Electric and Magnetic Fields on Spectral Lines. 521 



state to state approximately in the same way as that of the 

 electron in the stationary states of the hydrogen atom. 



On this interpretation we may naturally assume that the 

 appearance of douhle lines in the spectra of many elements * 

 is due to small perturbing forces originating in the confi- 

 guration of the inner electrons and having a different effect 

 on the motion of the outer electron according to different 

 positions of its orbits. From the fact that the frequency of 

 the components of double lines can be expressed by a formula 

 of the type (2), we may conclude, on the considerations of 

 section 2 and 3, that the perturbing forces in question are 

 of electrostatic and not of electromagnetic origin. As we 

 shall see, this view seems to offer a simple explanation of the 

 laws observed for the variation of the distances between 

 the components in a series of double lines. 



At a. distance from the centre of the atom, great in compa- 

 rison with the distances of the inner electrons, the total force 

 due to the nucleus and the inner electrons will be very nearly 

 equal to that from a nucleus of a single positive charge. At 

 a distance r the force may be expressed by 



+ 



Q 



r + 



125) 



where P, Q, . . . . may vary with the direction of the line 

 from the nucleus to the outer electron, as well as with the 

 time. The second term in (25) corresponds to a configuration 

 of the inner electrons and the nucleus equivalent to an electric 

 doublet. In case of such a configuration it will appear that 

 the condition of dissymmetry necessary for a different effect 

 on different orbits of the outer electron is satisfied. For 

 configurations more symmetrical, in which the centre of 

 gravity of the inner electrons coincides with that of the 



* The lines of the ordinary hydrogen spe -trum from a vacuum-tube 

 also appear as close doublets with high dispersion. Considering-, however, 

 the want of sharpness of the lines and the discrepancies between the 

 distance of components found by different observers, it seems probable 

 that the lines are not true doublets, but are due to an effect of the electric 

 field in the discharge. This is also indicated by the fact that the distance 

 between the components observed increases with the number of the 

 line, contrary to the behaviour of ordinary double lines. The distance 

 between the components observed by Paschen and Back (loc. cit.) was 

 020 . 10~ 8 cm. and 0-24 . 10~ 8 cm. for II a and II/3 respectively. According 

 to Stark's experiments on lip this corresponds to a resolution produced 

 by an electric force of about 900 volt per cm. The ratio between an 

 electric resolution of H a and IT^ should, according to the calculations of 

 section 2, be 0'76 ; the ratio between the components observed is 

 20/24 or 083. 



