a piece of coal, you will find, more or less
clearly, markings like those which are seen in a piece of wood.
Sometimes they are very distinct indeed. Coal abounds in impressions
of leaves, ferns, and stems, and fossil remains of plants and
tree-trunks are found in numbers in coal-seams.

Coal is a vegetable substance. The wide coal-fields of Britain and
other lands are the _fossil_ remains of vast forests.

Long ages ago, as it seems, broad and luxuriant forests flourished
over the earth. In many parts generation after generation of trees
lived and died and decayed, leaving no trace of their existence,
beyond a little layer of black mould, soon to be carried away by wind
and water. Coal could only be formed where there were bogs and
quagmires.

But in bogs and quagmires, and in shallow lakes of low-lying lands,
there were great gatherings of slowly-decaying vegetable remains,
trees, plants, and ferns all mingling together. Then after a while the
low lands would sink and the ocean pouring in would cover them with
layers of protecting sand or mud; and sometimes the land would rise
again, and fresh forests would spring into life, only to be in their
turn overwhelmed anew, and covered by fresh sandy or earthy deposits.

These buried forests lay through the ages following, slowly hardening
into the black and shining coal, so useful now to man.

The coal is found thus in thin or thick seams, with other rock-layers
between, telling each its history of centuries long past. In one place
no less than sixteen such beds of coal are found, one below another,
each divided from the next above and the next underneath by beds of
clay or sand or shale. The forests could not have grown in the sea,
and the earth-layers could not have been formed on land, therefore
many land-risings and sinkings must have taken place. Each bed
probably tells the tale of a succession of forests....

* * * * *

Before going on to a sketch of the early ages of the Earth's
history--ages stretching back long long before the time of Adam--it is
needful to think yet for a little longer about the manner in which
that history is written, and the way in which it has to be read.

For the record is one difficult to make out, and its style of
expression is often dark and mysterious. There is scarcely any other
volume in the great Book of Nature, which the student is so likely to
misread as this one. It is very needful, therefore,