6 THE ROYAL SOCIETY OF CANADA 



elements the shell giving rise to the K series is surrounded by two or 

 more shells of electrons, a state of affairs very different from that 

 obtaining in hydrogen and helium where the electrons giving rise to 

 the K series are the only electrons outside the nucleus. X-ray 

 phenomena are independent of chemical combination, presumably 

 because the shells of electrons involved in the phenomena are well 

 inside the atom and play no part in chemical combination. For the 

 very light elements it is conceivable that this indifference to chemical 

 state may not occur as the electrons giving rise to the X-rays possibly 

 play some part in chemical combination. It is possible, therefore, 

 that an examination of the nature of this border line radiation between 

 X-rays and ultra violet light may yield results of considerable im- 

 portance. 



Summary.- — ^The curve connecting the radiation from boron, 

 bombarded by electrons, with the energy of the electrons (expressed 

 in volts), shows a discontinuity at about 150 volts. This is taken 

 to be an indication that the K radiation of boron appears at this 

 critical potential, which is about the potential at which one would 

 expect to find it from an extrapolation of Moseley's law. 



