62 



INFLUENCE OF A MAGNETIC FIELD UPON THE SPARK SPECTR.V OF IRON AND TITANIUM. 



In Table 14 the ratios of classes given by the weighted means for the three magnitudes of displace- 

 ment are M : S, M : M, and L : L for both iron and titanium. Table 15 gives for the three magnitudes 

 of separation the ratios S : M, M : M, L : L, for both elements. There is thus good agreement as to magni- 

 tudes except for the first class in each table. A large proportion of the lines for this class come from 

 the region below X4000 and there is a sufficient scattering of high values for both separation and displace- 

 ment to put the means into dififerent classes when formed in this way. The behavior of the ratios of 

 weighted means in the two tables is interesting. Those in Table 15 decrease very nearly in the ratio 

 3:2:1 for the three classes in the iron table, and about 9 : 4 : 2 for titanium, showing that the displace- 

 ments increase in size much faster than the separations. The same material is used in Table 15, but here we 

 find an approximate constancy for iron and a gradual increase for titanium. It is probable that the 

 change as shown in Table 14 is a real one and that it is obscured in Table 15 by the large difference in 

 range of values of separations and displacements. The limits of this range are in the ratio of about i to 

 3 for the separations (omitting a few extreme values) and about i to 10 for the displacements. Thus, 

 in Table 14, when the displacements are grouped so as to increase in magnitude, there is a much smaller 

 variation among corresponding values of separation than we have among the displacement values when 

 the separations are graded as in Table 15. The widely divergent values of displacement scattered through 

 Table 15 would thus act to make the ratios of means more or less discordant. 



A classification byDuffield (64(0 maybe used in comparing the displacements measured by him with 

 the corresponding Zeeman separations for iron. He forms three main groups according to amount of 

 displacement. Table 16 gives the mean separation and displacement for each of these groups, at first 

 singly, then combined so as to form two groups with more lines in each. 



Table 16. Means of Separation and Displacement for Duffield's Displacement Groups. 



We see that separation and displacement are of the same order of magnitude throughout. In the 

 last two lines the larger number of values gives means of higher weight. These means show as before 

 that a much larger range is covered by the displacements than by the separations. 



Two additional points are to be considered in this comparison. The first is the rate of increase of 

 the two effects with magnetic field and pressure, respectively. Duffield found that the displacements of 

 lines belonging to the three groups treated in Table 16 have very different rates of increase with increase 

 of pressure, the lines of Group III showing the most rapid change. A corresponding phenomenon in the 

 Zeeman effect would mean a different rate of increase of separation with field-strength for different lines. 

 We are not certain that this does not e.xist, since the proportionality of separation to field-strength has 

 been estabhshed by careful measurement for only a very few lines, but no evidence of a difference for 

 different sets of lines has thus far been presented. 



The second point is the relation of the variation of separation and displacement with the wave-length. 

 In Tables 14 and 15 the division into regions of wave-lengths shows the distribution of magnitudes in 

 these regions. Following down the columns headed "No. of Lines" in each table, we see that the propor- 

 tion of small values for both separation and displacement is greater in the region of short wave-lengths. 



