[ 455 ] 



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XLI. On the Phosphoresced Gloiv in Gases. By John 

 B. B. Burke, M.A. {Dublin), B.A. (Res.) Cantab., Trinity 

 College, Cambridge. 



[Continued from p. 356.] 



Section IV, i y 



On the Conductivity of the Glow. 



TUBE was constracted with two pairs o£ wire- 

 gauze electrodes a b and c d, occupying positions 

 in the tube as shown in fig. 4. The wire-gauze screens were 

 placed with their planes at right angles to the axis of the tube. 

 The electrodes were carefully insulated, and the outside of the 

 tube was surrounded with tinfoil which was put to earth. 



The distance between each pair of electrodes was 1 cm. 

 approximately. The electrodes a b were first put to earth 

 whilst there was a difference of potential between c d, and the 



Fiar. 4 



A 



gas was found to conduct after the passage of each spark, even 

 when there was no glow, but the conductivity was greatly 

 increased as soon as the glow travelled down the tube. There 

 was no appreciable increase in the conductivity when the glow 

 was in the bulb alone. The conductivity due to the passage 

 of the spark alone was doubtless that observed by Schuster 

 (Proc. Roy. Soc 1887, p. 372). 



The fact that the great rise in the conductivity does not 

 occur until the glow travels down the tube shows that it is 

 not due to radiation from the glow itself. 



The method of measuring the conductivity was as follows: — 

 The electrode c was connected to one pole of four Leclanche's 

 batteries in series, the other pole being to earth ; whilst the 

 electrode d was connected to one pair of quadrants of a 

 quadrant electrometer, the other pair being to earth. Great 

 difficulty was experienced at first in trying to screen off com- 

 pletely ordinary electrostatic effects from the Wimshurst, the 



