Hunt — On the Action of Waves on Sea-beaches, 8fc. 269 



Chesil Bank. He writes, " It is remarkable, that the large shingle 

 found at about the level of high-water, and such of the large pebbles 

 as may occasionally be found at higher levels upon the Bank, have 

 generally a flatter form than those under water. It is important 

 to notice, that all the shingle near Portland is generally less 

 spherical than that at some distance to the westward, as this proves 

 that it has been longer exposed to the grinding action of the sea." 

 (0. 21.) As this segregation of shingle according to form is a 

 common beach phenomenon, it seems possible that the difference in 

 the flatness of the Chesil shingle may arise from difference of form 

 in the rock- fragments from which the shingle was originally derived. 

 I am not aware that it has been shown that wave-action tends to 

 grind spherical shingle flat ; and there is no doubt that spheroidal 

 forms are found in very small shingle. 



The effect of specific gravity in influencing distribution I have 

 seen well exempKfied in the case of some fine metallic sand collected 

 by the waves at the highest level in one of the coves in Torbay. 

 In this instance the highest and lowest deposits were fine sands, the 

 intermediate expanse of tidal strand being rocky, with some shingle. 

 I may here point out how likely these exceptional cases are to per- 

 plex the student of wave-action. In my own case, after having 

 studied beaches for many months, and taken a large series of photo- 

 graphs, I came across a beach in Mudstone Bay, near Berry Head, 

 which seemed to falsify many of my conclusions. Spherical and 

 flat shingle of all sizes was intermixed with sand in hopeless con- 

 fusion. The explanation was to be found in the surrounding 

 rocks, consisting as they do of limestone, slate, and haematite. 

 Shingle derived from such sources naturally differed much both in 

 form and specific gravity. The slate had the advantage in form, 

 the haematite in weight, and the result was that the flat slate 

 shingle and the spheroidal haematite shingle were evenly matched 

 in their competition for highest place. 



We have now briefly considered the effect of waves of different 

 sizes on shingle of different form and specific gravity, but have 

 taken no account of the rise and fall of the tide. Unless the weekly 

 variation in levels, owing to spring-tides and neaps, and the daily 

 variation in levels at high-water and low- water be taken into 

 consideration, some of the commonest beach phenomena may seem 

 paradoxical. 



