288 CARNEGIE INSTITUTION OF WASHINGTON. 



(15) The probable coincidence with prominences of the dark "fila- 

 ments" photographed on the sun's disk with a 13-foot spectrohelio- 

 graph is being investigated by various methods. 



(16) The various phenomena of the Zeeman efifect in sun-spots have 

 been photographed more perfectly than ever before. These include 

 the effects of plane, elliptical, and circular polarization, the resolution 

 of certain lines into at least five components, variations in the separa- 

 tion of the components due to differences in field strength, variations 

 in their relative intensity at different inclinations to the lines of force, 

 and other characteristic effects. 



(17) Good progress has been made in the long task of determining 

 the incUnation and period of revolution of the sun's magnetic axis. 



(18) An application of the Stark effect indicates that the intensity 

 of the sun's general electric field does not exceed 200 volts per centi- 

 meter at the hydrogen level. 



(19) From a discussion of solar observations it appears that, if the 

 positions of theFraunhofer lines are influenced by anomalous refraction, 

 the effect must be of the second order. The displacements of the 

 solar lines at the outer edges of spot penumbrse are not appreciably^ 

 affected by mutual influence, as required by the theory of anomalous 

 dispersion. Of 506 Unes, 67 to the violet of stronger lines show the 

 same residuals as the 64 to the red, and weak lines in the broad shading 

 of the strongest Hues in the solar spectrum show no systematic changes 

 in displacement as the strong lines are approached. 



(20) There appears to be no correspondence between the solar phe- 

 nomena and the degree of anomalous dispersion shown in the laboratory. 



(21) The general displacements of the iron lines in the solar atmos- 

 phere seem not to sustain the deductions from the theory. 



(22) Contrary to the deductions, the displacements to the red are 

 smaller for solar lines of medium intensity than for the stronger hues. 



(23) Many lines exhibiting characteristic pole and pressure effects in 

 the laboratory show displacements to the violet in the sun. 



(24) Classified by their displacements in the solar atmosphere, the 

 same iron lines group themselves together as when classified by pressure 

 shift. 



(25) The equatorial value of the solar rotation, determined from 26 

 lines upon 29 plates in the region X5018-X5316, is 1.949 km. per 

 second. For the years 1906 and 1908 the results w^ere 2.064 and 

 2.053 km., respectively. The progressive change emphasizes the ques- 

 tion of the constancy of the solar rotation. 



(26) The displacements between the east and west limbs at zero 

 latitude determined by the filar micrometer for three lines of inten- 

 sity 2 and for the magnesium Unes X5172 and X5183 give velocities of 

 1.962 km. and 2.044 km., respectively. Using the same plates and 

 Unes, displacements determined with the Koch microphotometer give 

 1.955 km. and 2.018 km., respectively. 



