KiLROE — Silurian and Metamoi^phic Rocks. 



149 



of transformation of sedimentary strata which culminated in granite. 

 Hence the indication used for these metamorphic rocks upon the map. 

 A section which I observed in Leckvarna, south of Lough Pee, and 

 west of the main road from Leenane to Kylemore, proves, as do other 

 such sections north of Kylemore Castle, where the two igneous rocks 

 adjoin, that the granite intrusion is the later. 



Fig. 11. — View in Leckvarna, of Hornblende Eock (cross-hatched), invaded by 

 granitic mass chiefly gneiss, containing unsheared eyes of granite (G). 



The granitic rock dovetails into mica-schist westward in Letter- 

 gesh, contains masses of serpentine (probably) after partially absorbed 

 areas of basic rock, and is itself in places highly sheared, so as to be 

 indistinguishable from mica-schist of sedimentary origin ; and where 

 it invades the great basic outcrop north of Kylemore, it takes up a 

 foliated arrangement of its constituents — probably fluxion -structure — 

 around the prominences of the older rock. This is well to be seen 

 in the small gap between Lough Acreragh and Lough Touther, and 

 the granitic rock occupies a considerable area from this locality north- 

 ward to the Silurian boundary, where it margins the newer formation 

 for 3^ miles. 



Another interesting igneous tract adjacent to the Silurian strata, 

 of older date and probably of the same age as that just described, is 

 to be seen on the north side of the inlet of Lough Mask, west of 

 Olonbur, and forming one or two islets near the western end of the 

 inlet. It contains detached pieces of hornblendic and metamorphic 

 rocks, as in the case of the granitic rock near Kylemore. These 

 igneous intrusions mark a zone of irruption, with probable dis- 

 turbance, margining the ancient sea in which the Silurian strata were 

 deposited. The existence of such a zone accounts for an important 

 interruption in the succession, in Llandovery times, seen on the south 



