444 On " Young's List of Chromo spheric Lines? [Mar. 20, 



conditions of temperature which enable us to observe the reversal 

 now of this set of lines, now of that, the more complex becomes the 

 possible origin. Some spectra are full of doublets : sodium and 

 potassium, as ordinarily mapped, may be said indeed to consist ex- 

 clusively of doublets ; others, again, are full of triplets, the wider 

 member being sometimes on the more, sometimes on the less, re- 

 frangible side. Doublets and triplets, as a rule, reverse themselves 

 more freely than the irregular lines in the same spectrum — which 

 particular doublet or triplet will reverse depending upon the tem- 

 perature, as if the cooler vapour to which the reversal is due varied 

 as in the case of fractional distillation. Some lines are clean cut in 

 their reversal ; others, again, to use the laboratory phrase, are fluffy to 

 a degree that must be seen to be appreciated, so much so, that when 

 photographed they appear merely as blurs upon the plate. 



The above results, which have been foreshadowed in my previous 

 papers, have led me to examine especially the intensities of the various 

 Fraunhofer lines, and to compare the intensities of the metallic lines 

 confronted with them in arc and sun photographs. I have done this 

 because it is worse than useless to proceed with this construction of 

 the large map now that four years' work has shown that the method 

 of impurity elimination has proved insufficient, until some other 

 method, embodying a higher law, can be used ; and to get this we 

 want work over the whole field. This examination I am making, not 

 only from K to G, over which my own photographs extend, but even 

 to &, by means of another series taken by Professor Roscoe, which he 

 has allowed me to inspect. 



In short, in this survey I have about 300 photographs to work upon. 

 I exhibit several of these photographs to the Society in anticipation of 

 a further communication. 



The upshot of this inquiry even already is as follows : — The dis- 

 crepancy which I pointed out, six years ago, between the solar and 

 terrestrial spectra of calcium is not an exceptional, but truly a typical 

 case. Variations of the same kind stare us in the face when the 

 minute anatomy of the spectrum of almost every one of the so-called 

 elements is studied. If, therefore, the argument for the existence of 

 our terrestrial elements in extra-terrestrial bodies, including the sun, 

 is to depend upon the perfect matching of the wave-lengths and in- 

 tensities of the metallic and Fraunhofer lines, then we are driven to 

 the conclusion that the elements with which we are acquainted here 



DO NOT EXIST IN THE SUN. 



