58 



Proceedings of the Rof/al Irish Acadeini[. 



so as regards the sharpness of the lines. Taken generally, the lines in botii 

 niobiirm and molybdenum are not so sharp as those of tungsten, and are also 

 greater in intensity. All three substances resemble each other in having very 



Table XI. 



-\ 



Displacement 



j 



A' 



2992- 10 



s - compt. through 



1 



35 X (1, 1, 2) 



32.54-23 





± -26 



67 X (1, 2, 2, 3) 



ZiU-2b 





X -11 



57 X (1, 2, 3) 



4123-99 





± -12 



31 X (1, 2, .3, 4, 6) 



4163-81 





r -13 



42 X (2, 3, 4, 6) 



4249-61 





± -35 



67 x(l, 2, 4) 



42S9-62 





? -17 



36 X (1, 2, .3, 5) 



4331-.56 



, ,. ■ 



± -36 



64 X (1, 2, 4) 



many triplets when the light is in the magnetic field. Among those triplet.^ 

 only a small proportion shows the normal interval between the components. 

 This property of having triplets of very varied separations is common to nearly 

 all substances; and it is only by consideiiug the lines which have many 

 components that points of resemblance and difference may be detected. The 

 analysis of the intervals occurring in such lines according to the Eunge rule 

 .shows that among these multiples a great variety of aliquot parts is to be 

 found, and no general law can be foimd under IjTng the aliquot parts occiuTing in 

 like substances. One finds in the Zeeman Effect of most of the elements lines 

 ■which break up into 3, 4, 5, and 6 components. On obser^^ng the lines which 

 have more than six components in tungsten and molybdenum it is seen 

 that, without a single exception, the numbers of the components are odd — 

 W (7, 9, 11, 13,' 15, 17, 19,=)*, Mo (7^ 9, 11). Now, though there are only five 

 lines in niobium which break up into more than six comp)onents, the number 

 of components is in each case even — Nh (8^, 10=). Tungsren and molybdenum 

 have an even valency, and niobium an odd valency. This suggests the law 

 that substances having an odd valencj' have an even number of components, 

 and substances with an even valency have an odd number of components for 

 lines which break up into more than six components. This law is absolutely 

 true for these three substances. An examination of all the available results 

 for other substances shows that the law is not general; but that odd numbers 



* The index shows tlie numher of times repeatpd. 



