98 Scientific Proceedings, Royal Dublin Society. 



DUBLIN. 



The slate rocks, when they occur in the north portion of the 

 county, at Howth, and to the southward, bordering Wicklow, are 

 employed for common building purposes ; but in general they are 

 not used as they might be, bricks being greatly run after in many 

 places. Bricks are more economical for finer kinds of work ; as 

 although the slate may be easily and cheaply procured, the mortar 

 working and setting, which is necessary to make neat masonry of 

 it renders it more expensive than brick. 



FERMANAGH. 



Metamorphosed Ordovician, Arenig (?), or Cambrian (?) rocks 

 occupy a small area near Pettigoe and Belleek, at the north-west 

 of the county, and a smaller one to the north-east, at Lack ; and 

 the slates and schists in these are locally used for common walling 

 purposes. 



In the Slievebeagh Series (Carboniferous, vide Sands and Sand- 

 stones, page 524, vol. v.), in the south-east of the county, in 

 the different tracts of Calp and Coal-measures, there are shales ; 

 but these are only very locally used. 



GALWAY. 



In Yar Connaught, or the country west of Loughs Mask and 

 Corrib, many of the rocks are of slaty character, but usually meta- 

 morphosed into micalyte or allied schists. The probable ages 

 {Ordovician, Arenig, and Cambrian (?)) of these rocks have already 

 been discussed (Sands and Sandstones, page 517, vol. v.). Over 

 these, to the north, and extending into the county Mayo, are slaty 

 rocks of Silurian age, while margining these and the older metamor- 

 phic rocks are the Lower Carboniferous. The slate rocks that occur 

 in these different geological groups are more or less locally used for 

 eommon walling purposes ; but there is no very great demand for 

 them anywhere, the villages and hamlets being few and far 

 between ; and the stones required are procured on the surface of 

 the ground, or any place where they will cost least in the getting. 

 In building Kylemore Castle, in the north of the county, the stone 

 for general walling purposes was blasted out of the site to be 



