192 CARNEGIE INSTITUTION OF WASHINGTON. 



been commented on in previous reports. These investigations have 

 been continued, and an account of the search for additional Hnes 

 showing the effect and of a study of the apparent variation of field- 

 strength with level in the solar atmosphere has now appeared as 

 Contribution No. 148. 



Measures of displacements are given for 26 additional lines, belong- 

 ing to the elements iron, chromium, nickel, vanadium, and titanium; 

 18 other lines, all of them susceptible to the influence of magnetic 

 fields in sun-spots, show no measurable shift. The 26 lines, which 

 through changes in position indicate the presence of a magnetic 

 field, confirm the results in Contribution No. 71, and seem to place 

 beyond reasonable doubt the conclusion that the sun behaves approxi- 

 mately as a uniformly magnetized sphere, with its magnetic axis 

 slightly inclined to the solar axis of rotation and a polarity corre- 

 sponding to that of the earth. 



Laboratory data are available for 27 of the 30 lines known to be 

 influenced by the sun's general field. Combined with displacements 

 observed in the solar spectrum, these yield for each line a value of the 

 field-strength at the magnetic pole. The results show that the field 

 decreases with increasing values of the Rowland intensity of the 

 respective lines. Since line-intensity increases with the level at which 

 the various lines originate, it would appear that the strength of the 

 sun's general field falls off rapidly with increasing elevation in the 

 solar atmosphere. 



Using Mitchell's observations of the flash spectrum, we find that the 

 field now accessible to observation lies within the bounding surfaces 

 of a thin shell in the solar atmosphere, whose thickness seems to be 

 of the order of 150 km. Certain necessary corrections improve the 

 internal agreement and leave outstanding as discordant only 2 of the 

 27 lines. With proper allowance for peculiarities in the behavior of 

 different elements and in the Zeeman effect for individual fines, the 

 results indicate that definite values of the calculated field-strength 

 correspond to definite levels in the solar atmosphere. 



Systematic errors in the measured displacements varying with the 

 intensity of the spectral lines might explain the observed dependence 

 of field-strength upon line-intensity; but there is no indication of the 

 existence of such errors, and the internal evidence, on the other hand, 

 is strongly in favor of the hypothesis of changing field-strength with 

 changing level. 



The anomalous behavior of the lines which show no displacement is 

 not satisfactorily explained. Because of possible peculiarities of pres- 

 sure, temperature, and electrical conditions necessary for the emission 

 of these lines, they may originate outside the very limited region within 

 which it has been possible thus far to observe the sun's general field. 



