222 Scientific Proceedings, Royal Dublin Society. 



traversed by two sets of parallel joints, perpendicular to one another ; 

 so that the stone is cut up into rectangailar blocks of various widths, 

 and lengths up to twenty- five feet or more. As the soles or nearly 

 horizontal joints and the upright joints are at distances apart, from 

 six inches to three feet, and in some places to six, nine, or more feet, 

 there is every facility for raising, with wedge and windlass, ready 

 squared blocks of any scantling, and suitable for any kind of work 

 from setts and flagging to huge monoliths. Mr. Reilly, the super- 

 intendent, states that if required he could raise a block fifty feet in 

 length and nine or ten feet or more in the square. " About forty 

 years ago the stone was used by the Board of Works in building 

 Termon and Belmullet piers, and also the canal bridge at the latter 

 place, and now it appears to be of excellent quality, and shows 

 no traces of weathering." (P. J. Lynam.) 



At Annagh Head, also, near Erris Head, are handsome, clouded, 

 and streaked variegated felspathic rocks (Felsitic granite), capable 

 of being raised in large blocks. Specimens procured here were 

 found to cut and polish easily and well, with very good results 

 " The rock is red, and pink in colour, massively crystalline and 

 foliated ; it has all the appearance of being very well suited for the 

 manufacture of kaolin, or porcelain clay." (A. M' Henry.) Of a 

 polished hard specimen, Mr. Sibthorpe states " it has all the beauties 

 of a limestone and the hardness of a granite." 



[These rocks M'Henry considers to be Pre-Cambrian ; they and the associated 

 gneiss and schists are in aspect very similar to the Primary gneiss of Sutherlandshire.'] 



In the Owenmore Valley, west of Bangor, there is a small tract 

 of gneissose granite; the rock, however, is so much jointed that it is 

 not suitable for cut-stone purposes. 



Elvans, Felstones, Eurytes, Whinstones, Qtjartzytes, 



Schists. 



The elvans in (ralway and Mayo are very varied in age, colour, 

 and composition, graduating into felstones ; and the basic elvans 

 (granitone) into eurytes and whinstones. They occur more fre- 

 quently in or adjoining the granite area ; but they are not 

 uncommon in the schist of the western and north-western parts of 

 the county Gralway. Some of them, especially near the town of 

 Gralway, as already mentioned, are of great beauty and variety. 



