518 WRITINGS OP JOSEPH HENRY. [1877 



posed to his previous generalization, which conclusively 

 forces upon his mind the conviction that he is still far from 

 attaining his end ; that he has not yet seized upon the fun- 

 damental principle of the phenomena, which have grown 

 into a class under his hands. 



At this stage of the inquiry his self-esteem is much de- 

 pressed ; he throws aside for a while his apparatus, refers to 

 his library for new suggestions : the subject however is not 

 discharged from his mind; it still goes with him, and is 

 perpetually recurring ; it is mingled with his dreams, and is 

 seen associated with the every-day occurrences of life, until 

 at length, in some happy moment of inspiration, it may be 

 after refreshing sleep, the truth flashes upon him ; he catches 

 a more extended conception of the relations of the phenom- 

 ena ; a more comprehensive hypothesis is suggested, from 

 which he is enabled to deduce in succession a large number 

 of new conclusions to be submitted to the test of experi- 

 ments. These are all found to jdeld the expected results, 

 and the generalization which has thus been obtained is more 

 than an hypothesis ; it is entitled to the name of a verified 

 theory. The investigator now feels amply rewarded for all 

 his toil, and is conscious of the pleasure of the self-appreci- 

 ation which flows from having been initiated into the secrets 

 of nature, and allowed the place not merely of an humble 

 worshipper in the vestibule of the temple of science, but an 

 officiating priest at the altar. 



In this sketch of a successful investigation which I have 

 given, it will be observed that several faculties of the mind 

 are called into operation. First, the imagination — which 

 calls forth the forms of things unseen and gives them a local 

 habitation, must be active in presenting to the mind's eye a 

 definite conception of the modes of operation of the forces in 

 nature sufficient to produce the phenomena in question: 

 second, the logical power must be trained, in order to deduce 

 from the assumed-premises the conclusions necessary to test 

 the truth of the assumption in the form of an experiment: 

 and lastly the ingenuity must be taxed to invent the experi- 

 ment or to bring about the arrangement of apparatus adapted 

 to test the conclusions. 



