10 Preston—Radiating Phenomena in a Strong Magnetic Field. 
which fig. 3 corresponds to fig. 1, and fig. 4 to fig. 2. The action of the double 
image prism is thus to separate the middle from the side constituents, while, 
at the same time, it possesses the advantage of showing all the constituents 
simultaneously,* and shows each of them unblurred by overlapping with the 
others. 
The question now before us is, can the quartet shown in fig. 2 be derived 
from the triplet of fig. 1 by reversal of the central line A, or does the doubling 
of A depend upon other causes ? 
In answer to this question, as has been already remarked, the appearance of 
the doublet A is against the reversal hypothesis, and it is further established 
beyond all doubt, by means of my improved magnetic field, that the distance 
between the components of A increases proportionately to the strength of the field 
just as the distance between the side lines B and C increases with the strength of 
the field. Further, when & and @ are each a doublet or a triplet, the distance 
between the members of each of these doublets or triplets increases with the 
strength of the field in the same direct ratio. In fact, as the strength of the 
field increases, the system of lines which constitute A, B, and C separate 
laterally according to a uniform scale; and, in face of these facts, the reversal 
hypothesis becomes quite untenable. 
The general phenomenon, therefore, which remains to be explained is the 
resolution of each member of the normal triplet (fig. 1) into a doublet or a 
triplet or some other system; and, as we shall see immediately, the electro- 
magnetic theory proposed by Dr. Larmor + may be extended to embrace all the 
phenomena yet observed. Before proceeding to consider this explanation, 
however, it may be well to refer briefly to a particular type of modification 
which was recently announced as having been observed by MM. Becquerel and 
Deslandres,t and subsequently by Messrs. J. 8. Ames, R. F. Earhart, and 
H. M. Reese.§ This particular type is referred to by them as an example of 
‘reversed polarization,” that is a case in which the modified line shows as a 
triplet in the magnetic field, but in which the vibrations in the centre line A are 
parallel to the lines of force while the vibrations in B and Care perpendicular 
to the lines of force—the reverse of the normal case. Stated in this way, the 
phenomenon is very startling, and seems, at first sight, quite contradictory to all 
theoretical expectations. But if we return to fig. 4, and take into consideration 
the remarks already made, viz. that the components of A may be widely 
* This device was employed independently by the author and MM, Becquerel and Deslandres. 
A double-image prism was also used, in a different way by M. Cornu. 
+ Dr. J. Larmor, Phil. Mag., vol. xliv., p. 505, 1897. 
+ Comptes Rendus, t. 126, p. 997, April, 1898. 
§ Astrophysical Journal, vol. yin., p. 48, June, 1898. 
