Have you not a right to say, "These are all
but varieties of the same kind of thing--namely, vegetable matter?
They have a common origin--namely, woody fibre. And coal, or rather
culm, is the last link in a series of transformations from growing
vegetation?"
This is our first theory. Let us try to verify it, as scientific men
are in the habit of doing, by saying, If that be true, then something
else is likely to be true too.
If coal has all been vegetable soil, then it is likely that some of
it has not been quite converted into shapeless coal. It is likely
that there will be vegetable fibre still to be seen here and there;
perhaps leaves, perhaps even stems of trees, as in a peat bog. Let
us look for them.
You will not need to look far. The coal, and the sands and shales
which accompany the coal, are so full of plant-remains, that three
hundred species were known to Adolphe Brongniart as early as 1849,
and that number has largely increased since.
Now one point is specially noticeable about these plants of the coal;
namely, that they may at least have grown in swamps.
First, you will be interested if you study the coal flora, with the
abundance, beauty, and variety of the ferns. Now ferns in these
islands grow principally in rocky woods, because there, beside the
moisture, they get from decaying vegetable or decaying rock,
especially limestone, the carbonic acid which is their special food,
and which they do not get on our dry pastures, and still less in our
cultivated fields.
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