NOTES ON RIPPLE MARKS 129 



billows in the atmosphere can have anything to do with ripple 

 marks in dune sands. Do dune-sand ripple marks vary in size 

 with wind velocity and coarseness of the sand? They do not 

 vary very much. May ripple marks be formed by a like reaction 

 with bottom currents in deep water ? If so, their variation in size 

 may also be small. Such ripple marks, like those in sand dunes, 

 should always be unsymmetrical. Their sizes are probably 

 independent of depth of the water. 



