Outlines of the Earths History | Page 8

have
shown the existence at the present time of many hundred thousand
distinct species, the vast assemblage being arranged in a classification
which shows something as to the relationship which the forms bear to
each other, and furthermore that the kinds now living have not been
long in existence, but that at each stage in the history of the earth
another assemblage of species peopled the waters and the lands.
At first naturalists concerned themselves only with the external forms
of living creatures; but they soon came to perceive that the way in
which these organisms worked, their physiology, in a word, afforded
matters for extended inquiry. These researches have developed the
science of physiology, or the laws of bodily action, on many accounts
the most modern and extensive of our new acquisitions of natural
learning. Through these studies we have come to know something of
the laws or principles by which life is handed on from generation to
generation, and by which the gradations of structure have been
advanced from the simple creatures which appear like bits of animated
jelly to the body and mind of man.

The greatest contribution which modern naturalists have made to
knowledge concerns the origin of organic species. The students of a
century ago believed that all these different kinds had been suddenly
created either through natural law or by the immediate will of God. We
now know that from the beginning of organic life in the remote past to
the present day one kind of animal or plant has been in a natural and
essentially gradual way converted into the species which was to be its
successor, so that all the vast and complicated assemblage of kinds
which now exists has been derived by a process of change from the
forms which in earlier ages dwelt upon this planet. The exact manner in
which these alterations were produced is not yet determined, but in
large part it has evidently been brought about by the method indicated
by Mr. Darwin, through the survival of the fittest individuals in the
struggle for existence.
Until men came to have a clear conception as to the spherical form of
the earth, it was impossible for them to begin any intelligent inquiries
concerning its structure or history. The Greeks knew the earth to be a
sphere, but this knowledge was lost among the early Christian people,
and it was not until about four hundred years ago that men again came
to see that they dwelt upon a globe. On the basis of this understanding
the science of geology, which had in a way been founded by the Greeks,
was revived. As this science depends upon the knowledge which we
have gained of astronomy, physics, chemistry, and biology, all of
which branches of learning have to be used in explaining the history of
the earth, the advance which has been made has been relatively slow.
Geology as a whole is the least perfectly organized of all the divisions
of learning. A special difficulty peculiar to this science has also served
to hinder its development. All the other branches of learning deal
mainly, if not altogether, with the conditions of Nature as they now
exist. In this alone is it necessary at every step to take account of
actions which have been performed in the remote past.
It is an easy matter for the students of to-day to imagine that the earth
has long endured; but to our forefathers, who were educated in the view
that it had been brought from nothingness into existence about seven
thousand years ago, it was most difficult and for a time impossible to

believe in its real antiquity. Endeavouring, as they naturally did, to
account for all the wonderful revolutions, the history of which is
written in the pages of the great stone book, the early geologists
supposed this planet to have been the seat of frequent and violent
changes, each of which revolutionized its shape and destroyed its living
tenants. It was only very gradually that they became convinced that a
hundred million years or more have elapsed since the dawn of life on
the earth, and that in this vast period the march of events has been
steadfast, the changes taking place at about the same rate in which they
are now going on. As yet this conception as to the history of our sphere
has not become the general property of the people, but the fact of it is
recognised by all those who have attentively studied the matter. It is
now as well ascertained as any of the other truths which science has
disclosed to us.
It is instructive to note the historic outlines of scientific development.
The most conspicuous truth which this history discloses is that all
science has had its