326 Mr. F. C. Webb on "Inductive Circuits" or the 



given in his essay, several can be solved by the method the author 

 advocates. 



It has for some years past been acknowledged that the accu- 

 mulation of electricity on the interior surface of the gutta-percha 

 envelope of a submarine telegraph-conductor depends, in a cer- 

 tain manner, on the geometrical dimensions of the envelope and 

 its "specific inductive capacity," and that, by considering the 

 envelope as a conductor in the direction of its thickness, the 

 same formula which expresses its resistance to the conduction of 

 electricity from a given source represents also its resistance to the 

 accumulation of electricity on the surfaces of the envelope, the 

 constant expressing the specific resistance to conduction being 

 only altered to one expressing the specific resistance to " accumu- 

 lation" "excitation" or " induction" as the property of the 

 material to facilitate the accumulation on its surface has been 

 variously termed. 



Messrs. Siemens, in a paper read before the British Associa- 

 tion, 1860, observe, "According to Faraday's conception, the in- 

 ductive action is communicated (say, from the interior electrified 

 covering of a Ley den jar to the exterior) from atom to atom 

 through the dielectric. In one case the jar is represented by 

 the cable, the inner covering of which is formed by the surface 

 of the copper wire, the exterior by the water." 



" The laws which apply to the motion of heat and electricity 

 in conductors are accordingly directly applicable to electro- 

 induction, which may be expressed by the conductivity multi- 

 plied by a constant varying with the nature of the insulating 

 material." 



In 1861 M. Gaugain, in a note published February 18th in 

 the Comptes Rendus, on cylindrical condensers, observes, " It will 

 be seen that in the case, at least, of cylindrical condensers the 

 laws which regulate the propagation of electricity by excitation 

 do not differ from those which Ohm has established for propa- 

 gation by conductibility." 



The applications of Ohm's law to problems of electric accu- 

 mulation seem, however, until September 1861, to have been 

 confined entirely to the problem of a single cylindrical resist- 

 ance, the formula for which was given by Sir W. Thomson in 

 1855, Messrs. Siemens in 1859*, and M. Gaugain in 1861, 

 February 18. 



In September 1861 M. Gaugain applied it to the case of a 

 spherical condenser, and in the note describing them he observes, 

 " I have indicated in my preceding communication a general 

 principle by means of which all questions relative to condensers 



* Page 12, Government Report. This formula does not appear to be 

 correct, perhaps misprinted. 



