432 



Mr. J. N. Lockyer. Discussion of 



[Mar. 20, 



IY. Spectrum showing the Ba line at 4553 - 4 trumpeting. Here the line, 

 after proceeding to a considerable distance from the hottest region of 

 the arc as a fine reversed line, gradually expands towards its extremity. 



Flame-spectrum of Mn, showing the reversal of the triplet in the arc-flame. 



Flame-spectra of Ca, showing the gradual extinction first of K and then of H as the 

 flame recedes farthest from the arc. 



III. Discussion of " Young's List of Chromospheric Lines." 

 (Note I.) By J. Norman Logkyer, F.R.S. Received 

 March 5, 1879. 



[Plate 9.] 



In my paper read on the 12th December, 1878, I called attention to 

 the fact that, in the case of the metals discussed in that paper, with 

 the exception of hydrogen, there was a considerable discrepancy be- 

 tween the intensities of the lines seen in onr laboratories and the 

 number of times the lines had been seen by Young in his careful 

 researches on the chromosphere. 



In a preliminary note " On the Substances which produce the Chro- 

 mospheric Lines " I pointed out that the lines visible in the spectrum 

 of the chromosphere when a metallic prominence is observed are for the 

 most part basic lines, that is to say, with few exceptions, the longest 

 and brightest lines visible in the spectra of the so-called elements are 

 conspicuously absent ; instead of them we find fainter lines, which 

 Thalen has, in many instances, mapped as common to two elements. 



Since these papers were communicated to the Society I have con- 

 tinued this line of inquiry, and I now propose to state what I have 

 thus far done : — 



1. The maps of the spectra of calcium, barium, iron, and man- 

 ganese, submitted to the Society in an incomplete state when the 

 preliminary note was read, have been completed. In these the lengths 

 of the lines in the spectra of the metallic elements represent the in- 

 tensities given by Thalen, whose lines and wave-lengths I have followed 

 in all cases, while those of the lines visible in solar storms, represent 

 the number of times each line has been seen in the spectrum of the 

 chromosphere by Professor Young, to whose important work I have 

 drawn special attention in my last two communications. An inspec- 

 tion of these maps is sufficient to show that there is no connexion 

 whatever beyond that of wave-length between the spectra; it will 

 be gathered from the maps how the long lines seen in our laboratories 

 are suppressed and the feeble lines exalted in the spectrum of the 

 chromosphere, see Plate 9. The Mn map has been omitted on account 

 of its excessive complication. 



2. I have discussed the coincidences recorded in Angstrom's map 

 and Thalen tables in the sheets of the ' ; Spectre Normal," comprising 



