of the Vicinity of BuUin, 305 



situation of which renders it easy of access, and affords 

 many advantages to the observer. I shall subjoin to a 

 brief statement respecting the geological structure of that 

 country, an account oKscune nimerals of not very common 

 occurence recently found in Ireland. 



The citv of DuUin is placed in a flat country, at the di- 

 stance of about three miles from the sea, and about five miles 

 to the north of a ranae of mountams forming the verge of an 

 elevated district which extends from thence for more than 

 thirty miles to the south. This district is bounded on the 

 inland or western side by a continuation of the plain of the 

 neiirhbourhood of Dublin; and its breadth from the sea, 

 which forms its boundary to the cast, is generally about 

 four and twenty English nv.les. 



The basis of all the phin to the north and west of the 

 rnountains above mentioned, appears to be secondary (floetz) 

 limestone. 



The mountainous district itself is principally composed 

 of ])rimiiive rocks : it is traversed through its whole extent 

 by a broad tract of granite, which, taking its rise on the 

 shore at the south side ot Dublin bay, crosses the countv of 

 Wicklow in a sou ih- western direction ; being bounded by 

 incumbent rocks of great variety, the structure and relations 

 of which, as well as of the granitic mass, are in several 

 places very distinctly exhibited. 



The relative extent of the space occupied by the granite, 

 and by the rocks that occur between it and the calcareous 

 country, and the general position of their boundaries, may 

 be understood from the annexed sketch*; in which it is to 

 be remarked, that the places where the boundary is denoted 

 by a dotted line remain still to be explored, the line having 

 been there inserted only for the purpose of illustration. 



The granite has been observed in contact with other rocks 

 at the following places in the counties of Dublin and 

 Wicklow : viz. on its eastern boundary, — at Killitiey ; at 

 the southern extremity of the Scalp ; in the bed of the se- 

 cond streamlet which joins that oi ihc Powerscourt IVaterf all, 

 above the fall ; from the neighbourhood o^ Lwjgelaw to the 

 head of Lock Dan, and from thence to the upper part of 

 Gi':nmacana'is ; at Tonelagee ; at yjghavanag/i in the course 

 of the military road about a mile to the east of the barrack j 

 and at the western branch of the Coolbawn stream on the 

 north-west flank of the mountain Croghan Kivshela\. The 



•The sVjctches referred to in this paper will be given with our next 

 Number — Flaie VII. — Editor. 



+ Report on the Gold:nine by Messrs. Mills and Weaver. Transactions 

 of the JUublin Society, vol. iii. 



boundary 



