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HOBBS— CHARACTERISTICS OF THE 



[April 22, 



to accomplish the result with the less ponderous snow, and that the 

 resulting forms set quicker in the snow (see Fig. 32, a). 



Cornish has realized the full importance of snow-blast erosion 

 in modifying the form of snow drifts. His barchans of erosion, 

 in plan resemble the barchans of deposition from which they are 

 derived, but unlike the depositional forms their broader surface is 

 concave upward instead of convex, and their steeper face is toward 

 the wind (see Fig. 32, b). 



Fig. 32. Barchans in snow, a, of deposition ; b, of erosion (after 

 Cornish). 



Some facts of importance which concern the density of the 

 snow are emphasized by Cornish, and apply with especial force to 

 the surface snow of inland-ice. It was found that crusts upon the 

 surface of snow do not necessarily imply melting, but are produced 

 in temperatures below the fusion point. When the air temperatures 

 at Winnipeg ranged from 25° to — 28° F. the snow surface over 

 the river set so hard that the mocassined heel did not dent it. 

 Pieces of this snow broken off and held up to the sunlight showed 

 a " mosaic of small translucent icy blocks cemented firmly by 

 opaque ice." The effect upon snow density of the radiation from 

 the surface and of pressure from the wind, were strikingly brought 



