592 HISTORY OF GEOLOGY. 



plies was rejected with some contempt and ridicule ; and it was main 

 taiued, that the operation of the causes of geological change may pro- 

 perly and philosophically be held to have been uniform through all 

 ages and periods. On this opinion, and the grounds on which it has 

 been urged, we shall make a few concluding remarks. 



It must be granted at once, to the advocates of this geologica' 

 uniformity, that we are not arbitrarily to assume the existence of 

 catastrophes. The degree of uniformity and continuity with which 

 ten-emotive forces have acted, must be collected, not from any gratui- 

 tous hypothesis, but from the facts of the case. We must suppose 

 the causes which have produced geological phenomena, to have been 

 as similar to existing causes, and as dissimilar, as the effects teach us. 

 We are to avoid all bias in favor of powers deviating in kind and 

 degree from those which act at present ; a bias which, Mr. Lyell asserts, 

 has extensively prevailed among geologists. 



But when Mr. Lyell goes further, and considers it a merit in a course 

 of geological speculation that it rejects any difference between the in- 

 tensity of existing and of past causes, we conceive that he errs no less 

 than those whom he censures. " An earnest and patient endeavor to 

 reconcile the former indication of change," 9 with any restricted class 

 of causes, a habit which he enjoins, is not, we may suggest, the 

 temper in which science ought to be pursued. The effects must them- 

 selves teach us the nature and intensity of the causes which have 

 operated ; and we are in danger of error, if we seek for slow and shun 

 violent agencies further than the facts naturally direct us, no less than 

 if we were parsimonious of time and prodigal of violence. Time, in- 

 exhaustible and ever accumulating his efficacy, can imdoubtedly do 

 much for the theorist in geology ; but force, whose limits we cannot 

 measure, and whose nature we cannot fathom, is also a power never 

 to be slighted : and to call in the one to protect us from the other, is 

 equally presumptuous, to whichever of the two our superstition leans. 

 To invoke Time, with ten thousand earthquakes, to overturn and set 

 on edge a mountain-chain, should the phenomena indicate the change 

 to have. been sudden and not successive, would be ill excused by plead- 

 ing the obligation of first appealing to known causes. 10 



9 Lyell, B. iv. c. i. p. 328, 4th ed. 



10 [2nd Ed.] [I have, in the text, quoted the fourth edition of Mr. Lyell'a 

 Principles, in which he recommends ''an earnest and patient endeavor to re- 

 concile the former indications of change with the evidence of gradual mutati<>r 



