424 



DR. W. M. HICKS : A CRITICAL STUDY OF SPECTRAL SERIES. 



a slight difference in the deduced S. Here the difference '14 would correspond to a 

 difference in mass of 27 electrons. 



Radium Emanation. The emanation does not apparently produce the two 

 spectra exhibited by Kr and X. The measurements in the spectrum are very scanty 

 compared with those in the latter. We have early rough determinations by RAMSAY 

 and associates.* More accurate and complete by RUTHERFORD and RoYot, and later 

 by WATSON.!J: In order to diminish the absorption by the electrodes RAMSAY also 

 used copper instead of Pt electrodes and found a number of new lines, the majority of 

 which have not been seen by succeeding observers. They have generally been 

 explained as due to contamination by xenon as they lie close to X lines within their 

 errors of observation. At first sight this explanation would seem to be very natural, 

 but RAMSAY was confident that there was no such contamination. I am inclined to 

 suspect that the opinion that these lines belong to X is too hasty. As is well known 

 BALY found quite a large number of lines in Kr and X coincident within his 

 observation errors, which indeed were much smaller than those in any measures yet 

 made in RaEm. Now as a fact those suspected lines of RAMSAY and CAMERON'S 

 are also very close to these Kr lint's. A strong argument also is this. There are a 

 number of strong lines undoubtedly belonging to the RaEm spectrum, and observed 

 by both RUTHERFORD and ROYD and by WATSON, which are also near strong X lines, 

 yet separated so far from them, that if RAMSAY and CAMERON had had X in their 

 tube they must have seen them and RaEm lines as double, one due to X and 

 the other to RaEm. Compare for instance the following lines : 



I therefore included these RAMSAY and CAMERON lines in the purview, with the result 

 that a considerable number were found to fall in with places in which they are 



* RAMSAY and SODDY, ' Roy. Soc. Proc.,' vol. 73, p. 346 (1904) ; RAMSAY and COLLIE, Ml, vol. 73, 

 p. 470 ; CAMERON and RAMSAY, ibid., A, vol. 81, p. 210 (1908). 



t RUTHERFORD and ROYDS, ' Phil. Mag.' (6), vol. 16, p. 313 (1908) : ROYDS, ibid., vol. 17, p. 202 

 (1909). 



t H. E. WATSON, 'Roy. Soc. Proc.,' A, vol. 83, p. 50 (1909). 



