266 Scientific Proceedings, Royal Dublin Society. 



I observed at the east cove, for the first time, that when a wave 

 breaks, and rushes up the beach, the wave-current turns to meet 

 the next wave, towards the sea, long before the advanced portion 

 ceases to flow onward, so that the forward current actually divides 



into two, one going up and the other down the strand By 



the turn of the tide, about 2.30, a steep ridge had been formed 

 between three and four feet high, close to (the) western rock bound- 

 ing the little cove. Small stones were shot up and over this ridge, 

 and big ones pulled down." 



The observations made on the 14th Oct. and 14th Nov. seem 

 to afford a solution of the problem as to the relative destructive 

 and accumulative actions of waves on shingle-beaches, and they 

 reconcile the apparently inconsistent observations of Mr. Palmer 

 and Sir John Coode. It is clear that the destructive and accumula- 

 tive actions may be going on at the same time. As a matter of 

 fact, they were both going on together on the days referred to, on 

 which occasions the waves were accumulating small stones, while 

 denuding the beach of large ones. I shall presently show how at 

 other times waves will reverse this action, accumulating the large 

 stones while carrying off the small ones. 



It is important to note that whilst the plunging waves, observed 

 on the 14th October, were driving forward the small stones and 

 drawing back the large ones, at a distance of a few yards waves 

 that, for some reason, were not breaking so heavily, were not assort- 

 ing the beach- stones in the same way. 



The action of the plunge of a wave in accumulating beach- 

 material can be conveniently studied when very small waves are 

 breaking on a sandy beach, and the sea is not disturbed by swells. 

 It will be seen that the plunge stirs up the sand at the starting^ 

 point of the forward current, and that some of this sand is carried 

 forward by the water in suspension. On the turn of the current 

 there is a moment of slack water, during which time the sand falls 

 to the bottom, whence it is not readily dislodged by the return 

 current, commencing as it does gradually, with no preliminary 

 plunge. In the case under consideration, should the sand be mixed 

 with mud, the latter, having no time to settle on the turn of the 

 water, is carried backwards as well as forwards in a state of 

 suspension. Now, it is only necessary for us to transform our 

 summer wavelets by gradual stages into storm waves, for us to 



