TRANSACTIONS OF THE SECTIONS. 113 



doubt that it is of tlic same age as tlie trachyte porphyry of Antrim, hoth being 

 referable, iu nil probability, to the great volcanic outbuists of the Miocene period. 



Considerable uncertainty exists regarding the relations of the Dowushire trachyte 

 to the volcanic rocks of the adjoining country. It only appears in two or three spots 

 ■within a small area ; but the probabilities are that it is a portion of an old neck from 

 which trachytic lava was erupted contemporaneously with that of Antrim. The 

 higher portion of the nuxss, as well as the original vent, have been removed by 

 denudation, and the district has since been deeply buried beneath Boulder-clay*. 



On tJie liaised Beach of the North-east of Ireland. By Professor Edward Hull, 

 F.ll.S., F.G.S., Director of the Geological Survey of Ireland. 



All along the eastern coast of Ireland, from Dublin Bay northward, there are to 

 be found at intervals distinct evidences that the coast has been raised in recent times. 

 These evidences are divisible into two kinds : — First, the occurrence of a narrow 

 fringe of varj'ing elevation, forming a terrace extending for some distance inland 

 from the coast, and composed of stratified sand and gravel containing marine shells 

 belonging to species now inhabiting the Irish Sea ; and, secondly, the existence of 

 old sea-worn dill's forming the inland margin of these terraces, which are now 

 bej'ond the reach of the highest tides. In the north of Ireland these cliffs are 

 penetrated by caves which have yielded bones of animals, some of which are extinct 

 in that part of the country, while the gravels of the old beach contain amongst the 

 sea-shells worked flints in considerable quantity in county Antrim, which prove 

 the elevation of the coast to have taken place since the human period. 



The occurrence of the caves near the Giant's Causeway and the island of Rathlin 

 was long ago noticed by Dr. Bryce and Mr. Andrews t, while the existence of tlint- 

 implements of human workmanship in the coast gravel of Larne and Belfast Lough 

 was first brought into notice by the late Mr. CI. V. Du Noj'er J ; but, as far as the 

 author had ascertained, no one has treated these littoral phenomena as a whole, or 

 shown that they belong to one period of general elevation along the whole coast- 

 line, and that they are represented by similar phenomena on the coast of Scotland 

 and the north of England. 



Localities. — Commencing from the southward, the raised beach may be observed 

 in several places around Dublin Bay, as along the coast of Ireland's Eye, forming 

 a well-marked terrace ; below Lowther Lodge, near Balljriggan, and in several 

 places south of the mouth of the Boyne, the elevation of the terrace varies from (j to 

 8 feet above high-water mark. 



Along the Downshire coast the gravelly terrace maj' frequently be observed, as 

 at Cloughy in the Ards, and along the coast at Killough and Ardglass to the south- 

 ern shores of Belfast Lough. Along this portion of the coast the maximum eleva- 

 tion is about 12 feet, as determined by Mr. Traill and the author §. On the north side 

 of the Lough, and around the shores of Larne and Island Magee, the gravel-beach 

 with shells may be obser\'ed at Bhanbuoy, near Carrickfergus, where its elevation 

 is 12 feet — at Kilroot, at Lame Harbour, and the eastern shore of Island Magee, 

 with shells and M'orked flints — and at numerous points along the Antrim coast, such 

 as the entrance to Glenarift", Red Bay, Bally castle Bay, and Eathlin Island, where 

 we have examples of old caves, sea-stacks, and shell-gravels reaching to an elevation 

 of 20 feet above high-water mark. 



It is in consequence of this gradually increasing elevation that the evidence of 

 the rising of the coast becomes more striking northward; and from the above data 

 it will be seen that the maxinuim elevation ranges from about feet in Dublin IJay 

 to 20 feet at the extreme north-eastern point of the Irish coast ; so that by an easy- 

 transition the elevation falls in with that of the " 2o-feet beach," lirst described 1 y 

 Mr. Smith, of Jordan Hill, Mr. Maclariu, and more recently by Professor Geikie||. 



* Messrs. E. Hull .ind J. L. AYavren, Explanatory Memoir to Sheet 36 of the Geological 

 Survey of Ireland ( 1871 ). 



t ]3rit. Assoc. Kep. 1834, pp. G58 & GGO. t Joern. Gcol. S'oc. London, ■( ols. xxiv. & xsv. 

 § Explanatory Memoir of the Geological Siu-vey of Ireland, fc'heets -19 & 50, p. 60. 

 II Scenery and Geology of Scotland. 



