dual opinion. There can, however, be little doubt that
they are sufficiently extensive to throw the balance of evidence
decisively in favour of some theory of _continuity_, as opposed
to any theory of intermittent and occasional action. The apparent
breaks which divide the great series of the stratified rocks
into a number of isolated formations, are not marks of mighty
and general convulsions of nature, but are simply indications
of the imperfection of our knowledge. Never, in all probability,
shall we be able to point to a complete series of deposits, or a
complete succession of life linking one great geological period
to another. Nevertheless, we may well feel sure that such deposits
and such an unbroken succession must have existed at one time.
We are compelled to believe that nowhere in the long series of
the fossiliferous rocks has there been a total break, but that
there must have been a complete continuity of life, and a more
or less complete continuity of sedimentation, from the Laurentian
period to the present day. One generation hands on the lamp of
life to the next, and each system of rocks is the direct offspring
of those which preceded it in time. Though there has not been
continuity in any given area, still the geological chain could
never have been snapped at one point, and taken up again at a
totally different one. Thus we arrive at the conviction that
_continuity_ is the fundamental law of geology, as it is of the
other sciences, and that the lines of demarcation between the
great formations are but gaps in our own knowledge.

CHAPTER V.

CONCLUSIONS TO BE DRAWN FROM FOSSILS.

We have already seen that geologists have been led by the study
of fossils to the all-important generalisation that the vast
series of the Fossiliferous or Sedimentary Rocks may be divided
into a number of definite groups or "formations," each of which is
characterised by its organic remains. It may simply be repeated here
that these formations are not properly and strictly characterised
by the occurrence in them of any one particular fossil. It may be
that a formation contains some particular fossil or fossils not
occurring out of that formation, and that in this way an observer
may identify a given group with tolerable certainty. It very often
happens, indeed, that some particular stratum, or sub-group of a
series, contains peculiar fossils, by which its existence may
be determined in various localities. As before re