CHAP. xii. GEOLOGICAL PRINCIPLES. 113 



and violent catastrophes may be again and again pro- 

 duced. 



During a period of more than forty years Sir Charles 

 Lyell continued to enlarge and improve his work, bring- 

 ing out eleven editions, the last of which was published 

 three years before his death ; and rarely has any scientific 

 work so completely justified its title, since it remains to 

 this day the best exposition of the " Principles of 

 Geology " the foundation on which the science itself 

 must be and has been built. The disciples and followers 

 of Lyell have been termed " Uniformitarians," on ac- 

 count of their belief that the causes which produced the 

 phenomena manifested to us in the crust of the earth 

 are essentially of the same nature as those acting now. 

 And, as is often the case, the use of the term as a nick- 

 name has led to a misconception as to the views of those 

 to whom it is applied. A few words on this point are 

 therefore called for. 



Modern objectors say that it is unphilosophical to 

 maintain that in our little experience of a few hundred, 

 or at most a few thousand, years, we can have witnessed 

 all forms and degrees of the action of natural forces ; that 

 we have no right to take the historical period as a fair 

 sample of all past geological ages; and that, as a mere 

 matter of probability, we ought to expect to find proofs 

 of greater earthquakes, more violent eruptions, more sud- 

 den upheavals, and more destructive floods, having 

 occurred during the vast eons of past time. ISTow this 

 argument is perfectly sound if limited to the occurrence 

 of extreme cases, but no.t if applied to averages. ISTo 

 uniformitarian will deny the probability of there having 

 been some greater convulsions in past geological ages 



