46 



Note by Mr. Norman Lockyer. 



[May 15, 



visibility o£ certain lines in the chromosphere do not appear to be in 

 accordance with Young's published tables, and as Messrs. Liveing and 

 Dewar have in a still later paper drawn theoretical conclusions from 

 these statements, I think it desirable to call attention to the fact, in 

 order to prevent any confusion which might otherwise arise. 

 It will be sufficient to refer to two cases : — 



I. Messrs. Liveing and Dewar state that two lines of aluminium, 

 the wave-lengths of which they give as 6245 and 6237, have each 

 been seen by Young eight times. 



According to Thalen's measurements, which are the best that we 

 possess, there are no lines of aluminium in these positions. He gives, 

 however, lines at 6244*0 and 6234-0. 



Young, moreover, states that he saw reversed a strong line {clearly 

 shown in Angstrom's map to be an iron line) at 6245*4, and a line 

 which he does not ascribe to any element at 6237*3, which is more 

 than three divisions of the scale from the position of the aluminium 

 line. 



II. In the case of potassium, Messrs. Liveing and Dewar give two 

 lines at wave-lengths 4044 and 4042 as having been seen by Young 

 three times. I know of no potassium lines at the places given ; 

 Young moreover has recorded the reversal of no potassium line in 

 this region. What Young distinctly states he saw, was the reversal 

 of the iron line at 4045 "0, which is one of the most marked iron lines 

 in the spectrum of the sun. To this reversal I referred in my paper of 

 December 12th.* 



It is perfectly true that there are two potassium lines in this region ; 

 they were not mapped by Thalen, and they were only seen as a single 

 line by Lecoq de Boisbaudranf and the wave-length, given as 4045, as 

 his dispersion was limited, did not enable us to determine its true 

 position with reference to the Fraunhofer lines. Last year, however, 

 I not only stated the double nature of this line on photographic evi- 

 dence,^; and pointed out that both components were absent from the 

 spectre normal, but I gave their wave-lengths as 4042*75 and 4046*28 

 (positions which will only find the last place of decimals altered, even 

 if it be altered, in the revision of the map now being proceeded with) , 

 and on the strength of them announced the existence of potassium 

 in the sun. Messrs. Liveing and Dewar do not state whence their 

 wave-lengths were derived, neither do they refer to my communication. 

 It would appear therefore not only that the reference to Young's work 

 in many cases is founded upon some misunderstanding, but that a 

 higher degree of accuracy than that employed by Messrs. Liveing and 

 Dewar is necessary to determine such coincidences. I may state 

 generally that my eleven years' work on this special branch has led 



* " Proceedings," vol. xxviii, p. 172. f " Spectres Lumineux," texte, p. 48. 



J " Proceedings," vol. xxvii, p. 280. 



