Energy in the Electrodeless Discharge. 205 



ordinates are conductivities in 10~ 6 amperes. The curves below 

 the line AB represent the readings of the hot wire galvanome- 

 ter. The ordinates taken downward represent the decrease 

 of current in the coil caused bj the discharge in the vessel. The 

 conductivities, it will be observed, are quite small at large pres- 

 sures. They rise suddenly to almost a maximum at the appear- 

 ance of the white discharge. 



In the case of air and carbon dioxide the conductivity 

 decreases slightly with decreasing pressure until the pressure 

 becomes -05 mm , when the discharge suddenly ceases and the con- 

 ductivity becomes zero. The conductivity in a gas may be 

 expressed by 



I = eK(V p + V n ). 



As the conductivity remains nearly constant, the number of 

 ions must decrease with decrease of pressure, since the mean 

 free path and also the ionic velocity increase rapidly with 

 decreasing pressures. 



The conductivity produced in carbon dioxide is consider- 

 ably less than that produced in air. That for hydrogen is less 

 for higher pressures and greater for lower pressures, than for 

 air. The last reading for hydrogen at *05 mm was not accurate 

 as the discharge began to fail and so gave too small a value. 

 The dotted curve is probably more nearly correct. 



The curves below the line AB are dependent on the energy 

 absorbed by the gas. It was quite noticeable that the vessel 

 became hotter at the pressures at which the white discharge 

 first appeared, than at lower pressures. The ordinates of the 

 curves taken downward may be shown to be proportional to 

 the energy absorbed by the gas, as follows : The Leyden jars 

 with the discharging circuit and gas form a free discharging 

 system, in which the current passing through the galvanometer 

 G- and the coil may be represented by 



C = Ae~ qt cos pt. 



The coil C having a small resistance, the energy is dissipated 

 in the gas and produces damping of the oscillations. The 

 damping is proportional to the energy absorbed, for the gal- 

 vanometer reads in amperes, while the energy is proportional 

 to the square of the current, consequently : 



Readings ccj e -2qt co ^ ptdt 



o 



2p* + 3q* 



pared to the other. 



cc — , when either p or q is large com- 



