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V.—Irish Tide Heights and Raised Beaches

Published online by Cambridge University Press:  01 May 2009

Extract

A Good deal of attention has been lately bestowed on the Raised Sea-beaches around the British Islands and the evidence afforded by them as to alterations in the level of the land. Some geologists seem to entertain the idea that such beaches were originally accumulated on horizontal lines; and they have drawn the conclusion, that when one portion is found to be higher than another, it necessarily indicates an uneven rise in the surface of the earth. This idea, however, is erroneous; and the object of this paper is to prove, from the data supplied by the Ordnance Survey and the Admiralty Charts, that the littoral deposits at present accumulating around Ireland are being formed at varying levels.

Type
Original Articles
Copyright
Copyright © Cambridge University Press 1876

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References

page 78 note 1 Nearly all the heights hereafter given are taken from the levellings of the Ordnance Survey, a few being added from the Admiralty Charts in those places where the Ordnance Survey had not stations.

page 79 note 1 It should be mentioned that the Ordnance Survey have adopted a slightly higher level for the mean water; they however in their calculation included the stations Cashla Bay (No. 18, Table IV.) and Mullaghmore (No. 20, Table IV.). Both these stations, however, are so situated that the heights of mean water thereat may be affected by “counter-tides” generated by land in their respective vicinities.

page 80 note 1 The reason for the rise of tide respectively at Courtown and Ballycastle being less than elsewhere is explained by Haughton in his pamphlet “On the Tides and Tidal Currents in the Irish Sea and English Channel”.

page 80 note 2 For an inquiry of the nature of this paper, the Admiralty heights are not very satisfactory, they not being as trustworthy as those given by the Ordnance, their sounding having been referred to beach marks at different harbours. They, however, give a general idea of the varying heights of the spring-tide at the different places mentioned.

page 81 note 1 The tide rises and falls much less on the east coast of Wexford than on its south and south-east coast, between Baginbun and Greenore Points; but we cannot give particulars, as on this sheet of the Admiralty Charts there is no tide table.

page 82 note 1 Round the coast of Great Britain, especially in some of the bays and estuaries, the difference between the heights of high spring-tide is much more marked than around the coast of Ireland.