THE LAWS OF GEOLOGICAL ACTION. 3 



theories to explain the common phenomena of the material 

 universe ; and most of these theories, however varied in their 

 details, turn out on examination to have a common root, and 

 to be based on the same elements. Modern geology has its 

 own theories on the same subject, and it will be well to glance 

 for a moment at the principles underlying the old and the new 

 views. 



It has been maintained, as a metaphysical hypothesis, that 

 there exists in the mind of man an inherent principle, in virtue 

 of which he believes and expects that what has been, will be ; 

 and that the course of nature will be a continuous and unin- 

 terrupted one. So far, however, from any such belief existing 

 as a necessary consequence of the constitution of the human 

 mind, the real fact seems to be that the contrary belief has 

 been almost universally prevalent. In all old religions, and 

 in the philosophical systems of almost all ancient nations, the 

 order of the universe has been regarded as distinctly unstable, 

 mutable, and temporary. A beginning and an end have always 

 been assumed, and the course of terrestrial events between 

 these two indefinite points has been regarded as liable to con- 

 stant interruption by revolutions and catastrophes of different 

 kinds, in many cases emanating from supernatural sources. 

 Few of the more ancient theological creeds, and still fewer of 

 the ancient philosophies, attained body and shape without 

 containing, in some form or another, the belief in the existence 

 of periodical convulsions, and of alternating cycles of destruc- 

 tion and repair. 



That geology, in its early infancy, should have become im- 

 bued with the spirit of this belief, is no more than might have 

 been expected ; and hence arose the at one time powerful and 

 generally-accepted doctrine of " Catastrophism." That the 

 succession of phenomena upon the globe, whereby the earth's 

 crust had assumed the configuration and composition which 

 we find it to possess, had been a discontinuous and broken 

 succession, was the almost inevitable conclusion of the older 

 geologists. Everywhere in their study of the rocks they met 

 with apparently impassable gaps, and breaches of continuity 

 that could not be bridged over. ' Everywhere they found them- 

 selves conducted abruptly from one system of deposits to 

 others totally different in mineral character or in stratigraphical 

 position. Everywhere they discovered that well-marked and 

 easily recognisable groups of animals and plants were succeeded, 

 without the intermediation of any obvious lapse of time, by 

 other assemblages of organic beings of a different character. 

 Everywhere they found evidence that the earth's crust had 



