VALUE OF SCIENTIFIC HYPOTHESES. 367 



Faraday was largely aided in discovering the law of 

 Qectro-dynamic induction by imagining the relations of 

 pace and ' lines of force ' which connect the poles of a 

 nagnet, the position of the induction wires, the direction 

 >f its motion, and the current produced in it. The exist- 

 ence of the current depended upon the position and motion 

 >f the wire ; the direction of the current depended upon 

 ihe direction of the motion of the wire and the direction 

 of polarity of the magnet ; its amount depended upon the 

 amount of magnetism, the degree of proximity of the 

 wire to the magnet, the velocity of the motion, and the 

 amount of conduction-resistance ; and all these conditions 

 had to be realised in his mind by the aid of the power of 

 conception, in order to obtain a clear idea of the action 

 and its explanation. 



No scientific subject can be read or studied by a true 

 student of nature without its exciting in his mind various 

 new questions. It is generally whilst intently meditating 

 on the special conditions, peculiarities, incomplete portions, 

 and unexplained effects of known experiments or facts 

 that new ideas arise. Often, also, whilst reading accounts 

 of new discoveries, perusing scientific articles or books, 

 collecting scientific information, preparing lessons or 

 lectures, classifying scientific knowledge, &c., hypothetical 

 questions suggest themselves. But it is only when scien- 

 tific subjects are studied with a determined resolution to 

 understand them clearly and completely, that the excite- 

 ment of genius, or inspiration of originality of the student 

 (if he has any), arises within him ; i.e., he combines by an 

 act of the memory and imagination some of his previous 

 knowledge with that which he is acquiring, and the 

 union of the two gives birth to new suggestions of an 

 original kind. It is oftentimes difficult to call to mind 



O 



how, in such cases^ an idea originated, because the inten- 



