Passage of Electricity through Gases. 173 



movements of the molecules, and that particles of electricity 

 pass from one covering to another. Electric vibrations might 

 also be communicated from one molecule to another. The 

 existence of a resistance to conduction is sought by Herwig 

 in the fact that in general the direction of movement of the 

 particles of bodies with their coverings in two successive 

 sections of the conductor is very different. In the passage, 

 therefore, of electric particles from one molecule to another 

 the direction of their movements must alter ; and the work 

 hereby done would correspond to the resistance, which would 

 be all the greater the greater was the energy of the movement 

 of the particles of the bodies, or the higher the temperature. 



In this case, however, no actual change in the direction of 

 movement takes place, but only a combination of two differ- 

 ently directed movements. If we resolve the entire move- 

 ments in three rectangular directions, on the passage of one 

 of these components from one molecule to another its vis viva 

 is merely added to that of the components perpendicular to it, 

 as in the combination of two perpendicular vibrations of light. 

 On the other hand, there may take place eventually a change in 

 the vis viva when two similarly directed components meet 

 together. But this alteration will in the mean be compen- 

 sated, since in a constant current as much electricity enters a 

 molecule as leaves it. 



If, then, we suppose a passage of electricity or of electric 

 vibrational movement from one molecule to another, the per- 

 petual impulse to motion, consequent on the electromotive 

 force in a constant current, must be compensated by a kind 

 of friction of the electric particles on the molecules of bodies, 

 by which the former will be entirely consumed. This fric- 

 tional resistance corresponds, under an equal electromotive 

 force, to the galvanic resistance to conduction. By this 

 means the vis viva of the electric motion passes to the particles 

 of bodies ; the vis viva of their heat-vibrations increases 

 in proportion to the resistance which they oppose to the cur- 

 rent *, &c. 



In consequence of the comparative ease with which the 

 molecules of bodies move at higher temperatures, especially 

 above the fusing-point, when their relative positions are less 

 rigidly maintained by the molecular forces, the communica- 

 tion of the movement of electricity to the single molecules of 

 bodies would then more easily ensue, and the resistance would 

 therefore increase. 



In fused and fluid metallic conductors meanwhile a part of 

 the electric conduction might result from the conveyance of 

 * Compare on this point Galvanismus (2), Bd. ii. S. 1168. 



