280 Scientific Proceedings, Royal Dublin Society. 



GrALWAY. 



Except the north-western portion of the county (Yar or West 

 Connaught), the rocks are principally Carboniferous Limestones, 

 with subordinate sandstones and shales ; but through these come 

 up detached exposures of Ordovicians. Yar Connaught is occupied 

 nearly altogether by metamorphosed Ordovicians and Cambrians, 

 with their associated Granytes and Granitic rocks ; but on them, to 

 the north, is a tract of Silurians. 



As it has been stated that some of the Yar Connaught rocks 

 are Laurentians, it may be pointed out that when Murchison 

 some years ago suggested that the oldest rocks of the county, 

 those of the Bennabeola Hills, were of that age, he afterwards 

 found reasons to withdraw his suggestion ; while the rocks now 

 stated to be of that age carry fossils of Llandeilo types. 



In the Carboniferous Limestones some good and rich silver-lead 

 accumulations have been worked ; but unfortunately, as at Caher- 

 glassan, near Gort, and elsewhere, on account of the cavernous 

 nature of the rock, and the low altitude of the county, they can- 

 not be profitably worked, the influx of water being too great. 

 Some of the lead mines in the south-east of the county are 

 supposed to be prehistoric, not having been worked since 1640, 

 and probably not for centuries previous. 



In the Metamorphic and Granitic rocks are many lodes and 

 indications of copper, sulphur ores, lead ? and zinc ; some very 

 rich bunches having been already extracted. All the mining 

 operations in the area have been on a small scale, proving the 

 lodes at the surface, but not in depth; and from what is now 

 known it would appear as if at some future time it might be the 

 seat of large and remunerative mining operations, more es- 

 pecially if reducing works were erected in the county, as, on 

 aoeount of the great preponderance of sulphur ores (pyrite and 

 pyrhatite) r the ores in their raw state will not bear the expense erf 

 long carriage. 



At intervals between 1620 to 1750 iron was extensively 

 smelted and milled in different places along Lough Derg, the 

 last furnace alight being that of "Woodford, belonging to the 

 Burkes of Marble Hill. In these furnaces the bog-iron-ore vtm 



