KINETIC OR MECHANICAL VIEW OF NATURE. 69 



quired gradually a physical l significance, for he had 

 very early convinced himself of the fact, known already 



that of gravity, which causes 

 particles to act on each other 

 through straight lines, ... is more 

 analogous to that of a series of mag- 

 netic needles. ... So that in what- 

 ever way I view it, and with great 

 suspicion of the influence of favourite 

 notions over myself, I cannot per- 

 ceive how the ordinary theory . . . 

 can be a correct representation of 

 that great natural principle of elec- 

 trical action" ('Exp. Res.,' No. 

 1231). "I have used the phrases lines 

 of inductive force and curved lines of 

 force in a general sense only. . . . 

 All I am anxious about at present 

 is, that a more particular meaning 

 should not be attached to the ex- 

 pressions used than I contemplate " 

 (ibid., No. 1304). And after hav- 

 ing referred to the agreement of his 

 results with those of Poisson, ar- 

 rived at by starting from " a very 

 different mode of action," and with 

 the experimental results of Snow 

 Harris, he concludes by saying, 

 ' ' I put forth my particular view 

 with doubt and fear, lest it should 

 not bear the test of general examina- 

 tion," &c. (No. 1306). 



1 It took more than ten years 

 before the purely geometrical or 

 conventional use of the term " lines 

 of force " ripened into a physical 

 conception. The latter is definitely 

 expounded in a paper in the ' Philos. 

 Magazine' for June 1852. We can 

 compare this gradual development 

 of a symbolical into a physical 

 theory with the gradual develop- 

 ment of the atomic theory ; atoms 

 and molecules becoming a physical 

 necessity to chemists long after 

 they had been used simply as a 

 convenient representation of the 

 laws of equivalence and of the fixed 

 proportions of combination (see 

 vol. i. of this work, chap, v., p. 

 432, &c.) Faraday, during the 



years 1840 to 1850, laboured at two 

 great problems : the one he solved 

 brilliantly and in the direction he 

 anticipated ; the other remains a 

 problem to this day. The first 

 refers to the action of magnets on 

 the dielectric. The dielectric, the 

 space which Continental philo- 

 sophers considered as a vacuum so 

 far as magnetic and electrical pheno- 

 mena are concerned, had been filled 

 by Young and Fresnel with the 

 luminiferous ether. Faraday sus- 

 pected that this luminiferous ether 

 cannot be insensible to magnetic 

 action, and he sought in the experi- 

 mental proof of the action of mag- 

 nets on rays of light in the sur- 

 rounding space a support for his 

 view of the part which the dielectric 

 plays in the transmission of electric 

 and magnetic action. After many 

 ineffectual attempts to prove this, 

 he could at last (November 1845) 

 announce his results to the Royal 

 Society as follows : ' ' These inef- 

 fectual exertions . . . could not 

 remove my strong persuasion de- 

 rived from philosophical considera- 

 tions ; and therefore I recently 

 resumed the inquiry by experiment 

 in a most strict and searching 

 manner, and have at last succeeded 

 in magnetising and electrifying a 

 ray of light, and in illuminating a 

 magnetic line of force. ... Em- 

 ploying a ray of light, we can tell, 

 by the eye, the direction of the 

 magnetic lines through a body ; and 

 by the alteration of the ray and its 

 optical effect on the eye, can see 

 the course of the lines just as we 

 can see the course of a thread of 

 glass or any other transparent sub- 

 stance, rendered visible by the 

 light " (' Exp. Res.,' vol. Hi., No. 2148 

 and note). The second problem 

 which Faraday attacked was to 

 prove a similar ' ' connection be- 



