AND OTHER WATER WAVES 87 



breakers is sometimes much greater. Now, this 

 means that their wave-length in deep water was 

 much greater than that observed during storms at 

 sea, and that the speed in deep water of these 

 subsequent waves was also much greater than that 

 of the waves then observed. But when the wind no 

 longer acts upon the water, there is no agent to 

 accelerate the waves. Theoretically, they should 

 travel by gravity at the same speed as that which 

 the action of the wind has induced, or, if there be 

 any change of speed while in deep water, it could 

 only be some very gradual diminution. A real 

 increase in the speed of transmission may be pro- 

 nounced with confidence to be an impossibility in 

 the absence of any new source of energy. 



The only possible explanation, therefore, is that 

 the waves of longer period which come in upon 

 the shore after storms are present, but escape 

 observation, during storms at sea. Not only so, 

 but they have attracted comparatively little atten- 

 tion from on board ship even after storms. 



The following observations of the swell, follow- 

 ing a westerly storm, were made by myself at 

 Branksome Chine, on the Dorsetshire coast, 

 between Bournemouth and Poole. The storm had 

 been violent and long at Bournemouth, and the 

 weather in the Atlantic exceptionally stormy. 



