The Mass-Spectra of Chemical Elements. 611 



Then we have, from (1) and (2), 



and 



Jo Jo 



Therefore 



Jo °7V« 



= [u 1 v/-v 1 lvj';^;[u 2 v/_v 2 u./]; ; 



It follows from (3), (4), and (5), that 



2 -/3 2 ) [ \ a U 1 Y 1 dx+ H" U 2 V 2 ^] = 0. 

 Tims F(a) = cannot have imaginary roots of the form 



£+17]. 



LIX. The Mass-Spectra of Chemical Elements. By F. W. 

 Aston, M.A., B.Sc, Clerk Maxwell Student of the Uni- 

 versity of Cambridge *. 



[Plate XV.] 



THE following paper is an account of some results 

 obtained by the analyses of gases by means of the 

 Positive Ray Spectrograph or, as it may be more con- 

 veniently termed, Mass-Spectrograph. The principle of 

 the method by which a focussed spectrum is obtained 

 depending solely on the ratio of mass to charge has already 

 been described f, but for the sake of others experimenting 

 in this field it is now proposed to give an account of the 

 actual apparatus in some detail. 



* Communicated by the Author. 



t K. W.A., Phil. Mag. xxxviii. Dec. 1919, p. 707. 



