184 



ANNUAL EEPORT SMITHSONIAN INSTITUTION, 19 30 



the behavor of lines from different layers reveals characteristic differ- 

 ences. This is shown particularly well in studies of solar rotation 

 and by the currents observed in the gases in the immediate 

 neighborhood of spots. 



Correlations in level 



A. DATA FROM VARIOUS SOURCES 

 tNorm=linear velocity for lines of medium level] 



Lines 



H3 and Ki Ca+.. 



Ha Hydrogen 



4226 Ca 



nigh-level Fe 



Medium-level Fe 

 4196 La+ 



Rotation 

 Obs.-Norm 



Km/sec. 

 4-0. 20 

 +0.11 

 +0.06 

 +0.02 

 0.00 

 -0.03 



Observers 



St. John and Ware... 

 Adaius and Evershed 



Adams -- 



Evershed 



Adams and Evershed 

 Adams 



Flow near 

 spots 



Kmlsec. 



in 1.80 



in 1.50 



in 0.06 



0.00 



out 0. 40 



out 0. 75 



Heights 



Km 

 12,000 



10, one 



2,100 



1,200 



4C0 



Low. 



B. SIMULTANEOUS OBSERVATIONS AT HIGH AND LOW LEVEL 



When the linear equatorial velocity of rotation given by iron 

 lines of medium intensity is taken for reference, the velocity given 

 by Ca+ is 0.2 km/sec. greater, with lower velocities for Ha, Ca 4227, 

 and high-level iron, corresponding to their separate and lower levels, 

 the lowest velocity being given by lines originating immediately 

 above the photosphere. The same arrangement of the levels is given 

 by the flow near spots, high velocity inw^ard, 1.80 km/sec. for Ca4-, 

 decreasing to zero for high-level Fe, and rising to maximum velocity 

 outward for the lines of lowest level. A like correlation is shown by 

 the heights taken from eclipse observations. 



CONSTITUTION OF THE SUN 



The present view conceives it as a completely gaseous sphere. For 

 the sun, built on the Eddington model, in which the radiation pres- 

 sure is a constant fraction of the total pressure, the temperature at 

 the center would be of the order of 29,000,000° K. The atoms in 

 the interior are highly ionized, but are not destroyed or transformed 

 into other elements, the only changes being the removal, more or 

 less complete, of the orbital electrons. The mean molecular weight 

 of the mixture of free electrons and nuclei is taken as 2.11. The 

 pressure in the deepest interior, 30,000,000,000 atmospheres, is so 



