THE ASTRONOMICAL VIEW OF NATURE. 



365 



upon experimental research.^ Chemistry had only just 

 entered the list of the exact sciences, by the use of the 

 balance, largely owing to Lavoisier and his followers. 



1 Although Faraday's ' Experi- 

 rneutal Researches iu Electricity ' 

 (1831-52) contain mostly what 

 chemists would call "qualitative" 

 investigations and only few exact 

 "quantitative" measurements 

 forming in this respect a very 

 remarkable contrast to Weber's 

 ' Electrodynamische Maasbestim- 

 mungen ' (1846-78) it is important 

 to remark that one of the methods 

 for exact measurement of the 

 electric current viz., by the chem- 

 ical decomposition of compounds 

 was established by Faraday in 

 1833 and 1834. He showed that 

 whenever decomposition took place 

 the quantities decomposed were in 

 proportion to the amount of elec- 

 tricity flowing through the circuit 

 and in proportion to the chemical 

 equivalents. Owing to the want of 

 a clear definition of quantity and 

 intensity of current, Berzelius op- 

 posed this view of Faraday's as 

 illogical, confounding the quan- 

 tity of substance decomposed with 

 the force required to set it free. 

 Clearer definitions and accumu- 

 lated experience have confirmed 

 Faraday's law, which is now 

 looked upon as one of the best es- 

 tablished general facts of chemical 

 and electrical science. Somewhat 

 earlier than Faraday, Georg Simon 

 Ohm established (1827, 'Die gal- 

 vanische Kette, mathematisch 

 bearbeitet') the proportionality of 

 the quantity of electricity passing 

 through a circuit with the electro- 

 motive force in the same conductor, 

 introduced the notion of electrical 

 resistance, and showed how this 

 varies as the length and inversely as 

 the thickness of the same conductor, 

 and is different in diSerent con- 

 ductors. The accuracy of Ohm's 



law, though elaborately tested by 

 Fechner and confirmed by Pouillet, 

 was frequently doubted; in France 

 it met with tardy recognition, and 

 in England some of the most im- 

 portant researches such as those of 

 Faraday were carried on without 

 reference to it. In the first edition 

 of Whewell's History it is not men- 

 tioned. When the second edition 

 was published (1847), Ohm had 

 received the Copley Medal of 

 the Royal Society (1841), and 

 Wheatstone had besides in the year 

 1843 drawn attention to the clear 

 definitions which Ohm had intro- 

 duced. The opinion has been ex- 

 pressed that Ohm found his law by 

 theoretical considerations based on 

 analogy with the flow of heat in 

 conductors, and that he subse- 

 quently proved it experimentally. 

 The publication of Ohm's collected 

 papers by Lommel ('Gesammelte 

 Abhandlungen,' Leipzig, 1892), how- 

 ever, disproves this opinion ; as his 

 experimental measurements had 

 during 182.5 and 1826 not without 

 some initial mistakes led him to 

 the well-known expression of the 

 relations of the different quantities 

 (see Lomniel's Introduction, p. vii). 

 Whereas in Germany it was a pure- 

 ly scientific interest that, namely, 

 of subjecting physical phenomena 

 to mathematical calculation which 

 induced Ohm, Gauss, and W^eber 

 to devise instruments and methods 

 for exact measurement, it was in 

 England mainly the practical re- 

 quirements of telegraphy which 

 created the desire for clear defini- 

 tions and exact methods. With 

 these requirements in view Wheat- 

 stone invented his instruments and 

 drew attention to the definitions of 

 Ohm. See his Bakerian Lecture for 



