FARADAY ON LINES OF FORCE. 443 



The law of action and reaction is true of electric, mag- 

 netic, as well as of gravitating attraction. The seat of 

 the attracting power is in the interval between the bodies, 

 whether electric, magnetic, or gravitating; and it is ex- 

 erted in every case along lines of physical force. Snch 

 w x as Newton's discovery. 



It was reserved for Faraday to direct renewed attention 

 to the part taken by the medium, or as he called it, the 

 dielectric, existing between electrified bodies, and to point 

 out the nature and properties of the lines of force extend- 

 ing between these bodies and indicating the state of strain 

 existing in this intervening space. Amplifying upon 

 Newton, he inferred the existence of both magnetic and 

 electric lines offeree u from the dual nature of the powers 

 (electricity and magnetism), and the necessity at all times 

 of a relation and dependence between the polarities of the 

 magnet and the positive and negative electrical surfaces. 1 



To pass beyond Newton's conception, in his time, was to 

 struggle against the limits of the human intellect. So 

 Faraday, in his epoch, dashed against the same barriers, 

 only to recoil baffled, but never disheartened. The effects 

 of the physical lines of force could be observed and dealt 

 with experimentally; but their intimate nature remained, 

 and still remains, unknown. That electricity and gravity 

 and magnetism might be but manifestations of but one 

 great controlling power pervading all matter was Newton's 

 conception. For this power, throughout his whole life, 

 Faraday searched. In this quest he made all his great 

 discoveries. 2 Again and again, he exhausts the matchless 

 powers of his imagination and his consummate experi- 

 mental skill upon the problem, only to fail. The genius 



at it; for bodies further off are not attracted by the magnet so much as by 

 the iron plate." Principia, b. iii., prop, xxiii. Bence Jones: Life and 

 Letters of Faraday. London, 1870, ii., 279. 



1 Faraday: Observations on the Magnetic Force. Proc. R. Inst., Jan. 

 21, 1853. Expl. Researches, vol. iii., 506. 



2 Bence Jones: Life and Letters of Faraday, London, 1870, vol. ii, 484. 





