Kinahan — On Granite and Metamorphic Rocks. 185 



Extending south-westward from Dublin Bay to near New 

 Eoss on the River Barrow, in the Cos. Dublin, Wicklow, Kildare, 

 Carlow, Kilkenny, and Wexford, is the great Leinster surface ex- 

 posure of intrusive granites, with outlying smaller exposures to 

 the S.W. in Kilkenny, and to the eastward in Wicklow and 

 "Wexford. In the last-mentioned county, in the Carnsore district, 

 a considerable proportion of the rock is granitic gneiss [granite of 

 metamorphic origin). 



South-east, south, and south-west of the Leinster granite range, 

 in the Cos. Wicklow, Wexford, Waterford, Kilkenny, Carlow, Kil- 

 dare, and Dublin, there are in the Cambrian, Ordovician, &c, beds, 

 sheets, masses, and dykes of doleryte (?), melaphyre, diabase, 

 euryte, felstone, and elvan ; the probable ages to which each belong 

 having been already discussed. Most of the older ones are more 

 or less altered ; some being also changed by methylotic action 

 into serpentine (oplujte), soapstone (steatgte), or other allied rocks. 



[The methylotic rocks have already been tabled and described in the Paper on 

 Irish Makbles and Limestones (vol. v., pp. 404-412). 



In the area of the Leinster granite range, the granite is generally used for all build- 

 ing purposes ; but in the Co. Wexford, in the neighbourhood of the granite outliers, that 

 rock is rarely used, the houses, walls, and fences being built of clay. 



When quarries are opened the stones are rarely used, except for farm fences and 

 road material ; for the latter a quarry will not be opened if gravel can be obtained, 

 even though it may have to be carted for miles. In places where very superior road 

 metal could be easily procured by quarrying in the granite or whinstone, this will not 

 be resorted to, although the roads have to remain nearly impassable in consequence.] 



The granite varies greatly in quality ; some of it is very 

 coarsely crystalline, some very fine ; it is of every degree of 

 durability ; some hard durable varieties are good for tool work, 

 others not so. Their different qualities will be mentioned in con- 

 nexion with the different quarries and districts. In some places 

 the granite in use is procured solely from loose blocks and erratics ; 

 the latter in places occurring in greater or less quantities outside 

 the limits of the granite areas. Formerly the granite of those 

 districts, where it has two " grains," along which the stones split 

 readily, with plugs, into rectangular pieces, was in great de- 

 mand, being easily and cheaply wrought into columns, pillars, 

 farm- rollers, posts, sills, jambs, &c, procurable in considerable 

 lengths, and capable of long bearings. Of late years, however, it 



SCIEN. PKOC. K.D.S. VOL. VI., PT. IV. U 



