Lower Palceo zoic Rocks of the South-East of Ireland. 511 



are themselves covered by a thickness of yet another three or four thousand 

 feet, at least, of these higher rocks. This would give a total thickness often or 

 twelve thousand feet for the Cam bro- Silurian rocks. Farther to the north- 

 west, the beds appear to be inclined pretty equally in both directions, and then, 

 as we approach closely on the granite of Mount Leinster and Mount Blackstairs 

 and the neighbourhood, the beds appear to be rising to the N. W., with a pre- 

 vailing dip to the S. E. This south-easterly inclination on the flanks of the 

 granite, however, has rarely so high an angle as is found to prevail at a distance 

 from it. One circumstance is very remarkable, — that after the bedded traps have 

 taken their final plunge to the north-west, they never reappear at the surface 

 in that direction over the whole of the county of Wexford, and the adjacent parts 

 of Carlow and Wicklow. We must therefore suppose that the beds in con- 

 tact with the granite over all that portion of the area belong to the uppermost 

 part of the Cambro-Silurian series of our district, that which lies above the traps. 



The line of bedded traps before spoken of terminates on the coast at Tara 

 Hill, about four miles north of Courtown. About four miles north of that again 

 is Arklow Head, where there is to be seen a very interesting mass of bedded 

 felstone ash, and ashy porphyry containing rounded pebbles, together with beds 

 of trappean conglomerate, interstratified with slate rocks and associated with 

 intrusive greenstones and elvan dykes.* 



The general dip here is to the south-east ; and from Arklow, all up the val- 

 ley of Ovoca, and over all the country between it and the town of Wicklow, 

 south-easterly dips, at a very high angle, are much more numerous than north- 

 westerly ones. In this district, accordingly, we find the bedded traps rea ppear- 

 ing at the surface in great force, as the beds rise towards the N. W., forming 

 several lofty hills, and associated, as in Wexford, with intrusive greenstones 

 and other igneous rocks. 



From under this trappean series there rise, still farther to the north-west, 

 the lower part of the Cambro-Silurian beds, like that between the traps and 

 the Cambrian base in Wexford, and, as we should expect, we shortly find this 

 Cambrian base itself appearing at the surface from underneath the Cambro-Silu- ' 

 rian rocks, and forming the areas already described under the head B. 



So far, then, the position and lie of the rocks in Wicklow and Wexford 

 lead to harmonious results; they each point to the beds lying between Arklow 



• See Paper on Arklow Head by Mr. Jukes, Journil of the Geological Society of Dublin, vol. vii. 



