THE STELLAR EVIDENCE. 81 



present, and the lines of the cleveite gases, oxygen, nitrogen, and 

 carbon now appear for the first time. 



Associating this with the former result, we get as distinct evidence 

 that an increase of the gas lines in the spectrum accompanies the disap- 

 pearance of the enhanced lines, as that an increased development of the 

 enhanced lines accompanies the decrease of the arc lines. 



To take iron as an example, for the sake of simplicity ; it will be 

 seen that the actual stellar phenomena might have been predicted up 

 to a certain point, from a consideration of laboratory and solar phe- 

 nomena. But the stars carry us further than our predictions ; we see 

 the gradual increase of hydrogen and cleveite gases. The facts 

 demonstrate that as temperature increases hydrogen increases, .and, 

 together with the cleveite gases not obvious before, finally replaces 

 iron which has disappeared. 



This is one of the great stellar revelations, and it must be re- 

 membered that we have now hundreds of photographs which we can- 

 bring together to study the gradual change. There are no " breaks in- 

 strata." One of the most wonderful things about this line of work to 

 my mind is the simplicity, coupled with continuity, of the phenomena. 

 It carries conviction with it. 



We have then to face the fact that on the dissociation hypothesis r 

 as the metals which exist at the temperature of the arc are broken up 

 into finer forms, which I have termed proto-metals, at the fourth stage- 

 of heat (that of the high tension spark) which gives us the enhanced 

 spectrum ; so the proto-metals are themselves broken up at some tem- 

 perature which we cannot reach in our laboratories into other simpler 

 gaseous forms, the cleveite gases, oxygen, nitrogen and carbon being 

 among them. 



Does the story end here 1 No, there is a still higher stage ; after 

 the cleveite gases have disappeared as the arc lines and enhanced lines 

 did at the lower stages ; the new form of hydrogen to which I have 

 before called attention and which we may think of as "proto 

 hydrogen," makes its appearance. But there are already evidences 

 that even this is not the end of the simplifications brought about by 

 the transcendental stellar temperatures we are now discussing. 



It must always be remembered that the Spottiswoode coil (giving a- 

 40-inch spark) with a tremendous battery of condensers only carries 

 up to 7 Cygni, by which I mean that using this coil we obtain the 

 enhanced lines of the proto-metals of very nearly the same relative 

 intensities as those under which they appear in that star. 



In the stars then we have a few distinct changes of spectra : these 

 changes we know independently by the increase in. the length of the 

 spectrum towards the ultra-violet accompany stages of increased tern- 



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