uld have stopped in that position if they had got there.

At the same time, it is proper to remark that I do not presume to suggest
that all coal must needs have the same structure; or that there may not
be coals in which the proportions of wood and spores, or spore-cases, are
very different 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."[2]

[Footnote 2: _Acadian Geology_, 2nd edition, p. 135.]

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