In the first place, we may postulate that the world had a beginning, and, equally, that the existing terrestrial order had a beginning.
However far back we may go, geology does not, and cannot, reach the actual beginning of the world; and we are, therefore, left simply to our own speculations on this point.

With regard, however, to the existing terrestrial order, a great deal can be discovered, and to do so is one of the principal tasks of geological science.
The first steps in the production of that order lie buried in the profound and unsearchable depths of a past so prolonged as to present itself to our finite minds as almost in eternity.
The last steps are in the prophetic future, and can be but dimly guessed at.

Between the remote past and the distant future, we have, however, a long period which is fairly open to inspection; and in saying a "long" period, it is to be borne in mind that this term is used in its _geological_ sense.

Within this period, enormously long as it is when measured by human standards, we can trace with reasonable certainty the progressive march of events, and can determine the laws of geological action, by which the present order of things has been brought about.
The natural belief on this subject doubtless is, that the world, such as we now see it, possessed its present form and configuration from the beginning.

Nothing can be more natural than the belief that the present continents and oceans have always been where they are now; that we have always had the same mountains and plains; that our rivers have always had their present courses, and our lakes their present positions; that our climate has always been the same; and that our animals and plants have always been identical with those now familiar to us.