capital coating for pills; for the resinous
powder prevents the drug from being wetted by the saliva, and thus
bars the nauseous flavour from the sensitive papillae of the tongue.

But this resinous matter, which lies in the walls of the spores and
sporangia, is a substance not easily altered by air and water,
and hence tends to preserve these bodies, just as the bituminized
cerecloth preserves an Egyptian mummy; while, on the other hand, the
merely woody stem and leaves tend to rot, as fast as the wood of the
mummy's coffin has rotted. Thus the mixed heap of spores, leaves,
and stems in the coal-forest would be persistently searched by the
long-continued action of air and rain; the leaves and stems would
gradually be reduced to little but their carbon, or, in other words,
to the condition of mineral charcoal in which we find them; while the
spores and sporangia remained as a comparatively unaltered and compact
residuum.

There is, indeed, tolerably clear evidence that the coal must, under
some circumstances, have been converted into a substance hard enough
to be rolled into pebbles, while it yet lay at the surface of the
earth; for in some seams of coal, the courses of rivulets, which must
have been living water, while the stratum in which their remains are
found was still at the surface, have been observed to contain rolled
pebbles of the very coal through which the stream has cut its way.

The structural facts are such as to leave no alternative but to adopt
the view of the origin of such coal as I have described, which has
just been stated; but, happily, the process is not without analogy at
the present day. I possess a specimen of what is called "white coal"
from Australia. It is an inflammable material, burning with a bright
flame, and having much the consistence and appearance of oat-cake,
which, I am informed, covers a considerable area. It consists, almost
entirely, of a compacted mass of spores and spore-cases. But the fine
particles of blown sand which are scattered through it, show that it
must have accumulated, subaerially, upon the surface of a soil covered
by a forest of cryptogamous plants, probably tree-ferns.

As regards this important point of the subaerial region of coal, I am
glad to find myself in entire accordance with Principal Dawson,
who bases his conclusions upon other, but no less forcible,
considerations. In a passage, which is the continuation of that
already cited, he writes:--