Vol. 57.] INTRUSIVE TUEF-LIKE EOCKS IN IRELAND. 



489 



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

 and of their associated felsites, 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 laccolites. 



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

 their true character and disposition have been overlooked in Ireland. 

 Judging from what we know of so-called ' contemporaneous igneous 

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

 position 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 Epoch, 

 as in Ireland. 



Discussion. 

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



