an Electric Source, and Line Spectra. 



787 



hydrogen series (Phil. Mag. vol. xxix. p. 714), i.e. & = 5'05 

 • 2 This gives, by (30), 



microns" 



K,= 



5-05. 1Q- 8 



47r 2 a 2 



1-53 . 10 7 , 



(31) 



in round figures, valid for A =oo according to the dispersion 

 formula k = x + /3/(l — y 2 \~ 2 ). For the first hydrogen line, 

 H a , we should have, according to the same formula, 

 K=2*59.10 7 , and so on. Similar figures would follow from 

 the constants of Tables I. and II. In short, the permittivity 

 of the atomic sources responsible for the line spectra turns out 

 to he of the order of 10 7 , as was mentioned previously. 



Under these conditions the "lines" emitted are exceed- 

 ingly sharp, as may be easily judged from the above results 

 obtained in the case of the comparatively small permittivity 

 K = 500, and still better from the following Table for K= 10\ 

 in which the factor ce 2 /a has been taken as unit intensity of 

 radiation. 



Table V. 



\/a. 



J. 



300- 



225- 



1-9 . lO" 7 

 6-1 . icr 7 

 1-5 . 10 -7 

 3-1 .1CT 6 

 5-9 .10~ 6 

 1-53 . 10" 5 

 882. 10~ 5 

 7-41 . 10 -3 ] 

 2*377 units. ! 

 495*36 (max.) | 



3-99 . icr 2 j 

 421 . 10 -4 

 4-9 .10 -6 

 



180- 



150- 



140- 



139-80 



13985 



(139-8450 



! 13984493 



1 13984491 



^139-8447 



139-843S 



139-835 



139-829 (M 



The second and following branches (from v x to i/ 2 , &c.) have 

 very much the same character. The above, first, branch 

 consists practically of a very sharp "line," or narrow band, 

 ranging over (or less than) the bracketed figures. The 

 corresponding wave-length interval is 8\. = , 0003a, so that 



