THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



NOVEMBER 1898. 



XLV. On the Deflexion by Magnetic Force of the Electric 

 Discharge through Gases. By J. Henry, M.A., B.E. 

 (R.U.I.), Trinity College, Cambridge; 1851 Exhibition 

 Science Scholar, Queen's College, Galway*. 



THE experiments described in the following paper were 

 undertaken for the purpose of finding the explanation 

 of the change produced in the magnetic deflexion of the 

 electric discharge between a pair of electrodes in a rarefied 

 gas, when the gas carrying the discharge is changed: this 

 effect of the gas on the magnetic deflexion of the discharge 

 through it had been noticed by Professor Thomson. 



It is well known that the electric discharge between a pair 

 of electrodes in a rarefied gas is deflected by a magnetic force 

 at right angles to the direction of discharge, in somewhat the 

 same way as a flexible and elastic conducting string would be, 

 if it were stretched between the electrodes and carried a 

 current in the same direction as that in which the discharge 

 passes through the gas ; the discharge in the gas, like the 

 string, is deflected from the straight line between the electrodes 

 wmile the magnetic force acts, and returns to the straight 

 path again as soon as the magnetic force is removed (' Recent 

 Researches,' p. 131, par. 127). 



Description of Apparatus. 



The apparatus used in my experiments consisted of: — 

 A vacuum-tube with an air-pump and a mercury-manometer 



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

 PhiL Mag. S. 5. Vol. 46. No. 282. Nov. 189s. 2 H 



