Part IT.—Magnetie Perturbations of the Spectral Lines. 11 
separated, while B and C are not sensibly separated, or coincide, we see that the 
case cited by the French and American authors, if it exists, presents no further 
difficulty, bemg merely an extreme case of the ordinary quartet form shown in 
fig. 4. Thus, in fig. 5 we have a quartet in which the separation of the central 
part A is nearly as great as that of the side lines B and @, while in fig. 6 the 
case is shown in which the separation of the components of A exceeds that of the 
side lines B and (@; and, in fig. 7, the extreme case is shown in which B and C 
coincide, or are not visibly separated, while A is divided into two widely-separated 
parts. This, then, is the so-called “reversed polarization” type, which, if it 
exists, forms merely the end link in a continuous chain, and offers no special 
theoretical difficulties. Once the ordinary quartet is explained, all the foregoing 
forms become explained, and follow in sequence as expected variations. For the 
cause which converts A into a doublet may be sufficiently active to separate 
A A A 
tea =_=_—__— ——$— 
B C B Y 
Fie. 5. Fie. 6. Fic. 7 (not observed ?). 
the constituents of A by an amount which may be either greater or less than 
the separation of the side lines B and 0. 
But it is very doubtful if the extreme type (fig. 7) has yet been observed ; for 
although the present writer made an early study of the spectrum of iron, which 
is the spectrum in which some of the lines are said to show the so-called 
phenomenon of ‘reversed polarization,” yet in no case has he been able to detect 
the peculiarity described above. In fact, as I have stated elsewhere,* the 
spectrum of iron presents no specially new types of effect, and on my photo- 
graphic plates the lines referred to by the French and American observers as 
showing reversed polarization do not show B and Cas coincident lines, but show 
B and Cas two broad, weak lines overlapping at their inner edges, so that a dark 
rib runs down the centre, giving BC the appearance of a dark central line (on 
the negative) winged by two broader and fainter bands. It is thus likely that 
these lines are really quartets in which A is a doublet and B and C are broad and 
* Proc. Roy. Soc., January, 1898. The doublets referred to in this paper turned out, on further 
resolution, to be quartets. 
