KINETIC OK MECHANICAL VIEW OF NATL Ut. 09 



([uired gradually a physical* signiHcance, for he had 

 very early couviriced himself of the fact, known already 



that of gravity, which causes 

 particles to act on each otlier 

 through straight lines, ... is more 

 analogous to that of a series of mag- 

 netic needles. . . . So that in wliat- 

 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 cf 

 that great natural principle of elec- 

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

 r2:}l ). "1 have used tlie phrases lines 

 of inductive force and curved linesoi 

 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 tlian 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 mj' particular view 

 with doubt and fear, lest it should 

 not bear the test of general examina- 

 tion," &c. (No. 1300). 



^ It took more than ten j'ears 

 before the purely geometrical or 

 conventional use of the term " lines 

 of force " ripened into a pliysical 

 conception. The latter is definitely 

 expounded in a i)apcr in the ' Philos. 

 Magazine' for June 1852. We can 

 compare this gradual development 

 of a symbolical into a physical 

 theorj' 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 1810 to 18o0, la»j<)uretl at two 

 great problemn : the one he iiolve<i 

 brilliantly and in tlie direction he 

 anticipated ; the otlier remains a 

 problem to this day. The first 

 refers to the action of magnetic on 

 the dielectric. The dielectric, the 

 space which Continental philo- 

 sophers considered as a vacuum no 

 far as magnetic and electrical i.henu- 

 mena are concerned, had Ijeen filled 

 by Young and Fresnel with the 

 luminifennis ether. Faraday sus- 

 pected that this luminiferous ether 

 cannot be insensible U) magnetic 

 action, and he .sought in the exi>eri- 

 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 attemjjts to prove this, 

 he could at last (November 1845) 

 announce his results to the Royal 

 Society iis follows: "These inef- 

 fectual exertions . . . could not 

 remove my strong jiersuasion de- 

 rived from philo3oi)hical considera- 

 tions ; and therefore I recently 

 resumed the inquiry by exf>erinient 

 in a most strict and searching 

 manner, and have at last succeeded 

 in magnetising and electrifijing a 

 ray of light, and in illumiiuitiixg a 

 magnetic line of force. . . . Em- 

 ploying a ray of light, we can tell, 

 by the eye, the direction of the 

 magnetic lines througli a body ; and 

 by the alteration of the ray and it* 

 optical effect on the eye, can sec 

 tlie course of the lines just as we 

 can see the course of a thread of 

 glass or any other trans|)arent sub- 

 stance, rendereil visible bv the 

 light " (' Exp. Res.,' vol. iii., N.'). 2148 

 and note). The second problem 

 which Faraday attjicked was to 

 prove a similar "connection l>e- 



