Hunt — On the Action of Waves on 8ea-beaches, 8fc. 261 



when they need to be good swimmers to escape heing battered on 

 the rocks." 



On the return journey the aim of the surf- riders is to " mount 

 the biggest billow, which carries them shorewards at lightning 



speed Should the rider fail to keep his plank at exactly the 



right angle on the crest of the green billow he will be overtaken by 

 the breaking surf of the wave which follows, and to avoid this must 

 again dive beneath it, and swim out to sea to make a fresh start." 

 From the above description it would appear that so long as he can 

 avoid the breaking crest the Hawaian " surf -rider " can swim out 

 to sea encumbered with his surf-board in the face of " great green 

 billows " (that) " come rushing in with overwhelming force," and 

 that by skilfully taking advantage of the steep slopes at or near 

 their crests he can return to the shore with the speed of the waves 

 themselves. 



In the preceding pages I have endeavoured to show that there 

 is no evidence that a wave of oscillation is transformed into a wave 

 of translation on passing into shallow water, and that the observed 

 motions of floating objects can be explained without assuming the 

 existence of such waves of translation. My next step will be to in- 

 vestigate the actions of waves on objects lying within their reach 

 on the sea-bottom, with a view to ascertain whether the wave 

 of translation can be equally well dispensed with in their case. 

 This part of my subject may be considered under two heads, viz.: 

 (1) the action of waves before plunging, and (2) their action after 

 plunging. 



The first of these sections has been dealt with incidentally in my 

 Paper on " Ripple-mark," from which the following passage may be 

 quoted, as recording an observation in point : — 



" One fine and almost calm day in the summer of 1881, being 

 at Broadsands, in Torbay, and seeing that the strand was covered 

 with ripple-marks, I proceeded to watch carefully the action of the 

 water, with the view of ascertaining, if possible, the process of their 

 formation. Floating in my boat a few yards from the shore, in 

 about eighteen inches of water, I narrowly scanned the efiect of the 

 very gentle swell that was breaking on the beach. I observed that 

 a small shell lying in one of the furrows, instead of being steadily 

 washed shorewards by the incoming waves, was washed backwards 



