the North East of Ireland. 201 



Ing the wall of the dyke has undergone a great degree of induration, 

 its cement assuming the appearance of a compact hornstone ; thus it 

 has been enabled to oppose to the sea a resistance almost equal to 

 that of the basalt itself, and is still seen adhering on the sides of the 

 advanced crags above mentioned. 



From the most northerly of the two cliffs a ridge extends 

 towards the ascent of Lurgethan on the south-west, running through 

 the townland of Killnadore ; in several points along this ridge, and 

 particularly at Nockans and Tully, a very remarkable formation of 

 porphyry may be traced. Dr. Berger* considers it as clinkstone 

 porphyry and describes two varieties here noticed by him j one of 

 them distinguished by a reddish brown and the other by a bluish grey 

 colour, both containing concretions of glassy quartz and of calcareous 

 spar, the latter of which in the first variety occurs in the form 

 of detached crystals, but forms veins in the second. He adds that 

 it crops out in independent masses. He mentions also Court Mar- 

 tin, an old entrenchment near Cushendahl, on the road to 

 Cushendon, as another locality of the porphyry. 



From the observations made by Mr. Buckland and myself on 

 these rocks we were induced to believe that they were associated 

 with and subordinate to the old red sandstone. The position of the 

 ridge of Killnadore is distinctly indicated in the section. 



On the north of this ridge is the mouth of the river Balyeemin 

 on which the little village known by the double name of Newton 



* la an earlier part of the paper it was erroneously stated that this porphyry had 

 escaped Dr. Berger's notice, and the editor did not discover his mistake till the state of 

 the press rendered it necessary to substitute acknowledgment for correction. His over- 

 sight arose from the circumstance of its being described among the floetz trap series, 

 though its connection with the old red sandstone and its position near the foot of Lur- 

 gethan, while the floetz trap is confined to the summit of that mountain, certainly 

 renders its introduction in such a place an act of very questionable propriety. 



Vol. III. 2 c 



