﻿K C. Pickering — Ultra. Violet Spectrum. 



225 



Table I. 



Xo. 



D-R. 



C-R. 



372-0 



3 



+ •037 



— ■087 



373-0 



5 



+ •032 



— •070 



374"0 



3 



+ •037 



— •077 



375-0 



3 



+ •023 



-•070 



376-0 



3 



+ •003 



-•060 



377-0 



2 



+ •005 



-•075 



378-0 



3 



+ •007 



-•093 



379-0 



3 



— •003 



-•097 



380-0 



3 



-•007 



— •023 



-381-0 



1 



+ •020 



-•070 



382-0 



3 



-•017 



— •073 



383-0 



5 



— •030 



-•084 



384-0 



2 



-•030 



— •090 



385-0 



6 



-•027 



— •102 



386-0 



5 



-•026 



-•086 



387 



3 



— •027 



-•133 



388-0 



2 



— •045 



-•150 



389-0 



3 



-•067 



-•153 



390-0 



6 



— •062 



-•128 



393-0 



5 



-•042 



—•084 



392-0 



3 



— •057 



-•107 



393-0 



2 



-•080 



— •100 



394-0 



2 



-•075 



— •100 



The results of table I are combined in table II, where each 

 group extends over five units. An inspection of these tables 







Table 



II. 





X 



No. 





D-R. 



C-R. 



375-0 



16 





+ •023 



— •070 



380-0 



13 





-•003 



-•079 



385-0 



21 





— •028 



-•097 



390-0 



19 





-•055 



-•119 



shows that the maps differ systematically, the wave-lengths 

 according to the map of Dr. Draper being too great for the 

 lines of short wave-lengths. The relation is very closely repre- 

 sented by the formula, 



D — R = -0052 (379-6 — D), 



in which D and R represent the wave-lengths according to Dr. 

 Draper and Professor Rowland respectively. 



Representing by C the wave-lengths according to Cornu, we 

 have in like manner the correction, 



C -R = '003 (351-7 - C). 



Where the wave-lengths are only carried to hundredths of a 

 unit the corrections may be more readily applied by means of 

 table III, which gives the limits within which each correction 

 of one hundredth of a unit is to be applied. The first part of 

 the table gives the corrections of Dr. Draper's map, the second 

 the corrections of M. Cornu's map. 



