Kinahan — On Granite and Metamorphic Rocks. 195 



These stones are very suitable for this class of work, as there 

 are in them two systems of " grain," or concealed lines of split- 

 ting, in planes perpendicular to one another, along which the 

 quarrymen can split the rocks, with plugs, to any required 

 scantling. 



[The operation of plugging, as practised in the south-east of Ireland, consists in 

 making a row of round jumper holes, into which treble plugs are driven. If the stone 

 is kind, the holes are from five to twelve inches deep, according to the size of the 

 block ; if the stone is tough, the holes must be deeper. "Where a block has been split 

 into slabs, these are again split with flat wedges into posts, sills, &c. Most of 

 the inhabitants of these counties are quarrymen, and are skilled in splitting up 

 the blocks, and many of thm spend their spare time as stonecutters.] 



In this area the granite, for the most part, is not what can be 

 called a first-class stone, being often more or less rotten or flaky, 

 or even a growan, so that good stones cannot be procured every- 

 where. Those places in which good stone is known to exist are 

 mentioned below. 



Although granite has been so generally used in recent times, 

 yet, as pointed out by Wilkinson, " in the ancient buildings of 

 Co. Wicklow, slate-rock was the material more generally employed, 

 mixed with rolled field-stones of quartz and grauite. ... In the 

 buildings at the Seven Churches, Grlendalough, the granite blocks 

 are in many places much corroded by the weather, while the slate- 

 stones indicate, by their present state, a greater durability." 

 Some of the quoins in St. Kevin's Kitchen are of granite, which 

 rock was also partly used in the Round Tower, " the semicircular 

 arch in the doorway of which is cut out of a solid block of granite. 

 There is also a very peculiar and ancient archway constructed of 

 granite, which forms part of a gate-house, through which an old 

 paved road was constructed. Large flat-bedded stones of tins road 

 still remain. The peculiarly worked bed and arched joints of this 

 gateway indicate a rude and primitive construction." 



CO. WICKLOW. 



Granites. 



Golden Grove and Balhjknockan, near Blessington (Leinster type), 

 generally known in the trade as "Blessington stone." Bright grey, 

 more felspathic and more easily worked than the Kingstown and 



