40 "N RAYS 



marked effect was obtained by interposing 

 the quartz plate between the source and the 

 sulphide, quite close to the latter. 



In these experiments, the secondary emis- 

 sion by the quartz is added to the " N " rays 

 directly emanating from the source. This 

 secondary emission has, indeed, its origin in the 

 whole mass of the quartz, and not at the surface 

 only, for if several plates of quartz be succes- 

 sively placed on top of each other, the effect 

 is seen to increase with each added plate. Ice- 

 land spar, fluor spar, barite, glass, etc., behave 

 like quartz. The filament of a Nernst lamp 

 remains active for several hours after the lamp 

 is extinguished. 



A piece of gold, laterally brought near to 

 the sulphide while it is being subjected to " N " 

 rays, increases its glow (note 10) ; lead, plati- 

 num, silver, zinc, etc., produce the same effects. 

 These actions persist after the extinction of 

 " N " rays, as in the case of quartz. Neverthe- 

 less, the property of secondary ray emission 

 only permeates slowly through a metallic mass. 

 Thus, if one of the faces of a sheet of lead 

 2 mms. thick has been exposed to " N " rays for 



