6 
PROCEEDINGS OE SOCIETIES. 
Sphenopteris Hibernica, Lepidodendron minutum and Griffiihii (the 
last of which was discovered by Dr. Carte in the course of the last 
year), led to the adoption of the lines of boundary which have been 
published on the last, as well as on previous editions of my Geological 
Map. 
Subsequently, through the researches of my friends, Professors 
Haughton and Jukes, as well as those of myself, imperfect casts of these 
plants were found very far beneath the boundary which I had originally 
adopted, and hence the extent of the district which I had allotted to these 
lower Carboniferous rocks will be found much too circumscribed. The 
principle, however, upon which I set out, remains intact, and as often 
contended for, both by Professor Haughton and myself, in numerous 
papers, I would again say, that the base of the Carboniferous system 
will extend to any zone of these plants, no matter at what depth, or in 
connexion with what rocks soever, found. That this may have the effect 
of sweeping the whole of the fish, beds of Scotland,* 4 with the similar 
rocks of Glamorganshire in Wales, hitherto considered to be Devonian, 
into the Carboniferous system, I am not prepared to deny, as it is only 
a natural inference from the principle which I have laid down. It is true 
that I have preserved the established territories of the Old Eed Sand¬ 
stone on my Map, curtailing it only of the Plant or Yellow Sandstone 
beds, as I was not prepared to risk a controversy, merely upon the 
grounds of the well-known conformity between the two series, without a 
sufficiency of fossil evidence,—statements founded upon hypothesis, no 
matter how well grounded soever they may appear, but upon less than 
indisputable scientific principles, being still open to the charge of being 
mere speculation or guess; and especially as I found that up to the pre¬ 
sent time it has been as much as I could do to defend the innovations 
which I had already made, even though the Irish geologists generally, 
and especially Mr. Haughton and Mr. Jukes, who, I trust, will favour 
us with their views, have all arrived at similar conclusions. 
* Note added in the Press. —R.G.—These Scotch beds would appear to be rather high in 
the series, from the discovery of Sphenopteris Hibernica in them by Professor E. Forbes, with 
which we have Fenestella associated at the Roughty River and Tallow Bridge; and, as re¬ 
marked Mr. Jukes and Mr. Salter, this plant is accompanied by undoubted Carboniferous 
Mollusca in the strata known as the Coomhola Grits; hut I wish to guard myself strongly, 
against the mistake of its being supposed that I intend to make dogmatic assertions re - 
lative to the lower non-fossiliferous beds of the true Old Red Sandstone. On the contrary, 
I agree with the opinion so frequently and so well expressed by Professor Haughton, 
namely, that in considerable thicknesses of doubtful strata, without the guide of fossils, 
it becomes comparatively a matter of indifference as to the series with which we classify 
them, provided that they are sufficiently distinguished for recognition by any convenient 
term generally agreed upon. 
I find this remark to be the more necessary, as, at the last Meeting of the British 
Association, held in Dublin, Colonel Portlock had fallen into a mistake of this kind; 
and subsequently, my friend Mr. Jukes, in his “ Manual of Geology,” page 436, has, 
by a similar oversight, ascribed to me a share in opinions of which I am wholly un¬ 
conscious. 
