CH. xiv.] FIRST LIST OF LINES. 183 



Element in the spectrum, of 



KirchholFs numbers. Wave-lengths. which corresponding lines 



had been recorded. 



1567-5 5233-6 (V) 



1613-8 5197-9 (?) 



1867-0 5017.6 Iron. 



1871-5 5014-8 Bright line. 



2001-5 4923-1 Iron. 



2003-4 4921-3 (?) 



2054-0 4880-5 (?) Band or line near 



black line, very 

 delicate. 



When this list was communicated to the Koyal Society I 

 remarked : 



" I refrain from dwelling on this list at present, except to point 

 out that taking iron as an instance, and assuming that the iron 

 lines mapped by Angstrom and Rirchhoff are dice to iron only, I have 

 only been able up to the, present time to detect three lines out of the total 

 number (460) in the spectrum of the lower regions of the chromo- 

 sphere a fact full of promise as regards the results of future 

 laboratory work. The same remark applies to magnesium and 

 barium." 



It will be seen at a glance how variously the known 

 chemical substances were spectroscopically represented, and 

 what a large percentage of lines there was about which we 

 knew absolutely nothing. 



It is true we had all the then known lines of hydrogen, but 

 sodium was only represented by 2 lines out of 9 ; magne- 

 sium by 3 out of 7 ; barium by 2 out of 26 ; and iron by 

 3 out of 460 ! 



Further, while the lines of sodium and magnesium were the 

 brightest in the spectra of those elements, the lines of the 

 other known bodies were not. 1 



1 The two barium lines contained in my list are the two strongest barium lines 

 in the F to b region, but are not the strongest barium lines. The line of nickel 

 seen is one of the brightest nickel lines visible in the arc, but not the brightest 

 seen in the spark, as mapped by Thalen. 



