﻿32 



Dr. H. Sfarasfield and Mr. H. P. Walmslev 



of the unsymmetrical broadening of the primary lines away 

 from the bright secondaries, which would be expected from 

 the shape of the intensity curve for f \ aberration already 

 referred to on p. 28. 



It may also be mentioned that if the aperture of the 

 echelon is reduced from 33 to 14 steps — which would reduce 

 the maximum cubic aberration from *75\ to *057\ — the first 

 secondary maxima of the line 1 appear as faint lines of 

 equal intensity on either side of it. 



Scale of Intensify provided by the Secondary Maxima. 



The intensities of the first seven secondaries on the side 

 where they are brightened by the aberration are given, for the 

 special cases we have plotted, in Table II. The corresponding- 

 values for the standard case are also given for comparison. 



Table II. 



Relative Intensities of Primary and Secondary Maxima for 



the first seven Secondaries on the brightened side. 



Aberration... 



1/4 A. 



1/2 \. 



3/4 X. 



0. 



Number of 

 apertures ... 33 



19 



33 



19 



33 



19 



00 



P 



1 

 •14 

 •042 

 •017 

 •009 

 •006 

 •004 

 •003 



1 



•154 

 •045 

 •019 



•on 



•0069 

 •0050 

 •0040 



1 



•30 

 •10 

 •042 

 •020 



•on 



•007 

 •005 



1 



•32 



-12 



•05 



•02 



•014 



•009 



•006 



1 



•54 



•24 



•10 



•048 



■028 



•016 



•mn 



1 



•61 

 •28 

 •12 

 •06 

 •03 

 •02 

 •01 



1 



•0472 

 •0165 

 •0083 

 •0050 

 •0034 

 •0024 

 •0018 



1 



o 





4 ,. 



5 



6 



7 







P -94 



•93 



•76 



•74 



•54 



•50 



1 



The intensities of the secondaries are expressed in terms of the intensity of 

 the primary to which they belong. The bottom line gives the relative 

 intensities of the primaries. 



When the aberration in an echelon spectrum is large, the 

 series of secondary maxima which appear in the photographs 

 provide a convenient scale of relative intensities which may 

 possibly prove useful in comparing the intensities of spectrum 

 lines. For example, referring again to the photograph of 

 the green mercury line in Plate IV., the intensity of the 



