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



bawn and others near Aughrira all forming narrow bands at the surface, and 

 all running from N. E. to S. W. 



If again we look at the felstones of Ovoca, we should see great masses of trap 

 interstratified with the slate continued for some distance to the N. E. by means 

 of beds of felstone and beds of ash, but terminating quite abruptly on the S. W. 

 at the very same meridian line mentioned before. Following on the strike 

 to the south-west, no other igneous rocks are to be seen, but elvan dykes leading 

 up to the large granitic mass of Croghan Kinshela. 



In short, while the whole of this part of the country from Wicklow Head 

 to Tinahely and Shillelagh has a persistent strike from N. E. to S. W., and a 

 nearly persistent dip at a high angle to the S. E. ; and while it is all equally full 

 of various igneous rocks, running for the most part in narrow bands parallel to 

 the strike of the beds, still, if we draw a N. and S. line through the town of 

 Eathdrum, or very slightly to the west of it, all the igneous rocks to the east of 

 that line are traps (felstone or greenstone), with many beds of trappean ash, and 

 scarcely even a single elvan dyke, while all those to the west of that line are 

 granites and elvans, without a single bed of compact felstone, or of trappean 

 ash of any description, and with no other trap rock than some very highly crys- 

 talline greenstones on the south of Croghan Kinshela. 



Two explanations might be offered of these facts: — 



First, we may suppose the beds of aqueous rock to be the same through- 

 out, and that the flows of molten trap and deposition of trappean ashes and 

 debris were confined to the eastern side of the meridian line mentioned above, 

 while the intrusion of igneous rocks at a subsequent period was confined to 

 the west of that line. 



Or we may suppose that the contemporaneous traps being confined as above, 

 the subsequent intrusions of igneous rock only formed granitic masses in the 

 one case where those traps were absent ; while in the other, where they pene- 

 trated into the trappean group, they produced the greenstones of West Aston 

 and other places. The difference of the two kinds of igneous rocks would in 

 this case result from the difference of the materials with which they came in 

 contact, the molten mass absorbing some additional bases in the eastern part 

 of the district, so that the mass which elsewhere cooled into granite here be- 

 came converted into greenstone. 



