218 Mr Purvis , The influence of a strong magnetic field on the 
an ordinary reversal and a separation produced by the magnetic 
field. The vapour of the metal was pulled out in a direction 
perpendicular to the line joining the magnetic poles, and the 
possible production of reversals thereby would interfere with the 
clear separation of the lines due to the effect of the field alone. 
The same apparatus was used as in the earlier experiments. 
The strength of the field was 39,980 units ; the column X gives the 
wave length of the undisturbed line ; the measured distances 
between the constituents of the divided lines are omitted, and only 
the values of d\f \ 2 calculated therefrom are inserted, and in the 
same units as employed before ; a + sign means that the con- 
stituents were on the side of greater wave length, and a — sign of 
shorter wave length. The column marked “ intensity ” gives a 
description of the unaffected lines ; the numbers represent the 
intensities of the lines, the lowest numbers describing lines of 
greatest intensities, 1 being the strongest ; r that the lines were 
often reversed normally, n that they were nebulous and h that 
they were broad and wide. The letters s and p signify, as before, 
that the constituents vibrated so that their electric vectors were 
respectively perpendicular or parallel to the lines of force. 
It was fairly easy to compare the divided lines when their 
general appearance was very similar and the number of con- 
stituents more than three ; there was more certainty in the com- 
parison than when the lines divided into three only. But too 
much stress should not be laid upon the general appearance of the 
normal undivided lines because occasionally it happened that lines 
which were somewhat dissimilar, and particularly in reversals, 
produced fairly comparable constituents. 
Further, it has been noticed before, in the study of other metals, 
that there were some lines divided into three whose components 
appeared to be abnormally polarised. It is possible that these 
were lines yielding five constituents, like Sb 2877T (p. 221), and the 
two extreme ones of which were too weak to be seen or to leave 
their images on the photographic plate, and the result was the 
description of a triplet with abnormal polarisation of the con- 
stituents. 
The lines were identified by comparison with the measurements 
and descriptions of Exner and Haschek (Site. d. k. Ahad. Wien, 
Vol. cvi. (1897) n A . Abth. pp. 54 (Pb), 59 (Sn), 345 (Bi), and 
346 (Sb), and Yol. evil. (1898) p. 792 for Au). As is well known, 
the metals Pb and Sn are placed in the same chemical family, and 
Sb and Bi are grouped similarly, and also the four metals have 
many comparable chemical and physical relationships. In the fol- 
lowing notes only the strongest lines of the metals are described ; 
those lines which yielded well marked images after a maximum 
exposure of 30 minutes when vibrating in the magnetic field. 
