In reflecting on the statement, thus briefly made, of the main facts
connected with the origin of the coal formed during the carboniferous
epoch, two or three considerations suggest themselves.

In the first place, the great phantom of geological time rises before
the student of this, as of all other, fragments of the history of our
earth--springing irrepressibly out of the facts, like the Djin from
the jar which the fisherman so incautiously opened; and like the Djin
again, being vaporous, shifting, and indefinable, but unmistakably
gigantic. However modest the bases of one's calculation may be,
the minimum of time assignable to the coal period remains something
stupendous.

Principal Dawson is the last person likely to be guilty of
exaggeration in this matter, and it will be well to consider what he
has to say about it:--

"The rate of accumulation of coal was very slow. The climate
of the period, in the northern temperate zone, was of such
a character that the true conifers show rings of growth, not
larger, nor much less distinct, than those of many of their
modern congeners. The _Sigillariae_ and _Calamites_ were not,
as often supposed, composed wholly, or even principally, of
lax and soft tissues, or necessarily short-lived. The former
had, it is true, a very thick inner bark; but their dense
woody axis, their thick and nearly imperishable outer bark,
and their scanty and rigid foliage, would indicate no very
rapid growth or decay. In the case of the _Sigillariae_, the
variations in the leaf-scars in different parts of the trunk,
the intercalation of new ridges at the surface representing