150 JAMES CLERK MAXWELL 



* Xewton "of Electricity/ It i* icrfect in furni and unaMuul* 

 aMe in accuracy, and it in summed up in a formula from 

 which all lite phenomena may le deduced, and which must 

 always remain the cardinal formula of electro-dyniuiiics. 



41 The itictbod of AniiH-fv, however, though ciwt into an 

 inductive form, doe.s not allow UH to trace the formation of tho 

 ideas whicli guide*! it. Wo can scarcely liclievc that AmiPro 

 really discovered the law of action ly means of tho experi- 

 ments which he de>criles. Wo are led to8ti.s|fct, what, indeed, 

 he tells us himself, that ho discovered the law ly .some proccsa 

 which he lias nut shown us, and that when he hud afterward** 

 built up a j>erfect demonstration, he removed all tnicea of the 

 scaffolding by which he had built it" 



The experimental evidence for Ampere's theory, 

 so far, at least, as it was possible to obtain it from 

 experiments on closed circuits, was rendered unim- 

 peachable by \V. Weber about 1S4'>, while in tho 

 previous year Grassman and K. K Neumann both 

 published laws for the attraction l>etwccn two elements 

 of current which dilVer from that of Ampere, but lead 

 to the same result for closed circuits. In a paper 

 published in 1H40 Weber announced his hypothesis 

 connecting together electrostatic and electro-dynamic 

 action. In this paper he siip|xswl that tho force 

 between two particles of clertrieity de|*nds on tho 

 motion of the particles as well us on their distance 

 apart. A somewhat similar theory was proposed by 

 Gauss and published after his death in his collected 

 works. It has been shown, however, that Gauss' 

 theory is inconsistent with the conservation of energy. 

 Weber's theory avoids this inconsistency and leads, tor 

 closed circuits, to the same results as Ampere. It has 

 been proved, however, by Von Hclmholtx, that, under 

 certain circumstances, according to it, a l.ody would 



