regular a manner over so wide an area.

Each of the British coal-fields is fairly extensive. The Yorkshire and
Derbyshire coal-fields, together with the Lancashire coal-field, with
which they were at one time in geological connection, give us an area of
nearly 1000 square miles, and other British coal-fields show at least
some hundreds of square miles. And yet, spread over them, we find a
series of beds of coal which in many cases extend throughout the whole
area with apparent regularity. If we take it, as there seems every reason
to believe was the case, that almost all these coal-fields were not only
being formed at the same time, but were in most instances in continuation
with one another, this regularity of deposition of comparatively narrow
beds of coal, appears all the more remarkable.

The question at once suggests itself, Which of two things is probable?
Are we to believe that all this vegetable matter was brought down by some
mighty river and deposited in its delta, or that the coal-plants grew
just where we now find the coal?

Formerly it was supposed that coal was formed out of dead leaves and
trees, the refuse of the vegetation of the land, which had been carried
down by rivers into the sea and deposited at their mouths, in the same
way that sand and mud, as we have seen, are swept down and deposited. If
this were so, the extent of the deposits would require a river with an
enormous embouchure, and we should be scarcely warranted in believing
that such peaceful conditions would there prevail as to allow of the
layers of coal to be laid down with so little disturbance and with such
regularity over these wide areas. But the great objection to this theory
is, that not only do the remains still retain their perfection of
structure, but they are comparatively _pure,--i.e.,_ unmixed with