File:The Quarterly journal of the Geological Society of London (13205997113).jpg

IS47..
LYELL ON THE COAL-FIELD OF EASTERN VIRGINIA.
269
" In this (Fig. 3.) the fibres (A) are larger in diameter, covered with
prominent dots or glands, each often having a dark spot in the centre.
The perforations in the tubes (B) are often filled up with circular
discs (as at C), which have a central dark spot (D), or are transparent
throughout (E) . The perforations of some of the tubes are so closely
placed and so much elongated transversely (F), that the tube resem-
bles the scalariform ducts of a fern.
Blackheath Specimen .Creek Mines).
Fig. 4.
" The fibres of this specimen, fig. 4. (A), are smaller and moreclosely
packed, covered with more numerous prominent dots or glands ; the
latter have almost uniformly a central spot (A'), are extremely minute,
very caducous, and are often star-shaped (A"), or of various outline.
The tubes are very rarely seen, and have many series of generally
transversely elongated perforations (B)."
Next to the ferns, the most abundant vegetable remains in the coal-
measures under consideration are two species of Calamites and the
Eqiiisetum columnare, especially the former, and the bark of the
Calamites is usually converted into coal. It is therefore natural to
conjecture, that the thin layers resembling charcoal may have been
derived from Calamites, a plant of which the botanical structure is
still unknown. Dr. Hooker, in reply to this suggestion, tells me that
some fossil charcoal in the Museum of the Geological Society, from
the English coal formation, supposed to be derived from Calamites,
is very like that of the Virginia coal above described.
The cities of New York and Philadelphia have for many years
supplied themselves with coal from the Blackheath mines, for the
manufacture of gas for lighting their streets and houses. The annual
quantity taken by Philadelphia alone has of late years amounted to
10,000 tons. It will appear from the annexed table of analyses of
specimens of coal, which Mr. P. H. Henry has had the kindness to
make for me, that the proportion of volatile ingredients — hydrogen,
nitrogen and oxygen — in this newer coal of the James River comes
exceedingly close to that found in the older coal of America, which it so
much resembles in aspect and structure. The specimen from Tuscaloosa
in Alabama was from the old coal formation described by me in the
Journal of this Society for 1846, vol. ii. page 2/8, in which are found
precisely the same plants as in the coal of the Appalachians, of Nova
Scotia, and of the north of England. The other three specimens, from