PREFACE. IX 



ployments. It is well known that, by obeying the laws 

 of Nature, we learn how to employ them ; and by studying 

 the principles of science, and the action of the human 

 mind in original research, we may reasonably expect to 

 learn the essential conditions upon which success in scien- 

 tific discovery depends. 



Hitherto the nature and methods of original scientific 

 inquiry have been insufficiently studied, and the success 

 achieved in it has, therefore, been attributed too much to 

 accident, to strong imagination, and exceptional natural 

 ability ; and too little to the less brilliant qualifications 

 of steady thought, self-development, industry, and perse- 

 verance. No pretence, however, is made to impart by 

 extraneous aid the faculties of imagination and invention, 

 and the , quick perception of difference and resemblance. 

 But whilst great aptitude for scientific discovery must, like 

 any other rare and peculiar ability, be born in the man, 

 it is certain that it may, like those other natural abilities, 

 be assisted by advice and developed by experience ; and 

 to supply such advice is one of the objects of this 

 treatise. 



It must be remembered that the simple or qualitative 

 discovery of new truths usually precedes quantitative re- 

 search, and such further research must be conducted 

 according to logical as well as mathematical rules. Hence 

 the suggestions and remarks of the following treatise will 

 be almost wholly confined to the logical aspect of the 

 subject. 



The very magnitude of the subject makes it impos- 

 sible to treat it thoroughly. A complete treatise would 



