294 DELL SYSTEM TECUXICAL JOURNAL 



entire group, the A' e\cilati(jii-p()tentiiil, is also represented by a 

 straight Hne, the A' line, which may be taken as coincident with the 

 lowest-lying line in the graph, provided that we translate frequencies 



into potentials by the relation \' = lii'/c (both frequencies and 



He H Be B 



Fig. U— Excitation-potentials of lifilit elements, correlated with (lisplaccincnts 

 of A' electrons. (Cf. footnote 20.) 



potentials are laid off along the axis of abscissae). This A' line, it 

 must be realized, i-xiends the whole way from atomic number \r2 

 to atomic nimiber \'2. 



The circles upon tiie graph represent e.vcitation-potentials inferior 

 to 1000 volts, observed by Kurth. Three of these lie very dose to 

 the downward prolongation of the K line; the almost inevitable 

 inference is, that in these three cases the excitation consists in the 

 extraction of one of the electrons nearest the nucleus. The others 

 lie so much above the extended A'-line that they must belong to a 

 distinct class. Maii\- .iddilioiial measiiretnents lia\e been made 



