SUMMARY OF RESULTS. 



The leading features in this investigation may be summarized as follows: 



1 . The effect of a magnetic field upon the spark spectra of iron and titanium has been studied for a 

 total number of 1120 lines between the limits X3660 and X 6743. The character of the magnetic separa- 

 tion is given, with weighted measurements as complete as was permitted by the magnetic fields available. 



2. The types of resolution, ranging from lines unaffected by the magnetic field to those having thirteen 

 and possibly more components, have been classified and the important features of each class have been 

 discussed. 



3. The relation of the measured separations to the "normal interval" 



e H 



m \-KV 

 has been studied for all t>'pes of resolution. A large majority of the separations of triplets and quadru- 

 plets show a close relation to this interval, while the generality with which the more complex tj-pes show 

 the spacing of their components to be simply related to this interval indicates a full confirmation of 

 Runge's law. 



4. Many cases of "magnetic duplicates," i.e., lines exactly similar in resolution, with the same inter- 

 vals between components, have been found among the more complex types, indicating close similarity 

 in the light vibrations which give rise to these lines. Large groups of lines showing triplet separation 

 are similar in this respect. 



5. The large range of wave-length covered has made it possible to observe the rate of increase of 

 magnetic separation with the wave-length. This increase is such that the mean value of AX/X^ for suc- 

 cessive intervals throughout this range shows a close approach to constancy for both iron and titanium, 

 with no systematic variation. The conclusion is that for these spectra the mean separation of Zeeman 

 components varies as the square of the wave-length. 



6. Cases of unsymmetrical separation of Zeeman components, so distinct as to be classed as abnormal, 

 have been pointed out. The theory of Voigt concerning a slight dissymmetry in the intensity and spacing 

 of the components of triplets has been tested for a number of iron lines, with the result that this effect 

 appears to be real in many cases, although some lines fail to show such a difference. 



7. The enhanced lines of the two elements have been compared with those showing no enhancement 

 in the spark, both as to type and magnitude of separation. The only difference between the behavior 

 of the two classes in the magnetic field appears to be that among the stronger enhanced fines of titanium 

 the triplet type strongly predominates, the separations usually being of medium amount and not closely 

 related to the interval a. 



8. On account of a possible similarity between the actions of the magnetic field and of pressure around 

 the light source as displacing agencies, a detailed comparison has been made of the magnetic separations 

 and corresponding pressure displacements for these spectra. It was proved that a close correspondence 

 does not exist, but there is a general agreement as to magnitude of the two effects when the means for 

 large numbers of lines are considered. 



In conclusion, I wish to acknowledge my great obligations to Mr. Hale for his unfailing support and 

 interest in the equipment and development of the physical laboratory and for much advice as to the 

 conduct of the investigations. A great deal of credit is due also to Miss Wickham and to Miss Griffin 

 for their careful and often diflficult work in the measurement and reduction of the photographs. The 

 large number of spectrograms required to do justice to the iron spectrum, in particular, increased the 

 work of measurement out of proportion to the total number of lines treated. 

 64 



