238 CARNEGIE INSTITUTION OF WASHINGTON. 



and the writer, who are continuing the work, therefore relate for the 

 most part to the displacements of unresolved lines on adjoining strips 

 of the compound quarter-wave pkte, used with a Nicol prism when the 

 spectra v;ere photographed in the second order of the 75-foot spectro- 

 graph of the 150-foot tower telescope. At the violet end, where the 

 measures were begun, these displacements are small, but they increase 

 greatly toward the red. WTien the mean of a considerable number of 

 lines in each region is taken, it is interesting to observe the increase 

 of shift with wave-length, both for mixed lines and for the more 

 homogeneous material afforded by single elements, though these are 

 complicated by the effects of level and the varying laboratory separa- 

 tions corresponding to individual lines. 



Abnormal lines offer another interesting and important subject of 

 study, which is also being pursued by the writer and his associates. 

 As Mr. St. John Ims pointed out, the peculiar displacements of the 

 p-components in certain spot triplets may result partially (perhaps 

 even exclusively) from such mutual influences of closely adjoining 

 lines as he has observed in his studies of the solar spectrum. This ques- 

 tion is being attacked from several different points of view with the 

 hope of clearing it up completely. 



The results of a further attempt to determine whether measurable 

 electric fields exist in sun-spots are described below (p. 291). 



EXPANSION IN SUN-SPOT VORTEX. 



To account for the low temperatures of sun-spots by expansion of 

 the ascending gases in the vortex, Mr. Russell finds that it is neces- 

 sary to assume that the latter come from a depth at which the tempera- 

 ture is at least 10,000° C. It is probable that the temperature at the 

 bottom of the ascending part of the vortex is at least 20,000° C, and 

 that the expansion in volume on rising to the surface is more thaa 

 forty-fold. 



IONIZATION IN SOLAR AND STELLAR ATMOSPHERES. 



The theory of ionization in solar and stellar atmospheres, developed 

 by Dr. M.N. Saha, has been extended by Professor Russell to the case 

 where atoms of several kinds are present. Taking into accouot the 

 existence of a common dissociation product (electrons) it is found 

 that— 



(1) If in any stellar atmosphere the ratio of the number of atoms 

 which are ionized to those which are not is formed for different elements, 

 these ratios will bear proportions to one another which depend only 

 upon the temperature and not upon the pressure or the relative 

 abundance of the different elements. 



(2) The elements of lower ionization potential are always most 

 highly ionized. The range of temperature and pressure within which 

 both ionized and non-ionized atoms can coexist in sensible proportions 



