o animals. As each
dollar in gold that is received into a country permanently increases its
amount of circulating medium, and each dollar sent out permanently
decreases it until returned, so the carbonic acid sent into the
atmosphere by burning, decay, or respiration, becomes a permanent stock
of constantly changeable material, until it shall be locked up for a
time, as in a house which may last for centuries, or in an oak tree
which may stand for thousands of years. Still, at the decay of either of
these, the carbon which they contain must be again resolved into
carbonic acid.

[What are the coal-beds of Pennsylvania?

What are often found in them?]

The coal-beds of Pennsylvania are mines of carbon once abstracted from
the atmosphere by plants. In these coal-beds are often found fern
leaves, toads, whole trees, and in short all forms of organized matter.
These all existed as living things before the great floods, and at the
breaking away of the barriers of the immense lakes, of which our present
lakes were merely the deep holes in their beds, they were washed away
and deposited in masses so great as to take fire from their chemical
changes. It is by many supposed that this fire acting throughout the
entire mass (without the presence of air _to supply oxygen_ except on
the surface) caused it to become melted carbon, and to flow around those
bodies which still retained their shapes, changing them to coal without
destroying their structures. This coal, so long as it retains its
present form, is lost to the vegetable kingdom, and each ton that is
burned, by being changed into carbonic acid, adds to the ability of the
atmosphere to support an increased amount of vegetation.

[Explain the manner in which they become coal.

How does the burning of coal benefit vegetation?

Is carbon ever permanent in any of its forms?

What enables it to change its condition?]

Thus we see that, in the provisions of nature, carbon, the grand basis,
on which all organized matter is founded, is never permanent in any of
its forms. Oxygen is the carrier which enables it to change its
condition. For instance, let us suppose that we have a certain quantity
of charcoal; this is nearly pure carbon. We ignite it, and it unites
with the oxygen of the air, becomes carbonic acid, and floats away into
the atmosphere. The wind carries it through a forest, and the leaves of
the trees with their millions of mouths drink it in. By the assistance
o