Metals subjected to Rontgen Radiation. 



Ill 



affect surface-films of air or assist in liberating air occluded 

 in the metal. This opinion is supported by the fact that in 

 neither case was there a regularly increasing change with the 

 time. The first reading for Iron! and the second value for 

 Iroiio are the only ones which show a decided change. 



Effect of Ozone on Polished Plates. 



Hallwachs * finds in his experiments on photo-electric 

 fatigue that ozone in small quantities has an extraordinarily 

 large influence. For example, a copper plate had its sensibility 

 to these rays diminished as much in seven seconds when O'Ol 

 of one per cent, of ozone was added to the air as would occur 

 in a year if the ozone were absent from the air. We should 

 expect that ozone would have also a comparatively large effect 

 on the activity produced by the Rontgen rays. But no 

 abnormally large effect could be found. 



Ozone was generated by sparking between two coaxial 

 cylinders, and air mixed with the ozone was sucked through 

 the box by means of a water-pump. For fear the ozone 

 might dissociate if allowed to stand, the stream of ozonized 

 air was maintained during the entire experiment. A test for 

 ozone was made every hour on the air issuing from the box, 

 by passing it through a solution of potassium iodide and starch, 

 and a strong reaction occurred each time. When the experi- 

 ment was completed, the air in the box also smelled strongly 

 of the ozone. 



The first readings were taken with both plates in pure air. 

 Fifteen minutes later the ozone was added to the air sur- 

 rounding the test-plate. 



Table V. 



Exposure. 



Ikon. 



Ratio to 

 Standard Plate. 



CorpER. 



Ratio. 



ho iir 



100 

 97 

 97 

 97 

 98 



100 

 95 

 97 

 96 



i 



1 ., 



2 hours 



3 „ 





* Hallwachs, loc. cit. p. 381. 



