G, H, Kinahan — Tide Heights and Raised Beaches. 81 



from which it falls to 2 feet at Castletown send, co. Cork ; after 

 which to the EN.E. it rises, being 3 feet at Danmore,. on. the mouth 

 of Waterford Harbour. Farther eastward, at South Bay, north of 

 Greenore Point, east coast of Wexford, we learn from the Admiralty 

 Charts that it is approximately 1 foot ; while as we go northward 

 from G-reenore Point, it gradually falls to the zero at Courtown.^ 



In Tables II. and III. are recorded the differences between the rise 

 of the tides at the mouths and far up in the estuaries of the Barrow 

 and the mouth of the Shannon. From column v., Table II., we 

 learn that the difference between the height of high spring-tide at 

 Dunmore and New Koss is nearly 2 feet, while from the same 

 column in Table III. we find that between Kilbaha and Limerick 

 there is an increase of rise of more than 4 feet. 



Table No. IV. exhibits the tides in some bays and sea-loughs. 

 From it we see that mean water and high water of spring-tides 

 are higher in such places than in the adjoining open sea. In Galway 

 Bay the rise of tide seems at first sight exceptional, being lower at 

 Galway, the head of the bay, than at Cashla Bay, near its mouth. 

 This, however, may possibly be due in part to the Aran Islands 

 across the mouth of Galway Bay, which generate ''counter-tides," 

 and thus form a "Head of the Tide" hereabouts {see Haughton). 

 The excess of rise of the tide in this bay is more plainly seen from 

 the following heights taken from the Admiralty Charts : — 



Table Y. 



1 Galway Spring-tide rises 15 feet above its own low water. 



2 Cashla Bay „ . 16 ,, ,, 



3 Greatman Bay ... „ 15'5 ,, ,, 



4 Kilkeeran Cove ... ,, 15-25 ,, ,, 



5 Eoundstone Bay ... „ 13*75 „ ,, 



6 Slyne Head „ 13-25 „ „ 



Stations 1 to 6 are along the north shore of Galway Bay, while 

 station 7 is on the inside or N.E. shore of Illaunmore, the most 

 north-eastern and largest of the Aran Islands. 



In Donegal Bay there are also " counter- tides," for which reason 

 Mullaghmore (station 20, Table lY.) was not admitted into Table I. 

 These probably account for the high tide in this bay compared with 

 the height of the tide on the coast to the west and north, as pre- 

 viously shown by the heights from the Admiralt}^ Charts. 



Now since it is the agency of the spring-tide, principally, which 

 arranges the littoral gravels which would constitute Eaised Beaches if 

 uplifted, it follows from Tables I. 11. III. and IV., column v., that if 

 the present sea were to retreat, its margin would form a vertical I3'' 

 undulating line. This line may be sometimes even more undulating 

 than that now represented, as some parts of the coast are more open 

 to storm waves than others ; and if this occurred where the line was, 

 for reasons given above, already higher than its mean, the upward 



^ The tide rises and falls much less on the east coast of "Wexford than on its 

 south and south-east coast, between Baginbun and Greener e Points ; but we cannot 

 give particulars, as on this sheet of the Admiralty Charts there is no tide table. 



DECADE II. VOL. III.— NO. II. 6 



