694 Infra-red Emission Spectrum of the Mercury Arc. 



If these two lines should turn out to be the second and third 

 members of a triplet similar to the one already noted, there 

 would need to be a line at about 3*70 //,. A line in this 



Table II. 



Wave-length. 



Frequency. 



Difference. 



First subordinate triplet 



series. 



v — 2, p — m, d. m=3. 



3663-05 A.U. 

 3131-66 „ 

 2967-37 „ 



2729206 

 31922-98 

 33690-34 



463092 

 1767-36 



Second subordinate triplet 



series . 

 v=2, p — m, s. m = l'5. 



546097 A.U. 

 4358-66 „ 

 4046-78 „ 



18306-73 

 2293704 

 24704-23 



4631-31 

 1767-19 



Triplet 1-038 /x, 1-270 /i, 

 3'02 fi. 



30200 A.U. 

 12700 „ 

 10380 „ 



33103 

 7871-8 

 9631-4 



4561-5 

 1759-6 



Suggested triplet 1*09 ft, 

 1-367 11, 3-70 fi. 



37000 A.U. 

 13670 „ 

 10900 ., 



2702-7 

 7311-3 

 9171-7 



4608-6 

 1860-4 



position, however, was not observed in our investigation, but 

 as already mentioned this portion of the infra-red spectrum 

 was not examined so closely as the region of somewhat 

 shorter wave-lengths. 



VI. Summary of Results. 



I. Thirteen lines have been recorded in the infra-red 

 spectrum of the mercury arc between the wave-lengths 1'00/a 

 and 3'02/jl. 



II. The existence of the line near I'Olyu,, which was shown 

 to exist by Coblentz and Geer but which was not found by 

 later investigators, was confirmed by the finding of a line 

 at 1*038 fi. 



III. The existence of at least one line with a wave-length 

 longer than 1*70 //, was proved by the discovery of a line at 

 3*02 fi, which was also in confirmation of the work by 

 Coblentz and Geer. 



