Yol. 57.] INTRUSIVE TUFF-LIKE ROCKS IN IRELAND. 489 



The present disposition, character, and behaviour of these rocks, 

 and of their associated felsitcs, some of which are semivitreous and 

 exhibit flow-structure, seem to us best to be explained by con- 

 ceiving them to have been intruded among the strata as sills or 

 successions of sills, and in certain cases as rudely-outlined laccolitei. 



It is certain that, whatever the origin of the masses which we 

 describe, their true character and disposition have been overlooked in 

 Tr jland. Judging from what we know of so-called ' contemporaneous 

 igneous rocks' in the Lough Guitane district near Killarney, and their 

 disposition in the field, as well as of some of those in the Limerick 

 basin, we believe that more rigid examination of these areas would 

 reveal the existence of masses younger — possibly much younger — 

 than the surrounding sedimentary strata. The igneous rocks of 

 Wales have long been recognized to be the counterparts of those 

 in County Wexford, and it may ultimately be found that among 

 the great series of supposed volcanic rocks occurring in Wales are 

 some tuff-like masses of even later date than the Silurian Period, 

 as in Ireland.^ 



Discussion. 

 The President, Mr. Marr, Prof. Groom, and Prof. Watts spoke. 



^ [Mr. H. J. Seymour requests us to state that we have not quoted him 

 correctly in the foregoing pages. For the correct reading of his views, see 

 ' Summary of Progress of Gecl. Surv. of U.K. for 1899 ' pp. 179 & 180.— 

 J. U.K. 4- A. McK, October 22nd, 1001.'] 



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