TRANSACTIONS OF THE SECTIONS. 63 
consider the accidents which have, amid the great decomposition of organic 
matter, preserved to us those remains, generally enclosed in ironstone nodules, 
we pint feel confident that coming years will haye many an additional fact to 
disclose. 
Of the whole range of the carboniferous formation, perhaps the most interest- 
ing in several respects is the lower division. Many years ago Professor Phillips 
described the peculiar group of unquestionably marine shells occurring in the roof 
of the Halifax coals; and my friend Mr, Binney has traced throughout the length 
of Lancashire several seams which are thus characterized, and which lie invariably 
below the thick seams of the main coal-field. I have been greatly interested in 
hunting up the same group—the well-known Aviculo-pecten papyraceus, Gonvatites 
Lister, Orthoceras, and Lingula—in Derbyshire, in North Staffordshire, and in 
North Wales. Again, they occur very similarly in South Wales, at Merthyr and 
Nantyglo, and further west in the Kilkenny coal-field. I have devoted at intervals 
several days to the search for them along the outcrop of the Durham district, but 
hitherto unsuccessfully ; and whilst their occurrence lends great force to the pro- 
bability of the original unity and the subterranean connexion of most of our coal- 
fields, their apparent absence in the Durham and Cumberland lower coals appears to 
indicate a peculiar difference{in the conditions of deposition, The identification of 
distant seams, and of low as compared with high measures, appeared on this evidence 
very feasible ; but Mr. Hull has not long since shown that caution is still needed, 
by announcing the occurrence of the same group of fossils in the roof of what 
appears to be a higher seam in Lancashire. 
tis, I believe, only from the fossil side of the question that we can obtain a 
ee view of the position, with respect to true coal, of the cannel, the Torbane- 
ill or Boghead mineral, and bituminous shales. These yarious substances, whose 
affinities haye formed the subject of such serious litigation, may occur interstrati- 
fied with, and under circumstances analogous to, the seams which we all, without 
exception, recognize as coal; but when we come to examine their fossil character, 
the evidence thus obtained seems to me to point to quite a different mode of for- 
mation, On the one hand, observe in the coal the comparatively uninjured cellu- 
lar tissue of the vegetable mass, and the remarkable freedom from simultaneously 
deposited foreign matter; on the other hand, take the series beginning with the 
best cannels, and passing through the various grades of the carbonaceous and 
bituminous shales, the “parrots” and the “rattlers” and the “black bats,” and 
you find that in these latter an unbroken transition links the one to the other. In 
all of them the mashed and comminuted state of the carbonaceous element, and the 
frequent presence of fish-teeth, scales, and coprolites, and occasionally of mollusca, 
indicate conditions different enough to warrant a geological, let alone a technical 
separation. 
the shales which form the roof of a bed of coal be carefully examined, it will 
often be found that successive layers, from half an inch to several inches in thick- 
ness, are loaded with distinct kinds of remains, whether animal or vegetable. 
When they are of that homogeneous, fine-grained, and tenacious quality which 
constitutes what the colliers term a “good roof,’ the surface of the coal-seam 
appears to have been evenly and quietly covered with sediment; when the cap- 
ping is of sandstone or even of some of the rougher varieties of shale, it may some- 
times be seen that the coal has been eroded prior to its being covered up, and 
occasionally, as in the fine open exhibition of the Brockwell seam at Hownes Gill, 
near Shotley Bridge, came fragments of the coal lie strewed along the top of 
it, forming a coaly breccia. The under part of the shale or “bind” in actual contact 
with the coal is, with certain seams and in certain districts, a matted layer of large 
flattened stems of Stgillaria, Lepidodendron, &c., intermingled with fronds of ferns, 
whilst at a few inches higher we reach a band consisting exclusively of the flag- 
like leaves of Poacites, or a bed containing fish-remains and the Unio-like shells 
which recent researches have divided into several genera. In other cases, as 
notably in the “ Bottom Hard” coal of Shipley in Derbyshire, the immediate roof 
exhibits millions of a small brown “ Unio” ; and as you walk in the workings, you 
look up at the bottom of a “mussel-bed” where whole generations of the mollusk 
appear to have lived and died. Time would fail me were I to attempt to specify 
