NEW ACTIONS PRODUCED BY " N" RAYS 37 



still occurs when the " N " rays traverse the 

 reflecting surface from the inside towards the 

 outside. 



All these actions of " N " rays on light 

 require an appreciable time-interval for appear- 

 ing and disappearing. I was unable, although 

 I varied the experiment in a great many ways, 

 to observe any action of " N " rays on the 

 refracted light. 



I will here make the following general 

 remark concerning the observation of " N " 

 rays. The aptitude for catching small varia- 

 tions in luminous intensity is very different 

 in different persons ; some see from the outset, 

 and without any difficulty, the reinforcing action 

 produced by " N " rays on the brightness of a 

 small luminous source ; for others, these pheno- 

 mena lie almost at the limit of what they are 

 able to discern, and it is only after a certain 

 amount of practice that they succeed in catch- 

 ing them easily, and in observing them with 

 complete certainty. The smallness of the effects 

 and the delicacy of their observation must not 

 deter us from a study which puts us in posses- 

 sion of radiations hitherto unknown. I have 



