246 WAVES OF SAND AND SNOW 



principal condition for the formation of an undu- 

 lating track by sledge traffic is, therefore, that the 

 material scraped from the road should be adhesive. 

 Neither pre-existing inequality of surface nor rapid 

 driving of the sledge is necessary for their forma- 

 tion. The undulations produced by dragging the 

 iron mould backwards and forwards over the same 

 ground averaged 2 feet 8" 5 2 inches in length from 

 crest to crest, i.e., 3*52 times the length of the 

 sledge. The cahots on the quarry track were 3*225 

 times as long as the sledge. 



In order to ascertain if the ridges on the quarry 

 track travelled downhill I put in iron pegs to mark 

 their position, hoping that observations could be 

 made after my departure ; but the pegs could not 

 then be found. The opinion of the manager of 

 the quarry is that the ridges do not travel' ; he 

 says they become " too hard to move, being all 

 as if crusted and cemented together." The road, 

 he informs me, has to be remade from time to 

 time, the ridges being hacked up, with considerable 

 labour, and the material strewn in the hollows. 

 The symmetrical form of the ridges supports the 

 impression of their immobility, particularly as the 

 sledge only traverses them in one direction. It 

 must not be forgotten that the condition of ,the 

 track varies with the weather. When the road is 



