244 



Scientific Proceedings, Royal Dublin Society. 



Opikions as to the Motion of Shingle tjndek "Watek. 



Sir E. Belcher. 



"... the waves during heavy gales 

 exercised power at very great depths ; he 

 had seen evidence of it in water fourteen 

 fathoms deep. He thought the tide cur- 

 rent did not affect depths of more than 

 12 or 14 feet."— K. 49. 



Professor Airy. 



"Although a swell might roll up the 

 centre of the English Channel, yet there 

 was a tendency in all such places for the 

 direction of the waves to change gradu- 

 ally, as towards the general line of shore, 

 and to roll pebbles that way. He qmte 

 agreed in the opinion that very little was 

 ascribable to the action of the tide." — 

 C. 38. 



Mr. Scott Exjssell. 



" It did not appear from the Admiralty 

 charts, that near these shingle beaches 

 there were any tidal currents of sufficient 

 velocity to move stones of the bulk of 

 those forming the banks ; therefore he 

 was warranted in attributing their for- 

 mation, chiefly, if not entirely, to the 

 action of wind- waves in conjunction with 

 the local causes he had endeavoured to 

 point out." — K. 63. 



Mr. K. A. C. Austen. 



"This process, by which masses of 

 solid materials can be planed off parallel 

 with the sea level, is due to the action of 

 wind or surface-waves, inasmuch as in 

 calm weather, when I have had opportu- 

 nities of passmg over some of these plat- 

 forms, I have felt convinced that the only 

 other agent, namely the tidal streams, 



Mr. J. M. Eendel. 



"... his own opinion was, that shin- 

 gle coiild scarcely be moved by the 

 heaviest waves, at greater depths than 

 three fathoms." — E. 64. 



Mr. Joseph Gibbs. 



"... the movement of the beach in 

 question was not so much due to the 

 ordinary flow, as to what might be termed 

 submarine currents, which had the power 

 of carrying pebbles along the shore at 

 great depths until the waves cast them 

 up as shingle." — C. 35. 



Mr. G. H. KiNAHAN. 



" . . .at Chesil the driftage is due to 

 the flow-tide current, augmented by 

 waves caused by the prevailing winds, 

 while at Cahore the driftage is solely due 

 to the flow-tide currents, its effect being 

 modified by adverse wind- waves ; . . . 

 the sorting of the pebbles on Chesil 

 beach is probably principally caused by 

 the progressive increase in the velocity of 

 the tidal current as it approaches the 

 nodal or hinge-line of the tide in the 

 English Channel."— Q.J. G.S., 1877, 

 p. 41. 



Mr. J. Thornhill Harrison. 



" No wind-waves acting upon a beach 

 would ever have excavated the bed of the 

 bay to its present depth, and some other 

 forces must therefore have been in opera- 

 tion. Among those forces, he believed, 

 were the tidal action, which was very 

 considerable in the bay, and the ground'^ 

 swells, which came into it with enormous 



