398 Lord Blythswood and Dr. Marchant on 



The mean values obtained from these measurements there- 

 fore give : — 



H 



= 8-5 xlO" 6 , 



^=28-3xl0- 6 , ^g = 14*95 xlO" 13 , 



H 



^ 3 = 4-3x10-*, 



B\ 

 8\, 



= 4-5 xlO- 13 . 



_^3 



X 2 E 



2-28x10- 



X being expressed in 10 -10 metres. 



The green line of mercury (5460) behaves somewhat dif- 

 ferently under the action of a magnetic field. With a weak 

 field of about 6000 c.G.s. units the line splits into a triplet, as 

 shown in the photographs, both with single and double 

 orders. 



As the field increases in strength the inner component of 

 the line, which is perceptibly broadened under the weak field, 

 splits into a triplet, at the same time each of the outer lines 

 splits into a doublet, the resultant being a septet. The single- 

 order photograph shows the line as it ultimately appears in 

 the strong field. It is to be noticed, however, that the outer 

 lines are reallv due to three orders. 



B A' 



Fig. 9.1 



B' A' 



Outer comp. 

 with map:. 



B 'yfy? c 



without mag. 



B 



(1) 



B A C 



B A C 

 (3) 



In fig. 9 (1) represents the appearance under a field of 

 about 16,000 units ; (2) shows the condition under a slightly 

 stronger field, the centre line of the inner three being due to the 

 coincidence of the outermost components of the orders. In 

 (3) (the condition shown in the photograph with a field of 

 20,000 units) the lines completely overlap. Conditions (1) 

 and (2) are well shown in the photograph of the green line 

 taken along the lines of force. At the top and bottom of the 

 line, nearer the edges of the hole in the pole-piece, the field is 

 considerably stronger than at the centre. At the ends of the line, 

 therefore, we have the condition shown at (2) , at the centre of 



