[mclennan-dearle] spectrum OF THE MERCURY ARC 



191 



lines given by Paschen at 1-207^ and l-202/£. The line at l-lTOpL 

 probably represents the same one as Paschen's at 1 • 188/z. The maxi- 

 mum observed at 1 • 128/( was also found by Paschen and Lehmann but 

 the maxima at 1 • 090/y. and 1 • 067/z are new. As mentioned before, 

 the maxima at 1-038/^ and 1-045/i probably refer to the same line. 

 The line at l-01/( was also observed by Paschen and by Lehmann 

 at 1-015^. 



An energy curve showing the maximum at 3 • 02/i is given in Fig. 8 

 and others showing the new lines at 1-27//, 1-090/i, and l-067^( are 



104 3.06 



WAVr LLHCTn in^ 



Fig. 8. 



given in Figs. 9 and 10. It will be noted that the maxima at 1-27/1 

 and 3 -02^1 are fairly sharp while those shown in Fig. 10 are somewhat 

 broader. 



A comparison of the intensities assigned to the various lines by the 

 different investigators affords an interesting study, Paschen says in 

 his paper that he found the line at 1 -014// was the most intense in the 

 whole mercury spectrum and that on the same relative scale, as that 

 recorded in Table I., he found the mercury green line at A = 5461 A°U. 

 was represented by an intensity of 42, i.e., rather more ^han one- 

 half of the intensity of the line 1-014//. In the measurements of the 

 writers it was found that if the energy in the line at 1 -014/1 be repre- 

 sented by 30 that in the line at A = 5461 A°U. was found to be rep- 

 resented by 40, or one-third more than that of the line 1-014/f. On 

 looking at Lehmann's results it will be seen that though there is no 

 value given for the intensity of the green line that of the line 1 -OlSfi 

 is given by him as the weakest in the infra-red spectrum. This was 

 probably due to the method of registering the spectrum used by 



Sec. Ill, 1915—14 



