6 PRINCIPLES OF PALAEONTOLOGY. 



globe is but, as it were, the birth of yesterday, were driven of 

 necessity to the conclusion that its history had been checkered 

 by the intermittent action of paroxysmal and almost inconceiva- 

 bly potent forces. The Uniformitarians, on the other hand, 

 maintaining the " adequacy of existing causes," and denying that 

 the known physical forces ever acted in past time with greater 

 intensity than they do at present, are, equally of necessity, driven 

 to the conclusion that 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 in- 

 numerable 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 doctrine 

 of uniformity that order has been evolved slowly, and, accord- 

 ing to law, from a pre-existing order. Any doctrine of catas- 

 trophism, on the other hand, carries with it, by implication, the 

 belief that the present order of things was brought about sud- 

 denly 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 prin- 

 cipal tasks of geological science. The first steps in the produc- 

 tion 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 an 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 reason- 

 able certainty the progressive march of events, and can deter- 

 mine 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 nat- 



