GEOLOGY 129 



ulated facts and of fundamental principles deduced from 

 them. 



The one first formulated, and the one that constitutes 

 the foundation on which the whole superstructure of the sci- 

 ence has been built, is the Doctrine of Uniformitarianism. It 

 is practically the one fundamental doctrine of modern geol- 

 ogy. According to this doctrine, the earth has been brought 

 to its existing condition through the operation of processes 

 that are still in operation on and in the earth. The essence 

 of this doctrine is included in the sentence: "The earth was 

 not made, but is being made." The work of earth building 

 is going on now, and, so far as our evidence can guide us, 

 it is being made now in the same way and at about the same 

 rate as it has been made in the past. The earth was not made 

 and finished for the reception of life, either plant or animal, 

 but these appeared at their proper places and in proper order 

 as the result of passing but favorable conditions, and they will 

 disappear in the same way. The many and various manifesta- 

 tions of the earth's development in the past and at present are 

 all passing phases. 



The same processes that we see going on around us at 

 the present time: the journey of earth materials — it may be 

 by stages with long time intervals of rest between — to the 

 sea ; the distribution of this material over the bottoms of shal- 

 low seas in stratified beds ; the breaking up of rock by the 

 irresistible powers of air; the growth of plants and animals 

 and the entombment of their remains in the waste products 

 of a distintegrating land ; the incessant wear of the sea on the 

 land, as well as its compensating action in building bars ; the 

 slow movements of the land surface upward or downward 

 with respect to the earth's datum plane — the sea; — all these 

 various activities that are facts of daily observation have, 

 through their action in the past, brought about the slow 

 changes in the earth which we designate as the earth's devel- 



