582 Mr. J. Beete Jukes and the Rev. Samuel Haughton on the 



formation still retains its former strike, and still dips from S. E. to N. W., and 

 the traps plunge to the N. W. under a band of slates, in which few or no 

 igneous rocks are to be seen. 



It remains doubtful, however, whether the greater surface expansion of the 

 traps in "Waterford be due to a really greater thickness of these rocks, or to 

 luidulations and contortions in the rocks, or to repetition by means of faults. 

 Perhaps all these influences may be combined to produce the effect. 



E. — The Camhro- Silurian area of Kildare and Wicklow is separated from 

 the preceding area D by the granite of the main area F. It occupies a space 

 of about twenty-five miles in length, by seven or eight in width. The mean 

 direction of its two longest boundaries is about N. 20° E. or N. N. E. ; that of the 

 two shorter nearly E. and W. It is remai'kable that each pair of boundaries 

 is parallel, although in both cases one boundary is the margin of the uprising 

 and intruding granite, and the other that of the overlying unconformable Car- 

 boniferous Limestone. 



The strike of the beds in this area is also parallel to that of its longest boun- 

 daries, or, almost without exception, N. N. E. and S. S. W. The dip of the beds 

 on the immediate margin of the granite is W.N. W. at comparatively low an- 

 gles, but over all the rest of the area the angle of inclination is very high, rarely 

 less than 60°, and oftener 70' or 80". It is very remarkable that although the 

 flexures are apparently bold and numerous, the general tendency of the whole 

 mass seems to be to dip towards the granite, the higher beds coming in in the 

 direction of the granite, and the lower ones appearing to crop out on the north- 

 westerly margin of the area. 



The rocks, indeed, which strike from Kilcullen to Ballitore have, in their 

 green and purple hues and gritty beds, no slight resemblance to some of the 

 Cambrian rocks of areas A and B. 



Numerous beds of trappean ash, generally resembling a greenstone ash, and 

 often mingled with much sandy debris, are iuterstratified with the slates through 

 the centre of the area, and towards the margin of the granite. Few masses 

 of actual trap, however, occur till we reach the north-eastern limits of the area 

 in the neighbourhood of Ballynascorney Gap, where large masses of coarse 

 porphyry, containing dull green crystals of felspar, in a blue compact base, 

 make their appearance. These seem to be clearly intrusive, and to produce 

 some considerable amount of alteration on the adjacent slates. 



