176 Scientific Proceedings, Royal Dublin Society. 



As has been mentioned, and as will be more particularly referred 

 to when describing the different granite areas, a very general 

 characteristic of the intrusive granites is a structure similar to the 

 " grain " in the oldest granite of the Leinster range. 



SUMMAKY. 



The Galway granitic gneiss, or foliated granite, and the similar 

 rock in the Co. Donegal, are not found intruded into the associated 

 schists. 



The granitic gneiss of N.E. Mayo, and certain courses in the 

 Grlenties district, Co. Mayo, are found intruded into the associated 

 schists. 



The Slieve Croob granite, Co. Down, and its associated elvans, 

 were intruded into the associated schist prior to foliation being 

 developed in it. 



The oldest (Post-Ordovician) granite of the Leinster range is 

 intruded into the associated schists. The structure called the 

 " grain " possibly was developed during the cooling ; and it is per- 

 fectly independent of any structure in the associated schists, while 

 the schistosity along the S.E. margin seems in part to have 

 relations to the foliation in the adjoining schists. 



Elvans and porphyries and some felstones often have charac- 

 teristics more or less allied to those of the intrusive granite. But 

 they are seldom capable of being raised in blocks of large scant- 

 ling ; and many of them are not suitable for long bearings. 

 Some of them, however, break up naturally into squarish blocks, 

 eminently suitable for building purposes ; they usually dress and 

 saw well; while some of them, when polished, are handsome 

 stones. A few of the polished stones lately brought into the 

 market by the Millars of the Gralway Marble Works are allied 

 with or belong to this class. Some of the felspathic rocks (granult/te) 

 should be eminently suitable for the manufacture of glass. 



The whinstones, including the granitic or coarse varieties 

 (granitone, &c), often break up more or less irregularly, some 

 being rubbly ; others, however, make good building-stones, or are 

 suitable for cut and even polished work. As already pointed out, 

 polish on basalt and other whinstone is very durable if the stone 

 does not contain much iron. When of good quality, these can be 



