242 WAVES OF SAND AND SNOW 



depression was scooped out to leeward of the initial 

 inequality, then a mound was thrown up to leeward 

 of the depression, and another trough was scoured 

 out to leeward of this, and so on, wave by wave, 

 the group of undulations continually extending. 

 There was, however, one important difference 

 between the experimental cahots and those usually 

 produced by sledge traffic. The former, as the 

 experiment was continued, became more and more 

 unsymmetrical in profile, with a gentle weather 

 slope and a steep lee slope, whereas the latter are 

 symmetrical. 



I decided to change my model sledge, and 

 obtained a small mould, 925 inches long, used 

 for casting lead, which was very heavy, weighing 

 14 lb., and was suitably shaped, having the form 

 of a barge. 



With this I began again, drawing it along slowly 

 and without the employment of an initial inequality. 

 The small, heavy sledge sank somewhat in the 

 loose, dry, sandy, or gravelly surface of the higher 

 parts of the beach, driving before it a mound of 

 loose particles, as in the former experiments. The 

 furrow quickly deepened as the sledge was drawn 

 backwards and forwards over the same track. My 

 back was turned as I hauled, so that I did not 

 see the sledge, but presently I noticed a change 



