476 On the unknown Chromospheric Substance of Young. [Apr. 3, 



of matter to heights where it does not properly belong. It would 

 seem very probable that both these lines are due to the same substance 

 which causes the D 3 line." 



Again, in a letter to " Nature," June, 1872, Young says, " I confess 

 I am sorry that the spectrum of iron shows a bright line coincident 

 with 1474 (K) ; for, all things considered, I cannot think that iron 

 vapour has anything to do with this line in the spectrum of the corona, 

 and the coincidence has only served to mislead. But there are in the 

 spectrum many cases of lines belonging to the spectra of different 

 metals coinciding, if not absolutely, yet so closely, that no existing 

 spectroscope can separate them, and I am disposed to believe that the 

 close coincidence is not accidental, but probably points to some phy- 

 sical relationship, some similarity of molecular constitution perhaps, 

 between the metals concerned. . . . So, in the case of the green 

 coronal matter, is it not likely that though not iron it may turn out 

 to bear some important relation to that metal ?" In 1876 he proves 

 that the coronal line 1474 is not actually coincident with the line of 

 iron. 



In the catalogue of bright lines observed by Young at Sherman in 

 the Rocky Mountains, to which we have directed special attention in 

 one of our previous communications, it appears that the above-men- 

 tioned lines 1 and 82, along with D 3 , were as persistently present as 

 hydrogen, the only other line approaching them in frequency of occur- 

 rence being the green coronal line 1474 of Kirchhoff, which was 

 present on 90 occasions out of 100. It has occurred to us that these 

 four lines may belong to the same substance. An analogy in the 

 ratio of the wave-lengths of certain groups of lines occurring in diffe- 

 rent metals has been already pointed out by Stoney, Mascart, Salet, 

 Boisbaudran, and Cornu ; and without any special reductions, or 

 claims to an exact ratio in whole numbers, the following analogies are 

 worthy of note : — 



Hydrogen. 



Lithium. 



Magnesium. 



Chromospheric 

 substance. 



Wave-length : — 



(1) 6563-9 



(2) 4862-1 



(3) 4340 



(4) 4102-4 



Eatio of wave-lengt 

 (1) (2)&(4) 

 111 

 20 27 32 



(1) 6706 



(2) 6102 



(3) 4970 



(4) 4604 



(5) 4130 

 h of— 



(1) (3)&(5) 

 111 

 20 26*9 31-6 



(1) 5183 



(2) 3837-8 



(3) 3335 



(1) (2) (3) 

 111 



20 27 31 -1 



(1) 7055 * 



(2) 5874-9 



(3) 5315-9 



(4) 4471-2 



(1) (3) & (4) 



1 1 & 1 

 20 26-5 31-6 



* This wave-length is not so accurately known as the other rays belonging to the 

 chromosphere. 



