56 PHYSICS 



(1834). Again, it was not till 1853 that further marked advances 

 were made by Hittorf's (1853-59) strikingly original researches 

 on the motions of the ions. Later Clausius (1857) suggested an ade- 

 quate theory of electrolysis, which was subsequently to be specialized 

 in the dissociation hypothesis of Arrhenius (1881, 1884). To the 

 elaborate investigations of F. Kohlrausch (1879, et seq.}, however, 

 science owes the fundamental law of the independent velocities of 

 migration of the ions. 



Polarization discovered by Ritter in 1803 became in the hands 

 of Plante (1859-1879) an invaluable means for the storage of energy, 

 an application which was further improved by Faure (1880). 



Steady Flow 



The fundamental law of the steady flow of electricity, in spite 

 of its simplicity, proved to be peculiarly elusive. True, Cavendish 

 (1771-81) had definite notions of electrostatic resistance as depend- 

 ent on length section and potential, but his intuitions were lost to 

 the world. Davy (1820), from his experiments on the resistances of 

 conductors, seems to have arrived at the law of sections, though he 

 obscured it in a misleading statement. Barlow (1825) and Becquerel 

 (1825-26), the latter operating with the ingenious differential gal- 

 vanometer of his own invention, were not more definite. Surface 

 effects were frequently suspected. Ohm himself, in his first paper 

 (1825), confused resistance with the polarization of his battery, and 

 it was not till the next year (1826) that he discovered the true 

 law, eventually promulgated in his epoch-making Die galvanische 

 Kette (1827). 



It is well known that Ohm's mathematical deductions were un- 

 fortunate, and would have left a gap between electrostatics and 

 voltaic electricity. But after Ohm's law had been further experi- 

 mentally established by Fechner (1830), the correct theory was 

 given by Kirchhoff (1849) in a way to bridge over the gap specified. 

 Kirchhoff approached the question gradually, considering first the 

 distribution of current in a plane conductor (1845-46), from which 

 he passed to the laws of distribution in branched conductors (1847- 

 48) laws which now find such universal application. In his great 

 paper, moreover, Kirchhoff gives the general equation for the act- 

 ivity of the circuit and from this Clausius (1852) soon after deduced 

 the Joule effect theoretically. The law, though virtually implied 

 in Riess's results (1837), was experimentally discovered by Joule 

 (1841). 



As bearing critically or otherwise on Ohm's law we may mention 

 the researches of Helmholtz (1852), of Maxwell (1876), the solution 

 of difficult problems in regard to terminals or of the resistance of 



