rent from those which I have examined. All
I repeat is, that none of the coals which have come under my notice
have enabled me to observe such a difference. But, according to
Principal Dawson, who has so sedulously examined the fossil remains of
plants in North America, it is otherwise with the vast accumulations
of coal in that country.

"The true coal," says Dr. Dawson, "consists principally of
the flattened bark of Sigillarioid and other trees, intermixed
with leaves of Ferns and _Cordaites_, and other herbaceous
_debris_, and with fragments of decayed wood, constituting
'mineral charcoal,' all these materials having manifestly
alike grown and accumulated where we find them."[1]

[Footnote 1: "Acadian Geology," 2nd edition, p. 138.]

When I had the pleasure of seeing Principal Dawson in London last
summer, I showed him my sections of coal, and begged him to re-examine
some of the American coals on his return to Canada, with an eye to the
presence of spores and sporangia, such as I was able to show him in
our English and Scotch coals. He has been good enough to do so; and in
a letter dated September 26th, 1870, he informs me that--

"Indications of spore-cases are rare, except in certain coarse
shaly coals and portions of coals, and in the roofs of the
seams. The most marked case I have yet met with is the shaly
coal referred to as containing _Sporangites_ in my paper
on the conditions of accumulation of coal (_Journal of the
Geological Society_, vol. xxii. pp. 115, 139, and 165). The
purer coals certainly consist principally of cubical tissues
with some true woody matter, and the spore-cases, &c.,
are chiefly in the coarse and shaly layers. This is my old
doctrine in my two papers in the _Journal of the Geological
Society_, and I see nothing to modify it. Your observations,
however, make it probable that the frequent _clear spots_ in
the cannels are spore-cases."

Dr. Dawson's results are the more remarkable, as the numerous
specimens of British coal, from various localities, which I have
examined, tell one tale as to the predominance of the spore and
sporangium element in their composition; and as it is exactly in the
finest and purest coals, such as the "Better-Bed" coal of Lowmoor,
that the spores and sporangia obviously constitute almost the entire
mass of the deposit.

Coal, such as that which has been described, is always found