214 Scientific Proceedings, Royal Dublin Society. 



In the Glengariff Grits (Silurian) there are in the islands of 

 Yalentia and Beginish, as also in the'ad joining mainland (Bally- 

 carbery), whinstones, felstones, and tuffs (conglomerate). These 

 appear along the lines of stratification for the most part, and on 

 account of the associated tuffs might be considered as interbedded ; 

 in places, however, thej are evidently, in part, intrusive ; more 

 especially the felstones, as these have baked all the rocks in con- 

 tact with them. These rocks do not seem to be put to any use ; 

 yet some of the whinstones might be capable of being wrought 

 into good paying-setts, kerbing, &c, while freight in return ships 

 from the western coast ought to be very low. Quarries could 

 easily be opened on Yalentia, or perhaps more easily on Beginish, 

 or the mainland. The small dykes of whinstone, observed else- 

 where, it is unnecessary to describe. 



In the Killarney district adjoining the Horses' Glen (Mangerton), 

 and in Glenflesk, there is a considerable exposure of euryte and its 

 associated tuffs. These have been considered to be more or less 

 inter-stratified with the associated Silurians ; but this may be a 

 misconception ; the mass is perhaps the remains of a volcanic cone 

 that protrudes into the associated rocks, which were deposited 

 around and over it. The apparent continuation of the tuff into the 

 associated grits and shales seems to be due to detritus from the 

 tuff, deposited as tuffoid rocks from time to time, they thus 

 having a tuff composition, but being of an age long subsequent to 

 that of the accumulation of the volcanic cone. 



These rocks have not been utilized, except for local purposes ; 

 yet some of them, especially in Glenflesk, are handsomely spotted, 

 and porphyritic, in shades of red and purple, and ought to be 

 valuable, if polished for ornamental purposes. 



Near Lough Guitane there is a rock mapped by Du Noyer as 

 felstone tuff. It is light-green in places, porphyritic, compact, 

 can be raised in large blocks ; should cut and polish well. 



In the Bearhaven promontory, Co. Cork, in the Devonians of 

 Cod's Head, Dursey Island, Crow Head Promontory, Horn Point, 

 and between Kilkinnikin and Dunboy, there are whinstones, some 

 being in dykes or other intrudes, while some seem to be inter- 

 bedded. The dykes of Crow Head Promontory are distinct from 

 the others, and may possibly be of Tertiary age. All these rocks 

 are more or less inaccessible, and do not seem to have been utilized. 



