M. E. Edlund on the Nature of Galvanic Resistance. 209 



followed by the rest of the known fluids. Another contradic- 

 tion arising from the assumption that the resistance is indepen- 

 dent of the intensity is the following : — The electromotive force 

 is operative during the whole time the current continues. If, 

 then, the conductor placed no obstacle to the motion occasioned 

 by that force, the velocity must, according to ordinary mecha- 

 nical laws, unceasingly rise (that is, the intensity of the current 

 must continually increase) as long as the electromotive force was 

 acting. If, on the other hand, the conductor opposes to the 

 motion a resistance independent of the intensity of the current, 

 two cases may occur : namely, the resistance is as great or 

 greater than the acceleration produced by the electromotive 

 force; or it is less than this. But it is clear that, in the former 

 case no current can commence, and that in the latter the current 

 must continually increase in intensity. To preserve the current- 

 intensity constant is, under this assumption, and applying the 

 usual mechanical principles, impossible. If, however, contrary 

 to all analogy with the rest of material substances, we deny vis 

 inertia to the electric fluid, this contradiction can, it is true, be 

 discharged. An accelerative force acting on a material mass 

 which is destitute of vis inertia (that is to say, which instantly 

 comes to rest as soon as the force ceases to act), cannot give 

 this mass an accelerated motion. As Clausius remarks*, in the 

 deduction of Ohm's law it has in reality been tacitly assumed 

 that an electric mass has no vis inertia, or else that this is so 

 little that no account need be taken of it. People have thus 

 been able to maintain the constancy of the current-intensity, 

 although it was assumed that the resistance is independent of it, 

 But surely we have no right to attribute to the electric fluid 

 qualities which contradict the universal nature of matter. We 

 will, in conclusion, direct attention to the following relation : — 

 A galvanic current divides itself between two conductors in the 

 inverse ratio of their resistances. If, then, as has been hitherto 

 assumed, the resistance were actually constant, and were in the 

 one conductor greater, but in the other less, than the accelerating 

 force, the current must pass exclusively through the latter. This 

 would be a case exactly like the following : — Through a tube 

 with a certain cross section, which divides into two branches of 

 the same cross section, a fluid is urged by a pressure applied at 

 the extremity of the main tube. If a counterpressure be applied 

 in one of the branches greater, and in the other less than the 

 pressure mentioned, the fluid must flow exclusively through the 

 latter branch. Here, therefore, the assumption that galvanic 

 resistance is independent of the intensity of the current appears 

 to be contradicted by experiment. It is quite different if the 

 * Pogg. Ann. vol. lxxxvii. p. 424. 

 Phil. Mag. S. 4. Vol. 40. No. 305. Sept. 1873. Q 



