162 Uranium Radiation and Electrical Conduction. 



the surface. On account of the rapidity of diffusion * of the 

 ions, the discharging-power of a metal gauze, with openings 

 very large compared with the diameter of a carrier, may be 

 considerable. The table below gives some results obtained for 

 the discharging-power of fine copper gauze. The copper 

 gauze had two strands per millim., and the area occupied by 

 the metal was roughly equal to the area of the openings. The 

 gauzes filled the cross-section of the tube at A (fig. 9), and 

 were tightly pressed together. The conductivity of the air 

 was tested after its passage through the gauzes, the velocity 

 of the air along the tube being kept approximately constant. 

 The rates of leak per minute due to the air after its passage 

 through different numbers of gauzes is given below. 



Number of Gauzes. 



Rate of leak in divisions 

 per minute. 







44 



32-5 

 26 5 

 195 

 10-5 

 6 



1 



2 



3 



4 



5 





After passing through 5 gauzes the conductivity of the air 

 has fallen to less than ^ of its original value. Experiments 

 were tried with gauzes of different degrees of coarseness with 

 the same general result. The discharging-power varies with 

 the coarseness of the gauze, and appears to depend more on 

 the ratio of the area of metal to the area of the openings than 

 on the actual size of the opening. If a copper gauze has such 

 a power of removing the carriers from the gas, we can readily 

 see why a small plug of cotton-wool should completely abstract 

 the ions from the gas passing through it. The rapid loss of 

 conductivity is thus due to the smallness of the carrier and 

 the consequent rapidity of diffusion. 



§ 19. General Remarks. 



The cause and origin of the radiation continuously emitted 

 by uranium and its salts still remain a mystery. All the 

 results that have been obtained point to the conclusion that 

 uranium gives out types of radiation which, as regards their 

 effect on gases, are similar to Rontgen rays and the secondary 

 radiation emitted by metals when Rontgen rays fall upon 

 them. If there is no polarization or refraction the similarity 

 * Townsend, Phil. Mag. June 1898. 



