L. Bell — Ultra-violet Spectrum of Cadmium. 429 



mination was in every case less than 0"1 tenth meter, and in 

 many cases decidedly less. 



The series of photographs contained about forty lines, of 

 which some thirty were distinct enough to admit of accurate 

 measurement. One or two of this number were somewhat 

 troublesome on account of being quite nebulous, particularly 

 one or two lines in the extreme ultra-violet. Some of the 

 fainter lines were omitted and the total number of lines accu- 

 rately determined in the entire spectrum was thirty, of which 

 the wave-lengths are subjoined. The first column contains the 

 values thus obtained, while the second and third respectively 

 contain the values given by Hartley and by Cornu. The vis- 

 ible lines are included in the table. 



Bell. 



Hartley. 



Cornu. 



6438-77 







5379-22 







5338-50 







5086-09 







4800-15 



4799 







4678-39 



4676 



7 





4414-19 



4414 



5 





3611-75 



3611 



8 





3609-39 



3609 



6 



3609- 



3534-69 



3535 









3466-70 



3466 



8 





3465-22 



3465 



4 



3465-5 



3402-68 



3402 



9 



3401-5 



3260-12 



3260 



2 





3251-77 



3251 



8 





3249-40 



3249 



5 



3247- 



3084-28 



3084 



3 





2979-87 



2979 



9 





2880-25 



2880 



1 





2836-45 



2836 



1 





2748-45 



2747 



7 



2747-7 



2572-95 



2572 



2 



2572-3 



2329-22 



2329 



5 





2321-14 



2321 



6 





2312-83 



2313 



6 



2313-5 



2288-01 



2288 



9 





2264-88 









2264-42 



2265 



9 (mean) 



2265-5 (mean) 



2193-98 



2196 



4 



2194-5 



2143-75 



2146 



8 



2144- 



In comparing these values it must be borne in mind that the 

 determinations of absolute wave-length on which they are 

 based are not the same, since the author's work is founded on 

 the scale of Professor Eowland's photographed map. This is 



