Chap. XII.] COAL-FIELDS OF ENGLAND AND WALES. 
295 
difference of their fossils and their place in the order of the deposits, they might 
be mistaken. It is the strong lithological resemblance which led Mr. Jukes to 
compare with them the lowest slaty rocks of Devonshire, which, containing very- 
different fossils, stand, in my opinion, precisely in the same position as that in 
which Sedgwick, De la Beche, and Phillips, as well as myself, have placed them. 
(See above, pp. 282 & 284). Undulating over very wide areas, the Carboniferous 
Limestone is usually much obscured by gravel, shingle, and clay. Even when the 
limestones form natural escarpments, they exhibit no seams of coal worthy of 
notice — as, for example, on the south bank of Lough Erne, and in the hills near 
Florence Court to the south of Enniskillen, where they exhibit a splendid suc- 
cession and contain numerous fossils, including large Product! in the lower, and 
Posidonomyfe in the higher strata. In the Cork district, indeed (where the 
lower schists are so slaty and crystalline that lithologically they resemble much 
older rocks), a little coal of slight value has been found — a very feeble represen- 
tative of the great Scotch coal-deposits of similar age. 
The limestone series of Ireland is proved to be of exclusively marine origin, 
from the multitude of well-preserved fossils it contains ; and of these Sir Richard 
Griffith (with the assistance of Professor M'Coy) some time ago prepared a de- 
scription of about 500 species *, some of which are stated to be identical with 
those of the Devonian rocks, but altogether different from those of the Silurian 
system. These lower members of the system constitute, as before stated, by far 
the larger portion of all that is Carboniferous in Ireland, and are surmounted 
(but very partially) by grits and sandstones, in which, at four localities (Kilkenny 
in the south, and Ballycastle, Dungannon, and Coal Island in the north), a few 
thin beds of coal are situated ; but as, with the exception of the Kilkenny coal- 
field, they are of comparatively slight and only local value, and have no special 
bearing on the object of this work, I refrain from saying more respecting them. 
The Lower Carboniferous strata hitherto spoken of (or the sandstones, shales, 
limestones, and grits) are, all over Europe and North America, for the most part 
of marine origin. The arenaceous and schistose lower strata have, indeed, 
strong mineral and zoological affinities to the upper portion of the underlying De- 
vonian rocks, into which they graduate. On the whole, however, and notably 
in its great central masses, this lower division is distinguished from the Devonian 
by its chief animal remains (including certain genera of Fishes), and, above all, 
by the intermixture of many more terrestrial Plants than are known in any beds 
of the preceding epoch. "With repeated evidences of thin seams of coal being 
intercalated with bands of limestone of exclusively marine or estuary cha- 
racter, it is indeed a fair inference that much of the vegetable matter out 
of which such Lower Coal was formed had been often transported in large 
matted masses from the mouths of great rivers, or drifted from the shores of 
broad jungles, into the adjacent seas, and so became commingled with marine 
remains. 
Upper Carboniferous series, or productive Coal-Jields of England and Wales. — 
When we examine the nature of the great overlying coal-strata, an order of things 
is opened out to us to a great extent different from that which prevailed during 
the formation of the Lower Carboniferous rocks. 
If, indeed, we turn to Germany and France, we see a general physical pheno- 
menon sufficient to explain the change from marine to prevailing terrestrial con- 
ditions. In those countries the Lower Carboniferous strata had been dislocated 
and inclined before the Upper Coal-deposits began to be accumulated on their 
* A Synopsis of the Characters of the Carboniferous Limestone Fossils of Ireland, 1844. 
