228 



Solar Eclipse of 1900, May 28. 



[Dec. 17, 



e( Solar Eclipse of 1900, May 28. — General Discussion of Spectro- 

 scopic Besults." By J. Evershed, F.B.A.S. Communicated 

 by the Joint Permanent Eclipse Committee. Received Decem- 

 ber 17, 1902,— Bead January 22, 1903. 



(Abstract.) 



In a general way the conclusions arrived at from the discussion of 

 the spectra obtained in 1898 are amply confirmed and extended by the 

 present results. It is now shown that every strong dark line of the solar 

 spectrum exceeding Rowland's intensity 7 is found in these spectra 

 as a bright line ; and the great majority of the bright lines of the 

 flash spectrum, excluding hydrogen and helium lines, coincide with 

 dark lines of intensity not less than 3. 



Most of the bright arcs of the flash spectrum are well-defined 

 narrow lines admitting of considerable accuracy in the measures, and 

 the present determinations of wave-length indicate that the coinci- 

 dence of the bright lines with the dark lines is exact within *05 t.m. 

 for all the well-defined lines. 



As regards the relative intensities of the lines of any one element 

 in the flash and Fraunhofer spectra, my previous results require 

 modification and extension as follows: The relative intensities of 

 isolated lines of an element in the flash spectrum are in general, but 

 not exact, agreement with those of the same element in the solar 

 spectrum, and those lines which are exceptionally strong in the flash 

 are in most cases lines which are enhanced in the spark spectrum of 

 the element. 



All of the more prominent enhanced lines of iron and titanium, as 

 determined by Sir Norman Lockyer, are found to coincide with strong 

 lines in the flash, but owing to the compound nature of some of the 

 lines, it is not certain that all of these have abnormal intensities in 

 the flash. 



There is no evidence of differences in the relative intensities of the 

 lines of an element in the higher or lower regions of the flash layer, 

 and the enhanced lines appear to predominate throughout the entire 

 depth of the radiating stratum. The enhanced lines are equally 

 prominent in the polar regions and in low latitudes, and the flash 

 spectrum generally is now found to be the same in all latitudes and 

 shows no essential change after an interval of five years. 



An explanation of the abnormal intensities of the enhanced lines in 

 the flash spectrum is now offered, which depends on the assumption 

 of a continuous circulation of the solar gases in a radial direction ; 

 the highly heated ascending gases giving the predominant features to 

 the flash spectrum, whilst the cooler more diffused gases, slowly 

 subsiding, determine the character of the absorption spectrum. 



