Conductivity along a Glow Discharge and in Flames. 355 



the resistance R, viz. : the greater R the smaller the absorp- 

 tion in the added system and the bigger therefore the current 

 in the parallel wires, for here (2) reduces to 



p"=-.l-2a. 



As the resonance curves at this stage (current squared in 

 Lecher wires plotted against I) become more and more flat 

 the smaller the resistance R, it is practically possible to leave 

 the length I constant and to measure the absorption in the 

 added system B (fig. 1) by the fall in the current in 

 the Lecher system, and at the same time be sure that for the 

 said range of the resistance R all current measurements are 

 made under resonance conditions. 



Therefore over the range considered an increase in the 

 conductivity of the concentrated system manifests itself in a 

 fall of the current in the wires. And a very simple means of 

 making sure that one is working within the conditional range 

 is afforded by the fact that little or no change in the length I 

 is necessary to keep the parallel wire system in resonance as R 

 changes from go to a big finite value. The working condition 

 is therefore similar to that of an oscillatory circuit of a con- 

 centrated capacity, resistance and self-inductance, where 

 the capacity or self-inductance is shunted by a big resist- 

 ance, the current being measured in the main oscillatory 

 circuit. 



The apparatus used for the measurement of the absorption 

 in various parts of an independent glow-discharge is described 

 in another paper. In fig. 3 ADBO is the parallel wire system. 

 At B (BC~jA.) the leads E to the Duddell galvanometer end 

 freely over the Lecher system, while at A the discharge-tube 

 FG is brought between the wires through a hole in the 

 ebonite piece H, supported in turn by the slider K. By 

 the aid of a string running over a pulley the discharge-tube 

 could be lowered gradually from a distance, while sliding 

 through the hole in H. This movement of the discharge-tube 

 has to be effected from a certain distance, as the approach of 

 the hand near the free ends of the Lecher wires disturbs the 

 resonance. A rubber tube at L connects the apparatus with 

 a Gaede pump and drying and filling apparatus. V indicates 

 the position of the generator. 



The glow-discharge, started, if necessary, with an induc- 

 tion-coil, is maintained by a 1000-volt storage-battery with a 

 water-resistance and microampere meter in series. The total 

 length of the parallel wire system was never longer than 



