8 Preston— Radiating Phenomena in a Strong Magnetic Field. 
magnetic field, and determine if the components of the supposed reversed line 
remained at the same distance apart, or became more widely separated as the 
strength of the field increased. 
The extent to which I was able to increase the strength of the field at that 
time was not. sufficient, however, to enable me to determine with certainty 
whether the reversal hypothesis was absolutely untenable or not. For 
although the components of the supposed reversed line appeared to separate 
continuously with increase of the magnetic field, yet this separation was not 
sufficiently great to overthrow the reversal hypothesis, for it might be said 
that the wider gap between the lines was due to the absorption-band being 
merely a little wider. ‘The weight of evidence, however, appeared to be against 
the reversal theory ; and, in order to push this test to a definite conclusion, I had 
a powerful electromagnet of special design built, which, it was hoped, would give 
a field sufficiently strong to determine matters decisively. I am happy to be able 
to state that this magnet has in every way acted up to expectation ; and, thanks to 
the courtesy of the University authorities and of the Curator, Dr. W. E. Adeney,* 
I was able to resume work at the Royal University with the improved apparatus ; 
and it was soon found that the reversal theory must be abandoned, and that the 
explanation of the quartets and other deviations from the normal triplet type 
must be sought for in other agencies. 
Before proceeding to the description of these more recent results, we shall 
refer for a moment to figs. 1 and 2, in order that the explanation which follows 
may be more easily intelligible. In fig. 1, the three lines A, B, C, are supposed 
to represent a triplet of the normal type, ito which the majority of spectral 
lines becomes resolved by the action of the magnetic field when the light is 
viewed across the lines of force. The vibrations in B and C are parallel to 
their length, while the vibrations in A are in the perpendicular direction. In 
the same way, fig. 2 represents a quartet produced by the magnetic field, or, 
if we may say so, a triplet in which the middle line A has become converted, 
by some cause or other, into a doublet. The lines B and C, as before, have 
their vibrations parallel to their length, while the pair of lines A have their 
vibrations in the perpendicular direction. We may, therefore, refer to the 
B and C as the sides, and to A as the middle, of the resolved line, even when 
B and @ are complex as well as A: for B and C, in some: cases, are also 
resolved into doublets or triplets, but they are always distinguished from A by 
the fact that their plane of polarization is perpendicular to that of A. Thus, 
in general, each of the members, A, B, C, of the triplet, fig. 1, may become 
* Throughout this and the previous investigations I am deeply indebted to Dr. Adeney, for he kindly 
invited me to the Royal University laboratories, and facilitated my work under conditions which necessarily 
interfered with his own researches, 
