266 WAVES OF SAND AND SNOW 



The last case which I shall cite of one of these 

 very slow streams is that of the upper part of the 

 Bourne^ the little brook which gives its name to 

 Bournemouth. This has been canalized where it 

 flows through the Pleasure Gardens. In the upper 

 part, beyond the gardens of the Corporation, where 

 the stream flows through the Durrant estate, there 

 are some reaches where the bottom is covered with 

 clean sand. In one of these the course of thle: 

 stream is perfectly straight, and it flows between 

 perpendicular banks about seven feet apart. The 

 depth was 3' 7 5 inches, and the current flowed at 

 the speed of 0-85 foot per second. The sand was 

 in ripples of the form just described — i.e., with 

 broad and nearly flat crests, and were not only 

 fairly regular in wave-length but stretched almost 

 the whole way across the stream in continuous 

 ridges at right angles to the banks. Forty-six 

 consecutive ripples had an average wave-length of 

 6 inches, and an average height of approximately 

 0"3 5 inch. I saw these in 191 1, fifteen years after 

 I first observed the same type of sand-ripple in 

 winding channels. Not until I saw the regularity 

 of the ridges in the canalized stream did I realize 

 that so slow a current could produce such regular 

 ripples. I had noticed, however, something of the 

 same kind with regard to water-waves. I have 



