[Footnote: Read before the New York Academy of Sciences, February 6,
1882.]
By J.S. NEWBERRY.
What are called the carbon minerals--peat, lignite, coal, graphite,
asphalt, petroleum, etc.--are, properly speaking, not minerals at
all, as they are organic substances, and have no definite chemical
composition or crystalline forms. They are, in fact, chiefly the
products or phases of a progressive and inevitable change in
plant-tissue, which, like all organic matter, is an unstable compound
and destined to decomposition.
In virtue of a mysterious and inscrutable force which resides in the
microscopic embryo of the seed, a tree begins its growth. For a brief
interval, this growth is maintained by the prepared food stored in the
cotyledons, and this suffices to produce and to bring into functional
activity--some root-fibrils below and leaves above, with which
the independent and self-sustained life of the individual begins.
Henceforward, perhaps for a thousand years, this life goes on, active in
summer and dormant in winter, absorbing the sunlight as a motive power
which it controls and guides. Its instruments are the discriminating
cells at the extremities of the root-fibrils, which search for, select,
and absorb the crude aliment adapted to the needs of the plant to which
they belong, and the chlorophyl cells--the lungs and stomach of the
tree--in the leaves. During all the years of the growth of the plant,
these organs are mainly occupied in breaking the strongly riveted bonds
that unite oxygen and carbon in carbonic acid; appropriating the carbon
and driving off most of the oxygen. In the end, if the tree is, e. g.,
a _Sequoia_, some hundreds of tons of solid, organized tissue have been
raised into a column hundreds of feet in height, in opposition to the
force of gravitation and to the affinities of inorganic chemistry.
The time comes, however, sooner or later, when the power which has
created and the life that has pervaded this wonderful structure
abandon it. The affinities of inorganic chemistry immediately reassert
themselves, in ordinary circumstances rapidly tearing down the ephemeral
fabric.
The disintegration of organic tissue, when deserted by the force which
has animated and preserved it, gives rise to the phenomena which form
the theme of this paper.
Most animal-tissue decomposes with great rapidity, and plant tissue,
when not protected, soon decays. This decay is essentially oxidation,
since its final result is the restoration to the atmosphere of carbonic
acid, which is broken up in plant-growth by the appropriation of its
carbon. Hence it is a kind of combustion, although this term is more
generally applied to very rapid oxidation, with the evolution of
sensible light and heat. But, whether the process goes on rapidly or
slowly, the same force is evolved that is absorbed in the growth of
plant-tissue; and by accelerating and guiding its evolution, we are able
to utilize this force in the production at will of heat, light, and
their correlatives, chemical affinity, motive power, electricity, and
magnetism. The decomposition of plants may, however, be more or less
retarded, and it then takes the form of a destructive distillation,
the constituents reacting upon each other, and forming temporary
combinations, part of which are evolved, and part remain behind. Water
is the great extinguisher of this as of the more rapid oxidation that we
call combustion; and the decomposition of plant-tissue under water is
extremely slow, from the partial exclusion of oxygen. Buried under thick
and nearly impervious masses of clay, where the exclusion of oxygen is
still more nearly complete, the decomposition is so far retarded that
plant-tissue, which is destroyed by combustion almost instantaneously,
and if exposed to "the elements"--moisture with a free access of
oxygen--decays in a year or two, may be but partially consumed when
millions of years have passed. The final result is, however, inevitable,
and always the same, viz., the oxidation and escape of the organic
mutter, and the concentration of the inorganic matter woven into its
composition--in it, but not of it--forming what we call the ash of the
plant.
Since the decomposition of organic matter commences the instant it is
abandoned by the creative and conservative vital force, and proceeds
uninterruptedly, whether slowly or rapidly, to the final result, it is
evident that each moment in the progress of this decomposition presents
us with a phase of structure and composition different from that which
preceded and from that which follows it. Hence the succession of these
phases forms a complete sliding scale, which is graphically shown in
the following diagram, where the organic constituents of plant
tissue--carbon, hydrogen, oxygen, and nitrogen--appear gradually
diminishing to extinction, while the ash remains nearly constant, but
relatively increasing, till it is the sole representative of the fabric.
[Illustration: DIAGRAM SHOWING THE GENETIC RELATIONS OF THE CARBON
MINERALS.]
We may cut this triangle of residual products where we please, and by
careful analysis determine accurately the chemical composition of a
section at this point, and we may please ourselves with the illusion, as
many chemists have done, that the definite proportions found represent
the formula of a specific compound; but an adjacent section above or
below would show a different composition, and so in the entire triangle
we should find an infinite series of formulae, or rather no constant
formulae at all. We should also find that the slice, taken at any point
while lying in the laboratory or undergoing chemical treatment, would
change in composition, and become a different substance.
In the same way we can snatch a brand from the fire at any stage of its
decomposition, or analyze a decaying tree trunk during any month of its
existence, and thus manufacture as many chemical formulae as we like,
and give them specific names; but it is evident that this is child's
play, not science. The truth is, the slowly decomposing tissue of the
plants of past ages has given us a series of phases which we have
grouped under distinct names, and we have called one group peat, one
lignite, another coal, another anthracite, and another graphite. We have
spaced off the scale, and called all within certain lines by a common
name; but this does not give us a common composition for all the
material within these lines. Hence we see that any effort to define or
describe coal, lignite, or anthracite accurately must be a failure,
because neither has a fixed composition, neither is a distinct
substance, but simply a conventional group of substances which form part
of an infinite and indivisible series.
But this sliding scale of solid compounds, which we designate by
the names given above, is not the only product of the natural and
spontaneous distillation of plant tissue. Part of the original organic
mass remains, though constantly wasting, to represent it; another part
escapes, either completely oxidized as carbonic acid and water, or in
a volatile or liquid form, still retaining its organic character, and
destined to future oxidation, known as carbureted hydrogen, olefiant
gas, petroleum, etc.
Hence, in the decomposition of vegetable tissue, two classes of
resultant compounds are formed, one residual and the other evolved; and
the genesis and relation of the carbon minerals may be accurately shown
by the following diagram:
PLANT TISSUE
_________________
|
_Residual Products_ | _Evolved Products_
|
Peat. }
| }
Lignite. }
| } { Carbonic Acid.
Bitumious Coal. } { Carbonic Oxide.
| } { Carbureted Hydrogen, etc.
Semi-bitumious " } { Water.
| } { {Maltha.
Anthracite. } { { |
| } { {Asphalt etc.
Graphitie Anthracite. } { Petro- { |
| } { leum {Asphaltic Coal.
Graphite. } { |
| } {Asphaltic Anthracite.
Ash. } { |
{ " Graphite.
[NOTE.--In this diagram, the vertical line connecting the names of the
residual products (and of the derivatives of petroleum) indicates that
each succeeding one is produced by further alteration from that which
precedes it, and not independently. Also, the arrangement of the braces
is designed to show that any or all of the evolved products are given
off at each stage of alteration.]
The theory here proposed has not been evolved from my inner
consciousness, but has grown from careful study, through many years, of
facts in the field. A brief sketch of the evidence in favor of it is all
that we have space for here.