f decaying vegetation would only be possible where
the physical conditions of the country allowed of an abundant rainfall,
and depressions in the surface of the land to retain the moisture. Where
extensive deforesting operations have taken place, peat-bogs have often
been formed, and many of those in existence in Europe undoubtedly owe
their formation to that destruction of forests which went on under the
sway of the Romans. Natural drainage would soon be obstructed by fallen
trees, and the formation of marsh-land would follow; then with the growth
of marsh-plants and their successive annual decay, a peaty mass would
collect, which would quickly grow in thickness without let or hindrance.

In considering the existence of inland peat-bogs, we must not lose sight
of the fact that there are subterranean forest-beds on various parts of
our coasts, which also rest upon their own beds of peaty matter, and very
possibly, when in the future they are covered up by marine deposits, they
will have fairly started on their way towards becoming coal.

Peat-bogs do not wholly consist of peat, and nothing else. The trunks of
such trees as the oak, yew, and fir, are often found mingled with the
remains of mosses and reeds, and these often assume a decidedly coaly
aspect. From the famous Bog of Allen in Ireland, pieces of oak, generally
known as "bog-oak," which have been buried for generations in peat, have
been excavated. These are as black as any coal can well be, and are
sufficiently hard to allow of their being used in the manufacture of
brooches and other ornamental objects. Another use to which peat of some
kinds has been put is in the manufacture of yarn, the result being a
material which is said to resemble brown worsted. On digging a ditch to
drain a part of a bog in Maine, U.S., in which peat to a depth of twenty
feet had accumulated, a substance similar to cannel coal itself was
found. As we shall see presently, cannel coal is one of the earliest
stages of true coal, and the discovery proved that under certain
conditions as to heat and pressure, which in this case happened to be
present, the materials which form peat may also be metamorphosed into
true coal.

Darwin, in his well-known "Voyage in the _Beagle_" gives a peculiarly
interesting description of the condition of the peat-beds in the Chonos
Archipelago, off the Chilian coast, and of their mode of formation. "In
these islands," he says, "cryptogamic plants find a most