8 Prkston — Radiating Phenomena in a Strong Magnetic Field. 



magnetic field, and determine if the components of the supposed reversed line 

 remained at tlie 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 ajDparatus ; 

 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, into 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 C 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 



* T]irougliout tliis and tlie previous investigations I am deeply indebted to Dr. Adeney, for he kindly 

 invited me to the Royal (Jniversity laboratories, and facilitated my work under conditions which necessarily 

 interfered with his own researches. 



