

 spherical particles ^V inch in diameter — /.^., of the 



