190 Correspondence — 0. Fisher. 



have seen, it would appear that, no matter how the wind blows, it has 

 very little effect on shingle beaches, except while the tide is coming 

 in ; on sand beaches, however, it is otherwise, as the wind acts most 

 while the tide is out, as it has a greater extent of bare sand to blow 

 over. Perhaps, however, it is not fair to draw a comparison between 

 the tidal work in the open seas west and south of Ireland with that 

 effected in the narrow seas round England, as in the first there may 

 be great oceanic waves rolling in, unaccompanied by wind, which, 

 as on the previously-mentioned coast of Mayo, may obliterate all 

 windwork ; while in narrow English seas Avindwork ought to be 

 more effective, CoL Greenwood in his letter (Geol. Mag. March 

 1874, p. 143) states: "It is the prevalent S.W. wind which throws 

 beaches across the mouths of our streams on the south coast," — while 

 I would suggest that it is the incoming tidal current from the 

 W.S.W., aided in part by the wind, that is the great worker ; for if 

 wind could act alone, in no place would we find a beach travelling 

 up wind. 



On a coast where there are never any breakers or high waves 

 except during winds, a vessel could not be floated by the tidal cur- 

 rent over one of these sea-banks. But all shores are not so situated ; 

 for at Aranmore, at the entrance of Galway Bay, on the 15th Aug. 

 1862, during a perfect calm, a wave, over twenty-five feet high, came 

 in and swept 15 people off who were fishing on the Glassan rock : 

 while at the same island, in a.d. 1640, a wave, at least 60 feet high, 

 came in and swept over the low portion of the island known as 

 the Blind Sound [Mem. Geol. Survey, Ex. Sheets, 103 and 113, p. 12J. 

 But in general great waves are due to the incoming tide with a wind 

 blowing in a similar direction. G. H. Kinahan. 



ON THE OEIGIN OF THE ESTUARY OF THE FLEET. REPLY TO 

 MR. KINAHAN. 



Sir, — Mr. Kinahan has not attempted to disprove my theory of 

 the formation of the Elect, but has substituted another which he 

 prefers. I have, however, some objections to offer to it. He con- 

 siders the shore-line of the Elect to have been formed by marine 

 erosion. That this has not been the case appears evident from a 

 mere inspection of the Ordnance Map. Compare, along the whole 

 sheet, the outline of the open coast with that within the Fleet, and it 

 will be seen at a glance that its character is totally different. " The 

 old marginal cliffs " of the Fleet, supposed to have been degraded 

 into slopes, never, in fact, existed. There are no cliffs old or new 

 except the very low ones, which have been formed by the lap of the 

 small waves got up within its confined area. 



Mr. Kinahan says that " as long as the lagoon exists, so must the 

 Chesil Bank, as the waters of the Fleet keep the bank from travelling 

 inwards." This is incorrect, because the bank does travel inwards, 

 slowly but surely, as may be seen by examining its inner margin. 

 In heavy storms, like that of 1824, the sea washes over it, and 

 heaps of shingle are thrust forwards into the Fleet, where they re- 

 main undisturbed. 



