COMPARISON OF RESULTS FOR ZEEMAN EFFECT AND FOR PRESSURE DISPLACEMENT. 



59 



The fifth and sixth columns contain ratios of Zeeman separation to pressure displacement, the one 

 numerical, the other of letters denoting the order of magnitude. In the numerical ratios for iron the 

 values of Humphreys are used for the sake of uniformity, those of Dullield for an almost equal pressure 

 being taken when a Une was not measured by the former. In the case of titanium the values of Gale 

 are the more numerous and are used in the ratios when possible. The letters S, M and L in the sixth 

 column stand for small, medium and large values, respectively, of separation and displacement. The 

 limits covered by these classes are as follows: 



The reasons for this classification are given later. 



The question as to whether there is a close proportionality between magnetic separation and pressure 

 shift is decided in a definite manner by the sixth column in Tables 11 and 12, giving the numerical 

 ratio of separation to displacement. The separations for each spectrum are taken for a constant field 

 and the displacements for a constant pressure. The probable errors in measurement can explain only 

 in a very small degree the larger differences in these ratios. For iron the ratio-values run from 0.72 to 

 14.36, for titanium from 1.05 to 22.42. The distribution between these limits is such that any range 

 which might reasonably be assumed as due to poor measurements covers but a fraction of the lines. 

 Thus in Table 11, ratios ranging from 2.00 to 5.00 take in 90 out of 173 lines, or 52 per cent; the same 

 range for titamum includes 67 out of 122 lines, or 55 per cent. The range from 3.00 to 5.00 in the two 

 spectra covers 35 and 34 per cent respectively. 



The lack of constancy in the ratio being apparent, the question arises as to whether there is any real 

 connection between separation and displacement. A broad classification of the values in order of magni- 

 tude may be of service in this connection. For this purpose the separation and displacement values are 

 classified as small, medium and large, the range for each class being given above. The ratios showing 

 the comparative magnitudes of separation and displacement for each line are given in the sixth col- 

 umn of the tables. The displacement measures for titanium run in general larger than for iron, so that 

 a higher point of division between the medium and large classes is chosen. The following summary of 

 the data will show to what extent a general agreement exists between the Zeeman and pressure phenomena. 



The ratios of classes from Tables 11 and 12 enable us to form Table 13, in which the 173 iron and 122 

 titanium lines are placed in three main groups. Group i consists of the ratios S : S, M : M, L: L, and 

 shows that the separation and displacement for the corresponding lines are relatively of the same order. 

 Group 2 contains those lines for which separation and displacement are not in the same, but in adjacent, 

 classes; while for Group 3 the separation and displacement are of very different magnitude, one small 

 and the other large. Those lines which show no Zeeman effect, but distinct pressure displacement, are also 

 in Group 3, the letter being associated with S, M, or L according to the magnitude of the displacement. 



It will be seen that 44 per cent of the iron lines are in good agreement as to order of magnitude, 

 44 per cent show a probable discordance, while 12 per cent strongly contradict the hj'pothesis of 

 equality of relative magnitude. Titanium shows a somewhat larger proportion of its lines in poor agree- 

 ment as to separation and displacement. This indicates clearly that the two phenomena are not very 

 closely related as regards size of one increasing with size of the other. The large number of lines in Group 

 2 renders any positive conclusion difficult on account of the possible influence of errors of measurement. 



