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III. 



ON THE EPIDIORITE AND MICA SCHISTS OF KILLINEY 

 PARK, CO. DUBLIN. By PEOE. J. P. O'REILLY, C.E. 



(Plates III. and IY.). 



[Eead January 22, 1900.] 



The relations of the granite with, the mica schists in the neighhour- 

 hood of Killiney, Co. Dublin, are very fully gone into in the memoir 

 explanatory of the sheets of the Geological Survey of Ireland, Nos. 102 

 and 112 (1875). On p. 33 particulars are given as to the mica schist, 

 and its alteration from Lower Silurian slate, which, the writer of the 

 memoir observes, may be more especially seen over the rugged ground 

 of Roche's Hill and that lying to the west of Killiney Park. 

 Describing the Lower Silurian slate, he says : — 



"This mass of slate consists of beds of gray mica slate, with 

 bands of gray, close-grained grits, usually micaceous, but very 

 compact, the dips of all being invariably to the south-east, at from 

 40° to 60°. This high, steady inclination of the beds gives them the 

 appearance of dipping down into the granite, and on a level surface 

 would make them seem as if they were interstratified with it. The 

 fall of the ground, however, and the exposure in the cliffs show that 

 the beds are cut off by the granite below, and that they rest in 

 wedge-shaped troughs of that rock, the outline of which has no 

 relation to the dip or strike of the beds." 



At p. 34, describing in detail the relations of the mica schists and 

 granites to the west of the patch on which is situated Victoria Castle, 

 he says : — 



" To the west of this the slates appear in great force, and extend 

 northwards into the granite under the village of Killiney, and close 

 to the elevation marked 480 on the map, having, however, a long 

 narrow tongue of granite stretching into them for the distance of 

 350 yards between Killiney and the elevation just named. The 

 maximum width of the mass of slate is over 500 yards. To the south 

 of Killiney village the dip of these beds is south, at 70° to 80°. 



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