406 



On the Passage of Electricity through Gases, 



conduction takes place even when the system is not exposed 

 to the direct radiation fron the exhausted tube ; we think it 

 probable therefore that the gas itself radiates after being ex- 

 posed to the Rontgen rays. 



To test this we tried the following experiuient. AB, CD 



Fig. 6. 



S 



are two concentric cylinders made of thick lead tubing, the 

 base of the inner one was cardboard, so as to allow Rontgen 

 rays to pass through the gas in the inner cylinder. A metal 

 ring was placed between the two cylinders and connected 

 with one pair of quadrants of an electrometer so as to allow 

 the leak from it when raised to a high potential to be mea- 

 sured. A slit was cut in the inner cylinder in such a place 

 and of such a size that no rays could pass through it directly 

 from the bulb. The apparatus was filled with chlorine, as 

 this gas is one which gives a very rapid rate of leak. When 

 the slit was left open there was a rapid leak due to the diffu- 

 sion from the inner cylinder of gas which had been exposed 

 to Rontgen rays. When, however, the slit was covered up 

 with a strip of paper the leak wholly disappeared, though the 

 ring connected with the electrometer was placed at the same 

 level as the slit and therefore exposed to any radiation that 

 might come from the gas. This radiation, if it exists, must 

 therefore either be of very feeble intensity or else it must 

 differ from the Rontgen rays in not making a gas through 

 which it passes a conductor of electricity. We are inclined 

 to think that when Rontgen rays are incident on a metallic 

 surface the " diffusely reflected w rays are not of the same 

 character as the incident ones, and have not nearly the same 

 power of rendering a gas through which they pass a conductor 

 of electricity. We base this opinion on the experiments we 

 have made to detect the existence of electrical effects due to 

 the u reflected " rays ; though we have made many attempts 

 we have never been able to detect the existence of any electrical 



