166 WAVES OF THE SEA 



An important part of the explanation is in the 

 seaward currents generated during such weather, 

 with which I shall have to deal presently, and 

 for the moment I will only specify that part of 

 the mechanism of removal which is due to the 

 waves considered as merely oscillating i.e., with- 

 out any resultant current. When the sea is very 

 rough the agitation of the bottom -water is so 

 violent that the sand cannot settle. It must be 

 remembered that wherever there is a swirl of water 

 with an upward velocity of even as little as 

 2 inches per second the sand cannot sink. Thus, 

 as may be readily perceived by the eye, the rough 

 water becomes turbid with the sand, as if the sand 

 were so much mud, and the mechanism of shore- 

 ward transport of quickly subsiding particles no 

 longer applies. The sand behaves, in fact, more 

 like mud or dust, and (even if there were no sea- 

 ward undertow or other seaward currents) it would 

 tend to shift to deeper water where the bottom 

 agitation is not too great to allow it to settle. 



On the Undertow 



At Branksome Chine there is a typical sandy 

 shore of moderate slope, which is not exposed to 

 strong tidal currents. The exposure is southerly, 

 and there is a headland a few miles to the westward. 



