PROGRESS IN ASTROPHYSICS — ABBOT. 



181 



2. SOUNDING THE SOLAR DEPTHS. 



St. John's investigations of radial motion in the neighborhood of 

 sun spots have led him to further very interesting results. For it 

 appears that if one takes the various lines of iron as found in the 



Pig. 1.- 



Pressure Elevation 

 in aim's in km. 

 - H3K3 

 <?5000 



0.0 



^^-^— Mgb.ba,' 



Chromospjn^re 



|-,'_^'0,AI 15-^0 >Fe (15-40) Ley^l of velocity-inversion 





Fe 



Reversing layef 



|l' 8 7^ 



ll| ■!'- 



-Fe. 

 -^Fe 



Fe 



/ 4- 



' 3- 



I'l 



llM 0°/— 



III I 00() ■ 



III I / 



Sim I / 



§11111 ^ 



■sill' I ''- 

 «ii I ( 



< 111 I I I 



-^-Fe. 



->;.-'^Fe 

 7-^->-Fe 



^— Fe 



Fe ^^\ 



,''> Fe.Ba, 



-Hb 



-Vertical section of reversing layer and chromosphere, showing distribution of 

 radial velocities of sun spots. 



The lengths of solid lines are proportional to radial displacements of the corresponding 

 Praunhofer lines. Arrows indicate direction of flow. The rounded head of the cyclonic 

 disturbance is suggested by the broken-line curve enveloping the outward velocities. 

 Broken lines with arrows refer to possible velocities below the accessible levels. Lines 

 of force of the magnetic held are indicated in the usual way. — From Report on Mount 

 Wilson Solar Observatory, by George E. Hale, Twelfth Year Book Carnegie Institution of 

 Washington, 1913. 



sun's spectrum, classifying them according to their f aintness after the 

 manner of Rowland, the fainter lines show greater displacements 

 and thereby more rapid outflowing in the sun-spot whirls than do the 

 brighter ones. In fact, the brightest iron lines show less than a 



