140 THE ROYAL SOCIETY OF CANADA 



of these two radiations would result in electrons being lifted from their 

 stable orbit to the (1.5, s) orbit. They would therefore be in the 

 condition to return to their stable orbits either by emission of radia- 

 tion of wave lengths X = 5460.97 Â.U. and X = 4046.78 Â.U. followed 

 by the emission of radiations where frequencies are given by j' = (1.5, S) 

 — (2, p), and j'=(1.5, S) — {2, ps). This would seem to account 

 satisfactorily from the observed increased emission of the radiation 

 of the wave length X = 5460.97 A.U. from the quartz tube. 



It would have been of interest to see whether there was also 

 an increased emission of radiation of the wave length X = 4046.78 A.U. 

 from the quartz tube, but as indicated above, this was not found to be 

 practicable. 



During the course of the investigation the attention of the 

 writer was drawn to a paper by Fuchtbauer^ dealing with the same 

 subject. In Fuchtbauer's experiments a tube of quartz containing 

 mercur>^ vapour was exposed to the light issuing from a quartz mercury 

 vapour arc lamp of special design. It was so arranged that by cooling 

 when desired, one end of the tube with ether and carbon dioxide 

 snow, all the mercury vapour could be taken from the part of the 

 tube exposed to the light from the lamp. With this arrangement it 

 was found that when the tube was filled with mercury vapour the 

 radiation of wavelengths X = 4046.18 Â.U., X = 4358.66 Â.U. and 

 X = 5460.97 A.U. which issued from the free end of the tube was 

 very much greater than when the exposed part of the tube was deprived 

 of mercury vapour. These experiments, it will be seen, confirm the 

 results obtained in the present investigation but in them the part 

 played by the ordinary scattering of light by atoms was not eliminated 

 as it was in the present investigation by the use of the two tubes. 



It should be pointed out, however, that in Fuchtbauer's experi- 

 ments wavelengths which belonged to the enhanced series did not ex- 

 hibit the strengthening shewn in the case of the arc lines X = 5460.97 

 Â.U. and X = 4358.66 Â.U. 



In conclusion the writer wishes to express his indebtedness to 

 Professor J. C. McLennan, F.R.S., for suggesting the problem and 

 for continuous assistance during the investigation. 



The Physical Laboratory, 

 University of Toronto. 

 May 1, 1921. 



«Fuchtbauer, Physik. Zeitschr XXI. P. 635, 1920. 



