30 " N RAYS 



lead to the supposition that they might also have 

 a heating effect on the bodies subjected to their 

 action. To test the matter experimentally, I 

 installed a thermopile of Rubens' connected to 

 an enclosed galvanometer. The action of " N " 

 rays on this apparatus was absolutely nil, even 

 in the most favorable conditions, though a candle 

 placed 1 2 metres away from the thermopile gave 

 a deflection of about o'5 mm. on the scale. I 

 conducted the experiment not only with " N " 

 rays proceeding from an Auer burner, but also 

 with those from the sun on the 3rd of July, 1904, 

 at midday. The rays were very intense, for 

 when I placed in front of the thermopile a tube 

 containing calcium sulphide, which had been 

 feebly excited by exposure to the sun, its glow 

 was greatly increased, but was diminished by 

 the interposition of a lead screen or the hand. 

 M. H. Rubens made the same observation, as 

 he was kind enough to write me, his apparatus 

 being much more sensitive even than mine. I 

 nevertheless thought it useful to determine 

 directly whether the incandescent platinum wire 

 was not heated by the action of " N " rays. 

 To this end, I had recourse to the study of 



