311 



Article XIII. 



On the Laws of the Conducting Powers of If ires of different 

 Lengths and Diameters for Electricity ; hy^. Lenz. 



(Read to the Academy of St. Petersburgh, the 28th of November, 1834.) 



From the Memoires de V Academie Imperiale des Sciences de St. Petersbourg : 

 VI'"^. series, torn. i. 183.5. 



J. HOUGH Van Marum, Priestley, Children, Harris, and Davy* had 

 previous to Galvani's brilliant discoverj' endeavoured to determine the 

 conductibility of different metal wires by discharges of the Leyden bat- 

 tery, yet the first more accurate experiments on this subject were made 

 at a later period by means of the electromotor and the voltaic pile ; but, 

 strange to say, these later and more accurate experiments have led to 

 results at variance with each other. Whilst the experiments of Davy, 

 Pouillet, Becquerel, Christie, Ohm, and Fechner j^rove the law that 

 wires of the same metal conduct electricity inversely as their lengths, 

 and directly as their sections — that is to say, as the squares of their 

 diameters — Barlow and Cumming consider, according to their experi- 

 ments, that the conductibility is inversely proportionate to the square 

 of the lengths, and directly as the diameters of the wires (or as the 

 square roots of their sections). Ritchie, whose observations on this sub- 

 ject are the most recent (Phil. Trans, for 1833, p. 313), but who, un- 

 fortunately, like most English authors, is totally unacquainted with the 

 works of the German natural philosophers Ohm and Fechner, endea- 

 vours to explain this contradiction by assuming that the conductibility 

 of the wires vanes according to the force of the current ; for having 

 connected two wires with two different batteries, he found by means of 

 his galvanometer that the strength of the currents were not in the 

 same proportion to each other. He explains this according to his own 

 view of the conductibility of electricity in the following manner : 



" Let us suppose that there is no actual transfer of electricity along 

 the wire, but that all the phaenomena of deflection, &c. result from a 

 definite arrangement of the electric fluid essentially belonging to the 

 wire itself. Let us further suppose that a section of wire contains one 

 hundred particles of electricity, and that the battery is capable of ar- 



• [M. Lenz is here in error; the experiments of Children, Davy, and Harris 

 were all made subsequently to the discovery of Galvani.— Edit.] 



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