SNOW-WAVES AND SNOW-RIPPLES 95 



Double tail of snow-powder — Single train of black smoke, 

 but double track of steam, from chimneys — How fallen 

 leaves drift before the wind — On " banner clouds " and on 

 sandbanks to leeward of promontories — On the action of 

 an obliquely crossing wind upon the swell of the sea. 



Loose snow has two conditions, which depend 

 upon temperature. Near the melting-point, 32° 

 Fahrenheit, the particles are soft and adhesive. 

 Near zero Fahrenheit and below this temperature 

 they do not adhere but glide easily over one 

 another. In England and Scotland I studied 

 ripples in the first kind, or moist, snow. In order 

 to see the effect of wind upon the second kind, 

 or dry, snow, I spent a winter in Canada, crossing 

 from Montreal to Vancouver and back again. I 

 also studied there the forms of the banks or drifts 

 produced by the action of wind in the neighbour- 

 hood of fixed obstacles . I examined, too, the forms 

 which gravity gives to the caps of snow which 

 collect upon prominences in still weather. This 

 last piece of research being naturally incidental 

 to the tour, may, I thifik, be properly described 

 in this book, although the forms are not waves, 

 or produced by eddies. 



Ripples in Moist Snow. 



The following observations were made in 

 England and Scotland at temperatures but little 



