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CHAPTER VIII. 

 OF CLASSIFICATION BY SERIES. 



1. THUS far, we have considered the principles 

 of scientific classification so far only as relates to the 

 formation of natural groups; and at this point most 

 of those who have attempted a theory of natural 

 arrangement, including, among the rest, Mr. Whewell, 

 have stopped. There remains, however, another and 

 a not less important portion of the theory, which has 

 not yet, so far as I am aware, been systematically 

 treated of by any writer except M. Comte. This is, 

 the arrangement of the natural groups into a natural 

 series. 



The end of Classification, as an instrument for the 

 investigation of nature, is (as before stated) to make 

 us think of those objects together, which have the 

 greatest number of important common properties ; and 

 which therefore we have oftenest occasion, in the 

 course of our inductions, for taking into joint consi- 

 sideration. Our ideas of objects are thus brought 

 into the order most conducive to the successful pro- 

 secution of inductive inquiries generally. But when 

 the purpose is to facilitate some particular inductive 

 inquiry, more is required. To be instrumental to 

 that purpose, the classification must bring those objects 

 together, the simultaneous contemplation of which is 

 likely to throw most light upon the particular subject. 

 That subject being the laws of some phenomenon, or 

 some set of connected phenomena; the very pheno- 

 menon or set of phenomena in question must be chosen 

 as the groundwork of the classification. 



The requisites of a classification intended to faci- 



VOL. II. Y 



