508 PEOCEEDiNGS or THE GEOLOGICAL SOCIETY. [June 6, 



stone, and which dips south, or under the limestone. The latter can 

 be traced, coming up in bosses or covered by a green band of vege- 

 tation, from the Glencoughan Eiver, running parallel to, and a short 

 distance from, the Clifden Eoad, to a house called the Canal Stage, 

 where it crosses from the north to the south side of the road, whence 

 it still strikes westwards and passes beneath the waters of Ballyna- 

 hinch Lake. 



The mass of limestone which lies between the gneissose rocks and 

 the quartz-rocks probably exhibits itself, on the south side of the Con- 

 nemara Mountains, in more than one band. The limestone and its 

 associated strata have been greatly contorted in this part of the 

 county of Galway, and denudation has also aided in removing the 

 connecting links of the contortions — but not to such an extent as in 

 the country which lies on the north side of it ; and by these agencies 

 the strata have been frequently repeated on the surface. 



The quartz-rocks which occur on the northern margins of the 

 limestone give rise to the bold mountainous scenery of Connemara. 

 They form the Twelve Bens, and have in many spots a very 

 distinct stratification, and a strike which conforms with that of 

 the limestones. They are, among the Twelve Bens, thrown into 

 great anticlinals and synchnals ; and in one of these latter, which 

 forms the east and west valley of the Owenghn Eiver (the stream 

 which flows into the sea at Chfden), serpentinous limestone also 

 occurs. Between the Owenghn valley on the north and the lime- 

 stone band which passes under Ballynahinch Lake on the south, 

 there is an anticlinal of quartz-rocks. The upper portion of the 

 Owenglin valley is occupied by a district called Barnanoraun ; and 

 here the principal quarries of serpentinous limestone occur. 



The strike of these limestones here is also east and west ; but the 

 chp cannot be made out, as the strata are excessively contorted. 



The serpentinous limestones of Barnanoraun thin out towards the 

 east as they approach the quartz -rocks of Benbreen, the mountain at 

 the head of the valley. This thinning out, however, is the result of 

 denudation. 



The north as well as the south margin of the valley of the Owen- 

 glin is flanked by quartz-rocks ; and the contortions which have taken 

 place among the rocks near the centre of the synclinal of the Owen- 

 glin valley have so far destroyed the original lamination of the 

 limestone strata as to open out irregular interspaces ; and in some 

 cases the original hmestone has disappeared, its place being supplied 

 by white carbonate of Hme. The serpentinous limestone is here 

 much hghter in colour than that of the more southern band, owing 

 to the serpentine being of a lighter green colour than that which 

 occurs at Lisoughter and its neighbourhood. 



"With reference to the quartz-rocks of the Connemara district, the 

 arrangement of these and their relations to the limestones and gneis- 

 sose strata can be well seen in traversing the country which Hes 

 between the Twelve Bens of Connemara on the west and the Maame 

 Tork range of mountains on the east. These ranges are separated 

 from each other by a wide valley having a north-west and south- 



