mical composition. One very
palpable proof of the carbonaceous character of tree-trunks suggests
itself. Take in your hand a few dead twigs or sticks from which the
leaves have long since dropped; pull away the dead parts of the ivy which
has been creeping over the summer-house; or clasp a gnarled old monster
of the forest in your arms, and you will quickly find your hand covered
with a black smut, which is nothing but the result of the first stage
which the living plant has made, in its progress towards its condition as
dead coal. But an easy, though rough, chemical proof of the constituents
of wood, can be made by placing a few pieces of wood in a medium-sized
test-tube, and holding it over a flame. In a short time a certain
quantity of steam will be driven off, next the gaseous constituents of
wood, and finally nothing will be left but a few pieces of black brittle
charcoal. The process is of course the same in a fire-grate, only that
here more complete combustion of the wood takes place, owing to its being
intimately exposed to the action of the flames. If we adopt the same
experiment with some pieces of coal, the action is similar, only that in
this case the quantity of gases given off is not so great, coal
containing a greater proportion of carbon than wood, owing to the fact
that, during its long burial in the bowels of the earth, it has been
acted upon in such a way as to lose a great part of its volatile
constituents.

From processes, therefore, which are to be seen going on around us, it is
easily possible to satisfy ourselves that vegetation will in the long run
undergo such changes as will result in the formation of coal.

There are certain parts in most countries, and particularly in Ireland,
where masses of vegetation have undergone a still further stage in
metamorphism, namely, in the well-known and famous peat-bogs. Ireland is
_par excellence_ the land of bogs, some three millions of acres being
said to be covered by them, and they yield an almost inexhaustible supply
of peat. One of the peat-bogs near the Shannon is between two and three
miles in breadth and no less than fifty in length, whilst its depth
varies from 13 feet to as much as 47 feet. Peat-bogs have in no way
ceased to be formed, for at their surfaces the peat-moss grows afresh
every year; and rushes, horse-tails, and reeds of all descriptions grow
and thrive each year upon the ruins of their ancestors. The formation of
such accumulations o