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XL On the Electrical Conductivity of Flames Containing Salt Vapours, 
By Harold A. Wilson, B.Sc. [Lond. and Vic.), 1851 Exhibition Scholar, 
Cavendish Laboratory, Cambridge. 
Communicated by Professor J, J. Thomson, F.R.S. 
Received March 10,—Read April 27, 1899. 
In a recent paperon the electrical conductivity and luminosity of flames containing; 
salt vapours, by Professor A. Smithells, Mr. H. M. Dawson, and the writer, the 
similarity between the conductivity of flames and that of gases exposed to Ilontgen 
rays was pointed out, and it was shown that the relation of the current between two 
electrodes in the flame to the potential difference between them could he represented 
by the formulm 
C = i -h ^’lE, 
vhere C = the current, 
E = the P.D, between the electrodes. 
I, hi, ^2 are constants, and i is defined by the second ecjuation. 
When E is large, these equations become 
C = I + yt-iE, 
and if hi = 0, then they reduce to 
which represents the relation between the current and P.D. for the conductivity of 
Rcintgenised gases. (See a paper by J. J. Thomson and E. Ruthereord, ‘ Phil. 
Mag.,’ Nov., 1896.) 
The experiments described in the present paper were undertaken with the object of 
following up the analogy betw^een the conductivity of salt vapours and that of 
Ptontgenised gases, and especially of getting some information about the velocities of 
the ions in the flame itself. 
The paper is divided into the following sections :— 
* Abstract at ‘ Roy. Soc. Proc.,’ vol. 64, p. 142. 
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