ilised
world. In geology, the study of large maps is as important as it is
said to be in politics; and sections, on a true scale, are even more
important, in so far as they are essential to the apprehension of the
extraordinary insignificance of geological perturbations in relation
to the whole mass of our planet. It should never be forgotten that
what we call 'catastrophes,' are, in relation to the earth, changes,
the equivalents of which would be well represented by the development
of a few pimples, or the scratch of a pin, on a man's head. Vast
regions of the earth's surface remain geologically unknown; but the
area already fairly explored is many times greater than it was in
1837; and, in many parts of Europe and the United States, the
structure of the superficial crust of the earth has been investigated
with great minuteness.

The parallel between Biology and Geology, which I have drawn, is
further illustrated by the modern growth of that branch of the science
known as Petrology, which answers to Histology, and has made the
microscope as essential an instrument to the geological as to the
biological investigator.

The evidence of the importance of causes now in operation has been
wonderfully enlarged by the study of glacial phenomena; by that of
earthquakes and volcanoes; and by that of the efficacy of heat and
cold, wind, rain, and rivers as agents of denudation and transport. On
the other hand, the exploration of coral reefs and of the deposits now
taking place at the bottom of the great oceans, has proved that, in
animal and plant life, we have agents of reconstruction of a potency
hitherto unsuspected.

There is no study better fitted than that of geology to impress upon
men of general culture that conviction of the unbroken sequence of the
order of natural phenomena, throughout the duration of the universe,
which is the great, and perhaps the most important, effect of the
increase of natural knowledge.

THE END.

FOOTNOTES:

[A] There are excellent remarks to the same effect in
Zeller's _Philosophie der Griechen_, Theil II. Abth. ii p.
407, and in Eucken's _Die Methode der Aristotelischen,
Forschung_, pp. 136 _et seq_.

[B] Fresnel, after a brilliant career of discovery in some
of the most difficult regions of physico-mathematical
science, died at thirty-nine years of age. The following
passage of a letter from him to Young (written in November
1824),