196 CARNEGIE INSTITUTION OF WASHINGTON. 



The principal results of the year may be summarized as follows : 



(1) Observations of the Zeeman effect at various solar latitudes 

 indicate that the sun is a magnet, with magnetic poles at or near the 

 poles of rotation. 



(2) The polarity of the sun corresponds with that of the earth — • 

 a conclusion which may prove to have an important bearing on 

 theories of terrestrial magnetism. 



(3) If, in harmony with one of these theories, the magnetism of 

 the sun is caused by the axial rotation of a body acting as though 

 it carried a residual volume charge, the sign of the charge comes out 

 negative. 



(4) Many of the solar lines fail to show the Zeeman effect due to 

 the sun's general field. A tentative hypothesis ascribes this fact 

 to a rapid decrease in the strength of the field at increasing levels 

 in the solar atmosphere. 



(5) A first approximate value for the vertical intensity of the sun's 

 general field at the poles is 50 gausses, which is about one-hundredth 

 of the intensity of the most powerful sun-spot fields and about 80 

 times that of the earth's field. 



(6) For a normal Zeeman triplet the theoretical curve of displace- 

 ments produced in the spectrum by the sun's general magnetic field 

 is a sine curve, with zero values near the equator and the poles and 

 maxima near 45° north and south latitudes. 



(7) The effect on these displacements of the elliptical polarization 

 produced by the mirrors of the tower telescope is negligible under 

 the normal conditions of observation. 



(8) An extended investigation of radial motion in sun-spots gives 

 results in entire accord with Evershed's hypothesis that the line 

 displacements are due to a movement of the solar vapors tangential 

 to the solar surface and radial to the axis of the spot vortex. 



(9) The proportionality between displacements and wave-lengths 

 shows that the phenomenon represents an actual flow of the gases 

 of the reversing layer out of spots and of the chromospheric gases 

 into spots. 



(10) The outward velocities increase with distance below a neutral 

 level, while the inward velocities increase with distance above this 

 level, which is the level of velocity inversion. 



(11) A consideration of the quality and the quantity of the mate- 

 rials and of the amount of energy involved in the flow inward at 

 high levels and the flow outward at low levels indicates that they do 

 not of themselves form a vortex system. 



(12) The type of vortex indicated is that of the terrestrial tornado 

 or hurricane. The actual vortex is deep-seated, the outflov/ into 

 the reversing layer being a portion of its upper part, while the inflow 

 from the chromosphere is a secondary effect. 



