74 "jV" RAYS 



actions, the modification undergone by the 

 luminous emission consist in a change in its 

 distribution along the different directions com- 

 prised between the ^normal and the tangent 

 plane to the luminous surface. 



On the Comparative Action of Heat and" N" 

 Rays on Phosphorescence (March 14, 1904). 



I have recently indicated that, whilst the 

 action of " N " rays increases the quantity of 

 light emitted by a phosphorescent screen in a 

 normal direction, it diminishes the quantity of 

 light emitted very obliquely (see the pre- 

 ceding communication). As is well known, 

 heat also acts on phosphorescence, whose 

 brilliancy it temporarily increases. When in- 

 vestigating whether this action of heat offered 

 the same peculiarities as that of " N " rays, 

 with regard to the direction of the emitted 

 light, I found that, on the contrary, heat pro- 

 duces an increase in brilliancy in all direc- 

 tions comprised between the normal and the 



