201 



CHAP. IV. 



ON THEORIES IN GENERAL,' AND ON THE MODES AND 

 CONSIDERATIONS BY WHICH THEY ARE TO BE VERI- 

 FIED. 



(136.) It has been shown, in the preceding chap- 

 ter, that there are three modes by which the objects 

 of nature may be classified ; and that one of these 

 — that is, the natural system — is alone conducive to 

 the advancement of natural history as a physical 

 science. To this, therefore, we shall hereafter con- 

 fine our attention ; because the principles of this 

 science must be discovered by a similar series of 

 inductive generalisations to those used in every de- 

 partment of natural philosophy, " through which one 

 spirit reigns, and one method of enquiry applies." 



(137.) Let us suppose, then, that an entomo- 

 logical student, with a well-filled cabinet of unar- 

 ranged insects, having his mind well stored with 

 those simple facts regarding their structure and 

 economy which he is to look upon as solid data — let 

 us suppose him to commence the arrangement of 

 the objects before him, according to what he thinks 

 their true affinities, and with a view of verifying or 

 discovering their natural arrangement. He com- 

 mences by placing, one after the other, those species 

 which bear the greatest mutual resemblance ; and 

 for a time he proceeds so satisfactorily, — he finds the 

 several links of the chain, as it were, fit into each 



