only the latter is the continuation and natural sequence of the former
series of changes.

In the Laurentian rocks of Canada are large accumulations of
carbonaceous matter, all of which is graphite, and that which is
universally conceded to be derived from plant-tissue. The oxidation of
graphite is artificially difficult, and in nature's laboratory slow; but
it is inevitable, as we see in the decomposition of its outcrops and the
blanching of exposed surfaces of clouded marbles, where the coloring is
graphite. Thus the end is reached, and by observations in the field,
the origin and relationship of the different carbon solids derived from
organic tissue are demonstrated.

It only remains to be said, in regard to them, that all the changes
enumerated may be imitated artificially, and that the stages of
decomposition which we have designated by the names graphite,
anthracite, coal, lignite, are not necessary results of the
decomposition of plant-tissue. A fallen tree may slowly consume away,
and all its carbonaceous matter may be oxidized and dissipated without
exhibiting the phases of lignite, coal, etc.; and lignite and coal,
when exposed to air and moisture, are burned away to ashes in the same
manner, simply because in these cases complete oxidation of the carbon
takes place, particle by particle, and the mass is not affected as a
whole in such a way as to assume the intermediate stages referred to.
Chemical analysis, however, proves that the process is essentially the
same, although the physical results are different.


EVOLVED PRODUCTS.