548 Scientific Proceedings, Royal Dublin Society. 



Glass. — In Cork there were two large glass-houses for the 

 manufacture of flint-glass, with extensive premises for cutting, 

 engraving, &c, attached to each. One ceased to exist ahout 1835, 

 and the other before 1840. The sand used seems to have been 

 imported. 



DONEGAL.* 



For the most part this county is occupied by granitic, gneissose, 

 and schistose rocks. These, from recent researches, are known to 

 belong to two distinct geological groups, the older probably repre- 

 senting rocks equivalent to the Cambrian and the Arenig, while 

 the later represent the Ordovician and perhaps, in part, the Llan- 

 dovery or May Hill Sandstone. On these older rocks, in places, 

 such as at Ballymastocker Bay, Fanad ; Muff, Lough Foyle ; along 

 the mearing of the Co. Fermanagh, to the northward of Pettigoe ; 

 and in the neighbourhoods of Killybeg, Donegal, and Bally- 

 shannon, there are Carboniferous rocks of greater or less extent, 

 that in Fanad being a mere patch. 



Cambrian and Arenig. — The sandstones, grits, and quartz- 

 rocks which occur in the strata supposed to represent these geological 

 groups are now all more or less altered into quartzytes, gneiss, 

 and foliated granite. But some of the quartzytes, especially some 

 of those in the gneiss and foliated granite, are even-bedded, and, 

 when also regularly jointed, they are excellent material for walls 

 and such like ; but they will not bear dressing. Many of the 

 altered quartz-rocks are splintery. In places, however, they are 

 massive, and capable of being raised in large blocks ; and, under 

 such circumstances, they are more or less suitable for foundations, 

 sea walls, and other heavy work. 



Ordovician and Llandovery (?). — The sandstones and quartz- 

 rocks which are supposed to belong to the rocks equivalent to some 

 of these groups are, in a great measure, altered into quartzyte. 

 Some, however, are unaltered or very little altered, as sandstones 

 occur in the Eathmullen district, between the ridge called the 

 Devil's Backbone and Lough Swilly; also in the barony o£ 

 Eaphoe, south of Lough and Grlen Swilly. In the Eathmullen 

 district some of these stones dress fairly well, but are liable to 

 discolour. Those in Creeve Mountain, about three miles north- 

 * See " Notes added in the Press." 



