178 Mr. J. N. Lockyer. Researches in Spectrum [Dec. 12. 



satisfied from former experiments that occluded hydrogen behaves in 

 this respect like ordinary hydrogen, I begged my friend, Mr. W. C. 

 Koberts, F.R.S., Chemist to the Mint, to charge a piece of palladium 

 with hydrogen for me. This he at once did ; and I take this present 

 opportunity to express my obligation to him. I exhibit to the Society 

 a photograph of this palladium and of indium side by side. It will be 

 seen that one form of hydrogen in indium has distinctly recorded 

 itself on the plate, while that in palladium has not left a trace. I 

 should add that the palladium was kept in a sealed tube till the 

 moment of making the experiment, and that special precautions were 

 taken to prevent the two pieces between which the arc was taken 

 from becoming unduly heated. 



To sum up, then, the facts with regard to hydrogen ; we have h 

 differentiated from the other lines by its appearance alone in indium ; 

 by its absence during the eclipse of 1875, when the other lines were 

 photographed; by its existence as a short line only in the chromo- 

 sphere of the sun, and by the fact that in the experiments of 1869 a 

 very high temperature was needed to cause it to make its appearance. 



With regard to the isolation of the F line I have already referred to 

 other experiments in 1869, in which Dr. Frankland and myself got it 

 alone.* 'I exhibit to the Society a globe containing hydrogen, which 

 gives us the F line without either the red or the blue one. 



The accompanying drawing shows how these lines are integrated in 

 the spectrum of the sun. 



Fig. 6. 



% C F C 



I r _j 



I have other evidence which, if confirmed, leads to the conclusion 

 that the substance which gives us the non-reversed line in the chromo- 

 sphere and the line at 1474 of Kirchhoffs scale, termed the coronal 

 line, are really other forms of hydrogen. One of these is possibly 

 more simple than that which gives us h alone, the other more complex 

 than that which gives us F alone. The evidence on this point is of 

 such extreme importance to solar physics, and throws so much light 

 on star structure generally, that I am now engaged in discussing it y 

 and shall therefore reserve it for a special communication. 



In the meantime I content myself by giving a diagram, in which 

 I have arranged the various groupings of hydrogen as they appear to 



* See also Plucker, " Phil. Trans.," Part I, p. 21. 



