282 WAVES OF SAND AND SNOW 



greater prominence. When the current and the 

 progressive water-waves are in the same direction 

 the latter no doubt assist in producing the un- 

 symmetrical sand-ripples called current-mark, and, 

 I expect, make them a little steeper than they 

 would be if formed by current alone. In a shallow 

 rock basin in a mountain torrent in Switzerland 



1 found a patch of rippled sand left bare. From 

 its position I could be sure that the ripples had 

 been produced by a throbbing and pulsating 

 current. The sand was sufficiently tenacious to 

 stand vertically, so that I was able to cut a longi- 

 tudinal section and make an impression of the 

 profile on paper. I found that eleven consecu- 

 tive ripples had an average wave-length of 

 0443 inch and an average height of 0057 inch, 

 the length, therefore, being 78 times as great 

 as the height, which, though less steep than the 

 ripple-mark of the sea-shore, is steeper than the 

 ripples and waves which I have measured in 

 steadier currents. 



At Grange, in Lancashire, I measured unsym- 

 metrical sand-ripples still covered to a depth of 



2 inches by water. The water was then stagnant 

 owing to the subsidence of the tide, but the ripples 

 had been obviously formed in a current, and the 

 situation was such that there was probably some 



