NATURE 



[November 2, 1899 



Fig. 2. — Zinc. 



Zn 

 4811 



Cd 



4800 



Zn 



4722 



Zn Cd 



4680 4678 



Fig. I. Fig. 3. — Zinc and Cadmium. 



Explanation of Plate. 



In the accompanying plate, Fig. i shows the effect produced on the violet line of cadmium 4678. At the top, a, we have the 

 iine photographed with the magnet unexcited, that is, in the free field. Underneath this, at b, the same line is photographed with 

 the magnet excited, but the field is not strong enough to resolve it into its three constituents. It accordingly appears to be merely 

 broadened by the magnetic field. A Nicol's prism was then introduced into the path of the light and the line photographed in the 

 same magnetic field, with the result shown at </, where the middle is seen to be removed from the affected line, so that it appears 

 as a doublet. The nicol was then turned through a right angle, and the line again photographed in the same field. The result is 

 shown at c, which proves that the sides of the broadened line have been cut off, while the middle has been allowed to pass. This 

 agrees with the supposition that the magnetic field resolves the line into a triplet, but does not absolutely prove it. 



The further resolution necessary to prove this point is shown in Figs. 2 and 3. In Fig. 2, a photograph of the zinc lines 481 1, 

 4722 and 4680 is shown, and it will be observed that 4680 shows as a pure triplet, while the others do not. Fig. 3 is a photo- 

 -graph in a still stronger field taken from a spark passing between two electrodes, one of cadmium and one of zinc, so that the lines 

 of cadmium and zinc are obtained simultaneously under precisely the same circumstances. It will be seen that the lines most 

 =affected are 4678 of cadmium and 4680 of zinc, and these both show as pure triplets, while the lines 4722 and 4800 show 

 :as quartets. 



NO. 1566, VOL. 61] 



