SNOW-WAVES AND SNOW-RIPPLES 125 



minute, whereas the aeolian sand-ripples of the 

 same wave-length which I observed in 1896 

 travelled under the action of a wind of the same 

 strength at the rate of 0-5 inch per minute. 



For a time all the ripples in the above-mentioned 

 patch of sand-snow grew pari passu, each ripple 

 of the group having approximately the same length 

 and height, but after a time this state of affairs 

 suddenly changed, the rear ridge — that is, the one 

 most to windward — beginning to increase in height 

 very quickly. I think the change began as soon 

 as the patch of drifted snow-sand rose above the 

 level of the surrounding hard surface. When the 

 windward ridge raised its crest above the others I 

 saw that the wind eddied in its lee, and obser'ved 

 that some of the snow-sand in the centre of the 

 patch was travelling backwards towards the weather 

 ridge. The other ripples, hitherto so sharply 

 defined in the low sunlight, became indistinct and 

 were soon quite obliterated, except in two very 

 small areas on the sides of the drift at its lee 

 end. The patch of snow-sand had now become 

 crescentic, a space in the middle having been swept 

 bare by the return current. It had become, in 

 fact, a crescentic snow-wave or snow-barchan, and 

 the small areas where rippling remained were the 

 tips of the horns or cusps. At first the profile 



