25 



but absolutely inapplicable to the purposes of 

 science. A geological system is, in truth, hypo- 

 thetical, only in as far as it is incomplete : such 

 a system points out its own defects ; and every 

 addition of knowledge, either demolishes an hy- 

 pothesis, or converts it into a legitimate theory. 



The last objection of any apparent weight 

 which has been offered against a geological clas- 

 sification is, that different mineral compounds, 

 or rocks, are enumerated under one name, and 

 that the same rock is also sometimes described 

 by two names. 



This objection is merely a modification of the 

 second ; and it involves the very difficult question 

 of a nomenclature ; a difficulty from which the 

 mineralogical method of arrangement is not ex- 

 empt. That part of the subject will be examined 

 at more length immediately : it is first necessary 

 to state other objections which have been over- 

 looked by the authors who have engaged in this 

 discussion ; as it is desirable that all the imper- 

 fections of each system should be stated with 

 equal fairness. 



