On the Discharge of Electricity through Gases. 317 



# 22 (titt) 



THE BAKERIAN LECTURE. " Experiments on the Discharge of 

 Electricity through Gases. Sketch of a Theory."* By 

 ARTHUR SCHUSTER, Ph.D., F.R.S. Received May 7. Read 

 June 19, 1884. 



[PLATE 4.] 



In the following pages I give an account of several new phenomena, 

 some of which have a direct bearing on the theory of the discharge of 

 electricity through gases. Although I hope that the experiments may 

 be judged independently of any theory, their description may be ren- 

 dered a little more clear and interesting if I begin with a short expla- 

 nation of the theoretical views to which they seem to me to point. 



These theoretical conclusions will be looked at favourably, I think, 

 by those who have been trained up with the ideas of Faraday and 

 Maxwell ; for they must have always considered it likely that the 

 conduction of electricity through gases is more probably due to some- 

 thing resembling the electrolytic conduction in liquids than to the 

 direct passage of electricity from one molecule to another. My 

 experiments with mercury vapour argue very strongly in favour of 

 this view. 



Fundamental Points of the Theory. 



I know, from private conversations, that many of those well able to 

 judge consider some electrolytic action in a gas as probable whenever 

 an electric discharge takes place through it. But owing, no doubt, 

 to the want of experimental evidence, very little has been published 

 bearing on this point. Mr. J. J. Thomsonf has recently supported 

 this view. His ideas are of utility for the explanation of some 

 phenomena attending the spark discharges, but they furnish no clue 

 towards the explanation of the asymmetry of the glow discharge, and 

 of some appearances which by many are considered as characteristic 

 and fundamental in the passage of electricity through gases. No 

 consistent attempt towards a systematic theoretical discussion of 

 these facts has yet been made. 



I am afraid that I can only offer a very crude beginning of such a 

 discussion, but I have sufficient confidence in the correctness of its 

 fundamental views to submit them to the judgment of the scientific 



* I have not in this preliminary paper been able to do full justice to those to 

 whose labours I think it is chiefly due that this subject has become ripe for theo- 

 retical deduction. I may mention here the names of De La Rue and Miiller, 

 Crookes, Goldstein, Gustav Wiedemann and Ruhlmann, and Eilhard Wiedemann ; 

 but the two authors whom I have most often found it necessary to consult are 

 undoubtedly Faraday and Hittorf. 



f " Phil. Mag.," June, 1883. 



T 2 



