a well has been sunk into it.

The plants which have gone to make up the coal are not at once apparent
to the naked eye. We have to search among the shales and clays and
sandstones which enclose the coal-seams, and in these we find petrified
specimens which enable us to build up in our mind pictures of the
vegetable creation which formed the jungles and forests of these
immensely remote ages, and which, densely packed together on the old
forest floor of those days, is now apparent to us as coal.

[Illustration: Fig. 2.--_Annularia radiata._ Carboniferous sandstone.]

A very large proportion of the plants which have been found in the
coal-bearing strata consists of numerous species of ferns, the number of
actual species which have been preserved for us in our English coal,
being double the number now existing in Europe. The greater part of these
do not seem to have been very much larger than our own living ferns, and,
indeed, many of them bear a close resemblance to some of our own living
species. The impressions they have left on the shales of the
coal-measures are most striking, and point to a time when the sandy clay
which imbedded them was borne by water in a very tranquil manner, to be
deposited where the ferns had grown, enveloping them gradually, and
consolidating them into their mass of future shale. In one species known
as the _neuropteris_, the nerves of the leaves are as clear and as
apparent as in a newly-grown fern, the name being derived from two Greek
words meaning "nerve-fern." It is interesting to consider the history of
such a leaf, throughout the ages that have elapsed since it was part of a
living fern. First it grew up as a new frond, then gradually unfolded
itself, and developed into the perfect fern. Then it became cut off by
the rising waters, and buried beneath an accumulation of sediment, and