Shingle on the East Coasts of New Zealand. S3 



always as above. The results stated were observed shortly 

 after there had been a full beach, surplus shingle having 

 formed what may, perhaps, more accurately be described as 

 a high beach. Consideration of the subject, since the 

 observations were made, leads the author to believe that 

 after the denuding of the beach of its surplus shingle and 

 the forming of a low beach, the result of waves continuing 

 to. strike the shore obliquely would depend chiefly upon 

 whether there were, or were not, a further supply of shingle 

 ready to be carried on to the portion of the beach under 

 observation : that is, whether there were surplus shingle 

 lying near on the side from which the waves were moving 

 or not. 



If there were a further supply of shingle, the lower part 

 of the beach would probably not be flattened to any great 

 extent by waves striking the shore obliquely ; or, if flattened 

 for a time during changes in the weather, it would be covered 

 shortly with fresh shingle. If there were no further supply 

 of shingle, the beach would be still further denuded, would be 

 reduced in width and have a still natter slope ; the material 

 would probably become smaller and smaller and in time 

 perhaps sand only would be visible above the water-line. 

 This action would go on till the beach disappeared 

 altogether, or became so much reduced as to afford no 

 protection to the shore which, if of yielding material, would 

 begin to wear away. 



The result of waves striking the shore nearly at right 

 angles, when there was a full beach down to low- water 

 level, would probably not be noticeable during a short 

 period of time, unless in the exceptional case of the slope 

 below low-water level being steeper than above that level. 

 In such a case, these waves would tend to draw the material 

 downwards, make the beach wider, and gradually reduce 

 the slope. Fine material would not be thrown up unless 

 the slope became very flat from some other action going on 

 at the same time. Long continued action of waves nearly 

 at right angles on a full beach would gradually reduce the 

 material by constant attrition ; the finer particles would then 

 be drawn downwards under the water-line, In this 

 way, shingle moving towards one part of a beach may 

 slowly disappear, instead of accumulating, as it does 

 when the supply is too large to be all disposed of in this 

 way. 



g2 



