[mclennan-dearle] spectrum OF THE MERCURY ARC 



193 



Paschen^ that if the vapour pressure in his lamp was increased, the 

 relative intensity of the line 1-014// came out still higher, while with 

 a low vapour-pressure the intensity of the two lines was about equal. 

 This may explain the values of the intensities found for these lines in 

 the present investigation. 



Table II. 



In looking for series relationships among the lines given in the 

 first column of Table I., it was seen that the frequency differences 

 for the lines 1 • 038//, 1 • 27// and 3 • 02/^ are practically the same as those 

 which characterise the subordinate series triplets in the mercury 

 spectrum given by 7 = 2, p — m, d and y = 2, p — m, s. This will be 

 evident from the numbers given in Table II. It will be noted, too, 

 that the frequency difference between the line given in our list at 

 l-09/£ and the one given by Paschen at 1-367 is equal to 1860-4, 

 which approximates, as the table shows, to the frequency difference 

 between the second and third numbers of the triplets of the two 

 subordinate series mentioned above. If these two lines should turn 

 out to be the second and third numbers of a triplet similar to the one 

 iPaschen, Ann. d. Phys. 27. 13. p. 559, 1908. 



