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XXIII. On the Electrical Resistance of Gases. By E. Edlund, 

 Professor of Physics at the Swedish Royal Academy of 

 Sciences*. 



§1. 



THE resistance opposed by gases to the propagation of 

 electricity has shown itself to be different in several 

 respects from that produced by solid or liquid conductors. I 

 shall in this memoir take these differences into consideration, 

 and endeavour to show how they are to be explained. 



1st. In order that the current may traverse a solid or liquid 

 conductor, there is no need of a certain amount of electromo- 

 tive force. However slight the electromotive force may be, 

 the current will nevertheless pass, although of course it 

 becomes less intense as the force is diminished or the resist- 

 ance increased. Only when the force is equal to nil will the 

 current become equal to nil. With gases, on the contrary, the 

 circumstances change. For the current to be able to traverse 

 a gas the source of electricity must have a certain amount of 

 electromotive force, or be capable of producing a certain elec- 

 trical tension, the amount of which depends moreover on the 

 chemical nature, the density, and the temperature of the gas, 

 but never falls below a certain limit in given circumstances. 

 For any electromotive force below that limit the gas is a per- 

 fect insulator. 



2ndly. The quantity of heat produced by an electric current 

 in its passage through a solid or liquid conductor is, as is 

 known, proportional to the square of the intensity of the cur- 

 rent. In gases, on the contrary, the amount of heat is pro- 

 portional to the first power of the intensity of the current, 

 and not to its square. This remarkable property of gases was 

 first observed by Gr. Wiedemann t; and later it was completely 

 demonstrated by Naccari and Bellati that the quantity of heat 

 evolved is really proportional to the quantity of electricity 

 which has passed \. 



3rdly. For solid and liquid conductors the quantity of heat 

 developed, under conditions in all other respects equal, by a 

 given current, is inversely proportional to the cross section of 

 the conductor; while the quantity of heat developed in a column 

 of gas is independent of the section of the latter. This propo- 

 sition has in like manner been demonstrated experimentally 

 by G. Wiedemann, as well as by Naccari and Bellati. 



4thly. In a solid or liquid conductor the resistance is in- 



* Translated from a copy, communicated by the Author, of the memoir 

 forming No. 7, vol. vi of the Bihang till K Svenska Vct.-AJcad. Handlingar. 

 t Pogg. Ann. cxlv. p. 237. 

 % Beibldtter zu den Ann. der Ph. und Ch. ii. p. 720 (1878). 



