Dr. S. Guggenlieimer on the Spark-discharge. 311 



But when the galvanometer-arm is closed during the next 

 60°, the current through the galvanometer is in the opposite 

 direction, for it is represented by the area EFG ; thus 

 R<f would appear less than R e . 



These experiments were made in the New Physical Labo- 

 ratory of the Owens College, Manchester: where, in order to 

 complete the research, I hope to be able to investigate the 

 relations between the magnitude and phase of the " bismuth 

 E.M.F." and the field-strength ; also to investigate the whole 

 effect at the temperature of liquid air. 



XXVIII. Note on the Spark-discharge . 



By SlEGFR. GUGGENHEIMER, Ph.D.* 



fflHE interest in the phenomena accompanying the spark- 

 X discharge in gases has been revived recently by a dis- 

 cussion between Mr. Swyngedauwf and Prof. Warburg |. 

 The complete discordance between the opinions of these 

 authors led me to undertake the experiments described below 

 with the view eventually to decide the question at issue. I 

 may at once say that the result of my experiments and 

 theoretical considerations is to confirm the views of Prof. 

 Warburg. 



1. The fact that the spark-potential is independent of the 

 nature of the radiation employed to shorten the time of re- 

 tardation (Warburg's Verzogerung) made it seem probable 

 that this potential depends upon the momentary state, i. e. 

 upon the degree of ionization of the gas. Therefore it was 

 to be expected that the " Verzogerung " would also be de- 

 stroyed, or at least shortened, if, instead of using direct 

 radiation, we introduce a sufficient number of ions in the 

 space containing the sparking system. The experiments 

 confirmed this expectation. 



2. In the sides of a brass tube 20 cm. long and 3 cm. 

 interior diameter were fitted two ebonite plugs facing one 

 another. Through each of these plugs passed a brass wire 

 terminated inside the tube by a brass ball of 7 mm. diameter. 



* Communicated by Prof. J. J. Thomson, F.R.S. 



t R. Swyngedauw, Joarn. de Plnjs. ix. j). 488 (1900); Bichat & 

 Swyngedauw, Rapports of the Paris Congress, iii. p. 164 (1900). 



X E. Warburg, Verhandlunqen der Dentsch. Phys. GeselL ii. p. 212 

 (1900). 



Y2 



