204 Davis — Electrical Conductivity and Absolution of 



ent on the degree of exhaustion and the nature of the 

 gas in the vessel. The amount of heat developed was very 

 great, showing that the gas within the vessel was absorbing a 

 great deal of energy from the system. The drop-back of the 

 galvanometer appears to be due directly to the absorption of 

 energy by the gas. Prof. J. J. Thomson* has shown this effect 

 by other methods : That if two coils be placed in series, the 

 presence of a discharging vessel in one coil cuts down the 

 current sufficiently to stop the discharge in the other; also 

 that the discharge in an annular vessel prevents the effect 



in another vessel placed within the "annular one. This screen- 

 ing effect has recently been more fully investigated by E. 

 Lecher. f The conductivity, as measured by the current pass- 

 ing between the electrodes E and E /? was found also to vary 

 with the degree of exhaustion and the nature of the gas. The 

 readings were taken as follows : The vessel was either removed 

 from the coil or contained the gas at atmospheric pressure. 

 The alternating current was turned on the induction coil and 

 the sparks allowed to pass until a steady state was indicated by 

 the galvanometer G. Then the vessel was placed in the coil and 

 exhausted. The pressures were measured by a McLoud gauge. 

 The two galvanometers and the pressure were read at the same 

 time. 



The curves obtained are shown in figure 3. The curves 

 above the line represent the conductivities of air, hydrogen and 

 carbon dioxide. The abscissae are decreasing pressures and the 



* Recent Researches. \ Deutsche Phys. Ges., No. 13, 1902. 



