228 Scientific Proceedings, Royal Dublin Society. 



Hornblende Rock. — Four or five exposures are met with in the 

 granite and schists, north and south of Foxford ; one about a mile 

 south of that town, containing large crystals of hornblende, white 

 felspar, brown and black mica, &c. All these rocks are foliated, 

 the foliation being parallel to that in the adjoining granite or 

 schist ; but they have distinct, well-marked boundaries. The rock 

 is very tough, (g.s.m.) 



Felstones. — Very few intrusions of this rock are reported from 

 this district. One occurs on the east slope of Letter Hill, westward 

 of Castlebar. 



As in other districts, the Schists that split into flat-bedded 

 stones are suitable for walling, and are much used locally. In 

 some places, as in the neighbourhood of Ballysadare, and in a more 

 limited area south of Lough Grill, and about Nephin Mountain the 

 ordinary schist is replaced by quartzitic rock or quartzyte. In the 

 vicinity of Westport is the peculiar pebbly quartzyte, suitable for 

 rough, heavy work, which has already been recorded among the 

 Arenaceous Eocks (vol. v., p. 587). 



Outlying Localities. 



In the Silurian rocks of the Curlew Mountain range (Cos. Sligo 

 and Roscommon) there are Eurytes, similar to those of Mayo and 

 Gralway {Bundorragha Eurytes, ante, p. 223), except that these are 

 associated with peculiar tuffs or tuffose rocks. There are also 

 intrudes of whinstone. 



[The Silurian eurytes in the Mangerton district, Co. Kerry, are associated ■with 

 tuffs, or, perhaps more properly, tuffose rocks {ante, p. 214) ; those of the Killary dis- 

 trict (Gal way and Mayo) are usually not associated with tuffs ; they occur only in the 

 neighbourhood of Lough-na-fooey and the Kilbride district ; hut here the tuffs are 

 peculiar, as in general there seems to he no hard boundary between them and the rocks 

 that seem to he normal euryte. In the Fintona district, hereafter mentioned, there are 

 other peculiarities ; as rocks that seem to be true eurytes are divided up into plates, so 

 thin that some of them may be described as coarse slates. Near Cushendall, Co. Antrim, 

 the rock occurs only as an intrude.] 



In the hills westward of Lough Oara there are several exposures 

 of euryte, which has quite a normal aspect ; yet the greater part of 

 this is in beds or layers, from a few inches to a few feet in thick- 

 ness, as though the exposures were, at least in part, tuffs or tuffose 

 rocks. 



