Carbon composing a peat bed is simply unconsumed carbon. The carbon
or smoke that arises from every chimney and furnace when measurably
shut up from immediate union with oxygen, remains an unburnt fuel
precisely the same in kind as the unburnt carbon fuel of the peat bogs.
Were we to collect the unburnt carbon from our chimneys in piles,
where moisture and air could have free access, it would take fire
spontaneously and burn, just as peat dug from the bog sometimes takes
fire and burns.
The millions of fires from foundries, volcanoes, etc., are forming fuel
wherever soot is formed, and were it not for the ever active oxygen
of the air, it would all descend upon the earth as fuel and become
incorporated in forming sedimentary beds. This is our claim for the
coal, which as unconsumed carbon arose beyond the reach of destroying
oxygen, from the heated, glowing furnace of our globe, and in time
returned to the earth.
When the plant dies and begins to decay one of its constituent
elements, carbon, oxydizes by slow combustion and returns to the air as
an invisible gas. It is but accidental when a particle fails to become
oxydized and remains as unconsumed carbon. An exceedingly small part of
vegetation remains unburnt.
Coal veins, which are from one foot to three hundred feet thick, would
make a stratum around the earth ten feet thick. Fifty pounds of coal
will yield 10,000 gallons of carbonic acid. Then calling eight gallons
equal to one cubic foot the astonishing fact comes out that the coal
beds actually draw from the atmosphere an ocean of carbonic acid
which would have covered the globe to the depth of 12,500 feet, which
would have destroyed all animal life. Even three or four per cent. of
carbonic acid in our present atmosphere would be fatal to animal life.
Hence it is clear that coal cannot be attributed to vegetable origin.