MOUNT WILSON SOLAR OBSERVATORY. 209 



the peiiumbrse of sun-spots may be referred, with great probabilitj^ 

 to a low-lying vortex. The inflow of the chromospheric gases seems 

 to follow (in part, at least) from the general downward movement of 

 these gases. Professor Stormer's investigations indicate that the 

 production of stream-line structure in the Ha flocculi is probably due 

 to the magnetic field, which may act mainly as a directing force upon 

 the inward-moving ions. At the level of the H2 calcium flocculi the 

 relatively quiescent state of the gases and the great inertia of the 

 calcium ions are conditions very unfavorable to the formation of 

 stream-lines. Hence, as observation indicates, these should appear 

 most clearly at the higher level of the Ha flocculi. On the basis of 

 Professor Stormer's theorj^ there would probably be some relation- 

 ship between the definit«ness of the lines of force structure and the 

 strength of the field in the spot. An examination of the evidence 

 seems to indicate that this is the case. 



In a second paper on radial motion in sun-spots, Dr. Charles E. 

 St. John gives a very comprehensive and illuminating discussion of the 

 distribution of the elements in the solar atmosphere. When the dis- 

 placements of the lines of different elements are compared, it appears 

 that the displacements of lines of like intensity differ. By the aid of 

 the iron scale referred to above, it is possible to determine the rela- 

 tive levels in terms of this scale at which the lines of other elements 

 are produced. In this way a chart has been plotted which represents 

 the distribution of the various elements in the solar atmosphere and 

 offers a convenient means of finding the approximate level repre- 

 sented by a line of given intensity belonging to any of these elements. 



Many important conclusions reached in the paper are summarized 

 in the introduction of this report. Its chief feature is a discussion of 

 the bearing of Mr. St. John's results on eclipse observations, modifi- 

 cation of spot lines as a function of level, displacements at the sun's 

 limb, solar rotation and level, magnetic field and level, anomalous 

 dispersion, and solar and terrestrial analogies. In all cases a remark- 

 ably close agreement is found between the levels represented by the 

 radial displacement measures and those indicated by other classes of 

 observations. It is evident that great possibilities of research lie open 

 in this field, which promises us a more intimate knowledge of the 

 solar atmosphere than we now have of the atmosphere of the earth. 



Tertiary Standards with the Plane Grating. 



In a second paper on the testing and selection of standard lines 

 of the international system, Mr. St. John and Miss Ware have 

 examined the secondary standards from X4282 to X 5506 as to their 

 consistency among themselves, and have determined the wave- 

 lengths in international units of a series of 198 lines in the arc spec- 

 trum of iron from X4118 to X 5506. The region from X5371 to 



