AMPERE'S HYPOTHESES. 60 1 



CHAPTER X. 

 GENERAL THEORIES. 



618. AMPERE'S HYPOTHESES. In order to establish the ele- 

 mentary formula of electrodynamic actions, Ampere relied solely on 

 the hypothesis of central forces, and on certain experimental facts, 

 without any particular view as to the nature of electrical currents 

 themselves. Nevertheless, from the year 1822, he "endeavoured to 

 account for the force which is exerted between two elements of 

 conducting wires, by the action of the fluid, which is distributed in 

 space, and whose vibrations produce the phenomena of light." 

 Ampere pointed out another mode of conceiving the phenomena : 

 " If we suppose that molecules of electricity put in motion in 

 conducting wires by the action of the battery, are continually 

 changing their places, uniting every moment to form neutral fluids, 

 separating, and then quickly uniting with other molecules of the 

 fluid of the opposite kind, it is not contradictory to assume that 

 from the actions which are inversely as the squares of the distances 

 separating the molecules, a force might be produced between 

 two elements of conducting wires, which depends not only on 

 their distance, but also on the directions of the two elements 

 along which the electrical molecules are moving, uniting with 

 molecules of the opposite kind, and then separating the moment 

 after to unite with others." Mkmoires de VInstitut for 1823, 

 pp. 294 and 299. Ampere did not follow the development of these 

 ideas any further ; he did not think the time had come to do it 

 with utility. 



The hypotheses of Ampere have been taken up from time to time 

 by various physicists, particularly by Weber and by Maxwell : we 

 shall give a summary of the theories proposed. 



619. FORMULAE OF GAUSS AND OF WEBER. If we bring into 

 play the reciprocal actions of the electrical masses which circulate in 

 conductors, the action of the two electrical masses m and ;;/' must be 



