78 



SCIENTIFIC THOUGHT. 



48. 

 His series 

 of works 

 on the 

 theory of 

 electricity. 



tionaiy series of works, ' On Faraday's Lines of Force,' 

 was published in December 1855. The series was 

 completed by the appearance in 1873 of his great work 

 on ' Electricity and Magnetism,' which has formed the 

 centre of a large literature to which all the scientific 

 schools of Europe and America have contributed. Histori- 

 cally, Maxwell brought together two distinct and very 

 fruitful lines of reasoning, due to Faraday and Thomson.^ 

 He was impressed with the desideratum of every physical 

 theory bearing on any large class of phenomena — viz., 

 that it must be mathematical and physical at the same 

 time. His own theory had to embrace and unite all the 

 purely arithmetical and geometrical regularities which 

 had been discovered, and which at that time were 

 known to describe correctly the facts of electric, mag- 



" poaching upon Thomson's electri- 

 cal preserves." In the preface to the 

 treatise on electricity and magnet- 

 ism, he refers to the apparent dis- 

 crepancy between the views of 

 Faraday and the mathematicians, 

 and he states that he had arrived 

 at " the conviction that this dis- 

 crepancy did not arise from either 

 party being wrong. I was first 

 convinced of this," he proceeds, " by 

 Sir William Thomson, to whose 

 advice and assistance, as well as to 

 his published papers, I owe most of 

 what I have learned on the subject. 

 ^ In a different reference we may 

 say that Maxwell's theory was pre- 

 pared by three independent lines of 

 research, starting respectively in 

 France, Germany, and England : (1) 

 The investigation of the actions at 

 a distance of electrified and mag- 

 netised bodies, and of electric 

 currents, which found mathemati- 

 cal expression in the formula of 

 Coulomb and Ampere. The full 



significance and capabilities of the 

 formula) of electrostatic and mag- 

 netic action had been demonstrated 

 by Thomson, who especially showed 

 that these relations were not 

 necessarily confined to the physical 

 theory which had been elaborated 

 on the Continent, but that, mutatis 

 mutandis, they lent themselves 

 equally well to the physical ideas of 

 Faraday. (2) The exact measure- 

 ments of magnetic, electro-dynamic, 

 and galvanic action started bj' Ohm 

 and Gauss in Germany, and much 

 extended by Weber. (3) The idea 

 of physical lines of force, filling 

 space and representing action 

 through contiguous particles, not 

 at a distance, elaborated by Fara- 

 day. These tliree lines of research 

 were brought together in the 

 theory of Maxwell, which in the 

 beginning professed to be only a 

 mathematical but ended by being a 

 physical theory. 



