Kinahan — On Irish Arenaceous Rocks. 587 



but, as already pointed out, this is Highly improbable, if not 

 impossible. Some of them, undoubtedly, are the equivalents of 

 the Ordovicians, and the rest are probably the equivalents of the 

 Arenig, or possibly part of the Cambrian. North of Balla, to the 

 eastward of Castlebar, is a small outlying mass of Coal-measures. 



Cambrian, or Arenig. — These, as just now mentioned, are, 

 for the most part, metamorphosed into schist, gneiss, or granite. 

 There are, however, some quartzytes and quartz-rock, capable of 

 being raised in large blocks suitable for rough work ; but they are 

 seldom used, as other stones, as easily procured, are preferred. 

 They can also be utilized as road metal. 



Ordovician. — These, like the older rocks, are in general meta- 

 morphosed ; but in places, more especially to the eastward, north 

 of the eastern continuation of the Erriff valley, they are not. In 

 the unaltered portions there are some very massive grits and sand- 

 stones that would be valuable for piers, foundations, and such 

 rough massive work, but that they are backward and very inacces- 

 sible. There is also a pebbly quartzyte, very suitable for piers ; 

 but it does not appear to have been much utilized. 



Between Foxford and Swinford are flags of great dimensions. 

 Symes considered that they are due to water freezing in the joints 

 that split off huge plates, some as large as the side of an ordinary 

 cabin. They might be more utilized than they are. 



In the north-west of the county (Erris), "between Benmore 

 and Belderg Harbour, also along the coast of Broad Haven, between 

 JDawish Cellar and Blind Harbour, flaggy quartzytes, in unlimited 

 quantities, light-browns and greys, maybe had of any sizes and thick- 

 nesses ; these are well suited for street flagging, and some beds are 

 •easily and cheaply wrought into paving setts. The flags between 

 Dawish Cellar and Blind Harbour could be shipped from either 

 Grubatnockan or Belmullet, and those of Benmore from Belderg. 

 It is proposed to join the latter quarries by a tramway to the 

 harbour and erect a pier there." — {A. M'Henry.) 



Silurian. — These rocks are both of the ordinary and " Old 

 lied Sandstone" types, the latter predominating, and consisting, 

 for the most part, of purplish or reddish conglomerates and sand- 

 stones, while the others are principally shades of grey, blue, and 

 green argillaceous rock, in which are grits and sandstones. In one 

 •tract, east and south-east of Louisburgh, they are in part meta- 



