6 The Irish Naiwalist January, 



Valley, Croghan Kinshelagli. A number of igneous and 

 metamorphic rocks from Mayo, Galway, and Tyrone were 

 examined, but without success. The objections of the owner 

 at present prevent further examination of the one hopeful 

 district in Co. Wicklow ; and there is much to be said for his 

 views on the subject. If, however, he preserves the right to 

 prevent indiscriminate mining on his land, a scientific survey 

 might perhaps be some day rendered possible. 



THK SO-CALLED VOLCANIC TUFFS IN OLDER IRISH STRATA. 



Messrs. J. R. Kilroe and A. M'Henry {Quart. Journ. Geol. 

 Soc. Londo7h vol. Ivii., igoi, p. 479), call attention to the intru- 

 sive character of many rocks hitherto mapped as volcanic 

 tuffs, especially among the Silurian beds of southern Ireland. 

 They show, in the course of a useful and salutarj- paper, how 

 brecciation has occurred in dykes during the flow of the ma- 

 terial, and that often the supposed tuffs may be much later than 

 the rocks in which they lie. On p. 488 the Leinster granite is 

 referred to as of Old Red Sandstone age ; though connected 

 with the Caledonian folding, it certainly may be contemporan- 

 eous with the earliest marine Devonian elsewhere. We doubt, 

 however, if volcanic action began in the south of Ireland 

 *' after the limestone of Bala age was formed." There is 

 indeed, convincing evidence to the contrary, at any rate in 

 the region of Kildare and Dublin (see Gardiner and Reynolds, 

 QuarL Journ. Geol. Soc. London^ vol. lii., p. 604 ; vol. liii., p. 

 534, and liv., p. 147). 



In the Geological Magazine for igoij p. 515, the late Mr. 

 Joseph Nolan objected to the inclusion of the Forkill agglo- 

 merate in Co. Armagh among the intrusive breccias of Messrs. 

 Kilroe and M'Henry. He denied the existence in it of an 

 andesitic matrix, and urged that the mass resulted from sub- 

 aerial explosions — at least, we read this meaning into his 

 quaint word "seriform." It is clear that microscopic exam- 

 ination of this rock is needed, as well as in the cases cited 

 by Messrs. Kilroe and M'Henry. Slieve Gullion, we may 

 remark, is here twice printed as Slieve Gallion, a slip that 

 unfailingly escapes English editors. 



