6 PRINCIPLES OF PALZONTOLOGY. 
the world is truly in its “hoary eld,” and that its present state 
is really the result of the tranquil and regulated action of 
known forces through unnumbered and innumerable centuries. 
The most important point for us, in the present connection, 
is the bearing of these opposing doctrines upon the question 
as to the origin of the existing terrestrial order. On any doc- 
trine of uniformity that order has been evolved slowly, and, 
according to law, from a pre-existing order. Any doctrine of 
catastrophism, on the other hand, carries with it, by implica- 
tion, the belief that the present order of things was brought 
about suddenly and irrespective of any pre-existent order; and 
it is important to hold clear ideas as to which of these beliefs 
is the true one. 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 un- 
searchable depths of a past so prolonged as to present itself to 
our finite minds as almost an eternity. The last steps are in 
the prophetic future, and can be but dimly guessed at. Be- 
tween 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 pre- 
sent 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. Nothing could be more natural 
than such a belief, and nothing could be further removed from 
the actual truth On the contrary, a very slight acquaintance 
with geology shows us, in the words of Sir John Herschel, that 
