On the Reflexion of Cathode Rays. i33 



the reflector was so turned that its orientation did not satisfy 

 this condition, no charge arrived into the cylinder. The 

 existence of reflexion having thus been shown, I found that 

 the amount of charge reflected into the Faraday cylinder, the 

 position of the reflector remaining constant, was not equal 

 for different metals. In these experiments the two faces of 

 the reflector consisted of different metals which could be 

 interchanged by turning the reflector through 180°. By 

 measuring successively the charge reflected into the inner 

 cylinder by two different metals, and — for a normal angle of 

 incidence — the charge conducted to earth through a galva- 

 nometer connected with the reflector, the absolute coefficients 

 of reflexion for normal incidence, indicating the whole re- 

 flected charge, could be determined. This amount of reflexion 

 was about for 



Platinum 37 per cent. 



Copper 34 ,, 



Aluminium 22 „ 



Lampblack 17 ,, 



These values would be a little greater, if the second reflexion 

 were considered. 



These are the principal results of my researches. It is 

 true, I have not specially emphasized the fact that the orien- 

 tation of the anticathode affected the amount of reflected rays, 

 because I examined at that time only the total amount of 

 reflected charge, without investigating its variation with the 

 angle of incidence and the distribution of the reflected rays in 

 space. But, from several statements, it is evident that these 

 differences of the charge conveyed to the Faraday cylinder, 

 under different orientation of the reflector, were well known 

 to me. 



On p. 57 I distinctly assert that the amount of charge 

 imparted to the anticathode reflector was measured by con- 

 necting the reflector to earth through a galvanometer, the 

 angle of incidence being normal, while the charge conveyed 

 to the Faraday cylinder by the reflected cathode rays was 

 measured with an oblique angle between the anticathode 

 surface and the incident cathode stream, in order to make as 

 large as possible the charge arriving in the inner cylinder. 

 This oblique angle was about 60°. In this position of the 

 reflector the amount of reflected charge, conveyed to the 

 cylinder, was a maximum, in all other positions it was very 

 much smaller. On the other hand, the ratio of the two 

 charges obtained with two different metals in the same 

 position was equal for every angle of incidence. This ratio. 



