SCHISTOSE EOCKS OF NOETHERN DONEGAL. 241 



The President said that he had been unable to examine the spe- 

 cimens in minute detail, but had carefully looked through them. 

 Of the so-called granites, seven out of eight were certainly, and 

 the remaining one probably, granites. They gave indication of 

 considerable crushing since their first crystallization. Of other 

 rocks there was good evidence of two series, one agreeing in 

 general characters with Scotch schists, the other with the Pebidian 

 of Wales. He doubted Mr. Teall's evidence of the production of 

 all schists by crushing. As regards mineral character, he thought 

 that the general condition and amount of alteration of rocks, rather 

 than their actual mineral composition, should be employed for 

 correlation. 



The Author, in reply, suggested that the production of the 

 garnets in the limestone might be due to a chemical action of water 

 from the granite in contact. He regarded a grit as " mineralized " 

 when distinct mineral folia had been produced between the grains. 

 The omission of the word " jSTorthern " before " Donegal " in the 

 title of his paper was an oversight, which he would correct. He 

 had not attempted to definitely correlate the Donegal rocks with 

 any American system, but had merely pointed out certain litholo- 

 gical analogies. His identification of Pebidian rocks in Ireland had 

 not been based only on lithological affinities, but he had specially 

 insisted on their state of crystallization and upon the fact that in 

 Wexford they occurred side by side with unaltered Cambrian and 

 Ordovician sediments, separated from them by sharp lines. The 

 difficulties suggested by some of his critics would, he thought, be 

 removed if it were remembered that in some of the British localities 

 the Pebidian rocks were mainly of volcanic origin. He had com- 

 pared the Lough-Poyle series with the British Pebidian in the non- 

 volcanic districts. 



