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 Pi-OYDf, and later 
by Watson.| 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 diie to contamination by xenon as they lie close to X lines within their 
erroi's 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, wliich 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 lines. A strong argument also is this. There are a 
number of strong lines undoubtedly belonging to the PoaEm 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 Pi.amsay 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 :— 
RaEm. 
X. 
Kr. 
C. and R. 
R. and R. 
W. 
(5) 4681 
(10) 4680-92 
(9) 4681-01 
(5) 4683-76 
(4) 4680-57 
(10) 4626-5 
(8) 4625 - 58 
(10) 4625-66 
(15) 4624-46 
(10) 4605 
(4) 4604-46 
(8) 4604-58 
(10) 4603-21 
(3) 4578-5 
(7) 4577-77 
(8) 4578-0 
(6) 4577-36 
(6) 4577-40 
(8) 4463-5 
(7) 4459-3 
(10) 4460-0 
(20) 4462-38 
(1) 4463-88 
(3) 4189 
(4) 4187-97 
(5) 4188-2 
(10) 4193-25 
(6) 4114 
(6)4114-62 
(6) 4114-71 
(7) 4116-25 
(1) 4113-90 
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, ibid., 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). 
I H. E. Watson, ‘Roy. Soc. Proc.,’ A, vol. 83, p. 50 (1909). 
