Green — Carboniferous Rocks of N. Wales. 11 



Plate II, 

 Fig. 6. Coomassig Cliff, 1100 feet high, forming one side of a glen or coom, near 

 Sneem, Co. Kerry, Ireland. 



7. Innishnabro, one of the Blasket Islands, off the coast of Kerry. The nearly 



vertically-bedded rocks are pierced by large openings, one above another. 



8. Lines of dislocation or division in Drift, (sand, clay, and gravel,) at Golden- 



grove, Co. Tipperary, Ireland. — (See Explanation of Sheet 126, Mems. 

 Geol. Survey of Ireland). 



III. — On the Lower Cakboniferous Books of North Wales. 

 By A. H. Gkeen, M.A., F.G.S. 



IT is well known that, though the Coal Fields of Lancashire and 

 North Wales are now parted from one another at the surface 

 hy a broad tract of New Eed Sandstone, there is reason to believe 

 that the two are connected underground, and are both parts of one 

 and the same great deposit ; and that the beds which in Lancashire and 

 Cheshire dip out of sight below the Eed measures, reappear in Flint- 

 shire and Denbighshire. Attempts have been made, I believe, to 

 identify the individual coal-beds of the two districts, but I do not 

 know with what success. During a short stay at Llangollen, some 

 years ago, I ventured on a like task for the Lower Carboniferous 

 Eocks, and though the time at my disposal allowed of only scanty 

 observations, these were recorded in my note-book, in hopes that an 

 opportunity might occur of filling in the sketch thus roughly traced 

 out. No such chance has befallen, or seems likely to befall me, and 

 in the hope that the notes I then made may aid some one who, with 

 more leisure, is willing to attempt a full solution of this problem, I 

 now put them forward as a rough approximation. 



The beds between the Coal Measures and the Mountain Limestone 

 in North Wales have generally been classed as Millstone G-rit, but I 

 must beg leave to draw attention to the fact that this designation 

 is an excessively vague one, the limits of that sub-formation being 

 very differently defined by different authors. We must therefore, 

 before we can have any definite meaning in calling a group of 

 beds Millstone Grit, state whose classification we are following. 

 Li the present paper I wiU use that laid down by the Geological 

 Survey for the Carboniferous Eocks of Lancashire, which is as 

 follows : — 



Lower Coal Measures. 

 f First Grit, or " Eough Eock." 

 Shale. 

 Millstone ' ^^'^^^^ ^^'i*' o'" " Haslingden Flags." 

 Grit "^ Shale. (" Brooksbottom beds.") 



Third Grit. (First millstone of some authors.) 

 I Shale, 

 t. Fourth Grit. (The second millstone of some authors.) 



r ( Shales. 

 I 1. ~ " " 



ToREDALE ] 1- JoredaleGrit. 

 Eocks ^ I Shales. 



I 2. Yoredale sandstones. 

 l^ 3. Black shales with thin earthy limestones. 

 Carboniferous or Mountain Limestone. 

 My wish was to determine whether the above sub-divisions, or any 



