20 "N RAYS 



The foregoing leads one to think that the 

 emission of radiations susceptible of traversing 

 metals, etc., is an extremely general pheno- 

 menon. First observed in the emission of a 

 focus tube, it was also met in that of ordinary 

 sources of light and heat. For shortness, I will 

 henceforward designate these rays by the name 

 of " N " rays. 1 



I would draw attention to the fact that 

 these " N " rays comprise a very large variety 

 of radiations ; for while those which issue from 

 an Auer burner have refractive indices greater 

 than 2, there are others, amongst those emitted 

 by a Crookes' tube, whose index is inferior to 

 1*52, for if a pencil of these rays is made to 

 impinge on an equilateral quartz prism, parallel 

 to the edges and normal to one of the faces, an 

 emerging pencil is obtained which is very 

 much spread out. 



Up to this time the only means of detect- 

 ing the presence of " N " rays was by their 



1 From the name of the town of Nancy, these re- 

 searches having been made at the Nancy University. In 

 conformity with a usage which has become established, I 

 now employ the letter "N" instead of "n," which I had 

 at first adopted. 



