246 



Seientific Proceedings^ Royal Dublin Society. 



Opinions as to the Eelatite Motion oe Laege ash Smail Shingle 

 AxoNG Shoee. 



Professor (now Sir George) Airy. 



"... the progression in smallness of 

 the pebbles pointed to the direction from 

 which the current or fluctuation must 

 have transported them . . . ; they must 

 have been transported from the end of 

 the bank, where they were large, towards 

 the end where they were small." — P. 32. 



Admiral Spratt. 



" . . . On one occasion, on the coast 

 of Egypt, he put overboard five bags of 

 clinkers, weighing from 3 lbs., 4 lbs., and 

 5 lbs., to a few ounces; and on visiting 

 the spot a fortnight afterwards to 

 examine the effect of wave-action, he 

 found at 450 yards to leeward the largest 

 pieces of clinker nearest the point of start- 

 ing, one weighing 3^ lbs. and the other 

 2 lbs. ; at 700 yards and 800 yards they 

 weighed less than 1 lb., and at 1500 

 or 1600 yards, from J to J oz. only. 

 Thus the heaviest and largest pieces did 

 not travel the farthest, but the contrary. 

 —P. 31. 



Mr. A. Geikie. 



" A prevalent wind, by creating a cur- 

 rent in a given direction, or a strong 

 tidal current setting along a coast-line, 

 will cause the shingle to travel coastwise, 

 the stones getting more and more rounded 

 and reduced in size as they recede from 

 their sources. The ChesH Bank, which 

 runs as a natural breakwater 16 miles 

 long connecting the Isle of Portland 

 with the mainland of Dorsetshire, con- 

 sists of rounded shingle which is con- 

 stantly being driven westwards." — Text- 

 Huok of Geology, p. 435. 



Mr. (now Sir John) Coode. 



"... the cause of the large shingle 

 being found, at what is called ' to leeward ' 

 upon any beach, is due to the fact of the 

 large pebbles moving more readily than 

 the small, . . . " — C. 25. 



Mr. Eedman. 



" Undoubtedly the largest shingle tra- 

 velled to leeward, . . . " — P. 44. 



Mr. T. Mellard Ebadb. 

 " It was not, as Sir John Coode sup- 

 posed, that the large stones were the more 

 easily moved, for the reverse could be 

 readily proved, . . . the large stones, in 

 fact, travelled up a lesser gradient, and 

 consequently to a greater distance." — 

 P. 24. 



Sir Charles Lyell 



"... admitted the apparent paradox of 

 the largest pebbles at the ChesH Bank 

 being found to leeward ; or farthest from 

 the source whence they were derived ; as 

 he took it for granted that they did come 

 from the westward. . . . " — R. 47. 



"... throughout the Chesil Bank the 

 pebbles increase gradually in size as we 

 proceed south-eastward, or as we go far- 

 ther from the quarter which supplied 

 them." — Lyell's Principles Geol. vol. i. 

 p. 539, 11th ed. 



Mr. E. A. C. Austen. 

 "Along our own southern coasts the, 

 movement of shingle is from west to 

 east, and on the opposite coast of France 

 it is the same. ... On the Chesil beach 

 may be collected pebbles of limestone, 

 greenstone, trap, and old red sandstone, 

 derived from the older rocks of South 

 Devon."— Q.J.G.S. vol. vi. pp. 72, 73. 



