s proof of any
exceptional paroxysms. Rather, we find ourselves compelled to regard
igneous rocks as an aggregate effect of innumerable eruptions, of
various degrees of violence, at various times, and to consider mountain
chains as the accumulative results of these eruptions. The incumbent
crust of the earth is never allowed to attain that strength and
coherence which would be necessary in order to allow the volcanic force
to accumulate and form an explosive charge capable of producing a grand
paroxysmal eruption. The subterranean power, on the contrary, displays,
even in its most energetic efforts, an intermittent and mitigated
intensity. There are no proofs that the igneous rocks were produced more
abundantly at remote periods.

Nor can we find proof of catastrophic discontinuity when we examine
fossil plants and fossil animals. On the contrary, we find a progressive
development of organic life at successive geological periods.

In Palaeozoic strata the entire want of plants of the most complex
organisation is very striking, for not a single dicotyledonous
angiosperm has yet been found, and only one undoubted monocotyledon. In
Secondary, or Mesozoic, times, palms and some other monocotyledons
appeared; but not till the Upper Cretaceous era do we meet with the
principal classes and orders of the vegetable kingdom as now known.
Through the Tertiary ages the forms were perpetually changing, but
always becoming more and more like, generically and specifically, to
those now in being. On the whole, therefore, we find progressive
development of plant life in the course of the ages.

In the case of animal life, progression is equally evident.
Palaeontological research leads to the conclusion that the invertebrate
animals flourished before the vertebrate, and that in the latter class
fish, reptiles, birds, and mammalia made their appearance in a
chronological order analogous to that in which they would be arranged
zoologically according to an advancing scale of perfection in their
organisation. In regard to the mammalia themselves, they have been
divided by Professor Owen into four sub-classes by reference to
modifications of their brain. The two lowest are met with in the
Secondary strata. The next in grade is found in Tertiary strata. And the
highest of all, of which man is the sole representative, has not yet
been detected in deposits older than the Post-Tertiary.

It is true that in passing from the older to the newer