172 Mr. J. N. Lockyer on Recent 



lute in the case of such metals as iron), the intensity of 

 the iron-lines which we get in our laboratories is equivalented 

 by the intensity of the so-called iron-lines which we assume to 

 exist in the spectrum of the sun. That is the great argument, 

 in fact, for the existence of iron in the sun. But when we 

 leave the iron group of metals, we find others in which this 

 coincidence, this great similarity of intensity from one end of 

 the spectrum to the other, is very considerably changed. We 

 get in the case of calcium very thick lines of calcium corre- 

 sponding with very thin lines in the sun, and we get thin lines 

 of calcium corresponding w T ith very thick lines in the sun. In 

 fact, the two thickest lines which have already been mapped 

 m the spectrum of the sun are lines due to calcium. If we 

 photographed the spectrum of calcium with a very weak arc in 

 that electric lamp, they would scarcely be visible at all. If, 

 however, we pass from the tension of the arc to the tension 

 which is obtainable with the use of a very large coil, then we can 

 make the spectrum which we get artificially correspond exactly 

 with the spectrum with which the sun presents us naturally ; 

 and the more we increase the tension (the larger the coil and 

 the larger the jar we employ), the more can we make our ter- 

 restrial calcium vibrate in harmony, so to speak, with the cal- 

 cium which occupies a very definite region in the atmosphere 

 of the sun. Now this gives us this very precious teaching: — 

 We know that the vapour of calcium occupies such and such a po- 

 sition in the sun; we know that to get the two things in harmony, 

 as I said before, we must employ a very large induction-coil ; 

 and we know, again, that if we do employ a large induction- 

 coil, all these beautiful flutings in the car&on-spectrum which 

 have been thrown on the screen disappear utterly. That kind 

 of carbon is no longer present in the reaction ; but instead of 

 it we have a new kind of carbon which is only competent to 

 give us bright lines. We know, fourthly, that those bright lines 

 do not exist reversed in the spectrum of the sun. Therefore 

 the carbon must exist higher than the calcium, in a region of 

 lower temperature. 



In what I have said up to the present moment (and I have 

 just touched very slightly on the physical side of the work, 

 because I believe that in the future it w T ill be most rich in 

 teachings of the kind I have indicated), I must remind you 

 that I have dealt solely with the Fraunhofer lines. Now it is 

 knowledge ten years old, that if we observe the solar spectrum 

 with that considerable dispersion which is now, I think, impe- 

 rative if we are to do much good with it, there are bright lines 

 in the ordinary solar spectrum side by side with the dark ones. 



