80 THE POPULAR SCIENCE MONTHLY. 



were on the other side of the curve. The light of the star is grad- 

 ually blotted out by an enormous quantity of carbon compounds 

 in some form or other, till at last the star gets blood-red (group 

 VI), and finally is lost to human ken. The solar atmosphere at 

 present contains chiefly iron, calcium, and other similar metals, 

 but the hydrogen is disappearing, and there is possibly the slight- 

 est trace of carbon, but that trace is so small as to be somewhat 

 doubtful. The composition of the sun's atmosphere at present is, 

 moreover, almost identical with that of a mixture of meteorites 

 driven into vapor by a strong electric current, and, if we except 

 hydrogen, there is scarcely a line of any importance in the spec- 

 trum of the one which is not represented in the spectrum of the 

 other. Calcium, aluminium, iron, manganese, and certain lines of 

 nickel and other substances, are present. By means of such ex- 

 periments as this, the wonderfully close connection between the 

 gases at present existing in the atmosphere of the sun and the 

 gases obtained from the volatilization of meteorites is put before 

 us in the clearest and most convincing manner. 



With regard to the fact that carbon comes in and takes the 

 place of highest importance in the atmospheres of these cooling 

 bodies, it is worth while to remark that if, as seems possible, these 

 permanent gaseous compounds of carbon with different substances 

 like oxygen, nitrogen, and hydrogen, and probably hydrogen itself, 

 are kept away from the swarm during its condensation by that 

 form of radiant energy of the center which is evidenced in the 

 case of the sun by its tail-producing action on comets, it is easy 

 to imagine that when that radiant energy is reduced, the carbon 

 compounds will gradually approach the central body, until at 

 length the flickering energy is no longer able to keep these per- 

 manent gases away, and then the surroundings of the central 

 body are invaded by these gases in such tremendous quantity 

 that an absorption is produced which first turns the cooler star 

 blood-red, and finally blots it out. 



There are several very interesting questions connected with 

 this. Suppose, for instance, that we attempt to discuss the future 

 of that magnificent nebula in Andromeda, the true structure of 

 which Mr. Roberts has recently revealed to us. It is already sus- 

 pected that the two subsidiary swarms partake of the motion and 

 form a part of the system. Those smaller swarms will naturally 

 condense before the larger ones. Let us imagine ourselves no 

 longer dealing with anything so far away, but with the solar sys- 

 tem when it was in that stage. The central sun having this cor- 

 don round it can only be formed of those substances which are not 

 repelled by its radiant energy ; it will, therefore, be chiefly a mass 

 of metallic vapor. The masses near it for the same reason will 

 be also chiefly of metallic vapors, and their density will be high ; 



