SNOW- WAVES AND SNOW-RIPPLES 101 



Waves in Dry Drifting Snow. 



I arrived in Canada on December 15, 1900, 

 and found the country around Montreal snow- 

 covered, but until January 5th I saw no undulations 

 with their steeper side turned to leeward — nothing, 

 indeed, but groovings facing the wind. After the 

 New Year, however, the temperature fell, we had 

 what is called in Canada " zero weather," and the 

 newly fallen snow particles being dry and not 

 adhering by dampness or by regelation to one 

 another, behaved quite differently. 



On January 5th I went out at 10.30 a.m. to 

 the fields on the west of Montreal. The tempera- 

 ture was 8° below zero Fahrenheit ; i.e., there 

 were 40° of frost, the sun was shining, and the 

 wind blew with a velocity of thirty miles an hour, 

 recorded at the McGill College Observatory. 

 During the preceding night 3 inches of fresh 

 snow had fallen upon the hard re -frozen surface 

 of the old snow. This new, light, dry snow the 

 wind was rapidly removing to places of shelter. 

 On the lee side of a swell in the ground I found 

 a group of waves, some of which are shown in 

 Plate 'XII. They resembled the aeolian waves 

 in dry sand which I observed at Helwan, having 

 the cliffs on the lee side, but they were flatter than 



