CHAP. XXI.] THE SIMPLEST ELEMENTS APPEAR FIRST. 163 



We cannot suppose that the absence of the principal series means 

 a greater simplicity, because I have shown that only about half the 

 lines in the spectrum of each of these substances has yet been picked 

 up in the series, and if the series represent the vibrations of. a single 

 particle, of course the lines which are not represented in the series, by 

 theory must represent the vibrations of some other particles. So that 

 there we are face to face with the possibility of a greater complexity of 

 the particles which produce the series than of those which in the 

 stars give us the lines not in the series. These then are other simple 

 forms. 



Coming further down in stellar temperatures we find oxygen ; 

 here we deal with six series instead of three, or two, as in the case of 

 magnesium and calcium ; and even then, as I have pointed out, we do 

 not deal with above half the lines of the gas as we can see them at a 

 higher temperature. This then, seems to suggest that in the hottest 

 stars there are very various stabilities of very various forms : in short, 

 there seems to be there as here distinctly the survival of the fittest ; 

 otherwise how can we account for the fact that certainly in the hottest 

 stars we get three metals, magnesium, calcium and silicium, before we 

 have indication of any other, and that where we have those metals and 

 bring our series touch-stone to them, we find that instead of being very 

 simple they are really very complex as they exist here. However this 

 may be, we are now assured that there is a much greater quantity of 

 some apparently more complex forms in the hotter stars than of the more 

 simple ones ; and that is a matter which the chemists, when they come 

 to inquire into these questions which we are now considering, will 

 certainly have to face. This suggests, too, another very interesting 

 question. A great many simple organic forms appear in the strati- 

 graphic series at a late period ; some of the simplest forms died out, 

 others remained. Now, it may be that some of the more simple forms 

 in inorganic evolution, as in organic evolution, really represent later 

 introductions ; but, however this may be, it is perfectly certain that 

 we have not an absolute parallel between the results of the spectro 

 scopic observations of series and the spectroscopic observations of 

 stars. 



In all these changes we seem to be brought into presence of succes- 

 sive complications, due to reduction of temperature, but there is a 

 longer series of complications in some substances than in others. 

 Of the origin of proto-magnesium and proto-calcium the stars as yet 

 tell us nothing ; but it is difficult to believe that the earliest forms of 

 the other metals are not built up of some of the constituents of the 

 heat ranges represented by those between y Argus and a Crucis, and 

 that their other complications began later. 



M 2 



