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Repulsive Eject upon Poles of Electric Arc. 705 



The results of the experiments on the electrical conduc- 

 tivity of flame tracks and of their transfers point to water 

 molecules being" one of the active substances, but the experi- 

 ments with carbon monoxide and with sparks show that the 

 effects cannot be attributed to water molecules alone. 



The author has obtained some evidence that the transfer 

 in vaciwoi a breath figure to the sensitive surface of a photo- 

 graphic plate is capable of development, but the necessary 

 conditions are as yet uncertain and require further investi- 

 gation. 



Xing- Edward's School, 



Birmingham, 

 Feb. 21, 1922. 





LXVI Repulsive Effect upon the Poles of the Electric Arc. 

 By A. Sellerio *. 



1. TN December 1919 Prof. W. G. Duffield published 

 JL the results of a careful series of experiments 

 carried out in conjunction with Messrs. Burnham and 

 Davis, on the same subject as the present paper f . 



As similar experiments made by me are not mentioned 

 there, it seems that my Note % of 1916 is unknown to 

 the authors. It may be useful to put together both the 

 results concerning this interesting subject § ; but before 

 doing so, I must observe that in evaluating my readings 

 I did not take account of the electromagnetic force V 

 due to the earth's magnetic field, and of the electro- 

 dynamic action E between the fixed and the movable parts 

 of the circuit. In recommencing my experiments some 

 years ago, I remarked that V, E were on the contrary not 

 to be neglected, and in the meantime I was notified of 

 Prof. Duffield's work, in which the different sources of error 

 are accurately separated. His investigation enables me 

 to estimate the corrections concerning my results, without 

 further trials. 



* Communicated by the Author. 



t Phil. Trans. Roy* Soc. of London, A, vol. ccxx. p. 109 (1919). A 

 further note on metallic and composite arcs is recorded in Science Abs. 

 1920 (Roy. Soc. Proc. xcvii. p. 326 (1920)). 



X A. Sellerio, " Effetto di repulsione nell' arco elettrico," Nuovo 

 Cimento, xi. p. 67 (1916). This paper and the first noticed of 

 Prof. DufHeld will be denoted by the initials S. and D. 



§ Doifield'a research was the subject of a note by Mr. Ratner, Phil.. 

 Mag", xl. p. 511 (1920), and Prof. Ty'ndall, ibidem, p. 780. 



