360 Prof. J. J. Thomson : Experiments on 



by observing the rate at which the conductivity in B in- 

 creased — the rate of flow of air through the tube being- 

 kept constant— the effect of these processes on the con- 

 ductivity of the modified gas could be determined. Thus a 

 plug of glass-wool was placed in the tube, and it was found 

 that the modified gas could pass through this without losing- 

 its conductivity. 



If the conductivity of the modified gas did not arise from 

 some process of continuous ionization, but was due to the 

 presence of ions placed once for all in a gas in which there 

 was no further creation of ions, it should be destroyed 

 like that of gases sucked from flames by passing the gas 

 through a strong electric field. To test this point a long- 

 metal tube, about 1 metre long and 1 cm. in diameter, with 

 an insulated wire along its axis, was inserted between the 

 vessels A and B. The modified gas could pass through this 

 tube when there was a potential-difference of 1000 volts 

 between the wire and the tube without losing its conductivity. 

 Thus, in this respect, the modified gas resembles a gas mixed 

 with the " emanation " from thorium. Rutherford has shown 

 that in this case the conductivity is not destroyed by a strong- 

 electric field. 



The modified gas passed through a tube filled with wire 

 gauze heated to a dull red heat without losing its conduc- 

 tivity • when, however, the gauze was at a bright red heat the 

 conductivity was destroyed. 



The conductivity was also destroyed when the gas passed 

 slowly through a spiral tube immersed in a freezing-mixture 

 of ether and solid carbonic acid. 



The conductivity can be taken out of the gas by passing- 

 it slowly through a tube filled with glass beads moistened 

 with sulphuric acid ; if the gas is merely allowed to bubble 

 through sulphuric acid it escapes with a considerable amount 

 of conductivity. 



Experiments with a Gouy Sprayer. 



The water-pump arrangement, although very convenient 

 for testing the effects of water and air, was not suitable for 

 use with other liquids and gases. To test the effect of different 

 liquids air was forced through a Gouy spray. The air, after 

 passing through the sprayer, was found to have a high con- 

 ductivity, and when it passed into either of the testing- vessels 

 A or B, the saturation-current through this vessel was 

 increased. By measuring the increase produced after the 

 current of air from the sprayer had passed into the testing 

 vessel for a given time an estimate could be formed of the 



