THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



OCTOBER 1887, 



XXXVIII. On Hot Gases as Conductors of Electricity . 



By John Buchanan, B.Sc* 



[Plate VIII.] 



THE measurements described below were made in the 

 spring of 1886 in the Physical Laboratory of Uni- 

 versity College, London. They were designed with the 

 object of getting an approximate idea of the magnitude of 

 the quantities that enter into the phenomena of the discharge 

 of electricity by a flame. 



The method used was essentially that ordinarily employed 

 in connexion with the measurement of extremely high re- 

 sistances, viz. by means of a condenser of known capacity 

 and a quadrant-electrometert. 



I am not aware that this method has been used before for 

 measurements connected with hot gases. 



Two flat pieces of platinum-foil (c, figure), 2'5 centim. 

 square, were placed with their planes nearly parallel and 

 vertical. They were joined by platinum wires to the re- 

 spective binding-screws A and B of a condenser of 1 micro- 

 farad capacity. The condenser was charged from a battery 

 of Leclanche cells. A Thomson's quadrant-electrometer, 

 D, served to indicate the changes in the condenser-potentials 

 in the usual way, by the motion of a spot of light over a 

 scale. A gas-flame, reduced to the smallest size compatible 

 with its existence, was placed between the two pieces of 

 platinum-foil. The form of the gas-burner was such that the 



* Communicated by the Author. 



t Clerk Maxwell's ' Electricity and Magnetism,' 2nd ed., vol. i. § 355. 



Phil. Mag. S. 5. Vol. 24. No. 149. Oct. 1887, X 



