200 



Mr. J. Norman Lockyer. 



different spectral lines in different stars when the apparent differ- 

 ences are such as to suggest the objection to which I am now 

 referring. 



It is not a question of the absence of elements, but of the 

 absence of certain molecular complexities of each element, which 

 separates the spectrum of the sun from those of the stars of various 

 orders. 



The Connexion between Chromospheric and Stellar Phenomena. 



The objection having been met, I now proceed to discuss the 

 connexion between the sun and stars, and in order to bridge the 

 gap which separates them, it is necessary to bring forward the very 

 latest solar results as a basis of inquiry. 



The chromosphere, which represents that part of the atmosphere 

 with which we have chiefly to do in the light of § 2, is well pour- 

 tray ed in the photographs of the Eclipses of 1893 and 1896. So 

 complete is the record, that it is quite sufficient for our present pur- 

 pose, and is to be the more relied on since it represents it at the 

 same instant of time. I have elsewhere pointed out that Young's list of 

 chromospheric lines may be misleading because it is a summation of 

 results obtained at different times and of different conditions ; pro- 

 minences even may be, and doubtless are, involved. I have already 

 stated the order in which the various substances thin out ; the 

 lengths and intensity of the lines are faithfully recorded in the 

 photographs. 



An examination of the eclipse photographs shows that the tem- 

 perature of the most luminous calcium vapour at the sun's limb is 

 not far from that of the electric spark, the blue line being feeble as 

 compared with the H and K lines, which we have seen to be enhanced 

 on passing from the arc to the spark. 



Many of the characteristic arc lines of iron appear in the chromo- 

 spheric spectra as photographed at the two eclipses, and those which 

 I have recently shown to be enhanced in the spark are all present in 

 the chromosphere of 1896, and most of them in that of 1893. In the 

 chromosphere of 1896, the enhanced lines are all of greater intensity 

 than the corresponding Fraunhofer lines, and they are also relatively 

 stronger, as referred to the arc lines, than they are in the experi- 

 mental spark. Hence, incandescent iron vapour in the chromosphere 

 must beat a temperature at least as high as that of our hottest spark, 

 and certainly higher than that of the iron vapour which is most 

 effective in the production of Fraunhofer lines. 



The characteristic spark line of magnesium at wave-length 4481 

 is not represented in the chromospheric spectra of 1893 and 1896, 

 but other lines which are common to the arc and spark were recorded 



