L'8 1IIST01IY OF GALVANISM. 



At almost every meeting of tlie Academy, during the remainder 01 

 that year and the beginning of the following one, he had new dove- 

 lopements or new confirmations of his theory to announce. The most 

 hypothetical part of his theory, the proposition that magnets might 

 be considered in their effects as identical with spiral voltaic wires, 

 he asserted from the very first. The mutual attraction and repulsion 

 of voltaic wires, the laws of this action, the deduction of the ob- 

 served facts from it by calculation, the determination, by new expe- 

 riments, of the constant quantities which entered into his formulae, 

 followed in rapid succession. The theory must be briefly stated. It 

 had already been seen that parallel voltaic currents attracted each 

 other ; when, instead of being parallel, they were situate in any direc- 

 tions, they still exerted attractive and repulsive forces depending on 

 the distance, and on the directions of each element of both currents. 

 Add to this doctrine the hypothetical constitution of magnets, namely, 

 that a voltaic current runs round the axis of each particle, and we 

 have the means of calculating a vast variety of results which may be 

 compared with experiment. But the laws of the elementary forces 

 required further fixation. What functions are the forces of the dis- 

 tance and the directions of the elements ? 



To extract from experiment an answer to this inquiry was far from 

 easy, for the elementary forces were mathematically connected with 

 the observed facts, by a double mathematical integration ; a long, 

 and, while the constant coefficients remained undefined, hardly a pos- 

 sible operation. Ampere made some trials in this way, but his hap- 

 pier genius suggested to him a better path. It occurred to him, that 

 if his integrals, without being specially found, could be shown to 

 vanish upon the whole, under certain conditions of the problem, this 

 circumstance would correspond to arrangements of his apparatus in 

 which a state of equilibrium was preserved, however the form of some 

 of the parts might be changed. He found two such cases, which 

 were of great importance to the theory. The first of these cases 

 proved that the force exerted by any element of the voltaic wire 

 might be resolved into other forces by a theorem resembling the well- 

 known proposition of the parallelogram of forces. This was proved 

 by showing that the action of a straight wire is the same with that of 

 another wire which joins the same extremities, but is bent and con- 

 torted in any way whatever. But ; t still remained necessary to deter- 

 mine two fundamental quantities; one which expressed the power of 

 'he distance according to which the force varied ; the other, the de- 



