668 HISTORY OF GEOLOGY. 



the operation of the causes of geological change 

 may properly 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 geological uniformity, that we are not arbitra- 

 rily to assume the existence of catastrophes. The 

 degree of uniformity and continuity with which ter- 

 remotive forces have acted, must be collected, not 

 from any gratuitous 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 

 favour 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 intensity of 

 existing and of past causes, we conceive that he 

 errs no less than those whom he censures. "An 

 earnest and patient endeavour to reconcile the 

 former indications 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 themselves teach 

 us the nature and intensity of the causes which 

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



