50 



Mr. Lockyer. Spectra of Stars. 



[Jan. 24, 



He sliows that the work already done enables him to confirm the 

 presence of Sr, Pb, Cd, K, Ce and U, and also that it indicates the pro- 

 bability of the presence of Ya, Pd, Mo, In, Li, Rb, Cs, Bi, Sn, La, Gl, 

 Yt or Er. 



IV. Note on the Bright Lines in the Spectra of Stars and 

 Nebulas." By J. Norman Lockyer, F.B.S. Received 

 December 31, 1877. 



Owing to absence from England in April last, I have only just become 

 acquainted with Dr. Huggins' paper, in reply to that by Mr. Stone, on 

 the above subject. As Mr. Stone has again directed attention to the 

 matter, I am anxious to say that I agree with him so entirely* that 

 two years ago I searched for indications of a large chromosphere in 

 the case of a Lyras and some other stars. I believe I have had glimpses 

 of bright lines at F and b, but if this discussion had not arisen I should 



* I append an extract from a lecture on the Structure of Nebula? and Stars, 

 which. I gave at Manchester in the autumn of 1876 (" Manchester Science Lec- 

 tures "), to show the perfect accord there is between us. "There are nebulse and 

 stars with spectra so similar that if one had the evidence of the spectroscope alone, it 

 might be impossible to decide which was nebula and which was star. Now this 

 may be a little startling to some of you, and therefore it is only fair I should explain 

 it. The stars, you know, are so remote from us that in the most powerful telescopes 

 to which spectroscopes are applied, they appear only as the finest points of light. 

 Now these points of light, it is not absurd to imagine, may in some instances be two 

 millions, or perhaps even three millions, of miles in real diameter. We know that 

 our own sun, which is certainly not the largest star in the heavens, is nearly one 

 million miles in diameter ; that is to say, the true sun, the true stellar nucleus, is 

 one million miles in diameter. Now when I dealt in my second lecture with the 

 physical constitution of the sun, I pointed out that the sun which we see, the sun 

 which sends us the majority of the light we receive, is but a small kernel in a 

 gigantic nut, so that the diameter of the real sun may be, say, two million miles. 

 Suppose then that some stars have very large coronal atmospheres ; if the area of 

 the coronal atmosphere is small compared with the area of the section of the true 

 disc of the sun, of course we shall get an ordinary spectrum of the star ; that is to 

 say, we shall get the indications of absorption which make us class the stars apart ; 

 we shall get a continuous spectrum barred by dark lines. But suppose that the 

 area of the coronal atmosphere is something very considerable indeed, let us assume 

 that it has an area, say fifty times greater than the section of the kernel of the star 

 itself ; now, although each unit of surface of that coronal atmosphere may be much 

 less luminous than an equal unit of surface of the true star at the centre, yet if the 

 area be very large, the spectroscopic writing of that large area will become visible 

 side by side with the dark lines due to the brilliant region in the centre where we 

 can study absorption ; other lines (bright ones) proceeding from the exterior por- 

 tion of that star will be visible in the spectrum of the apparent point -we call a star. 

 Now it is difficult to say whether such a body as that is a star or a nebula. We may 

 look upon it as a nebula in a certain stage of condensation ; we may look upon it 

 as a star at a certain stage of growth." 



